Patent Publication Number: US-2011049854-A1

Title: Assembly for mounting a steering wheel on the steering column of an automobile

Description:
The present invention relates to an arrangement making it possible to angularly position and rigidly attach a steering wheel to a steering column. 
     The invention finds a particularly advantageous, but not exclusive, application in the motor vehicle field. 
     In order to attach a steering wheel to a steering column, it is known practice to use a simple screw which, on the one hand, is housed in a through hole arranged at the center of the hub of said steering wheel, and on the other hand is screwed into a tapping machined axially at the end of said steering column. In order to reduce production costs as much as possible, it is a standard fastening screw that is conventionally used on the industrial scale. 
     The action of this fastening screw is usually supplemented by splines that are more particularly responsible for transmitting the rotary forces between the steering wheel and the steering column. In this way, a first set of splines is normally arranged in the hole passing through the steering wheel, while a second extends along the steering column. The assembly is arranged so as to engage longitudinally when the steering wheel is inserted into the end of the steering column. 
     In practice, the two sets of splines are also used to angularly position the steering wheel relative to the steering column. The presence of an error-preventing system makes it possible to define a single mounting position, in which the steering wheel is perfectly centered when the steered wheels associated with the steering column are absolutely straight. 
     This type of arrangement, however, has the drawback of causing mounting difficulties some of which are likely to harm the quality of assembly, and even to cause damage. 
     Specifically, by virtue of its standard character, the fastening screw has a length that is usually longer than that of the hole arranged through the hub of the steering wheel. Consequently, it is capable of being screwed into the tapping of the steering column before the two sets of splines are longitudinally engaged. 
     By forcing a little, which is relatively easy since screwing is usually a mechanized operation, it is possible to fix the steering wheel without it being correctly positioned from an angular point of view, despite the presence of the error-preventing system. 
     In this way therefore and at best, the steering wheel will have to be reinstalled subsequently during an awkward reworking job. But at worst, it will absolutely be necessary to replace the steering wheel due to the damage to its splines, because the hub is these days usually made of magnesium. 
     Therefore, the technical problem to be solved by the subject of the present invention is to propose an arrangement for mounting a steering wheel on a steering column of a motor vehicle, said arrangement comprising on the one hand first splines that are made on the steering wheel and that are intended to be fitted into second splines extending along the steering column and, on the other hand, a fastening screw that is designed to be engaged through the steering wheel and to interact with a tapping arranged axially at the end of the steering column, an arrangement which would make it possible to prevent the problems of the prior art by ensuring notably a precise angular positioning of the steering wheel while remaining compatible with the use of a standard fastening screw. 
     The solution to the technical problem posed consists, according to the present invention, in that, once engaged through the steering wheel, the fastening screw is capable of being screwed into the tapping if and only if the first splines and the second splines are at least partially fitted. 
     The principle therefore consists in allowing the steering wheel to be fastened only if the latter is previously positioned appropriately at the end of the steering column. Specifically the assembly is arranged so that it is impossible to screw the fastening screw into the tapping unless the steering wheel is correctly oriented angularly relative to the steering column. 
     In contrast, this means that, if the steering wheel is placed in the only position compatible with the error-preventing system, the longitudinal fitting of the splines will be able to occur naturally, thus validating the angular positioning step. Gradually as the steering wheel is inserted on the end of the steering column, the fastening screw will progressively approach the tapping until they make actual contact. The screwing operation proper can then commence; the fastening step being completed only with the steering wheel butting against the steering column and the tightening of the fastening screw in the tapping. 
     As opposed to what happens in the prior art, the steps of angular positioning and of fastening can in no circumstances occur in a concomitant manner. The arrangement that is the subject of the invention imposes a precise order of mounting, in which the angular setting of the steering wheel must mandatorily occur before application of the fastening step. 
     Be that as it may, the invention as thus defined has the advantage of systematically ensuring an appropriate angular positioning of the steering wheel. This makes it possible to prevent both rework and scrappage and therefore, in the end, to limit the costs of mounting. 
     It is moreover important to specify that the invention is independent of the length of the screw which may therefore remain completely standard. It is in fact the relative positioning between the screw, the tapping and the two types of splines that is adapted so that said screw can interact with said tapping only after at least partial fitting of said splines, that is to say only after the angular positioning of the steering wheel. 
     The present invention also relates to the features that will emerge during the following description and that are to be considered in isolation or in all their possible technical combinations. 
    
    
     
       This description, given as a nonlimiting example, is intended to provide a better understanding of what the invention involves and how it can be embodied. It is moreover given with reference to the appended drawings in which: 
         FIG. 1  is an axial section illustrating the mounting of a steering wheel on a steering column of a motor vehicle. 
         FIG. 2  is a view similar to  FIG. 1 , but once the mounting is complete. 
     
    
    
     For reasons of clarity, the same elements have been indicated by identical reference numbers. Similarly, only the elements essential for the understanding of the invention have been shown and this is done in a schematic manner and not to scale. 
       FIGS. 1 and 2  therefore show an arrangement  1  which makes it possible both to angularly position and to rigidly attach a steering wheel  10  to a steering column  20  of a motor vehicle. In this respect, it can now be seen that the steering wheel  10  is firmly intended to be inserted onto the end  21  of the steering column  20 . This is why it is furnished with a hub  11  at the center of which a through hole  12  is arranged the shape of which substantially matches that of the most distal portion  22  of the column  20 . 
     With respect more particularly to the angular positioning of the steering wheel  10 , the arrangement  1  makes use of a conventional system of matching splines. On the steering wheel  10  there is therefore a first series of splines  13  arranged longitudinally inside the through hole  12 , while, on the steering column  20 , note the presence of a second series of splines  23  which are also placed longitudinally and extend radially. By virtue of the existence of an error-preventing system that cannot be seen here, the assembly is arranged so that there is only one angular position in which the first splines  13  can fit longitudinally into the second splines  23  when the steering wheel  10  is inserted onto the steering column  20 . 
     With respect however to securing the steering wheel  10  to the steering column  20 , the arrangement  1  provides a fastening screw  30  which is capable, on the one hand, of being engaged through the steering wheel  10 , and, on the other hand, of interacting with a tapping  40  arranged axially at the end  21  of said column  20 . Very logically, it is in the through hole  12  that the fastening screw  30  is engaged through the steering wheel  10 , since it is responsible for receiving the distal portion  22  of the steering column  20 ; the head  31  of the screw  30  then pressing against the front face of the hub  11 . 
     As can be seen notably in  FIG. 1 , and according to the subject of the present invention, once engaged through the steering wheel  10 , the fastening screw  30  is capable of being screwed into the tapping  40  if and only if the first splines  13  and the second splines  23  are at least partially engaged. 
     It is clear in this instance that it is not simply the combined presence of the first splines  13 , the second splines  23 , the fastening screw  30  and the tapping  40  that constitutes the invention, such an association being perfectly well known in the prior art. But it is the relative disposition between these various elements relative to one another that makes it possible to separate and sequence over time the steps of angular positioning and of fastening. 
     As a result of this, a multitude of embodiments are possible, depending on the size of the various elements and of their installation on their respective supports. Thought is given here notably to the fact that the fastening screw  30  can be longer or shorter than the through hole  12 , and/or that the tapping  40  can be arranged to a greater or lesser depth inside the steering column  20 , and/or that the second splines  23  can be arranged directly next to or further back from the end  21  of the steering column  20 , and/or that the first splines  13  can be larger or smaller. 
     According to a currently preferred embodiment of the invention, the arrangement  1  also comprises a housing  24  that is arranged upstream of the tapping  40  relative to the end  21  of the steering column  20 . 
     This means in other words that the tapping  40  is arranged at a distance from the end  21  of the steering column  20 . This feature makes it possible here above all to compensate for the fact that the fastening screw  30  is longer than the through hole  12 . According to  FIG. 1 , the depth of the housing is fixed so that the thread of the screw  30  cannot reach that of the tapping unless the first splines  13  are engaged in the second splines  23 . 
     According to a particular feature of this embodiment, the second splines  23  extend notably over the portion of steering column  20  in which the housing  24  is arranged. 
     In this particular embodiment, chosen only as an example, the housing  24  is in fact a bore that is concentric with the tapping  40  and that has a section matching that of the fastening screw  30 . 
     This feature advantageously allows the housing  24  to fulfill a guidance function with respect to the threaded portion of the fastening screw  30 , which accordingly makes it easier to secure the steering wheel  10  to the end  21  of the steering column  20 . 
     According to another particular feature of the invention, the second splines  23  also extend over the portion of the steering column  20  inside which the tapping  40  is arranged. 
     The value of this feature is that it allows the second splines  23  to be very long. It is therefore possible to give them a size that is comparable with that of the first splines  13 , which, in the end, makes it possible to optimize the transmission of the rotary forces between the steering wheel  10  and the steering column  20 . 
     According to another particular feature of the invention, the first splines  13  extend substantially over the whole length of the through hole  12  in the steering wheel  10 , which is designed to receive the distal portion  22  of the steering column  20 . 
     Here again, the objective is to reinforce the connection between the steering wheel  10  and the steering column  20 , it being understood that it makes sense only if the length of the first splines  13  is substantially equivalent to that of the second splines  23 . 
     Clearly, the invention relates more generally to any motor vehicle furnished with a steering column  20  that can be operated by means of a steering wheel  10 , and also having an arrangement  1  as described above.