Automatic Transmission Shift Control Thermal Protection
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Solution Overview
Problem
Existing shift control devices for automatic transmissions fail to adequately protect frictional engaging elements from thermal damage, particularly during frequent shifting on winding roads, as they either suppress ATF temperature rise insufficiently or compromise drive force transmission.
Innovation Solution
A shift control device that computes the temperature of frictional engaging elements, compares it to a reference temperature, and delays upshift timing by a predetermined period when the temperature is higher, ensuring sufficient drive force and preventing thermal damage, with the delay canceled when engine rotational speed reaches a set value to prevent over-revolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If ATF temperature suppression is implemented by reducing engine output torque, then ATF temperature rise is suppressed, but the drive force desired by the operator cannot be sufficiently transmitted
Solution Approach 1:
The control device performs preliminary cooling of the frictional engaging element by delaying upshift timing before thermal damage occurs. By computing the temperature of the frictional engaging element in advance and proactively delaying the upshift operation when temperature exceeds reference values, the system cools the element through heat exchange with ATF during the delay period, preventing thermal damage while maintaining normal drive force transmission.
2Temperature
If upshift timing is delayed to reduce heat generation, then thermal damage to frictional engaging element is prevented, but engine over-revolution occurs
Solution Approach 1:
The control device dynamically adjusts the upshift timing based on the computed temperature parameter of the frictional engaging element. When the temperature exceeds the reference temperature, the system changes the timing parameter by delaying upshift; when temperature is within acceptable ranges, normal upshift timing is restored. This parameter-based adaptive control prevents both thermal damage and engine over-revolution.
3Productivity
If frequent shift control is performed on winding roads, then shift quality is maintained, but thermal damage to frictional engaging element occurs due to heat accumulation
Solution Approach 1:
The control device implements a feedback mechanism by continuously computing the temperature of the frictional engaging element based on shift operation history and heat generation patterns. This computed temperature information feeds back to the shift control logic, which adjusts upshift timing decisions accordingly. When temperature approaches dangerous levels, the system reduces shift frequency or delays upshift to allow cooling, preventing thermal damage while maintaining shift quality within safe operating parameters.
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 solution effectively protects frictional engaging elements from thermal damage while ensuring a sufficient drive force is transmitted, preventing overheating and maintaining engine performance.
Implementation Method 1
the frictional engaging element heated to high temperatures in the shift operation is cooled by heat exchange or the like with a hydraulic fluid or automatic transmission fluid (ATF) for the automatic transmission
Implementation Method 2
the amount of heat generated from the frictional engaging element subjected to shifting tends to increase in the automatic transmission
Data Source
AI summary
A shift control device for an automatic transmission having a plurality of frictional engaging elements adapted to be selectively engaged to perform shift control. The shift control device includes a computing unit for computing the temperature of at least one of the frictional engaging elements to be engaged in shifting, a comparing unit for comparing the temperature computed by the computing unit with a reference temperature, and an upshift delaying unit for delaying the timing of upshift using the frictional engaging element to be engaged by a predetermined time period when the temperature computed by the computing unit is higher than the reference temperature.