Slip Lock-Up Control Device for Vehicle Torque Fluctuation
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Solution Overview
Problem
Conventional slip lock-up control systems experience fluctuations in engine torque and speed due to unstable engine conditions, leading to discomfort for drivers through increased exhaust noise.
Innovation Solution
A slip lock-up control device that adjusts the lock-up pressure difference command to a second, averaged command when in an engine torque unstable range, reducing load fluctuations and stabilizing engine speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If engine torque information is estimated by passing through a first-order lag filter having a time constant determined based on engine dynamics, then the engine torque estimated value can be obtained, but the engine torque estimated value fluctuates in the engine unstable range causing exhaust noise fluctuation
Solution Approach 1:
The patent applies dynamics by making the filter time constant variable rather than fixed. The control device switches between a first filter time constant (for stable engine ranges) and a second filter time constant (for unstable engine ranges), allowing the filtering characteristics to adapt dynamically to engine operating conditions. This resolves the contradiction by maintaining measurement precision through appropriate filtering while ensuring stability by adjusting the filter response based on engine state.
Solution Approach 2:
The patent changes the parameter of filter time constant based on engine operating range. When the engine is in an unstable range, a second filter time constant is used that provides more averaging of pressure difference fluctuations, whereas in stable ranges, a first filter time constant is used for more responsive tracking. This parameter change allows the system to maintain both accuracy and stability under different operating conditions.
2Speed
If the lock-up pressure difference command responds quickly to engine torque changes, then the slip lock-up control responsiveness is improved, but the load fluctuation received by the engine increases causing rotation fluctuation
Solution Approach 1:
The patent makes the control system dynamic by adjusting the filter time constant based on engine operating conditions. In unstable engine ranges, the second filter time constant provides more averaging, reducing the responsiveness slightly but significantly improving stability. In stable ranges, the first filter time constant allows faster response. This dynamic adjustment resolves the contradiction between responsiveness and stability.
Solution Approach 2:
The patent introduces the filter as an intermediary between the engine torque estimation and the lock-up pressure difference command. The filter acts as a mediator that smooths out fluctuations in unstable ranges while maintaining responsiveness in stable ranges, preventing direct transmission of torque fluctuations to the clutch control and thereby stabilizing engine speed.
3Reliability
If the first-order lag filter with a short time constant is used, then the engine torque estimation follows engine dynamics closely, but the exhaust noise fluctuation increases due to engine rotation fluctuation
Solution Approach 1:
The patent changes the filter time constant parameter based on engine operating range. In unstable ranges where exhaust noise fluctuation is problematic, a second filter time constant with longer averaging is used to suppress noise. In stable ranges, a first filter time constant with shorter averaging maintains accurate torque conversion. This parameter adaptation resolves the contradiction between reliability and harmful noise effects.
Data Source
AI summary
A slip lock-up control device for a vehicle includes a torque converter having a lock-up clutch, and a slip lock-up controller. The slip lock-up controller performs slip lock-up control using a lock-up pressure difference command to match an actual slip rotational speed to a target slip rotational speed based on engine torque information indicative of input torque, when a lock-up engagement condition is fulfilled when the lock-up clutch is in a released state. During the slip lock-up control, when in an engine torque unstable range for which an engine torque has a rise gradient with respect to a rise change of an engine speed, the slip lock-up controller sets the lock-up pressure difference command to a second lock-up pressure difference command for which a pressure difference fluctuation is averaged more than a first lock-up pressure difference command used in a range other than the engine torque unstable range.