Gearbox structure for dual electric drive units

Abstract

A gearbox design for dual electric drive units, each drive unit having an electric motor and a transmission, allows for compact and cost-effective packaging of the transmission within the housing in which the electric motor is mounted.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 448,164, filed March 7, 2023, the disclosure of which is incorporated herein by reference as if fully set forth herein.

[0002] Technical Field The present disclosure relates to a gearbox design for a dual electric drive unit. [Background technology]

[0003] Referring to FIG. 1 , an exemplary prior art dual electric drive unit is generally designated by the reference numeral 2. Dual electric drive unit 2 includes a housing assembly 4 and a pair of electric drive units 6, 8. Housing assembly 4 includes a first housing member 10, a second housing member 12, and an intermediate housing member 14 disposed between first and second housing members 10, 12. Intermediate housing member 14 cooperates with first housing member 10 and second housing member 12 to define one or more cavities (e.g., cavities 16, 18, respectively) capable of receiving portions of electric drive units 6, 8. Each of electric drive units 6, 8 includes an electric motor 20 and a transmission 22 having a plurality of gears, including a transmission input gear 30, a transmission output gear 32, and, optionally, one or more pairs of intermediate gears 34. Transmission input gear 30 is attached to an input shaft 40, and transmission output gear 32 is attached to an output shaft 42. When a pair of intermediate gears 34 is used in the transmission 22 , each pair of intermediate gears 34 is mounted on an associated intermediate shaft 44 .

[0004] Each of the input shaft 40, output shaft 42, and intermediate shaft 44 of electric drive unit 6 is mounted on a respective pair of shaft bearings 50, with one shaft bearing 50 located in the first housing member 10 and a second shaft bearing 50 located in the middle housing member 14. Similarly, each of the input shaft 40, output shaft 42, and intermediate shaft 44 of electric drive unit 8 is mounted on a respective pair of shaft bearings 50, with one shaft bearing 50 located in the first housing member 10 and a second shaft bearing 50 located in the middle housing member 14. While the three-part configuration of housing assembly 4 allows for efficient mounting of the shaft bearings of each of electric drive units 6, 8, the middle housing member 14 adds mass and volume to the dual electric drive unit 2, making this configuration somewhat inefficient. Therefore, there is a need for a dual electric drive unit having a relatively small housing that does not use a middle housing member. Summary of the Invention

[0005] This section provides a general summary of the disclosure and is not a comprehensive disclosure of its entire scope or every feature.

[0006] In one aspect, the present disclosure provides a dual electric drive unit including a housing assembly, a first electric drive unit, a first bearing, a second electric drive unit, a second bearing, a third bearing, and a fourth bearing. The housing assembly includes a first housing member and a second housing member. The first electric drive unit includes a first electric motor, a first transmission, and a first output member. The first electric motor is coupled to the first housing member. The first transmission is disposed within the housing assembly and includes a first shaft and a first transmission input gear. The first shaft is driven by the first electric motor and defines a first bearing mount, a second bearing mount, and a third bearing mount. The first bearing is mounted to the first housing member and received on the first bearing mount. The first bearing is configured to support the first shaft for rotation about the input axis relative to the housing assembly. The second electric drive unit has a second electric motor, a second transmission, and a second output member. The second electric motor is coupled to the second housing member. The second transmission is disposed within the housing assembly and has a second shaft and a second transmission input gear. The second shaft is driven by the second electric motor and defines a fourth bearing mount, a fifth bearing mount, and a sixth bearing mount. A second bearing is attached to the second housing member and received on the sixth bearing mount. The second bearing is configured to support the second shaft for rotation about the input axis relative to the housing assembly. A third bearing is received on the second bearing mount and the fourth bearing mount and supports one of the first and second shafts for rotation relative to the other of the first and second shafts. A fourth bearing is received on the third bearing mount and the fifth bearing mount and supports one of the first and second shafts for rotation relative to the other of the first and second shafts, and a portion of one of the first and second shafts is received coaxially around the other of the first and second shafts.

[0007] Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. [Brief explanation of the drawings]

[0008] The drawings described herein are for the purpose of illustrating selected embodiments only, not all possible embodiments, and are not intended to limit the scope of the present disclosure.

[0009] [Figure 1] FIG. 1 is a schematic diagram of a dual electric drive unit constructed in accordance with the teachings of the prior art.

[0010] [Figure 2] FIG. 2 is a schematic diagram of a dual electric drive unit constructed in accordance with the teachings of the present disclosure.

[0011] [Figure 3] FIG. 3 is a cross-sectional view of a portion of the dual electric drive unit of FIG.

[0012] [Figure 4] 4 is a perspective view of a portion of the dual electric drive unit of FIG. 2 showing the transmission input gears of the transmissions of each drive unit.

[0013] [Figure 5] FIG. 5 is an exploded perspective view of a portion of the dual electric drive unit depicted in FIG. [Figure 6] FIG. 6 is an exploded perspective view of a portion of the dual electric drive unit depicted in FIG.

[0014] [Figure 7] FIG. 7 is a cross-sectional view of a portion of a dual electric drive unit with alternating intermediate gear and bearing arrangements suitable for the embodiment of FIGS.

[0015] [Figure 8] FIG. 8 is a cross-sectional view similar to FIG. 4, but showing an alternative configuration of the input gear for the transmission. [Figure 9] FIG. 8 is a cross-sectional view similar to FIG. 4, but showing an alternative configuration of the input gear for the transmission.

[0016] Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0017] 2 , an exemplary dual electric drive unit constructed in accordance with the teachings of the present disclosure is generally designated by the reference numeral 100. Dual electric drive unit 100 may include a housing assembly 102, a first drive unit 104, and a second drive unit 106. First drive unit 104 may have a first motor 110 and a first transmission 112, while second drive unit 106 may have a second motor 118 and a second transmission 120.

[0018] 2 and 3, the housing assembly 102 can have a first housing member 124 and a second housing member 126 fixedly coupled together by a plurality of threaded fasteners (not shown). The first and second housing members 124 and 126 can cooperate to form a drive unit cavity 102a configured to accommodate the first and second transmissions 112 and 120. The first housing member 124 defines a first motor mount 124a, a first input shaft bore 124b, and a first input bearing bore 274. The second housing member 126 defines a second motor mount 126b and a second input shaft bore 278.

[0019] The first motor 110 may be fixedly coupled to the first motor mount 124a, for example, by a plurality of threaded fasteners (not shown), such that the motor output shaft (not shown) of the first motor 110 extends through the first input shaft bore 124b and into the drive unit cavity 102a. A rotary seal (not shown) may be attached to the first housing member 124 to form a seal between the first housing member 124 and the motor output shaft of the first motor 110 or a portion of the first transmission 112 to which the motor output shaft of the first motor 110 is rotatably coupled.

[0020] The first transmission 112 can be similar to the transmission 22 (FIG. 1) and can include a first transmission input gear 200, a first transmission output gear (not specifically shown), and optionally one or more pairs of intermediate reduction gears (not specifically shown). The first transmission input gear 200 can be coupled to the motor output shaft of the first motor 110 so as to rotate together with the motor output shaft of the first motor 110 about the input shaft A1. The first transmission output gear can be rotatable about the output shaft A2. In a situation where the first transmission 112 does not include any pair of intermediate reduction gears, the first transmission input gear 200 can be meshed and engaged with the first transmission output gear. If one or more pairs of intermediate reduction gears are included, the one or more pairs of intermediate reduction gears can be disposed in a power transmission path between the first transmission input gear 200 and the first transmission output gear. For example, if a single pair of intermediate reduction gears is used, a first gear of the pair of intermediate reduction gears can be meshed and engaged with the first transmission input gear 200, and a second gear of the pair of intermediate reduction gears can be meshed and engaged with the first transmission output gear to be coupled to the first gear of the pair of intermediate reduction gears for rotation about a respective intermediate shaft. The first transmission 112 is operable to transfer rotational power between the first motor 110 and the output member OM1 of the first drive unit 104.

[0021] Similarly, the second transmission 120 can be configured similarly to the transmission 22 (FIG. 1) and can include a second transmission input gear 202, a second transmission output gear (not specifically shown), and optionally one or more pairs of intermediate reduction gears (not specifically shown). The second transmission input gear 202 can be coupled to the motor output shaft of the second motor 118 to rotate therewith about the input shaft A1. The second transmission output gear can be rotatable about the output shaft A2. In situations where the second transmission 120 does not include any pair of intermediate reduction gears, the second transmission input gear 202 can be meshed and engaged with the second transmission output gear. If one or more pairs of intermediate reduction gears are included, one or more pairs of intermediate reduction gears can be disposed in a power transmission path between the second transmission input gear 202 and the second transmission output gear. For example, if a single pair of intermediate reduction gears is used, a first gear of the pair of intermediate reduction gears can be meshed and engaged with the second transmission input gear 202, and a second gear of the pair of intermediate reduction gears can be meshed and engaged with the second transmission output gear to couple the first gear of the pair of intermediate reduction gears to rotate about their respective intermediate shafts. The second transmission 120 is operable to transfer rotational power between the second motor 118 and the output member OM2 of the second drive unit 106.

[0022] It will be appreciated that bearing arrangements may be used to support the first and second transmission input gears 200, 202 relative to the housing assembly 102 for rotation about the input shaft A1, to support the first and second transmission output gears relative to the housing assembly 102 for rotation about the output shaft A2, and, if included, to support each pair of intermediate reduction gears about their respective intermediate shafts. It will also be understood that each bearing arrangement may be generally similar. As such, the bearing arrangements described below are shown and described only in conjunction with the first and second transmission input gears or in conjunction with only a single pair of intermediate reduction gears for each of the first and second transmissions.

[0023] 3 to 6, a first bearing arrangement is shown in conjunction with a first transmission input gear 200 and a second transmission input gear 202. In this example, the first transmission input gear 200 has a first hub 210, a first gear portion 212, and a first shaft portion 214, the second transmission input gear 202 has a second hub 220 and a second gear portion 222, and the bearing arrangement includes a first tapered roller bearing 230, a second tapered roller bearing 232, a needle bearing 234, and a third tapered roller bearing 236.

[0024] The first hub 210 may define an internally splined opening configured to mesh with an externally splined segment (not shown) on a motor output shaft of a first motor ( FIG. 2 ). A first gear portion 212 may extend radially outward from the first hub 210 and may define a plurality of first gear teeth. A first bearing mount 240 may be formed on the first hub 210 and may terminate at a first shoulder 242. A first shaft portion 214 may be fixedly coupled to the first hub 210 and may extend axially away from the first hub 210 along the rotational axis of the first transmission input gear 200. A second bearing mount 244 may be formed on the first shaft portion 214 proximate an intersection of the first hub 210 and the first shaft portion 214 and may terminate at a second shoulder 246. A third bearing mount 248 may be formed on the first shaft portion 214 proximate the distal end of the first shaft portion 214 .

[0025] The second hub 220 may define an internally splined opening configured to mesh with an externally splined segment (not shown) on the motor output shaft of the second motor 118 ( FIG. 2 ) and a shaft opening 260 configured to receive the first shaft portion 214 therein. The second gear portion 222 may extend radially outward from the second hub 220 and may define a plurality of second gear teeth. A fourth bearing mount 264 may be formed on the second hub 220 on a first side of the second gear portion 222 and may terminate at a third shoulder 266. A fifth bearing mount 268 may be formed on the second hub 220. A sixth bearing mount 270 may be formed on the second hub 220 on a second side of the second gear portion 222 opposite the first side. The sixth bearing mount may terminate at a fourth shoulder 272.

[0026] The first tapered roller bearing 230 may be mounted on a first bearing mount 240 on the first hub 210 of the first transmission input gear 200 and in a seventh bearing mount 274 formed in the first housing member 124. The first tapered roller bearing 230 may abut against a first shoulder 242. In the example provided, the first tapered roller bearing 230 has an inner bearing race received on the first bearing mount 240 on the first hub 210 and abutting against the first shoulder 242, an outer bearing race received in a bore of the first housing member 124, and a plurality of tapered rollers disposed between the inner bearing race and the outer bearing race.

[0027] The second tapered roller bearing 232 may be mounted in the second bearing mount 244 and the fourth bearing mount 264. The second tapered roller bearing 232 may abut a second shoulder 246 of the first shaft portion 214 and abut a third shoulder 266 of the second hub 220. In the example provided, the second tapered roller bearing 232 has an inner bearing race received on the second bearing mount 244 on the first shaft portion 214 and abutting the second shoulder 246, an outer bearing race received in a bore in the second hub 220 that defines the fourth bearing mount 264, and a plurality of tapered rollers disposed between the inner and outer bearing races.

[0028] The needle bearing 234 may be mounted in a third bearing mount 248 at the end of the first shaft portion 214 and in a fifth bearing mount 268 on the second hub 220. In the embodiment provided, the fifth bearing mount 268 is formed in a bore in the second hub 220.

[0029] The third tapered roller bearing 236 may be mounted on a sixth bearing mount 270 on the second hub 220 of the second transmission input gear 202 and mounted in an eighth bearing mount 278 formed in the second housing member 126. The third tapered roller bearing 236 may abut against the fourth shoulder 272. In the example provided, the third tapered roller bearing 236 has an inner bearing race received on the sixth bearing mount 270 of the second hub 220 and abutting against the fourth shoulder 272, an outer bearing race received in a bore of the second housing member 126, and a plurality of tapered rollers disposed between the inner bearing race and the outer bearing race.

[0030] The bearing arrangement depicted in FIG. 7 is shown supporting a pair of intermediate gears 300, 302. The pair of intermediate gears 300 includes a first intermediate gear 304a, a second intermediate gear 306a, and a shaft portion 308a extending through the first intermediate gear 304a and the second intermediate gear 306a. The first intermediate gear 304a, the second intermediate gear 306a, and the shaft portion 308a are coupled to one another for common rotation about an axis, and all or a portion of the pair of intermediate gears 300 may be unitarily and integrally formed (e.g., the second intermediate gear 306a and the shaft portion 308a may be unitarily and integrally formed, and the first intermediate gear 304a may be assembled and fixedly coupled to the shaft portion 308a).

[0031] Similarly, the pair of intermediate gears 302 includes a first intermediate gear 304b, a second intermediate gear 306b, and a shaft portion 308b. The first intermediate gear 304b, the second intermediate gear 306b, and the shaft portion 308b are coupled to one another for common rotation about an axis, and all or a portion of the pair of intermediate gears 302 may be unitarily and integrally formed (e.g., the second intermediate gear 306b and the shaft portion 308b may be unitarily and integrally formed, and the first intermediate gear 304b may be assembled and fixedly coupled to the shaft portion 308b). The shaft portion 308b defines a shaft bore 314 through which the shaft portion 308a is received.

[0032] The bearing arrangement may include a first bearing 330 , a second bearing 332 , a first needle bearing 334 , a second needle bearing 336 , a first thrust element 338 , and a second thrust element 340 .

[0033] The first bearing 330 is disposed between the first intermediate gear 304a and the shaft portion 308a on the opposite side of the second intermediate gear 306a. The first bearing 330 has an inner bearing race mounted directly to the shaft portion 308a, an outer bearing race mounted in a bore 350 of the first housing member 124, and a plurality of rolling elements disposed between the inner and outer bearing races. Similarly, the second bearing 332 is disposed between the first intermediate gear 306b and the shaft portion 308b on the opposite side of the second intermediate gear 306b. The second bearing 332 has an inner bearing race mounted directly to a portion of the shaft portion 308a extending through the pair of intermediate gears 302, an outer bearing race mounted in a bore 352 of the second housing member 126, and a plurality of rolling elements disposed between the inner and outer bearing races.

[0034] First and second needle bearings 334 and 336 are received between shaft portions 308a and 308b and support pair of intermediate gears 302 for rotation about an axis relative to pair of intermediate gears 300.

[0035] The first and second thrust elements 338 and 340 can be configured to limit thrust of the pair of intermediate gears 302 relative to the pair of intermediate gears 300. In the example provided, each of the first and second thrust elements 338 and 340 is a thrust washer, with the first thrust element 338 received on the shaft portion 308a between the first intermediate gear 304a and the shaft portion 308b, and the second thrust element 340 received on the shaft portion 308a between the second intermediate gear 306b and a retaining ring 360 attached to the shaft portion 308a on the side of the second thrust element 340 opposite the shaft portion 308b.

[0036] As will be appreciated, the first and second bearings 330 and 332 may be any type of bearing. In the illustrated example, the first and second bearings 330 and 332 are deep groove ball bearings, which are generally smaller and more efficient than tapered roller bearings. If desired, each intermediate gear of each pair of intermediate gears can be formed with opposite-handed helical teeth to limit thrust generation. For example, the first intermediate gears 304a and 304b can be formed with left-handed helical teeth, and the second intermediate gears 306a and 306b can be formed with right-handed helical teeth.

[0037] 8, a third bearing arrangement is shown in conjunction with first and second transmission input gears 200b and 202b. In this example, first transmission input gear 200b includes first hub 210b, first gear portion 212b, and first shaft portion 214b, second transmission input gear 202b includes second hub 220b and second gear portion 222b, and the bearing arrangement includes first bearing 330b, second bearing 232b, third bearing 234b, and fourth bearing 332b.

[0038] The first hub 210b may define an internally splined opening configured to meshingly engage with an externally splined segment (not shown) on a motor output shaft of the first motor ( FIG. 2 ). The first gear portion 212b may extend radially outward from the first hub 210b and may define a plurality of first gear teeth. The first bearing mount 240b may be formed on the first hub 210b and may terminate at a first shoulder 242b. The first shaft portion 214b may be fixedly coupled to the first hub 210b and may extend axially away from the first hub 210b along the rotational axis of the first transmission input gear 200b. The second bearing mount 244b may be formed on the first shaft portion 214 proximate an intersection of the first hub 210b and the first shaft portion 214. A third bearing mount 248b may be formed on the first shaft portion 214 adjacent to the distal end of the first shaft portion 214.

[0039] The second hub 220b may define an internally splined opening configured to mesh with an externally splined segment (not shown) on the motor output shaft of the second motor 118 (FIG. 2) and a shaft opening 260b configured to receive the first shaft portion 214b therein. The second gear portion 222b may extend radially outward from the second hub 220b and may define a plurality of second gear teeth. A fourth bearing mount 264b may be formed on the second hub 220b on a first side of the second gear portion 222b. A fifth bearing mount 268b may be formed on the second hub 220b. A sixth bearing mount 270b may be formed on the second hub 220b on a second side of the second gear portion 222b opposite the first side. The sixth bearing mount may terminate in a fourth shoulder 272b.

[0040] The first bearing 330b may be mounted on the first bearing mount 240b on the first hub 210b of the first transmission input gear 200b and in a seventh bearing mount (not shown) formed in the first housing member (not shown). The first bearing 330b may abut the first shoulder 242b. In the example provided, the first bearing 330b has an inner bearing race received on the first bearing mount 240b on the first hub 210b and abutting the first shoulder 242b, an outer bearing race received in a bore of the first housing member 124b, and a plurality of rolling elements disposed between the inner bearing race and the outer bearing race.

[0041] The second bearing 232b can be mounted in the second bearing mount 244b and the fourth bearing mount 264b. In the example provided, the second bearing 332 is a needle bearing having an inner bearing race received on the second bearing mount 244 on the first shaft portion 214 and abutting the second shoulder 246, an outer bearing race received in a bore of the second hub 220 that defines the fourth bearing mount 264, and a plurality of rollers disposed between the inner bearing race and the outer bearing base.

[0042] The third bearing 234b may be mounted on a third bearing mount 248b at the end of the first shaft portion 214b and on a fifth bearing mount 268b on the second hub 220b. In the example provided, the third bearing 234b is a needle bearing and the fifth bearing mount 268b is formed within a bore in the second hub 220b.

[0043] The fourth bearing 332b may be mounted on the sixth bearing mount 270b on the second hub 220b of the second transmission input gear 202b and on an eighth bearing mount (not shown) formed in the second housing member (not shown). The fourth bearing 332b may abut the second shoulder 246b. In the example embodiment provided, the fourth bearing 332b is received on the sixth bearing mount 270b on the second hub 220b and has an inner bearing race abutting the second shoulder 246b, an outer bearing race received in a bore in the second housing member (not shown), and a plurality of rolling elements disposed between the inner and outer bearing races.

[0044] A thrust face may be coupled to the first shaft portion 214b and the second hub 220b to control axial thrust between the first and second transmission input gears 200b and 202b. In the example provided, the first shaft portion 214b defines a first thrust face 400 and a stem 402 that protrudes axially away from the first thrust face 400. The stem 402 has a first stem portion having a first diameter and a second stem portion having a second, smaller diameter, thereby forming a second stem shoulder at the second stem portion where it meets the first stem portion. A thrust washer 410 is attached to the second stem portion and fixedly coupled to the stem 402 via a threaded fastener. The thrust washer 410 forms a second thrust face 414. A gap or space is disposed along the stem between the first and second thrust faces 400 and 414. An annular protrusion 420 is coupled to the second hub 220b and extends radially into the space between the first thrust face 400 and the second thrust face 414. The annular protrusion 420 forms a first complementary thrust surface configured to cooperate with the first thrust face 400 to limit thrust tending to drive the first transmission input gear 200b toward the second transmission input gear 202b, and a second complementary thrust surface configured to cooperate with the second thrust face to limit thrust tending to drive the first transmission input gear 200b away from the second transmission input gear 202b.

[0045] 9 is similar to the example of FIG. 8 except that it includes a second thrust washer 500 used to limit thrust tending to drive the first transmission input gear 200c toward the second transmission input gear 202c, and simplifies the stem 402c so that the annular protrusion 420c and first thrust washer 410c limit thrust tending to drive the first transmission input gear 200c away from the second transmission input gear 202c. The second thrust washer 500 is received over the first shaft portion 214 and is positioned against a first thrust surface 400c formed on the first gear portion 212c where the first shaft portion 214c intersects with the first gear portion 212c, and a complementary first thrust surface 510 formed on the axial end of the second hub 220c. A first thrust washer 410c is attached to the axial end of the stem 402c and defines a second thrust surface 520 engageable with a complementary second thrust surface 522 formed on the annular projection 420c.

[0046] It will be appreciated that the deep groove ball bearings shown in the examples of Figures 8 and 9 can be replaced with tapered roll bearings.

[0047] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the present disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, may be interchangeable and used in selected embodiments even if not specifically shown or described. The same can be varied in various ways. Such variations are not considered a departure from the present disclosure, and all such variations are intended to be included within the scope of the present disclosure.

Claims

1. A dual electric drive unit, the dual electric drive unit comprising: a housing assembly (102) having a first housing member (124) and a second housing member (126); a first electric drive unit (104) having a first electric motor (110), a first transmission (112), and a first output member (OM1), the first electric motor (110) coupled to the first housing member (124), the first transmission (112) disposed within the housing assembly (102) and having a first shaft (214) and a first transmission input gear (200), the first shaft (214) driven by the first electric motor (110), and defining a first bearing mount (240), a second bearing mount (244), and a third bearing mount (248); a first bearing (230) mounted to the first housing member (124) and received on the first bearing mount (240), the first bearing (230) configured to support a first shaft (214) for rotation about an input axis (A1) relative to the housing assembly (102); a second electric drive unit (106) having a second electric motor (118), a second transmission (120), and a second output member (OM2), the second electric motor (118) coupled to the second housing member (126), the second transmission (120) disposed within the housing assembly (102) and having a second shaft (220) and a second transmission input gear (202), the second shaft (220) driven by the second electric motor (118), and defining a fourth bearing mount (264), a fifth bearing mount (268), and a sixth bearing mount (270); a second bearing (236) attached to the second housing member (126) and received on the sixth bearing mount (270), the second bearing (236) configured to support a second shaft (220) for rotation about the input axis (A1) relative to the housing assembly (102); a third bearing (232) received on the second bearing mount (244) and the fourth bearing mount (264), the third bearing (232) supporting one of the first and second shafts (214, 220) for rotation relative to the other of the first and second shafts (214, 220); a fourth bearing (234) received on the third bearing mount (248) and the fifth bearing mount (268), the fourth bearing (234) supporting the one of the first and second shafts (214, 220) for rotation relative to the other one of the first and second shafts (214, 220); A dual electric drive unit, wherein the portion of one of the first and second shafts (214, 220) is coaxially received about the other one of the first and second shafts (214, 220).

2. The dual electric drive unit of claim 1, wherein at least one of the third bearing (232) and the fourth bearing (234) is a roller bearing.

3. The dual electric drive unit of claim 2, wherein the third bearing (232) is a needle bearing.

4. The dual electric drive unit of claim 2, wherein the fourth bearing (234) is a needle bearing.

5. The dual electric drive unit of claim 1, further comprising a thrust washer (500) disposed between the first shaft (214) and the second shaft (220).

6. 2. The dual electric drive unit of claim 1, wherein each of the first shaft and the second shaft has an internally splined opening configured to receive a motor output shaft of one of each of the first and second electric motors.

7. 2. The dual electric unit of claim 1, wherein the first transmission further includes a first shaft portion and first and second intermediate gears coupled to the first shaft portion for common rotation, and the second transmission further includes a second shaft portion and third and fourth intermediate gears coupled to the second shaft portion for common rotation, one of the first and second shaft portions being coaxially received within the other of the first and second shaft portions.

8. The dual electric drive unit of claim 7, wherein a pair of needle bearings (334, 336) are received between the first and second shaft portions (308a, 308b).

9. 8. The dual electric drive unit of claim 7, further comprising a first thrust washer (338) disposed between the first and third intermediate gears (304a, 304b) along the rotational axes of the first and second shaft portions (308a, 308b).

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