JP2006299846A - Internal gear pump - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an internal gear pump for reducing complexity on the clearance control between a housing and an outer rotor. <P>SOLUTION: This internal gear pump 1 has a first port and a second port symmetrically arranged to the first axis for connecting a shutting-in part having the maximum volume and a meshing part having the minimum volume among a plurality of pump rooms formed between an internal teeth gear of the outer rotor 30 and an external teeth gear of an inner rotor 40 and opening in a plurality of these pump rooms. Radial directional clearance formed between an outer rotor storage part and the outer rotor, is arranged so that the second axis direction respectively orthogonal to this first axis and a driving shaft becomes smaller than the first axis direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an internal gear pump that performs suction and discharge of fluid.

  Conventionally, in an internal gear pump, among a plurality of pump chambers formed between an outer rotor having an internal gear and an inner rotor having an external gear, a confining portion having a maximum volume is sandwiched. The pump chamber on one side communicates with the suction passage, and the pump chamber on the other side communicates with the discharge passage. In the discharge side pump chamber, the pump discharge pressure acts in a direction in which the outer rotor is separated from the inner rotor. Therefore, there is a problem in that an engagement gap is excessively generated between the internal gear of the outer rotor and the external gear of the inner rotor, and oil leakage occurs.

In order to solve this problem, for example, in the internal gear pump disclosed in Patent Document 1, the outer rotor is mounted by introducing the discharge pressure to the outer periphery of the outer rotor on the discharge side and introducing the suction pressure to the outer periphery of the outer rotor on the suction side. Pressing against the inner rotor side reduces the meshing gap between the internal gear and the external gear.
Japanese Patent Application Laid-Open No. 11-117876

  However, in the above prior art, the structure is such that the outer rotor is positively shifted by introducing the discharge pressure and the suction pressure to the outer periphery of the outer rotor. Therefore, if the clearance is too small, a sufficient amount of deviation of the outer rotor can be secured. If it is not or too large, the pressure leak inside the pump becomes large, and there is a problem that the clearance management between the housing and the outer rotor is complicated.

  The present invention has been made paying attention to the above problems, and an object of the present invention is to provide an internal gear pump in which the complexity of the clearance management between the housing and the outer rotor is reduced.

  In order to achieve the above object, in the present invention, a housing having an outer rotor accommodating portion, an outer rotor that is rotatably accommodated in the outer rotor accommodating portion and has an internal gear on the outer rotor accommodating portion side, and an outer rotor accommodating portion side of the outer rotor. An inner rotor that is rotatably provided and has an external gear that meshes with the internal gear on the outer peripheral side, a drive shaft that is connected to the inner rotor and that drives the inner rotor to rotate in forward and reverse directions, and an internal gear of the outer rotor Of the plurality of pump chambers formed between the inner gear and the external gear of the inner rotor are provided symmetrically with respect to the first axis connecting the confining portion having the maximum volume and the meshing portion having the minimum volume. A first port and a second port that open to a plurality of pump chambers, and are formed between the outer rotor accommodating portion and the outer rotor. Radial clearance portion, the than the first axial direction is provided so that the second axial direction perpendicular respectively to the first axis and the drive shaft is reduced.

  Therefore, by providing the second axis direction perpendicular to the first axis to be small, it is possible to provide an internal gear pump that reduces the complexity of the clearance management between the housing and the outer rotor.

  Hereinafter, the best mode for realizing the internal gear pump of the present invention will be described based on Example 1 shown in the drawings.

[System configuration of power steering system using internal gear pump]
Example 1 will be described with reference to FIGS. FIG. 1 is a system configuration diagram of a power steering apparatus to which an internal gear pump 1 of the present application is applied. When the driver steers the steering wheel 2a, the pinion shaft 2d is driven through the steering shaft 2b and the column shaft 2c, and the rack shaft 4a is moved in the axial direction by a so-called rack and pinion mechanism to steer the front wheels. The steering shaft 2b is provided with a torque sensor 3a that detects the steering torque of the driver, and outputs a torque signal to the control unit 3b.

  The rack shaft 4a is provided with a power steering mechanism that assists the movement of the rack shaft 4a according to the steering torque of the driver. This power steering mechanism is provided with a reversible internal gear pump 1 driven by a motor 1a and a cylinder 4b for moving the rack shaft 4a left and right. An axially movable piston 4c is provided inside the cylinder 4b, and a first cylinder chamber 4d and a second cylinder chamber 4e are defined by the piston 4c.

  The first cylinder chamber 4d and the internal gear pump 1 are connected via a first oil passage 5a, and the second cylinder chamber 4e and the internal gear pump 1 are connected via a second oil passage 5b. The first and second oil passages 5a and 5b are connected to the reservoir tank 8 via the first and second suction oil passages 8a and 8b, respectively, and the first and second suction oil passages 8a and 8b are respectively sucked. Check valves 7e and 7f are provided.

  The intake check valves 7e and 7f prevent backflow to the reservoir tank 8 side, and oil can be supplied from the reservoir tank 8 when the oil in the first and second oil passages 8a and 8b is insufficient. Yes.

  The first and second oil passages 5a and 5b are connected by the first and second communication passages 6a and 6b without the internal gear pump 1, and the first and second communication passages 6a and 6b are respectively connected to the first and second communication passages 6a and 6b. The two connecting portions 9a and 9b are connected by the third communication path 6c. The third communication passage 6c is provided with a normally-open electromagnetic switching valve 9 for communication / blocking.

  First and second check valves 7a and 7b are provided on the first communication passage 6a and between the first connection portion 9a and the first and second oil passages 5a and 5b, respectively. The first check valve 7a allows only the flow from the first oil passage 5a to the first connection portion 9a, and the second check valve 7b allows only the flow from the second oil passage 5b to the first connection portion 9a. Is provided.

  On the other hand, third and fourth check valves 7c and 7d are provided on the second communication passage 6b and between the second connection portion 9b and the first and second oil passages 5a and 5b, respectively. The third check valve 7c allows only the flow from the second oil passage 5b to the second connection portion 9b, and the fourth check valve 7d allows only the flow from the first oil passage 5a to the second connection portion 9b. Is provided.

  In addition to the torque signal from the torque sensor 3a, a switch signal from the ignition switch, an engine speed signal from the engine speed sensor, a vehicle speed signal from the vehicle speed sensor, and the like are input to the control unit 3b. The steering assist force is determined, and a command signal is output to the motor 1a and the electromagnetic switching valve 9.

[Configuration of internal gear pump]
(Axial sectional view)
FIG. 2 is an axial sectional view of the internal gear pump 1. The internal gear pump 1 is a so-called bidirectional pump, and includes first and second housings 10 and 20, an outer rotor 30, an inner rotor 40, a drive shaft 50, and a cam ring 60. For the sake of explanation, the axial direction of the internal gear pump 1 is defined as the z axis, and the direction from the suction port 210 to the discharge port 220 in the plane perpendicular to the z axis is defined as the x axis.

  The cam ring 60 is an annular member, and is accommodated in the first and second housings 10 and 20, and the outer rotor 30 and the inner rotor 40 are accommodated in the annular rings. In addition, the inner periphery 61 (outer rotor accommodating part) of the cam ring 60 which accommodates the outer rotor 30 is not a perfect circle, but is a long hole combining two semicircles (see FIG. 3).

  In addition, a first suction port 110 is provided in the z-axis positive surface 11 of the first housing 10 in the region in the x-axis negative direction from the line I-II in the drawing, and the first suction port 110 is provided in the region in the x-axis positive direction. One discharge port 120 is provided.

(Axial front view)
FIG. 3 is an axial front view of the internal gear pump 1 with the second housing 20 removed, and FIG. 4 is an axial front view of the first housing 10. Further, it is defined as a y-axis orthogonal to the x-axis and the z-axis (see FIG. 2), and this y-axis has a positive meshing portion direction between the outer rotor 30 and the inner rotor 40.

  The cam ring 60 houses the outer rotor 30 inside the circular pipe, and the inner rotor 40 is housed inside the outer rotor 30. Here, the inner periphery 61 of the cam ring 60 is provided in the shape of a long hole that is a combination of two semicircles. The length of the long-axis side in the y-axis direction (first axial direction) is a, and the short-axis side is in the x-axis direction. (Second axis) is provided at b (a> b).

  The outer rotor 30 has an internal gear 310 on the inner periphery 61, and is rotatably accommodated on the cam ring 60 on the outer peripheral surface 320, and meshes with the external gear 410 of the inner rotor 40 in the internal gear 310.

  The internal gear 310 and the external gear 410 are provided at the same pitch, and the number of teeth of the internal gear 310 is one more than the number of teeth of the external gear 410. The number of teeth of the internal gear 310 may be two or more with respect to the number of teeth of the external gear 410 and is not particularly limited.

  Since the number of teeth of the internal gear 310 is one more than the number of teeth of the external gear 410, when the internal gear 310 and the external gear 410 are meshed with each other, they are eccentrically engaged with each other, and the inner rotor 40 is engaged with the center O of the outer rotor 30. The center O ′ of is shifted to the y-axis positive direction side. A pump chamber 500 separated by the internal gear 310 and the external gear 410 is formed by the eccentricity.

  A suction port 110 and a discharge port 120 are provided at a position corresponding to the pump chamber 500 in the first housing 10. The suction and discharge ports 110 and 120 are crescent-shaped recesses symmetrical with respect to the III-III straight line, respectively, and supply and discharge oil to and from the pump chamber 500 through communication with the suction and discharge oil passages 5a and 5b, respectively.

  The suction and discharge ports 110 and 120 in the first housing 10 are provided with suction and discharge side oil grooves 111 and 121 extending in the x-axis direction. The suction-side and discharge-side oil grooves 111 and 121 are provided on the negative side of the y-axis with respect to the axial center O of the first housing 10, and the clearance D between the cam ring 60 and the outer rotor 30 and the suction and discharge ports 110 and 120 are connected. The hydraulic pressure of the suction and discharge ports 110 and 120 is introduced into the clearance D through communication.

  Due to the eccentricity of the outer rotor 30 and the inner rotor 40, the internal gear 310 and the external gear 410 mesh closely with each other toward the y-axis positive direction, and are completely meshed with each other at the end A in the y-axis positive direction. It becomes volume. Further, the meshing is disengaged toward the y-axis negative direction, and the meshing is completely disengaged at the end B in the y-axis negative direction to reach the maximum pump volume. The clearance between the internal gear 310 and the external gear 410 at the y-axis negative direction end B is provided to be substantially zero while avoiding contact.

  That is, when the inner rotor 40 and the outer rotor 30 are rotated counterclockwise, the x-axis negative direction side region (corresponding to the first and second suction ports 110 and 210) in the pump chamber 500 is rotated. Accordingly, the suction area 510 increases in volume, and the x-axis positive direction area (corresponding to the first and second discharge ports 120 and 220) becomes a discharge area 520 whose volume decreases with rotation. When rotating clockwise, suction and discharge are reversed.

  A drive shaft 50 provided in parallel with the z-axis is connected to the motor 1a (see FIG. 1) to drive the inner rotor 40. As the drive shaft 50 rotates, the inner rotor 40 and the outer rotor 30 are rotationally driven by the meshing of the inner rotor 40 and the outer rotor 30. The internal gear pump 1 functions as a bidirectional pump when the drive shaft 50 rotates forward and backward.

(Details of sliding contact surface between cam ring and outer rotor)
As described above, the inner circumference 61 of the cam ring 60 is provided in the shape of a long hole formed by combining two semicircles, the length in the y-axis direction is a, and the length in the x-axis direction is b (a> b). Yes.

  Therefore, in order to rotatably provide the outer rotor 30 on the inner periphery 61 of the cam ring 60, the diameter of the outer rotor 30 is necessarily equal to or less than b. On the other hand, if the outer rotor 30 moves in the x-axis direction within the cam ring 60, the suction volume and the discharge volume fluctuate.

  For this reason, the diameter of the outer rotor 30 is set to be slightly smaller than the short-diameter side diameter b of the inner periphery 61 so as to be able to rotate while restricting movement in the x-axis direction within the cam ring inner periphery 61.

  Along with this, the sliding contact portion between the outer rotor 30 and the cam ring 60 becomes the short diameter side end portion 62 of the inner periphery 61, that is, the intersection of the inner periphery 61 and the x axis. On the other hand, since the length of the inner periphery 61 in the y-axis direction is a (a> b), it does not come into contact with the outer rotor 30 at the long diameter side end 63, that is, at the intersection of the y-axis and the inner periphery 61.

  As a result, the radial clearance D between the cam ring 60 and the outer rotor 30 is formed smaller in the x-axis (second axis) direction than in the y-axis (first axis) direction. In the circumference 61, it is accommodated so as to be able to shift in the y-axis direction. In the present embodiment, the gap between the cam ring 60 and the outer rotor 30 is 90 to 110 μm in the y-axis direction and 20 to 40 μm in the x-axis direction, but is not particularly limited.

(Positioning of housing and cam ring)
First and second axial holes 610 and 620 are provided at positions corresponding to the y-axis positive and negative end portions A and B of the cam ring 60, respectively. Positioning pins 630 are inserted into the first and second axial holes 610 and 620, respectively, and inserted into the positioning holes 130 and 230 (see FIG. 3) provided in the first and second housings 10 and 20, respectively. The second housings 10 and 20 and the cam ring 60 are positioned.

  Here, the first and second housings 10 and 20 support a drive shaft 50, and an inner rotor 40 is provided on the drive shaft 50. That is, the positioning accuracy in the x-axis direction between the cam ring 60 that houses the outer rotor 30 and the first and second housings 10 and 20 that hold the inner rotor 40 via the drive shaft 50 is ensured.

  Thereby, the positioning accuracy of the inner rotor 40 and the outer rotor 30 in the x-axis direction can be secured, and the positioning accuracy of the cam ring 60 relative to the first and second housings 10 and 20 in the x-axis direction can be secured.

[Oil introduction into clearance and deviation of outer rotor]
FIG. 5 is a diagram showing the introduction of oil into the clearance D and the shift of the outer rotor 30 when the pump is driven. For the sake of explanation, only the suction and discharge ports 110 and 120, the suction side, and the discharge side oil grooves 111 and 121 are shown for the first housing 10.

  Oil is supplied from the suction-side and discharge-side oil grooves 111 and 121 to the region D1 on the negative y-axis side in the clearance D by driving the pump, and the hydraulic pressure in the region D1 rises to be different from the region D2 on the positive y-axis side. Pressure is generated.

  Here, the oil tries to flow into the region D <b> 2 through between the short diameter side end 62 of the cam ring inner periphery 61 and the outer rotor 30, but the short diameter side end 62 is in sliding contact with the outer rotor 30. The road area is difficult to be secured, and it is difficult for oil to flow from the region D1 to the region D2.

  Accordingly, when the pump is driven, a differential pressure is generated in the regions D1 and D2, and the outer rotor 30 is biased in the positive y-axis direction by this differential pressure. As described above, the outer rotor 30 is accommodated so as to be able to shift in the y-axis direction while being restricted from moving in the x-axis direction by the long-hole-shaped cam ring 60. Therefore, the outer rotor 30 is biased in the positive y-axis direction by the differential pressure. Shift.

  The inner rotor 40 does not shift in the y-axis direction because the inner rotor 40 rotates integrally with the drive shaft 50 with respect to the outer rotor 30 that shifts. Therefore, the tooth surfaces of the internal gear 310 of the outer rotor 30 and the external gear 410 of the inner rotor 40 approach each other as the outer rotor 30 shifts in the positive y-axis direction.

  Even in the y-axis negative direction end B where the internal gear 310 and the external gear 410 are completely disengaged, the gap between the tooth surfaces of the rotors 30 and 40 is reduced. As a result, the flow path area at the Y-axis negative direction end B is reduced, and the amount of leakage from the discharge region 520 to the suction region 510 is reduced.

  Thus, by making the inner periphery 61 of the cam ring 60 a long hole in the y-axis direction, it is possible to secure the amount of deviation in the y-axis positive direction of the outer rotor 30 to reduce leakage and to secure pump performance. . Further, since the movement of the outer rotor 30 in the x-axis direction is restricted at the short-axis side end portion 62 in the x-axis direction, it is possible to prevent the pump performance from deteriorating by suppressing the volume fluctuations of the suction and discharge regions 510 and 520 in the pump chamber 500. .

  Furthermore, since the short diameter side end portion 62 of the cam ring inner periphery 61 is in sliding contact with the outer rotor 30 at high speed, it is necessary to improve the dimensional accuracy. However, since the long diameter side end portion 63 is not always in sliding contact with the outer rotor 30, the long diameter side end portion. There is no need to increase the dimensional accuracy of 63. Therefore, it becomes possible to reduce the high-precision machining location in the cam ring 60, and it can be set as the apparatus excellent in processability and cost efficiency. In addition, since the cam ring inner periphery 61 is a long hole, the assemblability is improved.

  Here, since the deviation amount of the outer rotor 30 is defined by the major axis a of the cam ring inner periphery 61, a desired deviation amount can be obtained by adjusting the value of the major axis a. If the outer rotor 30 is shifted too much in the positive y-axis direction, the gap between the tooth surfaces becomes too small and the rotors 30 and 40 interfere with each other. Therefore, the major axis a of the cam ring inner periphery 61 is set so that the tooth surfaces do not interfere with each other. In addition, leakage reduction and tooth surface interference avoidance can be ensured at the same time.

  In addition, by positively introducing the high pressure of the suction and discharge ports 110 and 120 into the clearance D between the cam ring 60 and the outer rotor 30 by the suction and discharge side oil grooves 111 and 121, the end portion in the y-axis negative direction The amount of leakage at B can be reduced, and the meshability between the outer rotor 30 and the inner rotor 40 can be improved.

[Contrast of the effects of the conventional example and the embodiment of the present application]
Conventionally, in the internal gear pump, since one side communicates with the suction passage and the other side communicates with the discharge passage across the confining portion where the volume of the pump chamber becomes maximum, the inner teeth of the outer rotor A meshing gap is excessively generated between the gear and the external gear of the inner rotor, and leakage occurs. Therefore, in the prior art, the discharge pressure is introduced to the outer periphery of the outer rotor on the discharge side, the suction pressure is introduced to the outer periphery of the outer rotor on the suction side, and the outer rotor is pressed against the inner rotor side, thereby meshing the internal gear and the external gear. The gap is reduced.

  However, in the above prior art, since the outer rotor is positively shifted by introducing discharge pressure and suction pressure to the outer periphery of the outer rotor, if the clearance is too small, a sufficient amount of deviation of the outer rotor cannot be secured. . Moreover, since the pressure leak in a pump will become large when too large, there existed a problem that the clearance management between a housing and an outer rotor was complicated.

  On the other hand, in this embodiment, the inner periphery 61 of the annular cam ring 60 that rotatably accommodates the outer rotor 30 is provided in the shape of a long hole formed by combining two semicircles. Further, the inner circumference 61 has a long axis side in the y-axis (first axis) direction connecting the meshing portion and the closed portion of the internal gear 310 of the outer rotor 30 and the external gear 410 of the inner rotor 40, and is the same in the radial direction as the y-axis. A long hole having a short diameter side in the x-axis (second axis) direction perpendicular to the y-axis in a plane, and the radial gap formed between the cam ring 60 and the outer rotor 30 is larger than the y-axis direction. The x-axis direction perpendicular to the y-axis is set small.

  Thereby, by making the inner periphery 61 of the cam ring 60 a long hole in the y-axis direction, the y-axis positive direction shift amount of the outer rotor 30 can be ensured, leakage can be reduced, and pump performance can be ensured. Further, since the movement of the outer rotor 30 in the x-axis direction is restricted at the short-axis side end portion 62 in the x-axis direction, it is possible to prevent the pump performance from deteriorating by suppressing the volume fluctuations of the suction and discharge regions 510 and 520 in the pump chamber 500. .

Furthermore, since the short diameter side end portion 62 of the cam ring inner periphery 61 is in sliding contact with the outer rotor 30 at high speed, it is necessary to improve the dimensional accuracy. However, since the long diameter side end portion 63 is not always in sliding contact with the outer rotor 30, the long diameter side end portion is required. There is no need to increase the dimensional accuracy of 63. Therefore, it becomes possible to reduce the high-precision machining location in the cam ring 60, and it can be set as the apparatus excellent in processability and cost efficiency. In addition, since the cam ring inner periphery 61 is a long hole, the assemblability is improved.
(Other examples)

  As described above, the best mode for carrying out the present invention has been described based on the first embodiment. However, the specific configuration of the present invention is not limited to each embodiment and does not depart from the gist of the present invention. Such design changes are included in the present invention.

  Further, technical ideas other than the claims that can be grasped from the above embodiments will be described below together with the effects thereof.

(A) In the internal gear pump according to claim 1,
A first oil groove which is a sliding contact surface with the outer rotor of the housing and which is provided on the side of the closing portion and communicates with the first port;
An internal gear pump, further comprising: a second oil groove that is provided on the side of the closing portion and is in a sliding contact surface with the outer rotor of the housing and communicates with the second port.

  The first and second oil grooves positively introduce the high pressures of the first and second ports into the gap between the cam ring and the outer rotor, thereby reducing the amount of leakage at the confined portion and engaging the outer rotor and the inner rotor. Can be improved.

(B) In the internal gear pump according to claim 1,
The housing is provided on the outer peripheral side of the outer rotor and is engaged with the cam ring having an engagement hole, first and second housings provided on both sides in the axial direction of the cam ring, and the first or second A positioning pin for positioning the second member;
An internal gear pump characterized in that a pair of the engagement holes are provided on the first axis.

  By providing the positioning pin on the first axis, it is possible to ensure the positioning accuracy of the cam ring with respect to the first and second housings in the second axis direction. The first and second housings support a drive shaft, and an inner rotor is provided on the drive shaft. That is, the positioning of the inner rotor and the outer rotor in the second axial direction is ensured by ensuring the positioning accuracy in the second axial direction of the cam ring that houses the outer rotor and the first and second housings that hold the inner rotor via the drive shaft. Accuracy can be ensured.

(C) In the internal gear pump according to claim 1,
2. The internal gear pump according to claim 1, wherein the outer rotor accommodating portion is a long hole that is long in the first axial direction in which two semicircles are combined.

  It is possible to easily form the outer rotor accommodating portion whose second axial direction is smaller than the first axial direction.

1 is a system configuration diagram of a power steering device to which an internal gear pump of the present application is applied. It is an axial sectional view of the internal gear pump. It is a top view of the internal gear pump which removed the 2nd housing. It is an axial front view of the first housing. It is a figure which shows the flow of the oil at the time of a pump drive, and the deviation of an outer rotor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal gear pump 1a Motor 10, 20 1st, 2nd housing 11 Z-axis positive | positive direction surface 30 Outer rotor 40 Inner rotor 50 Drive shaft 60 Cam ring 61 Cam ring inner periphery 62 Short diameter side edge part 63 Long diameter side edge part 110,120 Suction , Discharge ports 111, 121 suction, discharge side oil grooves 130, 230 first and second positioning holes 210, 220 suction, discharge port 310 internal gear 320 outer peripheral surface 410 external gear 500 pump chambers 510, 520 suction, discharge area 610, 620 First and second axial holes 630 Positioning pin A y-axis positive direction end B y-axis negative direction end D Clearance D1 y-axis negative direction region D2 y-axis positive direction region

Claims (1)

A housing having an outer rotor accommodating portion;
An outer rotor that is rotatably accommodated in the outer rotor accommodating portion and has an internal gear on the inner peripheral side;
An inner rotor that is rotatably provided on the inner peripheral side of the outer rotor and has an external gear that meshes with the internal gear on the outer peripheral side;
A drive shaft that is connected to the inner rotor and that rotates the inner rotor in forward and reverse directions;
With respect to a first axis connecting a confining portion having a maximum volume and a meshing portion having a minimum volume among a plurality of pump chambers formed between the internal gear of the outer rotor and the external gear of the inner rotor. A first port and a second port that are provided symmetrically and open to the plurality of pump chambers;
The radial gap formed between the outer rotor accommodating portion and the outer rotor is smaller in the second axial direction perpendicular to the first axis and the drive shaft than in the first axial direction. Inscribed gear pump.

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