Rack bush and rack pinion type steering apparatus having rack bush for vehicle

Disclosed is a rack bush and a rack pinion type steering apparatus having the rack bush for a vehicle, which can smoothly support a load in an axial direction and a vertical direction of a rack bar so that it is possible to reduce abnormal abrasion of the rack bush, reduce a rattle noise caused by external force transferred through the rack bar during movement of the rack bar, and prevent damage to the rack bar and a pinion through distribution of the load due to an external impact on the shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rack bush and a rack pinion type steering apparatus having the rack bush for a vehicle. More particularly, the present invention relates to a rack bush and a rack pinion type steering apparatus having the rack bush for a vehicle, which can smoothly support a load in an axial direction and a vertical direction of a rack bar so that it is possible to reduce abnormal abrasion of the rack bush, reduce a rattle noise caused by external force transferred through the rack bar during movement of the rack bar, and prevent damage to the rack bar and a pinion through distribution of the load due to an external impact on the shaft.

2. Description of the Prior Art

A steering apparatus is generally equipped between a driver's seat and wheels for moving the wheels by a driver. The steering apparatus includes a steering shaft located in a lower side of the steering wheel of the driver's seat, a gear box connected with the steering shaft, and a rack bar connected to wheels while extending in a left and right direction so as to directly operate the wheels according to an operation of the gear box.

FIG. 1is a partial cross-sectional view illustrating a rack pinion type steering apparatus for a vehicle according to a prior art.

As illustrated inFIG. 1, a gear box125that is connected with a rack housing137in a side direction is provided at a lower side of a steering wheel110and a steering shaft115.

The gear box125includes an input shaft120on an internal upper side of the gear box125, in which the input shaft120is connected to the steering shaft115to receive rotational force generated in the steering wheel110.

The gear box125includes a pinion (not shown) provided at an internal lower side of the gear box125, in which the pinion (not shown) rotates by the rotational force transferred through the input shaft120and has teeth in an outer peripheral portion of its end. Further, the gear box125includes the rack housing137at a lower outer side of the gear box125, in which the rack housing137is integrally formed with the gear box125and extending in both side directions.

The rack housing137is a hollow pipe and has opened entrances in both sides. Further, the rack housing137includes a rack bush160and a rack stopper165at one side of the opened entrance and a bellows150at an outer peripheral side of the rack housing137.

The rack housing137includes a rack bar140having a rack at a center of the rack bar140in an inner side of the rack housing137, so that the rack bar140can be teeth-assembled with a pinion formed in the gear box125.

The rack bar140linearly moves in an axial direction in an inner side of the rack housing137, and includes a rack at a center of the rack bar140so that the rack bar140can be teeth-assembled with the pinion of the gear box125. A left side and a right side of the rack bar140is connected with a tie rod155through an inner ball joint of which a ball is inserted into and assembled with a ball housing175, thereby steering the wheels.

In the meantime, the rack bush160is provided at one opened side of the rack housing137so as to support the rack bar140and guide the movement of the rack bar140.

The rack bush160is shaped like a hollow pipe, of which an outer peripheral surface is in contact with and fixed to an inner peripheral surface and a stepped portion135of the rack housing137and an inner peripheral surface is in contact with an outer peripheral surface of the inserted rack bar140, to guide the sliding of the rack bar140. A rack stopper165is pressed into the rack housing137at the other end of the rack bush160.

That is, the rack stopper165is installed at the end of the rack bush160, in which the rack stopper165shaped like a hollow pipe is in contact with the rack bush160so as to seal the rack housing137and fixed to the inner peripheral surface of the rack housing137, thereby preventing the rack bush160from being separated.

The rack bush and the rack pinion type steering apparatus having the rack bush for a vehicle according to the prior art has a problem in that the load in an axial direction and a vertical direction of the rack bar is transferred to the rack bush through the rack bar, the rack bush, and the rack housing during the steering of the steering wheel of the driver, so that abnormal abrasion and noise in the rack bush are generated.

Further, the rack bush fails to smoothly support the load in an axial direction and a vertical direction of the rack bar so that the rack bar and the pinion shaft are damaged due to the impact transferred from the outside through a road surface.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and the present invention provides a rack bush and a rack pinion type steering apparatus having the rack bush for a vehicle, which can smoothly support a load in an axial direction and a vertical direction of a rack bar so that it is possible to reduce abnormal abrasion of the rack bush, reduce a rattle noise caused by external force transferred through the rack bar during movement of the rack bar, and prevent damage to the rack bar and a pinion through distribution of the load due to an external impact on the shaft.

In accordance with an aspect of the present invention, there is provided a rack bush, including: a bush body shaped like a hollow pipe, of which an outer peripheral surface is assembled with an inner side of a rack housing and an inner peripheral surface is assembled with a rack bar, the bush body including at least one stepped portion, by which the outer peripheral surface of the bush body has multiple outer diameters decreasing from one side end to another side end, so that the bush body is supported by the rack bar and the rack housing and maintains rigidity, at least one first slit formed by incising said one side end in an axial direction, and at least one second slit formed by incising said another side end in the axial direction and being spaced apart from the first slit, said at least one first slit and said at least one second slit being misaligned to each other; and an elastic member having an annular shape and being in close contact with the outer peripheral surface of the bush body.

In accordance with another aspect of the present invention, there is provided a rack pinion type steering apparatus for a vehicle, including: a rack housing assembled with a rack bush at an inner side of the rack housing; and a rack bar supported by an inner peripheral surface of the rack bush to reciprocate in the rack housing, in which the rack bush includes: a bush body shaped like a hollow pipe, of which an outer peripheral surface is assembled with an inner side of a rack housing and an inner peripheral surface is assembled with a rack bar, the bush body including at least one stepped portion, by which the outer peripheral surface of the bush body has multiple outer diameters decreasing from one side end to another side end, so that the bush body is supported by the rack bar and the rack housing and maintains rigidity, at least one first slit formed by incising said one side end in an axial direction, and at least one second slit formed by incising said another side end in the axial direction and being spaced apart from the first slit, said at least one first slit and said at least one second slit being misaligned to each other; and an elastic member having an annular shape and being in contact with the outer peripheral surface of the bush body.

Accordingly, there is an effect in that the rack bush and the rack pinion type steering apparatus having the rack bush for a vehicle according to the present invention can smoothly support the load in an axial direction and a vertical direction of a rack bar so that it is possible to reduce abnormal abrasion of the rack bush, reduce a rattle noise caused by external force transferred through the rack bar during movement of the rack bar, and prevent damage to the rack bar and the pinion through distribution of the load due to an external impact on the shaft.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the same elements will be designated by the same reference numerals although they are shown in different drawings. In the following description, detailed explanation of known related functions and constitutions may be omitted to avoid unnecessarily obscuring the subject manner of the present invention.

Further, a term of a first, a second, A, B, (a), (b), and the like may be used for describing a constructional element of the present invention. Such a term is only for discriminating the corresponding constructional element from another constructional element, but does not limit a nature, a sequence, or an order of the corresponding constructional element. If it is described that a constructional element is “linked”, “assembled”, or “connected” with another constructional element, the constructional element may be directly linked or connected to another constructional element, but it will be additionally appreciated that another constructional element can be further “linked”, “assembled”, or “connected” between each of the constructional elements.

FIG. 2is an exploded perspective view illustrating a rack bush according to a first embodiment of the present invention,FIG. 3is a cross-sectional view illustrating a rack bush according to a first embodiment of the present invention,FIG. 4is a cross-sectional view illustrating a rack bush according to a second embodiment of the present invention, andFIG. 5is a cross-sectional view illustrating a rack bush according to a third embodiment of the present invention.

As illustrated inFIGS. 2 and 3, a rack bush200according to a first embodiment of the present invention is shaped like a hollow pipe, of which an outer peripheral surface is assembled with an inner surface of a rack housing137and an inner peripheral surface is assembled with a rack bar140. The rack bush200includes a bush body210that includes at least one stepped portion, by which the outer peripheral surface of the bush body has multiple outer diameters decreasing from one side end to the other side end of the rack bush200, so that the bush body210can be supported by the rack bar140and the rack housing137and maintains its rigidity, at least one first slit219formed by incising of the one side end in an axial direction of the rack bush200, and at least one second slit221formed by incising the other side end in an axial direction and being spaced apart from the first slit221, said at least one first slit219and said at least one second slit221being misaligned to each other, and an elastic member230that has an annular shape and is in contact and assembled with an outer peripheral surface of the bush body210.

The stepped portion of the bush body210includes a large diameter portion213assembled with and supported by the rack housing137and a small diameter portion217assembled with the outer peripheral surface of the elastic member230. Otherwise, the stepped portion of the bush body210includes a large diameter portion213assembled with and supported by the rack housing137, a middle diameter portion215, which has stepped outer diameters decreasing from the large diameter portion213, and a small diameter portion217, which has stepped outer diameters decreasing from the middle diameter portion215and an outer peripheral surface assembled with the elastic member230.

The rack bar140converts the rotation movement of the steering shaft into the linear movement and reciprocates in the rack housing137in an axial direction. Left and right ends of the rack bar140are connected with a tie rod (reference number155ofFIG. 1) through an inner ball joint of which a ball is inserted into and assembled with a ball housing (reference number175ofFIG. 1), to steer the wheels.

The rack bar140that is teeth-assembled with a pinion of the steering shaft linearly reciprocates in a left and right direction within the rack housing137during the steering of the steering wheel of the driver.

At this time, the rack bar140is supported by the rack bush200that is assembled with the inner side of the rack housing137, to linearly reciprocate. The rack bush200according to the first embodiment of the present invention includes the first slit219and the second slit221on the large diameter portion213and the small diameter portion217or the large diameter portion213, the middle diameter portion215, and the small diameter portion217, which have stepped outer diameters, so that the rack bush200elastically deforms, i.e. shrinks and releases, by itself with those slits or elastically deforms, i.e. shrinks and releases, between the rack housing137and the rack bar140by elastic force of the elastic member230assembled with the small diameter portion217. Therefore, impact energy transferred through the rack bar140decreases so that the noise is decreased, and the rack bush200is in contact with the rack bar140so that it is possible to prevent the noise caused by clearance between the rack bar140and the rack bush200.

The bush body210is in contact with the rack bar140and the rack housing137to slide so that it is preferable that the bush body210is made from a material having abrasion resistance, low friction property, predetermined flexure and rigidity, and low elastic property against heat, such as a material including an engineering plastic base material including Poly Acetal (Poly Oxy Methylene, POM), Polyamide (PA), Polycarbonate (PC), Polyimide (PI), Poly Butylene Terephthalate (PBT), natural rubber, or a synthetic resin including Polyester Elastomer (PE).

The rack bush200according to the first embodiment of the present invention is shaped like a hollow pipe so that the rack bush200is assembled with an inner side of the rack housing137and the rack bar140is inserted into the inner peripheral surface of the rack bush200, thereby enabling the rack bar140to linearly move.

The bush body210includes the stepped portion having the stepped outer diameter of the outer peripheral surface of the bush body210, so that the bush body210is supported by the rack bar140and the rack housing137and maintains its rigidity. The stepped portion includes the large diameter portion213and the small diameter portion217, or the large diameter portion213, the middle diameter portion215, and the small diameter portion217.

The large diameter portion213is supported by the stepped portion135of the rack housing137so that the rack bush200is fixed to the rack housing137without interworking of the rack bush200with the rack bar140during the linear movement of the rack bar140. Further, one side of the elastic member230that is assembled with the small diameter portion217is supported by the stepped portion between the large diameter portion213and the small diameter portion217or the stepped portion between the middle diameter portion215and the small diameter portion217so that the rack bush200can be assembled with the rack housing137without skidding.

Further, the bush body210has the stepped outer peripheral surface decreasing from the large diameter portion213to the small diameter portion217so that the bush body210can easily elastically deform in a diameter direction of the bush body210while maintaining the entire rigidity of the bush body210.

Further, in the bush body210, the outer peripheral surfaces of the stepped portion of the large diameter portion213and the small diameter portion217or the outer peripheral surface of the stepped portion of the middle diameter portion215and the small diameter portion217are slantingly connected, so that the elastic member230can make the bush body210be in contact with the rack bar140and the rack housing137by the elastic force while moving from the small diameter portion217to the middle diameter portion215or from the small diameter portion217to the large diameter portion213during the linear movement of the rack bar140.

The bush body210includes an enlarged diameter portion243having an inner diameter increasing from the middle diameter portion215to the large diameter portion213in the inner peripheral surface of the bush body210in such a manner that the bush body210can be easily assembled with the rack bar140and prevent the increase of the sliding resistance of the rack bar140and the rack bush200even if the bending deformation is generated due to the manufacturing or durability progressing of the rack bar140.

Further, the bush body210includes the first slit219and the second slit221formed by incising the outer peripheral surface and the inner peripheral surface in the axial direction, respectively, so that the bush body210itself has the elastic force capable of shrinking and releasing when the rack bush200is assembled with the rack housing137.

The first slit219is formed by incising the end of the large diameter portion213in the axial direction and the second slit221is formed by incising the end of the small diameter portion217in the axial direction, in which the first slit219and the second slit221have the opening ends in the opposite direction.

That is, the first slit219is formed by incising the end from the large diameter portion213to the partial small diameter portion217in the axial direction so that it is opened in a direction of the end of the large diameter portion213, and the second slit221is formed by partially incising the small diameter portion217in the axial direction while leaving a part of the small diameter portion217so that the second slit is opened toward the small diameter portion217.

Further, the first slit219and the second slit221are alternately located in a circumferential direction while being spaced apart from each other so that it is possible to easily elastically deform the bush body210in a diameter direction and a protrusion233of the elastic body230to be described later is inserted into the first slit219and the second slit221.

In the meantime, the bush body210is assembled with the elastic member230in the outer peripheral surface of the bush body210, in which the elastic member230is coupled between the bush body210and the rack housing137and is elastically deformed so that it makes the bush body210shrink and the rack bar140come into contact with the rack bush210, thereby decreasing the rattle noise.

The elastic member230has an annular shape in which the inner diameter of the elastic member230is smaller than the outer diameter of the bush body210and the width in the axial direction of the elastic member230is larger than a thickness in a diameter direction of the elastic member230. Further, the elastic member230is made from an elastic material, such as urethane, natural rubber, or Polyester Elastomer (PE). One side of the elastic member230is supported by the large diameter portion213or the middle diameter portion215and is in contact with the outer peripheral surface of the small diameter portion217.

Therefore, when the rack bush200is assembled with the rack housing137, the elastic member230assembled with the small diameter portion217does not skid any more.

The elastic member230has the protrusion233that is inserted to the first slit219or the second slit221on the inner peripheral surface of the elastic member230so that the protrusion233guides the assembling of the elastic member230with the bush body210and prevents the elastic member230from rotating or being separated from the bush body210during the sliding of the rack bar140.

Further, as illustrated inFIG. 4, the rack bush300according to a second embodiment of the present invention includes the elastic member230that includes an outer diameter groove237formed at a center of the outer peripheral surface in a diameter direction and inclined surfaces235formed at both ends of the outer peripheral surface.

Therefore, it is possible to reduce an area where the elastic member230is in contact with the inner peripheral surface of the rack housing137and improve the rigidity of the elastic member230, so that it is possible to prevent the elastic member230from being caught in the rack housing137during the assembling of the bush body210with the rack housing137.

Additionally, as illustrated inFIG. 5, the rack bush400according to a third embodiment of the present invention includes the elastic member230including an inner diameter groove241formed at the inner peripheral surface, an outer diameter groove237formed at the outer peripheral surface of the elastic member230, and the inclined surfaces235formed at both ends of the outer peripheral surface of the elastic member230. Therefore, the inner diameter groove241of the elastic member230is seated on a seating portion239protruding from the outer peripheral surface of the small diameter portion217of the bush body210in a diameter direction so that the bush body210is assembled with the elastic member230.

Therefore, it is possible to reduce the area where the elastic member230is in contact with the inner peripheral surface of the rack housing137and to improve the rigidity of the elastic member230, thereby preventing the elastic member230from being caught in the rack housing137during the assembling of the bush body210with the rack housing137. Further, it is possible to prevent the outer peripheral surface of the elastic member230from sliding in the axial direction during the compress of the elastic member230against the rack housing137, thereby preventing the increase of the sliding resistance between the rack bar140and the rack bush200.

As described above, referring toFIG. 5together withFIG. 1, the rack bush includes the rack housing137of which the inner surface is assembled with the rack bush and the rack bar140is teeth-assembled with the pinion and supported by the inner peripheral surface of the rack bush to convert the rotational movement of the steering shaft115into the linear movement while reciprocating in the rack housing137, to construct the rack pinion type steering apparatus for a vehicle.

Accordingly, the present invention having the above structure and shape has an effect of smoothly supporting the load in the axial direction and the vertical direction of the rack bar, thereby reducing abnormal abrasion of the rack bush, reducing the rattle noise caused by the external force transferred through the rack bar during the movement of the rack bar, and preventing the damage of the rack bar and the pinion shaft through distributing the load by outside impact.

In the above description, even though it is described that every constructional element in the embodiment of the present invention is operated through assembling with each other, the present invention is not necessarily limited to the embodiment. That is, at least one constructional element can be selectively assembled for operation within a range of the object of the present invention.

Further, the terms ‘include’, ‘construct’, or ‘have’ used in the above description have a meaning of including the corresponding constructional element as long as there is no specific contrary description. Therefore, it should be interpreted as further including another constructional element, not to exclude another constructional element. Every term including a technical or scientific term has an identical meaning that is generally understood by those skilled in the art if it is not differently defined. The general terms, such as a term defined in the dictionary, should be interpreted as the meaning according to a contextual meaning of the related technology, and should not be interpreted as an ideal or excessively formal meaning as long as they are not obviously defined in the present invention.

Although an exemplary embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims. While the present invention has been shown and described with reference to certain exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, an exemplary embodiment of the present invention has not been described for limiting purposes so that the scope and spirit of the invention may not be limited by the exemplary embodiment thereof. Accordingly, the scope of the invention is not to be limited by the above embodiments but by the claims and the equivalents thereof.