Micromechanical Sensor Torsion Stiffness Vibration Isolation
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Solution Overview
Problem
Micromechanical sensors are sensitive to external mechanical vibrations, particularly in environments like engine compartments of motor vehicles, where they can be affected by low-frequency vibrations, leading to cross-sensitivity and interference.
Innovation Solution
The micromechanical sensor incorporates a spring system with a torsion mode resonant frequency lower than the vibration mode resonant frequency, combined with a damping structure, to reduce sensitivity to external vibrations. This is achieved by configuring the torsion means with a short length and high stiffness, and using damping elements to counteract vibrational motions, thereby separating excitation frequencies and minimizing deflection out of the plane of vibration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the sensor uses a conventional spring system with longer torsion means, then the manufacturing is easier and structure is simpler, but the sensor becomes more sensitive to external mechanical vibrations and has higher cross-sensitivity
Solution Approach 1:
The patent changes the physical parameters of the torsion means by significantly reducing its length (to less than one-half, preferably less than one-third, particularly preferably less than one-fourth, very particularly preferably less than one-fifth of the rocker width) and adjusting its stiffness characteristics. This parameter change separates the first resonant frequency of the torsion mode from the second resonant frequency of the vibration mode, making the sensor insensitive to low-frequency vibrations (2,000 Hz to 10,000 Hz) while maintaining the desired torsional response.
Solution Approach 2:
The patent introduces a damping structure that dynamically counteracts vibrational motions of the rocker structure. The damping structure includes damping elements (such as damping electrodes and damping counter electrodes) that generate damping forces opposing the vibrational motion, thereby reducing the amplitude of unwanted vibrations without affecting the primary sensing function.
2Measurement precision
If the torsion means length is greatly shortened to increase in-plane stiffness, then the second resonant frequency increases disproportionately and cross-sensitivity decreases, but the manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise parameter ranges for the torsion means length (less than one-half, preferably less than one-third, particularly preferably less than one-fourth, very particularly preferably less than one-fifth of the rocker width) to achieve the desired frequency separation. These parameter changes are designed to provide robust performance across the specified range, balancing manufacturing feasibility with performance requirements.
Solution Approach 2:
The patent performs preliminary design optimization by pre-calculating and pre-setting the torsion means length and stiffness characteristics during the design phase to achieve the target frequency separation. This preliminary action ensures that the sensor meets performance specifications before manufacturing, reducing the need for post-manufacturing adjustments and minimizing the impact of manufacturing tolerances.
3Adaptability or versatility
If the sensor operates in engine compartment environments with low-frequency vibrations, then it must handle harsh conditions, but conventional sensors generate false signals due to cross-sensitivity
Solution Approach 1:
The patent modifies the resonant frequency parameters of the spring system by shortening the torsion means and adjusting its stiffness, thereby separating the first resonant frequency (torsion mode) from the second resonant frequency (vibration mode). This frequency separation ensures that low-frequency vibrations (2,000 Hz to 10,000 Hz) typical of engine compartment environments do not excite the sensing mode, eliminating false signals while maintaining adaptability to harsh environments.
Solution Approach 2:
The patent converts the harmful effect of low-frequency vibrations into a beneficial frequency separation mechanism. By designing the spring system with specific dimensional parameters, the vibrations that would normally cause cross-sensitivity are transformed into a design feature where the vibration frequency falls between the separated resonant frequencies, effectively filtering out interference and improving environmental robustness.
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 sensor becomes less sensitive to external interferences, with a reduced cross-sensitivity and increased damping of vibrational motions, allowing it to operate effectively in noisy environments like engine compartments without significant deformation or false signal generation.
Implementation Method 1
a damping structure (30) is provided which is configured for damping a vibrational motion of the rocker structure (20) along the plane of vibration (100')
Implementation Method 2
The micromechanical sensor includes a spring system with a torsion mode, wherein the rocker structure (20) is connected to the substrate (10) via the spring system (40), wherein the spring system (40) has a torsion mode with a torsion axis (102')
Data Source
AI summary
A micromechanical sensor is provided which includes a substrate having a main plane of extension and a rocker structure which is connected to the substrate via a torsion means. The torsion means extends primarily along a torsion axis, and the torsion axis is situated essentially in parallel to the main plane of extension of the substrate. The rocker structure is pivotable about the torsion axis from a neutral position into a deflected position, and the rocker structure has a mass distribution which is asymmetrical with respect to the torsion axis. The mass distribution is designed in such a way that a torsional motion of the rocker structure about the torsion axis is effected as a function of an inertial force which is oriented along a Z direction which is essentially perpendicular to the main plane of extension of the substrate.