Carrier for planetary gear train

Abstract

A carrier for a planetary gear train, the carrier comprising a hub disposed about a rotational axis, the hub having an outer cylindrical surface including a plurality of splines extending in a longitudinal direction parallel to the rotational axis; and a deck extending away from the hub in a radial direction transverse to the longitudinal direction. The deck defines a plurality of holes therethrough, each of the plurality of holes being configured to receive a shaft of one of a plurality of planetary gears, the hub being disposed between the plurality of holes and the rotational axis along the radial direction. The splines have a parameter value (P) not less than 2.5 and not greater than 6.0.

Description

Technical Field

[0001] The present invention relates generally to gear trains for axle power transfer and, more particularly, to splines for coupling a planetary gear carrier to another gear in a truck final drive assembly. Background Art

[0002] Gear trains are known for transmitting mechanical axle power and for regulating the speed and / or torque properties of the axle power transmitted therethrough. One example of a known gear train arrangement is a double reduction planetary gear train, which has been used in final drive assemblies between drive axles and wheels of trucks. A double reduction planetary gear train may include a first planetary gear arrangement operatively coupled to a second planetary gear arrangement, wherein each of the first and second planetary gear arrangements includes a sun gear, a ring gear, and at least one planet gear.

[0003] The planet gears in a planetary gear arrangement can be directly coupled to a first gear by direct meshing of corresponding gear teeth and indirectly coupled to a second gear through a carrier supporting the planet gears. Splined shaft connections have been used to directly couple a carrier-planet gear assembly to another component in a gear train.

[0004] U.S. Patent No. 8,714,656, entitled "Travel Drive Assembly for Dump Trucks" (hereinafter referred to as the "'656 Patent"), addresses the problem of increasing the strength of splines in travel drives in response to the need to increase the load capacity of existing trucks. The '656 Patent describes increasing the axial length of the spline teeth to as great a value as possible to achieve the desired improvement in spline strength. However, there are limits to the spline length that can be used to increase strength while meeting packaging and cost constraints. Therefore, there is a need for improved spline connections in truck propulsion trains.

[0005] It should be understood that this background description is created to assist the reader and is not intended to limit what is known in the art regarding any of the issues identified. Summary of the Invention

[0006] In one aspect, the present invention describes a carrier for mounting a plurality of planetary gears in a planetary gear train. The carrier includes a hub arranged about an axis of rotation, the hub having an outer cylindrical surface, the outer cylindrical surface including a plurality of splines extending along a longitudinal direction, the longitudinal direction being parallel to the axis of rotation; and a deck extending away from the hub in a radial direction, the radial direction being transverse to the longitudinal direction. The deck defines a plurality of holes therethrough, each of the plurality of holes being configured to receive a shaft of one of the plurality of planetary gears. The hub is arranged along the radial direction between the plurality of holes and the axis of rotation. The spline has a parameter value (P) not less than 2.5 and not greater than 6.0. The parameter (P) is defined as

[0007]

[0008] Where T = surface tensile strength of multiple splines, GPa;

[0009] L s = total length of multiple splines along the longitudinal direction, mm;

[0010] D b = the bottom diameter of multiple splines, mm;

[0011] N = the total number of splines in the plurality of splines;

[0012] D r = root diameter of multiple splines, mm; and

[0013] D o =Outer diameter of multiple splines, mm.

[0014] In another aspect, the present invention describes a final drive for a truck. The final drive includes a first planetary gear train comprising a first sun gear, a first ring gear, and a first plurality of planet gears mounted to a first carrier; and a second planetary gear train comprising a second sun gear, a second ring gear, and a second plurality of planet gears mounted to a second carrier. The first carrier includes a hub disposed about a rotational axis, the hub having an outer cylindrical surface including a plurality of splines extending in a longitudinal direction parallel to the rotational axis, the splines of the first carrier directly coupling with the internal splines of the second sun gear such that the first carrier and the second sun gear are fixed for rotation about the rotational axis; and a deck extending away from the hub in a radial direction transverse to the longitudinal direction, the deck defining a plurality of apertures therethrough. Each of the first plurality of planet gears is mounted to a corresponding aperture of the first carrier via an axle disposed through the corresponding aperture such that each of the first plurality of planet gears is free to rotate relative to the first carrier about the corresponding axis. The spline has a parameter (P) value of not less than 2.5 and not more than 6.0. Parameter (P) is defined as

[0015]

[0016] Where T = surface tensile strength of multiple splines, GPa;

[0017] L s = total length of multiple splines along the longitudinal direction, mm;

[0018] D b = the bottom diameter of multiple splines, mm;

[0019] N = the total number of splines in the plurality of splines;

[0020] D r = root diameter of multiple splines, mm; and

[0021] D o =Outer diameter of multiple splines, mm.

[0022] In another aspect, the present invention describes a mining truck. The mining truck includes a frame and a propulsion drive train coupled to the frame. The propulsion drive train includes a prime mover operably connected to a propulsion wheel via a final drive for transmitting mechanical shaft power therebetween. The final drive includes a first planetary gear train operably coupled to the prime mover via a drive shaft, the first planetary gear train including a first sun gear, a first ring gear, and a first plurality of planet gears mounted to a first carrier; and a second planetary gear train including a second sun gear, a second ring gear, and a second plurality of planet gears mounted to a second carrier. The propulsion wheel is rotationally fixed to an output member of the second planetary gear train.

[0023] The first carrier includes a hub disposed about a rotation axis, the hub having an outer cylindrical surface including a plurality of splines extending in a longitudinal direction parallel to the rotation axis, the splines of the first carrier being directly coupled to the internal splines of the second sun gear such that the first carrier and the second sun gear are fixed for rotation about the rotation axis; and a deck extending away from the hub in a radial direction transverse to the longitudinal direction, the deck defining a plurality of holes therethrough. Each of the first plurality of planetary gears is mounted to a corresponding hole of the first carrier via an axle disposed through the corresponding hole such that each of the first plurality of planetary gears is free to rotate relative to the first carrier about the corresponding axis.

[0024] The outer diameter of the plurality of splines is not less than 250 mm and not more than 259 mm, and the total number of splines is not less than 58 and not more than 64. The splines have a parameter (P) value of not less than 3.0 and not more than 5.2. Parameter (P) is defined as

[0025]

[0026] Where T = surface tensile strength of multiple splines, GPa;

[0027] L s = total length of multiple splines along the longitudinal direction, mm;

[0028] D b = the bottom diameter of multiple splines, mm;

[0029] N = the total number of splines in the plurality of splines;

[0030] D r = root diameter of multiple splines, mm; and

[0031] D o =Outer diameter of multiple splines, mm. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a side view of a machine according to one aspect of the present invention.

[0033] Figure 2 is a rear view of a machine according to one aspect of the present invention.

[0034] Figure 3 is a schematic diagram of a propulsion powertrain according to one aspect of the present invention.

[0035] Figure 4 is a schematic diagram of a final drive according to one aspect of the present invention.

[0036] Figure 5 is a cross-sectional view of a final drive according to one aspect of the present invention.

[0037] Figure 6 is a cross-sectional view of a final drive according to one aspect of the present invention.

[0038] Figure 7 is a perspective view of a bracket according to one aspect of the present invention.

[0039] Figure 8 is a plan view of a bracket according to one aspect of the present invention.

[0040] Figure 9 is a cross-sectional view of a bracket according to one aspect of the present invention.

[0041] Figure 10 is a plan view of a spline on a wheel hub according to one aspect of the present invention. DETAILED DESCRIPTION

[0042] Aspects of the present invention will now be described in detail with reference to the drawings, wherein like reference numerals refer to like elements throughout unless otherwise specified.

[0043] Figure 1A side view of a machine 100 is shown that is powered by a prime mover 104 that is configured to convert stored energy into mechanical power. Prime mover 104 can be an internal combustion engine configured to convert chemical energy into mechanical energy, an electric motor configured to convert electrical energy into mechanical energy, a combination thereof, or any other prime mover known in the art. According to one aspect of the invention, prime mover 104 does not include an internal combustion engine, and according to another aspect of the invention, prime mover 104 does not include an electric motor.

[0044] The machine 100 may be a road vehicle, such as a truck used in transportation, or may be any other type of machine that performs operations associated with an industry such as mining, construction, farming, transportation, forestry, or any other industry known in the art. For example, the machine may be an off-highway truck; an on-highway truck; a marine machine; an earth-moving machine, such as a wheel loader, an excavator, a dump truck, a backhoe, or a motor grader; a material handling device; a feller buncher; and the like. Figure 1 The particular machine 100 shown is a dump truck having a material handling bed 118 operated by an actuator 120 .

[0045] Machine 100 includes at least one propulsion device 112 that rotates or translates relative to a frame 114 of machine 100 to propel machine 100 across work surface 110. At least one propulsion device 112 may include wheels, continuous track assemblies, combinations thereof, or any other ground propulsion device known in the art.

[0046] Propulsion devices 112 are operatively coupled to prime movers 104 to transmit shaft power therebetween, thereby achieving a propulsion function. Additionally, a final drive assembly 116 may be included in the propulsion powertrain between prime movers 104 and at least one propulsion device 112 .

[0047] Figure 2 1 shows a rear view of a machine 100 according to one aspect of the present invention. The final drive assembly 116 can be coupled to the differential 130 via an axle tube 132 and a spindle 134. In addition, the axle tube 132 and the spindle 134 can surround the drive shaft ( Figure 2 134 and 136. The final drive assembly 116 may be axle-mounted, axle-mounted, and / or axle-mounted shaft (not shown) for transmitting mechanical shaft power between the differential 130 and the propulsion device 112 via the final drive assembly 116. The spindle 134 may be fixed to the axle tube 132 such that the spindle 134 does not rotate relative to the axle tube 132. Additionally, some portions of the final drive assembly 116 may be fixed to the spindle 134 such that these portions do not rotate relative to the spindle 134, while other portions of the final drive assembly that are directly or indirectly coupled to the propulsion device 112 may be free to rotate relative to the spindle 134. Portions of the final drive assembly 116 may be fixed to the spindle via a reaction hub coupled therebetween.

[0048] It should be understood that Figure 2 The differential 130 and axle tube 132 shown in FIG are non-limiting examples and may be replaced with other arrangements known in the art, such as an electric motor having a stator and / or housing fixed to a spindle 134 and an output rotor shaft operatively coupled to the final drive assembly 116 for transmitting mechanical shaft power therebetween.

[0049] Figure 3 A schematic diagram of a propulsion powertrain 140 according to one aspect of the present invention is shown. In propulsion powertrain 140, the input of differential 130 is operatively coupled to prime mover 104 via transfer gearbox 142 for transmitting mechanical shaft power therebetween. Furthermore, each propulsion device 112 is operatively coupled to the output of differential 130 via drive shaft 144 and final drive assembly 116 for transmitting mechanical shaft power therebetween. Thus, each propulsion device 112 can receive mechanical shaft power from prime mover 104 via propulsion powertrain 140.

[0050] According to one aspect of the present invention, final drive assembly 116 is a speed reduction gear train such that the rotational speed of propulsion device 112 is less than the rotational speed of drive shaft 144 by operation of final drive assembly 116. Furthermore, the final drive assembly may not include a speed increasing gear train.

[0051] Now see Figure 4-6 , Figure 4 A schematic diagram of a final drive assembly 116 is shown according to one aspect of the present invention; Figure 5 shows a cross-sectional view of a final drive assembly 116 according to one aspect of the present invention; Figure 6 A cross-sectional view of a final drive assembly 116 according to one aspect of the present invention is shown. The final drive assembly 116 may include a double reduction planetary gear train including a first stage planetary gear train 200 and a second stage planetary gear train 202 operatively coupled to the first stage planetary gear train 200.

[0052] The first-stage sun gear 204 of the first-stage planetary gear train 200 can receive mechanical shaft power from the drive shaft 144 through a direct or indirect coupling of the drive shaft 144 to the first-stage sun gear 204. For example, the first-stage sun gear 204 can be directly coupled to the drive shaft 144 via a spline connection, an interference fit, a welded connection, a keyed connection, a combination thereof, or any other arrangement known in the art for coupling a gear to a shaft. As a result, the drive shaft 144 and the first-stage sun gear 204 can be fixed for rotation about a first axis of rotation 206.

[0053] The first-stage sun gear 204 can be directly coupled to one or more first-stage planetary gears 210, for example, by intermeshing the gear teeth of the first-stage sun gear 204 with the gear teeth of one or more first-stage planetary gears 210, for transmitting mechanical shaft power therebetween. Furthermore, the first-stage planetary gears 210 can be mounted on a first-stage carrier 212 such that each first-stage planetary gear 210 can freely rotate about its own second axis 214, which defines the axis of rotation of each first-stage planetary gear 210 relative to the first-stage carrier 212.

[0054] Each first-stage planetary gear 210 can also be directly coupled to a first-stage ring gear 216, for example, by intermeshing the gear teeth of each first-stage planetary gear 210 with the gear teeth of the first-stage ring gear 216, for transmitting mechanical shaft power therebetween. According to one aspect of the present invention, the first-stage ring gear 216 can be mechanically grounded to the spindle 134 such that the first-stage ring gear 216 is fixed for rotation with the spindle 134. The first-stage ring gear 216 can be mechanically grounded to the spindle 134 via a reaction hub 250 coupled therebetween.

[0055] Mechanical grounding of first stage ring gear 216 to spindle 134 may be achieved by directly coupling first stage ring gear 216 in contact with spindle 134 via a bolted connection, welded connection, splined connection, interference connection, combinations thereof, or any other suitable connection known in the art. Alternatively, first stage ring gear 216 may be indirectly coupled to spindle 134 via an intermediate structure (e.g., reaction hub 250) secured to both first stage ring gear 216 and spindle 134.

[0056] Thus, the first stage carrier 212 can rotate about the first axis of rotation 206 while each of the first stage planet gears 210 rotates relative to the first stage carrier 212 about its respective second axis 214. However, it should be understood that other arrangements of the first stage planetary gear train 200 are within the scope of the present invention. For example, the first stage ring gear 216 can freely rotate about the first axis of rotation 206 while one of the first stage sun gear 204 or the first stage carrier 212 is mechanically connected to the spindle 134, or the first stage sun gear 204 can be fixed for rotation with the first stage carrier 212.

[0057] The second-stage sun gear 230 of the second-stage planetary gear train 202 can receive mechanical shaft power from the hub 218 of the first-stage carrier 212 through a direct coupling of the hub 218 to the second-stage sun gear 230. For example, the second-stage sun gear 230 can be directly coupled to the hub 218 of the first-stage carrier 212 via a spline connection. As a result, the first-stage carrier 212 and the second-stage sun gear 230 can be fixed for rotation about a third axis of rotation 232. According to one aspect of the present invention, the third axis of rotation 232 can be coaxial with the first axis of rotation 206.

[0058] The second-stage sun gear 230 can be directly coupled to one or more second-stage planet gears 234, for example, by intermeshing the gear teeth of the second-stage sun gear 230 with the gear teeth of one or more second-stage planet gears 234, for transmitting mechanical shaft power therebetween. Furthermore, the second-stage planet gears 234 can be mounted on a second-stage carrier 236 such that each second-stage planet gear 234 can freely rotate about its own fourth axis 238, which defines the axis of rotation of each second-stage planet gear 234 relative to the second-stage carrier 236.

[0059] Each second-stage planetary gear 234 can also be directly coupled to a second-stage ring gear 240, for example, by intermeshing the gear teeth of each second-stage planetary gear 234 with the gear teeth of the second-stage ring gear 240, for transmitting mechanical shaft power therebetween. According to one aspect of the present invention, the second-stage ring gear 240 can be mechanically grounded to the spindle 134 such that the second-stage ring gear 240 is fixed for rotation with the spindle 134. The second-stage ring gear 240 can be mechanically grounded to the spindle 134 via a reaction hub 250 coupled therebetween.

[0060] Mechanical grounding of second stage ring gear 240 to spindle 134 may be achieved by directly coupling second stage ring gear 240 in contact with spindle 134 via bolting, welding, splined connection, interference fit, combinations thereof, or any other suitable connection known in the art. Alternatively, second stage ring gear 240 may be indirectly coupled to spindle 134 via an intermediate structure (e.g., reaction hub 250) secured to both second stage ring gear 240 and spindle 134.

[0061] Thus, the second stage carrier 236 can rotate about the third axis of rotation 232 while each second stage planet gear 234 rotates about its corresponding fourth axis 238 relative to the second stage carrier 236. The propulsion device 112 can, in turn, be directly or indirectly coupled to the second stage carrier 236 to drive the propulsion device 112 to rotate relative to the spindle 134 about the third axis of rotation 232.

[0062] However, it should be understood that other arrangements of the second stage planetary gear train 202 are within the scope of the present invention. For example, the second stage ring gear 240 can freely rotate about the third axis of rotation 232 while one of the second stage sun gear 230 or the second stage carrier 236 is mechanically grounded to the spindle 134, or the second stage sun gear 230 can be fixed for rotation with the second stage carrier 236.

[0063] Figure 6 The cutting plane of the cross section shown in is a plane including the first rotation axis 206 and the third rotation axis 232 , and the plane cuts through the first stage carrier 212 and the second stage carrier 236 , but does not cut through either the first stage planetary gears 210 or the second stage planetary gears 234 . Figure 5 The cutting plane of the cross section shown in is a plane including the first rotation axis 206, the third rotation axis 232, the second axis 214 for the two first stage planetary gears 210 arranged on opposite sides of the first stage carrier 212, and the fourth axis 238 for the two second stage planetary gears 234 arranged on opposite sides of the second stage carrier 236. Figure 5 and Figure 6 In the non-limiting aspect shown, the first axis of rotation 206 is coaxial with the third axis of rotation 232 .

[0064] Reference Figure 5 and Figure 6 The propulsion device 112 may include a rim 260 configured to receive a tire and hold the tire fixed for rotation with the rim 260 for propulsive engagement with the work surface 110. The rim 260 may be fixed to the second-stage bracket 236 via an output hub 262 such that the rim 260, the output hub 262, and the second-stage bracket 236 are all fixed for rotation about the third axis of rotation 232. The output hub 262 may be integrated with the second-stage bracket 236 as a one-piece assembly, or the output hub 262 may be a separate component fastened to the second-stage bracket 236 by any suitable fastening means known in the art. The output hub 262 may be fastened to the rim 260 by bolts, rivets, welding, combinations thereof, or any other suitable fastening means known in the art.

[0065] See also Figure 7-9 , Figure 7 is a perspective view of a first stage bracket 212 according to one aspect of the present invention; Figure 8 is a plan view of a first stage bracket 212 according to one aspect of the present invention; Figure 9 is a cross-sectional view of a first stage bracket 212 according to one aspect of the present invention. Figure 7-9In each of the embodiments, an axial direction 300 extends parallel to the first rotational axis 206 ; a radial direction 302 extends transverse to the axial direction 300 ; and a circumferential direction 304 extends circumferentially around the axial direction 300 . Figure 9 The cutting plane is Figure 8 Section line 9 - 9 is shown passing through the first rotational axis 206 along a radial direction 302 .

[0066] The first stage cradle 212 may include a hub 218 and a first deck 310 extending away from the hub 218 in a radial direction 302. The first stage cradle 212 may further include a second deck 312 spaced apart from the first deck 310 in an axial direction 300 and extending away from the hub 218 in the radial direction 302. The first deck 310 may be secured to the second deck 312 via one or more webs 314 extending in the axial direction 300. The first deck 310 may be located between the second deck 312 and the hub 218 in the axial direction 300. An outer circumferential surface 318 of one or both of the first deck 310 and the second deck 312 may be a cylindrical surface extending in a circumferential direction 304 about the first axis of rotation 206 and in an axial direction.

[0067] The hub 218 has an outer surface 316 extending in a circumferential direction 304 about the first rotational axis 206. The outer surface 316 may include a cylindrical surface 320 defining a plurality of splines 322. Each spline 322 extends along the axial direction 300, and adjacent splines 322 are distributed about the hub 218 along the circumferential direction 304. The plurality of splines 322 may be evenly distributed about the circumferential direction 304 such that, within applicable manufacturing tolerances, the distance between adjacent splines 322 is uniform throughout the plurality of splines 322. Furthermore, the plurality of splines 322 may have a total length 324 extending along the axial direction 300 (see FIG. 2 ). Figure 9 Each spline in the plurality of splines 322 may have the same nominal overall length 324 within applicable manufacturing tolerances.

[0068] According to one aspect of the present invention, the total number of splines in the plurality of splines 322 is advantageously in the range of 58 to 64. According to another aspect of the present invention, the total number of splines 322 is equal to 60. However, it should be understood that the plurality of splines 322 may include any number of splines to suit a particular application.

[0069] Hub 218 may also have an inner surface 326 that extends in circumferential direction 304 about first rotational axis 206. Outer surface 316 and inner surface 326 may define a thickness of hub 218 in radial direction 302. Alternatively, hub 218 may not have inner surface 326 and instead extend solidly from first rotational axis 206 to outer surface 316.

[0070] The first deck 310 can define a first plurality of holes 330 therethrough, and the second deck 312 can define a second plurality of holes 332 therethrough. Each hole in the first plurality of holes 330 and a corresponding hole in the second plurality of holes 332 can be centered about the second axis 214, which defines an axis of rotation for a planetary gear mounted to the first stage carrier 212 via the corresponding hole, wherein each second axis 214 is parallel to the axial direction 300. As a result, each hole in the first plurality of holes 330 can directly face a corresponding hole in the second plurality of holes 332 along the axial direction 300.

[0071] The total number of holes in the first plurality of holes 330 may be equal to the total number of holes in the second plurality of holes 332 such that each hole in the first plurality of holes 330 uniquely pairs with a corresponding hole in the second plurality of holes 332 along the corresponding second axis 214 .

[0072] Reference Figure 5 Each first-stage planet gear 210 may be coupled to the first-stage carrier 212 via a shaft 340 that extends through a corresponding hole in the first plurality of holes 330 and the second plurality of holes 332. Furthermore, each first-stage planet gear 210 may be rotationally engaged with each shaft 340 via a bearing 342 disposed therebetween, such that each first-stage planet gear 210 is free to rotate relative to its corresponding shaft 340 about the corresponding second axis 214.

[0073] According to one aspect of the present invention, the first-stage planetary gear train 200 includes a total of four first-stage planetary gears 210. According to another aspect of the present invention, the first-stage planetary gear train 200 includes at least two first-stage planetary gears 210. However, it should be understood that the first-stage planetary gear train 200 may include any number of first-stage planetary gears 210 to suit a particular application.

[0074] Each second stage planet gear 234 can be coupled to the second stage carrier 236 via a shaft 346, and each second stage planet gear 234 can rotationally engage each shaft 346 via a bearing 348 disposed therebetween. Each second stage planet gear 234 is then free to rotate relative to its respective shaft 346 about the corresponding fourth axis 238.

[0075] Figure 10is a plan view of the splines 322 on the hub 218 according to one aspect of the present invention. Each spline tooth 322 can be at least partially defined by a root surface 400, a first side surface 402, a tip surface 404, and a second side surface 406. According to one aspect of the present invention, the first side surface 402, the second side surface 406, or both can embody an involute curve in a plane defined only by the radial direction 302 and the circumferential direction 304. However, it should be understood that the first side surface 402 and the second side surface 406 can embody any profile suitable for a particular application. Although Figure 10 The tip surface 404 and the root surface 400 are shown as including rounded corners, but it should be understood that the tip surface 404, the root surface 400, or both may be flat and not have rounded corners.

[0076] Tip surface 404 may define an outer diameter 410 (D o ), the root surface 400 may define a root diameter (D r ) 412. Although the outer diameter 410 and the root diameter 412 are Figure 10 The dimension relative to the first axis of rotation 206 is obviously the radius, but it should be understood that the diameter can be defined as Figure 10 According to one aspect of the present invention, outer diameter 410 is the diameter of a circle that surrounds plurality of splines 322 in a plane defined exclusively by radial direction 302 and circumferential direction 304, within manufacturing tolerances. According to another aspect of the present invention, root diameter 412 may be the diameter of a circle that inscribes root surface 400 in a plane defined solely by radial direction 302 and circumferential direction 304, within manufacturing tolerances.

[0077] For the design and analysis of splines, according to Equation 1, the pitch diameter 416 (D p ) and pressure angle To define the bottom diameter 414 (D b ) may be useful.

[0078]

[0079] In addition, the pitch circle diameter D p It can be defined by the total number of splines (N) and the module of the splines (M) according to Equation 2.

[0080] D p =N·M Equation 2

[0081] The module (M) can be defined as the inverse of the spline pitch circle (1 / pitch circle).

[0082] In addition, the parameter (P) according to Equation 3 can also be used for the design and analysis of splines.

[0083]

[0084] Where: T = surface tensile strength of multiple splines, Gigapascals (GPa);

[0085] L s = total length of multiple splines along the longitudinal direction, millimeters (mm);

[0086] D b = the bottom diameter of multiple splines, mm;

[0087] N = the total number of splines in the plurality of splines;

[0088] D r = root diameter of multiple splines, mm; and

[0089] D o =Outer diameter of multiple splines, mm.

[0090] The tensile strength of the plurality of splines may be evaluated on the tip surface 404, the first side surface 402, the second side surface 406, the root surface 400, or a combination thereof. According to one aspect of the invention, the tensile strength of the plurality of splines is evaluated on the tip surface 404.

[0091] According to one aspect of the present invention, the material of the hub 218 and the splines 322 is ductile iron. According to another aspect of the present invention, the material of the hub 218 and the splines 322 is ductile iron according to ASTM International Standard ASTM A536. According to another aspect of the present invention, the material of the hub 218 and the splines 322 is ductile iron according to ASTM International Standard ASTM A536, having a grade of 100-70-03. However, it should be understood that other suitable materials are within the scope of the present invention.

[0092] For a given material of the hub 218 and the spacer 322, heat treatment, case hardening, or a combination thereof may be applied to adjust the final surface tensile strength of the spline 322. According to one aspect of the present invention, the heat treatment of the spline 322 may be performed by rotational hardening, wherein the spline 322 may be rotated in front of a heat source to achieve a target surface tensile strength of the spline 322. According to another aspect of the present invention, the heat treatment of the spline 322 may be performed by a tooth-by-tooth method, wherein an induction heating source is disposed between the tooth sides of adjacent spline teeth around a circumferential direction 304 to achieve a target surface tensile strength of the spline 322. Non-limiting examples of case hardening methods include nitriding, carburizing, and boriding. However, it will be understood that other suitable heat treatments or case hardening methods are also within the scope of the present invention for adjusting the surface tensile strength of the spline 322.

[0093] Industrial Applicability

[0094] The present invention is generally applicable to gear trains, and more particularly to splines of planet gear carriers in final drive planetary gear trains.

[0095] Final drive assembly 116 is subject to stringent and competitive constraints regarding strength, lifespan, package size, operability, and cost. In an exemplary application in a mine, a mining truck may be required to operate up a steep grade with a maximum payload to transport ore from the mine floor to the mine rim. In such an application, the steep and continuous rise of the working surface combined with the heavy payload places extreme stress on the propulsion drive train and presents particular challenges in terms of final drive component life and operability due to available gear selection limitations imposed by the final drive torque.

[0096] The volume available for final drive packaging is limited by the fact that the final drive is largely enclosed within the rim of the corresponding wheel. Consequently, the ability to make final drive components larger to extend component life and broaden truck maneuverability may be limited by the available packaging volume within the rim, not to mention practical cost constraints. Furthermore, applying specialized materials to increase strength and life within packaging constraints may be cost-prohibitive. Furthermore, dimensional deformation during heat treatment may impose practical limits on the surface tensile strength achievable through hardening.

[0097] The applicant has identified designs for carrier splines in final drives that outperform conventional approaches by applying the parameter (P) defined above in Equation 3. These superior designs increase component life under increased loads, widen available gear ratios during steep climbs, conform to conventional packaging and cost constraints, and are advantageously defined within a critical range of values ​​for parameter (P).

[0098] According to the first aspect of the present invention, these superior designs correspond to a range of parameter (P) values ​​between 2.5 and 6.0. Designs with parameter (P) values ​​below 2.5 may not provide adequate component life and gear selection operability, while designs with parameter (P) values ​​above 6.0 may not fit within packaging and cost constraints.

[0099] According to the second aspect of the invention, the advantageous design corresponds to the conditions in the above-mentioned first aspect, and the outer diameter of the spline 322 is in the range from 250 mm to 259 mm, and the total number of spline teeth (N) is in the range from 58 to 64.

[0100] According to a third aspect of the present invention, an advantageous design corresponds to the conditions of any one of the first or second aspects described above, and the total length of the plurality of splines is in the range of 35 mm to 140 mm.

[0101] According to a fourth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to third aspects described above, and the surface tensile strength of the plurality of splines is in the range of 0.6 GPa to 2.5 GPa.

[0102] According to a fifth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to fourth aspects described above, and parameter (P) is in the range of 3.0 to 5.2. A design with a parameter value (P) lower than 3.0 may not provide sufficient component life and gear selection operability, while a design with a parameter value (P) higher than 5.2 may not be suitable for packaging and cost constraints.

[0103] According to a sixth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to fifth aspects described above, and the total length of the plurality of splines is within a range of 35 mm to 95 mm.

[0104] According to a seventh aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to sixth aspects described above, and the surface tensile strength of the plurality of splines is within a range of 1.0 GPa to 2.5 GPa.

[0105] According to an eighth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to seventh aspects described above, and parameter (P) is in the range of 3.2 to 4.0. A design with a parameter value (P) lower than 3.2 may not provide sufficient component life and gear selection operability, while a design with a parameter value (P) higher than 4.0 may not be suitable for packaging and cost constraints.

[0106] According to a ninth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to eighth aspects described above, and the total length of the plurality of splines is within a range of 60 mm to 80 mm.

[0107] According to a tenth aspect of the present invention, a favorable design corresponds to the conditions of any one of the first to ninth aspects described above, and the surface tensile strength of the plurality of splines is within a range of 1.0 GPa to 2.0 GPa.

[0108] It should be understood that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other implementations of the present invention may differ in detail from the foregoing examples. All references to the present invention or examples thereof are intended to reference the specific examples discussed at that point and are not intended to imply any limitation on the scope of the present invention more generally. All distinctions and inconsistent language regarding certain features are intended to indicate a lack of preference for those features, but not to exclude them from the scope of the present invention entirely, unless otherwise indicated.

[0109] Listing features in alternatives is considered to provide support for disclaiming any alternative features by negative limitation in the claims.

[0110] Recitation of ranges of values ​​herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context.

Claims

1. A carrier for mounting a plurality of planetary gears in a planetary gear train, the carrier comprising: a hub disposed about an axis of rotation, the hub having an outer cylindrical surface including a plurality of splines extending in a longitudinal direction parallel to the axis of rotation; as well as a deck extending away from the hub in a radial direction, the radial direction being transverse to the longitudinal direction, The deck defines a plurality of holes therethrough, each of the plurality of holes being configured to receive a shaft (340) of one of the plurality of planetary gears, the hub being disposed between the plurality of holes and the rotational axis along the radial direction, The spline has a parameter value (P) not less than 2.5 and not more than 6.0, The parameter (P) is defined as follows Where T = surface tensile strength of multiple splines, GPa; L s = total length of multiple splines along the longitudinal direction, mm; D b = the bottom diameter of multiple splines, mm; N = the total number of splines in the plurality of splines; D r = root diameter of multiple splines, mm; and D o =Outer diameter of multiple splines, mm. 2 . The bracket according to claim 1 , wherein an outer diameter of the plurality of splines is not less than 250 mm and not more than 259 mm, and a total number of the splines is not less than 58 and not more than 64. 3 . The bracket according to claim 1 , wherein the total length of the plurality of splines is not less than 35 mm and not more than 140 mm. 4 . The bracket according to claim 1 , wherein a surface tensile strength of the plurality of splines is not less than 0.6 GPa and not more than 2.5 GPa.

5. The bracket according to any one of claims 1 to 4, wherein the parameter (P) is not less than 3.0 and not more than 5.

2.

6. The bracket according to any one of claims 1 to 5, wherein the parameter (P) is not less than 3.2 and not more than 4.

0.

7. The bracket according to any one of claims 1 to 6, wherein a total length of the plurality of splines is not less than 35 mm and not more than 95 mm.

8. The bracket according to any one of claims 1 to 7, wherein a surface tensile strength of the plurality of splines is not less than 1.0 GPa and not more than 2.5 GPa.

9. The bracket according to any one of claims 1 to 8, wherein a total length of the plurality of splines is not less than 60 mm and not more than 80 mm.

10. The bracket according to any one of claims 1 to 9, wherein a surface tensile strength of the plurality of splines is not less than 1.0 GPa and not more than 2.0 GPa.

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