Patent Description:
Many vehicles utilize a beam axle to support the vehicle. At least some of these axles are a drive axle capable of propelling the vehicle. Typically, an internal combustion engine is coupled to the drive axle via a driveshaft. Increasingly, manufacturers have turned to electric and hybrid propulsion systems for increased performance and efficiency. An axle assembly in accordance with the prior art is known from document <CIT>.

Accordingly, there is a need to provide an axle assembly that allows one or more electric machines to be packaged into the vehicle while optimizing efficiency and performance.

The present invention is aimed at one or more of the problems identified above.

Accordingly, the present invention provides an axle assembly for a vehicle with increased performance and efficiency. This is achieved by the invention as defined by independent claim <NUM>.

Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings.

With reference to the Figures, wherein like numerals indicate like parts throughout the several views, the present invention includes an electric axle assembly for use with a vehicle such as, for example, a frame rail truck and/or a body-on-frame truck. The electric axle assembly propels the vehicle by transferring motive power to a ground surface. For example, in one embodiment, the axle assembly may be used with a vehicle including a frame rail assembly. The axle assembly may be coupled between a pair of wheel assemblies for transmitting power to opposing axle shafts. In the illustrated embodiment, the axle assembly includes two electric machines combined with a two speed transmission configuration to give both launch performance and velocity performance. In addition, the axle assembly includes a drive unit housing that integrates the electric motor and transmission compactly, supplies cooling for heat dissipation and transmits vehicle loads to suspension components. The axle architecture configuration of the electric axle assembly allows a two motor electric axle to package within the chassis rails of a standard truck with standard suspension. The double electric machine allows the system enough power for launch using smaller electric machines.

In the embodiment shown, the wheels of the vehicle are coupled to the electric axle assembly thereby supporting the vehicle for conveyance along the ground. For example, the vehicle wheels may be coupled to opposing ends of the electric axle assembly. The wheels may be arranged in a dual wheel configuration, wherein the wheels are coupled in pairs to each end of the electric axle assembly. Generally, dual wheels are used in applications requiring a greater payload capacity. However, it should be appreciated that a single wheel may be coupled to each end of the electric axle assembly. Furthermore, drive devices other than wheels may be coupled to the electric axle assembly. For example, crawler tracks or an inclined rail cog wheel may be used. The electric axle assembly may be mounted to the vehicle in a front drive configuration, or in a rear drive configuration. The electric axle assembly may also be mounted to a vehicle that was not originally equipped with an electric axle assembly. For example, the electric axle assembly can be retrofit to these vehicles to offer an electric driveline upgrade.

In general, the axle assembly may be used with a vehicle including a chassis upon which a body and other equipment is mounted. For example, a cab, a cargo box, a lift boom, or a hitch system may be mounted to the chassis. The chassis includes frame rails; suspension components such as springs, dampers, and trailing arms; and brake components such as air cylinders, brake calipers, brake rotors, brake drums, brake hoses, and the like. In one embodiment, at least some of the suspension components movably couple the electric axle assembly to the frame rails and allow the electric axle assembly to move relative to the frame rails as the vehicle is operated. The electric axle assembly is generally mounted perpendicular to the frame rails such that the vehicle travels in a direction aligned with the frame rails. For example, an axle centerline may be defined through the electric axle assembly and extends outwardly from sides of the vehicle.

The vehicle may be configured as an electric vehicle or a hybrid-electric vehicle. In one example of an electric vehicle, electricity to power the electric axle assembly may be stored in a battery mounted to the chassis. Alternatively, electricity may be provided from an external power source, such as an overhead wire or third rail system. If the vehicle is configured as a hybrid-electric vehicle, an internal combustion engine may be mounted to the chassis and coupled to a generator.

Referring to <FIG>, in the illustrated embodiment, the electric axle assembly <NUM> includes a reduction assembly <NUM> that is driven by a pair of electric machines <NUM>, <NUM>. In order to improve launch and velocity performance of the vehicle, the reduction assembly <NUM> is selectively shiftable between a first ratio and a second ratio. Each of the electric machines <NUM>, <NUM> are coupled to the reduction assembly <NUM> to power to the wheels at either the first ratio or the second ratio. The electric machines <NUM>, <NUM> may be DC or AC motors, brushed or brushless, and other types commonly known in the art. The electric machines <NUM>, <NUM> may be motor generator machines capable of both outputting mechanical energy to propel the vehicle as well as generating electrical energy to charge a battery or slow the vehicle.

Each electric machine <NUM>, <NUM> includes a rotor shaft <NUM> that protrudes from the electric machine <NUM>, <NUM>. A drive pinion <NUM> is fixed to the rotor shaft <NUM> and engagable with the reduction assembly <NUM>. The rotor shaft <NUM> defines a rotor axis <NUM> that extends through the electric machine <NUM>, <NUM>. In the illustrated embodiment, the pair of electric machines <NUM>, <NUM> includes a first electric machine <NUM> and a second electric machine <NUM> that are generally oriented transverse to the vehicle chassis (as shown in <FIG>). Each electric machine <NUM>, <NUM> is oriented in the same direction and in parallel alignment such that each rotor axis <NUM> is parallel to the other and parallel to an axle centerline <NUM>. The first and second electric machines <NUM>, <NUM> are arranged with the second electric machine <NUM> positioned behind the first electric machine <NUM> along a longitudinal axis of the vehicle. In one embodiment, the electric machine <NUM>, <NUM> includes direct oil cooling, which allows increased heat rejection over known water jacket cooling systems. The electric machine <NUM>, <NUM> includes a direct oil cooling system that is configured to directly cool the motor windings. In one embodiment, the electric machine <NUM>, <NUM> may include an IPM, <NUM>-phase motor with <NUM> kW peak power, <NUM> kW for <NUM> and <NUM> kW continuous power, <NUM> peak torque, <NUM> for <NUM> and <NUM> continuous torque, <NUM> RPM, and <NUM> V (550v to 750v) Voltage, which higher power available at 750V.

In the illustrated embodiment, the axle assembly <NUM> includes a first axle shaft <NUM> and a second axle shaft <NUM> orientated along the axle centerline <NUM>. The first axle shaft <NUM> is orientated along a first axis of rotation <NUM> and the second axle shaft <NUM> is orientated along the first axis of rotation <NUM>. The first axle shaft <NUM> and the second axle shaft <NUM> extend along the first axis of rotation <NUM> in opposite directions. The first electric machine <NUM> is orientated along a second axis of rotation <NUM> that is substantially parallel with the first axis of rotation <NUM>. The second electric machine <NUM> is spaced from the first electric machine <NUM> and orientated along a third axis of rotation <NUM> that is substantially parallel with the first axis of rotation <NUM>.

Generally, the reduction assembly <NUM> has an input <NUM> and an output <NUM>. The electric machines <NUM>, <NUM> rotate the input <NUM> and the axle shafts <NUM>, <NUM> are rotated by the output <NUM>. The reduction assembly <NUM> includes a common gear reduction <NUM> that is driven by the first and the second electric machines <NUM>, <NUM>, a differential gear set <NUM> that is driven by the common gear reduction <NUM> to transfer rotational torque from the first and second electric machines <NUM>, <NUM> to the first and second axle shafts <NUM>, <NUM>, and a speed change mechanism <NUM> that is coupled between the common gear reduction <NUM> and the differential gear set <NUM> to change the rotational torque transferred to the first and second axle shafts <NUM>, <NUM>. The input <NUM> includes the common gear reduction <NUM> that is engaged with each of the electric machines <NUM>, <NUM>, and the output <NUM> includes the differential gear set <NUM> that rotates the first and second axle shafts <NUM>, <NUM> while allowing a relative difference of speed between each axle shaft. The differential gear set <NUM> may be locking, open, limited slip and the like.

The common gear reduction <NUM> includes an input shaft <NUM> and an input drive wheel <NUM> that is fixedly coupled to the input shaft <NUM>. The input drive wheel <NUM> is engaged with the first and second electric machines <NUM>, <NUM> for transferring the rotational torque from the first and second electric machines <NUM>, <NUM> to the input shaft <NUM>. For example, the input drive wheel <NUM> is coupled to the drive pinion <NUM> of each electric machine <NUM>, <NUM> in a meshed arrangement and is driven by the electric machines <NUM>, <NUM>. The input shaft <NUM> is orientated coaxially with the first axis of rotation <NUM> and includes an inner surface <NUM> (shown in <FIG>) that defines an input shaft bore <NUM> that is sized and shaped to receive the first axle shaft <NUM> therethrough. The input drive wheel <NUM> is coupled to the input shaft <NUM> to transfer torque from the electric machines <NUM>, <NUM> to the input shaft <NUM>. The input shaft <NUM> defines the bore <NUM> along the first axis of rotation <NUM> through which the first axle shaft <NUM> extends, and includes two ends rotatably supported by bearings.

In the illustrated embodiment, the speed change mechanism <NUM> includes a reduction gear set <NUM> that is driven by the common gear reduction <NUM> and an output gear set <NUM> that is driven by the reduction gear set <NUM>. The reduction gear set <NUM> includes a first reduction gear <NUM>, a second reduction gear <NUM>, and a shift mechanism <NUM>. The first reduction gear <NUM> is coupled to the output gear set <NUM>, and the second reduction gear <NUM> is coupled to the output gear set <NUM>. The shift mechanism <NUM> is positioned between the first reduction gear <NUM> and the second reduction gear <NUM> and configured to selectively engage the first reduction gear <NUM> and the second reduction gear <NUM>. The two reduction gears <NUM>, <NUM> are each rotatably supported on the input shaft <NUM>. The first reduction gear <NUM> corresponds to the first ratio of the reduction assembly <NUM>, and the second reduction gear <NUM> corresponds to the second ratio of the reduction assembly <NUM>. In one embodiment shown in <FIG>, the first reduction gear <NUM> has a smaller diameter than the second reduction gear <NUM>. In other embodiments shown in <FIG> and <FIG>, the first reduction gear <NUM> has a larger diameter than the second reduction gear <NUM>. In addition, in other embodiments, the first reduction gear <NUM> and the second reduction gear <NUM> may each have substantially the same diameter. In the illustrated embodiment, each of the reduction gears <NUM>, <NUM> can spin freely on the input shaft <NUM> such that when the corresponding ratio is not engaged, no torque is transferred between the input shaft <NUM> and the reduction gears <NUM>, <NUM>. In one embodiment, each reduction gear <NUM>, <NUM> includes a splined portion engageable with the shift mechanism <NUM> to rotatably couple the reduction gears <NUM>, <NUM> to the input shaft <NUM>.

In the illustrated embodiment, the shift mechanism <NUM> includes a shift sleeve <NUM> (shown in <FIG>), a shift fork <NUM> (shown in <FIG>), and an actuator <NUM>. The shift sleeve <NUM> is rotatably coupled to the input shaft <NUM> such that the shift sleeve <NUM> and the input shaft <NUM> rotate at the same speed. The shift fork <NUM> is operably coupled to the actuator <NUM> and to the shift sleeve <NUM> such that movement of the actuator <NUM> causes the shift fork <NUM> to slide the shift sleeve <NUM> along the input shaft <NUM>. The shift sleeve <NUM> is selectively engageable with the first reduction gear <NUM> and the second reduction gear <NUM> to place the reduction assembly <NUM> in either the first ratio or the second ratio, respectively. The shift sleeve <NUM> and the reduction gears <NUM>, <NUM> include mating engagement features that, when engaged, rotatably couple the reduction gears <NUM>, <NUM> to the input shaft <NUM>. The engagement features may include splines, a dog clutch, or a synchronizer to aid shifting.

Additionally, the shift fork <NUM> and shift sleeve <NUM> may be movable into a neutral position where neither of the reduction gears <NUM>, <NUM> are engaged with the shift sleeve <NUM>. The actuator <NUM> may be controlled manually or automatically. The actuator <NUM> may be responsive to hydraulic pressure, pneumatic pressure, or electronic signals generated by a control module. Alternatively, the actuator <NUM> may include a mechanical linkage controlled by an operator.

The output gear set <NUM> includes an output counter shaft <NUM> and a pair of output gears <NUM>, <NUM> that are fixedly coupled to the output counter shaft <NUM>. Each output gear <NUM>, <NUM> is coupled to a corresponding reduction gear <NUM>, <NUM>. The counter shaft <NUM> has two ends rotatably supported by bearings. The pair of output gears includes a first output gear <NUM> that is engaged with the first reduction gear <NUM>, and a second output gear <NUM> that is engaged with the second reduction gear <NUM>. The first output gear <NUM> and the second output gear <NUM> are supported on and rotatably fixed to the counter shaft <NUM> such that the first and second output gears <NUM>, <NUM> and the counter shaft <NUM> rotate at the same speed. In one embodiment shown in <FIG>, the first output gear <NUM> has a larger diameter than the second output gear <NUM>. In other embodiments shown in <FIG> and <FIG>, the first output gear <NUM> has a smaller diameter than the second output gear <NUM>. In addition, in other embodiments, the first output gear <NUM> and the second output gear <NUM> may each have substantially the same diameter.

Referring to <FIG>, in one embodiment, the output gear set <NUM> includes an output pinion <NUM> that is coupled to an end of the counter shaft <NUM>. The output pinion <NUM> is coupled to the differential gear set <NUM> and is engaged with a ring gear <NUM> of the differential gear set <NUM> for transferring rotational torque from the output shaft <NUM> to the differential gear set <NUM> and axle shafts <NUM>, <NUM>. <FIG> illustrate the power flow through the reduction assembly <NUM>. <FIG> illustrates the power flow with the reduction assembly <NUM> in the first ratio, represented by line <NUM>. <FIG> illustrates the power flow with the reduction assembly <NUM> in the second ratio, represented by line <NUM>. As will be discussed below, the axle assembly <NUM> includes the shift mechanism <NUM> to selectively engage either the first ratio or the second ratio.

Referring to <FIG>, with the reduction assembly <NUM> in the first ratio <NUM>, torque that is generated by one or both of the electric machines <NUM>, <NUM>, is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the first reduction gear <NUM>. The first reduction gear <NUM> is engaged with the first output gear <NUM> to transfer torque to the output counter shaft <NUM>. The output counter shaft <NUM> rotates the output pinion <NUM> at the same rate as the first output gear <NUM>. Rotation of the counter shaft <NUM> rotates the output pinion <NUM>, thereby rotating the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

Referring to <FIG>, with the reduction assembly <NUM> in the second ratio <NUM>, torque that is generated in one or both of the electric machines <NUM>, <NUM> is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the second reduction gear <NUM>. The second reduction gear <NUM> is engaged with the second output gear <NUM> to transfer torque to the output counter shaft <NUM>. The output counter shaft <NUM> rotates the output pinion <NUM>, thereby rotating the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

In one embodiment, as shown in <FIG>, the reduction assembly <NUM> may include a second output gear set <NUM> that is driven by the reduction gear set <NUM>. The second output gear set <NUM> includes a second output counter shaft <NUM> and a third output gear <NUM>. The third output gear <NUM> is supported on and rotatably fixed to the second output counter shaft <NUM> such that the third output gear <NUM> and the second output counter shaft <NUM> rotate at the same speed. The third output gear <NUM> is engaged with the second reduction gear <NUM>. A second output pinion <NUM> is coupled to an end of the second output counter shaft <NUM>. The second output pinion <NUM> is coupled to the differential gear set <NUM> and engages with the ring gear <NUM> of the differential gear set <NUM> for transferring rotational torque from the second output counter shaft <NUM> to the differential gear set <NUM> and axle shafts <NUM>, <NUM>. The output pinions <NUM>, <NUM> each engaged with the ring gear <NUM> to transfer rotation from the output counter shafts <NUM>, <NUM>, to the differential gear set <NUM> and axle shafts <NUM>, <NUM>. <FIG> illustrate the power flow through the reduction assembly <NUM> in the first ratio <NUM> and the second ratio <NUM>.

Referring to <FIG>, with the reduction assembly <NUM> in the first ratio <NUM>, torque generated in one or both of the electric machines <NUM>, <NUM> is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the first reduction gear <NUM>. The first reduction gear <NUM> is engaged with the first output gear <NUM> to transfer torque to the first counter shaft <NUM>. The first counter shaft <NUM> rotates the first output pinion <NUM> at the same rate as the first output gear <NUM>. The first counter shaft <NUM> also rotates the second output gear <NUM> at the same speed as the first output gear <NUM>. Some of the torque from the first counter shaft <NUM> is transferred to the second counter shaft <NUM> due to engagement of the second reduction gear <NUM> with both the second output gear <NUM> and the third output gear <NUM>. Each of the counter shafts <NUM>, <NUM> rotates the respective output pinion <NUM>, <NUM>, thereby rotating the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

Referring to <FIG>, with the reduction assembly <NUM> in the second ratio <NUM>, torque generated in one or both of the electric machines <NUM>, <NUM> is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the second reduction gear <NUM>. The second reduction gear <NUM> is engaged with the second output gear <NUM> to transfer torque to the first counter shaft <NUM>, and with the third output gear <NUM> to transfer torque to the second counter shaft <NUM>. Each of the counter shafts <NUM>, <NUM> rotates the respective output pinion <NUM>, <NUM> and thereby the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

With reference to <FIG>, in one embodiment, the reduction assembly <NUM> includes a planetary gear set <NUM> that is coupled between the speed change mechanism <NUM> and the differential gear set <NUM> for driving the differential gear set <NUM>. The planetary gear set <NUM> includes a planetary ring gear <NUM>, planetary gears <NUM>, a sun gear <NUM>, and a planetary gear shaft <NUM>. The planetary ring gear <NUM> is arranged about the first axis of rotation <NUM> and is rotatably fixed in position. The planetary gear shaft <NUM> is coupled between the sun gear <NUM> and the second reduction gear <NUM> such that each rotate about the first axis of rotation <NUM> at the same speed. The planetary gear shaft <NUM> is orientated coaxially with the first axis of rotation <NUM> and is rotatable about the input shaft <NUM>. The planetary gear shaft <NUM> extends between a first shaft end <NUM> and a second shaft end <NUM>. The first shaft end <NUM> is fixedly coupled to the second reduction gear <NUM>, and the sun gear <NUM> is fixedly coupled to the second shaft end <NUM>. Each of the planetary gears <NUM> is radially arranged about the sun gear <NUM> and engaged with the sun gear <NUM> and the planetary ring gear <NUM>. The planetary gears <NUM> are rotatably supported on the ring gear <NUM> of the differential gear set <NUM> to transfer torque to the differential gear set <NUM>. Rotation of the planetary gear shaft <NUM> rotates the sun gear <NUM>, which rotates the planetary gears <NUM>. The planetary gears <NUM> are constrained by the planetary ring gear <NUM> and orbit the first axis of rotation <NUM> causing the differential gear set <NUM> to rotate. In one embodiment, as shown in <FIG>, the second shaft end <NUM> may be at least partially supported from the input shaft <NUM> of the common gear reduction <NUM> with a tapered bearing positioned between the outer surface of the input shaft <NUM> and the inner surface of the planetary gear shaft <NUM>.

Referring specifically to <FIG>, with the reduction assembly <NUM> in the first ratio <NUM>, torque that is generated in one or both of the electric machines <NUM>, <NUM> is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the first reduction gear <NUM>. The first reduction gear <NUM> is engaged with the first output gear <NUM> to transfer torque to the output counter shaft <NUM>. Rotation of the output counter shaft <NUM> is transferred to the planetary gear shaft <NUM> via the engagement of the second output gear <NUM> and the second reduction gear <NUM>. The planetary gear shaft <NUM> rotates the sun gear <NUM> at the same rate as the second reduction gear <NUM>. The sun gear <NUM> causes the planetary gears <NUM> to rotate and orbit within the planetary ring gear <NUM>, thereby rotating the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

Referring specifically to <FIG>, with the reduction assembly <NUM> in the second ratio <NUM>, torque that is generated in one or both of the electric machines <NUM>, <NUM> is transferred to the input shaft <NUM> via the drive pinions <NUM> and the input drive wheel <NUM>. The input shaft <NUM> rotates the shift sleeve <NUM>, which is engaged with the second reduction gear <NUM>. As the second reduction gear <NUM> is coupled to the planetary gear shaft <NUM>, the input shaft <NUM>, the planetary gear shaft <NUM>, and the sun gear <NUM> all rotate at the same speed. Rotation of the sun gear <NUM> causes the planetary gears <NUM> to rotate and orbit within the planetary ring gear <NUM>, thereby rotating the differential gear set <NUM> and axle shafts <NUM>, <NUM>.

With reference to <FIG>, in the exemplary embodiment, the axle assembly <NUM> defines a three-dimensional Cartesian coordinate system that includes three mutually perpendicular axes X, Y, and Z that extend through the axle assembly <NUM>. Specifically, the X-axis is orientated to extend substantially parallel with the axle centerline <NUM>, the Y-axis is oriented to extend substantially perpendicular to the X-axis, and the Z-axis is oriented substantially perpendicular to the X-axis and the Y-axis.

In the illustrated embodiment, The first electric machine <NUM> and the second electric machine <NUM> are orientated in a same direction. The common gear reduction <NUM> is rotatable about a fourth axis of rotation <NUM> and is driven by the first and second electric machines <NUM>, <NUM>. In the illustrated embodiment, the fourth axis of rotation <NUM> is orientated coaxially with the first axis of rotation <NUM>. The differential gear set <NUM> is disposed about the first axis of rotation <NUM> and is coupled to and driven by the common gear reduction <NUM> to transfer rotational torque from the first and second electric machines <NUM>, <NUM> to the first and second axle shafts <NUM>, <NUM>. The speed change mechanism <NUM> is coupled between the common gear reduction <NUM> and the differential gear set <NUM> to change the rotational torque that is transferred to the first and second axle shafts <NUM>, <NUM>. The speed change mechanism <NUM> includes the reduction gear set <NUM> that is rotatable about the first axis of rotation <NUM> and is driven by the common gear reduction <NUM>, and the output gear set <NUM> that is rotatable about a fifth axis of rotation <NUM> and driven by the reduction gear set <NUM>. The fifth axis of rotation <NUM> is substantially parallel with the first axis of rotation <NUM>. For example, the input shaft <NUM> rotates about the fourth axis of rotation <NUM> that is coaxial with the first axis of rotation <NUM>, and the output counter shaft <NUM> rotates about the fifth axis of rotation <NUM> that is parallel and spaced from the first axis of rotation <NUM>.

With reference to <FIG>, in the illustrated embodiment, each electric machine <NUM>, <NUM> is spaced a vertical distance <NUM> from the axle shafts <NUM>, <NUM> along a vertical Z-axis, and spaced a horizontal distance <NUM> from the axle shafts <NUM>, <NUM> along a horizontal Y-axis. For example, the second axis of rotation <NUM> of the first electric machine <NUM> and the third axis of rotation <NUM> of the second electric machine <NUM> are each spaced a vertical distance <NUM> from the first axis of rotation <NUM> of the axle shafts <NUM>, <NUM> as measured along the vertical Z-axis. In one embodiment, as shown in <FIG>, each electric machine <NUM>, <NUM> is spaced the same vertical distance from the axle shafts <NUM>, <NUM>. In another embodiment, as shown in <FIG>, the first electric machine <NUM> is spaced a first vertical distance <NUM> from the axle shafts <NUM>, <NUM> and the second electric machine <NUM> is spaced a second vertical distance <NUM> from the axle shafts <NUM>, <NUM> that is different from the first vertical distance <NUM>. In addition, as shown in <FIG>, the rotor shaft <NUM> of each electric machine <NUM>, <NUM> is spaced a horizontal distance <NUM> from the axle shafts <NUM>, <NUM> as measured along a horizontal Y-axis. For example, the second axis of rotation <NUM> of the first electric machine <NUM> and the third axis of rotation <NUM> of the second electric machine <NUM> are each spaced a horizontal distance <NUM> from the first axis of rotation <NUM> of the axle shafts <NUM>, <NUM> as measured along the horizontal Y-axis. In one embodiment, as show in <FIG>, each electric machine <NUM>, <NUM> is spaced the same horizontal distance from the axle shafts <NUM>, <NUM>. In another embodiment, as shown in <FIG>, the first electric machine <NUM> is spaced a first horizontal distance <NUM> from the axle shafts <NUM>, <NUM> and the second electric machine <NUM> is spaced a second horizontal distance <NUM> from the axle shafts <NUM>, <NUM> that is different from the first horizontal distance <NUM>.

With reference to <FIG>, in the illustrated embodiment, the second axis of rotation <NUM> of the first electric machine <NUM> and the third axis of rotation <NUM> of the second electric machine <NUM> are orientated at a same radial distance from the first axis of rotation <NUM>. The second axis of rotation <NUM> is spaced a first horizontal distance <NUM> from the first axis of rotation <NUM> and the third axis of rotation <NUM> is spaced a second horizontal distance <NUM> from the first axis of rotation <NUM> that is different than the first horizontal distance <NUM>. In addition, the second axis of rotation <NUM> of the first electric machine <NUM> is spaced a first vertical distance <NUM> from the first axis of rotation <NUM> and the third axis of rotation <NUM> of the second electric machine <NUM> is spaced a second vertical distance <NUM> from the first axis of rotation <NUM> that is different than the first vertical distance <NUM>.

In the illustrated embodiment, the speed change mechanism <NUM> is orientated between the first electric machine <NUM> and the second electric machine <NUM> along the horizontal Y-axis. In addition, the fifth axis of rotation <NUM> of the output gear set <NUM> is spaced a first radial distance <NUM> from the second axis of rotation <NUM> of the first electric machine <NUM> and a second radial distance <NUM> from the third axis of rotation <NUM> of the second electric machine <NUM> that is different from the first radial distance <NUM>. In one embodiment, as shown in <FIG>, the first and second electric machines <NUM>, <NUM> include a length <NUM> defined along the X-axis between a first end <NUM> and a second end <NUM>. The common gear reduction <NUM> is positioned at the first end <NUM> of the first and second electric machines <NUM>, <NUM> and the differential gear set <NUM> is positioned at the opposite second end <NUM> of the first and second electric machines <NUM>, <NUM>, such that the first and second electric machines <NUM>, <NUM> are orientated between the input drive wheel <NUM> and the differential gear set <NUM> along the X-axis.

In an embodiment, in which the axle assembly includes the second output gear set <NUM>, the second output gear set <NUM> is rotatable about a sixth axis of rotation <NUM> (shown in <FIG>) that is substantially parallel with the first axis of rotation <NUM> and driven by the reduction gear set <NUM>.

Referring to <FIG>, in the illustrated embodiment, the axle assembly <NUM> includes a drive unit housing <NUM> enclosing the reduction assembly <NUM> therein. The drive unit housing <NUM> includes a plurality of sidewalls <NUM> that extent between a first side <NUM> and a second side <NUM>, and between an upper portion <NUM> and a lower portion <NUM>. The drive unit housing <NUM> also includes an inner surface <NUM> that defines an interior cavity <NUM> enclosing the first and second electric machines <NUM>, <NUM>, the common gear reduction <NUM>, the differential gear set <NUM>, and the speed change mechanism <NUM> within the interior cavity <NUM>. The first and second axle shafts <NUM>, <NUM> are partially disposed within the interior cavity <NUM> and extend out of the drive unit housing <NUM> is opposite directions. In one embodiment, the axle assembly <NUM> may include an integrated oil cooler & pump system for circulation cooling fluid within the drive unit housing <NUM> for cooling the reduction assembly <NUM>.

In the illustrated embodiment, with reference to <FIG>, the interior cavity <NUM> of the drive unit housing <NUM> includes a central cavity represented by area <NUM>, a lower cavity represented by area <NUM>, a first machine cavity represented by area <NUM>, and a second machine cavity represented by area <NUM>. The central cavity <NUM> includes the fourth axis of rotation <NUM> of the common gear reduction <NUM> and the first axis of rotation <NUM> of the first and second axle shafts <NUM>, <NUM> disposed within the central cavity <NUM>. The lower cavity <NUM> is disposed below the central cavity <NUM> and is configured to accumulate a volume of gearbox fluid with the speed change mechanism <NUM> at least partially immersed in the lower cavity <NUM>, and with the first and second electric machines <NUM>, <NUM> spaced from the lower cavity <NUM>. For example, the reduction gear set <NUM> of the speed change mechanism <NUM> may be disposed within the central cavity <NUM> and the output gear set <NUM> of the speed change mechanism <NUM> may be disposed within the lower cavity <NUM>, with the output gear set <NUM> partially immersed within the accumulated volume of gearbox fluid.

The first machine cavity <NUM> is disposed above the lower cavity <NUM> and is adjacent to the central cavity <NUM> on one side of the first axis of rotation <NUM>. The first machine cavity <NUM> includes the second axis of rotation <NUM> of the first electric machine <NUM> disposed within the first machine cavity <NUM>. The second machine cavity <NUM> includes the third axis of rotation <NUM> of the second electric machine <NUM> disposed within the second machine cavity <NUM>. The second machine cavity <NUM> is disposed above the lower cavity <NUM> and is adjacent to the central cavity <NUM> on an opposing side of the first axis of rotation <NUM> from the first machine cavity <NUM>. In one embodiment, the second machine cavity <NUM> is at least partially above the first machine cavity <NUM> with the third axis of rotation <NUM> of the second electric machine <NUM> disposed within the second machine cavity <NUM>.

In the illustrated embodiment, the inner surface <NUM> of the drive unit housing <NUM> includes a lower inner surface <NUM> that partially defines the lower cavity <NUM>, a first upper inner surface <NUM> that partially defines the first machine cavity <NUM>, and a second upper inner surface <NUM> that partially defines the second machine cavity <NUM>. The first upper inner surface <NUM> spaced a first vertical distance <NUM> from the lower inner surface <NUM> and the second upper inner surface <NUM> is spaced a second vertical distance <NUM> from the lower inner surface <NUM> that is greater than the first vertical distance <NUM>. In addition, the first upper inner surface <NUM> is positioned a vertical distance from the first axis of rotation <NUM> that is greater than the vertical distance from the second upper inner surface <NUM> to the first axis of rotation <NUM>.

The inner surface <NUM> of the drive unit housing <NUM> also includes a first end surface <NUM> that partially defines the first machine cavity <NUM> and an opposite second end surface <NUM> that partially defines the second machine cavity <NUM>. The first end surface <NUM> of the first machine cavity <NUM> is spaced a first horizontal distance <NUM> from the first axis of rotation <NUM>, and the second end surface <NUM> of the second machine cavity <NUM> is spaced a second horizontal distance <NUM> from the first axis of rotation <NUM> that is greater than the first horizontal distance <NUM> of the first end surface <NUM>.

In one embodiment, the axle assembly <NUM> includes a first support member <NUM> that is mounted to the first side <NUM> of the drive unit housing <NUM>, and a second support member <NUM> that is mounted to the second side <NUM> of the drive unit housing <NUM>. The axle assembly <NUM> also includes an axle support coupling assembly <NUM> that is configured to couple the first support member <NUM> and the second support member <NUM> to the drive unit housing <NUM> such that forces experienced by the drive unit housing <NUM> are transferred to the first and second support members <NUM>, <NUM>.

In the illustrated embodiment, the first support member <NUM> mounted to the first side <NUM> of the drive unit housing <NUM> and includes a first flange <NUM> that extends to the lower portion <NUM> of the drive unit housing <NUM>. The second support member <NUM> is mounted to the second side <NUM> of the drive unit housing <NUM> and includes a second flange <NUM> that extends to the lower portion <NUM> of the drive unit housing <NUM>. The coupling assembly <NUM> includes a plurality of interior support cavities <NUM> that extend though the lower portion <NUM> of the drive unit housing <NUM> from the first side <NUM> to the second side <NUM>, and a plurality of fastener assemblies <NUM> that are inserted through the interior support cavities <NUM> and mounted to both of the first and second flanges <NUM>, <NUM> thereby supporting the entire drive unit housing <NUM> such that forces experienced by the drive unit housing <NUM> are transferred to the first and second support members <NUM>, <NUM>.

In one embodiment, the axle assembly <NUM> includes a two-piece drive unit housing <NUM> having including a base unit <NUM> and a cover <NUM> that is coupled to the base unit <NUM> to define the interior cavity <NUM>. As shown, the base unit <NUM> is deeper than the cover <NUM>. It is to be appreciated, that the base unit <NUM> and the cover <NUM> may be of any suitable size and may be equal halves of the drive unit housing <NUM> without deviating from the overall scope of the invention. The cover <NUM> is coupled to the base unit <NUM> with a plurality of fasteners extending around a perimeter of the cover <NUM>. The first support member <NUM> is coupled to the cover <NUM> and includes a first shaft opening <NUM> with the first axle shaft <NUM> extending through the first shaft opening <NUM> and having the first flange <NUM> extending to the lower portion of the cover <NUM>. The second support member <NUM> is coupled to the base unit <NUM> and includes a second shaft opening <NUM> with the second axle shaft <NUM> extending through the second shaft opening <NUM> and having the first flange <NUM> extending to the lower portion of the base unit <NUM>. The plurality of interior support cavities <NUM> extend through the lower portions of the base unit <NUM> and the cover <NUM>. The plurality of fastener assemblies <NUM> are inserted through the interior support cavities <NUM> and mounted to both of the first and second flanges <NUM>, <NUM> to couple the first support member <NUM>, the second support member <NUM>, the base unit <NUM>, and the cover <NUM> together.

The first and second support members <NUM>, <NUM> are each coupled to the drive unit housing <NUM> and extend outwardly from the drive unit housing <NUM> in opposite directions along the axle centerline <NUM>. Each support member <NUM>, <NUM> is coupled to the drive unit housing <NUM> and the corresponding axle shafts <NUM>, <NUM> extending through each support member <NUM>, <NUM> coaxial with the axle centerline <NUM>.

The coupling assembly <NUM> is formed along the lower portion <NUM> of the drive unit housing <NUM> and includes the plurality of interior support cavities <NUM> that extend though the drive unit housing <NUM>, and the plurality of fastener assemblies <NUM> inserted through the interior support cavities <NUM>. Each interior support cavity <NUM> extends through the cover <NUM> and the base unit <NUM>, and is sized and shaped to receive a corresponding fastener assembly <NUM> therethrough to facilitate coupling the first support member <NUM> to the second support member <NUM>.

In one embodiment, the first support member <NUM> includes a center portion having a substantially domed-shaped first outer surface <NUM> and a mounting flange <NUM> that extends outwardly from the center portion. The mounting flange <NUM> includes a plurality of openings defined along a perimeter of the mounting flange <NUM> that are each sized and shaped to receive corresponding fasteners therethrough to facilitate coupling the first support member <NUM> to the cover <NUM>. The first flange <NUM> extends radially outwardly from the center portion towards the lower portion <NUM> of the cover <NUM>. The first flange <NUM> includes a plurality of support openings that are sized and shaped to receive a corresponding fastener assembly <NUM> therethrough. The first support member <NUM> may also include a plurality of first support ribs <NUM> defined along the first outer surface <NUM> of the center portion. The first support ribs <NUM> extend outwardly from the center portion towards an outer edge of the first support member <NUM>. In the illustrated embodiment, the outer edge of the first support member <NUM> is defined by the first flange <NUM> and the mounting flange <NUM> and includes a cross-section having a substantially teardrop shape.

The second support member <NUM> includes a center portion having a substantially domed-shaped second outer surface <NUM> and a mounting flange <NUM> that extends outwardly from the center portion. A plurality of openings are defined along a perimeter of the mounting flange <NUM> and are each sized and shaped to receive corresponding fasteners therethrough to facilitate coupling the second support member <NUM> to the base unit <NUM>. The second flange <NUM> extends radially outwardly from the center portion towards the lower portion <NUM> of the base unit <NUM>. The second flange <NUM> includes a plurality of support openings that are each sized and shaped to receive a corresponding fastener assembly <NUM> therethrough. A plurality of second support ribs <NUM> are defined along the second outer surface <NUM> of the center portion and extend outwardly from the center portion towards an outer edge of the second support member <NUM>. The outer edge of the second support member <NUM> is defined by the second flange <NUM> and the mounting flange <NUM> and includes a cross-section having a substantially teardrop shape.

In the illustrated embodiment, each fastener assembly <NUM> includes a support bolt/rod <NUM> that is inserted through a corresponding interior support cavity <NUM> and extends outwardly from a corresponding first support opening <NUM> defined through the first flange <NUM> and a corresponding second support opening <NUM> defined through the second flange <NUM>. Each end of the support bolt <NUM> includes a threaded portion. A fastening nut and washer <NUM> is coupled to each end of the support bolt <NUM> and is configured to couple the first support member <NUM> to the second support member <NUM>, and to compress the first support member <NUM> and the second support member <NUM> towards the drive unit housing <NUM>. For example, as each fastening nut is tightened, the fastening nut and washer assembly <NUM> contacts an outer surface of the corresponding flanges <NUM>, <NUM> to compress the first support member <NUM> and the second support member <NUM> towards the drive unit housing <NUM>.

In one embodiment, the axle assembly <NUM> may also include a first axle tube <NUM> and a second axle tube <NUM>. The first axle tube <NUM> extends outwardly from the center portion of the first support member <NUM> along the axle centerline <NUM>. The plurality of first support ribs <NUM> are defined along the outer surface of the center portion and extend from the first axle tube <NUM> towards the first flange <NUM>. The second axle tube <NUM> that extends outwardly from the center portion of the second support member <NUM> along the axle centerline <NUM>. The plurality of second support ribs <NUM> are defined along the outer surface of the center portion and extend from the second axle tube <NUM> towards the second flange <NUM>.

The weight and loads experienced by the drive unit housing <NUM>, which is preferably formed of aluminum, are carried by the coupling assembly <NUM> and first and second support members <NUM>, <NUM>, which are preferably formed of steel. In particular, the weight and loads experienced by the drive unit housing <NUM> are carried by the support members <NUM>, <NUM>, bolts <NUM>, the flanges <NUM>, <NUM>, and axle tubes <NUM>, <NUM>. This configuration allows the drive unit housing <NUM> to be formed of a lightweight material, such as aluminum. As mentioned above, the first support member <NUM>, the second support member, and the fastener assemblies <NUM> are preferably formed of steel. In other embodiments, the first and second support members <NUM>, <NUM>, the fastener assemblies <NUM>, and the drive unit housing <NUM> can be formed of alternative materials and/or combination of suitable materials.

Referring to <FIG>, in one embodiment, the present invention includes a vehicle assembly <NUM> including a frame rail assembly <NUM> and the axle assembly <NUM>. The frame rail assembly <NUM> includes a pair of parallel frame rails <NUM>, <NUM> and a plurality of cross beams <NUM> that are coupled to the parallel frame rails <NUM>, <NUM>. The parallel frame rails <NUM>, <NUM> are orientated along a longitudinal axis <NUM> of the vehicle assembly <NUM> and are spaced apart along a transverse axis <NUM> of the vehicle assembly <NUM> that is perpendicular to the longitudinal axis <NUM>.

The plurality of cross beams <NUM> are coupled between the pair of parallel frame rails <NUM>, <NUM> and are spaced along the longitudinal axis <NUM> to define a plurality of equipment cavities <NUM>. For example, in the illustrated embodiment, the plurality of cross beams <NUM> includes a first cross beam <NUM> and a second cross beam <NUM> that is spaced from the first cross beam <NUM> along the longitudinal axis <NUM> such that an equipment cavity <NUM> is defined between the interior surfaces of the pair of parallel frame rails <NUM>, <NUM>, the first cross beam <NUM>, and the second cross beam <NUM>. The drive unit housing <NUM> is mounted to the frame rail assembly <NUM> such that the drive unit housing <NUM> is positioned within the equipment cavity <NUM> and is orientated below a horizontal plane that is defined by the first and second cross beams <NUM>, <NUM>.

In the illustrated embodiment, the vehicle assembly <NUM> includes a plurality of suspension components that are mounted to the frame rails <NUM>, <NUM> and are positioned within the equipment cavity <NUM>. For example, the plurality of suspension components may include a first group of suspension components <NUM> that are coupled to a first frame rail <NUM> of the pair of parallel frame rails, and a second group of suspension components <NUM> that are coupled to a second frame rail <NUM> of the pair of parallel frame rails. The drive unit housing <NUM> is suspended within the equipment cavity <NUM> such that the drive unit housing <NUM> is positioned between the first and second groups of suspension components <NUM>, <NUM>.

The plurality of suspension components may include a first strut member <NUM> that is coupled to the first frame rail, and a second strut member <NUM> that is coupled to the second frame rail <NUM> such that a horizontal gap <NUM> is defined along the transverse axis <NUM> between the first strut member <NUM> and the second strut member <NUM> within the equipment cavity <NUM>. The drive unit housing <NUM> is suspended within the equipment cavity <NUM> and positioned within the gap defined between the first strut member <NUM> and the second strut member <NUM>. In addition, the distance between the first and second frame rails <NUM>, <NUM> defines a cavity width <NUM> of the equipment cavity measured along the transverse axis <NUM>. The drive unit housing <NUM> may include a housing width <NUM> that is defined between the first and second sides <NUM>, <NUM> measured the transverse axis <NUM> that is less than the cavity width <NUM>.

In one embodiment, the axle assembly <NUM> may include the drive unit housing <NUM>, the two axle tubes <NUM>, <NUM>, and two wheel ends <NUM>. Each of the axle tubes <NUM>, <NUM> is coupled to the drive unit housing <NUM> at a proximal end and to one of the wheel ends <NUM> at a distal end. The axle tubes <NUM>, <NUM> protrude along the axle centerline <NUM> from opposing sides of the drive unit housing <NUM>. The axle shafts <NUM>, <NUM> are disposed in each corresponding axle tube <NUM>, <NUM> coaxial with the axle centerline <NUM>. As shown in <FIG>, each axle shaft <NUM>, <NUM> is coupled to one of the wheel ends <NUM> to transfer torque to respective wheels. The wheels are coupled to the wheel ends <NUM> and rotate about the axle centerline <NUM> relative to the drive unit housing <NUM>. Each of the wheel ends <NUM> may include a hub assembly. For example, the hub assembly may be a full-float wheel hub, a semi-float wheel hub, a planetary reduction hub, or a portal hub.

In the illustrated embodiment, the axle assembly <NUM> includes the drive unit housing <NUM> with the reduction assembly <NUM> positioned within the drive unit housing <NUM>, and the pair of axle shafts <NUM>, <NUM> are coupled to the reduction assembly <NUM> and extending radially outwardly from opposite ends of the reduction assembly <NUM> along the first axis of rotation <NUM>. The axle assembly <NUM> may also include a pair of wheel ends <NUM> and a braking assembly <NUM> that is coupled to each wheel end <NUM>. Each wheel end <NUM> is coupled to an end of a corresponding axle shaft <NUM>, <NUM>. The braking assembly <NUM> may include an air cylinder, brake hoses, brake drums, brake rotors, brake calipers, and the like.

In one embodiment, the axle assembly <NUM> may include a mounting assemblies <NUM> extending outwardly from opposite ends of the drive unit housing <NUM>. Each mounting assembly <NUM> includes a suspension mounting location for mounting a suspension system of a vehicle to the axle assembly <NUM>. In addition, the drive unit housing <NUM> includes a support bracket <NUM> (shown in <FIG>) that is coupled to the upper portion <NUM> of the drive unit housing <NUM>. The vehicle assembly <NUM> includes a stabilizer bar <NUM> that is pivotably coupled to one of the parallel frame rails <NUM>, <NUM>, and is pivotably coupled to the support bracket <NUM> of the drive unit housing <NUM> for suspending the drive unit housing <NUM> within the equipment cavity <NUM> and beneath the cross beams. For example, in one embodiment, the vehicle assembly includes a panhard rod that is coupled to the support bracket <NUM> and to the first frame rail <NUM> (shown in <FIG>) for supporting the drive unit housing <NUM> from the frame rail assembly <NUM>.

Referring to <FIG>, in the illustrated embodiment, the axle assembly <NUM> is adapted for use with a vehicle <NUM> including a frame rail assembly <NUM> and a wheel assembly that is coupled to the axle assembly <NUM> for supporting the axle assembly <NUM> from a ground surface. The wheel assembly includes one or more wheels that are coupled to each wheel end <NUM> of the axle assembly <NUM> to support the vehicle and transfer motive power from the axle assembly <NUM> to the ground surface. A mounting assembly <NUM> is coupled to the frame rail assembly <NUM> and to the axle assembly <NUM> such that the frame rail assembly <NUM> is supported by the axle assembly <NUM> and the wheel assembly from the ground surface. The mounting assembly <NUM> may include suspension arms that are coupled to one or more suspension mounting locations on the axle assembly <NUM>. The vehicle may be an electric vehicle or a hybrid vehicle with an electric motor and internal combustion generator / motor. Advantageously, the mounting assembly <NUM> may be configured to retrofit the axle assembly <NUM> to a vehicle. For example, a frame rail truck originally equipped with a traditional axle assembly may utilize the axle assembly <NUM> in place of the traditional axle assembly.

In the illustrated embodiment, the vehicle <NUM> may include a plurality of axle assemblies <NUM>. For example, as shown in <FIG>, the vehicle may include a first electric axle assembly <NUM> that is coupled to a first wheel assembly <NUM>, and a second electric axle assembly <NUM> that is coupled to a second wheel assembly <NUM>. In one embodiment, as shown in <FIG>, the first electric axle assembly <NUM> and the second electric axle assembly <NUM> are orientated in the same direction. Each of the first and second electric axle assemblies <NUM>, <NUM> include a panhard rod that is orientated substantially parallel to the axle shafts <NUM>, <NUM> and coupled between the cross beams <NUM> and the vehicle frame rail assembly <NUM> for supporting each of the axle assemblies <NUM>, <NUM> from the vehicle frame rail assembly <NUM>. In addition, as shown in <FIG>, each of the first and second electric axle assemblies <NUM>, <NUM> include the first electric machine <NUM> and the second electric machine <NUM> orientated in the same position with respect to the corresponding axle shafts <NUM>, <NUM>. For example, as shown in <FIG>, each of the first and second axle assemblies <NUM>, <NUM> include the second electric machine <NUM> spaced a different vertical distance from the axle shafts <NUM>, <NUM> than the first electric machine <NUM>.

In another embodiment, the first electric axle assembly <NUM> and the second electric axle assembly <NUM> are oriented in opposing directions. For example, as shown in <FIG>, the first electric axle assembly <NUM> includes the electric machines positioned adjacent the first frame rail <NUM>, and the second electric axle assembly <NUM> includes the electric machines positioned adjacent the opposite second frame rail <NUM>. In addition, each of the first and second electric axle assemblies <NUM>, <NUM> may include a rod assembly <NUM> coupled between a corresponding cross beams <NUM> and the vehicle frame rail assembly <NUM> for supporting each of the electric axle assemblies <NUM>, <NUM> from the vehicle frame rail assembly <NUM>. Each rod assembly <NUM> includes a pair of support rods extending outwardly from the drive unit housing <NUM> in a "v"-shape orientation. Each support rod extends between the support bracket <NUM> and the vehicle frame rail assembly <NUM>, and is orientated at an oblique angle with respect to the first axis of rotation <NUM>. In the illustrated embodiment, each rod assembly <NUM> is coupled to a common cross beams <NUM>.

In one embodiment, the first electric axle assembly <NUM> and the second electric axle assembly <NUM> may be oriented in the same direction, with the first electric axle assembly <NUM> having electric machines having a different orientation with respect to the axle shafts <NUM>, <NUM> than the electric machines of the second electric axle assembly <NUM>. For example, the first electric axle assembly <NUM> includes the first electric machine <NUM> spaced a farther vertical distance from the axle shafts <NUM>, <NUM> than the second electric machine <NUM>, and the second electric axle assembly <NUM> includes the second electric machine <NUM> spaced a farther vertical distance from the axle shafts <NUM>, <NUM> than the first electric machine <NUM>.

Claim 1:
An axle assembly (<NUM>) comprising:
a first axle shaft (<NUM>) orientated along a first axis of rotation (<NUM>);
a second axle shaft (<NUM>) orientated along said first axis of rotation (<NUM>) with said first and second axle shafts (<NUM>, <NUM>) extending in opposite directions;
a first electric machine (<NUM>) orientated along a second axis of rotation (<NUM>) substantially parallel with said first axis of rotation (<NUM>);
a second electric machine (<NUM>) spaced from said first electric machine (<NUM>) and orientated along a third axis of rotation (<NUM>) substantially parallel with said first axis of rotation (<NUM>);
a common gear reduction (<NUM>) rotatable about a fourth axis of rotation (<NUM>) and driven by said first and second electric machines (<NUM>, <NUM>); and
a speed change mechanism (<NUM>) coupled to said common gear reduction (<NUM>) to change the rotational torque transferred to said first and second axle shafts (<NUM>, <NUM>),
wherein
said common gear reduction (<NUM>) includes an input shaft (<NUM>) and an input drive wheel (<NUM>) fixedly coupled to said input shaft (<NUM>), said input drive wheel (<NUM>) engaging said first and second electric machines (<NUM>, <NUM>) for transferring the rotational torque from said first and second electric machines (<NUM>, <NUM>) to said input shaft (<NUM>), said input shaft (<NUM>) orientated coaxially with said first axis of rotation (<NUM>) and including an inner surface (<NUM>) that defines a input shaft bore (<NUM>) configured to receive said first axle shaft (<NUM>) therethrough
characterized in that
said speed change mechanism (<NUM>) includes a reduction gear set (<NUM>) rotatable about said first axis of rotation (<NUM>) and driven by said common gear reduction (<NUM>), and an output gear set (<NUM>) rotatable about a fifth axis of rotation (<NUM>) substantially parallel with said first axis of rotation (<NUM>) and driven by said reduction gear set (<NUM>); and
said reduction gear set (<NUM>) includes a first reduction gear (<NUM>) and a second reduction gear (<NUM>) rotatable about said input shaft (<NUM>), and a shift mechanism (<NUM>) coupled to said input shaft (<NUM>) and positioned between said first reduction gear (<NUM>) and said second reduction gear (<NUM>) for selectively transferring torque from said input shaft (<NUM>) to said first reduction gear (<NUM>) and said second reduction gear (<NUM>).