JP2008001251A - Pump device and power steering device applied with pump device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pump device capable of reducing a load of a pump by preventing galling between the both side tip end edge of an outer tooth and an opposed inner side surface of a housing by absorbing an inclination of an inner rotor. <P>SOLUTION: A reversible pump device 9 is provided in the interior of a pump housing 26 and discharges a working oil to a hydraulic power cylinder, and tapered surfaces 34a, 34b having a downward inclination shape along a tip end side are formed on both outside surfaces of respective outer teeth 29a of the inner rotor 29. Clearances C, C are formed between the both tapered surfaces, and opposed inside surfaces 26c, 26d of a pump body 26a and a rear cover 26b, and the inclination is absorbed by the clearances to prevent the galling when the inner rotor 29 is inclined in the fore-and-aft axial direction through a drive shaft 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement of a pump device applied to, for example, a power steering device of a vehicle.

  As this type of conventional pump device, one described in the following Patent Document 1 applied to the power steering device is known.

  An outline of a power steering apparatus will be described. A steering shaft attached to a steering wheel, an output shaft connected to a lower end portion of the steering shaft, a rack and pinion mechanism provided at a lower end portion of the output shaft, A hydraulic power cylinder connected to a rack of a rack and pinion mechanism, and a reversible type for relatively supplying hydraulic oil to the left and right first and second hydraulic chambers of the hydraulic power cylinder via the first passage and the second passage. Pump device.

  The pump device is a trochoid pump with an internal gear type pump element, and an inner rotor having a plurality of external teeth on the outer peripheral side is rotated forward or reverse by a drive shaft connected to an electric motor, A plurality of pump chamber volumes between inner teeth of the outer rotor meshed with the inner rotor are increased / decreased to perform pumping action by suction and discharge of hydraulic oil.

As a result, the hydraulic oil in one hydraulic chamber of the hydraulic power cylinder is supplied from the suction port of the pump device to the pump chamber via one passage, and is further discharged from the pump chamber to the hydraulic pressure via the other passage. It is supplied to the other hydraulic chamber of the power cylinder. As a result, the steering assist force of the rack and pinion mechanism is applied.
Japanese Patent Laying-Open No. 2005-41301 (FIGS. 1 and 2)

  By the way, in the reversible pump device, in general, when the drive shaft is rotatably assembled in the housing via the bearings on both ends, there is a slight amount due to the positional accuracy of the bearing and the like. Assembly errors will occur.

  When the pump action is performed by rotating the inner rotor and the outer rotor by the rotation of the drive shaft, the reaction force of the high discharge pressure discharged from the discharge port causes a relatively large bending load in the radial direction of the drive shaft. Then, the drive shaft may be slightly tilted in the radial direction due to the influence of the assembly error of the drive shaft.

  For this reason, the inner rotor coupled to the drive shaft is also tilted in the front-rear direction (axial direction), and the leading edge of the outer surface on one side of the outer teeth of the inner rotor is opposite to both inner surfaces of the housing. This causes a so-called twisting. Therefore, the sliding resistance of the inner rotor due to such twisting increases, and the rotational load torque of the pump increases.

  As a result, not only the driving load of the electric motor is increased, but also the vibration of the pump is caused.

  The present invention has been devised in view of the above-mentioned conventional situation, and the invention according to claim 1 is based on the premise of a pump structure of a general trochoid pump, and particularly in the axial direction of the working chamber of the housing. The gap between the side surface and the outer surface in the axial direction of the inner rotor facing the inner surface is formed so as to gradually increase from the center side on the drive shaft side to the outer peripheral portion on the outer rotor side. It is characterized by that.

  In the present invention, the gap (side clearance) between the outer surface of the inner rotor and the inner surface of the housing facing the outer surface is formed so as to increase from the central side to the outer peripheral side. When the inner rotor also tilts toward the inner surface of one side of the housing along with the tilt in the radial direction of the drive shaft due to the reaction force such as the discharge pressure of the pump, the gap absorbs the tilt and the inner rotor Partial interference between the front end edge of the outer peripheral portion of the outer surface of the rotor and the inner surface of the housing, that is, occurrence of contact with the shoulder can be reliably prevented.

  As a result, an increase in the rotational load of the pump can be suppressed, and the driving load of the motor can also be reduced.

  According to a second aspect of the present invention, the pump device is applied to a power steering device for a vehicle. A hydraulic power cylinder for assisting a steering force of a steering mechanism connected to a steering wheel, and a pair of pressures of the hydraulic power cylinder. A pump for supplying hydraulic pressure to the chamber; an electric motor for driving the pump; a steering torque detecting means for detecting a steering torque of the steering mechanism; and a steering torque detected by the steering torque detecting means. A motor control circuit for outputting a drive command signal to the electric motor.

  Further, the pump device has the same configuration as that of the first aspect of the invention, and in particular, an axial inner surface of the working chamber of the housing and an axial outer surface of the inner rotor facing the inner surface. The gap between them is formed so as to gradually increase from the central portion side on the drive shaft side to the outer peripheral portion on the outer rotor side.

  Therefore, this invention can obtain the same effects as those of the first aspect of the invention.

  The invention according to claim 3 is that the inner side surface of the working chamber facing the outer side surface of the inner rotor of the housing is formed in a substantially flat surface, while the axial width of both outer side surfaces of the inner rotor is A clearance groove is formed so as to gradually decrease from the center portion side to the outer peripheral portion side of the inner rotor, and the clearance is formed between the inner surface of the working chamber of the housing and the clearance groove of the inner rotor. It is characterized by that.

  According to this invention, even if the inner rotor rotates while tilting with respect to the housing, the tilt can be absorbed by the gap, and therefore, by direct metal contact between the inner surface and the outer surface. The occurrence of galling can be prevented.

  Hereinafter, an embodiment in which a pump device according to the present invention is applied to a power steering device for a vehicle will be described in detail with reference to the drawings.

  FIG. 5 is a schematic diagram of a hydraulic circuit of the power steering apparatus of the present invention. The hydraulic power cylinder 1 is linked to a rack and pinion mechanism R which is a steering mechanism linked to a steering wheel (not shown), and the hydraulic power cylinder. 1 includes a hydraulic circuit 2 that supplies and discharges hydraulic pressure.

  In the hydraulic power cylinder 1, a piston rod 3 connected to the rack of the rack and pinion mechanism passes through a cylindrical cylinder portion 1a extending in the vehicle body width direction. A piston 4 that slides in the portion 1a is fixed. Further, the first hydraulic chamber 5 and the second hydraulic chamber 6 which are left and right pressure chambers are separated by a piston 4 in the cylindrical cylinder portion 1a.

  The hydraulic circuit 2 includes a pair of first and second passages 7 and 8 each having one end connected to the hydraulic chambers 5 and 6, and a reversible that selectively supplies and discharges hydraulic pressure to the passages 7 and 8. Pump device 9, first and second discharge passages 11, 12 connected in the middle of the first and second passages 7, 8, each downstream end communicating with the reservoir tank 10, and both the discharges A control provided between the passages 11 and 12 to relatively open and close the discharge passages 11 and 12 according to the differential pressure in the passages 7 and 8 to relatively switch the communication with the reservoir tank 10. And a valve 13.

  The other ends of the first and second passages 7 and 8 are connected to discharge ports (respective suction ports) to be described later of the pump device 9.

  A pair of compensation passages 14 and 15 that are suction passages are provided on the upstream side of the first and second passages 7 and 8, respectively. There are provided first and second check valves 16 and 17 that are one-way valves that allow inflow of hydraulic oil only in the direction of suction.

  In the discharge passages 11 and 12, the discharge passages 11a and 12a at the downstream ends communicate with the interior of the reservoir tank 10, and hydraulic oil is supplied only from the passages 7 and 8 into the reservoir tank 10 through the collected discharge holes. A check valve 18 that allows inflow is provided.

  The control valve 13 includes a pair of first and second valve holes in which the discharge passages 11 and 12 communicate with each other on the center side which are in communication with each other, and a bottomed cylindrical valve body fixed inside each valve hole. And a pair of first members that are slidably provided inside the valve bodies and relatively open and close the discharge passages 11 and 12 based on the pressure difference between the first and second passages 7 and 8. The second poppet valve bodies 13a, 13b and the poppet valve bodies 13a, 13b, that is, in the axial direction, are slidably provided in the sliding holes communicating between the valve holes at the center. And a free piston 13c that is a piston member that controls the relative operating positions of the valve bodies 13a and 13b.

  Each poppet valve body 13a, 13b is urged in the direction of the free piston 13c by the spring force of the first and second coil springs 13d, 13e mounted between the rear end portion and the bottom surface of the valve body, When the pump device 9 is not in operation, the neutral position is maintained, and in this state, the valve portions are seated on the first and second valve seats, and the communication between the discharge passages 11 and 12 and the discharge passages 11a and 12a is blocked. The so-called normally closed type.

  A fail-safe mechanism 20 is provided between the first and second passages 7 and 8. The fail-safe mechanism 20 includes a communication passage 21 that communicates between the first and second passages 7 and 8, an electromagnetic switching valve 22 that is provided at a substantially central position of the communication passage 21 via a passage hole, and the communication passage. The first and second check valves 23a and 23b are provided at both ends of the passage 21 and allow hydraulic fluid to flow only from the first and second passages 7 and 8 toward the passage hole. . The electromagnetic switching valve 22 is a two-way, two-position type, and shuts off the communication path 21 during normal operation of the apparatus by an output signal from an electronic controller (not shown). The hydraulic oil in each of the hydraulic chambers 5 and 6 is configured to be capable of displacement flow.

  As shown in FIGS. 3 and 4, the pump device 9 is arranged in a vertical type, and a trochoidal pump element 24 that controls the pump action, and an electric motor 25 that drives the pump element 24 to rotate forward and backward. It consists of and.

  As shown in FIGS. 2 and 3, the pump element 24 is fixed to the inside of the pump housing 26 with bolts, and includes a cam ring 27 constituting a part of the pump housing 26, and an outer peripheral surface of the cam ring 27. An outer rotor 28 that is rotatably held on the surface 27a and has a plurality of inner teeth 28a formed on the inner peripheral side, and is disposed on the inner side of the outer rotor 28. An inner rotor 29 having meshing external teeth 29a, a drive shaft 30 that is disposed through the housing 26, and is coupled to the inner rotor 29 through a central hole 29c, and the like.

  Further, a plurality of pump chambers 31 are formed between the inner and outer teeth 28a, 29a of the inner rotor 29 and the outer rotor 28, and are arranged in a substantially crescent shape opposed to each other with the drive shaft 30 sandwiched inside the pump housing 26. A pair of discharge ports (suction ports) 32 and 33 are formed, and the end portions of the passages 7 and 8 communicate with each other through the discharge ports (suction ports) 32 and 33.

  As shown in FIGS. 2 and 3, the inner peripheral surface 27 of the cam ring 27 has a pump discharge pressure over a predetermined angular range including a pump confining portion T having the maximum volume among the plurality of pump chambers 31. Introducing grooves 35 are formed. The introduction groove 35 includes a circumferential groove 35a formed in a substantially arc shape along the circumferential direction at the center position in the width direction of the inner circumferential surface 27a of the cam ring 27, the circumferential groove 35a, the discharge port 32, 32 is formed by axial grooves 35b and 35b that communicate with the H. Further, communication grooves 37a and 37b for guiding discharge pressure to the axial grooves 35b and 35b are formed on the outer sides of the discharge ports (suction ports) 32 and 33, respectively.

  The drive shaft 30 is controlled to rotate forward and backward by the electric motor 25. The electric motor 25 rotates and stops the drive shaft 30 by a control current output from an electronic controller as a motor control unit based on a detection signal output from a torque sensor (not shown) as a steering load detection unit. In addition, forward and reverse rotation control is performed.

  As shown in FIG. 3, the pump housing 26 is mainly configured by a pump body 26 a and a rear cover 26 b in which main elements of the pump such as the inner rotor 29 and the outer roller 28 are accommodated together, The outer side surfaces 28b, 28b and 29b, 29b of the inner rotor 29 and the outer rotor 28 slide between the inner side surfaces 26c, 26d of the pump body 26a and the rear cover 26b facing each other with a minute side clearance. It has become.

  The rear cover 26b is fixed while being positioned by a locating pin by a plurality of bolts (not shown) through the annular plate 18d from the front end axial direction of the pump body 26a.

  The reservoir tank 10 is coupled to the front end portion of the pump body 26a by bolts so as to cover the entire main elements of the pump such as the rear cover 26b, the inner and the outer rotors 28 and 29, and has an upper end opening at the cylindrical upper end portion. Is closed by the cap 10a.

  As shown in FIGS. 1 and 2, the inner rotor 29 has tapered surfaces 34a and 34b which are relief grooves that are inclined downward from the base end sides of the outer side surfaces of the external teeth 29a along the distal end edges. Is formed.

  Both the tapered surfaces 34a, 34b are set to a minute inclination angle that can absorb the inclination when the inner rotor 29 is slightly inclined in the front-rear direction via the drive shaft 30 due to discharge pressure or the like. The tapered surfaces 34a and 34b form wedge-shaped gaps C and C between the opposing pump body 26a and the inner side surfaces 26c and 26d of the rear cover 26b.

  Hereinafter, the operation of the present embodiment will be described. First, when the driver maintains the steering wheel in a neutral state, for example, while the vehicle is traveling straight ahead, no control current is output from the electronic controller to the electric motor 25, and the pump Element 24 is deactivated.

  In this case, since no differential pressure is generated in the passages 7 and 8, the poppet valve bodies 13a and 13b maintain the neutral position via the free piston 13c by the spring force of the coil springs 13d and 13e. Therefore, each valve portion is seated on each valve seat, and the communication between each discharge passage 11, 12 and each discharge passage 11a, 12a is blocked.

  Thereafter, when the steering wheel is rotated, for example, in the right direction, the electric motor 24 is rotated in one direction by the control current from the electronic controller, and the inner rotor 29 and the outer rotor 28 are driven forward, for example.

  By this pumping action, the hydraulic oil in the second passage 8 is supplied from the suction port 32 of the pump device 9 to each pump chamber 31, where it is pressurized and discharged from the other discharge port 33 into the first passage 7. At the same time, the hydraulic oil in the reservoir tank 10 pushes and opens the ball valve body of the second check valve 17 against the spring force of the valve spring from the compensation passage 15 and from the suction port 32 to the pump chamber 31. And flows into the first passage 7 and the first hydraulic chamber 5 to compensate for the shortage.

  On the other hand, when the steering wheel is returned to the original state from the rotation operation state in the right direction and further rotated in the left direction, the pump element 24 is reversed by the electronic controller via the electric motor 25.

  Therefore, this time, contrary to the above, the hydraulic oil on the first passage 7 side is discharged to the second passage 8 and the hydraulic oil in the reservoir tank 10 passes through the compensation passage 14 and the first check valve. Sixteen ball valve bodies are pushed open against the spring force of the valve spring and discharged from the pump chamber 31 to the second passage 8 and supplied to the second hydraulic chamber 6 through the second back pressure chamber in the same manner as described above. .

  Further, one of the poppet valves 13a to 13c of the control valve 13 is operated by the selective supply / discharge action of the hydraulic oil from the one of the passages 7, 8 to the one hydraulic chamber 5, 6. The hydraulic oil is discharged from the hydraulic chambers 5 and 6 on the low pressure side, and the pressure is quickly reduced.

  As described above, when the steering wheel is rotated left and right, the internal pressure of the one of the passages 7 and 8 that is at a low pressure can be quickly reduced. Torque fluctuations are prevented from occurring, and a good steering feeling can be obtained.

  Further, according to the present embodiment, as described above, the tapered surfaces 34a and 34b are formed on both outer side surfaces of the respective external teeth 29a of the inner rotor 29, thereby causing the reaction force such as the discharge pressure. When the drive shaft 30 is inclined in the radial direction and the inner rotor 29 is also inclined in the front-rear axis direction, the gaps C and C absorb the inclination.

  Therefore, it is possible to reliably prevent partial interference between the front end edges of the outer side surfaces of the outer teeth 29a of the inner rotor 29 and the inner side surfaces 26c and 26d of the pump body 26a and the rear cover 26b, that is, occurrence of contact with each other. It is possible to prevent galling due to direct metal contact between the inner side surfaces 26c and 26d and the outer edge of the outer teeth 29a. The

  As a result, an increase in the rotational load of the pump element 24 can be suppressed, so that the driving load of the electric motor 25 can also be reduced.

  In addition, when the pump is rotating at a low speed, the pressurized hydraulic oil in the pump chamber 31 easily leaks from the high-pressure side pump chamber 31 to the low-pressure side pump chamber 31 through the gaps C and C. For this reason, the intermittent driving | operation which becomes the repetition of a pump stop can be suppressed.

  On the other hand, when the pump rotates at high speed, the hydraulic oil passing through the gaps C and C is pulled back from the low pressure side pump chamber 31 to the high pressure side pump chamber 31 by the frictional resistance as the inner rotor 29 rotates. It becomes an action. For this reason, excessive leakage of the discharge hydraulic oil can be prevented.

  The leaking action of the hydraulic oil between the pump chambers 31 based on the rotational speed V of the pump will be described with reference to FIG.

That is, the leakage amount Q determined by the leakage of the parallel gaps C and C is
^{Q = b · h 3/12} · μ · L × (p1-p2) -b · h / 2 × V
It can be expressed from the following formula. Here, b is the width in the radial direction of the gaps C and C, h is the thickness of the gaps C and C, L is the width in the circumferential direction of the gaps C and C, and p1 is the width of the pump chamber 31. The pressure on the low pressure side, p 2, is the pressure on the high pressure side of the pump chamber 31.

  As is apparent from this equation, the leakage amount Q from the gaps C and C varies with the rotational speed V of the inner rotor 29, and the leakage direction also varies. That is, when the rotational speed V is low, the hydraulic oil leaks from the high-pressure pump chamber 31 toward the low-pressure pump chamber 31 through the gaps C and C. In particular, since the rotational speed V is faster on the outer peripheral side (front end) than on the inner peripheral side (base end) of the outer teeth 29a, the inner side is more likely to leak when the pump is rotating at a lower speed, and the outer side is less likely to leak. Become.

  Therefore, it is possible to suppress intermittent operation that is likely to occur at the time of low pump rotation and is repeated stoppage of pump operation.

  On the other hand, when the rotational speed V increases, the flow resistance of the hydraulic fluid passing through the gaps C and C increases, and the leakage amount Q from the high pressure side to the low pressure side decreases, and conversely from the low pressure side to the high pressure side. The phenomenon of being pulled back to occurs. For this reason, excessive leakage of the discharge hydraulic oil can be prevented.

  Therefore, it is possible to suppress the deterioration of the steering feeling and the deterioration of the fuel consumption due to the intermittent sudden decrease of the steering assist force.

  Further, since each of the tapered surfaces 34a, 34b is formed in a gradually inclined shape from the proximal end side to the distal end side of the outer teeth 29a, the hydraulic oil is drawn back in proportion to the radial distance from the rotation center of the inner rotor 29. An effect can be obtained.

  Further, as described above, the outer rotor 28 is moved by the arrow in FIG. 2 by the discharge pressure introduced into the circumferential groove 35a from the axial groove 35b in the introduction groove 35 formed in the inner circumferential surface 27a of the cam ring 27. As shown, it can be pressed against the inner rotor 29 by pressing in the direction of the drive shaft 30. That is, the tip of the inner tooth 28 a of the outer rotor 28 is pressed against the tip of the outer tooth 29 a of the inner rotor 29 at the pump confinement portion T. As a result, the so-called tip clearance between the two 28a and 29a is sufficiently reduced.

  Therefore, the sealing performance at the pump confinement portion T is improved, and the pump discharge efficiency is improved.

  Further, since the structure of the introduction groove 35 is simple, the processing operation is facilitated, and the increase in cost can be suppressed.

  FIG. 7 shows a second embodiment of the present invention. In addition to the structure of the tapered surfaces 34a and 34b of the inner rotor 29, the both sides of the inner teeth 29a of the outer rotor 29 descend from the proximal end side to the distal end side. The inclined second tapered surfaces 36a and 36b are formed.

  The second taper surfaces 36a and 36b are formed in substantially the same inclination angle as the first taper surfaces 34a and 34b. The second taper surfaces 36a and 36b, the pump body 26a and the rear cover 26b Wedge-shaped second gaps C2 and C2 are also formed between the opposed inner side surfaces 26c and 26d.

  Therefore, as described above, when the inner rotor 29 is slightly inclined during the pump operation and the outer rotor 28 is also inclined through the meshed teeth 28a and 29a, the second gaps 36a and 36b Since the inclination is absorbed, the leading edges of the both side surfaces of each inner tooth 28a do not come into direct contact with each of the inner side surfaces 26c and 26d, and the occurrence of the twisting can be surely prevented.

  Therefore, in this embodiment, since the twisting of the teeth 29a and 28a of both the inner rotor 29 and the outer rotor 28 and the inner surfaces 26c and 26d is prevented, the load on the pump can be further suppressed. . As a result, the load on the electric motor 25 is also reduced, and the size can be reduced.

  Also in this embodiment, since the introduction groove 35 is provided, the same effect as described above can be obtained.

  The present invention is not limited to the configuration of the embodiment, and for example, the tapered surfaces 34a, 34b, 36a, 36b can be formed on the corresponding inner side surfaces 26c, 26d. .

  Further, the inclination angle of each tapered surface 34a, 34b, 36a, 36b can be arbitrarily changed based on conditions such as the specification and size of the pump.

  Furthermore, this pump device can be applied to devices other than the power steering device.

The technical ideas other than the invention described in the claims, as grasped from the embodiment, will be described below.
(A) A tapered surface in which the axial dimension of the inner rotor gradually decreases from the center side toward the outer peripheral portion is formed on the outer peripheral portions of both outer side surfaces in the axial direction of the inner rotor. The pump device according to claim 1, wherein the gap is formed between the inner surface and the inner surface.

By making the outer peripheral portion of the outer surface of the inner rotor a tapered surface, for example, it is possible to obtain the effect of returning the hydraulic oil in proportion to the radial distance from the rotation center of the inner rotor when the pump is rotating at a low speed.
(B) Over a predetermined angular range including a pump confining portion having a maximum volume of the plurality of pump chambers between the inner peripheral surface of the housing and the outer peripheral surface of the outer rotor facing the inner peripheral surface. The pump device according to claim 1, wherein a pump discharge pressure is introduced.

According to this invention, the pump discharge pressure introduced acts on the pump confinement portion side of the outer rotor, and a force acts to push the tip of the inner teeth of the outer rotor toward the tip of the outer teeth of the inner rotor. For this reason, the sealing performance between the tip of the internal tooth and the tip of the external tooth is improved, and leakage of the pump discharge pressure from the discharge side to the suction side in the pump confinement portion can be sufficiently prevented.
(C) An introduction groove for introducing pump discharge pressure over a predetermined angular range including a pump confining portion having a maximum volume among the plurality of pump chambers is formed on an inner peripheral surface of the cam ring. Item 2. The pump device according to Item 1.

Since the outer rotor can be pressed in the direction of the inner rotor by the discharge pressure introduced into the introduction groove, the same effect as that of the invention (b) can be obtained.
(D) The discharge pressure introduction groove is constituted by a circumferential groove formed over the circumferential direction of the inner peripheral surface of the housing, and an axial groove that communicates the circumferential groove with the discharge port. The pump device as described in (c) above.

  It becomes possible to effectively transmit the discharge pressure discharged to the discharge port from the axial groove to the outer peripheral surface of the outer rotor through the inside of the circumferential groove.

It is the sectional view on the AA line of FIG. 2 which shows 1st Embodiment of the pump apparatus of this invention. It is a front view which shows the pump element of this embodiment. It is a disassembled perspective view which shows the pump apparatus of this embodiment. It is a partial longitudinal cross-sectional view which shows the pump apparatus of this embodiment. It is a schematic diagram of a hydraulic circuit provided for this embodiment. It is explanatory drawing which shows the leak effect | action of the hydraulic fluid of this embodiment. It is principal part sectional drawing which shows 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Hydraulic power cylinder 2 ... Hydraulic circuit 7 * 8 ... 1st, 2nd channel | path 9 ... Pump apparatus 26 ... Pump housing 26a ... Pump body 26b ... Rear cover 26c, 26d ... Inner side surface 27 ... Cam ring 28 ... Outer rotor 28a ... Inside Tooth 29 ... Inner rotor 29a ... External tooth 30 ... Drive shaft 32, 33 ... Discharge port (suction port)
34a, 34b ... Tapered surface

Claims (3)

An outer rotor housed rotatably inside the housing and having a plurality of internal teeth on the inner circumference side;
An inner rotor that is rotatably provided on the inner peripheral side of the outer rotor and has a plurality of external teeth that mesh with the inner teeth on the outer peripheral side;
A drive shaft coupled to the inner rotor for driving the inner rotor to rotate;
A suction port that opens to a suction region in which the volume of the pump chamber increases with rotation of the drive shaft among a plurality of pump chambers formed between the inner teeth of the outer rotor and the outer teeth of the inner rotor;
A discharge port that opens to a discharge region in which the volume of the pump decreases with rotation of the drive shaft among the plurality of pump chambers;
In a pump device comprising:
A gap between the inner side surface in the axial direction of the housing and the outer side surface in the axial direction of the inner rotor facing the inner side surface extends from the center portion side on the drive shaft side to the outer peripheral portion on the outer rotor side. The pump apparatus is characterized by being formed so as to become gradually larger. A hydraulic power cylinder that assists the steering force of the steering mechanism coupled to the steering wheel;
A pump for supplying hydraulic pressure to a pair of pressure chambers of the hydraulic power cylinder;
An electric motor for driving the pump;
Steering torque detection means for detecting steering torque of the steering mechanism;
A motor control circuit for outputting a drive command signal to the electric motor based on the steering torque detected by the steering torque detecting means;
With
The pump is
An outer rotor housed rotatably inside the housing and having a plurality of internal teeth on the inner circumference side;
An inner rotor that is rotatably provided on the inner peripheral side of the outer rotor and has a plurality of external teeth that mesh with the inner teeth on the outer peripheral side;
A drive shaft coupled to the inner rotor for driving the inner rotor to rotate;
A suction port that opens to a suction region in which the volume of the pump chamber increases with rotation of the drive shaft among a plurality of pump chambers formed between the inner teeth of the outer rotor and the outer teeth of the inner rotor;
A discharge port that opens to a discharge region in which the volume of the pump decreases as the drive shaft rotates among the plurality of pump chambers,
A gap between the inner side surface in the axial direction of the housing and the outer side surface in the axial direction of the inner rotor facing the inner side surface extends from the center portion side on the drive shaft side to the outer peripheral portion on the outer rotor side. The power steering device is formed so as to gradually increase in size. While forming an inner surface facing the outer surface of the inner rotor of the housing in a substantially flat shape,
An escape groove is formed so that the axial width between the outer side surfaces of the inner rotor gradually decreases from the center side to the outer peripheral side of the inner rotor, and the inner side surface of the housing and the inner rotor The pump device according to claim 1, wherein the gap is formed between the clearance groove.

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