Clutch Coupling Device Hydraulic Pressure Control
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Solution Overview
Problem
Existing clutch devices face challenges in accurately correcting operating pressure on the second side of the piston, leading to fluctuations in torque transmission due to pressure variations in the coolant return line.
Innovation Solution
A hydraulic resistance cascade is introduced between the coolant supply and return lines, with a 3/3-way valve and restrictors to create an intermediate pressure that adjusts the operating pressure independently of coolant pressure, ensuring precise torque transmission and preventing excessive pressure damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the pressure of the cooling oil flow acts on the second side of the piston to cool the friction elements, then the friction elements are cooled effectively, but the operating pressure fluctuates due to pressure variations in the coolant return line
Solution Approach 1:
The hydraulic system is segmented into two independent circuits: a cooling circuit that supplies coolant to the friction elements, and a pressure control circuit that independently regulates operating pressure. The pressure control circuit branches off before the coolant supply to the friction elements, allowing separate control of cooling flow and pressure activation.
Solution Approach 2:
A pressure control valve acts as an intermediary between the hydraulic resistance cascade and the friction elements. This valve receives corrected operating pressure from the pressure control circuit and uses it to activate the friction elements, isolating the pressure control mechanism from direct exposure to coolant pressure variations.
2Ease of operation
If a valve is provided to correct operating pressure based on control pressure, then activation of friction elements can be controlled, but the correction does not accurately account for pressure on the second side of the piston
Solution Approach 1:
The system implements feedback by sensing the operating pressure at the friction elements and using this information to automatically adjust the control pressure. The pressure control valve receives feedback from the actual operating conditions and modifies the control signal accordingly, creating a closed-loop control system that accurately maintains the desired pressure differential.
3Stress or pressure
If the pressure present outside the clutch is applied to the valve to compensate for pressure variations, then some correction is achieved, but the correction is not accurate to the actual pressure on the second side of the piston
Solution Approach 1:
The pressure control circuit extracts the pressure control function from the main cooling circuit. By branching off the pressure control line before the coolant supply to the friction elements and creating a separate feedback loop, the system extracts accurate pressure information independent of coolant pressure variations, enabling precise correction without being affected by the cooling system's pressure fluctuations.
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 solution allows for accurate activation of friction elements without torque fluctuations, ensuring comfortable engagement and disengagement of the clutch, and prevents damage from excessive pressures, maintaining consistent cooling and lubrication.
Implementation Method 1
The clutch device is designed as a hydraulic resistance cascade and is connected between coolant supply and coolant return lines... The hydraulic resistance cascade has two resistances via which a bypass oil flow flows from the coolant supply line to the coolant return line. An intermediate pressure is brought about between the hydraulic resistances.
Implementation Method 2
The valve is a 3/3-way valve. The valve has a connection to the clutch, with a working pressure line and with a zero outlet which communicates with a transmission sump. In this connection, the valve can occupy three operating positions.
Implementation Method 3
The slide has in an end region a slide bore with a piston arranged therein, which bore communicates with a peripheral groove of the slide. Operating pressure is present in the peripheral groove and, via a duct, is also present in the slide bore. The operating pressure is thus led back to an area on the slide corresponding in size to the piston area.
Data Source
AI summary
A clutch device for a motor vehicle has friction elements around which coolant flows and which, by way of a piston, can be pressed against one another for torque transmission. The first piston side is acted on with operating pressure, and the second piston side is acted on with coolant pressure. A valve, by which the operating pressure can be set, and a device which makes a reaction of the coolant pressure on the operating pressure possible are provided. The device is designed as a hydraulic resistance cascade and is connected between coolant supply and coolant return lines of the friction elements. A return pressure line branches off in the center of the hydraulic resistance cascade and is connected to the valve.