MEMS Movable Mass Stopper Mechanism for Controlled Rebound
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Solution Overview
Problem
Existing MEMS devices with static-block stoppers face issues of adhesion and structural damage due to unpredictable rebound directions of movable masses after impact, and the stop forces applied by these stoppers are not balanced, leading to potential damage and unpredictable movement.
Innovation Solution
The MEMS device employs L-shaped stopper elements with rotating arms that apply balanced stop forces by clamping the movable mass transversely, using coupling elements to rotate the stopper elements around vertical axes, ensuring controlled and predictable rebound directions and reducing the risk of damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If static-block stopper elements are used to limit the movement of the movable mass, then the full stroke is defined and normal operation is allowed, but the stop forces applied may cause adhesion of the movable mass and/or damage to the structure
Solution Approach 1:
The stopper elements are made rotatable about vertical axes rather than being fixed static blocks. This dynamic capability allows the stopper elements to rotate during impact events, dissipating energy and reducing the magnitude of stop forces applied to the movable mass, thereby preventing adhesion and structural damage while still defining the full stroke limit
Solution Approach 2:
The stopper elements are positioned and oriented in advance to face the movable mass from directions transverse to the motion direction. This preliminary arrangement ensures that when the movable mass reaches the full stroke position, the stop forces are applied in a controlled manner from multiple directions, preventing unpredictable rebound and reducing peak impact forces
2Length of moving object
If static-block stopper elements are used to limit the movement of the movable mass, then the maximum displacement is defined, but the rebound direction of the movable mass after impact is unpredictable
Solution Approach 1:
The stopper elements are configured with asymmetric orientations, with each stopper element facing the movable mass from a specific direction transverse to the motion direction. This asymmetric arrangement ensures that the stop forces are applied in a controlled, predictable manner, guiding the rebound direction of the movable mass in a predetermined pattern rather than allowing random rebound directions
3Length of moving object
If stopper elements with patterned surfaces are used to limit stress at the interface, then the full stroke is determined, but the stop forces remain high and may cause damage
Solution Approach 1:
The rotatable nature of the stopper elements allows them to dynamically respond to impact forces by rotating about vertical axes. This rotation mechanism dissipates impact energy and reduces the magnitude of stop forces applied to the movable mass, preventing damage while maintaining the full stroke definition
Solution Approach 2:
The stopper elements are oriented to apply forces in directions transverse to the primary motion direction, rather than directly opposing the motion. This dimensional change in force application reduces the peak stop forces while still effectively limiting the full stroke of the movable mass
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 solution provides a more controlled and predictable rebound direction for the movable mass, reducing the risk of structural damage and ensuring safe operation by applying lower stop forces, thus maintaining the device's integrity and functionality.
Implementation Method 1
stopper elements (7) arranged around the movable mass (3) and coupled to the supporting body (2) through anchors (9) by means of connection elements (8) configured to allow the rotation of the stopper elements (7) around respective rotation axes R
Implementation Method 2
the stopper arms (7B) come into contact with the movable mass (3) and clamp it, applying stop forces FC
Implementation Method 3
a movable mass 3 coupled to the supporting body 2 so as to be able to oscillate along one or more motion directions within a range I of admissible positions
Implementation Method 4
the movable mass 3 oscillating in response to forces applied in the motion direction D
Data Source
Figure 1~3
Figure 4~5
Figure 6~7
AI summary
Microelectromechanical device (1) comprising a supporting body (2), containing semiconductor material and a movable mass (3), constrained to the supporting body with a relative degree of freedom with respect to at least one motion direction (D), within a range (I) of admissible positions. The device also comprises stopper elements (7), operable by the movable mass due to movements along the at least one motion direction and configured to apply stop forces (FC) to opposite sides of the movable mass, transversely to the at least one motion direction, when the movable mass reaches a respective endpoint (I1, I2) of the range of admissible positions, so as to prevent the movable mass from exceeding the respective endpoint.