Torque Detection Device Tubular Magnet Molding
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Solution Overview
Problem
Existing torque detection devices face issues with tubular magnets cracking due to molding pressure during assembly, which complicates the assembly process and increases costs.
Innovation Solution
The torque detection device fixes the tubular magnet to a rotating body by molding a synthetic resin body on the outer circumferential portion, distributing the molding pressure along the longitudinal direction to prevent cracking and reducing the amount of molding material needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the tubular magnet is molded with synthetic resin material and externally fitted to the input shaft, then the workability during assembly is improved, but the number of manufacturing steps increases
Solution Approach 1:
The patent combines the molding process and the fixing process into a single integrated operation. The synthetic resin material is molded directly onto the input shaft, simultaneously achieving both the molding of the tubular magnet and its fixation to the shaft, thereby eliminating separate assembly steps
2Device complexity
If the tubular magnet is molded in the cavity with molten synthetic resin material, then the assembly process is simplified, but the tubular magnet may crack due to molding pressure
Solution Approach 1:
The patent applies different properties to different parts of the synthetic resin material. The resin is formulated to be soft and flexible at the molding stage to accommodate the tubular magnet without cracking, and then hardens to provide strong fixation. This local variation in material properties allows both simplified assembly and crack prevention
3Strength
If radial inner pressure is applied to the tubular magnet during assembly, then the tubular magnet can be fixed to the input shaft, but cracks are likely to occur at the inner circumferential portion
Solution Approach 1:
Instead of applying pressure radially inward to the tubular magnet, the patent inverts the approach by having the tubular magnet press against the synthetic resin material during molding. The resin material deforms under this pressure and then hardens, creating fixation without subjecting the magnet to damaging radial inner pressure
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 approach prevents cracking of the tubular magnet, simplifies the assembly process, and reduces costs by minimizing the amount of molding material required, while ensuring the tubular magnet remains securely fixed and maintains its magnetic characteristics.
Implementation Method 1
when the molding is carried out in the cavity, the molding pressure of the molten synthetic resin material injected in the cavity is applied to an inner circumferential face of the tubular magnet
Implementation Method 2
a tubular magnet, provided by sintering ferrite powder into a tubular shape
Data Source
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AI summary
An inventive torque detection device includes: a magnetic circuit forming member having a tubular magnet provided at a first rotating body, and a magnetic ring that is located circumferentially of the tubular magnet and rotated together with a second rotating body connected to the first rotating body; a magnetic flux collecting ring part for collecting a generated magnetic flux; a detection part for detecting, based on a density of the collected magnetic flux, a torque applied to the first or second rotating body; and a molded body that is molded at an outer circumferential portion of the first rotating body, and is joined to longitudinal both sides of the tubular magnet so as to fix the tubular magnet to the first rotating body. A molding pressure, generated when the tubular magnet is molded, is applied in the longitudinal direction of the tubular magnet.