JP2011064327A - Worm reduction gear and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress generation of tooth hammering noise at a warm reduction gear 16. <P>SOLUTION: A torsion coil spring 30 imparts the elasticity in such a direction as to go to a warm wheel through a preload pad 70 to a warm shaft 29. The preload pad 70 regulates a displacement in the width direction through a partial side face of a holder 61 fixed on a gear housing 22. By an elastic deformation of the preload pad 70 itself based on the elasticity of the torsion coil spring 30, the side face of the preload pad 70 is brought into contact with the partial side face of the holder 61, thus reducing a clearance between the preload pad 70 and the partial side face. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The worm speed reducer and the electric power steering device according to the present invention are incorporated in, for example, an automobile steering device, and use the output of the electric motor as auxiliary power, so that the driver has enough power to operate the steering wheel. Used for mitigation. In addition to the electric power steering device, the worm speed reducer according to the present invention is used by being incorporated in a linear actuator incorporated in various mechanical devices such as an electric bed, an electric table, an electric chair, and a lifter.

A power steering device is widely used as a device to reduce the force required for the driver to operate the steering wheel when giving a steering angle to the steered wheels (usually the front wheels except for special vehicles such as forklifts) Has been. In addition, an electric power steering apparatus that uses an electric motor as an auxiliary power source in such a power steering apparatus has begun to spread in recent years. The electric power steering device can be made smaller and lighter than the hydraulic power steering device, has advantages such as easy control of the magnitude (torque) of auxiliary power and less power loss of the engine. FIG. 23 schematically shows a conventionally known basic configuration of such an electric power steering apparatus.

  A torque sensor 3 for detecting the direction and magnitude of torque applied from the steering wheel 1 to the steering shaft 2 and a speed reducer 4 are provided at an intermediate portion of the steering shaft 2 that rotates based on the operation of the steering wheel 1. Provided. The output side of the speed reducer 4 is coupled to the intermediate portion of the steering shaft 2, and the input side is coupled to the rotating shaft of the electric motor 5. The detection signal of the torque sensor 3 is input to a controller 6 for controlling energization to the electric motor 5 together with a signal representing the vehicle speed. Further, as the speed reducer 4, a worm speed reducer having a large lead angle and having reversibility in the power transmission direction is generally used. That is, a worm wheel that is a rotational force receiving member is fixed to an intermediate portion of the steering shaft 2 and a worm of a worm shaft that is a rotational force applying member and is fixedly coupled to the rotational shaft of the electric motor 5 is connected to the worm wheel. Meshing.

When the steering wheel 1 is operated to rotate the steering shaft 2 in order to give a steering angle to the steering wheel 14, the torque sensor 3 detects the rotation direction and torque of the steering shaft 2, and the detected value is obtained. A representative signal is sent to the controller 6. Then, the controller 6 energizes the electric motor 5 to rotate the steering shaft 2 in the same direction as the rotation direction based on the steering wheel 1 via the speed reducer 4. As a result, the tip end portion (the lower end portion in FIG. 23 ) of the steering shaft 2 rotates with a torque larger than the torque based on the force applied from the steering wheel 1.

Such rotation of the tip of the steering shaft 2 is transmitted to the input shaft 10 of the steering gear 9 via the universal joints 7 and 7 and the intermediate shaft 8. The input shaft 10 rotates the pinion 11 constituting the steering gear 9 and pushes and pulls the tie rod 13 through the rack 12 to give a desired steering angle to the steered wheels 14. As is clear from the above description, the torque transmitted from the distal end portion of the steering shaft 2 to the intermediate shaft 8 via the universal joint 7 is the base end portion of the steering shaft 2 (the upper end in FIG. 23 ) . Is larger by the amount of auxiliary power applied from the electric motor 5 via the speed reducer 4 than the torque applied to the first component). 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 auxiliary power.

  In the case of the electric power steering apparatus generally used conventionally as described above, a worm reduction gear is used as the reduction gear 4 provided between the electric motor 5 and the steering shaft 2. However, this worm reducer has inevitable backlash. The backlash increases as dimensional errors and assembly errors of the worm shaft, worm wheel, and bearings for supporting these members, which are constituent members of the worm reducer, increase. If there is a large backlash, the tooth surfaces of the worm wheel and the worm strongly collide with each other, and an unpleasant rattling sound may be generated.

  For example, when a vibration load is applied to the steering shaft 2 from the wheel side due to a rough road surface, an unpleasant rattling sound is generated due to the presence of the backlash. Further, when the tooth surfaces of the worm wheel and the worm collide with each other, the steering feeling when steering the steering wheel is deteriorated.

  On the other hand, it is also conceivable to reduce the backlash by appropriately combining the constituent members of the worm reduction gear in consideration of dimensional accuracy. However, when the backlash is reduced in this way, the management of the dimensional accuracy and the assembling work become troublesome, which causes an increase in cost. Moreover, in recent years, since the auxiliary power tends to be increased, the wear on the tooth surfaces of the worm wheel and the worm increases, and the backlash is more likely to occur. When such rattling noise based on backlash leaks into the interior space of an automobile, it causes discomfort to the passenger.

In view of such circumstances, Patent Documents 1, 3, and 4 disclose a worm speed reducer that considers reducing backlash at the meshing portion between the worm wheel and the worm shaft. Each structure that suppresses the occurrence of a beating sound is described. Of these, the worm speed reducer described in Patent Document 3 is incorporated into an electric power steering apparatus together with the electric motor 114 and generated according to the steering torque applied to the steering shaft 113, as shown in FIGS. The auxiliary torque obtained by decelerating the rotation of the electric motor 114 with the worm reducer 115 is applied to the steering shaft 113. For this purpose, a worm wheel 116 constituting the worm speed reducer 115 is externally fitted and fixed to a part of the steering shaft 113, and the worm 118 of the worm shaft 117 is engaged with the worm wheel 116. Both ends of the worm shaft 117 are rotatably supported inside the gear housing 119 by a pair of rolling bearings 120a and 120b. The base end portion (left end portion in FIG. 24) of the worm shaft 117 is connected to one end portion (right end portion in FIG. 24) of the rotating shaft 121 of the electric motor 114.

The pair of rolling bearings 120a and 120b is disposed between the outer peripheral surface of the tip end portion (the right end portion in FIG. 24) of the worm shaft 117 and the inner peripheral surface of the concave hole 122 provided in the gear housing 119. One of the rolling bearings 120b and the elasticity applying means 123 are provided. The elastic force imparting means 123 includes an inner diameter side cylindrical portion 124 and an outer diameter side cylindrical portion 125 each made of metal, and an annular ring portion 126 made of rubber or synthetic resin, which connects both the cylindrical portions 124 and 125 to each other. Consists of. The inner diameter side cylindrical portion 124 is eccentric to the worm wheel 116 side with respect to the outer diameter side cylindrical portion 125. The outer diameter side cylindrical portion 125 of the elasticity applying means 123 is fitted and fixed in the concave hole 122, and the inner ring 127 of one rolling bearing 120b fixed to the inner side of the inner diameter side cylindrical portion 124 is connected to the worm. The tip end portion of the shaft 117 is fitted and fixed. With this configuration, an elastic force in a direction toward the worm wheel 116 (upward in FIGS. 24 and 25) is applied to the tip of the worm shaft 117, and the worm shaft 117 is oscillated and displaced toward the worm wheel 116. . A screw hole 128 of the gear housing 119 is formed on one surface (left end surface in FIG. 24) of the other rolling bearing 120a of the pair of rolling bearings 120a and 120b that supports the base end portion of the worm shaft 117. The front end surface of the screw ring 129 coupled to is pressed. With this configuration, the internal clearance in the axial direction of the pair of rolling bearings 120a and 120b is reduced, and rattling of the rolling bearings 120a and 120b is suppressed.

According to the worm speed reducer described in Patent Document 3 as described above, the backlash existing in the meshing portion between the worm 118 and the worm wheel 116 of the worm shaft 117 can be suppressed to a certain extent. The occurrence of rattling noise can be suppressed to some extent.

In the case of the worm speed reducer described in Patent Document 3 as described above, the worm shaft 117 is supported with respect to the gear housing 119 so as to be able to swing and displace. However, the center axis of the oscillating displacement of the worm shaft 117 is set to a position passing through a point on the center axis of the worm shaft 117 such as the center of the rolling bearing 120a for supporting the base end portion of the worm shaft 117. In the case where it is provided, there is a problem that a difference occurs in the return of the steering wheel (not shown) in both rotation directions. There is also a problem that the difference between the two rotational directions of the force required for the driver to operate the steering wheel increases. The reason will be described below.

First, the case where the worm shaft 117 is rotationally driven by the electric motor 114 and the driving force is transmitted from the worm shaft 117 to the worm wheel 116 will be considered with reference to the schematic diagrams shown in FIGS. In FIGS. 26A and 26B, the electric motor 114 is rotationally driven in the opposite direction with the same size. In FIGS. 26A and 26B, the shaft angle between the worm shaft 117 and the worm wheel 116 is 90 degrees. In this state, the tooth surfaces of the worm shaft 117 and the worm wheel 116 are twisted with respect to the central axes of the worm shaft 117 and the worm wheel 116, and a pressure angle exists on these tooth surfaces. For this reason, the worm wheel 116 to the worm shaft 117 has component forces F in three directions, the axial direction and the radial direction of the worm shaft 117, and the tangential direction of the pitch circle of the worm. _a1 , F _r1 , F _u1 A reaction force having

Each of these component forces F _a1 , F _r1 , F _u1 Among these, the component force F in the axial direction of the worm shaft 117 is _a1 Is a component force F applied from the worm shaft 117 to the worm wheel 116 in the tangential direction of the pitch circle of the worm wheel 116. _u2 And the same size in the opposite direction. Further, the component force F in the radial direction of the worm shaft 117 _r1 Is a component force F applied from the worm shaft 117 to the worm wheel 116 in the radial direction of the worm wheel 116. _r2 And the same size in the opposite direction. Also, the component force F in the tangential direction of the worm _u1 Is a component force F applied from the worm shaft 117 to the worm wheel 116 in the axial direction of the worm wheel 116. _a2 And the same size in the opposite direction. For this reason, in the case of the structure shown in FIGS. 24 and 25, the radial component force F is applied to the worm shaft 117. _r1 In order to prevent the tooth surfaces of the worm and the worm wheel 116 from being separated from each other even when the worm shaft 117 is added, the worm wheel 117 is attached to the worm shaft 117 by the elastic force applying means 123 (FIGS. 24 and 25). An appropriate amount of elasticity in the direction toward 116 is applied.

Further, the reaction force applied from the worm wheel 116 to the worm shaft 117 is shifted from the central axis of the worm shaft 117 toward the worm wheel 116, and the meshing portion between the worm of the worm shaft 117 and the worm wheel 116. Act on. For this reason, when the swing center of the worm shaft 117 is provided at a position passing through the central axis of the worm shaft 117, the axial component force F _a1 As a result, a moment about the center of the swing acts on the worm shaft 117. The direction of the moment is reversed when the worm shaft 117 rotates in both directions. This will be described in more detail with reference to FIGS.

27 and 28, the base end portion (the left end portion of FIGS. 27 and 28) of the worm shaft 117 is rotated to a fixed portion (not shown) by the rolling bearing 120a and is slightly rotated around the center o of the rolling bearing 120a. The rocking displacement is supported. Further, the worm shaft 117 is rotationally driven in the opposite direction to the same size in the case shown in FIG. 27 and the case shown in FIG. In such a state, the reaction force in the opposite direction between the case shown in FIG. 27 and the case shown in FIG. 28 with respect to the axial direction of the worm shaft 117 at the meshing portion of the worm shaft 117 and the worm wheel 116. F _a1 Is added to the worm shaft 117 from the worm wheel 116. Further, the distance in the radial direction of the worm shaft 117 between the meshing portion and the swing center o of the worm shaft 117 is d. ₁₁₇  D ₁₁₇  ・ F _a1 A moment M having a magnitude acting on the worm shaft 117 acts on the worm shaft 117. The direction of the moment M is opposite between the case shown in FIG. 27 and the case shown in FIG. The distance between the meshing portion and the swing center o of the worm shaft 117 in the axial direction of the worm shaft 117 is L ₁₁₇  If M / L ₁₁₇  Size of force F _m  However, the mesh portion acts in the radial direction of the worm shaft 117. This force F _m  The directions of action are opposite in the case shown in FIG. 27 and in the case shown in FIG. For this reason, the actual force F in consideration of the moment M acting in the radial direction from the worm wheel 116 to the worm shaft 117 at the meshing portion. _r1 The size of ′ is small when the worm wheel 116 rotates in one direction shown in FIG. _r1 '= F _r1 -F _m  ), Which is large when rotating in the other direction shown in FIG. _r1 '= F _r1 + F _m  )Become.

Thus, the actual force F acting on the worm shaft 117 in the radial direction at the meshing portion. _r1 When 'is increased and the worm wheel 116 rotates in the other direction (as shown in FIG. 28), the worm tooth surface of the worm shaft 117 is easily separated from the tooth surface of the worm wheel 116. On the other hand, when the force with which these tooth surfaces are pressed against each other is increased, the rotational torque of the worm wheel 116 and the worm shaft 117 increases. From such a situation, when the worm wheel 116 rotates in the other direction, it is necessary to achieve both of keeping the tooth surfaces apart from each other and not excessively increasing the pressing force between the tooth surfaces. In consideration, the elasticity applied to the worm shaft 117 by the elasticity applying means needs to be set to an appropriate predetermined value. However, even when the elasticity is set in this way, when the worm wheel 116 rotates in one direction, it is inevitable that the force with which the tooth surfaces are pressed against each other becomes excessive. For this reason, when returning the vehicle from turning to straight running, the steering wheel returns to the neutral state, the return performance deteriorates in one direction, or the force required for the driver to rotate the steering wheel in one direction The problem is that the difference between the return performance and the force in both directions of rotation of the steering wheel becomes large.

JP 2000-43739 A JP 2002-37094 A JP 2001-322554 A JP 2002-67992 A

In view of such circumstances, the present invention provides a structure in which elastic force in a direction toward the worm wheel is applied to the worm shaft in order to suppress generation of rattling noise at a meshing portion between the worm and the worm wheel of the worm shaft. Thus, the present invention has been invented to suppress the difference between the rotational directions of the force required to rotate the member to which the worm wheel is fixed and the return performance of the member rotating to the neutral state.

The worm speed reducer according to the present invention includes a worm wheel, a worm shaft, and an elastic body, and the elastic body is an elastic force applying unit that applies an elastic force to the worm shaft in a direction toward the worm wheel .
The worm shaft is supported so as to be capable of rotating and swinging with respect to the gear housing, and engages a worm provided at an intermediate portion with the worm wheel.
Further, the swinging central axis of the worm shaft is provided in parallel with the central axis of the worm wheel at a position shifted from the central axis of the worm shaft toward the worm wheel.

Further, when the worm speed reducer of the present invention is implemented , preferably , as described in claim 2 , the worm shaft includes the intersection of the pitch circle of the worm and the worm wheel, and the central axis of the worm shaft An axis that passes through one point on a parallel straight line and is parallel to the central axis of the worm wheel is defined as the oscillation central axis of the worm shaft.

More preferably, as described in claim 3 , a bearing holder for supporting at least one of a pair of bearings rotatably supporting both end portions of the worm shaft is provided on the gear. It supports the housing so that it can swing.

More preferably, as described in claim 4 , with respect to the axial direction of the worm shaft, a bearing on the electric motor side of a pair of bearings that rotatably supports portions near both ends of the worm shaft, and the worm Between the worm of the shaft and the meshing portion of the worm wheel, a swing center axis of the worm shaft is provided.

More preferably, as described in claim 5 , in the worm speed reducer described in any one of claims 1 to 4 , the worm shaft worm and the worm wheel meshing portion are connected to the worm shaft. On the side opposite to the swinging central axis, there is provided an elastic force applying means for applying an elastic force in the direction toward the worm wheel to the worm shaft.

More preferably, as described in claim 6 , in the worm reducer described in any one of claims 1 to 5 , a bearing that rotatably supports a portion near one end of the worm shaft is supported. The bearing holder is supported on the gear housing by the swing shaft so as to be swingable and displaceable between the gear housing and the swing shaft or between the bearing holder and the swing shaft. Is provided.

Further, when the worm speed reducer according to any one of claims 1 to 5 described above is implemented, preferably, as described in claim 7 , a bearing that rotatably supports a portion near one end of the worm shaft is supported. The bearing holder is supported on the gear housing by a swing shaft so as to be swingable and displaceable at least between the gear housing and the swing shaft or between the bearing holder and the swing shaft. An elastic ring, a part of which is an elastic material, is provided, and the rigidity of the elastic ring with respect to the radial direction of the oscillating central axis of the worm shaft is varied in the circumferential direction.

Further, when implementing the worm speed reducer according to any one of claims 1 to 4 , preferably, as described in claim 8 , between the worm shaft and the rotating shaft of the electric motor, The worm shaft is provided with elasticity applying means for applying elasticity in the direction toward the worm wheel.

Further, when the worm speed reducer according to any one of the first to fourth aspects described above is implemented, preferably, as described in the ninth aspect , the end portions near the both ends of the worm shaft are rotatably supported. Between the bearing holder for supporting at least one of the pair of bearings and the gear housing, there is provided an elasticity applying means for applying elasticity in the direction toward the worm wheel to the worm shaft.

When implementing the worm speed reducer according to any one of claims 1 to 9 , preferably, as described in claim 10 , a pair of bearings for supporting portions near both ends of the worm shaft. By providing an elastic material between one of the bearings away from the swing central shaft and the gear housing, the swing displacement of the worm shaft with respect to the gear housing is enabled.

When implementing the worm speed reducer according to any one of claims 1 to 9 , preferably, as described in claim 11 , a pair of bearings for supporting portions near both ends of the worm shaft. By providing a second elastic ring, at least part of which is made of an elastic material, between one of the bearings away from the swinging central axis of the worm shaft and the gear housing, The swing displacement of the worm shaft is made possible, and the rigidity of the second elastic ring is made different depending on the swing displacement direction of the worm shaft and another direction.

When the worm speed reducer according to claim 10 or 11 is implemented, preferably, as described in claim 12 , an elastic material provided between the one bearing and the gear housing. Alternatively, the second elastic ring is provided with a stopper for restricting the oscillating displacement of the worm shaft.

Further, when the worm speed reducer according to any one of claims 1 to 12 is implemented, preferably, as described in claim 13 , the rotating shaft and the worm shaft of the electric motor are made of an elastic material. Connect through.

Further, when implementing the worm speed reducer according to any one of the first to thirteenth aspects described above, preferably, as described in the fourteenth aspect , the end portions near the both ends of the worm shaft are rotatably supported. Grease is filled between a bearing holder for supporting at least one of the pair of bearings and the gear housing.

Further, when the worm speed reducer according to any one of claims 1 to 14 described above is implemented, preferably, as described in claim 15 , the worm shaft is rotatably supported at both ends thereof. A bearing holder for supporting at least one of the pair of bearings is made of a magnesium alloy.

According to a sixteenth aspect of the present invention, there is provided an electric power steering apparatus according to the present invention, wherein a steering shaft having a steering wheel at a rear end portion, a pinion provided at a front end side of the steering shaft, and the pinion or the pinion A rack engaged with the member, the worm speed reducer according to any one of claims 1 to 15 , an electric motor for rotationally driving the worm shaft, and a direction of torque applied to the steering shaft or pinion. A torque sensor for detecting the magnitude and a controller for controlling the driving state of the electric motor based on a signal input from the torque sensor. The worm wheel is fixed to any member of the steering shaft, the pinion, and a sub-pinion that meshes with the rack at a position away from the pinion.

  In the case of the worm speed reducer of the present invention and the electric power steering apparatus incorporating the worm speed reducer, as described above, the elastic body gives elasticity in the direction toward the worm wheel to the worm shaft. For this reason, it is possible to apply a preload to the meshing portion between the worm wheel and the worm shaft with an inexpensive structure, and it is possible to suppress generation of an annoying rattling noise at the meshing portion.

In addition, according to the present invention , the electric power steering apparatus incorporating the worm speed reducer can suppress the difference between the force required to rotate the steering wheel and the return performance of the steering wheel in both rotational directions. .

That is, in the case of the worm speed reducer of the present invention, the oscillating central axis of the worm shaft is provided at a position shifted from the central axis of the worm shaft toward the worm wheel side in parallel with the central axis of the worm wheel. Yes. For this reason, when a driving force is transmitted from the worm shaft to the worm wheel, a reaction force is applied from the worm wheel to the worm shaft in the axial direction of the worm shaft. Based on the force, the moment generated in the worm shaft can be reduced or made zero. Accordingly, it is possible to suppress the radial reaction force applied from the worm wheel to the worm shaft from fluctuating due to the influence of the moment. Thus, it is possible to suppress the difference between the rotational directions of the force required to rotate the member to which the worm wheel is fixed and the return performance of rotating the member to the neutral state. As a result, in the case of an electric power steering apparatus incorporating the worm speed reducer of the present invention as described above, the difference in the rotational direction between the force required to rotate the steering wheel and the return performance of the steering wheel is different. Can be suppressed.

According to the second aspect of the present invention, when driving force is transmitted from the worm shaft to the worm wheel, a reaction force is applied from the worm wheel to the worm shaft in the axial direction of the worm shaft. Nevertheless, it is possible to eliminate (set to 0) a moment on the worm shaft based on the reaction force in the axial direction. For this reason, it is possible to eliminate the difference between the rotational directions of the force required to rotate the member to which the worm wheel is fixed and the return performance of rotating the member to the neutral state.

Further, according to the invention described in claim 3 described above, one of the bearings that has been conventionally used can be used as one of the bearings, and the one bearing can be oscillated and displaced with respect to the gear housing. It can be supported and cost rise can be suppressed.

According to the invention described in claim 4 described above, a large preload is applied to the meshing portion between the worm and the worm wheel of the worm shaft while reducing the swing displacement amount of the end of the worm shaft on the electric motor side. It can be applied, and the generation of an annoying rattling noise at the meshing portion can be more effectively suppressed.

According to the invention described in claim 5 described above, the amount of elastic deformation of the elastic body constituting the elastic force applying means can be increased, and the amount of elastic force applied to the worm shaft can be easily adjusted.

According to the invention described in claim 6 described above, it is possible to suppress the occurrence of rattling noise at the meshing portion without increasing the rotational torque of the worm shaft. In other words, when the worm shaft is supported with respect to the gear housing so as not to be displaced in the axial direction, the worm shaft is likely to rotate when a rotational vibration is input to the worm wheel. Further, since the worm shaft is connected to the rotating shaft of the electric motor having a large moment of inertia, the worm shaft is transmitted between the tooth surfaces of the worm shaft and the worm wheel based on the rotational vibration of the worm wheel. Strength increases. Therefore, even when this force is applied, in order to prevent the tooth surfaces from separating from each other, it is necessary to increase the elasticity applied by the elasticity applying means, but when this elasticity is excessive, Therefore, the rotational torque of the worm shaft increases. On the other hand, according to the worm speed reducer described in claim 6 , when rotational vibration is input to the worm wheel, the worm shaft can be easily displaced in the axial direction, and the worm shaft can be rotated. It can be difficult. For this reason, the force transmitted between the both tooth surfaces can be reduced. As a result, the tooth surfaces can be prevented from separating without increasing the rotational torque of the worm shaft, and the generation of the rattling noise can be suppressed. Furthermore, it is possible to make it difficult to transmit the vibration based on the contact between the two tooth surfaces to the gear housing, and to suppress the generation of abnormal noise based on this vibration.

Further, according to the invention described in claim 7 , the rigidity of the elastic ring in the axial direction of the worm shaft is lowered, so that the rigidity of the elastic ring as a whole is ensured and the worm is secured to the gear housing. The shaft can be easily displaced in the axial direction. Therefore, an increase in the rotational torque of the worm shaft can be suppressed more effectively.

According to the invention described in claim 8 described above, the axial internal gap is relatively small as one of the bearings for supporting the end of the worm shaft on the electric motor side while suppressing the generation of abnormal noise. Large, deep groove ball bearings can be used, reducing costs.

Further, according to the invention described in claim 9 , the meshing portion between the worm and the worm wheel of the worm shaft without increasing the total length of the portion formed by connecting the worm shaft and the rotating shaft of the electric motor. Can be preloaded.

According to the invention described in claim 10 described above, the effect of suppressing the occurrence of rattling noise at the meshing portion between the worm and the worm wheel of the worm shaft can be obtained without impairing the effect of suppressing the occurrence of rattling noise. The generation of noise due to the collision between the end and one of the bearings supporting the end can be prevented.

According to the eleventh aspect of the present invention described above, the worm shaft is more easily displaced toward the worm wheel while preventing the worm shaft from being displaced in an unintended direction. Generation of rattling noise at the meshing portion between the worm and the worm wheel can be more effectively suppressed.

Further, according to the invention described in claim 12 , it is possible to prevent the worm shaft from being excessively swung and displaced.

According to the invention described in claim 13 , it is difficult to transmit rotational vibration between the rotating shaft of the electric motor and the worm shaft.

According to the invention described in claim 14 , the worm shaft is based on the reaction force applied from the worm wheel to the worm shaft when the driving force is transmitted between the worm shaft and the worm wheel. However, when it tends to move away from the worm wheel, the bearing holder can be made difficult to swing and displace. In addition, when the driving force increases and the reaction force increases, the speed at which the worm shaft moves away from the worm wheel tends to increase. In this case, however, the viscosity resistance of the grease also increases. The swinging displacement of the holder can be suppressed. For this reason, it is possible to easily prevent the tooth surfaces of the worm shaft and the worm wheel from separating from each other.

According to the invention described in claim 15 , the vibration generated in the worm shaft due to the contact between the tooth surfaces of the worm shaft and the worm wheel can be easily absorbed by the bearing holder. This vibration can be hardly transmitted to the housing.

The figure which cuts and shows a 1st example of embodiment of this invention. Partial sectional view taken along the C-C section of FIG. D-D sectional view of FIG. Sectional drawing of an electric motor. Partially enlarged view of FIG. 2. E-E sectional view of FIG. FF sectional drawing. The figure similar to FIG. 6 which shows the 2nd example of embodiment of this invention. Cross-section G-G of FIG. 8. The figure similar to FIG. 8 which shows the 3rd example of embodiment of this invention. The figure similar to FIG. 5 which shows the 4th example . H-H cross-sectional view of FIG. 11. The expanded sectional view equivalent to the I section of Drawing 2 showing the 5th example of an embodiment of the invention. The figure similar to FIG. 5 which shows the 6th example . The expanded sectional view equivalent to the J section of Drawing 14 showing the 7th example . The figure similar to FIG. 15 which shows the said 8th example . FIG. 17 is a cross-sectional view taken along the line KK in FIG. 16 showing only the elastic ring. The expanded sectional view equivalent to the L section of Drawing 14 showing the 9th example of an embodiment of the invention. The figure similar to FIG. 18 which shows the 10th example . M-M sectional view of FIG. 19. The figure which shows an example of the structure which provided the electric motor in the peripheral part of a pinion. The figure which shows an example of the structure which provided the electric motor in the peripheral part of a subpinion. BRIEF DESCRIPTION OF THE DRAWINGS Schematic which shows the whole structure of the electric power steering apparatus used as the object of this invention. Sectional drawing which shows an example of the conventional structure of a worm reduction gear. FIG . 25 is a cross-sectional view of FIG. The schematic perspective view which shows the component of the force added to these both members, when transmitting a driving force between a worm shaft and a worm wheel. The schematic sectional drawing for demonstrating the direction of the reaction force added to a worm axis | shaft from a worm wheel at the time of the rotational drive of a predetermined direction of an electric motor. The schematic sectional drawing for demonstrating the direction of the reaction force added to a worm shaft from a worm wheel at the time of the rotational drive of the direction opposite to the said predetermined direction of an electric motor.

[ First example of embodiment]
FIGS. 1-7 has shown the 1st example of embodiment of this invention corresponding to Claims 1-5,16 . The electric power steering apparatus of this example includes a steering shaft 2 having a steering wheel 1 fixed to the 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. A worm reduction gear 16a, a pinion 11 (see FIG. 23 ) provided on the front end side of the steering shaft 2, a rack 12 (see FIG. 23 ) meshed with the pinion 11 or a member supported by the pinion 11, and torque The sensor 3 (refer FIG. 23 ), the electric motor 31, and the controller 6 (refer FIG. 23 ) are provided.

  Of these, the steering shaft 2 is formed by combining the outer shaft 17 and the inner shaft 18 with a spline engaging portion so that rotational force can be transmitted and displacement in the axial direction is possible. In the case of this example, the front end portion of the outer shaft 17 and the rear end portion of the inner shaft 18 are spline-engaged and joined via a synthetic resin. Therefore, the outer shaft 17 and the inner shaft 18 can be shortened by breaking the synthetic resin at the time of collision.

  Further, the cylindrical steering column 15 inserted through the steering shaft 2 is formed by combining the outer column 19 and the inner column 20 in a telescope shape, and absorbs energy caused by the impact when an axial impact is applied. However, it has a so-called collapsible structure in which the overall length is reduced. The front end portion of the inner column 20 is coupled and fixed to the rear end surface of the main body portion 135 of the main body portion 135 and the cover 136 constituting the gear housing 22a. The gear housing 22a is formed by connecting the cover 136 to a front end portion of the main body 135 with a bolt or the like (not shown). The inner shaft 18 is inserted into the gear housing 22a, and the front end portion of the inner shaft 18 is projected from the front end surface of the cover 136.

  The steering column 15 is supported by a support bracket 24 at a middle portion thereof on a part of the vehicle body 26 such as the lower surface of the dashboard. In addition, when a locking portion (not shown) is provided between the support bracket 24 and the vehicle body 26 and an impact in a forward direction is applied to the support bracket 24, the support bracket 24 is separated from the locking portion. I try to come off. The upper end portion of the gear housing 22a 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 height position of the steering wheel 1 can be freely adjusted. Such a tilt mechanism and a telescopic mechanism are well known in the art, and are not characteristic features of this example, and thus detailed description thereof is omitted.

The inner shaft 18 is constituted by connecting a first inner shaft 138 and a second inner shaft 139 by a torsion bar 140 ( FIGS. 2 and 3 ). The torsion bar 140 is inserted inside the second inner shaft 139, and the rear end portion (right end portion in FIG. 3 ) of the torsion bar 140 is connected to the front end portion ( FIG. 3 ) of the first inner shaft 138 . The front end portion (left end portion in FIG. 3 ) of the torsion bar 140 is coupled to the front end portion (left end portion in FIG. 3 ) of the second inner shaft 139. The torque sensor 3 determines the torque applied from the steering wheel 1 to the steering shaft 2 based on the relative rotation direction and the relative rotation amount of the first and second inner shafts 138 and 139 based on the twist of the torsion bar 140. The direction and size are detected, and a signal (detection signal) representing the detected value is sent to the controller 6. In response to this detection signal, the controller 6 sends a drive signal to the electric motor 31 to generate auxiliary torque with a predetermined magnitude in a predetermined direction.

A portion of the front end portion of the second inner shaft 139 that protrudes from the front end surface of the cover 136 constituting the gear housing 22a is a rear end portion of the intermediate shaft 8 ( FIG. 1 ) via the universal joint 7 . It is linked to. Further, an input shaft 10 ( FIG. 1 ) of the steering gear 9 is connected to the front end portion of the intermediate shaft 8 via another universal joint 7. The pinion 11 is coupled to the input shaft 10. The rack 12 is engaged with the pinion 11. In order to prevent the vibration applied to the intermediate shaft 8 from the ground via the wheels to be transmitted to the steering wheel 1, a vibration absorbing device can be provided in each of the universal joints 7 and 7.

The worm speed reducer 16a includes a worm wheel 28 that can be fitted and fixed to a part of the second inner shaft 139 , a worm shaft 29, and elasticity applying means 137. The elasticity applying means 137 includes a torsion coil spring 141 and a preload pad 142.

Further, the worm wheel 28 and the worm shaft 29 are provided inside the gear housing 22 a, and the worm wheel 28 and the worm 27 provided at the intermediate portion of the worm shaft 29 are engaged with each other. The electric motor 31 includes a case 23 coupled and fixed to the gear housing 22 a, a permanent magnet stator 39 ( FIG. 4 ) provided on the inner peripheral surface of the case 23, and an inner side of the case 23. And a rotor 38 ( FIG. 4 ) provided in a state of being opposed to the stator 39 at an intermediate portion of the rotation shaft 32.

Further, a first ball bearing 34 is provided between the inner peripheral surface of the recessed hole 41 provided in the center of the bottom plate portion 40 constituting the case 23 and the outer peripheral surface of the base end portion of the rotating shaft 32. The base end portion (the left end portion in FIGS. 2 and 4 ) of the rotary shaft 32 is rotatably supported by the case 23. Further, a second ball bearing 35 is provided between the inner peripheral edge of the partition wall portion 42 provided on the inner peripheral edge of the intermediate portion of the case 23 and the outer peripheral surface of the intermediate portion of the rotary shaft 32, An intermediate portion of the rotating shaft 32 is rotatably supported.

Further, a female spline portion 50 provided on the inner peripheral surface of the base end portion (the left end portion in FIGS. 2 and 5 ) of the worm shaft 29 is provided with a male spline portion 51 provided at the distal end portion of the rotating shaft 32 of the electric motor 31. The ends of the shafts 29 and 32 are connected to each other by a spline engaging portion 33 formed by spline engagement. With this configuration, the worm shaft 29 rotates together with the rotating shaft 32.

A bearing holder 149 is provided inside the gear housing 22a, and the worm shaft 29 is rotatably supported by the bearing holder 149. The bearing holder 149 connects the large-diameter cylindrical portion 150 and the small-diameter cylindrical portion 151 by an annular portion 152. An outer ring 57 constituting the third ball bearing 36 is fitted and fixed inside the large diameter cylindrical portion 150. Further, one end surface in the axial direction of the outer ring 57 (the right end surface in FIGS. 2 and 5 ) abuts against one surface (the left side surface in FIGS. 2 and 5 ) of the circular ring portion 152 and the other end surface in the axial direction of the outer ring 57 ( The left end surface in FIGS. 2 and 5 is held down by a locking ring 154 that is locked to the inner peripheral surface of the large-diameter cylindrical portion 150. Further, the inner ring 52 constituting the third ball bearing 36 is externally fixed to a portion of the outer peripheral surface near the base end of the worm shaft 29 that coincides with the spline engaging portion 33 in the axial direction. Further, one end surface in the axial direction of the inner ring 52 (the right end surface in FIGS. 2 and 5 ) abuts against the side surface of the flange portion 53 provided on the outer peripheral surface near the base end of the worm shaft 29, and the shaft of the inner ring 52. The other end surface in the direction (left end surface in FIGS. 2 and 5 ) is held down by a locking ring 155 that is locked to the inner peripheral surface of the base end portion of the worm shaft 29. The third ball bearing 36 is preferably a four-point contact type ball bearing.

Furthermore, in the case of this example, the bearing holder 149 is supported on the inner side of the gear housing 22a so as to freely swing. For this purpose, a pair of first through-holes are provided at two positions on the worm wheel 28 side (upper side in FIGS. 2 and 5 ) on the diametrically opposite side of a part of the small diameter cylindrical portion 151 constituting the bearing holder 149 . 158 and 158 are formed. Then, as shown in FIG. 6 , a rocking shaft 159 is inserted into the bearing holder 149 through the first through holes 158 and 158 while avoiding the worm shaft 29, and each of the first The portions near both ends of the swing shaft 159 are fitted into the through holes 158 and 158 by gap fitting. Further, at both ends of the swing shaft 159, portions protruding from the respective first through holes 158 and 158 to the outside of the bearing holder 149 are provided in the main body 135 constituting the gear housing 22a. The concave hole 160 and the second through-hole 161 are respectively fitted by gap fitting.

  Further, a wall portion 162 constituting the cover 136 of the gear housing 22a is overlaid on the outer peripheral surface of the portion of the main body 135 where the second through-hole 161 is provided, so that the second through-hole 161 is provided. The rocking shaft 159 is prevented from coming off from the bottom. With this configuration, the bearing holder 149 is supported by the gear housing 22a so as to freely swing and displace around the swing shaft 159. Unlike the case of this example, the portions near both ends of the swing shaft 159 are fastened to one of the first through holes 158 and 158 and the concave hole 160 and the second through hole 161. It can also be fixed internally by fitting.

In the case of this example, the worm 27 of the worm shaft 29 and the worm are located at positions shifted from the central axis o ₁ ( FIGS. 2, 3, 5 ) of the worm shaft 29 toward the worm wheel 28. includes a pitch circle P _1, P ₂ of the intersection x of the wheel 28 (Fig. 2,3,5), a point on the center axis o ₁ parallel to the straight line L of the worm shaft 29 Q (FIGS. 2, 5) The axis parallel to the central axis o ₂ ( FIGS. 2 and 3 ) of the worm wheel 28 passing through is used as the central axis of the swing shaft 159.

On the other hand, the tip of the worm shaft 29 (the right end in FIGS. 2 and 5 ) is rotatably supported by a fourth ball bearing 37 inside the gear housing 22a. For this purpose, the outer ring 60 constituting the fourth ball bearing 37 is fixed to a second bearing holder 164 fixed inside the gear housing 22a. The second bearing holder 164 has an L-shaped cross section and is formed in an annular shape as a whole . The outer ring is placed inside a cylindrical portion 165 provided on one side of the second bearing holder 164 (the left side in FIGS. 60 is fixed internally. In addition, a substantially cylindrical bush 167 made of an elastic material is loosely fitted on a large-diameter portion 166 provided on a portion outside the worm 27 on the outer peripheral surface near the tip of the worm shaft 29. And the front-end | tip part of the said worm shaft 29 is protruded from the axial direction one end surface (right end surface of FIG. 2 , 5 ) of this bush 167 through the inner side of this bush 167. As shown in FIG . In addition, an inner ring 65 constituting the fourth ball bearing 37 is externally fitted and fixed to an intermediate portion in the axial direction of the bush 167. Further, the axial end face of the inner ring 65 (left end face in FIG. 2 and 5), the other axial end portion of the bush 167 on the inner surface of the outward flange portion 169 provided on the (left end in FIGS. 2, 5) By abutting, the inner ring 65 is positioned in the axial direction. Further, by providing a minute gap between the inner peripheral surface of the bush 167 and the outer peripheral surface of the large-diameter portion 166, the worm shaft 29 is inclined with respect to the bush 167 within a predetermined range (radial displacement). Is possible.

Further, a preload pad 142 constituting the elasticity applying means 137 is provided between the other end surface of the second bearing holder 164 (the right end surface in FIGS. 2 and 5 ) and the bottom surface of the recessed hole 72 provided in the gear housing 22a. The small-diameter portion 171 provided at the tip of the worm shaft 29 is inserted into a part of the preload pad 142 without rattling. As shown in detail in FIG. 7 , the preload pad 142 has a shape in which one side portion of the two radially opposite sides of the outer peripheral surface of the cylinder is removed by injection molding of a synthetic resin mixed with a solid lubricant. Made. In addition, the flat portions 172 and 172 and the arm portions 173 and 173 are placed at two positions on the radially opposite side of the outer peripheral surface of the preload pad 142, respectively, on the worm wheel 28 side (upper side in FIG. 7 ), It is provided at the end of the worm wheel 28 and the opposite side (lower side in FIG. 7 ). The small diameter portion 171 of the worm shaft 29 is inserted into a through hole 174 formed so as to penetrate the central portion of the preload pad 142 in the axial direction. The inner peripheral surface of the through hole 174 has a function as a slide bearing that supports the small diameter portion 171. In addition, the inner peripheral surfaces of both end portions of the through hole 174 are tapered surfaces whose diameter increases toward the opening end. Such a preload pad 142 is supported inside the concave hole 72 provided in the gear housing 22a so as to be displaceable within a predetermined range.

  The torsion coil spring 141 is provided around the preload pad 142. Then, a pair of locking portions 175 and 175 provided at two positions opposite to the radial direction at both ends of the torsion coil spring 141 are positioned at two positions opposite to the radial direction on the other end face of the second bearing holder 164. Are locked to one side of a pair of locking protrusions 176 and 176 provided in a state protruding in the axial direction. Further, the leading ends of the locking projections 176 and 176 are fitted in holes (not shown) provided at two positions on the bottom surface of the concave hole 72. With this configuration, the positions of the locking projections 176 and 176 with respect to the gear housing 22a are restricted. Then, the inner peripheral edge of the torsion coil spring 141 is elastically pressed against the first partial cylindrical surface portion 177 provided on the opposite side of the worm wheel 28 in the outer peripheral surface of the preload pad 142, thereby Elasticity in the direction toward the worm wheel 28 is applied to the distal end portion via the preload pad 142.

That is, in a state before the tip of the worm shaft 29 is inserted into the through hole 174 provided in the preload pad 142, the central axis of the through hole 174 is on one side with respect to the central axis of the second bearing holder 164. (Upper side of FIGS. 2 , 3 , 5 , and 7 ). For this reason, when the tip of the worm shaft 29 is inserted inside the through hole 174 provided in the preload pad 142, the diameter of the torsion coil spring 141 is elasticized by the first partial cylindrical surface portion 177 provided in the preload pad 142. Will be pushed out. Then, the torsion coil spring 141 tends to elastically return in the direction of rewinding (reducing the diameter), and elasticity in the direction toward the worm wheel 28 is applied from the torsion coil spring 141 to the tip of the worm shaft 29. The With this configuration, the distance between the central shafts of the second inner shaft 139 to which the worm wheel 28 is fitted and fixed and the worm shaft 29 is elastically reduced. As a result, the tooth surfaces of the worm 27 of the worm shaft 29 and the worm wheel 28 come into contact with each other with a preload applied.

  In the case of this example, the radius of curvature of the second partial cylindrical surface portion 178 provided on the worm wheel 28 side in the outer peripheral surface of the preload pad 142 is smaller than the radius of curvature of the first partial cylindrical surface portion 177. is doing. In addition, in the state where the torsion coil spring 141 is provided around the preload pad 142, the surface of each one-turn wire element constituting the torsion coil spring 141, and another wire element adjacent to each wire element. A gap in the axial direction is provided between the two surfaces (between lines).

  On the other hand, in order to assemble the worm shaft 29, the third ball bearing 36 and the bearing holder 149 inside the gear housing 22a, first, the third worm shaft 29 is placed around the base end portion of the worm shaft 29. The ball bearing 36 and the bearing holder 149 are assembled. Next, the worm shaft 29, the third ball bearing 36, and the bearing holder 149 are disposed inside the gear housing 22a. The first through holes 158 and 158 provided in the bearing holder 149 and the concave holes 160 and the second holes provided at two positions facing each other in a part of the main body 135 constituting the gear housing 22a. The rocking shaft 159 is inserted into and supported by the first and second through holes 158 and 161 and the concave hole 160 in a state where the through hole 161 is aligned. Further, the main body 135 and the cover 136 are overlapped with the wall 162 constituting the cover 136 of the gear housing 22a on the portion of the main body 135 where the second through-hole 161 is provided. Are coupled by a bolt or the like (not shown).

As described above, in the case of the worm speed reducer of this example and the electric power steering apparatus incorporating the worm speed reducer, the elastic force applying means 137 including the torsion coil spring 141 and the preload pad 142 is attached to the tip of the worm shaft 29. The elasticity in the direction toward the worm wheel 28 is applied. For this reason, it is possible to apply a preload to the meshing portion of the worm wheel 28 and the worm 27 of the worm shaft 29 with an inexpensive structure, and to suppress the occurrence of rattling noise at the meshing portion. In addition, in the case of this example, the swing shaft 159 which is the swing center axis of the worm shaft 29 is shifted to the worm wheel 28 side from the center axis o ₁ of the worm shaft 29. It is provided in parallel with the central axis o ₂ of the worm wheel 28. Therefore, when the driving force of the electric motor 31 is transmitted from the worm shaft 29 to the worm wheel 28, a reaction force is applied from the worm wheel 28 to the worm shaft 29 in the axial direction of the worm shaft 29. Nevertheless, the moment generated in the worm shaft 29 can be reduced or made zero based on the reaction force in the axial direction. Therefore, the reaction force in the radial direction applied from the worm wheel 28 to the worm shaft 29 can be prevented from fluctuating due to the influence of the moment. Therefore, it is possible to suppress the difference in the rotational direction between the force required to rotate the steering wheel 1 and the return performance of the steering wheel 1.

In particular, in the case of this example, the pitch circle P ₁ between the worm 27 of the worm shaft 29 and the worm wheel 28 is a position shifted from the center axis o ₁ of the worm shaft 29 to the worm wheel 28 side. , P ₂ , and passing through one point Q on the straight line L parallel to the central axis o ₁ of the worm shaft 29, an axis parallel to the central axis o ₂ of the worm wheel 28 is defined as the oscillation axis. 159 is the central axis. Therefore, although a reaction force is applied from the worm wheel 28 to the worm shaft 29 in the axial direction of the worm shaft 29, a moment is generated in the worm shaft 29 based on the reaction force in the axial direction. Can be eliminated (set to 0). Accordingly, it is possible to eliminate the difference in the rotational direction between the force required to rotate the steering wheel 1 and the return performance of the steering wheel 1.

  In the case of this example, the bearing holder 149 that supports the third ball bearing 36 is supported by the gear housing 22a so as to be able to swing and displace. For this reason, as this third ball bearing 36, the third ball bearing 36 is not used in which a swinging shaft is fixed to a part of the outer ring, and a conventionally used one is used. The gear housing 22a can be supported so as to be able to swing and can suppress an increase in cost.

  Furthermore, in the case of this example, among the third and fourth ball bearings 36 and 37 that support both end portions of the worm shaft 29 with respect to the axial direction of the worm shaft 29, the third on the electric motor 31 side. The swing shaft 159 is provided between the ball bearing 36 and the meshing portion between the worm 27 and the worm wheel 28 of the worm shaft 29. For this reason, it is possible to apply a large preload to the meshing portion while reducing the amount of rocking displacement of the proximal end portion of the worm shaft 29 on the electric motor 31 side. Generation can be suppressed more effectively. Unlike the case of this example, when the swing shaft is provided on the opposite side of the electric motor 31 with respect to the meshing portion, the swing displacement of the base end portion of the worm shaft 29 is increased.

  Further, with respect to the meshing portion, the elasticity applying means 137 is provided on the side opposite to the swing shaft 159. For this reason, the amount of elastic deformation of the torsion coil spring 141 constituting the elastic force applying means 137 can be increased, and the amount of elastic force applied to the worm shaft 29 can be easily adjusted.

  In the case of this example, since the preload pad 142 is made of a synthetic resin, the tip of the worm shaft 29 can be easily inserted into the through hole 174 provided in the preload pad 142. Further, when the surface of each one-turn wire element constituting the torsion coil spring 141 and the surface of another wire element adjacent to each wire element are in axial contact, this contact portion The occurrence of friction causes the elasticity applied to the worm shaft 29 by the torsion coil spring 141 to be inappropriately changed. On the other hand, in the case of this example, since an axial gap is provided between the surfaces of each of the above-described one wire material elements and the surfaces of these wire material elements and other wire material elements adjacent to each other. A predetermined elasticity can be applied to the worm shaft 29 more stably.

[ Second Example of Embodiment]
FIGS. 8-9 has shown the 2nd example of embodiment of this invention corresponding to Claims 1-7,16 . In the case of this example, the outer peripheral surface near the both ends of the rocking shaft 159 for freely supporting the rocking displacement of the bearing holder 149 with respect to the gear housing 22a, and the respective first passages provided on the bearing holder 149. Elastic rings 179 and 179 are provided between the inner peripheral surfaces of the holes 158 and 158, respectively. These elastic rings 179 and 179 are formed by connecting an inner diameter side cylindrical portion 180 and an outer diameter side cylindrical portion 181 that are made of metal concentrically with each other by rubber connecting portions 182 and 182 that are elastic materials. Yes. That is, the connecting portions 182 and 182 are vulcanized and bonded to the cylindrical portions 180 and 181 to connect the cylindrical portions 180 and 181 to each other. Further, the connecting portions 182 and 182 are provided in a state of being separated from each other at two positions on the opposite side in the radial direction between the cylindrical portions 180 and 181. Specifically, at the two positions (the two positions on both ends in the vertical direction in FIGS. 8 and 9 ) of the end portion between the worm wheel 28 (see FIGS. 2, 3, and 5 ) and the opposite side of the intermediate portion . The connecting portions 182 and 182 are provided, and both end portions with respect to the axial direction of the worm shaft 29 (the both ends in the front and back directions in FIG. 2 , FIG. 3) are 90 degrees out of phase with the portions where the connecting portions 182 and 182 are provided . The left and right end portions) are space portions 183 and 183. With this configuration, the rigidity of the elastic rings 179 and 179 with respect to the radial direction of the swing shaft 159 differs in the circumferential direction. Further, the rigidity of the elastic rings 179 and 179 with respect to the axial direction of the worm shaft 29 is lowered.

According to the worm speed reducer of this example, the rattling noise is generated at the meshing portion between the worm 27 of the worm shaft 29 and the worm wheel 28 without increasing the rotational torque of the worm shaft 29. It can be suppressed. That is, when the worm shaft 29 is supported with respect to the gear housing 22a so as not to be displaced in the axial direction, the worm shaft 29 can easily rotate when a rotational vibration is input to the worm wheel 28. Become. Since the worm shaft 29 is connected to the rotating shaft 32 (see FIGS. 2, 4 and 5 ) of the electric motor 31 having a large moment of inertia, the worm shaft 29 is driven by the rotational vibration of the worm wheel 28. The force transmitted between the tooth surfaces of the worm 27 and the worm wheel 28 is increased. Therefore, in order to prevent the tooth surfaces from separating even when this force is applied, it is necessary to increase the elasticity applied to the worm shaft 29 by the elasticity applying means 137 (see FIG. 2 and the like) . When the elasticity becomes excessive, the rotational torque of the worm shaft 29 is increased. On the other hand, in the case of this example, elastic rings 179 and 179, each of which is made of an elastic material, are provided between the bearing holder 149 and the swing shaft 159. Therefore, when rotational vibration is input to the worm wheel 28, the worm shaft 29 can be easily displaced in the axial direction, and the worm shaft 29 can be made difficult to rotate. For this reason, the force transmitted between the tooth surfaces can be reduced. As a result, the tooth surfaces can be prevented from separating without increasing the rotational torque of the worm shaft 29, and the occurrence of rattling noise at the meshing portion can be suppressed. Furthermore, it is possible to make it difficult to transmit the vibration based on the contact between these two tooth surfaces to the gear housing 22a, and to suppress the generation of abnormal noise based on this vibration.

In the case of this example, the rigidity of the elastic rings 179 and 179 is made different in the circumferential direction, and the rigidity of the elastic rings 179 and 179 in the axial direction of the worm shaft 29 is lowered. For this reason, it is possible to easily displace the worm shaft 29 in the axial direction with respect to the gear housing 22a while securing the rigidity required for each of the elastic rings 179 and 179. Therefore, an increase in the rotational torque of the worm shaft 29 can be more effectively suppressed.
Since other configurations and operations are the same as those in the first example of the embodiment shown in FIGS. 1 to 7 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted. .

[ Third example of embodiment]
FIG. 10 shows a third example of the embodiment of the present invention, which also corresponds to claims 1 to 7 and 16 . In the case of this example, the elastic rings 179 and 179 used in the second example of the embodiment shown in FIGS. 8 to 9 are connected to the concave holes 160 and the second through holes 161 provided in the gear housing 22a. It is provided between the inner peripheral surface and the outer peripheral surfaces of both ends of the swing shaft 159. Other structures and operations are the same as in the second example of the embodiment described above. In the structures of the second and third examples of the embodiment shown in FIGS. 8 to 10 described above, an elastomer other than rubber, a synthetic resin, or the like is used as an elastic material constituting the connecting portion 182 of the elastic ring 179. You can also. Further, the entire elastic ring 179 can be made of an elastic material such as synthetic resin.

[ Fourth Example of Embodiment]
FIGS. 11 to 12 show a fourth example of an embodiment of the present invention corresponding to claims 1 to 4 , 8 , 10 to 12 and 16 . In the case of this example, in the structure of the first example of the embodiment shown in FIGS. 1 to 7 described above, the coil spring 186 that is the elasticity applying means is connected to the rotating shaft 32 of the electric motor 31, the worm shaft 29, and the like. Between. That is, in the case of this example, a recess 184 is provided on one end surface (the right end surface in FIG. 11 ) of the rotating shaft 32, and the bottom surface of the recess 184 and the base end surface of the worm shaft 29 (the left end surface in FIG. 11 ) . The coil spring 186 is provided between the bottom surface of the spline hole 185 provided in FIG. The coil spring 186 gives the worm shaft 29 elasticity in a direction away from the rotary shaft 32. Also in this example, as in the first to third examples of the above-described embodiment, the swing shaft 159 serving as the swing center of the worm shaft 29 is replaced with the central axis o _{1 of the} worm shaft 29. It is provided at a position shifted from the top toward the worm wheel 28 (upper side in FIG. 11 ). With this configuration, the worm shaft 29 is elastically oscillated and displaced toward the worm wheel 28 with the oscillating shaft 159 as the center.

In the case of this example, the outer peripheral surface of the tip portion of the worm shaft 29 is a simple cylindrical surface that is not stepped, and this tip portion is disposed inside the concave hole 72 provided in the gear housing 22a. Yes. An elastic ring 187 corresponding to the second elastic ring described in claims 11 and 12 between the inner peripheral surface of the concave hole 72 and the outer peripheral surface of the tip of the worm shaft 29, and a fourth A ball bearing 37 is provided. Of these, the fourth ball bearing 37 is provided around the tip of the worm shaft 29 by fitting the inner ring 65 to the tip of the worm shaft 29.

Further, as shown in detail in FIG. 12 , the elastic ring 187 includes an inner diameter side cylindrical portion 188 and an outer diameter side cylindrical portion 189, each of which is made of metal, and a connecting portion made of an elastic material such as an elastomer such as rubber. By 190 and 190, it couple | bonds concentrically with each other. Further, these connecting portions 190 and 190 are provided in a state of being separated from each other at two positions on the opposite side in the radial direction between the cylindrical portions 188 and 189. Specifically, only the two positions on both ends in the direction (left-right direction in FIG. 12 ) in which the phase differs by 90 degrees with respect to the oscillating displacement direction (vertical direction in FIG. 12 ) of the worm shaft 29 in the portion in between . Each connecting portion 190, 190 is provided. With this configuration, the rigidity of the elastic ring 187 is reduced in the direction of the oscillating displacement of the worm shaft 29, and is increased in the direction different from the oscillating displacement direction by 90 degrees.

  In the case of this example, the outer diameter side cylindrical portion 189 located between both inner diameter side and outer diameter side cylindrical portions 188 and 189 at both ends in the swing displacement direction of the worm shaft 29. Stop portions 191 and 191 having circular arc cross-sections made of an elastic material such as an elastomer such as rubber are provided at two positions on the inner peripheral surface of the rubber. Further, a minute gap is provided between the inner peripheral surface of each of the stopper portions 191 and 191 and the outer peripheral surface of the inner diameter side cylindrical portion 188. Each of the stopper portions 191 and 191 is in contact with the outer peripheral surface of the inner diameter side cylindrical portion 188 when the worm shaft 29 tends to swing and displace excessively. Prevent dynamic displacement. Such an elastic ring 187 is configured to externally fix and fix the inner diameter side cylindrical portion 188 to the outer ring 60 that constitutes the fourth ball bearing 37, and to the outer diameter side in the concave hole 72 provided in the gear housing 22a. The cylindrical portion 189 is fitted and fixed to be provided between the worm shaft 29 and the gear housing 22a.

  In the case of this example configured as described above, the coil spring 186 is provided between one end surface of the rotating shaft 32 of the electric motor 31 and the base end surface of the worm shaft 29. A preload based on the elasticity of the coil spring 186 can be applied to the third ball bearing 36 via the locking ring 155 locked to the end. For this reason, it is possible to use a deep groove type ball bearing having a relatively large axial clearance as the third ball bearing 36 while suppressing the generation of abnormal noise, and the cost can be reduced.

  In the case of this example, an elastic ring 187 is provided between the gear housing 22a and the fourth ball bearing 37 that supports the tip of the worm shaft 29, whereby the worm shaft 29 with respect to the gear housing 22a is provided. Oscillating displacement is possible. For this reason, the tip of the worm shaft 29 and the fourth ball bearing 37 collide with each other without impairing the effect of suppressing the generation of rattling noise at the meshing portion of the worm shaft 29 with the worm 27 and the worm wheel 28. Generation of abnormal noise due to mixing can be prevented.

  Further, in the case of this example, the rigidity of the elastic ring 187 provided between the fourth ball bearing 37 and the gear housing 22a is lowered with respect to the oscillating displacement direction of the worm shaft 29. It is higher in the direction where the phase is different from the swing displacement direction by 90 degrees. For this reason, while preventing the worm shaft 29 from being displaced in an unintended direction, the worm wheel 29 can be more easily swung to the worm wheel 28 side, and the rattling noise at the meshing portion can be improved. Can be more effectively suppressed.

In the case of this example, since the elastic ring 187 is provided with stopper portions 191 and 191 for restricting the displacement of the worm shaft 29, the worm shaft 29 is excessively displaced. Can be prevented.
Since other configurations and operations are the same as those in the first example of the embodiment shown in FIGS. 1 to 7 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted. .

[ Fifth Example of Embodiment]
FIG. 13 shows a fifth example of an embodiment of the present invention corresponding to claims 1 to 4 , 9 to 12 and 16 . In the case of this example, in the structure of the fourth example of the embodiment shown in FIG. Yes. That is, in this example, the coil spring 186 is placed between the inner surface of the gear housing 22a and the bottom of the concave hole 192 provided in the outer peripheral surface of the large-diameter cylindrical portion 150 constituting the bearing holder 149. Provided. The coil spring 186 imparts radial elasticity to the proximal end portion of the worm shaft 29. Further, the coil spring 186 is provided in a position shifted with respect to the base end side of the worm shaft 29 with respect to the axial direction of the worm shaft 29 with respect to the swing shaft 159 serving as the swing center of the worm shaft 29. . With this configuration, the worm shaft 29 is elastically oscillated and displaced toward the worm wheel 28 around the oscillating shaft 159.

In the case of this example, preload can be applied to the meshing portion without increasing the total length of the portion formed by connecting the worm shaft 29 and the rotating shaft 32 of the electric motor 31.
Other configurations and operations are the same as in the case of the fourth example of the embodiment shown in FIGS. 11 to 12 described above . .

[ Sixth Example of Embodiment]
FIG. 14 shows a sixth example of the embodiment of the invention corresponding to claims 1 to 4 , 8 , 10, and 16 . In the case of this example, the third and fourth ball bearings 36 and 37 for supporting both ends of the worm shaft 29 in the structure of the fourth example of the embodiment shown in FIGS. Is supported by a bearing holder 149a. For this reason, in the case of this example, the overall length of the small-diameter cylindrical portion 151a constituting the bearing holder 149a is increased, and a through hole 193 is provided in a part in the circumferential direction at the axial intermediate portion of the small-diameter cylindrical portion 151a. Forming. The worm shaft 29 is provided inside the bearing holder 149a, and the worm shaft 29 is provided between the outer peripheral surface of the proximal end portion of the worm shaft 29 and the inner peripheral surface of the large-diameter cylindrical portion 150 constituting the bearing holder 149a. Third and fourth ball bearings 36 and 37 are provided between the outer peripheral surface of the distal end portion of the shaft 29 and the inner peripheral surface of the distal end portion of the small-diameter cylindrical portion 151a, respectively. Further, a distal end outer peripheral surface of the small diameter cylinder portion 151a, between the inner peripheral surface of the concavity 72 provided in the gear housing 22a, the elastic ring 194 (Claim 10 made of an elastic material such as elastomer, rubber Corresponding to the described elastic material). Further, a part of the worm 27 of the worm shaft 29 that is exposed to the outside of the small-diameter cylindrical portion 151 a from the through hole 193 provided in the small-diameter cylindrical portion 151 a is engaged with the worm wheel 28.

In the case of this example, as in the case of the fourth example of the embodiment shown in FIGS. 11 to 12 described above, the teeth at the meshing portion between the worm 27 and the worm wheel 28 of the worm shaft 29 are described. Without impairing the effect of suppressing the occurrence of the hitting sound, it is possible to prevent the generation of noise due to the contact between the tip of the worm shaft 29 and the fourth ball bearing 37, and the worm shaft 29 can be prevented from excessively shaking. Dynamic displacement can be prevented.
Since other configurations and operations are the same as in the case of the fourth example of the embodiment shown in FIGS. 11 to 12 described above, the same parts are denoted by the same reference numerals, and redundant description is omitted. .

[ Seventh example of embodiment]
FIG. 15 shows a seventh example of the embodiment of the present invention, which also corresponds to the first to fourth , eighth , tenth and sixteenth aspects . In the case of this example, in the structure of the sixth example of the embodiment shown in FIG. 14 described above, a part of the gear housing 22a is disposed on a portion of the gear housing 22a facing the tip surface of the worm shaft 29. A through hole 195 that penetrates both the inner and outer surfaces is formed. In addition, a bottomed cylindrical cap 196 made of an elastic material such as an elastomer such as rubber or a synthetic resin is fitted and fixed to the through hole 195. And the front-end | tip part of the small diameter cylinder part 151a which comprises the bearing holder 149a is fitted and supported by the protrusion 198 provided in the front-end | tip part internal peripheral surface of the cylinder part 197 which comprises this cap 196. In the case of this example, the cap 196 corresponds to the elastic material described in claim 10 .
Since other configurations and operations are the same as in the case of the sixth example of the embodiment shown in FIG. 14 described above, a duplicate description is omitted.

[ Eighth Example of Embodiment]
FIGS. 16-17 has shown the 8th example of embodiment of this invention corresponding to Claims 1-4 , 8 , 10-12 , 16. FIG. In the case of this example, in the structure of the sixth example of the embodiment shown in FIG. 14 described above, a plate portion 199 is provided to close the tip opening of the small diameter cylindrical portion 151a of the bearing holder 149a. A shaft portion 200 protruding in the axial direction is provided at the center of the tip surface. An elastic ring 201 corresponding to the second elastic ring according to claim 11 is provided between the outer peripheral surface of the shaft portion 200 and the inner peripheral surface of the recessed hole 72 provided in the gear housing 22a. Yes. As shown in detail in FIG. 17 , the elastic ring 201 includes an outer diameter side cylindrical portion 202 and an inner diameter side cylindrical portion 203 each made of metal, and a connecting portion 204 made of an elastic material such as an elastomer such as rubber. They are concentrically connected to each other. Further, one axial half (the left half in FIG. 16 ) of the outer diameter side cylindrical portion 202 protrudes in the axial direction from one axial end surface (the left end surface in FIG. 16 ) of the inner diameter side cylindrical portion 203 . Thus, the total length of the outer diameter side cylindrical portion 202 is made larger than the total length of the inner diameter side cylindrical portion 203. Further, a protruding portion 205 protruding in the axial direction is provided on the outer peripheral edge portion of one end surface in the axial direction of the connecting portion 204 (the left end surface in FIG. 16 ), and this protruding portion 205 is provided as the shaft of the outer diameter side cylindrical portion 202. It is coupled to the inner circumferential surface of the directional piece half.

  Further, a part of the connecting portion 204 is located at both ends of the worm shaft 29 in the oscillating displacement direction (vertical direction in FIGS. 16 and 17), and has two through-holes extending in the axial direction on the opposite side in the radial direction. 206 and 206 are provided. With this configuration, the rigidity of the elastic ring 201 is lowered in the direction of the oscillating displacement of the worm shaft 29 and is increased in the direction different from the oscillating displacement direction by 90 degrees. Such an elastic ring 201 has the outer cylindrical portion 202 fitted and fixed in a concave hole 72 provided in the gear housing 22a, and the inner diameter side of the shaft portion 200 provided on the front end surface of the bearing holder 149a. The cylindrical portion 203 is fitted and fixed so as to be provided between the gear housing 22a and the shaft portion 200. Further, the outer peripheral surface of the distal end portion of the small-diameter cylindrical portion 151a constituting the bearing holder 149a is opposed to the inner peripheral surface of the protrusion 205 provided in the connecting portion 204 with a minute gap. In the case of this example, the protrusion 205 corresponds to a stopper for restricting the oscillating displacement of the worm shaft 29.

In the case of this example, the elastic ring 201 has a low rigidity portion and the protrusion 205 that functions as a stopper portion that prevents excessive oscillating displacement of the worm shaft 29. It is shifted in the axial direction.
Since other configurations and operations are the same as in the case of the sixth example of the embodiment shown in FIG. 14 described above, the same parts are denoted by the same reference numerals and redundant description is omitted.

[ Ninth Embodiment]
FIG. 18 shows a ninth example of the embodiment of the invention corresponding to claims 1-4 , 9 , 10, and 16 . In the case of this example, it has a structure in which the structure of the fifth example of the embodiment shown in FIG. 13 is combined with the structure of the sixth example of the embodiment shown in FIG . That is, in the case of this example, the structure of the sixth example embodiment shown in FIG. 14, for supporting the the third ball bearing 36 a fourth ball bearing 37 (see FIG. 14), the bearing holder A coil spring 186 is provided in the radial direction of the bearing holder 149a between the outer peripheral surface of the large-diameter cylindrical portion 150 constituting the 149a and the inner surface of the gear housing 22a.
Other configurations and operations are the same as those of the fifth example of the embodiment shown in FIG. 13 and the sixth example of the embodiment shown in FIG. The description which attaches | subjects a code | symbol and overlaps is abbreviate | omitted.

[ Tenth example of embodiment]
Next, FIGS. 19 to 20 show a tenth example of the embodiment of the invention corresponding to claims 1 to 4 , 10 , 13, and 16. FIG. In the case of this example, in the structure of the sixth example of the embodiment shown in FIG. 14 described above, one end portion (the right end portion in FIG. 19 ) of the rotating shaft 32a of the electric motor 31 and the base end of the worm shaft 29a. Part (left end part in FIG. 19 ) is connected via a coupling ring 207 made of an elastic material in a state in which relative rotation is prevented. As shown in detail in FIG. 20 , the coupling ring 207 is formed in a cylindrical shape by an elastic material such as an elastomer such as rubber, and is provided at a plurality of positions at equal intervals in the circumferential direction (eight positions in the example shown in the figure). The through holes 208, 208 having a substantially triangular cross section penetrating in the axial direction are formed.

Further, there are a plurality of circumferential positions of a portion near the outer diameter of the base end surface (left end surface in FIG. 19 ) of the worm shaft 29a and a portion near the outer diameter of one end surface (right end surface in FIG. 19 ) of the rotating shaft 32a ( In the example shown in the figure, at four positions), projections 209a and 209b projecting in the axial direction are provided at positions aligned with the other through holes 208 and 208 provided in the coupling ring 207, respectively. These protrusions 209a and 209b can be fitted into the through holes 208 and 208 provided in the coupling ring 207 without rattling. The protrusions 209a and 209a provided on the worm shaft 29a and the protrusions 209b and 209b provided on the rotary shaft 32a are connected to the through holes 208 and 208 from both axial sides of the coupling ring 207. The worm shaft 29a and the rotating shaft 32a are connected to each other via the coupling ring 207 by being internally fitted without rattling in the circumferential direction. In the case of this example, a coil spring 186 is provided between the bottom surface of the recessed hole 210 provided in the central portion of the base end surface of the worm shaft 29a and the central portion of the one end surface of the rotating shaft 32a. Elasticity in a direction away from the rotation shaft 32a is applied to the shaft 29a.

In the case of this example, the worm shaft 29a and the rotating shaft 32a are connected via a connecting ring 207. For this reason, it is difficult to transmit rotational vibration between the rotating shaft 32a and the worm shaft 29a.
Since other configurations and operations are the same as in the case of the sixth example of the embodiment shown in FIG. 14 described above, the same parts are denoted by the same reference numerals and redundant description is omitted.

  Although not shown in the drawings, unlike the case of this example, a plurality of first holes are formed in place of the through holes 208 and 208 at the positions where the through holes 208 and 208 provided in the coupling ring 207 are formed. The second recesses can be provided alternately in the circumferential direction. In this case, the bottoms of the first and second recesses are opposite to each other with respect to the axial direction of the coupling ring 207. The projections 209a and 209a provided on the base end surface of the worm shaft 29a and the projections 209b and 209b provided on one end surface of the rotary shaft 32a are respectively connected to the first and second recesses. By fitting, the worm shaft 29a and the rotating shaft 32a are connected via the coupling ring 207.

Further, as a configuration corresponding to the fourteenth aspect, in the first to tenth examples of the above-described embodiment, third and fourth ball shafts 36 that rotatably support portions near both ends of the worm shafts 29 and 29a. , 37 can be filled with grease between the bearing holders 149 and 149a that support at least one of the ball bearings 36 (or 37) and the gear housing 22a. When such a configuration is adopted, when a driving force is transmitted between the worm shafts 29 and 29a and the worm wheel 28, the reaction force applied from the worm wheel 28 to the worm shafts 29 and 29a is based on the reaction force. Thus, when the worm shafts 29 and 29a tend to move away from the worm wheel 28, the bearing holders 149 and 149a can be hardly swung and displaced. In addition, when the driving force increases and the reaction force increases, the speed at which the worm shafts 29 and 29a are separated from the worm wheel 28 tends to increase. In this case, however, the viscous resistance of the grease also increases. . For this reason, the swing displacement of the bearing holders 149 and 149a can be suppressed, and the tooth surfaces of the worm 20 and the worm wheel 28 of the worm shafts 29 and 29a can be easily prevented from separating.

Further, as a configuration corresponding to claim 15 , in the first to tenth examples of the above-described embodiment, third and fourth ball bearings 36 that rotatably support portions near both ends of the worm shafts 29, 29a. The bearing holders 149 and 149a that support at least one of the ball bearings 36 (or 37) can be made of a magnesium alloy. In the case of employing such a configuration, the vibration generated in the worm shaft 29,29a by abutment of the tooth faces of the worm 27 and the worm wheel 28 of the worm shaft 29,29a, the bearing holder 149, Since it can be easily absorbed by 149a, it is difficult to transmit this vibration to the gear housing 22a.

In the case of the first to tenth examples of the above-described embodiment, the pinion 11 fixed to the end of the pinion shaft 10 (see FIG. 23 ) and the rack 10 (see FIG. 23 ) are directly meshed with each other. The present invention according to claims 1 to 16 is not limited to such a structure. For example, a pin provided at the lower end of the pinion shaft is engaged in a long hole of a pinion gear provided separately from the pinion shaft so that the displacement of the long hole in the length direction can be freely engaged. And a structure incorporating a so-called vehicle speed responsive variable gear ratio mechanism (VGS) that changes the ratio of the displacement amount of the rack to the rotation angle of the steering shaft according to the vehicle speed, and the first to first embodiments described above . It can also be combined with 10 examples of structures.

Further, the present invention according to claims 1 to 16 is not limited to the structure in which the electric motor 31 is provided around the steering shaft 2. For example, as shown in FIG. 21 , an electric motor 31 can be provided in the peripheral portion of the pinion 11 (see FIG. 23 ) engaged with the rack 12. In the case of the structure shown in FIG. 21 , the worm wheel constituting the worm reduction gear 16a is fixed to the pinion 11 or a part of the member supported by the pinion 11. In the case of the structure shown in FIG. 21 , the torque sensor 3 (see FIG. 23 ) can be provided not on the periphery of the steering shaft 2 but on the periphery of the pinion 11. Even with such a structure shown in FIG. 21 , the present invention according to claims 1 to 16 can be carried out.

Furthermore, as shown in FIG. 22 , the electric motor 31 can be provided in a peripheral portion of the sub-pinion 211 that is engaged with a part of the rack 12 that is disengaged from the engaging portion with the pinion 11. In the case of the structure shown in FIG. 22 , the worm wheel fixed to the sub-pinion 211 and the worm shaft 29 (29a) are engaged with each other. Even in the case of the structure shown in FIG. 22 , the torque sensor 3 (see FIG. 23 ) can be provided in the peripheral portion of the pinion 11. In the case of the structure shown in FIG. 22 , the vibration transmitted from the ground to the pinion 11 through the wheel to the intermediate portion of the intermediate shaft 8 is prevented from being transmitted to the steering wheel 1. The shock absorber 212 is provided. For example, the shock absorber 212 is configured by combining an inner shaft and an outer shaft in a telescopic manner, and by connecting an elastic material between the peripheral surfaces of the two shafts. Even with such a structure shown in FIG. 22 , the present invention according to claims 1 to 16 can be implemented.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Torque sensor 4 Reduction gear 5 Electric motor 6 Controller 7 Universal joint 8 Intermediate shaft 9 Steering gear 10 Input shaft 11 Pinion 12 Rack 13 Tie rod 14 Steering wheel 15 Steering column 15
16a Worm reducer 17 Outer shaft 18 Inner shaft 19 Outer column 20 Inner column
22a Gear housing 23 Case 24 Support bracket 26 Car body 27 Worm 28 Worm wheel
29 Worm shaft
31 Electric motor 32, 32a Rotating shaft 33 Spline engaging portion 34 First ball bearing 35 Second ball bearing 36 Third ball bearing 37 Fourth ball bearing
38 rotor
39 Stator 40 Bottom plate part 41 Concave hole 42 Bulkhead part
50 female spline 51 male spline 52 inner ring 53 collar
57 outer ring
60 outer ring
65 inner ring
72 concave holes
113 Steering shaft 114 Electric motor 115 Worm speed reducer 116 Worm wheel 117 Worm shaft 118 Worm 119 Gear housing 120a, 120b Rolling bearing 121 Rotating shaft 122 Recessed hole 123 Elasticity imparting means 124 Inner diameter side cylindrical portion 125 Outer diameter side cylindrical portion 126 Circle Portion 127 Inner ring 128 Screw hole 129 Screw ring
135 Main body 136 Cover 137 Elasticity imparting means 138 First inner shaft 139 Second inner shaft 140 Torsion bar 141 Torsion coil spring 142 Preload pad 149, 149a Bearing holder 150 Large diameter cylindrical portion 151, 151a Small diameter cylindrical portion 152 Annulus Portion 154 Locking ring 155 Locking ring 158 First through hole 159 Oscillating shaft 160 Recessed hole 161 Second through hole 162 Wall portion 164 Second bearing holder 165 Tube portion 166 Large diameter portion 167 Bush 169 Outward flange 171 Small diameter part 172 Flat part 173 Arm part 174 Through hole 175 Locking part 176 Locking protrusion 177 First part cylindrical surface part 178 Second part cylindrical surface part 179 Elastic ring 180 Inner diameter side cylindrical part 181 Outer diameter side cylindrical part 182 Connection part 183 Space 184 Recess 185 Spline hole 186 Coil spring 187 Elasticity Ring 188 Inner diameter side cylindrical portion 189 Outer diameter side cylindrical portion 190 Connecting portion 191 Stopper portion 192 Concave hole 193 Through hole 194 Elastic ring 195 Through hole 196 Cap 197 Tube portion 198 Projection portion 199 Plate portion 200 Shaft portion 201 Elastic ring 202 Outer diameter Side cylindrical portion 203 Inner diameter side cylindrical portion 204 Connecting portion 205 Protruding portion 206 Through hole 207 Coupling ring 208 Through hole 209a, 209b Protruding portion 210 Recessed hole 211 Sub-pinion 212 Shock absorber

Claims (28)

  A worm speed reducer that includes a worm wheel, a worm shaft, and an elastic body, and the elastic body imparts elasticity to the worm shaft in a direction toward the worm wheel.   The elastic body gives elasticity to the worm shaft in the direction toward the worm wheel via the preload pad. This worm wheel can be fixed to the assist shaft, and the worm shaft is close to both ends. The portion is supported on the inside of the gear housing by a pair of bearings, and a worm provided at an intermediate portion meshes with the worm wheel, and the preload pad is the gear housing or a member fixed to the gear housing. Displacement in a predetermined direction is restricted by a guide surface provided on the front surface, and the clearance from the guide surface is eliminated or reduced by elastic deformation of the preload pad itself based on the elasticity of the elastic body. Item 1. The worm speed reducer according to item 1.   The elastic body gives elasticity to the worm shaft in the direction toward the worm wheel via the preload pad. This worm wheel can be fixed to the assist shaft, and the worm shaft is close to both ends. The portion is supported on the inner side of the gear housing by a pair of bearings, and a worm provided at an intermediate portion meshes with the worm wheel, and the preload pad includes a pair of elements, and the gear housing or the Displacement in a predetermined direction is regulated by a guide surface provided on a member fixed to the gear housing, and the guide element is displaced by moving the pair of elements away from each other based on the elasticity of the elastic body. The worm reduction gear according to claim 1, wherein a gap with the surface is eliminated or reduced.   The displaceable direction of the preload pad along the guide surface is inclined with respect to a virtual plane including a central axis of the worm shaft and a meshing portion between the worm and the worm wheel provided on the worm shaft. The worm reduction gear according to claim 3.   A steering shaft provided with a steering wheel at the rear end, a pinion provided on the front end side of the steering shaft, a rack meshed with the pinion or a member supported by the pinion, and any one of claims 2 to 4 The described worm reducer, an electric motor for rotationally driving the worm shaft, a torque sensor for detecting the direction and magnitude of torque applied to the steering shaft or pinion, and a signal input from the torque sensor And a controller for controlling the driving state of the electric motor based on any one of the steering shaft, the pinion, and the sub-pinion that meshes with the rack at a position away from the pinion. An electric power steering device which is such a member.   The elastic body is elastic means, and the worm shaft is supported so as to be capable of rotating and swinging with respect to the gear housing, and the worm provided at the intermediate portion meshes with the worm wheel. The worm speed reducer according to claim 1, wherein the swinging central axis is provided in a position shifted from the central axis of the worm shaft toward the worm wheel side in parallel with the central axis of the worm wheel.   An axis parallel to the central axis of the worm wheel passing through a point on a straight line including the intersection of the pitch circles of the worm and the worm wheel on the worm shaft and parallel to the central axis of the worm axis The worm speed reducer according to claim 6, wherein the worm speed reducer is a dynamic center axis.   7. A bearing holder for supporting at least one of a pair of bearings rotatably supporting portions near both ends of the worm shaft is supported so as to be able to swing and displace with respect to the gear housing. Item 8. The worm speed reducer according to item 7.   With respect to the axial direction of the worm shaft, between the bearing on the electric motor side of the pair of bearings that rotatably supports portions near both ends of the worm shaft, and the mesh portion of the worm shaft and the worm wheel, The worm speed reducer according to any one of claims 6 to 8, wherein a swing center axis of the worm shaft is provided.   With respect to the meshing portion of the worm shaft and the worm wheel, the worm shaft is provided with an elastic means for applying an elastic force in the direction toward the worm wheel on the opposite side of the oscillating central axis of the worm shaft. Item 10. The worm speed reducer according to any one of Items 6 to 9.   A bearing holder for supporting a bearing that rotatably supports a portion near one end of the worm shaft is supported on the gear housing so as to be capable of swinging displacement by a swing shaft. The gear housing, the swing shaft, The worm speed reducer according to any one of claims 6 to 10, wherein an elastic material is provided between the bearing holder and the swing shaft.   A bearing holder for supporting a bearing that rotatably supports a portion near one end of the worm shaft is supported on the gear housing so as to be capable of swinging displacement by a swing shaft. The gear housing, the swing shaft, Between the bearing holder and the swing shaft, at least part of which is an elastic ring, and the rigidity of the elastic ring with respect to the radial direction of the swing center shaft of the worm shaft is set in the circumferential direction. The worm speed reducer according to claim 6, wherein the worm speed reducer is different.   The worm speed reducer according to any one of claims 6 to 9, further comprising an elastic force applying means for applying an elastic force in a direction toward the worm wheel to the worm shaft between the worm shaft and the rotating shaft of the electric motor. .   Elasticity in the direction toward the worm wheel is applied to the worm shaft between the bearing holder and the gear housing for supporting at least one of the pair of bearings rotatably supporting the portions near both ends of the worm shaft. The worm speed reducer according to any one of claims 6 to 9, further comprising elasticity applying means for applying.   By providing an elastic material between one of the pair of bearings supporting the portions near the both ends of the worm shaft and the gear housing away from the center axis of swinging of the worm shaft, the above-mentioned gear housing is provided. The worm speed reducer according to any one of claims 6 to 14, wherein the worm shaft can be swung and displaced.   A second elastic ring, at least a part of which is made of an elastic material, is provided between one of the pair of bearings supporting the portions near the both ends of the worm shaft and the gear housing that is distant from the oscillation center shaft. As a result, the worm shaft can be oscillated and displaced with respect to the gear housing, and the rigidity of the second elastic ring is different depending on the oscillating displacement direction of the worm shaft and another direction. The worm speed reducer according to any one of claims 6 to 14.   The worm according to claim 15 or 16, wherein a stopper portion for restricting the oscillating displacement of the worm shaft is provided on an elastic material or a second elastic ring provided between the one bearing and the gear housing. Decelerator.   The worm speed reducer according to any one of claims 6 to 17, wherein the rotating shaft of the electric motor and the worm shaft are connected via an elastic material.   The grease is filled between a bearing holder for supporting at least one of a pair of bearings rotatably supporting both end portions of the worm shaft and a gear housing. The worm speed reducer described above.   The worm reduction gear according to any one of claims 6 to 19, wherein a bearing holder for supporting at least one of a pair of bearings rotatably supporting portions near both ends of the worm shaft is made of a magnesium alloy. Machine.   A steering shaft provided with a steering wheel at a rear end, a pinion provided on the front end side of the steering shaft, a rack meshed with the pinion or a member supported by the pinion, and any one of claims 6 to 20 The described worm reducer, an electric motor for rotationally driving the worm shaft, a torque sensor for detecting the direction and magnitude of torque applied to the steering shaft or pinion, and a signal input from the torque sensor A controller for controlling the driving state of the electric motor based on any one of the worm wheel, the steering shaft, the pinion, and the sub-pinion that meshes with the rack at a position away from the pinion. An electric power steering device fixed to the member.   The elastic body gives elasticity to the worm shaft in the direction toward the worm wheel via the preload pad. The worm wheel can be fixed to the assist shaft, and the worm shaft is close to one end. The part is supported by the first bearing and the other end part is supported by the second bearing on the inner side of the gear housing, and the worm provided in the intermediate part meshes with the worm wheel, and the first bearing The second bearing is covered with a synthetic resin buffer member fixed to the gear housing at least a part of the outer peripheral surface and both axial side surfaces. The axial displacement of the second bearing relative to the buffer member is restricted, and the axial displacement of the worm shaft relative to the preload pad and the second bearing is allowed. It is, worm reduction gear according to claim 1.   23. The worm speed reducer according to claim 22, wherein the shock absorbing member is provided with a notch extending over the entire length in the axial direction in a part of the circumferential direction.   23. The second bearing is prevented from axial displacement of the second bearing with respect to the buffer member and is allowed to be radially displaced with respect to the buffer member. Or the worm reduction gear according to claim 23.   The worm speed reducer according to any one of claims 22 to 24, wherein an elastic member is provided between the buffer member and the gear housing or between the buffer member and the second bearing.   The worm reducer according to any one of claims 22 to 25, wherein the buffer member is composed of a pair of elements having a shape obtained by dividing the buffer member into two by a virtual plane including the central axis of the buffer member.   27. The worm speed reducer according to claim 26, wherein the surface direction of the butting surfaces of the pair of elements is made to coincide with the direction in which the elastic force is applied to the worm shaft by the elastic body.   A steering shaft provided with a steering wheel at a rear end portion, a pinion provided on the front end side of the steering shaft, a rack meshed with the pinion or a member supported by the pinion, and any one of claims 22 to 27 The described worm reducer, an electric motor for rotationally driving the worm shaft, a torque sensor for detecting the direction and magnitude of torque applied to the steering shaft or pinion, and a signal input from the torque sensor And a controller for controlling the driving state of the electric motor based on any one of the steering shaft, the pinion, and the sub-pinion that meshes with the rack at a position away from the pinion. An electric power steering device which is such a member.

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