Abstract:
The invention concerns a shock strut for a Mac Pherson wheel suspension comprising a shock absorber with a body ( 21 ) and a rod ( 22 ). A coil spring ( 24 ) is mounted on a lower spring retainer ( 23 ) integral with the shock absorber body ( 21 ). The first turn of the spring ( 24 ) of the MacPherson strut can be immobilized on and relative to the lower spring retainer ( 23 ) in various predetermined positions on the lower spring retainer ( 23 ).

Description:
RELATED APPLICATIONS  
       [0001]    The present application is a continuation of U.S. patent application Ser. No. 09/673,759 (now allowed), which is a National Stage of International Application No. PCT/FR00/00302, filed Feb. 9, 2000. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    Field of the Invention  
           [0003]    The invention relates to a strut for a wheel suspension of the Mac Pherson type, comprising a shock absorber with a body and a rod. The rod is surrounded by a coil spring. The coil spring is mounted preloaded between a bottom seat of a lower spring retainer secured to the shock absorber body and an upper seat of an upper spring retainer through which the shock absorber rod passes. The shock absorber body is mounted securely to a hub carrier defining an axis of rotation of the wheel.  
           [0004]    Document EP-O 780 250 A2 and U.S. Pat. No. 5,947,459 describe a precise adjustment of a Mac Pherson suspension strut, using adjusting means arranged on the strut and preferably employing an appropriate measurement bench. To obtain correct operation of the strut, the shear force applied to the shock absorber rod has to be precisely controlled. To achieve this, it is known practice for the axis of the spring to be inclined with respect to the axis of the shock absorber rod with an inclination that is calculated to minimize the shear force on the shock absorber rod. However, it is also known that the resultant of the forces exerted by the spring is liable to exert a moment about the pivot axis, which moment has to be well controlled.  
         SUMMARY OF THE INVENTION  
         [0005]    One object of the invention is to provide a new strut that allows for quick and precise adjustment and which is simple and economical to manufacture.  
           [0006]    In order to achieve this objective, the present invention provides a strut for a wheel suspension of the Mac Pherson type, comprising a shock absorber with a body and a rod surrounded by a coil spring. The coil spring is mounted between a lower spring retainer that is secured to the shock absorber body and an upper spring retainer through which the shock absorber rod passes. The shock absorber body is securely mounted to a hub carrier defining an axis of rotation of the wheel. The strut comprises means for immobilizing the first turn of the spring on and with respect to the lower spring retainer in various predetermined positions on the lower spring retainer.  
           [0007]    The spring has one end that extends transversely to a direction of translation defined by the various predetermined positions and has a part which is roughly straight and parallel to the direction of translation.  
           [0008]    In a first alternative form of the invention, the end of the spring extends transversely to the direction of translation and has an indexing configuration.  
           [0009]    In a first embodiment of this first alternative form, this indexing configuration involves at least one orifice through which a mechanical means of connection to the lower spring retainer can pass.  
           [0010]    In a second embodiment of this first alternative form, this indexing configuration involves at least one curved end which can be inserted in an indexing orifice chosen from a number of orifices made in the lower spring retainer.  
           [0011]    In a second alternative form of the invention, corresponding to a third embodiment, the end of the spring extends transversely to the direction of translation and can be secured to the lower spring retainer by a means at least partially surrounding said end. This means at least partially surrounding the end of the spring is advantageously configured as a collar or a curved tab. This collar or curved-tab configuration has a means of attachment by a mechanical coupling means to the lower spring retainer.  
           [0012]    In both alternative forms of the invention, the mechanical means of coupling to the lower spring retainer is preferably a replaceable means and can be of the screw, pin, bolt or similar type.  
           [0013]    In a preferred embodiment, the straight part parallel to the direction of translation is parallel to the direction of forward travel of a vehicle for which the strut is intended.  
           [0014]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed.  
           [0015]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate various embodiments of the invention and together with the description, serve to explain the principles of the invention. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0016]    [0016]FIG. 1 diagrammatically depicts a view from above in the direction of arrow I of FIG. 2 of a first embodiment of the invention.  
         [0017]    [0017]FIG. 2 diagrammatically depicts a view in section on the line II-II of FIG. 1 of the first embodiment of the invention.  
         [0018]    [0018]FIG. 3 diagrammatically depicts a view in section on the line III-III of FIG. 1 of the first embodiment of the invention.  
         [0019]    [0019]FIG. 4 diagrammatically depicts a view in the direction of arrow IV of FIG. 5 of a second embodiment of the invention.  
         [0020]    [0020]FIG. 5 diagrammatically depicts a view in section on the line V-V of FIG. 4 of the second embodiment of the invention.  
         [0021]    [0021]FIG. 6 diagrammatically depicts a view in section on the line VI-VI of FIG. 4 of the second embodiment of the invention.  
         [0022]    [0022]FIG. 7 diagrammatically depicts a view in the direction of arrow VII of FIG. 8 of a third embodiment of the invention.  
         [0023]    [0023]FIG. 8 diagrammatically depicts a view in section on the line VIII-VIII of FIG. 7 of the third embodiment of the invention.  
         [0024]    [0024]FIG. 9 diagrammatically depicts a view in section on the line IX-IX of FIG. 7 of the third embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0025]    Reference will now be made in detail to the present invention.  
         [0026]    FIGS.  1  to  3  illustrate a Mac Pherson suspension strut comprising a shock absorber with a body  1  and a rod  2 . A lower spring retainer  3  is mounted securely on the body of the shock absorber and a spring  4  is mounted between the lower spring retainer  3  and an upper spring retainer, not depicted.  
         [0027]    The coil spring  4  has a helical part  4   a , a straight part  4   b  guided in translation in a configuration  3   a ,  3   b  forming a channel for translation in the direction T.  
         [0028]    One end  4   c  of the spring, curved transversely with respect to the straight part  4   b , is roughly perpendicular to this straight part  4   b . The end  4   c  therefore extends transversely and roughly at right angles to the direction T of translation.  
         [0029]    The end part  4   c  of the coil spring  4  has, at  5 , an indexing arrangement produced in the form of an orifice through which an elastic pin  6  can pass. The elastic pin  6  can be positioned in one of the three orifices  7 ,  8  or  9  to position the end  4   c  of the spring with respect to the spring retainer  3 .  
         [0030]    Because the coil spring bears on the lower spring retainer  3  along the line  10 , the spring can be shifted into a position corresponding to the orifice  7  or to the orifice  9  while at the same time keeping the line  10  pressing against the lower spring retainer  3 .  
         [0031]    This first embodiment allows the position of the spring to be adjusted with respect to the axis of the shock absorber in a simple and economical way, for example by shifting the end  4   c  using a mallet until it is in the chosen position corresponding to the desired adjustment of the inclination of the spring with respect to the axis of the shock absorber once the elastic pin  6  has been extracted.  
         [0032]    FIGS.  4  to  6  show a Mac Pherson suspension strut comprising a shock absorber with a body  11  and a rod  12 , a lower spring retainer  13  secured to the shock absorber body  11 , a coil spring  14  bearing on the lower spring retainer  13  and mounted between the lower spring retainer  13  and an upper spring retainer, not depicted.  
         [0033]    The coil spring  14  has a circular end  14   a, a  straight end  14   b  and a curved end  14   c  roughly perpendicular to the straight end  14   b . The straight end  14   b  is guided in translation in the direction T by a channel determined by two raised parts  13   a  and  13   b  of the lower spring retainer  13 .  
         [0034]    The end  14   c  roughly perpendicular to the direction of translation T has a curved and preferably tapered end  15 . The curved end  15  can be inserted in an indexing orifice  16  chosen from the three orifices  16 ,  17  and  18  made in the lower spring retainer  13 .  
         [0035]    To move the spring  14  from one chosen position to another indexing position, a tool is inserted into the space  19  to lift the curved end  15  of the spring  14  and move it into a chosen position. Pressure is then exerted on the outer edge  20  of the bent end  15  to insert this end  15  into an orifice  17  or  18 .  
         [0036]    With reference to FIGS.  7  to  9 , a Mac Pherson suspension strut comprises a shock absorber with a body  21  and a rod  22 , a lower spring retainer  23  secured to the body of the shock absorber and a coil spring  24  mounted between the lower spring retainer  23  and an upper spring retainer, not depicted.  
         [0037]    The spring  24  has a helical portion  24   a, a  straight portion  24   b  and an end  24   c  roughly perpendicular to the straight end  24   b . The straight end  24   b  is guided in translation in the direction T by a configuration forming a translation channel delimited by a wave shape  13   a  and a rim  23   b.    
         [0038]    All that is required to move the spring  24  is for the end  24   c  to be moved in translation in the direction T. The end  24   c  is secured to the spring retainer  23  by a means  25  at least partially surrounding the end  24   c . This means  25  preferably has a collar or curved-tab configuration capable of being fixed removably to the lower spring retainer  23 . To do this, use is made, for example, of a screw  26 , or a pin, or a bolt, or any other similar mechanical fastening means such as a rivet.  
         [0039]    The screw  26  is screwed into an orifice  27  in the end of the curved tab  25  and into a corresponding hole or tapping  28 ,  29  or  30  made in the lower spring retainer  23 .  
         [0040]    Adjustment in this embodiment can be carried out in a similar way to the way described with reference to the first embodiment of FIGS.  1  to  3 , such as by using a mallet or some other appropriate instrument able to make the spring  24  move. The screw  26  can be partially loosened to allow prior geometric adjustment, before the spring  24  is fastened in position using the curved tab  25 .  
         [0041]    The spring  4 ,  14  or  24  has a configuration that allows it to be moved in translation in a predetermined direction corresponding to it being guided by a corresponding configuration of the lower spring retainer  3 ,  13  or  23 .  
         [0042]    Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.  
         [0043]    All of the documents cited throughout the specification are incorporated herein by reference.