JP6950433B2 - Shaft connection structure and electric power steering device - Google Patents

Description

The present invention relates to a shaft connecting structure for connecting a first rotating member and a second rotating member arranged concentrically in the axial direction, and an electric power steering device having the shaft connecting structure.

Conventionally, in an electric power steering device, an assist mechanism that applies an assist force to a steering mechanism includes an electric motor and a worm gear mechanism, and the rotation shaft of the electric motor and the worm shaft of the worm gear mechanism are connected by a shaft connection structure using an elastic member. It is connected. The worm shaft is elastically connected to the rotation shaft of the electric motor, and the impact when the rotation direction of the electric motor is reversed is absorbed by the elastic deformation of the elastic member. As a result, the impact when the rotation direction of the electric motor is reversed is suppressed from being transmitted to the steering wheel, which contributes to the improvement of the steering feeling. (See, for example, Patent Document 1).

The shaft connecting structure described in Patent Document 1 includes a first member fixed to a rotating shaft of an electric motor, a second member fixed to a worm shaft, and rubber interposed between the first member and the second member. It is configured to have an intermediate member made of an elastic body such as the above. The first member is provided with a plurality of connecting protrusions protruding in the axial direction, and the second member is provided with a plurality of first radial protrusions arranged between the plurality of connecting protrusions of the first member. There is. The intermediate member has a plurality of second radial protrusions arranged between the plurality of connecting protrusions of the first member and the plurality of first radial protrusions of the second member. The torque of the electric motor is transmitted from the connecting protrusion of the first member to the first radial protrusion of the second member via the second radial protrusion of the intermediate member, and further transmitted from the second member to the worm shaft.

JP-A-2017-36767

In the shaft connecting structure described in Patent Document 1, if there is a gap between the second radial projection of the intermediate member and the connecting projection of the first member or the first radial projection of the second member, the rotation of the electric motor starts. This gap is clogged at the time or when the rotation direction is reversed, and an abnormal noise (collision sound of the second radial protrusion) is generated especially at a low temperature when the elastic body becomes hard. Therefore, it is necessary to arrange the second radial projection of the intermediate member in a compressed state between the connecting projection and the first radial projection. Since this assembly work is performed by elastically deforming the intermediate member, the work is highly difficult and has been a factor in increasing the manufacturing cost. Further, when this shaft connection structure is used in an electric power steering device, it is particularly difficult to work because the intermediate member must be combined with the first member or the second member inside the housing, which makes visual work difficult. It was highly sexual.

Therefore, the present invention provides a shaft connection structure and an electric power steering device that are easy to assemble and can suppress the generation of abnormal noise when the first and second rotating members start rotating or when the rotation direction is reversed. With the goal.

The present invention is a shaft connecting structure for connecting a first rotating member and a second rotating member concentrically arranged side by side in the axial direction in order to achieve the above object, and the first rotating member. The first connecting member fixed to the end portion, the second connecting member fixed to the end portion of the second rotating member, and the second connecting member interposed between the first connecting member and the second connecting member. The first connecting member includes one connecting member and an intermediate member made of a material softer than the second connecting member, and the first connecting member is on the side of the second connecting member along an axial direction parallel to the rotation axis of the first rotating member. The second connecting member has a plurality of first protrusions extending toward the rotation axis and provided at predetermined intervals in the circumferential direction around the rotation axis, and the second connecting member is parallel to the rotation axis of the second rotation member. A plurality of second protrusions extending toward the first connecting member side along the axial direction and arranged between the plurality of first protrusions, and the intermediate member extending radially from the central portion. The arm portion is arranged so as to be compressed in the circumferential direction between the side surface of the first protrusion and the side surface of the second protrusion, and the arm portion is arranged in the extending direction thereof. The first portion of the bulging portion, which integrally has a base portion having a rectangular cross-sectional shape and a bulging portion bulging from the base portion toward the side surface of the first protrusion or the second protrusion. The axial contact length of the protrusion or the contact surface of the second protrusion with the side surface is from the base end portion of the arm portion corresponding to the central portion side of the intermediate member to the tip end portion of the arm portion in the extending direction. Provided is a shaft connection structure that continuously lengthens toward a portion.

Further, in order to achieve the above object, the present invention includes a steering mechanism that steers the steering wheel according to the steering of the steering wheel, and an assist mechanism that applies an assist force to the steering mechanism. Includes an electric motor, a worm shaft connected to the output rotation shaft of the electric motor, and a worm gear mechanism having a worm wheel that meshes with the worm shaft, and the output rotation shaft and the worm shaft are the claims 1 to 5. Provided is an electric power steering device connected by the shaft connecting mechanism according to any one of the above items.

According to the present invention, it is possible to easily assemble a shaft connection structure and an electric power steering device in which the generation of abnormal noise is suppressed at the start of rotation of the first and second rotating members or when the rotation direction is reversed. ..

It is a schematic diagram which shows the structural example of the electric power steering apparatus which concerns on 1st Embodiment of this invention. (A) is a cross-sectional view showing a part of the assist mechanism together with the housing. (B) is an enlarged view showing a part of (a) in an enlarged manner. It is a perspective view which shows the power transmission joint together with the peripheral member. (A) and (b) are perspective views which show the intermediate member. It is a front view which shows the surface of the intermediate member on the 2nd connecting member side together with the cross section of a part of the 1st connecting member and the 2nd connecting member 7. (A) is an enlarged perspective view showing a part of the intermediate member, (b) is a sectional view taken along line AA of (a), and (c) is a sectional view taken along line BB of (a). be. (A) is a perspective view which shows a part of the intermediate member which concerns on 2nd Embodiment of this invention. (B) is the cross-sectional shape of the tip of the arm on the CC line shown in (a), and (b) is the cross-sectional shape of the base end of the arm on the DD line shown in (a). show. (A) is a perspective view which shows the whole of the intermediate member which concerns on 3rd Embodiment of this invention. (B) is the cross-sectional shape of the tip of the arm on the EE line shown in (a), and (b) is the cross-sectional shape of the base end of the arm on the FF line shown in (a). show.

[First Embodiment]
The first embodiment of the present invention will be described with reference to FIGS. 1 to 6. It should be noted that the embodiments described below are shown as suitable specific examples for carrying out the present invention, and there are some parts that specifically exemplify various technically preferable technical matters. , The technical scope of the present invention is not limited to this specific aspect.

(Configuration of electric power steering device)
FIG. 1 is a schematic view showing a configuration example of an electric power steering device according to the first embodiment of the present invention.

The electric power steering device 1 includes a steering mechanism 10, an assist mechanism 2 that applies an assist force that assists the driver's steering operation to the steering mechanism 10, and a controller 20 that controls the assist mechanism 2.

The steering mechanism 10 includes a steering wheel 11 that is rotationally operated by the driver, a steering shaft 12 that is connected to the steering wheel 11, and a rack shaft 13 that extends in the vehicle width direction of the vehicle. The left and right steering wheels 19 are steered according to the steering operation of 11.

The steering shaft 12 is formed between a column shaft 121 in which the steering wheel 11 is fixed to one end, a pinion shaft 123 having pinion teeth 123a that mesh with the rack teeth 13a of the rack shaft 13, and the column shaft 121 and the pinion shaft 123. It has an intervening intermediate shaft 122. The column shaft 121 and the intermediate shaft 122 are connected by a universal joint 124, and the intermediate shaft 122 and the pinion shaft 123 are connected by a universal joint 125.

The column shaft 121 is configured by connecting the upper shaft 121a and the lower shaft 121b by a torsion bar 140 of the torque sensor 14. The torque sensor 14 detects the steering torque applied to the steering wheel 11 by the driver by twisting the torsion bar 140.

The rack shaft 13 is housed in a cylindrical rack housing 15 so as to be movable in the axial direction. The rack shaft 13 is formed with rack teeth 13a formed of oblique teeth along the axial direction thereof, and the rack teeth 13a mesh with the pinion teeth 123a of the pinion shaft 123. Ball joint sockets 16 are fixed to both ends of the rack shaft 13, and tie rods 17 connected to these ball joint sockets 16 are connected to the left and right steering wheels 19 via knuckle arms (not shown). A bellows 18 made of bellows-shaped rubber, resin, or the like is arranged on the outer peripheral side of the ball joint socket 16.

When the steering wheel 11 is rotated, the pinion shaft 123 connected to the steering wheel 11 via the column shaft 121 and the intermediate shaft 122 rotates, and the rack shaft 13 is moved by the engagement between the pinion teeth 123a and the rack teeth 13a. It moves linearly in the axial direction. The linear motion of the rack shaft 13 causes the left and right steering wheels 19 to be steered via the tie rod 17.

The assist mechanism 2 has an electric motor 3 and a worm gear mechanism 4 as a speed reducer that reduces the rotation of the electric motor 3. The worm gear mechanism 4 has a worm shaft 41 connected to the output rotation shaft of the electric motor 3 and a worm wheel 42 that rotates integrally with the lower shaft 121b. Are meshed with each other. The controller 20 supplies a motor current to the electric motor 3 based on the vehicle speed and the steering torque detected by the torque sensor 14, and controls the electric motor 3.

FIG. 2A is a partial cross-sectional view showing a part of the assist mechanism 2 together with the housing 5. FIG. 2B is an enlarged view showing a part of FIG. 2A in an enlarged manner. The worm gear mechanism 4 is housed in the housing 5, and the main body 30 of the electric motor 3 is attached to the housing 5. The output rotating shaft 31 and the worm shaft 41 of the electric motor 3 are arranged concentrically side by side in the axial direction and are connected by a power transmission joint 9 embodied by the shaft connecting structure of the present invention. The output rotating shaft 31 is an aspect of the first rotating member of the present invention, and the worm shaft 41 is an aspect of the second rotating member of the present invention. Details of the shaft connection structure and the power transmission joint 9 will be described later.

The worm shaft 41 has a tooth portion 413 between the first end portion 411 on the electric motor 3 side, the second end portion 412 on the opposite side of the electric motor 3, and the first end portion 411 and the second end portion 412. And have one. The first end portion 411 is supported by the first bearing 51, and the second end portion 412 is supported by the second bearing 52.

The worm wheel 42 has a core metal portion 421 and a tooth portion 422 made of resin. The tooth portion 422 is fitted and fixed to the outer periphery of the core metal portion 421, and rotates integrally with the core metal portion 421. The lower shaft 121b is inserted through the center of the core metal portion 421, and the core metal portion 421 rotates integrally with the lower shaft 121b.

_{The rotation axis O 2} of the worm shaft 41 is perpendicular to the longitudinal direction of the lower shaft 121b, and substantially coincides with _{the rotation axis O 1 of the output rotation shaft 31 of the electric motor 3.} The torque of the electric motor 3 is transmitted from the output rotating shaft 31 to the worm shaft 41, decelerated by the meshing of the teeth 413 and 422, and transmitted to the worm wheel 42. Then, the worm wheel 42 applies an assist force to the lower shaft 121b.

The housing 5 houses an urging mechanism 53 that elastically biases the second end 412 of the worm shaft 41 toward the worm wheel 42 via the second bearing 52. In the housing 5, the opening 50 for assembling the urging mechanism 53 is closed by the lid member 54. The urging mechanism 53 is arranged in a compressed state between the bearing holder 531 having the bearing seat portion 531a and the spring seat portion 531b, the spring seat portion 531b of the bearing holder 531 and the spring seat portion 5a on the housing 5 side. It also has a compression coil spring 532. The urging mechanism 53 moves in a direction in which the tooth portion 413 of the worm shaft 41 and the tooth portion 422 of the worm wheel 42 are deeply meshed with the center C of the first bearing 51 as a fulcrum due to the restoring force of the compression coil spring 532. The second end 412 of the worm shaft 41 is urged.

The bearing holder 531, the outer ring 521 of the second bearing 52 held in a bearing seat 531a, and is supported by the advance and retract the housing 5 along a direction perpendicular to the rotational axis O ₂ of the worm shaft 41. Bearing seat portion 531a has a cylindrical shape, the spring seat 531b is parallel to protrude the rotation axis O ₂ from one location in the circumferential direction of the bearing seat 531a. The inner ring 522 of the second bearing 52 is fitted onto the second end 412 of the worm shaft 41, and a plurality of spherical rolling elements 523 are arranged between the inner ring 522 and the outer ring 521.

As shown in FIG. 2B, the first bearing 51 includes an outer ring 511 and an inner ring 512, a plurality of spherical rolling elements 513, and a sealing member 514 that seals the bearing internal space between the outer ring 511 and the inner ring 512. have. The first end portion 411 of the worm shaft 41 has a large diameter portion 411a and a small diameter portion 411b, and an inner ring 512 is externally fitted to the large diameter portion 411a. The outer ring 511 is fixed by a ring-shaped fixing member 55 screwed onto the inner surface of the housing 5.

The power transmission joint 9 includes a first connecting member 6 fixed to the output rotating shaft 31 of the electric motor 3, a second connecting member 7 fixed to the worm shaft 41, and a first connecting member 6 and a second connecting member 7. It is provided with an intermediate member 8 arranged between the two. The intermediate member 8 is made of a material softer than the first connecting member 6 and the second connecting member 7, and in the present embodiment, the intermediate member 8 is made of an elastic body such as rubber. More specifically, NBR (nitrile rubber) can be preferably used as this elastic body. The intermediate member 8 is formed by injection molding in which a molten material is injected into a mold cavity having an upper mold and a lower mold that move relative to each other in the axial direction.

The first connecting member 6 has a metal ring 60 and a resin portion 61, and the metal ring 60 is integrated with the resin portion 61 by insert molding. The relative rotation of the metal ring 60 and the output rotating shaft 31 is restricted by, for example, serration fitting or spline fitting, and the tip portion 311 of the output rotating shaft 31 is press-fitted into the fitting hole 600 of the metal ring 60.

The second connecting member 7 has a metal ring 70 and a resin portion 71, and the metal ring 70 is integrated with the resin portion 71 by insert molding. The relative rotation of the metal ring 70 and the worm shaft 41 is regulated by, for example, serration fitting or spline fitting, and the small diameter portion 411b of the worm shaft 41 is press-fitted into the fitting hole 700 of the metal ring 70.

Hereinafter, the configuration of the power transmission joint 9 will be described in detail with reference to FIGS. 3 to 6. FIG. 3 is a perspective view showing the first connecting member 6, the second connecting member 7, and the intermediate member 8 of the power transmission joint 9 together with the first end portion 411, the first bearing 51, and the fixing member 55 of the worm shaft 41. It is a figure. 4 (a) and 4 (b) are perspective views showing the intermediate member 8. FIG. 5 is a front view showing a surface of the intermediate member 8 on the second connecting member 7 side together with a cross section of a part of the first connecting member 6 and the second connecting member 7. 6 (a) is an enlarged perspective view showing a part of the intermediate member 8, FIG. 6 (b) is a sectional view taken along line AA of FIG. 6 (a), and FIG. 6 (c) is FIG. It is a cross-sectional view taken along the line BB of (a).

The resin portion 61 of the first connecting member 6 includes a cylindrical portion 62 in which the metal ring 60 is arranged at the center, an annular plate-shaped base portion 63 provided so as to project from the cylindrical portion 62 to the outer diameter side, and a base. integrally has a part 63 and a first protrusion 64 a plurality of extending toward the second coupling member 7 side along the axial direction parallel with the rotational axis O ₁ of the output rotary shaft 31 of the electric motor 3. A plurality of first protrusions 64 are provided in the circumferential direction about the rotation axis O ₁ with a predetermined gap. In the present embodiment, the resin portion 61 has four first protrusions 64, and FIG. 3 shows three first protrusions 64 among them. In FIG. 5, the first protrusion 64 of the first connecting member 6 is shown in a cross section orthogonal to the axial direction.

The resin portion 71 of the second connecting member 7 includes a cylindrical portion 72 in which the metal ring 70 is arranged at the center, an annular plate-shaped base portion 73 provided so as to project from the cylindrical portion 72 to the outer diameter side, and a base. It integrally has a plurality of second protrusions 74 extending from the portion 73 toward the first connecting member 6 side along an axial direction parallel to _{the rotation axis O 2} of the worm shaft 41. A plurality of second protrusions 74 are provided with a predetermined gap in the circumferential direction about the rotation axis O _2, it is disposed between the plurality of first protrusions 64. In the present embodiment, the resin portion 71 has four second protrusions 74. In FIG. 5, the second protrusion 74 of the second connecting member 7 is shown in a cross section orthogonal to the axial direction.

The intermediate member 8 includes a cylindrical portion 81 arranged between the cylindrical portion 62 of the first connecting member 6 and the cylindrical portion 72 of the second connecting member 7, and a lid portion 82 that closes one side of the cylindrical portion 81. A plurality of arm portions 83 projecting outward in the radial direction of the cylindrical portion 81 and a pair of arm portions 83 adjacent to each other in the circumferential direction of the cylindrical portion 81 among the plurality of arm portions 83 are connected on one side in the axial direction. It integrally has a plate-shaped connecting portion 84.

As shown in FIGS. 4A and 4B, the lid portion 82 projects from the disc-shaped wall portion 820 continuous with the connecting portion 84 and the central portion of the wall portion 820 toward the first connecting member 6. It has a first boss portion 821 and a second boss portion 822 protruding from the central portion of the wall portion 820 toward the second connecting member 7. An annular groove 823 surrounding the first boss portion 821 is formed on the surface of the wall portion 820 on the side of the first connecting member 6. Further, an annular protrusion 824 surrounding the second boss portion 822 is formed on the surface of the wall portion 820 on the side of the second connecting member 7.

The plurality of arm portions 83 are formed so as to extend radially from the central portion of the intermediate member 8. In the present embodiment, the intermediate member 8 is provided with eight arm portions 83. Each arm 83 has a first facing surface 83a facing the side surface 64a of the first protrusion 64 of the first connecting member 6 and a second facing surface facing the side surface 74a of the second protrusion 74 of the second connecting member 7. It has 83b and is arranged so as to be compressed in the circumferential direction between the side surface 64a of the first protrusion 64 and the side surface 74a of the second protrusion 74. The side surface 64a of the first protrusion 64 is a plane parallel to the axial direction of the first connecting member 6, and the side surface 74a of the second protrusion 74 is a plane parallel to the axial direction of the second connecting member 7.

The two arm portions 83 sandwiching the second protrusion 74 of the second connecting member 7 form a pair, and the pair of arm portions 83 are at the ends of the intermediate member 8 on the first connecting member 6 side in the axial direction. It is connected in the circumferential direction by the connecting portion 84. As a result, the strength of the intermediate member 8 is increased. The connecting portion 84 has a fan shape when viewed from the axial direction of the intermediate member 8, and is arranged so as to face the tip surface 74b of the second protrusion 74. As a result, it is possible to prevent erroneous assembly of the intermediate member 8 by reversing the front and back sides.

FIG. 6A is a perspective view showing the first facing surface 83a side of one of the arm portions 83 connected by the connecting portion 84 in a natural state in which each arm portion 83 of the intermediate member 8 is not compressed. It is a figure. 6 (b) and 6 (c) show the cross-sectional shape of the arm 83 in a cross section orthogonal to the extending direction (the radial direction of the intermediate member 8) of the arm 83, and FIG. 6 (b) is FIG. 6 (a). ) Shows the cross-sectional shape of the arm 83 near the tip end, and FIG. 6 (c) shows the cross-sectional shape of the arm 83 near the base end of the arm 83 shown in FIG. 6 (a). , Each shown.

The arm portion 83 integrally has a base portion 831 having a rectangular cross-sectional shape in the above cross section and a bulging portion 832 that bulges in the circumferential direction from the base portion 831. The shape of the base 831 on the arm 83 is a rectangular parallelepiped. In FIGS. 6 (b) and 6 (c), the virtual boundary line between the base portion 831 and the bulging portion 832 is shown by a broken line. In the present embodiment, the bulging portion 832 is provided only on one side of the base portion 831, but the bulging portion 832 may be provided on both sides of the base portion 831. However, by providing the bulging portion 832 only on the first protrusion 64 side opposite to the connecting portion 84, it is forcibly removed during injection molding (a part of the molded body is elastically deformed and taken out from the mold). It is possible to mold the intermediate member 8 without it. That is, when the bulging portion 832 is provided on the second protrusion 74 side, the upper or lower mold for forming the second facing surface 83b of the arm portion 83 cannot be pulled out to the connecting portion 84 side, and the connecting portion cannot be pulled out. It is necessary to forcibly pull out on the side opposite to 84, but in the present embodiment, the second facing surface 83b is a flat surface parallel to the axial direction, and there is no need for such forcibly pulling out. The intermediate member 8 can be molded with high accuracy by preventing deformation of the molded body.

In the present embodiment, the bulging portion 832 bulges from the base portion 831 toward the side surface 64a of the first protrusion 64. In the bulging portion 832, the top surface (flat surface including the apex in the bulging direction of the bulging portion 832) 832a in contact with the side surface 64a of the first protrusion 64 is an intermediate member 8 toward the tip end side of the arm portion 83. It has a trapezoidal shape with a wide axial width. As shown in FIGS. 6B and 6C, the axial length of the top surface 832a at the tip of the arm 83 is L _1, and the axial length of the top surface 832a at the base end of the arm 83 is L1. the When _{L 2, L 1} is shorter than the entire axial length of the first opposing face 83a of the arm portion 83, _{L 2} is shorter than _{L 1.} The preferred length of L _{2 is one-} fourth to two-thirds of L 1.

Further, as shown in FIGS. 6 (b) and 6 (c), the height of the bulge from the base 831 (the boundary line) of the bulge 832 at the tip of the arm 83 is set to H _1, and the height of the bulge of the arm 83 is defined as H 1. When the bulging height from the base portion 831 of the bulging portion 832 at the proximal end and _{H 2, H 1} is equal to _{H 2.}

The first facing surface 83a of the arm portion 83 includes a first inclined surface 832b on the connecting portion 84 side of the top surface 832a and a second inclined surface 832c on the side opposite to the connecting portion 84 of the top surface 832a. The first inclined surface 832b and the second inclined surface 832c are formed in a range from the base end side of the arm portion 83, which is the outer peripheral surface of the intermediate member 8, to the tip end surface 83c, with respect to the axial direction and the circumferential direction of the intermediate member 8. And are inclined in opposite directions. The boundary line 832d between the top surface 832a and the first inclined surface 832b is inclined with respect to the radial direction of the intermediate member 8 so as to approach the connecting portion 84 toward the tip end side of the arm portion 83. The boundary line 832e between the top surface 832a and the second inclined surface 832c is inclined with respect to the radial direction of the intermediate member 8 so as to be farther from the connecting portion 84 toward the tip end side of the arm portion 83.

According to the above configuration of the arm portion 83, when the intermediate member 8 is arranged between the first connecting member 6 and the second connecting member 7, the contact surface of the bulging portion 832 with the side surface 64a of the first protrusion 64. The contact length in the axial direction becomes continuously longer from the base end portion to the tip end portion of the arm portion 83. As a result, for example, when the surface pressure of the top surface 832a when torque is transmitted between the first connecting member 6 and the second connecting member 7 by the intermediate member 8 is uniform, the base is formed at the tip of the arm portion 83. Greater force is transmitted than at the edges.

At the time of assembling the electric power steering device 1, the output rotating shaft 31 of the electric motor 3 and the worm shaft 41 are connected in the housing 5 by the shaft connecting structure by the power transmission joint 9. The work procedure at the time of this work is not particularly limited, but for example, the first step of fixing the first connecting member 6 to the output rotating shaft 31 of the electric motor 3 and the worm shaft 41 supported in the housing 5. The second connecting member 7 is fixed to the first end portion 411 of the above, and the intermediate member 8 is attached to the second connecting member 7, and the electric motor 3 is attached to the housing 5 after the first step and the second step. It is performed by the third step. In the third step, the positions of the gaps between the first facing surfaces 83a of the plurality of arm portions 83 of the intermediate member 8 and the first protrusions 64 of the first connecting member 6 in the intermediate member 8 are aligned with each other visually by the operator. The output rotation shaft 31 is aligned, and in that state, the main body 30 of the electric motor 3 is fixed to the housing 5.

(Actions and effects of the first embodiment)
According to the first embodiment described above, since the bulging portion 832 is provided on the arm portion 83 of the intermediate member 8, when the intermediate member 8 and the first connecting member 6 are combined, they are relative to each other in the rotation direction. Even if there is a specific misalignment, the first protrusion 64 of the first connecting member 6 comes into contact with the first inclined surface 832b of the bulging portion 832, and the acting force and reaction force acting on this contacting portion cause it. At least one of the output rotating shaft 31 and the worm shaft 41 rotates, the misalignment is eliminated, and the assembly can be performed normally. As a result, the power transmission joint 9 and the electric power steering device 1 can be easily assembled. Further, since the arm portion 83 is arranged compressed in the circumferential direction between the side surface 64a of the first protrusion 64 and the side surface 74a of the second protrusion 74 of the second connecting member 7, when the electric motor 3 starts to rotate. Alternatively, the generation of abnormal noise when the rotation direction is reversed is suppressed.

Further, by providing the bulging portion 832 on the arm portion 83, the first facing surface 83a of the arm portion 83 is curved, so that the side surface 64a of the first protrusion 64 of the first connecting member 6 on the first facing surface 83a However, in the present embodiment, the axial contact length of the contact surface between the first facing surface 83a of the arm portion 83 and the side surface 64a of the first protrusion 64 is the base end portion of the arm portion 83. Since it becomes continuously longer from the tip to the tip, a force larger than that of the base is transmitted at the tip of the arm 83, and T (torque) = F (force) x r (radius from the rotation axis). As is clear from the relationship, it is possible to transmit sufficient torque. _{Assuming that the axial length L 2} of the top surface 832a at the base end portion of the arm portion 83 is the same as the axial length L ₁ at the tip end portion, when the intermediate member 8 and the first connecting member 6 are combined. Although the resistance becomes large and the assembly becomes difficult, in the present embodiment, the assembly is further facilitated by making _{L 2} smaller than L _1.

Further, in the present embodiment, since the first facing surface 83a of the arm portion 83 includes the second inclined surface 832c, it is mainly between the central portions of the first protrusion 64 and the second protrusion 74 in the axial direction. The torque is transmitted, and the torque can be transmitted between the first connecting member 6 and the second connecting member 7 without imposing an excessive load on the resin portions 61 and 71. That is, if torque is transmitted between the tip end portion of the first protrusion 64 in the protrusion direction (axial direction) and the base end portion of the second protrusion 74 in the protrusion direction (axial direction), the first protrusion 64 The deformation of the first connecting member 6 tends to increase, and the load on the resin portion 61 of the first connecting member 6 increases. However, according to the present embodiment, such a problem can be suppressed.

Further, in the present embodiment, the bulging portion 832 is provided only on the first facing surface 83a side, and the bulging portion 832 is provided on the second facing surface 83b side facing the second protrusion 74. Therefore, it is not necessary to forcibly remove the molded body from the mold at the time of molding the intermediate member 8, and it is possible to prevent the intermediate member 8 as a molded body from being deformed by this forcible removal.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. 7 (a) to 7 (c). In the present embodiment, the shape of the arm portion 83 of the intermediate member 8 is different from that of the first embodiment, and the other parts are the same as those of the first embodiment. , Detailed description of other parts will be omitted. Further, in FIGS. 7A to 7C, components common to those described in the first embodiment are designated by the same reference numerals and duplicated description will be omitted.

FIG. 7A is a perspective view showing the first facing surface 83a side of one of the pair of arm portions 83 in the intermediate member 8 according to the present embodiment. 7 (b) and 7 (c) show the cross-sectional shape of the arm 83 in a cross section orthogonal to the extending direction of the arm 83, and FIG. 7 (b) is the line CC shown in FIG. 7 (a). FIG. 7B shows the cross-sectional shape of the tip end portion of the arm portion 83, and FIG. 7B shows the cross-sectional shape of the base end portion of the arm portion 83 on the DD line shown in FIG. 7A.

In the present embodiment, in a natural state in which the arm 83 of the intermediate member 8 is not compressed, the height of the bulge 832 from the base 831 is continuously increased from the base end to the tip of the arm 83. It gets higher. Further, the corner portion 833 on the second protrusion 74 side at the end portion of the base portion 831 opposite to the connecting portion 84 is chamfered by the inclined surface 83d inclined with respect to the axial direction of the intermediate member 8.

As shown in FIGS. 7 (b) and 7 (c), the height of the bulge from the base 831 of the bulge 832 at the tip of the arm 83 is H _1, and the bulge at the base end of the arm 83. bulging height from the base 831 of 832 When _{H 2, H 1} is greater than _{H 2.} Therefore, when torque is transmitted between the first connecting member 6 and the second connecting member 7, a larger force is transmitted at the tip end portion of the arm portion 83 as compared with the first embodiment. ..

Further, since the corner portion 833 of the arm portion 83 is chamfered by the inclined surface 83d inclined with respect to the axial direction of the intermediate member 8, the intermediate member 8 and the second connecting member 7 are also chamfered in the rotational direction. Alignment can be easily performed. As a result, when assembling the electric power steering device 1, even if the intermediate member 8 is attached to the first connecting member 6 in advance and the main body 30 of the electric motor 3 is attached to the housing 5, the work can be easily performed. It will be possible.

[Third Embodiment]
Next, a third embodiment of the present invention will be described with reference to FIGS. 8A to 8C. In the present embodiment, the intermediate member 8 is not provided with the connecting portion 84, and the arm portion 83 is provided with bulging portions 832 on both sides of the base portion 831. Since the other configurations are the same as those of the first embodiment, the same reference numerals are given to the components common to those described in the first embodiment in FIGS. 8A to 8C. The duplicate explanation will be omitted.

FIG. 8A is a perspective view showing an intermediate member 8 according to the present embodiment. 8 (b) and 8 (c) show the cross-sectional shape of the arm 83 in a cross section orthogonal to the extending direction of the arm 83, and FIG. 8 (b) is the line EE shown in FIG. 8 (a). FIG. 8B shows the cross-sectional shape of the arm portion 83 in the vicinity of the tip end portion, and FIG. 8B shows the cross-sectional shape of the arm portion 83 in the vicinity of the base end portion on the FF line shown in FIG. 8A.

As shown in FIGS. 8 (b) and 8 (c), in the present embodiment, each arm portion 83 integrally has a base portion 831 and a pair of bulging portions 832. Of the pair of bulging portions 832, one bulging portion 832 bulges toward the side surface 64a of the first protrusion 64 of the first connecting member 6, and the other bulging portion 832 is the second of the second connecting member 7. It bulges toward the side surface 74a of the protrusion 74. It is also possible to omit any one of these one or the other bulging portion 832.

In each of the bulging portions 832, the top surface 832a has a trapezoidal shape in which the width of the intermediate member 8 in the axial direction becomes wider toward the tip end side of the arm portion 83, and the axial direction of the top surface 832a at the tip end portion of the arm portion 83. The length L ₁ is longer than _{the axial length L 2} of the top surface 832a at the base end of the arm 83. Further, the bulge height from the base 831 of the bulge 832 at the tip of the arm 83 is H _1, and the bulge height from the base 831 of the bulge 832 at the base end of the arm 83 is H. _{If it is 2} , H ₁ is equal to _{H 2.} In addition, H ₁ may be made larger than H _2.

The present embodiment also has the same actions and effects as the first embodiment. Further, since the intermediate member 8 does not have the connecting portion 84, even if the bulging portions 832 are provided on both sides of the base portion 831, the intermediate member 8 can be formed without forcibly pulling out.

(Additional note)
Although the present invention has been described above based on the first to third embodiments, these embodiments do not limit the invention according to the claims. It should also be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention. Further, the present invention can be appropriately modified without departing from the spirit thereof, and the configurations of the respective embodiments can be appropriately combined and implemented.

Further, in the above embodiment, the case where the shaft connection structure of the present invention is applied to the assist mechanism 2 of the electric power steering device 1 has been described, but the shaft connection structure of the present invention is, for example, a drive source of an electric motor. Of course, it can also be applied to other applications such as automobile drive trains and machine tools. The configuration of the electric power steering device 1 is not limited to the column assist type illustrated in FIG. 1, for example, a pinion assist type that applies an assist force to the pinion shaft 123, or a second one that does not constitute the steering shaft 12. A so-called double pinion type (dual pinion type) in which the pinion shaft is meshed with the rack shaft 13 and the second pinion shaft is rotated by the torque of an electric motor decelerated by the worm gear mechanism to give an assist force to the rack shaft 13. It is also possible to apply the present invention to the object.

1 ... Electric power steering device 10 ... Steering mechanism 11 ... Steering wheel 19 ... Steering wheel 2 ... Assist mechanism 3 ... Electric motor 31 ... Output rotating shaft (first rotating member) 4 ... Worm gear mechanism 41 ... Worm shaft (second rotating member) 6 ... 1st connecting member 64 ... 1st protrusion 64a ... Side surface 7 ... 2nd connecting member 74 ... 2nd protrusion 74a ... Side surface 8 ... Intermediate member 83 ... Arm 831 ... Base 832 ... Swelling part 832a ... Top surface 833 ... Corner 83d ... Inclined surface 84 ... Connecting parts O ₁ , O ₂ ... Rotating axis

Claims (6)

It is an axial connection structure that connects the first rotating member and the second rotating member that are arranged concentrically in the axial direction.
The first connecting member fixed to the end of the first rotating member,
A second connecting member fixed to the end of the second rotating member,
It is provided between the first connecting member and the second connecting member, and includes the first connecting member and an intermediate member made of a material softer than the second connecting member.
The first connecting member extends toward the second connecting member side along an axial direction parallel to the rotation axis of the first rotating member, and has a predetermined interval in the circumferential direction around the rotating axis. It has a plurality of first protrusions provided, and has a plurality of first protrusions.
The second connecting member extends toward the first connecting member side along an axial direction parallel to the rotation axis of the second rotating member, and is arranged between the plurality of first protrusions. Has protrusions
The intermediate member has a plurality of arms extending radially from the central portion, and the arms are arranged so as to be compressed in the circumferential direction between the side surface of the first protrusion and the side surface of the second protrusion. Has been
The arm portion integrally has a base portion having a rectangular cross-sectional shape orthogonal to the extending direction thereof and a bulging portion that bulges from the base portion toward the side surface of the first protrusion or the second protrusion. death,
Said axial contact length of the contact surface between the side surface of the first protrusion or the second protrusion in the protruding portion, from the intermediate said central portion and the arm portion corresponding to the side of the base end portion of the member, the Continuously lengthens toward the tip of the arm in the extending direction,
Shaft connection structure. The intermediate member has a trapezoidal shape in which the top surface of the bulging portion in contact with the side surface becomes wider in the axial direction toward the tip end side of the arm portion.
The shaft connection structure according to claim 1. In the intermediate member, the height of the bulge from the base of the bulge continuously increases from the base end to the tip of the arm in a natural state in which the arm is not compressed.
The shaft connection structure according to claim 1 or 2. The intermediate member has a connecting portion for connecting the pair of arm portions sandwiching the second protrusion in the circumferential direction, and the connecting portion is arranged so as to face the tip surface of the second protrusion. The bulge is provided only on the first protrusion side of the base.
The shaft connecting structure according to any one of claims 1 to 3. The corner portion on the first protrusion side at the end portion of the base portion opposite to the connecting portion is chamfered by an inclined surface inclined with respect to the axial direction.
The shaft connection structure according to claim 4. It is provided with a steering mechanism that steers the steering wheel according to the steering of the steering wheel and an assist mechanism that applies an assist force to the steering mechanism.
The assist mechanism includes an electric motor, a worm shaft connected to an output rotation shaft of the electric motor, and a worm gear mechanism having a worm wheel that meshes with the worm shaft.
The output rotating shaft and the worm shaft are connected by the shaft connecting mechanism according to any one of claims 1 to 5.
Electric power steering device.

Images