Transmission with torsional damper

The present teachings provide for a torsional damper and a transmission having a torsional damper. The torsional damper can include first and second members. The first member can include a first hub, a first outer portion, and a plurality of first spokes. The first hub can be non-rotatably coupled to an input member of the transmission. The first spokes can extend radially between the first hub and the first outer portion. The first spokes can couple the first outer portion to the first hub. The second member can include a second hub and a second outer portion. The second hub can be non-rotatably coupled to an output member of the transmission. The second outer portion can be radially outward of the second hub and can be fixedly coupled to the second hub and to the first outer portion.

FIELD

The present disclosure relates to a transmission with a torsional damper.

BACKGROUND

Transmissions typically include rotating shafts that transmit high levels of torque from an input member to an output member. Additionally, drive modules that employ one or more electric motors that are selectively operable to provide propulsion and/or torque vectoring capabilities typically include input shafts that couple the electric motor to the transmission. Such input shafts can provide torque intermittently or in frequently reversing directions, which can induce mechanical shock through the transmission components. In order to reduce mechanical shock, reduce wear on various components in the transmission, and to dampen gear noises caused by the transmission error, some degree of torsional compliance or torsional flexibility within the rotating components of the transmission is desirable. However, torsional compliance can be difficult to achieve in a rotating shaft or in the connection between two rotating shafts, while maintaining adequate strength for transferring high levels of torque through the transmission and minimizing packaging size of the transmission. Adequate torsional compliance can be particularly difficult to achieve in a hollow rotating shaft or in the connection between two hollow rotating shafts.

SUMMARY

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

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

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

DETAILED DESCRIPTION

With reference toFIG. 1of the drawings, an exemplary vehicle8is depicted with a power train P, a conventional front-wheel drive drivetrain F that can be driven by the power train P, and a drive module10that is constructed in accordance with the teachings of the present disclosure. The power train P can include an internal combustion engine E and a transmission T that can be driven by the engine. The transmission T can output rotary power to the front-wheel drivetrain F, which can transmit rotary power to drive a pair of front vehicle wheels WF. The drive module10can be selectively operated to transmit rotary power to a pair of rear vehicle wheels WR.

With reference toFIG. 2, the drive module10is illustrated in greater detail. In the example provided, the drive module10can include a housing12, an electric motor14, an input pinion16, a transmission18, a differential assembly20, a torsional damper22, and first and second axle shafts24and26. The housing12can define a structure in which the input pinion16, the transmission18and the differential assembly20can be housed. The electric motor14can include a stator28which can be fixedly coupled to the housing12, a rotor30, and a hollow output shaft32. The rotor30can be fixedly coupled to the output shaft32for common rotation about an axis34. The output shaft32can be supported within the housing12by a first bearing36and a second bearing38. The output shaft32can be coupled to the torsional damper22for common rotation about the axis34. The input pinion16can include a pinion shaft40and a pinion gear42mounted to the pinion shaft40for common rotation about the axis34. The pinion shaft40can be supported within the housing12by a third bearing44and coupled to the torsional damper22for common rotation about the axis34. The torsional damper22is described in greater detail below. While described herein with reference to the drive module10, it will be appreciated that the torsional damper22of the present disclosure is applicable to other power transmitting components where torsional compliance is desirable.

The pinion gear42can be drivingly coupled to the transmission18to transmit torque therebetween. The transmission18can be drivingly coupled to the differential assembly20to transmit torque therebetween. It will be appreciated that any type of transmission arrangement could be employed between the electric motor14and the differential assembly20. In the particular example provided, the transmission18is a single planetary stage transmission that is disposed concentrically about the rotational axis34of the output shaft32of the electric motor14. It is appreciated that other types of transmissions can be used such as dual planetary stage transmissions, compound planetary transmissions, or non-planetary transmissions for example. The transmission18can include the input pinion gear42, which is a sun gear of the transmission18, a ring gear50, a plurality of compound planet gears52and a planet carrier54. The ring gear50can be disposed concentrically about the input pinion16(i.e. about axis34) and can be non-rotatably coupled to the housing12in which the transmission18and the differential assembly20are received. The ring gear50can include a plurality of internal teeth58.

Each of the compound planet gears52can include a first planet gear portion60and a second planet gear portion62. The first planet gear portion60can include a hub110and a plurality of teeth112that are disposed about the hub110and meshingly engaged to the input pinion gear42. The second planet gear portion62can be fixedly coupled to the hub110of the first planet gear portion60for rotation therewith and can include a plurality of teeth114and a journal116that is disposed on an axial end that is opposite the end that is coupled to the hub110. The teeth114of the second planet gear portion62can be meshingly engaged with the internal teeth58of the ring gear50. The first and second planet gear portions60and62can have different pitch diameters.

The planet carrier54can include a first carrier body120, a second carrier body122, a plurality of fourth bearings124, and a plurality of fifth bearings126. The fourth bearings124, which can be ball bearings, can be fixedly mounted to the first carrier body120and can support the hubs110of the first planet gear portions60for rotation relative to the first carrier body120. The fifth bearings126, which can be roller needle bearings, can be fixedly mounted to the second carrier body122and can support the journal116of the second planet gear portions62for rotation relative to the second carrier body122.

It will be appreciated that any type of differential arrangement could be employed to transfer differential toque between the transmission18and the first and second axle shafts24,26. In the particular example provided, the differential assembly20can include a differential casing210and differential gear set212. The differential gear set212can include a cross-pin214, a plurality of bevel pinions216, and a pair of side gears218. The differential casing210can be coupled to the first carrier body120and/or the second carrier body122for rotation therewith about the rotational axis34and can define a cavity220into which the bevel pinions216and the side gears218can be received. The cross-pin214can be coupled to the differential casing210perpendicular to the rotational axis34. The bevel pinions216can be rotatably mounted on the cross-pin214. The side gears218can be rotatable about the rotational axis34and can be meshingly engaged with the bevel pinions216.

Each of the first and second axle shafts24and26can be coupled to a corresponding one of the side gears218for rotation therewith. The third bearing44can be radially between the pinion shaft40and a portion of the differential casing210, such that the third bearing44supports the pinion shaft40for rotation relative to the differential carrier210. The first axle shaft24can extend through the hollow pinion shaft40, the torsional damper22, and the output shaft32. The second axle shaft26can extend from the differential carrier210in an opposite axial direction from the first axle shaft24. Each of the first and second axle shafts24and26can be drivingly coupled to one of the rear vehicle wheels WR (FIG. 1).

With additional reference toFIG. 3-5, the torsional damper22is illustrated in greater detail. The torsional damper22can include an input member310and an output member314. The input member310can include a first hub318and a first disc322coupled to the first hub318for common rotation about the axis34. The first disc322can extend radially outward from the first hub318to a first outer portion326of the first disc322. The first hub318can be a generally cylindrical member that can extend axially outward from the first disc322in an axial direction that is away from the output member314and can define a central aperture330. The central aperture330can be disposed about the axis34and concentric with the output shaft32. The first hub318can be fixedly coupled to the output shaft32for common rotation. In the example provided, the first hub318includes a plurality of internal splines334disposed about the central aperture330that are meshingly engaged with a plurality of external splines338formed on an axial end of the output shaft32. It is understood that other methods of fixedly coupling the output shaft32to the first hub318can be used. The input member310can be unitarily formed of a single piece of material (e.g. a metal blank).

The output member314can include a second hub342and a second disc346coupled to the second hub342for common rotation about the axis34. The second disc346can extend radially outward from the second hub342to a second outer portion350of the output member314. The second hub342can be a generally cylindrical member that can extend axially outward from the second disc346in an axial direction that is away from the input member310and can define a central aperture354. The central aperture354can be disposed about the axis34and concentric with the output shaft32. The second hub342can be fixedly coupled to the pinion shaft40for common rotation. In the example provided, the second hub342includes a plurality of internal splines358disposed about the central aperture354that are meshingly engaged with a plurality of external splines362formed on an axial end of the pinion shaft40. It is understood that other methods of fixedly coupling the pinion shaft40to the second hub342can be used. The output member314can be unitarily formed of a single piece of material (e.g. metal blank).

The first and second outer portions326,350of the input and output members310,314can be fixedly coupled together for common rotation about the axis34. In the example provided, the first and second outer portions326,350are fixedly coupled by a plurality of fasteners366disposed circumferentially about the first and second outer portions326,350. With specific reference toFIG. 4, the fasteners366can extend through a plurality of bores370formed in the first and second outer portions326,350and which can be evenly spaced about the first and second outer portions326,350. In the example provided, the fasteners366are a plurality of rivets, though other types of fasteners can be used, such as bolts or screws for example. In an alternative construction, not specifically shown, the first and second outer portions326,350can be welded together, such as by one or more welds disposed about the perimeter of the torsional damper22for example.

The first and second outer portions326,350can be coupled together such that an inner face374of the input member310can oppose and be spaced apart from an inner face378of the output member314. The inner face374of the input member310can be defined by the first hub318and the portion of the first disc322that is radially inward of the first outer portion326. The inner face378of the output member314can be defined by the second hub342and the portion of the second disc346that is radially inward of the second outer portion350. In the example provided, the first and second outer portions326,350of the input and output members310,314extend axially outward from the corresponding inner faces374,378toward each other such that the first and second outer portions326,350abut each other and the inner faces374,378are spaced apart from each other. The splines334,358of the first and second hub318,342and the splines338,362of the output shaft32and the pinion shaft40can be configured such that the output shaft32and the pinion shaft40are axially spaced apart.

The first disc322, the second disc346, or both can include a plurality of spokes410circumferentially spaced about the corresponding discs322,346. The spokes410can be fixedly coupled at one end to the corresponding first or second hub318,342, and can extend radially outward from the first or second hub318,342to be fixedly coupled to the corresponding first or second outer portions326,350. In the example provided, both the input member310and the output member314include spokes410, such that a first set of the spokes410extend between the first hub318and the first outer portion326, and a second set of the spokes410extend between the second hub342and the second outer portion350. The spokes410can be evenly spaced about the corresponding discs322,346. The spokes410can be separated by circumferentially spaced apertures414(FIG. 3). In the example provided, the apertures414are generally a tear-drop or pedal shape, being narrower proximate to the hub318,342and wider proximate to the outer portions326,350, though other shapes or configurations can be used. In the example provided, each outer portion326,350forms a ring shape about the outermost perimeter of the torsional damper22such that the apertures414are closed (i.e. each of the spokes410of the input member310are coupled together by the first outer portion326and each of the spokes410of the output member314are coupled together by the second outer portion350). In an alternative construction, not specifically shown, the apertures414can be open at the perimeter of the torsional damper22, such that each spoke410of the input member310can have a free end that is coupled to a free end of a corresponding spoke410of the output member. In the example provided, the input and output members310,314each have fourteen spokes, though other numbers of spokes can be used. Each spoke410can have a minimum width418(FIG. 5) that is greater than a maximum axial thickness422of the spoke410(FIG. 4). The number of fasteners366can equal the number of spokes410and each of the fasteners366can be circumferentially aligned with one of the spokes410, though other configurations can be used.

In the example provided, the input member310and the output member314can be mirror images of each other, including the same number of spokes410and the same diameters of the central apertures330,354of the hubs318,342, though other configurations can be used. For example, the input member310can have a different number of spokes410from the output member314, and/or the hubs318,342can be configured to be coupled to different sized shafts. For example, the central aperture354of the output member314can be a different diameter from the central aperture330of the input member310, to accommodate a pinion shaft40of a different diameter than the output shaft32. Likewise, the first hub318can be coupled to the pinion shaft40in a different manner than the second hub342and the output shaft32.

In operation, the electric motor14can drive rotation of the output shaft32about the axis34. The output shaft32can provide torque through the torsional damper22to the pinion shaft40as shown by arrow510(FIG. 5). In this way, the output shaft32can provide input torque to the first hub318. The first hub318can provide torque to spokes410of the first disc322. The spokes410of the first disc322can provide torque to the first outer portion326. The first outer portion326can provide torque to the second outer portion350(e.g. through the fasteners366). The second outer portion350can provide torque to the spokes410of the second disc346. The spokes410of the second disc346can provide torque to the second hub342. The second hub342can provide torque to the pinion shaft40.

When the amount of torque transferred through the torsional damper22is high, such as during sudden starts, stops, or changes in direction of the rotation of either the output shaft32or the pinion shaft40, the torque can cause the spokes410of the input member310and/or the output member314to flex. For example with reference toFIG. 5, a first point A on the first hub318can be aligned along an axis514that runs through the axis34and a second point B on the first outer portion326(e.g. the center of the fastener366). When the torque is relatively low, the spokes410do not flex and points A and B remain aligned (i.e. rotate together at the same rate) while the torsional damper22rotates about the axis34. When the torque input into the first hub318is high, the spokes410can flex such that point A can initially rotate through a greater rotational angle δ than point B (e.g. points A′ and B′). Point B can remain momentarily stationary (shown as B′) or initially rotate an amount less than point A, such that A′ and B′ are momentarily not aligned. After the initial impulse of torque, the resiliency of the spokes410can cause the first outer portion326to realign with the first hub318. It is understood that points A, B, A′, and B′ are shown for illustrative purposes and their respective locations are not to scale. The resiliency of the spokes410can provide torsional compliance between the output shaft32and the pinion shaft40. The spokes410can be any suitable material, such as a metal for example. In the example provided, the amount of torsional compliance can be approximately 4,000 newton-meters per radian, though the spokes410can be configured to provide more or less compliance depending on the requirements of the drive module10. The torsional compliance provided by the torsional damper22can thus reduce mechanical shock through the transmission18, reduce wear on various components in the transmission18, and otherwise dampen gear noises caused by the transmission error (e.g. caused by gear tolerances).

While described above with reference to the torsional damper22coupling a hollow output shaft32to a hollow pinion shaft40, the torsional damper22of the present teachings is applicable for providing torsional compliance between other types of shafts, such as two solid shafts or between a solid shaft and a hollow shaft for example.

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,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of 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.