Gearbox with torsion damper

Abstract

Gearbox (18) with: an input element (32), wherein the input element (32) has a hollow tubular shape, an output element (40), wherein the output element (40) has a hollow tubular shape, and a torsion damper (22) comprising: a first member (310) having a first hub (318), a first outer portion (326), and a plurality of first spokes (410), the first hub (318) being non-rotatably coupled to the input member (32) for common rotation with the input member (32) about an axis (34), the first outer portion (326) being radially outward of the first hub (318), the first spokes (410) extending radially between the first hub (318) and the first outer portion (326), the first spokes (410) coupling the first outer portion (326) to the first hub (318), and a second member (314) having a second hub (342) and a second outer portion (350), the second hub (342) being non-rotatably coupled to the output member (40) for common rotation with the output member (40) about the axis (34), the second outer portion (350) being radially outward of the second hub (342) and fixedly coupled to the second hub (342) and to the first outer portion (326), the first and second hubs (318, 342) defining a central opening (354), and a first shaft (24) drivingly coupled to one of the input member (32) or the output member (40) for receiving torque from one of the input member (32) or the output member (40), the shaft being supported for rotation about the axis (34) relative to the input member (32) and the output member (40), the first shaft (24) being concentrically received in the input member and output member (32, 40).

Description

AREA

[0001] The present disclosure relates to a transmission with a torsional damper. BACKGROUND

[0002] This section provides background information related to the present disclosure that is not necessarily prior art.

[0003] Transmissions typically include rotating shafts that transmit high torques from an input member to an output member. Additionally, drive modules that utilize one or more electric motors selectively operable to provide drive and / or torque distribution capabilities typically include drive shafts that couple the electric motor to the transmission. Such drive shafts may provide torque intermittently or in frequently reversing directions, which can induce mechanical shock through the transmission components. To reduce mechanical shock, reduce wear on various components within the transmission, and dampen noise caused by transmission failure, some degree of torsional resilience or flexibility in the rotating components of the transmission is desirable.However, torsional flexibility can be difficult to achieve in a rotating shaft or in the connection between two rotating shafts while maintaining adequate strength for transmitting high torques through the gearbox and minimizing the gearbox's packaging size. Adequate torsional flexibility can be particularly difficult to achieve in a hollow rotating shaft or in the connection between two hollow rotating shafts.

[0004] US Pat. No. 5,324,234 A describes a torsion damper with a first hub and a second hub, with a first outer element attached to the first hub and a second outer element attached to the second hub. The outer elements are, in turn, connected to one another. SUMMARY

[0005] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its full scope or all of its features.

[0006] The present teachings provide a transmission including an input member, an output member, and a torsional damper. The torsional damper may include a first member and a second member. The first member may include a first hub, a first outer portion, and a plurality of first spokes. The first hub may be non-rotatably coupled to the input member for common rotation with the input member about an axis. The first outer portion may be radially outward from the first hub. The first spokes may extend radially between the first hub and the first outer portion. The first spokes may couple the first outer portion to the first hub. The second member may include a second hub and a second outer portion. The second hub may be non-rotatably coupled to the output member for common rotation with the output member about the axis.The second outer portion may be located radially outward of the second hub and may be fixedly coupled to the second hub and to the first outer portion.

[0007] The present teachings further provide a transmission including a housing, a first shaft, a second shaft, and a torsional damper. The first shaft may be supported within the housing for rotation about an axis. The second shaft may be concentrically received within the first shaft. The torsional damper may comprise a first member and a second member. The first member may comprise a first hub and a plurality of first spokes. The first hub may define a central opening coaxial with the axis. A proximal end of each first spoke may be fixedly coupled to the first hub. Each first spoke may extend radially outward from the first hub to a distal end of the first spoke. The second member may comprise a second hub and an outer portion. The second hub may define a central opening coaxial with the axis.The outer portion may be fixedly coupled to the second hub and may extend radially outward from the second hub. The outer portion may be fixedly coupled to the distal end of each first spoke. One of the first and second hubs may be fixedly coupled to the first shaft for common rotation about the axis. The second shaft may extend through the central openings of the first and second hubs and may be drivingly coupled to the other of the first and second hubs.

[0008] The present teachings further provide a torsional damper for connecting an input member to an output member. The torsional damper may include a first member and a second member. The first member may be disposed about an axis and may include a first hub and a first disc. The first hub may be adapted to be non-rotatably coupled to the first shaft. The first disc may define a plurality of first spokes. A proximal end of each first spoke may be fixedly coupled to the first hub. Each first spoke may extend radially outward from the first hub to a distal end of the first spoke. The second member may be disposed about the axis and may include a second hub and a second disc. The second hub may be adapted to be non-rotatably coupled to the second shaft. The second disc may be fixedly coupled to the second hub and may extend radially outward from the second hub.The second disc may be rigidly coupled to the distal end of each first spoke.

[0009] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are for purposes of illustration only and are not intended to limit the scope of the present disclosure. DRAWINGS

[0010] The drawings described herein are intended to illustrate selected embodiments only and not all possible implementations and are not intended to limit the scope of the present disclosure. Fig. 1 is a schematic representation of a vehicle having a drive module constructed in accordance with the teachings of the present disclosure; Fig. 2 is a longitudinal sectional view of an example of a drive module taken along a rotational axis of an output shaft of an electric motor of the drive module, showing a torsional damper according to the present disclosure; Fig. 3 is a perspective view of the torsion damper of Fig. 2; Fig. 4 is a sectional view of the torsion damper taken along line 4-4 of Fig. 3; and Fig. 5 is a plan view of a portion of the torsion damper of Fig. 2.

[0011] Corresponding reference numerals in the individual views of the drawings indicate corresponding parts. DETAILED DESCRIPTION

[0012] Exemplary embodiments will now be described in more detail with reference to the accompanying drawings.

[0013] With reference to Fig. 1 of the drawings, an exemplary vehicle 8 is shown having a powertrain P, a conventional front-wheel drive powertrain F that can be driven by the powertrain P, and a drive module 10 constructed in accordance with the teachings of the present disclosure. The powertrain P may include an internal combustion engine E and a transmission T that can be driven by the engine. The transmission T can output rotational power to the front-wheel drivetrain F, which can transmit the rotational power to drive two vehicle front wheels WF. The drive module 10 can be selectively operated to transmit the rotational power to two vehicle rear wheels WR.

[0014] With reference to Fig. 2, the drive module 10 is shown in more detail. In the example provided, the drive module 10 may include a housing 12, an electric motor 14, a drive pinion 16, a transmission 18, a differential assembly 20, a torsional damper 22, and first and second axle shafts 24 and 26. The housing 12 may define a structure in which the drive pinion 16, the transmission 18, and the differential assembly 20 may be housed. The electric motor 14 may include a stator 28, which may be fixedly coupled to the housing 12, a rotor 30, and a hollow output shaft 32. The rotor 30 may be fixedly coupled to the output shaft 32 for common rotation about an axis 34. The output shaft 32 may be retained within the housing 12 by a first bearing 36 and a second bearing 38. The output shaft 32 can be coupled to the torsion damper 22 for common rotation about the axis 34.The drive pinion 16 may include a pinion shaft 40 and a pinion gear 42 mounted on the pinion shaft 40 for common rotation about the axis 34. The pinion shaft 40 may be retained by a third bearing 44 in the housing 12 and coupled to the torsional damper 22 for common rotation about the axis 34. The torsional damper 22 is described in more detail below. While the torsional damper 22 of the present disclosure is described herein with reference to the drive module 10, it is understood that it is applicable to other power-transmitting components where torsional resilience is desirable.

[0015] The pinion gear 42 may be drivingly coupled to the transmission 18 to transmit torque therebetween. The transmission 18 may be drivingly coupled to the differential assembly 20 to transmit torque therebetween. It is understood that any type of gearing arrangement could be used between the electric motor 14 and the differential assembly 20. In the particular example provided, the transmission 18 is a single-stage planetary gear concentrically disposed about the rotational axis 34 of the output shaft 32 of the electric motor 14. It is understood that other types of gearing may be used, such as double-stage planetary gears, compound planetary gears, or non-planetary gears. The transmission 18 may include the input pinion gear 42, which is a sun gear of the transmission 18, a ring gear 50, a plurality of compound planet gears 52, and a planet carrier 54. The ring gear 50 may be concentrically disposed about the input pinion gear 16 (i.e.about the axis 34) and may be non-rotatably coupled to the housing 12 in which the transmission 18 and the differential assembly 20 are housed. The ring gear 50 may include a plurality of internal teeth 58.

[0016] Each of the compound planetary gears 52 may include a first planetary gear member 60 and a second planetary gear member 62. The first planetary gear member 60 may include a hub 110 and a plurality of teeth 112 disposed about the hub 110 and meshing with the pinion gear 42. The second planetary gear member 62 may be fixedly coupled to the hub 110 of the first planetary gear member 60 for rotation therewith and may include a plurality of teeth 114 and a journal 116 disposed at an axial end opposite the end coupled to the hub 110. The teeth 114 of the second planetary gear member 62 may mesh with the inner teeth 58 of the ring gear member 50. The first and second planetary gear members 60 and 62 may have different pitch diameters.

[0017] The planetary carrier 54 may include a first carrier body 120, a second carrier body 122, a plurality of fourth bearings 124, and a plurality of fifth bearings 126. The fourth bearings 124, which may be ball bearings, may be fixedly mounted to the first carrier body 120 and may support the hubs 110 of the first planetary gear members 60 for rotation relative to the first carrier body 120. The fifth bearings 126, which may be needle bearings, may be fixedly mounted to the second carrier body 122 and may support the journal 116 of the second planetary gear members 62 for rotation relative to the second carrier body 122.

[0018] It will be appreciated that any type of differential assembly may be used to transmit differential torque between the transmission 18 and the first and second axle shafts 24, 26. In the particular example provided, the differential assembly 20 may include a differential case 210 and a differential gear set 212. The differential gear set 212 may include a cross pin 214, a plurality of pinion gears 216, and two side gears 218. The differential case 210 may be coupled to the first carrier body 120 and / or the second carrier body 122 for rotation therewith about the rotational axis 34 and may define a cavity 220 in which the pinion gears 216 and the side gears 218 may be received. The cross pin 214 may be coupled to the differential case 210 perpendicular to the rotational axis 34. The drive bevel gears 216 can be rotatably mounted on the cross pin 214.The side wheels 218 can be rotatable about the rotation axis 34 and can engage with the drive bevel gears 216.

[0019] Each of the first and second axle shafts 24 and 26 may be coupled to a corresponding one of the side wheels 218 for rotation therewith. The third bearing 44 may be radially disposed between the pinion shaft 40 and a portion of the differential case 210 such that the third bearing 44 supports the pinion shaft 40 for rotation relative to the differential carrier 210. The first axle shaft 24 may extend through the hollow pinion shaft 40, the torsion damper 22, and the output shaft 32. The second axle shaft 26 may extend from the differential carrier 210 in the opposite axial direction from the first axle shaft 24. Each of the first and second axle shafts 24 and 26 may be drivingly coupled to one of the vehicle rear wheels WR ( Fig. 1) be coupled.

[0020] With additional reference to Fig. 3-5, the torsional damper 22 is shown in more detail. The torsional damper 22 may include an input member 310 and an output member 314. The input member 310 may include a first hub 318 and a first disc 322 coupled to the first hub 318 for common rotation about the axis 34. The first disc 322 may extend radially outward from the first hub 318 to a first outer portion 326 of the first disc 322. The first hub 318 may be a generally cylindrical member that extends axially outward from the first disc 322 in an axial direction away from the output member 314 and may define a central opening 330. The central opening 330 may be disposed about the axis 34 and concentric with the output shaft 32. The first hub 318 may be fixedly coupled to the output shaft 32 for common rotation.In the example provided, the first hub 318 includes a plurality of internal splines 334 disposed around the central opening 330, which engage a plurality of external splines 338 formed at an axial end of the output shaft 32. It is contemplated that other methods for fixedly coupling the output shaft 32 to the first hub 318 may be used. The input member 310 may be formed as a unit from a single piece of material (e.g., a metal blank).

[0021] The output member 314 may include a second hub 342 and a second disc 346 coupled to the second hub 342 for common rotation about the axis 34. The second disc 346 may extend radially outward from the second hub 342 to a second outer portion 350 of the output member 314. The second hub 342 may be a generally cylindrical member extending axially outward from the second disc 346 in an axial direction away from the input member 310 and may define a central opening 354. The central opening 354 may be disposed about the axis 34 and concentric with the output shaft 32. The second hub 342 may be fixedly coupled to the pinion shaft 40 for common rotation.In the example provided, the second hub 342 includes a plurality of internal splines 358 disposed around the central opening 354 that engage a plurality of external splines 362 formed at an axial end of the pinion shaft 40. It is contemplated that other methods for fixedly coupling the pinion shaft 40 to the second hub 342 may be used. The output member 314 may be formed as a unit from a single piece of material (e.g., a metal blank).

[0022] The first and second outer portions 326, 350 of the input and output members 310, 314 may be fixedly coupled together for common rotation about the axis 34. In the example provided, the first and second outer portions 326, 350 are fixedly coupled by a plurality of fasteners 366 disposed around the periphery of the first and second outer portions 326, 350. With particular reference to Fig. 4, the fasteners 366 may extend through a plurality of bores 370 formed in the first and second outer portions 326, 350, which may be evenly spaced around the first and second outer portions 326, 350. In the example provided, the fasteners 366 are a plurality of rivets, although other types of fasteners may be used, such as bolts or screws. In an alternative construction, not specifically shown, the first and second outer portions 326, 350 may be welded together, such as by one or more welds disposed, for example, around the perimeter of the torsion damper 22.

[0023] The first and second outer portions 326, 350 may also be coupled together such that an inner surface 374 of the input member 310 may spacedly oppose an inner surface 378 of the output member 314. The inner surface 374 of the input member 310 may be defined by the first hub 318 and the portion of the first disc 322 that lies radially inward of the first outer portion 326. The inner surface 378 of the output member 314 may be defined by the second hub 342 and the portion of the second disc 346 that lies radially inward of the second outer portion 350. In the example provided, the first and second outer portions 326, 350 of the input and output members 310, 314 extend axially outwardly from the respective inner surfaces 374, 378 toward each other such that the first and second outer portions 326, 350 are adjacent to each other and the inner surfaces 374, 378 are spaced apart from each other.The splines 334, 358 of the first and second hubs 318, 342 and the splines 338, 362 of the output shaft 32 and the pinion shaft 40 may be configured such that the output shaft 32 and the pinion shaft 40 are axially spaced apart.

[0024] The first disc 322, the second disc 346, or both may include a plurality of spokes 410 spaced apart around the circumference of the respective disc 322, 346. The spokes 410 may be fixedly coupled at one end to the respective first or second hub 318, 342 and may extend radially outward from the first or second hub 318, 342 to be fixedly coupled to the respective first or second outer portion 326, 350. In the example provided, both the input member 310 and the output member 314 include spokes 410 such that a first set of spokes 410 extends between the first hub 318 and the first outer portion 326, and a second set of spokes 410 extends between the second hub 342 and the second outer portion 350. The spokes 410 may be arranged at a uniform distance around the corresponding disc 322, 346. The spokes 410 may be guided through openings 414 ( Fig. 3) that are evenly spaced around the circumference. In the example provided, the openings 414 generally have a teardrop or pedal shape, being narrower near the hub 318, 342 and wider near the outer portion 326, 350, although other shapes or configurations may be used. In the example provided, each outer portion 326, 350 forms a ring shape around the outermost periphery of the torsional damper 22 such that the openings 414 are closed (i.e., the spokes 410 of the input member 310 are coupled together by the first outer portion 326 and the spokes 410 of the output member 314 are coupled together by the second outer portion 350).In an alternative construction, not specifically shown, the openings 414 may be open at the periphery of the torsional damper 22, so that each spoke 410 of the input member 310 may have a free end coupled to a free end of a corresponding spoke 410 of the output member. In the example provided, the input and output members 310, 314 each have fourteen spokes, although other numbers of spokes may be used. Each spoke 410 may have a minimum width 418 (. Fig. 5) which are greater than a maximum axial thickness 422 of the spoke 410 ( Fig. 4). The number of fasteners 366 may be equal to the number of spokes 410, and each of the fasteners 366 may be circumferentially aligned with one of the spokes 410, although other configurations may be used.

[0025] In the example provided, the input member 310 and the output member 314 may be mirror images of each other, including the same number of spokes 410 and the same diameters of the central openings 330, 354 of the hubs 318, 342, although other configurations may be used. For example, the input member 310 may have a different number of spokes 410 than the output member 314 and / or the hubs 318, 342 may be configured to couple to different sized shafts. For example, the central opening 354 of the output member 314 may have a different diameter than the central opening 330 of the input member 310 to accommodate a pinion shaft 40 with a different diameter than the output shaft 32. Likewise, the first hub 318 may be coupled to the pinion shaft 40 in a different manner than the second hub 342 and the output shaft 32.

[0026] In operation, the electric motor 14 can drive rotation of the output shaft 32 about the axis 34. The output shaft 32 can provide torque to the pinion shaft 40 through the torsion damper 22, as indicated by arrow 510 ( Fig. 5). In this way, the output shaft 32 can provide input torque to the first hub 318. The first hub 318 can provide torque to the spokes 410 of the first disk 322. The spokes 410 of the first disk 322 can provide torque to the first outer portion 326. The first outer portion 326 can provide torque to the second outer portion 350 (e.g., through the fasteners 366). The second outer portion 350 can provide torque to the spokes 410 of the second disk 346. The spokes 410 of the second disk 346 can provide torque to the second hub 342. The second hub 342 can provide torque to the pinion shaft 40.

[0027] When the torque transmitted through the torsional damper 22 is high, such as during sudden starts, stops, or changes in the direction of rotation of either the output shaft 32 or the pinion shaft 40, the torque may cause bending of the spokes 410 of the input member 310 and / or the output member 314. For example, with reference to Fig.5, a first point A on the first hub 318 may be aligned along an axis 514 passing through the axis 34 and a second point B on the first outer portion 326 (e.g., the center point of the fastener 366). When the torque is relatively low, the spokes 410 do not bend, and points A and B remain aligned (i.e., rotate together at the same speed) while the torsional damper 22 rotates about the axis 34. When the torque input to the first hub 318 is high, the spokes 410 may bend so that point A initially rotates through a larger angle of rotation δ than point B (e.g., points A' and B'). Point B may temporarily remain stationary (shown as B') or initially rotate to a lesser extent than point A so that A' and B' are temporarily out of alignment.After the initial torque pulse, the elasticity of the spokes 410 may cause the first outer portion 326 to realign with the first hub 318. Points A, B, A', and B' are assumed to be illustrative and their corresponding locations are not to scale. The elasticity of the spokes 410 may provide torsional elasticity between the output shaft 32 and the pinion shaft 40. The spokes 410 may be made of any suitable material, such as a metal. In the example provided, the amount of torsional elasticity may be approximately 4,000 Newton meters per radian, although the spokes 410 may be designed to provide more or less elasticity depending on the requirements of the drive module 10.The torsional elasticity provided by the torsional damper 22 can thus reduce the mechanical shock through the transmission 18, reduce the wear of various components in the transmission 18, and otherwise dampen transmission noise caused by the transmission fault (e.g., caused by transmission tolerances).

[0028] Although coupling a hollow output shaft 32 to a hollow pinion shaft 40 was described above with reference to the torsional damper 22, the torsional damper 22 of the present teachings is applicable to provide torsional resilience between other types of shafts, such as two solid shafts or between a solid shaft and a hollow shaft.

[0029] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or limiting of the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where appropriate, are interchangeable and may be used in a selected embodiment even if not specifically shown or described. They may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

[0030] Example embodiments are provided for a thorough disclosure and to fully explain the scope to those skilled in the art. Numerous specific details are set forth, such as examples of particular components, devices, and methods, in order to provide a thorough understanding of embodiments of the present disclosure. Those skilled in the art will recognize that specific details need not be employed, that example embodiments may be embodied in many different forms, and that none should be construed as limiting the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail.

[0031] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," "an" and "the" can also include the plural forms unless the context clearly requires otherwise. The terms "comprises," "comprising," "having," and "having" are inclusive and therefore specify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0032] When an element or layer is referred to as being "on," "engaging," "connected," or "coupled to" another element or layer, it may be directly on, engaging, connected, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly engaging," "directly connected," or "directly coupled to" another element or layer, there may be no intervening elements or layers. Other terms used to describe the relationship between elements should be interpreted similarly (e.g., "between" versus "directly between," "adjacent" versus "directly adjacent," etc.). As used herein, the term "and / or" includes any and all combinations of one or more of the related listed elements.

[0033] Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers, and / or sections, these elements, components, regions, layers, and / or sections should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer, and / or section from another region, layer, or section. Terms such as "first," "second," and other numerical terms, when used herein, do not imply a sequence or order unless clearly indicated by the context.Thus, a first element, component, region, layer, or portion, as discussed below, could be referred to as a second element, component, region, layer, or portion without departing from the teachings of the exemplary embodiments.

Claims

[1] Gearbox (18) with: an input element (32), wherein the input element (32) has a hollow tubular shape, an output element (40), wherein the output element (40) has a hollow tubular shape, and a torsion damper (22) comprising: a first member (310) having a first hub (318), a first outer portion (326), and a plurality of first spokes (410), the first hub (318) being non-rotatably coupled to the input member (32) for common rotation with the input member (32) about an axis (34), the first outer portion (326) being radially outward of the first hub (318), the first spokes (410) extending radially between the first hub (318) and the first outer portion (326), the first spokes (410) coupling the first outer portion (326) to the first hub (318), and a second member (314) having a second hub (342) and a second outer portion (350), the second hub (342) being non-rotatably coupled to the output member (40) for common rotation with the output member (40) about the axis (34), the second outer portion (350) being radially outward of the second hub (342) and fixedly coupled to the second hub (342) and to the first outer portion (326), the first and second hubs (318, 342) defining a central opening (354), and a first shaft (24) drivingly coupled to one of the input member (32) or the output member (40) for receiving torque from one of the input member (32) or the output member (40), the shaft being supported for rotation about the axis (34) relative to the input member (32) and the output member (40), the first shaft (24) being concentrically received in the input member and output member (32, 40). [2] The transmission (18) of claim 1, wherein the second member (314) comprises a plurality of second spokes (410), the second spokes (410) extending radially between the second hub (342) and the second outer portion (350) and fixedly coupling the second hub (342) to the second outer portion (350). [3] The transmission (18) of claim 1, further comprising a gear set (42, 50, 52, 54) drivingly coupled to the output member (40) to receive torque from the output member (40), wherein the shaft (24) is drivingly coupled to the gear set (42, 50, 52, 54) to receive torque from the output member (40) through the gear set (42, 50, 52, 54). [4] The transmission (18) of claim 3 further comprising an electric motor (14) having a stator (28) and a rotor (30), the rotor (30) being drivingly coupled to the input member (32). [5] Transmission (18) according to claim 4, wherein the rotor (30) is fixedly coupled to the drive element (32) for common rotation about the axis (34). [6] The transmission (18) of claim 3 further comprising a second shaft (26), wherein the gear set (42, 50, 52, 54) includes a differential (20) configured to that it receives an input torque from the output element (40) and delivers a differential torque to the first and second shafts (24, 26). [7] The transmission (18) of claim 1, wherein the first member (310) defines a first surface (374) and the second member (314) defines a second surface (378) opposite the first surface (374) and axially spaced from the first surface (374). [8] The transmission (18) of claim 1, further comprising a plurality of fasteners (366), each of the fasteners (366) extending axially between the first and second outer portions (326, 350) to fixedly couple the first and second outer portions (326, 350). [9] The transmission (18) of claim 8, wherein the first member (310) is a first unitary body defining the first hub (318), the first spokes (410), and the first outer portion (326), and wherein the second member (314) is a second unitary body defining the second hub (342) and the second outer portion (350). [10] Gearbox (18) with: a housing (12), a first shaft (32) supported in the housing (12) for rotation about an axis (34), a second shaft (24) which is concentrically received in the first shaft (32), a torsion damper (22) comprising: a first member (310) having a first hub (318) and a plurality of first spokes (410), the first hub (318) defining a central opening (354) coaxial with the axis (34), a proximal end of each first spoke (410) being fixedly coupled to the first hub (318), each first spoke (410) extending radially outward from the first hub (318) to a distal end of the first spoke (410), and a second member (314) having a second hub (342) and an outer portion (350), the second hub (342) defining a central opening (354) coaxial with the axis (34), the outer portion (350) being fixedly coupled to the second hub (342) and extending radially outwardly from the second hub (342), the outer portion (350) being fixedly coupled to the distal end of each first spoke (410); wherein one of the first and second hubs (318, 342) is fixedly coupled to the first shaft (32) for common rotation about the axis (34), and wherein the second shaft (24) extends through the central openings (354) of the first and second hubs (318, 342) and is drivingly coupled to the other of the first and second hubs while being rotatable about the axis (34) relative to the first and second hubs (318, 342). [11] The transmission (18) of claim 10 further comprising a third shaft (40) rotatably mounted in the housing (12) about the axis (34) and concentric with the second shaft (24), wherein the central opening (354) of the first hub (318) defines a first set of internal gears (334) that mate with a first set of external gears (338) defined by the first shaft (32), and the central opening (354) of the second hub (342) defines a second set of internal gears (358) that mate with a second set of external gears (362) defined by the third shaft (40). [12] The transmission (18) of claim 10, wherein the outer portion (350) of the second member (314) comprises a plurality of second spokes (410), a proximal end of each second spoke (410) being fixedly coupled to the second hub (342), each second spoke (410) extending radially outwardly from the second hub (342) to a distal end of the second spoke (410), the distal end of each second spoke (410) being fixedly coupled to a distal end of a corresponding one of the first spokes (410). [13] The transmission (18) of claim 10, further comprising a gear set (42, 50, 52, 54) and a third shaft (40), the third shaft (40) being coupled for common rotation with the other of the first and second hubs (318, 342), the gear set (42, 50, 52, 54) being drivingly coupled to the third shaft (40) to receive torque from the third shaft (40), the second shaft (24) being drivingly coupled to the gear set (42, 50, 52, 54) to receive torque from the gear set (42, 50, 52, 54), the second shaft (24) being concentrically received in the first and third shafts (32, 40). [14] The transmission (18) of claim 13 further comprising an electric motor (14) having a stator (28) and a rotor (30), the rotor (30) being coupled to the first shaft (32) for common rotation about the axis (34). [15] The transmission (18) of claim 13 further comprising a fourth shaft, wherein the gear set (42, 50, 52, 54) includes a differential (20) configured to receive input torque from the third shaft (40) and output differential torque to the second and fourth shafts (26, 32). [16] The transmission (18) of claim 10, wherein the first member (310) defines a first surface (374) and the second member (314) defines a second surface (378) opposite the first surface (374) and axially spaced from the first surface (374). [17] The transmission (18) of claim 10, further comprising a plurality of fasteners (366), each of the fasteners (366) extending axially between one of the distal ends of the first spokes (410) and the outer portion (350) to fixedly couple the distal ends of the first spokes (410) to the outer portion (350). [18] The transmission (18) of claim 17, wherein the first member (310) is a unitary body defining the first hub (318) and the first spokes (410) and wherein the second member (314) is a unitary body defining the second hub (342) and the second outer portion (350). [19] The transmission (18) of claim 10, wherein the distal ends of the first spokes (410) are fixedly coupled together around an outer radial periphery of the first member (310). [20] The transmission (18) of claim 1, wherein the first hub (318) defines a first set of internal gears (334) that mesh with a first set of external gears (338) defined by the input member (32), and the second hub (342) defines a second set of internal gears (358) that mesh with a second set of external gears (362) defined by the output member (40).

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