JP2013203156A - Reduction gear device of electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simply prevent a toothed belt from moving in a belt width direction in an electric power steering device having a reduction gear device using the toothed belt.SOLUTION: In a reduction gear device of an electric power steering device, a tooth-width-directional tooth face of a driving-side toothed pulley 30 has a concave surface 101, and a tooth-width-directional tooth face of a toothed belt 50 has a convex surface 102 contacting and engaging the concave surface 101 in a convex/concave manner. A tooth-width-directional tooth face shape of the driving-side toothed pulley 30 is formed by extending the middle short concave surface 101 which is shortest in the center in the tooth width direction over the entire region of the tooth width, and a tooth-width-directional tooth face shape of the toothed belt 50 is formed by extending the middle tall convex surface 102 which is tallest in the center in the tooth width direction over the entire region of the tooth width. Further, the middle short concave surface 101 and middle tall convex surface 102 are curved respectively.

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.

JP2007-153300

  In the speed reducer of the electric power steering apparatus described in Patent Document 1, when the toothed belt circulates by the rotation of the toothed pulley, the toothed belt moves in the belt width direction.

  When the toothed pulley around which the toothed belt is wound is provided with flange members that regulate the belt winding position on both sides of the toothed portion, both end surfaces of the toothed belt are flanged by movement of the toothed belt in the belt width direction. There is a risk of abrasion damage due to friction.

  An object of the present invention is to easily prevent movement of a toothed belt in the belt width direction in an electric power steering apparatus having a reduction gear using a toothed belt.

  Another object of the present invention is to eliminate the need for a flange member for regulating the belt winding position in a toothed pulley.

  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, each toothed pulley on the driving side and the driven side; The tooth surface in the tooth width direction on one side of the toothed belt is provided with a concave surface, and the tooth surface in the tooth width direction on the other side is provided with a convex surface in contact with the concave surface.

  According to a second aspect of the present invention, in the first aspect of the present invention, the tooth surface in the tooth width direction of each of the toothed pulleys on the driving side and the driven side and one of the toothed belts is at the center in the tooth width direction. The lowest medium-low concave surface is extended over the entire tooth width, and the tooth surface shape in the tooth width direction on the other side is the highest medium-high convex surface in the center of the tooth width direction over the entire tooth width. It is intended to be extended.

  According to a third aspect of the present invention, in the second aspect of the present invention, each of the medium-low concave surface and the medium-high convex surface is curved.

  According to a fourth aspect of the present invention, in the second aspect of the present invention, each of the medium-low concave surface and the medium-high convex surface is formed in a V shape.

  According to a fifth aspect of the present invention, in the first aspect of the present invention, the tooth-side shape in the tooth width direction of one of the toothed pulleys on the driving side and the driven side and one of the toothed belts is a part of the tooth width direction. The tooth surface in the tooth width direction on the other of them is provided with a protrusion meshing with the above-mentioned recess in a part of the tooth width direction.

  The invention according to claim 6 is an electric power steering apparatus including the speed reducer according to any one of claims 1 to 5.

(Claims 1 and 6)
(a) In the electric power steering apparatus having a reduction gear using a toothed belt, each toothed pulley on the driving side and the driven side, and a tooth surface in the tooth width direction on one of the toothed belts is provided with a concave surface. The tooth surface in the tooth width direction on the other side has a convex surface that contacts the concave surface. As a result, the toothed belt is stabilized by positioning the central part of the toothed belt in the belt width direction at the lowest part of the concave surface of the tooth surface in the tooth width direction of the toothed pulley or the highest part of the convex surface during rotation. Therefore, movement in the belt width direction can be easily prevented.

  (b) When the toothed pulley around which the toothed belt is wound is provided with flange members that restrict the belt winding position on both sides of the toothed portion, both end surfaces of the toothed belt are moved by movement in the belt width direction. Can be prevented from rubbing against the flange member.

  (c) In the toothed pulley around which the toothed belt is wound, it is possible to eliminate the need for a flange member for regulating the belt winding position on both sides of the tooth portion.

(Claim 2)
(d) The toothed pulley on each of the driving side and the driven side, and the tooth surface in the tooth width direction on one of the toothed belts has the lowest mid-low concave surface at the center in the tooth width direction over the entire tooth width. The tooth surface in the tooth width direction of the other one of them is extended so that the middle-high convex surface having the highest shape in the center in the tooth width direction extends over the entire tooth width. Thus, during rotation, the toothed belt has the belt width direction center portion of the toothed belt at the lowest portion of the concave surface provided at the center of the tooth surface in the tooth width direction of the toothed pulley or the highest portion of the convex surface. It is positioned and stabilized, and can be reliably prevented from moving in the belt width direction.

(Claim 3)
(e) By making each of the medium-low concave surface and the medium-high convex surface curved, the contact between each toothed pulley and the toothed belt is smoothed, and the wear of the toothed belt is reduced. Can do.

(Claim 4)
(f) By making each of the medium-low concave surface and the medium-high convex surface V-shaped, the processing of each toothed pulley and toothed belt can be simplified.

(Claim 5)
(g) Each toothed pulley on the driving side and driven side, and the tooth surface shape in the tooth width direction on one of the toothed belts has a recess in a part in the tooth width direction, and the tooth in the tooth width direction on the other of them. The surface shape is provided with a convex portion that meshes with the concave portion in a part of the tooth width direction. As a result, the toothed belt meshes with a specific portion of the upper surface in the tooth width direction of each toothed pulley during rotation, and can be easily prevented from moving in the belt width direction.

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 a schematic diagram illustrating an example of contact between the toothed surfaces of the toothed pulley and the toothed belt. FIG. 4 is a schematic diagram showing another example of contact between the tooth surfaces of the toothed pulley and the toothed belt. FIG. 5 is a schematic diagram showing another example of contact between the tooth surfaces of the toothed pulley and the toothed belt. FIG. 6 is a schematic diagram showing another example of contact between the toothed surfaces of the toothed pulley and the toothed belt. FIG. 7 is a schematic diagram showing another example of contact between the tooth surfaces of the toothed pulley and the toothed belt.

  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 FIG. 2, the drive-side toothed pulley 30 includes flange members 33 and 34 having a larger outer diameter than the tooth portion 31 </ b> A on both sides of the tooth portion 31 </ b> A included in the drive shaft 32 of the pulley body 31. 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.

  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.

  As shown in FIG. 2, 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.

  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 toothed belt 50 wound around the drive-side toothed pulley 30 from moving in the belt width direction.

  In the embodiment of FIG. 3, the tooth width direction tooth surface of the driving-side toothed pulley 30 includes a concave surface 101, and the tooth width direction tooth surface of the toothed belt 50 comes into contact with the concave surface 101 to engage with the concave and convex portions. 102. In the present embodiment, a toothed belt is formed by extending a middle-low concave surface 101 whose tooth surface shape in the tooth width direction of the driving side toothed pulley 30 is the lowest at the center in the tooth width direction over the entire tooth width. 50 is provided with a medium-to-high convex surface 102 whose tooth surface shape in the tooth width direction is the highest at the center in the tooth width direction, extending over the entire tooth width. Furthermore, each of the middle-low concave surface 101 and the middle-high convex surface 102 is curved.

  The embodiment of FIG. 4 differs from the embodiment of FIG. 3 in that each of the middle-low concave surface 101 and the middle-high convex surface 102 is V-shaped.

  In the embodiment of FIG. 5, the tooth width direction tooth surface of the driving-side toothed pulley 30 includes a convex surface 111, and the tooth width direction tooth surface of the toothed belt 50 contacts the convex surface 111 and engages with the concave and convex surfaces. 112. In the present embodiment, the toothed belt 50 is formed by extending a middle-high convex surface 111 whose tooth surface shape in the tooth width direction of the drive side toothed pulley 30 is the highest in the center of the tooth width direction over the entire tooth width. The tooth surface in the tooth width direction is provided with a medium-low concave surface 112 that is the lowest at the center in the tooth width direction so as to extend over the entire tooth width. Further, each of the middle-high convex surface 111 and the middle-low concave surface 112 is curved.

  The embodiment of FIG. 6 differs from the embodiment of FIG. 5 in that each of the middle-high convex surface 111 and the middle-low convex surface 112 is V-shaped.

According to the embodiment of FIGS. 3 to 5, the following operational effects are obtained.
(a) During rotation, the toothed belt 50 is arranged in the belt width direction of the toothed belt 50 at the lowest portion of the concave surface 101 of the tooth surface in the tooth width direction of the driving side pulley 30 or the highest portion of the convex surface 111. The center portion is generally positioned and stabilized, and movement in the belt width direction can be easily prevented.

  (b) When the drive side toothed pulley 30 around which the toothed belt 50 is wound is provided with flange members 33 and 34 for restricting the belt winding position on both sides of the tooth portion 31A, the toothed belt 50 is provided. It is possible to avoid rubbing the both end faces against the flange members 33 and 34 due to the movement in the belt width direction.

  (c) In the drive side toothed pulley 30 around which the toothed belt 50 is wound, the flange members 33 and 34 for restricting the belt winding position on both sides of the tooth portion 31A can be eliminated.

  (d) During rotation, the toothed belt 50 is provided at the lowest position of the concave surface 101 provided at the center of the tooth surface in the tooth width direction of the driving side toothed pulley 30 or at the highest position of the convex surface 111. The belt width direction center is positioned and stabilized, and movement in the belt width direction can be reliably prevented.

  (e) By making each of the middle and low concave surfaces 101 and 112 and the middle and high convex surfaces 102 and 111 have a curved shape, the drive side toothed pulley 30 and the toothed belt 50 can be smoothly contacted, The wear of the attached belt 50 can be reduced.

  (f) Since each of the medium-low concave surface 101 and the medium-high convex surface 111 is V-shaped, the processing of each drive-side toothed pulley 30 and the toothed belt 50 can be simplified.

  In the embodiment of FIG. 7, the tooth surface shape in the tooth width direction of the driving-side toothed pulley 30 is a part in the tooth width direction. The tooth surface shape is provided with a convex portion 122 that meshes with the concave portion 121 at a part in the tooth width direction, in this embodiment, at the center portion.

  According to the embodiment shown in FIG. 7, the toothed belt 50 is engaged with a specific portion of the upper surface of the driving-side toothed pulley 30 in the tooth width direction during rotation, so that the movement in the belt width direction can be easily performed. Can be prevented.

  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, the present invention is not limited to a driving-side toothed pulley on which a toothed belt is wound, but also has a tooth surface shape in the tooth width direction of a driven-side toothed pulley on which a toothed belt is wound as a concave surface or a convex surface. good.

  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 apparatus that transmits to a rack shaft via a power transmission mechanism including a driven side toothed pulley connected via a toothed belt, each toothed pulley on the driving side and the driven side, The tooth surface in the tooth width direction on one side has a concave surface, and the tooth surface in the tooth width direction on the other side has a convex surface in contact with the concave surface. Thereby, in the electric power steering apparatus having the reduction gear using the toothed belt, the movement of the toothed belt in the belt width direction can be easily prevented. Moreover, according to this invention, the flange member which controls a belt winding position in a toothed pulley can be made unnecessary.

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Housing 14 Rack shaft 20 Electric motor 20A Rotating shaft 30 Drive side toothed pulley 40 Drive side toothed pulley 50 Toothed belt 101 Concave surface 102 Convex surface 111 Convex surface 112 Concave surface 121 Concave portion 122 Convex portion

Claims (6)

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
Each toothed pulley on the drive side and the driven side, and the tooth width direction tooth surface on one of the toothed belts has a concave surface, and the other tooth width direction tooth surface has a convex surface that contacts the concave surface. A reduction device for an electric power steering device. Each of the toothed pulleys on the drive side and the driven side, and the tooth surface shape in the tooth width direction on one of the toothed belts is extended across the entire width of the tooth width in the center in the tooth width direction. And
The speed reducer for an electric power steering apparatus according to claim 1, wherein a middle-to-high convex surface having the highest tooth surface in the tooth width direction at the center of the other one is extended over the entire tooth width.   The reduction device for an electric power steering apparatus according to claim 2, wherein each of the medium-low concave surface and the medium-high convex surface is curved.   The reduction device for an electric power steering apparatus according to claim 2, wherein each of the medium-low concave surface and the medium-high convex surface has a V shape.   Each toothed pulley on the drive side and driven side, and the tooth surface shape in the tooth width direction on one of the toothed belts has a recess in a part of the tooth width direction, and the tooth surface shape in the tooth width direction on the other of them is The reduction device for an electric power steering apparatus according to claim 1, wherein a convex portion that meshes with the concave portion is provided in a part of the tooth width direction.   An electric power steering apparatus comprising the speed reducer according to claim 1.

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