Lockup Control Device for Automatic Transmission Torque Converter
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Solution Overview
Problem
Conventional lockup control systems in vehicles with automatic transmissions and torque converters face issues with fuel consumption and drivability due to premature lockup cancellation when drivers switch between accelerator and brake pedals, leading to shortened fuel-cut times and engine rpm fluctuations.
Innovation Solution
A lockup control device that sets the lockup-canceling vehicle speed lower when the accelerator is released and the brake is activated, and maintains this speed for a predetermined period to prevent premature lockup cancellation during pedal switching, using delay timers to adjust lockup-canceling vehicle speeds based on driver input changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the lockup-canceling vehicle speed is set to a lower value when the brake is ON to improve fuel consumption during coasting, then fuel consumption improves, but the lockup state is prematurely canceled when the driver switches from accelerator to brake pedal, causing engine rpm fluctuations and poor drivability
Solution Approach 1:
The lockup control device dynamically adjusts the lockup-canceling vehicle speed threshold based on the temporal state of pedal operations. When a pedal switch operation is detected, the control device temporarily modifies the vehicle speed threshold for lockup cancellation, allowing the lockup state to be maintained at lower speeds during the transition period. This dynamic adjustment prevents premature lockup cancellation during pedal switching while still enabling fuel-efficient lockup operation during sustained coasting conditions.
Solution Approach 2:
The control device performs preliminary detection of pedal switch operations and proactively adjusts the lockup control parameters before the actual lockup cancellation would occur. By detecting the pedal switch operation in advance and setting a temporary threshold modification, the system prevents the problematic lockup cancellation that would otherwise occur when the vehicle speed crosses the standard threshold during pedal transitions.
2Use of energy by moving object
If the lockup state is maintained at lower vehicle speeds during pedal switching, then fuel-cut time is extended and fuel consumption improves, but the lockup state may be unnecessarily canceled during normal deceleration when the brake is ON
Solution Approach 1:
The control device applies periodic or temporary modifications to the lockup-canceling vehicle speed threshold based on detected pedal switch operations. The temporary threshold modification is applied only for a predetermined period after pedal switch detection, allowing the lockup state to be maintained during the transition phase while automatically reverting to normal threshold behavior after the predetermined period expires or when deceleration continues normally.
Solution Approach 2:
The control device changes the parameter (vehicle speed threshold) for lockup cancellation based on the detected operational state. When pedal switching is detected, the threshold parameter is temporarily adjusted to a lower value, allowing lockup maintenance at speeds that would normally trigger cancellation. This parameter change is conditional and reversible, adapting the system behavior to the specific driving context.
Data Source
AI summary
Excellent fuel consumption and drivability are achieved by properly controlling the lockup-canceling timing in a vehicle with an automatic transmission equipped with a torque converter having lockup features. Conventionally, the lockup got cancelled when it was determined that the vehicle speed was lower than a first lockup-canceling vehicle speed used when the accelerator was OFF at the same time the brakes were OFF. Herein, however a delay timer is activated after the accelerator is released (OFF) to set a second lockup-canceling vehicle speed, which is slower than the first lockup-canceling vehicle speed and which is used when the brake is activated (ON). As a result, the lockup will not be cancelled until the vehicle speed reaches the second vehicle speed, and the lockup period can be ensured for a longer period of time.