JP5401912B2 - Electric power steering device - Google Patents

Description

  The present invention relates to a rack-cross type electric power steering apparatus.

  Conventionally, it has a rack shaft that is moved in the axial direction in response to a steering operation, and a hollow shaft that is arranged coaxially with the rack shaft and is rotated by a motor. A so-called rack-cross type electric power steering device is known as an electric power steering device that applies assist force to a steering system by converting it into motion (see, for example, Patent Document 1 and Patent Document 2). A rack-cross type electric power steering device has a drive shaft rotated by a motor arranged so that its axis is oblique to a rack shaft (hollow shaft), a drive bevel gear is provided on the drive shaft, and the hollow shaft A driven bevel gear meshing with the drive bevel gear is provided, and the rotation of the drive shaft by the motor is transmitted to the hollow shaft via the drive bevel gear and the driven bevel gear.

  In this type of rack-cross type electric power steering device, the drive shaft and the hollow shaft are rotationally connected by the drive bevel gear and the driven bevel gear. There is a risk of noise and the like, and it is necessary to keep the meshing accuracy between the two bevel gears properly.

  Therefore, in the electric power steering apparatus described in Patent Document 1, the inner housing 4 in which a driving bevel gear (driving gear 6) or a driven bevel gear (driven gear 19b) is rotatably supported via bearings 7 and 20 is provided. , 14 can be adjusted in the axial direction with respect to the gear housing by a screw adjusting mechanism, and the drive bevel gear (driven bevel gear) is moved to a position where backlash with the driven bevel gear (drive bevel gear) is removed. It is supposed to be fixed.

  On the other hand, in the electric power steering apparatus described in Patent Document 2, the first housing 31 that rotatably supports the driven bevel gear (driven gear 22) and the first housing 31 that rotatably supports the drive bevel gear (drive gear 22). 2 The housing 32 can be adjusted relative to the rotational direction or radial direction of the driven bevel gear to eliminate backlash between the drive bevel gear and the driven bevel gear.

According to the electric power steering apparatus described in Patent Literature 1 and Patent Literature 2, there is a feature that the driving bevel gear and the driven bevel gear can be assembled in an appropriate meshing state in which the backlash is removed.
JP 2004-122858 A JP 2003-252212 A

  However, in the electric power steering apparatus as described in Patent Document 1 or Patent Document 2, even if the backlash adjustment can be properly performed at the time of assembly, backlash occurs between the bevel gears due to the change over time. There are problems that arise. In particular, in this type of electric power steering device, one bevel gear (driven bevel gear) is made of synthetic resin and the other bevel gear (drive) is driven to prevent noise caused by meshing of the drive bevel gear and the driven bevel gear. Since the bevel gear is made of metal, the bevel gear made of synthetic resin gradually wears with use. For this reason, there has been a problem that it is difficult to suppress the occurrence of rattling noise and the like due to backlash over a long period of time.

  The present invention has been made in view of the above-described conventional problems, and changes the idea of removing backlash between the driving bevel gear and the driven bevel gear, and generates rattling noise even if there is backlash. An object of the present invention is to provide an electric power steering apparatus that can be stably suppressed over a long period of time.

In order to solve the above-mentioned problems, a feature of the invention according to claim 1 is that a gear housing, a rack shaft provided in the gear housing so as to be movable in the axial direction, and a rotatable hollow through which the rack shaft is inserted. A shaft, a ball screw mechanism that converts the rotation of the hollow shaft into an axial movement of the rack shaft, a drive shaft that is disposed obliquely to the hollow shaft in the gear housing and rotated by an electric motor, and An electric power steering apparatus comprising a drive bevel gear provided on a drive shaft and a driven bevel gear provided on the hollow shaft and meshing with the drive bevel gear, wherein the first sliding ring is provided on the hollow shaft. and disposed, on the drive shaft, arranged a second sliding ring slidably frictional engagement with the resilient contact pressure to the first sliding ring, said first sliding ring and before The second sliding ring is made of metal, is to either of these first sliding ring and the second sliding ring, mounted on said hollow shaft through an elastic ring or on the drive shaft.

Feature of the invention according to claim 2, in claim 1, wherein the second sliding ring, by the drive shaft is assembled to the gear housing, the first sliding ring to compress the elastic ring It is configured to be frictionally engaged with the elastic contact pressure.

According to the first aspect of the present invention, the first sliding ring is disposed on the hollow shaft through which the rack shaft is inserted, and the first sliding ring is slid with elastic contact pressure on the driving shaft rotated by the motor. Since the second sliding ring that is movably frictionally engaged is provided, the drive bevel gear when the rotation direction of the electric motor is reversed by the frictional engagement action of the first sliding ring and the second sliding ring And the relative rotational speed of the driven bevel gear can be suppressed. Thereby, even if a backlash exists between the driving bevel gear and the driven bevel gear, it is possible to suppress the occurrence of rattling noise and vibration.
In addition, since one of the first and second sliding rings made of metal is mounted on the hollow shaft or the drive shaft via the elastic ring, the first sliding ring and the second sliding ring are connected by the elastic ring. Between the driving bevel gear and the driven bevel gear when the rotation direction of the electric motor is reversed, while the elastic contact pressure can be applied between the first and second sliding rings. Can be stably maintained over a long period of time.

According to the invention of claim 2, the second sliding ring, by the drive shaft is assembled to the gear housing, it is frictionally engaged with the elastic contact pressure with the first sliding ring to compress the elastic ring Thus, the first sliding ring and the second sliding ring can be frictionally engaged with each other so as to obtain an elastic contact pressure only by assembling the drive shaft to the gear housing.

  Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the electric power steering apparatus 10 according to the present embodiment has a rack shaft 11 that is moved in the axial direction according to a steering operation, and the rack shaft 11 is inserted and rotated by an electric motor 12. The hollow shaft 13, the ball screw mechanism 14 for converting the rotation of the hollow shaft 13 into the axial movement of the rack shaft 11, and the drive shaft 15 for transmitting the rotation of the electric motor 12 to the hollow shaft 13 via a bevel gear mechanism described later. And.

  The electric power steering apparatus 10 includes a gear housing 17 that houses a rack shaft 11, a hollow shaft 13, a ball screw mechanism 14, and a drive shaft 15. A first housing hole 21 and a second housing hole 22 formed in a substantially cylindrical shape are formed in the gear housing 17. The first storage hole 21 has an axis parallel to the rack shaft 11, and the second storage hole 22 obliquely intersects the axis of the first storage hole 21 with an acute angle. The second storage hole 22 is formed so that one end is opened in the first storage hole 21 and the other end is opened outside the gear housing 17.

  A cylindrical hollow shaft 13 is housed in the first housing hole 21 of the gear housing 17 along the axis thereof, and the hollow shaft 13 is rotatably supported by the gear housing 17 at both ends by bearings 23 and 24. Yes. On the outer periphery of the hollow shaft 13, a metal ring body 26 in which a driven bevel gear 25 made of synthetic resin is cast on the outer periphery is key-engaged and fixed by a tightening nut 44.

  In the first housing hole 21 of the gear housing 17, the rack shaft 11 passing through the hollow shaft 13 is supported so as to be reciprocally movable in the axial direction by a guide bush 27 built in the gear housing 17 and a rack guide (not shown). Has been. A screw groove 11 a is formed on the outer periphery of the rack shaft 11, and the screw groove 11 a is formed into a plurality of screw grooves (not shown) formed on the inner periphery of a ball nut 28 that is integrally attached to one end of the hollow shaft 13. It is screwed through a moving ball. The rack shaft 11 having the thread groove 11a, the ball nut 28 mounted on the hollow shaft 13, and the rolling ball constitute a ball screw mechanism 14. By this ball screw mechanism 14, the rotation of the hollow shaft 13 is controlled by the rack shaft. 11 axial motions.

  The drive shaft unit 30 is mounted in the second housing hole 22 of the gear housing 17. The drive shaft unit 30 has a cylindrical case 31a that is accommodated in the second accommodation hole 22 at one end, and a bearing case 31 that has a motor attachment portion 31b that is fixed to the gear housing 17 by an attachment bolt 32 at the other end. The drive case 15 is supported on the drive shaft 15 so as to be rotatable around an axis that is oblique to the axis of the rack shaft 11 via two bearings 33 that are axially spaced apart from the bearing case 31. A drive bevel gear 35 that meshes with the bevel gear 25 is provided.

  The driving bevel gear 35 is made of metal and has a smaller diameter than the driven bevel gear 25. The meshing of the drive bevel gear 35 made of metal and the driven bevel gear 25 made of synthetic resin suppresses the generation of noise due to the meshing of the drive bevel gear 35 and the driven bevel gear 25 and the electric motor 12. The rotation is decelerated and transmitted to the hollow shaft 13.

  The electric motor 12 is installed in the motor mounting portion 31 b of the bearing case 31, and one end of the output shaft 12 a of the electric motor 12 is connected to one end of the drive shaft 15 supported by the cylindrical portion 31 a of the bearing case 31. Yes. Thereby, the rotation of the drive shaft 15 driven by the electric motor 12 is transmitted to the hollow shaft 13 via the drive bevel gear 35 and the driven bevel gear 25, and the rotation of the hollow shaft 13 is transmitted to the rack shaft by the ball screw mechanism 14. 11 axial motions. Accordingly, the rack shaft 11 is moved by the electric motor 12 in a direction corresponding to the steering of the steering wheel by the steering of the driver, and the manual steering of the driving is assisted.

  As shown in detail in FIG. 2, a rubber elastic ring 40 is attached to the outer periphery of the ring body 26 fixed to the outer periphery of the hollow shaft 13, and a metal first slide is attached to the outer periphery of the elastic ring 40. A ring 41 is disposed on the same axis as the hollow shaft 13. The outer peripheral surface of the first sliding ring 41 is formed at an inclination angle substantially the same as the pitch cone angle of the driven bevel gear 25.

  On the other hand, on the drive shaft 15 to which the drive bevel gear 35 is attached, a metal second sliding ring 42 having an outer peripheral surface slidably engaged with the outer peripheral surface of the first sliding ring 41 is disposed. The drive bevel gear 35 is integrally coupled to the drive bevel gear 35 by a fastening bolt 43. The outer peripheral surface of the second sliding ring 42 is formed at an inclination angle substantially the same as the pitch cone angle of the drive bevel gear 35 so as to frictionally engage with the first sliding ring 41 over substantially the entire length in the width direction. It has become.

  In this case, the outer diameter of one of the first sliding ring 41 and the second sliding ring 42 is set to be slightly larger than the pitch circle of the driven bevel gear 25 or the driving bevel gear 35, thereby When the moving ring 41 and the second sliding ring 42 are frictionally engaged, the elastic ring 40 is pressed and contracted to decenter the first sliding ring 41, and the first sliding ring 41 and the second sliding ring 42 are In the meantime, an elastic contact pressure by the elastic ring 40 is obtained. The elastic ring 40, the first sliding ring 41, and the second sliding ring 42 allow the first sliding ring 41 on the hollow shaft 13 and the second sliding ring 42 on the drive shaft 15 to be elastically contacted with each other. The friction engagement means 45 is configured to be slidably frictionally engaged.

  The second sliding ring 42 mounted on the drive shaft 15 accommodates the drive shaft unit 30 that rotatably supports the drive shaft 15 via the bearing 33 in the second storage hole 22, thereby allowing the second slide ring 42 to be mounted on the hollow shaft 13. The first sliding ring 41 is frictionally engaged with the elastic ring 40 while being compressed. At the same time, the drive bevel gear 35 on the drive shaft 15 is meshed with the driven bevel gear 25 on the hollow shaft 13. The bearing case 31 is fixed to the gear housing 17 by the mounting bolt 32 in a state where the bearing case 31 of the drive shaft unit 30 is housed to a predetermined position where it abuts against the end face of the gear housing 17.

  Next, the operation of the electric power steering apparatus 10 in the above-described embodiment will be described. When a steering wheel (not shown) is steered, steering torque is input to a pinion shaft (not shown), and the rack shaft 11 is moved in the axial direction by the rack and pinion mechanism.

  The steering torque input to the pinion shaft is detected by a torque sensor (not shown), the electric motor 12 is controlled based on this steering torque, and the drive shaft 15 is driven to rotate in one direction. The rotation of the drive shaft 15 is transmitted to the hollow shaft 13 via the drive bevel gear 35 and the driven bevel gear 25, and the ball nut 28 is rotated. As the ball nut 28 rotates, the rack shaft 11 is moved in the axial direction by the ball screw mechanism 14. In this way, the assist force by the electric motor 12 is applied to the rack shaft 11, the steered wheels (not shown) are steered by the assist force, and the steering force of the steering wheel by the driver is reduced.

  By the way, in the electric power steering apparatus 10 having the above-described configuration, the resin driven bevel gear 25 is worn with use, and backlash occurs between the driven bevel gear 25 and the drive bevel gear 35 due to wear. In this case, the effect of backlash is that the driving bevel gear 35 is instantaneously rotated relative to the driven bevel gear 25 by the amount corresponding to the backlash when the turning direction of the steering wheel is switched and the rotation direction of the electric motor 12 is reversed. Then, when the driving bevel gear 35 is brought into impact contact with the driven bevel gear 25, a problem arises in that rattling noise and vibration are generated.

  However, in the present embodiment, since the first sliding ring 41 on the hollow shaft 13 and the second sliding ring 42 on the drive shaft 15 are frictionally engaged by the elastic force of the elastic ring 40, the electric motor The relative rotational speed between the drive bevel gear 35 and the driven bevel gear 25 when the rotation direction of the motor 12 is reversed can be suppressed, and rattling noise and vibration can be prevented from being generated.

  Further, even when the driving bevel gear 35 and the driven bevel gear 25 are in a state of transmitting rotation, the rotational torque fluctuation can be reduced by the frictional engagement between the first sliding ring 41 and the second sliding ring 42. it can.

  Therefore, even if the driven bevel gear 25 made of resin is worn with use and a backlash occurs with the drive bevel gear 35, the adverse effect due to the backlash does not become obvious, and the occurrence of rattling noise and vibration can be suppressed. This also means that it is not necessary to finely adjust so as to eliminate the backlash between the driving bevel gear 35 and the driven bevel gear 25 during the initial assembly of the electric power steering device 10. 10 can be easily assembled.

  According to the above embodiment, the first sliding ring 41 is disposed on the outer periphery of the metal ring body 26 on the hollow shaft 13 through which the rack shaft 11 is inserted via the elastic ring 40, Since the second sliding ring 42 slidably engaged with the first sliding ring 41 is disposed on the first sliding ring 41, the first sliding ring 41 and the second sliding ring 42 are electrically driven by the frictional engagement action. The relative rotational speed between the driving bevel gear 35 and the driven bevel gear 25 when the rotation direction of the motor 12 is reversed can be suppressed. Thereby, even if a backlash exists between the driving bevel gear 35 and the driven bevel gear 25, the generation of rattling noise and vibration between the driving bevel gear 35 and the driven bevel gear 25 is effectively suppressed. This makes it possible to maintain the steering feeling well over a long period of time.

  Further, even if there is a backlash between the drive bevel gear 35 and the driven bevel gear 25, the generation of rattling noise and vibration can be suppressed. Therefore, when the electric power steering device 10 is assembled, the drive bevel gear 35 and the driven bevel gear 35 are driven. There is no need to finely adjust the backlash with the bevel gear 25, which makes it possible to easily assemble the electric power steering device 10.

  Furthermore, according to the above-described embodiment, the first and second sliding rings 41 and 42 are made of metal, and the first sliding ring 41 is mounted on the hollow shaft 13 via the elastic ring 40. An elastic contact pressure can be applied between the first sliding ring 41 and the second sliding ring 42 by the ring 40, and wear of the first and second sliding rings 41, 42 can be reduced. The effect of suppressing the relative rotational speed between the driving bevel gear 35 and the driven bevel gear 25 when the rotation direction of the twelve rotation is reversed can be stably maintained over a long period of time. In addition, since the driving bevel gear 35 is made of metal and the driven bevel gear 25 is made of resin, noise caused by the engagement of the driving bevel gear 35 and the driven bevel gear 25 can be suppressed.

  In the above-described embodiment, the example in which the elastic ring 40 is interposed between the hollow shaft 13 and the first sliding ring 41 has been described. However, the elastic ring 40 is replaced with the hollow shaft 13 and the first sliding ring. Similar effects can be obtained by interposing between the drive shaft 15 and the second sliding ring 42 instead of interposing it between 41 and 41.

  In the above-described embodiment, the example in which the first sliding ring 41 on the hollow shaft 13 and the second sliding ring 42 on the drive shaft 15 are made of metal has been described. The rings 41 and 42 are not necessarily made of metal, and can be made of, for example, hard resin.

  In the above-described embodiment, the example in which the driven bevel gear 25 is made of synthetic resin in order to suppress the noise caused by the engagement of the drive bevel gear 35 and the driven bevel gear 25 has been described. Making it is not necessarily a requirement for the present invention, and both the driving bevel gear 35 and the driven bevel gear 25 may be made of metal.

  In the above-described embodiment, the example in which the first sliding ring 41 is disposed on the outer periphery of the metal ring body 26 of the driven bevel gear 25 via the elastic ring 40 has been described. Can also be arranged on the outer periphery of the hollow shaft 13 via an elastic ring 40.

  Further, in the above-described embodiment, the drive shaft unit 30 having the bearing case 31 that rotatably supports the drive shaft 15 via the bearing 33 is configured to be fixed to the gear housing 17. Can also be supported directly on the gear housing 17 via a bearing 33.

  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 sectional drawing of the principal part of the electric power steering apparatus which shows embodiment of this invention. It is a principal part expanded sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 11 ... Rack shaft, 12 ... Electric motor, 13 ... Hollow shaft, 14 ... Ball screw mechanism, 15 ... Drive shaft, 17 ... Gear housing, 25 ... Driven bevel gear, 31 ... Bearing case, 35 ... drive bevel gear, 40 ... elastic ring, 41 ... first sliding ring, 42 ... second sliding ring.

Claims (2)

A gear housing, a rack shaft provided in the gear housing so as to be movable in the axial direction, a rotatable hollow shaft through which the rack shaft is inserted, and rotation of the hollow shaft converted into axial movement of the rack shaft A ball screw mechanism, a drive shaft that is arranged obliquely with the hollow shaft in the gear housing and rotated by an electric motor, a drive bevel gear provided on the drive shaft, and a drive shaft provided on the hollow shaft An electric power steering device comprising a driven bevel gear meshing with the driven bevel gear;
On the hollow shaft, the first sliding ring is arranged, on the drive shaft, arranged a second sliding ring to frictionally engage slidably with a resilient contact pressure on the first sliding ring ,
The first sliding ring and the second sliding ring are made of metal, and one of the first sliding ring and the second sliding ring is placed on the hollow shaft or the drive shaft via an elastic ring. An electric power steering apparatus characterized by being attached to a motor. 2. The second sliding ring according to claim 1 , wherein the drive shaft is assembled to the gear housing, and the elastic ring is compressed and frictionally engaged with the first sliding ring with an elastic contact pressure. An electric power steering apparatus characterized by being configured as described above.

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