Abstract:
A steering column adjustable height and inclination of steering wheel has a singularity of control lever for controlling clamping/unclamping of a telescopic mechanism and a tilting mechanism for the adjustment. An energizing direction inverting mechanism inverts direction of biasing force applied to the lever by an energizing member from clamping direction to unclamping direction halfway through operation of the lever by a driver.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a steering column, and more particularly to a steering column for motor vehicle including at least any of a telescopic mechanism and a tilting mechanism.  
       BACKGROUND OF THE INVENTION  
       [0002]     The telescopic mechanism and the tilting mechanism aim at adjusting back-and-forth position and tilt angle of a steering wheel to the easiest-to-manipulate position according to the driver&#39;s body form and taste.  
         [0003]     The telescopic mechanism and the tilting mechanism are respectively provided with a column clamp which is clamped/unclamped for adjusting the steering wheel to back-and-forth position and a tilt head clamp which is also clamped/unclamped for adjusting tilt angle of the steering wheel. During these adjustments, the clamping condition of these column clamp and tilt head clamp is once cancelled and after back-and-forth position and tilt angle are adjusted under such condition, these are clamped again.  
         [0004]     As a means for maintaining the clamping conditions of the column clamp and the tilt head clamp after back-and-forth position and tilt angle of the steering wheel are adjusted, each clamping device uses a spring. There has been disclosed in the British Patent No. 281375 a steering column which enables adjustment of back-and-forth position and tilt angle of the steering wheel using a single control lever which can be manipulated without removing a hand from the steering wheel.  
         [0005]     In the steering column disclosed in the British Patent, the control lever is always retreated to a retreat position away from the steering wheel because it is pulled with force of a tensile spring in view of preventing an accident that the driver&#39;s hand is in contact with the control lever during the driving. On the occasion of adjusting the steering wheel, if the control level is pulled with a hand toward the steering wheel, the control level is pulled toward the steering wheel against the tensile spring. Movement of this control lever is transmitted to the column clamp for back-and-forth position adjustment provided away from the control lever via a cable movable in a flexible tube. Accordingly, the column clamp is unclamped.  
         [0006]     Moreover, with movement of this control lever, the tilt head clamp for adjusting tilt angle provided in the periphery of this control lever operates toward unclamping side against a compression spring and a plate spring. When the steering wheel is manipulated with both hands, back-and-forth position and tilt angle of the steering wheel are adjusted, and the control lever is freed from fingers under the condition that the control lever is maintained with the fingers, the control lever is returned to the retreat position with forces of the tensile spring and compression spring and the column clamp and tilt head clamp are clamped.  
         [0007]     In the steering column, adjustment of the steering wheel must be conducted while the control lever is continuously left in the unclamping condition. Since a spring force increases with increase in displacement thereof, the maximum force is required at the end position of the unclamping side where the spring is displaced to the most extent. Therefore, manipulation ability becomes worse because the steering wheel must be adjusted while a large force for maintaining the unclamping condition is continuously applied to the control level.  
         [0008]     Moreover, if a longer control lever is used to increase a lever ratio in order to reduce the force for operating the control lever, manipulations of switches provided in the periphery of steering wheel are impeded and in addition the longer control lever interferes with an instrument panel at the time of secondary collision. Accordingly, here rises a demerit that the space for allocating the control lever is restricted.  
       SUMMARY OF THE INVENTION  
       [0009]     The present invention relates to a steering column provided with a telescopic mechanism and/or a tilting mechanism which can realize, with both hands, adjustment of back-and-forth position and/or tilt angle of the steering wheel by setting the telescopic mechanism and/or tilting mechanism to the unclamping condition with manipulation of the control lever and thereafter maintaining such unclamping condition even after the control lever is freed from the fingers. Moreover, the present invention can provide a steering column for operation capability of the control lever by gradually reducing the force required to manipulate the control lever as the control lever comes close to the end part of the unclamping side.  
         [0010]     According to a profile of the present invention, the steering column of the present invention comprises a telescopic mechanism for adjusting back-and-forth position of the steering wheel, a tilting mechanism for adjusting tilt angle of the steering wheel, a clamping/unclamping mechanism for clamping/unclamping the telescopic mechanism, a clamping/unclamping mechanism for clamping/unclamping the tilting mechanism, a single control lever for clamping/unclamping both clamping/unclamping mechanisms to the, a first energizing member for energizing the control lever, an energizing direction inverting mechanism for inverting the direction in which the first energizing member energizes the control lever, a control lever maintaining mechanism for maintaining the control lever in at least any of the clamping side control lever end or the unclamping side control lever end. In this steering column of the present invention, the energizing direction inverting mechanism inverts the direction in which the first energizing member energizes the control lever and the control lever maintaining mechanism maintains the control lever at the manipulation end of the unclamping side.  
         [0011]     Since the unclamping condition is maintained as described above, a driver can easily adjust back-and-forth position and/or tilt angle of the steering wheel.  
         [0012]     According to another profile of the present invention, the steering column of the present invention comprises a telescopic mechanism for adjusting back-and-forth position of the steering wheel, a tilting mechanism for adjusting tilt angle of the steering wheel, a clamping/unclamping mechanism for clamping/unclamping the telescopic mechanism, a clamping/unclamping mechanism for clamping/unclamping the tilting mechanism, a single control lever for clamping/unclamping both clamping/unclamping mechanisms, and an energizing member for energizing the control lever to the side for clamping the clamping/unclamping mechanism, wherein as the control lever is operated toward the unclamping side control lever end from the clamping side control lever end, an energizing force of the energizing member working for the control lever can be reduced.  
         [0013]     Accordingly, only a small force is required for operating the control lever in the unclamping direction resulting in the effect that manipulation ability of the control lever can be improved. Moreover, only a small force is required for manipulation of the control lever, the control lever can be formed in compact size, manipulations of the switches in the periphery of the steering wheel are not impeded, and limitation on the space for allocating the control lever can be eliminated.  
         [0014]     Other objects and advantages besides those discussed above shall be apparent to those skilled in the art from the description of a preferred embodiment of the invention which follows. In the description, reference is made to accompanying drawings, which form a part thereof, and which illustrate an example of the invention. Such example, however, is not exhaustive of various embodiments of the invention, and therefore reference is made to the claims which follow the description for determining the scope of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is an outside view of a steering column  1  of the present invention.  
         [0016]      FIG. 2  is a top view including a partial cross-sectional view when the steering column  1  is observed from the direction P in  FIG. 3 .  
         [0017]      FIG. 3  is an enlarged view of the essential portion of  FIG. 1 , wherein the steering column  1  is partially cut away.  
         [0018]      FIG. 4  is a bottom view when the steering column  1  is observed in the direction Q of  FIG. 3 .  
         [0019]      FIG. 5  is a cross-sectional view along the line A-A in  FIG. 3 .  
         [0020]      FIG. 6  is a side view of  FIG. 1  which is partially cut away to indicate adjustment of tilt position of the steering column  1 .  
         [0021]      FIG. 7  is a cross-sectional view along the line B-B in  FIG. 3 .  
         [0022]      FIG. 8  is a cross-sectional view along the line C-C in  FIG. 3 .  
         [0023]      FIG. 9  is a cross-sectional view along the line D-D in  FIG. 3 .  
         [0024]      FIG. 10 a  partially enlarged view of  FIG. 8  indicating the rotating position of a column shaft  6  in the unclamping condition.  
         [0025]      FIG. 11  is a partially enlarged view of  FIG. 8  indicating the rotating position of the column shaft  6  in the clamping condition.  
         [0026]      FIG. 12 ( 1 ) is an operation explanation diagram illustrating an energizing direction inverting mechanism  8  and a control lever maintaining mechanism  89  of the present invention to show the condition that the control lever  7  is located at the clamping side control lever end a.  
         [0027]      FIG. 12 ( 2 ) is an operation explanation diagram illustrating the energizing direction inverting mechanism  8  and the control lever maintaining mechanism  89  of the present invention to show the condition that an engaging pin  471 , a center axis  81 , and the center of the engaging pin  821  are aligned on the line in the course of the operation to attract the control lever  7 .  
         [0028]      FIG. 12 ( 3 ) is an operation explanation diagram illustrating the energizing direction inverting mechanism  8  and the control lever maintaining mechanism  89  of the present invention to show the condition that the control lever  7  is allocated at the unclamping side control lever end b.  
         [0029]      FIG. 13  is an operation explanation diagram illustrating the energizing direction inverting mechanism  8  and the control lever maintaining mechanism  89  of the present invention to show the other embodiment.  
         [0030]      FIG. 14 ( 1 ) is a front elevation diagram of the steering column  1  of a third embodiment of the present invention to show the condition that the control lever is located at the clamping side control lever end a.  
         [0031]      FIG. 14 ( 2 ) is a right side elevation diagram of the steering column  1  of the third embodiment of the present invention.  
         [0032]      FIG. 15  is a front elevation diagram of the steering column of the third embodiment of the present invention to show the condition that the control lever is located at the unclamping side control lever end b.  
         [0033]      FIG. 16 ( 1 ) is a front elevation diagram of the steering column of the third embodiment of the present invention to show the condition that the control lever is located at the clamping side control lever end a.  
         [0034]      FIG. 16 ( 2 ) is a right side elevation diagram of the steering column  1  of the third embodiment of the present invention.  
         [0035]      FIG. 17  is a front elevation diagram of the steering column of a fourth embodiment of the present invention to show the condition that the control lever is located at the unclamping side control lever end b.  
         [0036]      FIG. 18  is a graph illustrating the relationship between a rocking angle of the control lever and the force applied to the control lever in the steering column  1  of the third embodiment of the present invention.  
         [0037]      FIG. 19  is a graph illustrating the relationship between a rocking angle of the control lever and the force applied to the control lever in the steering column  1  of a fourth embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
     First Embodiment  
       [0038]     The present invention will be described with reference to the accompanying drawings.  FIG. 1  to  FIG. 12  illustrate a steering column of the first embodiment of the present invention. According to this steering column, the clamping/unclamping mechanisms of both telescopic mechanism and tilting mechanism can be manipulated simultaneously in one direction of a single control lever. Moreover, when a driver takes a hand off the control lever, the unclamping condition of both telescopic mechanism and tilting mechanism can be maintained.  
         [0000]     General Outline:  
         [0039]      FIG. 1  is an outside view of the steering column  1  of the present invention. The steering column  1  comprises a fixed column member  2 , a moving column member  3 , a column head  31 , a tilt head  4 , a wheel shaft  5 , a column clamp  21 , a tilt head clamp  41 , and a control lever  7 .  
         [0040]     The fixed column member  2  is provided with mounting sections  221 ,  222  for mounting to a vehicle body  91 . The fixed column member  2  supports the moving column member  3  unrotatably around the center axis but movable in the direction of the center axis. The moving column member  3  is also provided with the column head  31  at the right end side thereof. This column head  31  supports the tilt head  4  which is tilted around the center axis  43 . This tilt head  4  rotatably supports the wheel shaft  5 , allowing the steering wheel  92  to be fixed at the right end part thereof.  
         [0041]     The column head  31  is provided with the column clamp shaft  6  which is rotatable around the axis parallel to the center axis of the moving column member  3 . The fixed column member  2  is also provided with the column clamp  21 , which can relatively move against the column clamp shaft  6 . With rotation of the column clamp shaft  6 , the moving column member  3  can be set to the clamping/unclamping conditions for the fixed column member  2 .  
         [0042]     Moreover, the column head  31  is provided with the tilt head clamp  41  for clamping/unclamping the tilt head  4  for the column head  31 . The tilt head  4  supports a single control lever  7 . This control lever  7  is allocated at the position away from the steering wheel  92 . Accordingly, when the steering wheel  92  is operated during the driving, the driver&#39;s hand is freed from contact with the control lever  7  so that the moving column member  3  or the tilt head  4  is never unclamped. In addition, manipulations of switches provided in the periphery of the steering wheel  92  are never impeded.  
         [0043]     When the control lever  7  is rocked in the direction approaching to the steering wheel  92 , a driven lever  714  ( FIG. 4 ) rocks following the control lever  7  to rotate a column clamp shaft  6 . This rotation is transferred to the column clamp  21 , unclamping the moving column member  3 . Moreover, with the operation for rocking the control lever  7  in the direction approaching to the steering wheel  92 , the tilt head  4  is unclamped simultaneously.  
         [0044]     The left end of the wheel shaft  5  is connected, within the steering column  1 , to a universal joint  931  and is also connected to a mechanism for operating the direction of front wheels through a pair of an upper intermediate shaft  941  and a lower intermediate shaft  942  (shown in  FIG. 2 ) which are splined and a lower universal joint  932 .  
         [0000]     Tilt Head Clamp:  
         [0045]      FIG. 2  is a partly cutaway top view of the steering column observed from the upper direction (P) in  FIG. 3 .  FIG. 3  is an enlarged partly cutaway view of the essential portion of the steering column  1  of  FIG. 1 .  FIG. 4  is a bottom view of the steering column  1  observed from the lower direction (Q) of  FIG. 3 .  FIG. 6  is an enlarged partly cutaway view of the steering column  1 , illustrating the condition for adjusting the tilt angle of steering wheel. Here, a solid line in  FIG. 1  and  FIG. 4  indicates the condition before the control lever  7  is pulled, while a chain line indicates the condition that the control lever  7  is pulled toward the steering wheel  92 .  FIG. 5  and  FIG. 7  are respectively cross-sectional views along the lines A-A and B-B in  FIG. 3 .  
         [0046]     The tilt head clamp  41  is constituted as described below. That is, the column head  31  is fitted with a segment gear  33  having the center at a tilt center shaft  43  using a bolt  34 . Leaving a space against the segment gear  33 , the tilt head  4  is provided with a back contact member  341 . Meanwhile, a left gear portion  442  of a gear arm  44  supported rotatably on the center of shaft  44  with the tilt head  4  and a projecting portion  71  are provided within the space. The lever center axis  72 A ( FIG. 4 ,  FIG. 5 ) is fitted to the tilt head  4  and a driven lever  714  ( FIG. 4 ,  FIG. 5 ) rocking around the center of the lever center axis  73 A is integrally formed with the projecting portion  71 .  
         [0047]     In  FIG. 3 , when the projecting portion  71  is pushed in the left direction, the projecting portion  71  also pushes the gear portion  442  from the rear surface thereof. Accordingly, the gear portion  442  is pushed toward the segment gear  33  so that the teeth of both gears may be engaged with each other. When the gear portion  442  pushes the segment gear  33 , the back contact member  341  receives a reaction force applied to the projecting portion  71 . Therefore, the tilt head  4  is fixed to the column head  31 . The tilt head  4  is locked at a stepped position in an angular location where the gear portion  442  engages with the segment gear  33 . When the projecting portion  71  moves toward the right in  FIG. 2 , the gear arm  44  rotates counterclockwise in  FIG. 3  around the center of shaft  441  with the gravity of the gear arm  44 . Accordingly, the teeth of these gears are disengaged and the tilt head clamp  41  is unclamped.  
         [0000]     Universal Joint and Intermediate Shaft:  
         [0048]     As illustrated in  FIG. 2 , an upper universal joint  931  is constituted between the right end of the upper intermediate shaft  941  and the left end of the wheel shaft  5 . Since the center of the universal joint  931  is laid on the shaft line of the tilt center shaft  43 , if the tilt head  4  is tilted, the universal joint is freed from influence of such tilt.  
         [0049]     A lower intermediate shaft  942  is supported rotatably with the fixed column member  2  and the lower intermediate shaft  942  and the upper intermediate shaft  941  are splined. Therefore, the moving column member  3  can be moved in the right and left directions in  FIG. 2 . Without relationship of the moving position of the moving column member  3 , rotation of the upper intermediate shaft  941  can be transferred to the lower intermediate shaft  942  because of the spline-coupling of the lower intermediate shaft  942  and the upper intermediate shaft  941 . Moreover, rotation of the steering wheel  92  can also be transferred to the lower intermediate shaft  942  even by adjusting the back-and-forth position of the steering wheel  92 . Fixed Column Member and Moving Column Member:  
         [0050]     As illustrated in  FIG. 3 , a long hole  32  is formed along the shaft direction within a cylindrical portion of the moving column member  3  and this long hole  32  is engaged with a stopper member  22  provided to the fixed column member  2 . Since the moving column member  3  is prevented in release from and rotation against the fixed column member  2  with the long hole  32  and stopper member  22 , it can move in the shaft direction within the range defined by the long hole  32  within the fixed column member  2 . A cushioning stopper  311  provided at the left end surface of the column head  31  is the cushioning material formed of rubber, synthetic resin or the like provided to prevent impactive collision between metal components when the column head  31  collides, during the adjustment, with the right end surface of the fixed column member  2 .  
         [0000]     Column Clamp:  
         [0051]     A structure of the column clamp  21  will be described with reference to  FIG. 8 ,  FIG. 9 ,  FIG. 10  and  FIG. 11 .  FIG. 8  is a cross-sectional view along the line C-C in  FIG. 3 .  FIG. 9  is a cross-sectional view along the line D-D in  FIG. 3 . FIG.  10  and  FIG. 11  are partly enlarged diagrams of  FIG. 8 , illustrating the relationship between the rotating position and the clamping/unclamping conditions of the column clamp shaft  6 . The column clamp  21  is provided to the fixed column member  2  and includes a first wedge  211 , a second wedge  212 , a clamp bar  213 , and reaction members  2141 ,  2142 .  
         [0052]     The fixed column member  2  is provided with a wedge hole  215  in the horizontal direction and a part of the wedge hole  215  is opened to a cavity of the fixed column member  2 . The first wedge  211  and second wedge  212  respectively have the sloping surfaces  2111 ,  2112  and these wedges are accommodated within the wedge hole  215  in the manner that the sloping surfaces  2111  and  2112  are opposed with each other. The sloping surfaces  2111 ,  2112  of two wedges are provided facing to the external circumference of the cylindrical portion of the moving column member  3 .  
         [0053]     The first wedge  211  and second wedge  212  are respectively provided with clamp bar holes  2113 ,  2114  and a clamp bar  213  is provided through this clamp bar hole. At both ends of the clamp bar  213 , reaction members  2141 ,  2142  which are larger than the clamp bar holes  2113 ,  2114  in the external diameter are fixed. The clamp bar  213  is provided with a column clamp shaft hole  216  which is in contact with one reaction member  2142  and a non-circular shape cross-sectional portion which is substantially elliptical in shape of the column clamp shaft  6  is inserted into this column clamp shaft hole  216 .  
         [0054]     At one end of the column clamp shaft  6 , a rocking arm  61  is secured. The non-circular shape cross-sectional portion of the column clamp shaft  6  is inclined, in the unclamping condition, to a large extent in the elliptical longer diameter direction as illustrated in  FIG. 10 , while the longer diameter direction is directed, in the clamping condition, in the direction near to the shaft direction of the clamp bard  213  as illustrated in  FIG. 11 . When the rocking arm  61  is turned to rock from the condition of  FIG. 10  with the structure described above, the column clamp shaft  6  rotates resulting in the condition of  FIG. 11 . In this case, when the reaction member  2142  is pressed toward the left with one of the elliptical longer diameter portions, the clamp bard  213  is pulled toward the left and the reaction member  2141  pushes the first wedge  211  toward the left. Meanwhile, the second wedge  212  is pressed toward the right with the other of the elliptical longer diameter portions.  
         [0055]     As a result, two wedges are mutually coming closer, respective sloping surfaces  2111 ,  2112  press the external circumference of the cylindrical portion of the moving column member  3  and the moving column member  3  is clamped for the fixed column member  2 . Since the first wedge  211  and the second wedge  212  can move integrally a little in the right and left directions, the unbalanced condition in which only one wedge intensively presses the moving column member  3  is never generated.  
         [0056]     When the rocking arm  61  is turned to rock in an opposite direction, the first wedge  211  and the second wedge  212  move to separate with each other with the movement inverted from that described above, canceling the clamping condition of the moving column member  3 .  
         [0000]     Operations of Control Lever:  
         [0057]     Next, movement of control lever  7  and members interlocking with such movement will be described. As illustrated in  FIG. 4 ,  FIG. 5  and  FIG. 6 , the control lever  7  is provided for locking at the left side surface of the tilt head  4 . Moreover, at the lower surface of the tilt head  4 , a driven lever  714  which is driven to rock with operations of the control lever  7 , a pusher plate  73  integrally extending to the left from the driven lever  714 , and a projecting portion  71  integrally formed to the driven lever  714  can be seen. The driven lever  714  and pusher plate  73  are respectively formed in the shape of inverse alphabet L as a whole.  
         [0058]     Moreover, at the side surface of the tilt head  4 , the energizing direction inverting mechanism  8  and control lever maintaining mechanism  89  can be seen.  FIG. 4  illustrates a couple of conditions using a solid line and a chain line. In one condition, the control lever  7  is operated (namely, the control lever end is pulled toward the steering wheel  92 ) to adjust the entire part, back-and-forth position and tilt angle of the control lever  7 . In the other condition, the operation end part is returned in the direction where the control lever  7  is located away from the steering wheel  92 .  FIG. 1  also illustrates a couple of conditions with a chain line and a solid line. In one condition, the control lever  7  is operated (called the unclamping side control lever end b). In the other condition, the control end part is returned in the direction where the control lever  7  is located away from the steering wheel  92  (called the clamping side control lever end a).  
         [0059]     The control lever  7  is pivoted to rock with the lever center axis  72 C threaded into the side surface of the tilt head  4 . Moreover, the energizing direction inverting mechanism  8  is loaded to the center shaft  81  ( FIG. 7 ) which is threaded into the side surface of the tilt head  4 . The energizing direction inverting mechanism  8  is constituted with a rocking lever  82 , an engaging pin  821 , a pinion  83 , and a segment gear  84 . The rocking lever  82  is pivoted to rock with the center shaft  81  and the pinion  83  is formed to a boss portion of the rocking lever  82 . This pinion  83  engages with the segment gear  84  ( FIG. 12 ( 1 ) to  FIG. 12 ( 3 )) formed to the control lever  7 .  
         [0060]     Moreover, a spring  715  is extended between the engaging pin  821  fitted to the rocking lever  82  and an engaging pin  471  fitted to a bracket  47  formed at the left end part of the tilt head  4 . This spring  715  always energizes clockwise the control lever  7  through the rocking lever  82 , pinion  83 , and segment gear  84 .  
         [0061]     On the control lever  7 , a fork-type engaging depression  717  ( FIG. 12 ( 1 ) to  FIG. 12 ( 3 )) is formed. An engaging projection  718  at the end part of the driven lever  714  is inserted into the engaging depression  717 . Therefore, the driven lever  714  follows up the operations of the control lever  7  to rock around the center of the lever center axis  72 A.  
         [0062]     In the condition before the control lever  7  is pulled indicated by a solid line in  FIG. 4  (clamping side control lever end a), since the control lever  7  is located at the rocking end part in the clockwise direction with a spring force of the spring  715 , the projection  71  of driven lever  714  is pushed to the left to clamp the tilt head  4 . When the control lever  7  is pulled toward the steering wheel  92  during adjustment of the tilting mechanism position and telescopic mechanism position, the driven lever  714  is rocked clockwise around the center of the lever center axis  72 A. Accordingly, when the control lever  7  turns to rock to the position indicated by a chain line in  FIG. 4  (unclamping side control lever end b), the projection  71  integrated with the driven lever  714  moves to the right to unclamp the tilt head clamp  41 .  
         [0063]     When the control lever  7  moves to the position indicated with a chain line (unclamping side control lever end b) from the position indicated with a solid line (clamping side control lever end a) in  FIG. 4 , the pusher plate  73  integrated with the driven lever  714  pushes a pusher rod  77  and the column clamp  21  described above is unclamped. Accordingly, the pulling operation of the single control lever  7  simultaneously realizes the unclamping operation of the tilt head clamp  41  and the unclamping operation of the column clamp  21 .  
         [0064]     The pusher rod  77  ( FIG. 9 ) is supported to slide with a rib  312  in the left side of the column head  31  and with a rib  313  in the right side thereof in the direction parallel to the tilt center shaft  43 . The pusher rod  77  is inserted into a spring  741  to energize a collar  746  in the left direction of  FIG. 9  and the right end thereof is provided with a small long hole  743  in the right angle direction. The right end of the pusher rod  77  axially engages with one end of the rocking arm  6  through this long hole  743 . The long hole  743  is provided to absorb amount of displacement in the relative position to the rocking arm  61  when the pusher rod  77  moves in the shaft direction.  
         [0065]     The spring  741  energizes the pusher rod  77  in the left direction ( FIG. 9 ). The rocking arm  61  axially engaging at the end part of left side is energized to rotate clockwise. The spring force imparted to the rocking arm  61  maintains the column clamp shaft  6  to the clamping position ( FIG. 11 , it should be noted that the right and left are inverted because direction is opposite in  FIG. 11  and  FIG. 9 ). Position of the rocking arm  61  in this case is indicated with a solid line.  
         [0000]     Energizing Direction Inverting Mechanism:  
         [0066]     A structure and operations of the energizing direction inverting mechanism  8  will be described with reference to  FIG. 12 ( 1 ) to  FIG. 12 ( 3 ).  FIG. 12 ( 1 ) is an operation explanation diagram showing the condition that the control lever  7  is located at the control lever end a in the clamping side (condition before the control lever  7  is pulled) indicated with a solid line in  FIG. 4 .  FIG. 12 ( 2 ) is an operation explanation diagram showing the condition that the center of the engaging pin  471 , center shaft  81 , and engaging pin  821  are aligned on a line in the course of the operation to pull to control lever  7  toward the steering wheel  92 .  FIG. 12 ( 3 ) is an operation explanation diagram showing the condition that the control lever  7  is located at the control lever end b in the unclamping side (condition after the control lever  7  is pulled) indicated with a chain line in  FIG. 1  and  FIG. 4 .  
         [0067]     In  FIG. 12 ( 1 ), since the clamping side control lever end a pushes counterclockwise (direction of the arrow mark Rc) the rocking lever  82  toward the rocking end around the center of the center axis  81  via the engaging pin  821  with a spring force Fa of the spring  15  and also pushes clockwise the segment gear  84  engaged with the pinion  83 , a spring force (Fb indicated by the white arrow mark) the control lever  7  is applied to the control lever  7  and therefore the control lever  7  is energized clockwise (direction of the arrow mark Rd) toward the rocking end.  
         [0068]     In this case, the projection  71  of the driven lever  714  is pushed toward the left, setting the tilt head clamp  41  to the clamping condition. Moreover, the pusher plate  73  integrated with the driven lever  714  is located at the position indicated with a solid line in  FIG. 4  and therefore the column clamp  21  is also in the clamping condition.  
         [0069]     When the control lever  7  is pulled toward the steering wheel  92 , the control lever  7  turns counterclockwise (direction of arrow mark Rb) to rock around the center of the lever center axis  72 C as illustrated in  FIG. 12 ( 2 ) and the segment gear  84  rotates clockwise (direction of arrow mark Ra) the pinion  83 . Accordingly, the rocking lever  82  integrated with the pinion  83  also turns clockwise (direction of arrow mark Ra) to rock. Here, in  FIG. 12 ( 1 ) to  FIG. 12 ( 3 ), the arrow marks Ra and Rc indicate the rocking direction of the rocking lever  82 , while the arrow marks Rb, Rd indicate the rocking direction of the control lever  7 . Moreover, the white arrow marks Fa, Fb, Fc indicate the energizing direction of the spring  715  working for the rocking lever  82  and control lever  7 .  
         [0070]     When the rocking lever  82  turns clockwise (direction of arrow mark Ra) to rock, the center of the engaging pin  821  comes close to the line connecting the engaging pin  471  and the center axis  81 . Accordingly, the length of the perpendicular line drooped from the center of the center axis  81  to the vector of the energizing force (white arrow mark Fa) of the spring  715  working for the engaging pin  821  comes close to zero. Therefore, a moment of the force working for the engaging pin  821  by the spring  715  to turn counterclockwise the rocking lever  82  to rock also gradually comes close to zero.  
         [0071]     Accordingly, a clockwise force (white arrow mark Fb) of the spring  715  working for the control lever  7  gradually comes close to zero as it comes close to the position where the centers of the engaging pin  471 , center axis  81  and engaging pin  821  are aligned on a line. As a result, an operation force required to attract the control lever  7  toward the steering wheel  92  against the force of the spring  715  gradually comes close to zero. In this timing, the driven lever  714  driven by the control lever  7  turns clockwise to rock around the center of the lever center axis  72 A and the projection  71  integrated with the driven lever  714  moves to the right, accelerating the unclamping operation of the tilt head clamp  41 .  
         [0072]     Simultaneously, since the pusher plate  73  integrated with the driven lever  714  pushes the pusher rod  77  against the force of the spring  741 , the unclamping operation of the column clamp  21  described above is further continued. Therefore, a force to push the pusher rod  77  against the force of the spring  741  is gradually added as the force required to attract the control lever  7  toward the steering wheel  92 .  
         [0073]     When the control lever  7  is further attracted toward the steering wheel  92 , the centers of the engaging pin  471 , center axis  81 , engaging pin  821  are aligned on a line as illustrated in  FIG. 12 ( 2 ), and a moment of the force of the spring  715  to turn counterclockwise the rocking lever  82  to rock is reduced to zero. When the control lever  7  is further attracted toward the steering wheel  92 , the engaging pin  821  is apart from the line connecting the centers of the engaging pin  471  and the center axis  81  and turns clockwise (direction of arrow mark Ra) to rock.  
         [0074]     In this timing, as illustrated in  FIG. 12 ( 3 ), a force of the spring  715  energizes clockwise the rocking lever  82  around the center of the center axis  81  through the engaging pin  821  and also energizes counterclockwise the segment gear  84  engaged with the pinion  83 . Accordingly, a counterclockwise force (white arrow mark Fc) is applied to the control lever  7 . Namely, direction of the energizing force of the spring  715  applied to the control lever is inverted at the boundary defined with the line where the centers of the engaging pin  471 , center axis  81 , and the engaging pin  821  are aligned.  
         [0075]     As the rocking lever  82  turns clockwise (direction of arrow mark Ra) to rock and becomes apart from the position where the centers of the engaging pin  471 , center axis  81 , and engaging pin  821  are aligned on a line, length of the perpendicular line drooped from the center of the center axis  81  to the vector of the force (white arrow mark Fa) of the spring  715  working for the engaging pin  821  becomes longer gradually. Accordingly, a moment of the force working for the engaging pin  821  by the spring  715  to turn clockwise (direction of arrow mark Ra) the rocking lever  82  is gradually increased.  
         [0076]     Therefore, a counterclockwise force (white arrow mark Fc) of the spring  715  working for the control lever  7  is gradually increased. As a result, since the force required to push the pusher rod  77  against the force of the spring  741  is gradually reduced, the force required by the pusher plate  73  to attract the control lever  7  toward the steering wheel  92  is also gradually reduced.  
         [0077]     When the control lever  7  reaches the control lever end b in the unclamping side in  FIG. 12 ( 3 ), the projection  71  integrated with the driven lever  714  moves up to the right end, completing the unclamping operation of the tilt head clamp  4 . Simultaneously, the pusher plate  73  integrated with the driven lever  714  pushes the pusher rod  77 , completing the unclamping operation of the column clamp  21 .  
         [0078]     As a result, even when a driver takes a hand off the control lever  7 , the control lever  7  maintains the stationary condition at the unclamping side control lever end b illustrated in  FIG. 12 ( 3 ) in order to maintain the unclamping condition of the tilt head clamp  4  and the column clamp  21 . Accordingly, back-and-forth position and tilt angle of the steering wheel  92  can be adjusted easily under the condition that the steering wheel  92  is maintained with both hands.  
         [0079]     Upon completion of adjustment of back-and-forth position and tilt angle of the steering wheel  92 , a driver takes a hand off the steering wheel  92  and pushes with the same hand the control lever  7  apart from the steering wheel  92 . Thereby, the tilt head clamp  41  and column clamp  21  are clamped in the inverse sequence of the operation described above and the condition is returned to that of  FIG. 12 ( 1 ).  
         [0080]     When a driver takes a hand off the control lever  7 , since the control lever  7  is energized clockwise with the spring  715 , the control lever  7  maintains the stationary condition at the control lever end a in the clamping side of  FIG. 12 ( 1 ). This clamping condition is maintained even after the driver takes a hand off the control lever  7 .  
         [0000]     Control Lever Maintaining Mechanism:  
         [0081]     A structure and operations of the control lever maintaining mechanism  89  will be described with reference to  FIG. 12 ( 1 ) to F 12 ( 3 ). A counterclockwise force (white arrow mark Fc) working for the control lever  7  with the force (white arrow mark Fa) of the spring  715  at the control lever end b in the unclamping side of  FIG. 12 ( 3 ) is preferably set equal to or a little larger than the force required to push the pusher rod  77  against the force of the spring  741  for column clamp  21 .  
         [0082]     Namely, when the energizing force of the spring  715  is increased, a larger force is required to push the control lever  7  to the clamping position a from the unclamping side control lever end b as much as the increment. Moreover, a larger force is also required to pull the control lever  7  to the unclamping side control lever end b from the end a in the clamping side.  
         [0083]     In view of eliminating such event, the energizing force of the spring  715  is set equal to or a little larger than that required to push the pusher rod  77 . On the other hand, it suggests that the control lever  7  can move easily in the unclamping side control lever end b. Therefore, the control lever  7  probably happens to be displaced with inertia, that is, with impact and vibration during the adjusting operation for adjusting back-and-forth position and tilt angle of the steering wheel  92 .  
         [0084]     In order to eliminate such trouble, the tilt head  4  is provided with a control lever maintaining mechanism  89  to maintain the control lever  7  to the unclamping side control lever end b. As illustrated in  FIG. 12 ( 1 ) to  FIG. 12 ( 3 ), the control lever maintaining mechanism  89  comprises a support pin  86 , a plate spring  87  having the U-shape engaging projection  871  at the right side end thereof, and an engaging groove  882  in the unclamping side formed at an arcuate guide surface  881  of the control lever  7 .  
         [0085]     The support pin  86  is secured to the side surface of tilt head  4  and includes an almost cylindrical shaft having two parallel side surfaces. At the left side of the plate spring  87 , a rectangular base  872  is integrally formed. To this base  872 , an almost cylindrical hole having two parallel side surfaces is formed. The plate spring  87  is secured to the support pin  86  because the almost cylindrical hole of the base  872  is engaged tightly with the almost cylindrical shaft of the support pin  86 .  
         [0086]     The support pins  86 ,  87  are allocated within a window-shape cutaway hole  88  opened to the control lever  7 . At the lower side of the cutaway hole  88 , the arcuate guide surface  881  is formed and the lower surface of the engaging projection  871  at the right end of the plate spring  87  is in contact with this guide surface  881  with a downward force of the plate spring  87 . The center of the arcuate guide surface  881  is located at the center of the lever center axis  72 C of the control lever  7 . Accordingly, even if the control lever  7  turns to rock to any position, the lower surface of the engaging projection  871  is always sliding in contact with the guide surface  881 .  
         [0087]     To the guide surface  881 , an arcuate unclamping side engaging groove  882  is formed. When the control lever  7  reaches the control lever end b in the unclamping side illustrated in  FIG. 12 ( 3 ), the engaging projection  871  at the right end of the plate spring  87  is energized to the lower side with the plate spring  87  to enter the unclamping side engaging groove  882 . With engagement of the engaging projection  871  and the unclamping side engaging groove  882 , the control lever  7  is maintained at the unclamping side control lever end b.  
         [0088]     Accordingly, a problem that the control lever  7  is likely displaced to the clamping side control lever end a from the unclamping side control lever end b with an impact generated by position adjustment of the steering wheel  92  can be eliminated.  
         [0000]     Steering Wheel Adjustment:  
         [0089]     Manipulations and operations of members required for adjustment of back-and-forth position and tilt angle of the steering wheel  92  will be described below.  
         [0000]     Adjustment of Tilt Angle and Back-And-Forth Position (Length of Steering Column)  
         [0090]     For the adjustment of tilt angle and back-and-forth position of the steering wheel  92 , a driver takes off a hand the steering wheel  92  and pulls (direction of arrow mark Rb) the control lever  7  in the forward direction (toward the unclamping side control lever end b from the clamping side control lever end a) with the same hand. Accordingly, the control lever  7  turns clockwise to rock the driven lever  714  around the center of the lever center axis  72 A as illustrated in  FIG. 4 .  
         [0091]     When the driven lever  714  is rocked, the projection  71  moves to the right in  FIG. 3  and a gear arm  44  rotates counterclockwise with the gravity thereof. With rotation of the gear arm  44 , engagement between the tooth of segment gear  33  and the tooth of gear  442  of the gear arm  44  is lost, and the tilt head  4  is capable of adjusting the tilt angle. Moreover, the pusher plate  73  rocks up to the position indicated by a chain line to push the pusher rod  77  up to the position indicated by the dotted line in the right direction of  FIG. 9 , overcoming the force of the spring  741 .  
         [0092]     Movement toward the right of the pusher rod  77  causes rocking of the rocking arm  61  and therefore counterclockwise rotation of a column clamp shaft  6 . When the column clamp shaft  6  rotates, this shaft, which has been in the condition that the longer-diameter portion thereof is almost horizontal as illustrated in  FIG. 11 , is inclined as illustrated in  FIG. 10 . Therefore, the first wedge  211  and the second wedge  212  which are closed each other as illustrated in  FIG. 8  are separated, canceling the clamping condition of the moving column member  3 .  
         [0093]     The energizing direction inverting mechanism  8  changes the direction to energize the control lever  7  with the spring  715  to the counterclockwise direction (white arrow mark Fc) from clockwise direction (white arrow mark Fb) when the centers of the engaging pin  471 , center axis  71 , engaging pin  821  are aligned on a line ( FIG. 12 ( 2 )) in the course of the unclamping operation of the tilt head clamp  41  and column clamp  21 .  
         [0094]     Accordingly, a force of the spring  715  is applied to the pusher plate  73  for column clamp  21  as the force to push the pusher rod  77  against the force of the spring  715  and thereby operating force of a driver required to pull the control lever  7  toward the steering wheel  92  can be reduced.  
         [0095]     When the control lever  7  reaches the unclamping side control lever end b as illustrated in  FIG. 12 ( 3 ), the control lever  7  is surely maintained at the unclamping side control lever end b, because the engaging projection at the end of the plate spring  87  enters the unclamping side engaging groove  882 . Therefore, a driver can easily adjust back-and-forth position and tilt angle of the steering wheel  92  by taking a hand off the control lever  7  and then gripping the steering wheel  92  with both hands.  
         [0096]     Upon completion of adjustment of back-and-forth position and tilt angle of the steering wheel  92 , a driver takes a hand off the steering wheel  92  and pushes the control lever  7  with the hand taken off. With clockwise rocking of the control lever  7 , the engaging projection  871  at the end of the plate spring  87  is pushed out of the unclamping side engaging groove  882  and the lower surface of the engaging projection  871  slides along the guide surface  881 .  
         [0097]     In the energizing direction inverting mechanism  8 , when the centers of the engaging pin  471 , center axis  81 , and engaging pin  821  are aligned ( FIG. 12 ( 2 )) on a line in the course of the clamping operation of the tilt head clamp  41  and column clamp  21 , the direction in which the control lever  7  is energized with the spring  715  is inverted to the clockwise direction (white arrow mark Fb) from the counterclockwise direction (white arrow mark Fc). Accordingly, the control lever  7  turns clockwise to rock with the force of the spring  715 , reducing the force required to push the control lever  7 .  
         [0098]     Therefore, the control lever  7  causes the driven lever  714  to rock counterclockwise around the center of the lever center axis  72 A with the force of the spring  715 . As a result, the projection  71  moves to the left in  FIG. 3 , the teeth of segment gear  33  engage with the teeth of the gear  442 , and the tilt head  4  is clamped with the column head  31 . Simultaneously, the pusher plate  73  turns to rock up to the position indicated with a solid line and the pusher rod  77  returns to the position indicated with a solid line in the left direction in  FIG. 9  with the force of the spring  741 .  
         [0099]     Movement toward the left of the pusher rod  77  generates rocking of the rocking arm  61  and thereby also generates clockwise rotation of the column clamp shaft  6 . When the column clamp shaft  6  rotates, the column clamp shaft  6  which has been inclined in the longer-diameter portion thereof as illustrated in  FIG. 10  turns to the condition where the longer-diameter portion becomes horizontal as illustrated in  FIG. 11 .  
         [0100]     Accordingly, since the first wedge  211  and the second wedge  212  illustrated in  FIG. 8  come close with each other, the moving column member  3  is clamped. Since the energizing direction inverting mechanism  8  maintains the clamping side control lever end a of the control lever  7  with the force of the spring  715  even when a driver takes a hand off the control lever  7 , the clamping condition of the column clamp  21  and tilt head clamp  41  is maintained.  
         [0101]     When the tilt head clamp  41  is unclamped, a downward force is generated as if a person were drooping with the head in accordance with the weight thereof. Therefore, an intensive spring  45  for counter-balance ( FIG. 3 ,  FIG. 4 ) is provided. Here, it is possible to cancel such downward force with this spring  45  or to impart, to the tilt head  4 , the force to maintain the steering wheel  92  at the highest tilting position in order to make easier the driver&#39;s getting on and off.  
         [0102]     As described above, according to this steering column, since the direction to energize the control lever  7  with the spring  715  is inverted with the energizing direction inverting mechanism  8  to the unclamping direction from the clamping direction in the course of the operation for unclamping the tilt head clamp  41  and column clamp  21  by operating the control lever  7  in the unclamping direction, it is no longer required to continuously apply a large force for operating the control lever  7  in the unclamping direction.  
         [0103]     Moreover, even when a hand is taken off the control lever  7  during the unclamping of the telescopic mechanism and tilting mechanism, the control lever  7  is surely maintained at the unclamping side control lever end b with the control lever maintaining mechanism. Therefore, it is no longer required to continuously apply the force for maintaining above condition. In addition, since the control lever never happens to be displaced to the clamping side control lever end a from the unclamping side control lever end b with an impact generated when the steering wheel position is adjusted, the steering wheel position can be adjusted smoothly.  
         [0104]     The mechanisms described above can naturally be adapted to the steering column which is provided with any of the tilt head clamp and the column clamp.  
       Second Embodiment  
       [0105]     A modification example of the control lever maintaining mechanism  89  is illustrated in  FIG. 13 . In this example, a detecting means for issuing an alarm to a driver by detecting whether the control lever  7  is in the clamping side control lever end a or not. Moreover, a clamping side engaging groove  883  is also additionally provided to the clamping side control lever end a so that the control lever  7  cannot be rocked displacing toward the unclamping side control lever end b from the clamping side control lever end a.  
         [0106]     The control lever maintaining mechanism  89  is structured so that the clamping side engaging groove  883  is formed to the guide surface  881  in the right side of the unclamping side engaging groove  882  and when the control lever  7  reaches the clamping side control lever end a, the engaging projection  871  in the right side of the plate spring  87  enters the clamping side engaging groove  883  by receiving the downward force of the plate spring  87 . With engagement between the engaging projection  871  and the clamping side engaging groove  883 , the control lever  7  is maintained at the clamping side control lever end a.  
         [0107]     Moreover, the lower surface of the engaging projection  871  entering the clamping side engaging groove  883  is detected with a roller type contactor of a limit switch  884  fixed to the tilt head  4 . Accordingly, when the control lever  7  is not set to the clamping side control lever end a, driver&#39;s attention can be awaken with lighting of a red alarm display lamp or the like. The plate spring  87  may be replaced with any type of spring as it can satisfy the requirement. For example, a torsional spring or ball plunger or the like can be used.  
       Third Embodiment  
       [0108]     A third embodiment shows an example in which the control lever of a different structure is employed. Here,  FIG. 14 ( 1 ) is a front elevation diagram showing the condition that the control lever is set to the clamping side control lever end a, while  FIG. 14 ( 2 ) is a right side elevation diagram of  FIG. 14 ( 1 ).  FIG. 13  is a front elevation diagram showing the condition that the control lever is set to the unclamping side control lever end b.  
         [0109]     In  FIG. 14  and  FIG. 15 , the L-shape control lever  7  formed of an operating portion  701  and the spring engaging portion  702  is pivotally supported to rock with the lever center axis  704 . The spring  705  is fixed in its right end at a fixing position  707  of the fixing portion  706 , while engaged with an engaging hole  703  in its left side at the left end of the spring engaging portion  702 .  
         [0110]     As illustrated in  FIG. 14 ( 2 ), the control lever  7  is provided, around the lever center axis  704 , with the tilt head clamp  41  which is formed, for example, of a cam mechanism which functions as a stopper at the clamping end and unclamping end. With the rocking of the control lever  7 , the clamping/unclamping mechanism of the tilting mechanism can be manipulated. When the control lever  7  rocks to the clamping side control lever end (a) indicated with a solid line in  FIG. 14 ( 1 ), the clamping/unclamping mechanism of the tilting mechanism can be clamped with the cam mechanism of the tilt head clamp  41 . When the control lever  7  rocks to the unclamping side control lever end (b) indicated with a chain line in  FIG. 14 ( 1 ), the clamping/unclamping mechanism of the tilting mechanism can be unclamped with the cam mechanism of the tilt head clam  41 .  
         [0111]      FIG. 18  is a graph showing the relationship between a rocking angle of the control lever  7  and an energizing force applied to the control lever  7 . The horizontal axis of FIG.  18  indicate a rocking angle of the control lever  7 , while the vertical axis indicates amplitude of the energizing force applied to the control lever  7  from the spring  705 . In  FIG. 18 , a chain line  501  indicates amplitude of the force applied to the control lever  7  by the conventional spring, while a solid line  502  indicates amplitude of the force applied to the control lever  7  by the spring  705 . The conventional spring gradually increases the force to be applied to the control lever  7  as the control lever  7  is operated toward the unclamping side control lever end b. Therefore, operation of the control lever  7  has required a considerably large operating force.  
         [0112]     At the clamping side control lever end a in  FIG. 14 ( 1 ) and  FIG. 18 , the force (white arrow mark Fa) of spring  705  energizes, through the engaging hole  703 , the spring engaging portion  702  toward the rocking end in the clockwise direction around the center of the lever center axis  704 , the operating portion  701  is always pushed clockwise (white arrow mark Fb) and the control lever  7  is energized clockwise to the rocking end.  
         [0113]     At the clamping side control lever end a, since the length of the perpendicular line drooped to the vector of the force (white arrow mark Fa) of the spring working for the engaging hole  703  from the center of the lever center axis  704  becomes maximum, a moment of the force of the spring  705  to rock clockwise the operating portion  701  becomes maximum. Therefore, the force applied to the operating portion  701  also becomes maximum F 1 . In this timing, the clamping/unclamping mechanism of the tilting mechanism is clamped with the cam mechanism of the tilt head clamp  41  of the control lever  7 .  
         [0114]     When a driver maintains the control lever  7  with a hand and pulls toward the unclamping side control lever end b, the center of the engaging hole  703  comes close to the line connecting the fixing position  707  at the right end of the spring  705  and the lever center axis  704 . Accordingly, the length of the perpendicular line drooped to the vector of the force (white arrow mark Fa) of the spring  705  working for the engaging hole  703  from the center of the lever center axis  704  gradually comes close to zero. Therefore, a moment of the force working for the engaging hole  703  caused by the spring  705  to rock clockwise the spring engaging portion  702  gradually comes close to zero.  
         [0115]     Accordingly, as indicated with a solid line  502  of  FIG. 18 , the clockwise force (white arrow mark Fb) caused by the spring  705  working for the operating portion  701  gradually comes close to zero as it comes close to the position where the centers of the fixing position  707 , lever center axis  704 , and the engaging hole  703  are aligned on the line. As a result, the operating force required to attract the operating portion  701  toward the unclamping side control lever end b gradually comes close to zero against the force of the spring  705 .  
         [0116]     When the operating portion  701  rocks as much as the rocking angle α and reaches the unclamping side control lever end b as illustrated in  FIG. 15 , the clockwise force (white arrow mark Fb) of the spring  705  working for the operating portion  701  becomes almost zero and the operating portion  701  can be manipulated with a light operating force. In this case, the clamping/unclamping mechanism of the tilting mechanism is unclamped with the cam mechanism of the tilt head clamp  41  of the control lever  7 . Moreover, when the operating portion  701  is rocked counterclockwise a little to the position of the unclamping side control lever end b passing over the unclamping side control lever end b of  FIG. 15  (position where the centers of the fixing position  707 , lever center axis  704  and engaging hole  703  are aligned on the line), the spring  705  energizes counterclockwise the operating portion  701 . Accordingly, the tilt head clamp  41  can surely be maintained in the unclamping condition.  
         [0117]     As a result, even when a hand takes off the control portion  701 , the operating portion  701  is maintained to the condition that it stops at the unclamping side control lever end b illustrated in  FIG. 15 , maintaining the unclamping condition of the tilt head clamp  41 . Therefore, the tilt angle of the steering wheel can be adjusted easily under the condition that the steering wheel is maintained with both hands.  
         [0118]     When adjustment of the tilt angle of the steering wheel is completed, a driver takes a hand off the steering wheel and pushes the operating portion  701  toward the clamping side control lever end a with the hand which has taken off the steering wheel. Thereby, the center of engaging hole  703  isolates from the line connecting the fixing position  707  at the right end of the spring  705  and the lever center axis  704  and thereby the length of the perpendicular line drooped from the center of the lever center axis  704  to the vector of the force (white arrow mark Fa) of the spring working for the engaging hole  703  gradually becomes longer.  
         [0119]     Accordingly, since a moment of the force working for the engaging hole  703  of the spring  705  to rock clockwise the spring engaging portion  702  gradually becomes larger, the clamp operation of the tilt head clamp  41  can be performed only when a driver gives a small force to the operating portion  701 , resulting in the condition of  FIG. 14 ( 1 ).  
         [0120]     When a driver takes a hand off the operating portion  701 , the control lever  7 , which is imparted the clockwise force of the spring  705 , maintains the stationary condition at the clamping side control lever end a of  FIG. 14  ( 1 ). This clamping condition is maintained even when the take takes off the operating portion  701 .  
       Fourth Embodiment  
       [0121]     A fourth embodiment describes an example having introduced a different structure of the control lever. Here,  FIG. 16 ( 1 ) is a front elevation diagram illustrating the condition that the control lever  7  is set to the clamping side control lever end a.  FIG. 16 ( 2 ) is a right side elevation diagram of  FIG. 16 ( 1 ).  FIG. 17  is a front elevation diagram illustrating the condition that the control lever  7  is set to the unclamping side control lever end b.  
         [0122]     In  FIG. 16 ( 1 ) and  FIG. 17 , the L-shape control lever  7  formed of the operating portion  701  and spring engaging portion  702  is pivotally supported to rock with the lever center axis  704 . The one spring  705  is fixed at its right end to the fixing portion  706  in the fixing position  707  and is also engaged at its left end to the engaging hole  703  in the left end of the spring engaging portion  702 . Moreover, the other spring  708  is fixed at its left end to the other fixing portion  710  and the right end of the spring  708  engages with the engaging hole  709  at the intermediate part of the operating portion  701 .  
         [0123]     As illustrated in  FIG. 16 ( 2 ), the control lever  7  is provided, around the lever center axis  704 , with the tilt head clamp  41  formed, for example, of the cam mechanism which functions as a stopper of the clamp end and unclamp end. Therefore, the clamping/unclamping mechanism of the tilting mechanism can be operated with the rocking of the control lever  7 . Moreover, the column clamp  21  formed of a wedge mechanism is provided to the intermediate portion of the operating portion  701  and thereby since the control lever  7  turns to rock, the clamping/unclamping mechanism of the telescopic mechanism can be operated.  
         [0124]     When the control lever  7  rocks to the clamping side control lever end a indicated with a solid line in  FIG. 16 ( 1 ), the clamping/unclamping mechanisms of the tilting mechanism and telescopic mechanism can be clamped simultaneously with the cam mechanism of the tilt head clamp  41  and the wedge mechanism of the column clamp  21 . When the control lever  7  rocks to the unclamping side control lever end b indicated with a chain line in  FIG. 16 ( 1 ), the clamping/unclamping mechanisms of the tilting mechanism and telescopic mechanism can be unclamped simultaneously with the cam mechanism of the tilting mechanism and the wedge mechanism of the column clamp  21 .  
         [0125]      FIG. 19  is a graph illustrating relationship between rocking angle of the control lever  7  and amplitude of the force working for the control lever  7 . The horizontal axis of  FIG. 19  indicates rocking angle of the control lever  7 , while the vertical axis, amplitude of the force working for the control lever  7  with the springs  705 ,  708 . A chain line  601  in FIG.  19  indicates amplitude of the force working for the control lever  7  with the spring  708 , a broken line  601  indicates amplitude of the force working for the control lever  7  with the spring  705 , and a solid line indicates amplitude of the force working for the control lever  7  with the combined force of the springs  708  and  705 .  
         [0126]     At the clamping side control lever end a of  FIG. 16 ( 1 ) and  FIG. 19 , the force (white arrow mark Fa) of the spring  705  energizes clockwise the spring engaging portion  702  around the center of the lever center axis  704  through the engaging hole  703 . Moreover, the force (white arrow mark Fd) of the spring  708  energizes clockwise the operating portion  701  around the center of the lever center axis  704  through the engaging hole  709 . Accordingly, the clockwise force (white arrow mark Fb) always energizes the operating portion  701  and the control lever  7  is energized clockwise to the rocking end.  
         [0127]     At the clamping side control lever end a, the force (white arrow mark Fa) of the spring  705  increases the force to rock clockwise the operating portion  701  to the maximum value F 3 . Moreover, the force (white arrow mark Fd) of the spring  708  increases the force to rock clockwise the operating portion  701  to the minimum value F 4 .  
         [0128]     As a result, the combined forces of the springs  705  and  708  provides the maximum energizing force F 2  (F 2 =F 3 +F 4 ). This maximum energizing force F 2  is working as the force to rock clockwise the operating portion  701  at the clamping side control lever end a. In this case, the clamping/unclamping mechanisms of the tilting mechanism and telescopic mechanism are clamped with the cam mechanism of the tilt head clamp  41  of the control lever  7  and the wedge mechanism of the column clamp  21 .  
         [0129]     When a driver maintains the operating portion  701  with a hand and then pulls toward the unclamping side control lever end b, the center of the engaging hole  703  comes close to the line connecting the fixing position  707  at the right end of the spring  705  and the lever center axis  704 . Accordingly, the length of the perpendicular line drooped to the vector of the force (white arrow mark Fa) of the spring  705  working for the engaging hole  703  from the center of the lever center axis  704  gradually comes close to zero. Therefore, a moment of the force working for the engaging hole  703  with the spring  705  to rock clockwise the spring engaging portion  702  gradually comes close to zero. When the operating portion  701  rocks only for the rocking angle β, the center of the engaging hole  703  reaches the line connecting the fixing position  707  at the right end of the spring  705  and the lever center axis  704  and the moment of the force working for the engaging hole  703  with the spring  705  becomes zero.  
         [0130]     Thereafter, when the operating portion  701  is pulled toward the unclamping side control lever end b, the center of the engaging force  703  moves downward taking off the line connecting the fixing position  707  at the right end of the spring  705  and the lever center axis  704 . Thereby, the force to rock the spring engaging portion  702  is inverted to the counterclockwise direction from the clockwise direction. Accordingly, since the length of the perpendicular line drooped to the vector of the force (white arrow mark Fa) of the spring  705  working for the engaging hole  703  from the center of the lever center axis  704  gradually becomes longer, a moment of the force to rock counterclockwise the spring engaging portion  702  with the spring  705  gradually becomes longer.  
         [0131]     Force of the other spring  708  gradually increases in amplitude as indicated by a chain line  601  of  FIG. 19  but direction of the force working for the operating portion  701  is still constant. As a result, as the operating portion  701  comes close to the unclamping side control lever end b, the clockwise force (white arrow mark Fb) combined with the springs  705  and  708  working for the operating portion  701  gradually comes close to zero as indicated by a solid line  603  of  FIG. 19 . Accordingly, the operating force required to pull the operating portion  701  toward the unclamping side control lever end b gradually becomes close to zero against the force of the springs  705  and  708 .  
         [0132]     When the operating portion  701  rocks only for the rocking angle γ and reaching the unclamping side control lever end b as indicated in  FIG. 17 , the clockwise force (white arrow mark Fb) combined with the springs  705 ,  708  working for the operating portion  701  becomes almost zero and thereby the operating portion  701  can be manipulated with a light force. In this case, the clamping/unclamping mechanisms of the tilting mechanism and telescopic mechanism are unclamped with the cam mechanism of the tilt head clamp  41  of the control lever  7  and the wedge mechanism of the column clamp  21 .  
         [0133]     As a result, even when a driver takes a hand off the operating portion  701 , the operating portion  701  is maintained in the condition that it stops at the unclamping side control lever end b illustrated in  FIG. 17 , maintaining the unclamping condition of the tilt head clamp  41  and column clamp  21 . Therefore, the tilt angle and back-and-forth of the steering wheel can be adjusted easily while the steering wheel can be maintained with both hands.  
         [0134]     Upon completion of adjustment of tilt angle of the steering wheel, a driver takes a hand off the steering wheel and pushes with the same hand the operating portion  701  to the clamping side control lever end a. Accordingly, since the force combined with the springs  705  and  708  to rock clockwise the operating portion  701  gradually becomes larger, the tilt head clamp  41  and column clamp  21  can be clamped only by adding small force to the operating portion  701  and return to the condition of  FIG. 16 ( 1 ).  
         [0135]     When a driver takes a hand off the operating portion  701 , since the control lever  7  is imparted the clockwise force combined with the springs  705  and  708 , the control lever  7  maintains the stationary condition at the clamping side control lever end a of  FIG. 16 ( 1 ). This clamping condition is maintained even when a driver takes a hand off the operating portion  701 . In above two embodiments, the force working for the operating portion  701  with the spring  705  and combination of the springs  705  and  708  at the unclamping side control lever end b is reduced to almost zero but this force many also be set to the range of about ±10N. Moreover, the spring force characteristics  601 ,  602  illustrated in  FIG. 19  are never limited to those shown in the figure. Namely, any characteristic may be useful when the combined force  603  is gradually reduced as the operating portion  701  comes close to the unclamping side control lever end b and the combined force becomes almost zero when the operating portion comes to the unclamping side control lever end b. In addition, the energizing force characteristics  502 ,  603  are not limited to the linear characteristics and may be the non-linear energizing force characteristics.  
         [0136]     Although only preferred embodiments are specifically illustrated and described herein, it will be appreciated that many modifications and variations of the present invention are possible in light of the above teachings and within the purview of the appended claims without departing from the spirit and intended scope of the invention.