JP2006044449A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device capable of miniaturizing a supporting part of a drive gear, reducing degradation of the engagement state by the engagement reaction force, and reducing sounding by the engagement reaction force. <P>SOLUTION: The electric power steering device comprises a worm 3 which is connected in an interlocking manner to an output shaft 1a of an electric motor 1 and has a shaft part 3b on the side opposite to the electric motor 1, a worm wheel 4 to be engaged with the worm 3, a rolling bearing 8 to be fitted to the shaft part 3b, a housing 7 to movably support the rolling bearing 8 in a direction in which the inter-core distance H of the worm 3 and the worm wheel 4 becomes long and short, a leaf spring 14 to elastically press the rolling bearing 8 in a direction in which the inter-core distance H becomes shorter, and a synthetic resin-made case 20 having a guide part 22a which stores the rolling bearing 8 and the leaf spring 14 and guides the movement of the rolling bearing 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric power steering apparatus using an electric motor as a generation source of a steering assist force.

  An electric power steering device for a vehicle includes an electric motor for assisting steering and a reduction gear mechanism that transmits a rotational force of the electric motor to the steering means, and the operation of the steering means according to the operation of the operation member is It is configured to assist by the rotation of the electric motor and reduce the labor burden on the driver for steering.

  The reduction gear mechanism includes a worm as a drive gear interlocking with the rotation of the electric motor, and a worm wheel as a driven gear meshing with the worm, and is rotatably supported in a housing having an accommodation hole. .

In the electric power steering apparatus using the reduction gear mechanism as described above, in order to reduce the backlash amount at the meshing portion of the worm and the worm wheel and reduce the rattling noise due to the backlash at the time of turning, A spring ring is provided for repressing the anti-electric motor side of the worm whose both end shaft portions are supported by rolling bearings in a direction in which the distance between the centers of the worm and the worm wheel is shortened and preloading the meshing portion (for example, Patent Document 1).
JP 2001-315653 A

  However, the spring ring of Patent Document 1 is vulcanized and bonded to the inner ring member fitted to the outer ring of the rolling bearing, the outer ring member fitted to the housing hole of the housing, and the inner ring member and the outer ring member. Therefore, there is a problem that the support portion of the worm becomes large.

  The present invention has been made in view of such circumstances, and can reduce the size of the support portion of the drive gear, reduce the deterioration of the meshing state due to the meshing reaction force, and further reduce the noise caused by the meshing reaction force. An object is to provide an electric power steering device that can be reduced.

  An electric power steering device according to a first aspect of the present invention is interlocked and connected to an output shaft of an electric motor, a drive gear having a shaft portion on the opposite side of the electric motor, and a driven gear that meshes with the drive gear and is connected to steering means. A bearing fitted to the shaft, a support member that supports the bearing so that the distance between the centers of the drive gear and the driven gear is longer, and the distance between the bearings is shorter. An electric power steering apparatus including a spring body that elastically presses in a direction includes a case made of a synthetic resin having a guide portion that accommodates the bearing and the spring body and guides the movement of the bearing.

  In the first invention, the bearing fitted to the shaft portion of the drive gear opposite to the electric motor and the spring body for elastically pressing the bearing are accommodated in the synthetic resin case, and the case is a bearing. The movement of the drive gear can be suppressed to the side crossing the direction in which the distance between the cores becomes longer and shorter, and the spring body can be brought into contact with the inner surface of the case. Can be reduced.

  In the electric power steering apparatus according to a second aspect of the invention, the case includes a moving body that is fitted to the outer peripheral portion of the bearing so as to be able to move integrally with the bearing, and a fixed body that accommodates the moving body so as to be movable. The spring body is disposed between the inner surface of the fixed body and the bearing.

  In the second invention, the stationary body of the case is fixed to the support member, and the movable body movably accommodated in the stationary body moves integrally with the bearing. The movement can be eliminated and the noise due to the meshing reaction force can be further reduced. Moreover, since the spring body is disposed between the inner surface of the fixed body and the bearing, it is possible to reduce the noise generated by the spring body.

  In the electric power steering apparatus according to a third aspect of the invention, the support member has an insertion hole into which the fixed body is inserted, and a viscoelastic body is disposed between the insertion hole and the fixed body. It is characterized by.

  In the third invention, since the viscoelastic body can absorb the variation in the size of the insertion hole of the support member, and the vibration propagating to the drive gear can be absorbed by the viscoelastic body, the electric motor When the abnormal noise generated on the side propagates to the drive gear, the vibration of the drive gear due to the abnormal noise can be suppressed, and the abnormal noise can be suppressed from being transmitted from the steering means to the operation member. Moreover, it can suppress that a vibration propagates to a supporting member.

  According to the first aspect of the present invention, it is possible to suppress the drive gear from moving to the side intersecting the direction in which the distance between the cores becomes longer and shorter, and to reduce the noise generated by the spring body.

  According to the second aspect of the present invention, there is no relative movement of the bearing and the moving body due to the meshing reaction force, and it is possible to further reduce the noise caused by the meshing reaction force and to reduce the noise caused by the spring body.

  According to the third invention, the variation in the size of the insertion hole of the support member can be absorbed by the viscoelastic body, and the vibration of the drive gear due to the abnormal noise generated on the electric motor side can be suppressed. Transmission from the steering means to the operation member can be suppressed. Moreover, it can suppress that a vibration propagates to a supporting member.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is an enlarged cross-sectional view showing a configuration of a main part of an electric power steering apparatus according to the present invention, FIG. 2 is a cross-sectional view taken along line II-II in FIG. 1, and FIG. It is.

  The electric power steering device includes an electric motor 1 for assisting steering, a worm 3 as a driving gear interlocked and connected to an output shaft 1 a of the electric motor 1 via a shaft coupling 2, and a driven gear meshing with the worm 3. The reduction gear mechanism A having the worm wheel 4 and the steering means 5 connected to the worm wheel 4 are provided.

  The steering means 5 is connected to a steering wheel B (operation member) for steering at one end, a first steering shaft 51 having a cylindrical portion 51a at the other end, and inserted into the cylindrical portion 51a. One end is connected to the cylinder portion 51a of the first steering shaft 51, the torsion bar 52 is twisted by the action of the steering torque applied to the steering wheel B, and the other end is connected to the other end of the torsion bar 52. A second steering shaft 53 connected to the wheel 4 is provided, and the second steering shaft 53 is connected to, for example, a rack and pinion type steering mechanism (not shown) via a universal joint.

  The worm 3 of the reduction gear mechanism A has shaft portions 3 a and 3 b at both rotation center portions, and one shaft portion 3 a is freely rotatable to an aluminum housing 7 as a support member via a rolling bearing 6. In a state where it is housed and supported, it is linked to the output shaft 1a of the electric motor 1 and a rolling bearing 8 is fitted to the other shaft portion 3b. The shaft coupling 2 that interlocks and connects the shaft portion 3a to the output shaft 1a is configured so that the worm 3 can be slightly swung around a position near the center of the rolling bearing 6 in the axial direction.

  The worm wheel 4 includes a synthetic resin annular tooth body 4a having teeth on the outer periphery and a metal core member 4b coupled to the inside of the annular tooth body 4a. The core member 4b is a second steering member. The shaft 53 is fitted and fixed in the middle. Further, the ringing tooth 4a made of synthetic resin reduces the noise caused by meshing with the worm 3.

  The housing 7 accommodates the worm 3, the first accommodating portion 7 a that rotatably supports the shaft portions 3 a and 3 b of the worm 3 via the rolling bearings 6 and 8, and the worm wheel 4. 4 includes a second steering shaft 53 and a second housing portion 7 b that supports the second steering shaft 53 via two rolling bearings 9 and 10 fitted to the second steering shaft 53.

  The first accommodating portion 7a is elongated in the axial direction of the worm 3, and at one end in the longitudinal direction, a support hole 71 for supporting the rolling bearing 6 by loose fitting, a stepped portion 72 connected to the support hole 71, and An annular groove 73 and a motor mounting portion 74 are provided, and a corrugated retaining ring 11 that contacts the outer ring of the rolling bearing 6 and fixes the outer ring to the stepped portion 72 is fitted into the annular groove 73. Yes. Further, the electric motor 1 is attached to the motor attachment portion 74.

  At the other end of the first housing portion 7a, a fitting hole 75 for fitting and supporting the case 20 fitted to the outer peripheral portion of the rolling bearing 8 and a screw hole 76 penetrating from the fitting hole 75 to the counter-electric motor side are provided. The lid 12 is screwed into the screw hole 76. The insertion holes 75 are opposed to the two surfaces facing away from each other in the direction in which the center distance H between the worm 3 and the worm wheel 4 becomes longer and shorter, and the two faces facing away from each other in the direction orthogonal to the direction in which the center distance H becomes longer and shorter. A case 20 made of synthetic resin is held in the fitting hole 75 by being fitted inside.

  The case 20 is made of a synthetic resin concave body that is fitted to the outer peripheral portion of the rolling bearing 8 so as to be integrally movable with the rolling bearing 8, and a synthetic resin that accommodates the movable body 21 in a movable manner. And the fixed body 22 is fitted into the insertion hole 75 via the viscoelastic body 13 having the rectangular cylinder shape.

  The moving body 21 has an arc inner surface 21 a having a circumference longer than the half circumference of the outer circumference of the rolling bearing 8, and the arc inner surface 21 a is fitted to the outer circumference of the rolling bearing 8.

  The fixed body 22 has a square cylinder shape that is slightly smaller than the insertion hole 75, and guides the movement of the rolling bearing 8 and the moving body 21 on the two surfaces orthogonal to the direction in which the inter-center distance H becomes longer or shorter. The gaps 20a that allow the movement of the moving body 21 in the direction in which the distance H between the cores becomes longer and shorter between the two surfaces on the side where the distance H between the edges becomes longer and the moving body 21. , 20a are provided. Further, one surface on the side where the inter-center distance H is increased is defined as a concave surface 22b, and the inter-center distance H is shortened between the concave surface 22b and the outer peripheral portion on the side where the inter-center distance H of the rolling bearing 8 is increased. A leaf spring 14 is provided as a spring body that elastically presses the rolling bearing 8. The leaf spring 14 is made of a flat spring steel plate. The viscoelastic body 13 is made of a rubber material or a flexible synthetic resin material, and is disposed between the insertion hole 75 and the fixed body 22.

  The housing 7 includes a torque sensor 15 for detecting a steering torque applied to the steering wheel B by a relative rotational displacement amount of the steering shafts 51 and 53 according to the twist of the torsion bar 52. The torque sensor 15 The electric motor 1 is configured to be driven and controlled based on the torque detected by the motor.

  In the electric power steering apparatus configured as described above, the rolling bearing 6 press-fitted into the shaft portion 3 a of the worm 3 is loosely fitted into the support hole 71, and the rolling bearing 8 press-fitted into the shaft portion 3 b is provided in the case 20. The leaf spring 14 in the case 20 is fitted into the movable body 21 and abuts against the outer peripheral surface of the rolling bearing 8, and the rolling bearing 8 and the worm 3 are elastically pressed in the direction in which the inter-center distance H is shortened, and the worm 3 and the worm wheel. Preload is applied to the meshing part 4.

  The worm 3 to which the preload has been applied moves in the direction in which the center distance H becomes shorter around the position in the vicinity of the center in the axial direction of the rolling bearing 6, and the backlash amount of the meshing portion can be reduced. The rattling noise can be reduced. Moreover, a movable body 21 made of synthetic resin is fitted to the outer peripheral portion of the rolling bearing 8 so as to be able to move integrally, and the movable body 21 can move along the guide portions 22 a and 22 a of the fixed body 22. Therefore, even when the meshing state of the meshing portion changes due to wear of the meshing portion, expansion or contraction due to temperature change of the worm wheel 4, the worm 3 can be smoothly moved by the elastic pressure of the leaf spring 14. Further, a leaf spring 14 is provided on the side where the inter-center distance H becomes longer, and a synthetic resin case 20 restricts the movement of the rolling bearing 8 on the side crossing the direction where the inter-center distance H becomes longer or shorter. Therefore, the meshing state of the meshing portion can be maintained, the deterioration of the meshing state due to the meshing reaction force can be reduced, and further, the noise caused by the meshing reaction force can be reduced.

  Further, since the leaf spring 14 elastically presses the rolling bearing 8 in the case 20, when the worm 3 and the rolling bearing 8 are moved in the direction in which the inter-center distance H is increased by the meshing reaction force, the leaf spring 14 contacts the housing 7. It is possible to prevent contact and to eliminate the sound produced by the leaf spring 14.

  In addition, since the viscoelastic body 13 is disposed between the insertion hole 75 of the housing 7 and the case 20, variations in the size of the insertion hole 75 can be absorbed by the viscoelastic body 13. Further, when vibration generated in the shaft coupling 2 portion or the like propagates to the worm 3, this vibration can be absorbed by the viscoelastic body 13, so that abnormal noise generated on the electric motor 1 side propagates to the worm 3. The vibration of the worm 3 due to this abnormal noise can be suppressed, and the transmission of the abnormal noise from the steering means 5 to the steering wheel B can be suppressed.

  In the above-described embodiment, the worm 3 is configured to be movable in the direction in which the center distance H becomes longer or shorter. However, for example, the worm wheel 4 can be moved in the direction in which the center distance H becomes longer or shorter. You may comprise. FIG. 4 is a cross-sectional view showing another embodiment. The electric power steering apparatus of this embodiment has a steering shaft 54 with one end connected to a steering wheel for steering and the worm wheel 4 fitted and fixed to the other end, and the steering shaft 54 is rotatably supported. An aluminum housing 7, a worm 3 rotatably supported in the housing 7 via a rolling bearing, and an electric motor 1. The worm wheel 4 includes an annular tooth body 4a made of a synthetic resin and a metal core member 4b.

  One end of the steering shaft 54 is supported on the housing 7 by a rolling bearing (not shown), and rolling bearings 9 and 10 are fitted and fixed to both sides of the worm wheel 4 on the other end side of the steering shaft 54. Yes. The rolling bearing 10 on the other end side with respect to the worm wheel 4 is fitted and fixed in the first fitting hole 77 in the housing 7, and the rolling bearing 9 on the one end side with respect to the worm wheel 4 is fitted in the second inside of the housing 7. The fitting hole 78 is loosely fitted, and a slight gap 78 a is provided between the second fitting hole 78 and the rolling bearing 9.

  The center-to-center distance H1 between the first fitting hole 77 and the fitting hole on which the worm 3 is supported is made smaller than the center-to-center distance H between the worm 3 and the worm wheel 4, and the steering shaft 54 is a rolling bearing at one end. And the rolling bearing 10 at the other end are slightly bent, and the worm wheel 4 is elastically pressed against the worm 3 by the bending restoring force of the steering shaft 51.

  According to the embodiment of FIG. 4, since the worm wheel 4 is elastically pressed against the worm 3 by the bending restoring force of the steering shaft 54, the worm wheel 4 having the synthetic resin annular tooth body 4a is caused by a decrease in the ambient temperature. When the mesh portion contracts or the mesh portion wears, the backlash amount of the mesh portion can be reduced within the gap 78a, and the generation of abnormal noise due to the backlash can be reduced. Further, when the worm wheel 4 expands due to an increase in ambient temperature, the worm wheel 4 can be moved in the direction in which the inter-center distance H is increased within the gap 78a, and the torque increase at the meshing portion can be mitigated. .

In the embodiment described above, the rolling bearing 8 is used as a bearing for supporting the worm 3 on the side opposite to the electric motor. However, a sliding bearing may be used.
Further, in the embodiment described above, the case 20 having the moving body 21 and the fixed body 22 is used. However, the case 20 eliminates the moving body 21 and includes guide portions 22 a and 22 a for guiding the movement of the rolling bearing 8. It is good also as a structure which has the fixed body 22 which has. In this case, the outer ring of the rolling bearing 8 comes into contact with the guide portions 22a and 22a to guide the movement in the direction in which the center distance H becomes longer or shorter.

  In the embodiment described above, the viscoelastic body 13 is disposed between the insertion hole 75 and the fixed body 22. However, the viscoelastic body 13 is eliminated and the case 20 is directly inserted into the insertion hole 75. It is good also as composition to do.

  In the embodiment described above, the reduction gear mechanism A is the worm gear provided with the worm 3 as the driving gear and the worm wheel 4 as the driven gear, but may be a bevel gear, a hypoid gear, or a helical gear. .

It is an expanded sectional view showing the composition of the important section of the electric power steering device concerning the present invention. It is sectional drawing of the II-II line of FIG. It is sectional drawing which shows the whole structure of the electric power steering apparatus which concerns on this invention. It is sectional drawing which shows other embodiment of an electric power steering device.

Explanation of symbols

1 Electric motor 1a Output shaft 3 Worm (drive gear)
3b Shaft 4 Worm wheel (driven gear)
5 Steering means 7 Housing (support member)
75 Insertion hole 8 Rolling bearing (bearing)
13 Viscoelastic body 14 Leaf spring (spring body)
20 Case 21 Moving body 22 Fixed body 22a Guide part H Center distance

Claims (3)

  A drive gear coupled to the output shaft of the electric motor, having a shaft portion on the opposite side of the electric motor, a driven gear meshing with the drive gear and connected to the steering means, and a bearing fitted to the shaft portion And a supporting member that supports the bearing so that the distance between the centers of the drive gear and the driven gear is long and short, and a spring body that elastically pressurizes the bearing in the direction that shortens the distance between the cores. An electric power steering apparatus comprising a case made of a synthetic resin that accommodates the bearing and the spring body and has a guide portion that guides the movement of the bearing.   The case includes a moving body that is fitted to the outer peripheral portion of the bearing so as to be able to move integrally with the bearing, and a fixed body that movably accommodates the moving body. The electric power steering apparatus according to claim 1, wherein the spring body is disposed between the bearing and the bearing.   The electric power steering apparatus according to claim 2, wherein the support member has an insertion hole into which the fixed body is inserted, and a viscoelastic body is disposed between the insertion hole and the fixed body.

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