JP2011226327A - Fuel feeder for gas engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel feeder for a gas engine adapted to reduce an amount of fuel that leaks out to a cam housing of a fuel pump and to prevent the life of the pump from being shortened without bringing about a rise of cost.SOLUTION: The fuel pump includes, in a reciprocatingly displaceable manner, a diaphragm 304 which air- and liquid-tightly partitions between a cam housing 301 side, the cam housing 301 being eccentrically extended from an outer periphery of a plunger 302, and a fuel compression chamber 300 side, in which a leakage fuel reservoir chamber 305 is formed on the fuel compression chamber 300 side across the diaphragm 304, a fuel carry-back passage 306 is formed to extend from the leakage fuel reservoir chamber 305 to communicate with an interior of a fuel tank 2, and a gas-phase connection tubing is formed to extend from a space on the cam housing 301 side to communicate with an interior of the fuel tank across the diaphragm 304.

Description

  The present invention relates to a fuel supply device for a gas engine, and in particular, a fuel supply device that includes a plunger reciprocating fuel pump in the middle of a fuel supply pipe connecting a fuel tank and a fuel injection valve to supply fuel to the gas engine. About.

  2. Description of the Related Art Conventionally, a plunger reciprocating type fuel pump that converts the rotation of a cam shaft by a predetermined driving means into a linear reciprocating operation of a plunger and pumps fuel is known. Of the fuel supply devices that are equipped with such a fuel pump and inject and supply fuel to the intake passage of the engine, light oil is used as fuel, and the light oil itself has a predetermined viscosity. It also serves as a lubricant between the cylinders, and the leakage of fuel to the cam chamber side is not a problem.

  On the other hand, in a fuel supply device for a gas engine using a liquefied gas fuel such as LPG (liquefied petroleum gas) or DME (dimethyl ether), the viscosity of the fuel is significantly lower than that of the aforementioned light oil. It is known that even if a rod seal is provided, the fuel leaks from the fuel pressurizing chamber side through the gap between the plunger and the cylinder to the cam chamber side, and the lubricity in the cam chamber tends to be impaired.

  For example, since DME has a low boiling point and is easy to vaporize, it is necessary to maintain a relatively high pressure in the fuel supply passage. It is said that the lubricant such as grease injected into the rolling bearing and the cam bearing is washed away, and the lubricity of the bearing portion is remarkably deteriorated to greatly impair the pump life.

  In response to this problem, Japanese Patent Application Laid-Open No. 6-173811 discloses another fuel oil having higher viscosity and lubricity than the fuel to be supplied in the fuel supply apparatus using the low-viscosity and low-lubrication liquefied gas fuel. It has been proposed that the pump pressurizes, and that the pressurized hydraulic oil is introduced into the hydraulic oil chamber of another diaphragm device arranged in the fuel supply path, and the fuel is pressurized via the diaphragm. The pump life is easy to ensure while reducing the amount of fuel leakage.

  Japanese Patent Application Laid-Open No. 10-281029 provides a passage connecting the plunger lower chamber of the fuel pump and the combustion chamber side of the engine, and this passage opens in the engine intake stroke, and passes through the gap between the plunger and the cylinder. It has also been proposed that fuel (DME) to be sucked into the intake passage before reaching the cam chamber.

  However, the fuel supply device described in the former patent document tends to be disadvantageous in terms of cost because it uses many parts and has a complicated structure. On the other hand, the fuel supply device described in the latter patent document has a large amount of fuel flowing into the plunger lower chamber in addition to the positive pressure gas fuel vaporized when the engine is stopped easily leaking to the outside through the intake passage. As a result, the sealing performance on the outer periphery of the plunger is likely to deteriorate, and therefore it is not possible to completely prevent the fuel from leaking from the plunger lower chamber to the cam chamber.

JP-A-6-173811 JP-A-10-281029

  The present invention is intended to solve the above-described problems, and in a fuel supply device for a gas engine, the amount of fuel leaking into the cam chamber of the fuel pump is reduced without increasing the cost, and the pump It is an object to be able to avoid shortening the service life.

  In order to solve the above-described problems, the present invention provides a fuel supply pipe extending from a fuel tank to an injector, a plunger reciprocating fuel pump disposed in the middle of the fuel supply pipe, A fuel supply system that has a leaked fuel recovery passage for returning the fuel that has entered the gap between the cylinder inner peripheral surface and the plunger outer peripheral surface to the fuel tank, and supplies the fuel to the gas engine by pumping the fuel to the injector by driving the fuel pump In the apparatus, the fuel pump reciprocates a diaphragm that extends in the centrifugal direction from the outer periphery of the plunger and divides the diaphragm between the cam chamber side and the fuel pressurizing chamber side in a gas-liquid tight manner following the reciprocating operation of the plunger. A space for storing leaked fuel is formed on the outer periphery of the plunger on the fuel pressurizing chamber side with the diaphragm in between. Since the extended leak fuel return passage communicating with the interior fuel tank, a gas phase connecting passage from the space of the cam chamber side across the diaphragm has to communicate with each other extends to the inside of the fuel tank.

  As described above, the fuel leaks to the cam chamber side by a simple configuration in which a diaphragm that gas-liquid-tightly partitions between the fuel pressurizing chamber side and the cam chamber side is provided on the outer periphery of the plunger of the fuel pump. This makes it possible to reliably avoid this, and by connecting both spaces partitioned by the diaphragm to the inside of the fuel tank, the pressure in both spaces sandwiching the diaphragm is balanced and the diaphragm is protected from damage due to pressure. be able to.

  In this case, the leaked fuel recovery passage is connected / communicated to the liquid phase portion of the fuel tank, and the gas phase connecting passage is connected / communicated to the gas phase portion of the fuel tank. In this case, it is easy to maintain the pressure balance in both spaces sandwiching the diaphragm while avoiding the backflow of liquid phase fuel to the cam chamber side and the backflow of gas phase fuel to the fuel pressurization chamber side.

  Further, in the above-described fuel supply device for a gas engine, the leaked fuel recovery passage and the gas phase connecting passage are connected by a bypass pipe, and the bypass pipe is directed from the gas phase connecting passage side to the leaked fuel recovery passage side. If a check valve that allows flow and blocks reverse flow is provided, it is easier to maintain a balanced pressure in both spaces sandwiching the diaphragm.

  According to the present invention in which a diaphragm for dividing the fuel pressurizing chamber side and the cam chamber side is provided on the outer periphery of the plunger of the fuel pump so that both spaces sandwiching the diaphragm communicate with the fuel tank side, respectively, and the cost increases with a simple configuration. In addition, the amount of fuel leaking into the cam chamber can be reduced, and the shortening of the pump life can be reliably avoided.

1 is a layout view of a fuel supply system for a gas engine in which a fuel supply device according to an embodiment of the present invention is provided. It is a fragmentary longitudinal cross-sectional view of the fuel pump of the fuel supply apparatus of FIG.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 shows a layout view of a fuel supply system of a gas engine 1 provided with a fuel supply device 3 of the present embodiment. In the intake passage 10 of the gas engine 1, injectors 12a, 12b, 12c, and 12d are disposed. A fuel supply pipe 31 extending from the fuel tank 2 includes a fuel pump 30 in the middle of the fuel rail 11 and the fuel rail 11. The liquefied gas fuel such as LPG and DME stored in the fuel tank 2 is pumped and injected into the intake passage 10.

  A fuel pump 30, a fuel supply pipe 31 that extends from the fuel tank 2 and is connected to the injectors 12 a, 12 b, 12 c, and 12 d and a leaked fuel recovery passage / gas phase connection passage that will be described later And connecting the fuel tank 2 to the fuel tank 2 and the low-pressure pump 35 disposed upstream of the fuel pump 30 constitute the fuel supply device 3 of the present embodiment.

  The fuel pump 30 disposed in the middle of the fuel supply pipe 31 is a plunger reciprocating pump, and returns the fuel that has entered the gap between the cylinder inner peripheral surface and the plunger outer peripheral surface from the fuel pressurizing chamber to the fuel tank 2. The fuel return pipe 32 is extended and connected to the upstream side of the low pressure pump 35 of the fuel supply pipe 31, and the leaked fuel recovery passage from the fuel pump 30 is substantially connected to and communicated with the fuel tank 2. It has become.

  FIG. 2 is an enlarged partial longitudinal sectional view for explaining the detailed configuration of the fuel pump 30 of FIG. As described above, in the conventional fuel supply device, it is difficult to prevent the fuel from leaking to the cam chamber through the gap between the cylinder inner peripheral surface and the plunger outer peripheral surface of the fuel pump. Accordingly, in the present invention, a diaphragm 304 that partitions the cam chamber 301 side and the fuel pressurization chamber 300 side in a gas-liquid tight manner is provided on the outer peripheral portion of the plunger 303 of the fuel pump 30. In this configuration, the fuel that has entered the gap on the outer peripheral surface is completely prevented from entering the cam chamber 301.

  The diaphragm 304 extends from the outer peripheral surface on the distal end side of the plunger 303 in the centrifugal direction of the plunger central axis, and is an inner peripheral surface of a space formed in a disk shape having a diameter larger than the inner diameter of the cylinder on the distal end opening side of the cylinder 302. The space formed on the fuel pressurization chamber 300 side across the diaphragm 304 is slidable by the plunger 303. It is a donut disk shape having a width that allows a reciprocating displacement operation of the diaphragm 304 following the operation, and serves as a leaked fuel storage chamber 305 for temporarily storing leaked fuel.

  A fuel return passage 306 extends from the leaked fuel storage chamber 305, and this constitutes a leaked fuel recovery passage together with the fuel return pipe 32, and is connected to and communicated with the liquid phase portion of the fuel tank 2. Therefore, even if the fuel to be used has a low viscosity like DME and passes through a relatively large amount of clearance between the inner peripheral surface of the cylinder 302 and the outer peripheral surface of the plunger 303, this is temporarily stored in the leak fuel storage chamber 305. At the same time, since the fuel can be returned to the fuel tank 2 via the fuel return passage 306, it is possible to completely prevent the leaked fuel from leaking to the cam chamber 301.

  Further, in this fuel supply device 3, as shown in FIG. 1, a gas phase communication pipe 33 serving as a gas phase connecting passage that connects the gas phase portion of the cam chamber 301 and the gas phase portion of the fuel tank 2 is provided in the fuel tank 2. It is connected to and communicated with the phase part. As a result, the pressures in the two spaces sandwiching the diaphragm 304 are balanced, and the diaphragm 304 can be protected from damage due to the pressure, thereby making it easy to avoid shortening the device life.

  As described above, the gas phase communication pipe 33 is connected to the gas phase portion of the fuel tank 2, and the fuel return pipe 32 is connected to the liquid phase portion of the fuel tank 2. The pressure balance between the two spaces sandwiching the diaphragm 304 is easily maintained while avoiding the backflow of fuel and the backflow of gas-phase fuel to the fuel pressurizing chamber 300 side.

  Further, in the present embodiment, as shown in FIG. 1, the fuel return pipe 32 and the gas phase communication pipe 33 are connected by a bypass pipe 36, and fuel leaked from the gas phase connecting passage side in the middle of the bypass pipe 36. A check valve 36a is provided as a check valve that allows the flow toward the recovery passage and blocks the reverse flow, and the balance of the pressures in both spaces sandwiching the diaphragm 304 is more easily maintained.

  Then, when the cam shaft 301a of the cam chamber 301 is rotationally driven, the plunger 303 reciprocally slides (usually in the vertical direction), and the fuel introduced into the fuel pressurizing chamber 300 through the upstream fuel supply pipe 31. And the fuel is sent to the gas engine 1 through the fuel supply pipe 31 on the downstream side. However, as the internal pressure of the fuel pressurizing chamber 300 is increased, the fuel is supplied to the inner peripheral surface of the cylinder 302 and the outer periphery of the plunger 303. Passes through the gaps in the surface.

  This leaked fuel is completely prevented from entering the cam chamber 301 by the diaphragm 304 provided on the outer periphery on the tip end side of the plunger 303, and is temporarily stored in the leaked fuel storage chamber 305 formed close to the diaphragm 304. Thereafter, the fuel is returned to the liquid phase portion of the fuel tank 2 through the fuel return passage 306 and the fuel return pipe 32 which are leaked fuel recovery passages.

  At this time, the pressure balance is maintained in both spaces sandwiching the diaphragm 304 that performs the reciprocating displacement operation, and in particular, the fuel tank 2 after the initial pump assembly by the action of the check valve 36a disposed in the bypass pipe 36. It is possible to maintain a pressure balance at the time of opening, and it is possible to reliably prevent the diaphragm 304 from being damaged. Therefore, the rotary bearings 301b and 301c attached to the camshaft 301 in the cam chamber 301 operate in a fuel gas phase (steam) atmosphere, and the lubricity is maintained for a long time without washing away the lubricant. Therefore, shortening of the pump life due to leaked fuel can be avoided.

  As described above, in the fuel supply device of the gas engine, the present invention reduces the amount of fuel leaking into the cam chamber of the fuel pump without increasing the cost and avoids shortening the pump life. be able to.

  DESCRIPTION OF SYMBOLS 1 Gas engine, 2 Fuel tank, 3 Fuel supply apparatus, 10 Intake passage, 12a, 12b, 12c, 12d Injector, 30 Fuel pump, 31 Fuel supply piping, 32 Fuel return piping, 33 Gas-phase communication piping, 36 Bypass piping, 36a Check valve, 300 Fuel pressurizing chamber, 301 Cam chamber, 302 Cylinder, 303 Plunger, 304 Diaphragm, 305 Leakage fuel storage chamber, 306 Fuel return passage

Claims (3)

A fuel supply pipe extending from the fuel tank to the injector; a plunger reciprocating fuel pump disposed in the middle of the fuel supply pipe; and a gap between the cylinder inner peripheral surface and the plunger outer peripheral surface of the fuel pump. A fuel supply passage including a leaked fuel recovery passage for returning the invaded fuel to the fuel tank, and supplying the fuel to the gas engine by pumping the fuel to the injector by driving the fuel pump. A diaphragm that extends in the centrifugal direction from the outer periphery of the plunger and divides the cam chamber side and the fuel pressurization chamber side in a gas-liquid tight manner is provided in a state that can be displaced back and forth following the reciprocation of the plunger. In addition, a space for storing leaked fuel is formed on the outer peripheral side of the plunger on the fuel pressurizing chamber side with the diaphragm interposed therebetween. A fuel recovery passage is extended to communicate with the inside of the fuel tank, and a gas phase connecting passage is extended from the space on the cam chamber side across the diaphragm to communicate with the interior of the fuel tank. Gas engine fuel supply device.   2. The leak fuel recovery passage is connected / communicatively connected to a liquid phase portion of the fuel tank, and the gas phase connecting passage is connected / communicated to a gas phase portion of the fuel tank. The gas engine fuel supply device described in 1. The leakage fuel recovery passage and the gas phase connection passage are connected by a bypass pipe, and the flow from the gas phase connection passage side to the leakage fuel recovery passage side is allowed to the bypass pipe and the reverse flow is prevented. A fuel supply device for a gas engine according to claim 1 or 2, wherein a check valve is provided.

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