Monolithic Inertial Mass Assembly for Piezoelectric Beam Reliability
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Solution Overview
Problem
The existing Piezoelectric Energy Harvester (PEH) devices face challenges in achieving a 20-year lifespan due to issues with the bonding process of the inertial mass to the PZT beam, including chemical binding material degradation, difficulty in controlling the bonding process, and improper glue quantity, which affects the device's flexibility and energy harvesting efficiency.
Innovation Solution
A monolithic inertial mass with an axial slit is used, allowing for a secure and controlled assembly of the PZT beam, employing techniques like wire electro-erosion or additive material deposition, and securing methods such as temperature deformation or crimping to ensure a stable and efficient energy harvesting system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If chemical binding material is used to bond inertial mass to PZT beam, then assembly is simplified, but reliability deteriorates due to material degradation over time
Solution Approach 1:
The patent removes the chemical bonding material from the system entirely. Instead of using adhesive to bond the inertial mass to the PZT beam, it employs a mechanical interlocking solution where the inertial mass features a recess that receives the PZT beam, eliminating the bonding material and its associated reliability issues.
Solution Approach 2:
The patent replaces the chemical bonding system with a mechanical attachment system. The inertial mass is secured to the PZT beam through a mechanical recess-and-fit structure, substituting chemical adhesion with mechanical interlocking that does not degrade over time.
2Ease of manufacture
If bonding process is used to attach inertial mass to PZT beam, then assembly is achieved, but manufacturing precision deteriorates due to difficulty in controlling glue quantity
Solution Approach 1:
The patent eliminates the bonding material from the assembly process, removing the source of manufacturing precision problems. The mechanical recess structure allows for precise positioning and attachment without requiring controlled application of adhesive material.
Solution Approach 2:
The recess is pre-formed in the inertial mass during manufacturing, establishing the precise positioning geometry in advance. This preliminary structural preparation eliminates the need for precise bonding control during assembly, as the mechanical fit inherently provides the required precision.
3Strength
If excessive glue is applied in bonding process, then inertial mass is securely attached, but device flexibility deteriorates due to improper glue quantity affecting PZT beam movement
Solution Approach 1:
The patent removes the bonding material that causes flexibility problems. The mechanical recess structure provides secure attachment through precise geometric fit rather than through adhesive, eliminating the trade-off between bond strength and device flexibility.
Solution Approach 2:
The patent replaces the adhesive bonding system with a mechanical interlocking system. The recess in the inertial mass receives the PZT beam in a way that provides secure attachment while maintaining the flexibility needed for proper device operation, as the mechanical fit allows controlled movement without excessive adhesive restriction.
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 guarantees a 20-year lifespan for the PEH device, simplifies the assembly process, and optimizes vibratory characteristics, leading to enhanced energy harvesting efficiency and power autonomy for medical implants like leadless capsules.
Implementation Method 1
a piezoelectric transducer, PZT, beam, that is elastically deformable in bending and that extends in axial direction between a clamped proximal end and a free distal end, and an inertial mass, that is mounted at the free distal end of the PZT beam and mobile in transverse direction. The pendular unit is adapted to convert a mechanical energy produced by oscillations of the pendular unit under the effect of external stresses undergone by the module into an oscillating electrical signal collected by surface electrodes of the PZT beam.
Data Source
AI summary
The pendular unit comprises a piezoelectric transducer beam (22), and an inertial mass mounted at the free distal end of the beam (22). The inertial mass (26) is a monolithic part including a cavity in the form of an axial slit (64), with two opposite longitudinal surfaces (74) extending along a central axis of the inertial mass (26). The axial slit (64) opens out on the proximal side of the inertial mass (26), and receives the free distal end of the beam (22), secured between the two opposite longitudinal surfaces (74) of the axial slit (64).