Motor Case Sensor Layout for Accurate Rotor Position Detection
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Solution Overview
Problem
Electric work machines may not be driven appropriately due to reduced detection accuracy of magnetic sensors, which is exacerbated by external interference and heat from the rotor.
Innovation Solution
The electric work machine incorporates a motor case that houses the stator, rotor, and sensor magnets, with the sensor board and magnetic sensors protected within the motor case, along with a cooling fan to reduce heat exposure and external interference, ensuring accurate detection of rotor position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic sensors are placed inside the motor case to detect rotor position, then detection accuracy is improved, but the sensors are exposed to heat from the rotor and external interference, which reduces reliability
Solution Approach 1:
A non-magnetic heat insulating plate is introduced as an intermediary component between the magnetic sensors and the rotor. This plate serves dual functions: it thermally isolates the sensors from rotor heat while maintaining magnetic field transparency, thus preserving detection accuracy while improving sensor reliability through thermal protection
Solution Approach 2:
The heat insulating plate is strategically positioned only in the region where thermal protection is needed for the magnetic sensors, while maintaining overall magnetic field detection capability. The plate's material properties are specifically selected to be non-magnetic and heat-insulating, providing localized protection without compromising the sensing function
2Measurement precision
If the sensor board is positioned close to the rotor for accurate detection, then measurement precision is improved, but heat exposure from the rotor increases, affecting sensor performance
Solution Approach 1:
The non-magnetic heat insulating plate acts as a thermal intermediary that allows the sensor board to remain positioned close to the rotor for accurate detection while blocking heat transfer from the rotor to the sensors, thus maintaining both precision and acceptable temperature levels
Solution Approach 2:
The thermal conductivity parameter of the plate is specifically selected to be low (heat-insulating) while maintaining magnetic permeability, creating a selective barrier that changes the thermal parameter relationship between the rotor and sensors without affecting magnetic field detection
3Reliability
If the motor case structure is modified to protect sensors from heat and interference, then reliability is improved, but device complexity increases
Solution Approach 1:
The heat insulating plate performs multiple functions simultaneously: thermal insulation, magnetic field transparency, and structural support for the sensor board. This multi-functionality reduces the need for additional separate components, thereby improving reliability without proportionally increasing device complexity
Solution Approach 2:
The protective function against heat and interference is merged into a single heat insulating plate component rather than requiring separate protective structures, simplifying the overall motor case design while achieving the desired reliability improvement
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 motor case protects the sensor magnets and board from external interference and heat, maintaining detection accuracy of the magnetic sensors, enabling appropriate control of the motor and proper operation of the electric work machine.
Implementation Method 1
a magnetic sensor located inside the motor case to detect the magnet
Implementation Method 2
a cooling fan to reduce heat exposure and external interference
Data Source
AI summary
An electric work machine is driven appropriately. An electric work machine includes a motor including a stator, a rotor rotatable relative to the stator, and a rotor shaft fixed to the rotor, an output unit drivable by the rotor shaft, a motor case accommodating the stator and the rotor, a magnet located inside the motor case and rotatable by the rotor, and a magnetic sensor located inside the motor case to detect the magnet.