JP2007120592A - Power transmission mechanism, electric power steering device incorporating it, ring with elastic tooth, and manufacturing method of ring with elastic tooth - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To lower the height of each tooth of male and female spline parts 47b, 48b disposed to a rotary shaft 29 and a worm shaft 27, respectively, and sufficiently secure durability by inexpensive structure. <P>SOLUTION: A ring 49a with elastic teeth made of an elastic material is spline-engaged with the male and female spline parts 47b, 48b. Bottoms of internal teeth 51b of a ring 49b with elastic teeth are positioned outside tooth bottoms of external teeth 50b in a diameter direction. In a state that the ring 49b with elastic teeth is installed between the spline parts 47b, 48b, the teeth of the spline part 47b are circumferentially superimposed with the teeth of the spline part 48b. T<SB>1</SB>is larger than the T<SB>2</SB>and T<SB>3</SB>, when the thickness of the center part in a radial direction of the ring 49b with elastic teeth disposed between parts circumferentially superimposed of the teeth of the spline parts 47b, 48b is defined as T<SB>1</SB>, thicknesses of both ends in a radial direction of ring 49b with elastic teeth other than the superimposed parts are defined as T<SB>2</SB>, T<SB>3</SB>. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is applied, for example, to an electric power steering device for reducing the force required for a driver to operate a steering wheel by incorporating the output of an electric motor as auxiliary power into an automobile steering device. The present invention relates to a power transmission mechanism to be incorporated, and an improvement in an elastic toothed ring used in the power transmission mechanism.

  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. 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. FIG. 10 schematically shows an example of a conventionally known basic configuration of such an electric power steering apparatus.

  This electric power steering device is provided with a speed reducer 4 between a steering shaft 2 having a steering wheel 1 fixed to a base end portion (upper end portion in FIG. 10) and an electric motor 3, and the power of the electric motor 3 is supplied. The transmission can be transmitted to the steering shaft 2 via the speed reducer 4. When the steering shaft 2 is rotated by operating the steering wheel 1 in order to give a steering angle to the steering wheel 14, the torque sensor 5 detects the rotation direction and torque of the steering shaft 2, and the detection signal is sent to the controller. Send to 6. Based on this detection signal, the controller 6 energizes the electric motor 3 and rotates the steering shaft 2 in the same direction as the rotation direction based on the operation of the steering wheel 1 via the speed reducer 4. As a result, the tip end portion (the lower end portion in FIG. 10) of the steering shaft 2 rotates with a torque larger than the torque based on the force applied from the steering wheel 1. The distal end portion of the steering shaft 2 is transmitted to the input shaft 10 of the steering gear 9 through the universal joints 7 and 7 and the intermediate shaft 8. The input shaft 10 rotates the pinion 11, pushes and pulls the tie rod 13 through the rack 12, and gives a desired steering angle to the steered wheel 14. As is clear from this explanation, the force required for the driver to operate the steering wheel 1 to give the steering angle to the steered wheel 14 is applied from the electric motor 3 to the steering shaft 2 via the speed reducer 4. It becomes small as much as the auxiliary power applied.

  In the case of such an electric power steering apparatus, a worm speed reducer composed of a worm shaft and a worm wheel has been generally used as the speed reducer 4 provided between the steering shaft 2 and the electric motor 3. Yes. The rotating shaft of the electric motor 3 and the input shaft constituting the speed reducer 4 are formed by spline engagement between a male spline portion provided on one of these shafts and a spline portion provided on the other. In general, the spline engaging portions are connected so as to be able to transmit power.

  However, when a worm reducer is used as the reducer 4, if the inevitable backlash existing between the tooth surfaces of the worm shaft worm and the worm wheel increases, the tooth surfaces strongly collide with each other, An annoying rattling noise can occur. For example, when a vibration load is applied to the steering shaft 2 from the wheel side due to a rough road surface, an unpleasant rattling sound is generated due to the presence of the backlash. For these reasons, in recent years, an elastic force imparting means is provided between the gear housing constituting the worm speed reducer and the worm shaft, and the elastic force imparting means imparts the elastic force in the direction toward the worm wheel to the worm shaft. However, it is considered to suppress the backlash (reduce or reduce it to 0) and suppress the occurrence of the rattling noise.

  However, when the generation of the rattling noise is suppressed by the configuration provided with such elasticity applying means, the spline mechanism provided between these two shafts is used to incline the worm shaft with respect to the rotating shaft of the electric motor 3. There is a possibility that a part of each tooth constituting the joint is beaten. On the other hand, when the rigidity of both the male and female spline parts constituting the spline engaging part is increased, the teeth can be prevented from being beaten, but the tooth surfaces of these spline parts are It is easy to generate a rattling noise between the two. For this reason, in order to suppress the occurrence of rattling noise while enabling the inclination of the worm shaft with respect to the rotation shaft of the electric motor 3, the gap between the two spline portions provided on both the shafts is strictly regulated. However, it is necessary to carry out difficult work such as management, which causes an increase in cost of the electric power steering apparatus.

  In view of such circumstances, in the case of the power transmission mechanism described in Patent Document 1 and an electric power steering device incorporating the same, a female spline portion provided at the end of the worm shaft, an electric motor An elastic toothed ring, part of which is made of an elastic material, is provided between the male spline part provided on the rotating shaft, and power can be transmitted between the two shafts via the elastic toothed ring. Yes. 11 to 17 show a conventional structure of an electric power steering apparatus incorporating the power transmission mechanism described in Patent Document 1. As shown in FIG.

  This electric power steering apparatus includes a steering shaft 2 having a steering wheel 1 fixed to a rear end portion (right end portion in FIG. 11), a steering column 15 through which the steering shaft 2 can be inserted, and an auxiliary torque applied to the steering shaft 2. And an assist device 16 for imparting.

  The steering shaft 2 is configured by combining an outer shaft 17 provided on the rear end side (right side in FIG. 11) of the vehicle and an inner shaft 18 provided on the front end side (left side in FIG. 11) so as to transmit a rotational force. Become. The inner shaft 18 connects a first inner shaft 22 provided on the rear end side of the vehicle and a second inner shaft 23 provided on the front end side by a torsion bar 24 (FIG. 12). The front end portion (left end portion in FIG. 11) of the steering column 15 is coupled and fixed to the rear end surface (right end surface in FIG. 11) of the gear housing 21 supported by a part of the vehicle body 19. The front end portion of the inner shaft 18 is inserted into the gear housing 21 and protrudes from the front end surface of the gear housing 21. The input shaft 10 of the steering gear 9 is coupled to the front end portion of the inner shaft 18 projecting from the front end surface via the universal joints 7 and 7 and the intermediate shaft 8 so that power can be transmitted. A pinion 11 (see FIG. 10) is fixed to the input shaft 10, and the pinion 11 is meshed with a rack 12 (see FIG. 10). Accordingly, as the steering shaft 2 rotates, the tie rods 13 and 13 are pushed and pulled through the rack 12 to give a desired steering angle to the steered wheels 14 (see FIG. 10).

  As shown in FIGS. 12 to 17, the assist device 16 includes a worm wheel 26, a worm shaft 27, elasticity applying means 31 for applying elasticity to the worm shaft 27, an electric motor 28, and a power transmission mechanism. 30 and a torque sensor 5 and a controller 6 (see FIG. 10). Of these, the worm wheel 26 is externally fitted and fixed to an intermediate portion of the second inner shaft 23 provided on the front end side of the inner shaft 18. The elastic force imparting means 31 includes a stepped cylindrical bearing holder 32, first and second ball bearings 33 and 34, a swing shaft 35, a coil provided on the inside of the gear housing 21, respectively. And a spring 36. The worm wheel 26 and the worm shaft 27 are provided inside the gear housing 21, and the worm 37 provided at an intermediate portion of the worm shaft 27 and the worm wheel 26 are engaged with each other. The worm shaft 27 and the worm wheel 26 constitute the worm speed reducer 20. The worm shaft 27 corresponds to the driven shaft described in the claims.

  The torque sensor 5 is added to the steering shaft 1 from the steering wheel 1 based on the relative rotational direction and the relative rotational amount of the first and second inner shafts 22 and 23 based on the twist of the torsion bar 24. The direction and magnitude of the torque to be generated are detected, and a signal (detection signal) representing the detected value is sent to the controller 6. In response to the detection signal, the controller 6 sends a drive signal to the electric motor 28 to generate auxiliary torque with a predetermined magnitude in a predetermined direction.

  The distal end portion (right end portion in FIGS. 12 to 14) of the rotating shaft 29 of the electric motor 28 and the base end portion (left end portion in FIGS. 12 to 14) of the worm shaft 27 are driven by the power transmission mechanism 30. Are connected to each other. The power transmission mechanism 30 includes a male spline portion 47 (FIGS. 12 to 14) provided at the distal end portion of the rotating shaft 29 and a female spline portion 48 (FIGS. 12 to 14) provided at the proximal end portion of the worm shaft 27. And an elastic toothed ring 49 provided between the two spline portions 47 and 48. The rotary shaft 29 corresponds to the drive shaft recited in the claims, and both end portions are rotatably supported by a case 38 constituting the electric motor 28 by third and fourth ball bearings (not shown). is doing. A rotor (not shown) facing the stator is provided at the intermediate portion of the rotating shaft 29.

  As shown in detail in FIGS. 16 to 17, the elastic toothed ring 49 has outer teeth 50 that are spline-engaged with the female spline portion 48 on the outer peripheral surface, and the male spline portion 47 and spline-engaged on the inner peripheral surface. Each has internal teeth 51 to be used. Such an elastic toothed ring 49 includes external tooth element portions 54 projecting to the outer diameter side at a plurality of circumferentially equidistant positions on the outer peripheral surface of the main body 52 formed of a synthetic rubber, which is an elastic material. Similarly, inner tooth element portions 55 and 55 projecting toward the inner diameter side are formed over the entire length in the axial direction at a plurality of equally spaced circumferential positions on the inner peripheral surface.

  Further, a woven fabric 56a such as a nylon canvas is provided on the outer diameter side surface of each external tooth element portion 54, 54 and the outer peripheral surface of the main body portion 52 between these external tooth element portions 54, 54. It is stuck in a continuous state over the entire circumference of the outer peripheral surface. The external teeth 50 are configured by the external tooth element portions 54 and 54 and the portion of the woven fabric 56a covering the outer diameter side surfaces of the external tooth element portions 54 and 54. Further, a woven fabric 56b such as a nylon canvas is provided on the inner diameter side surface of each of the internal tooth element portions 55, 55 and between the inner peripheral element portions 55, 55 on the inner peripheral surface of the main body portion 52. Affixed over the entire circumference of the inner peripheral surface. The internal teeth 51 are constituted by the internal tooth element portions 55 and 55 and a portion of the woven fabric 56b covering the inner diameter side surfaces of the internal tooth element portions 55 and 55. With this configuration, the outer teeth 50 and the inner teeth 51 are provided on the outer diameter side and the inner diameter side of the elastic toothed ring 49, respectively.

  The elastic toothed ring 49 configured as described above is configured so that the outer teeth 50 are engaged with the female spline portion 48 and the inner teeth 51 are engaged with the male spline portion 47, respectively. The distal end portion of the rotating shaft 29 and the proximal end portion of the worm shaft 27 are coupled so that the relative rotation of both the shafts 29 and 27 is impossible. With this configuration, the worm shaft 27 rotates together with the rotating shaft 29.

  On the other hand, the bearing holder 32 is provided inside the gear housing 21, and the worm shaft 27 is rotatably supported inside the bearing holder 32. In the bearing holder 32, a large-diameter cylindrical portion 39 and a small-diameter cylindrical portion 40 that are concentric with each other are connected by a step portion 41. The bearing holder 32 is supported on the inner side of the gear housing 21 by a swing shaft 35 supported by the gear housing 21 so as to freely swing around the swing shaft 35. Further, the base end portion (the left end portion in FIGS. 12 to 14) of the worm shaft 27 is rotatably supported by the first ball bearing 33 inside the large-diameter cylindrical portion 39 of the bearing holder 32. . The tip of the worm shaft 27 (the right end in FIGS. 12 to 14) is rotatably supported by the second ball bearing 34 inside the small diameter cylindrical portion 40 of the bearing holder 32.

  Further, an elastic ring 43 is provided between the outer peripheral surface of the distal end portion of the small diameter cylindrical portion 40 and the inner peripheral surface of the concave hole 42 provided in the inner surface of the gear housing 21. Further, a through hole 44 that penetrates both the inner and outer peripheral surfaces is formed in a part in the circumferential direction of the intermediate portion in the longitudinal direction of the small diameter cylindrical portion 40, and the worm wheel 26 and the worm shaft are passed through the through hole 44. 27 worms 37 are engaged with each other.

  Further, a concave hole 45 is formed in a part in the circumferential direction of the outer peripheral surface of the large-diameter cylindrical portion 39 constituting the bearing holder 32, and between the bottom surface of the concave hole 45 and the inner surface of the gear housing 21, A coil spring 36 is provided. The coil spring 36 imparts radial elasticity to the base end portion of the worm shaft 27 via the bearing holder 32 and the first ball bearing 33. With this configuration, the worm shaft 27 is elastically oscillated and displaced in the direction toward the worm wheel 26 around the oscillating shaft 35. Then, the distance between the central axes of the second inner shaft 23 and the worm shaft 27 to which the worm wheel 26 is fitted and fixed is elastically reduced, and the teeth between the worm 37 and the worm wheel 26 are elastically contracted. The surfaces come into contact with each other with a preload applied. With this configuration, it is possible to suppress the occurrence of rattling noise at the meshing portions of both the members 37 and 26.

  In the case of the power transmission mechanism described in Patent Document 1 and the electric power steering apparatus incorporating the power transmission mechanism configured as described above, the female spline portion 48 provided on the worm shaft 27 and the rotating shaft of the electric motor 28 are provided. An elastic toothed ring 49 is provided between the male spline portion 47 provided on 29. For this reason, it is possible to prevent the tooth surfaces of the male and female spline portions 47 and 48 from directly colliding with each other, and it is possible to prevent the generation of noise due to the collision between the tooth surfaces. In addition, external teeth 50, which are external tooth elements 54 and 54 made of synthetic rubber, are provided on the outer diameter side of the elastic toothed ring 49, and partly on the inner diameter side of the elastic toothed ring 49. Is provided with internal teeth 51 which are internal tooth element portions 55, 55 made of synthetic rubber. For this reason, it is possible to reduce annoying noise caused by the contact between the tooth surfaces of the male and female spline portions 47 and 48 and the tooth surfaces of the inner tooth 51 and the outer tooth 50 of the elastic toothed ring 49, Or disappear. Further, it is not necessary to reduce the bending rigidity between the rotating shaft 29 and the worm shaft 27 of the electric motor 28 in order to suppress the generation of this annoying abnormal noise.

  In addition, since the internal tooth element portions 55 and 55 and the external tooth element portions 54 and 54 are made of synthetic rubber, which is an elastic material, inevitable dimensions existing in the male and female spline portions 47 and 48. The error can be easily absorbed by the inner teeth 51 and the outer teeth 50, and the size management and the assembly work can be easily performed. For this reason, it is possible to suppress an increase in cost of the power transmission mechanism and the electric power steering apparatus incorporating the same. Further, even when there is an eccentric error or declination error in both the male and female spline portions 47 and 48, power is transmitted between the rotating shaft 29 of the electric motor 28 and the worm shaft 27 while absorbing these errors. Can be connected to each other.

  As a result, according to the conventional structure described in Patent Document 1 shown in FIGS. 11 to 17 described above, the cost is not increased and the bending rigidity between the rotating shaft 29 and the worm shaft 27 is not lowered. , Can suppress the generation of harsh noises. In the case of the structure shown in FIGS. 11 to 17 described above, synthetic rubber is used as an elastic material constituting the main body 52 of the elastic toothed ring 49, but instead of this synthetic rubber, Elastomers other than synthetic rubber, synthetic resins, and the like can also be used.

[Description of Prior Invention]
According to the conventional structure shown in FIGS. 11 to 17 described above, such operations and effects can be obtained. However, in the case of the power transmission mechanism of this conventional structure, the rotation shaft 29 and the driven shaft, which are drive shafts, are used. There is still room for improvement in terms of increasing the power that can be transmitted to and from the worm shaft 27 and reducing the size of the power transmission mechanism 30. In view of such circumstances, the inventor of the present invention invented a power transmission mechanism incorporated in an electric power steering device prior to the present invention. Next, this power transmission mechanism will be described with reference to FIGS.

  This power transmission mechanism 30a couples the rotating shaft 29 of the electric motor 28 and the worm shaft 27 so that power can be transmitted. Since the structure other than the power transmission mechanism 30a is the same as that of the conventional structure described in Patent Document 1 shown in FIGS. The illustration and description are omitted or simplified, and the following description will focus on the features of the prior invention. In the case of the power transmission mechanism 30a, a male spline portion 47a provided at the distal end portion (right end portion in FIG. 18) of the rotating shaft 29 and a female spline portion provided at the proximal end portion (left end portion in FIG. 18) of the worm shaft 27. An elastic toothed ring 49a made of an elastic material such as synthetic rubber is provided between the spline portion 48a.

  As shown in detail in FIG. 20, the elastic toothed ring 49a includes external tooth element portions 54a and 54a having arc-shaped cross sections provided at a plurality of circumferentially equidistant positions located at the outer diameter side end, The internal teeth element portions 55a and 55a having a circular arc cross section provided at a plurality of circumferentially equidistant positions located at the side end portions are circularly connected via a plurality of connecting portions 64 and 64 provided at a radial center portion. It is made to continue alternately in the circumferential direction. The entire elastic toothed ring 49a is formed in a cylindrical shape. The external tooth element portions 54a and 54a, the internal tooth element portions 55a and 55a, and the connecting portions 64 and 64 are all made of an elastic material and are integrally formed. Further, woven fabrics 56a and 56b (see FIGS. 16 and 17) are not attached to the inner and outer peripheral surfaces of the elastic toothed ring 49a. The external tooth elements 54a, 54a and the portions near the outer peripheral surfaces of the connecting portions 64, 64 constitute external teeth 50a that are spline-engaged with the female spline portion 48a. Further, the internal teeth 51a that are spline-engaged with the male spline portion 47a are constituted by the internal tooth element portions 55a, 55a and the portions near the inner peripheral surfaces of the connecting portions 64, 64. Because of this configuration, the top of the external tooth 50a of the elastic toothed ring 49a and the top of the internal tooth 51a are displaced from each other in the circumferential direction, and the top of the external tooth 50a is the bottom of the internal tooth 51a. Moreover, the tops of the inner teeth 51a are opposed to the tooth bottoms of the outer teeth 50a in the radial direction.

  Further, with respect to the radial direction of the elastic toothed ring 49a, the bottom of the external tooth 50a is brought close to the top (tooth top surface) of the internal tooth 51a. Further, with respect to the radial direction, the tooth bottom portion of the inner tooth 51a is brought close to the top portion (tooth tip surface) of the outer tooth 50a. And the tooth bottom part of this internal tooth 51a is located in the diameter direction outer side of the said elastic toothed ring 49a rather than the tooth bottom part of the said external tooth 50a. With such elastic toothed rings 49a provided between the male spline portion 47a and the female spline portion 48a, the teeth of the male spline portion 47a and the teeth of the female spline portion 48a are These male and female spline portions 47a and 48a are overlapped in the circumferential direction. For example, when a virtual circle concentric with the elastic toothed ring 49a shown by a two-dot chain line a in FIG. 20 is considered, each tooth of the male spline portion 47a and the female spline portion 48a are arranged on the circumference of the virtual circle. Each tooth is present.

  18-20, the elastic toothed ring is provided between the male spline portion 47a provided on the rotating shaft 29 of the electric motor 28 and the female spline portion 48a provided on the worm shaft 27. In the state where 49a is provided, the teeth of the male spline portion 47a and the teeth of the female spline portion 48a are overlapped in the circumferential direction of the male and female spline portions 47a and 48a. On the other hand, in the case of the conventional structure shown in FIGS. 11 to 17 described above, the bottom portion of the external tooth 50 is positioned on the outer side in the diameter direction than the bottom portion of the internal tooth 51. In the case of such a conventional structure and a structure in which the woven fabrics 56b and 56a (see FIGS. 16 and 17) are not attached to the inner and outer peripheral surfaces, the rotating shaft 29 and the worm shaft 27 of the electric motor 28 When power is transmitted between the elastic toothed rings 49, large forces are exerted on the elastic toothed rings 49 by applying forces in the opposite directions with respect to the circumferential direction to the inner diameter side portion and the outer diameter side portions of the elastic toothed rings 49. Power may be added. On the other hand, in the case of the structure of the prior invention, as described above, the teeth of the male and female spline portions 47a and 48a are overlapped in the circumferential direction of both the spline portions 47a and 48a. Therefore, even when power is transmitted between the shafts 29 and 27, it is possible to prevent a large shearing force from being applied to the elastic toothed ring 49a. Further, in the case of the structure of the above-mentioned invention, when transmitting power between the shafts 29 and 27, the elastic material constituting the elastic toothed ring 49a is the male and female spline portions 47a, The elastic toothed ring 49a to which compression force is mainly applied during use is more than the elastic toothed ring to which shear force is mainly applied during use, although it is compressed between teeth adjacent in the circumferential direction 48a. Is not easily damaged. Therefore, the power that can be transmitted between the shafts 29 and 27 can be increased. In addition, in the case of the structure of the previous invention, the top of the external tooth 50a and the top of the internal tooth 51a are displaced in the circumferential direction, and the bottom of the internal tooth 51a is the tooth of the external tooth 50a. It is located on the outside in the diameter direction from the bottom. For this reason, the radial dimension of the elastic toothed ring 49a can be reduced to some extent, and the power transmission mechanism 30a can be downsized.

However, in the case of the structure of the prior invention shown in FIGS. 18 to 20 described above, there is still room for improvement in terms of reducing the size in the radial direction of the elastic toothed ring 49a and reducing the size of the power transmission mechanism 30a. is there.
On the other hand, it is considered that the male and female spline portions 47a and 48a of the rotating shaft 29 and the worm shaft 27 of the electric motor 28 are formed by forging in order to increase mass productivity. That is, when both the spline portions 47a and 48a are made separately from the rotary shaft 29 and the worm shaft 27 by using sintered metal, not only the number of parts increases but also the number of assembly steps increases. For this reason, the cost increases. Further, when both the spline portions 47a and 48a are formed by cutting, the cost increases. For this reason, conventionally, both male and female spline portions provided on the rotating shaft and worm shaft of the electric motor have been formed by forging into a portion integral with these shafts. In this case as well, considering that costs are kept low, it is necessary to form the spline portions 47a and 48a by forging.

However, when the male and female spline portions 47a and 48a are formed by forging, the heights (tooth heights) h ₁ and h ₂ (FIG. 20) of the teeth of the male and female spline portions 47a and 48a are as follows. Larger ones cannot be made, and the problem arises that the heights h ₁ and h _{2 of} each tooth are limited in production. On the other hand, when the heights h ₁ and h ₂ of each tooth are reduced so that the male and female spline portions 47a and 48a are formed by forging, the teeth of each of the spline portions 47a and 48a are formed. The radial dimension T (FIG. 20) of the overlap portion, which is a portion overlapping in the circumferential direction, becomes small. If this radial dimension T becomes too small, the load applied to the central portion in the radial direction of the elastic toothed ring 49a existing in the power (torque) transmission portion between the two spline portions 47a, 48a increases. The durability of the elastic toothed ring 49a is lowered. The radial dimension T of the overlap portion is a difference between ½ of the diameter d ₁ of the tip circle of the male spline portion 47a and ½ of the diameter d ₂ of the tip circle of the female spline portion 48a. Equal to {T = (d ₁ −d ₂ ) / 2}. Further, when the durability test of the power transmission mechanism 30a was performed, portions of the elastic toothed ring 49a where the teeth of both the spline portions 47a and 48a overlap each other in the circumferential direction (overlap portions). It was found that the part existing between the two was most easily damaged. As apparent from such circumstances, the dimension T of the overlap portion becomes excessively small, or the thickness W of the portion of the elastic toothed ring 49a existing between the overlap portions (see FIG. 20) becomes smaller, which causes a decrease in durability of the power transmission mechanism 30a.

In addition, the present inventor rounded and formed a plate material made of an elastic material in which crests and troughs are alternately arranged in the length direction into a cylindrical shape in order to improve the mass productivity of the elastic toothed ring. By doing so, it was considered that the elastic toothed ring was assembled (set) between the male and female spline portions 47a and 48a. However, if the thickness of the plate-shaped material is uniformly large over the entire length, it is difficult to round the plate-shaped material into a cylindrical shape, and it may be set between the two spline portions 47a and 48a. There is also a problem that said it will be difficult.
As prior art documents related to the present invention, there is Patent Document 2 in addition to Patent Document 1.

JP 2005-69470 A JP 2002-211141 A

  In view of such circumstances, the present invention has an inexpensive structure that can reduce the height of each tooth of the male and female spline portions provided on the drive shaft and the driven shaft, and sufficiently ensures durability. Invented accordingly.

Of the power transmission mechanism of the present invention, the electric power steering apparatus incorporating the same, the elastic toothed ring, and the manufacturing method thereof, the power transmission mechanism described in claim 1 is the prior invention shown in FIGS. Like the structure of
It is provided between the drive shaft and the driven shaft and is used for transmitting power between these two shafts, and includes a female spline portion, a male spline portion, and an elastic toothed ring.
Of these, the female spline portion is provided on the inner peripheral surface of the end portion of one of the two shafts.
The male spline portion is provided on the outer peripheral surface of the end portion of the other shaft of the two shafts.
The elastic toothed ring has external teeth that are spline-engaged with the female spline portion on its outer peripheral surface, and inner teeth that are spline-engaged with the male spline portion on its inner peripheral surface. The elastic toothed ring is integrally provided with a plurality of external tooth element portions and internal tooth element portions each made of an elastic material on the outer diameter side and the inner diameter side.
The elastic toothed ring includes not only a cylindrical shape as a whole but also a cylindrical shape as a whole.

In particular, among the power transmission mechanisms of the present invention, in the power transmission mechanism described in claim 1,
The teeth of the female spline portion provided on one of the drive shaft and the driven shaft and the teeth of the male spline portion provided on the other shaft are arranged in the circumferential direction of both the spline portions. Is superimposed (overlapped). Then, the thickness of the elastic toothed ring existing between the portions of these spline portions that overlap in the circumferential direction of each tooth is determined by the elasticity that deviates from between the portions of these teeth that overlap in the circumferential direction. It is larger than the thickness of the toothed ring.

  Preferably, as described in claim 2, in the configuration described in claim 1, the elastic toothed ring includes an elastic material main body, an outer diameter side of the main body, and And a woven fabric provided in a state of being integrally attached to at least one of the inner diameter side, and the elasticity existing between the overlapping portions in the circumferential direction of each tooth of the male and female spline portions The thickness of the toothed ring is set to be larger than the thickness of the elastic toothed ring deviated from between the portions of these teeth that overlap in the circumferential direction.

  Preferably, as described in claim 3, in the configuration described in claim 1 above, the elastic toothed ring includes element portions made of an elastic material provided at a plurality of locations in the circumferential direction. And a woven cloth provided in a state of being integrally attached to at least one side of these element portions, and present between the portions of the male and female spline portions that overlap each other in the circumferential direction. The thickness of the elastic toothed ring is larger than the thickness of the elastic toothed ring made of only a woven fabric that is out of the circumferentially overlapping portions of these teeth.

  More preferably, as described in claim 4, the elastic toothed ring is provided with a pair of woven fabrics on the outer diameter side and the inner diameter side. The thickness of the one woven fabric to be engaged is made larger than the thickness of the other woven fabric to be engaged with the driven shaft.

The electric power steering apparatus according to claim 5 is:
The rotation shaft of the electric motor and the input shaft constituting the speed reducer are coupled so as to be able to transmit power by the power transmission mechanism as described above.

Furthermore, the electric power steering apparatus according to claim 6 is:
The output shaft of the speed reducer or the rotating shaft of the electric motor and the ball nut are coupled to each other by a power transmission mechanism as described above so that power can be transmitted.

The elastic toothed ring according to claim 7 is:
An elastic toothed ring for use in the power transmission mechanism according to claim 1, wherein the outer peripheral surface has outer teeth and the inner peripheral surface has inner teeth. In addition, a plurality of external tooth element portions and internal tooth element portions, each of which is made of an elastic material, are integrally provided, and the thickness of the central portion in the radial direction is made larger than the thickness of the radial end portion. Yes.

Moreover, the manufacturing method of the elastic toothed ring described in claim 8 is:
The method for manufacturing an elastic toothed ring according to claim 7, wherein at least a part is made of an elastic material, and crests and troughs are alternately continuous in the length direction, and crests By bending a plate-like element in a cylindrical shape, the thickness of the portion existing between the top of the valley and the bottom of the valley is greater than the thickness of at least one of the top of the peak and the bottom of the valley Build an elastic toothed ring.

  In the case of the power transmission mechanism of the present invention using the elastic toothed ring or the like of the present invention as described above and the electric power steering apparatus incorporating the same, there is an elastic tooth between the female spline part and the male spline part. A ring is provided. For this reason, it is possible to prevent the tooth surfaces of both the male and female spline parts from directly abutting, as in the conventional structure and the previous invention shown in FIGS. It is possible to prevent the generation of abnormal noise. Further, a plurality of external tooth elements made of elastic material are provided on the outer diameter side of the elastic toothed ring, and a plurality of internal tooth elements made of elastic material are provided on the inner diameter side of the elastic toothed ring. For this reason, it is possible to reduce or eliminate annoying noise caused by the contact between the tooth surfaces of both the male and female spline portions and the tooth surfaces of the internal and external teeth of the elastic toothed ring. Further, it is not necessary to reduce the bending rigidity of the drive shaft and the driven shaft in order to suppress the generation of this annoying abnormal noise.

  Moreover, since each of the internal tooth element portions and each external tooth element portion are made of an elastic material, the inevitable dimensional errors existing in both the male and female spline portions can be easily absorbed by the elastic toothed ring, Dimension management and assembly work can be performed easily. For this reason, it is possible to suppress an increase in cost of the power transmission mechanism and the electric power steering apparatus incorporating the same. Therefore, it is possible to suppress the generation of annoying noise without increasing the cost and reducing the bending rigidity of the drive shaft and the driven shaft.

  Furthermore, even if there is an eccentric error or declination error in both the male and female spline parts, the drive shaft and the driven shaft can be connected so as to be able to transmit power while absorbing these errors. It becomes possible. In addition, when a woven fabric is applied to the outer peripheral surface and the inner peripheral surface of the elastic toothed ring, it is possible to effectively prevent the elastic material from tearing and the tooth surface from coming off.

  In particular, in the case of the present invention, each tooth of the female spline portion provided on one of the drive shaft and the driven shaft and each tooth of the male spline portion provided on the other shaft are The power transmission mechanism can be downsized because these spline portions are overlapped (overlapped) in the circumferential direction. Further, when power is transmitted between the drive shaft and the driven shaft, it is possible to prevent a large shearing force from being applied to the elastic toothed ring. When transmitting power between the two shafts, the compression force is applied to a part of the elastic toothed ring that exists between the teeth adjacent to each other in the circumferential direction of the male and female spline parts. However, the elastic toothed ring to which the compressive force is mainly applied is less likely to break than the elastic toothed ring to which the shear force is mainly applied. For this reason, the power (allowable transmission power) that can be transmitted between the drive shaft and the driven shaft can be increased. For this reason, it is not necessary to increase the size of the structure.

In addition, in the case of the present invention, the thickness of the elastic toothed ring existing between the portions of the male and female spline portions overlapping in the circumferential direction is superimposed in the circumferential direction of these teeth. It is larger than the thickness of the elastic toothed ring that is out of the space between the parts. Therefore, it is possible to increase the power that can be transmitted between the two shafts while reducing the thickness of the elastic toothed ring that is radially opposed to the tooth bottom of each tooth of the male and female splines. Can increase the sex. In addition, since the thickness of the elastic toothed ring facing the bottom of each tooth of the male and female spline parts can be reduced, the height (tooth height) of each tooth of the male and female spline parts can be reduced. Easy to do. For this reason, it is possible to easily form the male and female spline parts by forging, increase the mass productivity, and reduce the manufacturing cost. Moreover, despite the fact that the height of each tooth of the male and female spline portions is reduced, it is possible to sufficiently secure the radial dimension of the overlap portion, which is a portion that overlaps the circumferential direction of these teeth. . Therefore, sufficient durability can be secured. In addition, since the thickness of the elastic toothed ring that is out of the circumferential direction of the teeth of both the male and female splines can be reduced, the material cost can be reduced and the manufacturing cost can be reduced. Can be reduced.
As a result, according to the present invention, it is possible to reduce the height of each tooth of the male and female spline portions provided on the drive shaft and the driven shaft, and to obtain a structure that is inexpensive and sufficiently secure the durability. It is done.

  Further, according to the present invention, even when an elastic toothed ring is formed by bending a plate-like element, at least a part of which is made of an elastic material, into a cylindrical shape, the radial direction of a plurality of circumferential directions of the elastic toothed ring. Since the thickness of the end portion can be reduced, the plate-like element can be easily rounded into a cylindrical shape. In addition, it is possible to easily perform the work of assembling (setting) the elastic toothed ring made by rounding into a cylindrical shape between the male spline part and the female spline part. For this reason, it is possible to improve the moldability and assembly of the elastic toothed ring.

  In addition, according to the configurations described in claims 2 and 3, since the woven fabric is integrally attached to the main body or the element portion made of elastic material, the elastic material is torn off or the tooth surface is peeled off. Can be effectively prevented. Further, since each external tooth element portion and each internal tooth element portion can be hardly deformed, the power that can be transmitted between the drive shaft and the driven shaft can be further increased, and the durability can be further improved. And according to the structure described in Claim 3, improvement of durability and shortening of the height of each tooth | gear of each male and female spline part can be made compatible more highly. For this reason, the formability by the forging process of each tooth of each spline part can be further improved. Further, when the elastic toothed ring is made by bending the plate-like element into a cylindrical shape, the moldability and assembling property of the elastic toothed ring can be further improved.

  Moreover, according to the structure described in Claim 4, durability can fully be ensured, reducing cost. Further, the height of each tooth of the male and female spline portions can be shortened more effectively. That is, of the pair of woven fabrics provided on the outer diameter side and the inner diameter side of the elastic toothed ring, one woven fabric engaged with the drive shaft has a male spline portion (or female spline) provided on the drive shaft. Since the driving force is applied directly from the part) without using an elastic material, the burden on one woven fabric is large. On the other hand, since the driving force acts on the other woven fabric engaged with the driven shaft through the elastic material of the elastic toothed ring, the driving force acts on the other woven fabric. The burden added is small. For this reason, even if the thickness of the other woven fabric is reduced, sufficient durability can be ensured, and the height of each tooth of the male and female spline portions can be shortened more effectively, and the other woven fabric can be shortened. The material cost of the cloth can be suppressed, and the cost can be reduced.

  Moreover, according to the manufacturing method of the elastic toothed ring described in claim 8, the mass productivity of the elastic toothed ring can be increased, and the cost can be further reduced.

[First example of embodiment of the invention]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1, 5 and 7. The power transmission mechanism using the elastic toothed ring of this example and the electric power steering apparatus incorporating the same are characterized by the rotation shaft 29 of the electric motor 28 as a drive shaft and the worm shaft 27 as the driven shaft. This is in that the structure of the power transmission mechanism 30b that enables power transmission between them is devised. In this example, the structure and operation of the electric power steering device excluding the power transmission mechanism 30b are the same as those of the conventional structure shown in FIGS. 11 to 17 and the prior invention shown in FIGS. It is the same. For this reason, illustrations and descriptions relating to the conventional structure and the structure of the prior invention are omitted or simplified, and the following description will focus on the features of this example.

  In the case of this example, a male spline portion 47b provided on the outer peripheral surface of the distal end portion of the rotating shaft 29 of the electric motor 28 that is a drive shaft, and a female provided on the inner peripheral surface of the proximal end portion of the worm shaft 27 that is a driven shaft. The power transmission mechanism 30b is constituted by the spline portion 48b and the elastic toothed ring 49b provided between the male and female spline portions 47b and 48b.

  This elastic toothed ring 49b is made of an elastic material such as synthetic rubber, as in the case of the previous invention shown in FIGS. In the case of the illustrated example, external tooth element portions 54b and 54b having an arc cross section are provided over the entire length in the axial direction (front and back directions in FIGS. 1 and 2). Further, internal tooth element portions 55b and 55b having arc-shaped cross sections are provided at a plurality of circumferentially equidistantly spaced locations (six locations in the illustrated example) located at the inner diameter side end of the elastic toothed ring 49b. It is provided over the entire axial length. And each said external-tooth element part 54b, 54b and each said internal-tooth element part 55b, 55b are alternately continued regarding the circumferential direction via several connection part 64a, 64a provided in radial direction center part. It is molded in one piece. Then, the external teeth 50b are connected to the internal tooth element portions 55a and 55a and the connecting portions 64a and 64a by the external tooth element portions 54b and 54b and the portions near the outer peripheral surfaces of the connecting portions 64a and 64a. The inner teeth 51b are respectively configured by the portions near the inner peripheral surface.

Furthermore, with respect to the radial direction of the elastic toothed ring 49b, the tooth bottom portion of the external tooth 50b is brought close to the top portion (tooth tip surface) of the internal tooth 51b. Further, with respect to the radial direction, the tooth bottom portion of the inner tooth 51b is brought close to the top portion (tooth tip surface) of the outer tooth 50b. And the tooth bottom part of the said inner tooth 51b is located in the diameter direction outer side of the said elastic toothed ring 49b rather than the tooth bottom part of the said outer tooth 50b. Accordingly, the diameter d ₁ ′ of the pitch circle passing through each bottom of the inner tooth 51b is larger than the diameter d ₂ ′ of the pitch circle passing through each bottom of the outer tooth 50b (d ₁ ′> d ₂ ′). ). Further, the thickness of each connecting portion 64a, 64a existing between each external tooth element portion 54b, 54b and each internal tooth element portion 55b, 55b in the diameter direction central portion of the elastic toothed ring 49b. T ₁ of the circumferentially central portion of each of the external tooth element portions 54b and 54b and each of the internal tooth element portions 55b and 55b existing at the inner diameter side end portion and the outer diameter side end portion of the elastic toothed ring 49b. Thicknesses T ₂ and T ₃ are larger (thicker) than T ₃ (T ₁ > T ₂ and T ₁ > T ₃ ).

  As shown in FIG. 2, the elastic toothed ring 49b configured as described above allows the outer teeth 50b to be engaged with the female spline portion 48b and the inner teeth 51b to be engaged with the male spline portion 47b, respectively. Therefore, it is provided between the male and female spline portions 47b and 48b. And the front-end | tip part of the rotating shaft 29 of the said electric motor 28 and the base end part of the worm shaft 27 are connected by the said elastic toothed ring 49b so that relative rotation of these both shafts 29 and 27 is impossible. For this reason, the worm shaft 27 rotates together with the rotating shaft 29.

Furthermore, in the case of this example, with the elastic toothed ring 49b provided between the male spline portion 47b and the female spline portion 48b, each tooth of the male spline portion 47b and the female spline portion 48b Each tooth is overlapped (overlapped) in the circumferential direction of both the male and female spline portions 47b and 48b. Therefore, for example, when a virtual circle concentric with the elastic toothed ring 49b shown by a two-dot chain line a ′ in FIG. 2 is considered, each tooth of the male spline portion 47b and the above-mentioned teeth are arranged on the circumference of the virtual circle. Each tooth of the female spline part 48b exists. And each said connection part 64a, 64a which is a radial direction center part of the elastic toothed ring 49b which exists between the parts which overlap in the circumferential direction of each tooth | gear of both these male and female spline parts 47b, 48b. the thickness T _1, out from between the parts between which overlaps in a circumferential direction of each tooth, a radial end portions of the elastic toothed ring 49b, each external tooth element portion 54b, 54b and each The thicknesses T ₂ and T _{3 of the} inner peripheral element portions 55b and 55b are larger (thicker) than the thicknesses T ₂ and T ₃ (T ₁ > T ₂ and T ₁ > T ₃ ).

  In the case of the power transmission mechanism 30b incorporating the elastic toothed ring of the present example configured as described above and the electric power steering apparatus incorporating the power transmission mechanism 30b, the prior art shown in FIGS. As in the case of the structure and the previous invention shown in FIGS. 18 to 20, it is difficult to increase the cost and reduce the bending rigidity between the rotating shaft 29 and the worm shaft 27 of the electric motor 28. The generation of sound can be suppressed.

  In particular, in the case of this example, the teeth of the female spline portion 48b provided on the worm shaft 27 and the teeth of the male spline portion 47b provided on the rotating shaft 29 are connected to the male and female spline portions 47b. 48b are overlapped (overlapped) in the circumferential direction. For this reason, the dimension of the power transmission part in the diameter direction can be reduced, and the power transmission mechanism 30b can be downsized. Further, when power is transmitted between the rotating shaft 29 and the worm shaft 27, it is possible to prevent a large shearing force from being applied to the elastic toothed ring 49b. When power is transmitted between the shafts 29 and 27, the circumferential direction of the elastic toothed ring 49b existing between the teeth adjacent to each other in the circumferential direction of the male and female spline portions 47b and 48b. Although the compressive force is applied to a plurality of places, the elastic toothed ring 49b to which the compressive force is mainly applied is less likely to be damaged than the elastic toothed ring to which the shear force is mainly applied. For this reason, the power (allowable transmission power) that can be transmitted between the rotating shaft 29 and the worm shaft 27 can be increased. For this reason, it is not necessary to increase the size of the structure.

In addition, in the case of this example, the thickness T ₁ of the elastic toothed ring 49b existing between the portions of the male and female spline portions 47b and 48b that overlap each other in the circumferential direction is set to The thicknesses T ₂ and T _{3 of} the elastic toothed ring 49b that is out of the gap are made larger (T ₁ > T ₂ and T ₁ > T ₃ ). For this reason, while reducing the thicknesses T ₂ and T ₃ at both ends in the radial direction of the elastic toothed ring 49b, which are opposed to the tooth bottoms of the teeth of the male and female spline portions 47b and 48b in the radial direction, Power that can be transmitted between the shafts 29 and 27 can be increased, and durability can be increased.

In addition, since the thicknesses T ₂ and T ₃ of both ends in the radial direction of the elastic toothed ring 49b facing the tooth bottom of each tooth of the male and female spline portions 47b and 48b in the radial direction can be reduced, The height (tooth height) h ₁ ′ and h ₂ ′ (FIG. 2) of each tooth of the female spline portions 47b and 48b can be easily reduced. For this reason, it is possible to easily form the male and female spline portions 47b and 48b by forging, increase the mass productivity, and reduce the manufacturing cost. In addition, although the heights h ₁ ′ and h ₂ ′ of the teeth of the male and female spline portions 47b and 48b are reduced, they are overlapping portions in the circumferential direction of these teeth. The radial dimension T ′ of the part can be sufficiently secured. Therefore, sufficient durability can be secured. Further, the thicknesses T ₂ and T ₃ of both ends in the radial direction of the elastic toothed ring 49b, which are out of the circumferential direction of the teeth of both the male and female spline portions 47b and 48b, are reduced. Therefore, the material cost can be reduced and the manufacturing cost can be reduced.
As a result, according to this example, the heights h ₁ ′ and h ₂ ′ of the teeth of the male and female spline portions 47b and 48b provided on the rotating shaft 29 and the worm shaft 27 can be reduced, and the cost is low. And the structure which can fully ensure durability can be obtained.

[Second example of the embodiment of the present invention]
Next, FIG. 3 shows a second example of an embodiment of the present invention corresponding to claims 1, 2, 4, 5, and 7. In the case of this example, unlike the case of the first example shown in FIGS. 1 and 2 described above, the outer peripheral surface and inner periphery of the main body 61 made of an elastic material such as synthetic rubber, which constitutes the elastic toothed ring 49c. A pair of woven fabrics 56a and 56b are provided on the surface in a state of being integrally attached over the entire circumference. Of the pair of woven fabrics 56a and 56b, the outer woven fabric 56a, the outer peripheral element portions 54b and 54b to which the woven fabric 56a is attached, and the outer peripheries of the connecting portions 64a and 64a. An outer tooth 50b is constituted by the portion near the surface. Of the pair of woven fabrics 56a and 56b, the woven fabric 56b on the inner diameter side, the inner tooth element portions 55b and 55b to which the woven fabric 56b is adhered, and the inner circumferences of the connecting portions 64a and 64a. An inner tooth 51b is constituted by the portion near the surface.

In the case of this example, of the pair of woven fabrics 56a and 56b, the inner woven fabric 56b that engages with the male spline portion 47b (see FIG. 2) of the rotating shaft 29 of the electric motor 28 is used. The thickness t ₁ is larger than the thickness t ₂ of the outer woven fabric 56a that engages with the female spline portion 48b (see FIG. 2) of the worm shaft 27 (t ₁ > t ₂ ). Further, in a state where the elastic toothed ring 49c is provided between the rotating shaft 29 and the worm shaft 27, between the portions of the male and female spline portions 47b and 48b that overlap each other in the circumferential direction. The thickness T ₁ ′ of the portion formed by adhering a pair of woven fabrics 56a, 56b to the connecting portions 64a, 64a, which is the radial center portion of the elastic toothed ring 49c, A pair of woven fabrics 56a and 56b are attached to the external tooth element portions 54b and 54b, which are the outer diameter side ends of the elastic toothed ring 49c, which are separated from each other between the overlapping portions of the teeth in the circumferential direction. It is larger than the thickness T ₂ ′ of the center portion in the circumferential direction of the part formed by wearing (T ₁ ′> T ₂ ′). Further, the thickness T ₁ ′ of the portion formed by adhering a pair of woven fabrics 56a and 56b to the connecting portions 64a and 64a is set in the circumferential direction of the teeth of the male and female spline portions 47b and 48b. Of the portion formed by adhering a pair of woven fabrics 56a and 56b to the internal tooth element portions 55b and 55b, which are the inner diameter side ends of the elastic toothed ring 49c, which are separated from each other between the overlapping portions. It is larger than the thickness T ₃ ′ of the central portion in the circumferential direction (T ₁ ′> T ₃ ′).

  In the case of the present example configured as described above, since the pair of woven fabrics 56a and 56b are integrally attached to the main body 61 made of an elastic material constituting the elastic toothed ring 49c, this elasticity is provided. It is possible to effectively prevent material tearing and tooth surface peeling. Further, since the external tooth element portions 54b and 54b and the internal tooth element portions 55b and 55b can be hardly deformed, the power that can be transmitted between the rotary shaft 29 and the worm shaft 27 can be further increased, and the durability can be increased. Can be further improved.

  Further, according to the configuration of this example, it is possible to sufficiently ensure the durability while reducing the cost. In addition, the height of each tooth of the male and female spline portions 47b and 48b can be shortened more effectively. That is, of the pair of woven fabrics 56a and 56b provided on the outer diameter side and the inner diameter side of the elastic toothed ring 49c, the woven fabric 56b on the inner diameter side that engages with the rotating shaft 29 of the electric motor 28, which is the drive shaft. In addition, since the driving force is directly applied from the male spline portion 47b provided on the rotating shaft 29 without using an elastic material, the load applied to the woven fabric 56b on the inner diameter side is large. On the other hand, the driving force is applied to the outer woven fabric 56a engaged with the worm shaft 27, which is a driven shaft, via the elastic material body 61 of the elastic toothed ring 49c. Since a force based on the force acts, the load applied to the woven fabric 56a on the inner diameter side is small. For this reason, even if the thickness of the woven fabric 56a on the inner diameter side is reduced, sufficient durability can be secured, and the height of each tooth of the male and female spline portions 47b and 48b can be shortened more effectively. In addition, the material cost of the woven fabric 56a on the outer diameter side can be suppressed, and the cost can be reduced.

On the other hand, as shown in FIG. 4, the thickness of the main body 61 made of an elastic material constituting the elastic toothed ring 62 is made equal over the entire circumference, and both the inner and outer peripheral surfaces of the main body 61 are arranged. The thicknesses t ₁ ′ and t ₂ ′ of the pair of woven fabrics 56a and 56b adhered to each other are made equal (t ₁ = t ₂ ), and each of the male and female spline portions 47b and 48b (see FIG. 2) The thickness T _{4 of the} central portion in the radial direction of the elastic toothed ring 62 existing between the portions overlapping in the circumferential direction of the teeth, and the diameter of the elastic toothed ring 62 deviated from between these portions. Consider a structure deviating from the present invention in which the thicknesses T ₅ and T ₆ at both ends in the direction are made equal (T ₄ = T ₅ = T ₆ ). In the case of such a structure shown in FIG. 4, the thickness T _{4 of the} central portion in the radial direction of the elastic toothed ring 62 and the thickness T ₁ ′ (FIG. 3) of the central portion in the radial direction in this example Are the same (T ₄ = T ₁ ′), the diameter of the elastic toothed ring 62 becomes larger than that in this example. In addition, the height (tooth height) of each tooth of the male and female spline portions 47b and 48b is larger than that in this example, and it is difficult to form the male and female spline portions 47b and 48b by forging. become. This causes a significant increase in manufacturing costs. Moreover, the thicknesses T ₅ and T ₆ at both ends in the radial direction of the elastic toothed ring 62 that are out of the circumferentially overlapping portions of the teeth of the male and female spline portions 47b and 48b are large. Therefore, the material cost cannot be reduced, which causes the manufacturing cost to further increase.
In the case of this example, as described above, since the thickness of a part of the elastic toothed ring 49c is appropriately regulated in relation to the thickness of the other part, such a structure shown in FIG. Any inconveniences that arise in this case can be eliminated. In this example, since the other configurations and operations are the same as those in the case of the first example shown in FIGS. 1 and 2 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted.

[Third example of the embodiment of the invention]
FIG. 5 shows a third example of an embodiment of the present invention corresponding to claims 1, 3 to 5, and 7. In the case of this example, elastic toothed rings 49d are provided with element parts 63, 63 made of an elastic material such as synthetic rubber provided at a plurality of positions in the circumferential direction, and inner diameter side and outer diameter side of these element parts 63, 63. And a pair of woven fabrics 56a and 56b provided in a state of being integrally attached while being sandwiched from both sides in the radial direction. Of the pair of woven fabrics 56a and 56b, the outer woven fabric 56a and the outer teeth 50b of the respective element portions 63 and 63 closer to the outer peripheral surface of the elastic toothed ring 49d. It is composed. Of the pair of woven fabrics 56a and 56b, the inner teeth 51b are formed by the woven fabric 56b on the inner diameter side and the portions of the element portions 63 and 63 closer to the inner peripheral surface of the elastic toothed ring 49d. It is composed. In the case of this example, the portion near the outer peripheral surface of each of the element portions 63, 63 corresponds to the external tooth element portion described in claim 1, and the portion near the inner peripheral surface of each of the element portions 63, 63 is claimed in claim. 1 corresponds to the internal tooth element portion described in 1.

Each of the male and female spline portions 47b and 48b (see FIG. 2) is provided with the elastic toothed ring 49d provided between the rotating shaft 29 of the electric motor 28 and the worm shaft 27 (see FIG. 2). The elastic toothed ring 49d, which has a thickness T ₁ ′ at the center portion in the radial direction of the elastic toothed ring 49d existing between the portions overlapping in the circumferential direction of the tooth, is deviated from between the portions. The thicknesses T ₇ and T _{8 of a} plurality of portions in the circumferential direction consisting only of a pair of woven fabrics 56a and 56b existing at both ends in the radial direction on the outer diameter side and the inner diameter side of the outer diameter side are made larger (T ₁ ′). > T ₇ and T ₁ ′> T ₈ ). Also in the case of this example, as in the case of the second example shown in FIG. 3 described above, the thickness t ₁ of the inner woven fabric 56a is set to be greater than the thickness t ₂ of the outer woven fabric 56b. (T ₁ > t ₂ ).

In the case of this example configured as described above, it is possible to achieve both higher levels of durability and shorter heights of the teeth of the male and female spline portions 47b and 48b. That is, in the case of this example, the durability can be improved to the same extent as in the case of the second example shown in FIG. 3, and the elastic teeth facing the tooth bottoms of the male and female spline portions 47b and 48b. The thickness of a plurality of circumferential positions existing on the inner diameter side, outer diameter side, and both ends in the radial direction of the attached ring 49d can be made smaller than in the case of the second example shown in FIG. For this reason, the moldability by the forging process of each tooth of each said spline part 47b, 48b can be improved more.
Other configurations and operations are the same as in the case of the second example shown in FIG. 3 described above, and therefore, the same parts are denoted by the same reference numerals and redundant description is omitted.

[Fourth example of embodiment of the invention] Next, FIGS. 6 to 7 show a fourth example of an embodiment of the present invention corresponding to claims 1, 5, 7, and 8. FIG. In the case of the elastic toothed ring 49e of this example, it has the same structure as the elastic toothed ring 49b made of an elastic material such as the synthetic rubber shown in FIGS. In addition, a discontinuous portion 65 is provided over the entire length in the axial direction. In order to manufacture such an elastic toothed ring 49e, in the case of the manufacturing method of the elastic toothed ring of this example, it is longer than the dimension in the width direction (x direction in FIG. 7) as shown in FIG. It is made of a long plate-like element 66 having a considerably large dimension in the vertical direction (y direction in FIG. 7).

The plate-like element 66 is made of an elastic material, and peaks 67 and 67 and valleys 68 and 68 are alternately continued in the length direction. Further, the thicknesses T ₁ at a plurality of portions in the longitudinal direction existing between the tops of the peaks 67 and 67 and the bottoms of the valleys 68 and 68 are determined as the other portions of the plate-like element 66. It is larger than the thickness T ₂ of the tops of the portions 67 and 67 and the thickness T ₃ of the bottoms of the valleys 68 and 68 (T ₁ > T ₂ and T ₁ > T ₃ ). And the bottom part of each trough part 68, 68 (or the top part of each peak part 67, 67) so that both ends of the length direction of such a plate-shaped element 66 may be faced | matched or it may oppose through a micro clearance gap. 6 is formed into an elastic toothed ring 49e as shown in FIG. 6, and the male spline portion 47b provided on the rotating shaft 29 of the electric motor 28 is bent into a cylindrical shape. The elastic toothed ring 49e is assembled between the spline portions 47b and 48b while being engaged with a female spline portion 48b (see FIG. 2) provided on the worm shaft 27.

In the case of this example configured as described above, the elastic toothed ring 49e is formed into a circular shape by bending the plate-like element 66 made of an elastic material into a cylindrical shape. Thicknesses T ₃ , T _{3 of} the plate-like element 66 in the longitudinal direction (the bottoms of the valleys 68, 68 and the tops of the peaks 67, 67), which are the inner diameter side and the outer diameter side both ends of the circumferential positions. ₂ can be reduced. Therefore, the plate element 66 can be easily rounded into a cylindrical shape with a small force. Also, the elastic toothed ring 49e made by rounding into a cylindrical shape can be easily assembled (set) between the male spline portion 47b and the female spline portion 48b. For this reason, it is possible to improve the moldability and assembly of the elastic toothed ring 49e. Further, since the elastic toothed ring 49e is made from the plate-like element 66, the mass productivity can be increased and the cost can be further reduced.
Since other configurations and operations are the same as those in the first example shown in FIGS. 1 and 2 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted.

[Fifth Embodiment of the Invention]
Next, FIGS. 8 to 9 show a fifth example of the embodiment of the invention corresponding to claims 1, 5, 6, and 7. In the case of the electric power steering apparatus of this example, unlike the case of the above-described examples, the auxiliary torque of the electric motor 28 is applied to the steering shaft 2 (see FIGS. 10 to 12) via the worm reducer. Absent. In the case of this example, a so-called rack-assist type electric power steering apparatus that applies auxiliary torque of the electric motor 28 to the rack 12 via a helical gear type reduction gear 80 and a ball screw mechanism 81 is provided. The present invention is applied. That is, in the case of this example, the electric motor 28 is provided on the side of the rack 12. Further, the rotary shaft 29 of the electric motor 28 is connected to the input shaft 82 of the helical gear type reduction gear 80, and the output gear 83 serving as the output shaft of the reduction gear 80 and the ball nut 84 are connected to each other. ing. The output gear 83 and the ball nut 84 are provided so as to be fitted around the rack 12. A plurality of balls 87, 87 are provided between an inner diameter side ball screw groove 85 provided on a partial outer peripheral surface of the rack 12 and an outer diameter side ball screw groove 86 provided on the inner peripheral surface of the ball nut 84. It is provided to roll freely. The ball nut 84 is supported only rotatably with respect to the housing 88. The rack 12 supports only the axial displacement with respect to the housing 88.

  When the steering wheel 1 (see FIGS. 10 and 11) is operated with such a rack-assist type electric power steering device, a torque sensor (not shown) provided around the steering shaft 2 or the pinion 11 is used for this steering. The direction and magnitude of torque applied to the shaft 2 or the pinion 11 are detected. Then, the controller 6 (see FIG. 10) energizes the electric motor 28 based on the signal input from the torque sensor, and rotates the ball nut 84 via the speed reducer 80. The rack 12 is displaced in the axial direction by the rotation of the ball nut 84.

  In particular, in the case of this example, a female spline portion 48c provided on the inner peripheral surface of the distal end portion of the rotating shaft 29 of the electric motor 28 and one end portion of the input shaft 82 of the speed reducer 80 (the left end portion in FIGS. 8 to 9). ) An elastic toothed ring 49b similar to that of the first example of the embodiment shown in FIGS. 1 and 2 is provided between the male spline portion 47c provided on the outer peripheral surface, and this elastic toothed ring. By 49b, the rotating shaft 29 and the input shaft 82 are coupled so that power can be transmitted. The teeth of the male spline portion 47c and the female spline portion 48c are overlapped in the circumferential direction of both the spline portions 47c and 48c.

  Furthermore, a female spline portion 48d provided on the output gear 83 of the speed reducer 80, a male spline portion 47d formed on the small diameter cylindrical portion 90 provided on one end portion (the left end portion in FIGS. 8 to 9) of the ball nut 84, In the meantime, an elastic toothed ring 49b similar to that in the first example of the embodiment shown in FIGS. The elastic geared ring 49b couples the output gear 83 and the ball nut 84 so that power can be transmitted. Further, the teeth of the male spline portion 47d and the female spline portion 48d are overlapped in the circumferential direction of both the spline portions 47d and 48d. Also in this example, the elastic toothed rings 49b and 49b are provided in some of the power transmission parts, and the thickness of a part of these elastic toothed rings 49b and 49b is equal to the thickness of the other part. Appropriately regulated in relation. Therefore, it is possible to suppress the generation of abnormal noise at each power transmission unit at a low cost, and each of the male and female components provided on the rotary shaft 29 and the input shaft 82, the output gear 83 and the small diameter cylindrical portion 90 are provided. The height of each tooth of the spline portions 47c, 47d, 48c, and 48d can be reduced, and sufficient durability can be secured. In the scope of the present invention, instead of the elastic toothed rings 49b and 49b, the elastic toothed rings 49c to 49e used in the second to fourth examples of the embodiment shown in FIGS. Of course, it is possible to adopt a structure using the.

  Although not shown in the drawings, the rack assist type electric power steering apparatus has an electric motor including a rotating shaft of the electric motor and a rotating shaft of the ball nut in addition to the structure shown in FIGS. In addition to being provided around the rack so as to be positioned on the same axis, the rotating shaft of the electric motor and the ball nut may be directly connected without a reduction gear. Even in the electric power steering apparatus having such a structure, the same structure as the power transmission mechanisms of the first to fourth examples described above can be adopted for the power transmission part between the rotating shaft of the electric motor and the ball nut.

Sectional drawing which shows the elastic toothed ring integrated in the power transmission mechanism of the 1st example of embodiment of this invention. The figure equivalent to FIG. 20 which shows the power transmission mechanism which integrated the elastic toothed ring of FIG. 1 between the male spline part provided in the rotating shaft, and the female spline part provided in the worm shaft. Sectional drawing which shows the elastic toothed ring integrated in the power transmission mechanism of the 2nd example of embodiment of this invention. Sectional drawing which shows the elastic toothed ring which made thickness equal over the perimeter and remove | deviates from this invention. Sectional drawing which shows the elastic toothed ring integrated in the power transmission mechanism of the 3rd example of embodiment of this invention. The perspective view which shows the elastic toothed ring integrated in the power transmission mechanism of the 4th example. The perspective view which shows the plate-shaped element which comprises the elastic toothed ring of FIG. The fragmentary sectional view which shows the rack-assist type electric power steering device of the 5th example of an embodiment of the invention. The A section expanded sectional view of FIG. BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole structure of one example of the electric power steering apparatus used as the object of this invention. The figure which cuts and shows one example of the conventional structure of an electric power steering device. The fragmentary sectional view of the BB part of FIG. The elements on larger scale of FIG. The C section enlarged view of FIG. DD sectional drawing. The expansion perspective view of the elastic toothed ring used for the power transmission mechanism of FIG. The figure which expands and shows the EE cross section of FIG. The disassembled perspective view which cuts some and shows the power transmission mechanism of the prior invention invented prior to the present invention. The perspective view which cut | disconnects and shows a part in the state which combined the power transmission mechanism of FIG. The figure at the time of cut | disconnecting FIG. 19 by the virtual plane F. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Electric motor 4 Reduction gear 5 Torque sensor 6 Controller 7 Universal joint 8 Intermediate shaft 9 Steering gear 10 Input shaft 11 Pinion 12 Rack 13 Tie rod 14 Steering wheel 15 Steering column 16 Assist device 17 Outer shaft 18 Inner Shaft 19 Car body 20 Worm speed reducer 21 Gear housing 22 First inner shaft 23 Second inner shaft 24 Torsion bar 26 Worm wheel 27 Worm shaft 28 Electric motor 29 Rotating shaft 30, 30a, 30b Power transmission mechanism 31 Elasticity imparting means 32 Bearing holder 33 First ball bearing 34 Second ball bearing 35 Oscillating shaft 36 Coil spring 37 Worm 38 Case 39 Large diameter cylindrical portion 40 Small diameter cylindrical portion 41 Stepped portion 42 Concave 43 elastic ring 44 through-hole 45 concave hole 47, 47a-47d male spline part 48, 48a-48d female spline part 49, 49a-49e elastic toothed ring 50, 50a, 50b outer tooth 51, 51a, 51b inner tooth 52 body Part 54, 54a, 54b External tooth element part 55, 55a, 55b Internal tooth element part 56a, 56b Woven fabric 61 Main body part 62 Elastic toothed ring 63 Element part 64, 64a Connection part 65 Discontinuous part 66 Plate element 67 Mountain Part 68 valley part 80 speed reducer 81 ball screw mechanism 82 input shaft 83 output gear 84 ball nut 85 inner diameter side ball screw groove 86 outer diameter side ball screw groove 87 ball 88 housing 90 small diameter cylindrical part

Claims (8)

A power transmission mechanism provided between the drive shaft and the driven shaft for transmitting power between the two shafts;
A female spline portion provided on the inner peripheral surface of the end of one of these shafts, a male spline portion provided on the outer peripheral surface of the end of the other shaft, and an outer surface that engages with the female spline portion. An elastic toothed ring having teeth on its outer peripheral surface and inner teeth on its inner peripheral surface that engage with the male spline portion on its inner peripheral surface. The elastic toothed ring is provided on the outer diameter side and the inner diameter side. In the power transmission mechanism in which a plurality of external tooth element portions and internal tooth element portions each made of an elastic material are integrally provided,
The teeth of the female spline portion provided on one of the drive shaft and the driven shaft and the teeth of the male spline portion provided on the other shaft are arranged in the circumferential direction of both the spline portions. The thickness of the elastic toothed ring that exists between the portions of the splines that overlap each other in the circumferential direction is between the portions that overlap each other in the circumferential direction of these teeth. The power transmission mechanism is characterized in that it is larger than the thickness of the elastic toothed ring that is removed from the power.   The elastic toothed ring includes a main body portion made of an elastic material and a woven fabric provided in a state of being integrally attached to at least one of the outer diameter side and the inner diameter side of the main body portion. The thickness of the elastic toothed ring existing between the circumferentially overlapping portions of each tooth of the spline part is determined by the elastic toothed ring deviated from between the circumferentially overlapping portions of each tooth. The power transmission mechanism according to claim 1, wherein the power transmission mechanism is larger than the thickness.   The elastic toothed ring is provided with element portions made of an elastic material provided at a plurality of locations in the circumferential direction, and a woven fabric provided in a state of being integrally attached to at least one side of these element portions. The woven fabric in which the thickness of the elastic toothed ring existing between the circumferentially overlapping portions of each tooth of both female spline portions is removed from between the circumferentially overlapping portions of these respective teeth. The power transmission mechanism according to claim 1, wherein the power transmission mechanism is made larger than a thickness of the elastic toothed ring made of only.   The elastic toothed ring is provided with a pair of woven fabrics on the outer diameter side and the inner diameter side, and the thickness of one of the woven fabrics that engages with the drive shaft is related to the driven shaft. The power transmission mechanism according to any one of claims 1 to 3, wherein the power transmission mechanism is larger than the thickness of the other woven fabric to be joined.   An electric power steering apparatus in which a rotation shaft of an electric motor and an input shaft constituting a speed reducer are coupled by a power transmission mechanism described in any one of claims 1 to 4 so that power can be transmitted.   An electric power steering in which an output shaft of a reduction gear or a rotary shaft of an electric motor and a ball nut are coupled to each other by a power transmission mechanism described in any one of claims 1 to 4 so that power can be transmitted. apparatus.   An elastic toothed ring for use in the power transmission mechanism according to claim 1, wherein the outer peripheral surface has outer teeth and the inner peripheral surface has inner teeth. A plurality of external tooth elements and internal tooth elements, each of which is made of an elastic material, are integrally provided, and the thickness of the central portion in the radial direction is larger than the thickness of the radial end portions. ring.   It is a manufacturing method of the elastic toothed ring of Claim 7, Comprising: At least one part is made of an elastic material, and a peak part and a trough part continue alternately in the length direction, and the top part of a peak part By bending a plate-like element that is larger than at least one of the top of the peak and the bottom of the valley into a cylindrical shape, the thickness of the portion that exists between the bottom of the valley and the bottom of the valley is elastic. An elastic toothed ring manufacturing method for making a toothed ring.

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