JP2013159203A - Electric power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve workability in adjusting a tension of a belt.SOLUTION: An electric power steering device 100 is configured to perform steering assist by transmitting, by the intermediary of a belt 33, a rotary power of a driving pulley 31 connected coaxially with a rotary shaft of an electric motor to a driven pulley 32 connected coaxially with a rotary member of a steering device. The electric power steering device 100 includes a belt tension adjusting mechanism (A) adjusting the distance S between centers of the driving pulley 31 and the driven pulley 32 by rotating a motor housing 22, which rotatably supports the driving pulley 31, relatively to a steering housing 14, which rotatably supports the driven pulley 32, and adjusting the tension of the belt 33. The belt tension adjusting mechanism (A) is provided with a worm wheel mechanism 40 capable of rotating the motor housing 22 relatively to the steering housing 14.

Description

  The present invention transmits the rotational force of an electric power steering device, in particular, a driving pulley that is coaxially coupled to a rotating shaft of an electric motor, to a driven pulley that is coaxially coupled to a rotating member of the steering device via a belt. The present invention relates to an electric power steering device configured to perform steering assist.

  This type of electric power steering apparatus is disclosed, for example, in Patent Document 1 below. In the electric power steering device described in Patent Document 1 below, an adjustment collar (which makes the motor housing non-rotatable) interposed between a steering device housing (steering housing) and an electric motor housing (motor housing). The drive pulley is supported rotatably, and the mounting hole provided in the steering housing (the center of which is rotatably mounted in the mounting hole eccentric to the rotation center of the drive pulley) The belt tension is adjusted by rotating the belt.

JP-A-2005-324708

  By the way, in the electric power steering device described in Patent Document 1, the adjustment collar is assembled to the steering housing while the adjustment collar is rotated with respect to the steering housing to adjust the belt tension (after adjustment). In this case, a jig for fixing the rotation phase of the adjustment collar and the steering housing is necessary, and workability is poor.

The present invention has been made to solve the above problems,
It is configured to perform steering assist by transmitting the rotational force of a driving pulley that is coaxially coupled to the rotating shaft of the electric motor to a driven pulley that is coaxially coupled to the rotating member of the steering device via a belt. In the electric power steering device,
By rotating the motor housing that rotatably supports the drive pulley relative to the steering housing that rotatably supports the driven pulley, the center distance between the drive pulley and the driven pulley (distance between the rotation centers) ) And a belt tension adjustment mechanism for adjusting the tension of the belt is provided,
The belt tension adjusting mechanism includes a worm wheel mechanism capable of rotating the motor housing relative to the steering housing. In the belt tension adjusting mechanism, the rotation center of the drive pulley relative to the motor housing is set to rotate the motor housing relative to the steering housing so that the belt tension can be adjusted by rotating the motor housing relative to the steering housing. The required amount is eccentric with respect to the center.

  In this case, the worm wheel mechanism may include a worm wheel provided in the motor housing and a cylindrical worm that is rotatably provided in the steering housing and engages with the worm wheel. Further, the worm wheel mechanism may have zero reverse transmission efficiency (transmission efficiency when the cylindrical worm is rotated from the worm wheel).

  In the electric power steering apparatus according to the present invention, the center distance between the driving pulley and the driven pulley is adjusted by the belt tension adjusting mechanism by rotating the motor housing relative to the steering housing by the worm wheel mechanism. It is possible to adjust the tension of the belt. For this reason, it is possible to effectively use the reverse transmission property of the worm wheel mechanism (characteristic that rotation is difficult to be transmitted from the worm wheel to the cylindrical worm), and after adjusting the belt tension, the rotational phase of both housings It is possible to improve the workability of fixing. In particular, when the reverse transmission efficiency is zero in the worm wheel mechanism, the center distance between the driving pulley and the driven pulley is prevented from changing in the direction of decreasing the tension, and after the belt tension adjustment Since the belt tension adjustment state is maintained, the rotational phases of the two housings can be easily fixed.

  In the electric power steering apparatus according to the present invention, the belt tension can be adjusted by rotating the motor housing relative to the steering housing by the worm wheel mechanism. However, even if the belt tension becomes higher than the target value due to individual differences (manufacturing errors) of the belt, the belt tension can be easily lowered by the reverse rotation operation of the cylindrical worm with the worm wheel mechanism. Is possible. Such an effect cannot be obtained when a rotation direction restricting means (one-way mechanism) that allows relative rotation in the rotation direction in which the belt tension increases and restricts reverse rotation is provided between the housings. .

1 is a partially cutaway partial front view schematically showing an embodiment of an electric power steering apparatus according to the present invention. FIG. 2 is an exploded perspective view of the electric power steering device shown in FIG. 1. FIG. 3 is a perspective view of the steering housing shown in FIGS. 1 and 2 and a cylindrical worm assembled to the steering housing. FIG. 2 is a side view schematically showing a relationship among a drive pulley, a driven pulley, a belt, a worm wheel mechanism and the like shown in FIG.

  Embodiments of the present invention will be described below with reference to the drawings. 1 to 4 show an embodiment of an electric power steering apparatus according to the present invention. In the electric power steering apparatus 100, an electric power is applied to a rack shaft 11 (ball screw shaft) arranged in the vehicle width direction. A rotating shaft 21 of the motor 20 is arranged in parallel. The electric power steering apparatus 100 includes a rack type steering apparatus 10 and an electric motor 20, and the rotational force of the drive pulley 31 (coaxially connected to the rotating shaft 21 of the electric motor 20 so that torque can be transmitted). (Rotational force) is transmitted via a toothed belt 33 to a driven pulley 32 that is coaxially coupled to a ball nut 12 that is a rotating member of the steering device 10 so as to be able to transmit torque, so that steering assist is performed. It is configured. The driven pulley 32 is assembled to the step portion of the ball nut 12, and is positioned and fixed (fixed to prevent detachment) by the fixing nut 17.

  A rack-type steering device 10 is known per se, and a rack shaft 11 connected to a steering wheel (not shown) via a pinion shaft (not shown) and a steering shaft (not shown) or the like is used for steering. The housing 14 is supported so as to be movable in the vehicle width direction. In the steering device 10, the ball nut 12 is rotatably mounted on the steering housing 14 via the bearing 13. Further, the ball nut 12 and the bearing 13 are positioned and fixed by a fixing nut 15 assembled to the ball nut 12 and a fixing nut 16 assembled to the steering housing 14.

  Further, in the steering device 10, the steering housing 14 is assembled so as to be divided into a left housing 14L and a right housing 14R at a place where the drive pulley 31, the driven pulley 32, the belt 33 and the like are assembled. As shown in FIG. 2, the left housing 14 </ b> L and the right housing 14 </ b> R are integrally connected by three bolts 18 at a lower portion and integrally connected by three bolts 19 at an upper portion. ing. A removable cover 14Rc is provided at an upper portion of the right housing 14R, and the belt 33 can be attached to and detached from the drive pulley 31 by removing the cover 14Rc.

  Each bolt 18 is for integrally connecting the left housing 14L and the right housing 14R after the belt 33 is assembled to the driven pulley 32, and is inserted into the insertion round hole 14La provided in the left housing 14L. It is configured to be inserted and screwed into a screw hole 14Ra provided in the right housing 14R. On the other hand, each bolt 19 adjusts the left housing 14L, the right housing 14R, and the motor housing 22 after the tension of the belt 33 attached to the driving pulley 31 and the driven pulley 32 is adjusted by a belt tension adjusting mechanism A described later. This is for integral connection, and is configured to be inserted into insertion long holes 14Lb and 14Rb provided in the left housing 14L and the right housing 14R and screwed into a screw hole 22a provided in the motor housing 22. Has been.

  The electric motor 20 is configured to be driven according to a steering torque transmitted from the steering wheel to the steering shaft. For this reason, the rotation of the rotating shaft 21 is transmitted to the ball nut 12 via the driving pulley 31, the belt 33, and the driven pulley 32, and is used as the axial driving force (assist force) of the rack shaft 11, so that the steering assist is performed. Done. The rotating shaft 21 and the drive pulley 31 are rotatably assembled to the motor housing 22 of the electric motor 20.

  Incidentally, in this embodiment, a belt tension adjusting mechanism A for adjusting the tension of the belt 33 is provided between the steering housing 14 and the motor housing 22 of the steering device 10. The belt tension adjusting mechanism A includes a motor housing 22 that rotatably supports the rotating shaft 21 and the driving pulley 31 with respect to the steering housing 14 that rotatably supports the driven pulley 32 with each bolt 19 loosened. By rotating relative to each other about the housing rotation center O1, a center distance S between the drive pulley 31 and the driven pulley 32 (the rotation center O2 of the drive pulley 31 and the rotation center O3 of the driven pulley 32 (the rotation center of the ball nut 12)). Is adjusted to adjust the tension of the belt 33 and includes a worm wheel mechanism 40 capable of rotating the motor housing 22 relative to the steering housing 14 (FIG. 4). reference). It should be noted that the rotation shaft 21 and the rotation center O2 of the drive pulley 31 with respect to the motor housing 22 are eccentric from the rotation center O1 of the motor housing 22 with respect to the steering housing 14 by a required amount.

  The worm wheel mechanism 40 includes a worm wheel 41 provided integrally with the motor housing 22 and a cylindrical worm 42 that is rotatably provided on the steering housing 14 and engages with the worm wheel 41. The worm wheel 41 is formed in an arc shape, and the center thereof coincides with the housing rotation center O1. The cylindrical worm 42 is assembled so as to be rotatable with respect to the steering housing 14 and immovable in the axial direction, and has a hexagonal operation hole 42a for mounting a rotation operation tool (not shown) at one end. Provided (see FIG. 3).

  In this worm wheel mechanism 40, the worm wheel 41 is rotated in one direction around the axis by rotating the cylindrical worm 42 in one direction around the axis by a rotation operation tool (not shown), thereby rotating the worm wheel 41 in one direction (counterclockwise in FIG. 4). The belt 33 can be increased in tension, and by rotating the cylindrical worm 42 in the other direction around the axis, the housing rotation center O1 is set as the center. The worm wheel 41 can be rotated in the other direction (the clockwise direction in FIG. 4), and the tension of the belt 33 can be reduced.

  In the worm wheel mechanism 40, the reverse transmission efficiency (transmission efficiency when the cylindrical worm 42 is rotated from the worm wheel 41) is zero (a configuration in which the cylindrical worm 42 cannot be rotated from the worm wheel 41). For this reason, the cylindrical worm 42 cannot be rotated from the worm wheel 41, and the worm wheel 41 does not rotate in the clockwise direction of FIG. And the distance S between the driven pulleys 32 is prevented from changing in the direction of decreasing the tension (the distance S between the cores is shortened).

  In the electric power steering apparatus 100 of this embodiment configured as described above, the belt pulley adjustment mechanism A drives the drive pulley 31 by rotating the motor housing 22 relative to the steering housing 14 by the worm wheel mechanism 40. And the distance S between the driven pulleys 32 can be adjusted, and the tension of the belt 33 can be adjusted. For this reason, it is possible to effectively use the reverse transmission property of the worm wheel mechanism 40 (characteristic that rotation is difficult to be transmitted from the worm wheel 41 to the cylindrical worm 42). It is possible to improve the workability of fixing the rotation phases of the housings 14 and 22 with the respective bolts 19. In particular, in this embodiment, since the reverse transmission efficiency is zero in the worm wheel mechanism 40, the inter-center distance S between the drive pulley 31 and the driven pulley 32 is prevented from changing in the direction of decreasing tension. Since the tension adjustment state of the belt 33 is maintained after adjusting the tension of the belt 33, the rotational phases of both the housings 14 and 22 can be easily fixed by the bolts 19.

  In the electric power steering apparatus 100 of this embodiment, the tension of the belt 33 can be adjusted by rotating the motor housing 22 relative to the steering housing 14 by the worm wheel mechanism 40. When the tension of the belt 33 is adjusted, even if the tension of the belt 33 becomes higher than the target value due to individual differences (manufacturing errors) of the belt 33, the worm wheel mechanism 40 reversely rotates the cylindrical worm 42. The tension of the belt 33 can be easily lowered to the target value. In order to achieve this effect, a rotation direction restricting means (one-way mechanism) is provided between the housings (14, 22) to allow relative rotation in the rotation direction in which the tension of the belt (33) increases and to restrict reverse rotation. It is something that cannot be obtained in some cases.

  In the above-described embodiment, the worm wheel mechanism 40 is configured by the worm wheel 41 provided integrally with the motor housing 22 and the cylindrical worm 42 rotatably provided on the steering housing 14 and engaged with the worm wheel 41. However, instead of this, the worm wheel mechanism is constituted by a worm wheel provided integrally with the steering housing and a cylindrical worm that is rotatably provided on the motor housing and engages with the worm wheel. Is also possible. In the above-described embodiment, the rotation phases of the housings 14 and 22 are fixed by the bolts 19. However, the configuration for fixing the rotation phases of the housings 14 and 22 can be changed as appropriate. There is no limitation to the configuration of the above embodiment.

  In the above-described embodiment, the present invention is applied to the electric power steering device in which the electric motor is disposed in parallel with the rack shaft disposed in the vehicle width direction. Also, various electric power steering devices (for example, an electric power steering device in which an electric motor is arranged in parallel with respect to a steering shaft arranged in the vehicle front-rear direction) are implemented in the same manner or appropriately modified. Is possible.

DESCRIPTION OF SYMBOLS 10 ... Steering device, 11 ... Rack shaft (ball screw shaft), 12 ... Ball nut (rotating member), 13 ... Bearing, 14 ... Steering housing, 20 ... Electric motor, 21 ... Rotating shaft, 22 ... Motor housing, 31 ... Drive pulley, 32 ... driven pulley, 33 ... belt, S ... center distance between drive pulley and driven pulley, A ... belt tension adjusting mechanism, 40 ... worm wheel mechanism, 41 ... worm wheel, 42 ... cylindrical worm, 100 ... Electric power steering device

Claims (3)

It is configured to perform steering assist by transmitting the rotational force of a driving pulley that is coaxially coupled to the rotating shaft of the electric motor to a driven pulley that is coaxially coupled to the rotating member of the steering device via a belt. In the electric power steering device,
By adjusting the distance between the drive pulley and the driven pulley by relatively rotating the motor housing that rotatably supports the drive pulley with respect to the steering housing that rotatably supports the driven pulley, A belt tension adjusting mechanism for adjusting the tension of the belt is provided;
The electric power steering apparatus according to claim 1, wherein the belt tension adjusting mechanism includes a worm wheel mechanism capable of rotating the motor housing relative to the steering housing. In claim 1,
2. The electric power steering apparatus according to claim 1, wherein the worm wheel mechanism includes a worm wheel provided in the motor housing and a cylindrical worm that is rotatably provided in the steering housing and engages with the worm wheel. In claim 1 or 2,
The worm wheel mechanism is an electric power steering apparatus characterized in that reverse transmission efficiency is zero.

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