JP2004124915A - Piston type high pressure pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piston type high pressure pump capable of suppressing an influence on a low pressure side by high pressure fluctuation in a pump chamber 17, improving the durability and reliability of a seal member 43 by easing the influence of pressure fluctuation on the seal member 43 due to a lip seal, and reducing a cost by cutting down a return line. <P>SOLUTION: This piston type high pressure pump is made by paying attention to the fact that a throttle or a pressure easing portion 52 by a check valve or a sliding clearance is provided between an suction port 14 side and the seal member 43, and the influence of the pressure changes transmitted to the seal member 43 is minimized by the pressure easing portion 52. Inlet pressure in the suction port 14 side positioned upstream to an intake valve 3 is enabled to be led to a circumferential surface of a piston 7, and the pressure easing portion 52 is provided between the suction port 14 side and the seal member 43 side contacting on the circumferential surface of the piston 7. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a piston-type high-pressure pump, and more particularly to a piston-type high-pressure pump such as a pump for gasoline and other low-viscosity fuels and other fluid pumps.
[0002]
[Prior art]
A conventional piston-type high-pressure pump (for example, Patent Document 1) will be outlined based on FIG.
FIG. 8 is a longitudinal sectional view of a piston type high pressure pump 1 applied to, for example, a high pressure gasoline pump. The piston type high pressure pump 1 is a single cylinder type high pressure gasoline pump, and includes a pump housing 2 and a suction valve. 3, a discharge valve 4, a control valve 5 by an electromagnetic valve, a piston barrel 6 (plunger barrel), a piston 7 (plunger), a tappet 8, a pump driving cam 9, and a low-pressure damper 10. Have.
[0003]
An annular suction passage 15 and a communication passage 16 are formed in the pump housing 2 from a suction port 14 (suction port) connected to the fuel tank 11, the feed pump 12 and the low-pressure regulator 13. The low pressure pulsation is reduced to reach the suction valve 3.
[0004]
The suction valve 3 faces a pump chamber 17 formed in the piston barrel 6. A high pressure port 18 is formed across the pump housing 2 and the piston barrel 6 so as to penetrate the pump chamber 17 at right angles to the reciprocating direction of the piston 7, and the discharge chamber 4 and the discharge valve 4 are connected to the pump chamber 17 via the high pressure port 18. The control valve 5 faces similarly, and the head of the piston 7 also faces the pump chamber 17.
[0005]
The discharge valve 4 enables high-pressure fuel to be discharged from a discharge port 19 (discharge port) to, for example, a common rail 20 (pressure accumulator). The common rails 20 are connected with the fuel injection valves 21 as many as the number of cylinders of the engine.
[0006]
The control valve 5 controls the timing of pumping the fuel in the pump chamber 17, in particular, starting (opening of the discharge valve 4) or ending (closing of the discharge valve 4) a solenoid 22, an armature 23, and a valve body. 24 and a seat portion 25 of the valve body 24.
When the valve body 24 is lifted from the seat portion 25, the pump chamber 17 and the annular suction passage 15 can be communicated from the pump chamber 17 via the shaft passage 26 and the suction-side communication passage 27.
[0007]
A suction pressure guide passage, an inner wall annular groove 29, and a leak hole 30 are formed in communication with the shaft passage. A circumferential groove 31 is formed in the piston 7 at a substantially middle position in the length direction in the circumferential direction, and the low pressure side passage 33 and the return port 34 are connected to the fuel tank 11 through an orifice 32 formed in the pump housing 2. It is possible to reflux.
The low-pressure side passage 33 communicates with the circumferential portion on the tappet 8 side (the lower side in the figure) from the circumferential groove 31 of the piston 7 via the leak passage 35.
Therefore, the portion of the circumferential groove 31 of the piston 7 receives the suction pressure in the annular suction passage 15 via the suction pressure guide passage 28, and the circumferential portion below the circumferential groove 31 is the fuel tank. This means that a pressure equivalent to the low pressure of the eleventh portion is received.
[0008]
Next, a first seal mechanism 36 between the pump housing 2 and the piston barrel 6, a second seal mechanism 37 between the piston 7 and the piston barrel 6, and a gap between the lower part of the piston 7 and the tappet 8 The third seal mechanism 38 will be described.
The first seal mechanism 36 seals between the high pressure section (pump chamber 9) and the suction pressure section (suction port 14 or suction passage 15), and forms a metal between the pump housing 2 and the piston barrel 6. It has a seal portion 39 (face seal portion), a high-pressure side O-ring 40, and a backup ring 41 to seal high pressure in the pump chamber 17.
[0009]
The second seal mechanism 37 seals between a suction pressure portion and a low pressure portion leaking from around the piston 7. The second seal mechanism 37 has a suction pressure side O-ring 42, and has a leak hole pressure-separated by the orifice 32. A seal is provided between 30 or the circumferential groove 31 and the low pressure side passage 33 or the leak passage 35.
[0010]
The third seal mechanism 38 seals the gap between the low-pressure section and the cam 9. The third seal mechanism 38 is provided with a seal member 43 such as a lip seal at a lower portion (below the circumferential groove 31) of the piston 7 and a pump housing 2. A low-pressure side O-ring 44 is provided between the piston barrel 6 and the piston barrel 6. Thus, a seal is provided between the spring chamber 46 accommodating the tappet spring 45 in the tappet 8 and the low-pressure side passage 33 or the leak passage 35.
[0011]
9 is an enlarged cross-sectional view of the seal member 43. The seal member 43 includes a lip portion 43A made of polytetrafluoroethylene (PTFE) or another synthetic resin, a support portion 43B made of stainless steel or another metal, To separate gasoline from the leak passage 35 or between the piston barrel 6 and the piston 7 from oil from the spring chamber 46.
[0012]
In the piston-type high-pressure pump 1 having such a configuration, there is a problem of pressure fluctuation due to its driving.
In the fuel intake stroke, the intake valve 3 is “open”, and the discharge valve 4 and the control valve 5 are “closed”. The control valve 5 closes the solenoid 22 by energizing the solenoid 22 to save driving energy.
Next, in the rising stroke (compression stroke, discharge stroke) of the piston 7, the suction valve 3 is closed, and when a predetermined valve opening pressure is reached, the discharge valve 4 is opened.
In the discharge end state, the control valve 5 is opened, and the discharge of the fuel from the discharge valve 4 ends.
In the compression stroke, by adjusting the valve opening timing of the control valve 5, the timing of the end of fluid discharge of the discharge valve 4 is controlled to adjust the discharge amount.
[0013]
Contrary to the drive for controlling the timing of the end of fluid discharge of the discharge valve 4 by adjusting the opening timing of the control valve 5 as described above, the fluid discharge of the discharge valve 4 by adjusting the closing timing of the control valve 5 Driving that controls the start timing is also possible.
[0014]
FIG. 10 is an explanatory diagram showing a graph of the discharge start timing variable control in the operation of the piston type high pressure pump 1, wherein the pressure change in the common rail 20 (I), the pressure change in the pump chamber 17 (II), and the piston type Pressure change (III) in the low-pressure line (low-pressure passage from feed pump 12 to suction port 14) outside high-pressure pump 1, and low-pressure line (suction passage 15 to suction-side communication passage 27 and shaft passage in piston-type high-pressure pump 1) 26 shows the pressure change (IV) of the low-pressure passage to 26.
As shown in the figure, in the case of this variable displacement single plunger type piston type high pressure pump 1, the control valve 5 is “open” until the fuel discharge is started. The line (low-pressure passage from the suction passage 15 to the shaft passage 26) communicates with each other, and a change in the chamber pressure of the pump chamber 17 is released to the low-pressure side, and a large pressure fluctuation occurs in the low-pressure chamber of the piston-type high-pressure pump 1. I do.
That is, even when the control valve 5 is "open" when the piston 7 is raised, the pressure fluctuation P1 occurs in the pump chamber 17, and this pressure fluctuation P1 is large in the pressure change (IV) in the low pressure line in the piston type high pressure pump 1. Pressure fluctuation P2 will be generated.
[0015]
On the other hand, from the viewpoint of the cost of the entire piston type high-pressure pump 1, it is desirable to eliminate the return port 34. However, if the return port 34 is omitted, the above-mentioned large pressure fluctuation will cause the shaft passage 26, the suction pressure induction passage 28, the inner wall annular groove, and the like. 29, the leak hole 30, the orifice 32, the low-pressure side passage 33, and the leak passage 35 act on the sealing member 43 such as a lip seal, thereby deteriorating the reliability of the sealing function.
[0016]
FIG. 11 is an explanatory diagram showing a graph of the discharge end timing variable control in the operation of the piston type high-pressure pump 1. As in FIG. 10, the pressure change in the common rail 20 (I) and the pressure change in the pump chamber 17 are changed. (II), pressure change in a low-pressure line (low-pressure passage from feed pump 12 to suction port 14) outside piston-type high-pressure pump 1 (III), and low-pressure line (suction passage 15 to suction side) in piston-type high-pressure pump 1 The pressure change (IV) of the communication passage 27 and the low-pressure passage leading to the shaft passage 26 is shown.
Also in this control, a change in the chamber pressure in the pump chamber 17 is released to the low pressure side, and a large pressure fluctuation occurs in the low pressure chamber of the piston type high pressure pump 1. That is, as shown in FIG. 11, the pressure fluctuation (high pressure spill P3) in the pump chamber 17 causes a large pressure fluctuation P4 in the pressure change (IV) in the low pressure line in the piston type high pressure pump 1.
Therefore, even in the case of the discharge end timing variable control, if the return port 34 is omitted, the large pressure fluctuation acts on the sealing member 43 such as a lip seal, which lowers the reliability.
[0017]
[Patent Document 1]
JP-A-2002-54531
[Problems to be solved by the invention]
The present invention has been made in view of the above problems, and has as its object to provide a piston-type high-pressure pump in which a return port to a fluid tank is omitted.
[0019]
Another object of the present invention is to provide a piston-type high-pressure pump capable of suppressing the influence of high-pressure fluctuations in a pump chamber on a low-pressure side and improving the reliability of a sealing member such as a lip seal.
[0020]
Another object of the present invention is to provide a piston-type high-pressure pump capable of reducing pressure fluctuations on a seal member caused by a lip seal or the like as much as possible and reducing the influence thereof.
[0021]
Another object of the present invention is to provide a piston-type high-pressure pump capable of improving the durability of a sealing member such as a lip seal or the like, and reducing the cost by reducing the number of return lines.
[0022]
Another object of the present invention is to provide a piston-type high-pressure pump capable of coping with the reliability of a seal member against pressure fluctuation with a simple configuration and at low cost.
[0023]
[Means for Solving the Problems]
That is, according to the present invention, a pressure relief portion such as a throttle or a check valve or a sliding clearance is provided between the suction port side and the seal member side (lip seal side), and the pressure relief portion transmits the pressure to the seal member and the like. It focuses on minimizing the effects of pressure fluctuations, and reciprocates in a piston barrel that forms a suction chamber and a discharge valve for a fluid, a pump chamber communicating with the suction valve and the discharge valve, and the piston barrel. Accordingly, a piston-type high-pressure pump having a piston for sucking fluid from the suction valve and discharging a fluid from the discharge valve, and a cam for driving the piston, wherein the piston is provided upstream of the suction valve. If the suction pressure on the suction port side located at Moni, and the suction port side, a piston-type high pressure pump, wherein the seal member side in contact with the circumferential surface of the piston, in that a pressure relief portion between.
[0024]
The cam reciprocates the piston via a tappet, and the seal member can seal a spring chamber accommodating a tappet spring in the tappet and the suction port side.
[0025]
The pressure relief unit can be used as a throttle.
[0026]
The pressure relief section can be used as a check valve.
[0027]
The pressure relieving section may use this as a sliding clearance between the piston and the piston barrel.
[0028]
The sealing member may be a lip seal.
[0029]
In the piston type high-pressure pump according to the present invention, a pressure relief portion such as a throttle or a check valve or a sliding clearance is provided between the seal member side such as a lip seal and the suction port side, and the pressure relief portion is used to seal the seal member and the like. Since the pressure fluctuation is minimized, the pressure acting on the seal member can be reduced, the damage to the seal member can be avoided, and the durability and reliability thereof can be improved.
Therefore, even if the piston-type high-pressure pump itself is not provided with a return port or a leak hole, an orifice, a low-pressure side passage, and a leak passage connected to the return port, the influence on the seal member is reduced and the cost is reduced. can do.
[0030]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, a piston type high pressure pump 50 according to a first embodiment of the present invention will be described with reference to FIGS. However, the same parts as those in FIGS. 8 to 11 are denoted by the same reference numerals, and detailed description thereof will be omitted.
FIG. 1 is a schematic circuit diagram of a piston-type high-pressure pump 50, and FIG. 2 is a longitudinal sectional view of the same. The piston-type high-pressure pump 50 is connected between the feed pump 12 and the common rail 20, and is controlled. By the valve 5, for example, the discharge start timing can be variably controlled.
In the piston type high-pressure pump 50, the return port 34 (FIG. 8) and the return lines such as the circumferential groove 31, the leak hole 30, the orifice 32, and the low-pressure side passage 33 communicating with the return port 34 are eliminated to reduce the cost. I am planning.
[0031]
As shown in FIG. 2 in particular, the piston type high pressure pump 50 includes a pump housing 2, a suction valve 3, a discharge valve 4, a control valve 5 including a solenoid valve, a piston It has a barrel 6 (plunger barrel), a piston 7 (plunger), a tappet 8, a cam 9 for driving a pump having three ridges, and a low-pressure damper 10.
[0032]
The suction port 14, the annular suction passage 15, and the communication passage 16 are formed in the pump housing 2, and low-pressure pulsation of the sucked fuel is reduced by the low-pressure damper 10 to reach the suction valve 3.
[0033]
The suction valve 3 faces the pump chamber 17 formed in the piston barrel 6.
The discharge valve 4 and the control valve 5 similarly face the pump chamber 17 via the high-pressure port 18, and the head of the piston 7 also faces the pump chamber 17.
[0034]
The control valve 5 controls the timing of pumping the fuel in the pump chamber 17, particularly the timing of starting (opening the discharge valve 4) or ending (closing the discharge valve 4).
That is, when the control valve 5 is de-energized and, for example, turned off, the communication between the pump chamber 17 and the annular suction passage 15 from the pump chamber 17 via the shaft passage 26 and the suction-side communication passage 27 is cut off. Thus, the discharge start timing can be variably controlled.
[0035]
The suction pressure guide passage 28 and the inner wall annular groove 29 are formed in communication with the shaft passage 26.
[0036]
In the piston type high-pressure pump 1 (FIG. 8), a circumferential groove 31 formed in the piston 7 at a substantially middle position in the longitudinal direction, a leak hole 30 formed in the piston barrel 6, and the pump housing 2 are formed. The formed orifice 32 and the low-pressure side passage 33 are omitted, and the return port 34 for returning to the fuel tank 11 is omitted.
Instead, the suction pressure side O-ring 42 is omitted, and the stepped annular groove 51 in which the suction pressure side O-ring 42 has been fitted communicates with the inner wall annular groove 29 so as to communicate with the stepped annular groove 51. A pressure relief section 52 is provided in the leak passage 35. Of course, without forming the stepped annular groove 51, the inner wall annular groove 29 may be extended downward in the drawing to communicate with the pressure relief portion 52.
[0037]
The pressure relief section 52 faces the seal member 43 from the upstream side.
Therefore, when the control valve 5 is in the open state, the circumferential portion of the piston 7 in contact with the seal member 43 passes through the suction pressure guiding passage 28, the inner wall annular groove 29, the stepped annular groove 51, and the pressure relief portion 52. This means that a pressure equal to the low pressure in the suction pressure section (the suction port 14 or the annular suction passage 15) is received.
[0038]
The first seal mechanism 36 between the pump housing 2 and the piston barrel 6 is provided with a metal seal portion 39 (face seal) between the pump housing 2 and the piston barrel 6, similarly to the piston type high pressure pump 1 (FIG. 8). ), A high-pressure side O-ring 40, and a backup ring 41 to seal the high pressure in the pump chamber 17.
[0039]
The second seal mechanism 37 between the piston 7 and the piston barrel 6 is practically not provided because the suction pressure side O-ring 42 is omitted as described above.
[0040]
A third seal mechanism 38 between the lower part of the piston 7 and the tappet 8 seals between the low-pressure part and the cam 9, and a seal member 43 such as a lip seal is provided below the piston 7. A low pressure side O-ring 44 is provided between the pump housing 2 and the piston barrel 6. Thus, a seal is provided between the spring chamber 46 accommodating the tappet spring 45 in the tappet 8 and the pressure relieving section 52.
[0041]
The pressure relieving section 52 only needs to be able to relieve the pressure applied to the seal member 43, and its specific configuration is arbitrary.
For example, FIG. 3 is an enlarged cross-sectional view illustrating an example of the pressure relief unit 52. As the configuration of the pressure relief unit 52, an orifice 53 (throttle) that connects the suction port 14 side and the seal member 43 side is adopted. Can be.
Large pressure fluctuations from the suction passage 15 side are also mitigated by the orifice 53, so that large pressure fluctuations are not transmitted to the seal member 43.
[0042]
FIG. 4 is an enlarged cross-sectional view illustrating another example of the pressure relaxation unit 52. As the configuration of the pressure relaxation unit 52, a check valve 54 can be employed.
The check valve 54 has a ball valve 56 that seats in the seat portion 55, a valve spring 57 that urges the ball valve 56 toward the seat portion 55, and a spring seat 58.
The spring setting force of the valve spring 57 is reduced to reduce the pressure difference between the suction port 14 and the seal member 43 when there is no pressure fluctuation.
Therefore, a large pressure fluctuation from the suction port 14 side is also prevented from being directly transmitted to the seal member 43 side by the check valve 54, and the pressure from the seal member 43 side is transmitted only in one direction (direction of the suction port 14). And does not transmit a large pressure fluctuation to the seal member 43.
[0043]
FIG. 5 is an explanatory view schematically showing a pressure change (IV) of a low-pressure line (a low-pressure passage from the suction port 14 to the suction-side communication passage 27 and the shaft passage 26) in the piston-type high-pressure pump 50, and is indicated by a dotted line. The large pressure fluctuation P2 in the conventional piston-type high-pressure pump 1 as shown by, is reduced as shown by the solid line.
[0044]
FIG. 6 is a longitudinal sectional view of a piston type high pressure pump 60 according to a second embodiment of the present invention. The piston type high pressure pump 60 is connected between the feed pump 12 and the common rail 20 and is controlled. The valve 5 can variably control the discharge end timing.
In the piston type high-pressure pump 60, the return port 34 and the like are omitted as in the case of the piston type high-pressure pump 50 to reduce the cost.
[0045]
The configuration of the piston type high pressure pump 60 is substantially the same as that of the piston type high pressure pump 50, but the function of the control valve 5 is opposite to that of the piston type high pressure pump 50.
That is, the control valve 5 variably controls the end of discharge by the discharge valve 4.
[0046]
In the piston-type high-pressure pump 60 having such a configuration, similarly to the piston-type high-pressure pump 50 (FIG. 2), by providing the pressure relief portion 52, the adverse effect of the pressure fluctuation on the seal member 43 can be avoided, and the leak hole 30, The cost can be reduced by omitting the circumferential groove 31, the orifice 32, the low pressure side passage 33, the return port 34, and the like.
[0047]
FIG. 7 is a longitudinal sectional view of a piston type high pressure pump 70 according to a third embodiment of the present invention. The piston type high pressure pump 70 is connected between the feed pump 12 and the common rail 20 and is controlled. The discharge start timing or the end timing of the discharge can be variably controlled by the valve 5.
In the piston-type high-pressure pump 70, as in the piston-type high-pressure pump 50 (FIG. 2), the orifice 32, the low-pressure side passage 33, the return port 34, and the like are omitted to reduce costs.
[0048]
However, in the piston type high pressure pump 70, unlike the piston type high pressure pump 50 (FIG. 2) and the piston type high pressure pump 60 (FIG. 6), the leak hole 30 of the piston barrel 6 in the piston type high pressure pump 1 (FIG. 8). And the circumferential groove 31 of the piston 7 is left. Further, similarly to the piston type high pressure pump 50 and the piston type high pressure pump 60, the orifice 32, the low pressure side passage 33 and the return port 34 are omitted, and the pressure relief part 52 is replaced with the orifice 53 (FIG. 3) and the check valve 54 (FIG. It is provided in a form different from 4).
That is, the suction pressure guide passage 28 is communicated with the leak hole 30 and the circumferential groove 31 through the inner wall annular groove 29 and the stepped annular groove 51, and the sliding clearance 71 between the circumferential groove 31 and the piston 7 is pressurized. The relaxation portion 52 is configured to transmit the low pressure leaking from the sliding clearance 71 to the seal member 43.
[0049]
In the piston-type high-pressure pump 70 having such a configuration, the return port 34 can be omitted, and a large pressure fluctuation in the low-pressure suction pressure from the suction pressure portion (the suction port 14) can be reduced by the sliding clearance 71. Thereby, the adverse effect of the pressure fluctuation on the seal member 43 can be avoided.
[0050]
【The invention's effect】
As described above, according to the present invention, since the pressure reducing portion is provided in the low-pressure passage in the piston-type high-pressure pump, pressure fluctuation in a sealing member such as a lip seal can be reduced, and its durability can be improved. This can contribute to cost reduction and improvement in reliability.
[Brief description of the drawings]
FIG. 1 is a schematic circuit diagram of a piston-type high-pressure pump 50 according to a first embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of the same.
FIG. 3 is an enlarged cross-sectional view showing one example of a pressure relaxation section 52.
FIG. 4 is an enlarged sectional view showing another example of the pressure relaxation section 52.
FIG. 5 is an explanatory view schematically showing a pressure change (III) of a low-pressure line (a low-pressure passage from the suction port 14 to the suction-side communication passage 27 and the shaft passage 26) in the piston-type high-pressure pump 50.
FIG. 6 is a longitudinal sectional view of a piston type high pressure pump 60 according to a second embodiment of the present invention.
FIG. 7 is a longitudinal sectional view of a piston type high pressure pump 70 according to a third embodiment of the present invention.
FIG. 8 is a longitudinal sectional view of a piston type high pressure pump 1 applied to a conventional high pressure gasoline pump and the like.
FIG. 9 is an enlarged cross-sectional view of the same sealing member 43.
FIG. 10 is an explanatory diagram showing a graph of discharge start timing variable control in the operation of the piston type high pressure pump 1;
FIG. 11 is an explanatory diagram showing a graph of discharge end timing variable control in the operation of the piston type high-pressure pump 1;
[Explanation of symbols]
1 Piston type high pressure pump (Fig. 8)
2 pump housing 3 suction valve 4 discharge valve 5 control valve (solenoid valve)
6. Piston barrel (plunger barrel)
7 piston (plunger)
8 Tappet 9 Pump driving cam 10 Low pressure damper 11 Fuel tank 12 Feed pump 13 Low pressure regulator 14 Suction port 15 Suction passage 16 Communication passage 17 Pump chamber 18 High pressure port 19 Discharge port (discharge port)
20 common rail (accumulator)
Reference Signs List 21 fuel injection valve 22 solenoid 23 armature 24 valve body 25 seat portion 26 shaft passage 27 suction side communication passage 28 suction pressure induction passage 29 inner wall annular groove 30 leak hole 31 circumferential groove 32 orifice 33 low pressure side passage 34 return port 35 leak passage 36 First seal mechanism 37 Second seal mechanism 38 Third seal mechanism 39 Metal seal part (face seal part)
40 High pressure side O-ring 41 Backup ring 42 Suction pressure side O-ring 43 Seal member (lip seal)
43A Lip portion of seal member 43 (FIG. 9)
43B Supporting part of seal member 43 (FIG. 9)
44 Low pressure side O-ring 45 Tappet spring 46 Spring chamber 50 Piston type high pressure pump (first embodiment, FIGS. 1 and 2)
51 Step annular groove 52 Pressure relief section 53 Orifice (restrictor, pressure relief section, FIG. 3)
54 Check valve (pressure relief part, Fig. 4)
55 Seat portion 56 Ball valve 57 Valve spring 58 Spring seat 60 Piston type high pressure pump (Second embodiment, FIG. 6)
70 piston type high pressure pump (third embodiment, FIG. 7)
71 Sliding clearance (pressure relief part)
P1 Pressure fluctuation occurring in pump chamber 17 (FIG. 10)
P2 Large pressure fluctuation in low pressure line caused by pressure fluctuation P1 (Fig. 10)
P3 Pressure fluctuation of pump chamber 17 (high pressure spill) (Fig. 11)
P4 Large pressure fluctuation in low pressure line caused by high pressure spill P3 (Fig. 11)

Claims (6)

A fluid suction valve and a discharge valve,
A piston barrel forming a pump chamber communicating with the suction valve and the discharge valve,
A piston that reciprocates in the piston barrel to perform suction of fluid from the suction valve and discharge of fluid from the discharge valve,
A piston-type high-pressure pump having a cam for driving the piston,
While allowing the suction pressure on the suction port side located upstream of the suction valve to be guided to the circumferential surface of the piston,
A piston type high pressure pump characterized in that a pressure relief portion is provided between the suction port side and the seal member side in contact with the circumferential surface of the piston. The cam reciprocates the piston via a tappet,
2. The piston type high pressure pump according to claim 1, wherein the seal member seals a spring chamber accommodating a tappet spring in the tappet and the suction port side. 2. The piston type high pressure pump according to claim 1, wherein the pressure relief section is a throttle. 2. The piston type high pressure pump according to claim 1, wherein the pressure relief unit is a check valve. The piston-type high-pressure pump according to claim 1, wherein the pressure relief portion is a sliding clearance between the piston and the piston barrel. The piston type high pressure pump according to claim 1, wherein the seal member is a lip seal.

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