JP2014019291A - Actuator unit and vehicular steering device including the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an actuator unit capable of suppressing the generation of an abnormal sound for a long time while enabling a smooth movement of a worm shaft in the axial direction, and a vehicular steering device including the same.SOLUTION: A worm shaft 24 is accommodated inside a worm shaft accommodation part 32 of a housing 31 in such a manner that it is movable in the axial direction, and a cylindrical resin member 49 having self-lubricating property is provided on the outer periphery of a second bearing 38 which rotatably supports the other end part 24b of the worm shaft 24. A spring member 42, which energizes the other end part 24b of the worm shaft 24, includes: a pair of base parts 71 arranged in the circumferential direction of the second bearing 38 at an interval; and a curved spring part 72 which connects the pair of base parts 71 with each other and which elastically deforms by coming into contact with the resin member 49.

Description

  The present invention relates to an actuator unit and a vehicle steering apparatus including the actuator unit.

  2. Description of the Related Art Conventionally, there is an actuator unit that decelerates and outputs the rotation of a motor by a worm reducer formed by meshing a worm shaft and a worm wheel. Such an actuator unit is used, for example, as a steering force assisting device that generates an assist force for assisting a driver's steering operation in a vehicle steering device.

  By the way, in the vehicle steering apparatus provided with the actuator unit as described above, a rattling noise may occur, for example, when the steering direction is switched due to the backlash of the worm speed reducer. Therefore, in this type of actuator unit, one end of the worm shaft is tiltably connected to the motor shaft, and the other end is biased to tilt the worm shaft so as to be close to the worm wheel. There is one that removes backlash (for example, Patent Document 1). In Patent Document 1, a curved leaf spring that is curved so as to surround the outer periphery of a bearing that rotatably supports the other end of the worm shaft is used as a member that tilts the worm shaft.

  Specifically, as shown in FIG. 6, the curved leaf spring 91 includes an arcuate arc portion 93 that contacts the outer ring 92 a of the bearing 92, and a bend that bends radially outward from both circumferential ends of the arc portion 93. A portion 94 and a spring portion 95 extending in the circumferential direction from the tip of the bent portion 94 are provided. The housing 97 that houses the worm shaft 96 is formed with a housing recess 98 that houses the spring portion 95. The curved leaf spring 91 urges the worm shaft 96 via the bearing 92 by the spring portion 95 coming into contact with the bottom surface 98a of the housing recess 98 and elastically deforming.

Japanese Patent Laid-Open No. 2004-203154 JP 2012-101649 A

  However, in the configuration of Patent Document 1 described above, when steering is performed in a minute range where no assist force is applied, the worm shaft is not driven by the motor, so the worm shaft is rotated by the worm wheel that is rotated by the driver's steering. It will be. Therefore, the driver cannot steer without applying a torque exceeding the frictional force (static frictional force) acting between the worm shaft and the worm wheel at the start of steering, which is a so-called catching feeling. As a result, there is a risk of lowering the steering feeling during minute steering.

  In consideration of this point, in recent years, a vehicle steering apparatus has been proposed in which a worm shaft is supported in a housing so as to be movable in the axial direction (for example, Patent Document 2). In this vehicle steering apparatus, since the worm shaft moves in the axial direction, the worm wheel rotates without rotating the worm shaft, so that the feeling of catching can be reduced.

  Here, in order to ensure smooth axial movement of the worm shaft, it is conceivable to provide a cylindrical resin member having self-lubricating properties on the outer periphery of the bearing supporting the other end. However, in the conventional curved leaf spring 91, the circumferential end of the arc portion 93 serves as a fulcrum when the spring portion 95 is elastically deformed, and the elastic force generated in the spring portion 95 is indicated by a thick arrow in FIG. As shown in FIG. 3, the circular arc portion 93 is concentrated on the circumferential end portion via the bent portion 94. Therefore, when a resin member is attached to the outer periphery of the bearing 92, a portion of the resin member that contacts the circumferential end of the arc portion 93 is likely to be worn. When the wear amount of the resin member is increased, the deformation amount of the spring portion 95 is decreased, so that the worm shaft cannot be sufficiently biased, and there is a possibility that abnormal noise is generated.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to enable smooth movement of the worm shaft in the axial direction and suppress the generation of abnormal noise over a long period of time. An object of the present invention is to provide an actuator unit and a vehicle steering apparatus including the actuator unit.

  In order to achieve the above object, an invention according to claim 1 includes a motor, a worm shaft coupled to the motor via a shaft joint so as to be tiltable, and a worm reduction gear having a worm wheel meshing with the worm shaft. An actuator unit comprising: a housing that houses the worm speed reducer; and a spring member that biases the other end of the worm shaft opposite to the one end connected to the motor toward the worm wheel. The worm shaft is accommodated in the housing so as to be movable in the axial direction of the worm shaft, and a resin member having a self-lubricating property is provided on an outer periphery of a bearing that rotatably supports the other end portion. The spring member connects the pair of bases arranged at intervals in the circumferential direction of the bearing and the pair of bases and the tree. In contact with the manufacturing member and summarized in that and a curved spring portion elastically deformed.

  According to the above configuration, since the resin member is provided on the outer periphery of the bearing, the worm shaft can be smoothly moved in the axial direction. Further, the curved spring portion of the spring member is elastically deformed in contact with the resin member, thereby directly applying an elastic force to the resin member and biasing the other end portion of the worm shaft. And the curved spring part is formed so as to connect between a pair of base parts arranged at intervals in the circumferential direction of the bearing, and it becomes possible to contact over a wide range of the resin member. It can suppress that the elastic force of a spring member (bending spring part) concentrates on a part of resin-made members. As a result, the resin member is less likely to be worn, and the elastic force of the spring member can be maintained over a long period of time, and the generation of abnormal noise (tooth rattling noise) can be suppressed.

  The invention according to claim 2 is characterized in that, in the actuator unit according to claim 1, the spring member has a detent portion for restricting rotation of the spring member by engaging with the housing. .

According to the above configuration, since the rotation of the spring member around the bearing can be restricted, the other end portion of the worm shaft can be stably biased toward the worm wheel.
The gist of a third aspect of the invention is a vehicle steering apparatus that generates an assist force for assisting a steering operation by the actuator unit according to the first or second aspect.

  According to the above configuration, since the worm shaft can be smoothly moved in the axial direction by the resin member, it is possible to realize a good steering feeling by reducing the feeling of catching, and the resin member is less likely to be worn. Generation of abnormal noise can be suppressed by maintaining the elastic force of the spring member over a long period of time.

  According to the present invention, it is possible to provide an actuator unit capable of suppressing the generation of abnormal noise over a long period of time while enabling smooth movement of the worm shaft in the axial direction, and a vehicle steering apparatus including the actuator unit. .

1 is a schematic configuration diagram of a vehicle steering apparatus according to an embodiment. The fragmentary sectional view of the steering force auxiliary device of one embodiment. Sectional drawing of the spring member vicinity of one Embodiment (AA sectional drawing of FIG. 2). Sectional drawing (BB sectional drawing of FIG. 2) of the shaft coupling of one Embodiment. Sectional drawing of the spring member vicinity of another example. Sectional drawing of the conventional curved leaf spring vicinity.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in the vehicle steering apparatus 1, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. Thereby, 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. The steering shaft 3 is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. The reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to the knuckle (not shown) via the tie rods 11 connected to both ends of the rack shaft 5, whereby the steering angle of the steered wheels 12, That is, the traveling direction of the vehicle is changed.

  In addition, the vehicle steering apparatus 1 includes a steering force assisting device 21 as an actuator unit that applies an assist force for assisting a steering operation to the steering system. The steering force assisting device 21 includes a motor 22 serving as a drive source, and a worm speed reducer 26 that meshes with a worm shaft 24 connected to the motor 22 and a worm wheel 25 connected to the column shaft 8. That is, the vehicle steering apparatus 1 of the present embodiment is configured as a so-called column assist type electric power steering apparatus. The vehicle steering apparatus 1 is configured to apply the motor torque as an assist force to the steering system by decelerating the rotation of the motor 22 by the worm reducer 26 and transmitting it to the column shaft 8.

Next, the configuration of the steering force assisting device will be described in detail.
As shown in FIG. 2, the steering force assisting device 21 includes a housing 31 that houses the worm speed reducer 26. The housing 31 includes a worm shaft housing portion 32 that houses the worm shaft 24, and a worm wheel housing portion 33 that is formed continuously with the worm shaft housing portion 32 and that houses the worm wheel 25. The worm shaft accommodating portion 32 is a cylindrical space extending in the axial direction (left and right direction in FIG. 2) of the worm shaft 24, and one end side (right side in FIG. 2) has a motor fixing hole 34 to which the motor 22 is fixed. Communicating with Further, the other end side (the left side in FIG. 2) of the worm shaft accommodating portion 32 is opened to the outside and is closed by the end cover 35.

  The motor 22 is fixed to the motor fixing hole 34 so that the axial direction of the motor shaft 36 is orthogonal to the axial direction of the column shaft 8 (steering shaft 3) penetrating the housing 31. The worm shaft 24 connected to the motor shaft 36 is rotatably supported by first and second bearings 37 and 38 provided in the housing 31 at both ends, and is connected to the steering shaft 3. It is meshed with the worm wheel 25. Thereby, the rotation of the motor 22 is decelerated by the worm shaft 24 and the worm wheel 25 and transmitted to the column shaft 8. In the present embodiment, ball bearings are adopted as the first and second bearings 37 and 38, and outer rings 37a and 38a, inner rings 37b and 38b, and balls 37c and 38c interposed therebetween, respectively. It is comprised by.

  Here, the steering force assisting device 21 of the present embodiment includes a backlash adjusting mechanism that removes backlash by adjusting the inter-axis distance between the worm shaft 24 and the worm wheel 25 that constitute the worm speed reducer 26. It has been incorporated. That is, the worm shaft 24 has one end portion (right end portion in FIG. 2) 24a connected to the motor shaft 36 by the shaft coupling 41 so as to be tiltable, and the other end portion (left end portion in FIG. 2) 24b. Is biased by the spring member 42 in the direction approaching the worm wheel 25 (substantially downward in FIG. 2). The worm shaft 24 is housed in the worm shaft housing portion 32 so as to be movable in the axial direction of the worm shaft 24.

  More specifically, the first bearing 37 that supports the one end portion 24a of the worm shaft 24 has a relatively large internal clearance, and the outer ring 37a is radially disposed on the outer periphery of the first bearing 37. A cylindrical member 43 that presses inward is fitted. Thereby, tilting of the one end 24a of the worm shaft 24 is allowed while suppressing the generation of abnormal noise in the first bearing 37. The first bearing 37 is fixed in the worm shaft housing portion 32 by the fixing member 44 together with the cylindrical member 43. The one end 24a of the worm shaft 24 has a large diameter portion 45 formed continuously on one end side of the tooth portion (worm) 24c, and a medium diameter formed continuously on one axial end side of the large diameter portion 45. It has the small diameter part 47 continuously formed in the axial direction one end side of the part 46 and the medium diameter part 46. As shown in FIG. The worm shaft 24 is axially movable with respect to the first bearing 37 (housing 31) by fitting the intermediate diameter portion 46 with a clearance with respect to the inner ring 37b of the first bearing 37. .

  On the other hand, the 2nd bearing 38 as a bearing which supports the other end part 24b of the worm shaft 24 is provided so that the movement to the radial direction and an axial direction is possible. Specifically, the opening 48 on the other end side of the worm shaft housing portion 32 is formed so that its inner diameter is larger than the outer diameter of the second bearing 38. The second bearing 38 is disposed in the opening 48 so as to be spaced from the end cover 35 so as to be movable in the radial direction and the axial direction. Further, as shown in FIG. 3, a cylindrical resin member 49 is provided on the outer periphery of the outer ring 38 a of the second bearing 38. The resin member 49 is subjected to crowning, and is formed so that the central portion in the axial direction is more convex than both ends. The resin member 49 of the present embodiment is made of a self-lubricating resin material such as PTFE (polytetrafluoroethylene) or POM (polyacetal). The other end 24 b of the worm shaft 24 is press-fitted into the inner ring 38 b of the second bearing 38. As a result, the worm shaft 24 moves in the axial direction integrally with the second bearing 38. As described above, the worm shaft 24 is rotatably supported by the first and second bearings 37 and 38 while being allowed to tilt and move in the axial direction with respect to the motor shaft 36.

  In addition, as shown in FIG. 2, dampers 51 are provided at both ends of the first bearing 37. Each damper 51 includes a stopper 52 disposed adjacent to the first bearing 37 and a plate 54 disposed with an elastic body 53 made of an elastic material sandwiched between the stoppers 52. The stopper 52 is formed in an annular shape, and its inner peripheral edge is formed so as to face the large diameter portion 45 of the worm shaft 24 and the fitting portion 62a of the flange boss 62 constituting the shaft coupling 41 described later in the axial direction. Has been. Further, gaps are provided between the stopper 52 and the fitting portion 62a arranged on one end side of the first bearing 37, and between the stopper 52 and the large diameter portion 45 arranged on the other end side, respectively. ing. The elastic body 53 and the plate 54 are each formed in an annular shape, and are fitted to the outer periphery of the fitting portion 62 a or the large diameter portion 45. Therefore, the worm shaft 24 can be moved in the axial direction by compressing the elastic body 53 within this gap, and the worm shaft 24 can be moved in the axial direction by the large diameter portion 45 or the fitting portion 62a coming into contact with the stopper 52. Being regulated. This prevents the worm shaft 24 from moving excessively in the axial direction when the motor 22 is driven.

Next, the configuration of the shaft coupling will be described.
The shaft coupling 41 includes a pair of flange bosses 61 and 62 and a rubber spring 63 made of an elastic material interposed therebetween. The flange bosses 61 and 62 are each formed in a substantially annular shape. The flange boss 61 is fixed so as to rotate integrally with the motor shaft 36 by fitting the fitting portion 61 a to the motor shaft 36, and the flange boss 62 has a fitting portion 62 a that is a small diameter portion 47 of the worm shaft 24. Is fixed to the worm shaft 24 so as to be integrally rotatable. The flange bosses 61 and 62 are formed with a plurality of engaging claws 61b and 62b that protrude in opposite directions. As shown in FIG. 4, the rubber spring 63 has an annular main body 63a and an engaging portion 63b extending from the main body 63a outward in the radial direction. The flange bosses 61 and 62 are assembled so that the engaging claws 61b and 62b are alternately arranged in the circumferential direction, and the rubber spring 63 is engaged between the engaging claws 61b and 62b. Is assembled so that is pinched. Therefore, the shaft coupling 41 is configured to allow the flange boss 62 to tilt with respect to the flange boss 61 by the elastic deformation of the rubber spring 63, that is, to tilt the worm shaft 24 with respect to the motor shaft 36.

Next, the configuration of the spring member will be described in detail.
As shown in FIG. 3, the spring member 42 connects the pair of base portions 71 arranged at intervals in the circumferential direction of the second bearing 38 and the pair of base portions 71 and contacts the resin member 49. And a curved spring portion 72 that is elastically deformed. Specifically, the bases 71 are arranged with an interval of about 180 degrees in the circumferential direction of the second bearing 38. Each base portion 71 is formed in a plate shape in which an end portion (upper end portion in FIG. 3) opposite to the worm wheel 25 is bent, and a corner portion 71 a thereof is an inner periphery of the opening portion 48 of the worm shaft housing portion 32. It is in contact with the surface. The curved spring portion 72 is connected to the end portion of the base 71 on the worm wheel 25 side, and is formed in an arc shape that is convex on the opposite side of the worm wheel 25. The arc formed by the curved spring portion 72 is set to have a curvature that is substantially equal to that of the resin member 49, and the curved spring portion 72 is substantially in contact with the outer periphery of the resin member 49. The curved spring portion 72 contacts the resin member 49 and elastically deforms with the base portion 71 as a fulcrum, thereby directly applying an elastic force to the resin member 49 and causing the other end portion 24b of the worm shaft 24 to warm. It is biased toward the wheel 25 side.

  The spring member 42 includes an arcuate extension 73 extending along the curved spring 72 from the end of each base 71 opposite to the worm wheel 25, and radially outward from the tip of each extension 73. It has a substantially L-shaped protruding portion 74 that protrudes. On the other hand, an accommodation recess 75 in which the protrusion 74 is accommodated is formed on the inner peripheral surface of the opening 48. The spring member 42 is restricted from rotating around the second bearing 38 by the protrusion 74 engaging the side surface 75 a of the housing recess 75. That is, in the present embodiment, the protrusion 74 functions as a rotation stopper. Note that the protrusion 74 receives a reaction force generated when the curved spring portion 72 urges the other end portion 24 b of the worm shaft 24 by contacting the bottom surface 75 b of the housing recess 75.

Next, the operation of the vehicle steering device (steering force assist device) of the present embodiment will be described.
The worm shaft 24 tilts when the other end 24 b is urged by the spring member 42. As a result, the worm shaft 24 comes close to the worm wheel 25 and the backlash is removed. When steering is performed in a minute range (dead zone) where no assist force is applied, the tooth portion 25a of the worm wheel 25 and the tooth portion 24c of the worm shaft 24 are slid by the axial movement of the worm shaft 24. The worm wheel 25 rotates without moving. This reduces the feeling of catching at the start of steering.

As described above, according to the present embodiment, the following effects can be obtained.
(1) Since the curved spring portion 72 of the spring member 42 is formed so as to be elastically deformed in contact with the resin member 49, an elastic force is directly applied to the resin member 49 to bias the other end 24b. To do. The curved spring portion 72 connects the pair of base portions 71 arranged at an interval of about 180 degrees in the circumferential direction of the second bearing 38 and substantially entirely contacts the outer periphery of the resin member 49. Since it is formed in an arc shape, the elastic force of the spring member 42 (curved spring portion 72) is suppressed from being concentrated on a part of the resin member 49. Therefore, the resin member 49 is less likely to be worn, and the elastic force of the spring member 42 can be maintained over a long period of time, so that the generation of abnormal noise (gap sound) can be suppressed. Further, since the resin member 49 is provided on the outer periphery of the outer ring 38a of the second bearing 38, the friction between the resin member 49 and the spring member 42 is reduced, and the worm shaft 24 is smoothly axially moved. It becomes possible to move. Thereby, a feeling of catching can be reduced and a favorable steering feeling can be realized.

  (2) By engaging the spring member 42 with the housing recess 75 formed on the inner peripheral surface of the opening 48 of the worm shaft housing portion 32, the spring member 42 rotates around the second bearing 38. Since the restricting projection 74 is formed, the other end 24b of the worm shaft 24 can be stably biased toward the worm wheel 25.

In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, the protrusion 74 may have a function as a spring that biases the worm shaft 24.

  In the above embodiment, the spring member 42 is provided with the protrusion 74 that functions as a rotation stopper. However, the present invention is not limited thereto, and for example, as shown in FIG. A recess 81 into which 71a is fitted may be formed, and the rotation of the spring member 42 may be restricted by the corner 71a. That is, in this case, the base 71 functions as a rotation stopper. In the above embodiment, the spring member 42 does not have to be provided with a rotation stopper.

  In the above embodiment, the first bearing 37 is fixed to the housing 31, but the present invention is not limited to this, and the first bearing 37 is provided so as to be movable in the axial direction of the worm shaft 24 with respect to the housing 31. The one end 24a may be moved together.

  In the above embodiment, the actuator unit of the present invention is applied to a steering force assisting device that is mounted on a vehicle steering device and generates an assist force. However, the present invention is not limited to this, and is applied to a drive source used for other purposes. May be.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle steering device, 21 ... Steering force auxiliary device, 22 ... Motor, 24 ... Worm shaft, 24a ... One end, 24b ... Other end, 25 ... Worm wheel, 26 ... Worm speed reducer, 31 ... Housing, 32 DESCRIPTION OF SYMBOLS ... Worm shaft accommodating part, 36 ... Motor shaft, 37 ... 1st bearing, 38 ... 2nd bearing, 41 ... Shaft coupling, 42 ... Spring member, 49 ... Resin member, 51 ... Damper, 71 ... Base, 72 ... Bent spring part, 73 ... Extension part, 74 ... Projection part, 75 ... Housing recess, 81 ... Recess.

Claims (3)

A motor, a worm shaft coupled to the motor via a shaft joint so as to be tiltable, a worm reduction gear having a worm wheel meshing with the worm shaft, a housing for housing the worm reduction gear, and the worm shaft in the worm shaft In an actuator unit comprising a spring member that biases the other end opposite to the one end connected to the motor to the worm wheel side,
The worm shaft is accommodated in the housing so as to be movable in the axial direction of the worm shaft,
On the outer periphery of the bearing that rotatably supports the other end, a resin member having self-lubricating properties is provided,
The spring member includes a pair of base portions arranged at intervals in the circumferential direction of the bearing, and a curved spring portion that connects the pair of base portions and contacts the resin member and elastically deforms. An actuator unit characterized by The actuator unit according to claim 1, wherein
The actuator unit according to claim 1, wherein the spring member has a rotation preventing portion that restricts rotation of the spring member by engaging with the housing.   A vehicle steering apparatus, wherein an assist force for assisting a steering operation is generated by the actuator unit according to claim 1.