Abstract:
Desired is a function of tilting up a steering wheel to allow a driver to get on or off easily. An object of the invention is to strengthen the coupling between a steering wheel and a steering boss and reduce the degree of backlash by using a ball and a ball receiving dent to couple the steering wheel to the steering boss and increasing the pressure applied to the ball, and to provide smooth coupling between the steering wheel and the steering boss by holding the ball from inside as a coupling member tending to protrude from a tapered hole and smoothly guiding the ball into a recess for coupling.

Description:
BACKGROUND OF THE INVENTION 
   I. Field of the Invention 
   The present invention relates to a steering wheel tilt device having a function of tilting up a steering wheel to allow a driver to get on or off easily. 
   II. Description of the Related Art 
   Up to now, a steering wheel of a vehicle is fixed, and a lower portion of the steering wheel interferes with a leg of a driver when the driver gets on or off. Thus, the driver finds it difficult to get on or off. In order to solve this problem, therefore, there have been adopted a method of tilting up an entire steering including a steering shaft (see JP 2000-272524 A) and a method of tilting up only the steering wheel. 
   However, according to the method of moving the entire steering including the steering shaft, a corresponding mechanism needs to be provided already in the initial phase of manufacture. Thus, this method is not applicable to vehicles unequipped with such a mechanism, for example, sports utility vehicles and the like. 
   According to the current method of tilting up only the steering wheel, two components, which are provided on a steering wheel side and a steering boss side respectively as a basic structure, are coupled together by a spring-loaded pawl or the like. These components include a hinge shape as a combination of a projecting portion and a depressed portion. A certain difference in dimension is set between the projecting portion, which can be inserted into the depressed portion, and the depressed portion to ensure smoothness in mounting/removing operations. Thus, the occurrence of backlash results from a radial load in steering the steering wheel when the two components are coupled together. 
   In addition, it is also possible to adopt a construction in which a steering wheel is removably mounted (see JP 2002-178933 A). This construction also serves to eliminate interference of the steering wheel when a driver gets on or off. However, after having removed the steering wheel and got off, the driver must bother to carry the steering wheel about or mount it again. 
   In the foregoing construction in which the steering wheel is removably mounted, it is also conceivable to simply provide a socket and a plug with a rotational shaft for making a hinge movement to tilt up the steering wheel. In this construction, however, when a force for holding a ball is increased to suppress backlash, a large force is required to disconnect the steering wheel, which makes opening/closing movements thereof difficult. When the force for holding the ball is reduced to facilitate the opening/closing movements, backlash is caused. 
   SUMMARY OF THE INVENTION 
   The present invention has been made in view of the foregoing circumstances, and it is therefore an object of the invention to strengthen the coupling between a steering wheel and a steering boss and reduce the degree of backlash by using a ball and a ball receiving dent to couple the steering wheel to the steering boss and increasing the pressure applied to the ball, and to provide smooth coupling between the steering wheel and the steering boss by holding the ball from inside as a coupling member tending to protrude from a tapered hole and smoothly guiding the ball into a recess for coupling in coupling the steering wheel to the steering boss. 
   To attain the above-mentioned object, according to the first aspect of the present application is characterized in a steering wheel tilt device including: 
   a socket having a back face to which one of a steering wheel and a steering boss is mounted; 
   a plug having a back face to which the other of the steering wheel and the steering boss is mounted, for being fitted to the socket; 
   a first rotational shaft for pivoting the socket at one end thereof and the plug at one end thereof to realize a fitted state or a released state of the socket and the plug; 
   a second rotational shaft extending parallel to the first rotational shaft in a vicinity of an inside of the first rotational shaft on the socket side; 
   a sleeve arm having one end pivoted on the second rotational shaft and the other end located in a direction perpendicular to the second rotational shaft, for realizing the fitted state or the released state of the socket and the plug through a rotational movement of the other end; 
   a plate-type projection member with a predetermined thickness, which projects in such a direction as to face the plug and is provided on the socket such that one face thereof is in contact with the sleeve arm and parallel thereto; 
   a projection member provided on the plug side in contact with the other face side of the plate-type projection member in the fitted state of the socket and the plug; 
   a tapered hole for movably accommodating a ball from the one face side of the plate-type projection member to the other face side thereof, the tapered hole being composed of a large-diameter hole located on the one face side and having a larger diameter than the ball and a small-diameter hole located on the other face side and having a smaller diameter than the ball; 
   a first spring member provided between the sleeve arm and the socket, for pressing the ball toward the small-diameter hole to prevent the part of the sleeve arm from protruding from the large-diameter hole when the one end of the sleeve arm has been rotationally moved toward the plug to realize the fitted state of the socket and the plug; and 
   a recess provided on the projection member side, for receiving a part of the ball protruding from the small-diameter hole, 
   in which the ball is held fixed at three points, namely, by a part of the recess, a part of the tapered hole, and a part of the sleeve arm. 
   According to a first aspect of the present invention, the socket and the plug can make a hinge movement due to the existence of the first rotational shaft. Thus, the steering wheel can be tilted up, so the driver is allowed to get on or off easily. According to the present invention, a force is applied from the first spring member to the sleeve arm perpendicularly toward the plug in fitting the socket to the plug, so a larger force can be applied to the ball as the coupling member than in the case of conventional products. When the socket and the plug are fitted to each other, a part of the sleeve arm presses the ball due to the force of the first spring member. Owing to this pressure, the ball is pressed by a part of the recess of the plug and a part of the tapered hole. As a result, three-point fixation with a large force can be realized. Thus, secure coupling is achieved, and backlash can be suppressed. 
   According to an other aspect of the present invention, the ball is prevented from protruding from the small-diameter hole due to the recess for accommodating part of the ball. Therefore, when the socket and the plug are fitted to each other through a rotational movement, the ball does not interfere with the projection member of the plug. Consequently, smooth coupling is made possible. 
   According to a still other aspect of the present invention, after the projection member of the plug has come into contact with an inner cam, the inner cam is pushed up to stop the ball from being held by the inner cam. The ball, which can now move toward the inner cam, is thrust out of the tapered hole due to a pressure applied from the sleeve arm. Thus, the sleeve arm rotates toward the plug and the ball is prevented from being thrust out toward the small-diameter hole until the inner cam is pushed up. Therefore, the ball to which a pressing force is applied from the sleeve arm need not be thrust out toward the large-diameter hole during rotation, and rotation for fitting the socket to the plug is made possible with a small force. When the inner cam is pushed up, the ball receiving dent of the projecting portion appears subsequently to the inner cam. Therefore, the protruding ball smoothly enters the ball receiving dent. As a result, secure coupling can be achieved without a large force. 
   According to a still other aspect of the present invention, a dead pin is in a dead pin hole arranged in the projection member in fitting the socket to the plug. Therefore, the sleeve arm cannot be rotated in releasing the socket from the plug, unless the safety trigger is pulled to remove the dead pin from the dead pin hole. Thus, the sleeve arm is prevented from rotating unexpectedly to release the socket from the plug. Consequently, the steering wheel can be operated safely. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the accompanying drawings: 
       FIGS. 1A to 1C  show modes of use of a steering wheel tilt device according to the present invention, consisting of  FIG. 1A  as an exploded perspective view of the steering wheel tilt device,  FIG. 1B  as a perspective view showing a fitted state of the steering wheel tilt device, and  FIG. 1C  as a perspective view showing a tilted state of the steering wheel tilt device; 
       FIG. 2  is an outline perspective view of a tilted state of a steering wheel tilt device according to a first embodiment of the present invention; 
       FIG. 3  is an outline perspective view of a fitted state of the steering wheel tilt device according to the first embodiment of the present invention; 
       FIG. 4  is a lateral view of the steering wheel tilt device according to the first embodiment of the present invention; 
       FIG. 5  is a lateral cross-sectional view of the steering wheel tilt device according to the first embodiment of the present invention; 
       FIG. 6  is a cross-sectional view of the steering wheel tilt device according to the first embodiment of the present invention, taken along a line A-A″ of  FIG. 4 ; 
       FIG. 7  is an enlarged cross-sectional view of a region B of  FIG. 6 ; 
       FIGS. 8A to 8E  are an operating step views of the steering wheel tilt device from the fitted state thereof to the tilted state thereof, consisting of  FIG. 8A  as a lateral view of the steering wheel tilt device with a safe trigger pulled,  FIG. 8B  as a lateral view of the steering wheel tilt device with a lever raised,  FIG. 8C  as a lateral view of the steering wheel tilt device at the time when a tilting movement thereof is started,  FIG. 8D  as a lateral view of the steering wheel tilt device at the time when an inner cam starts rotating, and  FIG. 8E  as a lateral view of the steering wheel tilt device at the time when the inner cam has stopped rotating; 
       FIG. 9  is a cross-sectional view taken along a line D-D″ of  FIG. 8B ; 
       FIGS. 10A to 10C  are an operating step views of the steering wheel tilt device from the tilted state thereof to the fitted state thereof, consisting of  FIG. 10A  as a lateral view of the steering wheel tilt device in the tilted state,  FIG. 10B  as a lateral view of the steering wheel tilt device at the time when the inner cam is in contact with a projection member, and  FIG. 10C  as a lateral view of the steering wheel tilt device at the time when a dead pin is in contact with the projection member; 
       FIG. 11  is a lateral view of sleeve arms as viewed from inside; 
       FIGS. 12A and 12B  are an enlarged views of the projection member, consisting of  FIG. 12A  as a lateral view of the projection member and  FIG. 12B  as a cross-sectional view taken along a line F-F″ of  FIG. 12A ; 
       FIGS. 13A and 13B  show a steering wheel tilt device according to a sixth embodiment of the present invention respectively, consisting of  FIG. 13A  as a lateral cross-sectional view of the steering wheel tilt device and  FIG. 13B  as a cross-sectional view taken along a line E-E″ of  FIG. 13A ; 
       FIG. 14  is an outline perspective view of a tilted state of the steering wheel tilt device according to the sixth embodiment of the present invention; 
       FIG. 15  is an outline perspective view of a fitted state of the steering wheel tilt device according to the sixth embodiment of the present invention; and 
       FIG. 16  is an enlarged cross-sectional view of tapered holes of the plate-type projection member according to the first embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of a steering wheel tilt device according to the present invention will be described in detail with reference to the drawings. 
   First Embodiment 
     FIGS. 1A to 1C  are explanatory views each showing a mode of use of the steering wheel tilt device according to the present invention.  FIG. 2  is an outline view of a tilted state of the steering wheel tilt device.  FIG. 3  is an outline view of a fitted state of the steering wheel tilt device.  FIG. 4  is a lateral view of the steering wheel tilt device.  FIG. 5  is a lateral cross-sectional view of the steering wheel tilt device.  FIG. 6  is a cross-sectional view taken along a line A-A″ of  FIG. 4 .  FIG. 7  is an enlarged view of a region B of  FIG. 6 .  FIGS. 8A to 8E  are transitional views of tilt-up operations from a fitted state of the steering wheel tilt device.  FIG. 9  is a cross-sectional view taken along a line D-D″ of  FIG. 8A .  FIGS. 10A to 10C  are step views of coupling operations from a tilted state of the steering wheel tilt device.  FIG. 11  is a lateral view of left and right sleeve arms as viewed from inside.  FIG. 12A  is a lateral view of a projecting portion.  FIG. 12B  is a cross-sectional view taken along a line F-F″ of  FIG. 12A . 
   First, a basic construction of the steering wheel tilt device according to this embodiment of the present invention is illustrated.  FIG. 1A  is an exploded perspective view of the steering wheel tilt device.  FIG. 1B  is a perspective view showing a fitted state of the steering wheel tilt device.  FIG. 1C  is a perspective view showing a tilted state of the steering wheel tilt device. 
   The steering wheel tilt device according to this embodiment of the present invention is equipped with a socket  3  and a plug  4  each fitted to a steering wheel  1  and a steering boss  2 . The socket  3  and the plug  4  are opened and closed through a hinge movement. In this example, the socket  3  is fitted to the steering wheel  1 , and the plug  4  is fitted to the steering/boss  2 . For convenience of explanation, it will be assumed hereinafter that a front side represents a side opening through the hinge movement and that a rear side represents a side having a first rotational shaft  30  (see  FIGS. 4 and 5 ) for the hinge movement. 
   Next, the construction of the steering wheel tilt device according to the present invention will be described with reference to  FIGS. 2 and 3  as well. 
   The socket  3  is provided with two L-shaped plate-type projection members  5  that are laterally symmetrical to each other. Tapered holes  6  are formed through front portions of the plate-type projection members  5  respectively, and balls  7  are installed in the tapered holes  6  respectively. Small-diameter holes  33  (see  FIG. 16 ) of the tapered holes  6  are smaller in diameter than the balls  7 . Thus, the balls  7  are prevented from falling inside. In addition, large-diameter holes  34  (see  FIG. 16 ) of the tapered holes  6  are larger in diameter than the balls  7 . A hole through which the first rotational shaft  30  (see  FIG. 4 ) for making a hinge movement passes is formed through a rear portion of each of the plate-type projection members  5 . Moreover, sleeve arms  8  are disposed in contact with the plate-type projection members  5  respectively. The sleeve arms  8  rotate around a second rotational shaft  10  with which the plate-type projection members  5  are provided. Furthermore, a lever  16  is connected to ends of the sleeve arms  8 . The lever  16  is accompanied with a safety trigger  17 , which is provided on the plug  4  side with a dead pin  18  being a safety device. An inner cam  9  is disposed inside the plate-type projection members  5 , and inner cam stoppers  12  are provided at ends of the inner cam  9  respectively. In addition, inner cam grooves  13 , through which the inner cam stoppers  12  pass respectively, are provided inside the ends of the plate-type projection members  5  respectively. A projection member  19  for engaging the plate-type projection members  5  is disposed on the plug  4 . Recess  20  for receiving the balls  7  respectively are formed in the projection member  19  on the left and right thereof respectively. Permanent magnets  23  are provided on a face of the projection member  19  on the socket  3  side. A dead pin canceller dent  22  is provided at a corner between the face of the projection member  19  on the socket  3  side and a front face of the projection member  19 . A dead pin hole  21  is formed in the front face of the projection member  19 . 
   Next, the outline of operations of the respective portions will be described. 
   First, the sleeve arms  8  will be described. The sleeve arms  8 , which are laterally disposed in contact with outsides of the plate-type projection members  5  respectively, can make a rotational movement around the second rotational shaft  10 . As shown in  FIG. 5 , the second rotational shaft  10  is located at a position of each of the plate-type projection members  5  which is in front of the first rotational shaft  30  and closer to the plug  4  than the first rotational shaft  30 . When the sleeve arms  8  are rotated toward the socket  3  in releasing the socket  3  from the plug  4 , the sleeve arms  8  rotate around the second rotational shaft  10 . As a result, the socket  3 , to which a force is applied, makes a hinge movement around the first rotational shaft  30 . When the sleeve arms  8  are rotated toward the plug  4  in fitting the socket  3  to the plug  4 , the second rotational shaft  10  is fixed because the sleeve arms  8  are in contact with the balls  7  respectively, and the socket  3  makes a hinge movement around the first rotational shaft  30  together with the sleeve arms  8 . The sleeve arms  8  are provided with step portions having recesses such that the balls  7  are partially accommodated therein respectively when the sleeve arms  8  are rotated. The step portions assume a shape shown in  FIG. 11 . Thus, the balls  7  are accommodated in the recesses in releasing the socket  3  from the plug  4 , and move through the step portions to stop at suitable positions in fitting the socket  3  to the plug  4  through rotation. 
   When the sleeve arms  8  are rotated toward the socket  3 , the sleeve arms  8  come into contact with the socket  3  at such positions that even the maximum distance from the circumference of each of the recesses of the sleeve arms  8  to the circumference of each of the large-diameter holes  34  (see  FIG. 16 ) of the tapered holes  6  does not exceed the diameter of the balls  7 , and are prevented from rotating any further. Thus, the balls  7  can be prevented from falling respectively from holes that are formed of the large-diameter holes  34  (see  FIG. 16 ) of the tapered holes  6  and the recesses of the sleeve arms  8 . When the sleeve arms  8  are rotated toward the plug  4 , terminal ends of the sleeve arms  8  on the second rotational shaft  10  side come into contact with the plate-type projection members  5  respectively at such positions that even the maximum distance from an upper portion of each of the sleeve arms  8  to the circumference of each of the large-diameter holes  34  (see  FIG. 16 ) of the tapered holes  6  does not exceed the diameter of the balls  7 . Thus, the balls  7  are prevented from falling respectively from the large-diameter holes  34  (see  FIG. 16 ) of the tapered holes  6 . In addition, first spring members  11  are disposed between the socket  3  and the sleeve arms  8  respectively as shown in  FIG. 5 . Each of the first spring members  11  vertically applies to a corresponding one of the sleeves  8  a force urging it to move away from the socket  3 . 
   Next, the inner cam  9 , the inner cam stoppers  12 , and the inner cam grooves  13  will be described with reference to  FIG. 8 . The inner cam  9 , which assumes the shape of a plate and has the inner cam stoppers  12  at a left end and a right end thereof respectively, is disposed in contact with the insides of the plate-type projection members  5  (see  FIG. 2 ). The plate-type projection members  5  have the inner cam grooves  13  respectively, and the inner cam stoppers  12  move within the inner cam grooves  13  respectively. The inner cam grooves  13  do not extend to ends of the plate-type projection members  5  on the plug  4  side respectively (see  FIG. 2 ). In addition, as shown in  FIG. 8C , the inner cam  9  can make a rotational movement around a third rotational shaft  14 . The inner cam  9  has second spring members  15  on the third rotational shaft  14 , and a force pressing the inner cam  9  toward the plug  4  is applied to the inner cam  9 . Furthermore, when the inner cam  9  rotates toward the plug  4 , the inner cam stoppers  12  come into contact with terminal ends of the inner cam grooves  13  respectively at such positions that a bottom face of the inner cam  9  exceeds the diameter of the small-diameter holes  33  (see  FIG. 16 ) of the tapered holes  6  and that even the maximum distance from an upper face of the inner cam  9  to the circumference of each of the small-diameter holes  33  (see  FIG. 16 ) of the tapered holes  6  does not exceed the diameter of the balls  7 , and are prevented from rotating any further. Thus, even when the inner cam  9  has been lowered to its lowermost position, the balls  7  can be supported from inside. A rear portion of the projection member  19  is elevated than a front portion thereof by one step. When the socket  3  is fitted to the plug  4 , the inner cam  9  is stopped in contact with the rear portion of the projection member  19 . 
   Next, the lever  16 , the dead pin  18 , and the safety trigger  17  will be described. Front ends of the left sleeve arm  8  and the right sleeve arm  8  are connected to the lever  16  (see  FIG. 2 ). As shown in  FIG. 8A , the lever  16  is accompanied with the safety trigger  17 , which moves backward and forward in a direction perpendicular to the plug  4 . The dead pin  18 , which is long enough to reach the plug  4  in a state of connection, is connected to a rear end of the safety trigger  17 . A third spring member  24  is disposed between the dead pin  18  and the lever  16  to press the safety trigger  17  and the dead pin  18  backward. Thus, when the third spring member  24  is expanded in fitting the socket  3  to the plug  4 , the dead pin  18  reaches the plug  4 . When the third spring member  24  is contracted, the dead pin  18  moves away from the plug  4 . 
   Next, the projection member  19  will be described. The projection member  19  is so provided as to enter a space between the plate-type projection members  5  (see  FIG. 2 ). The projection member  19  has in a front-left portion thereof and a front-right portion thereof the ball receiving recesses  20  into which the balls  7  move respectively (see  FIG. 2 ). Thus, the balls  7  are accommodated in the recesses  20  respectively when the socket  3  is fitted to the plug  4 . The centers of circles of the recesses  20  are respectively located slightly closer to the plug  4  than centers of the small-diameter holes  33  (see  FIG. 16 ) of the tapered holes  6  at the time when the socket  3  is fitted to the plug  4 . In addition, the recesses  20  have been each chipped off with a gentle slope as shown in  FIG. 12  toward a surface, in the direction of the socket  3 . 
   The dead pin hole  21  is formed in the front face of the projection member  19  (see  FIG. 2 ). Thus, the dead pin  18  is accommodated in the dead pin hole  21  when the socket  3  is fitted to the plug  4 . Furthermore, the projection member  19  has the dead pin canceller dent  22 , which has been smoothly chipped off toward a surface thereof from the center of a side on a front face of the projection member  19  on the socket  3  side in the direction of the dead pin hole  21  (see  FIG. 2 ). Thus, the dead pin  18  is smoothly accommodated in the dead pin canceller dent  22 . In addition, the permanent magnets  23  are installed on the face of the projection member  19  on the socket  3  side at a front portion thereof. 
   Next, the construction of this embodiment of the present invention in fitting the socket  3  to the plug  4  will be described. 
   Referring to  FIG. 5 , each of the first spring members  11  applies a force acting toward the plug  4  to a corresponding one of the sleeve arms  8  at a position shifted to the left of the second rotational shaft  10  in  FIG. 5 , so the sleeve arms  8  are urged to rotate around the second rotational shaft  10  toward the plug  4 : Thus, inclines shown in  FIG. 11 , which are provided on the insides of the sleeve arms  8  respectively, thrust the balls  7  into the tapered holes  6  respectively as shown in  FIG. 6 . The recesses  20  have centers of circular dents which are offset from the centers of the tapered holes  6  respectively toward the plug  4 . Therefore, the balls  7 , which are pressed by the inclines on the insides of the sleeve arms  8  respectively, come into contact with the recesses  20  at a point a, with the sleeve arms  8  at a point b, and with the tapered holes  6  at a point c as shown in  FIG. 7 . 
   Thus, there is generated a large force for bringing the socket  3  and the plug  4  into tight contact with each other, so the socket  3  and the plug  4  are securely fitted to each other. Accordingly, the degree of backlash can be reduced when the socket  3  and the plug  4  are fitted to each other. 
   Next, the operation of the safety device according to this embodiment of the present invention will be described. 
   In this embodiment of the present invention, first, each of the first spring members  11  constantly applies a force to the dead pin  18 , which is connected to the safety trigger  17 , toward the plug  4 . Thus, the end of the dead pin  18  is in the dead pin hole  21  formed in the projection member  19 . As shown in  FIG. 8A , the end of the dead pin  18  comes out of the dead pin hole  21  when the safety trigger  17  is pulled forward. Thus, the lever  16  can be rotated toward the socket  3  as shown in  FIG. 8B . 
   Thus, even when an attempt is made to rotate the lever  16  toward the socket  3 , the dead pin  18  serves as a latch and thus prevents the lever  16  from being moved unexpectedly unless the safety trigger  17  is pulled. Accordingly, the steering wheel is prevented from being tilted up unexpectedly while driving or the like, so driving safety is guaranteed. 
   Next, the tilt-up operation according to this embodiment of the present invention will be described with reference to  FIGS. 8A to 8E . 
   When the lever  16  is pulled up after the safety device has been removed as described above, the sleeve arms  8  connected to the lever  16  also rise as shown in  FIG. 9 , so there is no pressing force acting from the sleeve arms  8  toward the large-diameter holes  34  of the tapered holes  6 . Then, since the tapered holes  6  have a large diameter as to the outer circumferences thereof, the balls  7  move outward. When the balls  7  move outward to reach the height of a top plane of the projection member  19  while moving, the socket  3  and the plug  4  are released from each other. Then, the socket  4  starts making a hinge movement as shown in  FIG. 8C . At this moment, the second spring members  15  and the permanent magnets  23  apply a pressing force to the inner cam  9  toward the plug  4 , so the inner cam  9  starts rotating around the third rotational shaft  14  toward the plug  4 . As shown in  FIG. 8D , while the socket  3  increases in gradient, the inner cam  9  also rotates toward the plug  4  and increases in gradient. When the inner cam  9  continues to rotate, the inner cam stoppers  12  come into contact with the terminal ends of the inner cam grooves  13  respectively and stop. At this moment, the balls  7  are held from inside by lateral faces of the inner cam  9 . Thus, the balls  7  cannot move inward, so the sleeve arms  8  are in contact with the balls  7  respectively while being held thereby respectively. Accordingly, although the first spring members  11  apply forces to the sleeve arms  8  respectively toward the plug  4 , the sleeve arms  8  do not rotate any further toward the plug  4  from a state of contact with the balls  7 . When the hinge movement is further continued, the steering wheel  1  can be tilted up to 90° (see  FIG. 10A ). 
   Next, the fitting operation according to this embodiment of the present invention will be described with reference to  FIGS. 10A to 10C . 
   First, as shown in  FIG. 10B , when the steering wheel  1  to which the socket  3  is fitted is pressed toward the steering boss  2 , the socket  3  starts making a hinge movement toward the plug  4 , and the inner cam  9  then comes into contact with the face of the projection member  19  on the socket  3  side to be pressed thereby. Therefore, the inner cam  9  rotates around the third rotational shaft  14  toward the socket  3 . At this moment, the balls  7  are held from inside by the lateral faces of the inner cam  9  respectively when the steering wheel  1  is tilted. Therefore, the balls  7  are located inside the plate-type projection members  5  respectively without protruding from the small-diameter holes  33  (see  FIG. 16 ) of the tapered holes  6 . After the inner cam  9  has started rotating and been released, the balls  7  are held by the lateral faces of the protruding members  19  respectively and thus still do not protrude inward. Accordingly, the hinge movement is not stopped through contact between the balls  7  and the face of the projection member  19  on the socket  3  side. After that, the balls  7 , which have been held by the lateral faces of the projection member  19 , are guided by gentle inclines of the recesses  20  shown in  FIG. 12  on the socket  3  side to enter the recesses  20  respectively (see  FIG. 10C ). At this moment, the dead pin  18  is pressed by the third spring members  24  to protrude and thus come into contact with the projection member  19 . When the end of the dead pin  18  comes into contact with the dead pin canceller dent  22  at the center of the front of the projection member  19 , the dead pin  18  is thrust forward along the slope of the dead pin canceller dent  22  due to inclination thereof. Upon reaching the dead pin hole  21 , the dead pin  18  enters the dead pin hole  21 . 
   Second Embodiment 
   A steering wheel tilt device according to the second embodiment of the present invention will be described with reference to  FIGS. 13A and 13B .  FIG. 13A  is a lateral cross-sectional view in this embodiment of the present invention. Referring to  FIG. 13A , in the vicinity of the first rotational shaft  30 , a hole  29  and two through-holes  25  are arranged on the socket  3  side and the plug  4  side respectively.  FIG. 13B  is a cross-sectional view taken along a line E-E″. Referring to  FIG. 13B , grub screws  28  are in the hole  29 . Balls  27  for giving resistance to rotation and a coil  26  are disposed in the through-hole  25 . The steering wheel tilt device according to the second embodiment of the present invention is obtained by providing the steering wheel tilt device according to the first embodiment of the present invention with a construction for stopping the socket  3  in its open state at an arbitrary position desired by an operator. 
   First, the through-holes  25  are opened in the projection member  19  in the vicinity of the first rotational shaft  30  in making a hinge movement, and the balls  27 , which are slightly smaller in diameter than the through-holes  25 , are so placed in the through-holes  25  as to sandwich the coil spring  26 . Subsequently, the hole  29  is opened in each of the plate-type projection members  5  at such a portion as is located on the same circumference as a locus passed by the through-holes  25  in making the hinge movement. The grub screws  28 , whose ends are designed as dent ends, are disposed in the hole  29  in contact with the inside of the projection member  19 . The dent of each grub screw  28  has a diameter smaller than that of each ball  27  or a depth smaller than the radius thereof. 
   Thus, when an angle which the socket  3  forms with the plug  4  corresponds to an angle that the hole  29  coincides in position with each of the through-holes  25 , the balls  27  are accommodated in the dents of the grub screws  28  respectively and thereby offer increased resistance. Accordingly, the socket  3  can be stopped at that angle. In this embodiment of the present invention, the two through-holes  25  are formed through the projection member  19 , and the balls  27  are accommodated in the two dents of the grub screws  28  respectively, so a two-stage movement is realized. However, if the grub screws  28  are adjusted, the balls  27  are also accommodated in steps created between tapered portions of the tips of the grub screws  28  and inner diameter portions of female screws respectively. Therefore, an increase in resistance is achieved at that angle as well, and the socket  3  can be stopped at that angle as well. Alternatively, it is also appropriate to provide the single through-hole  25 . In addition, the number of the through-holes  25  can be increased to a suitable number as long as they are confined within an angular range of 90° or less. 
   In this embodiment of the present invention, the number of stop positions of the socket  3  is adjusted by changing the number of the through-holes  25 . However, the number of the stop positions of the socket  3  can also be adjusted by changing the number of holes  29 . 
   Third Embodiment 
   A steering wheel tilt device according to the third embodiment of the present invention is obtained by providing the steering wheel tilt device according to the first embodiment of the present invention with a construction for removing the socket  3  from the plug  4 . 
   A bolt is used as the center of the first rotational shaft  30  when the socket  3  and the plug  4  make a hinge movement. In this embodiment of the present invention, a projecting portion is cut open outward in a hole for supporting the bolt. Thus, the socket  3  can be removed from the plug  4  after the steering wheel  1  has been tilted up. 
   Fourth Embodiment 
   A steering wheel tilt device according to the fourth embodiment of the present invention is obtained by modifying the steering wheel tilt device according to the first embodiment of the present invention such that the lateral faces of the projection member  19  are tapered instead of being made perpendicular to a bottom face thereof. 
   In this embodiment of the present invention, the projection member  19  is thinner on the socket  3  side than on the plug  4  side, and thus likely to pass between the plate-type projection members  5 . Thus, even if the projection member  19  is made on the plug  4  side just as wide as the plate-type projection members  5 , the plate-type projection members  5  do not hit the face of the projection member  19  on the socket  3  side. As a result, the projection member  19  and the plate-type projection members  5  can be coupled together tightly. Accordingly, the degree of tightness between the plate-type projection members  5  and the projection member  19  on the plug  4  side is increased, so they can be firmly coupled together. 
   Fifth Embodiment 
   A steering wheel tilt device according to the fifth embodiment of the present invention is obtained by modifying the steering wheel tilt device according to the first embodiment of the present invention such that the plate-type projection members  5 , the tapered holes  6  and the recesses  20  that are located on the left and right of the projection member  19 , and the balls  7  on the left and right are arranged laterally asymmetrically. 
   In this embodiment of the present invention, interference points of the respective members for preventing the creation of backlash at the time of coupling are laterally asymmetrical to each other. Given this assumption, any four points do not exist on a same plane, so there is no inclination toward movement for a force applied in any specific direction. In consequence, the degree of backlash can further be reduced. 
   Sixth Embodiment 
   A steering wheel tilt device according to the sixth embodiment of the present invention will be described with reference to  FIGS. 14 and 15 . The steering wheel tilt device according to the sixth embodiment of the present invention is obtained by modifying the steering wheel tilt device according to the first embodiment of the present invention such that the inner cam  9  has a recess extending from a front portion thereof to a rear portion thereof, electrodes  31  are so installed as to pass through the recess when the inner cam  9  is coupled to the projection member  19 , and terminals  32  are arranged to come into contact with the electrodes  31  respectively when the plug  4  is coupled to the socket  3 . 
   Thus, even when components of an electric system are installed on the steering wheel  1  and the steering boss  2 , cables of the electric system do not cause any hindrance during a hinge movement. There is no risk of the cables being cut off either.