JP2013194901A - Reduction gear of electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a ball nut from being inclined due to a tension of a toothed belt in an electric power steering device having a reduction gear using the toothed belt.SOLUTION: In a reduction gear of an electric power steering device 10, a toothed belt 50 wound around a drive-side toothed pulley 30 and a driven-side toothed pulley 40, a ball nut 62, and a bearing 63 of the ball nut 62 are arranged at the same position along an axial direction of a rack shaft 14.

Description

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

  As described in Patent Documents 1 and 2, as a reduction device for an electric power steering device, a rack shaft is supported on a housing so as to be linearly movable, and an electric motor is attached to the housing and coupled to a rotating shaft of the electric motor. Some have transmitted the rotational force of a pulley with a pulley to a 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 power transmission mechanism of the reduction gear described in Patent Documents 1 and 2, a ball screw is provided on the rack shaft, and a ball nut that meshes with the ball screw via the ball is supported by a bearing supported on the housing. The driven toothed pulley is fixed. Thereby, the rotation of the drive side toothed pulley by the electric motor is converted into the linear movement of the rack shaft.

JP2003-291830 JP2004-314770

  In the reduction device of the electric power steering device described in Patent Document 1, when viewed from the direction perpendicular to the axis of the rack shaft, within the belt width of the toothed belt wound around the driving-side toothed pulley and the driven-side toothed pulley. Neither ball nut nor ball nut bearing is arranged.

  In the reduction device for the electric power steering device described in Patent Document 2, when viewed from the direction perpendicular to the axis of the rack shaft, the belt width of the toothed belt wound around the driving-side toothed pulley and the driven-side toothed pulley is within the belt width. Although the ball nut is arranged, the ball nut bearing is not arranged.

  By the way, with respect to the ball screw and the ball, the ball nut cannot be reduced to zero due to the ease of assembling and friction, and the play becomes a radial gap. For this reason, the ball nut and / or the bearing thereof are not disposed within the belt width of the toothed belt wound around the driving-side toothed pulley and the driven-side toothed pulley as viewed from the direction perpendicular to the axis of the rack shaft. In the case of offset, the tension of the toothed belt acting on the ball nut via the driven-side toothed pulley becomes the rotational moment around the bearing of the ball nut, and the ball nut is inclined with respect to the ball screw. . The tilt of the ball nut causes a twist between the ball nut, the ball, and the ball screw, which impairs the friction performance and the operation sound.

  The subject of this invention is preventing the inclination of a ball nut by the tension | tensile_strength of a toothed belt in the electric power steering apparatus which has a reduction gear using a toothed belt.

  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. Is transmitted to the rack shaft via a power transmission mechanism including a driven-side toothed pulley connected to a pulley with a toothed belt. The power transmission mechanism is provided with a ball screw on the rack shaft, In a reduction device for an electric power steering device in which a ball nut engaged through a ball is supported by a bearing supported by a housing and a driven toothed pulley is fixed to the ball nut, a driving side toothed pulley and a driven side The toothed belt wound around the toothed pulley, the ball nut, and the ball nut bearing are arranged at the same position along the axial direction of the rack shaft. It is.

  The invention according to claim 2 is the belt of the toothed belt that is further wound around the driving-side toothed pulley and the driven-side toothed pulley in the invention according to claim 1 when viewed from the direction perpendicular to the axis of the rack shaft. A ball nut and a ball nut bearing are arranged within the width.

  According to a third aspect of the present invention, in the invention according to the first or second aspect, the drive-side toothed pulley is provided with bearings on both sides of a tooth portion provided in the pulley body, and both the housings are provided via these bearings. It is intended to be supported.

  According to a fourth aspect of the present invention, in the invention according to any one of the first to third aspects, the driven-side toothed pulley includes a tooth portion on an outer periphery of the outer cylindrical portion of the cup-shaped pulley body, The inner cylinder part which protrudes toward the cup inner side enclosed by the said outer cylinder part from the center of the cup bottom part of a pulley main body is provided, and this inner cylinder part is inserted and fixed to a ball nut.

  The invention according to claim 5 is an electric power steering apparatus including the speed reducer according to any one of claims 1 to 4.

(Claims 1 and 5)
(a) In an electric power steering apparatus having a reduction gear using a toothed belt, a toothed belt wound around a driving-side toothed pulley and a driven-side toothed pulley, a ball nut, and a ball nut bearing, Arranged at the same position along the axial direction of the rack shaft. As a result, the tension of the toothed belt acting on the ball nut (the range where the ball is between the ball screw and the ball nut) via the driven-side toothed pulley is perpendicular to the axis passing through the ball nut and its bearing. Therefore, there is no rotational moment around the bearing of the ball nut, and the ball nut is not tilted with respect to the ball screw. That is, since there is no inclination of the ball nut which causes a twist between the ball nut, the ball and the ball screw, the friction performance and the operation sound are not impaired.

(Claim 2)
(b) The ball nut and the ball nut bearing are disposed within the belt width of the toothed belt wound around the driving-side toothed pulley and the driven-side toothed pulley when viewed from the direction perpendicular to the rack shaft. did. Thereby, the above-mentioned (a) can be realized reliably.

(Claim 3)
(c) The drive-side toothed pulley is provided with bearings on both sides of the tooth portion provided on the pulley body, and is supported at both ends by the housing via these bearings. As a result, the tension of the toothed belt in which the driving side toothed pulley is stably arranged in parallel with the driven side toothed pulley around the rack shaft, the ball nut, and the ball nut bearing and wound around the driving side toothed pulley. However, it acts in a direction perpendicular to the axis passing through the ball nut and its bearing.

(Claim 4)
(d) The driven-side toothed pulley has a tooth portion on the outer periphery of the outer cylindrical portion of the cup-shaped pulley body, and is directed from the center of the cup bottom portion of the cup-shaped pulley main body toward the inside of the cup surrounded by the outer cylindrical portion. The inner cylinder part which protruded in this way was provided, and this inner cylinder part was inserted and fixed to the ball nut. By using this driven side toothed pulley, the above-mentioned (a) and (b) can be realized reliably.

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 flange members 33 and 34 having a larger outer diameter than the tooth portion 31A on both sides of the tooth portion 31A provided on the drive shaft 32 of the pulley body 31. Prepare. The flange 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.

  The drive-side toothed pulley 30 is loaded with rolling bearings 35 and 36 on each of the drive shafts 32 extending on both sides of the tooth portion 31A of the pulley body 31, and is supported by the bearing housing 21 through these bearings 35 and 36. Is done.

  The bearing 35 is loaded and fixed in a bearing holding hole near the motor of the bearing housing 21. The bearing 35 has its both end faces of the outer ring 35 </ b> A sandwiched between the stepped portion 21 </ b> J of the bearing holding hole near the motor of the bearing housing 21 and the retaining ring 35 </ b> C engaged with the bearing holding hole of the bearing housing 21. Is done. The bearing 35 includes an inner ring 35B loaded with a flange member 33 on a drive shaft 32 extended to one side of a tooth portion 31A of the pulley body 31 and a retaining ring 35D engaged with the drive shaft 32 and teeth of the pulley body 31. The flange member 33 is sandwiched and fixed between the end surface near the motor of the portion 31A.

  The bearing 36 is loaded and fixed in a bearing holding hole of the bearing housing 21 near the anti-motor. The bearing 36 is fixedly loaded with the outer ring 36 </ b> A in the bearing holding hole of the bearing housing 21 near the non-motor. The bearing 36 is loaded and fixed to a drive shaft 32 in which the inner ring 36B extends to the other side of the tooth portion 31A of the pulley body 31, and the inner ring 36B and the end surface of the pulley body 31 on the side opposite to the motor of the tooth portion 31A. A flange member 34 is sandwiched and fixed therebetween.

  The driven-side toothed pulley 40 includes a tooth portion 41A on the outer periphery of the outer cylindrical portion a of the cup-shaped pulley body 41 as shown in FIGS. The driven-side toothed pulley 40 includes an inner cylinder portion b protruding from the center of the cup bottom of the cup-shaped pulley body 41 toward the inside of the cup surrounded by the outer cylinder portion a. The inner cylinder part b constitutes a hollow cylindrical boss 42 that is coaxial with the outer cylinder part a, and the boss 42 is inserted into and fixed to a ball nut 62 described later. The driven-side toothed pulley 40 is a cup-shaped pulley body 41 in which the outer cylinder part a and the inner cylinder part b are arranged on the same side in the axial direction with respect to the cup bottom part.

  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 prevent the ball nut 62 from being inclined due to the tension of the toothed belt 50.

  As shown in FIG. 3, the electric power steering device 10 includes a toothed belt 50 wound around a driving side toothed pulley 30 and a driven side toothed pulley 40, and a ball nut 62 (in the ball nut 62, a ball screw 60. The range in which the balls 61 are in between) and the bearings 63 of the ball nuts 62 are arranged at the same position along the axial direction of the rack shaft 14.

  In other words, the electric power steering device 10 has a belt width of the toothed belt 50 wound around the driving-side toothed pulley 30 and the driven-side toothed pulley 40 when viewed from the direction perpendicular to the rack shaft 14 (FIG. 3). In W, a ball nut 62 (a range where the ball 61 is located between the ball nut 62 and the ball screw 60) and a bearing 63 of the ball nut 62 are disposed.

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, the toothed belt 50 wound around the driving side toothed pulley 30 and the driven side toothed pulley 40, the ball nut 62, and the ball The bearing 63 of the nut 62 is disposed at the same position along the axial direction of the rack shaft 14. As a result, the tension of the toothed belt 50 acting on the ball nut 62 (in the range where the ball 61 is between the ball screw 60 and the ball nut 62) via the driven-side toothed pulley 40 is reduced. It acts in the direction perpendicular to the axis passing through the bearing 63, and does not cause a rotational moment around the bearing 63 of the ball nut 62, and the ball nut 62 is not inclined with respect to the ball screw 60. In other words, since there is no inclination of the ball nut 62 that causes a twist between the ball nut 62, the ball 61, and the ball screw 60, the friction performance and the operation sound are not impaired.

  (b) a ball nut 62 within the belt width W of the toothed belt 50 wound around the driving-side toothed pulley 30 and the driven-side toothed pulley 40 when viewed from the direction perpendicular to the rack shaft 14; A bearing 63 for the ball nut 62 is disposed. Thereby, the above-mentioned (a) can be realized reliably.

  (c) The drive-side toothed pulley 30 is provided with bearings 35 and 36 on both sides of the tooth portion 31A provided on the pulley body 31 and is supported at both ends by the bearing housing 21 via these bearings 35 and 36. As a result, the driving-side toothed pulley 30 is stably arranged in parallel with the driven-side toothed pulley 40 around the rack shaft 14, the ball nut 62, and the bearing 63 of the ball nut 62, and is wound around the driving-side toothed pulley 30. The tension of the toothed belt 50 to be applied surely acts in the direction perpendicular to the axis passing through the ball nut 62 and its bearing 63.

  (d) The driven-side toothed pulley 40 includes a tooth portion 41A on the outer periphery of the outer cylindrical portion a of the cup-shaped pulley main body 41, and extends from the center of the cup bottom of the cup-shaped pulley main body 41 to the outer cylindrical portion a. The inner cylinder part b which protrudes toward the inner side of the enclosed cup was provided, and this inner cylinder part b was inserted into the ball nut 62 and fixed. By using this driven side toothed pulley 40, the above-mentioned (a) and (b) can be realized reliably.

  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.

  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. The power is transmitted to the rack shaft via a power transmission mechanism including a driven-side toothed pulley connected via a belt, and the power transmission mechanism is provided with a ball screw on the rack shaft and the ball screw via the ball. In a reduction device for an electric power steering device in which a meshing ball nut is supported by a bearing supported by a housing and a driven toothed pulley is fixed to the ball nut, a driving toothed pulley and a driven toothed pulley The wound toothed belt, the ball nut, and the ball nut bearing were arranged at the same position along the axial direction of the rack shaft. Thereby, in the electric power steering apparatus having the reduction gear using the toothed belt, the inclination of the ball nut due to the tension of the toothed belt can be prevented.

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Gear housing 14 Rack shaft 20 Electric motor 20A Rotating shaft 21 Bearing housing 30 Drive side toothed pulley 31 Pulley body 31A Tooth part 35, 36 Bearing 40 Driven side toothed pulley 41 Pulley body 41A Tooth part 50 Tooth With belt 60 Ball screw 61 Ball 62 Ball nut 63 Bearing a Outer cylinder part b Inner cylinder part w Belt width

Claims (5)

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. Is transmitted to the rack shaft through a power transmission mechanism including a driven-side toothed pulley connected to
The power transmission mechanism includes a ball screw provided on the rack shaft, a ball nut meshed with the ball screw via the ball is supported by a bearing supported on the housing, and a driven toothed pulley is fixed to the ball nut. In the reduction device of the electric power steering device,
A toothed belt wound around a driving-side toothed pulley and a driven-side toothed pulley, a ball nut, and a bearing of the ball nut are arranged at the same position along the axial direction of the rack shaft. Reducer for electric power steering device.   A ball nut and a ball nut bearing are arranged within the belt width of the toothed belt wound around the driving-side toothed pulley and the driven-side toothed pulley as viewed from the direction perpendicular to the rack shaft. The reduction device for an electric power steering apparatus according to claim 1.   The speed reduction of the electric power steering apparatus according to claim 1 or 2, wherein the drive-side toothed pulley is provided with bearings on both sides of a tooth portion provided in the pulley body, and is supported at both ends by the housing via these bearings. apparatus.   The driven toothed pulley has a tooth portion on the outer periphery of the outer cylindrical portion of the cup-shaped pulley body, and protrudes from the center of the cup bottom portion of the cup-shaped pulley main body toward the inside of the cup surrounded by the outer cylindrical portion. The speed reducer for an electric power steering apparatus according to any one of claims 1 to 3, further comprising a cylindrical portion, wherein the inner cylindrical portion is inserted and fixed to a ball nut.   An electric power steering apparatus comprising the speed reducer according to claim 1.

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