JP2010001966A - Rotating shaft coupling, and rotation drive with worm reducer - Google Patents

Abstract

A shaft preload portion 20a made of an elastic material is elastic when a spline hole 11b provided at a proximal end portion of a worm 8 is inclined with respect to a spline shaft portion 12a provided at a distal end portion of an output shaft 10 of an electric motor. The structure which can prevent bending deformation is realized.
Of the back end surface 24a of the spline hole 11b and the front end surface 25 of the shaft preloading portion 20a that are in contact with each other, the back end surface 24a is a partially spherical concave surface, and the front end surface 25 is the back end surface 24a. And a partially spherical convex surface having the same radius of curvature. By adopting such a configuration, the above-mentioned problem is solved by moving the contact position of the tip end face 25 with respect to the back end face 24a as the inclination occurs.
[Selection] Figure 4

Description

  The present invention relates to an improvement of a rotary drive device with a worm speed reducer that can be used as, for example, an electric power steering device, and a rotary shaft joint that can be used by being incorporated therein.

  A power steering device is widely used as a device to reduce 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) Has been. 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.

  For example, Patent Document 1 describes an electric power steering device as shown in FIGS. A front end portion of a steering shaft 2 that is a driven shaft and 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 that mesh with the worm wheel 4 are provided in the axially intermediate portion of the worm shaft 6, and both ends of the worm 8 that is rotationally driven by the electric motor 7 that is a rotational drive device are a pair of deep groove ball bearings or the like. Are rotatably supported in the housing 3 by rolling bearings 9a and 9b. In order to rotationally drive the worm 8 by the output shaft 10 which is the drive shaft of the electric motor 7, a spline hole 11 is formed at the base end portion (right end portion in FIG. 7) of the worm shaft 6 and the base of the worm shaft 6. It forms in the state opened to an end surface. A spline shaft 12 is formed at the tip of the output shaft 10. The spline shaft portion 12 and the spline hole 11 are spline-engaged so that the output shaft 10 and the worm shaft 6 are freely coupled to transmit rotational force.

  Further, in the case of the conventional structure shown in FIG. 7, in order to eliminate backlash at the meshing portion between the worm wheel 4 and the worm tooth 5, the tip portion (the left end portion in FIG. 7) of the worm shaft 6 is connected to the worm wheel. The wheel 4 is elastically pressed toward the wheel 4. That is, the pressing piece 13 is externally fitted to a portion protruding from the leading end side rolling bearing 9 a at the tip of the worm shaft 6, and an elastic member such as a coil spring 14 is provided between the pressing piece 13 and the housing 3. Provided. The worm teeth 5 are pressed against the worm wheel 4 by the coil spring 14 via the pressing piece 13. With such a configuration, backlash between the worm teeth 5 and the worm wheel 4 is suppressed, and the meshing portion between the worm wheel 4 and the worm teeth 5 when the electric motor 7 is started or when the rotation direction is switched. The generation of rattling noise in the case is suppressed.

  In the electric power steering apparatus as described above, it is possible to suppress the occurrence of rattling noise at the meshing portion between the worm wheel 4 and the worm tooth 5, but the spline engagement between the spline shaft portion 12 and the spline hole 11. Generation of rattling noise at the joint cannot be suppressed. In particular, it is necessary to provide a certain gap in the spline engaging portion. The reason for this is to make it easy to perform spline engagement between the spline hole 11 and the spline shaft portion 12, and further, backlash between the worm wheel 4 and the worm teeth 5. This is because the tip end portion of the worm shaft 6 can be oscillated and displaced toward the worm wheel 4. Based on the gap between the spline engaging portions provided for these reasons, the side surfaces of the male spline teeth and the side surfaces of the female spline teeth are formed at the spline engaging portions when the electric motor 7 is started or when the rotation direction is switched. Noise and vibration are generated based on the collision with

  Japanese Patent Application No. 2007-203450 discloses a structure as shown in FIGS. 8 to 9 as a structure that can effectively prevent the occurrence of such a problem. In the case of the structure of the prior invention shown in FIGS. 8 to 9, the spline hole 11 a is opened at the base end portion of the worm shaft 6 and the base end surface of the worm shaft 6 is opened as in the case of the conventional structure described above. The worm shaft 6 is formed concentrically. Further, a spline shaft portion 12 a is formed concentrically with the output shaft 10 at the distal end portion of the output shaft 10 of the electric motor 7 (see FIG. 7). The spline shaft portion 12a and the spline hole 11a are spline-engaged to couple the output shaft 10 and the worm shaft 6 so as to be able to transmit rotational force.

  The spline shaft portion 12 a has a tip half portion as a small diameter portion 15 and a base half portion as a large diameter portion 16. The male spline teeth formed on the outer peripheral surfaces of the small-diameter portion 15 and the large-diameter portion 16 and the female spline teeth formed on the inner peripheral surface of the spline hole 11a are similar, but different in size. That is, the size of the outer peripheral surface of the small diameter portion 15 is made sufficiently smaller than the size of the inner peripheral surface of the spline hole 11a, and the size of the outer peripheral surface of the large diameter portion 16 is slightly reduced. ing. And between the outer peripheral surface of the said small diameter part 15 and the inner peripheral surface of the said spline hole 11a, and between the front end surface 23 of the said spline shaft part 12a, and the back end surface 24 of the said spline hole 11a, the elastic member 17 is provided. The large-diameter portion 15 is spline-engaged with the spline hole 11a through a small gap.

  The elastic member 17 is integrally made of rubber such as nitrile rubber, silicon rubber, urethane rubber, ethylene acrylic rubber, hydrogenated nitrile rubber, or an elastic material such as thermoplastic elastomer such as polyurethane or synthetic resin. It consists of a buffer cylinder portion 18 that is a buffer member, a connecting portion 19, and a shaft preload portion 20 that is a shaft preload member. Among these, the buffer cylinder portion 18 can be externally fitted to the small diameter portion 15 of the spline shaft portion 12a, and is formed in a six star cylinder shape according to the outer peripheral surface shape of the small diameter portion 15. The size of the inner peripheral surface of the buffer cylinder portion 18 in the free state is preferably slightly smaller than the size of the outer peripheral surface of the small diameter portion 15, so that the buffer cylinder portion 18 is connected to the small diameter portion 15. It is designed to be fitted with a light interference fit. In addition, the size of the outer peripheral surface of the buffer cylinder 18 is slightly larger than the size of the outer peripheral surface of the large diameter portion 16, and is slightly larger or slightly larger than the inner peripheral surface of the spline hole 11a. To make it smaller. Thereby, the buffer cylinder 18 can be fitted into the spline hole 11a by a light interference fit or a gap fit. In the state in which the electric power steering apparatus is assembled, such a buffer cylinder portion 18 is installed between the outer peripheral surface of the small diameter portion 15 and the inner peripheral surface of the spline hole 11a.

  The connecting portion 19 is provided so as to close the opening on the front end side of the buffer cylinder portion 18, and the shaft preload portion 20 extends from the inner peripheral edge portion of the connecting portion 19 to the buffer cylinder portion 18. And projecting in the opposite axial direction. In the case of the illustrated example, the shaft preload portion 20 has a bottomed cylindrical shape with the tip side closed. With the electric power steering device assembled, such a shaft preload portion 20 is elastically compressed in the axial direction between the tip surface 23 of the spline shaft portion 12a and the back end surface 24 of the spline hole 11a. Installed. The shaft preload portion 20 may be a hollow body that is not clogged with elasticity to the center as described above, or a solid body that is clogged with an elastic material to the center. Whether it is a hollow body or a solid body is selected by design consideration according to the required elasticity.

  In the case of the electric power steering device of the prior invention configured as described above, when the auxiliary power is applied from the electric motor 7 to the steering shaft 2 (see FIG. 7), the electric motor 7 is as follows. Torque is transmitted from the output shaft 10 to the worm 8. First, when the auxiliary power is small, the worm 8 is connected to the worm 8 from the output shaft 10 via the buffer cylinder portion 18 of the elastic member 17 installed between the small diameter portion 15 of the spline shaft portion 12a and the spline hole 11a. Torque is transmitted to At this time, the side surface of the male spline tooth provided on the outer peripheral surface of the large diameter portion 16 of the spline shaft portion 12a does not contact the side surface of the female spline tooth provided on the inner peripheral surface of the spline hole 11a. On the other hand, when the auxiliary power increases, the amount of elastic deformation in the circumferential direction of the buffer cylinder 18 increases, and the side surface of the male spline teeth provided on the outer peripheral surface of the large diameter portion 16 and the spline hole The side surface of the female spline teeth provided on the inner peripheral surface of 11a abuts. In this state, the spline engaging portion between the large-diameter portion 16 and the spline hole 11a transmits torque that cannot be transmitted by the elasticity of the buffer cylinder portion 18. In the process of increasing the auxiliary power, the side surface of the male spline tooth and the side surface of the female spline tooth collide, but this collision is performed slowly based on the elasticity of the buffer cylinder portion 18. For this reason, it is possible to effectively prevent the occurrence of noise and vibration called rattling noise due to this collision.

Further, when the electric power steering device of the above-described invention is operated, the output shaft 10 and the worm 6 rattle in the axial direction. The shaft preloading portion 20 of the elastic member 17 causes the output shaft 10 and the worm to move. 6 is elastically pressed in a direction away from each other. For this reason, generation | occurrence | production of the noise and vibration accompanying the said shakiness can be prevented effectively.
In the case of the structure of the prior invention described above, the buffer cylinder portion 18 and the shaft preload portion 20 are configured as an integral elastic member 17 coupled via the connecting portion 19. The buffer cylinder portion 18 and the shaft preload portion 20 can be easily assembled between the output shaft 10 and the worm 8. That is, not only the space for assembling the elastic member 17 is reduced, but also the operation of assembling the elastic member 17 can be performed easily.

  However, the structure of the above-described prior invention still has room for improvement. That is, in the case of the structure of the prior invention described above, the elasticity of the coil spring 14 is used to suppress backlash between the worm wheel 4 and the worm tooth 5 as in the case of the conventional structure shown in FIG. Further, a configuration is adopted in which the tip of the worm 8 is oscillated and displaced toward the worm wheel 4. Thus, when the tip of the worm 8 is oscillated and displaced toward the worm wheel 4, the spline hole 11a is inclined with respect to the spline shaft portion 12a. However, in the case of the structure of the above-described prior invention, the back end surface 24 of the spline hole 11a is a conical concave surface, and the tip edge of the shaft preloading portion 20 is only displaced in the axial direction on the back end surface 24. And engaged in a state where radial displacement is also prevented. Therefore, when the spline hole 11a is inclined with respect to the spline shaft portion 12a as described above, the shaft preload portion 20 is elastically bent and deformed, and the shaft preload portion 20 is elastically restored. Works. Since this restoring force is a force that resists the elasticity of the coil spring 14, a part of the elasticity of the coil spring 14 is offset by the restoring force. As a result, there arises a problem that the effect of suppressing the backlash is reduced. In addition, it is not preferable that the shaft preload portion 20 is elastically bent and deformed as described above because the durability of the shaft preload portion 20 is reduced.

JP 2004-306898 A

  In view of the above-described circumstances, the rotary shaft joint and the rotary drive device with the worm reducer according to the present invention have a spline hole provided at the ends of both rotary shafts when the pair of rotary shafts are inclined to each other. The invention was invented to realize a structure capable of preventing the shaft preload member from being elastically bent and deformed between the back end surface and the tip surface of the spline shaft portion.

Of the rotary shaft joint and the rotary drive device with a worm reducer according to the present invention, the rotary shaft joint described in claim 1 is provided at the end of one of the pair of rotary shafts at the end surface of the end. A bottomed spline hole provided in an open state and the end of the other rotary shaft of the two rotary shafts, and torque between the rotary shafts with respect to the spline hole. Between the spline shaft portion that is spline-engaged to allow transmission and allow slight inclination between the two rotation shafts, and between the back end surface of the spline hole and the tip surface of the spline shaft portion And a shaft preload member made of an elastic material elastically compressed in the axial direction.
In particular, in the rotary shaft coupling according to claim 1, the back end surface of the spline hole is a partially spherical concave surface, and the surface of the shaft preload member in contact with the deep end surface is the curvature of the partial spherical concave surface. A partially spherical convex surface having a radius of curvature equal to or less than the radius is used.

When the rotary shaft coupling of the present invention having the above-described features is carried out, it is preferable that a cylindrical shock absorber made of an elastic material is provided between the outer peripheral surface of the spline shaft portion and the inner peripheral surface of the spline hole. Hold the member.
In this case, more preferably, the shaft preload member and the buffer member are integrally formed via a connecting portion.

When the rotary shaft coupling of the present invention as described above is implemented, the shape of the shaft preload member can be made spherical, for example, as in the invention described in claim 2.
When the rotary shaft joint of the present invention as described above is implemented, preferably, as in the invention described in claim 3, the surface of the shaft preload member and the surface of the mating member (the back end surface of the spline hole) And a lubricant such as grease is interposed in the contact portion with the tip surface of the spline shaft portion.

According to a fourth aspect of the present invention, there is provided a rotary drive device with a worm reduction gear on the outer surface of a housing and a driven shaft rotatably supported in the housing, concentrically with the driven shaft. A worm wheel supported and rotated together with the driven shaft, a worm rotatably supported in the housing in mesh with the worm wheel, and a distal end portion of the drive shaft at the base end portion of the worm. , A rotation drive device coupled and fixed to the housing in a state of being coupled by a rotary shaft joint, and applying a preload by pressing the worm toward the worm wheel and applying a preload to the meshing portion between the worm and the worm wheel Means.
In particular, in the rotary drive device with a worm speed reducer described in claim 4, the rotary shaft joint is the rotary shaft joint of the present invention described above.

  In addition, the rotary drive device with a worm speed reducer of the present invention as described above can be used as an electric power steering device, for example. In this case, the driven shaft is a rotating shaft that is rotated by an operation of the steering wheel and gives a steering angle to the steered wheels as it rotates. As such a rotating shaft, in addition to the steering shaft 2 shown in FIG. 6, the intermediate shaft 21, the input shaft (pinion shaft) of the steering gear unit 22, and the like can be employed. Of course, the fixed portion for supporting the housing differs depending on which of the rotating shafts. The rotary drive device is an electric motor, and the drive shaft is an output shaft of the electric motor.

  According to the rotary shaft coupling and the rotary drive device with the worm speed reducer of the present invention configured as described above, the shaft preload member with respect to the back end surface of the spline hole is inclined as the spline hole and the spline shaft portion are inclined to each other. The surface contact position can be moved. Based on the movement of the contact position, the shaft preload member can be prevented or suppressed from being elastically bent and deformed. For this reason, it is possible to prevent or suppress the occurrence of problems such as an elastic restoring force acting in the direction of preventing the inclination on the shaft preload member or a decrease in durability of the shaft preload member.

Further, in the case of the invention described in claim 2, as the spline hole and the spline shaft portion are inclined with respect to each other, the contact position of the surface of the shaft preload member with respect to the back end surface of the spline hole and the spline shaft portion The contact position of the surface of the shaft preload member with respect to the tip surface can be moved. For this reason, it is possible to more effectively prevent the shaft preload member from being elastically bent and deformed based on the movement of each contact position.
Moreover, in the case of the invention described in claim 3, the movement of each contact position can be performed smoothly by the action of the lubricant.

[First example of embodiment]
1 to 4 show a first example of an embodiment of the present invention corresponding to claims 1, 3 and 4. The feature of this example is that the shapes of the back end surface 24a of the spline hole 11b and the tip end surface 25 of the shaft preloading portion 20a constituting the elastic member 17a, which are in contact with each other in use, are devised. . The structure and operation of other parts are substantially the same as the structure of the previous invention shown in FIGS. For this reason, the same parts are denoted by the same reference numerals, and overlapping illustrations and descriptions are omitted or simplified. Hereinafter, the characteristic parts of this example and parts different from the structure of the above-described invention will be mainly described.

  In the case of this example, the back end surface 24a of the spline hole 11b is a partially spherical concave surface, and the tip surface 25 of the shaft preload portion 20a is a partially spherical convex surface having the same radius of curvature as the back end surface 24a. The entire end face 25 is brought into contact with the back end face 24a via a film of grease as a lubricant. Further, the centers of curvature of the back end face 24a and the tip end face 25 coincide with the inclination center O between the spline hole 11b and the spline shaft portion 12a shown in FIG. In the case of this example, the outer peripheral surface of the shaft preload portion 20a is a tapered surface whose diameter dimension decreases toward the tip side. The shaft preload portion 20a is a solid body filled with an elastic material up to the center.

  According to the electric power steering device of the present example configured as described above, as shown in the order of (A) → (B) in FIG. 4, the spline hole 11b is inclined with respect to the spline shaft portion 12a. The contact position (the center point) of the tip surface 25 of the shaft preload portion 20a with respect to the back end surface 24a of the spline hole 11b can be moved smoothly. Based on the movement of the contact position (the center point thereof), the shaft preload portion 20a can be prevented or suppressed from being elastically bent and deformed. For this reason, it is possible to prevent or suppress the elastic restoring force {force against the elastic force of the coil spring 14 (see FIG. 7)} acting on the shaft preloading portion 20a from preventing the inclination. Therefore, the effect of suppressing the backlash between the worm wheel 4 and the worm 8 can be prevented or suppressed. Further, it is possible to prevent the occurrence of a problem that the durability of the shaft preload portion 20a is lowered due to the occurrence of the elastic bending deformation.

[Second Example of Embodiment]
FIG. 5 shows a second example of an embodiment of the present invention corresponding to claims 1 to 4. In the case of this example, what is the elastic member 17b that includes the buffer cylinder 18 and the shaft preload member 26 that is installed between the tip end surface 23 of the spline shaft portion 12a and the back end surface 24a of the spline hole 11b? It is a separate and independent member. In the case of this example, the shaft preload member 26 is formed in a spherical shape as a whole by the same elastic material as the elastic member 17b. The radius of the spherical shaft preload member 26 (the radius of curvature of the outer peripheral surface) is smaller than the radius of curvature of the back end surface 24a of the spline hole 11b. The elastic member 17b includes the buffer cylinder portion 18 and a flat plate portion 27 that closes the tip opening of the buffer cylinder portion 18. The shaft preload member 26 is elastically compressed and clamped between the side surface of the flat plate portion 27 and the back end surface 24a of the spline hole 11b. Also in the case of this example, grease, which is a lubricant, is interposed between the outer peripheral surface of the buffer cylinder portion 18 and the side surface of the flat plate portion 27 and the back end surface 24a that are in contact with each other.

  In the case of this example configured as described above, as the spline hole 11b is inclined with respect to the spline shaft portion 12a, the back end surface 24a of the spline hole 11b and the side surface of the flat plate portion 27 of the elastic member 17b The contact position (the center point) of the outer peripheral surface of the shaft preload member 26 can be moved smoothly. Then, it is possible to effectively prevent the shaft preload member 26 from being elastically bent and deformed based on the movement of each contact position (the center point thereof). Other configurations and operations are the same as those of the first example described above.

The partial cutaway perspective view of a joint part showing the 1st example of an embodiment of the invention. The partial cutting exploded perspective view of a joint part. The elastic member is shown, (A) is a side view, (B) is the figure seen from the right side of (A). The joint part is shown, (A) is the state in which the central axes of two connected components corresponded, (B) is a partially cutaway side view showing the same mismatched state. The figure similar to FIG. 1 which shows the 2nd example of embodiment of this invention. The partial cutaway side view of the whole structure of the electric power steering device which shows an example of the conventional structure. The expanded XX sectional drawing of FIG. The enlarged view equivalent to the Y section of FIG. 7 which shows the structure of a prior invention. The elastic member is shown, (A) is the perspective view seen from the Z arrow direction of FIG. 8, (B) is the half part cut perspective view seen from the same direction as (A), (C) is (A) and The perspective view seen from the reverse direction.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Housing 4 Worm wheel 5 Worm tooth 6 Worm shaft 7 Electric motor 8 Worm 9a, 9b Rolling bearing 10 Output shaft 11, 11a, 11b Spline hole 12, 12a Spline shaft part 13 Pressing piece 14 Coil spring 15 Small diameter portion 16 Large diameter portion 17, 17a, 17b Elastic member 18 Buffer cylinder portion 19 Connection portion 20, 20a Shaft preloading portion 21 Intermediate shaft 22 Steering gear unit 23 Front end surface 24, 24a Back end surface 25 Front end surface 26 Axial preloading member 27 Flat plate Part

Claims (4)

  A bottomed spline hole provided at the end of one of the pair of rotating shafts so as to open to the end surface of the end, and the end of the other rotating shaft of the two rotating shafts The spline shaft is provided in the spline hole so that torque can be transmitted between the two rotation shafts and the inclination generated between the two rotation shafts is allowed to be splined to the spline hole. A rotary shaft coupling comprising a spline hole and a shaft preloading member made of an elastic material elastically compressed in the axial direction between the back end surface of the spline hole and the tip end surface of the spline shaft portion. A rotary shaft characterized in that the back end surface of the shaft is a partially spherical concave surface, and the surface of the shaft preload member that contacts the back end surface is a partially spherical convex surface having a radius of curvature equal to or less than the radius of curvature of the partial spherical concave surface. Fittings.   The rotary shaft coupling according to claim 1, wherein the shape of the shaft preload member is spherical.   The rotary shaft coupling according to any one of claims 1 to 2, wherein a lubricant is interposed in a contact portion between the surface of the shaft preload member and the surface of the counterpart member.   A housing, a worm wheel that is supported concentrically with the driven shaft on the outer peripheral surface of a driven shaft that is rotatably supported in the housing, and rotates with the driven shaft, and is engaged with the worm wheel. A worm rotatably supported in the housing, a rotary drive device coupled and fixed to the housing in a state in which a distal end portion of the drive shaft is coupled to a base end portion of the worm by a rotary shaft joint, and the worm In a rotary drive device with a worm speed reducer provided with a preload applying means for applying a preload to a meshing portion between the worm and the worm wheel by pressing toward the worm wheel, the rotary shaft coupling includes: A rotary drive device with a worm speed reducer, wherein the rotary shaft coupling is any one of the three.

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