Pulse Wave Sensor With Cr Film and Tuned Strain Body Thickness
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Solution Overview
Problem
Conventional pulse wave sensors face a challenge in achieving a balance between sensitivity and rigidity, as they require thin strain generating bodies for sensitivity but also need durability.
Innovation Solution
A pulse wave sensor design incorporating a strain generating body with a circular opening, covered by a resin layer and equipped with a strain gauge featuring a Cr mixed phase film resistor, where specific thickness and diameter ranges are defined for various materials to ensure compatibility between sensitivity and rigidity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a thin strain generating body is used to ensure sensitivity, then sensitivity is improved, but durability and rigidity deteriorate
Solution Approach 1:
The patent applies parameter changes by precisely controlling the thickness of the strain generating body within specific ranges (0.059≤t≤0.124mm for d=32mm, 0.046≤t≤0.099mm for d=22mm) to achieve optimal balance between sensitivity and rigidity. This quantitative parameter optimization allows the thin structure to maintain both detection sensitivity and structural durability
Solution Approach 2:
The patent uses composite material structure combining SUS (stainless steel) or copper as the strain generating body material with a resin layer covering one surface. This composite construction provides both the sensitivity of thin metal structures and the protective durability of resin coating, resolving the contradiction between thinness and strength
2Measurement precision
If a thin strain generating body is used to ensure sensitivity, then sensitivity is improved, but durability deteriorates
Solution Approach 1:
The patent applies beforehand cushioning by providing a resin layer that covers one surface of the strain generating body before it is exposed to the measurement environment. This resin coating acts as a protective barrier that prevents damage and corrosion, ensuring durability while maintaining the thin structure's sensitivity
Solution Approach 2:
The patent optimizes the thickness parameter within specific ranges to ensure the strain generating body is thin enough for sensitivity but thick enough to maintain structural integrity and durability under operational conditions
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 design achieves both sensitivity and rigidity, allowing for reliable and stable pulse wave detection, with sensitivity of 0.1 mV/V or more and resistance to plastic deformation under 50 g load.
Implementation Method 1
a strain gauge provided on the other surface of the strain generating body positioned on a side opposite to the one surface, the strain gauge including a Cr mixed phase film as a resistor
Data Source
AI summary
Pulse wave sensor includes strain generating body with circular opening, resin layer covering strain generating body's one surface, and strain gauge provided on strain generating body's other surface opposite to one surface and including Cr mixed phase film as resistor. Where circular opening diameter is d [mm] and strain generating body thickness is t [mm], when material of strain generating body is SUS and d is 32, 22, 13, and 7, required range of t is 0.059≤t≤0.124, 0.046≤t≤0.099, 0.030≤t≤0.067, and 0.026≤t≤0.034, respectively, when the material is copper and d is 32, 22, 13, and 7, required range of t is 0.084≤t≤0.166, 0.066≤t≤0.132, 0.044≤t≤0.088, and 0.032≤t≤0.050, respectively, and when the material is aluminum and d is 32, 22, 13, and 7, required range of t is 0.097≤t≤0.212, 0.079≤t<0.168, 0.050<<0.107, 0.038<t<0.063, respectively. Pulse wave sensor detects pulse wave based on change in resistance value of resistor upon deformation of strain generating body.