JP3094751B2 - Fuel injection device for internal combustion engine - Google Patents

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 in-cylinder fuel injection valve for injecting fuel into a cylinder and an intake passage injection fuel injection valve for injecting fuel into an engine intake passage are provided. 2. Description of the Related Art A fuel injection device for an internal combustion engine equipped with a fuel pump for supplying fuel to a valve is known (JP-A-63-13).
No. 8120).

[0003]

However, the fuel tank
For in-cylinder injection despite low residual fuel in the tank
When fuel injection is performed from the fuel injection valve, the fuel pump
Fuel may be supplied to the pump,
Therefore, there is a problem that the fuel pump may break down, for example, seizure may occur .

[0004]

According to the present invention, there is provided an in-cylinder fuel injection valve for injecting fuel into a cylinder, and fuel is injected into an engine intake passage inner cylinder. An in-cylinder fuel injection valve for injecting fuel into an engine intake passage and an in-cylinder fuel injection valve for supplying fuel from a fuel tank to the in-cylinder fuel injection valve. In a fuel injection device for an internal combustion engine equipped with a fuel pump, the amount of residual fuel in a fuel tank is determined in advance.
When the amount is smaller than the set amount , the fuel injection from the in-cylinder injection fuel injection valve is prohibited, and the fuel is injected from the intake passage injection fuel injection valve.

[0005]

[Function] The remaining amount of fuel in the fuel tank is smaller than the set amount.
Fuel injection from in-cylinder fuel injection valve is prohibited
Then , fuel is injected from the intake passage fuel injection valve.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG.
a. Each cylinder 1a is connected to a common surge tank 3 via a corresponding intake branch pipe 2. The surge tank 3 is connected to an air flow meter 4 via an intake duct 4.
a, the air flow meter 4a is connected to the air cleaner 5
Connected to. A throttle valve 7 driven by a step motor 6 is arranged in the intake duct 4. The throttle valve 7 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly increased. On the other hand, each cylinder 1 a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9.

Each cylinder 1a has an in-cylinder injection fuel injection valve 11 for injecting fuel toward the cylinder and an intake port injection fuel injection valve 12 for injecting fuel toward the intake port. Each can be attached. These fuel injection valves 1
1 and 12 are controlled based on the output signal of the electronic control unit 30, respectively. The in-cylinder fuel injection valve 11
Is connected to a common fuel distribution pipe 13 for each in-cylinder fuel injection valve 11, and this fuel distribution pipe 13 is connected to the fuel distribution pipe 1.
3 is connected to an engine-driven high-pressure pump 15 via a check valve 14 that can be circulated toward the pump 3. As shown in FIG. 1, the discharge side of the high-pressure pump 15 is connected to the high-pressure pump 1 via an electromagnetic valve 15a.
5 is connected to the suction side. As the opening of the solenoid valve 15a is smaller, the amount of fuel supplied from the high-pressure pump 15 into the fuel distribution pipe 13 is increased, and when the solenoid valve 15a is fully opened, the fuel from the high-pressure pump 15 to the fuel distribution pipe 13 is increased. The supply is stopped. The solenoid valve 15a is controlled based on an output signal of the electronic control unit 30. On the other hand, each intake port injection fuel injection valve 12 is
Are connected to a common fuel distribution pipe 16. The fuel distribution pipe 16 and the high pressure pump 15 are connected to a low pressure pump 18 via a common fuel pressure regulator 17, and the low pressure pump 18 is connected to a fuel tank 20 via a fuel filter 19. The fuel pressure regulator 17 returns a part of the fuel discharged from the low pressure pump 18 to the fuel tank 20 when the fuel pressure of the fuel discharged from the low pressure pump 18 becomes higher than a predetermined set fuel pressure. The fuel pressure supplied to the port injection fuel injection valve 12 and the fuel pressure supplied to the high-pressure pump 15 are prevented from becoming higher than the set fuel pressure. Further, a flow valve 21 is provided between the high-pressure pump 15 and the fuel pressure regulator 17 as shown in FIG. The flow valve 21 is normally opened, but when the flow valve 21 is closed, the fuel supply from the low pressure pump 18 to the high pressure pump 15 is stopped. The flow valve 21 is controlled based on an output signal of the electronic control unit 30.

Referring again to FIG. 1, the electronic control unit 30 comprises a digital computer and a bidirectional bus 31.
(Read only memory) 32, RAM (random access memory) 33, C
A PU (microprocessor) 34, an input port 35 and an output port 36 are provided. The air flow meter 4a generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 4a is input to an input port 35 via an AD converter 37. A fuel amount sensor 38 for generating an output voltage proportional to the amount of fuel in the fuel tank is attached to the fuel tank 20, and the output voltage of the fuel amount sensor 38 is input to an input port 35 via an AD converter 39. . A fuel pressure sensor 40 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 13 is attached to the fuel distribution pipe 13, and the output voltage of the fuel pressure sensor 40 is an AD converter 41.
Through the input port 35. An oxygen concentration sensor 42 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 8 upstream of the catalyst 9, and the output voltage of the oxygen concentration sensor 42 is supplied to an input port 35 via an AD converter 43. Is input to Accelerator pedal 10
Is connected to a load sensor 44 that generates an output voltage proportional to the amount of depression of the accelerator pedal 10, and the output voltage of the load sensor 44 is input to an input port 35 via an AD converter 45. The input port 35 is connected to a rotation speed sensor 46 that generates an output pulse indicating the engine rotation speed.
On the other hand, the output port 36 is connected to the step motor 6, each in-cylinder injection fuel injection valve 11, each intake port injection fuel injection valve 12, the solenoid valve 15a, and the flow valve 21 via the corresponding drive circuit 47.

FIG. 2 is a side sectional view of the cylinder 1a. Referring to FIG. 2, reference numeral 61 denotes a cylinder block;
Is a piston having a concave portion 62a formed on the top surface, 63 is a cylinder head fixed on a cylinder block 61, 6
Reference numeral 4 denotes a combustion chamber formed between the piston 62 and the cylinder head 63; 65, an intake valve; 66, an exhaust valve; 67, an intake port; 68, an exhaust port;
The intake port 67 is configured such that the air flowing into the combustion chamber 64 generates a swirling flow around the cylinder axis.
The recess 62 a is formed to extend from the peripheral edge of the piston 62 located on the side of the in-cylinder fuel injection valve 11 toward the center of the piston 62, and to extend upward below the ignition plug 69.

FIG. 3 shows a fuel supply method when the intake port injection is performed, and FIG. 4 shows a fuel supply method when the in-cylinder injection is performed. In the embodiment shown in FIG. 1, either the intake port injection or the in-cylinder injection is performed depending on the engine speed N and the depression amount L of the accelerator pedal 10, as shown in FIG. In FIG. 5, a third region is provided between the region in which the intake port injection is to be performed and the region in which the in-cylinder injection is to be performed. A part of the amount may be injected into the intake port and the remaining fuel may be injected into the cylinder from the in-cylinder fuel injection valve 11 at the end of the compression stroke. When the engine operation state is in the region where the intake port injection is to be performed in FIG. 5, fuel injection F is performed from the intake port injection fuel injection valve 12 into the intake port 67 at the beginning of the engine intake stroke as shown in FIG. Next, air is sucked in through the intake valve 65, and as a result, the fuel is diffused while being vaporized by the swirling flow, so that the inside of the combustion chamber 64 is almost uniformly filled with the air-fuel mixture. This mixture is ignited by an ignition plug 69. When the intake port injection is performed by the intake port injection fuel injection valve 12, the fuel injection from the in-cylinder injection fuel injection valve 11 is stopped. At this time, the solenoid valve 15a is fully opened and the fuel supply from the high pressure pump 15 is stopped. The supply of fuel to the pipe 13 is stopped. On the other hand, when the engine operating state is in the region where in-cylinder injection is to be performed in FIG. 5, as shown in FIG. The fuel F is injected toward. The fuel F travels along the inner peripheral surface of the recess 62a, and then travels upward below the ignition plug 69, whereby an air-fuel mixture G is formed in the recess 62a as shown in FIG. 4B. At this time, the inside of the combustion chamber 64 other than the concave portion 62a is filled with air. The mixture is then ignited by a spark plug 69. When the in-cylinder injection is performed by the in-cylinder fuel injection valve 11, the fuel injection from the intake port injection fuel injection valve 12 is stopped.

In the embodiment shown in FIG. 1, when in-cylinder injection is to be performed by the in-cylinder fuel injection valve 11, the fuel pressure PF in the fuel distribution pipe 13 becomes a predetermined constant target fuel pressure. Thus, the amount of fuel supplied from the high-pressure pump 15 to the fuel distribution pipe 13 is controlled. However, if the in-cylinder injection is performed by the in-cylinder fuel injection valve 11 when the high-pressure pump 15 or the solenoid valve 15a fails, for example, a normal amount of fuel can be supplied from the high-pressure pump 15 to the fuel distribution pipe 13. As a result, the fuel distribution pipe 13
Since the internal fuel pressure PF cannot be set to the target fuel pressure, the amount of fuel injected from the in-cylinder fuel injection valve 11 deviates from the required fuel amount. Therefore, in the embodiment shown in FIG. 1, an appropriate pressure range for properly performing the fuel injection from the in-cylinder fuel injection valve 11 is predetermined, and the fuel pressure PF in the fuel distribution pipe 13 is increased from this pressure range. When it deviates, the fuel injection from the in-cylinder fuel injection valve 11 is stopped, and the fuel injection from the intake port injection fuel injection valve 12 is performed. For this reason, the engine has a fuel injection valve 1 for intake port injection.
2 can supply the required amount of fuel, and at this time, the engine can be prevented from being stopped.

On the other hand, in the embodiment shown in FIG. 1, the engine air-fuel ratio is controlled based on the output signals of the air flow meter 4a and the oxygen concentration sensor 42 so as to become the target air-fuel ratio. That is, when the engine air-fuel ratio is lean (lean), the fuel injection amount is increased by increasing the air-fuel ratio correction coefficient KAF, and when the engine air-fuel ratio is rich (rich), the air-fuel ratio correction coefficient KAF is decreased. As a result, the fuel injection amount is reduced. However, the high-pressure pump 15 and the solenoid valve 1
If the in-cylinder fuel injection valve 11 performs in-cylinder injection in the case where the 5a or the in-cylinder fuel injection valve 11 has failed, as described above,
The amount of fuel injected from the engine deviates from the required fuel amount.
Accordingly, in the embodiment shown in FIG.
An air-fuel ratio correction coefficient range appropriate for performing the fuel injection from No. 1 in advance is determined in advance, and even when the air-fuel ratio correction coefficient KAF deviates from this air-fuel ratio correction coefficient range, the in-cylinder fuel injection valve 11 Is stopped, and fuel is injected from the intake port injection fuel injection valve 12. For this reason, the engine includes a fuel injection valve 12 for intake port injection.
Can supply the required amount of fuel, and the engine can be prevented from being stopped at this time.

If the in-cylinder injection is performed by the in-cylinder fuel injection valve 11 when the amount of fuel in the fuel tank 20 is small, the fuel containing air may be supplied to the high-pressure pump 15. If fuel containing air is supplied to the high-pressure pump 15, the high-pressure pump 15 may be burned. If air is mixed into the fuel distribution pipe 13, the amount of fuel injected from the in-cylinder fuel injection valve 11 is regulated. Will deviate from the amount of fuel. Therefore, in the embodiment shown in FIG. 1, the fuel amount V in the fuel tank 20 is set to a predetermined set fuel amount V
When the value becomes 0 or less, the flow valve 21 is closed to stop the in-cylinder injection by the in-cylinder fuel injection valve 11 and to perform the intake port injection by the intake port injection fuel injection valve 11. As a result, air is prevented from being mixed into the high-pressure pump 15 or the fuel distribution pipe 13, so that the seizure of the high-pressure pump 15 can be prevented and the amount of fuel supplied to the engine can be prevented from deviating from the normal amount of fuel. .

In the embodiment shown in FIG. 1, when the fuel injection from the in-cylinder fuel injection valve 11 is stopped, the in-cylinder fuel injection valve 11 is closed by the fuel pressure in the fuel distribution pipe 13. The valve state is maintained. However, if the fuel pressure in the fuel distribution pipe 13 is low when the fuel injection by the in-cylinder fuel injection valve 11 is stopped, the in-cylinder fuel injection valve 11 may be opened by the combustion pressure in the combustion chamber 64. When the in-cylinder fuel injection valve 11 is opened when fuel injection from the in-cylinder fuel injection valve 11 is stopped, the combustion chamber 6
The combustion gas in the cylinder 4 flows into the in-cylinder fuel injection valve 11, and when the fuel is to be injected from the in-cylinder fuel injection valve 11, the amount of fuel injected from the in-cylinder fuel injection valve 11 is reduced. It deviates from the regular fuel amount. Further, when the combustion gas in the combustion chamber 64 flows into the in-cylinder fuel injection valve 11 into the in-cylinder fuel injection valve 11, the nozzle of the in-cylinder fuel injection valve 11 is caused by soot in the combustion gas. Clogging may occur, and as a result, fuel injection from the in-cylinder fuel injection valve 11 may not be possible. Therefore, in the embodiment shown in FIG. 1, a set pressure P0 is set in advance for the fuel pressure PF in the fuel distribution pipe 13 so that the in-cylinder fuel injection valve 11 is not opened by the combustion pressure in the combustion chamber 64. If the fuel pressure PF in the fuel distribution pipe 13 is lower than the set pressure P0 when the intake port injection by the intake port injection fuel injection valve 12 is to be performed, the fuel pressure PF in the fuel distribution pipe 13 becomes equal to or higher than the set pressure P0. As described above, the fuel is supplied from the high-pressure pump 15 into the fuel distribution pipe 13. As a result, it is possible to prevent the in-cylinder fuel injection valve 11 from opening due to the combustion pressure in the combustion chamber 64 when the fuel injection from the in-cylinder fuel injection valve 11 is stopped. However, in the embodiment shown in FIG. 1, the intake port injection is performed by the intake port injection fuel injection valve 12 even when the high-pressure pump 15 fails as described above. In the case where the intake port injection is performed due to a failure of the fuel cell, there is a possibility that the fuel pressure PF in the fuel distribution pipe 13 cannot be increased to the set pressure P0. Therefore, in the present embodiment, when the fuel pressure PF in the fuel distribution pipe 13 is still lower than the set pressure P0 after a predetermined set time has elapsed after the fuel injection from the in-cylinder fuel injection valve 11 is stopped. Close the flow valve 21 and the solenoid valve 15a.
Is fully opened.

Next, a routine for executing the above-described embodiment will be described with reference to FIGS. These routines are executed by interruption every predetermined time. First, referring to FIG. 6, in step 80, the currently performed fuel injection is performed by the in-cylinder fuel injection valve 1.
1 is determined. When the in-cylinder injection is being performed, the routine proceeds to step 81, and when the intake port injection is being performed, the routine proceeds to step 86. In step 81, it is determined whether the fuel pressure PF in the fuel distribution pipe 13 is higher than the allowable minimum pressure P1. PF> P1
In step 82, the routine proceeds to step 82, where it is determined whether the fuel pressure PF in the fuel distribution pipe 13 is lower than the allowable maximum pressure P2. When PF <P2, the routine proceeds to step 83, where it is determined whether the air-fuel ratio correction coefficient KAF is smaller than the allowable minimum value K1. When KAF> K1, the routine proceeds to step 84, where it is determined whether or not the air-fuel ratio correction coefficient KAF is larger than the allowable maximum value K2. When KAF <K2, the routine proceeds to step 85, where it is determined whether the fuel amount V in the fuel tank 20 is larger than a predetermined fuel amount V0. When V> V0, the process proceeds to step 86, where the first counter C1 is reset. This first
The counter C1 has PF ≦ P1 (step 81), PF ≧ P
2 (step 82), KAF ≦ K1 (step 83),
KAF ≧ K2 (step 84), V ≦ V0 (step 8)
5) shows the time from when any one of 5) is established. Next, at step 87, PF ≦ P1 (step 8
1), PF ≧ P2 (step 82), KAF ≦ K1 (step 83), KAF ≧ K2 (step 84), V ≦ V
0 (step 85) is satisfied for a predetermined period of time, that is, when the first counter C
When 1 becomes the set value C1M, the flag set to is reset.

On the other hand, PF ≦ P1 (step 81), PF
≧ P2 (step 82), KAF ≦ K1 (step 8
3) When any one of KAF ≧ K2 (step 84) and V ≦ V0 (step 85) is satisfied, the routine proceeds to step 88, where it is determined whether or not the first counter C1 has reached the set value C1M. When C1 <C1M, the routine proceeds to step 89, where the first counter C1 is counted. C
When 1 = C1M, the routine proceeds to step 90, where a flag is set.

Referring now to FIG. 7, in step 100, it is determined whether a flag has been set. If the flag has not been set, the routine proceeds to step 101, where the in-cylinder fuel injection valve 11 is used based on the map shown in FIG.
It is determined whether or not in-cylinder injection should be performed. When in-cylinder injection is to be performed, the routine proceeds to step 102, in-cylinder injection is performed by the in-cylinder fuel injection valve 11, and when intake port injection is to be performed, the routine proceeds to step 103, where the intake port fuel injection valve 12 controls the intake port. Perform injection.
On the other hand, when the flag is set in step 100, the routine proceeds to step 103, where the intake port injection fuel injection valve 12 performs intake port injection.

Referring to FIG. 8, in step 110, it is determined whether or not in-cylinder injection is currently being performed. When the in-cylinder injection is being performed, the routine proceeds to step 111, where the opening of the solenoid valve 15a is controlled such that the fuel pressure PF in the fuel distribution pipe 13 becomes the target fuel pressure. Then step 112
Then, the second counter C2 is reset. When the intake port injection is being performed, the process proceeds from step 111 to step 113, where it is determined whether or not the fuel pressure PF in the fuel distribution pipe 13 is lower than a predetermined set pressure P0. This set pressure is determined so that P1 <P0 <P2. When PF ≧ P0, the process proceeds to step 114,
The second counter C2 is reset. Then step 1
Proceeding to 15, the solenoid valve 15a is fully opened. On the other hand, PF
If <P0, the routine proceeds to step 116, where the solenoid valve 15a
Is fully closed. Next, the routine proceeds to step 117, where the second counter C2 is counted. The second counter C2 indicates the time during which the fuel supply from the high-pressure pump 15 to the fuel distribution pipe 13 is performed while the intake port injection is being performed. Next, at step 118, it is determined whether or not the second counter C2 has reached the set value C2M. When C2 <C2M, the processing cycle ends, and when C2 = C2M, the routine proceeds to step 119, where the flow valve 21 is closed. Next, the routine proceeds to step 115, where the solenoid valve 15a is fully opened.

[0019]

According to the present invention, the failure of the fuel pump can be prevented .

[Brief description of the drawings]

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

FIG. 2 is a side sectional view of the internal combustion engine.

FIG. 3 is a side sectional view of the internal combustion engine illustrating intake port injection.

FIG. 4 is a side sectional view of the internal combustion engine illustrating in-cylinder injection.

FIG. 5 is a diagram illustrating a fuel injection method.

FIG. 6 is a flowchart for executing the embodiment.

FIG. 7 is a flowchart for executing the embodiment.

FIG. 8 is a flowchart for executing the embodiment.

[Explanation of symbols]

 7 ... Throttle valve 11 ... In-cylinder injection fuel injection valve 12 ... Intake port injection fuel injection valve 13 ... Fuel distribution pipe 15 ... High pressure pump 15a ... Electromagnetic valve 18 ... Low pressure pump 20 ... Fuel tank 64 ... Combustion chamber 67 ... Intake port

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) F02D 41/00-41/40 F02D 45/00

Claims (1)

(57) [Claims] 1. An in-cylinder fuel injection valve for injecting fuel into a cylinder and an intake passage injection fuel injection valve for injecting fuel into an engine intake passage. the fuel injection system of an internal combustion engine having a fuel pump for supplying fuel from the fuel tank to the injection valve, fuel
The amount of residual fuel in the tank is less than a predetermined amount.
No Sometimes the fuel injection from in-cylinder injection type fuel injection valve prohibition
A fuel injection device for an internal combustion engine, which stops and injects fuel from a fuel injection valve for intake passage injection.