Steering Knuckle Assembly

This invention relates to motor vehicle suspension components and particularly, to a steering knuckle assembly adapted to support a front axle.

Conventional steering knuckles are typically constructed as one-piece forged or cast units. These integral units provide a wheel bearing carrier, torque arms for supporting a disc type brake caliper, and points of attachment for suspension joints. Although these steering knuckles perform satisfactorily, it is desirable to provide enhanced structural and cost optimization of the steering knuckle assembly structure design. It is particularly desirable to reduce the weight of the steering knuckle assembly since weight reductions in this area provide the advantages of reducing both total vehicle weight and suspension unsprung mass. Overall weight reductions improve performance and fuel efficiency. Reductions in unsprung mass are desired since they are capable of providing significant improvements in vehicle ride and handling. It is a further objective to provide an improved steering knuckle assembly which can be produced at a lower cost than current designs. It is additionally desirable to provide an improved steering knuckle assembly which is adaptable to different motor vehicle applications. Another advantgeous feature is the provision of positive mechanical retention of a wheel bearing assembly within the steering knuckle assembly.

The above desirable improvements in a steering knuckle assembly are provided by this invention. In accordance with the preferred embodiment of this invention, a steering knuckle assembly is described which is formed from two mechanically attached components. A bearing carrier is preferably produced by conventional casting or forging processes and includes the wheel bearing carrier and torque reaction arms for mounting a disc brake caliper assembly. The remaining portion of the steering knuckle assembly is formed by a concave shell-shaped housing preferably manufactured using metal stamping processes. The stamped sheet metal housing may be reinforced with one or more internally disposed plates. Mounting bushings for suspension components such as ball joints, struts and steering links are installed and preferably welded to the stamped housing and reinforcing plates. This composite structure provides a significant weight advantage as compared with conventional designs primarily due to the use of stamped components. Use of such components further reduces total cost due to the relative cost advantage of tooling for stamped metal parts as compared to that for casting and machining operations. The steering knuckle assembly according to this invention is easily adapted to different motor vehicle applications merely by changing the configuration of the stamped housing, enabling the same cast or forged bearing carrier component to be used for various applications. As assembled, the steering knuckle assembly according to a preferred embodiment of this invention mechanically traps the wheel bearing assembly within the steering knuckle. Prior art steering knuckle constructions conventionally employ only interference or press fit engagement of these components. The means for retaining the wheel bearing assembly within the steering knuckle assembly according to this invention is therefore more secure and reliable than that provided by prior art designs.

Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.

FIG. 1 is a perspective view of a steering knuckle assembly in accordance with this invention shown from an inboard viewing position and shown with associated components including a cartridge-type wheel bearing, a disc brake rotor, and a drive hub;

FIG. 2 is an exploded perspective view of the steering knuckle assembly according to this invention showing the components thereof in unassembled positions and further showing associated components including a hub, disc brake rotor, brake caliper, and several suspension components; and

FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1 showing the various components of the steering knuckle assembly with associated suspension components.

A steering knuckle assembly in accordance with this invention is shown in the drawings and is generally designated by reference character 10. The primary components of steering knuckle assembly 10 are knuckle housing 12 and bearing carrier 14. Steering knuckle assembly 10 is designed to rotatably mount disc brake rotor 16 and hub 20, and provide a mount for disc brake caliper assembly 18, which is made of caliper 22 and shoes 24. Steering knuckle assembly 10 further provides mounting points for various suspension components, such as ball joints 38 and 40, and steering link 42. Alternately, knuckle assembly 10 could be configured to accept other types of suspension components such as strut type suspension units, etc. Steering knuckle assembly 10 described and illustrated herein is intended for use with a driven axle. The novel features of this invention, however, are also applicable to non-driven axle configurations.

Bearing carrier 14 is preferably made by a casting or forging process. Bearing carrier 14 includes an axially elongated internal bore 26 which is dimensioned to accept cartridge wheel bearing assembly 28. Preferably, the diameter dimensions are chosen to provide slight interference between bore 26 and wheel bearing assembly 28 thereby providing "press fit"0 installation of the bearing. Although such installation is not necessary to fasten wheel bearing 28 within knuckle assembly 10 if the mechanical trapping feature described below is employed, a press fit is desirable to avoid rattling and provide accurate bearing alignment. Bore 26 terminates at its outboard end in a radially inward ridge which forms shoulder 30. The diameter of shoulder 30 is significantly less than the outer diameter of bearing assembly 28, so that the shoulder acts as an abutment to axially retain the wheel bearing from being withdrawn from bearing carrier 14. Bearing carrier 14 further includes an integrally formed pair of radially extending and angularly offset torque arms 32 and 34. Torque arms 32 and 34 are configured to accept disc brake caliper 22 and disc brake shoes 24. Torque arms 32 and 34 provide reaction points enabling caliper assembly 18 to exert a frictional retarding force upon disc brake rotor 16. Bearing carrier 14 further forms a radially extending flange 36 having a plurality of threaded bores 44 therethrough. Threaded bores 44 are radially spaced to encircle bore 26.

Steering knuckle housing 12 is preferably formed from sheet metal stock. Housing 12 could be formed by a progressive die metal stamping process wherein parts are moved from one work station to the next as they are formed from metal blanks to finished parts. Since housing 12 requires a considerable degree of deformation of the metal, mild steel is a preferred material. Housing 12 is formed in the shape of a concave shell and includes a generally flat center surface 46, and a peripheral edge flange portion 48 extending generally transverse from the center surface. Within center surface 46 is central aperture 50. Aperture 50 preferably has a diameter or a cross-sectional dimension smaller than the outer diameter of cartridge wheel bearing assembly 28. This configuration provides another abutment for mechanically trapping cartridge wheel bearing assembly 28 within bearing carrier 14. Radially spaced around aperture 50 are a plurality of fastener bores 52 which are positioned for registry with threaded bores 44. A plurality of threaded fasteners 54 pass through fastener bores 52 and threadingly engage threaded bores 44 to thereby clampingly interconnect steering knuckle housing 12 to bearing carrier 14.

It is necessary during assembly of knuckle housing 12 to bearing carrier 14 to insure the desired relative angular relationship between these components. Therefore, it is desirable to provide means for preventing assembly unless the components are properly oriented. This feature is accomplished for the embodiment shown in the drawings by unevenly radially spacing bores 44 and 52 so that they become aligned only when the desired relationship exists. Other possible approaches include keying the parts together such that the parts interengage only in the desired assembled part position.

Additional fasteners 102 are provided which are threaded into bores 106 of bearing carrier 14. Fasteners 102 enable the attachment of a conventional splash shield (not shown) which aids in protecting the inboard surface of disc brake rotor 16 from contamination. Fasteners 102 further preferably include a rounded nose 108 which fits within bore 104 of knuckle housing 12. The bores 106 and 104 are preferably spaced to provide the alignment only when the components are properly assembled, as discussed above.

Typically, suspension components which are attached to steering knuckle assembly 10 include tapered shaft portions, which are inserted within correspondingly tapered bores of the knuckle. Threaded fasteners are used to tightly engage the tapered shaft within the tapered bore. In order to accommodate such fastening methods, several suspension mounting bushings 56, 58 and 64 are employed which are welded or otherwise connected to housing 12. These bushings include an internal tapered bore which corresponds to the taper of the associated suspension component. Typically, upper and lower suspension ball joints 38 and 40 are attached to the steering knuckle at points on a vertical or nearly vertical axis. Such positioning enables steering rotation of the associated wheel about that axis. In order to enhance the strength of engagement between bushings 56 and 58, and knuckle housing 12, it is further desirable to install upper and lower ball joint bushing reinforcing plates 60 and 62 respectively, which are welded or otherwise attached to the inside surface of steering knuckle housing 12. Preferably, flange 48 and the reinforcing plates are welded to bushings 56 and 58 at axially spaced positions to enhance the structural integrity of the fastening of these components. In order to provide additional reinforcing of the knuckle housing 12 structure, reinforcing plates 60 and 62 may be extended radially inward toward central bore 50 and further may be provided with bores which are collinear with bores 52. This configuration enables threaded fasteners 54 to clampingly engage the reinforcing plates.

Motor vehicle steering is provided by movement of steering link 42 which causes knuckle assembly 10 and the attached wheel to pivot about a vertical axis. In order to achieve steering movement, it is necessary to mount a steering link attaching point a radial distance from the axis extending between upper and lower ball joint bushings 56 and 58. A mounting location for steering link 42 is provided by forming peripheral edge flange 48 so that it becomes pinched together thereby forming spaced apart generally parallel surfaces, as best shown in FIGS. 1 and 2. Steering link bushing 64 is installed between these surfaces of flange 48, and bores are provided therethrough to enable attachment of steering link 42. Additional reinforcement of knuckle housing 12 near the point of attachment of steering link bushing 64 is provided by steering link bushing reinforcing plate 66 which is welded to flange 48 near bushing 64.

Wheel bearing assembly 28, preferably employed in connection with steering knuckle assembly 10, is a cartridge-type bearing assembly. These types of bearing assemblies are integral units which have permanently assembled inner and outer races. Wheel bearing assembly 28 is sealed from the environment by inner and outer bearing seals 68 and 70. Preferably, seals 68 and 70 are identical, thereby enabling reversible installation of bearing 28. An additional seal 96 is preferably provided which is press fit into knuckle housing aperture 50. Seal 96 includes sealing lips which make sliding contact with drive shaft 72 thereby further acting to prevent contamination of wheel bearing assembly 28. Seals 68 and 70 preferably sealingly contact seal 96 and hub 20 respectively. Drive shaft 72 typically would include one or two constant velocity type universal joints 74. Universal joints 74 permit a degree of relative angular disalignment between portions of drive shaft 72, enabling suspension travel without damaging the drive shaft. Drive shaft 72 further forms an extending splined shaft 78 having a threaded end 80. Hub 20 forms an internal splined surface which corresponds and mates with the splines of shaft 78. Hub 20 further forms a radially extending flange 82 which provides a mounting location for a plurality of wheel mounting studs 84. Hub 20 has a cylindrical surface or nose 86 which preferably frictionally engages the inner race of cartridge wheel bearing assembly 28 when these parts are assembled.

Disc brake rotor 16 may be a conventional integral unit or preferably a composite type having a stamped sheet metal inner hub 88 with an outer cast rotor surface 90. The composite configuration of rotor 16 provides a more mass efficient unit. Hub 88 includes a plurality of radially spaced bores 92 which receive wheel mounting studs 84.

The assembly and operation of steering knuckle assembly 10 will now be described in detail. The assembly of the various components is best explained with particular reference to the exploded pictorial view of FIG. 2. During initial assembly, cartridge bearing assembly 28 is pressfit within bore 26 of bearing carrier 14. Due to the presence of shoulder 30, it is necessary to load and press cartridge wheel bearing assembly 28 from the inboard side of bearing carrier 14. Bearing assembly 28 is depressed within bore 26 until it engages shoulder 30 which prevents further displacement.

Steering knuckle housing 12, having reinforcing plates 60, 62 and 66 welded thereto, is loaded into position such that fastening bores 52 are aligned with threaded bores 44. Thereafter, threaded fasteners 54 are threadably installed, thereby fixing these two components. Since central aperture 50 preferably has a radial dimension smaller than the diameter of the outer race of cartridge wheel bearing 28, the bearing becomes trapped between abutments formed by steering knuckle housing 12 and shoulder 30 of bearing carrier 14. Bearing 28 is therefore retained within steering knuckle assembly 10 both by press fit and mechanical trapping engagement. This fastening approach provides more secure engagement of wheel bearing assembly 28 than according to prior art designs wherein a press fit is the only mechanism used to secure the wheel bearing. Seal 96 is press fit into aperture 50 of housing 12. Hub 20 is preferably press fit into the inner race of cartridge bearing assembly 28. The entire assembly becomes mounted to the motor vehicle by threadingly attaching ball joints 38 and 40, and steering link 42 to the associated bushings attached to steering knuckle housing 12. Drive shaft 72 is installed such that splined portion 78 thereof passes through and engages within a correspondingly splined internal bore of hub 20. Finally, rotor 16, caliper 22 and brake shoes 24 are installed.

While the above description constitutes the preferred embodiments of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.