Four-Pole Wiper Motor Reduces Inertia and Weight
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Solution Overview
Problem
Wiper motors used in vehicle wiper devices face challenges with increased weight and size due to the need for thicker yokes for magnetic flux, leading to higher inertia and reduced control accuracy.
Innovation Solution
A wiper motor design utilizing a four-pole magnet with alternately disposed magnetic poles, a speed reduction mechanism, and an absolute position detecting sensor to control the armature rotation, reducing weight and size while enhancing wiping accuracy by using a two-brush configuration and a sensor magnet for precise control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a two-pole magnet and two brushes are used to enable forward and reverse rotation, then the motor can achieve bidirectional rotation control, but the yoke thickness must be increased to accommodate the magnetic flux, resulting in increased weight and size
Solution Approach 1:
The patent changes the magnetic pole configuration from two-pole to four-pole, and adjusts the brush spacing from 180 degrees to 90 degrees. This parameter change allows the use of a thinner yoke while maintaining bidirectional rotation capability, thereby reducing motor weight and size without sacrificing adaptability
2Adaptability or versatility
If a two-pole magnet and two brushes are used to enable forward and reverse rotation, then the motor can achieve bidirectional rotation control, but the yoke thickness must be increased to accommodate the magnetic flux, resulting in increased inertia
Solution Approach 1:
By changing the magnetic pole configuration to four poles and positioning brushes at 90-degree intervals, the patent reduces the required yoke thickness. This reduction in yoke thickness directly decreases the overall mass of the motor, thereby reducing inertia while maintaining the ability to control forward and reverse rotation
3Adaptability or versatility
If a two-pole magnet and two brushes are used to enable forward and reverse rotation, then the motor can achieve bidirectional rotation control, but the yoke thickness must be increased to accommodate the magnetic flux, resulting in deteriorated control accuracy of the wiper
Solution Approach 1:
The patent implements parameter changes including four-pole magnet configuration and 90-degree brush spacing, which reduce motor weight and inertia. The reduced inertia enables more precise and responsive control of the wiper arm, improving control accuracy while maintaining bidirectional rotation capability
Solution Approach 2:
The patent incorporates an absolute position detection sensor that provides feedback on the armature shaft position. This feedback mechanism enables precise control of the wiper arm position and speed, compensating for any potential losses from the modified motor configuration and ensuring high control accuracy
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 improved weight and size reduction, lower inertia, and enhanced control accuracy and responsiveness of the wiper motor, allowing for more precise wiping operations.
Implementation Method 1
a magnet formed with four poles in which different magnetic poles are alternately disposed on an inner peripheral surface of the yoke
Implementation Method 2
an armature including an armature shaft which has one end rotatably supported by a bottom portion of the yoke, a commutator which is fixed to the armature shaft, and a core which is fixed to the armature shaft and around which a winding wire is wound, wherein the armature is rotatably disposed on an inner side of the magnet
Implementation Method 3
an absolute position detecting sensor disposed so as to face the sensor magnet; and a control board having the absolute position detecting sensor attached thereto, the control board being disposed between the gear housing and the gear housing cover, and configured to control the rotation of the armature shaft by using a signal corresponding to the change of magnetic field generated by the sensor magnet and detected by the absolute position detecting sensor
Data Source
AI summary
A wiper motor has: a magnet disposed on the yoke and formed with at least four poles; an armature disposed on an inner side of the magnet; a speed reduction mechanism unit having an output shaft for transmitting the rotation of the armature shaft; a gear housing connected to the yoke; a gear housing cover covering an opening of the gear housing; a magnet attached to the output shaft of the speed reduction mechanism unit; an absolute position detecting sensor disposed so as to face the magnet; and a control board having the absolute position detecting sensor attached thereto, the control board being disposed between the gear housing and the gear housing cover, and configured to control the rotation of the armature shaft.