JP2009299776A - Worm reduction gear and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a worm reduction gear having a nonslip structure of a first rolling bearing, superior in assembling work efficiency, and capable of simplifying maintenance and management work. <P>SOLUTION: A spacer ring 37 is fitted in a fitting recessed part 41 formed on an inner surface of a housing 7, and a butting part 40 constituting this spacer ring 37 is butted against one end surface in the axial direction of an outer ring 24 constituting the first rolling bearing 21. A retaining ring 38 is locked in a locking groove 45 formed in a part dislocated to one end side in the axial direction from the spacer ring 37 by a part of an inner surface of the fitting recessed part 41 while pressing its one surface to this spacer ring 37. Thus, nonslip of the first rolling bearing 21 can be attained by the retaining ring 38 via this spacer ring 37. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The worm speed reducer and the electric power steering apparatus according to the present invention are incorporated in a steering apparatus of an automobile and use an electric motor as auxiliary power to reduce the force required for the driver to operate the steering wheel. To use.

  As a power steering device for reducing the force required for the driver to operate the steering wheel during steering, an electric power steering device using an electric motor as auxiliary power is widely known. Conventionally, an electric power steering apparatus having a structure as shown in FIGS. 7 to 9 is known. Among these, the one shown in FIG. 7 obtains auxiliary power by the electric motor 2 installed in the steering column 1 portion. Further, in the device shown in FIG. 8, auxiliary power is obtained by the electric motor 2 installed in the steering gear 3 portion. Further, in the apparatus shown in FIG. 9, the rack 4 is driven by the steering gear 3, and at the same time, the rack 4 is driven by the electric motor 2 provided separately from the steering gear 3 to obtain auxiliary power.

  In any of the structures described in FIGS. 7 to 9, the rotational force of the electric motor 2 is transmitted to the driven shaft after the torque is increased at the same time as being decelerated by the worm reducer. In the case of the structure shown in FIG. 7, the driven shaft is a steering shaft 5 (a rotating shaft connected to the steering shaft 5) rotatably supported in the steering column 1. In the case of the structure shown in FIG. 8, the pinion shaft (or the rotating shaft connected thereto) serving as the output shaft of the steering gear 3 serves as the driven shaft. Furthermore, in the case of the structure shown in FIG. 9, the rotating shaft for driving the pinion meshed with the rack 4 is the driven shaft. Since the basic structure of the worm speed reducer is the same in any of the structures shown in FIGS. 7 to 9, the worm speed reducer having the conventional structure will be described below with reference to FIGS. I will explain.

  10-11 has shown what was described in patent document 1 as an example of the worm reduction gear of a conventional structure. As shown in FIG. 10, the worm speed reducer 6 includes a housing 7, a worm wheel 8, and a worm shaft 9. Of these, the housing 7 supports and fixes the electric motor 2 on the outer surface, and the drive shaft 10 and the driven shaft 11 which are output shafts of the electric motor 2 are twisted relative to each other inside. Each is arranged to be freely rotatable. The worm wheel 8 is supported concentrically with the driven shaft 11 by a key engagement, a spline engagement or the like at an intermediate portion of the driven shaft 11 and rotates together with the driven shaft 11. On the other hand, the worm shaft 9 has a proximal end portion coupled to a distal end portion of the drive shaft 10 concentrically with the drive shaft 10. In the illustrated example, the distal end portion of the drive shaft 10 and the proximal end portion of the worm shaft 9 are coupled freely using a coupling (elastic coupling) 12 to transmit rotational force.

  As shown in FIG. 11, the coupling 12 includes first and second connecting members 13 and 14 and an elastic buffer 15. Of these, the first connecting member 13 is fitted and fixed to the base end portion of the worm shaft 9 by serration fitting, and the meshing teeth 16 and 16 are located at three circumferentially equidistant positions on the distal end surface thereof. Is provided. On the other hand, the second connecting member 14 is fitted and fixed to the distal end portion of the drive shaft 10, and meshing teeth 17 and 17 are also provided at three circumferentially equidistant positions on the distal end surface. . The elastic shock absorber 15 has, on its outer peripheral surface, meshing portions 18, 18 that can mesh with the meshing teeth 16, 16, and meshing portions 19, 19 that can mesh with the meshing teeth 17, 17. Are provided alternately in the circumferential direction. And in the state which clamped the said elastic buffer body 15 which has such a structure between said 1st, 2nd connection members 13 and 14, each said meshing teeth 16, 19 said each meshing tooth 16, 17 are engaged (engaged) with each other. This prevents rattling or abnormal noise from occurring at the joint between the drive shaft 10 and the worm shaft 9.

  Further, the worm shaft 9 is engaged with the worm wheel 8 in the state where the worm 20 provided at the intermediate portion is engaged with the worm wheel 8, and the portions near both ends are placed inside the housing 7 by the first and second rolling bearings 21 and 22. It is supported rotatably. For this purpose, an inner ring 23 that constitutes the first rolling bearing 21 is fitted on a portion near the base end of the worm shaft 9 (a portion near the right end in FIG. 10), and a part of the inner surface of the housing 7 is fitted. The outer ring 24 constituting the first rolling bearing 21 is fitted inside. In addition, a substantially C-shaped retaining ring 26 is engaged in a retaining groove 25 formed in a part of the inner surface of the housing 7 that is disengaged from the outer ring 24 toward one end side in the axial direction (right end side in FIG. 10). The first rolling bearing 21 is prevented from coming off in the axial direction (on the proximal end side of the worm shaft 9 and in the right direction in FIG. 10). The other end surface in the axial direction of the outer ring 24 (the left end surface in FIG. 10) is abutted against a step surface 27 formed on the inner surface of the housing 7.

  On the other hand, in order to rotatably support the portion near the tip of the worm shaft 9 (the portion near the left end in FIG. 10), an inner ring 28 constituting the second rolling bearing 22 is provided at the portion near the tip of the worm shaft 9. The outer ring 29 that constitutes the second rolling bearing 22 is fitted through a cylindrical leaf spring 30 into a part of the inner surface of the housing 7. The leaf spring 30 imparts elasticity in the direction toward the worm wheel 8 to the worm 20, and rattling noise and rattling occur at the meshing portion between the worm 20 and the worm wheel 8. It is preventing.

  When the electric power steering apparatus including the worm speed reducer 6 having the above-described configuration is operated, the electric motor 2 is connected to the worm wheel via the worm shaft 9 based on a signal from a torque sensor (not shown). 8 is rotated with a predetermined torque in a predetermined direction. As a result, auxiliary torque from the electric motor 2 is applied to the driven shaft 11 supporting the worm wheel 8 in addition to torque applied from the steering wheel 31 (see FIGS. 7 to 9). As a result, the driven shaft 11 tends to rotate with a torque larger than the torque applied from the steering wheel 31, and the reduction of the force (steering force) required for the driver to operate the steering wheel 31 is reduced. I can plan.

  By the way, during the assembly work of the worm speed reducer 6 having the above-described configuration, the worm shaft 9 has a first connection that constitutes the first rolling bearing 21 and the coupling 12 at a portion near the base end thereof. The member 13 is assembled in the housing 7 in a state of being assembled in advance. Therefore, in order to lock the retaining ring 26 in the retaining groove 25 formed on the inner surface of the housing 7, the retaining ring 26 is inserted inside the housing 7 as shown by a chain line in FIG. It is necessary to pass the outer diameter side of the first connecting member 13 in a state where the diameter is elastically reduced (a reduced diameter state) until possible. Therefore, in order to employ the retaining structure by the retaining ring 26, it is necessary that the outer diameter dimension of the first connecting member 13 is smaller than the inner diameter dimension of the retaining ring 26 in the reduced diameter state. .

  Further, the inner diameter dimension of the retaining ring 26 in the reduced diameter state is such that the retaining ring 26 and the retaining ring 26 are in the state where the retaining ring 26 is retained in the retaining groove 25 (the diameter is elastically restored). In order to secure a sufficient width (H) of facing the outer ring 24 constituting the first rolling bearing 21, for example, as shown in FIG. 10, the inner ring dimension of the axial end of the outer ring 24 is larger than that of the outer ring 24. At least, it is reduced by twice (2L) the locking allowance (L) for the locking groove 25. Thus, in order to effectively prevent the retaining ring 26 from coming off, the outer diameter of the first connecting member 13 needs to be sufficiently smaller than the inner diameter of the axial end of the outer ring 24. If such a condition is not satisfied, the retaining structure by the retaining ring 26 cannot be substantially employed. It should be noted that when the first connecting member 13 is externally fitted to the base end portion of the worm shaft 9 after the retaining ring 26 is mounted, a large thrust load is applied to the first rolling bearing 21. Since this first rolling bearing 21 may be damaged, it is not preferable.

  In view of such circumstances, for example, Japanese Patent Application No. 2007-319900 discloses a structure for preventing the first rolling bearing from coming off by means other than a retaining ring. FIG. 12 shows an example of a worm reduction gear disclosed in the above Japanese Patent Application No. 2007-319900. In the case of the example of the structure according to the previous invention shown in FIG. 12, the first and second connecting members connect the distal end portion of the drive shaft 10 that is the output shaft of the electric motor 2 and the proximal end portion of the worm shaft 9. It is connected by a coupling 12a comprising 13a, 14a and an elastic buffer 15a. The specific configuration of the coupling 12a will be described in a first example of an embodiment to be described later, and detailed description thereof will be omitted. Hereinafter, the first connecting member 13a will be omitted. The explanation will be focused on.

  The first connecting member 13 a is fitted and fixed to the base end of the worm shaft 9, and the outer diameter thereof is the same as the inner diameter of the axial end of the outer ring 24 constituting the first rolling bearing 21. It is almost the same. Therefore, in order to prevent the first rolling bearing 21 from coming off, even if an attempt is made to employ a retaining structure with a retaining ring 26 (see FIG. 10) as in the conventional structure described above, The outer diameter side of the first connecting member 13a cannot be passed.

  Therefore, in the case of the worm speed reducer 6a having the structure according to the previous invention, the first rolling bearing 21 is prevented from coming off by using an annular support plate 32 and a plurality of bolts 33. ing. Of these, the support plate 32 has a slightly larger inner diameter than the outer diameter of the first connecting member 13a. In the case of the structure according to the previous invention, the support plate 32 having such a configuration is connected to the outer diameter side of the first connecting member 13a fitted and fixed to the base end portion of the worm shaft 9. After passing, the portion closer to the inner diameter on one side (the left side surface in FIG. 12) is abutted against one axial end surface (the right end surface in FIG. 12) of the outer ring 24. In this state, the intermediate portion in the radial direction or the portion near the outer diameter of the support plate 32 is supported and fixed by the bolts 33 with respect to the step surface 34 formed on the inner surface of the housing 7.

  However, when the retaining structure using the support plate 32 and the plurality of bolts 33 as described above is employed, a tool is inserted from the opening (the electric motor 2 side) of the housing 7 and each of the bolts described above. 33 need to be screwed together and further tightened. For this reason, it is inevitable that the assembly workability is deteriorated as compared with the case where the retaining structure using the retaining ring 26 (see FIG. 10) described above is employed. Furthermore, since it is necessary to manage the tightening torque of each bolt 33, the number of man-hours required for the assembly work is also increased.

  In addition to the retaining structure disclosed in the prior invention as described above, the retaining structure of the rolling bearing includes, for example, structures described in Patent Documents 2 to 4. Of these, Patent Document 2 describes a structure that uses a partition plate having a substantially L-shaped cross section and a plurality of bolts to prevent the rolling bearing from coming off. However, in the case of the structure described in Patent Document 2, as in the case of the structure disclosed in the above-described prior invention, a plurality of bolts are used. Create management problems. Also, in Patent Document 3, a tool such as a plier is attached to this member so that a retaining structure using a retaining ring can be adopted even when the outer diameter of a member provided adjacent to the rolling bearing is large. A technique for forming a working hole for insertion is described. However, forming such a working hole itself requires a lot of man-hours, and the assembling work using the working hole is also poor in workability. Furthermore, Patent Document 4 describes a structure for preventing the rolling bearing from coming off by using a nut member that can be screwed into the housing. However, when such a retaining structure using a nut member is adopted, a special tool is required to tighten the nut member, resulting in an increase in cost. Furthermore, it is necessary to manage the tightening torque of the nut member.

Japanese Patent Laid-Open No. 2004-203154 JP 2001-213333 A Japanese Patent No. 3948078 JP 2004-232675 A

  In view of the circumstances as described above, the present invention includes a worm speed reducer having a retaining structure for a rolling bearing and a worm speed reducer that is excellent in assembling workability and simplifies parts production and parts management work. Invented to realize an electric power steering apparatus.

Of the worm reducer and the electric power steering apparatus according to the present invention, the worm reducer includes a housing, a worm wheel, and a worm shaft.
Of these, the worm wheel is arranged concentrically with the driven shaft on the outer peripheral surface of the driven shaft rotatably supported in the housing, and rotates together with the driven shaft.
The worm shaft has a base end portion coupled to a drive shaft that exists in a twisted position with respect to the driven shaft in the housing. Further, in a state where a worm provided at the intermediate portion is engaged with the worm wheel, the portions near both ends are rotatably supported by a pair of bearings inside the housing.

  In particular, in the worm speed reducer according to claim 1, a spacer ring is provided on an axial end surface of an outer ring constituting a rolling bearing which is a bearing disposed on the base end side of the worm shaft among the two bearings. Is hitting. The spacer ring is prevented from being displaced in a direction away from the rolling bearing disposed on the base end side of the worm shaft by a retaining ring locked to the inner surface of the housing.

  Further, in the worm speed reducer according to claim 2, a spacer ring is provided on the axial end surface of the outer ring constituting the rolling bearing which is a bearing disposed on the base end side of the worm shaft among the two bearings. Is hitting. The spacer ring is prevented from being displaced in a direction away from the rolling bearing disposed on the base end side of the worm shaft by a caulking portion formed by plastically deforming a part of the inner surface of the housing. Yes.

  When carrying out the invention described in claims 1 and 2 as described above, for example, as in the invention described in claim 3, the front end portion of the drive shaft and the base end portion of the worm shaft are coupled to each other. Connect with Of the members constituting this coupling, the outer diameter of the member assembled to the proximal end portion of the worm shaft is defined as the outer diameter of a rolling bearing that is a bearing disposed on the proximal end side of the worm shaft. Make it smaller than the dimensions. Further, the inner diameter of the inner surface of the housing where the spacer ring is fitted is made larger than the inner diameter of the portion where the outer ring of the rolling bearing is fitted.

In carrying out the present invention, the spacer ring is fitted and fixed to the inside of the housing by press-fitting as in the invention described in claim 4, for example.
Furthermore, when the present invention is carried out, as in the invention described in claim 5, for example, the worm is given elasticity in the direction toward the worm wheel.

According to a sixth aspect of the present invention, an electric power steering apparatus includes a rotating shaft, an electric motor, and a worm reducer.
Of these, the rotating shaft rotates based on the operation of the steering wheel, and gives the steering wheel a steering angle corresponding to the amount of rotation.
The electric motor is for applying an auxiliary force to the rotating shaft.
Further, the worm speed reducer is provided between the output shaft of the electric motor and the rotating shaft, and transmits the rotation of the output shaft to the rotating shaft.
In particular, in the electric power steering apparatus of the present invention, the worm speed reducer is the worm speed reducer of the present invention as described above, the rotating shaft is the driven shaft, and the output shaft is the It is a drive shaft.

According to the worm speed reducer and electric power steering apparatus of the present invention as described above, the bearing (located on the base end side of the worm shaft) is excellent in assembling workability and simplifies parts manufacturing and parts management work. Thus, a worm reduction gear and an electric power steering device having a retaining structure for the rolling bearing) can be obtained.
That is, according to the present invention, the rolling bearing of the rolling bearing is interposed via the spacer ring by the retaining ring (in the case of the invention according to claim 1) or the caulking portion (in the case of the invention according to claim 2) formed on the inner surface of the housing. You can try to prevent it from coming off. For this reason, in the case of the present invention, it is not necessary to use a member that requires tightening work such as a bolt in order to prevent the rolling bearing from coming off. Therefore, it is possible to improve the assembly workability. In addition, since it is not necessary to use complicated parts or many parts, not only can the parts manufacture and parts management be facilitated, but also there is no need to manage the tightening torque, thus simplifying the assembly work. You can also do things.
According to the invention described in claim 4, it is possible to prevent the spacer ring from rattling in the radial direction within the housing. For this reason, generation | occurrence | production of the noise by the shakiness of this spacer ring can be prevented.

[First example of embodiment]
1-4 show a first example of an embodiment of the present invention corresponding to claims 1 and 3 to 6. The feature of this example is the structure for preventing the first rolling bearing 21 from coming off so as to rotatably support the proximal end portion of the worm shaft 9 with respect to the housing 7. The overall configuration of the electric power steering apparatus is the same as a conventionally known structure, for example, as shown in FIGS. Further, the basic structure of the worm speed reducer 6b of this example is the same as that of the worm speed reducers 6 and 6a having the conventional structure and the structure according to the previous invention. Therefore, the overlapping description is omitted or simplified. The description will focus on the characteristic part of this example and the part that has not been described previously.

  Also in the case of the worm reduction gear 6b of this example, the distal end portion of the drive shaft 10 that is the output shaft of the electric motor 2 and the proximal end portion of the worm shaft 9 are the same as in the case of the structure according to the above-described prior invention. The transmission of rotational force is freely connected by the coupling 12a. The coupling 12a includes a first connecting member 13a fitted and fixed to the proximal end portion of the worm shaft 9, a second connecting member 14a fitted and fixed to the distal end portion of the drive shaft 10, and these It comprises an elastic buffer 15a provided between the first and second connecting members 13a, 14a.

  As shown in FIG. 4, the front end surface of the first connecting member 13a is provided with meshing teeth 16a, 16a at three positions at equal intervals in the circumferential direction. Also on the tip surface of 14a, meshing teeth 17a, 17a are provided at three positions at equal intervals in the circumferential direction. Further, the circumferential side surfaces of both the meshing teeth 16a and 17a are concave arc surfaces. The elastic buffer 15a includes an annular support ring 35 having a larger outer diameter than the first and second connecting members 13a and 14a, a circumferential direction of an inner peripheral surface of the support ring 35, and the like. It consists of substantially spherical buffer parts 36, 36 provided at six positions. These buffer portions 36 and 36 are sandwiched between the circumferential side surfaces of the meshing teeth 16a and 17a adjacent in the circumferential direction in the assembled state of the coupling 12a.

  As described above, also in the case of this example, the distal end portion of the drive shaft 10 and the proximal end portion of the worm shaft 9 are substantially the same as the inner diameter of the outer ring 24 constituting the first rolling bearing 21. It is connected by a coupling 12a having a first connecting member 13a having a diameter. Therefore, in order to prevent the first rolling bearing 21 from coming off, it is not possible to employ a retaining structure by the retaining ring 26 (see FIG. 10) as in the case of the conventional structure described above.

  Therefore, in the case of this example, the first rolling bearing 21 is prevented from coming off by using a spacer ring 37 having a substantially L-shaped cross section and a retaining ring 38 having a substantially C-shaped (circular shape). I have to. Among them, the spacer ring 37 has a cylindrical fitting portion 39 and an inward hook shape provided on the inner peripheral surface of one end portion in the axial direction (left end portion in FIGS. 1 and 2) of the fitting portion 39 over the entire circumference. The abutting part 40 is provided. Of these, the fitting portion 39 has an inner diameter dimension of the elastic buffer 15a (support ring 35) constituting the coupling 12a arranged on the inner diameter side of the fitting portion 39 in the assembled state of the worm speed reducer 6b. It is larger than the outer diameter, and the inner diameter of the abutting portion 40 is larger than the outer diameter of the first connecting member 13a.

  The spacer ring 37 having such a configuration has a larger inner diameter than the portion in which the outer ring 24 is fitted and formed on the inner surface of the housing 7, and the fitting ring 41 has a cylindrical inner surface. The inner fitting is fixed by press-fitting (light press-fitting) the fitting part 39. In this state, one surface of the abutting portion 40 (the left side surface in FIGS. 1 and 2) is connected to one end surface in the axial direction of the outer ring 24 constituting the first rolling bearing 21 (the right end surface in FIGS. 1 and 2). It hits all around. As a result, the outer ring 24 is sandwiched between one surface of the abutting portion 40 and the stepped surface 27 formed on the inner surface of the housing 7.

  The retaining ring 38 is formed by punching and forming a plate made of an elastic material such as spring steel or stainless spring steel, and is formed in a substantially C-shaped ring shape. Have Further, as shown in FIG. 3, a pair of locking arm portions 43 and 43 are formed at both end portions corresponding to the discontinuous portion 42 of the retaining ring 38 so as to protrude to the inner diameter side. . The locking arms 43 and 43 are formed with locking holes 44 and 44 for engaging the leading end of a gripping part of a tool (not shown) such as a pliers.

  The retaining ring 38 having such a configuration is a portion of the inner surface of the fitting recess 41 that is disengaged from the spacer ring 37 (fitting portion 39) to one axial end side (the right end side in FIGS. 1 and 2). It is locked in the locking groove 45 formed in the above. In this state, one surface of the retaining ring 38 (the left side surface in FIGS. 1 and 2) is pressed against the other axial end surface (the right end surface in FIGS. 1 and 2) of the fitting portion 39 constituting the spacer ring 37. ing. Thereby, the spacer ring 37 is prevented from being displaced in the direction away from the first rolling bearing 21 (the right side in FIGS. 1 and 2 and the surface side in FIG. 3).

  With the configuration as described above, in the case of this example, when torque is transmitted between the worm 20 and the worm wheel 8, it acts on the worm shaft 9 toward the base end side (right side in FIGS. 1 and 2). An axial force can be supported by the retaining ring 38 via the first rolling bearing 21 and the spacer ring 37. Therefore, the first rolling bearing 21 can be prevented from coming off in the axial direction (toward the base end side of the worm shaft 9). That is, in the case of this example, the first rolling bearing 21 is prevented from coming off via the spacer ring 37 by the retaining ring 38 that is latched to the inner surface of the housing 7.

  Further, in the case of this example, a pressing piece 44 is externally fitted to a portion protruding in the axial direction from the second rolling bearing 22 at the tip end portion of the worm shaft 9. A coil spring 45, which is an elastic member, is provided between the housing 7 and the housing 7. Then, a part of the outer peripheral surface of the coil spring 45 that is partly locked to the pressing piece 44 is abutted against a part of the inner surface of the housing 7 opposite to the worm wheel 8, whereby the worm 20 is pressed toward the worm wheel 8. Therefore, also in this example, it is possible to prevent rattling noise and rattling from occurring at the meshing portion of the worm 20 and the worm wheel 8.

  In the assembly process of the worm speed reducer 6b of this example having the above-described configuration, the work for assembling the spacer ring 37 and the retaining ring 38 is performed as follows. In the case of this example as well, the work for assembling the spacer ring 37 and the retaining ring 38 is the first operation that constitutes the first rolling bearing 21 and the coupling 12a at the portion near the base end of the worm shaft 9. This is performed after the coupling members 13a are assembled in the housing 7 in the assembled state.

  First, in the case of this example, the spacer ring 37 is press-fitted into the fitting concave portion 41 formed on the inner surface of the housing 7 from the abutting portion 40 side. Then, one surface (the left side surface in FIGS. 1 and 2) of the abutting portion 40 is arranged around the entire circumference on one axial end surface (the right end surface in FIGS. 1 and 2) of the outer ring 24 constituting the first rolling bearing 21. I hit it. Since the inner diameter of the abutting portion 40 is larger than the outer diameter of the first connecting member 13a, the abutting portion 40 is in the process of press-fitting the spacer ring 37 into the fitting recess 41. The inner peripheral edge of the first connecting member 13a does not interfere with the outer peripheral edge of the first connecting member 13a.

  As described above, after the spacer ring 37 is fitted and fixed in the fitting recess 41 by press fitting, the retaining ring 38 is elastically reduced in diameter in the fitting recess 41. To enter. Specifically, the diameter of the retaining ring 38 is elastically reduced by engaging the front end of a gripping part of a tool such as a plier in the locking holes 44 of the retaining ring 38. Then, it is caused to enter the fitting recess 41. If one side (the left side in FIGS. 1 and 2) of the retaining ring 38 comes into contact with the other axial end surface (the right end in FIGS. 1 and 2) of the fitting portion 39 constituting the spacer ring 37. Then, the diameter of the retaining ring 38 is elastically restored, and the portion closer to the outer diameter of the retaining ring 38 is retained in the retaining groove 45. In the case of this example, the outer peripheral edge of the other surface of the retaining ring 38 (the right side surface in FIGS. 1 and 2) is inclined in the direction of decreasing the width dimension toward the outer side in the radial direction and The inner surface of the locking groove 45 facing the other surface of the ring 38 is inclined in a direction in which the opening width is increased toward the opening (inner side in the radial direction). Accordingly, a pressing force is applied to the spacer ring 37 while the retaining ring 38 is locked, and the locking operation of the retaining ring 38 is facilitated.

  As described above, after the spacer ring 37 and the retaining ring 38 are assembled, the base end portion of the worm shaft 9 and the tip end portion of the drive shaft 10 are connected. Specifically, the first connecting member 13a fitted and fixed to the base end portion of the worm shaft 9 and the second connecting member 14a previously fitted and fixed to the distal end portion of the drive shaft 10 are meshed. Between the circumferential side surfaces of the teeth 16a and 17a, the buffer portions 36 and 36 constituting the elastic buffer body 15a are connected in a sandwiched state.

According to the worm speed reducer 6b of the present example having the above-described configuration and assembled through the above-described steps, the following excellent effects can be obtained.
That is, in this example, the spacer ring 37 is prevented from being displaced in the direction away from the first rolling bearing 21 by the retaining ring 38 locked to the inner surface of the housing 7. Thus, it is possible to prevent the first rolling bearing 21 from coming off.
Therefore, in the case of this example, in order to prevent the first rolling bearing 21 from coming off, it is not necessary to perform a tightening operation of a fastening member such as a bolt, and the assembly workability can be improved. Moreover, in the case of this example, since the spacer ring 37 is press-fitted into the fitting recess 41 formed on the inner surface of the housing 7 by light press-fitting, this press-fitting operation can be easily performed. Further, the operation of locking the retaining ring 38 in the retaining groove 45 can be performed in a state where no member such as the elastic buffer 15a is present on the inner diameter side of the retaining ring 38, so that the workability can be improved.
Furthermore, in the case of this example, it is not necessary to manage the tightening torque of a fastening member such as a bolt, so that the assembly work can be simplified.

  In the case of this example, the spacer ring 37 has a substantially L-shaped cross section, and the spacer ring 37 is fitted in the fitting recess 41 having a larger diameter than the portion in which the outer ring 24 is fitted. Then, on the inner diameter side of the spacer ring 37 (fitting portion 39), the coupling 12a (the elastic buffer body 15a constituting the coupling 12a) having an outer diameter dimension similar to the outer diameter dimension of the first rolling bearing 21 is provided. Can be placed. In short, in the case of this example, the shape of the inner peripheral surface of the spacer ring 37 is regulated so as not to interfere with the coupling 12a. Therefore, in the case of this example, even when such a large-diameter coupling 12a is used, it is possible to prevent the first rolling bearing 21 from coming off by preventing interference with the coupling 12a. I can plan.

  Further, in the case of this example, the spacer ring 37 is fitted and fixed by being press-fitted into the large-diameter fitting recess 41 formed on the inner surface of the housing 7. Can be prevented from being displaced in the radial direction. For this reason, it is possible to prevent noise from being generated based on the radial play of the spacer ring 37. In addition, the spacer ring 37 can exert a resistance to displacement in a direction away from the first rolling bearing 21.

[Second Example of Embodiment]
FIGS. 5-6 has shown the 2nd example of embodiment of this invention corresponding to Claims 2-6. In the case of this example, the caulking portions 46, 46 formed on the inner surface of the housing 7 indicate that the spacer ring 37 a is displaced in the direction away from the first rolling bearing 21 (the right side in FIG. 5 and the surface side in FIG. 6). To prevent. For this reason, in the case of this example, the spacer ring 37a is fitted and fixed by press-fitting into a fitting recess 41a formed on the inner surface of the housing 7 and having a larger diameter than the portion where the outer ring 24 is fitted. In this state, the inner peripheral edge of the opening of the fitting recess 41a is pressed by a pressing jig (not shown) having a plurality of (four in this example) pressing portions. Thus, the caulking portions 46 and 46 are formed at the inner peripheral edge of the fitting recess 41a by plastically deforming the pressed portion and its peripheral portion inward in the radial direction. Then, these caulking portions 46, 46 hold down the other axial end surface (the right end surface in FIG. 5) of the fitting portion 39a constituting the spacer ring 37a, and the spacer ring 37a serves as the first rolling bearing. Displacement in a direction away from 21 is prevented. For this reason, in the case of this example, the axial dimension of the spacer ring 37a (fitting portion 39a) is made larger than in the case of the first example of the embodiment described above.

In the case of this example, in order to prevent the first rolling bearing 21 from coming off, a retaining ring 38 (see FIGS. 1 to 3) as in the first example of the embodiment described above is used. No need to use it. For this reason, the number of parts can be reduced, and the cost for parts processing and parts management can be reduced. In addition, since the work for forming each of the caulking portions 46 and 46 can be performed at one time (in one time) using the pressing jig as described above, when tightening a plurality of bolts. Compared to this, the assembly workability can be improved.
In the case of carrying out this example, a tongue-like portion or a built-up portion for forming the above-mentioned caulking portions 46, 46 is formed in advance at a plurality of positions on the inner peripheral edge of the opening of the fitting recess 41a. You can also leave.
Other configurations and operations are the same as those of the first example of the above-described embodiment, and thus overlapping illustrations and descriptions are omitted.

  In the first example of the embodiment described above, the structure in which the retaining ring is locked to one end side in the axial direction of the spacer ring has been described. However, the position where the retaining ring is locked is not limited to such a position. That is, the retaining ring is engaged in a state where it is suspended between the inner locking groove formed on the outer peripheral surface of the intermediate portion in the axial direction of the spacer ring and the outer locking groove formed on the inner surface of the housing (fitting recess). You can also stop. When such a configuration is employed, the retaining ring is mounted in the inner locking groove prior to press-fitting the spacer ring into the fitting recess. Then, when the spacer ring is press-fitted into the fitting recess, the retaining ring passes through a portion near the opening of the fitting recess with its diameter elastically reduced. Then, in a state where the retaining ring is aligned with the outer locking groove, the diameter thereof is elastically restored and is stretched between the outer locking groove and the inner locking groove. According to such a configuration, the assembly work of the spacer ring and the retaining ring can be performed at the same time, so that the number of work steps can be shortened and the assembly workability can be further improved. Furthermore, the bearing for supporting the tip side of the worm shaft is not limited to a rolling bearing but may be a sliding bearing.

Sectional drawing of the worm gear reducer which shows the 1st example of embodiment of this invention. The A section expanded sectional view of FIG. 1 similarly. B-O-O'-B sectional drawing of FIG. 2 similarly. The disassembled perspective view which similarly takes out and shows a coupling. The figure similar to FIG. 2 which shows the 2nd example of embodiment of this invention. The same figure as FIG. 1 is a partially cut side view showing a first example of an electric power steering apparatus that is an object of the present invention. FIG. The partial cutting side view which shows the 2nd example. The partial cutting side view which shows the 3rd example. Sectional drawing which shows an example of the worm reduction gear of a conventional structure. The exploded perspective view which takes out and shows a coupling. Sectional drawing which shows an example of the worm reduction gear of the structure which concerns on a prior invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Steering column 2 Electric motor 3 Steering gear 4 Rack 5 Steering shaft 6, 6a, 6b Worm speed reducer 7 Housing 8 Worm wheel 9 Worm shaft 10 Drive shaft 11 Driven shaft 12, 12a Coupling 13, 13a First connection member DESCRIPTION OF SYMBOLS 14, 14a 2nd connection member 15, 15a Elastic buffer body 16 Engagement tooth 17 Engagement tooth 18 Engagement part 19 Engagement part 20 Worm 21 1st rolling bearing 22 2nd rolling bearing 23 Inner ring 24 Outer ring 25 Locking groove 26 Stopping Ring 27 Stepped surface 28 Inner ring 29 Outer ring 30 Leaf spring 31 Steering wheel 32 Support plate 33 Bolt 34 Stepped surface 35 Support ring 36 Buffer part 37, 37a Spacer ring 38 Retaining ring 39, 39a Fitting part 40 Abutting part 41, 41a Fitting Joint recess 42 Discontinuous part 4 Locking arms 44 engaging holes 45 engaging grooves 46 crimped portion

Claims (6)

  A housing, a worm wheel that is supported concentrically with the driven shaft on an outer peripheral surface of a driven shaft rotatably supported in the housing, and rotates with the driven shaft; and the driven shaft within the housing A base end portion is coupled to a drive shaft that exists in a twisted position, and a pair of bearings are disposed at both ends on the inner side of the housing in a state where a worm provided at an intermediate portion is engaged with the worm wheel. In the worm speed reducer provided with a worm shaft that is rotatably supported by the shaft, the axial end face of the outer ring constituting the rolling bearing which is a bearing disposed on the base end side of the worm shaft among these bearings A spacer ring is abutted against the rolling ring disposed on the base end side of the worm shaft by a retaining ring locked to the inner surface of the housing. Worm reducer, characterized in that is prevented from being displaced in a direction away Ukara.   A housing, a worm wheel that is supported concentrically with the driven shaft on an outer peripheral surface of a driven shaft rotatably supported in the housing, and rotates with the driven shaft; and the driven shaft within the housing A base end portion is coupled to a drive shaft that exists in a twisted position, and a pair of bearings are disposed at both ends on the inner side of the housing in a state where a worm provided at an intermediate portion is engaged with the worm wheel. In the worm speed reducer provided with a worm shaft that is rotatably supported by the shaft, the axial end face of the outer ring constituting the rolling bearing which is a bearing disposed on the base end side of the worm shaft among these bearings A spacer ring is abutted against the worm, and the spacer ring is formed by plastically deforming a part of the inner surface of the housing, and the worm Worm reducer, characterized in that is prevented from being displaced in a direction away from the rolling bearing which is disposed on the base end side.   The distal end portion of the drive shaft and the proximal end portion of the worm shaft are connected by a coupling, and among the members constituting this coupling, the outer diameter dimension of the member assembled to the proximal end portion of the worm shaft is The outer diameter of a rolling bearing, which is a bearing disposed on the base end side of the worm shaft, is smaller than the outer diameter of the rolling bearing, and the inner diameter of the inner surface of the housing where the spacer ring is fitted is fitted into the outer ring of the rolling bearing. The worm speed reducer according to claim 1, wherein the worm speed reducer is larger than an inner diameter of the portion.   The worm speed reducer according to any one of claims 1 to 3, wherein the spacer ring is fitted and fixed inside the housing by press fitting.   The worm speed reducer according to any one of claims 1 to 4, wherein the worm is given elasticity in a direction toward the worm wheel.   A rotating shaft that rotates based on the operation of the steering wheel and gives a steering angle corresponding to the amount of rotation to the steering wheel, an electric motor for giving auxiliary force to the rotating shaft, an output shaft of the electric motor, An electric power steering apparatus comprising a worm reducer provided between the rotary shaft and transmitting the rotation of the output shaft to the rotary shaft. An electric power steering apparatus according to any one of the preceding claims, wherein the rotating shaft is a driven shaft and the output shaft is a driving shaft.

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