Multiple-disc Clutch Torque Control via Current Correction
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Solution Overview
Problem
In driving force transmission devices with multiple-disc clutches lubricated by a lubricant, the output torque sometimes increases over time even when the pressing force remains constant, leading to inaccuracies in torque transmission.
Innovation Solution
A control device that computes a torque command value based on vehicle state, corrects a current command value by a correction amount in a constant-torque state, and supplies the corrected current to the pressing mechanism, ensuring accurate torque transmission by adjusting the electric current supplied to the multiple-disc clutch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the pressing force of the pressing mechanism is kept constant, then the structure is simple and easy to control, but the transmission torque accuracy deteriorates over time due to torque increase
Solution Approach 1:
The pressing force is made dynamically adjustable rather than constant. The control device computes a corrected current command value that varies over time based on the duration since torque command value change, allowing the pressing mechanism to adapt its pressing force to compensate for torque increase, thereby maintaining transmission torque accuracy while keeping the mechanism structure relatively simple
Solution Approach 2:
The pressing force parameter is changed over time through current correction. The control device modifies the current command value supplied to the pressing mechanism based on the elapsed time since the torque command value changed, effectively adjusting the pressing force parameter to counteract the torque increase phenomenon
2Manufacturing precision
If the current command value is increased to compensate for torque increase, then the transmission torque accuracy is improved, but the energy consumption increases
Solution Approach 1:
Instead of applying excessive current correction always, the control device applies partial correction only when and where needed. The correction amount is determined by the duration since torque command value change, applying just enough current adjustment to compensate for torque increase without unnecessary energy consumption during periods when correction is not required
3Manufacturing precision
If the pressing force is increased to maintain torque accuracy, then the transmission torque accuracy is improved, but the friction and heat generation increase
Solution Approach 1:
The pressing force is dynamically adjusted only when torque command value changes occur, rather than being continuously high. The control device computes corrected current based on the duration since the last torque command change, applying pressing force adjustments only during transition periods to maintain torque accuracy while minimizing unnecessary friction and heat generation during steady-state operation
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
Enhances the accuracy of transmission torque when the torque command value becomes constant, reducing errors caused by changes in torque command rates and lubricant dynamics.
Implementation Method 1
a multiple-disc clutch that includes a plurality of clutch plates among which frictional sliding is lubricated by a lubricant
Implementation Method 2
frictional sliding among clutch plates is lubricated by a lubricant
Implementation Method 3
a pressing mechanism that presses the multiple-disc clutch at a pressing force depending on an electric current that is supplied
Data Source
AI summary
A driving force transmission device includes an input rotation member, an output rotation member, a multiple-disc clutch, a pressing mechanism, and a control device including a current supply circuit. The control device is configured to compute a torque command value, to compute a current command value, to correct the current command value, and to control the current supply circuit such that an electric current depending on the current command value is supplied to the pressing mechanism. The control device is configure to correct the current command value by a correction amount in a constant-torque state after the torque command value changes, the constant-torque state being a state where a change rate of the torque command value is in a predetermined range, the correction amount depending on a duration of the constant-torque state.