Wet Clutch Piston Stroke Learning for Precision Engagement
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Solution Overview
Problem
The existing methods for learning the half-engagement state of a wet multiple disk clutch in power transmission devices are prone to precision errors due to fluctuations in working fluid temperature and static friction, especially when the vehicle is started under high load conditions, leading to unstable operation and inaccurate detection of the clutch engagement point.
Innovation Solution
A clutch control unit that moves the clutch piston over its entire stroke during the learning process, using a detector to find the rotational speed difference between the turbine and transmission input shaft, and stores the engagement amount when the difference reaches a predetermined value, thereby avoiding errors caused by temperature fluctuations and static friction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the clutch piston is kept stationary during learning, then the detection process is simpler, but the detection precision deteriorates due to static friction and temperature fluctuations
Solution Approach 1:
The patent applies the dynamics principle by moving the clutch piston over its entire stroke during the learning process rather than keeping it stationary. This dynamic movement transitions the friction from static to dynamic, reducing friction variability and improving detection precision. The piston movement also facilitates temperature stabilization of the working fluid, further enhancing measurement accuracy.
2Measurement precision
If the clutch piston is moved over the whole stroke during learning, then the detection precision improves by transitioning from static to dynamic friction, but the learning process time increases
Solution Approach 1:
The patent applies preliminary action by moving the clutch piston over its entire stroke at the beginning of the learning process. This preliminary movement prepares the system by stabilizing the working fluid temperature and transitioning friction to dynamic state, ensuring accurate detection when the actual engagement point is measured later.
3Power
If the vehicle is started under high load conditions, then the vehicle performance is improved, but the working fluid temperature fluctuates causing detection errors
Solution Approach 1:
The patent applies parameter changes by actively managing the clutch piston position and working fluid temperature during the learning process. By moving the piston over the entire stroke, the system stabilizes the working fluid temperature and transitions friction characteristics, making the detection process robust against temperature fluctuations caused by high load vehicle starting conditions.
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
This approach improves the precision of detecting the clutch engagement point by transitioning from static to dynamic friction, reducing errors and maintaining stable operation, as evident from the reduced fluctuation in learned values and enhanced detection precision.
Implementation Method 1
If a working fluid is fed into a hydraulic chamber at the back of the clutch piston 36, the friction disks are pressure-contacted and the clutch engages.
Implementation Method 2
If the working fluid is drained, the clutch piston 36 is pushed by a spring 37 whereby the friction disks separate and the clutch is disengaged.
Implementation Method 3
there are alternately arranged a plurality of friction disks 34 attached to a member that is fitted by spline to the clutch input shaft 32 and a plurality of friction disks 35 attached to a member that is fitted by spline to the clutch output shaft 33
Data Source
AI summary
A power transmission device for a vehicle equipped with a wet multiple disk clutch for disconnecting the power at the time of gearshift by using a clutch controller, wherein the amount of engagement where the clutch is half-engaged is learned maintaining precision. In the present invention, the clutch controller of the wet multiple disk clutch moves a clutch piston over the whole stroke thereof by using the working fluid for varying the amount of engagement at the start of learning the amount of engagement at a point where the clutch starts half-engaging and, immediately thereafter, the amount the clutch is half-engaged is detected. Upon moving the clutch piston, the working fluid present among the friction disks of the wet multiple disk clutch is drained and is replaced by the new working fluid avoiding detection error caused by the fluctuation in the temperature of the working fluid and eliminating unstable operation of the clutch piston caused by static friction of a large resistance. The amount of engagement at the point where the clutch starts half-engaging is determined by gradually increasing the amount of engagement after the clutch is disengaged and detecting a change in the rotational speed of the clutch input shaft.