JP4234352B2 - Liquefied gas fuel supply device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquefied gas fuel supply apparatus for an internal combustion engine, and more particularly to a liquefied gas fuel supply apparatus that can improve the startability of the engine.
[0002]
[Prior art]
Regarding a liquefied gas fuel supply device that pressurizes liquefied gas fuel such as LPG stored in a fuel tank, sends it to a delivery pipe, and injects it by an injector provided in the delivery pipe and supplies it to an engine, No. 502473 and the like. According to the publication, the fuel having a variable vapor pressure stored in the tank and depending on the ambient temperature in the tank is fueled at an absolute pressure that is maintained at a pressure higher than the variable vapor pressure in the tank by a certain differential pressure. Is pumped to the fuel inflow side rail (delivery pipe in this application) and the injector, the absolute pressure of the fuel is monitored, and the fuel injection pulse width is changed by the absolute pressure of the fuel together with other normal engine parameters.
[0003]
[Problems to be solved by the invention]
However, in the configuration disclosed in the above publication, fuel may leak little by little from the minute gap in the valve portion of the injector while the engine is stopped, and liquefied gas fuel may accumulate in the intake manifold. At this time, not only the fuel in the delivery pipe (inner diameter 8 mm) but also the fuel in the pipe from the fuel tank to the pressure regulator downstream of the delivery pipe may leak into the intake manifold. In this case, when the engine is started, there is a possibility that the time required for starting the engine may be extremely increased due to the rich fuel filled in the intake manifold. As a countermeasure, it is conceivable to reduce the leakage amount by reducing the inner diameter of the delivery pipe or the fuel supply pipe, but there is a limit in securing the maximum fuel flow rate at the maximum engine output.
[0004]
In addition, since the fuel in the pipe returns to the fuel tank as time passes after the engine stops, the fuel in the pipe is depressurized and vaporized, and the time required for starting the engine is filled until the liquid is filled in the pipe when the engine is restarted. May increase. That is, when the pressure in the pipe is high, it may be due to the rich fuel in the intake manifold, and when the pressure in the pipe is low, the time required for starting the engine may increase in any case due to the lack of injected fuel. There is. Therefore, an object of the present invention is to provide a liquefied gas fuel supply apparatus that can suppress an increase in engine start time even when the pressure in the pipe is high or low.
[0005]
[Means for Solving the Problems]
In order to solve the above problem, the invention of claim 1 is directed to pressurizing a liquefied gas fuel in a fuel tank by a fuel pump and sending it to a delivery pipe, and supplying the fuel to the engine by an injector connected to the delivery pipe. with it, in the produced liquefied gas fuel supply device so as to return the surplus fuel to the fuel tank, a delivery shut-off valve at the inlet portion of said delivery pipe, digits set the open-ku valve only for the downstream direction in the outlet section It is characterized by. The invention according to claim 2 is characterized in that the delivery cutoff valve is closed when the engine is stopped and opened when the engine is started . The invention of claim 3 is characterized in that a pressure regulator is disposed on the downstream side of the valve that opens only in the downstream direction.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a liquefied gas fuel supply apparatus according to an embodiment of the present invention. In FIG. 1, a fuel tank 2 containing liquefied gas fuel 1 has a filling unit 3 for injecting fuel, a level cage 4 for displaying the amount of fuel, and a fuel pressure in the fuel tank 2 for detecting the fuel pressure. A tank fuel pressure sensor 5, a fuel pump 7 for pressurizing and feeding fuel to the delivery pipe 6, a pressure regulator 8 for adjusting the fuel pressure in the delivery pipe 6, and a fuel temperature in the fuel tank 2 are measured. Each of the first fuel temperature sensors 9 is attached. The tank fuel pressure sensor 5 and the first fuel temperature sensor 9 are connected to an ECU (11) for controlling the engine 10 via an electric wiring (not shown).
[0008]
A fuel supply pipe 12 is connected to the tip of the fuel pump 7 and communicates with a delivery pipe 6 fixed to an intake manifold 13. A tank shut-off valve 14 is provided near the outlet of the fuel tank 2 in the middle of the fuel supply pipe 12 and is opened and closed by an electric signal from the ECU (11) via an electric wiring (not shown). A delivery cutoff valve 15 is provided in the vicinity of the delivery pipe 6 in the middle of the fuel supply pipe 12, and is opened and closed together with the tank cutoff valve 14 by an electrical signal from the ECU (11) via electrical wiring. A plurality of injectors 16 are sandwiched between the delivery pipe 6 and the intake manifold 13, and the fuel in the delivery pipe 6 is injected into the engine 10 by an electrical signal from the ECU (11). The delivery pipe 6 is provided with a delivery fuel pressure sensor 17 for detecting the fuel pressure in the delivery pipe 6 and a second fuel temperature sensor 18 for detecting the fuel temperature. The delivery fuel pressure sensor 17 and the second fuel temperature sensor 18 are connected to the ECU (11) via electric wiring (not shown). The inner diameter of the fuel passage of the delivery pipe 6 is 4-7 mm. When the inner diameter of the delivery pipe 6 is less than 4 mm, the required flow rate cannot be ensured due to the pipe resistance, and when the inner diameter exceeds 7 mm, the fuel leaks into the intake manifold 13 and becomes rich fuel. As described above, having an inner diameter of 4 to 7 mm has a critical significance.
[0009]
A return pipe 19 constituting a fuel pipe is connected to the outlet of the delivery pipe 6 and communicates with the upper part of the fuel tank 2. A first check valve 20 is provided in the vicinity of the delivery pipe 6 in the middle of the return pipe 19 so as to prevent backflow from the return pipe 19. A second check valve 21 is provided in the vicinity of the fuel tank 2 in the middle of the return pipe 19 so as to prevent backflow from the fuel tank 2. A pressure regulator 8 is provided at the end of the return pipe 19 in the fuel tank 2 so as to adjust the fuel pressure in the delivery pipe 6. Excess fuel resulting from the adjustment is configured to flow directly into the fuel tank 2 from the pressure regulator 8. The fuel supply pipe 12, the delivery pipe 6, and the return pipe 19 constitute a fuel pipe.
[0010]
Next, the operation of this embodiment will be described. When the engine 10 is stopped, the delivery shut-off valve 15 and the tank shut-off valve 14 are closed by an electric signal from the ECU (11) based on an engine stop signal such as an ignition signal or engine speed or hydraulic pressure. Thereafter, as the temperature in the engine room rises, the fuel pressure in the delivery pipe 6 rises, and evaporative fuel may leak from a minute gap in the valve portion of the injector 16. Since the fuel is limited to the fuel in the delivery pipe 6 between the check valve 20 and the check valve 20, the amount of leakage into the intake manifold 13 is reduced as compared with the conventional case. Further, since the fuel in the fuel supply pipe 12 is prevented by the tank shutoff valve 14 from returning to the fuel tank 2, the fuel in the fuel supply pipe 12 is immediately supplied to the engine when the engine 10 is restarted. Therefore, the engine start time does not increase. When the engine 10 is started, the delivery cutoff valve 15 and the tank cutoff valve 14 are opened.
[0011]
FIG. 2 is a graph showing the results of a comparative test between this embodiment and the comparative technique. The fuel pipe inner diameter of the delivery pipe used for the test was 6 mm, and the liquefied gas fuel used was LPG fuel. FIG. 2A is a graph showing the LPG concentration (VOL%) in the intake manifold (intake pipe) 13 with respect to the elapsed time after the engine is stopped. FIG. 2B is a graph showing engine start time (seconds) with respect to LPG concentration (VOL%) in the intake pipe. 2A and 2B, in the specification without the delivery shutoff valve 15 and the check valve used as a comparative technique, the LPG concentration in the intake pipe after 120 minutes is approximately 11 VOL%, and the engine start time is 1.6. It takes seconds. On the other hand, in this embodiment, the LPG concentration in the intake pipe 13 is approximately 6 VOL%, which is half that of the comparative technique, and the starting time is 1.3 seconds. The difference between the two intake pipe LPG concentrations tends to increase as the elapsed time after the engine stops increases.
[0012]
Since this invention is comprised as mentioned above, there exist the following effects. That is, in the first and second aspects of the invention, the delivery shutoff valve is provided at the inlet of the delivery pipe, and the valve that opens only in the downstream direction is provided at the outlet of the delivery pipe, so that the delivery shutoff is performed when the engine is stopped. By closing the valve and opening it when the engine is started, the amount of fuel that leaks into the intake manifold from the minute gap in the injector valve when the engine is stopped is limited to the fuel in the delivery pipe, reducing the amount of leakage. Therefore, the restart time of the engine can be shortened. In the invention of claim 3, since the pressure regulator is disposed on the downstream side of the valve that opens only in the downstream direction, the fuel pressure in the delivery pipe can be adjusted.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of a liquefied gas fuel supply apparatus according to an embodiment of the present invention.
FIG. 2 (a) is a graph showing the LPG concentration in the intake pipe with respect to the elapsed time after engine stop.
FIG. 2B is a graph showing the engine start time with respect to the LPG concentration in the intake pipe.
[Explanation of symbols]
1 liquefied gas fuel 2 fuel tank 6 delivery pipe 7 fuel pump 8 pressure regulator 10 engine 12 fuel supply pipe 14 tank shut-off valve 15 delivery shut-off valve 16 injector 19 return pipe 20 first check valve

Claims (3)

The liquefied gas fuel in the fuel tank is pressurized by a fuel pump and sent to a delivery pipe via a fuel supply pipe. Fuel is supplied to the engine by an injector connected to the delivery pipe, and surplus fuel is supplied via a return pipe. In the liquefied gas fuel supply apparatus configured to return to the fuel tank, a delivery shut-off valve is provided at an inlet portion of the delivery pipe, and a valve that opens only in a downstream direction is provided at an outlet portion of the delivery pipe, The liquefied gas fuel supply device for the engine.   The liquefied gas fuel supply device according to claim 1, wherein the delivery shut-off valve is closed when the engine is stopped and opened when the engine is started.   The liquefied gas fuel supply device according to claim 1 or 2, wherein a pressure regulator is disposed on the downstream side of the valve that opens only in the downstream direction.

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