JP2010184599A - Electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric power steering device allowing easy mounting of a belt tensioner and adjustment of tension after assembling a belt. <P>SOLUTION: In this power steering device, the belt tensioner 57 for imparting tension to the belt 41 for connecting a driving pulley 37 and a driven pulley 40 is constituted of a cylindrical hole 50 formed in a housing 15 for housing a speed reduction mechanism 28, a yoke 52 which is slidably fitted to the cylindrical hole 50 and rotatably holds a pressing roller 51 for pressing the belt 41 at a distal end, a plug 53 screwed to be adjustable in position at an open end of the cylindrical hole 50, and a spring 55 interposed between the plug 53 and the yoke 52 to energize the yoke 52 toward the belt 41. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electric power steering apparatus that generates a steering assist force by an electric motor.

  In the electric power steering apparatus, an electric motor is arranged in parallel with a ball nut screwed through a ball to a ball screw shaft formed on a rack shaft, a drive pulley is connected to the motor shaft of the electric motor, and the ball nut is connected to the ball nut. There is a motor parallel type electric power steering apparatus provided with a speed reduction mechanism including a belt transmission mechanism in which a driven pulley is attached and the driving pulley and the driven pulley are connected via a belt.

  In this type of electric power steering apparatus, the belt tension affects the friction, operating noise, durability, etc. of the electric power steering apparatus. An adjustable belt tensioner is provided.

JP 2003-220958 A

  However, since the belt tension varies with the temperature change due to the season and use, it is necessary to always keep the belt tension properly. However, in the case of the one described in Patent Document 1, adjustment of the belt tension after assembly is required. In addition, the belt tensioner has a complicated structure and is not easily assembled.

  The present invention has been made in order to solve the above-described conventional problems, and an object thereof is to provide an electric power steering device in which the belt tensioner can be easily attached and the tension can be adjusted after the belt is assembled. To do.

  In order to solve the above problems, the invention according to claim 1 is characterized in that an electric motor that generates a steering assist force, a speed reduction mechanism that decelerates the rotation of the electric motor, and an output rotation of the speed reduction mechanism are adjusted to the left and right of the vehicle. A conversion mechanism that converts the steering shaft extending in a direction into an axial movement, and the speed reduction mechanism includes a small-diameter drive pulley that is rotated by an electric motor, and a large-diameter that is disposed so as to surround the steering shaft. A driven pulley, a belt connecting the drive pulley and the driven pulley, and a belt tensioner that applies tension to the belt, the belt tensioner having a cylindrical hole formed in a housing that houses the speed reduction mechanism; A yoke that is slidably fitted in the cylindrical hole and rotatably holds a pressing roller that presses the belt at the tip, and a plug that is screwed to the opening end of the cylindrical hole so that the position can be adjusted. Is that it is constituted by a spring for biasing said belt said yoke interposed between the plug and the yoke.

  The invention according to claim 2 is characterized in that, in claim 1, the plug has a threaded portion on the outer periphery, and the position of the threaded portion can be adjusted to a screw hole formed on the inner periphery of the open end of the cylindrical hole. After being screwed, it is locked to the housing by a lock nut screwed to the screw portion.

  The invention according to claim 3 is characterized in that in claim 1 or 2, in claim 1 or 2, the drive pulley and the driven pulley are constituted by toothed pulleys, and the belt is constituted by a toothed belt. It is configured.

  According to the invention according to claim 1 configured as described above, the belt tensioner that applies tension to the belt that connects the driving pulley and the driven pulley includes the cylindrical hole formed in the housing that houses the speed reduction mechanism, and the cylinder A yoke that slidably fits in the hole and rotatably holds a pressing roller that presses the belt at the tip, a plug that is screwed to the opening end of the cylindrical hole so as to be adjustable, and a gap between the plug and the yoke The belt tensioner can be easily assembled from the outside of the housing after assembling the belt to the driving and driven pulleys because it is constituted by a spring that is inserted and biases the yoke toward the belt. In addition, the belt tension can be adjusted with a simple operation by simply adjusting the position of the plug from the outside of the housing.

  According to the invention of claim 2, the plug has a threaded portion on the outer periphery, and the threaded portion is screwed to the threaded hole formed on the inner periphery of the opening end of the cylindrical hole so as to be position-adjustable. Therefore, when adjusting the belt tension, the belt tension can be adjusted appropriately and easily by loosening the lock nut and rotating the plug.

  According to the invention of claim 3, the drive pulley and the driven pulley are constituted by toothed pulleys, and the belt is constituted by a toothed belt. Thus, the driven pulley can be reliably transmitted without slipping.

It is a mimetic diagram showing an electric power steering device concerning an embodiment of the invention. It is sectional drawing which shows the specific structure of the arrow 2 part of FIG. It is sectional drawing cut | disconnected along the 3-3 line of FIG. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an electric power steering apparatus 10 according to the present embodiment. The electric power steering apparatus 10 includes a steering shaft 12 connected to a steering wheel 11 as a steering member, and a distal end portion of the steering shaft 12. , A rack shaft 14 as a steering shaft that meshes with the pinion shaft 13, and a housing 15 that houses the pinion shaft 13 and the rack shaft 14. The pinion shaft 13 is supported by the housing 15 so as to be rotatable about an axis that intersects the axis of the rack shaft 14. It is supported movably.

  Tie rods 16 are connected to both ends of the rack shaft 14, and these tie rods 16 are connected to the steered wheels 17 via unillustrated knuckle arms. As a result, when the steering wheel 11 is operated and the steering shaft 12 is rotated, this rotation is converted into a linear motion of the rack shaft 14 by the rack and pinion mechanism including the pinion shaft 13 and the rack shaft 14, via the tie rod 16. The steered wheel 17 is steered.

  The steering shaft 12 is divided into an input shaft 21 connected to the steering wheel 11 and an output shaft 22 connected to the pinion shaft 13, and the input shaft 21 and the output shaft 22 are on the same axis line via a torsion bar 23. Are connected to each other so as to be relatively rotatable.

  In addition, the electric power steering apparatus 10 includes a torque sensor 24 that detects a steering torque based on a relative rotational displacement amount of the input shaft 21 and the output shaft 22, and an electric motor 25 for assisting steering. The detection result of the torque sensor 24 is given to the control unit 26, and the control unit 26 controls the voltage applied to the electric motor 25 via the motor control unit 27 based on the torque detection result, the vehicle speed detection result, and the like.

  The rotation of the electric motor 25 is decelerated by a speed reduction mechanism 28 including a pulley / belt transmission mechanism, and the output rotation of the speed reduction mechanism 28 is transmitted to a conversion mechanism 29 including a ball screw mechanism. The conversion mechanism 29 converts the output rotation of the speed reduction mechanism 28 into the axial movement of the rack shaft 14, thereby assisting steering.

  FIGS. 2 and 3 show a specific configuration of a speed reduction mechanism 28 including a pulley / belt transmission mechanism and a conversion mechanism 29 including a ball screw mechanism. The housing 15 accommodates the speed reduction mechanism 28 and the conversion mechanism 29. A reduction housing 31 is provided, and a motor housing 32 to which the electric motor 25 is attached is coupled to the reduction housing 31. A drive shaft 33 is supported on the motor housing 32 via a bearing 34 so as to be rotatable on the same axis as the motor shaft 35 of the electric motor 25, and one end of the drive shaft 33 is connected to the motor shaft 35 via a joint 36. Has been. A pulley 37 with a small-diameter drive tooth having a helical tooth formed on the outer periphery is integrally provided at the tip of the drive shaft 33. A ring-shaped driven shaft 38 is supported on the motor housing 32 via a bearing 39 so as to be rotatable about an axis parallel to the drive shaft 33. A large-diameter driven toothed pulley 40 having helical teeth formed on the outer periphery is integrally attached to the outer periphery of one end of the driven shaft 38, and between the driven toothed pulley 40 and the driving toothed pulley 37. Further, a toothed belt (timing belt) 41 meshing with the pulleys 37 and 40 is stretched. As a result, the rotation of the drive toothed pulley 37 applied by the electric motor 25 is transmitted to the driven toothed pulley 40 via the toothed belt 41 without slipping.

  A ball nut 43 is integrally provided on the inner periphery of the driven shaft 38, and a ball screw shaft 44 formed integrally with the rack shaft 14 is inserted in the axial direction. The ball screw shaft 44 and the ball nut 43 are screwed together via a ball 45, whereby when the ball nut 40 is rotated, the ball screw shaft 41 (rack shaft 14) is moved in the axial direction. Yes.

  The drive toothed pulley 37, the driven toothed pulley 40 and the toothed belt 41 constitute the speed reduction mechanism 28, and the ball nut 43, the ball screw shaft 44 and the ball 45 constitute the conversion mechanism 29. ing.

  As shown in FIGS. 3 and 4, the deceleration housing 31 has a cylindrical hole 50 that opens toward the toothed belt 41 at an intermediate position between the driving toothed pulley 37 and the driven toothed pulley 40. , 40 is formed in an axial direction perpendicular to the 40 axis. The opening end of the cylindrical hole 50 is opened to the outside of the speed reduction housing 31. A yoke 52 holding a pressing roller 51 rotatably around an axis parallel to the axis of the toothed pulleys 37 and 40 is slidably fitted in the cylindrical hole 50. A screw hole 50 a is formed on the inner periphery of the open end of the cylindrical hole 50, and a screw portion 53 a formed on the outer periphery of the plug 53 is screwed into the screw hole 50 a, and the position of the plug 53 is adjusted with respect to the cylindrical hole 50. It can be done. A spring 55 is inserted in a compressed state between the yoke 52 and the plug 53, and the yoke 52 is pressed toward the toothed belt 41 by the urging force of the spring 55, and the pressing roller 51 is moved to the toothed belt 41. Is applied to apply tension to the toothed belt 41. A lock nut 56 is screwed into the threaded portion 53 a of the plug 53, and after the position of the plug 53 is adjusted with respect to the cylindrical hole 50, the lock nut 56 is tightened to the opening end surface of the cylindrical hole 50. It can be locked in position.

  The above-described cylindrical hole 50, yoke 52, plug 53, spring 55, and the like constitute a belt tensioner 57 that applies tension to the toothed belt 41.

  The belt tensioner 57 configured as described above can be easily assembled from the outside of the housing 15 (deceleration housing 31) after the toothed belt 41 is assembled to the toothed pulleys 37 and 40, and the belt tensioner 57 Adjustment can also be performed from the outside of the housing 15 (deceleration housing 31) by a simple operation of simply loosening the lock nut 56 and rotating the plug 53.

  Next, the operation of the electric power steering apparatus 10 in the above-described embodiment will be described. When the steering wheel 11 is steered, a steering torque is input to the steering shaft 12 and the pinion shaft 13 is rotated. The steering torque input to the steering shaft 12 is detected by the torque sensor 24, and the electric motor 25 is controlled based on the detected steering torque to generate a steering assist torque. The steering assist torque by the electric motor 25 is transmitted from the drive shaft 33 to the ball nut 43 through the drive toothed pulley 37, the toothed belt 41 and the driven toothed pulley 40, and the ball screw shaft 44 is rotated by the rotation of the ball nut 43. As a result, the rack shaft 14 is moved in the axial direction. As the rack shaft 14 moves in the axial direction, the steered wheels 17 are steered through the tie rods 16 and the knuckle arms, and the steering force of the steering wheel 11 by the driver is reduced.

  By the way, the belt tensioner 57 can be assembled from the outside of the housing 15 (deceleration housing 31) after the toothed belt 41 is assembled to the toothed pulleys 37 and 40. That is, after the toothed belt 41 is assembled to the toothed pulleys 37 and 40, the yoke 52 holding the pressing roller 51 is fitted into the cylindrical hole 50 of the speed reduction housing 31, and then the spring 55 is placed in the cylindrical hole 50. Is inserted. In this state, the plug 53 is screwed into the opening end of the cylindrical hole 50, the position is adjusted so that the compression amount of the spring 55 is appropriately set, and the lock nut 56 is locked at that position.

  In the above-described embodiment, the belt tensioner 57 is configured by the driving toothed pulley 37, the driven toothed pulley 40, and the toothed belt 41. However, the pulleys 37, 40 and the belt 41 are not necessarily toothed. For example, the teeth can be eliminated by increasing the frictional engagement force between the pulleys 37 and 40 and the belt 41.

  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.

  The electric power steering apparatus according to the present invention is suitable for adjusting the belt tension of a speed reduction mechanism that transmits the rotation of an electric motor to a steering shaft by reducing the speed by a drive pulley, a belt, and a driven pulley.

  DESCRIPTION OF SYMBOLS 10 ... Electric power steering apparatus, 11 ... Steering member, 14 ... Steering shaft, 15 ... Housing, 25 ... Electric motor, 28 ... Deceleration mechanism, 29 ... Conversion mechanism, 33 ... Drive shaft, 37 ... Drive pulley, 38 ... Drive shaft 40 ... driven pulley, 41 ... belt, 43 ... ball nut, 44 ... ball screw shaft, 45 ... ball, 50 ... cylindrical hole, 51 ... pressing roller, 52 ... yoke, 53 ... plug, 55 ... spring, 56 ... lock Nut, 57 ... belt tensioner.

Claims (3)

An electric motor that generates a steering assist force, a speed reduction mechanism that decelerates the rotation of the electric motor, and a conversion mechanism that converts the output rotation of the speed reduction mechanism into an axial movement of a steering shaft extending in the left-right direction of the vehicle. Prepared,
The reduction mechanism includes a small-diameter driving pulley that is rotated by an electric motor, a large-diameter driven pulley that is disposed so as to surround the steering shaft, a belt that connects the driving pulley and the driven pulley, and the belt. Including a belt tensioner for applying tension,
The belt tensioner includes a cylindrical hole formed in a housing that accommodates the speed reduction mechanism, a yoke that rotatably holds a pressing roller that is slidably fitted into the cylindrical hole and presses the belt at a tip, A plug screwed to the opening end of the cylindrical hole so as to be position-adjustable, and a spring inserted between the plug and the yoke to bias the yoke toward the belt. Electric power steering device.   2. The plug according to claim 1, wherein the plug has a threaded portion on an outer periphery, and the threaded portion is screwed to a threaded hole formed on an inner periphery of the opening end of the cylindrical hole so that the position of the plug is adjustable, An electric power steering apparatus, wherein the electric power steering apparatus is locked to the housing by a lock nut to be screwed.   3. The electric power steering apparatus according to claim 1, wherein the driving pulley and the driven pulley are constituted by toothed pulleys, and the belt is constituted by a toothed belt.

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