JP4541257B2 - Spark ignition engine - Google Patents

Description

  The present invention relates to a spark ignition engine, and more particularly to a spark ignition engine capable of promoting the vaporization of injected fuel.

Some conventional spark ignition engines are configured to inject fuel from an injector into an intake port provided in a cylinder head, as in the present invention.
This type of engine has an advantage that an air-fuel ratio can be obtained more accurately than a carburetor, and excellent exhaust gas characteristics and output characteristics can be obtained.

  However, the conventional engine is configured such that the fuel injection hole of the injector is directed to the intake valve port and fuel injection is started during the intake stroke of the cylinder, and the injected fuel passes through the intake valve port and burns together with the intake air. It flows into the chamber.

The above prior art has the following problems.
<Problem> Evaporation of the injected fuel tends to be insufficient.
Since the injected fuel has no room to absorb heat in the intake port, its vaporization tends to be insufficient. For this reason, it is difficult to improve various characteristics such as exhaust gas characteristics, output characteristics, and fuel consumption characteristics.

  An object of the present invention is to provide a spark ignition engine capable of solving the above-described problems, that is, a spark ignition engine capable of promoting vaporization of injected fuel.

Invention specific matters of the invention according to claim 1 are as follows.
As illustrated in FIG. 1, in a spark ignition engine configured to inject fuel from an injector (3) into an intake port (2) provided in a cylinder head (1),
As illustrated in FIGS. 1, 2 (A), (B), and FIG. 5, the fuel injection holes (35) and (36) of the injector (3) are directed toward the inner wall surface of the intake port (2).
As illustrated in FIG. 3, a four-cycle in-line two-cylinder structure has a crankpin phase difference of 360 °, and as illustrated in FIG. 2B, the compression stroke of one cylinder during one cycle In the two synchronization periods synchronized with the exhaust stroke of the other cylinder, fuel injection is started (3a) once per synchronization period with a phase difference of a crank angle of 360 °. Make the fuel collide with the inner wall of the intake port (2),
As illustrated in FIG. 1, when viewed in a direction parallel to the cylinder center axis (30) (31), the cylinder head (1) perpendicular to the left-right direction is the direction of arrangement of the plurality of cylinders (5) (6). The width direction of the front and rear direction, any one of them as the back,
As illustrated in FIG. 1, one throttle body (7) is used for a pair of adjacent left and right cylinders (5) and (6), and this throttle body (7) is arranged behind the cylinder head (1). The throttle body (7) is provided with one throttle intake passage (7a) and one throttle valve (8),
As illustrated in FIG. 1, a central intake port wall (34) is led out from between the valve ports (5a) and (6a) of the left and right cylinders (5) and (6) toward the throttle intake passage (7a). The central intake port wall (34) gradually narrows in the left-right direction as it approaches the throttle intake passage (7a), and in the cylinder head (1), the intake port (2) is connected to one intake port. the branched structure of V-shaped toward each intake valve port (5a) (6a) of the inlet (4) right and left cylinders adjacent to each other from (5) (6), formed in the left and right of the central intake port wall (34) through the intake port (2) which is, each valve port and (5a) (6a) without the intervention of the intake manifold, is communicated into the one throttle intake passage (7a), next to each other in series two-cylinder fit the left and right cylinders (5) each intake valve ports of (6) (5a) (6a) is in the intake port of the branching structure of the V-shaped (2) , Without using the intake manifold, a structure in which the intake air is supplied,
As illustrated in FIG. 1, one injector (3) is attached to the one throttle body (7), and as illustrated in FIG. 1, the front end of the injector (3) is connected to the front central intake port wall ( 34), left and right fuel injection holes (35), (36) are arranged at the front end of the injector (3), and the fuel injected simultaneously from the left and right fuel injection holes (35), (36) is divided into left and right. and the left and right respectively central intake port wall (34) and so as to collide with the inner wall surface of the intake port of the V-shaped (2), spark-ignition engine, characterized in that.

(Invention according to Claim 1)
<Effect> Vaporization of injected fuel is promoted.
As illustrated in FIG. 1 and FIG. 2 (A), the injected fuel collides with the inner wall surface of the intake port (2), so that the fuel contacts the collision location and spreads to the periphery thereof, The heat of the inner wall surface of the intake port (2) is received and its vaporization is promoted. In the present invention, as illustrated in FIG. 2B, since fuel injection is started (3a) during the exhaust stroke, the vaporization time can be made longer than when fuel injection is started during the intake stroke. , Advantageous for vaporization. Further, during the exhaust stroke, compression heat, combustion heat, and exhaust heat are stored on the inner wall surface of the intake port (2) through the compression stroke, explosion stroke, and exhaust stroke. The temperature of the wall surface is high, which is also advantageous for vaporization.

<Effect> The number of parts can be reduced.
As illustrated in FIG. 1, since one throttle body (7) is used for a pair of adjacent left and right cylinders (5) and (6), the number of throttle bodies (7) may be half the number of cylinders. The number of parts can be reduced.

<Effect> It is possible to prevent the fuel from being vaporized in the injector.
As illustrated in FIGS. 1 and 2A, since the injector (3) is attached to the throttle body (7), the injector (3) is changed from the cylinder head (1) to the case where the injector is attached to the cylinder head. The heat input to the fuel can be suppressed, and the vaporization of the fuel in the injector (3) can be prevented.

<Effect> The number of parts can be reduced.
As illustrated in FIG. 1, since one injector (3) is used for one throttle body (7), the number of injectors (3) can be half of the number of cylinders, and the number of parts can be reduced. it can.

<Effect> An equal amount of fuel can be accurately distributed to the left and right cylinders.
As illustrated in FIG. 1 and FIG. 5, fuels injected simultaneously from left and right fuel injection holes (35) and (36) are injected into the left and right sides of the central intake port wall (34), respectively. (2) The cylinders on the left and right sides (5), (6) are compared with the case where the fuel injected from a single fuel injection hole collides with the central intake port wall and is diverted to the left and right. An equal amount of fuel can be accurately distributed to each other.

<Effect> The injector structure and injection control are simplified.
As illustrated in FIG. 1, since the fuel is injected from the left and right fuel injection holes (35) and (36) at the same time, the structure of the injector (3) and the injection are compared with the case of injecting at different times. Control is simplified.

<Effect> It is advantageous for vaporization of injected fuel.
As illustrated in FIG. 2B, during one cycle, fuel injection is started (3a) in two synchronization periods in which the compression stroke of one cylinder and the exhaust stroke of the other cylinder are synchronized. This is advantageous for vaporizing the injected fuel. During this period, compression heat, combustion heat, and exhaust heat are accumulated on the inner wall surface of the intake port (2) from one cylinder through the compression stroke, explosion stroke, and exhaust stroke, and from the other cylinder This is because the heat of compression during the compression stroke is transmitted and the temperature of the inner wall surface of the intake port is high.

<Effect> The state of the fuel distributed to the left and right cylinders can be made uniform.
As illustrated in FIG. 2B, since the start of fuel injection (3a) performed twice in one cycle is performed with a phase difference of a crank angle of 360 °, the left and right cylinders (5) ( The state of the fuel distributed to 6) can be made uniform. When this phase difference deviates from 360 °, the crank angle from the start of the first fuel injection (3a) to the start of the intake stroke of one cylinder in one cycle and the start of the second fuel injection (3a) The crank angle until the intake stroke of the other cylinder starts is different from that of the other cylinder, and it is difficult to equalize the state of fuel distributed to the left and right cylinders (5) and (6).

<Effect> The width of the throttle body in the left-right direction can be shortened.
As illustrated in FIG. 1, the central intake port wall (34) is gradually narrowed in the left-right direction as it approaches the throttle intake passage (7 a), so that the width in the left-right direction is constant. Compared to the above, the width of the throttle body (7) in the left-right direction can be shortened.

<Effect> It is advantageous for vaporization of injected fuel.
As illustrated in FIG. 1, the intake port (2) is connected to the intake valve ports (5) a (6a) of the left and right cylinders (5) and (6) adjacent to each other from one intake port inlet (4). 6 and 7, the intake port (2) has a central intake port wall (34) as compared to the case where the intake port (2) is divided into left and right by the central intake port wall (34). The intake ports (2) formed on both sides approach the inter-cylinder portion (38) having a high temperature. For this reason, the temperature of the inner wall surface of the intake port (2) is high, which is advantageous for vaporizing the injected fuel.
(Invention of Claim 2)
In addition to the effect of the invention according to claim 1, the following effect is achieved.
<Effect> It is advantageous for vaporization of injected fuel.
As illustrated in FIG. 1 and FIG. 2 (A), the fuel injected separately at the front and rear is collided with the left and right sides of the central intake port wall (34) and the inner wall surface of the intake port (2). The injected fuel spreads over a wide range in the front-rear direction on the inner wall surface of the intake port (2). This is advantageous for vaporizing the injected fuel.
(Invention according to claim 3)
In addition to the invention according to claim 1 or claim 2, the following effects are provided.
<Effect> It is advantageous for vaporization of injected fuel.
As illustrated in FIG. 2B, since the fuel injection is started (3a) in the latter half of the exhaust stroke, it is advantageous for vaporization of the injected fuel. This is because in the second half of the exhaust stroke, the time during which the exhaust heat is stored on the inner wall surface of the intake port (2) becomes longer than in the first half of the exhaust stroke.
(Invention of Claim 4)
In addition to the invention according to claim 3, the following operational effects are provided.
<Effect> It is advantageous for vaporization of injected fuel.
As illustrated in FIG. 2B, since the fuel injection is started (3a) in the period of 31 ° to 25 ° before the exhaust stroke ends at the crank angle, it is advantageous for vaporization of the injected fuel. Become. If fuel injection is started at 31 ° before the end of the exhaust stroke at the crank angle, the time during which exhaust heat is stored on the inner wall surface of the intake port (2) is relatively short, and the inner wall surface of the intake port (2) There is a risk that the temperature of the fuel will not rise sufficiently and the vaporization of fuel will be insufficient. Also, if fuel injection is started after 25 ° before the end of the exhaust stroke at the crank angle, the fuel vaporization time is too short and the fuel vaporization may be insufficient. On the other hand, if fuel injection is started (3a) at a crank angle of 31 ° to 25 ° before the end of the exhaust stroke, there is no possibility of the above and it is advantageous for vaporization of the injected fuel.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 to FIG. 5 are diagrams for explaining a spark ignition engine according to an embodiment of the present invention. In this embodiment, a water-cooled vertical two-cylinder gasoline spark ignition engine will be described.

The outline of the embodiment of the present invention is as follows.
As shown in FIG. 4, the cylinder head (1) is assembled to the upper part of the cylinder block (15), and the head cover (16) is assembled to the upper part of the cylinder head (1). An oil pan (17) is assembled to the lower part of the cylinder block (15). A gear case (18) is assembled to the left part of the cylinder block (15), and a belt case (19) is assembled to the left part of the gear case (18). A cooling fan (20) is disposed on the left side of the belt case (19). A flywheel (26) is disposed on the right side of the cylinder block (15). A throttle body (7) is assembled in front of the cylinder head (1). A governor lever (21) of a mechanical governor and a governor spring (22) are arranged in front of the cylinder block (15). This engine includes an electronic fuel injection device.

The outline of the electronic fuel injection device of this engine is as follows.
As shown in FIG. 1, fuel is injected from an injector (3) into an intake port (2) provided in a cylinder head (1). A throttle valve (8) and an injector (3) are attached to the throttle body (7). The throttle valve (8) is linked to the governor lever (21) of the mechanical governor. An intake pressure sensor (9) for detecting the intake pressure downstream of the throttle valve (8), an engine speed sensor (10), and a control means (11) are provided. The intake pressure sensor (9) and the engine speed are provided. The number sensor (10) is linked to the injector (3) via the control means (11), and the intake pressure detected by the intake pressure sensor (9), the engine speed detected by the engine speed sensor (10), and Based on the above, the control means (11) adjusts the fuel injection amount from the injector (3) according to the calculated intake air amount. Although gasoline is used as the fuel, other liquid fuels or liquefied gas fuels can also be used. A liquid fuel refers to a fuel that is liquid at normal temperature and pressure (15 ° C. to 20 ° C., 760 mmHg), and a liquefied gas fuel refers to a gas that is a gas at normal temperature and pressure but is liquid under pressure. Since the present invention promotes the vaporization of the fuel, the effect is conspicuous when a liquid fuel that is hard to vaporize is used rather than a gas fuel that is easily vaporized after fuel injection.

The details of the electronic fuel injection device are as follows.
As shown in FIG. 2 (A), the injector (3) is attached to the upper portion of the throttle body (7). As shown in FIG. 1, the injector (3) is connected to a fuel pump (24) provided in the fuel tank (23). Fuel is pumped from the fuel tank (23) to the injector (3) by a fuel pump (24). Then, the fuel injection amount is adjusted by controlling the fuel injection period from the injector (3) by the control means (11). The control means (11) is a microcomputer. The control means (11) also controls the ignition timing.

The device of the electronic fuel injection device is as follows.
As shown in FIGS. 1, 2 (A), (B), and FIG. 5, the four-cycle series 2 in which the fuel injection holes (35) and (36) of the injector (3) are directed toward the inner wall surface of the intake port (2). With the cylinder structure, the phase difference of the crankpin is 360 ° and the phase difference of the crank angle is 360 ° in two synchronization periods in which the compression stroke of one cylinder and the exhaust stroke of the other cylinder are synchronized during one cycle. Thus, the fuel injection is started (3a) only once per synchronization period, and the injected fuel collides with the inner wall surface of the intake port (2).

As shown in FIG. 1, when viewed in a direction parallel to the cylinder center axis (30) (31), the cylinder head (1) is orthogonal to the direction of arrangement of the two cylinders (5) (6) in the left-right direction. One throttle body (7) is used for a pair of adjacent left and right cylinders (5) and (6), with the width direction of the cylinder being the front-rear direction and any one of them being the rear, and this throttle body (7) is a cylinder Arranged behind the head (1), the throttle body (7) is provided with one throttle intake passage (7a) and one throttle valve (8). A central intake port wall (34) is led out from between the valve ports (5a) and (6a) of the left and right cylinders (5) and (6) toward the throttle intake passage (7a), and the central intake port wall (34) In the cylinder head (1), the intake port (2) is adjacent to each other from one intake port inlet (4) so that the width in the left-right direction gradually becomes narrower as it approaches the throttle intake passage (7a). fit the left and right cylinders (5) (6) each intake valve ports for (5a) a branched structure V-shaped towards the (6a), the intake port formed in the left and right of the central intake port wall (34) (2) The valve ports (5a) and (6a) are communicated with the throttle intake passage (7a) without an intake manifold. Left and right cylinders adjacent to each other in series two-cylinder (5) each intake valve ports of (6) (5a) (6a) is by the intake port of the branching structure of the V-shaped (2), without using the intake manifold The intake air is supplied.

As shown in FIGS. 1 and 2A, an injector (3) is attached to the throttle body (7). One injector (3) is used for one throttle body (7). As shown in FIG. 1, the front end of the injector (3) faces the front central intake port wall (34), and left and right fuel injection holes (35) and (36) are arranged at the front end of the injector (3). , collisions fuel injected simultaneously divided into right and left from the left and right of the fuel injection holes (35) (36), left and right, respectively the central intake port wall (34), the inner wall surface of the intake port of the V-shaped (2) I try to let them. As shown in FIG. 5, the left and right fuel injection holes (35) and (36) are paired, and two pairs are arranged at the front end of the injector (3), as shown in FIGS. the fuel injected at the same time is divided into front and rear from the two pairs ones, left and right, respectively the central intake port wall (34), the inner wall surface of the intake port (2), and so as to collide shifted back and forth. Further, the fuel is injected from the left and right fuel injection holes (35) and (36) at the same time.

  As shown in FIG. 2A, the direction of the cylinder axis (30) (31) is the vertical direction, the head cover (16) is up, the cylinder block (15) is down, and the crankshaft (37 ), The injected fuel is injected obliquely downward from the port inlet (4) of the intake port (2) into the intake port (2), and below the inner wall surface of the intake port (2). Collide from above diagonally. In FIG. 1, FIG. 2 (A), and FIG. 5, the direction of fuel injection is shown by the arrow. 1 and 2A, the fuel collides with the inner wall surface of the intake port (2) at the tip position of the arrow.

  As shown in FIG. 1, the width of the central intake port wall (34) in the left-right direction is gradually narrowed as it approaches the throttle intake passage (7a). The intake port (2) has a V-shaped branch structure from the single intake port inlet (4) toward the intake valve ports (5a) and (6a) of the left and right cylinders (5) and (6) adjacent to each other. . As shown in FIG. 1, the fuel injected from the left and right fuel injection holes (35) and (36) at the same time is injected to the left and right of the central intake port wall (34). ) Collides with the inner wall surface of (33). Since this engine has two cylinders and the intake port (2) branches in a V shape, there is no need to use an intake manifold.

The details of the injection start timing are as follows.
As shown in FIG. 2 (B), with a 4-cycle in-line 2-cylinder structure, the crankpin phase difference is 360 °, and the compression stroke of one cylinder and the exhaust stroke of the other cylinder are synchronized during one cycle. The fuel injection is started (3a) during the two synchronization periods. That is, as shown in FIG. 2B, during the period in which the first cylinder (5) is in the compression stroke and the second cylinder (6) is in the exhaust stroke, it is directed toward the inner wall surface of the intake port (2). Then, fuel injection from the injector (3) is started (3a). Conversely, during the period in which the second cylinder (6) is in the compression stroke and the first cylinder (5) is in the exhaust stroke, it is directed toward the inner wall surface of the intake port (2) from the injector (3). Fuel injection is started (3a). The start timing of fuel injection is also controlled by the control means (11). Reference numerals (39) and (40) in FIG. 3 denote crank pins.

  Specifically, as shown in FIG. 2 (B), during the period in which the first cylinder (5) is in the latter half of the compression stroke and the second cylinder (6) is in the latter half of the exhaust stroke, the injector (3) Fuel injection is started (3a). The fuel injection from the injector (3) is started (3a) while the second cylinder (6) is in the second half of the compression stroke and the first cylinder (5) is in the second half of the exhaust stroke.

  Preferably, the first cylinder (5) has a crank angle of 31 ° to 25 ° before the end of the compression stroke, and the second cylinder (6) has a crank angle of 31 ° to 25 ° before the end of the exhaust stroke. The fuel injection from the injector (3) is started (3a). In addition, during the period when the second cylinder (6) is at a crank angle of 31 ° to 25 ° before the end of the compression stroke and the first cylinder (5) is at the crank angle of 31 ° to 25 ° before the end of the exhaust stroke, the injector The fuel injection from (3) is started (3a). There is a risk that the amount of heat stored in the cylinder head (1) will be insufficient at an earlier time, and there is a risk that the fuel vaporization time will be insufficient at a later time.

  The start of fuel injection (3a), which is performed twice in one cycle, is performed with a phase difference of a crank angle of 360 °. Similar to the adjustment of the fuel injection amount, the control means (11) starts the fuel injection based on the intake pressure detected by the intake pressure sensor (9) and the engine speed detected by the engine speed sensor (10). Adjust the time of 3a).

Other ideas are as follows.
As shown in FIG. 1, the engine temperature detecting means (12), the intake bypass passage (13) for communicating the intake upstream side and the intake downstream side of the throttle valve (8), and the intake bypass passage (13) are opened and closed. A bypass valve (14) for connecting the engine temperature detection means (12) to the bypass valve (14) via the control means (11), and when the engine temperature is lower than a predetermined value, the control means ( 11) opens the bypass valve (14). Although the coolant temperature detection sensor is used for the engine temperature detection means (12), an engine temperature detection sensor may be used instead.

When the rate of decrease of the intake pressure detected by the intake pressure sensor (9) is larger than a predetermined value, the bypass valve (14) is opened for a predetermined time by the control of the control means (11). When the rate of decrease of the intake pressure detected by the intake pressure sensor (9) is larger than a predetermined value, the bypass valve (14) increases as the rate of decrease of the intake pressure increases under the control of the control means (11). Increase the valve opening time. When the rate of decrease of the intake pressure detected by the intake pressure sensor (9) is smaller than a predetermined value, the bypass valve (14) is closed except when the engine temperature is lower than the predetermined value. In addition, the code | symbol (41) in FIG. 1, FIG. 2 (A) is an exhaust port.
This embodiment has the following effects.
<Effect> The engine can be manufactured at low cost.
As illustrated in FIG. 1, the throttle valve (8) is linked to a mechanical governor and is based on the intake pressure detected by the intake pressure sensor (9) and the engine speed detected by the engine speed sensor (10). Since the control means (11) adjusts the fuel injection from the injector (3), the fuel corresponding to the intake air amount can be injected without using expensive electronic parts such as an electronic governor and an air flow sensor. The engine can be manufactured at a low cost.
<Effect> It is possible to stabilize idle rotation during cold weather.
As illustrated in FIG. 1, when the engine temperature is lower than a predetermined value, the control means (11) opens the bypass valve (14), so that the idling rotation during cold can be stabilized. Can do. During cold weather, the rotational resistance increases because the viscosity of the engine oil increases, and the idling rotation tends to become unstable. However, in the present invention, by opening the bypass valve (14) during cold weather, the fuel injection amount is increased by the amount of intake air replenished from the intake bypass passage (13), and this fuel is supplied to the intake port (2). Since it can be quickly vaporized by the heat of the inner wall surface, it is possible to stabilize idle rotation during cold weather.
<Effect> The engine stall can be suppressed.
As illustrated in FIG. 1, when the rate of decrease of the intake pressure detected by the intake pressure sensor (9) is greater than a predetermined value, the bypass valve (14) is controlled for a predetermined time by the control of the control means (11). Since the valve is opened, engine stall can be suppressed. When the mechanical governor is used, if the load suddenly decreases, the throttle valve (8) overshoots to the valve closing side, the intake amount is insufficient, and engine stall may occur due to insufficient mixture. In the present invention, the sign of the overshoot is detected by detecting the reduction speed of the intake pressure, and the intake bypass passage (8) is opened before the overshoot of the throttle valve (8), so Since the shortage of intake air is prevented, engine stall can be suppressed.
<Effect> The engine stall suppressing function can be enhanced.
Since the valve opening time of the bypass valve (14) is lengthened as the rate of decrease of the intake pressure increases, the engine stall suppressing function can be enhanced. The greater the rate of decrease of the intake pressure, the greater the degree of overshoot of the throttle valve (8) toward the valve closing side, and the time for the throttle valve (8) to return to the proper opening is delayed, and engine stalling tends to occur. For this reason, in the present invention, as the rate of decrease of the intake pressure increases, the valve opening time of the bypass valve (14) is lengthened to enhance the engine stall suppression function.
<Effect> The fuel consumption can be lowered.
As the rate of decrease of the intake pressure is smaller, the valve opening time of the bypass valve (14) is shortened, so that fuel is not supplied unnecessarily and fuel consumption can be lowered.

FIG. 6 shows the first reference form, and FIG. 7 shows the second reference form.
In the first reference form shown in FIG. 6, the width of the left and right direction of the central intake port wall (34) gradually narrows as it approaches the throttle intake passage (7a), as in FIG. Unlike the one shown in FIG. 1, the intake port (2) is not a branched structure, but is a separated structure separated left and right with a central intake port wall (34) interposed therebetween.
In the second reference form shown in FIG. 7, unlike the one in FIG. 1, the left and right widths of the central intake port wall (34) are uniform, and the intake port (2) is not a branched structure, but the central intake port wall (34 ) Between the left and right sides.
These reference forms have the same configuration and function as the embodiment except for the above differences. 6 and 7, the direction of fuel injection is indicated by an arrow. 6 and 7, the fuel collides with the inner wall surface of the intake port (2) at the tip position of the arrow.

It is a cross-sectional top view of the cylinder head of the engine which concerns on embodiment of this invention, and its circumference | surroundings. 2A is a cross-sectional view taken along the line II-II in FIG. 1, and FIG. 2B is a diagram for explaining the timing of starting fuel injection. 1 is a longitudinal sectional view of an engine according to an embodiment of the present invention. It is an external view of the engine of FIG. It is a front view of the injector front end used with the engine of FIG. It is a schematic diagram of Reference Embodiment 1 of the present invention, and corresponds to FIG. It is a schematic diagram of the reference form 2 of the present invention, and corresponds to FIG.

  (1) ... Cylinder head, (2) ... Intake port, (3) ... Injector, (3a) ... Start, (4) ... Port inlet, (5) ... Cylinder, (6) ... Cylinder, (5a) · ( 6a) Intake valve port, (7) Throttle body, (7a) Throttle intake passage, (8) Throttle valve, (9) Intake pressure sensor, (10) Engine speed sensor, (11) Control means, (12) Engine temperature detection means, (13) Intake bypass passage, (14) Bypass valve, (30) Cylinder center axis, (31) Cylinder center axis, (34) Central intake port Wall, (35) Fuel injection hole, (36) Fuel injection hole, (37) Center axis of crankshaft.

Claims (4)

In a spark ignition engine configured to inject fuel from an injector (3) into an intake port (2) provided in a cylinder head (1),
The fuel injection holes (35), (36) of the injector (3) are directed toward the inner wall surface of the intake port (2),
With a 4-cycle in-line 2-cylinder structure, the crankpin phase difference is 360 °, and during one cycle, the crank angle is divided into two synchronization periods in which the compression stroke of one cylinder and the exhaust stroke of the other cylinder are synchronized. With the phase difference of 360 °, the fuel injection is started (3a) only once per synchronization period, and the injected fuel collides with the inner wall surface of the intake port (2).
When viewed in a direction parallel to the cylinder center axis (30) (31), the arrangement direction of the plurality of cylinders (5) (6) is the left-right direction, and the width direction of the cylinder head (1) orthogonal thereto is the front-rear direction. Any one of them as the back,
One throttle body (7) is used for a pair of adjacent left and right cylinders (5) and (6), and this throttle body (7) is arranged behind the cylinder head (1). Provided with one throttle intake passage (7a) and one throttle valve (8),
A central intake port wall (34) is led out from between the valve ports (5a) and (6a) of the left and right cylinders (5) and (6) toward the throttle intake passage (7a), and the central intake port wall (34) In the cylinder head (1), the intake port (2) is adjacent to each other from one intake port inlet (4) so that the width in the left-right direction gradually becomes narrower as it approaches the throttle intake passage (7a). fit the left and right cylinders (5) (6) each intake valve ports for (5a) a branched structure V-shaped towards the (6a), the intake port formed in the left and right of the central intake port wall (34) (2) The left and right cylinders (5) (5) (5) (6) are connected to the one throttle intake passage (7a) without an intake manifold, and are adjacent to each other in two in-line cylinders. by each intake valve ports of 6) (5a) (6a), said intake port of the branching structure of the V-shaped (2), an intake manifold Without using, as a structure in which the intake air is supplied,
One injector (3) is attached to the one throttle body (7), the front end of the injector (3) is directed to the front central intake port wall (34), and the left and right sides of the front end of the injector (3) are The fuel injection holes (35) and (36) are arranged, and the fuel injected from the left and right fuel injection holes (35) and (36) is divided into left and right at the left and right of the central intake port wall (34), respectively. said so as to collide with the inner wall surface of the intake port (2), spark-ignition engine, characterized in that the. The spark ignition engine according to claim 1,
A pair of left and right fuel injection holes (35) and (36) are arranged at the front end of the injector (3), and a pair of fuel is injected into the front and rear of each pair, and the fuel injected at the same time is divided into a central intake port. in the right and left walls (34), the inner wall surface of the intake port (2), and so as to collide shifted back and forth, a spark ignition engine, characterized in that. The spark ignition type engine according to claim 1 or 2,
A spark ignition engine characterized in that fuel injection is started (3a) in the second half of the exhaust stroke of the cylinders (5) and (6). The spark ignition engine according to claim 3,
A spark ignition engine characterized in that fuel injection is started (3a) in a period of 31 ° to 25 ° before the exhaust stroke ends at a crank angle.

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