JP2007032520A - Variable displacement vane pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable displacement vane pump with high relief responsiveness of pump discharge pressure. <P>SOLUTION: This variable displacement vane pump 20 comprises first and second cam chambers 38, 39 pressing a cam ring 31 in the directions the eccentric amount thereof relative to a rotor 25 is reduced and increased by introducing a working fluid, a drain passage 40 draining the working fluid from the second cam chamber 39, and a control valve 36 controlling the flow of the working fluid draining from the second cam chamber 39 through the drain passage 40 according to a pressure difference across a flow detection orifice 35. The vane pump further comprises a relief passage 72 draining the working fluid from the second cam chamber 39 and a branch passage 71 leading the working fluid into the first cam chamber 38. A relief valve 61 is interposed in the relief passage 72. The relief valve 61 comprises a spool 62 moved by receiving a pump delivery pressure. The spool 62 opens the relief passage 72 as the pump delivery pressure rises to drain the working fluid from the second cam chamber 39 and leads the working fluid from the branch passage 71 into the first cam chamber 38. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an improvement of a variable displacement vane pump used for a drive source of a power steering of a vehicle.

  Conventionally, this type of variable displacement vane pump is shown in FIG. 3 (see Patent Document 1).

  Explaining this, the vane pump changes the pump capacity by changing the amount of eccentricity of the cam ring 1 with respect to the rotor, and the discharge flow rate is controlled.

  In the vane pump, the suction region and the discharge region in the cam ring 1 are connected to the suction passage 2 and the pump discharge passage 3, respectively, and the flow rate detection orifice 5 is interposed in the pump discharge passage 3 upstream of the pump discharge port 4. The control valve 6 is actuated by the differential pressure across the flow rate detection orifice 5.

  The cam ring 1 is biased in a direction to increase the eccentric amount by the cam spring 7, and the opposite position of the outer periphery of the cam ring 1 is opposite to the first cam chamber 8 that reduces the eccentric amount of the cam ring 1 by the introduced working fluid. A second cam chamber 9 for increasing the eccentric amount of the cam ring 1 is formed.

  The working fluid upstream of the flow rate detection orifice 5 is introduced into the first and second cam chambers 8 and 9, respectively. The second cam chamber 9 communicates with the upstream of the flow rate detection orifice 5 through the orifice 19, and the opening area of the passage 18 connected to the second cam chamber 9 is changed by the control valve 6. Is adjusted by meter-out control.

  The control valve 6 includes a spool 12 that opens and closes the drain passage 10, a return spring 13 that urges the spool 12 in a direction to close the drain passage 10, and first and second spools defined at both ends of the spool 12. Chambers 14 and 15.

  The control valve 6 controls the eccentric amount of the cam ring 1 so that the spool 12 changes the opening area of the passage 18 in response to the differential pressure across the flow rate detection orifice 5, and thereby the discharge flow rate becomes a set value.

  The upstream side of the flow rate detection orifice 5 communicates with the first spool chamber 14, and the downstream side of the flow rate detection orifice 5 communicates with the second spool chamber 15 via the orifice. The spool 12 moves to a position where the generated force and the return spring 13 are balanced, and the opening area between the passage 18 and the drain passage 10 is controlled to increase or decrease according to the amount of movement of the spool 12.

  The flow rate detection orifice 5 is constituted by a variable orifice that reduces the opening area as the eccentric amount of the cam ring 1 decreases, and the discharge flow rate decreases as the rotational speed of the rotor increases.

  As the load on the hydraulic actuator 16 increases, the load pressure generated at the pump discharge port increases. The vane pump includes a relief mechanism that keeps the load pressure below a set value.

  As a relief mechanism, a relief valve 17 is interposed in the relief passage 11 connected to the second spool chamber 15. The relief valve 17 opens the relief passage 11 when the pump discharge pressure led to the second spool chamber 15 rises above a set value.

When the load pressure of the fluid pressure actuator 16 increases beyond the set value, the pump discharge pressure is controlled through the next operation stroke.
(1) Pump discharge pressure rises above the set value.
(2) The relief valve 17 opens the relief passage 11.
(3) The pressure in the second spool chamber 15 is released through the relief passage 11.
(4) The spool 12 moves in the valve opening direction and opens between the passage 18 and the drain passage 10.
(5) The pressure in the second cam chamber 9 is released through the passage 18 and the drain passage 10.
(6) The cam ring 1 moves in a direction that reduces the amount of eccentricity.
(7) Pump discharge pressure decreases.

In this way, when the load pressure rises above the set value, the vane pump moves the cam ring 1 to keep the pump discharge pressure below the set value, thereby eliminating the need for a relief valve that allows part of the working fluid to escape from the pump discharge passage 3. The working fluid does not circulate in the circuit unnecessarily, and problems such as a rise in temperature of the working fluid and generation of noise do not occur.
JP 2002-147374 A

  However, in such a conventional variable displacement vane pump, after the pump discharge pressure rises above the set value, the relief valve 17 opens, the spool 12 moves, and the eccentric amount of the cam ring 1 decreases. However, there is a problem that it takes time until the pump discharge pressure decreases, and the relief response of the pump discharge pressure is low.

  The present invention has been made in view of the above problems, and an object thereof is to provide a variable displacement vane pump having a high relief response of pump discharge pressure.

  The present invention relates to a plurality of vanes projecting slidably from a rotating rotor, a cam ring that slidably contacts the tip of each vane to define a pump chamber, and a pump discharge that guides a working fluid discharged from the pump chamber A first flow chamber, a flow rate detection orifice interposed in the pump discharge passage, first and second cam chambers for pressing the cam ring in a direction in which the amount of eccentricity with respect to the rotor decreases and in a direction in which the eccentric amount with respect to the rotor increases. A variable displacement vane pump comprising a drain passage for draining working fluid from a two-cam chamber and a control valve for controlling the flow rate of the working fluid draining from the second cam chamber through the drain passage in response to a differential pressure across the flow rate detection orifice Apply.

  A relief passage for draining the working fluid from the second cam chamber is provided, and a relief valve is provided in the relief passage. The relief valve is provided with a spool that moves by receiving pump discharge pressure. As the pressure rises, the relief passage is opened and the working fluid is drained from the second cam chamber.

  According to the present invention, the relief valve receives the pump discharge pressure, and the moving spool opens the relief passage. Therefore, after the pump discharge pressure rises, the relief pressure is released to reduce the eccentric amount of the cam ring. The operating time can be shortened and the relief response of the pump discharge pressure can be improved.

  When the load pressure of the vane pump exceeds the set value, the eccentric amount of the cam ring is controlled with good responsiveness through the relief valve to reduce the pump discharge flow rate and keep the pump discharge pressure below the set value. In addition, wasteful energy consumption can be reduced, and fluctuations in pump discharge pressure can be suppressed to stabilize the operation of the load.

  Hereinafter, an embodiment in which the present invention is applied to a vane pump provided as a fluid pressure source of a power steering device mounted on a vehicle will be described with reference to the accompanying drawings.

  As shown in FIG. 1, the vane pump 20 includes a rotor 25 that is rotatably mounted on a body 21, a plurality of vanes 24 that slidably protrude from the rotor 25, and a cam ring 31 that surrounds each vane 24. Configured as the subject. Each vane 24 slides in and out of the rotating rotor 25 in the radial direction and slides the tip of the vane 24 to the inner peripheral surface of the cam ring 31 to expand and contract the pump chamber between the vanes 24.

  In the rotor 25, rotation from the engine is transmitted to the drive shaft 26 via a pulley, a belt, and the like (not shown), and rotates counterclockwise in the drawing. The working fluid is sucked into a pump chamber (not shown) in a suction region (not shown) into the pump chamber that expands between the vanes 24 as the rotor 25 rotates, and the working fluid is discharged from the pump chamber that contracts between the vanes 24. And is supplied to the fluid pressure actuator 46 of the power steering device via the pump discharge passage 33.

  An adapter ring 22 is interposed in the pump housing recess 21 a of the body 21, and a cam ring 31 is interposed inside the adapter ring 22.

  As a variable capacity mechanism, the cam ring 31 is swingably supported by the adapter ring 22 via a pin 32. A first cam chamber 38 and a second cam chamber 39 are defined between the adapter ring 22 and the cam ring 31, and the cam ring 31 is pinned by the pressure difference of the working fluid introduced into the first and second cam chambers 38 and 39. Oscillates via 32, and the pump capacity changes. When the cam ring 31 is displaced maximum in the direction of the first cam chamber 38, the amount of eccentricity with respect to the rotor 24 is maximized. Conversely, when the cam ring 31 is displaced maximum in the direction of the second cam chamber 39, the amount of eccentricity is minimized.

  Since the center axis of the cam ring 31 and the center axis of the pin 32 are offset, a force that causes the cam ring 31 to move rightward in the drawing is generated by the pressure generated inside the cam ring 31.

  The body 21 is provided with a feedback pin 47 that passes through the adapter ring 22 and follows the cam ring 31. A cam spring 37 is interposed between the feedback pin 47 and the plug 48 via a plunger 49, and the cam ring 31 is urged by the cam spring 37 in a direction to increase the amount of eccentricity.

  The plug 48 has a cylinder portion in which a plunger 49 is slidably fitted. A flow rate detection orifice 35 is opened in the cylinder portion, and the opening area of the flow rate detection orifice 35 is determined by the plunger 49 in accordance with the eccentric amount of the cam ring 31. be changed. The opening area of the flow rate detection orifice 35 is maximized when the cam ring 31 is displaced to the maximum in the direction of the first cam chamber 38, and conversely is minimized when the cam ring 31 is displaced to the maximum in the direction of the second cam chamber 39.

  A control valve 36 is interposed in the body 21. The flow rate detection orifice 35 is interposed in the middle of the pump discharge passage 33, and the control valve 36 is operated by the differential pressure across the flow rate detection orifice 35. The control valve 36 adjusts the drive pressure guided to the first cam chamber 38 and the second cam chamber 39 by the differential pressure across the flow rate detection orifice 35, thereby adjusting the eccentric amount of the cam ring 31 so that the discharge flow rate becomes a set value. Control.

  The working fluid upstream of the flow rate detection orifice 35 is introduced into the first and second cam chambers 38 and 39, respectively. The second cam chamber 39 communicates with the upstream of the flow rate detection orifice 35 via the orifice 59, and the opening area of the drain passage 40 connected to the second cam chamber 39 is changed by the control valve 36. The amount is adjusted by meter-out control.

  The control valve 36 includes a spool 52 that opens and closes the drain passage 40, a return spring 53 that urges the spool 52 in a direction to close the drain passage 40, and first and second spools defined at both ends of the spool 52. Chambers 54 and 55.

  The control valve 36 controls the amount of eccentricity of the cam ring 31 so that the spool 52 changes the opening area of the drain passage 40 in response to the differential pressure across the flow rate detection orifice 35 and thereby the discharge flow rate becomes a set value.

  The upstream side of the flow rate detection orifice 35 communicates with the first spool chamber 54, and the downstream side of the flow rate detection orifice 35 communicates with the second spool chamber 55 via the orifice 57, and is generated by the differential pressure across the flow rate detection orifice 35. The spool 52 moves at a position where the return force 53 and the return spring 53 are balanced, and the opening area between the second cam chamber 39 and the drain passage 40 is controlled to increase or decrease in accordance with the amount of movement of the spool 52.

  As the load of the hydraulic actuator 46 increases, the load pressure generated at the pump discharge port 34 increases. The vane pump 20 includes a relief valve 61 that keeps the load pressure below a set value.

  The relief valve 61 includes a spool 62 that responds to the pump discharge pressure upstream of the flow rate detection orifice 35, and when the pump discharge pressure increases to a set value or more, the spool 62 opens the relief passage 72 and opens the branch passage. The working fluid is guided from 71 to the first cam chamber 38.

  As a result, as the first cam chamber 38 is pressurized and the second cam chamber 9 is depressurized, the cam ring 31 moves in a direction to decrease the eccentric amount, the pump capacity is reduced, and the pump discharge pressure is reduced. The pressure is reduced to the set value.

  The spool 62 of the relief valve 61 is slidably inserted in the valve housing hole 63 of the body 21 and is urged in the valve closing direction by a relief spring 69.

  The spool 62 has first and second land portions 64 and 65. The first and second land portions 64 and 65 define a driving pressure chamber 66 and first and second drain chambers 67 and 68, respectively. .

  The first drain chamber 67 is defined between the first and second land portions 64 and 65 and communicates with the tank side.

  The second drain chamber 68 is defined between the second land portion 65 and the bottom portion of the valve accommodation hole 63 and communicates with the tank side.

  The relief spring 69 is interposed between the second land portion 65 and the bottom of the valve accommodating hole 63 by being compressed.

  The driving pressure chamber 66 is defined between the first land portion 64 and the plug 70 and communicates with the pump discharge passage 33. The spool 62 moves in the valve opening direction (right direction in the drawing) against the relief spring 69 as the pump discharge pressure guided to the drive pressure chamber 66 increases.

  A branch passage 71 that communicates with the first cam chamber 38 is connected to the valve housing hole 63, and a through hole 72 that communicates with the second cam chamber 39 is connected via an annular groove 73.

  A plurality of notches 75 are formed in the second land portion 65. Each notch 75 has a base end that opens into the first drain chamber 67 and a tip that extends toward the annular groove 73. When the spool 62 is in the closed position in the figure, the communication between each notch 75 and the annular groove 73 is blocked, and the relief passage 72 is closed. As the spool 62 moves beyond the predetermined value in the valve opening direction (right direction in the figure), the area of each notch 75 facing the annular groove 73 gradually increases, and the opening area of the relief passage 72 becomes the spool 62. It increases according to the amount of movement.

  The vane pump 20 is configured as described above, and the operation and effect will be described next.

  The working fluid sucked into the suction region in the cam ring 31 from a suction passage (not shown) is pressurized by the pump action of each vane 24, passes through the flow rate detection orifice 35 of the pump discharge passage 33, and passes from the pump discharge port 34 to the fluid pressure actuator 46. Supplied to. The working fluid passing through the flow rate detection orifice 35 passes through the gap between the adapter ring 22 of the pump housing recess 21a from the inside of the hollow plug 48 and the plunger 49 as shown by the arrow in the figure, and from the through hole 29 of the body 21 to the pump. It flows to the discharge port 34.

  At this time, a pressure difference is generated before and after the flow rate detection orifice 35, and this differential pressure is introduced into the first spool chamber 54 and the second spool chamber 55 of the control valve 36. In the control valve 36, the spool 52 is moved to a position where the force due to the pressure introduced into the first and second spool chambers 54 and 55 and the force of the return spring 53 are balanced.

  The working fluid in the second cam chamber 39 is not discharged until the spool 52 moves in the right direction in the drawing, and the cam ring 31 is at the maximum eccentric position by the force of the cam spring 37 and the force generated in the second cam chamber 39. At this time, the vane pump 20 discharges at the maximum capacity, and increases the discharge flow rate substantially in proportion to the rotational speed of the rotor 25. As a result, the steering assist force provided by the fluid pressure actuator 46 can be sufficiently ensured when the vehicle is stationary, for example, at the time of operation where the rotational speed of the rotor 25 is low.

  When the spool 52 moves in the right direction in the drawing as the differential pressure across the flow rate detection orifice 35 increases, the working fluid in the second cam chamber 39 passes through the notch 58 in accordance with the amount of movement of the spool 52. And the working fluid is introduced into the first cam chamber 38, and the cam ring 31 moves to the right in the drawing in accordance with the pressure difference between the first and second cam chambers 38 and 39 to reduce the amount of eccentricity. . In this way, the vane pump 20 is adjusted to a capacity corresponding to the differential pressure across the flow rate detection orifice 35.

  As the amount of eccentricity of the cam ring 31 decreases, the amount of eccentricity is transmitted to the feedback pin 47 and the opening area of the flow rate detection orifice 35 decreases via the plunger 49, so that the rotational speed of the rotor 25 exceeds a predetermined value. As it rises, the discharge flow rate of the vane pump 20 gradually decreases. As a result, the steering assist force applied by the fluid pressure actuator 46 when the vehicle is traveling is adjusted appropriately.

  On the other hand, when the pump discharge pressure rises above the set value, the spool 62 of the relief valve 61 opens the relief passage 72 in response to the pump discharge pressure, and a part of the working fluid discharged from the pump chamber is second. Draining through the cam chamber 39 and the relief passage 72 reduces the pressure of the second cam chamber 9 and guides the working fluid from the branch passage 71 to the first cam chamber 38 so that the cam ring 31 reduces the amount of eccentricity. It moves to reduce the pump capacity, and the pump discharge pressure is reduced to the set value.

  Thus, by moving the cam ring 31 and suppressing the pump discharge pressure below the set value, a relief valve for releasing a part of the working fluid from the pump discharge passage 33 becomes unnecessary, and the working fluid does not circulate in the circuit wastefully. Thus, problems such as a rise in temperature of the working fluid and generation of noise can be avoided.

When the load pressure of the fluid pressure actuator 46 increases beyond the set value, the vane pump 20 controls the pump discharge pressure through the next operation stroke.
(1) Pump discharge pressure rises above the set value.
(2) The spool 62 moves in the valve opening direction and opens the relief passage 72 and the branch passage 71, respectively.
(5) The pressure in the second cam chamber 39 decreases, and the pressure in the first cam chamber 38 increases.
(6) The cam ring 31 moves in a direction that reduces the amount of eccentricity.
(7) Pump discharge pressure decreases.

  When the operation stroke of the vane pump 20 is compared with the operation stroke of the conventional device, the vane pump 20 does not have the operation strokes (3) and (4) in the conventional device, so that the relief response of the pump discharge pressure is increased accordingly. Enhanced.

  That is, the relief valve 61 receives the pump discharge pressure, and the spool 62 that moves in response to the pump discharge pressure opens the relief passage 72. Therefore, after the pump discharge pressure rises, the pressure in the second cam chamber 39 is released to reduce the eccentric amount of the cam ring 31. The operation time required for the pump can be shortened, and the relief response of the pump discharge pressure can be improved.

  The relief valve 61 is slidably received in the valve housing hole 63, a driving pressure chamber 66 to which pump discharge pressure for driving the spool 62 in the valve opening direction is guided, and urges the spool 62 in the valve closing direction. Since the opening area of the relief passage 72 increases as the pump discharge pressure guided to the drive pressure chamber 66 rises above the set value, the second cam chamber is provided according to the pump discharge pressure. The pressure of 39 can be adjusted accurately.

  In addition, the opening of the branch passage 71 of the above (2) further contributes to the operation responsiveness of the cam ring 31.

  When the load pressure rises above the set value, the vane pump 20 controls the eccentric amount of the cam ring 31 with good responsiveness through the relief valve 61 to reduce the pump discharge flow rate, thereby reducing wasteful energy consumption. At the same time, the operation of the fluid pressure actuator 46 can be stabilized.

  Next, another embodiment shown in FIG. 2 will be described. In addition, the same code | symbol is attached | subjected to the same structure part as the said embodiment.

  A third land portion 77 having a smaller diameter than the first and second land portions 64 and 65 is formed in the spool 62, and the third land portion 77 is slidably fitted to the valve housing hole small diameter portion 74. A back pressure chamber 75 is defined between the third land portion 77 and the valve housing hole small diameter portion 74, and the pump discharge passage 33 is connected to the back pressure chamber 75.

The pressure receiving area with respect to the back pressure chamber 75 of the spool 62 is made smaller than the pressure receiving area with respect to the driving pressure chamber 66. That is, the pressure receiving area of the third land portion 77 facing the back pressure chamber 75 is set smaller than the pressure receiving area of the first land portion 64 facing the driving pressure chamber 66. In this case, the spool 62 is guided to the driving pressure chamber 66. The spool 62 is pressed in the valve opening direction (right direction in the figure) by the pump discharge pressure, and is pressed in the valve closing direction (left direction in the figure) by the pump discharge pressure guided to the back pressure chamber 75. As the pump discharge pressure acting on the pressure receiving area difference between the one land portion 64 and the third land portion 77 increases, the pump spring moves against the relief spring 69 in the valve opening direction (right direction in the figure).

  Thus, by reducing the force for driving the spool 62 in the valve opening direction, the urging force of the relief spring 69 can be set small, and the relief valve 61 can be downsized.

  In each embodiment, the pump discharge pressure upstream of the flow rate detection orifice 35 is guided to the drive pressure chamber 66 of the relief valve 61, but the pump discharge pressure downstream of the flow rate detection orifice 35 is not limited thereto. It may be guided.

  The present invention is not limited to the above-described embodiment, and it is obvious that various modifications can be made within the scope of the technical idea.

  The variable displacement vane pump of the present invention can be used not only for the fluid pressure source of the power steering apparatus but also for other machines.

Sectional drawing of the variable displacement vane pump which shows embodiment of this invention. Sectional drawing of the variable displacement vane pump which shows other embodiment. The fluid pressure circuit diagram of the variable capacity vane pump which shows a prior art example.

Explanation of symbols

20 Vane Pump 25 Rotor 31 Cam Ring 33 Pump Discharge Passage 34 Pump Discharge Port 35 Flow Detection Orifice 36 Control Valve 37 Cam Spring 38 First Cam Chamber 39 Second Cam Chamber 40 Drain Passage 60 Relief Passage 61 Relief Valve 62 Spool 63 Valve Housing Hole 64 First land portion 65 Second land portion 66 Driving pressure chamber 69 Relief spring 71 Branch passage 75 Back pressure chamber

Claims (4)

A plurality of vanes projecting slidably from the rotating rotor, a cam ring defining a pump chamber by sliding the tip of each vane, and a pump discharge passage for guiding a working fluid discharged from the pump chamber; A flow rate detection orifice interposed in the pump discharge passage, first and second cam chambers for pressing the cam ring in a direction in which the amount of eccentricity with respect to the rotor decreases and in a direction in which the eccentric amount increases with the introduction of the working fluid, A drain passage for draining the working fluid from the second cam chamber; and a control valve for controlling a flow rate of the working fluid drained from the second cam chamber through the drain passage in response to a differential pressure across the flow rate detection orifice. In variable displacement vane pumps,
A relief passage for draining the working fluid from the second cam chamber is provided, and a relief valve is provided in the relief passage, and the relief valve is provided with a spool that moves by receiving pump discharge pressure. A variable displacement vane pump characterized by opening the relief passage as it rises and draining the working fluid from the second cam chamber.   The relief valve includes a spool that is slidably received in the valve housing hole, a driving pressure chamber to which pressure for driving the spool in the valve opening direction is guided, and a relief spring that biases the spool in the valve closing direction. The pump discharge passage is connected to the driving pressure chamber, and the opening area of the relief passage increases as the pump discharge pressure guided to the driving pressure chamber rises above a set value. The variable capacity vane pump according to claim 1.   The relief valve includes a back pressure chamber to which pressure for driving the spool in the valve closing direction is guided, the pump discharge passage is connected to the back pressure chamber, and a pressure receiving area of the spool with respect to the back pressure chamber is determined as the driving pressure. The variable capacity vane pump according to claim 2, wherein the pressure receiving area for the chamber is smaller than the pressure receiving area. A branch passage for allowing the working fluid to flow into the first cam chamber from the pump discharge passage;
The said relief valve opens the said branch channel | path as the pump discharge pressure guide | induced to the said drive pressure chamber rises exceeding a setting value, The one of Claim 1 to 3 characterized by the above-mentioned. Variable displacement vane pump.

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