JP2764515B2 - Fuel supply device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel supply device for an internal combustion engine, and more particularly, to a technique for ensuring the accuracy of an injection amount at the time of the switching in a fuel supply device that switches between two pressure regulators.

[0002]

2. Description of the Related Art Conventionally, as a fuel supply device for an internal combustion engine, the pressure of fuel supplied to a fuel injection valve is adjusted, and the fuel injection valve is opened and controlled for a time corresponding to a required fuel amount. There is known a configuration in which required fuel is injected and supplied to an engine. In such a fuel supply device, if the pressure difference between the supply pressure of the fuel to the fuel injection valve and the intake pressure near the injection hole of the fuel injection valve is not constant, the constant fuel corresponding to the valve opening time of the injection valve is generated. It cannot be supplied. Then, the suction negative pressure on the downstream side of the throttle valve is led to the reference pressure chamber of the pressure regulator for adjusting the fuel supply pressure to the fuel injection valve, and when the differential pressure between the suction negative pressure and the fuel pressure becomes a predetermined value or more, A return passage for returning fuel to the fuel tank is opened to keep the pressure difference constant (see Japanese Patent Application Laid-Open No. Sho 60-212634).

[0003]

However, in the above-described fuel supply device, it is necessary to maintain the fuel pressure even when the required fuel amount is rapidly increased. Therefore, the fuel is discharged from the fuel pump more than the required amount. The excess supplied fuel is returned from the pressure regulator as excess fuel from the return passage into the fuel tank.

Here, the pressure regulator is
Since the fuel is generally arranged near the engine, the surplus fuel returned from the pressure regulator into the fuel tank is fuel that has been heated by the heat of the engine and has become hot, and the surplus fuel is stored in the fuel tank. Reverting the temperature increases the temperature of the fuel in the fuel tank, and causes the generation of fuel vapor in the fuel tank.

Therefore, the pressure regulator is disposed near a fuel pump (fuel tank) to return excess fuel to the fuel tank before the fuel is warmed by the engine.
Further, in such a configuration, the fuel vapor accumulated in the fuel supply passage near the injection valve cannot be expelled at the time of starting. The pressure regulator is operated, and the fuel pressure is normally adjusted by the pressure regulator on the upstream side.

However, in a system in which two pressure regulators are switched as described above, a delay in the initial response of the pressure regulator causes disturbance in the fuel pressure supplied to the fuel injection valve at the time of switching, and injection is performed at this time. However, there is a problem that an error occurs in the fuel injection amount (see FIG. 5). The present invention has been made in view of the above problems, and in a fuel supply device that uses two pressure regulators by switching between them, even if fuel pressure is disturbed when switching between the pressure regulators, it is possible to prevent the accuracy of the injection amount from deteriorating. The purpose is to be able to.

[0007]

Therefore, a fuel supply device for an internal combustion engine according to the present invention is configured as shown in FIG. In FIG. 1, the pressure regulator returns fuel to the fuel tank when the pressure difference between the pressure of the fuel pumped from the fuel tank through the fuel supply passage by the fuel pump and the reference pressure is equal to or higher than a predetermined value. The pressure difference is adjusted to be constant by opening a passage, and the fuel adjusted to a predetermined pressure by the pressure regulator is
In this configuration, fuel is supplied to the engine by a fuel injection valve that is intermittently controlled to open.

Here, in the present invention, the pressure regulator is disposed on the downstream side and the upstream side of the fuel supply passage, respectively. Then, the switching means includes the aforementioned 2
One of the two pressure regulators is selectively operated. Further, the switching condition detecting means detects the switching condition of the two pressure regulators, and the switching control means synchronizes with the injection end timing of the fuel injection valve after the switching condition is detected by the switching condition detecting means. And controlling the switching means to switch the pressure regulator.

[0009]

According to this structure, two pressure regulators are provided on the upstream side and the downstream side of the fuel supply passage, respectively, and one of these pressure regulators is selectively operated according to a switching condition. Although the two pressure regulators are switched and used, the pressure regulators are not switched immediately even when the switching condition is detected, but in synchronization with the injection end timing of the fuel injection valve after the switching condition is detected. The switching is actually executed.

That is, if the switching is performed during the injection, and if the fuel pressure is disturbed by the switching, this will lead to an error in the injection amount, so that even if the fuel pressure is disturbed, the injection period is not affected. In order to prevent the pressure regulator from being switched, the pressure regulator is switched after the injection is completed after the switching condition is detected, so that the fuel pressure disturbance accompanying the switching occurs during the injection interval. did.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. In FIG. 2 showing a system configuration of one embodiment,
Air is drawn into the internal combustion engine 1 from the air cleaner 2 via the intake duct 3, the throttle chamber 4, the intake collector 5 and the intake manifold 6.

A fuel injection valve 7 is provided in each branch of the intake manifold 6 for each cylinder. The fuel injection valve 7 is an electromagnetic fuel injection valve that is energized to open when the solenoid is energized, closed when energized, and intermittently according to the pulse width of an injection pulse signal sent from the control unit 21 described later. The fuel is adjusted to a predetermined pressure and injected to each branch of the intake manifold 6.

The fuel injection valve 7 does not need to be provided for each cylinder, but may be provided with only one fuel injection valve 7 common to each cylinder. The control unit 21 includes a microcomputer including a CPU, a ROM, a RAM, an A / D converter, and an input / output interface, receives input signals from various sensors, and based on the input signals, will be described later. Calculates the pulse width Ti (valve opening control time of the fuel injection valve 7) of the injection pulse signal, and outputs the injection pulse signal of the pulse width i to the fuel injection valve 7 at a predetermined timing, so that the engine 1 Electronic control of the fuel supply of the vehicle.

The various sensors include an intake duct 3
Air flow meter 18 that measures the volume flow of intake air inside
And outputs a signal corresponding to the intake air flow rate Q of the engine 1. A crank angle sensor 19 is provided on the crankshaft or on a shaft (for example, a camshaft) that rotates in synchronization with the crankshaft.
And outputs a reference angle signal REF for each reference crank angle position and a unit angle signal POS for each unit crank angle. Here, the engine rotation speed Ne can be calculated by measuring the cycle of the reference angle signal REF or the number of occurrences of the unit angle signal POS within a predetermined time.

Further, a water temperature sensor 20 for detecting a cooling water temperature Tw of the water jacket of the engine 1 is provided.
Here, the control unit 21 calculates the basic injection pulse width Tp based on the intake air flow rate Q and the engine rotation speed Ne, and calculates various correction coefficients COEF based on the engine operating state such as the cooling water temperature Tw. Then, the basic injection pulse width Tp is corrected by the various correction coefficients COEF to calculate an effective injection pulse width Te (← Tp × COEF). Further, a voltage correction Ts for correcting a change in the effective valve opening time of the fuel injection valve 7 due to a change in the power supply voltage is set according to the power supply voltage, and the voltage correction Ts is added to the effective injection pulse width Te. And the final injection pulse width Ti (←
Te + Ts) is set.

Next, an injection pulse signal having the injection pulse width Ti is output to the fuel injection valve 7 at a predetermined timing, and the fuel corresponding to the effective injection pulse width Te is injected and supplied from the fuel injection valve 7 to obtain a predetermined air-fuel ratio. To form an air-fuel mixture.
The fuel injected from the fuel injection valve 7 is supplied to the fuel tank 8.
Is stored within. And in this fuel tank 8,
A fuel pump 9 is provided therein, and fuel sucked and pumped by the fuel pump 9 passes through a fuel supply pipe 13 (fuel supply passage) in which two pressure regulators 10 and 11 and a fuel filter 12 are interposed. The fuel is distributed and supplied to each fuel injection valve 7.

The upstream pressure regulator 10
Is disposed near the fuel tank 8, and a negative pressure of the engine 1 is introduced into the reference pressure chamber from the intake collector 5 through the pressure introducing pipe 14 through the pressure introducing pipe 14. When the pressure difference from the negative pressure (reference pressure) becomes equal to or greater than a predetermined value, the fuel pressure is adjusted so that the pressure difference is constant by opening the return passage 15a and returning the fuel to the fuel tank 8. If the differential pressure is kept constant, the amount of fuel injected and supplied with respect to the valve opening time of the fuel injection valve 7 has a linear characteristic, so that the injection amount can be controlled as the valve opening time.

The fuel that has passed through the upstream pressure regulator 10 is filtered by a fuel filter 12 and then introduced into a downstream pressure regulator 11 disposed relatively close to the engine 1. The pressure regulator 11 on the downstream side also opens and closes the return passage 15b according to the differential pressure between the suction negative pressure of the engine 1 introduced through the pressure introducing pipe 14 and the fuel pressure, similarly to the pressure regulator 10. And a fuel pressure adjusting function for keeping the differential pressure constant.

In the return passage 15a of the pressure regulator 10 on the upstream side, an electromagnetic on-off valve 16 controlled to be opened and closed by the control unit 21 is interposed. When the solenoid on-off valve 16 is closed, fuel cannot be returned to the tank via the return passage 15a, so that the pressure regulator 10 loses the function of adjusting the fuel pressure, and the fuel pressure is adjusted by the pressure regulator 11 on the downstream side. You will be On the other hand, when the electromagnetic on-off valve 16 is opened, the fuel pressure is adjusted by the upstream-side pressure regulator 10, so that the downstream-side pressure regulator 11 substantially loses its function, and the downstream-side pressure regulator
Return fuel returned to the tank from 11 will be almost zero.

As described above, one of the two pressure regulators 10 and 11 can be selectively operated by opening and closing the electromagnetic on-off valve 16, and the electromagnetic on-off valve 16 is used in this embodiment. It corresponds to the switching means in the example. By the way, since the pressure regulator 11 on the downstream side is provided at a position close to the engine 1, the return fuel returned from the pressure regulator 11 is the high temperature fuel heated by the engine, and the high temperature return fuel is stored in the tank. Causes fuel vapor to occur. For this reason, control unit 21
Normally, the pressure regulator 10 on the upstream side is caused to function by opening the electromagnetic on-off valve 16, and control is performed such that excess fuel is returned to the tank before the fuel is warmed by the engine.

On the other hand, at the time of starting, there is a possibility that fuel vapor is accumulated in the fuel supply pipe 13 near the fuel injection valve 7, and such fuel vapor deteriorates the accuracy of the injected fuel amount. Need to be kicked out. Therefore, the control unit 21 closes the electromagnetic on-off valve 16 at the time of starting and causes the pressure regulator 11 on the downstream side to adjust the fuel pressure so that the fuel supply pipe near the fuel injection valve 7 is opened.
The fuel is circulated in the tank 13 so that the fuel vapor is returned to the tank together with the surplus fuel.

Here, according to the flow chart shown in FIG. 3, the control unit 21 controls the opening and closing of the solenoid on-off valve 16, that is, the two pressure regulators 10, 11
Will be described in detail. In this embodiment, the function as the switching control means is as shown in FIG.
Control unit as shown in the flowchart
21 is provided as software.

In the flowchart of FIG. 3, first, in step 1 (S1 in the figure, the same applies hereinafter),
It is determined whether or not it is immediately after the start switch 17 has been switched ON / OFF. If it is immediately after the switching has been performed, the process proceeds to step 2, and after the start switch 17 has been switched ON / OFF, has the first injection (including the injection being performed at the time of switching) been performed? It is determined whether or not.

If it is determined that the first fuel injection has been performed, the process proceeds to step 3, where it is determined whether or not the first fuel injection has just been completed. If it is immediately after the end of the first injection, the process proceeds to step 4, where ON / OFF of the start switch 17 is determined. If the start switch 17 is determined to be ON and the engine is starting,
Proceeding to step 5, the solenoid on-off valve 16 is closed, and the pressure regulator 11 on the downstream side is operated to adjust the fuel pressure. On the other hand, if it is determined that the start switch 17 is OFF, the routine proceeds to step 6, where the electromagnetic on-off valve 16 is opened, and the pressure regulator 10 on the upstream side is operated to adjust the fuel pressure. Therefore, the start switch 17 corresponds to the switching condition detecting means in this embodiment.

In the control shown in the flowchart of FIG. 3, basically, a condition during which the pressure regulator 11 on the downstream side is operated during start-up when the start switch 17 is ON is set, and when the start switch 17 is switched from ON to OFF. Although the pressure regulator 10 on the upstream side is made to function, the pressure regulator is not switched in synchronization with the ON / OFF switching of the start switch 17, but after the ON / OFF switching is performed,
The actual switching is executed after the first injection end timing (see FIG. 4).

That is, when the pressure regulators 10 and 11 are switched (open / close switching of the electromagnetic on / off valve 16), the fuel pressure is disturbed due to a delay in response of the pressure regulators 10 and 11, and injection is performed at this time. This causes an error in the injection amount. Therefore, the switching is executed in synchronization with the injection end timing so that the disturbance of the fuel pressure generated due to the switching control of the pressure regulator does not occur during the injection. If the switching of the pressure regulator is executed in synchronization with the injection end timing, the disturbance of the fuel pressure does not occur during the injection interval and does not adversely affect the injection.

In the present embodiment, the ON state of the start switch 17 is set as a condition (switching condition) for using the downstream pressure regulator 11, but the condition for selectively using the two pressure regulators is not limited. Further, the configuration for making the two pressure regulators selectively function is not limited to the electromagnetic on-off valve 16 interposed in the return passage 15a.

[0028]

As described above, according to the present invention, in a configuration in which pressure regulators are disposed on the upstream side and the downstream side of the fuel supply passage, respectively, and these two pressure regulators are switched based on predetermined conditions, Even if the fuel pressure is disturbed at the time of the switching, it is possible to avoid that the accuracy of the injection amount is deteriorated due to the disturbance of the fuel pressure,
There is an effect that the accuracy of fuel injection can be improved.

[Brief description of the drawings]

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

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

FIG. 3 is a flowchart showing switching control of a pressure regulator in the embodiment.

FIG. 4 is a time chart showing switching characteristics in the embodiment.

FIG. 5 is a time chart for explaining a problem of the conventional switching control.

[Explanation of symbols]

 Reference Signs List 1 engine 7 fuel injection valve 8 fuel tank 9 fuel pump 10, 11 pressure regulator 13 fuel supply pipe 14 pressure introduction pipe 15a, 15b return passage 16 solenoid on-off valve 17 start switch 21 control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Investigated field (Int.Cl. ⁶ , DB name) F02D 41/06 345 F02D 41/02 345 F02M 37/00 F02M 37/20 F02M 69/00 340

Claims (1)

(57) [Claims] A return passage for returning fuel to the fuel tank when a pressure difference between a reference pressure and a pressure of the fuel pumped from the fuel tank via the fuel supply passage by the fuel pump is equal to or higher than a predetermined value. A pressure regulator that regulates the differential pressure to be constant, and supplies fuel, which is adjusted to a predetermined pressure by the pressure regulator, to the engine by a fuel injection valve that is intermittently opened and controlled. A fuel supply device, wherein the pressure regulator is disposed on each of a downstream side and an upstream side of the fuel supply passage, and a switching unit for selectively operating one of the two pressure regulators; Switching condition detecting means for detecting a switching condition of the pressure regulator, and switching by the switching condition detecting means. Switching control means for controlling the switching means in synchronization with the injection end timing of the fuel injection valve after a switching condition is detected to switch the pressure regulator. For supplying fuel to an internal combustion engine.