Piezoelectric Pressure Sensor Single Crystal Design
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Solution Overview
Problem
Piezoelectric pressure sensors used in high-performance internal combustion engines face challenges with high temperature and pressure loads, leading to potential breakdowns of the piezoelectric measuring element, which can result in structural complexity, compactness issues, and risk of sensor parts entering the combustion chamber, causing damage.
Innovation Solution
A piezoelectric pressure sensor design where a single crystal element is clamped between a pressure plunger and a reference electrode, with a laterally positioned electrically insulating sleeve, ensuring the crystal element's fragments are held in place, maintaining membrane support and thermal properties, even if it breaks, and utilizing either transverse or longitudinal piezo effects depending on the crystal shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multiple disc-shaped or rod-shaped crystal elements are used in conventional pressure sensors, then the sensor can withstand high pressures, but the structural complexity increases and the risk of fragments entering the combustion chamber increases
Solution Approach 1:
The patent merges multiple separate crystal elements into a single monolithic piezoelectric crystal body. This single crystal element replaces the conventional stack of disc-shaped or ring-shaped crystal elements, reducing structural complexity while maintaining the ability to withstand high pressures up to 1000 bar through optimized geometry and material properties.
Solution Approach 2:
The single crystal element is designed with specific geometric segmentation including a flat base surface, a curved lateral surface, and a top surface with a central opening. This segmentation optimizes stress distribution and prevents catastrophic failure into multiple fragments, addressing both strength requirements and fragment containment.
2Measurement precision
If multiple crystal elements are used to measure high pressures, then measurement capability is improved, but the height of the sensor increases
Solution Approach 1:
The patent transitions from a multi-element stacked design (increasing height in the axial direction) to a single crystal element with optimized three-dimensional geometry. The curved lateral surface and central opening create a compact form factor that reduces overall sensor height while maintaining pressure measurement precision through the piezoelectric effect.
3Reliability
If crystal elements are clamped with minimal contact to reduce breakage risk, then reliability improves, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by designing specific clamping features at critical locations: a flat base surface for stable mounting, a curved lateral surface for controlled contact, and a top surface with central opening for electrode access. This localized optimization of surface geometry provides reliable clamping while accommodating manufacturing tolerances through the inherent compliance of the curved surfaces.
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 enhances robustness, maintains sensitivity, and prevents internal damage by keeping the sensor membrane intact and reducing thermal stress, achieving a compact and structurally simple solution suitable for high-pressure environments.
Implementation Method 1
a piezoelectric measuring element (4) arranged between a sensor membrane (5) located on the front of the inner housing (10) and a housing shoulder (11a, 11b) of the inner housing (10), wherein the piezoelectric measuring element (4) consists of a single crystal element (6a, 6b)
Data Source
Figure 1~3
Figure 4
AI summary
The invention relates to a piezoelectric pressure sensor for measuring high pressures, comprising a housing (1) that can be inserted into a measuring bore and a piezoelectric measuring element (4) arranged between a sensor membrane (5) located on the front of the housing (1) and an inner housing shoulder (11a; 11b). According to the invention, the piezoelectric measuring element (4) consists of a single crystal element (6a; 6b) which is clamped with its base surface (13) and its opposite top surface (14) between a pressure plunger (9) of the sensor membrane (5) and a discharge electrode (8) supported on the housing shoulder (11a; 11b), wherein a lateral surface (7a; 7b) of the crystal element (6a; 6b) connecting the base surface (13) with the top surface (14) largely rests against a positioning sleeve (12a; 12b) arranged in the housing (1).