JP5964775B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering apparatus.

  Conventionally, in a power steering apparatus, a 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.

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 that can eliminate the difference between the left and right torques.

  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 one 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 are formed in 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 is reduced.

  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.

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 Example 1. 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.

  Hereinafter, embodiments for realizing an integral type power steering device of the present invention will be described with reference to the drawings.

[Example 1]
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) that transmits to the steering wheel via And a limiter valve 9 that is a stroke limiter that limits the stroke of the piston 7 (movement in the x-axis direction) by reducing the pressure chamber on the high pressure side (increasing the pressure chamber on the low pressure side) when the required steering angle is reached, It is composed of The rack teeth 71 of the rack 70 are constant gear ratio (CGR) rack teeth in which a plurality of teeth arranged in the axial direction have substantially the same reduction ratio.

  The device 1 is accommodated in a 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 into the inner periphery of 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 input shaft 2 at the negative end in the x-axis direction is inserted into the inner periphery of the torsion bar accommodating portion 40 at the positive end in the x-axis direction, 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 connects the second pressure chamber 17 and the discharge port, and a second bleeding valve 22 having the same structure as the first bleeding valve 21 is provided on the communication passage. ing. 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 on the second pressure chamber 17 side, the housing volume becomes relatively larger than the first pressure chamber 16 side. 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. A plurality of three teeth that are aligned in the circumferential direction of the circumference having the center O1 and mesh with the rack teeth 71 of the rack 70 (hereinafter referred to as teeth a, teeth b, and teeth c when the three teeth are expressed individually) To describe.) 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 tooth a and the tooth c are formed in different shapes on the left and right tooth surfaces, respectively, 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 side, the rack 70 advances to the left side in FIG. 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 to the right side, the meshing point moves with the tooth surface c (2) of the tooth c, and this meshing point moves on the tooth surface c (2) toward the lower right side in FIG. (Hereinafter, this movement state is referred to as (2) state.) Here, the angle at which the mesh point moves to the tooth surface c (2) of the tooth c is set as a predetermined angle, and an output characteristic different from that in contact with the tooth b is set. The tooth surface c (2) is formed on the tooth tip side from the middle portion in the tooth height direction, and details will be described later.

  If the steering wheel is cut back to the right side and then turned back toward the neutral position, the meshing point moves between the tooth c and the tooth surface c (2-1). 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 to the left side, the meshing point moves with the tooth surface a (4) of the tooth a, and this meshing point moves on the tooth surface a (4) toward the lower left side in FIG. (Hereafter, this movement state is described as (4).) Here, the angle at which the mesh point moves to the tooth surface a (4) of the tooth a is set as a predetermined angle, and output characteristics different from that when the tooth a is in contact with the tooth b are set. The tooth surface a (4) is formed on the tooth tip side from the middle portion in the tooth height direction, and details will be described later.
When the steering wheel is cut back to the left side and then turned back toward the neutral position, the meshing point moves with 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.

  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 is performed after left steering, 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 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 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 where the switch-back 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 the tooth surface c (2-1) of the tooth a. 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.

Returning 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 a state at a certain angle of the state (4). 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 (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. The state (ii) in FIG. 5 represents the state at an angle of the state (4-1). 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 right steering is started from the neutral state, the state shifts to the (2) state via the (1) state. The state (iii) in FIG. 6 represents a state at a certain angle of the state (2). 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 transitions to the (1-1) state via the (2-1) state. The state (iv) in FIG. 7 represents a state at an angle of the (2-1) state. At the time of switching back after right steering, the first hydraulic pressure chamber 16 having 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 profiles of a (4) and c (2) are different from the tooth surface profiles formed 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 so as to increase toward the right steering. As a result, 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.

[Effect of Example 1]
Hereinafter, effects produced by the device 1 of the first embodiment 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 rotation axis of the torsion bar housing portion 40 as the axial direction, the piston 7 provided in the housing 11 so as to be movable in the axial direction, the piston 7 is provided, and the interior of the housing 11 is A piston seal 70a (seal part) that is divided into a first pressure chamber 16 provided on one side and a second pressure chamber 17 provided on the other side in the axial direction, and a valve housing provided in the housing 10 12 (rotary valve accommodating portion) and the valve housing 12 are operated with relative rotation between the input shaft 2 and the torsion bar accommodating portion 40, and the hydraulic fluid supplied from an external hydraulic pressure source is selectively 1st pressure chamber 16 and 1st 2 Rotor 60 (rotary valve) to be supplied to the pressure chamber 17, a ball screw mechanism 5 (first reduction gear) that converts the rotational motion of the torsion bar housing 40 into the axial motion of the piston 7, A rack tooth 71 that is formed on one side in the axial direction from the piston seal 70a and disposed in the second pressure chamber, and is provided in the second pressure chamber 17 so as to mesh with the rack tooth 71. And a second gear reducer configured to transmit a steering force to the steered wheels by converting the motion of the gears into a rotational motion, and a meshing point between the rack teeth 71 and the sector gear 8 and the sector gear 8 When the distance from the center of rotation O1 is the pitch circle radius PCR, the second reduction gear reduces the pitch circle radii r (large), R (when the piston 7 moves in the direction in which the volume of the second pressure chamber 17 increases. Large) (first pitch circle radius) and the piston 7 in the direction that the volume of the second pressure chamber 17 decreases The pitch circle radii r (small) and R (small) (second pitch circle radius) when moving are the magnitude of the output torque of the sector gear 8 and the rotation of the steering wheel with respect to the steering operation in one direction of the steering wheel rotation. Different radii are formed so that the difference in the magnitude of the output torque with respect to the steering operation in the other direction is reduced.
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. Provided with a plurality of teeth a, b, c arranged around the rotation center O1 of the motion in the circumferential direction, the difference between r (large), R (large) and r (small), R (small) 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.
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 that the profiles thereof are different from each other.
That is, since the sector gear 8 is a variable gear ratio gear, a tooth polishing operation 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 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 of the tooth surface in the tooth height direction is near the handle neutral position, 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.

(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 this 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.
In other words, in the second pressure chamber 17, which is the pressure chamber on the larger volume side, there is a possibility that the degree of influence of expansion and 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 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. Provided with a plurality of teeth a, b, c arranged around the rotation center O1 of the motion in the circumferential direction, the difference between r (large), R (large) and r (small), R (small) 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.
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.

(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.
That is, since the sector gear 8 is a variable gear ratio gear, a tooth polishing operation 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.

(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 of the tooth surface in the tooth height direction is near the handle neutral position, 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 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 this output characteristic difference can be performed.

(14) In the power steering device described in (13) 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.

(15) In the power steering device described in (9) 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.

(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 rotation axis of the torsion bar housing portion 40 as the axial direction, the piston 7 provided in the housing 11 so as to be movable in the axial direction, the piston 7 is provided, and the interior of the housing 11 is A piston seal 70a (seal part) that is divided into a first pressure chamber 16 provided on one side and a second pressure chamber 17 provided on the other side in the axial direction, and a valve housing provided in the housing 10 12 (rotary valve accommodating portion) and the valve housing 12 are operated with relative rotation between the input shaft 2 and the torsion bar accommodating portion 40, and the hydraulic fluid supplied from an external hydraulic pressure source is selectively With the first pressure chamber 16 2 Rotor 60 (rotary valve) to be supplied to the pressure chamber 17, a ball screw mechanism 5 (first reduction gear) that converts the rotational motion of the torsion bar housing 40 into the axial motion of the piston 7, A rack tooth 71 that is formed on one side in the axial direction from the piston seal 70a and disposed in the second pressure chamber, and is provided in the second pressure chamber 17 so as to mesh with the rack tooth 71. And a second gear reducer configured to transmit a steering force to the steered wheels by converting the motion of the gears into a rotational motion, and a meshing point between the rack teeth 71 and the sector gear 8 and the sector gear 8 When the distance from the center of rotation O1 is the pitch circle radius PCR, the second reduction gear reduces the pitch circle radii r (large), R (when the piston 7 moves in the direction in which the volume of the second pressure chamber 17 increases. Large) (first pitch circle radius) and the piston 7 in the direction that the volume of the second pressure chamber 17 decreases The pitch circle radii r (small) and R (small) (second pitch circle radius) when moving are the magnitude of the output torque of the sector gear 8 and the rotation of the steering wheel with respect to 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 in the other direction is reduced.
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.

(17) In the power steering device described in (16) above, the difference between r (large), R (large) and r (small), R (small) is that the steering wheel is rotated 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 this output characteristic difference can be performed.

(18) In the power steering device described in (16) 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.

(19) In the power steering device according to (16), the region formed such 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.

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 (4)

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 rotational axis of the output shaft is the 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 motion of the output shaft into motion of the piston in the axial direction;
Said than the sealing portion of the piston is formed on the one side of the axial, and the rack teeth disposed on the second pressure chamber, disposed in said second pressure chamber to fit the rack teeth mesh with the 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. size difference of the output torque relative to the steering operation is formed at different radii to reduce,
The first pitch circle radius is formed to be larger than the second pitch circle radius,
The power steering device according to claim 1, wherein a volume of the first pressure chamber is smaller than a volume of the second pressure chamber . The power steering apparatus according to claim 1, 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 is provided with 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. In the power steering device according to claim 1 or 2 ,
The sector gear is a variable gear ratio sector gear in which a plurality of teeth arranged in a circumferential direction around the rotational 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. The power steering apparatus according to claim 1, wherein
Of the first pitch radius and the second pitch circle radius, when the working fluid is supplied to the larger volume of the first pressure chamber and the second pressure chamber, the rack teeth and the sector gear are A power steering device, wherein a pitch circle radius on a meshing side is formed to be larger than the other pitch circle radius.

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