JP2022092094A - Worm reduction gear - Google Patents

Abstract

To provide a worm reduction gear in which an outer ring constituting a rolling bearing can be effectively prevent from being displaced relative to a gear housing made of synthetic resin.SOLUTION: A worm reduction gear comprises: a gear housing 21; and a rolling bearing 19 that has an outer ring 35 serving as a stationary ring supported by the gear housing 21 and is used for rotatably supporting a worm wheel relative to the gear housing 21. The outer ring 35 has, in an outer periphery thereof, an outer ring recessed portion 44 serving as an outer ring engaging portion. The gear housing 21 is an injection molded product of synthetic resin and having the outer ring 35 as an insert component and has a housing projection 47 serving as a housing engagement portion that is engaged with the outer ring recessed portion 44 in such a manner that the gear housing 21 and the outer ring 35 are prevented from being displaced relative to each other in an axial direction and a circumferential direction of the outer ring 35.SELECTED DRAWING: Figure 4

Description

The present invention relates to a worm reducer.

In an automobile steering device, when the steering wheel is rotated by the driver's operation, the rotation of the steering wheel is transmitted to the pinion shaft of the steering gear unit via the steering shaft and the intermediate shaft, and the rotation of the rack shaft of the steering gear unit is transmitted. Converted to linear motion. As a result, the pair of tie rods is pushed and pulled, and the pair of steering wheels are given a steering angle according to the amount of operation of the steering wheel.

Further, in recent years, an electric power steering device that uses an electric motor as an auxiliary power source to reduce the force required for the driver to operate the steering wheel has become widespread. The electric power steering device includes a worm reducer that can obtain a large reduction ratio as a reducer for increasing the torque of the electric motor.

The worm reducer is a worm wheel that is rotatably supported by the gear housing and has wheel teeth on the outer peripheral surface, and worm teeth that are rotatably supported by the gear housing and mesh with the wheel teeth on the outer peripheral surface. With a worm that has. The torque of the electric motor is increased by being transmitted to the worm wheel via the worm, and then is applied as auxiliary power to the steering force transmission member such as the steering shaft, the pinion shaft, or the rack shaft. This reduces the force required for the driver to operate the steering wheel.

Further, as described in Japanese Patent Application Laid-Open No. 2016-117426 (Patent Document 1) and the like, the worm wheel constituting the worm reducer is rotatable with respect to the gear housing by using a rolling bearing. Is supported by. Such rolling bearings have a large axial load, specifically, an axial load based on the gear reaction force acting on the worm wheel, an axial load input from the steering wheel side at the time of a secondary collision, and a wheel. Axial load input from the wheel side is applied when the wheel rides on a rim stone. Therefore, a retaining ring (snap ring) is used to prevent the rolling bearing from being displaced in the axial direction with respect to the gear housing. Specifically, the outer peripheral edge of the retaining ring is locked to the locking groove provided on the inner peripheral surface of the gear housing. Then, the outer ring constituting the rolling bearing internally fitted to the inner peripheral surface of the gear housing is provided on the inner peripheral surface of the gear housing and the portion of the retaining ring that protrudes radially inward from the locking groove. By sandwiching the rolling bearing in the axial direction, the rolling bearing is prevented from being displaced in the axial direction.

Japanese Unexamined Patent Publication No. 2016-117426

In recent years, there has been an increasing demand for low fuel consumption of automobiles, and further weight reduction of automobile components is being promoted. In view of such circumstances, it is considered that the gear housing constituting the worm reducer is made of synthetic resin instead of metal such as iron alloy or aluminum alloy.

However, when the gear housing is made of synthetic resin, creep deformation may occur in the locking groove due to the axial load and radial outward load (reaction force) applied to the locking groove from the metal retaining ring. be. For this reason, rattling may occur between the locking groove and the retaining ring, and it may not be possible to sufficiently prevent the axial displacement of the rolling bearing.

It is an object of the present invention to provide a worm reducer capable of effectively preventing the outer ring constituting the rolling bearing from being displaced with respect to the gear housing made of synthetic resin.

The worm reducer of one aspect of the present invention has a gear housing and an outer ring which is a stationary wheel supported by the gear housing, and is used to rotatably support the worm wheel with respect to the gear housing. It is equipped with a rolling bearing.
The outer ring has an outer ring engaging portion on the outer peripheral surface.
The gear housing is an injection-molded product made of a synthetic resin having the outer ring as an insert component, and the outer ring is prevented from being displaced relative to each other with respect to the axial direction and the circumferential direction of the outer ring. It has a housing engaging portion that engages with the engaging portion.

In the worm reducer of one aspect of the present invention, the outer ring engaging portion is composed of an outer ring recess that is recessed inward in the radial direction and extends in the circumferential direction.
The bottom of the outer ring recess is composed of a knurled portion having an uneven shape in the circumferential direction.
The housing engaging portion is composed of a housing convex portion that has entered the inside of the outer ring concave portion, the housing convex portion is unevenly engaged with the outer ring concave portion, and the radial tip portion of the housing convex portion is formed. It is unevenly engaged with the knurled portion.

In the worm reducer of one aspect of the present invention, the outer ring has a deep groove type outer ring track on the inner peripheral surface.
The entire outer ring recess is arranged at a position displaced in the axial direction with respect to the axial center portion of the outer ring track.

In the worm reducer according to one aspect of the present invention, the portion of the outer ring recess located radially outside the knurled portion is formed by an inclined recess having a shape in which the axial width decreases toward the radial inside. It is configured.

In the worm reducer of one aspect of the present invention, the outer ring engaging portion is composed of an outer ring convex portion that protrudes outward in the radial direction and extends in the circumferential direction.
The radial tip portion of the outer ring convex portion is composed of a knurled portion having an uneven shape in the circumferential direction.
The housing engaging portion is composed of a housing concave portion in which the outer ring convex portion is inserted into the inside thereof, the housing concave portion is unevenly engaged with the outer ring convex portion, and the bottom portion of the housing concave portion is the knurled portion. It is unevenly engaged with the part.

In the worm reducer according to one aspect of the present invention, the portion of the outer ring convex portion located radially inside the knurled portion has an inclined convex shape in which the axial width decreases toward the radial outer side. It is composed of parts.

In the worm reducer of one aspect of the present invention, the outer ring engaging portion is provided over the entire circumference of the outer peripheral surface of the outer ring.

In the worm reducer of one aspect of the present invention, the outer ring engaging portion is not connected over the entire circumference of the outer peripheral surface of the outer ring, and the circumferential side surface of the outer ring engaging portion and the circumferential direction of the housing engaging portion. The sides are engaged. In this case, in the worm reducer according to one aspect of the present invention, the outer ring engaging portions are provided at a plurality of locations separated in the circumferential direction of the outer peripheral surface of the outer ring.

In the worm reducer of one aspect of the present invention, the gear housing has a holding surface that contacts at least one of the side surfaces of the outer ring on both sides in the axial direction.

The worm reducer of one aspect of the present invention is incorporated in an electric power steering device.

According to one aspect of the present invention, it is possible to provide a worm reducer that can effectively prevent the outer ring constituting the rolling bearing from being displaced in both the axial direction and the circumferential direction with respect to the gear housing made of synthetic resin.

FIG. 1 is a partially cut side view of an electric power steering device according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of the electric assist device of the first example of the embodiment of the present invention cut along a virtual plane including the central axis of the output shaft and parallel to the paper surface of FIG. FIG. 3 is a perspective view of a gear housing and a rolling bearing according to an embodiment of the present invention. FIG. 4 is an enlarged view of part A of FIG. FIG. 5 is a view of the outer ring of the rolling bearing shown in FIG. 4 as viewed from the outside in the radial direction. FIG. 6 is a diagram schematically showing a process of manufacturing a gear housing constituting the worm reducer of the first example of the embodiment of the present invention by injection molding. FIG. 7 is a diagram corresponding to FIG. 3, showing a second example of the embodiment of the present invention. FIG. 8 is a diagram corresponding to FIG. 3, showing a modified example of the second example of the embodiment of the present invention. FIG. 9 is a diagram corresponding to FIG. 3, showing a third example of the embodiment of the present invention. FIG. 10 is a diagram corresponding to FIG. 4, showing a fourth example of the embodiment of the present invention. FIG. 11 is a diagram corresponding to FIG. 3, showing a fifth example of the embodiment of the present invention. FIG. 12 is a diagram corresponding to FIG. 3, showing a modified example of the fifth example of the embodiment of the present invention.

[First example of the embodiment]
A first example of the embodiment of the present invention will be described with reference to FIGS. 1 to 6.

This example is an example in which the worm reducer of the present invention is incorporated into an electric power steering device of an automobile. In the following description of the electric power steering device, the front-rear direction refers to the front-rear direction of the automobile.

The electric power steering device 1 of this example is a column assist type electric power steering device, and includes a steering wheel 2, a steering shaft 3, a steering column 4, a pair of universal joints 5a and 5b, and an intermediate shaft 6. A steering gear unit 7, a pair of tie rods 8, and an electric assist device 9 are provided.

The steering wheel 2 is fixed to the rear end of the steering shaft 3 rotatably supported inside the steering column 4. The front end of the steering shaft 3 is inserted inside the housing case 10 fixed to the front end of the steering column 4, and is connected to the output shaft 12 via the torsion bar 11.

The rotation of the output shaft 12 is transmitted to the pinion shaft 13 of the steering gear unit 7 via a pair of universal joints 5a and 5b and an intermediate shaft 6. Then, by converting the rotation of the pinion shaft 13 into a linear motion of a rack axis (not shown), the pair of tie rods 8 is pushed and pulled, and the steering wheel is given a steering angle.

The electric assist device 9 is a device that generates an auxiliary torque for reducing the force required for the driver to operate the steering wheel 2, and includes a torque sensor 14, an ECU (not shown), an electric motor 15, and worm deceleration. It is equipped with a machine 16.

The torque sensor 14 is arranged around the output shaft 12 and detects the twisting direction and the twisting amount of the torsion bar 11. The ECU determines the auxiliary torque based on the information on the steering torque calculated based on the twist direction and the twist amount of the torsion bar 11 detected by the torque sensor 14, and the information on the vehicle speed measured by the vehicle speed sensor (not shown). do. The electric motor 15 is fixed to the housing case 10, and the energization direction and energization amount are controlled by the ECU. The worm reducer 16 increases the torque of the electric motor 15 and transmits it to the output shaft 12. As a result, since the auxiliary torque is applied to the output shaft 12, it becomes possible to push and pull the pair of tie rods 8 with a force larger than the force applied to the steering wheel 2 by the driver.

Hereinafter, a specific configuration of the worm reducer 16 will be described.

As shown in FIG. 2, the worm reducer 16 includes a gear housing 21 and a rolling bearing 19. The rolling bearing 19 has an outer ring 35 which is a stationary wheel supported by the gear housing 21, and is used to rotatably support the worm wheel 18 with respect to the gear housing 21.

In this example, such a worm reducer 16 includes a housing case 10, a worm (not shown), a worm wheel 18, an output shaft 12, and a pair of rolling bearings 19 and 20.

The housing case 10 includes a plurality of gear housings 21 arranged on the front side, a cover housing 22 arranged on the rear side, and an intermediate plate 23 arranged between the gear housing 21 and the cover housing 22 in the front-rear direction. It is connected in the front-rear direction by the bolts 24 of the book (two in the illustrated example).

The gear housing 21 is an injection-molded product made of synthetic resin. Such a gear housing 21 includes a worm wheel accommodating portion 25, a worm accommodating portion 26, and a pivot portion 27.

The worm wheel accommodating portion 25 has a substantially cylindrical tubular portion 28 arranged coaxially with the output shaft 12, and a substantially hollow circular plate shape bent inward in the radial direction from the front end portion of the tubular portion 28. The side plate portion 29 is provided with a substantially cylindrical support tubular portion 30 connected to the radially inner end portion of the side plate portion 29 and arranged coaxially with the tubular portion 28. Further, the worm wheel accommodating portion 25 includes a coupling flange 31 projecting outward in the radial direction from two locations on the opposite side in the radial direction of the rear end portion of the tubular portion 28. Each of the coupling flanges 31 has a screw hole 32 for screwing the bolt 24. Further, the worm wheel accommodating portion 25 is provided with reinforcing ribs 64 spanning the rear side surface of the side plate portion 29 and the outer peripheral surface of the support cylinder portion 30 at a plurality of locations in the circumferential direction. As shown in FIGS. 2 and 3, each of the ribs 64 has a triangular plate shape in which the radial height from the outer peripheral surface of the support cylinder portion 30 gradually increases toward the front side in the axial direction.

The worm accommodating portion 26 is configured to have a substantially cylindrical shape as a whole, and is connected to a part of the outer peripheral edge portion of the worm wheel accommodating portion 25 in the circumferential direction. The inner space of the worm accommodating portion 26 communicates with the inner space of the worm wheel accommodating portion 25. The central axis of the worm accommodating portion 26 is in a twisted position with respect to the central axis of the worm wheel accommodating portion 25.

The pivot portion 27 is a portion that cantilevers and supports the housing case 10 with respect to the vehicle body so as to be able to swing displacement around the pivot axis arranged in the width direction of the vehicle body. The base end portion of the pivot portion 27 is connected to a part of the outer peripheral edge portion of the worm wheel accommodating portion 25 in the circumferential direction, and extends toward the front side.

In the structure of this example, a thermoplastic resin material can be preferably used as the synthetic resin constituting the gear housing 21.

In this case, examples of the thermoplastic resin (base resin) include polyphenylene sulfide resin (PPS), polyamide resin, thermoplastic polyimide, polyetheretherketone (PEEK), and thermoplastic polyester resin (PET, PBT). Can be used. Polyphenylene sulfide resin (PPS) can be preferably used because there is little dimensional change due to water absorption.

Examples of the reinforcing material contained in the base resin include inorganic fibers such as glass fiber, carbon fiber, silicon carbide fiber, alumina fiber, boron fiber, and metal fiber (metal types are stainless steel, iron, and aluminum), and aramid. It can contain organic fibers such as fibers, aromatic polyimide fibers, and liquid crystal polyester fibers. Among these reinforcing materials, glass fiber and carbon fiber can be preferably used because good reinforcing property can be obtained. Specifically, when polyphenylene sulfide resin is used as the base resin, those containing 10% glass fiber (PPS-GF10%), those containing 40% glass fiber (PPS-GF40%), and carbon fiber are used. Those containing 30% (PPS-CF 30%) and the like can be used. The content of the reinforcing material contained in the base resin is preferably regulated to 10% by mass or more and 50% by mass or less. It is also possible to omit (do not include) the reinforcing material.

Each of the cover housing 22 and the intermediate plate 23 is a cast iron-based alloy, a die-cast molded product of a light alloy such as an aluminum alloy, an injection-molded product of a synthetic resin, or the like. When each of the cover housing 22 and the intermediate plate 23 is made of a synthetic resin, the thermoplastic resin material as described above can be preferably used as the synthetic resin. Each of the cover housing 22 and the intermediate plate 23 has holes 33, 34 for inserting bolts 24 at the radially outer ends. In this example, the torque sensor 14 is located around the rear end of the output shaft 12 between the cover housing 22 and the intermediate plate 23 in the axial direction.

The worm is rotatably supported inside the worm accommodating portion 26 by a rolling bearing (not shown). The base end portion of the worm is coupled to the output shaft of the electric motor 15 so as to be able to transmit torque.

The worm wheel 18 is arranged inside the worm wheel accommodating portion 25, and is externally fitted and fixed to the axial intermediate portion of the output shaft 12. Further, in this state, the worm wheel 18 meshes the wheel teeth 17 provided on the outer peripheral surface with the worm teeth provided on the outer peripheral surface of the worm. Therefore, the torque of the electric motor 15 is increased by being transmitted to the worm wheel 18 via the worm, and then is applied to the output shaft 12 as an auxiliary torque.

The output shaft 12 is rotatably supported inside the housing case 10 by a pair of rolling bearings 19 and 20. Specifically, the portion of the output shaft 12 adjacent to the front side of the worm wheel 18 is rotatably supported by the rolling bearing 19 with respect to the support cylinder portion 30 constituting the gear housing 21. Further, the portion of the output shaft 12 adjacent to the rear side of the worm wheel 18 is rotatably supported by the rolling bearing 20 with respect to the radially inner end of the intermediate plate 23.

In this example, the rolling bearing 19 is a deep groove type ball bearing, and as shown in FIG. 4, includes an outer ring 35, an inner ring 36, a plurality of balls 37, and a seal ring 38. In the case of carrying out the present invention, the rolling bearing is not limited to the deep groove type ball bearing, and various rolling bearings can be adopted.

The outer ring 35 is made of a hard metal such as bearing steel to form an annular shape as a whole. The outer ring 35 is provided with a deep groove type outer ring track 39 having an arc-shaped cross-sectional shape in the axial middle portion of the inner peripheral surface over the entire circumference, and seal rings are provided at both ends of the inner peripheral surface in the axial direction. A locking groove 40 capable of locking the radially outer end of the 38 is provided over the entire circumference. The outer ring 35 is supported and fixed in the radial direction of the support cylinder portion 30 constituting the gear housing 21.

The inner ring 36 is made of a hard metal such as bearing steel to form an annular shape as a whole. The inner ring 36 is provided with a deep groove type inner ring track 41 having an arc-shaped cross-sectional shape in the axial middle portion of the outer peripheral surface over the entire circumference, and seal sliding contact grooves are provided at both ends of the outer peripheral surface in the axial direction. 42 is provided all around. The inner ring 36 is tightly fitted to the axially intermediate portion of the output shaft 12, that is, is externally fitted and fixed by press fitting.

The inner ring 36 can also be externally fitted to the axially intermediate portion of the output shaft 12 by gap fitting. In this case, for example, by engaging the inner peripheral edge portion of the retaining ring with respect to the locking groove provided on the outer peripheral surface of the output shaft, the retaining ring is radially outward from the locking groove. The inner ring 36 can be axially sandwiched between the protruding portion and the radially inner end of the worm wheel 18 fitted and fixed to the output shaft. This makes it possible to prevent the inner ring 36 and the output shaft 12 from being displaced relative to each other in the axial direction.

Each of the plurality of balls 37 is made of an iron-based alloy such as bearing steel or ceramics, is arranged between the outer ring track 39 and the inner ring track 41, and is rotatably held by a cage (not shown). Has been done.

The seal ring 38 closes the front end opening of the rolling element installation space 43 existing between the inner peripheral surface of the outer ring 35 and the outer peripheral surface of the inner ring 36. For this purpose, the seal ring 38 has its radially outer end locked in the locking groove 40 on the front side of the outer ring 35, and the tip of the seal lip provided at the radially inner end. Is slidably contacted with the inner surface of the seal sliding contact groove 42 on the front side of the inner ring 36 over the entire circumference.

On the other hand, in the structure of this example, the rear end opening of the rolling element installation space 43 is not closed by the seal ring, and the rolling element installation space 43 and the inner space of the gear housing 21 communicate with each other. In the seal ring 38, the lubricant existing in the rolling element installation space 43 and the inner space of the gear housing 21 leaks to the outside, and foreign matter such as dust from the outside leaks to the inside space of the rolling element installation space 43 and the gear housing 21. It is prevented from invading.

In particular, in the structure of this example, the outer ring 35 has an outer ring engaging portion (44) on the outer peripheral surface. Further, the gear housing 21 is an injection-molded product of synthetic resin having the outer ring 35 as an insert component, and prevents the gear housing 21 and the outer ring 35 from being relatively displaced with respect to the axial direction and the circumferential direction of the outer ring 35. Has a housing engaging portion (47) that engages with the outer ring engaging portion.

In this example, the outer ring engaging portion is composed of an outer ring recess 44 that is recessed inward in the radial direction and extends in the circumferential direction. In this example, the entire outer ring recess 44 is arranged at a position axially deviated from the axial center portion of the outer ring track 39, and more specifically, with respect to the axial center portion of the outer ring track 39. It is placed in a position shifted to the front side. In FIG. 4, the chain line α represents a virtual straight line orthogonal to the central axis of the outer ring 35 and passing through the central portion in the axial direction of the outer ring track 39. In this example, the outer ring recess 44 is provided over the entire circumference of the outer peripheral surface of the outer ring 35. In the case of carrying out the present invention, the entire outer ring recess may be arranged at a position on the outer peripheral surface of the outer ring that is offset rearward with respect to the central portion in the axial direction of the outer ring track. Regarding the axial width and radial depth of the outer ring recess 44, and the axial arrangement location, as long as the axial displacement of the outer ring 35 is prevented by the engagement with the housing convex portion 47 described later. Moreover, as long as the rigidity of the outer ring 35 is ensured, it can be arbitrarily determined. For example, the outer ring recess 44 may have an axial width of 1.12 mm or less and a radial depth of 0.4 mm or more.

The bottom of the outer ring recess 44 is composed of a knurled portion 45 having an uneven shape in the circumferential direction. In this example, the knurled portion 45 has a flatfish structure in which the forming direction of the concave portion and the convex portion is the axial direction, as shown in FIG. However, when the present invention is carried out, the knurled portion may have a twill structure in which the forming directions of the concave portion and the convex portion are inclined and intersect with each other in the axial direction.

In this example, the portion of the outer ring recess 44 located radially outside the knurled portion 45 is composed of an inclined recess 61 having a shape in which the axial width decreases toward the inside in the radial direction. In the illustrated example, each of the side surfaces 46 on both sides of the inclined recess 61 in the axial direction has a shape that approaches the central side in the axial direction of the outer ring recess 44 toward the inner side in the radial direction. More specifically, each of the side surfaces 46 on both sides of the inclined recess 61 in the axial direction has an S-shaped cross-sectional shape. However, each of the side surfaces of the inclined recess on both sides in the axial direction may have a linear cross-sectional shape, that is, may be formed by a conical surface.

In the case of carrying out the present invention, the side surface of the inclined recess on one side in the axial direction is formed of a flat surface orthogonal to the central axis of the outer ring, and the side surface of the inclined recess on the other side in the axial direction has a diameter. It can also be configured by a surface having a shape that approaches the axial center side of the outer ring recess toward the inside in the direction. Further, each of the side surfaces of the inclined recess on both sides in the axial direction may be formed of a flat surface orthogonal to the central axis of the outer ring. Further, when the present invention is carried out, the portion of the outer ring recess located radially outside the knurled portion is composed of an inclined recess having a shape in which the axial width increases toward the inside in the radial direction. You can also do it.

Further, in the structure of this example, the entire bottom portion (knurled portion 45) of the outer ring recess 44 is arranged at a position displaced in the axial direction with respect to the locking groove 40 on the front side of the outer ring 35, and more specifically. Is arranged at a position shifted to the rear side with respect to the locking groove 40.

The outer ring recess 44 has, for example, a step of forming a circumferential groove having a shape in which the bottom portion is formed of a cylindrical surface and the axial width decreases toward the inside in the radial direction by cutting, and the circumferential direction. The knurled portion 45 can be formed at the bottom of the groove separately from the step of forming the knurled portion 45 by the rolling process.

In this example, the housing engaging portion is composed of a housing convex portion 47 that has entered the inside of the outer ring concave portion 44, the housing convex portion 47 is concavely engaged with the outer ring concave portion 44, and the housing convex portion 47 is formed. The radial tip, which is the inner end in the radial direction, is unevenly engaged with the knurled portion 45.

That is, the housing convex portion 47 is composed of a part of the synthetic resin that has entered the inside of the outer ring recess 44 when the gear housing 21 is manufactured by injection molding of the synthetic resin, and the entire inside of the outer ring recess 44 is covered. I'm filling it. Therefore, the housing convex portion 47 has an outer surface (surface) shape that matches the inner surface (surface) shape of the outer ring concave portion 44. Further, such a housing convex portion 47 has a convex portion 48 at the tip end portion in the radial direction, which fills the entire inside of the concave portion constituting the knurled portion 45. With the above configuration, the housing convex portion 47 is unevenly engaged with the outer ring concave portion 44, and the radial tip portion of the housing convex portion 47 is unevenly engaged with the knurled portion 45.

Further, in this example, the gear housing 21 has a holding surface 49 that contacts the front side surface of the outer ring 35. That is, in this example, the gear housing 21 has an inward flange portion 50 projecting inward in the radial direction at the front end portion of the support cylinder portion 30 over the entire circumference. The holding surface 49 constitutes the rear side surface of the inward flange portion 50, and is in contact with the front side surface of the outer ring 35.

In this example, when the gear housing 21 as described above is manufactured by injection molding of a synthetic resin having the outer ring 35 as an insert component, the rolling bearing 19 is assembled in advance. Then, as shown in FIG. 6, the mold element 52a on one side (front side) in the axial direction and the other side in the axial direction (on the other side in the axial direction) with the inner ring 36 of the rolling bearing 19 fitted on the support shaft 51 which is a dummy output shaft. The outer ring 35 of the rolling bearing 19 is set inside the mold 53 formed by combining a plurality of mold elements including the mold element 52b on the rear side). In this state, a molten synthetic resin is injected into the cavity 54 formed between the mold 53 and the outer ring 35 through the nozzle 55, and then the synthetic resin is cooled and solidified in the cavity 54 to cool and solidify the gear. Mold the housing 21. In this example, with the molding of such a gear housing 21, a housing convex portion 47 that engages with the outer ring recess 44 and a holding surface 49 that contacts the front side surface of the outer ring 35 are formed. After molding the gear housing 21, the support shaft 51 is pulled out from the inside of the inner ring 36, and the mold 53 is opened to take out the gear housing 21 integrated with the outer ring 35 from the inside of the mold 53.

According to the structure of this example as described above, it is possible to effectively prevent the outer ring 35 constituting the rolling bearing 19 from being displaced in both the axial direction and the circumferential direction with respect to the gear housing 21 made of synthetic resin.

That is, in the structure of this example, the housing convex portion 47 provided in the gear housing 21 is engaged with the outer ring concave portion 44 extending in the circumferential direction provided on the outer peripheral surface of the outer ring 35. Therefore, a large axial load on the rolling bearing 19, specifically, an axial load based on the gear reaction force acting on the worm wheel 18, and a shaft input from the steering wheel 2 side, that is, the rear side at the time of a secondary collision. Effectively prevents the outer ring 35 from being displaced in the axial direction with respect to the gear housing 21 even when a directional load or an axial load input from the wheel side, that is, the front side is applied when the wheel rides on a rim stone. can.

Further, in the structure of this example, the radial tip portion of the housing convex portion 47 is concavely engaged with the knurled portion 45 having a concave-convex shape in the circumferential direction provided at the bottom of the outer ring concave portion 44. Therefore, it is possible to effectively prevent the outer ring 35 from being displaced in the circumferential direction with respect to the gear housing 21, that is, creep rotation due to the rotational load applied to the rolling bearing 19.

Further, in the structure of this example, the entire outer ring recess 44 provided on the outer peripheral surface of the outer ring 35 is arranged at a position displaced in the axial direction with respect to the central portion in the axial direction of the outer ring track 39. Therefore, the wall thickness in the radial direction of the entire outer ring 35 can be kept small. That is, from the viewpoint of ensuring rigidity, the outer ring 35 of the rolling bearing 19 which is a deep groove ball bearing is the deepest part of the outer ring track 39, and the outer ring which is the portion of the outer ring track 39 where the ball 37 rolls and contacts. At the same axial position as the axial center portion of the track 39, a predetermined or greater radial wall thickness is required. Therefore, when the outer ring recess 44 is arranged at the same axial position as the axial center portion of the outer ring track 39, the radial wall thickness of the entire outer ring is ensured in order to secure the wall thickness at the axial position or more. Needs to be large. On the other hand, in the structure of this example, the entire outer ring recess 44 is arranged at a position displaced in the axial direction with respect to the central portion in the axial direction of the outer ring track 39. Therefore, even when a predetermined or greater radial wall thickness is secured at the same axial position as the axial center portion of the outer ring track 39, the radial wall thickness of the entire outer ring 35 can be kept small.

Further, the axial load input from the wheel side is more frequently applied to the rolling bearing 19 than the axial load input from the steering wheel 2 side due to the secondary collision. In this regard, in the structure of this example, the outer ring recess 44 provided on the outer peripheral surface of the outer ring 35 is arranged at a position shifted forward with respect to the axial center portion of the outer ring track 39. Therefore, it is easy to secure the support rigidity on the front side of the outer ring 35 with respect to the gear housing 21. That is, in the structure of this example, the portion of the gear housing 21 in which the outer ring 35 is fitted is displaced forward from the axial center portion of the outer ring track 39 (that is, the side plate portion 29 and ribs are radially outward. A portion where the radial height of the 64 is large) and a portion shifted to the rear side of the axial center portion of the outer ring track 39 (that is, a portion where the radial height of the rib 64 is small on the radial outer side). It is more rigid than the existing part). Then, in the structure of this example, the outer ring concave portion 44 and the housing convex portion 47 are engaged with each other at such a position in the axial direction where the rigidity of the gear housing 21 is high. Therefore, it is easy to secure the support rigidity on the front side of the outer ring 35 with respect to the gear housing 21.

Further, in the structure of this example, the inclined recess 61 constituting the portion of the outer ring recess 44 located radially outside the knurled portion 45 has a shape in which the axial width decreases toward the inside in the radial direction. .. Therefore, it is easy to perform groove processing for forming the outer ring recess 44. Further, when the gear housing 21 is injection-molded, the molten synthetic resin easily enters the entire inside of the outer ring concave portion 44, and it becomes easy to secure the moldability of the housing convex portion 47.

Further, in the structure of this example, the entire bottom portion (knurled portion 45) of the outer ring recess 44 is arranged at a position displaced in the axial direction with respect to the locking groove 40 on the front side of the outer ring 35. Therefore, it becomes easy to secure the wall thickness at the same axial position as the locking groove 40 on the front side of the outer ring 35.

Further, in the structure of this example, the holding surface 49 provided in the gear housing 21 is in contact with the front side surface of the outer ring 35. Therefore, even when an axial load input from the steering wheel 2 side is applied at the time of a secondary collision, it is possible to more effectively prevent the outer ring 35 from being displaced forward with respect to the gear housing 21 in the axial direction.

Further, in the structure of this example, in order to prevent the outer ring 35 from being displaced in the axial direction with respect to the gear housing 21, a metal retaining ring locked in the locking groove provided in the gear housing 21 is provided. do not use. For this reason, the axial load and the radial outward load (reaction force) applied from the retaining ring to the locking groove cause creep deformation in the locking groove, and rattling occurs between the locking groove and the retaining ring. However, there is no inconvenience that the outer ring 35 cannot be sufficiently prevented from being displaced in the axial direction. In addition, since the retaining ring is not used, the number of parts and the assembly man-hours can be reduced accordingly, and the manufacturing cost can be suppressed.

[Second example of the embodiment]
A second example of the embodiment of the present invention will be described with reference to FIG. 7.

In this example, the outer ring 35a constituting the rolling bearing 19 is not only at a position shifted forward with respect to the axial center portion of the outer ring track 39, but also with respect to the axial center portion of the outer ring track 39. The outer ring recess 44 is also provided at a position shifted to the rear side. A housing protrusion 47 provided on the gear housing 21 is engaged with each of the two outer ring recesses 44. As described above, in the structure of this example, since the outer ring concave portion 44 and the housing convex portion 47 are provided with two engaging portions, the gear housing 21 is compared with the structure of the first example of the embodiment. It is possible to more effectively prevent the outer ring 35a from being displaced in the axial direction and the circumferential direction.

In the structure of this example, the axial width of the outer ring recess 44 on the front side and the axial width of the outer ring recess 44 on the rear side are equal to each other. As in the modified example of the second example of the embodiment, in the outer ring 35b, the axial width of the outer ring concave portion 44 (and the housing convex portion 47) on the front side and the axial direction of the outer ring concave portion 44a (and the housing convex portion 47a) on the rear side. The widths can also be different from each other. In the modified example shown in FIG. 8, the axial width of the outer ring recess 44 on the front side is larger than the axial width of the outer ring recess 44a on the rear side. The axial width of the outer ring recess on the side can also be made larger than the axial width of the outer ring recess on the front side. Further, when the present invention is carried out, the depth of the outer ring recess on the front side and the depth of the outer ring recess on the rear side can be made different from each other.
Other configurations and effects are the same as in the first embodiment.

[Third example of the embodiment]
A third example of the embodiment of the present invention will be described with reference to FIG.

In this example, the gear housing 21 has a holding surface 49a that contacts the rear side surface of the outer ring 35 in addition to the holding surface 49 that contacts the front side surface of the outer ring 35. That is, in this example, the gear housing 21 has an inward flange portion 50a protruding inward in the radial direction at the rear end portion of the support cylinder portion 30 over the entire circumference. The holding surface 49a constitutes the front side surface of the inward flange portion 50a and is in contact with the rear side surface of the outer ring 35. Therefore, in the structure of this example, it is possible to more effectively prevent the outer ring 35 from being displaced rearward with respect to the gear housing 21 even when an axial load input from the wheel side is applied.
Other configurations and effects are the same as in the first embodiment.

[Fourth Example of Embodiment]
A fourth example of the embodiment of the present invention will be described with reference to FIG.

In the structure of this example, the outer ring recesses 44b are not connected over the entire circumference, and are provided at a plurality of locations separated in the circumferential direction of the outer peripheral surface of the outer ring 35c (in the illustrated example, a plurality of locations at equal intervals in the circumferential direction). ing. That is, in the structure of this example, in the outer ring 35c, there is a partition portion 63 that is not recessed inward in the radial direction between the two outer ring recesses 44b adjacent to each other in the circumferential direction. A housing protrusion of a gear housing (not shown) is engaged with each of the outer ring recesses 44b. In such a structure of this example, the circumferential side surface constituting the inner surface of the outer ring recess 44b, that is, the circumferential side surface of the partition portion 63 and the circumferential side surface of the housing convex portion are engaged with each other. Therefore, it is possible to more effectively prevent the outer ring 35c from being displaced in the circumferential direction with respect to the gear housing. In the case of carrying out the present invention, when the outer ring is provided with a partition portion, the number of the partition portions may be any number (one or more). Further, the number of partition portions and outer ring recesses, the length in the circumferential direction, the width in the axial direction, and the like can be arbitrarily determined within a range in which machining such as plastic working or rolling is possible.
Other configurations and effects are the same as in the first embodiment.

[Fifth Example of Embodiment]
A fifth example of the embodiment of the present invention will be described with reference to FIG.

In this example, the outer ring engaging portion provided on the outer peripheral surface of the outer ring 35d is composed of an outer ring convex portion 56 that protrudes outward in the radial direction and extends in the circumferential direction. In this example, the entire outer ring convex portion 56 is arranged at a position displaced in the axial direction with respect to the axial central portion of the outer ring track 39, and more specifically, in the axial central portion of the outer ring track 39. On the other hand, it is located at a position shifted to the front side. In this example, the outer ring convex portion 56 is provided over the entire circumference of the outer peripheral surface of the outer ring 35d. Regarding the axial width and radial height of the outer ring convex portion 56, and the axial arrangement location, as long as the axial displacement of the outer ring 35d is prevented by the engagement with the housing recess 59 described later. Moreover, as long as the rigidity of the outer ring 35d is secured, it can be arbitrarily determined. The larger the axial width and the radial height of the outer ring convex portion 56, the easier it is to secure the support rigidity of the outer ring 35d with respect to the gear housing 21.

The radial tip portion of the outer ring convex portion 56 is composed of a knurled portion 57 having an uneven shape in the circumferential direction. In this example, the knurled portion 57 has a flat structure in which the forming direction of the concave portion and the convex portion is the axial direction. However, when the present invention is carried out, the knurled portion may have a twill structure in which the forming directions of the concave portion and the convex portion are inclined and intersect with each other in the axial direction.

In this example, the portion of the outer ring convex portion 56 located radially inside the knurled portion 57 is composed of an inclined convex portion 62 having a shape in which the axial width decreases toward the radial outer side. .. In the illustrated example, each of the side surfaces 58 on both sides of the inclined convex portion 62 in the axial direction has a shape so as to approach the central side in the axial direction of the outer ring convex portion 56 toward the outer side in the radial direction. More specifically, each of the side surfaces 58 on both sides of the inclined convex portion 62 in the axial direction has an S-shaped cross-sectional shape. However, each of the side surfaces of the inclined convex portion on both sides in the axial direction has a linear cross-sectional shape, that is, can be configured by a conical surface.

In the case of carrying out the present invention, the side surface of the inclined convex portion on one side in the axial direction is formed by a flat surface orthogonal to the central axis of the outer ring, and the side surface of the inclined convex portion on the other side in the axial direction is formed. It can also be configured by a surface having a shape that approaches the axial center side of the outer ring convex portion toward the outer side in the radial direction. Further, each of the side surfaces of the inclined convex portion on both sides in the axial direction may be formed of a flat surface orthogonal to the central axis of the outer ring. Further, in the case of carrying out the present invention, the portion of the outer ring convex portion located on the inner side in the radial direction from the knurled portion is more than the inclined convex portion having a shape in which the axial width increases toward the outer side in the radial direction. It can also be configured.

In the outer ring convex portion 56, for example, a circumferential convex portion having a shape in which the outer peripheral surface is formed of a cylindrical surface and the axial width decreases toward the outer side in the radial direction is machined or rolled. It can be divided into a step of forming by plastic working and a step of forming a knurled portion 57 at the radial tip portion of the circumferential convex portion by threading. Alternatively, the entire outer ring convex portion 56 can be formed by plastic working such as cutting or rolling.

In this example, the housing engaging portion provided in the gear housing 21 is composed of a housing concave portion 59 in which the outer ring convex portion 56 is inserted into the inside thereof, and the housing concave portion 59 is unevenly engaged with the outer ring convex portion 56. Moreover, the bottom portion of the housing recess 59 is unevenly engaged with the knurled portion 57.

That is, the housing recess 59 covers the entire outer surface (surface) of the outer ring convex portion 56. Therefore, the housing recess 59 has an inner surface (surface) shape that matches the outer surface shape of the outer ring convex portion 56. Further, such a housing recess 59 has a convex portion 60 at the bottom, which fills the entire inside of the recess constituting the knurled portion 57. With the above configuration, the housing concave portion 59 is unevenly engaged with the outer ring convex portion 56, and the bottom portion of the housing concave portion 59 is unevenly engaged with the knurled portion 57.

Even with the structure of this example as described above, it is possible to effectively prevent the outer ring 35d constituting the rolling bearing 19 from being displaced with respect to the gear housing 21 made of synthetic resin.

That is, in the structure of this example, the housing recess 59 provided in the gear housing 21 is engaged with the outer ring convex portion 56 extending in the circumferential direction provided on the outer peripheral surface of the outer ring 35d. Therefore, it is possible to effectively prevent the outer ring 35d from being displaced in the axial direction with respect to the gear housing 21.

Further, in the structure of this example, the bottom portion of the housing recess 59 is concavely engaged with the knurled portion 57 having a concave-convex shape in the circumferential direction provided at the radial tip portion of the outer ring convex portion 56. Therefore, it is possible to effectively prevent the outer ring 35d from being displaced in the circumferential direction with respect to the gear housing 21.

Further, in the structure of this example, the inclined convex portion 62, which is a portion of the outer ring convex portion 56 located radially inside the knurled portion 57, has a shape in which the axial width decreases toward the radial outer side. Have. Therefore, it is easy to perform processing for forming the outer ring convex portion 56. Further, when the gear housing 21 is injection-molded, the entire surface of the outer ring convex portion 56 is easily covered with the melted synthetic resin, and the formability of the housing concave portion 59 is easily ensured. In the case of carrying out the present invention, the portion of the outer ring convex portion located on the inner side in the radial direction from the knurled portion is composed of the inclined convex portion having a shape in which the axial width increases toward the outer side in the radial direction. In this case, since the outer ring convex portion has a structure in which the outer ring convex portion bites into the synthetic resin constituting the gear housing 21, it becomes easy to secure the bonding strength of the outer ring convex portion to the gear housing 21.

In the structure of this example, the outer ring convex portion 56 is arranged on the outer peripheral surface of the outer ring 35d at a position displaced in the axial direction with respect to the axial center portion of the outer ring track 39. However, unlike the case where the outer ring concave portion is formed on the outer peripheral surface of the outer ring, when the outer ring convex portion is formed on the outer peripheral surface of the outer ring, the radial wall thickness of the outer ring decreases with the formation of the outer ring convex portion. There is no. Therefore, when the present invention is carried out, as in the modified example of the fifth embodiment of the embodiment shown in FIG. 12, the outer ring convex portion 56 is placed on the outer peripheral surface of the outer ring 35e in the axial direction of the outer ring track 39. It can also be formed in the same axial position as the central part. Further, when the present invention is carried out, the outer ring convex portion extending in the circumferential direction does not have to be connected over the entire circumference. That is, it is also possible to have a notch portion which is a portion where the outer ring convex portion is not provided at at least one place in the circumferential direction. Then, by engaging the synthetic resin constituting the gear housing in the circumferential direction with such a notch, it is possible to more effectively prevent the rotation of the outer ring with respect to the gear housing.
Other configurations and effects are the same as in the first embodiment.

When the present invention is carried out, the structures of the examples of the embodiments can be appropriately combined and carried out within a range that does not cause a contradiction.

The worm reducer of the present invention is not limited to the column assist type electric power steering device, but can be incorporated into, for example, an electric power steering device having various structures such as a pinion assist type, a rack assist type, and a dual pinion type, and also steer. It can be incorporated into a by-wire steering device to contribute to the weight reduction of these devices.

1 Electric power steering device 2 Steering wheel 3 Steering shaft 4 Steering column 5a, 5b Flexible joint 6 Intermediate shaft 7 Steering gear unit 8 Tie rod 9 Electric assist device 10 Housing case 11 Torsion bar 12 Output shaft 13 Pinion shaft 14 Torque sensor 15 Electric motor 16 Worm reducer 17 Wheel teeth 18 Warm wheel 19 Rolling bearing 20 Rolling bearing 21 Gear housing 22 Cover housing 23 Intermediate plate 24 Bolt 25 Warm wheel housing 26 Warm housing 27 Pivot 28 Cylindrical 29 Side plate 30 Support cylinder 31 Coupling flange 32 Screw hole 33 Through hole 34 Through hole 35, 35a, 35b, 35c, 35d, 35e Outer ring 36 Inner ring 37 Ball 38 Seal ring 39 Outer ring track 40 Locking groove 41 Inner ring track 42 Seal sliding groove 43 Rolling element installation Space 44, 44a, 44b Outer ring recess 45 Rollet part 46 Side surface 47, 47a, 47b Housing convex part 48 Convex part 49, 49a Holding surface 50, 50a Inward flange part 51 Support shaft 52a, 52b Mold element 53 Mold 54 Cavity 55 Nozzle 56 Outer ring convex part 57 Rollet part 58 Side surface 59 Housing concave part 60 Convex part 61 Inclined concave part 62 Inclined convex part 63 Partition part 64 Rib

Claims (10)

With the gear housing
It has an outer ring, which is a stationary wheel supported by the gear housing, and includes a rolling bearing, which is used to rotatably support the worm wheel with respect to the gear housing.
The outer ring has an outer ring engaging portion on the outer peripheral surface and has an outer ring engaging portion.
The gear housing is an injection-molded product made of a synthetic resin having the outer ring as an insert component, and the outer ring is prevented from being displaced relative to each other with respect to the axial direction and the circumferential direction of the outer ring. Has a housing engaging portion that engages the engaging portion,
Warm reducer. The outer ring engaging portion is composed of an outer ring recess that is recessed inward in the radial direction and extends in the circumferential direction.
The bottom of the outer ring recess is composed of a knurled portion having an uneven shape in the circumferential direction.
The housing engaging portion is composed of a housing convex portion that has entered the inside of the outer ring concave portion, the housing convex portion is unevenly engaged with the outer ring concave portion, and the radial tip portion of the housing convex portion is formed. Concavo-convex engagement with the knurled portion,
The worm reducer according to claim 1. The outer ring has a deep groove type outer ring track on the inner peripheral surface.
The entire outer ring recess is arranged at a position displaced in the axial direction with respect to the axial center portion of the outer ring track.
The worm reducer according to claim 2. The portion of the outer ring recess located radially outside the knurled portion is composed of an inclined recess having a shape in which the axial width decreases toward the inside in the radial direction.
The worm reducer according to claim 2 or 3. The outer ring engaging portion is composed of an outer ring convex portion that protrudes outward in the radial direction and extends in the circumferential direction.
The radial tip portion of the outer ring convex portion is composed of a knurled portion having an uneven shape in the circumferential direction.
The housing engaging portion is composed of a housing concave portion in which the outer ring convex portion is inserted into the inside thereof, the housing concave portion is unevenly engaged with the outer ring convex portion, and the bottom portion of the housing concave portion is the knurled portion. Unevenly engaged with the part,
The worm reducer according to claim 1. The portion of the outer ring convex portion located radially inside the knurled portion is composed of an inclined convex portion having a shape in which the axial width decreases toward the radial outer side.
The worm reducer according to claim 5. The outer ring engaging portion is provided over the entire circumference of the outer peripheral surface of the outer ring.
The worm reducer according to any one of claims 1 to 6. The outer ring engaging portion is not connected over the entire circumference of the outer peripheral surface of the outer ring, and the circumferential side surface of the outer ring engaging portion and the circumferential side surface of the housing engaging portion are engaged.
The worm reducer according to any one of claims 1 to 6. The gear housing has a holding surface that contacts at least one of the side surfaces of the outer ring on both sides in the axial direction.
The worm reducer according to any one of claims 1 to 8. Built into the electric power steering system,
The worm reducer according to any one of claims 1 to 9.

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