Ultrasonic Sensor Viscoelastic Damping for Reverberation Control
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Solution Overview
Problem
Ultrasonic sensors face challenges in reducing reverberation, which interferes with the detection of minimum distances to obstacles due to uncontrolled manufacturing processes and inadequate damping techniques, leading to varying reverberation characteristics and impaired sensor performance.
Innovation Solution
The ultrasonic sensor design incorporates a ring-shaped inner supporter with a viscoelastic filler and a tabular member of higher rigidity, facilitating shear deformation and viscoelastic damping to efficiently dissipate vibrational energy, thereby reducing reverberation and improving resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a vibration isolator and elastic member are placed inside the cylindrical case to prevent resonance, then residual vibration is reduced, but the vibration of the side surface of the case cannot be sufficiently reduced and reverberation cannot be sufficiently reduced
Solution Approach 1:
The case is divided into an inner case and an outer case that are separate and independent structures. The inner case contains the piezoelectric element and vibration isolator, while the outer case provides structural support. This segmentation allows the inner case to vibrate independently without transmitting vibration to the outer case, effectively reducing side surface vibration and reverberation.
Solution Approach 2:
A viscoelastic filler is introduced as an intermediary damping material between the inner case and outer case. This filler absorbs vibrational energy and prevents resonance between the two cases, thereby reducing reverberation while maintaining the benefits of the vibration isolator and elastic member.
2Reliability
If sealing silicone resin is disposed inside the case with predetermined hardness to reduce variations in reverberation characteristics, then reverberation characteristics are controlled, but physical properties widely vary and manufacturing process control is difficult
Solution Approach 1:
The invention changes the material parameter from silicone resin to foam material, which has more stable and predictable physical properties. This substitution reduces variations in reverberation characteristics while making the manufacturing process easier to control, as foam materials have more consistent density and damping characteristics.
Solution Approach 2:
The invention uses a composite structure combining the inner case, outer case, and foam material filled between them. This composite design leverages the advantages of each material: the rigid cases provide structural integrity while the foam provides consistent damping, achieving reliable reverberation control with easier manufacturing.
3Device complexity
If the case and terminal plate vibrate in an integrated manner with a terminal plate fixed to the opening, then structural simplicity is achieved, but the vibration of the side surface of the case cannot be sufficiently reduced
Solution Approach 1:
The case is segmented into inner and outer cases that are not rigidly connected. This segmentation allows the inner case to vibrate independently while the outer case remains relatively stationary, reducing side surface vibration without significantly increasing overall structural complexity.
Solution Approach 2:
The vibrating components (piezoelectric element and inner case) are extracted and isolated from the outer case structure. This extraction allows the inner case to vibrate freely for ultrasonic wave generation while the outer case provides a stable mounting surface for the terminal plate, reducing coupled vibration.
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 design effectively reduces reverberation, enhancing the sensor's ability to detect obstacles with improved resolution and mechanical damping, while maintaining a compact form factor and cost-effectiveness.
Implementation Method 1
a viscoelastic filler disposed inside the central hole and on the flat portion of the inner supporter; a tabular member having a rigidity higher than that of the filler and disposed on the flat portion of the inner supporter so as to face the flat portion with the filler interposed therebetween
Implementation Method 2
facilitating shear deformation and viscoelastic damping to efficiently dissipate vibrational energy
Implementation Method 3
When a voltage is applied to the piezoelectric element 101, the piezoelectric element 101 is induced to vibrate in radial directions or in the thickness direction thereof
Implementation Method 4
the vibrating surface of the case 100 vibrates so as to emit ultrasonic waves into the air
Implementation Method 5
the resolution of minimum distances to detected obstacles
Data Source
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AI summary
[Object] To provide an ultrasonic sensor capable of improving the resolution of a minimum distance to a detected obstacle by damping unwanted vibration of a side surface of a case and reducing the reverberation time. [Solving Means] An ultrasonic sensor includes a cylindrical outer case 1 with a bottom and a piezoelectric element 3 fixed to the inner side of the bottom portion 1a of the outer case. A ring-shaped inner case 2 having a central hole 2b extending in the axial direction in the central portion thereof is disposed inside the sidewall portion of the outer case 1. A flat portion 2d is formed around the central hole 2b of the inner case 2, and an viscoelastic filler 6 is disposed so as to extend from the central hole 2b to the flat portion 2d of the inner case 2. A tabular member 7 is disposed on the flat portion 2d so as to face the flat portion with the filler 6 interposed therebetween. When the inner case 2 vibrates, shear deformation occurs in the filler 6 interposed between the flat portion 2d and the tabular member 7 since the tabular member 7 is not substantially deformed, and the vibration is reduced by the viscoelastic damping effect.