It is known to provide an electric or hybrid vehicle with an axle assembly using electric motors to drive selected wheels on the vehicle.
The invention relates to an improved axle assembly for an electric or hybrid vehicle, which includes electrically powered drive motors for respectively driving one or more vehicle wheels. The axle assembly preferably includes a dual motor arrangement, wherein two electric motors are arranged end-to-end. Each motor includes an inverter that is directly connected to its respective motor. The inverters preferably are mounted on opposite sides of the axle assembly and convert DC power from the vehicle's battery and power generation system to AC power to drive the motors. In addition, each motor includes a gearbox assembly coupled between an output of the motor and a corresponding support mechanism, such as a constant-velocity (CV) joint, operatively connected to a wheel. Each gearbox assembly selectively transfers torque or rotational movement from an output shaft of the motor to the wheel.
In one aspect of the invention, the electric axle assembly of the invention includes a pair of the electric motors, which are arranged back-to-back with a single cooling manifold located between inboard adjacent ends of the motors. The inboard ends of the motors are secured to opposite faces of the cooling manifold wherein an axis of rotation of each motor output shaft is aligned in registry with the axis of the other motor so that the cooling manifold maintains said motors in axial alignment.
The motors are disposed within separate, respective motor housings and the cooling manifold seals an inboard end of each housing. Each motor includes one of the power inverters, which is electrically connected thereto. The power inverters are disposed on opposite forward and rearward sides of the electric axle assembly. Liquid coolant is supplied to the motors and inverters to cool the motors and associated power inverters during driving of the vehicle.
More specifically, the coolant flows from the vehicle heat exchanger along various flow passageways, which preferably are defined by appropriate tubing, piping or the like. The passageways split a flow of lower temperature or cooled coolant, which is fed separately through each motor in parallel. More particularly, the coolant enters the cooling manifold through a single inlet wherein an internal inlet cooling channel provided within the cooling manifold directs the coolant into multiple inlet ports in the inboard end of each motor to thereby absorb heat from the motors and cool same. After cooling the motors, the heated coolant is discharged from the inboard end of each motor through outlet ports back into an internal outlet cooling channel in the cooling manifold where the coolant is again merged into a single flow. The heated coolant exits the cooling manifold at a single location and is then fed to a first inverter to cool same and then serially into the second inverter for cooling. After the second inverter, the coolant returns to the heat exchanger for subsequent cooling and refeeding of the cooled coolant back to the cooling manifold, motors and inverters. The cooling manifold therefore performs the additional function of defining flow paths or passageways to allow cooling of the motors.
In another aspect of the invention, the electric axle assembly provides a modular construction, which readily allows for assembly of a dual motor configuration while also allowing for a modified single motor configuration, or the provision of alternate configurations of a gearbox assembly. The axle assembly includes a first electric motor housed within a first motor housing and a second electric motor housed within a second motor housing. More specifically, each motor housing includes a cylindrical chamber in which the motor is inserted separately and independently of the other motor. Preferably, the cooling manifold is formed as a cooling manifold plate formed in a uniformly thick, plate shape. Once one or more motors are installed, the cooling manifold plate is positioned between the inboard end of each of the first and second motor housings. As referenced above, the cooling manifold plate axially aligns the first and second motors and encloses the first and second motors in the respective cylindrical chambers of the respective motor housings. The first motor is mounted or fixedly secured to a first side of the cooling manifold plate and the second motor is mounted or fixedly secured to a second side of the cooling manifold plate. As described above, the cooling manifold plate delivers coolant to the first and second motors to cool the motors.
Still further, in another aspect of the invention, each motor drives its respective gearbox assembly, wherein a first gear-set housing is fixedly secured to an outboard end of the first motor housing and houses a gear reduction and clutch mechanism that is coupled between the first motor and an output hub that in turn is operatively coupled to a first vehicle wheel. The gear reduction and clutch mechanism reduces a rotational speed output by the first motor and increases an output torque. The inventive gear reduction and clutch mechanism includes a brake band assembly that is selectively operable to disconnect the first motor from the first vehicle wheel.
Similarly, in the dual motor configuration, a second gear-set housing is fixedly secured to an outboard end of the second motor housing and houses a gear reduction and clutch mechanism that is coupled between the second motor and a second output hub that in turn is operatively coupled to a second vehicle wheel. The gear reduction and clutch mechanism reduces a rotational speed output by the second motor and increases an output torque. Here again, the gear reduction and clutch mechanism includes a brake band assembly that is selectively operable to disconnect the second motor from the second vehicle wheel.
More particularly, each gear reduction and clutch mechanism is coupled between the outboard end of each electric motor and its respective vehicle wheel. The gear reduction mechanism includes a planetary gear system to provide speed and torque conversion between the electric motor and the vehicle wheel. Preferably, the planetary gear system includes a primary ring gear having an integrated brake drum or outer surface, which is part of a band brake assembly. The planetary gear system preferably is a double planetary gear system having two gear sets with one of the gear sets having the primary ring gear cooperating with the band brake assembly. Alternatively, the planetary gear system could have only one gear set, or two or more gear sets. The band brake assembly also includes a band brake, which engages and releases the outer surface of the ring gear for the purpose of connecting and disconnecting the electric motor with the vehicle wheel. For example, when the band brake is engaged with the outer surface of the ring gear, the output of the electric motor is transmitted through the gear reduction mechanism to drive the vehicle wheel. On the other hand, when the band brake is released from the outer surface of the ring gear, the output of the electric motor is not transmitted through the gear reduction mechanism. In other words, when the band brake is released from the outer surface of the ring gear, the electric motor is disconnected from the vehicle wheel.
Each motor housing also includes a secondary chamber on front and back sides of the cylindrical chamber for additional components. For example, a first power inverter is directly connected to the first motor and is positioned in the secondary chamber of the first and second motor housings. A first cover plate is affixed to the first and second motor housings to enclose the first power inverter within the secondary chambers. Similarly, a second power inverter is directly connected to the second motor and is positioned in the secondary chamber of the first and second motor housings. A second cover plate is affixed to the first and second motor housings to enclose the second power inverter within the secondary chambers.
The gearbox assembly of the invention further also may be formed as a two-speed transmission unit which is connectable to and driven by the motors. In a first embodiment, a clutch may be provided in combination with a clutch to
Other objects and purposes of the invention, and variations thereof, will be apparent upon reading the following specification and inspecting the accompanying drawings.
Certain terminology will be used in the following description for convenience and reference only, and will not be limiting. For example, the words “upwardly”, “downwardly”, “rightwardly” and “leftwardly” will refer to directions in the drawings to which reference is made. The words “inwardly” and “outwardly” will refer to directions toward and away from, respectively, the geometric center of the arrangement and designated parts thereof. Said terminology will include the words specifically mentioned, derivatives thereof, and words of similar import.