JP4999346B2 - Rack and pinion steering system - Google Patents

Description

  The present invention relates to a rack and pinion type steering apparatus.

  As shown in FIGS. 8 and 9, a conventional rack and pinion type steering device as described in Patent Document 1 rotatably supports a pinion 2 rotated by a steering operation on a gear housing 1 and meshes with the pinion 2. A rack bar 3 having matching rack teeth 3A is supported on the gear housing 1 so as to be linearly movable, and a rack guide 4 is provided on the gear housing 1 for slidably supporting the back surface of the rack bar 3 with respect to the rack teeth 3A. The rack guide 4 receives the spring force of the coil spring 6 backed up by the cap 5 screwed to the gear housing 1, and presses the rack teeth 3 </ b> A of the rack bar 3 against the pinion 2.

Further, as shown in FIG. 8, the rack and pinion type steering device connects the tie rod 8 to the end of the rack bar 3 protruding from the open end of the gear housing 1 via the joint 7 so that the wheel connected to the tie rod 8 can be steered. To do. And since the bending force acting on the rack bar 3 from the tie rod 8 side is maximized at the time of maximum steering where the rack bar 3 protrudes most from the open end of the gear housing 1, in order to improve the bending strength of the rack bar 3, The tooth back hardened layer 9 is formed by bringing electrodes into contact with both sides of a predetermined range of the back surface of the rack bar 3 with respect to the rack teeth 3A. At this time, electrode marks 9 </ b> A and 9 </ b> A are formed on both sides of the back hardened layer 9 on the back surface of the rack bar 3.
Patent 3586905

  In the conventional technique, the rack guide of the rack bar 3 is prevented so that the electrode trace 9A generated on the back surface of the rack bar 3 does not scratch the rack guide 4 when forming the hardened back layer 9 on the back surface of the rack bar 3. 4, the electrodes are brought into contact with both outer sides of the entire sliding range L, and the electrode marks 9 </ b> A and 9 </ b> A are positioned outside the entire sliding range L. However, the proper range L0 of the indented hardened layer 9 that is essentially required on the back surface of the rack bar 3 acts on the rack bar 3 during maximum steering when the rack bar 3 protrudes most from the open end of the gear housing 1. It suffices to include a portion facing the opening end of the gear housing 1 that serves as a bending fulcrum with respect to the maximum bending force (FIG. 8B). Nevertheless, in the prior art in which the back hardened layer 9 is formed in the entire sliding range L of the rack bar 3 with respect to the rack guide 4, the back hardened layer 9 becomes longer than the appropriate range L0. This causes a large heat treatment distortion in the rack bar 3 and makes it difficult to correct it.

  It is an object of the present invention to shorten the range of the hardened back layer formed on the back surface of the rack bar to an appropriate range and to reduce heat treatment strain caused to the rack bar.

According to the first aspect of the present invention, a pinion rotated by a steering operation is rotatably supported by a gear housing, a rack bar having rack teeth meshing with the pinion is supported linearly by the gear housing, and the rack teeth of the rack bar are provided. In a rack and pinion type steering apparatus in which a rack guide is installed on a gear housing that slidably supports the back surface of the rack bar and receives the spring force of the elastic pressing means to press the rack teeth of the rack bar against the pinion. A fixed range excluding both ends of the entire sliding range with respect to the rack teeth on the rear side with respect to the rack teeth, and a fixed range on the back side including a portion facing the open end at the time of maximum steering where the rack bar protrudes most from the open end of the gear housing. by contacting the electrodes on both ends of, among the back surface, all Suridohan against the rack guide In a range excluding the both ends of the rack bar to form a howler hardened layer within a predetermined range of the back including the portion facing the opening end at the maximum steering most protruding from the open end of the gear housing, the rack guide Of the back surface of the rack bar with respect to the rack teeth, the back surface hardened layer and the electrode traces at both ends thereof escape and the back surface is slidably supported.

  According to a second aspect of the present invention, in the first aspect of the invention, the rack guide is configured by assembling a sliding plate to the rack guide main body, and the sliding plate has a curved cross section that follows the back surface of the rack bar. A curved surface portion provided along the longitudinal direction of the rack bar, a medium-high groove shape portion provided with a groove-shaped cross-section separated from the back surface of the rack bar at the center of the curved cross-section of the curved surface portion, and a medium-high groove shape portion. The rack guide main body has a protruding portion that protrudes outward from the back surface, and the rack guide body follows the curved surface portion of the sliding plate so that the curved surface portion can be fitted, and the middle of the sliding plate at the center of the curved concave portion. It has a groove-like recess that allows the middle and high groove-like portions to be fitted along the groove-like portion, and a hole that is formed in the bottom of the groove-like recess so that the protrusion of the sliding plate can be inserted. It is what I did.

(Claim 1)
(a) A certain range of the rear surface of the rack bar with respect to the rack teeth, and the electrodes are in contact with both ends of the predetermined range of the rear surface including at least a portion facing the open end when the rack bar is most protruded from the open end of the gear housing. By doing so, a hardened back layer is formed in a certain range on the back surface. Therefore, the range of the hardened back layer formed on the back surface of the rack bar is defined as a bending fulcrum with respect to the maximum bending force that acts on the rack bar at the maximum steering when the rack bar protrudes most from the opening end of the gear housing. It can be shortened to an appropriate range L0 that is essentially required on the back surface of the rack bar, including the portion facing the open end of the gear housing. Thereby, the heat-treatment distortion caused to a rack bar can be reduced.

  (b) Of the rear surface of the rack bar with respect to the rack teeth, the rack guide escapes the hardened layer of the teeth and the electrode traces at both ends thereof and supports the rear surface slidably. Therefore, even if the range L0 of the back hardened layer formed on the back surface of the rack bar is shorter than the total sliding range L of the rack bar with respect to the rack guide, the electrode traces at both ends of the back hardened layer are There will be no scratches.

(Claim 2)
(c) When the rack guide is configured by assembling the sliding plate to the rack guide body, the sliding plate has a middle-high groove-like portion along the longitudinal direction of the rack bar, and the rack guide body has a middle height of the sliding plate. By having the groove-shaped recess that allows the groove-shaped portion to be fitted, the rack guide has a back-hardened layer and both ends of the back surface of the rack bar with respect to the rack teeth due to the presence of the medium-high groove-shaped portion of the sliding plate The electrode trace can be surely escaped and the back surface can be slidably supported.

  1 is a cross-sectional view showing a rack and pinion type steering device, FIG. 2 is a cross-sectional view taken along the line II-II in FIG. 1, FIG. 3 is an enlarged view of the main part of FIG. 5 is a cross-sectional view taken along line VV in FIG. 4, FIG. 6 is a perspective view showing a sliding plate, FIG. 7 is a front view showing a rack guide body, FIG. 8 is a schematic view showing a conventional example, and FIG. It is sectional drawing which follows the IX-IX line of 8.

  1 and 2 is an electric power steering device, and includes a gear housing 11 that is fixed to a vehicle body frame or the like. A pinion shaft 14 is connected to a steering shaft 12 rotated by a steering operation via a torsion bar 13, a pinion 15 is provided on the pinion shaft 14, and the steering shaft 12 and the pinion shaft 14 are connected to the gear housing 11 by bearings 12A, 14A and 14B. It is supported rotatably.

  The steering device 10 supports a rack bar 16 having rack teeth 17 meshing with a pinion 15 on a gear housing 11 by a bearing (not shown) and a rack guide 20 so as to be linearly movable. The rack guide 20 is fitted into a round hole 21 provided in the gear housing 11, is screwed into the gear housing 11, and is supported on the back by a cap 23 fixed by a lock nut 22 via a coil spring 24. The back surface of the 16 rack teeth 17 is slidably supported. The rack guide 20 presses the rack teeth 17 of the rack bar 16 against the pinion 15 by receiving the spring force of the coil spring 24 as an elastic pressing means.

  The steering device 10 has both ends of the rack bar 16 projecting to the left and right of the gear housing 11, and a rack end 25 is screwed and fixed to these ends, and one end of a tie rod 26 is connected to the rack end 25 via a joint. Then, a wheel is connected to the other end of the tie rod 26 so that the left and right wheels can be steered.

  The steering device 10 is provided with a steering torque detection device 27 between the steering shaft 12 and the pinion shaft 14 inside the gear housing 11. In addition, an electric motor (not shown) is built around the rack bar 16 inside the gear housing 11, and the rotation of the electric motor is converted into a linear motion of the rack bar 16 by a ball screw (not shown).

  Accordingly, the drive current of the electric motor is determined by a vehicle speed sensor (not shown) or a control unit that has obtained the detection result of the steering torque detector 27, and the electric motor torque that is an appropriate steering assist force according to the vehicle speed and the steering torque is determined. It is applied to the rack bar 16.

  However, in the steering device 10, the bending force acting on the rack bar 16 from the side of the tie rod 26 is maximized when the rack bar 16 protrudes most from the open end 11A of the gear housing 11 as shown in FIG. On the other hand, in order to improve the bending strength of the rack bar 16, the back hardened layer 30 is formed in a certain range on the back surface of the rack bar 16 with respect to the rack teeth 17. The rack bar 16 is formed by forming rack teeth 17 so that a string is provided on a part of an arc-shaped outer periphery of a circular cross section, and the tooth back hardened layer 30 is a central axis C of the circular arc of the rack bar 16. Is formed at the center of the back surface on the opposite side to the rack teeth 17 sandwiching the rack teeth 17 and over a certain range along the longitudinal direction of the rack bar 16. That is, using an induction hardening apparatus, electrodes are brought into contact with both sides of the heat treatment range along the longitudinal direction of the back surface of the rack bar 16 so that a high-frequency current flows directly in the heat treatment range and an induction current flows in the heat treatment range. By heating the range and then cooling the heat treatment range heated to a predetermined quenching temperature, the denture hardened layer 30 as a hardened and hardened layer is formed in the heat treatment range. In the longitudinal direction of the back surface of the rack bar 16, electrode traces 31, 31 that are the above-described electrode contact traces are formed on both sides of the denture hardened layer 30.

  In the present embodiment, the rear surface of the rack bar 16 with respect to the rack teeth 17 is in a certain range L0, and the rack bar 16 is relative to the opening end 11A at the time of maximum steering (FIG. 2) where the rack bar 16 projects most from the opening end 11A of the gear housing 11. The above-mentioned electrodes are brought into contact with both ends of a predetermined range L0 on the back surface including at least a portion to be formed, thereby forming a hardened back layer 30 in the predetermined range L0 on the back surface. That is, the maximum bending force that acts on the rack bar 16 during the maximum steering when the rack bar 16 protrudes most from the opening end 11A of the gear housing 11 within the range of the hardened layer 30 formed on the back surface of the rack bar 16. On the other hand, it is shortened to an appropriate range L0 that is essentially required on the back surface of the rack bar 16 including a portion facing the opening end 11A of the gear housing 11 that becomes the bending fulcrum P (FIG. 2).

  At this time, as shown in FIG. 3, the rack guide 20 slidably supports the back surface on the opposite side of the rack teeth 17 sandwiching the central axis c of the circular arc of the rack bar 16. The back-hardened layer 30 and the electrode traces 31, 31 at both ends thereof escape and the back surface is slidably supported.

  Specifically, the rack guide 20 is configured by assembling the sliding plate 40 to the rack guide main body 50 as shown in FIGS. The rack guide body 50 is fitted into the round hole 21 of the gear housing 11, the coil spring 24 is supported by the cap 23 screwed into the gear housing 11, and the rack guide body 50 is supported on the back by the spring force of the coil spring 24, The above-described back surface of the rack bar 16 is slidably supported by the sliding plate 40 assembled to the rack guide body 50.

  As shown in FIGS. 4, 5, and 7, the sliding plate 40 includes left and right curved surface portions 41, 41 each having an arcuate curved section that follows the back surface of the rack bar 16 along the longitudinal direction of the rack bar 16, The middle and high groove portions 42 having a groove-like cross section separated from the back surface of the rack bar 16 at the center of the curved cross sections of the curved surface portions 41, 41 along the longitudinal direction of the rack bar 16, and the outside of the middle and high groove portion 42 from the back surface. It has the projection part 43 which protrudes in the direction. The sliding plate 40 slidably supports the above-described back surface of the rack bar 16 by the left and right curved surface portions 41, 41, and the denture hardened layer 30 on the back surface of the rack bar 16 and both ends thereof by the middle and high groove portions 42. The electrode traces 31, 31 escape.

  As shown in FIGS. 4 to 6, the rack guide main body 50 has a generally short cylinder shape. The rack guide main body 50 is provided on the front surface along the center axis of the short cylinder, and follows the curved surface portion 41 of the sliding plate 40 so that the curved surface portion 41 can be fitted, and the center of the curved concave portion 51. A groove-like recess 52 that enables the middle-high groove-like portion 42 to be fitted following the middle-high groove-like portion 42 of the sliding plate 40, and a protrusion 43 of the sliding plate 40 that is formed in the bottom of the groove-like recess 52. And a hole 53 that enables the sliding plate 40 to be positioned and held with respect to the rack guide main body 50. The rack guide body 50 is provided with a stepped stopper 51A on the outer edge of the curved concave portion 51 for retaining and holding the outer peripheral edge of the curved surface portion 41 of the sliding plate 40 fitted in the curved concave portion 51, and the groove-shaped concave portion. Stepped stoppers 52 </ b> A are provided at both ends of the groove-shaped recess 52 so as to be engaged with and held at both ends of the middle / high groove-shaped portion 42 of the sliding plate 40 fitted to the groove 52. The rack guide main body 50 includes a large-diameter hole 54 that houses one end of the coil spring 24 on the back side of the short cylinder, and the hole 53 is opened to the large-diameter hole 54. The other end of the coil spring 24 is accommodated in the large diameter hole 23 </ b> A of the cap 23.

According to the present embodiment, the following operational effects can be obtained.
(a) A constant range L0 of the back surface of the rack bar 16 with respect to the rack teeth 17 and a constant value of the back surface including at least a portion facing the open end 11A at the maximum steering when the rack bar 16 protrudes most from the open end 11A of the gear housing 11. By bringing electrodes into contact with both ends of the range L0, the hardened back layer 30 is formed in a certain range L0 on the back surface. Therefore, the range L0 of the hardened back layer 30 formed on the back surface of the rack bar 16 is set to the maximum bending that will act on the rack bar 16 during maximum steering when the rack bar 16 protrudes most from the opening end 11A of the gear housing 11. It can be shortened to an appropriate range L0 that is essentially required on the back surface of the rack bar 16 including the portion facing the opening end 11A of the gear housing 11 that becomes the bending fulcrum P with respect to the force. Thereby, the heat treatment distortion caused to the rack bar 16 can be reduced.

  (b) Among the back surfaces of the rack bar 16 with respect to the rack teeth 17, the rack guide 20 escapes the tooth-back quenching layer 30 and the electrode traces 31 at both ends thereof and supports the back surface in a slidable manner. Therefore, even if the range L 0 of the back hardened layer 30 formed on the back surface of the rack bar 16 is shorter than the total sliding range L of the rack bar 16 with respect to the rack guide 20, The electrode trace 31 does not scratch the rack guide 20.

  (c) When the rack guide 20 is configured by assembling the sliding plate 40 to the rack guide main body 50, the sliding plate 40 has middle and high groove portions 42 along the longitudinal direction of the rack bar 16, and the rack guide main body 50 has a groove-like recess 52 that allows the middle and high groove portions 42 of the sliding plate 40 to be fitted, so that the rack teeth of the rack bar 16 are supported by the rack guide 20 due to the presence of the middle and high groove portions 42 of the sliding plate 40. Among the back surfaces with respect to 17, the back-hardened layer 30 and the electrode traces 31 at both ends thereof can be surely escaped and the back surface can be slidably supported.

  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.

FIG. 1 is a cross-sectional view showing a rack and pinion type steering device. FIG. 2 is a sectional view taken along line II-II in FIG. FIG. 3 is an enlarged view of a main part of FIG. FIG. 4 is a cross-sectional view showing the rack guide. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is a perspective view showing the sliding plate. FIG. 7 is a front view showing the rack guide body. FIG. 8 is a schematic diagram showing a conventional example. 9 is a cross-sectional view taken along line IX-IX in FIG.

Explanation of symbols

10 Steering device 11 Gear housing 15 Pinion 16 Rack bar 17 Rack tooth 20 Rack guide 24 Coil spring (elastic pressing means)
30 Hardened layer of teeth 31 Electrode mark 40 Sliding plate 41 Curved surface portion 42 Middle / high groove portion 43 Projection portion 50 Rack guide body 51 Curved recess portion 52 Groove recess portion 53 Hole portion
L Full sliding range
L0 proper range

Claims (2)

A pinion that is rotated by steering operation is rotatably supported on the gear housing,
A rack bar having rack teeth meshing with the pinion is supported by the gear housing so as to be linearly movable,
A rack and pinion type steering device in which a rack guide that slidably supports the back surface of the rack bar with respect to the rack teeth and that receives the spring force of the elastic pressing means and presses the rack teeth of the rack bar against the pinion is installed in the gear housing. In
A back surface including a portion of the back surface of the rack bar with respect to the rack teeth, which is a fixed range excluding both ends of the entire sliding range with respect to the rack guide and includes a portion corresponding to the open end at the maximum steering where the rack bar protrudes most from the open end of the gear housing. The electrode is brought into contact with both ends of the predetermined range of the rear surface of the rear surface of the rear surface of the rear surface of the rear surface of the rack housing, and the rack bar protrudes most from the open end of the gear housing. Forming a hardened back layer in a certain area on the back including the part facing the open end ;
A rack and pinion type steering device, wherein a rack guide escapes a back-hardened layer and electrode traces at both ends of the rack bar with respect to the rack teeth of the rack bar and slidably supports the back surface. The rack guide is configured by assembling a sliding plate to the rack guide body,
The sliding plate has a curved surface portion having a curved cross section following the back surface of the rack bar along the longitudinal direction of the rack bar, and a groove-shaped cross section spaced apart from the back surface of the rack bar at the center of the curved cross section of the curved surface portion. Having a middle-high groove-like portion provided along the direction, and a protrusion protruding outward from the back surface of the middle-high groove-like portion,
The rack guide main body has a curved concave portion that allows the curved surface portion to be fitted along the curved surface portion of the sliding plate, and the middle and high groove shaped portion that fits the middle and high groove shape portion of the sliding plate at the center of the curved concave portion. The rack-and-pinion steering device according to claim 1, further comprising a groove-shaped recess that enables fitting, and a hole that is formed in the bottom of the groove-shaped recess so that the protrusion of the sliding plate can be fitted therein.

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