WO2005012748A1

WO2005012748A1 - Power transmission mechanism and electric power steering device with the mechanism assembled therein

Info

Publication number: WO2005012748A1
Application number: PCT/JP2004/011177
Authority: WO
Inventors: Atsushi Maeda; Kazuo Chikaraishi
Original assignee: Nsk Ltd.; Nsk Steering Systems Co., Ltd.
Priority date: 2003-08-05
Filing date: 2004-08-04
Publication date: 2005-02-10
Also published as: JP2005069470A

Abstract

A power transmission mechanism and an electric power steering device with the mechanism assembled therein, where, in the power transmission mechanism, abnormal noise is suppressed without unnecessarily increasing costs and reducing bending rigidity of a drive shaft and a driven shaft. A ring (49) with elastic teeth, having external teeth (50) on the outer periphery and internal teeth (51) on the inner periphery, is provided between a male spline portion (47) on the outer periphery of a rotating shaft (40) of an electric motor (30) and a female spline portion (48) on the inner periphery of a worm shaft (29). In the ring with elastic teeth, woven fabrics are adhered to the outer periphery and the inner periphery, and annular core wires are contained inside a synthetic-rubber body portion (52). The external teeth are spline-engaged with the female spline portion and the internal teeth are spline-engaged with the male spline portion.

Description

Specification

Power transmission mechanism and electric power steering device incorporating the same

[0001] The present invention relates to an electric power steering system which is incorporated in a steering device of an automobile and uses the output of an electric motor as auxiliary power to reduce driver force S and the force required to operate a steering wheel. It relates to the improvement of the power transmission mechanism incorporated in equipment.

Background art

[0002] Power steering is a device for reducing the force required for a driver to operate a steering wheel when giving a steering angle to a steered wheel (except for a special vehicle such as a forklift or the like, which is usually a front wheel). The device is widely used. In addition, in such a power steering apparatus, an electric power steering apparatus using an electric motor as an auxiliary power source has begun to be widely used in recent years. The electric power steering device has advantages such as being smaller and lighter than the hydraulic power steering device, easily controlling the magnitude (torque) of the auxiliary power, and reducing the power loss of the engine. FIG. 33 schematically shows an example of a conventionally known basic configuration of such an electric power steering apparatus.

[0003] In a middle portion of the steering shaft 2 that rotates based on the operation of the steering wheel 1, a tonnole sensor 3 for detecting the direction and magnitude of the torque applied to the steering shaft 2 from the steering wheel 1, and a reduction gear 4 Are provided. The output side of the speed reducer 4 is connected to an intermediate portion of the steering shaft 2, and the input side is connected to the rotation shaft of the electric motor 5. The detection signal of the torque sensor 3 is input to a controller 6 for controlling the energization of the electric motor 5 together with a signal indicating the vehicle speed. A worm speed reducer having a large lead angle and having reversibility with respect to the power transmission direction has been generally used as the speed reducer 4. That is, the worm wheel, which is a rotational force receiving member, is fixed to the intermediate portion of the steering shaft 2, and the worm of the worm shaft, which is a rotational force applying member and is fixedly connected to the rotating shaft of the electric motor 5, is connected to the worm wheel. And combine them. When the steering wheel 1 is operated to rotate the steering shaft 2 to impart a steering angle to the steered wheels 14, the torque sensor 3 detects the rotation direction and the torque of the steering shaft 2. , And sends a signal representing the detected value to the controller 6. Then, the controller 6 energizes the electric motor 5 to rotate the steering shaft 2 via the speed reducer 4 in the same direction as the rotation direction based on the steering wheel 1. As a result, the tip end (the lower end in FIG. 33) of the steering shaft 2 rotates with a torque larger than the torque based on the force applied from the steering wheel 1.

[0005] Such rotation of the distal end of the steering shaft 2 is transmitted to the input shaft 10 of the steering gear 9 via the universal joint 7 and the intermediate shaft 8. The input shaft 10 rotates a pinion 11 constituting the steering gear 9, pushes and pulls a tie rod 13 through a rack 12, and gives a desired steering angle to the steered wheels 14. As is clear from the above description, the torque transmitted from the distal end of the steering shaft 2 to the intermediate shaft 8 via the universal joint 7 is transmitted from the steering wheel 1 to the base end of the steering shaft 2 (FIG. 33). (The upper end of the motor) is greater by the auxiliary power applied from the electric motor 5 via the speed reducer 4. Therefore, the force required for the driver to operate the steering wheel 1 to give the steering angle to the steered wheels 14 can be reduced by the amount of the auxiliary power.

[0006] In the case of the electric power steering apparatus generally used in the past as described above, a worm speed reducer is used as the speed reducer 4 provided between the electric motor 5 and the steering shaft 2. . Further, the output shaft of the electric motor 5 and the input shaft constituting the reduction gear 4 are spline-engaged with a male spline portion provided on one of the two shafts and a female spline portion provided on the other. It is common practice to connect with a spline engagement part. However, when the output shaft and the input shaft, each of which are made of metal, are connected by the spline engagement portion, the male spline portion and the female spline portion provided on both shafts are fitted with a negative gap ( If it is an interference fit, the assembling work becomes considerably troublesome. Under such circumstances, the male and female spline portions are conventionally fitted with a positive gap (the gap is fitted). However, when this gap is increased, when the gap becomes large, the However, the tooth flanks constituting the male and female splines are in strong abutment with each other, producing an unpleasant rattling sound. It becomes easy to grow. Therefore, it is necessary to regulate this gap as small as possible with a positive value. However, for this purpose, it is necessary to strictly control the dimensions of each part, which significantly increases the cost of the electric power steering device.

[0007] On the other hand, if the unavoidable backlash existing between the tooth surfaces of the worm of the worm shaft and the worm wheel constituting the worm speed reducer becomes large, these tooth surfaces strongly abut each other, and are unpleasant. Rattling noise may occur. For example, when a vibration load is applied to the steering shaft 2 from the wheel side due to a rough road surface or the like, an unpleasant rattling sound is generated due to the presence of the backlash. In view of such circumstances, in recent years, elasticity applying means is provided between a gear housing constituting a worm reduction gear and a worm shaft, and the elasticity applying means allows the worm shaft to move in a direction toward the worm wheel.弹 It is considered to give power. According to this configuration, the backlash existing at the joint between the worm of the worm shaft and the worm wheel can be suppressed, so that the occurrence of the rattling noise can be suppressed.

[0008] However, in order to suppress the generation of the rattling noise with this configuration, the spline engagement portion provided between these two shafts is provided in order to incline the worm shaft with respect to the rotation shaft of the electric motor 5 described above. There is a possibility that a part of each tooth that constitutes the slab is cut off. On the other hand, if the rigidity of the male and female splines that make up this spline engagement part is increased to prevent these teeth from being digged, the space between the tooth surfaces of these spline parts is increased. The rattling noise at the wheel is more likely to occur. For this reason, in order to allow the worm shaft to tilt with respect to the rotation shaft of the electric motor 5 and to suppress the rattling noise, the gap between the male and female splines is more strictly regulated. However, such difficult work must be performed, which further increases the cost of the electric power steering device.

[0009] On the other hand, it is considered that the end of the worm shaft and the end of the rotating shaft of the electric motor 5 are connected by an elastic joint that does not have a spline engagement portion. Therefore, it is necessary to greatly change the design of these two shafts, which inevitably increases the cost.

[0010] In view of such circumstances, in the case of the structure described in Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-34256), one end of the worm shaft and the rotating shaft of the electric motor is used. Provided in the department Between the male spline portion and the female spline portion provided at the other end, there is provided an o-ring whose cross-sectional diameter changes in the circumferential direction. According to this configuration, a portion of the o-ring having a large cross-sectional diameter can partially expand the part between the male and female splines, thereby allowing the male and female splines to be expanded. Can be brought into strong contact with each other. For this reason, it is possible that the occurrence of rattling noise caused by the abutment of the tooth surfaces of the male and female splines with a relatively inexpensive structure may be suppressed.

[0011] However, in the structure described in Patent Document 1, when both the worm shaft and the rotating shaft of the electric motor are rotatably supported by a bearing on a fixed portion, the male and female members are used. In order to make the two spline portions partially contact each other, the bending stiffness of at least one of the worm shaft and the rotating shaft must be reduced to some extent. On the other hand, if the bending stiffness of these two shafts cannot be reduced, it may not be possible to sufficiently suppress the generation of abnormal noise due to the collision of the tooth surfaces of the male and female splines. . Also, in the case where there is an eccentric error between the worm shaft and the rotating shaft in advance, or when these two shafts are not located coaxially and there is an eccentric error in both shafts, etc. Some of the male and female splines cannot make strong contact with each other, and the generation of abnormal noise due to the abutment of the tooth surfaces of both splines cannot be sufficiently suppressed. There is.

[0012] In recent years, a so-called rack-assist type electric power steering apparatus has been considered in which the rotational force of an electric motor is converted into an axial force by a ball screw mechanism and the force is applied to a rack as auxiliary power. Has been used in practice. In such a rack assist type electric power steering apparatus, the output shaft of the speed reducer or the rotation shaft of the electric motor is connected to the ball nut constituting the ball screw mechanism by a spline engaging portion. However, if the gap existing between the tooth surfaces of the male spline portion and the female spline portion constituting the spline engagement portion becomes large, and these tooth surfaces strongly abut each other, an unpleasant rattling sound is generated. Is more likely to occur. For this reason, even in the case of such a rack assist type electric power steering device, the spline between the rotating shaft of the electric motor and the worm shaft in the electric power steering device using the worm speed reducer described above is used. The same disadvantages as in the case of the engaging portion occur. [0013] On the other hand, in recent years, a force different from the technical field described above, in recent years, a toothed belt in which a plurality of pulleys are provided on both sides thereof between a plurality of pulleys, each of which is rotatably supported on a fixed portion. In some cases, the rotational force can be freely transmitted between these pulleys.

Patent Document 1: JP 2003-34256 A

Disclosure of the invention

Problems to be solved by the invention

[0015] In view of the above-mentioned circumstances, the present invention devises a structure of a toothed belt having a plurality of teeth provided on both side surfaces thereof, and also devises a part using this structure to reduce costs. Power transmission mechanism built into an electric power steering device, etc., that raises the shaft and lowers the bending stiffness between the drive shaft and the driven shaft. Things.

Means for solving the problem

[0016] The power transmission mechanism of the present invention is provided between a drive shaft and a driven shaft in an electric power steering device, and is for transmitting power between these two shafts. For this purpose, the power transmission mechanism of the present invention includes a female spline portion, a male spline portion, and an elastic toothed ring.

[0017] Of these, the female spline portion is provided on the inner circumferential surface at the end of one of the two shafts. On the other hand, the male spline portion is provided on the outer peripheral surface of the end of the other of the two shafts.

[0018] The elastic toothed ring has external teeth that spline-engage with the female spline portion on its outer peripheral surface, and internal teeth that spline-engage with the male spline portion on its inner peripheral surface. I do.

In the elastic toothed ring, a plurality of external tooth element portions and a plurality of internal tooth element portions each made of an elastic material and radially protruding are provided integrally on the outer diameter side and the inner diameter side, respectively. On the outer peripheral surface, the outer diameter side surface of each of the external tooth element portions and a portion between these external tooth element portions, and on the inner peripheral surface, the inner diameter side surface of each of the internal tooth element portions and each of the internal tooth element portions The outer teeth and the inner teeth are formed by adhering a woven fabric to the middle part. [0020] The above-mentioned elastic toothed rings include not only those having a cylindrical shape as a whole but also those having a cylindrical shape as a whole.

Further, in the electric power steering apparatus of the present invention, the output shaft of the electric motor, which is the driven shaft and the driven shaft, and the input shaft that constitutes the reduction gear are connected to the power transmission of the present invention as described above. The transmission of power is freely connected by a mechanism.

The invention's effect

[0022] In the case of the above-described power transmission mechanism of the present invention and the electric power steering apparatus incorporating the same, an elastic toothed ring is provided between the female spline section and the male spline section. For this reason, it is possible to prevent the tooth surfaces of both spline portions from directly abutting each other, and it is possible to prevent the generation of abnormal noise due to the abutting of these tooth surfaces. Further, external teeth provided with a plurality of elastic external tooth element portions are provided on the outer diameter side of the elastic toothed ring, and a plurality of elastic materials are provided on the inner diameter side of the elastic toothed ring. An internal tooth having an internal tooth element portion is provided. For this reason, abnormal noise caused by collision between the tooth surfaces of the male and female spline portions and the tooth surfaces of the internal teeth and the external teeth of the elastic toothed ring can be reduced or eliminated.

Further, in the case of the present invention, unlike the case of the conventional structure described in Patent Document 1, the bending stiffness of the drive shaft and the driven shaft is reduced, and a part of these two shafts is connected to each other. It is not necessary to abut strongly. Further, since each of the internal tooth element portions and each external tooth element portion are made of an elastic material, inevitable dimensional errors present in the male and female spline portions can be easily absorbed by the internal teeth and the external teeth. , 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 of the present invention and the electric power steering apparatus incorporating the power transmission mechanism.

Further, even when there is an eccentricity error or an eccentricity error in the male and female spline portions, the drive shaft and the driven shaft can freely transmit power while absorbing these errors. It becomes possible to connect.

[0025] Further, in the case of the present invention, the outer peripheral surface of the elastic toothed ring, the outer diameter side surface of each of the external tooth element parts, the portion between these external tooth element parts, and the elastic toothed ring. A woven cloth is adhered to each of the above-mentioned internal tooth element portions and a portion between these internal tooth element portions on the inner peripheral surface. For this reason, after the root of each of the external tooth element portions and the internal tooth element portions, which are made of an elastic material, Breakage and tearing of the tooth surface can be prevented. When the woven fabric is adhered to the outer peripheral surface and the inner peripheral surface of the elastic toothed ring so as to be continuous over the entire circumference, the outer tooth element portion and the inner tooth element portion are also applied. Can be hardly deformed. Therefore, the power that can be transmitted between the drive shaft and the driven shaft can be increased, and the durability can be improved.

[0026] Therefore, according to the power transmission mechanism of the present invention and the electric power steering apparatus incorporating the same, it is unnecessary to increase the cost or to reduce the bending rigidity between the drive shaft and the driven shaft. The occurrence of abnormal noise can be suppressed.

Brief Description of Drawings

FIG. 1 is a diagram showing a first embodiment of the present invention with a part thereof cut away.

[FIG. 2] FIG. 2 is a partial cross-sectional view taken along a line AA of FIG.

[FIG. 3] FIG. 3 is a cross-sectional view taken along the line BB of FIG. 2, partially omitted.

FIG. 4 is a cross-sectional view of the electric motor.

FIG. 5 is a partially enlarged view of FIG. 2.

FIG. 6 is an enlarged view of a portion C in FIG. 5.

FIG. 7 is a sectional view taken along the line DD of FIG.

FIG. 8 is a perspective view of an elastic toothed ring.

[FIG. 9] FIG. 9 is a sectional view taken along line EE of FIG.

FIG. 10 is an enlarged view showing a section taken along line FF of FIG. 5.

[FIG. 11] FIG. 11 shows a case where the main body of the elastic toothed ring is made only of an elastic material, and FIG. 10 for explaining the disadvantages to be improved when the elastic modulus of the elastic material is low. FIG.

[Fig. 12] Fig. 12 shows a case where the swing center axis of the worm shaft is provided so as to intersect at right angles with the center axis of the first ball bearing that is rotatably supported on the gear housing. FIG. 6 is a schematic cross-sectional view for explaining a direction of a reaction force applied from the worm wheel to the worm shaft when the rotor is driven to rotate in a predetermined direction.

FIG. 13 is a schematic cross-sectional view for explaining the direction of a reaction force applied to the worm shaft from the worm wheel when the electric motor is driven to rotate in a direction opposite to the above-described predetermined direction.

FIG. 14 is a view similar to FIG. 9, showing an elastic toothed ring used in Embodiment 2 of the present invention. It is.

FIG. 15 is a view similar to FIG. 9, showing an elastic toothed ring used in Embodiment 3.

FIG. 16 is a perspective view of an elastic toothed ring used in Example 4;

FIG. 17 is a sectional view taken along line GG of FIG.

FIG. 18 is a view similar to FIG. 10, but showing a case where the elastic material constituting the elastic toothed ring has a high elastic modulus in Embodiment 4 of the present invention.

FIG. 19 is a view similar to FIG. 9, showing an elastic toothed ring used in Example 5;

FIG. 20 is a view similar to FIG. 9, illustrating an elastic toothed ring used in Example 6;

FIG. 21 is a partial cutaway view showing a rack-assist type electric power steering device according to the seventh embodiment.

FIG. 22 is an enlarged view of a portion H in FIG. 21.

FIG. 23 is a perspective view of an elastic toothed ring used in Embodiment 8 of the present invention.

FIG. 24 is an end view of the elastic toothed ring.

FIG. 25 is a diagram showing a method of manufacturing a plurality of elastic toothed rings from a columnar material in the order of steps in Example 8 of the present invention.

[FIG. 26] FIG. 26 is a view similar to FIG. 25, when the diameter of the columnar material is made the same as the diameter of the elastic toothed ring.

FIG. 27 is a perspective view of an elastic toothed ring used in Embodiment 9 of the present invention.

FIG. 28 is an end view of the elastic toothed ring.

FIG. 29 is an end view of an elastic toothed ring used in Embodiment 10.

FIG. 30 is an end view of an elastic toothed ring used in Example 11 of the present invention.

FIG. 31 is an end view of an elastic toothed ring used in Example 12;

FIG. 32 is an end view of an elastic toothed ring used in Example 13;

[FIG. 33] FIG. 33 is a schematic view showing an entire structure of an example of an electric power steering apparatus to which the present invention is applied.

Explanation of symbols

1 Steering wheel

2 Steering shaft Torque sensor

Decelerator

Electric motor

Controller

Universal joint

Intermediate shaft Steering gear Input shaft

Pinion

Rack

Tie rod

Steering wheel

Steering column assist device

Outer shaft Inner shaft Outer column Inner column Gear housing First inner shaft Second inner shaft Toshiba 3 bar Support bracket Body

Elasticity imparting means Worm wheel Worm shaft

Electric motor Power transmission mechanism

Bearing holder

First ball bearing

Second ball bearing Coil spring

Warm

Case

Stator

, 40a rotating shaft

Rotor

Bottom plate

Hollow

Third ball bearing

Partition wall

Fourth ball bearing

Male spline 咅

Female spline 咅

, 49a—49k elastic toothed ring external teeth

Internal teeth

, 52a body

Core wire

External tooth element

Internal tooth element

a, 56b woven cloth

Column

Large diameter part Step surface

Incomplete part Large diameter cylinder Small diameter cylinder Outer ring

Step

Lock ring Inner ring

Tsubabe

Locking ring First through hole Main body

Kano Kuichi

Hollow

Second through hole Wall

Hollow

Elastic ring recess

Decelerator

Output gear Bonore nut Inner diameter ball stirrer Outer diameter ball stirrer Ball

Housing Female spline input shaft 87 Male spline 咅

88 Female spline 咅

89 Male spline

90 through hole

91 Input shaft

92 Worm reducer

93 discontinuity

94 Plate element

95 cylindrical material

96 Main unit

97 cylindrical material

98 Ball screw mechanism

BEST MODE FOR CARRYING OUT THE INVENTION

[0029] When the above-described power transmission mechanism of the present invention and the electric power steering apparatus incorporating the same are implemented, preferably, the elastic toothed ring constitutes each external tooth element part and each internal tooth element part. A core material made of a material having a higher elastic modulus than the elastic material is provided.

[0030] According to this preferred configuration, the rigidity of the elastic toothed ring can be improved, the power that can be transmitted between the drive shaft and the driven shaft can be increased, and the durability can be further improved. Things come out.

[0031] More preferably, the core material is formed into any one of an annular shape, a cylindrical shape, an annular shape, and an annular shape, and the outer diameter side and the inner diameter of the core material. A plurality of external tooth elements and internal tooth elements are integrally provided on each side.

[0032] According to this more preferable configuration, the inevitable dimensional error existing in both the male and female spline portions is easily absorbed by the internal teeth and the external teeth, and the transmission between the drive shaft and the driven shaft is performed. It is possible to easily achieve both higher power and improved durability at a higher level.

That is, the forces acting on the internal teeth and the external teeth from the male and female splines are The shear force acts in the opposite direction with respect to the circumferential direction of the teeth and the external teeth. On the other hand, in the case of the present invention, the elastic toothed ring has a plurality of external teeth on the outer diameter side and the inner diameter side of the core material formed in an annular shape, a cylindrical shape, a missing annular shape or a missing cylindrical shape. An element portion and an internal tooth element portion are provided, and the elastic modulus of the material forming the core is higher than the elastic modulus of the elastic material forming the elastic toothed ring. For this reason, the rigidity of the portion between the external teeth and the internal teeth of the elastic toothed ring can be increased, and the external tooth element portion and the internal teeth described above can be compared with a case where the intermediate portion is made of only the elastic material. The deformation of the element portion can be suppressed. Therefore, the power that can be transmitted between the drive shaft and the driven shaft can be increased, and the durability can be improved. Moreover, the rigidity of each of the external tooth element portions and each internal tooth element portion does not need to be excessively increased. For this reason, the inevitable dimensional errors existing in the male and female splines are easily absorbed by the internal and external teeth, and the power that can be transmitted between the drive shaft and the driven shaft is increased, and the durability is improved. Can be easily achieved at a higher level.

[0034] More preferably, the core material is a core wire formed in an annular shape or a partially annular shape.

According to this more preferred configuration, the bending rigidity of the elastic toothed ring does not need to be excessively increased, and even when the driven shaft is inclined with respect to the drive shaft, this inclination is hindered by the elastic toothed ring. It becomes difficult to be.

[0036] More preferably, the elastic material forming each of the external tooth element parts and each internal tooth element part is a synthetic rubber.

According to this more preferred configuration, it is possible to further suppress an increase in cost of the power transmission mechanism and the electric power steering apparatus incorporating the power transmission mechanism.

[0038] More preferably, a part of the member provided with the female spline portion or the male spline portion is provided.

And a displacement preventing portion for preventing displacement of the elastic toothed ring in the axial direction.

According to this more preferable configuration, it is possible to prevent the elastic toothed ring from being partially released between the male and female spline portions.

[0040] More preferably, the elastic toothed ring is a plate having an external tooth element portion and an internal tooth element portion on both side surfaces, and having a circular or linear cross section having a central angle of 180 degrees or less. Element

It is made by bending into a cylindrical shape or a partially cylindrical shape.

[0041] According to this more preferable configuration, the production per unit during mass production of the elastic toothed ring is performed. Costs can be kept low. That is, this elastic toothed ring can be manufactured as follows. First, the external tooth element portion is provided on the outer diameter side and the internal tooth element portion is provided on the inner diameter side. The circumferential length of the elastic toothed ring to be obtained is at least twice as large as the circumferential length. Make a cylindrical material. Woven cloth is adhered to the inner peripheral surface and the outer peripheral surface of the cylindrical material. Then, when producing this cylindrical material, the non-solidified non-solidified material is fed into the cavity with the woven fabric set on the inner and outer peripheral surfaces of the cavity of the molding die. Next, a plurality of plate-like elements are obtained by cutting the cylindrical material taken out of the cavity at a plurality of locations in the circumferential direction. Next, a plurality of elastic toothed rings are obtained by bending each of these plate-like elements into a cylindrical shape or a partially cylindrical shape. In this way, a plurality of elastic toothed rings can be obtained by feeding the elastic material before solidification into the cavity and performing a forming operation to obtain one cylindrical material larger than the elastic toothed ring to be obtained. Can be For this reason, the manufacturing operation time per unit of the elastic toothed ring can be reduced. As a result, the production cost per unit during mass production of the elastic toothed ring can be reduced. When the diameter of the cylindrical material is sufficiently larger than the diameter of the elastic toothed ring to be obtained, the axial length of the cylindrical material is changed to the axial length of the elastic toothed ring. More than twice as large. Therefore, by cutting the cylindrical material at one or more locations in the axial direction, the number of elastic toothed rings obtained by molding one cylindrical material is increased, and the Manufacturing cost can be kept lower.

[0042] In the electric power steering device of the present invention, for example, the output shaft of the electric motor and the input shaft that constitutes the reduction gear are freely connected to each other by the power transmission mechanism of the present invention. However, when the electric power steering device is implemented, more preferably, the speed reducer is a worm speed reducer, and the worm shaft is provided with elasticity in a direction toward the worm wheel.

[0043] According to this configuration, it is possible to suppress the generation of rattling noise at the joint between the worm of the worm shaft and the worm wheel.

On the other hand, in the rack-assist type electric power steering device, the output shaft of the speed reducer or the rotating shaft of the electric motor and the ball nut can be freely transmitted by the above-described power transmission mechanism. Join. [0045] Also, preferably, in the electric power steering device, auxiliary force transmission between an output shaft of the electric motor and a member to which auxiliary power is applied by the electric motor via a speed reducer or a ball nut. The torsional breaking strength of the elastic material forming the elastic toothed ring is made smaller than the minimum breaking strength of the rotation transmitting members other than the elastic toothed ring in the rotation transmitting member constituting the path.

[0046] According to this further preferred configuration, when the steering wheel is rotated to the maximum, the rotation of the steering shaft is prevented by the steering stopper, and the inertia force of the electric motor is applied to the members constituting the auxiliary force transmission path. Thus, even when a force is applied in a direction in which the vehicle continues to rotate, it is possible to more effectively prevent a situation in which steering becomes impossible during driving of the vehicle. That is, in this case, among the rotation transmitting members of the auxiliary force transmission path, an excessive torque difference is generated between the rotating transmission members engaged with each other, and each of the rotation transmitting members is caused by a large impact force. It may be easily damaged. Therefore, if no countermeasures are taken, there is a possibility that these rotating members will engage with each other so that they cannot rotate the steering wheel in the desired direction with the driver's force. . On the other hand, when the above-described more preferable configuration is adopted, when an excessive torque difference is generated between the rotation transmitting members constituting the auxiliary force transmission path, the rotation transmitting members among the rotation transmitting members may be used. The elastic toothed ring can be broken first. In this case, the auxiliary force of the electric motor cannot be transmitted to the steering shaft or a member connected to the steering shaft. However, among the above rotation transmitting members, the rotation transmitting members other than the elastic toothed ring can be hardly damaged. For this reason, the steering wheel can be easily rotated in a desired direction by the driver's force, and the occurrence of a situation in which steering becomes impossible during driving of the vehicle can be more effectively prevented.

Example 1

FIG. 110 shows a first embodiment of the power transmission mechanism of the present invention. The electric power steering apparatus according to the present embodiment includes a steering shaft 2 having a steering wheel 1 fixed to a rear end, a steering column 15 through which the steering shaft 2 can be inserted, and an auxiliary torque applied to the steering shaft 2. Assisting device 16, a pinion 11 (see FIG. 33) provided at the front end of the steering shaft 2, and the pinion 11 or the pinion 11. A rack 12 (see FIG. 33) combined with a member supported by the two-on 11 is provided.

[0048] Of these, the steering shaft 2 is formed by combining an outer shaft 17 and an inner shaft 18 by a spline engagement portion so that rotational force can be transmitted and displacement in the axial direction is possible. In the case of the present embodiment, the front end of the outer shaft 17 and the rear end of the inner shaft 18 are spline-engaged and connected via a synthetic resin. Therefore, when the outer shaft 17 and the inner shaft 18 collide with each other, the synthetic resin can be broken at the time of collision to reduce the overall length.

[0049] Further, the cylindrical steering column 15 passing through the steering shaft 2 is formed by combining an outer column 19 and an inner column 20 in a telescopic shape. It has a so-called collapsible structure in which the overall length is reduced while absorbing the energy generated by the device. The front end of the inner column 20 is connected and fixed to the rear end face of the main body 70 of the main body 70 and the cover 71 constituting the gear housing 21. The gear housing 21 is formed by connecting the cover 71 to a front end of the main body 70 by bolts or the like (not shown). Further, the inner shaft 18 is inserted into the inside of the gear housing 21, and the front end of the inner shaft 18 projects from the front end surface of the cover 71. In such an inner shaft 18, a first inner shaft 22 provided on the rear end side and a second inner shaft 23 provided on the front end side are arranged coaxially. Front ends are connected by torsion bar 24 (Fig. 3)

The steering column 15 has an intermediate portion supported by a support bracket 25 on a part of the vehicle body 26 such as a lower surface of a dashboard. Further, a not-shown locking portion is provided between the support bracket 25 and the vehicle body 26, and when the support bracket 25 is subjected to a frontward or downward impact, the support bracket 25 Remove from the locking part. The upper end of the gear housing 21 is also supported by a part of the vehicle body 26. Further, by providing a tilt mechanism and a telescopic mechanism, the front-rear position and the height position of the steering wheel 1 can be freely adjusted. Such a tilt mechanism and a telescopic mechanism are well known in the related art, and are not characteristic features of the present invention, and therefore, detailed description thereof will be omitted. The protruding portion of the front end of the second inner shaft 23 at the front end surface of the gear housing 21 is connected to the rear end of the intermediate shaft 8 (FIG. 1) via the universal joint 7. are doing. An input shaft 10 (FIG. 1) of a steering gear 9 is connected to the front end of the intermediate shaft 8 via another universal joint 7. The pinion 11 is connected to the input shaft 10. The rack 12 is combined with the pinion 11. Incidentally, in order to prevent the vibration applied to the intermediate shaft 8 from the ground via the wheels from being transmitted to the steering wheel 1, a vibration absorbing device can be provided in each of the universal joints 7, 7.

As shown in FIG. 2-7, the assist device 16 includes a worm wheel 28 that can be externally fixed to the intermediate portion of the second inner shaft 23 and a worm shaft 29 that is a driven shaft. , An elasticity applying means 27, an electric motor 30, a power transmission mechanism 31, a torque sensor 3 (see FIG. 33), and a controller 6 (see FIG. 33). The elasticity applying means 27 includes a stepped cylindrical bearing holder 32 provided inside the gear housing 21, first and second ball bearings 33 and 34, and a swing shaft 35. , A coil spring 36. The worm wheel 28 and the worm shaft 29 constitute a worm speed reducer 92.

[0053] The torque sensor 3 determines the relative rotation direction and the relative rotation amount of the first and second inner shafts 22 and 23 constituting the inner shaft 18 based on the torsion of the torsion bar 24 based on the relative rotation direction and the relative rotation amount. Then, the direction and magnitude of the torque applied to the steering shaft 18 are detected, and a signal (detection signal) representing the detected value is sent to the controller 6. Then, in response to the detection signal, the controller 6 sends a driving signal to the electric motor 30 to generate an auxiliary torque of a predetermined magnitude in a predetermined direction.

The worm wheel 28 and the worm shaft 29 are provided inside the gear housing 21. The worm wheel 28 is combined with a worm 37 provided at an intermediate portion of the worm shaft 29. I have. The electric motor 30 includes a case 38 fixedly connected to the gear housing 21, a permanent magnet stator 39 (FIG. 4) provided on an inner peripheral surface of the case 38, and an inner side of the case 38. A rotating shaft 40 as a driving shaft is provided, and a rotor 41 (FIG. 4) provided in a middle portion of the rotating shaft 40 so as to face the stator 39.

Further, between the inner peripheral surface of the concave hole 43 provided at the center of the bottom plate portion 42 constituting the case 38 and the outer peripheral surface of the base end (the left end in FIG. 4) of the rotating shaft 40. In addition, a third ball bearing 44 is provided, The base end of the rotating shaft 40 is rotatably supported by the case 38. Further, a fourth ball bearing 46 is provided between the inner peripheral edge of the partition wall 45 provided on the inner peripheral edge of the intermediate portion of the case 38 and the outer peripheral surface of the intermediate portion of the rotary shaft 40, and The intermediate portion of the rotating shaft 40 is rotatably supported.

[0056] Further, the power transmission mechanism 31 includes a distal end portion of the rotary shaft 40 of the electric motor 30 (right end portion of Figs. 2, 5, and 6) and a base end portion of the worm shaft 29 (Figs. 2, 5, 6). Between the two shafts 40 and 29. To this end, the power transmission mechanism 31 includes a male spline portion 47 provided at the distal end of the rotary shaft 40, a female spline portion 48 provided at the base end of the worm shaft 29, and both spline portions 47, The elastic force is provided by an elastic toothed ring 49 provided between the two. Among these, the elastic toothed ring 49 has external teeth 50 which are spline-engaged with the female spline portion 48 (FIGS. 2, 5, 6) on its outer peripheral surface, as shown in FIG. The surface has internal teeth 51 that engage with the male spline portion 47 (FIGS. 2, 5, and 6).

[0057] In such an elastic toothed ring 49, a plurality of core wires 53 are wrapped at a plurality of positions in the axial direction inside a cylindrical main body 52 made of synthetic rubber as an elastic material. Each of these core wires 53 is formed in an annular shape with reinforcing fibers such as glass fiber, carbon fiber, and aramide fiber. The reinforcing fibers forming each of the core wires 53 have a higher elastic modulus than the synthetic rubber forming the main body 52. External tooth elements 54 projecting toward the outer diameter side are formed over the entire length in the axial direction at a plurality of locations on the outer peripheral surface of the main body 52 at equal intervals in the circumferential direction. Further, an internal tooth element portion 55 protruding toward the inner diameter side is formed at a plurality of locations at equal intervals in the circumferential direction on the inner peripheral surface of the main body portion 52 over the entire length in the axial direction. The cross-sectional shape of each of the external tooth element portions 54 and the internal tooth element portions 55 in a direction orthogonal to the center axis of the main body portion 52 is a single arc. Note that the cross-sectional shape may be a shape formed by connecting a plurality of circular arcs.

Further, a woven cloth 56a such as nylon canvas is provided on the outer diameter side surface of each of the external tooth element portions 54 and a portion between the external tooth element portions 54 on the outer peripheral surface of the main body portion 52. By adhering in a state of being continuous over the entire periphery of the surface, the outer diameter side portion of each of the external tooth element portion 54 and the main body portion 52 is covered with the woven fabric 56a. Each of these external tooth element portions 54 is The above-mentioned external teeth 50 are constituted by a portion of the outer tooth side of each external tooth element portion 54 covered with the cloth 56a. Also, a woven fabric 56b such as nylon canvas is provided on the inner diameter side surface of each of the internal tooth element portions 55 and the portion between the internal tooth element portions 55 on the inner peripheral surface of the main body portion 52. By adhering in a state of being continuous over the entire circumference, the inner diameter side portions of the main body portion 52 and the internal tooth element portions 55 are covered with the woven fabric 56b. The internal teeth 51 are constituted by the internal tooth element portions 55 and a portion of the woven fabric 56b covering the inner surface of the internal tooth element portions 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 plurality of core wires 53, respectively. In addition, the positions and the numbers of the external tooth element portions 54 and the internal tooth element portions 55 in the circumferential direction are the same between the external tooth element portions 54 and the internal tooth element portions 55. For this reason, the positions in the circumferential direction of the top of each of the external tooth element portions 54 and the top of the internal tooth element portion 55 coincide with each other.

[0059] The elastic toothed ring 49 having the above-described structure is configured such that the external teeth 50 are spline-engaged with the female spline portion 48, and the internal teeth 51 are spline-engaged with the male spline portion 47. The distal end of the rotating shaft 40 of the motor 30 and the proximal end of the worm shaft 29 are connected so that the relative rotation of these two shafts 40 and 29 is impossible. With this configuration, the worm shaft 29 rotates together with the rotation shaft 40.

In the case of the present embodiment, the male spline portion 47 is formed on the outer peripheral surface of the cylindrical portion 57 (FIGS. 5 and 6) near the tip of the rotating shaft 40 of the electric motor 30. A large-diameter portion 58 (FIGS. 5 and 6) having a diameter larger than the outer diameter of the proximal end portion of the cylindrical portion 57 is provided in a portion off the proximal end side. The diameter of the large-diameter portion 58 is larger than the diameter of the tip circle of the internal teeth 51 constituting the elastic toothed ring 49. The stepped surface 59 (FIGS. 5 and 6), which is a continuous portion between the outer peripheral surface of the large diameter portion 58 and the outer peripheral surface of the cylindrical portion 57, has one end surface of the elastic toothed ring 49 (FIGS. 2, 5, and 5). 6 (left end face). The tooth bottom was inclined at one end (right end in FIGS. 2, 5 and 6) of the female spline 48 provided at the base end of the worm shaft 29 in such a direction that the tooth bottom became shallower toward one end. Incomplete part 60 is provided. The other end face (the right end face in FIGS. 2, 5, and 6) of the elastic toothed ring 49 is opposed to the incomplete portion 60. With this configuration, the axial displacement of the elastic toothed ring 49 is restricted by the step surface 59 and the incomplete portion 60. In the case of this embodiment, the step surface 59 and the incomplete portion 60 This corresponds to the displacement prevention section described in Item 6.

The bearing holder 32 is provided inside the gear housing 21, and the worm shaft 29 is rotatably supported inside the bearing holder 32. The bearing holder 32 is formed in a stepped cylindrical shape in which a large-diameter cylindrical portion 61 provided at a base end portion and a small-diameter cylindrical portion 62 provided at a first half portion are connected by a step portion 64. An outer ring 63 constituting the above-described first ball bearing 33 is internally fitted and fixed inside the large-diameter cylindrical portion 61. Also, one axial end face of the outer ring 63 (the right end face in FIGS. 2 and 5) is brought into contact with one surface of the stepped portion 64 (the left side face in FIGS. 2 and 5), and the other end face of the outer ring 63 in the axial direction. (Left end surfaces in FIGS. 2 and 5) are held down by a locking ring 65 that is locked to the inner peripheral surface of the large-diameter cylindrical portion 61. Further, an inner ring 66 constituting the first ball bearing 33 is externally fitted and fixed to a portion of the outer peripheral surface near the base end of the worm shaft 29 that coincides with the elastic toothed ring 49 in the axial direction. Further, one end surface in the axial direction of the inner ring 66 (the right end surface in FIGS. 2, 5, and 6) is brought into contact with the side surface of a flange portion 67 provided on the outer peripheral surface of the worm shaft 29 near the base end. The other end surface in the axial direction (the left end surface in FIGS. 2, 5, and 6) is held down by a locking ring 68 that is locked to the outer peripheral surface of the base end portion of the worm shaft 29. Note that a four-point contact type ball bearing is preferably used as the first ball bearing 33.

Further, in the case of the present embodiment, the bearing holder 32 is supported inside the gear housing 21 so as to freely swing. For this purpose, a pair of first diametrically opposed members is provided at two positions on the base end of the small-diameter cylindrical portion 62 constituting the bearing holder 32 on the worm wheel 28 side (upper side in FIGS. 2 and 5) in the radial direction. A through hole 69 is formed. Then, as shown in FIG. 7, the swing shaft 35 is inserted through the first through holes 69 into the inside of the bearing holder 32 while avoiding the worm shaft 29. Portions near both ends of the swing shaft 35 are fitted in the through holes 69 by gap fitting. Further, at both ends of the swinging shaft 35, portions protruding from the respective first through holes 69 to the outside of the bearing holder 32 are provided with concave holes 72 provided in the main body 70 constituting the gear housing 21. And the second through hole 73 are fitted inside each other by gap fitting. With this configuration, the bearing holder 32 is freely supported by the gear housing 21 for a swing displacement about the swing shaft 35.

In the case of the present embodiment, the wall portion 74 forming the cover 71 of the gear housing 21 is provided on the outer peripheral surface of the main body portion 70 where the second through hole 73 is provided. Superimpose Thus, the end of the swing shaft 35 from the second through hole 73 is prevented from coming off. Also, unlike the case of the present embodiment, the first and second through holes 69 and one of the concave hole 72 and the second through hole 73 are tightly fitted with the portions near both ends of the swing shaft 35. Can also be fixed internally.

[0064] Also, the center axis o of the worm shaft 29 (Figs. 2, 3, 57)

1

Includes the intersection x (FIGS. 2, 3) of the pitch circles P, P between the worm 37 of the worm shaft 29 and the worm wheel 28, which is a position shifted to the 8 side, and is parallel to the central axis o of the worm shaft 29.

One point Q (Figs. 2 and 5) on a straight line L is defined. When defined in this way, the axis passing through this point Q and parallel to the central axis o of the worm wheel 28 (FIGS. 2, 3) is

2

The center axis of the swing shaft 35 is used.

Further, the tip (the right end in FIG. 2) of the worm shaft 29 is rotatably supported by the second ball bearing 34 inside the small-diameter cylindrical portion 62 constituting the bearing holder 32. are doing. Further, an elastic ring 76 made of a viscous material such as an elastomer such as rubber is provided between the outer peripheral surface of the distal end portion of the small-diameter cylindrical portion 62 and the inner peripheral surface of the concave hole 75 provided in the gear housing 21. It is set up. Also, a through hole 90 is formed in a part in the circumferential direction at the axially intermediate portion of the small-diameter cylindrical portion 62, and a part of the worm 37 of the worm shaft 29, and the small-diameter cylindrical portion 62 is The portion exposed to the worm wheel is combined with the worm wheel 28.

Further, a concave hole 77 is formed in a part of the outer peripheral surface of the large-diameter cylindrical portion 61 constituting the bearing holder 32 in the circumferential direction, and the bottom surface of the concave hole 77 and the inner surface of the gear housing 21 are formed. The coil spring 36 is provided between them. The coil spring 36 provides a radial elasticity to the base end of the worm shaft 29 via the bearing holder 32 and the first ball bearing 33. With this configuration, the worm shaft 29 is elastically displaced about the oscillating shaft 35 in the direction of the worm wheel 28 and elastically displaced. Then, the distance between the central axes of the second inner shaft 23 to which the worm wheel 28 is externally fitted and fixed and the worm shaft 29 is naturally reduced, and the teeth of the worm 37 and the worm wheel 28 are reduced. The surfaces come into contact with each other in a state where a preload is applied.

As described above, in the case of the power transmission mechanism of the present embodiment and the electric power steering apparatus incorporating the same, the female spline portion 48 provided on the worm shaft 29 and the electric motor 3 An elastic toothed ring 49 is provided between the rotation shaft 40 and the male spline 47 provided on the rotation shaft 40. For this reason, it is possible to prevent the tooth surfaces of the male and female spline portions 47 and 48 from directly abutting with each other, and to prevent generation of abnormal noise due to the abutting of these tooth surfaces. Further, on the outer diameter side of the above-mentioned elastic toothed ring 49, external teeth 50 comprising a plurality of synthetic rubber external tooth element parts 54 and a part of the woven fabric 56a are provided. On the inner diameter side, there are provided internal teeth 51 composed of a plurality of internal rubber element portions 55 made of synthetic rubber and a part of the woven fabric 56b. For this reason, a force capable of reducing abnormal noise caused by collision between the tooth surfaces of the male and female spline portions 47 and 48 and the internal teeth 51 and the external teeth 50 of the elastic toothed ring 49, or Can be lost.

Further, in the case of the present embodiment, unlike the case of the conventional structure described in Patent Document 1 described above, the bending stiffness of the worm shaft 29 and the rotating shaft 40 is reduced, so that these two shafts 29, There is no need to make parts of the 40 abut strongly. In addition, since each of the internal tooth element portions 55 and each external tooth element portion 54 are made of synthetic rubber, which is an elastic material, inevitable dimensional errors existing in the male and female spline portions 47 and 48 are eliminated. It can be easily absorbed by the teeth 51 and the external teeth 50, so that dimensional control and assembling work can be easily performed. For this reason, it is possible to suppress an increase in cost of the power transmission mechanism of the present embodiment and the electric power steering apparatus incorporating the power transmission mechanism.

[0069] Further, even when the male and female spline portions 47 and 48 have eccentric errors and angular errors, the rotary shaft of the electric motor 30 and the worm shaft 29 are connected while absorbing these errors. Power transmission can be connected freely.

Further, in the case of the present embodiment, the woven fabric 56a is provided on the outer diameter side surface of each of the external tooth element portions 54 and the portion between the external tooth element portions 54 on the outer peripheral surface of the main body portion 52. At the same time, a woven fabric 56b is adhered to the inner-diameter side surface of each of the internal tooth element parts 55 and the internal tooth element part 55 on the inner peripheral surface of the main body part 52. Therefore, it is possible to prevent the root of each of the external tooth element portions 54 and each of the internal tooth element portions 55, which are made of synthetic rubber, from being torn, and to prevent the tooth surfaces from being damaged. Moreover, as in the present embodiment, when the woven fabrics 56a and 56b are attached to the outer peripheral surface and the inner peripheral surface of the elastic toothed ring 49 so as to be continuous over the entire circumference, respectively. Can deform these external tooth element portions 54 and internal tooth element portions 55. Therefore, the power that can be transmitted between the rotating shaft 40 of the electric motor 30 and the worm shaft 29 can be increased, and the durability can be improved. As a result, the power transmission mechanism of this embodiment and the electric power steering incorporating the power transmission mechanism are provided. According to the swinging device, it is possible to suppress the generation of unpleasant noises that would increase the cost or lower the bending rigidity between the rotating shaft 40 of the electric motor 30 and the foam shaft 29.

Further, in the case of the present embodiment, since each of the external tooth element portions 54 and each of the internal tooth element portions 55 are made of synthetic rubber, the elastic deformation amount is reduced by the inexpensive elastic toothed ring 49. Can be relatively large. For this reason, the cost increase of the power transmission mechanism and the electric power steering device incorporating the power transmission mechanism can be further suppressed. In the case of the present embodiment, a synthetic rubber is used as the elastic material constituting the main body 52 of the elastic toothed ring 49. Instead of this synthetic rubber, an elastomer other than synthetic rubber is used. Resins and the like can also be used. In the case of the present embodiment, the axial displacement of the elastic toothed ring 49 is controlled by the step surface 59 provided on the rotating shaft 40 of the electric motor 30 and the incomplete portion 60 provided on the female spline portion 48. It is regulated by For this reason, the elastic toothed ring 49 can be prevented from coming off from the portion between the male spline portion 47 provided on the rotating shaft 40 and the female spline portion 48 provided on the worm shaft 29.

Further, in the case of the present embodiment, the elastic toothed ring 49 is provided with a core wire 53 having a material elasticity higher than that of the synthetic rubber constituting the main body 52. For this reason, the rigidity of the elastic toothed ring 49 can be further improved, the power that can be transmitted between the rotating shaft 40 and the worm shaft 29 of the electric motor 30 can be increased, and the durability can be further improved. Can be improved.

Further, in the case of the present embodiment, each of the core wires 53 is formed in an annular shape, and a plurality of external tooth element portions 54 are respectively provided on the outer diameter side and the inner diameter side of each core wire 53. And the internal tooth element portion 55 are integrally provided. In the case of the present embodiment, the inevitable dimensional errors existing in the male and female spline portions 47 and 48 are easily absorbed by the internal teeth 51 and the external teeth 50 provided on the elastic toothed ring 49. It is possible to easily achieve higher levels of power that can be transmitted between the rotating shaft 40 and the worm shaft 29 and improve durability while also improving the durability.

That is, the force acting on the internal teeth 51 and the external teeth 50 from the male and female spline portions 47 and 48 is the shear force acting in the opposite direction with respect to the circumferential direction of the internal teeth 51 and the external teeth 50. It becomes. On the other hand, in the case of the present embodiment, the elastic toothed ring 49 is formed in an annular shape. The plurality of external tooth element portions 54 and the internal tooth element portions 55 are provided on the outer diameter side and the inner diameter side of each core wire 53, and the elastic modulus of the reinforcing fiber constituting each core wire 53 is synthesized. It is higher than the elastic modulus of rubber. For this reason, the rigidity of the main body 52, which is the portion between the outer teeth 50 and the inner teeth 51 of the elastic toothed ring 49, can be increased, and compared with the case where the main body 52 is made of only elastic material. Thus, the deformation of the external tooth element portions 54 and the internal tooth element portions 55 can be suppressed. Therefore, the dynamic force that can be transmitted between the rotating shaft 40 and the worm shaft 29 can be increased, and the durability can be improved.

That is, in the case of the present embodiment, as shown in detail in FIG. 10, an annular core wire 53 is provided inside a main body 52 constituting the above-mentioned elastic toothed ring 49. The rigidity of the radial middle part of the part 52 can be increased. For this reason, even though the rotating shaft 40 of the electric motor 30 tends to rotate with respect to the worm shaft 29 when the electric motor 30 is driven to rotate, the deformation of the internal teeth 51 and the external teeth 50 is prevented. Can be suppressed. On the other hand, unlike the case of the present embodiment, as shown in FIG. 11, when the main body 52a of the elastic toothed ring 49 is made of a single synthetic rubber having no core wire, the elasticity of the synthetic rubber is reduced. When the ratio is reduced, the rigidity of the radially intermediate portion of the main body 52a decreases. Therefore, the radially intermediate portion of the elastic toothed ring 49 is easily elastically deformed, and the external tooth element 54 and the internal tooth element 55 are also easily elastically deformed. Therefore, when the electric motor 30 is driven to rotate, the rotating shaft 40 is easily rotated with respect to the worm shaft 29, and the spline link between the male and female spline portions 47 and 48 and the internal teeth 51 and the external teeth 50 is formed. It becomes easy to come off. As a result, in the case of the structure shown in FIG. 11, the power that can be transmitted between the rotating shaft 40 and the worm shaft 29 is reduced, and the durability is reduced. In the case of the present embodiment, as described above, since the core wire 53 is provided inside the main body 52, such a disadvantage can be caused. The power that can be transmitted can be increased, and the durability can be improved. Moreover, the rigidity of the external tooth element portions 54 and the internal tooth element portions 55 does not need to be excessively increased. Therefore, unavoidable dimensional errors existing in the male and female splines 47 and 48 are easily absorbed by the internal teeth 51 and the external teeth 50, and transmitted between the rotary shaft 40 and the worm shaft 29. It is possible to easily achieve both higher power and improved durability at a higher level.

In the case of the present embodiment, a plurality of core wires formed in an annular shape inside the main body 52 are provided. 53 are provided. Therefore, the bending rigidity of the elastic toothed ring 49 does not need to be excessively increased, and even when the worm shaft 29 is inclined with respect to the rotating shaft 40, the inclination is prevented by the elastic toothed ring 49. "Become.

Further, in the case of the present embodiment, the tip portion of the worm shaft 29 is provided by the elasticity applying means 27 including the coil spring 36, the bearing holder 32, and the first and second ball bearings 33, 34. In addition, the worm wheel 28 is provided with elasticity in the direction of the directional force. Therefore, a preload can be applied to the joint between the worm wheel 28 and the worm 37 of the worm shaft 29, and the occurrence of rattling noise at this joint can be suppressed. In this embodiment, the worm 37 of the worm shaft 29 is pressed against the worm wheel 28, so that the worm shaft 29 can be inclined with respect to the rotation shaft 40 of the electric motor 30. Therefore, unlike the case of the present embodiment, when the worm shaft 29 and the rotating shaft 40 are directly connected without passing through the elastic toothed ring 49, the male spline portion provided on the rotating shaft 40 is used. The clearance between the spline 47 and the female spline portion 48 provided on the worm shaft 29 increases, and the tooth surfaces of the spline portions 47 and 48 strongly abut against each other, so that abnormal noise is easily generated. On the other hand, in the case of the present embodiment, as described above, the male spline portion 47 provided on the rotary shaft 40 of the electric motor 30 and the female spline portion 48 provided on An elastic toothed ring 49 is provided therebetween, and the rotation shaft 40 and the worm shaft 29 are connected via the elastic toothed ring 49. For this reason, in the case of the present embodiment, the worm shaft 29 can be largely inclined while preventing the generation of abnormal noise due to the abutment of the male and female spline portions 47 and 48 with each other. A predetermined preload can be easily applied to the joint between the worm wheel 28 and the worm 37.

The tooth surfaces of the worm 37 and the worm wheel 28 of the worm shaft 29 are twisted with respect to the center axis of the worm shaft 29 and the worm wheel 28. For this reason, unlike the case of the present embodiment, the swing center axis of the worm shaft 29 is provided so as to intersect at right angles with the center axis of the first ball bearing 33 that is rotatably supported only on the gear housing 21. In this case, if the worm shaft 29 is provided with an elasticity applying means for applying an elastic force in the worm wheel 28 to the worm wheel 28, a difference occurs in the return of the steering wheel 1 in both rotation directions. The problem described above arises. In addition, there arises a problem that the difference in the force required for the driver to operate the steering wheel 1 in both rotation directions increases. For this reason This will be described below with reference to FIGS.

As shown in FIGS. 12 and 13, the base end of the worm shaft 29 is rotated by a first ball bearing 33 into a gear housing (not shown) and the center o of the first ball bearing 33 is Consider a case in which a slight swinging displacement about the center is freely supported. Further, the worm shaft 29 is driven to rotate in the opposite directions in the case shown in FIG. 12 and the case shown in FIG. In such a state, at the joint between the worm of the worm shaft 29 and the worm wheel 28, the axial direction of the worm shaft 29 is opposite to each other in the case shown in FIG. 12 and the case shown in FIG. Reaction force Fa force is applied to the worm shaft 29 from the worm wheel 28. Further, in the joint portion, the reaction force Fr force having the same magnitude in the radial direction of the worm shaft 29 in the case shown in FIGS. 12 and 13 is applied to the worm shaft 29 from the worm wheel 28. .

[0080] Further, when a distance between the joint portion and the swing center o of the worm shaft 29 in the radial direction of the worm shaft 29 is d, a moment M force having a magnitude of d-Fa. Acts on the shaft 29. The direction of the moment M is opposite to each other in the case shown in FIG. 12 and the case shown in FIG. And, the swing center of the joint portion and the worm shaft 29. Assuming that the distance in the axial direction of the worm shaft 29 is L, a force Fm having a magnitude of M / L acts in the radial direction of the worm shaft 29 at the joint. The direction of action of this force Fm is opposite to each other in the case shown in FIG. 12 and the case shown in FIG. Therefore, the magnitude of the actual force Fr ′ acting radially from the worm wheel 28 to the worm shaft 29 at the joint portion in consideration of the moment M is as shown in FIG. In other words, it becomes smaller when rotating in one direction (Fr '= Fr-Fm), and becomes larger when rotating in the other direction (Fr' = Fr + Fm), as shown in FIG.

As described above, when the actual force Fr ′ acting radially on the worm shaft 29 at the joint portion increases, and the worm wheel 28 rotates in the other direction (the case shown in FIG. 13), The worm tooth surface of the worm shaft 29 is easily separated from the tooth surface of the worm wheel 28. For this reason, the elastic force applied to the worm wheel 29 by the elasticity applying means (not shown) to the worm wheel 28 in the opposite direction is set large in consideration of the case where the worm wheel 28 rotates in the other direction. There is a need. However, the elasticity is large like this If the worm wheel 28 is rotated in the negative direction (in the case shown in FIG. 12), the force of pressing the tooth surfaces against each other becomes excessive. Therefore, when returning the vehicle from turning to straight running, the steering wheel 1 returns to the neutral state, the return performance deteriorates in the minus direction, and the force required for the driver to rotate the steering wheel 1 is reduced by one. There is a problem in that the return performance and the force in the two directions of rotation of the steering wheel 1 become large in these directions.

On the other hand, in the case of the present embodiment, the swing shaft 35, which is the swing center axis of the worm shaft 29, is the center axis of the worm shaft 29. It is shifted from above to the worm wheel 28 side

1

The worm wheel 28 is provided at a position parallel to the central axis o of the worm wheel 28. For this reason,

2

When the driving force of the electric motor 30 is transmitted from the worm shaft 29 to the worm wheel 28, despite the fact that a reaction force is applied to the worm shaft 29 from the worm wheel 28 in the axial direction of the worm shaft 29, The moment generated on the worm shaft 29 based on the axial reaction force can be reduced or reduced to zero. Therefore, it is possible to suppress the radial reaction force applied from the worm wheel 28 to the worm shaft 29 from fluctuating due to the influence of the moment. Therefore, it is possible to suppress the difference between the force required to rotate the steering wheel 1 and the return performance of the steering wheel 1 in both rotation directions.

[0083] In particular, in the case of the present embodiment, the worm wheel 29 is positioned from the center axis o of the worm shaft 29.

1

Pitch circle P between the worm 20 of the worm shaft 29 and the worm wheel 28 at a position shifted to the wheel 28 side.

1, including the intersection point X of P, passing through one point Q on the 2 1 straight line L parallel to the central axis o of the worm axis 29, and passing an axis parallel to the central axis o of the worm wheel 28,

2

The center axis of the swing shaft 35 is set. Therefore, although a reaction force is applied from the worm wheel 28 to the warm shaft 29 in the axial direction of the worm shaft 29, a moment is applied to the worm shaft 29 based on the reaction force in the axial direction. Can be eliminated (set to 0). Therefore, it is possible to eliminate the difference between the force required to rotate the steering wheel 1 and the return performance of the steering wheel 1 in both rotation directions.

In the case of the present embodiment, the displacement preventing portion formed by the step surface 59 provided on the rotating shaft 40 of the electric motor 30 and the incomplete portion 60 provided on the female spline portion 48 provides The axial displacement of the elastic toothed ring 49 is regulated. However, the power transmission mechanism of the present invention It is not limited to such a structure. For example, in the above-described power transmission mechanism of the present embodiment,

In addition to the incomplete portion of the female spline portion and the stepped surface provided on the member having the male spline portion, the female spline portion is provided with a displacement preventing portion for preventing the axial displacement of the elastic toothed ring 49. The tapered surface or the bottom of the spline hole provided on the member having the surface, or the step surface is referred to.

Further, in the structure of the present embodiment, the transmission of the assisting force between the rotating shaft 40 of the electric motor 30 and the steering shaft 2 to which the assisting force is applied by the electric motor 30 via the worm reducer 92. Each of the rotation transmitting members of the second inner shaft 23, the worm wheel 28, the worm shaft 29, the elastic toothed ring 49, and the rotary shaft 40 constituting the path, except for the elastic toothed ring 49. Of the members 23, 28, 29, and 40, the torsional breaking strength of the synthetic rubber constituting the elastic toothed ring 49 can be made smaller than the minimum breaking strength.

[0086] With such a configuration, it is possible to more effectively prevent occurrence of a situation in which steering cannot be performed during driving of the vehicle. That is, when the steering wheel 1 is rotated to the maximum during the turning of the vehicle, the steering wheel 1 and the steering shaft 2 are prevented from rotating by the steering stopper (not shown). On the other hand, the rotation transmitting members 23, 28, 29, 49, and 40 constituting the auxiliary force transmission path receive a force in a direction in which the electric motor 30 continues to rotate due to the inertial force of the electric motor 30. In this case, an excessive torque difference is generated between the rotation transmitting members among the rotation transmitting members 23, 28, 29, 49, and 40 of the auxiliary force transmission path, and these rotation transmitting members 23, 28, 29, 49, 40 may be easily damaged by large impact force. For example, of these rotation transmitting members 23, 28, 29, 49, 40, the worm wheel 28 or the worm shaft 29 may be easily damaged. If no countermeasures are taken, this damage will cause the two members 28 and 29 to engage with each other so that they can be joined together. There is a possibility that the steering wheel 1 cannot be rotated in a desired direction.

On the other hand, as described above, the assist force between the rotating shaft 40 of the electric motor 30 and the steering shaft 2 to which the assist force is applied by the electric motor 30 via the worm speed reducer 92 is used. The rotation transmission members 23, 28, 29, 49, and 40 that constitute the transmission path Of the members 23, 28, 29, and 40 other than the other members, when the structure that the torsional breaking strength of the synthetic rubber forming the elastic toothed ring 49 is made smaller than the minimum breaking strength is adopted. , It is possible to cause such inconvenience. That is, according to this configuration, while the rotation of the steering wheel 1 is prevented by the steering stop, the inertial force of the electric motor 30 is applied to the rotation transmitting members 23, 28, 29, 49, and 40 that constitute the auxiliary force transmission path. When an excessive torque difference is generated between these rotation transmitting members 23, 28, 29, 49, 40 due to the application of a force in the direction in which the rotation is continued, the members 23, 28, 29, 49 , 40, the elastic toothed ring 49 can be broken first. Therefore, among the rotation transmitting members 23, 28, 29, 49, and 40 constituting the auxiliary force transmission path, members 23, 28, 29, and 40 other than the elastic toothed ring 49 can be hardly damaged. Also, if the elastic toothed ring 49 is broken such that the inner diameter side and the outer diameter side face each other in opposite directions, the steering wheel 2 is prevented from rotating smoothly. . That is, when the elastic toothed ring 49 is broken in this way, the rotating shaft 40 of the electric motor 30 and the worm shaft 29 are idle. In this case, the rotation of the electric motor 30 cannot be transmitted to the worm shaft 29. However, among the rotation transmitting members 23, 28, 29, 49, and 40, members other than the elastic ring 49 can be damaged. For this reason, the steering wheel 2 can be easily rotated in a desired direction by the driver's force, and the occurrence of a situation in which steering becomes impossible during driving of the automobile can be more effectively prevented.

Example 2

Next, FIG. 14 shows a second embodiment according to the power transmission mechanism of the present invention. In the case of the present embodiment, the positions of the outer teeth 50 and the inner teeth 51 constituting the elastic toothed ring 49a in the circumferential direction are shifted from each other by 1/2 pitch. With this configuration, the top of the external teeth 50 and the bottom of the internal teeth 51 radially oppose the bottom of the external teeth 50 and the top of the internal teeth 51, respectively.

In the case of this embodiment, the top of each tooth of the female spline portion 48 (see FIG. 2 etc.) provided on the worm shaft 29 and the male spline provided on the rotating shaft 40 of the electric motor 30 The worm shaft 29 and the rotating shaft 40 are spline-engaged with the elastic toothed ring 49a in a state where the top of each tooth of the portion 47 (see FIG. 2 etc.) is displaced in the circumferential direction. Therefore, the female spline section 4 The top of each tooth of No. 8 and the top of each tooth of the male spline portion 47 face the portion of the elastic toothed ring 49a whose thickness in the radial direction is large. Therefore, even if a dimensional error or an assembly error occurs in the male and female spline portions 47 and 48, these errors are eliminated by the portion of the elastic toothed ring 49a having a large radial thickness. It can be easily absorbed by the minute.

The other configurations and operations are the same as those in the first embodiment described above, and therefore, the same portions are denoted by the same reference characters, and redundant description will be omitted.

Example 3

FIG. 15 shows a third embodiment according to the power transmission mechanism of the present invention. In the case of the present embodiment, the cross-sectional shape of the external teeth 50 and the internal teeth 51 constituting the elastic toothed ring 49b is trapezoidal.

[0092] Since other configurations and operations are the same as those in the first embodiment shown in Fig. 110 described above, the same reference numerals are given to the same parts, and duplicate description is omitted. .

Example 4

[0093] Next, Figs. 16-18 show a fourth embodiment of the power transmission mechanism of the present invention. In the present embodiment, unlike the above-described embodiments, the core wire 53 (see FIG. 8 and the like) is not provided on the elastic toothed ring 49c. That is, in the case of the present embodiment, the elastic toothed ring 49c is attached to the outer peripheral surface and the inner surface of a simple synthetic rubber main body portion 52a (a non-encapsulating core 53). An external tooth element portion 54 and an internal element portion 55 are provided at a plurality of locations on the circumferential surface at equal intervals in the circumferential direction.

[0094] A woven cloth 56a such as nylon canvas is attached to the outer diameter side surface of each of the external tooth element portions 54 and the portion between the external tooth element portions 54 on the outer peripheral surface of the main body portion 52a. Accordingly, the outer diameter side portions of the external tooth element portion 54 and the main body portion 52a are covered with the woven fabric 56a. The external teeth 50 are formed by the external tooth element portions 54 and the portions of the woven fabric 56a covering the outer diameter side surfaces of the external tooth element portions 54. Also, by attaching a woven fabric 56b such as nylon canvas to the inner diameter side surface of each internal tooth element portion 55 and the portion between the internal tooth element portions 55 on the inner peripheral surface of the main body portion 52a. The inner side portions of the main body portion 52a and the internal tooth element portions 55 are covered with the woven fabric 56b. Then, each of the internal tooth element parts 55 The portion of the woven fabric 56b covering the inner diameter side surface of each of the internal tooth element portions 55 constitutes the internal teeth 51.

[0095] In the case of the present embodiment configured as described above, since the core wire 53 is not provided on the elastic toothed ring 49c, the diameter of the elastic toothed ring 49c is larger than in each of the above-described embodiments. There is a possibility that the rigidity of the middle part in the direction will decrease. For this reason, in this embodiment, the dynamic power that can be transmitted between the rotating shaft 40 and the worm shaft 29 of the electric motor 30 is lower than in each of the above-described embodiments, and the durability is reduced. There is a possibility. However, also in the case of the present embodiment, the woven fabrics 56a and 56b are adhered to the outer peripheral surface and the inner peripheral surface of the main body 52a, respectively, so as to be continuous over the entire circumference. For this reason, by appropriately setting the elastic modulus of the synthetic rubber constituting the main body portion 52a to a certain value or more, the rotation shaft 40 and the worm shaft 29 (see FIGS. 2, 5, 6, etc.) The power that can be transmitted between them can be increased to the extent that practical problems do not occur, and the durability can be sufficiently ensured.

[0096] Since other configurations and operations are the same as those in the first embodiment shown in Fig. 110 described above, the same reference numerals are given to the same parts, and the duplicate description is omitted. .

Example 5

Next, FIG. 19 shows a fifth embodiment according to the power transmission mechanism of the present invention. In the case of this embodiment, in the structure of the fourth embodiment shown in FIG. 1618 described above, the circle of each of the external tooth element portions 54 and 54 and each of the internal tooth element portions 55 and 55 that constitute the elastic toothed ring 49d. Position in the circumferential direction,

The other configurations and operations are the same as those of the embodiment 2 shown in FIG. 14 and the embodiment 4 shown in FIGS. 16-18 described above. The duplicate description will be omitted.

Example 6

Next, FIG. 20 shows a fifth embodiment according to the power transmission mechanism of the present invention. In the case of the present embodiment, the cross-sectional shape of each of the external tooth element portions 54, 54 and each of the internal tooth element portions 55, 55 constituting the elastic toothed ring 49e is trapezoidal.

[0100] Other configurations and operations are the same as those of the fourth embodiment shown in Figs. 16 to 18 described above, and therefore, the same parts are denoted by the same reference numerals and overlapping description will be omitted. Example 7

Next, FIGS. 21-22 show a seventh embodiment according to the electric power steering apparatus of the present invention. In the case of the electric power steering apparatus according to the present embodiment, unlike the above-described embodiments, the auxiliary tonnole of the electric motor 30 is provided to the steering shaft 2 (see FIG. 1 and the like) via the worm speed reducer. Not. In the case of the present embodiment, a so-called rack-assist type electric power steering device for applying the auxiliary torque of the electric motor 30 to the rack 12 via the helical gear type reduction gear 78 and the ball screw mechanism 98. The present invention is applied to the present invention. That is, in the case of the present embodiment, the electric motor 30 is provided on the side of the rack 12. Also, the rotating shaft 40a of the electric motor 30 is connected to the input shaft 91 of the helical gear type reduction gear 78, and the output gear 79 serving as the output shaft of the reduction gear 78 is connected to the ball nut 80. ing. The output gear 79 and the ball nut 80 are provided so as to be fitted around the rack 12 around the rack 12. Then, a plurality of balls 83 are transferred between an inner diameter ball screw groove 81 provided on a part of the outer peripheral surface of the rack 12 and an outer diameter ball screw groove 82 provided on an inner peripheral surface of the ball nut 80. It is provided movably. Further, the ball nut 80 is supported only rotatably with respect to the housing 84. Further, the rack 12 is freely supported by the housing 84 so as to freely displace only in the axial direction.

When the steering wheel 1 (see FIG. 1) is operated in such a rack-assisted electric power steering apparatus, a torque sensor (not shown) provided around the steering shaft 2 or the pinion 11 is used. Detects the direction and magnitude of torque applied to steering shaft 2 or pinion 11. Then, the controller 6 (see FIG. 33) energizes the electric motor 30 based on the signal input from the tonnole sensor, and rotates the ball nut 80 via the speed reducer 78. The rotation of the ball nut 80 causes the rack 12 to be displaced in the axial direction.

[0103] In particular, in the case of the present embodiment, a female spline portion 85 provided at the tip of the rotating shaft 40a of the electric motor 30 and one end of the input shaft 91 of the speed reducer 78 (Figs. An elastic toothed ring 49 similar to that of the first embodiment shown in FIG. 110 described above is provided between the male spline portion 87 provided at the left end portion) and the elastic toothed ring 49 described above. The rotating shaft 40a and the input shaft 86 are connected so that power can be transmitted. Further, the output gear 79 of the speed reducer 78 Between the female spline portion 88 provided and the male spline portion 89 provided on the ball nut 80, an elastic toothed ring 49 similar to that of the embodiment 1 shown in FIG. The output gear 79 and the ball nut 80 are connected by the elastic toothed ring 49 so that power can be transmitted. Also in the case of this embodiment, since the elastic toothed ring 49 is provided in some of the power transmission portions, generation of abnormal noise in each of the power transmission portions can be suppressed at low cost. Note that, in the scope of the present invention, instead of each of the elastic toothed rings 49, a ring having another shape and another structure such as the elastic toothed rings 49a and 49e used in the above-described Examples 2-6 is used. Of course you can.

[0104] Although not shown, the rack-assist type electric power steering device is different from the structure shown in Fig. 2122 described above in that an electric motor is connected to the rotating shaft of the electric motor and the rotating shaft of the ball nut. Are provided around the rack so as to be coaxial with each other, and the rotating shaft of the electric motor and the ball nut may be directly connected without a reduction gear. Also in the electric power steering device having such a structure, the elastic toothed rings 49, 49a-49e used in the above-described embodiments are used for the power transmission portion between the rotation shaft of the electric motor and the ball nut. Can do things.

[0105] Furthermore, a rotation transmission member that forms an auxiliary force transmission path between the rotating shaft of the electric motor and the rack, which is a member to which the auxiliary force of the electric motor is applied via a speed reducer or a ball nut. Thus, the torsional breaking strength of the elastic toothed ring can be made smaller than the minimum breaking strength of the members other than the elastic toothed ring. Then, when this configuration is adopted, the occurrence of a situation in which steering becomes impossible during driving of the vehicle can be more effectively prevented.

Next, FIGS. 23-25 show an eighth embodiment of the power transmission mechanism of the present invention. In the case of the present embodiment, the elastic toothed ring 49f is formed in a partially cylindrical shape having a discontinuous portion 93 at a part in the circumferential direction in the structure of the first embodiment shown in FIG. ing. Further, an external tooth element portion 54 and an internal tooth element portion 55 are formed over the entire length in the axial direction at a plurality of circumferentially equidistant places on the inner diameter side and outer diameter side of the elastic toothed ring 49f. . In addition, the above-mentioned elastic toothed ring 49f is provided at a plurality of places at equal intervals in the length direction on both sides of the front and back surfaces over the entire width direction. A plate-like element 94 having an external tooth element portion 54 and an internal tooth element portion 55 and having an arc-shaped cross section is formed by bending into a partially cylindrical shape. That is, the elastic toothed ring 49f is manufactured as follows. First, as shown in FIG. 25 (A), a cylindrical raw material 95 which is continuous over the entire circumference and has no discontinuous portions (cuts) is produced. The cylindrical material 95 includes a main body 96 formed in a cylindrical shape by synthetic rubber, and a plurality of core wires 53 wrapped in a state of being spaced apart at a plurality of positions in the axial direction of the main body 96. The core wire 53 is formed in an annular shape with reinforcing fibers such as glass fiber, carbon fiber, and aramide fiber. Further, the reinforced fiber forming each of the core wires 53 has a higher elastic modulus than the synthetic rubber forming the main body 96.

[0107] Further, the external tooth element portion 54 formed over the entire length in the axial direction at a plurality of circumferentially equal intervals on the outer peripheral surface of the main body portion 96, and a woven fabric such as nylon canvas attached to the outer peripheral surface. The outer teeth 50 are constituted by the cloth 56a. Further, an internal tooth element portion 55 formed over the entire length in the axial direction at a plurality of locations at equal intervals in the circumferential direction on the inner peripheral surface of the main body portion 96, and a woven fabric 56b such as nylon canvas adhered to the inner peripheral surface. Thus, the internal teeth 51 are formed. The positions and the numbers of the external tooth element portions 54 and the internal tooth element portions 55 in the circumferential direction are the same between the external tooth element portions 54 and the internal tooth element portions 55. Further, the outer diameter D of the cylindrical material 95 should be obtained.

1

Integer multiple of 2 times or more the outer diameter D of the elastic toothed ring 49f (3 times in the example shown)

2

Like, it is big enough. Accordingly, the circumferential length of the cylindrical material 95 is increased to an integral multiple of twice or more (three times in the example shown) the circumferential length of the elastic toothed ring 49f.

[0108] When manufacturing the cylindrical material 95 configured as described above, a shaft-shaped die (mold shaft) for molding, in which grooves for internal teeth in the axial direction are formed at a plurality of circumferential positions on the outer peripheral surface. A cylindrical mold that covers (sets) a woven cloth, winds a plurality of core wires from above, and further forms a groove for external teeth in the circumferential direction on the inner peripheral surface at a plurality of locations around the core wire. The synthetic rubber (solid rubber) before solidification is placed in the cavity between the outer peripheral surface of the mold shaft and the inner peripheral surface of the cylindrical mold with the woven cloth fitted (set) over the ). Then, after the synthetic rubber is solidified by vulcanization, a cylindrical product 95 is manufactured by taking out a finished product of the cylindrical material 95 from the cavity. Next, as shown in FIG. 25 (B), the cylindrical material 95 is cut at a plurality of locations in the axial direction (three locations in the illustrated example) and at a plurality of locations in the circumferential direction (in the example illustrated). Is By cutting at three places, a plurality of plate-like elements 94 having an arc-shaped cross section are obtained. In the case of the example shown in the figure, the central angle of the circular arc that is the cross-sectional shape of each of the plate-like elements 94 is 120 degrees. Next, as shown in FIG. 25 (C), each of these plate-like elements 94 is bent into a partially-cylindrical shape having a small diameter to obtain a plurality of elastic toothed rings 49f. Of the plurality of elastic toothed rings 49f, one elastic toothed ring 49f is connected to a male spline portion 47 provided on the rotating shaft 40 of the electric motor 30 and a female spline portion 48 provided on the worm shaft 29. By engaging with both the spline portions 47 and 48, a rotation transmitting portion is formed.

[0109] In the case of the present embodiment configured as described above, since the elastic toothed ring 49f is manufactured as described above, the manufacturing cost per unit during mass production of the elastic toothed ring 49f is reduced. Can be. That is, in order to manufacture the elastic toothed ring 49f, a cylindrical material 95 having a diameter larger than the diameter of the elastic toothed ring 49f is manufactured by feeding synthetic rubber before solidification into the cavity, and the cylindrical material 95 is formed. A plurality of plate-like elements 94 are made by cutting the plate material 95 at a plurality of positions in the axial direction and a plurality of positions in the circumferential direction. Then, a plurality of elastic toothed rings 49f are formed by bending each of these plate-like elements 94 into a partially cylindrical shape. In this way, the synthetic rubber before solidification is fed into the cavity to obtain one cylindrical material 95.By performing one molding operation, a plurality of elastic toothed rings 49f can be obtained, so that the elastic toothed It is possible to reduce the time required for manufacturing work per unit of the ring 49f. As a result, it is possible to reduce the manufacturing cost per unit during mass production of this elastic toothed ring 49f.

[0110] In particular, as in the present embodiment, the outer diameter D of the cylindrical material 95 is set to the elastic toothed ring 49f to be obtained.

1

When the outer diameter D is sufficiently larger than the outer diameter D (D> D), the shaft of this elastic toothed ring 49f

2 1 2

The ratio L / L of the axial length L1 of this cylindrical material 95 to the length L in the axial direction is sufficiently large.

2 1 2

I can do it. In the illustrated example, the ratio L / L can be increased to 4. A cylindrical material like this

1 2

The reason why the ratio L / L can be increased when the diameter of 95 is increased is as follows.

1 2

There are two reasons. First, as a first reason, when the diameter of the mold for manufacturing the cylindrical material 95 is increased, even if the length of the mold in the axial direction is increased, the manufacturing of the mold is not possible. In some cases, the processing accuracy of this mold can be sufficiently ensured. That is, the shape accuracy of the cylindrical material 95 is greatly affected by the processing accuracy of the mold. And the calo of this mold In order to ensure good accuracy, the bending stiffness of the mold must be equal to or larger than a predetermined value. However, when the thickness and material of the mold are the same and the diameter of the mold is reduced, the bending rigidity is set to the predetermined value unless the length of the mold in the axial direction is reduced. It cannot be larger than the size. In other words, when the diameter of the mold is small and the length in the axial direction is large, the bending rigidity of the mold is easily reduced, and it is difficult to sufficiently secure the bending rigidity. If this bending stiffness cannot be sufficiently ensured, it will be difficult to ensure sufficient processing accuracy of this mold. On the other hand, when the diameter of the mold is increased, the bending stiffness is increased even if the axial length of the mold is increased while the thickness and material of the mold are kept the same. It can be larger than the specified size. Therefore, the outer diameter D of the cylindrical material 95 is replaced by the outer diameter D of the elastic toothed ring 49f to be obtained.

In the case of the present embodiment, which is sufficiently larger than 1 2, it is possible to ensure good machining accuracy of the mold, despite the fact that the axial length of the mold is increased. The ratio L / L of the axial length of the elastic toothed ring 49f to the axial length L of the above-mentioned elastic toothed ring 49f is 2 or more (Fig.

1 2 1 2

In the example shown, it can be increased to 4).

Further, when the outer diameter D of the cylindrical material 95 is increased, the elastic toothed ring to be obtained is required.

1

Increase the ratio L / L of the axial length L of this cylindrical material 95 to the axial length L of 49f.

2 1 1 2 As a second reason, when the diameter of the cylindrical material 95 is increased, even if the axial length L of the cylindrical material 95 is increased, the cylindrical material 95 can be reduced. Manufactured by mold

1

In some cases, the radius of the mold can be reduced. That is, in order to ensure good shape accuracy of the cylindrical material 95, it is only necessary to secure the processing accuracy of the above-mentioned mold. We need to keep it small. On the other hand, in the case of the present embodiment in which the diameter of the cylindrical material 95 is increased, the diameter of the mold can be increased, and the axial length of the mold can be increased. Regardless, the radius of this mold can be reduced. For these first and second reasons, when the diameter of the cylindrical material 95 is increased, the shape of the elastic toothed ring 49f to be obtained should be obtained while maintaining good shape accuracy of the cylindrical material 95. Of the axial length L of this cylindrical material 95 with respect to the axial length L

/ L can be increased compared to 2 1. For example, as shown in FIG.

twenty one

When making an elastic toothed ring 49f from a cylindrical material 97 without a part, this cylindrical material 97 When the outer diameter D of the elastic toothed ring 49f is made the same as the outer diameter D2 of this elastic toothed ring 49f (D '= D),

1 2

The ratio L L force of the axial length L of the cylindrical material 97 to the axial length L 2 of the elastic toothed ring 49 f is small. In contrast, in the case of the structure shown in FIG.

1 1 2

The axial length L of the cylindrical material 95 with respect to the axial length L of the elastic toothed ring 49f to be obtained

2

The ratio L / L can be increased to 4.

1 1 2

[0112] As a result, in the case of the present embodiment, after the cylindrical material 95 is manufactured, the cylindrical material 95 can be cut at many points in the axial direction, and can be obtained by molding one cylindrical material 95. The number of elastic toothed rings 49f to be provided can be increased. For this reason, the production cost per unit during mass production of the elastic toothed ring 49f can be reduced. Even in the case of using a cylindrical elastic toothed ring 49f having a cylindrical shape as in the present embodiment, the expansion and contraction of the elastic toothed ring 49f in the diameter direction can be performed by the male spline portion 47 of the rotary shaft 40 of the electric motor 30. And the female spline portion 48 of the worm shaft 29 (see FIGS. 2, 5, and 6). Therefore, as in the above-described embodiments, it is possible to freely connect the two shafts 40 and 29 to each other to transmit power.

[0113] Since other configurations and operations are the same as those in the first embodiment shown in Fig. 110 described above, the same parts are denoted by the same reference numerals and overlapping description will be omitted. .

Example 9

Next, FIGS. 27-28 show a ninth embodiment according to the power transmission mechanism of the present invention. In the case of the present embodiment, the elastic toothed ring 49g is formed in a partially cylindrical shape having a discontinuous portion 93 at a part in the circumferential direction in the structure of the fourth embodiment shown in FIGS. ing. That is, in the case of the elastic toothed ring 49g constituting the structure of the present embodiment, the main body 52a is simply made of synthetic rubber that does not enclose the core 53 (see FIGS. 8-10 and the like). A discontinuous portion 93 is provided on a part of the elastic toothed ring 49g in the circumferential direction.

[0115] In this embodiment using the elastic toothed ring 49g without the core wire 53 provided inside as described above, compared to the case of the embodiment 8 shown in Figs. The rigidity of the attached ring 49g may be reduced. However, in the case of this embodiment, the woven fabrics 56a and 56b are adhered to the outer peripheral surface and the inner peripheral surface of the elastic toothed ring 49g in a state of being continuous over the entire circumference. Therefore, the elastic modulus of the synthetic rubber constituting the main body portion 52a is set to a certain value or more. By properly setting, the power that can be transmitted between the rotating shaft 40 of the electric motor 30 and the worm shaft 29 can be increased to a level that does not cause a practical problem, and the durability can be sufficiently ensured.

[0116] Other configurations and operations are the same as those of the fourth embodiment shown in Fig. 1618 and the eighth embodiment shown in Fig. 2325 described above. The same reference numerals are given and duplicate description is omitted.

Example 10

Next, FIG. 29 shows a tenth embodiment according to the power transmission mechanism of the present invention. In the case of this embodiment, the elastic toothed ring 49h is formed in a partially cylindrical shape having a discontinuous portion 93 at a part in the circumferential direction in the structure of the second embodiment shown in FIG. 14 described above. . That is, in the case of the elastic toothed ring 49h constituting the structure of the present embodiment, the positions in the circumferential direction of each external tooth element portion 54 and each internal tooth element portion 55 are shifted by 1/2 pitch, and A discontinuous portion 93 is provided in a part of the circumferential direction, so that the shape is a broken cylinder. A plurality of core wires 53 are embedded in the main body 52.

The other configurations and operations are the same as those in Embodiment 2 shown in FIG. 14 and Embodiment 8 shown in FIGS. 23 to 25, and the same reference numerals are used for the same parts. A duplicate description will be omitted with the addition of.

Example 11

Next, FIG. 30 shows an eleventh embodiment according to the power transmission mechanism of the present invention. In the case of this embodiment, the elastic toothed ring 49i is formed in a partially cylindrical shape having a discontinuous portion 93 at a part in the circumferential direction in the structure of the third embodiment shown in FIG. 15 described above. I have. That is, in the case of the elastic toothed ring 49i constituting the structure of the present embodiment, the cross-sectional shape of each external tooth element part 54 and each internal tooth element part 55 is trapezoidal, and the discontinuous part is By providing 93, it has a cylindrical shape. Further, a plurality of core wires 53 are covered inside the main body 52.

The other configurations and operations are the same as those of the third embodiment shown in FIG. 15 described above and the eighth embodiment shown in FIGS. A duplicate description will be omitted with the addition of.

Example 12 FIG. 31 shows a twelfth embodiment according to the power transmission mechanism of the present invention. In the case of this embodiment, in the structure of the tenth embodiment shown in FIG. 29 described above, the main body 52a constituting the elastic toothed ring 49j is made of a simple synthetic rubber that does not cover the core 53.

[0122] Other configurations and operations are the same as those of the ninth embodiment shown in Fig. 2728 and the tenth embodiment shown in Fig. 29, and the same reference numerals are given to the same parts. Repeated description is omitted.

Example 13

Next, FIG. 32 shows a thirteenth embodiment according to the power transmission mechanism of the present invention. In the case of this embodiment, in the structure of the eleventh embodiment shown in FIG. 30 described above, the main body 52a constituting the elastic toothed ring 49k is made of a simple synthetic rubber that does not cover the core 53.

[0124] Other configurations and operations are the same as those of the ninth embodiment shown in Figs. 27 to 28 and the eleventh embodiment shown in Fig. 30. Therefore, duplicate description will be omitted.

Industrial potential

[0125] According to the present invention, an electric power steering device or the like capable of suppressing generation of an unpleasant noise that raises the cost or lowers the bending rigidity between the drive shaft and the driven shaft. Is provided.

Claims

The scope of the claims

[1] A power transmission mechanism provided between a drive shaft and a driven shaft for transmitting power between the two shafts, wherein an inner peripheral portion of an end of one of the two shafts is provided. The female spline portion provided on the outer surface, the male spline portion provided on the outer peripheral surface of the end of the other shaft, and the external teeth that spline engage with the female spline portion are provided on the outer peripheral surface thereof. And an elastic toothed ring having, on its inner peripheral surface, an internal tooth engaged with the spline, and the elastic toothed ring is made of an elastic material on the outer diameter side and the inner diameter side, and protrudes in the radial direction. A plurality of external tooth element portions and internal tooth element portions are integrally provided, and the outer peripheral surface of the outer diameter side surface of each of the external tooth element portions and a portion between the external tooth element portions, and a On the peripheral surface, on the inner diameter side surface of each of the internal tooth element parts and the portion between these internal tooth element parts, respectively. By wearing bonded woven, the power transmission mechanism is obtained by constituting the internal teeth and the outer teeth.

[2] The elastic toothed ring according to claim 1, wherein the elastic toothed ring is provided with a core made of a material having a higher elastic modulus than the elastic material forming each external tooth element part and each internal tooth element part. Power transmission mechanism described.

[3] The core material is formed into any one of an annular shape, a cylindrical shape, a missing annular shape, and a missing cylindrical shape, and a plurality of core materials are provided on the outer diameter side and the inner diameter side of the core material, respectively. 3. The power transmission mechanism according to claim 2, wherein the external tooth element portion and the internal tooth element portion are provided integrally.

[4] The power transmission mechanism according to claim 2 or 3, wherein the core material is a core wire formed in an annular shape or a partially annular shape.

[5] The elastic material constituting each external tooth element part and each internal tooth element part is synthetic rubber.

4. The power transmission mechanism according to any one of 4.

[6] The member according to any one of [15] to [15], wherein a displacement preventing portion for preventing displacement of the elastic toothed ring in the axial direction is provided on a part of the member provided with the female spline portion or the male spline portion. Power transmission mechanism described.

[7] An elastic toothed ring is a cylindrical or linear plate-like element having an external tooth element part and an internal tooth element part on both sides and having a cross-section with a central angle of 180 degrees or less. 17. The power transmission mechanism according to claim 16, wherein the power transmission mechanism is formed by bending and forming into a partially cylindrical shape.

[8] An electric power steering device in which an output shaft of an electric motor and an input shaft constituting a speed reducer are freely coupled to transmit power by the power transmission mechanism according to any one of claims 17 to 17.

9. The electric power steering device according to claim 8, wherein the speed reducer is a worm speed reducer, and the worm shaft applies a force in a direction toward the worm wheel.

[10] An electric power steering device in which an output shaft of a reduction gear or a rotation shaft of an electric motor and a ball nut are freely coupled to each other by a power transmission mechanism according to any one of claims 17 to 17. .

[11] A rotation transmission member that constitutes an auxiliary force transmission path between the output shaft of the electric motor and a member to which the electric motor is provided with an auxiliary force via a speed reducer or a ball nut, and is a rotation transmission member other than an elastic toothed ring. The electric power steering according to any one of claims 810, wherein the torsional breaking strength of the elastic material forming the elastic toothed ring is smaller than the minimum breaking strength of the breaking strength of the rotation transmitting member. apparatus.

[12] A woven fabric is set on the inner peripheral surface and the outer peripheral surface of the mold cavity, and the non-solidified material is fed into the cavity, and the elastic material is solidified. Parts are provided on the inner diameter side, and a cylindrical material having a woven cloth adhered to the inner peripheral surface and the outer peripheral surface is obtained, and then the cylindrical material taken out of the cavity is removed. A plurality of plate-shaped elements are obtained by cutting at a plurality of locations in the circumferential direction, and a plurality of elastic toothed rings are obtained by bending the plurality of plate-shaped elements into a cylindrical shape or a non-cylindrical shape. A method for producing an elastic toothed ring, comprising: