JP2000274329A - Fuel injection device for internal combustion engine - Google Patents

Abstract

[PROBLEMS] To provide a fuel injection device for an internal combustion engine capable of supplying fuel to a cylinder even when a supplied fuel pressure is low, without providing a large electric drive type external pump. SOLUTION: A solenoid type injector 6 is provided together with a piezo type injector 3 to supply fuel to a cylinder 2. As a result, even when fuel cannot be supplied to the cylinder 3 by the piezo injector 3, that is, when fuel pressure supplied to the injector is low, fuel is supplied to the cylinder 2 by the solenoid injector 6. Can be supplied. That is, it is possible to eliminate the need to provide a large electrically driven external pump to increase the fuel pressure supplied to the injector.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fuel injection device for an internal combustion engine.

[0002]

2. Description of the Related Art Conventionally, a fuel injection device for an internal combustion engine provided with a piezoelectrically driven fuel injection valve for supplying fuel to a cylinder is known. An example of this type of fuel injection device for an internal combustion engine is disclosed in, for example, JP-A-6-173812. A fuel injection device for an internal combustion engine described in JP-A-6-173812 supplies fuel at a relatively high pressure to a piezoelectrically driven fuel injection valve and operates a piezoelectric element actuator to thereby supply fuel to a cylinder. Can be supplied.

[0003]

[Problems to be Solved by the Invention] Japanese Patent Application No. Hei 6-17381
In the fuel injection device for an internal combustion engine described in Japanese Patent Publication No. 2 (1993), in order to supply fuel to a cylinder, fuel at a relatively high pressure must be supplied to a piezoelectrically driven fuel injection valve.
In the first place, by using a piezoelectrically driven fuel injection valve as a fuel injection device, it is possible to control the opening of the fuel injection valve even when a higher fuel pressure is supplied, thereby injecting fuel at a higher fuel pressure. Is possible, and atomization of the fuel is improved.However, the piezoelectrically-driven fuel injection valve is provided with a valve-closing force against the high fuel pressure. The valve opening force is given by the sum of the driving force of the piezoelectric driving portion and the driving force. Therefore, in the case of the piezoelectrically driven fuel injection valve, it is necessary that a relatively high pressure fuel be supplied during its operation. After the first explosion in the cylinder, the fuel pressure of the high-pressure pump driven by the rotational force of the crankshaft is sufficient due to the combustion pressure in the cylinder, but the first explosion is performed in the cylinder In the past, because of the insufficient discharge by the high-pressure pump, it takes a long time to start, or it is necessary to increase the fuel discharge capability of an externally driven external pump.

That is, in the fuel injection device of the internal combustion engine described in Japanese Patent Application Laid-Open No. 6-173812, high-pressure fuel is supplied to the piezoelectrically driven fuel injection valve before the first explosion is performed in the cylinder. In addition, a relatively large electrically driven external pump must be provided.

In view of the above problems, the present invention provides a method of supplying fuel to a cylinder without providing a large electrically driven external pump, that is, even when the pressure of the fuel supplied to the fuel injection valve is low. It is another object of the present invention to provide a fuel injection device for an internal combustion engine that can hasten start-up.

[0006]

According to the first aspect of the present invention, an electromagnetically driven fuel injector and a piezoelectrically driven fuel injector are provided for supplying fuel to a cylinder, and the piezoelectrically driven fuel injector is provided. When the pressure of the fuel supplied to the injection valve is low, fuel is supplied to the cylinder by the electromagnetically driven fuel injection valve, and when the pressure of the fuel supplied to the piezoelectrically driven fuel injection valve is high, A fuel injection device for an internal combustion engine is provided, in which fuel is supplied to the cylinder by a piezoelectrically driven fuel injection valve.

In the fuel injection device for an internal combustion engine according to the present invention, an electromagnetically driven fuel injection valve and a piezoelectrically driven fuel injection valve are provided to supply fuel to the cylinder. Can supply fuel to the cylinder by the electromagnetically driven fuel injection valve even when fuel cannot be supplied to the cylinder, that is, when the pressure of the fuel supplied to the fuel injection valve is low. . That is, the starting can be hastened without providing a large electrically driven external pump to increase the pressure of the fuel supplied to the fuel injection valve.

According to the second aspect of the present invention, the time when the pressure of the fuel supplied to the piezoelectrically driven fuel injection valve is low is a time before the first explosion is performed in the cylinder. A fuel injection device for an internal combustion engine according to claim 1 is provided.

In the fuel injection device for an internal combustion engine according to the second aspect, even when the pressure of the fuel supplied to the fuel injection valve is low before the first explosion is performed in the cylinder, The start can be hastened without providing a large electrically driven external pump.

According to the third aspect of the present invention, the internal combustion engine is a multi-cylinder internal combustion engine, the piezoelectrically driven fuel injection valve is disposed in each cylinder, and the electromagnetically driven fuel injection valve is provided. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the injection valve is disposed in an intake cylinder extending to each cylinder.

In the fuel injection device for an internal combustion engine according to the third aspect of the invention, the electromagnetically driven fuel injection valve disposed in the intake pipe can speed up the start without providing a large electrically driven external pump, and can reduce the time required for starting the piezoelectric device. Since the driven fuel injection valve is arranged in each cylinder, it is possible to achieve the effects peculiar to direct injection, such as improving fuel efficiency as compared with the case where the piezoelectrically driven fuel injection valve is arranged in the intake port. it can.

According to a fourth aspect of the present invention, the internal combustion engine is a multi-cylinder internal combustion engine, and the electromagnetically driven fuel injection valve is disposed in a collective portion of a plurality of intake pipes extending to each cylinder. A fuel injection device for an internal combustion engine according to claim 1 is provided.

In the fuel injection device for an internal combustion engine according to the present invention, the electromagnetically driven fuel injection valve is disposed in one collective portion including a plurality of intake pipes extending to each cylinder.
The number of electromagnetically driven fuel injection valves can be reduced as compared with the case where the electromagnetically driven fuel injection valves are arranged in each intake port, and the cost of the fuel injection device for the internal combustion engine can be reduced.

According to the fifth aspect of the present invention, the electromagnetically driven fuel injection valve and the piezoelectrically driven fuel injection valve are arranged in the cylinder, and when a stratified mixture is to be formed in the cylinder, 2. The fuel for an internal combustion engine according to claim 1, wherein fuel is injected by said piezoelectrically driven fuel injection valve, and fuel is injected by said electromagnetically driven fuel injection valve when a homogeneous mixture is to be formed in said cylinder. An injection device is provided.

In the fuel injection device for an internal combustion engine according to the present invention, when a stratified mixture is to be formed in a cylinder, fuel is injected by a piezoelectrically driven fuel injection valve to form a homogeneous mixture in the cylinder. Since fuel is sometimes injected by the electromagnetically driven fuel injection valve, a desired air-fuel mixture can be formed according to the conditions for forming the air-fuel mixture.

[0016]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic configuration diagram of a first embodiment of a combustion injection device for an internal combustion engine according to the present invention. In FIG. 1, 1
Reference numeral denotes a four-cylinder internal combustion engine, reference numeral 2 denotes a cylinder, and reference numeral 3 denotes a piezoelectrically driven fuel injection valve (piezo injector) disposed in the cylinder 2 for directly injecting fuel into the cylinder 2. The piezo injector 3 is disclosed in, for example,
This is a known type of piezo injector as described in Japanese Patent Application Laid-Open No. 12-112. Reference numeral 4 denotes an intake manifold, 5 denotes an intake manifold assembly in which a plurality of intake pipes extending to each cylinder are gathered, and 6 denotes an electromagnetic solenoid arranged in the intake manifold assembly 5 for supplying fuel into the cylinder 2. It is a drive type fuel injection valve (solenoid type injector). The solenoid type injector 6 is a known type of a solenoid type injector as described in, for example, JP-A-62-90975.

Further, in FIG. 1, reference numeral 7 denotes a fuel delivery for supplying fuel to each piezo injector 3, and reference numeral 8 denotes a fuel pressure sensor for detecting a fuel pressure in the fuel delivery 7. Reference numeral 9 denotes a high-pressure pump driven by the rotational force of a crankshaft (not shown) to supply fuel to the fuel delivery 7 at a high fuel pressure. Reference numeral 10 denotes an electromagnetic spill valve for controlling the fuel pressure in the fuel delivery 7 to a predetermined fuel pressure, and reference numeral 11 denotes a high-pressure fuel pipe for communicating the high-pressure pump 9 with the fuel delivery 7. Reference numeral 12 denotes a low-pressure pump that is electrically driven to supply fuel to the solenoid injector 6, and reference numeral 13 denotes a pressure regulator that controls the fuel pressure supplied to the solenoid injector 6 to a predetermined fuel pressure. . 14 is the low pressure pump 1
2 is a low-pressure fuel pipe for communicating the solenoid type injector 6, 15 is a fuel tank, 16 is a fuel tank 15
It is a fuel suction pipe for sucking fuel inside. 17
Pumps the fuel pressurized by the high pressure pump 9 to the electromagnetic spill valve 1
0, a fuel return pipe for returning to the fuel tank 15 through 1
Reference numeral 8 denotes a fuel return pipe for returning the fuel pressurized by the low-pressure pump 12 to the fuel tank 15 via the pressure regulator 13. An electronic control unit (EC) 19 receives an electric signal from the fuel pressure sensor and outputs an electric signal for driving the piezo injector 3, the solenoid injector 6, the electromagnetic spill valve 10, and the low-pressure pump 12.
U).

FIG. 2 is a flowchart showing a control method of the solenoid type injector. As shown in FIG.
When the control of the solenoid injector 6 is started at a predetermined timing, first, in step 201, it is determined whether or not fuel injection is being performed by the piezo injector 3. If YES, the piezo injector 3
Therefore, it is determined that it is not necessary to inject fuel by the solenoid type injector 6 because the fuel pressure has risen to such an extent that fuel can be injected, and this routine ends. On the other hand, if NO, the process proceeds to step 202.

In step 202, it is determined whether or not the ignition switch is located at the ON position.
If YES, the process proceeds to step 203. On the other hand, at the time of NO, the fuel is not supplied to the solenoid-type injector 6 because the low-pressure pump 12 cannot be electrically driven.
Therefore, it is determined that the fuel cannot be injected by the solenoid type injector 6, and this routine ends. In step 203, fuel is supplied to the solenoid type injector 6 by electrically driving the low pressure pump 12. Next, at step 204, when there is a signal to inject fuel, specifically, from the start of rotation of the starter motor to the start of fuel injection by the piezo injector 3, fuel is injected from the solenoid injector 6. Then, fuel is supplied to the cylinder 2.

FIG. 3 is a flowchart showing a method for controlling the piezo injector. As shown in FIG. 3, when the control of the piezo injector 3 is started at a predetermined timing, first, in step 301, it is determined whether or not the ignition switch is located at the ON position. If YES, the process proceeds to step 302. On the other hand, NO
In this case, the crankshaft is not rotated by the starter motor, and the combustion of the internal combustion engine is not yet started, so that the crankshaft is not rotated by the combustion. Therefore, the high-pressure pump 9 is not operated, and the piezo-type injector is not operated. 3 is determined to be unable to supply fuel, and this routine ends.

Next, at step 302, it is determined whether or not the ignition switch is located at the START position and the starter motor has been started. If YES, the process proceeds to step 303. On the other hand, at the time of NO, the rotation of the crankshaft by the starter motor is not performed, and since the combustion of the internal combustion engine has not started yet, the rotation of the crankshaft by the combustion is not performed, so that the high-pressure pump 9 is not operated, It is determined that fuel cannot be supplied to the piezo injector 3, and this routine ends.

Next, at step 303, the cell motor is started and the fuel injection by the piezo type injector 3 is started, so that the first explosion is performed. As a result, the mechanical driving of the high pressure pump 9 is started, and the piezo type Fuel supply to the injector 3 is started. Next, at step 304, it is determined whether the fuel pressure P supplied to the piezo injector 3 has reached the set pressure P '(P≥P').
Is determined. If YES, proceed to step 306,
If NO, it is determined that the fuel pressure P supplied to the piezo injector 3 needs to be increased, and the routine proceeds to step 305. In step 305, the electromagnetic spill valve 10 is closed to increase the fuel pressure P supplied to the piezo injector 3 to the set pressure P ',
Return to step 304.

When YES is determined in step 304, that is, when the fuel pressure P supplied to the piezo injector 3 has increased to the set pressure P ', in step 306, the fuel pressure P is increased to the set pressure P'. The opening amount of the electromagnetic spill valve 10 is controlled so as to maintain the value. Next, at step 305, fuel is injected from the piezo injector 3 at a predetermined timing according to the operating conditions of the internal combustion engine,
Fuel is supplied to the cylinder 2.

FIG. 4 is a graph showing the relationship between the engine speed, the fuel pressure in the low-pressure fuel pipe, the injection rate of the solenoid injector, the fuel pressure in the high-pressure fuel pipe, and the injection rate of the piezo injector and time. . As shown in FIG. 4, when the ignition switch is placed in the ON position at time T _1, the low-pressure pump 12 is electrically driven, the fuel pressure in the low pressure fuel pipe 14 and the high pressure fuel pipe 11 is increased. Then, when the ignition switch is placed in the START position at time T _2, the starter motor is started, rises to the rotational speed the engine speed corresponds to the starter motor speed. At the same time (time T ₂ ), fuel injection by the solenoid injector 6 is started. The reason why the fuel injection by the solenoid type injector 6 is performed at a constant injection rate instead of at a pulsed injection rate as in the case of the piezo type injector 3;
That is, the reason why the solenoid-operated injector 6 continues to be opened is that firstly it is necessary to make the air-fuel ratio relatively rich at the time of the first explosion, and secondly that the fuel pressure supplied by the low-pressure pump 12 is relatively low. This is because the fuel injection period is low, so that it is necessary to lengthen the fuel injection period in order to secure a necessary and sufficient fuel injection amount.

[0026] air-fuel ratio is formed necessary for combustion, is performed initial explosion of the engine at time T _3, the engine speed is increased to the idling speed. Further, as the engine speed increases, the discharge pressure of the high-pressure pump 9 also increases, and as a result, the fuel pressure in the high-pressure fuel pipe 7 also increases. That is, the fuel pressure P supplied to the piezo injector 3 also increases.
When the fuel pressure P rises to the set pressure P ′ at time T ₄ , fuel injection by the piezo injector 3 is started.
At the same time (time T ₄ ), the fuel injection by the solenoid-type injector 6 becomes unnecessary, and the process is terminated.

According to the present embodiment, since the solenoid type injector 6 and the piezo type injector 3 are provided to supply the fuel to the cylinder 2, the fuel cannot be supplied to the cylinder 2 by the piezo type injector 3. At this time, that is, even when the fuel pressure P is lower than the set pressure P ′ (until time T ₄ ), fuel can be supplied to the cylinder 2 by the solenoid injector 6. That is, it is possible to eliminate the need to provide a large electrically driven external pump to increase the fuel pressure supplied to the piezo injector.

Further, according to the present embodiment, since the solenoid-type injector 6 capable of injecting fuel even when the fuel pressure is low is provided, before the first explosion in which the low fuel pressure is supplied only by the rotation of the starter motor ( be time until T _3), without the need to provide a large electrically driven external pump,
Fuel can be supplied to the cylinder 2 by the solenoid type injector 6.

Further, according to the present embodiment, since the piezo injectors 3 are arranged in the respective cylinders 2, the piezo injectors 3 are directly arranged to improve the fuel efficiency as compared with the case where the piezo injectors are arranged in the intake ports. An effect peculiar to injection can be obtained.

Further, according to the present embodiment, since the solenoid-type injectors 6 are arranged in the intake manifold collecting section 5, the number of solenoid-type injectors is smaller than when the solenoid-type injectors are arranged in each intake port. And the cost of the fuel injection device for the internal combustion engine can be reduced.

FIG. 5 is a schematic partial sectional view of an internal combustion engine to which a second embodiment of the fuel injection device for an internal combustion engine according to the present invention is applied. More specifically, FIG. 5A is a diagram when a stratified mixture is to be formed in a cylinder, and FIG. 5B is a diagram when a homogeneous mixture is to be formed in a cylinder. FIG. 5 (a) and FIG.
In (b), 100 is a cylinder, 103 is a piezo injector similar to that of the first embodiment, and 106 is a model similar to that of the first embodiment. This is a solenoid type injector that is arranged in the cylinder 100, not in the manifold. 120 is an ignition plug, 121 is a combustion chamber. As shown in FIG. 5A, when a stratified air-fuel mixture is to be formed in the cylinder 100, that is, the air-fuel mixture near the ignition plug 120 is made relatively rich and the other air-fuel mixture is made relatively thin. When it should, fuel is injected by the piezo injector 103. Further, as shown in FIG. 5B, when a homogeneous mixture is to be formed in the cylinder 100, that is, when a homogeneous mixture is to be formed in the entire combustion chamber 121, the fuel is injected by the solenoid injector 106. Is done.

Further, for the same reason as described in the first embodiment, when the fuel pressure supplied to the injector is relatively low, the fuel is injected by the solenoid type injector 103, and when the fuel pressure is relatively high, the piezo type is used. Fuel is injected by the injector 106.

According to the present embodiment, fuel is injected by the piezo injector 103 when a stratified mixture is to be formed in the cylinder 100, and fuel is injected by the solenoid injector 106 when a homogeneous mixture is to be formed in the cylinder 100. Is injected, it is possible to form a desired air-fuel mixture without moving the injector according to the air-fuel mixture formation conditions, that is, without changing the fuel injection direction.

Further, according to this embodiment, when the fuel pressure supplied to the injector is low, the fuel is injected by the solenoid type injector 106. Therefore, even when the fuel cannot be supplied to the cylinder 100 by the piezo injector 103, that is, even when the fuel pressure supplied to the injector is low, the fuel is supplied to the cylinder 100 by the solenoid injector 106. Thus, a homogeneous air-fuel mixture can be formed in the cylinder 100. That is, it is possible to eliminate the need to provide a large electrically driven external pump to increase the fuel pressure supplied to the injector.

In the above-described embodiment, when a stratified mixture is to be formed in the cylinder 100, the piezo injector 1
03, the fuel is injected by the solenoid type injector 106 when a homogeneous mixture is to be formed in the cylinder 100. In another embodiment, the piezo type is used when the homogeneous mixture is to be formed in the cylinder. Fuel can be injected by the injector when fuel is injected by the injector and a stratified mixture is to be formed in the cylinder.

[0036]

According to the first aspect of the present invention, when fuel cannot be supplied to the cylinder by the piezoelectrically driven fuel injection valve, that is, when the pressure of the fuel supplied to the fuel injection valve is increased. Even when it is low, fuel can be supplied to the cylinder by the electromagnetically driven fuel injection valve. That is, the starting can be hastened without providing a large electrically driven external pump to increase the pressure of the fuel supplied to the fuel injection valve.

According to the second aspect of the present invention, even if the pressure before the first explosion is performed in the cylinder and the pressure of the fuel supplied to the fuel injection valve is low, a large electric power is generated. Startup can be accelerated without providing a driven external pump.

According to the third aspect of the present invention, the starting can be hastened without providing a large electric drive type external pump, and the piezoelectric drive type fuel injection valve is arranged in the intake port. Thus, effects peculiar to direct injection, such as improving fuel efficiency, can be achieved.

According to the fourth aspect of the present invention, the number of electromagnetically driven fuel injection valves can be reduced as compared with the case where the electromagnetically driven fuel injection valves are arranged in each intake port. The cost of the fuel injection device of the engine can be reduced.

According to the fifth aspect of the present invention, a desired air-fuel mixture can be formed according to the conditions for forming the air-fuel mixture.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of a combustion injection device for an internal combustion engine of the present invention.

FIG. 2 is a flowchart showing a control method of a solenoid type injector.

FIG. 3 is a flowchart illustrating a control method of a piezo injector.

FIG. 4 is a diagram showing the relationship between engine speed, fuel pressure in a low-pressure fuel pipe, injection rate of a solenoid injector, fuel pressure in a high-pressure fuel pipe, and injection rate of a piezo injector, and time.

FIG. 5 is a schematic partial sectional view of an internal combustion engine to which a second embodiment of the fuel injection device for an internal combustion engine of the present invention is applied.

[Description of Signs] 2 ... Cylinder 3 ... Piezo type injector 6 ... Solenoid type injector 8 ... Fuel pressure sensor

Claims (5)

[Claims] 1. An electromagnetically driven fuel injection valve and a piezoelectrically driven fuel injection valve are provided for supplying fuel to a cylinder, and when the pressure of fuel supplied to the piezoelectrically driven fuel injection valve is low, Fuel is supplied to the cylinder by an electromagnetically driven fuel injection valve, and when the pressure of the fuel supplied to the piezoelectrically driven fuel injection valve is high, fuel is supplied to the cylinder by the piezoelectrically driven fuel injection valve. A fuel injection device for an internal combustion engine. 2. The internal combustion engine according to claim 1, wherein the time when the pressure of the fuel supplied to the piezoelectrically driven fuel injection valve is low is a time before the first explosion is performed in the cylinder. Fuel injection device. 3. The internal combustion engine is a multi-cylinder internal combustion engine, the piezoelectrically driven fuel injector is disposed in each cylinder, and the electromagnetically driven fuel injector extends to each cylinder. The fuel injection device for an internal combustion engine according to claim 1, wherein the fuel injection device is disposed in an intake pipe. 4. The internal combustion engine according to claim 1, wherein the internal combustion engine is a multi-cylinder internal combustion engine, and the electromagnetically driven fuel injection valve is disposed in a collection portion of a plurality of intake pipes extending to each cylinder. Engine fuel injector. 5. The electromagnetically driven fuel injection valve and the piezoelectrically driven fuel injection valve are arranged in the cylinder, and when a stratified mixture is to be formed in the cylinder, fuel is supplied by the piezoelectrically driven fuel injection valve. 2. The fuel injection device for an internal combustion engine according to claim 1, wherein the electromagnetically driven fuel injection valve injects fuel when a homogeneous mixture is to be formed in the cylinder.