Abstract:
Disclosed herewith is a telescopic type steering device that is high in vibration rigidity and good in feeling of steering has a lower column; an upper column telescopically coupled to the lower column; a steering shaft assembly having an upper axle member for mounting a steering wheel at the upper end and a lower axle member spline-coupled with the upper axle member so as to transmit steering torque to a steering mechanism of a car body from the wheel through the upper and lower axle members; a lower bearing for rotatably supporting the lower axle member at the lower side; an upper bearing for rotatably supporting the upper axle member at the upper side; and an intermediate bearing for rotatably supporting the steering shaft assembly at an intermediate position between the upper and lower bearings.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a steering device, more particularly to a telescopic type steering device in which an outer column and an inner column are fit to each other slidably in the axial direction to enable telescopic position adjustment of a steering wheel.  
       BACKGROUND OF THE INVENTION  
       [0002]     There is a telescopic type steering device, which enables telescopic position adjustment of a steering wheel by fitting an outer column and an inner column to each other slidably in the axial direction (US Patent Application Publication No. US 2003/0000330 A1).  
         [0003]     In such a steering device, a lower steering shaft is engaged with or fit by a spline or the like to an upper steering shaft that has a steering wheel mounted at the rear side of an object vehicle body to enable telescopic movement and transmit the turning of the steering wheel to a steering gear, thereby changing a steering angle of the wheels of the vehicle.  
         [0004]      FIG. 6  shows an expanded cross sectional view of a column of a conventional steering device. As shown in  FIG. 6 , a lower column (outer column)  1  is fit to a vehicle body  7  by a lower body mounting bracket  61  and by an upper body mounting bracket  62 . The outer circumference  21  of the cylindrical upper column (inner column)  2  is fit tightly to the inner circumference  11  of the hollow cylindrical lower column  1  telescopically and slidably in the axial direction.  
         [0005]     An upper steering shaft  31  is inserted in the center of the axis of the upper column  2  and the right end (vehicle body&#39;s rear side) of the upper steering shaft  31  is journaled rotationally by an upper bearing  41  press-fit to the right end (vehicle body&#39;s rear side) of the inner circumference  11  of the upper column  2 . A steering wheel  5  is mounted at the right end of the upper steering shaft  31 .  
         [0006]     A lower steering shaft  32  is inserted in the center of the axis of the inner circumference  11  of the lower column  1  and the left end (vehicle body&#39;s front side) of the lower steering shaft  32  is journaled rotationally by a lower bearing  42  press-fit to the left end (vehicle body&#39;s front side) of the inner circumference  11  of the lower column  1 . A male spline  321  is formed at the right side of the lower steering shaft  32  and the shaft  32  is engaged with a female spline  311  formed at the left side of the upper steering shaft  31 .  
         [0007]     Consequently, the turning of the steering wheel  5  is transmitted to a steering gear (not shown) through the upper steering shaft  31  and the lower steering shaft  32  to change the steering angle of the vehicle wheels regardless of the telescopic position of the upper column  2 .  
         [0008]     In the conventional steering device described above, a point of the right end of the upper steering shaft  31  is just journaled rotationally by the upper bearing  41  at the right end of the upper column  2  and a point of the left end of the upper steering shaft  31  is just journaled by the lower bearing  42  at the left end of the lower column  1 . Consequently, the space between the upper bearing  41  and the lower bearing  42  becomes large and this structure lowers the vibration rigidity of both the upper steering shaft  31  and the lower steering shaft  32 , thereby drivers come feel physical disorder. This is why the conventional steering device is not good for drivers.  
       SUMMARY OF THE INVENTION  
       [0009]     Under such circumstances it is an object of the present invention to provide a telescopic type steering device with a high vibration rigidity and enabling drivers to have a good feeling of steering respectively.  
         [0010]     In order to solve the above described conventional problems, the first aspect of the present invention inheres a steering device, comprising: a lower column; an upper column telescopically coupled to the lower column; a steering shaft for transmitting steering torque to a steering mechanism of a car body from the wheel; a lower bearing for rotatably supporting the steering shaft at the lower side; an upper bearing for rotatably supporting the steering shaft at the upper side; and an intermediate bearing for rotatably supporting the steering shaft at an intermediate position between the upper and lower bearings.  
         [0011]     The second aspect of the present invention inheres a steering device, comprising: a lower column; an upper column telescopically coupled to the lower column; a steering shaft assembly having an upper axle member for mounting a steering wheel at the upper end and a lower axle member spline-coupled with the upper axle member so as to transmit steering torque to a steering mechanism of a car body from the wheel through the upper and lower axle members; a lower bearing for rotatably supporting the lower axle member at the lower side; an upper bearing for rotatably supporting the upper axle member at the upper side; and an intermediate bearing for rotatably supporting the steering shaft assembly at an intermediate position between the upper and lower bearings.  
         [0012]     The third aspect of the present invention inheres a steering device according to claim  2 , wherein; the intermediate bearing supports the lower axle member along with the lower bearing.  
         [0013]     The fourth aspect of the present invention inheres a steering device according to claim  3 , wherein; the intermediate bearing is mounted in the upper part of the lower column.  
         [0014]     The fifth aspect of the present invention inheres a steering device according to claim  3 , wherein; the intermediate bearing is mounted in the upper column.  
         [0015]     The sixth aspect of the present invention inheres a steering device according to claim  2 , wherein; the intermediate bearing supports the upper axle member along with the upper bearing.  
         [0016]     The seventh aspect of the present invention inheres a steering device according to claim  6 , wherein; the intermediate bearing is mounted in the upper part of the lower column.  
         [0017]     The eighth aspect of the present invention inheres a steering device according to claim  6 , wherein; the intermediate bearing is mounted in the upper column.  
         [0018]     The ninth aspect of the present invention inheres a steering device according to claim  2  to  8 , wherein; the lower axle member has a female structure of a coupling and the upper axle member has a male structure of the coupling.  
         [0019]     The tenth aspect of the present invention inheres a steering device according to claim  2  to  8 , wherein; the lower axle member has a male structure of a coupling and the upper axle member has a female structure of the coupling.  
         [0020]     The eleventh aspect of the present invention inheres a steering device according to claim  2  to  8 , wherein; a needle bearing is used as the intermediate bearing.  
         [0021]     In the steering device of the present invention, the steering shaft assembly is rotatably supported at three points, that is, by lower, intermediate and upper bearings, so that the rigidity against vibration and the feeling of steering are improved. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0022]      FIG. 1  is an overall perspective view of a steering device  101  mounted on a vehicle;  
         [0023]      FIG. 2  is an expanded cross sectional view of a column of the steering device in a first embodiment of the present invention;  
         [0024]      FIG. 3  is an expanded cross sectional view of a portion around the intermediate bearing shown in  FIG. 2 ;  
         [0025]      FIG. 4  is an expanded cross sectional view of a column of a steering device in a second embodiment of the present invention;  
         [0026]      FIG. 5  is an expanded cross sectional view of a column of a steering device in a third embodiment of the present invention; and  
         [0027]      FIG. 6  is an expanded cross sectional view of a column of a conventional steering device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     Hereunder the first and second embodiments of the present invention will be described with reference to the attached drawings.  
       First Embodiment  
       [0029]      FIG. 1  shows an overall perspective view of a steering device  101  of the present invention, which is mounted on a vehicle. The steering device  101  journals a steering shaft  102  rotationally. The steering shaft  102  has a steering wheel  5  mounted on its top (vehicle body&#39;s rear side) and an intermediate shaft  104  linked to its lower end (vehicle body&#39;s front side) through a universal joint  103 .  
         [0030]     The intermediate shaft  104  has a universal joint  105  linked to its lower end and a steering gear composed of a rack and pinion mechanism, etc. is coupled to the universal joint  105 .  
         [0031]     If a driver turns the steering wheel  5 , the turning of the steering wheel  5  is transmitted to a steering gear  106  through the steering shaft  102 , the universal joint  103 , the intermediate shaft  104 , and the universal joint  105 , thereby a tie rod  107  is moved through the rack and pinion mechanism to change the steering angle of the vehicle wheels.  
         [0032]      FIGS. 2 and 3  show the steering device in the first embodiment of the present invention respectively.  FIG. 2  shows an expanded cross sectional view of a column of the steering device  101  in the first embodiment of the present invention.  FIG. 3  shows an expanded view of a portion around the intermediate bearing shown in  FIG. 2 .  
         [0033]     As shown in  FIGS. 2 and 3 , the lower column (outer column)  1  is composed by press-coupling the body&#39;s rear side of the body&#39;s front side lower column  12  with the body&#39;s front end of the body&#39;s rear side lower column  13 . The vehicle body&#39;s front side lower column  12  is fixed to the vehicle body  7  with a lower body mounting bracket  61  and the vehicle body&#39;s rear side lower column  13  is fixed to the vehicle body  7  with an upper vehicle body mounting bracket  62 .  
         [0034]     To the inner circumference  131  of the vehicle body&#39;s rear side lower column  13 , the outer circumference  21  of the hollow cylindrical upper column (inner column)  2  is fit tightly, telescopically, and slidably in the axial direction. The vehicle body&#39;s rear side lower column  13  has a slit (not shown) formed at a portion where the upper column  2  slides, so that the diameter of the vehicle body&#39;s rear side lower column  13  is shrank/expanded with a lever (not shown) to adjust the telescopic position of the upper column  2  at the time of diameter expansion.  
         [0035]     An upper steering shaft (inner steering shaft)  31  is inserted in the center of the axis of the upper column  2  and the right end (vehicle body&#39;s rear side) of the upper steering shaft  31  is journaled rotationally by an upper bearing  41  press-inserted in the right end (vehicle body&#39;s rear side) of the inner circumference  22  of the upper column  2 . And a steering wheel  5  is mounted at the right end (vehicle body&#39;s rear side) of the upper steering shaft  31 . As the upper bearing  41 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0036]     The lower steering shaft (outer steering shaft)  32  is inserted in the center of the axis of the inner circumference  121  of the vehicle body&#39;s front side lower column  12  and the left end (vehicle body&#39;s front side) is journaled rotationally by a lower bearing  42  press-fit to the left end (vehicle body&#39;s front side) of the inner circumference  121  of the vehicle body&#39;s front side lower column  12 . As the lower bearing  42 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0037]     A female spline  322  is formed at the right side of the lower steering shaft  32  and the female spline  322  is engaged slidably with a male spline  312  formed at the left side of the upper steering shaft  31 . Consequently, the turning of the steering wheel  5  is transmitted to the steering gear (not shown) through the steering wheel  5 , the upper steering shaft  31 , and the lower steering shaft  32  regardless of the telescopic position of the upper column  2 , thereby changing the steering angle of the vehicle wheels.  
         [0038]     The right end (vehicle body&#39;s rear side) of the lower steering shaft  32  is journaled rotationally by a needle bearing employed as an intermediate bearing. In other words, as shown in  FIG. 3 , the needle bearing  43  is composed of a thin plate ring-like core metal  431 , a rubber or resin cylindrical sealing part  432  united with the core metal  431 , and a plurality of needle rollers  435  held by a holder  434  in a ring-like groove  433  of the sealing part  432 .  
         [0039]     The outer circumferences of both the core metal  431  and the sealing part  432  are press-fit in a bearing hole  132  formed at the vehicle body&#39;s front side of the vehicle body&#39;s rear side lower column  13 , so that the core metal  431  and the sealing part  432  function as outer wheels of the needle bearing  43 . The inner diameter of the bearing hole  132  is formed smaller than the inner diameter of the inner circumference  131  of the vehicle body&#39;s rear side lower column  13 .  
         [0040]     The needle roller  435  is fitted outerly to the outer circumference  323  of the lower steering shaft  32  and sealing lips  436  provided at both sides of the inner circumference of the sealing part  432  come into contact with the outer circumference  323  of the lower steering shaft  32  to protect the needle roller  435  from external dust. Consequently, the needle bearing  43  journals the vehicle body&#39;s rear end of the lower steering shaft  32  with no play with respect to the vehicle body&#39;s rear side lower column  13 .  
         [0041]     As described above, in the steering device of the present invention, both ends of the lower steering shaft  32  are journaled rotationally at both ends of the lower column  1  by both the lower bearing  42  and the needle bearing  43  that functions as an intermediate bearing. Consequently, both ends of the upper steering shaft  31  engaged with the lower steering shaft  32  by a spline come to be journaled by the needle bearing  43 . Therefore the vibration rigidity becomes high in both the upper steering shaft  31  and the lower steering shaft  32  and the turning radium of the vehicle becomes small. The feeling of steering is thus improved.  
       Second Embodiment  
       [0042]     Next, a steering device in a second embodiment of the present invention will be described.  FIG. 4  shows an expanded cross sectional view of a column of the steering device  101  in the second embodiment of the present invention. In this second embodiment, only the differences from the first embodiment will be described, avoiding redundancy. In the first embodiment, the outer steering shaft is disposed at the lower side and the inner steering shaft is disposed at the upper side. In the steering device in this second embodiment, however, the outer steering shaft is disposed at the upper side and the lower steering shaft is disposed at the lower side.  
         [0043]     As shown in  FIG. 4 , the upper steering shaft (outer steering shaft)  31  is inserted in the center of the axis of the upper column  2  and the right end (vehicle body&#39;s rear side) of the upper steering shaft  31  is journaled rotationally by the upper bearing  41  press-fit to the right end (vehicle body&#39;s rear side) of the inner circumference  22  of the upper column  2 . And the steering wheel  5  is mounted at the right end (vehicle body&#39;s rear side) of the upper steering shaft  31 . As the upper bearing  41 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0044]     The lower steering shaft (inner steering shaft)  32  is press-fit in the center of the axis of the inner circumference  121  of the vehicle body&#39;s front side lower column  12  and the left end (vehicle body&#39;s front side) of the lower steering shaft  32  is journaled rotationally by a lower bearing  42  press-fit in the left end (vehicle body&#39;s front side) of the inner circumference  121  of the vehicle body&#39;s front side lower column  12 . As the upper bearing  41 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0045]     A male spline  321  is formed at the right side of the lower steering shaft  32  and it is engaged slidably with the female spline  311  formed at the left side of the upper steering shaft  31 . Consequently, the turning of the steering wheel  5  is transmitted to the steering gear (not shown) through both the upper steering shaft  31  and the lower steering shaft  32  regardless of the telescopic position of the upper column  2  to change the steering angle of the vehicle wheels.  
         [0046]     The right end (vehicle body&#39;s rear side) of the lower steering shaft  32  is journaled rotationally by the needle bearing  43  employed as an intermediate bearing. The detailed structure of the needle bearing  43  is the same as that in the first embodiment, so that the description will be omitted here. The needle bearing  43  is disposed closer to the vehicle body&#39;s front side than the intermediate position  44  of an interval L in the axial direction between the upper bearing  41  and the lower bearing  42  regardless of the position for telescopic adjustment of the upper column  2 .  
         [0047]     Also in the steering device in this second embodiment, both ends of the lower steering shaft  32  are journaled rotationally at both ends of the lower column  1  by the lower bearing  42  and the needle bearing  43 . Consequently, both ends of the upper steering shaft  31  engaged with the lower steering shaft  32  by a spline are also journaled by the upper bearing  41  and by the needle bearing  43 . Thus the vibration rigidity is high in both the upper steering shaft  31  and the lower steering shaft  32 . In addition, the turning radius of the vehicle becomes small, thereby the feeling of steering is improved.  
         [0048]     If a vertical force is applied to the steering wheel  5 , the upper steering shaft  31  begins rotating at a fulcrum assumed at the upper bearing  41 . However, because the needle bearing  43  is disposed toward the vehicle body&#39;s front side far from the upper bearing  41 , the turning of the upper steering shaft  31  is suppressed. The feeling of steering is thus improved.  
       Third Embodiment  
       [0049]     Next, a steering device in a third embodiment of the present invention will be described.  FIG. 5  shows an expanded cross sectional view of a column of the steering device  101  in the third embodiment of the present invention. In this embodiment, only the differences from the above embodiments will be described, avoiding redundancy. In the steering device in this third embodiment, a lower column and an upper column formed as one item respectively are used as an inner column and an outer column respectively. And a needle bearing is provided at the upper column side.  
         [0050]     As shown in  FIG. 5 , the lower column (inner column)  1  is formed as one item and the vehicle body&#39;s front side of the lower column  1  is fixed to the vehicle body  7  with a lower vehicle body mounting bracket  61  while the vehicle body&#39;s rear side of the lower column  1  is fixed to the vehicle body  7  with an upper vehicle body mounting bracket  62 .  
         [0051]     The vehicle body&#39;s front side of the inner circumference  22  of the hollow cylindrical upper column (outer column)  2  is fit to the vehicle body&#39;s rear side of the outer circumference  14  of the hollow cylindrical lower column  1  tightly, telescopically, and slidably in the axial direction. The upper column  2  has a slit (not shown) formed at a spot where the upper column  2  is fit outerly to the lower column  1 . The diameter of the upper column  2  is shrank/expanded with a lever (not shown) to adjust the telescopic position of the upper column  2  at the time of diameter expansion.  
         [0052]     As shown in  FIG. 5 , the upper steering shaft (outer steering shaft)  31  is inserted in the center of the axis of the upper column  2  formed as one item and the right end (vehicle body&#39;s rear side) of the inner circumference  22  of the upper column  2  is journaled rotationally by the upper bearing  41  press-fit to the right end (vehicle body&#39;s rear side) of the inner circumference  22  of the upper column  2 . And a steering wheel  5  is fixed to the right end (vehicle body&#39;s rear side) of the upper steering shaft  31 . As the upper bearing  41 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0053]     The lower steering shaft (inner steering shaft)  32  is inserted in the center of the axis of the inner circumference  15  of the lower column  1  formed as one item and the left end (vehicle body&#39;s front side) of the lower steering shaft  32  is journaled rotationally by the lower bearing  42  press-fit to the left end (vehicle body&#39;s front side) of the inner circumference  15  of the lower column  1 . As the lower bearing  42 , various types of bearings such as ball bearings, roller bearings, slide bearings, etc. may be used.  
         [0054]     A male spline  321  is formed at the right side of the lower steering shaft  32  and it is engaged slidably with a female spline  311  formed at the left side of the upper steering shaft  31 . Consequently, the turning of the steering wheel  5  is transmitted to the steering gear (not shown) through the upper steering shaft  31  and the lower steering shaft  32  regardless of the telescopic position of the upper column  2  to change the steering angle of the vehicle wheels.  
         [0055]     The outer circumference  313  of the vehicle body&#39;s front side of the upper steering shaft  31  is journaled rotationally to the vehicle body&#39;s front side of the inner circumference  22  of the upper column by a needle bearing  43  employed as an intermediate bearing. The detailed structure of the needle bearing  43  is the same as that in the first embodiment, so that the description will be omitted here.  
         [0056]     Also in the steering device in this third embodiment, both sides of the upper steering shaft  31  are journaled rotationally at both ends of the upper column  2  by the upper bearing  41  and the needle bearing  43 . Consequently, both ends of the lower steering shaft  32  engaged with the upper steering shaft  31  by a spline come to be journaled by the lower bearing  42  and by the needle bearing  43 . Thus the vibration rigidity is high in both the upper steering shaft  31  and the lower steering shaft  32 . In addition, the turning radium of the vehicle becomes small and the feeling of steeling is improved.  
         [0057]     In the third embodiment, the present invention is applied to a steering device that enables telescopic position to be adjusted manually. However the present invention may also be applied to a steering device that enables telescopic position to be adjusted by an electric-driven actuator. Furthermore, if a distance bracket is attached to the outer circumference of the outer column or inner column and this distance bracket is disposed between vehicle body mounting brackets, the present invention may be applied to a steering device that clamps/unclamps the telescopic position.  
         [0058]     In the above embodiments, the present invention is applied only to a steering device that adjusts telescopic positions. However the present invention may also be applied to a steering device that can adjust both telescopic positions and tilting positions. In addition, the present invention may be applied to a steering device that absorbs an impact load by enabling the outer column and the inner column to slide relatively in the axial direction, then the steering wheel to the vehicle body&#39;s front side as a collapse movement at a secondary collision.  
         [0059]     Furthermore, in the above embodiments, the steering shaft is divided into an upper steering shaft  31  and a lower steering shaft  32 , both of which can make telescopic movement. However the steering shaft may be formed as one item. If the steering shaft is formed as one item, the steering shaft can move relatively with respect to the lower bearing  42 . Furthermore, it is also possible to assume the lower column as an inner column and the upper column as an outer column to divide the upper column into two parts in the axial direction, then provide an intermediate bearing at the divided upper column side. Furthermore, the outer column may be divided into two parts in the axial direction. In this case, an intermediate bearing may be provided at the divided inner column side.  
         [0060]     Furthermore, in the above embodiments, the lower column  1  is composed of the vehicle body&#39;s front side lower column  12  and the vehicle body&#39;s rear side lower column  12  that are press-fit to each other. However the lower column  1  may be formed as one item. In addition, the material of both the lower column  1  and the upper column  2  may not be limited only to iron; it may be another material such as aluminum. The intermediate bearing may not be limited only to the needle bearing described above; it may be any of ball bearing and slide bearings.