A center take-off rack-and-pinion steering apparatus includes a cylindrical rack housing having an elongate hole extending in a longitudinal direction, a mounting bracket for mounting ends of a pair of tie rods on a rack shaft, and a slider interposed between the mounting bracket and the rack shaft and slidable in an inner periphery of the elongate hole. The inner periphery of the elongate hole and the slider include sliding contact sections that are brought into sliding contact with each other along with the slide of the slider slides. The sliding contact sections include at least a pair of curved sliding contact surfaces that are brought into sliding contact with each other in a curved shape when seen in an axial direction of the rack shaft.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a center take-off rack-and-pinion steering apparatus.

2. Description of Related Art

Examples of a steering apparatus include a so-called center take-off steering apparatus. In this type of steering apparatus, a tie rod connected to a wheel is taken out of a rack shaft at a central position in a right-and-left direction of a vehicle body. For example, a steering mechanism includes a rack shaft and a longitudinal cylindrical rack housing receiving the rack shaft. An elongate hole is formed in an intermediate portion of the rack housing in a longitudinal direction. Through the elongate hole, the rack shaft and the tie rod are connected to each other through a slider. The rack housing and the slider are brought into sliding contact with each other (see Japanese Unexamined Patent Publication Nos. 2000-62628 and 2001-151140).

In Japanese Unexamined Patent Publication No. 2000-62628, the rack housing includes a flat first sliding contact surface formed in the inner periphery of the elongate hole and a flat second sliding contact surface formed at an edge surrounding the elongate hole on an outer peripheral surface of the rack housing.

Furthermore, the slider has flat first and flat second sliding contact surfaces that are individually brought into sliding contact with the first and second sliding contact surfaces of the rack housing. The first sliding contact surface of the rack housing extends parallel to the longitudinal direction and a depth direction of the elongate hole. The second sliding contact surface of the rack housing is perpendicular to the first sliding contact surface of the rack housing.

In Japanese Unexamined Patent Publication No. 2000-62628, the first and second sliding contact surfaces that are perpendicular to each other are provided, so that the manufacturing cost of the steering apparatus is high.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a low-cost steering apparatus that can inhibit a rattle from occurring in a rack shaft.

According to a preferred aspect of the present invention, a center take-off rack-and-pinion steering apparatus is provided that includes a pinion rotating along with a steering member, a rack shaft that is meshed with the pinion and extends in an axial direction, and a cylindrical rack housing for supporting the rack shaft so as to be movable in the axial direction. The rack housing is formed with an elongate hole extending in a longitudinal direction parallel to the axial direction of the rack shaft. Furthermore, the center take-off rack-and-pinion steering apparatus includes a mounting bracket for mounting ends of a pair of tie rods for steering a pair of wheels on the rack shaft, and a slider interposed between the mounting bracket and the rack shaft and slidable in an inner periphery of the elongate hole. The inner periphery of the elongate hole and the slider include sliding contact sections that are brought into sliding contact with each other. The sliding contact sections include at least a pair of curved sliding contact surfaces that are brought into sliding contact with each other in a curved shape when seen in the axial direction of the rack shaft.

According to the present invention, the pair of curved sliding contact surfaces serving as sliding contact sections includes portions that are inclined to a width direction and a depth direction of the elongate hole which are perpendicular to the longitudinal direction of the elongate hole. Therefore, the movement of the slider can be regulated in the width direction and the depth direction of the elongate hole. As a result, a rattle hardly occurs in the rack shaft. Moreover, the rattle can be suppressed by a small number of curved sliding contact surfaces. Therefore, the configuration of the steering apparatus is simplified, and the manufacturing cost thereof is reduced.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An embodiment of the present invention will be described in detail while referring to the attached drawings. Although in the present embodiment, description is made in conformity with a case where a center take-off rack-and-pinion steering apparatus is an electric power steering apparatus, the present invention is not limited to the same. For example, it may be a manually steered steering apparatus.FIG. 1is a schematic view showing the schematic configuration of a center take-off rack-and-pinion steering apparatus according to an embodiment of the present invention.

Referring toFIG. 1, a center take-off rack-and-pinion steering apparatus1(merely referred to as a steering apparatus1hereinafter) includes a steering shaft4that transmits a steering torque applied to a steering wheel3serving as a steering member for steering wheels2and a steering mechanism5including a rack-and-pinion mechanism, for example, for steering the wheels2by the steering torque from the steering shaft4. Furthermore, the steering apparatus1includes an intermediate shaft6provided between the steering shaft4and the steering mechanism5and serving as a shaft coupling for transmitting rotation therebetween.

The steering shaft4is inserted through a steering column7and is rotatably supported by the steering column7. The steering column7is supported by a vehicle body9through a bracket8. The steering wheel3is connected to one end of the steering shaft4, and is rotatably supported thereon. The intermediate shaft6is connected to the other end of the steering shaft4.

The intermediate shaft6includes a power transmission shaft10, a universal joint11provided at one end of the intermediate shaft6, and a universal joint12provided at the other end of the intermediate shaft6.

The steering mechanism5includes a pinion13serving as an input shaft and a rack shaft14serving as a steering shaft extending in a right-and-left direction X of an automobile (direction perpendicular to the traveling direction of the automobile). The pinion13and the rack shaft14are supported by a housing15. Pinion teeth13aof the pinion13and rack teeth14aof the rack shaft14are meshed with each other.

The pinion13is rotatably supported on a gear housing32constituting a portion of the housing15. Furthermore, the rack shaft14is supported on a cylindrical rack housing33so as to be linearly and reciprocatingly movable. The rack housing33is fixed to the vehicle body9. A rack shaft14is connected through a tie rod28described later and a knuckle arm (not shown) to the corresponding wheel2.

When the steering wheel3is steered so that the steering shaft4is rotated, the rotation is converted into a linear motion of the rack shaft14along the right-and-left direction X of the automobile by the pinion teeth13aand the rack teeth14a. This allows steering of the wheel2.

The steering apparatus1is adapted so as to obtain a steering assist force depending on the steering torque. That is, the steering apparatus1includes a torque sensor16that detects a steering torque, an ECU (Electronic Control Unit)17serving as a control section, an electric motor18for steering assist, and a reduction gear mechanism19serving as a gear device. In the present embodiment, the electric motor18and the reduction gear mechanism19are provided in association with the steering column7.

The steering column7includes a column tube20and a housing21. The housing21accommodates and supports the torque sensor16. Furthermore, the housing21supports the electric motor18.

The steering shaft4includes an input shaft22, an output shaft23, and a torsion bar24as its axial lower portions, and includes a connection shaft25as an axial upper portion. The input shaft22and the output shaft23are connected to each other on the same axis through the torsion bar24. The input shaft22connects to the steering wheel3through the connection shaft25. The output shaft23connects to the intermediate shaft6. When the steering torque is inputted to the input shaft22, the torsion bar24is subjected to elastic torsional deformation. This causes the input shaft22and the output shaft23to rotate relative to each other.

The torque sensor16detects a torque on the basis of the amount of relative rotational displacement between the input shaft22and the output shaft23through the torsion bar24. The results of the torque detection by the torque sensor16are given to the ECU17.

The ECU17controls the electric motor18on the basis of the above-mentioned results of the torque detection and the results of vehicle speed detection given by a vehicle speed sensor (not shown).

When the steering wheel3is operated, the steering torque is detected by the torque sensor16, and the electric motor18produces a steering assist force depending on the results of the torque detection, the results of the vehicle speed detection, and the like. The steering assist force is transmitted to the steering mechanism5through the reduction gear mechanism19. In addition thereto, the movement of the steering wheel3is also transmitted to the steering mechanism5. As a result, the wheels2are steered, and the steering is assisted.

The steering apparatus1according to the present embodiment is configured as a center take-off steering apparatus. That is, the pair of tie rods28is taken out of a central position9ain the right-and-left direction X of the vehicle body9.

The steering mechanism5includes the pinion13, the rack shaft14, the housing15, the pair of tie rods28, which are described above, a connecting unit29that connects the pair of tie rods28and the rack shaft15to each other, and a dust cover30.

Each of the tie rods28is a stick-shaped connecting material for connecting the rack shaft14and the corresponding wheel2to each other in order to steer the wheel2upon receipt of linear displacement of the rack shaft14. An outer end28aserving as an end outside of each of the tie rods28is connected to the corresponding wheel2. An inner end28bserving as an end inside of each of the tie rods28is arranged at a substantially central position of the vehicle body9in the right-and-left direction X of the vehicle body9. The inner end28bof each of the tie rods28is connected to an intermediate portion in an axial direction X1of the rack shaft14.

FIG. 2is a partially sectional view of a principal part of the steering mechanism5shown inFIG. 1, showing a cross section taken along a line II-II ofFIG. 3.FIG. 3is a partially sectional view of a cross section taken along a line III-III ofFIG. 2.FIG. 4is an exploded perspective view of the principal part of the steering mechanism5, also schematically showing a peripheral part thereof.

Referring toFIGS. 2 and 4, the rack shaft14includes a pair of mounting sections31for mounting the connecting unit29in an intermediate portion in the axial direction X1. Each of the mounting sections31includes a recess31athat receives a spacer44in a slider38, described later, in the connecting unit29in a positioned state and a screw hole31cformed at the bottom31bof the recess31a. A fixing screw41, described later, in the connecting unit29is screwed into the screw hole31c.

Referring toFIGS. 1 and 3, the housing15supports the rack shaft14so as to be slidable along the axial direction X1of the rack shaft14. The housing15includes the gear housing32accommodating the pinion13and the longitudinal rack housing33in the shape of a long cylinder consecutively connected to the gear housing32. A longitudinal direction of the rack housing33is arranged parallel to the axial direction X1of the rack shaft14. One end of the rack housing33is fixed to the gear housing32. The rack housing33accommodates and supports the rack shaft14. An elongate hole34is formed in an intermediate portion in the longitudinal direction of the rack housing33.

A portion of the connecting unit29is passed through the elongate hole34. With the displacement of the rack shaft14in the axial direction X1, the elongate hole34having a length corresponding to a movement range of the connecting unit29is formed such that the connecting unit29is movable.

FIG. 5is a schematic partially broken perspective view of the elongate hole34and the slider38.FIG. 6is an enlarged view of the principal part shown inFIG. 3.

Referring toFIGS. 3 and 5, the elongate hole34extends long in parallel to the longitudinal direction of the rack housing33, and penetrates the inner periphery and the outer periphery of the rack housing33in a radial direction of the rack housing33. The radial direction corresponds to a depth direction W of the elongate hole34, and is a direction passing through a central position PO of the elongate hole34to a circumferential direction of the rack shaft14.

The elongate hole34is formed to be longer in the longitudinal direction U, and shorter in a short-side direction V. The longitudinal direction U is a direction parallel to the longitudinal direction of the rack housing33. The short-side direction V corresponds to a width direction of the elongate hole34, and is a direction perpendicular to the longitudinal direction U and the depth direction W of the elongate hole34. The short-side direction V is also referred to as a width direction V hereinafter.

The inner periphery34aof the elongate hole34includes a pair of curved sliding contact surfaces34bthat are brought into contact with a curved sliding contact surface38cserving as a sliding contact section of the slider38described later, and a pair of non-contact sections34cthat are not brought into contact with the slider38. The pair of non-contact sections34cis formed at both ends of the elongate hole34in the longitudinal direction U.

The pair of curved sliding contact surfaces34bis formed at a pair of edges opposed to each other in the short-side direction V of the elongate hole34in the inner periphery34aof the elongate hole34. The pair of curved sliding contact surfaces34bextends in parallel to the longitudinal direction U of the elongate hole34. Each of the curved sliding contact surfaces34bis formed like a drain pipe having a convex-curved surface serving as a curved surface. The convex-curved surface extends along the longitudinal direction U of the elongate hole34. The convex-curved surface forms a circular arc shape in cross section having a radius R of curvature in a cross section perpendicular to the longitudinal direction U of the elongate hole34. The shape in cross section is made constant irrespective of the position thereof in the longitudinal direction U. That is, the convex-curved surface includes a portion of a cylindrical surface.

The respective shapes in cross section of the pair of curbed sliding contact surfaces34b, e.g., the radii R of curvature have equal values. Furthermore, a pair of sliding contact sections34bis arranged in a linearly symmetrical relationship with respect to a central axis41cof the fixing screw41, as viewed along the axial direction X1of the rack shaft14.

Referring toFIGS. 3 and 6, each of the curved sliding contact surfaces34bhas a first section34baand a second section34bb. The first section34bais arranged farther from the rack shaft14in the depth direction W of the elongate hole34, and faces the outside of the rack housing33. The first sections34baof the pair of curved sliding contact surfaces34bare opposed to each other while being directed toward the outside of the rack housing33, and are inclined to the depth direction W of the elongate hole34. The first section34baconstitutes a chamfer formed in an inlet to the inner periphery34aof the elongate hole34.

The second section34bbis arranged closer to the rack shaft14to the depth direction W of the elongate hole34, and faces the inside of the rack housing33. The second sections34bbof the pair of curved sliding contact surfaces34bare opposed to each other while being directed toward the inside of the rack housing33, and are inclined to the depth direction W of the elongate hole34.

Referring toFIGS. 1 and 3, the dust cover30forms the shape of a cylinder extending in one direction, and is formed of a rubber member or a synthetic resin member serving as an elastic member so as to be extendable in a direction in which the dust cover30extends (longitudinal direction). The longitudinal direction of the dust cover30is arranged in parallel to the longitudinal direction of the rack housing33. The dust cover30covers the elongate hole34of the rack housing33.

Both ends35of the dust cover30in the longitudinal direction of the dust cover30are fixed to the cylinder of the rack housing33. The center36of the dust cover30in the longitudinal direction of the dust cover30is adapted to move along with the connecting unit29, and has a hole36cpenetrating the inside to the outside of the dust cover30. The hole36cis provided so as to connect the tie rod28and the rack shaft14to each other, and is passed by the spacer44and the fixing screw41in the slider38described later in the connecting unit29.

Referring toFIGS. 2 and 4, the connecting unit29includes a slider38that slides in the inner periphery34aof the elongate hole34of the rack housing33while moving integrally with the rack shaft14and a mounting bracket39for mounting the pair of tie rods28on the slider38. Furthermore, the connecting unit29includes a pair of spherical bearings40serving as couplings that individually and swingingly connect the mounting bracket39and the tie rods28to each other and a plurality of, e.g., two fixing screws41serving as fixtures that fix the mounting bracket39and the slider38to the rack shaft14.

The inner end28bof the tie rod28is connected to the rack shaft14through the spherical bearing40, the mounting bracket39, and the slider38. The number of fixing screws41may be plural or single, that is, the number of fixing screws41may be at least one. In the present embodiment, description is made in conformity with a case where the number of fixing screws41is two.

The spherical bearing40includes a ball and a receptacle forming the shape of a recess receiving the ball. The ball forms a partially spherical surface, and is fixed to the inner end28bof the corresponding tie rod28. Furthermore, the receptacle forms a partially spherical surface. The center of the partially spherical surface of the ball (which coincides with the center of the partially spherical surface of the receptacle) is the center of the spherical bearing40. Around the center of the spherical bearing40, the corresponding tie rod28is adapted to be swingable. Furthermore, the receptacle has a mounting screw for mounting on the mounting bracket39provided so as to project as its support shaft. The mounting screw and the receptacle are separately formed, and are fixed to each other. A male screw is formed in the mounting screw.

The mounting bracket39is provided to mount the inner end28bof each of the tie rods28to the rack shaft14. The mounting bracket39includes a base39aopposed to the slider38and a supporting section39bserving as an arm projecting from the base39a. The base39aand the supporting section39bform a T shape and are integrally formed of a single member.

The base39aincludes a pair of screw insertion holes39cpenetrating the base39a. The fixing screw41is inserted through the screw insertion hole39c. Furthermore, the base39aincludes an opposed section39dopposed to the dust cover30. At least a portion of the opposed section39dis abutted against the dust cover30.

The supporting section39bextends from the base39aat a central position of the base39ain the axial direction X1. That is, the supporting section39brises from the base39a, and extends in a direction perpendicularly crossing the axial direction X1and away from the rack shaft14in the depth direction W of the elongate hole34. The supporting section39bis connected to the pair of spherical bearings40, and supports the inner ends28bof the pair of tie rods28through the pair of spherical bearings40. Specifically, the supporting section39bhas a screw hole penetrating the supporting section39bin a direction parallel to the axial direction X1. Mounting screws in the pair of spherical bearings40are screwed into the screw hole on both sides.

The fixing screw41is fixed to the rack shaft14after penetrating the mounting bracket39and the slider38. Specifically, the fixing screw41is a bolt, and includes a head41aand a shaft41bformed with a male screw.

Although the central axis41cof the fixing screw41is parallel to the depth direction W of the elongate hole34, and perpendicularly crosses the central axis14cof the rack shaft14in the present embodiment, the central axis41cmay be arranged to offset in the width direction V of the elongate hole34.

The male screw of the shaft41bin the fixing screw41is screwed into the screw hole31cof the mounting section31in the rack shaft14. The mounting bracket39and the slider38are clamped between the head41aof the fixing screw41and the bottom31bof the recess31ain the mounting section31in the rack shaft14.

The slider38is fixed to the mounting section31in the rack shaft14so as to be movable integrally with the rack shaft14. The slider38is interposed between the mounting bracket39and the rack shaft14, and connects both the mounting bracket39and the rack shaft14to each other. The slider38holds the center36of the dust cover30so as to be integrally movable.

Referring toFIGS. 3 and 4, the slider38includes a first connecting section38aconnected to the rack shaft14in a fixed state, a second connecting section38bconnected to the mounting bracket39in a fixed state, and a curved sliding contact surface38cslidably fitted in the inner periphery34aof the elongate hole34of the rack housing33. Furthermore, the slider38includes a holding section38dopposed to the mounting bracket39for holding the dust cover30in a clamped state and an insertion hole38ethrough which the fixing screw41is inserted. Although the sections38a,38b,38c,38dor38e, each are provided in plural, at least one of each may be sufficient.

Referring toFIGS. 2 and 3, the slider38includes a main body42and two projections43. The two projections43are formed similarly to each other.

The main body42is arranged closer to the rack shaft14than the holding section38d. The main body42includes the first connecting section38a, the curved sliding contact surface38c, and the holding section38d, described above. Each of the projections43is constituted by a portion closer to a front end than the holding section38din the slider38, and projects from the main body42in a direction perpendicularly crossing the axial direction X1of the rack shaft14. Each of the projections43includes the second connecting section38b. Furthermore, the insertion hole38epenetrates the main body42and the corresponding projection43.

Specifically, the slider38includes a pair of cylindrical spacers44respectively corresponding to the tie rods28and a connector45that connects the spacers44to each other. The pair of spacers44and the connector45are separately formed, and are combined with each other to constitute the slider38.

Referring toFIGS. 2 and 4, the spacer44connects the rack shaft14inside of the rack housing33and the base39ain the mounting bracket39outside of the rack housing33so as to be movable integrally with each other in a state of being spaced apart from each other. The spacer44includes a first section44ahaving a relatively large diameter arranged closer to the rack shaft14and a second section44bhaving a relatively small diameter arranged closer to the mounting bracket39than the first section44a. The first section44aand the second section44bare integrally formed. The insertion hole38epenetrates the first and second sections44aand44b.

The first section44aincludes the first connecting section38a. The first section44apositions the rack shaft14and the connector45in a direction adjacent to each other. Furthermore, the first section44aregulates relative rotation between the rack shaft14and the connector45around the axis41cof the fixing screw41. The second section44bincludes the second connecting section38b. An outer peripheral surface of the second section44bis formed into a cylindrical surface. The outer peripheral surface of the second section44bis connected to an outer peripheral surface of the first section44athrough an end surface44cof the first section44a.

The connector45is formed of a synthetic resin member having a low sliding resistance. The connector45includes a pair of annular sections45bfor individually holding a pair of spacers44and a connecting section45cfor connecting a pair of annular sections45bto each other. Each of the annular sections45bis received by the end surface44cof the spacer44. Each of the annular sections45bhas an insertion hole45a. A front end of the second section44bin the spacer44serving as the corresponding projection43is inserted through each of the insertion holes45a. The connector45includes the curved sliding contact surface38cand the holding section38d.

Referring toFIGS. 3 and 4, the curved sliding contact surface38cis provided on a pair of side surfaces of the pair of annular sections45bin the connector45. Four curved sliding contact surfaces38care formed as the entire slider38. The two curved sliding contact surfaces38cprovided in one of the annular sections45band the two curved sliding contact surfaces38cprovided in the other annular section45bare formed similarly to each other, and are spaced apart from each other at a predetermined distance in the longitudinal direction U of the elongate hole34. Description is made about the one annular section45b.

Referring toFIGS. 3 and 5, each of the curved sliding contact surfaces38cis arranged so as to be opposed to the curved sliding contact surface34bin the inner periphery34aof the elongate hole34. Each of the curved sliding contact surfaces38cis formed like a drain pipe having a concave-curved surface serving as a curved surface opposite to the opposed curved sliding contact surface34band in an opposite direction thereto. The concave-curved surface includes a portion of a cylindrical surface. Each of the curved sliding contact surfaces38cextends in parallel to the longitudinal direction U of the elongate hole34and forms a circular arc shape in cross section having a radius R of curvature, similarly to the curved sliding contact surface34bin the inner periphery34aof the elongate hole34. The radius of curvature of the circular arc shape in cross section of the curved sliding contact surface38cmay be a value equal to the radius of curvature of a circular arc shape in cross section of the curved sliding contact surface34b, or may be an approximate value within a predetermined range that approximates the equal value (0% to 10% of the equal value).

Referring toFIGS. 3 and 6, each of the curved sliding contact surfaces38cincludes a first section38cathat is brought into sliding contact with the first section34ba(corresponding to a chamfer) in the corresponding curved sliding contact surface34band a second section38cbthat is brought into sliding contact with the second section34bbin the corresponding curved sliding contact surface34b.

Each of the curved sliding contact surfaces38cin the slider38and the curved sliding contact surface34bin the inner periphery34aof the elongate hole34are opposed to each other, and are in contact with each other in a surface contact state so as to be movable relative to each other in the longitudinal direction U of the elongate hole34. Both the curved sliding contact surfaces38cand34bare brought into sliding contact with each other along with the slide of the slider38. The rack housing33and the slider38are adapted not to contact with each other in a portion other than the corresponding curved sliding contact surfaces34band38c.

Referring toFIGS. 1 and 3, when an external force from the wheel2is exerted bilaterally on the depth direction W of the elongate hole34through the tie rods28and the mounting bracket39, for example, the curved sliding contact surface38cin the slider38and the curved sliding contact surface34bin the elongate hole34are abutted against each other. Thus, the above-mentioned external force is received to prevent the rack shaft14from bilateral moving in the depth direction W of the elongate hole34. Therefore, a rattle can be inhibited from occurring in the rack shaft14. Furthermore, when the external force is exerted bilaterally on the width direction V of the elongate hole34, a rattle is also inhibited from occurring in the rack shaft14in the same manner.

FIGS. 7A to 7Care schematic views of the slider38and the elongate hole34shown inFIG. 2.FIG. 7Aillustrates a state where the slider38is incorporated into the elongate hole34,FIG. 7Billustrates a state where the slider38reaches one end in its movement range, andFIG. 7Cillustrates a state where the slider38reaches the other end in the movement range. The slider38at a position shown inFIG. 7Bis also indicated by a two-dot and dash line inFIG. 7c.

Referring toFIGS. 5 and 7A, the elongate hole34has an opening46for incorporating the slider38into the rack housing33.

The opening46constitutes the above-mentioned non-contact section34c, and no curved sliding contact surface34bis provided on both sides of the opening46to the width direction V. The opening46has a size that can pass the slider38. That is, the dimension L1of the opening46to the width direction V of the elongate hole34is made larger than the minimum distance L3between the curved sliding contact surfaces34bin the elongate hole34(L1>L3), and is made larger than the maximum dimension L4of the curved sliding contact surface38cin the slider38(L1>L4).

The dimension L2of the opening46to the longitudinal direction U of the elongate hole34is made larger than the maximum dimension L5of the connector45serving as a portion of the slider38, and arranged within the elongate hole34(L2>L5).

Referring toFIGS. 1,7B and7C, the opening46is arranged at the one end34dof the elongate hole34to the longitudinal direction U of the elongate hole34. Furthermore, the opening46is arranged outside a region U1where the slider38is movable at the normal time in the elongate hole34. The region U1is a region occupied by the slider38while moving when the steering wheel3is rotated from one end to the other end of the rotational movement range thereof. The opening46is covered with the dust cover30.

Referring toFIG. 7A, even when the minimum distance L3between the curved sliding contact surfaces34bin the elongate hole34is smaller than the maximum dimension L4of the curved sliding contact surfaces38cin the slider38(L3<L4) to the width direction V of the elongate hole34, the curved sliding contact surface38cin the slider38can be easily assembled into the curved sliding contact surface34bin the elongate hole34through the opening46.

Referring toFIGS. 1 and 4, the steering apparatus1according to the present embodiment is a center take-off steering apparatus so adapted that the rotation of the pinion13that rotates along with the steering wheel3serving a steering member is converted into linear displacement of the rack shaft14extending in the right-and-left direction X of the vehicle body9, and the pair of tie rods28for steering the pair of wheels2is taken out of the central position9ain the right-and-left direction X of the vehicle body9upon receipt of the linear displacement. The steering apparatus1includes the cylindrical rack housing33that supports the rack shaft14so as to be slidable in the axial direction X1and has the elongate hole34extending in the longitudinal direction U, the mounting bracket39for mounting the inner end28bof each of the tie rods28on the rack shaft14, and the slider38that is interposed between the mounting bracket39and the rack shaft14and slides on the inner periphery34aof the elongate hole34. The inner periphery34aof the elongate hole34and the slider38have curved sliding contact surfaces34band38crespectively that are brought into sliding contact with each other along with the slide of the slider38, and the curved sliding contact surfaces34band38ceach form curved shapes as viewed from the axial direction X1of the rack shaft14.

According to the present embodiment, the curved sliding contact surface34bin a curved shape of the rack housing33includes a portion inclined to the width direction V and the depth direction W of the elongate hole34perpendicular to the longitudinal direction U of the elongate hole34, so that the movement of the slider38to the width direction V and the depth direction W of the elongate hole34can be regulated. As a result, a rattle does not easily occur in the rack shaft14. Moreover, the rattle can be suppressed with a small number of curved surfaces. Therefore, the configuration of the steering apparatus1is simplified, and the manufacturing cost thereof is reduced.

Furthermore, the curved sliding contact surface34bincludes the first section34ba(corresponding to the chamfer) directed toward the outside of the rack housing33and the second section34bbdirected toward the inside of the rack housing33. The curved sliding contact surface38cincludes the first and second sections38caand38cbso as to be brought into sliding contact with the sections34baand34bbrespectively. This allows regulation of the bilateral movement of the slider38to the depth direction W of the elongate hole34, so that a rattle hardly occurs further in the rack shaft14.

The curved sliding contact surface38cin the slider38and the curved sliding contact surface34bin the elongate hole34that slide-contact with each other are provided in opposite directions on both sides individually in the width direction V of the elongate hole34. Thus, the external force can be reliably received on both sides of the width direction V.

Furthermore, the following modified example can be considered with respect to the present embodiment. In the following description, the points different from those in the above-mentioned embodiment will be mainly described. The same constituent elements are assigned the same reference numerals and hence, the description thereof is omitted.

For example, as shown inFIG. 8, the curved sliding contact surfaces34band38cmay be provided on one side of the width direction V of the elongate hole34, and flat sliding contact surfaces341and381may be brought into sliding contact with each other on the other side thereof.

Furthermore, as shown inFIG. 9, the second sections34bband38cbmay be removed, and only the first sections34baand38caserving as chamfers may constitute the curved sliding contact surfaces34band38crespectively.

A curved sliding contact surface made of a concave-curved surface may be provided in the inner periphery34aof the elongate hole34, and a curved sliding contact surface made of a convex-curved surface may be provided on a side surface of the slider38, though not illustrated.

In order to easily assemble the slider38, the rack housing33may be divided into a plurality of components, if appropriate. For example, the rack housing33may be divided at an intermediate portion to its longitudinal direction, and the elongate hole34may be openable in the longitudinal direction U.

Although the above-mentioned steering apparatus1uses an electric motor as a driving source to obtain a steering assist force, a hydraulic power cylinder serving as a hydraulic actuator may be utilized. Furthermore, a driving source to obtain a steering assist force may be provided in the rack housing33in addition to the steering column7.

The present application corresponds and claims the benefit of priority from Japanese Patent Application No. 2007-63569, filed with the Japan Patent Office on Mar. 13, 2007, the content of which is incorporated herein by reference in its entirety.