Transmission Torque Management via Fluid Temperature Adaptation
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Solution Overview
Problem
Automatic transmissions face challenges in accurately controlling torque distribution due to variations in transmission components over time and environmental factors, leading to potential component damage and inefficiencies during shifting processes.
Innovation Solution
A method that involves repeatedly measuring transmission output torque and input speed, estimating transmission component torque, and adjusting engine torque to maintain a predetermined limit value, using a combination of models and closed-loop control to adapt to changing conditions and prevent overstressing of transmission components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the transmission operates at high speed ratio to multiply engine torque for improved acceleration at low speed, then the acceleration performance is improved, but the transmission components are subjected to higher stress and risk of damage
Solution Approach 1:
The system dynamically changes the torque limit parameter based on transmission fluid temperature. As temperature increases, the torque limit is reduced to protect components from excessive stress. This parameter adaptation resolves the contradiction by allowing high torque multiplication when cool (improving acceleration) while reducing torque when hot (protecting components).
Solution Approach 2:
The controller continuously monitors transmission fluid temperature and adjusts the torque limit accordingly. This feedback mechanism ensures that when temperature rises indicating component stress or potential damage, the torque limit is automatically reduced to prevent further stress, thus resolving the contradiction between acceleration performance and component protection.
2Ease of operation
If the controller adjusts torque capacity of shift elements to enable smooth shifting, then shift smoothness is improved, but the complexity of the control system increases
Solution Approach 1:
The system pre-calculates and stores torque limit values for different transmission fluid temperatures. When a shift is commanded, the controller retrieves the appropriate torque limit from pre-computed tables rather than calculating it in real-time. This preliminary action simplifies the control logic while maintaining smooth shifting performance.
Solution Approach 2:
The controller adjusts the torque capacity parameter of shift elements based on transmission fluid temperature. By changing this parameter dynamically, the system achieves smooth shifts under varying thermal conditions without requiring complex adaptive control algorithms, thus improving shift smoothness while limiting control system complexity.
3Loss of energy
If the transmission operates at low speed ratio for fuel efficient cruising at high vehicle speed, then fuel efficiency is improved, but the engine must operate at higher speeds which increases engine wear
Solution Approach 1:
The system dynamically adjusts the torque limit based on transmission fluid temperature to enable optimal engine operation. When the transmission is cool, higher torque limits allow the engine to operate at lower speeds for the same power output, reducing wear. As the transmission warms up, the torque limit is adjusted to maintain efficient operation while accounting for changed friction characteristics, thus balancing fuel efficiency and engine service life.
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 enhances the accuracy and efficiency of torque control, reducing the risk of component damage and improving shift smoothness by continuously refining models based on real-time data and adapting to environmental and operational changes.
Implementation Method 1
A common launch device is a torque converter which includes an impeller driven by the engine and a turbine driving the gearbox input. Torque is transferred from the impeller to the turbine hydro-dynamically.
Data Source
AI summary
A method of operating a vehicle includes measuring a transmission output torque, measuring impeller and turbine speeds, estimating a transmission component torque, and adjusting an engine torque to avoid overstressing a transmission component such as a gear. The method does not rely on an accurate estimate of engine torque. Furthermore, the method does not rely on a fixed transmission torque rating in each gear ratio.