SMA Shift Element for Automatic Transmissions Without Hydraulics
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Solution Overview
Problem
Hydraulically actuated friction shift elements in automatic transmissions face challenges in maintaining hydraulic pressure and require complex designs with strict cleanliness guidelines, making them difficult to manage effectively.
Innovation Solution
The implementation of a shape-memory alloy shifter coupled to an actuating plate that compresses friction plates to engage or disengage gear ratios in automatic transmissions, eliminating the need for hydraulic fluid by using a shape-memory alloy helical coil spring mechanism to adjust the friction shifting element between engaged and disengaged configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If hydraulically actuated friction shift elements are used, then gear shifting capability is achieved, but system complexity and maintenance difficulty increase due to hydraulic pressure requirements
Solution Approach 1:
The patent replaces the hydraulic actuation system with a shape memory alloy (SMA) based mechanical actuation system. The SMA shifter element directly actuates the friction plates through thermal activation, eliminating hydraulic fluid, pressure vessels, control valves, and associated plumbing. This substitution reduces system complexity while maintaining gear shifting capability.
Solution Approach 2:
The patent extracts and removes the entire hydraulic actuation subsystem from the transmission system. By using SMA material that responds directly to temperature changes, the design eliminates the need for hydraulic fluid reservoirs, pumps, and pressure control mechanisms, thereby simplifying the overall system architecture.
2Ease of operation
If hydraulically actuated friction shift elements are used, then gear shifting is achieved, but cleanliness requirements become stricter due to debris sensitivity
Solution Approach 1:
By replacing the hydraulic fluid-based actuation system with a solid-state shape memory alloy mechanism, the patent eliminates the closed hydraulic circuit that is susceptible to contamination. The SMA-based system has no fluid to degrade or become contaminated, thereby removing the cleanliness maintenance burden while preserving gear shifting function.
3Reliability
If hydraulically actuated friction shift elements are used, then shift engagement is achieved, but design complexity increases due to O-rings and drilled passageways
Solution Approach 1:
The patent removes O-rings, drilled passageways, and other hydraulic system components from the design. The SMA shifter element uses a straightforward thermal expansion and phase transformation mechanism that requires no sealing elements or complex internal passages, thereby reducing component complexity while maintaining reliable shift engagement.
4Force
If hydraulic pressure is maintained for friction shift elements, then actuation force is sufficient, but system complexity and maintenance burden increase
Solution Approach 1:
The patent substitutes the hydraulic pressure generation and maintenance system with a shape memory alloy thermal activation system. The SMA material generates sufficient actuation force through its phase transformation properties when heated, eliminating the need for hydraulic pumps, pressure regulators, and fluid reservoirs, thereby reducing system complexity while maintaining adequate actuation force for friction plate engagement.
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 simplifies the design, reduces the complexity of maintaining hydraulic pressure, and enhances the reliability of gear shifts by using a non-hydraulic mechanism, improving the operational efficiency and cleanliness of automatic transmission systems.
Implementation Method 1
A shape-memory alloy shifter is coupled to the actuating plate. The shape-memory alloy shifter is configured for moving the actuating plate along the axial direction between an engaged configuration and a disengaged configuration.
Data Source
AI summary
A friction shifting element includes a plurality of first friction plates. A plurality of second friction plates is interleaved with the plurality of first friction plates. The friction shifting element also includes an actuating plate. A shape-memory alloy shifter is configured for moving the actuating plate along an axial direction between an engaged configuration and a disengaged configuration. The actuating plate compresses the plurality of first friction plates and the plurality of second friction plates together when the actuating plate is in the engaged configuration.