JP6907858B2 - Warm reducer - Google Patents

Description

The present invention relates to, for example, a worm reducer used by being incorporated in an electric power steering device.

FIG. 15 shows an example of a conventional structure of a steering device for an automobile. The rotation of the steering wheel 1 is transmitted to the input shaft 3 of the steering gear unit 2, and the pair of left and right tie rods 4 are pushed and pulled along with the rotation of the input shaft 3 to give a steering angle to the front wheels. The steering wheel 1 is supported and fixed to the rear end portion of the steering shaft 5, and the steering shaft 5 is rotatably supported by the steering column 6 in a state of being inserted into the cylindrical steering column 6 in the axial direction. There is. The front end of the steering shaft 5 is connected to the rear end of the intermediate shaft 8 via a universal joint 7, and the front end of the intermediate shaft 8 is connected to the input shaft 3 via another universal joint 9. ..

In the illustrated example, an electric power steering device is incorporated to reduce the force required to operate the steering wheel 1 using the electric motor 10 as an auxiliary power source. A speed reducer is incorporated in the electric power steering device, and as this speed reducer, a worm speed reducer having a large lead angle and having reversibility with respect to the power transmission direction is generally used. FIG. 16 shows an example of a conventional structure of a worm reducer described in Japanese Patent No. 4381024. The worm reducer 11 includes a housing 12, a worm wheel 13, and a worm 14.

The housing 12 is supported and fixed to the electric motor 10, is present at a twisted position with respect to the wheel accommodating portion 15 and the wheel accommodating portion 15, and the axial intermediate portion is opened in the wheel accommodating portion 15. It has a worm accommodating portion 16. The worm wheel 13 has wheel teeth 48 on the outer peripheral surface and is rotatably supported inside the wheel accommodating portion 15. The steering shaft is located near the front end of the driven shaft 5 (see FIG. 15). It is supported and fixed coaxially with 5.

The worm 14 has worm teeth 17 that mesh with the wheel teeth 48 on the outer peripheral surface of the intermediate portion in the axial direction. The worm 14 is rotatably supported inside the worm accommodating portion 16 by a pair of rolling bearings 18a and 18b such as deep groove ball bearings at two positions in the axial direction sandwiching the worm teeth 17. Of the pair of rolling bearings 18a and 18b, the outer ring of the rolling bearing 18a on the tip side of the worm 14 is press-fitted into the holder 19 which is tightly fitted inside the portion near the inner end of the worm accommodating portion 16. .. Further, the inner ring of the rolling bearing 18a on the tip end side of the worm 14 is externally fitted to the large diameter portion 20 provided at the portion near the tip end of the worm 14 and separated from the worm teeth 17 via an elastic bush 21. Has been done. On the other hand, the outer ring of the rolling bearing 18b on the base end side of the worm 14 is press-fitted into the opening of the worm accommodating portion 16, and the inner ring of the rolling bearing 18b on the base end side of the worm 14 is on the base end of the worm 14. It is fitted on the outside with a gap fit. The output shaft of the electric motor 10 which is a drive shaft of the worm 14 is connected to a base end portion (left end portion in FIG. 16). That is, the worm 14 can be rotationally driven by the electric motor 10.

In the conventional worm reducer 11, there is an unavoidable backlash in the meshing portion between the wheel teeth 48 and the worm teeth 17 based on the dimensional error and the assembly error of the members constituting the worm reducer 11. Based on the presence of this backlash, when the rotation direction of the steering shaft 5 is changed, a jarring rattling noise may be generated at the meshing portion. On the other hand, in the illustrated example, a minute gap is provided between the inner peripheral surface of the inner ring of the rolling bearing 18b on the proximal end side and the outer peripheral surface of the proximal end portion of the worm 14, and the proximal end portion of the worm 14 is a worm. A slight swing displacement is supported with respect to the accommodating portion 16. A minute gap is provided between the outer peripheral surface of the large diameter portion 20 provided near the tip of the worm 14 and the inner peripheral surface of the bush 21. A synthetic resin preload pad 22 is tightly fitted to the tip of the worm 14, and a torsion coil spring 23 is provided between the preload pad 22 and the holder 19. The torsion coil spring 23 causes the tip of the worm 14 to be orthogonal to the central axis of the worm wheel 13 and the central axis of the worm 14 (vertical direction in FIG. 16) via the preload pad 22 on the worm wheel 13 side. It is elastically pressed toward (upper side of FIG. 16). As a result, backlash between the wheel teeth 48 and the worm teeth 17 is suppressed, and the generation of rattling noise is suppressed.

Further, in the conventional worm reducer 11, it is known that the rolling bearing 18a on the tip side is directly press-fitted into the tip-side portion of the worm 14. In this case, the rolling bearing 18a on the tip side is premised on a structure that is not separated from the worm 14, but it may be necessary to separate the rolling bearing 18a from the worm 14.

Japanese Patent No. 4381024

In view of the above circumstances, it is an object of the present invention to realize a structure in which a bearing fitted on the tip of the worm can be easily separated from the worm.

The worm reducer of the present invention includes a housing, a worm wheel, a worm, a bearing, an inner diameter side holder, an outer diameter side holder, and an elastic urging member in the circumferential direction.
The housing has a holding recess on the inner peripheral surface.
The worm wheel has wheel teeth on the outer peripheral surface.
The worm has worm teeth on the outer peripheral surface that mesh with the wheel teeth.
The bearing is fitted onto the tip of the worm.
The inner diameter side holder has a bearing holding portion for internally fitting and holding the bearing.
The outer diameter side holder has a holder holding portion and is internally fitted and held in the holding recess. The holder holding portion internally fits and holds the inner diameter side holder so that it can be relatively rotationally moved and is displaced in a direction orthogonal to the central axis of the worm wheel and the central axis of the worm.
The circumferential elastic urging member is configured to elastically urge the inner diameter side holder with respect to the outer diameter side holder in a direction in which the holder is rotated in the circumferential direction.
Further, the outer peripheral surface of the inner diameter side holder and the inner peripheral surface of the outer diameter side holder are such that when the inner diameter side holder rotates in the circumferential direction with respect to the outer diameter side holder, the bearing is mounted on the worm wheel. It is formed so as to be displaced in a direction orthogonal to the central axis of the worm and the central axis of the worm.
In particular, in the worm reducer of the present invention, the inner peripheral surface of the bearing holding portion is cut so as to open from the axial end surface of the inner diameter side holder and have an axial length at least longer than the axial length of the bearing. Notches are provided.

The bearing includes, for example, an outer ring having an outer ring track on the inner peripheral surface, an inner ring having an inner ring track on the outer peripheral surface, and a rolling element rotatably arranged between the outer ring track and the inner ring track. Rolling bearings with and can be used. When a rolling bearing is used as the bearing, more specifically, a radial ball bearing, a radial roller bearing, a radial tapered roller bearing, or the like can be used. Alternatively, a plain bearing may be used as the bearing.

When the present invention is carried out, for example, a plurality of notches are provided in the circumferential direction on the inner peripheral surface of the bearing holding portion.

Further, when the present invention is carried out, for example, the outer peripheral surface of the inner diameter side holder meshes with the wheel teeth and the worm teeth in a direction orthogonal to the central axis of the worm wheel and the central axis of the worm. A portion located on the side far from the portion, and having first and second inner diameter side curved portions on both sides in the circumferential direction with respect to the central axis of the worm wheel and the surface passing through the central axis of the worm, respectively.
The outer diameter side holder is provided on a portion of the inner peripheral surface of the holder holding portion that faces the first and second inner diameter side curved surfaces, and the inner diameter side holder is peripheral to the holder holding portion. It has first and second outer diameter side curved surfaces that come into contact with the first and second inner diameter side curved surfaces when rotated in a direction.
The notch is provided between the first and second inner diameter side curved surfaces in the circumferential direction.

In the case of carrying out the present invention, for example, the outer diameter side holder is provided in a state of being bent inward in the radial direction from the axially other side edge of the holder holding portion. The bearing and the side plate portion of the outer diameter side holder are arranged apart from each other in the axial direction.

In addition, in the specification, "inner fitting holding" includes a case where a part in the circumferential direction is held inward with a portion in contact with each other and a gap is formed in another part in the circumferential direction.

In the worm reducer of the present invention as described above, the inner peripheral surface of the bearing holding portion is opened from the axial end surface of the inner diameter side holder and has an axial length longer than the axial length of the bearing. A notch to have is provided. As a result, a part of the bearing pulling device can be inserted into the notch to pull out the bearing from the worm, and a structure in which the bearing externally fitted to the tip of the worm can be easily separated from the worm can be realized.

FIG. 1 is a partially cut perspective view showing a worm reducer according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the worm reducer of the present embodiment. FIG. 3 is a perspective view showing the housing taken out. FIG. 4 (A) is a perspective view showing an outer diameter side holder to which a leaf spring and a torsion coil spring are attached in the worm reducer of the present embodiment, and FIG. 4 (B) is a perspective view showing FIG. 4 (A). Is a perspective view of the outer diameter side holder viewed from the opposite side in the axial direction. FIG. 5 is an enlarged perspective view of a main part showing a state in which each of the members constituting the worm reducer of the present embodiment is disassembled. FIG. 6 is a perspective view showing the inner diameter side holder together with the bearing. 7 (A) and 7 (B) are cross-sectional views for explaining the contact position between the outer peripheral surface of the inner diameter side holder and the inner peripheral surface of the outer diameter side holder. FIG. 8A is a schematic cross-sectional view for explaining the direction of the meshing reaction force applied to the worm from the worm wheel when the electric motor is rotationally driven in a predetermined direction, and FIG. 8B is a diagram. 8 (A) is a sectional view taken along line VIII-VIII. 9 (A) is a schematic cross-sectional view for explaining the direction of the meshing reaction force applied to the worm from the worm wheel when the electric motor is rotationally driven in a direction opposite to a predetermined direction, and FIG. 9 (B) is a schematic cross-sectional view. Is a cross-sectional view taken along the line IX-IX of FIG. 9A. FIG. 10 is a diagram corresponding to FIG. 9B, which shows the direction of the meshing reaction force in two directions applied from the worm wheel to the worm when the electric motor is rotationally driven in both directions. FIG. 11 is an end view of the worm reducer showing a state in which a pin is inserted into the groove of the inner diameter side holder and the groove of the outer diameter side holder. FIG. 12 is a diagram for explaining a process of pulling out the bearing from the worm reducer. FIG. 13 is a diagram for explaining a process of pulling out the bearing from the worm reducer. FIG. 14 is a cross-sectional view showing a state in which the bearing extraction device is mounted on the bearing of the worm reducer. FIG. 15 is a partially cut side view showing an example of a steering device having a conventional structure. FIG. 16 is an enlarged cross-sectional view of XVI-XVI of FIG.

Hereinafter, the worm reducer according to the embodiment of the present invention will be described with reference to FIGS. 1 to 14. The worm reducer of the present embodiment includes a housing 12a, a worm wheel 13, and a worm 14 in the same manner as the worm reducer 11 having the conventional structure shown in FIG. The housing 12a has a wheel accommodating portion 15 and a worm accommodating portion 16a that exists at a twisted position with respect to the wheel accommodating portion 15 and has an axial intermediate portion opened in the wheel accommodating portion 15. An annular holding recess 24 is provided on the inner peripheral surface of one end (left end in FIGS. 1 and 2) of the worm accommodating portion 16a in the axial direction. The worm reducer of the present embodiment describes a case where the worm teeth 17 of the worm 14 are twisted to the right.

The worm wheel 13 has wheel teeth 48 on the outer peripheral surface and is rotatably supported inside the wheel accommodating portion 15. The steering shaft is located near the front end of the driven shaft 5 (see FIG. 15). It is supported and fixed coaxially with 5. As the worm wheel 13, for example, a wheel tooth 48 made of synthetic resin is bonded and fixed around a disk-shaped member made of a metal material. Alternatively, the entire worm wheel 13 may be made of a metal material or a synthetic resin.

The worm 14 is made of a metal material, and in a state where the worm teeth 17 provided in the intermediate portion in the axial direction are meshed with the wheel teeth 48, the base end portion is connected to the output shaft of the electric motor 10 so as to be able to transmit torque. Has been done. The worm 14 is rotatably supported by the worm accommodating portion 16a of the housing 12a so as to be swing-displaced around the base end portion. For this purpose, a pair of rolling bearings 18b and 18c are externally fitted at two positions on both sides of the worm 14 in the axial direction with the worm teeth 17 sandwiched between them. The pair of rolling bearings 18b and 18c are each composed of a single row deep groove type radial ball bearing, a radial roller bearing, a radial tapered roller bearing and the like.

A specific structure for supporting the worm 14 on the worm accommodating portion 16a rotatably and capable of swinging displacement centered on the proximal end portion will be described with reference to FIG. 16 relating to the prior art. A bearing fitting portion 49 is provided in the opening of the worm accommodating portion 16a, and one end portion in the axial direction (right end portion in FIG. 16) of the bearing fitting portion 49 is a step portion 50 on the housing side facing the other in the axial direction. Is provided. One side surface of the outer ring 51 constituting the rolling bearing 18b on the base end side in the axial direction is abutted against the step portion 50 on the housing side, and the outer peripheral surface of the outer ring 51 is internally fitted into the bearing fitting portion 49 by tightening. There is. On the other side surface in the axial direction of the outer ring 51 (the left side surface in FIG. 16), a retaining ring 52 is locked to a portion of the opening of the worm accommodating portion 16a adjacent to the other side in the axial direction of the bearing fitting portion 49. One side surface in the axial direction is abutted, thereby regulating the axial displacement of the outer ring 51. A small diameter portion 53 is provided at the base end portion of the worm 14, and a worm side step portion 54 facing the other in the axial direction is provided at one end portion in the axial direction of the small diameter portion 53. One side surface of the inner ring 57 constituting the rolling bearing 18b on the base end side is abutted against the worm side step portion 54 via an elastic body 55 such as a disc spring, and the inner peripheral surface of the inner ring 57 has a small diameter portion. It is externally fitted to 53 with a gap fit. The tip surface (one side surface in the axial direction) of the nut 56 screwed into the other end portion in the axial direction of the small diameter portion 53 is abutted on the other side surface in the axial direction of the inner ring 57 via the elastic body 55. In other words, the inner ring 57 is elastically sandwiched between the worm-side step portion 54 and the nut 56 via a pair of elastic bodies 55 in a state where the inner ring 57 is fitted to the small diameter portion 53 by a gap fit. There is. As a result, the base end portion of the worm 14 is supported by the opening of the worm accommodating portion 16a via the rolling bearing 18b on the base end side.

However, the structure for supporting the worm 14 to the worm accommodating portion 16a so as to be able to swing displacement about the base end portion is not limited to the structure of the present embodiment. That is, for example, by increasing the internal gap of the rolling bearing 18b on the proximal end side, the worm 14 can be configured to be able to swing and displace around the proximal end portion. Alternatively, a bearing is not provided around the base end portion of the worm 14, and the output shaft of the electric motor 10 and the base end portion of the worm 14 are connected via a joint provided with an elastic member that can be elastically deformed in the radial direction. Is also good.

The tip end portion (left end portion in FIG. 2) of the worm 14 is supported in the holding recess 24 of the worm accommodating portion 16a by a rolling bearing 18c on the tip side so as to be able to rotate and slightly move in perspective with respect to the worm wheel 13. Specifically, the inner ring constituting the rolling bearing 18c on the tip side is externally fitted and fixed to the tip end portion of the worm 14. However, it is also possible to adopt a configuration in which the inner ring of the rolling bearing 18c on the tip side is loosely fitted to the tip portion of the worm 14 so as not to rattle in the radial direction. On the other hand, between the outer ring of the rolling bearing 18c on the tip side and the holding recess 24 of the worm accommodating portion 16a, an inner diameter side holder 25, an outer diameter side holder 26, and a leaf spring 27 which is a member for imparting elasticity in the radial direction And a torsion coil spring 28 which is an elastic urging member in the circumferential direction are provided. Further, the axial one-sided opening of the holding recess 24 is closed by a disk-shaped cover 68 after assembly.

The holding recess 24 is composed of a large diameter portion 58 on one side in the axial direction (left side in FIGS. 1 and 2) and a small diameter portion 59 on the other side in the axial direction (right side in FIGS. 1 and 2).

The inner diameter side holder 25 is made of a synthetic resin such as PPS (polyphenylene sulfide), PA (polyamide), POM (polyacetal), or a light alloy such as an aluminum alloy or a magnesium alloy, and is formed in a substantially cylindrical shape as a whole. Has been done. The inner diameter side holder 25 includes a cylindrical holder main body 29, and a bearing holding portion 30 for inner fitting and holding the outer ring constituting the rolling bearing 18c on the tip side is provided on the inner peripheral surface of the holder main body 29. There is. The inner diameter of the bearing holding portion 30 is slightly smaller than the outer diameter of the outer ring of the rolling bearing 18c on the tip side, and the outer ring of the rolling bearing 18c on the tip side is tightly fitted to the bearing holding portion 30. There is. However, the inner diameter of the bearing holding portion 30 is the same as or slightly larger than the outer diameter of the outer ring of the rolling bearing 18c on the tip side, so that the outer ring of the rolling bearing 18c on the tip side is radially larger than the bearing holding portion 30. It can also be configured to hold the inner fitting loosely so as not to rattle.

Of the outer peripheral surface of the holder body 29, with respect to the first direction D1 (vertical direction in FIG. 7) orthogonal to the central axis of the worm wheel 13 and the central axis of the worm 14, from the meshing portion between the worm tooth 17 and the wheel tooth 48. The first and second parts are located on the distant side (upper part in FIG. 7) and on both sides in the circumferential direction with respect to _{the central axis of the worm wheel 13 and the surface P passing through the central axis O 14 of the worm 14.} The inner diameter side curved portions 31 and 80 are provided, respectively. The first and second inner diameter side curved surfaces 31 and 80 are formed as a composite curved surface in which a plurality of curved surfaces having different radii of curvature are smoothly continuous.

Further, as shown in FIGS. 5 and 6, the inner diameter side holder 25 has an outer peripheral surface adjacent to the other side in the circumferential direction (the meshing portion side between the worm tooth 17 and the wheel tooth 48) of the first inner diameter side curved surface portion 31. A locking step portion 86a is formed in the portion of. When the inner diameter side holder 25 is held by the outer diameter side holder 26, the locking step portion 86a crosses the slit 85a (see FIG. 4) described later formed in the outer diameter side holder 26 when viewed from the axial direction. It is formed.
Further, the inner diameter side holder 25 is formed with two axial slits 87 extending in the axial direction from one end surface in the axial direction over the entire radial direction. As a result, the stress when the bearing 18c is press-fitted into the inner diameter side holder 25 can be relaxed.

Further, on the inner peripheral surface of the bearing holding portion 30 of the inner diameter side holder 25 of the present embodiment, the rolling bearing 18c on the tip side, which will be described later, is separated from the worm 14, so that the axial end surface of the inner diameter side holder 25 (FIG. 14). A pair of notches 82, 82 that open from the right end surface) and have an axial length that is at least longer than the axial length of the rolling bearing 18c are provided. In the present embodiment, the pair of notches 82 are provided so as to penetrate the inner peripheral surface of the bearing holding portion 30 in the axial direction. Further, the pair of notches 82 are provided at positions facing each other in the circumferential direction in the same phase as the axial slits 87. Therefore, the notches 82 also press-fit the bearing 18c into the inner diameter side holder 25. The stress at the time is relaxed.

The outer diameter side holder 26 is made of a synthetic resin such as PPS (polyphenylene sulfide), PA (polyamide), POM (polyacetal), or a light alloy such as an aluminum alloy or a magnesium alloy, and has a substantially cylindrical outer diameter. A side cylinder portion 34, a side plate portion 35, and an inner diameter side cylinder portion 36 are provided. The outer diameter side cylinder portion 34 has a substantially cylindrical shape, and a holder holding portion 38 is provided on the inner diameter side. The holder holding portion 38 is for holding the inner diameter side holder 25 so as to be able to swing around the central axis of the worm 14 and to be displaced in the first direction D1. A first outer diameter side curved surface portion 39 is provided on a portion of the inner peripheral surface of the holder holding portion 38 facing the first inner diameter side curved surface portion 31, and the portion facing the second inner diameter side curved surface portion 80. A second outer diameter side curved surface portion 81 is provided in the portion to be used. In the present embodiment, the first outer diameter side curved surface portion 39 and the second outer diameter side curved surface portion 81 are composed of a single partial cylindrical surface.
That is, in the present embodiment, the first inner diameter side curved surface portion 31 and the second inner diameter side curved surface portion 80 are composed of a composite curved surface in which a plurality of curved surfaces having different radii of curvature are smoothly continuous. The outer diameter side curved surface portion 39 and the second outer diameter side curved surface portion 81 are formed of a single partial cylindrical surface.
The outer diameter side holder 26 may be made of the same material as the inner diameter side holder 25, or may be made of different materials.

Therefore, in the present embodiment, as shown in FIG. 7, contact portions (sliding contact portions) between the inner peripheral surface of the holder holding portion 38 and the outer peripheral surface of the inner diameter side holder 25 are provided at two locations.
Further, these two contact portions are from the meshing portion when the worm wheel 13 rotates in both directions in the inferior angle region X formed by the two lines connected to _{the central axis O 14 of the worm 14.} direction of the reaction force _{f r1, f r2} meshing applied to the worm 14 is provided so as to be located.
This region X is located on the side far from the meshing portion between the worm tooth 17 and the wheel tooth 48 with respect to the first direction D1.
The meshing reaction forces _fr1 and _fr2 are forces generated at the tip of the worm 14 based on the meshing reaction force acting on the meshing portion between the worm tooth 17 and the wheel tooth 48, which will be described later.

Incidentally, the abutting portions of the two places, as shown in FIG. 7 (A) and FIG. 7 (B), the irrespective of the circumferential position of the inner diameter side holder 25 with respect to the outer diameter side holder 26, meshing reaction force f _r1 , F _r2 are formed so as to satisfy the relationship with the direction.

In the present embodiment, the meshing imaginary straight line beta ₁ which is perpendicular to the direction of the reaction force f _r1, f _r2, and beta _2, the contact portion between the outer peripheral surface of the inner diameter side holder 25, the inner circumferential surface of the holder holding portion 38 The distance between the tangents γ ₁ and γ ₂ becomes wider toward the meshing portion side of the worm tooth 17 and the wheel tooth 48. That is, when the worm wheel 13 is rotated in one _{direction, the contact portion between the virtual straight line β 1} orthogonal to the direction of the _{meshing reaction force fr1} applied to the tip portion of the worm 14 and the first inner diameter side curved surface portion 31. The distance between the first outer diameter side curved surface portion 39 and the tangent line γ ₁ is widened toward the other in the circumferential direction (lower left in FIG. 7). On the other hand, when the worm wheel 13 is rotated in the other direction, the holder is held at the contact portion between the _{virtual straight line β 2} orthogonal to the direction of the _{meshing reaction force fr2 applied to the tip of the worm 14 and the inner diameter side holder 25.} The distance between the inner peripheral surface of the portion 38 and the tangent line γ ₂ becomes wider toward one side in the circumferential direction (lower right in FIG. 7). Specifically, the virtual straight line beta _1, and beta _2, tangent gamma _1, the angle theta ₁ formed by the gamma _2, theta ₂ is, so that the order of 5 ° to 30 °, the inner diameter side holder 25 and the outer diameter side The shape of the holder 26 is regulated.

Further, FIG. 7 shows a state in which the inner diameter side holder 25 rotates in the circumferential direction and the other (counterclockwise direction shown in FIG. 7) in the order of (A) → (B). In this way, even when the inner diameter side holder 25 is rotated in the other direction in the circumferential direction, the contact portion between the first inner diameter side curved surface portion 31 and the first outer diameter side curved surface portion 39, and the second The phases of the other contact portions between the inner diameter side curved surface portion 80 and the second outer diameter side curved surface portion 81 are hardly changed. In this case, the inner diameter side holder 25 and the rolling bearing 18c held by the inner diameter side holder 25 do not substantially move in the left-right direction of FIG. 7, and the worm wheel 13 is located downward, that is, with respect to the first direction D1. Displace only towards the side. Therefore, such a displacement is caused by the above-mentioned first inner diameter side curved surface portion 31, the first outer diameter side curved surface portion 39, the second inner diameter side curved surface portion 80, and the second outer diameter side curved surface portion 81. Given by shape.

Further, if such a displacement is given, the first inner diameter side curved surface portion 31, the first outer diameter side curved surface portion 39, the second inner diameter side curved surface portion 80, and the second outer diameter are provided. The shape of the side curved surface portion 81 is not limited. For example, the first inner diameter side curved surface portion 31 and the second inner diameter side curved surface portion 80 are single partial cylindrical surfaces, and the first outer diameter side curved surface portion 39 and the second outer diameter side curved surface portion 81 are the radius of curvature. It can also be configured by a composite curved surface in which a plurality of curved surfaces different from each other are smoothly continuous. Alternatively, the first inner diameter side curved surface portion 31, the first outer diameter side curved surface portion 39, the second inner diameter side curved surface portion 80, and the second outer diameter side curved surface portion 81 are all formed of a composite curved surface. May be good.

Further, on the outer peripheral surface of the outer diameter side tubular portion 34, in the first direction, the axial direction of the end portion (upper end portion in FIGS. 1 and 4) on the side far from the meshing portion between the worm tooth 17 and the wheel tooth 48 and the like. A flat surface portion 61 orthogonal to the first direction is provided on the half portion. Further, on the outer peripheral surface of the outer diameter side tubular portion 34, the holding pin portion 62 having a semicircular shape when viewed from the axial direction is formed on the axial half portion of the end portion far from the meshing portion in the first direction. The base end (one half in the axial direction) is supported. A slit 63 is provided between the flat surface portion 61 and the inner surface of the tip portion (other half portion in the axial direction) of the holding pin portion 62. In other words, the flat surface portion 61 and the inner surface of the tip end portion of the holding pin portion 62 face each other with a minute gap in the radial direction. However, the installation positions of the flat surface portion 61 and the holding pin portion 62 are set on the outer peripheral surface of the outer diameter side cylinder portion 34 from the end portion on the outer peripheral surface of the outer diameter side cylinder portion 34 on the side far from the meshing portion between the worm tooth 17 and the wheel tooth 48 in the first direction. It can be a portion slightly deviated in the circumferential direction. In any case, on the outer peripheral surface of the outer diameter side cylinder portion 34, the outer diameter of the portion deviated from the flat surface portion 61 in the circumferential direction changes in the axial direction. No, it has a single cylindrical surface.

The side plate portion 35 has a substantially circular ring plate shape, and is provided in a state of being bent inward in the radial direction from the other side edge in the axial direction of the outer diameter side cylinder portion 34. The side plate portion 35 is provided with a slit 85a that penetrates in the axial direction and extends along a substantially circumferential direction so that one arm portion 47a of the torsion coil spring 28 described later is inserted.

The inner diameter side tubular portion 36 has a substantially cylindrical shape, and is provided in a state of being bent from the inner peripheral edge of the side plate portion 35 to the other side in the axial direction. A pair of eaves 65, 65 is provided at the other end edge of the inner diameter side cylinder portion 36 in the axial direction so as to bend outward in the radial direction from two positions on the opposite side with respect to the first direction. The outer diameter of the pair of eaves 65, 65 is smaller than the inner diameter of the small diameter portion 59 of the holding recess 24.

The outer diameter side holder 26 is located at a position different in the circumferential direction from the pair of eaves 65, 65 provided on the other end edge of the inner diameter side cylinder portion 36 in the axial direction, and is substantially opposite to the slit 85a in the radial direction. A locking notch 71a having an axially recessed edge at the other end in the axial direction is provided at such a position.

The outer diameter side holder 26 can be displaced in the holding recess 24 of the worm accommodating portion 16a in the first direction and in the second direction parallel to the central axis of the worm wheel 13 and orthogonal to the central axis of the worm 14. In addition, it is fitted in a state in which rotation with respect to the worm accommodating portion 16a is substantially blocked. That is, between the outer peripheral surface of the outer diameter side tubular portion 34 and the inner peripheral surface of the large diameter portion 58, both side portions in the second direction and the end portions on the side far from the meshing portion in the first direction are formed. With a gap provided, the outer diameter side cylinder portion 34 is internally fitted into the large diameter portion 58, and the inner diameter side cylinder portion 36a is internally fitted into the small diameter portion 59 by gap fitting. An engaging recess 45 recessed outward in the radial direction is provided at one position in the circumferential direction of the large diameter portion 58, and the engaging recess 45 and the holding pin portion 62 of the outer diameter side holder 26 are loosened. By engaging, the rotation of the outer diameter side holder 26 with respect to the worm accommodating portion 16a is substantially prevented.

The leaf spring 27 is made of an elastic metal plate and includes a flat plate-shaped base portion 66 and a pair of partially cylindrical arm portions 67, 67 extending in the circumferential direction from both side edges of the base portion 66. The axial length of the base 66 is shorter than the axial length of the pair of arms 67, 67. In other words, as shown in FIG. 4, a notch 69 having an opening on one side edge in the axial direction is provided at the central portion in the circumferential direction of the leaf spring 27. The leaf spring 27 is supported by the outer diameter side holder 26 by inserting the base portion 66 into the slit 63 of the outer diameter side holder 26. Further, inward pieces 92 bent from one end in the axial direction to the inner diameter side are provided at both ends of the pair of arm portions 67, 67 in the circumferential direction, and the leaf spring 27 is provided with respect to the outer diameter side holder 26. When supported, the inward-facing piece 92 faces the side plate portion 35 and is positioned in the axial direction.

The curvature of the pair of arm portions 67, 67 is smaller than the curvature of the inner peripheral surface of the large diameter portion 58 of the holding recess 24. Therefore, when the outer diameter side holder 26 is fitted in the holding recess 24, both ends of the pair of arm portions 67, 67 constituting the leaf spring 27 in the circumferential direction are on the inner peripheral surface of the large diameter portion 58. It is pressed elastically. Therefore, when the tip of the worm 14 is displaced in the direction away from the worm wheel 13 in the first direction based on the meshing reaction force applied to the worm 14 from the meshing portion between the wheel teeth 48 and the worm teeth 17, the leaf spring 27 As a result, a force (elasticity) that elastically presses the tip of the worm 14 toward the worm wheel 13 in the first direction D1, that is, the perspective direction with respect to the worm wheel 13, is applied to the tip of the worm 14. Granted. The spring constant of the leaf spring 27 is set sufficiently small.

In a state where the meshing portion does not apply a reaction force to the worm 14, the outer peripheral surface of the outer diameter side cylinder portion 34 of the outer diameter side holder 26 and the inner peripheral surface of the large diameter portion 58 of the holding recess 24 are formed. The dimensions of each of the constituent members are adjusted so that they abut at the portions (lower ends of FIGS. 1 and 2) whose phases in the circumferential direction coincide with the meshing portions.

In the present embodiment, the torsion coil spring 28 is installed on the portion on the worm wheel 13 side (the portion on the other side in the axial direction; the right portion in FIGS. 1 and 2) of the axially both side portions of the rolling bearing 18c on the tip side. ing. The torsion coil spring 28 is formed by bending and molding a metal wire, and includes a coil portion 46 and a pair of arm portions 47a and 47b. The inner diameter side cylinder portion 36 of the outer diameter side holder 26 is inserted through the coil portion 46. The inner diameter of the coil portion 46 in the free state in which the torsion coil spring 28 is not exerting elasticity is smaller than the outer diameter of the pair of eaves 65, 65, and the torsion coil spring 28 has the inner diameter side cylinder portion 36a. It is prevented from getting out of. One of the pair of arm portions 47a and 47b, one arm portion 47a, is provided in a state of extending outward in the radial direction and then extending in the axial direction, penetrates the slit 85a of the outer diameter side holder 26, and extends on the inner diameter side. It is pressed against the locking step portion 86a of the holder 25. The other arm portion 47b is provided so as to extend inward in the radial direction, and is locked to the locking notch portion 71a. When the locking step portion 86a is elastically pressed toward the other in the circumferential direction by one arm portion 47a, the inner diameter side holder 25 is elastic in the direction of rotating in the circumferential direction with respect to the outer diameter side holder 26. Be urged to. The elastic force in the direction of rotating the inner diameter side holder 25 with respect to the outer diameter side holder 26 in the circumferential direction is the first and second inner diameter side curved portions 31, 80 of the inner diameter side holder 25, and the outer diameter side holder 26. By engaging with the first and second outer diameter side curved portions 39, 81, the inner diameter side holder 25 and the tip portion of the worm 14 are elastically directed toward the worm wheel 13 side in the radial direction. It is converted into a pressing force.

In the present embodiment, the worm teeth 17 are twisted to the right, the torsion coil springs 28 are right-handed, and the inner diameter side holder 25 is rotated in the counterclockwise direction of FIG. It has become. However, the twisting direction of the worm tooth 17, the winding direction of the torsion coil spring 28, and the rotation direction of the inner diameter side holder 25 can be designed by combining arbitrary directions.

In the present embodiment, the elasticity of the torsion coil spring 28 is adjusted so that the engagement resistance at the engagement portion between the worm tooth 17 and the wheel tooth 48 does not become excessively large, and the elasticity of the torsion coil spring 28 is adjusted. Based on the above, the force that elastically presses the tip of the worm 14 toward the worm wheel 13 in the first direction D1 is sufficiently reduced.

In the worm reducer of the present embodiment, on the outer peripheral surface of the inner diameter side holder 25, a portion located on the outer peripheral surface of the inner diameter side holder 25 on the side far from the meshing portion between the worm tooth 17 and the wheel tooth 48 with respect to the first direction D1, and the worm wheel The outer diameter side holder 26 has first and second inner diameter side curved surface portions 31 and 80 on both sides in the circumferential direction with respect to the surface passing through the central axis and the central axis of the worm 14, and the outer diameter side holder 26 is the inner circumference of the holder holding portion 38. The first and second inner diameter side holders 25 are provided on the surfaces facing the first and second inner diameter side curved surface portions 31 and 80, and when the inner diameter side holder 25 rotates in the circumferential direction with respect to the holder holding portion 38, the first and second inner diameter side holders 25 It has first and second outer diameter side curved portions 39, 81 that come into contact with the inner diameter side curved portions 31, 80 of the above. As a result, the torsion coil spring 28 elastically urges the inner diameter side holder 25 against the outer diameter side holder 26 in the direction of rotating in the circumferential direction, and the inner diameter side holder 25, and thus the worm 14. The tip of the wheel can be converted into a force elastically urging toward the worm wheel 13 side in the first direction D1. Therefore, backlash at the meshing portion between the worm teeth 17 and the wheel teeth 48 is suppressed, and dimensional errors and assembly errors of the members constituting the worm reducer, and wear of the tooth surfaces of the wheel teeth 48 and the worm teeth 17 are suppressed. Regardless of the above, the variation in the meshing position between the worm tooth 17 and the wheel tooth 48 can be suppressed. That is, if a dimensional error or an assembly error occurs in each of the members constituting the worm reducer, or if the tooth surfaces of the wheel teeth 48 and the worm teeth 17 are worn, the inner diameter side holder is based on the elasticity of the torsion coil spring 28. 25 is displaced in the first direction D1 to correct the deviation of the meshing position between the wheel teeth 48 and the worm teeth 17. Therefore, in the worm reducer of the present embodiment, such dimensional errors and assembly errors can be effectively absorbed without particularly increasing the dimensional accuracy and assembly accuracy of the members constituting the worm reducer. The variation in the meshing position between the worm tooth 17 and the wheel tooth 48 is suppressed, and even when the tooth surface of the wheel tooth 48 is worn, the variation in the meshing position is prevented. As a result, the generation of rattling noise at the meshing portion between the worm tooth 17 and the wheel tooth 48 is more effectively prevented.

Further, in the worm reducer of the present embodiment, between the outer peripheral surface of the outer diameter side holder 26 and the inner peripheral surface of the holding recess 24, both side portions in the second direction D2 and the worm in the first direction D1 are wormed. A gap for allowing the outer diameter side holder 26 to be displaced based on the meshing reaction force applied to the worm 14 when the worm reducer is operated, at the end of the tooth 17 and the wheel tooth 48 on the side far from the meshing portion. Is provided. Therefore, when a reaction force is applied to the worm 14 from the meshing portion between the worm tooth 17 and the wheel tooth 48 during operation of the worm reducer, the end of the gap on the side far from the meshing portion in the first direction Based on the presence of a gap in the located portion, the tip of the worm 14 is displaced in the direction away from the worm wheel 13 with respect to the first direction D1 while elastically crushing the leaf spring 27. As a result, the meshed state of the wheel teeth 48 and the worm teeth 17 is properly maintained. Further, in the present embodiment, the leaf spring 27 is supported in the slit 63 of the outer diameter side holder 26. Therefore, when the operation of the worm reducer is stopped and the reaction force is not applied to the worm 14 from the meshing portion, the leaf spring 27 presses the worm 14 toward the worm wheel 13 in the first direction D1, and the worm 14 is pressed. Returns to its original position. That is, the outer peripheral surface of the outer diameter side holder 26 and the inner peripheral surface of the holding recess 24 come into contact with each other at a portion where the phase in the circumferential direction coincides with the meshing portion between the worm tooth 17 and the wheel tooth 48. Therefore, the gap in the portion of the gap located at the end on the side far from the meshing portion in the first direction D1 can be maintained for a long period of time.

The amount by which the tip of the worm 14 can be displaced in the first direction D1 is the amount of the gap between the outer peripheral surface of the outer diameter side holder 26 and the inner peripheral surface of the holding recess 24 in the first direction D1. It depends on the radial dimension of the gap in the portion located at the end on the side far from the meshing portion between the worm tooth 17 and the wheel tooth 48. This radial dimension management (adjustment) can be achieved by adjusting the assembling position of the outer diameter side holder 26 with respect to the holding recess 24. Therefore, it is possible to relatively easily secure an amount in which the tip portion of the worm 14 can be displaced in the first direction D1, and it is possible to suppress an increase in the manufacturing cost of the worm reducer.

In the present embodiment, since the spring constant of the leaf spring 27 is sufficiently small, the rotation speed of the worm wheel 13 and the worm 14, the magnitude of the torque transmitted by the meshing portion between the worm tooth 17 and the wheel tooth 48, and the inside of the housing 12a. The change in the meshing resistance at the meshing portion can be reduced regardless of the change in the distance between the central axes of the worm wheel 13 and the worm 14 due to the temperature change.

In the present embodiment, the meshing imaginary straight line beta ₁ which is perpendicular to the direction of the reaction force f _r1, f _r2, and beta _2, the contact portion between the outer peripheral surface of the inner diameter side holder 25, the inner circumferential surface of the holder holding portion 38 The distance between the tangents γ ₁ and γ ₂ becomes wider toward the meshing portion side between the worm tooth 17 and the wheel tooth 48. Therefore, of the forces that the tip of the worm 14 is elastically pressed toward the worm wheel 13 side in the first direction D1, the force based on the elasticity of the torsion coil spring 28 becomes the elasticity of the leaf spring 27. Although it is smaller than the base force, the meshing reaction forces _fr1 and _fr2 prevent the inner diameter side holder 25 from being rotated in the circumferential direction with respect to the outer diameter side holder 26. In short, the _{change in the meshing distance based on the meshing reaction forces fr1} and _fr2 can be absorbed only by the elastic deformation of the leaf spring 27, and the torsion coil spring 28 can be prevented from elastically deforming by this distance change.

In the present embodiment, the first and second inner diameter side curved surfaces 31 and 80 are provided on the outer peripheral surface of the inner diameter side holder 25, and the first and second outer diameter sides are provided on the inner peripheral surface of the holder holding portion 38. Curved surface portions 39 and 81 are provided. In particular, in the worm reducer of the present embodiment, the contact portion (sliding contact) between the inner peripheral surface of the holder holding portion 38 and the outer peripheral surface of the inner diameter side holder 25 is connected to _{the central axis O 14 of the worm 14.} in the region X of minor angle formed by two lines, the direction of the reaction force f _r1, f _r2 meshing applied to the worm 14 is provided so as to be located. By doing so, when the meshing reaction forces _fr1 and _fr2 are input, the reaction force can always be received at the two contact portions. Assuming that there is a reaction force f _r1, f _r2 meshing outside the region X, it will receive a reaction force in the only abutment one position, abutment of the other would be separated from each other.

Therefore, regardless of the direction of rotation of the worm 14, the meshing reaction force _{f r1, f r2,} and reliably transmitted to the outer diameter side holder 26, a reaction force _{f r1, f r2} meshing, radially outer holder 26 and the plate It can be supported more effectively by the housing 12a via the spring 27. The meshing reaction force applied to the worm 14 from the meshing portion between the worm tooth 17 and the wheel tooth 48 includes not only the component in the first direction D1 orthogonal to the central axis of the worm wheel 13 and the central axis of the worm 14, but also the component in the first direction D1. A component in the second direction D2 orthogonal to the first direction D1 is also included. This point will be described below with reference to FIGS. 12 to 14.

The worm teeth 17 of the worm 14 are spirally formed on the outer peripheral surface of the axially intermediate portion of the worm 14. Therefore, when the worm 14 is rotationally driven and the driving force is transmitted from the worm 14 to the worm wheel 13, the components in the three directions of x, y, and z in FIGS. 8 and 9 are transmitted from the worm wheel 13 to the worm 14. The meshing reaction force including is applied. In the case shown in FIG. 8 and the case shown in FIG. 9, the magnitude of the driving force applied to the worm 14 is the same, but the acting direction of the driving force, that is, the rotation direction of the worm 14 is opposite to each other. ing. Therefore, the worm wheel 13 rotates in opposite directions in the case shown in FIG. 8 and the case shown in FIG. When the worm 14 is rotationally driven, the components in the three directions of x, y, and z in FIGS. 8 and 9 are formed in the meshing portion between the wheel teeth 48 and the worm teeth 17 with respect to the worm 14 from the worm wheel 13. An apparent meshing reaction force having a component force of F _x , F _y , and F _{z is applied.} Of the component forces F _x , F _y , and F _z , F _x and F _z are the case where the worm wheel 13 rotates in one direction (the direction indicated by the arrow A in FIG. 8 (A)) as shown in FIG. , As shown in FIG. 9, the worm wheel 13 rotates in the other direction (the direction indicated by the arrow B in FIG. 9A), and the directions are opposite to each other.

On the other hand, when the distance between the meshing portion between the worm tooth 17 and the wheel tooth 48 and the swing center o of the worm 14 with respect to the radial direction of the worm 14 is d ₁₄ , the size is _{d 14} · F _x. The moment M acts on the worm 14. Therefore, the distance between the engagement portion and the pivot center o the axial direction of the worm 14 in the case of the L _14, the magnitude of the force F _r of the M / L ₁₄ based on the moment M, radially of the worm 14 ( It acts in the upward direction of FIG. 8 and the downward direction of FIG. The acting direction of this force F _r is opposite to each other in the case shown in FIG. 8 and the case shown in FIG. _{Therefore, the magnitude of the actual force F y} ′ in the y direction in consideration of the moment M acting on the worm 14 from the worm wheel 13 at the meshing portion between the worm tooth 17 and the wheel tooth 48 is as shown in FIG. , When the worm wheel 13 rotates in one direction, F _y ´ = F _y −F _r and becomes smaller. As shown in FIG. 9, when the worm wheel 13 rotates in the other direction, F _y ´ = F _y + F _r and becomes large. Therefore, the resultant force F'of the actual meshing component force acting on the meshing portion in the y and z directions becomes smaller as shown by the arrow C in FIG. 10 when the worm wheel 13 rotates in one direction, and the worm When the wheel 13 rotates in the other direction, it becomes larger as shown by an arrow D in FIG. As can be seen from the direction of the resultant force F', regardless of the direction in which the worm wheel 13 rotates, the meshing reaction force applied to the worm 14 from the meshing portion has a first direction D1 (FIGS. 8 and 9). (Vertical direction) and the second direction D2 (front and back directions of FIGS. 8 (A) and 9 (A), left and right directions of FIGS. 8 (B), 9 (B) and 10) are included. You can see that there is.

Meshing reaction force described above f _r1, f _r2, these arrows C, based on the meshing reaction force F'in meshing portion between the worm teeth 17 and the wheel teeth 48 shown by D, and generating the tip of the worm 14 It is power.

When the worm wheel 13 rotates in one direction, the component force in the virtual plane orthogonal to the central axis of the worm 14 among the meshing reaction forces applied to the worm 14 from the meshing portion is, for example, the second direction D2. On the other hand, it acts in the counterclockwise direction of FIG. 7 in the direction of 90 ° to 135 ° (in the example of FIG. 7, about 135 °). On the other hand, when the worm wheel 13 rotates in the other direction, the component force in the virtual plane orthogonal to the central axis of the worm 14 among the meshing reaction forces applied to the worm 14 from the meshing portion is, for example, a second. It acts in a direction of 0 ° to 45 ° (about 15 ° in the example of FIG. 7) in the counterclockwise direction of FIG. 7 with respect to the direction D2.

In the present embodiment, the first inner diameter side curved surface portion 31 abuts on the first outer diameter side curved surface portion 39, and the second inner diameter side curved surface portion 80 abuts on the second outer diameter side curved surface portion 81. ing. Therefore, regardless of the rotation direction of the worm 14, the meshing reaction force applied to the worm 14 from the meshing portion is surely transmitted to the outer diameter side holder 26, and this meshing reaction force can be more effectively supported by the housing 12a.

Further, in the worm reducer of the present embodiment, a portion of the outer peripheral surface of the outer diameter side holder 26 whose phase in the circumferential direction coincides with the meshing portion in a state where the meshing reaction force is not applied from the meshing portion to the worm 14. The leaf spring 27 is in contact with the inner peripheral surface of the holding recess 24, and the leaf spring 27 is sandwiched between the holding recess 24 and the outer peripheral surface of the outer diameter side holder 26. Therefore, when the rotation direction of the output shaft of the electric motor 10 changes, the displacement of the tip end portion of the worm 14 in the second direction D2 is suppressed to be smaller than that of the structure shown in FIG. , The generation of rattling noise at the meshing portion can be suppressed more reliably.

Further, in the present embodiment, the torsion coil spring 28 is installed on the portion on the worm wheel 13 side (the portion on the other side in the axial direction) of the portions on both sides in the axial direction of the rolling bearing 18c on the tip side. Therefore, the dimension of the worm accommodating portion 16a of the housing 12a in the axial direction can be suppressed to a small size, and the worm reducer can be easily reduced in size and weight.
Further, since the inner diameter side holder 25, the outer diameter side holder 26, the leaf spring 27, and the torsion coil spring 28 can be combined into a non-separable sub-assembly unit, the assembly work of the worm reducer can be facilitated.

When assembling the worm reducer of the present embodiment, first, the base end portion of the worm 14 can be rotated and slightly swung by the rolling bearing 18b on the base end side in the worm accommodating portion 16a of the housing 12a. Support. Next, the inner diameter side holder 25 is internally fitted and held in the outer diameter side holder 26, the coil portion 46 of the torsion coil spring 28 is inserted into the inner diameter side cylinder portion 36 of the outer diameter side holder 26, and a pair of arm portions. 47a and 47b are pressed against the locking step portion 86a of the inner diameter side holder 25 and the locking notch portion 71a of the outer diameter side holder 26. Then, the base 66 of the leaf spring 27 is inserted into the slit 63 of the outer diameter side holder 26, and the leaf spring 27 is supported by the outer diameter side holder 26. In this way, in a state where the inner diameter side holder 25, the outer diameter side holder 26, the leaf spring 27, and the torsion coil spring 28 are non-separably combined into a sub-assembly unit, the sub-assembly unit is combined with the holding recess 24. Assemble between the rolling bearing 18c on the tip side. In this case, the outer ring of the rolling bearing 18c on the tip side is press-fitted into the bearing holding portion 30 of the inner diameter side holder 25. Then, by elastically restoring the leaf spring 27, the outer diameter side holder 26 is internally fitted and held in the holding recess 24 so as to be displaced in the first direction D1.

Here, pins are inserted into the inner peripheral surface of the outer diameter side holder 26 and the outer peripheral surface of the inner diameter side holder 25 at positions facing each other on the worm wheel 13 side of _{the central axis O 14 of the worm 14 in the first direction.} Grooves 88a and 88b are formed. As a result, the inner diameter side holder 25 and the outer diameter side holder 26 are phase-determined by inserting the pin 89 into the pin insertion grooves 88a and 88b. Therefore, the inner diameter side holder 25 and the outer diameter side are formed by two contact portions between the inner peripheral surface of the outer diameter side holder 26 and the outer peripheral surface of the inner diameter side holder 25 and the portion into which the pin 89 is inserted. The holder 26 is temporarily positioned in the vertical direction and phased in the rotational direction. In this state, the bearing 18c, the inner diameter side holder 25, and the outer diameter side holder 26 can be easily attached to the housing, and the worm 14 can be easily assembled. When the pin 89 is pulled out from the pin insertion grooves 88a and 88b after the worm 14 is assembled, the inner diameter side holder 25 rotates to urge the worm 14.

In the present embodiment, the inner peripheral surface of the outer diameter side holder 26 and the outer peripheral surface of the inner diameter side holder 25 are set as pins 89 as a positioning member for relatively positioning the outer diameter side holder 26 and the inner diameter side holder 25. Is provided with pin insertion grooves 88a and 88b, but the positioning member is not limited to the pin, and the engaging portion into which the positioning member can be inserted is not limited to this. For example, engaging protrusions may be formed on the inner peripheral surface of the outer diameter side holder 26 and the outer peripheral surface of the inner diameter side holder 25 as a portion into which the positioning member can be inserted.
Further, in the present embodiment, the outer diameter side holder 26 and the inner diameter side holder 25 are provided with pin insertion grooves 88a and 88b as positioning means for relatively positioning the outer diameter side holder 26 and the inner diameter side holder 25. Although provided, the present invention is not limited to this, and may be a convex portion.

The method of assembling the worm reducer of the present embodiment is not limited to the above method. For example, after the rolling bearing 18c on the tip side is press-fitted into the bearing holding portion 30 of the inner diameter side holder 25, the outer diameter side holder 26 can be inserted into the outer diameter side of the inner diameter side holder 25.

On the other hand, in the present embodiment, as shown in FIGS. 12 and 13, the bearing pulling device 100 is used when separating the rolling bearing 18c on the tip side from the portion near the tip of the worm 14. In this case, since the outer ring of the rolling bearing 18c is press-fitted into the bearing holding portion 30 of the inner diameter side holder 25, it is a sub-assembly having the inner diameter side holder 25, the outer diameter side holder 26, the leaf spring 27, and the torsion coil spring 28. The unit is separated from the worm 14 with the separation of the rolling bearing 18c.

The bearing extraction device 100 is fitted and fixed to a screw shaft 101 having a male screw portion 101a on the outer peripheral surface, a small diameter shaft portion 102 having a female screw portion 102a screwed with the male screw portion 101a on the inner peripheral surface, and a small diameter shaft portion 102. It has a large-diameter shaft portion 103 and a large-diameter shaft portion 103. On the outer peripheral surface of the large-diameter shaft portion 103, a pair of extending portions 105 and 106 extending outward in the radial direction are provided at two positions in the circumferential direction that are 180 ° out of phase. The pair of extending portions 105 and 106 are provided with claw portions 107 and 107 extending in the axial direction, respectively, and are provided with holes 105a and 106a into which a jig (not shown) can be inserted. The small diameter shaft portion 102 and the large diameter shaft portion 103 may be integrally formed.

The claws 107 and 107 are formed to have a size that allows them to be inserted into the outer peripheral surfaces of the outer ring of the bearing 18c and the notches 82 and 82 of the inner diameter side holder 25, and these tip portions form the axial end surfaces of the outer ring. It is formed by bending inward in the radial direction so as to support it.

Therefore, as shown in FIG. 14, when the rolling bearing 18c is pulled out from the worm 14, the claws 107, 107 of the bearing pulling device 100 are inserted into the notches 82, 82 of the inner diameter side holder 25, and the shaft of the outer ring is inserted. It is brought into contact with the inner end surface in the direction (the left end surface in FIG. 14). When the screw shaft 101 is rotated in this state, the tip surface of the screw shaft 101 is pressed against the tip surface 14a of the worm 14, and by further rotating the screw shaft 101, the claws 107 and 107 of the rolling bearing 18c By pushing the inner end surface in the axial direction to the outer side in the axial direction (right side in FIG. 14), the rolling bearing 18c can be pulled out from the portion near the tip of the worm 14.

Further, in the present embodiment, the notches 82 and 82 are provided between the first and second inner diameter side curved surface portions 31 and 80 in the circumferential direction, so that the notches 82 and 82 are provided at two locations. it is suppressed affect the reaction force f _r1, f _r2 meshing is input to the abutting portion.

Further, the rolling bearing 18c and the side plate portion 35 of the outer diameter side holder 26 are sandwiched by the inward step portion 32 (see FIG. 2) of the inner diameter side holder 25 having a diameter smaller than the outer peripheral surface of the rolling bearing 18c. , Are arranged apart in the axial direction. Since the notches 82 and 82 cut out the inward step portion 32, the tip portions of the claw portions 107 and 107 bent toward the inner diameter side are rolled, and the axial end surface of the bearing 18c and the side plate portion of the outer diameter side holder 26 are formed. It can be easily inserted between the 35 and the 35.

The number of notches 82, 82 formed in the inner diameter side holder 25 is not limited to the two locations of the present embodiment, and is 3 in the circumferential direction according to the number of claws 107, 107 of the bearing extraction device 100. It may be provided at more than one place.
Further, in the present embodiment, the notches 82 and 82 are formed so as to penetrate the inner diameter side holder 25 in the axial direction, but are opened from the axial end surface (right end surface in FIG. 14) of the inner diameter side holder 25. It suffices as long as it has at least an axial length longer than the axial length of the rolling bearing 18c. That is, the notches 82 and 82 may have an axial length for the tip portions of the claw portions 107 and 107 to be hooked on the axial inner end surface of the rolling bearing 18c to enter.

The present invention is not limited to the above-described embodiment, and can be appropriately modified and improved.
For example, when the worm reducer of the present invention is implemented, the radial elasticity applying force member that imparts elasticity to the outer diameter side holder 26 in the direction toward the worm wheel 13 side with respect to the first direction D1 is a plate. The spring 27 is not limited to the spring 27, and may be, for example, an O ring locked to the outer peripheral surface of the outer diameter side holder. Further, the elastic member provided between the outer diameter side holder 26 and the holding recess 24 can elastically pull the outer diameter side holder 26 toward the worm wheel 13 in the first direction D1. .. Alternatively, the radial elasticity imparting member may be omitted. In this case, based on the meshing reaction force between the worm teeth 17 and the wheel teeth 48, the tip of the worm 14 is displaced in the direction away from the worm wheel 13 with respect to the first direction D1, and then the operation of the worm reducer is stopped. Then, the inner diameter side holder 25 is displaced in the first direction D1 based on the elasticity of the torsion coil spring 28, so that the displacement of the tip portion of the worm 14 is compensated.

Further, the elastic urging member in the circumferential direction that elastically urges the inner diameter side holder 25 with respect to the outer diameter side holder 26 in the direction of rotating toward the other in the circumferential direction is not limited to the above-mentioned torsion coil spring 28. A compression coil spring or a leaf spring made of an elastomer can also be used. Further, the elastic member provided between the inner diameter side holder 25 and the outer diameter side holder 26 may have a structure that elastically pulls the inner diameter side holder 25 in the direction of rotating the inner diameter side holder 25 toward the other in the circumferential direction.

1 Steering wheel 2 Steering gear unit 3 Input shaft 4 Tie rod 5 Steering shaft 6 Steering column 7 Universal joint 8 Intermediate shaft 9 Universal joint 10 Electric motor 11 Warm reducer 12, 12a Housing 13 Warm wheel 14 Warm 15 Wheel housing 16, 16a Worm accommodating part 17 Warm teeth 18a to 18c Rolling bearing 19 Holder 20 Large diameter part 21 Bush 22 Preload pad 23 Torsional coil spring 24 Holding recess 25 Inner diameter side holder 26 Outer diameter side holder 27 Leaf spring 28 Torsional coil spring 29 Holder body 30 Bearing Holding part 31 First inner diameter side curved part 34 Outer diameter side cylinder part 35 Side plate part 36 Inner diameter side cylinder part 38 Holder holding part 39 First outer diameter side curved part 46 Coil part 47a, 47b Arm part 48 Wheel tooth 49 Bearing Fitting part 50 Housing side stepped part 51 Outer ring 52 Stop ring 53 Small diameter part 54 Warm side stepped part 55 Elastic body 56 Nut 57 Inner ring 58 Large diameter part 59 Small diameter part 61 Flat surface part 62 Holding pin part 63 Slit 65 Bearing part 66 Base part 67 Arm 68 Cover 69 Notch 71a Locking notch 80 Second inner diameter side curved part 81 Second outer diameter side curved part 82 Notch

Claims (4)

A housing with a holding recess on the inner peripheral surface,
A worm wheel with wheel teeth on the outer peripheral surface,
A worm having worm teeth that mesh with the wheel teeth on the outer peripheral surface,
A bearing fitted to the tip of the worm and
An inner diameter side holder having a bearing holding portion for internally fitting and holding the bearing,
The holding recess has a holder holding portion that allows the inner diameter side holder to be relatively rotatable and internally fitted and held to be displaced in a direction orthogonal to the central axis of the worm wheel and the central axis of the worm. The outer diameter side holder that is internally fitted and held in
An elastic urging member in the circumferential direction that elastically urges the inner diameter side holder in a direction that rotates the outer diameter side holder in the circumferential direction.
With
The outer peripheral surface of the inner diameter side holder and the inner peripheral surface of the outer diameter side holder are such that when the inner diameter side holder rotates in the circumferential direction with respect to the outer diameter side holder, the bearing is centered on the worm wheel. In a worm reducer, which is formed so as to be displaced in a direction orthogonal to the shaft and the central axis of the worm.
A worm reducer having an inner peripheral surface of the bearing holding portion provided with a notch that opens from the axial end surface of the inner diameter side holder and has an axial length that is at least longer than the axial length of the bearing. The worm reducer according to claim 1, wherein a plurality of notches are provided in the circumferential direction on the inner peripheral surface of the bearing holding portion. The outer peripheral surface of the inner diameter side holder is a portion located on the side distant from the meshing portion between the wheel teeth and the worm teeth in a direction orthogonal to the central axis of the worm wheel and the central axis of the worm, and said. It has first and second inner diameter side curved portions on both sides in the circumferential direction with respect to the central axis of the worm wheel and the surface passing through the central axis of the worm.
The outer diameter side holder is provided on a portion of the inner peripheral surface of the holder holding portion that faces the first and second inner diameter side curved surfaces, and the inner diameter side holder is peripheral to the holder holding portion. It has first and second outer diameter side curved surfaces that come into contact with the first and second inner diameter side curved surfaces when rotated in a direction.
The worm reducer according to claim 1 or 2, wherein the notch is provided between the first and second inner diameter side curved surfaces in the circumferential direction. The outer diameter side holder includes a substantially circular ring plate-shaped side plate portion provided in a state of being bent inward in the radial direction from the other side edge in the axial direction of the holder holding portion.
The worm reducer according to any one of claims 1 to 3, wherein the bearing and the side plate portion of the outer diameter side holder are arranged apart from each other in the axial direction.

Images