Patent Publication Number: US-11378077-B2

Title: Gear pump device having three member seal mechanism containing fitted insertion part to seal axial face of gear pump between inner and outer gear

Description:
TECHNICAL FIELD 
     The present invention relates to a gear pump device. 
     BACKGROUND ART 
     Gear pump devices include a gear pump constituted of an outer gear and an inner gear meshed with each other, a seal mechanism for partitioning between a low pressure side and a high pressure side, and a case for receiving them. The seal mechanism includes an outer member, an annular rubber member and an inner member. Each member of the seal mechanism is urged in a predetermined direction by a discharge pressure. That is, due to the discharge pressure, the outer member abuts against one axial end face of the outer gear and one axial end face of the inner gear, and the inner member abuts against an inner wall surface of a housing (case), thereby exhibiting a sealing function. If the outer member is strongly pressed by the discharge pressure, a pressing force thereof against the outer gear is increased (a contact surface pressure is increased). Then, a sliding resistance is increased and thus a driving torque for the gear pump is increased. However, if a contact area between the outer member and the outer gear and inner gear is decreased in order to decrease the sliding resistance, the pressing force is reduced and thus sealing property is reduced. 
     Thus, for example, in Japanese Patent Application Publication No. 2016-28192, a gear pump device is disclosed, in which an abutting portion (protrusion) provided on an outer circumference of an outer member abuts against a cylinder, thereby dispersing a pressing force. As a result, a driving torque for the gear pump is reduced. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-2016-28192 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the above gear pump device, the outer member is increased in size by a size corresponding to the abutting portion, and correspondingly, a volume of a pressure chamber (discharge chamber) is decreased. Also, since an aspect, in which the cylinder receives a force, is varied depending on the shape and position of the abutting portion (protrusion), a relatively high accuracy is required for manufacturing and designing. That is, the gear pump device has room for improvement in terms of volumetric efficiency and manufacturability (ease of manufacture). 
     The present invention has been made keeping in mind the above problems, and an object thereof is to provide a gear pump device, which enables further improvement in volumetric efficiency and manufacturability and also makes it possible to ensure sealing property and to reduce a driving torque. 
     Solution to Problem 
     A gear pump device according to the present embodiment includes a gear pump having an outer gear and an inner gear, wherein the outer gear has an internal tooth portion and the outer gear and the inner gear are configured to be meshed with each other while forming a plurality of void portions therebetween, wherein the gear pump is configured to suck and discharge a fluid as the outer gear and the inner gear are rotated by rotation of a shaft; a case defining a receiving portion, in which the gear pump is received; and a seal mechanism arranged between the case and the gear pump and configured to partition a low pressure side, which includes a suction side of the gear pump sucking a fluid and the periphery of the shaft, and a high pressure side, which includes a discharge chamber of the gear pump allowing the fluid to be discharged therein; wherein the seal mechanism includes: an annular rubber member for sealing between the low pressure side and the high pressure side while surrounding the low pressure side; an outer member having one seal surface abutting against the annular rubber member and the other seal surface abutting against one axial end face of the outer gear and also against one axial end face of the inner gear; and an inner member having an outer circumferential wall allowing the annular rubber member to be mounted thereon and configured to be fitted in the outer member, wherein the inner member is configured to abut against an inner wall surface of the case opposite to the one axial end face of the inner gear, wherein the inner member has a notch on an axial end portion of the outer circumferential wall facing the inner gear, wherein the notch is configured to be recessed radially inward of the inner gear and thus to define a depressed part together with the one axial end face of the inner gear, wherein the outer member has an insertion part configured to be arranged in the depressed part and also to abut against the one axial end portion of the inner gear, wherein the insertion part constitutes a part of the other seal surface. 
     Advantageous Effects of Invention 
     According to the present invention, the insertion part of the outer member abutting against the one axial end face of the inner gear is inserted in the depressed part defined by the notch of the inner member and the inner gear. Since the insertion part abuts against the one axial end face of the inner gear, it is possible to secure a required contact area between the outer member and each of the one axial end face of the outer gear and the one axial end face of the inner gear, thereby obtaining a suitable seal area. Also, it is possible to reduce an area (pressure receiving surface), in which the outer member receives the discharge pressure, by an area of the insertion part arranged in the depressed part. As a result, it is possible to reduce a pressing force of the outer member against the outer gear and the inner gear. That is, it is possible to reduce a driving torque for the gear pump while ensuring sealing property of the outer member. Further, according to the present invention, the insertion part is formed on the outer member, but the notch, in which the insertion part is to be received, is formed on the inner member, thereby further improving volumetric efficiency. Further, in terms of manufacturing, the axial end portion of the member is cut out and the insertion part is formed to correspond thereto, and thus the formation position and shape thereof allow designing and manufacturing to be relatively easily performed. That is, manufacturability can be further improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic view of a vehicle brake device employing a gear pump device of the present embodiment. 
         FIG. 2  is a sectional view of the gear pump device of the present embodiment. 
         FIG. 3  is a sectional view taken along a line III-III in  FIG. 2 . 
         FIG. 4( a )  is a front view of an inner member of the present embodiment. 
         FIG. 4( b )  is a sectional view taken along a line IVb-IVb′ in  FIG. 4( a ) . 
         FIG. 5( a )  is a front view of an outer member of the present embodiment. 
         FIG. 5( b )  is a right side view of the outer member of the present embodiment. 
         FIG. 5( c )  is a sectional view taken along a line Vc-Vc′ in  FIG. 5( a ) . 
         FIG. 6  is a schematic sectional view of a seal mechanism and a gear pump of the present embodiment. 
         FIG. 7  is a conceptual diagram explaining a discharge pressure exerted on the outer member of the present embedment. 
         FIG. 8  is a schematic sectional view of a seal mechanism and a gear pump according to a modification of the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, a basic configuration of a vehicle brake device will be described with reference to  FIG. 1 . Herein, an example, in which the vehicle brake device according to the present invention is applied to a vehicle having a hydraulic circuit constituted of front and rear conduits, will be described. 
     In  FIG. 1 , if a driver treads on a brake pedal  11  as a brake operation member, a tread force is boosted by a booster  12  and then presses master pistons  13   a ,  13   b  arranged in a master cylinder (hereinafter, referred to as a M/C)  13 . Thus, M/C pressures, which are the same, are respectively generated in a primary chamber  13   c  and a secondary camber  13   d , which are partitioned by the master pistons  13   a ,  13   b . The M/C pressure is transmitted to each of wheel cylinders (hereinafter, referred to as W/C)  14 ,  15 ,  34 ,  35  via an actuator  50 . The M/C  13  is provided with a master reservoir  13   e  having passages communicated with the primary chamber  13   c  and the secondary camber  13   d , respectively. 
     The actuator  50  has a first conduit system  50   a  and a second conduit system  50   b . The first conduit system  50   a  is a rear system for controlling a brake fluid pressure applied to a right rear wheel RR and a left rear wheel RL, and the second conduit system  50   b  is a front system for controlling a brake fluid pressure applied to a left front wheel FL and a right front wheel FR. Since configurations of the systems  50   a ,  50   b  are the same, only the first conduit system  50   a  will be described below and the description of the second conduit system  50   b  will be omitted. 
     The first conduit system  50   a  has a conduit A serving as a main conduit for transmitting the M/C pressure, as described above, to the W/C  14  provided on the left rear wheel RL and the W/C  15  provided on the right rear wheel RR so as to generate a W/C pressure. Also, the conduit A is provided with a first differential pressure control valve  16  capable of being controlled to a communication state and a differential pressure state. During normal braking, at which a driver operates the brake pedal  11  (when a vehicle motion control is not being executed), the first differential pressure control valve  16  has a valve position adjusted such that the first differential pressure control valve  16  is in the communication state. The valve position of the first differential pressure control valve  16  is adjusted such that the first differential pressure control valve  16  becomes an increased differential pressure state as an electric current value flowing through a solenoid coil thereof is increased. 
     When the first differential pressure control valve  16  is in the differential pressure state, a brake fluid is allowed to flow only from the W/Cs  14 ,  15  to the M/C  13 , only when a brake fluid pressure on the side of the W/Cs  14 ,  15  becomes larger than the M/C pressure by a predetermined value or more. Therefore, the pressure on the side of the W/Cs  14 ,  15  is kept not to become larger than that on the side of the M/C  13  by the predetermined value or more. 
     Also, the conduit A is branched into two conduits A 1 , A 2  on the side of the W/Cs  14 ,  15  downstream of the first differential pressure control valve  16 . The conduit A 1  is provided with a first pressure increase control valve  17  for controlling an increase in brake fluid pressure to the W/C  14 , and the conduit A 2  is provided with a second pressure increase control valve  18  for controlling an increase in brake fluid pressure to the W/C  15 . 
     The first and second pressure increase control valves  17 ,  18  are constructed by a two-position electromagnetic valve capable of being controlled to communication/interruption states. Specifically, the first and second pressure increase control valves  17 ,  18  are a normal open type, which is controlled to become a communication state when a control electric current flowing through a solenoid coil provided in the first and second pressure increase control valves  17 ,  18  becomes zero (when not energized) and also to become an interruption state when the control electric current flows through the solenoid coil (when energized). 
     A first pressure decrease control valve  21  and a second pressure decrease control valve  22  are respectively arranged on a conduit B serving as a pressure decrease conduit for connecting points on the conduit A, which are located between each of the first and second pressure increase control valves  17 ,  18  and the respective W/Cs  14 ,  15 , with a pressure regulation reservoir  20 . The first and second pressure decrease control valves  21 ,  22  are constructed by a two-position electromagnetic valve capable of being controlled to communication/interruption states. Also, the first and second pressure decrease control valves  21 ,  22  are a normal closed type. 
     A conduit C serving as a reflux conduit is arranged between the pressure regulation reservoir  20  and the conduit A as the main conduit. The conduit C is provided with a gear pump  19  driven by a motor  60  and configured to suck a brake fluid from the pressure regulation reservoir  20  and then to discharge the brake fluid to the side of the M/C  13  or to the side of the W/Cs  14 ,  15 . The motor  60  is driven by controlling energization to a motor relay (not shown). 
     Further, a conduit D serving as an auxiliary conduit is provided between the pressure regulation reservoir  20  and the M/C  13 . Through the conduit D, the gear pump  19  sucks a brake fluid from the M/C  13  and then discharges the brake fluid to the conduit A, so that during the vehicle motion control, the brake fluid is supplied to the side of the W/Cs  14 ,  15  and thus increases a W/C pressure of the corresponding wheels. 
     Meanwhile, although the first conduit system  50   a  has been described herein, the second conduit system  50   b  has the same configuration, and accordingly the second conduit system  50   b  has the same components as those provided in the first conduit system  50   a . Specifically, the second conduit system  50   b  includes a second differential pressure control valve  36  corresponding to the first differential pressure control valve  16 ; third and fourth pressure increase control valves  37 ,  38  corresponding to the first and second pressure increase control valves  17 ,  18 ; third and fourth pressure decrease control valves  41 ,  42  corresponding to the first and second pressure decrease control valves  21 ,  22 ; a gear pump  39  corresponding to the gear pump  19 ; a pressure regulation reservoir  40  corresponding to the pressure regulation reservoir  20 ; and conduits E to H corresponding to the conduits A to D. 
     Also, a brake ECU  70  corresponds to a control system for a brake control system  1  and is constructed by a known microcomputer including CPU, ROM, RAM, I/O, and the like. The brake ECU  70  is configured to execute processing, such as various calculations, in accordance with a program stored in ROM or the like, and also to execute a vehicle motion control, such as anti-skid control. That is, the brake ECU  70  calculates various physical quantities based on detection of sensors (not shown), determines whether or not to execute a vehicle motion control based on the calculation results, and then when executing the vehicle motion control, obtains a control quantity for a wheel to be controlled, i.e., a W/C pressure to be generated in the W/C of the wheel to be controlled. On the basis of the results, the brake ECU  70  executes control of current supply to each of the control valves  16  to  18 ,  21 ,  22 ,  36  to  38 ,  41 ,  42  and also control of an current amount of the motor  60  for driving the gear pumps  19 ,  39 , thereby controlling the W/C pressure of the wheel to be controlled. As a result, the vehicle motion control is performed. 
     For example, when a pressure cannot be generated in the M/C  13  as in traction control or anti-skid control, the gear pumps  19 ,  39  are driven and also the first and second differential pressure control valves  16 ,  36  are brought into the differential pressure state. As a result, a brake fluid is supplied to downstream sides of the first and second differential pressure control valves  16 ,  36 , i.e., to the sides of the W/Cs  14 ,  15 ,  34 ,  35  through the conduits D, H. Then, by suitably controlling the first to fourth pressure increase control valves  17 ,  18 ,  37 ,  38  or the first to fourth pressure decrease control valves,  21 ,  22 ,  41 ,  42 , the W/C pressure of the wheel to be controlled is controlled to be increased or decreased, so that the W/C pressure becomes a desired control quantity. 
     Also, during anti-skid (ABS) control, the first to fourth pressure increase control valves  17 ,  18 ,  37 ,  38  or the first to fourth pressure decrease control valves,  21 ,  22 ,  41 ,  42  are suitably controlled and also the gear pumps  19 ,  39  are driven, thereby controlling the W/C pressure to be increased or decreased. As a result, the W/C pressure is controlled to become a desired control quantity. 
     Next, the detailed structure of a gear pump device of the vehicle brake device configured as described above will be described with reference to  FIGS. 2 and 3 .  FIG. 2  shows a state where a pump main body  100  is mounted on a housing  101  of the actuator  50 . For example, the pump main body  100  is attached such that a vertical direction on the paper surface is a vertical direction of a vehicle. Meanwhile, in the representation of the figures, a seal mechanism in  FIG. 2  is represented in a conventional shape, and seal mechanisms shown in  FIGS. 4 to 6  are seal mechanisms  111 ,  115  of the present embodiment. 
     As described above, the vehicle brake device is constituted of the first conduit system  50   a  and the second conduit system  50   b . Therefore, the pump main body  100  is provided with two gear pumps, including the gear pump  19  for the first conduit system  50   a  and the gear pump  39  for the second conduit system  50   b.    
     The gear pumps  19 ,  39  built in the pump main body  100  are driven by rotating a rotational shaft  54 , which is supported on a first bearing  51  and a second bearing  52 , using the motor  60 . A casing defining an exterior shape of the pump main body  100  has a cylinder  71  and a plug  72 , which are made of aluminum. The first bearing  51  has an outer ring  51   a  and needle rollers  51   b . The second bearing  52  has an inner ring  52   a , an outer ring  52   b  and rolling elements  52   c . The first bearing  51  is arranged in the cylinder  71  and the second bearing  52  is arranged in the plug  72 . 
     The casing of the pump main body  100  is constructed by press-fitting and integrating one end of the cylinder  71  into the plug  72  while the cylinder  71  is coaxially arranged with the plug  72 . Also, the pump main body  100  is constructed by equipping therein the gear pumps  19 ,  39 , various seal members and the like, in addition to the cylinder  71  and the plug  72 . 
     In this way, the pump main body  100  is constructed to have an integral structure. The pump main body  100  formed in such an integral structure is inserted into a generally cylindrical recess portion  101   a , which is formed in the housing  101  made of aluminum, from a right direction on the paper surface. Also, a ring-shaped male thread member (screw)  102  is screwed with a female thread groove  101   b  formed in an inlet of the recess portion  101   a , thereby fixing the pump main body  100  to the housing  101 . Due to screwing of the male thread member  102 , the pump main body  100  is prevented from falling out of the housing  101 . 
     Hereinafter, a direction, in which the pump main body  100  is inserted into the recess portion  101   a  of the housing  101 , is simply referred to as an insertion direction. Also, an axial direction of the pump main body  100  (corresponding to an axial direction of the rotational shaft  54 ) is referred to as a pump axial direction or simply an axial direction; a circumferential direction of the pump main body  100  (corresponding to a circumferential direction of the rotational shaft  54 ) is referred to as a pump circumferential direction or simply a circumferential direction; and a radial direction of the pump main body  100  (corresponding to a radial direction of the rotational shaft  54 ) is referred to as a pump radial direction or simply a radial direction. 
     Also, a second circular recess portion  101   c  is formed at a location in the recess portion  101   a  of the housing  101 , which corresponds to a distal end of the rotational shaft  54  (left end in  FIG. 2 ), among distal end locations forward in the insertion direction. A diameter of the second recess portion  101   c  is larger than a diameter of the rotational shaft  54  and the distal end of the rotational shaft  54  is positioned in the second recess portion  101   c . As a result, the rotational shaft  54  is configured so as not to be in contact with the housing  101 . 
     The cylinder  71  and the plug  72  are provided with center holes  71   a ,  72   a , respectively. The rotational shaft  54  is inserted in the center holes  71   a ,  72   a  and also supported by the first bearing  51  fixed on an inner circumference of the center hole  71   a  formed in the cylinder  71  and the second bearing  52  fixed on an inner circumference of the center hole  72   a  formed in the plug  72 . The gear pumps  19 ,  39  are respectively equipped on both sides of the first bearing  51 , i.e., in a region, which is located in front of the first bearing  51  in the insertion direction, and a region, which is located between the first bearing  51  and the second bearing  52 . 
     The gear pump  19  is arranged in a gear chamber (corresponding to a “receiving portion”)  100   a  constructed by a circular counterbore recessed in one end face of the cylinder  71  and is configured as an internal gear pump (trochoid pump) driven by the rotational shaft  54  inserted through the gear chamber  100   a . The housing  101  and the cylinder  71  correspond to the casing. 
     Specifically, the gear pump  19  has a rotational part constituted of an outer gear  19   a  having an internal tooth portion formed on an inner circumference thereof and an inner gear  19   b  having an external tooth portion formed on an outer circumference thereof and is configured such that the rotational shaft  54  is inserted through a hole formed at the center of the inner gear  19   b . Also, a key  54   b  is fitted in a hole  54   a  formed in the rotational shaft  54 , and thus a torque can be transmitted to the inner gear  19   b  via the key  54   b.    
     The internal tooth portion and the external tooth portion formed respectively on the outer gear  19   a  and the inner gear  19   b  are meshed with each other to define a plurality of void portions  19   c  therebetween. Also, the void portions  19   c  are varied in size by rotation of the rotational shaft  54 , thereby causing a brake fluid to be sucked or discharged. 
     On the other hand, the gear pump  39  is arranged in a gear chamber (receiving portion)  100   b  constructed by a circular counterbore recessed in the other end face of the cylinder  71  and is driven by the rotational shaft  54  inserted through the gear chamber  100   b . Like the gear pump  19 , the gear pump  39  has an outer gear  39   a  and an inner gear  39   b  and is constructed as an internal gear pump, in which a brake fluid is sucked or discharged by a plurality of void portions  39   c  formed by tooth portions thereof meshed with each other. The gear pump  39  is arranged as if the gear pump  19  is rotated by approximately 180° about the rotational shaft  54 . Due to this arrangement, the suction-side void portions  19   c ,  39   c  and the discharge-side void portions  19   c ,  39   c  of each of the gear pumps  19 ,  39  are symmetrically positioned with respect to the rotational shaft  54 , so that forces exerted on the rotational shaft  54  by a brake fluid pressure on the discharge sides, which is a high pressure, can cancel out each other. The gear pumps,  19 ,  39  basically have the same structure, but thicknesses thereof in the pump axial direction are different from each other in order to make suction and discharge amounts thereof different from each other. 
     On the one end face side of the cylinder  71 , the seal mechanism  111  for urging the gear pump  19  toward the cylinder  71  is provided on a side of the gear pump  19  opposite to the cylinder  71 , i.e., between the cylinder  71  and gear pump  19 , and the housing  101 . Also, on the other end face side of the cylinder  71 , the seal mechanism  115  for urging the gear pump  39  toward the cylinder  71  is provided on a side of the gear pump  39  opposite to the cylinder  71 , i.e., between the cylinder  71  and gear pump  39 , and the plug  72 . 
     The seal mechanism  111  is configured as a ring-shaped member having a hollow portion allowing the rotational shaft  54  to be inserted therein and presses the outer gear  19   a  and the inner gear  19   b  toward the cylinder  71 . As a result, the seal mechanism  111  is configured to seal between a relatively low pressure portion and a relatively high pressure portion on one end face side of the gear pump  19 . Specifically, the seal mechanism  111  exhibits a sealing function by abutting against a bottom surface of the recess portion  101   a , which corresponds to an outskirts of the housing  101 , and also against a desired location on the outer gear  19   a  or the inner gear  19   b.    
     The seal mechanism  111  is constituted of a hollow frame-shaped inner member  112 , an annular rubber member  113  and a hollow frame-shaped outer member  114 . The inner member  112  is fitted in the outer member  114  with the annular rubber member  113  arranged between an outer circumferential wall of the inner member  112  and an inner circumferential wall of the outer member  114 . 
     Next, a configuration of each of components  112  to  114  constituting the seal mechanism  111  will be described with reference to  FIGS. 4 and 5 . As shown in  FIG. 4 , the inner member  112  is constituted of a resin portion  112   a  and a metal ring  112   b . The resin portion  112   a  and the metal ring  112   b  are integrated with each other by integrally molding (insert-molding) the metal ring  112   b  during molding of the resin portion  112   a.    
     The resin portion  112   a  has a hollow frame shape, in which a hollow portion  112   c  is formed to allow the rotational shaft  54  to be arranged therein. Herein, the hollow portion  112   c  has a plurality of slits  112   d  formed along the pump axial direction so that a diameter thereof is partially expanded relative to the rotational shaft  54 , although the hollow portion  112   c  may have a circular shape to conform to an outer circumferential shape of the rotational shaft  54 . The metal ring  112   b  is concentrically arranged with the hollow portion  112   c . The metal ring  112   b  is provided to reinforce the resin portion  112   a , including the periphery of the hollow portion  112   c.    
     Also, a part of the resin portion  112   a , in which no slit  112   d  is formed, protrudes inward of the metal ring  112   b , and a part thereof, in which the slits  112   d  are formed, is recessed up to a location of the metal ring  112   b . In addition, a distance from a part of an inner wall surface of the hollow portion  112   c , which is not the slits  112   d , to the center of the hollow portion  112   c  is equal to a radius of the rotational shaft  54 . 
     In the case of this structure, a part of the inner member  112 , which becomes a sliding surface relative to the rotational shaft  54 , is the part of the hollow portion  112   c , in which no slit  112   d  is formed, thereby preventing the metal ring  112   b  from coming in contact with the rotational shaft  54 . If the inner wall surface of the hollow portion  112   c  is constructed by the metal ring  112   b  and also serves as a surface abutting against the rotational shaft  54 , it is possible to position the rotational shaft  54  in the pump radial direction by adjusting a gap between an outer circumferential surface of the rotational shaft  54  and the inner wall surface of the hollow portion  112   c  in accordance with a dimensional tolerance of the metal ring  112   b.    
     An exterior shape of the inner member  112  is configured to have a radius smaller than that of the void portions  19   c  at a location thereon, which corresponds to the right side on the paper surface of  FIG. 4( a ) , i.e., the discharge side of the gear pump  19 , which has a high pressure, and also to have a radius larger than that of the void portions  19   c  at a location thereon, which corresponds to the left side on the paper surface, i.e., the suction side of the gear pump  19 , which has a low pressure. Therefore, when the annular rubber member  113  is fitted onto the outer circumferential wall of the inner member  112 , the periphery of the rotational shaft  54  or the suction side of the gear pump  19 , which has a low pressure, is positioned inward of the annular rubber member  113 , whereas the discharge side of the gear pump  19 , which has a high pressure, is positioned outward of the annular rubber member  113 . 
     Also, when the gear pump  19  sucks and discharges a brake fluid, a discharge pressure, which is a high pressure, is applied to the annular rubber member  113  and thus the annular rubber member  113  is pressed against the outer circumferential wall of the inner member  112  inward in the pump radial direction. Therefore, the outer circumferential wall of the inner member  112  serves as a pressure receiving surface receiving a pressure from the annular rubber member  113  inward in the pump radial direction. The pressure receiving surface is configured to generate a propulsive force in a direction moving the inner member  112  away from the gear pump  19  in the pump axial direction. In the present embodiment, a part of the pressure receiving surface is formed as a tapered surface  112   e . Specifically, a flange portion (collar portion)  112   f  extending around the outer circumferential wall of the inner member  112  is provided on a side of the outer circumferential wall of the inner member  112  opposite to the gear pump  19  (on a side thereof away from the gear pump  19 ), and also a surface of the flange portion  112   f  facing the gear pump  19  is formed as the tapered surface  112   e . Also, as described below, the inner member  112  has a notch  112   g  extending around the outer circumferential wall at an end portion of the outer circumferential wall near to the gear pump  19 . 
     The annular rubber member  113  is constructed by an O-ring or the like and is configured to be fitted on the outer circumferential wall of the inner member  112  and thus to be arranged between the inner member  112  and the outer member  114 . The annular rubber member  113  is configured to have an increased contact pressure against the receiving pressure surface of the inner member  112  in accordance with an increase in discharge pressure during driving of the gear pump  19 , and also to seal between the discharge side of the gear pump  19 , which has a high pressure, and the periphery of the rotational shaft  54  or the suction side of the gear pump  19 , which have a low pressure, by abutting against the bottom surface (corresponding to an “inner wall surface”) of the recess portion  101   a . The annular rubber member  113  may be formed in a shape following the exterior shape of the inner member  112 . However, it is preferable that the annular rubber member  113  having a circular shape is elastically deformed to conform to the exterior shape of the inner member  112  and then to be fitted onto the outer circumferential wall of the inner member  112 . 
     The outer member  114  is configured to seal between a low pressure side and a high pressure side on a pump-axial end face of the gear pump  19 . As shown in  FIGS. 5( a ) to 5( c ) , the outer member  114  is formed in a hollow frame shape, and an interior shape of a hollow part  114   a  thereof is configured to correspond to the exterior shape of the inner member  112 . Also, the outer member  114  is constructed by a stepped plate having a recess part  114   b  and a protrusion part  114   c  formed on an end face thereof facing the gear pump  19 , and the protrusion part  114   c  is configured to abut against one end face of both gears  19   a ,  19   b  or one end face of the cylinder  71 . 
     The protrusion part  114   c  has a first sealing part  114   d , a second sealing part  114   e  and a third sealing part  114   h . The first sealing part  114   d  and the second sealing part  114   e  are respectively provided at a site, over which the void portions  19   c  are transited from a communication state with a suction port  81  (as described below) to a communication state with a discharge chamber  80  (as described below), and at a site, over which the void portions  19   c  are transited from the communication state with the discharge chamber  80  to the communication state with the suction portion  81 . That is, the first sealing part  114   d  is arranged at a site corresponding to a part of the plurality of void portions  19   c , which has the largest volume, and the second sealing part  114   e  is arranged at a site corresponding to a part of the plurality of void portions  19   c , which has the smallest volume. The sealing parts  114   d ,  114   e  are configured to abut against the one end face of both gears  19   a ,  19   b , thereby sealing the void portions  19   c  and also sealing between the low pressure side and the high pressure side thereon. The third sealing part  114   h  is a portion located between the first sealing part  114   d  and the second sealing part  114   e  and is configured to abut against the one end face of the cylinder  71 , thereby sealing between the low pressure side and the high pressure side thereon. 
     The recess part  114   b  is communicated with the discharge chamber  80 , thereby allowing a discharge pressure, which is a high pressure, to be introduced therein. Therefore, when the gear pump  19  discharges a high pressure, the high discharge pressure is introduced to the outer circumference of the outer member  114  including the inside of the recess part  114   b . Due to the discharge pressure, there is a possibility that the outer member  114  is deformed and clamps the inner member  112 . 
     Also, the inner member  112  and the annular rubber member  113  are fitted into the outer member  114  from a side thereof opposite to the gear pump  19 . A protruding wall  114   f  having a shape corresponding to the annular rubber member  113  is formed on an end face  114   j  of the outer member  114  opposite to the gear pump  19  (end face  114   j  away from the gear pump  19 ). The annular rubber member  113  is arranged to face an inner circumferential wall of the protruding wall  114   f . As a result, the outer member  114  is accurately aligned with the inner member  112  and the annular rubber member  113 . 
     In addition, a protrusion-shaped anti-rotation part  114   g  is formed at a site on an end face of the outer member  114  facing the gear pump  19 , which is located outward of the protrusion part  114   c  in the pump radial direction (see  FIG. 5( c ) ). The anti-rotation part  114   g  is inserted in a recess portion (not shown) formed in the cylinder  71 , thereby preventing the outer member  114  from rotating relative to the cylinder  71 . 
     As shown in  FIG. 2 , an outer diameter of the seal mechanism  111  is set to be smaller than an inner diameter of the recess portion  101   a  of the housing  101  at least on the left side on the paper surface of  FIG. 2 . Therefore, the seal mechanism  111  is configured to allow a brake fluid to flow through a gap between the seal mechanism  111  and the recess portion  101   a  of the housing  101  on the left side on the paper surface. The gap forms the discharge chamber  80  and thus is connected to a discharge conduit  90  formed in the bottom of the recess portion  101   a  of the housing  101 . Due to this structure, the gear pump  19  can discharge a brake fluid through the discharge chamber  80  and the discharge conduit  90  as a discharge path. 
     In the cylinder  71 , the suction port  81  is formed to be communicated with suction-side void portions  19   c  of the gear pump  19 . The suction port  81  extends from an end face of the cylinder  71  facing the gear pump  19  up to an outer circumferential surface thereof and is connected to a suction conduit  91  provided on a side surface of the recess portion  101   a  of the housing  101 . Due to this structure, the gear pump  19  can introduce a brake fluid through the suction conduit  91  and the suction port  81  as a suction path. 
     On the other hand, the seal mechanism  115  is also constructed by a ring-shaped member having a center portion allowing the rotational shaft  54  to be inserted therein and presses the outer gear  39   a  and the inner gear  39   b  toward the cylinder  71 , thereby sealing between a relatively low pressure portion and a relatively high pressure portion on one end face side of the gear pump  39 . Specifically, the seal mechanism  115  exhibits a sealing function by abutting against an end face of a part of the plug  72 , in which the seal mechanism  115  is received, and also against a desired location on the outer gear  39   a  or the inner gear  39   b.    
     The seal mechanism  115  is also constituted of a hollow frame-shaped inner member  116 , an annular rubber member  117  and a hollow frame-shaped outer member  118 . The inner member  116  is fitted in the outer member  118  with the annular rubber member  117  arranged between an outer circumferential wall of the inner member  116  and an inner circumferential wall of the outer member  118 . The seal mechanism  115  is different from the seal mechanism  111  as described above, in that a surface thereof forming a seal is reverse to that of the seal mechanism  111 . Therefore, the seal mechanism  115  is formed in a shape symmetric to the seal mechanism  111 , but is arranged to have a phase offset from the seal mechanism  111  by 180° about the rotational shaft  54 . However, the basic structure of the seal mechanism  115  is the same as that of the seal mechanism  111 , and accordingly the detailed structure of the seal mechanism  115  will not be described. 
     Meanwhile, an outer diameter of the seal mechanism  115  is set to be smaller than an inner diameter of the plug  72  at least on the right side on the paper surface. Therefore, the seal mechanism  115  is configured to allow a brake fluid to flow through a gap between the seal mechanism  115  and the plug  72  on the right side on the paper surface. The gap forms a discharge chamber  82  and thus is connected to a communication passage  72   b  formed in the plug  72  and a discharge conduit  92  formed in the side surface of the recess portion  101   a  of the housing  101 . Due to this structure, the gear pump  39  can discharge a brake fluid through the discharge chamber  82 , the communication passage  72   b  and the discharge conduit  92  as a discharge path. 
     Meanwhile, end faces of the cylinder  71  facing the gear pumps  19 ,  29 , respectively, become seal surfaces too. Therefore, the gear pumps  19 ,  39  come in tight contact with the seal surfaces, respectively, to form mechanical seals, thereby sealing between a relatively low pressure portion and a relatively high pressure portion on the other end face side of the gear pumps  19 ,  39 . 
     Further, in the cylinder  71 , a suction port  83  is formed to be communicated with the suction-side void portions  39   c  of the gear pump  39 . The suction port  83  extends from an end face of the cylinder  71  facing the gear pump  39  up to an outer circumferential surface thereof and is connected to a suction conduit  93  provided on a side surface of the recess portion  101   a  of the housing  101 . Due to this structure, the gear pump  39  can introduce a brake fluid through the suction conduit  93  and the suction port  83  as a suction path. Meanwhile, the suction conduit  91  and the discharge conduit  90  in  FIG. 2  correspond to the conduit C in  FIG. 1 , and also the suction conduit  93  and the discharge conduit  92  correspond to the conduit G in  FIG. 1 . 
     Further, a seal member  120  constituted of an annular resin member  120   a  and an annular rubber member  120   b  is received in a part of the center hole  71   a  of the cylinder  71 , which is located rearward of the first bearing  51  in the insertion direction. As a result, sealing between two conduit systems in the center hole  71   a  of the cylinder  71  is obtained. In the center hole  72   a  of the plug  72 , which has a stepped shape, a seal member  121  constituted of an elastic ring  121   a  and a ring-shaped resin member  121   b  is received therein. Due to an elastic force of the elastic ring  121   a , the resin member  121   b  is pressed to come in contact with the rotational shaft  54 . 
     Further, the diameter of the center hole  72   a  of the plug  72  is partially enlarged even on a rearward side thereof in the insertion direction, and this portion is equipped with an oil seal (seal member)  122 . Also, on the outer circumference of the pump main body  100 , O-rings  73   a  to  73   d  as an annular seal member are provided to seal each of parts thereon. In order to allow the O-rings  73   a  to  73   d  to be arranged, groove portions  74   a  to  74   d  are provided on the outer circumference of the pump main body  100 . 
     The gear pump device configured as described above performs a pumping operation for sucking and discharging a brake fluid as the rotational shaft  54  of the gear pumps  19 ,  39  built therein is rotated by the motor  60 . As a result, the vehicle motion control, such as anti-skid control, is performed by the vehicle brake device. 
     Also, in the gear pump device, a discharge pressure of each of the gear pumps  19 ,  39  is introduced into the discharge chambers  80 ,  82 , respectively, in accordance with the pumping operation. At as a result, the discharge pressure, which is a high pressure, is applied to the end face of each of the outer members  114 ,  118  of both the seal mechanisms  111 ,  115 , which is opposite to the gear pumps  19 ,  39 , respectively. Therefore, the high discharge pressure is applied to press the outer members  114 ,  118  toward the cylinder  71 , so that seal surfaces of the outer members  114 ,  118  (distal surface of the protrusion part  114   c  in the case of the seal mechanism  111 ) are pressed against the gear pumps  19 ,  39 , thereby pressing the other pump-axial end face of the gear pumps  19 ,  39  against the cylinder  71 . As a result, the one pump-axial end face of the gear pumps  19 ,  39  is sealed by both the seal mechanisms  111 ,  115 , and the other pump-axial end face of the gear pumps  19 ,  39  is mechanically sealed by the cylinder  71 . 
     Also, if the discharge pressure of each of the gear pumps  19 ,  39  is introduced into the discharge chambers  80 ,  82 , respectively, in accordance with pumping operation, the annular rubber members  113 ,  117  press the pressure receiving surfaces of the inner members  111 ,  116 , respectively, in a normal direction thereto due to the discharge pressure. Then, the pressure receiving surface of the inner member  112  is pressed in the normal direction thereto, and thus a propulsive force is generated to move the inner member  112  away from the gear pump  19 , so that the inner member  112  is caused to abut against the bottom surface of the recess portion  101   a , thereby eliminating a gap therebetween. The same is true for the inner member  116 . That is, the pressure receiving surface of the inner member  116  is pressed in the normal direction thereto, and thus a propulsive force is generated to move the inner member  116  away from the gear pump  39 , so that the inner member  116  is caused to abut against the end face of the plug  72 , thereby eliminating a gap therebetween. 
     Also, the annular rubber members  113 ,  117  are pressed against the bottom surface of the recess portion  101   a  or the end face of the plug  72  due to the high discharge pressure. Therefore, the annular rubber member  113  and the inner member  112  can seal between a low pressure side inward of the annular rubber member  113  and a high pressure side outward thereof. Also, the annular rubber member  117  and the inner member  116  can seal between a low pressure side inward of the annular rubber member  117  and a high pressure side outward thereof. 
     In this way, by causing the inner members  112 ,  116  to abut against the bottom surface of the recess portion  101   a  or the end face of the plug  72 , it is possible to eliminate a gap therebetween and also to accurately seal between the low pressure side and the high pressure side. 
     The gear pump device of the present embodiment includes the gear pump  19  having the outer gear  19   a  and the inner gear  19   b , wherein the outer gear  19   a  has an internal tooth portion and the outer gear  19   a  and the inner gear  19   b  are configured to be meshed with each other while forming a plurality of void portions  19   c  therebetween, wherein the gear pump  19  is configured to suck and discharge a fluid as the outer gear  19   a  and the inner gear  19   b  are rotated by rotation of the shaft  54 ; the cylinder  71  and the housing  101  defining the receiving portion  100   a , in which the gear pump  19  is received; and the seal mechanism  111  arranged between the cylinder  71  and the housing  101  and the gear pump  19  and configured to partition a low pressure side, which includes a suction side of the gear pump  19  sucking a fluid and the periphery of the shaft  54 , and a high pressure side, which includes the discharge chamber  80  of the gear pump  19  allowing the fluid to be discharged therein; wherein the seal mechanism  111  includes the annular rubber member  113  for sealing between the low pressure side and the high pressure side while surrounding the low pressure side; the outer member  114  having the one seal surface  114   j  abutting against the annular rubber member  113  and the other seal surface (end face of the protrusion part  114   c ) abutting against one axial end face of the outer gear  19   a  and also against one axial end face of the inner gear  19   b ; and the inner member  112  having an outer circumferential wall allowing the annular rubber member  113  to be mounted thereon and configured to be fitted in the outer member  114  (in an inner circumference thereof), wherein the inner member  112  is configured to abut against an inner wall surface of the cylinder  71  and the housing  101  opposite to the one axial end face of the inner gear  19   b  (inner wall surface opposite to the gear pump  19 ). 
     (Features of Seal Mechanism) 
     Now, features of the seal mechanism  111  of the present embodiment will be described with reference to  FIGS. 6 and 7 . Meanwhile, the seal mechanism  115  has the same configuration, and accordingly, the description thereof will be omitted. Also,  FIGS. 6 and 7  are a conceptual diagram showing a cross section (schematic sectional view), where lines which are visible behind the cross section are omitted. 
     As shown in  FIG. 6 , the inner member  112  has the notch  112   g  on an axial end portion of the outer circumferential wall thereof facing the inner gear  19   b . The notch  112   g  is configured to be recessed radially inward of the inner gear  19   b  and thus to define a depressed part  1   a  together with one axial end face  19   b   1  of the inner gear  19   b . The notch  112   g  is an annular stepped portion (depressed part) formed by cutting out an axial edge portion of the outer circumferential wall of the inner member  112  continuously over the entire periphery thereof (to extend therearound). That is, the notch  112   g  is an annular portion of the inner member  112 , which is continuously formed over the entire periphery of the outer circumferential wall of the inner member  112 . One axial part of the inner member  112  is formed in a step shape by the notch  112   g . If the inner member  112  is arranged against the gear pump  19 , the depressed part  1   a  (also referred to as an annular groove or annular recess) is defined by the notch  112   g  and the one axial end face  19   b   1 . The one axial end face  19   b   1  of the inner gear  19   b  forms one side surface of the depressed part  1   a.    
     The outer member  114  has an insertion part  114   i  configured to be arranged in the depressed part  1   a  and also to abut against the one axial end face  19   b   1  of the inner gear  19   b . That is, the insertion part  114   i  constitutes a part of a seal surface of the outer member  114  (corresponding to “the other seal surface”) configured to abut against and seal the gear pump  19 . The insertion part  114   i  is inserted in the depressed part  1   a . The insertion part  114   i  is an annular portion of the outer member  114  (herein, an annular protrusion portion), which is continuously formed over the entire periphery on the inner circumference (inner circumferential wall) of the outer member  114 . The insertion part  114   i  protrudes inward in the pump-radial direction from an axial end portion (edge portion) of the inner circumferential wall of the outer member  114  facing the inner gear  19   b . The insertion part  114   i  can also be referred to as an annular protrusion portion extending around the inner circumferential wall. 
     A length of the insertion part  114   i  in the pump axial direction is smaller than a length in the pump axial direction from the end face  114   j  (corresponding to “the one seal surface”) abutting against the annular rubber member  113  to a distal end face of the protrusion part  114   c  (a part of the other seal surface). A clearance  1   b  is defined between the insertion part  114   i  and the notch  112   g . The clearance  1   b  is isolated from the high pressure side (high pressure region) by the annular rubber member  113  and thus is kept at a low pressure. The insertion part  114   i  is formed to be inserted in the depressed part  1   a  with the clearance  1   b  defined therebetween. 
     The outer member  114  externally includes the protrusion part  114   c  forming a part of an abutting surface against the gear pump  19  and configured to partition the low pressure side (low pressure region) and the high pressure side (high pressure region); a base part  114   k  serving as a base portion, from which the protrusion part  114   c  protrudes, and forming a part of the end face  114   j  away from the gear pump  19 ; the recess part  114   b  located on an outer circumference side of the base part  114   k  and configured so as not to abut against the gear pump  19 ; the protruding wall  114   f  protruding from the outer circumference-side end portion of the recess part  114   b  in a direction away from the gear pump  19 ; and the insertion part  114   i  forming a part of the abutting surface against the gear pump  19  and protruding inward from an inner circumference-side end portion of the protrusion part  114   c.    
     That is, as shown in  FIG. 7 , an end face  114   z  (hatched region) of the outer member  114  facing the gear pump  19 , which abuts against the gear pump  19  and thus serves as a seal surface, is constructed by the protrusion part  114   c  and the insertion part  114   i . Also, a surface  114   y  (hatched region) of the outer member  114 , on which a pressing force against the gear pump  19  due to a discharge pressure is exerted, is formed by the base part  114   k . The recess part  114   b  and the protruding wall  114   f  receive the discharge pressure from both sides in the pump axial direction, and accordingly forces due to the discharge pressure are cancelled out each other. The outer member  114  receives the discharge pressure directly or via the annular rubber member  113 . Due to the discharge fluid having a high pressure, the annular rubber member  113  is pushed and crushed against the recess portion  101   a  of the housing  101 , the outer circumferential wall of the inner member  112  and the end face  114   j  of the outer member  114 , thereby exhibiting sealing property. The protrusion part  114   c , the base part  114   k  and the insertion part  114   i  can also be referred to as a sealing portion in the outer member  114 . 
     According to the present embodiment, the insertion part  114   i  abutting against the one axial end face  19   b   1  of the inner gear  19   b  is inserted in the depressed part  1   a  defined by the notch  112   g  of the inner member  112  and the inner gear  19   b . Since the insertion part  114   i  abuts against the inner gear  19   b , it is possible to secure a required contact area between the outer member  114  and the one axial end face of the gear pump  19  (one axial end face  19   a   1  of the outer gear  19   a  and one axial end face  19   b   1  of the inner gear  19   b ). In order to ensure a required sealing property, it is first necessary to secure a predetermined contact area. 
     Also, it is possible to reduce an area of the surface (excluding the canceled portion)  114   y , in which the outer member  114  receives the discharge pressure in the pump axial direction, i.e., an area of an end face of the base part  114   k  by an area of the insertion part  114   i  arranged in the depressed part  1   a . As a result, it is possible to reduce a pressing force of the outer member  114  against the gear pump  19 . If the pressing force is reduced, a sliding resistance between the outer member  114  and the gear pump  19  is reduced and thus a required driving torque is also reduced. In this way, according to the present embodiment, sealing property (contact area) can be ensured by the insertion part  114   i  and also the pressing force due to the discharge pressure can be reduced by arranging a part of the outer member  114  (insertion part  114   i ) in the depressed part  1   a . That is, according to the present embodiment, it is possible to reduce a driving torque for the gear pump  19  while ensuring sealing property of the outer member  114 . However, in order to ensure sealing property, a predetermined contact area and a predetermined pressure receiving area (pressing force) are required. Therefore, all of the protrusion part  114   c , the base part  114   k  and the insertion part  114   i  cannot be arranged in the depressed part  1   a , and thus the protrusion part  114   c  and the base part  114   k  need to have a suitable radial width. 
     Further, according to the present embodiment, the insertion part  114   i  is formed on the outer member  114 , but the notch  112   g , in which the insertion part  114   i  is to be received, is formed on the inner member  112 . Therefore, a decrease in volume of a pressure chamber (e.g., a volume in the recess portion  101   a ) is prevented and thus volumetric efficiency can be further improved. Further, in terms of designing and manufacturing, the axial end portion (edge portion) of the member is cut out and the insertion part is formed to correspond thereto, and thus the formation position and shape allow designing and manufacturing to be relatively easily performed. In addition, adjustment of a driving torque for the gear pump  19  is just sufficient if a depth of the notch  112   g  (length of the insertion part  114   i ) is adjusted, thereby allowing manufacturing to be relatively easily performed. That is, manufacturability is further improved. 
     In particular, the gear pump device used for the brake actuator  50  is small in size, and also the outer member  114  and the inner member  112  which are components thereof are further smaller. Therefore, a simpler shape is preferable. That is, as compared with the case where minute protrusions are formed at specific locations as in a gear pump described in JP-A-2016-28192, it is easier to form a cutout or protrusion over the entire periphery of the edge portion and it is also relatively easy to adjust a driving torque (i.e., an area receiving a discharge pressure). 
     Further, the outer circumferential portion of the inner member  112  is formed in a stepped shape by the notch  112   g , so that the annular rubber member  113  is arranged on an upper stage side (outer circumference side) and the insertion part  114   i  is arranged on a lower stage side (inner circumference side). Therefore, galling of the seal is prevented. In addition, in a cross section (radial cross section) as in  FIG. 6 , the inner member  112  is formed such that the outer circumferential wall thereof (excluding the tapered surface  112   e  and the notch  112   g ) and the inner circumference-side end face of the outer gear  19   a  are aligned on a straight line. By forming the notch  112   g  to have such a positional relationship, a structure can be effectively obtained, in which the minimum required pressure receiving area (the minimum required radial width of the protrusion part  114   c ) is provided. 
     Modifications 
     A modification of the present embodiment will be described with reference to  FIG. 8 .  FIG. 8  is a conceptual diagram corresponding to  FIG. 6 . In the description of the modification, reference can be made to the foregoing description and drawings. As shown in  FIG. 8 , according to a configuration of the modification, a length of the insertion part  114   i  in the axial direction is equal to a length in the axial direction from the end face  114   j  of the outer member  114  to the distal end face of the protrusion part  114   c . That is, the insertion part  114   i  is formed to have the same width as that of a portion constituted by the protrusion part  114   c  and the base part  114   k . As a result, the outer member  114  can be formed in a shape similar to that of a conventional outer member  114 . The insertion part  114   i  according to the modification is, for example, an inner circumference-side end portion of a protrusion portion of the conventional outer member  114 . 
     The notch  112   g  of the inner member  112  is formed to correspond to a shape of the insertion part  114   i  and thus to allow the insertion part  114   i  to be arranged therein. Like the present embodiment, the notch  112   g  and the one axial end face  19   b   1  of the inner gear  19   b  define the depressed part  1   a . The insertion part  114   i  is inserted in the depressed part  1   a  with a clearance  1   b  defined therebetween. Even due to this configuration, the same effects as those of the present embodiment are exhibited. 
     (Others) 
     The present invention is not limited to the foregoing embodiments. For example, the notch  112   g  and/or the insertion part  114   i  may have any other shapes and, for example, may be formed in a shape with a tapered surface, an unevenness shape, such as a gear meshing shape or a wave shape (i.e., a recess and/or a protrusion formed discontinuously in the pump circumferential direction), or an elliptical shape. However, for the shape of the notch  112   g  or/and the insertion part  114   i , a continuously formed annular shape can be more easily manufactured and assembled, as compared with a discontinuous unevenness shape. In addition, for example, in the cross section as in  FIG. 6 , the inner member  112  may be formed such that the outer circumferential wall thereof (excluding the tapered surface  112   e  and the notch  112   g ) is positioned more toward the lower side (inner circumference side) or upper side (outer circumference side) than the inner circumference-side end face of the outer gear  19   a . Further, the inner member  112  may be formed of a member (e.g., metal) having a Young&#39;s modulus higher than that of the outer member  114 .