JP5133090B2 - Power steering device - Google Patents

Description

  The present invention relates to a power steering device such as an electric power steering device and a hydraulic power steering device.

  In the power steering apparatus, as described in Patent Document 1, a pinion connected to a steering shaft is engaged with a rack shaft in a gear box, and a rack guide that presses the rack shaft against the pinion is inserted into a cylinder portion provided in the gear box. There is something. The rack guide eliminates the play of the meshing portion between the pinion and the rack shaft, thereby stabilizing the steering operation. FIG. 5 schematically shows a rack shaft 2 and a rack guide 3 provided in the cylinder portion 1 of the gear box, and the rack guide 3 is not shown by a compression spring 5 supported on the back by an adjusting bolt 4. It pushes against the pinion.

In this power steering apparatus, an O-ring 6 provided on the outer periphery of the rack guide 3 is brought into sliding contact with the inner periphery of the cylinder portion 1, and the outer periphery of the rack guide 3 that vibrates due to road surface vibration or the like is the inner periphery of the cylinder portion 1. Generation of rattling noise (slight vibration) that collides with
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  The O-ring 6 provided on the outer periphery of the rack guide 3 slides substantially the same with respect to the inner periphery of the cylinder portion 1 in both directions in which the rack guide 3 moves away from the pinion and in the direction in which the rack guide 3 approaches the pinion. Generate resistance. The O-ring 6 makes the rack guide 3 difficult to separate from the rack shaft 2 due to the sliding resistance generated in the direction in which the rack guide 3 moves away from the pinion. On the contrary, the O-ring 6 makes it difficult to press the rack guide 3 against the rack shaft 2 due to the sliding resistance generated in the direction in which the rack guide 3 approaches the pinion. For this reason, when the rack shaft 2 moves away from the normal meshing position with the pinion and then the rack guide 3 tries to press the rack shaft 2 against the pinion, the movement of the rack guide 3 is delayed by the sliding resistance of the O-ring 6. End up.

  That is, the road surface reaction force at the time of steering operation causes the rack shaft 2 to bend from the straight state, the rack shaft 2 tends to move away from the normal meshing position with the pinion, and the rack guide 3 is moved to the rack shaft 2 by the spring force of the compression spring 5. Is maintained in the normal meshing position with the pinion, the O-ring 6 makes it easy to press the rack guide 3 against the rack shaft 2 due to the sliding resistance with the cylinder portion 1. By this, correct engagement with the pinion is maintained.

  However, after the rack shaft 2 moves away from the normal meshing position with the pinion due to a large road surface reaction force, the rack guide 3 tries to push the rack shaft 2 back to the normal meshing position with the pinion by the spring force of the compression spring 5. When this occurs, the O-ring 6 is difficult to press against the rack shaft 2 of the rack guide 3 due to sliding resistance with the cylinder portion 1, and as a result, the rack shaft 2 is difficult to smoothly return to the correct meshing position with the pinion.

  SUMMARY OF THE INVENTION An object of the present invention is to improve vibration proofing and slidability of a rack guide when the rack guide is used to stabilize the engagement between the rack shaft and the pinion.

The invention of claim 1 is a power steering device in which a pinion connected to a steering shaft is engaged with a rack shaft in a gear box, and a rack guide that presses the rack shaft against the pinion is inserted into a cylinder portion provided in the gear box. rack guide an elastic member is loaded in an annular groove in the outer periphery of the elastic body, an annular loaded in an annular groove in the outer periphery of the rack guide, the axial direction of the rack guide at the periphery of the cross-section perpendicular to the circumferential direction of the annular And a friction lip having a habit of gradually expanding toward the anti-pinion side along the frictional lip, and the friction lip is brought into sliding contact with the inner periphery of the cylinder portion.

  According to a second aspect of the present invention, in the first aspect of the present invention, the elastic body has an annular shape provided in an annular groove on the outer periphery of the rack guide, and the inner peripheral portion of the cross section perpendicular to the annular circumferential direction of the elastic body is racked. The mounting portion is engaged with the annular groove of the guide, and the outer peripheral portion of the cross section is a friction lip.

  According to a third aspect of the present invention, in the second aspect of the present invention, the cross section perpendicular to the annular circumferential direction of the elastic body is U-shaped or V-shaped.

(Claim 1)
(a) The elastic body provided on the outer periphery of the rack guide has a friction lip having a habit of gradually expanding from the outer periphery of the rack guide toward the non-pinion side along the axial direction of the rack guide. It was brought into sliding contact with the inner periphery of the part.

  The elastic body provided on the outer periphery of the rack guide is (1) in the direction in which the rack guide is away from the pinion, the sliding resistance that the inner periphery of the cylinder portion exerts on the friction lip of the elastic body becomes the force that expands the friction lip, The sliding resistance is further increased, and the increased sliding resistance makes it easy to press the rack guide against the rack shaft. On the other hand, (2) In the direction in which the rack guide approaches the pinion, the sliding resistance that the inner circumference of the cylinder part exerts on the friction lip of the elastic body becomes the force that reduces the diameter of the friction lip, and the sliding resistance is further reduced Thus, the reduced sliding resistance makes it easy to press the rack guide against the rack shaft.

  Therefore, the road surface reaction force during steering operation causes the rack shaft to bend from the straight state, the rack shaft tries to move away from the normal meshing position with the pinion, and the rack guide makes the rack shaft normal to the pinion by the spring force of the compression spring. When trying to maintain the meshing position, the elastic body makes it easy to press the rack guide against the rack shaft due to the sliding resistance described in (1) above with the cylinder part. As a result, the rack shaft is correctly connected to the pinion by the rack guide. The meshing is held.

  On the other hand, after the rack shaft is separated from the normal meshing position with the pinion due to a large road surface reaction force, the rack guide is elastic when it tries to push the rack shaft back to the normal meshing position with the pinion by the spring force of the compression spring. The body makes it easy to press the rack guide against the rack shaft due to the sliding resistance of (2) above with the cylinder portion, and as a result, the rack shaft can be smoothly returned to the correct meshing position with the pinion.

  (b) Since the friction lip of the elastic body provided on the outer periphery of the rack guide is in sliding contact with the inner periphery of the cylinder, the vibration isolation performance of the rack guide can be improved. Generation of rattling sound (fine vibration sound) in which the outer periphery of the rack guide that vibrates due to road surface vibration or the like collides with the inner periphery of the cylinder portion is prevented.

(Claim 2)
(c) The elastic body has an annular shape provided in the annular groove on the outer periphery of the rack guide, and the inner peripheral portion of the cross section perpendicular to the annular circumferential direction of the elastic body is a mounting portion that is engaged with the annular groove of the rack guide, By using the outer peripheral portion of the cross section as a friction lip, the elastic bodies (a) and (b) provided on the outer periphery of the rack guide can be easily configured.

(Claim 3)
(d) By making the cross section perpendicular to the annular circumferential direction of the elastic body of (c) described above into a U-shape or V-shape, the elastic body of (c) described above can be simplified and configured easily.

  1 is an overall view showing an electric power steering apparatus, FIG. 2 is a sectional view taken along line II-II in FIG. 1, FIG. 3 is a schematic sectional view showing an elastic body provided in the rack guide, and FIG. FIG. 5 is a schematic cross-sectional view showing a conventional example of an elastic body provided in a rack guide.

  As shown in FIGS. 1 and 2, the electric power steering apparatus 10 includes a gear box 11 (first to second gear boxes 11 </ b> A to 11 </ b> B) fixed to a vehicle body frame or the like by a bracket (not shown). Then, a pinion shaft 14 is connected to a steering shaft 12 to which a steering wheel is coupled via a torsion bar 13, a pinion 15 is provided on the pinion shaft 14, and a rack shaft 16 having a rack 16 A meshing with the pinion 15 is provided. The first gear box 11A is supported so as to be movable left and right. Both ends of the rack shaft 16 protrude to the left and right of the first housing 11A, and tie rods 17A and 17B are connected to these ends, and the left and right wheels can be steered via the tie rods 17A and 17B by the left and right movement of the rack shaft 16. To. The steering shaft 12 and the pinion shaft 14 are supported by the gear box 11 via bearings 12A, 14A, and 14B.

  As shown in FIG. 2, the electric power steering device 10 inserts a rack guide 20 into a cylinder portion 18 provided in a portion facing the pinion 15 with one end of the rack shaft 16 sandwiched in the first housing 11A. . The rack guide 20 (seat 21) is repelled to the rack shaft 16 side by a compression spring 23 supported on the back by an adjusting bolt 22 screwed to the cylinder portion 18, and presses the rack 16A of the rack shaft 16 against the pinion 15. The one end of the rack shaft 16 is slidably supported. Reference numeral 24 denotes a lock nut for the bolt 22. The other end of the rack shaft 16 is supported by the first housing 11A by a bearing (not shown).

  In the electric power steering device 10, a steering torque detection device 30 is provided between the steering shaft 12 and the pinion shaft 14. As shown in FIG. 2, the steering torque detection device 30 is provided with two detection coils 31 and 32 surrounding the cylindrical core 33 engaged with the steering shaft 12 and the pinion shaft 14 in the second housing 11B. . The core 33 includes a vertical groove 35 that engages with the guide pin 34 of the pinion shaft 14 so as to be movable only in the axial direction, and includes a spiral groove 37 that engages with the slider pin 36 of the steering shaft 12. As a result, a steering torque applied to the steering wheel is applied to the steering shaft 12, and when a relative displacement in the rotational direction occurs between the steering shaft 12 and the pinion shaft 14 due to elastic torsional deformation of the torsion bar 13, The displacement in the rotational direction of the pinion shaft 14 causes the core 33 to be displaced in the axial direction, and the inductance of the detection coils 31 and 32 due to the magnetic change around the detection coils 31 and 32 due to the displacement of the core 33 changes. . That is, when the core 33 moves to the steering shaft 12 side, the inductance of the detection coil 31 that is closer to the core 33 is increased, and the inductance of the detection coil 32 that is moved away from the core 33 is decreased. Can be detected.

  The electric power steering apparatus 10 has a motor housing 41 of the electric motor 40 interposed at one end side of the first housing 11A. The electric motor 40 includes a stator (not shown) that is incorporated and fixed on the inner periphery of the motor housing 41 and a rotor (not shown) that is rotatably arranged on the inner periphery side of the stator. The rotor has a hollow rotating shaft (not shown) disposed around the rack shaft 16 over the longitudinal direction of the motor housing 41, and a ball nut (not shown) fixed to one end of the rotating shaft is attached to the rack shaft 16. A steel ball is held between a ball screw (not shown) provided. The electric motor 40 converts the rotation of the ball nut into a linear motion of the rack shaft 16 by a ball screw.

Therefore, the electric power steering device 10 operates as follows.
(1) When the steering torque detected by the steering torque detection device 30 is lower than a predetermined value, the steering assist force is unnecessary and the electric motor 40 is not driven.

  (2) Since the steering assist force is required when the steering torque detected by the steering torque detection device 30 exceeds a predetermined value, the electric motor 40 is driven. In the electric motor 40, the stator coil is energized so as to generate a necessary steering assist force, and the rotor is driven to rotate by a magnetic field generated in the stator. The torque generated by the motor 40 is transmitted from the rotor to the ball nut via the rotation shaft, and the rotation of the ball nut is converted into a linear motion of the rack shaft 16 by the ball screw, and applied to the wheels interlocking with the rack shaft 16 as a steering assist force. The

  In the following, a detailed description will be given of a structure that improves the vibration isolation and sliding performance of the rack guide 20 with respect to the cylinder portion 18 of the gear box 11 when the rack shaft 20 and the pinion 15 are stably meshed using the rack guide 20. .

  As shown in FIG. 3, the rack guide 20 has a cylindrical shape that is inserted into the cylinder portion 18, and has a concave surface 20 </ b> A that is loaded with an arc-shaped sheet 21 along the outer periphery of the rack shaft 16 on the front end surface. Is provided with a concave hole 20B into which one end of the compression spring 23 is inserted, and an annular groove 20C in which an elastic body 25 is provided on the outer peripheral surface.

  The elastic body 25 is made of rubber, resin, or the like, and has an umbrella shape that gradually increases in diameter from the outer periphery of the rack guide 20 toward the anti-pinion 15 side (side away from the pinion 15) along the axial direction of the rack guide 20. The friction lip 26 has a habit of gradually expanding toward the anti-pinion 15 side, and the friction lip 26 is slidably contacted with the inner periphery of the cylinder portion 18. The elastic body 25 of the present embodiment has an annular shape that is loaded into the annular groove 20C on the outer periphery of the rack guide 20, has a U-shaped cross section orthogonal to the annular circumferential direction of the elastic body 25, and an inner periphery of the U-shaped cross section. The portion is a mounting portion 25A that is engaged with the annular groove 20C of the rack guide 20, and the outer peripheral portion of the cross section is a friction lip 26. The elastic body 25 has a U-shaped cross section with the inner peripheral portion and the outer peripheral portion connected to the pinion 15 side, and the mounting portion 25A, which is the inner peripheral portion, is fitted into the annular groove 20C of the rack guide 20 and is engaged. When the guide 20 is inserted into the inner periphery of the cylinder portion 18, the distal end portion of the friction lip 26, which is the outer peripheral portion of the U-shaped cross section, is pushed into the inner periphery of the cylinder portion 18 and elastically reduced in diameter. The habit of gradually expanding toward the anti-pinion 15 side as described above due to the spring reaction force of this elastic contraction is provided.

  As shown in FIG. 4, the elastic body 25 of the present invention has an annular shape loaded in an annular groove 20 </ b> C on the outer periphery of the rack guide 20, and has a V-shaped cross section perpendicular to the annular circumferential direction of the elastic body 25. The inner peripheral portion of the letter-shaped cross section may be a mounting portion 25A that is engaged with the annular groove 20C of the rack guide 20, and the outer peripheral portion of the cross section may be the friction lip 26.

According to the present embodiment, the following operational effects can be obtained.
(a) The elastic body 25 provided on the outer periphery of the rack guide 20 has a friction lip 26 having a habit of gradually expanding from the outer periphery of the rack guide 20 toward the anti-pinion 15 side along the axial direction of the rack guide 20. The friction lip 26 was brought into sliding contact with the inner periphery of the cylinder portion 18.

  The elastic body 25 provided on the outer periphery of the rack guide 20 has (1) the sliding resistance exerted by the inner periphery of the cylinder portion 18 on the friction lip 26 of the elastic body 25 in the direction in which the rack guide 20 is separated from the pinion 15. The sliding resistance is further increased and the rack guide 20 is not easily separated from the rack shaft 16 by the increased sliding resistance. On the other hand, (2) in the direction in which the rack guide 20 approaches the pinion 15, the sliding resistance that the inner periphery of the cylinder portion 18 exerts on the friction lip 26 of the elastic body 25 becomes a force that reduces the diameter of the friction lip 26. The resistance is further reduced, and the rack guide 20 is easily pressed against the rack shaft 16 by the reduced sliding resistance.

  Accordingly, the road surface reaction force at the time of steering operation causes the rack shaft 16 to bend from the straight state, the rack shaft 16 tends to move away from the normal meshing position with the pinion 15, and the rack guide 20 is moved by the spring force of the compression spring. As a result, the elastic body 25 makes it easy to press the rack guide 20 against the rack shaft 16 due to the sliding resistance of (1) described above with the cylinder portion 18 when maintaining the normal engagement position with the pinion 15. The rack shaft 16 is held in proper meshing with the pinion 15 by the rack guide 20.

  On the other hand, after the rack shaft 16 is separated from the normal engagement position with the pinion 15 due to a large road surface reaction force, the rack guide 20 tries to push the rack shaft 16 back to the normal engagement position with the pinion 15 by the spring force of the compression spring. The elastic body 25 makes it easy to press the rack guide 20 against the rack shaft 16 due to the sliding resistance of the cylinder part 18 as described in (2) above. As a result, the rack shaft 16 smoothly moves to the correct meshing position with the pinion 15. I can return.

  (b) Since the friction lip 26 of the elastic body 25 provided on the outer periphery of the rack guide 20 is in sliding contact with the inner periphery of the cylinder, the vibration isolation performance of the rack guide 20 can be improved. Generation of rattling noise (fine vibration noise) in which the outer periphery of the rack guide 20 that vibrates due to road surface vibration or the like collides with the inner periphery of the cylinder portion 18 is prevented.

  (c) The elastic body 25 has an annular shape provided in the annular groove 20C on the outer periphery of the rack guide 20, and the inner peripheral portion of the cross section perpendicular to the annular circumferential direction of the elastic body 25 is engaged with the annular groove 20C of the rack guide 20. The above-described elastic body 25 (a) and (b) provided on the outer periphery of the rack guide 20 can be easily configured by using the mounting portion 25A and the outer peripheral portion of the cross section as the friction lip 26.

  (d) By making the cross section orthogonal to the annular circumferential direction of the elastic body 25 of the above (c) U-shaped or V-shaped, the elastic body 25 of the above (c) can be simplified and configured easily.

  The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration of the present invention is not limited to this embodiment, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention. For example, the elastic body of the present invention may be provided at a plurality of locations in the circumferential direction of the outer periphery of the rack guide, or may be bonded integrally to the outer periphery of the rack guide.

  Further, the present invention is not limited to the electric power steering device but can be applied to a hydraulic power steering device.

FIG. 1 is an overall view showing an electric power steering apparatus. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is a schematic cross-sectional view showing an elastic body provided in the rack guide. FIG. 4 is a schematic cross-sectional view showing a modification of the elastic body provided in the rack guide. FIG. 5 is a schematic cross-sectional view showing a conventional example of an elastic body provided in a rack guide.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Electric power steering apparatus 11 Gear box 12 Steering shaft 15 Pinion 16 Rack shaft 18 Cylinder part 20 Rack guide 20C Annular groove 25 Elastic body 25A Mounting part 26 Friction lip

Claims (3)

In a power steering device in which a pinion connected to a steering shaft is engaged with a rack shaft in a gear box, and a rack guide that presses the rack shaft against the pinion is inserted into a cylinder portion provided in the gear box.
Load an elastic body into the annular groove on the outer periphery of the rack guide,
Elastic body, an annular loaded in an annular groove in the outer periphery of the rack guide, comprising a habit to extend progressively toward the counter-pinion side in the outer peripheral portion of the cross-section perpendicular to the circumferential direction of the annular along the axial direction of the rack guide And a friction lip that is slidably contacted with the inner periphery of the cylinder portion.   The elastic body has an annular shape provided in an annular groove on the outer periphery of the rack guide, and an inner peripheral portion of a cross section perpendicular to the annular circumferential direction of the elastic body is a mounting portion that is engaged with the annular groove of the rack guide. The power steering apparatus according to claim 1, wherein an outer peripheral portion of the motor is a friction lip.   The power steering apparatus according to claim 2, wherein a cross section of the elastic body perpendicular to the annular circumferential direction is U-shaped or V-shaped.

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