JP6904475B2 - Torque transmission fittings and electric power steering device - Google Patents

Description

The present invention relates to a torque transmission joint incorporated in various mechanical devices for transmitting torque between a drive shaft and a driven shaft, and an electric power steering device incorporating the torque transmission joint.

18 and 19 show an example of a conventional electric power steering device described in Japanese Patent Application Laid-Open No. 2004-306988. This electric power steering device includes a steering shaft 2 having a steering wheel 1 attached to a rear end portion, a housing 3 that rotatably supports the front end portion of the steering shaft 2, and a portion rotationally driven by the steering shaft 2. The worm wheel 4 is fixed, and the worm tooth 5 that meshes with the worm wheel 4 is provided in the intermediate portion in the axial direction, and the worm 7 is rotationally driven by the electric motor 6.

Both ends of the worm 7 in the axial direction are rotatably supported in the housing 3 by a pair of rolling bearings 8 and 9 such as deep groove ball bearings. A pressing piece 10 is externally fitted to a portion of the tip of the worm 7 that protrudes from the rolling bearing 8, and an urging mechanism such as a coil spring 11 is arranged between the pressing piece 10 and the housing 3. .. The coil spring 11 urges the worm teeth 5 of the worm 7 toward the worm wheel 4 via the pressing piece 10. With such a configuration, the generation of rattling noise due to backlash between the worm teeth 5 and the worm wheel 4 is suppressed.

In the conventional electric power steering device, the generation of rattling noise at the meshing portion between the worm teeth 5 and the worm wheel 4 is suppressed, but the tip of the output shaft 12 of the electric motor 6 and the base end of the worm 7 are suppressed. There is room for improvement from the viewpoint of suppressing the generation of abnormal noise at the joint with the part. This point will be described below.

In the conventional electric power steering device, in order to connect the tip end portion of the output shaft 12 of the electric motor 6 and the base end portion of the worm 7 to enable torque transmission, the spline hole 13 at the base end portion of the worm 7 and the spline hole 13 , The spline shaft portion 14 at the tip of the output shaft 12 is spline-engaged. If the spline shaft portion 14 and the spline hole 13 are spline-engaged with the circumferential gap set to zero, that is, in the absence of backlash, the tip end portion of the output shaft 12 and the base end portion of the worm 7 are engaged. No abnormal noise is generated at the spline engaging portion with. However, in reality, there is backlash in this spline engaging portion. In particular, in the structure in which the worm teeth 5 are urged toward the worm wheel 4, the worm 7 needs to be oscillated and displaced, and the backlash of the spline engaging portion cannot be completely eliminated. Therefore, the conventional electric power steering device has been improved from the viewpoint of suppressing the generation of abnormal noise due to the backlash of the spline engaging portion when the rotation direction of the output shaft 12 of the electric motor 6 is reversed. There is room for.

On the other hand, Japanese Patent Application Laid-Open No. 2012-131249 states that the output shaft of the electric motor and the worm are coupled to each other via a metal columnar power transmission member so that the worm can be smoothly oscillated. The structure that can be used is described. However, even in such a structure, in order to swing and displace the worm, spline shafts provided at both ends of the power transmission member and spline holes provided at the respective ends of the worm and the output shaft of the electric motor. There is a backlash in each of the spline engaging portions with and. Therefore, even in such a structure, there is room for improvement from the viewpoint of suppressing the generation of abnormal noise caused by these backlashes.

Japanese Unexamined Patent Publication No. 2004-306988 Japanese Unexamined Patent Publication No. 2012-131249

The present invention has been made in view of the above circumstances, and provides a torque transmission joint and an electric power steering device capable of suppressing the generation of abnormal noise when reversing the rotation direction of the drive shaft. The purpose is.

The torque transmission joint of the present invention includes an intermediate transmission member, a pair of end transmission members, and an elastic member.

The intermediate transmission member has intermediate transmission teeth provided at a plurality of locations in the circumferential direction and axial outer surfaces arranged on both sides in the axial direction.

The pair of end transmission members are arranged on both sides in the axial direction of the intermediate transmission member, and each of the pair of end transmission members has end transmission teeth provided at a plurality of locations in the circumferential direction and the ends. It is arranged on the lateral side in the axial direction from the partial transmission tooth, and has an end side surface portion facing any of the lateral outer surfaces in the axial direction.

The elastic member is assembled to the intermediate transmission member, arranged at a plurality of positions in the circumferential direction, and has insertion holes through which the end transmission teeth are inserted in the axial direction. In a state where the end transmission tooth inserts the insertion hole in the axial direction, the end transmission tooth and the intermediate transmission tooth are arranged alternately in the circumferential direction and through a gap in the circumferential direction. The circumferential distance between the circumferential edges of the insertion hole is smaller than the circumferential distance between adjacent intermediate transmission teeth among the intermediate transmission teeth.

Further, in the radial direction toward the range of said intermediate transmission member and said end side portion axially opposed, said elastic member, protrudes axially outward from the axial outer surface of said intermediate transfer member. That is, the axially outer side of the axial side portions of the elastic member, than the axially outer side of the axial sides of the during transmission member, the side surface portions of said pair of end transduction member Located closer to you.
Further, the end transmission tooth of one end transmission member of the pair of end transmission members and the end transmission tooth of the other end transmission member of the pair of end transmission members. Are axially opposed to each other through an axial gap.
Further, the axial distance between the end side surface portions of the pair of end transmission members is larger than the axial width dimension of the coupling between the intermediate transmission member and the elastic member.

Preferably, the elastic member projects radially inward with respect to the intermediate transmission member. That is, the radial gap existing between the tip surface of the end transmission tooth and the bottom surface of the insertion hole is the adjacent pair of the tip surface of the end transmission tooth and the intermediate transmission tooth. It is smaller than the radial gap that exists between the intermediate transmission teeth and the bottom surface.

The elastic member may be provided with elastic protrusions projecting toward the central side in the circumferential direction at least one of the side edges of the insertion holes in the circumferential direction in the radial direction. Preferably, the elastic projections are provided on the radial outer edges of the respective circumferential edges of the insertion hole.

The elastic member may be provided with protruding portions projecting outward in the axial direction at a plurality of locations in the circumferential direction facing the side surface portion of the end portion in the axial direction.

The electric power steering device of the present invention includes a housing, a worm wheel, a worm, and an electric motor.

The worm wheel is rotatably supported with respect to the housing.

The worm is rotatably supported by the housing in a state of being meshed with the worm wheel.

The electric motor has an output shaft for rotationally driving the worm.

In particular, the electric power steering device of the present invention has a torque transmission joint that enables torque transmission between the output shaft of the electric motor and the worm. Be prepared.

The torque transmission joint is composed of the torque transmission joint of the present invention. One end transmission member of the pair of end transmission members is fixedly or integrally formed at the tip end of the output shaft of the electric motor. Further, the other end transmission member of the pair of end transmission members is fixedly or integrally formed at the base end portion of the worm.

In the electric power steering device of the present invention, the worm can swing with respect to the output shaft of the electric motor, and the worm is placed on the worm wheel between the tip of the worm and the housing. It can be provided with an urging mechanism for urging toward.

According to the torque transmission joint and the electric power steering device of the present invention, a drive shaft in which one end transmission member of a pair of end transmission members is fixed or integrally molded, and a pair of end transmission members Of the driven shaft in which the other end transmission member of the member is fixed or integrally molded, it is possible to suppress the generation of abnormal noise when the rotation direction of the drive shaft is reversed.

FIG. 1 is a partially cut side view showing the electric power steering device of the first example of the embodiment. FIG. 2 is an enlarged view of part A of FIG. 1, which is shown with a part omitted. FIG. 3 is a perspective view of the torque transmission joint of the first example of the embodiment. FIG. 4 is a view of the torque transmission joint of the first example of the embodiment as viewed from the outside in the radial direction. FIG. 5 is a view of the torque transmission joint of the first example of the embodiment as viewed from the side in the axial direction of FIG. FIG. 6 is a cross-sectional view taken along the line BB of FIG. FIG. 7 is a cross-sectional view taken along the line COC of FIG. FIG. 8 is an enlarged view of the upper right portion of FIG. 7. FIG. 9 is a cross-sectional view taken along the line DD of FIG. FIG. 10 is a cross-sectional view taken along the line EE of FIG. FIG. 11 is a cross-sectional view corresponding to the cross-sectional view taken along the line BB of FIG. 5, showing a combined body of the intermediate transmission member and the elastic member taken out from the torque transmission joint of the first example of the embodiment. 12 (a) to 12 (c) are views showing an intermediate transmission member of the torque transmission joint of the first example of the embodiment, and FIG. 12 (a) is a side view of one of the views. 12 (b) is a sectional view taken along line FF of FIG. 12 (a), and FIG. 12 (c) is a side view of the other. 13 (a) to 13 (c) are views showing the elastic member of the torque transmission joint of the first example of the embodiment, and FIG. 13 (a) is a side view of one side, FIG. (B) is a cross-sectional view taken along the line GG of FIG. 13 (a), and FIG. 13 (c) is a side view of the other. 14 is a view showing an end transmission member of the torque transmission joint of the first example of the embodiment, FIG. 14 (a) is an end view, and FIG. 14 (b) is FIG. 14 (a). ) Is a cross-sectional view taken along the line HH. FIG. 15 is a view of the joint between the intermediate transmission member and the elastic member of the torque transmission joint of the second example of the embodiment as viewed from the side in the axial direction. FIG. 16 is a diagram corresponding to FIG. 7 regarding the torque transmission joint of the second example of the embodiment. FIG. 17 is an enlarged view of the upper right portion of FIG. FIG. 18 is a partially cut side view showing an example of the conventional structure of the electric power steering device. FIG. 19 is an enlarged I-I cross-sectional view of FIG.

[First Example of Embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. 1 to 14. The electric power steering device of this example is rotatably supported by the housing 3, the worm wheel 4 rotatably supported by the housing 3, and the worm wheel 4 in a state of being meshed with the worm wheel 4. A worm 7a and an electric motor 6 having an output shaft 12a for rotationally driving the worm 7a are provided. The housing 3 rotatably supports the front end (see FIGS. 18 and 19) of the steering shaft 2 to which the steering wheel 1 is attached to the rear end. The worm wheel 4 is fixed to a portion that is rotationally driven by the steering shaft 2. More specifically, the worm 7a has worm teeth 5 that mesh with the worm wheel 4 in the axial intermediate portion, and both ends in the axial direction of the worm 7a are a pair of rolling bearings 8 and 9 such as deep groove ball bearings. Is rotatably supported in the housing 3.

An urging mechanism 15 including an elastic body such as a coil spring or a leaf spring is provided between the rolling bearing 8 fitted to the tip of the worm 7a and the housing 3. Based on the elasticity of the elastic body of the urging mechanism 15, the worm teeth 5 of the worm 7a are pressed or urged toward the worm wheel 4. With such a configuration, the generation of rattling noise due to backlash between the worm teeth 5 and the worm wheel 4 is suppressed.

The electric power steering device of the present invention includes a torque transmission joint 16 that enables torque transmission between the output shaft 12a of the electric motor 6 serving as the driving shaft and the worm 7a serving as the driven shaft. In this example, the tip end portion of the output shaft 12a of the electric motor 6 and the base end portion of the worm 7a, which are arranged in series with each other in the axial direction, are connected via a torque transmission joint 16.

The torque transmission joint 16 includes an intermediate transmission member 17, a pair of end transmission members 18, and an elastic member 19. One end transmission member 18 (on the right side in FIGS. 2, 4, 6 and 7) constituting a pair of end transmission members 18 is attached to the output shaft 12a. The other end transmission member 18 (left in FIGS. 2, 4, 6, and 7) is attached to the base end of the worm 7a. The intermediate transmission member 17 transmits torque between one end transmission member 18 and the other end transmission member 18. The elastic member 19 is made of an elastic material containing rubber and other elastomers and cushions between one end transmission member 18 and the intermediate transmission member and between the other end transmission member 18 and the intermediate transmission member 17. Demonstrate function.

In the following description, the inside and outside of each member constituting the torque transmission joint 16 in the axial direction is based on the central portion in the axial direction of the torque transmission joint 16 in the assembled state of the torque transmission joint 16. That is, the central side of the torque transmission joint 16 in the axial direction corresponds to the inner side in the axial direction, and both sides of the torque transmission joint 16 in the axial direction correspond to the outer side in the axial direction.

The intermediate transmission member 17 is made of a material that is less likely to be elastically deformed (higher rigidity) than the elastic material constituting the elastic member 19, and is formed in an annular shape as a whole. Materials constituting the intermediate transmission member 17 include a belt material reinforced with cloth, a synthetic resin such as PPS, PEEK, and polyamide mixed with reinforcing fibers as necessary, an iron alloy such as carbon steel, and an aluminum alloy. Metal is mentioned. The intermediate transmission member 17 is formed by subjecting these materials to processing such as injection molding, casting, forging, sintering, and cutting.

The intermediate transmission member 17 has intermediate transmission teeth 21 at a plurality of positions in the circumferential direction. In this example, as shown in FIGS. 12A to 12C, the intermediate transmission member 17 includes a cylindrical intermediate tubular portion 20, and the intermediate transmission teeth 21 are radially inside the intermediate tubular portion 20. The portions are arranged radially at a plurality of locations at equal intervals in the circumferential direction. Further, the intermediate transmission member 17 has axial outer surfaces arranged on both axially side portions of the intermediate tubular portion 20.

The intermediate tubular portion 20 has circumferential recesses 22 that open to the axial outer surfaces on both sides in the radial intermediate portions on both sides in the axial direction. The circumferential recess 22 extends in the circumferential direction of the intermediate transmission member 17 and over the entire circumference of the intermediate transmission member 17. The inner diameter side peripheral surface 23 and the outer diameter side peripheral surface 24 constituting the inner surface of the circumferential recess 22 are cylindrical surfaces centered on the central axis of the intermediate transmission member 17. The intermediate tubular portion 20 has a cylindrical covering portion 25 projecting on both axially sides at the radial outer ends of both axially oriented portions. The inner peripheral surface of the covering portion 25 constitutes a single cylindrical surface with the outer diameter side peripheral surface 24 of the circumferential recess 22.

Each radial outer end of the intermediate transmission tooth 21 is coupled to the inner peripheral surface of the intermediate tubular portion 20. In the illustrated example, the opposing circumferential sides of a pair of adjacent intermediate transmission teeth 21 consist of planes parallel to each other. As will be described later, the end transmission teeth 37 constituting the end transmission member 18 are inserted from both sides in the axial direction into the portion between the pair of adjacent intermediate transmission teeth 21, and the intermediate transmission teeth 21 and the end transmission are transmitted to each other. The teeth 37 are arranged alternately in the circumferential direction.

An engaging convex portion 26 projecting in the axial direction is provided at the central portion in the circumferential direction of the outer surface in the axial direction of each of the intermediate transmission teeth 21. The engaging convex portion 26 has a substantially rectangular shape when viewed from the axial direction and extends in the radial direction of the intermediate transmission member 17. Further, the radial outer portion of the axial outer surface which is the tip surface of the engaging convex portion 26 is composed of the inclined side surface portion 27. The inclined side surface portion 27 is inclined in the direction toward the inner side in the axial direction toward the outer side in the radial direction. Further, on the axial outer half of the radial inner side surface of the engaging convex portions 26 arranged every other in the circumferential direction of the engaging convex portions 26, the claw portions 28 protruding inward in the radial direction are provided. It is equipped. The tip surface of the engaging convex portion 26 including the inclined side surface portion 27 forms a part of the axial outer surface of the intermediate transmission member 17, and is located on the outermost axial direction of the axial outer surface of the intermediate transmission member 17. ..

The elastic member 19 of this example is composed of a pair of elastic members 19. Each of the pair of elastic members 19 is formed of an elastic material in a ring shape as a whole. Specific examples of the elastic material constituting the elastic member 19 include rubbers such as NBR and HNBR, and elastomers such as polyurethane and silicon. In this example, each of the pair of elastic members 19 has the same shape and the same size as each other. A pair of elastic members 19 are symmetrically assembled on both sides of the intermediate transmission member 17 in the axial direction.

As shown in FIGS. 13 (a) to 13 (c), each of the pair of elastic members 19 has engaging recesses 29, which are through holes, at a plurality of positions in the circumferential direction in the same phase as the intermediate transmission teeth 21. Have. Further, the elastic member 19 has slit-shaped insertion holes 30 at a plurality of positions in the circumferential direction in the same phase as the interdental portion (interdental portion) of the pair of adjacent intermediate transmission teeth 21. In the elastic member 19 of this example, the engaging recesses 29 and the insertion holes 30 are alternately arranged in the circumferential direction.

The engaging recess 29 has a substantially rectangular shape when viewed from the axial direction and extends in the radial direction of the elastic member 19. The engaging recess 29 engages with the engaging protrusion 26 provided on the axially outer surface of the intermediate transmission tooth 21 to prevent the elastic member 19 from rotating relative to the intermediate transmission member 17.

Among the elastic members 19, the axially outer portion of the radially inner portion of the engaging recess 29 is provided with a thinning portion having a shape such that the engaging recess 29 is extended radially inward. An axially inner portion of the radial inner portion of the engaging recess 29 is provided with an engaging beam 31 extending in the circumferential direction.

The insertion hole 30 extends in the radial direction of the elastic member 19 and opens at the inner peripheral edge of the elastic member 19. As will be described later, the end transmission teeth 37 of the end transmission member 18 are inserted into the insertion hole 30 from the outside in the axial direction. As shown in FIGS. 9 and 10, the circumferential distance t ₃₀ between the circumferential edges of the insertion hole 30 is smaller than _{the circumferential distance T 21} between the adjacent intermediate transmission teeth 21 _{(t 30} <. T ₂₁ ).

The elastic member 19 may be provided with an elastic protrusion 32 projecting toward the central side in the circumferential direction at least one side edge of the insertion hole 30 in the circumferential direction. In this example, elastic protrusions 32 that project toward the central side in the circumferential direction are provided on the radial outer portions of both peripheral edges of the insertion hole 30. In this case, the circumferential distance between the tip surfaces of the elastic protrusions 32 facing in the circumferential direction corresponds to _{the circumferential distance t 30 between the circumferential distances of the insertion holes 30.} In this example, the circumferential distance between the portions radially deviated from the elastic protrusion 32 is also smaller than _{the circumferential distance T 21 between the adjacent intermediate transmission teeth 21.} The shape of the elastic protrusion 32 seen from the axial direction is a convex arc shape. Of the circumferential edges of the insertion hole 30, the portions radially deviated from the elastic protrusions 32 are flat portions parallel to each other.

When the present invention is carried out, the shape and formation position of the elastic protrusion 32 are not limited to the structure shown in the figure. For example, other shapes such as a triangle and a trapezoid can be adopted as the shape of the elastic protrusion 32 when viewed from the axial direction. The elastic protrusions are preferably arranged at the radial outer portions of the circumferential edges of the insertion hole, but can also be arranged at the radial center of the circumferential edges of the insertion hole, for example. The number of elastic protrusions is not limited to one, and may be a plurality. The elastic protrusion 32 may be omitted, and one or both of the circumferential edges of the insertion hole may be formed of a flat portion.

The elastic member 19 has a circumferential convex portion 33 protruding inward in the axial direction at a radial outer end portion located radially outside the engaging recess 29 and the insertion hole 30. The circumferential convex portion 33 extends in the circumferential direction of the elastic member 19 and over the entire circumference of the elastic member 19.

The radial intermediate portion of the axial outer surface of the elastic member 19 is composed of an inclined side surface portion 34. The inclined side surface portion 34 is inclined in the direction toward the inner side in the axial direction toward the outer side in the radial direction.

The pair of elastic members 19 are symmetrically assembled on both sides of the intermediate transmission member 17 in the axial direction to form a coupling body 35 of the intermediate transmission member 17 and the pair of elastic members 19. In the state where the coupling body 35 is formed, the pair of elastic members 19 covers the axial outer surfaces on both sides of the intermediate transmission member 17.

In the state where the combined body 35 is configured, the circumferential convex portion 33 of the elastic member 19 is press-fitted into the circumferential concave portion 22 of the intermediate transmission member 17, and the circumferential convex portion 23 and the circumferential convex portion of the circumferential concave 22 are convex. The inner peripheral surface of the portion 33, the outer diameter side peripheral surface 24 of the circumferential concave portion 22, and the outer peripheral surface of the circumferential convex portion 33 are both elastically contacted and strongly frictionally engaged. Further, the elastic member 19 is tightly fitted to the covering portion 25 of the intermediate transmission member 17, and the inner peripheral surface of the covering portion 25 and the outer peripheral surface of the elastic member 19 are elastically contacted and strongly frictionally engaged. .. By these frictional engagements, the displacement of the elastic member 19 with respect to the intermediate transmission member 17 in the axial direction and the separation of the intermediate transmission member 17 and the elastic member 19 are prevented. Further, since the outer peripheral surface of the elastic member 19 is covered by the covering portion 25, the intermediate transmission member 17 and the elastic member are caused by other articles colliding with or being caught by the outer peripheral surface of the elastic member 19 during transportation. The separation from 19 is planned. When the present invention is carried out, for example, a structure having at least one gap in the circumferential direction between the inner peripheral side peripheral surface 23 and the inner peripheral surface of the circumferential convex portion 33, the outer diameter side peripheral surface 24 A structure in which a gap is provided at at least one peripheral surface of the circumferential convex portion 33 in the circumferential direction, only on one peripheral surface of the inner diameter side peripheral surface 23 and the outer diameter side peripheral surface 24 in the circumferential direction. A structure in which the peripheral surfaces of the convex portion 33 are elastically contacted, a structure in which a gap is provided between the inner peripheral surface of the covering portion 25 and the outer peripheral surface of the elastic member 19, and at least one in the circumferential direction of the circumferential convex portion 33. A structure in which a discontinuity is provided at a location can also be adopted.

By inserting and engaging the engaging convex portion 26 of the intermediate transmission member 17 inside the engaging recess 29 of the elastic member 19, the relative rotation between the intermediate transmission member 17 and the elastic member 19 is prevented. Further, the claw portion 28 provided on the inner side in the radial direction of the engaging convex portion 26 engages with the lateral outer surface of the engaging beam 31 in the axial direction. As a result, the elastic member 19 is prevented from being displaced outward in the axial direction with respect to the intermediate transmission member 17, and the intermediate transmission member 17 and the elastic member 19 are prevented from being separated from each other. With the elastic member 19 attached to the intermediate transmission member 17, the slit-shaped insertion hole 30 is arranged at a position in phase with the intermediate portion between the pair of adjacent intermediate transmission teeth 21.

The axially outer surface of the elastic member 19 is located axially outside of the tip surface of the engaging convex portion 26, which is the most axially outermost of the axially outer surfaces on both sides of the intermediate transmission member 17. That is, the elastic member 19 projects axially outward from the axially outer surfaces on both sides of the intermediate transmission member 17. Therefore, the axial width dimension W ₃₅ of the coupling 35 is larger than _{the axial width dimension W 17} of the intermediate transmission member 17 _{(W 35} > W ₁₇ ). Further, the inner peripheral surface of the elastic member 19 is located radially inside the radial inner surface of the intermediate transmission tooth 21 of the intermediate transmission member 17 and the radial inner edge of the claw portion 28. That is, the elastic member 19 projects radially inward from the intermediate transmission member 17.

In this example, in the radial intermediate portion of the axial outer surface on both sides of the coupling 35 of the intermediate transmission member 17 and the pair of elastic members 19, the inclination is inclined in the axial inward direction toward the radial outer side. Side surfaces 27 and 34 are arranged.

Each of the pair of end transmission members 18 is formed in an annular shape as a whole. Examples of the material constituting the end transmission member 18 include synthetic resins such as PPS, PEEK, and polyamide mixed with reinforcing fibers as needed, and metals such as iron alloys, copper alloys, and aluminum alloys. The end transmission member 18 is formed by subjecting these materials to processing such as injection molding, casting, forging, sintering, and cutting. In this example, the pair of end transmission members 18 have the same shape and size as each other. A pair of end transmission members 18 engage axially both sides of a coupling 35 of an intermediate transmission member 17 and a pair of elastic members 19.

As shown in FIGS. 14 (a) and 14 (B), each of the pair of end transmission members 18 has a cylindrical end cylinder portion 36 which is an end connecting portion and a plurality of end transmission members. It has teeth 37 and a ring-shaped collar 38. The radial inner end of the collar 38 is coupled to the axial outer end of the end tube 36. Each of the plurality of end transmission teeth 37 has a substantially rectangular plate shape, and is radially arranged at a plurality of locations at equal intervals in the circumferential direction on the outer side in the radial direction of the end tubular portion 36. Each radial inner end of the end transmission tooth 37 is coupled to the outer peripheral surface of the end cylinder 36, and each axial outer end of the end transmission tooth 37 is axial to the collar 38. It is connected to the end side surface portion 39 which is the inner surface surface.

A pair of end transmission members 18 from the axial inner end to the middle are inserted radially inward on both axial sides of the coupling 35. In this state, the end transmission tooth 37 provided on the one end transmission member 18 (on the right side in FIGS. 2, 4, 6, and 7) is circumferentially oriented into the insertion hole 30 of the one elastic member 19. It engages without rattling (for example, with a circumferential tightening allowance) and engages with the intermediate transmission tooth 21 of the intermediate transmission member 17 via a circumferential gap. Further, the end transmission teeth 37 of the other end transmission member 18 (left in FIGS. 2, 4, 6 and 7) do not rattle in the circumferential direction in the insertion hole 30 of the other elastic member 19. Engage (for example, with a circumferential tightening allowance) and engage with the intermediate transmission teeth 21 of the intermediate transmission member 17 through a circumferential gap. That is, as shown in FIG. 10, there is a circumferential gap α between the circumferential side surfaces of the end transmission tooth 37 and the intermediate transmission tooth 21. When carrying out the present invention, the end transmission tooth 37 can be engaged with the insertion hole 30 of the elastic member 19 via a circumferential gap. However, also in this case, the circumferential gap α is made larger than this circumferential gap.

In this example, as shown in FIG. 10, a radial gap β is interposed between the radial outer end surface which is the tip surface of the end transmission tooth 37 and the bottom surface of the insertion hole 30, and the end transmission tooth 37 A radial gap γ is interposed between the radial outer end surface and the bottom surface (inner peripheral surface of the intermediate tubular portion 20) between the pair of adjacent intermediate transmission teeth 21. The radial gap β is smaller than the radial gap γ (β <γ). Further, a radial gap ε is interposed between the bottom surface of the portion between the pair of adjacent end transmission teeth 37 (the outer peripheral surface of the end cylinder portion 36) and the inner peripheral surface of the elastic member 19 so as to be adjacent to each other. A radial gap η is interposed between the bottom surface of the portion between the pair of end transmission teeth 37 and the radial inner end surface which is the tip surface of the intermediate transmission tooth 21. The radial gap ε is smaller than the radial gap η (ε <η).

In this example, as shown in FIGS. 7 and 8, the axial outer surfaces of the pair of elastic members 19 and the axial outer surfaces of the plurality of engaging protrusions 26, which are the axial outer surfaces on both sides of the coupling 35. The side surface and the end side surface portion 39 of the pair of end transmission members 18 face each other in the axial direction.

With the torque transmission joint 16 of this example assembled to the electric power steering device, the end cylinder portion 36 of one end transmission member 18 is attached to the tip of the output shaft 12a (see FIGS. 1 and 2). On the other hand, the outer fitting is fixed by a structure capable of transmitting torque such as a cylindrical surface fitting having a tightening margin, a spline fitting having a tightening margin, and caulking. Further, the end tubular portion 36 of the other end transmission member 18 is externally fitted and fixed to the base end portion of the worm 7a (see FIGS. 1 and 2) in the same manner as the one end transmission member 18. However, the end transmission member 18 can also be formed integrally with the tip end of the output shaft 12a and the base end portion of the worm 7a. _{As shown in FIG. 8, the axial distance L 39} between the end side surface portions 39 of the pair of end transmission members 18 is larger than the axial width dimension W _{35 of the coupling 35.} (L ₃₉ > W ₃₅ ). Therefore, the axial distance L ₃₉ is larger than _{the axial width dimension W 17} of the intermediate transmission member 17 _{(L 39} > W ₁₇ ). In this example, the axial position of the coupling 35 is regulated by the respective end side surface portions 39 of the pair of end transmission members 18. That is, the coupling body 35 can be displaced in the axial direction only between the end side surface portions 39 of the pair of end transmission members 18.

In the electric power steering device of this example, when the torque transmitted between the output shaft 12a and the worm 7a of the electric motor 6 is relatively small, the rotational torque of the output shaft 12a is one of the end transmission members. 18, one elastic member 19, the intermediate transmission member 17, the other elastic member 19, the other end transmission member 18, and the worm 7a are transmitted in this order. Specifically, the rotational torque of the output shaft 12a is transmitted from one end transmission member 18 to one elastic member 19 through an engaging portion between the end transmission tooth 37 and the insertion hole 30. The torque transmitted to one elastic member 19 is transmitted to the intermediate transmission member 17 through the engaging portion between the engaging concave portion 29 of the one elastic member 19 and the engaging convex portion 26 of the intermediate transmission member 17. The torque transmitted to the intermediate transmission member 17 is transmitted to the other elastic member 19 through the engaging portion between the engaging convex portion 26 of the intermediate transmitting member 17 and the engaging concave portion 29 of the other elastic member 19. The torque transmitted to the other elastic member 19 is transmitted to the other end transmission member 18 and the worm 7a through the engaging portion between the insertion hole 30 and the end transmission tooth 37.

On the other hand, when the torque transmitted between the output shaft 12a and the worm 7a becomes large, a part of one elastic member 19 is subjected to the circumferential direction by the end transmission tooth 37 of the one end transmission member 18. And a part of the other elastic member 19 is elastically crushed in the circumferential direction by the end transmission teeth 37 of the other end transmission member 18. Then, the peripheral side surfaces of the end transmission tooth 37 of one end transmission member 18, the end transmission tooth 37 of the other end transmission member 18, and the intermediate transmission tooth 21 of the intermediate transmission member 17 are respectively. Direct contact. Since the momentum of these contacts is weakened by the elastic deformation of one elastic member 19 and the other elastic member 19, the generation of abnormal noise due to the contact is suppressed. In this state, most of the rotational torque of the output shaft 12a is directly transmitted from one end transmission member 18 to the intermediate transmission member 17, and most of the torque transmitted to the intermediate transmission member 17 is the intermediate transmission tooth 21. Is directly transmitted to the other end transmission member 18. Further, the remaining torque is transmitted from the output shaft 12a to the worm 7a in the same manner as in the case where the torque is small as described above.

In this example, even when the rotation direction of the output shaft 12a of the electric motor 6 is reversed, the end transmission teeth 37 of one end transmission member 18 and the end transmission teeth 37 of the other end transmission member 18 are Since the momentum of contact between the circumferential side surfaces of the intermediate transmission member 17 with the intermediate transmission tooth 21 is weakened by the elastic deformation of one elastic member 19 and the other elastic member 19, abnormal noise due to the contact is weakened. Is suppressed.

In this example, the circumferential side surfaces of the pair of adjacent intermediate transmission teeth 21 facing each other are parallel planes, and the circumferential side surfaces of the end transmission teeth 37 are also parallel planes. It has become. However, when the present invention is carried out, the side surfaces in the circumferential direction of the intermediate transmission tooth 21 and the end transmission tooth 37 are adjacent to each other in the circumferential direction so that they can easily come into contact with each other (surface contact) during torque transmission. At least one of a configuration in which the circumferential side surfaces of the pair of intermediate transmission teeth 21 facing each other are inclined to each other and a configuration in which both side surfaces in the circumferential direction of the end transmission teeth 37 are inclined to each other is adopted. You can also do it.

As described above, in the electric power steering device of this example, the torsional rigidity of the torque transmission joint 16 is reduced when the torque to be transmitted is small and increased when the torque to be transmitted is large. Has characteristics. However, when the present invention is carried out, for example, the torsional rigidity of the torque transmission joint 16 is increased in two stages by making the size of the circumferential gap α different between the pair of end transmission members 18. Can be more than.

For each of the pair of end transmission members 18, there is a radial gap between the engagement portion between the end transmission tooth 37 and the elastic member 19 and the engagement portion between the end transmission tooth 37 and the intermediate transmission tooth 21. Β, γ, ε, η intervene. _{Further, the axial distance L 39} between the end side surface portions 39 of the pair of end transmission members 18 is larger than the axial width dimension W _{35 of the coupling 35 (L 39} > W). ₃₅ ). Further, the radial intermediate portions of the axially outer surfaces on both sides of the coupling 35, which are axially opposed to the respective end side surface portions 39 of the pair of end transmission members 18, are axially oriented toward the outer side in the radial direction. The inclined side surface portions 27 and 34 are inclined inward. Therefore, the inclination of the central axes of the coupling body 35 and the pair of end transmission members 18 can be reasonably allowed. Although it is out of the technical scope of the present invention _{, the axial distance L 39} between the end side surface portions 39 of the pair of end transmission members 18 is the axial width dimension W of the intermediate transmission member 17. If it is larger than _{17, (L 39} > W ₁₇ ), the axial width dimension of the coupling 35 can be _{W 35} or less (L ₃₉ ≤ W _35).

In this example, the relations of β <γ and ε <η are established with respect to the radial gaps β, γ, ε, and η. Therefore, even if a large eccentricity or inclination occurs between the pair of end transmission members 18, based on the presence of the elastic member 19, the portion between the pair of adjacent end transmission teeth 37 It is prevented that the bottom surface abuts on the tip surface of the intermediate transmission tooth 21 and that the tip surface of the end transmission tooth 37 abuts on the bottom surface of the intermediate portion between the adjacent pair of intermediate transmission teeth 21. Even if these surfaces come into contact with each other, the momentum of the contact is weakened by the elastic deformation of the elastic member 19, so that the generation of abnormal noise due to the contact is suppressed.

In this example, at least in the radial range in which the intermediate transmission member 17 and the end side surface portion 39 of the end transmission member 18 face each other in the axial direction, the axial outer surface of the elastic member 19 is in the axial direction of the engaging convex portion 26. It is located on the outer side in the axial direction from the outer side surface. Therefore, the intermediate transmission member 17 is displaced in the axial direction between the end side surface portions 39 of the pair of end transmission members 18, and a large eccentricity is generated between the pair of end transmission members 18. Even when tilting or the like occurs, it is possible to prevent the end side surface portion 39 from coming into contact with the axially outer surface of the engaging convex portion 26 based on the presence of the elastic member 19. Even if the elastic member 19 is elastically crushed and the end side surface portion 39 abuts on the axially outer surface of the engaging convex portion 26, the momentum of these abutments is due to the elastic deformation of the elastic member 19. Since it is weakened, the generation of abnormal noise due to contact is suppressed.

In this example, the engaging convex portion 26 of the intermediate transmission member 17 and the pair of elastic members 19 constituting the coupling 35 are axially outer surfaces and the pair of end transmission members 18 with the end side surface portions 39. Are axially opposed to each other. Therefore, the intermediate transmission member 17 is displaced in the axial direction between the end side surface portions 39 of the pair of end transmission members 18, and a large eccentricity or inclination is caused between the pair of end transmission members 18. Even if such a situation occurs, the end side surface portion 39 comes into contact with the axial outer surface of the elastic member 19 or the axial outer surface of the engaging convex portion 26, and the effect of stabilizing the posture of the coupling 35, that is, , The centering effect of the conjugate 35 can be obtained. As a result, in the torque transmission joint of this example, torque is smoothly transmitted.

In this example, the intermediate transmission teeth are provided on the radial inner side of the intermediate transmission member, and the end transmission teeth are provided on the radial outer side of the pair of end transmission members. However, when the present invention is carried out, the intermediate transmission tooth is provided on the radial outer portion of the intermediate transmission member, and the end transmission tooth is provided on the radial inner portion of the end transmission member. It can also be adopted.

In this example, the elastic member is composed of a pair of elastic members including an elastic member that engages with one end transmission member and an elastic member that engages with the other end transmission member. However, in the case of carrying out the present invention, the elastic member shall be composed of one elastic member including a portion engaging with one end transmission member and a portion engaging with the other end transmission member. You can also. In this case, the elastic member can be assembled to the intermediate transmission member by utilizing the elasticity of the elastic member.

In the case of carrying out the present invention, if the relative rotation between the intermediate transmission member and the elastic member can be prevented, the number and circumferential positions of the engaging protrusions of the intermediate transmission member and the engaging concave portion of the elastic member The number of and the position in the circumferential direction are not particularly limited.

[Second Example of Embodiment]
A second example of the embodiment will be described with reference to FIGS. 15 to 17. In this example, each of the pair of elastic members 19 has a plurality of protrusions 40. These projecting portions 40 are located in a radial range in which the intermediate transmission member 17 and the end side surface portion 39 of the end transmission member 18 face each other in the axial direction. It protrudes outward from the location in the axial direction. More specifically, the projecting portion 40 projects outward one by one from the portion between the engaging recess 29 (engaging beam 31) adjacent to each other in the circumferential direction and the insertion hole 30. In the illustrated example, the protruding portion 40 has a conical trapezoidal shape in which the outer diameter dimension becomes smaller toward the outer side in the axial direction.

In this example, the intermediate transmission member 17 is displaced in the axial direction between the end side surface portions 39 of the pair of end transmission members 18, or a large eccentricity is observed between the pair of end transmission members 18. The axis of the engaging convex portion 26 between the end side surface portion 39 and the intermediate transmission member 17 based on the fact that the axial outer end surface of the protruding portion 40 abuts on the end side surface portion 39 even when the protrusion 40 is tilted or the like. It becomes more difficult for the outer surface in the direction to come into contact with the outer surface.

When carrying out the present invention, the shape and number of the protrusions 40 are not particularly limited. However, from the viewpoint of facilitating the effect that the end side surface portion 39 is less likely to come into contact with the axially outer surface of the engaging convex portion 26 of the intermediate transmission member 17, the projecting portions 40 are provided at three or more locations in the circumferential direction. Is desirable. Further, the radial position of the protruding portion 40 is not particularly limited as long as it is in a range of the elastic member 19 that faces the end side surface portion 39 in the axial direction. However, from the viewpoint of allowing eccentricity and inclination between the pair of end transmission members 18, it is desirable that the protrusion 40 is provided at the radial inner end of the elastic member 19 as in this example. .. Other configurations and operations are similar to those of the first embodiment.

1 Steering wheel 2 Steering shaft 3 Housing 4 Warm wheel 5 Warm teeth 6 Electric motor 7, 7a Warm 8 Rolling bearing 9 Rolling bearing 10 Pressing piece 11 Coil spring 12, 12a Output shaft 13 Spline hole 14 Spline shaft 15 Biasing mechanism 16 Torque transmission joint 17 Intermediate transmission member 18 End transmission member 19 Elastic member 20 Intermediate cylinder part 21 Intermediate transmission tooth 22 Circumferential recess 23 Inner diameter side peripheral surface 24 Outer diameter side peripheral surface 25 Covering part 26 Engaging convex part 27 Inclined side surface Part 28 Claw part 29 Engagement concave part 30 Insertion hole 31 Engagement beam 32 Elastic protrusion 33 Circumferential convex part 34 Inclined side part 35 Coupled body 36 End part tubular part 37 End transmission tooth 38 Collar 39 End side side part 40 Department

Claims (5)

An intermediate transmission member having intermediate transmission teeth provided at a plurality of locations in the circumferential direction and axial outer surfaces arranged on both sides in the axial direction.
One of the end transmission teeth arranged on both sides in the axial direction of the intermediate transmission member and provided at a plurality of locations in the circumferential direction, and the end transmission teeth arranged axially outside the end transmission teeth and on the outer surface in the axial direction. A pair of end transmission members having end side surfaces facing the
An elastic member that is assembled to the intermediate transmission member, is arranged at a plurality of locations in the circumferential direction, and has an insertion hole through which the end transmission tooth is inserted in the axial direction.
With
With the end transmitting teeth inserting the insertion holes in the axial direction, the end transmitting teeth and the intermediate transmitting teeth are arranged alternately in the circumferential direction and through the circumferential gap, and
The circumferential distance between the circumferential edges of the insertion hole is smaller than the circumferential distance between adjacent intermediate transmission teeth among the intermediate transmission teeth .
In the radial range in which the intermediate transmission member and the end side surface portion face each other in the axial direction, the elastic member projects axially outward from the axial outer surface of the intermediate transmission member.
The end transmission tooth of one end transmission member of the pair of end transmission members and the end transmission tooth of the other end transmission member of the pair of end transmission members , Facing axially through an axial gap,
The axial distance between the end side surfaces of the pair of end transmission members is larger than the axial width dimension of the coupling between the intermediate transmission member and the elastic member.
Torque transmission joint. The torque transmission joint according to claim 1, wherein the elastic member projects radially inward from the intermediate transmission member. The elastic member according to claim 1 or 2 , wherein the elastic member includes an elastic protrusion projecting toward the central side in the circumferential direction at least one side edge of each of the peripheral edges of the insertion hole in the radial direction. Torque transmission joint. The torque transmission joint according to any one of claims 1 to 3 , wherein the elastic member is provided with protruding portions protruding outward in the axial direction at a plurality of locations in the circumferential direction facing the side surface portion of the end portion in the axial direction. With the housing
A worm wheel that is rotatably supported against the housing
A worm that is rotatably supported with respect to the housing while meshed with the worm wheel.
An electric motor having an output shaft for rotationally driving the worm, and
It is an electric power steering device equipped with
A torque transmission joint is provided between the output shaft of the electric motor and the worm to enable torque transmission between the output shaft of the electric motor and the worm, and the torque transmission joint is provided. The torque transmission joint according to any one of claims 1 to 4 , wherein one end transmission member of the pair of end transmission members is fixed to or fixed to the tip end of the output shaft of the electric motor. It is integrally formed, and the other end transmission member of the pair of end transmission members is fixedly or integrally formed at the base end portion of the worm.
Electric power steering device.

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