JPH074330A - Fuel pressure control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To insure quick start of an engine while preventing vapor lock. CONSTITUTION:Fuel injection valves 2 are connected to a fuel distributing pipe 3, and the fuel distributing pipe 3 is connected to a high pressure pump 5 and a low pressure pump 7 through a fuel feed pipe 4. A relief valve 10 is fitted to the fuel distributing pipe 3. When an ignition switch 12 is ON, the fuel pumps 5, 7 are driven, and at this time the discharge quantity of the high pressure pump 5 is controlled to discharge the maximum quantity. Hereby the fuel pressure in the fuel distributing pipe 3 reaches the valve opening pressure of the relief valve 10, and air in the fuel distributing pipe 3 is let flow out together with fuel from the rtelief valve 10. Further the relief valve 10 is arranged on the highest position of the fuel passages 3, 4, and hence air in the fuel passages 3, 4 can be favorably let flow out. After the lapse of a set time since the fuel pressure in the fuel distributing pipe 3 reaches the valve opening pressure of the relief valve 10, the discharge quantity of the high pressure pump 5 is controlled so that the fuel pressure in the fuel distributing pipe 3 is the target fuel pressure.

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art A fuel relief solenoid valve is arranged in a fuel passage extending from a fuel pump to a fuel injection valve, and when the temperature in the fuel passage at the time of engine start is higher than a preset temperature, the drive of a starter motor is prohibited and A fuel pressure control device for an internal combustion engine is known in which a fuel pump is driven while an electromagnetic valve is opened so that the fuel in the fuel passage is caused to flow out from the electromagnetic valve (see Japanese Patent Laid-Open No. 57-200663). . In this fuel pressure control device for an internal combustion engine, when the temperature in the fuel passage at the time of engine startup is higher than the set temperature, bubbles existing in the fuel passage are caused to flow out from the solenoid valve together with the fuel to prevent vapor lock. When the temperature in the fuel passage becomes lower than the set temperature, the prohibition of the drive of the starter motor is released and the solenoid valve is closed.

[0003]

However, when the temperature in the fuel passage at the time of engine start is higher than the set temperature as in the fuel pressure control apparatus described above, the drive of the starter motor is prohibited to prevent vapor lock. The starter motor cannot be driven until the temperature in the passage becomes lower than the set temperature, that is, the engine cannot be started, and as a result, it takes time to start the engine, for example, from when the starter motor switch is turned on until the engine starts. There is a problem. Further, when air is mixed into the fuel passage from the seal portion provided in the fuel pump, the fuel passage, or the fuel injection valve while the engine is stopped, the temperature in the fuel passage at the time of starting the engine is the same as in the above fuel pressure control device. When the temperature is higher than the set temperature, the solenoid valve is opened and the fuel pump is driven to allow the bubbles in the fuel passage to flow out from the solenoid valve together with the fuel. There is a problem that the valve is not opened, and as a result the air in this fuel passage is not discharged from the solenoid valve.

[0004]

In order to solve the above-mentioned problems, according to the present invention, the fuel escape valve is opened at a predetermined constant pressure at the highest position of the fuel passage from the fuel pump to the fuel injection valve. A relief valve is installed to increase the discharge amount of the fuel pump to the discharge amount at which the relief valve opens and excess fuel flows out from the relief valve when the engine is started, and the fuel pressure in the fuel passage is increased in other engine operating conditions. The fuel pump has a discharge amount control device for controlling the discharge amount from the fuel pump so as to maintain the target fuel pressure below the relief valve opening pressure.

[0005]

When the engine is started, the fuel pressure in the fuel passage is maintained at the fuel pressure required for starting the engine, and the bubbles in the fuel passage are discharged from the relief valve together with the fuel. In other engine operating states, the discharge amount from the fuel pump is controlled so that the fuel pressure in the fuel passage is maintained at the target fuel pressure.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an engine body 1 has four cylinders 1.
a, and each cylinder 1a is provided with a fuel injection valve 2. Each fuel injection valve 2 is connected to a common fuel distribution pipe 3 for all fuel injection valves, and the fuel distribution pipe 3 is arranged via a fuel supply pipe 4 into a high pressure pump 5 and a low pressure pump 7 arranged in a fuel tank 6. Connected to. Therefore, in the embodiment shown in FIG. 1, the fuel passage is composed of the fuel distribution pipe 3 and the fuel supply pipe 4, and the fuel pump is a high pressure pump 5 and a low pressure pump 7.
Composed of and. In the embodiment shown in FIG. 1, the fuel is directly injected from each fuel injection valve 2 into each combustion chamber (not shown) of the cylinder 1a, so that the fuel pressure in the fuel distribution pipe 3 is relatively small. The high pressure pump 5 is provided because it needs to be high. The low-pressure pump 7 is composed of a pump whose discharge amount cannot be controlled.
It is composed of, for example, a reciprocating pump whose discharge amount can be controlled by returning from a. A pressure regulator 8 and a fuel filter 9 are arranged in the fuel supply pipe 4 between the high pressure pump 5 and the low pressure pump 7, and the pressure regulator 8 maintains a constant fuel pressure of the fuel supplied to the high pressure pump 5. It The fuel return passage 5 a of the high pressure pump 5 and the fuel return passage 8 a of the pressure regulator 8 are connected to the fuel escape passage 11.

A relief valve 10 for releasing the fuel is connected to the fuel distribution pipe 3, and the relief valve 10 is connected to the fuel relief passage 1.
1, the relief valve 10 is attached to the highest position of the fuel distribution pipe 3 and the fuel supply pipe 4 as shown in FIG. Further, in the embodiment shown in FIG. 1, the relief valve 10 is composed of a check valve which can flow from the fuel distribution pipe 3 toward the fuel tank 6,
This check valve opens at a preset set pressure. Therefore, when the fuel pressure in the fuel distribution pipe 3 reaches the valve opening pressure of the relief valve 10, the relief valve 10 opens and the fuel distribution pipe 3
The fuel inside is discharged from the relief valve 10 into the fuel escape passage 11 to maintain the fuel pressure in the fuel distribution pipe 3 at the relief valve 10 opening pressure, and as a result, the fuel pressure in the fuel distribution pipe 3 becomes excessively high. Is prevented.

As shown in FIG. 1, the key switch 12 includes an ignition switch 13 and a starter motor switch 14. The ignition switch 13 is connected to the battery 15 on the one hand, and the starter motor switch 14 and the CPU 34 of the electronic control unit 30 on the other hand.
Connected to. The starter motor switch 14 is connected to the starter motor 16. Ignition switch 13
When the power is turned on, power is supplied from the battery 15 to the CPU 34, and at this time, the starter motor switch 14
When is turned on, electric power is also supplied to the starter motor 16.

The electronic control unit 30 comprises a digital computer, and a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input which are mutually connected via a bidirectional bus 51. A port 35 and an output port 36 are provided. A pressure sensor 37 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 3 is attached to the fuel distribution pipe 3, and the output voltage of the pressure sensor 37 is an A / D converter 38.
Is input to the input port 35 via. An air flow meter 39 that generates an output voltage proportional to an intake air amount is attached to an intake passage (not shown) of the engine 1, and the output voltage of the air flow meter 39 is input to an input port 35 via an A / D converter 40. Is entered. Further, the rotation speed sensor 41 that generates an output pulse representing the engine rotation speed is connected to the input port 3
Connected to 5. Further, an output pulse indicating that the starter motor switch 14 is in the ON state is input port 3
Input to 5. On the other hand, the output port 36 is connected to each fuel injection valve 2, the high pressure pump 5, and the low pressure pump 7 via the corresponding drive circuit 42.

When the engine 1 is stopped, the fuel pressure in the fuel distribution pipe 3 may gradually decrease due to, for example, fuel leakage. At this time, it is necessary to control the discharge amount of the high pressure pump 5 at the time of starting the engine to increase the fuel pressure in the fuel distribution pipe 3 to a predetermined set pressure. On the other hand, when the engine 1 is stopped, air is introduced into the fuel distribution pipe 3 and the fuel supply pipe 4 from the seal portion provided in the fuel injection valve 2, the high pressure pump 5, the low pressure pump 7, the fuel distribution pipe 3, or the fuel supply pipe 4. When mixed, it may cause so-called vapor lock. However, if the engine 1 is started while air is present in the fuel distribution pipe 3 and the fuel supply pipe 4, even if the discharge amount of the high-pressure pump 5 is controlled so as to increase the fuel pressure in the fuel distribution pipe 3, the fuel distribution pipe is also controlled. Since the air in 3 is compressed, it takes a considerable time for the fuel pressure in the fuel distribution pipe 3 and the fuel supply pipe 4 to rise to the set pressure. Further, when the engine 1 is started while air is present in the fuel distribution pipe 3 and the fuel supply pipe 4, air is injected from the fuel injection valve 2 into the cylinders 1a together with the fuel. The injection amount will deviate from the regular injection amount. Therefore, in the embodiment according to the present invention, the discharge amount of the high-pressure pump 5 is controlled to the maximum discharge amount at the time of starting the engine, and the fuel pressure in the fuel distribution pipe 3 is changed to the relief valve 10 opening pressure to make the fuel distribution pipe 3 and the fuel supply pipe. Relief valve 1 with air in 4 along with excess fuel
The fuel is allowed to flow from 0 into the passage 11. Moreover, in the embodiment shown in FIG. 1, the relief valve 10 is provided at the highest position of the fuel distribution pipe 3 and the fuel supply pipe 4, so that the air in the fuel supply pipe 3 can be easily discharged from the relief valve 10. Can be drained. Therefore, the vapor lock can be prevented, and as a result, a quick engine start can be ensured and the injection of air from the fuel injection valve 2 can be prevented. When the fuel in the fuel distribution pipe 3 and the fuel supply pipe 4 is heated, the fuel may be vaporized and bubbles may be generated. However, when the bubbles are generated, the bubbles are also formed in the fuel distribution pipe. 3 and the air and fuel in the fuel supply pipe 4 flow out from the relief valve 10.
As a result, vapor lock is reliably prevented.

On the other hand, in other engine operating states, the discharge amount of the high-pressure pump 5 is feedback controlled so that the fuel pressure in the fuel distribution pipe 3 becomes a predetermined target fuel pressure. This target fuel pressure is set lower than the valve opening pressure of the relief valve 10, that is, when the fuel pressure in the fuel distribution pipe 3 is maintained at this target fuel pressure, the relief valve 1
0 does not open the valve. The target fuel pressure may be changed according to the engine load or the engine speed.

Next, the operation of the internal combustion engine 1 will be described with reference to FIG. When the ignition switch 13 is turned on, the high pressure pump 5 and the low pressure pump 7 are driven. At this time, the discharge amount FQ of the high pressure pump 5 is controlled to the maximum discharge amount FQM. As a result, the fuel pressure P in the fuel distribution pipe 3 rises to the valve opening pressure PM of the relief valve 10, and the relief valve 10 opens, so that the air in the fuel distribution pipe 3 and the fuel supply pipe 4 relieves together with the fuel. The fuel escapes from the valve 10 into the fuel escape passage 11. In the embodiment shown in FIG. 1, the discharge amount FQ of the high-pressure pump 5 is maintained at the maximum discharge amount FQM until the fuel pressure P in the fuel distribution pipe 3 reaches PM and a predetermined set time t0 elapses. . Therefore, the air in the fuel distribution pipe 3 and the fuel supply pipe 4 can surely flow out from the relief valve 10. Next, when the set time t0 elapses after the fuel pressure P in the fuel distribution pipe 3 reaches PM, the fuel pressure in the fuel distribution pipe 3 changes to the relief valve 10
The discharge amount FQ of the high-pressure pump 5 is feedback-controlled so as to be maintained at the target fuel pressure P0 set lower than the valve opening pressure of.

By the way, when the ignition switch 13 is turned on, the starter motor switch 14 can be turned on. When the starter motor switch 14 is turned on, the starter motor 16 is driven, but at this time, it is necessary to start fuel injection from each fuel injection valve 2. In the embodiment according to the present invention, when the ignition switch 13 is turned on, that is, before the starter motor switch 14 is turned on, the high pressure pump 5 and the low pressure pump 7 are driven and the fuel pressure in the fuel distribution pipe 3 is changed. Since the pressure is rapidly increased, the air in the fuel distribution pipe 3 and the fuel supply pipe 4 can be made to flow out from the relief valve 10 together with the surplus fuel, and fuel injection can be performed from the fuel injection valve 2 while preventing vapor lock. As a result, ignition switch 1
Starter motor 1 at any time after 3 is turned on
6 can be driven, thus ensuring a fast engine start.

By the way, in the embodiment according to the present invention, the basic fuel injection time T is a function of the engine speed N and the engine load Q / N (intake air amount Q / engine speed N) in the map shown in FIG. It is pre-stored in the ROM 32 in the form of. This basic fuel injection time T is the optimum fuel injection time when the fuel pressure P in the fuel distribution pipe 3 is the set pressure P0. However, for example, if the fuel injection is performed from the fuel injection valve 2 for the basic fuel injection time T when the fuel pressure P in the fuel distribution pipe 3 becomes higher than the set pressure P0, the fuel injection amount at this time is the optimum fuel injection amount. Will be more than. Therefore, in the embodiment according to the present invention, as shown in FIG.
A correction coefficient k which is 1 when the internal fuel pressure P is P0 and which decreases as the fuel pressure P in the fuel distribution pipe 3 increases, is used to determine the fuel injection time TAU based on the following equation. . TAU = k · T

A flow chart for carrying out the above-described embodiment is shown in FIGS. The routine shown in FIG. 5 is first executed when the ignition switch 13 is turned on. Referring to FIG. 5, when the ignition switch 13 is turned on, the low pressure pump 7 and the high pressure pump 5 are first turned on in steps 51 and 52.
At this time, in step 53, the discharge amount F of the high-pressure pump 5
Q is controlled to the maximum discharge amount FQM. Next, at step 54, a flag (described later) is reset, and at step 55, a counter C (described later) is reset.

The routine shown in FIG. 6 is executed by interruption at regular time intervals after the ignition switch 13 is turned on. Referring to FIG. 6, first, at step 61, whether the flag set when the set time t0 has elapsed after the fuel pressure P in the fuel distribution pipe 3 became the opening pressure of the relief valve 10 is set or not. Is determined. When the flag is set in step 61, the process proceeds to step 65, while when the flag is not set, the process proceeds to step 62. Immediately after the ignition switch 13 is turned on, the flag is not set, so the routine proceeds to step 62, where step 62
Then, it is determined whether or not the fuel pressure P in the fuel distribution pipe 3 detected by the pressure sensor 37 is the valve opening pressure PM of the relief valve 10. When P = PM, the routine proceeds to step 63, where P ≠ PM. At some time, the processing cycle is ended.
In step 63, it is judged whether or not the counter C representing the time after P = PM is established is the set value CM, and when C = CM, that is, the set time t0 is established after P = PM is established. When (FIG. 2) has elapsed, the routine proceeds to step 64, where a flag is set, and then the routine proceeds to step 65.
On the other hand, when C ≠ CM, the counter C is counted in step 66 and the processing cycle is ended. In step 65, the fuel pressure P in the fuel distribution pipe 3 is the target fuel pressure P0.
The discharge amount FQ of the high-pressure pump 5 is feedback-controlled so as to be maintained at.

The routine shown in FIG. 7 is executed by interruption at regular time intervals after the starter motor switch 14 is turned on. Referring to FIG. 7, first, at step 71, the basic fuel time T is calculated based on the map of FIG. 3, then at step 72, the correction coefficient k is calculated based on the diagram of FIG. 4, and at step 73, the fuel injection time T is calculated. TAU is calculated.

FIG. 8 shows a second embodiment according to the present invention. In the embodiment shown in FIG. 8 as well, the relief valve 10 is mounted at the highest position of the fuel distribution pipe 3 and the fuel supply pipe 4, but in this embodiment, the top surface 8 of the fuel distribution pipe 80.
0a has a slope toward the relief valve 10. Therefore, the air in the fuel distribution pipe 3 and the fuel supply pipe 4 can be satisfactorily discharged from the relief valve 10. The other operations of the internal combustion engine 1 are similar to those of the above-described first embodiment, and therefore the description thereof will be omitted.

In the above embodiment, the high pressure pump 5 and the low pressure pump 7 are started when the ignition switch 13 is turned on, and the discharge amount of the high pressure pump 5 at this time is controlled to the maximum discharge amount. However, for example, when the starter motor switch 14 is turned on, the high pressure pump 5 and the low pressure pump 7 may be started and the discharge amount of the high pressure pump 5 at this time may be controlled to the maximum discharge amount. Alternatively, the low-pressure pump 7 is composed of an electrically driven pump, the high-pressure pump 5 is composed of an engine-driven pump, and when the ignition switch 13 is turned on, only the low-pressure pump 7 is started, and then the starter motor switch 14 is operated. The high pressure pump 5 may be started when turned on, and the discharge amount of the high pressure pump 5 at this time may be controlled to the maximum discharge amount. Further, in the above-described embodiment, the discharge amount of the high-pressure pump 5 is feedback-controlled after the set time t0 elapses after the fuel pressure in the fuel distribution pipe 3 reaches the relief valve 10 opening pressure. However, for example, the discharge amount of the high-pressure pump 5 may be feedback-controlled after the starter motor switch 14 is turned off.

Further, in the above-described embodiment, the relief valve 10 is composed of a check valve. However, relief valve 1
The solenoid valve 0 may be configured so that the solenoid valve is controlled to open and close according to the fuel pressure in the fuel distribution pipe 3 detected by the pressure sensor 37. Further, in the above-described embodiment, the discharge amount of the high pressure pump 5 is controlled to the maximum discharge amount at the time of starting the engine.
The discharge amount may be such that the internal fuel pressure becomes the relief valve 10 opening pressure.

[0021]

When the engine is started, the discharge amount of the fuel pump is set so that the relief valve opens, and the relief valve is mounted at the highest position of the fuel passage, so that the air in the fuel passage can be easily discharged. It can flow out from the relief valve, and at this time, the fuel pressure in the fuel passage is maintained at the fuel pressure necessary for starting the engine, so that quick engine starting can be ensured.

[Brief description of drawings]

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

FIG. 2 is a diagram showing changes with time in fuel pressure in a high-pressure pump and a fuel distribution pipe.

FIG. 3 is a diagram showing a basic fuel injection time.

FIG. 4 is a diagram showing a correction coefficient.

FIG. 5 is a flowchart for driving a high pressure pump and a low pressure pump.

FIG. 6 is a flowchart for controlling a fuel discharge amount.

FIG. 7 is a flowchart for controlling fuel injection time.

FIG. 8 is an overall view of an internal combustion engine showing a second embodiment.

[Explanation of symbols]

 2 ... Fuel injection valve 3 ... Fuel distribution pipe 4 ... Fuel supply pipe 5 ... High pressure pump 6 ... Fuel tank 7 ... Low pressure pump 10 ... Relief valve 13 ... Ignition switch 14 ... Starter motor switch 16 ... Starter motor 37 ... Pressure sensor

Claims (1)

[Claims] 1. A fuel relief relief valve that opens at a predetermined constant pressure is arranged at the highest position of a fuel passage from a fuel pump to a fuel injection valve, and the discharge amount of the fuel pump is relieved when the engine is started. The valve opens to increase the amount of excess fuel discharged to the relief valve, and in other engine operating conditions, the fuel pressure in the fuel passage is maintained at the target fuel pressure below the relief valve opening pressure. A fuel pressure control device for an internal combustion engine, comprising a fuel pump discharge amount control device for controlling the discharge amount.