Brushless Wiper Motor Rotor Structure for High Speed and Torque
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Brushless motors used in wiper motors face challenges in achieving high-speed rotation and high torque while maintaining cost-effectiveness, as existing methods either require increased magnet usage for high torque or struggle with high-speed rotation due to high inductance values.
Innovation Solution
A motor design featuring a stator with radially inward teeth and a rotor with ferrite magnets and salient poles, where the radial thickness of magnets is smaller at ends than at intermediate portions, and salient poles protrude radially outward, reducing inductance and demagnetizing fields, and setting electrical angles to optimize torque and reduce cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the current supply is advanced and widened to achieve high-speed rotation, then motor speed increases, but inductance of d-axis and q-axis becomes high which prevents easy speed increase
Solution Approach 1:
The patent changes the geometric parameters of the rotor structure, specifically setting the width of salient poles to 40° or less in electrical angle and optimizing the ratio between number of magnetic poles and teeth to 2:3. These parameter changes reduce the inductance values of both d-axis and q-axis, enabling high-speed rotation through advance and wide angle current supply without being constrained by high inductance.
2Force
If the amount of magnets is increased to achieve high torque, then torque increases, but magnet cost increases
Solution Approach 1:
The patent optimizes geometric parameters including setting salient pole width to 40° or less in electrical angle and the ratio of magnetic poles to teeth to 2:3. These parameter optimizations improve torque efficiency, allowing high torque output with reduced magnet quantity, thereby suppressing magnet cost while achieving the desired torque performance.
3Speed
If salient pole width is reduced to reduce inductance, then high-speed rotation becomes easier, but torque generation may be affected
Solution Approach 1:
The patent sets the salient pole width to 40° or less in electrical angle, which reduces inductance and facilitates high-speed rotation. Simultaneously, the patent optimizes the ratio between the number of magnetic poles and teeth to 2:3, ensuring adequate torque generation despite the reduced salient pole width. This combination of parameter changes achieves both high-speed rotation capability and sufficient torque output.
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 design achieves high-speed rotation and torque while suppressing torque ripple and cogging, and maintaining cost-effectiveness by using ferrite magnets instead of rare earth magnets, enhancing magnetic flux concentration and reducing demagnetization.
Implementation Method 1
In the stator, an interlinkage magnetic flux is formed by supplying power to the coil
Implementation Method 2
a magnetic attractive force or repulsive force is generated between the interlinkage magnetic flux formed in the stator and the permanent magnets disposed in the rotor core, which causes the rotor to rotate continuously
Data Source
Figure 1
Figure 2
Figure 3
AI summary
A motor (2)includes: a stator (8) that includes a stator core (20) being ring-shaped and a plurality of teeth (22) that protrudes radially inward from an inner peripheral surface of the stator core (20); coils (24) wound around the teeth (22); a shaft (31) that rotates around a rotation axis on the radial inner side of the stator core (20); a rotor core (32) that is fixed to the shaft (31) and takes the rotation axis as a radial center; magnets (33) which are disposed on an outer peripheral surface (32b) of the rotor core (32) and a radial thickness of which at end portions (33s) on both sides in the circumferential direction around the rotation axis is smaller than a radial thickness in a circumferential intermediate portion; and salient poles (35) that are formed between magnets (33) adjacent in the circumferential direction of the outer peripheral surface (32b) of the rotor core (32) and protrude radially outward from the end portions (33s) of the magnets (33) in the circumferential direction, the width dimensions of the salient poles (35) in the radial direction being set to 40° or less in a form of an electrical angle.