JP2013193715A - Reduction gear of electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric power steering apparatus which includes a reduction gear using a toothed belt, and which eliminates the risk of disabling steering assistance, by preventing the toothed belt from coming off from a toothed pulley, even when a flange member is unfixed from a pulley body of the toothed pulley.SOLUTION: In a reduction gear of an electric power steering apparatus 10, a gap G between an inner wall surface A of a housing 11, which faces a flange member 34 of a toothed pulley 30, and the flange member 34 of the toothed pulley 30 is set smaller in dimension than an insertion length L by which an attachment shaft part 34A of the flange member 34 is inserted into an attachment hole 31H of a pulley body 31.

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 toothed pulley which fixed the flange member to the pulley main body fits the flange member to the pulley main body, and is caulked to prevent it from coming off, as described in Patent Document 2.

JP2007-153300 JP2004-183742

  In the speed reducer of the electric power steering apparatus described in Patent Document 1, the toothed pulley is fitted with a flange member to the pulley body, and is crimped, or press-fitted, screwed, bonded, etc., as described in Patent Document 2. It is fixed with.

  However, if the flange member is not fixed to the pulley body of the toothed pulley for some reason and the flange member falls off, the toothed belt comes off from the toothed pulley. The rotational force of the electric motor is not transmitted to the rack shaft, and steering assist by the electric motor becomes impossible.

  An object of the present invention is to remove a toothed belt from a toothed pulley even if the flange member is not fixed to the pulley body of the toothed pulley in an electric power steering device having a reduction gear using a toothed belt. An object of the present invention is to provide an electric power steering device that prevents the steering assist from being impossible.

  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 toothed pulley is a tooth portion on one end side of the pulley body. A flange member having an outer diameter larger than that of the tooth portion is fixed to one side of the pulley body, and the flange member is inserted into an attachment hole drilled on the central axis at one end of the pulley body, A flange portion provided at one end of the mounting shaft portion and projecting in the radial direction, and a gap between the inner wall surface of the housing facing the flange member of the toothed pulley and the flange member of the toothed pulley, Mounting shaft portion of the flange member is obtained by the so set smaller than the insertion length which is inserted into the mounting hole of the pulley body.

  The invention according to claim 2 is an electric power steering apparatus including the speed reduction device according to claim 1.

(Claims 1 and 2)
(a) In an electric power steering apparatus having a reduction gear using a toothed belt, a flange member of a toothed pulley is attached by being inserted into an attachment hole formed on a central axis at one end of the pulley body. And a flange portion provided at one end of the mounting shaft portion and projecting in the radial direction, and a gap between the inner wall surface of the housing facing the flange member of the toothed pulley and the flange member of the toothed pulley is flanged. The mounting shaft portion of the member is set smaller than the insertion length inserted into the mounting hole of the pulley body.

  Therefore, even if the flange member is not fixed to the pulley body of the toothed pulley, and the flange member mounting shaft is about to come out of the pulley body mounting hole, the flange member mounting shaft portion is completely pulled out of the pulley body mounting hole. At a stage where the flange member does not exist, the flange portion of the flange member hits the inner wall surface of the housing. As a result, the flange member does not fall out of the gap between the inner wall surface of the housing and the end surface of the pulley body facing the flange member. Therefore, the toothed pulley continues to rotate with the flange portion of the flange member applied to the inner wall surface of the housing. When the toothed belt is wound around the toothed pulley, the toothed belt is caught on the flange member to prevent the toothed belt from falling off, and continues to transmit the rotational force of the electric motor to the rack shaft. The steering assist by the electric motor is not disabled.

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.

  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. The bearing 36 is positioned between both end surfaces of the outer ring 36 </ b> A between the stepped portion 21 </ b> K near the motor of the large-diameter bearing holding hole of the bearing housing 21 and the retaining ring 36 </ b> C engaged with the bearing holding hole of the bearing housing 21. Has been fixed. The inner ring 36 </ b> B of the bearing 36 sandwiches the flange member 33 between the end surface of the tooth portion 31 </ b> A of the pulley main 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 apparatus 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 72 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, in the electric power steering apparatus 10, even if the flange member 34 is not fixed to the pulley body 31 of the driving side toothed pulley 30, the toothed belt 50 is prevented from falling off from the driving side toothed pulley 30. In order to provide an electric power aligning device that is not likely to be incapable of steering assist, the following configuration is provided.

  As shown in FIG. 3, the electric power steering apparatus 10 is configured such that the driving-side toothed pulley 30 is provided on one side of the tooth portion 31 </ b> A provided on the side opposite to the driving shaft 32 of the pulley body 31 ( As described above, the flange member 34 having an outer diameter larger than that of the tooth portion 31A is fixed to the side.

  The flange member 34 is inserted into a mounting hole 31H drilled on the central axis at the end opposite to the drive shaft 32 of the pulley body 31, and is attached by press fitting, screwing, bonding, caulking, etc. 34A and a flange portion 34B provided at one end of the mounting shaft portion 34A and projecting in the radial direction. The flange member 34 is, for example, a press-molded product, the attachment shaft portion 34A is formed of a hollow cylinder, and the flange portion 34B is an annular plate (plate thickness b) extended radially outward from one end of the tube of the attachment shaft portion 34A. ). The flange member 34 is attached so that the attachment shaft portion 34A is inserted into the attachment hole 31H of the pulley body 31, and the flange portion 34B is brought into contact with the opening end surface of the attachment hole 31H of the pulley body 31.

  At this time, the flange member 34 of the driving-side toothed pulley 30 and the inner wall surface A of the gear housing 11 (second gear housing 11B) facing the pulley 30 in the axial direction, and the flange member 34 of the driving-side toothed pulley 30 The gap G with the end surface B of the flange portion 34B is set to be smaller than the insertion length L in which the attachment shaft portion 34A of the flange member 34 is inserted into the attachment hole 31H of the pulley body 31 (G <L).

  The axial length of the mounting shaft portion 34A and the flange portion 34B of the flange member 34 of the drive side toothed pulley 30 is a, and the plate thickness of the flange portion 34B of the flange member 34 of the drive side toothed pulley 30 is b. When the gap between the inner wall surface A of the gear housing 11 (second gear housing 11B) and the end face of the pulley body 31 of the driving-side toothed pulley 30 opposite thereto is K, G = K−b, L = a -B, and according to these, K <a. That is, when G <L, the gap K between the inner wall surface A of the gear housing 11 (second gear housing 11B) and the end surface of the pulley main body 31 of the driving-side toothed pulley 30 opposite thereto is the total length a of the flange member 34. Smaller.

According to the present embodiment, the following operational effects can be obtained.
(a) In the electric power steering apparatus 10 having a speed reducer using the toothed belt 50, the flange member 34 of the driving-side toothed pulley 30 is inserted into a mounting hole 31H formed on the central axis at one end of the pulley body 31. The housing 11 includes a mounting shaft portion 34A that is inserted and mounted, and a flange portion 34B that is provided at one end of the mounting shaft portion 34A and projects in the radial direction. The housing 11 faces the flange member 34 of the drive-side toothed pulley 30. A gap G between the wall surface A and the flange member 34 of the drive-side toothed pulley 30 is set to be smaller than an insertion length L in which the attachment shaft portion 34A of the flange member 34 is inserted into the attachment hole 31H of the pulley body 31. The

  Therefore, even if the fixing of the flange member 34 to the pulley body 31 of the driving-side toothed pulley 30 is released and the attachment shaft portion 34A of the flange member 34 tries to come out of the attachment hole 31H of the pulley body 31, the attachment shaft portion of the flange member 34 The flange portion 34B of the flange member 34 contacts the inner wall surface A of the housing 11 at a stage where 34A does not completely come out of the attachment hole 31H of the pulley body 31. Thereby, the flange member 34 does not fall out from the gap G between the inner wall surface A of the housing 11 and the end surface of the pulley body 31 opposite to the inner wall surface A. Therefore, the drive-side toothed pulley 30 continues to rotate with the flange portion 34 </ b> B of the flange member 34 applied to the inner wall surface A of the housing 11. In a state where the toothed belt 50 is wound around the driving side toothed pulley 30, the toothed belt 50 is caught on the flange member 34 to be prevented from falling off and continues to transmit the rotational force of the electric motor 20 to the rack shaft 14. The steering assist by the electric motor 20 is not disabled.

  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 the present invention, even if the flange member is fixed to one end side of the pulley body of the driven-side toothed pulley, the flange member is inserted into a mounting hole formed on the central axis of one end of the pulley body. And an inner wall surface of the housing facing the flange member of the toothed pulley, and a flange of the toothed pulley. The gap with the member may be set smaller than the insertion length in which the attachment shaft portion of the flange member is inserted into the attachment hole of the pulley body.

  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 including a driven-side toothed pulley connected via a toothed belt, the toothed pulley is placed on one side of the tooth portion on one end side of the pulley body. A flange member having an outer diameter larger than that of the tooth portion is fixed, and the flange member is inserted into an attachment hole drilled on the central shaft at one end of the pulley body, and attached to the attachment shaft portion. A flange portion provided at one end and projecting in the radial direction, and a clearance between the inner wall surface of the housing facing the flange member of the toothed pulley and the flange member of the toothed pulley is defined as a flange member. Mounting shaft portion is set smaller than the insertion length which is inserted into the mounting hole of the pulley body. Thereby, in the electric power steering apparatus having a reduction gear using a toothed belt, even if the flange member is fixed to the pulley body of the toothed pulley, the toothed belt is prevented from falling off from the toothed pulley, It is possible to provide an electric power steering device that does not cause the possibility of steering assist being impossible.

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Housing 14 Rack shaft 20 Electric motor 20A Rotating shaft 30 Drive side toothed pulley 31 Pulley main body 31A Tooth portion 31H Mounting hole 32 Drive shaft 34 Flange member 34A Mounting shaft portion 34B Flange portion 40 Drive side toothed pulley 50 Toothed belt A Inner wall surface G Gap L Insertion length

Claims (2)

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 toothed pulley is formed by fixing a flange member having a larger outer diameter than the tooth part on one side of the tooth part on one end side of the pulley body,
The flange member includes an attachment shaft portion that is inserted and attached to an attachment hole formed on the central shaft at one end of the pulley body, and a flange portion that is provided at one end of the attachment shaft portion and projects in the radial direction.
The clearance between the inner wall surface of the housing facing the flange member of the toothed pulley and the flange member of the toothed pulley is set smaller than the insertion length in which the mounting shaft portion of the flange member is inserted into the pulley body mounting hole. A reduction device for an electric power steering device.   An electric power steering apparatus comprising the speed reducer according to claim 1.

Images