JP6605982B2 - Power steering device - Google Patents

Description

  The present invention relates to a so-called rack assist type power steering device which is applied to, for example, a steering device of an automobile and assists the movement of a rack shaft by the rotational force of a motor transmitted via a belt.

  As a conventional rack assist type power steering device, for example, one described in Patent Document 1 below is known.

  That is, this power steering device is linked to the steering wheel via a well-known rack and pinion mechanism, and an input-side pulley fixed to the outer periphery of the tip of the output shaft of the electric motor driven and controlled by a predetermined control device. An output side pulley that is provided on the outer periphery of the rack shaft via a ball screw mechanism and is arranged in parallel in the radial direction with respect to the input side pulley is connected by a belt member, so that the rotational force of the electric motor is reduced to the rack. It is configured to be converted and transmitted to the axial movement force of the shaft.

  In the power steering apparatus, a motor housing that houses a motor element of the electric motor is fastened by a plurality of bolts to a housing that houses the rack shaft, both pulleys, and a belt member. That is, a plurality of bolt insertion holes formed through the housing are formed in an arc shape so that the rotation shaft of the input pulley is eccentric while the bolts are inserted through the bolt insertion holes. By rotating the motor housing integral with the motor element relative to the housing, tension can be applied to the belt as the electric motor is assembled.

JP 2015-47977 A

  By the way, in the conventional power steering apparatus, the housing for housing the rack shaft, the two pulleys, and the belt member includes a first housing and a second housing, with a reduction mechanism housing portion for housing both the pulleys and the belt member as a boundary. In the case where the electric motor is arranged on the non-bearing side (opposite side of the bearing), the tension of the belt member is not obtained unless the first and second housings are combined. Adjustment cannot be made.

  However, if the tension of the belt member is adjusted after the two housings are combined, the belt member is wound around one side of the output pulley in advance, and the speed reduction mechanism is accommodated with the belt member slackened. By accommodating in the section, tension is applied to the slack belt member when the electric motor is assembled.

  However, when assembling the electric motor, since the state of the belt member wound around the output pulley cannot be confirmed, appropriate winding such as one side of the belt member riding on the flange portion of the output pulley is not possible. There was a possibility that it could not be performed.

  The present invention has been devised in view of such a technical problem, and provides a power steering device that can suppress a drop of a belt member from an output pulley.

  The present invention provides a steered shaft that is used to steer a steered wheel by moving in the axial direction as the steering wheel rotates, a substantially cylindrical nut provided on the outer peripheral side of the steered shaft, the nut, A plurality of balls that roll and circulate in a ball circulation groove formed between the turning shaft and the rotation of the nut in the axial direction while reducing the rotation speed of the nut. A ball screw mechanism for converting to an electric motor, an electric motor for generating a steering assist force for assisting an axial movement force of the steered shaft according to a steering state, and an outer peripheral side of one end of the nut. A bearing that is rotatably supported, an output-side pulley that is provided on the outer peripheral side of the other end of the nut so as to be integrally rotatable with the nut and has flange portions on both sides in the width direction, and an outer peripheral side of the output shaft of the electric motor Is provided so that it can rotate integrally An input pulley having flange portions on both sides in the width direction, and a belt member wound between the output pulley and the input pulley, and transmits the output of the electric motor to the steered shaft. A transmission mechanism, a first housing having a bearing housing portion that houses the bearing on the inner peripheral side, and a transmission that is disposed to face the bearing housing portion of the first housing and houses the transmission mechanism on the inner peripheral side A housing formed by joining a second housing having a mechanism housing portion and a side surface of the transmission mechanism housing portion facing the first housing are formed so as to penetrate the input side pulley from the outside of the transmission mechanism housing portion. Between the through-hole provided so as to be insertable into the inner peripheral side, and the contact point between the flange portion of both pulleys and the tangent common to the outer edge of the flange portion of both pulleys, the outer surface of the belt member is opposed Biography A protruding portion that is provided by projecting at least a part of the inner side surface of the mechanism housing portion and restricts the belt member from falling off the output-side pulley. The input-side pulley inserted into the transmission mechanism housing portion together with the output shaft of the electric motor through the through hole from outside the housing while being wound around the side pulley. By rotating in the direction away from the output pulley, the other circumferential side is wound around the input pulley.

  According to the present invention, the protruding portion provided on the housing can regulate the dropping of the belt member wound around the output-side pulley from the output-side pulley, and the belt member can be appropriately assembled.

1 is a front view of a power steering device according to the present invention. It is sectional drawing which follows the axial direction of the rack axis | shaft which concerns on the transmission mechanism vicinity shown in FIG. It is a figure equivalent to the AA line cross section of FIG. 2 showing 1st Embodiment of this invention. It is a principal part enlarged view of FIG. FIG. 3 is a sectional view taken along line B-B in FIG. 2. It is a perspective view showing the state before the motor unit assembly | attachment used for description of the assembly | attachment work process of a belt. It is a figure equivalent to the AA line cross section of FIG. 2 showing 2nd Embodiment of this invention.

  Hereinafter, embodiments of a power steering apparatus according to the present invention will be described in detail with reference to the drawings. In the following embodiment, the power steering device is applied to a steering device for an automobile as in the conventional case.

[First Embodiment]
1 to 6 show a first embodiment of a power steering apparatus according to the present invention. As shown in FIGS. 1 and 2, this power steering apparatus is linked so that one end side can rotate integrally with a steering wheel (not shown). The input shaft 1 is connected to the other end of the input shaft 1 via a torsion bar (not shown) so as to be relatively rotatable, and the other end is linked to a steered wheel (not shown) via a rack and pinion mechanism 3. The output shaft 2 is arranged on the outer peripheral side of the input shaft 1 and various sensors such as a torque sensor 4 for detecting a steering torque based on the relative rotational displacement between the input shaft 1 and the output shaft 2 and a vehicle speed sensor (not shown). A motor unit 30 that applies a steering assist torque according to the steering torque of the driver to the rack shaft 5 to be described later based on the detection result by the sensor, and the output (rotational force) of the motor unit 30 while decelerating A transmission mechanism 20 for transmitting converted into axial movement force of the rack shaft 5, and is mainly comprised.

  The rack and pinion mechanism 3 includes a pinion tooth (not shown) formed on the outer periphery of one end of the output shaft 2 and a predetermined range in the axial direction of the rack shaft 5 arranged so as to be substantially orthogonal to one end of the output shaft 2. The rack shaft 5 is moved in the axial direction according to the rotation direction of the output shaft 2. The axial ends of the rack shaft 5 are linked to left and right steered wheels via tie rods and knuckle arms (not shown), respectively, and the rack shaft 5 moves in the axial direction so that the knuckle arms are pulled via the tie rods. By doing so, the direction of each steered wheel is changed.

  The housing 10 is divided into a first housing 11 that accommodates one end side of the rack shaft 5 in the axial direction and a second housing 12 that accommodates the other end side of the rack shaft 5. The housings 11 and 12 are fastened via a plurality of bolts B1 to B3. Here, in the divided structure of the housing 10, the divided surface is configured to be an axial position corresponding to the outer peripheral side of a nut 25 constituting a ball screw 24 described later.

  The first housing 11 has a substantially cylindrical first rack shaft accommodating portion 11a that accommodates one end side of the rack shaft 5, and an enlarged diameter at the end of the first rack shaft accommodating portion 11a on the second housing 12 side. And is provided adjacent to the outer end side of the bearing holding portion 11b, and the lock nut 7 is screwed to the bearing. 6 is provided with a female threaded portion 11c for clamping and fixing the outer ring 6a, and a first flange portion 11d extending in the outer peripheral area of the female threaded portion 11c and used for joining to the second housing 12.

  Here, the bearing 6 is formed integrally with an outer ring 6a housed in a bearing holding portion 11b and fixed to be secured by a lock nut 7, and one axial end portion of a nut 25 radially opposed to the outer ring 6a. The inner ring 6b and a plurality of rolling elements 6c accommodated so as to roll between the outer ring 6a and the inner ring 6b.

  The second housing 12 includes a substantially cylindrical second rack shaft housing portion 12a that houses the other end side of the rack shaft 5, and an outer peripheral side of an end portion of the second rack shaft housing portion 12a on the first housing 11 side. And a second flange portion 12b that serves to join the first housing 11, and a transmission mechanism housing portion 13 that is recessed on the inner peripheral side of the second flange portion 12b and serves to house the transmission mechanism 20. And comprising.

  As shown in FIGS. 2 and 3, the transmission mechanism accommodating portion 13 is formed in the peripheral area of the second reference axis A2, and includes an input-side pulley accommodating portion 13a for accommodating an input-side pulley 21 described later, An output side pulley accommodating portion 13b that is formed in a peripheral area of the first reference axis A1 and serves to accommodate an output side pulley 22 described later, and the both pulley accommodating portions 13a, 13b so as to communicate with each other. A belt accommodating portion 13c that is defined on the basis of a tangent common to 13b and serves to accommodate a belt 23 described later.

  Further, as shown in FIGS. 3 and 4, a protrusion 14 is provided on the inner side surface on one side of the belt accommodating portion 13 c for use in the belt 23 drop-off regulation described later. The protrusion 14 is provided between the contacts P1 and P2 between the flanges 21b and 22c of the input pulley 21 and the output pulley 22 and a tangent TP common to the outer edges of the flanges 21b and 22c. It is formed by projecting at least a part of the inner surface on one side of the belt accommodating portion 13c toward the belt 23 side.

  In other words, the protruding portion 14 is a common tangent TW between the housing portions 13a and 13b that connects the outer edge of the input side pulley housing portion 13a and the outer edge of the output side pulley housing portion 13b (see the phantom line in FIG. 4). ) Is offset substantially inward by a predetermined amount X so as to be formed in a substantially ridge shape.

  And the protrusion part 14 formed in this protrusion shape is provided adjacent to the output side pulley accommodating part 13b in the area | region between both said contact P1, P2, and the said contact P2 in the output side pulley 22 side, and The minimum gap Cx is equal to or less than the thickness Tx of the belt 23.

  An adjustment hole for communicating with the outside of the housing 10 (second housing 12) and adjusting the tension of the belt 23 is provided on a side surface on one side of the belt accommodating portion 13c so as to overlap with the protrusion 14. 15 is formed through. On the inner end side of the adjustment hole 15, a female screw portion 15 a for screwing the plug 8 for sealing the adjustment hole 15 is formed, and when the tension of the belt 23 is not adjusted. The adjustment hole 15 is sealed by the plug 8 screwed through the female screw portion 15a.

  As shown in FIG. 2, the transmission mechanism 20 is provided on the outer peripheral side of the distal end portion of an output shaft 36 of an electric motor 31 to be described later so as to be integrally rotatable. An input-side pulley 21 that rotates about the center and a peripheral rotation side of the rack shaft 5 are provided so as to be relatively rotatable, and a first reference axis A1 corresponding to the axis of the rack shaft 5 is based on the rotational force of the input-side pulley 21. A belt that is wound between the rotating output pulley 22 and the pulleys 21, 22, and is used for synchronous rotation of the pulleys 21, 22 by transmitting the rotation of the input pulley 21 to the output pulley 21. 23 and a ball screw 24 that is interposed between the output pulley 22 and the rack shaft 5 and converts the rotation of the output pulley 22 into an axial movement of the rack shaft 5 while decelerating the rotation of the output pulley 22. It is entirely accommodated in the transmission mechanism housing portion 13.

  The input pulley 21 has a substantially cylindrical shape with a relatively small diameter as compared with the output pulley 22 and is press-fitted into the output shaft 36 of the electric motor 31 through a through hole 21a formed through the inner periphery. Thus, the output shaft 36 and the output shaft 36 can be rotated together.

  The input-side pulley 21 is provided with a pair of substantially annular flange portions 21b and 21b on both end sides in the axial direction so as to expand in diameter, and both the flange portions 21b and 21b serve as both flange portions. Between 21b and 21b, the belt winding part 21c used for winding of the said belt 23 at the upper end side is formed along the circumferential direction.

  The output-side pulley 22 has a substantially bottomed cylindrical shape, and a fitting recess 22a for opening to a nut 25 (described later) is formed at one end in the axial direction, and the rack shaft 5 is provided at the other end wall. A shaft insertion hole 22b is inserted therethrough. That is, the output pulley 22 is fitted into a nut 25, which will be described later, via a fitting recess 22a from the second housing 12 side, and a plurality of bolt insertion holes (illustrated) provided in the outer peripheral area of the shaft insertion hole 22b. The nut 25 is provided so as to be rotatable integrally with the nut 25 via a plurality of bolts B <b> 4 inserted through the outer side.

  Further, the output pulley 22 is provided with a pair of substantially annular flange portions 22c, 22c on both ends in the axial direction so as to expand in diameter, and both the flange portions 22c, 22c are used to form both flange portions. Between 22c and 22c, the belt winding part 22d used for winding of the lower end side of the said belt 23 is formed along the circumferential direction.

  The belt 23 is a V-belt in which glass fiber, steel wire, or the like is embedded as a core material. The belt 23 has flange portions 22c, 22c on one side in the circumferential direction of the output pulley 22 (on the second housing 12 side). By being accommodated on the inner peripheral side with respect to the outer edge, a predetermined rigidity is set so that the other side (first housing 11 side) can be accommodated on the inner peripheral side of the flange portions 22c and 22c.

  The ball screw 24 is formed in a cylindrical shape surrounding the rack shaft 5, a nut 25 provided so as to be rotatable relative to the rack shaft 5, and a helical shaft provided on the outer periphery of the rack shaft 5. A ball circulation groove 26 having a predetermined lead angle constituted by a ball screw groove 26a and a spiral nut-side ball screw groove 26b provided on the inner periphery of the nut 25, and rolling in the ball circulation groove 26 It is mainly composed of a plurality of balls 27 that can be interposed, and a cylindrical tube 28 that connects both ends of the ball circulation groove 26 and serves to circulate the balls 27 between both ends of the ball circulation groove 26. Has been.

  As shown in FIGS. 1 and 2, the motor unit 30 is attached and fixed to the outer side of the transmission mechanism accommodating portion 13 of the second housing 12 at one end in the axial direction from which an output shaft 36 to be described later projects, and the steering assist torque. And an electronic controller 32 that is attached to the other end of the electric motor 31 and that controls the electric motor 31 according to a steering torque, a vehicle speed, and the like. It is. The motor unit 30 is attached and fixed to the housing 10 by fastening a motor housing 33 (described later) together with the first and second housings 11 and 12 via a plurality of bolts B1 to B3.

  The electric motor 31 is a so-called three-phase AC type surface magnet type synchronous motor, and is a substantially bottomed cylindrical motor housing in which one end in the axial direction facing the second flange portion 12b is closed and the other end is opened. 33, a substantially cylindrical stator 34 fixed to the inner peripheral surface of the motor housing 33 by shrink fitting, a substantially cylindrical rotor 35 provided on the inner peripheral side of the stator 34, and an inner periphery of the rotor 35 And an output shaft 36 that outputs the rotation of the rotor 35, and the bolts B <b> 1 to B <b> 3 that are formed in a bag shape are screwed to the outer peripheral portion of one end of the motor housing 33. A plurality of female screw holes 33a are provided.

  The electronic controller 32 includes a substantially cylindrical body 37a whose one end in the axial direction is fitted to the outer peripheral side of the other end of the motor housing 33, and a cover 37b that closes the other end of the body 37a. And a control board 39 on which an electronic component such as a microcomputer for controlling the energization of the electric motor 31 based on the output signal of the rotation angle sensor 38 is mounted. 37 is attached so as to close the opening on the other end side of the motor housing 33, and is configured integrally with the electric motor 31.

  Further, the motor housing 33 is attached to the housing 10 via an inter-axis adjusting means for adjusting an inter-axis distance Sx between the first reference axis A1 and the second reference axis A2, and via the inter-axis adjusting means. A belt wound between the pulleys 21 and 22 by changing the inter-axis distance Sx between the first reference axis A1 and the second reference axis A2 by rotating the motor housing 33 relative to the housing 10. 23 tension can be adjusted.

  As shown in FIGS. 2, 3, and 5, the inter-axis adjusting means is provided on the outer peripheral edge of the first flange portion 21 b and the second flange portion 22 c, and when the motor housing 33 is rotated relative to the housing 10. Are substantially slit-shaped first bolt insertion holes 41 to 43 and second bolt insertion holes 44 to 46 that are notched along the track of the bolts B1 to B3, and protrudes from the outer peripheral side of one end of the motor housing 33. The bag-shaped female screw holes 47 to 49 into which the bolts B1 to B3 are screwed and the first and second bolt insertion holes 41 to 43 and 44 to 46 are inserted into the female screw holes 47 to 49, thereby being screwed. It is mainly comprised from the volt | bolt B1-B3 used for fastening of both the housings 10 and 33, and the relative rotation support mechanism 50 used to support the relative rotation of the motor housing 33 with respect to the housing 10.

  That is, the inter-axis adjusting means is parallel to the first reference axis A1 and the second reference axis A2 and in a radial direction with respect to both the reference axes A1 and A2 when supported by the relative rotation support mechanism 50. By rotating the motor housing 33 relative to the housing 10 (second housing 12) around a third reference axis A3 provided so as to be offset by Y, the distance between the axes of the reference axes A1 and A2 is increased. It is possible to change Sx.

  The relative rotation support mechanism 50 protrudes from the joint surface of the motor housing 33 with the second housing 12 so as to have a circular cross section with the third reference axis A3 as the center, and has an inner periphery electrically driven. A cross section centered on the third reference axis A3 at the joint surface between the fitting insertion portion 51 in which a shaft insertion hole 51a for penetrating the output shaft 36 of the motor 31 and the motor housing 33 of the second housing 12 is formed. A receiving portion 52 that is recessed so as to have a circular shape, is fitted with the fitting insertion portion 51 on the inner peripheral side thereof, and has an inner peripheral surface that can be relatively rotated, and is mainly configured.

  The receiving portion 52 has a through hole 52a for insertion from the outside of the input pulley 21 fixed to the output shaft 36 of the electric motor 31 on the side surface of the transmission mechanism accommodating portion 13 constituting the end wall. Is formed through. The through hole 52a is set to have a predetermined inner diameter centered on the second reference axis A2, and an allowance for adjusting the reference axes A1, A2 by the inter-axis adjusting means is secured.

  Hereinafter, the assembly work of the belt 23 in the power steering apparatus will be described.

  First, after the bearing 6 is assembled while the one end side of the rack shaft 5 to which the ball screw 24 is assembled is housed in the first rack shaft housing portion 11a of the first housing 11, the nut 25 of the ball screw 24 and so on are assembled. The output pulley 22 is fitted on the outer periphery of the end, and the output pulley 22 is fixed to the nut 25 with a bolt B4.

  Subsequently, after the belt 23 is wound around the belt winding portion 22d of the output side pulley 22, the other end side of the rack shaft 5 is connected to the second rack shaft housing portion 12a of the second housing 12 as shown in FIG. The flange portion 12b of the second housing 12 is joined to the flange portion 11d of the first housing 11 while being housed inside.

  After joining both the housings 11 and 12, the input side pulley 21 is press-fitted and fixed to the outer periphery of the front end portion of the output shaft 36 in the motor unit 30 assembled in advance, and then the input side pulley 21 is attached to the second housing 12. The belt 23 is inserted into the transmission mechanism housing portion 13 (input side pulley housing portion 13a) through the through hole 52a, and the upper end side of the belt 23 is wound around the belt winding portion 21c of the input side pulley 21.

  Here, conventionally, when the belt 23 is wound around the input-side pulley 21, the belt 23 is not yet tensioned, so that all or a part of the belt 23 is detached from the output-side pulley 22 ( However, it is not possible to confirm the state of the belt 23 being wound around the output pulley 22 by joining both the housings 11 and 12 to the flange 22b and 22b. As a result, it is difficult to properly wind the belt 23 around the output pulley 22.

  On the other hand, in the power steering device according to the present embodiment, as shown in FIGS. 3 and 4, the contact points P <b> 1 and P <b> 2 between the flanges 21 b and 22 c of the input side pulley 21 and the output side pulley 22 and the tangent line TP. Since the protruding portion 14 is provided between the belt 23 and the belt 23, the protruding portion 14 can regulate the dropping of the belt 23 wound around the belt winding portion 22 d of the output side pulley 22. As a result, the state in which the belt 23 is wound around the belt winding portion 22d is maintained, and appropriate winding of the belt 23 around the pulleys 21 and 22 can be ensured.

  Thus, after the belt 23 is wound around the pulleys 21 and 22, the bolts B1 to B3 are connected to the first and second bolt insertion holes 41 to 43 and 44 to 46 of the first and second housings 11 and 12, respectively. And is screwed into the female screw holes 47 to 49 of the motor housing 33 to temporarily fix the motor housing 33 to the housing 10.

  Then, after temporarily fixing the motor unit 30, tension is applied and adjusted to the belt 23. That is, the motor housing 33 is rotated relative to the housing 10 while the housing 10 is fixed in a temporarily fixed state where the motor housing 33 can be rotated relative to the housing 10.

  Specifically, while confirming the tension of the belt 23 through the adjustment hole 15, the motor housing 33 and the input pulley are connected to the housing 10 and the output pulley, respectively, around the third reference axis A3. The second reference axis A2 is relatively rotated in the direction of separation, that is, the direction of separation of the second reference axis A2 with respect to the first reference axis A1.

  Then, when the tension of the belt 23 reaches a specified value, the relative rotation is stopped, and the bolts B1 to B3 are further tightened while the phase is maintained, and the housings 10 and 33 are completely fastened. As a result, the assembly work of the belt 23 is completed.

  As described above, in the power steering apparatus according to the present embodiment, the housing 10 (second housing) is disposed between the contacts P1 and P2 between the flanges 21b and 22c of the input pulley 21 and the output pulley 22 and the tangent TP. 12) is provided with a protruding portion 14 formed by protruding a part of the protruding portion 14). For this reason, the protrusion 14 can restrict the belt 23 that is wound around the output pulley 22 from dropping from the output pulley 22, and is provided for proper assembly of the belt 23.

  Specifically, the belt 23 is configured such that the minimum gap Cx between the protrusion 14 at the contact P2 with the tangent TP of the output pulley 22 is equal to or less than the thickness Tx of the belt 23. Can be achieved.

  Further, in the power steering apparatus, in the transmission mechanism housing portion 13, the protrusion 14 is provided adjacent to the output-side pulley housing portion 13b that is the subject of the dropout regulation. Thereby, dropping of the belt 23 from the output side pulley 22 can be more effectively regulated.

  Further, the protrusion 14 is provided with an adjustment hole 15 that communicates the inside and outside of the transmission mechanism housing 13 to adjust the tension of the belt 23. In this way, by providing the adjustment hole 15 using the protrusion 14 that can have a relatively large thickness, a large adjustment allowance for the adjustment hole 15 can be achieved without increasing the thickness of the housing 10. Can be secured.

  In addition, the projecting portion 14 is provided on one side (the side on which the plug 82 is screwed) of the inner surfaces of the transmission mechanism accommodating portion 13 facing the straight portions 23a and 23a (see FIG. 3) of the belt 23. It is provided only on the inner surface. As described above, by providing the protrusion 14 only on the inner surface on one side of the transmission mechanism accommodating portion 13, the weight of the housing 10 increases due to the provision of the protrusion 14, and thus the weight of the power steering device increases. Can be suppressed.

  Further, when the protrusion 14 is disposed on the inner surface on one side of the housing 10, in the power steering device, the belt 23 is located on one side in the circumferential direction of the output side pulley 22 rather than the outer edges of the flange portions 22 c and 22 c. By being accommodated on the inner peripheral side, the rigidity is set such that it can be accommodated on the inner peripheral side of the flange portions 22c and 22c also on the other side. That is, by setting such rigidity, it is only necessary to arrange the protrusion 14 on the inner side surface on the one side, and there is an advantage that an increase in the weight of the power steering device can be suppressed.

[Second Embodiment]
FIG. 7 shows a second embodiment of the power steering apparatus according to the present invention, which is a modification of the method for restricting the belt 23 from dropping according to the first embodiment. In addition, since it is the same as that of the said 1st Embodiment about another structure, below, only a different structure from the said 1st Embodiment is demonstrated based on FIG.

  That is, in the power steering device according to the present embodiment, the radial direction between the inner side surface of the transmission mechanism housing portion 13 facing the outer side surface of the belt 23 and the outer edges of the flange portions 22c and 22c of the output side pulley 22 is determined. The interval Cy is set to be equal to or less than the thickness Tx of the belt 23.

  As described above, in the power steering device according to the present embodiment, the distance Cy between the inner surfaces of the transmission mechanism accommodating portion 13 and the outer edges of the flange portions 22c and 22c of the output pulley 22 is the thickness Tx of the belt 23. The output side pulley 22 of the belt 23 wound around the output side pulley 22 with the flange portions 22c and 22c of the output side pulley 22 constituting the narrow interval Cy is set as follows. The belt 23 can be prevented from falling off, and the belt 23 can be appropriately assembled.

  The present invention is not limited to the configuration of the embodiment. For example, the protrusion 14 is a protrusion formed over almost the entire longitudinal range of the belt accommodating portion 13c as exemplified in the embodiment. In addition, as long as it is a form capable of achieving the effects of the present invention, such as a protrusion formed by projecting a part of the inner surface of the belt accommodating portion 13c, it can be freely set according to the specifications of the power steering device to be applied. Can be changed.

  As the power steering device based on the embodiment described above, for example, the following modes can be considered.

  That is, in one aspect of the power steering apparatus, the power steering device is provided on the outer periphery side of the steered shaft and the steered shaft that is used to steer the steered wheels by moving in the axial direction as the steering wheel rotates. A cylindrical nut and a plurality of balls that roll and circulate in a ball circulation groove formed between the nut and the turning shaft, and reduce the rotational speed of the nut while reducing the rotational speed of the nut. A ball screw mechanism that converts rotation into axial movement of the steered shaft, an electric motor that generates a steering assist force that assists axial movement force of the steered shaft according to a steering state, and one end of the nut A bearing provided on the outer peripheral side of the nut and rotatably supporting the nut; an output-side pulley provided on the outer peripheral side of the other end of the nut so as to rotate integrally with the nut and having flange portions on both sides in the width direction; An input pulley that is provided on the outer peripheral side of the output shaft of the electric motor so as to be integrally rotatable, has flange portions on both sides in the width direction, and a belt member that is wound between the output pulley and the input pulley. A transmission mechanism for transmitting the output of the electric motor to the steered shaft, a first housing having a bearing housing portion for housing the bearing on the inner peripheral side, and facing the bearing housing portion of the first housing And a housing formed by joining a second housing having a transmission mechanism accommodating portion for accommodating the transmission mechanism on the inner peripheral side, and penetratingly formed on a side surface of the transmission mechanism accommodating portion facing the first housing A through hole provided so that the input-side pulley can be inserted from the outside into the inner peripheral side of the transmission mechanism housing portion, a flange portion of the two pulleys, and a common contact between the outer edges of the flange portions of the two pulleys. A protrusion for restricting the belt member from falling off from the output side pulley, by projecting at least a part of the inner surface of the transmission mechanism housing portion facing the outer surface of the belt member. The belt member is housed in the transmission mechanism housing portion in a state where one side in the circumferential direction is wound around the output-side pulley, and the output of the electric motor is output from the outside of the housing through the through hole. The other side in the circumferential direction is wound around the input-side pulley by rotating the input-side pulley inserted into the transmission mechanism housing portion together with the shaft in a direction away from the output-side pulley.

  In a preferred aspect of the power steering apparatus, a minimum gap between the contact point of the output pulley with the tangent and the protrusion is configured to be equal to or less than the thickness of the belt member.

  In another preferred aspect, in any one of the aspects of the power steering apparatus, the protrusion has an adjustment hole that communicates the inside and the outside of the transmission mechanism housing part and serves to adjust the tension of the belt member.

  In still another preferred aspect, in any one of the aspects of the power steering device, the transmission mechanism accommodating portion includes an input-side accommodating portion that accommodates the input-side pulley on one side in the extending direction of the belt member, and the other side. And the output side accommodating portion that accommodates the output side pulley, and the projecting portion is provided adjacent to the output side accommodating portion in the transmission mechanism accommodating portion.

  In still another preferred aspect, in any one of the aspects of the power steering device, the protrusion is an inner surface on one side of the inner surface facing the pair of linear portions of the belt member in the transmission mechanism housing portion. It is provided only on the side.

  In still another preferred aspect, in any one of the aspects of the power steering device, the belt member is accommodated on the inner peripheral side of the outer edge of the flange portion on the one side in the circumferential direction of the output pulley, and the other. Also on the side, the rigidity is set so as to be accommodated on the inner peripheral side of the flange portion.

  From another point of view, the power steering device has a substantially cylindrical shape provided on the outer peripheral side of the steered shaft for turning the steered wheels by moving in the axial direction as the steering wheel rotates. And a plurality of balls that roll and circulate in a ball circulation groove formed between the nut and the steering shaft, and rotate the nut while reducing the rotation speed of the nut. A ball screw mechanism for converting the steered shaft into axial movement, an electric motor for generating a steering assist force for assisting the axial moving force of the steered shaft according to a steering state, and an outer periphery of one end of the nut A bearing that is rotatably provided to support the nut, and an output-side pulley that is provided on the outer peripheral side of the other end of the nut so as to be integrally rotatable with the nut and has flange portions on both sides in the width direction; Electric motor An input pulley having flanges on both sides in the width direction, and a belt member wound between the output pulley and the input pulley, provided on the outer peripheral side of the force shaft so as to be integrally rotatable; A transmission mechanism for transmitting the output of the motor to the steered shaft, a first housing having a bearing housing portion for housing the bearing on the inner peripheral side, and the bearing housing portion of the first housing. A housing formed by joining a second housing having a transmission mechanism accommodating portion that accommodates the transmission mechanism on the inner peripheral side, and is formed to penetrate the side surface of the transmission mechanism accommodating portion facing the first housing. A through hole provided so that the input side pulley can be inserted into the inner peripheral side of the transmission mechanism housing portion, and the inner surface of the transmission mechanism housing portion facing the outer surface of the belt member and the output Side pulley The distance between the outer edges of the flange portion and the radial direction is set to be equal to or less than the thickness of the belt member, and the belt member is accommodated in the transmission mechanism in a state where one side in the circumferential direction is wound around the output-side pulley. The input-side pulley inserted into the transmission mechanism housing portion together with the output shaft of the electric motor through the through hole from the outside of the housing is rotated in a direction away from the output-side pulley. By doing so, the other circumferential side is wound around the input side pulley.

5 ... Rack shaft (steering shaft)
DESCRIPTION OF SYMBOLS 10 ... Housing 11 ... 1st housing 12 ... 2nd housing 13 ... Transmission mechanism accommodating part 14 ... Protrusion part 20 ... Transmission mechanism 21 ... Input side pulley 21b ... Flange part 22 ... Output side pulley 22c ... Flange part 23 ... Belt (belt Element)
24 ... Ball screw (ball screw mechanism)
25 ... Nut 26 ... Ball circulation groove 27 ... Ball 31 ... Electric motor 36 ... Output shaft 52a ... Through hole

Claims (5)

A steered shaft that is used to steer the steered wheels by moving in the axial direction along with the rotation of the steering wheel, a substantially cylindrical nut provided on the outer peripheral side of the steered shaft, the nut and the steered shaft A plurality of balls that roll and circulate in a ball circulation groove formed between them, and the rotation of the nut is converted into the axial movement of the steered shaft while reducing the rotation speed of the nut. A ball screw mechanism;
An electric motor for generating a steering assist force for assisting an axial movement force of the steered shaft according to a steering state;
A bearing provided on the outer peripheral side of one end of the nut, and rotatably supporting the nut;
Provided on the outer peripheral side of the other end portion of the nut so as to be integrally rotatable with the nut, an output side pulley having flange portions on both sides in the width direction, and provided integrally rotatable on the outer peripheral side of the output shaft of the electric motor, An input- side pulley having flange portions on both sides in the width direction; and a belt member wound between the output-side pulley and the input-side pulley, and transmits the output of the electric motor to the steered shaft. A transmission mechanism;
A first housing having a bearing housing portion that houses the bearing on the inner peripheral side, and a transmission mechanism housing portion that is disposed to face the bearing housing portion of the first housing and houses the transmission mechanism on the inner peripheral side. A housing formed by joining a second housing having
A through-hole formed in a side surface of the transmission mechanism housing portion facing the first housing and provided so that the input-side pulley can be inserted from the outside into the inner peripheral side of the transmission mechanism housing portion;
At least a part of the inner surface of the transmission mechanism housing portion that faces the outer surface of the belt member is projected between the contact points of the flange portions of the pulleys and a tangent common to the outer edges of the flange portions of the pulleys. A protrusion that restricts the belt member from falling off from the output pulley, and
With
The minimum gap between the contact point of the output pulley and the tangent line and the protrusion is configured to be equal to or less than the thickness of the belt member,
The belt member is accommodated in the transmission mechanism accommodating portion in a state where one circumferential side is wound around the output pulley, and the transmission mechanism is accommodated together with the output shaft of the electric motor from the outside through the through hole. A power steering device, wherein the other side in the circumferential direction is wound around the input-side pulley by rotating the input-side pulley inserted into the section in a direction away from the output-side pulley.   2. The power steering apparatus according to claim 1, wherein the protrusion has an adjustment hole that communicates the inside and outside of the transmission mechanism housing portion and serves to adjust the tension of the belt member. The transmission mechanism accommodating portion has an input side accommodating portion that accommodates the input side pulley on one side in the extending direction of the belt member, and an output side accommodating portion that accommodates the output side pulley on the other side,
2. The power steering apparatus according to claim 1, wherein the projecting portion is provided adjacent to the output side accommodating portion in the transmission mechanism accommodating portion.   The said protrusion part is provided only in the inner surface of one side among the inner surfaces which face a pair of linear part of the said belt member in the said transmission mechanism accommodating part. Power steering device. The belt member is set to be rigid enough to be accommodated on the inner peripheral side of the flange portion on the other side by being accommodated on the inner peripheral side of the outer edge of the flange portion on one side in the circumferential direction of the output pulley. The power steering device according to claim 4 , wherein the power steering device is provided.

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