JP4473047B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus.

The electric power steering device described in Patent Document 1 supports a rack shaft on a gear housing so as to be linearly movable, and an electric motor is attached to the gear housing, and the rotational force of a driving pulley coupled to the rotating shaft of the electric motor is The power is transmitted to the rack shaft through a power transmission mechanism including a driven pulley connected to the driving pulley via a belt. An electric motor assists the steering force that the driver steers the steering wheel and moves the rack shaft with which the pinion connected to the steering shaft engages.
JP2003-220959

  In Patent Document 1, a tension adjusting mechanism for adjusting the tension of the belt is provided in order to prevent the belt wound around the driving pulley and the driven pulley from loosening and eventually coming off. This belt tension adjusting mechanism changes the distance between the driving pulley and the driven pulley, and is complicated.

Challenge of the present invention is the electric power steering apparatus, backlash between the tooth surface of the drive gear and a driven gear constituting a power transmission mechanism of the electric motor, with a simple structure, is to enable easily adjusted .

According to the first aspect of the invention , the rack shaft is supported on the gear housing so as to be linearly movable, and an electric motor is attached to the gear housing, and the driven gear fixed to the rotating shaft of the electric motor is engaged with the driving gear. In an electric power steering apparatus that transmits power to a rack shaft through a power transmission mechanism including a gear, an electric motor can be fixed, and a holder that supports a drive gear can be attached to the gear housing. It has an attachment fulcrum hole into which one attachment shaft is inserted and an attachment adjustment hole into which the other attachment shaft on the gear housing side is attached, and is oscillated with the attachment fulcrum hole as an oscillation fulcrum and driven with the drive gear. The distance between the shafts of the gears can be adjusted, and the size of the mounting adjustment hole of the holder regulates the maximum adjustment range of the distance between the drive gear and the driven gear, and this maximum adjustment range is driven. It is obtained so as to be smaller than the height of the teeth of the gear and the driven gear.

According to a second aspect of the present invention, in the first aspect of the invention, the mounting adjustment hole of the holder is a large-diameter round hole larger than the diameter of the mounting fulcrum hole .

According to a third aspect of the present invention, in the first aspect of the invention, the attachment adjustment hole of the holder is a long hole larger than the diameter of the attachment fulcrum hole .

(Claim 1 )
(a) The center of rotation of the drive gear relative to the gear housing can be displaced by simply swinging the holder supporting the electric motor and the drive gear around the mounting fulcrum hole to the gear housing. As a result, the drive gear and the driven gear The backlash between the tooth surfaces can be adjusted by making the distance between the shafts close to and away from each other. Therefore, the backlash between the tooth surfaces of the drive gear and the driven gear can be easily adjusted with a simple configuration that does not use special parts for the backlash adjustment structure and has a small number of parts and assembly steps. By appropriately setting the meshing between the drive gear and the driven gear, it is possible to stabilize the steering assist by the electric motor.

(b) The maximum adjustment width of the distance between the drive gear and the driven gear, which is regulated by the hole size of the holder adjustment hole, is smaller than the height of the teeth. It is avoided that the steering assist becomes impossible without the disengagement of those even if they are loosened.

(Claim 2 )
(c) The above-described (a) and (b) can be realized by a simple process in which the mounting adjustment hole of the holder is a large-diameter round hole.

(Claim 3 )
(d) The above-described (a) and (b) can be realized by a simple process in which the attachment adjustment hole of the holder is a long hole.

FIG. 1 is an overall side view showing an electric power steering apparatus of a reference example , FIG. 2 is a cross-sectional view showing the main part of the electric power steering apparatus, FIG. 3 shows the electric power steering apparatus before mounting the electric motor, and FIG. FIG. 4 is a sectional view showing the holder, FIG. 5 is a front view showing the holder, FIG. 6 shows the joint on the electric motor side, (A) is a sectional view, and (B) is a sectional view. FIG. 7 shows a joint on the drive pulley side, (A) is a sectional view, (B) is a front view, FIG. 8 shows an intermediate joint, (A) is a front view, and (B) is a side view, 9A and 9B show a belt tension adjusting structure of the electric power steering apparatus, FIG. 9A is a front view, FIG. 9B is an enlarged view showing a meshed state of the driven pulley and the belt, and FIG. 10 is a front view showing a modified example of the holder. the principal part of the electric power steering apparatus of FIG. 11 embodiment A to cross section.

( Reference example ) (FIGS. 1 to 10)
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.

  As shown in FIG. 2, the electric power steering apparatus 10 fixes the electric motor 20 to a holder 22 (FIGS. 4 and 5) by a mounting bolt 21 (not shown), and the holder 22 is fixed to a first gear housing by a mounting bolt 23. 11A is detachable. FIG. 3 shows a state in which the holder 22 is attached to the first gear housing 11A with the attaching bolt 23, and the electric motor 20 is not yet attached to the holder 22 (21A in FIG. 3 is an electric motor attaching screw hole). The holder 22 attached to the first gear housing 11A and inserted into the first gear housing 11A has a certain gap between the inner periphery of the gear housings 11A and 11B, and is a holder for the first gear housing 11A. 22 is allowed to swing as described later.

  At this time, the holder 22 supports the central shaft 25 of the drive pulley 24, and the joint 26 </ b> A (FIG. 6) at the shaft end of the rotating shaft 20 </ b> A of the electric motor 20 and the joint 26 </ b> B at the shaft end of the central shaft 25 (FIG. 7). Are engaged with each other in the axial direction in a state where intermediate joints 26C (FIG. 8) such as rubber are sandwiched between teeth a and b provided at a plurality of positions in the circumferential direction. The drive pulley 24 is supported at both ends of the center shaft 25 by the holder 22 by bearings 27 and 28. Reference numeral 29 denotes a retaining ring for fixing the outer ring of the bearing 28.

  The electric power steering apparatus 10 is provided with a ball screw 30 on the rack shaft 14, a ball nut 32 that meshes with the ball screw 30 via a ball 31, and a bearing 33 supported by the gear housing 11 (first gear housing 11 </ b> A). Thus, the ball nut 32 is rotatably supported. Reference numeral 34 denotes an outer ring fixing nut of the bearing 33. A driven pulley 36 is fixed to the outer periphery of the ball nut 32 by a lock nut 35.

  The electric power steering apparatus 10 wraps a belt 37 around a drive pulley 24 on the electric motor 20 side and a driven pulley 36 on the ball nut 32 side, and rotates the rotational force of the drive pulley 24 from the belt 37 via the driven pulley 36. This is transmitted to the nut 32, and consequently to the rack shaft 14, and the rack shaft 14 is linearly moved.

  The electric power steering apparatus 10 passes the rack shaft 14 supported by the first gear housing 11A through the second gear housing 11B, covers the holder 22 attached to the first gear housing 11A with the second gear housing 11B, The first gear housing 11 </ b> A and the second gear housing 11 </ b> B are fastened with a plurality of fastening bolts 16. At this time, as shown in FIG. 2, the first gear housing 11A and the second gear housing 11B are driven by the plurality of cylindrical knock pins 16A so that both end portions of the knock pins 16A are driven and aligned. The fastening bolt 16 inserted through 16A is screwed and fastened. Some fastening bolts 16 are screwed to the first gear housing 11A through the knock pins 16A, and other fastening bolts 16 are screwed to the second gear housing 11B through the knock pins 16A.

  However, the electric power steering apparatus 10 has the following configuration in order to reduce the swing of the rack shaft 14 supported by the gear housings 11A and 11B.

  In the second gear housing 11 </ b> B, a portion facing the ball nut 32 supported by the first gear housing 11 </ b> A is a bush support portion 17, and the bush 40 is bridged between the ball nut 32 and the bush support portion 17. The bush 40 is press-fitted into the inner peripheral portion on the tip end side of the ball nut 32 and is fixedly provided. The bush 40 is linearly slid on the rack shaft 14 while being rotatably supported by the inner peripheral portion of the bush support portion 17. Support as possible.

  The bush 40 has a part in the axial direction of the outer periphery of a cylindrical body made of metal or the like as a sliding part with the bush support part 17, and an entire inner periphery as a sliding part with the rack shaft 14. The sliding portion is obtained by providing a lubrication coating layer such as an oil-containing polyacetal resin or a tetrafluoroethylene resin on the surface of the cylindrical body by coating or the like.

  Further, the electric power steering apparatus 10 has the following configuration in order to make it possible to adjust the tension of the belt 37 wound around the drive pulley 24 and the driven pulley 36 that constitute the power transmission mechanism of the electric motor 20.

  3, 5, and 9, the holder 22 includes an attachment fulcrum hole 22 </ b> A into which one attachment bolt 23 as one attachment shaft that is screwed into the first gear housing 11 </ b> A is inserted, The flange 22F is provided with an attachment adjusting hole 22B into which the other attachment bolt 23 as another attachment shaft screwed to the 1 gear housing 11A side is inserted. The holder 22 is swung with the mounting fulcrum hole 22A inserted into one mounting bolt 23 as a swinging fulcrum, and the distance between the shafts of the driving pulley 24 and the driven pulley 36 is adjusted, and the other mounting bolt 23 is mounted. Is inserted into the mounting adjustment hole 22B, and both mounting bolts 23 are fastened and fixed to the first gear housing 11A.

  The attachment adjustment hole 22B of the holder 22 forms a large-diameter round hole larger than the diameter of the round hole-like attachment fulcrum hole 22A. At this time, the hole size of the mounting adjustment hole 22B is the maximum adjustment width of the inter-axis distance between the drive pulley 24 and the driven pulley 36 (the drive pulley 24 (center shaft 25) corresponding to the swing angle K of the holder 22 in FIG. 9). The maximum adjustment width is made smaller than the tooth height h of the belt 37 that meshes with the drive pulley 24 and the driven pulley 36 (FIG. 9B).

The electric power steering device 10 is assembled by the following procedure, for example.
(1) A ball nut 32 meshed with the ball screw 30 of the rack shaft 14 and to which the driven pulley 36 is fixed is supported on the first gear housing 11A by the bearing 33. A bush 40 is provided on the ball nut 32.

  (2) The holder 22 that supports the drive pulley 24 and to which the electric motor 20 is attached is fixed to the first gear housing 11A with the attachment bolt 23. At this time, a belt 37 is wound around the driving pulley 24 supported by the holder 22.

  (3) The belt 37 wound around the drive pulley 24 is wound around the driven pulley 36. The holder 22 is swung using the mounting fulcrum hole 22A inserted into one mounting bolt 23 of the holder 22 as a swing fulcrum, the distance between the drive pulley 24 and the driven pulley 36 is adjusted, and a constant tension is applied to the belt 37. The other mounting bolt 23 is inserted into the mounting adjustment hole 22B of the holder 22, and both mounting bolts 23 are fastened to the first gear housing 11A. The electric motor 20 of the above (2) may be attached to the holder 22 after this (3).

  (4) The bush support portion 17 of the second gear housing 11B is inserted into the bush 40 provided on the ball nut 32 described in (1) above, and the second gear housing 11B is fastened to the first gear housing 11A by the fastening bolt 16. To do.

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 drive pulley 24 based on the torque generated by the electric motor 20 is transmitted from the belt 37 to the ball nut 32 via the driven pulley 36, and becomes a steering assist force that linearly moves the rack shaft 14 via the ball screw 30.

According to the reference example , the following effects can be obtained.
(a) The center of rotation of the drive pulley 24 relative to the gear housing 11A can be displaced by simply swinging the holder 22 supporting the electric motor 20 and the drive pulley 24 around the attachment fulcrum hole 22A to the gear housing 11A. As a result, the distance between the axes of the drive pulley 24 and the driven pulley 36 can be made close to and away from each other, and the tension of the belt 37 wound around the pulleys 24 and 36 can be adjusted. Accordingly, the tension of the belt 37 wound around the drive pulley 24 and the driven pulley 36 can be easily achieved by a simple configuration with few parts and assembly man-hours without using special parts for the belt tension adjusting structure. The adjustment can be made to prevent the belt 37 from being loosened and eventually removed, and the steering assist by the electric motor 20 can be stabilized.

  (b) Since the maximum adjustment width of the inter-shaft distance between the drive pulley 24 and the driven pulley 36, which is regulated by the hole size of the attachment adjustment hole 22B of the holder 22, is made smaller than the height of the teeth of the belt 37, the attachment adjustment hole 22B Therefore, even if the mounting bolt 23 is loosened, the belt 37 does not come off and the steering assist is prevented from being disabled.

  (c) The above-described (a) and (b) can be realized by a simple process of making the attachment adjustment hole 22B of the holder 22 into a large-diameter round hole.

  FIG. 10 is a modification of the holder 22. When the holder 22 is provided with the attachment fulcrum hole 22A and the attachment adjustment hole 22B in the flange 22F, the attachment adjustment hole 22B is a long hole larger than the diameter of the attachment fulcrum hole 22A. The above-described (a) and (b) can be realized by a simple process in which the attachment adjusting hole 22B of the holder 22 is a long hole.

( Example ) (FIG. 11)
The embodiment differs from the reference example in that the drive pulley 24 is replaced with the drive gear 51 and the driven pulley 36 is replaced with the driven gear 52.

That is, in the electric power steering apparatus 10 of the embodiment , the drive gear 51 is coupled to the rotating shaft 20A of the electric motor 20, the driven gear 52 is coupled to the ball nut 32, and the drive gear 51 and the driven gear 52 are meshed. It is a thing.

Even in the embodiment , the electric motor 20 can be fixed, the holder 22 that supports the drive gear 51 can be attached to the gear housing 11A, and the holder 22 can swing with the mounting fulcrum hole 22A as a swing fulcrum. Thus, the distance between the drive gear 51 and the driven gear 52 can be adjusted.

Therefore, according to an Example , there exist the following effects.
(a) The center of rotation of the drive gear 51 relative to the gear housing 11A can be displaced simply by swinging the holder 22 supporting the electric motor 20 and the drive gear 51 around the attachment fulcrum hole 22A to the gear housing 11A. As a result, the distance between the axes of the drive gear 51 and the driven gear 52 can be made close to and away from each other, and the backlash between the tooth surfaces can be adjusted. Therefore, the backlash between the tooth surfaces of the drive gear 51 and the driven gear 52 can be easily adjusted with a simple configuration that does not use special parts for the backlash adjustment structure and has few parts and assembly steps. In addition, the engagement of the drive gear 51 and the driven gear 52 can be set appropriately, and the steering assist by the electric motor 20 can be stabilized.

  (b) Since the maximum adjustment width of the inter-shaft distance between the drive gear 51 and the driven gear 52 regulated by the hole size of the attachment adjustment hole 22B of the holder 22 is made smaller than the height of the teeth, Therefore, even if the mounting bolt 23 for loosening is loosened, it is possible to prevent the steering assist from being disabled without disengaging them.

  (c) The above-described (a) and (b) can be realized by a simple process in which the attachment adjusting hole 22B of the holder 22 is a long hole.

  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.

FIG. 1 is an overall side view showing an electric power steering apparatus of a reference example . FIG. 2 is a cross-sectional view showing a main part of the electric power steering apparatus. 3A and 3B show the electric power steering apparatus before the electric motor is mounted, in which FIG. 3A is a sectional view and FIG. 3B is a side view. FIG. 4 is a sectional view showing the holder. FIG. 5 is a front view showing the holder. 6A and 6B show a joint on the electric motor side, where FIG. 6A is a cross-sectional view and FIG. 6B is a front view. FIG. 7 shows a joint on the drive pulley side, (A) is a sectional view, and (B) is a front view. FIG. 8 shows the intermediate joint, (A) is a front view, and (B) is a side view. 9A and 9B show a belt tension adjusting structure of the electric power steering apparatus, where FIG. 9A is a front view and FIG. 9B is an enlarged view showing a meshed state of a driven pulley and a belt. FIG. 10 is a front view showing a modified example of the holder. FIG. 11 is a cross-sectional view showing a main part of the electric power steering apparatus of the embodiment .

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Gear housing 14 Rack shaft 20 Electric motor 20A Rotating shaft 22 Holder 22A Mounting fulcrum hole 22B Mounting adjustment hole 23 Mounting bolt (mounting shaft)
51 Drive gear 52 Driven gear

Claims (3)

A power transmission mechanism including a driven gear that supports the rack shaft so that the rack shaft can be linearly moved on the gear housing, an electric motor attached to the gear housing, and the rotational force of the driving gear fixed to the rotating shaft of the electric motor meshes with the driving gear. In the electric power steering device that transmits to the rack shaft via
The electric motor can be fixed, and the holder that supports the drive gear can be attached to the gear housing.
The holder includes an attachment fulcrum hole in which one attachment shaft on the gear housing side is inserted and an attachment adjustment hole in which the other attachment shaft on the gear housing side is attached. The distance between the drive gear and the driven gear can be adjusted .
The size of the mounting adjustment hole of the holder regulates the maximum adjustment width of the distance between the drive gear and the driven gear, and the maximum adjustment width is made smaller than the height of the teeth of the drive gear and the driven gear. Power steering device. The electric power steering apparatus according to claim 1, wherein the attachment adjustment hole of the holder is a large-diameter round hole larger than the diameter of the attachment fulcrum hole. The electric power steering device according to claim 1, wherein the attachment adjustment hole of the holder is a long hole larger than the diameter of the attachment fulcrum hole.

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