Abstract:
A steering column apparatus comprising: a steering column provided with a body-side bracket mounted to a body strength member to have a pair of side plate portions opposed each other to be extended in a vertical direction, and a substantially cylindrical distance unit for supporting a steering shaft to be rotatable therein and having a pair of pressed and expanding portions formed to be expanded by plastic working to be pressed and supported by the side plate portions of the body-side bracket; and an adjusting mechanism capable of adjusting a position of the steering column with respect to the side plate portions of the body-side bracket within a predetermined range, wherein the steering column is formed with a reinforcement portion for enhancing the clamping rigidity of the distance unit with respect to the side plate portions.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a steering column for constituting a steering device for a car or the like, and more specifically, to a technology for enhancing the rigidity or the like of a column distance unit for fixing the steering column on the car body.  
       RELATED BACKGROUND ART  
       [0002]     Since a steering apparatus of a vehicle is to be used (for steering) by many and unspecific drivers, it is desirable that the position of a steering wheel is adjustable in compliance with the physique or the posture of each driver. In order to satisfy such desire, a tilt adjusting mechanism or a telescopic adjusting mechanism is widely employed not only for passenger cars, but also for freight cars.  
         [0003]     The tilt adjusting mechanism is a mechanism to adjust the position of a steering wheel in the up-and-down direction, and is constituted by a tilt pivot for rockably supporting a steering column, a tilt position fixing means for fixing the steering column at a desired position (rocking angle), and the others. On the other hand, the telescopic adjusting mechanism is a mechanism for adjusting the position of the steering wheel in the back-and-forth direction (the axial direction of the steering shaft), and is constituted by an expandable unit of a double tube type or the like to be used for expansion and/or contraction of the steering shaft, a telescopic position fixing means for fixing the steering shaft at a desired position (with an amount of expansion/contraction), and the others.  
         [0004]     Hitherto, it is general that, as the tilt position fixing means, a distance bracket formed of a steel plate is connected to a steering column formed of a steel pipe by welding and this distance bracket is pressed to be fixed by a body-side bracket which is formed of a steel plate. However, with such an arrangement, the number of the constituent parts and that of the welding steps are increased, and moreover, variable inconveniences are inevitably caused by thermal distortion, etc., at the welding. As a result, it is proposed in Japanese Patent Application Laid-Open No. 10-7003 or the like (hereinafter called the prior art) a structure in which a distance unit for fixing the steering column on the body-side bracket is formed to be expanded by plastic working.  
         [0005]      FIG. 7  is a perspective view showing a steering column of the prior art as a single unit, and  FIG. 8  is a vertical cross-sectional view of a distance unit of a steering column supported by a body-side upper bracket in a steering column apparatus. This steering column  21  is formed of a steel pipe in a cylindrical form, and pressed portions  25 ,  27  are formed to be expanded in the lower portions of the distance unit  29  in  FIG. 7  and  FIG. 8 . Pressed surfaces  51 ,  53  are formed on side surfaces of the pressed portions  25 ,  27 , and a through hole  71  through which a tilt bolt  31  is inserted is formed on each of the pressed surfaces  51 ,  53 . In this steering column apparatus, a nut  33  advances to the tilt bolt  31  by thread-engagement therewith upon rotation of a tilt adjusting lever  35  which is disposed on a side surface of the body-side bracket  3 , so as to compress and release the steering column  21  by the use of the body-side bracket  3 . According to the steering column apparatus of the prior art, it is possible to reduce the number of the constituent parts and that of the welding steps to reduce the manufacturing cost, and at the same time, to prevent inconveniences which may be caused by the thermal distortion or the like at the welding.  
         [0006]     However, the above-described steering column apparatus of the prior art has the following drawbacks. For example, when a driver fastens the tilt lever  35 , the parts other that the pressed portions  25 ,  27  in the distance unit  29  (the upper and lower portions in  FIG. 9 ) are flexed, so that the operative feeling becomes very bad and a secured fixing of the steering column  21  by the use of the body-side bracket  3  becomes unfeasible. Moreover, when the driver clamps the tilt lever  35  with a clamping force exceeding a predetermined value, the distance unit  29  may be flexed beyond the limit of its elasticity so as to be plastically deformed. Then, these inconveniences become conspicuous when the steering column is formed of a thin steel pipe, which results in an obstacle to reduction of the weight of the steering apparatus.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention has been contrived taking the above circumstances into consideration, and an object thereof is to provide a steering column apparatus which can enhance the rigidity of a distance unit while reducing the number of the constituent parts as well as the manufacturing cost.  
         [0008]     In order to solve the above problems, according to the present invention, there is provided a steering column apparatus comprising: a steering column provided with a body-side bracket mounted to a vehicle body strength member to have a pair of side plate portions facing each other to be extended in a vertical direction, and a substantially cylindrical distance unit for supporting a steering shaft to be rotatable therein and having a pair of pressed and expanding portions formed to be expanded by plastic working to be pressed and supported by the side plate portions of the body-side bracket; and an adjusting mechanism capable of adjusting a position of the steering column with respect to the side plate portions of the body-side bracket within a predetermined range, wherein the steering column is formed with a reinforcement portion for enhancing the clamping rigidity of the distance unit with respect to the side plate portions.  
         [0009]     According to the steering column apparatus of the present invention, it is preferable that the reinforcement portion is formed by coupling the pressed and expanding portions together in at least one of an upper portion and a lower portion of the pressed and expanding portions.  
         [0010]     According to the steering column apparatus of the present invention, it is preferable that the convex portion is comprised of a plurality of convex streaks and the concave portion is comprised of a plurality of concave streaks.  
         [0011]     According to the steering column apparatus of the present invention, it is preferable that the steering column is adjustable at least in one of a tilting direction or a telescopic direction with respect to the body-side bracket.  
         [0012]     According to the steering column apparatus of the present invention, it is preferable that the plastic working is performed by hydroforming.  
         [0013]     According to the present invention, the rigidity of the entire distance unit is enhanced and deflection is difficult to be caused even when a great clamping force is applied on the pressed portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a side view of a steering column apparatus according to a first embodiment of the present invention;  
         [0015]      FIG. 2A  is an enlarged cross-sectional view taken along A-A line in  FIG. 1 , leaving a steering shaft omitted;  
         [0016]      FIG. 2B  is an enlarged cross-sectional view taken along B-B line in  FIG. 1 ;  
         [0017]      FIG. 3  is a perspective view of an upper column according to the first embodiment;  
         [0018]      FIG. 4  is a side view of the upper column according to the first embodiment;  
         [0019]      FIG. 5  is a perspective view of an upper column according to a second embodiment;  
         [0020]      FIG. 6  is a perspective view of an upper column according to a third embodiment;  
         [0021]      FIG. 7  is a perspective view of a steering column as a single unit according to the prior art;  
         [0022]      FIG. 8  is a longitudinal cross-sectional view of the distance unit of the steering column according to the prior art; and  
         [0023]      FIG. 9  is a longitudinal cross-sectional view for showing a variation of the distance unit of the steering column according to the prior art. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     Description will be made below on an embodiment of a steering column apparatus according to the present invention.  
         [0025]      FIG. 1  is a side view of a steering column apparatus according to the first embodiment of the present invention, and  FIG. 2A  is an enlarged cross-sectional view taken along A-A line in  FIG. 1 , provided that a steering shaft  13  is omitted in  FIG. 1 .  
         [0026]     The steering column  1  is attached to a vehicle body-side strength member  7  through a fixed upper bracket  3  formed of a steel plate by press-forming to serve as a vehicle body-side bracket and a pivot bracket  5  formed of alluminium alloy by die casting, so as to support an upper steering shaft (hereinafter simply called the steering shaft)  13  to be rotatable through bearings  9 ,  11 .  
         [0027]     The upper bracket  3  has integrally a pair of body-side mounting portions  3   a ,  3   b  having the width in the length direction of the steering shaft, and being extended symmetrically in a direction perpendicular to an extending direction of the steering shaft, that is, the right-and-left direction in  FIG. 2A , so as to be secured to the body-side strength member  7  by the use of fixing members (not shown) such as bolts, and a pair of side plate portions  3   c ,  3   d  which are bent substantially at right angles at the inner ends of body-side mounting portions  3   a ,  3   b  of the upper bracket  3  to be extended in vertical directions respectively.  
         [0028]     While a steering wheel (not shown) is attached to an upper end of the steering shaft  13 , a lower steering shaft is coupled to a lower end of the steering shaft  13  through a universal joint, which leads to a rack and pinion mechanism of a steering mechanism. Tilt adjusting holes  15   a ,  15   b  are formed on the side wall portions  3   c ,  3   d  of the upper bracket  3 .  
         [0029]     The steering column  1  is comprised of an upper column  21  formed of a steel pipe by hydroforming and a lower column  23  of a steel pipe fitted in the upper column  21  to be slidable. The upper column  21  is generally in the form of a cylinder, but is formed with a pair of right and left pressed and expanding portions  25 ,  27  in  FIG. 2A  to be pressed and sandwiched by the side plate portions  3   c ,  3   d  at the positions corresponding to these side plate portions  3   c ,  3   d  of the upper bracket  3  and a distance unit  29  whose bottom  28  is expanded and connect the expanding portions  25 ,  27  at the lower end. On flat surface portions  51 ,  53  of the expanding portions  25 ,  27 , there are formed elongated holes  37 ,  37  respectively extending in the axial direction, corresponding to elongated holes  15   a ,  15   b  formed on the side plate portions  3   c ,  3   d  of the upper bracket  3 . An adjusting bolt  31  is inserted through the elongated holes  15   a ,  15   b  and the elongated holes  37 ,  37 , and the distance unit  29  is pressed and fixed with a predetermined clamping force to the fixed upper bracket  3  by the adjusting nut  33 , as described later.  
         [0030]     The adjusting nut  33  and an adjusting lever  35  are interposed between a nut  31   a  thread-engaged with the adjusting bolt  31  and secured thereto and one of the side plate portions  3   d  of the upper bracket  3 . The adjusting nut  33  and the adjusting lever  35  are in a mutually integrated rotational relationship since a substantially conical projection of the adjusting nut  33  is fitted in a substantially conical recess of the adjusting lever  35 . In addition, a thread portion of the adjusting bolt  31  is thread-engaged with a thread portion of the adjusting bolt  33 .  
         [0031]     A surface contacting with the side plate portion  3   c  of a head portion  31   b  of the adjusting bolt  31  has a cross-section in a substantially rectangular form, and is fitted in the elongated hole  15   a  formed on the side plate portion  3   c  of the upper bracket  3  to permit no rotation of the adjusting bolt  31 .  
         [0032]     The adjusting lever  35  is thus manually rotated to clamp the flat surface portions  51 ,  53  of the distance unit  29  by the side plate portions  3   c ,  3   d  or to release this clamping.  
         [0033]     Such a clamping or releasing operation as described above may be performed by a known cam mechanism, instead of the adjusting nut  33 .  
         [0034]     The elongated holes  37 ,  37  formed on the flat surface portions  51 ,  53  of the column expanded portions  25 ,  27  and extended in parallel to the column shaft are used for adjusting the telescopic position of the steering column.  
         [0035]     On the other hand, the pivot bracket  5   a  has a pair of body mounting portions  5   a  which are extended horizontally, as shown in  FIG. 2B , and are secured to the body-side strength member  7  by bolts, or the like. A pair of vertical plate portions  5   b ,  5   c  which are extended in parallel in a vertical direction from the body mounting portions  5   a  are formed on the pivot bracket  5 .  
         [0036]     A column-side lower bracket  41  secured to a lower part of the lower column  23  integrally comprises flat plate portions  41   b ,  41   c  which are extended in the up-and-down direction, corresponding to the vertical plate portions  5   b ,  5   c  of the pivot bracket  5  and which are respectively in pressure contact therewith. The vertical plate portions  5   b ,  5   c  and the flat plate portions  41   b ,  41   c  of the column-side lower bracket are respectively formed with round holes arrayed in the horizontal direction, and the bolt  43  is inserted through these round holes to clamp those plate portions with the nut  45 .  
         [0037]     In the present embodiment, the column-side lower bracket  41  is formed by press-forming separately from the lower column  23 , and is fixed to the lower column  23  by welding. However, the column-side lower bracket  41  may be integrally formed by expanding the lower column  23  by hydro-bulging or the like, in the same manner as the distance unit described above. A cut-away portion  47  in a substantially U shape is formed on the pivot bracket  5  to be open forward, and the pivot bolt  43  is inserted in the rear end side of the cut-away portion  47 .  
         [0038]     The steering column  1  is arranged to be rockable as a whole around the pivot bolt  43 . The driver can adjust a vertical position of the steering wheel (in the up-and-down direction in  FIG. 1 ) within a range in which the adjusting bolt  31  is moved in the tilt adjusting elongated holes  15   a ,  15   b  by operating the adjusting lever  35 . Moreover, the upper column  21  is slidable with respect to the lower column  23 , so that the driver can adjust the front and back positions of the steering wheel (in the right-and-left direction in  FIG. 1 ) within a range in which the adjusting bolt  31  is moved in the elongated holes  37  for telescopic adjustment by operating the adjusting lever  35 .  
         [0039]     On the upper column  21  of the present embodiment, the pressed and expanding portions  25 ,  27  are formed with the flat surface portions  51 ,  53  which are brought into contact with the inner surfaces of the vertical side plate portions  3   c ,  3   d  of the fixed upper bracket  3 , and three beads  55 ,  57  are formed, respectively, on an upper part and a lower part of the distance unit  29 .  FIG. 3  is a perspective view of this arrangement, while  FIG. 4  shows a lateral view thereof. Each of the beads  55 ,  57  is formed at least along the length of the elongated hole  37  so as to couple the pressed portions  25 ,  27  together, thereby reinforcing the upper column. The number of such beads may be increased to meet a desired strength.  
         [0040]     A mode of an operation of the present embodiment will be described in the following.  
         [0041]     When the position of the steering wheel becomes inappropriate because of a change of drivers, or the like, with the steering column apparatus of the first embodiment, first the driver rotates the adjusting lever  35  clockwise to loosen the adjusting nut  33  with respect to the adjusting bolt  31 . Then, the axial force of the adjusting bolt  31  which has worked on the distance unit  29  of the upper column  21  through the upper bracket  3  is extinguished so that the steering column  1  is allowed to rock in a predetermined amount which is determined by the elongated holes  15   a ,  15   b  around the pivot bolt  43  and, at the same time, the upper column  21  is also allowed to slide in a predetermined amount which is determined by the elongated holes  37 ,  37  with respect to the lower column  23 . With this operation, the driver can tiltingly or telescopically move the steering column  1  to adjust the steering wheel to a desired position.  
         [0042]     Upon completion of the positional adjustment of the steering wheel, the driver rotates the adjusting lever  35  counter-clockwise to clamp the adjusting nut  33  with respect to the adjusting bolt  31 . Then, a predetermined axial force is generated in the adjusting bolt  31  so that the inner surfaces of the fixed upper bracket  3  are brought into pressure contact with the pressed flat surface portions  51 ,  53  of the distance unit  29 . As a result, the upper column  21  (that is, the steering wheel) is fixed at a desired position with respect to the upper bracket  3 .  
         [0043]     On this occasion, since the beads  55 ,  57  for coupling the pressed and expanding portions  25 ,  27  are provided in an upper part and a lower part of the distance unit  29  in the present embodiment, the rigidity of the distance unit  29  is conspicuously high, compared with that of the prior art described above. With this structure, the upper column  21  can be supported by the fixed upper bracket  3  without fail, and a vibration of the steering shaft  13  and that of the steering wheel in running can be suppressed. In addition, an unintentional movement of the upper column  21  and the like at collision of the car is difficult to occur. If an excessive axial force is generated in the adjusting bolt  31  when the adjusting lever  35  is clamped by a strong clamping force, elastic or plastic deformation of the distance unit  29  is difficult to occur so that a stable clamping is feasible for a long time.  
         [0044]      FIG. 5  is a perspective view of an upper column according to the second embodiment, and  FIG. 6  is a perspective view of the upper column according to the third embodiment. Each of these embodiments employs a structure substantially the same as that of the first embodiment. However, in the second embodiment three grooves  61  depressed in the column are formed on the distance unit  29 , instead of the beads. On the other hand, a wide R-shaped band type convex portion  63  is provided on the distance unit  29  in the third embodiment. These grooves  61  and the convex portion  63  are formed at least along the length of the elongated hole  37 , in the similar manner as in the first embodiment, so as to connect the pressed and expanding portions  25 ,  27  and a mode of operation thereof is also the same as that in the first embodiment.  
         [0045]     Embodiments of the present invention are not limited to those described above. For example, the size and the shape of a cross section of the convex portion or the concave portion for connecting the pressed and expanding portions, and the number or the pitch of these portions can be properly determined in accordance with designing reasons, or the like. These convex and concave portions may be provided on the upper side, on the lower side, or on the bottom of the pressed and expanding portions. The convex and concave portions may be properly combined with each other. The shape of a cross section of the bead may be substantially triangular, rectangular, or R-shaped. The material for the steering column may be steel pipe or alluminium. The steering column may be plastically processed by explosive bulging, rubber bulging, or press-forming, instead of hydroforming. In the embodiments described above, the present invention is applied to a steering column apparatus of a telescopic type. However, the present invention may be applied to a steering column apparatus which is provided only with a tilting mechanism or only with a telescopic mechanism. The described steering column comprises the upper column and the lower column which are separately formed. However, the upper column and the lower column may be integrally formed. Also, not only the distance unit, but also the lower bracket may be formed integrally. Specific structures of the steering apparatus and the material, the shape, and the like, of each of the constituent parts thereof can be properly changed within the scope and spirit of the present invention.  
         [0046]     As described above, according to the steering column apparatus of the present invention, the rigidity of the whole column distance unit which is pressed and supported by the body-side bracket is improved and is difficult to be deflected even if a great clamping force is applied onto the pressed portion, the steering column can be supported by the body-side bracket without fail, a vibration of the steering shaft or that of the steering wheel in running can be suppressed, and an unintentional movement of the steering column or the like at a collision of the car scarcely occur.