Hydraulic Clutch Controlled Leak for Pressure Overshoot
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Solution Overview
Problem
Hydraulic clutch control systems face pressure overshoot conditions due to lack of compliance and slow reaction times of solenoid valves, leading to harsh shift feel and poor controllability, especially during initial clutch fill.
Innovation Solution
A controlled leak is introduced in the clutch feed passage, only active during clutch trim and discontinued during full apply pressure, using a selectively blockable leak passage between the clutch feed passage and accumulator to provide compliance and prevent pressure overshoot.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a continuous leak is added to the clutch feed passage to eliminate pressure overshoot, then pressure stability is improved, but apply pressure efficiency deteriorates due to fluid loss
Solution Approach 1:
The leak passage is made dynamically controllable through a piston that responds to pressure differential. During trim phase, the piston positions to open the leak passage and provide compliance. During full apply phase, the piston positions to close the leak passage and prevent fluid loss. This dynamic adjustment resolves the contradiction by making the leak conditional rather than continuous.
Solution Approach 2:
The leak passage operates periodically based on clutch engagement phase. It is open during trim phase to prevent overshoot, then closes during full apply phase. This periodic operation pattern allows the system to benefit from compliance when needed while avoiding energy loss when not needed.
2Manufacturing precision
If solenoid valve reaction time is reduced to prevent pressure overshoot, then pressure control precision is improved, but device complexity and cost increase
Solution Approach 1:
The leak passage with piston acts as an intermediary compliance element between the solenoid valve and clutch. It absorbs pressure fluctuations and provides system compliance without requiring the solenoid valve to respond faster. This mediator allows the use of simpler, lower-cost solenoid valves while maintaining precise pressure control.
Solution Approach 2:
The leak passage provides beforehand cushioning by allowing controlled fluid escape during trim phase. This pre-established compliance path prevents pressure overshoot before it can occur, eliminating the need for ultra-fast solenoid response and enabling the use of more economical valve designs.
3Speed
If apply pressure is increased to overcome return spring force rapidly, then engagement speed is improved, but shift feel harshness increases
Solution Approach 1:
The system changes the compliance parameter dynamically through piston movement. During trim phase, the leak passage is open providing high compliance that softens pressure rise and improves shift feel. During full apply phase, the leak passage closes providing low compliance for rapid pressure establishment. This parameter change resolves the contradiction between soft engagement and fast response.
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 solution stabilizes the hydraulic clutch control system, improves shift feel, and allows the use of lower cost solenoid valves with slower response times, ensuring efficient and reliable clutch engagement.
Implementation Method 1
The piston is operable to selectively block fluid flow from the leak passage when the full apply condition is provided to the clutch by the trim regulator valve
Implementation Method 2
A selectively actuatable solenoid valve is disposed in fluid communication with the accumulator and the trim regulator valve
Implementation Method 3
The trim regulator valve has a full apply and a trim condition, which is operable to provide fluid pressure to the clutch via the clutch feed passage
Data Source
AI summary
The present invention provides a controlled leak within the clutch feed passage of the hydraulic clutch control system. The controlled leak will operate to provide compliance to the hydraulic clutch control system and may prevent pressure overshoot conditions during clutch trim. The controlled leak is only present during clutch trim and is discontinued during full apply conditions.