WO2002038924A1

WO2002038924A1 - Cylinder injection engine and method of controlling the engine

Info

Publication number: WO2002038924A1
Application number: PCT/JP2000/007623
Authority: WO
Inventors: Takuya Shiraishi; Toshiharu Nogi; Minoru Oosuga; Yuusuke Kihara
Original assignee: Hitachi, Ltd.
Priority date: 2000-10-30
Filing date: 2000-10-30
Publication date: 2002-05-16
Also published as: JPWO2002038924A1

Abstract

A cylinder injection engine capable of improving a fuel efficiency, and a method of controlling the engine, wherein a fuel injection nozzle (19) injects flat-shaped fuel spray into a cylinder, and an air flow control valve (6) generates air flow motion between the piston top surface and cylinder wall surface and the flat spray.

Description

TECHNICAL FIELD The present invention relates to a direct injection engine that directly injects fuel into a combustion chamber of an engine, and a control method thereof. BACKGROUND ART Conventionally, as a direct injection engine for directly injecting fuel into a combustion chamber, a MAN-FM system developed in the 1970s has been known. In this method, fuel is injected into a depression provided in the piston and ignites and burns before the spray spreads. However, this method used a pilot fuel injection valve that applied diesel technology at the time, so the response was slow and it was difficult to control the injection timing accurately. On the other hand, in the 1990's, with the advance of electronic control technology, electromagnetic fuel injectors with good responsiveness became mainstream, and the injection timing controllability developed remarkably. — As described in Japanese Patent Publication No. 115758, an in-cylinder injection system using high-pressure fuel has been developed. DISCLOSURE OF THE INVENTION However, in a direct injection (DI) system that injects fuel at such a high pressure, the pressure of the fuel is increased by driving a high-pressure fuel pump connected to a crankshaft or a camshaft of the engine. The pressure of the injected fuel is, for example, a high pressure of about 5 to 10 MPa, and the fuel is injected in the latter half of the compression stroke. The high-pressure fuel that has not been injected into the combustion chamber of the engine is depressurized through the high-pressure regulator and returns to the low-pressure pipe or fuel tank. The conventional high-pressure DI system had the problem that the power to increase the fuel pressure was one of the factors that deteriorated fuel efficiency. In addition, the high-pressure DI system is an additional component of the high-pressure fuel supply system in addition to the intake port injection (MPI) system that injects fuel into the intake port at a pressure of 0.3 MPa, which causes cost increase. . This increase in cost has prevented the in-cylinder injection engine from spreading to the market.

Also, in the conventional high-pressure DI system, fuel efficiency is improved by lean burn, but there is a problem that the fuel efficiency is not necessarily improved enough.

Another object of the present invention is to provide a direct injection engine capable of improving fuel efficiency and a control method thereof. In particular, the fuel pressure is lower than the pressure used in the conventional high-pressure DI system, the loss when the fuel is boosted is reduced, fuel efficiency is improved, and lean combustion is possible while keeping the fuel pressure low. Accordingly, it is an object of the present invention to provide an in-cylinder injection engine and a control method for the same performance as a high-pressure DI system, such as fuel efficiency and exhaust. Another object of the present invention is to provide an in-cylinder injection engine capable of further improving fuel efficiency in a high-pressure DI system and a control method thereof. In order to achieve the above object, the present invention relates to a direct injection engine having a fuel injection valve for injecting fuel into a cylinder to form a fuel spray, wherein the fuel injection valve comprises a flat fuel spray. And an air flow generating means for generating an air flow between the flat surface and the piston top surface and the cylinder wall surface. With this configuration, stratified combustion near the spark plug is enabled, and fuel efficiency can be improved.

According to another aspect of the present invention, there is provided an in-cylinder injection engine having a fuel injection valve that injects fuel into a cylinder to form a fuel spray, wherein the fuel injection valve has a flat fuel spray. An air layer generating means for injecting the gas into the cylinder and generating an air layer between the piston top surface and the cylinder wall surface and the flat spray is provided. With this configuration, stratified combustion near the spark plug is enabled, and fuel efficiency can be improved.

According to another aspect of the present invention, there is provided an in-cylinder injection engine having a fuel injection valve that injects fuel into a cylinder to form a fuel spray, wherein the fuel injection valve has a flat fuel spray. Injecting into the cylinder and flat injection on both sides of this flat spray An air flow generating means for generating an air flow by sandwiching the mist is provided. With this configuration, stratified charge combustion near the spark plug is enabled, and fuel efficiency can be improved.

In order to achieve the above object, the present invention provides a method for controlling an in-cylinder injection engine having a fuel injection valve for injecting fuel into a cylinder to form a fuel spray. The injection valve is provided with air flow generating means for injecting the flat fuel spray into the cylinder and generating air flow between the piston top surface and the cylinder wall surface and the flat spray, and the air flow generating means for the engine by the air flow generating means. After the air flow is formed in the combustion chamber, the fuel is injected from the fuel injection valve at any timing from the intake stroke to the first half of the compression stroke. By this method, stratified combustion near the spark plug can be performed, and the fuel efficiency can be improved. BEST MODE FOR CARRYING OUT THE INVENTION The in-cylinder injection engine and a control method thereof according to a first embodiment of the present invention will be described below with reference to FIGS. 1 to 28.

First, a system configuration of the direct injection engine according to the present embodiment will be described with reference to FIG.

FIG. 1 is a system configuration diagram of a direct injection engine according to a first embodiment of the present invention.

The engine 21 includes a crank mechanism 24, and the volume of the combustion chamber 22 is changed by the operation of the piston 23 connected to the crank mechanism 24. Air is sucked into the engine 21 by the up and down movement of the piston 23, and the gas after combustion is discharged. At the time of air intake, the cam 7 opens the intake valve 35. Also, when exhausting the gas after combustion, the cam 7 opens the exhaust valve 36. The engine 21 is cooled by cooling water flowing in the cooling water passage 20.

The amount of intake air is controlled by a throttle valve 3 arranged in an intake pipe 4. The throttle valve 3 is an electronically controlled throttle valve driven by a motor. You. The control unit 1 takes in the change amount of the accelerator pedal as an electric signal and controls the opening of the throttle valve 3 according to the electric signal. An air amount sensor 2 provided upstream of the throttle valve 3 measures the amount of air taken into the engine 21. The inhaled air fills a collector 5 provided in the intake pipe 4. The collector 5 has an effect of suppressing a pressure fluctuation in the intake pipe 4. The collector 5 is connected to an EGR passage 27. The £ 01 passage 27 connects the exhaust pipe 12 and the collector 5 and an EGR control valve 9 is provided on the way. The control unit 1 controls the EGR control valve 9 to vary the EGR gas return flow. In the collector 5, the EGR gas and the intake air are mixed. The mixed gas is drawn into the combustion chamber 22 of the engine 21. An air flow control valve 6 provided downstream of the collector 5 generates an air flow in the combustion chamber 22.

The fuel 17 stored in the fuel tank 16 is supplied to the fuel injection valve 19 after the pressure is increased to a preset value by the fuel pump 18. The control unit 1 calculates an injection pulse width based on the value measured by the air amount sensor 2 so as to attain a preset air-fuel ratio, and supplies an injection pulse signal to the fuel injection valve 19. The fuel injection valve 19 injects fuel directly into the cylinder of the engine 21, that is, into the combustion chamber 22 according to an injection signal from the control unit 1. The fuel pump 18 also operates based on the control signal from the control unit.

The exhaust gas discharged from the combustion chamber 22 removes harmful components (for example, HC, NOX, CO) in the exhaust gas by the catalyst 11 attached to the exhaust pipe 12. Further, the catalyst 14 may be added in order to remove components that have not been completely purified by the catalyst 11. An air-fuel ratio sensor 10 is mounted upstream of the catalyst 11, an exhaust gas temperature sensor 13 is mounted upstream of the catalyst 14, and an oxygen sensor is mounted downstream of the catalyst 14. Sensor 15 is installed. These sensors 10, 13, and 15 constantly sense various kinds of information on exhaust gas and reflect the information in control unit 1.

The number of revolutions of the engine 21 is measured using, for example, an output signal of a crank angle sensor 25 attached to a crankshaft 24 and a pickup 26, and is taken into the control unit 1. A feature of this embodiment is that, in the in-cylinder injection engine having the configuration shown in FIG. 1, the fuel pressure supplied from the fuel pump 18 to the fuel injection valve 19 is the fuel pressure of the conventional high-pressure DI 5-1 That is, it is set to about 2 MPa, which is lower than OMPa. As a result, the structure of the fuel pump can be simplified and the cost can be reduced. Further, in the conventional high pressure DI engine, a feed pump that is disposed in the fuel tank 16 and supplies fuel to the high pressure fuel pump is required, but in the present embodiment, the feed pump is not used. It is.

As described above, when the fuel supply pressure is set to about 2 MPa, in the latter half of the compression stroke in which the pressure in the combustion chamber 22 becomes high, the pressure inside the combustion chamber 22 becomes the fuel injection valve 1 Since it is higher than the pressure of the fuel injected from 9, fuel cannot be injected. Therefore, in the present embodiment, the injection possible period is set from the intake stroke in which the pressure in the combustion chamber 22 becomes about the atmospheric pressure to the first half of the compression stroke. In order to achieve stratified combustion with an air-fuel ratio of 40 or more, it is necessary to centralize an ignitable mixture (air-fuel ratio of about 10 to 14) around the spark plug. However, when the injection timing is from the intake stroke to the first half of the compression stroke, stratification (concentration of the air-fuel mixture around the spark plug) becomes difficult because the injected fuel spray tends to diffuse. Therefore, in the present embodiment, as described later with reference to FIGS. 2 and 3, the fuel spray injected from the fuel injection valve 19 is formed as flat spray, and both sides of the flat spray are sandwiched by air flow. The mixture is concentrated around the spark plug.

Next, a method for stratifying under low fuel pressure in the in-cylinder injection engine according to the present embodiment will be described with reference to FIGS.

FIG. 2 is a bottom view of the direct injection engine according to the first embodiment of the present invention. That is, FIG. 2, for example, shows a state in which the engine head 30 constituting one combustion chamber 22 of a four-cylinder engine is viewed from the piston side.

FIG. 3 is a sectional view of the direct injection engine according to the first embodiment of the present invention. That is, FIG. 3 shows a cross section including the spark plug 34 of the engine shown in FIG. 2 and 3, the same reference numerals as those in FIG. 1 indicate the same parts.

In Fig. 2, the piston reciprocates in the vertical direction (Z-axis direction) toward the drawing. The round hole 3 1 is an engine block that does not show the engine head 30 This is a hole through which a bolt for fixing to is mounted. In the cooling water passage 20, cooling water for cooling the engine flows. The combustion chamber 22 is provided with an intake valve 35, exhaust pulp 36, and a spark plug 34.

As shown in FIGS. 2 and 3, fuel 38 is injected into the combustion chamber 22 from the injection port 33 of the fuel injection valve 19 attached to the engine head 30. The points in this embodiment are the shape of the spray 38 to be injected and the air flow 37 generated in the combustion chamber 22. The central axis of the combustion injector 19 is parallel to the XY plane.

The fuel spray 38 injected into the combustion chamber 22 has a flat shape that is narrow in the X-axis direction (on the XY plane) as shown in FIG. 2 and spread on the YZ plane as shown in FIG. It is. The configuration of the fuel injection valve 19 for injecting such flat spray will be described later with reference to FIG.

The air flow 37 (37A, 37B) generated in the combustion chamber 22 passes through two intake valves 35 as shown in FIG. Yes, creates air flow between piston top and cylinder wall and flat spray. That is, the air flow 37 A. 37 B is formed on both sides of the fuel spray 38 so as to sandwich the fuel spray 38. The air flow 37 is an airflow that rotates in the combustion chamber 22 in the vertical direction as shown in FIG. Here, the vertical direction is a rotation in the YZ plane shown in FIG. This air current can be regarded as forming an air layer because the flow velocity decreases over time.

As described above, the fuel spray 38 injected into the combustion chamber 22 is sandwiched between the air flows 37A and 37B, and diffuses outward (in the X-axis direction) of the combustion chamber 22. Is prevented and centralized in the center. Since the pressure of the fuel injected from the fuel injection valve 19 is lower than that of the conventional high-pressure DI, the injectable period is from the intake stroke to the first half of the compression stroke. When the fuel is injected at such a timing, the fuel spray tends to spread in the combustion chamber 22. In the present embodiment, however, the mixture is prevented from diffusing by sandwiching the spray between two air flows. can do. The trapped air-fuel mixture is held in the center of the combustion chamber 22 until the latter half of the compression stroke, and can be concentrated around the ignition flag 34 and stratified. Therefore, fuel injection at a lower pressure than before is possible, and stratified combustion is also possible. Conventional high-pressure DI As in the case of, lean combustion with an air-fuel ratio of about 40 is possible, so that fuel efficiency and exhaust performance can be improved as in the conventional high-pressure DI.

Next, the shape of the flat spray injected from the fuel injection valve in the in-cylinder injection engine according to the present embodiment will be described with reference to FIGS.

FIGS. 4 and 5 are explanatory diagrams of the shape of the fuel spray injected from the combustion injection valve used in the direct injection engine according to the first embodiment of the present invention. FIG. 4 shows the spray shape on the Y-Z plane shown in FIG. FIG. 5 shows the spray shape on the XY plane shown in FIG. 4 and 5, the same reference numerals as those in FIGS. 2 and 3 indicate the same parts.

FIG. 6 is a cross-sectional view of the direct injection engine according to the first embodiment of the present invention in the compression stroke. The same reference numerals as those in FIGS. 1 to 3 indicate the same parts. FIG. 7 is an explanatory diagram of a change in the air-fuel ratio depending on the spray shape of the direct injection engine according to the first embodiment of the present invention.

As shown in FIGS. 4 and 5, the fuel supplied from the fuel supply port 40 passes through the inside of the fuel injection valve 19 and is injected as a fuel spray 38 from the injection port in the nozzle 42 of the hull. As shown in FIG. 4, the spray angle of the fuel spray 38 on the XY plane shown in FIG. 2 is 0 t. Also, as shown in FIG. 5, the spray angle of the fuel spray 38 in the YZ plane shown in FIG. The spray angle 0 t is a flat spray smaller than the spray angle Sc.

The spray angle 0c shown in FIG. 4 is the same as the spray angle of a normal high-pressure DI fuel injection valve. As shown in FIG. 3, when the spray angle Sc increases, the fuel spray is directly blown onto the inner cylindrical wall of the combustion chamber 22, the top face of the combustion chamber 22, and the spark plug 34. Will adhere to the walls and the like. In order to avoid them, the spray angle 0c is, for example, in the range of 60 to 80 degrees.

Next, the spray angle 0 t will be described with reference to FIGS. Fig. 6 shows the condition inside the combustion chamber at the timing corresponding to the ignition timing in the latter half of the compression stroke. A simulation was performed on the air-fuel mixture distribution in the combustion chamber at the timing corresponding to the ignition timing in the latter half of the compression stroke when flat spray was injected at the bottom dead center. Figure 7 shows the area around the plug (radius around the plug gap) when the spray angle 0 t was changed. The area of 3.5 m: The air-fuel ratio of the arrow A in the figure) is shown.

As shown in FIG. 7, when the spray angle 0 t is 45 degrees, the air-fuel ratio around the plug is about 33, and becomes about 15 at 22.5 degrees. Furthermore, if it is set to 8 degrees, the air-fuel ratio around the plug will be 14. In stratified combustion, the air-fuel ratio of the entire combustion chamber is about 40, but ignitable mixture with an air-fuel ratio of 15 or less needs to be concentrated around the plug. Therefore, in the case of the combustion method in which the flat spray is sandwiched between air flows as in the present embodiment, the spray angle St of the narrow flat spray is set to 22.5 degrees or less, which is necessary for stratified combustion. It was found that an air-fuel mixture with an appropriate air-fuel ratio could be formed around the plug.

Next, the configuration of the fuel injection valve used in the direct injection engine according to the present embodiment will be described with reference to FIGS.

First, the overall configuration of the fuel injection valve used in the direct injection engine according to the present embodiment will be described with reference to FIGS. 8 and 9.

FIG. 8 is a cross-sectional view showing the overall configuration of the fuel injection valve used in the direct injection engine according to the first embodiment of the present invention. FIG. 9 is a cross-sectional view taken along line AA of FIG.

The fuel supplied from the fuel supply port 40 shown in FIG. 4 passes through the center hole of the core 51 disposed at the center of the fuel injection valve 19, and passes through the fuel passage 58 provided in the plunger 57. Through the fuel reservoir 60 inside the nozzle 42. 'A valve body 63 for shutting off the injection port 64 and the fuel reservoir 60 is attached to the tip of the plunger 57. The plunger 57 and the valve element 63 are pressed against the injection port 64 by the action of the spring 52. The pressing force can be adjusted by a spring adjuster 53. An atomizer 65 is attached to the tip of the nozzle 64. The atomizer 65 is for forming a flat spray, and details thereof will be described later with reference to FIGS. 10 to 12.

An electric signal (current) from the control unit 1 shown in FIG. 1 is conducted to the coil 50 arranged in the pop pin 54 shown in FIG. 6 via the connector 41 shown in FIG. When the coil 50 is energized, a magnetic force is generated around the coil 50. The anchor 56 joined to the plunger 57 by welding or the like is attracted by the magnetic force generated by the coil 50, and is repelled by the spring force to pull up the plunger 57. I can. The plunger 57 is raised to a point where it strikes the stop 59, and maintains a constant stroke while current is flowing through the coil 50. When the energization of the coil 50 is completed, the plunger 57 is pressed against the injection port 64 by the action of the spring 52, and shuts off the fuel reservoir 60 and the injection port 64. The nozzle 42 that forms the fuel reservoir 60 together with the plunger 57 is joined to the body 55 of the fuel injection valve 19 by welding or the like. A nozzle 61 having a groove for imparting swirling to the fuel is mounted in the nozzle 42 so as to improve the atomization of the injected fuel. The spooler 61 is arranged in the nozzle 42 as shown in FIG. The stirrer has a turning groove 61 extending in a tangential direction of the valve element 63. The fuel that has passed through the swirl groove 62 of the spooler 61 from the fuel reservoir 60 passes through the gap between the valve body 63 and the injection port 64 and is injected from the opening of the atomizer 65.

Next, the structure of the atomizer of the fuel injection valve used in the direct injection engine according to the present embodiment will be described with reference to FIGS.

FIG. 10 is a cross-sectional view illustrating a configuration of an atomizer of a fuel injection valve used in the direct injection engine according to the first embodiment of the present invention. FIG. 11 is a sectional view taken along the arrow B in FIG. FIG. 12 is a bottom view of FIG.

As shown in FIGS. 10 to 12, the atomizer 65 includes a cross slit groove including an upper slit 66 and lower slits 67A and 67B. The upper slit 66 is disposed so as to pass through the central axis of the valve body 63. The lower slits 67A and 67B are arranged so as to be orthogonal to the upper slit 66, respectively. The lower slits 67 A, 67 B are provided at a distance of 0.5 W 1 from the center axis of the valve body 63. The atomizer 65 is joined to the tip of the nozzle 42 by welding or the like.

When the fuel flows from the upper slit 66 to the lower slits 67A and 67B, a contraction occurs, and a thin film smaller than the slit width is formed in the lower slit 67, and atomization is promoted. The narrow spray angle 0 t of the flat spray is determined by the width W 1 between the lower slit 67 A and the lower slit 67 A. For example, when the spray angle 0 t is 22.5 degrees, the width W1 is 2.2 mm. As the width W 1 becomes smaller, the spray angle 0 t becomes smaller. The wider spray angle Θ c is the length L 1 of the lower slit 2 7 and the lower slit 2 It is determined by the groove depth D1 of 7. For example, when the spray angle Sc is 70 degrees, the length L1 is 3 mm and the groove depth D1 is 0.5 mm.

As described above, in the present embodiment, the flat spray can be formed only by joining the atomizer 65 to the tip of the existing fuel injection valve, so that the manufacture is easy. Further, by changing the shape of the cross slit groove, the spray angle of the flat spray can be relatively easily changed in design.

Next, in the fuel injection valve using the slit grooves 66 and 67 shown in FIGS. 10 to 12, the fuel flow rate can be determined by the following equation (1).

Q i ^ (ΔΡ)… (1)

Q f: fuel flow

a: Flow coefficient

A: Channel area

ΔΡ: P f — P c

P f: Fuel pressure

P c: Combustion chamber pressure

It is.

That is, the fuel flow rate Q is proportional to the square root of the pressure difference (ΔΡ) between the fuel pressure P f and the pressure at the injection location, that is, the combustion chamber pressure P c. Furthermore, it is proportional to the channel area A.

However, in the case of a conventional fuel injection valve (without the atomizer 65 in Fig. 8), the swirled fuel is biased to the wall of the nozzle by centrifugal force, and an air flow is generated at the center of the nozzle. As a result, in the case of the conventional injection valve, only about half of the cross-sectional area of the injection port is used as the flow passage area. In addition, since the ratio between the cross-sectional area of the injection port and the area of the flow path changes depending on the shape of the groove of the slurry, that is, the swirling force applied to the fuel, the flow coefficient α is not constant, and it is difficult to design the injection valve.

On the other hand, in the slit injector according to the present embodiment shown in FIGS. Since the entire cross-sectional area of the slit groove is used as the flow channel area, the flow coefficient α in Equation (1) is 1. If the fuel pressure is kept almost constant, the fuel flow rate can be determined only by the flow passage area, and the injection valve design becomes easy. In the case of the cross-slit type injection valve shown in FIG. 8, the flow path area is the area of the portion 69 where the upper slit 66 and the lower slit 67 overlap. That is, the flow path area is also the opening area of the nozzle 42. Next, the relationship between the flow path area and the fuel flow rate in the cross-slit type fuel injection valve used in the direct injection engine according to the present embodiment will be described with reference to FIG.

FIG. 13 is an explanatory diagram of the relationship between the flow area and the fuel flow rate in the cross-slit fuel injection valve used in the direct injection engine according to the first embodiment of the present invention.

In FIG. 13, the horizontal axis represents the flow path cross-sectional area (mm ² ), and the vertical axis represents the fuel flow rate. The channel cross-sectional area is the area of a portion 69 where the upper slit 66 and the lower slit 67 overlap. The fuel flow rate is represented by a flow rate per minute in a state where the plunger 57 is sucked by the coil 50 and is fully charged. From the test results of atomizers of various shapes in which the fuel pressure was set at 2MPa and the flow path area was changed, as shown by the solid line, it was found that the flow path area and the fuel flow rate were almost proportional.

If the target engine is a 4-cylinder 0.66L, the displacement per cylinder will be 165 cc. In this case, since the fuel flow rate is 260 cCZ, the flow path area is 0.16 mm ² . If the target engine is a 2.5-liter 4-cylinder engine, the displacement per cylinder will be 625 cc. In this case, since the fuel flow rate is 98 Occ / min, the flow path area is 0.60 mm ² . That is, the exhaust amount of one cylinder skilled Insufficient For 165 cc~625 cc, the flow channel area are those may be the ^{0. 16 mm 2 ~ 0 · 60mm} 2. The foregoing is the case for 4-cylinder, in the case of 6-cylinder and 8 - cylinder, exhaust amount per cylinder, 165 cc~625 cc for a range of flow channel area is 0. 16 mm ² ~0 It should be 60 mm ² .

As for engines that currently use high-pressure DI, the displacement per cylinder of the engine is in the range of 400 to 50 Occ. Engines in this range have bore diameters of 80 to 90 mm for each cylinder. In this case, the required flow rate to cover the entire operation range is about 600 to 80 OccZ. Flow passage area for morphism injection the required flow rate thus becomes approximately 0. 35~0. 5mm ^2. Next, another configuration of the atomizer of the fuel injection valve used in the in-cylinder injection engine according to the present embodiment will be described with reference to FIGS. 14 to 16.

FIG. 14 is a cross-sectional view showing the configuration of another atomizer of the fuel injection valve used in the direct injection engine according to the first embodiment of the present invention. FIG. 15 is a cross-sectional view taken along the arrow B in FIG. FIG. 16 is a bottom view of FIG.

The overall configuration of the fuel injection valve according to the present embodiment is the same as that shown in FIG. In the present embodiment, an injection port 64 is provided at the tip of the nozzle 4 2 ′, and as shown in FIG. 16, the shape of the injection port 64 is an elongated slit shape. The narrow spray angle 0 t of the flat spray is determined by the narrow width W 2 of the nozzle 64 and the height D 2 of the nozzle 64. The wider spray angle 0 c is determined by the opening angle θ 1 of the nozzles 64.

Next, the configuration and operation of the air flow control valve used in the direct injection engine according to the present embodiment will be described with reference to FIGS.

First, the configuration of the air flow control valve used in the direct injection engine according to the present embodiment will be described with reference to FIGS.

FIG. 17 is a perspective view of the in-cylinder injection engine according to the first embodiment of the present invention as viewed from above. FIG. 18 is a view on arrow C of FIG. FIG. 19 is a perspective view of the in-cylinder injection engine according to the first embodiment of the present invention as viewed from above. FIG. 20 is a view on arrow D of FIG. 1 to 3 indicate the same parts.

FIGS. 17 and 18 show a state in which the air flow control valve 6 is closed. The fuel injection valve 19 is installed in a mounting hole 79 between two passages where the intake port 72 is branched. The flat spray is injected on the surface including the fuel injector mounting position 79 and the spark plug 34, but it is necessary to minimize the interference with the air flow to prevent the diffusion of the fuel spray. . Therefore, it is desirable that the air flow for sandwiching the fuel spray be located as far away from the center of the combustion chamber as possible. For this purpose, bulkheads 76A and 76B are provided in the intake port 72 and the valved port. In addition, an air flow control plate 73 that constitutes the air flow control valve 6 is installed in the inner passages 78 A and 78 B separated by the bulkheads 76 A and 76 B to prevent air flow. I do. A connection shaft 7 4 passes through the intake port 7 2, and the air flow control plate 7 3 is attached to the shaft 74 by mounting screws 75. The connecting shaft 74 is configured to be rotatable by a drive device (not shown) (for example, a step motor, a diaphragm, or the like). Therefore, it is possible to adjust the air flow according to the operating conditions. In the state shown in FIGS. 17 and 18, the air flowing through the intake port 72 passes through the passages 77 A and 77 B outside the partition walls 76 A and 76 B, It flows like arrows El and E2. Here, the straightening of the air flow can prevent interference between flat spray and air flow in the combustion chamber. This is effective when performing stratified combustion.

On the other hand, FIGS. 19 and 20 show a state in which the air flow control valve 6 is opened. In this state, the air flowing through the intake port 72 flows to both the passages 77 A, 77 B, 78 A, and 78 B separated by the partition walls 76 A, 76 B. The flow flows like arrows E 1 A, E 1 B, E 2 A, and E 2 B. Flows such as arrows E 1 B and E 2 B are effective for homogeneous combustion because they serve to diffuse the fuel spray near the center of the cylinder. During homogeneous combustion, the output torque can be improved by efficiently mixing the fuel spray and intake air and increasing the air utilization rate.

Next, the operation of the air flow control valve used in the direct injection engine according to the present embodiment will be described with reference to FIG.

FIG. 21 is an explanatory diagram of the relationship between the open / closed state of the air flow control valve and the flow velocity distribution in the intake port in the direct injection engine according to the first embodiment of the present invention.

In Fig. 21, the horizontal axis represents the horizontal position in the intake port, and the vertical axis represents the flow velocity normalized at the maximum flow. Note that the flow velocity shown on the vertical axis is a position downstream of the air flow control valve 6 by a distance L2 as shown in FIG. The distance L2 is, for example, 10 mm.

When the control valve 73 is fully closed, there is almost no flow in the inner passages 78A, 788B of the bulkheads 76A, 176B, and there is a rapid flow in the outer passages 77A, 77B. I have. On the other hand, when the control valve 73 is fully opened, substantially uniform flows are generated in the inner and outer passages of the partition walls 76A and 76B. The drop in the flow velocity near the port wall and the bulkhead is due to frictional resistance between the solid wall and the fluid.

Next, referring to FIGS. 22 and 23, the in-cylinder injection engine according to the present embodiment is used. Another configuration of the air flow control valve will be described.

FIG. 22 is a perspective view of another configuration of the direct injection engine according to the first embodiment of the present invention as viewed from above. FIG. 23 is a view on arrow F of FIG. The same reference numerals in FIGS. 17 to 20 denote the same parts.

In this example, the air flow control valve 6 'is applied to an engine having independent intake ports 72A and 72B. In-cylinder injection engines tend to have fuel injectors 19 between two intake ports, so designs that increase the space between intake ports to secure fuel injector mounting positions 79 are becoming mainstream. . Even in such a case, by providing the air flow control plates 73A and 73B as the air flow control valves 6 'at the intake ports 72A and 72B, respectively, as shown in FIG. Similarly, the air flow can be formed by closing the air flow control valve 6 ′.

As described above, by adopting a configuration in which the flat spray is sandwiched by air flows, stratified combustion can be performed even when the injection timing is the first half of the intake stroke to the compression stroke, and mixing during homogeneous combustion can be achieved by opening and closing the air flow control valve. Can promote and improve output.

Next, the configuration and operation of the fuel supply system used in the direct injection engine according to the present embodiment will be described with reference to FIGS.

First, the configuration of the fuel pump 18 in the fuel supply system used for the direct injection engine according to the present embodiment will be described with reference to FIGS. 24 and 25.

FIG. 24 is a partial cross-sectional view showing a configuration of a fuel pump in a fuel supply system used in the direct injection engine according to the first embodiment of the present invention. FIG. 25 is a view taken in the direction of arrow B—B in FIG.

While the conventional high-pressure DI system has two pumps, a feed pump and a high-pressure fuel pump, in the piping from the fuel tank to the engine, this embodiment uses only one pump. I have. Conventionally, a high-pressure fuel pump has no capacity to suck in fluid, and a feed pump has been used to supply fuel to the high-pressure fuel pump. High-pressure fuel pumps are mainly driven by engine power, and are installed near the engine. As a result, it cannot be located below the fuel tank position, so a feed pump is inevitably required in high-pressure DI systems. On the other hand, in this embodiment, since the fuel pressure is low, the pump structure is simplified, and the power source for driving the pump and the degree of freedom of the arrangement of the pump are increased.

As shown in FIGS. 24 and 25, the fuel pump 18 is a gear pump having a structure in which fuel is delivered by rotation of two gears 102, 103. The pump 18 is rotated by connecting a power source to the power coupling 100. The shaft 107 connected to the coupling 100 is rotatably supported by a bearing 101. The drive gear 102 is fixed to the shaft 107. The driven gear 103 is engaged with the drive gear 102.

The fuel enters through the suction port 108, is conveyed to the discharge port 109 side by the rotation of the drive gear 102 and the driven gear 103, and is discharged. By providing a regulator for controlling the pressure in the pipe connected to the discharge side, the fuel pressure can be controlled. The drive gear 102 and the driven gear 103 are interposed between the two side plates 104 and 105, and have a structure for preventing fuel from leaking to the gear side. The side plates 104 and 105 are supported by thrust bearings 106.

As described above, by using one pump that can secure the required fuel pressure with a simple configuration, the fuel pump can be simplified and the cost can be reduced.

Next, the configuration and operation of the fuel supply system used in the in-cylinder injection engine according to the present embodiment will be described with reference to FIG.

FIG. 26 is a system configuration diagram showing a configuration of a fuel supply system used for the direct injection engine according to the first embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts.

Pump 18 is located in fuel 86 in fuel tank 87. The pump 18 is driven by a motor 89 arranged outside the fuel tank 87. A pipe 83 to the engine is connected to a discharge port of the pump 18, and is connected to a common rail 81. In the middle of the pipe 83, a regulator 84 for adjusting the fuel pressure and a fuel pressure sensor 82 for sensing the fuel pressure in the pipe are mounted.

Regulayer 84 is to mechanically adjust the fuel pressure to a preset value. In addition, based on the signal from the fuel pressure sensor 82, the fuel pressure It may be one that controls the force. Further, the control unit 1 issues a control command to the impeller 8.8 for controlling the rotation speed of the motor 89 based on the output signal of the fuel pressure sensor 82 to control the motor rotation speed, that is, the pump rotation speed. I do. Next, the relationship between the rotation speed of the gear pump and the efficiency will be described with reference to FIG. FIG. 27 is an explanatory diagram showing the relationship between the rotation speed and the efficiency of the gear pump of the fuel pump used in the direct injection engine according to the first embodiment of the present invention.

In Fig. 27, the horizontal axis indicates (pump rotation speed (rpm) Z maximum rotation speed (rpm)), and the vertical axis indicates pump efficiency (%). The efficiency of the gear pump described in FIGS. 24 and 25 tends to decrease as the rotational speed decreases. The drop in pump efficiency is due to leakage from the gear gap or the gap on the side plate side. However, since the leaked valve returns to the fuel tank as it is, there is no particular problem. Therefore, the control unit 1 is used to control the number of pumps 18 to control the amount of fuel discharged from the pump 18.

Next, another configuration and operation of the fuel supply system used in the direct injection engine according to the present embodiment will be described with reference to FIG.

FIG. 28 is a system configuration diagram showing another configuration of the fuel supply system used for the direct injection engine according to the first embodiment of the present invention. The same reference numerals as those in FIG. 26 indicate the same parts.

In this example, the fuel pump 18 is driven by the engine, and is arranged near the engine. The fuel tank 87 is provided with a shutoff valve 92 that closes the opening from the fuel supply port 91. Air is pumped into the fuel tank 87 by a pump 90 driven by a motor 89 to pressurize the space inside the fuel tank 87. By pressurizing the inside of the fuel tank 87, it is possible to supply fuel to the fuel injection valve 19 with one fuel pump 18 even when the suction capacity of the fuel pump 18 is low.

In the above description, the system that injects fuel into the cylinder at a lower pressure than the conventional high-pressure DI has been described.In particular, as shown in FIGS. 2 and 3, the flat fuel spray is sandwiched by air flow. Thus, the prevention of fuel spray diffusion and stratification around the spark plug is applicable to high-pressure DI. In recent high pressure DI, Although stratified combustion is performed at an air-fuel ratio of about 40, the use of flat spray and air flow can further increase the air-fuel ratio and improve exhaust and fuel efficiency.

As described above, according to the present embodiment, the fuel efficiency of the direct injection engine can be further improved.

In addition, the fuel pressure is lower than the pressure used in the conventional high-pressure DI system, the loss during pressurization of fuel and fuel is reduced, fuel efficiency is improved, and lean combustion is possible while keeping the fuel pressure low. As a result, the fuel efficiency and exhaust performance can be made equal to those of the high-pressure DI system. Since the fuel pressure can be reduced, the fuel supply system can be simplified by using only one fuel pump.

Also, in the high-pressure DI system, fuel efficiency can be further improved. INDUSTRIAL APPLICABILITY According to the present invention, fuel efficiency in a direct injection engine can be further improved.

Claims

The scope of the claims

1. An in-cylinder injection engine having a fuel injection valve for injecting fuel into a cylinder to form a fuel spray,

The fuel injection valve (19) injects a flat fuel spray (38) into the cylinder, and generates an air flow (37) between the top of the piston and the cylinder wall and the flat spray. An in-cylinder injection engine comprising (6).

2. The in-cylinder injection engine according to claim 1,

The fuel injection valve (19) has a spray angle 0c on an X-Z plane formed by a cylinder center axis (Z axis) and an X axis perpendicular to the Z axis and directed toward the intake side. An in-cylinder injection engine that forms a flat spray having a spray angle greater than 0 c on an XY plane formed by a Y axis and an X axis perpendicular to the axis.

3. The in-cylinder injection engine according to claim 1,

The fuel injection valve (19), the nozzle opening area of the tip of 0.1 from 6 to 0.6 0 direct injection engine, which is a (mm ^2).

4. The in-cylinder injection engine according to claim 1,

The air flow control means (6) includes a partition (76) for dividing an intake boat communicating with an intake valve of the engine into right and left, and an air for controlling the flow of air into one of the passages divided by the partition. An in-cylinder injection engine comprising a flow control plate (73).

5. The in-cylinder injection engine according to claim 1,

An in-cylinder injection engine, comprising a single pump (18) for pressurizing fuel in a pipe halfway from a fuel tank to a fuel injection valve attached to the engine.

6. An in-cylinder injection engine having a fuel injection valve for injecting fuel into a cylinder to form a fuel spray, The fuel injection valve (19) has an air layer generating means (6) for injecting flat fuel spray into the cylinder and generating an air layer between the piston top surface and the cylinder wall surface and the flat spray. An in-cylinder injection engine characterized in that:

7. In a cylinder injection engine having a fuel injection valve that injects fuel into a cylinder to form a fuel spray,

The fuel injection valve (19) is provided with air flow generating means (6) for injecting flat fuel spray into a cylinder and generating air flow on both sides of the flat spray so as to sandwich the flat spray. An in-cylinder injection engine characterized in that:

8. A method of controlling an in-cylinder injection engine that controls an in-cylinder injection engine having a fuel injection valve that injects fuel into a cylinder to form a fuel spray,

The fuel injection valve (19) injects a flat fuel spray (38) into the cylinder and generates an air flow (37) between the piston top surface and the cylinder wall and the flat spray. With (6),

After the air flow is formed in the combustion chamber of the engine by the air flow generation means, fuel is injected from the fuel injection valve at any timing from the intake stroke to the first half of the compression stroke. Control method.