Skewed Rotor Core Structure for Lower Cogging Torque
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Solution Overview
Problem
The existing electric power steering (EPS) motor manufacturing processes are complex and time-consuming, with difficulties in managing the skew angle of rotor cores, which also results in higher cogging torque.
Innovation Solution
The motor design features a rotor with stacked first and second rotor cores, where the surfaces and holes are misaligned in the circumferential direction, allowing for easier assembly and alignment without separate guides, reducing manufacturing processes and time, and minimizing cogging torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If multiple rotor cores are assembled to form a skew, then cogging torque is reduced, but the number of manufacturing processes and process time increase
Solution Approach 1:
The patent merges multiple rotor cores into a single integrated rotor core structure. The first and second rotor cores are formed as one piece with misaligned surfaces and aligned holes, eliminating the need for separate assembly processes while maintaining the skew configuration that reduces cogging torque.
Solution Approach 2:
The rotor core is segmented into multiple functional regions (first rotor core region and second rotor core region) within a single structure. This segmentation allows different portions to have different orientations (misaligned surfaces) while maintaining alignment of through-holes, achieving cogging torque reduction without multiple assembly steps.
2Object-generated harmful factors
If multiple rotor cores are assembled to form a skew, then cogging torque is reduced, but skew angle management becomes difficult
Solution Approach 1:
The rotor core employs asymmetric design where the first and second rotor core surfaces are intentionally misaligned in the circumferential direction by a predetermined angle. This asymmetric configuration creates the skew effect needed to reduce cogging torque while the aligned through-holes provide a reference for consistent manufacturing.
Solution Approach 2:
The invention changes the geometric parameters of the rotor core by creating misaligned surfaces at specific angles while maintaining aligned through-holes. This parameter configuration allows the skew angle to be built into the mold design, making it easier to manage during manufacturing rather than requiring precise post-assembly adjustment.
3Object-generated harmful factors
If rotor cores are misaligned in circumferential direction, then cogging torque is reduced, but manufacturing complexity increases
Solution Approach 1:
The misaligned rotor core structure serves multiple functions simultaneously: it reduces cogging torque through skew configuration, provides aligned through-holes for magnet insertion and shaft mounting, and creates distinct regions for different magnetic pole arrangements. This multi-functionality reduces the need for additional components or assembly steps.
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 significantly reduces cogging torque, simplifies the management of rotor skew angles, and decreases the number of manufacturing processes and time required, enhancing the efficiency and stability of the motor.
Implementation Method 1
An electric power steering (EPS) system controls a vehicle's steering shaft to be driven by driving a motor using an electronic control unit (ECU) according to driving conditions detected by a vehicle speed sensor, a torque angle sensor, a torque sensor, and the like. The motor includes a stator and a rotor.
Implementation Method 2
A cogging torque may be generated due to a difference in magnetic permeability between the stator formed of a metal material and an open slot which is a space that is empty when the rotor rotates.
Data Source
AI summary
The present invention may provide a motor including a rotor and a stator disposed to correspond to the rotor, wherein the rotor includes a first rotor core and a second rotor core stacked on each other in an axial direction, the first rotor core includes a first surface on which a magnet is disposed and a first hole which passes through the first rotor core in the axial direction, the second rotor core includes a second surface on which a magnet is disposed and a second hole which passes through the second rotor core in the axial direction, the first surface and the second surface are disposed to be misaligned with each other around a center in the axial direction, and the first hole and the second hole are disposed to be aligned with each other.