vane pump

Abstract

To improve operating efficiency of a vane pump.SOLUTION: A vane pump 100 comprises a cam ring 4, and a body side plate 30 as a side member provided in contact with one side surface of the cam ring 4. The body side plate 30 comprises a first back pressure groove 34 as a back pressure groove communicating with a back pressure chamber 5 in suction regions 42a and 42c in which the capacity of a pump chamber 6 is expanded. The first back pressure groove 34 comprises a high-pressure groove 34a as a first groove for guiding working fluid to the back pressure chamber 5, and a low-pressure groove 34b as a second groove for guiding the working fluid to the back pressure chamber 5 closer to the forward side in the rotation direction of a rotor 2 than the back pressure chamber 5 to which the high-pressure groove 34a guides the working fluid, and guiding the working fluid having a lower pressure than that of the working fluid to be guided by the high-pressure groove 34a, to the back pressure chamber 5. The working fluid is selectively guided to the back pressure chamber 5 from the high-pressure groove 34a or the low-pressure groove 34b in association with rotation of the rotor 2.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a vane pump. [Background technology]

[0002] Patent Document 1 discloses a vane pump including a rotor that is driven to rotate, multiple slits opening on the outer peripheral surface of the rotor, multiple vanes slidably received in the slits, a cam ring having an inner peripheral cam surface against which the tips of the multiple vanes slide as the rotor rotates, a pair of side members arranged on either side of the rotor and the cam ring, and a pump chamber defined by the rotor, the cam ring, adjacent vanes, and the pair of side members. A back pressure chamber is defined by the inner peripheral surface of the slit and the base ends of the vanes, and high-pressure working fluid is introduced into the back pressure chamber from a discharge port provided in one of the side members. The vanes are urged in a direction protruding from the slits by the fluid pressure in the back pressure chamber pressing against their base ends and centrifugal force acting as the rotor rotates, causing the tips of the vanes to slide against the inner peripheral cam surface of the cam ring. As the rotor rotates, the vanes protrude from the slits, expanding the volume of the pump chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-41484 Summary of the Invention [Problem to be solved by the invention]

[0004] In a vane pump such as that described in Patent Document 1, when the pressure of the working fluid introduced into the back pressure chamber is high, the vane is strongly pressed against the inner cam surface, which increases the frictional force generated between the vane and the inner cam surface, which may result in a loss of rotational torque of the rotor and a decrease in the operating efficiency of the vane pump.

[0005] The present invention has been made in consideration of the above problems, and has an object to improve the operating efficiency of a vane pump. [Means for solving the problem]

[0006] the back pressure chamber is defined by the base ends of the vanes within the slits; the side member has a back pressure groove communicating with the back pressure chamber in a suction region where the volume of the pump chamber expands; and the back pressure groove has a first groove that guides working fluid to the back pressure chamber, and a second groove that guides working fluid to the back pressure chamber forward in the direction of rotation of the rotor than the back pressure chamber to which the first groove guides working fluid, and that guides working fluid of a lower pressure than the working fluid guided by the first groove to the back pressure chamber; and the working fluid is selectively guided into the back pressure chamber from the first groove or the second groove as the rotor rotates.

[0007] In this invention, the backpressure grooves communicate with the backpressure chamber in the suction region, with the first groove directing high-pressure working fluid to the backpressure chamber on the rear side of the rotor's rotational direction, and the second groove directing low-pressure working fluid to the backpressure chamber on the front side of the rotor's rotational direction. Therefore, in the suction region, the pressure of the working fluid directed to the backpressure chamber is high in the region where the vane protrusion changes significantly (the rear side of the rotor's rotational direction), and low in the region where the vane protrusion changes only slightly (the front side of the rotor's rotational direction). This reduces the force pressing the vane toward the inner cam surface in the region where the vane protrusion changes only slightly, thereby reducing the frictional force generated between the vane and the inner cam surface. Furthermore, in the region where the vane protrusion changes only slightly, the vane can be protruded and brought into sliding contact with the inner cam surface with a small force, so even if the pressure of the working fluid in the backpressure chamber is low, the operation of the vane pump is not affected. This reduces the loss of rotor rotational torque and improves the operating efficiency of the vane pump.

[0008] The present invention is also characterized in that the second groove is provided separately from the first groove so as not to communicate with the first groove.

[0009] In this invention, by dividing the back pressure groove into a first groove and a second groove, the frictional force generated between the vane and the inner cam surface can be reduced in the region where the change in the vane protrusion amount is small.

[0010] In addition, the present invention is characterized in that the side member further has a suction port that introduces the working fluid into the pump chamber, and a communication groove that communicates between the second groove and the suction port.

[0011] In this aspect of the invention, the second groove and the suction port are connected to each other by the communication groove, so that low-pressure working fluid can be guided to the second groove.

[0012] The present invention is also characterized in that the communication groove is provided in a direction shifted from the extending direction of the slit.

[0013] The present invention is also characterized in that the slits are provided extending radially along the radial direction of the rotor, and the communication grooves are provided extending linearly and deviated from the radial direction of the rotor.

[0014] In these inventions, the communicating groove can be prevented from interfering with the sliding of the vane within the slit.

[0015] In addition, the present invention is characterized in that the inner cam surface has a first curved surface provided in the suction area, the radial dimension between which the rotor rotates increasing at a constant rate along the direction of rotation of the rotor, and a second curved surface that is continuous with the first curved surface and is provided in the suction area further forward in the direction of rotation of the rotor than the first curved surface, the radial dimension between which the rotor rotates decreasing along the direction of rotation of the rotor, and the second groove begins to communicate with the back pressure chamber at a position corresponding to the boundary between the first curved surface and the second curved surface as the rotor rotates.

[0016] In this invention, the second curved surface has a small change in radial dimension relative to the rotor along the rotor rotation direction. Therefore, when the vane slides against the second curved surface, the change in the vane protrusion amount with rotor rotation is small. Therefore, the second groove communicates with the back pressure chamber from a region where the change in the vane protrusion amount with rotor rotation begins to decrease, and guides low-pressure working fluid to the back pressure chamber. Therefore, the second groove can efficiently reduce the friction force generated between the vane and the inner cam surface in the region where the change in the vane protrusion amount is small. [Effects of the Invention]

[0017] According to the present invention, the operating efficiency of the vane pump can be improved. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a cross-sectional view of a vane pump according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view of the rotor, vanes, and cam ring, showing the rotor, vanes, and cam ring assembled together. [Figure 3] 3 is an enlarged view of a transition portion of the inner cam surface of FIG. 2. [Figure 4] 6 is a graph showing the relationship between the protrusion amount of the vane in the suction region and the rotation amount of the rotor. [Figure 5] FIG. [Figure 6] FIG. 10 is a front view of the cover-side side plate. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, a vane pump according to an embodiment of the present invention will be described with reference to the drawings. The vane pump is used as a fluid pressure supply source for fluid pressure devices (e.g., a power steering device, a transmission, etc.) mounted on a vehicle. Here, a vane pump using hydraulic oil as the working fluid will be described, but other fluids such as hydraulic water may also be used as the working fluid.

[0020] 1 and 2, a vane pump 100 includes a pump body 10 in which a pump accommodating recess 10A is formed, a pump cover 20 that covers the opening of the pump accommodating recess 10A and is fixed to the pump body 10, a drive shaft 1 that is rotatably supported by the pump body 10 and the pump cover 20 via bearings 11 and 12, a rotor 2 that is connected to the drive shaft 1 and driven to rotate, a plurality of slits 2s that open on the outer peripheral surface of the rotor 2, a plurality of vanes 3 that are slidably received in the slits 2s, and a cam ring 4 that has an inner peripheral cam surface 4a against which tip ends 3a of the vanes 3 slide as the rotor 2 rotates. The cam ring 4 accommodates the rotor 2 and the vanes 3.

[0021] The vane pump 100 is driven by a drive device (not shown), such as an engine, and generates fluid pressure by rotating a rotor 2 connected to a drive shaft 1 counterclockwise as shown by the arrow in Figure 2.

[0022] In the following, the direction along the rotation axis of the rotor 2 will be referred to as the "axial direction," the radial direction centered on the rotation axis of the rotor 2 will be referred to as the "radial direction," and the direction in which the rotor 2 rotates when the vane pump 100 is operating will be referred to as the "rotation direction."

[0023] As shown in FIG. 1, the vane pump 100 further includes a body-side side plate 30 as a side member provided at one axial end of the rotor 2 and in contact with one side of the rotor 2 and the cam ring 4, and a cover-side side plate 40 provided at the other axial end of the rotor 2 and in contact with the other side of the rotor 2 and the cam ring 4.

[0024] The body-side side plate 30 is provided between the bottom surface of the pump accommodating recess 10A and the rotor 2. One axial end face of the rotor 2 slides against the body-side side plate 30, and one axial end face of the cam ring 4 abuts against it. The cover-side side plate 40 is provided between the rotor 2 and the pump cover 20. The other axial end face of the rotor 2 slides against the cover-side side plate 40, and the other axial end face of the cam ring 4 abuts against it.

[0025] In this way, the body-side side plate 30 and the cover-side side plate 40 are arranged facing both side surfaces of the rotor 2 and the cam ring 4. In other words, the body-side side plate 30 and the cover-side side plate 40 are arranged with the rotor 2 and the cam ring 4 sandwiched between them in the axial direction.

[0026] The body-side side plate 30, rotor 2, cam ring 4, and cover-side side plate 40 are housed in a pump accommodating recess 10A of the pump body 10. In this state, the pump cover 20 is attached to the pump body 10, thereby sealing the pump accommodating recess 10A.

[0027] 2, a plurality of slits 2s are formed in the rotor 2, extending radially along the radial direction of the rotor 2. The openings of the slits 2s are formed in raised portions 23 that rise radially outward from the outer periphery of the rotor 2.

[0028] The vane 3 is formed in the shape of a rectangular plate. The vane 3 is slidably inserted into the slit 2s and has a tip end 3a, which is the end protruding from the slit 2s, and a base end 3b, which is the end opposite to the tip end 3a. Within the slit 2s, a back pressure chamber 5 is defined by the base end 3b of the vane 3. As will be described later, the back pressure chamber 5 communicates with the high pressure chamber 14 or the low pressure chamber 21, and hydraulic oil is guided into the back pressure chamber 5 from the high pressure chamber 14 or the low pressure chamber 21. The pressure of the hydraulic oil guided to the back pressure chamber 5 presses the vane 3 in the direction protruding from the slit 2s.

[0029] The cam ring 4 is an annular member having an inner cam surface 4a, which is a substantially oval inner surface, and pin holes 4b through which positioning pins 8 are inserted. The inner cam surface 4a is the surface against which the tips 3a of the multiple vanes 3 slide as the rotor 2 rotates.

[0030] When the rotor 2 rotates, centrifugal force is generated in the vanes 3. This centrifugal force presses the vanes 3 in a direction that causes them to protrude from the slits 2s. In other words, the vanes 3 are pressed in a direction that causes them to protrude from the slits 2s (radially outward) by the fluid pressure in the back pressure chamber 5 pressing against the base ends 3b and the centrifugal force that acts as the rotor 2 rotates. When the vanes 3 are pressed radially outward, the tip ends 3a of the vanes 3 come into sliding contact with the inner cam surface 4a of the cam ring 4. As a result, a pump chamber 6 is defined inside the cam ring 4 by the outer circumferential surface of the rotor 2, the inner cam surface 4a of the cam ring 4, and a pair of adjacent vanes 3.

[0031] The inner cam surface 4a is formed in a substantially elliptical shape. Therefore, the volume of the pump chamber 6 repeatedly expands and contracts with the rotation of the rotor 2. Hydraulic oil is sucked in the expansion region (suction region) where the pump chamber 6 expands, and hydraulic oil is discharged in the contraction region (discharge region) where the pump chamber 6 contracts.

[0032] 2, the vane pump 100 according to this embodiment has a first suction region 42a and a first discharge region 42b where the vane 3 makes a first reciprocating motion, and a second suction region 42c and a second discharge region 42d where the vane 3 makes a second reciprocating motion. During one rotation of the rotor 2, the pump chamber 6 expands in the first suction region 42a, contracts in the first discharge region 42b, expands in the second suction region 42c, and contracts in the second discharge region 42d. The vane pump 100 has two suction regions 42a, 42c and two discharge regions 42b, 42d, but is not limited thereto and may have one or three or more suction regions and one or three or more discharge regions.

[0033] The inner peripheral cam surface 4a has a first curved surface 141 that is provided in each of the suction regions 42a and 42c and whose radial dimension between the rotor 2 and the first curved surface 141 increases at a constant rate along the rotation direction of the rotor 2, and a second curved surface 142 that is continuous with the first curved surface 141 and is provided in each of the suction regions 42a and 42c forward of the first curved surface 141 along the rotation direction of the rotor 2 and whose radial dimension between the rotor 2 and the first curved surface 142 increases at a constant rate along the rotation direction of the rotor 2, compared to the first curved surface 141. The boundary between the first curved surface 141 and the second curved surface 142 is referred to as a boundary 143.

[0034] Specifically, the radial dimension between the first curved surface 141 and the rotor 2 is the radial dimension between the first curved surface 141 and the portion of the rotor 2 where the slit 2s opens. For example, taking the first curved surface 141 as an example, the radial dimension between the first curved surface 141 and the rotor 2 is the radial dimension A between the protruding portion 23 of the rotor 2 and the first curved surface 141, as shown in FIG. 3. Note that, for convenience of explanation, FIG. 3 omits the illustration of the components provided on the body-side side plate 30. In other words, the radial dimension between the first curved surface 141 and the rotor 2 corresponds to the amount of protrusion of the vane 3 from the slit 2s of the rotor 2. Furthermore, the amount of change in the radial dimension between the first curved surface 141 and the rotor 2 corresponds to the change in the amount of protrusion of the vane 3. The same applies to the second curved surface 142.

[0035] The vane 3 protrudes from the slit 2s from the first curved surface 141 to the second curved surface 142 until it reaches the maximum protrusion amount. The first curved surface 141 is provided so that the radial dimension between the vane 3 and the rotor 2 increases at a constant rate along the rotational direction of the rotor 2. Therefore, when the vane 3 is in sliding contact with the first curved surface 141 as the rotor 2 rotates, the vane 3 protrudes from the slit 2s at a constant speed, as shown in FIG. 4. The second curved surface 142 is provided so that the radial dimension between the vane 3 and the rotor 2 decreases along the rotational direction of the rotor 2. Therefore, when the vane 3 passes through the boundary 143 and is in sliding contact with the second curved surface 142, the speed at which the vane 3 protrudes from the slit 2s gradually decreases. When the protrusion amount of the vane 3 reaches the maximum, the speed at which the vane 3 protrudes from the slit 2s becomes zero. Thus, in the suction regions 42a and 42c, the change in the protruding amount of the vanes 3 is large on the rear side in the rotation direction of the rotor 2, and small on the front side in the rotation direction of the rotor 2.

[0036] 1, an annular high-pressure chamber 14 is defined by the pump body 10 and the body-side side plate 30 on the bottom side of the pump accommodating recess 10A of the pump body 10. The high-pressure chamber 14 is connected to a fluid pressure device 70 (e.g., a power steering device, a transmission, etc.) outside the vane pump 100 via a discharge passage 62. The discharge passage 62 is a passage provided on the vane pump 100 side, for example.

[0037] A low-pressure chamber 21 is formed in the pump cover 20, and a bypass passage 13 that communicates with the low-pressure chamber 21 is formed on the inner circumferential surface of the pump accommodating recess 10A. Two bypass passages 13 are provided at positions opposite each other across the cam ring 4. The low-pressure chamber 21 is connected to the tank 60 via a suction passage 61.

[0038] 1 and 2, cam ring 4 has cutouts 4c and 4d that penetrate from its outer peripheral surface to inner peripheral cam surface 4a. Cutout 4c opens to the side surface that contacts body-side side plate 30, and cutout 4d opens to the side surface that contacts cover-side side plate 40.

[0039] Fig. 5 is a front view of body-side side plate 30 as seen from the side of cam ring 4. As shown in Fig. 5, body-side side plate 30 is a plate-like member having sliding surface 30a along which the side surface of vane 3 slides, discharge ports 31 formed to correspond to discharge regions 42b and 42d, respectively, through hole 32 through which drive shaft 1 is inserted, suction ports 33 formed to correspond to suction regions 42a and 42c, respectively, and pin holes 39 through which positioning pins 8 are inserted.

[0040] Two discharge ports 31 are provided at opposing positions across a through hole 32. Each discharge port 31 is formed in an arc shape with the through hole 32 as its center. The discharge port 31 penetrates the body-side side plate 30 and communicates with a high-pressure chamber 14 formed in the pump body 10. The discharge port 31 guides the hydraulic oil discharged from the pump chamber 6 to the high-pressure chamber 14. The hydraulic oil that has flowed into the high-pressure chamber 14 is supplied to a fluid pressure device 70 outside the vane pump 100 through a discharge passage 62 (see FIG. 1).

[0041] The suction ports 33 are provided at two positions facing each other across the through hole 32. The suction ports 33 are formed at positions corresponding to the bypass passages 13 of the pump accommodating recess 10A. The suction ports 33 are formed to have a concave shape that opens radially outward. The outer peripheral ends of the suction ports 33 reach the outer peripheral surface of the body-side side plate 30.

[0042] 1, when the body-side side plate 30 is attached to the cam ring 4, the suction port 33 of the body-side side plate 30 faces the cutout portion 4c of the cam ring 4. The hydraulic oil in the bypass passage 13 is guided to the pump chamber 6 through the gap between the cutout portion 4c and the suction port 33. The suction port 33 guides the hydraulic oil from the low-pressure chamber 21 to the pump chamber 6.

[0043] As shown in FIG. 5, a groove-shaped notch 36 is formed in the sliding surface 30a of the body-side side plate 30. The notch 36 is provided at the end of the discharge port 31 on the communication start side where communication with the pump chamber 6 begins as the rotor 2 rotates, and communicates with the discharge port 31. The notch 36 is formed so that the opening area gradually increases in the direction of rotation of the rotor 2. By forming the notch 36, hydraulic oil is supplied to the pump chamber 6 through the notch 36 at a stage before the pump chamber 6 directly opens to the discharge port 31. This increases the pressure in the pump chamber 6, preventing a sudden pressure fluctuation in the high-pressure chamber 14.

[0044] The body-side side plate 30 has a pair of back pressure grooves, i.e., first back pressure grooves 34, respectively provided in the suction regions 42a, 42c, second back pressure grooves 35, respectively provided in the discharge regions 42b, 42d, and a communication groove 37 that connects a low pressure groove 34b (described later) of the first back pressure groove 34 to the suction port 33. The back pressure grooves 34, 35 are arranged in an arc shape centered on the through hole 32 and open to the sliding surface 30a. The pair of first back pressure grooves 34 are arranged to face each other across the through hole 32. The pair of second back pressure grooves 35 are arranged to face each other across the through hole 32. The pair of second back pressure grooves 35 are arranged at positions shifted approximately 90° from the pair of first back pressure grooves 34, centered on the through hole 32. The back pressure grooves 34, 35 overlap and communicate with multiple back pressure chambers 5 as the rotor 2 rotates. The first back pressure groove 34 communicates with the back pressure chamber 5 in the suction regions 42a and 42c, and the second back pressure groove 35 communicates with the back pressure chamber 5 in the discharge regions 42b and 42d.

[0045] The first back pressure groove 34 has a high-pressure groove 34a as a first groove that guides hydraulic oil to the back pressure chamber 5, and a low-pressure groove 34b that is located forward of the high-pressure groove 34a in the rotational direction of the rotor 2 and that guides hydraulic oil of a lower pressure than the hydraulic oil guided by the high-pressure groove 34a to the back pressure chamber 5. The low-pressure groove 34b is located separately from the high-pressure groove 34a so as not to communicate with the high-pressure groove 34a. In this embodiment, the first back pressure groove 34 is composed of two grooves, the high-pressure groove 34a and the low-pressure groove 34b.

[0046] The high-pressure groove 34a is formed in an arc shape. As shown in FIG. 1 , the high-pressure groove 34a penetrates the body-side side plate 30 and communicates with the high-pressure chamber 14. As a result, high-pressure hydraulic oil from the discharge port 31 is guided to the backpressure chamber 5 through the high-pressure chamber 14 and the high-pressure groove 34a. The high-pressure groove 34a is formed in a region corresponding to the first curved surface 141 of the inner peripheral cam surface 4a of the cam ring 4. Specifically, in the front view shown in FIG. 2 , the high-pressure groove 34a is formed so that the first curved surface 141 is located on a straight line extending from the rotational center axis O of the rotor 2 through the high-pressure groove 34a. In other words, the backpressure chamber 5 presses the vane 3 toward the first curved surface 141 by the hydraulic oil guided through the high-pressure groove 34a, causing the vane 3 to slide against the first curved surface 141.

[0047] Low-pressure groove 34b is formed in an arc shape. Low-pressure groove 34b does not penetrate body-side side plate 30 and does not communicate with high-pressure chamber 14. Low-pressure groove 34b communicates with suction port 33 through communication groove 37. As a result, low-pressure hydraulic oil from suction port 33 is guided to back-pressure chamber 5 through communication groove 37 and low-pressure groove 34b. Low-pressure groove 34b is formed in an area corresponding to second curved surface 142 of inner peripheral cam surface 4a of cam ring 4, and as rotor 2 rotates, low-pressure groove 34b begins to communicate with back-pressure chamber 5 at a position corresponding to boundary 143 between first curved surface 141 and second curved surface 142. Specifically, in the front view shown in FIG. 2 , low-pressure groove 34b is arranged such that second curved surface 142 is located on a line extending from the central axis O of rotation of rotor 2 through low-pressure groove 34b, and boundary 143 is located on a line extending from the central axis O of rotation through the rear end of low-pressure groove 34b in the rotational direction. In other words, hydraulic oil guided to back-pressure chamber 5 through low-pressure groove 34b presses vane 3 toward second curved surface 142, causing vane 3 to slide against second curved surface 142. In this manner, low-pressure groove 34b guides hydraulic fluid to back-pressure chamber 5 that is located forward in the rotational direction of rotor 2 relative to back-pressure chamber 5 to which high-pressure groove 34a guides hydraulic oil. In vane pump 100 of this embodiment, hydraulic oil is selectively guided to back-pressure chamber 5 from high-pressure groove 34a or low-pressure groove 34b as rotor 2 rotates.

[0048] The communication groove 37 extends linearly between the low-pressure groove 34b and the suction port 33 and opens to the sliding surface 30a of the body-side side plate 30. The communication groove 37 does not penetrate the body-side side plate 30 and does not communicate with the high-pressure chamber 14. Therefore, only low-pressure hydraulic oil from the suction port 33 is guided to the low-pressure groove 34b through the communication groove 37. The communication groove 37 is provided offset from the extension direction of the slit 2s. Specifically, the communication groove 37 is provided offset from the radial direction of the rotor 2. In this embodiment, the communication groove 37 extends from the rear end of the low-pressure groove 34b in the rotation direction of the rotor 2 to the suction port 33. Therefore, the communication groove 37 does not hinder the sliding of the vane 3 within the slit 2s. Note that the communication groove 37 may be provided along the extension direction of the slit 2s, although this would hinder the sliding of the vane 3.

[0049] The second back pressure groove 35 is provided through the body-side side plate 30 and communicates with the high-pressure chamber 14. As a result, high-pressure hydraulic oil from the discharge port 31 is guided to the back pressure chamber 5 through the high-pressure chamber 14 and the second back pressure groove 35. The hydraulic oil guided to the back pressure chamber 5 through the second back pressure groove 35 presses the vane 3 toward the inner cam surface 4a in the discharge regions 42b and 42d, causing the vane 3 to slide against the inner cam surface 4a.

[0050] 6 is a front view of cover-side side plate 40 as viewed from the pump cover 20 side. As shown in Fig. 6, cover-side side plate 40 is a plate-like member having sliding surface 40a (see Fig. 1) on which the side surface of vane 3 slides, through-hole 42 through which drive shaft 1 passes, notches 43 formed to correspond to suction areas 42a and 42c, respectively, and pin hole 49 through which positioning pin 8 passes. Cover-side side plate 40 is positioned relative to cam ring 4 and body-side side plate 30 by positioning pin 8.

[0051] Two notches 43 are provided at opposing positions across the through hole 42. The notches 43 are formed in pump accommodating recess 10A at positions corresponding to bypass passage 13. The notches 43 are provided so as to open radially outward. As shown in FIG. 1, when cover-side side plate 40 is assembled to cam ring 4, notch 43 of cover-side side plate 40 faces notch 4d of cam ring 4. The hydraulic oil in bypass passage 13 and low-pressure chamber 21 is guided to pump chamber 6 through notch 43 and notch 4d.

[0052] Thus, the pair of suction ports 33 are located in the suction regions 42a and 42c, and the pair of discharge ports 31 are located in the discharge regions 42b and 42d. Furthermore, hydraulic oil is introduced into the pump chamber 6 from both axial sides through the suction ports 33 and the cutout portions 43 of the cover-side side plate 40.

[0053] Next, the operation of the vane pump 100 will be described.

[0054] When the drive shaft 1 is driven to rotate by the power of a drive device (not shown), such as an engine, the rotor 2 rotates in the direction indicated by the arrow in FIG. 2. As the rotor 2 rotates, the pump chambers 6 located in the suction regions 42a and 42c expand. As a result, hydraulic oil in the tank 60 is sucked into the pump chambers 6 through the suction passage 61, the low-pressure chamber 21, the suction port 33, and the notch 43 in the cover-side side plate 40, as shown in FIG. 1. As the rotor 2 rotates, the pump chambers 6 located in the discharge regions 42b and 42d contract. As a result, hydraulic oil in the pump chambers 6 is discharged to the high-pressure chamber 14 through the discharge port 31 (see FIG. 2). The hydraulic oil discharged to the high-pressure chamber 14 is supplied to an external fluid pressure device 70 through the discharge passage 62. In the vane pump 100 of this embodiment, each pump chamber 6 repeatedly draws in and discharges hydraulic oil twice during one rotation of the rotor 2.

[0055] A portion of the hydraulic oil discharged into the high-pressure chamber 14 is supplied to the back pressure chamber 5 through the back pressure grooves 34, 35 and presses the base end 3b of the vane 3 toward the inner circumferential cam surface 4a. Therefore, the vane 3 is pressed in a direction protruding from the slit 2s by the fluid pressure in the back pressure chamber 5 pressing the base end 3b and the centrifugal force acting in conjunction with the rotation of the rotor 2. As a result, the tip end 3a of the vane 3 rotates while making sliding contact with the inner circumferential cam surface 4a of the cam ring 4, and the hydraulic oil in the pump chamber 6 is discharged from the discharge port 31 without leaking between the tip end 3a of the vane 3 and the inner circumferential cam surface 4a of the cam ring 4.

[0056] If the pressure of the hydraulic oil introduced into the back pressure chamber is high, the vane is pressed strongly against the inner cam surface, increasing the frictional force generated between the vane and the inner cam surface. This can result in a loss of rotational torque of the rotor and a decrease in the operating efficiency of the vane pump. However, if the pressure of the hydraulic oil introduced into the back pressure chamber is low, the vane cannot protrude toward the inner cam surface in the suction region and contact the inner cam surface, causing hydraulic oil in the pump chamber to leak between the tip of the vane and the inner cam surface of the cam ring.

[0057] In contrast, in the vane pump 100 of this embodiment, as described above, the suction regions 42a, 42c are provided with the first backpressure groove 34 having the high-pressure groove 34a and the low-pressure groove 34b. The first backpressure groove 34 communicates with the backpressure chamber 5 in the suction regions 42a, 42c. The high-pressure groove 34a guides high-pressure hydraulic oil from the high-pressure chamber 14 to the backpressure chamber 5 on the rear side in the rotation direction of the rotor 2, and the low-pressure groove 34b guides low-pressure hydraulic oil from the low-pressure chamber 21 to the backpressure chamber 5 on the front side in the rotation direction of the rotor 2. Furthermore, in the suction regions 42a, 42c, the change in the protrusion amount of the vane 3 is large on the front side in the rotation direction of the rotor 2, and the change in the protrusion amount of the vane 3 is small on the rear side in the rotation direction of the rotor 2. Therefore, in the suction regions 42a and 42c, the pressure of the hydraulic oil introduced into the back pressure chamber 5 is high in the region where the change in the protrusion amount of the vane 3 is large (rearward in the direction of rotation of the rotor 2), and the pressure of the hydraulic oil introduced into the back pressure chamber 5 is low in the region where the change in the protrusion amount of the vane 3 is small (forward in the direction of rotation of the rotor 2). As a result, in the region where the change in the protrusion amount of the vane 3 is small, the force pressing the vane 3 toward the inner cam surface 4a is small, and the frictional force generated between the vane 3 and the inner cam surface 4a is also small. Furthermore, in the region where the change in the protrusion amount of the vane 3 is small, the vane 3 can be protruded and brought into sliding contact with the inner cam surface 4a with a small force. Therefore, even if the pressure of the hydraulic oil in the back pressure chamber 5 is low in this region, it does not affect the operation of the vane pump 100. This reduces the loss of rotational torque of the rotor 2 and improves the operating efficiency of the vane pump 100.

[0058] Furthermore, in vane pump 100, low-pressure groove 34b begins to communicate with back-pressure chamber 5 at a position corresponding to boundary 143 between first curved surface 141 and second curved surface 142 as rotor 2 rotates. Therefore, low-pressure groove 34b communicates with back-pressure chamber 5 from the region where the change in the protrusion amount of vane 3 associated with the rotation of rotor 2 begins to become small, and guides low-pressure hydraulic oil to back-pressure chamber 5. Therefore, low-pressure groove 34b can efficiently reduce the frictional force generated between vane 3 and inner cam surface 4a in the region where the change in the protrusion amount of vane 3 is small.

[0059] According to the present embodiment described above, the following effects are achieved.

[0060] In the vane pump 100, the first back pressure groove 34 communicates with the back pressure chamber 5 in the suction regions 42a and 42c, with the high-pressure groove 34a directing high-pressure hydraulic oil to the back pressure chamber 5 on the rear side of the rotor 2 in the rotational direction, and the low-pressure groove 34b directing low-pressure hydraulic oil to the back pressure chamber 5 on the front side of the rotor 2 in the rotational direction. As a result, in a region where the change in the protrusion amount of the vane 3 is small, the force pressing the vane 3 toward the inner cam surface 4a is small, and the frictional force generated between the vane 3 and the inner cam surface 4a is reduced. Furthermore, in a region where the change in the protrusion amount of the vane 3 is small, the vane 3 can be protruded and brought into sliding contact with the inner cam surface 4a with a small force, so that even if the pressure of the hydraulic oil in the back pressure chamber 5 is small, the operation of the vane pump 100 is not affected. This reduces loss of rotational torque of the rotor 2 and improves the operating efficiency of the vane pump 100.

[0061] In vane pump 100, low-pressure groove 34b begins to communicate with back-pressure chamber 5 at a position corresponding to boundary 143 between first curved surface 141 and second curved surface 142 as rotor 2 rotates. Low-pressure groove 34b communicates with back-pressure chamber 5 from a region where changes in the amount of protrusion of vane 3 associated with rotation of rotor 2 begin to become small, and guides low-pressure hydraulic oil to back-pressure chamber 5. Therefore, low-pressure groove 34b can efficiently reduce the frictional force generated between vane 3 and inner cam surface 4a in a region where changes in the amount of protrusion of vane 3 are small.

[0062] Next, modified examples of this embodiment will be described. The following modified examples are also within the scope of the present invention, and it is possible to combine the configurations shown in the modified examples with the configurations described in the above embodiment, or to combine the configurations described in the following different modified examples.

[0063] <Variation 1> In the above embodiment, the low-pressure groove 34b is provided so as to begin to communicate with the back-pressure chamber 5 at a position corresponding to the boundary 143 between the first curved surface 141 and the second curved surface 142 as the rotor 2 rotates. However, the present invention is not limited to this, and the low-pressure groove 34b may be provided further forward in the rotational direction of the rotor 2 than the high-pressure groove 34a in the suction regions 42a and 42c. Also, in the above embodiment, the high-pressure groove 34a and the low-pressure groove 34b are provided separately so as not to communicate with each other. However, the present invention is not limited to this, and the high-pressure groove 34a and the low-pressure groove 34b may be provided so as to communicate with each other via a throttle or the like. Furthermore, in the above embodiment, the first back-pressure groove 34 is formed by two grooves, the high-pressure groove 34a and the low-pressure groove 34b. However, the present invention is not limited to this, and the first back-pressure groove 34 may be formed by three or more grooves. Even in this case, the first back-pressure groove 34 is provided so that the groove located forward in the rotational direction of the rotor 2 in the suction regions 42a and 42c guides the low-pressure working fluid to the back-pressure chamber 5. These configurations also provide the same effects as the above embodiment.

[0064] <Variation 2> In the above embodiment, the communication groove 37 is provided linearly between the low-pressure groove 34b and the suction port 33. However, the present invention is not limited to this, and the communication groove 37 may be provided in an arc shape. Furthermore, the communication groove 37 does not necessarily have to be provided between the low-pressure groove 34b and the suction port 33, as long as it can guide a working fluid having a lower pressure than the working fluid guided to the high-pressure groove 34a to the low-pressure groove 34b. For example, the communication groove 37 may be configured to guide the low-pressure working fluid from the low-pressure chamber 21 to the low-pressure groove 34b. Even with these configurations, the same effects as those of the above embodiment can be achieved.

[0065] <Variation 3> In the above embodiment, the vane pump 100 includes a body-side side plate 30 as a side member provided at one axial end of the rotor 2 and in contact with one side surface of the cam ring 4, and a cover-side side plate 40 provided at the other axial end of the rotor 2 and in contact with the other side surfaces of the rotor 2 and the cam ring 4. However, the vane pump 100 may not include the cover-side side plate 40, and may have a configuration in which the cam ring 4 is sandwiched between the pump cover 20 and the body-side side plate 30 in contact with each other.

[0066] <Variation 4> In the above embodiment, the slits 2s are provided so as to extend radially along the radial direction of the rotor 2. However, the slits 2s may be provided linearly and offset from the radial direction of the rotor 2. For example, the slits 2s may be provided in the rotor 2 so as to form a spiral shape.

[0067] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0068] The vane pump 100 includes a rotor 2 that is driven to rotate, a plurality of slits 2s that open on the outer peripheral surface of the rotor 2, a plurality of vanes 3 that are slidably received in the slits 2s, a cam ring 4 that has an inner peripheral cam surface 4a against which tip ends 3a of the vanes 3 slide as the rotor 2 rotates, a body-side side plate 30 that serves as a side member that is provided in contact with one side surface of the cam ring 4, a pump chamber 6 that is defined by the rotor 2, the cam ring 4, and a pair of adjacent vanes 3, and a back pressure chamber 5 that is defined within the slits 2s by base ends 3b of the vanes 3. The plate 30 has a first back pressure groove 34 as a back pressure groove that communicates with the back pressure chamber 5 in the suction regions 42a, 42c where the volume of the pump chamber 6 expands. The first back pressure groove 34 has a high-pressure groove 34a as a first groove that guides the working fluid to the back pressure chamber 5, and a low-pressure groove 34b as a second groove that guides the working fluid to the back pressure chamber 5 that is further forward in the rotation direction of the rotor 2 than the back pressure chamber 5 to which the high-pressure groove 34a guides the working fluid, and that guides the working fluid of a lower pressure than the working fluid guided by the high-pressure groove 34a to the back pressure chamber 5. The working fluid is selectively guided to the back pressure chamber 5 from the high-pressure groove 34a or the low-pressure groove 34b as the rotor 2 rotates.

[0069] In this configuration, the first backpressure groove 34 communicates with the backpressure chamber 5 in the suction regions 42a and 42c, with the high-pressure groove 34a directing high-pressure working fluid to the backpressure chamber 5 on the rear side in the rotational direction of the rotor 2 and the low-pressure groove 34b directing low-pressure working fluid to the backpressure chamber 5 on the front side in the rotational direction of the rotor 2. Therefore, in the suction regions 42a and 42c, the pressure of the working fluid directed to the backpressure chamber 5 is high in the region where the change in the protrusion amount of the vane 3 is large (the rear side in the rotational direction of the rotor 2), and the pressure of the working fluid directed to the backpressure chamber 5 is low in the region where the change in the protrusion amount of the vane 3 is small (the front side in the rotational direction of the rotor 2). As a result, in the region where the change in the protrusion amount of the vane 3 is small, the force pressing the vane 3 toward the inner cam surface 4a is reduced, and the frictional force generated between the vane 3 and the inner cam surface 4a is reduced. Furthermore, in the region where the change in the protrusion amount of the vane 3 is small, the vane 3 can be protruded and brought into sliding contact with the inner cam surface 4a with a small force, so even if the pressure of the working fluid in the back pressure chamber 5 is small, it does not affect the operation of the vane pump 100. This reduces the loss of rotational torque of the rotor 2 and improves the operating efficiency of the vane pump 100.

[0070] In the vane pump 100, the low-pressure groove 34b is provided separately from the high-pressure groove 34a so as not to communicate with the high-pressure groove 34a.

[0071] In this configuration, by dividing the first back pressure groove 34 into a high pressure groove 34a and a low pressure groove 34b, the friction force generated between the vane 3 and the inner cam surface 4a can be reduced in the region where the change in the protrusion amount of the vane 3 is small.

[0072] In the vane pump 100, the body side plate 30 further has a suction port 33 that introduces the working fluid into the pump chamber 6, and a communication groove 37 that connects the low-pressure groove 34b and the suction port 33.

[0073] In this configuration, the low-pressure groove 34b and the suction port 33 communicate with each other through the communication groove 37, so that low-pressure working fluid can be guided to the low-pressure groove 34b.

[0074] In the vane pump 100, the communication groove 37 is provided so as to be offset from the direction in which the slit 2s extends.

[0075] In the vane pump 100, the slits 2s are provided so as to extend radially along the radial direction of the rotor 2, and the communication grooves 37 are provided so as to extend linearly and deviate from the radial direction of the rotor 2.

[0076] In these configurations, the communicating groove 37 can be prevented from interfering with the sliding of the vane 3 within the slit 2s.

[0077] In addition, in the vane pump 100, the inner cam surface 4a has a first curved surface 141 provided in the suction regions 42a, 42c, and the radial dimension between the rotor 2 and the first curved surface 141 increases at a constant rate along the rotation direction of the rotor 2, and a second curved surface 142 that is continuous with the first curved surface 141 and is provided in the suction regions 42a, 42c further forward in the rotation direction of the rotor 2 than the first curved surface 141, and the radial dimension between the rotor 2 and the second curved surface 142 decreases along the rotation direction of the rotor 2, and the low-pressure groove 34b begins to communicate with the back pressure chamber 5 at a position corresponding to the boundary 143 between the first curved surface 141 and the second curved surface 142 as the rotor 2 rotates.

[0078] In this configuration, the amount of change in the radial dimension between the second curved surface 142 and the rotor 2 becomes small along the direction of rotation of the rotor 2. Therefore, when the vane 3 slides on the second curved surface 142, the change in the amount of protrusion of the vane 3 that accompanies the rotation of the rotor 2 is small. Therefore, the low-pressure groove 34b communicates with the back-pressure chamber 5 from the region where the change in the amount of protrusion of the vane 3 that accompanies the rotation of the rotor 2 begins to become small, and guides low-pressure working fluid to the back-pressure chamber 5. Therefore, the low-pressure groove 34b can efficiently reduce the frictional force generated between the vane 3 and the inner cam surface 4a in the region where the change in the amount of protrusion of the vane 3 is small.

[0079] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments. [Explanation of symbols]

[0080] 2 rotor, 2s slit, 3 vane, 3a tip portion, 3b base portion, 4 cam ring, 4a inner cam surface, 5 back pressure chamber, 6 pump chamber, 30 body side plate (side member), 33 suction port, 34 first back pressure groove (back pressure groove), 34a high pressure groove (first groove), 34b low pressure groove (second groove), 37 communicating groove, 42a, 42c suction area, 141 first curved surface, 142 second curved surface, 143 boundary, 100 vane pump

Claims

1. a rotor that is driven to rotate; a plurality of slits opening on the outer peripheral surface of the rotor; a plurality of vanes slidably received in the slits; a cam ring having an inner peripheral cam surface with which the tip end of the vane slides as the rotor rotates; a side member provided in contact with one side surface of the cam ring; a pump chamber defined by the rotor, the cam ring, and a pair of adjacent vanes; a back pressure chamber defined by the base end of the vane within the slit, the side member has a back pressure groove communicating with the back pressure chamber in a suction region where the volume of the pump chamber expands; The back pressure groove is a first groove for guiding a working fluid to the back pressure chamber; a second groove that guides the working fluid to the back pressure chamber that is located forward in the rotational direction of the rotor than the back pressure chamber to which the first groove guides the working fluid, and that guides the working fluid having a lower pressure than the working fluid guided by the first groove to the back pressure chamber, A vane pump, characterized in that the working fluid is selectively introduced into the back pressure chamber from the first groove or the second groove as the rotor rotates.

2. 2. The vane pump according to claim 1, The vane pump according to claim 1, wherein the second groove is separated from the first groove so as not to communicate with the first groove.

3. 3. The vane pump according to claim 2, a side member that further includes a suction port that introduces working fluid into the pump chamber, and a communication groove that connects the second groove with the suction port;

4. 4. The vane pump according to claim 3, The vane pump according to claim 1, wherein the communication groove is provided so as to be offset from the extending direction of the slit.

5. 5. The vane pump according to claim 4, the slits are provided to extend radially along the radial direction of the rotor, The vane pump according to claim 1, wherein the communication groove extends linearly and is offset from a radial direction of the rotor.

6. 3. The vane pump according to claim 2, the inner peripheral cam surface is a first curved surface provided in the suction region, the first curved surface having a radial dimension between the rotor and the first curved surface increasing at a constant rate along the rotation direction of the rotor; a second curved surface that is continuous with the first curved surface and is provided in the suction region on the forward side of the first curved surface in the direction of rotation of the rotor, and in which a change in a radial dimension between the second curved surface and the rotor becomes smaller along the direction of rotation of the rotor, The vane pump according to claim 1, wherein the second groove begins to communicate with the back pressure chamber at a position corresponding to a boundary between the first curved surface and the second curved surface as the rotor rotates.

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