JP2008175080A - Fuel feeding apparatus of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fuel feeding apparatus that secures a fuel pressure during an abnormal condition of a high-pressure fuel pump, in a fuel feeding apparatus of internal combustion engine provided with a high-pressure fuel pump of engine drive type and a low-pressure fuel pump of electric type for feeding fuel to the high-pressure fuel pump. <P>SOLUTION: When such an abnormal condition that a high-pressure fuel pump 14 is not boosted is detected, operation of the high-pressure fuel pump 14 is interrupted, and a relief valve 34 on high-pressure side interposed in a return piping 33 and configured to be opened arbitrarily, is opened, and a fuel that has been discharged from a low-pressure fuel pump 13 is fed to a fuel gallery pope 32 through the return pipe 14, bypassing the high-pressure fuel pump 14. As a result, the fuel pressure in the fuel gallery pipe 32 is secured, so that a fuel injection from a fuel injection valve 15 is performed. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a fuel supply device for an internal combustion engine that includes an engine-driven high-pressure fuel pump and an electric low-pressure fuel pump that supplies fuel to the high-pressure fuel pump.

  In Patent Document 1, the fuel discharged from the electric low pressure fuel pump is regulated to a predetermined low pressure value by a low pressure regulator, and the fuel regulated to the predetermined low pressure value is used as the engine driven high pressure fuel pump. A fuel supply device for an internal combustion engine that adjusts the fuel discharged from the high pressure fuel pump to a predetermined high pressure value by a high pressure regulator and supplies the fuel adjusted to the predetermined high pressure value to a fuel injection valve Is disclosed.

Similarly, Patent Document 2 discloses that in this type of fuel supply apparatus, when an abnormality of the high-pressure fuel pump is detected, fail-safe control for driving the fuel pump is performed by a function of the fuel pressure and the required fuel supply amount. ing.
Japanese Patent Laid-Open No. 9-236060 Special Table 2000-511992

However, in Patent Document 2, even if there is a correlation between the required fuel supply amount of the engine and the discharge amount of the low pressure fuel pump, the required fuel amount may not be satisfied during a transient or the like when the high pressure fuel pump fails. there were.
The present invention has been made in view of the above-described problems, and an object of the present invention is to satisfy the required fuel supply amount to the maximum even during a transition when an engine-driven high-pressure fuel pump is abnormal.

Therefore, the invention described in claim 1 includes an engine-driven high-pressure fuel pump and an electric low-pressure fuel pump that supplies fuel to the high-pressure fuel pump, and the fuel discharged from the high-pressure fuel pump is supplied to the internal combustion engine. In the fuel supply device of the internal combustion engine to supply,
When the high pressure fuel pump is abnormal, the fuel discharged from the low pressure fuel pump is supplied to the internal combustion engine by bypassing the high pressure fuel pump.

According to the above invention, it is possible to control the amount of fuel directly supplied to the engine by the discharge amount from the low-pressure fuel pump.
Thus, by controlling the discharge amount from the low-pressure fuel pump to be the maximum or the vicinity thereof, the request can be satisfied even when the required fuel supply amount is large, such as during a transition.
The invention according to claim 2
A low-pressure relief valve for returning surplus fuel discharged from the low-pressure fuel pump to a low-pressure source is arbitrarily opened and closed, and the fuel discharged from the low-pressure fuel pump bypasses the high-pressure fuel pump and is an internal combustion engine. When the fuel is supplied to the fuel tank, the low pressure side relief valve is closed to stop the return of fuel.

According to the above invention, when the high pressure fuel pump is abnormal and the high pressure fuel pump is bypassed from the low pressure fuel pump and supplied to the internal combustion engine, the low pressure side relief valve is closed to stop the return of fuel.
As a result, it is possible to perform control that maximizes the discharge amount from the low-pressure fuel pump.
The invention according to claim 3
When the fuel discharged from the low-pressure fuel pump is supplied to the internal combustion engine bypassing the high-pressure fuel pump, the maximum flow rate of the low-pressure fuel pump is restricted to an upper limit value or less.

When bypassing the high pressure fuel pump from the low pressure fuel pump and supplying it to the internal combustion engine when the high pressure fuel pump is abnormal, a certain amount of fuel is also discharged from the high pressure fuel pump, and when combined with the discharge amount from the low pressure fuel pump, Sometimes the required fuel supply is exceeded.
According to the invention which concerns on Claim 3, it can suppress that a fuel supply amount becomes excess by restrict | limiting the maximum flow volume of a low pressure fuel pump below an upper limit in the above cases.

Embodiments of the present invention will be described below.
FIG. 1 is a system configuration diagram of a fuel supply device for an internal combustion engine according to an embodiment.
In FIG. 1, a fuel tank 12 for storing fuel to be supplied to a vehicle internal combustion engine 11 is provided, and the fuel in the fuel tank 12 passes through an electric low-pressure fuel pump 13 and an engine-driven high-pressure fuel pump 14. Then, the pressure is fed to the fuel injection valve 15.

The fuel injection valve 15 opens and drives the valve body with electromagnetic force generated by an electromagnetic coil, and injects fuel directly into each combustion chamber of the internal combustion engine 11, for example.
The low pressure fuel pump 13 pumps the fuel sucked from the fuel tank 12 to the high pressure fuel pump 14 via the low pressure fuel pipe 16.
A return pipe 17 for returning the fuel into the fuel tank 12 from the middle of the low-pressure fuel pipe 16 is provided, and a low-pressure regulator 18 for adjusting the fuel pressure in the low-pressure fuel pipe 16 is provided in the middle of the return pipe 17. Provided.

The low-pressure regulator 18 is normally opened when the pressure in the low-pressure fuel pipe 16 exceeds a predetermined low-pressure value, and returns the fuel into the fuel tank 12 via the return pipe 17. It has a function to prevent the fuel pressure from exceeding a predetermined low pressure value.
Further, the low pressure regulator 18 is kept closed when the high pressure fuel pump 14 is abnormal, and has a fail-safe function that stops the return of fuel and maximizes the discharge amount from the low pressure fuel pump.

For this reason, it is comprised so that it can close arbitrarily by energization of a solenoid.
The high-pressure fuel pump 14 includes a high-pressure pump control solenoid 21, a pilot valve 22, a suction valve 23, a pump chamber 24, and a discharge valve 25.
The suction valve 23 is a one-way valve that controls the supply of the low-pressure fuel sent through the low-pressure fuel pipe 16 into the pump chamber 24, and the high pressure in the pump chamber 24 acts in the valve closing direction so that the pump The fuel pressurized in the chamber 24 is prevented from flowing out to the low pressure fuel pipe 16 side.

The intake valve 23 is controlled to be opened and closed by a pilot valve 22 driven by a high pressure pump control solenoid 21.
In the non-energized state of the solenoid 21, the pilot valve 22 is pushed out by the spring 21a, so that the suction valve 23 is held in the open state. The suction valve 23 is held in the closed state by being pulled toward the solenoid 21 against the urging force.

A plunger 24a is fitted into the pump chamber 24 so as to be reciprocally movable, and the plunger 24a is reciprocated by a pump driving cam provided on the cam shaft of the engine 11.
Here, if the solenoid 21 is energized and the intake valve 23 is kept closed during a predetermined period when the plunger 24a is raised, the fuel in the pump chamber 24 is boosted, and the pump chamber 24 When the internal pressure exceeds a predetermined value, the discharge valve 25, which is a one-way valve, is opened to discharge high-pressure fuel.

The discharge valve 25 is connected to a fuel gallery pipe 32 via a high-pressure fuel pipe 31, and the fuel pressurized to a high pressure by the high-pressure fuel pump 14 is distributed to each fuel injection valve 15 connected to the fuel gallery pipe 32. Supplied.
A relief pipe 33 is provided for connecting the fuel gallery pipe 32 and the low-pressure fuel pipe 16. The relief pipe 33 opens when the fuel pressure in the fuel gallery pipe 32 becomes an abnormally high pressure. A relief valve 34 which is a one-way valve is provided.

Here, the relief pipe 33 serves as a passage for supplying the fuel discharged from the low pressure fuel pump 13 to the engine (fuel gallery pipe 32) by bypassing the high pressure fuel pump 13 when the high pressure fuel pump 14 is abnormal. Use. For this reason, the relief valve 34 is forcibly opened by an electromagnetic driving force.
Specifically, as shown in FIG. 2, a valve element 34a urged by a spring 34b of a relief valve 34 is provided in the same manner as the high pressure pump control solenoid 21, pilot valve 22, and intake valve 23. The pilot valve 34c driven by energization of the solenoid 34b may be forcibly opened.

  In this configuration, since the valve opening pressure of the relief valve 34 is set to a high pressure, it is necessary to increase the electromagnetic driving force of the solenoid 33b. Therefore, as shown in FIG. 3, a passage 33a that passes through the relief valve 34 and a passage 33b that bypasses the relief valve 34 are provided in parallel, and a switching valve 35 that operates to select and pass through one of the passages. It is good also as a structure which electromagnetically drives.

A fuel pressure sensor 41 for detecting the fuel pressure in the fuel gallery pipe 32 is provided, and the control unit 51 controls the energization timing of the solenoid 21 so that the fuel pressure detected by the fuel pressure sensor 41 becomes the target fuel pressure. To do.
The control unit 51 includes a microcomputer, and in addition to the fuel pressure sensor 41, an air flow meter 42 for detecting the intake air amount of the engine 11, a crank angle sensor 43 for detecting the crank angle of the engine 11, and the engine 11 A detection signal from a throttle opening sensor 44 that detects the opening of a throttle valve that adjusts the intake air amount is input, and an ON / OFF signal of a starter switch 45 is input.

Then, the control unit 51 determines the target high fuel pressure on the high pressure side from the engine load detected based on the detection signals of the various sensors, and the fuel pressure detected by the fuel pressure sensor 41 becomes the target high fuel pressure. In addition, the energization timing of the solenoid 21 is feedback-controlled.
FIG. 4 shows a second embodiment of the system configuration.

Differences from the first embodiment will be described.
The relief valve 34 has only a mechanical function as a one-way valve that opens when the fuel pressure in the fuel gallery pipe 32 becomes abnormally high.
On the other hand, in addition to the return pipe 17, one end of the bypass pipe 61 is connected to the output side of the low pressure regulator 18, and the other end of the bypass pipe 61 is connected to the high pressure fuel pipe 31.

When the high-pressure fuel pump 14 is abnormal, the upstream pipe of the low-pressure regulator 18 ′ and the bypass pipe 61 are opened, and the fuel discharged from the low-pressure fuel pump 13 is bypassed by the high-pressure fuel pump 14 and the engine (fuel It is configured to supply to the gallery pipe 32).
Specifically, as shown in FIG. 5, the valve body 18 a ′ of the low pressure regulator 18 ′ adjusts the discharge pressure in response to the discharge fuel pressure from the low pressure fuel pump 13 while communicating with or shutting off the return pipe 17. What is necessary is just to set it as the structure which drives the said valve body 18a 'compulsorily by energization of solenoid 18b', and maintains the position connected to the said bypass piping 61. FIG.

FIG. 6 shows a third embodiment of the system configuration.
In this embodiment, the low-pressure regulator 18 is the same as in the first embodiment, the relief valve 34 is the same as in the second embodiment, and the low-pressure fuel pipe 16 and the high-pressure fuel pipe 31 (or the fuel gallery pipe 32) A bypass pipe 71 is newly provided, and an electromagnetically driven on-off valve 72 that can be freely opened and closed is interposed in the bypass pipe 71.

Normally, the on-off valve 71 is closed. However, when the high-pressure fuel pump 14 is abnormal, the on-off valve 71 is opened and discharged from the low-pressure fuel pump 13 while the low-pressure regulator 18 is kept closed. The fuel is supplied to the engine (fuel gallery pipe 32) via the bypass pipe 71 (substantially the same as the structure shown in FIG. 3).
Further, as shown in the flowchart of FIG. 7, the control unit 51 diagnoses the presence or absence of an abnormality in the high-pressure fuel pump 14, particularly an abnormality in which the fuel pressure is insufficient.

In step S1, it is determined whether the target fuel pressure is a predetermined value or more.
When the target fuel pressure is equal to or greater than a predetermined value, the process proceeds to step S2, and it is determined whether the fuel pressure detected by the fuel pressure sensor 41 is equal to or greater than a lower limit determination value that is significantly lower than the predetermined value.
When it is determined in step S2 that the fuel pressure is less than the lower limit determination value, the process proceeds to step S3, and it is diagnosed that the high-pressure fuel pump 14 has a failure that cannot increase the fuel pressure. For example, the drive circuit of the high-pressure pump control solenoid 21 is disconnected.

When it is determined in step S2 that the fuel pressure is equal to or higher than the lower limit determination value, the process proceeds to step S4, and the differential pressure between the target fuel pressure and the actual fuel pressure continues for a predetermined time after the target fuel pressure is updated and exceeds the threshold value. Determine if it is maintained.
If the determination in step S4 is YES, the process proceeds to step S5, and the high-pressure fuel pump 14 is able to increase the pressure, but diagnoses that the abnormality is incomplete or too large in delay.

If the determination in step S4 is NO, the process proceeds to step S6, and the high-pressure fuel pump 14 is diagnosed as normal.
FIG. 8 shows a first embodiment of control of the low-pressure fuel pump 13 based on the diagnosis result of the high-pressure fuel pump 14.
In step S11, it is determined whether or not the high-pressure fuel pump 14 has an abnormality that cannot be increased.

  When it is determined that the high-pressure fuel pump 14 cannot be pressurized, the process proceeds to step S12, the low-pressure fuel pump 13 is fully opened (maximum discharge amount), and the discharged fuel from the low-pressure fuel pump 13 is discharged to the high-pressure fuel pump. Bypass 14 and supply directly to the engine. The control for supplying the discharged fuel from the low-pressure fuel pump 13 to the engine bypassing the high-pressure fuel pump 14 is performed as described in the above-described embodiments (the same applies to the following embodiments).

When it is determined in step S11 that the high-pressure fuel pump 14 is not abnormal, the process proceeds to step S13, where a function of adjusting the discharge pressure of the low-pressure fuel pump 13 by cutting off the energization of the low-pressure regulator 18 is provided. The low pressure fuel pump 13 is driven with a control amount (discharge amount) set according to the state, and the discharged fuel is supplied to the high pressure fuel pump 14.
In this way, when the high-pressure fuel pump 14 is abnormal, the low-pressure fuel pump 13 is fully opened, so even if the fuel pressure cannot be increased by the high-pressure fuel pump 14, the fuel gallery is used by the fuel discharged from the low-pressure fuel pump 13. The fuel pressure in the pipe 32, that is, the injection pressure from the fuel injection valve 15 can be ensured to be as high as possible, the compression stroke injection can be performed without hindrance, and the vehicle can be retracted.

FIG. 9 shows a second embodiment of control of the low-pressure fuel pump 13 based on the diagnosis result of the high-pressure fuel pump 14.
In step S21, the control amount of the low-pressure fuel pump 13 is calculated according to the vehicle operating state (engine speed, load, fuel pressure, etc.).
In step S22, it is determined whether or not the high pressure fuel pump 14 is in an abnormal state where the pressure can be increased.

  When it is determined that the high pressure fuel pump 14 is in an abnormal state where the pressure can be increased, the process proceeds to step S23 and the supply of the fuel discharged from the low pressure fuel pump 13 to the high pressure fuel pump 14 is continued and the high pressure fuel pump 14 is bypassed. Supply to the organization. When the high-pressure fuel pump 14 is capable of boosting pressure, although it is unstable, it is easier to ensure the necessary amount if it is discharged from the high-pressure fuel pump 14, so the combined supply described above is performed.

  In step S24, it is determined whether the control amount of the low-pressure fuel pump 13 exceeds the upper limit set value H. As described above, when fuel is simultaneously supplied from the high-pressure fuel pump 14 and the low-pressure fuel pump 13 to the engine, the fuel pressure may be excessively higher than usual, so this determination is performed. The upper limit set value H is set to such a value that the linearity with respect to the control amount of the injection amount of the fuel injection valve 15 is maintained, and that the fuel leakage from the fuel injection valve 15 and an excessive load are not applied to the fuel pipe.

When it is determined in step S23 that the upper limit set value H is exceeded, the process proceeds to step S24, and the control amount is limited as the upper limit set value H.
When it is determined in step S23 that the upper limit set value H has not been exceeded, the process proceeds to step S25 to determine whether the control amount is less than the lower limit set value L. Since the control amount in step S21 is set for the normal time according to the operating state, when the fuel discharged from the low-pressure fuel pump 13 is supplied directly to the engine, it may be too low. I do. The lower limit set value L is set to a value that can maintain linearity with respect to the control amount of the discharge amount of the low-pressure fuel pump 13 and the injection amount of the fuel injection valve 15 and can reduce or suppress the vapor from the fuel.

When it is determined in step S25 that the control amount is less than the lower limit set value L, the process proceeds to step S26, where the control amount is limited as the lower limit set value L.
In this way, when the high pressure fuel pump 14 is in an abnormal state where the pressure can be raised, the low pressure fuel pump 13 and the high pressure fuel pump 14 simultaneously supply fuel to the engine, and the control amount from the low pressure fuel pump 13 is set to the lower limit. By regulating to a range between the set value L and the upper limit set value H, the instability of the high-pressure fuel pump 14 can be compensated, the amount of fuel supplied to the engine, and the fuel pressure can be stabilized. Fuel leakage, vapor generation, etc. can be suppressed.

It should be noted that the embodiment that is limited to the upper limit set value H or less and the embodiment that is limited to the lower limit set value L or more have certain effects.
FIG. 10 shows a third embodiment of control of the low-pressure fuel pump 13 based on the diagnosis result of the high-pressure fuel pump 14.
In step S31, it is determined whether the high-pressure fuel pump 14 is abnormal.

When it is determined that the high-pressure fuel pump 14 is not abnormal (normal), the process proceeds to step S32, and the low-pressure fuel pump 13 is driven at a reference pressure (for example, 350 kPa). This is automatically adjusted by the low pressure regulator 18 during normal operation, but a fuel pressure sensor for detecting the fuel pressure on the low pressure side may be separately provided and feedback controlled.
On the other hand, when it is determined that the high pressure fuel pump 14 is abnormal, the process proceeds to step S33, where the operation of the high pressure fuel pump 14 is stopped, and the discharged fuel from the low pressure fuel pump 13 is bypassed by the high pressure fuel pump 14 and the engine. And is driven to a high pressure (several MPa). Although it may be a fully open operation, feedback control may be performed so that the fuel pressure from the fuel pressure sensor is detected and a high set fuel pressure is obtained.

In step S34, it is determined whether the required fuel consumption by fuel injection from the fuel injection valve, such as the high speed range of the engine, exceeds an upper limit set value Fh that is difficult to cover by direct supply of fuel discharged from the low-pressure fuel pump 1. judge. In addition, the calculated value of following Formula can be used for request | requirement fuel consumption.
Required fuel consumption = Ne x Ti x α
Where Ne: engine speed
Ti: Basic fuel injection amount
α: Air-fuel ratio feedback correction coefficient When it is determined that the required fuel consumption exceeds the upper limit set value Fh, the routine proceeds to step S35, where fuel cut (fuel supply to the engine is stopped), specifically, the fuel injection valve 15 Stop operation.

By the fuel cut, the fuel pressure in the fuel gallery pipe 32 is increased, and fuel injection at a high pressure thereafter becomes possible.
That is, when the high-pressure fuel pump 14 is abnormal, when the required fuel consumption is large, such as in a high speed range, if fuel injection is performed as required, the fuel pressure becomes insufficient and normal fuel injection cannot be performed. After the fuel pressure is cut and the fuel pressure is increased so that normal fuel injection can be performed, the fuel consumption is reduced to a required fuel consumption amount that allows retreat travel, and then normal fuel injection is resumed. Further, according to this configuration, it is possible to prevent the exhaust purification catalyst from deteriorating due to lean air-fuel ratio due to fuel injection with insufficient fuel pressure.

  FIG. 11 shows a fourth embodiment of control of the low pressure fuel pump 13 based on the diagnosis result of the high pressure fuel pump 14. This embodiment is a form close to the configuration of the first to third embodiments described above, and can deal with various abnormalities. In this embodiment, the relief valve 34 is constituted by an electromagnetic on-off valve. However, the discharge fuel of the low-pressure fuel pump 13 may be supplied to the engine by bypassing the high-pressure fuel pump 14 by another method. Applicable.

In step S41, it is determined whether the high-pressure fuel pump 14 is abnormal.
When it is determined that the high-pressure fuel pump 14 is abnormal, the process proceeds to step S42, and it is determined whether the high-pressure fuel pump 14 is abnormal so that the pressure can be increased.
If it is determined that the pressure can be increased, the process proceeds to step S43, the relief valve 34 is maintained open, and the fuel discharged from the low pressure fuel pump 13 is supplied to the engine bypassing the high pressure fuel pump 14. The high-pressure pump control solenoid 21 is controlled as usual to drive the high-pressure fuel pump 14 and supply the fuel boosted by the high-pressure fuel pump 14 to the engine.

On the other hand, if it is determined in step S42 that the high-pressure fuel pump 14 cannot be boosted, the process proceeds to step S44 where the high-pressure pump control solenoid 21 is turned off to stop the operation of the high-pressure fuel pump 14 and the relief valve 34 is turned on. Maintaining the valve open, the low-pressure fuel pump 13 is fully opened, and the discharged fuel is supplied to the engine bypassing the high-pressure fuel pump 14.
After starting fail-safe control when the high-pressure fuel pump is abnormal in this way, the process proceeds to step S45, where the actual fuel pressure in the fuel gallery pipe 32 detected by the fuel pressure sensor 41 is the fuel from the fuel injection valve 15 in the compression stroke. It is determined whether the fuel pressure is lower than the lower limit fuel pressure (for example, 3 MPa) at which injection is possible.

When it is determined that the actual fuel pressure is less than the lower limit fuel pressure, the routine proceeds to step S46, where the fuel is cut, the fuel consumption is eliminated, the actual fuel pressure in the fuel gallery pipe 32 is increased, and the fuel injection from the fuel injection valve 15 is performed. Make it possible.
When it is determined in step S41 that the high-pressure fuel pump 14 is normal, the process proceeds to step S47, and it is determined whether the actual fuel pressure is maintained at a value smaller than a value obtained by adding a predetermined value α (> 0) to the target fuel pressure. .

When it is determined that the actual fuel pressure is smaller than (target fuel pressure + α), the process proceeds to step S48, the relief valve 34 is closed, the fuel discharged from the low-pressure fuel pump 13 is supplied only to the high-pressure fuel pump 14, and the high-pressure fuel pump 14 is driven to supply high-pressure discharged fuel to the engine.
When it is determined in step S47 that the actual fuel pressure is equal to or higher than (target fuel pressure + α) and the fuel pressure is too high, the process proceeds to step S48, and the relief valve 34 is opened to relieve the fuel, thereby causing the fuel gallery pipe 32 to be opened. , The fuel leakage from the fuel injection valve 15 is prevented, and the durability of the fuel pipe is ensured.

When the relief valve 34 is configured with only a mechanical check valve as in the second and third embodiments, if the high-pressure fuel pump 14 is determined to be normal, normal operation is performed. When the fuel pressure becomes higher than a predetermined level, the relief valve 34 opens in response to the fuel pressure, and the fuel is relieved and the pressure is reduced.
In this way, all the effects of the first to third embodiments can be obtained.

In the embodiment described above, it is possible to supply the discharged fuel from the low-pressure fuel pump to the engine by bypassing the high-pressure fuel pump by closing the low-pressure relief valve to the fuel tank of the low-pressure regulator. However, the present invention can also be applied to those not provided with such a low-pressure regulator.
Here, technical ideas other than the claims that can be grasped from the above embodiment will be described together with effects.
(A) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 3,
The high-pressure relief valve interposed in the return pipe that returns surplus fuel from the high-pressure fuel pipe downstream of the high-pressure fuel pump to the discharge side of the low-pressure fuel pump can be arbitrarily opened,
When the fuel discharged from the low-pressure fuel pump is supplied to the internal combustion engine bypassing the high-pressure fuel pump, the fuel is supplied via the return passage by opening the high-pressure relief valve. To do.

According to the above invention, the fuel discharged from the low pressure fuel pump can be supplied to the internal combustion engine by bypassing the high pressure fuel pump only by adding the function of the high pressure side relief valve.
(B) In the fuel supply device for an internal combustion engine according to any one of claims 1 and 3,
The low-pressure side relief valve is configured to arbitrarily open the low-pressure fuel pump discharge side and the high-pressure fuel pump downstream side,
When the fuel discharged from the low-pressure fuel pump is supplied to the internal combustion engine bypassing the high-pressure fuel pump, the low-pressure relief valve is connected to the low-pressure fuel pump discharge side and the high-pressure fuel pipe downstream of the high-pressure fuel pump. It is characterized by supplying by driving to open.

According to the above invention, the fuel discharged from the low-pressure fuel pump can be supplied to the internal combustion engine by bypassing the high-pressure fuel pump only by adding the function of the low-pressure relief valve and a part of the fuel piping.
(C) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 3,
A bypass passage connecting the low-pressure fuel pump discharge side and the high-pressure fuel pipe downstream of the high-pressure fuel pump is provided, and an on-off valve that can be arbitrarily opened and closed is provided in the bypass passage,
When the fuel discharged from the low-pressure fuel pump is supplied to the internal combustion engine by bypassing the high-pressure fuel pump, the on-off valve is opened and supplied through the bypass passage.

According to the above invention, the fuel discharged from the low-pressure fuel pump can be supplied to the internal combustion engine by bypassing the high-pressure fuel pump with a highly reliable configuration in which a dedicated fuel pipe and an on-off valve are added.
(D) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 3 and (a) to (c),
When the high pressure side fuel pump cannot be boosted, the low pressure side fuel pump is fully opened.

According to the above invention, when the high pressure side fuel pump cannot be boosted, the fuel pressure supplied to the engine (fuel injection valve) can be maximized by fully opening the low pressure side fuel pump.
(E) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 3 and (a) to (c),
When the high pressure side fuel pump can raise the pressure, the fuel discharged from the low pressure side fuel pump is also supplied to the high pressure fuel pump to drive the high pressure side fuel pump, and the discharged fuel from the high pressure side fuel pump and the low pressure fuel pump are The discharged fuel is supplied to the engine.

According to the above-described invention, when the high pressure side fuel pump can be boosted, the high pressure fuel pump is also operated and fuel is supplied to the engine from the two fuel pumps, so that the fuel pressure at the time of the abnormality can be ensured as much as possible. .
(F) In the fuel supply device for an internal combustion engine described in (e) above,
When there is an abnormality in which the high-pressure side fuel pump can increase the pressure, the discharge amount from the low-pressure fuel pump is restricted to at least one of an upper limit value and a lower limit value or more.

According to the above invention, even if the discharge amount from the high-pressure side fuel pump is unstable, the amount of fuel supplied to the engine is limited to a stable range, the fuel pressure becomes excessive, the fuel leakage from the fuel injection valve and the fuel piping It is possible to prevent a decrease in the durability of the fuel or to prevent the generation of vapor from the fuel.
(G) In the fuel supply device for an internal combustion engine according to any one of claims 1 to 3 and (a) to (f),
When the fuel discharged from the low pressure fuel pump is supplied to the internal combustion engine by bypassing the high pressure fuel pump, the fuel injection valve is operated in a situation where the amount of fuel supplied from the low pressure fuel pump to the engine is insufficient. It is characterized by stopping.

  According to the above invention, the fuel injection is performed by performing the fuel cut in a situation where the amount of fuel supplied from the low pressure fuel pump to the engine is insufficient and the fuel pressure necessary for the injection from the fuel injection valve cannot be secured. The fuel pressure can be increased so as to enable injection from the valve.

The system block diagram which shows the 1st form of the fuel supply apparatus which concerns on this invention. The outline sectional view showing the composition of an example of the relief valve on the high pressure side used for the above-mentioned fuel supply device. The outline sectional view showing the composition of another example of the above-mentioned high-pressure side relief valve. The system block diagram which shows the 2nd form of a fuel supply apparatus. FIG. 3 is a schematic cross-sectional view showing a configuration of a low-pressure relief valve used in the fuel supply device. The system block diagram which shows the 3rd form of a fuel supply apparatus. The flowchart which shows the control which diagnoses the presence or absence of abnormality of a high pressure fuel pump. The flowchart which shows 1st Embodiment of control of the low pressure fuel pump based on the diagnostic result of the said high pressure fuel pump. Similarly, the flowchart which shows 2nd Embodiment of control of a low pressure fuel pump. Similarly, the flowchart which shows 3rd Embodiment of control of a low pressure fuel pump. Similarly, the flowchart which shows 4th Embodiment of control of a low pressure fuel pump.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Internal combustion engine, 12 ... Fuel tank, 13 ... Low pressure fuel pump, 14 ... High pressure fuel pump, 15 ... Fuel injection valve, 16 ... Low pressure fuel piping, 17 ... Return piping, 18, 18 '... Low pressure regulator, 21 ... High pressure Pump control solenoid, 22 ... pilot valve, 23 ... intake valve, 24 ... pump chamber, 25 ... discharge valve, 31 ... high pressure fuel pipe, 32 ... fuel gallery pipe, 33 ... relief pipe, 34 ... relief valve, 41 ... fuel pressure sensor , 42 ... Air flow meter, 43 ... Crank angle sensor, 44 ... Throttle opening sensor, 45 ... Starter switch, 51 ... Control unit, 61 ... Bypass piping, 71 ... Bypass piping, 72 ... Open / close valve

Claims (3)

An internal combustion engine fuel supply apparatus comprising: an engine-driven high pressure fuel pump; and an electric low pressure fuel pump that supplies fuel to the high pressure fuel pump, wherein the fuel discharged from the high pressure fuel pump is supplied to the internal combustion engine. ,
A fuel supply apparatus for an internal combustion engine, wherein the fuel discharged from the low pressure fuel pump is supplied to the internal combustion engine by bypassing the high pressure fuel pump when the high pressure fuel pump is abnormal.   A low-pressure relief valve for returning surplus fuel discharged from the low-pressure fuel pump to a low-pressure source can be arbitrarily closed, and the fuel discharged from the low-pressure fuel pump bypasses the high-pressure fuel pump and is 2. The fuel supply device for an internal combustion engine according to claim 1, wherein when the engine is supplied, the low pressure side relief valve is closed to stop the return of fuel.   2. The maximum flow rate of the low pressure fuel pump is restricted to an upper limit value or less when the fuel discharged from the low pressure fuel pump is supplied to the internal combustion engine bypassing the high pressure fuel pump. Item 3. A fuel supply device for an internal combustion engine according to Item 2.

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