JP4374499B2 - Fuel pump - Google Patents

Description

  The present invention relates to a fuel pump, and more particularly, to a fuel pump for a liquefied gas fuel supply device that supplies liquefied gas fuel, such as LPG and DME, which is more easily vaporized than gasoline, to a fuel injection valve in a liquid state.

  A liquefied gas fuel supply device that injects liquefied gas fuel such as LPG and DME in a fuel tank with a fuel pump and injects the liquefied gas fuel from a fuel injection valve to an intake pipe of an engine as a liquid is disclosed in, for example, Japanese Patent Application Laid-Open No. 2003-120443. Widely known as described.

  The liquefied gas fuel supply apparatus described in the above publication is arranged on the engine 50 side through the fuel supply line 9A with fuel pressurized by a low-pressure fuel pump 10a disposed in the fuel tank 10 as shown in FIG. The high pressure fuel pump 19 supplies the fuel injection valve 8 with a higher pressure.

  Further, the surplus fuel that has not been injected by the fuel injection valve 8 is returned to the fuel tank 10 by the fuel return pipe 9B, but is stored in the fuel tank 10 by heating the return fuel in the vicinity of the engine 50. As the temperature of the fuel that is being used rises gradually, in the case of liquefied gas fuel that tends to fluctuate under the influence of temperature, the fuel injection amount becomes unstable due to fluctuations in the injection pressure, which adversely affects engine operability. Will give. In addition, if the fuel tank pressure rises due to an increase in the fuel temperature in the fuel tank, this pressure may exceed the fuel supply pressure of the gas supply station, and in the worst case, fuel refilling becomes impossible. There is.

  Therefore, Japanese Patent Laid-Open No. 2001-295726 discloses a returnless system that has been widely adopted in gasoline fuel supply apparatuses in recent years and that is adopted in a liquefied gas fuel supply apparatus. This method can avoid an increase in the fuel temperature in the fuel tank because the fuel heated in the vicinity of the engine does not return to a high temperature. However, in this case, the residence time of the fuel is longer in the fuel rail and the fuel injection valve than in the return method, so that the fuel temperature rises at this portion to generate bubbles, and the fuel injection amount is accurately controlled. It can be difficult.

  For this reason, it is generally performed that the discharge pressure of the fuel pump is significantly higher than that of the gasoline fuel supply device to suppress the generation of bubbles. However, even in this case, if the fuel temperature rises excessively, the generation of bubbles cannot be avoided, or the pressure limit of the lip seal in the pump will be exceeded. Providing pressure resistance leads to an increase in manufacturing cost.

  On the other hand, in Japanese Patent Laid-Open No. 7-27030, a return-less system is normally used, but only when the fuel in the fuel rail reaches a predetermined temperature or higher, the return system is switched to increase the fuel temperature in the fuel rail. There has been proposed a fuel supply device that avoids the above. However, since the ratio of propane and butane varies depending on the sales region in LPG, it is not sufficient to simply switch to the return method when necessary based on the returnless method.

On the other hand, recently, a high-pressure fuel pump of a liquefied gas fuel supply apparatus that employs a method of forcibly displacing a diaphragm with a cam has been widely used. However, even in this method, when using a LPG having a composition that is easily vaporized, if the pump pressure is set to a high pressure, a large pressure difference is generated between the front and back of the diaphragm, and the pump part is likely to be damaged. Prone to problems.
JP 2003-120443 A JP 2001-295726 A JP-A-7-27030

  The present invention is intended to solve the above-described problems, and the manufacturing cost of a fuel pump for a liquefied gas fuel supply device that supplies liquefied gas fuel to a fuel injection valve while supplying the liquefied gas fuel in a liquid state is reduced. It is an object of the present invention to make it possible to stably exhibit a suitable fuel delivery pressure while being able to cope with various types of liquefied gas fuels having different boiling points without increasing the temperature.

  Therefore, the present invention relates to a fuel pump of a liquefied gas fuel supply device that pressurizes liquefied gas fuel stored in a fuel tank and sends the fuel liquefied fuel to a fuel injection valve as a liquid. The power section is provided with a primary pressurizing chamber that pressurizes hydraulic oil as a reciprocating motion of a linear motion piston through a predetermined power transmission means through rotation of an electric motor or engine, and is provided on the fuel tank side or engine side. The primary pressurizing chamber of the power unit is disposed on the fuel tank side with a secondary pressurizing chamber for introducing the hydraulic oil separated by the isolating means and a pump chamber for introducing the fuel. Is connected to the secondary pressurizing chamber of the pump unit, and pressure pulsation of hydraulic oil generated in the power unit is introduced into the pump unit, and the fuel tank is changed by the volume variation of the pump chamber due to deformation or movement of the isolating means. The liquefied gas fuel in the click was assumed that the pressure-delivery.

  As described above, the fuel pump is separated into two parts, that is, the pump part and the power part, so that an electric motor or an engine can be selected as a drive source of the power part and the fuel pump in the liquefied gas fuel supply apparatus The configuration can be easily changed. For example, a liquefied gas fuel with a relatively high vaporization temperature uses an easily controlled electric motor as the drive source, and a liquefied gas fuel with a relatively low vaporization temperature uses a high output engine as the drive source. By reusing the parts, it is possible to stably exert a suitable fuel delivery pressure corresponding to various fuel compositions without increasing the cost. In addition, since the power unit is a direct acting piston pump and the power transmission to the pump unit is performed with hydraulic oil, the power transmission from the power unit to the pump unit is reliable and highly efficient regardless of the location of these installation locations. It will be something.

  Further, assuming that the power transmission section is provided with a power transmission chamber in which the power transmission means is housed, the power transmission chamber communicates with the primary pressurizing chamber and is filled with hydraulic oil. If it is used as oil, smooth operation of the power transmission means can be ensured over a long period of time without requiring replenishment of lubricating oil, and communication between this power transmission chamber and the primary pressurizing chamber can be established. This is because a communication hole that penetrates from the outer peripheral side of the piston inserted into the cylinder hole drilled from the power transmission chamber side to the primary pressure chamber side opens to the power transmission chamber side at a predetermined timing in the piston stroke. For example, if the primary pressurizing chamber opens near the piston position where the maximum expansion occurs, the inconvenience of pressure leaking to the power transmission chamber when the piston stroke is pressurized can be avoided.

  Furthermore, the power transmission chamber is filled with a hydraulic oil chamber that holds a predetermined amount of hydraulic oil and the fuel vapor pressure in the fuel tank gas phase portion is constantly applied to the power transmission chamber. If the fuel vapor pressure is constantly applied to the generated hydraulic oil, the amount of hydraulic oil can be maintained properly without the need to frequently replenish the hydraulic oil that operates the pump unit, and the pressure difference between the hydraulic oil and fuel can be maintained. Therefore, the durability of the apparatus is improved.

  Furthermore, if the isolation means of the pump part is a diaphragm or a bellows, the secondary pressurizing chamber filled with the hydraulic oil and the pump chamber filled with the fuel are reliably separated from each other and the energy at the time of power transmission is also obtained. In addition to this, the pressure difference between the secondary pressurizing chamber and the pump chamber is less likely to occur during operation of the fuel pump, and the burden on the diaphragm or bellows does not become excessive. It can be set as the pump part excellent in durability.

  In addition, if the check valve on the inlet side of the pump part is mechanically opened and closed at a predetermined timing by a valve opening and closing means that uses a predetermined power source, a conventional fuel pump that opens and closes only by the fuel pressure difference Compared to the above, energy loss due to valve resistance at the time of fuel suction is minimized and valve opening / closing timing is optimized to improve pump efficiency. When using an electric motor as the drive source for the power unit If the valve opening and closing means is a cam mechanism that utilizes the rotation of the electric motor to open and close the inlet side check valve, the valve can be reliably opened and closed in conjunction with the pump operation with a simple configuration, If the cam-type valve opening / closing means part and the hydraulic oil introduction part are communicated to use the hydraulic oil as the lubricating oil for the cam, a smooth valve can be obtained without replenishing the lubricating oil over a long period of time. Open and close It is possible to realize the work.

  In addition, when an engine is used as the drive source of the power unit, a motor-driven cam or electromagnetic solenoid is used as the valve opening / closing means, and the inlet-side check valve is opened and closed under the control of the control unit that detects the operation timing of the power unit. If this is the case, for example, it is possible to detect the rotation period for operating the power unit with an engine crank sensor, etc., and to control the opening and closing of the check valve in accordance with this, so that the appropriate timing can be achieved without depending on the pump operation. Thus, the inlet check valve can be reliably opened and closed.

  According to the present invention, a suitable fuel delivery pressure can be stably exhibited without difficulty in increasing production costs and easily corresponding to various types of liquefied gas fuels having different vaporization temperatures.

  A first embodiment of the present invention will be described with reference to the drawings. Referring to FIG. 1 showing a layout of a liquefied gas fuel supply device 1A provided with a fuel pump 2 according to the present embodiment, a fuel tank A fuel supply line 9 </ b> A is connected to the fuel rail 7 from 10, and fuel is distributed from the fuel rail 7 to the fuel injection valve 8 disposed in the intake pipe 52 of the engine 50. The fuel rail 7 is connected to the fuel tank 10 by a fuel return pipe line 9B.

  Two shutoff valves 5a and 5b are disposed in the fuel supply line 9A, and a fuel return pipe that returns from the inside of the fuel tank 10 into the fuel tank 10 before the shutoff valve 5a on the fuel tank 10 side. 9C branches and the pressure regulator 3 is provided in this fuel return piping 9C. On the other hand, an orifice 6 and a shut-off valve 5c, which are throttles, are arranged in the fuel return piping 9B, and a relief valve 1c is arranged in a bypass pipe 9a that bypasses the orifice 6 and the shut-off valve 5c. .

  The liquefied gas fuel supply apparatus 1A of the present embodiment is suitable for LPG having a large butane component and a relatively high vaporization temperature. Further, similarly to the conventional liquefied gas fuel supply device, a control unit 11 and various sensors (not shown) for inputting the engine operating state are provided, and in addition, a temperature sensor 12 for correcting the fuel injection amount, a pressure A sensor 13 is attached to the fuel rail 7.

  The fuel pump 2 according to the present embodiment is installed inside the fuel tank 10 as one substantially cylindrical device, in which the pump unit 2A and the power unit 2B using the electric motor 40 as a drive source are integrally coupled. It is characterized by. That is, in the fuel pump 2, the pump portion 2A and the power portion 2B are formed as separate bodies, and both can be easily attached and detached according to the purpose of use, and can be applied as a single body or as a separate body. When the fuel used has a relatively high boiling point, it is not necessary to discharge the fuel to be sent to the fuel supply line 9A at a high pressure even when the returnless system is used. Therefore, the low-power electric motor 40 is used as a drive source. This is because it is sufficient to arrange the power unit 2B and the pump unit 2A in the fuel tank 10 as a unit. In addition, the use of the electric motor 40 is advantageous in that it can be stably driven without being affected by the engine operating state, and thus the fuel injection amount can be easily controlled well.

  In addition to this, in the conventional fuel supply apparatus shown in FIG. 7, the high pressure pump 19 is attached to the engine 50 so that the heat affects the pump function and the temperature of the fuel passing therethrough is increased. In the present embodiment, control of the fuel injection amount is difficult, but in this embodiment, the influence of environmental temperature changes on the fuel pump 2 and the supplied fuel is extremely small.

  In addition, the control unit 11 switches the output signal from the temperature sensor 12 among the temperature sensor 12 and the pressure sensor 13 for fuel injection control attached to the fuel rail 7 to switch between the return method and the returnless method. It is used as data. That is, normally, a return-less system in which the shutoff valve 5c of the fuel return pipeline 9B is closed is used, and the shutoff valve 5c is opened when the fuel in the fuel rail 7 becomes equal to or higher than a preset temperature. The surplus fuel is programmed to return to the fuel tank 10 as follows. In addition to this, the control unit 11 detects the engine load state with a plurality of sensors (not shown), and changes the fuel discharge amount by changing the rotation speed of the electric motor 40 according to the load. .

  Referring to the longitudinal sectional view of FIG. 2 for explaining the details of fuel pump 2 in the present embodiment, power portion 2B formed in a substantially cylindrical shape is on the upper end side of drive shaft 26a extending to the upper surface side. The electric motor 40 is a direct-acting piston pump that is driven by a drive shaft connected thereto, and the upper surface of the electric motor 40 faces the top wall side of the fuel tank 10. The lower end side of the drive shaft 26a protrudes into a swash plate chamber 28 which is a substantially cylindrical space as a power transmission chamber, and a swash plate 26b for driving the piston is fixed to the center as a power transmission means. Rotates when driven to generate up and down waves on its lower surface side.

  Slippers 26c, 26c, and 26c are disposed at intervals of 120 degrees around the rotation axis so as to slidably contact the lower surface of the swash plate 26b. , 29a, 29a are opened in the bottom wall of the swash plate chamber 28. In each cylinder hole 29a, a piston 29 is inserted with a piston spring 29b disposed inside, and a primary pressurizing chamber 25 is formed on the lower end side thereof.

  A substantially spherical head provided on the upper end side of each piston 29 is inserted into a recess provided on the lower surface of each slipper 26c, and converts a wave generated on the lower surface of the swash plate 26b into a linear vertical movement. ing. Further, a cam shaft 26d is inserted at the lower end side of the drive shaft 26a so that the upper end side can be attached and detached and cannot rotate in the circumferential direction, and the lower end side is inserted into the pump portion 2A side described later.

  On the other hand, the pump part 2A is also formed in a substantially cylindrical shape like the power part 2B, and is connected and fixed to the lower surface side of the power part 2B having substantially the same diameter by a bolt or the like (not shown). The suction port 20a is directed to the position. The pump unit 2A includes three secondary pressurizing chambers 27, 27, 27 at positions corresponding to the cylinder hole 29a of the power unit 2B, and an elastic material such as rubber is provided in the secondary pressurizing chamber 27. The outer hydraulic oil and the inner fuel are completely separated from each other with the inside as a fuel chamber 24, and the pressure fluctuation of the hydraulic oil generated in the power section 2B is used as the fuel delivery pressure. A bellows pump to be converted is formed. The pump chamber 24 communicates with the fuel supply line 9A through the fuel discharge port 20b through the outlet side check valve 22B, and passes through the fuel suction port 20a through the fuel check port 22A. It communicates with the 10 side. A diaphragm may be provided instead of the bellows 23 as the separating means.

  The inlet-side check valve 22A disposed in the vicinity of the fuel suction port 20a of the pump unit 2A is a cam type on-off valve that mechanically opens and closes the fuel inflow path using the rotation of the motor 40. That is, the cam chamber 21 that houses the tip end side of the camshaft 26d provided with the cam 21a is provided near the center bottom of the pump portion 2A, and is synchronized with the expansion / contraction operation of the bellows 23 by the rotation of the swash plate 26b. The valve body 22a on the distal end side of the valve shaft 22b pushed out by rotation of the set cam 21a opens from the valve seat 22c, and the cam 21a further rotates by the action of the valve spring 22e. The valve shaft 22b is pushed back to close.

  As described above, the pump part 2A and the power part 2B constituting the fuel pump 2 are formed as separate parts, but the primary pressurizing chamber 25 of the power part 2B is a secondary part of the pump part 2A. The pressurizing chamber 27 is connected to the connecting passage 30A, and the swash plate chamber 28, the primary pressurizing chamber 25, the connecting passage 30A, and the secondary pressurizing chamber 27 are filled with hydraulic oil. In addition to this, a hydraulic oil chamber 28b filled with hydraulic oil is provided on the upper surface side of the power section 2B. The drive shaft 26a penetrates the hydraulic oil chamber 28b and the hydraulic oil is replenished to the swash plate chamber 28 side. The outer surface of the top wall 28c is exposed to the gas phase portion of the fuel tank 10, and the fuel vapor pressure is constantly applied to the hydraulic oil. The top wall 28c is provided with an elastic plate such as rubber so that it can be bent by pressure fluctuations inside and outside, or a hard plate member is slidably arranged up and down so that no pressure difference is produced between inside and outside. It should be.

  The swash plate chamber 28 communicates with the cam chamber 21 on the pump portion 2A side and is filled with hydraulic oil through an insertion hole 26e through which a cam shaft 26d fixed to the lower end side of the drive shaft 26a is inserted. The cam chamber 21 is provided by being drilled from the bottom surface side of the pump portion 2A. The plug body 21b is fitted into the opening portion of the cam chamber 21 so that the hydraulic oil does not leak to the fuel tank 10 side. Further, a lip seal 22d is disposed in close contact with the peripheral surface of the valve shaft 22b with which the cam 21a abuts, so that the hydraulic oil in the cam chamber 21 does not leak into the valve chamber 22d.

  FIG. 3 shows a cross-sectional view taken along the line XX, which is a divided part of the fuel pump 2 of FIG. The fuel pump 2 includes three pump mechanisms having the above-described secondary pressurizing chambers 27 at intervals of 120 degrees with respect to the central axis, and these are set so as to deliver fuel at different timings. The fuel is discharged continuously from the fuel discharge port 20b. And in order to connect these to one fuel discharge port 20b, the annular fuel convergence path 20c is provided in the upper surface side of the pump part 1A, and the fuel path downstream of the outlet side check valve 22B of each pump mechanism Respectively open to the fuel convergence path 20c, and one of the fuel passages communicates with the fuel discharge hole 20a.

  Hereinafter, the operation of the liquefied gas fuel supply apparatus 1A of the present embodiment will be described. Referring to FIG. 2, the drive shaft 26a of the power unit 2B is rotated by the drive of the electric motor 40, whereby the swash plate 26b is rotated, and the piston 29 on the lower surface side thereof moves up and down. As a result, pressure fluctuations occur in the hydraulic oil in the primary pressurizing chamber 25, which is transmitted as a sine wave pulsation to the secondary pressurizing chamber 27 of the pump section 2A through the connection path 30A.

  When the fuel pressure in the pump chamber 24 exceeds the hydraulic oil pressure in the secondary pressurizing chamber 27 and the bellows 23 expands, the rotation of the cam 21a set on the camshaft 26d in accordance with this timing causes the valve chamber 22d side. The valve shaft 22b protruding inwardly separates the valve body 22a from the valve seat 22c and opens the inlet side check valve 22A, through which the fuel in the fuel tank 10 flows into the pump chamber 24. When the swash plate 26b further rotates and the piston 29 descends, the pressure in the secondary pressurizing chamber 27 rises and the bellows 23 contracts. Then, the fuel in the pump chamber 24 is discharged from the fuel discharge port 20b through the outlet side check valve 22B, and is sent out toward the fuel injection valve 8 disposed on the fuel rail 7 through the fuel supply line 9A. The The cam chamber 21 in which the cam 21a is disposed communicates with the swash plate chamber 28 side and is always filled with hydraulic oil, so that this becomes lubricating oil for the cam 21a, and the cam operation is always smooth.

  The suction / discharge of the fuel by the expansion / contraction of the bellows 23 uses the pressure fluctuation of the hydraulic oil as a transmission means, but the outer periphery of the piston 29 is near the top dead center where the piston 29 of the pump unit 2B is raised. A communication hole 29d formed in the surface opens to the swash plate chamber 28 side, and the fuel oil pressure on the fuel tank 10 side is applied to the hydraulic oil chamber 28b and the swash plate chamber 28, and the primary pressurizing chamber 25 and the secondary pressurizing chamber. 27, the pressure of the hydraulic oil is always stable, loss of power transmission is less likely to occur, and a large pressure difference between the inside and outside of the bellows 23 is less likely to occur, so the burden on the bellows 23 is relatively small. Its durability is sufficiently secured. Even when a diaphragm is provided instead of the bellows 23, the same effect can be expected.

  The fuel from the fuel supply line 9A to the fuel rail 7 provided with the plurality of fuel injection valves 8 is adjusted to a preset pressure by the pressure regulator 3 provided in the fuel return pipe 9C. Even when the fuel supply method is a returnless method in which the shutoff valve 5c is closed, fuel can be injected from the fuel injection valve 8 into the intake pipe line 52 with a stable injection pressure. Therefore, the fluctuation of the fuel injection amount due to the pressure pulsation by the fuel pump 2 and the influence of the environmental temperature change is relatively small, and the return fuel returns to the fuel tank 10 via the pressure regulator 3 inside the tank 10. There is almost no fear that the temperature inside the fuel tank 10 will rise.

  The control unit 11 opens the shutoff valve 5c of the fuel return pipe 9B when the fuel temperature detected by the temperature sensor 12 disposed on the fuel rail 7 exceeds a predetermined temperature set and stored in the storage means. Since the return method is to return the surplus fuel to the fuel tank 10, it is avoided that the fuel temperature in the fuel rail 7 rises excessively and vaporizes, but the fuel temperature in the fuel rail 7 is a predetermined value. When the pressure drops below, the shut-off valve 5c is closed and the returnless system is used, so that the temperature in the fuel tank 10 does not rise excessively due to the return fuel.

  On the other hand, even in the case of the return method, the flow rate of the return fuel is limited by the orifice 6 disposed in the upstream proximity position of the shutoff valve 5c, so that the fuel pressure in the fuel rail 7 is higher than a predetermined lower limit pressure. Since it does not decrease, the fuel injection pressure is stably maintained. Further, the bypass pipe 9a bypassing the shutoff valve 5c and the orifice 6 is provided with a relief valve 1c on the way, so that when the pressure in the fuel rail 7 exceeds a predetermined upper limit pressure, this is replaced with a fuel tank. The fuel injection pressure is maintained constant by letting it go to the 10th side.

  FIG. 4 shows an arrangement of a liquefied gas fuel supply apparatus 1B according to the second embodiment of the present invention. This liquefied gas fuel supply apparatus 1B is a fuel pump 2 in the liquefied gas fuel supply apparatus 1A of FIG. Is characterized in that it is connected to a pump unit 1A arranged in the fuel tank 10 by a pipe 30B (pressure pipe).

  That is, in the liquefied gas fuel supply apparatus 1B of the present embodiment, since the fuel pump 2 is formed separately from the pump part 2A and the power part 2B and can be easily divided, the power part 2B is removed and arranged on the engine 50 side. However, the fuel discharge pressure can be significantly increased by using the engine 50 as a drive source. That is, when liquefied gas fuel having a low vaporization temperature is used, the pump system is switched in order to maintain the fuel pressure in the fuel supply line 9A at a high pressure, and when LPG having a large amount of propane is used. It is suitable.

  In the power unit 2B, a pulley 41A provided on the end side of the crankshaft 51 of the engine 50 and a pulley 41B provided on the end side of the drive shaft 26a are connected by a conduction belt 42, and the rotation of the crankshaft is driven by 1: 1. It is transmitted to the part 2B and is attached to the main body of the engine 50, and is arranged in the fuel tank 10 by long pipes 30B, 30B, 30B connecting from the front of the vehicle with the engine room to the rear of the vehicle with the fuel tank 10. Connected to the pump section 2A. Then, the rotation of the crankshaft 51 of the engine 50 causes the piston 29 to reciprocate, causing a pressure fluctuation in the primary pressurizing chamber 25, and a substantially sinusoidal pulsation passes through the pipe 30B and the secondary addition of the pump unit 2A. The point transmitted to the pressure chamber 27 to drive the pump unit 2A is the same as that of the liquefied gas fuel supply apparatus 1A of FIG.

  However, the present embodiment is characterized in that the discharge pressure can be made extremely high by using the engine 50 having a much higher output than the electric motor 40 as a power source, and an LPG having a low vaporization temperature. In this case, the fuel pressure in the fuel supply line 9A and the fuel rail 7 can be maintained at a very high pressure, and its vaporization can be reliably prevented.

  As a system for mechanically opening and closing the inlet side check valve of the pump unit 2A in the present embodiment, FIG. 5 shows an arrangement in which an inlet side check valve 22C using an electric motor 43 is arranged, and FIG. An inlet side check valve 22D using a solenoid 44 is provided. That is, in these systems, the control unit 11 detects the rotational position and rotational speed of the crankshaft 51 of the engine 50 with the crank sensor 14, and based on this, the operation timing (piston position) of the power unit 2B is grasped. The inlet side check valves 22C and 22D are mechanically opened and closed at a timing in accordance with the above. Thereby, in addition to minimizing the loss of fuel delivery due to the valve resistance, the opening and closing of the inlet side check valve can be accurately performed, and the pump efficiency can be improved. The same applies if a cam pulse sensor for directly detecting the rotational position and rotational speed of the swash plate 26b is provided on the power unit 2B side instead of the crank sensor 14.

  In the system using the electric motor 43 in FIG. 5, the camshaft 26f is shorter than the camshaft 26d in FIG. 2, and in the system using the electromagnetic solenoid 44 in FIG. 6, the cam chamber 21 and the valve chamber 22d are replaced. The sealing member 22f which seals communication with is inserted. In addition, the connecting surfaces of the pump unit 2A and the power unit 2B are commonly sealed by fixing lid members 20c and 20d with bolts or the like. Further, in the method shown in FIG. 5, if a communication groove is provided on the lower surface of the lid member 20c for communicating hydraulic fluid from the connection hole portion of the pipe 30B to the portion through which the camshaft penetrates, the insertion hole 26e and the cam chamber 21 are always provided. It will be filled with hydraulic oil, and it will be easy to maintain smooth cam operation.

  As described above, the pump unit and the power unit constituting the fuel pump can be separated into separate parts so that the power source can be easily switched between the electric motor and the engine. Thus, it is possible to easily cope with various types of liquefied gas fuels having different vaporization temperatures without raising the fuel vapor, and the controllability of the fuel injection amount can be further improved.

The layout which shows 1st embodiment of this invention. The longitudinal cross-sectional view which shows the detail of the fuel pump of FIG. Sectional drawing which follows the XX line of FIG. The layout which shows 2nd embodiment of this invention. FIG. 6 is a longitudinal sectional view showing a case where an electric motor is used to drive an inlet side check valve of the fuel pump of FIG. 5. FIG. 6 is a longitudinal sectional view showing a case where an electromagnetic solenoid is used to drive an inlet side check valve of the fuel pump of FIG. 5. The layout which shows a prior art example.

Explanation of symbols

1A, 1B liquefied gas fuel supply device, 2 fuel pump, 2A pump section, 2B power section, 10 fuel tank, 11 control unit, 14 crank sensor, 20a fuel inlet, 20b fuel outlet, 21 cam chamber, 21a cam, 22A, 22C, 22D Inlet side check valve, 22B Outlet side check valve, 23 Bellows, 24 Pump chamber, 25 Primary pressurizing chamber, 26a Drive shaft, 26b Swash plate, 26c Slipper, 27 Secondary pressurizing chamber, 28 Swash plate chamber, 29 piston, 30A connection path, 30B piping, 40, 43 electric motor, 44 electromagnetic solenoid, 50 engine

Claims (4)

And the dynamic force portion and the pump portion is formed as a separate body which can be divided and coupled, hydraulic oil as reciprocating operation of the linear piston through a predetermined power transmission means the rotation of the power unit is an electric motor or engine A primary pressurizing chamber for pressurization is disposed on the fuel tank side or the engine side, and the pump unit includes a secondary pressurization chamber for introducing hydraulic oil isolated by the isolating means and a pump chamber for introducing fuel. A pressure pulsation of hydraulic oil generated in the power unit is introduced into the pump unit by being connected to a primary pressurizing chamber of the power unit and a secondary pressurizing chamber of the pump unit. The liquefied gas fuel in the fuel tank is pressurized and sent out by the volume variation of the pump chamber due to the deformation or movement of the isolating means, the liquefied gas fuel stored in the fuel tank is pressurized, and the fuel injection valve remains liquid. Liquid to send In the fuel pump of the gas fuel supply apparatus, the power section includes a power transmission chamber that houses the power transmission means, and the power transmission chamber communicates with the primary pressurizing chamber and is filled with hydraulic oil. The hydraulic oil chamber is used as lubricating oil for the power transmission means, and a hydraulic oil chamber that holds a predetermined amount of hydraulic oil and constantly receives the fuel vapor pressure in the gas phase of the fuel tank communicates with the power transmission chamber. The fuel pump is provided so that the fuel vapor pressure is constantly applied to the hydraulic oil in the power transmission chamber . The communication between the power transmission chamber and the primary pressurizing chamber is such that the communication hole penetrating from the outer peripheral side of the piston inserted into the cylinder hole drilled from the power transmitting chamber side to the primary pressurizing chamber side is the piston stroke. The fuel pump according to claim 1 , wherein the fuel pump is opened to the power transmission chamber side at a predetermined timing. The inlet-side check valve of the pump unit is mechanically opened and closed at a predetermined timing by a valve opening / closing means using a predetermined power source, and an electric motor is used as a drive source for the power unit. a fuel pump, the valve opening and closing means is a fuel pump, as described in the inlet side according to claim 1 or 2 which is intended for opening and closing the check valve by a cam mechanism which utilizes the rotation of the electric motor. 4. The fuel pump according to claim 3, wherein the valve opening / closing means by the cam mechanism communicates with a hydraulic oil introduction portion and uses the hydraulic oil as lubricating oil for the cam .

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