Patent Description:
Heavy-duty vehicles, such as trucks, tractor-trailers or trailers and the like, typically utilize a pair of wheel end assemblies attached to respective opposite ends of an axle. Multiple axle and wheel end assemblies may be used on a heavy-duty vehicle. Each wheel end assembly typically includes a hub, also referred to as a wheel hub, that is supported on a spindle of an axle for relative rotation by a bearing assembly. The bearing assembly includes an inboard bearing and an outboard bearing, which may be separated by a bearing spacer. The spindle has an attachment end portion, or skirt, with an outer diameter that is substantially equal to an outer diameter of an end portion of an axle central tube to which the spindle will be attached.

A spindle nut assembly is threaded onto threads formed on an outboard end of the spindle to secure the bearing assembly and hub on the spindle. The spindle nut assembly typically includes an inboard nut, a lock washer, an outboard nut, and a set screw, as is known. In addition to retaining the position of the bearings and any spacer, the spindle nut assembly may provide a clamping force for a desired axial preload to the bearings, and any bearing spacer, to a predetermined level. For normal operation of the wheel end assembly to occur, the bearings are lubricated with grease or oil from a lubrication chamber that contains a relatively large quantity of expensive lubrication material.

In many heavy-duty vehicle wheel end assembly configurations, a brake drum of a brake assembly and a wheel rim are mounted on the hub. In order to facilitate correct mounting and alignment of the brake drum and wheel rim the hub is formed with a flange that includes a precise mounting surface. Mounting studs are attached to the flange. The brake drum and the wheel rim are formed with openings that slide over the mounting studs, that enable the drum and wheel rim to be fastened and clamped against the mounting surface of the hub flange.

While most wheel end assemblies include these general features, the design and arrangement of the hub and other components may vary according to the specific vehicle design and its anticipated uses. Moreover, the design and construction of prior art hubs exhibit limitations in hub formation, which lead to disadvantages, such as having a relatively large volume cavity for expensive lubrication material to occupy and a barrel having an outer diameter of at least <NUM> (<NUM> inches), with undesirable relatively heavy weight, using relatively large quantities of materials for construction and associated relatively high cost of manufacture.

Many known heavy-duty vehicle hubs typically are made by casting a cylindrical shape from aluminum or a ferrous material, such as iron. The cast shape is then machined to precisely form critical surfaces that keep the inboard and outboard bearings, the seals, and the mounting surface in precise alignment relative to the spindle. In the prior art, most heavy-duty vehicle hubs have been cast due to the strength that is required of the hub and the complex profile or configuration of the hub.

Cast materials, iron in particular, that is needed to withstand the operating loads that the hub will experience often result in relatively thick walls of the hub which yield an undesirably heavy hub. Such relatively heavy weight of the hub increases fuel consumption of the heavy-duty vehicle and decreases the load that the heavy-duty vehicle may carry and thereby undesirably increases the cost of vehicle operation. Furthermore, some casting designs include one or two thick portions serving as gates to provide better material fill during the casting process and add weight to the hub. The gates typically extend axially only for a portion of the length of the cavity. It is, therefore, desirable to provide a hub that is as light as it can possibly be and meets all requirements for operation on a heavy-duty vehicle.

Because heavy-duty vehicle hubs experience significant operational loads, increased fatigue strength is an important property, which must be balanced against the desire to minimize the weight of the hub. It is desirable to achieve as much fatigue strength in a hub as is economically feasible and/or to optimize the strength-to-weight ratio of the hub. Metals that are readily cast, such as ductile iron, aluminum and certain grades of steel, often have limited strength. As a result, in order to increase the strength of the hub, portions of the hub are relatively thick so that the weight and associated cost of the hub are often undesirably increased. For this reason, it is desirable to develop a hub construction that employs materials and structure which provide increased strength or other desirable properties, while reducing hub weight and cost.

The disadvantages, drawbacks and limitations associated with some previously known hubs make it desirable to develop an improved hub construction that is relatively light in weight and that can withstand stress and strain during operation of the heavy-duty vehicle, especially when carrying a relatively heavy load. <CIT> suggests a split-type hub having a flange portion formed separately from a hub body. <CIT> suggests a hub having a two-part flange portion formed separately from a hub body. A further example of a wheel hub is known from <CIT>.

A summary is provided to introduce concepts in a form that are described in detail below. This summary is not intended to identify key factors or essential features of the concepts, nor is it intended to limit the scope of the concepts.

Disadvantages, drawbacks and limitations associated with previously known hubs are overcome with a hub constructed and manufactured according to the concepts described herein. The concepts can provide a relatively lighter weight hub that can withstand stress concentrations encountered during operation of a heavy-duty vehicle and reduce material use and cost. This is accomplished with an improved hub as set forth in claim <NUM>.

An improved hub, according to one aspect, is intended for use in a wheel end assembly of a heavy-duty vehicle that receives and mounts a wheel for rotation. The hub is provided as set forth in claim <NUM>.

The following description and drawings set forth at least one illustrative aspect or implementation of the disclosed subject matter. These are indicative of but a few of the various ways in which one or more aspects or implementations may be employed. Further features of the disclosed subject matter will become apparent to those skilled in the art from reading the following description with reference to the accompanying drawings, in which:.

The disclosed subject matter is described with reference to the drawings, in which like reference numerals are used to refer to like elements throughout the description and drawings. For exemplary purposes, details are set forth in at least one aspect to provide an understanding of the disclosed subject matter. It will be understood, however, that the disclosed subject matter can be practiced and implemented without these specific details.

To better understand the hub according to one aspect of the disclosed subject matter, a prior art hub <NUM> for a heavy-duty vehicle is shown in <FIG> and described. The hub <NUM> is for mounting on inboard and outboard bearings (not shown) for rotation relative to an axle spindle (not shown) in a known manner. The hub <NUM> has a body <NUM> with a relatively thick barrel wall <NUM> and indicated by respective thicknesses TP1 and TP2. A hubcap (not shown) may be mounted on an end portion <NUM> of the hub <NUM> in a known manner. A flange <NUM> extends radially outward from the body <NUM> of the hub <NUM>. Openings <NUM> are formed in the flange <NUM> of the hub <NUM>. Each of the openings <NUM> receives a respective wheel mounting stud <NUM> as is known. A brake drum (not shown and a tire and wheel assembly (not shown) are mounted on the flange <NUM> and retained by threading and tightening nuts (not shown) onto the wheel mounting studs <NUM>.

For lubrication of the inboard and outboard bearings, a suitable amount of lubricant (not shown) is introduced into a cavity <NUM> formed in the body <NUM> of the hub <NUM>. The prior art hub <NUM> typically is formed as a casting. Critical surfaces are machined to relatively tight tolerances on the hub <NUM>, and include an inboard bearing receiving bore <NUM>, an outboard bearing receiving bore <NUM> and a mounting surface <NUM> of the flange <NUM>.

The hub <NUM> is typically cast from ductile iron and then machined. The prior art hub <NUM> has a relatively rapid section modulus change at the interface region X1 or X2 between mounting flange <NUM> and body <NUM>. Such a rapid section modulus change at this interface generally reduces the fatigue strength of prior art hub <NUM>. To accommodate the rapid section modulus change, the walls of the barrel <NUM> of the body <NUM> are formed to have relatively large thicknesses TP1 and TP2 and render the hub <NUM> relatively heavy.

Such casting, machining and rapid section modulus change leads to disadvantages, drawbacks and limitations associated with the use of a relatively large amount of material causing relatively heavy weight of the hub <NUM>. Such disadvantages, drawbacks and limitations of the prior art hub <NUM> make it desirable to develop a hub that is lighter in weight, more economical to manufacture and exhibits good physical properties. The concepts presented by the disclosed subject matter satisfy this desire.

Turning to <FIG>, an exemplary aspect of a one-piece integrally cast hub for a heavy-duty vehicle is indicated generally by the reference numeral <NUM>. The use of, and reference to, the term "heavy-duty vehicle" is for the purpose of convenience and intended to include trucks, trailers and tractor-trailers or semi-trailers and the like.

The hub <NUM> is to be operatively mounted on inboard and outboard bearings (not shown) for rotation relative to an axle spindle (not shown) in a known manner. The hub <NUM> is relatively smaller in size than prior art hubs <NUM> and has a substantially cylindrical body <NUM>. The hub <NUM> also has a barrel portion or barrel <NUM> located intermediate axially opposite ends of the cylindrical body <NUM>. The barrel portion <NUM> is made with a relatively thin wall as indicated by respective thicknesses T1 and T2 (<FIG>). The barrel portion <NUM> extends substantially concentric with a longitudinal central axis A of the cylindrical body <NUM> of the hub <NUM>. The barrel portion <NUM> has respective thicknesses T1, T2 that are continuous and substantially the same over their axial extent.

It is desirable for the hub <NUM> to be as light as possible, yet strong enough to withstand the forces it encounters during operation of the heavy-duty vehicle. This is referred to as optimization of the strength-to-weight ratio of the hub <NUM>. In order to optimize the strength-to-weight ratio of the cast hub <NUM>, an innovative hub structure manufactured in accordance with an aspect of the disclosed subject matter is provided.

The hub <NUM> is integrally cast as one piece. The hub <NUM> may be cast from any suitable material for its intended application, such as ductile iron, austempered ductile iron (ADI) or an economically castable grade of steel. The hub <NUM> may be cast with an internal sand core and/or an external sand core. If internal and external sand cores are used, care must be taken to precisely position the cores relative to one another to yield a quality hub <NUM>.

The barrel portion <NUM> of the cylindrical body <NUM> is defined, at least partially, by a cylindrical inner wall surface <NUM> and a cylindrical outer wall surface <NUM>. The cylindrical inner wall surface <NUM> and the cylindrical outer wall surface <NUM> preferably extend substantially parallel to, and concentric with, one another. The cylindrical inner wall surface <NUM> is preferably substantially parallel to the longitudinal central axis A of the cylindrical body <NUM> of the hub <NUM>. The cylindrical inner wall surface <NUM> is preferably of the same diameter over its entire axial extent between annular shoulders <NUM> and <NUM>. The outer wall surface <NUM> may be circular and smooth to better distribute stresses in the barrel portion <NUM> as the hub <NUM> rotates under load during use.

An inboard bearing receiving bore <NUM> and an outboard bearing receiving bore <NUM> are formed in the cylindrical body <NUM>. Each of the bearing receiving bores <NUM>, <NUM> is located in a respective axially opposite end portion of the cylindrical body <NUM>. Both of the bearing receiving bores <NUM> and <NUM> have a diameter in the range from about <NUM> (about <NUM> inches) to about <NUM> (about <NUM> inches). It should be apparent that the cylindrical inner wall surface <NUM> and the cylindrical outer wall surface <NUM> may each or both extend at an angle relative to the longitudinal central axis A and the cylindrical inner wall surface and the cylindrical outer wall surface may extend at something other than parallel substantially to one another.

The cylindrical inner wall surface <NUM> of the barrel <NUM> has a diameter of about <NUM> (about <NUM> inches). The barrel <NUM> has a thickness T1, T2 in between the cylindrical inner wall surface <NUM> and the cylindrical outer wall surface <NUM> that is the same over essentially the entire axial extent of the barrel. The cylindrical outer wall surface <NUM> of the barrel <NUM> has a diameter D2 of about <NUM> (about <NUM> inches).

A lubrication chamber <NUM> is formed in the cylindrical body <NUM> of the hub <NUM>. The lubrication chamber <NUM> receives a suitable lubricant, such as grease or oil, to provide lubrication to the bearings that support the hub <NUM>, as is known. Since the overall size of the hub <NUM> is relatively small, the lubrication chamber is relatively small and contains less quantity of the relatively expensive lubrication material.

The cylindrical body <NUM> may have a plurality of axially extending reinforcing ribs <NUM> within the lubrication chamber <NUM>, of substantially equal thicknesses. The cylindrical body <NUM> preferably has at least three reinforcing ribs <NUM> (seven reinforcing ribs are used in the exemplary aspect) that are equally circumferentially spaced to provide strength in the hub <NUM>. The thickness T1 of the barrel portion <NUM> where no reinforcing ribs are located may be in the range of about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) and preferably in the range of about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). The thickness T2 of the barrel portion <NUM> where reinforcing ribs <NUM> are located may be in the range of about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) and preferably in the range of about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). It should be apparent that the reinforcing ribs <NUM> may or may not be employed in the hub <NUM> and this is dependent upon factors such as the intended use, the materials selected for casting and the required performance properties and characteristics of the hub. The reinforcing ribs <NUM> not only serve to strengthen the cylindrical body <NUM> but may act to distribute or force lubrication from the lubrication chamber <NUM> and/or in a direction toward at least one of the bearing receiving bores <NUM>, <NUM>. The reinforcing ribs <NUM> may have any suitable width and shape taken in a circumferential direction. The reinforcing ribs <NUM> may also have a radial inward facing surface with a profile or projection to enhance the distribution of lubrication.

A flange <NUM> extends radially outward from the cylindrical body <NUM> of the hub <NUM>. The flange <NUM> extends substantially perpendicular to the longitudinal central axis A of the hub <NUM>. The flange <NUM> is located entirely between the bearing receiving bores <NUM>, <NUM> in the cylindrical body <NUM> of the hub <NUM>. The flange <NUM> and cylindrical body <NUM> are integrally cast as one-piece. The flange <NUM> is machined to provide an outboard flat mounting surface <NUM> that extends perpendicular to the longitudinal central axis A of the hub <NUM>.

A reservoir or channel <NUM> is formed in the cylindrical body <NUM> and extends from the lubrication chamber <NUM> in the hub <NUM>. A majority of the volume of the reservoir channel <NUM> is located radially under the axial extent of the flange <NUM>. The reservoir channel <NUM> may have a portion with an inner diameter D1 (<FIG>) that is greater than the outer diameter D2 of the cylindrical outer wall surface <NUM> of the barrel <NUM>. The reservoir channel <NUM> provides a volume for additional lubricant to occupy and further lessens the weight of the hub <NUM> by displacing metal material. Locating the reservoir channel <NUM> in the area of the flange <NUM> makes available a relatively large amount of lubrication near the inboard bearing receiving bore <NUM> where better lubrication is often needed. The reinforcing ribs may axially bridge or span the reservoir channel <NUM>, as illustrated in <FIG>, <FIG> and <FIG>. Each reinforcing rib <NUM> extends axially between the bearing receiving bores <NUM>, <NUM> from the reservoir channel <NUM> to at least the barrel portion <NUM>.

A plurality of circumferentially arranged and spaced apart openings <NUM> may be formed in the flange <NUM> of the hub <NUM>. Each of the openings <NUM> receives a respective wheel mounting stud (not shown) as is known. A brake drum (not shown) and a tire and wheel assembly (not shown) may be mounted against the flange <NUM> on the wheel mounting studs and retained by tightening nuts (not shown) onto the wheel mounting studs.

The barrel <NUM> of the hub <NUM> necks down, or has an outer diameter D2 slightly smaller than the outer diameter D3 of a circumferential envelope <NUM> that surrounds the outboard bearing receiving bore <NUM> (<FIG>). The barrel <NUM> may have an outer diameter D2 in the range from about <NUM> (about <NUM> inches) to about <NUM> (about <NUM> inches) and preferably having an outer diameter of about <NUM> (about <NUM> inches). The circumferential envelope <NUM> has an outer diameter D3 where the hub <NUM> has no hubcap retaining structure and a thickness T3. The circumferential envelope <NUM> may have an outer diameter D3 in the range from about <NUM> (about <NUM> inches) to about <NUM> (about <NUM> inches) and preferably having an outer diameter of about <NUM> (about <NUM> inches). The cylindrical body <NUM> of the hub <NUM> has a ratio (D2/D3) of the outer diameter D2 of the barrel <NUM> to the outer diameter D3 of the circumferential envelope <NUM> in the range from about <NUM> to about <NUM> and preferably about <NUM>. The thickness T3 of the envelope <NUM> is substantially the same as the thicknesses T1 and T2 of the barrel portion <NUM>.

The barrel <NUM> and the circumferential envelope <NUM> have substantially the same thickness T1 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) and preferably in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). Thus, the hub <NUM> has ratio D3/T1 of a diameter D3 of the circumferential envelope <NUM> to the thickness T1 of the circumferential envelope ratio (D3/T1) in the range of about <NUM> to about <NUM> and preferably in the range from about <NUM> to about <NUM> with the circumferential envelope <NUM> diameter D3 being about <NUM> (about <NUM> inches). Because the barrel <NUM> and the circumferential envelope <NUM> of the hub <NUM> are relatively thin, a hubcap seat flange <NUM> (<FIG> and <FIG>) is formed with an outer diameter D4 which is greater than the diameter D3 of the circumferential envelope <NUM>. The outer diameter D4 of the hubcap seat flange <NUM> may be about <NUM> (about <NUM> inches) to provide sufficient structure for a hubcap and/or gasket to engage and seal.

The barrel <NUM> of the hub <NUM> has a thickness T2 where a reinforcing rib <NUM> is located that is in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) and preferably in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). The barrel <NUM> of the hub <NUM> has a thickness T1 where a rib is not located that is in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) and preferably in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). Thus, the hub <NUM> has ratio D2/T1 of an outer diameter D2 of the barrel <NUM> to the thickness T1 in the barrel in the range from about <NUM> to about <NUM> and preferably in the range from about <NUM> to about <NUM> where no rib is present with the barrel having an outside diameter D2 of about <NUM> (about <NUM> inches). The hub <NUM> also has ratio (D2/T2) of an outer diameter D2 of the barrel <NUM> to the thickness T2 in the barrel in the range from about <NUM> to about <NUM> and preferably in the range from about <NUM> to about <NUM> where a reinforcing rib <NUM> is present with the barrel having an outside diameter D2 of about <NUM> (about <NUM> inches).

The hub <NUM> may have an integrally cast first transition segment <NUM> (<FIG>) extending between the cylindrical outer wall surface <NUM> of the cylindrical body <NUM> and a first or inboard surface <NUM> (<FIG>) of the flange <NUM>. The first transition segment <NUM> may be formed with a specific profile taken in a plane extending radially from the longitudinal central axis A, when viewed as illustrated in <FIG> and <FIG>. The specific profile of the first transition segment <NUM> may be made up of two flat portions and four radius portions that smoothly transition into a specific pattern or order to avoid undesirable localized stress concentrations. A plurality of circumferentially spaced and radially extending individual stud bosses <NUM> are provided on the flange <NUM> of the hub <NUM> through which the openings <NUM> are formed. An area between adjacent stud bosses <NUM> is not needed for structural strength and can be axially thinner than the thickness of the stud bosses or completely absent to reduce overall weight of the hub <NUM>. The individual stud bosses <NUM> are provided instead of a full continuous ring where the flange <NUM> has a constant and uniform axially extending thickness. The axial extent or thickness E1 of each of the stud bosses <NUM> is greater than the axial extent or thickness E2 of the flange <NUM>.

For example, the first transition segment has a first transition portion <NUM> that may be arcuate with a relatively large radius R1 in the range from about <NUM> (about <NUM> inches) to about <NUM> (about <NUM> inches). A second transition portion <NUM> extends smoothly from the first transition portion <NUM>, may be straight and extend at an angle in the range from about <NUM>° to about <NUM>° relative to the longitudinal central axis A of the hub <NUM> for a distance in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A third transition portion <NUM> extends smoothly from the second transition portion <NUM>, and may be arcuate with a radius R2 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A fourth transition portion <NUM> extends smoothly from the third transition portion <NUM>, may be straight and extend at an angle in the range from about <NUM>° to about <NUM>° relative to the longitudinal central axis A of the hub <NUM> for a distance in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A fifth transition portion <NUM> extends smoothly from the fourth transition portion <NUM>, and may be arcuate with a radius R3 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A sixth transition portion <NUM> extends smoothly from the fifth transition portion <NUM>, may be straight and extend at an angle in the range from about <NUM>° to about <NUM>° relative to the longitudinal central axis A of the hub <NUM> for a distance in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch) before blending smoothly into the area between adjacent stud bosses <NUM>. All of the transition portions of the first transition segment <NUM> blend smoothly with adjacent transition portions.

The hub <NUM> may have an integrally cast second transition segment <NUM> extending between the cylindrical outer wall surface <NUM> and a second or outboard surface <NUM> of the flange <NUM>. The second surface <NUM> of the flange <NUM> is on an opposite side of the flange from the first surface <NUM> and the stud bosses <NUM>. The second transition segment <NUM> may also be formed with a specific profile taken in a plane extending radially from the longitudinal central axis A, when viewed as illustrated in <FIG>. The specific profile of the second transition segment <NUM> may be made up of two flat portions and three radius portions that smoothly transition into a specific pattern or order to avoid undesirable localized stress concentrations.

For example, a first transition portion <NUM> may be arcuate with a radius R5 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inches). A second transition portion <NUM> extends smoothly from the first transition portion <NUM>, may be straight and extend at an angle in the range from about <NUM>° to about <NUM>° relative to the longitudinal central axis A of the hub <NUM> for a distance in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A third transition portion <NUM> extends smoothly from the second transition portion <NUM> and may be arcuate with a radius R6 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inches). A fourth transition portion <NUM> extends smoothly from the third transition portion <NUM>, may be straight and extend at an angle in the range from about <NUM>° to about <NUM>° relative to the longitudinal central axis A of the hub <NUM> for a distance in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). A fifth transition portion <NUM> extends smoothly from the fourth transition portion <NUM>, and may be arcuate with a relatively small radius R7 in the range from about <NUM> (about <NUM> inch) to about <NUM> (about <NUM> inch). All of the transition portions of the second transition segment <NUM> blend smoothly with adjacent transition portions.

The transition portion <NUM> of the second transition segment <NUM> may extend axially inward of the surface <NUM> of the flange <NUM> to form a relief <NUM> in the flange. The relief <NUM> in the second transition segment <NUM> may extend axially into the flange <NUM> from the outboard surface <NUM> a distance F1. The distance F1 may be any suitable distance for the relief <NUM>. The relief <NUM> serves to require less material used in casting the hub <NUM> to further lighten the hub. A relief <NUM> may be formed in the first transition segment <NUM> or the flange <NUM> near where they blend together (<FIG>).

The hub <NUM> may have a plurality of brake drum and wheel mounting pilots <NUM> spaced from the barrel <NUM>. The inner surface of the mounting pilots <NUM> may be spaced from the outer surface of the barrel <NUM> by about <NUM> (about <NUM> inch) The mounting pilots <NUM> are evenly and circumferentially spaced apart about the flange <NUM> and second transition segment <NUM> of the hub <NUM> to facilitate proper alignment of a brake drum, if any, and the wheel rim on the hub. While five mounting pilots <NUM> are shown, any suitable number of mounting pilots may be employed. When a drum brake is employed with hub <NUM>, the pilots <NUM> are needed in order to accurately position a brake drum and the wheel rim on the outboard surface <NUM> of the flange <NUM> to ensure proper alignment and operation of brake components and the wheel end assembly relative to the longitudinal central axis A of the hub. The relief <NUM> advantageously reduces stress in the second transition segment <NUM>. It will be apparent that the illustrated hub <NUM> is intended for use in wheel end assemblies with drum braking systems. With some modification to the geometry of the hub <NUM>, it may be employed in wheel end assemblies with air disc braking systems. The hub <NUM> may also have mounting structure <NUM> for a hubcap (not shown) formed in the circumferential envelope <NUM> of the cylindrical body <NUM>. There may also be another relief <NUM> located radially outward of each mounting pilot <NUM> to reduce stress at the base of the pilots <NUM>. Each of the reliefs <NUM> extends axially into the flange <NUM> and is located adjacent the intersection of the flange and the mounting pilot <NUM>.

The hub <NUM> may have an opening <NUM> (<FIG>) formed in the barrel <NUM> and through a reinforcing rib <NUM>, or in the alternative have a boss (not shown) extending from the cylindrical inner wall surface <NUM> or the cylindrical outer wall surface <NUM>. The opening <NUM> or boss offers an area for lubrication fill structure (not shown) to be threaded into and does not require a separate built-up or thicker area in the casting of the hub <NUM> which would add weight.

Hub <NUM> reduces weight by employing a structure that utilizes less material. In this manner, hub <NUM> includes a relatively thinner wall thickness T1, T2 when compared to the wall thickness TP1, TP2, respectively, of the prior art hub <NUM>. Furthermore, the area between adjacent stud bosses <NUM> can be axially thinner than the thickness of the stud bosses themselves or completely absent to reduce overall weight of the hub <NUM>. Such a construction employs less material used for casting the hub <NUM>, which optimizes the strength-to-weight ratio of hub <NUM>, and reduces the weight and cost of the hub when compared to the prior art hub <NUM>. By casting the hub <NUM>, the amount of material needed to form the hub is reduced which desirably reduces the cost associated with forming the hub.

The hub <NUM> weighs in the range of about <NUM>% to about <NUM>% of what some known prior art hubs weigh while meeting all the performance requirements as the prior art hubs. Thus, less weight results in more cargo that can be carried in the heavy-duty vehicle.

The use of a relatively thin barrel <NUM> with at least one of the profiled first and second transition segments <NUM>, <NUM>, respectively, enables less severe and rapid changing section modulus between the flange <NUM> and the barrel at the first and/or second transition segments, which improves the strength and fatigue life of the hub <NUM>. Moreover, casting the hub <NUM> enables first and second transition segments <NUM>, <NUM> between the flange <NUM> and the barrel <NUM> to be formed with a gentle, smooth transition profile, which in turn provides less severe and rapid changing section modulus. The hub <NUM> has a less rapid section modulus change. Such a less rapid section modulus change reduces the stress in the transition segments <NUM>, <NUM> and improves the fatigue strength of hub <NUM> when compared to prior art hub <NUM>. In this manner, the hub <NUM> provides a structure that optimizes the performance characteristics and properties of the hub, such as the strength-to-weight ratio of the hub while minimizing the amount of material needed to form the hub.

By employing the barrel <NUM> with the reservoir channel <NUM> extending radially under the flange <NUM>, the size of lubrication chamber <NUM> is increased, which provides the hub <NUM> with the ability to provide sufficient lubrication to the bearings when the lubrication chamber is properly filled. The reservoir channel <NUM> also displaces material used to cast the hub <NUM>, therefore further reducing weight and cost to manufacture the hub <NUM>. It is noted that the barrel <NUM> essentially extends from the reservoir channel <NUM> to near the outboard bearing receiving bore <NUM>. By the inner surfaces of the mounting pilots <NUM> being spaced from the outer surface of the barrel <NUM>, there is no material that is used to provide reinforcement for the mounting pilots and, thus, weight is saved.

The above-described construction of the cast hub <NUM> provides a hub that is lighter in weight, more economical to manufacture, and exhibits improved physical characteristics and properties when compared to the prior art hub <NUM>. The cast hub <NUM> maximizes strength and minimizes weight by incorporating specific longitudinal cross-section profiles along with ratios and/or relationships of various diameters D2, D3 with each other and to certain thicknesses T1, T2 of the walls of the barrel <NUM>. The cast hub <NUM> also provides a sufficiently strong structure that contains relatively less of the expensive lubrication material when compared to the prior art hub <NUM>.

The disclosed subject matter successfully incorporates a relatively lightweight one-piece integrally cast hub <NUM> into a wheel end assembly for heavy-duty vehicles. More particularly, the hub <NUM> minimizes the amount of raw material employed to form the hub when compared to prior art hub <NUM>, which decreases the cost of forming the hub. The hub <NUM> has an optimized strength-to-weight ratio to improve certain performance characteristics and properties such as increased fatigue life, enabling the hub to be lighter in weight, to include an improved strength-to-weight ratio, and desirably reducing the cost of the hub.

It is to be understood that materials other than those described above may be employed for the hub <NUM> without affecting the overall concept or operation of the invention. It is also to be understood that the hub <NUM> finds application in all types of known heavy-duty vehicles.

Claim 1:
A hub for a heavy-duty vehicle and for mounting a wheel for relative rotation, the hub comprising:
a substantially cylindrical body (<NUM>) having axially opposite end portions and a longitudinal central axis;
a pair of bearing-receiving bores (<NUM>,<NUM>) formed in the cylindrical body, each one of the pair of bearing-receiving bores being located at a respective axially opposite end portion of the cylindrical body;
a circumferential envelope (<NUM>) located about one of the pair of bearing-receiving bores (<NUM>), the circumferential envelope having an outer diameter (D3) formed on the cylindrical body (<NUM>);
a flange (<NUM>) integrally formed with and extending radially outward from the cylindrical body (<NUM>) at a location between the pair of bearing-receiving bores (<NUM>,<NUM>);
a barrel portion (<NUM>) of the cylindrical body extending between the flange (<NUM>) and the circumferential envelope (<NUM>),
characterised in that the barrel portion has an outer diameter (D2) smaller than that of the outer diameter (D3) of the circumferential envelope (<NUM>) such that a ratio of the outer diameter (D2) of the barrel portion to the outer diameter (D3) of the circumferential envelope (<NUM>) is in a range from <NUM> to <NUM>.