JPH0718386B2 - Liquefied gas control method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a liquefied gas control method in a system for injecting liquefied gas into an intake passage to supply it to an engine, and is mainly used in a fuel supply system of an automobile engine. To be done.

2. Description of the Related Art As is well known from Japanese Patent Publication No. 53-44613, a system for supplying a liquid fuel such as gasoline to a spark ignition engine of an automobile by an injection system is well known in the Japanese Patent Publication No. 53-44613. It is designed to inject the fuel whose pressure has been adjusted to the intake passage from the injection valve, and has a supply pipeline from the fuel tank to the injection valve via the fuel pump and a return pipeline to the fuel tank via the pressure regulator. There is.

On the other hand, it has been proposed to inject a liquefied gas fuel such as LPG into the intake passage by utilizing the pressure of the fuel itself (Japanese Patent Laid-Open Nos. 59-82556 and 59-108855). At a pressure around the inside of the container, when it is thermally affected, it easily evaporates and the pressure changes drastically, which is a serious practical problem.

Therefore, it is conceivable that the same system as the liquid fuel supply system is used to further pressurize the liquefied gas with a pump and supply it to the intake passage. Can be expected. By the way, in the case of liquefied gas, since the fuel in the fuel tank is already at a considerably high pressure, open / close valves are provided in the supply line and the return line, and these open / close valves are closed when the engine is stopped to save the fuel. It is necessary to consider to prevent leakage. However,
In such a configuration, when the opening / closing operation of the on-off valve and the start / stop of the fuel pump are performed simultaneously, particularly when the opening / closing of the on-off valve and the activation of the fuel pump are simultaneously performed, the opening / closing valve between the two on-off valves of the fuel supply system is When the fuel is charged at a high pressure in 1, the pressure drops to the same pressure as in the fuel tank at the same time when the valve is opened, so bubbles are generated and it becomes difficult to raise the pressure to a predetermined pressure by the fuel pump. Also, when the fuel enclosed between the two on-off valves of the fuel supply system has the same pressure as in the fuel tank, no bubbles are generated when the valve is opened, but it is possible to increase the pressure to a predetermined level by the fuel pump. It takes a long time, and in any case, it takes a considerable time to accurately inject the required amount of fuel, and proper fuel control at the time of engine start cannot be performed.

The present invention solves the above-mentioned problems of the fuel supply system that uses liquefied gas, and keeps the fuel supply system, especially the vicinity of the injection valve, at a high pressure while the engine is stopped and keeps almost the same level. An object is to provide a liquefied gas control method that can be started in a state.

The liquefied gas control method according to the present invention is provided with an on-off valve in each of a supply line from a fuel tank to a fuel pump to an injection valve and a return line to a fuel tank via a pressure regulator. At the time of stop, the on-off valve of the supply line is closed and the fuel pump is stopped after the on-off valve of the return line is closed, and when the engine is started, the on-off valve of the supply line is opened and the fuel pump is stopped. The opening and closing valve of the return pipe is opened after the activation of the above.

Embodiment An embodiment of the present invention will be described with reference to the drawings. In FIG. 1, an on-off valve 3, a filter 4, a supply valve 2 extending from a fuel tank 1 made of a pressure-resistant container to an injection valve 8 opened to an intake passage 12 and a filter 4, Two fuel pumps 5, 6 and an on-off valve 7 are provided in order, and a pressure regulator 10 and an on-off valve 11 are provided in order on a return line 9 extending from the injection valve 8 to the fuel tank 1.

Each of the three on-off valves 3, 7, 11 is an electromagnetic valve that is opened and closed by an electromagnetic force, and is driven by a drive signal sent from the electronic control unit 13 together with the fuel pumps 5 and 6. The on-off valve 3 provided close to the fuel tank 1 of the supply pipe 2 is for safety as is generally provided in a system handling liquefied gas. Further, in the present embodiment, two fuel pumps 5 and 6 are provided so that when the liquefied gas flowing out from the fuel tank 1 is temporarily reduced in pressure at the pump inlet to generate bubbles, the liquefied gas is directly sent to the injection valve 8. This is to eliminate the inconvenience of changing the injection amount. That is, even if bubbles are generated at the inlet of the first-stage fuel pump 5, the bubbles are reduced or eliminated by the pressurizing action in the pump. Even if the pressure is lowered by feeding the liquefied gas at a higher pressure than that, new bubbles are not generated, and the bubbles are completely extinguished by the pressurizing action in the pump, and the liquefied gas in the liquid phase is sent to the injection valve 8. .

Further, the pressure regulator 10 has a well-known structure including a fuel chamber 16 and a diaphragm chamber 17 which are partitioned by a diaphragm 15 having a valve 14 in the center thereof, but a spring 18 biased toward the valve 14 is closed. The diaphragm chamber in which the
Unlike the intake manifold for liquid fuel, 17 is connected to the gas phase portion of the fuel tank 1 by a conduit 19. Therefore, the fuel pressure of the injection valve 8 is adjusted according to the pressure difference between the inlet pressure of the fuel pump 5 and the outlet pressure of the fuel pump 6.

In this embodiment having such a configuration, all three open / close valves 3, 7, 11 are open and the fuel pumps 5, 6 are driven during engine operation. When the engine is stopped, the injection valve 8 first stops the injection of fuel according to a command from the control unit 13, and at the same time or with a slight delay, the on-off valve 11 of the return line 9 is closed. 6
There is a high pressure between the valve and the on-off valve 11. Next, after issuing a closing command to the on-off valve 11, a predetermined time has elapsed, the on-off valves 3,7 of the supply pipeline 2
Is closed and the fuel pumps 5 and 6 are stopped, but these commands are issued at the same time or after issuing the closing command of the opening / closing valve 7 and the closing command of another opening / closing valve 3 and the fuel pump. Issue 5 and 6 stop commands. As a result, while the engine is stopped, the high-pressure fuel is maintained in the part including the injection valve 8 and the pressure regulator 10 between the on-off valve 3 or 7 and the on-off valve 11.

When the engine is started, the opening / closing valves 3 and 7 of the supply line 2 are first opened and the fuel pumps 5 and 6 are started by a command from the control unit 13. These commands may be issued at the same time, or may be issued in the order of the opening command of the opening / closing valve 3, the starting command of the fuel pumps 5 and 6, and the opening command of the opening / closing valve 7.
Next, after issuing these commands and opening and closing the on-off valve 11 of the return line 9 after a lapse of a predetermined time, the fuel pressure drops when the on-off valves 3 and 7 of the supply line 2 are opened. Open / close valve 1
Since the fuel pumps 5 and 6 are operated with the valve 1 closed, the pressure drop around the injection valve 8 is slight and there is no concern about the formation of bubbles, and the opening / closing valve 11 is opened after the pressure is restored. As a result, the time required for pressure recovery can be shortened. The injection valve 8 starts fuel injection at the same time when the fuel pumps 5 and 6 are started or after this, but after a certain period of time elapses, the pressure drop due to the opening of the on-off valves 3 and 7 and the abnormal pressure rise due to the closing of the on-off valve 11. The pressure sensor 20 is installed near the injection valve 8 in consideration of the case where
The injection time is corrected until the pressure adjustment by 10 is normalized.

FIG. 2 is a diagram for explaining an example of the timing of opening / closing the on-off valves 3, 7, 11 and starting / stopping the fuel pump.
The opening / closing valve 11 is closed first when the engine is stopped and the valve is closed last when the engine is started, and the opening / closing of the opening / closing valves 3, 7 and the start / stop of the fuel pumps 5, 6 are arbitrary.

Effects of the Invention According to the present invention, the timing of opening / closing the on-off valve provided in the supply line and the timing of starting / stopping the fuel pump and opening / closing the on-off valve provided in the return line is controlled so that the return line is opened / closed when the engine is stopped. Since the valve is closed first and the opening / closing valve of the return line is opened lastly when the engine is started, the fuel between the two opening / closing valves is stopped when the engine is stopped. Is maintained in a high pressure state, and bubbles are less likely to be generated even when heated by engine heat. Moreover, even if a pressure drop occurs at the time of engine starting, it immediately recovers to a predetermined pressure in a short time to accurately supply the required amount of fuel. It becomes possible to inject, and fuel control at the time of engine start can be performed properly.

[Brief description of drawings]

FIG. 1 is a layout diagram showing an embodiment of the present invention, and FIG. 2 is a diagram for explaining the timings of opening / closing the on-off valve and starting / stopping the fuel pump. 1 …… Fuel tank, 2 …… Supply pipeline, 5,6 …… Fuel pump,
7, 11 …… Open / close valve, 8 …… Injection valve, 9 …… Return line, 10 …… Pressure regulator, 13 …… Control unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tomio Dobashi 5-12 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside the Nippon Gasifier Co., Ltd. (72) Inventor Masaaki Fujisaki 5-1-1 Kita-Shinagawa, Shinagawa-ku, Tokyo No. 12 NIPPON carburetor factory (56) References

Claims (1)

[Claims] 1. An on-off valve for a return pipe when an engine is stopped, each of which is provided with an on-off valve in a supply line from a fuel tank to a fuel pump to an injection valve and a return line to a fuel tank via a pressure regulator. After closing the valve, the on-off valve of the supply line is closed and the fuel pump is stopped. When the engine is started, the on-off valve of the supply line is opened and the fuel pump is started, and then the return line is closed. A method for controlling a liquefied gas, characterized in that the on-off valve of the above is opened.