Rotation Sensor Unit Coaxial Encoder Positioning
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Solution Overview
Problem
Conventional rotation sensor units require machining to form recesses in shafts for encoder fitting, limiting material choices to non-magnetic materials and complicating the positioning of encoders for accurate magnetism detection.
Innovation Solution
A rotation sensor unit design that positions the encoder coaxially with the shaft using a holder fitted to the inner diameter surface of the inner race, allowing for radial positioning without forming a hole in the shaft, and utilizing non-magnetic or magnetic materials for the holder and shaft to maintain magnetic field integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a recess is formed in the shaft to fit the encoder, then the encoder can be positioned coaxially with the shaft, but the shaft material is limited to non-magnetic materials and additional machining processes are required
Solution Approach 1:
A holder is introduced as an intermediary component between the shaft and the encoder. The holder is fitted to the inner diameter surface of the inner race and provides a mounting structure for the encoder, eliminating the need to machine recesses in the shaft. This mediator component simplifies the shaft manufacturing process while maintaining precise encoder positioning.
Solution Approach 2:
The positioning function is segmented from the shaft to a separate holder component. Instead of integrating the encoder directly into the shaft through recesses, the system is divided into the shaft, the holder (fitted to the inner race), and the encoder, allowing each component to be manufactured independently with optimal material selection and processing.
2Reliability
If the shaft is made of non-magnetic material to prevent flux interference, then magnetic field integrity is maintained, but material selection is restricted
Solution Approach 1:
The holder acts as a non-magnetic intermediary between the magnetic encoder and the shaft. This allows the shaft to be made of magnetic material while the holder (made of non-magnetic material) ensures that magnetic flux from the encoder to the detection element is not intercepted, thus maintaining magnetic field integrity while expanding material selection flexibility.
3Measurement precision
If the encoder area is made much smaller than the shaft end surface, then detection accuracy is improved, but the encoder becomes more difficult to position and stabilize
Solution Approach 1:
The holder serves as a precise positioning intermediary that facilitates accurate placement of the small-area encoder on the inner race. The holder provides reference surfaces and mounting features that enable stable and precise positioning of the compact encoder, overcoming the difficulty of positioning small components with high accuracy.
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 encoder positioning without machining the shaft, allows for the use of magnetic materials for the shaft, and reduces part count and complexity by creating a magnetically shielded space, enhancing detection accuracy and unit compactness.
Implementation Method 1
The encoder is a magnet comprising north and south poles provided alternately in a circumferential direction around an axis of the shaft
Data Source
AI summary
A rotation sensor unit includes an encoder, a holder radially positioning the encoder, and a rolling bearing having an inner race. The rolling bearing is fitted around the shaft so that one end of the inner diameter surface of the inner race protrudes from the end of the outer diameter surface of the shaft. The holder has a screwed portion fitted in the inner race, positioning the encoder coaxially with the shaft. The holder is non-magnetic, having a retaining portion in which the encoder is axially pressed. The encoder is a plastic magnet, with protrusions and recesses formed integrally on its outer diameter surface and biting the inner diameter surface of the retaining portion to prevent the encoder from rotating. With the holder screwed to the shaft, the encoder is disposed between the magnetism detection element and the one end of the shaft.