SMA Actuator Latch Assembly Decoupling Strategy
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Solution Overview
Problem
Existing latch assemblies for vehicles lack efficient and quiet operation, particularly in utilizing shape memory alloy (SMA) actuators, as they often require strategic decoupling to improve performance and reduce noise and size compared to solenoid actuators.
Innovation Solution
A latch assembly incorporating a shape memory alloy (SMA) actuator with a decoupled interface between the SMA actuator and striker, allowing the SMA wire and return spring to return to their original positions at different rates, and featuring a connecting link and actuator lever arm that pivotably rotates or linearly translates to engage a closing surface, enhancing packaging and noise reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a solenoid actuator is used in the latch assembly, then the actuator can provide strong force, but the device size and weight increase, and noise is generated
Solution Approach 1:
The patent replaces the solenoid actuator (electromechanical system) with a shape memory alloy actuator that utilizes thermal-mechanical properties of SMA material. The SMA actuator converts thermal energy directly into mechanical motion through phase transformation, eliminating the need for traditional electromagnetic coils, magnets, and moving parts, thereby reducing weight and noise while maintaining actuation force
Solution Approach 2:
The patent changes the operating parameters of the actuator system by using shape memory alloy material properties (phase transformation temperature, transformation strain) instead of electromagnetic parameters. The SMA wire undergoes reversible phase transformation between martensite and austenite phases, converting thermal input into controlled mechanical displacement and force, achieving quiet and lightweight operation
2Force
If a solenoid actuator is used in the latch assembly, then the actuator can provide strong force, but the device volume increases
Solution Approach 1:
The patent replaces the bulky solenoid actuator with a compact shape memory alloy actuator. The SMA-based mechanism eliminates large electromagnetic components, allowing for a much smaller actuator housing and overall latch assembly volume while maintaining the necessary actuation force through the high-strain capability of shape memory alloy materials
Solution Approach 2:
The patent implements a nested configuration where the SMA wire is positioned within the actuator housing, with the actuator lever arm rotating within the housing boundaries. The connecting link mechanism is integrated within the same space, allowing multiple components to occupy overlapping or nested spatial volumes, thereby minimizing the overall device footprint
3Device complexity
If the striker is directly coupled to the SMA actuator, then the mechanism is simpler, but the SMA actuator is impacted during closure and performance deteriorates
Solution Approach 1:
The patent segments the actuation mechanism into distinct functional components: the SMA actuator for controlled opening motion, and the striker with pawl for engagement and closing functions. This segmentation allows the SMA actuator to operate independently without being subjected to impact loads during closure, preserving its performance and longevity
Solution Approach 2:
The patent introduces an intermediate mechanism (connecting link and actuator lever arm) between the SMA actuator and the striker. This intermediary transmission mechanism decouples the SMA actuator from direct contact with the striker, allowing the actuator to provide precise opening motion while the intermediate mechanism handles the engagement and closing operations, protecting the SMA actuator from impact damage
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 SMA actuator-based latch assembly provides a quieter, lighter, and more compact solution with improved performance, allowing for efficient opening and closing of vehicle compartments without impacting the SMA actuator during closure, and enabling cost-effective implementation in various vehicle applications.
Implementation Method 1
a shape memory alloy (SMA) actuator including an actuator housing, an SMA wire, and an actuator lever arm. The actuator lever arm is configured to pivotably rotate or linearly translate with respect to the actuator housing upon activation of the SMA wire
Implementation Method 2
Shape memory alloy (SMA) actuators can be used to facilitate movement of one or more components in a latch assembly. For example, U.S. Pat. No. 10,435,918 to Weber et al. discloses a latch system that includes an SMA wire which contracts when current is applied to it
Implementation Method 3
the decoupled interface allows for the return spring and the SMA wire to return to original positions at different rates of speed
Data Source
AI summary
A latch assembly for a vehicle, in applications such as an armrest console or a glove box, includes a shape memory alloy (SMA) actuator. The SMA actuator includes an actuator housing, an SMA wire, and an actuator lever arm. The actuator lever arm is configured to pivotably rotate or linearly translate with respect to the actuator housing upon activation of the SMA wire. A connecting link is coupled to the actuator lever arm. The connecting link is configured to translate linearly along a connecting link axis when the actuator lever arm pivotably rotates or linearly translates. A striker is coupled to the connecting link and configured to rotate about a striker axis to engage a closing surface.