JP2010116090A - Worm reduction gear and electric power steering device - Google Patents

Abstract

Achieving elastic support in the radial direction of a worm shaft, the urging in the axial direction, the urging in the inter-axis proximity direction, and the urging in the advance angle correction direction can be adjusted independently. A simple worm reducer.
An urging means 8 includes an inter-axis proximity urging means 8B that urges the worm 1 and the worm wheel 3 to reduce the inter-axis distance in the inter-axis direction, and the inter-axial proximity. And a lead angle correction biasing means 8L that biases the worm 1 in a direction perpendicular to the axial direction of the worm shaft 2 and in a direction in which the advance angle of the worm 1 is larger than the advance angle of the worm wheel 3. The body 7 was provided with a bearing housing recess 7b fixed to the lid 6 and receiving the bearing 2a without a gap.
[Selection] Figure 1

Description

  The present invention relates to a worm reduction gear including a worm and a worm wheel, and an electric power steering apparatus using the worm reduction gear.

  In the worm speed reducer described in Patent Document 1, a pressing member (reference numeral 17 in the same document) is used to urge the worm shaft in the axial direction, urge the worm in the worm wheel direction, and elastically support the worm shaft. It is said that there is an effect (paragraph [0017] in the same document) that the worm shaft bearing is constrained in the radial direction by a member (reference numeral 16 in the same document) and no harsh noise or vibration is generated during operation.

  However, in the method of Patent Document 1, since the urging in the axial direction and the urging in the worm wheel direction change at the same time, it is difficult to meet the request to change each independently. It seemed.

  On the other hand, the worm speed reducer described in Patent Document 2 supports one bearing of the worm shaft with a lid that is detachable from the case of the worm speed reducer, and the worm wheel direction is at a constant angle between the bearing and the case. A backlash adjusting means (not shown in the same document) that can adjust not only the inter-axis distance between the worm and the worm wheel but also the advance angle of the two, by providing a gap in the direction inclined in the direction (angle λ). The reference 8) of the same document is provided.

  However, the urging means (symbols 6 and 6 'of the same document) provided in the backlash adjusting means of Patent Document 2 is limited to one direction of urging for the adjustment, and the adjustment direction of the inter-axis distance. The bias in each direction of the adjustment direction of the advance angle (referred to as “advance angle correction direction”) could not be adjusted independently.

JP 2007-247734 A (reference numeral 17 in FIG. 2) Japanese Patent Laying-Open No. 2008-039049 (reference numeral 8 in FIG. 1)

  The present invention is intended to ameliorate the above problem, and while achieving elastic support in the radial direction of the worm shaft, the urging in the axial direction, the urging in the inter-axis proximity direction, and the advance angle correction direction It is an object of the present invention to provide a worm speed reducer that can be adjusted independently and independently of the urging force, and an electric power steering apparatus using the worm speed reducer.

The worm speed reducer of the present invention is a worm speed reducer provided with a worm and a worm wheel, and the bearing of at least one end of the worm shaft of the worm is supported by a lid that can be attached to and detached from the case of the worm speed reducer. And between the lid, the bearing, and the case, between the elastic body that urges the worm shaft in the axial direction, the bearing, and a bearing hole provided in the case to accommodate the bearing. Includes a gap for changing an inter-axis distance between the worm and the worm wheel, and includes a biasing unit that biases the bearing in a predetermined direction within the gap with respect to the bearing hole portion,
The biasing means includes an inter-axis proximity biasing means for biasing the axial distance between the worm and the worm wheel so as to reduce a distance between the two axes, the inter-axis proximity biasing means, And a lead angle correction biasing means for biasing the worm in a direction perpendicular to the axial direction of the worm shaft so that the lead angle of the worm is larger than the lead angle of the worm wheel, and the elastic body includes the lid or A bearing housing recess is provided which is fixed to the bearing hole and receives the bearing without a gap.

  The electric power steering apparatus of the present invention is characterized in that the worm reducer is used for driving a steering output shaft.

According to the worm speed reducer of the present invention, the worm speed reducer includes a worm and a worm wheel, and the lid of at least one end of the worm shaft of the worm is detachable from the case of the worm speed reducer. An elastic body that urges the worm shaft in the axial direction between the lid, the bearing, and the case; and a bearing hole provided in the case to accommodate the bearing; There is a gap for changing an inter-axis distance between the worm and the worm wheel, and biasing means for biasing the bearing in a predetermined direction within the gap with respect to the bearing hole portion. Prepared,
The biasing means includes an inter-axis proximity biasing means for biasing the axial distance between the worm and the worm wheel so as to reduce a distance between the two axes, the inter-axis proximity biasing means, And a lead angle correction biasing means for biasing the worm in a direction perpendicular to the axial direction of the worm shaft so that the lead angle of the worm is larger than the lead angle of the worm wheel, and the elastic body includes the lid or Since the bearing housing recess is fixed to the bearing hole and receives the bearing without gaps, the worm shaft is elastically supported in the radial direction, and the urging in the axial direction and the proximity between the shafts are performed. And the urging in the advance angle correction direction can be adjusted separately and independently.

  Since the electric power steering apparatus of the present invention uses the worm reducer for driving the steering output shaft, the effect of the worm reducer is exhibited as an electric power steering apparatus.

  Embodiments of the present invention will be described below with reference to the drawings.

Embodiment 1

  1A and 1B show an example of a worm speed reducer according to the present invention, in which FIG. 1A is a cross-sectional view of an essential part thereof, FIG. 1B is a view taken along an arrow A thereof, and FIG. 2A is a bearing of FIG. The figure which shows only a hole part, (b) is sectional drawing which shows the cover of Fig.1 (a), (c) is sectional drawing which shows the elastic body of Fig.1 (a), (d) is the urging means of FIG. (E) is a side view of (d).

  The worm speed reducer 10 is a worm speed reducer that transmits power using the worm 1 and the worm wheel 3 that meshes with the worm 1. For example, the rotation of the steering output shaft of an electric power steering device that assists the steering of an automobile. It is used for.

  The worm speed reducer 10 includes the worm 1, a worm shaft 2 provided with the worm 1, the worm wheel 3, and a steering output shaft 12 that supports the worm wheel 3 by rotating it synchronously.

  In addition to the above basic configuration, the worm speed reducer 10 supports a bearing 2a at least one end of the worm shaft 2 with a lid 6 that can be attached to and detached from the case 4 of the worm speed reducer 10, and the lid 6, the bearing 2a, and the case 4 is provided with an elastic body 7 that urges the worm shaft 2 in the axial direction and seals between the lid 6 and the case 4.

  The worm reducer 10 has a twisted position (relationship between the shaft center line of the steering output shaft 12 of the worm wheel 3 and the shaft center line of the worm shaft 2). It is a common relationship.

  Corresponding to this relationship, the worm speed reducer 10 includes an inter-shaft proximity urging means 8B that urges the bearing 2a at one end of the worm shaft 2 in the direction of the steering output shaft 12 of the worm wheel 3 (the inter-axial proximity direction). The lead angle correction biasing means 8L biases the lead angle of the worm 1 in a direction orthogonal to the axial direction of the worm shaft 2 and the lead angle of the worm wheel 3 in a direction perpendicular to the axial direction of the worm shaft 2. Biasing means 8 is provided.

  Further, as will be described in detail with reference to FIG. 2, the elastic body 7 is provided with a bearing housing recess 7b that is fixed to the lid 6 and that fits the bearing 2a without a gap, thereby allowing the bearing 2a, that is, the worm shaft 2 to be radially disposed. Elastically supported to restrain. The radial restraint prevents the bearing 2a from coming into contact with the case 4.

  Here, as can be seen from FIG. 1A, the lid 6 can move forward and backward with respect to the case 4 in the axial direction of the worm shaft 2, and one of the bearings 6 a of the lid 6 and the case 4 and the worm shaft 2. The elastic body 7 interposed between the case 4 urges (presses) the worm shaft 2 in the axial direction and simultaneously seals the space between the case 4 and the lid 6 from the outside.

  FIG. 1B is a view as seen from the direction of arrow A in FIG. 1A, and shows a state in which the lid 6 and the elastic body 7 are removed.

  The elastic body 7 achieves the urging of the worm shaft 2 in the axial direction by utilizing the force from the lid 6, and is also interposed between the case 4 and the lid 6, and the case 4 and the lid 6. The seal between the two has also been achieved.

  In addition, this elastic body 7 also plays the role which suppresses backlash and eliminates an axial clearance by urging the worm shaft 2 in the axial direction.

  Here, the urging direction in the axial direction by the elastic body 7 with respect to the worm shaft 2, the urging direction by the inter-axis proximity urging means 8B, and the urging direction by the advance angle correcting urging means 8L are respectively Since they are orthogonal, changing the biasing force in one direction does not affect the biasing force in the other biasing direction.

  That is, the worm speed reducer 10 achieves elastic support in the radial direction of the worm shaft 2, while urging the shaft in the axial direction, urging in the inter-axis proximity direction, and in the advance angle correction direction. The biasing can be adjusted separately and independently.

  In addition, the worm speed reducer 10 is simultaneously provided when the elastic body 7 is interposed between the lid 6 of the worm speed reducer 10 and the worm shaft 2 and the gear shaft 2 is urged in the axial direction by the elastic body 7. The problem of sealing can also be solved.

  The structure of the above-described characteristic portion of the worm reduction gear 10 will be described in more detail with reference to FIG.

  FIG. 2A shows a portion where the case 4 receives the bearing 2a and the lid 6 except for the worm shaft 2 and the bearing 2a from the arrow view of FIG. 1B.

  As shown in FIG. 2 (a), in this portion of the case 4, a worm accommodating portion 4a for accommodating the worm 2 is seen in the innermost portion, and then a bearing hole portion 4b for accommodating the bearing 2a in the forward direction; A lid female screw hole 4f that is screw-engaged with the lid 6 has an inner diameter larger than that of the bearing hole portion 4b.

  As shown in FIG. 1 (b), the inner diameter of the bearing hole 4b is larger than the outer diameter of the bearing 2a, and is eccentric to the left by 45 degrees obliquely upward in this figure by the larger outer diameter. Therefore, the gap C between the inner periphery of the bearing hole 4b and the outer periphery of the bearing 2a in the upper left part of the 45 ° diagonally is the largest, and the gap between both in the lower 45 ° diagonally lower part on the opposite side is zero. It has become.

  A gap CB is formed at a position corresponding to the interaxial proximity biasing means 8B, and a gap CL is formed at a position corresponding to the advance angle correction biasing means 8L.

  A step portion between the bearing hole portion 4b and the lid female screw hole 4f is a seal surface 4e with which the elastic body 7 comes into surface contact. Two urging means accommodating recesses 4c and 4d for accommodating the two urging means 8B and 8L described above are provided at two locations on the outer periphery of the bearing hole portion 4b.

  The urging means accommodation recess 4c accommodates the inter-axis proximity urging means 8B, and the urging means accommodation recess 4d accommodates the advance angle correction urging means 8L8.

  The urging means 8B and 8L accommodated in the urging means accommodating recesses 4c and 4d do not protrude from the seal surface 4e, or when protruding, the elastic body 7 is provided with a relief portion. Is for sealing the sealing surface 4e including the peripheral edges of the urging means housing recesses 4c, 4d.

  The lid 6 shown in FIG. 2 (b) has a disk shape in which a male screw portion 6b that engages with the female screw hole 4f for the lid of the case 4 is provided on the outer periphery, and an elastic body 7 is provided on one end face side in the radial direction. An elastic body fitting recess 6a is provided that is fixed by being fixed to the upper end, and a hexagonal turning recess 6c, for example, is provided on the other end face for rotating and fixing the lid 6.

  The peripheral edge portion 6d of the elastic body fitting recess 6a of the lid 6 is in contact with the seal surface 4e of the case 4 and serves to tighten and fix the screw engagement between the male screw portion 6b and the female screw hole 4f for the lid. Yes.

  The elastic body 7 shown in FIG. 2 (c) is formed of natural rubber or rubber-based synthetic resin, has a disc ring shape as a whole, and fits into the elastic body fitting recess 6a of the lid 6 without gaps. On the opposite side of the joint portion 7a to the axial direction, a bearing housing recess 7b that fits the bearing of the worm shaft 2 without a gap, and an end surface of the bearing housing recess 7b, which is in contact with the seal surface 4e of the case 4 And a sealing surface 7c.

  The height of the sealing surface 7 c (the total thickness of the elastic body 7) is such that the peripheral edge 6 d of the lid 6 into which the elastic body 7 is fitted contacts the sealing surface 4 e of the case 4 when the peripheral edge 6 d contacts the sealing surface 4 e of the case 4. It is assumed that the elastic body is projected from the recessed portion 6a to such an extent that a sealing effect can be exhibited.

  The depth of the bearing receiving recess 7b is such that a necessary and sufficient biasing force is applied to the bearing 2a of the worm 2 when the peripheral edge 6d of the lid 6 into which the elastic body 7 is fitted contacts the seal surface 4e of the case 4. The depth of it. This urging force can be adjusted by changing the depth of the bearing housing recess 7b and the material and thickness (deflection allowance) of the elastic body 7.

  The urging means 8 (8B, 8L) is a rectangular spring steel plate bent 90 degrees along a fold line parallel to one side thereof to form a "U" shape as a whole. It becomes an open end through 8a. The pressing protrusion 8a is for avoiding the edge of the opening end from hitting the bearing 2a, and for pressing the bearing 2a at the central portion of the axial length of the bearing 2a.

  This urging means 8 generates an elastic urging force in the direction in which the distance between the opening portions of the “U” shape increases or decreases, and at this time, the pressing protrusion 8a contacts the bearing 2a. Then, the elastic biasing force is applied to the bearing 2a.

  In this example, the urging means 8B and 8L have the same shape and give the same urging force. However, the urging forces may be different using spring steel plates having different thicknesses. It can be done. In addition, a coil spring, a highly elastic synthetic resin molded product, or the like may be used as the urging means.

  By providing the case 4 having such a configuration, the lid 6 and the elastic body 7, according to the gear device 10, as described above, the peripheral edge 6 d of the lid 6 is simply the sealing surface 4 e of the case 4. It is possible to apply a necessary and sufficient urging force to the bearing 2a of the worm 2 and to seal the outside between the case 4 and the lid 6 simply by contacting and fixing.

  Note that the seal by the elastic body 7 achieves the sealing function of the gear device 10 for these because the influence of rainwater, sand dust, etc. is placed in a harsh environment, especially when installed as an electric power steering device outside the vehicle. The meaning of doing is important.

  The two urging means 8B and 8L urge the bearing 2a in the above-described direction. The inter-axis proximity urging means 8B is provided between the worm 1 and the worm wheel 3 within the gap CB. This is effective for adjusting the inter-tooth gap (backlash) and reducing the rattle noise.

  The advance angle correction biasing means 8L is configured so that the advance angle of the worm is larger than the advance angle of the worm wheel in the range of the clearance CL, and the adjustment means described in Patent Document 2 (reference numerals 8 to 8C in the same document). ), That is, without lowering the meshing efficiency between the two, it is possible to achieve good meshing between the two while high accuracy is not required for machining of the worm and the worm wheel and assembly is easy ( The effect of paragraphs [0063] to [0065]) of Patent Document 2 is exhibited.

  Also, since the urging directions of the two urging means 8B and 8L are orthogonal to each other, there is a feature that one urging force does not affect the other urging force, and each can be adjusted independently. it can. In addition, the urging force of the worm shaft 2 by the elastic body 7 is also orthogonal to the urging directions of the urging means 8B and 8L, and the urging forces in these three directions are independently adjusted. Is possible.

  In response to the urging force of these urging means 8, the elastic means 7 plays a role of buffering the urging force within the elastic range of the bearing 2a while being fixed to the lid 6 in the radial direction. Coordinated and moderate backlash adjustment and maintenance, thereby reducing rattle noise and achieving good meshing between the worm 1 and the worm wheel 3.

  As can be seen from the above description, the worm speed reducer 10 is configured such that the bearing 2a on one side of the worm shaft 2 is accommodated in the bearing hole portion 4b with the gap C, and is provided in the bearing hole portion 4b. With a simple configuration in which the bearing 2a is elastically supported by the elastic body 7 that is urged in the axial direction while being urged by the urging means 8B and 8L that urge in the orthogonal direction, It is characterized in that the effect of the present invention is exhibited.

Embodiment 2

  FIGS. 3A, 3B, and 3C are cross-sectional views of main parts showing other examples of the worm speed reducer of the present invention. Accordingly, the same parts as those already described may be denoted by the same reference numerals and redundant description may be omitted.

  Compared to the worm reducer 10 in FIG. 1, the worm reducer 10A in FIG. 3A has the elastic body 7 restrained and supported in the radial direction on the case 4A side, and restrained in the radial direction on the lid 6A. However, it is different in that it receives a pressing force in the axial direction on the worm shaft 2.

  For this reason, an elastic body receiving portion 4g is provided on the front side of the bearing hole portion 4b to receive the elastic body 7 in a radial direction without any gap. On the other hand, the surface of the lid 6A that contacts the elastic body 7 is a flat pressing surface portion 6e that does not have a recess for fitting.

  The axial length of the lid 6A is longer than that of the lid 6 in FIG. A lock nut 6g is provided at the protruding portion. The lock nut 6g is used to fix the lid 6A to the case 4A with a screw at a position where the forward / backward position of the lid 6A allows the urging force of the elastic body and the sealing function to be suitably exerted.

  Thus, according to the worm speed reducer 10A, while achieving the same effect as the worm speed reducer 10 of FIG. 1, that is, the elastic support in the radial direction of the worm shaft, the urging in the axial direction and the proximity between the shafts are achieved. The urging in the direction and the urging in the advance angle correction direction can be adjusted separately and independently, and the sealing effect is also exhibited.

  Moreover, in this worm speed reducer 10A, since the elastic body 7 is fixed to the case 4A side, there is an effect that the axial alignment with the case 4A is more reliably performed.

  In the worm speed reducer 10B of FIG. 3B, the screw tightening and fixing of the lid 6B to the case 4B is achieved by the contact step 4h on the case 4B side as compared with the worm speed reducer 10A of FIG. The point is different.

  The contact step portion 4h is in contact with the outer periphery of the tip of the male screw portion 6b of the lid 6B to fix the lid 6B with screws.

  Thus, according to the worm speed reducer 10B, the same effect as the worm speed reducer 10A of FIG. 3 is exhibited.

  In the worm speed reducer 10C in FIG. 3C, compared to the worm speed reducer 10A in FIG. 3A, the screw tightening and fixing of the lid 6C to the case 4C is performed on the contact step 4i on the case 4C side and the lid 6C side. This is different from the contact end portion 6h.

  The contact step portion 4i comes into contact with a contact end portion 6h provided on the outer periphery of the front end of the male screw portion 6b of the lid 6C to fix the lid 6C with screws. Corresponding to this configuration, the pressing surface portion 6e 'of the lid 6C is in a position recessed from the contact end portion 6h, but does not restrain the elastic body 7 in the radial direction.

  Thus, according to the worm speed reducer 10C, the same effect as the worm speed reducer 10A of FIG. 3 is exhibited. In addition, the clearance gap between the inner periphery of said contact step part 4h, 4i and the outer periphery of the elastic body 7 may or may not exist.

Embodiment 3

  4A and 4B show another example of the worm speed reducer of the present invention. FIG. 4A is a cross-sectional view of the main part thereof, and FIG.

  The worm speed reducer 10D of FIG. 4 is different from the worm speed reducer 10 of FIG. 1 in that the elastic body 7A does not exhibit a sealing function between the lid 6D and the case 4D by pressing the lid 6D. .

  For this reason, the end surface 7d of the elastic body 7A is not in full contact with the seal surface 4e 'of the bearing hole portion 4b, and is not in contact with the peripheral edges of the biasing means accommodating recesses 4c and 4d. Accordingly, the outer diameter of the elastic body 7A is small, and correspondingly, the diameter of the female screw hole 4j for the lid of the case 4D and the male screw portion 6i of the lid 6D that is screw-engaged therewith are also reduced.

  Sealing from the outside between the lid 6D and the case 4D is achieved by interposing a sealant such as a silicon sealant 7s between the lid female screw hole 4j and the male screw portion 6i.

  Thus, according to this worm speed reducer 10D, while achieving the same effect as the worm speed reducer 10 of FIG. 1, that is, the elastic support in the radial direction of the worm shaft, the urging in the axial direction and the proximity between the shafts are achieved. The effect that the urging in the direction and the urging in the advance angle correction direction can be adjusted separately and independently can be exhibited.

Embodiment 4

  FIG. 5 (a) is a diagram conceptually showing the overall configuration of an electric power steering apparatus using the worm reducer of FIG. 1, and FIG. 5 (b) is a cross-sectional view of the main part of FIG.

  The electric power steering apparatus 20 includes the worm speed reducer 10, the steering input shaft 11, the steering output shaft 12, the torsion bar 13, the steering rack 14, the steering housing 15, and the torque sensor 16 of FIG. Reference numeral 9 denotes an electric motor that drives the worm shaft 2 to rotate.

  A steering wheel H for steering operation is connected to a steering input shaft 11, the steering input shaft 11 and the steering output shaft 12 are connected via a torsion bar 13, and torque generated in the torsion bar 13 during steering is measured by a torque sensor. 16, the steering output shaft 12 that rotates together with the worm wheel 3 is rotationally driven by the worm speed reducer 10.

  Since the steering output shaft 12 is provided with a steering pinion 12a that meshes with the steering rack 14, the steering rack 14 slides, and steering assist of the wheels T of an automobile or the like is performed in accordance with this sliding.

  The electric power steering device 20 assists the steering force as described above. At this time, the worm speed reducer 10 is used to drive the steering output shaft 12.

  Therefore, the electric power steering apparatus 20 can exhibit the effect of the worm speed reducer 10 as an electric power steering apparatus. In the case where the electric power steering device uses the worm speed reducers 10A to 10D instead of the worm speed reducer 10, the effects of the worm speed reducers 10A to 10D can be exhibited as the electric power steering device.

  The worm speed reducer and the electric power steering apparatus of the present invention are not limited to the above-described embodiments, and various modifications and combinations are possible within the scope and the scope of the embodiments described in the claims. These modifications and combinations are also included in the scope of the right.

  The worm speed reducer and electric power steering device according to the present invention achieves elastic support in the radial direction of the worm shaft, while urging it in the axial direction, urging in the proximity direction between the shafts, and in the advance angle correction direction. It can be used in industrial fields where it is required that the urging force can be adjusted separately and independently.

An example of the worm speed reducer of this invention is shown, (a) is the principal part sectional drawing, (b) is the A arrow directional view. (A) is a figure which shows only the bearing hole part of FIG.1 (b), (b) is sectional drawing which shows the lid | cover of FIG.1 (a), (c) is sectional drawing which shows the elastic body of FIG.1 (a). , (D) is an enlarged front view showing the urging means of FIG. 1 (d), and (e) is a side view of (d). (A), (b), (c) is principal part sectional drawing which shows the other examples of the worm reduction gear of this invention. The other example of the worm speed reducer of this invention is shown, (a) is the principal part sectional drawing, (b) is the B arrow directional view. (A) is a figure which shows notionally the whole structure of the electric power steering apparatus using the worm reduction gear of FIG. 1, (b) is principal part sectional drawing of (a).

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Worm 2 Worm shaft 2a Bearing 3 Worm wheel 4-4D Case 4b Bearing hole part 4g Elastic body receiving part 6-6D Cover 7-7A Elastic body 8 (8B, 8L) Energizing means 8B (8) Proximity between shafts Means 8L (8) Lead angle correction urging means 10 to 10D Worm reducer 12 Steering output shaft 20 Electric power steering device

Claims (3)

A worm reducer comprising a worm and a worm wheel,
A bearing at least one end of the worm shaft of the worm is supported by a lid that can be attached to and detached from the case of the worm speed reducer, and the worm shaft is attached in the axial direction between the lid, the bearing, and the case. Between the elastic body to be energized, the bearing, and a bearing hole provided in the case to accommodate the bearing, there is a gap for changing an inter-axis distance between the worm and the worm wheel, Urging means for urging the bearing in a predetermined direction within the bearing hole portion;
The biasing means includes an inter-axis proximity biasing means for biasing the axial distance between the worm and the worm wheel so as to reduce a distance between the two axes, the inter-axis proximity biasing means, A lead angle correction biasing means for biasing in a direction perpendicular to the axial direction of the worm shaft so that the lead angle of the worm is larger than the lead angle of the worm wheel;
The elastic body includes a bearing housing recess that is fixed to the lid or the bearing hole and that fits the bearing without a gap.   The worm speed reducer according to claim 1 or 2, wherein the elastic body is interposed between the lid and the case and exhibits a sealing function between the lid and the case.   3. An electric power steering apparatus, wherein the worm speed reducer according to claim 1 or 2 is used to drive a steering output shaft.

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