JP2019199089A - Steering unit - Google Patents

Abstract

To provide a steering unit capable of preventing an abnormal sound stemming from sliding of a rack, and upgrading assembling efficiency.SOLUTION: A rack-and-pinion type steering unit 100 includes a housing 57 that accommodates a rack shaft 63 and pinion shaft, and sustains engagement of a rack tooth and pinion tooth, and cylindrical rack bushes 65 that are disposed at respective ends in a longitudinal direction of the housing 57 in order to support the rack shaft 63. The housing 57 has a circumferential groove 69 formed in an inner circumference opposed to the rack bushes 65. The rack bush 65 includes an axial-direction slit extending from one of the ends to the other end in an axial direction, and a projection that juts out of the bush periphery to outside in a radial direction. The projection is inserted into the circumferential groove 69 with an inclined surface 79, a jutting height into outside in the radial direction of which gradually diminishes in the axial direction, brought into contact with a groove opening edge of the circumferential groove 69 and elastically constrained to move to outside in the radial direction.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a steering device.

  In a vehicle steering device, the rotation of a pinion shaft accompanying a steering operation is converted into a reciprocating motion of a rack shaft. Usually, in such a rack and pinion type steering device, the rack shaft is supported in the radial direction by a rack bush interposed between the rack shaft and the cylindrical housing. The rack bush has a flange, which is inserted into the circumferential groove of the housing. A minute gap exists in the axial direction between the circumferential groove of the housing and the flange of the rack bush. Therefore, when the rack bar slides in the axial direction, the rack bush may be dragged by friction, and may move in the axial direction by a minute gap to generate a hitting sound. Further, the steering rigidity cannot be obtained while the rack bar is moving through the minute gap.

For example, Patent Documents 1 to 6 shown below are known as prior arts for taking measures against the above problem. In the steering device of Patent Document 1, an annular flange is formed at one end of a rack bush, and an annular flexible body such as an O-ring is inserted in both axial directions of the flange.
In the rack shaft support structures of Patent Documents 2 and 3, a recess that forms a gap is formed on the outer periphery of the rack bush, and the engagement protrusion (flange) can be elastically deformed in the radial direction by the gap. The engagement protrusion is press-fitted into the.
In the rack and pinion type steering device of Patent Document 4, a triangular pyramid-shaped rib is provided on one of axial end surfaces of the fitting projection (flange) of the rack bush.
In the bearing mechanism including the sliding bearing of Patent Document 5, a cylindrical protrusion is provided on a flange (flange) of the sliding bearing (bush) to restrict the axial movement of the rack bush with respect to the housing.
In the steering device of Patent Document 6, each facing surface of the concave portion in the housing is formed in a tapered shape so that the inner diameter thereof becomes linearly smaller as the distance from the convex portion inserted into the concave portion increases. By compressing the O-rings at the respective opposing surfaces, the O-rings press the rack bush radially inward.

JP 2007-50762 A JP 2007-1331025 A JP-A-6-115439 JP 2008-265590 A JP 2013-47560 A JP2013-6470A

  However, in the configurations of the above-described Patent Documents 1 to 6, although the rack bushing sound caused by the operation of the rack shaft can be suppressed, there is still room for improvement in terms of assembly. In addition, even if the rack bush flange is inserted into the recess of the housing, the gap is not necessarily sufficiently packed, and it is desired to make the gap between the housing engaging groove and the rack bush flange less likely to occur. There is.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a steering device capable of making it difficult to generate a gap between an engagement groove of a housing and a flange of a bush while improving assemblability.

The present invention has the following configuration.
A rack and pinion type steering device,
A housing that accommodates the rack shaft and the pinion shaft, and holds the rack teeth of the rack shaft and the pinion teeth of the pinion shaft;
A cylindrical rack bush arranged at both longitudinal ends of the housing and supporting the rack shaft so as to be slidable in the axial direction;
With
The housing is formed with a circumferential groove on the inner periphery facing the rack bush,
The rack bush has an axial slit extending from one end to the other end in the axial direction, and a protrusion protruding radially outward from the bush outer peripheral surface,
The projecting portion has an inclined surface in which the projecting height outward in the radial direction gradually decreases with respect to the axial direction in contact with the groove opening edge of the circumferential groove, and is elastically biased outward in the radial direction. Steering device inserted in the circumferential groove.

  According to the steering device of the present invention, it is possible to make it difficult to generate a gap between the engagement groove of the housing and the flange of the bush while improving the assemblability.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure for describing embodiment of this invention, and is the whole steering device block diagram of the example of 1st structure. FIG. 2 is an enlarged front view showing a part of the steering gear mechanism of FIG. 1. FIG. 3 is an enlarged view of the vicinity of part A in FIG. 2. FIG. 4 is a perspective view of a rack bush shown in FIG. 3. It is an expanded sectional view of the circumferential groove of a housing and the flange of a rack bush. (A) is operation | movement explanatory drawing when a rack axis | shaft moves to one axial direction, (B) is operation | movement explanatory drawing when a rack axis | shaft moves to the other axial direction. It is a principal part expanded sectional view of a steering device provided with the rack bush of a 2nd structural example. It is a perspective view of the rack bush shown in FIG. It is operation | movement explanatory drawing of the opposing wall part which pinches | interposes the radial direction slit of the rack bush shown in FIG. It is a principal part expanded sectional view of a steering device provided with the rack bush of a 3rd structural example. It is a perspective view of the rack bush shown in FIG. It is BB sectional drawing of the rack bush shown in FIG.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
<First configuration example>
FIG. 1 is a diagram for explaining an embodiment of the present invention, and is an overall configuration diagram of a steering device of a first configuration example.
The steering device 100 having this configuration includes a steering shaft 13 to which a steering wheel 11 is connected. The steering shaft 13 is rotatably held by the steering column 15. On the vehicle front end (left end in FIG. 1) side of the steering shaft 13, a worm speed reducer 17 that applies steering assist torque to the steering shaft 13 and an electric motor 19 that generates steering assist torque in the worm speed reducer 17 are configured. The steering assist mechanism 21 is connected.

  An intermediate shaft 27 is connected to the output shaft 23 of the worm reducer 17 via a universal joint 25, and this intermediate shaft 27 is connected to a pinion shaft 33 of a rack and pinion type steering gear mechanism 31 via a universal joint 29. Is done. A rack shaft (not shown) of the steering gear mechanism 31 is connected to a steered wheel (not shown) via a tie rod 35.

  The steering shaft 13 has an outer shaft 37 and an inner shaft 39, and the front end portion of the outer shaft 37 and the rear end portion of the inner shaft 39 are spline-coupled. The cylindrical steering column 15 inserted through the steering shaft 13 has a so-called collapsible structure in which an outer column 43 and an inner column 45 are combined in a telescope shape.

  The front end portion of the inner column 45 is fixed to the rear end surface of the speed reducer housing 47 of the worm speed reducer 17, and the inner shaft 39 is inserted into the speed reducer housing 47. The front end portion of the inner shaft 39 is connected to the output shaft 23 protruding from the front end surface of the speed reducer housing 47.

  The outer column 43 of the steering column 15 is supported by the vehicle body side member 51 by the upper bracket 49 so that the tilt and telescopic position can be adjusted. At the same time, the speed reducer housing 47 in the steering assist mechanism 21 is supported so as to be swingable in the vertical direction around a pivot pin 55 rotatably supported by a lower bracket 53 attached to the vehicle body side member 51.

FIG. 2 is an enlarged front view showing a part of the steering gear mechanism 31 of FIG.
The steering gear mechanism 31 is a rack and pinion type in which a pinion tooth 59 connected to the pinion shaft 33 and a rack shaft 63 having a rack tooth 61 meshing with the pinion tooth 59 are disposed inside the housing 57. Composed. That is, the housing 57 accommodates the rack shaft 63 and the pinion shaft 33 and holds the meshing of the rack teeth 61 of the rack shaft 63 and the pinion teeth 59 of the pinion shaft 33. The steering gear mechanism 31 converts the rotational motion transmitted to the pinion shaft 33 into a straight motion of the rack shaft 63. Here, the rack shaft 63 is held slidably in the axial direction by rack bushes 65 for holding the rack shaft disposed at both ends in the longitudinal direction of the housing 57. The tie rod 35 is connected to both ends of the rack shaft 63 via ball joints 67.

FIG. 3 is an enlarged view of the vicinity of portion A in FIG.
The rack bush 65 is an integrally molded product obtained by, for example, injection molding a synthetic resin material having elasticity. Preferred examples of the synthetic resin include thermoplastic synthetic resins such as polyacetal resin, polyamide resin, polyethylene resin, and ethylene tetrafluoride resin.

  The housing 57 is formed with a circumferential groove 69 on the inner periphery facing the rack bush 65. The circumferential groove 69 forms an annular space on the inner periphery of the housing 57. In the circumferential groove 69, a later-described protrusion of the rack bush 65 is inserted.

  In this configuration example, the circumferential groove 69 of the housing 57 is formed by a groove having a rectangular cross section in the axial direction. Therefore, the circumferential groove 69 is arranged with a pair of parallel inner walls of the groove facing each other with an annular space interposed therebetween. The circumferential groove 69 forms a groove opening edge 71 at the boundary with the inner periphery of the housing 57. The groove opening edge 71 is a substantially right angle (edge). The inner periphery of the housing 57 is recessed from the groove opening edge 71 to the groove bottom of the circumferential groove 69.

4 is a perspective view of the rack bush 65 shown in FIG.
The rack bush 65 includes a cylindrical bush main body 73 and a plurality of protrusions that are formed at one end in the axial direction of the bush main body 73 and project radially outward from the bush outer peripheral surface. The plurality of protrusions are formed in a flange shape as a whole. A recess 75 for an ejector pin when the rack bush 65 is removed from the resin molding die is formed on the axial end surface of the protrusion. Hereinafter, these protrusions are referred to as flanges 77. The protruding front end side of the flange 77 is inserted into a circumferential groove 69 of the housing 57 shown in FIG.

  The flange 77 has inclined surfaces 79 on both sides in the axial direction, and the height of the protrusion outward in the radial direction gradually decreases from the center in the axial direction toward both sides in the axial direction. That is, the flange 77 is formed in a tapered shape that becomes thinner toward the protruding tip in the axial direction in the cross section including the axis of the bush main body 73. The rack bush 65 is inserted into the circumferential groove 69 of the housing 57 with a flange 77 being elastically urged radially outward.

FIG. 5 is an enlarged cross-sectional view of the circumferential groove 69 of the housing 57 and the flange 77 of the rack bush 65.
The rack bush 65 of this configuration has a pair of inclined surfaces 79 formed on the flange 77. In addition, the inclined surface 79 of the flange 77 may be formed on either side in the axial direction in addition to the configuration formed on both sides in the axial direction. The axial maximum dimension Wb on the protruding proximal end side of the flange 77 is larger than the axial dimension Wg of the circumferential groove 69 of the housing 57. Further, the axial dimension Wt of the flat portion 78 (cylindrical surface excluding the inclined surface) on the protruding tip side is smaller than the axial dimension Wg of the circumferential groove 69 of the housing 57.

  As shown in FIG. 4, the rack bush 65 has a plurality of axial slits 81 extending from one end portion toward the other end portion in the axial direction. The axial slit 81 includes a slit having an open end on the flange side and a slit having an open end on the opposite flange side, and both are formed in a range in which the other end portion does not divide the rack bush 65. An axial slit 81 having an open end on the flange side is formed by cutting the flange 77. These axial slits 81 can easily reduce the flange outer diameter when the flange 77 is inserted into the circumferential groove 69 of the housing 57. The axial slits 81 in the illustrated example are formed at a total of 10 locations, 4 on the flange side and 6 on the non-flange side, but the number of slits is not limited thereto.

  In this configuration, the flange 77 is formed on the entire circumference other than the portion where the axial slit 81 of the rack bush 65 is formed. In addition, the flange 77 can also be provided partially along the circumferential direction. In that case, it is preferable that the flanges 77 are equally arranged in the circumferential direction, such as every 90 ° or every 120 °, and more preferably provided at the center between the slits.

  A plurality of (two in the illustrated example) circumferential grooves 83 are formed on the outer periphery of the bush main body 73 having an opening formed by the axial slit 81 so as to cross the axial slit 81. O-rings 85, which are elastic rings, are mounted in the circumferential grooves 83, respectively. The O-ring 85 is provided so as to protrude radially outward from the outer periphery of the bush, and abuts on the inner peripheral surface of the housing 57 in which the bush main body 73 is accommodated. The O-ring 85 is provided at a position offset from the flange 77 in the axial direction. The elastic material forming the O-ring 85 may be any of natural rubber, synthetic rubber, and thermoplastic synthetic resin having elasticity, such as polyester elastomer.

  The rack bush 65 having the O-ring 85 attached to the circumferential groove 83 is press-fitted into the inner peripheral surface of the housing 57 via the O-ring 85. When the rack bush 65 is press-fitted into the housing 57, the rack bush 65 is pressed radially inward via the O-ring 85, the interval between the axial slits 81 is narrowed, and the bush inner diameter is reduced. Thereby, the rack bush 65 has no gap with the outer diameter surface of the rack shaft 63.

Next, a procedure for assembling the rack bush 65 of the first configuration example to the steering gear mechanism 31 will be described.
To assemble the steering gear mechanism 31, first, in a state where the pinion shaft 33 and the rack shaft 63 are not attached to the housing 57, the axial end surface from which the rack bush 65 becomes the non-formation side of the flange 77 from the end surface side of the housing 57. Insert from. The rack bush 65 is inserted in a state where the outer peripheral surface of the flange 77 is compressed radially inward using a predetermined jig. Thereafter, the jig is removed at a position where the flange 77 and the circumferential groove 69 of the housing 57 coincide with each other, and the flange 77 is expanded in diameter by its elasticity. As a result, the flange 77 is fitted into the circumferential groove 69.

  Next, the rack shaft 63 is inserted through the inner peripheral surface of the cylindrical portion of the rack bush 65, and the rack shaft 63 is held in a state of being in sliding contact with the inner peripheral surface of the rack bush 65. Thereafter, a pair of sockets constituting the ball joint 67 is mounted on the rack shaft 63, and the rack shaft 63 is slidably held on the housing 57 via the rack bush 65. Then, the tie rod 35 is connected to the rack shaft 63 via the ball joint 67.

  Next, the pinion shaft 33 is mounted on the housing 57, and the pinion teeth 59 formed on the pinion shaft 33 are engaged with the rack teeth 61 of the rack shaft 63. Then, the pinion shaft 33 is connected to the intermediate shaft 27 to which the steering column 15 and the steering assist mechanism 21 are connected via the universal joint 29. Thus, the assembly of the rack and pinion type steering device 100 is completed. The socket of the ball joint 67 may be attached to the rack shaft 63 after the pinion shaft 33 is mounted on the housing 57.

  By steering the steering wheel 11 in this state, the steering torque transmitted to the steering wheel 11 is transmitted to the steering assist mechanism 21 via the steering shaft 13. Then, the steering torque is detected by a steering torque sensor (not shown) disposed in the steering assist mechanism 21. Next, a steering assist current command value is calculated by a control device (not shown) based on the steering torque and the vehicle speed detected by a vehicle speed sensor (not shown). Based on this steering assist current command value, the electric motor 19 is driven and controlled. Thereby, a steering assist torque corresponding to the steering torque is generated from the electric motor 19, and the generated steering assist torque is decelerated by the worm speed reducer 17 and transmitted to the steering shaft 13.

  The steering torque and steering assist torque transmitted to the steering shaft 13 are transmitted to the pinion shaft 33 of the steering gear mechanism 31 via the intermediate shaft 27. The pinion shaft 33 has pinion teeth 59 meshing with the rack teeth 61 of the rack shaft 63, the transmitted torque is transmitted to the rack shaft 63, and the rack shaft 63 is moved in the axial direction.

  When the rack shaft 63 moves in the axial direction in this way, the tie rod 35 connected to the rack shaft 63 via the ball joint 67 also moves in the axial direction, and a steered wheel (not shown) steers in response thereto. As a result, the vehicle turns.

  When the rack shaft 63 moves in the axial direction, the rack shaft 63 is slidably held on the inner peripheral surface of the rack bush 65. Therefore, a load for moving the rack shaft 63 is transmitted to the rack bush 65 by the frictional force between the rack shaft 63 and the inner peripheral surface of the rack bush 65.

Next, the operation of the rack bush 65 configured as described above will be described.
6A is an operation explanatory diagram when the rack shaft 63 moves in one axial direction, and FIG. 6B is an operation explanatory diagram when the rack shaft 63 moves in the other axial direction.
Here, the force that the flange 77 receives from the groove opening edge 71 of the housing 57 is F1, and the force that the flange 77 expands due to the elastic restoring force is F2. F3 is the force that the rack bushing 65 is pulled by friction when the rack shaft 63 moves in one axial direction, and F4 is the force that the rack bushing 65 is pulled by friction when the rack shaft 63 moves in the other axial direction. To do. When the rack bush 65 receives an axial force due to the movement of the rack shaft 63, the inclined surface 79 on the side on which the axial force acts receives the reaction force from the groove opening edge 71, and the rack bush 65 moves in the axial direction. Will be regulated.

  In particular, when the inclined surfaces 79 are formed on both sides of the flange 77 in the axial direction, the reaction force from the groove opening edge 71 is generated in a well-balanced manner, and a gap is generated in the axial direction due to the load of F3 and F4. Blocked by the force of F2. That is, an axial gap is less likely to occur between the circumferential groove 69 and the flange 77. According to this, the rack bush 65 can suppress the occurrence of sound hit by the gap between the inclined surface 79 on the side on which the axial force acts and the groove opening edge 71.

  Further, when the rack bush 65 is attached to the housing 57, if the flange 77 is inserted into the circumferential groove 69, the inclined surfaces 79 on both axial sides of the flange 77 are in contact with the groove opening edge 71. . For this reason, it is possible to realize the packing by a simple assembling work simply by mounting. That is, the assembly property of the rack bush 65 to the steering gear mechanism 31 is improved. In addition, since the inclined surface 79 of the flange 77 is elastically biased and brought into contact (elastic contact) with the circumferential groove 69, manufacturing tolerances of the flange 77 and the circumferential groove 69 can be relaxed, and manufacturing costs can be reduced.

  And since the rack bush 65 of this structure is formed with a synthetic resin material, it can provide favorable elasticity to the rack bush 65 itself. Thereby, a favorable elastic restoring force is imparted to the flange 77, and the effect of narrowing the gap with the circumferential groove 69 can be enhanced.

  Since the circumferential groove 69 has a rectangular cross section in the axial direction, the groove opening edge 71 has an annular corner. Further, as described above, the flange 77 has the relationship between the axial dimension Wt of the flat portion 78 on the protruding tip side, the maximum axial dimension Wb on the protruding proximal end side, and the axial dimension Wg of the circumferential groove 69. Wt <Wg <Wb. Therefore, the inclined surface 79 can be stably brought into contact with the corner of the groove opening edge 71, and the flat portion 78 on the protruding tip side of the flange 77 interferes with the groove bottom of the circumferential groove 69, the groove inner wall surface, and the like. Can be surely prevented.

  As described above, when the flange 77 is inserted into the circumferential groove 69 of the housing 57 while being elastically biased outward in the radial direction, the inclined surfaces 79 on both sides in the axial direction are groove openings of the circumferential groove 69. It will be in the state contact | abutted to the edge 71. FIG. Thereby, the axial movement of the rack bushing 65 is restricted, and the rack bushing 65 does not generate a gap that can move in the axial direction.

  Further, the rack bush 65 is preloaded on the inner peripheral surface of the housing 57 by the elastic repulsive force of the O-ring 85. As a result, the occurrence of gaps in the radial direction of the rack bush 65 can be suppressed, and the radial gap can be reduced.

  That is, the rack bush 65 cooperates with the action of eliminating the radial gap by the reaction force acting between the inclined surface 79 and the groove opening edge 71 and the action of eliminating the radial gap by the O-ring 85. The radial gap can be reduced in the entire axial direction of the bush 65. Further, since the positions of the axial backlash filling portion by the flange 77 and the radial backlash filling portion by the O-ring 85 are shifted in the axial direction, the rack bush 65 receives an impact load. In addition, it is difficult to affect each function.

  In addition, the effect of the above-described backlash filling is more conspicuous in the configuration in which the inclined surface 79 of the flange 77 is formed on both sides in the axial direction than in the configuration in which the inclined surface 79 is formed on one side in the axial direction. Further, when the inclined surfaces 79 are formed on both sides in the axial direction, the effect of preventing the hitting sound can be enhanced as compared with the case where the inclined surfaces 79 are formed only on one side in the axial direction.

<Second configuration example>
Next, a second configuration example of the steering device of the present invention will be described.
FIG. 7 is an enlarged cross-sectional view of a main part of a steering apparatus including the rack bush 87 of the second configuration example. In the following description, the same members and parts as those shown in FIGS. 1 to 6 are denoted by the same reference numerals, and redundant description is omitted or simplified.

  The steering device 200 of this configuration has a radial slit 91 in the flange 89 of the rack bush 87. The radial slit 91 is recessed inward in the radial direction at the axial center and is formed along the circumferential direction.

FIG. 8 is a perspective view of the rack bush 87 shown in FIG.
The radial slit 91 opens at the slit inner wall surface of the bush main body 73 formed by dividing the flange 89 by the axial slit 81. The flange 89 is opposed to the pair of opposing wall portions 93 by the radial slit 91 with the radial slit 91 interposed therebetween. The surface opposite to the radial slit 91 of each opposing wall portion 93 is the inclined surface 79 described above. Since the flange 89 is formed with the radial slit 91, the pair of opposing wall portions 93 can be slightly elastically deformed toward the inside of the radial slit 91, that is, in a direction approaching each other. Yes.

Next, the operation of the above configuration will be described.
FIG. 9 is an operation explanatory view of the opposing wall portion 93 that sandwiches the radial slit 91 of the rack bush 87 shown in FIG.
In the steering device 200, when the flange 89 is elastically biased and inserted into the circumferential groove 69, the inclined surfaces 79 on both sides in the axial direction receive a reaction force from the groove opening edge 71. Due to this reaction force, the opposing wall portions 93 on both sides of the flange 89 facing each other across the radial slit 91 fall to the inside of the radial slit 91 and slightly elastically deform as shown in FIG. For this reason, the flange 89 is further restrained from generating an axial gap between the flange 89 and the circumferential groove 69 due to the elastic restoring force of the opposing wall portion 93. As a result, it is possible to realize more reliable packing.

  Further, when the flange 89 is tapered, the rack bush 87 has a dimension on the inner diameter side of the flange 89 at the contact between the groove opening edge 71 of the circumferential groove 69 of the housing 57 and the inclined surface 79 of the flange 89. It changes sensitively. For this reason, the manner in which the inner diameter of the bush and the outer diameter of the rack are changed may change the rack sliding force sensitively. Depending on the contact position between the groove opening edge 71 and the inclined surface 79, the rack bush 87 may be inclined from the axial direction. However, according to the steering device 200 of this configuration, even in such a case, the opposing wall portion 93 is easily elastically deformed by the radial slit 91, so that the inclination of the rack bush 87 and the change in the rack sliding force can be further reduced. It can be reliably suppressed.

<Third configuration example>
Next, a third configuration example of the steering device will be described.
FIG. 10 is an enlarged cross-sectional view of a main part of a steering apparatus including the rack bush 95 of the third configuration example.
The steering device 300 having this configuration has a large diameter portion 97 on the inner peripheral surface of the rack bush 95. The large-diameter portion 97 is formed in the axial region where the flange 89 of the rack bush 95 is formed with a larger diameter than other inner peripheral surfaces. That is, the back side which is the inner diameter side of the flange 89 is thinned in the radial direction by the large diameter portion 97.

FIG. 11 is a perspective view of the rack bush 95 shown in FIG.
By forming the large diameter portion 97 on the inner peripheral surface of the rack bush 95, one end in the axial direction where the flange 89 is provided is easily deformed radially inward and outward (in the direction of arrow P in FIG. 11). In this configuration, since the flange 89 is divided in the circumferential direction by the axial slit 81, the arcuate divided cylindrical wall portion sandwiched between the pair of adjacent axial slits 81 is radially inward and outward. It is easy to displace.

12 is a cross-sectional view of the rack bush 95 shown in FIG. 11 taken along the line BB.
The rack bush 95 is provided with a large diameter portion 97 on the inner peripheral surface, so that a step is formed between the rack bush 95 and the inner peripheral surface in contact with the rack shaft 63. This step forms a gap d with the large-diameter portion 97 of the rack bush 95 inserted on the rack shaft 63. The rack bush 95 can sufficiently secure a preload that elastically biases the flange 89 to the circumferential groove 69 (see FIG. 10) by the gap d. The rack bush 95 is press-fitted into the circumferential groove 69 of the housing 57 by this preload, and is mainly loosened in the axial direction. The gap d is a so-called escape portion. The gap d which becomes the escape portion weakens the press-fitting reaction force of the flange 89 to make it easy to bend. Thereby, the assembling property of the rack bush 95 to the steering gear mechanism becomes better.

  Further, since the O-ring 85 and the flange 89 are disposed so as to be offset from each other in the axial direction, the reaction force acting on the flange 89 on one end side of the rack bush reduces the diameter of the flange 89 and the bush main body portion on the other end side. The end of 73 is expanded. Therefore, at the end of the bush body 73, the radial gap between the rack bush 95 and the housing 57 is narrowed, increasing the radial backlash effect, and the diameter between the rack bush 95 and the rack shaft 63. A gap in the direction widens, the contact pressure between the rack shaft 63 and the rack bush 95 decreases, and the sliding force of the rack shaft 63 decreases. Furthermore, the presence of the gap d reduces the contact area between the rack shaft 63 and the rack bush 95, and this also reduces the sliding resistance of the rack shaft 63.

  According to the steering device 300 having the above-described configuration, the rack bush 95 has the large-diameter portion 97 in which the inner peripheral surface is expanded in the axial region where the flange 89 is provided. Therefore, the rack bush 95 has a gap d formed between the large-diameter portion 97 and the outer peripheral surface of the rack shaft 63, and the flange 89 allows displacement in the direction away from the circumferential groove 69 (in the radial direction). . Therefore, the rack bush 95 can be easily assembled by displacing the flange 89 to the gap d when assembled to the housing 57, that is, with a low insertion resistance. In addition to this, the flange 89 is brought into contact with the groove opening edge 71 (see FIGS. 6A and 6B) in a state where the gap d is displaced, thereby generating an elastic restoring force to cause the flange 89 to move. Can be elastically biased. As a result, both radial and axial correction can be achieved with higher accuracy.

  Further, in the configuration in which the inclined surface 79 of the flange 89 is in contact with the circumferential groove 69, it is difficult to manage the inner diameter dimension of the back side of the flange 89. The rack bush 95 is provided with a large-diameter portion 97 on the inner peripheral surface so that a relief portion is formed. Therefore, the inner diameter of the back side portion of the flange 89 does not slide too strongly against the rack shaft 63. . Thereby, according to the steering apparatus 300 provided with the rack bush 95 of this structure, a rack sliding force can be stabilized more.

  According to the steering device having each configuration described above, a gap between the circumferential groove (engagement groove) of the housing and the flange of the rack bush can be made less likely to be generated while improving assemblability.

  As described above, the present invention is not limited to the above-described embodiments, and those skilled in the art can make changes and applications based on combinations of the configurations of the embodiments, descriptions in the specification, and well-known techniques. This is also the scope of the present invention, and is included in the scope of seeking protection.

  For example, in the above configuration example, the case where a plurality of axial slits are provided has been described as an example, but it is sufficient that at least one axial slit is provided.

As described above, the following items are disclosed in this specification.
(1) A rack-and-pinion type steering device that houses a rack shaft and a pinion shaft and holds the mesh of the rack teeth of the rack shaft and the pinion teeth of the pinion shaft, and the longitudinal direction of the housing A cylindrical rack bush arranged at both ends and supporting the rack shaft so as to be slidable in the axial direction, and the housing has a circumferential groove formed on an inner periphery thereof facing the rack bush, The rack bush has an axial slit extending from one end portion toward the other end portion with respect to the axial direction, and a protruding portion protruding radially outward from the outer peripheral surface of the bush, and the protruding portion is the radial direction An inclined surface whose outward projecting height gradually decreases in the axial direction is brought into contact with the groove opening edge of the circumferential groove, and is inserted into the circumferential groove in a state of being elastically biased radially outward. Steering device.
According to this steering apparatus, the inclined surface is formed on the protrusion of the rack bush, and the protrusion is elastically biased radially outward while the inclined surface is in contact with the groove opening edge of the circumferential groove. Inserted into the circumferential groove. Therefore, the rack bush does not generate a gap that allows the rack bush to move in the axial direction because the inclined surface of the protrusion comes into contact with the groove opening edge of the circumferential groove. That is, the rack bushing is securely packed in the axial direction with respect to the housing. In addition, when the rack bush is mounted on the housing, if the protrusion is inserted into the circumferential groove, the inclined surface of the protrusion will be in contact with the groove opening edge. Realize a reliable packing. That is, the assemblability is improved.

(2) The steering device according to (1), wherein the inclined surfaces of the protrusions are a pair of inclined surfaces in which the protrusion height decreases from an axially central portion toward both axial sides.
According to this steering apparatus, since the pair of inclined surfaces are formed on the protrusion, the groove opening edge of the circumferential groove is in contact with both inclined surfaces uniformly, and the reaction force from the groove opening edge is generated in a balanced manner. . As a result, an axial gap is less likely to occur between the circumferential groove and the protrusion.

(3) The steering device according to (1) or (2), wherein the protrusion includes a radial slit that is recessed radially inward at a central portion in an axial direction along the circumferential direction.
According to this steering device, when the protrusion is inserted while being elastically biased into the circumferential groove, the inclined surfaces on both sides in the axial direction receive reaction force from the groove opening edge. Due to this reaction force, the opposing wall portions on both sides facing each other across the radial slit are slightly elastically deformed toward the radial slit. For this reason, generation | occurrence | production of the axial clearance gap between a protrusion part and a circumferential groove is further suppressed by the elastic restoring force of an opposing wall part. As a result, more reliable filling is achieved.

(4) The rack bush has any one of (1) to (3) having a large-diameter portion that is larger in diameter than other inner peripheral surfaces on the inner peripheral surface of the axial region where the protrusions are formed. Steering device.
According to this steering device, the rack bush has a large-diameter portion in which the inner peripheral surface is expanded in the axial region where the protrusion is provided. Therefore, the rack bush is provided with a gap between the large diameter portion and the outer peripheral surface of the rack shaft. This gap allows the protrusion to displace radially inwardly away from the circumferential groove. For this reason, the rack bush can be easily assembled by displacing the protruding portion toward the gap when assembled to the housing, that is, the rack bush can be assembled with a small insertion resistance. In addition to this, when the protrusion is brought into contact with the groove opening edge while being displaced into the gap, a larger elastic restoring force can be generated to elastically bias the protrusion. As a result, both radial and axial corrections are possible.

(5) The rack bush according to any one of (1) to (4), which is made of a synthetic resin material.
According to this steering device, the rack bush can be made of a synthetic resin material, whereby good elasticity can be imparted to the rack bush. Thereby, a favorable elastic restoring force can be imparted to the projecting portion, and the gathering action between the circumferential grooves can be enhanced.

(6) The steering device according to any one of (1) to (5), wherein the rack bush includes an elastic ring that protrudes radially outward from the outer periphery of the bush and contacts the inner peripheral surface of the housing.
According to this steering apparatus, the rack bush is preloaded on the inner peripheral surface of the housing also by the elastic ring. In this way, radial radial packing can be performed. Further, since the positions of the radial backlash filling portion and the axial backlash filling portion are shifted in the axial direction, even when an impact load is applied, the respective functions can be hardly affected.

(7) The steering device according to any one of (1) to (6), wherein the circumferential groove of the housing is a groove having a rectangular cross section in the axial direction.
According to this steering device, the circumferential cross-section of the circumferential groove is rectangular, so that the groove opening edge is an annular corner. The protrusion can stably abut the inclined surface at this corner, and the other part of the flange can be prevented from interfering with the groove bottom of the circumferential groove.

(8) Any one of (1) to (7), wherein the inclined surface of the protrusion is in contact with a groove opening edge of the circumferential groove of the housing to restrict axial movement of the rack bush. Steering device.
According to this steering device, when the rack bush receives an axial force due to the sliding of the rack shaft, the surface of the protruding portion on the side on which the axial force acts acts from the groove opening edge on the axially inner side of the circumferential groove. Receive reaction force. At that time, in the rack bush, the contact state between the inclined surface of the protrusion and the groove opening edge is maintained by the elastic force radially outward. Thereby, the axial movement of the rack bush is restricted. Therefore, a gap that causes a hitting sound is not generated between the surface of the protrusion on the non-acting side of the axial force and the groove opening edge. In addition, when the rack bush is mounted on the housing, if the protrusion is inserted into the circumferential groove, the inclined surface of the protrusion will be in contact with the groove opening edge. This will make it easier.

33 Pinion shaft 57 Housing 59 Pinion teeth 61 Rack teeth 63 Rack shaft 65 Rack bushing 69 Circumferential groove 71 Groove opening edge 77 Flange (projection)
79 Inclined surface 81 Axial slit 85 O-ring (elastic ring)
87 Rack bushing 89 Flange (projection)
91 Radial slit 95 Rack bush 97 Large diameter portion 100 Steering device 200 Steering device 300 Steering device

Claims (8)

A rack and pinion type steering device,
A housing that accommodates the rack shaft and the pinion shaft, and holds the rack teeth of the rack shaft and the pinion teeth of the pinion shaft;
A cylindrical rack bush disposed at both longitudinal ends of the housing and supporting the rack shaft so as to be slidable in the axial direction;
With
The housing is formed with a circumferential groove on the inner periphery facing the rack bush,
The rack bush has an axial slit extending from one end portion to the other end portion in the axial direction, and a protrusion protruding radially outward from the outer peripheral surface of the bush,
The projecting portion has an inclined surface in which the projecting height outward in the radial direction gradually decreases with respect to the axial direction in contact with the groove opening edge of the circumferential groove, and is elastically biased outward in the radial direction. Steering device inserted in the circumferential groove.   2. The steering apparatus according to claim 1, wherein the inclined surfaces of the protrusions are a pair of inclined surfaces in which the protruding height decreases from the axially central portion toward both axial sides.   The steering device according to claim 1 or 2, wherein a radial slit that is recessed radially inward is formed along a circumferential direction in the projection central portion.   The said rack bush has a large diameter part larger diameter than another internal peripheral surface in the internal peripheral surface of the axial direction area | region in which the said projection part was formed. Steering device.   The steering device according to any one of claims 1 to 4, wherein the rack bush is made of a synthetic resin material.   The steering apparatus according to any one of claims 1 to 5, wherein the rack bush includes an elastic ring that protrudes radially outward from an outer periphery of the bush and contacts an inner peripheral surface of the housing.   The steering device according to any one of claims 1 to 6, wherein the circumferential groove of the housing is a groove having a rectangular cross section in the axial direction.   The said inclined surface of the said protrusion part contacts the groove opening edge of the said circumferential groove of the said housing, and the axial direction movement of the said rack bush is controlled as described in any one of Claims 1-7. Steering device.

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