Vane pump

Abstract

To reduce a drive torque of a rotor in a vane pump.SOLUTION: A vane pump 100 includes: a rotor 2; a vane 3; a cam ring 4; a pump chamber 6 defined by the rotor 2, the cam ring 4, and the pair of adjacent vanes 3; a suction port 31 for guiding fluid into the pump chamber 6; and an ejection port 41 for guiding the fluid ejected from the pump chamber 6. The ejection port 41 is formed beyond a rear side in a rotational direction from a shrink start point 80 at which a shrinkage of the pump chamber 6 starts by a rotation of the rotor 2 or a front side in a rotational direction from a shrink end point 81 at which the shrinkage of the pump chamber 6 ends. Alternatively, the suction port 31 is formed beyond a rear side in a rotational direction from an expansion start point 82 at which an expansion of the pump chamber 6 starts by a rotation of the rotor 2 or a front side in a rotational direction from an expansion end point 83 at which the expansion of the pump chamber 6 ends.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Patent Document 1 discloses a vane pump including a cam ring, a rotor driven by a drive shaft, and vanes inserted into slots of the rotor. A pump chamber is defined by the rotor, the cam ring, and a pair of adjacent vanes. Pressure plates are provided on the front and back surfaces of the cam ring, respectively, and a suction port and a discharge port are formed in the pressure plates. The suction port guides the working fluid into the pump chamber, and the discharge port guides the working fluid discharged from the pump chamber.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the vane pump as described in Patent Document 1, after the pump chamber contracts and the pressure in the pump chamber increases, the pump chamber communicates with the discharge port and the working fluid in the pump chamber is guided to the discharge port. However, since the pressure in the pump chamber acts on both sides of the vane in the rotational direction, 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 rotational direction increases. Therefore, there is a risk that the driving torque of the rotor increases.

[0005] The present invention has been made in view of the above problems, and an object thereof is to reduce the driving torque of the rotor in a vane pump.

Means for Solving the Problems

[0006] The present invention relates to a vane pump, comprising a rotor connected to a drive shaft and rotationally driven, a plurality of vanes provided so as to be reciprocally movable in the radial direction with respect to the rotor, a cam ring having an inner peripheral cam surface with which the tip of the vane is in sliding contact as the rotor rotates, a pump chamber defined by the rotor, the cam ring, and a pair of adjacent vanes, a suction port for guiding fluid into the pump chamber, and a discharge port for guiding the fluid discharged from the pump chamber, wherein the discharge port is formed beyond the contraction start point at which the pump chamber begins to contract as the rotor rotates or beyond the forward side in the rotational direction from the contraction end point at which the contraction of the pump chamber ends, or the suction port is formed beyond the expansion start point at which the pump chamber begins to expand as the rotor rotates or beyond the forward side in the rotational direction from the expansion end point at which the expansion of the pump chamber ends.

[0007] In this invention, since the discharge port is formed beyond the contraction start point or the contraction end point, the pump chamber communicates with the discharge port at the contraction start point or the contraction end point. Therefore, the increase in the pressure inside the pump chamber is suppressed. Alternatively, since the suction port is formed beyond the expansion start point or the expansion end point, the pump chamber communicates with the suction port at the expansion start point or the expansion end point. Therefore, the decrease in the pressure inside the pump chamber is suppressed. Thus, the driving torque of the rotor can be reduced.

[0008] Further, in the present invention, the suction port and the discharge port are each provided so as to face each other with the drive shaft interposed therebetween.

[0009] In the present invention, the vane pump is an unbalanced vane pump provided with one suction port and one discharge port each. Generally, balanced pumps are used in regions with high discharge pressures, while unbalanced pumps are used in regions with low discharge pressures. In the case of a balanced vane pump, when the discharge pressure is relatively high, if the pressure in the pump chamber is low when the pump chamber communicates with the discharge port, fluid will flow backward from the discharge port into the pump chamber, causing pulsation in the discharge pressure. However, in the case of an unbalanced vane pump, when the discharge pressure is low, even if the pressure in the pump chamber is low when the pump chamber communicates with the discharge port, the influence of discharge pressure pulsation is small. Therefore, it is possible to reduce the driving torque of the rotor while suppressing the influence of discharge pressure pulsation.

[0010] Furthermore, the present invention further includes a side member provided in contact with the side surface of the cam ring. The side member is formed with a suction-side through hole for guiding fluid into the pump chamber and a discharge-side through hole for guiding fluid discharged from the pump chamber. The cam ring is formed with a suction-side notch formed opposite to the suction-side through hole for guiding fluid into the suction-side through hole and a discharge-side notch formed opposite to the discharge-side through hole for guiding fluid discharged from the discharge-side through hole. 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. At least one of the discharge-side through hole and the discharge-side notch is formed beyond the rear side in the rotational direction from the start point of contraction or beyond the front side in the rotational direction from the end point of contraction, or at least one of the suction-side through hole and the suction-side notch is formed beyond the rear side in the rotational direction from the start point of expansion or beyond the front side in the rotational direction from the end point of expansion.

[0011] In the present invention, the positions of the suction-side through hole and the suction-side notch, and the positions of the discharge-side through hole and the discharge-side notch can adjust the timing when the pump chamber starts to communicate with the suction port and the discharge port and the timing when the communication between the pump chamber and the suction port and the discharge port ends.

[0012] Further, in the present invention, the inner peripheral cam surface has a minor diameter portion with a relatively short diameter from the rotation center of the rotor and a major diameter portion with a relatively long diameter from the rotation center of the rotor, and the pump chamber, on the minor diameter portion side, starts to communicate with the suction side notch prior to the suction side through hole as the rotor rotates, and the communication with the discharge side notch ends after the communication with the discharge side through hole ends.

[0013] In this invention, on the minor diameter portion side where the opening areas of the suction side through hole and the discharge side through hole with respect to the pump chamber are small, at the expansion start point, the pump chamber communicates with the suction side notch prior to the suction side through hole, and at the contraction end point, the pump chamber ends the communication with the discharge side notch after the communication with the discharge side through hole ends. Therefore, at the expansion start point and the contraction end point, since the fluid flows easily, the decrease in the pressure inside the pump chamber is suppressed, and the increase in the pressure inside the pump chamber is also suppressed.

Advantages of the Invention

[0014] According to the present invention, the driving torque of the rotor in the vane pump can be reduced.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0016] Hereinafter, with reference to the drawings, the vane pump 100 according to an embodiment of the present invention will be described. The vane pump 100 is mounted on a vehicle, for example. The vane pump 100 supplies oil as a fluid through a discharge passage 62 (see FIG. 1) to lubricate the gear 70. Note that the vane pump 100 may supply other fluids than oil. Further, the supply target of the fluid by the vane pump 100 may not be the gear 70, and for example, a fluid for cooling a device such as an electric motor mounted on the vehicle may be supplied through the discharge passage 62.

[0017] FIG. 1 is a cross-sectional view of the vane pump 100, and FIG. 2 is a plan view of the rotor 2, the vanes 3, the cam ring 4, and the side plate 30 with the cover 50 removed. Further, in FIG. 2, the portions of the suction-side through-hole 32 and the discharge-side through-hole 42 covered and hidden by the rotor 2, the vanes 3, and the cam ring 4 are indicated by dotted lines.

[0018] As shown in FIGS. 1 and 2, the vane pump 100 includes a rotor 2 that is connected to a drive shaft 1 and is rotationally driven, a plurality of slits 2s (see FIG. 2) that open on the outer peripheral surface of the rotor 2, and a plurality of vanes 3 (see FIG. 2) that are slidably inserted into the slits 2s of the rotor 2 and are provided so as to be reciprocally movable in the radial direction with respect to the rotor 2, a cam ring 4 having an inner peripheral cam surface 4a with which the tip portion 3a (see FIG. 2) of the vane 3 is in sliding contact as the rotor 2 rotates, a side plate 30 as a side member that is provided in contact with one side surface (the lower side surface in FIG. 1) of the cam ring 4, and a cover 50 that is provided in contact with the other side surface (the upper side surface in FIG. 1) of the cam ring 4. The cam ring 4 houses the rotor 2 and the vanes 3. In the present embodiment, the side plate 30, the cam ring 4, and the cover 50 do not form a housing but constitute the body of the vane pump 100. Note that the side plate 30, the cam ring 4, and the cover 50 may be housed in a housing.

[0019] The vane pump 100 is driven by a driving 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 penetrate the side plate 30 while not penetrating the cover 50. A bearing 17 is provided on the outer peripheral surface of the drive shaft 1 and a rotor 2 is connected thereto. The drive shaft 1 is rotatably supported by the side plate 30 via the bearing 17. The side plate 30, the cam ring 4, and the cover 50 are integrally fixed by fixing members (not shown) such as bolts. The vane pump 100 generates fluid pressure when the rotor 2 is rotationally driven clockwise as indicated by the arrow in FIG. 2.

[0020] Hereinafter, the direction along the rotation axis of the rotor 2 (in other words, the drive shaft 1) is referred to as the "axial direction", the radial direction centered on the rotation axis of the rotor 2 is referred to as the "radial direction", and the direction in which the rotor 2 rotates is referred to as the "circumferential direction".

[0021] The side plate 30 and the cover 50 are arranged with the rotor 2 and the cam ring 4 sandwiched in the axial direction. One side surface (the lower side surface in FIG. 1) of the rotor 2 is in sliding contact with the side plate 30 and one side surface of the cam ring 4 is in contact therewith. 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 and attached. One side surface (the upper side surface in FIG. 1) of the rotor 2 is in sliding contact with the cover 50 and the other side surface of the cam ring 4 is in contact therewith.

[0022] As shown in FIG. 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.

[0023] The vane 3 is formed in a rectangular flat plate shape. The vane 3 is slidably inserted into the slit 2s, and has a tip portion 3a which is an end portion in the direction protruding from the slit 2s, and a base end portion 3b which is an end portion on the side opposite to the tip portion 3a. In the slit 2s, a back pressure chamber 5 is defined by the base end portion 3b of the vane 3. The back pressure chamber 5 communicates with a discharge port 41 as will be described later, and high-pressure hydraulic oil is guided from the discharge port 41 into the back pressure chamber 5. The vane 3 is pressed in the direction of protruding from the slit 2s by the pressure of the hydraulic oil guided into the back pressure chamber 5.

[0024] When the rotor 2 rotates, a centrifugal force is generated in the vane 3. Due to this centrifugal force, the vane 3 is pressed in the direction of protruding from the slit 2s. That is, the vane 3 is pressed in the direction of protruding from the slit 2s (radially outward) by the fluid pressure of the back pressure chamber 5 that presses the base end portion 3b and the centrifugal force acting with the rotation of the rotor 2. When the vane 3 is pressed radially outward, the tip portion 3a of the vane 3 comes into sliding contact with the inner peripheral cam surface 4a of the cam ring 4. Thereby, inside the cam ring 4, a pump chamber 6 is partitioned by the outer peripheral surface of the rotor 2, the inner peripheral cam surface 4a of the cam ring 4, and a pair of adjacent vanes 3.

[0025] The cam ring 4 is an annular member having an inner peripheral cam surface 4a which is a substantially oval-shaped inner peripheral surface. The inner peripheral cam surface 4a is a surface with which the tip portions 3a of a plurality of vanes 3 come into sliding contact as the rotor 2 rotates.

[0026] The inner peripheral cam surface 4a is eccentric with respect to the rotation center O of the rotor 2. The inner peripheral cam surface 4a has a minor diameter portion 4b with a relatively short diameter from the rotation center O of the rotor 2 and a major diameter portion 4c with 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 repeats expansion and contraction. In the expansion region (suction region) where the pump chamber 6 expands, hydraulic oil is sucked in, and in the contraction region (discharge region) where the pump chamber 6 contracts, hydraulic oil is discharged. In the present embodiment, when the rotor 2 makes one rotation, the pump chamber 6 expands and contracts once each. Details of the expansion and contraction of the pump chamber 6 will be described later.

[0027] As shown in FIG. 2, the vane pump 100 includes a suction port 31 that guides oil into the pump chamber 6 and a discharge port 41 that guides the oil discharged from the pump chamber 6. The suction port 31 is composed of a suction-side through hole 32 formed in the side plate 30 and a suction-side notch 33 formed in the cam ring 4 (see FIGS. 1 and 4). The discharge port 41 is composed of a discharge-side through hole 42 formed in the side plate 30 and a discharge-side notch 43 formed in the cam ring 4 (see FIGS. 1 and 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 the present embodiment, the interval between adjacent vanes 3 in the circumferential direction of the rotor 2 is set smaller than the interval between the suction port 31 and the discharge port 41 in the circumferential direction of the rotor 2. Thereby, since one pump chamber 6 does not communicate with the suction port 31 and the discharge port 41 at the same time, internal leakage of the pump can be reduced and volumetric efficiency can be improved. Details of the configurations of the suction port 31 and the discharge port 41 will be described later.

[0028] As shown in FIGS. 2 and 3, the suction-side through hole 32 and the discharge-side through hole 42 are formed in the side plate 30. Further, a back pressure groove 35 (see FIG. 3) that opens on the surface of the side plate 30 and communicates with the back pressure chamber 5 is formed in the side plate 30.

[0029] The suction-side through hole 32 is formed in an arc shape so as to partially or entirely penetrate the side plate 30 and correspond to the suction region. In the present 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 for positively guiding oil into the pump chamber 6. Since a notch whose cross-sectional area gradually changes along the circumferential direction is not for positively guiding oil into the pump chamber 6, it is 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 into the pump chamber 6 through the tank passage 61 and the suction-side through hole 32.

[0030] The discharge-side through hole 42 is formed in an arc shape so as to correspond to the discharge region, with part or all of it penetrating the side plate 30. 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 provided so as to face each other with the drive shaft 1 interposed therebetween. The discharge-side through hole 42 has a substantially constant cross-sectional area along the circumferential direction and is for actively guiding the oil discharged from the pump chamber 6. A notch whose cross-sectional area gradually changes along the circumferential direction is not included in the discharge port 41 because it is not for actively guiding the oil discharged from the pump chamber 6. 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, the 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.

[0031] The back pressure groove 35 overlaps and communicates with a plurality of back pressure chambers 5 as the rotor 2 rotates. The back pressure groove 35 includes a suction-side back pressure groove 35a formed in an arc shape so as to correspond to the suction region, a discharge-side back pressure groove 35b formed in an arc shape so as to correspond to the discharge region, and a communication groove 35c that communicates 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 communication groove 35c are formed to open on the surface of the side plate 30 so as to face the rotor 2. The suction-side back pressure groove 35a communicates with the discharge-side through hole 42 through a high-pressure groove 36 formed so as not to open on the surface of the side plate 30, as shown by the dotted line in FIG. 3. Two communication grooves 35c are formed to communicate the circumferentially adjacent ends of the suction-side back pressure groove 35a and the discharge-side back pressure groove 35b, respectively. As a result, the 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. The back pressure chamber 5 presses the vane 3 toward the inner circumferential cam surface 4a with the oil guided through the back pressure groove 35, causing the vane 3 to be in sliding contact with the inner circumferential cam surface 4a.

[0032] As described above, the vane pump 100 of the present 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 unbalanced 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 becomes large, so an unbalanced load acts on the drive shaft 1, affecting the operation of the vane pump 100. Therefore, the vane pump 100 is used for applications such as lubrication and cooling of the gear 70, which may have a low discharge pressure.

[0033] In the present embodiment, as described above, since the inner peripheral cam surface 4a is eccentric with respect to the rotation center O of the rotor 2, on the minor diameter portion 4b side of the inner peripheral cam surface 4a, the suction-side through-hole 32 and the discharge-side through-hole 42 are almost covered by the cam ring 4 (see FIG. 2). On the other hand, on the major diameter portion 4c side of the inner peripheral cam surface 4a, the suction-side through-hole 32 and the discharge-side through-hole 42 are hardly covered by the cam ring 4. Therefore, on the minor diameter portion 4b side of the inner peripheral cam surface 4a, oil from the suction-side through-hole 32 is guided into the pump chamber 6, and the oil discharged from the pump chamber 6 is guided to the discharge-side through-hole 42. Thus, the suction-side notch 33 and the discharge-side notch 43 are formed in the cam ring 4, respectively.

[0034] As shown in FIG. 4, the suction-side notch 33 is formed to face the suction-side through-hole 32. The suction-side notch 33 is formed in an arc shape so as to correspond to the suction region. The discharge-side notch 43 is formed to face the discharge-side through-hole 42. The discharge-side notch 43 is formed in an arc shape so as to correspond to the discharge region. In the present embodiment, the suction-side notch 33 is formed longer in the circumferential direction than the discharge-side notch 43. The suction-side notch 33 and the discharge-side notch 43 are, in other words, formed to open on the surface of the cam ring 4 facing the side plate 30.

[0035] The suction-side notch 33 is formed to extend toward the minor-diameter portion 4b of the inner peripheral cam surface 4a from the suction-side through hole 32. In other words, at the suction port 31, the front-end portion 31a on the rotation-direction front side of the rotor 2 becomes the suction-side through hole 32 (see FIGS. 2 and 3), and the rear-end portion 31b on the rotation-direction rear side becomes the suction-side notch 33. By forming the suction-side notch 33, even if the suction-side through hole 32 is covered by the cam ring 4 on the minor-diameter portion 4b side of the inner peripheral cam surface 4a, the oil from the suction-side through hole 32 can be guided to the pump chamber 6 through the suction-side notch 33. Further, the discharge-side notch 43 is formed to extend toward the minor-diameter portion 4b of the inner peripheral cam surface 4a from the discharge-side through hole 42. In other words, at the discharge port 41, the front-end portion 41a on the rotation-direction front side of the rotor 2 becomes the discharge-side notch 43, and the rear-end portion 41b on the rotation-direction rear side becomes 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 minor-diameter portion 4b side of the inner peripheral cam surface 4a, the oil discharged from the pump chamber 6 can be guided to the discharge-side through hole 42 through the discharge-side notch 43.

[0036] Here, 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 in the vicinity of the suction-discharge transition region where the transition from the suction region to the discharge region occurs, if 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 is large, the resistance force against the driving force for rotating the rotor 2 becomes large. In this case, there is a risk that the driving torque of the rotor 2 becomes large. For this countermeasure, in the vane pump 100 of the present embodiment, in correspondence with the expansion and contraction of the pump chamber 6, the suction port 31 and the discharge port 41 are formed at the following positions.

[0037] FIG. 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) with reference to the position of the dashed-dotted line A shown in FIG. 2. In FIG. 5, the positions where the suction port 31 and the discharge port 41 are formed are also shown.

[0038] As shown in Fig. 5, the cam radius is minimum near the minor axis portion 4b between the front end 41a in the rotational direction of the discharge port 41 and the rear end 31b in the rotational direction of the suction port 31, and maximum near the major axis portion 4c between the front end 31a in the rotational direction of the suction port 31 and the rear end 41b in the rotational direction of the discharge port 41. Near the minor axis portion 4b, the cam radius hardly changes (section I), and near the major axis portion 4c, the cam radius also hardly changes (section II). Between the minor axis portion 4b and the major axis portion 4c, a suction region where the cam radius gradually increases (section III) and a discharge region where the cam radius gradually decreases (section IV) are formed. In other words, section I shown in Fig. 5 is a discharge-suction transition region that transitions from the discharge region to the suction region, and section II shown in Fig. 5 is a suction-discharge transition region that transitions from the suction region to the discharge region.

[0039] Strictly speaking, although the cam radius slightly changes near the minor axis portion 4b and near the major axis portion 4c (sections I and II), it does not change the cam radius (in other words, the volume of the pump chamber 6) to actively suck in and discharge oil. In other words, in this specification and the claims, "the pump chamber contracts" means that the pump chamber 6 contracts to actively discharge oil from the pump chamber 6 in the discharge region. Also, "the pump chamber expands" means that the pump chamber 6 expands to actively guide oil into the pump chamber 6 in the suction region. Further in other words, in the suction region, the cam radius increases with a larger change amount than in the discharge-suction transition region, and in the discharge region, the cam radius decreases with a larger change amount than in the suction-discharge transition region.

[0040] At the boundary between the suction-discharge transition region (interval II) and the discharge region (interval IV), the cam radius begins to gradually decrease from a state where it is substantially unchanged. The boundary between the suction-discharge transition region and the discharge region becomes the contraction start point 80 at which the pump chamber 6 begins to contract as the rotor 2 rotates. That is, the contraction start point 80 is the inflection point at which the volume of the pump chamber 6 changes from a state where it is substantially unchanged to contraction. Also, at the boundary between the discharge region and the discharge-suction transition region (interval I), the cam radius changes from a state where it gradually decreases to a state where it is substantially unchanged. The boundary between the discharge region and the discharge-suction transition region becomes the contraction end point 81 at which the contraction of the pump chamber 6 ends as the rotor 2 rotates. That is, the contraction end point 81 is the inflection point at which the volume of the pump chamber 6 changes from a state where it gradually contracts to a state where it is substantially unchanged.

[0041] At the boundary between the discharge-suction transition region and the suction region (interval III), the cam radius begins to gradually increase from a state where it is substantially unchanged. The boundary between the discharge-suction transition region and the suction region becomes the expansion start point 82 at which the pump chamber 6 begins to expand as the rotor 2 rotates. That is, the expansion start point 82 is the inflection point at which the volume of the pump chamber 6 changes from a state where it is substantially unchanged to expansion. Also, at the boundary between the suction region and the suction-discharge transition region, the cam radius changes from a state where it gradually increases to a state where it is substantially unchanged. The boundary between the suction region and the suction-discharge transition region becomes the expansion end point 83 at which the expansion of the pump chamber 6 ends as the rotor 2 rotates. That is, the expansion end point 83 is the inflection point at which the volume of the pump chamber 6 changes from a state where it gradually expands to a state where it is substantially unchanged. In FIGS. 2-4, 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-dotted lines.

[0042] FIG. 6(a) shows an enlarged view of the positions of the adjacent vanes 3d that define the pump chamber 6 which starts to contract at the contraction start point 80, and FIG. 6(b) shows an enlarged view of the positions of the adjacent vanes 3e that define the pump chamber 6 which finishes contracting at the 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 in the circumferential direction 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 to the rear side in the rotation direction of the rotor 2 (see FIGS. 2 and 3), and the discharge-side notch 43 is formed beyond the contraction end point 81 to the front side in the rotation direction 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 with a large opening area. Thus, even when the pump chamber 6 contracts, the oil is not retained in the pump chamber 6 but is guided to the discharge port 41, so that an increase in the pressure in the pump chamber 6 is suppressed.

[0043] Also, FIG. 6(c) shows an enlarged view of the positions of the adjacent vanes 3f that define the pump chamber 6 which starts to expand at the expansion start point 82, and FIG. 6(d) shows an enlarged view of the positions of the adjacent vanes 3g that define the pump chamber 6 which finishes expanding 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 in the circumferential direction 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 to the rear side in the rotation direction of the rotor 2 (see FIG. 4), and the suction-side through hole 32 is formed beyond the expansion end point 83 to the front side in the rotation 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 with a large opening area. Thus, even when the pump chamber 6 expands, the oil is guided to the pump chamber 6 through the suction port 31, so that a decrease in the pressure in the pump chamber 6 is suppressed.

[0044] As described above, in the vane pump 100 of the present embodiment, since the discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81, the pump chamber 6 communicates with the discharge port 41 with a large opening area at the time when the contraction start point 80 is reached (the state shown in FIG. 6(a)) and at the time when the contraction end point 81 is reached (the state shown in FIG. 6(b)). Therefore, as described above, even when the pump chamber 6 contracts, the oil is not retained in the pump chamber 6 but is guided to the discharge port 41, so that an increase in the pressure in the pump chamber 6 is suppressed. Further, since the suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83, the pump chamber 6 communicates with the suction port 31 with a large opening area at the time when the expansion start point 82 is reached (the state shown in FIG. 6(c)) and at the time when the expansion end point 83 is reached (the state shown in FIG. 6(d)). Therefore, as described above, even when the pump chamber 6 expands, the oil is guided into the pump chamber 6 through the suction port 31, so that a decrease in the pressure in the pump chamber 6 is suppressed. Thus, particularly on the suction-discharge transition region side, 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.

[0045] Also, on the discharge-suction transition region side, the driving torque of the rotor 2 can be reduced. Specifically, in the vicinity of the contraction end point 81, the cam radius of the rear one in the rotation direction is larger among the two vanes 3 partitioning the pump chamber 6, and the pressure receiving area receiving the pressure in the pump chamber 6 is large. Therefore, in the vicinity of the contraction end point 81, although the pressure in the pump chamber 6 acts as a resistance force against the driving force for rotating the rotor 2, in the vane pump 100, an increase in the pressure in the pump chamber 6 in the vicinity of the contraction end point 81 is suppressed, so that the driving torque of the rotor 2 can be reduced. Further, in the vicinity of the expansion start point 82, the cam radius of the front one in the rotation direction is larger among the two vanes 3 partitioning the pump chamber 6, and the pressure receiving area receiving the pressure in the pump chamber 6 is large. Therefore, in the vicinity of the expansion start point 82, the pressure in the pump chamber 6 acts as a driving force for rotating the rotor 2, and in the vane pump 100, a decrease in the pressure in the pump chamber 6 in the vicinity of the expansion start point 82 is suppressed, so that the driving torque of the rotor 2 can be reduced.

[0046] Also, in a balanced vane pump, since a plurality of suction ports are provided facing each other and a plurality of discharge ports are provided facing each other, even if the pressure difference between the discharge port and the suction port is large, no eccentric load acts on the drive shaft. Therefore, in a balanced vane pump, the discharge pressure can be made relatively large. Generally, balanced pumps are used in regions with high discharge pressures, and unbalanced pumps are used in regions with low discharge pressures. When the discharge pressure of the pump is large, if the pressure in the pump chamber is low when the pump chamber communicates with the discharge port, there is a risk that fluid will flow backward from the discharge port into the pump chamber, causing pulsation of the discharge pressure. That is, in a balanced vane pump, which is generally used in a region with a large discharge pressure, when suction ports and discharge ports are provided as in the vane pump 100 of the present embodiment, the driving torque of the rotor can be reduced, but since the pump chamber communicates with the discharge port in a state where the pressure in the pump chamber is low, there is a risk of pulsation of the discharge pressure. On the other hand, the vane pump 100 of the present embodiment is an unbalanced vane pump in which one suction port 31 and one discharge port 41 are provided, and is generally used in a region with a low discharge pressure. In the unbalanced vane pump 100, since the discharge pressure is low as described above, even if the pressure in the pump chamber 6 is low when the pump chamber 6 communicates with the discharge port 41, the influence of the pulsation of the discharge pressure is small. Therefore, it is possible to reduce the driving torque of the rotor 2 while suppressing the influence of the pulsation of the discharge pressure.

[0047] Furthermore, in the vane pump 100 of the present embodiment, compared with a balanced vane pump, since the number of ports is small, the number of vanes 3 can be reduced. Therefore, the manufacturing cost of the vane pump 100 can be reduced, and since the total frictional force generated between each vane 3 and the inner peripheral cam surface 4a is reduced, the driving torque of the rotor 2 can be reduced.

[0048] Further, in the vane pump 100 of the present embodiment, 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 can adjust the timing at which the pump chamber 6 starts to communicate with the suction port 31 and the discharge port 41 and the timing at which the communication between the pump chamber 6 and the suction port 31 and the discharge port 41 ends.

[0049] Specifically, on the short-diameter portion 4b side, 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, after the communication between the pump chamber 6 and the discharge-side through hole 42 ends, the communication between the pump chamber 6 and the discharge-side notch 43 ends. In the vane pump 100, on the short-diameter portion 4b side of the inner peripheral cam surface 4a, since the suction-side through hole 32 and the discharge-side through hole 42 are covered by the cam ring 4, the opening areas of the suction-side through hole 32 and the discharge-side through hole 42 with respect to the pump chamber 6 are small. However, by forming the suction-side notch 33 and the discharge-side notch 43 in this way, at the expansion start point 82 and the contraction end point 81, oil easily flows between the pump chamber 6 and each port 31, 41, so that a decrease in the pressure in the pump chamber 6 is suppressed and an increase in the pressure in the pump chamber 6 is suppressed.

[0050] Also, on the long-diameter portion 4c side, at the expansion end point 83, after the communication between the pump chamber 6 and the suction-side notch 33 ends, the communication between the pump chamber 6 and the suction-side through hole 32 ends, and at the contraction start point 80, the pump chamber 6 communicates with the discharge-side through hole 42 before the discharge-side notch 43. In the vane pump 100, on the long-diameter portion 4c side of the inner peripheral cam surface 4a, since the suction-side through hole 32 and the discharge-side through hole 42 are not covered by the cam ring 4, the opening areas of the suction-side through hole 32 and the discharge-side through hole 42 with respect 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 that a decrease in the pressure in the pump chamber 6 is suppressed and an increase in the pressure in the pump chamber 6 is suppressed.

[0051] According to the present embodiment described above, the following effects can be obtained.

[0052] In the vane pump 100, since the discharge port 41 is formed beyond the contraction start point 80 and the contraction end point 81, the pump chamber 6 communicates with the discharge port 41 at the contraction start point 80 and the contraction end point 81. Therefore, the increase in the pressure inside the pump chamber 6 is suppressed. Further, since the suction port 31 is formed beyond the expansion start point 82 and the expansion end point 83, the pump chamber 6 communicates with the suction port 31 at the expansion start point 82 and the expansion end point 83. Therefore, the decrease in the pressure inside the pump chamber 6 is suppressed. Thus, the driving torque of the rotor 2 can be reduced.

[0053] Next, a modification of this embodiment will be described. The following modifications are also within the scope of the present invention, and it is also possible to combine the configurations shown in the modifications with the configurations described in the above-described embodiment, or to combine the configurations described in the following different modifications with each other.

[0054] <Modification 1> In the above embodiment, the vane pump 100 is an unbalanced vane pump in which one suction port 31 and one discharge port 41 are provided. In an unbalanced vane pump, since the discharge pressure is low, even if the pressure inside the pump chamber 6 is low when the pump chamber 6 communicates with the discharge port 41, the influence of the pulsation of the discharge pressure is small, and the driving torque of the rotor 2 can be reduced while suppressing the influence of the pulsation of the discharge pressure. 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 or the like.

[0055] <Modification 2> In the above-described 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. In the vane pump 100, the discharge port 41 may be formed beyond the contraction start point 80 or the contraction end point 81, or the suction port 31 may be formed beyond the expansion start point 82 or the expansion end point 83. That is, in the vane pump 100, at least one of the following configurations (i)-(iv) may be satisfied: (i) the discharge port 41 is formed beyond the contraction start point 80 on the rear side in the rotation direction; (ii) the discharge port 41 is formed beyond the contraction end point 81 on the front side in the rotation direction; (iii) the suction port 31 is formed beyond the expansion start point 82 on the rear side in the rotation direction; (iv) the suction port 31 is formed beyond the expansion end point 83 on the front side in the rotation direction. In other words, in the suction port 31, 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 may extend beyond the expansion start point 82 or the expansion end point 83. Also, in the discharge port 41, 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 may extend beyond the contraction start point 80 or the contraction end point 81. Even with this configuration, the increase in the pressure in the pump chamber 6 is suppressed, or the decrease in the pressure in the pump chamber 6 is suppressed, so that the driving torque of the rotor 2 can be reduced. However, from the viewpoint of reducing the driving torque of the rotor 2, it is preferable to have all the configurations of (i)-(iv) as in the vane pump 100 of the above-described embodiment.

[0056] <Modified Example 3> In the above-described 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, the discharge-side notch 43 may be formed beyond the contraction start point 80, or the suction-side notch 33 may be formed beyond the expansion end point 83. Also, the discharge-side notch 43 may be formed without extending beyond the contraction start point 80 and the contraction end point 81, or the suction-side notch 33 may be formed without extending beyond the expansion start point 82 and the expansion end point 83.

[0057] <Modification Example 4> In the above-described embodiment, the cam ring 4 is formed with a suction-side notch 33 that faces the suction-side through hole 32 and guides oil to the suction-side through hole 32, and a discharge-side notch 43 that faces the discharge-side through hole 42 and guides the oil discharged from the discharge-side through hole 42. However, the present invention is not limited to this. The suction-side notch 33 and the discharge-side notch 43 may not be formed in the cam ring 4, and the suction port 31 may be formed only by the suction-side through hole 32, and the discharge port 41 may be formed only by the discharge-side through hole 42.

[0058] <Modification Example 5> In the above-described embodiment, the interval between adjacent vanes 3 in the circumferential direction of the rotor 2 is set to be smaller than the interval 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. The interval between adjacent vanes 3 in the circumferential direction of the rotor 2 may be set to be larger than the interval 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 the pressure increase due to the slight compression of the pump chamber 6 that occurs in the flat portion 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 driving torque of the rotor 2.

[0059] Hereinafter, the configurations, operations, and effects of the embodiments of the present invention will be collectively described.

[0060] The vane pump 100 includes a rotor 2 connected to a drive shaft 1 and rotationally driven, a plurality of vanes 3 provided to be reciprocally movable in the radial direction with respect to the rotor 2, a cam ring 4 having an inner circumferential cam surface 4a with which the tip 3a of the vane 3 is in sliding contact 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, a suction port 31 for guiding fluid into 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 beyond the contraction start point 80 where the pump chamber 6 begins to contract or beyond the contraction end point 81 where the contraction of the pump chamber 6 ends in the rearward direction of the rotation direction as the rotor 2 rotates, or the suction port 31 is formed beyond the expansion start point 82 where the pump chamber 6 begins to expand or beyond the expansion end point 83 where the expansion of the pump chamber 6 ends in the forward direction of the rotation direction as the rotor 2 rotates.

[0061] In this configuration, since the discharge port 41 is formed beyond the contraction start point 80 or the contraction end point 81, the pump chamber 6 communicates with the discharge port 41 at the contraction start point 80 or the contraction end point 81. Therefore, the increase in the pressure inside the pump chamber 6 is suppressed. Alternatively, since the suction port 31 is formed beyond the expansion start point 82 or the expansion end point 83, the pump chamber 6 communicates with the suction port 31 at the expansion start point 82 or the expansion end point 83. Therefore, the decrease in the pressure inside the pump chamber 6 is suppressed. Thus, the driving torque of the rotor 2 can be reduced.

[0062] Also, in the vane pump 100, the suction port 31 and the discharge port 41 are provided one by one so as to face each other with the drive shaft 1 interposed therebetween.

[0063] In this configuration, the vane pump 100 is an unbalanced vane pump 100 with one suction port 31 and one discharge port 41 provided respectively. Generally, balanced pumps are used in regions with high discharge pressures, while unbalanced pumps are used in regions with low discharge pressures. In the case of a balanced vane pump, when the discharge pressure is relatively high, if the pressure in the pump chamber is low when the pump chamber communicates with the discharge port, fluid will flow back from the discharge port into the pump chamber, causing pulsations in the discharge pressure. However, in the case of an unbalanced vane pump 100, when the discharge pressure is low, even if the pressure in the pump chamber 6 is low when the pump chamber 6 communicates with the discharge port 41, the influence of discharge pressure pulsations is small. Therefore, it is possible to reduce the driving torque of the rotor 2 while suppressing the influence of discharge pressure pulsations.

[0064] Further, the vane pump 100 further includes a side plate 30 as a side member provided in contact with the side surface of the cam ring 4. In the side plate 30, a suction side through hole 32 for guiding fluid to the pump chamber 6 and a discharge side through hole 42 for guiding the fluid discharged from the pump chamber 6 are formed. In the cam ring 4, a suction side notch 33 formed opposite to the suction side through hole 32 for guiding fluid to the suction side through hole 32 and a discharge side notch 43 formed opposite to the discharge side through hole 42 for guiding the fluid discharged from the discharge side through hole 42 are formed. The suction port 31 is the suction side through hole 32 and the suction side notch 33, and the discharge port 41 is the discharge side through hole 42 and the discharge side notch 43. At least one of the discharge side through hole 42 and the discharge side notch 43 is formed beyond the rear side in the rotational direction from the contraction start point 80 or beyond the front side in the rotational direction from the contraction end point 81, or at least one of the suction side through hole 32 and the suction side notch 33 is formed beyond the rear side in the rotational direction from the expansion start point 82 or beyond the front side in the rotational direction from the expansion end point 83.

[0065] In this configuration, 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 can adjust the timing at which the pump chamber 6 starts to communicate with the suction port 31 and the discharge port 41 and the timing at which the communication between the pump chamber 6 and the suction port 31 and the discharge port 41 ends.

[0066] Further, in the vane pump 100, the inner peripheral cam surface 4a has a minor diameter portion 4b with a relatively short diameter from the rotation center O of the rotor 2 and a major diameter portion 4c with a relatively long diameter from the rotation center O of the rotor 2. The pump chamber 6, on the minor diameter portion 4b side, starts to communicate with the suction side notch 33 prior to the suction side through hole 32 as the rotor 2 rotates, and the communication with the discharge side notch 43 ends after the communication with the discharge side through hole 42 ends.

[0067] In this configuration, on the minor diameter portion 4b side where the opening areas of the suction side through hole 32 and the discharge side through hole 42 with respect to the pump chamber 6 are small, at the expansion start point 82, the pump chamber 6 communicates with the suction side notch 33 prior to the suction side through hole 32, and at the contraction end point 81, the communication of the pump chamber 6 with the discharge side notch 43 ends after the communication with the discharge side through hole 42 ends. Therefore, at the expansion start point 82 and the contraction end point 81, since the fluid flows easily, the decrease in the pressure inside the pump chamber 6 is suppressed, and the increase in the pressure inside the pump chamber 6 is also suppressed.

[0068] As described above, the embodiments of the present invention have been described. However, the above embodiments merely show a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments.

Explanation of Reference Numerals

[0069] 1... drive shaft, 2... rotor, 3... vane, 3a... tip portion, 4... cam ring, 4a... inner peripheral cam surface, 4b... minor diameter portion, 4c... major diameter portion, 6... pump chamber, 30... side plate (side member), 31... suction port, 32... suction side through hole, 33... suction side notch, 41... discharge port, 42... discharge side through hole, 43... discharge side notch, 80... contraction start point, 81... contraction end point, 82... expansion start point, 83... expansion end point, 100... vane pump, O... rotation center

Claims

1. A rotor connected to a drive shaft and rotationally driven, a plurality of vanes provided so as to be reciprocally movable in the radial direction with respect to the rotor, a cam ring having an inner peripheral cam surface with which the tip of the vane slidably contacts as the rotor rotates, a pump chamber defined by the rotor, the cam ring, and a pair of adjacent vanes, a suction port for guiding fluid into the pump chamber, a discharge port for guiding fluid discharged from the pump chamber, and comprising: The discharge port is formed beyond the rear side in the rotational direction from the contraction start point at which the pump chamber begins to contract as the rotor rotates or beyond the front side in the rotational direction from the contraction end point at which the contraction of the pump chamber ends, or the suction port is formed beyond the rear side in the rotational direction from the expansion start point at which the pump chamber begins to expand as the rotor rotates or beyond the front side in the rotational direction from the expansion end point at which the expansion of the pump chamber ends. A vane pump characterized by that.

2. The vane pump according to claim 1, wherein the suction port and the discharge port are provided one by one so as to face each other with the drive shaft interposed therebetween. A vane pump characterized by that.

3. The vane pump according to claim 1, further comprising a side member provided in contact with the side surface of the cam ring, wherein a suction side through hole for guiding fluid into the pump chamber and a discharge side through hole for guiding fluid discharged from the pump chamber are formed in the side member, in the cam ring, a suction side notch formed to face the suction side through hole for guiding fluid into the suction side through hole and a discharge side notch formed to face the discharge side through hole for guiding fluid discharged from the discharge side through hole are formed, the suction port is the suction side through hole and the suction side notch, the discharge port is the discharge side through hole and the discharge side notch, at least one of the discharge side through hole and the discharge side notch is formed beyond the rear side in the rotational direction from the contraction start point or beyond the front side 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 beyond the rear side in the rotational direction from the expansion start point or beyond the front side in the rotational direction from the expansion end point. A vane pump characterized by that.

4. The vane pump according to claim 3, The inner peripheral cam surface has a minor diameter portion with a relatively short diameter from the rotation center of the rotor and a major diameter portion with a relatively long diameter from the rotation center of the rotor. The pump chamber is characterized in that, on the minor diameter portion side, as the rotor rotates, it starts to communicate with the suction side notch before the suction side through hole and the communication with the discharge side notch ends after the communication with the discharge side through hole ends. It is a vane pump.

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