Driveshaft Speed Sensor Assembly with Axial Slots
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Solution Overview
Problem
Existing driveshaft speed sensors in turbomachinery face challenges due to excessive mass and volume, making them unsuitable for placement on the driveshaft forward of the compressor impeller, where high temperatures, pressures, and vibrations necessitate accurate speed measurement.
Innovation Solution
A driveshaft speed sensor assembly featuring a sensing portion with an axial bore and radially spaced axial slots that induce a change in the magnetic reluctance of an electromagnetic sensor as the driveshaft rotates, generating an output signal representative of rotational speed, allowing for accurate measurement without the need for a large exciter rotor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional exciter rotor with multiple teeth is used for shaft speed sensing, then the sensor can detect rotational speed through magnetic reluctance changes, but the exciter rotor has excessive mass and volume for placement on the driveshaft forward of the compressor impeller
Solution Approach 1:
The invention extracts the speed-sensing function from a separate exciter rotor and integrates it directly into the driveshaft by forming axial slots radially spaced around the driveshaft periphery. These slots penetrate through the driveshaft into the axial bore, eliminating the need for a separate exciter rotor component while maintaining the magnetic reluctance change mechanism for speed detection.
Solution Approach 2:
The invention merges the exciter function and the driveshaft into a single integrated structure. The axial slots are formed directly in the driveshaft material, combining the rotational element with the sensing element, thereby eliminating the mass and volume of a separate exciter rotor while preserving the speed sensing capability through magnetic reluctance variations.
2Measurement precision
If a cup member with perforations is used as an exciter rotor, then the magnetic circuit reluctance changes during rotation for speed sensing, but the assembly still has excessive volume for the intended application
Solution Approach 1:
The invention extracts the exciter functionality from a separate cup member assembly and integrates it directly into the driveshaft structure. The axial slots are formed by boring or machining the driveshaft itself, eliminating the need for a separate cup member with perforations and reducing the overall sensor assembly volume.
Solution Approach 2:
The driveshaft serves multiple functions: it transmits mechanical power and simultaneously acts as the exciter element for speed sensing. The axial slots formed in the driveshaft perform the dual role of maintaining structural integrity while creating the magnetic reluctance variations needed for speed detection, eliminating the need for separate exciter components.
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 solution enables accurate driveshaft speed measurement with reduced sensor mass and volume, suitable for high-stress environments, providing reliable rotational speed data and positional accuracy through induced pulses or frequency signals.
Implementation Method 1
rotation of the driveshaft causes the slots in the sensing portion to sequentially pass through the magnetic circuit of the electromagnetic sensor, thereby causing a change in the reluctance of its magnetic circuit that induces the electromagnetic sensor to generate an output signal
Implementation Method 2
a change in the reluctance of its magnetic circuit that induces the electromagnetic sensor to generate an output signal that is representative of the rotational speed of the driveshaft
Data Source
AI summary
A speed sensor assembly comprises: a driveshaft with a driveshaft axis, a sensing portion of the driveshaft having an axial bore along the driveshaft axis and multiple axial slots radially spaced around the sensing portion that penetrate through the driveshaft into the axial bore; and at least one electromagnetic sensor with a magnetic circuit proximate the sensing portion of the driveshaft; wherein rotation of the driveshaft causes the slots in the sensing portion to sequentially pass through the magnetic circuit of the electromagnetic sensor, thereby causing a change in the reluctance of its magnetic circuit that induces the electromagnetic sensor to generate an output signal that is representative of the rotational speed of the driveshaft.