JP2019007538A - Worm reduction gear - Google Patents

Abstract

To realize a structure capable of preventing an excessive force based on a meshing reaction force from acting on a spring constituting an urging member.
An outer peripheral surface of a second bearing is formed by pressing a biasing member main body in an axial direction by a pressing member constituting the biasing member. To the other side of the worm shaft 17 in the direction approaching the worm wheel. When the worm shaft 17 moves away from the worm wheel, the second bearing 20 is brought into contact with a pair of stopper portions 37a and 37b provided on the guide member 21 for guiding the movement of the second bearing 20. This prevents the worm shaft 17 from moving further in the direction away from the worm wheel.
[Selection] Figure 4

Description

  The present invention relates to a worm reduction gear incorporated in an electric power steering device or the like.

  The power steering device is widely used to reduce the force required for the driver to operate the steering wheel. There are two types of power steering devices: an electric power steering device that uses an electric motor as an auxiliary power source, and a hydraulic power steering device that uses hydraulic pressure as an auxiliary power source. Among these, the electric power steering device can be configured to be smaller and lighter than the hydraulic power steering device, and it has advantages such as easy control of the size of auxiliary power and less power loss of the engine. It has become.

  In the electric power steering device, auxiliary power of the electric motor is applied to a steering rotation shaft that rotates based on an operation of a steering wheel via a reduction gear. As such a speed reducer, a worm speed reducer is widely used because a large reduction ratio can be obtained.

  However, because there is an inevitable backlash at the meshing part of the worm wheel and worm shaft constituting the worm reducer, it is easy to generate rattling noise when the rotation direction of the worm wheel changes. There's a problem.

  In Japanese Patent Laid-Open No. 2016-23760, among a pair of bearings for rotatably supporting the worm shaft with respect to the housing, a spring is provided between the bearing disposed on the tip side of the worm shaft and the housing. There is disclosed a structure in which an urging member configured to be arranged is arranged to urge the tip of the worm shaft toward the worm wheel. According to such a structure, backlash of the meshing portion can be suppressed, and generation of rattling noise can be suppressed.

JP 2016-23760 A

  By the way, if the torque is reversely input to the steering rotation shaft to which the worm wheel is fixed, for example, when the wheel climbs on the curb, an excessive meshing reaction force may be applied from the worm wheel to the worm shaft. . When such an excessive meshing reaction force is applied to the worm shaft, the tip of the worm shaft is pressed in a direction away from the worm wheel. As a result, the spring constituting the biasing member may be plastically deformed.

  The present invention has been made in view of the circumstances as described above, and realizes a structure of a worm speed reducer that can prevent an excessive force based on a meshing reaction force from acting on a spring constituting a biasing member. The purpose is that.

The worm speed reducer of the present invention includes a housing, a worm shaft, a worm wheel, a first bearing, a second bearing, a biasing member, and a pair of guide surfaces.
The worm shaft is disposed inside the housing, and has one axial end connected to the motor output shaft of the electric motor so that the worm shaft can swing.
The worm wheel is disposed inside the housing and meshes with the worm shaft.
The first bearing supports one side of the worm shaft in the axial direction so as to be rotatable with respect to the housing.
The second bearing rotatably supports the other axial side of the worm shaft.
The biasing member biases the other axial side portion of the worm shaft in a direction approaching the worm wheel via the second bearing, and is directed substantially parallel to the central axis of the worm wheel. A biasing member main body having a central axis and disposed inside the housing so as to be movable in the axial direction, a pressing member pressing the biasing member main body in the axial direction, and a center of the biasing member main body The shaft is supported by the biasing member main body inclined toward the worm shaft toward the rear side in the pressing direction by the pressing member with respect to the shaft, and a part thereof is brought into contact with the outer peripheral surface of the second bearing. And a leaf spring.
The pair of guide surfaces are arranged on both outer sides of the second bearing with respect to the axial direction of the worm wheel, and guide the distance movement of the second bearing with respect to the worm wheel.
In the worm speed reducer according to the present invention, when the worm shaft is displaced by a predetermined amount in a direction away from the worm wheel, the second bearing is separated from the worm wheel by contacting the second bearing. And a stopper portion for preventing further movement.

  In the present invention, each of the pair of guide surfaces can be provided on a guide member fitted inside the housing.

  In the present invention, the stopper portion can be provided on the guide member.

  In the present invention, the stopper portion can be provided in the housing.

  When the stopper portion is provided in the housing, the stopper portion can have a positioning function in the circumferential direction of the guide member.

  In this invention, the part which contacts the outer peripheral surface of said 2nd bearing among the said stopper parts can also be made from an elastic material.

  In the present invention, the stopper portion may be provided on both outer sides of the second bearing with respect to the axial direction of the worm wheel.

  ADVANTAGE OF THE INVENTION According to this invention, it can prevent that the excessive force based on a meshing reaction force acts on the spring which comprises an urging | biasing member.

FIG. 1 is a partially cutaway side view of a steering apparatus including a worm reduction gear according to a first example of an embodiment. FIG. 2 is a cross-sectional view taken along line AA of FIG. 1 showing a first example of the embodiment. 3 is a cross-sectional view taken along the line BB of FIG. 1 showing a first example of the embodiment. FIG. 4 is a cross-sectional view taken along the line CC of FIG. 2 showing a first example of the embodiment. FIG. 5A is a diagram illustrating a state in which the worm shaft is moved in a direction away from the worm wheel until the second bearing comes into contact with the pair of stopper portions in the first example of the embodiment. B) is a view showing a state in which the worm shaft has moved in a direction away from the worm wheel with respect to the structure of the comparative example having no stopper portion. FIG. 6 is a diagram corresponding to FIG. 4 and showing a second example of the embodiment. FIG. 7 is a diagram corresponding to FIG. 4 and showing a third example of the embodiment.

[First example of embodiment]
A first example of the embodiment will be described with reference to FIGS.

<Overall structure of electric power steering device>
The electric power steering apparatus is a column assist type electric power steering apparatus, and includes a steering wheel 1, a steering shaft 2, a steering column 3, a pair of universal joints 4a and 4b, an intermediate shaft 5, and a steering gear unit. 6, a pair of tie rods 7, and an electric assist device 8.

  The steering wheel 1 is attached to a rear end portion of a steering shaft 2 that is rotatably supported inside the steering column 3. A front end portion of the steering shaft 2 is disposed inside a housing 9 fixed to the front end portion of the steering column 3, and is connected to the output shaft 11 via a torsion bar 10.

  The output shaft 11 is rotatably supported inside the housing 9 via a pair of rolling bearings 12a and 12b. The rotation of the output shaft 11 is transmitted to the pinion shaft 13 of the steering gear unit 6 through the pair of universal joints 4a and 4b and the intermediate shaft 5. Then, by converting the rotation of the pinion shaft 13 into a linear motion of a rack (not shown), the pair of tie rods 7 are pushed and pulled to give a steering angle to the steered wheels.

  The electric assist device 8 reduces the force required for the driver to operate the steering wheel 1, and includes a torque sensor 14, an ECU (not shown), an electric motor 15, and a worm reducer 16. .

  The torque sensor 14 is disposed around the output shaft 11 and detects the twist direction and the twist amount of the output shaft 11. The ECU determines the auxiliary torque based on information on the steering torque calculated based on the twist direction and the amount of twist of the output shaft 11 detected by the torque sensor 14, information on the vehicle speed measured by a vehicle speed sensor (not shown), and the like. To do. The electric motor 15 is supported and fixed to the housing 9, and the energization direction and the energization amount are controlled by the ECU. The worm reducer 16 decelerates the rotational force of the electric motor 15 and transmits it to the output shaft 11. As a result, since an auxiliary torque is applied to the output shaft 11, the pair of tie rods 7 can be pushed and pulled with a force larger than the force applied to the steering wheel 1.

<Structure of worm reducer>
The worm speed reducer 16 includes a housing 9, a worm shaft 17, a worm wheel 18, a first bearing 19, a second bearing 20, a guide member 21, and an urging member 22.

  The worm shaft 17 has a first support shaft portion 23 on one side in the axial direction and a second support shaft portion 24 on the other side in the axial direction. A worm tooth portion 25 is provided at an axially intermediate portion between the support shaft portion 24 and the support shaft portion 24. Such a worm shaft 17 is arranged inside a bottomed cylindrical worm shaft housing portion 26 constituting the housing 9. The base end, which is one end in the axial direction of the worm shaft 17, can transmit a rotational force to the motor output shaft 15 a of the electric motor 15 by spline engagement or the like. Oscillating displacement is connected. Note that the end of the worm shaft 17 on one side in the axial direction is connected to the motor output shaft 15a via a connecting member that enables transmission of other rotational force such as a torque transmission joint provided with an elastic body. It is also possible to connect the shafts so as to be able to swing.

  The worm wheel 18 has a worm wheel tooth portion 27 that meshes with the worm tooth portion 25 on the outer peripheral surface, and is fixed to the output shaft 11. Such a worm wheel 18 is disposed inside a cylindrical worm wheel housing portion 28 that constitutes the housing 9. Since the electric power steering device of this example is a column assist type, the worm wheel 18 is fixed to the output shaft 11. However, in the pinion assist type electric power steering device, the worm wheel is fixed to the pinion shaft. .

  The inner peripheral surface of the worm shaft housing portion 26 is formed in a concave cylindrical surface shape, and a part in the circumferential direction of the axial intermediate portion opens into the worm wheel housing portion 28. Therefore, the internal space of the worm shaft housing portion 26 and the internal space of the worm wheel housing portion 28 are connected to each other.

  The first bearing 19 is a single-row deep groove type or a four-point contact type ball bearing, and includes an annular inner ring 29 and an outer ring 30, and a plurality of balls 31. Among these, the inner ring 29 is fitted and fixed to the first support shaft portion 23 of the worm shaft 17, while the outer ring 30 is fixed to the opening portion of the worm shaft housing portion 26. Further, the first bearing 19 has a radial gap between the inner ring 29 and the outer ring 30 and the ball 31. In this example, the first bearing 19 that connects the base end portion of the worm shaft 17 to the motor output shaft 15a so as to be capable of swinging displacement and rotatably supports the first support shaft portion 23 of the worm shaft 17. Therefore, the worm shaft 17 is supported so as to be swingable with respect to the worm shaft housing portion 26 with the center of the first bearing 19 as a fulcrum.

  The second bearing 20 is a single-row deep groove type ball bearing, and includes an annular inner ring 32 and an outer ring 33, and a plurality of balls 34. Of these, the inner ring 32 is fitted and fixed to the second support shaft portion 24 of the worm shaft 17, while the outer ring 33 is a guide member that is fitted and fixed to the inner portion of the worm shaft accommodating portion 26. 21 is disposed inside.

  The guide member 21 is made of, for example, a synthetic resin and has a substantially U shape as a whole. The guide member 21 is fitted and fixed inside the worm shaft housing portion 26 by press fitting. The guide member 21 has a partially cylindrical bottom plate portion 35 and an X direction (vertical direction in FIG. 4) perpendicular to the axial direction of the worm shaft 17 and the axial direction of the worm wheel 18 from both ends of the bottom plate portion 35, respectively. A pair of extended side plate portions 36a and 36b, and a pair of stopper portions 37a and 37b provided at the front end portions of the side plate portions 36a and 36b so as to protrude toward each other. Yes. The outer peripheral surface of such a guide member 21 is formed in a convex cylindrical surface shape.

  The opposing surfaces of the pair of side plate portions 36a, 36b are each a flat surface and are a pair of guide surfaces 38a, 38b parallel to each other. The pair of guide surfaces 38 a and 38 b are arranged on both outer sides of the second bearing 20 with respect to the axial direction of the worm wheel 18 and in parallel with the X direction. The distance between the pair of guide surfaces 38 a and 38 b is slightly larger than the outer diameter of the second bearing 20. For this reason, the pair of guide surfaces 38 a and 38 b guide the movement in the X direction, which is the perspective movement of the second bearing 20 with respect to the worm wheel 18.

  The mutually opposing surfaces of the pair of stopper portions 37a and 37b are inclined in a direction closer to each other as the distance from the worm wheel 18 with respect to the X direction is a pair of flat stopper surfaces 39a and 39b. . A distance between the pair of stopper surfaces 39a and 39b is farthest from the worm wheel 18 in the X direction and is sufficiently smaller than the outer diameter of the second bearing 20. Therefore, in this example, the second bearing 20 is allowed to move relative to the worm wheel 18 until the outer peripheral surface of the outer ring 33 constituting the second bearing 20 contacts the pair of stopper surfaces 39a and 39b. As shown in FIG. 5A, after the outer peripheral surface of the outer ring 33 comes into contact with the pair of stopper surfaces 39a and 39b, the second bearing 20 is further away from the worm wheel 18 (upper direction in FIG. 5). ) To move to. The formation position of the pair of stopper surfaces 39a and 39b in the X direction is caused by the contact with the outer peripheral surface of the second bearing 20 whose displacement is blocked by the pair of stopper surfaces 39a and 39b. In order to prevent plastic deformation, it is determined in consideration of the inclination angle of the leaf spring 42 and the yield stress.

  The biasing member 22 biases the other axial side of the worm shaft 17 in the direction approaching the worm wheel 18 (downward in FIGS. 2 and 4) via the second bearing 20. It has a main body 40, a pressing member 41, and a leaf spring 42. Such an urging member 22 is disposed inside the urging member accommodating portion 43 constituting the housing 9.

The urging member accommodating portion 43 is provided on the opposite side of the worm wheel accommodating portion 28 with respect to the worm shaft accommodating portion 26 (the upper side in FIGS. 2 and 4) and at a twisted position with respect to the worm shaft accommodating portion 26. It has been. A central axis O ₄₃ of the urging member accommodating portion 43 is disposed substantially parallel to the central axis O ₁₈ of the worm wheel 18. The inner peripheral surface of the urging member accommodating portion 43 is configured as a concave cylindrical surface, and a part in the circumferential direction of the axial intermediate portion opens into the worm shaft accommodating portion 26. Therefore, the internal space of the biasing member housing portion 43 and the internal space of the worm shaft housing portion 26 are connected to each other. The urging member accommodating portion 43 is open only at one end (right side in FIG. 4) in the axial direction. A bottomed cylindrical lid member 44 is internally fitted or screwed to the opening of the biasing member accommodating portion 43.

The urging member main body 40 is generally formed in a rod shape, and the inner side of the urging member accommodating portion 43 is in a state where its own central axis O ₄₀ is aligned with the central axis O ₄₃ of the urging member accommodating portion 43. It is arranged to be able to move in the axial direction. Thus, the center axis O ₄₀ of the biasing member body 40 is substantially arranged in parallel to the center axis O ₁₈ of the worm wheel 18. That is, the center axis O ₄₀ of the biasing member body 40 is not limited to a perfectly parallel to the center axis O ₁₈ of the worm wheel 18, as will be described later, based on the pressing force of the pressing member 41, the biasing member body As long as the leaf spring 42 fixed to 40 is pressed against the outer peripheral surface of the second bearing 20 and the second support shaft portion 24 of the worm shaft 17 can be biased in the direction approaching the worm wheel 18, the leaf spring 42 can be inclined. Specifically, the inclination angle of the central axis O ₄₀ of the biasing member main body 40 with respect to the central axis O ₁₈ of the worm wheel 18 is set to about 0 ° ± 10 °. The biasing member main body 40 has an outer surface facing away from the worm shaft 17 in the X direction as a convex cylindrical surface 45 having a radius of curvature substantially equal to the radius of curvature of the inner peripheral surface of the biasing member accommodating portion 43. .

  The biasing member main body 40 has a cylindrical portion 46 on one side in the axial direction close to the lid member 44, and a semicircular half-section in the axial intermediate portion adjacent to the other axial side of the cylindrical portion 46. A cylindrical portion 47 is provided, and a mounting portion 48 is provided on the other axial side adjacent to the other axial side of the semi-cylindrical portion 47. The surface of the mounting portion 48 that faces the worm shaft 17 side with respect to the X direction is a flat surface, and is a mounting surface 49 that is inclined in a direction approaching the worm shaft 17 toward one side in the axial direction.

  The pressing member 41 is formed of a spring member such as a compression coil spring, for example, and is elastically compressed between the bottom surface of the cylindrical portion 46 of the biasing member main body 40 and the bottom surface of the bottomed cylindrical lid member 44. It is arranged in the state. Thereby, the biasing member main body 40 is elastically pressed toward the other side in the axial direction. Therefore, the pressing direction by the pressing member 41 coincides with the axial direction of the urging member main body 40, the front side with respect to the pressing direction corresponds to the other axial direction of the urging member main body 40, and the rear side with respect to the pressing direction. This corresponds to one side of the urging member main body 40 in the axial direction. Further, most of the pressing member 41 is disposed inside the lid member 44 and the cylindrical portion 46.

The base end of the leaf spring 42 on one side in the longitudinal direction (left side in FIG. 4) is fixed to the mounting surface 49 by mounting pins 50. For this reason, the leaf spring 42 is disposed along the attachment surface 49 in a free state, and is one side in the axial direction of the urging member main body 40 with respect to the central axis O ₄₀ of the urging member main body 40 (FIG. 4). It is inclined in a direction approaching the worm shaft 17 as it goes to the right side. In other words, the leaf spring 42 is inclined with respect to the central axis O ₄₀ of the urging member main body 40 in a direction approaching the worm shaft 17 toward the rear side in the pressing direction by the pressing member 41. Specifically, the inclination angle of the mounting surface 49 with respect to the central axis O ₄₀ of the biasing member main body 40 is set to about 1 to 20 degrees. The total length of the leaf spring 42 is limited to a length that allows the front end portion on the other side in the longitudinal direction (the right side in FIG. 4) to contact the end portion on the other axial side of the cylindrical portion 46. Further, in a state where the end portion on the other side in the longitudinal direction of the leaf spring 42 is in contact with the end portion on the other side in the axial direction of the cylindrical portion 46, there is a cross section between the back surface of the leaf spring 42 and the semi-cylindrical portion 47. A trapezoidal gap 51 exists. The leaf spring 42 can be bent and deformed so that its longitudinal intermediate portion enters the gap 51.

  The biasing member 22 of this example is a leaf spring 42 fixed to the biasing member main body 40 by pressing the biasing member main body 40 toward the other side in the axial direction (left side in FIG. 4) by the pressing member 41. Is pressed against the outer peripheral surface of the outer ring 33 constituting the second bearing 20. Then, the second support shaft portion 24 of the worm shaft 17 is urged through the second bearing 20 in a direction approaching the worm wheel 18, and the worm shaft 17 is supported by using the center of the first bearing 19 as a fulcrum. It is swung with respect to the accommodating portion 26. Accordingly, the worm tooth portion 25 is elastically pressed against the worm wheel tooth portion 27. As a result, it is possible to effectively prevent the occurrence of rattling noise at the meshing portion between the worm tooth portion 25 and the worm wheel tooth portion 27. Note that the pressing force of the pressing member 41 is appropriately adjusted so that the meshing resistance of the meshing portion between the worm tooth portion 25 and the worm wheel tooth portion 27 does not become excessively large.

Further, when wear occurs at the meshing portion between the worm tooth portion 25 and the worm wheel tooth portion 27, the position of the biasing member main body 40 is moved to the other side in the axial direction based on the pressing force by the pressing member 41. The leaf spring 42 is inclined with respect to the central axis O ₄₀ of the urging member main body 40 so as to approach the worm shaft 17 toward the rear side with respect to the pressing direction by the pressing member 41. By moving to the other side in the direction, the contact position between the leaf spring 42 and the second bearing 20 can be moved closer to the worm wheel 18 (lower side in FIG. 4). Thus, the swing angle of the worm shaft 17 can be automatically increased according to the amount of wear generated at the meshing portion. Therefore, even when wear occurs in the meshing portion, generation of rattling noise can be suppressed.

  Further, in this example, when the meshing reaction force is applied from the worm wheel 18 to the worm shaft 17, and the worm shaft 17 moves away from the worm wheel 18, the leaf spring 42 is bent and deformed by the second bearing 20. Therefore, it is possible to prevent the surface pressure of the meshing portion from becoming excessive. Further, the worm shaft 17 moves away from the worm wheel 18 due to the tolerance of the coaxiality between the central axis of the worm shaft 17 and the central axis of the worm tooth portion 25 and the influence of thermal expansion occurring in peripheral members such as the worm wheel 18. In this case, it is possible to prevent the surface pressure of the meshing portion from becoming excessive because the leaf spring 42 is bent and deformed.

  In addition, in this example, when an excessive meshing reaction force is applied from the worm wheel 18 to the worm shaft 17 due to the wheel climbing on the curbstone, as shown in FIG. The worm shaft 17 can be prevented from moving further in the direction away from the worm wheel 18 by the contact between the outer peripheral surface of the worm wheel and the pair of stopper surfaces 39a and 39b. For this reason, it is possible to prevent an excessive force based on the meshing reaction force from acting on the leaf spring 42. Therefore, it is possible to effectively prevent the deformation amount of the leaf spring 42 generated due to the contact between the second bearing 20 and the leaf spring 42 from being excessive, and plastic deformation such as bending deformation or compression deformation from occurring in the leaf spring 42.

  On the other hand, as shown in FIG. 5B, in the structure of the comparative example that does not have the stopper portions 37a and 37b, the movement of the worm shaft 17 in the direction away from the worm wheel 18 is performed by a member other than the leaf spring 42. Is not limited. For this reason, in the structure of the comparative example, the amount of movement δ2 of the worm shaft 17 is larger than the amount of movement of the worm shaft 17 in the structure of this example having the stopper portions 37a and 37b (δ2> δ1). Accordingly, the amount of deformation of the leaf spring 42 becomes excessive, and plastic deformation is likely to occur in the leaf spring 42. Here, as shown in FIG. 5B, if the depth of the gap 51 in the X direction is reduced, the bending deformation of the leaf spring 42 can be suppressed, but instead, the compression deformation occurs. It becomes easy. On the other hand, in this example, since the movement of the worm shaft 17 can be limited by the pair of stopper surfaces 39a and 39b, the amount of bending that occurs in the leaf spring 42 can be suppressed to such an extent that plastic deformation does not occur. The elastic force of the leaf spring 42 is such that the biasing member main body 40 is pressed by the pressing member before the leaf spring 42 is elastically deformed when an excessive meshing reaction force is applied from the worm wheel 18 to the worm shaft 17. The pressure member 41 is appropriately adjusted so as not to be displaced backward with respect to the pressing direction of the pressing member 41 against the pressing force of the pressing member 41.

[Second Example of Embodiment]
A second example of the embodiment will be described with reference to FIG. In this example, the stopper surfaces 39c and 39d of the stopper portions 37a and 37b are made of an elastic material. Specifically, elastic plates 52a and 52b each made of rubber, elastomer, synthetic resin or the like are attached to the mutually opposing surfaces of the stopper portions 37a and 37b by fixing means such as adhesion. The surfaces of the elastic plates 52a and 52b are used as stopper surfaces 39c and 39d, respectively.

  In this example having the above-described configuration, it is possible to prevent the occurrence of contact hitting sound when the outer peripheral surface of the outer ring 33 constituting the second bearing 20 abuts against the stopper surfaces 39c and 39d. Other configurations and operational effects are the same as in the first example of the embodiment.

[Third example of embodiment]
A third example of the embodiment will be described with reference to FIG. In this example, the pair of stopper portions 37c and 37d are provided not on the guide member 21a but on a part of the housing 9a. Specifically, the axial direction of the worm wheel 18 (see FIG. 2 and FIG. 3) at the boundary between the internal space of the worm shaft housing portion 26 and the internal space of the biasing member housing portion 43 in the inner surface of the housing 9a. A pair of stopper portions 37c and 37d are provided so as to protrude in a direction approaching each other.

  Of the opposing surfaces of the pair of stopper portions 37c and 37d, the worm wheel side half in the X direction (vertical direction in FIG. 7) orthogonal to the axial direction of the worm shaft 17 and the axial direction of the worm wheel 18 respectively. The parts are inclined in a direction approaching each other as the distance from the worm wheel 18 in the X direction is a pair of flat stopper surfaces 39a and 39b.

  In this example, since the pair of stopper portions 37c and 37d are provided in a part of the housing 9a, the guide member 21a that does not include the stopper portion is used. Specifically, the guide member 21a includes only a partially cylindrical bottom plate portion 35 and a pair of side plate portions 36a and 36b extending from both ends of the bottom plate portion 35 in the X direction.

  Further, in this example, the respective front end surfaces of the pair of side plate portions 36a and 36b are brought into contact with one side surface (the lower side surface of FIG. 7) of the pair of stopper portions 37c and 37d, thereby the circumference of the guide member 21a. Positioning with respect to the direction is intended. That is, the guide surfaces 38a, 38b of the pair of side plate portions 36a, 36b in a state where the respective tip surfaces of the pair of side plate portions 36a, 36b are abutted against one side surface of the pair of stopper portions 37c, 37d. Are arranged in parallel with the X direction. In addition, such a configuration prevents the guide member 21a from rotating inside the worm shaft housing portion 26. About another structure and an effect, it is the same as the 1st example of embodiment.

  The structures of the examples of the embodiments can be combined as appropriate as long as no contradiction occurs. In each example of the embodiment, the structure in which two stopper portions that limit the movement of the second bearing in the direction away from the worm wheel are described as an example, but only one stopper portion can be provided. Two or more can be provided.

DESCRIPTION OF SYMBOLS 1 Steering wheel 2 Steering shaft 3 Steering column 4a, 4b Universal joint 5 Intermediate shaft 6 Steering gear unit 7 Tie rod 8 Electric assist device 9, 9a Housing 10 Torsion bar 11 Output shaft 12a, 12b Rolling bearing 13 Pinion shaft 14 Torque sensor 15 Electric Motor 16 Worm reducer 17 Worm shaft 18 Worm wheel 19 First bearing 20 Second bearing 21, 21a Guide member 22 Energizing member 23 First support shaft portion 24 Second support shaft portion 25 Warm tooth portion 26 Worm shaft housing portion 27 Worm wheel tooth part 28 Worm wheel accommodating part 29 Inner ring 30 Outer ring 31 Ball 32 Inner ring 33 Outer ring 34 Ball 35 Bottom plate part 36a, 36b Side plate part 37a, 37b, 37c, 37d Stopper Portion 38a, 38b Guide surface 39a, 39b, 39c, 39d Stopper surface 40 Energizing member body 41 Pressing member 42 Leaf spring 43 Energizing member accommodating portion 44 Lid member 45 Convex cylindrical surface 46 Cylindrical portion 47 Semi-cylindrical portion 48 Mounting portion 49 Mounting surface 50 Mounting pin 51 Gap 52a, 52b Elastic plate

Claims (7)

A worm reducer comprising a housing, a worm shaft, a worm wheel, a first bearing, a second bearing, a biasing member, and a pair of guide surfaces,
The worm shaft is disposed inside the housing, and is connected to the motor output shaft of the electric motor at one end in the axial direction so that the worm shaft can swing.
The worm wheel is disposed inside the housing and meshes with the worm shaft;
The first bearing supports an axial one side portion of the worm shaft so as to be rotatable with respect to the housing,
The second bearing is rotatably supported on the other axial side of the worm shaft,
The biasing member biases the other axial side portion of the worm shaft in a direction approaching the worm wheel via the second bearing, and is directed substantially parallel to the central axis of the worm wheel. A biasing member main body having a central axis and disposed inside the housing so as to be movable in the axial direction, a pressing member pressing the biasing member main body in the axial direction, and a center of the biasing member main body A plate which is supported by the biasing member main body and is partly brought into contact with the outer peripheral surface of the second bearing, being inclined in a direction approaching the worm shaft toward the rear side in the pressing direction by the pressing member with respect to the shaft. And a spring,
The pair of guide surfaces are disposed on both outer sides of the second bearing with respect to the axial direction of the worm wheel, and guide the distance movement of the second bearing with respect to the worm wheel,
And,
A stopper that prevents the second bearing from moving further in the direction away from the worm wheel by contacting the second bearing when the worm shaft is displaced by a predetermined amount in the direction away from the worm wheel. Comprising a part,
Worm reducer.   The worm speed reducer according to claim 1, wherein each of the pair of guide surfaces is provided on a guide member fitted inside the housing.   The worm speed reducer according to claim 2, wherein the stopper portion is provided on the guide member.   The worm speed reducer according to claim 1, wherein the stopper portion is provided in the housing.   The worm speed reducer according to claim 4, wherein the stopper portion has a positioning function in a circumferential direction of the guide member.   The worm speed reducer according to any one of claims 1 to 5, wherein a portion of the stopper portion that contacts the outer peripheral surface of the second bearing is made of an elastic material.   The worm speed reducer according to any one of claims 1 to 6, wherein the stopper portion is provided on both outer sides of the second bearing with respect to the axial direction of the worm wheel.

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