Fuel supply pump

Abstract

To inhibit a piston of a discharge valve of a fuel supply pump from being inclined, and suppress reverse flow of fuel from a common rail side to a compression chamber side.SOLUTION: In a fuel supply pump (10) equipped with a suction valve (63) for introducing fuel to a compression chamber (77) and a discharge valve (80) for discharging fuel compressed in the compression chamber (77), the discharge valve (80) includes: a piston (81) having an abutment part (82) that abuts against a valve seat part (61e), which is held slidably in a valve insertion hole (61d); a retainer (91) held in the valve insertion hole (61d); and a spring (99) sandwiched by the piston (81) and the retainer (91) for energizing the piston (81) toward the valve seat part (61e). Part of the piston (81) is supported by the retainer (91) in a slidable manner.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a fuel supply pump.

Background Art

[0002] As a fuel injection system for injecting fuel into an internal combustion engine, a common rail fuel injection system (also referred to as a common rail system) that supplies fuel to a plurality of fuel injection valves via a common rail (accumulator) that accumulates pressurized fuel is known. In the common rail system, a low-pressure pump sends the fuel in the fuel tank to the fuel supply pump, and the fuel supply pump pressurizes the fuel and pumps it to the common rail.

[0003] The fuel supply pump includes a suction valve that is opened when the volume of a pressurizing chamber for pressurizing fuel expands and supplies low-pressure fuel to the pressurizing chamber, and a discharge valve that is opened when the pressure of the fuel pressurized in the pressurizing chamber exceeds a predetermined pressure and discharges high-pressure fuel. For example, as shown in Patent Document 1, the discharge valve employs a check valve structure that blocks the flow of fuel from the common rail side to the pressurizing chamber side in order to maintain the pressure in the common rail.

[0004] FIG. 5 is a schematic diagram showing a configuration example of a discharge valve having a check valve structure provided in a conventional fuel supply pump. The discharge valve 180 is assembled in a valve insertion hole 155 that is continuously formed in a discharge oil passage 153 that communicates with a pressurizing chamber (not shown) provided in the plunger barrel 151. The discharge valve 180 includes a piston 161, a retainer 171, and a spring 179.

[0005] The piston 161 has a head 163 having a contact portion 162 that contacts a valve seat portion 157 formed at a step portion at the boundary between the discharge oil passage 153 and the valve insertion hole 155, a large-diameter portion 164 that is continuously provided on the head 163 and whose outer peripheral surface slides on the inner peripheral surface of the valve insertion hole 155, and an internal hole 165 that opens at an end on the large-diameter portion 164 side. A communication hole 166 that communicates the outer peripheral surface of the head 163 and the internal hole 165 is formed in the head 163.

[0006] The retainer 171 has an outer peripheral surface that contacts the inner peripheral surface of the valve insertion hole 155 and is press-fitted and fixed into the valve insertion hole 155. The retainer 171 has an internal hole 173 that opens at both ends. The spring 179 is sandwiched between a stepped portion formed in the internal hole 165 of the piston 161 and a stepped portion formed in the internal hole 173 of the retainer 171 and is disposed across the internal hole 165 of the piston 161 and the internal hole 173 of the retainer 171. The spring 179 constantly biases the piston 161 toward the valve seat portion 157.

[0007] The discharge valve 180 opens when the force that tries to separate the piston 161 from the valve seat portion 157 due to the pressure of the pressurized fuel exceeds the biasing force of the spring 179 and the force that presses the piston 161 against the valve seat portion 157 due to the pressure on the common rail side (not shown), and discharges high-pressure fuel.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Here, when the discharge valve 180 is configured using a piston-type valve body instead of a ball-type valve body as exemplified in FIG. 5, the piston 161 may tilt and slide with respect to the axial direction. When the piston 161 slides in a tilted state, the sliding portion wears and the sliding friction resistance increases, delaying the closing of the discharge valve 180. If the closing of the discharge valve 180 is delayed, a part of the high-pressure fuel pumped to the common rail side may flow back to the pressure chamber side, possibly reducing the pressure in the common rail. As a result, the fuel injection amount may be insufficient, and there is a possibility that the torque required for the internal combustion engine cannot be output.

[0010] The present invention has been made in view of the above problems, and provides a fuel supply pump capable of suppressing the inclination of the piston of the discharge valve and suppressing the backflow of fuel from the common rail side to the pressure chamber side.

Means for Solving the Problems

[0011] In order to solve the above problems, according to an aspect of the present invention, in a fuel supply pump including a suction valve for introducing fuel into a pressure chamber and a discharge valve for discharging the fuel pressurized in the pressure chamber, the discharge valve has a contact portion that contacts a valve seat portion, a piston slidably held in a valve insertion hole, a retainer held in the valve insertion hole, and a spring sandwiched between the piston and the retainer and biasing the piston toward the valve seat portion, and a fuel supply pump is provided in which a part of the piston is slidably supported by the retainer.

Effects of the Invention

[0012] As described above, according to the present invention, it is possible to suppress the inclination of the piston of the discharge valve and suppress the backflow of fuel from the common rail side to the pressure chamber side.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0014] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and drawings, components having substantially the same functional configuration are denoted by the same reference numerals, and redundant descriptions are omitted.

[0015] <1. Fuel injection system> First, an example of a fuel injection system for an internal combustion engine to which a fuel supply pump according to an embodiment of the present disclosure can be applied will be described.

[0016] FIG. 1 shows a configuration example of a fuel injection system 1 of a diesel engine including a fuel supply pump according to the present embodiment. The fuel injection system 1 is configured as a common rail system including a common rail 19. In the present embodiment, the internal combustion engine is a diesel engine, but the type of the internal combustion engine is not particularly limited.

[0017] The fuel injection system 1 includes a fuel tank 3, a feed pump (low-pressure pump) 5 that discharges fuel from the fuel tank 3, a fuel supply pump (high-pressure pump) 10 that pressurizes and pumps the fuel, a common rail 19 that accumulates the fuel pumped from the fuel supply pump 10, and a fuel injection valve (injector) 30 that injects the fuel distributed by the common rail 19 into the cylinders of the internal combustion engine.

[0018] The feed pump 5 has a function of discharging the fuel (diesel oil) in the fuel tank 3 and supplying it to the fuel supply pump 10 via the low-pressure passage 7. The feed pump 5 may be an electric pump or a gear pump that is rotationally driven by the power of the internal combustion engine. The low-pressure passage 7 is provided with a filter 9 between the feed pump 5 and the fuel supply pump 10.

[0019] The fuel supplied from the feed pump 5 has its flow rate controlled by the proportional control valve 13 and is supplied to the pressurizing chamber of the fuel supply pump 10. The surplus fuel is discharged into the return passage 25 via an overflow valve (not shown) provided in parallel with the proportional control valve 13 and is refluxed to the fuel tank 3. The fuel supply pump 10 is rotationally driven by the power of the internal combustion engine, pressurizes the fuel supplied to the pressurizing chamber, and pumps it toward the common rail 19 via the high-pressure fuel passage 15.

[0020] The common rail 19 accumulates the fuel pumped from the fuel supply pump 10, brings it to a high-pressure state, and distributes it to each fuel injection valve 30 at a uniform pressure. The common rail 19 is provided with a pressure sensor 21 for detecting the pressure in the common rail 19 (also referred to as the "rail pressure") and a pressure regulating valve 23 for regulating the rail pressure. The control device 17 controls the drive of the proportional control valve 13 to control the flow rate of the high-pressure fuel supplied to the common rail 19, and controls the drive of the pressure regulating valve 23 so that the rail pressure detected by the pressure sensor 21 becomes a desired pressure. The fuel discharged via the pressure regulating valve 23 is refluxed to the fuel tank 3 via the return passage 29.

[0021] The high-pressure fuel distributed from the common rail 19 to each fuel injection valve 30 flows into a pressure control chamber (not shown) of the fuel injection valve 30. The high-pressure fuel flowing into the pressure control chamber biases the valve body in the direction of closing the injection holes. By discharging a part of the high-pressure fuel in the pressure control chamber, the biasing force of the valve body is weakened, and fuel is injected from the injection holes into the cylinder of the internal combustion engine. The control device 17 controls the drive of the fuel injection valve 30 based on the rail pressure and the target injection amount. At this time, the fuel discharged from the pressure control chamber is refluxed to the fuel tank 3 via a return passage (return pipe) 27 connected to the fuel injection valve 30.

[0022] <2. Fuel Supply Pump> Subsequently, a configuration example of the fuel supply pump according to the present embodiment will be described.

[0023] Figure 2 is a cross-sectional view showing the main part of the fuel supply pump 10. In the following description, when referring to the up, down, left, and right directions, it indicates the up, down, left, and right directions in the drawing, and does not indicate the vertical and horizontal directions in the operating state of the fuel supply pump.

[0024] In the illustrated fuel supply pump 10, a pump unit 55 is assembled in a cylinder 53 formed in a pump housing 51. The pump housing 51 has a cam chamber 52 in which a cam 59 is rotatably disposed, and a cylinder 53 provided in communication with the cam chamber 52. The cylinder 53 is formed to extend in a direction orthogonal to the rotation axis of the cam 59. The cam 59 is located below the cylinder 53.

[0025] The pump unit 55 includes a plunger barrel 61, a suction valve 63, a discharge valve 80, a plunger 57, a spring seat 65, a tappet spring 67, and a tappet 69, respectively.

[0026] The plunger barrel 61 is attached to the cylinder 53. The plunger barrel 61 has a plunger sliding hole 61a that slidably supports the plunger 57, and a valve insertion hole 61b that is continuously provided from the plunger sliding hole 61a and to which the suction valve 63 is attached. Further, the plunger barrel 61 has a discharge oil passage 61c that extends in a direction intersecting the axial direction of the plunger sliding hole 61a, and a valve insertion hole 61d that is continuously provided in the discharge oil passage 61c and to which the discharge valve 80 is attached.

[0027] The spring seat 65 is locked to the lower end portion of the plunger 57. The lower end portion of the plunger 57 abuts on the upper surface of the tappet 69. The tappet spring 67 is provided sandwiched between the plunger barrel 61 and the spring seat 65, and biases the plunger 57 downward. The lower end of the tappet spring 67 abuts on the outer edge portion of the spring seat 65.

[0028] The tappet 69 is interposed between the plunger 57 and the cam 59 and is slidably provided within the cylinder 53. The tappet 69 includes a tappet body 71 and a roller 75. The spring seat 65 is arranged in contact with the upper surface of the tappet body 71. The roller 75 is rotatably held at the lower part of the tappet body 71. The tappet 69 pushes up the plunger 57 against the biasing force of the tappet spring 67 as the cam 59 rotates.

[0029] A part of the plunger sliding hole 61a is partitioned by the upper surface of the plunger 57 and the lower surface of the intake valve 63 to form a pressurizing chamber 77. The discharge oil passage 61c is provided at a position facing the pressurizing chamber 77.

[0030] As the tappet 69 and the plunger 57 move downward due to the biasing force of the tappet spring 67 as the cam 59 rotates, the volume of the pressurizing chamber 77 expands. At this time, while the discharge valve 80 is closed, the intake valve 63 is opened and fuel is inhaled into the pressurizing chamber 77. Also, as the tappet 69 and the plunger 57 move upward against the biasing force of the tappet spring 67 as the cam 59 rotates, the volume of the pressurizing chamber 77 shrinks and the fuel in the pressurizing chamber 77 is pressurized. At this time, while the intake valve 63 is closed, the discharge valve 80 is opened and high-pressure fuel is pumped toward the common rail 19.

[0031] Figure 3 is a cross-sectional view showing the discharge valve 80 assembled to the plunger barrel 61, and Figure 4 is a perspective view showing the components of the discharge valve 80. The discharge valve 80 is assembled into a valve insertion hole 61d provided in the plunger barrel 61. The discharge valve 80 includes a piston 81, a retainer 91, and a spring 99.

[0032] The piston 81 has a contact portion 82 that contacts a valve seat portion 61e formed at a stepped portion at the boundary between the discharge oil passage 61c and the valve insertion hole 61d, and is slidably held within the valve insertion hole 61d. The piston 81 has a head portion 83 having the contact portion 82, a sliding portion 84 that is continuously provided to the head portion 83 and whose outer peripheral surface slides with the inner peripheral surface of the valve insertion hole 61d, and a piston small-diameter portion 86 provided on the side opposite to the head portion 83 with the sliding portion 84 interposed therebetween. Further, the piston 81 has a piston internal hole 87 that opens at the end on the piston small-diameter portion 86 side, and a communication hole 88 that communicates the outer peripheral surface of the head portion 83 and the piston internal hole 87. One or a plurality of notches 85 through which fuel can pass are provided on the outer peripheral surface of the sliding portion 84.

[0033] The retainer 91 includes a retainer large-diameter portion 93 that contacts the inner peripheral surface of the valve insertion hole 61d, a retainer small-diameter portion 92 provided on the piston 81 side relative to the retainer large-diameter portion 93, and a retainer internal hole 94 that opens at the ends on the retainer large-diameter portion 93 side and the retainer small-diameter portion 92 side, respectively. The piston small-diameter portion 86 of the piston 81 is inserted into the retainer internal hole 94 from the end on the retainer small-diameter portion 92 side and is slidably supported.

[0034] The spring 99 is disposed so as to surround the retainer small-diameter portion 92, and is sandwiched by a first stepped portion 89 formed by the sliding portion 84 and the piston small-diameter portion 86, and a second stepped portion 95 formed by the retainer large-diameter portion 93 and the retainer small-diameter portion 92. The spring 99 constantly biases the piston 81 toward the valve seat portion 61e.

[0035] The discharge valve 80 opens when the force that attempts to separate the piston 81 from the valve seat portion 61e due to the pressure of the fuel pressurized within the pressurizing chamber 77 exceeds the biasing force of the spring 99 and the force that presses the piston 81 against the valve seat portion 61e due to the pressure on the common rail side (not shown), and discharges the high-pressure fuel.

[0036] In the fuel supply pump 10 according to this embodiment, the spring 99 of the discharge valve 80 is arranged on the outer peripheral side of the piston 81 and the retainer 91, and the advance and retreat movement of the piston 81 is guided by the retainer internal hole 94 of the retainer 91. Therefore, as shown in FIG. 3, the length L of the sliding portion when the piston 81 moves forward and backward can be made longer than the length L of the sliding portion according to the configuration of the conventional discharge valve 180 shown in FIG. 5. Therefore, when the clearance of the sliding portion is formed with the same design accuracy, the inclination of the piston 81 can be suppressed.

[0037] Specifically, in the discharge valve 180 of the conventional fuel supply pump shown in FIG. 5, the piston 161 and the retainer 171 are arranged side by side in the axial direction without fitting together, and the spring 179 is arranged inside the piston 161 and the retainer 171. For this reason, the length L of the sliding portion of the piston 161 is restricted. On the other hand, in the discharge valve 80 of the fuel supply pump 10 according to this embodiment, the spring 99 is arranged on the outer peripheral side of the piston 81 and the retainer 91, and the piston 81 is slidably supported by the retainer internal hole 94 of the retainer 91. Therefore, the axial length of the piston small diameter portion 86 of the piston 81 can be increased without changing the overall length of the discharge valve 80, and the length L of the sliding portion of the piston 81 can be increased. Therefore, the inclination angle of the piston 81 can be reduced.

[0038] Note that since the notch 85 is provided in the sliding portion 84 of the piston 81, when the piston 81 moves and the spring 99 is compressed, the fuel existing in the space where the spring 99 is arranged can be discharged to the head 83 side. Therefore, it is possible to prevent the resistance from increasing when the piston 81 moves and the discharge valve 80 opens.

[0039] <3. Effects> Subsequently, the effects of the fuel supply pump 10 according to this embodiment will be described.

[0040] The fuel supply pump 10 according to this embodiment includes a suction valve 63 for introducing fuel into the pressurizing chamber 77 and a discharge valve 80 for discharging the fuel pressurized in the pressurizing chamber 77. The discharge valve 80 has a contact portion 82 that contacts the valve seat portion 61e, a piston 81 slidably held in the valve insertion hole 61d, a retainer 91 held in the valve insertion hole 61d, and a spring 99 that is sandwiched between the piston 81 and the retainer 91 and biases the piston 81 toward the valve seat portion 61e. A part of the piston 81 is slidably supported by the retainer 91.

[0041] Therefore, without changing the design of the plunger barrel 61 or the overall length of the discharge valve 80, the axial length of the piston small diameter portion 86 of the piston 81 can be increased, and the length L of the sliding portion of the piston 81 can be increased. Accordingly, the inclination angle of the piston 81 can be reduced, and wear of the sliding portion can be suppressed. Thereby, an increase in the sliding frictional resistance of the piston 81 is suppressed, and backflow of fuel from the common rail side to the pressurizing chamber side can be suppressed.

[0042] Further, in the fuel supply pump 10 according to this embodiment, the piston small diameter portion 86 of the piston 81 is inserted into the retainer inner hole 94 of the retainer 91 and is slidably supported. For this reason, the step formed in the passage of the high-pressure fuel formed by the piston inner hole 87 of the piston 81 and the retainer inner hole 94 of the retainer 91 is reduced, and the resistance to the flow of fuel can be reduced.

[0043] Further, in the fuel supply pump 10 according to this embodiment, the spring 99 is arranged so as to surround the periphery of the retainer small diameter portion 92, and is sandwiched by a first step portion 89 formed by the sliding portion 84 and the piston small diameter portion 86 and a second step portion 95 formed by the retainer large diameter portion 93 and the retainer small diameter portion 92. For this reason, compared with the configuration of the conventional discharge valve 180 shown in FIG. 5, the diameter of the spring 99 is increased, and the stability during expansion and contraction of the spring 99 can be enhanced.

[0044] Also, in the fuel supply pump 10 according to the present embodiment, the retainer 91 has a retainer small-diameter portion 92 and a retainer large-diameter portion 93. Therefore, when the retainer 91 is press-fitted into the valve insertion hole 61d, it is possible to prevent the retainer 91 from being press-fitted in the wrong direction.

[0045] As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is obvious that those having ordinary knowledge in the technical field to which the present invention pertains can conceive of various modification examples or correction examples within the scope of the technical idea described in the claims, and these are naturally understood to belong to the technical scope of the present invention.

Explanation of Reference Numerals

[0046] 10: Fuel supply pump 51: Pump housing 61: Plunger barrel 61c: Discharge oil passage 61d: Valve insertion hole 61e: Valve seat portion 77: Pressurization chamber 80: Discharge valve 81: Piston 82: Contact portion 83: Head 84: Sliding portion 85: Notch 86: Piston small-diameter portion 87: Piston internal hole 88: Communication hole 89: First stepped portion 91: Retainer 92: Retainer small-diameter portion 93: Retainer large-diameter portion 94: Retainer internal hole 95: Second stepped portion 99: Spring

Claims

1. In a fuel supply pump (10) including an intake valve (63) for introducing fuel into a pressurizing chamber (77) and a discharge valve (80) for discharging the fuel pressurized in the pressurizing chamber (77), the discharge valve (80) has a contact portion (82) that contacts a valve seat portion (61e), a piston (81) slidably held in a valve insertion hole (61d), a retainer (91) held in the valve insertion hole (61d), and a spring (99) sandwiched between the piston (81) and the retainer (91) and biasing the piston (81) toward the valve seat portion (61e). A part of the piston (81) is slidably supported by the retainer (91). A fuel supply pump.

2. The piston (81) includes a head portion (83) having the contact portion (82), a sliding portion (84) having an outer peripheral surface that slides on the inner peripheral surface of the valve insertion hole (61d), a piston small diameter portion (86) provided on the side opposite to the head portion (83) with the sliding portion (84) interposed therebetween, a piston internal hole (87) opening at an end on the piston small diameter portion (86) side, and a communication hole (88) communicating the outer peripheral surface of the head portion (83) and the piston internal hole (87). The retainer (91) includes a retainer large diameter portion (93) in contact with the valve insertion hole (61d), a retainer small diameter portion (92) provided closer to the piston (81) than the retainer large diameter portion (93), and a retainer internal hole (94) opening at an end on the retainer large diameter portion (93) side and an end on the retainer small diameter portion (92) side, respectively. The piston small diameter portion (86) is inserted into the retainer internal hole (94) from an end on the retainer small diameter portion (92) side and is slidably supported. The fuel supply pump according to claim 1.

3. The spring (99) is disposed so as to surround the retainer small diameter portion (92), and is sandwiched between a first step portion (89) formed by the sliding portion (84) and the piston small diameter portion (86) and a second step portion (95) formed by the retainer large diameter portion (93) and the retainer small diameter portion (92). The fuel supply pump according to claim 2.

Images