Self-contained electric axle for all-wheel drive

A driveline (12) of a motor vehicle having an internal combustion engine (10) for propelling the vehicle and method of assembly can include a self-contained drive axle assembly (35). The self-contained drive axle assembly (35) can include an electric motor (18) for propelling the motor vehicle mounted coaxial with and sheathing a first portion of the drive axle assembly (35) and a disconnect clutch (20) mounted coaxial with and sheathing a second portion of the drive axle assembly (35) for selectively connecting powered rotation between the electric motor (18) and a gear box (14). The drive axle assembly (35) can include the gear box (14) having at least one of a transmission (15) and a power take off unit (40) mounted coaxial with and sheathing a third portion of the drive axle assembly (35) for transferring powered rotation to a pair of wheels (16a, 16b) through the drive axle assembly (35).

FIELD OF THE INVENTION

The invention relates to hybrid drive systems for motor vehicles, and more specifically, to an integrated electric motor and axle assembly for use in hybrid motor vehicles.

BACKGROUND

Known motor vehicles can include an internal combustion engine and an electrical drive apparatus, e.g. an electric motor, as primary sources of power for propelling the motor vehicle. Operation of the vehicle can additionally include a hybrid source of power based on an interaction between the internal combustion engine and the electrical drive apparatus. Known hybrid powertrains generally do not perform or handle as well as comparable vehicles powered by an internal combustion engine due to energy lost during normal operation of the vehicle. Many known hybrid powertrains are used on two-wheel drive vehicles to drive a single axle of a vehicle due to focus on efficient and economical operation. In an all-wheel drive vehicle, rotational input is applied to a second axle driving a second pair of wheels by a second electric drive machine and a first or front axle driving a first pair of wheels is driven by the powertrain. Energy convertors and various powertrains have been disclosed in U.S. Pat. No. 7,854,278; U.S. Pat. No. 7,836,992; U.S. Pat. No. 7,398,841; U.S. Pat. No. 7,040,186; and U.S. Pat. No. 6,699,151. All-wheel drive hybrid vehicles have been disclosed in U.S. Pat. No. 7,921,949; U.S. Pat. No. 7,464,779; U.S. Pat. No. 6,880,664; U.S. Pat. No. 6,595,308; and U.S. Pat. No. 6,205,379.

SUMMARY

Hybrid powertrains dissipate waste energy in the form of hot exhaust gases during normal operation. It can be desirable to provide an energy conversion apparatus to recover the waste energy and convert the waste energy into useable energy for more efficiently powering the vehicle. It can also be desirable to provide a gear box acting as an interface between a first and second pair of wheels in the all-wheel drive vehicle for reducing the amount of torque needed to be generated by the electric motor in order to drive both drivelines. It can further be desirable to provide a disconnect mechanism for disconnecting the electric motor from a gearbox transferring torque between wheels of the vehicle to prevent over speed rotation of the electric motor. Disconnecting the gear box from the electric motor can allow the gear box and the electric motor to rotate independently to reduce drag. An all-wheel drive vehicle can include a self-contained electric axle and power generation system using energy lost during normal operation of the vehicle, such as exhaust heat or regenerative braking. The power generation system can be operated independently from the vehicle power system and can include a mechanical system, power system, and a control system.

A motor vehicle having an internal combustion engine for propelling the motor vehicle while dissipating waste energy during operation can include a driveline for transferring torque between at least one pair of wheels. The driveline can have a self-contained drive axle including an electric motor, a disconnect clutch, and a gear box. The electric motor can propel the motor vehicle and can be mounted coaxial with and sheathing a first portion of the drive axle assembly. The disconnect clutch can be mounted coaxial with and sheathing a second portion of the drive axle assembly for selectively connecting powered rotation between the electric motor and the gear box. The gear box can include at least one of a transmission and a power take off unit and can be mounted coaxial with and sheathing a third portion of the drive axle assembly for transferring powered rotation to the at least one pair of wheels through the drive axle assembly.

An all-wheel drive motor vehicle can have an internal combustion engine for propelling the motor vehicle while dissipating waste energy during operation. The all-wheel drive motor vehicle can include a first driveline for transferring torque between at least one pair of wheels, a second driveline for transferring torque between a second pair of wheels, a power supply system, and a control system. The first driveline can include a self-contained drive axle assembly having an electric motor for propelling the motor vehicle mounted coaxial with and sheathing a first portion of the drive axle assembly, a disconnect clutch mounted coaxial with and sheathing a second portion of the drive axle assembly for selectively connecting powered rotation between the electric motor, and a gear box including at least one of a transmission and a power take off unit. The gear box can be mounted coaxial with and sheathing a third portion of the drive axle assembly. The power take off unit can transfer powered rotation to the at least one pair of wheels through the drive axle assembly and from the first driveline to the second driveline. The power supply system can recover waste energy dissipated by the motor vehicle during normal operation, convert the waste energy to electrical energy for rotating the electric motor, and store the converted energy until needed. The control system can have at least a first and second vehicle sensor and an electronic control unit. The first vehicle sensor can detect a rotary speed of the electric motor and the electronic control unit can selectively control the disconnect clutch when the rotary speed detected by the first vehicle sensor exceeds a threshold speed. The second vehicle sensor can detect operating characteristics of the motor vehicle and the electronic control unit can selectively control actuation of the electric motor in response to the second vehicle sensor.

Assembling a driveline in a motor vehicle can include assembling a self-contained drive axle assembly. The method can include mounting an electric motor for propelling the motor vehicle coaxial with and sheathing a first portion of the drive axle assembly. The method can further include connecting a disconnect clutch mounted coaxial with and sheathing a second portion of the drive axle assembly for selectively connecting powered rotation between the electric motor and a gear box. The method can further include positioning the gear box having at least one of a transmission and a power take off unit. The gear box can be mounted coaxial with and sheathing a third portion of the drive axle assembly for transferring powered rotation to at least one pair of wheels through the drive axle assembly.

DETAILED DESCRIPTION

Referring now toFIG. 1, a motor vehicle can have an internal combustion engine10for propelling the motor vehicle while dissipating waste energy during operation and a driveline12for transferring torque between at least one pair of wheels16a,16b. The motor vehicle can have a first driveline12driving the first pair of wheels16a,16band a second driveline36driving a second pair of wheels38a,38b. The motor vehicle can be operable in an all-wheel drive mode such that rotary power is transferred from the first driveline12to the second driveline36. The first driveline12can include a first axle assembly34connecting the first pair of wheels16a,16b. The first driveline12can include a self-contained drive axle assembly35for driving the first pair of wheels16a,16b. The first axle assembly34can include the self-contained drive axle assembly35. The first axle assembly34can also include a first differential connecting a pair of half axle shafts35a,35b. Each of the pair of half axle shafts35a,35bcan be drivingly connected to a corresponding one of the first pair of wheels16a,16b. The second driveline36can include a second axle assembly44connecting the second pair of wheels38a,38b. The second axle assembly44can include a second differential for connecting the second pair of wheels38a,38bthrough a second pair of half axle shafts.

The self-contained drive axle assembly35can include an electric drive apparatus, or electric motor18, for propelling the motor vehicle. The electric motor18can be mounted coaxial with the drive axle assembly35between each of the first pair of wheels16a,16b. The electric motor18can sheath a first portion of the drive axle assembly35. The self-contained drive axle assembly35can further include a disconnect clutch20mounted coaxial with and sheathing a second portion of the drive axle assembly35and a gear box14mounted coaxial with and sheathing a third portion of the drive axle assembly35. The disconnect clutch20can selectively connect powered rotation between the electric motor18and the gear box14. The gear box14can include at least one of a transmission15and a power take off unit40. The transmission15can transfer powered rotation from the electric motor18and/or a drive shaft19of the internal combustion engine to the first pair of wheels16a,16bthrough the drive axle assembly35and a transmission clutch assembly21. In an all-wheel drive motor vehicle having a first and second driveline12,36, the power take off unit40can transfer rotary power from the first driveline12to the second driveline36when the motor vehicle is in an all-wheel drive mode. The internal combustion engine10can deliver drive torque to the first axle assembly34through the transmission15of the gear box14. The electric motor18, disconnect clutch20, and gear box14can be located in a housing23of the self-contained drive axle assembly35and mounted for driving rotation of the first differential between each of the first pair of wheels16a,16b. By way of example and not limitation, the housing23can include different housing unit portions, such that the different housing unit portions can include one portion enclosing the electric motor18, one portion enclosing the disconnect clutch20, and one portion enclosing the gear box14, where the different housing unit portions can be combined and connected with respect to one another into the self-contained drive axle assembly35.

By way of example and not limitation, the gear box14can include a planetary gear assembly for controlling drive torque transferred from the internal combustion engine10and the electric motor18through the first differential connecting the pair of half axle shafts35a,35bto each of the first pair of wheels16a,16b. The planetary gear assembly can include a configuration of a sun gear, a ring gear, and a plurality of planetary gears rotatably supported by a planetary gear carrier. Planetary gear assemblies are generally known in the art, and are considered to be within the level of those skilled in the art, and therefore require no further explanation here. The disconnect clutch20can selectively connect the electric motor18and the gear box14. By way of example and not limitation, at least one output shaft rotatable by the electric motor18can rotate the sun gear of the planetary gear assembly within the gear box14to provide drive torque to the first pair of wheels16a,16b. By way of example and not limitation, the ring gear can be held stationary and the rotation of the rotor shaft and the sun gear can cause the plurality of planetary gears to rotate and drive the planetary gear carrier at a reduced speed. The planetary gear carrier can drive the first differential connecting half axle shafts35a,35b. Power can be transferred through a configuration of pinions and side gears, as known by those skilled in the art, to half axle shafts35a,35bfor driving each of the first pair of wheels16a,16b.

The driveline12can further include a power supply system22for recovering waste energy discharged by the internal combustion engine10, converting the waste energy to electrical energy for rotating the electric motor18, and storing the electrical energy. The power supply system22can recover waste energy dissipated during normal operation of the motor vehicle and can convert the waste energy to electrical energy. The power supply system22can then store the electrical energy in a power store32. The power supply system22can include a thermoelectric generator29recovering waste exhaust heat energy from an exhaust line30of the internal combustion engine10. The power store32can have at least one of a battery pack32aand a capacitor32b. The electric motor18can be in electrical communication with the power store32through a control switch42connecting the electric motor18and the at least one of the battery pack32aand capacitor32b. The driveline12can further include a control system24having at least one vehicle sensor26a,26bfor detecting operating characteristics of the motor vehicle and an electronic control unit28. The electronic control unit28can control actuation of the electric motor18, actuation of the disconnect clutch20, and operation of the power supply system22based on a control program stored in memory in response to the vehicle sensor26a,26b. The electronic control unit28can include a microcomputer having a central processing unit, random-access memory, read-only memory, and an input-output actuator interface. By way of example and not limitation, the at least one vehicle sensor26a,26bcan include an accelerator position sensor, brake status switch, power store temperature sensor, power store state of charge sensor, engine speed sensor, motor speed sensor, and drive shaft speed sensor which can sense the speed of the driveshaft19driven by the internal combustion engine10for transferring rotary power to the first axle assembly34.

The at least one vehicle sensor26a,26bcan include a first vehicle sensor26afor detecting a rotary speed of the electric motor18. The control unit28can disengage the disconnect clutch20when the rotary speed detected by the first vehicle sensor26aexceeds a threshold speed such that the electric motor18and the gear box14can rotate independently with respect to one another when the disconnect clutch20is disengaged. The control system24can include a second vehicle sensor26bin electronic communication with the switch42where the electronic control unit28can switch the switch between a charging position, a discharging position, and an isolation position in response to the vehicle sensor26b. The charging position can be defined by the power supply system22recovering energy from the electric motor18, the discharging position can be defined by the power supply system22delivering electrical power to the electric motor18, and the isolation position can be defined by the power supply system isolated with respect to the electric motor18.

In operation, the motor vehicle can be operable in one of an internal combustion engine mode, an electric mode, and a hybrid mode. The internal combustion engine mode can be defined by the internal combustion engine10solely propelling the motor vehicle, and the electric mode can be defined by the electric motor18solely propelling the motor vehicle. The hybrid mode can be defined by the combination of the internal combustion engine10and the electric motor18propelling the vehicle. The motor vehicle can be shifted between the modes selectively by a vehicle driver or automatically by the control system24depending on various vehicle operating conditions, including by way of example and not limitation, vehicle speed, accelerator demand, and battery charge status. The engine10can be operable on any type or kind of fuel, such as gasoline, diesel, hydrogen, ethanol, biodiesel, or any other suitable fuels or combination of fuels.

When the vehicle is operating in the electric mode or hybrid mode, the control system24can selectively switch the switch42in response to the vehicle sensor26b. The at least one vehicle sensor26bcan detect an electric potential of the electric motor18. If the vehicle sensor26bdetects that the electric potential of the electric motor18is greater than an electric potential of the power store32, the electronic control unit28can switch the switch42into the charging position, such that the power supply system22can recover energy from the electric motor18. If the vehicle sensor26bdetects that the electric potential of the electric motor18is less than the electric potential of the power store32, the electronic control unit28can switch the switch42into the discharging position, such that the power supply system22can deliver electrical power to the electric motor18to propel the vehicle. When the motor vehicle is operating at a slower speed and a driver desires to brake the rotating wheels, the electric motor18continues to rotate while being propelled by the inertia of the vehicle and the switch42is placed in the charging position to generate drag acting against the continued rotation of the wheels corresponding to movement of the vehicle. The rotation of the electric motor18acts as drag against rotation of the wheels, or regenerative braking, and creates a high electric potential in the electric motor18to be recovered and stored in the power store32.

When the vehicle is operating in the internal combustion engine mode and the electric motor18is not propelling the vehicle, the switch42can be switched into the isolation position. In the internal combustion engine mode, the electric motor18can be back-driven by the rotation of the first pair of wheels16a,16b. When the vehicle sensor26adetects the electric motor18is rotating faster than a threshold speed, the disconnect clutch20can be actuated by the electronic control unit28for selectively disconnecting the electric motor18and the gear box14. When the disconnect clutch20is disengaged, the electric motor18and the gear box14can rotate independently such that rotary power is not transferred from the first pair of wheels16a,16bto the electric motor18. Disconnecting the electric motor18and the gear box14can prevent over speed rotation of the electric motor18and reduces drag within the driveline12. When the motor vehicle is propelled by the internal combustion engine10in the engine mode and the hybrid mode, the thermoelectric generator29of the power supply system22can recover waste exhaust heat energy from the exhaust line30and convert the exhaust heat energy to electrical energy for rotating the electric motor18. The thermoelectric generator29can be configured as known by one skilled in the art. The converted electrical energy can then be stored in the power store32until the electronic control unit28switches the switch42into the discharging position for rotating the electric motor18.

A driveline12can be assembled in a motor vehicle. The method can include assembling a self-contained drive axle assembly35. Assembling the self-contained drive axle assembly35can include mounting an electric motor18for propelling the motor vehicle coaxial with and sheathing a first portion of the drive axle assembly35, connecting a disconnect clutch20mounted coaxial with and sheathing a second portion of the drive axle assembly35for selectively connecting powered rotation between the electric motor18and a gear box14and positioning the gear box14. The gear box14can include at least one of a transmission15and a power take off unit40and can be mounted coaxial with and sheathing a third portion of the drive axle assembly35for transferring powered rotation to at least one pair of wheels16a,16bthrough the drive axle assembly35.