JP2007168613A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To stabilize engagement of a drive gear and a driven gear in a decelerator of an electric power steering device. <P>SOLUTION: Rotation of an output shaft 42 of an electric motor 40 assembled to a housing 10 is decelerated in the decelerator 50, the decelerated rotation is converted to axial displacement of a rack bar 20 by a ball screw mechanism 30, and steering force is given to the rack bar 20. The decelerator is provided with the conical drive gear 51 connected to the output shaft 42 of the electric motor 40; the conical driven gear 52 connected to a nut 32 of the ball screw mechanism 30; an elastic coupling 43 making the drive gear 51 movable in an axial direction and a rubber 55 (movement allowance means). Further, the decelerator 50 is provided with respective springs 56 for urging the drive gear 51 form a large diameter part 51a side to a small diameter part 51b side to resiliently engage with the driven gear 52; a spring retainer 57 and an adjustment screw 58 (urging mechanism). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an electric power steering device, and more particularly, to an electric power steering device including a reduction gear for reducing the rotation of an output shaft of an electric motor.

As one of this type of electric power steering device, the rotation of the output shaft of the electric motor assembled in the housing is decelerated by a speed reducer, and this decelerated rotation is converted into the axial displacement of the rack bar by a displacement conversion mechanism. Some are converted so that an axial force is applied to the rack bar, and is described in, for example, Patent Document 1 below.
JP 2005-145431 A

  In the electric power steering apparatus described in Patent Document 1, a reduction gear includes a drive gear connected to an output shaft of an electric motor via a support shaft, and a ball screw mechanism as an input member of a displacement conversion mechanism. A driven gear connected to the nut is provided. The drive gear is attached to the housing via a support shaft and a cylindrical adjustment collar. The adjustment collar has a support hole that is eccentric by a predetermined amount from the center axis, and the support shaft is rotatably supported by the support hole.

  By the way, in the electric power steering apparatus described in Patent Document 1, the backlash between the drive gear and the driven gear is adjusted as follows. First, before connecting the output shaft of the electric motor and the support shaft of the drive gear, the drive gear is assembled to the housing via the support shaft and the adjustment collar and meshed with the driven gear. Next, the adjustment collar is rotated by a predetermined angle, and the backlash between the drive gear and the driven gear is set to a predetermined amount. After setting the backlash, the output shaft of the electric motor and the support shaft of the drive gear are connected, and the electric motor main body is assembled to the housing according to the assembled position after the setting.

  However, in the electric power steering device described in Patent Document 1, when adjusting the backlash between the drive gear and the driven gear, it is necessary to always remove the electric motor main body from the housing, and between the drive gear and the driven gear. After the backlash is set to a predetermined value, it is necessary to assemble the electric motor main body to the housing again, which is complicated. Even if the backlash between the driving gear and the driven gear is set to a predetermined value, the reduction ratio of the reduction gear is set to a large value, and so on, due to slight rattling between the driving gear and the driven gear. The engagement between the drive gear and the driven gear tends to become unstable, and there is a high possibility that abnormal noise and vibration will occur during the engagement.

  Therefore, the present invention provides an electric power steering apparatus that can easily adjust the backlash between the drive gear and the driven gear and can stabilize the meshing between the drive gear and the driven gear in order to cope with the above-described problem. Its purpose is to do.

  In order to achieve the above object, in the present invention, the rotation of the output shaft of the electric motor assembled in the housing is decelerated by the speed reducer, and this decelerated rotation is converted into the axial displacement of the rack bar by the displacement conversion mechanism. In the electric power steering apparatus configured to be converted to apply an axial force (axial force) to the rack bar, the speed reducer has a conical shape connected to the output shaft of the electric motor. A drive gear, a conical driven gear connected to the input member of the displacement conversion mechanism and meshing with the drive gear, and a movement enabling at least one of the drive gear and the driven gear to move in the axial direction An allowance means and the gear, which is movable in the axial direction by the movement allowance means, are urged in the axial direction from the large-diameter portion side to the small-diameter portion side so that the both gears are elastically engaged. It is characterized in that it comprises a cell biasing means. In this case, for example, the movement allowing means may include a configuration that allows the drive gear to move in the axial direction together with a support shaft that supports the drive gear. It is also possible to have a configuration that enables movement in the axial direction with respect to the support shaft that supports the boss. In addition, the movement permitting means may be configured to be movable in the radial direction together with a support shaft that supports the drive gear, for example.

  In this electric power steering device, the drive gear and the driven gear are both formed in a conical shape, and at least one of the two gears is axially moved from the large diameter side to the small diameter side by the biasing means. Energized, both gears are engaged in a resilient manner. Accordingly, the biasing force in the axial direction of the biasing means generates a force component in the meshing direction (radial direction) according to the meshing angle of both gears, so that the meshing of both gears is strengthened and both gears are Being engaged in a resilient manner. For this reason, the backlash between both gears is automatically maintained at a predetermined size, and the meshing of both gears can be stabilized. As a result, not only the operation of setting the backlash between the two gears to a predetermined size over a long period when the urging force by the urging means is maintained at a predetermined value, but also the operation of removing the electric motor body from the housing and The installation work to the housing becomes unnecessary.

  In carrying out the present invention, the urging means may include an adjustment mechanism capable of adjusting an urging force for urging the one gear in the axial direction from the large-diameter portion side toward the small-diameter portion side. Is possible.

  In this case, the biasing means is provided with an adjustment mechanism capable of adjusting the biasing force. Therefore, when the urging force by the urging means is not maintained at the predetermined value, the urging force by the urging means can be easily set to the predetermined value by operating the adjustment mechanism.

  Hereinafter, each embodiment of the present invention will be described with reference to the drawings. FIG. 1 schematically shows a main part of an electric power steering apparatus according to a first embodiment of the present invention. In the electric power steering apparatus according to the first embodiment, the electric power steering apparatus extends in the left-right direction of the vehicle. The rack bar 20, the ball screw mechanism 30, the electric motor 40, and the speed reducer 50 are assembled to the housing 10 assembled to the vehicle body (not shown).

  The rack bar 20 is assembled in the housing 10 so as to be movable and non-rotatable in the left-right direction of the vehicle (the axial direction of the rack bar 20). The rack bar 20 is engaged with a pinion (not shown) of an input shaft by a rack gear (not shown) so as to be able to transmit an axial force, and tie rods and knuckle arms (not shown) at both left and right ends penetrating the housing 10. For example, it is connected to a steered wheel (not shown) so that axial force can be transmitted.

  The ball screw mechanism 30 is provided coaxially with the rack bar 20 and includes a screw shaft 31, nuts 32, and a large number of balls 33. The screw shaft 31 is formed integrally with the rack bar 20. The nut 32 is assembled on the outer periphery of the screw shaft 31 via the bearings 34 and 35 to the housing 10 so as to be rotatable around the axis of the screw shaft 31 and not movable in the left-right direction of the vehicle. A large number of balls 33 are rotatably held between a spiral groove formed on the outer periphery of the screw shaft 31 and a spiral groove formed on the inner periphery of the nut 32.

  The electric motor 40 is fixed to the outer wall of the housing 10 by the electric motor main body 41, and the rotation of the rotor (not shown) is output to the outside via the output shaft 42. The output shaft 42 is connected to a support shaft 53 that supports a drive gear 51 described later via an elastic joint 43 so that torque can be transmitted. The elastic joint 43 is a well-known structure formed by combining a pair of concavo-convex elastic bodies that can be engaged with each other, and the axial direction and diameter of the support shaft 53 with respect to the output shaft 42 according to the elastic deformation thereof. A predetermined amount of movement in the direction is allowed.

  The reducer 50 is interposed between the output shaft 42 of the electric motor 40 and the nut 32 of the ball screw mechanism 30, and includes a drive gear 51 and a driven gear 52. The drive gear 51 and the driven gear 52 are parallel-shaft specification conical gears set to a predetermined reduction gear ratio, the drive gear 51 is integrally fixed coaxially with the support shaft 53, and the driven gear 52 is connected to the nut 32. It is fixed integrally on the same axis. As a result, the rotation of the output shaft 42 of the electric motor 40 is decelerated by the speed reducer 50, and the decelerated rotation is converted into the axial displacement of the rack bar 20 by the ball screw mechanism 30, and the axial force is applied to the rack bar 20. (Axial force) is applied. The ball screw mechanism 30 functions as a displacement conversion mechanism, and the nut 32 functions as an input member of the displacement conversion mechanism.

  The support shaft 53 passes through the drive gear 51 in the axial direction, and is assembled to the housing 10 via the bearing 54 at the end on the large diameter portion 51a side of the drive gear 51 so as to be rotatable about the axis. A rubber 55 is interposed between the outer periphery of the outer ring of the bearing 54 and the housing 10, and a predetermined amount of movement in the axial direction and the radial direction of the bearing 54 is allowed according to the elastic deformation of the rubber 55.

  A pair of springs 56 and 56 and a spring retainer 57 are interposed between the end face of the outer ring of the bearing 54 and the housing 10. Each spring 56 is interposed between the bearing 54 and the spring retainer 57 in a predetermined compression state so that a predetermined pressing force is maintained, and the drive gear 51 is increased in diameter through the bearing 54 and the support shaft 53. It is biased in the axial direction from the portion 51a side toward the small diameter portion 51b side.

  Thus, the drive gear 51 moves together with the support shaft 53 and the bearing 54 by a predetermined amount in the axial direction toward the output shaft 42 of the electric motor 40 along with the elastic deformation of the rubber 55 and the elastic joint 43 in the axial direction. . When the rubber 55 and the elastic joint 43 are elastically deformed in the radial direction, the drive gear 51 is movable in the radial direction together with the support shaft 53 and the bearing 54. The rubber 55 and the elastic joint 43 function as a movement allowing unit.

  The spring retainer 57 is assembled to the housing 10 together with an adjusting screw 58, a guide (not shown), and the like. The adjustment screw 58 is screw-coupled with a female screw portion 10 a formed in the housing 10, and the spring retainer 57 is movable in the axial direction of the support shaft 53 in accordance with the rotation operation of the adjustment screw 58. Thereby, the pressing force of each spring 56 can be adjusted according to the rotation operation of the adjusting screw 58 from the outside of the housing 10. Each spring 56, spring retainer 57, and adjustment screw 58 function as an urging means, and the spring retainer 57, adjustment screw 58, and female thread portion 10a of the housing 10 also function as an adjustment mechanism.

  In the first embodiment configured as described above, in the state where the electric motor 40 and the speed reducer 50 are assembled to the housing 10, the pressing force in the axial direction of each spring 56 passes from the bearing 54 through the support shaft 53. Transmitted to the drive gear 51, the drive gear 51 moves in the axial direction by a predetermined amount toward the output shaft 42 of the electric motor 40. Accordingly, a force component in the meshing direction (radial direction) is generated according to the meshing angle between the drive gear 51 and the driven gear 52, so that the meshing of both the gears 51, 52 is strengthened and the both gears 51, 52 are elastic. It becomes biting by the beginning. For this reason, the backlash between both the gears 51 and 52 is automatically maintained at a predetermined size, and the meshing of both the gears 51 and 52 is stabilized.

  As a result, the operation of setting the backlash between the drive gear 51 and the driven gear 52 to a predetermined size over a long period in which the pressing force by each spring 56 is maintained at a predetermined value, as well as the electric motor main body 41. Removal work from the housing 10 and attachment work to the housing 10 are not required.

  In the first embodiment, each of the springs 56 functioning as a biasing means is provided with a drive gear 51 that is formed smaller than the driven gear 52 in order to set the reduction ratio of the reduction gear 50 large. Since the spring retainer 57 and the adjusting screw 58 are used to urge in the axial direction from the large diameter portion 51a side to the small diameter portion 51b side, the urging means can be configured compactly.

  In the first embodiment, the shock absorption characteristics of the springs 56 effectively absorb the shock generated when the gears 51 and 52 are engaged with each other, and the generation of sound and vibration during the engagement is suppressed. . Even if a sudden radial force acts on the meshing portion of both gears 51 and 52 due to the meshing accuracy and assembly accuracy of both gears 51 and 52, the force is applied to rubber 55 and It is effectively absorbed by the elastic deformation of the elastic joint 43.

  Further, in the first embodiment, each spring 56 is interposed between the outer ring (non-rotating portion) of the bearing 54 and the spring retainer 57, and is not easily affected by the rotation of the support shaft 53 and the drive gear 51. ing. Therefore, since the durability of each spring 56 is ensured, the pressing force of each spring 56 is maintained at a predetermined value for a longer period, and the adjustment work of the backlash between the two gears 51 and 52 is not required for a longer period. Become. When the urging force by each spring 56 is no longer maintained at a predetermined value, the urging force by each spring 56 can be easily set to a predetermined value by rotating the adjustment screw 58 outside the housing 10. . The use of a plurality of springs 56 can increase the degree of freedom in adjusting the pressing force. However, the number of springs to be used can be changed as appropriate. For example, the number of parts can be reduced by using only one spring. You may make it reduce.

  In the first embodiment, the drive gear 51 is configured to be movable in the axial direction together with the support shaft 53, but instead, for example, as shown in FIG. It is also possible to configure and implement such that the support shaft 53 can move in the axial direction. In addition, since it is the same as that of the said 1st Embodiment about the other structure of this 2nd Embodiment, the same code | symbol is attached | subjected to the member which performs the same function as the said 1st Embodiment, and description is abbreviate | omitted. .

  In the second embodiment, the drive gear 51 and the support shaft 53 are connected by the spline coupling S, so that the drive gear 51 can move in the axial direction with respect to the support shaft 53 and cannot rotate about the axis. . The spline connection S functions as a movement allowance means. A spring 61, a spring retainer 62, and an adjustment screw 63 are interposed between the drive gear 51 and the housing 10.

  The spring 61 is interposed between the large-diameter portion 51a of the drive gear 51 and the spring retainer 62 so as to maintain a predetermined pressing force, and the drive gear 51 is inserted from the large-diameter portion 51a side. It is pressed in the axial direction toward the small diameter portion 51b. A stopper 53a that can be engaged with the small-diameter portion 51b of the drive gear 51 is integrally provided on the outer periphery of the end portion of the support shaft 53 on the bearing 54 side. The maximum amount of movement toward the bearing 54 is defined.

  The spring retainer 62 has a disk shape having a center hole 62a having an inner diameter larger than the outer diameter of the support shaft 53, and the support shaft 53 is inserted through the center hole 62a. It is assembled so that it can rotate around. The adjustment screw 63 is formed in an annular shape, and the spring retainer 62 is rotatably supported by an annular groove 63a formed on the inner periphery thereof. The adjustment screw 63 is formed on the housing 10 by a male screw portion 63b formed on the outer periphery thereof. The female threaded portion 10b is screwed so as to be movable in the axial direction. The adjustment screw 63 can be rotated from the outside of the housing 10.

  Thereby, the pressing force of the spring 61 can be adjusted according to the rotation operation of the adjusting screw 63 from the outside of the housing 10. The spring 61, the spring retainer 62, and the adjustment screw 63 serve as an urging means, and the spring retainer 62, the adjustment screw 63, and the female screw portion 10b of the housing 10 serve as an adjustment mechanism.

  In the second embodiment configured as described above, the drive gear 51 and the support shaft 53 are relatively movable in the axial direction by the spline coupling S and are not relatively rotatable around the axis. Accordingly, the drive gear 51 rotates together with the support shaft 53 in the same manner as in the first embodiment, but the spring 61 and the spring retainer 62 rotate around the shaft together with the drive gear 51 in the first embodiment. Is different.

  In the second embodiment, only the drive gear 51 is urged directly in the axial direction from the large diameter portion 51a side to the small diameter portion 51b side by the spring 61, so that it is compared with the first embodiment. Thus, the pressing force of the spring 61 as the biasing means can be set small. Also in the second embodiment, the impact absorption characteristics of the spring 61 suppress the generation of sound and vibration when the gears 51 and 52 are engaged. Further, even when a sudden radial force acts on the meshing portion of both the gears 51, 52, the force is effectively absorbed by the elastic deformation of the rubber 55 and the elastic joint 43.

  In the first embodiment and the second embodiment, the bearing 54 is assembled to the housing 10 via the rubber 55 so that the movement of the drive gear 51 in the axial direction is allowed. However, in addition to or in addition to this, for example, the driven gear 52 is coupled to the nut 32 via an elastic body such as rubber so that the driven gear 52 is allowed to move in the axial direction. It is also possible.

  In the first embodiment and the like, the bearing 54 is assembled to the housing 10 via the rubber 55 so that the drive gear 51 is allowed to move in the radial direction. However, in addition to or in addition to this, for example, the bearings 34 and 35 are assembled to the housing 10 via an elastic body such as rubber so that the driven gear 52 is allowed to move in the radial direction. In addition, an elastic body such as rubber may be interposed between the driven gear 52 and the nut 32 so that the driven gear 52 is allowed to move in the radial direction. is there. According to this, when a sudden radial force acts on the meshing portion of the drive gear 51 and the driven gear 52 due to the meshing accuracy and assembly accuracy of the drive gear 51 and the driven gear 52, The force is absorbed by the elastic deformation of the elastic body.

  Further, in each of the above-described embodiments, the drive gear and the driven gear are implemented using the parallel shaft specification conical gears 51 and 52. However, the drive gear and the driven gear are implemented using, for example, a cross shaft specification cone gear. It is also possible to do.

1 is a front sectional view schematically showing a main part of an electric power steering apparatus according to a first embodiment of the present invention. It is front sectional drawing which shows roughly the principal part of the electric power steering apparatus which concerns on 2nd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Housing, 10a ... Female thread part (adjustment mechanism), 20 ... Rack bar, 30 ... Ball screw mechanism (displacement conversion mechanism), 31 ... Screw shaft, 32 ... Nut (input member), 33 ... Ball, 40 ... Electric motor , 42 ... output shaft, 43 ... elastic joint (movement permitting means), 50 ... reduction gear, 51 ... drive gear, 51a ... large diameter part, 51b ... small diameter part, 52 ... driven gear, 53 ... support shaft, 54 ... bearing , 55 ... rubber (movement allowing means), 56 ... spring (biasing means), 57 ... spring retainer (biasing means, adjusting mechanism), 58 ... adjusting screw (biasing means, adjusting mechanism), S ... spline coupling ( Movement permitting means), 61 ... Spring (biasing means), 62 ... Spring retainer (biasing means, adjusting mechanism), 63 ... Adjusting screw (biasing means, adjusting mechanism), 10b ... Female thread portion (adjusting mechanism)

Claims (5)

The rotation of the output shaft of the electric motor assembled in the housing is decelerated by the speed reducer, and the decelerated rotation is converted into the displacement of the rack bar in the axial direction by the displacement conversion mechanism, and an axial force is applied to the rack bar. In the electric power steering device configured to be
The speed reducer includes a conical drive gear coupled to the output shaft of the electric motor, a conical driven gear coupled to the input member of the displacement conversion mechanism and meshed with the drive gear, the drive gear, and the Movement permitting means for allowing at least one of the driven gears to move in the axial direction, and the gear that is movable in the axial direction by the movement allowing means from the large diameter side toward the small diameter side. An electric power steering apparatus, comprising: an urging unit that urges the gears in a direction and elastically meshes the two gears. In the electric power steering apparatus according to claim 1,
The electric power steering apparatus characterized in that the movement permitting means is configured to be able to move the drive gear in the axial direction together with a support shaft that supports the drive gear. In the electric power steering apparatus according to claim 1,
The electric power steering apparatus according to claim 1, wherein the movement permitting means is configured to be capable of moving the drive gear in an axial direction relative to a support shaft that supports the drive gear. In the electric power steering apparatus according to any one of claims 1 to 3,
The electric power steering apparatus according to claim 1, wherein the movement permitting means is configured to move the drive gear in a radial direction together with a support shaft that supports the drive gear. In the electric power steering apparatus according to any one of claims 1 to 4,
The electric power steering apparatus characterized in that the urging means includes an adjustment mechanism capable of adjusting an urging force for urging the one gear in the axial direction from the large diameter portion toward the small diameter portion. .

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