JP2016020718A - Torque transmission member and connecting part of drive shaft and driven shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a structure which can suppress the generation of backlash at each engagement part, and can absorb an alignment error between both shafts, related to a torque transmission member which is engaged with outer teeth and inner teeth arranged at a drive shaft and a driven shaft, respectively, and transmits torque between both the shafts.SOLUTION: A torque transmission member 15 is constituted by combining a pair of torque transmission elements 17a, 17b which are arranged at both sides in an axial direction, and an intermediate element 18 which is arranged at an intermediate part in the axial direction. An elastic tooth part 28 which is elastically engaged with outer teeth without causing wobbling is arranged at an internal peripheral face of the intermediate element 18. In a state that protrusions 27a, 27b which are formed at the intermediate element 18 are inserted into insertion holes 23a, 23b of the torque transmission elements 17a, 17b, phases related to circumferential directions of a pair of outside-diameter side tooth elements 22a, 22b which are arranged at external peripheral faces of the torque transmission elements 17a, 17b are displaced from each other.SELECTED DRAWING: Figure 2

Description

  The present invention is incorporated in various mechanical devices such as an electric power steering device and used for transmitting torque between a drive shaft and a driven shaft, and the drive shaft and the driven shaft. Relating to the joint of

  Power steering devices are widely used as devices for reducing the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts). It is used. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has been widely used in recent years. The electric power steering device can be made smaller and lighter than the hydraulic power steering device, has advantages such as easy control of the magnitude (torque) of auxiliary power and less power loss of the engine.

  Various structures of the electric power steering apparatus are known. In any structure, the electric power steering device is electrically driven by a rotating shaft that is rotated by an operation of the steering wheel and gives a steering angle to the steered wheels as the rotation occurs. Auxiliary power of the motor is applied through a reduction gear. In general, a worm reducer is used as the reducer. 17 to 18 show an example of an electric power steering device using a worm reduction gear. A front end portion of a steering shaft 2 that is a rotating shaft that is rotated in a predetermined direction by the steering wheel 1 is rotatably supported inside the housing 3, and the worm wheel 4 is fixed to this portion. Worm teeth 5 meshing with the worm wheel 4 are provided in the axial direction intermediate portion of the worm shaft 6, and both ends of the worm 8 driven to rotate by the electric motor 7 are paired with a pair of rolling bearings 9 a such as a deep groove ball bearing, 9b is rotatably supported in the housing 3.

Further, in order to couple the distal end portion of the output shaft 10 of the electric motor 7 and the proximal end portion of the worm shaft 6 so that torque (rotational force) can be transmitted, the proximal end portion of the worm shaft 6 is A spline hole 12 having female spline teeth 11 corresponding to the inner teeth described in the claims is formed on the inner peripheral surface thereof in a state of opening to the base end surface of the worm shaft 6. Moreover, the spline shaft part 14 which has the male spline tooth | gear 13 equivalent to the outer tooth | gear described in the claim at the front-end | tip part of the said output shaft 10 is formed. The spline shaft portion 14 and the spline hole 12 are spline-engaged to couple the output shaft 10 and the worm shaft 6 so that torque can be transmitted.
The “spline” in the present specification and claims includes what is called “serration” with a fine pitch.

  By the way, in the case of the electric power steering apparatus configured as described above, a moderately large gap (backlash) is usually provided between the male spline teeth 13 and the female spline teeth 11. Yes. The reason for this is to facilitate the work of spline engagement between the spline shaft portion 14 and the spline hole 12. Further, as long as the center axis of the output shaft 10 and the center axis of the worm shaft 6 are slightly deviated from each other, it is necessary to rotate the output shaft 10 so that the spline engaging portion is not distorted. This is also to prevent the torque from rising. However, if there is backlash in the spline engaging portion, the spline engaging portion is likely to rattle, and the male spline teeth are instantly activated when the electric motor 7 is started or when the rotation direction is changed. The circumferential side surface of 13 and the circumferential side surface of the female spline tooth 11 collide with each other vigorously, causing an abnormal noise called a rattling noise.

  In view of such circumstances, for example, in Patent Document 1, the output shaft of the electric motor and the base end portion of the worm shaft are spline-engaged via a substantially cylindrical torque transmission member, and the spline engaging portion is connected to the spline engaging portion. A technique for preventing rattling at the spline engaging portion by filling a synthetic resin such as a thermoplastic elastomer is described. In the case of such a structure described in Patent Document 1, it is advantageous in terms of suppressing rattling at the spline engaging portion and preventing occurrence of rattling noise, but rattling at the spline engaging portion. It is only considered to prevent this, and is not considered for absorbing (compensating) alignment errors.

  That is, in the case of the structure described in Patent Document 1, due to the presence of an elastic material such as synthetic resin, the spline engagement portion does not have backlash or becomes extremely small even if it exists. For this reason, even when an alignment error such as misalignment occurs between a pair of shafts coupled to each other, it is difficult to absorb the alignment error. As a result, galling is likely to occur, which may cause problems such as an increase in torque and an increase in wear of spline teeth. On the other hand, in the electric power steering device, the positional relationship between the central axis of the output shaft 10 of the electric motor 7 and the central axis of the worm shaft 6 becomes inconsistent on the basis of assembly error and shape error integration. Error is likely to occur. For this reason, in the spline engaging portion of the electric power steering apparatus, it is desired that not only rattling can be prevented, but also that alignment errors can be absorbed.

  On the other hand, Patent Document 2 describes a technique that can prevent rattling and absorb alignment errors with respect to the coupling portion between the output shaft and the steering shaft of the electric motor constituting the electric power steering device. Yes. However, in the case of the technique described in Patent Document 2, the output shaft and the steering shaft are coupled via a coupling device (shaft coupling) that is a combination of a pair of connecting base bodies and a buffer member. Because of the coupling, the number of parts is large, the structure becomes complicated, and the assembly work becomes troublesome, leading to an increase in manufacturing cost. In addition, when transmitting torque, the buffer member sandwiched in the circumferential direction between the claw portions provided on both the connecting bases, a pair of rotation transmitting members connected to each other, and the two rotation transmitting members It is comprised from the intermediate | middle interposed member pinched | interposed between. For this reason, even when a misalignment occurs between the output shaft and the steering shaft, the rotation transmitting members are connected so as not to be relatively displaceable. It is hard to say that it can be absorbed sufficiently.

  In addition, there exists patent document 3 as another prior art document relevant to this invention. In Patent Document 3, a so-called scissors gear structure in which a main gear and a sub gear are combined so as to be rotatable relative to each other and a spring is disposed between the two gears is used, so that backlash occurs at a meshing portion with a mating tooth. An invention that suppresses the occurrence is described. However, in the case of the invention described in Patent Document 3, only a structure in which tooth portions (main gear and sub gear) are provided only on the outer peripheral surface is disclosed, and a structure in which tooth portions are provided on both inner and outer peripheral surfaces is adopted. There is no mention of preventing backlash from occurring.

JP-A-2005-240959 Japanese Patent No. 4779358 Japanese Utility Model Publication No. 7-10606

  In view of the circumstances as described above, the present invention relates to a torque transmission member that meshes with external teeth and internal teeth provided on a drive shaft and a driven shaft, respectively, and transmits torque between the shafts. The present invention has been invented to realize a structure capable of suppressing the occurrence of backlash and effectively absorbing the alignment error between the two shafts at the meshing portions of the external teeth and the internal teeth. Further, the present invention has been invented to realize the structure of the coupling portion between the drive shaft and the driven shaft using such a torque transmission member.

The torque transmission member of the present invention is provided between a drive shaft and a driven shaft that are arranged coaxially with each other, and transmits torque between these two shafts. An inner diameter side tooth portion meshing with an outer tooth provided on one shaft and an outer diameter side tooth portion meshing with an inner tooth provided on the other shaft of the two shafts are provided. The outer teeth and the inner teeth may be formed directly on the peripheral surface of the shaft, or may be formed on the peripheral surface of another member fixed to the shaft.
The torque transmission member is formed by combining a pair of torque transmission elements arranged on both sides in the axial direction and an intermediate element provided between the two torque transmission elements.
The two torque transmission elements are not connected to each other, and are substantially annular, respectively. Of the inner and outer peripheral surfaces, the inner peripheral surface includes an inner diameter side tooth element that forms the inner diameter side tooth portion, and the outer peripheral surface includes The outer diameter side tooth element which comprises the said outer diameter side tooth | gear part is each provided.
The intermediate element has a substantially annular shape, and is provided with a main body portion made of a material that is more easily elastically deformed than the two torque transmission elements, and protruding from both axial side surfaces of the main body portion to both axial sides. And a plurality of protrusions.
Also, an elastic tooth that elastically meshes with only one of the inner and outer peripheral surfaces of the main body portion without any rattling with the outer teeth and the inner teeth. Is provided.
In particular, in the case of the torque transmission member of the present invention, by inserting (for example, press-fitting) the protrusions into the insertion holes formed in the torque transmission elements, Of the pair of inner diameter side tooth elements provided on the inner peripheral surface and the pair of outer diameter side tooth elements provided on the outer peripheral surface in a state of being supported with respect to the intermediate element, at least in the radial direction, The phase in the circumferential direction of the pair of tooth elements located on the side opposite to the elastic tooth portion is shifted. Then, in a state where these both tooth elements are meshed with either one of the outer teeth and the inner teeth, the other teeth are pressed from both sides in the circumferential direction between these two tooth elements. To do.

  When implementing such a torque transmission member of the present invention, for example, as in the invention described in claim 2, the inner diameter side tooth elements and the outer diameter side tooth elements are involute teeth, As in the invention described in Item 3, the spline tooth profile is adopted. Further, these can be combined into an involute spline tooth profile.

  When the torque transmitting member of the present invention is implemented, for example, as in the invention described in claim 4, at least one tooth element among the inner diameter side tooth elements and the outer diameter side tooth elements. The width dimension in the circumferential direction is changed with respect to the axial direction, or at least one tooth element among the inner diameter side tooth elements and the outer diameter side tooth elements as in the invention described in claim 5. The tooth height is changed with respect to the axial direction. Also, these configurations can be carried out simultaneously.

The coupling portion between the drive shaft and the driven shaft of the present invention includes a drive shaft and a driven shaft that are coaxially arranged with each other, and a substantially annular torque transmission member that transmits torque between the two shafts. Is provided.
Of these two shafts, one shaft is provided with external teeth, and the other shaft is provided with internal teeth. The outer teeth and the inner teeth may be formed directly on the peripheral surface of the shaft, or may be formed on the peripheral surface of another member fixed to the shaft.
Of the inner and outer peripheral surfaces of the torque transmitting member, an inner diameter side tooth portion meshing with the outer teeth is provided on the inner peripheral surface, and an outer diameter side tooth portion engaging with the inner teeth is provided on the outer peripheral surface. It has been.
In particular, in the case of the coupling portion between the drive shaft and the driven shaft of the present invention, the torque transmission member is the torque transmission member of the present invention as described above.

According to the present invention having the above-described configuration, it is possible to suppress the occurrence of backlash at the meshing portions of the external teeth and the internal teeth provided on the drive shaft and the driven shaft, and An alignment error between the two can be effectively absorbed.
That is, in the case of the present invention, the elastic tooth portion provided on one of the peripheral surfaces of the main body portion of the intermediate element constituting the torque transmission member is either one of the outer teeth and the inner teeth. One tooth is elastically meshed without rattling. Of the pair of inner diameter side tooth elements and the pair of outer diameter side tooth elements provided in the pair of torque transmission elements constituting the torque transmission member, at least the radial direction opposite to the elastic tooth portion One of the external teeth and the internal teeth is pressed from both sides in the circumferential direction by a pair of tooth elements that are provided on the outer periphery and are out of phase with respect to the circumferential direction. For this reason, in the case of the present invention, the backlash at the meshing portion of any one of the external teeth and the internal teeth is caused by the elastic tooth portion to mesh with the other tooth. Can be effectively prevented by the pair of tooth elements that are out of phase with respect to the circumferential direction. Therefore, it is possible to suppress the occurrence of backlash at the meshing portions of the torque transmission member, the outer teeth, and the inner teeth.
Further, in the case of the present invention, without connecting a pair of torque transmission elements constituting the torque transmission member, these two torque transmission elements are utilized by using the protrusion provided on the intermediate element, It is supported only by this intermediate element. For this reason, since both the torque transmission elements can be easily displaced from each other, alignment errors between the two axes can be effectively absorbed.

  According to the invention described in claims 4 and 5, the contact area between the outer teeth and the inner diameter side tooth elements or the contact area between the inner teeth and the outer diameter side tooth elements can be reduced. Therefore, the external teeth and the inner diameter side tooth elements can be easily displaced relative to each other, or the inner teeth and the outer diameter side tooth elements can be easily displaced relative to each other. For this reason, alignment errors between the two axes can be absorbed more effectively.

Sectional drawing which shows the coupling | bond part of a drive shaft and a driven shaft which shows the 1st example of embodiment of this invention. Similarly disassembled perspective view. The exploded perspective view which takes out and shows a torque transmission member similarly. Similarly front view. The A section enlarged view of FIG. 4 similarly. The B arrow enlarged view of FIG. 4 similarly. The perspective view of a torque transmission member similarly. The perspective view of the torque transmission member which similarly shows the state seen from another direction. The front view (A) and the right view (B) which take out and show a torque transmission element similarly. Similarly CC sectional drawing of (A) of FIG. Similarly, a front view (A) and a right side view (B) showing the intermediate element taken out. The perspective view of an intermediate element similarly. The front view (A) of the torque transmission element which shows the 2nd example of embodiment of this invention, and the partial side view (B) which looked at (A) from the right side. The figure which similarly corresponds to FIG. The front view (A) of the torque transmission member which shows the 3rd example of embodiment of this invention, and the upper side view (B) which looked at (A) from the right side. The front view which shows another two examples of the torque transmission member used as the object of this invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. DD enlarged sectional view of FIG. 17 showing an example of a conventional structure of an electric power steering apparatus.

[First example of embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. In the case of this example, the front end portion of the output shaft 10a of the electric motor 7 (see FIGS. 17 and 18) constituting the electric power steering device and the base end portion of the worm shaft 6a constituting the worm type reduction gear. In the meantime, the torque transmission member 15 of this example is provided so that torque can be transmitted from the output shaft 10a to the worm shaft 6a. Since the configuration and operation of the entire electric power steering apparatus are the same as those of the conventionally known electric power steering apparatus including the structure shown in FIGS. 17 to 18, the description thereof will be omitted. The configuration and operation of the coupling portion between the output shaft 10a and the worm shaft 6a will be mainly described.

  The output shaft 10a and the worm shaft 6a are disposed coaxially with each other, and the base end portion of the worm shaft 6a has a larger outer diameter than the intermediate portion or the distal end portion. A diameter portion 16 is provided. A spline hole 12a is formed inside the large diameter portion 16 so as to open to the base end face. On the inner peripheral surface of the spline hole 12a, female spline teeth 11a corresponding to the inner teeth described in the claims are formed over the entire circumference. On the other hand, a spline shaft portion 14a is provided at the tip of the output shaft 10a. On the outer peripheral surface of the spline shaft portion 14a, male spline teeth 13a corresponding to the external teeth described in the claims are formed over the entire circumference. In the case of this example, the diameter of the circumscribed circle passing through the tip circle of the male spline teeth 13a is made sufficiently smaller than the diameter of the inscribed circle passing through the tip circle of the female spline teeth 11a, and the spline shaft portion 14a and the spline hole 12a are not directly engaged with the spline, but are engaged with each other via the torque transmission member 15, so that the output shaft 10a and the worm shaft 6a are coupled to each other so as to be able to transmit torque. Yes.

  The torque transmission member 15 has a substantially annular shape as a whole, and is provided at a portion between the pair of torque transmission elements 17a and 17b arranged on both sides in the axial direction and between the torque transmission elements 17a and 17b. The intermediate element 18 is combined. Inner diameter side teeth that mesh with the male spline teeth 13a formed on the outer peripheral surface of the tip end of the output shaft 10a on the inner peripheral surface (both ends of the inner peripheral surface) of the torque transmission member 15 having such a configuration. A part 19 is provided. On the other hand, an outer diameter side tooth portion 20 that meshes with the female spline teeth 11a formed on the inner peripheral surface of the base end portion of the worm shaft 6a on the outer peripheral surface (both ends of the outer peripheral surface) of the torque transmission member 15. Is provided.

  The torque transmitting elements 17a and 17b are substantially annular, and have the same shape except for the positions where the insertion holes 23a and 23b described later are formed in the circumferential direction. For example, a synthetic resin such as polyacetal resin or polyamide resin is used. It is made by injection molding or by a metal material. Of the both inner and outer peripheral surfaces of the torque transmitting elements 17a and 17b, inner diameter side tooth elements 21a and 21b, which are involute spline teeth, are formed on the outer peripheral surface. The outer diameter side tooth elements 22a and 22b, which are involute spline teeth, constituting the outer diameter side tooth portion 20, are respectively formed. Further, the torque transmitting elements 17a and 17b are respectively formed with insertion holes 23a and 23b penetrating in the axial direction at three circumferentially equidistant positions in the radial intermediate portion. Each of the insertion holes 23a and 23b is provided in an axially inner half of the both torque transmission elements 17a and 17b that faces the intermediate element 18 in the axial direction when the torque transmission member 15 is assembled. The large-diameter hole portion 24 and the small-diameter hole portion 25 provided in the axially outer half portion are configured. In the case of this example, the formation positions in the circumferential direction of the insertion holes 23a, 23b having such a configuration are slightly shifted between the torque transmitting elements 17a, 17b. The two torque transmission elements 17a and 17b are not directly connected to each other in the assembled state of the torque transmission member 15, but are connected only via the intermediate element 18.

The intermediate element 18 is made of a material that is more elastically deformed than the torque transmitting elements 17a and 17b, such as rubber and elastomer, and a substantially annular main body 26 and both axial sides of the main body 26. A plurality of (in the illustrated example, a total of six) protrusions 27a and 27b made of a rigid body such as metal, for example, are provided so as to protrude from the portion near the outer diameter of the surface to both sides in the axial direction. Note that the main body and the protrusions may be integrally formed of a material (rubber, elastomer, etc.) that is easily elastically deformed. Among these, an elastic tooth portion 28 is formed on the inner peripheral surface of the main body portion 26 and elastically meshes with the male spline teeth 13a formed on the outer peripheral surface of the distal end portion of the output shaft 10a without rattling. ing. The width dimension W ₂₈ in the circumferential direction in the free state of each tooth constituting the elastic tooth portion 28 is the width dimension W _{21 in} the circumferential direction of the inner diameter side tooth elements 21 a and 21 b (each tooth constituting the inner tooth side elements 21 a and 21 b). Bigger than. On the other hand, the outer peripheral surface of the main body portion 26 is a single cylindrical surface, and no tooth portion is provided. The outer diameter of the main body 26 is smaller than the diameter of a virtual circle passing through the root circle of the outer diameter side tooth elements 22a and 22b formed on the outer peripheral surfaces of the torque transmitting elements 17a and 17b. Yes.

  In addition, three protrusions 27a and 27a provided in a state protruding from one axial side surface of the main body portion 26, and three protrusions provided in a state protruding from the other axial side surface of the main body portion 26. The portions 27 b and 27 b are provided coaxially, and the base ends thereof are connected to each other inside the main body portion 26. In other words, in the case of this example, the base portion of the three shaft portions 29 and 29 having the axial center portion as the base portion and the axial end portions thereof as the projection portions 27a and 27b, respectively, is used as the main body portion 26. It is located inside. In the case of this example, constricted portions 30 and 30 having outer diameters smaller than the distal end portions are provided at the base end portions of both the protruding portions 27a and 27b. Further, the outer diameter dimension (outer diameter dimension of the tip portion) and the axial dimension of both the projecting portions 27a, 27a are the same as the large-diameter hole portions 24 of the insertion holes 23a, 23b formed in the torque transmitting elements 17a, 17b. , 24 are slightly larger than the inner diameter dimension and the axial dimension.

In the case of this example, the torque transmission member 15 is configured by combining the torque transmission elements 17a and 17b having the above-described configuration and the intermediate element 18. Specifically, the projecting portions 27a and 27b constituting the intermediate element 18 are press-fitted into the large-diameter holes 24 and 24 opened on the inner surfaces in the axial direction of the torque transmitting elements 17a and 17b, respectively. Thus, both the torque transmission elements 17 a and 17 b are respectively supported by the intermediate element 18 to form the torque transmission member 15. Especially in the case of this example, in a state where the torque transmission member 15 is assembled in this way, a pair of outer diameter side tooth elements 22a and 22b provided at both ends of the outer peripheral surface of the torque transmission member 15 The phase in the circumferential direction is shifted. Then, the protrusions 27a and 27b are elastically deformed (bent) in the circumferential direction so that the phase shift in the circumferential direction between the outer diameter side tooth elements 22a and 22b is reduced. Both the outer diameter side tooth elements 22a and 22b are meshed with the female spline teeth 11a. As a result, the female spline teeth 11a are pressed (clamped) from both sides in the circumferential direction by the both outer diameter side tooth elements 22a and 22b. In the case of this example, since the constricted portions 30 and 30 are provided at the base end portions of the projecting portions 27a and 27b, the projecting portions 27a and 27b can be bent with a light force.
Note that the degree of deviation (deviation amount, deviation angle) in the circumferential direction of each of the insertion holes 23a, 23b takes into account the rigidity of the projections 27a, 27b, and both the outer diameter side tooth elements 22a. 22b, the female spline teeth 11a are set to a size that can be held with light force from both sides in the circumferential direction.

  In the case of this example, not only the phase related to the circumferential direction of the both outer diameter side tooth elements 22a and 22b but also the phase related to the circumferential direction of the both inner diameter side tooth elements 21a and 21b (same direction). The same amount). However, of the torque transmission elements 17a and 17b, one side surface in the circumferential direction of the inner diameter side tooth element 21a provided in one torque transmission element 17a and the inner diameter side tooth element provided in the other torque transmission element 17b. The circumferential side surface of each tooth constituting the elastic tooth portion 28 protrudes in the circumferential direction from the other circumferential side surface of 21b. For this reason, the effect of suppressing backlash at the meshing portion with the male spline teeth 13 a is exhibited by elastic meshing with the elastic tooth portion 28. In the case of this example, the number of teeth constituting the elastic tooth portion 28 is the same as the number of teeth constituting the inner diameter side tooth elements 21a and 21b. Need not be the same. For example, the number of teeth constituting the elastic tooth portion is half the number of teeth constituting the inner diameter side tooth element (for example, the number of teeth constituting the elastic tooth portion is three and the inner diameter side tooth element is constituted. It is possible to adopt a configuration in which the number of teeth to be six is set to be able to project the elastic tooth portion in the circumferential direction from the inner diameter side tooth element at equally spaced positions in the circumferential direction.

In the case of this example having the above-described configuration, backlash is generated at the meshing portions of the male spline teeth 13a and the female spline teeth 11a provided on the output shaft 10a and the worm shaft 6a. While being able to suppress, the alignment error between both the shafts 6a and 10a can be absorbed effectively.
That is, in the case of this example, the elastic teeth 28 provided on the inner peripheral surface of the main body 26 of the intermediate element 18 are elastically meshed with the male spline teeth 13a without rattling. The female spline teeth are provided by a pair of outer diameter side tooth elements 22a and 22b provided at both ends of the outer peripheral surface of the torque transmission member 15 and shifted in the circumferential direction in the assembled state of the torque transmission member 15. 11a is pressed from both sides in the circumferential direction. Therefore, the backlash at the meshing portion with the male spline teeth 13a is effective by the elastic tooth portion 28, and the backlash at the meshing portion with the female spline teeth 11a is effective by the both outer diameter side tooth elements 22a and 22b. Can be prevented. Therefore, it is possible to suppress the occurrence of backlash at the meshing portions of the torque transmission member 15 and the male spline teeth 13a and the female spline teeth 11a.

  In the case of this example, the pair of torque transmission elements 17a and 17b constituting the torque transmission member 15 are not directly connected to each other, and both the torque transmission elements 17a and 17b are connected to the intermediate element 18. The protrusions 27a and 27b provided are supported only on the intermediate element 18. For this reason, since both the torque transmission elements 17a and 17b can be easily displaced from each other, alignment errors between the both shafts 6a and 10a can be effectively absorbed. Moreover, since the number of parts can be reduced as compared with the case where a coupling device is used as in the technique described in Patent Document 2 described above, the manufacturing cost can be reduced.

[Second Example of Embodiment]
A second example of the embodiment of the present invention will be described with reference to FIGS. The feature of this example is that the width dimension in the circumferential direction of the outer diameter side tooth elements 22c and 22d formed on the outer peripheral surfaces of the torque transmitting elements 17a and 17b is changed in the axial direction. More specifically, the width dimension in the circumferential direction of the both outer diameter side tooth elements 22c and 22d with respect to the outer half portions in the axial direction of the torque transmitting elements 17a and 17b is reduced toward the outer side in the axial direction. ing.

In the case of the torque transmission member 15 of this example having such a configuration, the contact area between the female spline teeth 11a (see FIG. 1 and the like) and the respective outer diameter side tooth elements 22c, 22d can be reduced, and the circumference A relief portion can be formed in a portion where the width dimension in the direction is reduced. Therefore, the female spline teeth 11a and the outer diameter side tooth elements 22c and 22d can be easily displaced relative to each other. Therefore, alignment errors between the worm shaft 6a and the output shaft 10a (see FIG. 1 and the like) can be absorbed more effectively.
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

[Third example of embodiment]
A third example of the embodiment of the present invention will be described with reference to FIG. The feature of this example is that the tooth heights of the outer diameter side tooth elements 22e and 22f formed on the outer peripheral surfaces of the torque transmitting elements 17a and 17b are changed in the axial direction. More specifically, the tooth lengths of the outer diameter side tooth elements 22e and 22f related to the axially outer halves of the torque transmitting elements 17a and 17b are made lower toward the outer side in the axial direction.

In the case of the torque transmission member 15 of this example having such a configuration, the contact area between the female spline teeth 11a (see FIG. 1 and the like) and the outer diameter side tooth elements 22e and 22f can be reduced, and the tooth height can be reduced. An escape portion can be formed in the portion where the diameter becomes smaller. Therefore, the female spline teeth 11a and the outer diameter side tooth elements 22e and 22f can be easily displaced relative to each other. For this reason, alignment errors between the worm shaft 6a and the output shaft 10a (see FIG. 1 and the like) can be absorbed more effectively.
About another structure and an effect, it is the same as that of the case of the 1st example of the said embodiment.

  When practicing the present invention, it is not limited to the structure in which the elastic tooth portion is provided on the inner peripheral surface of the intermediate element as in the structure of each example of the embodiment described above, and the elastic tooth portion is provided on the outer peripheral surface of the intermediate element. May be provided. Further, when providing an elastic tooth portion on the outer peripheral surface of the intermediate element in this way, the phase in the circumferential direction between the pair of inner diameter side tooth elements is shifted, and the outer teeth are circumferentially moved by these inner diameter side tooth elements. Press from both sides. Moreover, in the structure of each example of the above-described embodiment, an example in which each tooth shape is a spline tooth shape has been described. However, when implementing the present invention, each tooth shape is limited to a spline tooth shape. It is possible to adopt various shapes. Further, the engagement protrusion provided on the intermediate element is not limited to a structure that press-fits into the insertion hole formed in the torque transmission element. For example, the insertion hole is a stepped hole and the engagement protrusion is a base end portion. Uses an arrow-shaped one with a larger outer diameter at the tip, and a structure in which the stepped surface between the base end and the tip is engaged with the stepped surface of the insertion hole. You can also do it.

Further, in the case of the structure of each example of the above-described embodiment, the structure in which the formation position in the circumferential direction of the insertion hole is made different for the pair of torque transmission elements has been described as an example. In this case, by adopting the following configuration, the pair of torque transmission elements can have the same shape including the position of the insertion hole.
That is, as shown in FIG. 16A, with respect to the pair of torque transmission elements 17c and 17c, the circumferential direction related to each tooth constituting the outer diameter side tooth element 22e and each tooth constituting the inner diameter side tooth element 21c. Insertion holes 23c and 23c are formed on the symmetry axes α and α ′, respectively, so that the torque transmitting elements 17c and 17c have the same shape. In FIG. 16A, the insertion hole 23c indicated by a solid line is an insertion hole related to the near-side torque transmission element 17c formed on the symmetry axis α, and the insertion hole 23c indicated by a broken line is the target axis α. It is an insertion hole for the torque transmitting element 17c on the back side formed on the upper side. Instead, an intermediate element 18a having a phase difference in the circumferential direction between the protrusions provided on both sides in the axial direction is used. Alternatively, as shown in FIG. 16B, as a pair of torque transmission elements 17d and 17d, circumferential directions related to each tooth constituting the outer diameter side tooth element 22f and each tooth constituting the inner diameter side tooth element 21d. Are prepared with insertion holes 23d and 23d formed at positions slightly shifted in the circumferential direction from the symmetry axes α and α ′. Then, when combined with the intermediate element 18, one torque transmission element 17d is combined with the other torque transmission element 17d opposite to the front and back, and is formed in the torque transmission element 17d on the near side in FIG. The phases in the circumferential direction of the insertion holes 23d and 23d and the insertion holes 23d and 23d formed in the torque transmission element 17d on the back side are matched. According to the configuration as described above, since a pair of torque transmission elements can be shared, a cost reduction effect can be obtained.

  In the case of the structure of each example of the above-described embodiment, a spline hole in which inner teeth (spline teeth) are formed is formed at the base end portion of the worm shaft, and an outer tooth is formed at the distal end portion of the output shaft. The structure in which the spline shaft portion on which (spline teeth) are formed has been described as an example. However, when carrying out the present invention, for example, a spline shaft portion having external teeth (spline teeth) formed at the base end portion of the worm shaft is formed, and an internal tooth (spline teeth) is formed at the distal end portion of the output shaft. ) May be formed. In short, the structure of the proximal end portion of the worm shaft and the structure of the distal end portion of the output shaft may be reversed.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth | gear 6, 6a Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10, 10a Output shaft 11, 11a Female spline tooth | gear 12, 12a Spline hole 13, 13a Male spline Teeth 14, 14a Spline shaft portion 15 Torque transmission member 16 Large diameter portion 17a, 17b, 17c, 17d Torque transmission element 18, 18a Intermediate element 19 Inner diameter side tooth portion 20 Outer diameter side tooth portion 21a, 21b, 21c, 21d Inner diameter side Tooth element 22a, 22b, 22c, 22d, 22e, 22f Outer diameter side tooth element 23a, 23b, 23c, 23d Insertion hole 24 Large diameter hole part 25 Small diameter hole part 26 Body part 27a, 27b Protrusion part 28 Elastic tooth part 29 Axis Part 30 Constriction part

Claims (6)

It is provided between a drive shaft and a driven shaft that are arranged coaxially with each other, and transmits torque between the two shafts. An outer shaft provided on one of these shafts A torque transmission member provided with an inner diameter side tooth portion meshing with a tooth and an outer diameter side tooth portion meshing with an inner tooth provided on the other of these two shafts,
This torque transmission member is composed of a combination of a pair of torque transmission elements arranged on both sides in the axial direction and an intermediate element provided between the two torque transmission elements,
These torque transmission elements are not connected to each other, and are each substantially annular, and of the inner and outer peripheral surfaces, the inner peripheral surface includes an inner diameter side tooth element that constitutes the inner diameter side tooth portion, and the outer peripheral surface includes The outer diameter side tooth elements constituting the outer diameter side tooth portion are respectively provided,
The intermediate element has a substantially annular shape, and is provided with a main body portion made of a material that is more easily elastically deformed than the two torque transmission elements, and protruding from both axial side surfaces of the main body portion to both axial sides. A plurality of protrusions,
An elastic tooth portion that elastically meshes with any one of the outer teeth and the inner teeth without rattling only on one of the inner and outer peripheral surfaces of the main body portion. Provided,
1 is provided on the inner peripheral surface in a state where both the torque transmission elements are supported by the intermediate element by inserting the protrusions into insertion holes formed in the torque transmission elements, respectively. Of the pair of inner diameter side tooth elements and the pair of outer diameter side tooth elements provided on the outer peripheral surface, at least the circumferential direction of the pair of tooth elements located on the opposite side of the elastic tooth portion with respect to the radial direction The phase is shifted, and between these two tooth elements, the other tooth of the outer teeth and the inner teeth is pressed from both sides in the circumferential direction.
Torque transmission member characterized by things.   The torque transmission member according to claim 1, wherein each inner diameter side tooth element and each outer diameter side tooth element are involute teeth.   The torque transmission member according to claim 1, wherein each inner diameter side tooth element and each outer diameter side tooth element are spline teeth.   4. The width dimension in the circumferential direction of at least one tooth element among the inner diameter side tooth elements and the outer diameter side tooth elements is changed in the axial direction. The torque transmission member described in item 1.   5. The tooth length of at least one tooth element among the inner diameter side tooth elements and the outer diameter side tooth elements changes in the axial direction, according to claim 1. Torque transmission member. A driving shaft and a driven shaft that are arranged coaxially with each other, and a substantially annular torque transmission member that transmits torque between the two shafts. The inner shaft is provided on the other shaft, and the inner peripheral surface of the torque transmission member is provided with an inner diameter side tooth portion meshing with the outer tooth on the outer peripheral surface. Is a coupling portion of the drive shaft and the driven shaft, each provided with an outer diameter side tooth portion meshing with the inner tooth,
A coupling portion between a drive shaft and a driven shaft, wherein the torque transmission member is the torque transmission member according to any one of claims 1 to 5.

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