Abstract:
A steering apparatus includes a steering column rotating integrally with a steering wheel, a bracket supporting the steering column via a bearing in such a manner that the steering column is rotatable, and a fixation piece fixed to a vehicle body, where the bracket includes a locking hole, and during a normal state, the fixation piece is locked on a lower surface of an edge portion enclosing the locking hole thereby locking the bracket to the fixation piece, the bracket includes a pair of guided portions extending from opposing side portions of the locking hole toward the steering wheel, and during a secondary collision, the bracket moves forward to detach the fixation piece from the locking hole, and then, the fixation piece is locked on lower surfaces of the pair of guided portions, while guiding the pair of guided portions in the axial direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based on and claims priority under 35 U.S.C. 119 from Japanese Patent Application No. 2013-066585 filed on Mar. 27, 2013; the entire content of which is incorporated herein by reference. 
     BACKGROUND 
     1. Technical Field 
     The present invention relates to a steering apparatus. 
     2. Related Art 
     A forward collision (primary collision) of a vehicle is followed by a secondary collision in which a driver collides against a steering wheel. A configuration is known which moves, during such a secondary collision, the steering wheel and a steering column move forward in order to reduce an impact load transmitted from the steering wheel to the driver. 
     In this configuration, when the steering wheel and the steering column move forward, the steering column and the like may fall down onto the driver&#39;s legs due to the weights of the steering column and the like. Thus, a technique has been proposed which involves mounting of a new dedicated component for preventing fall-down of the steering column and the like (see Patent Literature 1 (JP-A-2011-195031) and Patent Literature 2 (JP-A-2011-207450)). 
     SUMMARY OF INVENTION 
     However, Patent Literatures 1 and 2 include the dedicated component for preventing fall-down, increasing the number of components of the apparatus. 
     Thus, an object of the present invention is to provide a steering apparatus that prevents the steering column and the like from falling down during a secondary collision without increasing the number of components of the apparatus. 
     As means for solving the above-described problem, an aspect of the present invention provides a steering apparatus including: a steering column extending forward from a steering wheel operated by a driver, and rotating integrally with the steering wheel; a bracket supporting the steering column via a bearing in such a manner that the steering column is rotatable, the bracket being in a relative positional relation with the steering column in an axial direction; and a fixation portion fixed to a vehicle body, in which the bracket has a locking hole which penetrates the bracket in an up-down direction and which is open on a steering wheel side, the fixation portion inserted through the locking hole, during a normal state, is locked on a lower surface of an edge portion of the bracket, enclosing the locking hole thereby locking the bracket to the fixation portion, the bracket includes a pair of guided portions extending toward the steering wheel from the portions of the bracket provided at a steering wheel side of the locking hole, and during a secondary collision, the bracket moves forward to detach the fixation portion from the locking hole, and then, the fixation portion is locked on lower surfaces of the pair of guided portions, while the fixation portion guides the pair of guided portions in the axial direction. 
     According to such a configuration, during a secondary collision, the bracket moves forward to detach the fixation portion from the locking hole, and then, the fixation portion is locked on the lower surfaces of the pair of guided portions. This prevents the steering column and the like from falling down. 
     Furthermore, the fixation portion guides the pair of guided portions in the axial direction (front-rear direction), allowing the steering column and the like to move forward easily without being tilted. Thus, an axial impact load input to the steering column and the like by a secondary collision can be appropriately absorbed by an appropriate impact absorption structure. In contrast, when the steering column and the like move forward while being tilted, the impact load is difficult to absorb. 
     Moreover, the pair of guided portions is a part of the bracket extending from the opposite sides of the steering wheel side opening of the locking hole toward the steering wheel. This prevents an increase in the number of components of the apparatus. 
     Furthermore, the steering apparatus may have a configuration in which an axial length of the pair of guided portions is larger than a length in which the steering column is moved during a secondary collision. 
     In such a configuration, the axial length of the pair of guided portions is larger than the length by which the steering column is movable during a secondary collision. This prevents the bracket from slipping off from the fixation portion. 
     Furthermore, the steering apparatus may have a configuration in which the bracket includes a coupling portion that couples steering wheel sides of the pair of guided portions together. 
     In such a configuration, the coupling portion coupling the steering wheel sides of the pair of guided portions together functions as a stopper for the fixation portion. This prevents the bracket from slipping off from the fixation portion. 
     Furthermore, the steering apparatus may have a configuration in which a distance between the pair of guided portions decreases gradually toward the steering wheel. 
     In such a configuration, an increased frictional force is exerted between the fixation portion and the pair of guided portions, allowing the impact load that is input in the axial direction to the steering column and the like to be appropriately attenuated. 
     The aspect of the present invention provides a steering apparatus that prevents the steering column and the like from falling down during a secondary collision without increasing the number of components of the apparatus. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view of a steering apparatus according to the present embodiment, showing a normal state; 
         FIG. 2  is a plan view of the steering apparatus according to the present embodiment, showing a secondary collision state; 
         FIG. 3  is a plan cross-sectional view of the steering apparatus according to the present embodiment, showing the normal state; 
         FIG. 4  is a plan cross-sectional view of the steering apparatus according to the present embodiment, showing the secondary collision state; 
         FIG. 5  is a perspective view of the steering apparatus according to the present embodiment as seen from right forward, the view showing the normal state; 
         FIG. 6  is a perspective view of the steering apparatus according to the present embodiment as seen from right forward, the view showing the secondary collision state; 
         FIG. 7A  and  FIG. 7B  are diagrams of a bracket and a fixation piece according to the present embodiment during the normal state, wherein  FIG. 7A  is a plan view and  FIG. 7B  is a cross-sectional view (vertical cross-sectional view) taken along line X 1 -X 1  in  FIG. 7A ; 
         FIG. 8A  to  FIG. 8C  are cross-sectional views taken along line X 2 -X 2  in  FIG. 7A , wherein  FIG. 8A  shows the extracted bracket,  FIG. 8B  shows the extracted fixation piece, and  FIG. 8C  shows an extracted fixation piece according to a variation; 
         FIG. 9A  and  FIG. 9B  are diagrams of the bracket and the fixation piece according to the present embodiment during a secondary collision, wherein  FIG. 9A  is a plan view and  FIG. 9B  is a cross-sectional view taken along line X 3 -X 3  in  FIG. 9A ; 
         FIG. 10  is graph showing an effect of the steering apparatus according to the present embodiment; 
         FIG. 11  is an enlarged plan view of a steering apparatus according to a variation during the normal state; and 
         FIG. 12  is an enlarged plan view of a steering apparatus according to a variation during the normal state. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     An embodiment of the present invention will be described with reference to  FIG. 1  to  FIG. 10 . 
     &lt;&lt;Configuration of the Steering Apparatus&gt;&gt; 
     A steering apparatus  1  is an electric power steering apparatus of a column assist type. 
     The steering apparatus  1  includes a steering column  11  (upper shaft), an input shaft  12 , a torsion bar  13 , and an output shaft  14 . The steering column  11  extends forward from a steering wheel (not shown in the drawings) operated by a driver and is adapted to rotate integrally with the steering wheel. That is, the steering wheel is fixed to a rear end of the steering column  11 . A front end of the steering column  11  and a rear end of the input shaft  12  are coupled together by serrations or the like (see  FIG. 3 ). The torsion bar  13  is fixed to each of the input shaft  12  and the output shaft  14  via a pin extending in a radial direction of the apparatus. The torsion bar  13  is twisted between the input shaft  12  and the output shaft  14 . However, the embodiment is not limited to the fixation method using the pin, and any other fixation method may be used which is based on, for example, knurling press fit. 
     The steering column  11  is rotatably supported by an outer pipe  22  via a bearing  21 . The bearing  21  is externally press-fitted on and fixed to the steering column  11  and is internally press-fitted on and fixed to an outer pipe  22 . The steering column  11  and the outer pipe  22  have a predetermined relative positional relation in an axial direction (front-rear direction) of the apparatus. However, the fixation method is not limited to this. For example, the bearing  21  may be fitted on the steering column  11  with a gap formed between the bearing  21  and the steering column  11  and is fixed to the steering column  11  via a clip or the like. 
     A front end of the input shaft  12  is rotatably supported by a rear housing  42  via a bearing  31 . The output shaft  14  is rotatably supported by a front housing  41  via a bearing  32 . A worm wheel  50  is fixed to the output shaft  14 . The worm wheel  50  includes core metal  51  fixed to the output shaft  14  and a gear tooth  52  fixed to the core metal  51 . The gear tooth  52  is meshed with a worm (not shown in the drawings) rotated by an electric motor  53  that generates an auxiliary force. 
     A cylindrical cover  43  that protects the input shaft  12  is fixed to a rear side of the rear housing  42 . A front end of the output shaft  14  is connected to a pinion shaft via a universal joint, and the pinion shaft is connected to a rack shaft via a rack and pinion mechanism. 
     The steering apparatus  1  includes a bracket  60  (upper bracket) and a fixation piece  70  (fixation portion) allowing the bracket  60  to be fixed to the vehicle body. 
     &lt;Bracket&gt; 
     The bracket  60  allows an outer pipe  22  (a rear upper side portion of the steering apparatus  1 , an upper portion) to be fixed to the vehicle body and is fixed to the outer pipe  22  via an adapter  23 . Thus, the bracket  60  has a predetermined relative positional relation with the steering column  11  in the axial direction. During a secondary collision, the steering column  11 , the outer pipe  22 , and the bracket  60  move integrally forward (see  FIG. 4 ). 
     However, the bracket  60  may avoid including the adapter  23  and may be fixed directly to the outer pipe  22 . 
     The bracket  60  includes a base portion  61  which is inversely U shaped in an axial view (as viewed in the front-rear direction) and which is fixed to the adapter  23 , a pair of flange portions  62  extending outward in a vehicle width direction from a lower left end and a lower right end, respectively, of the base portion  61 , and a pair of guided portions  63  extending from each flange portion  62  toward the steering wheel, located at the rear of the flange portion  62 . That is, the bracket  60  is an integrally molded plate-like component and includes the base portion  61 , the pair of flange portions  62 , and the four guided portions  63 . 
     &lt;Bracket—Flange Portion&gt; 
     Each flange portion  62  includes a locking hole  62   a  which penetrates the flange portion  62  in an up-down direction and which is open on a rear side (steering wheel side) (see  FIG. 7A  and  FIG. 7B  and  FIG. 9A  and  FIG. 9B ). The locking hole  62   a  is a hole through which the fixation piece  70  is inserted from the rear of the locking hole  62   a . In a normal state, the inserted fixation piece  70  is locked on lower surfaces  62   c  of edge portions  62   b  of the flange portion  62 , that enclose the locking hole  62   a  in the direction of a vehicle width. Thus, the fixation piece  70  locks the flange portion  62  in the up-down direction. 
     Furthermore, the locking hole  62   a  is shaped, in a planar view, substantially like a triangle with a vertex on a front side thereof, with the width of the locking hole  62   a  gradually increasing rearward. 
     &lt;Bracket—Guided Portions&gt; 
     The pair of guided portions  63  are elongate plate-like portions extending rearward from the opposite side portions  62   d  of the rear side opening of the locking hole  62   a . During a secondary collision, the guided portions  63  are locked by the fixation piece  70  detached from the locking hole  62   a , while the guide portions  63  are guided by the fixation piece  70  in the axial direction. 
     The axial length L1 of the guided portion  63  is set larger than a length by which the steering column  11  is moved during a secondary collision. More specifically, the axial length L1 of the guided portion  63  is set larger than a maximum length L2 by which the steering column  11  is moved during the secondary collision (see  FIG. 1  and  FIG. 3 ). This prevents the guided portion  63  from slipping off from the fixation piece  70 . The maximum length L2 by which the steering column  11  is moved according to the present embodiment is the distance from a front end of the outer pipe  22  during the normal state and a step portion of the rear housing  42  against which the outer pipe  22  collides during a secondary collision (see  FIG. 1  to  FIG. 4 ). 
     &lt;Fixation Piece&gt; 
     The fixation piece  70  is a thin plate-like component which is shaped like a rectangle in a planar view and which includes an attachment hole  70   a  formed in the center of the fixation piece  70 . The attachment hole  70   a  is a hole through which a bolt (not shown in the drawings) for attaching the fixation piece  70  to the vehicle body (a steering hanger and the like) is inserted. That is, the fixation piece  70  thus fixed to the vehicle body by the bolt is prevented from moving during the normal state and during a secondary collision. 
     The fixation piece  70  is substantially laterally-facing H shaped in a front-rear cross-sectional view (in an axial cross-sectional view) (see  FIG. 8B ). The fixation piece  70  includes a inserted portion  71  that is located in the center thereof in the up-down direction, a first locking portion  72  formed under the inserted portion  71  so as to be elongate in a lateral direction, and a second locking portion  73  formed over the inserted portion  71  so as to be elongate in the lateral direction. 
     &lt;Fixation Piece—Inserted Portion&gt; 
     The inserted portion  71  is inserted through the locking hole  62   a  from the rear of the locking hole  62   a . The inserted portion  71  is shaped, in a planar view, substantially like a triangle with a vertex on a front side thereof, with the width of the inserted portion  71  gradually increasing rearward, like the locking hole  62   a.    
     &lt;Fixation Piece—First Fixation Portion&gt; 
     The first locking portion  72  is locked on a lower surface  62   c  of the flange portion  62  during the normal state (see  FIG. 7B ) and is locked on and in sliding contact with a lower surface  63   a  of the guided portion  63  to guide the guided portion  63  in the front-rear direction in a case of a secondary collision (see  FIG. 9B ). Thus, the first locking portion  72  is locked on the lower surface  62   c  and the lower surface  63   a  to support the bracket  60  (the steering column  11  and the like) from below to prevent the bracket  60  from falling down. 
     &lt;Fixation Piece—Second Fixation Portion&gt; 
     The second locking portion  73  is locked on an upper surface  62   e  of the flange portion  62  during the normal state (see  FIG. 7B ) and is locked on and in sliding contact with an upper surface  63   b  of the guided portion  63  during a secondary collision (see  FIG. 9B ). Thus, the second locking portion  73  is locked on the upper surface  62   e  and the upper surface  63   b  to prevent the bracket  60  from moving upward. 
     That is, the first locking portion  72  and the second locking portion  73  sandwich the flange portion  62  and the guided portions  63  in the up-down direction. Thus, the bracket  60  is regulated in the up-down direction both during the normal state (see  FIG. 7B ) and during a secondary collision (see  FIG. 9B ). 
     Furthermore, four through-holes  73   a  are formed in the second locking portion  73  (see  FIG. 8B ). Four resin pins  81  (resin injections) are provided so as to penetrate the second locking portion  73  of the fixation piece  70  and the flange portion  62  during the normal state as shown in  FIG. 7A  and  FIG. 7B . The four pins  81  position the fixation piece  70  and the bracket  60  in the axial direction. 
     Alternatively, as shown in  FIG. 8C , four through-holes  72   a  may also be formed in the first locking portion  72  so that the pins  81  penetrate the second locking portion  73 , the flange portion  62 , and the first locking portion  72 . The number, diameter, and material of pins  81 , and a method for fixing the pins  81  may be varied as appropriate. 
     &lt;Effects of the Steering Apparatus&gt; 
     The above-described steering apparatus  1  exerts the following effects. 
     &lt;During the Normal State&gt; 
     The first locking portion  72  and the second, locking portion  73  sandwich the flange portion  62 , thus restraining the flange portion  62  (bracket  60 ) in the up-down direction even if the steering apparatus  1  vibrates up and down as a result of travel of the vehicle. 
     &lt;During a Secondary Collision&gt; 
     During a secondary collision, that is, after a front collision of the vehicle (primary collision), when the driver collides against the steering wheel (secondary collision), a forward load input to the steering wheel, the steering column  11 , the outer pipe  22 , and the bracket  60  increases to deform the resin pins  81  (see a section S1 in  FIG. 10 ). 
     Subsequently, when the forward load reaches a predetermined value, the pins  81  are broken (see a breaking point S2 in  FIG. 10 ) and the fixation piece  70  is detached from the locking hole  62   a . The steering wheel, the steering column  11 , the outer pipe  22 , and the bracket  60  slide integrally forward, that is, run idly (see a section S3 in  FIG. 10 ). 
     In this case, after the fixation piece  70  is detached from the locking hole  62   a , the first locking portion  72  of the fixation piece  70  supports the lower surfaces  63   a  of the guided portions  63  while in sliding contact with the lower surfaces  63   a  (see  FIG. 9B ), thus preventing the steering wheel, the steering column  11 , the outer pipe  22 , and the bracket  60  from falling down. This in turn prevents the driver&#39;s legs from being injured by the steering wheel or the like. 
     Furthermore, the steering column  11  and the like slide forward without being tilted, thus preventing a forward secondary collision load input to the steering column  11  and the like from varying during the slide (see a section S4 in  FIG. 10 ). Thus, the secondary collision load can be appropriately absorbed by an appropriate impact absorption structure. 
     &lt;Other Effects&gt; 
     The pair of guided portions  63  is a part of the bracket  60  and is not a component separate from the bracket  60  or an independent dedicated component. This prevents a possible increase in the number of components of the steering apparatus  1  and in the number of assembly steps for the steering apparatus  1 . 
     &lt;&lt;Variation&gt;&gt; 
     The embodiment of the present invention has been described. However, the present invention is not limited to the embodiment. For example, the embodiment may be varied as follows. 
     As shown in  FIG. 11 , the bracket  60  may include a coupling portion  64  that couples rear sides (steering wheel sides) of the pair of guided portions  63  together. In such a configuration, the coupling portion  64  abuts against the fixation piece  70  and functions as a stopper. This prevents the bracket  60  from being separated from the fixation piece  70 . 
     As shown in  FIG. 12 , a guided surface  63   c  of each guided portion  63  may be inclined so as to have a guide width gradually decreasing toward the rear side so that the distance between the pair of guided portions  63  may gradually decrease toward the steering wheel. In such a configuration, during a secondary collision, if the bracket  60  moves forward, a frictional force exerted between the fixation piece  70  and the pair of guided portions  63  increases to allow a load input to the bracket  60  as a result of a secondary collision to be appropriately attenuated. 
     In the above-described embodiment, the steering apparatus  1  is of the column assist type by way of example. Alternatively, the steering apparatus  1  may be, for example, a manual steering column without an assist function which is included in a system of a pinion assist type or a rack assist type.