WO2012174185A1

WO2012174185A1 - Steering knuckles with integrated arms

Info

Publication number: WO2012174185A1
Application number: PCT/US2012/042362
Authority: WO
Inventors: Jeremy CZANSTKE
Original assignee: Daimler Trucks North America Llc
Priority date: 2011-06-15
Filing date: 2012-06-14
Publication date: 2012-12-20

Abstract

Exemplary steering knuckles described herein can comprise a hub, a spindle, a tie-rod arm, and a steering arm integrated into a one-piece casting. The hub can comprise a toroidal shaped inner surface opposite the spindle with an annular recess around the toroidal shaped inner surface. The steering arm can comprise a yoke portion, a steering system connection portion, and a recessed opening through the steering arm between the yoke portion and the steering system connection portion. The tie-rod arm can comprise a yoke portion, a tie-rod connection portion, and a downward facing recess between the yoke portion and the tie-rod connection portion.

Description

STEERING KNUCKLES WITH INTEGRATED ARMS

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. Provisional Application No. 61/497,430, entitled "STEERING KNUCKLES WITH INTEGRATED ARMS" and filed June 15, 2011, which is incorporated herein by reference.

FIELD

This disclosure relates to steering systems for land vehicles.

BACKGROUND

Conventional steering knuckles comprise an assembly of two or more forged components that are secured together. In some examples, a hub, a spindle, and one or more arms are forged separately and then assembled together to form a steering knuckle.

SUMMARY

Exemplary steering knuckles described herein can comprise a monolithic casting comprising a hub, a spindle, a tie-rod arm, and a steering arm. The hub can comprise a toroidal shaped inner surface opposite the spindle. The hub can further comprise an annular recess around the toroidal shaped inner surface.

The steering arm can comprise a yoke portion, a steering system connection portion, and an opening through the steering arm between the yoke portion and the steering system connection portion. The steering arm can further comprise an upward facing recess around the opening. The steering arm can comprise a substantially straight rear side wall and a curved front side wall that together define a variable tapering of the steering arm between a yoke portion and a steering system connection portion. The tie-rod arm can comprise a yoke portion, a tie-rod connection portion, and a downward facing recess between the yoke portion and the tie-rod connection portion. The knuckle can further comprise at least three ribs interconnecting the hub and the steering arm. In some of these embodiments, the steering arm can comprise a yoke and the at least three ribs comprises a first rib extending from the yoke to a front portion of the hub, a second rib extending from the yoke to a rear portion of the hub, a third rib extending from the yoke to a rear wall of the steering arm, and a fourth rib extending along the rear wall of the steering arm spaced from the yoke.

The knuckle can further comprise a thrust ring positioned around the spindle adjacent to the hub and configured to create an enclosed annular void between the thrust ring and the casting.

Some steering knuckle embodiments comprise a central hub, a front brake flange on a front side of the hub, a rear brake flange on a rear side of the hub, a spindle extending outwardly from a center of the hub, a tie-rod arm extending rearwardly from a bottom of the hub and the rear brake flange and comprising a lower yoke, and a steering arm extending inwardly from a top of the hub and tops of the front and rear brake flanges and comprising an upper yoke. In these

embodiments, the steering arm can define a plurality of apertures and recesses within the steering arm and the volume of solid material in the steering arm can be less than the volume of the apertures and recesses. In some of these embodiments, the plurality of apertures and recesses within the steering arm comprise a drag link mounting aperture, an upper yoke aperture, and a non-circular intermediate aperture between the drag link mounting aperture and the upper yoke aperture. The plurality of apertures and recesses can further comprise an upwardly facing intermediate recess surrounding the intermediate aperture.

The foregoing and other objects, features, and advantages of the disclosed embodiments will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a top-rear perspective view of an exemplary axle assembly having a left and right steering knuckles coupled to an axle.

FIG. IB is a bottom view of the axle assembly of FIG. 1 A.

FIG. 2 is an outer-rear perspective view of the left knuckle of FIG. 1A.

FIG. 3A is a rear elevation view of the left knuckle of FIG. 1 A.

FIG. 3B is a cross-sectional rear elevation view of left knuckle of FIG. 1 A, taken along a vertical plane containing the center axis of the spindle 12.

FIG. 4 is an inner-bottom perspective view of the left knuckle of FIG. 1 A.

FIG. 5 is a top plan view of the left knuckle of FIG. 1 A.

FIG. 6 is a cross-sectional bottom view of the left knuckle of FIG. 1A, taken along a horizontal plane containing the center axis of the spindle 12, and showing the bottom side of an upper yoke region.

FIG. 7 is an inner perspective view of the left knuckle of FIG. 1 A.

FIG. 8 is an outer-bottom-rear perspective view of the right knuckle of FIG.

1A.

FIG. 9 is an inner-top-front perspective view of the right knuckle of FIG. 1A.

FIG. 10A is a top plan view of the right knuckle of FIG. 1A.

FIG. 10B is a cross-sectional rear view of the right knuckle of FIG. 1A, taken along a vertical plane containing the center axis of the spindle 12.

FIG. IOC is an enlarged view of a portion of FIG. 10B showing a radiused transition region between the spindle and the hub.

FIG. 11 A is a perspective view of an exemplary thrust ring of the axle assembly of FIG. 1A.

FIG. 1 IB is a cross-sectional view of the thrust ring of FIG. 11 A.

FIG. 12 is a cross-sectional view of the thrust ring of FIG. 11 A engaged with a transition region between the spindle and the hub of the left or right knuckle of FIG. 1A. DETAILED DESCRIPTION

Described herein are embodiments of an axle assembly for a vehicle and embodiments of left and right steering knuckles with integrated arms. The following description is exemplary in nature and is not intended to limit the scope, applicability, or configuration of the invention in any way. Various changes to the described embodiments may be made in the function and arrangement of the elements described herein without departing from the scope of the invention.

As used herein, the terms "a", "an" and "at least one" encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus "an" element is present. The terms "a plurality of and "plural" mean two or more of the specified element. As used herein, the term "and/or" used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase "A, B, and/or C" means "A," "B," "C," "A and B," "A and C," "B and C" or "A, B and C." As used herein, the term "coupled" generally means physically coupled or linked and does not exclude the presence of intermediate elements between the coupled items absent specific contrary language.

As shown in FIGS. 1A and IB, an exemplary embodiment of a an axle assembly 2, such as a front axle assembly, for a vehicle, such as a class-8 on- highway truck, can include an axle 4, such as an I-beam as shown, a left steering knuckle 6 coupled to a left end of the axle and a right steering knuckle 8 coupled to a right end of the axle. The front axle assembly 2 can be coupled to the rest of the vehicle via, inter alia, a suspension system and a steering system (not shown). The left knuckle 6 can support a front left wheel of the vehicle and the right knuckle 8 can support a right front wheel of the vehicle. FIG. 1A shows an exemplary axle assembly 2 from the top-rear, and FIG. IB shows the exemplary assembly from the bottom.

As used herein, including in the claims, the terms "left", "right", "front", "rear", "top" and "bottom" refer to conventional portions of a vehicle in which the front axle assembly 2 and/or knuckles 6, 8 are configured to be installed, from the perspective of a driver of the vehicle. Thus, the left side is the driver's side in the United States, the right side is the passenger's side in the United States, the bottom is the portion of the vehicle closest to the ground, the front end is the leading end of the vehicle when the vehicle is traveling forward and the rear end is the leading end when the vehicle is traveling in reverse. The term "frontward" means toward the front and the term "rearward" means toward the rear. The term "upper" means toward the top and the term "lower" means toward the bottom. Similarly, the terms "inner" and "inwardly" mean toward a longitudinally extending vertical center plane of the vehicle that divides the vehicle into left and right halves, and the terms "outer" and "outwardly" mean away from the center plane and toward the left or right side of the vehicle.

As shown in FIGS. 2-7, the left steering knuckle 6 can be a monolithic (defined as formed as a single piece or of unitary one piece construction, as opposed to two or more pieces formed separately and later attached together) structure that comprises a hub 10, a spindle 12 extending outwardly from a central portion of the hub, an upper yoke 14 extending inwardly from an upper portion of the hub, a lower yoke 16 extending inwardly from a lower portion of the hub, a tie-rod arm 18 that extends rearwardly and inwardly from the lower yoke and the lower portion of the hub, and a steering arm 20 that extends inwardly from the upper yoke and the upper portion of the hub. Less desirably, the knuckles 6, 8 can be comprised of plural assembled pieces. As shown in FIGS. 2, 11A, 1 IB and 12, a pressure ring, or thrust ring, 22 can be positioned around the spindle 12 adjacent the hub 10.

As shown in FIGS. 8-10, the right steering knuckle 8 can be similar to the left steering knuckle 6, except that it is mirrored about the center plane of the vehicle and lacks the steering arm 20.

As shown in FIGS. 3B, 4, 7 and 9-10, the hub 10 of the knuckles 6, 8 can comprise a central portion 30 that supports the spindle 12 and a brake flange 32 that extends around the central portion 30. The central portion 30 can have a contoured inwardly facing surface 31, as shown in FIGS. 3B, 6, 7, 9 and 10B. The surface 31 can be generally toroidal- shaped (a shape similar to the outer surface of half of a toroid). The central portion 30 can also include a cone-shaped central recess 42 and an annular recessed channel 37 that surrounds the surface 31 adjacent the brake flange 32. The brake flange 32 can include a front portion 33 and a rear portion 35, and a plurality of apertures 34 for mounting other components, such as brakes, to the knuckles. One or more of the apertures 34 can interrupt the toroidal shape of the surface 31, as shown in FIG. 7. The hub 10 can be supported by the upper yoke 14 and the lower yoke 16.

The inward-facing side of the hub 10 and the yokes 14, 16 can define a hollowed out region, or internal core, 36, as shown in FIGS. 3A, 3B, 4, 7, 9 and 10B. As shown in FIGS. 3B, 6, 7, 9 and 10B, the internal core 36 can include the annular recessed channel 37, an upper cavity 38 between the upper yoke 14 and the hub 10, and a lower cavity 40 between the lower yoke 16 and the hub, and the central recess 42 extending into the center of the central portion 30 of the hub. The hollow internal core 36 can help minimize the total volume of material in the hub 10, while maintaining sufficient structural strength in the knuckle between the yokes 14, 16 and the spindle 12.

As shown in FIGS. 3B and 10B, the upper and lower yokes 14, 16 can comprise annular wall structures that define aligned upper and lower apertures 15, 17 (the upper yoke 14 defines the upper aperture 15 and the lower yoke 16 defines the lower aperture 17), which can be used to mount the knuckles 6, 8 to the respective ends of the axle 4, as shown in FIGS. 1A and IB. The end portions of the axle 4 can be pivotably coupled to the yokes 14, 16 of the respective knuckles 6, 8 such that the knuckles can pivot about a central axis that extends through the center of the apertures 15, 17.

As shown in FIGS. 2, 4 and 7-9 , the tie-rod arm 18 can extend rearwardly and inwardly from the lower yoke 14 and the brake flange 32. The tie-rod arm 18 can include an annular wall or opening-defining structure 46 at a distal end portion that defines an aperture 47 for coupling the tie-rod arm 18 to a tie-rod (not shown). For example, a tie-rod can couple the tie-rod arm 18 of the left knuckle 6 to the tie- rod arm 18 of the right knuckle 8, such that the two knuckles move in unison.

The tie-rod arm 18 can further comprise a downward facing recess 48 (shown in FIGS. 4 and 8). The recess 48 can be positioned in a generally thicker, wider portion of the tie-rod arm 18 that is adjacent to the lower yoke 16. The recess 48 can open downwardly to prevent collection of water and reduce corrosion issues. The recess 48 can have a generally rectangular shape defined between an inner surface 51 of an inward wall 50, an inner surface 53 of an outward wall 52, a lower surface 55 of an upper wall 54, a front surface 56, and a rear surface 57. The rear surface 57 can be rounded and can be sloped to extend rearwardly moving from the upper surface 55 toward the lower perimeter of the recess 48. The upper surface 55 can have a perimeter that is smaller than the lower periphery. Like the internal core 36, the recess 48 can help minimize the total volume of material in the tie-rod arm 18, and thus reduce the overall weight of the knuckles, while maintaining sufficient structural strength in the tie-rod arm between the opening 47 and the lower yoke 16.

The walls 50, 52, 54 can form a generally "U" shaped cross-sectional profile when the arm 18 is cut at the recess 48 in a plane perpendicular to the front-rear direction. The walls 50, 52, 54 can provide sufficient structural integrity in the tie- rod arm 18 in the region of the recess 48 with a minimal cross-sectional area. As shown in FIGS. 4 and 8, additional recesses 58 and 59 can be defined at the juncture of the tie-rod arm 18 and the lower yoke 16 to further reduce the mass of the region and reduce stress concentrations. The recess 58 can be formed in a lower, outward facing surface of the junction between the arm 18 and the yoke 16, while the recess 59 can be formed in a lower, inward facing surface of the junction.

The lower region of the knuckles that comprises the tie-rod arm 18 and the lower yoke 16 can have a total mass that is about 20% to about 40% less than the total mass would be if this region did not include the recesses 48, 58 and 59 (i.e., if those recesses were filled in).

As shown in FIG. 5, the left knuckle 6 includes the steering arm 20 that extends inwardly from the upper yoke 14 and the hub 10. The steering arm 20 can include a steering system connection portion, which can comprise an annular wall structure 60 at a distal, inward end portion that defines an aperture 61 for coupling the steering arm 20 to a member of the steering system (not shown), such as a drag link. In many vehicles, the steering column and other portions of the steering system are located primarily on the left side of the vehicle, and thus the left knuckle 6 includes the steering arm 20 and the right knuckles 8 does not. In other vehicles, the steering system is located primarily on the right side of the vehicle, in which case the left knuckle 6 may not include the steering arm 20 and the right knuckle can include the steering arm. In other embodiments, both the left and right knuckles can include steering arms 20.

As shown in FIG. 5, the steering arm 20 can include an upwardly facing recess 62 in an intermediate portion of the steering arm between the upper yoke 14 and the annular wall structure 60. The recess 62 can be defined by an inner surface 65 of a front wall 64, an inner surface 67 of a rear wall 66, and an upper surface 69 of a lower wall 68. The recess 62 can be generally egg shaped, or tear drop shaped, having a larger diameter outward surface 71 and a smaller diameter inward surface 73 that forms an acute angle between the surfaces 65 and 66. The walls 64 and 66, and the surfaces 65 and 67, become closer together moving outwardly from the outward surface 71 toward the inward surface 73. The surfaces 65, 66, 71 and 73 extend away from one another moving upward from the lower surface 69 toward the outer perimeter of the recess 62.

The steering arm 20 can also include an aperture 70 within the recess 62 that extends through the lower wall 68 adjacent the outward wall 71. The recess 62 and/or the aperture 70 can help reduce the volume a material in the steering arm 20 while maintaining sufficient structural strength in the steering arm to transfer forces between the steering system and the rest of the knuckle 6.

A wrist portion 72 of the steering arm adjacent the aperture 61 can have an increased width such that the wrist portion 72 has increased strength to resist loading from the drag link and reduce stresses due to bending and torsion.

The total volume of solid material in the steering arm and upper yoke region can be less than the volume of the apertures and the recesses in the steering arm and upper yoke region. The apertures and recesses of the steering arm and upper yoke region can comprise the drag link mounting aperture 61, the upper yoke aperture 14, the intermediate aperture 70, and the recess 62. The apertures and recesses can further comprise recesses 80, 82, 90 and 92 defined by the ribs adjacent to the upper yoke 14 (see FIGS. 5 and 6). The steering arm and upper yoke region can together form a generally right triangular shape when viewed from the top, (as shown by the dashed outline in FIGS. 5), with the front wall 64 generally forming the hypotenuse of the triangle, the rear wall 66 forming the longer leg of the triangle, and the outward surface of the brake flange 32 forming the shorter leg of the triangle. This asymmetric triangular shape can increase the moment of inertia of the steering arm and more optimally transfer loads between the hub 10, the upper yoke 14, and the distal aperture 61, with minimal total mass and stress.

As shown in FIGS. 5 and 6, the intersection region between the steering arm 20, the upper yoke 14 and the brake flange 32 can include a complex geometry designed to minimize mass while providing sufficient strength and stiffness to transmit forces between the steering system, the front axle 4, and the hub 10 of the left knuckle 6.

As shown in FIG. 5, the upper side of this intersection region can include a front rib 74, an intermediate rib 76, a rear rib 78, and an inward rib 79. The front rib 74 can extend outwardly from an outer front portion of the upper yoke 14 to the front portion 33 of the brake flange 32. The intermediate rib 76 can extend rearwardly and outwardly from a rear, outer portion of the yoke 14 to the rear portion 35 of the brake flange 32. The front rib 74, the outward portion of the yoke 14, and the intermediate rib 76 can define a recess 80 between them. The recess 80 can have a generally trapezoidal shape that is open in the outward direction along the break flange 32. The rear rib 78 can extend outwardly from the outer wall 66 of the steering arm 20 to the rear portion 35 of the brake flange 32. The inner rib 79 can extend rearwardly and inwardly from a rear, inward portion of the upper yoke 14 to the rear wall 66 and the rear rib 78. The intermediate rib 76, a rear portion of the yoke 14, the inward rib 79 and the rear rib 78 can define another recess 82 between them. The recess 82 can have a generally triangular, or dome-triangular, shape, and can have a small lateral opening at an outward end between the intermediate rib 76 and the rear rib 78.

The ribs 74, 76, 78, 79, the upper yoke 14, and recesses 80 and 82 at the intersection region between the upper yoke 14, steering arm 20 and the hub 10 can provide sufficient strength and stiffness to transfer loads while minimizing the amount and weight of material in the region. The combination of the front rib 74 and the intermediate rib 76 can help distribute loads from the yoke 14 around the front and rear portions 33, 35 of the break flange 32, rather than being concentrated in the intermediate part of the hub adjacent the recess 80. The rear rib can direct part of the loads from the steering system directly from aperture 61 to the hub 10 without passing through the yoke 14. In some embodiments, the ribs 74, 76, and 79, along with the walls 64 and 66, can form a generally "X" shaped pattern with the yoke 14 forming the middle of the "X" shape. This "X" shaped rib/wall pattern can help optimally distribute forces throughout the dashed triangular region that includes the steering arm 20, yoke 14 and the intersection region.

As shown in FIG. 6, the lower side of the intersection region between the upper yoke 14, steering arm 20, and hub 10 can also include a complex geometry. The lower side of the intersection region can include a front rib 84, an intermediate rib 86, a rear rib 88, an inward rib 89, and recesses 90 and 92 that correspond in position with the ribs on the upper side of this region. The recess 90 can have a generally trapezoidal shape that is open at an outward side facing the break flange 32. The recess 90 can form part of the upper cavity 38 of the internal core 36 (see FIG. 3B). The recess 92 can have a generally triangular shape, with a front vertex interrupted by the yoke 14 and an outward vertex interrupted by a feature 93 that forms an internal bolt hole in the rear portion of the break flange 35. Similar to the aperture 70 and the recess 62 (see FIG. 5), in some embodiments, an aperture (not shown) can extend between, or replace, the recesses 82 (FIG. 5) and 92 (FIG. 6), and/or an aperture (not shown) can extend between, or replace, the recesses 80 (FIG. 5) and 90 (FIG. 6).

The exemplary generally right triangular shaped region (dashed region in FIG. 5) comprising the steering arm 20, the upper yoke 14, and the intersection region can have a total mass that is about 40% to about 50% less than what the total mass would be if this region did not include the recess 62, the aperture 70, the recesses 80, 82, 90, 92, and others described above. As shown in FIGS. 2, 3 A and IOC, the intersection between the spindle 12 and hub 10 can include a curved transition area 98 to reduce stress concentrations and increase fatigue strength at this region. The curved transition area 98 can include a parabolic shaped fillet 99 (see FIGS. IOC and 12).

In addition, a pressure ring 22 can be included that is positioned around the spindle 12 at the transition area 98. As shown in FIGS. 11A and 1 IB, the ring 22 can have a first annular exterior peripheral edge or side wall surface 100, a second annular end wall surface 102, a third interior annular side wall surface 104 that can be of a right cylindrical shape, a fourth annular end wall surface 106 opposed to the surface 102, and a fifth interior annular surface 108 that extends between surfaces 104 and 106. The surface 108 can have an increasing radius moving from surface 104 toward surface 106 and can define a frustoconical void. The first and second surfaces 100, 102 can be exposed and not contact the transition area 98, while the third surface 104 can contact the spindle 12 and the fourth surface can contact the hub 10 when the ring 22 is installed on the knuckle, as shown in FIGS. 2 and 12.

The third surface 104 that contacts the spindle 12 can have a width that is larger than the width of the fourth surface 106 that contacts the hub 10; however, the radius of the third surface 104 can be smaller than the radius of the fourth surface 106. In this way, the contact area between the surface 104 and the spindle 12 can be

approximately equal to, or slightly larger or smaller than, the contact area between the surface 106 and the hub 10. The fifth surface 108 can extend between the third and fourth surfaces adjacent the fillet 99 without contacting the knuckle. The first and second surfaces 100, 102 can alternatively be one common surface with a curvature. When the ring 22 is installed on the spindle 12, the ring can help transfer forces between the hub 10 and the spindle 12 without passing through the fillet 99, thereby and reducing stress on the transition area 98 between the hub 10 and spindle 12. The transitions between the fifth surface 108 and the third and fourth surfaces 104, 106 can be slightly radiused to reduce stress concentrations at those locations. In some embodiments, the ring 22 can reduce the stress on the transition area 98 to about the same as if the radius of the fillet 99 were about five times greater than shown in FIG. IOC. For example, in some embodiments, the effective radius of the parabolic fillet 99 can be about 2.9 mm, and the addition of the ring 22 can create an effective radius of about 15 mm.

As shown in FIGS. 7 and 9, the toroidal shape of the inner surface 31 of the central portion 30 of the hub 10 can further reduce the total mass of the hub 10 while optimally minimizing stress and maintaining sufficient strength and stiffness to support the spindle 12. Because most of the stress from spindle forces is transferred to the hub 10 adjacent the transition area 98, the toroidal central portion 30 of the hub 10 can include more material adjacent the transition area 98 and less material adjacent the central cavity 42 and the recessed channel 37. The mass of the central portion 30 of the hub 10 can be about 25% to about 50% less than if the recessed channel 37 and the central cavity 42 were filled in.

The knuckles 6, 8 and the rings 22 can be comprised of metallic material including one or more different metals and/or other components. In some embodiments, the knuckles 6, 8 can be comprised of iron, such as ASTM

897/897M-06 austempered ductile iron grade 900/650/09. In such embodiments, the knuckle material can have an ultimate strength of at least 900 N/mm , a yield strength of at least 650 N/mm , a percent elongation in 50 mm of at least 9%, and an impact energy of at least 100 J. The rings 22 can be comprised of steel, such as SAE/AISI 1045 steel, and can have an ultimate strength of from 550-750 N/mm², a yield strength of about 280 N/mm , a minimum percent elongation of about 10% and a minimum percentage reduction in area of about 25%.

In some embodiments, some of the features described above can be included while other features are not included. For example, the right knuckle 8 can include the tie-rod arm 18, but not the steering arm 20. For another example, in some embodiments of the left knuckle 6, the steering arm 20 can include the recess 62 but not the aperture 70. In some embodiments, the steering arm 20 can be free of both the recess 62 and the aperture 70, but can still include the ribs and recesses in the intersection region adjacent the upper yoke 14. In some embodiments, the tie-rod arm 18 may not include the downwardly facing recess 48, while in other

embodiments, the recess 48 can include a cored aperture passing through the upper wall 54. Similarly, the size, shape and/or material of each of the features disclosed herein can be varied to some degree without departing from the purpose of the features. Thus, this disclosure should be understood to include many different embodiments that include all the different possible combinations and subcombinations of the features described herein and in varying sizes, shapes and materials.

Depending upon the material used and the size and/or the presence of the various recesses, apertures, ribs and other features described above, the total mass of the left knuckle 6 can be less than 40 kg, less than 30 kg, and/or less than 20 kg, such as about 18.4 kg. Similarly, the total mass of the right knuckle 8 can be less than 40 kg, less than 30 kg, less than 20 kg, and/or less than 15 kg, such as about

14.8 kg. The rings 22 can have a mass of about 0.2 kg to about 0.4 kg each, such as about 0.316 kg each. The overall reduction in mass achieved with the described embodiments can result in a front steer axle assembly 2 for a class-8 on-highway truck that weighs up to, or greater than, 50 pounds less than a conventional front steer axle assembly.

The knuckles 6, 8 described herein comprise monolithic castings and can include detailed, highly contoured geometries that can be difficult to create using traditional forging methods. Instead, the knuckles are desirably formed using a casting process that allows for the formation of more intricate geometries and thinner walls. For example, the inner surface of the hub 10 can include several intricate cavities and apertures that may be difficult or impossible to create with traditional forging methods, but are possible with casting methods. In addition, the plurality of ribs and recesses of the arms and yoke regions can also be made possible by using a casting method.

An exemplary casting method for creating the described embodiments can include "sand casting" and/or the use of an internal "sand core", which is not possible with forging methods. The use of an internal sand core can allow for the removal of large volumes of material from the inside of the knuckle geometry, such as at the internal core 36. Conventional casting methods can result in so-called "die- lock" when a portion of the die becomes physically inhibited, or trapped, by the geometry of a cast part and cannot be easily removed. With the use of a sand core, the portion of the die that would otherwise be trapped can be formed from sand- based material such that it can readily be broken down into smaller elements such that it can be removed from the cast knuckle. For example, the integration of the tie- rod arm 18 and the steering arm 20 with the yokes 14, 16 and the hub 10 in the left knuckle 6 can create the internal core area that would result in die-lock using traditional casting methods. But by using a sand core to form those portions of the knuckle, the sand core can readily be removed after the knuckle is cast.

In view of the many possible embodiments to which the principles disclosed herein may be applied, it should be recognized that the illustrated embodiments are only exemplary and should not be taken as limiting the scope of the disclosure.

Rather, the scope of the disclosure is defined by the following claims. We therefore claim all that comes within the scope of these claims.

Claims

We claim:

1. A steering knuckle comprising a hub, a spindle, a tie-rod arm, and a steering arm, the knuckle comprising a toroidal shaped inner surface of the hub opposite the spindle and an annular recess around the toroidal shaped inner surface.

2. The steering knuckle of claim 1, comprising a recessed opening through the steering arm between a yoke portion of the steering arm and a steering system connection portion of the steering arm.

3. The steering knuckle of either claim 1 or claim 2, comprising at least three ribs interconnecting the steering arm and the hub, the ribs comprising a first rib extending from an upper yoke to a front portion of the hub, a second rib extending from the upper yoke to a rear portion of the hub, a third rib extending from the upper yoke to a rear wall of the steering arm, and a fourth rib extending along the rear wall of the steering arm spaced from the upper yoke.

4. The steering knuckle of any one of claims 1-3, wherein the knuckle is a monolithic unitary one-piece cast knuckle.

5. A steering knuckle, comprising:

a monolithic casting comprising a hub, a spindle, a tie-rod arm, and a steering arm.

6. The knuckle of claim 5, wherein the hub comprises a toroidal shaped inner surface opposite the spindle.

7. The knuckle of claim 6, the hub further comprising an annular recess around the toroidal shaped inner surface.

8. The knuckle of any one of claims 5-7, wherein the steering arm comprises a yoke portion, a steering system connection portion, and an opening through the steering arm between the yoke portion and the steering system connection portion.

9. The knuckle of claim 8, wherein the steering arm further comprises an upward facing recess around the opening.

10. The knuckle of any one of claims 5-9, wherein the steering arm comprises a substantially straight rear side wall and a curved front side wall that together define a variable tapering of the steering arm between a yoke portion and a steering system connection portion.

11. The knuckle of any one of claims 5-10, wherein the tie-rod arm comprises a yoke portion, a tie-rod connection portion, and a downward facing recess between the yoke portion and the tie-rod connection portion.

12. The knuckle of any one of claims 5-11, the casting further comprising at least three ribs interconnecting the hub and the steering arm.

13. The knuckle of claim 12, wherein the steering arm comprises a yoke and the at least three ribs comprises a first rib extending from the yoke to a front portion of the hub, a second rib extending from the yoke to a rear portion of the hub, a third rib extending from the yoke to a rear wall of the steering arm, and a fourth rib extending along the rear wall of the steering arm spaced from the yoke.

14. The knuckle of any one of claims 5-13, further comprising a thrust ring positioned around the spindle adjacent to the hub, the thrust ring configured to create an enclosed annular void between the thrust ring and the casting.

15. A steering knuckle comprising a central hub, a front brake flange on a front side of the hub, a rear brake flange on a rear side of the hub, a spindle extending outwardly from a center of the hub, a tie-rod arm extending rearwardly from a bottom of the hub and the rear brake flange and comprising a lower yoke, and a steering arm extending inwardly from a top of the hub and tops of the front and rear brake flanges and comprising an upper yoke;

wherein the steering arm defines a plurality of apertures and recesses within the steering arm and the volume of solid material in the steering arm is less than the volume of the apertures and recesses.

16. The knuckle of claim 15, wherein the plurality of apertures and recesses within the steering arm comprise a drag link mounting aperture, an upper yoke aperture, and a non-circular intermediate aperture between the drag link mounting aperture and the upper yoke aperture.

17. The knuckle of either claim 15 or claim 16, wherein the plurality of apertures and recesses further comprises an upwardly facing intermediate recess surrounding the intermediate aperture.

18. The knuckle of any one of claims 15-17, wherein the steering arm further comprises a first upper rib extending from the upper yoke to the front brake flange, a second upper rib extending from the upper yoke to the rear brake flange, and a third upper rib extending along a rear edge of the steering arm to the rear brake flange, wherein the upper ribs at least partially define at least two upper recesses in the steering arm adjacent to the upper yoke.

19. The knuckle of any one of claims 15-18, wherein the steering arm further comprises a first lower rib extending from the upper yoke to the front brake flange, a second lower rib extending from the upper yoke to the rear brake flange, and a third upper rib extending along a rear edge of the steering arm to the rear brake flange, wherein the lower ribs at least partially define at least two lower recesses in the steering arm adjacent to the upper yoke.

20. The knuckle of any one of claims 15-19, wherein the knuckle is monolithic unitary one-piece knuckle.