JPH06294366A - Fuel injection device for internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent atomization of the actual engine A / F from the target A / F and promote atomization of the injected fuel. [Structure] Intake duct 11 downstream of air flow meter 12
And the injection valve 14 disposed in the intake port 6 between the air passage 3
1, 33 are connected. An air pump 32 is arranged in the air passages 31 and 33, compressed air discharged from the air pump 32 is supplied to the injection valve 14, and the compressed air is injected from the injection valve 14 together with the fuel into the intake port 6. The fuel injection amount is controlled based on the air amount detected by the air flow meter 12. The discharge pressure of the air pump is controlled according to the negative pressure introduced into the negative pressure chamber 38 of the air pump 32 so that the compressed air amount ejected from the injection valve 14 becomes the target air amount. All the compressed air discharged from the air pump 32 is constantly supplied to the injection valve 14, and the compressed air is ejected from the injection valve 14 into the intake port 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art An injection valve is arranged in an intake passage downstream of an air flow meter, an air passage branched from an intake passage downstream of the air flow meter is connected to the injection valve, and an air pump is arranged in the air passage to discharge the air from the air pump. There is known a fuel injection device for an internal combustion engine in which the compressed air thus supplied is supplied to an injection valve and the compressed air is injected together with fuel from the injection valve into an intake passage (see Japanese Patent Laid-Open No. 5-44603). In this fuel injection device for an internal combustion engine, compressed air is collided with the fuel to promote atomization of the fuel. Further, in this fuel injection device, the fuel is jetted into the intake passage at a high speed together with the compressed air, so that the fuel is prevented from diffusing in the intake passage, and as a result, the fuel adheres to the inner wall surface of the intake passage. Be blocked.

[0003]

By the way, the above-mentioned fuel injection device for an internal combustion engine is provided with a discharge pressure control device. In this discharge pressure control device, a part of the compressed air discharged from the air pump is flown through the air return passage. The discharge pressure of the air pump is made constant by returning to the intake passage downstream of the meter. That is, when the discharge pressure of the air pump becomes higher than a predetermined set pressure, the opening degree of the air return passage is increased to increase the amount of air returned to the intake passage through the air return passage, while the discharge pressure of the air pump is increased. When is lower than the set pressure, the discharge pressure of the air pump is maintained constant by decreasing the opening degree of the air return passage to reduce the amount of air returned to the intake passage via the air return passage. However, although the air that has passed through the air flow meter and the amount of which is detected by the air flow meter is composed of the air that has flowed into the intake passage downstream of the air passage and the air that has flowed into the air passage, the above-mentioned fuel injection is performed. When a part of the compressed air flowing in the air passage is returned to the inside of the intake passage downstream of the air flow meter in order to make the discharge pressure of the air pump constant as in the device, the air is returned through the air return passage. The air returned into the intake passage will flow into the combustion chamber later than the remaining air.Therefore, the amount of air actually flowing into the combustion chamber is the amount of air detected by the air flow meter, especially during transient engine operation. As a result, the fuel injection amount is determined based on the air amount detected by the air flow meter. There is a problem that deviates from the actual engine A / F is the target A / F.

[0004]

In order to solve the above problems, according to the present invention, an injection valve is arranged in the intake passage downstream of the air flow meter, and an air passage branched from the intake passage downstream of the air flow meter is injected. An air pump is connected to the valve and an air pump is arranged in the air passage, compressed air discharged from the air pump is supplied to the injection valve, the compressed air is injected from the injection valve together with the fuel into the intake passage, and is detected by the air flow meter. In a fuel injection device for an internal combustion engine, which controls the fuel injection amount based on the air amount, the air pump is composed of an air pump whose discharge pressure is controllable, and the amount of compressed air ejected from an injection valve is the operating state of the engine. When the discharge pressure of the air pump is controlled so that the target air amount is determined according to the above, all compressed air discharged from the air pump is constantly supplied to the injection valve. So that is ejected into the intake passage from the injection valve the compressed air.

[0005]

Since the discharge pressure of the air pump is controlled so that the amount of compressed air ejected from the injection valve becomes the target air amount, all the compressed air discharged from the air pump is supplied to the injection valve, and therefore the engine A / It is prevented that F shifts from the target A / F.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, 1 is a cylinder block,
2 is a piston that reciprocates in the cylinder block 1, 3 is a cylinder head fixed on the cylinder block 1, 4
Is a combustion chamber formed between the piston 2 and the inner wall surface of the cylinder head 3, 5 is an intake valve, 6 is an intake port, 7 is an exhaust valve, 8
Indicate exhaust ports, respectively. The intake port 6 is connected to a common surge tank 10 via a corresponding branch pipe 9, and the surge tank 10 is connected to an air cleaner 13 via a common intake duct 11 and an air flow meter 12.
An injection valve 14 is arranged in each intake port 6, and the structure of the injection valve 14 will be described next with reference to FIG.

Referring to FIG. 2, the injection valve 14 includes a fuel injection valve 15 and an air control valve 16. The fuel injection valve 15 is inserted into a fuel injection valve insertion hole 18 formed in the housing 17, and the fuel injection valve insertion hole 1 below the fuel injection valve 15 is inserted.
A fuel air nozzle 19 and a long nozzle 20 are inserted in the unit 8. A fuel guide hole 21 is provided in the fuel air nozzle 19.
And a fuel air hole 22 is formed in the long nozzle 20, and the fuel guide hole 21, the fuel air hole 22 and the injection port of the fuel injection valve 15 are aligned with each other.
5, the fuel air nozzle 19 and the long nozzle 20 are fixed at regular positions in the fuel injection valve insertion hole 18. A bidirectional nozzle 24 having a pair of fuel air ejection holes 23 is attached to the tip of the long nozzle 20, and the fuel air holes 22 are communicated with the intake port 6 through the fuel air ejection holes 23. On the other hand, the air control valve 16 is inserted into the air control valve insertion hole 25 formed in the housing 17,
The injection port is fixed at a regular position in the air control valve insertion hole 25. The air control valve insertion hole 25 is connected to the annular air chamber 27 formed between the inner peripheral surface of the fuel injection valve insertion hole 18 and the outer peripheral surface of the fuel air nozzle 19 via the air supply hole 26, and the annular air chamber 27 is connected to the fuel air It communicates with the inside of the fuel guide hole 21 through a compressed air ejection hole 28 formed in the nozzle 19. An air supply passage 31 described later is connected to the air control valve 16.

In the embodiment according to the present invention, the air control valve 1
6, as shown in FIG. 3, the fuel injection valve 15 is opened for a set time To before the fuel injection valve 15 is opened, and the fuel injection valve 15 is closed for a set time Tc and then closed. The times To and Tc are constant regardless of the engine operating state.
As a result, when the fuel is injected from the fuel injection valve 15 to the inner end surface of the fuel guide hole 21, the injected fuel is already injected into the air control valve 1.
6, the annular air chamber 27 and the compressed air ejection holes 2
Since it collides with the compressed air flowing in the fuel guide hole 21 and the fuel air hole 22 via 8, the atomization of this injected fuel is promoted. Further, the compressed air ejected from the air control valve 16 after the fuel injection valve 15 is closed causes the fuel guide hole 21, the fuel air hole 22 and each fuel air ejection hole 2 to be compressed.
It is prevented that the injected fuel remains in the fuel cell 3, and as a result, the amount of fuel supplied into the combustion chamber 4 is prevented from deviating from the regular fuel amount. These fuel and compressed air are then ejected from the fuel air ejection holes 23 into the corresponding intake ports 6.

Further, the fuel injection time TAU is the engine load Q / N (intake air amount Q / engine speed N) and the engine speed calculated based on the outputs of the air flow meter 12 and the speed sensor 60 (FIG. 1). It is stored in advance in the ROM 52 (FIG. 1) in the form of a map as shown in FIG. 4 as a function of N. In the embodiment according to the present invention, the fuel injection pressure is constantly controlled so that the fuel injection amount is proportional to the fuel injection time TAU. On the other hand, the compressed air injection time is T
It is obtained by o + TAU + Tc, and therefore the compressed air injection time is also a function of the engine load Q / N and the engine speed N. In the embodiment according to the present invention, the fuel injection valve 1
5 and the air control valve 16 are controlled to open and close based on the output signal of the electronic control unit 50, and when power is supplied to the fuel injection valve 15 and the air control valve 16 based on the output signal of the electronic control unit 50, these fuels are supplied. The injection valve 15 and the air control valve 16 are adapted to open.

Further, as shown in FIG. 2, an annular P is formed between the inner peripheral surface of the fuel injection valve insertion hole 18 and the outer peripheral surface of the long nozzle 20.
A TC heater 29 is arranged, and in the embodiment according to the present invention, the PTC heater 29 has a predetermined engine cooling water temperature before completion of engine warm-up, that is, detected by a water temperature sensor 58 (FIG. 1) attached to the engine body 1. It is activated when the water temperature is lower than the set temperature. As a result, the long nozzle 20 and the two-way nozzle 24 are heated, so that the fuel air holes 2
It is possible to heat the injected fuel and the compressed air flowing in the fuel injection holes 2 and the respective fuel air ejection holes 23, and thus further promote the atomization of the injected fuel flowing in the fuel air holes 25 and the respective fuel air ejection holes 27. be able to.

Referring again to FIG. 1, the intake duct 11 between the air flow meter 12 and the throttle valve 30 is connected to an air pump 32 via an air supply passage 31 forming an air passage, and the air pump 32 is a compression forming an air passage. It is connected to the air control valve 16 (FIG. 2) of the injection valve 14 via the air passage 33. In the embodiment according to the present invention, the air pump 32 comprises a reciprocating air pump.
Referring to FIG. 5 showing the structure of No. 2, 34 is a cylinder,
Reference numeral 35 is a rotary shaft, 36 is a piston reciprocating in the cylinder 34, 37 is a compression chamber, 38 is a negative pressure chamber separated from the compression chamber 37 by a diaphragm 39, and 40 is a negative pressure chamber 38.
The reference numeral 41 designates a compression spring disposed inside, and 41 indicates a discharge pressure control piston mounted on the diaphragm 39 and disposed inside the compression chamber 37. As shown in FIGS. 1 and 5, the compression chamber 3
7, an air supply passage 31 is connected via a reed valve 42, and a compressed air passage 33 is connected via a reed valve 43. On the other hand, in the negative pressure chamber 38, the negative pressure introducing passage 4
4, the branch pipe 9 is connected to the inside of the negative pressure chamber 38.
The negative pressure generated inside is introduced through the negative pressure introducing passage 44. In the embodiment according to the present invention, the rotary shaft 35 is connected to the crank shaft (not shown) of the engine 1.

The discharge pressure control piston 41 is displaced together with the diaphragm 39 according to the pressure in the negative pressure chamber 38, and changes the discharge pressure of the air pump 32. That is, when the discharge pressure control piston 41 is displaced upward together with the diaphragm 39, the volume of the compression chamber 37 formed between the discharge pressure control piston 41 and the piston 36 increases, so that the air pump 32
Volume efficiency of the air pump 32 is reduced, and as a result, the air pump 32
The discharge pressure of is reduced. On the other hand, when the discharge pressure control piston 41 is displaced downward together with the diaphragm 39, the volume of the compression chamber 37 is reduced, so that the volumetric efficiency of the air pump 32 is increased, and as a result, the discharge pressure of the air pump 32 is increased.

As shown in FIG. 1, the electronic control unit 5
0 is a digital computer, bidirectional bus 5
ROM (Read Only Memory) 52, RAM (Random Access Memory) 53, C mutually connected via 1
It has a PU (microprocessor) 54, an input port 55 and an output port 56. The air flow meter 12 generates an output voltage proportional to the air flow rate, and this output voltage is input to the input port 55 via the AD converter 57.
A water temperature sensor 58 that generates a voltage proportional to the engine cooling water temperature is attached to the engine body 1, and the output voltage of the water temperature sensor 58 is input to the input port 55 via the AD converter 59. Further, a rotation speed sensor 60 that generates an output pulse representing the engine rotation speed is connected to the input port 55. On the other hand, the output port 56 is connected to each injection valve 14 via the corresponding drive circuit 61.

In the first embodiment according to the present invention, the compressed air injection amount per unit valve opening time of the air control valve 16 is set to a predetermined constant amount regardless of the engine operating state. Air injection pressure, that is, air pump 3
The pressure difference between the discharge pressure 2 and the pressure inside the branch pipe 9 is maintained at a predetermined constant pressure difference regardless of the engine operating state. In the embodiment according to the present invention, the fuel injection amount per unit opening time of the fuel injection valve 15 is controlled to a predetermined constant amount which does not depend on the engine operating state, and as a result, the unit opening time of the air control valve 16 is controlled. By maintaining the compressed air injection amount per hit constant regardless of the engine operating state, the ratio between the fuel injection amount and the compressed air amount to be collided with the injected fuel is always maintained constant. Therefore, it is possible to prevent the atomization of the injected fuel due to the collision of the compressed fuel with the injected fuel from varying depending on the engine operating state.

By the way, the discharge pressure of the air pump 32 is set higher than the target discharge pressure, and a part of the compressed air discharged from the air pump 32 is returned to the intake duct 11, for example, and the discharge pressure of the air pump 32 and the branch pipe. If the differential pressure from the pressure inside 9 is controlled to the target differential pressure, the amount of air actually flowing into the combustion chamber 4 will deviate from the intake air amount Q detected by the air flow meter 12, and therefore When the fuel injection amount is determined based on the intake air amount Q as in the embodiment according to the invention, the actual engine A / F deviates from the target A / F.
Further, if the discharge pressure of the air pump 32 is set higher than the target discharge pressure in this way, the power of the air pump 32 is increased, so that the air pump 32 is driven by the engine 1 as in the embodiment of the present invention. If this is set, the pump loss of the engine will increase and the fuel efficiency of the engine will deteriorate. Therefore, in the first embodiment according to the present invention, the volume of the compression chamber 37 of the air pump 32 is changed according to the pressure in the branch pipe 9 to make the differential pressure between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 constant. Thus, the discharge pressure of the air pump 32 is controlled.

That is, the negative pressure generated in the branch pipe 9 is introduced into the negative pressure chamber 38 of the air pump 32 through the negative pressure introducing passage 44, and the discharge pressure control piston 41 is proportional to the magnitude of this negative pressure. Are displaced together with the diaphragm 39. At this time, the discharge pressure control piston 41 is controlled so that the discharge pressure of the air pump 32 in the volume of the compression chamber 37 obtained by the displacement of the discharge pressure control piston 41 becomes the target discharge pressure, that is, the discharge pressure of the air pump 32 and the branch pressure. The pipe 9 is displaced so that the pressure difference from the pressure in the pipe 9 becomes constant. Therefore, the air pump 32
A portion of the compressed air discharged from the
The differential pressure between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 can be maintained constant without returning to the inside of 1, so that the actual engine A / F is prevented from deviating from the target A / F. it can. Further, in the first embodiment according to the present invention, since the discharge pressure of the air pump 32 is the target discharge pressure, all the compressed air discharged from the air pump 32 is supplied to the air control valve 16 and, as a result, the air pump 32. The power to drive the can be minimized. The compressed air supplied from the air pump 32 to the air control valve 16 is then injected into the intake port 6.

FIG. 6 shows the relationship between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 in the first embodiment of the present invention. In FIG. 6, the solid line shows the discharge pressure of the air pump 32, and the broken line shows the branch pipe 9. The internal pressure is shown. In the first embodiment, the differential pressure ΔP between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 is maintained constant regardless of the engine operating state. As a result, the compressed air injection amount per unit opening time of the air control valve 16 can be maintained constant regardless of the engine operating state.

7 and 8 show a second embodiment according to the present invention. In the embodiment shown in FIGS. 7 and 8, the same components as those in FIG. 1 are designated by the same reference numerals, and the electronic control unit is omitted in FIG. As shown in FIGS. 7 and 8, in the second embodiment, a negative pressure control device 61 is provided in the negative pressure introducing passage 44 that connects the negative pressure chamber 38 and the branch pipe 9. Referring to FIGS. 7 and 8, 62 is a negative pressure control chamber, 63 is a branch from the negative pressure introducing passage 44, and the negative pressure control chamber 6 is provided.
Reference numeral 64 denotes a negative pressure passage communicated with the inside of the negative pressure passage, 64 denotes a compressed air pressure chamber separated from the negative pressure control chamber 62 by a diaphragm 65, and 66 denotes a compression spring arranged in the negative pressure control chamber 62. The negative pressure control chamber 62 is connected to the intake duct 11 between the air flow meter 12 and the throttle valve 30 via the atmospheric pressure introducing passage 67, and therefore, the negative pressure control chamber 62 has an intake air between the air flow meter 12 and the throttle valve 30. Almost atmospheric pressure in the duct 11 is introduced through the atmospheric pressure introduction passage 67. On the other hand, the compressed air pressure chamber 64 is connected to the air control valve insertion hole 25 (see FIG. 2) of the injection valve 14 via the compressed air pressure introduction passage 68. The compressed air pressure is introduced through the compressed air pressure introduction passage 68. A valve 69 is attached to the diaphragm 65 as shown in FIG.
Is displaced together with the diaphragm 65 according to the pressure difference between the pressure inside the negative pressure control chamber 62 and the pressure inside the compressed air pressure chamber 64 to open or close the negative pressure passage 63.

In the second embodiment of the present invention, the compressed air injection amount per unit opening time of the air control valve 16 increases as the pressure in the branch pipe 9 decreases, that is, in the branch pipe 9. The discharge pressure of the air pump 32 is made to match a substantially constant set pressure that does not depend on the engine operating state so that the lower the pressure is, the larger the differential pressure between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 becomes. . In the second embodiment, the discharge pressure of the air pump 32 is set to be higher than the atmospheric pressure by a predetermined set pressure. However, the atmospheric pressure can be regarded as substantially constant regardless of the engine operating state, so the air pump. By increasing the discharge pressure of 32 to the atmospheric pressure by a predetermined set pressure, the air pump 32
It can be considered that the discharge pressure of is maintained substantially constant. When the pressure in the branch pipe 9 is lower, that is, when the engine load is lower, the compressed air injection amount per unit opening time of the air control valve 16 is increased, and when the pressure in the branch pipe 9 is lower, the fuel injection is performed. The ratio of the injection amount of compressed air to the injection amount is increased, and as a result, the collision action of the injected fuel and the compressed air is increased, so that atomization of the injected fuel is promoted. In an ordinary internal combustion engine, the combustion chamber 4 (Fig. 1) during engine low load operation
The combustion of the air-fuel mixture in the combustion chamber 4 is apt to be deteriorated. Therefore, as in the second embodiment of the present invention, by promoting atomization of the injected fuel especially during low-engine operation of the engine, the air-fuel mixture in the combustion chamber 4 is also operated during low-engine operation. Can be satisfactorily burned.

When the discharge pressure of the air pump 32 becomes lower than the set pressure determined by the spring force of the compression spring 66, the pressure in the compressed air pressure chamber 64 causes the pressure in the negative pressure control chamber 62 to exceed the force acting on the diaphragm 65. The pressure acting on the diaphragm 65 becomes larger due to the atmospheric pressure and the spring force of the compression spring 66, which causes the valve 69, together with the diaphragm 65, to move upward in FIG. 8 to open the negative pressure passage 63. . When the negative pressure passage 63 is opened, the negative pressure introduced into the negative pressure chamber 38 via the negative pressure introducing passage 44 is reduced by the atmospheric pressure introduced into the negative pressure control chamber 62, and as a result, the discharge pressure control piston 41 is urged downward together with the diaphragm 39 by the compression spring 40, and the volume of the compression chamber 37 is reduced.
The discharge pressure of 2 is increased. On the other hand, the air pump 32
Is higher than the set pressure, the atmospheric pressure introduced into the negative pressure control chamber 62 and the force exerted on the diaphragm 65 by the spring force of the compression spring 66 cause the pressure introduced into the compressed air pressure chamber 64. The force acting on the diaphragm 65 becomes larger, and as a result, the valve 69 moves to the diaphragm 6
The negative pressure passage 63 is closed by being displaced downward together with 5. When the negative pressure passage 63 is closed, the negative pressure in the branch pipe 9 is directly introduced into the negative pressure chamber 38 via the negative pressure introduction passage 44, and as a result, the discharge pressure control piston 41 and the diaphragm 39 together with the compression spring 40. As a result, the volume of the compression chamber 37 is increased and the discharge pressure of the air pump 32 is reduced. It should be noted that all the compressed air discharged from the air pump 32 is supplied to the air control valve 16, and this compressed air is then injected into the intake port 6.

FIG. 9 shows the relationship between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 in the second embodiment of the present invention. In FIG. 9, the solid line shows the discharge pressure of the air pump 32, and the broken line shows the branch pipe 9. The internal pressure is shown. In the second embodiment, the differential pressure ΔP 'between the discharge pressure of the air pump 32 and the atmospheric pressure is maintained constant regardless of the engine operating state. Therefore, the differential pressure ΔP between the discharge pressure of the air pump 32 and the pressure in the branch pipe 9 becomes larger as the pressure in the branch pipe 9 becomes lower, and as a result, the compressed air injection amount per unit opening time of the air control valve 16 is increased. Will increase as the engine load decreases.

In the above-described embodiment, the air pump 32 is composed of an air pump whose discharge pressure can be controlled.
The compressed air pressure from the air control valve 16 is set to the target pressure by controlling the discharge pressure of. On the other hand, for example, it is conceivable that the air pump is composed of an air pump whose discharge pressure cannot be controlled, and the compressed air pressure from the air control valve 16 is set to a target pressure by controlling the opening period of the air control valve 16. That is, when the compressed air pressure by the air control valve 16 is higher than the target pressure, the opening period of the air control valve 16 is lengthened, while when the compressed air pressure is lower than the target pressure, the opening period of the air control valve 16 is shortened. Can be considered. However, in the embodiment according to the present invention, the air control valve 16 is opened only during the energized period. Therefore, if the opening period of the air control valve 16 is increased so as to reduce the compressed air pressure to the target pressure, the air control valve 16 is controlled. Valve 16
Power consumption increases because the energization period to the air control valve is extended, and the durability of the air control valve 16 deteriorates because the period in which the air control valve 16 is maintained in the open state is extended. . However, in the embodiment according to the present invention, since the compressed air pressure from the air control valve 16 is controlled to the target pressure by controlling the discharge pressure of the air pump 32, deterioration of durability of the air control valve 16 is prevented. To be done.

In the above embodiment, the injection valve 14 is attached to the cylinder head 10. However, the injection valve 14 may be mounted in the branch pipe 2. Alternatively, the compressed air passage 33 may be directly connected to the annular air chamber 27 without providing the air control valve 16.

[0024]

Since the discharge pressure of the air pump is controlled so that the amount of compressed air ejected from the injection valve becomes the target air amount, all the compressed air discharged from the air pump is supplied to the injection valve and then the intake passage. It is possible to prevent the amount of air that is injected into the combustion chamber and that actually flows into the combustion chamber from deviating from the amount of air detected by the air flow meter, and thus the actual engine A / F deviates from the target A / F. It is possible to prevent the engine A / F from deviating from the target A / F.

[Brief description of drawings]

FIG. 1 is an overall view of an internal combustion engine.

FIG. 2 is an enlarged side sectional view of an injection valve.

FIG. 3 is a diagram showing drive timings of a fuel injection valve and an air control valve.

FIG. 4 is a diagram showing a fuel injection time.

FIG. 5 is an enlarged side sectional view of the air pump.

FIG. 6 is a diagram showing the relationship between the discharge pressure of the air pump and the pressure in the branch pipe.

FIG. 7 is an overall view of an internal combustion engine showing a second embodiment.

FIG. 8 is an enlarged side sectional view of an air pump and a negative pressure control device according to a second embodiment.

FIG. 9 is a diagram showing the relationship between the discharge pressure of the air pump and the pressure in the branch pipe in the second embodiment.

[Explanation of symbols]

 6 ... Intake port 9 ... Branch pipe 11 ... Intake duct 12 ... Air flow meter 14 ... Injection valve 31, 33 ... Air passage 32 ... Air pump 37 ... Compression chamber 38 ... Negative pressure chamber 44 ... Negative pressure introduction passage

Claims (1)

[Claims] 1. An injection valve is arranged in an intake passage downstream of an air flow meter, an air passage branched from an intake passage downstream of the air flow meter is connected to the injection valve, and an air pump is arranged in the air passage to discharge from the air pump. The compressed fuel is supplied to the injection valve, the compressed air is injected from the injection valve together with the fuel into the intake passage, and the fuel injection amount is controlled based on the air amount detected by the air flow meter. In the injection device, the air pump is composed of an air pump whose discharge pressure is controllable, and the discharge pressure of the air pump is controlled so that the amount of compressed air ejected from the injection valve becomes a target air amount that is determined according to the operating state of the engine. All the compressed air discharged from the air pump is constantly supplied to the injection valve, and the compressed air is ejected from the injection valve into the intake passage. Fuel injection device for internal combustion engine.