Vane pump

Abstract

A vane pump (100) comprises: a rotor (2); vanes (3); a cam ring (4); a pump chamber (6) defined by the rotor (2), the cam ring (4), and a pair of adjacent vanes (3); a suction port (31) for guiding a fluid to the pump chamber (6); and a discharge port (41) for guiding the fluid discharged from the pump chamber (6). The discharge port (41) is formed to extend rearward in the rotation direction beyond a contraction start point (80) at which the pump chamber (6) starts to contract with the rotation of the rotor (2) or extend forward in the rotation direction beyond a contraction end point (81) at which the contraction of the pump chamber (6) ends. Alternatively, the suction port (31) is formed to extend rearward in the rotation direction beyond an expansion start point (82) at which the pump chamber (6) starts to expand with the rotation of the rotor (2) or extend forward in the rotation direction beyond an expansion end point (83) at which the expansion of the pump chamber (6) ends.

Description

vane pump

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

[0002] JP2013-50112A discloses a vane pump including a cam ring, a rotor driven by a drive shaft, and vanes inserted into slots in the rotor. A pump chamber is defined by the rotor, cam ring, and a pair of adjacent vanes. Pressure plates are provided on the front and back sides of the cam ring, respectively, and a suction port and a discharge port are formed in the pressure plates. The suction port introduces working fluid into the pump chamber, and the discharge port introduces working fluid discharged from the pump chamber.

[0003] In a vane pump such as that described in JP2013-50112A, the pump chamber contracts, increasing the pressure inside the pump chamber, and then the pump chamber communicates with the discharge port, leading to the working fluid being guided to the discharge port. However, because the pressure inside the pump chamber acts on the vane from both sides in the direction of rotation, if the pressure difference between the pump chamber on the suction port side and the pump chamber on the discharge port side across the vane is large, the force required to move the vane in the direction of rotation increases. This can result in a large rotor drive torque.

[0004] An object of the present invention is to reduce the driving torque of a rotor in a vane pump.

[0005] According to one aspect of the present invention, there is provided a vane pump comprising: a rotor connected to a drive shaft and driven to rotate; a plurality of vanes that are provided so as to be capable of reciprocating radially relative to the rotor; a cam ring having an inner cam surface against which the tips of the vanes slide as the rotor rotates; a pump chamber defined by the rotor, the cam ring, and a pair of adjacent vanes; an intake port that introduces fluid into the pump chamber; and a discharge port that introduces fluid discharged from the pump chamber; wherein the discharge port is formed either rearward of a contraction start point at which the pump chamber begins to contract as the rotor rotates, or forward of a contraction end point at which the contraction of the pump chamber ends; or the suction port is formed rearward of an expansion start point at which the pump chamber begins to expand as the rotor rotates, or forward of an expansion end point at which the expansion of the pump chamber ends.

[0006] Fig. 1 is a cross-sectional view of a vane pump according to an embodiment of the present invention. Fig. 2 is a plan view of the rotor, vanes, cam ring, and side plate with the pump cover removed. Fig. 3 is a plan view of the side plate, corresponding to Fig. 2. Fig. 4 is a plan view showing notches formed in the cam ring. Fig. 5 is a schematic diagram showing the positional relationship between the rotor rotation angle, cam radius, and ports. Fig. 6 is a schematic diagram showing the positional relationship between the vanes and ports at the contraction start point, contraction end point, expansion start point, and expansion end point.

[0007] A vane pump 100 according to an embodiment of the present invention will now be described with reference to the drawings. The vane pump 100 is mounted, for example, on a vehicle. The vane pump 100 supplies oil as a fluid through a discharge passage 62 (see FIG. 1 ) to lubricate a gear 70. Note that the vane pump 100 may supply a fluid other than oil. Furthermore, the vane pump 100 may supply a fluid other than oil to a target other than the gear 70. For example, the vane pump 100 may supply a fluid for cooling a device such as an electric motor mounted on the vehicle through the discharge passage 62.

[0008] Fig. 1 is a cross-sectional view of the vane pump 100, and Fig. 2 is a plan view of the rotor 2, vanes 3, cam ring 4, and side plate 30 with the cover 50 removed. In Fig. 2, the suction-side through-holes 32 and the discharge-side through-holes 42 that are hidden by the rotor 2, vanes 3, and cam ring 4 are indicated by dotted lines.

[0009] As shown in FIGS. 1 and 2 , the vane pump 100 includes a rotor 2 connected to a drive shaft 1 and driven to rotate, a plurality of slits 2s (see FIG. 2 ) opening on the outer peripheral surface of the rotor 2, a plurality of vanes 3 (see FIG. 2 ) slidably inserted into the slits 2s of the rotor 2 and reciprocating radially relative to the rotor 2, a cam ring 4 having an inner peripheral cam surface 4a against which tip ends 3a (see FIG. 2 ) of the vanes 3 slide as the rotor 2 rotates, a side plate 30 serving as a side member provided in contact with one side surface (the lower surface in FIG. 1 ) of the cam ring 4, and a cover 50 provided in contact with the other side surface (the upper surface in FIG. 1 ) of the cam ring 4. The cam ring 4 houses the rotor 2 and the vanes 3. In this embodiment, the side plate 30, the cam ring 4, and the cover 50 constitute the body of the vane pump 100 without being housed in a housing. Note that the side plate 30, the cam ring 4, and the cover 50 may also be housed in a housing.

[0010] The vane pump 100 is driven by a drive device (not shown), such as an engine or an electric motor. As shown in FIG. 1 , an insertion hole 15, through which the drive shaft 1 is inserted, is formed in the side plate 30 and the cover 50. The insertion hole 15 is formed so as to pass through the side plate 30 but not through the cover 50. A bearing 17 is provided on the outer circumferential surface of the drive shaft 1, and a rotor 2 is connected to the drive shaft 1. The drive shaft 1 is rotatably supported on the side plate 30 via the bearing 17. The side plate 30, the cam ring 4, and the cover 50 are fixed together by fixing members (not shown), such as bolts. The vane pump 100 generates fluid pressure when the rotor 2 is rotated clockwise as indicated by the arrow in FIG. 2 .

[0011] In the following, the direction along the rotation axis of the rotor 2 (in other words, the drive shaft 1) 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 will be referred to as the "circumferential direction."

[0012] The side plate 30 and the cover 50 are arranged with the rotor 2 and the cam ring 4 sandwiched between them in the axial direction. One side surface of the rotor 2 (the lower surface in FIG. 1 ) is in sliding contact with the side plate 30, and one side surface of the cam ring 4 is in contact with the side plate 30. The side plate 30 has a large diameter portion 30a, and the large diameter portion 30a is fixed to an attachment target (not shown), such as a vehicle. The other side surface of the rotor 2 (the upper surface in FIG. 1 ) is in sliding contact with the cover 50, and the other side surface of the cam ring 4 is in contact with the cover 50.

[0013] 2, a plurality of slits 2s are formed radially in the rotor 2. The slits 2s open to the outer periphery of the rotor 2.

[0014] 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 a discharge port 41, and high-pressure hydraulic oil is introduced into the back pressure chamber 5 from the discharge port 41. The pressure of the hydraulic oil introduced into the back pressure chamber 5 presses the vane 3 in the direction of protruding from the slit 2s.

[0015] When the rotor 2 rotates, centrifugal force is generated in the vanes 3. This centrifugal force presses the vanes 3 in a direction in which they protrude from the slits 2s. In other words, the vanes 3 are pressed in a direction in which they 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 acting 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 circumferential 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 circumferential cam surface 4a of the cam ring 4, and a pair of adjacent vanes 3.

[0016] The cam ring 4 is an annular member having an inner cam surface 4a, which is a substantially oval inner surface, against which the tips 3a of the vanes 3 slide as the rotor 2 rotates.

[0017] The inner cam surface 4a is eccentric with respect to the rotation center O of the rotor 2. The inner cam surface 4a has a short diameter portion 4b having a relatively short diameter from the rotation center O of the rotor 2, and a long diameter portion 4c having a relatively long diameter from the rotation center O of the rotor 2 (see FIG. 4). Therefore, as the rotor 2 rotates, the volume of the pump chamber 6 repeatedly expands and contracts. Hydraulic oil is sucked in an expansion region (suction region) where the pump chamber 6 expands, and hydraulic oil is discharged in a contraction region (discharge region) where the pump chamber 6 contracts. In this embodiment, the pump chamber 6 expands and contracts once per rotation of the rotor 2. The expansion and contraction of the pump chamber 6 will be described in detail below.

[0018] As shown in FIG. 2 , the vane pump 100 includes a suction port 31 that introduces oil into the pump chamber 6 and a discharge port 41 that introduces oil discharged from the pump chamber 6. The suction port 31 includes a suction-side through-hole 32 formed in the side plate 30 and a suction-side notch 33 (see FIGS. 1 and 4 ) formed in the cam ring 4. The discharge port 41 includes a discharge-side through-hole 42 formed in the side plate 30 and a discharge-side notch 43 (see FIGS. 1 and 4 ) formed in the cam ring 4. The suction port 31 is formed to correspond to the suction region, and the discharge port 41 is formed to correspond to the discharge region. In this embodiment, the distance between adjacent vanes 3 in the circumferential direction of the rotor 2 is set smaller than the distance between the suction port 31 and the discharge port 41 in the circumferential direction of the rotor 2. As a result, one pump chamber 6 does not communicate with both the suction port 31 and the discharge port 41 at the same time, reducing internal leakage within the pump and improving volumetric efficiency. The configurations of the suction port 31 and the discharge port 41 will be described in detail later.

[0019] 2 and 3, the suction-side through-hole 32 and the discharge-side through-hole 42 are formed in the side plate 30. The side plate 30 also has a back pressure groove 35 (see FIG. 3) that opens to the surface of the side plate 30 and communicates with the back pressure chamber 5.

[0020] The suction-side through hole 32 partially or entirely penetrates the side plate 30 and is formed in an arc shape to correspond to the suction region. In this embodiment, only one suction-side through hole 32 is formed. The suction-side through hole 32 has a substantially constant cross-sectional area along the circumferential direction and is intended to actively guide oil to the pump chamber 6. The notch, whose cross-sectional area gradually changes along the circumferential direction, is not intended to actively guide oil to the pump chamber 6 and is therefore not included in the suction port 31. As shown in FIG. 1 , the suction-side through hole 32 is connected to a tank passage 61 that guides oil from the tank 60. Therefore, oil from the tank 60 is guided to the pump chamber 6 via the tank passage 61 and the suction-side through hole 32.

[0021] The discharge-side through-hole 42 partially or entirely penetrates the side plate 30 and is formed in an arc shape corresponding to the discharge area. In this embodiment, only one discharge-side through-hole 42 is formed. The suction-side through-hole 32 and the discharge-side through-hole 42 are disposed opposite each other across the drive shaft 1. The discharge-side through-hole 42 has a substantially constant cross-sectional area along the circumferential direction and is intended to actively guide oil discharged from the pump chamber 6. The notch whose cross-sectional area gradually changes along the circumferential direction is not intended to actively guide oil discharged from the pump chamber 6 and is therefore not included in the discharge port 41. As shown in FIG. 1 , the discharge-side through-hole 42 is connected to a discharge passage 62 that guides oil to the gear 70. Therefore, oil discharged from the pump chamber 6 is guided to the gear 70 through the discharge-side through-hole 42 and the discharge passage 62, lubricating the gear 70.

[0022] The back pressure grooves 35 overlap and communicate with the multiple back pressure chambers 5 as the rotor 2 rotates. The back pressure grooves 35 include a suction-side back pressure groove 35a formed in an arc shape corresponding to the suction region, a discharge-side back pressure groove 35b formed in an arc shape corresponding to the discharge region, and a communicating groove 35c that communicates between the suction-side back pressure groove 35a and the discharge-side back pressure groove 35b. The suction-side back pressure groove 35a, the discharge-side back pressure groove 35b, and the communicating groove 35c are formed to open on the surface of the side plate 30 so as to face the rotor 2. As shown by the dotted line in FIG. 3 , the suction-side back pressure groove 35a communicates with the discharge-side through-hole 42 through a high-pressure groove 36 that is formed so as not to open on the surface of the side plate 30. Two communicating grooves 35c are formed, and they communicate with the circumferentially adjacent ends of the suction-side back pressure groove 35a and the discharge-side back pressure groove 35b. As a result, high-pressure oil from the discharge port 41 is guided to the back pressure chamber 5 through the high-pressure groove 36 and the back pressure groove 35. In the back pressure chamber 5, the oil guided through the back pressure groove 35 presses the vane 3 toward the inner cam surface 4a, causing the vane 3 to slide against the inner cam surface 4a.

[0023] As described above, the vane pump 100 of this embodiment is an unbalanced vane pump in which the suction-side through-hole 32 (suction port 31) and the discharge-side through-hole 42 (discharge port 41) face each other. In the unbalanced vane pump 100, an offset load acts on the rotor 2 due to the pressure difference between the discharge port 41 and the suction port 31. When the discharge pressure of the vane pump 100 is high, the pressure difference between the discharge port 41 and the suction port 31 increases, causing an offset load to act on the drive shaft 1 and affecting the operation of the vane pump 100. For this reason, the vane pump 100 is used for applications such as lubrication and cooling of the gear 70, which do not require a low discharge pressure.

[0024] In this embodiment, because the inner cam surface 4a is eccentric with respect to the rotation center O of the rotor 2 as described above, the suction-side through-hole 32 and the discharge-side through-hole 42 are almost entirely covered by the cam ring 4 on the side of the short diameter portion 4b of the inner cam surface 4a (see FIG. 2). On the other hand, the suction-side through-hole 32 and the discharge-side through-hole 42 are almost entirely not covered by the cam ring 4 on the side of the long diameter portion 4c of the inner cam surface 4a. Therefore, the suction-side notch 33 and the discharge-side notch 43 are formed in the cam ring 4 on the side of the short diameter portion 4b of the inner cam surface 4a to guide oil from the suction-side through-hole 32 to the pump chamber 6 and to guide oil discharged from the pump chamber 6 to the discharge-side through-hole 42.

[0025] As shown in FIG. 4 , the suction side notch 33 is formed opposite the suction side through hole 32. The suction side notch 33 is formed in an arc shape corresponding to the suction area. The discharge side notch 43 is formed opposite the discharge side through hole 42. The discharge side notch 43 is formed in an arc shape corresponding to the discharge area. In this embodiment, the suction side notch 33 is formed to be longer in the circumferential direction than the discharge side notch 43. In other words, the suction side notch 33 and the discharge side notch 43 are formed to open on the surface of the cam ring 4 that faces the side plate 30.

[0026] The suction-side notch 33 is formed to extend further toward the minor diameter portion 4b of the inner cam surface 4a than the suction-side through hole 32. In other words, in the suction port 31, the end portion 31a on the front side in the rotational direction of the rotor 2 becomes the suction-side through hole 32 (see FIGS. 2 and 3), and the end portion 31b on the rear side in the rotational direction becomes the suction-side notch 33. By forming the suction-side notch 33, even if the suction-side through hole 32 on the minor diameter portion 4b side of the inner cam surface 4a is covered by the cam ring 4, oil from the suction-side through hole 32 can be guided to the pump chamber 6 through the suction-side notch 33. Furthermore, the discharge-side notch 43 is formed to extend further toward the minor diameter portion 4b of the inner cam surface 4a than the discharge-side through hole 42. In other words, the discharge port 41 has an end 41a on the front side in the rotational direction of the rotor 2 as the discharge-side notch 43, and an end 41b on the rear side in the rotational direction as the discharge-side through-hole 42 (see FIGS. 2 and 3). By forming the discharge-side notch 43, even if the discharge-side through-hole 42 is covered by the cam ring 4 on the side of the short diameter portion 4b of the inner peripheral cam surface 4a, the formation of the discharge-side notch 43 allows the oil discharged from the pump chamber 6 to be guided to the discharge-side through-hole 42 through the discharge-side notch 43.

[0027] In the vane pump 100, the pressure in the pump chamber 6 acts on the vanes 3 from both sides in the rotation direction of the rotor 2. Therefore, particularly near the suction-discharge transition region where the suction region transitions to the discharge region, if there is a large pressure difference between the pump chamber 6 on the suction port 31 side and the pump chamber 6 on the discharge port 41 side across the vane 3, the resistance to the driving force that rotates the rotor 2 increases. In this case, there is a risk that the driving torque of the rotor 2 will increase. To address this issue, in the vane pump 100 of this embodiment, the suction port 31 and the discharge port 41 are formed at the following positions in accordance with the expansion and contraction of the pump chamber 6.

[0028] 5 is a schematic diagram showing the relationship between the rotation angle of the rotor 2 and the cam radius (the radial length between the rotation center O of the rotor 2 and the inner peripheral cam surface 4a) based on the position of the dashed dotted line A shown in Fig. 2. Fig. 5 also shows the positions where the suction port 31 and the discharge port 41 are formed.

[0029] As shown in FIG. 5 , the cam radius is smallest near the short diameter portion 4b between the forward end 41a of the discharge port 41 and the rear end 31b of the suction port 31, and is largest near the long diameter portion 4c between the forward end 31a of the suction port 31 and the rear end 41b of the discharge port 41. The cam radius remains almost constant near the short diameter portion 4b (section I), and also remains almost constant near the long diameter portion 4c (section II). Between the short diameter portion 4b and the long diameter portion 4c, there is a suction region (section III) where the cam radius gradually increases, and a discharge region (section IV) where the cam radius gradually decreases. In other words, section I shown in FIG. 5 is a discharge-suction transition region where the discharge region transitions to the suction region, and section II shown in FIG. 5 is a suction-discharge transition region where the suction region transitions to the discharge region.

[0030] Strictly speaking, although the cam radius changes slightly near the short diameter portion 4b and the long diameter portion 4c (sections I and II), the cam radius (in other words, the volume of the pump chamber 6) is not changed to actively suck in and discharge oil. In other words, in this specification and claims, "the pump chamber contracts" refers to the pump chamber 6 contracting to actively discharge oil from the pump chamber 6 in the discharge region. Furthermore, "the pump chamber expands" refers to the pump chamber 6 expanding to actively guide oil into the pump chamber 6 in the suction region. In other words, in the suction region, the cam radius increases by a larger amount than in the discharge-suction transition region, and in the discharge region, the cam radius decreases by a larger amount than in the suction-discharge transition region.

[0031] At the boundary between the suction-discharge transition region (section II) and the discharge region (section IV), the cam radius starts to gradually decrease from a substantially unchanged state. The boundary between the suction-discharge transition region and the discharge region is a contraction start point 80 where the pump chamber 6 starts to contract as the rotor 2 rotates. In other words, the contraction start point 80 is an inflection point where the volume of the pump chamber 6 changes from a substantially unchanged state to a contraction state. Also, at the boundary between the discharge region and the discharge-suction transition region (section I), the cam radius changes from a gradually decreasing state to a substantially unchanged state. The boundary between the discharge region and the discharge-suction transition region is a contraction end point 81 where the contraction of the pump chamber 6 ends as the rotor 2 rotates. In other words, the contraction end point 81 is an inflection point where the volume of the pump chamber 6 changes from a gradually contracting state to a substantially unchanged state.

[0032] At the boundary between the discharge-suction transition region and the suction region (section III), the cam radius starts to gradually increase from a substantially constant state. The boundary between the discharge-suction transition region and the suction region is the expansion start point 82 where the pump chamber 6 starts to expand as the rotor 2 rotates. In other words, the expansion start point 82 is an inflection point where the volume of the pump chamber 6 changes from a substantially constant state to an expansion state. Also, at the boundary between the suction region and the suction-discharge transition region, the cam radius changes from a gradually increasing state to a substantially constant state. The boundary between the suction region and the suction-discharge transition region is an expansion end point 83 where the expansion of the pump chamber 6 ends as the rotor 2 rotates. In other words, the expansion end point 83 is an inflection point where the volume of the pump chamber 6 changes from a gradually expanding state to a substantially constant state. Note that in Figures 2 to 4, the positions of the contraction start point 80, the contraction end point 81, the expansion start point 82, and the expansion end point 83 are indicated by dashed lines.

[0033] FIG. 6( a ) shows an enlarged view of the positions of adjacent vanes 3 d that define the pump chamber 6 that begins to contract at a contraction start point 80, and FIG. 6( b ) shows an enlarged view of the positions of adjacent vanes 3 e that define the pump chamber 6 that ends to contract at a contraction end point 81. The discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81. Specifically, the discharge port 41 is formed to extend circumferentially so as to include both the contraction start point 80 and the contraction end point 81. More specifically, in the discharge port 41, the discharge-side through-hole 42 is formed beyond the contraction start point 80 toward the rear in the direction of rotation of the rotor 2 (see FIGS. 2 and 3 ), and the discharge-side notch 43 is formed beyond the contraction end point 81 toward the front in the direction of rotation of the rotor 2 (see FIG. 4 ). Therefore, while the pump chamber 6 is contracting, the pump chamber 6 is always in communication with the discharge port 41 through a large opening area. Therefore, even if the pump chamber 6 contracts, the oil does not remain in the pump chamber 6 but is guided to the discharge port 41, so that an increase in pressure within the pump chamber 6 is suppressed.

[0034] 6(c) shows an enlarged view of the positions of adjacent vanes 3f that define the pump chamber 6 that begins to expand at the expansion start point 82, and FIG. 6(d) shows an enlarged view of the positions of adjacent vanes 3g that define the pump chamber 6 that ends to expand at the expansion end point 83. The suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83. Specifically, the suction port 31 is formed to extend circumferentially so as to include both the expansion start point 82 and the expansion end point 83. More specifically, in the suction port 31, the suction-side notch 33 is formed beyond the expansion start point 82 rearward in the rotational direction of the rotor 2 (see FIG. 4), and the suction-side through-hole 32 is formed beyond the expansion end point 83 forward in the rotational direction of the rotor 2 (see FIGS. 2 and 3). Therefore, while the pump chamber 6 is expanding, the pump chamber 6 is always in communication with the suction port 31 through a large opening area. Therefore, even if the pump chamber 6 expands, oil is guided to the pump chamber 6 through the suction port 31, so that a decrease in pressure within the pump chamber 6 is suppressed.

[0035] As described above, in the vane pump 100 of this embodiment, the discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81. Therefore, the pump chamber 6 is in communication with the discharge port 41 through a large opening area when the pump chamber 6 reaches the contraction start point 80 (the state shown in FIG. 6A ) and when the pump chamber 6 reaches the contraction end point 81 (the state shown in FIG. 6B ). Therefore, as described above, even when the pump chamber 6 contracts, oil does not remain in the pump chamber 6 but is guided to the discharge port 41, thereby suppressing an increase in pressure within the pump chamber 6. Furthermore, the suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83. Therefore, the pump chamber 6 is in communication with the suction port 31 through a large opening area when the pump chamber 6 reaches the expansion start point 82 (the state shown in FIG. 6C ) and when the pump chamber 6 reaches the expansion end point 83 (the state shown in FIG. 6D ). Therefore, as described above, even when the pump chamber 6 expands, oil is guided to the pump chamber 6 through the suction port 31, thereby suppressing a decrease in pressure within the pump chamber 6. Therefore, particularly in the suction-discharge transition region, the pressure difference between the pump chamber 6 on the suction port 31 side and the pump chamber 6 on the discharge port 41 side across the vane 3 can be reduced, and the driving torque of the rotor 2 can be reduced.

[0036] Furthermore, the driving torque of the rotor 2 can be reduced even in the discharge-suction transition region. Specifically, near the contraction end point 81, the rear vane 3, of the two vanes 3 that define the pump chamber 6, has a larger cam radius in the direction of rotation and a larger pressure-receiving area that receives the pressure in the pump chamber 6. Therefore, near the contraction end point 81, the pressure in the pump chamber 6 acts as a resistance force against the driving force that rotates the rotor 2. However, in the vane pump 100, the increase in pressure in the pump chamber 6 near the contraction end point 81 is suppressed, so the driving torque of the rotor 2 can be reduced. Furthermore, near the expansion start point 82, the front vane 3, of the two vanes 3 that define the pump chamber 6, has a larger cam radius in the direction of rotation and a larger pressure-receiving area that receives the pressure in the pump chamber 6. Therefore, near the expansion start point 82, the pressure in the pump chamber 6 acts as a driving force that rotates the rotor 2. In the vane pump 100, the decrease in pressure in the pump chamber 6 near the expansion start point 82 is suppressed, so the driving torque of the rotor 2 can be reduced.

[0037] Furthermore, in a balanced vane pump, multiple suction ports are provided opposite each other and multiple discharge ports are provided opposite each other. This prevents an unbalanced load from acting on the drive shaft even when the pressure difference between the discharge and suction ports is large. Therefore, a balanced vane pump can achieve a relatively high discharge pressure. Generally, balanced pumps are used in high discharge pressure ranges, while unbalanced pumps are used in low discharge pressure ranges. When the pump discharge pressure is high, if the pressure in the pump chamber is low when the pump chamber is connected to the discharge port, fluid may flow back from the discharge port to the pump chamber, resulting in discharge pressure pulsation. In other words, in a balanced vane pump, which is generally used in high discharge pressure ranges, providing suction ports and discharge ports as in the vane pump 100 of this embodiment can reduce the rotor drive torque. However, the pump chamber communicates with the discharge port when the pressure in the pump chamber is low, resulting in discharge pressure pulsation. In contrast, the vane pump 100 of this embodiment is an unbalanced vane pump provided with one suction port 31 and one discharge port 41, and is generally used in a low discharge pressure range. Since the unbalanced vane pump 100 has a low discharge pressure as described above, the influence of discharge pressure pulsation is small even if the pressure in the pump chamber 6 is low when the pump chamber 6 communicates with the discharge port 41. Therefore, the drive torque of the rotor 2 can be reduced while suppressing the influence of discharge pressure pulsation.

[0038] Furthermore, in the vane pump 100 of this embodiment, the number of ports is smaller than in a balanced vane pump, and therefore the number of vanes 3 can be reduced. This reduces the manufacturing cost of the vane pump 100, and also reduces the total frictional force generated between each vane 3 and the inner cam surface 4a, thereby reducing the drive torque of the rotor 2.

[0039] In addition, in the vane pump 100 of this embodiment, the timing at which the pump chamber 6 begins to communicate with the suction port 31 and the discharge port 41 and the timing at which communication between the pump chamber 6 and the suction port 31 and the discharge port 41 ends can be adjusted by adjusting the positions of the suction side through hole 32 and the suction side notch 33 and the positions of the discharge side through hole 42 and the discharge side notch 43.

[0040] Specifically, on the side of the short diameter portion 4b, at the expansion start point 82, the pump chamber 6 communicates with the suction-side notch 33 before the suction-side through-hole 32, and at the contraction end point 81, the pump chamber 6 finishes communicating with the discharge-side notch 43 after communication with the discharge-side through-hole 42 has finished. In the vane pump 100, on the side of the short diameter portion 4b of the inner peripheral cam surface 4a, the suction-side through-hole 32 and the discharge-side through-hole 42 are covered by the cam ring 4, so the opening areas of the suction-side through-hole 32 and the discharge-side through-hole 42 relative to the pump chamber 6 are small. However, by forming the suction-side notch 33 and the discharge-side notch 43 in this manner, oil can easily flow between the pump chamber 6 and each port 31, 41 at the expansion start point 82 and the contraction end point 81, so a decrease in pressure in the pump chamber 6 is suppressed and an increase in pressure in the pump chamber 6 is suppressed.

[0041] Furthermore, on the side of the long diameter portion 4c, at the expansion end point 83, the pump chamber 6 finishes communicating with the suction-side through-hole 32 after finishing communicating with the suction-side notch 33, and at the contraction start point 80, the pump chamber 6 communicates with the discharge-side through-hole 42 before communicating with the discharge-side notch 43. In the vane pump 100, on the side of the long diameter portion 4c of the inner peripheral cam surface 4a, the suction-side through-hole 32 and the discharge-side through-hole 42 are not covered by the cam ring 4, so the opening areas of the suction-side through-hole 32 and the discharge-side through-hole 42 relative to the pump chamber 6 are large. Therefore, at the expansion end point 83 and the contraction start point 80, oil easily flows between the pump chamber 6 and each port 31, 41, so a decrease in pressure in the pump chamber 6 is suppressed and an increase in pressure in the pump chamber 6 is suppressed.

[0042] According to the present embodiment described above, the following effects are achieved.

[0043] In the vane pump 100, the discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81, so the pump chamber 6 is connected to the discharge port 41 at the contraction start point 80 and the contraction end point 81. This prevents a rise in pressure within the pump chamber 6. Furthermore, the suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83, so the pump chamber 6 is connected to the suction port 31 at the expansion start point 82 and the expansion end point 83. This prevents a drop in pressure within the pump chamber 6. This reduces the drive torque of the rotor 2.

[0044] 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 different modified examples below.

[0045] <Modification 1> In the above embodiment, the vane pump 100 is an unbalanced vane pump provided with one suction port 31 and one discharge port 41. In an unbalanced vane pump, the discharge pressure is low, so that even if the pressure in the pump chamber 6 is low when the pump chamber 6 is in communication with the discharge port 41, the influence of discharge pressure pulsation is small, and it is possible to reduce the drive torque of the rotor 2 while suppressing the influence of discharge pressure pulsation. However, the vane pump 100 is not limited to an unbalanced vane pump, and may be a balanced vane pump when the discharge pressure is low, for example.

[0046] <Modification 2> In the above embodiment, the discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81, and the suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83. However, the vane pump 100 is not limited to this, and it is sufficient that the discharge port 41 is formed beyond the contraction start point 80 or the contraction end point 81, or the suction port 31 is formed beyond the expansion start point 82 or the expansion end point 83. In other words, it is sufficient that the vane pump 100 satisfies at least one of the following configurations (i) to (iv): (i) the discharge port 41 is formed beyond the contraction start point 80 on the rear side in the direction of rotation, (ii) the discharge port 41 is formed beyond the contraction end point 81 on the front side in the direction of rotation, (iii) the suction port 31 is formed beyond the expansion start point 82 on the rear side in the direction of rotation, or (iv) the suction port 31 is formed beyond the expansion end point 83 on the front side in the direction of rotation. In other words, in the suction port 31, it is sufficient that either the suction-side through-hole 32 formed in the side plate 30 or the suction-side notch 33 formed in the cam ring 4 is beyond the expansion start point 82 or the expansion end point 83. In addition, in the discharge port 41, it is sufficient that either the discharge-side through-hole 42 formed in the side plate 30 or the discharge-side notch 43 formed in the cam ring 4 is beyond the contraction start point 80 or the contraction end point 81. Even with this configuration, the increase in pressure in the pump chamber 6 is suppressed, or the decrease in pressure in the pump chamber 6 is suppressed, thereby reducing the drive torque of the rotor 2. However, from the perspective of reducing the drive torque of the rotor 2, it is preferable to have all of the configurations (i) to (iv) as in the vane pump 100 of the above embodiment.

[0047] <Modification 3> In the above embodiment, the discharge-side notch 43 is formed beyond the contraction end point 81, and the suction-side notch 33 is formed beyond the expansion start point 82. However, this is not limited to this, and the discharge-side notch 43 may be formed beyond the contraction start point 80, and the suction-side notch 33 may be formed beyond the expansion end point 83. Furthermore, the discharge-side notch 43 may be formed without passing the contraction start point 80 or the contraction end point 81, and the suction-side notch 33 may be formed without passing the expansion start point 82 or the expansion end point 83.

[0048] <Fourth Modification> In the above embodiment, cam ring 4 is formed with suction-side notches 33 formed opposite suction-side through holes 32 to guide oil to suction-side through holes 32, and discharge-side notches 43 formed opposite discharge-side through holes 42 to guide oil discharged from discharge-side through holes 42. However, the present invention is not limited to this, and cam ring 4 may not be formed with suction-side notches 33 and discharge-side notches 43, but rather suction ports 31 may be formed only by suction-side through holes 32, and discharge ports 41 may be formed only by discharge-side through holes 42.

[0049] <Modification 5> In the above embodiment, the distance between adjacent vanes 3 in the circumferential direction of the rotor 2 is set to be smaller than the distance between the suction port 31 and the discharge port 41 in the circumferential direction of the rotor 2. However, the present invention is not limited to this, and the distance between adjacent vanes 3 in the circumferential direction of the rotor 2 may be set to be larger than the distance between the suction port 31 and the discharge port 41 in the circumferential direction of the rotor 2. With this configuration, it is possible to suppress a pressure increase due to slight compression of the pump chamber 6 that occurs in the flat portions of the cam curve (in other words, the suction-discharge transition region and the discharge-suction transition region), and it is possible to reduce the drive torque of the rotor 2.

[0050] The configuration, operation, and effects of the embodiment of the present invention will be described below.

[0051] The vane pump 100 comprises a rotor 2 connected to a drive shaft 1 and driven to rotate, a plurality of vanes 3 arranged to be capable of reciprocating radially relative to the rotor 2, a cam ring 4 having an inner cam surface 4a against which the tip ends 3a of the vanes 3 slide as the rotor 2 rotates, a pump chamber 6 defined by the rotor 2, the cam ring 4 and a pair of adjacent vanes 3, an intake port 31 for guiding fluid to the pump chamber 6, and a discharge port 41 for guiding fluid discharged from the pump chamber 6, and the discharge port 41 is formed in the direction of rotation rearward of a contraction start point 80 at which the pump chamber 6 begins to contract as the rotor 2 rotates, or forward of a contraction end point 81 at which the contraction of the pump chamber 6 ends, or the suction port 31 is formed in the direction of rotation rearward of an expansion start point 82 at which the pump chamber 6 begins to expand as the rotor 2 rotates, or forward of an expansion end point 83 at which the expansion of the pump chamber 6 ends.

[0052] In this configuration, the discharge port 41 is formed beyond the contraction start point 80 or the contraction end point 81, so the pump chamber 6 is connected to the discharge port 41 at the contraction start point 80 or the contraction end point 81. This prevents a rise in pressure within the pump chamber 6. Alternatively, the suction port 31 is formed beyond the expansion start point 82 or the expansion end point 83, so the pump chamber 6 is connected to the suction port 31 at the expansion start point 82 or the expansion end point 83. This prevents a drop in pressure within the pump chamber 6. This reduces the drive torque of the rotor 2.

[0053] In addition, in the vane pump 100, the suction port 31 and the discharge port 41 are provided one each so as to face each other with the drive shaft 1 therebetween.

[0054] In this configuration, the vane pump 100 is an unbalanced vane pump 100 having one suction port 31 and one discharge port 41. Generally, balanced pumps are used in high discharge pressure ranges, while unbalanced pumps are used in low discharge pressure ranges. When the discharge pressure is relatively high, as in a balanced vane pump, if the pressure in the pump chamber is low when the pump chamber 6 is connected to the discharge port, fluid flows back from the discharge port to the pump chamber, causing discharge pressure pulsation. However, when the discharge pressure is low, as in the unbalanced vane pump 100, the impact of discharge pressure pulsation is small even if the pressure in the pump chamber 6 is low when the pump chamber 6 is connected to the discharge port 41. Therefore, the drive torque of the rotor 2 can be reduced while suppressing the impact of discharge pressure pulsation.

[0055] The vane pump 100 further includes a side plate 30 as a side member provided in contact with a side surface of the cam ring 4. The side plate 30 is formed with a suction-side through hole 32 for guiding fluid to the pump chamber 6 and a discharge-side through hole 42 for guiding fluid discharged from the pump chamber 6. The cam ring 4 is formed with a suction-side notch 33 facing the suction-side through hole 32 for guiding fluid to the suction-side through hole 32, and a discharge-side notch 44 facing the discharge-side through hole 42 for guiding fluid discharged from the discharge-side through hole 42. 3, the suction port 31 is a suction side through hole 32 and a suction side notch 33, the discharge port 41 is a discharge side through hole 42 and a discharge side notch 43, and at least one of the discharge side through hole 42 and the discharge side notch 43 is formed behind the contraction start point 80 in the rotational direction or forward of the contraction end point 81 in the rotational direction, or at least one of the suction side through hole 32 and the suction side notch 33 is formed behind the expansion start point 82 in the rotational direction or forward of the expansion end point 83 in the rotational direction.

[0056] In this configuration, the timing at which the pump chamber 6 begins to communicate with the suction port 31 and the discharge port 41 and the timing at which communication between the pump chamber 6 and the suction port 31 and the discharge port 41 ends can be adjusted by changing the positions of the suction side through hole 32 and the suction side notch 33 and the discharge side through hole 42 and the discharge side notch 43.

[0057] In addition, in the vane pump 100, the inner cam surface 4a has a short diameter portion 4b having a relatively short diameter from the center of rotation O of the rotor 2, and a long diameter portion 4c having a relatively long diameter from the center of rotation O of the rotor 2, and on the short diameter portion 4b side, as the rotor 2 rotates, the pump chamber 6 begins to communicate with the suction side notch 33 before the suction side through hole 32, and communication with the discharge side notch 43 ends after communication with the discharge side through hole 42 ends.

[0058] In this configuration, on the side of the short diameter portion 4b where the opening areas of the suction-side through-hole 32 and the discharge-side through-hole 42 relative to the pump chamber 6 are small, at the expansion start point 82, the pump chamber 6 communicates with the suction-side notch 33 before the suction-side through-hole 32, and at the contraction end point 81, the pump chamber 6 finishes communicating with the discharge-side through-hole 42 and then with the discharge-side notch 43. Therefore, at the expansion start point 82 and the contraction end point 81, fluid flows easily, so a decrease in pressure within the pump chamber 6 is suppressed and an increase in pressure within the pump chamber 6 is suppressed.

[0059] 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.

[0060] This application claims priority based on Japanese Patent Application No. 2023-201735, filed with the Japan Patent Office on November 29, 2023, the entire contents of which are incorporated herein by reference.

Claims

1. A vane pump comprising: a rotor connected to a drive shaft and driven to rotate; a plurality of vanes arranged to be capable of reciprocating radially relative to the rotor; a cam ring having an inner cam surface against which the tips of the vanes slide as the rotor rotates; a pump chamber defined by the rotor, the cam ring and a pair of adjacent vanes; a suction port for directing fluid to the pump chamber; and a discharge port for directing fluid discharged from the pump chamber, wherein the discharge port is formed rearward in the direction of rotation from a contraction start point at which the pump chamber begins to contract as the rotor rotates, or forward in the direction of rotation from a contraction end point at which the contraction of the pump chamber ends, or the suction port is formed rearward in the direction of rotation from an expansion start point at which the pump chamber begins to expand as the rotor rotates, or forward in the direction of rotation from an expansion end point at which the expansion of the pump chamber ends.

2. A vane pump according to claim 1, wherein the suction port and the discharge port are provided one each facing each other across the drive shaft.

3. A vane pump as claimed in claim 1, further comprising a side member provided in contact with a side surface of the cam ring, wherein the side member is formed with a suction side through hole for guiding fluid to the pump chamber and a discharge side through hole for guiding fluid discharged from the pump chamber, and the cam ring is formed with a suction side notch formed opposite the suction side through hole for guiding fluid to the suction side through hole and a discharge side notch formed opposite the discharge side through hole for guiding fluid discharged from the discharge side through hole, wherein the suction port is the suction side through hole and the suction side notch, and the discharge port is the discharge side through hole and the discharge side notch, a vane pump in which at least one of the discharge side through hole and the discharge side notch is formed rearward in the rotational direction from the contraction start point or forward in the rotational direction from the contraction end point, or at least one of the suction side through hole and the suction side notch is formed rearward in the rotational direction from the expansion start point or forward in the rotational direction from the expansion end point.

4. A vane pump as described in claim 3, wherein the inner cam surface has a short diameter portion having a relatively short diameter from the center of rotation of the rotor, and a long diameter portion having a relatively long diameter from the center of rotation of the rotor, and the pump chamber, on the short diameter portion side, begins to communicate with the suction side notch before the suction side through hole as the rotor rotates, and communication with the discharge side notch ends after communication with the discharge side through hole ends.

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