Force Sensor Assembly with Spring Preload
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Solution Overview
Problem
Existing force sensors are prone to damage from overloads, lack high measurement accuracy, are costly, and require complex packaging, while also being susceptible to wear, especially in applications requiring precise force measurement in unique packaging or high-volume production.
Innovation Solution
A force sensor assembly featuring a semiconductor sensor unit with a piezo-resistive element or force-sensing capacitor mounted on a substrate, utilizing a spring element for preload to shift overload protection and a guiding element for precise force transduction, ensuring accurate measurement by superposing externally applied and preload forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a force sensor uses a direct contact mechanism between transducer element and sensing surface, then the structure is simple, but the sensor is susceptible to wear and damage from overload
Solution Approach 1:
The patent introduces a spring element that applies a preload force to the transducer element before external forces are applied. This preload creates a controlled initial contact force between the transducer element and the sensing surface. When external forces exceed the preload, the spring element compresses, absorbing the excess force and preventing overload damage to the sensor. This beforehand cushioning mechanism protects the sensor from wear and damage while maintaining structural simplicity.
2Reliability
If a force sensor uses a preload mechanism to protect from overload, then the sensor is protected from damage, but the measurement system becomes more complex
Solution Approach 1:
The spring element automatically adjusts the preload force based on the external forces applied to the sensor. When external force increases, the spring compresses and reduces the preload accordingly, and vice versa. This self-adjusting mechanism eliminates the need for complex electronic control systems or additional actuators to maintain the preload, thereby protecting against overload while keeping the measurement system relatively simple.
3Measurement precision
If a force sensor uses a ball transducer element for precise force transduction, then measurement accuracy in normal direction is improved, but the sensor becomes vulnerable to damage from oblique forces
Solution Approach 1:
The spring element applies a preload force that presses the ball transducer element against the sensing surface with a controlled normal force. This preload creates a cushioning effect that absorbs oblique forces by allowing the spring to compress, preventing the ball element from experiencing damaging lateral loads. The ball element maintains precise measurement capability in the normal direction while the spring protects it from oblique force 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 solution provides high measurement accuracy, protects the sensor from overload, reduces costs, and enables precise force measurement while maintaining a wear-free operation, suitable for applications like electro-mechanical flight control and ultra-low cost load cells.
Implementation Method 1
The force sensor being adapted for outputting a measurement signal based on an effective force... The at least one resistive element exhibits a varying resistance responsive to deflection and/or stress of the diaphragm
Implementation Method 2
a spring element connected between the substrate and the force transducer, the spring element for providing a preload force pressing the force transducer to the force sensor
Data Source
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AI summary
The present invention relates to force sensor assembly (10) for measuring an effective force. The force sensor assembly comprises a force sensor (200) mounted on a substrate (100), the force sensor for outputting a measurement signal based on the effective force. The force sensor assembly further comprises a force transducer (300) for transducing an externally applied force (400) to the force sensor. The force sensor assembly further comprises a spring element (500) connected between the substrate (100) and the force transducer (300), the spring element (500) for providing a preload force pressing the force transducer (300) to the force sensor (200), wherein the measurement signal depends on a superposition of the externally applied force (400) and the preload force.