TWI741300B - Engine unit - Google Patents

Abstract

The engine unit 1 of the present invention has one intake port 12, one intake valve 22 and one injector 23 for one combustion chamber 11. When the fuel is injected from the injector 23 into a space where only the atmosphere is not installed in the engine unit, at a certain point immediately after the injection, the first plane that intersects the injection directions of the plurality of fuel droplets The fuel on S1 exists in a circle along the edge of the circle. Intake air in such a way that the fuel concentration in the first area A1 along the edge of the circle on the first plane S1 is higher than the fuel concentration in the second area A2 which is in contact with the entire inner peripheral end of the first area A1 During the stroke, fuel is injected from a plurality of injection holes.

Description

Engine unit

The present invention relates to an engine unit having an injector for injecting fuel in an intake passage portion.

Heretofore, there is known an engine unit having an injector for injecting fuel in an intake passage portion (for example, refer to Patent Document 1). The intake passage is connected to the intake port of the combustion chamber. The air inlet is opened and closed by the air inlet valve.

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2012-154209

An engine unit having an injector for injecting fuel in an intake passage portion needs to increase the degree of freedom in design of the concentration distribution of fuel in the combustion chamber. For example, there are situations where the fuel concentration in the combustion chamber needs to be uniform, or the fuel concentration around the spark plug needs to be higher than other parts.

The object of the present invention is to provide an engine unit that can increase the design freedom of the concentration distribution of fuel in the combustion chamber.

(1) The engine unit of the present invention is a four-stroke cycle device, and includes: a cylinder portion having at least one combustion chamber in which each part is formed by the inner surface of the cylinder hole, and is formed in the at least one combustion chamber At least one intake port, and the air that is connected to the at least one intake port and flows into the inside is supplied from the at least one intake port to the at least one cylinder intake passage portion of the at least one combustion chamber; At least one external intake passage portion, which is arranged outside the cylinder portion, is connected to the at least one cylinder intake passage portion, and the air flowing into the interior is supplied to the at least one cylinder intake passage portion; at least one An intake valve, which can be moved between a position where the at least one intake port is opened and a position where the at least one intake port is closed; at least one injector, each of which is capable of injecting fuel in a mist A plurality of injection holes, and the plurality of injection holes are provided in the cylinder intake passage portion or the external intake passage portion so as to be located in the cylinder intake passage portion or the external intake passage portion; and a control device, which Control the fuel injection of at least one of the above-mentioned injectors. The intake port, the intake valve, and the injector are provided one for each of the combustion chambers, and each constitutes a single intake port, a single intake valve, and a single intake port injector. The at least one cylinder intake passage portion and the at least one external intake passage portion include at least one single intake passage portion. The single intake passage portion is provided with one for each of the combustion chambers, and it is from the area where the injector for the single intake port is installed to the area up to the single intake port, so that the flow of air is not separated or not. The confluence is constituted by its internal means. The injector for the single intake port (a) is arranged to inject fuel toward the single intake port, and (b) is configured as follows: in a state where it is not installed in the engine unit When the fuel is injected into the atmosphere only, at a certain point immediately after the injection, (i) the first plane that intersects the injection direction of the plurality of fuel droplets injected from the above-mentioned single intake port with the injector The fuel on the above exists in a circle or an ellipse along at least a part of the edge of the circle or the ellipse, (ii) the area where the fuel exists on the first plane included in the above The fuel concentration in the first area where the outer peripheral end and the inner peripheral end are along at least a part of the edge of the one circle or the one ellipse is higher than that on the first plane and the entire inner peripheral end of the first area The fuel concentration in the second zone is (c) controlled by the control device by injecting fuel during the intake stroke and when the single intake valve is in the position to open the single intake port. The fuel supplied to one of the above-mentioned combustion chambers is the fuel injected from one of the above-mentioned single intake ports by an injector and passing through one of the above-mentioned single intake ports.

According to this structure, the engine unit of the present invention is a four-stroke cycle engine unit. The engine unit includes a cylinder section having at least one combustion chamber. Each part of at least one combustion chamber is formed by the inner surface of the cylinder bore. The cylinder section has at least one cylinder intake passage section. At least one cylinder intake passage portion is connected to at least one external intake passage portion arranged outside the cylinder portion. The air that has flowed into at least one external intake passage is supplied to at least one combustion chamber through at least one cylinder intake passage and at least one intake port. The engine unit has a single intake passage portion, a single intake port, a single intake valve, and a single intake port injector provided with one for each combustion chamber. That is, the engine unit has only the same number of single intake passages, single intake ports, single intake valves, and single intake port injectors as the number of combustion chambers. The at least one cylinder intake passage portion and the at least one external intake passage portion include at least one single intake passage portion. The single intake port is formed in the combustion chamber and connected to the single intake passage. A single air inlet valve opens and closes a single air inlet. The injector for a single intake port is provided in the cylinder intake passage portion or the external intake passage portion. Single inlet The passage portion includes at least a region from a location where the injector for a single intake port is provided to a single intake port. The single intake passage part is the area from the position where the injector for the single intake port is provided to the single intake port. The single intake passage portion is configured so that the flow of air passes without separation or merging. The injector for a single intake port has a plurality of injection holes for spraying fuel in the form of mist. The injector for a single intake port is arranged to inject fuel toward a single intake port. The fuel injection of the injector for a single intake port is controlled by the control device of the engine unit. The injector for a single intake port is controlled by the control device by injecting fuel when the single intake valve is in the position to open the single intake port during the intake stroke.

The injector for a single intake port is constructed as follows: when the injector for a single intake port is not installed in the engine unit and injects fuel into a space where only the atmosphere is, at a certain point immediately after the injection, Meet the following 2 necessary conditions. The first requirement is that the fuel on the first plane that intersects the injection directions of the plurality of fuel droplets injected by the injector from a single intake port is in a circle or an ellipse so as to follow the one. A circle or at least a part of the edge of the one ellipse exists. The second requirement is that it is contained in the area where fuel exists on the first plane and the fuel concentration in the first area where the outer and inner peripheral ends are along at least a part of the edge of the circle or the ellipse is higher than The concentration of fuel in the second area that is in contact with the entire inner peripheral end of the first area on the first plane. That is, the concentration of the mist-like fuel injected from a single intake port by the injector at the outer periphery is higher than the concentration at the center. The fuel-existing area on the first plane may or may not include the second area. The fuel supplied to one combustion chamber is only the fuel injected from one single intake port with an injector and passing through one single intake port.

Suppose that when the engine unit has multiple intake ports for one combustion chamber, it is provided with A plurality of intake passages respectively connected to a plurality of intake ports. The engine unit of the present invention has only one intake port for one combustion chamber. Therefore, the diameter of the single intake port and the cylinder hole of the present invention is the same as that of the present invention, and the diameter is larger than that of an engine unit with multiple intake ports for one combustion chamber. Therefore, the diameters of the single intake passage portion and the cylinder hole of the present invention are the same as those of the present invention, and the diameter of the intake passage portion of an engine unit having a plurality of intake ports for one combustion chamber is larger. With the larger diameter of the single intake passage portion, the injection angle of the fuel injected from the single intake port with the injector can be increased. The injection angle refers to the largest angle among the injection directions of a plurality of fuel droplets injected by an injector from a single intake port when viewed in a certain direction. The injection angle of the fuel injected by the injector from a single intake port is relatively large, and it is possible to reduce the diameter of the injected droplets while suppressing the contact of the injected droplets with each other. Due to the small diameter of the injected droplets, the droplets of fuel flowing into the combustion chamber can easily spread along the flow of air. In this way, the unevenness of the concentration distribution of the fuel in the combustion chamber is suppressed. That is, the engine unit of the present invention suppresses the unevenness of the fuel concentration distribution in the combustion chamber compared with an engine unit having a plurality of intake ports for one combustion chamber.

Assuming that the engine unit has two intake ports and one injector for one combustion chamber, two intake passages connected to a plurality of intake ports are connected to each other. In addition, the ejector is arranged on the upstream side of the air flow direction than the part where the two intake passages are connected. The injector injects fuel toward two intake ports. On the other hand, the engine unit of the present invention has one intake port and one injector for one combustion chamber. Therefore, the injector for a single intake port of the present invention can be arranged closer to the intake port compared to an injector of an engine unit having two intake ports and one injector for one combustion chamber. By arranging the injector for a single intake port close to the intake port, the injection angle of fuel injected from the injector for a single intake port can be further increased. As above As described above, the injection angle of the fuel injected by the injector from a single intake port is relatively large, and it is possible to reduce the diameter of the injected droplets while suppressing the contact of the plurality of injected droplets. Due to the small diameter of the injected droplets, the droplets of fuel flowing into the combustion chamber can easily spread along the flow of air. Therefore, the engine unit of the present invention further suppresses the unevenness of the fuel concentration distribution in the combustion chamber compared with an engine unit having a plurality of intake ports and one injector for one combustion chamber.

Suppose that when the engine unit has a plurality of intake ports for one combustion chamber, the air flowing into the combustion chamber from the plurality of intake ports collide with each other. On the other hand, the engine unit of the present invention has only one intake port for one combustion chamber, so there is no such air collision. In addition, compared with an engine unit having a plurality of intake ports for one combustion chamber, the intake ports can be arranged closer to the center axis of the cylinder bore. Therefore, the air flowing into the combustion chamber from the intake port is easily diffused uniformly along the circumferential direction of the inner surface of the cylinder hole. Therefore, the engine unit of the present invention further suppresses the unevenness of the fuel concentration distribution in the combustion chamber compared with an engine unit having a plurality of air intake ports for one combustion chamber.

By suppressing the unevenness of the fuel concentration distribution in the combustion chamber, assuming that the injection direction is adjusted, the concentration at a desired position in the combustion chamber can be increased. That is, it is easy to adjust the concentration distribution of fuel in the combustion chamber. Therefore, the engine unit of the present invention can increase the design freedom of the concentration distribution of fuel in the combustion chamber.

(2) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

If you observe the direction along the central axis of the cylinder hole, it can be observed The plane of the straight line at the center of the two injection directions that form the largest angle among the injection directions of the plurality of fuel droplets injected by the injector for the single intake port is defined as the second plane, and the line perpendicular to the second plane When observing the direction, the plane that can be observed to be the center of the two injection directions at the largest angle among the injection directions of the plurality of fuel droplets injected from the above-mentioned single intake port is set as the third plane , Assuming that the line of intersection between the second plane and the third plane is the injection centerline, the first plane is one of a plurality of planes passing through a point on the injection centerline among the areas where fuel exists on the plane. The plane in which the length in the direction parallel to the second plane becomes the shortest and the length in the direction parallel to the third plane of the fuel-existing area on the plane becomes the shortest.

According to this configuration, the first plane can be set as a plane that has the smallest unevenness in the distance from the plurality of injection holes of the injector for a single intake port to the first area among the plurality of planes passing through one point on the injection center line.

(3) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The injector for the single intake port is arranged and configured such that the injection center line passes through the single intake port.

Suppose that when the fuel injection center line does not pass through a single intake port, even if the fuel is injected in such a way that the first region becomes a ring, the amount of fuel passing through the gap between the single intake valve and the single intake port is also the same. It becomes uneven in the circumferential direction of the gap. Therefore, the concentration of fuel at a specific location in the combustion chamber is easy to increase. On the other hand, the single air inlet of the present invention is sprayed The injector injects fuel in a way that the centerline of the injection passes through a single intake port. Thereby, the unevenness of the fuel passing through the gap between the single intake valve and the single intake port is suppressed. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(4) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The injector for the single intake port is arranged and configured such that the injection center line passes through the second region.

(5) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The single intake valve has: an umbrella portion that can block the single intake port; and a rod portion that is connected to the umbrella portion and partly disposed in the single intake passage portion. The injector for the single intake port is arranged and constructed in such a manner that the injection center line passes through the rod portion of the single intake valve at a position where the single intake port is opened when viewed in the direction of the center axis of the cylinder bore.

According to this configuration, when viewed in the direction of the center axis of the cylinder bore, the injection center line is more likely to pass through the center of a single intake port or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(6) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The ejector for the single intake port passes through the rod and umbrella portion of the single intake valve at the position where the single intake port is opened when the injection center line is viewed in a direction orthogonal to the second plane Configuration and composition.

According to this configuration, when viewed in a direction orthogonal to the second plane, the injection center line passes through the center of the single intake port or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(7) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The injector for the single intake port is arranged and configured such that the injection center line passes through the rod portion and the umbrella portion of the single intake valve located at a position where the single intake port is opened.

According to this configuration, the injection center line passes through the center of the single intake port or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(8) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The cylinder intake passage portion and the external intake passage portion are specific for each of the combustion chambers. There is one set. The engine unit is provided with at least one throttle valve, and the at least one throttle valve is respectively arranged in the at least one external intake passage portion, and the flow direction of the air in the single intake passage portion is located more than the single The injector for the intake port is more upstream.

Let the volume of a space formed between the throttle valve in the closed position and the intake valve in the closed position be the downstream volume of the throttle valve. Assuming that the engine unit has a plurality of intake ports and one injector for one combustion chamber, as described above, the required distance between the injector and the intake port is relatively long. Therefore, the required distance between the throttle valve and the intake port is also longer. Compared with an engine unit having a plurality of intake ports and one injector for one combustion chamber, the engine unit of the present invention can arrange the throttle valve at a position close to the intake port. Therefore, the downstream volume of the throttle valve can be reduced.

Assuming that the engine unit has multiple intake ports, multiple injectors, and one throttle valve for one combustion chamber, it needs to be located more downstream than the throttle valve and more upstream than the injector. A plurality of intake passages provided in one combustion chamber are connected to each other. Therefore, the required distance between the throttle valve and the intake port is relatively long. Therefore, in the engine unit of the present invention, compared with an engine unit having a plurality of intake ports, a plurality of injectors, and a throttle valve for one combustion chamber, the throttle valve can be arranged at a position close to the intake port. Therefore, the downstream volume of the throttle valve of the engine unit of the present invention can be smaller than the downstream volume of the throttle valve of an engine unit having a plurality of intake ports, a plurality of injectors and a throttle valve for one combustion chamber.

Furthermore, the throttle downstream volume of an engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber is a space formed by connecting a plurality of intake passages. On the other hand, the downstream volume of the throttle valve of the engine unit of the present invention is formed in a space in one intake passage. Therefore, the downstream volume of the throttle valve of the engine unit of the present invention and the throttle valve of an engine unit having multiple intake ports, at least one injector and one throttle valve for one combustion chamber Compared with the downstream volume, it can be further reduced.

Assuming that the engine unit has one throttle valve for a plurality of combustion chambers, the downstream volume of the throttle valve is a space formed by connecting a plurality of intake passages provided for each combustion chamber. On the other hand, when the engine unit of the present invention has a plurality of combustion chambers, one throttle valve is provided for each combustion chamber. Therefore, the downstream volume of the throttle valve of the engine unit of the present invention is the space formed in one intake passage. Therefore, the downstream volume of the throttle valve of the engine unit of the present invention can be smaller than the downstream volume of the throttle valve of an engine unit having one throttle valve for a plurality of combustion chambers.

The smaller the downstream volume of the throttle valve, the more susceptible the pressure in the intake passage when the intake port is to be affected by the negative pressure (lower than atmospheric pressure) in the combustion chamber. That is, the smaller the volume downstream of the throttle valve, the lower the pressure in the intake passage during the intake stroke. This promotes the evaporation of fuel injected during the intake stroke. In addition, the air flowing into the combustion chamber from the intake port is easily diffused uniformly along the circumferential direction of the inner surface of the cylinder hole. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(9) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The injector for the single intake port is configured as follows: the first area on the first plane is a ring shape along the entire circumference of the edge of the one circle or the one ellipse, or along the one circle or A part of the edge of the above-mentioned one ellipse is non-circular, and the center of its outer peripheral end in the circumferential direction is located at a circle of 90° on the above-mentioned first plane having both ends passing through the two ends of the circumferential direction of the above-mentioned non-circular first region The outer side of the arc in the radial direction.

According to this configuration, the first region has a ring shape or a non-ring shape with a long circumferential length. Therefore, it is possible to reduce the diameter of the injected droplets in such a way that the contact of the plurality of injected droplets can be suppressed, and at the same time, a sufficient amount of fuel can be injected from a single intake port with the injector.

(10) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The single intake valve has: an umbrella portion that can block the single intake port; and a rod portion that is connected to the umbrella portion and partly disposed in the single intake passage portion. The injector for the single intake port is arranged at a position where the shortest distance between the plurality of injection holes and the center of the single intake port is less than three times the diameter of the single intake port.

According to this structure, the distance from the plurality of injection holes of the injector for a single intake port to the single intake port is relatively short. Therefore, it is possible to reliably increase the injection angle of fuel injected from a single intake port with the injector. As described above, the injection angle of the fuel injected by the injector from a single intake port is relatively large, and it is possible to reduce the diameter of the injected liquid droplets while suppressing the contact of the plurality of injected liquid droplets. With the smaller diameter of the injected droplets, the unevenness of the fuel concentration distribution in the combustion chamber can be further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(11) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The injector for the single intake port is arranged at a position where the shortest distance between the plurality of injection holes and the center of the single intake port is less than twice the length of the diameter of the single intake port Set.

According to this structure, the distance from the plurality of injection holes of the injector for a single intake port to the single intake port is further shorter, so that the injection angle of fuel injected from the injector for a single intake port can be further increased. Therefore, it is possible to prevent the ejected droplets from contacting each other while further reducing the diameter of the ejected droplets. Thereby, the unevenness of the concentration distribution of the fuel in the combustion chamber can be suppressed more reliably. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

(12) According to one aspect of the present invention, the engine unit of the present invention preferably has the following configuration.

The cylinder portion has at least one exhaust port formed in the at least one combustion chamber. At least one exhaust port is provided for one combustion chamber. The diameter of the air inlet is larger than the diameter of the air outlet.

According to this configuration, the diameter of the single air inlet is relatively large, and therefore the diameter of the single air inlet passage portion is also relatively large. As described above, by the larger diameter of the single intake passage portion, the injection angle of the fuel injected from the single intake port by the injector can be increased. The injection angle of the fuel injected by the injector from a single intake port is relatively large, and it is possible to reduce the diameter of the injected droplets while suppressing the contact of the injected droplets with each other. With the smaller diameter of the injected droplets, the unevenness of the fuel concentration distribution in the combustion chamber can be further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber can be further improved.

<Definition of Terms>

In the present invention, the "intake passage portion" means a structure that surrounds the space through which the air supplied to the combustion chamber passes.

The "single air inlet" in the present invention is not a space, but a structure. When the part that is in contact with a single intake valve and is blocked by a single intake valve is cylindrical, the "single intake port" in the present invention refers to contact with a single intake valve and is blocked by a single intake valve The end of the cylinder-shaped area near the combustion chamber among the two ends in the cylinder axis direction. That is, in the present invention, the "single intake port" refers to a ring-shaped linear portion that is in contact with a single intake valve and is blocked by a single intake valve. The "exhaust port" in the present invention also has the same definition.

Each part of at least one combustion chamber of the present invention is formed by the inner surface of the cylinder bore. When the engine unit of the present invention has a plurality of fuel chambers, the cylinder hole is provided for each of the plurality of combustion chambers. That is, the number of cylinder holes and combustion chambers of the engine unit is the same.

In the present invention, one intake port, one intake valve, and one injector are provided for each combustion chamber. That is, the engine unit of the present invention does not have a plurality of intake ports for one combustion chamber. The engine unit of the present invention does not have multiple intake valves for one combustion chamber. The engine unit of the present invention does not have multiple injectors for one combustion chamber.

In the present invention, "at least one cylinder intake passage portion and at least one external intake passage portion include at least one single intake passage portion" means that at least one cylinder intake passage portion and at least one external intake passage portion are included. One element of the air passage portion includes at least one single intake passage portion. Single intake passage The part may be included only in the intake passage part of at least one cylinder. A part of the single intake passage part may be included in at least one cylinder intake passage part, and the other part of the single intake passage part may be included in at least one external intake passage part. The number of cylinder intake passage portions may be the same as or different from the single intake passage portion. The number of external intake passage parts may be the same as or different from the single intake passage part. The number of cylinder intake passages may be the same as or different from the external intake passages.

The single intake passage of the present invention is from the area where the injector for the single intake port is provided to the area from the single intake port. In the present invention, the "area from the position where the injector for a single intake port is provided to the single intake port" may also include the injector for the single intake port and the cylinder intake passage portion or the external intake passage portion. All parts of the connection. In other words, "the area from the part where the injector for a single intake port is installed to the single intake port" may also include the part where the injector for a single intake port is connected to the cylinder intake passage part or the external intake passage part. The position in the flow direction of the exhaust gas that is farthest from a single air inlet.

In the present invention, spraying fuel in the form of mist means to inject a plurality of minute fuel droplets.

In the present invention, the "injection direction of a plurality of fuel droplets injected from a single intake port injector" refers to the injection direction of a plurality of liquid droplets injected from a single intake port injector in one injection. In more detail, it is the ejection direction of the droplets at the point in time when a plurality of droplets are respectively ejected from a single intake port with an ejector. In other words, the fuel injection direction can be expressed by a linear vector starting from the injector for a single intake port. Even when the moving direction of the droplet changes under the influence of the air flow, the ejection direction of the droplet will not change.

In the present invention, the fuel on the first plane may include vaporized fuel or only liquid fuel.

In the present invention, the presence of fuel on the first plane in a circle or an ellipse may mean that the fuel injected from a single intake port by an injector through one injection process is present in the first plane All the fuel above including gasified fuel exists in a circle or an ellipse. In the present invention, the presence of fuel on the first plane in a circle or an ellipse may mean that the fuel injected from a single intake port by an injector through one injection process is present in the first plane All the liquid fuel above exists in a circle or an ellipse.

In the present invention, the fuel-existing area on the first plane surrounds the fuel-existing area on the first plane. The area where fuel exists on the first plane may also include gaps between droplets.

In the present invention, when the outer peripheral end of the first area is along a part of the edge of a circle, the inner peripheral end of the first area is along a part of the edge of the circle. In the present invention, when the outer peripheral end of the first area is along the entire circumference of the edge of a circle, the inner peripheral end of the first area is also along the entire circumference of the edge of the circle.

In the present invention, when the outer peripheral end of the first area is along a part of the edge of an ellipse, the inner peripheral end of the first area is along a part of the edge of the ellipse. In the present invention, when the outer peripheral end of the first area is along the entire circumference of the edge of an ellipse, the inner peripheral end of the first area is also along the entire circumference of the edge of the ellipse.

As long as the outer peripheral end of the first region of the present invention is along at least a part of the edge of the circle or ellipse, it may not coincide with at least a part of the edge of the circle or ellipse. The outer periphery of the first area of the present invention is only To be along at least a part of the edge of the circle or ellipse, it may not be parallel to at least part of the edge of the circle or ellipse.

As long as the inner peripheral end of the first region of the present invention is along at least part of the edge of the circle or ellipse, it may not be parallel to at least part of the edge of the circle or ellipse.

In the present invention, when the first area is non-annular, the first area is an area surrounded by the outer peripheral end of the first area, the inner peripheral end of the first area, and both ends in the circumferential direction of the first area . Both ends in the circumferential direction of the first area may be linear, for example, or may be curvilinear expanding toward the outside of the first area.

In the present invention, when the first area is non-circular, the second area includes at least the entire inner peripheral end of the first area and a line segment that connects the inner peripheral end of the first area to both ends in the circumferential direction. area. The second area may only include this area.

In the present invention, an ellipse (oval) refers to a ring that includes only a curve or includes a curve and a line segment, and has a smooth convex shape. An ellipse can also be an ellipse formed by a collection of fixed points as the sum of the distances from two fixed points. In addition, an ellipse (oval) may also have a shape similar to an ellipse (ellipse). The ellipse can also be shaped like an egg. The ellipse can also be a shape formed by two semicircles and two line segments like a track and field race track. When the first area is a non-circular shape, as long as the outer and inner peripheral ends of the first area follow a line that can form an ellipse, the ellipse along the outer and inner peripheral ends of the first area cannot be specified. The overall shape is also acceptable.

The "concentration of fuel in the first zone" in the present invention may also be the surface density of the fuel in the first zone. Degree is the mass of fuel per unit area in the first zone. Alternatively, the "concentration of fuel in the first area" may be calculated by selecting a value on the first plane from the distribution of the mass of fuel per unit volume in a certain space including the first area. That is, the "concentration of fuel in the first zone" may also be the mass of fuel per unit volume in the first zone.

The definition of "fuel concentration in the second area" in the present invention is also the same as the definition of the above-mentioned "fuel concentration in the first area".

In the present invention, the "concentration of fuel in the first zone" and "the concentration of fuel in the second zone" may be the concentration of fuel including vaporized fuel, or may be the concentration of fuel not including vaporized fuel. In the present invention, the "first plane" is preferably set at a position close to the injector for a single intake port where most of the injected fuel can reach without vaporization. In this case, whether the "fuel concentration in the first zone" and the "fuel concentration in the second zone" include the vaporized fuel will generally not affect the "fuel concentration in the first zone" and the "fuel concentration in the inner peripheral zone". The size of the "density" has an impact.

In the present invention, "the concentration of fuel in the first region is higher than the concentration of fuel in the second region" means that the average value of the mass of fuel per unit volume or unit area in the first region is greater than that in the second region The average value of the volume or the mass of fuel per unit area.

The injector for a single intake port of the present invention is controlled by a control device by injecting fuel when the single intake valve is at the position of opening the single intake port during the intake stroke. The intake stroke time here refers to the intake stroke time of the combustion chamber connected to the single intake passage portion provided with the single intake port injector.

"When viewed in the direction of the central axis of the cylinder bore, it is possible to observe a plane passing through the center of the two injection directions at the largest angle among the injection directions of the fuel injected from a single intake port." "When viewed along the direction of the central axis of the cylinder hole" means when viewed along the direction of the central axis of the cylinder hole connected to the combustion chamber of the single intake passage part provided with the injector for the single intake port. Similarly, the description of "the ejector for a single intake port is arranged and constructed in such a way that the injection center line passes through the rod of the single intake valve at the position where the single intake port is opened when viewed in the direction of the central axis of the cylinder bore" The term "when viewed in the direction of the central axis of the cylinder hole" means when viewed in the direction of the central axis of the cylinder hole connected to the combustion chamber of the single intake passage portion provided with the injector for the single intake port.

In the present invention, "when viewed in the direction of the central axis of the cylinder hole" means the engine unit is viewed in the direction of the central axis of the cylinder hole. In more detail, it means that it is assumed to be viewed through a part of the engine unit.

The definition of "when viewed in a direction orthogonal to the second plane" in the present invention is also the same as described above.

In the present invention, "the injection center line passes through a single intake port" means that the injection center line passes through a single intake port connected to a single intake passage portion provided with an injector for a single intake port having the injection center line.

In the present invention, "the injection center line passes through the stem of a single intake valve" means that the injection center line passes through a single intake passage provided with an injector for a single intake port having the injection center line. A single intake valve that opens and closes a single intake port connected to the part.

In the present invention, "the center line of injection passes through the stem of a single intake valve at a position where a single intake port is opened" means that a single intake valve is located at any single intake port within the movable range of opening a single intake valve. In one position, the jet centerline passes through the rod. When a single intake valve is located at any position of a single intake port within the movable range of opening a single intake valve, when the injection center line passes through the rod, a single intake port within the movable range of opening a single intake valve In other positions, the jet centerline may not pass through the rod.

In the present invention and this specification, at least one (one) of the plurality of options includes all combinations that can be considered from the plurality of options. At least one (one) of the plurality of options may be any one of the plurality of options, or may be all the options of the plurality of options. For example, at least one of A, B, and C can be only A, or only B, or only C, or A and B, or A and C, or B and C, or Can be A, B and C.

In the scope of the patent application, the number of a certain constituent element is not clearly specified. When it is expressed in a singular when translated into English, the present invention may also have a plurality of such constituent elements. In addition, the present invention may have only one such constituent element.

In the present invention, the derivative words including (including), having (comprising), having (having) and the like are intended to include additional items in addition to the listed items and their equivalents.

In the present invention, the terms mounted, connected, coupled, and supported are used in a broad sense. Specifically, it not only includes direct installation, connection Connection, connection, support, but also indirect installation, connection, connection and support. Furthermore, connected and coupled are not limited to physical or mechanical connection/coupling. They also include direct or indirect electrical connection/combination.

As long as there are no other definitions, all terms used in this specification (including technical terms and scientific terms) have the same meaning as generally understood by the industry to which the present invention belongs. Terms such as those defined in commonly used dictionaries should be interpreted as having meaning consistent with the meaning in the context of the related technology and the present invention, and need not be interpreted in an idealized or excessively formalized meaning.

In this manual, the term "better" is non-exclusive. "Better" means "better, but not limited to this." In this specification, the configuration described as "preferable" achieves at least the above-mentioned effects obtained by the configuration of claim 1. In addition, in this manual, the term "may" is non-exclusive. "Also" means "Also, but not limited to this." In this specification, the configuration described as "may" achieves at least the above-mentioned effects obtained by the configuration of claim 1.

In the present invention, it is not limited to combine the constitutions of the above-mentioned other viewpoints with each other. Before describing the embodiments of the present invention in detail, it should be understood that the present invention is not limited by the detailed content of the configuration and arrangement of the constituent elements described in the following description or illustrated in the drawings. The present invention may also be an embodiment other than the following embodiment. The present invention may also be an embodiment in which various changes are made to the following embodiments. In addition, the present invention can be implemented by appropriately combining the following embodiments and modified examples.

According to the engine unit of the present invention, the design freedom of the concentration distribution of the fuel in the combustion chamber can be improved.

1: Engine unit

1A: Engine unit

3: External intake passage

4: Cylinder section

5: Cylinder block

6: Cylinder head

7: Head cover

8: Piston

10: Cylinder hole

11: Combustion chamber

12: Single air inlet

13: Exhaust port

14: Spark plug insertion port

20: Single intake passage

21: Cylinder intake passage

22: Single intake valve

22a: Umbrella

22b: pole

23: Injector for single intake port

24: Throttle valve

31: Cylinder exhaust passage

32: exhaust valve

50: control device

91: Engine unit

123: Injector for single intake port

823: ejector

910: Cylinder hole

911: Combustion Chamber

912: air inlet

913: Exhaust Port

914: Spark plug insertion port

919: Upstream intake passage

920: intake passage

922: intake valve

923: ejector

A1: Zone 1

A2: Area 2

A11: Zone 1

A12: Zone 2

A21: Zone 1

A22: Zone 2

A31: Zone 1

A32: Zone 2

A41: Zone 1

A42: Zone 2

A51: Zone 1

A52: Zone 2

A61: Zone 1

A62: Zone 2

A71: Zone 1

A72: Zone 2

A81: Zone 1

A82: Zone 2

A91: Zone 1

A92: Zone 2

Ac: The center of the circumference of the outer circumference of the first area

CA2: arc

CA3: arc

CA4: arc

CA6: arc

CA7: arc

CA8: arc

CA9: arc

Ci1: Jet center line

Ci21: Jet centerline

Ci31: Jet centerline

Ci41: Jet centerline

Ci51: Jet centerline

Ci61: Jet centerline

Ci71: Jet centerline

Ci81: Jet centerline

Ci91: Jet centerline

Ci80: Jet centerline

Cv1: The central axis of the rod

Cy1: The central axis of the cylinder bore

Cy9: cylinder axis

D1: distance

Dx: Arrow

Dy: Arrow

F1: Fuel

F9: Fuel

P1: The center of the air inlet

P2: Center of exhaust port

PD: Arrow

S1: first plane

S2: 2nd plane

S3: 3rd plane

S4: The plane of the entire circumference of the air inlet

S21: first plane

S31: first plane

S41: first plane

S51: first plane

S61: first plane

S71: first plane

S81: first plane

S91: first plane

S801: plane

Figure 1(a) of Figure 1 is a view of the engine unit of the embodiment viewed along the direction of the central axis of the cylinder bore. Fig. 1(b) is a cross-sectional view of the engine unit of the embodiment cut using the plane S1 shown in Fig. 1(a). Fig. 1(c) is a diagram showing the fuel injection state of the injector for a single intake port of the engine unit of the embodiment. Fig. 1(d) is a diagram showing an example of fuel on the plane S1 shown in Fig. 1(c). Fig. 1(e) is a diagram showing another example of fuel on the plane S1 shown in Fig. 1(c).

Fig. 2 is a cross-sectional view of an engine unit of a specific example of the embodiment.

Figure 3(a) of Figure 3 is a view of the combustion chamber of the engine unit of the embodiment viewed along the direction of the central axis of the cylinder bore, and Figure 3(b) is a cross-sectional view taken along the line III-III of Figure 3(a).

Fig. 4(a) of Fig. 4 is a diagram showing the fuel injection state of the injector for a single intake port of the engine unit of a specific example of the embodiment, and Fig. 4(b) shows the plane shown in Fig. 4(a) The graph of the concentration distribution of fuel on S1.

Fig. 5(a) of Fig. 5 is a diagram showing the fuel injection state of the previous injector for a single intake port, and Fig. 5(b) is a diagram showing the fuel concentration distribution on the plane S801 shown in Fig. 5(a)之图.

Fig. 6 is a graph showing the concentration distribution of fuel on the plane S1 shown in Fig. 4(a) and the concentration distribution of fuel on the plane S801 shown in Fig. 5(a).

Figures 7(a)~7(c) are cross-sectional views showing the behavior of multiple droplets of injected fuel in the engine unit of a specific example of the embodiment, and Figures 7(d)~7(f) are Observe the diagrams in Figure 7 (a) ~ Figure 7 (c) along the direction of the central axis of the cylinder hole.

Figures 8(a) to 8(c) of Figure 8 show the case of using the previous single inlet injector Figure 8(d)~Figure 8(f) is a diagram of the behavior of a plurality of droplets of injected fuel in the engine unit. Figure 8(a)~Figure 8(c) picture.

Figure 9(a) of Figure 9 is a view of the combustion chamber of the previous engine unit viewed along the direction of the central axis of the cylinder bore, Figure 9(b) is a cross-sectional view taken along line BB of Figure 9(a), and Figure 9(c) is Fig. 9(a) is a cross-sectional view taken along line CC.

Fig. 10 is a diagram showing the fuel injection state of the injector for a single intake port in a modified example.

Fig. 11 is a cross-sectional view of an engine unit equipped with a modified single inlet injector.

Figs. 12(a) to (c) are diagrams showing the first area and the second area on the first plane of the single-intake injector of a modified example.

Figs. 13(a) to (e) are diagrams showing the first area and the second area on the first plane of the single-intake injector of the modified example.

≪Implementation mode of the present invention≫

Hereinafter, an embodiment of the present invention will be described with reference to FIGS. 1(a) to 1(e). The engine unit 1 of this embodiment is a four-stroke cycle engine unit. As shown in Figure 1 (a) and Figure 1 (b), the engine unit 1 includes a cylinder portion 4, at least one external intake passage portion 3, at least one intake valve 22, at least one injector 23, and control装置50。 Device 50. The cylinder section 4 has at least one combustion chamber 11, at least one intake port 12, and at least one cylinder intake passage section 21. Part of each of at least one combustion chamber 11 is formed by the inner surface of the cylinder bore 10. At least one intake port 12 is formed in at least one combustion chamber 11. At least one cylinder intake passage portion 21 is connected to at least one intake port 12. The air that has flowed into at least one cylinder intake passage portion 21 is supplied from at least one intake port 12 to at least one combustion chamber 11. At least one external intake passage part 3 is arranged outside the cylinder part 4 and connected It is connected to at least one cylinder intake passage 21. The air flowing into the inside of at least one external intake passage portion 3 is supplied to at least one cylinder intake passage portion 21. At least one intake valve 22 is configured to be movable between a position where at least one intake port 12 is opened and a position where at least one intake port is closed. Each of at least one injector 23 has a plurality of injection holes capable of injecting fuel in a mist form. At least one injector 23 is provided in the cylinder intake passage portion 21 or the outer intake passage portion 3 such that a plurality of injection holes are located in the cylinder intake passage portion 21 or the outer intake passage portion 3. The control device 50 controls the injection of fuel by at least one injector 23.

One intake port 12, intake valve 22, and injector 23 are provided for each combustion chamber 11, and constitute a single intake port 12, a single intake valve 22, and a single intake port injector 23, respectively. At least one cylinder intake passage portion 21 and at least one external intake passage portion 3 include at least one single intake passage portion 20. The single intake passage portion 20 is provided for each combustion chamber 11. The single intake passage portion 20 is a region from a location where the injector 23 for a single intake port is provided to the single intake port 12. The single intake passage portion 20 is configured so that the air flows through the inside without separating or merging.

The single intake port injector 23 is arranged to inject fuel toward the single intake port 12. The single-port injector 23 is configured as follows: when the single-port injector 23 is not installed in the engine unit 1 and injects fuel into a space where only the atmosphere is located, at a certain point immediately after the injection At the moment, the following two necessary conditions are met. As shown in FIG. 1(c), a plane that intersects the injection directions of a plurality of fuel droplets injected from a single intake port injector 23 is referred to as a first plane S1. As shown in Figure 1(d) or Figure 1(e), the first necessary condition is that the fuel on the first plane S1 is in a circle or an ellipse so as to follow the circle or the ellipse At least one of Part of the way exists. The second requirement is the concentration of fuel in the first area A1 included in the fuel-existing area on the first plane S1 and whose outer and inner peripheral ends are along at least part of the edge of the circle or the ellipse It is higher than the fuel concentration in the second area A2 that is in contact with the entire inner peripheral end of the first area A1 on the first plane S1. That is, the concentration of the mist-like fuel F1 injected from the single intake port by the injector 23 is higher in the outer peripheral part than in the central part. The fuel supplied to one combustion chamber 11 is only the fuel injected from one single intake port injector 23 and passing through one single intake port 12.

Suppose that when the engine unit has a plurality of intake ports for one combustion chamber, a plurality of intake passage portions respectively connected to the plurality of intake ports are provided. The engine unit 1 of this embodiment has only one intake port 12 for one combustion chamber 11. Therefore, the diameters of the single intake port 12 and the cylinder hole of the present embodiment are the same as those of the present embodiment and have a larger diameter than the intake port of an engine unit having a plurality of intake ports for one combustion chamber. Therefore, the diameters of the single intake passage portion 20 and the cylinder bore of the present embodiment are the same as those of the present embodiment, and the diameter of the intake passage portion of an engine unit having a plurality of intake ports for one combustion chamber is larger. With the larger diameter of the single intake passage portion 20, the injection angle of the fuel injected from the single intake port injector 23 can be increased. The injection angle refers to the largest angle among the injection directions of a plurality of fuel droplets injected by an injector from a single intake port when viewed in a certain direction. Since the injection angle of the fuel injected by the injector 23 from a single intake port is relatively large, it is possible to reduce the diameter of the injected droplets while suppressing the contact of the plurality of injected droplets. Due to the small diameter of the injected droplets, the droplets of the fuel flowing into the combustion chamber 11 easily spread along the flow of air. Thereby, the unevenness of the concentration distribution of the fuel in the combustion chamber 11 is suppressed. That is, the engine unit 1 of the present embodiment suppresses the unevenness of the fuel concentration distribution in the combustion chamber 11 compared with the engine unit 1 having a plurality of intake ports 12 for one combustion chamber 11.

Assuming that the engine unit has two intake ports and one injector for one combustion chamber, two intake passages connected to a plurality of intake ports are connected to each other. In addition, the ejector is arranged on the upstream side of the air flow direction than the part where the two intake passages are connected. The injector injects fuel toward two intake ports. On the other hand, the engine unit 1 of this embodiment has one intake port 12 and one injector 23 for one combustion chamber 11. Therefore, the injector 23 for a single intake port of the present embodiment can be arranged closer to the intake port compared to an injector of an engine unit having two intake ports and one injector for one combustion chamber. By arranging the injector 23 for a single intake port at a position close to the intake port 12, the injection angle of the fuel injected from the injector 23 for a single intake port can be further increased. As described above, the injection angle of the fuel injected by the injector 23 from a single intake port is relatively large, and it is possible to reduce the diameter of the injected droplets while suppressing the contact of the plurality of injected droplets. Due to the small diameter of the injected droplets, the droplets of the fuel flowing into the combustion chamber 11 easily spread along the flow of air. Therefore, the engine unit 1 of the present embodiment further suppresses the unevenness of the fuel concentration distribution in the combustion chamber 11 compared to an engine unit having a plurality of intake ports and one injector for one combustion chamber.

Suppose that when the engine unit has a plurality of intake ports for one combustion chamber, the air flowing into the combustion chamber from the plurality of intake ports collide with each other. On the other hand, the engine unit 1 of this embodiment has only one intake port 12 for one combustion chamber 11, so there is no such collision of air. In addition, compared with an engine unit having a plurality of intake ports for one combustion chamber, the intake ports can be arranged closer to the center axis of the cylinder bore. Therefore, the air flowing into the combustion chamber 11 from the intake port 12 is easily diffused uniformly in the circumferential direction of the inner surface of the cylinder bore 10. Therefore, the engine unit 1 of the present embodiment further suppresses the unevenness of the fuel concentration distribution in the combustion chamber 11 compared to an engine unit having a plurality of intake ports for one combustion chamber.

By suppressing the unevenness of the fuel concentration distribution in the combustion chamber 11, assuming that the injection direction is adjusted, the concentration at a desired position in the combustion chamber 11 can be increased. That is, it is easy to adjust the concentration distribution of the fuel in the combustion chamber 11. Therefore, the engine unit 1 of this embodiment can increase the degree of freedom in designing the concentration distribution of fuel in the combustion chamber 11.

≪Specific examples of the embodiment of the present invention≫

Next, referring to FIGS. 2 to 9, the engine unit 1A as a specific example of the embodiment of the present invention will be described. Basically, the engine unit 1A of the specific example of the embodiment of the present invention has all the features of the engine unit 1 of the above-mentioned embodiment of the present invention. A description of the same parts as those of the engine unit 1 of the above-mentioned embodiment of the present invention will be omitted.

The engine unit 1A is mounted on, for example, a straddle-type vehicle. Straddle-type vehicles refer to all vehicles that ride in a state with the rider straddling on the saddle. Straddle-type vehicles include locomotives, three-wheeled locomotives, four-wheeled off-road vehicles (ATV: All Terrain Vehicle), water locomotives, and snowmobiles. Locomotives include scooter, locomotives with prime movers, and light locomotives with pedals. The engine unit 1A can also be installed in a car. The engine unit 1A can also be mounted on vehicles or devices other than automobiles and straddle-type vehicles.

As shown in FIG. 2, the engine unit 1A includes an engine body 2, one external intake passage portion 3, one external exhaust passage portion (not shown), and a control device 50. The external intake passage portion 3 and the external exhaust passage portion are connected to the engine body 2. The control device 50 controls the operation of the engine unit 1A. The control device 50 is connected to various sensors installed in the straddle-type vehicle.

The specific example of the engine body 2 is a single-cylinder engine. The engine body 2 is a four-stroke engine. A four-stroke engine refers to an engine that repeatedly performs intake stroke, compression stroke, combustion stroke (expansion stroke), and exhaust stroke. The engine body 2 is a gasoline engine. The cooling method of the engine body 2 is not particularly limited.

The engine body 2 includes a cylinder portion 4 having one cylinder hole 10 and a crankcase portion (not shown). Although illustration is omitted, a crankshaft is housed in the crankcase part. The central axis of the crankshaft is in the direction orthogonal to the paper in FIG. 2. The cylinder part 4 and the crankcase part are arranged on the central axis Cy1 of the cylinder bore 10. Hereinafter, the central axis Cy1 of the cylinder hole 10 is referred to as a cylinder axis Cy1.

The cylinder axis Cy1 is not only a line segment existing in the area where the cylinder hole 10 exists, but an infinitely extending straight line. The cylinder axis Cy1 is parallel to the upper and lower directions of the paper in FIG. 2. The upper and lower directions of the paper surface may be the same as the upper and lower directions of the straddle-type vehicle equipped with the engine unit 1A, or may not be inconsistent. In a straddle-type vehicle, the cylinder portion 4 constitutes the upper or front portion of the engine body 2. The cylinder axis Cy1 may be parallel to the up-down direction of the straddle-type vehicle, or may be inclined at an angle of 45° or less with respect to the up-down direction of the straddle-type vehicle. The cylinder axis Cy1 may be parallel to the front and rear direction of the straddle-type vehicle, or may be inclined at an angle less than 45° with respect to the front and rear direction of the straddle-type vehicle.

The cylinder section 4 has a cylinder block 5, a cylinder head 6, and a head cover 7. The cylinder block 5, the cylinder head 6, and the head cover 7 are sequentially connected side by side on the cylinder axis Cy1. The cylinder block 5 is connected to the crankcase part. In Figure 2, the cylinder block 5, the cylinder head 6 and the head cover 7 are independent components. However, at least two of the cylinder block 5, the cylinder head 6 and the head cover 7 may be integrally formed.

The cylinder hole 10 is formed inside the cylinder block 5. A piston 8 is slidably housed in the cylinder hole 10. The piston 8 is connected to the crankshaft via a connecting rod (not shown).

The cylinder section 4 has one combustion chamber 11. The combustion chamber 11 includes the lower surface of the cylinder head 6 in FIG. 2, the inner surface of the cylinder bore 10, and the upper surface of the piston 8 in FIG. 2. That is, a part of the combustion chamber 11 is formed by the inner surface of the cylinder hole 10.

As shown in FIG. 3( a ), one intake port 12 and one exhaust port 13 are formed in the combustion chamber 11. The air inlet 12 is an example of a single air inlet of the present invention. The intake port 12 and the exhaust port 13 are formed on the lower surface of the cylinder head 6 in FIG. 2. The intake port 12 and the exhaust port 13 have a circular shape. The diameter of the air inlet 12 is greater than the diameter of the air outlet 13. When viewed in the direction of the cylinder axis Cy1, the line segment connecting the center P1 of the intake port 12 and the center P2 of the exhaust port 13 passes through the cylinder axis Cy1 or its vicinity.

As shown in FIG. 3(a), one spark plug insertion port 14 is formed in the combustion chamber 11. The spark plug insertion port 14 has a circular shape. The diameter of the spark plug insertion port 14 is smaller than the diameters of the air inlet 12 and the air outlet 13. The spark plug insertion port 14 is arranged between the exhaust port 13 and the intake port 12 in the circumferential direction centered on the cylinder axis Cy1.

The engine unit 1A has a spark plug (not shown) inserted into the spark plug insertion port 14. The front end of the spark plug is arranged in the combustion chamber 11. Spark discharge occurs at the front end of the spark plug. With this spark discharge, the air-fuel mixture in the combustion chamber 11 is ignited. Furthermore, in this specification, mixed gas refers to a mixed gas of air and fuel. The spark plug is connected to the ignition coil (not shown). Ignition coil is stored for Electricity that generates spark discharge for spark plugs. When the air-fuel mixture is combusted in the combustion chamber 11, the piston 8 moves and the crankshaft (not shown) rotates.

As shown in FIG. 2, one cylinder intake passage 21 is formed in the cylinder head 6. The cylinder intake passage portion 21 is connected to the intake port 12 of the combustion chamber 11. The cylinder intake passage portion 21 is connected to the external intake passage portion 3. The external air intake passage part 3 may also include a plurality of independent parts. The air that has flowed into the external intake passage portion 3 is supplied to the combustion chamber 11 through the cylinder intake passage portion 21. The external air intake passage 3 may be connected to an air cleaner, or may include an air cleaner.

As shown in FIG. 2, a cylinder exhaust passage portion 31 is formed in the cylinder head 6. The cylinder exhaust passage portion 31 is connected to the exhaust port 13 of the combustion chamber 11. The gas (exhaust gas) generated by the combustion of the air-fuel mixture in the combustion chamber 11 is discharged to the cylinder exhaust passage portion 31. The cylinder exhaust passage portion 31 is connected to an external exhaust passage portion (not shown).

As shown in FIG. 2, the engine unit 1A has an intake valve 22 that opens and closes the intake port 12. The specific example of the intake valve 22 is an example of the single intake valve of the present invention. The intake valve 22 has an umbrella portion 22a and a rod portion 22b. As shown in FIG. 2, FIG. 3(a), and FIG. 3(b), the umbrella part 22a is formed in a substantially conical shape. The diameter (maximum diameter) of the umbrella portion 22a is approximately the same as the diameter of the air inlet 12. The umbrella portion 22a is configured to block the air inlet 12. When the intake valve 22 blocks the intake port 12, at least a part of the umbrella portion 22a is arranged in the cylinder intake passage portion 21. As shown in FIG. 2, the end surface of the umbrella portion 22 a facing the combustion chamber 11 is parallel to the plane S4 including the entire circumference of the intake port 12. The plane S4 is not a physically existing plane, but an imaginary plane.

The rod portion 22b is connected to the umbrella portion 22a. Specifically, the rod portion 22b is connected to the central portion of the umbrella portion 22a. The rod portion 22b is connected to the surface of the umbrella portion 22a facing the cylinder intake passage portion 21. A part of the rod portion 22b is arranged in the cylinder intake passage portion 21. The rod 22b extends linearly. Let the axis passing through the center of the rod portion 22b be the center axis Cv1. The central axis Cv1 of the rod portion 22b is orthogonal to the plane S4 including the entire circumference of the air inlet 12. The central axis Cv1 of the rod portion 22b is not only a line segment existing in the area where the rod portion 22b exists, but is a straight line extending indefinitely. The center axis Cv1 of the rod portion 22b passes through the center P1 of the air inlet 12. As shown in FIG. 3(a), when viewed in the direction of the cylinder axis Cy1, the central axis Cv1 of the rod portion 22b passes through the cylinder axis Cy1.

The intake valve 22 opens and closes the intake port 12 by moving back and forth along the central axis Cv1 of the rod portion 22b. The intake valve 22 indicated by a two-dot chain line in FIG. 2 is located in a closed position that closes (blocks) the intake port 12. The intake valve 22 indicated by a solid line in FIGS. 2, 3(a), and 3(b) is in an open position that opens (opens) the intake port 12. The open position of the intake valve 22 is a position where at least a part of the umbrella portion 22 a is arranged in the combustion chamber 11 and a gap is created between the umbrella portion 22 a and the intake port 12. The open position of the intake valve 22 is not limited to the position indicated by the solid line. The open position of the intake valve 22 includes all positions in the movable range of the intake valve 22 except for the closed position. The intake valve 22 is driven by a valve mechanism (not shown) and a spring (not shown) housed in the cylinder portion 4. The moving valve mechanism moves with the rotation of the crankshaft. The intake valve 22 is moved from a closed position to an open position by a valve moving mechanism, and is moved from an open position to a closed position by a spring.

The intake valve 22 is in the open position throughout at least a part of the intake stroke. The intake stroke refers to the period during which the piston 8 descends from the exhaust top dead center to the intake bottom dead center and the volume of the combustion chamber 11 increases. The point when the position of the intake valve 22 changes from the closed position to the open position can be slightly earlier than the intake stroke The beginning may be the same as the beginning of the intake stroke, or it may be slightly later than the beginning of the intake stroke. The time point when the intake valve 22 moves from the open position to the closed position may be slightly later than the end of the intake stroke, may be the same as the end of the intake stroke, or may be slightly earlier than the end of the intake stroke. The intake valve 22 may be in the open position throughout the entire period of the intake stroke, or may be in the open position throughout a part of the intake stroke.

As shown in FIG. 2, the engine unit 1A has one exhaust valve 32 that opens and closes the exhaust port 13. The exhaust valve 32 also includes an umbrella portion and a rod portion similarly to the intake valve 22. The basic shape and structure of the exhaust valve 32 are the same as those of the intake valve 22. The diameter of the umbrella portion of the exhaust valve 32 is smaller than the diameter of the umbrella portion 22a of the intake valve 22. The exhaust valve 32 is in an open position throughout at least a part of the exhaust stroke. The exhaust valve 32 is also driven by a valve mechanism (not shown) similarly to the intake valve 22. The valve mechanism may also include a variable valve timing device that changes the opening and closing timing of at least one of the intake valve 22 and the exhaust valve 32.

As shown in FIG. 2, the engine unit 1A has one throttle valve 24. The throttle valve 24 is arranged in the external intake passage portion 3. By changing the opening degree of the throttle valve 24, the amount of air supplied into the combustion chamber 11 is changed. The throttle valve 24 shown in FIG. 2 is in the closed position. When the throttle valve 24 is in the closed position, a little air is allowed to flow. It is also possible to connect a bypass passage portion bypassing the throttle valve 24 to the external intake passage portion 3. It is also possible to arrange a valve in the bypass passage. The throttle valve 24 may be connected to an unillustrated throttle valve operating part without passing through the control device 50. In this case, the opening degree of the throttle valve 24 is changed by the rider operating the throttle valve operating part. The throttle valve 24 is a valve whose opening degree can be controlled electronically, and can also be controlled by a control device 50. In this case, the control device 50 controls the throttle valve 24 based on the signal of the sensor that detects the operating state of the throttle valve operating part.

Figs. 2, 3(a) and 3(b) schematically show the flow of air in the combustion chamber 11 during the intake stroke and the intake valve 22 is in the open position. Furthermore, Fig. 3(b) is a cross-sectional view taken along the line III-III of Fig. 3(a), but the arrow in Fig. 3(b) also indicates the flow of air that appears before the cross-section. During the intake stroke, the piston 8 descends, whereby the air pressure of the combustion chamber 11 is reduced. The air in the external intake passage portion 3 and the cylinder intake passage portion 21 is introduced into the combustion chamber 11 by the negative pressure (pressure lower than the atmospheric pressure) of the combustion chamber 11. The air flows into the combustion chamber 11 through the annular gap between the umbrella portion 22a of the intake valve 22 and the intake port 12. The air flowing into the combustion chamber 11 first flows along the inner surface of the combustion chamber 11. The air diffused along the inner surface of the combustion chamber 11 is substantially uniformly diffused along the circumferential direction of the inner surface of the cylinder hole 10.

As shown in FIGS. 2 and 3(a), the engine unit 1A has one injector 23. The injector 23 is an example of the injector for a single intake port of the present invention. The injector 23 is provided in the external intake passage portion 3. The ejector 23 is arranged downstream of the throttle valve 24 in the air flow direction. Furthermore, the injector 23 may also be provided in the cylinder intake passage portion 21. The portion of the external intake passage portion 3 and the cylinder intake passage portion 21 that is downstream in the flow direction of the air from the position where the injector 23 is installed constitutes a single intake passage portion 20. The single air intake passage portion 20 is configured to pass through the inside of the air without separating or merging.

The injector 23 is arranged and configured to inject fuel toward the intake port 12. A plurality of injection holes are formed at the front end of the injector 23. The injector 23 injects fuel F1 in mist form from a plurality of injection holes. A plurality of injection holes are located in the cylinder intake passage portion 21. Furthermore, a plurality of injection holes may also be located in the outer intake passage portion 3 or the boundary between the cylinder intake passage portion 21 and the outer intake passage portion 3. The injector 23 is arranged to inject fuel into the single intake passage portion 20.

The injector 23 injects fuel during the intake stroke and when the intake valve 22 is in the open position. The fuel injection of the injector 23 is controlled by the control device 50. The engine unit 1A has a fuel tank (not shown) for storing fuel supplied to the injector 23, and a fuel pump arranged in the fuel tank. The fuel pump is connected to the injector 23 via a fuel hose (not shown). Driven by the fuel pump, the fuel in the fuel tank is supplied to the injector 23. The driving of the fuel pump is controlled by the control device 50.

The injector 23 simultaneously injects fuel from a plurality of injection holes. The diameter of the fuel droplets injected from the injector 23 is, for example, 50-60 μm. The diameter of the fuel droplets injected from the injector 23 is smaller than the diameter of the fuel droplets injected from a normal injector. The diameter of the fuel droplets injected from a general injector is, for example, 80-90 μm. Due to the small diameter of the fuel droplets, the fuel droplets are easy to evaporate. Therefore, there is no need to inject fuel before the intake stroke in order to ensure the time until evaporation. The diameter of the droplet is affected by the diameter of the injection hole, the pressure of the fuel supplied to the injector 23, and the viscosity of the fuel. The smaller the diameter of the jet hole, the smaller the diameter of the droplet. The diameters of the plurality of injection holes of the injector 23 may all be the same or different. The number and shape of the plurality of injection holes are not particularly limited. The surface on which a plurality of injection holes are formed may be, for example, a flat surface or a convex curved surface. The arrangement of a plurality of injection holes is also not particularly limited. For example, a plurality of injection holes may be arranged on one circle or on two or more concentric circles. The injector 23 is not one that injects fuel using a swirling flow (swirl flow).

In addition, the engine unit 1A does not have a fuel injection device other than one injector 23 for one combustion chamber 11. The fuel injection device herein includes not only those that inject fuel into the cylinder intake passage portion 21 or the outer intake passage portion 3, but also those that inject fuel into the combustion chamber 11. Fuel injection The injection device includes not only those having a plurality of injection holes, but also those having only one injection hole.

The injector 23 injects the fuel F1 in the form of a mist in a substantially conical shape. As shown in Figure 3(a), when viewed in the direction along the cylinder axis Cy1, the center of the two injection directions at the largest angle among the injection directions of the plurality of fuel droplets injected from the injector 23 can be observed The plane of the straight line is set to plane S2. In other words, the plane S2 is a straight line that halves the injection angle of the injector 23 when viewed along the direction of the cylinder axis Cy1. The plane S2 corresponds to the second plane of the present invention. As shown in FIG. 2, when viewed in a direction orthogonal to the plane S2, it can be observed that the center of the two injection directions that form the largest angle among the injection directions of the plurality of fuel droplets injected from the injector 23 can be observed. The plane of the straight line is set to plane S3. In other words, when the plane S3 is viewed in a direction orthogonal to the plane S2, it can be observed as a straight line that halves the injection angle of the injector 23. The plane S3 corresponds to the third plane of the present invention. The intersection of the plane S2 and the plane S3 is referred to as the ejection center line Ci1. The jet centerline Ci1 is an infinite straight line.

As shown in FIG. 2, the injection center line Ci1 of the injector 23 passes through the intake port 12. As shown in FIG. 3(a), when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 coincides with the center axis Cv1 of the rod portion 22b. When viewed in the direction of the cylinder axis Cy1, the injection centerline Ci1 passes through the cylinder axis Cy1. For example, as shown in FIG. 3(a), when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. As described above, the intake valve 22 moves along the central axis Cv1 of the rod portion 22b. Therefore, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 passes through the rod portion 22b and the umbrella portion 22a of the intake valve 22 in the closed position. Also, for example, as shown in FIG. 2, when viewed in a direction orthogonal to the plane S2, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. Along and plane S2 positive When viewed in the alternate direction, the injection centerline Ci1 passes through the umbrella portion 22a of the intake valve 22 in the closed position. When viewed in a direction orthogonal to the plane S2, the injection center line Ci1 does not pass through the stem 22b of the intake valve 22 in the closed position, but it can pass. According to the above, when viewed from any direction, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. That is, the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 in the open position. The injection center line Ci1 passes through the umbrella portion 22a of the intake valve 22 in the closed position. The injection center line Ci1 does not pass through the stem portion 22b of the intake valve 22 in the closed position, but can pass.

As shown in FIG. 2, the shortest distance between the plurality of injection holes and the center P1 of the intake port 12 is set as the distance D1. The distance D1 is less than 3 times the diameter of the air inlet 12 in length. The distance D1 is less than the length of 3 times the diameter of the intake valve 22. Therefore, the injector 23 is arranged relatively close to the intake port 12. The distance D1 can also be less than twice the length of the diameter of the air inlet 12. The distance D1 can also be less than twice the length of the diameter of the intake valve 22.

The graphs of the examples of the present invention shown in FIGS. 4(a), 4(b) and 6 are the results obtained by simulating the movement (flow) of the fuel injected from the injector 23. The simulation system uses Ricardo's VECTIS (registered trademark). The simulation assumes that the ejector 23 is not installed in the engine unit 1A and ejects into the atmosphere only. In other words, the spraying target is sprayed to the space where there is no object. The temperature of the space where only the atmosphere is injected with fuel is normal temperature. The pressure in the space where fuel is injected is atmospheric pressure only. The air-only space where fuel is injected is in a no-wind state. Furthermore, assuming that the volatility of fuel is lower than that of gasoline, the simulation is also carried out in consideration of the evaporation of fuel. FIG. 4(a) shows the distribution of fuel droplets observed in the Y direction that intersects the injection directions of a plurality of fuel droplets at a certain time point immediately after the fuel is injected from the injector 23. In more detail, the Y direction is orthogonal to the jet center line Ci1 direction. The gasified fuel is not shown in Figure 4(a). The vertical axis of FIG. 4(a) represents the distance from the injection center line Ci1 of the injection hole of the injector 23 in the direction. The horizontal axis of Fig. 4(a) represents the distance in the X direction orthogonal to the Y direction. In Figure 4(a), the shade of the color is used to indicate the size of the diameter of the fuel droplet. The darker the color, the larger the diameter.

As shown in FIG. 4(a), a plane orthogonal to the injection center line Ci1 is defined as a plane S1. Figure 4(b) shows the fuel concentration distribution on the plane S1. Fig. 4(b) shows the concentration distribution of fuel combined with gasified fuel and liquid fuel. Fig. 4(b) is to select the value on the plane S1 from the simulation result of the mass distribution of fuel per unit volume. The horizontal axis of Fig. 4(b) represents the distance in the X direction, and the vertical axis of Fig. 4(b) represents the distance in the Y direction. Figure 4(b) uses dark gray to indicate the area where the fuel concentration is zero, and light gray to indicate the area where the fuel concentration is higher than zero. Furthermore, in the simulation, the amount of vaporized fuel on the plane S1 is extremely small compared to the amount of liquid fuel. Therefore, although the illustration is omitted, the concentration distribution of the liquid fuel on the plane S1 is also approximately the same as in FIG. 4(b).

As shown in Fig. 4(b), the outline of the outer edge of the fuel-existing area on the plane S1 is approximately circular. That is, at a certain point immediately after the injection, the fuel on the plane S1 exists in a circle along the entire circumference of the edge of the circle. In this embodiment, the fuel-existing area on the plane S1 is annular. The fuel-existing area on the plane S1 includes the first area A11 having an outer circumference and an inner circumference along the entire circumference of the edge of the circle. The area where fuel exists on the plane S1 includes only the first area A11. The area on the plane S1 that is in contact with the entire inner peripheral end of the first area A11 is referred to as the second area A12. The injection center line Ci1 passes through the second area A12. There is no fuel in the second area A12. Therefore, the fuel concentration in the first area A11 is higher than the concentration in the second area A12. The injector 23 injects fuel in such a way that the concentration of the mist-like fuel F1 at the outer peripheral part is higher than the concentration at the central part.

Assuming that when the plane S1 is not orthogonal to the injection center line Ci1, the outline of the periphery of the fuel-existing area on the plane S1 is not a circle, but an ellipse. The plane S1 is a plurality of planes passing through a point on the injection centerline Ci1. The length of the fuel-existing area on the plane becomes the shortest in the X direction and the length of the fuel-existing area on the plane changes in the Y direction. The shortest plane. The plane S1 is the sum of the fuel-existing area on the plane and the direction parallel to the plane S2 among the plurality of planes passing through one point on the injection centerline Ci1. The plane where the length in the direction parallel to the plane S3 becomes the shortest. Therefore, the plane S1 is a plane that has the smallest unevenness in the distance from the plurality of injection holes of the injector 23 to the first area A11 among the plurality of planes passing through one point on the injection center line Ci1.

The concentration distribution of the fuel in the first area A11 is substantially constant in the circumferential direction of the first area A11. The graph of the example of the present invention in FIG. 6 shows the concentration distribution of fuel on a straight line passing through the injection center line Ci1 on the plane S1 of FIG. 4(a). The graph in Fig. 6 shows the concentration distribution of fuel combined with gasified fuel and liquid fuel. The horizontal axis of FIG. 6 represents the distance in the X direction, and the vertical axis of FIG. 6 represents the concentration of fuel. As shown in FIG. 6, in the middle of the inner peripheral end and the outer peripheral end of the first area A11, the fuel concentration in the first area A11 is the highest. Furthermore, although the illustration is omitted, the concentration distribution of the liquid fuel on the straight line passing through the injection center line Ci1 on the plane S1 is also substantially the same as in FIG. 6.

Assuming that the volatility of the fuel is the same as that of gasoline and the simulation is performed, the amount of fuel vaporized on the plane S1 is also very small compared to the amount of liquid fuel. Therefore, although the illustration is omitted, when the simulation is performed assuming that the volatility of the fuel is the same as that of gasoline, the concentration distribution of the fuel on the plane S1 is also approximately the same as that in Figs. 4(b) and 6. That is, assuming the volatility of the fuel When simulating the same situation as gasoline, the area where fuel exists on the plane S1 is also a substantially circular ring.

According to the simulation assuming that the fuel is injected from the injector 23 which is not installed in the engine unit 1A into the atmosphere only, the concentration of the fuel in the second area A12 is zero. However, when the fuel is actually injected from the injector 23 attached to the engine unit 1A, the fuel is present in the second area A12 for the following reasons. The injector 23 installed in the engine unit 1A injects fuel during the intake stroke and the intake valve 22 is in the open position. During the intake stroke and the intake valve 22 is in the open position, the air in the outer intake passage portion 3 and the cylinder intake passage portion 21 is sucked into the combustion chamber 11 by the negative pressure in the combustion chamber 11. By the flow of this air, the trajectory of the fuel droplets injected from the injector 23 is changed so as to approach the center of the single intake passage portion 20. Therefore, when fuel is injected from the injector 23 installed in the engine unit 1A, the concentration of the mist-like fuel F1 injected from the injector 23 at the center is greater than zero. Furthermore, when the fuel is injected from the injector 23 installed in the engine unit 1A, there may be an area where the concentration is zero in the center of the mist-like fuel F1. By changing the trajectory of the fuel droplets injected from the injector 23 to approach the center of the single intake passage portion 20, even if the injection angle is large, the adhesion of fuel to the inner surface of the single intake passage portion 20 is reduced.

Simulate a space where fuel is injected to atmospheric pressure and there is no wind. However, when fuel is injected from the injector 23 attached to the engine unit 1A during the intake stroke and the intake valve 22 is in the open position, the single intake passage portion 20 temporarily becomes a negative pressure. The negative pressure in the single intake passage portion 20 promotes the evaporation of the injected fuel. Therefore, at least a part of the fuel injected from the injector 23 may also evaporate before reaching the intake port 12.

The graphs of the previous examples of FIGS. 5(a), 5(b), and FIG. 6 show the simulation results of the case where the previous injector 823 is used. The simulation conditions other than the structure of the ejector are the same as the simulation of the ejector 23 described above. The amount of fuel injected from the previous injector 823 is the same as the simulation of the injector 23 described above. The diameter of the fuel droplet at the point of injection from the previous injector 823 is approximately the same as the simulation of the injector 23 described above. The vertical axis and horizontal axis of Fig. 5(a) and Fig. 5(b) are the same as Fig. 4(a) and Fig. 4(b). As shown in FIG. 5(a), the previous injector 823 injects fuel in a substantially conical shape similarly to the injector 23. When viewed in the Y direction, the injection angle of the previous injector 823 and the injection angle of the injector 23 are approximately the same. The center of the injection angle viewed in the Y direction of the previous injector 823 is set as the injection center line Ci80. The injection center line Ci80 is also the center of the injection angle viewed along the X direction of the injector 823. As shown in FIG. 5(a), a plane orthogonal to the injection center line Ci80 is defined as a plane S801. As shown in FIG. 5(b), the fuel-existing area on the plane S801 is not annular. The outline of the fuel-existing area on the plane S801 is approximately circular. As shown in the graph of the previous example in FIG. 6, the fuel concentration in the area where the fuel exists on the plane S801 is closer to the injection center line Ci80, the higher. In other words, the concentration in the outer peripheral part of the area where the fuel exists on the plane S801 is lower than the concentration in the center part of the area where the fuel exists on the plane S801. That is, the previous injector 823 injects the mist-like fuel in such a way that the concentration of the central part is higher than the concentration of the outer peripheral part. Furthermore, even if the vertical axis in FIG. 6 is changed to flow flux, the relative relationship between the two graphs in FIG. 6 is approximately the same. Flow flux refers to the flow rate per unit area.

Figures 7(a) to 7(f) schematically show the behavior of fuel droplets in the engine unit 1A. 8(a) to 8(f) schematically show the behavior of fuel droplets in the case of using the above-mentioned previous injector 823 instead of the injector 23. Figure 7(a)~Figure 7(f) and Figure 8(a)~Figure 8(f) use dots to indicate combustion Droplets of material. The size of the dot has nothing to do with the diameter of the droplet and is set to the same size. The vaporized fuel is not shown. Also, the droplets adhering to the single intake passage portion 20, the intake valve 22, and the combustion chamber 11 are not shown. Figs. 7(a) to 7(c) and Figs. 8(a) to 8(c) are views of the cross-section cut by the plane S2 when viewed in a direction orthogonal to the plane S2. Figure 7 (a) ~ Figure 7 (c) show different points in the intake stroke. Figure 8 (a) ~ Figure 8 (c) also show different points in the intake stroke. Figures 7(d)~7(f) are the diagrams of Figures 7(a)~7(c) viewed along the cylinder axis Cy1 respectively, and Figures 8(d)~8(f) are respectively along the cylinder axis Cy1 Observe the diagrams in Fig. 8(a) ~ Fig. 8(c) from the direction.

The injector 23 injects fuel in such a way that the concentration of the fuel in the outer periphery of the mist is higher than the concentration of the center. On the other hand, the previous injector 823 injects the mist-like fuel in a way that the concentration of the central part is higher than the concentration of the outer peripheral part. Therefore, from the comparison of Fig. 7(a) and Fig. 7(b) with Fig. 8(a) and Fig. 8(b), when the ejector 23 is used, compared with the previous ejector 823 , The amount of fuel adhered to the rod 22b on the plane S2 is less. Since the rod 22b exists only on and near the plane S2, when the injector 23 is used, the amount of fuel adhering to the entire rod 22b is smaller than when the previous injector 823 is used. In addition, the air in the single intake passage portion 20 is introduced into the combustion chamber 11 from the gap between the umbrella portion 22 a of the intake valve 22 and the intake port 12. The injector 23 injects fuel in such a way that the concentration of the fuel in the outer periphery of the mist is higher than the concentration of the center. In addition, the injector 23 injects fuel so that the injection center line Ci1 passes through the intake port 12. Therefore, most of the fuel injected from the injector 23 passes through the gap between the umbrella portion 22a of the intake valve 22 and the intake port 12. Therefore, compared with the case where the previous injector 823 is used, the amount of fuel adhered to the umbrella portion 22a is smaller.

The diameter of the fuel droplets injected from the injectors 23 and 823 is relatively small. Therefore, it flows into the combustion The fuel droplets in the chamber 11 move along the flow of air in the combustion chamber 11 shown in FIG. 2. A part of the fuel injected from the injectors 23 and 823 evaporates before reaching the combustion chamber 11. Of course, the vaporized fuel also moves in the combustion chamber 11 along the flow of air. The previous injector 823 injects the mist-like fuel in a way that the concentration of the central part is higher than the concentration of the outer peripheral part. Therefore, as shown in FIGS. 8(b), 8(c), 8(e) and 8(f), the droplets of the fuel injected from the previous injector 823 and flowing into the combustion chamber 11 are densely packed in In a narrow range, it moves along the flow of air. Although the illustration is omitted, the gasified fuel also moves along the flow of air in a state where it is densely packed in a relatively narrow range. On the other hand, as shown in FIGS. 7(b), 7(c), 7(e), and 7(f), the droplets of the fuel injected from the injector 23 and flowing into the combustion chamber 11 are dispersed in Move along the flow of air under a wide range of conditions. Although the illustration is omitted, the vaporized fuel is also dispersed in the combustion chamber 11 and moves along the flow of air in a state of being dispersed over a wide area. Therefore, the fuel (liquid and gaseous fuel) injected from the injector 23 rapidly diffuses in the combustion chamber 11 in a wider range than the fuel (liquid and gaseous fuel) injected from the previous injector 823.

The engine unit 91 shown in FIGS. 9(a), 9(b) and 9(c) is an example of the previous engine unit. As shown in FIG. 9A, the engine unit 91 has two intake valves 922 and one injector 923 for one combustion chamber 911. Two intake ports 912, two exhaust ports 913, and one spark plug insertion port 914 are formed in the combustion chamber 911. The two intake ports 912 are opened and closed by two intake valves 922. The two exhaust ports 913 are opened and closed by two exhaust valves (not shown). The spark plug insertion port 914 is arranged at a position surrounded by two intake ports 912 and two exhaust ports 913. Two intake passage portions 920 are respectively connected to the two intake ports 912. The two intake passage portions 920 are connected to one upstream intake passage portion 919. The injector 923 is arranged to inject fuel into the upstream intake passage portion 919. The injector 923 injects the fuel F9 in the form of mist toward the two intake ports 912. Injector 923 simultaneously injects towards two intake ports 912 Mist of fuel F9. The injector 923 can also inject mist-like fuel F9 toward the two intake ports 912 at different timings.

Two intake ports 912 are formed in the combustion chamber 911, so the required distance between the intake port 912 and the central axis Cy9 of the cylinder bore 910 is greater than the required distance between the intake port 12 and the central axis Cy1 of the cylinder bore 10 The distance is longer. In addition, a spark plug insertion port 914 is formed in a position of the combustion chamber 911 surrounded by two intake ports 912 and two exhaust ports 913. Therefore, the required distance between the intake port 912 and the cylinder axis Cy9 becomes longer.

Fig. 9(a), Fig. 9(b) and Fig. 9(c) schematically show the flow of air in the combustion chamber 911 during the intake stroke with arrows. Furthermore, Fig. 9(c) is a cross-sectional view taken along line C-C of Fig. 9(a), but the arrow in Fig. 9(c) also indicates the flow of air that appears before the cross-section. During the intake stroke, the air in the two intake passage portions 920 flows into the combustion chamber 911 from the two intake ports 912. When viewed in the direction of the cylinder axis Cy9, in the area between and near the two intake valves 922, the air flowing into the combustion chamber 911 from the two intake ports 912 collides with each other. In addition, the intake port 912 through which air flows is relatively far away from the cylinder axis Cy9. Furthermore, when viewed in the direction of the cylinder axis Cy9, the directions of the air flow passing through the vicinity of the intake ports 912 of the two intake passage portions 920 are substantially parallel, and are not in the direction of the cylinder axis Cy9. As a result, the air flowing in from the two intake ports 912 cannot be uniformly diffused along the circumferential direction of the inner surface of the cylinder bore 10, but is concentrated on a part of the circumferential direction of the inner surface of the cylinder bore 910 to generate air flow.

On the other hand, the engine unit 1A has only one intake port 12 for one combustion chamber 11, so the air flowing into the combustion chamber from the plurality of intake ports does not collide with each other. Also, for air to flow in The intake port 12 is close to the cylinder axis Cy1. Furthermore, when viewed in the direction of the cylinder axis Cy1, the direction of the air flow passing through the vicinity of the intake port 12 of the single intake passage portion 20 is toward the direction of the cylinder axis Cy1 as a whole. Therefore, the air flowing into the combustion chamber 11 from the intake port 12 is evenly diffused in the circumferential direction of the inner surface of the cylinder bore 10 compared to the previous engine unit 91. Thereby, compared with the previous engine unit 91, the unevenness of the concentration distribution of the fuel in the combustion chamber 11 is suppressed.

In the previous engine unit 91, the air flowing into the combustion chamber 911 from the two air intake ports 912 collided with each other. By the collision of the air, the fuel flowing along the air is atomized. It is believed that by atomizing the fuel in the combustion chamber, the unevenness of the combustion state is suppressed and the unburned fuel in the exhaust gas is reduced.

On the other hand, the engine unit 1A has only one intake port 12 for one combustion chamber 11. Therefore, no fuel atomization occurs due to the collision of air as described above. Here, it is assumed that the spray angle, the diameter of the droplet, and the concentration distribution of the mist-like fuel F9 injected from the injector 923 and the mist-like fuel F1 injected from the injector 23 are the same. In this case, it is considered that the engine unit 1A has greater unevenness in the combustion state compared to the engine unit 91, or there is more unburned fuel in the exhaust gas. However, compared with the engine unit 91, the air flowing into the combustion chamber of the engine unit 1A is more likely to diffuse uniformly in the circumferential direction of the inner surface of the cylinder hole. Therefore, even if the atomization of the fuel in the combustion chamber does not occur, the unevenness of the combustion state is suppressed, and the increase of unburned fuel in the exhaust gas is suppressed.

Let the volume of a space formed between the throttle valve 24 in the closed position and the intake valve 22 in the closed position be the downstream volume of the throttle valve. Since the engine unit 91 has a complex for one combustion chamber 911 There are several intake ports 912 and one injector 923, so as described in the embodiment of the present invention, the required distance between the injection hole of the injector 923 and the intake port 912 is relatively long. Therefore, the required distance between the throttle valve and the air inlet 912 is also longer. Therefore, the engine unit 1A can arrange the throttle valve 24 closer to the intake port 12 than the engine unit 91 having a plurality of intake ports 912 and one injector 923 for one combustion chamber 911. Therefore, the downstream volume of the throttle valve of the engine unit 1A can be reduced.

Assuming that the engine unit has multiple intake ports and multiple injectors for one combustion chamber, it is necessary to connect the one set for one combustion chamber at a position that is more downstream than the throttle valve and more upstream than the injector. Multiple intake passages. Therefore, the required distance between the throttle valve and the intake port is relatively long. Therefore, in the engine unit 1A, compared with an engine unit having a plurality of intake ports and a plurality of injectors for one combustion chamber, the throttle valve 24 can be arranged closer to the intake port 12. Therefore, the downstream volume of the throttle valve of the engine unit 1A can be reduced.

Furthermore, the throttle downstream volume of an engine unit having a plurality of intake ports, at least one injector, and one throttle valve for one combustion chamber is a space formed by connecting a plurality of intake passages. On the other hand, the downstream volume of the throttle valve of the engine unit 1A is formed in a space in one intake passage. Therefore, the downstream volume of the throttle valve of the engine unit 1A can be further compared with the downstream volume of the throttle valve of an engine unit having multiple intake ports, at least one injector, and one throttle valve for one combustion chamber. Decrease.

The smaller the downstream volume of the throttle valve is, the more easily the pressure in the single intake passage portion 20 when the intake port 12 is opened is affected by the negative pressure in the combustion chamber 11. That is, the smaller the downstream volume of the throttle valve, the lower the pressure in the single intake passage portion 20 during the intake stroke. This promotes the evaporation of fuel injected during the intake stroke. In addition, the air flowing into the combustion chamber 11 from the intake port 12 is easily diffused uniformly in the circumferential direction of the inner surface of the cylinder bore 10. Therefore, the fuel in the combustion chamber 11 is further suppressed. Uneven concentration distribution. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved. In addition, by promoting the evaporation of fuel, the adhesion of fuel to the inner surface of the single intake passage portion 20 and the intake valve 22 is reduced.

The injector 23 is arranged at a position where the shortest distance D1 between the center P1 of the intake port 12 and the plurality of injection holes is less than three times the diameter of the intake port 12. In this way, the distance from the plurality of injection holes to the intake port 12 is relatively short. Therefore, the injection angle of the fuel injected from the injector 23 can be increased reliably. As described above, since the injection angle of the fuel injected from the injector 23 is relatively large, it is possible to reduce the diameter of the injected liquid droplets while suppressing the contact of the plurality of injected liquid droplets. Due to the small diameter of the injected droplets, the unevenness of the fuel concentration distribution in the combustion chamber 11 can be further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved. When the shortest distance D1 between the plurality of injection holes and the center P1 of the intake port 12 is less than the length of twice the diameter of the intake port 12, the design of the concentration distribution of the fuel in the combustion chamber 11 can be further improved Degrees of freedom.

The injection centerline Ci1 of the injector 23 passes through the single intake port 12. Suppose that when the fuel is injected so that the injection center line Ci1 does not pass through the intake port 12, even if the fuel is injected in such a manner that the first area A11 becomes a ring, it passes through the gap between the single intake valve 22 and the single intake port 12. The amount of fuel also becomes uneven in the circumferential direction of the gap. The concentration of fuel at a specific location in the combustion chamber 11 is easy to increase. In this specific example, the injection center line Ci1 passes through the single intake port 12 to suppress the unevenness of the fuel passing through the gap between the single intake valve 22 and the single intake port 12. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved.

The injector 23 for a single intake port is arranged such that the injection center line Ci1 passes through the stem 22b of the intake valve 22 in the open position when viewed in the direction of the cylinder axis Cy1 (see FIG. 3(a)). Therefore, when viewed in the direction of the cylinder axis Cy1, the injection center line Ci1 is more likely to pass through the center P1 of the intake port 12 or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved.

The injector 23 is arranged such that the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 when the intake port 12 is opened when viewed in a direction orthogonal to the plane S2 (refer to FIG. 2). That is, when viewed in a direction orthogonal to the plane S2, the injection center line Ci1 passes through the center P1 of the intake port 12 or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved.

The injector 23 is arranged in such a way that the injection center line Ci1 passes through the stem portion 22b and the umbrella portion 22a of the intake valve 22 when the intake port 12 is opened. That is, the injection center line Ci1 passes through the center P1 of the intake port 12 or its vicinity. Therefore, the unevenness of the fuel concentration distribution in the combustion chamber 11 is further suppressed. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved.

The diameter of the air inlet 12 is greater than the diameter of the air outlet 13. Since the diameter of the intake port 12 is relatively large, the diameter of the single intake passage portion 20 is also relatively large. With the larger diameter of the single intake passage portion 20, the injection angle of the fuel injected from the injector 23 can be increased. Due to the large injection angle of the fuel injected from the injector 23, it is possible to reduce the diameter of the injected droplets while suppressing the contact of a plurality of injected droplets. The smaller diameter of the sprayed droplets can further suppress The fuel concentration distribution in the combustion chamber 11 is uneven. Therefore, the design freedom of the concentration distribution of the fuel in the combustion chamber 11 can be further improved.

Assuming that when considering the case of changing the two intake ports 912 of the engine unit 91 with two intake ports 912 for one combustion chamber 911 to one intake port as shown in FIG. 9, it is necessary to perform the intake stroke The amount of air supplied to one combustion chamber 911 is maintained. That is, the total cross-sectional area of the two intake passage portions 920 needs to be approximately the same as the cross-sectional area of one intake passage portion when the two intake ports 912 are changed to one intake port. Therefore, the total perimeter of the two intake passage portions 920 is longer than the perimeter of one intake passage portion when the two intake ports 912 are changed to one intake port. The longer the circumference of the intake passage, the larger the area of the inner surface of the intake passage. The industry should consider that when the two intake ports 912 of the engine unit 91 are changed to one intake port, as the area of the inner surface of the intake passage portion is increased, the fuel is distributed in the intake passage portion. Increased adhesion on the inner surface. In order to reduce the adhesion of fuel to the intake valve 922 and/or the intake passage portion 920, the previous engine unit 91 with two intake ports 912 in one combustion chamber 911 has a method where the concentration at the outer periphery is higher than the concentration at the center. Fuel is injected from the injector 923. Therefore, as long as you are a business, you should not consider making changes to increase fuel adhesion. In fact, according to the research of the inventor of the present case, as described above, compared with the engine unit 91 with two intake ports 912 for one combustion chamber 911, the droplets of the fuel injected from the injector can be reduced. diameter. It is understood that this promotes the evaporation of fuel, and therefore, it is possible to suppress adhesion of fuel to the intake passage portion and the intake valve compared to the conventional engine unit 91 having two intake ports 912 for one combustion chamber 911.

Furthermore, it is assumed that the fuel injection toward one intake port 912 of one injector 923 that injects fuel toward two intake ports 912 formed in one combustion chamber 911 is used for the injection of fuel toward one intake port 912 as shown in FIG. In the case of an injector in an engine unit with one combustion chamber having one intake port and one injector, it is necessary to maintain the amount of fuel supplied to one combustion chamber during the intake stroke. That is, the amount of fuel injected toward one intake port needs to be increased to approximately twice the amount of fuel injected toward one intake port in the injector 923 that injects fuel toward two intake ports 912. If the amount of fuel is increased, the droplets of the fuel will easily come into contact with each other. In this way, the fuel droplets are not easy to evaporate. Therefore, as long as you are an industry operator, you should consider the increase in fuel adhesion to the intake valve. In order to reduce the adhesion of fuel to the intake valve 922 and/or the intake passage portion 920, the previous engine unit 91 with two intake ports 912 in one combustion chamber 911 has a method where the concentration at the outer periphery is higher than the concentration at the center. Fuel is injected from the injector 923. Therefore, as long as you are a business, you should not consider making changes to increase fuel adhesion. In fact, according to the research conducted by the inventor of the present case, as described above, compared with the engine unit 91 having two intake ports 912 and one injector 923 for one combustion chamber 911, the self-injector injection can be reduced. The diameter of the fuel droplet. It can be seen that this promotes the evaporation of fuel, and therefore, compared with the conventional engine unit 91 having two intake ports 912 for one combustion chamber 911, adhesion of fuel to the intake passage portion and intake valve can be suppressed.

≪Examples of changes≫

The present invention is not limited to the above-mentioned embodiment and its specific examples, and various changes can be made as long as it is described in the scope of the patent application. Hereinafter, a modification example of the embodiment of the present invention will be described. In addition, for those having the same configuration as the above-mentioned configuration, the same reference numerals are used, and the description thereof is appropriately omitted. The above-mentioned embodiment, the specific examples of the embodiment, and the following modified examples can be appropriately combined and implemented.

<Variations of injectors for single intake port>

When the injector for a single intake port of the present invention injects fuel into a space where only the atmosphere is not installed in the engine unit, at a certain point immediately after the injection, the injector is used from a single intake port The fuel-existing area on the first plane where the injection directions of a plurality of injected fuel droplets intersect may also have two or more first areas. Alternatively, the area where fuel exists on the first plane may include areas other than the first area in addition to the first area. However, the area where fuel exists on the first plane does not include the area where the concentration of fuel is higher than that of the first area.

For example, the area where fuel exists on the first plane may include a second area that is in contact with the entire inner peripheral end of the first area. However, the fuel concentration in the first zone is higher than the fuel concentration in the second zone. That is, the average value of fuel mass per unit volume or unit area in the first area is greater than the average value of fuel mass per unit volume or unit area in the second area.

When the first area is non-annular as described below, the area where fuel exists on the first plane may also include an area located between the two ends of the first area in the circumferential direction. However, the fuel concentration in the area between the circumferential ends of the first area is the same as or lower than the fuel concentration in the first area.

When there are a plurality of first areas in the area where fuel exists on the first plane, the plurality of first areas may also be arranged in the circumferential direction along the edge of a circle or an ellipse.

At least a part of the outer peripheral end of the first region along the edge of a circle or an ellipse does not include the case where only a part of the outer peripheral end of the first region is along at least a part of the edge of a circle or an ellipse. Therefore, for example, when there is fuel along the entire circumference of the edge of the circle among two circles contained in an ellipse, the area where fuel exists along the entire circumference of the edge of the circle is not equivalent. In the first area of the present invention.

When the injector for a single intake port of the present invention injects fuel into a space where only the atmosphere is not installed in the engine unit, at a certain point immediately after the injection, the injector is used from a single intake port The fuel on the first plane where the injection directions of a plurality of injected fuel droplets intersect may also exist in a circle along a part of the edge of the circle. In this case, the fuel-existing area on the first plane includes a non-annular first area with an inner peripheral end and an outer peripheral end along a part of the edge of the circle. The fuel concentration in the non-annular first area is higher than the fuel concentration in the second area on the first plane that is in contact with the entire inner peripheral end of the first area. In this modified example, fuel may or may not be present in the second area. Fig. 10, Fig. 11, and Fig. 12(a) to Fig. 12(c) are diagrams showing three specific examples of the modification.

Fig. 10, Fig. 11, and Fig. 12(a) are explanatory diagrams of one modification. Figure 11 is a view of the engine unit viewed in a direction orthogonal to the second plane. 10 and 12(a) show the first area A21 and the second area A22 on the first plane S21. The second area A22 is an area surrounded by the entire inner peripheral end of the non-annular first area A21 and a line segment connecting both ends of the inner peripheral end of the first area A21. The outer peripheral end of the first area A21 is an arc with an angle of 90° or more. Therefore, as shown in FIG. 12(a), the center of the outer peripheral end of the first area A21 in the circumferential direction is located on the first plane S21 passing through both ends of the first area A21 in the circumferential direction. Diametrically outside. The arrow Dx shown in FIG. 10 indicates the direction on the first plane S21 parallel to the second plane, and the arrow Dy indicates the direction on the first plane S21 parallel to the third plane. The injection center line Ci21 passes through the second area A22. The first plane S21 is the shortest length in the Dx direction of the fuel-existing area of the plurality of planes passing through one point on the injection centerline Ci21, and the length of the Dy-direction of the fuel-existing area on the plane is the shortest. The plane where the length becomes the shortest.

FIG. 12(b) shows the first area A31 and the second area A32 on the first plane S31. The second area A32 is an area surrounded by the entire inner peripheral end of the first area A31 and a line segment connecting both ends of the inner peripheral end of the first area A31 in the peripheral direction. The outer peripheral end of the first area A31 is an arc with an angle of 90° or more. Therefore, the center in the circumferential direction of the outer peripheral end of the first area A31 is located outside the diameter direction of the 90° arc CA3 on the first plane S31 passing through both ends of the first area A31 in the circumferential direction. The injection center line Ci31 passes through the second area A32. The first plane S31 is a plurality of planes passing through a point on the injection center line Ci31. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest and the fuel-existing area on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

FIG. 12(c) shows the first area A41 and the second area A42 on the first plane S41. The second area A42 is an area surrounded by the entire inner peripheral end of the first area A41 and a line segment connecting both ends of the inner peripheral end of the first area A41 in the peripheral direction. 1 The outer circumference of area A41 is an arc whose angle is less than 90°. Therefore, the center in the circumferential direction of the outer peripheral end of the first area A41 is located inside the diametrical direction of the 90° arc CA4 on the first plane S41 passing through both ends of the first area A41 in the circumferential direction. The injection center line Ci41 passes through the first area A41. The first plane S41 is a plurality of planes passing through a point on the injection centerline Ci41. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest and the length of the fuel-existing plane on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

When the injector for a single intake port of the present invention injects fuel into a space where only the atmosphere is not installed in the engine unit, at a certain point immediately after the injection, the injector is used from a single intake port Combustion on the first plane where the injection directions of the injected plural fuel droplets intersect The material can also exist in an ellipse along the entire circumference of the edge of the ellipse. In this case, the fuel-existing area on the first plane includes the first ring-shaped area along the entire circumference of the ellipse. The fuel concentration in the first zone of the ring is higher than the fuel concentration in the second zone on the first plane that is in contact with the entire inner peripheral end of the first zone. In this modified example, fuel may or may not be present in the second area. Fig. 13(a) is a diagram showing a specific example of this modification. The shape of the ellipse is not limited to the shape shown in Fig. 13(a).

FIG. 13(a) shows the first area A51 and the second area A52 on the first plane S51. The injection center line Ci51 passes through the second area A52. The first plane S51 is a plurality of planes passing through one point on the injection centerline Ci51. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest and the length of the fuel-existing plane on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

When the injector for a single intake port of the present invention injects fuel into a space where only the atmosphere is not installed in the engine unit, at a certain point immediately after the injection, the injector is used from a single intake port The fuel on the first plane where the injection directions of the injected fuel droplets intersect may also exist in an ellipse along a part of the edge of the ellipse. In this case, the area where fuel exists on the first plane includes a non-annular first area along a part of the edge of the ellipse. The fuel concentration in the first zone of the ring is higher than the fuel concentration in the second zone on the first plane that is in contact with the entire inner peripheral end of the first zone. In this modified example, fuel may or may not be present in the second area. Fig. 13(b) to Fig. 13(e) are diagrams showing 4 specific examples of this modification. The shape of the ellipse is not limited to the shape shown in Figs. 13(b) to 13(e).

FIG. 13(b) shows the first area A61 and the second area A62 on the first plane S61. The second area A62 is an area surrounded by the entire inner peripheral end of the first area A61 and a line segment connecting both ends of the inner peripheral end of the first area A61 in the circumferential direction. The center in the circumferential direction of the outer peripheral end of the first area A61 is located outside the diameter direction of the 90° arc CA6 on the first plane S61 having both ends of the first area A61 in the circumferential direction. The injection center line Ci61 passes through the second area A62. The first plane S61 is a plurality of planes passing through a point on the injection center line Ci61. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest, and the fuel-existing area on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

FIG. 13(c) shows the first area A71 and the second area A72 on the first plane S71. The second area A72 is an area surrounded by the entire inner peripheral end of the first area A71 and a line segment connecting both ends of the inner peripheral end of the first area A71 in the peripheral direction. The center in the circumferential direction of the outer peripheral end of the first area A71 is located inside the diametrical direction of the 90° arc CA7 on the first plane S71 passing through both ends of the circumferential direction of the first area A71. The injection center line Ci71 passes through the second area A72. The first plane S71 is a plurality of planes passing through a point on the injection centerline Ci71. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest and the length of the fuel-existing plane on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

FIG. 13(d) shows the first area A81 and the second area A82 on the first plane S81. The second area A82 is an area surrounded by the entire inner peripheral end of the first area A81 and a line segment connecting both ends of the inner peripheral end of the first area A81 in the peripheral direction. The center in the circumferential direction of the outer peripheral end of the first area A81 is located outside the diameter direction of the 90° arc CA8 on the first plane S81 passing through both ends of the circumferential direction of the first area A81. The injection center line Ci81 passes through the second area A82. The first plane S81 series through spray The length of the fuel-existing area in the plane parallel to the second plane among the plural planes of a point on the centerline Ci81 becomes the shortest, and the fuel-existing area on the plane is the same as the third plane The plane where the length of the parallel direction becomes the shortest.

FIG. 13(e) shows the first area A91 and the second area A92 on the first plane S91. The second area A92 is an area surrounded by the entire inner peripheral end of the first area A91 and a line segment connecting both ends of the inner peripheral end of the first area A91 in the peripheral direction. The center in the circumferential direction of the outer peripheral end of the first area A91 is located outside the diameter direction of the 90° arc CA9 on the first plane S91 passing through both ends of the circumferential direction of the first area A91. The injection center line Ci91 passes through the first area A91. The first plane S91 is a plurality of planes passing through a point on the injection center line Ci91. The length of the fuel-existing area on the plane parallel to the second plane becomes the shortest and the length of the fuel-existing plane on the plane is the shortest. The plane where the length of the area parallel to the third plane becomes the shortest.

As shown in Figure 12(a), Figure 12(b), Figure 13(b), Figure 13(d), and Figure 13(e), the center in the circumferential direction outside the first area In the case of the outer side of the 90° arc on the first plane at both ends of the circumferential direction of the area, the circumferential length of the non-annular first area is longer. Therefore, it is possible to reduce the diameter of the injected droplets in such a way that the contact of the plurality of injected droplets can be suppressed, and at the same time, a sufficient amount of fuel can be injected from a single intake port with the injector.

Set the direction in which the piston descends during the intake stroke as the direction in which the piston descends. The descending direction of the piston is the direction parallel to the central axis of the cylinder bore. When the first area of the present invention is a non-annular shape along a part of the edge of a circle or an ellipse, the center of the outer peripheral end of the first area in the circumferential direction is preferably located away from the first area in the downward direction of the piston. The positions at both ends of the area in the circumferential direction. Figure 10, Figure 11 And Fig. 12 (a) shows a specific example of this modification. The arrow PD shown in FIG. 11 indicates the descending direction of the piston. As shown in Fig. 11, when viewed in the direction orthogonal to the second plane (Dy direction), the circumferential center Ac of the outer peripheral end of the non-annular first area A21 is located on the circumference away from the first area A21 in the piston descending direction The position at both ends of the direction. In this case, when viewed in the direction orthogonal to the second plane (Dy direction), the circumferential center Ac of the outer peripheral end of the non-annular first area A21 is located away from the injection center line Ci21 in the piston descending direction. According to this configuration, it is possible to prevent fuel from adhering to the stem portion 22b of the single intake valve 22.

Furthermore, when the first area of the present invention is a non-circular shape along a part of the edge of a circle or an ellipse, the peripheral center of the outer peripheral end of the first area may not be located away from the piston descending direction. Positions at both ends of the first area in the circumferential direction.

In the present invention, the ejection center line passes through the first area or the second area. When the first area is annular, the ejection center line passes through the second area. When the first area is non-circular, the ejection center line may pass through the second area or may pass through the first area.

The first plane of the present invention is preferably a plurality of planes passing through a point on the injection center line. The length of the fuel-existing area on the plane in the direction parallel to the second plane becomes the shortest and the existence on the plane The plane where the length of the fuel area in the direction parallel to the third plane becomes the shortest. Regarding the first plane, among the plurality of planes passing through one point on the injection center line, the plane with the smallest distance disparity from the plurality of injection holes of the injector for a single intake port to the first area can be set as the first flat. When the first plane of the present invention satisfies this condition, the first plane may or may not be orthogonal to the ejection center line. The first plane of the present invention may not satisfy this condition. When the first plane of the present invention does not meet this condition, the first plane can be aligned with the ejection centerline Orthogonal or not.

In the specific example of the embodiment, the concentration distribution of the fuel in the first area A1 is substantially constant in the circumferential direction of the first area A1. However, the concentration distribution of the fuel in the first area in the present invention may not be fixed in the circumferential direction of the first area. For example, the concentration distribution of fuel in the first area may also be asymmetrical with the first plane as the center. Also, for example, the concentration distribution of fuel in the first area may be asymmetrical with the second plane as the center. Also, for example, the concentration distribution of fuel in the first area may be asymmetrical with the third plane as the center.

Let the plane containing the center of the single intake port and the center axis of the cylinder hole be the fourth plane. In the specific example of the embodiment, the fourth plane is the same as the plane S2 (second plane). In the specific example of the embodiment, the fuel concentration on both sides of the plane S2 in the combustion chamber 11 is substantially the same. However, in the present invention, the fuel concentration may be higher in the space on both sides of the fourth plane in the combustion chamber where the spark plug insertion port is located. In order to realize this concentration distribution, the injector 23 of the specific example of the embodiment can be changed as follows. For example, the injection direction may be changed so that the injection center line Ci1 approaches the spark plug insertion port when viewed in the direction of the center axis of the cylinder hole. In addition, for example, the injection amount may be changed so that the concentrations on both sides of the second plane (plane S2) of the fuel injected from the injector 23 are different from each other. The injection amount can be adjusted by, for example, changing the size of the injection hole or the density of the arrangement of the injection hole.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the cylinder axis Cy1 when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the injector for a single intake port of the present invention may not pass through the center of the cylinder bore when viewed in the direction along the center axis of the cylinder bore Axis.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment coincides with the center axis Cv1 of the stem 22b of the intake valve 22 when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the injector for a single intake port of the present invention may not coincide with the center axis of the rod when viewed in the direction of the center axis of the cylinder bore.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the rod portion 22b and the umbrella portion 22a of the intake valve 22 in the open position when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the injector for a single intake port of the present invention may not pass through the stem of the single intake valve in the open position when viewed in the direction of the center axis of the cylinder bore. In addition, the injection center line of the injector for a single intake port of the present invention may not pass through the umbrella portion of the single intake valve in the open position when viewed along the direction of the center axis of the cylinder bore.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the rod portion 22b and the umbrella portion 22a of the intake valve 22 in the closed position when viewed in the direction of the cylinder axis Cy1. However, the injection center line of the injector for a single intake port of the present invention may not pass through the stem of the single intake valve in the closed position when viewed along the direction of the center axis of the cylinder bore.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the rod portion 22b and the umbrella portion 22a of the intake valve 22 in the open position when viewed in the direction orthogonal to the plane S2. However, the injection center line of the injector for a single intake port of the present invention may not pass through the stem of the single intake valve in the open position when viewed in a direction orthogonal to the second plane. Also, the single of the present invention The injection centerline of an injector for an intake port may not pass through the umbrella of a single intake valve in the open position when viewed in a direction orthogonal to the second plane. The injection center line of the injector for a single intake port of the present invention may not pass through both the umbrella portion and the rod portion of the single intake valve in the open position when viewed in a direction orthogonal to the second plane, or Pass only through the umbrella part and the rod part of the single intake valve in the open position, or only pass through the umbrella part and the rod part of the rod part of the single intake valve in the open position.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the stem portion 22b and the umbrella portion 22a of the single intake valve 22 in the open position. However, the injection center line of the injector for a single intake port of the present invention may not pass through the stem of the single intake valve in the open position. The injection center line of the injector for a single intake port of the present invention may not pass through the umbrella portion of the single intake valve in the open position. The injection center line of the injector for a single intake port of the present invention may not pass through both the umbrella part and the rod part of the single intake valve in the open position, or only pass through the umbrella part of the single intake valve in the open position. And the umbrella part in the rod part can also only pass through the umbrella part of the single intake valve and the rod part in the rod part in the open position.

The injection center line Ci1 of the injector 23A of the specific example of the embodiment passes through the intake port 12. However, the injection center line of the injector for a single intake port of the present invention may not pass through the intake port.

In the engine unit of the present invention, the shortest distance between the plurality of injection holes and the center of a single intake port may be longer than twice the diameter of the single intake port. The shortest distance between the plurality of injection holes and the center of a single air inlet can also be longer than 3 times the diameter of the single air inlet.

<Example of Variation of Exhaust Port>

The engine unit 1A of the specific example of the embodiment has only one exhaust port 13 for one combustion chamber 11. However, the engine unit of the present invention may have a plurality of exhaust ports for one combustion chamber. For example, one single intake port and two exhaust ports may be formed in one combustion chamber.

<Variations of single intake port and exhaust port>

In the specific example of the embodiment, the diameter of the intake port 12 is larger than the diameter of the exhaust port 13. However, in the present invention, the diameter of a single air inlet may be the same as the diameter of the air outlet, or may be smaller than the diameter of the air outlet.

<Variation of single intake valve>

In the specific example of the embodiment, the end surface of the umbrella portion 22a of the intake valve 22 facing the combustion chamber 11 is parallel to the plane S4 including the entire circumference of the intake port 12 (refer to FIG. 2). However, in the present invention, the end surface of the umbrella portion of the single intake valve facing the combustion chamber may not be parallel to the plane including the entire circumference of the single intake port.

In the specific example of the embodiment, the central axis Cv1 of the stem portion 22b of the intake valve 22 is orthogonal to the plane S4 including the entire circumference of the intake port 12 (refer to FIG. 2). However, in the present invention, the central axis of the stem of a single intake valve may not be orthogonal to the plane including the entire circumference of the single intake port.

In the specific example of the embodiment, the center axis Cv1 of the rod portion 22b of the intake valve 22 passes through the center P1 of the intake port 12 (refer to FIGS. 2 and 3(a)). However, in the present invention, the single intake valve The central axis of the rod may not pass through the center of a single air inlet.

In the specific example of the embodiment, the central axis Cv1 of the rod portion 22b of the intake valve 22 passes through the cylinder axis Cy1 when viewed in the direction of the cylinder axis Cy1 (refer to FIG. 3(a)). However, the central axis of the rod of the single intake valve of the present invention may not pass through the central axis of the cylinder bore when viewed in the direction of the central axis of the cylinder bore.

<Multi-cylinder engine>

The form of the engine unit 1A of the specific example of the embodiment is a single-cylinder engine. However, the form of the engine unit of the present invention can also be a multi-cylinder engine. That is, the engine unit of the present invention may also have a plurality of combustion chambers. The number of combustion chambers is not particularly limited. In this case, the engine unit has a single intake port, a single intake valve, an injector for a single intake port, and a single intake passage for each combustion chamber.

When the engine unit of the present invention has a plurality of combustion chambers, the engine unit has at least one cylinder intake passage portion and at least one external intake passage portion. The engine unit may also have a plurality of cylinder intake passages. For example, the engine unit may have one cylinder intake passage for each combustion chamber. In addition, the engine unit may have a plurality of external air intake passages. For example, the engine unit may have one external intake passage for each combustion chamber.

The number of cylinder intake passage parts may be the same as or less than the number of single intake passage parts. When the number of cylinder intake passage portions is less than the number of a single intake passage portion, the cylinder intake passage portion has a plurality of branch shapes and inflow ports through which air flows. When the number of cylinder intake passages is less than the number of single intake passages, the external The number of intake passages is the same as the number of cylinder intake passages. When the number of cylinder intake passages is the same as the number of single intake passages, the number of external intake passages may be the same as or less than the number of cylinder intake passages . That is, the number of external intake passage portions may be the same as or less than the number of single intake passage portions. When the number of external intake passages is less than the number of cylinder intake passages, the external intake passages have a plurality of branched shapes and inflow ports for air to flow in. In either case, the single air intake passage is constructed in such a way that the flow of air passes through the interior without separation or confluence.

When the engine unit of the present invention has a plurality of combustion chambers, the engine unit may also have a throttle valve for each combustion chamber. In this case, one cylinder intake passage and one external intake passage are provided for each combustion chamber. Each of the plurality of throttle valves is provided in the external intake passage portion.

When the engine unit of the present invention has a plurality of combustion chambers, the engine unit may also have a throttle valve for the plurality of combustion chambers. In this case, the external intake passage portion or the cylinder intake passage portion has a plurality of branch shapes and one inlet through which air flows. The number of cylinder intake passages is less than the number of single intake passages, or the number of external intake passages is less than the number of cylinder intake passages. A plurality of single intake passages are connected at positions that are more downstream than the throttle valve and more upstream than the ejector for a single intake port in the air flow direction. The throttle valve is provided in the external intake passage portion.

Let the volume of a space formed between the throttle valve in the closed position and the intake valve in the closed position be the downstream volume of the throttle valve. In the engine unit, there is a throttle valve for each combustion chamber When the shape is formed, the downstream volume of the throttle valve is formed in the space within one intake passage. On the other hand, when the engine unit has one throttle valve for a plurality of combustion chambers, the downstream volume of the throttle valve is a space formed by connecting a plurality of intake passages provided for each combustion chamber. Therefore, the downstream volume of the throttle valve of an engine unit having one throttle valve for each combustion chamber can be smaller than the downstream volume of the throttle valve of an engine unit having one throttle valve for a plurality of combustion chambers.

When the engine unit of the present invention has a plurality of combustion chambers, the timing of the intake strokes of the plurality of combustion chambers may be the same as each other. In addition, the timing of the intake strokes of any two combustion chambers among the plurality of combustion chambers may be different from each other, and the timing of the intake strokes of any two other combustion chambers among the plurality of combustion chambers may be the same as each other. In addition, the timing of the intake stroke of any one of the plurality of combustion chambers may be different from the timing of the intake stroke of any of the remaining combustion chambers. Furthermore, the timing of the intake stroke here is the same, and does not include the case where the intake stroke only partially overlaps.

When the engine unit of the present invention has a plurality of combustion chambers, the form of the engine unit can also be a multi-cylinder engine in which a plurality of combustion chambers are arranged in a straight line. In this case, the central axes of the plurality of cylinder holes of the engine unit are parallel or substantially parallel. In addition, the form of the engine unit may also be a V-type engine. The V-type engine has two cylinder bores arranged in a V shape when viewed along the central axis of the crankshaft. Moreover, in the case of a V-type engine with four or more cylinders, it has a plurality of cylinder holes arranged in parallel or substantially parallel to the central axis.

The first area of the present invention is equivalent to the outer peripheral area of the basic application (Japanese Patent Application 2018-100176) of this case. The second area of the present invention corresponds to the central area of the basic application of this case. The first plane of the present invention is an example of the third plane of the basic application of this case. The second plane phase of the present invention It should be the first plane of the basic application of this case. The third plane of the present invention is equivalent to the second plane of the basic application of this case.

1‧‧‧Engine unit

3‧‧‧External air intake passage

10‧‧‧Cylinder bore

11‧‧‧Combustion chamber

12‧‧‧Single air inlet

20‧‧‧Single intake passage

21‧‧‧Cylinder intake passage

22‧‧‧Single intake valve

23‧‧‧Ejector for single inlet

50‧‧‧Control device

A1‧‧‧Area 1

A2‧‧‧Section 2

Cy1‧‧‧The central axis of the cylinder bore

F1‧‧‧Fuel

S1‧‧‧1st plane

Claims (20)

An engine unit, which is a four-stroke cycle, is characterized by comprising: a cylinder portion having at least one combustion chamber formed by the inner surface of the cylinder hole, and at least one of the above-mentioned at least one combustion chamber. One intake port, and at least one cylinder intake passage portion of the at least one combustion chamber that is connected to the at least one intake port and flows into the inside and is supplied from the at least one intake port to the at least one cylinder intake passage portion of the at least one combustion chamber; An external intake passage portion, which is arranged outside the cylinder portion, is connected to the at least one cylinder intake passage portion, and the air flowing into the interior is supplied to the at least one cylinder intake passage portion; at least one intake A gas valve, which can be moved between a position where the at least one air intake port is opened and a position where the at least one air intake port is closed; at least one injector, each of which has a plurality of fuel sprays capable of spraying And the plurality of injection holes are provided in the cylinder intake passage portion or the external intake passage portion so as to be located in the cylinder intake passage portion or the external intake passage portion; and a control device that controls the above At least one injector for fuel injection; and the above-mentioned intake port, the above-mentioned intake valve, and the above-mentioned injector are provided with one each for each of the above-mentioned combustion chambers, respectively constituting a single intake port, a single intake valve, and In the injector for a single intake port, the at least one cylinder intake passage portion and the at least one external intake passage portion include at least one single intake passage portion, and the single intake passage portion is provided for each of the combustion chambers There is one, and the area from where the ejector for the single intake port is installed to the single intake port is constructed in such a way that the flow of air passes through the interior without separation or confluence, The injector for the single intake port (a) is arranged to inject fuel toward the single intake port, and (b) is configured to inject fuel to the atmosphere without being installed in the engine unit. In the case of space, at a certain point immediately after injection, (i) the fuel on the first plane that intersects the injection direction of the plurality of fuel droplets injected from the above-mentioned single intake port with the injector is at 1 A circle or an ellipse exists along at least a part of the edge of the aforementioned one circle or the aforementioned one ellipse, and (ii) is included in the fuel-existing area on the aforementioned first plane and its outer peripheral end is connected to The fuel concentration in the first area where the inner peripheral end is along at least a part of the edge of the one circle or the one ellipse is higher than that of the second area on the first plane that is in contact with the entire inner peripheral end of the first area The concentration of fuel, (c) during the intake stroke and when the single intake valve is at the position to open the single intake port, the fuel is injected and controlled by the control device, and the fuel system is supplied to one of the combustion chambers. Fuel injected by an injector from one of the above-mentioned single intake ports and passing through one of the above-mentioned single intake ports. The engine unit of claim 1, wherein the injector for a single intake port is configured to inject fuel in a mist form without using air. Such as the engine unit of claim 2, wherein the cylinder intake passage portion and the external intake passage portion are provided with one each for each of the combustion chambers, and the engine unit is equipped with at least one throttle valve, and the above-mentioned at least one Throttle valves are respectively arranged in the at least one external intake passage portion, and the flow of air in the single intake passage portion In the direction, it is located more upstream than the above-mentioned single-intake injector. The engine unit of claim 3, wherein the single intake valve has: an umbrella portion, which can block the single intake port; and a rod portion, which is connected to the umbrella portion, and a part is arranged in the single intake passage In the section; and the single air inlet injector is arranged at a position where the shortest distance between the plurality of injection holes and the center of the single air inlet is less than 3 times the diameter of the single air inlet. The engine unit of claim 4, wherein the shortest distance between the ejector for the single intake port arranged between the plurality of injection holes and the center of the single intake port is less than twice the diameter of the single intake port s position. Such as the engine unit of claim 1, wherein the cylinder intake passage portion and the external intake passage portion are provided with one each for each of the combustion chambers, and the engine unit is provided with at least one throttle valve, and the above-mentioned at least one Throttle valves are respectively arranged in the at least one external intake passage portion, and the air flow direction in the single intake passage portion is located more upstream than the ejector for the single intake port. The engine unit of claim 6, wherein the single intake valve has: an umbrella portion, which can block the single intake port; and a rod portion, which is connected to the umbrella portion and partly arranged in the single intake passage In the section; and the single air inlet injector is arranged at a position where the shortest distance between the plurality of injection holes and the center of the single air inlet is less than 3 times the diameter of the single air inlet. The engine unit of claim 7, wherein the shortest distance between the ejector for the single intake port arranged between the plurality of injection holes and the center of the single intake port is less than twice the diameter of the single intake port s position. The engine unit of claim 1, wherein the single intake valve has: an umbrella portion which can block the single intake port; and a rod portion which is connected to the umbrella portion and a part of which is arranged in the single intake passage In the section; and the single air inlet injector is arranged at a position where the shortest distance between the plurality of injection holes and the center of the single air inlet is less than 3 times the diameter of the single air inlet. The engine unit of claim 9, wherein the shortest distance between the ejector for the single intake port and the center of the plurality of injection holes and the center of the single intake port is less than twice the diameter of the single intake port s position. Such as the engine unit of any one of claims 1 to 10, in which, when viewed in the direction along the center axis of the cylinder bore, it is possible to observe droplets of a plurality of fuel injected from the single intake port with an injector The plane of the straight line at the center of the two injection directions that form the largest angle among the injection directions is set as the second plane. When viewed in a direction orthogonal to the second plane, it can be observed to pass through the single air inlet. The plane of the straight line at the center of the two injection directions that form the largest angle among the injection directions of the plurality of fuel droplets injected by the injector is referred to as the third plane, and the intersection of the above-mentioned second plane and the above-mentioned third plane is referred to as For the injection center line, the first plane is a plurality of planes passing through one point on the injection center line, and the length of the fuel-existing area on the plane in the direction parallel to the second plane becomes the shortest, and The plane where the length of the fuel-existing area in the direction parallel to the above-mentioned third plane becomes the shortest on this plane. Such as the engine unit of claim 11, wherein the injector for the single intake port is arranged and constructed such that the injection center line passes through the single intake port. Such as the engine unit of claim 11, where The injector for the single intake port is arranged and configured such that the injection center line passes through the second region. Such as the engine unit of claim 11, wherein the single intake valve has: an umbrella portion, which can block the single intake port; and a rod portion, which is connected to the umbrella portion, and a part of which is arranged in the single intake passage And the injector for the single intake port is arranged in such a way that the injection center line passes through the rod portion of the single intake valve at the position where the single intake port is opened when viewed in the direction of the center axis of the cylinder bore And composition. The engine unit of claim 11, wherein the injector for the single intake port passes through the single intake valve at a position where the single intake port is opened when viewed in a direction orthogonal to the second plane. The configuration and structure of the above-mentioned rod and umbrella. Such as the engine unit of claim 11, wherein the ejector for the single intake port is arranged in such a way that the injection center line passes through the rod portion and the umbrella portion of the single intake valve at a position where the single intake port is opened, and constitute. Such as the engine unit of claim 11, wherein the injector for the single intake port is configured as follows: the first area on the first plane is along the edge of the one circle or the one ellipse The entire circumference of the ring, or a non-ring shape along a part of the edge of the above 1 circle or the above 1 ellipse, and the center of the outer peripheral end in the circumferential direction is located at both ends of the circumferential direction passing through the first region of the non-ring shape The outer sides of the 90° arc on the first plane at both ends in the radial direction. Such as the engine unit of claim 11, wherein the cylinder portion has at least one exhaust port formed in the at least one combustion chamber, the exhaust port is provided with at least one of the combustion chambers, and the intake port is The diameter is larger than the diameter of the above-mentioned exhaust port. An engine unit according to any one of claims 1 to 10, wherein the injector for the single intake port is configured as follows: the first area on the first plane is along the one circle or the one ellipse The entire circumference of the edge of the ring or a non-ring shape along a part of the edge of the above 1 circle or the above 1 ellipse, and the center of the outer peripheral end in the circumferential direction is located in the circumferential direction with the first region passing through the above non-ring shape The outer side in the radial direction of the 90° arc on the above-mentioned first plane at both ends of the two ends. An engine unit according to any one of claims 1 to 10, wherein the cylinder portion has at least one exhaust port formed in the at least one combustion chamber, and at least one exhaust port is provided for one combustion chamber , The diameter of the air inlet is larger than the diameter of the air outlet.

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