Steering apparatus

A steering apparatus includes a fixed bracket, an outer column, an arm unit, an inner column, a steering shaft, and a tightening tool. The outer column includes a main holding body portion, a divided portion, and a tightening portion. The arm unit includes by a bifurcated arm portion that extends axially outward in a substantially bifurcated shape at the axial front side of the main holding body portion and a linking portion formed between the arms of the bifurcated arm portion. The inner column is held by the outer column. The steering shaft is pivotally supported by the linking portion. Two tightening plate pieces of the tightening portion are disposed inside two fixed side portions of the fixed bracket and tightenably connected by the tightening tool.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a steering apparatus which has increased rigidity in a fixed state of a steering column after positioning performed by tilt and telescopic adjustment and in which a play is inhibited and operation feeling of steering is improved.

2. Description of the Related Art

There are various steering apparatuses equipped with a tilt and telescopic adjustment mechanism. One of the typical structures of such steering apparatus is constituted by a fixed bracket mounted on a vehicle side, an inner column that rotatably supports a steering shaft, a steering support body that axially slidably supports the inner column, and a tightening means for tightening the inner column via the steering support body by tightening the fixed bracket.

It is especially important that the steering apparatus have good rigidity at the time of fixing in the correct position after the respective correct position has been determined in tilt and telescopic adjustment. For this purpose, efforts have been made to inhibit a play of a handle when a bending load acts upon the handle, that is, when a twisting force acts upon the handle in the up-down direction. The related art of this kind is disclosed in Japanese Patent Application Laid-open No. 2001-347953 and Republication of International Patent Application WO2004-085225.

The configuration disclosed in Japanese Patent Application Laid-open No. 2001-347953 will be described below. For the sake of convenience, reference symbols will be assigned to the principal components. An upper-side inner column (a) is axially slidably enclosed in and held by a lower-side outer column (b), and the inner column (a) is tightened via the outer column (b) by tightening plate portions on the opposite sides. A steering shaft is constituted by an upper shaft and a lower shaft that are joined so that they can slide with respect to each other in the front-rear direction of the vehicle, and the upper shaft and lower shaft are rotatably supported by the inner column (a) and outer column (b) respectively.

A pair of clamp members are provided outside the lower-side outer column (b) so as to enclose and hold the upper-side inner column (a), and an axial slot (c) is provide in the location where the pair of clamp members have been provided. No slot (c) is provided and a tubular shape is formed in other zones. The pair of clamp members are brought close to each other by a tightening bolt and the width of the slot (c) is reduced, whereby the upper-side inner column (a) is enclosed, held, and tightened by the pair of clamp members. Therefore, in Japanese Patent Application Laid-open No. 2001-347953, since the upper-side inner column (a) is directly tightened by the lower-side outer column (b), the rigidity of the two columns with respect to the vehicle body and the fixed bracket of the vehicle body can be increased.

However, Japanese Patent Application Laid-open No. 2001-347953 discloses a structure in which one side of the outer column (b), in which the slot (c) has been formed, along the axial direction of the column, that is, the axial end side of the outer column (b), is opened so as to be open axially to the outside, and an end portion of the slot (c) that is closed like a dead end is present at the central side in the axial direction of the outer column (b). As a result, the pushing pressures p, p, . . . by which the clamp members tighten the inner column (a) weaken gradually with the distance from the position of the tightening bolt in the axial direction of the inner column (a), and the pushing pressures p, p, . . . are practically not generated in the central zone in the axial direction that is the end portion of the slot (c) closed like a dead end. Therefore, the pushing force varies along the axial direction of the inner column (a) (seeFIG. 11A).

Further, in order to enable the telescopic sliding of the steering shaft, a certain gap has to be provided between the outer column (b) and inner column (a) to facilitate the mutual sliding thereof. As a result, even when the steering column is fixed in the tilt-telescopic position, a play occurs in the gap. The holding force of the outer column (b) that holds the inner column (a) and steering shaft can be decreased and the rigidity of the steering column with respect to the vehicle body can be reduced.

The tilt-telescopic steering apparatus disclosed in Republication of International Patent Application WO2004-085225 will be described below. In this apparatus, an inner column is axially movably supported by an outer jacket (d) that is supported on an upper bracket disposed at the vehicle body, and the inner column is tightened by a tightening means via the outer jacket (d), whereby a steering shaft is fixed in an adjustment position. A slot is provided in the outer jacket (d) along the entire axial length thereof. The steering shaft is constituted by an upper steering shaft and a lower steering shaft joined by a universal joint in the front-rear direction of the vehicle. The upper steering shaft is rotatably supported by the inner column. The outer jacket (d) extends in the axial direction of steering, and a clamp portion that supports the inner column from the outer circumferential side is formed integrally with the rear end of the side portion at the rear side of the vehicle.

Because the slit has a shape opened at both ends along the axial direction of the inner column, that is, a double-split shape, the variation of the force created by the clamp portions to tighten the inner column can be inhibited by comparison with a structure in which a portion of the slit is closed, for example, as described in Japanese Patent Application Laid-open No. 2001-347953. Further, the outer jacket (d) supports only the inner column, without supporting the steering shaft, and when the tilt-telescopic tightening is performed, surface contact is attained in a state in which no gap is present between the outer jacket (d) and inner column, and the inner column is pushed, supported and fixed. Therefore, the tightening force of the inner column with respect to the outer jacket (d) is further increased.

However, in the configuration described in Republication of International Patent Application WO2004-085225, the slit of the outer jacket (d) is formed axially from one side to the other side and there are absolutely no zones that are continuous in the circumferential direction of the outer jacket (d). As a result, the rigidity of the outer jacket (d) itself in the configuration described in Republication of International Patent Application WO2004-085225 is reduced by comparison with that in the case of an outer column in which a cylindrical portion continuous in the circumferential direction is present because one end of the slit in the axial direction is closed, as in the aforementioned configuration disclosed in Japanese Patent Application Laid-open No. 2001-347953.

A structure in which a universal joint between an upper steering shaft and a lower steering shaft is moved in a substantially front-rear direction with respect to a vehicle body to move a steering column in the front-rear direction is called a telescopic structure of a universal joint movement type, and a structure in which a steering column is moved in the front-rear direction by extending and contracting a steering shaft, without changing the position of the universal joint with respect to the vehicle body, is called a telescopic structure of a steering column movement type. The structure described in Republication of International Patent Application WO2004-085225 is of the universal joint movement type and no bearing support portion is present on the outer jacket (d). Therefore, when the structure is changed to that of the steering column movement type in order to improve the operation feeling, separate parts have to be added. The resultant drawback is that the increase in the number of parts and assembling operations raises the cost.

SUMMARY OF THE INVENTION

Therefore, the decrease in rigidity of the outer jacket (d) when the tilt-telescopic position of the steering column (e) is fixed causes a play of the steering column (e) and the rigidity of the steering column (e) with respect to the vehicle body decreases (seeFIG. 11B). Accordingly, it is an object (technical problem) of the present invention to increase the rigidity of the steering column when a tilt-telescopic position is fixed and inhibit a play of the steering column in a steering apparatus equipped with a tilt and telescopic adjustment mechanism, thereby improving the operation feeling of steering.

The inventors have conducted a comprehensive research aimed at the resolution of the above-described problems. The results obtained demonstrated that the problems can be resolved by a steering apparatus according to the invention, including a fixed bracket having fixed side portions at both sides in a widthwise direction, an outer column that is swingably mounted on the fixed bracket, an arm unit, an inner column, a steering shaft that is rotatably mounted on the arm unit and the inner column, and a tightening tool, wherein the outer column is constituted by a main holding body portion formed in a substantially hollow cylindrical shape, a divided portion that is formed along an axial direction of the main holding body portion, and a tightening portion comprising two tightening plate-like pieces formed in both side locations in a widthwise direction of the divided portion; the arm unit is constituted by a bifurcated arm portion that extends axially outward in a substantially bifurcated shape at an axial front side of the main holding body portion, and a linking portion formed between arms of the bifurcated arm portion; the inner column is held by the outer column; the steering shaft is pivotally supported by the linking portion, and the two tightening plate-like pieces of the tightening portion are disposed inside the two fixed side portions of the fixed bracket and tightenably connected by the tightening tool.

In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which a pivotal support portion serving as a tilt rotation center is provided in the bifurcated arm portion of the arm unit, a bearing portion is provided in the linking portion so as to be coaxial with the main holding body portion, an open cavity portion is provided between the outer column, the bifurcated arm portion, and the linking portion, the steering shaft is constituted by an upper shaft that is rotatably supported by the inner column and a lower shaft that is rotatably supported by the linking portion, the upper shaft and lower shaft being mated and joined so as to be axially slidable with each other, a mating location of the lower shaft and an axial front end portion of the upper shaft is positioned in the open cavity portion, and an axial front end portion of the inner column can move axially in the location of the open cavity portion.

In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which the divided portion is formed over the entire main holding body portion in the axial direction thereof. In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which the divided portion is formed from one end side to the other end side in the axial direction of the main holding body portion except for a portion of the main holding body portion, and a circumferential support portion with an inner wall surface continuous in the circumferential direction is formed at the other end portion in the axial direction of the main holding body portion.

In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which the bifurcated arm portion is formed so that the spacing thereof gradually increases axially outward from an axial end portion of the outer column. In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which a rotation stop member that is inserted into the divided portion and is free to slide is fixedly attached to a diametrically lower portion of the inner column. In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which a tightening through hole for the tightening tool is formed in the tightening portion. In accordance with the invention, the above-described problems can be resolved by the steering apparatus in which a guiding groove for the tightening tool is formed in a lower end surface of the tightening portion.

In accordance with the invention, the inner column is held in the main holding body portion of the outer column and the steering shaft is pivotally supported by the connection portion of the inner column and arm unit. Therefore, a more stable support can be performed in the axial direction, and even when a bending load acts upon the steering wheel, the steering shaft can be strongly held, and the operation feeling of steering can be improved.

Further, the bifurcated arm portion that protrudes axially outward of the outer column from an axial end portion of the outer column is formed in the arm unit, and the linking portion that is formed integrally with the bifurcated arm portion is present between the arms of the bifurcated arm portion. Therefore, the rigidity in the substantially horizontal diametrical direction can be increased and axially divided portions of the bifurcated arm portion can be reinforced. Thus, the bifurcated arm portion and the linking portion formed integrally between the arms of the bifurcated arm portion constitute a substantially truss-like skeletal structure of the outer column, the outer column, the arms of the bifurcated arm portion, and linking portion reinforce each other, the rigidity thereof can be increased, and the rigidity of the steering apparatus can be increased. Therefore, the rigidity of the steering column when a tilt-telescopic position is fixed is increased and a play of the steering column is inhibited, thereby improving the operation feeling of steering.

In accordance with the invention, the open cavity portion is formed between the outer column, arms of the bifurcated arm portion, and linking portion, and the inner column can move axially in the location of the open cavity portion. As a result, the opening in the axial front portion of the upper shaft can slidingly move in the axial center portion along the lower shaft, the effect of the axial center displacement of the lower shaft and upper shaft is reduced, and the deterioration of slidability can be prevented. Further, the length of the sliding portion relative to that of the inner column can be decreased, a processing region can be reduced, and cost can be reduced. In addition, the steering apparatus can be reduced in weight.

In accordance with the invention, the divided portion is formed over the entire main holding body portion in the axial direction thereof. Therefore, when the inner column is tightened and fixed by the outer column, a pushing force that tightens the outer circumference of the inner column from both horizontal diametrical sides of the outer column along the divided portion can be made substantially uniform in the axial direction. Therefore, the unevenness of the tightening force in the axial direction of the outer column can be inhibited and the tightening force can be made uniform along the axial direction. Therefore, the unevenness of the tightening force in the axial direction of the outer column can be inhibited and the tightening force can be made uniform along the axial direction.

Thus, as described above, by forming the divided portion that is entirely divided along the axial direction, it is possible to bring the two tightening plate-like pieces at both ends in the widthwise direction (horizontal diametrical direction of the outer column) of the divided portion closer to each other in a parallel state thereof, without displacement. As a result, the outer column can be fixed to the inner column uniformly over the entire range from the axially front side to the axially rear side, the columns can be fixed with higher stability, and the tightening force thereof can be further increased.

In accordance with the invention, the divided portion is formed from one end side to the other end side in the axial direction of the main holding body portion except for a portion of the main holding body portion, and a circumferential support portion with an inner wall surface continuous in the circumferential direction is formed at the front end portion in the axial direction of the main holding body portion. As a result, the rigidity in sliding support of the inner column by the main holding body portion in the outer column can be increased, a portion of the inner column that is positioned in the open cavity portion is supported by an annular frame body constituted by the front circumferential support portion, arm portions, and linking portion, strains and deformation of the inner column inside the open cavity portion region can be prevented, slidability of the inner column can be increased, and the rigidity of the entire steering apparatus can be increased.

In accordance with the invention, the bifurcated arm portion is formed so that the spacing thereof gradually increases axially outward from an axial end portion of the outer column. As a result, in a steering support body, a skeletal structure of a substantially trapezoidal shape is constituted by the outer column, bifurcated arm portion having two arms, and linking portion and a stronger structure can be obtained. In accordance with the invention, the unnecessary axial rotation of the inner column during the telescopic adjustment can be prevented. As a result, the telescopic adjustment can be performed without a play. In accordance with the invention, a tightening through hole is formed in both tightening pieces of the tightening portion. Therefore, by inserting a bolt of the tightening tool, it is possible to combine the principal structural components by assembling with the tightening tool. Further, in accordance with the invention, a guiding groove portion for the tightening tool is formed in the lower end surface of the tightening portion, thereby making it possible to reduce the outer column in size and weight.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below with reference to the appended drawings. As shown inFIG. 1andFIG. 2, a principal configuration in accordance with the present invention includes a fixed bracket1, an outer column2that is swingably mounted on the fixed bracket1, an arm unit A, a tightening tool5, an inner column6, and a steering shaft100. The fixed bracket1is constituted by fixed side portions11,11formed at both sides in the widthwise direction and an attachment top portion12. Adjustment holes13,13that extend in a substantially up-down direction or vertical direction are formed in the two fixed size portion11,11(seeFIG. 2A). The attachment top portion12is mounted on a predetermined position inside a vehicle, with a capsule member being interposed therebetween, and can absorb impact energy during collision.

As shown inFIG. 2CandFIG. 3, the arm unit A is constituted by a bifurcated arm portion3and a linking portion4. The outer column2is constituted by a main holding body portion21and a tightening portion22. As shown inFIG. 3, the main holding body portion21is formed in a substantially cylindrical shape with a hollow inner side. More specifically, the inside of the main holding body portion has a holding inner circumferential side surface portion21athat is formed to have a hollow shape and serves to hold the below-described inner column6. The main holding body portion21is formed to be slightly larger than the outer diameter of the inner column6. Further, the main holding body portion21is formed to have a length that makes it possible to support a substantially intermediate zone of the inner column6in the axial direction thereof in an appropriate axial direction, and the inner column6protrudes from the front end portion and axial rear end portion of the main holding body portion21. A divided portion211is formed at the diametrically lower side of the main holding body portion21(seeFIGS. 3C,3D, and3F). The front-rear direction as referred to herein is a direction corresponding to the front-rear direction of an automobile in a state in which the steering apparatus is mounted on the automobile.

The divided portion211is a portion in which the entire main holding body portion21or part thereof is divided from the axial front side towards the rear side (seeFIGS. 3A and 3F), and this divided portion is formed as a slit extending along the axial direction of the main holding body portion21. Edge portions at both sides of the divided portion211in the axial direction are divided end edges211a,211a. The two divided end edges211a,211ahave a flat surface shape along the axial direction, and by bringing them closer to each other, it is possible to decrease the diameter of the holding inner circumferential side surface portion21aand tighten and lock (fix) the inner column6that has been accommodated and mounted inside the main holding body portion21. As for the spacing of the divided portion211, because the two divided end edges211a,211aare parallel (includes also “substantially parallel”) to each other, the spacing is uniform (includes also “substantially uniform”) along the axial direction.

Two structural embodiments of the outer column2are possible. In the first embodiment, as shown inFIGS. 1 to 5, the divided portion211is formed over the entire main holding body portion21in the axial direction thereof. Thus, the divided portion211is formed over the entire holding inner circumferential side surface portion21ain the axial direction thereof and can be expanded diametrically in any location in the axial direction of the holding inner circumferential side surface portion21a. In the second embodiment of the outer column2, as shown inFIGS. 8 to 10, the divided portion211is formed from one end side to the other end side in the axial direction of the main holding body portion21, except for a portion of the main holding body portion.

A circumferential support portion212with a continuous inner wall surface in the circumferential direction is present at the other axial end portion of the main holding body portion21. The circumferential support portion212has an endless cylindrical or annular configuration in which no divided region is present. The circumferential support portion212is formed in the end portion location at the front side of the main holding body portion21. The inner column6is configured to be capable of sliding smoothly with respect to the circumferential support portion212in the axial direction thereof. More specifically, the inner diameter of the circumferential support portion212is slightly larger than the outer diameter of the inner column6.

As shown inFIGS. 3A,3D,3F, and3G, the tightening portion22is integrally formed at the lower portion of the outer column2. The tightening portion22is constituted by a two tightening plate-like pieces221,221in the form of substantially rectangular parallelepipeds. The tightening plate-like pieces221,221have a left-right symmetrical shape and are integrally formed in positions of two divided end edges211a,211aof the divided portion211.

The tightening plate-like pieces221,221of the tightening portion22have a widthwise size from positions directly below the two divided end edges211a,211ato positions of diametrically horizontal two ends of the main holding body portion21and are formed to extend perpendicular downward from diametrically horizontal two ends of the main holding body portion21. Further, the tightening plate-like piece221is formed to have a quadrangular shape such as rectangular or square shape as viewed from a side surface along the axial direction of the outer column2.

The total widthwise size of the tightening portion22(tightening plate-like pieces221,221) is substantially equal to the diameter of the outer circumference of the main holding body portion21. Further, the tightening portion22can be also formed to have a widthwise size that is slightly larger than the outer circumferential diameter of the main holding body portion21. A surface on the outer side of the tightening plate-like pieces221,221is called an outer side surface221a. The outer side surface221ais a flat surface so configured that the fixed side portion11can be brought into surface contact (includes also “almost surface contact”) with the outer side surface221aof the tightening plate-like piece221in a state in which the tightening plate-like pieces221,221of the tightening portion22are clamped by the two fixed side portions11,11of the fixed bracket1.

Tightening through holes222,222are formed in the tightening plate-like pieces221,221in the direction perpendicular to the axial direction of the outer column2and in the direction parallel to the horizontal diameter direction of the main holding body portion21. As shown inFIGS. 3B,3C,3F, and3G, the arm unit A is formed at the axial front side of the main holding body portion21. As mentioned hereinabove, the arm unit A is constituted by the bifurcated arm portion3and the linking portion4. More specifically, two arms of the bifurcated arm portions3are formed from the axial front side of the main holding body portion21.

In the arm unit A, the arms of the bifurcated arm portion3are formed so that the positions at both diametrically horizontal sides of the main holding body portion21serve as attachment base portions thereof. Further, the bifurcated arm portion3is formed to extend from an axial end portion of the outer column2outward on the axial front side of the outer column2(seeFIGS. 3A,3B, and3C). The bifurcated arm portion3is constituted by two arm pieces30,30. The two arm pieces30,30are formed with a left-right symmetry so as to face outward on the axial front side of the outer column2and so that the distance between the two arm pieces30,30expands gradually in the forward direction.

The arm pieces30,30of the bifurcated arm portion3are constituted by intermediate arm pieces31,31with a distance therebetween increasing gradually and end arm pieces32,32that are parallel to each other and extend further along the axial direction of the main holding body portion21from the outer ends of the intermediate arm pieces31,31. The intermediate arm piece31and the end arm piece32are formed integrally and continuously. Through holes33,33for pivotal support are formed in the end arm pieces32,32and serve as regions for pivotal connection and support on a lower bracket9for tilt. The bifurcated arm portion3is formed to have left-right symmetry in a plan upward view of the arm unit A.

A linking portion4is formed between the two arm pieces30,30of the bifurcated arm portion3. The linking portion4is formed to be positioned between the end arm pieces32,32of the two arm pieces30,30and in the center of the spacing of the end arm pieces32,32. An axial center line La that passes through the diametrical center of the main holding body portion21passes through the central position of the spacing of the end arm pieces32,32. In the linking portion4, connection pieces42,42are formed along the horizontal diameter of a substantially ring-shaped accommodation portion41, and the connection pieces42,42are formed integrally with the end arm pieces32,32of the bifurcated arm portion3(seeFIGS. 3B,3C,3F, and3G).

A round through hole is formed in the accommodation portion41, and the inner circumferential side surface41aof the through hole is formed as a flat cylindrical cavity. A bearing8is accommodated and fixed at the inner circumferential side surface41a. The bearing8serves to support rotatably the lower portion of a steering shaft100. Insertion holes41cthat pass through in the up-down direction from an outer circumferential side surface41bto the inner circumferential side surface41aare formed in the accommodation portion41(seeFIG. 3C).

A total of four insertion holes41care formed in the accommodation portion41, and each insertion hole41cpasses through the inner circumferential side surface41aof the accommodation portion41. More specifically, the insertion holes41care formed in four locations positioned on both sides of a vertical line Lv passing through a diameter center P of the round inner circumferential side surface41aof the accommodation portion41. Pin portions71,71of a circlip7having the pin portions71,71that are bifurcated and formed as wave-like curves are inserted into the insertion holes41c. The bearing8is fixed by the two pin portions71,71to prevent the bearing from falling out in the axial direction on the inner circumferential side surface41a(seeFIG. 3E,FIG. 7, etc.). Further, an open cavity portion S is provided between the front end portion of the main holding body portion21of the outer column2, the bifurcated arm portion3of the arm unit A, and the linking portion4.

In another possible embodiment, only a guide groove223is formed in the lower surface side of the tightening plate-like piece221, without forming the tightening through hole222in the tightening plate-like piece221of the outer column2(seeFIG. 4). In the guide groove223, a groove of a substantially semicircular cross-sectional shape is formed along the widthwise direction in the lower end surface of the tightening plate-like piece221. In the configuration of such an embodiment, only a bolt51of the tightening tool5passes through the guide groove223. In such an embodiment, the tightening plate-like piece221is miniaturized and the weight of steering apparatus can be reduced.

In a possible embodiment, a rotation stop member61is fixedly attached in the diametrically lower portion and on the outer circumference of the inner column6(seeFIGS. 1A,1C, and2B). The rotation stop member61is a plate-shaped member in the form of a substantially rectangular parallelepiped with a substantially gate-shaped cross section and is fixedly attached so that the longitudinal direction thereof coincides with an axial direction of the inner column6. A fixing member such as a screw or welding can be used as a means for fixedly attaching the rotation stop member. It is also possible to cut out part of the inner column6and mount the rotation stop member with a fixing member such as a screw so that part of the rotation stop member61is exposed to the outside in the cut-out portion.

When the inner column6is accommodated and mounted on the main holding unit portion21of the outer column2, the rotation stop member61is mounted so as to be accommodated in the divided portion211. Therefore, the widthwise size of the rotation stop member61is less than the smallest distance between the divided end edges211a,211aof the divided portion211, in a state of being tightened by the tightening tool5. By fixedly attaching the rotation stop member61to the inner column6, it is possible to restrict the inner column6so as to prevent the idle rotation thereof around the axis inside the divided portion211and prevent the inner column6from rotating unnecessarily around the axis with respect to the outer column2when the inner column6slides along the outer column2during telescopic adjustment or the like.

The steering shaft100is constituted by a lower shaft100aand an upper shaft100b(seeFIG. 8AandFIG. 10A). The lower shaft100aand upper shaft100bare mated and joined so as to be slidable with each other along the axial direction, and the steering shaft100has a structure such that the axial length thereof can be increased of decreased. More specifically, the upper shaft and lower shaft are slidably joined by a spline. The upper shaft100bof the steering shaft100is mounted by means of bearings on both axial end portions of the inner column6, and the upper shaft100bis configured to be capable of rotating about the axis with respect to the inner column6. Further, the lower shaft100ais rotatably supported by a bearing at the linking portion4.

The axial front end portion of the upper shaft100bis in a position substantially identical to that of the axial front end portion of the inner column6or slightly protrudes beyond it (seeFIG. 10A). The axial front end portion of the inner column6protrudes beyond the front end portion of the main holding body portion21and moves in the axial direction during telescopic adjustment inside the open cavity portion S between the front end portion of the main holding body portion21, the bifurcated arm portion3, and the linking portion4. As the inner column6moves in the axial direction, the upper shaft100balso moves in the axial direction. Further, the axial front end portion of the upper shaft100bslides along the lower shaft100aand moves inside the open cavity portion S (seeFIG. 10B).

Further, when the inner column6is mounted on the outer column2according to the second embodiment, the inner column6is supported by the main holding body portion21and continuously supported in the circumferential direction of the inner column6in the location of the circumferential support portion212(seeFIG. 8B). More particularly, the circumferential support portion212is formed at the axial front end portion of the main holding body portion21, and the vicinity of the axial front side of inner column6is supported over the entire outer circumference. The circumferential support portion212also supports the inner column6at the axial rear side of the open cavity portion S, and the support rigidity of the inner column6in the open cavity portion S is increased.

A method for assembling the main structural components in accordance with the present invention will be described below. The tightening plate-like pieces221,221of the tightening portion22of the outer column2are inserted between the fixed side portions11,11of the fixed bracket1and the bolt51of the tightening tool5is inserted into the adjustment holes13,13of the two fixed side portions11,11and the tightening through holes222,222that have been formed in the two tightening plate-like pieces221,221and mounted by tightening together with a lock lever portion53and a tightening cam54by a nut52. The thickness of the tightening cam54in the axial direction of the bolt51is changed by the rotation operation of the lock level portion53.

The rotation operation of the lock level portion53generates a tightening force in the entire tightening tool5, the fixed side portions11,11of the fixed bracket1are pushed to bring them closer together, the tightening plate-like pieces221,221of the tightening portion22are pushed by the fixed side portions11,11, and the tightening plate-like pieces221,221are tightened, whereby the spacing of the divided portion211of the main holding body portion21of the outer column2is reduced, and the inner column6mounted on the outer column2is locked (fixed) in the axial direction. In this case, the holding inner circumferential side surface portion21aof the outer column2and the outer circumferential side surface of the inner column6are in a surface contact state and the inner column is fixed in the axial direction by the increase of the force of friction with the inner column6.

Where the tightening of the tightening tool5is released, the distance between the fixed side portions11,11is increased, the distance between the tightening plate-like pieces221,221is also increased at the same time, locking of the inner column6by the outer column2is gradually weakened, and the inner column6moves in the axial direction. As a result, telescopic adjustment is made possible. At the same time, the outer column2can be tilt adjusted by moving up or down together with the bolt51of the tightening tool5with respect to the adjustment holes13,13of the fixed side portions11,11of the fixed bracket1.

In accordance with the present invention, the divided portion211that is divided along substantially the entire length is formed in the main holding body portion21of the outer column2along the axial direction therefore. Therefore, when the outer circumference of the inner column6is tightened and fixed by the main holding body portion21, the pushing forces p, p, . . . that tighten the outer circumference of the inner column6from diametrically horizontal both sides of the main holding body portion21along the axial diction of the divided portion211can be made substantially equal and uniform along the axial direction (seeFIG. 5A). Therefore, the unevenness of the tightening force along the axial direction of the main holding body portion21can be inhibited.

Further, the divided end edges211a,211aat both sides in the widthwise direction of the divided portion211(direction identical to the horizontal diameter direction of the main holding body portion21) and both tightening plate-like pieces221,221can be brought close to each other in a parallel state thereof, without displacement. As a result, the outer column2can be fixed more stably to the inner column6and the tightening force thereof can be further increased.

Further, the arm unit A is formed from an axial end portion of the outer column2, the bifurcated arm portion3with two arms protruding outward in the axial direction of the outer column2is formed in the arm unit A, and the linking portion4that is formed integrally with the bifurcated arm portion3is present between the arms of the bifurcated arm portion3. Therefore, the strength of the section that is divided along the entire length in the axial direction of the divided portion211can be increased. In other words, the bifurcated arm portion3with left and right arms connected integrally to the outer column2and the linking portion4that is formed integrally between the arms of the bifurcated arm portion3constitutes a substantially truss-like skeletal structure, as shown inFIG. 5B. As a result, sufficient reinforcement can be provided and the rigidity of the entire steering apparatus can be increased.

Therefore, the operation feeling of steering can be improved by increasing the rigidity when the steering column is fixed in a tilt-telescopic position. In addition, the inner column6and steering shaft100are supported by the main holding body portion21of the outer column2and the linking portion4of the arm unit A, and the inner column6and steering shaft100are supported with better stability along the axial direction (seeFIG. 5A).

Further, since the circumferential support portion212with a continuous inner wall surface in the circumferential direction is formed in the axial front end portion location of the main holding body portion21, the outer column2can support the inner column6with higher rigidity and the operation feeling of the steering wheel can be improved. Further, the steering shaft100is rotatably supported in the open cavity portion S by the linking portion4at the front side in the axial direction and by the main holding body portion21at the rear side in the axial direction. Therefore, the steering shaft100can be supported with good stability along the axial direction and the telescopic adjustment can be performed smoothly.