Patent Publication Number: US-11644031-B2

Title: Vane pump with tip-end-side guide surfaces provided between inner and outer notches of the discharge port and base-end-side guide surface provided in the back pressure port

Description:
TECHNICAL FIELD 
     The present invention relates to a vane pump. 
     BACKGROUND ART 
     JP2014-163307A discloses a vane pump provided with a rotor having a plurality of slits formed in a radiating pattern, vanes that are respectively freely slidably received in the slits, a cam ring having a cam face with which tip end portions of the vanes are brought into sliding contact, and a side member having a sliding contact surface with which side surface of the rotor is brought into sliding contact. In the vane pump disclosed in JP2014-163307A, discharge ports and back pressure ports are formed so as to serve as opening portions that open in the sliding contact surface of the side member. 
     Working fluid discharged from pump chambers that are defined between the rotor, the cam ring, and adjacent vanes is guided to the discharge ports. A part of the working fluid that has been guided to the discharge ports is guided through the back pressure ports to back pressure chambers provided on the base-end sides of the slits. The vanes are respectively pushed by the pressure in the back pressure chambers in the direction in which the vanes project out from the slits and are brought into sliding contact with the cam face. 
     SUMMARY OF INVENTION 
     The vane pump may be reverse rotated depending on its application embodiment. When the vane pump is reverse rotated, because the working fluid is not sufficiently supplied to the discharge ports and the back pressure ports, a state in which the vanes are not sufficiently pushed by the pressure in the back pressure chambers is established. 
     Thus, when the vane pump is reverse rotated, the vanes are separated away from the cam face. Because small gaps are formed between the vanes and the side member, if the vanes are separated away from the cam face, the vanes are inclined so as to fall down towards the side member, and there is a risk in that the tip end portion of the vane drops into the discharge port (the opening portion) and/or the base-end portion of the vane drops into the back pressure port (the opening portion). If the end portion of the vane drops into the opening portion that opens in the sliding contact surface of the side member, there is a risk in that the end portion of the vane moves within the opening portion along with the reverse rotation of the rotor and the end portion of the vane comes to hit an end portion of the opening portion, thereby causing the side member to be damaged. 
     An object of the present invention is to prevent the side member from being damaged. 
     According to one aspect of the present invention, a vane pump includes: a rotor having a plurality of slits formed in a radiating pattern, the rotor being rotationally driven; a plurality of vanes freely slidably received in the slits; a cam ring having a cam face with which tip end portions of the vanes come into sliding contact; a side member having a sliding contact surface with which side surfaces of the rotor and the vanes come into sliding contact; pump chambers defined by the rotor, the cam ring, and the adjacent vanes; a suction port configured to open in the sliding contact surface, the suction port being configured to guide working fluid to be sucked into the pump chambers; a discharge port configured to open in the sliding contact surface, the discharge port being configured to guide the working fluid discharged from the pump chambers; groove-shaped notches provided in the side member so as to extend from an end portion of the discharge port in a direction opposite from a forward rotation direction of the rotor; and back pressure chambers defined with base-end portions of the vanes in the slits. The notches includes: an inner notch located at an inner side of the end portion of the discharge port in a radial direction; and an outer notch located at an outer side of the end portion of the discharge port in the radial direction, and the side member has a tip-end-side guide surface provided between the inner notch and the outer notch so as to be continuous from the end portion of the discharge port, the tip-end-side guide surface being configured to push the tip end portions of the vanes upward and guides them toward the sliding contact surface of the side member when the rotor is rotated in a reverse rotation direction. 
     According to another aspect of the present invention, a vane pump comprising: a rotor having a plurality of slits formed in a radiating pattern, the rotor being rotationally driven; a plurality of vanes freely slidably received in the slits; a cam ring having a cam face with which tip end portions of the vanes come into sliding contact; a side member having a sliding contact surface with which side surfaces of the rotor and the vanes come into sliding contact; pump chambers defined by the rotor, the cam ring, and the adjacent vanes; a suction port configured to open in the sliding contact surface, the suction port being configured to guide working fluid to be sucked into the pump chambers; a discharge port configured to open in the sliding contact surface, the discharge port being configured to guide the working fluid discharged from the pump chambers; and back pressure chambers defined with base-end portions of the vanes in the slits. The side member has: a back pressure port configured to open in the sliding contact surface, the back pressure port being configured to communicate with the back pressure chambers; and a base-end-side guide surface provided on an end portion side of the back pressure port on a communication commencing side where the communication with the back pressure chambers commences as the rotor is forward rotated, the base-end-side guide surface being configured to push the base-end portions of the vanes upward and guide them toward the sliding contact surface of the side member as the rotor is rotated in a reverse rotation direction. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a sectional view of a vane pump according to an embodiment of the present invention. 
         FIG.  2    is a side view of a rotor, a cam ring, and a cover-side side plate of the vane pump according to the embodiment of the present invention. 
         FIG.  3    is a side view of the cover-side side plate of the vane pump according to the embodiment of the present invention. 
         FIG.  4    is a perspective view of the cover-side side plate of the vane pump according to the embodiment of the present invention. 
         FIG.  5    is a sectional view taken along a line V-V in  FIG.  3   . 
         FIG.  6    is a sectional view taken along a line VI-VI in  FIG.  3   . 
         FIG.  7 A  is a diagram showing a state in which a tip end portion of a vane is in contact with a tip-end-side guide surface. 
         FIG.  7 B  is a diagram showing a state in which the tip end portion of the vane moves along the tip-end-side guide surface. 
         FIG.  8 A  is a diagram showing a discharge port, notches, and the cam ring of the vane pump according to a comparative example of this embodiment. 
         FIG.  8 B  is a diagram showing the discharge port, the notches, and the cam ring of the vane pump according to this embodiment. 
         FIG.  9    is a sectional view taken along a line IX-IX in  FIG.  3   . 
         FIG.  10    is a sectional view taken along a line X-X in  FIG.  3   . 
         FIG.  11 A  is a diagram showing a state in which a base-end portion of the vane is in contact with a base-end-side guide surface. 
         FIG.  11 B  is a diagram showing a state in which the base-end portion of the vane moves along the base-end-side guide surface. 
         FIG.  12 A  is a sectional view showing an example of the tip-end-side guide surface that is formed so as to be curved. 
         FIG.  12 B  is a sectional view showing another example of the tip-end-side guide surface that is formed so as to be curved. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A vane pump  100  according to an embodiment of the present invention will be described with reference to the drawings. 
     The vane pump  100  is used as a fluid pressure source for a fluid pressure apparatus, such as, for example, a transmission, a power steering apparatus, and so forth that is mounted on vehicles and industrial machineries. In this embodiment, the fixed displacement vane pump  100  using working oil as working fluid will be described. The vane pump  100  may also be a variable displacement vane pump. 
       FIG.  1    is a sectional view of the vane pump  100 , and  FIG.  2    is a side view of a rotor  2 , a cam ring  4 , and a cover-side side plate  40 . As shown in  FIGS.  1  and  2   , the vane pump  100  is provided with: a pump body  10  that is formed with a pump accommodating concave portion  10 A; a pump cover  50  that is fixed to the pump body  10  so as to cover an opening portion of the pump accommodating concave portion  10 A; a driving shaft  1  that is rotatably supported by the pump body  10  and the pump cover  50  via bearings  19   a  and  19   b ; the rotor  2  that is linked with the driving shaft  1  and accommodated in the pump accommodating concave portion  10 A; vanes  3  that are respectively freely slidably received in slits  2   a  of the rotor  2 ; and the cam ring  4  that accommodates the rotor  2  and the vanes  3  and that has a cam face (an inner circumferential surface)  4   a  with which tip end portions  3   a  of the vanes  3  come into sliding contact. 
     The vane pump  100  is driven by a driving device (not shown), for example an engine, etc., and thereby, the rotor  2  linked to the driving shaft  1  is rotationally driven in the clockwise direction (forward rotation) as shown by an arrow in  FIG.  2    to generate the fluid pressure. 
     A plurality of slits  2   a  are formed in a radiating pattern in the rotor  2 . The slits  2   a  respectively open on an outer circumference of the rotor  2 . 
     The vanes  3  are inserted into the respective slits  2   a  so as to be freely slidably, and has the tip end portions  3   a  that are end portions in the direction projecting out from the slits  2   a  and base-end portions  3   b  that are end portions at the opposite side of the tip end portions  3   a . In the slits  2   a , back pressure chambers  9  are respectively defined on the bottom portion side of the slits  2 A with the base-end portions  3   b  of the vanes  3 . The working oil serving as the working fluid is guided to the back pressure chambers  9  from a high-pressure chamber  14 , which will be described below. The vanes  3  are respectively pushed by the pressure in the back pressure chambers  9  in the direction in which the vanes  3  project out from the slits  2   a.    
     The cam ring  4  is an annular member having the cam face  4   a  forming an inner circumferential surface having a substantially oval shape. As the vanes  3  are pushed by the pressure in the back pressure chambers  9  in the direction in which the vanes  3  project out from the slits  2   a , the tip end portions  3   a  of the vanes  3  are brought into sliding contact with the cam face  4   a  of the cam ring  4 . With such a configuration, pump chambers  6  are defined in the cam ring  4  by an outer circumferential surface of the rotor  2 , the cam face  4   a  of the cam ring  4 , and the adjacent vanes  3 . 
     Because the cam face  4   a  of the cam ring  4  has the substantially oval shape, as the rotor  2  is rotated, the displacement of each of the pump chambers  6 , which are defined by the respective vanes  3  in sliding contact with the cam face  4   a , is repeatedly expanded and contracted. The working oil is sucked in suction regions in which the pump chambers  6  are expanded, and the working oil is discharged in discharge regions in which the pump chambers  6  are contracted. 
     As shown in  FIG.  2   , the vane pump  100  has a first suction region  71  and a first discharge region  81 , in which the vanes  3  undergo first reciprocating movement, and a second suction region  72  and a second discharge region  82 , in which the vanes  3  undergo second reciprocating movement. While the rotor  2  completes a full rotation, the pump chambers  6  are expanded in the first suction region  71 , contracted in the first discharge region  81 , expanded in the second suction region  72 , and contracted in the second discharge region  82 . Although the vane pump  100  has two suction regions  71  and  72  and two discharge regions  81  and  82 , the configuration is not limited thereto, and the vane pump  100  may have a configuration in which a single suction region or three or more suction regions and a single discharge region or three or more discharge regions are provided. 
     As shown in  FIG.  1   , the vane pump  100  is further provided with a body-side side plate  30  and a cover-side side plate  40 . The body-side side plate  30  serves as a first side member that is provided on one end side of the rotor  2  in the axial direction and that comes into contact with one-side surfaces of the rotor  2  and the cam ring  4 , and the cover-side side plate  40  serves as a second side member that is provided on the other end side of the rotor  2  in the axial direction and that comes into contact with other-side surfaces of the rotor  2  and the cam ring  4 . 
     The body-side side plate  30  is provided between a bottom surface of the pump accommodating concave portion  10 A and the rotor  2 . First end surfaces of the rotor  2  and the vanes  3  in the axial direction come into sliding contact with the body-side side plate  30 , and a first end surface of the cam ring  4  in the axial direction comes into contact with the body-side side plate  30 . In other words, an end surface of the body-side side plate  30  functions as a sliding contact surface  30   a  with which the side surfaces of the rotor  2  and the vanes  3  come into sliding contact. The cover-side side plate  40  is provided between the rotor  2  and the pump cover  50 . Second end surfaces of the rotor  2  and the vanes  3  in the axial direction come into sliding contact with the cover-side side plate  40 , and a second end surface of the cam ring  4  in the axial direction comes into contact with the cover-side side plate  40 . In other words, an end surface of the cover-side side plate  40  functions as a sliding contact surface  40   a  with which the side surfaces of the rotor  2  and the vanes  3  come into sliding contact. By being configured as described above, the body-side side plate  30  and the cover-side side plate  40  are arranged in a state in which they respectively face both side surfaces of the rotor  2  and the cam ring  4 . 
     The body-side side plate  30 , the rotor  2 , the cam ring  4 , and the cover-side side plate  40  are accommodated in the pump accommodating concave portion  10 A of the pump body  10 . By attaching the pump cover  50  to the pump body  10  in this state, the pump accommodating concave portion  10 A is sealed. 
     An annular high-pressure chamber  14  is defined by the pump body  10  and the body-side side plate  30  on the bottom surface side of the pump accommodating concave portion  10 A of the pump body  10 . The high-pressure chamber  14  communicates with a fluid hydraulic apparatus  70  provided outside the vane pump  100  via a discharge passage  62 . 
     The pump cover  50  is formed with a suction pressure chamber  51  and bypass passages  13  that communicates with the suction pressure chamber  51  is formed in an inner circumferential surface of the pump accommodating concave portion  10 A. The bypass passages  13  are respectively provided at two positions that oppose to each other such that the cam ring  4  is located therebetween. The suction pressure chamber  51  is connected to a tank  60  via suction passages  61 . 
       FIG.  3    is a side view of the cover-side side plate  40 . As shown in  FIG.  3   , the cover-side side plate  40  is a disc-shaped member having two suction ports  41  that guide the working oil to be sucked into the pump chambers  6  and two discharge ports  42  that guide the working oil discharged from the pump chambers  6 . 
     The suction ports  41  are formed so as to open in the sliding contact surface  40   a  correspondingly to the suction regions  71  and  72  (see  FIG.  2   ). Each of the suction ports  41  is formed such that a part of an outer edge portion of the cover-side side plate  40  is cut away. As shown in  FIG.  1   , the suction ports  41  of the cover-side side plate  40  communicate with suction ports  31  of the body-side side plate  30  via the bypass passages  13  of the pump body  10 . Therefore, the working oil sucked from the suction passages  61  is guided to the pump chambers  6  through the suction ports  31  of the body-side side plate  30  and the suction ports  41  of the cover-side side plate  40 . 
     As shown in  FIG.  3   , the discharge ports  42  are formed as arc-shaped grooves so as to open in the sliding contact surface  40   a  correspondingly to the discharge regions  81  and  82  (see  FIG.  2   ), and the working oil in the pump chambers  6  is discharged to the high-pressure chamber  14 . In the sliding contact surface  40   a  of the cover-side side plate  40 , groove-shaped notches  20  are formed so as to communicate with end portions of the discharge ports  42 . The notches  20  will be described below in detail. 
     The cover-side side plate  40  is formed with four back pressure ports  160  that open in the sliding contact surface  40   a  and communicate with the back pressure chambers  9 . Back pressure ports  160 A provided in the first suction region  71  and back pressure ports  160 B provided in the first discharge region  81  are connected with each other at their end portions via communicating grooves  140 , and they are communicated with each other via the communicating grooves  140 . Similarly, the back pressure ports  160 A provided in the second suction region  72  and the back pressure ports  160 B provided in the second discharge region  82  are connected with each other at their end portions via the communicating grooves  140 , and they are communicated with each other via the communicating grooves  140 . 
     Relative rotation of the cam ring  4  and the cover-side side plate  40  is restricted by two positioning pins (not shown). With such a configuration, the suction ports  41  and the discharge ports  42  of the cover-side side plate  40  are aligned with respect to the suction regions  71  and  72  and the discharge regions  81  and  82 . 
     As shown in  FIG.  1   , similarly to the cover-side side plate  40 , the body-side side plate  30  is a disc-shaped member having the suction ports  31  that are formed so as to respectively correspond to the suction regions  71  and  72  and discharge ports (not shown) that are formed so as to respectively correspond to the discharge regions  81  and  82 . 
     The suction ports  31  are formed at positions that correspond to the bypass passages  13  of the pump accommodating concave portion  10 A. Each of the suction ports  31  is formed to have a concaved shape that opens radially outward. Each of the suction ports  31  extends such that its outer circumference end reaches an outer circumferential surface of the body-side side plate  30 . The working oil is supplied to the suction ports  31  via the suction pressure chamber  51  and the bypass passages  13  (see  FIG.  1   ). The suction ports  31  guide the thus supplied working oil into the pump chambers  6 . 
     The discharge ports (not shown) of the body-side side plate  30  are each formed to have an arc shape by penetrating therethrough and are in communication with the high-pressure chamber  14  formed in the pump body  10 . These discharge ports discharge the working oil that has been guided from the pump chambers  6  to the high-pressure chamber  14 . 
     The sliding contact surface  30   a  of the body-side side plate  30  is formed with back pressure ports  165  that are formed so at to oppose to the back pressure ports  160  of the above-described cover-side side plate  40 . The back pressure ports  165  are in communication with the high-pressure chamber  14  via back pressure passages  166 . 
     As the engine is driven and the driving shaft  1  is rotated, the rotor  2  linked to the driving shaft  1  is rotated. As a result, each of the pump chambers  6  in the cam ring  4  sucks the working oil through the suction ports  31  of the body-side side plate  30  and the suction ports  41  of the cover-side side plate  40  and discharges the working oil to the high-pressure chamber  14  through the discharge ports (not shown) of the body-side side plate  30  and the discharge ports  42  of the cover-side side plate  40 . The working oil that has entered the high-pressure chamber  14  is then supplied through the discharge passage  62  to the fluid pressure apparatus  70  provided outside the vane pump  100  (see  FIG.  1   ). As described above, each of the pump chambers  6  in the cam ring  4  supplies/discharges the working oil by the expansion/contraction caused along with the rotation of the rotor  2 . 
     Next, the notches  20  that are formed in the sliding contact surface  40   a  of the cover-side side plate  40  will be described in detail below with reference to  FIGS.  2  to  5   .  FIG.  4    is a perspective view of the cover-side side plate  40 , and  FIG.  5    is a sectional view taken along a line V-V in  FIG.  3   . As shown in  FIGS.  2  to  5   , in this embodiment, the cover-side side plate  40  has, as the notches  20 , inner notches  20   i  and outer notches  20   o  that are respectively provided on the outside of the inner notches  20   i  in the radial direction. 
     The outer notches  20   o  and the inner notches  20   i  are provided in the sliding contact surface  40   a  of the cover-side side plate  40  so as to respectively correspond to the two discharge ports  42 . Each of the discharge ports  42  has: an outer arc portion  121  and an inner arc portion  122  that are formed to have an arc shape extending along the circumferential direction of the rotor  2 ; and arc-shaped end-portion-side arc portions  123   a  and  123   b  that connect the outer arc portion  121  and the inner arc portion  122 . The inner arc portion  122  is provided on the inside of the outer arc portion  121  in the radial direction so as to oppose the outer arc portion  121 . The outer notch  20   o  and the inner notch  20   i  communicate with the discharge port  42  by being provided on the end-portion-side arc portion  123   a  that is an end portion of the discharge port  42  in the circumferential direction on the communication commencing side where the communication between the discharge port  42  and the pump chambers  6  commences as the rotor  2  is forward rotated. 
     The outer notch  20   o  and the inner notch  20   i  are each formed to have a groove shape that extends in the direction opposite from the forward rotation direction of the rotor  2  from the end-portion-side arc portion  123   a  that is the end portion of the discharge port  42  such that an opening area is gradually reduced towards the direction opposite from the forward rotation direction of the rotor  2 . In the above, the opening area of the notch  20  refers to a cross-sectional area of the notch  20  in a plane along the radial direction of the rotor  2 . The outer notch  20   o  is arranged on the outer circumferential side of the inner notch  20   i . In other words, the inner notch  20   i  is located at the inner side of the end-portion-side arc portion  123   a  of the discharge port  42  in the radial direction, and the outer notch  20   o  is located at the outer side of the end-portion-side arc portion  123   a  of the discharge ports  42  in the radial direction. The outer notch  20   o  is formed such that the length along the rotation direction of the rotor  2  (the circumferential direction) is longer than that of the inner notch  20   i.    
     The notch  20  presents a triangle shape having two straight lines extending linearly from a apex towards the discharge port  42  when viewed from the axial direction of the rotor  2  (see  FIG.  3   ). In the notch  20 , a cross-sectional shape is formed to have a V-shape in the plane along the radial direction of the rotor  2  (see  FIG.  5   ). In addition, the groove of the notch  20  is formed such that its depth is increased gradually towards the forward rotation direction of the rotor  2 . 
     As the pump chambers  6  communicate with the notch  20  by the forward rotation of the rotor  2 ; the adjacent pump chambers  6  communicate with each other through the notch  20 . Thereby, the high-pressure working oil from the discharge port  42  is guided from the pump chamber  6  on the forward side in the rotation direction to the pump chamber  6  on the rearward side in the rotation direction. Thus, the pressure in the pump chamber  6  on the rearward side in the rotation direction is gradually increased even before the pump chamber  6  communicates directly with the discharge port  42 , and therefore, a sudden pressure change when the pump chamber  6  communicates directly with the discharge port  42  is suppressed. 
     The outer notch  20   o  is formed so as to extend along the outer arc portion  121 , and the inner notch  20   i  is formed so as to extend along the inner arc portion  122 . The outer notch  20   o  is formed such that the opening edge portion of the outer notch  20   o  on the radially outer side of the base-end side (the discharge port  42  side) is located at the outside of the outer arc portion  121  in the radial direction. In other words, the outer notch  20   o  is formed so as to include a boundary portion between the outer arc portion  121  and the end-portion-side arc portion  123   a.    
     Furthermore, as shown in  FIGS.  2  and  5   , the outer notch  20   o  is formed such that, on the base-end side (the discharge port  42  side), the opening edge portion thereof on radially outer side is located at the outside of the cam face  4   a  of the cam ring  4  in the radial direction. In other words, the cam face  4   a  is located at the radially inside of the opening edge portion of the outer notches  20   o  on the radially outer side of the base-end side. Thus, a part of the base-end side of the outer notch  20   o  on the outer side in the radial direction is covered by the cam ring  4 . 
     An operation of the vane pump  100  will be described with reference to  FIGS.  1  and  2   . 
     As the driving shaft  1  is rotationally driven by a motive force from the driving device such as the engine, etc. (not shown), the rotor  2  is forward rotated in the direction shown by the arrow in  FIG.  2   . As the rotor  2  is forward rotated, the pump chambers  6  positioned in the suction regions  71  and  72  are expanded. Thereby, the working oil in the tank  60  is sucked into the pump chambers  6  through the suction passages  61  and the suction ports  31  and  41 . In addition, as the rotor  2  is forward rotated, the pump chambers  6  positioned in the discharge regions  81  and  82  are contracted. Thereby, the working oil in the pump chambers  6  is discharged to the high-pressure chamber  14  through the discharge ports  42 . The working oil that has been discharged to the high-pressure chamber  14  is then supplied to the external fluid pressure apparatus  70  through the discharge passage  62 . In the vane pump  100  according to this embodiment, as the rotor  2  completes a full rotation, the respective pump chambers  6  repeat the suction and discharge of the working oil twice. 
     A part of the working oil that discharged to the high-pressure chamber  14  is supplied to the back pressure chambers  9  through the back pressure passages  166  and the back pressure ports  165 ,  160 A, and  160 B, and thereby, the base-end portions  3   b  of the vanes  3  are pushed radially outward. Therefore, the vanes  3  are biased in the direction in which the vanes  3  project out from the slits  2   a  by a fluid pressure force from the back pressure chambers  9  pushing the base-end portions  3   b  and by a centrifugal force caused by the rotation of the rotor  2 . With such a configuration, because the tip end portions  3   a  of the vanes  3  rotate while coming into sliding contact with the cam face  4   a  of the cam ring  4 , the working oil in the pump chambers  6  is guided to the discharge ports  42  without leaking out from between the tip end portions  3   a  of the vanes  3  and the cam face  4   a  of the cam ring  4 . 
     As described above, when the rotor  2  is forward rotated, the working oil that has been sucked to the pump chambers  6  from the suction ports  31  and  41  is pressurized by the contraction of the pump chambers  6  and is discharged from the discharge ports  42 . In addition, the part of the working oil in the discharge ports  42  is guided to the back pressure chambers  9 , and the vanes  3  are pushed against the cam face  4   a  by the pressure in the back pressure chambers  9 . 
     However, the vane pump  100  may be reverse rotated depending on its application embodiment. When the vane pump  100  is reverse rotated, because the working fluid is not sufficiently supplied to the discharge ports  42  and the back pressure ports  160  and  165 , a state in which the vanes  3  are not sufficiently pushed by the pressure in the back pressure chambers  9  is established. 
     Thus, when the vane pump  100  is reverse rotated, the vane  3  is separated away from the cam face  4   a . Because small gaps are formed between the vane  3  and the pair of side plates  30  and  40 , if the vane  3  is separated away from the cam face  4   a , the vane  3  is inclined so as to fall down towards the side plates  30  or  40 , and there is a risk in that the tip end portion  3   a  of the vane  3  drops into the discharge port (the opening portion)  42  and/or the base-end portion  3   b  of the vane  3  drops into the back pressure port (the opening portion)  160  or  165 . If the end portion of the vane  3  drops into the opening portion that opens in the sliding contact surface  30   a  or  40   a  of the side plate  30  or  40 , there is a risk in that the end portion of the vane  3  moves within the opening portion along with the reverse rotation of the rotor  2  and the end portion of the vane  3  comes to hit the end portion of the opening portion, thereby causing the side plate  30  or  40  to be damaged. If the side plate  30  or  40  is damaged, fine metal pieces are formed, and there is a risk in that the vane pump  100  is broken due to the metal pieces bitten between the sliding contact surfaces  30   a  and  40   a  and the rotor  2 . 
     Thus, in this embodiment, the side plates  30  and  40  are respectively provided with guide surfaces (tip-end-side guide surfaces  130  and base-end-side guide surfaces  170 ) with which, even in a case in which the end portion of the vane  3  (the tip end portion  3   a  or the base-end portion  3   b ) drops into the opening portion (the discharge port  42 , or the back pressure port  165 ,  160 ) that opens in the sliding contact surface  30   a ,  40   a , the dropped end portion of the vane  3  (the tip end portion  3   a  or the base-end portion  3   b ) is pushed upward and guided to the sliding contact surface  30   a ,  40   a . Because the guide surfaces provided in the body-side side plate  30  and the guide surfaces provided in the cover-side side plate  40  have the same configuration, a representative description will be given on the guide surfaces provided in the cover-side side plate  40  in the following, and description of the guide surfaces provided in the body-side side plate  30  will be omitted. 
     The tip-end-side guide surfaces  130  that are provided correspondingly to the discharge ports  42  will be described in detail with reference to  FIGS.  3  to  6   .  FIG.  6    is a sectional view taken along a line VI-VI in  FIG.  3   . As shown in  FIGS.  3  to  6   , the tip-end-side guide surface  130  is formed between the inner notch  20   i  and the outer notch  20   o  so as to be continuous from the end-portion-side arc portion  123   a  of the discharge port  42 . The tip-end-side guide surface  130  is a flat surface that pushes the tip end portion  3   a  of the vane  3  upward and guides it toward the sliding contact surface  40   a  of the cover-side side plate  40  as the rotor  2  is rotated in the reverse rotation direction. 
     The tip-end-side guide surface  130  is connected to the inner notch  20   i  and the outer notch  20   o . A length of the tip-end-side guide surface  130  in the circumferential direction is shorter than the lengths of the outer notch  20   o  and the inner notch  20   i  in the circumferential direction. Thus, a tip end of the outer notch  20   o  and a tip end of the inner notch  20   i  are located away from the tip-end-side guide surface  130  by a predetermined distance in the direction opposite from the forward rotation direction. 
     As shown in  FIG.  6   , the end-portion-side arc portion  123   a  of the discharge port  42  is provided so as to be parallel with the rotation axis of the rotor  2 . The end-portion-side arc portion  123   a  of the discharge port  42  is formed so as to be erected perpendicularly upward from a bottom surface of the discharge port  42 . The tip-end-side guide surface  130  is formed to have a tapered shape in which the depth from the sliding contact surface  40   a  (the distance to the sliding contact surface  40   a  in the axial direction) is decreased in the reverse rotation direction of the rotor  2 . The tip-end-side guide surface  130  is linearly inclined toward the sliding contact surface  40   a  of the cover-side side plate  40  from an end portion of the end-portion-side arc portion  123   a  on the opposite side of the bottom surface, in other words the end portion of the end-portion-side arc portion  123   a  on the sliding contact surface  40   a  side (an upper end portion in the figure). The tip-end-side guide surface  130  may be a tapered surface that is linearly inclined toward the sliding contact surface  40   a  from the end surface on the opposite side from the sliding contact surface  40   a  (the bottom surface of the discharge port  42 ). 
     An axial direction distance h 1  from a corner portion that forms the boundary between the end-portion-side arc portion  123   a  and the tip-end-side guide surface  130  (in other words, the upper end portion of the end-portion-side arc portion  123   a  in the figure) to the sliding contact surface  40   a  is set so as to be greater than a maximum drop depth d 1  of the vane  3  (in other words, the distance in the axial direction from the sliding contact surface  40   a  to the tip end portion  3   a  of the vane  3  that has dropped at the greatest extent) (h 1 &gt;d 1 ). For the tip-end-side guide surface  130 , it is preferable that an inclined angle θ 1  relative to the sliding contact surface  40   a  be set so as to be greater than 0° and smaller than 45°. 
     Therefore, in a case in which the tip end portion  3   a  of the vane  3  has dropped into the discharge port  42  when the vane pump  100  is reverse rotated, as shown in  FIG.  7 A , the tip end portion  3   a  of the vane  3  comes into contact with the tip-end-side guide surface  130 . As shown in  FIG.  7 B , together with the movement of the vane  3  in the circumferential direction, the tip end portion  3   a  of the vane  3  that has come into contact with the tip-end-side guide surface  130  moves while being in sliding contact with the tip-end-side guide surface  130 . Because the tip end portion  3   a  of the vane  3  is pushed upward by the tip-end-side guide surface  130 , the inclination of the vane  3  is gradually corrected and the tip end portion  3   a  is guided to the sliding contact surface  40   a . Because the tip-end-side guide surface  130  is formed to have the tapered shape, the inclination of the vane  3  is corrected smoothly as the rotor  2  is reverse rotated. 
     Furthermore, the tip-end-side guide surface  130  is linearly inclined. Thus, compared with a case in which the tip-end-side guide surface  130  is inclined so as to be curved, a sliding resistance of the tip end portion  3   a  of the vane  3  moving along the tip-end-side guide surface  130  can be made constant, and so, it is possible to stably guide the tip end portion  3   a  of the vane  3  to the sliding contact surface  40   a  of the cover-side side plate  40 . 
     In a case in which the tip-end-side guide surface  130  is not provided, the tip end portion  3   a  of the vane  3  hits the end-portion-side arc portion  123   a  that is a side wall perpendicularly erected from the bottom surface of the discharge port  42 , and therefore, there is a risk of damage to the end-portion-side arc portion  123   a , such as chipping on the end-portion-side arc portion  123   a . In contrast, in this embodiment, the tip end portion  3   a  of the vane  3  comes to contact with the tip-end-side guide surface  130  and is guided to the sliding contact surface  40   a , and therefore, it is possible to prevent the discharge port  42  from being damaged. 
     Operational advantages that are achieved by employing the configuration according to this embodiment will be described with a comparison with a comparative example.  FIG.  8 A  is a schematic view showing a discharge port  92 , notches  920   i  and  920   o , and a cam ring  904  of a vane pump according to the comparative example of this embodiment, and  FIG.  8 B  is a schematic view showing the discharge ports  42 , the notches  20   i  and  20   o , and the cam ring  4  of the vane pump  100  according to this embodiment. In the figures, the cam rings  904  and  4  are shown by two-dot chain lines. 
     As shown in  FIG.  8 A , the discharge port  92  has: an outer arc portion  921  and an inner arc portion  922  that are formed to have an arc shape extending along the circumferential direction of the rotor  2 ; and arc-shaped end-portion-side arc portions  923   a  and  923   b  that connect the outer arc portion  921  and the inner arc portion  922 . The inner arc portion  922  is provided on the inner side of the outer arc portion  921  in the radial direction so as to oppose the outer arc portion  921 . 
     The outer notch  920   o  and the inner notch  920   i  extend in the circumferential direction from the end-portion-side arc portion  923   a . An outer end portion  923   c  that is a part of the end-portion-side arc portion  923   a  is provided between the outer notch  920   o  and the outer arc portion  921 , a center end portion  923   d  that is a part of the end-portion-side arc portion  923   a  is provided between the outer notch  920   o  and the inner notch  920   i , and an inner end portion  923   e  that is a part of the end-portion-side arc portion  923   a  is provided between the inner notch  920   i  and the inner arc portion  922 . In addition, the outer notch  920   o  is formed such that, on the base-end side (the discharge port  92  side), the opening edge portion thereof on radially outer side is located at the radially inside of a cam face  904   a  of the cam ring  904 . 
     Thus, in the comparative example according to this embodiment, in a case in which the vane pump is reverse rotated and the tip end portion  3   a  of the vane  3  has dropped into the discharge port  92 , there is a risk in that the tip end portion  3   a  of the vane  3  hits any of the outer end portion  923   c , the center end portion  923   d , and the inner end portion  923   e  and the side plate is damaged. The drop depth of the tip end portion  3   a  of the vane  3  on the outer side in the radial direction tends to be larger than that of the tip end portion  3   a  of the vane  3  on the inner side in the radial direction. 
     In contrast, in this embodiment, as shown in  FIG.  8 B , the outer notch  20   o  is formed such that the opening edge portion of the outer notch  20   o  on the radially outer side of the base-end side is located at the outside of the outer arc portion  121  in the radial direction. In other words, the outer notch  20   o  is formed so as to include the boundary portion between the outer arc portion  121  and the end-portion-side arc portion  123   a . Thus, the tip end portion  3   a  of the vane  3  that has dropped into the discharge port  42  is prevented from hitting the side wall of the discharge port  42  on the outside of the outer notch  20   o  in the radial direction. 
     The base-end-side guide surfaces  170  that are provided correspondingly to the back pressure ports  160 A will be described in detail with reference to  FIGS.  3 ,  4 ,  9 , and  10   .  FIG.  9    is a sectional view taken along a line IX-IX in  FIG.  3   , and  FIG.  10    is a sectional view taken along a line X-X in  FIG.  3   . As shown in  FIGS.  3 ,  4 ,  9 , and  10   , the base-end-side guide surfaces  170  are each provided on the end portion side of the back pressure port  160 A in the circumferential direction that is the communication commencing side where the communication between the back pressure port  160 A and the back pressure chambers  9  commences as the rotor  2  is forward rotated. The base-end-side guide surfaces  170  are each a flat surface that pushes the base-end portion  3   b  of the vane  3  upward and guides it toward the sliding contact surface  40   a  of the cover-side side plate  40  as the rotor  2  is rotated in the reverse rotation direction. 
     The back pressure ports  160 A each has a main body portion  161  and a narrow-width portion  162  that is provided so as to extend from an end portion  161   a  of the main body portion  161  in the circumferential direction and that has a width in the radial direction that is narrower than that of the main body portion  161 . The base-end-side guide surface  170  is provided so as to extend from the end portion  161   a  of the main body portion  161  in the circumferential direction and so as to be adjacent to the narrow-width portion  162 . 
     As shown in  FIG.  10   , the end portion  161   a  of the main body portion  161  is provided so as to be parallel with the rotation axis of the rotor  2 . The end portion  161   a  of the main body portion  161  is formed so as to be erected perpendicularly upward from a bottom surface of the back pressure port  160 . The base-end-side guide surface  170  is formed to have a tapered shape in which the depth from the sliding contact surface  40   a  (the distance to the sliding contact surface  40   a  in the axial direction) is decreased in the reverse rotation direction of the rotor  2 . The base-end-side guide surface  170  is linearly inclined toward the sliding contact surface  40   a  of the cover-side side plate  40  from an end portion of the end portion  161   a  on the opposite side of the bottom surface, in other words the end portion of the end portion  161   a  on the sliding contact surface  40   a  side (an upper end portion in the figure). The base-end-side guide surface  170  may be a tapered surface that is linearly inclined toward the sliding contact surface  40   a  from the end surface on the opposite side from the sliding contact surface  40   a  (the bottom surface of the back pressure port  160 ). 
     An axial direction distance h 2  from a corner portion that forms the boundary between the end portion  161   a  of the main body portion  161  and the base-end-side guide surface  170  (in other words, the upper end portion of the end portion  161   a  of the main body portion  161  in the figure) to the sliding contact surface  40   a  is set so as to be greater than the maximum drop depth d 2  of the vane  3  (in other words, the distance in the axial direction from the sliding contact surface  40   a  to the base-end portion  3   b  of the vane  3  that has dropped at the greatest extent) (h 2 &gt;d 2 ). For the base-end-side guide surface  170 , it is preferable that an inclined angle θ 2  relative to the sliding contact surface  40   a  be set so as to be greater than 0° and smaller than 45°. 
     Therefore, in a case in which the base-end portion  3   b  of the vane  3  has dropped into the back pressure port  160 A when the vane pump  100  is reverse rotated, as shown in  FIG.  11 A , the base-end portion  3   b  of the vane  3  comes into contact with the base-end-side guide surface  170 . As shown in  FIG.  11 B , together with the movement of the vane  3  in the circumferential direction, the base-end portion  3   b  of the vane  3  that has come into contact with the base-end-side guide surface  170  moves while being in sliding contact with the base-end-side guide surface  170 . Because the base-end portion  3   b  of the vane  3  is pushed upward by the base-end-side guide surface  170 , the inclination of the vane  3  is gradually corrected and the base-end portion  3   b  is guided to the sliding contact surface  40   a . Because the base-end-side guide surface  170  is formed to have the tapered shape, the inclination of the vane  3  is corrected smoothly as the rotor  2  is reverse rotated. 
     Furthermore, the base-end-side guide surface  170  is linearly inclined. Thus, compared with a case in which the base-end-side guide surface  170  inclined so as to be curved, the sliding resistance of the base-end portion  3   b  of the vane  3  moving along the base-end-side guide surface  170  can be made constant, and so, it is possible to stably guide the base-end portion  3   b  of the vane  3  to the sliding contact surface  40   a  of the cover-side side plate  40 . 
     In a case in which the base-end-side guide surface  170  is not provided, the base-end portion  3   b  of the vane  3  hits the end portion  161   a  perpendicularly erected from a bottom surface of the back pressure port  160 A, and therefore, there is a risk of damage to the end portion  161   a , such as chipping on the end portion  161   a . In addition, the drop depth of the base-end portion  3   b  of the vane  3  on the inner side in the radial direction tends to be larger than that of the base-end portion  3   b  of the vane  3  on the outer side in the radial direction. In this embodiment, the base-end-side guide surface  170  is provided on the inner side of the back pressure port  160 A in the radial direction. With such a configuration, the base-end portion  3   b  of the vane  3  that has dropped into the back pressure port  160 A comes to contact with the base-end-side guide surface  170  and is guided to the sliding contact surface  40   a , and therefore, it is possible to prevent the back pressure port  160 A from being damaged. 
     As shown in  FIGS.  3  and  4   , each of the back pressure ports  160 A is provided with the narrow-width portion  162  that extends from the end portion  161   a  of the main body portion  161  in the circumferential direction. Thus, by adjusting the length of the narrow-width portion  162  in the circumferential direction, it is possible to set, with a high accuracy, a range in the circumferential direction at which the communication with the back pressure chambers  9  is established, and therefore, it is possible to apply the back pressure to the vanes  3  evenly. 
     According to the above-described embodiment, following operational advantages can be achieved. 
     (1) The cover-side side plate  40  has the tip-end-side guide surfaces  130  that are each provided between the inner notch  20   i  and the outer notch  20   o  so as to be continuous from the end-portion-side arc portion  123   a  of the discharge port  42 , the tip-end-side guide surface  130  being configured to push the tip end portion  3   a  of the vane  3  upward and guide it toward the sliding contact surface  40   a  of the cover-side side plate  40  as the rotor  2  is rotated in the reverse rotation direction. According to such a configuration, even in a case in which the vane pump  100  is reverse rotated and the tip end portion  3   a  of the vane  3  has dropped into the discharge port  42 , the tip end portion  3   a  of the vane  3  can be guided to the sliding contact surface  40   a  of the cover-side side plate  40  along the tip-end-side guide surface  130 , and therefore, it is possible to prevent the damage of the cover-side side plate  40  caused by the collision between the tip end portion  3   a  of the vane  3  and the cover-side side plate  40 . Because the body-side side plate  30  is also provided with the tip-end-side guide surface  130  in a similar manner, it is possible to also prevent the damage of the body-side side plate  30  caused by the contact with the tip end portion  3   a  of the vane  3 . 
     (2) The cover-side side plate  40  has the base-end-side guide surfaces  170  each provided on the end portion side of the back pressure port  160  on the communication commencing side where the communication with the back pressure chamber  9  commences as the rotor  2  is forward rotated, the base-end-side guide surface  170  being configured to push the base-end portion  3   b  of the vane  3  upward and guide it toward the sliding contact surface  40   a  of the cover-side side plate  40  as the rotor  2  is rotated in the reverse rotation direction. According to such a configuration, even in a case in which the base-end portion  3   b  of the vane  3  has dropped into the back pressure port  160  when the vane pump  100  is reverse rotated, the base-end portion  3   b  of the vane  3  can be guided to the sliding contact surface  40   a  of the cover-side side plate  40  along the base-end-side guide surface  170 , and therefore, it is possible to prevent the damage of the cover-side side plate  40  caused by the collision between the base-end portion  3   b  of the vane  3  and the cover-side side plate  40 . Because the body-side side plate  30  is also provided with the base-end-side guide surfaces  170  in a similar manner, it is possible to also prevent the damage of the body-side side plate  30  caused by the contact with the base-end portions  3   b  of the vanes  3 . 
     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, to combine the configurations described in the above-described different embodiments, and to combine the configurations described in the following different modifications. 
     &lt;First Modification&gt; 
     In the above-mentioned embodiment, although a description has been given of an example in which the tip-end-side guide surface  130  and the base-end-side guide surface  170  have the linearly inclined tapered surface, the present invention is not limited to this configuration. As shown in  FIGS.  12 A and  12 B , the tip-end-side guide surfaces  230 A and  230 B may have the tapered surface that is inclined so as to be curved. Similarly, the base-end-side guide surface  170  may have the tapered surface that is inclined so as to be curved. 
     &lt;Second Modification&gt; 
     In the above-mentioned embodiment, although a description has been given of an example in which the base-end-side guide surfaces  170  are each provided so as to be adjacent to the narrow-width portion  162  of the back pressure port  160 , the present invention is not limited to this configuration. The narrow-width portion  162  may not be provided, and the base-end-side guide surface  170  may be provided so as to be continuous from the whole of the arc-shaped circumferential direction end portion of the back pressure port  160 . In addition, in the above-mentioned embodiment, although a description has been given of an example in which the narrow-width portions  162  are provided on the outer side in the radial direction, and the base-end-side guide surfaces  170  are provided on the inner side in the radial direction, the arrangement relationship for the narrow-width portions  162  and the base-end-side guide surfaces  170  may be inverted. 
     &lt;Third Modification&gt; 
     In the above-mentioned embodiment, although a description has been given of an example in which the notches  20  are formed such that the opening area is gradually decreased in the direction opposite from the forward rotation direction of the rotor  2 , the present invention is not limited to this configuration. For example, the notches  20  may be formed to have the groove shape whose opening area is constant along the rotation direction of the rotor  2 . 
     &lt;Fourth Modification&gt; 
     In the above-mentioned embodiment, although a description has been given of an example in which the outer notches  20   o  are formed so as to be longer than the inner notches  20   i  in the circumferential direction, the present invention is not limited to this configuration. The inner notches  20   i  may be formed so as to be longer than the outer notches  20   o  in the circumferential direction. 
     &lt;Fifth Modification&gt; 
     The communicating groove  140  through which the back pressure port  160 A and the back pressure port  160 B are communicated may be provided with a base-end-side guide surface that pushes the base-end portion  3   b  of the vane  3  upward and guide it toward the sliding contact surface  40   a . The communicating groove  140  provided with the base-end-side guide surface may be formed so as to extend along an outer edge of the back pressure port  160 A and the back pressure port  160 B on the inner circumferential side, or the communicating groove  140  may be formed so as to extend along the outer edge of the back pressure port  160 A and the back pressure port  160 B on the outer circumferential side. 
     &lt;Sixth Modification&gt; 
     In the above-described embodiment, although a description has been given of an example in which the tip-end-side guide surface  130  and the base-end-side guide surface  170  are formed on both of the cover-side side plate  40  and the body-side side plate  30 , the present invention is not limited to this configuration. The tip-end-side guide surface  130  and the base-end-side guide surface  170  may be formed on either one of the cover-side side plate  40  and the body-side side plate  30 . 
     &lt;Seventh Modification&gt; 
     In the above-described embodiment, although a description has been given of the vane pump  100  having the configuration in which the cam ring  4  and the rotor  2  are clamped by the pair of side plates  30  and  40 , as an example, the present invention is not limited to this configuration. For example, it may possible to employ a configuration in which the side plate  40  may be omitted, and the rotor  2  and the vanes  3  are brought into sliding contact with the pump cover  50 . In this case, the pump cover  50  functions as the side member. Thus, by forming the tip-end-side guide surface and the base-end-side guide surface in the pump cover  50 , it is possible to prevent the pump cover  50  from being damaged by preventing the collision of the vanes  3  and the opening portions opening in the sliding contact surface of the pump cover  50 . 
     The configurations, operations, and effects of the embodiment of the present invention configured as described above will be collectively described. 
     The vane pump  100  has: the rotor  2  having the plurality of slits  2   a  formed in a radiating pattern, the rotor  2  being rotationally driven; the plurality of vanes  3  freely slidably received in the slits  2   a ; the cam ring  4  having the cam face  4   a  with which the tip end portions  3   a  of the vanes  3  come into sliding contact; the side member (the body-side side plate  30 , the cover-side side plate  40 ) having the sliding contact surface  30   a ,  40   a  with which the side surfaces of the rotor  2  and the vanes  3  come into sliding contact; the pump chambers  6  defined by the rotor  2 , the cam ring  4 , and the adjacent vanes  3 ; the suction port  31 ,  41  configured to open in the sliding contact surface  30   a ,  40   a , the suction port  31 ,  41  being configured to guide the working fluid to be sucked into the pump chambers  6 ; the discharge port  42  configured to open in the sliding contact surface  30   a ,  40   a , the discharge port  42  being configured to guide the working fluid discharged from the pump chambers  6 ; the groove-shaped notches  20  provided in the side member (the body-side side plate  30 , the cover-side side plate  40 ) so as to extend from the end portion of the discharge port  42  (the end-portion-side arc portion  123   a ) in the direction opposite from the forward rotation direction of the rotor  2 ; and the back pressure chambers  9  defined with the base-end portions  3   b  of the vanes  3  in the slits  2   a , wherein the notches  20  include: the inner notch  20   i  located at the inner side of the end portion of the discharge port  42  (the end-portion-side arc portion  123   a ) in the radial direction; and the outer notch  20   o  located at the outer side of the end portion of the discharge port  42  (the end-portion-side arc portion  123   a ) in the radial direction, and the side member (the body-side side plate  30 , the cover-side side plate  40 ) has the tip-end-side guide surface  130 ,  230 A,  230 B provided between the inner notch  20   i  and the outer notch  20   o  so as to be continuous from the end portion of the discharge port  42  (the end-portion-side arc portion  123   a ), the tip-end-side guide surface  130 ,  230 A,  230 B being configured to push the tip end portion  3   a  of the vane  3  upward and guide it toward the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ) as the rotor  2  is rotated in the reverse rotation direction. 
     In this configuration, even in a case in which the tip end portion  3   a  of the vane  3  has dropped into the discharge port  42  when the vane pump  100  is reverse rotated, the tip end portion  3   a  of the vane  3  can be guided to the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ) along the tip-end-side guide surface  130 ,  230 A,  230 B, and therefore, it is possible to prevent the damage of the side member (the body-side side plate  30 , the cover-side side plate  40 ) caused by the collision between the tip end portion  3   a  of the vane  3  and the side member (the body-side side plate  30 , the cover-side side plate  40 ). 
     In the vane pump  100 , the tip-end-side guide surface  130 ,  230 A,  230 B is formed to have the tapered shape in which the depth from the sliding contact surface  30   a ,  40   a  is decreased in the reverse rotation direction of the rotor  2 . 
     In this configuration, the inclination of the vane  3  is corrected smoothly as the rotor  2  is reverse rotated. 
     In the vane pump  100 , the tip-end-side guide surface  130  is linearly inclined. 
     In this configuration, the sliding resistance of the tip end portion  3   a  of the vane  3  moving along the tip-end-side guide surface  130  can be made constant, and so, it is possible to stably guide the tip end portion  3   a  of the vane  3  to the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ). 
     In the vane pump  100 , the side member (the body-side side plate  30 , the cover-side side plate  40 ) has: the back pressure port  160 ,  165  configured to open in the sliding contact surface  30   a ,  40   a  and to communicate with the back pressure chambers  9 ; and the base-end-side guide surface  170  provided on the end portion side of the back pressure port  160 ,  165  on the communication commencing side where the communication with the back pressure chambers  9  commences as the rotor  2  is forward rotated, the base-end-side guide surface  170  being configured to push the base-end portion  3   b  of the vane  3  upward and guide it toward the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ) as the rotor  2  is rotated in the reverse rotation direction. 
     The vane pump  100  has: the rotor  2  having the plurality of slits  2   a  formed in a radiating pattern, the rotor  2  being rotationally driven; the plurality of vanes  3  freely slidably received in the slits  2   a ; the cam ring  4  having the cam face  4   a  with which the tip end portions  3   a  of the vanes  3  come into sliding contact; the side member (the body-side side plate  30 , the cover-side side plate  40 ) having the sliding contact surface  30   a ,  40   a  with which the side surfaces of the rotor  2  and the vanes  3  come into sliding contact; the pump chambers  6  defined by the rotor  2 , the cam ring  4 , and the adjacent vanes  3 ; the suction port  31 ,  41  configured to open in the sliding contact surface  30   a ,  40   a , the suction port  31 ,  41  being configured to guide the working fluid to be sucked into the pump chambers  6 ; the discharge port  42  configured to open in the sliding contact surface  30   a ,  40   a , the discharge port  42  being configured to guide the working fluid discharged from the pump chambers  6 ; and the back pressure chambers  9  defined with the base-end portions  3   b  of the vanes  3  in the slits  2   a , wherein the side member (the body-side side plate  30 , the cover-side side plate  40 ) has: the back pressure port  160 ,  165  configured to open in the sliding contact surface  30   a ,  40   a , the back pressure port  160 ,  165  being configured to communicate with the back pressure chambers  9 ; and the base-end-side guide surface  170  provided on the end portion side of the back pressure port  160 ,  165  on the communication commencing side where the communication with the back pressure chambers  9  commences as the rotor  2  is forward rotated, the base-end-side guide surface  170  being configured to push the base-end portions  3   b  of the vanes  3  upward and guide them toward the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ) as the rotor  2  is rotated in the reverse rotation direction. 
     In these configurations, even in a case in which the base-end portion  3   b  of the vane  3  has dropped into the back pressure port  160 ,  165  when the vane pump  100  is reverse rotated, the base-end portion  3   b  of the vane  3  can be guided to the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ) along the base-end-side guide surface  170 , and therefore, it is possible to prevent the damage of the side member (the body-side side plate  30 , the cover-side side plate  40 ) caused by the collision between the base-end portion  3   b  of the vane  3  and the side member (the body-side side plate  30 , the cover-side side plate  40 ). 
     In the vane pump  100 , the base-end-side guide surface  170  is formed to have the tapered shape in which the depth from the sliding contact surface  30   a ,  40   a  is decreased in the reverse rotation direction of the rotor  2 . 
     In this configuration, the inclination of the vanes  3  is corrected smoothly as the rotor  2  is reverse rotated. 
     In the vane pump  100 , the base-end-side guide surface  170  is linearly inclined. 
     In this configuration, the sliding resistance of the base-end portion  3   b  of the vane  3  moving along the base-end-side guide surface  170  can be made constant, and so, it is possible to stably guide the base-end portion  3   b  of the vane  3  to the sliding contact surface  30   a ,  40   a  of the side member (the body-side side plate  30 , the cover-side side plate  40 ). 
     In the vane pump  100 , the back pressure port  160 A has: the main body portion  161 ; and the narrow-width portion  162  provided so as to extend from the end portion  161   a  of the main body portion  161  in the circumferential direction, the narrow-width portion  162  having the radial-direction width narrower than the radial-direction width of the main body portion  161 , and the base-end-side guide surface  170  is provided so as to extend from the end portion  161   a  of the main body portion  161  in the circumferential direction and so as to be adjacent to the narrow-width portion  162 . 
     In this configuration, by providing the narrow-width portion  162 , it is possible to set, with a high accuracy, a range in the circumferential direction at which the communication with the back pressure chambers  9  is established. 
     Embodiments of the present invention were described above, but the above embodiments are merely examples of applications of the present invention, and the technical scope of the present invention is not limited to the specific constitutions of the above embodiments. 
     This application claims priority based on Japanese Patent Application No. 2018-206815 filed with the Japan Patent Office on Nov. 1, 2018, the entire contents of which are incorporated into this specification by reference.