Rack and Pinion Steering Gear

This invention relates to a rack and pinion steering gear for an automotive vehicle.

The rack and pinion steering gear disclosed herein includes an arrangement which yieldably maintains the rack in meshing engagement with the pinion. Because a rack and pinion steering apparatus is subjected to road stresses, the rattling effect of these stresses sometimes causes the pinion to become separated from the rack a very small amount, thereby changing the steering "feel" of the vehicle operator. Such a condition is obviously undesirable, and many arrangements have been suggested in the past to maintain the rack and pinion in meshing engagement. The arrangement disclosed in this application solves this problem in a better and a more cost-effective way than the apparatus known to the prior art.

The invention disclosed herein also includes a novel bearing arrangement which supports the pinion for rotation. This pinion bearing arrangement not only accounts for an axial thrust to which the pinion shaft is subjected when it is in use in a motor vehicle, but it is also designed so that substantially the same components may be used in both the manual rack and pinion steering gear disclosed herein, and the power rack and pinion steering gear, disclosed in copending application Ser. No. 642,280, filed Dec. 19, 1975, owned by the assigned of the present invention and incorporated herein by reference. The rack, the pinion, the housing, and the bearings are common to both the manual and the power rack and pinion mechanisms, and only a few additional components, such as a rotary valve and a manifolding fluid motor arrangement, need be added to the basic manual design in order to provide a power assist capability.

Therefore, an important object of our invention is to provide an improved capability for yieldably maintaining the rack in meshing engagement with the pinion in a rack and pinion steering gear.

Another important object of our invention is to provide an improved bearing arrangement for supporting the pinion and pinion shaft in the cross bore of a rack and pinion power steering gear.

Still another important object of our invention is to assure that all the component parts used in our power steering gear are also usable in a corresponding power rack and pinion gear, the power gear requiring only a few additional components to provide a power assist to the vehicle operator.

FIG. 1 is a fragmentary, longitudinal cross-sectional view of a power steering gear made pursuant to the teachings of our present invention;

FIG. 2 is a fragmentary, cross-sectional view taken substantially along lines 2--2 of FIG. 1;

FIG. 3 is a cross-sectional view taken substantially along lines 3--3 of FIG. 1.

Referring now to the drawings, a rack and pinion gearing generally indicated by the numeral 10 includes a housing 12 which defines a longitudinal bore 14 and cross bore 16 intersecting the longitudinal bore 14. The longitudinal bore 14 is stepped to define a larger diameter portion 18 and a smaller diameter portion 20. A plug 22 is received in the open end of the larger portion 18 of the bore 14 and is provided with an aperture 24 in which an annular bearing 26 is received. Another annular bearing 28 is received in the smaller diameter portion 20 of the bore 14, and a portion of the circumferential wall 30 of the bearing 28 is cut away as at 32 to define an opening 34 at the intersection of the cross bore 16 and the longitudinal bore 14. The side of the angular bearing 28 opposite the opening 34 is provided with a substantially flat surface 36 which covers a groove 38 provided in the wall of the smaller portion 20 of the bore 14. A leaf spring 40 is received in the groove 38 and extends substantially parallel to the axis of the longitudinal bore 14. The opposite ends 42, 44 of the leaf spring 40 bear against the annular bearing 28, and the mid portion 46 of the spring 40 engages the bottom of the groove 38, so that leaf spring 40 exerts a yielding force on the bearing 28, urging the latter upwardly viewing FIG. 2. The right-hand end, viewing FIG. 1, of the annular bearing 28 terminates in a radially projecting lip 48, one edge 50 of which faces the shoulder 52 defined between the larger and smaller diameter portion of the bore 14. A snap ring 54 engages the opposite face 56 of the lip 48 to thereby maintain the bearing 28 in the position illustrated in the drawings.

A rack 58 is slidably supported in the longitudinal bore 14 by the bearing 26 in the plug 22 and by the bearing 28. The opposite ends 60, 62 of the rack 58 extend from the corresponding ends of the bore 14 and are operatively connected to the right and left wheels, respectively, of the vehicle in a manner well known to those skilled in the art. The ends 60, 62 of the rack 58 are protected by conventional boots 64, 66.

A pinion assembly generally indicated by the numeral 68 is rotatably mounted in the cross bore 16. Assembly 68 includes a pinion shaft 70 which extends from the end of the bore 16 and a pinion 72 which is fixed to the shaft 70 and which is received in the opening 34 of the annular bearing 28 at the intersection of the cross bore 16 and the longitudinal bore 14. The teeth on the pinion 72 mesh with the teeth 74 on the rack 58, and the spring 40 bearing against the annular bearing 28 yieldably maintains the teeth 74 of the rack 58 in meshing engagement with the teeth of the pinion 72. The shaft 70 is operatively connected to the vehicle steering wheel, so that the latter, and therefore the pinion 72, is rotated in a clockwise direction when a right-hand turn is effected and a counterclockwise direction when a left-hand turn is effected.

The pinion assembly 68 is rotatably supported in the cross bore 16 by first bearing means generally indicated by the numeral 76 on one side of the intersection between the cross bore 16 and longitudinal bore 14 and by bearing means generally indicated by the numeral 78 on the opposite side of the intersection between the bores 14 and 16. The bearing means 78 is a conventional roller bearing and will not be described in further detail herein. The cross bore 16 is stepped to define a smaller diameter portion 80, and a larger diameter portion 82 with a shoulder 84 therebetween. Bearing means 76 includes a hardened bearing race 86 having an annular portion 88 which is press fitted on the pinion shaft 70 and which carries a radially extending portion 90 which projects into the larger diameter portion of the bore 82. Two sets of bearing elements 92, 94 are located between opposite sides of the radially extending portion 90 of the bearing race 86, a second bearing race 96, which is disposed against the shoulder 84, and a third bearing race 98. The bearing race 98 is retained in the position illustrated in the drawings by an annular lip 100 which projects from a cover member 102 which closes the open end of the bore 16 through which the pinion shaft 70 extends. The bearing races 90, 96 and 98, and bearing elements 92 and 94, are designed to take axial thrusts exerted on the pinion shaft 70. The shaft 70 is supported for rotation by the bearing means 78 and by bearing elements 104 which are located between the annular portion 88 of bearing race 86 and the smaller portion of the bore 16. The ends of the bearing elements 104 rest against the opposite side of the bearing race 96.

It should be noted that the manual power steering unit illustrated in the drawings may also be manufactured with a power assist using the same basic components illustrated in the figures, by adding a few additional components to provide the power assist. For example, the cover 102 with the lip 100 replaced by valve housing having a lip to retain the bearing race 98, and a manifolding arrangement may be placed in the larger diameter portion 18 of the longitudinal bore 14, between the rack 58 and the wall of the bore 14. Such a construction is disclosed in the aforementioned copending U.S. patent application Ser. No. ACSG 75-74A, owned by the assignee of the present invention and incorporated herein by reference.

In operation, when a right-hand turn is effected, the steering wheel, and therefore the pinion shaft 70, is rotated in a clockwise direction. Because of the meshing engagement with the pinion 72 and the rack 58, clockwise rotation of the pinion urges the rack 58 to the left viewing the Figure. Since the ends 60 and 62 of the rack 58 are connected to the left and right-hand wheels of the vehicle, respectively, movement of the rack 62 to the left pivots the wheels in a clockwise direction, therefore effecting the right-hand turn. On the other hand, a left-hand turn may be effected by rotating the steering wheel, and therefore the pinion shaft 70, in a counterclockwise direction, thereby urging the rack 58 to the right viewing the Figure, and pivoting the wheels in a counterclockwise direction, thereby effecting a left-hand turn. Throughout steering maneuvers, the leaf spring 40 bears against the flat portion 36 of the angular bearing 28 and exerts a yieldable load through the bearing 28 to the rack 58 to yieldably maintain the latter in meshing engagement with the pinion 72. This arrangement prevents undesirable "backlash" from occurring due to momentary separations between the pinion and the rack.