JP4506455B2 - Electric power steering device - Google Patents

Description

  The present invention relates to an electric power steering apparatus that transmits a rotational force of an electric motor used as a generation source of a steering assist force to a steered shaft and moves the steered shaft in the axial length direction to assist steering.

  An electric power steering device for a vehicle has a spiral groove and a steering shaft that moves in the axial length direction according to a steering operation, and a steering wheel that is arranged so that an output shaft intersects the axis of the steering shaft. An auxiliary electric motor, a helical gear that is interlocked with the output shaft, a helical gear that meshes with the small gear, and an outer periphery of the spiral groove are rotatably disposed. A rotating cylinder to which the large gear is fitted and fixed, first and second rolling bearings that rotatably support both ends of the rotating cylinder in the housing, and a rotational force of the rotating cylinder on the steering shaft. And a power conversion mechanism that converts it into a moving force in the axial direction and transmits it to the steered shaft (for example, Patent Document 1).

  The power conversion mechanism includes a female screw provided inside the rotary cylinder, a plurality of balls engaging with the spiral groove and the female screw, and two circulations provided on the outer peripheral portion of the rotary cylinder and provided in the rotary cylinder. A circulation member (circulator) that circulates the ball through the hole.

  The rotary cylinder is provided with a first rolling bearing on one side in the axial length direction, and the large gear and the second rolling bearing are externally fitted on the other side in the axial length direction from the edge on the other side, A nut for fixing the large gear and the circulation member are attached between the large gear on the other side in the axial direction and the second rolling bearing. In other words, on the other side in the axial length direction of the rotating cylinder, the first fitting portion to which the large gear is fitted, the male screw portion to which the nut is screwed, and the flat mounting on which the holder of the circulation member is placed. A mounting part, two circulation holes penetrating the flat mounting part, a screw hole for attaching a holder to the flat mounting part with a small screw, and a second fitting in which a second rolling bearing is fitted externally With a joint.

Further, the large gear includes a synthetic resin annular tooth body having helical teeth on the outer peripheral portion, and a metal annular core body fitted inside the annular tooth body. There is also known an electric power steering device having a rotation convex portion that prohibits relative rotation with the annular tooth body at a portion.
JP 2002-27497A

However, in the electric power steering apparatus in which the circulating member is provided in the rotating cylinder as described above, it is necessary to secure the area of the flat mounting portion in order to increase the fixing strength of the circulating member. Was designed to have a relatively large diameter. As a result, there were the following problems.
1) If the position of the small screw that fixes the holder of the circulating member is in the vicinity of the track of the female screw of the steered shaft, the allowance of the small screw on the rotating cylinder will be insufficient, taking into account the tolerance of parts such as the holder. Then, the axial force generated at the time of tightening the small screw is insufficient, and the circulating member is easily detached when the ball circulates in the circulating member.
2) The nut for fixing the large gear became large, which was a factor of high cost.
3) In the case where the large gear has a structure having an annular tooth body and an annular core body, the inner diameter of the annular core body becomes large, and the rotation convex portion provided on the outer peripheral portion of the annular core body and the teeth of the annular tooth body Since the distance from the bottom is insufficient, it is necessary to bias the rotation convex portion to the width direction one side with respect to the center in the width direction of the annular core body. Accordingly, there is a problem that directionality occurs during the molding of the annular core, and extra management for molding is required in consideration of the directionality.
4) In the case where the large gear has an annular tooth body and an annular core body, the position of the small gear does not change, whereas the annular core body has a large diameter and the radial dimension of the annular tooth body is insufficient. Therefore, the outer diameter of the rotating cylinder cannot be increased beyond a certain level.

  The present invention has been made in view of such circumstances, and one side in the axial direction in which the power conversion mechanism of the rotating cylinder is provided can be made large in diameter without being influenced by the large gear, and the large gear is provided. It is an object of the present invention to provide an electric power steering device capable of reducing the diameter of the other side in the axial length direction without being influenced by the power conversion mechanism.

  An electric power steering device according to a first aspect of the present invention includes a turning shaft that has a spiral groove and moves in the axial length direction in accordance with a steering operation, a small gear that is interlocked with an output shaft of an electric motor, A large gear that meshes with the gear, a rotating cylinder that is rotatably arranged around the spiral groove, and on which the large gear is fitted and fixed, a bearing that rotatably supports the rotating cylinder on a support member, An electric power steering apparatus comprising a power conversion mechanism that converts a rotational force of the rotating cylinder into a moving force in the axial length direction of the steered shaft and transmits the converted force to the steered shaft. Is provided with the power conversion mechanism, and on the other side in the axial direction of the rotating cylinder, the large gear and the bearing are externally fitted from an edge on the other side, and on the other side in the axial direction. And a fixing means for fixing the large gear to the other side in the axial direction through the bearing. I am characterized in.

  In the electric power steering device according to a second aspect of the present invention, the power conversion mechanism includes a plurality of balls that engage with the spiral groove, and a circulation member that is attached to an outer peripheral portion of the rotating cylinder and circulates the balls. The fixing means has a nut that is screwed to the other side in the axial direction, and the bearing is attached between the nut and the large gear.

  In the electric power steering apparatus according to a third aspect of the present invention, the large gear includes an annular tooth body made of synthetic resin having teeth on an outer peripheral portion, and an annular core body made of metal fitted into the annular tooth body. And a rotation convex portion that prohibits relative rotation with the annular tooth body at the center in the width direction of the outer peripheral portion of the annular core body.

  According to the first aspect of the present invention, the large gear and the bearing are externally fitted to the other side in the axial length direction of the rotary cylinder provided with the power conversion mechanism on one side in the axial length direction, and the large gear is further interposed via the bearing. Since the fixing means for fixing the shaft is provided on the other side in the axial direction, the portion of the rotary cylinder where the power conversion mechanism is provided can be made large in diameter without being influenced by the large gear, and is also affected by the power conversion mechanism. Therefore, the other side in the axial direction can be reduced in diameter, and the large gear can be reduced in diameter.

  According to the second aspect of the present invention, the large gear and the bearing can be fixed to the other side in the axial direction with one nut, the number of parts can be reduced, and the cost can be reduced.

  According to the third aspect of the invention, the inner diameter of the annular core body can be reduced, and the distance between the rotation convex portion provided on the outer peripheral portion of the annular core body and the root of the annular tooth body can be ensured. Since it can do, a rotation convex part can be arrange | positioned in the center part of the width direction of an annular core, and directionality does not generate | occur | produce at the time of shaping | molding of an annular core.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic diagram showing an overall configuration of an electric power steering apparatus according to the present invention, FIG. 2 is an enlarged cross-sectional view showing a configuration in which a part is omitted, and FIG. 3 is an enlarged cross-sectional view showing the configuration of a main part.

  In the electric power steering apparatus shown in FIGS. 1 to 3, one end portion is connected to the steering wheel via the universal joint 1 and the steering shaft 2, and the transmission shaft 3 having the pinion 3a at the other end portion meshes with the pinion 3a. The rack tooth 4a, the rack tooth 4a and the spiral groove 4b at a position spaced apart in the axial length direction thereof, and the steered shaft 4 capable of moving in the axial length direction, and the steered shaft 4 being movable A substantially cylindrical housing 5 for receiving and supporting, an electric motor 6 arranged outside the housing 5 so that the output shaft 6a intersects the axis of the steered shaft 4, and a helical gear linked to the output shaft 6a. The small gear 7, the helical gear 8 meshing with the small gear 7, and the outer periphery of the spiral groove 4 b are arranged coaxially with the steered shaft 4 so that the large gear 8 is externally fitted. The rotating cylinder 9 to be fixed and both ends of the rotating cylinder 9 are The first and second rolling bearings 10 and 11 that are rotatably supported in the ring 5 and the spiral groove 4b are engaged, and the rotational force of the rotating cylinder 9 is converted into a moving force in the axial direction of the steered shaft 4. A power conversion mechanism A that converts the power and transmits it to the steered shaft 4.

  The power conversion mechanism A includes a female screw 9a provided inside the rotary cylinder 9 corresponding to the spiral groove 4b, a plurality of balls 12 engaged with the female screw 9a and the spiral groove 4b, and a female screw 9a of the rotary cylinder 9. Two circulation holes (not shown) penetrating in the radial direction at the facing position, and a circulation member (circulator) 13 communicating with the circulation holes for circulating a plurality of balls 12 between the two circulation holes The circulation member 13 is attached to the outer peripheral portion of the rotary cylinder 9 by a holder 14 having a substantially Ω cross section.

  The housing 5 includes a first cylinder 51 that supports the rack tooth 4a side of the steered shaft 4, a second cylinder 52 that is coupled to the first cylinder 51 with a bolt or the like and that accommodates and supports the rotating cylinder 9, A third cylinder 53 connected to the second cylinder 52 by a bolt or the like and supporting the spiral groove 4b side of the steered shaft 4 is provided.

  First and second support portions 52a and 52b are provided inside both end portions of the second cylindrical body 52, and an annular convex portion 52c is provided at the center portion, respectively, and the first and second support portions 52a are provided. , 52b, the first and second rolling bearings 10 and 11 are rotatably supported by the rotary cylinder 9. A motor attachment portion 52e having a support hole 52d penetrating in a direction intersecting the axis of the second cylinder 52 is integrally provided on one side of the second cylinder 52, and the motor attachment The electric motor 6 is attached to the portion 52e with a plurality of bolts via the bearing cylinder 15.

  The bearing cylinder 15 has a cylindrical portion 15a fitted in the support hole 52d, and a flange portion 15b that expands from the cylindrical portion 15a, and is interlocked with the output shaft 6a inside the cylindrical portion 15a. A drive shaft 16 having a small gear 7 made of a bevel gear is rotatably supported via two rolling bearings 17 and 17, and the electric motor 6 is attached to the flange portion 15b.

  An internal thread 9a corresponding to the spiral groove 4b is provided inside the rotary cylinder 9, and first and second rolling bearings 10 and 11, a large gear 8 made of a bevel gear, and a circulation member 13 are provided on the outer periphery. And a nut 18 are attached. A flat mounting portion 9b on which the holder 14 of the circulating member 13 is mounted on the outer peripheral portion on one side in the axial length direction where the female screw 9a of the rotating cylinder 9 is provided, and the holder 14 is small in the flat mounting portion 9b. Screw holes (not shown) to be attached by screws 19, the two circulation holes, the first fitting portion 9c in which the first rolling bearing 10 is fitted, the axial direction of the first rolling bearing 10, and the like A flange portion 9d that restricts movement to the side is provided.

  On the other side in the axial length direction where the female screw 9a of the rotating cylinder 9 is not provided, the fitting portion 9e and the large gear on which the large gear 8, the movement regulating cylinder 20, and the second rolling bearing 11 are externally fitted from the other side edge. A flange portion 9f that restricts the movement of the shaft 8 in the axial length direction is provided. The fitting portion 9e is formed to have a smaller diameter than the outer diameter of the flange portion 9d, and a screw portion 9g is provided at an end portion of the fitting portion 9e, and a nut 18 as a fixing means to be screwed to the screw portion 9g. The large gear 8 is pressed against the flange 9d via the inner ring of the second rolling bearing 11 and the movement restricting cylinder 20 by tightening the second rolling bearing 11, and the second rolling bearing 11 is interposed between the nut 18 and the large gear 8. The large gear 8 and the inner ring of the angular second rolling bearing 11 are fixed.

  The large gear 8 includes an annular tooth body 81 made of a synthetic resin having teeth on the outer peripheral portion, and a metal annular core body 82 fitted in the annular tooth body 81, and the annular core body An anti-rotation convex portion 82 a that prohibits relative rotation with the annular tooth body 81 is provided on the outer peripheral portion of 82. The anti-rotation projections 82 a are provided in the circumferential center of the annular core 82 in the circumferential direction.

  In the electric power steering apparatus configured as described above, the rotating cylinder 9 has the circulation member 13 attached to one side in the axial length direction having the female screw 9a and the female screw 9a provided on the other side in the axial length direction. Since the non-fitting portion 9e is provided, the fitting portion 9e can be reduced in diameter without being affected by the power conversion mechanism A. Therefore, the large gear 8 attached to the fitting portion 9e can be reduced in size. By reducing the size of the large gear 8, the inner diameter of the annular core body 82 can be reduced, and the anti-rotation convex portion 82 a is arranged at the center in the width direction of the annular core body 82, and the anti-rotation convex portion 82 a and the annular tooth body 81. It is possible to secure a distance between the tooth bottom. As a result, the radial dimension of the annular tooth body 81 can be secured, and the directionality at the time of forming the annular tooth body 81 can be eliminated, thereby improving the molding workability. In addition, since the large gear 8 and the second rolling bearing 11 are fixed by the single nut 18, the entire length of the rotating cylinder 9 can be shortened, and the size around the rotating cylinder 9 can be reduced.

  Further, one side of the rotating cylinder 9 in the axial length direction can be made large in diameter without being influenced by the large gear 8. Therefore, even when the position of the small screw 19 for fixing the holder 14 of the circulating member 13 is in the vicinity of the track of the female screw 9a, the engagement allowance of the small screw 19 to the rotating cylinder 9 can be sufficiently secured. The axial force at the time of tightening the machine screw 19 can be sufficient, and the circulating member 13 can be prevented from coming off.

  In the electric power steering apparatus configured as described above, the steering force of the steering wheel is transmitted from the pinion 3a of the transmission shaft 3 to the rack teeth 4a of the steered shaft 4, and is generated as the steering wheel is steered. The electric motor 6 is driven and controlled according to the steering torque. The rotational force of the output shaft 6a generated by the electric motor 6 by this drive control is transmitted from the small gear 7 through the large gear 8 to the rotating cylinder 9, and the rotating cylinder 9 rotates. 9a, transmitted from the ball 12 to the spiral groove 4b, the steered shaft 4 is moved in the axial direction by the component force, and the force to be applied to the steering wheel for steering is reduced.

  In the embodiment described above, the power conversion mechanism A having the circulation member 13 is provided on one side in the axial length direction of the rotating cylinder 9, but the center of the rotating cylinder 9 in the axial length direction is also shown in FIG. It is good also as a structure which provided the power conversion mechanism A in the part. FIG. 4 is a sectional view showing another embodiment of the main part. The electric power steering apparatus of FIG. 4 has a female thread 9a inside the longitudinal center of the rotating cylinder 9, and a flat mounting section 9b outside the axial center of the rotating cylinder 9. The flat mounting section A circulating member 13 is attached to 9b by a holder 14 and a small screw, and a large gear 8 and a first rolling bearing 10 are fitted and held on one side in the axial length direction of the rotating cylinder 9, and the shaft of the rotating cylinder 9 is The second rolling bearing 11 is fitted and held on the other side in the long direction.

  With this configuration, the rotational force of the output shaft 6a can be applied from the large gear 8 to one side in the axial direction of the rotating cylinder 9, and therefore a relatively large load is applied from the large gear 8 to the rotating cylinder 9. In this case, the deflection of the rotary cylinder 9 due to the rotational force can be reduced, the swinging of the rotary cylinder 9 can be reduced, and the noise at the meshing portion of the small gear 7 and the large gear 8 can be eliminated.

  In the above-described embodiment, the ball screw mechanism is used as the power conversion mechanism A that converts the rotational force of the output shaft 6a into the moving force in the axial length direction. A plurality of power transmission rings each including an inner ring member having an engaging annular ring portion on its inner peripheral portion and an outer ring member that rotatably holds the outer peripheral portion of the inner ring member via a plurality of balls. A mechanism that is biased with respect to the axis of the steered shaft 4 and is held in the rotary cylinder 9 may be used.

  In addition, the electric power steering apparatus according to the present invention has a configuration in which the electric motor 6 is disposed at a position intersecting the axis of the steered shaft 4, and the electric motor 6 is disposed in parallel with the steered shaft 4. It may be a configuration. In this case, the small gear 7 and the large gear 8 may be spur gears as well as bevel gears.

  In the embodiment described above, the rolling bearings 10 and 11 are used as bearings for supporting the rotating cylinder. However, the bearings may be sliding bearings. Further, the large gear 8 is configured to include the annular tooth body 81 and the annular core body 82, and may be entirely made of synthetic resin or metal. Further, the nut 18 is used as a means for fixing the large gear 8. However, the nut 18 is constituted by means for preventing rotation of the large gear 8 with respect to the fitting portion 9e and means for preventing movement of the retaining ring or the like in the axial direction. May be.

1 is a schematic diagram showing an overall configuration of an electric power steering apparatus according to the present invention. It is an expanded sectional view showing composition which omitted a part of electric power steering device concerning the present invention. It is an expanded sectional view showing the composition of the important section of the electric power steering device concerning the present invention. It is sectional drawing which shows other embodiment of the principal part of the electric power steering apparatus which concerns on this invention.

Explanation of symbols

4 Steering shaft 4b Spiral groove 5 Housing (support member)
6 Electric motor 6a Output shaft 7 Small gear 8 Large gear 81 Annular tooth body 82 Annular core body 82a Non-rotating convex portion 9 Rotating cylinder 11 Second rolling bearing (bearing)
12 ball 13 circulating member 18 nut (fixing means)
A Power conversion mechanism

Claims (3)

  A steered shaft that has a spiral groove and moves in the axial length direction according to a steering operation, a small gear that is interlocked with the output shaft of the electric motor, a large gear that meshes with the small gear, and the spiral groove A rotating cylinder that is rotatably disposed around the outer periphery of the steering wheel, a bearing that rotatably fits the large gear, a bearing that rotatably supports the rotating cylinder on a support member, and a rotational force of the rotating cylinder that is applied to the turning shaft. In the electric power steering apparatus provided with a power conversion mechanism that converts the moving force in the axial length direction and transmits it to the steered shaft, the power conversion mechanism is provided on one side in the axial length direction of the rotating cylinder. The large gear and the bearing are externally fitted to the other side of the rotary cylinder in the axial direction from the other side edge, and the large gear is connected to the other side of the axial direction in the axial direction via the bearing. An electric power steering device comprising a fixing means for fixing to the other side in the axial direction   The power conversion mechanism includes a plurality of balls that engage with the spiral groove, and a circulation member that is attached to an outer peripheral portion of the rotating cylinder and circulates the balls, and the fixing means is in the axial direction. The electric power steering apparatus according to claim 1, further comprising a nut screwed to the other side, wherein the bearing is attached between the nut and the large gear. The large gear includes an annular tooth body made of a synthetic resin having teeth on an outer peripheral portion and a metal annular core body fitted in the annular tooth body, and the outer peripheral portion of the annular core body The electric power steering device according to claim 1 or 2, further comprising a rotation-protruding convex portion that prohibits relative rotation with the annular tooth body at a central portion in the width direction.

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