Ultrasonic Sensor Casing Segmentation for Stress Relief
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Solution Overview
Problem
Ultrasonic sensors face challenges in increasing sound pressure and frequency bandwidth without reducing resonant frequency, and are prone to breakage due to stress concentration at geometric discontinuities between metal and resin bonding joints.
Innovation Solution
The design includes a casing with a metal unit and a resin unit, where the geometric discontinuities are positioned away from the bonding joint, using materials like polyethersulfone, polyphenylene sulfide, and CFRP to distribute stress effectively, and incorporating a piezoelectric vibrator element mounted on a disk-shaped bottom plate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the planar vibrator made of metal and the cylindrical section made of resin are bonded by adhesive at the geometric discontinuities, then the sound pressure and frequency bandwidth can be increased, but the bonding joint portion is prone to breakage due to stress concentration
Solution Approach 1:
The casing is divided into three distinct sections: the metal cylindrical section, the intermediate resin section, and the bottom plate. This segmentation allows the geometric discontinuities to be distributed across different locations, preventing stress concentration at the bonding joint between metal and resin. The intermediate resin section acts as a buffer zone that separates the stress paths.
Solution Approach 2:
The resin cylindrical section serves as an intermediary element between the metal cylindrical section and the bottom plate. This intermediate resin section absorbs and distributes the stress that would otherwise concentrate at the bonding joint, thereby preventing breakage while maintaining the structural integrity needed for high sound pressure output.
2Power
If the planar vibrator made of metal and the cylindrical section made of resin are bonded by adhesive, then the frequency bandwidth can be widened, but the resonant frequency is reduced
Solution Approach 1:
Different sections of the casing are made from different materials with optimized properties: the metal cylindrical section provides structural strength and electrical conductivity, the intermediate resin section provides stress distribution and acoustic coupling, and the bottom plate provides vibration transmission. This local optimization allows wide frequency bandwidth without significantly reducing resonant frequency.
3Ease of manufacture
If the bonding joint portion is located at the same position as the geometric discontinuities, then the manufacturing process is simplified, but breakage occurs in the bonding joint portion due to stress concentration
Solution Approach 1:
The casing is segmented into three sections with the intermediate resin section positioned between the metal cylindrical section and the bottom plate. This segmentation strategically places the bonding joints away from the geometric discontinuities, reducing stress concentration while maintaining manufacturing simplicity through modular assembly.
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 configuration enhances sound pressure and frequency bandwidth while reducing the risk of breakage caused by stress concentration, maintaining resonant frequency and improving the reliability of the ultrasonic sensor.
Implementation Method 1
The piezoelectric vibrator element is mounted on the bottom plate
Data Source
AI summary
An ultrasonic sensor includes a casing and a piezoelectric vibrator element. The casing includes a first unit made of a metal and a second unit made of a resin. The first unit has a cylindrical or substantially cylindrical shape extending in a first direction. The second unit is connected to one end of the first unit in the first direction and includes a cylindrical section and a bottom plate. The cylindrical section extends in the first direction. The bottom plate is a disk-shaped portion which closes an end of the cylindrical section positioned farther away from the first unit in the first direction. The piezoelectric vibrator element is mounted on the bottom plate.