Hybrid Vehicle Torque Converter Control Strategy
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Solution Overview
Problem
Hybrid vehicles face challenges in efficiently managing torque delivery between engines and motors, particularly when the demanded impeller torque exceeds the motor's capacity, leading to suboptimal power transfer and potential engine start delays.
Innovation Solution
A controller-programmed strategy that adjusts motor torque based on torque converter bypass clutch capacity and estimated impeller speed, limiting motor torque to a value less than the maximum motor torque threshold, ensuring efficient power transfer and timely engine start by reserving torque for assist during engine start-up.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the motor delivers maximum torque when demanded impeller torque exceeds motor capacity, then the motor can meet peak torque demand, but power transfer efficiency deteriorates and engine start time increases
Solution Approach 1:
The controller performs preliminary action by limiting motor torque before the engine start event occurs. By proactively reducing motor torque to a level below maximum capacity when torque demand exceeds motor capability, the system prepares the torque converter and engine for imminent start-up, thereby reducing overall engine start time while maintaining adequate power transfer efficiency
2Power
If the motor delivers maximum torque continuously, then torque demand is fully met, but torque converter bypass clutch capacity is insufficient and power transfer efficiency decreases
Solution Approach 1:
The controller dynamically changes the motor torque parameter by limiting it to a value less than maximum motor torque when torque demand exceeds motor capability. This parameter adjustment optimizes the operating point of the torque converter, ensuring that the bypass clutch operates within its capacity range and maintaining efficient power transfer while still meeting torque demand through coordinated engine-motor operation
3Power
If the motor torque is increased to meet demanded impeller torque, then torque demand is satisfied, but engine start-up is delayed due to insufficient torque converter bypass clutch capacity
Solution Approach 1:
The controller performs preliminary action by preemptively limiting motor torque before the engine start event. This advance torque management allows the torque converter to build up appropriate speed differential and hydraulic pressure, preparing the system for faster engine engagement while ensuring the bypass clutch operates within its capacity, thereby reducing overall engine start duration
4Power
If the motor operates at maximum torque capacity, then peak power is delivered, but torque management efficiency deteriorates during engine start-up transition
Solution Approach 1:
The controller optimizes torque management efficiency by dynamically adjusting the motor torque parameter to a limited value rather than operating at maximum capacity. This parameter optimization enables smoother torque transition during engine start-up, improves coordination between motor and engine torque delivery, and enhances overall torque management efficiency while maintaining adequate power output through the combined powertrain system
Data Source
AI summary
A vehicle includes an engine, a motor, and a controller. The engine and motor are each configured to deliver torque to a torque converter impeller. The controller is programmed to, responsive to a demanded impeller torque exceeding an upper motor torque threshold while the motor alone is delivering torque to the impeller, increase motor torque to a value that is less than the threshold and that depends on a torque converter bypass clutch torque capacity and a torque converter turbine speed.