Friction Plate Engagement Control for Judder-Free Torque Transfer
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Solution Overview
Problem
Friction engagement elements in automatic transmissions experience judder vibration due to the negative slope characteristic of friction coefficients, leading to inefficiencies in fuel consumption and mechanical stress, as the friction coefficient increases with decreasing rotational difference, causing rapid torque changes and potential slippage.
Innovation Solution
A friction engagement element control system that includes friction plates with a negative slope characteristic, a rotational difference sensor, a filter to separate high-frequency vibration components, and a controller to adjust the pushing force, converting the negative slope characteristic into a positive slope, thereby reducing judder vibration and improving fuel efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If friction plates with negative slope characteristic are used to reduce pushing force, then fuel efficiency is improved, but judder vibration occurs due to rapid torque changes
Solution Approach 1:
The control system dynamically adjusts the pushing force during engagement based on real-time rotational difference detection. By continuously modifying the pushing force to compensate for the negative slope characteristic, the system maintains stable engagement without judder vibration while keeping the friction plates optimized for fuel efficiency.
Solution Approach 2:
The system uses rotational difference sensors to detect the state of engagement and feeds this information back to the controller. The controller then adjusts the pushing force accordingly to prevent judder vibration, creating a closed-loop control system that resolves the contradiction between fuel efficiency and vibration suppression.
2Use of energy by moving object
If pushing force is reduced to improve fuel efficiency, then energy consumption decreases, but engagement stability deteriorates due to negative slope characteristic
Solution Approach 1:
The pushing force is dynamically adjusted during the engagement process rather than being statically reduced. This dynamic adjustment maintains engagement stability by compensating for the negative slope characteristic at critical moments while still allowing for reduced average pushing force to improve energy efficiency.
Solution Approach 2:
The control system changes the pushing force parameter in real-time based on rotational difference detection. This parameter adjustment ensures stable engagement throughout the transition process while maintaining lower overall energy consumption compared to conventional constant high pushing force systems.
3Force
If friction coefficient increases with decreasing rotational difference, then torque transmission improves, but rapid torque changes cause mechanical stress and slippage
Solution Approach 1:
The control system applies preliminary counteracting force by increasing the pushing force before the rotational difference becomes too small. This preliminary action prevents the rapid torque changes that would otherwise cause mechanical stress and slippage, while still allowing effective torque transmission during stable engagement.
Solution Approach 2:
The system cushions against potential mechanical stress by dynamically adjusting the pushing force in advance. When rotational difference decreases, the controller increases pushing force to prevent sudden torque changes, effectively cushioning the system against mechanical stress and slippage before they can occur.
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 system effectively suppresses judder vibration and enhances fuel efficiency by reducing the pushing force required for engagement, while maintaining controllability and improving the speed of engagement and disengagement processes.
Implementation Method 1
a frictional force (engaging force) between the input-side friction plates and the output-side friction plates is increased by the pushing force generation means
Implementation Method 2
a rotational difference sensor configured to detect the rotational difference of the friction engagement element
Implementation Method 3
a filter configured to divide a variation in the rotational difference detected by the rotational difference sensor into a high-frequency component that is a vibration component and other low-frequency components
Implementation Method 4
a hydraulic piston which operates a piston by hydraulic pressure supplied from an oil pump
Implementation Method 5
an electromagnetic clutch for a four-wheel drive vehicle in which a pushing force is generated by an electromagnetic force without using the hydraulic pressure
Data Source
AI summary
A friction engagement element control system is provided, which includes a friction engagement element including friction plates, and an actuation system configured to engage an input-side friction plate with an output-side friction plate with a pushing force, the friction plates having a negative slope characteristic in which a friction coefficient thereof decreases as a rotational difference between the friction plates increases, a rotational difference sensor of the friction engagement element, a separator configured to divide a variation in the detected rotational difference into a high-frequency component that is a vibration component and other low-frequency components, and a controller configured to control a pushing force only for the vibration component of the rotational difference so that the negative slope characteristic becomes a positive slope characteristic in which a frictional force of the friction engagement element decreases as the rotational difference decreases, when engaging the friction engagement element.