JP2000018136A - Engine fuel injection valve and fuel injection method - Google Patents

Abstract

(57) [Summary] [Problem] A direct injection engine uses lean fuel combustion (air-fuel ratio 2).
The present invention provides a fuel injection valve and a fuel injection method that improve ignition, suppress soot emission, and realize combustion stability at high rotation speed even when the fuel injection rate is about 0 to 50). A fuel injection unit for directly injecting fuel into a cylinder of an engine, wherein a nozzle portion includes a valve body, a valve seat, a nozzle hole, and a fuel guide, wherein the fuel guides have different turning strengths. A plurality of fuel swirl passages are formed, and the plurality of fuel swirl passages are formed such that a swirl passage having a small swirl strength is closer to the nozzle hole than a swirl passage having a large swirl strength.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection valve for an engine and a fuel injection method for an engine, and more particularly to a fuel injection valve for a fuel injection device of a direct injection engine.

[0002]

2. Description of the Related Art In an ordinary engine, an air-fuel ratio (mass ratio between air and fuel) is used to reduce fuel consumption.
, That is, it is effective to make the amount of fuel in the air-fuel mixture lean to achieve lean combustion. However, when the air-fuel mixture is made lean, ignition of the fuel and propagation of the flame become unstable, and there is a tendency that stable combustion becomes difficult to occur.

[0003] In a direct injection type direct injection engine in which fuel is directly injected into a cylinder of an engine, an air-fuel mixture is collected near an ignition plug in stratified combustion, and stable combustion can be performed even with a lean air-fuel mixture. However, in order to collect the air-fuel mixture near the spark plug in the stratified charge combustion, it is necessary to inject the fuel from the nozzle a little before the ignition timing.
Therefore, the time from fuel injection to ignition is shorter than that of the conventional intake port injection engine,
Since the fuel is likely to be ignited before being sufficiently vaporized, in order to prevent this, it is necessary to promote the vaporization of the fuel by making the fuel droplets small during injection.

[0004] As a conventional technique for atomizing fuel by the nozzle portion of the fuel injection valve, there is a technique described in Japanese Patent Application Laid-Open No. 7-119584. This technology uses a swirl nozzle as a nozzle of a fuel injection valve, and has a sax hole between a swirl generator and an injection hole, and is inclined with respect to the swirl center line around the swirl center line at the swirl generator. The injection hole is drilled in the direction that is set, and the center of each circular hole formed when the sax hole is cut in a plane perpendicular to the swirl turning center line is substantially located at the center of the injection direction of the injection hole. It is.

With this configuration, the friction loss of the swirl fuel in the sax hole is reduced, and the swirl fuel having a strong swirling force is injected from the injection hole. If the swirl force of the swirl fuel is strong, the fuel is atomized. Is promoted. In addition to the strong swirling force of the fuel, the fuel injection pressure is increased by 5
Further atomization is achieved by injecting the fuel at a high pressure of about 12 MPa.

On the other hand, in a diesel engine, fuel is injected at a high pressure (20 MPa or more) without giving a turn to the fuel. In this case, the shape of the fuel spray from the fuel injection valve is as follows:
A relatively solid spray can be formed.

[0007]

However, as described above, in the method in which the fuel is swirled at the time of fuel injection, the shape of the spray is a hollow conical shape, and the fuel has a small amount at the center of the spray. Therefore, there is little opportunity for fuel and air to come into contact with each other and be mixed.There is a locally rich air-fuel mixture, soot is generated, and the air utilization rate is reduced in high load areas, resulting in low output. There are problems such as becoming.

FIG. 19 shows the state of the air-fuel mixture at a partial load in the conventional direct injection type direct injection engine 1 as described above, in which the fuel is simply swirled by the fuel injection valve 20. It is. In the above-mentioned system, when the turning force of the fuel is reduced, the spread angle of the spray 3 is reduced, and a part of the fuel colliding with the piston cavity 6 is
The vaporized fuel 4 is conveyed in the direction of the spark plug 2 on the upper surface of the fuel cell to help stabilize combustion. However, piston 7
There is a problem that most of the fuel intensively collided with the fuel becomes the fuel that forms the fuel liquid film 5 and generates soot.

On the other hand, FIG. 20 shows a state in which the turning force of the fuel is increased in the same conventional direct injection type direct injection engine 1 as in FIG. When the fuel turning force is increased, the collision with the piston 7 is reduced and soot generation can be suppressed. However, since the injected fuel has a hollow spray shape, the fuel sprayed at the center is small and the speed is low. Insufficient fuel (air-fuel mixture) conveyed in the direction of spark plug 2,
Combustion becomes unstable. In particular, in a region where the engine speed N is high, the speed of the air flow increases, and the spray fuel is easily flown. Therefore, there is a problem that the spray speed needs to be increased.

Further, in a system in which fuel is not swirled as in the diesel engine, it is necessary to further increase the pressure in order to promote atomization, and the spray speed increases accordingly. When the spraying speed increases, the cylinder easily collides with the cylinder wall surface, so that there is a problem that soot is generated particularly under a high load.

The present invention has been made in view of such a problem, and an object of the present invention is to provide ignition even when an in-cylinder injection engine is used for lean fuel combustion (air-fuel ratio of about 20 to 50). While reducing soot emissions,
Another object of the present invention is to provide a fuel injection valve and a fuel injection method that realize combustion stability at high rotation speed.

[0012]

In order to achieve the above object,
One aspect of the first basic fuel injection valve of the present invention is to inject fuel directly into a cylinder of an engine, and a valve portion, a valve seat, a nozzle hole, and a fuel guide are provided in a nozzle portion. Wherein the fuel guide body forms a plurality of fuel swirl passages having different swirl strengths, and the plurality of fuel swirl passages include a swirl passage having a small swirl strength located closer to the nozzle hole than a swirl passage having a large swirl strength. It is characterized by being formed.

As a specific mode of the fuel injection valve, the fuel swirl passage is offset by a predetermined distance from an imaginary line intersecting the center axis of the nozzle hole, and the swirl passage having a small swirl strength and the swirl strength are formed. The offset distance is different from the large turning path. In addition, the plurality of fuel swirl passages may be configured such that one or more passages are inclined toward an exit direction of a nozzle hole, and at least one unswirled fuel chamber that does not swirl fuel is formed inside the fuel swirl passage. It is characterized in that the fuel guide has a bypass fuel passage for bypassing fuel from upstream to downstream, and is constituted by a plurality of fuel passages having different passage areas.

According to a second basic aspect of the fuel injection valve of the present invention, the fuel guide has a plurality of fuel guide passages formed on an imaginary line intersecting a central axis of the nozzle hole. The fuel guide passage is characterized in that the fuel flows are configured to collide with each other.

Further, as a third basic aspect of the fuel injection valve of the present invention, the fuel guide body includes a plurality of fuel guide passages formed on an imaginary line intersecting a central axis of the plurality of nozzle holes. A plurality of fuel swirl passages are provided.

In a specific embodiment common to the basic fuel injection valve of the present invention, the fuel swirl passage or the fuel guide passage is a groove or a hole, and the valve body is a sphere or a cone. The passage area between the valve body and the valve seat is reduced toward the nozzle outlet to prevent the generation of a cavity.
On the other hand, in the fuel injection method of the present invention for directly injecting fuel into a cylinder of an engine, in direct fuel injection into a cylinder, two or more fuels having different spray angles are injected on the same central axis,
The two or more fuels having different spray angles are characterized by injecting a spray formed by a fuel having a small spray angle before a spray formed by a fuel having a large spray angle.

According to another aspect of the fuel injection method of the present invention for injecting fuel directly into a cylinder of an engine, two or more fuel sprays having different particle diameters are injected on the same central axis. In two or more different fuel sprays, a spray formed by a fuel having a large particle diameter is sprayed earlier than a spray formed by a fuel having a small particle diameter, and a spray angle is reduced. I have.

In the first basic fuel injection valve according to the present invention having the above-described structure, when spraying the fuel, the fuel spray formed by one fuel swirl passage and having a small spray spread angle is first sprayed. Jetting, and then jetting a spray having a large spray spread angle formed by another fuel swirl passage,
As a result, a spatially solid spray can be formed in the cylinder of the engine, and the spray fuel having a small divergence angle can be conveyed in the direction of the spark plug first, so that the emission of soot can be suppressed while suppressing the emission of soot. Can be stabilized.

Further, the second basic fuel injection valve according to the present invention does not provide offsets in a plurality of fuel guide passages of the fuel guide body, but on an imaginary line passing through the center of the fuel guide body and intersecting at right angles with each other. Since a plurality of fuel guide passages are provided, the fuel is injected from the opposed fuel guide passages to collide. Since the colliding fuel has a velocity component directed toward the center, the fuel becomes a solid fuel spray in which the fuel also exists at the center of the fuel spray.

Further, a third basic fuel injection valve according to the present invention forms a conical spray by a plurality of fuel guide passages,
Since the inner spray is generated by collision and the outer spray is swirled by the fuel swirl passage, a spatially solid spray can be formed in the cylinder of the engine. To prevent the fuel from concentrating too much on the center of the spray, the total cross-sectional area of the fuel guide passage with which the fuel collides is made smaller than the total cross-sectional area of the fuel swirl passage.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a fuel injection valve for an engine according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a direct injection engine 1 according to this embodiment.
1 shows the overall configuration including the control system of FIG.
In the cylinder injection engine 1, an intake pipe 47 and an exhaust pipe 48 are connected to a head section 50 of a cylinder 51, and an intake valve 46 and an exhaust valve 49 are arranged at the connection section. The head part 50 has a spark plug 2
A throttle valve 41 driven by an electric motor 42 is disposed upstream of the intake pipe 47, and an air flow meter 4 is provided in the intake pipe 47.
3 and a throttle valve opening detector 44 are attached. A piston 7 is disposed in the cylinder 51 so as to be vertically slidable, and a piston cavity 6 is formed on an upper surface of the piston 7.

The control device 45 of the engine 1 receives signals from the air flow meter 43 and the throttle valve opening detector 44 and signals such as the engine speed N and the accelerator opening α to calculate the ignition timing and fuel amount. Then, a signal is output to the ignition plug 2, the fuel injection valve 20, and the like to perform control. Inhalation pipe 47
Is measured by an air flow meter 44,
The amount of air is controlled by the throttle valve 41. The throttle valve 41
Is the accelerator pedal opening α by the electric motor 42.
May be controlled according to

When the engine 1 is partially loaded, the fuel injection valve 20 injects fuel at such a timing that the fuel remains in the piston cavity 6 (compression stroke—40 to 60 degrees before top dead center), and is ignited by the spark plug 2. However, during high-load operation, fuel is injected at a timing (intake stroke—about 330 to 180 degrees before top dead center) in which the fuel is uniformly dispersed in the cylinder 51.

The operating conditions of the engine 1 are determined by a signal from the air flow meter 43, the engine speed N, the throttle valve opening 44, the accelerator opening α and the like by the control device 45.
The fuel injection amount and injection timing of the fuel injection valve 20 are determined accordingly.

FIG. 2 shows the configuration of the fuel injection valve 20 of the present embodiment. The fuel injection valve 20 includes a fuel inlet connector section 27, a solenoid coil section 28, an electric connector section 29, a movable core 30, and a nozzle section 22 with a nozzle 31.
And a spherical valve element 21 at the end of the movable core 30.
The movable core 30 is pressed against the valve seat 25 by the coil spring 26. A fuel guide 23 is arranged around the spherical valve body 21 in the nozzle portion 22. When the solenoid coil portion 28 is energized, the movable core 30 is excited and acts to lift the movable core 30 by overcoming the urging force of the coil spring 26. When the movable core 30 is pulled up, the spherical valve 2
1 and the valve seat 25 open.

The fuel guided to the fuel injection valve 20 is supplied into the fuel inlet 27 from the fuel passage 27 a of the fuel inlet connector 27, and passes through the fuel guide 23, the spherical valve 21 and the valve seat 25 through the nozzle. 31 directly injects into the combustion chamber of the engine 1.

The spherical valve element 21 is usually provided with a spring 2
By the urging force of No. 6 and the fluid pressure of the fuel (5 MPa or more), the fuel is pressed against the valve seat 25 and the ejection of the fuel from the nozzle 31 is stopped.

When a current of about 100 volts is input through the electric connector 29 and a current flows through the solenoid 28, the valve 23 is pulled up by the electromagnetic force generated by the solenoid 28. The stopper 24 allows the position to be pulled up to be constant, thereby increasing the fuel measurement accuracy.

As described above, opening and closing of the spherical valve 21 from the valve seat 25 can be controlled by turning on and off the voltage of the solenoid coil portion 28, and the amount of fuel injected from the nozzle 31 can be controlled. It is desirable to control the current applied to the solenoid coil section 28 so that a large amount of current flows first to improve the responsiveness, and then to reduce the current to prevent heat generation of the solenoid.

FIGS. 3A and 3B show a first embodiment of the fuel guide 23 of the fuel injection valve 20 shown in FIG. 2, wherein FIG. 3A shows a horizontal section and FIG. 3B shows a vertical section. The fuel guide 23
Has a valve guide hole 35 for guiding the spherical valve 21 at the center thereof, and a fuel guide passage surface 36 around the valve guide hole 35. A fuel swirl hole 33b and a fuel swirl groove 34a are formed in parallel with virtual lines XX and YY passing through the center of the fuel guide 23 and intersecting at right angles to each other. The fuel swirl hole 33b and the fuel swirl groove 34a give swirl to the fuel, widen the spray angle of the fuel,
It is intended to atomize the fuel.

The offset amount L1 of the fuel swirl groove 34a is:
The fuel swirl hole 33b is smaller than the offset amount L2, and the opening of the fuel swirl groove 34a is located at a lower position close to the nozzle 31. With such a configuration, when spraying the fuel, the spray having a small spray spread angle of the fuel formed by the fuel swirl groove 34a is jetted first, and then the spray spread angle formed by the fuel swirl hole 33b is increased. The spray can be ejected. As a result, a spatially solid spray can be formed, and the spray fuel having a small spread angle can be conveyed in the direction of the spark plug 2 first, so that the soot is suppressed and the combustion is stabilized. be able to.

FIG. 4 shows a second embodiment of the fuel guide 23. In the first embodiment shown in FIG. 3, the fuel swirl grooves 34a and the fuel swirl holes 33b have different vertical positions of the openings, but in the second embodiment, the fuel swirl grooves 34a and 33b have different structures.
a and the vertical position of the fuel swirl groove 33a are the same.
When the offset amount of the fuel swirl groove or hole is small, the spread angle of the spray is small, and the spray speed increases. Fuel swirl groove 34
From the fuel forms a spray 3b, and the fuel swirl groove 3
The fuel ejected from 3a forms spray 3a with a larger swirling force. The conventional fuel injection valve is a single spray of only the spray 3a or the spray 3b, and is a hollow spray without fuel inside. If the vertical position of the opening of the fuel swirl groove or the hole is not changed, machining of the two swirl grooves can be performed on the same surface, so that there is an advantage that machining is easy.

FIG. 5 shows the fuel guide 23 of the fuel injection valve 20.
This shows a third embodiment of the present invention. The fuel swirl hole 34b is formed obliquely downward in the nozzle direction. Meanwhile, the fuel swirl hole
The opening 33b is located at the upper part and increases the offset L2. The spray formed by the fuel swirl holes 33b becomes the spray 3a having a large spread angle. The offset L1 of the fuel swirl hole 34b is smaller than the offset L2 of the fuel swirl hole 33b, and the swirl force is small. In addition, since the nozzle is inclined at an angle to the nozzle direction, the spray 3b having a small spread angle is provided.
To form Further, by obliquely opening the fuel swirl hole 34, the fuel can easily flow along the lower part of the valve body 21, and there is an effect that a cavity downstream of the valve body 21 generated by a normal swirl nozzle is reduced, and the solid state is realized. Is promoted.

FIG. 6 shows the fuel guide 23 of the fuel injection valve 20.
Is a fourth embodiment of the present invention. The fuel swirl groove 33a,
An annular groove 37 is provided in the opening of 34a. In this case, before the fuel swirled from the fuel swirl grooves 33a and 34a is jetted, unturned fuel is spouted from the annular groove 37. The unswirl fuel is atomized by the pressure of the fuel, but forms a spray having a small spray divergence angle, and the fuel swirl grooves 33a, 34a
The fuel is ejected prior to passing through the fuel, and is conveyed in the direction of the spark plug 2. If the amount of unswirled fuel is too large, the fuel concentrates on the piston 7 and collides with it, so that combustion with soot tends to occur. Therefore, the fuel injection amount is set to about 30% or less of the total injection amount at a partial load. For example, the volume of the annular groove 37 is set to about 4.5 mm ³ . FIG. 7 shows a fifth embodiment of the fuel guide 23 of the fuel injection valve 20. The fuel guide body 23 of the fifth embodiment includes a bypass passage 5 separate from the fuel swirl groove 34a and the fuel swirl hole 33b.
5, 56 are provided. Since the fuel passing through the bypass passages 55 and 56 is jetted without applying a swirling force, a spray having a small spray spread angle can be formed. The spray formed by the fuel swirl groove 33a and the fuel swirl hole 34b is distributed around the periphery, so that solidification can be realized.

FIG. 8 shows the fuel guide 23 of the fuel injection valve 20.
Of the sixth embodiment. By providing the opening of the bypass passage 55 only at a specific portion, the spray can be formed in a direction different from the nozzle axis. Further, as shown in a seventh embodiment of the fuel guide body 23 in FIG. 9, the area of the bypass passage 55a at a specific portion of the bypass passage 55 is made unequal to the area of the other bypass passages 55, so that the nozzle The spray can be formed in a direction different from the nozzle axis by controlling the velocity distribution in the inside. There is an advantage that the fuel injection direction can be set freely under conditions where the mounting layout of the fuel injection valve 20 is restricted. In addition, there is no need for processing for bending the nozzle in a specific direction.

FIG. 10 shows the fuel guide 2 of the fuel injection valve 20.
13 shows an eighth embodiment of the present invention. The fuel guide 2
Numeral 3 is provided on imaginary lines XX, YY passing through the center of the fuel guide 23 and intersecting at right angles with each other without offsetting the fuel swirl holes 33b, 34b. The fuel flows out from the fuel tanks 33b and 34b to collide with each other. Since the colliding fuel has a velocity component directed toward the center, the fuel becomes a solid fuel spray in which the fuel also exists at the center of the fuel spray.

FIG. 11 shows the fuel guide 2 of the fuel injection valve 20.
13 shows a ninth embodiment of the present invention. Fuel swirl groove 33a
And the fuel swirl hole 34b to form a conical spray, and a spray is formed inside the conical spray by collision. That is, the fuel is swirled and sprayed while offsetting the fuel swirl groove 33a, and the fuel swirl hole 34b is provided on the imaginary lines XX and YY passing through the center of the fuel guide 23 and intersecting at right angles to each other. The fuel is caused to flow out from the opposed fuel swirl holes 34b, 34b and collide. To prevent the fuel from concentrating too much on the center of the spray, the total cross-sectional area of the groove where the fuel collides is made smaller than the total cross-sectional area of the guide groove.

FIG. 12 shows the fuel guide 2 of the fuel injection valve 20.
3 shows an example in which the spherical valve element 21 in the first embodiment is changed. In the present embodiment, the spherical valve element 21 is formed in a conical shape. Due to the conical shape, a cavity is hardly present downstream of the spherical valve element 21, and hollowing of the fuel spray can be suppressed. The smaller the cone angle α, the smaller the spray angle and the higher the solidity.

FIG. 13 shows the fuel guide 2 of the fuel injection valve 20.
FIG. 12 shows the first embodiment of FIG. 3 in which the valve body has a conical shape as shown in FIG. As shown in FIG.
The gap 50 between the nozzle and the valve seat 25 is made narrower as approaching the nozzle 31. As shown in FIG.
When the gap 50 is made larger as the distance from the nozzle becomes closer, the flow becomes enlarged and a cavity is likely to occur. When a cavity is formed, a fuel-free hollow portion is formed downstream of the valve seat 25, and the spray tends to have a hollow shape. By further reducing the gap 50 between the valve seat 25 and the valve seat 25 as shown in (b), the flow can be stabilized, the generation of cavities can be prevented, and the spray can be solidified. Suppression of the cavity is also effective in stabilizing the injection amount, and has the advantage of improving measurement accuracy.

FIG. 14 shows the relationship between the combustion stability and the degree of soot generation with respect to the spray spread angle of the fuel spray by the fuel injection device of the engine of the present embodiment and the conventional example. As understood from FIG. 14, when the spread angle of the spray is reduced, the stability of combustion is improved even with the hollow spray, but at the same time, the discharge of soot increases. For this reason, it is difficult to achieve both combustion stability and soot, but in this embodiment,
The solidification of fuel spray prevents concentrated spray of fuel spray on the piston, and suppresses soot emission while stabilizing combustion.

FIG. 15 shows the relationship between the combustion stability and the emission characteristics of soot when the fuel injection timing and the ignition timing are changed in the present embodiment. When the ignition is performed at about 30 degrees after the fuel injection, the fuel is stabilized. This coincides with the time required for the injected fuel to reach the spark plug. Soot becomes lower when the fuel injection timing is advanced. In the conventional method, the increase in soot is even larger (not shown). This is because concentrated collision with the piston can be prevented. However, if the injection timing is too fast, the combustion will diffuse, and there will be no fuel near the spark plug, resulting in poor combustion stability. For this reason,
It is understood that solid spraying in which fuel does not concentrate and collide with the piston even when the injection timing is delayed is effective.

As described above, one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above embodiment, and does not depart from the spirit of the present invention described in the claims. Various changes can be made in the design.

For example, in the above embodiment, the fuel guide of the fuel injection valve is provided with two fuel swirl grooves (or fuel swirl holes) having different swirl strengths. Although the swirling flow is sprayed on the same central axis, three or more fuel swirling grooves (or fuel swirling holes) are provided on the fuel guide at different positions, and the swirling strengths are different. One or more fuel swirl flows may be generated.

Further, in the above-described embodiment, the fuel injection device in which fuel is injected from the side by the fuel injection valve has been described. However, as shown in FIGS. The present invention can be implemented even with the configuration provided in the above.

That is, as shown in FIG. 16, when the fuel 3 is injected from the fuel injection valve 20 during the compression stroke of the engine (FIG. 16 (a)), the timing at which the combustible mixture comes (FIG. 16) In (b)), the fuel is ignited by the ignition plug 2.

In FIG. 17, the fuel 3 (FIG. 17 (a)) injected from the fuel injection valve 20 in the latter half of the intake stroke is prevented from diffusing by the air swirl, and a combustible mixture comes ( In FIG. 17B, ignition is performed by the ignition plug 2. In this case, since the time from fuel injection to ignition is relatively long and the collision with the piston 7 is small,
Vaporization is promoted, soot is easily reduced.

Further, in FIG. 18, the fuel 3 (FIG. 18 (a)) injected from the fuel injection valve 20 in the latter half of the intake stroke is conveyed in the direction of the spark plug 2 by air tumble, and a combustible mixture comes ( In FIG. 18B, ignition is performed by the ignition plug 2. In this case, since the time from injection of fuel to ignition is relatively long, and collision with the piston 7 is small, vaporization is promoted and soot is easily reduced, but mixed with the ignition plug 7 depending on the engine speed. Since the time required to reach the energy differs, it is necessary to perform precise control according to the number of revolutions.

Although the above description is for stratified charge combustion, the fuel injection device of the present invention achieves the solidification of fuel spray even at high load operation of the engine, thereby enabling the mixing of air and fuel. Is promoted, soot emission can be suppressed and high output can be expected.

The fuel injection valve 20 shown in FIG.
As in the first embodiment of the fuel guide body 23, the offset amount L
1 is set smaller than the offset amount L2, the offset amount L1 is set to be smaller than the offset amount L2.
The swirling intensity applied to the fuel is small relative to the ones.
By increasing the swirling and increasing the spray angle to reduce the thickness of the liquid film, atomization can be promoted and the spray particle diameter can be reduced. This means that when the offset amount is reduced, the spray angle is reduced and the spray particle diameter is increased, while by increasing the offset amount, the spray angle is increased and the spray particle size is reduced.

In order to stabilize the lean combustion, it is important to surely supply the air-fuel mixture to the spark plug. In the first embodiment of the fuel guide 23 of the fuel injection valve 20, when the spray angle of the fuel is small, the particle diameter becomes large, and the fuel spray is hardly affected by the air flow in the cylinder. It is supplied in the direction of the spark plug by the energy.
This fuel spray with a large particle diameter can keep the spray speed high, and is vaporized on the upper surface of the piston cavity.
Since the fuel reaches the spark plug, the combustion can be stabilized. However, if there are too many sprays having a large particle size, vaporization will be insufficient and smoke will be generated.

The fuel spray having a large spray angle and a small particle diameter is easily affected by the air flow and is difficult to reach the spark plug. However, since the particle diameter is small, vaporization on the piston cavity is promoted. This has the effect of reducing smoke.

By spraying the fuel spray having a large particle size and the fuel spray having a small particle size in combination, it is possible to realize a fuel injection method which enables both promotion of ignition in lean combustion and reduction of smoke. .

That is, ignition is performed by a fuel spray having a large particle diameter at the initial stage of spraying, and thereafter, a main fuel spray having a small particle diameter is dispersed in the cavity, and a mixture based on the fuel spray having a small particle diameter is formed by the ignition flame. And propagated to perform combustion.

As described above, a method of injecting a fuel spray having a large particle diameter (particle diameter of 20 μm or more) prior to a fuel spray of a small particle diameter (less than 20 μm) and performing both injections on the same central axis. By doing so, it is possible to perform stable lean combustion while suppressing the emission of smoke.

FIG. 21 is an explanatory diagram of the present invention. The injector 1 is arranged, for example, at α = 45 degrees with respect to the piston surface. The fuel spray is formed in the axial direction of the injector 1. If the spray is symmetric, the injector is installed at an angle, so the lower spray in the figure is likely to collide with the piston, forming a liquid film on the piston surface, forming an over-enriched mixture, and causing smoke. More likely to occur.

By deflecting the spray by β with respect to the axial direction of the injector as shown in FIG. 22, the collision amount 40 in the piston direction can be reduced without changing the mounting layout of the injector. However, if β is set too large, the fuel tends to protrude from the piston cavity, and the amount of fuel in the direction of the spark plug decreases, and the stability of the fuel is reduced. Increase or cause dilution of engine oil. Further, even if the spray divergence angle is increased, the reaching length of the spray can be shortened, but the spray easily escapes from the cavity.

As shown in FIG. 23, the arrival lengths P1 and P2 of the spray
By using the different sprays, it is possible to prevent the fuel from adhering in the direction of the piston and to transport the fuel in the direction of the spark plug without protruding the fuel from the cavity. That is, both improvement in combustion stability and reduction in smoke emission can be achieved. This makes it possible to prevent fuel from adhering to the piston cavity without increasing the spray spread angle and the deflection angle, thereby reducing smoke.

FIG. 24 shows the deflection angle β and the liquid film adhesion rate to the piston cavity. The liquid film deposition rate was defined as the rate of fuel deposited on the piston with respect to the injected fuel. Increasing the deflection angle reduces the angle of incidence of the spray on the piston, thereby reducing the liquid film adhesion rate. Further, even if the deflection angle is the same, by making P1 / P2 larger than 1, the adhesion in the piston direction can be reduced, so that there is an effect that smoke can be reduced. On the other hand, if the deflection angle is too large as described above, the amount of fuel protruding from the cavity increases, which is not desirable. The deflection angle is desirably 20 degrees or less.

FIG. 25 has a swirl groove 33 for swirling the fuel. Offsets L1 and L2 may be the same. By changing the offset, sprays having different swirls can be formed, so that the degree of dispersion (solidification) of the sprays can be increased. By providing a bypass 55 for supplying unturned fuel to the orifice, the flow in the nozzle is deviated and the spray can be deflected.

FIG. 25 shows an example in which four bypasses 55 are used and the nozzles are deflected by nozzles.

FIG. 26 shows another embodiment. The fuel swirl grooves L1 and L2 may be the same. Further, the bypass passage of the vertical groove is made equal or not provided in this example. The fuel nozzle is machined at an angle to the axis of the injector. Thereby, the fuel spray can be formed in a direction deviated from the axis of the injector. P1 and P2 can be made asymmetric by selecting the positional relationship between the valve element and the nozzle. If it is deflected, the flow inside the nozzle will be disturbed, so there is also the effect of solid spraying, so that no bypass is provided or the volume is set to about 0.41 mcc. By not making the outlet angles of the nozzles orthogonal as shown in FIG. 27, the flow velocity distribution at the nozzle outlet becomes uneven, and P1 / P2 can be made larger than 1. The diameter of the nozzle is about 0.3 mm or more and 1 mm or less, and the deflection angle is 0.5 degree or more and 20 degrees or less. The fuel spray angle is desirably about 50 to 100 degrees. The mounting angle α is, for example, 45 degrees. The desired deflection angle depends on the mounting angle of the injector. That is, when the mounting angle is 36
In degrees, the deflection angle may be smaller than 45 degrees.

FIG. 28 shows the relationship between the angle γ of the nozzle end face from the nozzle orthogonal plane and P1 / P2. When γ is increased, P
1 / P2 can be increased. However, P1 / P
If the value of 2 is too large, the distribution of fuel in the direction of the spark plug becomes too large with respect to the direction of the piston, and problems such as smoldering of the spark plug tend to occur.
P1 / P2 is set to 2 or less.

FIG. 30 is a sectional view taken from above in FIG. Two intake valves are provided, and an air flow generation passage 60 that closes one side of the intake passage is provided. As a result, a swirling air flow is formed in the cylinder at a partial load. This helps to disperse the fuel in the piston cavity and transport it in the direction of the spark plug, thereby improving combustion stability and reducing smoke. In this case, in order to prevent the fuel from protruding due to the swirling air flow, the fuel injection direction is directed downstream of the swirling air flow and toward the cavity. Also in this case, P1 / P2 is set to be larger than 1 because fuel is likely to adhere to the piston. FIG. 31 shows an example of the engine test result. The smoke can be reduced by increasing the spray direction, that is, the deflection direction. However, if the deflection angle is too large, the spray will protrude from the cavity, so that smoke tends to increase. Therefore, the deflection angle is 2
0 degrees or less. In addition, when the deflection angle is small, the amount of fuel attached to the piston is large, smoke increases, and the amount of fuel in the direction of the spark plug decreases, so that the stability of combustion also decreases. If the deflection angle is too large, the fuel protrudes from the cavity, so that the stability of combustion is reduced. Also, P1 / P
By making 2 larger than 1, fuel adhesion to the piston can be reduced, so that smoke can be reduced.

FIG. 32 shows the relationship between P1 / P2 of the spray and the combustion stability. It is desirable that the combustion fluctuation is small because the engine is stable. By setting P1 / P2 in the range of 1 to 1.4, combustion fluctuation can be reduced. P1 / P2 is 1
With the above, the spray toward the spark plug decreases,
The ignitability decreases and the combustion fluctuation increases. On the other hand, P1 / P
If the size 2 is too large, the spray tends to protrude from the cavity, and it becomes difficult for combustion to collect around the spark plug.

FIG. 33 shows another embodiment of the present invention. As the turning groove, turning paths 34 and 55 having different offsets are provided. The swirl passage 55 is disposed upstream of the swirl passage 34 with respect to the fuel nozzle. When the spherical valve element 21 is lifted, fuel is ejected from the swirl passage 34 together with the fuel accumulated downstream of the swirl passage 55. By selecting the offset of the swirl passage 34 smaller than 55, first, a narrow spray is jetted, and then the fuel swirled by the passage 55 is jetted, and the spray is spread. The amount of fuel initially ejected can be controlled by the volume from the passage 55 to the nozzle, and the degree of dispersion can be adjusted by the offset amount of the passage 34.

FIG. 34 shows another embodiment.
The non-swirl chamber 56 is provided in order to further increase the downstream volume of the airbag. As a result, first, the fuel in the unswirled portion increases, and the amount of the initial spray can be increased.

FIG. 35 shows the relationship between the volume downstream of the swirl path and the initial spray amount. By increasing the downstream volume,
The initial spray amount can be increased.

As shown in FIG. 36, by increasing the offset of the swirl passage 34, the degree of dispersion of the initial spray can be increased and the particle diameter can be reduced.

Although the above description has been directed to the stratified combustion, even when the engine is operated under a high load, the solidification of the spray promotes the mixing of air and fuel, which is effective in suppressing soot emission and increasing the output.

[0071]

As can be understood from the above description, the fuel injection valve of the engine according to the present invention has a solid fuel spray shape of the fuel injection valve and forms a low-speed spray in the cylinder. Lean combustion (air-fuel ratio of about 20 to 50) is realized while suppressing soot emission in the injection engine. Further, even during high-load operation with the in-cylinder injection engine,
Soot emission can be suppressed, and the output of the engine can be improved.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a direct injection engine including a fuel injection valve according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a fuel injection valve of the fuel injection device of the present invention.

FIGS. 3A and 3B are cross-sectional views of a first embodiment showing details of a fuel guide of a nozzle portion of the fuel injection valve of FIG. 2, and FIG.

4A and 4B show a second embodiment of the fuel guide according to the present invention, in which FIG. 4A is a cross-sectional view, FIG.
(C) is a radial flow distribution diagram of the fuel spray on the AA cross section of (b).

5A is a cross-sectional view of a third embodiment of the fuel guide according to the present invention, FIG. 5B is a vertical cross-sectional view showing a fuel spray state, FIG.
(C) is a radial flow rate distribution diagram of the fuel spray.

6A and 6B show a fourth embodiment of the fuel guide according to the present invention, wherein FIG. 6A is a cross-sectional view, FIG.
(C) is a radial flow rate distribution diagram of the fuel spray.

7A is a cross-sectional view of a fifth embodiment of the fuel guide body of the present invention, FIG. 7B is a vertical cross-sectional view showing a fuel spray state,
(C) is a radial flow rate distribution diagram of the fuel spray.

8 (a) is a cross-sectional view and FIG. 8 (b) is a vertical cross-sectional view showing a fuel spray state in a sixth embodiment of the fuel guide according to the present invention.

9A and 9B are a cross-sectional view and a vertical cross-sectional view showing a fuel spray state in a fuel guide according to a seventh embodiment of the present invention.

FIG. 10 shows an eighth embodiment of the fuel guide according to the present invention, in which (a)
Is a transverse sectional view, (b) is a longitudinal sectional view showing a fuel spray state,
(C) is a radial flow rate distribution diagram of the fuel spray.

FIG. 11 shows a ninth embodiment of the fuel guide according to the present invention, wherein (a)
Is a transverse sectional view, (b) is a longitudinal sectional view showing a fuel spray state,
(C) is a radial flow rate distribution diagram of the fuel spray.

FIG. 12 shows a fuel guide according to a first embodiment of the present invention, in which a valve body is changed to a conical shape.
(B) is a longitudinal sectional view showing a fuel spray state, and (c) is a radial flow rate distribution diagram of the fuel spray.

13A and 13B show a fuel guide body according to a first embodiment of the present invention in which a valve body is changed to a conical shape. FIGS. 13A and 13B are longitudinal sectional views showing a fuel spray state, and FIG. 13C is a reference example. FIG. 3 is a longitudinal sectional view showing a fuel spray state.

FIG. 14 is a diagram showing the relationship between the degree of combustion stability and the degree of soot generation with respect to the spray spread angle of the fuel spray between the present invention and the conventional example.

FIG. 15 is a graph showing combustion stability or soot emission characteristics with respect to fuel injection timing and ignition timing according to the present invention;
(A) is a figure showing combustion stability, (b) is a figure showing soot characteristics.

FIG. 16 is a view showing another embodiment of the present invention, in which a combustion injection valve is arranged at a center of a cylinder body, and (a).
(B) is a diagram showing the time of fuel injection and the time of ignition.

FIG. 17 is a view showing still another embodiment of the present invention, in which a combustion injection valve is arranged at a cylinder center;
(A), (b) is a figure which shows the time of fuel injection and the time of ignition.

FIG. 18 is a view showing still another embodiment of the present invention, in which a combustion injection valve is arranged at a cylinder center,
(A), (b) is a figure which shows the time of fuel injection and the time of ignition.

FIG. 19 is a view showing a state of an air-fuel mixture in a cylinder at the time of fuel injection in a conventional in-cylinder fuel injection valve.

FIG. 20 is an explanatory diagram of a state of an in-cylinder mixture during fuel injection in a conventional in-cylinder fuel injection valve.

FIG. 21 is an operation explanatory diagram of the present invention.

FIG. 22 is an operation explanatory diagram of the present invention.

FIG. 23 is an operation explanatory diagram of the present invention.

FIG. 24 shows deflection angles and liquid film ejection rates.

FIG. 25 is a diagram illustrating the configuration and operation of a nozzle according to the present invention.

FIG. 26 is a diagram illustrating the configuration and operation of a nozzle according to the present invention.

FIG. 27 is a diagram illustrating the configuration and operation of a nozzle according to the present invention.

FIG. 28 shows the relationship between the angle of the nozzle end face and P1 / P2.

FIG. 29 shows an example of application to another engine.

FIG. 30 shows an example of application to another engine.

FIG. 31 shows an example of an engine test result.

FIG. 32 is a view showing a relationship between combustion stability levels.

FIG. 33 is a diagram illustrating the configuration and operation of a nozzle according to the present invention.

FIG. 34 is a diagram illustrating the configuration and operation of a nozzle according to the present invention.

FIG. 35 is a view showing the relationship between the volume downstream of the swirl path and the initial spray amount.

FIG. 36 is a drawing showing the relationship between the offset amount of the swirl path and the degree of dispersion and particle size of the initial spray.

[Explanation of symbols]

20: fuel injection valve, 21: spherical valve element, 22: nozzle part,
23: fuel guide, 25: valve seat, 26: coil spring, 27: fuel inlet connector, 28: solenoid coil, 29: electric connector, 30: movable core, 33
a, 34a: fuel swirl groove; 33b, 34b: fuel swirl hole.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoko Nakayama 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Minoru Osuka 7-1-1, Omika-cho, Hitachi City, Ibaraki Prefecture No.1 F term in Hitachi, Ltd. Hitachi Research Laboratory (reference) 3G066 AA02 AA05 AB02 AD12 BA02 BA14 BA16 BA24 CC06U CC14 CC15 CC20 CC32 CC34 CC43 CC48 CC66 CD28 CD30 CE22 DA01 DB09 DC04 DC09 DC11

Claims (27)

[Claims] A nozzle body, a valve seat, a nozzle hole, and
A fuel injection valve for an engine provided with a fuel guide, wherein the fuel guide forms a plurality of fuel swirl passages having different swirl strengths. 2. The fuel injection system according to claim 1, wherein the plurality of fuel swirl passages are formed such that a swirl passage having a small swirl strength is closer to the nozzle hole than a swirl passage having a large swirl strength. valve. 3. A valve body, a valve seat, a nozzle hole, and
A fuel injection valve for an engine including a fuel guide, wherein the fuel guide includes a plurality of fuel guide passages formed on an imaginary line intersecting a central axis of the nozzle hole, and the fuel guide passage includes a fuel flow passage. A fuel injection valve characterized in that the fuel injection valves are formed to collide with each other. 4. A valve body, a valve seat, a nozzle hole, and
In a fuel injection valve for an engine including a fuel guide, the fuel guide includes a plurality of fuel guide passages and a plurality of fuel swirl passages formed on an imaginary line intersecting a central axis of the plurality of nozzle holes. A fuel injection valve. 5. The fuel injection valve according to claim 1, wherein the fuel swirl passage or the fuel guide passage is a groove or a hole. 6. The fuel injection valve according to claim 1, wherein the fuel swirl passage is offset by a predetermined distance from an imaginary line intersecting a central axis of the nozzle hole. 7. The fuel injection according to claim 6, wherein the plurality of fuel swirl paths have different offset distances between a swirl path having a small swirl strength and a swirl path having a large swirl strength. valve. 8. The fuel injection valve according to claim 1, wherein the plurality of fuel swirl passages are formed such that one or more passages are inclined toward the exit direction of the nozzle hole. 9. The fuel injection valve according to claim 1, wherein at least one unswirled fuel chamber that does not swirl the fuel is formed inside the fuel swirl passage. 10. The fuel injection device according to claim 1, wherein the fuel guide has a bypass fuel passage for bypassing fuel from upstream to downstream. 11. The fuel cell system according to claim 10, wherein the bypass fuel passage comprises a plurality of fuel passages having different passage areas.
A fuel injection device according to claim 1. 12. The fuel injection valve according to claim 1, wherein the passage area between the valve body and the valve seat is reduced toward the nozzle outlet to prevent the generation of a cavity. 13. The fuel injection valve according to claim 1, wherein the valve body is a sphere or a cone. 14. A fuel injection method for directly injecting fuel into a cylinder of an engine, wherein two or more fuels having different spray angles are sprayed on the same central axis. 15. The two or more fuels having different spray angles,
15. The fuel injection method according to claim 14, wherein the spray formed by the fuel having the small spray angle is injected before the spray formed by the fuel having the large spray angle. 16. A fuel injection method for directly injecting fuel into a cylinder of an engine, wherein two or more fuel sprays having different particle diameters are injected on the same central axis. 17. The fuel spray for two or more fuel particles having different particle diameters includes a spray formed by a fuel having a large particle diameter and a fuel spray formed by a fuel having a small particle diameter.
2. The method of claim 1, wherein the spray angle is reduced.
7. The fuel injection method according to 6. 18. An internal combustion engine having an injection valve for directly injecting fuel into a cylinder, comprising an injector having an asymmetric arrival length in a fuel spray injection direction, wherein the fuel injection valve and the fuel injection for the engine are provided. Method. 19. A fuel injection valve and a fuel injection method for an engine according to claim 18, wherein the injector is arranged so that the spray having a long reaching length is directed toward the spark plug. 20. A fuel injection valve and a fuel injection method for an engine according to claim 18, wherein the injector is arranged so that the spray having a short arrival length is directed toward the piston. 21. An internal combustion engine provided with an injection valve for directly injecting fuel into a cylinder and a swirl generator for forming a swirling air flow in a cylinder, comprising an injector having an asymmetric arrival length in a fuel spray injection direction. A fuel injection valve and a fuel injection method for an engine. 22. The fuel injection valve and the fuel injection method for an engine according to claim 22, wherein the injector is arranged so that the spray having a long reaching length is directed toward the spark plug. 23. The fuel injection valve and the fuel injection method for an engine according to claim 22, wherein the injector is arranged so that the spray having a small arrival length is directed toward the piston. 24. The fuel injection valve and the fuel injection method for an engine according to claim 22, wherein the injector is arranged so that the spray having a long reaching length is directed to the downstream direction of the spark plug and the swirl airflow. 25. A fuel injection valve and a fuel injection method for an engine according to claim 18, wherein the area and the number of fuel passages for bypassing the swirl groove from upstream to downstream are asymmetric. 26. The injector according to claim 18, wherein a swirl groove is provided, and a nozzle portion provided downstream thereof is inclined with respect to an axial direction of the injector. Injection method. 27. The injector according to claim 18, wherein a swirl groove is provided, a nozzle portion provided downstream thereof is inclined with respect to an axial direction of the injector, and an end face of the nozzle is not orthogonal to the nozzle. A fuel injection valve and a fuel injection method for an engine.