Automatic Transmission Lock-Up Clutch Slip Control
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Solution Overview
Problem
Current automatic transmission control devices fail to optimize drivability and fuel economy on uphill roads while maintaining lock-up clutch durability, as the target slip ratio remains constant regardless of road conditions, leading to excessive heat generation and reduced durability.
Innovation Solution
A control device that selects appropriate target slip ratio maps based on the running range and gear position, distinguishing between level, uphill, and downhill roads, and between D range and manual mode, to adjust the lock-up clutch engagement condition dynamically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the lock-up clutch is engaged on an uphill road with a target slip ratio for a level road, then the drivability and fuel economy are improved, but the heat generation from the lock-up clutch becomes excessive, causing reduction in durability
Solution Approach 1:
The patent applies dynamics by making the target slip ratio adjustable based on running conditions. Specifically, the target slip ratio is changed according to whether the vehicle is running on a level road or an uphill road, as detected by the gradient detecting means. This dynamic adjustment allows the system to optimize fuel economy on level roads while preventing excessive heat generation on uphill roads, thereby resolving the contradiction between productivity and reliability
Solution Approach 2:
The patent changes the parameter of target slip ratio based on the detected running gradient. When an uphill road is detected, the target slip ratio is increased compared to the level road setting. This parameter change allows the lock-up clutch to operate with appropriate slip characteristics for the current condition, reducing heat generation on uphill roads while maintaining good fuel economy on level roads
2Reliability
If the lock-up clutch is disengaged at acceleration on an uphill road to maintain durability, then the heat generation is reduced, but the fuel economy and drivability are deteriorated
Solution Approach 1:
Instead of completely disengaging the lock-up clutch on uphill roads, the patent dynamically adjusts the target slip ratio based on the detected gradient. This dynamic control allows the clutch to remain engaged with optimized slip characteristics, maintaining both durability and fuel economy performance
Solution Approach 2:
The patent changes the target slip ratio parameter specifically for uphill conditions rather than simply disengaging the clutch. This parameter adjustment optimizes the balance between heat generation and torque transmission efficiency, resolving the contradiction between reliability and productivity
3Device complexity
If a fixed target slip ratio is used for all running conditions, then the control system is simple, but the heat generation on uphill roads becomes excessive and fuel economy cannot be optimized for different road gradients
Solution Approach 1:
The patent introduces dynamic adjustment of the target slip ratio based on detected running gradient, while keeping the overall control structure relatively simple. The gradient detecting means and the map selecting means add minimal complexity but enable the system to adapt to different road conditions, preventing excessive heat generation on uphill roads
Solution Approach 2:
The patent changes the target slip ratio parameter according to the detected gradient condition, using pre-stored maps for different gradient types. This approach adds minimal control complexity while significantly improving reliability by preventing overheating on uphill roads
Data Source
AI summary
A control device for an automatic transmission having a torque converter with a lock-up clutch provided between an engine and the automatic transmission, and a lock-up control device for controlling an engaged condition of the lock-up clutch. The control device includes a plurality of different target slip ratio maps each having a plurality of target slip ratio characteristic lines of the lock-up clutch predetermined according to a throttle angle, a first map selector for selecting one of the target slip ratio maps according to a running range, according to whether the running road is a level road/downhill road or an uphill road, and according to a gear position during running in the condition where an accelerator pedal is depressed, and a second map selector for selecting one of the target slip ratio maps according to a running range, according to whether the running road is a level road/uphill road or a downhill road, and according to a gear position during running in the condition where the accelerator pedal is undepressed.