JP2013249909A - Torque transmission joint, and electric power steering device - Google Patents

Abstract

A torque transmission joint 15a that can improve the workability of a buffer member 18a and reduce the manufacturing cost is realized.
A drive-side transmission member 16a that fixes a torque transmission joint 15a to an output shaft 12a of an electric motor, a driven-side transmission member 17a that is fixed to a proximal end portion of a worm shaft 6a, and both the transmission members 16a. , 17a and a buffer member 18a disposed between the two. The buffer member 18a is composed of a plurality of thin-walled cylindrical buffer cylinders 31, each made of an elastic material and independent of each other. Then, these buffer cylinders 31 are mounted on the driving side arm portion 21a provided on the driving side transmission member 16a, and the outer peripheral surfaces of these driving side arm portions 21a are respectively covered. As a result, the buffer cylinders 31 are respectively interposed between the drive side arm portion 21a of the drive side transmission member 16a and the driven side arm portion 23a of the driven side transmission member 17a.
[Selection] Figure 2

Description

  The torque transmission joint according to the present invention is incorporated in various mechanical devices and used to transmit torque between the drive shaft and the driven shaft. The electric power steering device of the present invention is used as a steering device for an automobile. By using an electric motor as an auxiliary power source, the driver can reduce the force required to operate the steering wheel. Is.

  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 begun to spread in recent years. Various structures of such an electric power steering apparatus are known, but in any structure, a rotating shaft that is rotated by the operation of the steering wheel and gives a steered angle to the steered wheels as it rotates. Auxiliary power of the electric motor is applied through a speed reducer. In general, a worm reducer is used as the reducer. In the case of an electric power steering device using a worm speed reducer, a worm that is rotationally driven by the electric motor and a worm wheel that rotates together with the rotating shaft are engaged with each other, and auxiliary power of the electric motor is applied to the rotating shaft. Communicate freely. However, in the case of a worm reducer, if no measures are taken, it is called a rattling sound when changing the rotation direction of the rotating shaft based on the backlash existing in the meshing portion of the worm and the worm wheel. Unpleasant noise may occur.

  Conventionally, as described in Patent Documents 1 to 3, it is considered that the worm is elastically pressed toward the worm wheel by an elastic member such as a spring as a structure that can suppress the generation of such rattling noise. ing. 6 to 7 show an example of the electric power steering device described in Patent Document 2 among them. A front end portion of the steering shaft 2 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. The worm teeth 5 meshing with the worm wheel 4 are provided in the axially intermediate portion of the worm shaft 6, and both end portions in the axial direction of the worm 8 driven to rotate by the electric motor 7 are a pair of rolling bearings such as a deep groove type ball bearing. 9a and 9b are rotatably supported in the housing 3. Further, a pressing piece 10 is externally fitted to a portion protruding from the rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 11 is provided between the pressing piece 10 and the housing 3. ing. The coil spring 11 presses the worm teeth 5 provided on the worm shaft 6 toward the worm wheel 4 through the pressing piece 10. With such a configuration, backlash between the worm teeth 5 and the worm wheel 4 is suppressed, and generation of the rattling noise is suppressed.

  In the case of the conventional structure as described above, it is possible to suppress the occurrence of the rattling noise at the meshing portion between the worm tooth 5 and the worm wheel 4, but the tip of the output shaft 12 of the electric motor 7 and the worm It is not possible to suppress the rattling noise generated at the connecting portion with the base end of the shaft 6. This point will be described below. In the case of the illustrated structure, a spline hole is formed in the base end portion of the worm shaft 6 in order to couple the tip end portion of the output shaft 12 of the electric motor 7 and the base end portion of the worm shaft 6 so that torque can be transmitted. 13 is formed in a state of opening to the base end face of the worm shaft 6. On the other hand, a spline shaft portion 14 is formed at the tip of the output shaft 12. The spline shaft portion 14 and the spline hole 13 are spline-engaged to couple the output shaft 12 and the worm shaft 6 so that torque can be transmitted.

  If the spline shaft portion 14 and the spline hole 13 are spline-engaged without any circumferential clearance (without backlash), the distal end portion of the output shaft 12 and the proximal end portion of the worm shaft 6 No rattling noise is generated at the coupling part (spline engaging part). However, in the actual case, a backlash exists in the spline engaging portion. In particular, in the case of a structure that suppresses backlash between the worm tooth 5 and the worm wheel 4 by the structure as shown in FIG. 7 described above, the spline is required to swing and displace the worm shaft 6. The backlash of the engaging part cannot be completely eliminated. For this reason, it is difficult to prevent the occurrence of rattling noise at the spline engaging portion.

  As a structure that can prevent the occurrence of such rattling noise, for example, in Patent Documents 4 and 5, the end of the drive shaft and the end of the driven shaft are used for torque transmission provided with an elastic buffer member. A structure in which coupling is performed via a coupling (coupling, shaft coupling) is described. 8 to 9 show a torque transmission joint 15 having a conventional structure described in Patent Document 4 among them. The torque transmission joint 15 includes a metal drive-side transmission member 16 that is supported concentrically with the distal end portion of the output shaft 12 of the electric motor that is the drive shaft, and the worm shaft 6 that is the driven shaft. The driven side transmission member 17 made of metal supported concentrically with the base end portion of the base end portion, and the rubber side provided between the driving side transmission member 16 and the driven side transmission member 17. A buffer member 18 and a steel ball 19 are provided.

  Of these, the drive-side transmission member 16 includes a disk-like drive-side base 20 that is supported at the tip end portion of the output shaft 12 so as not to be relatively rotatable, and the driven-side transmission member 17 among the drive-side base 20. Are provided with three drive-side arm portions 21 and 21 provided in a state of protruding in the axial direction intermittently in the circumferential direction. On the other hand, the driven-side transmission member 17 includes a disk-shaped driven-side base 22 that is supported on the base end portion of the worm shaft 6 so as not to be relatively rotatable, and of the driven-side base 22, the driving side On the surface facing the transmission member 16, there are provided three driven side arm portions 23, 23 provided so as to protrude in the axial direction intermittently in the circumferential direction. The buffer member 18 has a generally spur gear shape as a whole, and includes six cylindrical members 24 and six covered members extending radially from the outer peripheral surface of the cylindrical portion 24 in the radial direction (radial direction). Nipping portions 25 and 25 are provided.

  In the assembled state of the torque transmission joint 15, the driving side arm portions 21 and 21 and the driven side arm portions 23 and 23 are alternately arranged in the circumferential direction and adjacent to each other in the circumferential direction. The clamped portions 25 and 25 are interposed between the corresponding drive side arm portion 21 and the driven side arm portion 23, respectively. Further, the steel ball 19 is sandwiched between the distal end surface of the output shaft 12 and the proximal end surface of the worm shaft 6.

  In the case of the conventional torque transmission joint 15 having the above-described configuration, a rubber sandwiched portion 25 is provided between the drive side arm portion 21 and the driven side arm portion 23 adjacent to each other in the circumferential direction. 25 are respectively interposed (clamped). For this reason, it can prevent that the metal drive side arm part 21 and the to-be-driven side arm part 23 contact directly, and it can prevent effectively that the rattling noise as mentioned above generate | occur | produces. Further, during operation, the thrust force transmitted between the output shaft 12 and the worm shaft 6 can be transmitted via the steel ball 19, and this thrust force is not transmitted to the buffer member 18. It will end. For this reason, it is possible to easily ensure the durability of the buffer member 18 over a long period of time.

However, in the case of the torque transmission joint 15 having a conventional structure, the buffer member 18 is configured in a complicated shape as described above. For this reason, when such a buffer member 18 is manufactured by injection molding, the shape of the mold to be used becomes complicated and the manufacturing cost increases, and it is inevitable that the workability of the buffer member 18a is lowered. .
As prior art documents related to the present invention, there is Patent Document 6 in addition to Patent Documents 1 to 5 described above. Patent Document 6 describes an invention in which a buffer member is configured by superimposing three members in the axial direction. However, even in the case of the invention described in Patent Document 6, such a problem as described above cannot be solved.

JP 2000-43739 A JP 2004-306898 A JP-T-2006-513906 Japanese Utility Model Publication No. 3-73745 Japanese Patent No. 4523721 Japanese Patent No. 4779358

  In view of the circumstances as described above, the present invention provides a torque transmission joint that can improve the workability of the buffer member and reduce the manufacturing cost, and an electric power steering apparatus including the torque transmission joint. Invented to realize the above.

Of the torque transmission joint and the electric power steering apparatus according to the present invention, the torque transmission joint according to the first aspect of the present invention is based on the end portions of the drive shaft and the driven shaft that are arranged in series in the axial direction. Torque is transmitted between the drive shaft and the drive side transmission member supported concentrically with the drive shaft at the end of the drive shaft, and supported concentrically with the drive shaft at the end of the driven shaft. A driven-side transmission member, and a buffer member made of an elastic material provided between the driving-side transmission member and the driven-side transmission member.
Of these, the drive-side transmission member is intermittently provided in the circumferential direction on the drive-side base supported by the end of the drive shaft and the surface of the drive-side base that faces the driven-side transmission member. And a plurality of (for example, 2 to 5) drive-side arm portions provided in a state of protruding in the axial direction.
The driven-side transmission member has a driven-side base portion supported by an end portion of the driven shaft and a surface of the driven-side base portion facing the driving-side transmission member in the circumferential direction. Intermittently provided with a plurality (for example, 2 to 5) of driven side arm portions provided in a state of protruding in the axial direction.
And each drive side arm and each driven side arm are alternately arranged in the circumferential direction, and between the driving side arm and the driven side arm adjacent to each other in the circumferential direction, A part of the buffer member is interposed.

In particular, in the case of the torque transmission joint according to the present invention, the buffer member is composed of the same number of independent thin-walled buffer cylinders as the drive arm parts and the driven arm parts. Then, each of these buffer cylinders is externally fitted (attached) to any one (all) of each of the driving side arm parts and each of the driven side arm parts. The outer peripheral surface of each is covered.
When the torque transmission joint according to the present invention is implemented, the cross-sectional shapes of the drive side arm portions and the driven side arm portions and the shape of the buffer cylinders are not particularly limited. For example, as the cross-sectional shape of each driving side arm and each driven side arm, in addition to a polygon such as a trapezoid, a rectangle, a triangle, etc., a circle, an oval with a pair of straight portions, an ellipse, etc. Can be adopted. On the other hand, each buffer cylinder can be externally fitted to any one of the driving side arm parts and the driven side arm parts (matching the outer peripheral surface shape). However, the outer peripheral surface shape does not necessarily need to coincide with the outer peripheral surface shape of the arm portion to be fitted (similar shape).

  When implementing the torque transmission joint of the present invention as described above, for example, as in the invention described in claim 2, the circumferential side surfaces of the respective driving side arm portions and the respective driven side arm portions are arranged. Respectively exist substantially in the radial direction of the driving side transmission member and the driven side transmission member (including not only the case where the driving side transmission member and the driven side transmission member completely coincide with the radial direction but also the case where the inclination angle with respect to the radial direction is within ± 10 degrees. ).

  When the torque transmission joint of the present invention as described above is implemented, for example, as in the invention described in claim 3, the buffer cylinders are stacked in a plurality of buffer cylinder pieces in the axial direction. It consists of.

On the other hand, among the torque transmission joint and the electric power steering device of the present invention, the invention of the electric power steering device according to claim 4 includes a housing, a rotating shaft to be steered, a worm wheel, a worm, An electric motor and a torque transmission joint are provided.
Of these, the housing is supported by a fixed portion and does not rotate.
The rotating shaft for steering is provided so as to be rotatable with respect to the housing, and is rotated by an operation of a steering wheel, and gives a steering angle to the steered wheels in accordance with the rotation.
The worm wheel is supported on a part of the steering rotation shaft inside the housing, concentrically with the steering rotation shaft, and rotates together with the steering rotation shaft.
The worm is formed by providing worm teeth at an axial intermediate portion of the worm shaft. With the worm teeth meshed with the worm wheel, both axial end portions of the worm shaft are respectively attached to the housing by bearings. On the other hand, it is supported rotatably.
The electric motor is for rotating the worm.
Further, the torque transmission joint is provided between the output shaft of the electric motor and the worm shaft, and transmits torque between the two shafts. This is a transmission joint.

According to the torque transmission joint and the electric power steering apparatus of the present invention having the above-described configuration, the workability of the buffer member can be improved and the manufacturing cost can be reduced.
That is, in the case of the present invention, the buffer member made of an elastic material is formed into an independent thin-walled cylindrical shape that is fitted around either one of the driving side arm portion and the driven side arm portion, respectively. It consists of a buffer cylinder. For this reason, each of these buffer cylinders can be miniaturized and the shape thereof can be simplified. Moreover, such a buffer cylinder can be manufactured by extrusion molding, and even when it is manufactured by injection molding, the injection mold to be used can be reduced in size and simplified. Therefore, according to the present invention, the workability of the buffer member can be improved and the manufacturing cost can be reduced.

  Further, in the case of the invention described in claim 2, the circumferential side surface of the driving side arm portion constituting the driving side transmission member and the circumferential side surface of the driven side arm portion constituting the driven side transmission member By engaging with each other, the center axis of the driving side transmission member and the driven side transmission member can be aligned (centered).

  Further, in the case of the invention described in claim 3, it is possible to make the magnitude of elasticity different, the size, the shape, etc., between the plurality of buffer cylinder pieces constituting the buffer cylinder. For this reason, the timing at which the buffer cylinder piece is elastically deformed between the driving side arm part and the driven side arm part at the start of torque transmission or at the time of torque variation varies among the plurality of buffer cylinder pieces. It can be shifted (for example, it is made to be elastically deformed first from the buffer cylinder piece which is easily elastically deformed). Therefore, it is possible to improve the degree of freedom in adjusting the torque transmission characteristics (the relationship between the rotation amount of the output shaft and the transmission torque).

The principal part sectional view of the electric power steering device which incorporated the joint for torque transmission which shows the 1st example of an embodiment of the invention. The exploded perspective view which similarly takes out the joint for torque transmission, and shows typically. The expanded AA sectional view of Drawing 1 similarly. The end view which takes out and shows a buffer member similarly. The exploded perspective view which takes out the joint for torque transmission incorporated in the electric power steering device of the 2nd example of an embodiment of the invention, and shows it typically. The partial longitudinal section side view showing an example of the steering device for cars. The expanded BB sectional view of Drawing 6 showing an example of the conventional structure of an electric power steering device. The disassembled perspective view which shows the joint for torque transmission of the conventional structure. FIG. 4 is a cross-sectional view corresponding to FIG. 3.

[First example of embodiment]
1-4 show a first example of an embodiment of the present invention corresponding to claims 1, 2, and 4. FIG. In the case of this example, the torque of this example is between the distal end portion of the output shaft 12a of the electric motor 7 constituting the electric power steering device and the proximal end portion of the worm shaft 6a constituting the worm type reduction gear. A transmission joint 15a is provided so that torque can be transmitted from the output shaft 12a to the worm shaft 6a. The configuration and operation of the electric power steering apparatus excluding the torque transmission joint 15a are the same as those of the conventionally known electric power steering apparatus including the structure shown in FIGS. The description will be omitted, and the configuration and operation of the torque transmission joint 15a will be described below.

  The torque transmission joint 15a is provided at a distal end portion of the output shaft 12a, which is a drive shaft, at a drive side transmission member 16a supported concentrically with the distal end portion and at a proximal end portion of the worm shaft 6a, which is a driven shaft. A driven-side transmission member 17a supported concentrically with the base end, a buffer member 18a made of an elastic material provided between the driving-side transmission member 16a and the driven-side transmission member 17a, and a damper member 26; Is provided.

  Of these, the drive-side transmission member 16a is made of metal and includes a drive-side base portion 20a and four drive-side arm portions 21a and 21a. The drive-side base 20a has a disk shape, and a drive-side serration hole 27 that engages with a male serration formed on the outer peripheral surface of the tip end of the output shaft 12a is formed at the center. Each of the drive side arm portions 21a, 21a has a trapezoidal columnar shape (cross-section isosceles trapezoidal shape) whose width in the circumferential direction increases toward the outer side in the radial direction. They are provided on the outer diameter portion of the surface facing the driven transmission member 17a intermittently in the circumferential direction (with the phase shifted by 90 degrees) so as to protrude in the axial direction. Further, the circumferential side surfaces 28, 28 of the drive side arm portions 21a, 21a substantially exist in the radial direction (on the virtual plane including the central axis) of the drive side transmission member 16a (diameter). This includes not only the case where the direction completely coincides but also the case where the inclination angle with respect to the radial direction is within ± 10 degrees). The axial dimensions of the drive side arm portions 21a and 21a are the same as the axial direction dimensions of the driven side arm portions 23a and 23a described later.

  On the other hand, the driven-side transmission member 17a is made of metal and includes a driven-side base portion 22a and four driven-side arm portions 23a and 23a. Of these, the driven side base 22a has a disk shape, and a driven side serration hole 29 is formed in the center of the driven side serration hole 29 that engages with the male serration formed on the outer peripheral surface of the base end of the worm shaft 6a. Has been. Each of the driven side arm portions 23a, 23a has a trapezoidal columnar shape (cross-section isosceles trapezoidal shape) whose width in the circumferential direction increases toward the outer side in the radial direction. Thus, they are provided on the outer diameter portion of the surface facing the drive-side transmission member 16a intermittently in the circumferential direction (with the phase shifted by 90 degrees) so as to protrude in the axial direction. Further, the circumferential side surfaces 30, 30 of the driven side arm portions 23a, 23a are also substantially present in the radial direction of the driven side transmission member 17a (only when they completely coincide with the radial direction). Not including the case where the inclination angle with respect to the radial direction is within ± 10 degrees). In the case of the structure shown in the figure, the width dimension in the radial direction of each of the driving side arm portions 21a, 21a is made slightly smaller than the width dimension in the radial direction of each of the driven side arm portions 23a, 23a. The width dimension in the circumferential direction of each of the drive side arm portions 21a, 21a is set to about ½ of the width dimension in the circumferential direction of each of the driven side arm portions 23a, 23a.

  The buffer member 18a is composed of a total of four buffer cylinders 31 and 31, which are independent of each other, and are the same in number as the drive arm parts 21a and 21a and the driven arm parts 23a and 23a. Yes. Each of these buffer cylinders 31, 31 is integrally formed of an elastic material such as rubber, an elastomer such as vinyl, or a synthetic resin, and has an overall shape of a trapezoidal cylinder. The buffer cylinders 31 and 31 have a constant thickness over the entire circumference, and the axial dimensions of the buffer cylinders 31 and 31 are the same as those of the driving side arm portions 21a and 21a (and the driven side arm portions 23a and 23a). Equal to the axial dimension. In the case of this example, the buffer bodies 31, 31 having such a configuration are externally fitted (press-fitted) without rattling to all the drive side arm parts 21a, 21a. The outer peripheral surfaces of 21a and 21a are covered. Further, of the buffer cylinders 31, the portions existing on both sides in the circumferential direction in the assembled state to the respective drive side arm portions 21 a, 21 a are the respective drive side arm portions 21 a, The clamped portions 25a and 25a are elastically clamped (elastically deformed) between the driven arm portions 23a and 23a.

  In the case of this example, an elastic material such as elastomer or synthetic resin is extruded to form a long trapezoidal cylindrical intermediate material, and then the intermediate material has a predetermined length (driving side arm portions 21a, 21a and The buffer cylinders 31, 31 having the above-described configuration are obtained. However, the buffer cylinders 31 and 31 of this example are not only such extrusion molding, but also an outer mold having an inner surface shape that matches the outer surface shape of each of the buffer cylinders 31 and 31, and the inner surfaces of the buffer cylinders 31 and 31. It can also be made by injection molding using an inner mold having an outer surface shape that matches the shape.

  The damper member 26 is provided radially inward of the buffer cylinders 31 and 31 (buffer member 18a) between the drive side transmission member 16a and the driven side transmission member 17a. And a damper part body 33 that is externally fitted around the intermediate part in the axial direction of the post part 32 (externally fitted so as to allow displacement in the axial direction). Among these, the support | pillar part 32 is metal, and each edge part is loosely inserted in each said drive side and the driven side serration holes 27 and 29. As shown in FIG. The damper part body 33 is made of an elastic material such as rubber or synthetic resin, and its axial dimension is such that the buffer member 18a (buffer cylinders 31, 31) and the arm parts 21a on the driving side and driven side are respectively It is larger than the axial dimension of 23a. Such a damper portion main body 33 is inserted radially inward of the buffer cylinders 31 and 31 with a gap around the entire circumference, and is formed between the driving side base portion 20a and the driven side base portion 22a. It is clamped in the axial direction between the surfaces facing each other. In the case of this example, the damper main body 33 is elastic to some extent in the axial direction between the both end surfaces of the support column 32 and the distal end surface of the output shaft 12a and the proximal end surface of the worm shaft 6a. A gap of a size that disappears when deformed is provided.

  When assembling the torque transmission joint 15a of this example, first, the buffer cylinders 31 and 31 are respectively connected to the drive side arm portions 21a and 21a from the front end side of the drive side arm portions 21a and 21a. Wear without wobbling. Thereafter, the drive-side transmission member 16a and the driven-side transmission member 17a are combined in the axial direction so as to sandwich the damper member 26, and the drive-side arm portions 21a, 21a and the driven-side arms are combined. The portions 23a and 23a are alternately arranged in the circumferential direction. In this state, the clamped portions 25a and 25a constituting the buffer cylinders 31 and 31 are respectively positioned between the drive-side arm portion 21a and the driven-side arm portion 23a adjacent in the circumferential direction. .

In the case of the torque transmission joint 15a and the electric power steering device of the present example having the above-described configuration, the workability of the buffer member 18a can be improved and the manufacturing cost can be reduced.
That is, in the case of this example, the buffer member 18a made of an elastic material is composed of independent thin-walled cylindrical buffer cylinders 31 and 31 that are externally fitted to the drive side arm portions 21a and 21a, respectively. . For this reason, these buffer cylinders 31 and 31 can be reduced in size and the shape thereof can be simplified. Moreover, as described above, the buffer cylinders 31 and 31 can be easily manufactured by extrusion molding and cutting as described above, and the buffer member 18 having the conventional structure described above (see FIG. 8 and 9), the injection mold to be used can be reduced in size and simplified. Therefore, according to the structure of this example, the workability of the buffer member 18a can be improved and the manufacturing cost can be reduced.

  In the case of this example, the circumferential side surfaces 28 and 28 of the respective driving side arm portions 21a and 21a and the circumferential side surfaces 30 and 30 of the respective driven side arm portions 23a and 23a, respectively, The drive-side transmission member 16a and the driven-side transmission member 17a are substantially present in the radial direction. For this reason, even when the drive-side transmission member 16a and the driven-side transmission member 17a try to relatively displace each other in the radial direction, the circumferential side surfaces 28, 28 of the drive-side arm portions 21a, 21a, By engaging the circumferential side surfaces 30, 30 of the driven arm portions 23 a, 23 a via the buffer cylinders 31, 31 (held portions 25 a, 25 a), the driving transmission member 16a and the driven transmission member 17a can be aligned (centered). Specifically, for example, from the state shown in FIG. 3, when the drive side transmission member 16a attempts to relatively displace downward with respect to the driven side transmission member 17a, the upper side of the drive side transmission member 16a. The circumferential side surfaces 28, 28 of one driving side arm portion 21a are a circumferential side surface of a pair of driven side arm portions 23a, 23a provided on both sides in the circumferential direction of the driving side arm portion 21a. 30 and 30 are engaged (contacted). This prevents the drive-side transmission member 16a from being displaced further.

Also in the case of this example, as in the case of the conventional structure, each sandwiched portion made of an elastic material is provided between the drive side arm portion 21a and the driven side arm portion 23a adjacent in the circumferential direction. Since 25a and 25a are interposed, generation of rattling noise can be effectively prevented. Further, when a thrust force is applied between the output shaft 12a and the worm shaft 6a, the damper member 26 is disposed between the mutually opposing surfaces of the driving side base portion 20a and the driven side base portion 22a. Is elastically deformed (contracted) in the axial direction, and the remaining thrust force is transmitted while absorbing a part of the thrust force. Therefore, the thrust force transmitted between the output shaft 12a and the worm shaft 6a can be reduced. Further, since the thrust force can be effectively prevented from being transmitted to the buffer member 18a (buffer cylinders 31, 31), the durability of the buffer member 18a can be ensured over a long period of time.
Other configurations, operations, and effects are the same as those of the conventional torque transmission joint and the electric power steering apparatus described above.

[Second Example of Embodiment]
FIG. 5 shows a second example of an embodiment of the invention corresponding to all claims. A feature of the torque transmission joint 15b of this example is that the buffer cylinders 31a and 31a constituting the buffer member 18b are configured by stacking a plurality of buffer cylinder pieces 34 and 34a in the axial direction. Since the configuration and operational effects of the other parts are the same as in the case of the first example of the above-described embodiment, the explanation and illustration of the overlapping parts are omitted or simplified. The explanation will be focused on.

  In the case of this example, each of the buffer cylinders 31a and 31a has three shapes such as the buffer cylinders 31 and 31 used in the first example of the above-described embodiment divided into three (sliced into three) in the axial direction. The buffer cylinder pieces 34, 34a are configured by laminating them in the axial direction. In addition, the buffer cylinder piece 34a disposed at the center in the axial direction is made of a material that is easily elastically deformed as compared to the pair of buffer cylinder pieces 34, 34 disposed on both sides in the axial direction. Specifically, the buffer cylinder piece 34a is made of an elastically deformable material such as an elastomer such as rubber or vinyl, and the pair of buffer cylinder pieces 34, 34 disposed on both sides in the axial direction is made of an elastomer or the like. It is made of a synthetic resin such as polyacetal resin or polyamide resin, which is less likely to be elastically deformed. Further, the thickness of the buffer cylinder piece 34a arranged at the center in the axial direction is made slightly thicker than the thickness of the pair of buffer cylinder pieces 34, 34 arranged on both sides in the axial direction.

  Of the buffer cylinder pieces 34, 34a, the portions located on both sides in the circumferential direction in the assembled state to the drive side arm portions 21a, 21a are the drive side arm portions 21a, 21a when torque is transmitted. And the driven arm portions 23a and 23a are elastically clamped (elastically deformed), and are sandwiched in the axial direction so as to constitute the clamped portions 25b and 25b. It becomes.

In the case of this example having the above-described configuration, each of the buffer cylinders is first provided between the driving side arm portions 21a and 21a and the driven side arm portions 23a and 23a at the start of torque transmission or when the torque changes. The element sandwiching portions 35a and 35a of the buffer cylinder piece 34a, which is made of an elastically deformable material disposed at the center in the axial direction of 31a and 31a, are elastically deformed. Then, after the buffer cylinder piece 34a is elastically deformed by a predetermined amount, the element sandwiching portions 35 and 35 of the buffer cylinder pieces 34 and 34 disposed on both sides in the axial direction are elastically deformed. Thus, in the case of this example, the timing at which each of the buffer cylinder pieces 34, 34a is elastically deformed can be variously shifted between the plurality of buffer cylinder pieces 34, 34a. Therefore, it is possible to improve the degree of freedom in adjusting the torque transmission characteristics (the relationship between the rotation amount of the output shaft 12a and the transmission torque).
About another structure and an effect, it is the same as that of the case of the 1st example of embodiment mentioned above.

  In each example of the embodiment described above, only the case where the cross-sectional shape of the driving side arm portion and the driven side arm portion is trapezoidal and the buffer cylinder constituting the buffering member is trapezoidal cylindrical shape is shown. In carrying out the invention, the cross-sectional shape of each arm portion on the driving side and the driven side and the shape of the buffer cylinder are not limited to such shapes. For example, the cross-sectional shape of each arm on the driving side and the driven side is a polygon such as a rectangle or a triangle, a circle, an oval, an ellipse, etc., and the shape of the buffer is a rectangle cylinder, a triangle cylinder, etc. In addition, it may be formed in a cylindrical shape, a long cylindrical shape, an elliptical cylindrical shape, or the like. Further, the buffer cylinder does not need to have a constant thickness over the entire circumference. For example, a portion of the buffer cylinder that becomes the sandwiched portion may be thickened and the other portions may be thinned.

  Further, in the second example of the embodiment described above, the case where the buffer cylinder is constituted by three buffer cylinder pieces has been described, but the buffer cylinder is constituted by laminating a plurality of buffer cylinder pieces in the axial direction. In this case, the buffer cylinder may be constituted by two buffer cylinder pieces, or may be constituted by three or more (for example, four, five, or more) buffer cylinder pieces. Moreover, all the buffer cylinder pieces which comprise a buffer cylinder can also be made from the same material, and all the buffer cylinder pieces may be made from a different material.

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 Pressing piece 11 Coil spring 12, 12a Output shaft 13 Spline hole 14 Spline shaft part 15, 15a 15b Torque transmission joint 16, 16a Drive-side transmission member 17, 17a Drive-side transmission member 18, 18a, 18b Buffer member 19 Steel ball 20, 20a Drive-side base 21, 21a Drive-side arm portion 22, 22a Drive-side Base part 23, 23a Driven side arm part 24 Cylindrical part 25, 25a, 25b Clamped part 26 Damper member 27 Drive side serration hole 28 Circumferential side face 29 Driven side serration hole 30 Circumferential side face 31 Buffer cylinder 32 Strut part 33 Damper body 34, 34a Buffer cylinder piece 35, 35a Element holding part

Claims (4)

Torque is transmitted between the ends of the drive shaft and the driven shaft that are arranged in series with each other in the axial direction.
A drive-side transmission member supported concentrically with the drive shaft at an end of the drive shaft, a driven-side transmission member supported concentrically with the driven shaft at an end of the driven shaft, and these drive sides A buffer member made of an elastic material provided between the transmission member and the driven-side transmission member;
Of these, the drive-side transmission member is intermittently provided in the circumferential direction on the drive-side base supported by the end of the drive shaft and the surface of the drive-side base that faces the driven-side transmission member. , Each having a plurality of driving side arm portions provided in a state of protruding in the axial direction,
The driven-side transmission member is intermittently provided in a circumferential direction on a driven-side base supported by an end portion of the driven shaft and a surface of the driven-side base that faces the driving-side transmission member. And a plurality of driven side arms provided in a state of projecting in the axial direction,
The driving side arm portions and the driven side arm portions are alternately arranged in the circumferential direction, and the buffer is provided between the driving side arm portion and the driven side arm portion adjacent to each other in the circumferential direction. In the torque transmission joint that interposes some of the members,
The buffer member is composed of the same number of independent thin-walled buffer cylinders as the drive arm parts and the driven arm parts, and each of the buffer cylinders is provided with the drive arm parts. And the outer arm of each of the driven side arms and covering the outer peripheral surface of each of the arms,
A torque transmission joint characterized by   The joint for torque transmission according to claim 1, wherein the circumferential side surfaces of the driving side arm portion and the driven side arm portion substantially exist in the radial direction of the driving side transmission member and the driven side transmission member, respectively.   The joint for torque transmission according to claim 1, wherein the buffer cylinder is configured by stacking a plurality of buffer cylinder pieces in the axial direction.   A housing that is supported by a fixed portion and does not rotate, and a steering rotation that is provided rotatably with respect to the housing and is rotated by an operation of a steering wheel, and gives a steering angle to a steered wheel as it rotates. A shaft, a worm wheel that is supported concentrically with the steering rotation shaft inside the housing and rotates with the steering rotation shaft, and an axially intermediate portion of the worm shaft. A worm comprising worm teeth, in which the worm teeth are engaged with the worm wheel, and both end portions in the axial direction of the worm shaft are rotatably supported with respect to the housing by bearings, and the worm is rotated. It is possible to transmit torque by using a torque transmission joint between the output shaft of the electric motor and the worm shaft. In the electric power steering apparatus that continue to this torque-transmitting joint, a torque-transmitting joint as set forth in any one of claims 1 to 3, an electric power steering apparatus.

Images