Patent Application
20160159392
The present disclosure generally relates to steering knuckles for vehicles and, more particularly, to steering knuckles made from light weight materials like aluminum-based materials.
A steering knuckle, sometimes referred to as an upright or wheel carrier, rotatably holds a wheel and tire assembly and is connected to parts of the vehicle suspension and/or steering systems, such as control arms and tie rods. Because of its role in securely maintaining the wheels while the vehicle is being driven, a steering knuckle can be subjected to a number of stresses and forces acting upon it. In addition, some manufacturing processes involve press fitting a wheel bearing assembly into an opening in the steering knuckle that can introduce significant hoop or circumferential stresses in the part.
Traditionally, steering knuckles were made of cast iron or some other material possessing significant strength. These materials, however, are quite heavy and can add a fair amount of weight to the vehicle. Thus, it would be desirable to provide a steering knuckle that is strong enough to withstanding the various stresses and forces acting upon it, yet has a light weight construction in order to improve the fuel economy of the vehicle.
According to one aspect, there is a steering knuckle assembly for a vehicle, comprising a steering knuckle component and a reinforcing insert. The steering knuckle component is made of a first metal material and has a body portion and one or more attachment portions. The reinforcing insert is made of a second metal material and has an outer surface, an inner surface and a bearing opening, where the first metal material is lighter than the second metal material and the second metal material is harder than the first metal material. The steering knuckle component is at least partially formed around the reinforcing insert so that the outer surface of the reinforcing insert is encased in the first metal material and the inner surface of the reinforcing insert surrounds the bearing opening and forms a contact surface for a wheel bearing assembly.
According to another aspect, there is provided a method of forming a steering knuckle assembly for a vehicle. The method may comprise the steps of: positioning a reinforcing insert within a mold cavity of a die casting machine; introducing a molten aluminum-based material into the mold cavity of the die casting machine so that the molten material at least partially surrounds the reinforcing insert; applying pressure with the die casting machine to form a composite steering knuckle component with the integrally formed reinforcing insert; and removing the composite steering knuckle component from the die casting machine, wherein the integrally formed reinforcing insert includes an inner surface for receiving a wheel bearing assembly.
Preferred exemplary embodiments will hereinafter be described in conjunction with the appended drawings, wherein like designations denote like elements, and wherein:
A steering knuckle is a vehicle component that holds a wheel hub or spindle and is attached to various parts of the vehicle suspension and steering systems. More specifically, a steering knuckle rotatably holds a wheel hub or spindle and is typically connected to upper and lower control arms via corresponding ball joints, as well as a tie rod or other steering linkage. During manufacture of a steering knuckle assembly, a wheel bearing is sometimes press fit into an opening located towards the center of the steering knuckle. This press fitting may induce or otherwise result in hoop stresses, circumferential stresses, radial stresses and/or other types of stresses on the components involved (hereafter collectively referred to as ‘induced stresses’). Materials such as cast iron and steel are typically strong enough to withstand the induced stresses, however, they are quite heavy and can negatively impact the fuel economy of the vehicle. Lighter materials, like those based on aluminum, may not be strong enough on their own to withstand the induced forces and can crack or rupture upon press fitting the wheel bearing. The steering knuckle described herein is made from a lightweight material, such as an aluminum-based material, that is over-molded or cast around a reinforcing insert with an opening for receiving a press fit wheel bearing assembly. Therefore, the present steering knuckle assembly is lightweight, it uses an easy to manufacture press fitting for the wheel bearing, and it includes a reinforcing insert that is strong enough to withstand the various induced stresses.
Turning now to
Steering knuckle component 12 is designed to rotatably hold the wheel hub 26 while connecting to various components of the vehicle suspension and steering systems. According to the particular embodiment shown here, the steering knuckle component 12 has a multi-lobed configuration and includes a body portion 40, attachment portions 42, 44, 46, and an insert opening 48. Of course, other shapes, sizes, and configurations are certainly possible depending on the particular vehicle in which the steering knuckle component is used, as the drawing in
The body portion 40 makes up the majority of the steering knuckle component 12 and is designed to be strong enough to endure not only the induced stresses mentioned above, but also stresses caused by braking, cornering and/or other vehicle operations. The attachment portions 42, 44, 46 all extend from the body portion 40 and are designed to connect with the vehicle suspension or steering systems. For example, attachment portion 42, which can be in the shape of lobe or ear with an opening in the center, is intended to attach to an upper control arm (not shown); attachment portion 44 is designed for attachment to a lower control arm (not shown); and attachment portion 46 is intended for connection with a tie rod or some other linkage (not shown) that is part of the steering system. Attachment portions 42, 44, 46 can be used to attach or connect any suitable combination of suspension, steering or other components, including, but not limited to, control arms, steering arms, tie rods, shock absorbers, struts, ball joints, cams, bushings, bolts, bearings, etc. Insert opening 48 may be located towards the center of the body portion 40, and is sized to accommodate the reinforcing insert 14. In the embodiment of
The steering knuckle component 12 is preferably made out of a lightweight metal material, such as an aluminum-based material. As used herein, “aluminum-based material” broadly includes pure metals, metal alloys and/or any other materials wherein aluminum (Al) is the single largest constituent of the material on a wt % basis. This includes materials having greater than 50 wt % of aluminum, as well as those materials having less than 50 wt % of aluminum so long as aluminum is the single largest constituent. Some non-limiting examples of possible aluminum-based materials include, but are certainly not limited to, the following aluminum alloys: A356, A365, A367, A380, A383, B390, ADC10, ADC12, Aural-2, Silafont-36, and Catasil-37.
The reinforcing insert 14 is located within the body portion 40 of the steering knuckle component 12 and acts as a strengthened or reinforced sleeve for receiving the wheel bearing assembly 16. As mentioned above, there are a number of stresses (induced stresses and others) that may act upon the steering knuckle assembly 10, particularly in the area of the interface between the steering knuckle assembly 10 and the wheel bearing assembly 16. Aluminum-based materials are typically not strong or robust enough to withstand these forces by themselves, thus, the use of the reinforcing insert 14. According to one embodiment, the reinforcing insert 14 is placed within the mold cavity that is used to cast or otherwise form the steering knuckle component 12 so that the aluminum-based material of the steering knuckle can flow and solidify around the reinforcing insert, thereby locking it in place. A number of suitable processes may be used to perform this over-molding or casting operation, including different types of high pressure die casting (HPDC) and squeeze casting, as will be described below in more detail. In the exemplary embodiment shown in
The outer surface 60 is expected to come into contact with and be encased by molten aluminum-based or other material when the steering knuckle component 12 is formed around the reinforcing insert 14. Hence, it may be beneficial to provide the outer surface 60 with one or more interlocking features that promote bonding or attachment between the reinforcing insert 14 and the steering knuckle component 12. Some examples of such interlocking features are shown in
The inner surface 62, on the other hand, is designed to securely receive the wheel bearing assembly 16, which may be press-fit, maintained in place by snap ring 20, or by some other suitable means known in the art. The inner surface 62 of the reinforcing insert 14 forms a contact surface for the wheel bearing assembly 16 so that when the wheel bearing is installed in the steering knuckle assembly, an outer surface of the wheel bearing comes into intimate contact with the inner surface 62 of the insert. In one embodiment, the outer surface of the wheel bearing is a cylindrical surface that is slightly larger the corresponding cylindrical inner surface 62; this creates a press fit or interference fit between the two components. Arranging the reinforcing insert 14 within the steering knuckle component 12 so that its inner surface 62 is exposed to and acts as a contact surface for the wheel bearing assembly 16 can greatly strengthen the steering knuckle assembly 10 in the area of the opening 48 and help protect the assembly from the induced stresses that oftentimes occur during press fit installation. Stated differently, the reinforcing insert 14 with its inner surface 62 acting as a direct contact surface for the wheel bearing assembly 16 provides a circumferential support or brace to counteract the hoop or circumferential stresses caused during a press fit installation of the wheel bearing. The exact size, shape and configuration of the inner surface 62 of the reinforcing insert is largely dictated by the particular wheel bearing assembly 16 that is being installed and does not necessarily have to be a smooth cylindrical surface, although it can be.
The bearing opening 64 is formed in one or both of the axial ends of the reinforcing insert 14 and, like the inner surface 62, it is sized and shaped to receive the wheel bearing assembly 16. The insert opening 48 and the bearing opening 64 may be concentric or co-axial, but this is not required. In the embodiment illustrated in
The reinforcing insert 14 is preferably made from a strengthened material that is harder or stronger than the lightweight material used to make the steering knuckle component 12 and that is capable of withstanding the induced stresses and other forces involved. As used herein in the context of metal materials, the term “lighter” means that one metal material has a lower density (mass/unit volume) than another metal material, and the term “harder” means that one metal material has a higher surface hardness than another metal material. According to one exemplary embodiment, the reinforcing insert 14 is made from a strengthened ferrous-based material, such as cast or forged iron or steel, and the steering knuckle component 12 is made from a lightweight aluminum-based material. However, other material choices are certainly possible.
The wheel bearing assembly 16 allows a vehicle wheel to spin with minimal wear and friction, as is widely known and understood in the art, and may include an outer race 92, rolling elements 94, and an inner race 96. According to the particular embodiments shown here, the wheel bearing assembly or bearing housing 16 is securely inserted into the reinforcing insert 14 (e.g., via a press-fit arrangement) so that an outer surface of the outer race 92 contacts the inner surface 62 of the reinforcing insert. The rolling elements 94 roll between the inner and outer races 96 and 92 and may include ball bearings, roller bearings, roller thrust bearings, or tapered roller thrust bearings, or any other suitable bearing type known in the art. Use of other bearing components, bearing configurations and bearing arrangements, as well as snap rings or other parts, is certainly possible. Because the present steering knuckle assembly 10 may be used with any suitable type of wheel bearing and because wheel bearings are so widely known in the art, a further discussion of how wheel bearings work and are connected to the wheel hub 26, as well as other potential components, has been omitted.
Turning now to
In
It should be appreciated that the steering knuckle assembly embodiments shown in the drawings and described above only represent some of the possible configurations and that other configurations and arrangements could certainly be used instead. Moreover, any of the features shown or described in conjunction with any of the preceding embodiments, may be employed in the other embodiment as well.
Turning now to
In step 402, the reinforcing insert 14 is positioned in a mold cavity of a die casting machine. The die casting machine may vary depending on the particular casting method being used, however, some examples of potential methods include conventional aluminum die casting, high pressure die casting (HPDC), and squeeze casting (e.g., high-vacuum or vacuum-assist squeeze casting). Squeeze casting, for example, can combine some of the advantages of high pressure die casting (HPDC) and low pressure casting to provide net or near net-shape fabrication with high integrity and minimal shrinkage porosity. Furthermore, a composite steering knuckle formed by squeeze casting may have a more fine-grained, uniform microstructure with improved surface finish than those formed by comparable processes. Step 402 can be performed in a number of ways including automatically loading the reinforcing insert 14 with a robotic arm or other automated device, or manually loading the structural insert into the mold cavity. Reinforcing insert 14 may be properly oriented and held in place by structural features in the die casting machine itself, clamps, magnets, suction devices, gravity, or any other suitable means known in the art. The particulars of this step may be dictated by, among other things, the orientation of the die casting machine (horizontal, vertical, etc.) and the type of die casting machine being used (hydraulic, electric, hybrid, etc.). Step 402 may further include the step of coating the reinforcing insert 14 with a surface treatment or a reactive coating to chemically enhance the bond between the outer surface of the insert and the aluminum-based material flowing around it. Step 402 may also include coating the mold cavities with a lubrication medium to assist in later removal steps, including but not limited to, PTFEs or other graphite-based mediums, for example.
In step 404, a molten lightweight material, such as an aluminum-based material, is introduced into the mold cavity. Process parameters, like die temperature and pouring temperature should be adjusted to the particular process and component being formed, and may be dependent upon qualities of the aluminum-based material used such as melting temperature and thermal conductivity. Further, the amount of aluminum-based material will vary depending on the specifications of the desired steering knuckle component. Some potential benefits of using a squeeze casting process or the like is that it can result in a component or part with little to no “skin effect,” a rather uniform microstructure, and reduced gas and shrink porosity which, in turn, can improve part integrity.
Next, an appropriate amount of pressure is applied so that the steering knuckle component can form around the reinforcing insert, step 406. Again, the application of pressure will vary depending on the particular casting or other method being used, which may include conventional aluminum die casting, high pressure die casting (HPDC), or squeeze casting, to cite a few examples. Controlled mold cavity filling and pressure application during a squeeze casting method, for example, may assist in preventing the entrapment of gasses in the finished composite steering knuckle. The timing and amount of pressure applied will also vary depending on the particular application. This process is sometimes referred to in the present application as “over-molding,” even though it involves casting molten metal, as opposed to molding plastic. After step 406 is completed and the aluminum-based or other lightweight material has properly solidified, a composite steering knuckle component is fashioned with the reinforcing insert integrally formed within the steering knuckle component.
In step 408, the finished composite steering knuckle component can be removed from the die casting machine. The removal process can be performed in a number of ways including, for example, through automated means involving a robot, a part picker, or a part ejection mechanism, or with manual labor. As previously described, additional processing steps may include press fitting or otherwise installing a wheel bearing assembly or partial bearing assembly into the composite steering knuckle component. Press fitting the wheel bearing assembly or partial bearing may take place before or after an additional possible step of machining the reinforcing insert. Furthermore, press fitting the wheel bearing assembly can be less laborious and time consuming than other mounting methods, such as bolting the wheel bearing housing on, which is oftentimes the case with forged aluminum steering knuckles.
It is to be understood that the foregoing description is not a definition of the invention, but is a description of one or more preferred exemplary embodiments of the invention. The invention is not limited to the particular embodiment(s) disclosed herein, but rather is defined solely by the claims below. Furthermore, the statements contained in the foregoing description relate to particular embodiments and are not to be construed as limitations on the scope of the invention or on the definition of terms used in the claims, except where a term or phrase is expressly defined above. Various other embodiments and various changes and modifications to the disclosed embodiment(s) will become apparent to those skilled in the art. All such other embodiments, changes, and modifications are intended to come within the scope of the appended claims.
As used in this specification and claims, the terms “for example,” “e.g.,” “for instance,” “such as,” and “like,” and the verbs “comprising,” “having,” “including,” and their other verb forms, when used in conjunction with a listing of one or more components or other items, are each to be construed as open-ended, meaning that the listing is not to be considered as excluding other, additional components or items. Other terms are to be construed using their broadest reasonable meaning unless they are used in a context that requires a different interpretation.
This application claims the benefit of U.S. Provisional Ser. No. 61/861,548 filed on Aug. 2, 2013, the entire contents of which are incorporated herein by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/US2014/049607 | 8/4/2014 | WO | 00 |
| Number | Date | Country | |
|---|---|---|---|
| 61861548 | Aug 2013 | US |
