Frictional Element Protection in Automatic Transmissions
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Solution Overview
Problem
Automatic transmissions without a speed sensor for measuring the rotation number of frictional elements cannot detect burn time, leading to damage of these elements when engine rotation exceeds critical levels, necessitating a method to estimate and reduce engine rotation to prevent frictional element damage.
Innovation Solution
A method involving a control unit that calculates an equivalent rotation number of the frictional element using a trigonometric function based on a virtual right triangle, entering a protection mode when engine rotation exceeds a boundary value, and reducing engine torque if the calculated rotation number exceeds a critical value, thereby preventing frictional element damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a speed sensor is installed to measure the rotation number of the frictional element, then the burn time can be detected and frictional element damage can be prevented, but the device complexity and cost increase
Solution Approach 1:
The patent uses existing sensors (engine rotation sensor and turbine rotation sensor) as intermediaries to indirectly measure the frictional element's rotation number. Instead of installing a direct speed sensor on the frictional element, the control unit calculates the frictional element's rotation based on the relationship between engine rotation and turbine rotation, thereby preventing frictional element damage without adding complex sensing hardware.
Solution Approach 2:
The patent replaces the mechanical sensing approach (direct speed sensor installation) with a computational approach. The control unit uses trigonometric function equations to calculate the frictional element's rotation number based on measured engine and turbine rotations, substituting physical measurement with mathematical modeling to achieve the same protective function.
2Duration of action of stationary object
If the rotation number of the engine is reduced to protect the frictional element, then the frictional element lifespan is extended, but the power output and driving performance decrease
Solution Approach 1:
The control unit calculates the frictional element's rotation number in advance and predicts potential burnout conditions before they occur. When the calculated rotation exceeds safe thresholds, the system proactively reduces engine rotation to prevent damage, rather than waiting for actual burnout to happen. This preliminary intervention extends frictional element lifespan while minimizing impact on performance.
Solution Approach 2:
The system continuously monitors engine rotation and turbine rotation, calculates the frictional element's rotation in real-time, and provides feedback to the control unit. Based on this feedback, the control unit dynamically adjusts engine rotation to keep the frictional element within safe operating parameters, balancing protection needs with performance requirements.
Data Source
AI summary
A method of protecting a frictional element of a clutch for an automatic transmission includes calculating an equivalent rotation number X of a frictional element using a trigonometric function equation on the basis of a virtual right triangle, if a rotation number of an engine exceeds a predetermined boundary value during a driving in a constant speed stage over a predetermined shift stage of an automatic transmission, entering a frictional element protection mode, if the equivalent rotation number X of the frictional element exceeds a predetermined critical value in a state in which the control unit enters the frictional element protection mode, reducing the rotation number of the engine by applying a target engine torque limiting value.