JPH02305354A - Lpg supplier for engine - Google Patents

Abstract

PURPOSE:To avoid any thermal influence on an engine by returning surplus LPG to a cylinder via a pressure regulator in an engine room at the start of an engine so as to exhaust bubbles in a supply pipeline and the like, and after that, returning the surplus LPG to the cylinder via a pressure regulator near the cylinder. CONSTITUTION:Upon turning-on of a key switch, a pressure of LPG in a cylinder 5 is increased by a fuel pump 9, and the LPG is injected from a fuel injection valve 4, which is opened/closed by a drive current of a duty ratio according to an engine operative state, to an air suction pipe 5. The LPG is regulated at a specific value by a second pressure regulator 16 located in an engine room, and further, the surplus LPG is returned to the cylinder 5 via a returning pipeline 15 so that bubbles staying in a supply pipeline 6, the return pipeline 15 and the like can be speedily exhausted to the cylinder 15. Meanwhile, after an elapse of a predetermined time since an engine is operated, the pressure of the LPG is regulated by a first pressure regulator 12 positioned near the cylinder 5, and moreover, the surplus LPG is returned to the cylinder 15 via the return pipeline 11.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a device for supplying LPG to an engine by pressurizing it with a fuel pump and injecting it into an intake pipe from a fuel injection valve, and mainly applies to automobile engines. Used for LPG supply.

(Prior art) As a system for supplying LPG to a spark-ignition automobile engine, instead of LPG in a cylinder being depressurized and gasified in a vaporizer and sucked into the intake air stream in a mixer, the LPG is supplied as fuel in a liquid state without being depressurized and gasified. It has been proposed to inject into the intake air stream with an injection valve.

By the way, regarding an LPG supply device using a fuel injection valve, Japanese Patent Application Laid-open Nos. 59-82556 and 59-108855
As disclosed in the publications of the above issues, if the internal pressure of the cylinder is used as the injection pressure, it will easily gasify when subjected to thermal effects, resulting in extreme pressure fluctuations and extremely inaccurate metering by the fuel injection valve. Therefore, Utility Application No. 60-21997 (Utility Application No. 61-138860), No. 60-17741
As disclosed in each microfilm of No. 7 (Utility Model Application Publication No. 62-87162), Japanese Patent Application Publications No. 63-16160, No. 63-16161, No. 63-16162, and No. 63-18172. One idea is to further pressurize the LPG in the cylinder using a fuel pump to make it less likely to gasify, and then adjust the pressure to a predetermined pressure using a pressure regulator to obtain the injection pressure.

In such a system, excess LPG released from the pressure regulator is returned to the cylinder, but if the fuel injection valve and pressure regulator are installed far apart, air bubbles may form in the supply pipe etc. while the engine is stopped. There is an inconvenience that this buildup disturbs the functions of the fuel pump and pressure regulator, making it impossible to perform accurate injection from the fuel injection valve. Therefore, in automobiles, fuel injection valves and pressure regulators are installed in a narrow engine room, and excess LPG passing through the return passage from the pressure regulator to the fuel pump inlet is heated by the engine heat, causing thermal effects. The temperature of the LPG in the cylinder is higher than that of the LPG in the cylinder installed in the trunk room, where it is difficult to receive heat, and the LPG supply system is completely sealed and the LPG circulates, so when the engine is operated for a long time, the temperature of the LPG in the cylinder gradually decreases. As the temperature rises, the vapor pressure gradually increases, which is dangerous.

As a countermeasure, it has been considered to return excess LPG to the inlet side of the fuel pump instead of returning it to the cylinder, as disclosed in the microfilm of the above-mentioned Utility Model Application No. 1982-21997. LPG is pressurized by a fuel pump, so the pressure is higher than the internal pressure of the cylinder.
As a result, only excess LPG is supplied to the fuel pump and circulated, causing the temperature to rise at an accelerated rate, causing some gasification and increasing bubbles, making it impossible for the fuel pump to pressurize the fuel and reducing the amount injected from the fuel injection valve. This has the disadvantage of decreasing the engine speed and causing the engine to stop.

On the other hand, as disclosed in the microfilm of the above-mentioned Utility Model Application No. 177417, there is an improvement plan of installing a cooling device in the return path of excess LPG from the pressure regulator to the fuel pump inlet side, but the displacement is 2ρ. When tested with a standard automobile engine, the actual cooling capacity was 300 to 50
A cooler of about 0 Kcal/h is required, and the extra LPG required by the engine to operate it cannot be ignored, making it impractical in terms of fuel economy.

(Problems to be Solved by the Invention) The present invention further pressurizes the LPG in the cylinder with a fuel pump, adjusts it to a predetermined pressure with a pressure regulator, injects it into the intake pipe from the fuel injection valve, and returns excess LPG to the cylinder. In the system, when the engine was operated for a long time, the temperature of the LPG inside the cylinder rose, which was dangerous, and there was no countermeasure that could economically prevent the temperature rise without impairing normal fuel injection function. To provide an LPG supply device for an engine, which has been made to solve the above-mentioned problem, and which does not force the excess LPG to be returned to the cylinder to be cooled by a cooling device, does not cause the temperature to rise, and maintains a normal fuel injection function. It is an object.

(Means for solving the problem) Solving the problem of an engine LPG supply device that pressurizes LPG in a cylinder with a fuel pump, adjusts it to a predetermined pressure, injects it from a fuel injection valve, and returns excess LPG to the cylinder. The measures taken by the present invention to achieve this goal are astounding.

That is, a first pressure regulator installed in the vicinity of the cylinder, a second pressure regulator installed in the engine room, and a second pressure regulator that has the two pressure regulators separately and is connected to the cylinder. It includes one return pipe, a second return pipe, and a first on-off valve and a second on-off valve provided in the two return pipes, respectively.

When the engine starts, the first on-off valve closes and the second on-off valve opens, and after a period of time from the start, the first on-off valve opens and the second on-off valve opens. The valve is now closed.

(Function) When the engine starts, the first on-off valve closes and the second on-off valve opens, and the LPG injection pressure is adjusted by the second pressure regulator, and excess LPG is used as fuel. Since the gas is returned to the cylinder from near the injection valve, any air bubbles that may have accumulated in the supply pipe are completely discharged. When the time from start-up has elapsed, the first on-off valve opens and the second on-off valve closes, and the LPG injection pressure is adjusted by the first pressure regulator, and excess LPG is discharged from the cylinder. circulate near.

Therefore, complete liquid LPG without air bubbles is sent to the fuel injection valve, and the excess LPG is not affected by the heat of the engine, so the temperature of the LPG in the cylinder does not rise.

(Example) The present invention will be described in detail with reference to the drawings.

A fuel injection valve 4 is provided downstream of a throttle valve 3 in an intake pipe 2 that includes an intake manifold that distributes air-fuel mixture to each combustion chamber of the engine 1, and is connected to the fuel injection valve 4 from the liquid phase part of a cylinder 5. Filters 7 are sequentially inserted into the supplied supply pipe 6 from the cylinder 5 side.
, an electromagnetic shutoff valve 8, a fuel pump 9, and a fuel reservoir 10 are installed.

A first return pipe 11 is provided which branches from a portion of the supply pipe 6 between the fuel pump 9 and the fuel reservoir 10 and is connected to the gas phase portion of the cylinder 5.

A first pressure regulator 12 and a first electromagnetic on-off valve 13 are installed in this order. This pressure regulator 12 is of the well-known configuration of a diaphragm/valve hole that operates in response to the differential pressure between the outlet pressure and the inlet pressure introduced from the outlet side by a first conduit 14, and is a fuel pump 9. From fuel injection valve 4
The injection pressure of the LPG sent to is adjusted to a predetermined pressure.

Further, a second return pipe 15 connected to the inlet of the fuel injection valve 4 is provided, and a second pressure regulator 16 and a second electromagnetic on-off valve 17 are installed in this order. This pressure regulator 16 also has a well-known configuration of a diaphragm/valve hole that operates according to the differential pressure between the outlet pressure and the inlet pressure introduced from the outlet side by the second conduit 18, and the fuel pump 9
The injection pressure of the LPG sent to the fuel injection valve 4 is adjusted to a predetermined injection pressure, and a small-diameter bypass 19 is provided in parallel with the valve to constantly communicate the inlet side and the outlet side. Further, along the intake pipe 2, an opening sensor 21 of the throttle valve 3 and a pressure sensor 22 of the intake negative pressure are installed, a rotation speed sensor 23 is installed at the distributor of the engine 1, an oxygen sensor 24 is installed along the exhaust pipe 20, and a fuel reservoir is installed. 10, LPG temperature sensor 25
and a pressure sensor 26 are provided, respectively, and electrical signals from these sensors 21...26 are transmitted to a microcomputer including an A/D converter 28, a central processing unit 29, a drive circuit 30, etc. mounted on the automobile. The LP is inputted into the computer 27 and has an appropriate flow rate depending on the operating state of the engine 1.
A drive current with a predetermined duty ratio is sent from the drive circuit 30 to the fuel injection valve 4 so that G is supplied.

In a device having such a configuration, the cutoff valve 8 and the two on-off valves 13 and 17 are closed when the engine 1 is stopped, and when the key switch is turned on, the cutoff valve 8 and the on-off valve 17 are opened at the same time. The fuel pump 9 is driven, and the pressurized liquid LPG flowing out from the cylinder 5 is pumped to the fuel pump 9.
The fuel is further pressurized and injected into the intake pipe 2 from the fuel injection valve 4 which is driven to open and close with a drive current having a duty ratio according to the operating state of the engine 1. LP injected from fuel injection valve 4
G is injected into the intake pipe 2 at an injection pressure adjusted to a predetermined value by the second pressure regulator 16. Further, surplus LPG is returned to the cylinder 5 through the return pipe 15.

When the engine 1 starts operating, the second pressure regulator 16 has a bypass 19, so LPG passes from the inlet side to the outlet side until the set control pressure is reached, and the LPG is supplied. Air bubbles generated and accumulated in the conduit 6, return conduit 15, etc. while the engine is stopped are quickly discharged to the cylinder 5, and pressurization by the fuel pump 9 and pressure adjustment by the pressure regulator 16 are performed smoothly and accurately. When the air bubbles are completely discharged, the LPG is pressurized by the fuel pump 9 to a level higher than its vapor pressure.

After a period of time has elapsed since the key switch was turned on,
As described above, LPG flows through the supply pipe 6 in a completely liquid state, and is metered and injected at the fuel injection valve 4 at a pressure regulated by the second pressure regulator 16. When such a state occurs, that is, when the time has elapsed since the engine 1 started, the microcomputer 27
Alternatively, based on a command from a separately installed timer (not shown), the second on-off valve 17 is closed to close the second return pipe line 15, and the first on-off valve 13 is opened instead. The return conduit 11 is opened. Therefore, from now on, the first pressure regulator 12 will adjust the LPG to a predetermined injection pressure.

Here, the filter 7, the shutoff valve 8, the fuel pump 9, the first return pipe 11, its pressure regulator 12, and the on-off valve 13 are inside the trunk room shown by the arrow A-A, that is, outside the engine room, and are located outside the cylinder. It is located near 5. Further, the fuel reservoir 10, the second pressure regulator 16, and the on-off valve 17 are installed in the engine room indicated by the arrow BB.

In the above configuration, when the engine 1 is started, the second pressure regulator 16 in the engine room controls the LPG pressure. The temperature of the surplus LPG returned to the cylinder 5 through the second return pipe 15 hardly increases, and even if the temperature is high, it is closed in a short time, so the temperature of the LPG in the cylinder 5 increases significantly. I won't let you. Furthermore, since surplus LPG is returned to the cylinder 5 from the part near the fuel injection valve 4,
Air bubbles accumulated in the supply pipe 6 and the like while the engine is stopped can be thoroughly discharged at the beginning of operation. Then, when the time elapses after the engine 1 is started, the first pressure regulator 12 installed near the cylinder 4 outside the engine room comes to control the pressure of LPG, and the excess LPG
Since the fuel is returned to the cylinder 5 and circulated in a place not affected by the heat of the engine 1, the LPG temperature in the cylinder 5 does not rise even if the operation lasts for a long time.

(Effects of the Invention) As can be understood from the above explanation, according to the present invention, when the engine is started, excess LPG is first returned to the cylinder via the second pressure regulator in the engine room, thereby reducing the supply pipe. Air bubbles such as these are discharged and removed, and the functions of the fuel pump and pressure regulator are made smooth and accurate, and the amount of injection from the fuel injection valve is not disturbed. In addition, after this period of time has elapsed, excess LPG is returned to the cylinder via the first pressure regulator near the cylinder without being affected by the heat of the engine, allowing normal fuel injection even if the engine is operated for a long time. High safety can be achieved without increasing the LPG temperature within the cylinder without impairing functionality or increasing fuel consumption.

[Brief explanation of the drawing]

The drawings are layout diagrams showing embodiments of the present invention.

Claims (1)

[Claims] Engine LP pressurizes LPG in a cylinder (5) with a fuel pump (9), adjusts it to a predetermined pressure, injects it from a fuel injection valve (4), and returns excess LPG to the cylinder (5).
In the G supply device, a first pressure regulator (12) installed near the cylinder (5), a second pressure regulator (16) installed in the engine room, and the two pressure regulators. (12, 16) respectively, and the cylinders (5
) a first return pipe (11) and a second return pipe (15) connected to the two return pipes (11, 15);
The first on-off valve (13) and the second on-off valve (17) are respectively provided in the engine. The valve (17) is opened, and the first on-off valve (13) is opened and the second on-off valve (17) is closed after a certain period of time has elapsed since starting. An LPG supply device characterized by: