Patent Publication Number: US-2005140130-A1

Title: Vehicle steering column including a cardan joint

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a cardan joint for use in a vehicle steering column, including a first tubular yoke member, and a tubular connecting member mounted concentrically between the yoke member and the steering shaft of the column, characterized by the provision of first positioning means for rotationally orienting the yoke member relative to the connecting member, second positioning means for limiting the axial displacement of the yoke member relative to the connecting member, and third positioning means for rotationally orienting the connecting member relative to the steering shaft.  
      2. Description of the Related Art  
      Currently, the steering column of an automotive vehicle comprises two portions: a top portion, which is connected to the steering wheel, and a middle portion, which is connected to the gearbox that controls a steering rod for the steering wheels. The top portion and the middle portion are connected with each other by a homokinetic joint, called a cardan joint. This cardan joint includes a crossbar pivot member arranged between two yoke members one of which is connected with the top portion, while the other one is connected with the middle portion.  
      The yoke members of these known cardan joints normally consist of a single unitary monoblock element. Consequently, the means for locking the yoke member of the joint upon the corresponding steering transmission shaft has an axis with an orientation that is determined with respect to the axis of the cardan joint.  
      On modern vehicles, the engine compartment is very crowded, and the limited accessibility causes tightening of the clamp upon the steering transmission shaft to be a very delicate operation. This means that one must design a specific yoke member for each type of vehicle, thereby resulting in a higher production cost.  
      The present invention was developed to provide an improved cardan joint especially suitable for use in the steering column of an automotive vehicle, which will avoid the aforementioned drawbacks of the known devices, and which is suitable for use with all types of vehicles.  
     BRIEF SUMMARY OF THE INVENTION  
      According to a primary object of the invention, a cardan joint is provided for use in the steering column assembly of an automotive vehicle, characterized by the provision of a first tubular yoke member that is mounted concentrically on a tubular connecting member that in turn is mounted concentrically on the steering transmission shaft of the column, first and second positioning means being provided for rotationally and axially orienting the yoke member relative to the connecting member, respectively. Third positioning means may be provided for rotationally orienting the connecting member relative to the steering shaft.  
      According to a more specific object of the invention, the cardan joint includes a pivot pin that extends between two parallel arms of the yoke member, and a fastening bolt member operable to tightly fasten the connecting member to the steering transmission shaft. It includes a yoke member having a cylindrical end from which extend a pair of parallel spaced arm portions carrying the pivot axis, and a concentrically arranged connecting member that connects the yoke member to the steering shaft, the yoke member and connecting member having an axis that is common with the axis of the steering shaft. The connecting member is bifurcated at one end that is provided with a screw threaded fastening member that is operable to draw the bifurcated end portion of the connecting member into tight engagement with the outer peripheral surface of the steering shaft. The outer face of the connecting member and the inner face of the yoke member have conjugate shapes so as to bring about the desired rotational orientation between the cardan joint yoke member and the connecting element, thereby to obtain angular positioning means and rotational connection means for the connecting element with respect to the joint fork. Axial positioning means are provided between the connecting element and the joint yoke member.  
      To make sure that the cardan clamp consists of one and the same assembly, the conjugate shapes of the outer face and the inner face are dimensioned so as to obtain a certain tightening between the cylindrical portion and the cylindrical end and thus to obtain the means for axial connection between the connecting element and the joint yoke member.  
      According to another embodiment of the invention, the conjugate shapes of the outer face and of the inner face consist of grooves. According to another embodiment of the invention, the conjugate shapes of the outer face and of the inner face consist of shape saw tooth-like indentations.  
      The system for locking the cardan clamp used in the invention consists of the fact that the connecting element has a locking portion that comprises a cylindrical element with two locking elements. The two locking elements are separated by an axial cover that leads into an inner face of the cylindrical element, while the locking pin is essentially normal to said axial opening. Moreover, a transversal radially-inwardly directed tangential slot is provided on the cylindrical portion adjacent the locking elements. Finally, the locking means consist of a locking screw.  
      According to the invention, the connecting element has inner faces which have shapes that are conjugate with the steering transmission shaft so as to ensure the desired rotational orientation connection. Preferably, the conjugate shapes of the inner faces of the connecting element and the transmission shaft consist of grooves.  
      According to an embodiment of the invention, the cardan joint has a connecting element which consists of a forged and machined piece. According to another embodiment of the invention, the connecting element consists of a piece that is made of machined, shaped sheet metal. According to another embodiment of the invention, the connecting element consists of a cut and machined drawn piece.  
      The cardan joint according to the invention thus offers the advantage of presenting an assembly that is made from a joint yoke member which can be standard, with a connecting element that can also be standard. This permits large-series production with a lower cost. Moreover, a decisive advantage of the invention resides in the fact that it permits an orientation of the connecting element with respect to the joint yoke member so that the cardan joint will be adapted for use with each type of vehicle with more accessible and thus easier assembly. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      Other objects and advantages of the invention will become apparent from a study of the following specification when viewed in the light of the accompanying drawings, in which:  
       FIG. 1  is a side perspective view of one yoke member and connecting member assembly, and  
       FIG. 2  is a rear perspective view of the connecting member of  FIG. 1 ;  
       FIG. 3  is a side perspective view of a second embodiment of the yoke member and connecting member assembly, and  
       FIG. 4  is a front perspective view of the connecting member of  FIG. 3 ;  
       FIG. 5  is a sectional view of the connecting member of  FIG. 1 , and  
       FIG. 6  is a detailed view taken along the line  6 - 6  of  FIG. 5 ;  
       FIG. 5A  is a sectional view taken along the line  5 A- 5 A of  FIG. 1 ;  
       FIG. 7  is a detailed sectional view taken along the line  7 - 7  of  FIG. 5A ; and  
       FIG. 7A  is modification of the rotational orienting means of  FIG. 7 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Referring more particularly to  FIGS. 1 and 2 , the cardan joint of the present invention includes a first yoke or fork member  1  that is connected with the steering shaft  5  by means of a connecting member  2 . As shown in  FIG. 2 , the tubular connecting member  2  contains a through bore  27  that extends from a tubular first end portion  20  through a bifurcated second end portion  21 . The connecting member  2  is provided at its second end portion  21  an enlarged locking portion  2   a  that contains a longitudinal axially extending slot  35  that divides the enlarged portion into a pair of locking portions  31  and  32 . A pair of aligned openings  33  and  34  having a common transverse locking axis  4  are provided in the locking portions  31  and  32 , respectively, thereby to define the locking axis  4  that extends transversely of the longitudinal axis  6  of the steering shaft  5 . The bifurcated portion  21  of the connecting element  2  is arranged for locking engagement with the external surface of the steering shaft  5  by means of a threaded bolt member  40  that extends through the oversized opening  33  contained in locking portion  31 , and into threaded engagement with the corresponding bore  34  contained in the locking portion  32 .  
      Thus, upon tightening of the bolt  40  with the head portion thereof in engagement with the supporting face  36  of the oversized opening  33 , the threaded portion of the bolt engages the threaded opening  34  to draw the locking portions  31  and  32  together into tight locking engagement with the outer surface  22  of the shaft  5 , as shown in  FIG. 5A .  
      The tubular first end portion  20  of the connecting element  2  extends within a corresponding bore  15  ( FIG. 5A ) that is contained in one end of the tubular portion  10  of the joint yoke member  1 . At its other end, the yoke member  1  is provided with a pair of arm portions  11  and  12  that extend parallel with and on opposite sides of the longitudinal axis  6  of the steering shaft  5 . These arm portions  11  and  12  contained aligned openings  13  and  14  that are arranged parallel with and on opposite sides of the longitudinal axis  6  of the steering shaft  5 , which openings define a pivot axis  3  that extends normal to the longitudinal axis  6  of the steering shaft  5 . Connected with this pivot axis  3  is a second yoke member (not shown) that is rotated about its longitudinal axis through 90 degrees relative to the first fork member one. As is known in the art, pivot pin means (not shown) having an axis  3  extend through the openings  13  and  14  to connect the second yoke member (not shown) with the illustrated first yoke member, and with the steering gear box  42  of the vehicle steering system.  
      In accordance with a characterizing feature of the present invention, first positioning means are provided for rotationally orienting the cardan joint yoke member  1  with the connecting member  2  relative to the longitudinal axis  6  of the steering shaft  5 . To this end, the outer surface  22  of the tubular first end portion  20  of the connecting member  2  is provided with a plurality of circumferentially spaced, longitudinally-extending rib portions or protrusions  23  that extend within corresponding grooves  17  contained in the inner peripheral surface  15  of the yoke member  1 . In the embodiment of  FIG. 7 , the profiles of the ribs or protrusions  23  and the groove  17  are smooth, while in the modified embodiment of  FIG. 7A , the protrusions  24  and the recesses  18  have a sharp pointed saw tooth configuration.  
      Referring to  FIGS. 5 and 5   a , it will be seen that the connecting member contains adjacent the enlarged portion  21   a  a radially inwardly directed slot  26  that provides a certain degree of flexibility to the bifurcated enlarged portion  21   a . An annular rib provided on the outer face  22  of the first end portion  20  of the connecting member  2  defines an annular end face  25  that is arranged for engagement by a corresponding end face  16  of the tubular portion of the yoke member  1 , thereby to limit the axial displacement of the yoke member  1  relative to the connecting member  2 .  
      Referring now to  FIG. 6 , in accordance with another characterizing feature of the invention, third positioning means are provided for rotationally orienting the connecting member  2  relative to the steering shaft  5 . To this end, a plurality of circumferentially spaced longitudinally extending ribs or protrusions  7  are provided on the outer surface of the steering shaft  5  for engagement with corresponding grooves  28  is contained on the inner peripheral surface of the through bore  26  of the connecting member  2 . Thus, owing to the relationship of the first positioning means  17  and  23  of  FIG. 7  (and  18  and  24  of  FIG. 7A ), together with the third positioning means  7  and  28  of  FIG. 6 , the pivot axis  3  is always maintained that a desired orientation relative to the longitudinal axis  6  of the steering shaft  5 .  
      In the embodiment of  FIGS. 1 and 2 , the connecting element  2  is formed from a single sheet metal piece that is bifurcated at each end, the bifurcated portions at the first tubular end being welded together by a weld seam  42 . In the embodiment of  FIGS. 3 and 4 , the connecting member  2 ′ is formed as a single unitary casted and machined component. If desired, the connecting member could also be formed from a machine drawn piece.  
      As indicated above, the cooperation between the end face  16  of the fork member  1  with the support face  25  on the outer face  22  of the connecting member  2  limits the axial displacement of the fork member relative to the connecting member, thereby to further accurately position the pivot axis  3  relative to the longitudinal axis  6  of the steering shaft  5 .  
      While in accordance with the provisions of the Patent Statutes the preferred forms and embodiments of the invention have been illustrated and described, it will be apparent to those skilled in the art that various changes may be made without deviating from the inventive concepts set forth above.