JPH11257239A - Variable displacement plunger pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure a minimum supply flow rate of hydraulic operating fluid to hydraulic equipment even if a passage selector valve breaks down. SOLUTION: A plurality of pump units in a plunger pump 10 is divided into two sets, a first pump set Pa and a second pump set Pb. The discharge part of the first pump set Pa is connected direct to a discharge passage 30, while the discharge part of the second pump set Pb is connected to it via a confluent passage 27. The confluent passage 27 is provided with a check valve 32 and a branch drain passage 33 on the upstream side of the check valve 32. The drain passage 33 is provided with a solenoid valve 34 for opening or closing it. In this arrangement, even if the solenoid valve 34 breaks down, the first pump set Pa can ensure a minimum supply flow rate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plunger pump for use in a vehicle height adjusting device and the like, and more particularly, to a variable displacement plunger pump capable of arbitrarily adjusting a discharge capacity according to requirements of a hydraulic device to be used. About.

[0002]

2. Description of the Related Art As this kind of variable displacement plunger pump, a pump shown in Japanese Utility Model Publication No. 7-34215 has been proposed.

This variable displacement type plunger pump is provided with a plurality of pump units each including a fixed cylinder and a plunger which moves forward and backward in the fixed cylinder. This pump unit is combined with a first pump set having a small total discharge flow rate and a total sum of the pump units. The pump is divided into a second pump set having a large discharge flow rate, and the first pump set and the second pump set are respectively connected to the discharge passage through the flow path switching valve.

More specifically, as shown in FIG. 9, the flow path switching valve is configured such that the valve 3 is operated to the three positions by an actuator 2 such as a solenoid as shown in FIG. And the valves 3 are Q ₁ ,
When in the first stage position and second stage position indicated by Q ₂ is a set 4 of the first pump while the discharge portion 4a of the set 5 of the second pump
Or 5a communicates with the discharge passage 6, and the other discharge portion 5a or 4a communicates with the drain passage 7, and the valve 3
There discharge portion 4a of both pumps set 4, 5, 5a is adapted to communicate with the discharge passage 6 when in a third stage the position shown in FIG Q _3. Therefore, the flow rate of the working fluid discharged from the plunger pump 8 is switched in three stages by operating the flow path switching valve 1.

[0005]

However, in the above-mentioned conventional variable displacement plunger pump 8, the discharge portions of all the pump units (the discharge portions 4a of the two sets 4, 5).
5a) is connected to the discharge passage 6 through the flow path switching valve 1, so that when the valve 3 of the flow path switching valve 1 is locked due to some abnormality, supply of the hydraulic fluid to the hydraulic equipment side cannot be performed at all. As a result, the pressure in the hydraulic equipment decreases due to unavoidable system leaks and the like, and for example, when used in a vehicle height adjustment device or the like, the vehicle height is abnormally reduced.

Accordingly, the present invention provides a method of guaranteeing a minimum supply flow rate of hydraulic fluid to a hydraulic device even if an abnormality occurs in a flow path switching valve, and thereby influencing hydraulic equipment due to a failure of the flow path switching valve. Is to provide a variable displacement plunger pump that can minimize the minimum displacement.

[0007]

Means for Solving the Problems As means for solving the above-mentioned problems, the invention according to claim 1 is provided with a plurality of pump units each having a fixed cylinder and a plunger that moves in and out of the fixed cylinder. In a variable displacement plunger pump which is configured to select a discharge part of an arbitrary unit of the pump units and communicate with the discharge passage, an arbitrary part is obtained in order to obtain at least a minimum discharge flow required by a hydraulic device to be used. The discharge part of the pump unit is directly connected to the discharge passage, and the discharge part of the remaining pump unit is connected to a flow path switching valve for selectively switching to the discharge passage or the drain passage. In the case of the present invention, the hydraulic fluid is supplied with the hydraulic fluid from the pump unit directly connected to the discharge passage even when the flow path cannot be switched by the switching valve due to the abnormality of the switching valve.

According to a second aspect of the present invention, in the first aspect of the present invention, a pulse pressure reducing mechanism is provided in the suction chamber in the pump housing, and a drain passage of the flow path switching valve is connected to the suction chamber. In this case, the pulse pressure of the hydraulic fluid drained from the flow path switching valve is reduced by the pulse pressure reduction mechanism in the suction chamber.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the present invention will be described with reference to FIGS.
A description will be given based on FIG.

2 to 4, reference numeral 11 denotes a pump housing of the variable displacement plunger pump 10 according to the present invention, and reference numeral 12 denotes a bearing 1 mounted on the pump housing 11.
The drive shaft 15 supported via the reference numerals 3 and 14 is an eccentric cam integrally attached to the drive shaft 12.

The drive shaft 12 is connected to a pulley (not shown) at a base end protruding from the pump housing 11, and power of an engine of the automobile is transmitted through the pulley.

At a substantially central portion of the pump housing 11, a suction chamber 18 having a circular cross section connected to a reservoir tank 17 through a suction passage 16 is provided.
8, the eccentric cam 15 is rotatably accommodated. The peripheral wall of the suction chamber 18 has six cylinder holes 1.
9 (fixed cylinders) are formed radially at equal intervals in the circumferential direction. In each of the cylinder holes 19, a plunger 21 having a plurality of suction holes 20 in a side wall is housed so as to be able to advance and retreat, and a discharge valve is provided. A horizontal hole 23 containing the interior 22 is provided near the bottom. Each plunger 21 is urged radially inward by a spring 24 housed in the cylinder hole 19, and the tip end surface thereof is always in contact with the outer peripheral surface of the eccentric cam 15. Therefore, when the eccentric cam 15 rotates integrally with the drive shaft 12, each plunger 2
1 are sequentially pressed by the eccentric cam 15, and the suction holes 2
The hydraulic fluid sucked into the interior through the
Is discharged into the corresponding horizontal hole 23.

In the case of the plunger pump 10, each cylinder hole 19 and the corresponding plunger 21 constitute one pump unit 25. Therefore, in this embodiment, a total of six pump units 25 are arranged in the pump housing. In the six pump units 25, three units arranged alternately in the circumferential direction are respectively divided into a first set of pumps Pa and a second set of pumps Pb, and each set Pa, Pb discharges. Hydraulic fluid is the first
The air is introduced into the merging passage 26 and the second merging passage 27. In the figure, the pump unit 25 of the first set Pa of pumps is marked with ♯, and the pump unit 25 of the second set of pumps Pb is marked with *.

The first merging passage 26 is connected to the pump housing 1.
1 is formed in a substantially C-shaped portion on the rear side (the left side in FIG. 2),
The horizontal hole 23 of each pump unit 25 # forming the first pump group Pa is connected downstream of the discharge valve 22.
The first merging passage 26 is connected to the pump housing 1.
1, and is connected to a hydraulic device 29 such as a vehicle height adjustment device through a discharge hole 28 formed in the apparatus. In this embodiment, the first merging passage 26 and the discharge hole 28 constitute the discharge passage 30 in the present invention.

On the other hand, the second merging passage 27 is formed in an annular shape on the front side (right side in FIG. 2) of the pump housing 11, and each of the pump units 25 forming the second pump set Pb is formed.
Are connected on the downstream side of the discharge valve 22. As shown in FIG. 4, the second merging passage 27 is provided with a through hole 3 extending in the axial direction of the pump housing 11.
1 is connected to the first merging passage 26. The communication hole 31 is provided with a check valve 32 that allows the flow of the working fluid from the second junction passage 27 to the first junction passage 26.

Further, a suction chamber 18 is provided in the second joining passage 27.
A normally closed solenoid valve 34 that opens and closes the passage 33 appropriately in response to a control signal is provided in the middle of the drain passage 33. The solenoid valve 34, together with the check valve 32, constitutes a flow path switching valve in the present invention. In the off state shown by the upper half in FIG. 4, the drain passage 33 is closed, so that the inside of the second junction passage 27 The pressurized hydraulic fluid is supplied to the first junction passage 26 by opening the check valve 32, and in the ON state shown in the lower half of FIG. Is returned into the suction chamber 18.

In the figure, reference numeral 35 denotes a pump housing 11
Is a sealing device that seals between the drive shaft 12 and the pump housing 11 at the front end of the pump housing 11.
6, an inner seal 38 supported on the inner peripheral side of the retainer ring 37 and slidably in contact with the outer peripheral surface of the drive shaft 12, and supported on the outer peripheral surface of the retainer ring 37. And an outer seal 39 which comes into close contact with the inner peripheral surface of the concave portion 36 of the pump housing 11. The retainer ring 37 is provided with a step 36a on the bottom wall side of the concave portion 36 of the pump housing 11 and the concave portion 3a.
6 is arranged between the snap ring 40 fitted on the inner peripheral surface, and a slight axial sliding displacement is allowed between the stepped portion 36a and the snap ring 40.

Further, the axially inner portion of the sealing device 35 is in communication with the suction chamber 18 in the pump housing 11 through the bearing 13, and the axial sliding mechanism of the sealing device 35 is a pulse pressure reducing mechanism on the pump suction side. Is configured. That is, when a pressure change occurs in the suction chamber 18 during operation of the pump, the seal device 35 slides in the axial direction with the pressure change,
The pulse pressure is reduced by the volume change of the inner part of the seal device 35 due to the displacement.

This variable displacement plunger pump 10
FIG. 1 shows a simplified circuit configuration.

The overall configuration of the circuit will be re-arranged and described with reference to the figure. The first pump set Pa and the second pump set Pb
The pumps are operated by the rotation of the drive shaft 12, respectively. The discharge part of the first set of pumps Pa is directly connected to the discharge passage 30 (first merging passage 26), and the second set of pumps Pb is It is connected to the discharge passage 30 via the second junction passage 27. In the middle of the second merging passage 27,
A drain passage 33 having a solenoid valve 34 is formed in a branched manner, and a check valve 32 is interposed at a connection portion of the second merging passage 27 with the discharge passage 30 (the first merging passage 26).

Since the variable displacement plunger pump 10 has the above-described circuit configuration, when the drive shaft 12 rotates, the first pump set Pa and the second pump set Pb respectively perform a pumping action. But the discharge passage 3
The flow rate of the hydraulic fluid supplied to the hydraulic equipment 29 through 0 and Q ₁ mode shown in FIG. 5, the one Q ₂ 'mode.

The switching of the flow characteristics is performed by turning on / off the solenoid valve 34 as follows.

That is, the first pump set Pa is connected to the discharge passage 30.
, The hydraulic fluid discharged from the first pump set Pa is always supplied to the entire discharge passage 30, but the hydraulic fluid discharged from the second pump set Pb is supplied to the solenoid valve 34 by the solenoid valve 34. The drain passage 33 is turned on.
Is opened, it is returned to the suction chamber 18 through the drain passage 33 without being supplied to the discharge passage 30. Accordingly, the flow rate characteristic of the hydraulic fluid supplied to the hydraulic device 29 through the discharge passage 30 at this time, only by the flow characteristics of the set Pa of the first pump, i.e., the flow characteristic for Q ₁ mode.

When the solenoid valve 34 is turned off and the drain passage 33 is closed, the hydraulic fluid discharged from the second pump set Pb is supplied to the discharge passage 30 by opening the check valve 32. Become like Therefore,
At this time, the flow characteristic of the working fluid supplied to the hydraulic device 29 through the discharge passage 30 is a flow characteristic obtained by integrating the discharge flow of the first pump set Pa and the discharge flow of the second pump set Pb,
In other words, the flow characteristics Q ₂ 'mode.

In the variable displacement plunger pump 10, the first pump set Pa is directly connected to the discharge passage 30 without passing through the flow path switching valve (solenoid valve 34). Even if the locking is performed for some reason, the hydraulic device 29 can be reliably supplied with the discharge flow rate by the set Pa of the first pump with the lowest reduction. Therefore, the plunger pump 10 can surely avoid a decrease in the internal pressure due to a system leak or the like of the hydraulic device 29. Even when the plunger pump 10 is used as a hydraulic pressure source of the vehicle height adjusting device, the plunger pump 10 has a low Does not occur.

The variable displacement plunger pump 1
0, the second merging passage 27 (the second pump set P
Since the drain passage 33 connected to b) is configured to return to the suction chamber 18 provided with a pulse pressure reducing mechanism (seal device 35), the drain passage 33 is returned from the second merging passage 27 (the second pump set Pb). The pulse pressure of the hydraulic fluid can be reliably prevented without providing a separate special device outside the pump. Therefore, in the plunger pump 10, it is possible to reliably prevent the generation of abnormal noise and the like due to the pulse pressure without increasing the size and cost of the pump.

In the above description, the plurality of pump units 25 are divided into a first pump set Pa and a second pump set Pb,
The discharge part of the set of pumps Pb is connected to a solenoid valve as a flow path switching valve and the check valve 32. As shown in FIG. 6, a plurality of pump units are connected to the first set of pumps Pa and the second set of pumps.
The set of pumps Pb and the set of third pumps Pc are divided into three sets, and the discharge section of the first set of pumps Pa is directly connected to the discharge passage 30, while the discharge section of the second set of pumps Pb is connected to the third set of sets. A check valve 32 is provided at each discharge part of the pump set Pb, and the drain passage 33 is branched upstream of the check valve 32 at each discharge part, and these are connected to a three-position switching valve 134. You may do it. In this case, the flow path switching valve 13
According to the operating position of _{No. 4} , _three of Q ₁ , Q ₂ and Q ₃ shown in FIG.
The mode can be switched to the flow characteristic.

When obtaining the flow characteristics shown in FIG.
As shown in FIG. 8, the discharge part of the set Pb of the second pump and the discharge part of the set Pc of the third pump are simply selectively connected to the discharge passage 30 side and the drain passage 33 side by the flow path switching valve 234. You may do it.

[0029]

As described above, according to the first aspect of the present invention, the discharge portion of any pump unit is directly connected to the discharge passage so as to obtain at least the minimum discharge flow rate required by the hydraulic equipment used, and the remaining pump Since the discharge section of the unit is connected to a flow path switching valve that selectively switches to the discharge path or the drain path, even if an abnormality occurs in the flow path switching valve, the hydraulic pressure is supplied from the pump unit directly connected to the discharge path. It is possible to reliably supply a minimum flow of the working fluid to the equipment, and as a result, it is possible to minimize the influence on the hydraulic equipment due to the failure of the flow path switching valve.

According to a second aspect of the present invention, in the first aspect of the present invention, a pulse pressure reducing mechanism is provided in a suction chamber in a pump housing, and a drain passage of a flow path switching valve is connected to the suction chamber. The pulse pressure of the hydraulic fluid drained from the flow path switching valve can be reliably reduced by the pulse pressure reduction mechanism in the suction chamber without providing a pulse pressure reduction device externally. Therefore, according to the present invention, it is possible to reliably prevent the generation of abnormal noise due to the pulse pressure without increasing the size and cost of the pump.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing one embodiment of the present invention.

FIG. 2 is a sectional view of the embodiment, taken along line AA of FIG. 3;

FIG. 3 is a sectional view taken along the line BB of FIG. 2 showing the embodiment.

FIG. 4 is a sectional view of the embodiment, taken along line CC in FIG. 3;

FIG. 5 is a flow rate characteristic diagram showing the embodiment.

FIG. 6 is a schematic view showing another embodiment of the present invention.

FIG. 7 is a flow rate characteristic diagram showing the embodiment.

FIG. 8 is a schematic diagram showing still another embodiment of the present invention.

FIG. 9 is a schematic diagram showing a conventional technique.

[Explanation of symbols]

 10: Variable displacement plunger pump, 18: Suction chamber, 19: Cylinder hole (fixed cylinder), 21: Plunger, 25mm, 25 *: Pump unit, Pa: First pump set, Pb: Second pump set Reference numeral 30, a discharge passage, 32, a check valve (flow passage switching valve), 33, a drain passage, 34, a solenoid valve (flow passage switching valve), 35, a sealing device (pulse pressure reduction mechanism).

Claims (2)

[Claims] A plurality of pump units each including a fixed cylinder and a plunger that moves in and out of the fixed cylinder are provided, and a discharge unit of any of the pump units is selected to communicate with a discharge passage. In the variable displacement plunger pump, the discharge part of any pump unit is directly connected to the discharge passage so as to obtain at least the minimum discharge flow rate required by the hydraulic equipment used, and the discharge part of the remaining pump unit is A variable displacement plunger pump connected to a flow path switching valve for selectively switching to a discharge passage or a drain passage. 2. The variable displacement plunger pump according to claim 1, wherein a pulse pressure reducing mechanism is provided in a suction chamber in the pump housing, and a drain passage of a flow path switching valve is connected to the suction chamber.