Demountable Sensor Housing for EC Motor Repair
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Solution Overview
Problem
Existing electronically commutated motors in applications like lawnmowers are difficult to disassemble, repair, or fault-find once assembled and embedded in potting compound, requiring replacement of the entire motor and control assembly in case of failure.
Innovation Solution
The motor design features a demountable sensor housing with Hall effect sensors mounted on a secondary circuit board, allowing for precise positioning and easy replacement, along with a detachable control unit that can be secured with potting compound, enabling fault finding and repairs without replacing the entire motor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the motor and control electronics are constructed as a unitary unit with potting compound, then the motor is protected and compact, but disassembly, repair, or fault finding becomes impossible
Solution Approach 1:
The motor assembly is divided into separate functional modules: the motor housing with field pack, the sensor housing with Hall effect sensors, and the control electronics. This segmentation allows individual components to be accessed, removed, or replaced without disassembling the entire unit, resolving the contradiction between protective integration and repairability.
Solution Approach 2:
The Hall effect sensors are extracted from the potting compound and mounted on a separate circuit board within the sensor housing. This extraction enables the sensors to be independently accessed and replaced, eliminating the need to dismantle the entire motor assembly for sensor maintenance or fault finding.
2Measurement precision
If Hall effect sensors are positioned very close to rotor magnets (maximum 1.8mm), then measurement precision is improved, but positioning accuracy requirements increase
Solution Approach 1:
The sensor housing is pre-positioned and secured to the motor housing with locating features that establish the correct sensor-to-rotor distance before final assembly. This preliminary positioning action ensures that when the motor is assembled, the Hall effect sensors are automatically at the optimal distance from the rotor magnets, achieving both precise measurement and relaxed manufacturing tolerances.
Solution Approach 2:
The sensor housing acts as an intermediary component between the motor housing and the Hall effect sensors. It provides a rigid mounting structure with built-in locating features that maintain precise sensor positioning relative to the rotor, eliminating the need for complex alignment procedures during assembly.
3Reliability
If the entire motor assembly is replaced upon failure, then reliability is maintained, but cost and time loss increase
Solution Approach 1:
The motor assembly is segmented into independently serviceable components, allowing faulty parts such as Hall effect sensors or control electronics to be replaced individually rather than replacing the entire motor. This reduces both the time and cost of maintenance while maintaining system reliability.
Solution Approach 2:
Individual components that fail can be discarded and replaced while the functional portions of the motor assembly are recovered and retained. This selective replacement approach minimizes waste and reduces maintenance time compared to replacing the entire assembly.
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 design allows for the motor to be repaired and maintained without replacing the entire assembly, reducing costs and enabling precise sensor positioning for optimal performance, while also eliminating the need for potting compound around the field pack, enhancing reliability and maintainability.
Implementation Method 1
An essential part of an EC motor is the use of three Hall effect sensors to detect the position and rotation speed of the rotor, which contains permanent magnets
Data Source
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AI summary
We describe an electronically commutated motor assembly. The motor assembly includes a motor housing (20) which includes a motor housing aperture (52) and a sensor housing (42) within which one or more Hall effect sensors (44) are located. The sensor housing (42) is adapted to engage said motor housing aperture (52) to position said one or more Hall effect sensors (44) in slots between teeth of stator laminations of the motor.