Vehicle Drive-Train Lock-Up Clutch Control for Engine Braking
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Solution Overview
Problem
In vehicle drive-train systems, the lock-up clutch control faces challenges during coasting, where a large difference between input and output rotational speeds of the torque converter leads to insufficient engine braking, unstable lock-up control, and delayed engine re-engagement, resulting in poor deceleration and response.
Innovation Solution
A control device that includes a blipping control mechanism to temporarily increase engine output rotational speed using an electronic throttle valve during power-off downshifts, and a lock-up control device that engages or partially engages the lock-up clutch based on reduced rotational speed differences, allowing stable lock-up control and immediate deceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If lock-up control is executed when there is a large difference between input rotational speed and output rotational speed of torque converter, then engine braking can be provided, but the lock-up clutch may experience insufficient torque capacity, large shock, or excessive heat generation
Solution Approach 1:
The system performs preliminary actions by temporarily raising engine speed during shift operation and supplying standby pressure to the hydraulic actuator before lock-up control is executed. This prepares the lock-up clutch and torque converter for stable engagement by reducing the rotational speed difference in advance, preventing shock and excessive heat generation while enabling effective engine braking.
2Reliability
If lock-up control is not executed during coasting, then the lock-up clutch is protected from damage, but sufficient engine braking and deceleration cannot be obtained
Solution Approach 1:
The system dynamically adjusts the lock-up clutch engagement state based on operating conditions. During coasting with manual downshift request, the control device temporarily raises engine speed and supplies standby pressure to enable safe lock-up control execution, providing sufficient engine braking. The system transitions between protected disengaged state and controlled engaged state based on real-time conditions.
3Speed
If engine speed is raised during shift operation, then lock-up control can be enabled, but the rotational speed difference between input and output members may increase after shift completion
Solution Approach 1:
The control device continuously monitors the rotational speed difference between input and output members of the torque converter and adjusts engine speed accordingly. After shift operation completes, the system detects if the speed difference exceeds thresholds and responds by temporarily raising engine speed to reduce the difference, ensuring stable lock-up control conditions are maintained throughout the shift process.
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
Enables quick and stable engine braking and deceleration by reducing rotational speed differences, preventing torque capacity issues, shock, and excessive heat in the lock-up clutch, thus improving vehicle response and deceleration efficiency.
Implementation Method 1
an electronic throttle valve operable to change the output rotational speed of the engine based on an electric command
Implementation Method 2
a lock-up clutch operable to directly connect an input member and an output member of the torque converter with each other
Implementation Method 3
a torque converter provided between the automatic transmission and the engine
Data Source
AI summary
A control device of a vehicle drive-train system including an engine, an electronic throttle valve, an automatic transmission having a manual shift mode, a torque converter provided between the automatic transmission and the engine, and a lock-up clutch operable to directly connect an input member and an output member of the torque converter with each other includes a blipping control device that performs blipping control for temporarily increasing the output rotational speed of the engine by of the electronic throttle valve, when a power-off downshift is performed while the automatic transmission is in the manual shift mode; and a lock-up control device that engages or partially engages the lock-up clutch, based on a difference between a rotational speed of the output member of the torque converter and a rotational speed of the input member thereof, which the difference is reduced after the blipping control is started.