JP5326993B2 - Fuel supply pump - Google Patents

Description

  The present invention relates to a fuel supply pump that supplies fuel to an engine.

  Conventionally, a fuel supply pump slidably supports a plunger in a cylinder, forms a fuel pressurization chamber at one end of the plunger, and has a cam at the other end of the plunger, and responds to the movement of the plunger. By expanding and compressing the pressurizing chamber, the fuel is sucked into the pressurizing chamber and pressurized, and the pressurized fuel is discharged from the pressurizing chamber. Here, the driving force for driving the plunger in the direction of compressing the pressurizing chamber is given by the rotation of the cam, and the cam is rotated by being driven by the engine.

  By the way, in this fuel supply pump, fuel leaks from the pressurizing chamber through a sliding gap between the cylinder and the plunger. In order to prevent the fuel leaking from the pressurizing chamber from entering the region where the cam is disposed (that is, the region lubricated by the lubricating oil), it is necessary to provide a seal structure.

  For this reason, for example, in the fuel supply pump of Patent Document 1, various seal members that are in sliding contact with the plunger are arranged in the cylinder, and a fuel recovery path is provided in the cylinder. As a result, the leaked fuel is prevented from moving toward the cam and is guided to the recovery path and recovered in a predetermined tank.

  However, when it is necessary to discharge the fuel at a high pressure exceeding 100 MPa as in the recent accumulator type fuel injection device, the temperature of the leaked fuel becomes a high temperature exceeding 100 ° C. For this reason, when a sealing member is exposed to high temperature fuel, there exists a possibility that it may deteriorate early and may not fulfill | perform a function.

JP 2003-206825 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to prevent the seal member from prematurely deteriorating due to high-temperature fuel leaking from the pressurizing chamber in the fuel supply pump. It is in.

[Means of Claim 1]
The fuel supply pump according to claim 1 is a high pressure pump that slidably supports a plunger in a cylinder to form a fuel pressurizing chamber, a cam that provides a driving force for sliding the plunger in the cylinder, A tappet that is interposed between the plunger and the cam to transmit driving force from the cam to the plunger and that is slidably supported in a predetermined housing, compresses the pressure chamber according to the rotation of the cam. Alternatively, by expanding, the fuel is discharged from the pressurizing chamber or the fuel is sucked into the pressurizing chamber.

In addition, in the specific space that is defined by the cylinder, the plunger, the housing, and the tappet, and in which the sliding gap between the cylinder and the plunger and the sliding gap between the tappet and the housing are open, a part of the fuel toward the pressurizing chamber is present. Supplied.
Thereby, a part of the fuel going to the pressurizing chamber, that is, low temperature fuel is introduced into the specific space, and the cylinder, the plunger, the housing, the tappet and the like are cooled. For this reason, even if the seal member is exposed to a high-temperature fuel, the temperature of the seal member can be lowered directly or indirectly by the low-temperature fuel, so that the seal member may deteriorate early and not perform its function. Can be eliminated.

According to the fuel supply pump of the first aspect , the seal that seals the fuel leaking from the pressurizing chamber to the cam side in the sliding contact range between the tappet and the housing due to the sliding of the plunger and the cylinder. A structure is provided. Further, the fuel leaking from the pressurizing chamber leaks into the specific space.

  In this case, the seal member is exposed to the fuel that accumulates in the specific space, but the fuel that accumulates in the specific space is a mixture of high-temperature fuel that has leaked from the pressurization chamber and low-temperature fuel that is directed to the pressurization chamber. It is a thing. For this reason, since the seal member is exposed to a lower temperature fuel than the high temperature fuel leaking from the pressurizing chamber, it is possible to eliminate the possibility that the seal member deteriorates early and does not perform its function.

  Further, according to the fuel supply pump of the first aspect, the fuel sucked into the pressurizing chamber is discharged by the low pressure pump that sucks the fuel from the fuel tank and sends it to the pressurizing chamber, and is discharged by the low pressure pump. Part of the fuel is supplied to the specific space.
  Thereby, in order to implement | achieve the function which sends a fuel into a specific space, the existing low pressure pump can be utilized.

  [Means of claim 2]
  The fuel supply pump according to a second aspect includes a plurality of high-pressure pumps, cams, and tappets, and the specific space is formed for each high-pressure pump, and the specific spaces communicate with each other.
  Thereby, fuel can move freely between each specific space. For this reason, a possibility that the fuel of a specific space may become resistance with respect to a movement of a plunger or a tappet can be eliminated.

(A) is a whole block diagram of a fuel supply pump, (b) is AA sectional drawing of (a) (Example).

  The fuel supply pump of the embodiment includes a high pressure pump that slidably supports a plunger in a cylinder to form a fuel pressurizing chamber, a cam that provides a driving force for sliding the plunger in the cylinder, and the plunger and the cam And a tappet that is slidably supported in a predetermined housing, and compresses or expands the pressurizing chamber according to the rotation of the cam. Thus, the fuel is discharged from the pressurizing chamber or the fuel is sucked into the pressurizing chamber.

In addition, in the specific space that is defined by the cylinder, the plunger, the housing, and the tappet, and in which the sliding gap between the cylinder and the plunger and the sliding gap between the tappet and the housing are open, a part of the fuel toward the pressurizing chamber is present. Supplied.
In addition, a seal structure is provided in a sliding contact range between the tappet and the housing to seal fuel leaking from the pressurizing chamber due to sliding between the plunger and the cylinder from the cam side. Further, the fuel leaking from the pressurizing chamber leaks into the specific space.

Furthermore, the fuel supply pump includes a plurality of high-pressure pumps, cams, and tappets. The specific space is formed for each high-pressure pump, and the specific spaces communicate with each other.
The fuel sucked into the pressurizing chamber is discharged by a low-pressure pump that sucks fuel from the fuel tank and sends it to the pressurizing chamber, and a part of the fuel discharged by the low-pressure pump is supplied to the specific space.

[Configuration of Example]
The structure of the fuel supply pump 1 of an Example is demonstrated based on drawing.
The fuel supply pump 1 pressurizes and discharges fuel to be injected and supplied to a vehicle engine (not shown). For example, a common rail (not shown) that stores fuel discharged from the fuel supply pump 1, A fuel injection valve (not shown) that is arranged in each cylinder of the engine and receives fuel distribution from a common rail and injects fuel, and an electronic control device (not shown) that controls the operation of the fuel supply pump 1 and the fuel injection valve. Hereinafter, the pressure accumulation type fuel injection device is configured together with the ECU.

  The fuel supply pump 1 includes a high pressure pump 5 that slidably supports a plunger 3 in a cylinder 2 to form a fuel pressurizing chamber 4, and a cam 6 that provides a driving force for sliding the plunger 3 in the cylinder 2. And a tappet 8 that is interposed between the plunger 3 and the cam 6 and transmits a driving force from the cam 6 to the plunger 3 and is slidably supported in a predetermined housing 7.

  The fuel supply pump 1 is coaxially supported by the cylinder 2 and the tappet 8 and urges the plunger 3 and the tappet 8 in a direction opposite to the driving direction by the cam 6 and a fuel tank (not shown). A low pressure pump 12 that sucks fuel from the pressure chamber 4 and sends it to the pressurizing chamber 4, and an intake metering that adjusts the fuel sucked into the pressurizing chamber 4 between the pressurizing chamber 4 and the low pressure pump 12. And a valve (hereinafter referred to as SCV) 13.

  The high-pressure pump 5 forms a pressurizing chamber 4 at the upper end in the axial direction of the plunger 3, a check valve 15 is provided on the discharge side (downstream side) of the pressurizing chamber 4, and the suction side (upstream) of the pressurizing chamber 4. A check valve (not shown) is also provided on the side. Further, the lower end of the plunger 3 is urged downward by the spring 11 via the lower seat 16 and is always in contact with the tappet 8. Then, the volume of the pressurizing chamber 4 is reduced or expanded by the plunger 3 reciprocating up and down in the axial direction of the plunger 3.

  When the plunger 3 moves upward by the driving force transmitted from the cam 6 to reduce the volume of the pressurizing chamber 4 and the fuel in the pressurizing chamber 4 is compressed, the fuel in the pressurizing chamber 4 is The check valve 15 is opened by being increased to a pressure higher than the opening pressure of the check valve 15, and the increased fuel is discharged toward the common rail. Further, when the plunger 3 moves downward by the urging force of the spring 11 to increase the volume of the pressurizing chamber 4 and the fuel in the pressurizing chamber 4 is expanded and depressurized, the check valve 15 is closed, The fuel metered by the SCV 13 is sucked into the pressurizing chamber 4.

  The high pressure pump 5 is attached to a predetermined housing 7 so that the plunger 3 is arranged coaxially with the spring 11 and the tappet 8.

  The cam 6 is provided on a cam shaft 18 that is rotationally driven by an engine. For example, the cam 6 is at the same position with respect to the axial direction of the cam shaft 18 so that the plunger 3 reciprocates up and down twice per rotation of the cam shaft 18. Two are provided opposite to each other in the radial direction. Then, when the outer peripheral surface of the cam 6 comes into contact with the roller 19 of the tappet 8, a driving force for driving the plunger 3 upward is transmitted from the cam 6 to the tappet 8.

  Here, the cam shaft 18 has its one axial end supported on the bearing cover 21 and the other axial end on the housing 7 so that the cam 6 is accommodated in a cam chamber 20 provided in the housing 7. It is pivotally supported. In other words, the cam shaft 18 and the bearing cover 21 are arranged so that the cam 6 is accommodated in the cam chamber 20 and the cam chamber 20 is sealed with one end of the cam shaft 18 in the axial direction supported by the bearing cover 21. 7 is attached.

  The cam shaft 18 is pivotally supported by the bearing cover 21 and the housing 7 via bushes 23 and 24 on one end side and the other end side in the axial direction. Lubricating oil is supplied to the cam chamber 20, and the contact between the cam 6 and the roller 19, the sliding of the tappet 8, the shaft support of the cam shaft 18 and the like are lubricated. Seal members 25 and 26 for preventing the lubricating oil from leaking from the cam chamber 20 are disposed on one axial end side of the bush 23 and the other axial end side of the bush 24, respectively.

  The tappet 8 receives the contact of the plunger 3 biased by the spring 11 and supports the lower end of the spring 11 via the lower seat 16. Further, the tappet 8 rotatably supports a roller 19 below, and the roller 19 is always in contact with the outer peripheral surface of the cam 6. As a result, the tappet 8 is integrated with the plunger 3 and is moved upward by the driving force transmitted from the cam 6, and is moved downward by being biased by the spring 11.

  The tappet 8 is slidably supported in the housing 7, and fuel leaking from the pressurizing chamber 4 through the sliding gap between the cylinder 2 and the plunger 3 together with the housing 7, the cylinder 2 and the plunger 3. A leak chamber 29 for leaking is formed. That is, a sliding gap between the cylinder 2 and the plunger 3 is opened in the leak chamber 29, and fuel leaking from the pressurizing chamber 4 leaks. The tappet 8 is slidably supported in the housing 7 and divides the leak chamber 29 and the cam chamber 20 vertically.

The spring 11 is accommodated in the leak chamber 29 and supported at the upper end by the cylinder 2, and supported at the lower end by the tappet 8 through the lower seat 16.
The low-pressure pump 12 is, for example, a well-known trochoid pump, and operates by obtaining a driving force from the engine by the cam shaft 18. Other than the bush 24 and the seal member 26 in the axial direction of the cam shaft 18. The housing 7 is mounted on the end side.
In addition, the SCV 13 operates, for example, the amount of fuel sucked into the pressurizing chamber 4 by changing the valve opening degree by controlling the energization amount to a solenoid coil (not shown) of the SCV 13 by the ECU. It is.

[Features of Examples]
The features of the fuel supply pump 1 of the embodiment will be described with reference to FIG.
According to the fuel supply pump 1 of the embodiment, the seal structure for sealing the fuel leaking from the pressurizing chamber 4 to the cam chamber 20 is provided in the sliding contact range between the tappet 8 and the housing 7. That is, since the seal structure is provided not in the sliding contact range between the cylinder 2 and the plunger 3 but in the sliding contact range between the tappet 8 and the housing 7, the sealing structure is applied via the sliding gap between the cylinder 2 and the plunger 3. The fuel leaking from the pressure chamber 4 is accumulated in the leak chamber 29.

  The seal structure is formed, for example, when the seal member 31 accommodated in the housing 7 is in sliding contact with the outer peripheral surface of the tappet 8. The housing 7 is formed with a recovery path (not shown) for recovering the fuel that has been prevented from moving toward the cam chamber 20 by the seal member 31. The recovery path is provided so as to communicate with the fuel tank, and the fuel guided to the recovery path is recovered in the fuel tank.

  Here, the seal member 31 has a well-known structure with an X-shaped cross section and an annular shape, and a predetermined seal piece is in sliding contact with the outer peripheral surface of the tappet 8, whereby the fuel from the leak chamber 29 to the cam chamber 20 is transferred. Prevents leaks. An accommodation space 32 for accommodating the seal member 31 is provided so as to open in an annular shape on the sliding contact surface 33 with the tappet 8. Further, the collection path is connected to the accommodation space 32.

  The seal member 31 is in sliding contact with the outer peripheral surface of the tappet 8, thereby preventing fuel from leaking from the leak chamber 29 to the cam chamber 20 and leaking lubricating oil from the cam chamber 20 to the leak chamber 29. Is also blocked. That is, although a sliding gap between the tappet 8 and the housing 7 is opened in the leak chamber 29, the lubricating oil in the cam chamber 20 is blocked from flowing toward the leak chamber 29 by the seal member 31.

  The fuel supply pump 1 includes a plurality of high-pressure pumps 5 and tappets 8, and further includes cams 6 at a plurality of different positions in the axial direction of the cam shaft 18. The cams 6 at the respective positions are provided so that the phases of the plunger 3 and the tappet 8 of the high-pressure pump 5 to be driven are different from each other. Moreover, the leak chamber 29 is formed for each high-pressure pump 5, and the volume of each leak chamber 29 changes differently depending on the phases of the plunger 3 and the tappet 8 that form the leak chamber 29. The leak chambers 29 adjacent to each other in the axial direction of the camshaft 18 communicate with each other through the communication path 35.

  Furthermore, each leak chamber 29 is supplied with a part of the fuel discharged from the low-pressure pump 12 and directed to the pressurizing chamber 4. That is, each leak chamber 29 is provided with a supply flow path 36 leading to the discharge side of the low pressure pump 12 and a return flow path 37 leading to the suction side of the low pressure pump 12. The supplied fuel is returned to the suction side of the low-pressure pump 12 through the return flow path 37.

  Note that the openings in the leak chamber 29 of the supply flow path 36 and the return flow path 37 are provided at positions that are not blocked by the tappet 8 even when the plunger 3 and the tappet 8 are at top dead center. The opening of the return flow path 37 is provided below the opening of the supply flow path 36 so that the fuel can easily circulate between the low pressure pump 12 and the leak chamber 29.

[Effects of Examples]
According to the fuel supply pump 1 of the embodiment, the leak chamber 29 is supplied with a part of the fuel discharged from the low pressure pump 12 toward the pressurizing chamber 4. In addition, a seal structure for sealing fuel leaking from the pressurizing chamber 4 to the cam chamber 20 is provided in a sliding contact range between the tappet 8 and the housing 7.

  When the fuel is discharged at a high pressure exceeding 100 MPa as in the pressure accumulation type fuel injection device, the temperature of the fuel leaking into the leak chamber 29 becomes a high temperature exceeding 100 ° C. For this reason, there exists a possibility that the sealing member 31 may deteriorate early and may not perform the function by being exposed to high temperature fuel.

  Therefore, a part of the fuel going to the pressurizing chamber 4, that is, a low temperature fuel is introduced into the leak chamber 29, and the temperature of the fuel in the leak chamber 29 is lowered. As a result, since the seal member 31 is exposed to a relatively low temperature fuel, it is possible to eliminate the possibility that the seal member 31 deteriorates early and does not perform its function.

The fuel supply pump 1 includes a plurality of high-pressure pumps 5, cams 6, and tappets 8, and a leak chamber 29 is formed for each high-pressure pump 5. The leak chambers 29 adjacent to each other in the axial direction of the cam shaft 18 communicate with each other.
Thereby, the possibility that the fuel in the leak chamber 29 becomes resistance to the movement of the plunger 3 and the tappet 8 can be eliminated.

Each leak chamber 29 is supplied with a part of the fuel discharged from the low-pressure pump 12 toward the pressurizing chamber 4.
Thus, the existing low-pressure pump 12 can be used to realize the function of feeding fuel into the leak chamber 29.

[Modification]
The mode of the fuel supply pump 1 is not limited to the embodiment, and various modifications can be considered. For example, according to the fuel supply pump 1 of the embodiment, the seal structure is formed by arranging the seal member 31 in the housing 7 and slidingly contacting the outer periphery of the tappet 8. It may be arranged to be brought into sliding contact with the sliding contact surface 33 of the housing 7.
Further, the fuel injection device to which the fuel supply pump 1 should be applied is not limited to the pressure accumulation type. Further, when the seal structure is provided in the sliding contact range between the tappet 8 and the housing 7, various fuels such as light oil, gasoline, and liquefied gas fuel can be supplied.

DESCRIPTION OF SYMBOLS 1 Fuel supply pump 2 Cylinder 3 Plunger 4 Pressurization chamber 5 High pressure pump 6 Cam 7 Housing 8 Tappet 12 Low pressure pump 29 Leak chamber (specific space)

Claims (2)

A high-pressure pump that slidably supports a plunger in the cylinder to form a fuel pressurization chamber;
A cam for applying a driving force for sliding the plunger in the cylinder;
A tappet interposed between the plunger and the cam to transmit a driving force from the cam to the plunger and slidably supported in a predetermined housing;
In a fuel supply pump that discharges fuel from the pressurizing chamber or sucks fuel into the pressurizing chamber by compressing or expanding the pressurizing chamber according to rotation of the cam.
The pressurizing chamber is defined in the specific space defined by the cylinder, the plunger, the housing, and the tappet, and opened by a sliding gap between the cylinder and the plunger and a sliding gap between the tappet and the housing. some of the fuel is supplied toward the,
A seal structure is provided in a sliding contact range between the tappet and the housing to seal fuel leaking from the pressurizing chamber to the cam side by sliding between the plunger and the cylinder,
Fuel leaking from the pressurizing chamber leaks into the specific space,
The fuel sucked into the pressurizing chamber is discharged by a low pressure pump that sucks fuel from a fuel tank and sends it to the pressurizing chamber.
A fuel supply pump, wherein a part of the fuel discharged by the low-pressure pump is supplied to the specific space . The fuel supply pump according to claim 1, wherein
A plurality of the high-pressure pump, the cam and the tappet, respectively,
The specific space is formed for each of the high-pressure pumps,
Each of the specific spaces communicates with each other .

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