Torque Converter Clutch Control for Electric Drive Unit Loss Reduction
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Solution Overview
Problem
Electric traction motors face reduced speed-torque performance advantages at higher rotary speeds, necessitating oversizing to maintain output power, and existing solutions do not effectively minimize system losses during vehicle acceleration.
Innovation Solution
A powertrain system with a motor-driven hydrodynamic torque converter, where a controller regulates the electric traction motor and torque converter clutch to optimize motor speed and clutch state, allowing for efficient torque multiplication and minimizing system losses by transitioning between locked and unlocked states based on vehicle acceleration and speed thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the electric traction motor is oversized to maintain output power capability at higher rotary speeds, then the output power capability is improved, but the device complexity and cost increase
Solution Approach 1:
A torque converter is introduced as an intermediary device between the electric traction motor and the transmission system. The torque converter multiplies torque at higher rotary speeds, allowing the motor to be sized for optimal efficiency rather than maximum power output, thereby reducing motor size while maintaining system performance
Solution Approach 2:
The system changes the operating parameters by using a torque converter to modify the torque-speed characteristics. The torque converter enables the motor to operate in a more efficient parameter range while the torque converter itself handles the torque multiplication needed at higher speeds
2Loss of energy
If the torque converter clutch is locked to reduce slip and improve efficiency, then energy loss is reduced, but the torque multiplication capability is lost
Solution Approach 1:
The torque converter clutch is designed to dynamically transition between locked and unlocked states based on operating conditions. The control system monitors vehicle speed, torque demand, and efficiency requirements to determine the optimal clutch state, allowing the system to adapt between efficiency mode (locked) and torque multiplication mode (unlocked)
Solution Approach 2:
The clutch control system changes the operational parameters of the torque converter by transitioning between two distinct states: locked (for efficiency) and unlocked (for torque multiplication). This parameter change allows the system to optimize performance based on real-time operating conditions
3Power
If the motor speed is increased to achieve higher output power, then the output power is improved, but the torque output capability decreases
Solution Approach 1:
The torque converter acts as a mediator between the motor and the load, allowing the motor to operate at higher speeds for power output while the torque converter provides the necessary torque multiplication to the transmission system
Solution Approach 2:
The power transmission system is segmented into two functional components: the electric traction motor optimized for efficient power generation at various speeds, and the torque converter responsible for torque multiplication. This segmentation allows each component to operate in its optimal range
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables efficient torque multiplication and reduced system losses by optimizing motor speed and clutch state transitions, enhancing vehicle acceleration and powertrain efficiency without the need for oversized motors.
Implementation Method 1
an electrically-powered hydrodynamic torque converter may be used to boost the torque and power output of an electric traction motor
Implementation Method 2
The TCC is operable for selectively locking the pump to the turbine to allow the pump and turbine to rotate together in unison
Data Source
AI summary
A method for controlling an electric drive unit (EDU) having a motor-driven torque converter includes receiving a request signal indicative of a requested output torque of the EDU, and operating the motor at a target motor speed using the requested output torque. The target motor speed minimizes system losses while achieving the requested output torque. When the requested output torque remains below a calibrated threshold and a turbine speed is less than a corner speed of the motor, a torque converter clutch (TCC) transitions to or remains in a locked state. The controller commands the TCC to transition to an unlocked state to reach the target motor speed, thereby selectively enabling torque multiplication. A powertrain system includes a driven load and the EDU. A computer readable storage medium may include executable instructions for performing the method.