JP2013204800A - Reduction gear for electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the number of parts of a driving side toothed pulley while a belt position regulating function for the driving side toothed pulley is provided, in an electric power steering device with a reduction gear using a toothed belt.SOLUTION: In a reduction gear of an electric power steering device 10, a driving side toothed pulley 30 includes guide members 33, 34 larger in a diameter than a tooth part 31A of a drive shaft 32 of a pulley body 31 and fixed on both sides of the tooth part 31A, and at least one guide member 33 comprises an inner ring 36B of a bearing 36 for supporting the drive shaft 32 of the pulley body 31 to a housing 21.

Description

  The present invention relates to a reduction device for an electric power steering apparatus.

  As a reduction device for an electric power steering device, as described in Patent Document 1, a rack shaft is supported on a housing so as to be linearly movable, an electric motor is attached to the housing, and a drive-side toothed pulley coupled to the rotating shaft of the electric motor Is transmitted to the rack shaft via a power transmission mechanism including a driven side toothed pulley connected to the driving side toothed pulley via a toothed belt.

  In the reduction device of the electric power steering apparatus described in Patent Document 1, the driving-side toothed pulley and the driven-side toothed pulley are fixed on both sides of the pulley body with a flange member having a larger outer diameter than the toothed portion. Yes. The flange member of the toothed pulley regulates the winding position of the toothed belt wound around the tooth portion of the pulley main body and prevents its falling off.

  In addition, the flange member fixed to the pulley main body of a toothed pulley is comprised by the plate-shaped member as described in patent document 2. FIG.

JP2007-153300 JP2004-183742

  In the reduction device of the electric power steering device described in Patent Document 1, the toothed pulley has a flange member made of a plate-like member fixed to each side of the tooth portion of the pulley body, as described in Patent Document 2, There are many parts.

  An object of the present invention is to reduce the number of parts of a driving side toothed pulley in an electric power steering apparatus having a reduction gear using a toothed belt while having a belt position regulating function of the driving side toothed pulley. is there.

  According to the first aspect of the present invention, the rack shaft is supported on the housing so as to be linearly movable, the electric motor is attached to the housing, and the rotational force of the driving side toothed pulley coupled to the rotating shaft of the electric motor is applied to the driving side teeth. In a reduction device for an electric power steering device that transmits to a rack shaft via a power transmission mechanism including a driven-side toothed pulley connected to a toothed pulley via a toothed belt, the driving-side toothed pulley is connected to the driving shaft of the pulley body. A guide member having an outer diameter larger than that of the tooth portion is fixed to both sides of the tooth portion, and at least one guide member is constituted by an inner ring of a bearing that supports the drive shaft of the pulley body on the housing. It is a thing.

  According to a second aspect of the present invention, in the first aspect of the invention, the pulley main body has an end surface near the tooth portion of the pulley main body in the inner ring of the bearing, rather than an end surface near the tooth portion of the pulley main body in the outer ring of the bearing. It protrudes closer to the tooth part.

  According to a third aspect of the invention, in the second aspect of the invention, the width of the inner ring of the bearing is set larger than the width of the outer ring of the bearing.

  The invention according to claim 4 is an electric power steering apparatus including the speed reducer according to any one of claims 1 to 3.

(Claims 1 and 4)
(a) In an electric power steering apparatus having a reduction gear using a toothed belt, at least one guide member of the drive side toothed pulley is constituted by an inner ring of a bearing that supports the drive shaft of the pulley body on the housing. That is, the outer diameter of the inner ring of the bearing is made larger than the outer diameter of the teeth of the pulley body, and the inner ring of the bearing is used as at least one guide member of the driving-side toothed pulley. It is not necessary to provide a special guide member such as a shaped member. An end surface of the inner ring of the bearing near the tooth portion of the pulley body functions as a belt position regulating surface. The number of parts of the drive-side toothed pulley can be reduced while having the belt position regulating function of the drive-side toothed pulley.

(Claim 2)
(b) The end face of the inner ring of the bearing near the teeth of the pulley body is set to protrude closer to the teeth of the pulley body than the end face of the outer ring of the bearing near the teeth of the pulley body. The end face of the toothed belt wound around the drive side toothed pulley does not hit the outer ring.

(Claim 3)
(c) The width of the inner ring of the bearing is set larger than the width of the outer ring of the bearing. The end face of the toothed belt wound around the drive side toothed pulley does not hit the outer ring.

FIG. 1 is a front view showing the entire electric power steering apparatus. FIG. 2 is a cross-sectional view showing the speed reducer. FIG. 3 is an enlarged cross-sectional view showing a main part of the reduction gear.

  As shown in FIG. 1, the electric power steering apparatus 10 includes a first gear housing 11A and a second gear housing 11B in which the gear housing 11 is divided, and a steering input is input to the gear housing 11 (first gear housing 11A). The shaft 12 is supported, an output shaft (not shown) is connected to the input shaft 12 via a torsion bar 13, a pinion (not shown) is provided on the output shaft, and the rack shaft 14 meshing with the pinion is connected to the gear housing 11. It is supported so that it can move linearly in the left-right direction. A steering torque sensor (not shown) is provided between the input shaft 12 and the output shaft. The steering torque sensor detects the steering torque based on the relative rotational displacement generated between the input shaft 12 and the output shaft due to the elastic torsional deformation of the torsion bar caused by the steering torque applied to the steering wheel.

  The electric power steering apparatus 10 has both end portions of the rack shaft 14 projecting from both sides of the gear housing 11 (first gear housing 11A, second gear housing 11B), and tie rods 15A, 15B are connected to the end portions of the rack shaft 14, The left and right wheels can be steered via tie rods 15A and 15B that are linked to the 14 linear movements.

  The electric power steering device 10 includes an electric motor 20. The electric motor 20 is attached to a bearing housing 21 fixed to the first gear housing 11A, and the serration of the drive shaft 32 of the drive side toothed pulley 30 is coaxially coupled to the serration hole of the rotary shaft 20A of the electric motor 20. ing.

  The electric power steering device 10 has a large-diameter driven-side toothed pulley 40 connected to the small-diameter driving-side toothed pulley 30 via a toothed belt 50 by the rotational force of the driving-side toothed pulley 30 provided by the electric motor 20. Is transmitted to the rack shaft 14 through a power transmission mechanism including a speed reducer.

  As shown in FIGS. 2 and 3, the drive-side toothed pulley 30 has guide members 33 and 34 having outer diameters larger than those of the tooth portion 31A fixed to both sides of the tooth portion 31A of the drive shaft 32 of the pulley body 31. Prepare. The guide members 33 and 34 on both sides regulate the winding position of the toothed belt 50 wound around the tooth portion 31A and prevent the falling off.

  In the drive side toothed pulley 30, two rolling bearings 35 and 36 are loaded on a drive shaft 32 extending to one side of the tooth portion 31 </ b> A of the pulley body 31, and these bearings 35 and 36 are supported by the above-described bearing housing 21. doing. Here, the bearing 35 is sandwiched between both end surfaces of the outer ring 35 </ b> A by a stepped portion 21 </ b> J near the motor of the small-diameter bearing holding hole of the bearing housing 21 and a retaining ring 35 </ b> C engaged with the bearing holding hole of the bearing housing 21. The position of the inner ring 35B is fixed and the position of the inner ring 35B is fixed and restricted by a retaining ring 35D engaged with the drive shaft 32 at one end surface near the motor. In the bearing 36, the position of the outer ring 36 </ b> A is regulated by the stepped portion 21 </ b> K near the motor of the large-diameter bearing holding hole of the bearing housing 21, and the position of the inner ring 36 </ b> B is regulated by the end surface of the tooth portion 31 </ b> A of the pulley body 31 near the motor. .

  As shown in FIGS. 2 and 3, the driven-side toothed pulley 40 includes a tooth portion 41 </ b> A on the outer periphery of a cup-shaped pulley body 41, and a hollow cylindrical boss 42 at the center of the pulley body 41.

  The electric power steering apparatus 10 is provided with a ball screw 60 on the rack shaft 14, a ball nut 62 that meshes with the ball screw 60 via a ball 61, and a rolling bearing supported on the gear housing 11 (first gear housing 11 </ b> A). A ball nut 62 is rotatably supported by 63. The boss 42 of the driven-side toothed pulley 40 is fixed to the outer periphery of the ball nut 62. Here, the bearing 63 is positioned between both end surfaces of the outer ring 63A by a stepped portion 11J of the bearing holding hole of the first gear housing 11A and a bearing nut 64 screwed into the bearing holding hole of the first gear housing 11A. Regulated and fixed. The boss 42 of the driven-side toothed pulley 40 and the inner ring 63B of the bearing 63 are screwed to the outer periphery of the ball nut 62 at one end step 62J on the outer periphery of the ball nut 62 and the other end on the outer periphery of the ball nut 62. It is clamped and fixed between the locking nuts 65.

  The electric power steering device 10 includes a tooth portion 31A of the pulley body 31 of the driving-side toothed pulley 30 on the electric motor 20 side and a tooth portion 41A of the pulley body 41 of the driven-side toothed pulley 40 on the ball nut 62 side. The toothed belt 50 is wound around, and the rotational force of the driving side toothed pulley 30 is transmitted from the toothed belt 50 to the ball nut 62 via the driven side toothed pulley 40 and then to the rack shaft 14, and the rack shaft 14 is straightened. Move.

Hereinafter, the operation of the electric power steering apparatus 10 will be described.
(1) When the steering torque detected by the steering torque sensor is lower than a predetermined value, the steering assist force is unnecessary and the electric motor 20 is not driven.

  (2) Since the steering assist force is required when the steering torque detected by the steering torque sensor exceeds a predetermined value, the electric motor 20 is driven. The rotational force of the driving-side toothed pulley 30 based on the torque generated by the electric motor 20 is transmitted from the toothed belt 50 to the ball nut 62 via the driven-side toothed pulley 40, and the rack shaft 14 is straightened through the ball screw 60. The steering assist force is moved.

  However, the electric power steering apparatus 10 has the following configuration in order to reduce the number of parts of the driving side toothed pulley 30 while having the belt position regulating function of the driving side toothed pulley 30.

  In the electric power steering apparatus 10, as shown in FIG. 3, one guide member 33 of the drive-side toothed pulley 30 is configured by an inner ring 36 </ b> B of a bearing 36 that supports the drive shaft 32 of the pulley body 31 on the bearing housing 21. Yes. The outer diameter of the inner ring 36B of the bearing 36 serving as the guide member 33 is larger than the outer diameter of the tooth portion 31A of the pulley main body 31, and the winding position of the toothed belt 50 wound around the tooth portion 31A is regulated and dropped off. To prevent.

  The other guide member 34 of the drive-side toothed pulley 30 is made of, for example, a press-molded product, and is inserted into a mounting hole drilled on the central axis of the drive shaft 32 of the pulley body 31 and press-fitted.

  At this time, in the inner ring 36B of the bearing 36 constituting the guide member 33, the end surface Eb of the inner ring 36B near the tooth portion 31A of the pulley body 31 (the end surface Eb is in contact with the end surface of the tooth portion 31A near the motor. ) Protrudes closer to the tooth portion 31A of the pulley body 31 than the end face Ea of the outer ring 36A of the bearing 36 near the tooth portion 31A of the pulley body 31.

  Further, the width wb of the inner ring 36B of the bearing 36 constituting the guide member 33 is set to be larger than the width wa of the outer ring 36A of the bearing 36 (wb> wa).

According to the present embodiment, the following operational effects can be obtained.
(a) In the electric power steering apparatus 10 having a reduction gear using the toothed belt 50, at least one guide member 33 of the drive side toothed pulley 30 supports the drive shaft 32 of the pulley body 31 on the bearing housing 21. The inner ring 36B of the bearing 36 is used. That is, the outer diameter of the inner ring 36B of the bearing 36 is made larger than the outer diameter of the tooth portion 31A of the pulley body 31, and the inner ring 36B of the bearing 36 is used as at least one guide member of the driving-side toothed pulley 30. There is no need to provide a special guide member such as a plate-like member as the guide member. An end surface Eb of the inner ring 36B of the bearing 36 near the tooth portion 31A of the pulley body 31 functions as a belt position regulating surface. The number of parts of the drive-side toothed pulley 30 can be reduced while the belt position regulating function of the drive-side toothed pulley 30 is provided.

  (b) The end surface Eb near the tooth portion 31A of the pulley body 31 in the inner ring 36B of the bearing 36 is more than the end surface Ea near the tooth portion 31A of the pulley body 31 in the outer ring 36A of the bearing 36. It is set so as to protrude toward 31A. The end surface of the toothed belt 50 wound around the drive-side toothed pulley 30 does not hit the outer ring.

  (c) The width wb of the inner ring 36B of the bearing 36 is set larger than the width wa of the outer ring 36A of the bearing 36. The end surface of the toothed belt 50 wound around the drive-side toothed pulley 30 does not hit the outer ring.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, in a drive-side toothed pulley, when the drive shaft of the pulley body is supported at both ends by bearings arranged on both sides of the tooth portion, the guide members on both sides of the tooth portion of the pulley body are supported by inner rings of the both bearings. It may be configured.

  In the present invention, the rack shaft is supported on the housing so as to be linearly movable, and an electric motor is attached to the housing, and the rotational force of the driving-side toothed pulley coupled to the rotating shaft of the electric motor is applied to the driving-side toothed pulley. In a reduction device for an electric power steering device that transmits to a rack shaft via a power transmission mechanism that includes a driven side toothed pulley connected via a belt, the driving side toothed pulley of the tooth portion provided on the driving shaft of the pulley body A guide member having an outer diameter larger than that of the tooth portion is fixed on both sides, and at least one guide member is constituted by an inner ring of a bearing that supports the drive shaft of the pulley body on the housing. Thereby, in the electric power steering apparatus having the reduction gear using the toothed belt, the number of parts of the driving side toothed pulley can be reduced while the belt position regulating function of the driving side toothed pulley is provided.

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 14 Rack shaft 20 Electric motor 20A Rotating shaft 21 Bearing housing 30 Drive side toothed pulley 31 Pulley main body 31A Tooth part 32 Drive shaft 33, 34 Guide member 36 Bearing 36A Outer ring 36B Inner ring 40 Driven side toothed pulley 50 Toothed belt Ea, Eb End face wa, wb width

Claims (4)

The rack shaft is supported on the housing so that it can move linearly, and an electric motor is attached to the housing, and the rotational force of the driving-side toothed pulley coupled to the rotating shaft of the electric motor is applied to the driving-side toothed pulley via a toothed belt. In the reduction device of the electric power steering device that transmits to the rack shaft through the power transmission mechanism including the driven side toothed pulley connected to
The drive-side toothed pulley is formed by fixing a guide member having a larger outer diameter than the tooth part on both sides of the tooth part of the drive shaft of the pulley body,
A reduction device for an electric power steering device, wherein at least one guide member is constituted by an inner ring of a bearing that supports a drive shaft of a pulley body on a housing.   2. The electric power steering according to claim 1, wherein an end surface of the inner ring of the bearing near the tooth portion of the pulley body protrudes closer to a tooth portion of the pulley body than an end surface of the outer ring of the bearing near the tooth portion of the pulley body. Equipment speed reducer.   The speed reducer for an electric power steering apparatus according to claim 2, wherein a width of an inner ring of the bearing is set larger than a width of an outer ring of the bearing.   An electric power steering apparatus comprising the speed reducer according to claim 1.

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