JPS588265A - Improving method of startability of internal-combustion engine equipped with low pressure fuel injection device and low pressure fuel injection device used for practice of said method - Google Patents

Abstract

PURPOSE:To improve starting quality of an engine, by operating a fuel pump for a prescribed time even after the engine is stopped, increasing residual pressure of fuel in a fuel passage and suppressing generation of a vapor lock and reduction of the residual pressure in a fuel injection device. CONSTITUTION:A fuel shutoff valve 22, having a work delay timer circuit 24, is provided in a fuel return passage 16, while a fuel pump stop delay timer circuit 23 is provided to a fuel pump 4. If an ignition swtich is turned OFF, the fuel shutoff valve 22 is turned OFF, through the return passage 16 is shut off to stop an engine, the fuel pump 4 is continuously operated by the delay timer circuit 23 for a prescribed time T1, and pressure of fuel in a fuel passage 8 can be held by the action of a check valve 6. While if the ignition switch is turned ON, the fuel shutoff valve 22 is opened with the lapse of a prescribed time T2 by the work delay timer 24. In this way, generation of a vapor lock at high temperature time and reduction of residual pressure at low temperature time of a fuel injection device can be suppressed to improve starting quality of the engine.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a technology for supplying fuel to an internal combustion engine, and more particularly, to a method for improving the startability of an internal combustion engine equipped with a low-pressure fuel injection device, and a method for implementing the method. The present invention relates to a low pressure fuel injection device used.

Low pressure fuel injection devices for internal combustion engines are known.

This fuel injection device includes a fuel tank, a fuel pump for pressure-feeding fuel in the fuel tank, a low-pressure fuel injection valve installed in the intake system of an internal combustion engine, and a fuel pump and low-pressure fuel injection valve. It is equipped with a fuel supply path connecting the fuel supply path, nine check valves inserted in the fuel supply path, a fuel return path connecting the low pressure fuel injection valve and the fuel tank, and a pressure control valve inserted in the fuel return path. The pressure control valve controls the fuel pressure to a predetermined pressure, for example 1
Noodles/evs2? (By allowing the fuel to pass only when the pressure exceeds the limit and returning the fuel to the fuel tank via the fuel return path r, it is possible to maintain the fuel at a predetermined pressure between the pressure control valve and the check valve.) It has become.

The fuel maintained at a predetermined pressure in this manner is injected into the intake system by opening and opening the low pressure fuel injection valve in response to an electric signal. This fuel injection valve has a normal fuel injection valve of about 2.
It is designed to operate preferably at a pressure of approximately I Kg/6II2, as opposed to operating at pressures of 5'14/cm and above, and is therefore referred to as a low-pressure fuel injector. The reason for using such a fuel injection device that operates at a relatively low pressure is that it becomes possible to use a lower cost fuel pump.

However, in the so-called low-pressure fuel injection system as described above, the fuel pressure at the next start after the engine is stopped is the residual pressure between the check valve and the pressure control valve when the engine is stopped. This residual pressure depends on the set pressure of the pressure control valve, so the residual pressure of a normal fuel injection device is approximately 2.5 Kg/ctyt.
2, whereas in a low-pressure fuel injection system, it is extremely small at about I Kg / 5w2.

As a result, the fuel passage between the check valve and the pressure control valve is blocked and the boiling point of the hole fuel is lowered, resulting in a vapor lock in which the fuel vaporizes significantly when the engine is at high temperatures. The residual pressure further decreases due to volumetric contraction.As a result, a considerable amount of time is required for the next start-up.

An object of the present invention is to improve engine startability in a low-pressure fuel injection system by suppressing the occurrence of vapor lock when the engine is at high temperature and the decrease in residual pressure when the engine is at low temperature.

The above object is achieved by the method of the present invention, which is performed in a large internal combustion engine fully equipped with the low-pressure fuel injection system described above, by installing a fuel quick-cut valve in the fuel return path and turning on the engine's power switch. The fuel return path T- is cut off when rfJ is reached, and the fuel pump continues to operate for a predetermined period of time even after the engine is stopped. With this means, when the engine is stopped, a predetermined amount of fuel is further fed under pressure between the check valve and the fuel cutoff valve, so that fuel having a pressure higher than the set pressure of the pressure control valve is accumulated and held.

In order to prevent the pressure in the passageway from disappearing, it is desirable to open the fuel cutoff valve after a predetermined period of time has passed after the ignition switch is turned on.

The present invention also provides l! of the above method! This device provides a low-pressure fuel injection device Rk that can be used directly in the above-mentioned type of low-pressure fuel injection device. In addition, the fuel pump is equipped with a fuel pump stop delay timer so that when the ignition switch is turned off, the fuel pump stops operating for a predetermined period of time. The main point is to make it possible to stop the system.

Preferably, the fuel cutoff valve is provided with a fuel cutoff valve activation delay timer so that the fuel cutoff valve opens after a predetermined period of time when the Ig=y switch is turned on during a lateral start motion. In this way, it is possible to avoid the situation where the furnace fuel pressure valve opens immediately when the ignition switch is put into storage and the fuel pressure in the fuel passage disappears.

Are there fuel cutoff valves and pressure control valves in the fuel return path? A bypass may be provided, and this bypass may be provided with a second pressure control valve set at a higher pressure than the set pressure of the pressure control valve. With this arrangement, if the fuel pressure in the fuel passage exceeds the set pressure of the second pressure control valve when the fuel cutoff valve closes when the engine stops and the fuel pump continues to operate for a predetermined period of time, the fuel Since the fuel passes through the second pressure control valve and is discharged into the fuel return path, fuel is always maintained in the fuel passage at the pressure set by the second pressure control valve.

Hereinafter, the present invention will be described in detail with reference to Appendix 55wt*.

Fig. 2 is a schematic diagram of a low pressure fuel injection device, and this device includes a fuel tank 2, a fuel pump 1, a check valve 6, a fuel supply path 8,
Low pressure fuel injection valve 12 attached to throttle body 10
, pressure control valve 14. It consists of a fuel return path 16. The throttle body 10 has a throttle pulse 7'18 (and is connected to an intake manifold 20).The low pressure fuel injection valve 12 and the pressure control valve 14 are known ones, and the details are shown enlarged in FIG. This pressure control valve 1j
is set at a pressure of approximately 1Kf//1W, for example, so this pressure control valve 14 is closed during engine operation and after stopping.
The above pressure is maintained in the fuel supply passage 8 between the check valve 6 and the fuel injection valve 12 communicating therewith.

In accordance with the method of the invention, a fuel shutoff valve 2 is installed in the fuel return path 16.
As shown in the control flowchart of FIG. 2(a), when the ignition switch i is turned from ON to OFF, the fuel cutoff valve 22 is switched from PON to OFF. If the operation of the fuel pump 4 is continued for a predetermined time T, the fuel pressure in the fuel passage (shown by a thick line in FIG. 1) between the fuel cutoff valve 22 and the check valve 6 increases. The operating time of the fuel pump is approximately 2.5 kips of fuel pressure.
/cm2, and this time varies depending on the discharge flow rate of the fuel pump, but is generally about 0.5~cm2.
It can be set to 1 second. Due to the action of the check valve 60, the fuel pressure is maintained even after the fuel pump is stopped. In this way, it is possible to suppress the occurrence of vapor lock at high temperatures, and to compensate for the decrease in residual pressure at low temperatures.

11 [& When the ignition switch is turned on during operation, the fuel cutoff valve 22 opens immediately and prevents the fuel pressure from disappearing, thereby making it possible to inject high-pressure fuel vigorously during side start operation. In order to do this, please refer to Figure 2 (
As shown in 6), the fuel cutoff valve r is opened after a predetermined time T2 has elapsed after the ignition switch is turned on.

Next, refer to Figure 3 and below to find out the above method? A low-pressure fuel injection device of the present invention used for carrying out the invention will be explained.

FIG. 3 is a partially enlarged view of FIG. 1, in which the same # wax numbers are used for the same components, and the descriptions already made are omitted. According to the invention, the fuel pump 4 is provided with a fuel pump stop delay timer circuit 23. This timer circuit, as shown in FIG. 4, includes a relay connected in parallel to the ignition V circuit and Ig, and the relay circuit is grounded in parallel with the capacitor C. Just to be sure, when I turn off the ignition switch I, the capacitor C
The relay is energized and its 11Lat- is closed while the 4C stored charge is discharged through the =1L of the relay Ry. In this way, the operation of the fuel pump can be continued for a predetermined period of time after the ignition switch is opened.

In order to open the fuel cutoff valve 22 after a predetermined period of time by turning on the ignition switch when starting the engine, the fuel cutoff valve 22 is equipped with an operation delay timer circuit 24t.
- Provide. Figure 5 shows one example of this activation delay timer circuit.
This shows an example, relay Ry', transistor) Trs
It consists of a resistor a and a capacitor C'. Transistor Tr
The base side of the relay 3. is grounded via the capacitor C', and the left side of the relay 3. / is connected to the coil Kli, and the emitter is grounded. The relay &, t contacts are open at first. When the engine switch I is turned on, the capacitor CI is charged and the pace voltage of the transistor T is increased. When the base voltage reaches the trigger voltage, the flefter and emitter of the transistor become conductive and current from the power source flows through the coil of relay Ry', so that the contacts are attracted and current is supplied to the fuel cutoff valve. Therefore, the operation of the fuel cutoff valve is delayed. - FIG. 6 shows another embodiment of the low-pressure fuel injection device according to the invention, which has basically the same construction as the embodiment described above, and the same reference numerals are used for the same components. Differences from the above embodiment C. The fuel return path 16 includes a bypass 25 that bypasses the fuel cutoff valve 22 and the pressure control valve 14.
A second pressure control valve 26 is provided in this bypass.
is provided, and the arrangement order of the first pressure control valve 1A and the fuel line disconnection IP22 is reversed. This second pressure control valve 26 is set to operate at a higher pressure than the first pressure control valve. At this time, when the ignition switch is opened, the fuel cutoff valve 22
When the valve body 28 closes the inlet boat 30 of the pressure control valve 1j and allows the fuel pump A to continue operating for a while,
The fuel is maintained at a pressure equal to the set pressure of the second pressure control valve 26. The operating pressure of this second pressure control valve can be set to a pressure sufficient to completely suppress vapor lock and residual pressure, for example, 2.5 Kf/cm.

Providing such a second pressure control valve can prevent the fuel pump from overrunning for a longer period than necessary after the engine has stopped, or when the opening of the fuel cutoff valve is unnecessarily delayed when starting the engine. Since the fuel pressure is maintained at a predetermined pressure,
This has the effect of not causing damage to the piping. In addition,
In the embodiment of FIG. 6, the fuel cutoff valve 22 is connected to the pressure control valve 140 inlet boat. Even if the closing valve 9 is provided downstream of the pressure control valve 1j, for example at the position indicated by the arrow 52, the effect is the same.

As described above, the present invention increases the residual pressure of fuel in the fuel passage by operating the fuel pump for a predetermined period of time even after the engine has stopped, thereby preventing the occurrence of vapor lock and the like when the low-pressure fuel injection device is at high temperature. It is possible to suppress the reduction in residual pressure at low temperatures, shorten the starting time of the engine, and improve startability.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram of the low pressure fuel injection device of the present invention, Fig. 2 is a control flowchart, Fig. 3 is an enlarged view of a part of IrL Fig. 1, Fig. 4 is a diagram of the fuel pump stop delay timer circuit, Fig. 5 is a diagram of the fuel cutoff valve activation delay timer circuit, and Fig. g6 is an enlarged view of a part of another embodiment. 2...Fuel tank, 4 mm*・Fuel pump, 6・
... Check valve, 8. ... Fuel supply path, 10.
・Φ・Throttle bottom 1 12...Low pressure fuel injection valve, 14・■ Feeding pressure control valve, 16...Fuel return path, 22
0...Fuel cutoff valve, 2s;...Fuel pump stop delay timer circuit, 24...
...Fuel connection valve operation delay timer circuit, 2511@@
@Bypass, 26...Second pressure control valve. Patent applicant Toyota Motor Corporation Patent agent Akira Aoki Patent attorney Kazuyuki Nishidate Patent attorney Yoshi 1) Masayuki Patent attorney Akira Yamaguchi 1st m Figure 2

Claims (1)

[Claims] 1. A fuel tank, a fuel pump for pressure-feeding fuel in the fuel tank, a low-pressure fuel injection valve installed in the intake system of an internal combustion engine, and the fuel pump and low-pressure fuel. A fuel supply path connecting the injection valves, a check valve inserted in the fuel supply path, a fuel return path connecting the low pressure fuel injection valve and the fuel tank, and a pressure control inserted in the fuel return path. Startability of an internal combustion engine equipped with a low-pressure fuel injection device comprising a pressure control valve and a pressure control valve for holding fuel at a normal operating pressure between the pressure control valve and the check valve. [This is a method for improving the fuel return path, in which a fuel cutoff valve is provided in the fuel return path to disconnect the fuel return path when the engine ignition switch is turned off, and the fuel pump is When the switch is turned off, the engine continues to operate for a predetermined period of time and then stops, thereby holding fuel at a pressure t4 higher than the normal operating pressure between the fuel cut-off valve and the check valve when the engine is stopped. A method for improving startability of an internal combustion engine equipped with a low-pressure fuel injection device, characterized in that: 2. Starting an internal combustion engine equipped with a low-pressure fuel injection device according to claim 1, wherein the fuel cutoff valve is opened after a predetermined time has elapsed when an ignition switch is turned on during a side start operation. How to improve sex. (v) A fuel tank, a fuel pump for pressure-feeding the fuel in the fuel tank, a low-pressure fuel injection valve installed in the intake system of an internal combustion engine, and a fuel supply connecting the fuel pump and the low-pressure fuel injection valve. a check valve inserted in the scissors fuel supply path, a fuel return path connecting the low pressure fuel injection valve and the fuel tank, and a pressure control valve inserted in the fuel return path to control the pressure. In a low-pressure fuel injection system consisting of a pressure control valve for maintaining fuel at a normal operating pressure between a control valve and a reversal valve, the fuel return path includes an engine ignition switch. A fuel quick-cut valve that opens and closes according to the opening and opening is installed so that the fuel return path can be cut off when the ignition switch is turned off.The above fuel pump is also equipped with a fuel pump stop delay tie! A means is provided so that when the ignition switch is turned off, the fuel pump continues to operate for a predetermined time and then stops;
This low-pressure fuel injection system is designed to maintain fuel at a pressure higher than the normal operating pressure between the fuel cut-off valve and the check valve when the engine is stopped. 46 The above-mentioned school fee freshening valve is equipped with a fuel cutoff valve activation delay timer, so that when the engine is started,
Claim 5*, characterized in that the cough fuel cutoff valve can be opened after a predetermined period of time when the switch is turned on.
Low pressure fuel injector as described. The fuel return path is provided with a bypass that bypasses the bulk fuel backflow valve and the pressure control valve, and the bypass is provided with a second pressure control valve that operates at a second pressure higher than the normal operating pressure. A control valve is provided, so that when the engine is stopped, fuel at the second pressure t set by the second pressure control valve is held between the check valve and the second pressure control valve. The low-pressure fuel injection device according to claim 1, characterized in that -t is selected.