JP4539306B2 - Torque limit mechanism and variable transmission ratio mechanism with torque limit mechanism - Google Patents

Description

  The present invention relates to a transmission ratio variable mechanism that includes a torque limit mechanism and a torque limit mechanism and variably controls the ratio of the steered wheel turning angle to the steering angle of the steering wheel.

  A steering device including a transmission ratio variable mechanism that changes a ratio of a steering angle of a steered wheel to a steering angle of a steering wheel is described in Patent Document 1, for example. In Patent Document 1, as shown in FIG. 8 of Patent Document 1, the transmission ratio variable mechanism is a transmission shaft portion (input shaft) 280 to which the rotation of the steering wheel is transmitted, and a wheel that gives a turning angle to the steered wheels. A second steering shaft (output shaft) 120 that transmits rotation to the rudder rod (steering gear) 190; a steering gear box (transmission ratio variable housing) 11 that rotatably supports the transmission shaft portion 280 and the second steering shaft 120; The wave gear reducer 130, which is housed in the steering gear box 11 and transmits the rotation of the transmission shaft portion 280 to the second steering shaft 120, and the wave gear reducer 130 housed in the steering gear box 11 via the wave gear reducer 130. The rotation is transmitted to the second steering shaft 120 to operate the steering wheel. And a drive motor 150 (motor) for changing the ratio of the steered angle of the steering wheel relative angle. This type of transmission ratio variable mechanism variably controls the reduction ratio of the wave gear reducer 130 by controlling the rotation of the drive motor 150 according to the speed of the vehicle or the steering angular speed, and transmits the transmission gear from the transmission shaft portion 280 to the second steering shaft 120. The steering angle of the steering wheel is changed with respect to the steering angle of the steering wheel.

  In this type of transmission ratio variable mechanism, the motor shaft of the drive motor 150 is fixed to reduce the reduction ratio of the wave gear reducer 130 when no electric power is supplied to the drive motor 150 such as when the vehicle ignition is off. A motor shaft lock mechanism for fixing is provided. As shown in FIG. 8 attached to the present specification, this motor shaft locking mechanism includes a lock ring 102 inserted into the motor shaft 100 and having a plurality of lock grooves 101 formed in the outer periphery, and a motor in the steering gear box 103. A lock bar 106 is provided which is pivotally supported around a pivot 104 parallel to the shaft 100 and has an engaging claw portion 105 which can be engaged with the lock groove 101 at one end. An electromagnetic actuator 107 is attached to the other end of the lock bar 106, and a coil spring 108 is attached between the pivot 104 and the lock bar 106 to rotate and urge the engaging claw 105 in the direction to engage the lock groove 101. Has been. During the rotation control of the drive motor 150 by the electromagnetic actuator 107, the lock bar is rotated against the coil spring 108 to remove the engagement claw portion 105 from the lock groove 101, and the rotation control of the drive motor is not performed. The engaging claw 105 is engaged with the lock groove 101 by the coil spring 108 to fix the motor shaft 100.

By the way, in the motor shaft lock mechanism, when the wave gear reducer is fixed for some reason while the motor shaft 100 is fixed, the entire wave gear reducer can be rotated relative to the steering gear box 103. A torque limit ring 110 that slips when a predetermined torque is applied between the lock ring 102 and the motor shaft 100 is press-fitted. These lock ring 102, motor shaft 100 and torque limit ring 110 constitute a torque limit mechanism.
JP 2004-175336 A (paragraph numbers [0093] to [0102], FIG. 8)

  As shown in FIG. 9, the torque limit ring 110 has a shape in which a plurality of convex portions 111 are formed and peripheral portions 112 are provided at both ends, as shown in FIG. 9, and between the motor shaft 100 and the lock ring 102. When a force (torque) greater than a predetermined value is applied to the motor shaft 100, relative sliding between the motor shaft 100 and the lock ring 102 is permitted by the spring action obtained by elastic deformation of the convex portion 111.

  In this type of torque limit ring 110, since the surface pressure of the contact surface between the peripheral edge portion 112 and the motor shaft 100 at both ends is smaller than the surface pressure of the contact surface between the convex portion 111 and the lock ring 102, the peripheral edge portion 112 at both ends and the motor shaft. Slip between the contact surfaces of the motor 100 and relative rotation (slip) between the motor shaft 100 and the lock ring 102 is allowed. When the torque limit ring 110 is press-fitted, the center of the projection 111 is bent toward the motor shaft 100 and inserted. As a result, a pressing force acts on the peripheral portion 112 side from the convex portion 111, and this pressing force particularly acts on a connecting portion (bent portion) 112a between the peripheral portion 112 and the convex portion 111, thereby causing uneven surface pressure at the peripheral portion. Therefore, there is a problem that local wear occurs between the bent portion 112a and the motor shaft 100.

  The present invention has been made to solve the above-described conventional problems, and in the transmission ratio variable mechanism, prevents the occurrence of local wear between the bent portion of the torque limit ring and the motor shaft or the lock ring. With the goal.

A feature of the invention described in claim 1 for solving the above-mentioned problem is that it comprises a first member in the shape of a shaft and a second member attached to the first member, and the center of the cylindrical elastic member in the axial direction. Protrusions are formed on the parts, and peripheral edges extending in the axial direction are formed at both ends, and press-fitted between the first and second members to limit the transmission of torque between the first and second members In the torque limit mechanism having a torque limit ring, the torque limit ring has a convex portion in contact with one of the outer peripheral surface of the first member and the inner peripheral surface of the second member as a contact surface, and a peripheral portion with the other as a contact surface. The other contact surface is inclined with respect to the peripheral edge portion in the free state of the torque limit ring, and the surface pressure against the other contact surface in the assembled state is the peripheral edge portion. To be almost uniform over the entire area It is that they are.

The feature of the invention described in claim 2 is that an input shaft to which the rotation of the steering wheel is transmitted, an output shaft that transmits the rotation to a steering gear that gives a steered angle to the steered wheel, and the input shaft and the output shaft are rotated. A transmission ratio variable housing that can be supported, a reduction gear that is housed in the transmission ratio variable housing, and that transmits rotation of the input shaft to the output shaft, and that is housed in the transmission ratio variable housing and rotates to the output shaft via the reduction gear. A motor that transmits and changes the ratio of the steering angle of the steered wheel to the steering angle of the steering wheel, a lock ring that is mounted on the motor shaft of the motor, and a transmission ratio variable housing that is engaged with the lock ring. With a lock bar that can fix the motor shaft to the variable transmission ratio housing, a convex part is formed in the central part of the cylindrical elastic material in the axial direction A torque having a torque limit ring press-fitted between the motor shaft and the lock ring in order to limit the transmission of torque between the motor shaft and the lock ring. In the transmission ratio variable mechanism provided with the limit mechanism, the torque limit ring has the convex portion in contact with one of the outer peripheral surface of the first member and the inner peripheral surface of the second member as a contact surface, and the peripheral portion with the other as a contact surface. The other contact surface is inclined with respect to the peripheral edge portion in the free state of the torque limit ring, and in the assembled state, the surface pressure with respect to the other contact surface is the entire peripheral edge portion. It is made to become substantially uniform over.

According to the invention of claim 1 constructed as described above, the contact surface in contact with the periphery of the torque limit ring of the first member or the second member, the periphery torque limit ring at free state Since it is inclined with respect to the outer peripheral surface of the motor shaft, the peripheral edge is bent. Due to this bending, the bent portion between the convex portion and the peripheral portion performs a spring action, and generates a repulsive force against the pressing force. As a result, since the pressing force and the repulsive force cancel each other, the surface pressure of the peripheral portion becomes uniform, so that the outer peripheral surface of the first member or the inner peripheral surface of the second member and the bent portion contact with the peripheral portion. It is possible to prevent local wear during.

According to the invention according to claim 2 configured as described above, since each contact surface of the motor shaft is inclined with respect to the peripheral portions at both ends of the torque limit ring, the peripheral portion is the outer peripheral surface of the motor shaft. Bend to adhere to. By this bending, the bent portion between the convex portion and the peripheral portion performs a spring action and generates a repulsive force against the pressing force. As a result, since the pressing force and the repulsive force cancel each other, the surface pressure at the peripheral edge portion becomes uniform, so that local wear between the contact surface of the motor shaft or the lock ring and the bent portion can be prevented.

In FIG. 1, the power steering apparatus 10 is mainly configured by a steering gear box (transmission ratio variable housing) 11, a transmission ratio variable mechanism 12, and a hydraulic servo apparatus 13.

  The rotation of the handle 15 is transmitted to the handle-side shaft 14 of the hydraulic servo apparatus 13, and the rotation of the output shaft of the hydraulic servo apparatus 13 is shifted by the transmission ratio variable mechanism 12 and transmitted to the pinion shaft 17 of the rack and pinion mechanism 16. As a result, the steering force acting on the handle 15 is transmitted to the steered wheel 8 via the rack and pinion mechanism 16 that is a steering gear.

  The upper housing 18 and the lower housing 19 are coupled by bolts to constitute the steering gear box 11. A valve housing hole 18 a is formed in the upper housing 18, and a hydraulic servo valve device 13 is housed in the valve housing hole 18 a, and is an input shaft that is an output shaft of the hydraulic servo valve device 13 and an input shaft of the transmission ratio variable mechanism 12. A shaft 20 is supported by a bearing 21 so as to be rotatable about the central axis at one end of the valve housing hole 18a of the upper housing 18 on the lower housing 19 side. A gear chamber 19a is formed in the lower housing 19, and a rack and pinion mechanism 16 is accommodated in the gear chamber 19a. A pinion shaft (output shaft) 17 of the rack and pinion mechanism 16 is supported by the lower housing 19 by two bearings 22 and 23 so as to be rotatable around the central axis at two positions spaced apart in the central axial direction.

  A rack shaft 36 in which a rack 36 a meshed with the pinion shaft 17 is slidably mounted on the lower housing 19. As shown in FIG. 2, a cylinder tube 28 is fixed to the lower housing 19, and a piston 29 fixed to the rack shaft 36 is fitted to the cylinder tube 28 so as to partition the left and right cylinder chambers 28b and 28a. A device 30 is configured. A knuckle arm is connected to both projecting ends of the rack shaft 36 via a tie rod by a ball joint, and the steering wheel 8 is deflected by the axial movement of the rack shaft 36.

  A rotary valve 25 is formed on the handle side shaft 14 of the hydraulic servo valve device 13. A sleeve 26 connected to the input shaft 20 is fitted in the valve housing hole 18 a formed in the upper housing 18 so as to be rotatable around the central axis, and the rotary valve 25 is centered in the valve hole 27 formed in the sleeve 26. It is fitted so as to be rotatable around the axis. The hydraulic servo device 13 is constituted by the rotary valve 25, the sleeve 26, and the like, and the ports A and B communicated with the left and right chambers 28b and 28a of the cylinder device 28 according to the relative rotation of the rotary valve 25 and the sleeve 26 are hydraulic pressures. It is connected to ports P and T connected to the pump 34 and the tank 35, respectively. The input shaft 20 and the handle side shaft 14 are coupled to both ends of the torsion bar 31, respectively. When the steering shaft 14 does not act on the steering wheel 15 and the steering wheel shaft 14 is in a free state, the ports P and T are communicated, and the rotary valve 25 is relative to the sleeve 26 in a neutral position where no hydraulic pressure is generated in the ports A and B. Rotational positioning. The port T is opened at the upper end of the valve storage hole 18a. The handle-side shaft 14 has a through hole 32a through which the torsion bar 31 is inserted with a gap on the axis, and communication holes 33b and 33c that open to the through hole 32a are spaced apart in the axial direction in the radial direction. Has been drilled. As a result, the port T communicates with the rotary valve 25 through the upper end of the valve housing hole 18a, the communication hole 33b, the through hole 32a, and the communication hole 33c.

  The transmission ratio variable mechanism 12 has a function of making the ratio (transmission ratio) of the steered angle of the steered wheels 8 to the steering angle of the handle 15 variable according to the vehicle speed, for example.

  The transmission ratio variable mechanism 12 is housed on the hydraulic servo valve device 13 side in the lower housing 19. The pinion shaft 17 constitutes a part of the transmission ratio variable mechanism 12. The pinion shaft 17 includes a pinion shaft portion 37 that meshes with the rack shaft 36 and a large-diameter storage recess 39 that stores a speed reducer 38 including a wave gear mechanism described later. The housing recess 39 is integrally connected to a disk-like flange portion 37a formed on one end outer periphery of the pinion shaft portion 37 by serration coupling by press-fitting.

  The lower housing 19 accommodates the storage recess 39, a speed reducer (differential mechanism) 38, a motor (DC brushless motor) 41, and a motor shaft lock mechanism 42. For example, the speed reducer 38 includes a wave gear mechanism, and includes a driven gear 43, a stator gear 44, a wave generator 45, a flexible gear 46, and a rotation transmission engagement member 47, as will be described in detail later. ing.

  In the storage recess 39, a driven gear 43, a stator gear 44, and a rotation transmission engaging member 47 are stored in this order from the opening end side. The driven gear 43 is press-fitted and coupled to the storage recess 39, and the stator gear 44 and the rotation transmission engagement member 47 are coupled in the rotation direction so as to be rotatable within the storage recess 39.

  Gears having different numbers of teeth (the number of teeth of the driven gear 43 <the number of teeth of the stator gear 44) are formed on the inner peripheral surfaces of the driven gear 43 and the stator gear 44, respectively. Inside the driven gear 43 and the stator gear 44, a flexible gear 46 that meshes simultaneously with each gear is provided. That is, the teeth formed on the inside of the driven gear 43 and the stator gear 44 mesh with the teeth formed on the outside of the flexible gear 46 (the number of teeth is the same as the number of teeth of the driven gear 43). The inner side of the flexible gear 46 is fitted on the outer ring of the wave generator 45.

  A case 41 a of a motor 41 is fixed to the lower housing 19. The motor 41 has a motor shaft 48, and the motor shaft 48 is rotatably supported by the case 41 a via bearings 49 and 50 and is connected to a cam of the wave generator 45. The input shaft 20 is rotatably inserted into the motor shaft 48 and engaged with the rotation transmission engaging member 47.

  In this configuration, as shown in FIG. 1, when the motor shaft 48 of the motor 41 rotates, the cam of the wave generating device 45 rotates, and the flexible gear 46 is deformed into an elliptical shape within the stator gear 44, so that the driven gear 43 on the same axis. Rotate. That is, since the number of teeth of the driven gear 43 is smaller than the number of teeth of the stator gear 44, the driven gear 43 rotates by a difference in the number of teeth in the direction opposite to the rotation direction of the wave generating device 45 when the wave generating device 45 makes one rotation. That is, actuator operating angle = rotation angle of motor 41 × reduction ratio (reduction ratio = tooth number difference / number of teeth of driven gear 43). On the other hand, when the stator gear 44 is rotated by the rotation of the handle 15, an actuator operating angle is added and transmitted to the pinion shaft 17.

  The motor shaft locking mechanism 42 fixes (locks) the motor shaft 48 to the lower housing 19 when the power is turned off or the system is defective. As shown in FIG. 3, in the motor shaft locking mechanism 42, a lock bar 51 is attached to the rear wall of the case 41a so as to be swingable by a pivot 52. An engaging claw 51a is formed at one end of the lock bar 51, and an electromagnetic actuator 53 attached to the case 41a is connected to the other end. A lock ring 54 is attached to the rear end of the motor shaft 48 via a torque limit ring 55. These motor shaft (first member) 48, lock ring (second member) 54 and torque limit ring 55 constitute a torque limit mechanism.

  The torque limit ring 55 allows relative rotation (slip) between the motor shaft 48 and the lock ring 54 when a predetermined force (torque) is applied between the motor shaft 48 and the lock ring 54.

The torque limit ring 55 shown in FIGS. 4 and 5 extends in the axial direction at a plurality of convex portions 55a formed at the central portion in the axial direction of the cylindrical steel plate that is an elastic material, and at both ends of the convex portions 55a. It is comprised by the peripheral part 55b, 55c. The peripheral portions 55b and 55c are arranged in a free state before the torque limit ring 55 is compressed and assembled between the motor shaft 48 and the lock ring 54, as shown in FIG. An inclined surface having a predetermined angle θ with respect to the outer peripheral surface, and when the torque limit ring 55 is assembled between the motor shaft 48 and the lock ring 54, from the convex portion 55a side toward the peripheral portions 55b and 55c. A pressing force F is applied. The pressing force F tends to be larger at the base ends of the peripheral portions 55b and 55c than at the tip. However, the peripheral edge portions 55 b and 55 c are inclined at a predetermined angle θ with respect to the outer peripheral surface of the motor shaft 48, so that the peripheral edge portions 55 b and 55 c are bent when they are in close contact with the outer peripheral surface of the motor shaft 48. By this bending, the bent portion 56 between the convex portion 55a and the peripheral portions 55b and 55c performs a spring action, and generates a repulsive force that resists the pressing force. This repulsive force tends to be greater at the distal end side of the peripheral edge than at the proximal end side. As a result, the pressing force and the repulsive forces 55b and 55c cancel each other, so that the surface pressure of the peripheral portions 55b and 55c becomes uniform, and local wear between the bent portion 56 and the outer peripheral surface of the motor shaft 48 is prevented. .

  As shown in FIG. 3, a plurality of lock grooves 54a that engage with the engaging claws 51a are formed on the outer periphery of the lock ring 54 at equal intervals on the circumference. The coil spring 57 wound around the outer periphery of the pivot 52 has one end engaged with the lock bar 51 and the other end fixed to the pivot 52, and the lock bar 51 is swung around the axis of the pivot 52 by a torsional force. A rotational force that engages the pawl portion 51 a with the lock groove 54 a is applied to the lock bar 51. The electromagnetic actuator 53 applies to the lock bar 51 a rotational force that separates the engaging claw portion 51 a from the lock groove 54 a against the rotational force of the coil spring 57. As a result, the lock bar 51 is driven to engage and disengage the engagement claw portion 51a from the lock groove 54a with the pivot shaft 52 as the center, thereby permitting or preventing the rotation of the motor shaft 48.

  The controller 60 determines whether the engaging claw portion 51a and the locking groove 54a are engaged and disengaged by the electromagnetic actuator 53, and commands for operation. When the transmission ratio variable mechanism 12 operates normally, the control device 60 operates the electromagnetic actuator 53 to swing the lock bar 51 against the force of the coil spring 57 when the ignition of the vehicle is turned on. The engaging claw portion 51a is detached from the lock groove 54a. As a result, the rotation of the motor shaft 48 can be controlled by the motor 41, and the ratio (transmission ratio) of the steered wheel 8 to the steering angle of the steering wheel 15 can be changed according to the rotation angle of the motor shaft 48. It becomes possible. Further, the control device 60 stops the operation of the motor 41 and the electromagnetic actuator 53 by engaging the engaging claw portion 51a with the lock groove 54a when the power is turned off or when the system is defective, and the motor shaft 48 of the motor 41 is rotated. Block the transmission ratio to a predetermined value.

  Normally, as described above, when the ignition of the vehicle is turned on, the control device 60 operates the electromagnetic actuator 53 to disengage the engaging claw portion 51a from the lock groove 54a, and the motor shaft 48 by the motor 41. Can be rotated.

  When the handle 15 is rotated, the rotary valve 25 and the sleeve 26 are rotated relative to each other by twisting the torsion bar 31, and the pressure oil supplied from the hydraulic pump 34 is changed from the port A or B to the cylinder according to the rotation direction of the handle 15. The cylinder 30 is supplied to the cylinder left chamber 28b or the right chamber 28a of the device 30, and the rack shaft 36 is axially moved to deflect the steering wheel 8. At this time, when the steering angle applied to the steering shaft 14 is detected by a steering angle sensor (not shown) and the vehicle speed is detected by a vehicle speed sensor (not shown), the control device 60 is based on the vehicle speed and the steering angle. The target rudder angle is calculated. A control signal for controlling the motor 41 is output from the control device 60 based on the target steering angle.

  The control signal output from the control device 60 is sent to the motor 41 of the transmission ratio variable mechanism 12, and the motor 41 is rotationally driven based on this control signal. When the motor 41 is rotated, the cam of the wave generator 45 is rotated via the motor shaft 48, and the flexible gear 46 is rotated. The flexible gear 46 rotates in the stator gear 44 in a state of being deformed into an elliptical shape, and rotates the driven gear 43 on the same axis. At this time, since the number of teeth of the driven gear 43 is smaller than the number of teeth of the stator gear 44, when the wave generating device 45 rotates once, the driven gear 43 rotates by the difference in the number of teeth in the direction opposite to the rotation direction of the wave generating device 45. .

  The rotation of the driven gear 43 is transmitted to the pinion shaft 17 to cause the rack shaft 36 to move. Thereby, the ratio between the steering angle of the steering wheel 15 and the steering angle of the steering wheel 19 can be changed.

  Further, when the speed reducer 38 is fixed for some reason, the speed reducer 38 is in a fixed state, and the input shaft 20 and the pinion shaft 17 rotate together with the speed reducer 38. At this time, the control device 60 stops the change control of the reduction ratio of the reduction gear 38 by the motor 41, engages the engagement claw portion 51a with the lock groove 54a, and prevents the rotation of the motor shaft 48 of the motor 41. Therefore, when the handle 15 is operated, the motor shaft 48 is subjected to a rotational force for integrally rotating the input shaft 20, the pinion shaft 17 and the speed reducer 38, so that the motor shaft 48 is rotated. The torque limit ring 55 slips and the motor shaft 48 can rotate with respect to the lower housing 19. As a result, the input shaft 20, the pinion shaft 17 and the speed reducer 38 are integrally rotated, and the rotation is transmitted from the input shaft 20 to the pinion shaft 17.

4 and 5 , the example has been described in which the peripheral portions 55 b and 55 c of the torque limit ring 55 are in contact with the outer peripheral surface of the motor shaft 48 and the convex portion 55 a is in contact with the inner peripheral surface of the lock ring 54. The peripheral portions 55 b and 55 c may be in contact with the inner peripheral surface of the lock ring 54, and the convex portion 55 a may be in contact with the outer peripheral surface of the motor shaft 48.

Next, the first embodiment according to the present invention will be described based on FIG. 6 only with respect to differences from the torque limit ring 55 shown in FIGS. In the first embodiment, unlike the torque limit ring 55 shown in FIGS. 4 and 5, the peripheral portions 55b and 55c are not inclined surfaces, and the convex portions 55a and the peripheral portions 55b and 55c of the torque limit ring 55 are It is substantially parallel in a free state, and is characterized by a structure for attaching the torque limit ring 55 to the motor shaft 48. As shown in FIG. 6, in the first embodiment, an annular groove 61 is formed on the outer peripheral surface of the motor shaft 48. The annular groove 61 has side walls (contact surfaces) 61b and 61c on both sides of the bottom surface 61a inclined at a predetermined angle θ on the outer peripheral surface of the motor shaft 48, that is, the side walls 61b and 61c are separated from each other toward the opening. It is formed as follows. For this reason, the peripheral portions 55b and 55c are bent so as to be in close contact with the outer peripheral surface of the motor shaft 48, and by this bending, the bent portions between the convex portions 55a and the peripheral portions 55b and 55c form a spring action, and Generates a repulsive force that resists pressure. As a result, since the pressing force and the repulsive force cancel each other, the surface pressures of the peripheral portions 55b and 55c become uniform, so that local wear between the bent portion and the outer peripheral surface of the motor shaft can be prevented.

  In the above embodiment, the example has been described in which the peripheral portions 55 b and 55 c of the torque limit ring 55 are in contact with the outer peripheral surface of the motor shaft 48 and the convex portion 55 a is in contact with the inner peripheral surface of the lock ring 54. The peripheral portions 55 b and 55 c are in contact with the inner peripheral surface of the lock ring 54, the convex portion 55 a is in contact with the outer peripheral surface of the motor shaft 48, and the annular groove 61 is formed in the inner peripheral surface of the lock ring 54. You may do it.

Next, a second embodiment according to the present invention will be described with reference to FIG only for the difference from the first embodiment.

As shown in FIG. 7, in the second embodiment, in addition to the first embodiment, an annular groove is formed on the inner portion of the contact surface of the motor shaft 48 where the base ends of the peripheral portions 55b and 55c of the torque limit ring 55 contact. It is characterized in that 62 is engraved. Thus, by engraving the annular groove 62 at a position where the peripheral ends 55b and 55c where the local wear may occur, the lubricant is held in the annular groove 62, and the bent portion and the motor shaft are retained. Lubrication with the outer peripheral surface of 48 is performed, and local wear can be prevented. Further, even if local wear occurs in the bent portion, the wear powder is collected in the annular groove 62 and can be prevented from entering between the motor shaft 48 and the peripheral portions 55b and 55c. Can be prevented from fluctuating.

  In the above embodiment, the example has been described in which the peripheral portions 55 b and 55 c of the torque limit ring 55 are in contact with the outer peripheral surface of the motor shaft 48 and the convex portion 55 a is in contact with the inner peripheral surface of the lock ring 54. The peripheral portions 55b and 55c are in contact with the inner peripheral surface of the lock ring 54, the convex portion 55a is in contact with the outer peripheral surface of the motor shaft 48, and the annular groove 62 is formed on the inner peripheral surface of the lock ring 54. You may do it.

  In the above embodiment, the reduction gear 38 of the transmission ratio variable mechanism 12 has been described by taking a reduction gear made of a wave gear mechanism as an example. However, the reduction gear 38 is not limited to this, for example, a sun gear. , A planetary gear mechanism including an internal gear, a planetary gear, and the like.

  In the above-described embodiment, the example in which the transmission ratio variable mechanism 12 is used in the hydraulic power steering apparatus including the hydraulic servo apparatus 13 and the cylinder apparatus 28 has been described. The transmission ratio variable mechanism 12 having the torque limit mechanism in the embodiment may be used.

It is sectional drawing of the hydraulic power steering device provided with the transmission ratio variable mechanism. It is sectional drawing cut | disconnected along the II-II line | wire of FIG. It is sectional drawing cut | disconnected along the III-III line of FIG. It is an external view of a torque limit ring. It is a conceptual diagram at the time of the assembly | attachment of a torque limit ring. It is a conceptual diagram at the time of the assembly | attachment of the torque limit ring in the 1st Embodiment of this invention. It is a conceptual diagram at the time of the assembly | attachment of the torque limit ring in the 2nd Embodiment of this invention. It is a figure which shows an example of the conventional motor shaft lock mechanism. It is a conceptual diagram at the time of the assembly | attachment of the conventional torque limit ring.

Explanation of symbols

  8 ... Steering wheel, 10 ... Power steering device, 11 ... Steering gear box, 12 ... Transmission ratio variable mechanism, 13 ... Hydraulic servo device, 14 ... Handle side shaft, 15 ... Handle, 17 ... Pinion shaft (output shaft), DESCRIPTION OF SYMBOLS 18 ... Upper housing, 19 ... Lower housing, 20 ... Input shaft, 36 ... Rack shaft (output shaft), 38 ... Reduction gear, 41 ... Motor, 42 ... Motor shaft locking mechanism, 48 ... Motor shaft (1st member) ), 51 ... Lock bar, 54 ... Lock ring (second member), 55 ... Torque limit ring, 55a ... Projection, 55b, 55c ... Peripheral part, 56 ... Bent part (base end), 61, 62 ... Annular groove

Claims (2)

A peripheral portion that includes a first axial member and a second member that is attached to the first member, a convex portion is formed at a central portion in the axial direction of the cylindrical elastic member, and an axial direction extends at both ends. A torque limit mechanism having a torque limit ring press-fitted between the first and second members in order to limit transmission of torque between the first and second members,
The torque limit ring is assembled so that the convex portion is in contact with one of the outer peripheral surface of the first member and the inner peripheral surface of the second member as a contact surface, and the peripheral portion is in contact with the other as a contact surface. The other contact surface is inclined with respect to the peripheral edge portion in a free state of the torque limit ring, and the surface pressure with respect to the other contact surface in the assembled state is spread over the entire peripheral edge portion. A torque limit mechanism characterized by being substantially uniform. An input shaft to which the rotation of the steering wheel is transmitted, an output shaft that transmits the rotation to a steering gear that gives a steered angle to the steering wheel, and a transmission ratio variable housing that rotatably supports the input shaft and the output shaft; A reduction gear housed in the transmission ratio variable housing and transmitting the rotation of the input shaft to the output shaft, and the steering wheel steering by transmitting the rotation to the output shaft housed in the transmission ratio variable housing via the reduction gear. A motor that changes the ratio of the steering angle of the steered wheel to the angle; a lock ring that is mounted on the motor shaft of the motor; and a transmission ratio variable housing that engages with the lock ring and engages the motor shaft. And a lock bar that can be fixed to the variable transmission ratio housing, and at the central portion of the cylindrical elastic member in the axial direction. Torque is press-fitted between the motor shaft and the lock ring to limit the transmission of torque between the motor shaft and the lock ring. In a transmission ratio variable mechanism having a torque limit mechanism having a limit ring,
The torque limit ring is assembled so that the convex portion is in contact with one of the outer peripheral surface of the first member and the inner peripheral surface of the second member as a contact surface, and the peripheral portion is in contact with the other as a contact surface. The other contact surface is inclined with respect to the peripheral edge portion in a free state of the torque limit ring, and the surface pressure with respect to the other contact surface in the assembled state is spread over the entire peripheral edge portion. A transmission ratio variable mechanism provided with a torque limit mechanism characterized by being substantially uniform.

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