Automatic Transmission Shift Control Thermal Load Prediction
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Solution Overview
Problem
Conventional automatic transmission systems suffer from drivability issues due to premature wear of frictional elements caused by repeated thermal loading during continuous shifts, as they rely solely on time-based timers without considering the type of shift or input torque, leading to unnecessary shift prohibitions.
Innovation Solution
An automatic transmission system that calculates the current thermal load of frictional elements and predicts heat generation during shifts, allowing shifts in lower heat generation modes or prohibiting them when high thermal loads are predicted, thereby improving shift tolerance and preventing drivability deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timer-based continuous shift prohibition control is used, then the frictional element is protected from burnout, but shifts are prohibited even when the thermal load is low, leading to deterioration of drivability
Solution Approach 1:
The invention changes the control parameter from simple time-based prohibition to thermal load-based prohibition. The ECU calculates thermal load values based on shift history and frictional element characteristics, and only prohibits shifts when the thermal load exceeds a predetermined threshold. This allows shifts to be permitted when thermal load is low, improving drivability while still protecting against burnout when thermal load is high.
2Reliability
If the timer value is set with a sufficient margin to prevent frictional element damage, then the element is protected, but unnecessary shift prohibitions occur, reducing productivity
Solution Approach 1:
The invention replaces the fixed timer margin with a dynamic thermal load calculation that reflects actual frictional element conditions. By calculating thermal load based on accumulated shift data and frictional element characteristics, the system determines the precise threshold for shift prohibition, avoiding unnecessary prohibitions while maintaining adequate protection margins.
3Adaptability or versatility
If shifts are repeatedly engaged and disengaged during continuous shifts, then the transmission adapts to boundary region conditions, but thermal load accumulates causing burnout risk
Solution Approach 1:
The invention introduces feedback control by continuously monitoring thermal load accumulation during repeated shifts. The ECU calculates thermal load values based on shift history and compares them against thresholds, dynamically adjusting shift prohibition decisions. This feedback mechanism allows the system to adapt to boundary region conditions while preventing thermal load accumulation that would lead to burnout.
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
The system accurately determines whether to permit or prohibit shifts based on predicted thermal loads, reducing the risk of frictional element burnout and enhancing drivability by considering the specific conditions of each shift, thus improving shift tolerance and preventing unnecessary prohibitions.
Implementation Method 1
the same frictional elements are repeatedly engaged and disengaged over a long time period, and therefore the thermal load applied to the frictional elements increases (the temperature increases). As a result, the burns may occur on the frictional elements
Data Source
AI summary
An automatic transmission calculates a current thermal load state of the frictional element, predicts (S41), prior to the start of the shift, a heat generation amount of the frictional element during the shift, predicts (S42) a thermal load state of the frictional element upon shift completion on the basis of the current thermal load state of the frictional element and the predicted heat generation amount, determines (S43, S44, S45) whether to permit or prohibit the shift on the basis of the predicted thermal load state upon shift completion, and halts the determination as to whether to permit or prohibit the shift, made on the basis of the predicted thermal load state upon shift completion, when a shift mode of the shift is a second shift mode in which the heat generation amount is smaller than that of a first shift mode.