JP2010149574A - Electric power steering device - Google Patents

Abstract

An electric power steering device capable of suppressing the generation of rattling noise by suppressing a sudden displacement in a thrust direction of a helical gear constituting a gear reduction mechanism.
At least one gear constituting a gear reduction mechanism includes a metal shaft main body 33a, a metal annular gear 43 including a helical gear disposed on the outer peripheral side of the shaft main body, and a shaft main body. And an annular ring between the ring gear and an elastic ring 45 that elastically couples the shaft body and the ring gear. The elastic ring moves the ring gear relative to the shaft body in the radial direction and the axial direction. It is configured to be elastically coupled as possible.
[Selection] Figure 3

Description

  The present invention relates to an electric power steering device that can suppress gear rattling noise of a gear reduction mechanism.

In the electric power steering device, for example, as described in Patent Document 1, an electric motor is arranged in parallel with a rotatable ball nut that is screwed through a ball to a ball screw shaft formed on a rack shaft, A motor parallel type electric power steering system having a gear reduction mechanism in which a driving gear is connected to a motor shaft of an electric motor, a driven gear is provided on a ball nut, and the driving gear and the driven gear are engaged via an intermediate gear. There is a device.
JP 2008-105649 A

  In this type of electric power steering device, when the steering wheel (steering wheel) is steered in small increments, the drive gear repeats a sudden change in the rotational direction by the electric motor. In the case where the driving gear, driven gear, and intermediate gear of the gear reduction mechanism are constituted by helical gears, thrust in the thrust direction is applied to the intermediate gear when the driving gear repeats a sudden rotation direction change. The intermediate gear is suddenly displaced in the thrust direction due to the backlash between the gears and the influence of the backlash of the bearing that supports each gear. There is a problem that rattling noise is generated due to the sudden displacement of the intermediate gear in the thrust direction. In order to suppress this rattling noise, it is necessary to suppress the displacement of the intermediate gear in the thrust direction.

  The present invention has been made to solve the above-described conventional problems, and suppresses the occurrence of rattling noise by suppressing abrupt displacement of the helical gear constituting the gear reduction mechanism in the thrust direction. It is an object of the present invention to provide an electric power steering device that can be used.

  In order to solve the above problems, the invention according to claim 1 uses a gear reduction mechanism having a drive gear and a driven gear driven by an electric motor, and a ball screw mechanism operated via the gear reduction mechanism. An electric power steering device for assisting steering by the at least one gear constituting the gear reduction mechanism is a metal comprising a metal shaft main body and a helical gear disposed on the outer peripheral side of the shaft main body. And an elastic ring that is interposed in an annular space between the shaft main body and the annular gear and elastically couples the shaft main body and the annular gear. It is configured to be elastically coupled to the shaft main body so as to be relatively movable in the radial direction and the axial direction.

  The invention according to claim 2 is characterized in that, in claim 1, a reverse tapered surface whose diameter increases toward both ends is formed on the outer periphery of the shaft main body, and the shaft main body is formed on the inner periphery of the annular gear. A reverse taper surface having a shape complementary to the reverse taper surface is formed, and the elastic ring having a V-shaped cross section is fixed between the outer periphery of the shaft body and the inner periphery of the annular gear.

  The invention according to claim 3 is characterized in that, in claim 2, the elastic ring is made of a rubber material, and is fixed between the outer periphery of the shaft body and the inner periphery of the annular gear by vulcanization adhesion. It is that.

  According to a fourth aspect of the present invention, in the first aspect, the outer periphery of the shaft main body is formed with a tapered surface on one side in the axial direction and a straight portion on the other side. The elastic ring is bonded to the periphery, and the annular gear to which the elastic ring is bonded is fixed to the shaft body using a taper cone.

  According to the first aspect of the present invention, at least one gear constituting the gear reduction mechanism is made of a metal annular gear including a metal shaft main body and a helical gear disposed on the outer peripheral side of the shaft main body. And an elastic ring that is interposed in an annular space between the shaft main body and the annular gear and elastically couples the shaft main body and the annular gear, and the elastic ring has a radial direction and an axial direction with respect to the shaft main body. Since the drive gear is abruptly changed in the rotational direction by the electric motor, the helical gear can be prevented from being suddenly displaced in the thrust direction by the electric motor. Generation of a hitting sound can be suppressed.

  According to the second aspect of the present invention, the outer periphery of the shaft body is formed with a reverse tapered surface whose diameter increases toward both ends, and the inner periphery of the annular gear is complemented with the reverse tapered surface of the shaft body. A reverse-tapered surface is formed, and an elastic ring having a V-shaped cross section is fixed between the outer periphery of the shaft body and the inner periphery of the annular gear. The annular gear can be elastically coupled to the shaft body so as to be relatively movable in the radial direction and the axial direction with a simple configuration that is fixed between the inner periphery of the gear.

  The invention according to claim 3 is characterized in that the elastic ring is formed of a rubber material and is fixed by vulcanization adhesion between the outer periphery of the shaft main body and the inner periphery of the annular gear. Can be easily and reliably fixed between the outer periphery of the ring gear and the inner periphery of the annular gear.

  According to the invention of claim 4, a taper surface is formed on one side in the axial direction on the outer periphery of the shaft body, a straight portion is formed on the other side, and an elastic ring is bonded to the inner periphery of the annular gear. Since the annular gear to which the elastic ring is bonded is fixed to the shaft body using the taper cone, the annular gear to which the elastic ring is bonded by the taper cone can be easily assembled to the shaft body.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of a motor parallel type electric power steering apparatus 10 according to an embodiment of the present invention. In FIG. 1, an electric power steering apparatus 10 steers a steered wheel 12 by a steering shaft 14 that transmits a steering torque applied to a steering wheel 13 to steer the steered wheel 12, and the steering torque from the steering shaft 14. For example, a steering mechanism 15 composed of a rack and pinion mechanism, and an intermediate shaft 16 as a shaft coupling connecting the steering shaft 14 and the steering mechanism 15 are provided.

  The steering mechanism 15 includes a pinion shaft 17 serving as an input shaft, a rack shaft 18 serving as a steered shaft extending in a lateral direction of the automobile (a direction orthogonal to the straight traveling direction), and a housing 20 that supports the pinion shaft 17 and the rack shaft 18. And have. The pinion shaft 17 is rotatably supported by the housing 20, and the rack shaft 18 is supported by the housing 20 so as to be linearly reciprocable. The pinion teeth 17 a of the pinion shaft 17 are meshed with the rack teeth 18 a of the rack shaft 18. Both ends of the rack shaft 18 are connected to the steered wheels 12 via a tie rod (not shown) and a knuckle arm (not shown).

  Thereby, when the steering wheel 13 is steered, the steering torque is transmitted to the steering mechanism 15 via the steering shaft 14 and the like, and the pinion shaft 17 is rotated. The rotation of the pinion shaft 17 is converted into linear movement of the rack shaft 18 by the pinion teeth 17a and the rack teeth 18a, and the steered wheels 12 are steered.

  A ball screw shaft 21 is formed integrally with the rack shaft 18, and a ball nut 23 that is screwed to the ball screw shaft 21 via a ball 22 is supported concentrically with the rack shaft 18 so as to be rotatable only on the housing 20. Has been. The ball screw shaft 21, the ball 22, and the ball nut 23 constitute a ball screw mechanism 24 that converts the rotation of the ball nut 23 into the axial motion of the ball screw shaft 21.

  Furthermore, the electric power steering apparatus 10 includes a torque sensor 25 that detects steering torque, an electric motor 26 that is controlled based on the output of the torque sensor 25 and assists the steering torque, and a gear that decelerates the rotation of the electric motor 26. A speed reduction mechanism 27 is provided. The gear reduction mechanism 27 meshes with the drive gear 31 driven by the electric motor 26, the driven gear 32 provided on the ball nut 23, the drive gear 31 and the driven gear 32, and the rotation of the drive gear 31 is driven by the driven gear 31. And an intermediate gear 33 that transmits to 32.

  As shown in FIG. 2, the drive gear 31 of the gear reduction mechanism 27 is rotatably supported by the housing 20 (refer to FIG. 1) at both end shaft portions 31a and 31b via bearings 35a and 35b. A motor shaft 26a of the electric motor 26 is connected to the shaft portion 31a. The intermediate gear 33 that meshes with the drive gear 31 is rotatably supported by the housing 20 through shaft bearings 36a and 36b at both end shaft portions 33a and 33b. The driven gear 32 that meshes with the intermediate gear 33 is fixed to the outer periphery of the ball nut 23 by press fitting or the like. The ball nut 23 to which the driven gear 32 is fixed is supported by the housing 20 via a bearing 37 so as to be rotatable concentrically with the ball screw shaft 21.

  As shown in FIG. 2, the tooth portions of the driving gear 31, the driven gear 32, and the intermediate gear 33 are formed in a helical shape, and the driving gear 31, the driven gear 32, and the intermediate gear 33 are formed by a helical gear. The meshing rate is improved so that the meshing noise can be reduced. The rotation of the electric motor 26 is decelerated and transmitted to the ball nut 23 by a gear reduction mechanism 27 comprising the drive gear 31, the driven gear 32 and the intermediate gear 33.

  Next, the configuration of the intermediate gear 33 of the gear reduction mechanism 27 in the first embodiment will be described based on FIG. 3 and FIG. In FIG. 3, the intermediate gear 33 includes a metal shaft main body 41 having both end shaft portions 33a and 33b, and a metal annular gear 43 having tooth portions 42 engaged with the drive gear 31 and the driven gear 32 formed on the outer periphery. A rubber elastic ring 45 interposed in an annular space between the shaft main body 41 and the annular gear 43 is constituted. The outer peripheral surface of the shaft body 41 is formed with reverse tapered surfaces 41a and 41b whose diameters continuously increase toward both ends. As shown in FIG. 4, the reverse tapered surfaces 41a and 41b have a plurality of engaging grooves 41a1 and 41b1 (the engaging grooves 41b1 are not shown) along the tapered surfaces 41a and 41b at equal angular intervals on the circumference. Is formed. On the other hand, on the inner peripheral surface of the annular gear 43, reverse tapered surfaces 43a and 43b are formed to complement the reverse tapered surfaces 41a and 41b of the shaft body 41, and the reverse tapered surfaces 43a and 43b are along the tapered surface. A plurality of engaging grooves 43a1 and 43b1 (the engaging grooves 43b1 are not shown) are formed at equal angular intervals on the circumference. The reverse tapered surfaces 43 a and 43 b formed on the annular gear 43 are formed to have a diameter larger than the reverse tapered surfaces 41 a and 41 b formed on the shaft main body 41 by a predetermined amount. When arranged concentrically, an annular space having a uniform thickness is formed between the outer periphery of the shaft main body 41 and the inner periphery of the annular gear 43.

  The elastic ring 45 described above is integrally fixed between the outer periphery of the shaft body 41 and the inner periphery of the annular gear 43 by vulcanization adhesion. That is, after applying an adhesive to the outer periphery of the shaft body 41 and the inner periphery of the annular gear 43, the shaft body 41 and the annular gear 43 are concentrically accommodated in the mold, and unvulcanized rubber is injected in that state. Then, filling between the outer periphery of the shaft body 41 and the inner periphery of the annular gear 43, and heating and pressurizing for a predetermined time, the elastic ring 45 is vulcanized to the outer periphery of the shaft body 41 and the inner periphery of the annular gear 43, respectively. I try to bond them.

  The operation of the electric power steering apparatus 10 configured as described above will be described. When the steering wheel 13 is steered, steering torque is input to the pinion shaft 17, and the rack shaft 18 is moved in the axial direction via the steering mechanism 15 formed by the pinion shaft 17 and the rack shaft 18.

  The steering torque input to the pinion shaft 17 is detected by the torque sensor 25, and the electric motor 26 is rotationally controlled based on the detected steering torque to generate auxiliary torque. The auxiliary torque generated by the electric motor 26 is transmitted to the ball nut 23 via the drive gear 31, the intermediate gear 33, and the driven gear 32, and the ball screw shaft 21, that is, the rack shaft 18 moves in the axial direction by the rotation of the ball nut 23. Is done. As the rack shaft 18 moves in the axial direction, the steered wheels 12 are steered, and the steering force applied to the steering wheel 13 by the driver is assisted.

  At this time, since the drive gear 31, the driven gear 32 and the intermediate gear 33 constituting the gear reduction mechanism 27 are constituted by helical gears, a thrust force is applied to the intermediate gear 33 by the rotation of the drive gear 31. Join. In particular, when the steering wheel 13 is steered in small increments, the electric gear 26 causes the drive gear 31 to change rapidly in the rotational direction. As a result, the backlash between the driving gear 31, the intermediate gear 33, and the driven gear 32 and the backlash of the bearings 35a, 35b, 36a, 36b, 37 that support the driving gear 31, the intermediate gear 33, and the driven gear 32 are affected. Thus, the intermediate gear 33 is suddenly displaced in the thrust direction, but the sudden displacement of the intermediate gear 33 in the thrust direction is suppressed by the action of the elastic ring 45 having a V-shaped cross section. Is suppressed.

  According to the electric power steering apparatus 10 including the intermediate gear 33 according to the first embodiment described above, the intermediate gear 33 arranged between the drive gear 31 and the driven gear 32 is connected to the shaft main body 41 and the shaft. An annular gear 43 formed of a helical gear disposed on the outer peripheral side of the main body 41 and an elastic ring 45 having a V-shaped cross section interposed in an annular space between the shaft main body 41 and the annular gear 43. Therefore, the annular gear 43 can be moved relative to the shaft body 41 in the radial direction and the axial direction by compressing the elastic ring 45. Thereby, the sudden displacement of the intermediate gear 33 in the thrust direction due to the rotation of the drive gear 31 can be suppressed by the elastic ring 45, and the occurrence of rattling noise of the gear reduction mechanism 27 can be suppressed.

  Further, according to the first embodiment described above, the drive gear 31, the intermediate gear 33, and the driven gear 32 are constituted by helical gears. The mutual engagement rate can be increased, and the noise caused by the engagement can be effectively reduced in combination with the action of the elastic ring 45 described above.

  FIG. 5 shows a second embodiment of the present invention. The difference from the first embodiment is that the intermediate gear 33 can be easily manufactured without using means such as vulcanization adhesion. It is that. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

  That is, in the second embodiment, the taper surface 41b is formed only on one side of the shaft body 41 of the intermediate gear 33 in the axial direction, and the other side in the axial direction is the straight portion 41c. First, an elastic ring 45 having a constant wall thickness V-shaped cross section is fixed to the reverse tapered surfaces 43a and 43b on the inner periphery of the annular gear 43 by vulcanization bonding or the like, and the annular gear 43 to which the elastic ring 45 is bonded is attached. The tapered inner peripheral surface 45 b on one end side of the elastic ring 45 is fitted to the tapered surface 41 b of the shaft main body 41 by fitting from the straight portion 41 c side of the shaft main body 41. In this state, a tapered surface 50 a whose outer peripheral surface complements the tapered inner peripheral surface 45 a of the elastic ring 45 is formed between the tapered inner peripheral surface 45 a on the other end side of the elastic ring 45 and the straight portion 41 c of the shaft body 41. An annular taper cone 50 having an inner peripheral surface fitted to the straight portion 41c of the shaft main body 41 is inserted. The taper cone 50 is fixed to the taper surface 41a of the shaft main body 41 and the shaft main body 41 by tightening the taper cone 50 with a tightening nut 51 screwed into the shaft main body 41. The shaft body 41, the annular gear 43 and the elastic ring 45 are integrated.

  In this case, as shown in FIG. 6, the elastic ring 45 may be divided into two at the central portion in the axial direction to form conical elastic rings 145a and 145b. In addition, as described in the first embodiment, Similarly, an engagement groove may be formed on the outer periphery of the shaft body 41 and the inner periphery of the annular gear 43, and the elastic ring 45 may be engaged with the engagement groove to prevent rotation.

  According to the second embodiment described above, the shaft main body 41, the annular gear 43, and the elastic rings 45 (145a, 145b) are integrally assembled using the taper cone 50. The elastic ring 45 (145a, 145b) can be easily assembled between the outer periphery and the inner periphery of the annular gear 43.

  In the above-described embodiment, the intermediate gear 33 that meshes with the drive gear 31 and the driven gear 32 constituting the gear reduction mechanism 27 is divided into the shaft body 51 and the annular gear 53, and the elastic ring 45 is interposed therebetween. In the example described above, all the gears (the driving gear 31, the driven gear 32, and the intermediate gear 33) constituting the gear reduction mechanism 27 are connected to the shaft main body and the ring as shown in FIG. 3 or FIG. It is good also as a structure which divided | segmented into the gearwheel and interposed the elastic ring between them.

  In the above-described embodiment, an example in which the gear reduction mechanism 27 includes the drive gear 31, the intermediate gear 33, and the driven gear 32 has been described. However, the gear reduction mechanism 27 includes at least the drive gear 31 and the driven gear. In this case, one or both of the drive gear 31 and the driven gear 32 may be configured as shown in FIG. 3 or FIG.

  The elastic ring 45 does not necessarily have a V-shaped cross section as described in the embodiment, and can elastically couple the annular gear 43 to the shaft body 41 so as to be relatively movable in the radial direction and the axial direction. If it is. The elastic ring 45 is not limited to rubber and may be formed of an elastomer.

  Although the present invention has been described with reference to the embodiments, the present invention is not limited to the configurations described in the embodiments, and does not depart from the gist of the present invention described in the claims. It can take various forms.

It is a mimetic diagram showing an electric power steering device concerning an embodiment of the invention. It is the schematic which shows the gear reduction mechanism of FIG. It is sectional drawing of the intermediate | middle gear which comprises the gear reduction mechanism which shows the 1st Embodiment of this invention. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is sectional drawing of the intermediate gear which shows the 2nd Embodiment of this invention. It is a figure which shows the modification of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 24 ... Ball screw mechanism, 26 ... Electric motor, 27 ... Gear reduction mechanism, 31 ... Drive gear, 32 ... Driven gear, 33 ... Intermediate gear, 51 ... Shaft body, 51a, 51b ... Reverse taper Surface, 53 ... annular gear, 53a, 53b ... reverse tapered surface, 55 ... elastic ring.

Claims (4)

A gear reduction mechanism having a drive gear and a driven gear driven by an electric motor, and an electric power steering device for assisting steering using a ball screw mechanism operated via the gear reduction mechanism,
The at least one gear constituting the gear reduction mechanism includes a metal shaft main body, a metal annular gear including a helical gear disposed on the outer peripheral side of the shaft main body, the shaft main body and the annular The elastic ring is interposed in an annular space between the gear and elastically couples the shaft main body and the annular gear. The elastic ring connects the ring gear in the radial direction and the axial direction with respect to the shaft main body. An electric power steering apparatus characterized by being elastically coupled so as to be relatively movable.   In Claim 1, the outer periphery of the said shaft main body is formed with the reverse taper surface which a diameter expands toward both ends, The shape which complements the reverse taper surface of a shaft main body at the inner periphery of the said annular gearwheel An electric power steering device, wherein a reverse tapered surface is formed, and the elastic ring having a V-shaped cross section is fixed between an outer periphery of the shaft main body and an inner periphery of the annular gear.   3. The electric power steering according to claim 2, wherein the elastic ring is made of a rubber material, and is fixed by vulcanization adhesion between an outer periphery of the shaft body and an inner periphery of the annular gear. apparatus. 2. The outer periphery of the shaft main body according to claim 1, wherein a taper surface is formed on one side in the axial direction, a straight portion is formed on the other side, and the elastic ring is bonded to the inner periphery of the annular gear, An electric power steering apparatus characterized in that the annular gear to which an elastic ring is bonded is fixed to the shaft body using a taper cone.

Images