SMA Valve Timing Correction for Vehicle Seat Air Cells
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Solution Overview
Problem
SMA valves face challenges in controlling activation and deactivation delay times due to temperature dependence, making them unsuitable for precise timing requirements in vehicle seat massage systems and lumbar support applications.
Innovation Solution
A control unit that uses temperature data from a sensor to determine and correct activation and deactivation delay times by employing look-up tables or fitted functions, and further adjusts timing based on actual valve operation data to minimize deviations caused by environmental factors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SMA valves are used in vehicle seat massage systems, then the number of valves is reduced and cost is lowered, but the activation and deactivation delay times become temperature-dependent and imprecise
Solution Approach 1:
The patent implements a control unit that receives feedback from temperature sensors monitoring the SMA wire temperature. Based on this temperature feedback, the control unit dynamically adjusts the activation and deactivation timing of the SMA valve to compensate for temperature-dependent delay variations, thereby maintaining precise timing control across different operating conditions.
Solution Approach 2:
The patent changes the operational parameters of the SMA valve by actively monitoring and adjusting the activation/deactivation timing based on real-time temperature measurements. The control unit modifies the electrical activation cycle parameters (duration, intensity) according to the sensed temperature, optimizing the valve response time across the operating temperature range.
2Ease of operation
If the SMA wire is heated to activate the valve, then the valve opens to supply pressurized air, but the activation delay time varies with ambient temperature
Solution Approach 1:
The control unit performs preliminary action by pre-heating the SMA wire or pre-adjusting the activation parameters based on the sensed ambient temperature before the actual valve activation is needed. This anticipatory adjustment compensates for the temperature-dependent heating rate, ensuring consistent activation timing.
Solution Approach 2:
The temperature sensor provides continuous feedback on the SMA wire temperature, allowing the control unit to monitor the heating progress and adjust the activation timing dynamically. When the wire reaches the threshold temperature, the control unit triggers valve activation, compensating for variations in heating rate caused by different ambient temperatures.
3Ease of operation
If the SMA wire cools down to deactivate the valve, then the valve closes to stop air supply, but the deactivation delay time is strongly dependent on ambient temperature
Solution Approach 1:
The control unit continuously monitors the SMA wire temperature during the deactivation phase and uses this feedback to determine the optimal moment to cut off power and initiate cooling. Based on the ambient temperature feedback, the control unit adjusts the deactivation timing to compensate for varying cooling rates, ensuring consistent valve closure timing.
Solution Approach 2:
The control unit implements periodic measurement of the SMA wire temperature during the deactivation phase and uses this periodic feedback to timing the deactivation process. This allows the system to account for the strongly temperature-dependent cooling rate and adjust the deactivation cycle accordingly.
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 significantly reduces activation and deactivation delay times, enabling SMA valves to meet the precise timing needs of vehicle seat massage systems and lumbar support applications, ensuring consistent and reliable operation.
Implementation Method 1
A SMA material changes its microscopic structure at a threshold temperature such that a SMA element shortens upon exceeding the threshold temperature. In particular, a SMA material at room temperature is in the state of a metal with martensitic properties, whereas the structure transitions at a threshold temperature of about 80° C. into an austenitic structure.
Implementation Method 2
A SMA valve according to the invention further comprises a temperature sensor (12) for sensing the ambient temperature around the SMA wire (8).
Implementation Method 3
an actuator capable of acting on the plunger such that the actuator upon activation exerts a force on the plunger which moves the plunger away from the valve seat to an open position
Data Source
AI summary
The present invention is directed to a SMA valve for controlling air supply to an air cell in a vehicle seat, comprising a control unit arranged to open the valve in predetermined cycles, each cycle having predetermined activation start and stop times, by supplying an electrical activation power to a SMA wire which in turn acts on a valve element to open the valve for each cycle when the SMA wire shortens upon reaching the threshold temperature, and a temperature sensor for sensing the ambient temperature around the SMA wire. According to the invention the control unit is arranged to receive the temperature signal from the temperature sensor and to determine an activation delay time and an deactivation delay time in dependence on the temperature sensed by the temperature sensor, and to correct the activation start time and the activation stop time for the activation delay time and the deactivation delay time, respectively, to provide a corrected activation start time and a corrected activation stop time to be used for the next cycle.