Trunnion mount

Abstract: A unique trunnion mount for an axle assembly allows the axle to pivot about a longitudinal axis of a vehicle. The trunnion mount is comprised of two separate mounts, each of which is supported by an axle housing. The first mount is supported by the bearing cage on the input side of the axle housing. The second mount is attached to the opposite side of the axle housing and is comprised of a V-shaped bushing which presents angular exterior bearing surfaces which rotatably support the vehicle frame.

Description: This invention relates to an axle assembly, trunnion mount for an axle assembly and a vehicle axle bushing according to the preamble of claims 1, 9 and 14, respectively, which each allows the axle to pivot about a longitudinal axis of a vehicle. A typical axle assembly includes first and second driven wheels which are rotated by a driveshaft through a main differential. The axle assembly includes an axle housing which encloses the main differential and extends along a central axis between the driven wheels. The axle can be mounted to a vehicle frame by various methods. Some axle housings include spring pads or other mounting pads, located on a top surface of the axle housing between the main differential and the driven wheels. Brackets, springs, and other suspension components are attached to the axle housing via these mounting pads for supporting the vehicle frame on the axle. Other axles utilize a trunnion mount for mounting the axle assembly to a vehicle frame. A typical trunnion mount includes first and second mounts disposed on longitudinally opposite sides of the central axis near the main differential for supporting the axle housing on the vehicle. An axle with a trunnion mount allows rotation about a longitudinal axis of the vehicle. Current trunnion mounts use bearings for the first and second mounts. Usually, the first mount is supported by tapered roller bearings mounted on the pinion bearing cage located near the input shaft to the main differential while the second mount, attached to the opposite side of the main differential, is a tapered roller bearing or a straight cylindrical bushing which supports a vehicle frame bracket. These bearings react to both radial and axial forces that occur during the operation of the vehicle as a result of the duty cycle and vehicle loading. Over time, these forces cause the bearings to wear and eventually they need to be replaced. These bearings are expensive and require regular maintenance. US-A-3 811 699 which defines the closest prior art shows an axle assembly, a trunnion mount for an axle and a vehicle axle bushing. The axle assembly and the trunnion mount comprise two opposite bushings placed on opposite sides of the axle housing. Both bushings are sliding bearings one of which being a movable bearing and the other one being a fixed bearing. The fixed bearing is defined by four ring-shaped parts for reacting to axial and radial forces. US-A-3 861 764 discloses a radial and thrust bearing for a vehicle steering gear. Within a housing, a cylindrical shaft is rotatably mounted via a V-shaped bushing. There is no hint to use the bushing for an axle assembly. GB-A-1 407 405 discloses an assembly comprising a housing and a shaft. The housing has two spaced apart frustro-conical seats facing in opposite directions in order to support a rotating shaft within the housing. It would be desirable to reduce the axial and radial loading on the vehicle axle bearings so that longer component life can be achieved. It would also be desirable to replace the tapered roller bearing with a less expensive component. Thus, there is a need for an axle assembly a trunnion mount and a vehicle axle bushing comprised of components with a long service life which are inexpensive and easily maintained, and which can be properly assembled. This objects are achieved by claims 1, 9 and 14, respectively. The subject invention relates to a unique trunnion mount for connecting an axle assembly to a vehicle frame and which allows the axle to pivot about a longitudinal axis of a vehicle. The trunnion mount is comprised of two separate mounts, each of which is supported by an axle housing. Thus, each mount represents an interconnection between the axle assembly and the vehicle frame. The first mount is supported by a bearing cage on the input side of the axle housing. The second mount is on the opposite side of the axle housing and has a V-shaped bushing which presents angular exterior bearing surfaces to rotatably support the vehicle frame. The first mount reacts only to radial forces while the second mount reacts to both axial and radial forces occurring during operation of the vehicle. The inventive mount is preferably utilized in an axle assembly for a vehicle having first and second mount interfaces. The first mount interface includes a first bracket assembly extending downwardly from the vehicle frame. The first bracket assembly is rotatably supported on the bearing cage on the input side of the axle housing, thus comprising the first mount, i.e. the first interconnection between the axle assembly and the vehicle frame. The second mount interface includes a second bracket assembly extending downwardly from the vehicle frame. The second bracket assembly is supported on the V-shaped bushing located on the axle housing opposite from the bearing cage, thus comprising the second mount, i.e. the second interconnection between the axle assembly and the vehicle frame. The V-shaped bushing of the second mount presents a bearing surface for sliding engagement with an opposing bearing surface on the second bracket assembly. The bearing surface of the V-shaped bushing has two surfaces that are disposed at a angular relationship to a central bushing axis. The invention offers several advantages over prior art trunnion mounts because it decreases the loading on the front mount resulting in longer component life and decreases the overall cost by eliminating the expensive tapered roller bearing for the first or second mount by replacing it with a unique V-shaped bushing. Other advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein: Figure 1 is a perspective view of an axle assembly utilizing the subject invention; Figure 2 is a side view of the axle assembly of Figure 1 showing the subject invention in cross-section; Figure 3 is an enlarged view of the subject invention enclosed in circle 3 of Figure 2; and Figure 4 is a front view of the subject invention. A typical axle assembly 10, shown in Figure 1, includes first 12 and second 14 driven wheels which are rotated by a driveshaft 16 through a main differential 18. The driveshaft 16 enters an input side 20 of the main differential 18 and is supported on a bearing 22. The bearing 22 is well known in the art and is comprised of an inner race, an outer race, rolling elements, and a bearing cage 24. The axle assembly 10 includes an axle housing 26 which encloses the main differential 18 and extends along a central axis 28 between the driven wheels 12, 14. The axle 10 is mounted to a vehicle 30 by a trunnion mount, shown generally at 32, which allows the axle 10 to rotate or pivot about a longitudinal axis 34 of the vehicle 30 disposed transversely to the central axis 28 of the axle housing 26, as shown by the arrows in Figure 1. Trunnion mount 32 is comprised of two separate mounts for supporting axle assembly 10 on vehicle 30, a first mount 36 and a second mount 38, each supported by the axle housing 26 and which are disposed on longitudinally opposite sides of the central axis 28. Thus, each mount 36, 38 represents an interconnection between the axle assembly 10 and the vehicle frame. Trunnion mount 32 is preferably used with a vehicle 30 having first 40 and second 42 mount interfaces. The first mount interface 40 includes a first bracket assembly 44 extending downwardly from the vehicle frame. The first bracket assembly 44 is rotatably supported on the bearing cage 24 on the input side 20 of the axle housing 26, thus comprising the first mount 36, i.e., the first interconnection between the axle assembly 10 and the vehicle frame. The second mount interface 42 includes a second bracket assembly 45 extending downwardly from the vehicle frame. The second bracket assembly 45 is supported on a V-shaped bushing 46 located on the axle housing 26 opposite from the bearing cage 24, thus comprising the second mount 38, i.e. the second interconnection between the axle assembly 10 and the vehicle frame. The first mount 36 reacts only to radial forces, while the second mount 38 reacts to both axial and radial forces that occur during the operation of the vehicle 30 as a result of the vehicle's duty cycle and vehicle loading. As shown in Figure 2, the V-shaped bushing 46 of the second mount 38 presents a bearing surface 48 (48A and 48B) for sliding engagement with an opposing bearing surface 50 on the second bracket assembly 45. Either or both of the bearing surfaces 48, 50 can be sliding surfaces. The bearing surface 48 of the V-shaped bushing 46 is comprised of two surfaces 48A, 48B that are disposed at a angular relationship to a central bushing axis 52 which represents the centerline of the bushing 46. The bearing surfaces 48A, 48B originate at an apex located on the central bushing axis 52 and extend radially outwardly from opposite sides of the central bushing axis 52, thus forming a V-shape. It should be understood that the angular relationship between bearing surface 48A and the central bushing axis 52 can be of any various angles between zero and ninety degrees, as can the angular relationship between bearing surface 48B and the central bushing axis 52. While the angle between bearing surface 48A and the central bushing axis 52 is preferably identical to the angle between bearing surface 48B and the central bushing axis 52, the invention is not limited to this embodiment. Thus, it is possible for the angles between the bearing surfaces 48A and 48B and the central bushing axis 52 to be different from each other. While the bushing 46 of the preferred embodiment is comprised of two (2) pieces, an outer piece 54 and an inner piece 56, joined together to make a single bushing 46, it should be understood that the bushing 46 could be made as a single piece component. Thus, the descriptions in this application encompass both a two (2) piece and a single piece bushing 46. The A and B designations have been added to the numbers to indicate similar components of the inner 56 and outer 54 pieces of the bushing 46, respectively. For example, the bearing surface 48 represents the exterior surface of the bushing 46 which slidably engages the opposing surface 50 for rotatably supporting the axle assembly 10 on the vehicle 30. In the preferred embodiment, this bearing surface 48 is comprised of two components, an inner piece 56 and an outer piece 54, each of which has its own bearing surface 48A and 48B respectively. In the preferred embodiment, the outer 54 and inner 56 pieces of the bushing 46 are of frustroconical shape, however, it should be understood that other shapes can be used. When outer 54 and inner 56 pieces of frustroconical shape are used, it is preferred that the pieces 54, 56 be assembled such that the faces with the smaller cross sectional areas are mated together, resulting in symmetrical disposition about the central bushing axis 52. The outer piece 54 includes first 58 and second 60 faces and the inner piece 56 includes first 62 and second 64 faces. The first faces 58, 62 of the outer 54 and inner 56 pieces are of larger cross sectional area than the second faces 60, 64. The first face 62 of the inner piece 56 engages the axle housing 26 and the second face 60 of the outer piece 54 engages the second face 64 of the inner piece 56. Shims 66 can be placed between the outer 54 and inner 56 pieces for adjusting end play resulting from clearances between the outer 54 and inner 56 pieces. The axle housing 26 includes a circumferential extension 68 which engages a mating circumferentially disposed lip 70 on the inner piece 56. This extension 68 locates the inner piece 56 with respect to the axle housing 26 and ensures that the bushing 46 is properly assembled onto the axle assembly 10. Fasteners 72 (only one is shown) hold the outer 54 and inner 56 pieces together and attach the bushing 46 to the axle assembly 10. In the preferred embodiment bolts are used, however, any suitable fasteners known in the art can be used. Also, other joining methods such as welding or using adhesives could be used to hold the outer 54 and inner 56 pieces together. The outer 54 and inner 56 pieces also include hollow center portions 74 disposed about the longitudinal axis 34. These hollow center portions 74 help reduce the weight of the axle assembly 10. As shown in Figure 3, the bushing 46 includes an interior surface 76 (76A and 76B) and an exterior surface 78 (78A and 78B), with the bearing surface 48 (48A and 48B) of the bushing 46 being located on the exterior surface 78 (78A and 78B). As previously mentioned, the bushing 46 of the preferred embodiment is comprised of two pieces joined together to make a single bushing 46, but could be made as a single piece component. The A and B designations have been added to the numbers to indicate similar components of the inner 56 and outer 54 pieces of the bushing 46, respectively. Seals 84 are located between the exterior surface 78A, 78B of the bushing 46 and the opposing bearing surface 50. The seals 84 surround the outer 54 and inner 56 pieces of the bushing 46 and protect the bushing's bearing surface 48A, 48B from contaminants. In the preferred embodiment, the outer 54 and inner 56 pieces are formed from steel and include a nylon coating 92 on their exterior surfaces 78A, 78B. It should be understood that other materials can be used to make the outer 54 and inner 56 pieces and any bushing material known in the art can be used as the coating. The outer piece 54 of the bushing 46 is shown in Figure 4. The inner piece 56 is preferably of similar design and any descriptions applying to the outer piece 54 should be understood to also apply to the inner piece 56. The outer piece 54 includes grooves 86 for receiving lubricant on its exterior surface 78B. The grooves 86 are located such that the lubricant can be easily applied, thus providing easy maintenance. The outer 54 and inner 56 pieces include four (4) fastening holes 88 disposed radially around the longitudinal axis 34. These four fastening holes 88 are used for pre-assembly of the outer 54 and inner 56 pieces. The appropriate number of shims 66 are sandwiched between the outer 54 and inner 56 pieces and four bolts (not shown) are inserted into the four fastening holes 88 so that the pieces 54, 56 are firmly held together. This pre-assembly of the bushing 46 allows the correct preload to be set. The outer 54 and inner 56 pieces also include eight (8) bolt holes 90 for assembling the bushing 46 onto the axle housing 26. These holes 90 are also disposed radially around the longitudinal axis 34. Once the outer 54 and inner 56 pieces of the bushing 46 are assembled, the bushing 46 is placed against the axle housing 26 and eight (8) bolts (not shown) are inserted into the holes 90 so that the bushing 46 is securely fastened to the axle housing 26. While a drive axle assembly 10 has been described in this application, it should be understood that the inventive trunnion mount 32 with the V-shaped bushing 46 could be used on a non-drive axle. Also, while the bushing has been referred to as "V-shaped" throughout this application, it should be understood that the bushing is not limited to a specific V-shape where two straight-line surfaces intersect at a common point. That is, within the definition of V-shaped the surfaces themselves could be curved or otherwise non-linear or the two surfaces could terminate at a curved apex.

Claims: An axle assembly (10) for a vehicle having a longitudinal axis (34) comprising: an axle housing (26) extending along a central axis (28) to be disposed transversely to the longitudinal axis (34) of a vehicle and including first and second mounts (36, 38) disposed on longitudinally opposite sides of said central axis (28) for supporting said axle housing (26) on a vehicle, said second mount (38) including a bushing (46) having a central bushing axis (52) and presenting a bearing surface (48) for sliding engagement with an opposing bearing surface (50), said bushing (46) including an outer piece (54) and an inner piece (56) disposed on opposite sides of said central bushing axis (52) characterized in that said bearing surface (48) being disposed at an angular relationship relative to said central bushing axis (52) for reacting to both axial and radial forces, and that said axle housing (26) includes an extension (68) which engages a circumferentially disposed lip (70) of said inner piece (56) for locating said inner piece (56) with respect to said axle housing (26). An axle assembly (10) as set forth in claim 1 wherein said bearing surface (48) is comprised of two surfaces (48A, 48B), said surfaces (48A, 48B) originating at an apex on said central bushing axis (52) and extending radially outwardly from opposite sides of said central bushing axis (52) forming a V. An axle assembly (10) as set forth in claim 2 wherein said outer and inner pieces (54, 56) are generally frustroconical. An axle assembly (10) as set forth in claim 2 or 3 wherein said outer and inner pieces (54, 56) are symmetrically disposed about said central bushing axis (52). An axle assembly (10) as set forth in any of the preceding claims wherein said outer piece (54) is connected to said inner piece (56) by at least one fastener (72). An axle assembly (10) as set forth in any of the preceding claims wherein said outer and inner pieces (54, 56) include hollow center portions (74) for reducing the weight of said axle assembly (10). An axle assembly (10) as set forth in any of the preceding claims wherein said bushing (46) includes grooves (86) for receiving lubricant. An axle assembly (10) as set forth in any of the preceding claims wherein said first mount (36) is supported by a bearing cage, said first mount (36) reacting only to radial forces. A trunnion mount (32) for a vehicle comprising: a first member having a longitudinal axis (34); a second member in the form of an axle housing (26) extending along a central axis (28) to be disposed transversely to said longitudinal axis (34) of said first member; a first interface (40) depending from said first member; a second interface (42) depending from said first member and spaced apart from said first interface (40); a first mount (36) supported by said second member for engaging said first interface (40); and a second mount (38) supported by said second member longitudinally opposite from said first mount (36) for engaging said second interface (42), said second mount (38) including a bushing (46) having a central bushing axis (52) and presenting an exterior bearing surface (48) for sliding engagement with an opposing bearing surface (50) of said second interface (42), said bushing (46) including an outer piece (54) and an inner piece (56) disposed on opposite sides of said central bushing axis (52), characterized in that said bearing surface (48) being disposed at an angular relationship relative to said central bushing axis (52), whereby said first and second mounts rotatably support said first member on said second member, and that said axle housing (26) includes an extension (68) which engages a circumferentially disposed lip (70) of said inner piece (56) for locating said inner piece (56) with respect to said axle housing (26). A trunnion mount (32) as set forth in claim 9 wherein said exterior bearing surface (48) is comprised of two surfaces (48A, 48B), said surfaces (48A, 48B) originating at an apex on said central bushing axis (52) and extending radially outwardly from opposite sides of said central bushing axis (52) forming a V. A trunnion mount (32) as set forth in claim 9 or 10 wherein said bushing (46) includes an outer piece (54) and an inner piece (56) disposed on opposite sides of said central bushing axis (52), said inner piece (56) having a bearing surface (48A) and said outer piece (54) having bearing surface (48A) wherein said bearing surfaces (48A, 48B) of said inner and outer pieces (56, 54) together form said exterior bearing surface (48) of said bushing (46). A trunnion mount (32) as set forth in claim 11 wherein said bearing surfaces (48A, 48B) of said outer and inner pieces (54, 56) include grooves (86) for receiving lubricant. A trunnion mount (32) as set forth in claim 11 or 12 wherein said inner and outer pieces (54, 56) are joined together by at least one fastener (72). A vehicle axle bushing comprising: a vehicle mounting member (45) presenting an interior bearing surface (50); an axle housing (26) supported for movement relative to said vehicle mounting member (45) about a longitudinal vehicle axis (34); and a bushing having a first piece and a second piece supported by said axle housing (26) and disposed on opposite sides of a central bushing axis (52) orientated generally perpendicular to said longitudinal axis (34), said first piece including a first exterior bearing surface (48A) and second piece including a second exterior bearing surface (48B), characterized in that said first and second exterior bearing surfaces (48A, 48B) originate at an apex located on said central bushing axis (52) and extend radially outwardly from opposite sides of said central bushing axis (52) forming a V, and that said axle housing (26) includes an extension (68) which engages a circumferentially disposed lip (70) of said first piece for locating said first piece with respect to said axle housing (26). A vehicle axle bushing (46) as set forth in claim 14 wherein said first and second exterior bearing surfaces (48A, 48B) of said first and second pieces include grooves (86) for receiving lubricant. A vehicle axle bushing (46) as set forth in claim 14 or 15 including at least one shim (66) placed between said first and second pieces for adjusting end play. A vehicle axle bushing (46) as set forth in any of claims 14 to 16 wherein said first and second pieces are formed from steel and said first and second bearing surfaces (48A, 48B) are coated with nylon. A vehicle axle bushing (46) as set forth in any of claims 14 to 17 wherein said first and second pieces are held together by at least one fastener (72).

Inventors: EL-KASSOUF RAJI SAID, EL-KASSOUF, RAJI SAID
Applicants: MERITOR HEAVY VEHICLE SYS LTD, MERITOR HEAVY VEHICLE SYSTEMS, LLC
Application year: 1998
Main classification: B60G9
IPC codes: B60G9, F16C17, B60B35, B60K17