JP2012154432A - Worm reduction gear and electric power steering apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a worm reduction gear, along with an electric power steering apparatus, in which lubrication at a meshing part of a worm and a worm wheel can be favorably maintained.SOLUTION: The worm 16, a first bearing 32, a second bearing 33, and a worm collar 31 are integrally provided to thereby constitute a single worm unit 30, and the worm unit 30 is mounted to a second housing part 22 of a housing 20. As the worm collar 31 is present between the worm 16 and the inner circumferential surface of the housing 20 (second housing part 22), a space where grease can escape into is reduced. As a portion where grease applied on a meshing part between the worm 16 and the worm wheel 17 can escape into is reduced, the grease is restrained from escaping to a portion other than the meshing part.

Description

  The present invention relates to a worm reducer and an electric power steering apparatus.

  2. Description of the Related Art Conventionally, as an electric power steering apparatus for an automobile, one that drives and controls a steering assist motor based on a steering torque detected through a torque sensor is known. The rotation of the motor is decelerated via a worm reducer, and this reduced rotational force is applied to the steering shaft as a steering assist force. The worm speed reducer includes a worm coupled to a rotating shaft of a motor and a worm wheel provided on the steering shaft so as to be integrally rotatable. These worms and worm wheels are accommodated in a housing (see, for example, Patent Document 1).

Japanese Patent Laid-Open No. 11-171027

  In the conventional general worm speed reducer including Patent Document 1, grease is applied to the meshing portion between the worm and the worm wheel in order to ensure lubrication between them. However, there is a risk that the grease may flow to other parts than the meshing part and escape through the meshing of the worm and the worm wheel. For example, the worm is rotatably supported inside the housing via a bearing, and the outer diameter of the bearing is usually larger than the outer diameter of the worm. For this reason, a gap corresponding to the difference between the outer diameter of the worm and the outer diameter of the bearing is formed between the housing and the worm. When the grease in the meshing portion escapes into the gap, the lubrication effect of the meshing portion may decrease over time. If the proper lubrication state of the meshing part is not maintained, smooth transmission of the steering assist force is hindered, so that the driver feels a so-called catching feeling (steering torque ripple), which also reduces the steering feeling. Connected.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a worm speed reducer and an electric power steering device that can suitably maintain the lubrication of the meshing portion between the worm and the worm wheel. There is to do.

  According to a first aspect of the present invention, there is provided a worm speed reducer comprising a worm rotatably provided inside a housing via a bearing and a worm wheel meshing with the worm, wherein the worm and the bearing are accommodated and held. The gist is provided with a worm collar accommodated in a housing, and the worm collar is formed by opening a portion corresponding to a meshing portion between the worm and the worm wheel.

  In order to ensure smooth operation of the worm speed reducer, grease is applied to the meshing portions of the worm and the worm wheel. When the worm collar of the present invention is not present, there is a concern that the grease applied to the meshing portion escapes from the gap between the outer peripheral surface of the bearing and the outer peripheral surface of the worm. In this regard, according to the present invention, the gap is filled with the warm collar. For this reason, the part which grease escapes can be decreased. Therefore, since it becomes difficult for the grease to escape from the meshing portion, the lubrication of the meshing portion between the worm and the worm wheel by the grease is suitably maintained. The clearance between the outer periphery of the worm and the inner peripheral surface of the worm collar is preferably set smaller. This is because there are fewer parts where grease can escape.

  According to a second aspect of the present invention, the first bearing that supports the first end portion of the worm is fixed inside the worm collar, while the second bearing that also supports the second end portion is The worm collar is fitted to the inside of the housing outside the worm collar, and the worm collar is provided so as to be tiltable with a portion supported by the second bearing of the worm as a fulcrum. The gist thereof is that an urging mechanism that constantly urges toward the side is provided.

  According to the present invention, the gap between the worm and the worm wheel can be reduced by constantly urging the worm collar toward the worm wheel. Lubrication between the worm and the worm wheel is also preferably maintained.

  According to a third aspect of the present invention, in the worm speed reducer according to the second aspect, the urging mechanism is held in a compressed state by passing through the housing and contacting the outer peripheral surface of the worm collar. The gist is provided with an elastic body that applies an elastic force toward the worm wheel to the worm collar, and a flat portion is formed at a contact portion of the elastic body in the worm collar.

  According to the present invention, the elastic force of the elastic member is applied through the flat portion of the worm collar, so that the worm collar is suitably biased toward the worm wheel. Compared to the case where an elastic force is applied to a curved surface, a stable elastic force is easily applied.

  According to a fourth aspect of the present invention, in the worm speed reducer according to any one of the first to third aspects, a cylindrical worm wheel collar interposed between the worm wheel and the housing is provided. An opening is formed at a portion corresponding to the meshing portion of the worm wheel collar, and a grease reservoir for storing grease is provided in the vicinity of the opening on the inner peripheral surface of the worm wheel collar. This is the gist.

  According to the present invention, it is conceivable that the grease in the meshed portion between the worm and the worm wheel tends to escape in the rotational direction of the worm wheel, and the grease to escape is trapped in the grease reservoir. Then, the grease staying in the grease reservoir is supplied to the meshing portion of the worm and the worm wheel, so that the meshing portion is suitably kept in lubrication.

  According to a fifth aspect of the present invention, in the worm speed reducer according to any one of the first to fourth aspects, the housing can pass through a rotating shaft that rotates integrally with the worm wheel, and A detection device for detecting the rotation state of the rotation shaft can be attached, and a window for grease application for exposing the meshing portion to the outside is formed through the worm collar and the housing, respectively, The gist is that the detection device is closed by being attached to the housing.

  According to the present invention, grease is applied to the meshing portion between the worm and the worm wheel through the window that penetrates the housing and the worm collar. The window is preferably closed after the grease is applied. According to the invention, the window is closed by attaching the detection device to the housing. The assembly operation of the worm speed reducer is simpler than the case where the operation of attaching the detection device and the operation of closing the window with some member are performed separately.

The gist of the sixth aspect of the present invention is that the electric power steering apparatus includes the worm speed reducer according to any one of the first to fifth aspects.
The worm speed reducer according to any one of claims 1 to 5 is suitable as a speed reduction mechanism for an electric power steering apparatus.

  According to the present invention, since the escape of grease at the meshing portion between the worm and the worm wheel is suppressed, the lubrication at the meshing portion can be suitably maintained.

The block diagram which shows schematic structure of an electric power steering apparatus. Sectional drawing of a worm reduction gear. The disassembled perspective view of a worm reduction gear. The perspective view of a sensor unit and a worm reduction gear. The perspective view which shows the state which assembled | attached the sensor unit and the worm reduction gear. (A) is a perspective view of a worm unit, (b) is an exploded perspective view of a worm unit. The perspective view of a worm wheel collar.

Hereinafter, an embodiment in which the present invention is embodied in an electric power steering apparatus will be described with reference to FIGS.
<Outline of electric power steering device>
As shown in FIG. 1, in the electric power steering apparatus 1, a steering shaft 3 that rotates integrally with a handle 2 (steering wheel) is connected in order of a column shaft 8, an intermediate shaft 9, and a pinion shaft 10 from the handle 2 side. Become. The pinion shaft 10 is meshed with a rack portion 5a of a rack shaft 5 provided orthogonal to the pinion shaft 10. The rotation of the steering shaft 3 accompanying the steering operation is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4 including the pinion shaft 10 and the rack portion 5a. The reciprocating linear motion is transmitted to a knuckle arm (not shown) via tie rods 11 connected to both ends of the rack shaft 5, thereby changing the steering angle of the steered wheels 12.

  In addition, the electric power steering device 1 includes a steering force assist device (power assist unit) 13 that applies an assist force for assisting a steering operation to the steering system, and an electronic control device that controls the operation of the steering force assist device 13 ( ECU) 14.

  A motor 15, which is a drive source of the steering force assisting device 13, is operatively connected to the column shaft 8 via a speed reduction mechanism 18 including a worm 16 and a worm wheel 17. The rotational force of the motor 15 is decelerated by the speed reduction mechanism 18, and this reduced rotational force is transmitted as an assist force to the steering system, more precisely to the column shaft 8. The electronic control unit 14 controls the assist force as follows. That is, the electronic control unit 14 acquires the vehicle speed V through the vehicle speed sensor 19 provided on the steered wheels 12 and the like, and acquires the steering torque τ applied to the handle 2 through the torque sensor 7 provided on the column shaft 8. The electronic control unit 14 calculates a target assist force based on the vehicle speed V and the steering torque τ, and performs power feeding control of the motor 15 so as to generate the calculated target assist force. The assist force applied to the steering system is controlled through the power supply control of the motor 15.

<Deceleration mechanism>
Next, an outline of the speed reduction mechanism 18 will be described. As shown in FIG. 2, the housing 20 of the speed reduction mechanism 18 includes first, second, and third accommodating portions 21, 22, and 23. The first accommodating portion 21 is formed so as to open to the side portion (right side portion in the drawing) of the housing 20. The second accommodating portion 22 is formed in a cylindrical shape that communicates with the inner bottom portion of the first accommodating portion 21 and extends toward the opposite side (left side in the drawing) from the first accommodating portion 21. Further, in the second accommodating portion 22, the end opposite to the first accommodating portion 21 is open to the outside of the housing 20. The opened portion is closed by the lid 24. The third housing portion 23 is formed in a bottomed cylindrical shape extending in a direction perpendicular to the central axis of the second housing portion 22 (a direction perpendicular to the paper surface). Further, the third housing portion 23 communicates with the second housing portion 22 in a positional relationship in which the central axis of the third housing portion and the central axis of the second housing portion 22 are not twisted, that is, not parallel to each other. is doing.

  As shown in FIG. 3, a rectangular cutout window 25 is formed in a portion of the peripheral wall of the second housing portion 22 on the same side as the opening direction of the third housing portion 23. The cutout window 25 is continuous with the inside of the third housing portion 23. In the second housing part 22, a screw hole 26 is formed at the end opposite to the first housing part 21. The screw hole 26 opens in the direction opposite to the third housing portion 23. A hole 27 through which the column shaft 8 can be inserted is formed at the center of the bottom wall of the third housing portion 23.

  As shown in FIG. 2, the motor 15 is fixed to the first housing portion 21. A part of the output shaft 15 a and the main body 15 b of the motor 15 is maintained in a state of being inserted into the first housing portion 21.

  As shown in FIG. 3, a worm unit 30 having a cylindrical shape as a whole is accommodated in the second accommodating portion 22. The worm unit 30 includes the worm 16 described above. The worm 16 is provided in a state where a part including the central portion is exposed to the outside. The worm 16 is rotatably supported with respect to the second housing portion 22 and is connected to the output shaft 15 a of the motor 15 via the shaft coupling 40. Further, the worm unit 30 is constantly urged toward the third housing portion 23 by the urging mechanism 50.

  The worm wheel 17 is rotatably accommodated in the third accommodating portion 23. The worm wheel 17 meshes with the worm 16 via the communicating portions of the second and third accommodating portions 22 and 23. Further, as shown in FIG. 3, a cylindrical worm wheel collar 60 having an annular bottom portion is attached to the third housing portion 23. The worm wheel collar 60 covers the peripheral edge of the worm wheel 17. The worm wheel 17 is connected with the previous column shaft 8 passing therethrough.

  Therefore, the rotational force of the column shaft 8 is transmitted to the worm 16 via the worm wheel 17 in a state where no torque is generated in the motor 15. Further, the rotational force of the motor 15 is transmitted to the column shaft 8 via the worm 16 and the worm wheel 17.

  As shown in FIG. 4, the opening of the third housing portion 23 and the cutout window 25 are closed by the sensor housing 70 of the torque sensor 7. Further, the worm unit 30, the shaft coupling 40, the urging mechanism 50, the worm wheel collar 60, and the sensor housing 70 will be described in detail later.

<Warm unit>
Next, the worm unit will be described in detail. As shown in FIG. 6A, the worm unit 30 includes a worm 16, a worm collar 31, a first bearing 32, a second bearing 33, and a first joint 34 that constitutes the shaft coupling 40. It is assembled.

  As shown in FIG. 6B, the worm collar 31 is formed in a cylindrical shape with both ends opened, and its inner diameter is set slightly larger than the outer diameter of the worm 16. The inner diameter of the worm collar 31 is preferably set as small as possible within a range not interfering with the worm 16. An elliptical through hole 38 is formed in the central portion in the direction along the central axis of the worm collar 31. The through hole 38 is formed over a certain range along the central axis of the worm collar 31. The cut surface of the through hole 38 has a shape along a curved surface that protrudes toward the central axis of the worm collar 31. Further, the worm collar 31 is formed with a rectangular cutout window 35 continuing to the through hole 38. In the worm collar 31, the cutout window 35 is formed corresponding to the central portion of the through hole 38 in the long axis direction. The length of the cutout window 35 in the direction along the central axis of the worm collar 31 is set to be smaller than the length of the through hole 38 in the direction along the central axis of the worm collar 31. Further, in the first end portion (the lower end portion in FIG. 6B) of the worm collar 31, the portion opposite to the portion where the through hole 38 is formed is as shown in FIG. 6A. A cylindrical recess 36 is formed.

  A first bearing 32 is fixed to the first end of the worm collar 31 by being press-fitted. A worm 16 is inserted into the worm collar 31. The first end 16 a of the worm 16 is supported so as to be rotatable with respect to the worm collar 31 via the first bearing 32. A part of the tooth portion of the worm 16 is exposed to the outside through the through hole 38 and the cutout window 35. As shown in FIG. 2, the second end portion 16 b opposite to the first end portion 16 a of the worm 16 protrudes outside the worm collar 31. The second bearing 33 is fixed to the second end portion 16b by being press-fitted. The second end portion 16b also protrudes from the second bearing 33, and the first joint 34 is fixed to the protruding portion. The second end portion 16 b is connected to the output shaft 15 a of the motor 15 through a shaft coupling 40 configured to include the first joint 34.

  As shown in FIG. 2, the worm unit 30 is inserted into the second housing portion 22 through the first housing portion 21 with the end portion on the first bearing 32 side facing the second housing portion 22. Is done. The second bearing 33 is fitted with play in a portion near the first housing portion 21 on the inner peripheral surface of the second housing portion 22. Thereby, the worm unit 30 is held so as to be slightly swingable inside the second housing portion 22. A cylindrical fixed plug 37 is attached to the opening of the second storage portion 22 on the first storage portion 21 side. The distal end portion of the fixed plug 37 is in contact with the outer ring of the second bearing 33. Thereby, the displacement toward the motor 15 of the 2nd bearing 33 and by extension, the worm unit 30 is controlled. The worm unit 30 is suitably held inside the second housing portion 22.

  As shown in FIG. 2, in a state where the worm unit 30 is housed in the second housing portion 22, between the outer circumferential surface of the worm collar 31 and the inner circumferential surface of the second housing portion 22, A slight gap is formed. Further, the through hole 38 of the worm collar 31 opens toward the third housing portion 23 side. That is, the inside of the worm collar 31 and the inside of the third housing portion 23 communicate with each other through the through hole 38. The worm wheel 17 is engaged with the worm 16 through the through hole 38. Further, the recess 36 of the worm collar 31 coincides with the screw hole 26 of the housing 20.

<Shaft coupling>
Next, the shaft coupling 40 will be described. As shown in FIG. 2, the shaft coupling 40 includes a first joint 34, a second joint 41, and an elastic body 42 interposed between the first and second joints 34 and 41. . A plurality of engaging claws 34 a are formed on the side surface of the first joint 34 opposite to the worm 16. The second joint 41 is connected to the output shaft 15a of the motor 15 so as to be integrally rotatable, and a plurality of engagement claws 41a are formed on the side surface opposite to the motor 15. On the outer peripheral surface of the elastic body 42, a plurality of engagement recesses 42 a that engage with the engagement claws 34 a of the first joint 34 and a plurality of engagement recesses that engage with the engagement claws 41 a of the second joint 41. 42b are alternately formed around the central axis of the elastic body 42. When the engaging claws 34a and 41a are engaged with the engaging recesses 42a and 42b, torque can be transmitted between the worm 16 and the output shaft 15a. The elastic body 42 is maintained in a slightly compressed state by the first and second joints 34 and 41, and the elastic body 42 is elastically deformed, so that the worm unit 30 is tilted with respect to the output shaft 15a. Permissible. That is, the worm unit 30 tilts with respect to the central axis of the output shaft 15a around the portion of the worm 16 supported by the second bearing 33.

<Burning mechanism>
Next, the urging mechanism 50 will be described. As shown in the enlarged lower right of FIG. 3, the urging mechanism 50 includes a head 51 in which a hexagonal hole is formed, a male screw part 52 formed on the opposite side of the hexagonal hole of the head 51, and a male screw part 52. And a compression coil spring 53 provided at the tip of each. The outer diameter of the head 51 is set larger than the inner diameter of the screw hole 26 of the housing 20. The outer diameters of the male screw portion 52 and the compression coil spring 53 are set smaller than the inner diameter of the screw hole 26, respectively. Further, the outer diameter of the compression coil spring 53 is set smaller than the inner diameter of the recess 36 of the worm collar 31.

  As shown in FIG. 2, in the state where the worm unit 30 is inserted into the second housing portion 22, the male screw portion 52 is inserted while the compression coil spring 53 is inserted into the recess 36 of the worm collar 31 through the screw hole 26. Is tightened into the screw hole 26. Accordingly, the tip of the compression coil spring 53 gradually approaches the inner bottom surface of the recess 36 and eventually comes into contact with the inner bottom surface. When the male screw portion 52 is further tightened, the compression coil spring 53 is gradually compressed accordingly. The worm unit 30 is constantly urged toward the worm wheel 17 by the elastic force of the compression coil spring 53.

  The worm unit 30 tends to tilt counterclockwise in FIG. 2 around a portion supported by the second bearing 33 in the worm 16 (more precisely, the second end portion 16b). The tilt of the worm unit 30 is regulated by the worm 16 coming into contact with the worm wheel 17. By pressing the worm 16 against the worm wheel 17 in this way, it is possible to reduce the amount of backlash at the meshing portion of the worm 16 and the worm wheel 17. Further, it is assumed that the teeth of the worm 16 and the worm wheel 17 are worn over time. Even in this case, the worm unit 30 (worm 16) is tilted by the worn amount, so that the worm 16 and the worm 16 An increase in backlash at the meshing portion of the wheel 17 is suppressed.

  Thus, the urging mechanism 50 constantly urges the worm unit 30 toward the worm wheel 17 so that the distance between the rotation centers of the worm 16 and the worm wheel 17 is adjusted or maintained appropriately.

<Warm wheel color>
Next, the worm wheel collar 60 will be described. As shown in FIG. 7, the worm wheel collar 60 includes a cylindrical portion 61 having both ends opened, and an annular plate-like wall 62 provided on the inner peripheral edge of one opening of the cylindrical portion 61. The outer diameter of the cylindrical portion 61 is slightly smaller than the inner diameter of the third housing portion 23, and the inner diameter is also set slightly larger than the outer diameter of the worm wheel 17. In addition, an elliptical through hole 63 is formed in the cylindrical portion 61. The length of the long axis of the through hole 63 is set larger than the axial length of the through hole 38 of the worm collar 31. Further, the length of the short axis of the through hole 63 is set larger than the outer diameter of the worm 16.

  The worm wheel collar 60 is lightly press-fitted with the end opposite to the wall 62 facing the third accommodating portion 23. At this time, as shown in FIG. 2, the worm wheel collar 60 is mounted in the third housing portion 23 so that the through hole 63 thereof coincides with the through hole 38 of the worm collar 31. The cylindrical portion 61 is maintained in a state of being interposed between the outer peripheral portion of the worm wheel 17 and the inner peripheral surface of the third housing portion 23. Further, as shown in FIG. 4, the wall 62 is held in a state of covering the peripheral edge of the side surface exposed to the outside of the worm wheel 17.

  The worm wheel 17 meshes with the worm 16 through the through hole 63 of the worm wheel collar 60 and the through hole 38 of the worm collar 31. Since the worm wheel 17 does not interfere with the worm wheel collar 60 or the worm collar 31, the meshing state between the worm 16 and the worm wheel 17 is preferably maintained.

  Further, as shown in FIG. 7, a grease reservoir 64 is formed in the vicinity of the through hole 63 on the inner peripheral surface of the cylindrical portion 61. The grease reservoir 64 is composed of a number of concave grooves 65. In this example, two grease reservoirs 64 are provided on both sides of the through hole 63 along the rotation direction of the worm wheel 17 on the inner peripheral surface of the cylindrical portion 61.

<Sensor housing>
Next, the sensor housing 70 will be described. The sensor housing 70 holds various components of the torque sensor 7 such as an input shaft (not shown), a lower shaft, a torsion bar that connects these shafts, and a rotation angle sensor that detects the rotation angles of both shafts. The input shaft is connected to the handle 2 side portion of the column shaft 8, and the lower shaft is connected to the intermediate shaft 9 portion of the column shaft 8.

  As shown in FIG. 4, the sensor housing 70 includes a lid member 71 that closes the opening of the third housing portion 23, a sensing unit 72 provided on the surface of the lid member 71 (the left side surface in FIG. 4), and sensing The cylindrical support part 73 formed in the front end surface of the part 72 is provided. An input shaft or the like is inserted into the support portion 73. The outer diameter of the lid member 71 is set to be approximately the same as the outer diameter of the third housing portion 23. Further, a cover 74 is formed on the outer peripheral surface of the lid member 71 so as to project sideways. The cover 74 is formed in a rectangular shape that fits into the cutout window 25 of the housing 20.

  The sensor housing 70 is attached to the housing 20 so as to close the third housing portion 23 with the lid member 71 while making the cover 74 coincide with the cutout window 25 of the housing 20. Then, as shown in FIG. 5, the cover 74 just fits into the cutout window 25 when the back surface of the lid member 71 comes into contact with the opening edge of the third housing portion 23. Thus, the cutout window 25 is closed by the cover 74. In this state, the sensor housing 70 is fixed to the housing 20 by inserting and tightening the bolts 75 into the bolt insertion holes 71 a of the sensor housing 70.

<Assembly method of reduction mechanism>
Next, a method for assembling the speed reduction mechanism 18 will be described.
First, the worm unit 30 is assembled. That is, the first bearing 32 is press-fitted into the worm collar 31. Then, the worm 16 is inserted from the end of the worm collar 31 opposite to the first bearing 32, and the first end 16 a of the worm 16 is press-fitted into the first bearing 32. Then, the second bearing 33 and the first joint 34 are attached to the second end 16b of the worm 16, respectively. Thus, the assembly operation of the worm unit 30 is completed.

  Next, the assembled worm unit 30 is attached to the second accommodating portion 22. Further, the worm wheel 17 and the worm wheel collar 60 are respectively attached to the third housing portion 23 of the housing 20. Thereafter, the urging mechanism 50 is attached to the housing 20. That is, the male screw portion 52 is fastened to the screw hole 26 by rotating the head portion 51 using a hexagonal bar spanner or the like. As a result, the end of the worm unit 30 on the first bearing 32 side is always biased toward the worm wheel 17 by the elastic force of the compression coil spring 53.

Next, grease is applied to a meshing portion between the worm 16 and the worm wheel 17 through the cutout window 25 of the housing 20 and the cutout window 35 of the worm collar 31.
Finally, the sensor housing 70 is fixed to the housing 20. The assembly work of the speed reduction mechanism 18 is thus completed.

<Effect of Embodiment>
Therefore, according to the present embodiment, the following effects can be obtained.
(1) The worm 16, the first bearing 32, the second bearing 33, and the worm collar 31 are integrally provided to constitute a single worm unit 30. The worm unit 30 is attached to the second accommodating portion 22 of the housing 20. The presence of the worm collar 31 between the worm 16 and the inner peripheral surface of the housing 20 (second housing portion 22) reduces the space where grease can escape. Since the portion of the grease applied to the meshing portion between the worm 16 and the worm wheel 17 can be reduced, the grease is prevented from escaping to a portion other than the meshing portion. As a way for grease to escape, there is only a through hole 38 which is a portion corresponding to the meshing portion of the worm collar 31. This also contributes to concentrated lubrication at the meshing portion. Therefore, the lubrication of the meshing portion between the worm 16 and the worm wheel 17 is suitably maintained.

  (2) The urging mechanism 50 always urges the worm unit 30 toward the worm wheel 17. From the viewpoint of weight reduction, the worm wheel 17 may be formed of a synthetic resin. In particular, in this case, there is a concern that the gap between the worm wheel 17 and the worm 16 may increase due to wear of the teeth of the worm wheel 17 over time. In this case, there is a risk that lubrication of the meshing portion may be impaired due to the escape of grease through the gap. In this regard, by always applying an appropriate load toward the meshing portion of the worm 16 and the worm wheel 17 to the worm unit 30 (more precisely, the end of the first bearing 32), the meshing portion The lubrication state is maintained well. This is because, even when the worm wheel 17 is worn, the worm 16 (worm unit 30) tilts so as to eliminate a gap (backlash or the like) with the worm wheel 17 along with the wear. Further, since the backlash between the worm 16 and the worm wheel 17 is always maintained, the occurrence of rattling due to the aging of the worm wheel 17 is also suppressed. As a result, an increase in operating noise of the speed reduction mechanism 18 or torque fluctuation is also suppressed.

  (3) A recess 36 is provided in the worm collar 31. A pressing force in the meshing direction is applied to the worm collar 31 through the recess 36. That is, the compression coil spring 53 of the urging mechanism 50 is inserted into the recess 36 and the elastic force of the compression coil spring 53 is applied to the worm collar 31 via the inner bottom surface of the recess 36. Compared with the case where the elastic force of the compression coil spring 53 is applied to the curved surface portion, the worm unit 30 can be reliably and sufficiently pressed toward the worm wheel 17. In addition, a stable load can be applied to the worm unit 30.

  (4) A cutout window 35 is formed in the worm collar 31. Further, a cutout window 25 corresponding to the cutout window 35 is formed in the second housing portion 22 into which the worm unit 30 is inserted. For this reason, the grease can be easily applied to the meshing portions of the worm 16 and the worm wheel 17 through the cutout window 25 and the cutout window 35. In the speed reduction mechanism 18, a portion where lubrication is required is a meshing portion of the worm 16 and the worm wheel 17. The technique of directly applying grease to the meshing portion is optimal for the speed reduction mechanism 18. And since grease can be intensively applied to the meshing portion where lubrication is required, the amount of grease required can be reduced. For example, there is a technique in which grease is distributed and applied in a plurality of locations along the circumferential direction of the worm wheel 17, but the amount of grease required is smaller than that of the technique.

  Conventionally, there is also a method of enclosing grease in the entire circumferential direction of the worm wheel. In this method, grease is appropriately encapsulated in the meshing portion between the worm 16 and the worm wheel 17 that originally needs lubrication. Difficult to do. In this regard, according to the present example, it becomes possible to easily and appropriately enclose the grease in the meshing portion described above through the notch window 25 and the notch window 35.

  (5) A cover 74 that closes the cutout window 25 of the housing 20 is formed on the torque sensor 7 that is attached to the housing 20, more precisely, the sensor housing 70. For this reason, the notch window 25 can be closed by attaching the torque sensor 7 to the housing 20. Although it is conceivable that the cover 74 is configured as a separate member from the sensor housing 70 and the cover 74 and the sensor housing 70 are separately attached to the housing 20, the speed reduction mechanism 18 of the speed reduction mechanism 18 can be compared with this case. The number of assembly work steps can be reduced.

  (6) The worm wheel collar 60 is lightly press-fitted into the third housing portion 23. For this reason, rattling of the worm wheel collar 60 due to the operation of the speed reduction mechanism 18 is suppressed. This contributes to a reduction in operating noise of the speed reduction mechanism 18.

  (7) A grease reservoir 64 is provided in the vicinity of the through hole 63 of the worm wheel collar 60, that is, in the vicinity of the meshing portion of the worm 16 and the worm wheel 17. With the operation of the speed reduction mechanism 18, the grease filled in the meshing portion of the worm 16 and the worm wheel 17 gradually flows in the rotation direction of the worm wheel 17, and the flowed grease enters each groove 65 of the grease reservoir 64. Accumulate. Thereby, the grease applied to the meshing portion of the worm 16 and the worm wheel 17 is prevented from escaping in the rotational direction of the worm wheel 17. Further, when the grease accumulated in the grease reservoir 64 is supplied to the meshing portion of the worm 16 and the worm wheel 17, the lubrication state of the meshing portion is suitably maintained.

<Other embodiments>
The embodiment described above may be modified as follows.
In the worm wheel collar 60, the annular wall 62 may be omitted. That is, the worm wheel collar 60 is formed in a cylindrical shape with both ends opened. Even in this case, the grease reservoir 64 can be formed in the vicinity of the through-hole 63, and the lubrication of the meshing portion between the worm 16 and the worm wheel 17 can be suitably maintained.

  The first joint 34 may not be a component of the worm unit 30. That is, the first joint 34 or the shaft coupling 40 may be mounted after the worm unit 30 in the state where the first joint 34 is not attached is accommodated in the second accommodating portion 22.

  In place of the compression coil spring 53, an elastic body such as rubber may be employed. The worm unit 30 can be biased toward the worm wheel 17 by the elasticity of the elastic body.

  In this example, the worm unit 30 is pressed through the recess 36 of the worm collar 31, but the recess 36 may be omitted. In this case, for example, a flat portion is formed in the portion where the recess 36 of the worm collar 31 was formed. Even if the elastic force of the compression coil spring 53 is applied through this flat portion, the same effect as (3) of this example can be obtained.

  In addition, the concave portion 36 or the flat portion can be omitted. That is, the elastic force of the compression coil spring 53 may be applied to the outer peripheral surface (curved surface) of the worm collar 31. Even in this case, the worm unit 30 can be pressed toward the worm wheel 17 to some extent. Further, as a means for pressing the worm unit 30, an annular leaf spring or the like can be employed instead of the compression coil spring 53.

The worm wheel collar 60 may be omitted. Even if it does in this way, the effect similar to (1)-(5) of this example can be acquired.
-The biasing mechanism 50 may be omitted. In this case, the screw hole 26 of the housing 20 (second housing portion 22) and the recess 36 of the worm collar 31 can be omitted. Even in this case, the gap between the worm 16 and the inner peripheral surface of the housing 20 (second housing portion 22) is filled with the worm collar 31, so that the worm 16 and the worm wheel 17 are applied to the meshing portion. It is possible to suppress escape of the applied grease.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus, 7 ... Torque sensor (detection apparatus), 8 ... Column shaft (rotary shaft), 16 ... Worm, 16a ... 1st edge part, 16b ... 2nd edge part, 17 ... Worm wheel, DESCRIPTION OF SYMBOLS 18 ... Deceleration mechanism (worm reduction gear), 20 ... Housing, 25, 35 ... Notch window, 31 ... Worm collar, 32 ... 1st bearing, 33 ... 2nd bearing, 36 ... Recessed part (flat part), 50 ... Energizing mechanism, 53 ... compression coil spring (elastic body), 60 ... worm wheel collar, 63 ... through hole (opening), 64 ... grease reservoir (grease reservoir).

Claims (6)

In a worm speed reducer comprising a worm rotatably provided inside a housing via a bearing and a worm wheel meshing with the worm,
A worm speed reducer comprising a worm collar accommodated in the housing in a state in which the worm and the bearing are accommodated and held, wherein the worm collar has an opening corresponding to a meshing portion between the worm and the worm wheel. The worm reducer according to claim 1,
A first bearing that supports the first end of the worm is secured within the worm collar, while a second bearing that also supports the second end is external to the worm collar of the housing. After fitting inside, the worm collar is provided so as to be tiltable with a portion supported by the second bearing of the worm as a fulcrum,
A worm speed reducer comprising a biasing mechanism that constantly biases the worm collar toward the worm wheel. The worm reducer according to claim 2,
The biasing mechanism is held in a compressed state by passing through the housing and contacting the outer peripheral surface of the worm collar, and applies an elastic force toward the worm wheel to the worm collar. With
A worm speed reducer in which a flat portion is formed at a contact portion of the elastic body in the worm collar. In the worm speed reducer as described in any one of Claims 1-3,
A cylindrical worm wheel collar interposed between the worm wheel and the housing; an opening is formed in a portion corresponding to the meshing portion of the worm wheel collar; and an inner periphery of the worm wheel collar A worm reducer in which a grease reservoir for collecting grease is provided in the vicinity of the opening on the surface. In the worm reduction gear according to any one of claims 1 to 4,
The housing is capable of penetrating a rotating shaft that rotates integrally with the worm wheel, and can be attached with a detection device that detects the rotation state of the rotating shaft, and is used for grease application that exposes the meshing portion to the outside. A worm speed reducer in which a window is formed through each of the worm collar and the housing, and the window is closed when the detection device is attached to the housing.   An electric power steering apparatus comprising the worm speed reducer according to any one of claims 1 to 5.

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