Abstract:
A vehicular steering column of a low tilt type is supported to a body at upper and lower portions thereof to be tilted in whole about a hinge joint located on the lower portion, and more particularly to a shock absorbing steering column is designed to allow a steering column to slide forward when a vehicle driver gets a secondary shock against a steering wheel due to a vehicular collision, thereby absorbing a shock. In particular, the steering column is constructed in such a manner that, in order to absorb a shock in case of the vehicular collision, shock absorbing means is provided to a lower supporting structure of the steering column, and thus an initial shock imposed on the driver can be greatly decreased.

Description:
The present disclosure relates to subject matter contained in priority Korean Application No. 10-2003-0062325, filed on Sep. 6, 2003, which is herein expressly incorporated by reference in its entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a vehicular steering column of a low tilt type, supported to a body at upper and lower portions thereof to be tilted in whole about a hinge joint located on the lower portion, and more particularly to a shock absorbing steering column designed to allow a steering column to slide forward when a vehicle driver gets a secondary shock against a steering wheel due to a vehicular collision, thereby absorbing a shock. In particular, the present invention is characterized in that, in order to absorb a shock in case of the vehicular collision, shock absorbing means is provided to a lower supporting structure of the steering column so that an initial shock imposed on the driver can be greatly decreased. 
   2. Background of the Related Art 
   Such a steering column of the low tilt type is generally supported to a body at upper and lower portions thereof. The upper supporting structure is provided with a tilt unit for providing tilt operation of the steering column, while the lower supporting structure is provided with a hinge joint for allowing the steering column to be tilted in whole. 
   Because a vehicle driver frequently gets a secondary shock against the steering wheel when a vehicular collision occurs, the steering column must be designed to be capable of absorbing such a shock. Further, because of the vehicular collision, when being distorted at the front part, the body is deformed at the rear part where a driver is located. In this case, the steering column must be so designed that it is not pushed toward the driver if possible. To this end, a supporting structure of the steering column, which is fixed to the body, is constructed in a manner that the steering column performs a relative movement to the body when a predetermined shock is given. This construction can be implemented either by allowing the steering column to perform a relative movement to its own supporting structure when a shock is given, or by allowing the steering column and its own supporting structure to integrally perform a relative movement to the body. 
   For the foregoing purpose, a structure designed to allow the upper supporting structure of the steering column to be separated from the body when a vehicular collision occurs is disclosed from U.S. Pat. No. 5,899,116 as an example. Further, a structure designed to allow the steering column to perform a relative movement to its own supporting structure is disclosed from U.S. Pat. No. 6,019,391 as an example. 
   Further, a structure designed to allow a predetermined metallic strap to generate plastic deformation to absorb a shock when the steering column and the body carry out a relative movement to each other due to a collision is disclosed from U.S. Pat. Nos. 5,706,704 and 5,720,496 as examples. 
   Meanwhile, among the steering columns of the low tilt type, there is one comprising a means for absorbing a shock, which is provided to the lower supporting structure of the steering column. This conventional shock absorbing steering column, for example, is disclosed from GB Patent No. 2365826 (see FIGS. 1 and 2). 
   The structure as above is comprised of a bracket B fixedly attached to the body, a tilt steering supporting structure A fixedly attached to a steering column and provided with a slot A 1 , and a pivoting member  10  connecting the bracket B and the tilt steering supporting structure A. The slot A 1  is formed with a predetermined partition member  4 , thus preventing the pivoting member  10  from being deviated in place. In this case, when a shock is applied to the steering column due to a vehicular collision, the pivoting member  10  deforms the partition member  4  to slide along the slot A 1 , so that the shock can be absorbed. 
   However, the structure as above has a problem in that the shock is not appropriately absorbed, because the bracket B is stiffly fixed to the body. To be more specific, a process of giving a shock to a vehicle driver when the vehicle driver strikes the steering wheel is divided into two steps. 
   The first step is one occurring while the pivoting member  10  deforms the partition member  4  formed at the slot A 1 . The second step is one occurring while the pivoting member  10  slides along the slot A 1 . In the second step, the steering column slides in its own way to move forward, so that the shock is well absorbed. As a result, the shock given to the driver becomes still more decreased. 
   However, in the first step, the partition member  4  formed at the slot A 1  functions to strongly support the shock of the driver against the steering wheel until the partition member  4  is deformed by the pivoting member  10 , so that the shock of the driver who strikes the steering wheel can not be properly absorbed. Therefore, the conventional structure as above has a problem in that an initial shock generated when the driver strikes the steering wheel at first is not properly absorbed. 
   In this manner, the problem in that the initial shock is not properly absorbed resides in that the first step of giving the shock to the driver is performed in a very short time. To be more specific, the quantity of shock is determined by product of the magnitude of shock and the time of shock. Here, when the quantities of shocks are identical to each other, the longer the time of shock becomes, the smaller the magnitude of shock becomes in proportion to the lengthened time of shock. 
   Further, the conventional structure as above has another problem in that, when the partition member  4  formed at the slot A 1  is not deformed, the shock is not absorbed at all. This phenomenon may occur when the driver strikes the steering wheel in a relatively weak manner, when the shock is released to a certain extent by an airbag, or so forth. 
   SUMMARY OF THE INVENTION 
   Accordingly, the present invention has been made to solve the above-mentioned problems occurring in the prior art, and an object of the present invention is to provide a steering column of a low tilt type, in which a lower supporting structure is provided with shock absorbing means, thereby allowing a shock to be well absorbed. Particularly, by providing lower supporting structure with shock absorbing means, various effects can be obtained. For instance, it is possible to simplify an upper supporting structure and thus to add other functions as much. Further, the upper supporting structure makes it possible to avoid from interference with a driver when a vehicular collision occurs, because the upper supporting structure is located adjacently to the driver. 
   It is another object of the present invention to provide a steering column, provided with a plurality of shock absorbing means, thereby allowing a shock to be more effectively absorbed. 
   In order to accomplish these objects, according to the present invention, there is provided a shock absorbing steering column of a low tilt type, the shock absorbing steering column having a steering shaft and a steering column tube for rotatably supporting the steering shaft in an inward direction, and supported to a body at upper and lower portions thereof to allow for tilt operation in whole, the shock absorbing steering column comprising: a lower mounting bracket fixed to the body; a rotational bracket rotatably connected to the lower mounting bracket; a slide bracket fixed to the steering column tube and having a long hole formed along a longitudinal direction of the steering column tube; a connecting shaft passing through the long hole of the slide bracket and connected to the rotational bracket to support the slide bracket; and shock absorbing means for allowing the slide bracket and the connecting shaft to perform a relative movement when a vehicular collision occurs and absorbing a shock during a sliding movement. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention in conjunction with the accompanying drawings, in which: 
       FIGS. 1 and 2  illustrate a conventional shock absorbing steering column of a low tilt type; 
       FIG. 3  illustrates a preferred embodiment of the present invention; 
       FIG. 4  illustrates a strap structure according to a preferred embodiment of the present invention; 
       FIG. 5  is a cross-sectional view taken along line A–A′ of  FIG. 4 ; 
       FIG. 6  illustrates an operation of a steering column when a vehicular collision occurs according to one embodiment of the present invention; 
       FIG. 7  illustrates one example of an upper supporting structure of a steering column capable of combining with that of the present invention; and 
       FIG. 8  illustrates a state in which the steering column of the present invention is operated when a collision occurs. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. 
   As to the present invention, among other things, nothing is the matter with an upper supporting structure for supporting an upper portion of a steering column as far as the upper supporting structure is not deviated from the purpose of the present invention. 
   For instance, as shown in  FIG. 7 , this is equally true to an upper supporting structure comprising a main bracket  50  fixedly installed to a body via a capsule  60  and guiding tilt operation relative to a vertical wall on one side, a tilt plate  70  connected to the main bracket  50  and provided with a tilt slot  51 , a distance bracket  90  fixedly attached to the outer circumferential surface of a steering tube  80  supporting a steering shaft in a rotatable manner and having a pair of side walls formed with a through-hole, a tilt locking unit  40  provided to pass through tilt slots  51  and  71  and the through-hole of the distance bracket  90  and locking a tilt of the steering column. Here, the main bracket  50  is designed to provide separation from the capsule  60  when a collision occurs, so that the upper supporting structure and the steering column are generally allowed to move relatively to the body. 
   Returning to the present invention, a lower mounting bracket  103  is fixedly installed to the body as in  FIG. 3 . A rotational bracket  104  is rotatably coupled to the lower mounting bracket  103 . Thus, a hinge joint of the rotational bracket  104  to the lower mounting bracket  103  may function as a hinge point (hereinafter, referred to as a “first hinge point”) for tilt operation of the steering column. A slide bracket  105  is provided with a long hole  151  and fixed to a steering column tube  102 . Here, a reference numeral  101  indicates the steering shaft. 
   A connecting shaft  106  passes through the long hole  151  of the slide bracket  105  to be connected to the rotational bracket  104 , thus supporting the slide bracket  105 . In this case, preferably, the slide bracket  105  is rotatably installed to the connecting shaft  106 . Thereby, this rotatable connection of the slide bracket  105  to the connecting shaft  106  may function as another hinge point (hereinafter, referred to as a “second hinge point”) for tilt operation of the steering column. Further, the first and second hinge points may be organically operated to function as a hinge for tilt operation of the steering column. 
   Here, when the first hinge point functions as a hinge point for tilt operation of the steering column, a tilt slot provided to the upper supporting structure of the steering column must take a circular shape with the first hinge point centered. By comparison, when the second hinge point functions as a hinge point for tilt operation of the steering column, a tilt slot provided to the upper supporting structure of the steering column must take a circular shape with the second hinge point centered. However, when the first and second hinge points together function as a hinge point for tilt operation of the steering column, a tilt slot provided to the upper supporting structure of the steering column is not limited to such a shape. Thus, in the present invention, as long as the slide bracket  105  is rotatably connected to the connecting shaft  106 , there is an effect that no limitation is made to the shape of the tilt slot. 
   Shock absorbing means is used to absorb a shock while the connecting shaft  106  slides along the long hole  151  of the slide bracket  105 . To this end, the long hole  151  may be designed to have a reduced width on the region where the connecting shaft  106  slides, so that, while sliding along the long hole  151 , the connecting shaft  106  is subjected to a plastic deformation, thus absorbing the shock. Further, during such a sliding movement, friction is generated between the long hole  151  and the connecting shaft  106 . This friction may be used to absorb the shock. 
   Preferably, the shock absorbing means, as shown in  FIG. 3 , includes a bush  107  on the side of which a nose  171  is formed and which is inserted into the connecting shaft  106 , and a groove  152  into which a nose  171  can be inserted. 
   More preferably, the bush  107  and the connecting shaft  106  are rotatably connected to each other. Getting a shock, the nose  171  formed on the bush  107  is destroyed. At this time, the bush slides in the long hole  151  to absorb the shock. Preferably, the bush  107  may be made of a plastic material. 
   Alternatively, while the bush  107  slides in the long hole  151 , the long hole  151  may be forced to generate either plastic deformation or friction, and thus the shock is absorbed. 
   Further, preferably, the shock absorbing means, as shown in  FIG. 4 , includes a deformation-inducing part  153  provided to the slide bracket  105 , and a strap  108  of which one end is connected to the connecting shaft  106  and encloses the deformation-inducing part  153  in an “U” shape and the other end is a free end. 
   Therefore, in sliding, the slide bracket  105  pushes the strap  108  by which the deformation-inducing part  153  is enclosed in the “U” shape and continues to get the strap  108  to incur the plastic deformation, thus absorbing the shock. 
   As shown in  FIG. 5 , the deformation-inducing part  153  includes a main deformation part  153   a  and a guide part  153   b . Preferably, the deformation-inducing part  153  is designed to allow the strap  108  to be deformed into the “U” shape at all times under any situation. Without the guide part  153   b , the strap  108  sags downward on its own free end to resist deformation, and thus it would hardly perform its original function. 
   Further, the deformation-inducing part  153  is preferably made of a synthetic resin based material in order to decrease friction with the strap  108  in the course of inducing deformation of the strap  108 , and thus the strap  108  can be smoothly deformed into the “U” shape. It will be preferable to allow the deformation-inducing part  153  to be inserted into the slide bracket  105  as in  FIG. 5  and thus to be simply assembled. 
   As mentioned above, the present invention is constructed in such a manner that as shown in  FIG. 6 , when a shock F is given to the steering column, the rotational bracket  104  rotates from location L to location M relative to the lower mounting bracket  103 , thus forcing the steering column to move back as much. Therefore, in the course of the shock just before the connecting shaft  106  slides in the long hole  151 , the time taken to generate the shock is lengthened. Thereby, when a vehicle driver strikes the steering wheel to get a shock, a magnitude of the shock initially given to the driver is greatly decreased. Moreover, when sliding in the long hole  151 , the connecting shaft  106  continues to absorb the shock. 
   Meanwhile,  FIG. 8  illustrates a steering column of the present invention as a whole, in which the steering column is coupled with the upper supporting structure as in  FIG. 7 , and specifically a state in which the steering column of the present invention is operated when a collision occurs. 
   According to the present invention as mentioned above, there are the following effects. 
   First, the rotational bracket is rotatably connected to the lower mounting bracket, so that, when the vehicle driver strike the steering wheel due to a vehicular collision, an initial shock of the driver can be greatly reduced. 
   Second, the shock absorbing means is provided on the lower supporting structure, so that it is possible to simplify the upper supporting structure and thus to add other functions as much, and furthermore to make the upper supporting structure avoid from interference with the driver when a vehicular collision occurs because the upper supporting structure is located nearly to the driver. 
   Third, the bush with a nose is used as the shock absorbing means, so that, after a collision, the bush has only to be exchanged. This leads to an easy work and a decreased cost when the vehicle is repaired. 
   Fourth, the connecting shaft and the slide bracket are used to provide strap structure as the shock absorbing means, so that the shock absorbing means can be effectively provided. 
   Fifth, the upper supporting structure of the steering column is provided with the tilt slot, which is adapted to guide tilt operation of the steering column, so that the tilt slot can not be limited to its shape. 
   Although a preferred embodiment of the present invention has been described for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions can be made without departing from the scope and spirit of the invention as disclosed in the accompanying claims.