Coiled Shape Memory Alloy Thermocouple for Valve Stroke
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Solution Overview
Problem
Existing temperature-controlled valve devices for fluid flow, such as those used in hydraulic fan drives, face challenges in maintaining reliable temperature-dependent flow rate control due to limitations in thermocouple actuation, particularly requiring large control strokes which are impractical with solid-body shape memory alloy thermocouples.
Innovation Solution
A flow control valve with a thermocouple comprising a spring element with multiple windings, allowing for larger actuation strokes and a compact design, combined with a pressure compensator to maintain constant pressure drop across the orifice, independent of load pressure, and a return spring for hysteresis control in temperature-dependent operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a solid-body shape memory alloy thermocouple is used, then the thermocouple structure is compact, but the control stroke is too small for practical applications
Solution Approach 1:
The patent transforms the thermocouple from a linear solid-body structure to a coiled spring structure. By winding the shape memory alloy into multiple loops, the effective actuation length is multiplied while the overall device footprint remains compact. This dimensional transformation allows achieving large control strokes (multiple millimeters) without proportionally increasing the thermocouple's overall length.
Solution Approach 2:
The thermocouple is segmented into multiple coiled loops rather than being a single solid rod. Each loop contributes to the cumulative displacement, allowing the valve piston to achieve a large total control stroke through the additive effect of multiple loop expansions, while maintaining a compact overall structure.
2Productivity
If the valve piston control stroke is increased to achieve desired flow control, then the flow control range is improved, but the thermocouple length becomes impractically large
Solution Approach 1:
By coiling the thermocouple into multiple loops, the patent achieves a multiplication effect where the linear expansion of each loop accumulates to provide a large total control stroke. This allows the valve piston to traverse a sufficient distance for effective flow control without requiring an impractically long straight thermocouple.
3Measurement precision
If a pressure compensator is added to maintain constant pressure drop, then the flow control accuracy is improved, but the device complexity increases
Solution Approach 1:
The pressure compensator acts as an intermediary component that maintains constant pressure differential across the orifice by compensating for load pressure variations. This ensures that the flow control characteristic remains accurate and predictable regardless of downstream pressure changes, improving control precision without requiring complex electronic systems.
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
Enables reliable, temperature-dependent fluid flow control with a compact design, ensuring consistent flow rate characteristics across the control range and optimal heat coupling, independent of load pressure, and allows for adjustable maximum speed settings in fan drives.
Implementation Method 1
a spring element (61) made of a shape memory alloy which serves as a thermocouple
Implementation Method 2
A pressure compensator (21) connected to the tank connection (23) keeps the respective pressure drop across the orifice constant
Implementation Method 3
optimal heat coupling
Data Source
AI summary
A valve device for controlling a fluid flow includes a flow control valve (15) having a valve housing (19) with a supply connection (9) and a user connection (11). A valve piston (17) is guided inside the valve housing (19) longitudinally moveable and controls the passage to the user connection (11) by a thermocouple (61) via an orifice (37, 39) depending on the temperature of the fluid flow. A pressure compensator (21) is connected to the supply connection (9) and keeps the pressure drop across the orifice (37, 39) constant.