Wet Clutch Prefill Control for Shift Repeatability
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Solution Overview
Problem
Current hydraulic clutch filling processes suffer from poor repeatability due to variability in system parameters such as temperature, time between shifts, and fluid drainage, which are not adequately accounted for in existing control techniques, leading to inconsistent shift quality.
Innovation Solution
A method involving a prefill pulse or continuous signal is applied to the hydraulic clutch system using an electroproportional valve to prefill the fluid conduit and housing with hydraulic fluid, accounting for temperature and time between shifts, ensuring consistent fluid flow and reducing variability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If feedforward control with fixed calibration parameters is used, then the control system is simple to implement, but the clutch filling process exhibits poor repeatability due to system variability
Solution Approach 1:
The patent introduces feedback control by continuously monitoring the actual clutch filling process and adjusting the pressure profile in real-time based on measured system response. This closed-loop approach compensates for variability in air content, oil volume, temperature, and mechanical parameters, thereby improving filling repeatability while maintaining reasonable system complexity
Solution Approach 2:
The patent transitions from static calibration parameters to dynamic adaptive control. The system continuously adjusts control parameters based on real-time system state, accounting for changing conditions such as temperature variations, rotational speed, and time between shifts. This dynamic approach allows the system to adapt to varying operating conditions while maintaining consistent filling performance
2Adaptability or versatility
If temperature correction factors are applied, then temperature effects are partially compensated, but the system still fails to account for draining effects and time between shifts
Solution Approach 1:
The patent extends parameter compensation beyond temperature to include multiple influencing factors such as time between shifts, draining effects, rotational speed, and pressure-dependent leakage. By incorporating these additional parameters into the control algorithm, the system achieves more comprehensive compensation for varying operating conditions, thereby improving shift consistency
Solution Approach 2:
The patent applies preliminary action by pre-filling the clutch with hydraulic fluid before the actual engagement process. This preliminary filling step ensures that the clutch is properly primed and ready for engagement, compensating for potential draining effects and ensuring consistent filling behavior regardless of previous operating 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 significantly improves the repeatability of the clutch filling process, simplifying control and enhancing shift quality by making the system more robust and reducing the need for complex parameter compensation, with consistent pressure responses across varying conditions.
Implementation Method 1
increasing a pressure on a piston of the clutch
Implementation Method 2
The pump provides a housing with a hydraulic fluid. The fluid conduit connects the pump and the housing.
Implementation Method 3
The piston is movable into an extended position by a preloaded spring
Implementation Method 4
In the retracted position torque is transmittable through the clutch
Data Source
AI summary
A method and an apparatus for controlling a wet clutch are provided. The clutch comprises a pump, a piston, and a fluid conduit. The pump provides a housing with a hydraulic fluid. The piston is movably disposed in the housing and is movable into an extended position by a preloaded spring and into a retracted position by applying an engagement pressure on the piston by the hydraulic fluid. In the retracted position torque is transmittable through the clutch. The fluid conduit connects the pump and the housing. The method comprises the steps of prefilling the clutch by applying a prefill pressure on the piston, prefilling the fluid conduit line and the housing with the hydraulic fluid. The prefill pressure is lower than the engagement pressure required to move the piston into the retracted position.