Patent Grant
11305580
The disclosed subject matter generally relates to axles for vehicles. Particularly, the disclosed subject matter relates to an axle assembly for use in heavy-duty vehicles. The axle assembly includes an improved axle spindle with a profile that reduces stress concentration in the axle spindle. The axle spindle includes an integral ABS sensor bracket mounting locator. The disclosed subject matter also relates to methods of manufacturing the axle assembly and manufacturing the axle spindle.
Heavy-duty vehicles, such as trucks, tractor-trailers or trailers, typically utilize one or more axle assemblies. An axle assembly includes a pair of wheel end assemblies which are fixed to respective opposite ends of an axle central tube. Each wheel end assembly includes a hub that is supported on an axle spindle for relative rotation by a bearing system. The bearing system includes an inboard bearing and an outboard bearing. The axle 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 the axle central tube to which the axle spindle will be attached.
The axle spindle includes a cylindrical outer bearing surface for supporting at least the inboard bearing of the bearing system. The cylindrical outer bearing surface has an outer diameter that is smaller than the outer diameter of the attachment end portion of the axle spindle. Thus, there is a transition zone of decreasing outer diameter that extends from the attachment end portion of the axle spindle in a direction toward the cylindrical outer bearing surface.
The axle spindle has a shoulder region at an end of the transition zone. The shoulder region has an annular end surface that extends perpendicular to the cylindrical outer bearing surface. The annular end surface contact surface of the shoulder region engages the inboard bearing to position the inboard bearing along the axle spindle. An axle spindle nut configuration is threaded onto an end portion of the axle spindle to secure the bearing system on the axle spindle and to maintain the position of the bearings.
The transition zone and the shoulder region typically experience relatively heavy loads and forces during operation of heavy-duty vehicles. The relatively heavy loads and forces result in relatively high localized strain resulting in relatively large stress concentrations in the transition zone and the shoulder region. Depending on the design geometry in the transition zone and shoulder region, the axle spindle could have a relatively high rate of change in section modulus that could detrimentally affect the axle spindle. The axle spindle must be robust enough to withstand the relatively heavy loads and forces with associated relatively high stress and strain.
The axle spindle is formed during the manufacturing process with a large amount of material, such as steel, to be robust to withstand the relatively heavy loads and forces that the axle spindle experiences. This typically results in the axle spindle being relatively thick in the shoulder region and transition zone. This relatively thick area of the axle spindle is also formed for manufacturing reasons and for mounting accessory hardware. Therefore, the axle spindle can be relatively heavy that adds to the overall weight of the heavy-duty vehicle which results in a reduction in weight of the cargo that the heavy-duty vehicle may carry.
The annular end surface of the shoulder region is subject to wear, fretting, galling or deformation due to the relatively high axial forces applied by the inboard bearing during operation of the heavy-duty vehicle. Wear, fretting, galling or deformation of the annular end surface of the shoulder region, and possibly of the inboard bearing, occurs by constant contact and relatively high axial loads applied by the inboard bearing to the shoulder region. Such wear, fretting, galling or deformation can create excessive end play of the bearing system on the axle spindle and introduce resultant contaminants into the bearing system.
At least one attempt to eliminate the relatively thick axle spindle in the transition zone involved joining a separately manufactured collar to an axle spindle body formed from a hollow tube. The axle spindle body was produced by cold forming the hollow tube. The collar provides a bearing stop surface. However, this attempt involves additional machining and manufacturing operations to produce the collar and then welding or otherwise joining the collar to the transition zone of the axle spindle body. Care must be taken in positioning the collar axially on the axle spindle body to provide a proper location of the bearing stop surface on the finished axle spindle assembly. In order to properly locate the bearing stop surface on the axle spindle body, a frustoconical inner surface was machined on the collar that approximates the angle at which the transition zone extends. Manufacturing tolerances of the outer surface of a cold formed axle spindle body are generally greater than tolerances of a machining operation used on the collar. This collar and axle spindle body assembly may not produce desired location of the bearing stop surface or the squareness of the collar relative to the axle spindle body. All these additional steps and procedures tend to increase cost of manufacturing the axle spindle and increase the lead time to produce the axle spindle.
It is also known in another attempt that, for manufacturing reasons, a solid axle spindle is provided with a disruptive radial plunge cut in a bearing journal surface near a shoulder end surface. This plunge cut allows a roller burnishing tool to contact the bearing journal to yield a desired finish to the surface of the bearing journal. This configuration may not be optimal for the axle spindle to withstand the relatively heavy loads and large forces during operation of the heavy-duty vehicle.
The disadvantages associated with some previously known axle spindles make it desirable to develop an improved axle spindle that is relatively light in weight. It is also desirable to develop an improved axle spindle that has a shoulder region that may better withstand localized stress and strain and to minimize the wear, fretting, galling and/or deformation of the shoulder during operation of the heavy-duty vehicle. It is also desirable to provide an axle spindle with a relatively low rate of change in section modulus, especially in the shoulder region. It is desirable to provide a method of manufacturing the improved axle spindle. It is also desirable to provide an improved axle spindle capable of using standard or stock bearings or that may incorporate custom bearings which can benefit from advantageous features of the improved axle spindle. It is also desirable to provide a one-piece integrally formed tubular axle spindle that can reduce material costs and increase axle spindle and bearing life. It is further desirable to provide an axle spindle with means to easily locate and mount an antilock braking system sensor bracket.
A summary is provided to introduce concepts of the disclosed subject matter in a form that are described below. This summary is not intended to identify key factors or essential features of the disclosed subject matter, nor is it intended to limit the scope of the disclosed subject matter.
The disadvantages associated with known axle spindles are overcome with an axle assembly and axle spindle constructed and manufactured according to the disclosed subject matter. The concepts of the disclosed subject matter provide a relatively lighter weight one-piece integrally formed tubular axle spindle that can withstand localized stress concentrations encountered during operation of a heavy-duty vehicle, reduce material costs and increase axle spindle and bearing life. The disclosed subject matter also provides a way to efficiently locate and mount an antilock braking system answer bracket. The improved axle spindle has a relatively low rate of change in section modulus. The improved axle spindle is capable of using standard or stock bearings or that may incorporate custom bearings which can benefit from the improved features of the disclosed subject matter. The disclosed subject matter further provides a manufacturing method for an axle assembly and axle spindle.
The disclosed subject matter provides an axle assembly for a heavy-duty vehicle. The axle assembly includes a central tube and an axle spindle fixed to the central tube. The axle spindle receives at least one bearing assembly to support a hub for relative rotation. The axle spindle has a tubular first cylindrical section with a first outer diameter. An end surface on the first cylindrical section connects to the central tube of the axle spindle. A tubular second cylindrical section is integrally formed with and extends in a direction away from the first cylindrical section. The second section has at least one bearing support surface to receive and support a bearing assembly of the hub. The second section has a second outer diameter less than the first outer diameter. A tubular transition section is integrally formed with and located between the first cylindrical section and the second cylindrical section. The tubular transition section includes a chucking land pad. The chucking land pad engages a tool to cause relative rotation between the central tube and the axle spindle to create a friction weld.
An arcuate surface may define the chucking land pad. The arcuate surface extends substantially coaxially with at least one of the first cylindrical section or the tubular second cylindrical section. The chucking land pad may be a continuous cylindrical surface.
The axle spindle has an antilock braking system sensor bracket locator nub formed in the tubular transition section of the axle spindle. An antilock braking system bracket engages a surface of the antilock braking system sensor bracket locator nub and is fixed to the axle spindle.
An annular shoulder portion is formed at an end of the transition section adjacent the second cylindrical section. The shoulder portion has an annular shoulder surface for engaging an annular surface of the bearing assembly. The tubular transition section may have a rate of change in section modulus taken at an axial location between adjacent sections spaced apart in 0.050 inch increments from the annular shoulder surface in a direction toward the end surface of the tubular first cylindrical section that varies no more than about 14%.
At least one surface forms an annular profile located between the annular shoulder surface and the bearing support surface. The annular profile is defined by a surface having a third diameter that is not less than the second diameter of the bearing support surface of the tubular second cylindrical section.
The annular profile may include a first annular surface with a first radius taken in a plane containing a longitudinal central axis of the axle spindle. The first annular surface is located between the annular shoulder surface and the bearing support surface. The annular profile may also include a second annular surface with a second radius taken in a plane containing a longitudinal central axis of the axle spindle. The second annular surface is located between the first annular surface and the bearing support surface. The second radius of the second annular surface may be greater than the first radius of the first annular surface.
The annular profile may include a frustoconical segment extending radially inward from the annular shoulder surface. The annular profile may also have a radiused surface located between the frustoconical segment and the bearing support surface.
The disclosed subject matter also provides a method of making an axle assembly and an axle spindle for a heavy-duty vehicle. The method comprises the steps of providing a central tube and a hollow member. The axle spindle is produced by forming a first cylindrical section on the hollow member and has a first diameter. A second cylindrical section is formed on the hollow member integrally with and extending in a direction away from the first cylindrical section. The second cylindrical section has a second diameter less than the first diameter. A transition section is formed on the hollow member integrally with, and located between, the first cylindrical section and the second cylindrical section. The transition section tapers from the first cylindrical section to the second cylindrical section. A chucking land pad is formed on the transition section.
The axle assembly results when the axle spindle is friction welded to the central tube by a tool engaging the chucking land pad and rotating the axle spindle relative to the central tube. The chucking land pad is machined away to form a finished transition section. During the machining operation, an antilock braking system sensor bracket locator nub is formed. An antilock braking system sensor bracket is located on the antilock braking system sensor bracket locator nub. The antilock braking system sensor bracket is fixed to the axle spindle.
The following description and accompanying drawings set forth certain illustrative aspects and implementations of the disclosed subject matter. These are indicative of but a few of the various ways in which one or more aspects or implementations of the disclosed subject matter may be employed. Further features of the disclosed subject matter may become apparent to those skilled in the art from reading the description with reference to the accompanying drawings, in which:
The disclosed subject matter is described with reference to the drawings, in which like reference characters are used to refer to like elements throughout the description and drawings. For exemplary purposes, details are set forth in order to provide an understanding of the disclosed subject matter. It will be understood that the disclosed subject matter can be practiced and implemented without these specific details.
A wheel end assembly 20 (
The wheel end assembly 20 includes a hub 22 supported for relative rotation on the improved axle spindle 24 by a bearing system 26 comprising a pair set of tapered roller bearings, cups and cones. The improved axle spindle 24 can withstand the strain and stress concentrations associated with use on a heavy-duty vehicle and increase service life of the axle spindle and bearing system 26. The improved axle spindle 24 also has a portion with a relatively low rate of change in section modulus which could increase fatigue life. The improved axle spindle 24 further is relatively light in weight. The improved axle spindle 24 may also enable the development and use of relatively lighter weight bearings.
The axle central tube is hollow or tubular with a substantially round cross-section and has an annular end surface. The axle central tube may be made of any suitable material, such as steel. The axle central tube and the axle spindle 24 could have any cross-sectional shape, size and configuration. The axle spindle 24 is preferably hollow or tubular over its entire length and has a substantially round tubular end portion or skirt 28 with an annular end surface 40. The axle spindle 24 may be made of any suitable material, such as steel. Preferably, the inner and outer diameters of the axle central tube and the skirt 28 of the axle spindle 24 are substantially the same at their respective annular end surfaces. It is contemplated that the inner diameters of the axle and skirt 28 of the axle spindle 24 could be different. For example, the inner diameter ID of the skirt 28 could have a relatively smaller inner diameter than that of the axle central tube.
The annular end surface of the axle central tube and the annular end surface 40 of axle spindle 24 are joined together by any suitable method, such as by friction welding, according to one aspect. It will be appreciated that any suitable means of permanently joining the axle spindle 24 to the axle may be used, for example MIG, TIG, arc, oxyacetylene gas, laser, projection, butt or capacitance welding, and the like.
The tubular axle spindle 24 for the heavy-duty vehicle has a longitudinal central axis A and is illustrated, for exemplary purposes, as a “straight” or “non-tapered” axle spindle with axially spaced bearing support surfaces 42, 44 (
The bearing system 26 of the wheel end assembly 20 includes a bearing assembly or outboard bearing 46 received on the outboard bearing support surface 42 of the axle spindle 24. The bearing system 26 also includes a bearing assembly or an inboard bearing 48 which is received on the inboard bearing support surface 44 of the axle spindle 24. The bearings 46, 48 are illustrated as tapered roller bearings, but it will be appreciated that any suitable bearing may be employed.
The inboard bearing 48 is received in a bore 49 in the hub 22. The inboard bearing 48 has an annular inboard side surface 60 (best seen in
The outboard bearing 46 is received in a bore 50 in the hub 22. A spindle nut assembly 66 is threaded onto a threaded end portion of the axle spindle 24 and establishes the axial or longitudinal position of the outboard bearing 46 on the axle spindle and blocks or prevents any further outboard movement of the outboard bearing. A cavity 86 is defined by the outboard bearing 46, inboard bearing 48, axle spindle 24, hub 22 and a seal 52. The cavity 86 receives a suitable lubricant for the bearing system 26, such as grease or oil.
The axle spindle 24 has a tubular first cylindrical section 80 (
The axle spindle 24 has a tubular second cylindrical section 82 that extends in a direction away from the first cylindrical section 80 and is integrally formed with first cylindrical surface by suitable means, such as in a forging process. The second cylindrical section 82 extends coaxially with and is axially spaced from the first cylindrical section 80. The second cylindrical section 82 of the axle spindle 24 includes the bearing support surfaces 42, 44.
The bearing support surfaces 42, 44 receive and support an inner cylindrical surface, such as a bore, of a respective one of the bearings 46, 48 of the bearing system 26. The bearing support surfaces 42, 44 are precision machined to closely fit the inner cylindrical surfaces of the bearings 46, 48. The outer diameters of each of the bearing support surfaces 42, 44 are the same for a straight or non-tapered axle spindle 24, as illustrated and described. The bearing support surfaces 42, 44 of the second cylindrical section 82 have a bearing support diameter or an outer second diameter D2 that is less than the outer first diameter D1 of the first cylindrical section 80. The second diameter D2, for example, is in the range of about 3.4983 inches to about 3.5421 inches, for an axle spindle 24 when the outer first diameter D1 is the range of about 4.90 inches to about 6.00 inches. If the axle spindle 24 is of the tapered type, another cylindrical section would be spaced axially outboard from the inboard bearing support surface 44 and have an outer diameter less than the second outer diameter D2. The second cylindrical section 82 of the axle spindle 24 may have an inner diameter D4 of any suitable dimension, such as in the range of about 2.13 inches to about 2.60 inches, and preferably about 2.45 inches.
The inboard bearing 48 and outboard bearing 46 of the bearing system 26 may be the same in the exemplary aspect. The inboard bearing 48 and outboard bearing 46 may be any suitable bearing type but is preferably of the tapered roller bearing type. For example, the inboard bearing 48 has a plurality of rollers 100 (
A tubular transition section 120 (
An axially extending arcuate inner surface 124 of the transition section 120 tapers and blends smoothly from an inner surface of the first cylindrical section 80 at first transition or tangent point TP1 to an inner surface of the second cylindrical section 82 at second transition or tangent point TP2. The arcuate inner surface 124 may be formed with a relatively large radius Rc, taken in a plane containing the longitudinal central axis A. The radius Rc may be in the range of about 8.00 inches to about 12.00 inches, and preferably about 10.00 inches. At least a portion of the inner surface 124 in the transition section 120 may be of any suitable configuration, such as in the form of a spline, curve or straight line. In the illustrated aspect, the inner surface 124 also has an arcuate portion with a radius Ro that smoothly transitions in an outboard direction axially away from the first cylindrical section 80 at tangent point TP1 into the radius Ro. The radius Ro may be in the range of about 1.00 inch to about 3.00 inches, and preferably about 2.00 inches. The inner surface 124 also has an arcuate portion with a radius Ri that smoothly transitions with the radius Rc in an outboard direction axially from first cylindrical section 80 at the tangent point TP2. The radius Ri may be in the range of about 1.00 inch to about 3.00 inches, and preferably about 2.00 inches. The relationship among the radii Rc, Ro and Ri that define the inner surface 124 is that the radius Rc is greater than both radii Ro and Ri. The radius Ro may also be greater than the radius Ri. The start of radius Ri is radially inward at or near the axial location of annular shoulder surface 64 and extends in an inboard direction.
The transition section 120 of the axle spindle 24, thus, has a relatively thin radial wall thickness T taken anywhere along transition section when compared to most known forged axle spindles for heavy-duty vehicles taken at the same axial locations. The relatively thin radial wall thickness T of the transition section 120 results in a considerable weight and material savings of the axle spindle 24. An exemplary weight savings in the range of about 10% to about 18% for the axle spindle 24 with a 5.75-inch outer first diameter D1 for the same gross axle weight rating (GAWR) as a prior art axle spindle is achieved. The axle spindle 24 uses a lesser amount of material and provides cost savings in material and possibly processing for the same gross axle weight rating (GAWR). The axle spindle 24 is designed and manufactured to have a relatively small rate of section modulus change in the axial direction in the annular shoulder portion 62 of the transition section 120 at the same gross axle weight rating (GAWR) compared to previously known axle spindles, as is described below.
The annular shoulder portion 62 is preferably continuous in the circumferential direction and located in an end portion of the transition section 120 adjacent to the second cylindrical section 82. More specifically, the annular shoulder surface 64 forms the end of the shoulder portion 62 of the transition section 120 and from which the second cylindrical section 82 may extend. The annular shoulder portion 62 has a seal journal surface 63 (
The annular shoulder surface 64 extends in a radial direction from, and substantially perpendicular to, the longitudinal central axis A of the axle spindle 24. The annular shoulder surface 64 is preferably uninterrupted or continuous in the circumferential direction. The annular shoulder surface 64 may contact the annular side surface 60 (
The inboard bearing support surface 44, the outboard bearing support surface 42, and the annular shoulder surface 64 may be formed on the axle spindle 24 in the same machining process or operation. The threaded end portion 68 may also be cut or formed on the axle spindle 24 in the same machining process or operation that is used to form the inboard bearing support surface 44, outboard bearing support surface 42 and annular shoulder surface 64.
The axle spindle 24 may have a circumferentially continuous stress relieving annular profile 140 (
The annular profile 140 also may serve as a cavity that additional lubrication for the bearing system 26 can enter and be stored in or that fretted material from the annular shoulder surface 64 can enter in order to keep it out of the bearing system. The annular profile 140 also reduces the weight of the axle spindle 24 somewhat and may require less material to form the axle spindle resulting in a lighter weight axle spindle and less material usage. The annular profile 140 may be machined into axle spindle 24, formed during the forging operation or by other suitable methods of removing material or creating a specific profile. For example, the annular profile 140 may be formed in the same machining process or operation that is used to form inboard bearing support surface 44, outboard bearing support surface 42, annular shoulder surface 64 and threaded end portion 68.
The annular profile 140 provides a void area that does not contact the inboard bearing 48 of the bearing system 26. Even with the annular profile 140, the annular shoulder surface 64 engages the inner cone 104 of the inboard bearing 48 over substantially the same surface area as if no annular profile was present. This is because the backface radius Rbf (
The annular shoulder portion 62 of the axle spindle 24 typically experiences relatively heavy loads and stress, for example, bending stress, Hertzian contact stress and/or axial stress. Bending stress typically increases due to localized stress concentrations from a rapid section area change from quickly varying inner and outer diameters in the transition section 120. The axle spindle 24 of the disclosed subject matter has a relatively small rate of section area change in the axial direction in the annular shoulder portion 62 that results in a relatively low rate of section modulus change. The size and location of the annular profile 140 substantially lowers the peak bending stresses in the annular shoulder portion 62. The resulting decreased total stress level in the annular shoulder portion 62 lowers the potential for fretting and galling of the annular shoulder surface 64 and the side surface 60 of the inner cone 104. The relatively small rate of section modulus changes in the annular shoulder portion 62 may also reduce strain and, thus, localized stress concentrations in the shoulder portion 62 of the axle spindle 24 that may improve fatigue life.
The relatively small rate of section modulus change in axle spindle 24 enables the use of a less robust or thinner shoulder portion 62 and/or transition section 120 with a relatively smaller wall thickness T (
The annular profile 140 may have a radiused segment 144 (
By way of example, the radiused segment 144 of the annular profile 140 may have an annular surface defining a radiused portion 146 located between the annular shoulder surface 64 and the inboard bearing support surface 44 of the second cylindrical section 82. The radiused portion 146 helps transition the inboard bearing support surface 44 of the second cylindrical section 82 in a direction toward the annular shoulder surface 64. The radiused portion 146 has a radius R1. The radius R1 of the radiused portion 146 may be at least about 0.375 inch.
The radiused segment 144 of the annular profile 140 may have another annular surface defining a radiused portion 148 located between the radiused portion 146 and the annular shoulder surface 64 of the shoulder portion 62. The radiused portion 148 smoothly transitions the radiused portion 146 in a direction toward the annular shoulder surface 64. The radiused portion 148 has a radius R2 that is preferably less than the radiused surface R1 of the radiused portion 146. The radius R2 of the radiused portion 148 may be less than about 0.068 inch but preferably no less than about 0.060 inch. There may be some configurations where the radius R2 may be less than 0.060 inch. A ratio of the radius R1 to the radius R2 is preferably in a range from about 5:1 to about 10:1. There is no part of the annular surface of the radiused portion 146 and no part of the annular surface of the radiused portion 148 that extend radially inward of the inboard bearing support surface 44.
The radiused segment 144 of the annular profile 140 may optionally have yet another annular surface defining another radiused portion (not shown) located between the radiused portion 146 and the bearing support surface 44 of the second cylindrical section 82. This other radiused portion would have a radius that is preferably greater than the radius R1 of the radiused portion 146.
By way of example, the annular profile 140 may also have an inclined surface 142 (
Previously known axle assemblies typically incorporate a standard size central tube (not shown) for a heavy-duty vehicle that has an outer diameter of about 5.75 inches. The 5.75 inches standard size axle central tube typically has a wall thickness of about 0.312 inch. It is generally desired to match an outer diameter of an annular end surface of a tubular end portion or skirt of a prior art axle spindle to the outer diameter of the axle central tube to which it is to be fixed. Thus, the prior art axle spindles are relatively thick and heavy and contribute to the overall weight of the heavy-duty vehicle and, therefore, limit the amount of cargo or load that can be carried by the heavy-duty vehicle.
An example of a representative prior art axle spindle is illustrated in
In
A total weight reduction in the range of approximately 10% to approximately 18% is realized over the prior art axle spindle 160 with the improved axle spindle 24 having similar outer diameters and gross axle weight ratings (GAWRs). This total weight reduction is made possible by the annular profile 140 and the configuration of the inner surface 124 of that axle spindle 24 and how they lower stress concentrations in the transition section 120 and first cylindrical section 80. This weight savings reduces the overall weight of a heavy-duty vehicle and, therefore, allows more cargo to be carried in the heavy-duty vehicle.
Another aspect of the subject disclosure is a method of manufacturing the axle spindle 24 for a heavy-duty vehicle wheel end assembly 20. By way of example, the method includes the step of providing a hollow tubular member or cup-shaped preform to serve as a blank or initial workpiece. The first cylindrical section 80 is formed, preferably by a forging operation, on the tubular member to have a portion with the outer first diameter D1. The second cylindrical section 82 is formed, preferably by a forging operation, integrally in one-piece and coaxially with, and spaced from, the first cylindrical section 80. The second cylindrical section 82 has the second outer diameter D2 that is less than the outer first diameter D1. The tubular transition section 120 is formed, preferably by a forging operation, integrally and coaxially between the first cylindrical section 80 and the second cylindrical section 82. The tubular transition section 120 tapers radially inwardly in an outboard direction on both of the inner and outer surfaces 124, 122.
The annular shoulder portion 62 is formed at an outboard end portion of the tubular transition section 120, preferably by a forging operation, integrally and coaxially between the first cylindrical section 80 and the section 82. The annular shoulder surface 64 is rough formed during the forging operation and then final machined or ground at the outboard end of the annular shoulder portion 62 adjacent the second cylindrical section 82. The annular profile 140 is formed between the second cylindrical section 82 and the annular shoulder surface 64 of the annular shoulder portion 62. The step of forming the annular profile 140 may be done by a machining operation. The bearing support surfaces 42, 44 may be machined on the second cylindrical section 82 of the axle spindle 24.
The method may further include the step of forming the inner and outer surfaces 124, 122 of the tubular transition section 120 to desired profiles. The desired profiles provide at least a portion of the annular shoulder portion 62 and tubular transition section 120 with the relatively small rate of change of section modulus.
An axle spindle 224 for a heavy-duty vehicle according to another aspect is illustrated in
The axle spindle 224 is preferably a straight or non-tapered type of axle spindle. That is, the axle spindle 224 has a cylindrical section 282 that includes an inboard bearing support surface 244 with an outer diameter D9. The axle spindle 224 may include an inboard bearing 248 (only a portion of which is shown in
The annular shoulder surface 264 extends in a radial direction from, and substantially perpendicular to, the longitudinal central axis (not shown) of the axle spindle 224. The annular shoulder surface 264 is preferably uninterrupted or continuous circumferentially. The annular shoulder surface 264 contacts the annular side surface 260 of the inner cone 304 of the bearing 248 over a radial distance RD2.
The axle spindle 224 has a tubular transition section 320 (
The stress relieving annular profile 340 (
The radially extending distance, dimension or length RD2 of the annular shoulder surface 264 may be any suitable length and may depend on a particular application in which the axle spindle 224 will be used and what bearing may be employed. The annular profile 340 provides a void area that does not contact the annular side surface 260 of the bearing 248. Even with the annular profile 340, the annular shoulder surface 264 engages the inner cone 304 of the bearing 248 over substantially the same surface area as if no annular profile was present. This is because a backface clearance corner BFC (
The annular profile 340 may be of any suitable size and configuration that reduces strain and stress concentrations in the annular shoulder portion 262 of the axle spindle 224. By way of example, the annular profile 340 may have a continuous annular frustoconical segment or inclined surface 342 (
The annular profile 340 may also have an axially extending continuous radiused segment with a radiused annular surface 344 extending radially inward of, and from, the frustoconical segment of inclined surface 342. The radiused annular surface 344 of the annular profile 340 is located between the frustoconical segment of inclined surface 342 and the inboard bearing support surface 244 of the cylindrical section 282. The radiused annular surface 344 forms part of the bottom or radially inward portion, as viewed in
The radiused annular surface 344 of the annular profile 340 may be of any suitable size and shape that contributes to the reduction of strain and stress concentrations in the annular shoulder portion 262 of the axle spindle 224. The radiused annular surface 344 of the annular profile 340 has a radius R10. According to an exemplary aspect, the radiused annular surface 344 of the annular profile 340 may be configured with multiple or blended radii. Any suitable number of blended radii may be used to configure the radiused annular surface 344 of the annular profile 340. The radiused annular surface 344 of the annular profile 340 may have any suitable configuration or combination of configurations, such as an arc, spline or curve.
The annular profile 340 may have another annular surface 346 located between the radiused annular surface 344 and the inboard bearing support surface 244 of the cylindrical section 282. The annular surface 346 may be of any suitable size and shape that contributes to the reduction of strain and stress concentrations in the annular shoulder portion 262 of the axle spindle 224. The annular surface 346 smoothly transitions the radiused annular surface 344 in a direction toward the inboard bearing support surface 244 of the cylindrical section 282 with a relatively larger radius R12 than the radius R10 of radiused annular surface 344. For example, the annular surface 346 may have a radius R12 that preferably may be larger than the radius R10 of radiused annular surface 344. The radius R10 may be in the range of about 0.050 inch to about 0.075 inch, and preferably about 0.068 inch. The radius R12 may be in the range of about 0.500 inch to about 0.750 inch, and preferably about 0.557 inch. A ratio of the radius R12 of the annular surface 346 to the radius R10 of the radiused annular surface 344 is preferably in a range from about 5:1 to about 10:1. No part of the annular surface 346 and no part of the radiused annular surface 344 extend radially inward of the inboard bearing support surface 244.
The annular profile 340 may have yet another radiused annular surface 348 located between the radiused annular surface 346 and the bearing support surface 244 of the cylindrical section 282. The annular surface 348 transitions the annular surface 346 in a direction toward, and into, the bearing support surface 244 of the cylindrical section 282. The annular surface 348 has a radius R14. The radius R14 may be in the range of about 0.150 inch to about 0.500 inch, and preferably about 0.250 inch.
A peak or cusp 360 (
The annular shoulder portion 262 of the axle spindle 224 typically experiences relatively heavy loads and stress, for example, bending stress, Hertzian contact stress and/or axial stress. Bending stress typically increases due to stress concentration from a rapid section change of diameters. The annular profile 340 substantially lowers, or substantially removes, the peak bending stresses caused by the stress concentration in the annular shoulder portion 262. The resulting decreased total stress level in the annular shoulder portion 262 lowers the potential for fretting and galling of the annular shoulder surface 264 and the annular side surface 260 of the inner cone 304. The axle spindle 224 has a relatively small rate of section modulus change in the axial direction in the annular shoulder portion 262. The relatively smooth and/or small rate of section modulus change helps reduce localized stress concentrations and smoothly distributes stress to maintain or improve fatigue life. The decreased total stress level in the annular shoulder portion 262 may also enable the use of at least a thinner transition section 320.
Alternate geometry configurations of the annular profiles 140 and 340 are illustrated in
By way of example, the axle spindle 424a-d is preferably a straight or non-tapered type of axle spindle with the same bearing support surface 44. The axle spindle 424a-d has the annular shoulder portion 462 with an annular shoulder surface 464 that is common to the alternate geometry configurations illustrated in
The annular shoulder surface 464 forms the end of the annular shoulder portion 462 and the beginning of the bearing support surface 44. The annular shoulder surface 464 is preferably circumferentially uninterrupted or continuous. The annular shoulder surface 464 extends in a radial direction from, and substantially perpendicular to, a longitudinal central axis (not shown) of the axle spindle 424a-d.
The annular profile 440a-d (
The size and location of the annular profile 440a-d substantially lowers the peak bending stresses in the annular shoulder portion 462. The resulting decreased total stress level in the annular shoulder portion 462 lowers the potential for fretting and galling of the annular shoulder surface 464 of the annular shoulder portion 462. The relatively small rate of section modulus changes in the annular shoulder portion 462 may also reduce strain and, thus, stress concentrations in the shoulder portion 462. This relatively small rate of section modulus change enables the use of a less robust or thinner shoulder portion 462 compared to a prior art axle spindle. This structure of axle spindle 424a-d and the annular shoulder portion 462 may allow the use of relatively lighter weight bearings. The annular profile 440a-d may be of any suitable size and configuration that reduces strain and stress concentrations, as well as providing a relatively small rate of section modulus change, in the annular shoulder portion 462.
Specifically, a radiused surface 444a (
By way of example, the radiused surface 444a of the annular profile 440a may have an annular surface defining a radiused portion 446a located between the annular shoulder surface 464 and the inboard bearing support surface 44. The radiused portion 446a helps transition the inboard bearing support surface 44 in a direction toward the annular shoulder surface 464. The radiused portion 446a has a radius R41 (
The radiused surface 444a of the annular profile 440a may have another annular surface defining a radiused portion 448a located between the radiused portion 446a and the annular shoulder surface 464 of the shoulder portion 462. The radiused portion 448a transitions the radiused portion 446a in a direction toward the annular shoulder surface 464. The radiused portion 448a has a radius R42 that is preferably less than the radius R41 of the first radiused portion 446a. The radius R42 of the radiused portion 448 may be about 0.068 inch but no less than about 0.060 inch. A ratio of the first radius R41 to the second radius R42 is preferably in a range from about 5:1 to about 10:1. No part of the surface of the radiused portion 446a and no part of the surface of the radiused portion 448a have a diameter that is less than the diameter of the inboard bearing support surface 44.
The annular profile 440a may have an inclined surface or continuously annular frustoconical segment 442a (
The radiused surface 444a of the annular profile 440a is located between the frustoconical segment 442a and the bearing support surface 44. The radiused surface 444a forms the bottom or radially inward portion, as viewed in
Other important dimensions and relationships for the axle spindle 424a (
A ratio of D/C is 1.032 and no less than 1.03 for axle spindle 424a as long as the radius R42 is more than 0.060 inch. There may be some configurations where the radius R42 may be less than 0.060 inch. Where the radius R42 happens to be less than 0.060 inch, the ratio of D/C would be greater than 1.05 for axle spindle 424a. The axle spindle 424a also has a ratio of C/G of 1.445 and no less than 1.44.
An axle spindle 424b (
The radiused surface 444b may have an annular surface defining a radiused portion 446b located between the annular shoulder surface 464 and the inboard bearing support surface 44. The radiused portion 446b helps transition the inboard bearing support surface 44 in a direction toward the annular shoulder surface 464. The radiused portion 446b has a radius R41 (
The radiused surface 444b of the annular profile 440b may have another annular surface defining a radiused portion 448b located between the radiused portion 446b and the annular shoulder surface 464 of the shoulder portion 462. The radiused portion 448b transitions the radiused portion 446b in a direction toward the annular shoulder surface 464. The radiused portion 448b has a radius R42 that is preferably less than the radius R41 of the radiused portion 446b. The radius R42 of the radiused portion 448b may be about 0.075 inch but no less than 0.060 inch. A ratio of the radius R41 to the radius R42 is preferably in a range from about 5:1 to about 10:1. No part of the surface of the radiused portion 446b and no part of the surface of the radiused portion 448b have a diameter that is less than the diameter of the inboard bearing support surface 44.
The annular profile 440b may have an inclined surface or continuously annular frustoconical segment 442b (
The radiused surface 444b of the annular profile 440b is located between the frustoconical segment 442b and the bearing support surface 44 and includes radiused portions 446b and 448b. The radiused surface 444b forms the bottom or radially inward portion, as viewed in
The axle spindle 424b (
An axle spindle 424c (
The radiused surface 444c of the annular profile 440c may have an annular surface defining a first radiused portion 446c located between the annular shoulder surface 464 and the inboard bearing support surface 44. The first radiused portion 446c helps transition the inboard bearing support surface 44 in a direction toward the annular shoulder surface 464. The first radiused portion 446c has a first radius R41 (
The radiused surface 444c of the annular profile 440c may have another annular surface defining a radiused portion 448c located between the first radiused portion 446c and the annular shoulder surface 464 of the shoulder portion 462. The second radiused portion 448c transitions the radiused portion 446c in a direction toward the annular shoulder surface 464. The radiused portion 448c has a second radius R42 that is preferably less than the first radiused surface R41 of the first radiused portion 446. The second radius R42 of the second radiused portion 448c may be about 0.07 inch but no less than 0.060 inch. A ratio of the radius R41 to the radius R42 is preferably in a range from about 5:1 to about 10:1. No part of the surface of the radiused portion 446c and no part of the surface of the radiused portion 448c have a diameter that is less than the diameter of the inboard bearing support surface 44.
The annular profile 440c may have an inclined surface or continuously annular frustoconical segment 442c (
The radiused surface 444c of the annular profile 440c is located between the frustoconical segment 442c and the bearing support surface 44. The radiused surface 444c forms the bottom or radially inward portion, as viewed in
The axle spindle 424c (
An axle spindle 424d (
The radiused surface 444d of the annular profile 440d may have an annular surface defining a radiused portion 446d located between the annular shoulder surface 464 and the inboard bearing support surface 44. The radiused portion 446d helps transition toward the inboard bearing support surface 44 in a direction toward the annular shoulder surface 464. The radiused portion 446d has a radius R41 (
The radiused surface 444d of the annular profile 440d may have another annular surface defining a radiused portion 448d located between the first radiused portion 446d and the annular shoulder surface 464 of the shoulder portion 462. The radiused portion 448d transitions the radiused portion 446d in a direction toward the annular shoulder surface 464. The radiused portion 448d has a radius R42 that is preferably less than the radius R41 of the radiused portion 446. The radius R42 of the radiused portion 448d may be in the range of about 0.060 inch to about 0.125 inch and preferably about 0.094 inch. A ratio of the radius R41 to the radius R42 is preferably in a range from about 5:1 to about 10:1. No part of the surface of the radiused portion 446d and no part of the surface of the radiused portion 448d has a diameter less than the diameter of the inboard bearing support surface 44.
The axle spindle 424d (
The axle spindle 24, 224 of the subject disclosure possesses another important feature that contributes to providing a relatively strong and light weight axle spindle with a relatively thin-wall, as illustrated in
Lower stress and small rate of section modulus change result from a relatively wide choice of axially extending inner and outer surface profile parameters for the axle spindle 24, 224, such as radius size, and/or location of radiused surfaces. The lower stress and small rate of section modulus change is enabled by the configuration of an annular profile configuration and/or the inner and outer surface profiles of the axle spindle 24, 224. The axle spindle 24, 224 is designed and manufactured to have the relatively small rate of section modulus change in the axial direction in at least the annular shoulder portion 62 and possibly a portion of the tubular transition section 120.
By way of example, the representative axle spindle 24 (
The tubular transition section 120 is formed with a configuration that provides the relatively small rate of change in section modulus at least in the annular shoulder portion 62. The annular shoulder portion 62 has a portion with a rate of change of section modulus between adjacent analysis slices S1-S8 (
The annular shoulder portion 62 and tubular transition section 120 have a section modulus calculated at each slice S1-S8 over a predetermined analysis distance DA. In one particular analysis mode, the slices S1-S8 are equally spaced apart a distance d of 0.050 inch from the annular shoulder surface 64 in the inboard direction.
The results of the analysis of the prior art axle spindle is illustrated in
The results of the analysis of the axle spindle 24, according to one configuration of the subject disclosure, is illustrated in
The annular shoulder portion 62 of the axle spindle 24 typically experiences relatively heavy loads and stress, for example, bending stress, Hertzian contact stress and/or axial stress. Bending stress typically increases due to stress concentration from a rapid section change of diameters as evidenced by a rate of change in section modulus, such as that illustrated in
The advantages of the annular profile 140, 340, 440 and/or specific axially extending profiles of the outer surface 122 and inner surface 124 in certain regions of the axle spindle, such as the transition section 120, reduces stress concentrations. The smooth and small rate of change in section modulus in the axle spindle 24 may yield optimal physical and performance characteristics of the axle spindle, especially in the annular shoulder portion 62. The resultant structure of axle spindle 24 and the annular shoulder portion 62 provides a thinner and relatively lighter weight axle spindle. This is demonstrably illustrated by the differential wall thicknesses DWTi and DWTo (
The annular profile 140, 340, 440 and/or specific axially extending profiles of the outer surface 122 and inner surface 124 reduce strain and stress concentrations in the annular shoulder portion 62, 262 and transition section 120, 320 and, thus may increase the fatigue life of the axle spindle 24, 224. The annular profile 140, 340, 440 and/or specific axially extending profiles of the outer surface 122 and inner surface 124 also increase the life of the bearing 48, 248 because the axle spindle 24, 224 can decrease fretting of the annular shoulder surface 64, 264. The annular profile 140, 340, 440 can also increase the amount of time before fretting becomes an issue by providing additional space for lubricant to occupy and for receiving any dislodged material of the shoulder surface 64, 264 that occurs due to eventual fretting. The annular profile 140, 340, 440 may not completely prevent fretting or galling, as fretting and/or galling will eventually occur no matter what due to axial loading that occurs during operation of the heavy-duty vehicle.
The disclosed subject matter successfully incorporates a relatively lightweight one-piece integrally formed axle spindle 24, 224 into a wheel end assembly and axle assembly for heavy-duty vehicles. More specifically, the axle spindle 24, 224 of the disclosed subject matter can save weight and material by providing a relatively thinner wall than previously known axle spindles, yet still provide the requisite strength, performance characteristics, such as increased bearing life and durability, that are required in the transportation industry.
An axle assembly 600 for a heavy-duty vehicle, constructed according to an aspect of the disclosed subject matter, is illustrated in
The central tube 602 is hollow or tubular with any appropriate cross-sectional shape and size. Preferably, the central tube 602 has a round cross-section taken in a plane perpendicular to the longitudinal central axis A and axially opposite annular end surfaces 620. The central tube 602 is elongated with a length CTL (
Each of the of the axle spindles 604 is preferably hollow or tubular over its entire length ASL and has a round tubular end portion or skirt 622 with an annular end surface 624. Each of the of the axle spindles 604 also includes a tubular transition section 626 extending axially outboard from the tubular end portion or skirt 622 and reducing in outer diameter over its axial extent in a direction away from the annular end surface 624. The axle spindles 604 may be made of any suitable material, such as steel. Preferably, the inner and outer diameters of the tubular end portion or skirt 622 of the axle central tube 602 and of the axle spindle 604 are substantially the same at their respective annular end surfaces 620, 624. It is contemplated that the inner diameters of the central tube 602 and the skirt 622 could be different. Each of the axle spindles 604 may include the structure, features, properties and strength of the axle spindles 24, 224, 424 described above. Each of the axle spindles 604 may also include an antilock braking system sensor bracket locator nub 660 (
The annular end surface 620 of the axle central tube 602 and the annular end surface 624 of axle spindle 604 are joined together by any suitable method according to an aspect. It will be appreciated that any suitable means of permanently joining an axle spindle 604 to the central tube 602 may be used, for example friction, MIG, TIG, arc, oxyacetylene gas, laser, projection, butt or capacitance welding, and the like. It will be appreciated that while the central tube 602 is illustrated and described as having an axially continuous round tubular cross-section for exemplary purposes, it could apply equally to other axle types and configurations, such as a drive axle with rectangular mating surfaces. What matters in the disclosed subject matter is that the end surface 620 of the axle central tube 602 and the end surface 624 of axle spindle 604 are similar in shapes and sizes.
The axle spindle 604 includes an unfinished portion or chucking land pad 640 with a circumferentially continuous arcuate ring 642 located in the transition section 626 and generally extending to or near an outboard end portion of the axle spindle 604. The unfinished portion or chucking land pad 640 is illustrated in
One of the suitable manufacturing processes is friction welding. For example, the central tube 602 can be held in a fixed, non-rotating, position. The annular ring 642 of one of the axle spindles 604 is engaged and gripped by tool or chuck apparatus 644 (
The unfinished portion or chucking land pad 640 is removed or machined away to a finished or near finished condition is illustrated in solid lines in
The ABS sensor bracket locator nub 660 is used to locate an antilock braking system sensor bracket 682 (
The ABS sensor bracket locator nub 660 also aids in quickly and efficiently properly locating the antilock braking system sensor bracket 682 during manufacturing. For example, the axle spindle 604 axially receives the ABS sensor bracket 682 from the outboard direction of the axle spindle. The ABS sensor bracket 682 is moved axially inboard until at least one stop surface 684 (
The results of the analysis of the axle spindle 604 according to another configuration of the subject disclosure is illustrated in
The largest change in section modulus in the tubular transition section 626 is about 13% between adjacent slices occurs where the ABS sensor bracket locator nub 660 is located at about 1.86 inches inboard from the shoulder surface 662. This relatively smooth and/or small rate of section modulus change in the remainder of the axle spindle 604 reduces localized stress concentrations and smoothly distributes stress to maintain or improve fatigue life. It is believed that a rate of change in stress of less than about 20%, preferably less than 14% provides advantageous and desirable relatively lower localized and evenly distributed stress.
The tubular transition section 626 of the axle spindle 604 typically experiences relatively heavy loads and stress, for example, bending stress, Hertzian contact stress and/or axial stress. Bending stress typically increases due to stress concentration from a rapid section change of diameters as evidenced by a rate of change in section modulus, such as that illustrated in
The axle spindle of the disclosed subject matter provides an improved axle spindle that is relatively light in weight, reduces material use and cost and increase axle spindle and bearing life. The improved axle spindle may better withstand localized stress and strain and to minimize the wear, fretting, galling and/or deformation of the shoulder during operation of the heavy-duty vehicle. The improved axle spindle has a relatively low rate of change in section modulus, especially in the shoulder portion. The improved axle spindle incorporates structure to easily locate and mount an antilock braking system sensor bracket. The improved axle spindle may be efficiently integrally formed as one-piece. The improved axle spindle is capable of using standard or stock bearings or that may incorporate custom bearings which can benefit from the improved features of the disclosed subject matter. The disclosed subject matter also provides a method of manufacturing the improved axle spindle.
It is to be understood that the disclosed subject matter finds application in all types of axle assemblies, axle spindles and wheel end assemblies, without affecting the concept or implementation of the disclosed subject matter. While reference has been made generally to a heavy-duty vehicle for the purpose of convenience, it is with the understanding that such reference to a heavy-duty vehicle includes trucks, tractor-trailers or semi-trailers, and trailers, and the like.
In the foregoing description, certain terms have been used for brevity, clarity and understanding, but no unnecessary limitations are to be implied beyond the requirements of the prior art, because such terms are used for descriptive purposes and are intended to be broadly construed. The disclosed subject matter has been described and illustrated with reference to at least one specific aspect. It is understood that this description and illustration is by way of example and not limitation. Potential modifications and alterations will occur to others upon a reading and understanding of the disclosed subject matter, and it is understood that the disclosed subject matter includes all such modifications, alterations and equivalents.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 62/724,716 filed Aug. 30, 2018.
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