JPH06147064A - Fuel supply system of internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce an amunt of hot excess fuel to be returned to a fuel tank via a pressure regulator and check any temperature rise in a fuel tank. CONSTITUTION:This fuel supply system is provided with a second return passage returning fuel into a tank from a nearby spot at the downstream side of a fuel pump 2, and it is also provided with a flow control valve 9 at the upstream end of this second return passage 8. Here an amount of lift in a diaphragm of a pressure regulator 6 is detected by a sensor 11, and the extent of differential pressure between fuel supply pressure and inlet negative pressure is detected from the lift value. In succession, the extent of opening in the flow control valve 9 is adjusted according to the differential pressure, and a fuel quantity to be returned into the tank 1 is controlled via the second return passage 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine, and more particularly to a device for supplying fuel of a predetermined pressure to a fuel injection valve.

[0002]

2. Description of the Related Art Conventionally, in an electronically controlled fuel injection system for an internal combustion engine, the amount of fuel supplied to the engine has been controlled by the valve opening control time of the fuel injection valve. In such a fuel supply device, if the pressure difference between the fuel supply pressure to the fuel injection valve and the intake pressure in the vicinity of the injection hole of the fuel injection valve is not constant, a constant fuel will be provided corresponding to the valve opening time of the injection valve. You will not be able to supply it. Therefore, as shown in FIG. 6, an intake negative pressure on the downstream side of the throttle valve is provided in the reference pressure chamber of the pressure regulator 23 for adjusting the supply pressure of the fuel pumped from the fuel pump 22 to the fuel injection valve 21. A return passage for returning the fuel to the fuel tank 24 when the pressure difference between the pressure in the reference pressure chamber and the supply pressure from the fuel pump, that is, the pressure difference between the intake pressure and the fuel pressure at the injection hole becomes a predetermined value or more. 25 was opened to keep the differential pressure constant (see JP-A-60-212634).

In FIG. 6, reference numeral 26 is a fuel filter, and 27 is a fuel filter.
Is a fuel supply passage.

[0004]

By the way, in the fuel supply device as described above, the fuel supply pressure needs to be kept constant even if the required fuel amount increases suddenly. A large amount of fuel is discharged, and the excessively supplied fuel is to be returned from the pressure regulator to the fuel tank as excess fuel.

Since the surplus fuel returned from the pressure regulator to the fuel tank is warmed by the heat of the engine, returning the surplus fuel to the fuel tank raises the fuel temperature in the fuel tank. And then
Occasionally, fuel vapor was generated in the fuel tank. The present invention has been made in view of the above problems,
An object of the present invention is to provide a fuel supply device capable of suppressing the generation of excess fuel that causes a temperature rise in the fuel tank and stabilizing the pressure of the fuel sent to the fuel injection valve.

[0006]

Therefore, the fuel supply system for an internal combustion engine according to the present invention is constructed as shown in FIG. In FIG. 1, a fuel pump sucks fuel from a fuel tank and sends the fuel under pressure through a fuel supply passage to a fuel injection valve that injects the fuel into an intake pipe of the engine.

Further, the fuel pressure detecting means detects the pressure of the fuel which is pressure-fed from the fuel pump to the fuel injection valve.
The return flow control valve is provided in a return passage for returning the fuel from the fuel supply passage upstream of the fuel injection valve to the fuel tank, and adjusts the flow rate of the fuel returned to the fuel tank through the return passage. .

The return flow rate control means variably controls the opening of the return flow rate control valve based on the fuel pressure detected by the fuel pressure detection means.

[0009]

According to this structure, the pressure of the fuel supplied to the fuel injection valve is detected, and the flow rate of the fuel returned to the fuel tank via the return passage is controlled based on this fuel pressure. That is, a desired fuel pressure is obtained by controlling the flow rate of the fuel returned from the return passage into the fuel tank.

In such a configuration, since the return fuel can be controlled by the return flow control valve at a position close to the fuel pump, the return fuel is generated before it is warmed by the engine heat, and the return flow rate is increased. It is possible to keep the temperature of the fuel returned via the control valve low.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing the fuel supply device of one embodiment,
The fuel in the fuel tank 1 is sucked by the fuel pump 2, and the fuel discharged from the fuel pump 2 is pressure-fed to each fuel injection valve 4 through the fuel supply passage 3.

The fuel injection valve 4 is an electromagnetic fuel injection valve which is energized by a solenoid to open the valve, and deenergized to close the valve. The fuel injection valve 4 corresponds to a required fuel amount of an engine sent from a fuel injection control unit (not shown). The valve opening control is performed according to the drive pulse signal having the predetermined pulse width, and the fuel is injected and supplied into the intake pipe downstream of the throttle valve of the engine (not shown). A fuel filter 5 is provided in the fuel supply passage 3, and
The pressure regulator 6 is interposed. The suction negative pressure in the intake pipe on the downstream side of the throttle valve is introduced into the reference pressure chamber defined by the diaphragm of the pressure regulator 6, and the pressure of the fuel pumped from the fuel pump 2 is When the pressure difference from the suction negative pressure exceeds a predetermined value, the first return passage 7 for returning the fuel in the fuel supply passage 3 to the fuel tank 1 is opened. With this configuration, the pressure regulator 6 adjusts the fuel supply pressure so that the pressure difference between the fuel supply pressure and the suction negative pressure becomes constant.

Further, the fuel supply passage 3 near the fuel tank 1
A second return passage 8 is provided by branching from the above, and an electromagnetic return flow control valve 9 is provided at the upstream end of the second return passage 8 to open and close the return flow control valve 9. By performing duty control, the opening of the return flow control valve 9 is changed (the effective opening area of the second return passage 8 is changed), and the fuel returned to the fuel tank 1 via the second return passage 8 is changed. The flow rate can be adjusted. As the return flow control valve 9,
A linear solenoid valve, a rotary solenoid, a stepping motor or the like may be used.

The opening of the return flow control valve 9 is controlled by a control unit 10 having a built-in microcomputer. The control unit 10 receives a detection signal from a lift amount sensor 11 for detecting the lift amount of the diaphragm of the pressure regulator 6 (movement amount of the diaphragm in the direction to open the first return passage 7). There is.

The lift amount sensor 11 is, for example, one that detects the lift amount as the position of the iron core by moving an iron core, one end of which is supported by a diaphragm, into and out of a detection coil according to the lift of the diaphragm. be able to. The lift amount of the diaphragm detected by the lift amount sensor 11 is a parameter that correlates with the differential pressure between the fuel supply pressure and the suction negative pressure. When the lift amount is large, the fuel supply pressure from the fuel pump 2 is It is excessive with respect to the suction negative pressure, and the fuel tank 1 passes through the first return passage 7.
A large amount of fuel is returned to. Therefore, in the present embodiment, the lift amount sensor 11 corresponds to the fuel pressure detecting means, and the lift amount sensor 11 detects the fuel pressure as a differential pressure with respect to the suction negative pressure.

Since the pressure regulator 6 introduces the engine suction negative pressure as a reference pressure to open and close the first return passage 7, it is necessary to dispose the pressure regulator 6 in the vicinity of the engine. The fuel returned to the fuel tank 1 through the 1-return passage 7 returns to the fuel tank 1 while being warmed by the heat of the engine.
In this way, when high temperature fuel is returned to the fuel tank 1,
This causes the temperature inside the fuel tank 1 to rise, and a large amount of vapor may be generated in the fuel tank 1.

On the other hand, since the return fuel amount of the second return passage 8 is adjusted by the electromagnetic return flow control valve 9, the arrangement of the second return passage 8 is less restricted, and the second return passage 8 is provided near the downstream of the fuel pump 2 as described above. The fuel can be returned to the inside of the tank 1 before being warmed by the engine. Therefore, in this embodiment, the control unit 10 controls the opening degree of the return flow control valve 9 as shown in the flowchart of FIG.
The amount of fuel returned via the first return passage 7 that causes a temperature rise in the fuel tank 1 is suppressed.

In this embodiment, the function as the return flow rate control means is provided by the control unit 10 as software as shown in the flow chart of FIG. In the flowchart of FIG. 3, first, in step 1 (denoted as S1 in the figure; the same applies hereinafter), the lift amount of the diaphragm of the pressure regulator 6 detected by the lift amount sensor 11 is read.

In the next step 2, the detected lift amount is compared with a predetermined value. When the lift amount is larger than the predetermined value, it indicates that the fuel supply (discharge amount) from the fuel pump 2 is excessive and it is necessary to return a large amount of fuel to the fuel tank 1 as return fuel. From this, in this case, the routine proceeds to step 3, where the opening degree of the return flow rate control valve 9 is increased by a predetermined minute opening degree, and the flow rate of the fuel returned into the fuel tank 1 via the second return passage 8 is increased. I will let you. When the amount of fuel returned through the second return passage 8 increases, the fuel supply pressure to the fuel injection valve 4 side decreases, and the lift amount of the pressure regulator 6, that is, the return returned through the first return passage 7. The amount of fuel decreases.

The predetermined value means the first return passage 7
Is opened slightly, and a small amount of excess fuel is left in the first return passage 7
It is a value corresponding to the situation where the fuel is returned to the inside of the fuel tank 1, and when the lift amount matches the predetermined value, the required fuel supply pressure can be secured. That is, when a large amount of fuel is returned to the fuel tank 1 as excess fuel by the pressure regulator 6,
The fuel is supplied to the fuel tank 1 from a position in the vicinity of the fuel pump 2 (fuel tank 1) and before the influence of the engine heat.
Then, the amount of fuel returned to the vicinity of the engine and then returned to the fuel tank 1 via the first return passage 7 is reduced.

As described above, the fuel that would otherwise be returned to the fuel tank 1 as excess fuel from the pressure regulator 6 is returned to the fuel tank 1 from the upstream side in advance, so that the comparison before being warmed by the engine is made. Fuel having a low target temperature can be returned to the fuel tank 1 as surplus fuel, and the amount of fuel having a relatively high temperature returned from the pressure regulator 6 can be minimized. Therefore, it is possible to prevent the temperature of the fuel tank 1 from rising due to the fuel returned to the fuel tank 1 as surplus fuel, thereby avoiding the generation of a large amount of vapor in the fuel tank 1.

On the other hand, when the lift amount is smaller than the predetermined value, there is a possibility that the required supply pressure of fuel to the fuel injection valve 4 cannot be secured, so the routine proceeds to step 4, where the return flow control valve 9 is operated. The opening degree is decreased by a predetermined minute opening degree, the flow rate of the fuel returned to the fuel tank 1 through the second return passage 8 is decreased, and more fuel is injected into the injection valve 4.
To ensure the required supply pressure.

As described above, the pressure regulator 6
By adjusting the opening of the return flow rate control valve 9 in the direction of bringing the lift amount of the fuel injection valve 4 closer to a predetermined value, the fuel amount adjusted by the pressure regulator 6 and returned to the fuel tank 1 can be controlled to the minimum, and the fuel injection valve 4 It is possible to secure the necessary supply pressure for Further, since the amount of return fuel is adjusted near the downstream of the fuel pump 2 to adjust the supply pressure to a desired value, it is possible to stabilize the pressure in the fuel supply passage 3 near the fuel injection valve 4.

By the way, in the embodiment shown in FIG.
Although the fuel supply pressure is detected as the lift amount of the diaphragm of the pressure regulator 6 as a differential pressure with respect to the suction negative pressure, the fuel pressure sensor 12 for detecting the pressure in the fuel supply passage 3 is used as shown in FIG. The opening of the return flow control valve 9 may be adjusted according to the fuel pressure detected by the fuel pressure sensor 12 as fuel pressure detection means.

In FIG. 4, the same elements as those in FIG. 2 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 4, the pressure regulator 6 adjusts the return fuel so as to keep the differential pressure of the fuel pressure with respect to the suction negative pressure constant, so the opening of the return flow control valve 9, that is, the second return passage 8 In order to adjust the flow rate of the fuel returned to 1 with high accuracy, information on the suction negative pressure is required.

Therefore, in the system shown in FIG. 4, the detection signal from the boost sensor 13 for detecting the suction negative pressure of the engine is input to the control unit 10.
The control unit 10 calculates the differential pressure between the fuel pressure detected by the sensors 12 and 13 and the suction negative pressure, and controls the opening of the return flow control valve 9 in the direction in which the differential pressure approaches the target value.

Here, the target value of the differential pressure in the opening control of the return flow control valve 9 is set to be higher than the target differential pressure in the pressure regulator 6, and finally a slight surplus from the pressure regulator 6 is set. It is desirable for the fuel pressure to be stabilized so that the fuel is returned to the tank 1 and adjusted to the target differential pressure. Further, although the pressure regulator 6 is provided in the configuration shown in FIG. 4, the pressure regulator 6 may be omitted and the configuration shown in FIG. 5 may be adopted.

In the configuration shown in FIG. 5, for the control unit 10 for controlling the opening degree of the return flow control valve 9, the detection signal from the fuel pressure sensor 12 and the boost sensor 13 are used similarly to the configuration shown in FIG. The control unit 10 receives the return flow rate in order to match the differential pressure between the fuel pressure detected by the sensor and the suction negative pressure with the target differential pressure for fuel injection control. The opening degree of the control valve 9 is adjusted. That is, in the configuration shown in FIG. 5, since the pressure regulator 6 is omitted, the fuel warmed by the engine heat is never returned to the fuel tank 1.
All excess fuel generated to obtain the desired fuel pressure will be returned to the fuel tank 1 via the return flow control valve 9 before being warmed by the engine heat.

The configuration shown in FIGS. 2, 4 and 5 may be such that the discharge amount of the fuel pump 2 is variably controlled according to the required fuel amount of the engine. Further, in the embodiment shown in FIGS. 4 and 5, the fuel pressure sensor 12 and the boost sensor 13 are provided separately, but since the required information is the differential pressure between the fuel pressure and the suction negative pressure, A sensor that outputs a detection signal corresponding to the differential pressure between the intake negative pressure and the negative pressure is provided, and the opening of the return flow control valve 9 is controlled according to the differential pressure detected by the sensor. May be.

[0030]

As described above, according to the present invention, the excess fuel is returned to the fuel tank so that the required supply pressure of the fuel injection valve is reached, while the fuel warmed by the engine heat is stored in the fuel tank as excess fuel. It is possible to minimize the amount to be returned, thereby suppressing the temperature rise in the fuel tank due to the high temperature excess fuel.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is a diagram showing a system configuration of an embodiment of the present invention.

FIG. 3 is a flowchart showing return flow rate control according to the embodiment.

FIG. 4 is a diagram showing a system configuration of another embodiment using a fuel pressure sensor.

FIG. 5 is a diagram showing a system configuration of another embodiment in which a pressure regulator is omitted.

FIG. 6 is a system configuration diagram showing a conventional fuel supply device.

[Explanation of symbols]

 1 Fuel Tank 2 Fuel Pump 3 Fuel Supply Passage 4 Fuel Injection Valve 6 Pressure Regulator 7 First Return Passage 8 Second Return Passage 9 Return Flow Control Valve 10 Control Unit 11 Lift Amount Sensor 12 Fuel Pressure Sensor 13 Boost Sensor

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akira Ushigome 1167-1, Kasugawa-cho, Isesaki-shi, Gunma Nippon Electric Equipment Co., Ltd.

Claims (1)

[Claims] 1. A fuel pump for sucking fuel from a fuel tank and forcing the fuel to a fuel injection valve for injecting the fuel into an intake pipe of an engine through a fuel supply passage; and a pressure pump for feeding the fuel from the fuel pump to the fuel injection valve. A fuel pressure detecting means for detecting the pressure of the fuel, and a return passage for returning the fuel from the fuel supply passage upstream of the fuel injection valve to the fuel tank, and the fuel returned to the fuel tank through the return passage. A return flow rate control valve for adjusting the flow rate of the return flow rate control valve, and a return flow rate control means for variably controlling the opening degree of the return flow rate control valve based on the fuel pressure detected by the fuel pressure detection means. A fuel supply device for an internal combustion engine.