JP2007196853A - Worm speed reducer and electric power steering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the wrenching of a bearing, to suppress rise of operation torque, and to prevent the occurrence of a difference in the operation torque. <P>SOLUTION: A tilting mechanism 30 holding a motor side bearing 15 supporting a worm 11 around an axial line parallel with an output shaft 2 so as to tilt is provided. The tilting mechanism 30 is provided with an inner holder 32 having a pair of columnar supporting arms 31, 31 which becomes tilting axes of the worm 11 in a gear meshing direction, and holding an outer ring of the motor side bearing 15; and an outer holder 35 supporting the supporting arms 31, 31 of the inner holder 32. Therefore, the inner holder 32 rocks in a clearance between the outer holder 35 and the inner holder 32, so that the worm 11 can be held so as to tilt. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention detects a steering torque applied to a worm reducer and a steering wheel by a torque sensor, generates an auxiliary steering torque from an electric motor corresponding to the detected steering torque, and decelerates by the worm reducer. The present invention relates to an electric power steering device that transmits to an output shaft of a steering mechanism.

  In a steering system of an automobile, a so-called power steering device that performs steering assist using an external power source is widely adopted. Conventionally, vane type hydraulic pumps have been used as power sources for power steering devices, and many of these hydraulic pumps are driven by an engine. However, this type of power steering device has a large engine drive loss due to the constant drive of the hydraulic pump (several horsepower to about 10 horsepower at the maximum load), so it can be used in light vehicles with small displacement. It was difficult, and it was unavoidable that the fuel consumption of a car with a relatively large displacement was reduced to a level that could not be ignored.

  In order to solve these problems, an electric power steering device (Electric Power Steering, hereinafter referred to as EPS) using an electric motor as a power source has attracted attention in recent years. The EPS uses an in-vehicle battery as a power source for the electric motor, so there is no direct engine drive loss, and since the electric motor is started only at the steering assist time, a decrease in driving fuel consumption is suppressed, and electronic control is performed. It has the feature that it can be done very easily.

  In EPS, an auxiliary steering torque is generated from an electric motor in response to a steering torque applied to a steering wheel, and is decelerated by a power transmission mechanism (reduction gear) and transmitted to an output shaft of the steering mechanism. Yes.

  In EPS using a worm reducer as the power transmission mechanism (reduction gear), a worm wheel meshes with a worm on the drive shaft side of the electric motor, and this worm wheel is connected to the output shaft (for example, the steering mechanism) It is fitted to the pinion shaft and column shaft).

  By the way, in Patent Documents 1 and 2, the worm is configured to be tiltable by a clearance or an elastic body between the outer diameter of the worm and the inner diameter of the motor-side bearing.

  That is, in Patent Document 1, the outer ring of the first bearing is fixed to the housing, and the inner ring can be tilted about a substantially central portion in the axial direction. The worm and the output shaft of the motor are splined at two locations by a power transmission member inserted between them. When the worm is pressed toward the worm wheel, the worm and the output shaft of the motor are inclined with respect to the axial direction due to the looseness of the spline joint, and the backlash amount is adjusted by adjusting the mutual engagement of the worm and the worm wheel. Can be reduced. Since the joint portions are dispersed at two locations, torque can be transmitted smoothly by reducing the tilt angle, and the occurrence of rattling noise can be suppressed, and the contact between the tooth surfaces can be reduced and the durability can be improved.

In Patent Document 2, a rubber damper is interposed between the worm and the inner ring of the second bearing. The rubber damper is constituted by an elastic body and two cylindrical members on the inner diameter side and the outer diameter side of the elastic body. Thus, the worm can be reliably tilted (oscillated) with respect to the inner ring of the second bearing during preloading by the torsion spring, and the worm can be axially moved with respect to the inner ring of the second bearing. Can be displaceable.
JP-A-2004-237755 (P2004-237755A) JP 2004-189039 A (P2004-189039A)

  However, in the structures disclosed in Patent Documents 1 and 2, the motor-side bearing may be damaged, which may affect the operating torque.

  Further, the tilting amount is limited to be small, and when the worm and the inner diameter of the bearing come into contact with each other, the operating torque may be greatly increased by the repulsive force of the elastic body.

  Furthermore, if the clearance is increased to increase the amount of tilting, the worm may be violated by the inner diameter of the bearing, the fulcrum cannot be determined, and there may be a difference in operating torque in the rotational direction.

  The present invention has been made in view of the circumstances as described above, and is capable of preventing sag of a bearing, suppressing an increase in operating torque, and preventing a difference in operating torque from occurring. An object is to provide a machine and an electric power steering device.

In order to achieve the above object, a worm reducer according to the present invention is a worm reducer in which a worm wheel meshes with a worm on the drive shaft side of an electric motor.
The motor-side bearing for supporting the worm is provided with a tilting mechanism for tiltably holding an axis parallel to the output shaft.

Preferably, the tilt mechanism holds the worm so as to be tiltable in the gear meshing direction with the motor side bearing as a fulcrum,
The worm is fixed to the inner ring of the motor side bearing,
The tilt mechanism has a pair of cylindrical support arms that serve as axes of tilting the worm in the gear meshing direction with the motor side bearing position as the center, and an internal holder that holds the outer ring of the motor side bearing When,
An external holder that supports the cylindrical support arm of the internal holder via a slide bearing and a concave support member,
The outer holder is located on the outer periphery of the inner holder with a gap, and is fixed to the inner wall of the housing,
The inner holder swings in a gap between the outer holder and the inner holder, thereby holding the worm so as to be tiltable.

Preferably, the anti-motor side bearing for supporting the worm further includes a preload mechanism for applying a preload by pressing the worm against the worm wheel by an elastic force,
The spline coupling portion that couples the drive shaft of the electric motor and the worm can be inclined with a coupling member interposed.

  The electric power steering device according to the present invention detects a steering torque applied to a steering wheel by a torque sensor, and generates an auxiliary steering torque from the electric motor in response to the detected steering torque. 3. The vehicle is decelerated by the worm reducer according to any one of 3 and transmitted to the output shaft of the steering mechanism.

  According to the present invention, it is possible to prevent the bearing from being squeezed, to suppress an increase in operating torque, and to prevent a difference in operating torque from occurring.

  Hereinafter, a worm reducer and an electric power steering apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  In the present embodiment, generally, the bearing and the worm are fixed, and the bearing can be tilted with the support arm protruding from the bearing holder to the left and right. As a result, since the bearing and the worm are fixed, there is no sag of the bearing, the fulcrum is constant regardless of the direction of rotation, and the increase in operating torque can be suppressed, and there is no limit on the amount of tilting. .

  FIG. 1 is a cross-sectional view of an electric power steering apparatus according to an embodiment of the present invention.

  2 is a cross-sectional view of the tilt mechanism of the worm speed reducer shown in FIG. 1, and is a cross-sectional view taken along the line II-II in FIG.

  As shown in FIG. 1, the worm 11 is rotatable at both ends by a motor-side bearing 15 on the side close to the electric motor 10 and an anti-motor-side bearing 23 on the side far from the electric motor 10. I support it.

  The worm 11 is coupled to the drive shaft 10a of the electric motor 10 by spline fitting.

  The spline coupling portion can be tilted with a coupling member 17 interposed between the two splines (see Japanese Patent Application Laid-Open No. 2005-066970).

  The inner ring of the motor-side bearing 15 is fixed to the worm 11 and supported so as to be concentric with the worm 11 via a compressed rubber damper 18 between the flange 16 integrally provided on the worm 11. It is. Thus, the worm 11 can move in the axial direction with respect to the motor-side bearing 15 within the elastic range of the rubber damper 18.

  The non-motor side bearing 23 is provided with a preload mechanism 20 that applies a preload by pressing the non-motor side end of the worm 11 with an elastic force in a direction in which the worm 11 is brought closer to the worm wheel 12 (Patent Document: Japanese Patent Application Laid-Open No. 2004-2004) -306898).

  That is, the anti-motor side bearing 23, the bush 22, and the holder 24 are fitted to the large diameter portion 21 of the worm 11, and the preload pad 26 is provided on the small diameter portion 25 of the worm 11, and the outer peripheral surface thereof is provided. A torsion coil spring 27 is wound. Accordingly, it is possible to apply the preload by pressing the non-motor side end portion (small diameter portion 25) of the worm 11 with the elastic force in the direction approaching the worm wheel 12.

  In the present embodiment, as shown in FIG. 2, a tilting mechanism 30 is provided that holds the motor-side bearing 15 that supports the worm 11 so as to be tiltable about an axis parallel to the output shaft 2. . That is, the tilt mechanism 30 holds the worm 11 so as to be tiltable in the gear meshing direction with the motor-side bearing 15 as a fulcrum. The worm 11 is fixed to the inner ring of the motor side bearing 15 as described above.

  The tilting mechanism 30 has a pair of left and right support arms 31 and 31 (convex portions) in the form of a column that serves as a shaft for tilting the worm 11 in the gear meshing direction with the position of the motor-side bearing 15 as the center. A ring-shaped inner holder 32 for holding the outer ring of the side bearing 15 is provided.

  Further, the tilt mechanism 30 is provided with a ring-shaped external holder 35 that supports the columnar support arms 31 and 31 of the internal holder 32 via the slide bearings 33 and 33 and the concave support members 34 and 34. The outer holder 35 is positioned on the outer periphery of the inner holder 32 with a gap and is fixed to the inner wall of the housing 1. In addition, an elastic body (O-ring) 36 is provided as a play in the lateral direction between the outer holder 35 and the inner holder 32.

  Therefore, the inner holder 32 can hold the worm 11 in a tiltable manner by swinging in the gap between the outer holder 35 and the inner holder 32.

  From the above, in the present embodiment, since the motor-side bearing 15 and the worm 11 are fixed, the motor-side bearing 15 is not distorted.

  Further, since the worm 11 can be tilted without resistance with the support arms 31 and 31 (projections) of the inner holder 32 as fulcrums, the operating torque does not increase due to this portion.

  Furthermore, since the fulcrum of the motor side bearing 15 is constant regardless of the rotation direction, there is no difference in operating torque depending on the rotation direction.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation is possible.

1 is a cross-sectional view of an electric power steering device according to an embodiment of the present invention. It is sectional drawing of the tilting mechanism of the worm speed reducer shown in FIG. 1, and is sectional drawing along the II-II line of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2 Output shaft 10 Electric motor 10a Drive shaft 11 Worm 12 Worm wheel 15 Motor side bearing 16 Flange 17 Connecting member 18 Rubber damper 20 Preload mechanism 21 Large diameter part 22 Bushing 23 Anti motor side bearing 24 Holder 25 Small diameter part 26 Preload pad 27 Torsion coil spring 30 Tilt mechanism 31 Support arms 31, 31 (convex portion)
32 Internal holder 33 Slide bearing 34 Concave support member 35 External holder 36 Elastic body (O-ring)

Claims (4)

In the worm speed reducer in which the worm wheel meshes with the worm on the drive shaft side of the electric motor,
A worm speed reducer comprising: a tilting mechanism that holds the motor side bearing supporting the worm so as to be tiltable about an axis parallel to the output shaft. The tilt mechanism holds the worm so as to be tiltable in the gear meshing direction with the motor side bearing as a fulcrum,
The worm is fixed to the inner ring of the motor side bearing,
The tilt mechanism is
An inner holder for holding the outer ring of the motor side bearing, having a pair of cylindrical support arms that serve as axes of tilting the worm in the gear meshing direction around the motor side bearing position;
An external holder that supports the cylindrical support arm of the internal holder via a slide bearing and a concave support member,
The outer holder is located on the outer periphery of the inner holder with a gap, and is fixed to the inner wall of the housing,
The worm speed reducer according to claim 1, wherein the inner holder swings in a gap between the outer holder and the inner holder to hold the worm so as to be tiltable. A non-motor side bearing supporting the worm, further comprising a preload mechanism that applies a preload by pressing the worm against the worm wheel by an elastic force;
The worm speed reducer according to claim 2, wherein the spline coupling portion that couples the drive shaft of the electric motor and the worm can be tilted with a coupling member interposed therebetween.   The worm reduction gear according to any one of claims 1 to 3, wherein a steering torque applied to the steering wheel is detected by a torque sensor, and an auxiliary steering torque is generated from the electric motor in response to the detected steering torque. The electric power steering apparatus is characterized in that the electric power steering apparatus decelerates and transmits to the output shaft of the steering mechanism.

Images