CN210634625U

CN210634625U - Steering device

Info

Publication number: CN210634625U
Application number: CN201890000470.XU
Authority: CN
Inventors: 吉田高之; 增原和生; 拉尔斯·蔡特勒; 托比亚斯·魏因多夫
Original assignee: NSK Ltd
Current assignee: NSK Ltd
Priority date: 2017-01-26
Filing date: 2018-01-26
Publication date: 2020-05-29
Anticipated expiration: 2028-01-26
Also published as: WO2018139569A1; JP3225719U; JP2019199089A; DE212018000132U1

Abstract

A rack and pinion steering device is provided with: a housing that houses the rack shaft and the pinion shaft and holds the rack teeth and the pinion teeth in mesh; and a cylindrical rack bushing disposed at both longitudinal ends of the housing and supporting the rack shaft. The housing is formed with a circumferential groove on an inner periphery facing the rack bushing. The rack bushing has an axial slit extending from one end portion toward the other end portion in the axial direction, and a protrusion protruding radially outward from the outer peripheral surface of the bushing. The projection is inserted into the circumferential groove in a state where an inclined surface, which has a gradually decreasing projection height and projects radially outward, is in contact with a groove opening edge of the circumferential groove and is elastically biased radially outward.

Description

Steering device

Technical Field

The utility model relates to a turn to device.

Background

In a steering device for a vehicle, rotation of a pinion shaft accompanying a steering operation is converted into reciprocating motion of a rack shaft. In general, a rack shaft of such a rack and pinion steering system is radially supported by a rack bushing interposed between the rack shaft and a cylindrical housing. The rack bushing has a flange that is inserted into a circumferential groove of the housing. There is a slight gap in the axial direction between the circumferential groove of the housing and the flange of the rack bushing. Therefore, when the rack bar slides in the axial direction, the rack bushing is dragged by friction and moves in the axial direction by an amount corresponding to the minute gap, thereby generating a rattling sound in some cases. Further, while the rack bar is moving by the amount corresponding to the minute gap, the steering stiffness cannot be obtained.

As a conventional technique for taking measures against the above problems, for example, patent documents 1 to 6 shown below are known. In the steering device of patent document 1, an annular flange is formed at one end of a rack bushing, and flexible annular flexible bodies such as O-rings are inserted into both sides in the axial direction of the flange.

In the rack shaft support structures of patent documents 2 and 3, a concave portion for forming a gap is formed on the outer periphery of the rack bushing, and an engaging protrusion (flange) is elastically deformable in the radial direction by the gap and is pressed into an engaging groove of the end housing.

In the rack and pinion steering device of patent document 4, a triangular pyramid-shaped rib is provided on one side of an axial end face of a fitting convex portion (flange) of a rack bushing.

In the bearing mechanism provided with the sliding bearing of patent document 5, a cylindrical protrusion is provided on a flange (flange) of the sliding bearing (bushing) to restrict the movement of the rack bushing in the axial direction with respect to the housing.

In the steering device of patent document 6, each opposing surface of the recess in the housing is formed in a tapered shape inclined such that the inner diameter thereof linearly becomes smaller as it is farther from the convex portion inserted in the recess. Since the O-ring is compressed on each opposing surface, the O-ring presses the rack bushing radially inward.

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2007-50762

Patent document 2: japanese laid-open patent publication No. 2007-131025

Patent document 3: japanese laid-open patent publication No. 6-115439

Patent document 4: japanese laid-open patent publication No. 2008-265590

Patent document 5: japanese patent laid-open publication No. 2013-47560

Patent document 6: japanese patent laid-open publication No. 2013-6470

SUMMERY OF THE UTILITY MODEL

Problem to be solved by utility model

However, in the configurations of patent documents 1 to 6, although the knocking noise of the rack bushing due to the operation of the rack shaft can be suppressed, there is still room for improvement in terms of the assembling property. Further, even if the flange of the rack bushing is inserted into the recess of the housing, there is a demand for preventing sufficient backlash from being suppressed, and for making it more difficult to generate a gap between the engagement groove of the housing and the flange of the rack bushing.

Therefore, an object of the present invention is to provide a steering device that can improve assemblability and can make it more difficult for a gap to occur between an engagement groove of a housing and a flange of a bush.

Means for solving the problems

(1) A steering device is a rack and pinion steering device, and is provided with: a housing that houses a rack shaft and a pinion shaft and holds rack teeth of the rack shaft and pinion teeth of the pinion shaft in mesh; and a cylindrical rack bushing disposed at both longitudinal ends of the housing and supporting the rack shaft so as to be slidable in an axial direction, wherein the housing has a circumferential groove formed in an inner periphery facing the rack bushing, the rack bushing has a plurality of axial slits extending from one end toward the other end in the axial direction, and a protrusion provided in a split cylindrical wall portion split in the circumferential direction by the axial slits and protruding outward in the radial direction from an outer peripheral surface of the bushing, the protrusion is inserted into the circumferential groove in a state where an inclined surface whose protruding height protruding outward in the radial direction gradually decreases in the axial direction is in contact with a groove opening edge of the circumferential groove and is elastically biased outward in the radial direction, and the rack bushing has a large diameter portion having a diameter larger than that of the other inner peripheral surface at an inner peripheral surface of an axial region where the protrusion is formed, the large diameter portion forms a relief portion on the inner circumferential surface to allow displacement of the protrusion radially inward from the circumferential groove.

According to this steering device, the projection of the rack bushing is formed with an inclined surface which is in contact with the groove opening edge of the circumferential groove, and the projection is elastically urged radially outward and inserted into the circumferential groove of the housing. Therefore, by bringing the inclined surface of the projection into contact with the groove opening edge of the circumferential groove, a gap that can move in the axial direction is not generated between the rack bushing and the housing. That is, the rack bushing reliably restrains the backlash in the axial direction with respect to the housing. Further, when the rack bushing is assembled to the housing, the projection is inserted into the circumferential groove, the inclined surface of the projection comes into contact with the groove opening edge, and reliable backlash can be suppressed by a simple assembly operation of the assembly. Namely, the assembling property becomes good. Further, according to the steering device, the rack bushing has a large diameter portion formed by expanding the inner peripheral surface in an axial region where the projection portion is provided. Therefore, the rack bushing has a gap between the large diameter portion and the outer peripheral surface of the rack shaft. The clearance allows the projection to be displaced radially inward away from the circumferential groove. Therefore, when the rack bushing is assembled to the housing, the protrusion is displaced toward the space, so that the assembly can be facilitated, that is, the insertion resistance can be reduced. In addition, when the projection is in contact with the groove opening edge in a state displaced toward the gap, a larger elastic restoring force is generated to elastically bias the projection. As a result, the backlash can be suppressed in both the radial direction and the axial direction.

(2) In the steering device according to (1), the inclined surfaces of the projecting portion are a pair of inclined surfaces whose projecting heights become lower from the axial center portion toward both axial sides.

According to this steering device, since the pair of inclined surfaces are formed on the projecting portion, the groove opening edge of the circumferential groove uniformly abuts against both the inclined surfaces, and the reaction force from the groove opening edge is generated in a well-balanced manner. This makes it more difficult to generate an axial gap between the circumferential groove and the projection.

(3) In the steering device according to (1) or (2), a radial slit that is recessed radially inward is formed in the axial center portion of the projection portion in the circumferential direction.

According to this steering device, when the projection is elastically urged to be inserted into the circumferential groove, the inclined surfaces on both sides in the axial direction receive a reaction force from the groove opening edge. The protrusion elastically deforms slightly toward the radial slit side by the reaction force, with the opposing wall portions on both sides opposing each other across the radial slit. Therefore, the protrusion further suppresses the occurrence of an axial gap with the circumferential groove by the elastic restoring force of the opposing wall portion. Thereby, more reliable backlash suppression can be achieved.

(4) In the steering device according to any one of (1) to (3), the rack bushing is made of a synthetic resin material.

According to this steering device, by forming the rack bushing from a synthetic resin material, it is possible to impart good elasticity to the rack bushing. Thus, a good elastic restoring force can be applied to the protrusion portion, and a play restraining effect with the circumferential groove can be improved.

(5) In the steering device according to any one of (1) to (4), the rack bushing has an elastic ring provided to protrude radially outward from an outer periphery of the bushing and to come into contact with an inner peripheral surface of the housing.

According to this steering device, the rack bushing is also held by the elastic ring on the inner peripheral surface of the housing with a preload. This also enables radial play damping. Further, since the positions of the radial play suppressing portion and the axial play suppressing portion are displaced from each other in the axial direction, even when an impact load is applied, it is difficult to affect each function.

(6) In the steering device according to any one of (1) to (5), the circumferential groove of the housing is a groove having a rectangular axial cross section.

According to this steering device, since the circumferential groove has a rectangular axial cross section, the groove opening edge forms an annular corner. The protrusion can stably contact the inclined surface with the corner, and the other part of the flange does not interfere with the groove bottom of the circumferential groove.

(7) In the steering device according to any one of (1) to (6), the inclined surface of the protrusion contacts a groove opening edge of the circumferential groove of the housing to restrict axial movement of the rack bushing.

According to this steering device, when the rack bushing receives an axial force due to the sliding of the rack shaft, the surface of the projection on the side on which the axial force acts receives a reaction force from the groove opening edge on the axially inner side of the circumferential groove. At this time, the rack bushing maintains a contact state of the inclined surface of the protrusion and the groove opening edge by an elastic force toward the radial outside. Thereby, the axial movement of the rack bushing is restricted. Therefore, a gap which becomes a factor of generating the hitting sound is not generated between the surface of the projection on the non-acting side of the axial force and the groove opening edge. When the rack bushing is assembled to the housing, the protrusion is inserted into the circumferential groove, the inclined surface of the protrusion is in contact with the groove opening edge, and the backlash can be suppressed by a simple assembly operation of the assembly.

The utility model has the following effects.

According to the utility model discloses a turn to device can improve the assemblability to can make more difficult the production gap between the flange of the block groove of casing and bush.

Drawings

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.

Fig. 2 is a front view showing a part of the steering gear mechanism of fig. 1 in an enlarged manner.

Fig. 3 is an enlarged view of the vicinity of portion a of fig. 2.

Fig. 4 is a perspective view of the rack bushing shown in fig. 3.

Fig. 5 is an enlarged cross-sectional view of the circumferential groove of the housing and the flange of the rack bushing.

Fig. 6A is an explanatory view of the operation when the rack shaft moves to one side in the axial direction.

Fig. 6B is an explanatory view of the operation when the rack shaft moves to the other side in the axial direction.

Fig. 7 is an enlarged cross-sectional view of a main portion of a steering device including a rack bushing according to a second configuration example.

Fig. 8 is a perspective view of the rack bushing shown in fig. 7.

Fig. 9 is an explanatory view of the operation of the opposed wall portions of the rack bushing shown in fig. 8 with the radial slits therebetween.

Fig. 10 is an enlarged cross-sectional view of a main portion of a steering device including a rack bushing according to a third structural example.

Fig. 11 is a perspective view of the rack bushing shown in fig. 10.

Fig. 12 is a section view XII-XII of the rack bushing shown in fig. 11.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

< first structural example >

The steering device 100 of the present configuration has a steering shaft 13 connected to a steering wheel 11. The steering shaft 13 is rotatably held by a steering column 15. A steering assist mechanism 21 is connected to the vehicle front end (left end in fig. 1) side of the steering shaft 13, and the steering assist mechanism 21 is composed of a worm gear reducer 17 that applies a steering assist torque to the steering shaft 13 and an electric motor 19 that generates the steering assist torque in the worm gear reducer 17.

The intermediate shaft 27 is coupled to the output shaft 23 of the worm gear reducer 17 via a universal joint 25, and the intermediate shaft 27 is coupled to a pinion shaft 33 of a rack and pinion steering gear mechanism 31 via a universal joint 29. A rack shaft (not shown) of the steering gear mechanism 31 is coupled 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 a front end portion of the outer shaft 37 is spline-coupled to a rear end portion of the inner shaft 39. The cylindrical steering column 15 through which the steering shaft 13 is inserted has a so-called detachable structure in which the outer column 43 and the inner column 45 are combined in an extendable and retractable manner.

The front end of the inner column 45 is fixed to the rear end surface of a reduction gear housing 47 of the worm gear reducer 17, and the inner shaft 39 is inserted into the reduction gear housing 47. The front end of the inner shaft 39 is connected to the output shaft 23 protruding from the front end surface of the reduction gear case 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 positions can be adjusted. The reduction gear case 47 of the steering assist mechanism 21 is supported so as to be swingable in the vertical direction about a pivot pin 55, and the pivot pin 55 is rotatably supported by a lower bracket 53 attached to the vehicle body-side member 51.

Fig. 2 is a front view showing a part of the steering gear mechanism 31 of fig. 1 in an enlarged manner.

The steering gear mechanism 31 is configured in a rack-and-pinion type in which pinion teeth 59 coupled to the pinion shaft 33 and a rack shaft 63 having rack teeth 61 meshing with the pinion teeth 59 are arranged inside the housing 57. That is, the housing 57 houses the rack shaft 63 and the pinion shaft 33, and maintains the meshing of the rack teeth 61 of the rack shaft 63 with 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 linear motion of the rack shaft 63. Here, the rack shaft 63 is held slidably in the axial direction by rack bushings 65 for holding rack shafts disposed at both longitudinal end portions of the housing 57. Both ends of the rack shaft 63 are connected to the tie rods 35 via ball joints 67.

Fig. 3 is an enlarged view of the vicinity of portion a of fig. 2.

The rack bushing 65 is formed of, for example, an integrally molded product obtained by injection molding a synthetic resin material having elasticity. Preferred examples of the synthetic resin include thermoplastic synthetic resins such as polyoxymethylene resin, polyamide resin, polyethylene resin, and polytetrafluoroethylene resin.

The housing 57 forms a circumferential groove 69 on the inner periphery facing the rack bushing 65. The circumferential groove 69 forms an annular space on the inner periphery of the housing 57. A projection described below of the rack bushing 65 is inserted into the circumferential groove 69.

In the present configuration example, the circumferential groove 69 of the housing 57 is formed by a groove having a rectangular axial cross section. Therefore, the pair of parallel groove inner wall surfaces of the circumferential groove 69 are arranged to face each other with an annular space therebetween. The boundary between the circumferential groove 69 and the inner periphery of the housing 57 is a groove opening edge 71. The slot opening edge 71 is a substantially right-angled corner (edge). The inner periphery of the housing 57 is recessed from the groove opening edge 71 toward the groove bottom of the circumferential groove 69.

Fig. 4 is a perspective view of the rack bushing 65 shown in fig. 3.

The rack bushing 65 includes a cylindrical bushing body 73 and a plurality of protrusions formed at one end of the bushing body 73 in the axial direction and protruding outward in the radial direction from the bushing outer circumferential surface. The plurality of protrusions are integrally formed in a flange shape. A recess 75 for a plunger used when the rack bushing 65 is removed from the resin mold is formed in an axial end surface of the protrusion. Hereinafter, the protrusion is referred to as a flange 77. The protruding front end side of the flange 77 is inserted into the circumferential groove 69 of the housing 57 shown in fig. 3.

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

Fig. 5 is an enlarged cross-sectional view of the circumferential groove 69 of the housing 57 and the flange 77 of the rack bushing 65.

In the rack bushing 65 of the present configuration, a pair of inclined surfaces 79 are formed on the flange 77. The inclined surface 79 of the flange 77 may be formed on either side in the axial direction, in addition to both sides in the axial direction. The maximum axial dimension Wb of the flange 77 on the projecting base end side is larger than the axial dimension Wg of the circumferential groove 69 of the housing 57. The axial dimension Wt of the flat portion 78 (cylindrical surface excluding the inclined surface) on the projecting 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 bushing 65 has a plurality of axial slits 81 extending in the axial direction from one end toward the other end. The axial slit 81 is composed of a slit having an open end on the flange side and a slit having an open end on the opposite side of the flange side, and either end is formed in a range where the rack bushing 65 is not broken. An axial slit 81 having an opening end on the flange side is formed by cutting into the flange 77. When the flange 77 is inserted into the circumferential groove 69 of the housing 57, the outer diameter of the flange can be easily reduced by the axial slits 81. The axial slits 81 in the illustrated example are formed at four places on the flange side and six places on the opposite side of the flange side, and are formed at ten places in total, but the number of slits is not limited to this.

In this structure, the flange 77 is formed on the entire periphery of the rack bushing 65 except for the portion where the axial slit 81 is formed. The flange 77 can also be provided locally in the circumferential direction. In this case, the flanges 77 are preferably arranged at equal intervals in the circumferential direction at intervals of 90 ° and at intervals of 120 °, and are more preferably provided at the centers between the slits.

The bushing main body portion 73, which forms an opening portion by the axial slits 81, has a plurality of (two in the illustrated example) circumferential grooves 83 formed on its outer periphery so as to intersect the axial slits 81. O-rings 85 as elastic rings are fitted to the circumferential grooves 83, respectively. The O-ring 85 protrudes radially outward from the bushing outer periphery, and abuts against the inner peripheral surface of the housing 57 that houses the bushing body 73. O-ring 85 is disposed at a position axially offset from flange 77. As the elastic material forming the O-ring 85, any of natural rubber, synthetic rubber, and thermoplastic synthetic resin having elasticity, such as polyester elastomer, can be used.

The rack bushing 65 having the O-ring 85 fitted to the circumferential groove 83 is press-fitted to the inner circumferential surface of the housing 57 via the O-ring 85. When the rack bushing 65 is press-fitted into the housing 57, the rack bushing is pressed radially inward via the O-ring 85, and the gap between the axial slits 81 is narrowed, thereby reducing the bushing inner diameter. This eliminates a gap between the rack bushing 65 and the outer diameter surface of the rack shaft 63.

Next, an assembly procedure of the rack bushing 65 to the steering gear mechanism 31 in the first configuration example will be described.

To assemble the steering gear mechanism 31, first, the rack bush 65 is inserted from the end face side of the housing 57 in the axial direction, which is the non-forming side of the flange 77, from the end face side of the housing 57 in a state where the pinion shaft 33 and the rack shaft 63 are not mounted to the housing 57. The rack bushing 65 is inserted by a predetermined jig in a state in which the outer peripheral surface of the flange 77 is compressed radially inward. Thereafter, the jig is removed at a position where the flange 77 coincides with the circumferential groove 69 of the housing 57, and the flange 77 is expanded in diameter by its elasticity. Thereby, the flange 77 is fitted into the circumferential groove 69.

Next, the rack shaft 63 is inserted into the inner circumferential surface of the cylindrical portion of the rack bushing 65, and the rack shaft 63 is held in sliding contact with the inner circumferential surface of the rack bushing 65. Thereafter, a pair of ball sockets constituting a ball joint 67 are fitted to the rack shaft 63, and the rack shaft 63 is slidably held by the housing 57 via the rack bushing 65. The tie rod 35 is coupled to the rack shaft 63 via a ball joint 67.

Next, the pinion shaft 33 is fitted to 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. 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. Thereby, the assembly of the rack and pinion steering device 100 is completed. The ball and socket of the ball joint 67 may be mounted to the rack shaft 63 after the pinion shaft 33 is assembled to the housing 57.

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 by steering the steering wheel 11. The steering torque is detected by a steering torque sensor (not shown) disposed in the steering assist mechanism 21. Next, a control device (not shown) calculates a steering assist current command value based on the steering torque and the vehicle speed detected by a vehicle speed sensor (not shown), and controls the driving of the electric motor 19 based on the steering assist current command value. As a result, a steering assist torque corresponding to the steering torque is generated from the electric motor 19, and the generated steering assist torque is reduced in speed by the worm gear reducer 17 and then transmitted to the steering shaft 13.

The steering torque and the 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 teeth 59 of the pinion shaft 33 mesh with the rack teeth 61 of the rack shaft 63, and the transmitted torque is transmitted to the rack shaft 63, thereby moving the rack shaft 63 in the axial direction.

As the rack shaft 63 moves in the axial direction, the tie rod 35 coupled to the rack shaft 63 via the ball joint 67 also moves in the axial direction, and the steerable wheels (not shown) are steered accordingly, whereby the vehicle turns.

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

Next, the operation of the rack bushing 65 configured as described above will be described.

Fig. 6A is an explanatory view of the operation when the rack shaft 63 moves to one side in the axial direction, and fig. 6B is an explanatory view of the operation when the rack shaft 63 moves to the other side in the axial direction.

Here, F1 represents the force that the flange 77 receives from the groove opening edge 71 of the case 57, and F2 represents the force that the flange 77 expands in diameter by the elastic restoring force. A force by which the rack bushing 65 is pulled by friction when the rack shaft 63 moves to one side in the axial direction is F3, and a force by which the rack bushing 65 is pulled by friction when the rack shaft 63 moves to the other side in the axial direction is F4. When the rack bushing 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 a reaction force from the slot opening edge 71, and the axial movement of the rack bushing 65 is restricted.

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 if a gap is to be generated in the axial direction by the load of F3 or F4, the force of F2 prevents the gap. That is, it is more difficult to create an axial gap between the circumferential groove 69 and the flange 77. Accordingly, the rack bushing 65 can suppress the occurrence of rattling noise due to a gap between the inclined surface 79 on the side on which the axial force acts and the groove opening edge 71.

When the flange 77 is inserted into the circumferential groove 69 when the rack bushing 65 is fitted to the housing 57, the inclined surfaces 79 on both axial sides of the flange 77 come into contact with the groove opening edge 71. Therefore, the backlash can be suppressed only by a simple assembling work of the fitting. That is, the assembling property of the rack bushing 65 to the steering gear mechanism 31 is improved. Further, since the inclined surface 79 of the flange 77 is brought into contact (elastic contact) with the circumferential groove 69 in the elastically biased state, manufacturing errors of the flange 77 and the circumferential groove 69 can be alleviated, and manufacturing costs can be reduced.

Further, since the rack bushing 65 of the present configuration is formed of a synthetic resin material, it is possible to impart good elasticity to the rack bushing 65 itself. This imparts a favorable elastic restoring force to the flange 77, thereby improving the play suppression effect with the circumferential groove 69.

Since the circumferential groove 69 has a rectangular axial cross section, the groove opening edge 71 has an annular corner. As described above, the relationship among the axial dimension Wt of the flat portion 78 on the projecting tip end side of the flange 77, the axial maximum dimension Wb on the projecting base end side, and the axial dimension Wg of the circumferential groove 69 is 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 projecting tip end side of the flange 77 can be reliably prevented from interfering with the groove bottom of the circumferential groove 69, the groove inner wall surface, and the like.

As described above, when the flange 77 is elastically urged radially outward and inserted into the circumferential groove 69 of the housing 57, the inclined surfaces 79 on both sides in the axial direction come into contact with the groove opening edge 71 of the circumferential groove 69. This restricts the axial movement of the rack bushing 65, and a gap in which the rack bushing 65 can move in the axial direction is not generated.

The rack bushing 65 is also held in the inner peripheral surface of the housing 57 in a preloaded manner by the elastic repulsive force of the O-ring 85. This can suppress the occurrence of a gap in the radial direction of the rack bushing 65, thereby suppressing the radial backlash.

That is, the rack bushing 65 can suppress the radial gap over the entire axial region of the rack bushing 65 by the interaction of 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. Further, since the positions of the backlash suppressing portion in the axial direction of the flange 77 and the backlash suppressing portion in the radial direction of the O-ring 85 are arranged to be offset from each other in the axial direction, even when the rack bushing 65 receives an impact load, it is difficult to affect each function.

The effect of suppressing the backlash described above is more remarkable in the structure formed on both sides in the axial direction than in the structure in which the inclined surface 79 of the flange 77 is formed on one side in the axial direction. In addition, when the inclined surfaces 79 are formed on both sides in the axial direction, the effect of preventing the occurrence of the hitting sound can be improved as compared with the case where the inclined surfaces are formed only on one side in the axial direction.

< second structural example >

Next, a second configuration example of the steering device of the present invention will be explained.

Fig. 7 is an enlarged cross-sectional view of a main portion of a steering device including a rack bushing 87 according to a second configuration example. In the following description, the same components and portions as those shown in fig. 1 to 6A and 6B are denoted by the same reference numerals, and redundant description thereof will be omitted or simplified.

In the steering device 200 of the present configuration, the flange 89 of the rack bushing 87 has a radial slit 91. The radial slit 91 is recessed radially inward at an axial center portion and is formed in the circumferential direction.

Fig. 8 is a perspective view of the rack bushing 87 shown in fig. 7.

The radial slits 91 open on the slit inner wall surface of the bushing body 73 formed by the flange 89 being divided by the axial slits 81. Due to the radial slit 91, the pair of opposing walls 93 of the flange 89 face each other with the radial slit 91 therebetween. The surface of each opposing wall 93 opposite to the radial slit 91 is the inclined surface 79. By forming the radial slits 91 in the flange 89, the pair of opposing wall portions 93 can be elastically deformed slightly inward of the radial slits 91, i.e., in a direction of approaching each other.

Next, the operation of the above-described structure will be described.

Fig. 9 is an explanatory view of the operation of the opposing wall portion 93 of the rack bushing 87 shown in fig. 8 with the radial slit 91 therebetween.

In the steering device 200, when the flange 89 is elastically urged to be 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 opposing each other through the radial slit 91 are inclined inward of the radial slit 91 as shown in fig. 9, and are slightly elastically deformed. Therefore, the flange 89 is more prevented from generating an axial gap with the circumferential groove 69 by the elastic restoring force of the opposing wall 93. Thereby, more reliable backlash suppression can be achieved.

In the case where the flange 89 is tapered, the dimension of the rack bushing 87 on the inner diameter side of the flange 89 is sensitively changed in the manner of the abutment of the groove opening edge 71 of the circumferential groove 69 of the housing 57 and the inclined surface 79 of the flange 89. Therefore, there is a possibility that the manner of contact between the inner diameter of the bush and the outer diameter of the rack changes, and the rack sliding force sensitively changes. Depending on the position of the groove opening edge 71 in contact with the inclined surface 79, the rack bushing 87 may be inclined from the axial direction. However, according to the steering device 200 of the present configuration, even in such a case, the opposing wall portion 93 is easily elastically deformed by the radial slits 91, and thus the inclination of the rack bushing 87 and the change in the rack sliding force can be more reliably suppressed.

< third structural example >

Next, a third configuration example of the steering device will be explained.

Fig. 10 is an enlarged cross-sectional view of a main portion of a steering device including a rack bushing 95 according to a third structural example.

In the steering device 300 of the present configuration, the rack bushing 95 has a large diameter portion 97 on the inner circumferential surface thereof. The large diameter portion 97 is formed in an axial region of the rack bushing 95 where the flange 89 is formed so as to have a diameter larger than that of the other inner circumferential surface. That is, the inner side of the flange 89 is radially thin due to the large diameter portion 97.

Fig. 11 is a perspective view of the rack bushing 95 shown in fig. 10.

By forming the large diameter portion 97 on the inner peripheral surface of the rack bushing 95, the axial end side provided with the flange 89 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 slits 81, the arc-shaped divided cylindrical wall portion of the flange 89 sandwiched by the pair of adjacent axial slits 81 is easily displaced radially inward and outward.

Fig. 12 is a section view XII-XII of the rack bushing 95 shown in fig. 11.

The rack bushing 95 has a large diameter portion 97 on the inner peripheral surface thereof, and thus forms a step difference with the inner peripheral surface contacting the rack shaft 63. This step forms a gap d with a large diameter portion 97 of a rack bushing 95 fitted around the rack shaft 63. The rack bushing 95 can sufficiently secure the preload for elastically biasing the flange 89 toward the circumferential groove 69 (see fig. 10) by the gap d. Due to this pre-stress, the flange 89 is pressed into the circumferential groove 69 of the housing 57, so that the rack bushing 95 is mainly restrained from loosening in the axial direction. The gap d is a so-called relief portion. The clearance d serving as a relief portion weakens the press-fitting reaction force of the flange 89, and facilitates the bending. This improves the ease of assembling the rack bushing 95 to the steering gear mechanism.

Since the O-ring 85 and the flange 89 are arranged offset from each other in the axial direction, the reaction force acting on the flange 89 on one end side of the rack bushing reduces the diameter of the flange 89 and expands the diameter of the end portion of the bushing body 73 on the other end side. Therefore, at the end portion of the bushing main body portion 73, the radial gap between the rack bushing 95 and the housing 57 becomes narrow, the radial play suppression effect becomes high, and the radial gap between the rack bushing 95 and the rack shaft 63 becomes wide, the contact pressure of the rack shaft 63 and the rack bushing 95 is lowered, so that the sliding force of the rack shaft 63 is reduced. Further, the existence of the gap d reduces the contact area between the rack shaft 63 and the rack bushing 95, thereby reducing the sliding resistance of the rack shaft 63.

According to the steering device 300 configured as described above, the rack bushing 95 has the large diameter portion 97 formed by expanding the inner peripheral surface in the axial direction in which the flange 89 is provided. Therefore, a gap d is formed between the large diameter portion 97 of the rack bushing 95 and the outer peripheral surface of the rack shaft 63, allowing displacement of the flange 89 in a direction away from the circumferential groove 69 (radially inward). Therefore, when the rack bushing 95 is assembled to the housing 57, the flange 89 is displaced to the gap d, so that the assembly can be facilitated, that is, the insertion resistance can be reduced. In addition, in the state where the gap d is displaced, the flange 89 is brought into contact with the groove opening edge 71 (see fig. 6A and 6B), whereby an elastic restoring force is generated to elastically bias the flange 89. As a result, the backlash can be suppressed in both the radial direction and the axial direction with higher accuracy.

In the structure in which the inclined surface 79 of the flange 89 abuts against the circumferential groove 69, the inner diameter dimension of the back side of the flange 89 is difficult to control. The rack bushing 95 has a relief portion formed by providing the large diameter portion 97 on the inner peripheral surface, thereby eliminating the case where the inner diameter of the back side portion of the flange 89 is excessively strongly in contact with the rack shaft 63 and slides. Thus, according to the steering device 300 including the rack bushing 95 of the present configuration, the rack sliding force can be further stabilized.

According to the steering device having each of the above configurations, it is possible to improve the assembling property, and it is possible to further make it difficult to generate a gap between the circumferential groove (the engagement groove) of the housing and the flange of the rack bushing.

As described above, the present invention is not limited to the above-described embodiments, and modifications and applications based on a mode in which the respective configurations of the embodiments are combined with each other, a description of the specification, and a known technique by those skilled in the art are also within the intended scope of the present invention and are included in the scope of protection sought.

For example, in the above-described configuration example, the case where a plurality of axial slits are provided has been described as an example, but at least one axial slit may be provided.

The present application is based on the japanese patent application filed on 26.1.2017 (japanese patent application 2017-11912), the contents of which are hereby incorporated by reference.

Description of the symbols

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 bushing, 97-large diameter portion, 100-steering device, 200-steering device, 300-steering device.

Claims

1. A steering device is a rack and pinion steering device, and is characterized by comprising:

a housing that houses a rack shaft and a pinion shaft and holds rack teeth of the rack shaft and pinion teeth of the pinion shaft in mesh; and

a cylindrical rack bushing disposed at both longitudinal ends of the housing and supporting the rack shaft to be slidable in an axial direction,

the housing has a circumferential groove formed on an inner periphery thereof facing the rack bushing,

the rack bushing has a plurality of axial slits extending from one end portion toward the other end portion in the axial direction, and a protrusion portion provided on a split cylindrical wall portion divided in the circumferential direction by the axial slits and protruding outward in the radial direction from the outer circumferential surface of the bushing,

the protrusion is inserted into the circumferential groove in a state where an inclined surface whose protrusion height gradually decreases in the axial direction and which protrudes outward in the radial direction is brought into contact with a groove opening edge of the circumferential groove and elastically biased outward in the radial direction,

the rack bushing has a large diameter portion having a diameter larger than that of the other inner circumferential surface on the inner circumferential surface of the axial region where the protrusion is formed, and a relief portion is formed on the inner circumferential surface by the large diameter portion to allow displacement of the protrusion from the circumferential groove to the inside in the radial direction,

a plurality of circumferential grooves intersecting the axial slits are formed in the outer periphery of the bushing of the rack bushing at positions offset in the axial direction from the protrusions, and each of the circumferential grooves is provided with an elastic ring that protrudes radially outward from the outer periphery of the bushing and comes into contact with the inner peripheral surface of the housing.

2. Steering device according to claim 1,

the inclined surfaces of the protrusion are a pair of inclined surfaces whose protruding heights become lower from the axial center portion toward both axial sides.

3. Steering device according to claim 1 or 2,

the projection is formed with a radial slit recessed radially inward in the circumferential direction at the axial center portion.

4. Steering device according to claim 1 or 2,

the rack bushing is made of a synthetic resin material.

5. Steering device according to claim 1 or 2,

the circumferential groove of the housing is a groove having a rectangular axial cross section.

6. Steering device according to claim 1 or 2,

the inclined surface of the protrusion contacts a groove opening edge of the circumferential groove of the housing to restrict axial movement of the rack bushing.