Abstract:
A tilt mechanism for adjusting an angular position of an automotive steering column. The tilt mechanism includes an adjustment cylinder assembly having a fluid power cylinder, a fluid conduit and a valve. The adjustment cylinder assembly is configured in a closed-loop manner such that the fluid that is displaced from one side of the cylinder is directed to the other side of the cylinder. The valve is employed to inhibit the flow of fluid between the sides of the cylinder to thereby lock the tilt mechanism in a desired position.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention generally relates to vehicle steering systems and more particularly to a tilt mechanism for adjusting the position of a vehicle steering column.  
         BACKGROUND OF THE INVENTION  
         [0002]    Known tilt mechanisms for adjusting the angular position of a vehicle steering column typically employ rather complex linkage mechanisms for locking the steering column in a desired angular position. These linkage systems are typically limited to a relatively low number of discrete adjustment positions.  
           [0003]    Accordingly, there remains a need in the art for a tilt mechanism for adjusting the angular position of a vehicle steering column that is robust yet relatively simple in design and which provides a larger degree of adjustment.  
         SUMMARY OF THE INVENTION  
         [0004]    In one preferred form, the present invention provides a tilt mechanism for adjusting an angular position of an automotive steering column. The tilt mechanism includes a first structure that is adapted to be fixedly coupled to a vehicle frame, a second structure that is adapted to support the steering column and which is pivotably coupled to the first structure, and an adjustment cylinder assembly. The adjustment cylinder assembly includes a cylinder, a fluid conduit and a valve. The cylinder has a housing with a central bore, a piston slidingly disposed in the central bore and a rod that is fixedly coupled to the piston. The piston segregates the housing into a first cavity and a second cavity. The housing is pivotably coupled to one of the first and second structures. An end of the rod is pivotably coupled to the other one of the first and second structures. The fluid conduit operably couples the first and second cavities for fluid communication therebetween. The valve is coupled to the fluid conduit and is operable in a first condition, which permits fluid communication between the first and second cavities through the fluid conduit, and a second condition, which restricts fluid communication between the first and second cavities by inhibiting the flow of a working fluid through the fluid conduit.  
           [0005]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]    Additional advantages and features of the present invention will become apparent from the subsequent description and the appended claims, taken in conjunction with the accompanying drawings, wherein:  
         [0007]    [0007]FIG. 1 is a fragmentary side elevational view of a portion of a vehicle with parts being broken away to show a tilt mechanism constructed in accordance with the teachings of the present invention;  
         [0008]    [0008]FIG. 2 is a side elevational view of the tilt mechanism of FIG. 1; and  
         [0009]    [0009]FIG. 3 is a schematic view of a portion of the tilt mechanism of FIG. 1 illustrating the fluid circuitry in greater detail. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0010]    With reference to FIG. 1 of the drawings, a tilt mechanism constructed in accordance with the teachings of the present invention is generally indicated by reference numeral  10 . The tilt mechanism  10  is illustrated in operative association with a steering column  12 . The steering column  12  extends upwardly and rearwardly into the vehicle passenger compartment  14  and conventionally includes a suitable coupler (not shown) of known construction, which is coupled to a steering gear assembly for steering the wheels of a vehicle. A steering wheel  16 , which is configured to receive a steering input from a vehicle operator, is affixed to the opposite end of the steering column  12 .  
         [0011]    With additional reference to FIG. 2, the tilt mechanism  10  is illustrated to include a fixed yoke  20 , a pivoting yoke  22  and an adjustment cylinder assembly  24 . The fixed yoke  20  is configured to be affixed to the vehicle frame (not shown) and includes a pair of first mounting trunnions  30  and a second mounting trunnion  36 . The first mounting trunnions  30  are spaced apart from one another and cooperate to define a channel  32  therebetween. A first pin aperture is formed through the first mounting trunnions  30 . The second mounting trunnion  36  is spaced apart upwardly from the first mounting trunnions  30  and includes a second pin aperture (not specifically shown) formed therethrough along an axis that is generally parallel that of the first pin aperture.  
         [0012]    The pivoting yoke  22  includes a sleeve portion  40 , a third mounting trunnion  42  and a pair of fourth mounting trunnions  44 . The sleeve portion  40  includes an aperture (not specifically shown) that is sized to receive and rotatably support the steering column  12  proximate the steering wheel  16 . The third mounting trunnion  42  extends from the sleeve portion  40 . A third pin aperture (not specifically shown) is formed through the third mounting trunnion  42 . The fourth mounting trunnions  44  are spaced apart from one another, extending from the sleeve portion  40 . A fourth pin aperture  48  is formed through the fourth mounting trunnions  44  along an axis that is generally parallel that of the third pin aperture.  
         [0013]    The adjustment cylinder assembly  24  is illustrated to include a cylinder assembly  50 , a valve assembly  52  and a spring  54 . With additional reference to FIG. 3, the cylinder assembly  50  includes a housing  56 , first and second end caps  58  and  60 , respectively, a piston  62 , a rod  64  and a rod yoke  66 . The housing  56  is illustrated to be generally shaped as a hollow cylinder having a central bore  68 , a coupling pad  70  protruding from its midsection. A pair of fluid conduits  72  and  74  are formed into the housing  56 , each extending in a generally L-shaped manner from an end of the housing  56  to the face  76  of the coupling pad  70 .  
         [0014]    The first end cap  58  includes a cylindrical body  78  and a pair of end cap trunnions  80 . A fluid entry port  82  is formed into a first side  84  of the body  78 , while a rod aperture  86  is formed through the body  78 . The end cap trunnions  80  extend from a second side  88  of the body  78  and a fifth pin aperture  90  is formed through the end cap trunnions  80 .  
         [0015]    The second end cap  60  is constructed in a manner that is nearly identical to that of the first end cap  58 , except that the second end cap  60  does not include any end cap trunnions. The first and second end caps  58  and  60  are aligned to the housing  56  such that the fluid entry ports  82  of the first and second end caps  58  and  60  are aligned to the fluid conduits  72  and  74 , respectively, and fixedly secured to the opposite ends of the housing  56  to substantially close off the central bore  68 .  
         [0016]    The piston  62 , rod  64  and rod yoke  66  are conventional in their construction and need not be discussed in significant detail. Briefly, the piston  62  is sized to slidingly and sealingly engage the central bore  68  of the housing  56 . The rod  64  is coupled to the piston  62  such that the first and second ends  94  and  96 , respectively, extend from the opposite faces of the piston  62  and out of the rod apertures  86  in the first and second end caps  58  and  60 , respectively. A seal is disposed in each rod aperture  86  to seal against both the rod  64  and the housing  56 . The rod yoke  66  is fixedly coupled (via threaded engagement) to the second end  96  of the rod  64  and includes a sixth pin aperture  98 .  
         [0017]    The valve assembly  52  includes a valve body  100 , a valve element  102  and an actuator, such as a handle  104 . The valve body  100  includes a valve element aperture  106  that is configured to house the valve element  102 . In the particular embodiment illustrated, the valve body  100  also includes a pair of fluid conduits  108  and  110  that extending from a mounting flange  112  to the valve element aperture  106 . The mounting flange  112  is configured to mate to the coupling pad  70  such that the first and third fluid conduits  72  and  108  are in fluid connection with one another and the second and fourth fluid conduits  74  and  110  are in fluid connection with one another. In the example provided, seals (not shown) are disposed between the valve body  100  and the housing  56  and threaded fasteners (not shown) are employed to fixedly couple the valve body  100  to the housing  56 .  
         [0018]    The valve element  102  is disposed in the valve element aperture  106  and is movable between a first position, which permits fluid communication between the third and fourth fluid conduits  108  and  110 , and a second position, which inhibits fluid communication between the third and fourth fluid conduits  108  and  110 . In the particular embodiment illustrated, the valve element  102  is shown to be a spherical ball  120 , having a hole  122  formed therethrough and a seal member  124 , which is engaged to both the ball  120  and the sides of the valve element aperture  106 . The ball  120  is coupled for rotation with the handle  104  and thus operates much in the same manner as a conventional ball valve. When positioned in the first position, the hole  122  is rotated into alignment with the third and fourth fluid conduits  108  and  110  to permit fluid to flow through the ball  120 . When positioned in the second position, the hole  122  is rotated out of alignment with the third and fourth conduits  108  and  110  to inhibit the flow of fluid between the third and fourth conduits  108  and  110 .  
         [0019]    A first pivot pin  130 , which extends through the second pin aperture in the second mounting trunnion  36  and the third pin aperture in the third mounting trunnion  42 , pivotably couples the fixed yoke  20  and the pivoting yoke  22  to one another. A pair of second pivot pins  132  are employed to pivotably couple the first end cap  58  to the fixed yoke  20 . More specifically, each of the second pivot pins  132  extends through the first pin aperture in one of the first mounting trunnions  30  and one of the fifth pin apertures  90  in an associated one of the end cap trunnions  80 . A third pivot pin  134  is employed to pivotably couple the rod yoke  66  and the pivoting yoke  22 . More specifically, pivoting yoke  22  is positioned between the pair of fourth mounting trunnions  44  and the third pivot pin  134  is disposed through the fourth pin apertures  48  in the fourth mounting trunnions  44  and the sixth pin aperture  98  in the pivoting yoke  22 .  
         [0020]    A working fluid, such as a liquid or a compressed gas, is introduced into the cylinder assembly  50  and the valve assembly  52 . The working fluid is preferably an incompressible fluid, such as a light oil. An air bleed valve  140 , which is coupled to the valve body  100 , is in fluid communication with the third and fourth fluid conduits  108  and  110  and is employed to purge air from the cylinder assembly  50  and valve assembly  52 . The piston  62  segregates the central bore  68  into first and second cavities  144  and  146 , respectively. When the ball  120  is positioned in the first position, fluid may freely circulate between the first and second cavities  144  and  146  via the first, third, fourth and second fluid conduits  72 ,  108 ,  110  and  74 . Accordingly, the piston  62  may freely travel within the central bore  68  to thereby increase or reduce the amount by which the second end  96  of the rod  64  extends from the second end cap  60 . When the ball  120  is positioned in the second position, fluid cannot flow between the third and fourth fluid conduits  108  and  110  and fluid communication between the first and second cavities  144  and  146  is prevented. As such, the piston  62  and rod  64  are immovable relative to the housing  56  when the ball  120  is positioned in the second position and thereby fix the pivoting yoke  22  in a particular orientation since the amount by which the second end  96  of the rod  64  extends from the second end cap  60  is fixed. Those skilled in the art will understand that the degree to which the pivoting yoke  22  is locked in a particular orientation will depend upon the integrity of the closed-loop fluid circuit and the particular type of working fluid that is used. With regard to the latter issue, if the working fluid is a compressible fluid, such as nitrogen or air, the application of sufficient force onto the pivoting yoke  22  would cause the pivoting yoke  22  to move as the force exerted through the piston  62  would compress the fluid in one of the first and second cavities  144  and  146 .  
         [0021]    The spring  54  is disposed within the channel  32  between the first mounting trunnions  30  such that a first end  94  abuts a tab  150  that is formed on the fixed yoke  20  and the second end  96  abuts plunger  152  that is coupled to the first end  94  of the rod  64 . The spring  54  operably biases the rod  64  toward the housing  56  of the cylinder assembly  50  to thereby bias the pivoting yoke  22  upwardly.  
         [0022]    While the invention has been described in the specification and illustrated in the drawings with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the foregoing description and the appended claims.