Brake Pad Shear Sensor Layout for Low Cross-Talk Measurement
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Solution Overview
Problem
Existing piezoelectric shear sensors face challenges in efficient in-situ polarization and cross-talk between normal and tangential force measurements, complicating signal interpretation.
Innovation Solution
A shear force sensing device with a sheet of screen-printed piezoelectric material having interdigitated electrodes on opposite main faces, oriented for bulk polarization with a transverse electric field, allowing in-situ polarization using low voltage and minimizing normal field components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If traditional piezoelectric materials (quartz, tourmaline, Rochelle salt) are used, then the sensor can be manufactured with simple processes, but the piezoelectric response is relatively small
Solution Approach 1:
The patent changes the material parameters by transitioning from natural piezoelectric materials (quartz, tourmaline) to synthesized polycrystalline ferroelectric ceramics (PZT, barium titanate) that exhibit larger piezoelectric coefficients, thereby increasing the measurement sensitivity while maintaining manufacturability through established ceramic synthesis processes
Solution Approach 2:
The patent employs composite piezoelectric ceramic materials with specific compositions (PZT with various dopants) that combine multiple elements to achieve enhanced piezoelectric properties, utilizing the synergistic effects of different materials to maximize the piezoelectric response
2Measurement precision
If PZT piezoceramic materials are used, then larger electric voltages are induced after mechanical stress, but complex polarization procedures are required
Solution Approach 1:
The patent applies the polarization field during the manufacturing process itself, rather than as a separate post-processing step. The polarization electrodes are integrated into the sensor structure, and the polarization is performed while the sensor is being assembled, thereby simplifying the overall procedure and reducing the complexity of subsequent handling
Solution Approach 2:
The patent combines the polarization function with the sensor structure by integrating polarization electrodes directly into the sensor assembly. This merging of polarization and sensing functions eliminates the need for separate polarization treatment steps and simplifies the overall device complexity
3Measurement precision
If strong electric field polarization is applied to create asymmetry, then piezoelectric properties are enhanced, but domain walls shift back due to internal mechanical stresses
Solution Approach 1:
The patent optimizes the polarization field parameters (strength, duration, temperature) to achieve stable domain configuration. By carefully controlling these parameters during the polarization process, the patent ensures that the electric field is strong enough to create the necessary asymmetry but not so strong as to cause excessive domain wall shifts, thereby achieving both enhanced piezoelectric properties and improved stability
Solution Approach 2:
The patent creates localized regions of optimized domain structure through controlled polarization. By applying the electric field in a manner that accounts for local stress distributions within the ceramic material, the patent achieves uniform domain alignment that resists back-shiftting, thereby stabilizing the piezoelectric properties
4Measurement precision
If piezoelectric material is polarized below Curie Temperature, then lattice asymmetry is preserved and dipoles form, but polarization cannot be applied above Curie Temperature
Solution Approach 1:
The patent carefully controls the temperature parameter during polarization, maintaining it below the Curie temperature to preserve lattice asymmetry and dipole formation. This precise temperature control enables the polarization process to proceed effectively while ensuring the resulting sensor can operate across a wide temperature range, thereby achieving both measurement precision and adaptability
5Quantity of substance
If sintering is performed at high temperatures to achieve high density, then ceramic material density increases, but manufacturing complexity and energy consumption increase
Solution Approach 1:
The patent optimizes sintering parameters (temperature, time, atmosphere, pressure) to achieve high ceramic density with reduced energy input. By using advanced sintering techniques and carefully controlled parameter combinations, the patent attains dense ceramic structures at lower temperatures and shorter times compared to conventional sintering, thereby reducing energy consumption while maintaining high material density
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
Enables accurate shear force measurement by reducing cross-talk and enabling flexible polarization during or after sensor installation, enhancing signal clarity and production efficiency.
Implementation Method 1
Piezoelectricity is the electric charge that accumulates inside a particular type of solid materials in response to external applied mechanical stress
Implementation Method 2
a strong electric field of several kV/mm is applied to create an asymmetry in the previously unorganized ceramic compound. The electric field causes a reorientation of the spontaneous polarization
Data Source
AI summary
A vehicle brake pad (100) comprising: a support plate (21); a friction pad (20); at least a shear force sensing device; and an electrical circuit configured to collect signals from the shear force sensing device (1); wherein the shear force sensing device (1) comprises: a sheet (2) of piezoelectric material having a first and a second main faces (3, 4) parallel to each other identifying a shear stress direction(S); at least a first digitated reading electrode (5) located on the first main face (3); at least a second digitated reading electrode (6) located on the second main face (4), the first and second reading electrodes (5, 6) having digits (5a, 6a) aligned along a reading direction (R) orthogonal to the stress shear direction(S); at least a first digitated polarizing electrode (7) located on the first main face (3) and interdigitated with the first digitated reading electrode (5); and at least a second digitated polarizing electrode (8) located on the second main face (4) and interdigitated with the second digitated reading electrode (6); and wherein the piezoelectric material has a bulk electric polarization with vector field (E) transversally oriented to the reading direction (R), each pair of aligned digits (5a, 6a) of the first and second reading electrodes (5, 6) enclosing a respective zone (2a) of the piezoelectric material having the vector field (E) most tangentially oriented to the shear stress direction(S).