JP3966733B2 - Liquefied gas fuel supply system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquefied gas fuel supply system using liquefied gas as a fuel, and more particularly to a system for preventing leakage of liquefied gas fuel into an engine cylinder when the engine is stopped.
[0002]
[Prior art]
When liquefied gas fuel is injected into an engine cylinder and burned, it is necessary to pressurize the liquefied gas and supply it to the injection system in a liquid state, but particularly when used for a high compression engine such as a diesel engine, It is necessary to pressurize the liquefied gas at a very high pressure and supply it to the fuel injection system.
[0003]
Among various liquefied gases, dimethyl ether (hereinafter referred to as “DME”), which has a high cetane number and generates little PM and NOx, and extremely little soot, has been studied as a low-pollution fuel as a diesel fuel to replace light oil. However, since the viscosity is significantly lower than that of light oil, even if the injector has a metal-sealed solenoid valve due to the high fuel residual pressure in the fuel pipe when the engine is stopped, There is a problem that DME gradually leaks and stays therein, and abnormal combustion occurs when the engine is started.
[0004]
Various proposals have heretofore been made to solve this problem, and a typical example is German Patent No. 1961434 A1.
[0005]
The publication discloses a plurality of high-pressure liquid DMEs remaining in piping of a high-pressure fuel supply system including a common rail that supplies high-pressure fuel to an injector while the engine is stopped and a fuel return system that returns surplus fuel to the injector to a fuel tank. By opening and closing the valve device and collecting it in a low-pressure collection container (also called a purge tank), the injection hole of the injector is maintained at atmospheric pressure, and leakage of DME from the injection hole is prevented.
[0006]
[Problems to be solved by the invention]
However, the purge tank disclosed in the above publication inevitably has a large capacity in order to recover and store the high-pressure liquid residual DME in a low-pressure gas state, for example, a large tank having 180 liters. In addition to the particular difficulty in mounting, the cost of the equipment also increases, and there has been a problem in practical use.
[0007]
The present invention has been made in view of the above-described problems, and prevents the low-viscosity liquefied gas fuel such as DME from leaking from the nozzle of the fuel injector into the engine cylinder while the engine is stopped. It is an object of the present invention to provide a liquefied gas fuel supply system that has no problem in mountability on a vehicle and has a low apparatus cost.
[0008]
[Means for Solving the Problems]
The present invention uses the following technical means in order to solve the aforementioned problems.
[0009]
According to a first aspect of the present invention, fuel is supplied from a fuel tank that stores liquefied gas to a fuel injector to an engine via a high-pressure pump, and a pressure regulator that regulates the fuel injection pressure is used. In the liquefied gas fuel supply system for returning the fuel to the fuel tank,
A high-pressure path opening / closing valve that is provided in a high-pressure fuel supply path connected to the fuel injector from the high-pressure pump and opens and closes the high-pressure fuel supply path;
A fuel return path that returns fuel to the fuel tank via the pressure regulator, opens and closes the fuel return path, and bypasses the pressure regulator to a first bypass path that is connected to the fuel return path. A return path switching valve for switching,
A second bypass path that branches off from an isolation portion defined by the high-pressure path opening / closing valve and the return path switching valve and is connected to the fuel return path;
A bypass path opening / closing valve provided in the second bypass path for opening and closing the second bypass path;
A compressor provided in the second bypass path, which sucks and compresses the gas in the isolated portion and returns the gas to the fuel tank;
A gas-liquid sensor provided in the isolation portion and detecting a gas ratio of the isolation portion;
A pressure sensor provided in the isolation part and detecting the pressure of the isolation part;
When the engine is stopped, the high pressure path opening / closing valve, the return path switching valve, and the bypass path switching valve are opened / closed based on the detection values of the gas / liquid sensor and the pressure sensor, and the compressor is operated to enter the isolation portion. Control means for recovering remaining fuel in the fuel tank;
It is provided with.
[0010]
According to the above invention, the isolation portion defined by the high-pressure path opening / closing valve and the return path switching valve communicates with the injection hole of the fuel injector, and is connected to the fuel tank by the both valves. Compartment is set to a significantly smaller volume than that.
[0011]
Here, when the engine is stopped, the gas ratio and pressure of the isolated portion are detected, and the high pressure path on / off valve, return path switching valve, bypass path on / off valve and compressor are controlled based on both detected values. As will be described later, the high-pressure liquid fuel remaining in the isolation part is directly collected in the fuel tank, and after the residual fuel in the isolation part becomes gaseous, the pressure is reduced by the compressor until the pressure in the isolation part decreases to approximately atmospheric pressure. Since the suction is performed and the pressure is reduced, there is no fuel leakage from the injection hole of the fuel injector communicating with the isolated portion into the engine cylinder when the engine is stopped.
[0012]
According to a second aspect of the present invention, in the first aspect of the first aspect, when the engine is stopped, the high-pressure path opening / closing valve and the bypass path opening / closing valve are closed and the return path switching valve is closed. When the detected value of the gas-liquid sensor becomes equal to or greater than a set value, the return path switching valve is closed and the bypass path on / off valve is opened, and the compressor is operated, and the pressure sensor When the detected value is equal to or lower than a set value, the control is performed such that the operation of the compressor is stopped by closing the bypass path on-off valve.
[0013]
According to the above invention, when the engine is stopped, the high-pressure path on-off valve and the bypass path on-off valve are closed and the return path switching valve is switched to the first bypass path, leading to the injection hole of the fuel injector. The high pressure liquid fuel portion is partitioned to form an isolated portion, and the high pressure liquid fuel remaining in the isolated portion is returned directly to the fuel tank via the first bypass path.
[0014]
Here, the high-pressure liquid fuel remaining in the isolated part rapidly changes to a relatively low pressure gaseous fuel because the volume of the isolated part is small, and balances with the vapor pressure determined by the temperature of the isolated part. When the gas ratio of the isolated part detected by the liquid sensor exceeds the set value, the return path switching valve is closed and the bypass path on-off valve is opened and the compressor is operated, so the low pressure gaseous fuel in the isolated part is sucked and compressed by the compressor. So-called degassing is performed to return to the fuel tank via the second bypass path, and the isolated portion having a small volume is rapidly decompressed.
[0015]
When the pressure of the isolated portion detected by the pressure sensor reaches a set value (for example, atmospheric pressure), the bypass path on-off valve is closed and the compressor operation is stopped. Therefore, the injection hole of the fuel injector that communicates with the isolated portion However, it will be in an atmospheric pressure state where no fuel leaks.
[0016]
According to a third aspect of the present invention, the fuel is supplied from the fuel tank storing the liquefied gas to the fuel injector to the engine via the high pressure pump, and the pressure is adjusted to a predetermined fuel injection pressure. In the liquefied gas fuel supply system for returning the fuel to the fuel tank,
A high-pressure path opening / closing valve that is provided in a high-pressure fuel supply path connected to the fuel injector from the high-pressure pump and opens and closes the high-pressure fuel supply path;
A return path opening / closing valve provided in a fuel return path for returning the fuel to the fuel tank via the pressure regulator, and opening and closing the fuel return path;
A second bypass path that branches off from an isolation portion defined by the high-pressure path on-off valve and the return path on-off valve and is connected to the fuel return path;
A bypass path switching valve provided in the second bypass path, which opens and closes the second bypass path and bypasses the pressure regulator and switches to a third bypass path connected to the fuel return path;
A compressor provided in the second bypass path, which sucks and compresses the gas in the isolated portion and returns the gas to the fuel tank;
A gas-liquid sensor provided in the isolation portion and detecting a gas ratio of the isolation portion;
A pressure sensor provided in the isolation part and detecting the pressure of the isolation part;
When the engine is stopped, the high pressure path on / off valve, the return path on / off valve and the bypass path switching valve are opened / closed based on the detection values of the gas / liquid sensor and the pressure sensor, and the compressor is operated to enter the isolation portion. Control means for recovering remaining fuel in the fuel tank;
It is provided with.
[0017]
According to the above invention, the difference from the invention according to claim 1 is that a return path switching valve is used instead of the return path switching valve according to claim 1, and a bypass path switching valve is used. Therefore, the valve for partitioning the isolation portion is different from the valve for switching to the third bypass path corresponding to the first bypass path. Therefore, the function and effect described in the first aspect of the invention can be obtained.
[0018]
According to a fourth aspect of the present invention, in the third aspect of the present invention, when the engine is stopped, the high pressure path on / off valve and the return path on / off valve are closed and the bypass path switching valve is turned off. When switching to the third bypass path and the detected value of the gas-liquid sensor becomes equal to or greater than a set value, the bypass path switching valve is switched to the second bypass path and the compressor is operated, and the detected value of the pressure sensor Is controlled to close the bypass path switching valve and stop the operation of the compressor.
[0019]
According to the above invention, although the on-off valve and the switching valve to be controlled are different from those of the invention according to claim 2, when the engine is stopped, the high pressure liquid fuel remaining in the isolation portion is transferred to the third bypass path. The isolation part is made into low-pressure gaseous fuel by directly returning it to the fuel tank via the fuel tank, and then the isolation part is sucked back by the compressor through the second bypass path and returned to the fuel tank. The action of reducing the pressure to the atmospheric pressure is the same as that of the second aspect of the invention.
[0020]
According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, a temperature sensor is used instead of the gas-liquid sensor, and each detection of the temperature sensor and the pressure sensor is performed. The gas ratio of the isolation part is calculated based on the value, and the function of the gas-liquid sensor is substituted.
[0021]
According to the above invention, by using a temperature sensor instead of the gas-liquid sensor, the vapor pressure diagram of DME (see FIG. 9) depends on the temperature of the isolated portion and the pressure of the isolated portion detected by the pressure sensor. ), The gas ratio of the isolated portion is obtained, so that the function of the gas-liquid sensor is substituted.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to FIGS.
[0023]
FIG. 1 is a system configuration diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a fuel tank for storing liquefied gas. For example, DME having a vapor pressure of about 0.5 MPa at 20 ° C. is stored. Yes. A feed pump 2 is provided in the fuel tank 1 for increasing the pressure of DME to a predetermined pressure (for example, about 3 MPa) and feeding it. The DEM fed from the feed pump 2 is further fed to a predetermined pressure (for example, 25 MPa to 35 MPa). The high pressure pump 3 for raising the pressure to a high pressure is provided, and the high pressure DME is injected into each cylinder (not shown) of the engine 6 through the common rail 4 for accumulating the high pressure DME pumped from the high pressure pump 3. An injector 5 having a built-in electromagnetic valve (not shown) is provided.
[0024]
The high-pressure fuel supply path S connecting the high-pressure pump 3 and the common rail 4 is provided with a high-pressure path opening / closing valve 11 composed of an electromagnetic two-way valve that opens and closes the path S. Further, a fuel return path R is provided from the common rail 4 to the fuel tank 1 via a pressure regulator 7, and a high pressure surplus DME is sent from the common rail 4 by the pressure regulator 7 to a predetermined fuel injection pressure ( For example, the pressure is adjusted to 25 MPa to 35 MPa) and then returned to the fuel tank 1 through the fuel return path R through the cooler 8 and the check valve 9 made of, for example, a heat exchanger.
[0025]
The cooler 8 is used to cool the DME returning to the fuel tank 1 as much as possible and return it to the fuel tank 1, and the check valve 9 has excessive pressure in the fuel tank 1. In this case, DME is prevented from flowing back into the fuel return path R.
[0026]
Here, the fuel return path portion connecting the common rail 4 and the pressure regulator 7 opens and closes the fuel return path portion, and bypasses the pressure regulator 7 and is connected to the fuel return path R. A return path switching valve 12 comprising an electromagnetic three-way valve that can be switched to the path R1 is provided. Further, a second bypass path R2 branched from the common rail 4 and bypassing the pressure regulator 7 and connected to the fuel return path R is provided, and the second bypass path R2 includes the path R2 A bypass path opening / closing valve 13 and a compressor 10 are provided, each of which is an electromagnetic two-way valve that opens and closes.
[0027]
In the high-pressure fuel path portion including the common rail 4 and the injector 5, an isolation portion K that is partitioned by closing the high-pressure path opening / closing valve 11 and the return path switching valve 12 is formed, and the isolation portion K and each of the injectors 5 described above are formed. The nozzle holes (not shown) communicate with each other. The volume of the isolation portion K is such that when the engine is stopped, the residual DME is quickly collected in the fuel tank 1, so that the position where the valves 11 and 12 are disposed is much smaller than that of the fuel tank 1. Is set.
[0028]
Further, in the common rail 4, for example, a gas-liquid sensor 21 that detects a gas ratio by an impedance between electrodes and a pressure sensor 22 that detects a pressure are provided.
[0029]
The feed pump 2, the high pressure pump 3, the solenoid valve of each injector 5, the compressor 10, the high pressure path on / off valve 11, the return path switching valve 12, the bypass path on / off valve 13, the gas-liquid sensor 21, the pressure sensor 22, etc. The feed pump 2 and the high-pressure pump 3 are connected to an electronic control unit (hereinafter referred to as ECU) 30, and based on the engine start / stop operation classification and the detected values of the gas-liquid sensor 21 and the pressure sensor 22. The ECU 30 controls the operation of the compressor 10 and the opening / closing switching of the solenoid valve, the high pressure path switching valve 11, the return path switching valve 12, and the bypass path switching valve 13 of each injector 5.
[0030]
Next, FIG. 2 is a system configuration diagram showing a second embodiment of the present invention, and the same reference numerals as those in the first embodiment of FIG. 1 denote the same or equivalent parts.
[0031]
The difference from the first embodiment in terms of configuration is that, as shown in FIG. 2, instead of the return path switching valve 12, a return path on / off valve 14 made of an electromagnetic two-way valve is used. In addition, in place of the bypass path opening / closing valve 13 described above, a bypass path switching valve 15 made of an electromagnetic three-way valve is used.
[0032]
Accordingly, the isolation portion K is partitioned by a return path switching valve 14 instead of the return path switching valve 12, and the bypass path switching valve 15 and the fuel return path R are replaced by the first bypass path R1. A third bypass path R3 that communicates with each other, and switching to bypass the pressure regulating valve 7 is replaced by the bypass path switching valve 15 and the third bypass path R3 instead of the return path switching valve 12 and the first bypass path R1. The other points are the same as in the first embodiment of FIG.
[0033]
Next, the operation of the first example of the present embodiment will be described.
[0034]
First, at the time of engine start and operation, in FIG. 1, the feed pump 2 and the high-pressure pump 3 are operated by the ECU 30, and the solenoid valve, the high-pressure path opening / closing valve 11, and the return path switching valve 12 of each injector 5 are opened. In addition, the bypass path opening / closing valve 13 is closed. Therefore, the DME in the fuel tank 1 flows into the common rail 4 through the high-pressure fuel supply path S, accumulates pressure, and is injected into the cylinders (not shown) of the engine 6 from the injection holes of the injectors 5 to be injected into the engine 6. Starts. The surplus DME fuel injected into each cylinder is regulated by the pressure regulator 7, passes through the fuel return path R, passes through the cooler 8 and the check valve 9, and returns to the fuel tank 1 to start and operate the engine. A well-known fuel circulation is performed.
[0035]
Here, when the engine is stopped will be described based on the fuel flow path diagrams of FIGS. 3 and 4 and the control flowchart of FIG.
[0036]
First, when the engine is stopped, as shown in FIG. 7, an engine switch (not shown) is turned off (step 101), and this OFF signal is input to the ECU 30. As a result, the operation of the feed pump 2 and the high pressure pump 3 is stopped as is well known, and the solenoid valves of the injectors 5 are closed. In addition, in the present invention, the high pressure path on / off valve 11 is closed and the bypass path on / off valve 13 is closed. Is continuously closed (step 102), and the return path switching valve 12 is switched to the first bypass path R1 side (step 103).
[0037]
In this case, as shown by the arrows in FIG. 3, the high-pressure liquid DME remaining in the isolation portion K including the common rail 4 and each injector 5 passes through the return path switching valve 12 and is cooled via the first bypass path R1. 8 and the check valve 9, and the flow returns directly into the fuel tank 1.
[0038]
Here, since the isolated portion K has a small volume, the high-pressure liquid DME rapidly changes to a relatively low-pressure gaseous DME and balances with the vapor pressure determined by the temperature of the isolated portion K. In FIG. When the gas ratio of the isolated portion K detected directly by the gas-liquid sensor 21 becomes equal to or higher than a set value (for example, a gas ratio of 90% or higher) (step 104), the return path switching valve 12 is closed (step 105), and the bypass path The on-off valve 13 is opened (step 106), and the compressor 10 is operated (step 107). If the detection value of the gas-liquid sensor 21 is equal to or less than the set value in step 104, the process returns to step 102 and the above flow is repeated.
[0039]
Due to the operation of the compressor 10, the gaseous DME remaining in the isolation portion K (for example, as shown in FIG. 9, DME has a vapor pressure of about 2.2 MPa at 80 ° C.) is an arrow in FIG. As shown in FIG. 2, the air is sucked from the isolation portion K by the compressor 10 through the second bypass path R2, passes through the cooler 8 and the check valve 9, and returns to the fuel tank 1.
[0040]
Here, by the operation of the compressor 10, the inside of the isolated portion K is rapidly depressurized. However, as shown in FIG. 7, the pressure in the isolated portion K detected by the pressure sensor 22 is equal to or lower than a set value (for example, pressure 0). .12 MPa or less) (step 108), the bypass path on-off valve 13 is closed (step 109), and the operation of the compressor 10 is stopped (step 110). If the detected value of the pressure sensor 22 is greater than or equal to the set value in step 108, the process returns to step 105 and the above flow is repeated. As a result, the pressure of the isolation portion K leading to the injection hole of each injector 5 becomes close to atmospheric pressure, so that DME does not leak from the injection hole into the engine cylinder.
[0041]
Next, the operation of the second example of the present embodiment will be described.
[0042]
First, at the time of engine start and operation, the fuel circulation is the same as that in the case of the first embodiment, so that the description thereof is omitted.
[0043]
The engine stop will be described based on the fuel flow path diagrams of FIGS. 5 and 6 and the control flowchart of FIG. 8 while omitting the same parts as in the first embodiment.
[0044]
First, when the engine 6 is stopped, as shown in FIG. 8, the high pressure path on / off valve 11 and the return path on / off valve 14 are closed (step 202) by turning off the engine switch (step 201), and the bypass path switching valve 15 is turned on. Switching to the third bypass route R3 side (step 203).
[0045]
In this case, as indicated by an arrow in FIG. 5, the high-pressure liquid DME remaining in the isolation portion K passes through the bypass path switching valve 15 and the cooler 8 and the check valve 9 via the third bypass path R3. The flow returns directly into the fuel tank 1.
[0046]
Next, as shown in FIG. 8, when the gas ratio of the isolated portion K detected by the gas-liquid sensor 21 becomes equal to or higher than a set value (for example, a gas ratio of 90% or higher) (step 204), the bypass path switching valve 15 is set to the second. Is switched to the bypass path R2 side (step 205), and the compressor 10 is operated (step 206).
[0047]
In this case, the gaseous DME remaining in the isolation portion K is sucked into the compressor 10 via the second bypass path R2, as shown by the arrow in FIG. 6, passes through the cooler 8 and the check valve 9, The flow returns into the fuel tank 1. Then, as shown in FIG. 8, when the pressure of the isolated portion K detected by the pressure sensor 22 becomes a set value or less (for example, a pressure of 0.12 MPa or less) (step 207), the bypass path switching valve 15 is closed (step 208). ) Since the operation of the compressor 10 is stopped (step 209), DME does not leak into the cylinders of the engine from the injection holes of the injectors 5 as in the first embodiment.
[0048]
Next, in the present embodiment, a method of directly detecting the gas ratio of the isolated portion K with the gas-liquid sensor 21 is used. However, by using a temperature sensor instead of the gas-liquid sensor 21, it is detected with the temperature sensor. Based on the temperature of the isolated portion K and the pressure of the isolated portion K detected by the pressure sensor 22, it is possible to indirectly determine the gas ratio of the isolated portion K from the vapor pressure diagram of DME shown in FIG. is there.
[0049]
Furthermore, if the time required for switching from the first bypass path R1 or R3 side to the second bypass path R2 side is obtained in advance by experiment, this time is controlled by a timer so that the isolated portion K Therefore, the gas-liquid sensor 21 is abolished.
[0050]
Next, in this embodiment, the case where the present invention is applied to a common rail type fuel injection apparatus has been described, but the present invention can also be applied to a conventional jerk type fuel injection apparatus.
[0051]
In addition, although DME was taken up as liquefied gas fuel, the effect similar to a present Example will be acquired if it is liquefied gas with low viscosity like DME. Further, although the electromagnetic three-way valve is used as the switching valve for the fuel return path and the bypass path, the same function can be obtained by using two normal electromagnetic two-way valves.
[0052]
【The invention's effect】
Since the present invention is configured as described above, the following effects can be obtained.
[0053]
(1) Since each nozzle hole of each fuel injector communicating with the isolated portion is maintained at substantially atmospheric pressure when the engine is stopped, fuel leaks from each nozzle hole into each cylinder of the engine. This eliminates the occurrence of abnormal combustion when the engine is started.
[0054]
(2) Since there is no need for a large purge tank for collecting high-pressure liquid fuel, there is no problem in mounting on a vehicle, and the system is configured with a relatively simple configuration and simple control. Equipment cost is reduced.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing a first embodiment of the present invention.
FIG. 2 is a system configuration diagram showing a second embodiment of the present invention.
FIG. 3 is a path diagram showing a fuel flow at the beginning of engine stop according to the first embodiment.
FIG. 4 is a route diagram showing a fuel flow from the middle of engine stop according to the first embodiment.
FIG. 5 is a path diagram showing a fuel flow at the beginning of engine stop according to a second embodiment.
FIG. 6 is a route diagram showing a fuel flow from the middle of engine stop according to a second embodiment.
FIG. 7 is a control flowchart when the engine is stopped according to the first embodiment;
FIG. 8 is a control flowchart when the engine is stopped according to the second embodiment.
FIG. 9 is a vapor pressure diagram of DME (dimethyl ether).
[Explanation of symbols]
1 Fuel Tank 2 Feed Pump 3 High Pressure Pump 4 Common Rail 5 Fuel Injector (Injector)
6 Engine 7 Pressure regulator 8 Cooler 9 Check valve 10 Compressor 11 High pressure path opening / closing valve 12 Return path switching valve 13 Bypass path switching valve 14 Return path switching valve 15 Bypass path switching valve 21 Gas-liquid sensor 22 Pressure sensor 30 Electronic control Equipment (ECU)
S High-pressure fuel supply route R Fuel return route R1 First bypass route R2 Second bypass route R3 Third bypass route

Claims (5)

A liquefied gas fuel supply that supplies fuel to a fuel injector to an engine via a high-pressure pump from a fuel tank that stores liquefied gas and returns the fuel to the fuel tank via a pressure regulator that adjusts the fuel injection pressure to a predetermined level In the system,
A high-pressure path opening / closing valve that is provided in a high-pressure fuel supply path connected to the fuel injector from the high-pressure pump and opens and closes the high-pressure fuel supply path;
A fuel return path that returns fuel to the fuel tank via the pressure regulator, opens and closes the fuel return path, and bypasses the pressure regulator to a first bypass path that is connected to the fuel return path. A return path switching valve for switching,
A second bypass path that branches off from an isolation portion defined by the high-pressure path opening / closing valve and the return path switching valve and is connected to the fuel return path;
A bypass path opening / closing valve provided in the second bypass path for opening and closing the second bypass path;
A compressor provided in the second bypass path, which sucks and compresses the gas in the isolated portion and returns the gas to the fuel tank;
A gas-liquid sensor provided in the isolation portion and detecting a gas ratio of the isolation portion;
A pressure sensor provided in the isolation part and detecting the pressure of the isolation part;
When the engine is stopped, the high pressure path opening / closing valve, the return path switching valve, and the bypass path switching valve are opened / closed based on the detection values of the gas / liquid sensor and the pressure sensor, and the compressor is operated to enter the isolation portion. Control means for recovering remaining fuel in the fuel tank;
A liquefied gas fuel supply system comprising: When the engine is stopped, the high-pressure path opening / closing valve and the bypass path opening / closing valve are closed and the return path switching valve is switched to the first bypass path. When the detected value of the gas-liquid sensor becomes a set value or more, the return path Closes the switching valve and opens the bypass path on-off valve and operates the compressor, and controls to close the bypass path on-off valve and stop the compressor operation when the detected value of the pressure sensor becomes a set value or less. The liquefied gas fuel supply system according to claim 1. A liquefied gas fuel supply that supplies fuel to a fuel injector to an engine via a high-pressure pump from a fuel tank that stores liquefied gas and returns the fuel to the fuel tank via a pressure regulator that adjusts the fuel injection pressure to a predetermined level In the system,
A high-pressure path opening / closing valve that is provided in a high-pressure fuel supply path connected to the fuel injector from the high-pressure pump and opens and closes the high-pressure fuel supply path;
A return path opening / closing valve provided in a fuel return path for returning the fuel to the fuel tank via the pressure regulator, and opening and closing the fuel return path;
A second bypass path that branches off from an isolation portion defined by the high-pressure path on-off valve and the return path on-off valve and is connected to the fuel return path;
A bypass path switching valve provided in the second bypass path, which opens and closes the second bypass path and bypasses the pressure regulator and switches to a third bypass path connected to the fuel return path;
A compressor provided in the second bypass path, which sucks and compresses the gas in the isolated portion and returns the gas to the fuel tank;
A gas-liquid sensor provided in the isolation portion and detecting a gas ratio of the isolation portion;
A pressure sensor provided in the isolation part and detecting the pressure of the isolation part;
When the engine is stopped, the high pressure path on / off valve, the return path on / off valve and the bypass path switching valve are opened / closed based on the detection values of the gas / liquid sensor and the pressure sensor, and the compressor is operated to enter the isolation portion. Control means for recovering remaining fuel in the fuel tank;
A liquefied gas fuel supply system comprising: When the engine is stopped, the high-pressure path on-off valve and the return path on-off valve are closed and the bypass path switching valve is switched to the third bypass path. When the detected value of the gas-liquid sensor becomes a set value or more, the bypass path The switching valve is switched to the second bypass path and the compressor is operated, and when the detected value of the pressure sensor becomes a set value or less, the bypass path switching valve is closed and the operation of the compressor is stopped. The liquefied gas fuel supply system according to claim 3. A temperature sensor is used instead of the gas-liquid sensor, and the gas ratio of the isolation portion is calculated based on detection values of the temperature sensor and the pressure sensor, and the function of the gas-liquid sensor is substituted. The liquefied gas fuel supply system according to any one of claims 1 to 4.

Images