Abstract:
A rack and pinion steering gear ( 10 ) comprises a rack ( 14 ) and a housing ( 12 ) for receiving the rack. The housing ( 12 ) has a chamber ( 42 ) for receiving a rack supporting yoke ( 70 ). The chamber ( 42 ) has a threaded portion ( 44 ) with internal threads ( 45 ). A rack supporting yoke ( 70 ) is disposed in the chamber ( 42 ) and supports the rack ( 14 ) for movement in the housing ( 12 ). An externally threaded yoke plug ( 90 ) is screwed into the internal threads ( 45 ) of the threaded portion ( 44 ). An externally threaded lock nut ( 120 ) is screwed into the internal threads ( 45 ) of the threaded portion ( 44 ) and into abutting engagement with the yoke plug ( 90 ) to lock the yoke plug in the housing ( 12 ).

Description:
TECHNICAL FIELD 
     The present invention relates to a rack and pinion steering gear and a method of manufacturing a rack and pinion steering gear for use in turning steerable wheels. 
     BACKGROUND OF THE INVENTION 
     A known rack and pinion steering gear for use in turning steerable wheels of a vehicle includes a pinion which is disposed within a housing and which is operatively coupled with a vehicle steering wheel. A transversely extending rack is also disposed within the housing and is in meshing engagement with the pinion. Rotation of the steering wheel produces linear movement of the rack which causes the steerable wheels to turn laterally of the vehicle. 
     In the known rack and pinion steering gear, a yoke presses the rack into engagement with the pinion. The yoke is typically secured in the housing by a yoke plug which screws into the housing over an outboard end of the yoke. A helical spring is disposed between the yoke plug and the yoke to ensure firm meshing engagement between teeth on the rack and teeth on the pinion. 
     Various methods have been proposed for retaining the yoke plug in the housing in order to maintain the position of the yoke against the rack inside the housing. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, a rack and pinion steering gear comprises a rack and a housing for receiving the rack. The housing has a chamber for receiving a rack supporting yoke. The chamber has a threaded portion with internal threads. A rack supporting yoke is disposed in the chamber and supports the rack for movement in the housing. An externally threaded yoke plug is screwed into the internal threads of the threaded portion of the chamber. An externally threaded lock nut is screwed into the internal threads and into abutting engagement with the yoke plug to lock the yoke plug in the housing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, wherein: 
     FIG. 1 is a side view, partially in section, of a portion of a rack and pinion steering gear; 
     FIG. 2 is a sectional view taken generally along line  2 — 2  in FIG. 1; and 
     FIGS. 3-9 are side views, partially in section, depicting steps used in making parts of the rack and pinion steering gear of FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     As representative of the present invention, FIG. 1 illustrates a rack and pinion steering gear  10  which includes a housing  12 , a rack  14 , and a pinion  16 . 
     The housing  12  includes a pinion portion  20 , a rack portion  22 , and a yoke portion  24 . The pinion portion  20  has an axis  26  and includes an inner surface  28  (FIG. 2) that defines a pinion chamber  30  in the housing  12 . The rack portion  22  (FIG. 1) has an axis  32  which extends transverse to the axis  26 . The rack portion  22  has an inner surface  34  that defines a rack chamber  36  in the housing  12 . The yoke portion  24  is centered on a yoke axis  38  which extends transverse to the axis  26  and perpendicular to the axis  32 . The yoke portion  24  has an inner surface  40  (FIG. 2) that defines a yoke chamber  42  in the housing  12 . The inner surface  40  of the yoke portion  24  includes a threaded portion  44  having internal threads  45 . The pinion chamber  30 , the rack chamber  36  (FIG.  1 ), and the yoke chamber  42  (FIG. 2) intersect in a junction section  46  of the housing  12 . 
     The pinion  16  is disposed in the pinion chamber  30  and is rotatable about the axis  26 . The pinion  16  is operatively connected with a vehicle steering wheel (not shown) as is known in the art. The pinion  16  has an outer surface  48  which includes gear teeth  50 . 
     The rack  14  is partially disposed in the rack chamber  36  (FIG.  1 ). Opposite ends (not shown) of the rack  14  project beyond the housing  12  and are adapted to be connected with steerable vehicle wheels (not shown) as is known in the art. The rack  14  is movable in opposite directions along the axis  32  to effect turning of the steerable wheels in opposite directions. 
     The rack  14  (FIG. 2) has a generally cylindrical outer surface  60 . A portion of the outer surface  60  of the rack  14  includes rack teeth  64 . The rack teeth  64  mesh with the gear teeth  50  on the pinion  16  in the junction section  46  of the housing  12 . The outer surface  60  of the rack  14  comprises a cylindrical surface portion  66  which is diametrically opposite the rack teeth  64 . 
     The steering gear  10  further includes a yoke  70 , a yoke plug  90 , a yoke spring  110 , and a lock nut  120 . The yoke  70  is centered on the yoke axis  38  and is disposed in the yoke chamber  42 . The yoke  70  has a cylindrical outer surface  72  and first and second opposite end surfaces  74  and  76 , respectively. The outer surface  72  is complimentary to the inner surface  40  of the yoke chamber  42 . The first end surface  74  includes a concave surface  78  centered on the yoke axis  38 . A recess  80  is formed in the concave surface  78  and is centered on the yoke axis  38 . 
     The second end surface  76  of the yoke  70  includes an annular spring cavity  82  which is centered on the yoke axis  38  and defined by a cylindrical side wall  83  and an end wall  84 . A cylindrical spring pilot  86  projects from the end wall  84  and into the spring cavity  82 . The spring pilot  86  is centered on the yoke axis  38  and includes first and second pilot surfaces  87  and  88  which further define the spring cavity  82 . 
     The yoke plug  90  is centered on the yoke axis  38  and is disposed in the yoke chamber  42  in the housing  12 . The yoke plug  90  includes an outer surface  92  having external threads  94  which mate with the threaded portion  44  of the inner surface  40  of the yoke chamber  42 . The yoke plug  90  has an inner end wall  96  and an opposite outer end wall  98 . The yoke plug  90  includes a cylindrical undercut portion  100  which is centered on the yoke axis  38  and disposed between the inner end wall  96  and the outer end wall  98 . A hexagonal inner surface  102  is centered on the yoke axis  38  and extends from the undercut portion  100  to the outer end wall  98 . The outer end wall  98  extends radially between the hexagonal inner surface  102  and the outer surface  92  of the yoke plug  70 . 
     The lock nut  120  is centered on the yoke axis  38  and is disposed in the yoke chamber  42 . The lock nut  120  includes an outer surface  122  having external threads  124  that mate with the threaded portion  44  of the inner surface  40  of the yoke chamber  42 . The lock nut  120  has an inner end wall  126  and an opposite outer end wall  128 . The lock nut  120  further includes a hexagonal inner surface  130  which extends axially through the lock nut, between the inner and outer end walls  126  and  128 . The inner and outer end walls  126  and  128  extend radially between the inner surface  130  and the outer surface  122  of the lock nut  120 . 
     The yoke spring  110  is centered on the yoke axis  38  and is disposed between the yoke  70  and the yoke plug  90 . The yoke spring  110  comprises a helical spring which fits over the spring pilot  86  on the yoke  70 . A first end  114  of the yoke spring  110  engages end wall  84  of the yoke  70 . A second end  112  of the yoke spring  110  engages the inner end wall  96  of the yoke plug  90 . The yoke spring  110  biases the yoke  70  toward the rack  14 . 
     The inner end wall  126  of the lock nut  120  is in abutting engagement with the outer end wall  98  of the yoke plug  90 . The lock nut  120  helps to prevent the yoke plug  90  from loosening or becoming unscrewed. A thread sealant (not shown) may be applied to the threads  94  on the yoke plug  90 . The sealant helps to seal the yoke chamber  42  from the outside environment. The sealant may also help to prevent the yoke plug  90  from loosening or becoming unscrewed. 
     The hexagonal inner surfaces  102  and  130  of the yoke plug  90  and the lock nut  120 , respectively, allow the yoke plug and the lock nut to be tightened or loosened by tools (not shown) such as hexagonal wrenches. The hexagonal inner surface  130  of the lock nut  120  has larger internal dimensions than the hexagonal inner surface  102  of the yoke plug  90 . This allows a tool to extend through the hexagonal inner surface  130  of the lock nut  120  and be inserted into the hexagonal inner surface  102  of the yoke plug  90 . The tool can thus be rotated to tighten or loosen the yoke plug  90  when the lock nut  120  is positioned in the yoke chamber  42  adjacent to the yoke plug without tightening or loosening the lock nut  120 . 
     The external threads  94  of the yoke plug  90  and the external threads  124  of the lock nut  120  have the same crest diameter, root diameter, and pitch. This allows the yoke plug  90  and the lock nut  120  to be made concurrently, from a single piece of material. As illustrated in FIG. 3, a blank  200 , such as a piece of unmachined cylindrical stock material, is provided. The blank  200  is made of a metal material, such as steel or aluminum, and includes an axis  202  and an end portion  204 . 
     As illustrated in FIG. 4, the blank  200  is machined by known means to form outer cylindrical surfaces  206  and  208 , respectively, of a yoke plug portion  210  and a lock nut portion  212  of the blank  200 . The yoke plug portion  210  and the lock nut portion  212  are centered on the axis  202  and separated by a first portion  214  of the blank  200 . A second portion  216  separates the yoke plug portion  210  from the remainder of the blank  200 . External threads  218  (FIG. 5) are then machined on the outer surfaces  206  and  208  of the yoke plug portion  210  and the lock nut portion  212 , respectively. 
     As illustrated in FIG. 6, the blank  200  is next machined to form first and second inner cylindrical surfaces  220  and  222  which are centered on the axis  202 . The first cylindrical surface  220  has a first diameter and extends from the first portion  214  into the yoke plug portion  210 . The second cylindrical surface  222  has a second diameter, greater than the first diameter, and extends from the end portion  204  of the blank  200  through the lock nut portion  212  to the first cylindrical surface  220 . A tapered portion  224  may extend between the first and second cylindrical surfaces  220  and  222 . 
     The first and second cylindrical surfaces  220  and  222  are then finished to form a hexagonal inner surface  230  (FIG. 7) of the yoke plug portion  210  and a hexagonal inner surface  232  of the lock nut portion  212 . An undercut portion  234  (FIG. 8) is then machined in the yoke plug portion  210 . 
     The first and second portions  214  and  216  are then removed, thus separating the yoke plug portion  210  (FIG. 9) and the lock nut portion  212  from the blank  200  and from each other. As a result, a yoke plug  240  and a lock nut  242  are produced. The yoke plug  240  and the lock nut  242  in FIG. 9 are identical to the yoke plug  90  and the lock nut  120  of FIG.  2 . Thus, the yoke plug portion  210  and the lock nut portion  212  are machined like the yoke plug  90  and the lock nut  120 , respectively. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.