JP2012092686A - Vane pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vane pump that reduces a pressure loss of a suction distribution passage, and equally distributes a working fluid.SOLUTION: In the vane pump 1 used as a working fluid pressure supply source, a flow control valve 40 has a return valve port 13 which is opened at a spool accommodation hole 11 and opened and closed by a spool 41, and the suction distribution passage 53 has a return valve port extension passage 14 connected to the return valve port 13, a suction upstream passage 54 connected to the return valve port extension passage 14 and connected with a tank passage 16, and a suction downstream passage 56 branched into two suction pump ports 51, 52 from the suction upstream passage 54. The return valve port extension passage 14 and the suction upstream passage 54 are offset in their center lines R, O, respectively.

Description

  The present invention relates to a vane pump used as a working fluid pressure supply source.

  This type of vane pump includes a flow control valve that recirculates a part of the working fluid discharged from the vane pump mechanism to the suction distribution passage as surplus working fluid, and adjusts the pump discharge flow rate through this flow control valve to adjust the fluid pressure. Some control the flow rate of the working fluid sent to the equipment.

  The balanced vane pump is a vane pump mechanism that pressurizes and discharges the working fluid. As the rotor makes one revolution, each vane that follows the cam surface reciprocates twice, so that two suction areas and two discharges are generated. And a suction distribution passage for distributing the working fluid to the two suction areas.

  However, in a balanced vane pump provided with a flow control valve, when the flow control valve has a small opening, the surplus working fluid jet flowing from the flow control valve into the suction distribution passage is And the flow rate of the working fluid distributed in the suction distribution passage may be greatly different.

  In response to this, the vane pump disclosed in Patent Document 1 is provided with a plate-like rectifying wall in the middle of the suction distribution passage, and a working fluid in the suction distribution passage is applied to the rectification wall by applying a jet of surplus working fluid. The speed distribution is adjusted.

  In addition, the vane pump disclosed in Patent Document 2 has a difference in the passage opening area of the branch portion of the suction distribution passage so as to equalize the flow rate of the working fluid distributed in the suction distribution passage.

JP 2007-255335 A JP 2003-314470 A (Patent No. 3874694)

  However, in such a conventional vane pump, the flow control valve is opened and the working fluid is configured to provide a rectifying wall in the middle of the suction distribution passage or restrict the passage opening area of the branch portion of the suction distribution passage. When the flow rate is increased, the pressure loss in the suction distribution passage increases and the suction performance of the vane pump decreases.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a vane pump that reduces pressure loss in a suction distribution passage and that distributes a working fluid evenly.

  The present invention relates to a vane pump used as a working fluid pressure supply source, which is a vane pump mechanism that pressurizes and discharges working fluid, two suction pump ports that guide the working fluid sucked into the vane pump mechanism, and two suction pumps A suction distribution passage that distributes the working fluid sucked into the pump port, a tank passage that guides the working fluid to the suction distribution passage, and a part of the working fluid discharged from the vane pump mechanism as an excess working fluid to the suction distribution passage. A flow rate control valve for recirculation, and the flow rate control valve includes a spool receiving hole, a spool received in the spool receiving hole, and a return valve port that opens to the spool receiving hole and is opened and closed by the spool. The suction distribution passage is connected to the return valve port extension path connected to the return valve port and the return valve port extension path. A suction upstream passage portion connected to the tank passage and a suction downstream passage portion branching from the suction upstream passage portion to the two suction pump ports; and a return valve port extension passage and a suction upstream passage The part is characterized in that each center line is offset.

  According to the present invention, when the opening degree of the flow control valve is small, the direction of the jet of the surplus working fluid that flows obliquely from the return valve port follows the suction upstream passage in the process of passing through the return valve port extension path. By being deflected in this way, the flow rate and pressure of the working fluid distributed from the suction distribution passage to the two suction pump ports are equalized.

The jet of surplus working fluid flowing out from the return valve port is deflected against the inner wall surface of the return valve port extension path before joining with the working fluid flow led from the tank passage in the suction upstream passage portion, so that the return valve An increase in the pressure loss of the working fluid flowing through the suction upstream passage portion can be suppressed by the port extension path.

  This prevents cavitation from occurring at one of the suction pump ports when the vane pump operates at low speed, prevents the vane pump from generating vibrations and noise, and prevents suction of working fluid during high speed operation. It is performed smoothly and a decrease in the discharge flow rate of the vane pump is avoided.

The front view of the vane pump which shows embodiment of this invention. Sectional drawing which follows the AA line of FIG. Sectional drawing which follows the BB line of FIG. Sectional drawing which follows the CC line of FIG. 3 similarly. Sectional drawing of the vane pump which shows a comparative example. Sectional drawing which follows the DD line of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  The vane pump 1 shown in FIGS. 1 to 4 is used as a hydraulic pressure supply source for hydraulic equipment mounted on a vehicle, such as a power steering device or a transmission.

  The vane pump 1 uses a working oil (oil) as a working fluid, but a working fluid such as a water-soluble alternative liquid may be used instead of the working oil.

  As shown in FIG. 1, in the vane pump 1, the power of an engine (not shown) is transmitted to the end of the drive shaft 9, and the rotor 2 connected to the drive shaft 9 rotates.

  As shown in FIG. 2, the drive shaft 9 is rotatably supported by the pump body 10 and the pump cover 50. The pump body 10 is formed with a pump housing recess 10 a that houses the vane pump mechanism 6 that pressurizes and discharges the sucked hydraulic oil. The rotor 2, the plurality of vanes 3, the cam ring 4, the side plate 30, and the like are housed in the pump housing recess 10 a as the vane pump mechanism 6. A pump cover 50 is fastened to the pump body 10 via a plurality of bolts 18, and the pump housing recess 10 a is sealed by the pump cover 50.

  A high pressure chamber 20 is defined between the bottom of the pump housing recess 10 a of the pump body 10 and the side plate 30. The side plate 30 is pressed against the rear end face of the cam ring 4 by the pump discharge pressure guided to the high pressure chamber 20.

  In the rotor 2, a plurality of slits 5 having openings on the outer peripheral surface are radially formed at predetermined intervals. The vane 3 has a rectangular plate shape and is slidably inserted into the slit 5.

  In the cam ring 4, a plurality of pump chambers 7 are defined by the outer peripheral surface of the rotor 2, the cam surface 4 a of the cam ring 4, and the adjacent vanes 3.

  The cam ring 4 is an annular member in which the cam surface 4a has a substantially oval shape. As the rotor 2 rotates, the vane 3 rotates while sliding the tip of the vane 3 against the cam surface 4a, and the volume of the pump chamber 7 defined between the vanes 3 is expanded or contracted.

  In the balanced vane pump 1, each vane 3 following the cam surface 4a reciprocates twice as the rotor 2 makes one rotation, and has two suction areas and two discharge areas.

  As the pump suction passage, as shown in FIG. 4, the pump cover 50 is formed with two suction pump ports 51 and 52 and a suction distribution passage 53 that guides hydraulic oil to the suction pump ports 51 and 52. The suction pump ports 51 and 52 are arranged in two suction regions, and hydraulic oil is sucked into the pump chamber 7 that expands in the suction region from the two suction pump ports 51 and 52 (see the arrow in FIG. 4).

  As shown in FIG. 2, the pump discharge passage is formed in two pump pump ports 31, 32 formed in the side plate 30, the high-pressure chamber 20 communicating with the discharge pump ports 31, 32, and the pump body 10. And a discharge passage (not shown) for guiding the high-pressure chamber 20 to the hydraulic equipment. In two discharge regions, hydraulic oil is discharged from the pump chamber 7 whose volume is contracted to the two discharge pump ports 31 and 32 (see arrows in FIG. 2).

  A flow rate control valve 40 is accommodated in the pump body 10. The flow rate control valve 40 recirculates a part of the hydraulic oil discharged from the discharge pump ports 31 and 32 to the discharge passage (not shown) from the suction distribution passage 53 to the suction pump ports 51 and 52 as a surplus oil. The flow rate of the working fluid supplied to the hydraulic equipment and the pump discharge flow rate are adjusted to control the flow rate of the working fluid sent to the hydraulic equipment.

  As shown in FIG. 3, the flow control valve 40 includes a spool accommodation hole 11 formed in the pump body 10 and a spool 41 accommodated in the spool accommodation hole 11.

  The spool accommodation hole 11 extends in a direction substantially orthogonal to the drive shaft 9, and an inlet valve port 12, an outlet valve port (not shown), and a return valve port 13 are opened.

  The inlet valve port 12 constitutes a discharge passage, communicates with the discharge pump ports 31 and 32 via the high-pressure chamber 20, and guides hydraulic oil discharged from the pump chamber 7 to the spool accommodation hole 11.

  The outlet valve port constitutes a discharge passage, communicates with a pipe (not shown) connected to the pump body 10, and guides hydraulic oil flowing into the spool accommodation hole 11 to the hydraulic equipment.

  The return valve port 13 communicates with the suction distribution passage 53 and recirculates a part of the hydraulic oil flowing into the spool accommodation hole 11 to the suction pump ports 51 and 52 through the suction distribution passage 53 as surplus oil.

  A tank passage 16 communicating with a tank (not shown) is formed in the pump body 10. The tank passage 16 is connected to the suction upstream passage portion 54 of the suction distribution passage 53.

  Based on the above configuration, surplus hydraulic oil flowing out from the return valve port 13 is returned to the suction pump ports 51 and 52 through the suction distribution passage 53. The hydraulic fluid introduced from the tank passage 16 by the excess hydraulic fluid flowing into the suction distribution passage 53 from the return valve port 13 is sucked into the suction distribution passage 53 and guided to the Y-shaped suction downstream passage portion 56.

  The return valve port 13 is a hole having a circular cross section that opens in the cylindrical inner wall surface 11 a of the spool accommodation hole 11, and the land portion 42 of the spool 41 faces the return valve port 13. The opening area of the return valve port 13 is changed by the land portion 42 according to the stroke of the spool 41.

  A plug 49 is screwed onto the open end of the spool accommodation hole 11. A coiled valve spring 48 is compressed and interposed between the plug 49 and the spool 41. This valve spring 48 urges the spool 41 in the valve closing direction (rightward in FIG. 3).

  The spool 41 has a stopper portion 43 that protrudes in the axial direction from the tip thereof, and the stroke that moves in the valve closing direction is regulated by the stopper portion 43 coming into contact with the closed end surface of the spool accommodation hole 11.

  In the discharge passage, a flow rate control throttle (not shown) through which hydraulic oil sent from the outlet valve port to the hydraulic equipment passes, and a passage for guiding the pressure generated on the downstream side of the flow rate control throttle to the back chamber 47 of the spool 41 (see FIG. Not shown). The spool 41 moves in the axial direction of the spool housing hole 11 in response to the differential pressure across the flow control throttle, and changes the opening area of the return valve port 13.

  When the engine speed increases, the flow rate of the hydraulic oil discharged from the vane pump 1 increases, the differential pressure across the flow control throttle increases, and the spool 41 moves in the valve opening direction (leftward in FIG. 3). As a result, as the engine speed increases, the opening area of the return valve port 13 gradually increases, the flow rate of surplus hydraulic fluid that is diverted to the return valve port 13 increases, and the flow rate of hydraulic fluid that is sent to the hydraulic equipment is reduced. Be controlled.

  The surplus hydraulic oil flowing out from the return valve port 13 merges with the hydraulic oil guided from the tank passage 16 in the suction upstream passage portion 54 of the suction distribution passage 53, and then the suction branching into the Y shape of the suction distribution passage 53 The flow is divided into two hydraulic oil flows at the downstream passage portion 56 and sucked into the suction pump ports 51 and 52.

  The suction distribution passage 53 is a return formed coaxially with the return valve port 13 as means for equalizing the amount of hydraulic fluid that is divided into the two suction pump ports 51 and 52. The valve port extension path 14, and the return valve port extension path 14 and a suction upstream passage portion 54 formed by being offset in the axial direction of the spool 41 are provided. The return valve port extension path 14 extends from the return valve port 13. The flow of surplus working oil flowing out is deflected and guided to the suction upstream passage portion 54.

  Hereinafter, the configuration of the suction distribution passage 53 will be described.

  The suction distribution passage 53 includes a return valve port extension passage 14 and a suction upstream passage portion 54 formed in the pump body 10, and a Y-shaped suction downstream passage portion 56 formed in the pump cover 50.

  The return valve port extension path 14 is formed coaxially with the return valve port 13 and has a cylindrical inner wall surface 15 that is continuous with the return valve port 13 without a step.

  In FIG. 3, the center line R is a flow path center line of the return valve port 13 and the return valve port extension path 14.

  The return valve port 13 and the return valve port extension path 14 are arranged such that the center line R is substantially orthogonal to the center axis S of the flow control valve 40.

  The return valve port 13 and the return valve port extension path 14 are formed so that the cross section of the flow path perpendicular to the center line R is circular, but the present invention is not limited to this, and the cross section of the flow path is formed in a shape other than circular. Also good.

  A counter recess 19 is formed in the spool accommodation hole 11 on the extension of the return valve port extension path 14 and the return valve port 13. The return valve port extension path 14, the return valve port 13, and the opposed recess 19 are formed in the same process by drilling.

  The spool 41 has an annular land portion 42 and an annular groove 44 formed behind the land portion 42.

  In the flow control valve 40, when the spool 41 is in a stroke as shown in FIG. 3, the land portion 42 is located in the middle of the return valve port 13 and the opposed recess 19. In this state, the surplus hydraulic fluid flowing out from the return valve port 13 to the return valve port extension passage 14 flows so as to sandwich the land portion 42 and is prevented from becoming a biased flow inclined with respect to the passage center line R. It is done.

  The return valve port extension path 14 is formed in a cylindrical surface shape whose flow path cross-sectional area perpendicular to the center line R is constant, but is not limited to this, for example, the flow path cross-sectional area gradually increases from the upstream side to the downstream side. You may form in the taper shape which spreads.

  As shown in FIG. 3, the suction upstream passage portion 54 is formed as a flow path that extends linearly around a center line O that extends in a direction substantially parallel to the drive shaft 9.

  The return valve port extension path 14 is formed as a flow path extending linearly around a center line R extending in a direction substantially parallel to the drive shaft 9.

  The return valve port extension passage 14 has a choke dimension relationship in which the passage length L along the center line R is larger than the opening diameter D thereof.

  A passage sectional area perpendicular to the center line R of the return valve port extension passage 14 is formed smaller than a passage sectional area perpendicular to the center line O of the suction upstream passage portion 54.

  The center line O of the suction upstream passage portion 54 and the center line R of the return valve port extension passage 14 extend in parallel to each other and are offset from each other in the direction of the center axis S of the spool 41.

  The center line R of the return valve port extension path 14 is offset in the direction opposite to the valve opening direction (valve closing direction) of the flow control valve 40 with respect to the center line O of the suction upstream passage portion 54. The opening direction of the flow control valve 40 is the direction in which the spool 41 moves along the central axis S when the flow control valve 40 is opened (left direction in FIG. 3), and the closing direction of the flow control valve 40 Is the direction in which the spool 41 moves along its central axis S when the flow control valve 40 is closed (rightward in FIG. 3).

  The inner wall surface 15 of the return valve port extension passage 14 is continuous with the inner wall surface 55 of the suction upstream passage portion 54 in the right side in FIG. 3 without a step, and the left portion in FIG. 3 is the center of the suction upstream passage portion 54. It is formed so as to be connected to the part.

  The inner wall surface 15 of the return valve port extension path 14 has a portion (deflection wall portion) that deflects the jet of surplus hydraulic oil that flows out of the return valve port 13 in a biased manner toward the suction distribution passage 53. The dimension of the return valve port extension path 14 (flow path cross-sectional area, flow path length) is such that the jet of surplus hydraulic oil that flows out of the inner wall surface 15 of the return valve port extension path 14 from the return valve port 13 returns to the return valve. It is set by simulation or the like so as to hit an arbitrary position with respect to the inner wall surface 15 of the port extension path 14.

  As shown in FIG. 4, the Y-shaped suction downstream passage portion 56 includes a collecting passage portion 56c connected to the suction upstream passage portion 54 and a branch passage extending from the collecting passage portion 56c to one suction pump port 51. And a branch passage portion 56b extending from the collecting passage portion 56c to the other suction pump port 52.

  In FIG. 3, the suction upstream passage portion 54 and the collecting passage portion 56 c of the suction distribution passage 53 are formed as flow paths extending linearly with a center line O extending parallel to the drive shaft 9 as a center.

  When the opening degree of the flow control valve 40 is small, the surplus hydraulic oil jet flowing out from the return valve port 13 is a flow inclined with respect to the center line O of the suction distribution passage 53 as shown by an arrow in FIG. Become. The inclination direction of the surplus hydraulic oil jet is the valve opening direction (leftward in FIG. 3) in which the spool 41 moves with respect to the central axis S of the spool 41 when the flow control valve 40 is opened. Thus, the surplus hydraulic oil jet flowing out from the return valve port 13 in an oblique direction strikes the inner wall surface 15 of the return valve port extension passage 14 and is deflected to a flow along the center line O of the suction distribution passage 53.

  In this way, it is possible to suppress the distribution of the speed distribution of the excess hydraulic oil flow in the suction upstream passage portion 54, and the flow rate and pressure of the hydraulic oil flowing into the two branch passage portions 56a and 56b become equal, and the two suction ports Cavitation is prevented from occurring at one of the pump ports 51 and 52.

  Before the surplus hydraulic oil jet flowing out from the return valve port 13 merges with the surplus hydraulic oil flow and the hydraulic oil flow guided from the tank passage 16 in the suction upstream passage portion 54, Since it is deflected against the wall surface 15, the working oil flow passing through the suction upstream passage portion 54 becomes smooth, reducing the pressure loss of the working fluid flowing through the suction upstream passage portion 54, and at the branch passage portions 56 a and 56 b. The flow rate and pressure of the working fluid flowing in are equalized.

  5 and 6 are sectional views of a vane pump 1 that does not include the return valve port extension path 14 of the present invention as a comparative example. FIGS. 5 and 6 correspond to FIGS. 3 and 4 showing the embodiment of the present invention. Hereinafter, the operation of the vane pump 1 shown in FIGS. 5 and 6 will be described.

  When the opening degree of the flow control valve 40 is small, an orifice (flow path) having a crescent cross section is defined between the return valve port 13 having a circular cross section and the cylindrical land portion 42 of the spool 41. Therefore, the surplus hydraulic oil jet flowing from the return valve port 13 into the suction distribution passage 53 is generated when the flow control valve 40 is opened with respect to the center line O of the suction distribution passage 53 as indicated by an arrow in FIG. The spool 41 is inclined in the valve opening direction (leftward in FIG. 5) and becomes a biased flow toward a limited portion (left side in FIG. 6) of the inner wall surface of the suction upstream passage portion 54.

  When the flow rate of the hydraulic oil flowing into one branch passage portion 56a is significantly larger than the flow rate of the hydraulic oil flowing into the other branch passage portion 56b due to the inclination of the jet of excess hydraulic oil, the two suction pumps A difference in pressure occurs between the ports 51 and 52, causing cavitation at the suction pump port 51 on the lower pressure side, leading to a decrease in the discharge flow rate of the vane pump 1, as well as causing vibration and noise of the vane pump 1. become.

  Hereinafter, the gist, operation, and effect of the present embodiment will be described.

  In this embodiment, the vane pump 1 is used as a working fluid pressure supply source. The vane pump mechanism 6 pressurizes and discharges the working fluid, and the two suction pump ports 51 guide the working fluid sucked into the vane pump mechanism 6. , 52, a suction distribution passage 53 that distributes the working fluid sucked into the two suction pump ports 51, 52, a tank passage 16 that guides the working fluid to the suction distribution passage 53, and the vane pump mechanism 6. A flow rate control valve 40 that recirculates a part of the working fluid to the suction distribution passage 53 as an excess working fluid. The flow rate control valve 40 includes a spool accommodating hole 11 and a spool 41 accommodated in the spool accommodating hole 11. And a return valve port 13 opened to the spool housing hole 11 and opened / closed by the spool 41, and the suction distribution passage 5 The return valve port extension path 14 connected to the return valve port 13, the suction upstream path section 54 connected to the return valve port extension path 14 and connected to the tank passage 16, and the suction upstream path section 54 A suction downstream passage portion 56 that branches into two suction pump ports 51, 52, and the return valve port extension passage 14 and the suction upstream passage portion 54 are configured such that their center lines R, O are offset. And

  Based on the above configuration, when the opening degree of the flow control valve 40 is small, the direction of the jet of the surplus working fluid that flows obliquely out of the return valve port 13 is in the process of passing through the return valve port extension passage 14 and the suction upstream passage By being deflected along the portion 54, the flow rate and pressure of the working fluid distributed from the suction distribution passage 53 to the two suction pump ports 51 and 52 are equalized.

  The jet of surplus working fluid flowing out from the return valve port 13 strikes the inner wall surface 15 of the return valve port extension 14 before being merged with the working fluid flow guided from the tank passage 16 in the suction upstream passage 54. Therefore, it is possible to suppress an increase in the pressure loss of the working fluid flowing through the suction upstream passage portion 54 by the return valve port extension passage 14 having a small flow passage cross-sectional area.

  This prevents cavitation from occurring at one suction pump port 51 when the vane pump 1 operates at a low speed, prevents vibration and noise of the vane pump 1, and smoothly sucks the working fluid even at a high speed. The reduction of the discharge flow rate of the vane pump 1 is avoided.

  In the present embodiment, the center line R of the return valve port extension path 14 is offset with respect to the center line O of the suction upstream passage portion 54 in the direction opposite to the valve opening direction of the flow control valve 40.

  Based on the above configuration, the suction upstream passage portion 54 is connected to the return valve port extension passage in response to the jet of excess working fluid flowing out from the return valve port 13 flowing out so as to incline in the valve opening direction of the flow control valve 40 14 is offset in the valve opening direction of the flow rate control valve 40, so that the surplus working fluid jet flowing out from the valve port extension passage 14 is directed toward the center of the suction upstream passage 54, and the suction upstream passage It is smoothly deflected along the portion 54, the pressure loss of the working fluid flowing through the suction distribution passage 53 is reduced, and the suction performance of the vane pump 1 is prevented from being lowered.

  In this embodiment, the return valve port extension path 14 is formed coaxially with the return valve port 13 and has a cylindrical inner wall surface 15 that is deflected by surplus working fluid that flows obliquely out of the return valve port 13. It was.

  Based on the above configuration, the jet of the surplus working fluid that flows obliquely out of the return valve port 13 strikes the inner wall surface 15 of the return valve port extension passage 14 and is deflected along the suction upstream passage portion 54 smoothly. The pressure loss of the working fluid flowing through the suction distribution passage 53 can be reduced, and the suction performance of the vane pump 1 can be prevented from being lowered.

  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 vane pump of the present invention is not limited to a hydraulic device mounted on a vehicle, and can be used as a fluid pressure supply source for driving a load of, for example, a construction machine, a work machine, another machine, or a facility.

DESCRIPTION OF SYMBOLS 1 Vane pump 6 Vane pump mechanism 11 Spool accommodation hole 13 Return valve port 14 Return valve port extension path 15 Inner wall surface 16 Tank passage 40 Flow control valve 41 Spool 53 Suction distribution passage
54 Suction upstream passage portion 56 Suction downstream passage portion 56a Branch passage portion 56b Branch passage portion 56c Collecting passage portion

Claims (3)

A vane pump used as a working fluid pressure supply source,
A vane pump mechanism that pressurizes and discharges the working fluid;
Two suction pump ports for guiding the working fluid sucked into the vane pump mechanism;
A suction distribution passage for distributing the working fluid sucked into the two suction pump ports;
A tank passage for guiding a working fluid to the suction distribution passage;
A flow rate control valve for returning a part of the working fluid discharged from the vane pump mechanism to the suction distribution passage as surplus working fluid,
The flow control valve is
A spool receiving hole;
A spool housed in the spool housing hole;
A return valve port that opens in the spool receiving hole and is opened and closed by the spool, and
The suction distribution passage is
A return valve port extension connected to the return valve port;
A suction upstream passage portion connected to the return valve port extension passage and connected to the tank passage;
A suction downstream passage portion that branches from the suction upstream passage portion to the two suction pump ports;
A center line of the return valve port extension path and the suction upstream passage section are offset from each other.   The vane pump according to claim 1, wherein a center line of the return valve port extension path is offset in a direction opposite to a valve opening direction of the flow control valve with respect to a center line of the suction upstream passage portion. . The return valve port extension path is formed coaxially with the return valve port,
3. The vane pump according to claim 1, wherein the vane pump has a cylindrical inner wall surface which is deflected by surplus working fluid flowing obliquely from the return valve port.

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