Torque Converter Preloaded Turbine Piston Clutch Engagement
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Solution Overview
Problem
Torque converters with axially movable turbine pistons face challenges in maintaining clutch engagement during coast conditions due to turbine thrust, which can lead to clutch liftoff and inefficient fuel economy, especially when component tolerances result in large gaps at the friction interface.
Innovation Solution
Incorporating a resilient element, such as a diaphragm spring with radially inward and outward tabs, between the turbine shell and the front cover to apply a preload force, ensuring the clutch remains engaged by covering stack-up tolerances and preventing ballooning, and utilizing a multi-plate cone clutch for enhanced clutch capacity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a turbine piston is used to actuate the lockup clutch, then clutch capacity is enhanced, but clutch liftoff occurs during coast conditions due to turbine thrust
Solution Approach 1:
A resilient element (diaphragm spring) is pre-installed between the turbine piston and front cover to apply a preliminary preload force that counteracts the turbine thrust during coast conditions. This preliminary anti-action prevents clutch liftoff before it occurs, ensuring consistent clutch engagement during coast conditions while maintaining the enhanced clutch capacity provided by the turbine piston design.
2Ease of manufacture
If component tolerances are manufactured with standard precision, then manufacturing cost is reduced, but large gaps appear at the friction interface
Solution Approach 1:
The resilient element is installed beforehand to compensate for the cumulative effect of component tolerances (stack-up tolerances) in the friction interface. By providing a compliant element that can deform and maintain contact pressure, the system cushions against the gaps created by standard manufacturing tolerances, ensuring reliable clutch engagement without requiring expensive tight-tolerance manufacturing.
3Ease of operation
If the turbine is allowed to move axially freely, then response to pressure differentials is improved, but clutch engagement is lost during coast conditions
Solution Approach 1:
The resilient element acts as a counterforce mechanism that applies a preload in the opposite direction of the turbine thrust during coast conditions. This counterweight effect maintains the clutch engaged state while still allowing the turbine to respond to pressure differentials when needed, as the resilient element can compress and expand dynamically to accommodate operational requirements.
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 resilient element ensures consistent clutch engagement and improved fuel economy by maintaining contact during axial growth and adjusting to pressure differentials, enhancing coast engagement even at low apply flow and pressure.
Implementation Method 1
a resilient element, such as a diaphragm spring with radially inward and outward tabs, between the turbine shell and the front cover to apply a preload force
Implementation Method 2
utilizing a multi-plate cone clutch for enhanced clutch capacity
Data Source
AI summary
A torque converter comprising: a damper assembly including a spring retainer; and, a turbine assembly connected to the damper assembly, the turbine assembly including: a turbine shell including an axially movable turbine piston; a drive plate fixed to the turbine piston; and a diaphragm spring, the drive plate having openings for receiving the diaphragm spring; the diaphragm spring acting on the turbine piston with a preload force. In an example aspect, the diaphragm spring includes a plurality of radially inward tabs and the drive plate includes a plurality of openings for receiving the radially inward tabs.