JPH0343643A - Fuel feed device of fuel injection type engine - Google Patents

Abstract

PURPOSE:To reduce the power loss and improve the fuel consumption by on-and off-controlling a switching element for controlling the drive of a fuel feed pump that the differential pressure between pressure of a supplied fuel and intake pressure becomes a determined value. CONSTITUTION:In a power or electromagnetic fuel injection pump 13, the fuel in a fuel tank 12 is boosted and fed to an injection valve 7 through a fuel filter 11, a pressure regulator 10 and a delivery pipe 19. In the regulator 10, the valve opening is automatically controlled in the direction to keep the differential pressure Pd between the fuel pressure Pf supplied to the injection valve 7 and the intake pressure Pi of an intake manifold 3 at a determined value. In this case, a differential pressure detector 17 for detecting the differential pressure Pd is provided in the regulator 10. When the differential pressure Pd is larger than the determined value, the closing time ratio of a switching element 31 is made small by an error amplifier 27 to reduce the electric energy for driving the pump 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel supply device for a fuel injection type engine for a vehicle or the like.

[Conventional technology]

In engines that inject fuel pressurized to a relatively low pressure into the intake port, the pressure difference between the fuel pressure and the intake pressure at the intake port where it is to be injected must be maintained constant to ensure accurate fuel injection. Injection amount cannot be controlled.

This is because even if the fuel pressure is held constant, if the intake pressure fluctuates due to changes in operating conditions, the amount of fuel injected within the same injection time will change.For this reason, conventional , so that the fuel pressure is always higher than the intake manifold pressure by, for example, 2.55 kg/cut.
By providing a pressure regulator to bypass excess pressure, fuel pressure is always controlled in this way.

[Problem to be solved by the invention]

The conventional fuel pressure control method is to return excess pressure fuel from the pressure regulator to the fuel tank via the oil return path, so the fuel supply pump is designed to inject more fuel than is actually injected by the fuel injection valve. is pressurized. Therefore, the fuel that returns to the fuel tank through the oil return path is pressurized unnecessarily, resulting in a loss of power and reducing the efficiency and output of the engine.

The present invention aims to solve this problem by pressurizing the necessary amount of fuel so that the amount of bypassed fuel is almost zero or no, and also to obtain other effects accompanying this. be.

[Means to solve the problem]

As a means for solving the above problems, the present invention provides a fuel supply pump that pressurizes fuel and supplies it to a fuel injection valve;
a differential pressure detector that detects a differential pressure between the pressure of fuel fed to the fuel injection valve and the pressure of intake air; a switching element inserted in a power supply line that drives the fuel supply pump;
The present invention provides a fuel supply device for a fuel injection engine, comprising means for controlling the switching element intermittently so that the differential pressure detected by the differential pressure detector becomes a predetermined value.

[For production]

Since the present invention has the configuration as described above, the differential pressure between the pressure of the fuel fed to the fuel injection valve and the pressure of the intake air is always measured by the differential pressure detector.

If the differential pressure becomes larger than the predetermined value,
The means for controlling the switching element intermittently reduces the closed circuit time ratio of the switching element, thereby reducing the amount of power sent from the power line to drive the fuel supply pump. As a result, the rotational speed (frequency) or stroke volume of the fuel supply pump decreases, the amount of fuel discharged, and therefore the discharge pressure decreases, and the differential pressure detected by the differential pressure detector becomes a predetermined value.

Conversely, when the differential pressure becomes smaller than a predetermined value, the means for controlling the switching element intermittently increases the closed circuit time ratio of the switching element, increasing the amount of electricity sent to drive the fuel supply pump. let As a result, the rotational speed or stroke of the fuel supply pump increases, the amount of fuel discharged and therefore the discharge pressure increases, and the differential pressure becomes a predetermined value.

Needless to say, when the differential pressure is approximately maintained at a predetermined value, the closed circuit time ratio of the switching element is maintained as is, and the discharge amount of the fuel supply pump is maintained constant.

〔Example〕

In FIG. 1 showing the overall configuration of an embodiment of the present invention, ■ is a cylinder head of a fuel injection engine, 2 is an intake boat,
3 is an intake manifold or surge tank, 4 is a throttle valve, 5 is an intake valve, 6 is an idle speed control valve, 7 is a fuel injection valve, 8 is a cold start injector, 9 is a vacuum sensor, 10 is a pressure regulator to be described later, 11 12 is a fuel filter, 12 is a fuel tank 1. 13 is an electric or electromagnetic fuel supply pump, 1
4.15 is the oil supply path, 16 is the pressure regulator 10
2 shows an oil return path for returning excess fuel from the fuel tank 12 to the fuel tank 12.

As a feature of the present invention, the pressure regulator 10 of the illustrated embodiment is provided with a differential pressure detector 17, and the pipe line 1
The intake pressure Pi of the intake manifold 3 guided by 8
The differential pressure Pd between the fuel pressure Pf and the fuel pressure Pf supplied to the fuel injection valve 7 via the delivery vibe 19 is detected. The pressure regulator 10 basically has a structure and function as a well-known diaphragm type pressure regulating valve.
The differential pressure Pd between the fuel pressure Pf and the intake pressure P1 is always
For example, a valve opening (not shown) is automatically adjusted to maintain 2.55 kg/cI11, and excess fuel is returned to the fuel tank 12 through the oil return path 16.

Two embodiments of differential pressure detector 17 are shown in FIGS. 2 and 3. FIG. 2 shows one using a strain gauge, and the differential pressure detector 17 in this example has two pressure chambers 21 and 22 separated by a diaphragm 20, and the pressure chamber 21 is connected to an input port 23. The pressure chamber 22 receives the fuel pressure Pf through the reference port 24, and the pressure chamber 22 receives the intake pressure Pi of the intake manifold through the reference port 24. The amount of strain in the diaphragm 20 that is deformed by the differential pressure Pd between the fuel pressure Pf and the intake pressure Pi is measured as an electrical resistance value by a strain gauge 25 attached to the diaphragm 20, and an error shown in FIG. 1 is measured by a conductor 26. The signal is input to the amplifier 27. Note that 28 shown in FIG. 2 is a temperature compensator.

A voltage corresponding to the set reference pressure difference (reference pressure difference voltage) is inputted to the error amplifier 27 from the reference pressure difference setting device 29 through a conductor 26', and the amount of distortion of the diaphragm 20 of the differential pressure detector 17 is inputted to the error amplifier 27. Therefore, it is compared with the voltage corresponding to the differential pressure Pd, and an error signal corresponding to the difference is amplified and sent to the switching element 31 via the conductor 30 as a control signal.
is applied to The switching element is, for example, a thyristor or a power transistor, and is inserted into the power line 32 of a motor or solenoid coil (not shown) that drives the fuel supply pump 13. 32 is finely intermittent, the driving force of the fuel supply pump is increased or decreased, and the discharge amount is changed steplessly, so that the fuel pressure Pf is set to a predetermined pressure difference with respect to the intake pressure Pi, for example, 2.55 kg/c.
II! Adjust so that it has .

This operation is carried out extremely smoothly when there is almost no variation in the intake pressure P1 or when the variation is relatively slow, so the pressure regulator 10 passes through the oil return path 16 to the fuel tank.
The amount of fuel that returns to 2 becomes almost zero, and the fuel supply pump 13
Due to the variable speed operation of the fuel injection valve 7 (
And the amount consumed in the cold start injector 8) is sent to the pressure regulator 10 via the fuel supply line 14, 15 and the fuel filter 11 in just the right amount.

Therefore, the fuel supply pump 13 wastes power (electricity).
do not consume.

When the fluctuations in the intake pressure Pi are severe, it is difficult to control the fuel supply pump without any response delay to the fluctuations, but the control characteristics should not be limited to proportional operation, but should also include differential operation. It is possible to compensate to a certain extent by setting the predetermined value set in the reference pressure difference setting device 29 slightly higher, or by installing a pressure accumulator in the fuel passage just before the fuel injection valve 7 to alleviate sudden fuel pressure fluctuations. In practice, it is possible to reduce the amount of fuel that returns from the oil return path 16 to the fuel tank 12 to an extremely small amount.

FIG. 3 shows another embodiment of the differential pressure detector 17 in which a change in differential pressure is detected as a change in capacitance. In the figure, 33 and 34 are metal diaphragms, 35 is a capacitive sensing element, 36 is a conversion circuit that converts a change in capacitance, which is a detected value, into a change in voltage;
Components similar to those in the example shown in the figure are given the same reference numerals, and the description thereof will be omitted.

In addition, the diaphragm 20.3 in FIGS. 2 and 3
3 and 34 are explained as being independently provided in the differential pressure detector 17, but they are also provided in the pressure regulator 1.
It is also possible to use a zero diaphragm instead. That is, by configuring the pressure regulator 10 and the differential pressure detector 17 as one unit, the structure of the device can be greatly simplified. Furthermore, if very accurate control is not required, the pressure regulator 10 and the oil return path 16 can be omitted.

An example of an electric circuit is shown in FIG. Components that are substantially the same as those mentioned in the explanation of FIG. 1 are designated by the same reference numerals. The differential pressure measured at short intervals by the differential pressure detector 17 is converted into an electrical signal (voltage, etc.) and sent to the error amplifier 27, where it is compared with a voltage 29' set as a reference pressure.

The deviation is amplified and inputted to the PWM comparator 37, and compared with a triangular wave generated and inputted by a triangular wave oscillator 38 for performing pulse width modulation to generate a drive pulse. The drive pulse is amplified by a drive circuit 39 and connected to the base of a transistor 31', which is an example of a switching element (semiconductor switch).

The power supplied to the power supply line 32 is transmitted through the transistor 31
' energizes the motor 40 intermittently for a time corresponding to the width of the drive pulse, so if the pulse width changes, the motor 40
Therefore, the rotation speed of the pump 13 changes.

In the case of FIG. 4, the emitter of the transistor 31' is grounded, and the collector is connected to the drive motor 40 of the fuel supply pump 13.
is connected and receives power from the power line 32.

Note that 41 is a free wheel diode inserted in parallel to the motor 40. The transistor 31' and the drive motor 40, etc. may be connected as shown in Fig. 5, or if the transistor is a PNP type 31'', they are connected as shown in Fig. 6, but in either case, the basic The effect remains the same.

〔Effect of the invention〕

According to the present invention, when the fuel pressure is adjusted, it is possible to eliminate the loss of power caused by pressurizing the fuel that should be bypassed, thereby realizing a highly efficient fuel supply system and improving fuel efficiency. be done.

In addition, the fuel supply pump normally operates at a relatively low rotational speed (or vibration frequency), except when the engine is operated under high load.
This reduces the noise and vibrations generated by the pump operation, increasing the comfort of the vehicle.

In addition, the circuit opening relays and pump relays used in conventional bypass-type fuel pressure regulators, equipment related to the human output signals necessary to drive them, pressure regulators, and water temperature controls that control fuel pressure during high-temperature starts. Switches, vacuum switching valves, and equipment related to input/output signals necessary for driving them may also be omitted, making it possible to simplify the system and reduce costs.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the overall configuration of an embodiment of the present invention, Fig. 2 is a sectional view showing one embodiment of a differential pressure detector, and Fig. 3 is a conceptual diagram showing another embodiment of the differential pressure detector. , FIG. 4 is a schematic diagram of an electric circuit, and FIGS. 5 and 6 are circuit diagrams showing modifications of FIG. 4. DESCRIPTION OF SYMBOLS 1... Engine cylinder head, 2... Intake boat, 3... Intake manifold, 7... Fuel injection valve, 10... Pressure regulator, 12... Fuel tank, 13... Fuel Supply pump, 17... Differential pressure detector, 19... Delivery vibe, 20... Diaphragm, 25... Strain gauge, 27... Error amplifier, 29... Reference pressure difference setting device, 31 ... switching element, 32.
...Power line, 33.34...Metallic diaphragm, 35...Capacitive sensing element, 40...
Drive motor, 41...transistor.

Claims (1)

[Claims] a fuel supply pump that pressurizes fuel and supplies it to the fuel injection valve; a differential pressure detector that detects a differential pressure between the pressure of the fuel supplied to the fuel injection valve and the pressure of intake air; and the fuel supply pump. a switching element inserted into a power supply line that drives the fuel; and means for controlling the switching element intermittently so that the differential pressure detected by the differential pressure detector becomes a predetermined value. Fuel supply system for injection type engines.