JP4701873B2 - Bush bearing and automotive rack-pinion steering apparatus using the same - Google Patents

Description

  The present invention relates to a bush bearing, and more particularly to a bush bearing suitable for use in movably supporting a rack shaft in a rack-pinion type steering apparatus of an automobile.

Japanese Patent No. 3543352 publication

  In a rack-pinion type steering apparatus, a rack shaft having rack teeth that mesh with pinion teeth is movably supported by a gear box as a housing via a bush bearing. Various types of bushing bearings made of synthetic resin have been proposed, and such synthetic resin bushing bearings usually support the rack shaft so as to be movable with a tightening margin.

  In a bush bearing made of synthetic resin, if the rack shaft to be supported has a large allowance, the rack shaft can be firmly supported with a predetermined rigidity in the radial direction, but the rack shaft will be tightened tightly. The sliding friction resistance increases and the rack shaft cannot be supported with good movement characteristics. On the other hand, if the rack shaft to be supported has a small allowance, the rack shaft has a low sliding friction resistance. Can be expected, however, a large misalignment of the rack shaft and a gap between the rack shaft and the rack shaft are likely to occur, and the radial support is reduced. A hitting sound (gap sound) is also generated between the two.

  In the case of a synthetic resin bushing bearing, due to the stress relaxation of the synthetic resin due to creep deformation and thermal history, a gap is formed between the rack shaft and the radial support, which is reduced in the same manner as described above. (Gap noise) is likely to occur, and especially when radial shrinkage occurs due to stress relaxation of the synthetic resin, the allowance for the rack shaft may increase and the sliding friction resistance may increase. There is.

  In addition, when the synthetic resin bush bearing is used to slidably support the rack shaft in the rack-pinion steering device of an automobile, the inside of the gear box of the rack-pinion steering device is hermetically sealed. It becomes difficult for air to flow in and out of the box, and forced air flow causes abnormal noise or early disappearance of grease or other lubricants applied to the gap between the rack shaft. There is a fear.

  The present invention has been made in view of the above-mentioned points. The object of the present invention is to support the rack shaft with a predetermined rigidity in the radial direction and away from the teeth of the pinion, while in the axial direction. In addition, the present invention provides a bush bearing that can be movably supported with a low frictional resistance and that can reduce the effects of stress relaxation associated with creep deformation and thermal history, and a rack-pinion steering device for an automobile using the bush bearing.

  The bush bearing of the present invention comprises a synthetic resin bush having at least one circumferential groove on the outer peripheral surface, and an endless annular elastic member mounted in the circumferential groove of the bush. Are arranged in a concave or flat inner inner peripheral surface, an outer inner peripheral surface arranged outside the inner inner peripheral surface in the radial direction, and a portion corresponding to the inner inner peripheral surface in the radial direction. And at least one slit that allows the inner inner circumferential surface to move in the radial direction and the inner and outer directions, and the outer inner circumferential surface is defined by the inner inner circumferential surface and the outer inner circumferential surface. A gap is formed between the rack shaft and the outer peripheral surface of the rack shaft inserted into the through hole, and the inner inner peripheral surface is the outer peripheral surface opposite to the rack tooth side of the rack shaft. It comes to contact slidably.

  According to the bush bearing of the present invention, the bush is formed in a concave or flat inner inner peripheral surface, an outer inner peripheral surface disposed radially outward from the inner inner peripheral surface, and an inner inner peripheral surface in the radial direction. And at least one slit disposed in a corresponding portion, and the inner inner peripheral surface is slidably in contact with the outer peripheral surface of the rack shaft opposite to the rack tooth side, Since the endless annular elastic member is mounted in the circumferential groove of the bush, the rack shaft can be supported with a predetermined rigidity in the radial direction and away from the pinion teeth, and the rack shaft side of the rack shaft due to disturbance Can be supported by the inner inner peripheral surface, and can move freely with a low frictional resistance with respect to axial movement, and the outer inner peripheral surface is in contact with the outer peripheral surface of the rack shaft on the rack tooth side. To form a gap between them To have made it possible to reduce the influence of the stress relaxation due to creep deformation and thermal history I above coupled with.

  The synthetic resin as the material for forming the bushing is preferably a resin having excellent wear resistance and low friction characteristics, and having a predetermined flexibility and rigidity and low thermal expansion and contraction. Specifically, a polyacetal resin And a synthetic resin containing at least one of polyamide resin, polyolefin resin and fluororesin.

  The endless annular elastic member has a circular, elliptical, rectangular, or flat oval shape in cross section, but the present invention is not limited thereto, and the cross sectional X shape, the cross sectional U shape, the cross sectional trapezoidal shape, etc. Other shapes may be used, and preferably, natural rubber or synthetic rubber is used, but other elastic thermoplastic synthetic resins such as polyester elastomers may be used. A generally used O-ring can be preferably used as the endless annular elastic member.

  In the bush bearing of the present invention, the bush only needs to have at least one circumferential groove. When the outer circumferential surface includes a plurality of circumferential grooves, each circumferential groove It is preferable to attach an endless annular elastic member.

  The inner inner peripheral surface is slidably in contact with the outer peripheral surface of the rack shaft opposite to the rack tooth side so that the rack shaft can be supported with a predetermined rigidity in the radial direction and away from the pinion. The center angle θ1 with respect to the center of the rack shaft may be provided on the side opposite to the rack tooth side of the rack shaft, and preferably 60 ° or more with respect to the center of the rack shaft on the side opposite to the rack tooth side of the rack shaft. And more preferably a central angle θ1 of 180 ° or less, more preferably a central angle θ1 of 90 ° or more and 180 ° or less with respect to the center of the rack shaft on the side opposite to the rack tooth side of the rack shaft. Each has a central angle θ1 of not less than 120 ° and not more than 180 ° with respect to the center of the rack shaft on the opposite side of the rack tooth side of the rack shaft. Paired with each central angle θ1 Accordingly, with respect to the center of the rack shaft, the central angle θ2 of (360 ° −θ1), the central angle θ2 of (360 ° −θ1), and the central angle θ2 of (360 ° −θ1) are respectively set on the rack tooth side of the rack shaft. It is good to have. The inner inner peripheral surface may be continuous and single concave in the circumferential direction, preferably cylindrical, but alternatively, it is discontinuous (intermittent) in the circumferential direction. There may be a plurality of, preferably at least three, concave or planar ones.

  In the present invention, only one slit may be provided as long as the inner inner peripheral surface can be moved in the radial direction and in the inner and outer directions, but in order to make this evenly movable, a plurality of slits may be provided. It is good to have.

  In a preferred example, the slit opens at one end surface in the axial direction of the bush and extends to the middle of the other end surface in the axial direction of the bush in the axial direction, and in another preferred example, a circumferential groove in the axial direction. And a pair of circumferential slit portions extending in the circumferential direction, and an axial slit portion bridging the pair of circumferential slit portions and extending in the axial direction. .

  The slit that opens at one end surface in the axial direction of the bush and extends to the middle of the other end surface in the axial direction of the bush in the axial direction may be inclined with respect to the axial direction. Even if it has an inclined slit part which inclines, and a pair of axial slit parts which are arranged continuously with the inclined slit part with the inclined slit part in between in the axial direction and extend parallel to the axial direction Good.

  In the bush, one slit extends from one end surface in the axial direction of the bush to the front side of the other end surface in the axial direction of the bush, and the other slit extends from the other end surface in the axial direction of the bush to the axial direction of the bush. A plurality of slits may be provided so as to extend to the front of one end surface in the direction. In this case, the bush has a plurality of one slit and another one slit. A plurality of slits and another slit may be alternately arranged in the circumferential direction.

  In a preferred example, the bush is integrally provided on the outer peripheral surface of the main body having the inner inner peripheral surface, the outer inner peripheral surface and the circumferential groove, and is separated from each other in the circumferential direction. The plurality of protrusions are in contact with the inner peripheral surface of the housing through which the rack shaft passes.

  The bush bearing of the present invention forms a gap between the outer peripheral surface of the rack shaft on the rack tooth side of the rack shaft that is inserted into the through hole defined by the inner peripheral surface and the inner peripheral surface. In order to ensure that the bushing is arranged with respect to the rack shaft so that the inner inner circumferential surface is slidably in contact with the outer circumferential surface opposite to the rack tooth side of the rack shaft, Positioning means for determining the position of the bush with respect to the inner peripheral surface of the housing may be further provided.

  In a preferred example, the positioning means includes a protrusion integrally provided on the bush so as to fit in a recess provided on the inner peripheral surface of the housing.

  A rack-pinion type steering device for an automobile according to the present invention includes a pinion, a rack shaft having rack teeth meshing with the teeth of the pinion, a housing through which the rack shaft passes, and a housing fitted into the housing and the housing. The above-mentioned various types of bush bearings for supporting the rack shaft movably are provided.

  In the rack-pinion type steering apparatus of the present invention, the housing may be a gear housing that houses the pinion, or may be a hollow support member that supports the rack shaft together with the gear housing.

  According to the present invention, the rack shaft can be supported with a predetermined rigidity in the radial direction and away from the pinion teeth, while the axial movement can be supported movably with a low frictional resistance and creep deformation. Further, it is possible to provide a bush bearing capable of reducing the influence of stress relaxation associated with thermal history and a rack-pinion steering device for an automobile using the bush bearing.

  The invention will now be described in more detail with reference to the preferred embodiment examples shown in the drawings. The present invention is not limited to these examples.

  1 to 7, a rack-pinion type steering apparatus 1 for an automobile according to this embodiment includes a pinion (not shown: see Japanese Patent No. 3543651) and a rack tooth 2 that meshes with the teeth of the pinion. A shaft 3, a housing 4 through which the rack shaft 3 passes, and a bush bearing 5 that is fitted in the housing 4 and supports the rack shaft 3 movably in the A direction, which is the axial direction, with respect to the housing 4. is doing.

  The rack shaft 3 has a cylindrical outer peripheral surface 11 at a portion supported by the bush bearing 5, and the housing 4 has a cylindrical inner peripheral surface 12 on which the bush bearing 5 is fitted.

  The bush bearing 5 has a synthetic resin bush 17 having a circumferential groove 16 on its outer peripheral surface 15, and a natural rubber or synthetic rubber O-ring mounted on the circumferential groove 16 of the bush 17. And the positioning means 19 for determining the position of the bush 17 with respect to the inner peripheral surface 12 of the housing 4 in the B direction which is the circumferential direction.

  The bush 17 includes an outer peripheral surface 15, a circumferential groove 16, a cylindrical concave inner inner peripheral surface 21 as a concave shape, and a cylindrical concave surface disposed outside the inner inner peripheral surface 21 in the radial direction C. A main body portion 23 having an outer peripheral surface 22 and three protrusions 24 to 26 that are integrally provided on the outer peripheral surface 15 of the main body portion 23 and are spaced apart from each other in the B direction. Yes.

  In addition to the outer peripheral surface 15, the circumferential groove 16, the inner inner peripheral surface 21, and the outer inner peripheral surface 22, the main body portion 23 is disposed at a portion corresponding to the inner inner peripheral surface 21 in the C direction and the inner inner surface. Four slits 31 to 34 that allow the peripheral surface 21 to move in the C direction and inward and outward directions, a tapered surface 36 provided on the inner peripheral surface 21 at one end surface 35 in the A direction, and the A direction The other end surface 37 is provided with a tapered surface 38 provided on the inner inner peripheral surface 21.

  The inner inner peripheral surface 21 has a central angle θ1 of 180 ° with respect to the center O of the rack shaft 3 on the side opposite to the rack tooth 2 side of the rack shaft 3, and the inner inner peripheral surface 21 and the outer inner peripheral surface 22. In the outer peripheral surface 11 of the rack shaft 3 inserted into the through hole 40 defined by the above, the outer peripheral surface 41 opposite to the rack tooth 2 side is slidably contacted in the A direction.

  The outer peripheral surface 22 of the main body 23 having a central angle θ2 of (360 ° −θ1) = 180 ° with respect to the center O of the rack shaft 3 on the rack tooth 2 side of the rack shaft 3 is the rack of the rack shaft 3. A cylindrical gap 43 is formed with the outer peripheral surface 42 on the tooth 2 side.

  Each of the slits 31 to 34 opens at one end surface 35 of the main body portion 23 of the bush 17 and extends to the middle of the other end surface 37 of the bush in the A direction. The slits 31 and 32 are formed on the inner inner peripheral surface 21. Is adjacent to the protrusion 24 arranged corresponding to the substantially central portion in the B direction, and is arranged with the protrusion 24 sandwiched in the B direction, in the vicinity of one end portion in the B direction of the inner inner peripheral surface 21. The correspondingly disposed slit 33 is adjacent to the protrusion 25, and the slit 34 corresponding to the vicinity of the other end in the B direction of the inner inner peripheral surface 21 is adjacent to the protrusion 26.

  In the protrusions 24 to 26, the protrusion 24 is arranged corresponding to a substantially central portion in the B direction of the inner inner peripheral surface 21, and the protrusion 25 is located at one end in the B direction of the inner inner peripheral surface 21. The projections 26 are arranged corresponding to the other end neighborhood in the B direction of the inner inner peripheral surface 21, and each of the projections 24 to 26 is cylindrical in the C direction. The front end surface 44 is in close contact with the inner peripheral surface 12 of the housing 4 with the elastic force of the bush 17 made of synthetic resin, so that the bush 17 is connected to the inner peripheral surface of the housing 4 via the projections 24 to 26. 12 is fitted.

  The positioning means 19 includes a protrusion 45 formed integrally with one end surface 35 of the main body 23, and the protrusion 45 is formed in a recess 46 formed on the inner peripheral surface 12 of the housing 4 in the C direction. The bush 17 is prevented from rotating with respect to the housing 4 in the B direction, and the inner inner peripheral surface 21, the protrusions 24 to 26, and the slits 31 to 34 are formed in the rack shaft 3. The rack teeth 2 are positioned and arranged as shown in FIG.

  In the rack-pinion type steering device 1 described above, the rack shaft 3 is supported by the inner inner peripheral surface 21 of the bush bearing 5 so as to be slidable in the A direction. The separation of the pinion from the teeth can be suppressed, the meshing between the rack teeth 2 of the rack shaft 3 and the pinion teeth is maintained, and the occurrence of rattling noise due to the collision between the rack teeth 2 and the pinion teeth can be suppressed. Moreover, according to the bush bearing 5, the bush 17 corresponds to the inner inner peripheral surface 21 and the inner inner peripheral surface 21, the outer inner peripheral surface 22 disposed on the outer side in the C direction and the inner inner peripheral surface 21 in the C direction. The inner inner peripheral surface 21 comes into contact with the outer peripheral surface 41 opposite to the rack tooth 2 side of the rack shaft 3 slidably in the A direction. In addition, since the endless annular elastic member 18 is mounted in the circumferential groove 16 of the bush 17, the rack shaft 3 can be supported by the inner inner peripheral surface 21 on the side opposite to the rack tooth 2 side. Displacement of the rack shaft 3 to the side opposite to the rack tooth 2 side, that is, the displacement of the rack shaft 3 in the direction of loosening the engagement with the pinion teeth can be prevented by the inner inner peripheral surface 21, The surface 21 is based on the elastic force of the endless annular elastic member 18. As a result, the rack shaft 3 can be supported with a predetermined rigidity with respect to the direction C and away from the pinion teeth, and the outer inner peripheral surface 22 can be supported by the rack teeth of the rack shaft 3. Since the cylindrical gap 43 is formed between the outer peripheral surface 42 on the second side and the overall tightening of the rack shaft 3 is avoided, the rack shaft 3 is moved in the A direction. In addition to being movably supported with low frictional resistance, the effect of stress relaxation associated with creep deformation and thermal history of the bushing 17 can be reduced, and the rack shaft 3 can exhibit stable support over a long period of time. it can.

  In the bush bearing 5 described above, the bush 17 is provided with slits 31 to 34 that open at one end surface 35 of the bush 17 and extend to the middle of the other end surface 37 of the bush 17 in the A direction. 8 and FIG. 9, a pair of circumferential slit portions 51 and 52 that sandwich the circumferential groove 16 in the A direction and extend in the B direction, and a pair of circumferential slit portions 51 and 52, the slits 54 and 55 each having an axial slit portion 53 extending in the A direction, the axial slit portions 53 being adjacent to each other, and the axial slit portion 53. May be provided in the body portion 23 of the bush 17 in parallel with the B direction so as to correspond to the central portion of the inner inner peripheral surface 21 in the B direction. According to such slits 54 and 55, it is possible to reduce the possibility that the endless annular elastic member 18 attached to the circumferential groove 16 projects from the inner inner peripheral surface 21 to the through hole 40.

  Further, as shown in FIGS. 3 and 5, the slit 61 is provided in the body portion 23 of the bush 17 corresponding to the substantially central portion in the B direction of the outer inner peripheral surface 22 that is equivalent to each of the slits 31 to 34. May be.

It is the II sectional view taken on the line in FIG. 2 of an example of preferable embodiment of this invention. It is a left view of the example shown in FIG. It is a right view of the example shown in FIG. It is a top view of the example shown in FIG. It is a bottom view of the example shown in FIG. It is explanatory drawing of the example which used the example shown in FIG. 1 for the rack-pinion type steering device of a motor vehicle. It is a right view of the example shown in FIG. It is a top view of the other example of preferable embodiment of this invention. It is a top view which abbreviate | omitted the endless annular elastic member of the example shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rack-pinion type steering device 2 Rack tooth 3 Rack shaft 4 Housing 5 Bush bearing 15 Outer peripheral surface 16 Circumferential groove 17 Bush 18 Endless annular elastic member 21 Inner inner peripheral surface 22 Outer inner peripheral surface

Claims (3)

A bush made of synthetic resin having at least one circumferential groove on the outer circumferential surface, and an endless annular elastic member mounted on the circumferential groove of the bush, the bush comprising the outer circumferential surface and the circle in addition to the circumferential groove, movable concave inside inner circumferential surface, a radially outer inner peripheral surface and the inner inner peripheral surface arranged outside the inner inner peripheral surface in the radial direction in and out direction first shall be the second, the third and fourth main body portion of the four slits having respective, first spaced apart in the circumferential direction together integrally provided on the outer peripheral surface of the body portion A rack of rack shafts that includes three projections of first, second, and third, and the outer inner peripheral surface is inserted into a through hole defined by the inner inner peripheral surface and the outer inner peripheral surface. A gap is formed between the outer peripheral surface of the teeth and the inner inner peripheral surface is the rack shaft. The rack teeth side is adapted to slidably contact with the outer peripheral surface of the opposite side, each of the first third projections s, the rack shaft is adapted to contact with the inner peripheral surface of the through-housing Each of the first to fourth slits opens at one end surface in the axial direction of the main body and extends to the middle of the other end surface in the axial direction of the main body in the axial direction. The second slit is adjacent to the first projection provided on the outer peripheral surface of the main body portion corresponding to the central portion in the circumferential direction of the inner inner peripheral surface in the radial direction, and the first slit in the circumferential direction. The third slit is arranged on the outer peripheral surface of the main body portion corresponding to the radial direction near one end portion in the circumferential direction of the inner inner peripheral surface. The fourth slit is adjacent to the other in the circumferential direction of the inner inner peripheral surface. Is adjacent to the third protrusion provided on the outer peripheral surface of the main body corresponding to the vicinity of the portion, and the inner inner peripheral surface is 120 ° or more with respect to the center of the rack shaft on the side opposite to the rack tooth side of the rack shaft. The outer peripheral surface has a central angle θ1 of (360 ° −θ1) with respect to the center of the rack shaft on the rack tooth side of the rack shaft . bearing. The bush bearing according to claim 1, further comprising positioning means for determining a position of the bush in a circumferential direction with respect to an inner peripheral surface of the housing. A rack having a pinion, a rack shaft that meshes with the teeth of the pinion, a housing through which the rack shaft passes, and a rack shaft that is fitted to the housing and is movably supported with respect to the housing. A rack-pinion steering device for an automobile comprising the bush bearing according to 1 or 2.

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