WO2014148219A1

WO2014148219A1 - Power steering device

Info

Publication number: WO2014148219A1
Application number: PCT/JP2014/054811
Authority: WO
Inventors: 新居　利洋; 石川　正吾
Original assignee: 日立オートモティブシステムズステアリング株式会社
Priority date: 2013-03-22
Filing date: 2014-02-27
Publication date: 2014-09-25
Also published as: JP2014184848A; JP5964775B2; DE112014001565T5

Abstract

The purpose of the present invention is to provide an integral power steering device in which left-right torque differences can be resolved. In this power steering device, when the distance between the meshing point of a rack tooth (71) and a sector gear (8) and the center of rotation (O1) of the sector gear (8) is the pitch radius, the pitch radii r (large) and R (large) when a piston moves in the direction in which the volume of one pressure chamber increases and the pitch radii r (small) and R (small) when the piston moves in the direction in which the volume of the one pressure chamber decreases are formed so as to be mutually differing radii, such that reduced is the difference between the size of the output torque of the sector gear (8) with respect to a steering operation in one turning direction of a steering wheel and the size of the output torque with respect to a steering operation in the other turning direction of the steering wheel.

Description

Power steering device

The present invention relates to a power steering device.

Conventionally, in a power steering apparatus, the technique of Patent Document 1 is known as a technique for eliminating a steering torque difference between left and right steering operations. In this publication, when the assist torque is applied by electronic control, the left-right torque difference is eliminated by giving a characteristic that cancels the left-right difference of the steering load of the vehicle.

Patent Document 1: Japanese Utility Model Publication No. 10-278818

However, a hydraulic power steering device that is not an electric type and has a rotary valve has a problem that the left-right torque difference cannot be eliminated by the electronic control as described above.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an integral type power steering device capable of eliminating the left-right torque difference.

In order to achieve the above object, in the power steering device of the present invention, when the distance between the meshing point of the rack teeth and the sector gear and the rotation center of the sector gear is the radius of the pitch circle, the volume of the second pressure chamber increases. The first pitch circle radius, which is the pitch circle radius when the piston moves in the direction of, and the second pitch circle radius, which is the pitch circle radius when the piston moves in the direction in which the volume of the second pressure chamber decreases, is steered. The radii were formed at different radii so that the difference between the magnitude of the output torque of the sector gear with respect to the steering operation in one direction of the wheel rotation and the magnitude of the output torque with respect to the steering operation in the other direction of the steering wheel was reduced.

In the power steering device of the present invention, when the distance between the meshing point of the rack teeth and the sector gear and the rotation center of the sector gear is the pitch circle radius, the piston moves in the direction in which the volume of the second pressure chamber increases. The first pitch circle radius, which is the pitch circle radius, and the second pitch circle radius, which is the pitch circle radius when the piston moves in the direction in which the volume of the second pressure chamber decreases, is one of the rotational directions of the steering wheel. The teeth are formed in tooth surfaces having different radii so that the difference between the magnitude of the output torque of the sector gear with respect to the steering operation toward the side and the magnitude of the output torque with respect to the steering operation toward the other side in the rotation direction of the steering wheel is reduced.

1 is a cross-sectional view of an integral power steering apparatus according to a first embodiment. It is an expanded sectional view of the sector gear of Example 1. FIG. 3 is a pitch circle radius characteristic diagram showing the relationship between the steering angle of the steering wheel and the pitch circle radius in the power steering apparatus of the first embodiment. FIG. 5 is a schematic diagram illustrating a state in which the rack 70 moves to the right side in FIG. 4 when the left steering is turned in the first embodiment. FIG. 6 is a schematic diagram illustrating a state in which switching is performed after left steering in the first embodiment and the rack moves to the left in FIG. 5. FIG. 7 is a schematic diagram illustrating a state in which the rack 70 moves to the right side in FIG. 6 when the right steering is turned in the first embodiment. FIG. 8 is a schematic diagram illustrating a state in which switching is performed after the right steering in the first embodiment and the rack moves to the left side in FIG. 7. It is a characteristic view showing the gear characteristic of the variable gear ratio gear of Example 1. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a mode for realizing an integral type power steering device of the present invention will be described with reference to the drawings.

First, the overall configuration of the integral type power steering apparatus (hereinafter referred to as apparatus 1) of the first embodiment will be described with reference to FIG. FIG. 1 is a longitudinal sectional view of the device 1 before being mounted on a vehicle, cut along a plane that passes through the rotation center of the input shaft 2 and is perpendicular to the rotation axis of the sector gear 8. Hereinafter, for the sake of explanation, the x-axis is provided in the direction in which the input shaft 2 extends, and the side of the steering wheel (the right side in FIG. 1) is the positive direction.

The apparatus 1 is housed in a housing 10, an input shaft (stub shaft) 2 connected to a steering hole, and the housing 10, and the cylindrical interior of the housing 10 is divided into a first pressure chamber 16 and a second pressure chamber 17. On the outer periphery of the piston 7, the first reduction gear (ball screw mechanism 5) provided between the input shaft 2 and the piston 7 for converting the rotational motion of the input shaft 2 into the axial motion of the piston 7. The rack 70 is provided, and the sector gear 8 that meshes with the rack teeth 71 of the rack 70 to convert the axial motion of the rack 70 (piston 7) into rotational motion and is disposed in the second pressure chamber 17. The second reduction gear, the control valve 6 that selectively supplies hydraulic oil supplied from an external hydraulic source to the first pressure chamber 16 and the second pressure chamber 17, and the rotational movement of the sector gear 8 are linked to each other Transmission mechanism (pitman arm) ), And when the steering wheel rotation angle (steering angle) reaches the required steering angle, the pressure chamber on the high pressure side is depressurized (the pressure chamber on the low pressure side is increased), and the stroke of the piston 7 (moving in the x-axis direction) And a limiter valve 9 which is a stroke limiter to be limited. Note that the rack teeth 71 of the rack 70 are rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio, that is, a constant gear ratio (CGR).

The device 1 is accommodated in the housing 10. The housing 10 is formed in a cylindrical shape with a metal material such as aluminum, and includes a steering housing 11 that houses the piston 7 and the sector gear 8, and a valve housing 12 that is provided on the x-axis positive direction side of the steering housing 11 and houses the control valve 6. And a cover 13 for sealing the opening of the valve housing 12 on the positive side of the x-axis in a liquid-tight manner.

The input shaft 2 is rotatably supported on the cover 13 via a ball bearing 130. A hollow portion 20 is formed at the end of the input shaft 2 on the negative side of the x axis, and the end of the torsion bar 3 on the positive side of the x axis is inserted into the hollow portion 20. The outer periphery of the input shaft 2 on the x-axis negative direction side is inserted inside the rotor 60 formed in a substantially cylindrical shape. The input shaft 2, the torsion bar 3, and the rotor 60 are fixed by a pin 30 so as to rotate integrally. A screw shaft 4 is connected to the input shaft 2 via a torsion bar 3. A valve body 61 is formed integrally with the screw shaft 4 on the positive side of the screw shaft 4 in the x-axis direction. The valve body 61 is rotatably supported on the valve housing 12 via a ball bearing 120. A hollow rotor accommodating portion 610 is formed in the valve body 61, and the rotor 60 is rotatably accommodated in the rotor accommodating portion 610. A hollow torsion bar accommodating portion 40 is formed on the screw shaft 4 so as to communicate with the rotor accommodating portion 610, and the torsion bar 3 is accommodated in the torsion bar accommodating portion 40. The outer periphery of the x-axis negative direction end of the input shaft 2 is inserted inside the x-axis positive direction end of the torsion bar accommodating portion 40 and is rotatably supported by a bearing 41. The end of the torsion bar 3 on the negative side of the x axis is fixed to the end of the screw shaft 4 on the negative side of the x axis by a pin 31.

A piston 7 is provided on the screw shaft 4 via a ball screw mechanism 5 so as to be movable in the x-axis direction. The piston 7 is accommodated in a cylindrical cylinder portion 14 formed in the steering housing 11. The end of the cylinder part 14 on the x-axis positive direction side is open, but the end of the x-axis negative direction side is closed by the bottom part 140. The sector gear 8 is accommodated in a gear chamber 15 formed in the steering housing 11 and in a direction orthogonal to the cylinder portion 14. A pitman arm is connected to the sector gear 8. A piston seal 70 a is attached to the outer periphery of the piston 7. The cylinder portion 14 is divided into a first pressure chamber 16 and a second pressure chamber 17 by the piston seal 70a to constitute a power cylinder. The first pressure chamber 16 is located on the x-axis negative direction side of the piston seal 70 a of the cylinder portion 14, and the second pressure chamber 17 is located on the x-axis positive direction side of the piston seal 70 a of the cylinder portion 14 and the gear chamber 15.

The control valve 6 has a rotor 60 and a valve body 61. On the outer periphery of the rotor 60, a plurality of switching grooves 600 extending in the x-axis direction are provided at predetermined intervals. A plurality of first axial grooves 611 and second axial grooves 612 extending in the x-axis direction are formed at predetermined intervals on the inner periphery of the rotor housing portion 610 of the valve body 61 facing the outer periphery of the rotor 60. A suction side circumferential groove 121 and a first pressure chamber side circumferential groove 122 extending in the circumferential direction are formed on the inner circumferential surface of the valve housing 12 facing the outer circumference of the valve body 61 so as to be separated from each other in the x-axis direction. ing.

The valve body 61 has a first oil passage 613 communicating with the first axial groove 611 and the first pressure chamber side circumferential groove 122, and a second oil communicating with the second axial groove 612 and the second pressure chamber 17. A third oil passage 615 that connects the passage 614 and the inner periphery and the outer periphery of the valve body 61 is formed. The valve housing 12 is connected to a suction port 123 connected to an external oil pump, a fourth oil passage 124 communicating the suction port 123 and the suction side circumferential groove 121, and a first pressure chamber side circumferential groove 122. A fifth oil passage 125 is formed. A sixth oil passage 126 that connects the fifth oil passage 125 and the first pressure chamber 16 is formed in the steering housing 11. The switching groove 600 of the rotor 60, the first axial groove 611 of the valve body 61, and the second axial groove 612 of the hydraulic oil from the oil pump are caused by relative rotation between the input shaft 2 (rotor 60) and the valve body 61. A control valve 6 for switching the supply destination between the first pressure chamber 16 and the second pressure chamber 17 is formed.

The piston 7 is provided with a communication passage provided so as to communicate the first pressure chamber 16 and the second pressure chamber 17, and a first bleeding valve 21 is provided on the communication passage. The first bleeding valve 21 is composed of a spherical valve body provided in the middle of the communication path, valve seats formed on both sides of the valve body, and a pair of springs that urge the valve body from both sides. Yes. When the engine is off or running straight ahead, there is no differential pressure between the first pressure chamber 16 and the second pressure chamber 17, so the pair of springs causes the valve body to float from the valve seats on both sides. The pressure chamber 16 and the second pressure chamber 17 are in communication with each other. Since the device 1 is mounted on the vehicle so that the input shaft 2 faces vertically upward, the air accumulated in the first pressure chamber 16 is discharged to the second pressure chamber 17 side through the first bleeding valve 21. Is done.

On the other hand, the valve housing 21 is provided with a communication passage that communicates the second pressure chamber 17 and a discharge port (not shown), and a second bleeding valve having the same structure as the first bleeding valve 21 is provided on the communication passage. 22 is provided. Therefore, in the state where no differential pressure is generated between the second pressure chamber 17 and the discharge port, the air accumulated in the second pressure chamber 17 or the air discharged into the second pressure chamber via the first bleeding valve 21 Is discharged to the reservoir tank through the second bleeding valve and the discharge port.

When a differential pressure is generated between the chambers on both sides of the communication path, the first bleeding valve 21 and the second bleeding valve 22 are seated on the valve seat and block the communication of the communication path. The pressures in the first pressure chamber 16 and the second pressure chamber 17 can be appropriately maintained.

The second bleeding valve 22 can be omitted if necessary.

The limiter valve 9 reduces the pressure in the second pressure chamber 17 to the first pressure chamber 16 side when the piston 7 moves to the first predetermined position in the direction in which the volume of the first pressure chamber 16 decreases (x-axis negative direction). When the piston 7 moves to the second predetermined position in the direction in which the volume of the first valve 9a and the second pressure chamber 17 decreases (the x-axis positive direction) decreases, the pressure in the first pressure chamber 16 is And a second valve 9b that discharges to the pressure chamber 17 side. A first valve 9a is mounted on the steering housing 11 toward the first pressure chamber 16, and a second valve 9b is mounted on the second pressure chamber 17 (gear chamber 15). The first valve 9a and the second valve 9b are connected by a seventh oil passage 18 formed in the steering housing 11. FIG. 1 shows the first valve 9a and the second valve 9b in a state before the device 1 is mounted on the vehicle (before the position of the valve body 91 or the pin 95 is adjusted).

(Steering assist function)
When the steering wheel is steered so that the piston 7 moves to the first pressure chamber 16 side (x-axis negative direction side), hydraulic oil is supplied to the second pressure chamber 17 by the control valve 6. That is, the hydraulic oil discharged from the oil pump is suction port 123 → fourth oil passage 124 → first axial groove 611 → third oil passage 615 → switching groove 600 → second axial groove 612 → second oil passage. It passes through 614 and is supplied to the second pressure chamber 17. Since the pressure in the second pressure chamber 17 rises and an assist force that moves the piston 7 toward the first pressure chamber 16 acts by this pressure, the driver can steer the steering wheel with a light force.

On the other hand, when the steering wheel is steered so that the piston 7 moves to the second pressure chamber 17 side (x-axis positive direction side), hydraulic oil is supplied to the first pressure chamber 16 by the control valve 6. That is, the hydraulic oil discharged from the oil pump is suction port 123 → fourth oil passage 124 → first axial groove 611 → third oil passage 615 → switching groove 600 → first axial groove 611 → first oil passage 613 → the first pressure chamber side circumferential groove 122 → the fifth oil passage 125 → the sixth oil passage 126 is passed through and supplied to the first pressure chamber 16. Since the pressure in the first pressure chamber 16 rises and an assist force that moves the piston 7 toward the second pressure chamber 17 acts by this pressure, the driver can steer the steering wheel with a light force.

(Sector gear configuration)
Next, details of the configuration of the sector gear 8 of the first embodiment will be described. When applying the assist torque during left and right steering with the above configuration, it has been found that even if the same assist torque is applied during left and right steering, a slight torque difference occurs between the left and right during actual steering. In the first embodiment, the first pressure chamber 16 has a smaller hydraulic chamber volume and higher hydraulic rigidity than the second pressure chamber 17 in which the rack 70 and the sector gear 8 are accommodated. On the other hand, since the rack 70 and the sector gear 8 are accommodated in the second pressure chamber 17, the housing volume becomes relatively large with respect to the first pressure chamber 16. As a result, there is a possibility that the degree of influence of expansion deformation of the housing due to pressure or the amount of hydraulic fluid leaking from the pressure chamber may increase, and a decrease in hydraulic rigidity may cause a difference in left and right steering torque.

Therefore, in order to eliminate this left-right torque difference, the tooth surface shape of the sector gear 8 has been devised, thereby eliminating the left-right torque difference and providing a variable gear ratio (variable gear ratio) to change the steering gear ratio. It was decided to. Hereinafter, the tooth surface shape of the sector gear 8 will be described.

FIG. 2 is an enlarged sectional view of the sector gear according to the first embodiment. The sector gear 8 has a center O1 that is a connection point of the pitman arms and serves as a rotational center of the rotational motion. And it has a plurality of teeth which are arranged in the circumferential direction of the circumference having the center O1 and meshes with the rack teeth 71 of the rack 70, and in this embodiment, three teeth are provided. Further, a variable gear ratio is provided in which the plurality of teeth arranged in the circumferential direction have different reduction ratios. When this tooth meshes with the rack tooth 71 to rotate the sector gear 8, the steering gear ratio, which is the ratio of the amount of rotation of the sector gear 8 to the amount of movement of the rack 70, differs between right steering and left operation. It is formed (see FIG. 8).

Here, the left tooth in FIG. 2 is a tooth a, the central tooth is a tooth b, and the right tooth is a tooth c. The teeth a and c are formed in different shapes on the left and right tooth surfaces of each tooth a, tooth b, and tooth c, and the tooth b is formed in a symmetrical shape. In the state where the steering wheel is in the neutral position, the rack teeth 71 and the sector gear 8 have meshing points at neutral positions b1 and b2 located substantially at the center of the tooth surface of the tooth b.

When the steering wheel is steered to the right, the rack 70 moves to the left in FIG. 1, and the rack tooth 71 and the sector gear 8 have meshing points on the tooth surface b (1) of the tooth b at the start of steering. The point moves on the tooth surface b (1) toward the lower right side in FIG. 2 (hereinafter, this movement state is referred to as the (1) state). Thereafter, by further steering the steering wheel to the right, the mesh point moves between the tooth surface c (2) of the tooth c and the rack tooth 71, and this mesh point moves on the tooth surface c (2) in FIG. It moves toward the lower right side (hereinafter, this movement state is described as (2) state). Here, the angle at which the meshing point moves from the tooth surface b (1) of the tooth b to the tooth surface c (2) of the tooth c is set as a predetermined angle, and the output is different from when the tooth b is in contact with the tooth b. The characteristic is set. The tooth surface c (2) is formed on the tooth tip side with respect to the intermediate portion in the tooth height direction of the tooth c, and details will be described later.

When the steering wheel is cut to the right and then turned back toward the neutral position, the meshing point moves between the rack tooth 71 and the tooth surface c (2-1) of the tooth c. Then, after the meshing point moves on the tooth surface c (2-1) (hereinafter, this movement state is described as the (2-1) state), it meshes with the tooth surface b (1-1) of the tooth b. The point moves and then moves to the neutral position b2 (hereinafter, this moving state is referred to as the (1-1) state).

Similarly, when the steering wheel is steered to the left, the rack 70 advances to the right in FIG. 1, and the rack tooth 71 and the sector gear 8 have a meshing point on the tooth surface b (3) of the tooth b at the start of steering. The meshing point moves on the tooth surface b (3) toward the lower left side in FIG. 2 (hereinafter, this moving state is referred to as the (3) state). Thereafter, by further steering the steering wheel to the left side, the meshing point moves from the tooth surface b (3) between the rack tooth 71 and the tooth surface a (4) of the tooth a, and this meshing point is the tooth surface a. (4) Move upward on the left side in FIG. 2 (hereinafter, this movement state is described as (4)). Here, the angle at which the meshing point moves from the tooth surface b (3) of the tooth b to the tooth surface a (4) of the tooth a is set as a predetermined angle, and the output is different from when the tooth b is in contact with the tooth b. The characteristic is set. The tooth surface a (4) is formed on the tooth tip side with respect to the intermediate portion in the tooth height direction of the tooth a, and details will be described later.

When the steering wheel is cut to the left side and then turned back toward the neutral position, the meshing point moves between the rack tooth 71 and the tooth surface a (4-1) of the tooth a. Then, after the meshing point moves on the tooth surface a (4-1) (hereinafter, this movement state is described as the (4-1) state), it meshes with the tooth surface b (3-1) of the tooth b. The point moves and then moves to the neutral position b1 (hereinafter, this moving state is referred to as (3-1) state).

Here, the distance connecting the rotation center O1 of the sector gear 8 and the mesh point is defined as the pitch circle radius PCR. A large pitch circle radius means that the distance between the rotation center O1 and the meshing point is large, and the lever ratio increases, so that even if the same force is applied from the rack 70 to the sector gear 8, the pitman arm rotates. This means that the moving torque increases.

FIG. 3 is a pitch circle radius characteristic diagram showing the relationship between the steering angle of the steering wheel and the pitch circle radius in the power steering apparatus of the first embodiment. Near the center of the operating angle is a region achieved by the tooth b, the tooth surface of the tooth b has a symmetrical shape, and the pitch circle radius is also symmetrical on the left and right. Further, the (1) state and the (1-1) state are set to the same pitch circle radius PCR, and the (3) state and the (3-1) state are set to the same pitch circle radius PCR. FIG. 3 also shows the pitch circle radii in the teeth a and c in addition to the teeth b, and the setting of the pitch circle radius will be described later.

FIGS. 4 to 7 are schematic explanatory diagrams showing the hydraulic pressure relationship in the hydraulic chamber and the direction in which the force acts when turning and turning back at a certain steering angle during left and right steering. FIG. 4 shows a state where the rack 70 moves to the right side in FIG. 4 when the left steering is turned. Since the first hydraulic chamber 16 is a high pressure chamber and the second hydraulic chamber 17 is a low pressure chamber, the meshing point is the tooth surface a (4) of the tooth a. At this time, high pressure is introduced into the first hydraulic pressure chamber 16 having high hydraulic rigidity, so that a large pitch circle radius is not necessary, and the pitch circle radius is set as r (small). The state of FIG. 4 is defined as (i) state.

FIG. 5 shows a state in which switching back after left steering is performed and the rack 70 moves to the left side in FIG. Since the first hydraulic chamber 16 is a low-pressure chamber and the second hydraulic chamber 17 is a high-pressure chamber, the meshing point is on the tooth surface a (4-1) of the tooth a. At this time, since a high pressure is introduced into the second hydraulic chamber 17 having low hydraulic rigidity, a large pitch circle radius is required, and the pitch circle radius is set to r (large) (> r (small)). Yes. The state of FIG. 5 is defined as (ii) state.

Fig. 6 shows a state in which the rack 70 moves to the left side in Fig. 6 when the right steering is turned. Since the first hydraulic chamber 16 is a low pressure chamber and the second hydraulic chamber 17 is a high pressure chamber, the meshing point is on the tooth surface c (2) of the tooth c. At this time, since the high pressure is introduced into the second hydraulic pressure chamber 17 with low hydraulic rigidity, and a larger pitch circle radius is required than when turning the left steering, the pitch circle radius is set as R (large). Yes. The state of FIG. 6 is defined as (iii) state.

FIG. 7 shows a state in which switching is performed after the right steering and the rack 70 moves to the right side in FIG. Since the first hydraulic chamber 16 is a high pressure chamber and the second hydraulic chamber 17 is a low pressure chamber, the meshing point is on the tooth surface c (2-1) of the tooth c. At this time, since a high pressure is introduced into the first hydraulic chamber 16 having high hydraulic rigidity, a large pitch circle radius is not required, so the pitch circle radius is R (small) (<R (large)). Is set. The state of FIG. 7 is defined as (iv) state.

Referring back to FIG. 3, the setting of the pitch circle radius of the teeth a and c will be described. When left steering is started from the neutral position, the state shifts to the (4) state through the (3) state. The state (i) in FIG. 4 represents the state at a certain angle of the state (4) in FIG. During left steering, since the high pressure is introduced into the first hydraulic chamber 16 having high hydraulic rigidity, it is necessary to make the lever ratio smaller than that during right steering. Therefore, pitch circle radii r (small) and r (large) smaller than pitch circle radii R (small) and R (large) during right steering are set.

Next, when steering is performed to return to the neutral position from the time of turning the left steering, the state shifts to the (3-1) state via the (4-1) state in FIG. The state (ii) in FIG. 5 represents a state at an angle of the state (4-1) in FIG. When switching back after left steering, the second hydraulic chamber 17 having a large volume is a high-pressure chamber, so the lever ratio needs to be increased. Therefore, a larger pitch circle radius r (large) than the pitch circle radius r (small) in the state (i) is set.

When starting the right steering from the neutral state, it shifts to the (2) state via the (1) state. The state (iii) in FIG. 6 represents the state at a certain angle of the state (2) in FIG. Since the high pressure is introduced into the second hydraulic chamber 17 having a low hydraulic rigidity during the right steering, it is necessary to increase the lever ratio as compared with the left steering. Therefore, pitch circle radii R (small) and R (large) larger than the pitch circle radii r (small) and r (large) during left steering are set.

Next, when steering is performed to return to the neutral position from the time of turning the right steering, the state shifts to the (1-1) state via the (2-1) state. The state (iv) in FIG. 7 represents the state at a certain angle of the state (2-1) in FIG.

When turning back after right steering, the first hydraulic chamber 16 with high hydraulic rigidity is a high-pressure chamber, so there is no need to increase the lever ratio. Therefore, a pitch circle radius R (small) smaller than the pitch circle radius R (large) in the state (iii) is set.

That is, the tooth surface profile of a (4) and c (2) is different from the tooth surface profile composed of a (4-1) and c (2-1). At this time, since the rack teeth 71 of the rack 70 are formed with a constant gear ratio, there is no need to adjust the molding of the rack 70 when changing the steering gear ratio, and the rack teeth can be easily formed.

FIG. 8 is a characteristic diagram showing gear characteristics of the variable gear ratio gear of the first embodiment. As described above, when the pitch circle radius is set according to the steering angle and is set as the variable gear ratio gear, it is necessary to rotate the sector gear 8 more as the pitch circle radius becomes larger. Therefore, as shown in FIG. 8, the variable gear ratio with respect to the steering angle is set to be larger as the right steering is performed. Accordingly, the steering amount of the steered wheel with respect to the operation amount of the steering wheel maintains the same relationship regardless of whether the steering wheel is steered to the left or right.

Further, regions where different pitch circle radii are formed on the teeth a and teeth c are the rack teeth 71 in both the cutting process for forming the tooth surface shape of the rack teeth 71 or the sector gear 8 by cutting and the polishing process for polishing. Alternatively, it is formed by processing the sector gear 8. By forming the region in the cutting process, a larger output characteristic difference can be corrected.

Further, by forming the region in the polishing process, it is possible to correct the output characteristic difference more precisely.
Effects of First Embodiment Hereinafter, effects that the device 1 of the first embodiment has will be listed.

(1) A housing 10 formed in a cylindrical shape with a metal material, an input shaft 2 connected to a steering wheel and a torsion bar 3 connected to the torsion bar housing portion 40 ( Output shaft) and the piston 7 provided in the housing 11 so as to be movable in the axial direction when the direction in which the rotation shaft of the torsion bar accommodating portion 40 extends is defined as the axial direction. A piston seal 70a (seal part) that is divided into a first pressure chamber 16 provided on one side in the axial direction and a second pressure chamber 17 provided on the other side in the axial direction; Hydraulic fluid supplied from an external hydraulic pressure source, which is accommodated in the provided valve housing 12 (rotary valve accommodating portion), is actuated by relative rotation between the input shaft 2 and the torsion bar accommodating portion 40. Selective The ball screw mechanism 5 (first shaft) that converts the rotational motion of the rotor 60 (rotary valve) supplied to the first pressure chamber 16 and the second pressure chamber 17 and the torsion bar housing portion 40 into the axial motion of the piston 7. And a rack tooth 71 formed on one side of the piston 7 in the axial direction from the piston seal 70a of the piston 7 and disposed in the second pressure chamber, and in the second pressure chamber 17 so as to mesh with the rack tooth 71 A second reduction gear configured to transmit a steering force to the steered wheels by converting the axial motion of the piston 7 into a rotational motion, and a rack tooth 71 and a sector gear 8. Is the pitch circle radius PCR, the pitch circle when the piston 7 moves in the direction in which the volume of the second pressure chamber 17 increases. Radius r (large), R (large) (first pitch circle radius) and the volume of the second pressure chamber 17 are reduced. The pitch circle radii r (small) and R (small) (second pitch circle radius) when the piston 7 moves in the direction are the magnitude of the output torque of the sector gear 8 with respect to the steering operation in one direction of the steering wheel rotation. And different radii so as to reduce the difference in the magnitude of the output torque with respect to the steering operation to the other side in the rotation direction of the steering wheel.

Therefore, it is possible to correct the output characteristic difference for each rotation direction of the steering wheel due to the housing shape or the like.

(2) In the power steering device described in (1) above, the pitch circle radii r (large) and R (large) are formed to be larger than the pitch circle radii r (small) and R (small).

That is, since the rack 70 and the sector gear 8 are accommodated on the second pressure chamber 17 side, the housing volume becomes relatively larger than the first pressure chamber 16 side. As a result, the influence of expansion deformation of the housing 10 due to pressure or the amount of hydraulic fluid leakage from the pressure chamber may increase, but these problems can be solved by the magnitude relationship of (2) above.

(3) In the power steering apparatus described in (2) above, the rack teeth 71 are constant gear ratio rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio, and the sector gear 8 rotates. A plurality of teeth a, b, c arranged in the circumferential direction around the rotation center O1 of the motion, and the difference between r (large), R (large) and r (small), R (small) is the sector gear Each of the plurality of 8 teeth is provided such that the profiles of the pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tip are different from each other.

Since the rack tooth 71 side is composed of constant teeth, there is no need to adjust the pitch circle radius on the rack side, and the rack 70 can be easily formed.

(4) In the power steering device described in (2) above, the sector gear 8 is a variable gear having a plurality of teeth a, b, c arranged in the circumferential direction around the rotation center O1 of the rotational motion and having different reduction ratios. The gear ratio sector gear, the difference between r (large), R (large) and r (small), R (small) is formed on both sides of the sector gear 8 across the tooth tip with each tooth The pair of tooth surfaces are formed so as to have different profiles.

That is, since the sector gear 8 is a variable gear ratio gear, a tooth polishing work by computer position control is required for profile formation. By incorporating the pitch circle radius adjustment into the sector gear 8, the variable gear ratio forming step and the pitch circle radius adjustment step can be performed simultaneously.

(5) In the power steering device described in (4) above, the difference between r (large), R (large) and r (small), R (small) is a plurality of teeth a, b, c of the sector gear 8 Among the pair of tooth surfaces, the pair of tooth surfaces are provided so that the profiles of the pair of tooth surfaces are different from each other on the tooth tip side with respect to the intermediate portion in the tooth height direction.

That is, the intermediate portion of the tooth surface in the tooth height direction is near the meshing point when the handle is in the neutral position, and the meshing point when the steering angle is a predetermined angle or more is on the tooth tip side. When such a steering angle is equal to or larger than a predetermined angle, a difference in output characteristics for each steering direction is large. Therefore, adjustment according to the difference in output characteristics can be performed by adjusting the profile on the tooth tip side.

(6) In the power steering device described in (2) above, the difference between r (large), R (large) and r (small), R (small) is that the steering wheel is clockwise and counterclockwise from the neutral position. When rotated clockwise by a predetermined angle or more, r (large) and R (large) are formed to be larger than r (small) and R (small) in the region where the rack teeth 71 and the sector gear 8 mesh. .

Therefore, when the steering angle is equal to or larger than the predetermined angle, the output characteristic difference for each steering direction is large, so that adjustment according to the output characteristic difference can be performed.

(7) In the power steering device described in (6) above, the region formed so that r (large) and R (large) are larger than r (small) and R (small) When the steering operation is performed clockwise from the position and when the steering operation is performed counterclockwise, the same angle range is formed.

Therefore, it is possible to make uniform the output characteristic difference for each rotation direction of the steering wheel.

(8) In the power steering device described in (2) above, the region formed so that r (large) and R (large) are larger than r (small) and R (small) is the rack teeth 71 or It is formed by processing the rack teeth 71 or the sector gear 8 in both the cutting process for forming the tooth surface shape of the sector gear 8 by cutting and the polishing process for polishing.

That is, a larger output characteristic difference can be corrected by forming the region in the cutting process. Further, by forming the region in the polishing process, it is possible to correct the output characteristic difference more precisely.

(9) In the power steering device described in (1) above, of the first pressure chamber 16 and the second pressure chamber 17 out of r (large), R (large) and r (small), R (small) When the hydraulic fluid is supplied to the larger volume side, the pitch circle radius on the side where the rack teeth 71 and the sector gear 8 mesh is larger than the other pitch circle radius.

That is, in the second pressure chamber 17, which is the pressure chamber on the larger volume side, there is a possibility that the influence of expansion deformation of the housing due to pressure or the amount of hydraulic fluid leaking from the pressure chamber will increase. Therefore, this problem can be solved by increasing the pitch circle radius on the side where the rack teeth 71 and the sector gear 8 mesh with each other when the hydraulic fluid is supplied to the larger volume side.

(10) In the power steering apparatus described in (9) above, the rack teeth 71 are constant gear ratio rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio, and the sector gear 8 rotates. A plurality of teeth a, b, c arranged in the circumferential direction around the rotation center O1 of the motion, and the difference between r (large), R (large) and r (small), R (small) is the sector gear Each of the plurality of 8 teeth is provided such that the profiles of a pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tip are different from each other.

(11) In the power steering device according to (9), the sector gear 8 is a variable gear having a plurality of teeth a, b, and c arranged in the circumferential direction around the rotation center O1 of the rotational motion and having different reduction ratios. The gear ratio sector gear, the difference between r (large), R (large) and r (small), R (small) is formed on both sides of the sector gear 8 across the tooth tip with each tooth The pair of tooth surfaces are formed so that the profiles thereof are different from each other.

(12) In the power steering device described in (9) above, the difference between r (large), R (large) and r (small), R (small) is a plurality of teeth a, b, c of the sector gear 8 Of the pair of tooth surfaces, the profile of the pair of tooth surfaces is formed so as to be different from each other on the tooth tip side of the middle portion in the tooth height direction.

That is, the middle portion in the tooth height direction of the tooth surface is near the handle neutral, and the tooth tip side is when the steering angle is equal to or greater than a predetermined angle. When such a steering angle is equal to or greater than a predetermined angle, a difference in output characteristics for each steering direction is large. Therefore, adjustment according to the difference in output characteristics can be performed by performing adjustment on the tooth tip side.

(13) In the power steering device described in (9) above, the difference between r (large), R (large) and r (small), R (small) is predetermined in the clockwise direction from the neutral position of the steering wheel. When the steering wheel rotates more than a predetermined angle and when the steering wheel rotates more than a predetermined angle in the counterclockwise direction from the neutral position, the first pitch circle radius and the second pitch circle radius in the region where the rack teeth 71 and the sector gear 8 mesh with each other are R (large) so that the difference between the magnitude of the output torque of the sector gear with respect to the steering operation in one direction of rotation of the steering wheel and the magnitude of the output torque with respect to the steering operation in the direction of rotation of the steering wheel is reduced. , R (large), r (small), and R (small) are formed at different radii.

(14) In the power steering device described in (13) above, the magnitude of the output torque of the sector gear 8 with respect to the steering operation in one direction of the rotation of the steering wheel and the output torque with respect to the steering operation in the other direction of the steering wheel. The region where r (large), R (large), r (small), and R (small) are formed at different radii is steered clockwise from the neutral position of the steering wheel so that the difference from the size decreases. The same angle range is formed when the operation is performed and when the steering operation is performed counterclockwise.

(15) In the power steering device described in (9) above, the magnitude of the output torque of the sector gear 8 with respect to the steering operation in one direction of rotation of the steering wheel and the output torque with respect to the steering operation in the other direction of rotation of the steering wheel. The areas where r (large), R (large) and r (small), R (small) are formed at different radii so that the difference from the size is reduced are the tooth surface shape of the rack tooth 71 or sector gear 8. It is formed by processing the rack teeth 71 or the sector gear 8 in both the cutting process formed by cutting and the polishing process for polishing.

(16) A housing 10 formed in a cylindrical shape with a metal material, an input shaft 2 connected to the steering wheel, and a torsion bar 3 connected to the torsion bar accommodating portion 40 ( Output shaft), and the direction in which the rotation axis of the torsion bar accommodating portion 40 extends is defined as the axial direction, the piston 7 provided in the housing 11 so as to be movable in the axial direction, A piston seal 70a (seal part) that is divided into a first pressure chamber 16 provided on one side in the axial direction and a second pressure chamber 17 provided on the other side in the axial direction, and a housing 10 are provided. Selects the hydraulic fluid supplied from an external hydraulic pressure source, which is accommodated in the valve housing 12 (rotary valve accommodating portion) and the valve housing 12 and operates with relative rotation between the input shaft 2 and the torsion bar accommodating portion 40. Above A ball screw mechanism 5 (first reduction gear) that converts the rotational motion of the rotor 60 (rotary valve) supplied to the first pressure chamber 16 and the second pressure chamber 17 and the rotational motion of the torsion bar housing 40 into the axial motion of the piston 7 ) And a rack tooth 71 formed on one side of the piston 7 in the axial direction from the piston seal 70a of the piston 7 and disposed in the second pressure chamber, and provided in the second pressure chamber 17 so as to mesh with the rack tooth 71. A second gear reducer configured to transmit a steering force to the steered wheels by converting the axial movement of the piston 7 into a rotational movement, and the meshing of the rack teeth 71 and the sector gear 8 When the distance between the center point and the rotation center O1 of the sector gear 8 is the pitch circle radius PCR, the second speed reducer uses the pitch circle radius r when the piston 7 moves in the direction in which the volume of the second pressure chamber 17 increases. (Large), R (Large) (first pitch circle radius) and the direction in which the volume of the second pressure chamber 17 decreases The pitch circle radii r (small) and R (small) (second pitch radii) when the piston 7 moves are the magnitude of the output torque of the sector gear 8 and the steering for the steering operation in one direction of the steering wheel rotation. Tooth surfaces having different radii are formed so that the difference in the magnitude of the output torque with respect to the steering operation toward the other side in the rotational direction of the wheel is reduced.

(17) In the power steering device described in (16) above, the difference between r (large), R (large) and r (small), R (small) is predetermined in the clockwise direction from the neutral position of the steering wheel. R (L), R (L) and r (S) in the region where the rack teeth 71 and the sector gear 8 mesh with each other when the wheel rotates more than an angle or when the steering wheel rotates more than a predetermined angle counterclockwise from the neutral position. , R (small) so that the difference between the magnitude of the output torque of the sector gear 8 for the steering operation in one direction of the steering wheel rotation and the magnitude of the output torque for the steering operation in the other direction of the steering wheel is reduced. Are formed at different radii.

(18) In the power steering device according to (17), the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the output torque with respect to the steering operation in the other direction of rotation of the steering wheel The region where r (large), R (large) and r (small), R (small) are formed at different radii so that the difference in size of the steering wheel is different from the neutral position of the steering wheel in the clockwise direction. When the steering operation is performed in the same direction and when the steering operation is performed in the counterclockwise direction, the same angle range is formed.

(19) In the power steering device described in (16) above, the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the output torque with respect to the steering operation in the other direction of rotation of the steering wheel In order to reduce the difference in size, the area where r (large), R (large) and r (small), R (small) are formed at different radii is the rack tooth 71 or the tooth of the sector gear 8 It is formed by processing the rack teeth 71 or the sector gear 8 in both the cutting process for forming the surface shape by cutting and the polishing process for polishing.

Therefore, in the brake device according to each of the above-described embodiments of the present invention, the liquid leakage portion can be specified while generating a braking force.

As mentioned above, although the form for implementing this invention was demonstrated based on the Example, the concrete structure of this invention is not limited to the structure shown in the Example, and is the range which does not deviate from the summary of invention. Any design changes are included in the present invention.

This application claims priority based on Japanese Patent Application No. 2013-060852 filed on Mar. 22, 2013. The entire disclosure including the specification, claims, drawings, and abstract of Japanese Patent Application No. 2013-060852 filed on March 22, 2013 is incorporated herein by reference in its entirety.

The entire disclosure including the specification, claims, drawings, and abstract of Japanese Utility Model Publication No. 10-278818 is incorporated herein by reference in its entirety.
Explanation of symbols
2 Input shaft
5 Ball screw mechanism (first reduction gear)
6 Control valve
7 Piston
70 racks (second reducer)
8 Sector gear (second reducer)
10 Housing
11 Steering housing
12 Valve housing (rotary valve housing)
16 First pressure chamber
17 Second pressure chamber
60 Rotor (rotary valve)
70a Piston seal (seal part)

Claims

A housing formed in a cylindrical shape with a metal material;
An input shaft connected to the steering wheel and an output shaft connected via a torsion bar and provided rotatably in the housing;
When the direction in which the rotation shaft of the output shaft extends is an axial direction, a piston provided in the housing so as to be movable in the axial direction;
A seal portion provided in the piston, the interior of the housing being separated into a first pressure chamber provided on one side in the axial direction and a second pressure chamber provided on the other side in the axial direction; ,
A rotary valve housing provided in the housing;
The first pressure chamber and the second pressure chamber are accommodated in the rotary valve accommodating portion, operate according to the relative rotation of the input shaft and the output shaft, and selectively supply hydraulic fluid supplied from an external hydraulic pressure source. A rotary valve to be supplied to
A first speed reducer that converts rotational movement of the output shaft into movement of the piston in the axial direction;
A rack tooth that is formed on the other side in the axial direction from the seal portion of the piston and is disposed in the second pressure chamber; and is provided in the second pressure chamber so as to mesh with the rack tooth, A sector gear that transmits a steering force to the steered wheels by converting the axial motion of the piston into a rotational motion, and a second speed reducer comprising:
When the distance between the meshing point of the rack teeth and the sector gear and the rotation center of the sector gear is the pitch circle radius,
The second speed reducer includes a first pitch circle radius that is the pitch circle radius when the piston moves in a direction in which the volume of the second pressure chamber increases, and a direction in which the volume of the second pressure chamber decreases. The second pitch circle radius, which is the pitch circle radius when the piston moves, is the magnitude of the output torque of the sector gear with respect to the steering operation to one side of the rotation direction of the steering wheel and to the other side of the rotation direction of the steering wheel. A power steering device having different radii so as to reduce a difference between the magnitude of the output torque and the steering operation.
2. The power steering device according to claim 1, wherein the first pitch circle radius is formed to be larger than the second pitch circle radius.
3. The power steering apparatus according to claim 2, wherein the rack teeth are constant gear ratio rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio,
The sector gear includes a plurality of teeth arranged in a circumferential direction around the rotational center of the rotational movement,
The difference between the first pitch circle radius and the second pitch circle radius is that a profile of a pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tip for each of the plurality of teeth of the sector gear. A power steering device provided by being formed differently from each other.
The power steering device according to claim 2, wherein the sector gear is a variable gear ratio sector gear in which a plurality of teeth arranged in a circumferential direction around the rotation center of the rotational motion have different reduction ratios,
The difference between the first pitch circle radius and the second pitch circle radius is that the profile of the pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tips for each of the plurality of teeth of the sector gear is mutually A power steering device provided by being formed differently.
5. The power steering device according to claim 4, wherein a difference between the first pitch circle radius and the second pitch circle radius is a tooth height direction of the pair of tooth surfaces of the plurality of teeth of the sector gear. A power steering device, wherein the pair of tooth surfaces are formed so as to be different from each other on the tooth tip side with respect to the intermediate portion.
3. The power steering device according to claim 2, wherein a difference between the first pitch extension radius and the second pitch circle radius is obtained when the steering wheel rotates a predetermined angle or more in a clockwise direction and a counterclockwise direction from a neutral position. The power steering apparatus according to claim 1, wherein the first pitch circle radius is larger than the second pitch circle radius in a region where the rack teeth and the sector gear mesh.
7. The power steering device according to claim 6, wherein the region formed such that the first pitch circle radius is larger than the second pitch circle radius is when the steering operation is performed clockwise from a neutral position of a steering wheel. And a power steering device formed in the same angle range when the steering operation is performed counterclockwise.
3. The power steering device according to claim 2, wherein the region formed so that the first pitch circle radius is larger than the second pitch circle radius is obtained by cutting a tooth surface shape of the rack tooth or the sector gear. A power steering device characterized by being formed by processing the rack teeth or the sector gear in both the cutting step to be formed and the polishing step to perform polishing.
2. The power steering device according to claim 1, wherein hydraulic fluid is supplied to a larger volume side of the first pressure chamber and the second pressure chamber of the first pitch radius and the second pitch circle radius. The power steering device is characterized in that the pitch circle radius on the side where the rack teeth and the sector gear mesh with each other is larger than the other pitch circle radius.
10. The power steering device according to claim 9, wherein the rack teeth are constant gear ratio rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio,
The sector gear includes a plurality of teeth arranged in a circumferential direction around the rotational center of the rotational movement,
The difference between the first pitch circle radius and the second pitch circle radius is that a profile of a pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tip for each of the plurality of teeth of the sector gear. A power steering device provided by being formed differently from each other.
The power steering device according to claim 9, wherein the sector gear is a variable gear ratio sector gear in which a plurality of teeth arranged in a circumferential direction around the rotation center of the rotational motion have different reduction ratios,
The difference between the first pitch circle radius and the second pitch circle radius is that a profile of a pair of tooth surfaces formed on both sides in the circumferential direction across the tooth tip for each of the plurality of teeth of the sector gear. A power steering device provided by being formed differently from each other.
10. The power steering device according to claim 9, wherein a difference between the first pitch circle radius and the second pitch circle radius is an intermediate in a tooth height direction among the pair of tooth surfaces of the plurality of teeth of the sector gear. The power steering device is provided by forming the pair of tooth surfaces so that the profiles of the pair of tooth surfaces are different from each other on the tooth tip side of the portion.
10. The power steering device according to claim 9, wherein when the steering wheel rotates a predetermined angle or more clockwise from the neutral position and when the steering wheel rotates a predetermined angle or more counterclockwise from the neutral position, the rack teeth and In the region where the sector gear meshes, the first pitch circle radius and the second pitch circle radius are the magnitude of the output torque of the sector gear with respect to the steering operation to one side of the steering wheel rotation direction and the other side of the steering wheel rotation direction. A power steering device having different radii so as to reduce a difference in magnitude of the output torque with respect to a steering operation.
14. The power steering device according to claim 13, wherein the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the magnitude of the output torque with respect to a steering operation in the other direction of rotation of the steering wheel. The first pitch circle radius and the second pitch circle radius are formed in different radii so that the difference is reduced when the steering wheel is steered clockwise from the neutral position of the steering wheel and counterclockwise. A power steering device characterized by being formed in the same angle range when a steering operation is performed in a direction.
10. The power steering apparatus according to claim 9, wherein the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the magnitude of the output torque with respect to a steering operation in the other direction of rotation of the steering wheel. A region in which the first pitch circle radius and the second pitch circle radius are formed to have different radii so as to reduce the difference is a cutting step of forming a tooth surface shape of the rack tooth or the sector gear by cutting, and The power steering device is formed by processing the rack teeth or the sector gear in both of the polishing steps for polishing.
A housing formed in a cylindrical shape with a metal material;
An input shaft connected to the steering wheel and an output shaft connected via a torsion bar and provided rotatably in the housing;
When the direction in which the rotation shaft of the output shaft extends is an axial direction, a piston provided in the housing so as to be movable in the axial direction;
A seal portion provided in the piston, the interior of the housing being separated into a first pressure chamber provided on one side in the axial direction and a second pressure chamber provided on the other side in the axial direction; ,
A rotary valve housing provided in the housing;
The first pressure chamber and the second pressure chamber are accommodated in the rotary valve accommodating portion, operate according to the relative rotation of the input shaft and the output shaft, and selectively supply hydraulic fluid supplied from an external hydraulic pressure source. A rotary valve to be supplied to
A first speed reducer that converts rotational movement of the output shaft into movement of the piston in the axial direction;
A rack tooth that is formed on the other side in the axial direction from the seal portion of the piston and is disposed in the second pressure chamber; and is provided in the second pressure chamber so as to mesh with the rack tooth, A sector gear that transmits a steering force to the steered wheels by converting the axial motion of the piston into a rotational motion, and a second speed reducer comprising:
When the distance between the meshing point of the rack teeth and the sector gear and the rotation center of the sector gear is the pitch circle radius,
The second speed reducer includes a first pitch circle radius that is the pitch circle radius when the piston moves in a direction in which the volume of the second pressure chamber increases, and a direction in which the volume of the second pressure chamber decreases. The second pitch circle radius, which is the pitch circle radius when the piston moves, is the magnitude of the output torque of the sector gear with respect to the steering operation to one side of the steering wheel rotation direction and the other side of the steering wheel rotation direction. A power steering device having a tooth surface shape having different radii so as to reduce a difference in magnitude of the output torque with respect to the steering operation.
17. The power steering device according to claim 16, wherein the rack teeth and the steering wheel are rotated when the steering wheel is rotated by a predetermined angle or more clockwise from the neutral position and when the steering wheel is rotated by a predetermined angle or more counterclockwise from the neutral position. In the region where the sector gear is engaged, the first pitch circle radius and the second pitch circle radius are the magnitude of the output torque of the sector gear with respect to the steering operation in one direction of the steering wheel rotation and the other direction in the rotation direction of the steering wheel. A power steering device having different radii so as to reduce a difference in magnitude of the output torque with respect to the steering operation.
18. The power steering device according to claim 17, wherein the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the magnitude of the output torque with respect to a steering operation in the other direction of rotation of the steering wheel. The first pitch circle radius and the second pitch circle radius are formed in different radii so that the difference is reduced when the steering wheel is steered clockwise from the neutral position of the steering wheel and counterclockwise. A power steering device characterized by being formed in the same angle range when a steering operation is performed in a direction.
17. The power steering device according to claim 16, wherein the magnitude of the output torque of the sector gear with respect to a steering operation in one direction of rotation of the steering wheel and the magnitude of the output torque with respect to a steering operation in the other direction of rotation of the steering wheel. A region in which the first pitch circle radius and the second pitch circle radius are formed to have different radii so as to reduce the difference is a cutting step of forming a tooth surface shape of the rack tooth or the sector gear by cutting, and The power steering device is formed by processing the rack teeth or the sector gear in both of the polishing steps for polishing.