Brushless Motor Sensor Arrangement for Wiper Precision
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Solution Overview
Problem
Conventional brushless motors for wiper apparatuses face challenges in achieving high-precision control and size/weight reduction due to suboptimal sensor arrangements, leading to detection precision issues and increased component count.
Innovation Solution
A brushless motor design with a specific sensor arrangement where the first and second sensors face a magnet on one surface and a third sensor faces the magnet between them on an opposite surface, allowing equal distances for precise control and reducing the number of components by mounting all sensors on a single board, enabling closer magnet placement without increasing size or weight.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If Hall ICs are arranged at given intervals along the rotation direction on a single control board, then the number of components is reduced, but the detection precision deteriorates due to unequal distances from the magnet
Solution Approach 1:
The patent transitions from a two-dimensional arrangement (all sensors on one surface) to a three-dimensional arrangement (sensors on both surfaces of the control board). By placing the third Hall IC on the opposite surface of the control board, the patent achieves equal distances from all three Hall ICs to the magnet while maintaining a compact single-board structure, thus resolving the contradiction between component reduction and detection precision.
2Measurement precision
If the diameter of the magnet for the rotating shaft is increased to improve angle detection precision, then the detection precision improves, but the size and weight of the motor increase
Solution Approach 1:
The patent utilizes the third dimension (depth/thickness of the control board) by mounting sensors on both surfaces. This allows the magnet to be positioned closer to the sensors without increasing its diameter, achieving high detection precision while maintaining a compact motor size and weight.
Solution Approach 2:
The patent replaces the mechanical approach of increasing magnet diameter with a spatial arrangement approach using three Hall ICs positioned at equal distances on both surfaces of the control board. This substitution achieves the same detection precision goal without the penalty of increased size and weight.
3Measurement precision
If the distance between the magnet and Hall ICs is reduced to improve detection precision, then the detection precision improves, but the layout difficulty increases and size must be increased to ensure clearance
Solution Approach 1:
By utilizing both surfaces of the control board, the patent creates additional spatial freedom for component layout. The third Hall IC on the opposite surface can be positioned to achieve equal distances to the magnet, simplifying the layout process and reducing clearance requirements compared to a single-surface arrangement.
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 configuration enhances angle detection precision and reduces the motor's size and weight by allowing precise control of the motor unit while minimizing component count and complexity.
Implementation Method 1
three Hall ICs facing the magnet for the rotating shaft and one MR sensor facing the magnet for the output shaft are provided on a surface of the control board which faces the rotating shaft and the output shaft
Implementation Method 2
one MR sensor facing the magnet for the output shaft are provided on a surface of the control board which faces the rotating shaft and the output shaft
Data Source
AI summary
An object of the present invention is to provide a brushless motor and a wiper apparatus which allow high-precision control of a motor unit, and which can be reduced in size and weight. The first surface (91) of the control board (90) is provided on the same side as the rotating shaft (46) and the output shaft (51) so as to face the sensor magnet (MG1), the first and second Hall ICs (94a) and (94b) are mounted on the first surface (91). The second surface (92) of the control board (90) is provided on the opposite side from the first surface (91), and the third Hall IC (94c) is mounted on the second surface (92), and located between the first and second Hall ICs (94a) and (94b) so as to face the sensor magnet (MG1). In addition, the MR sensor (95) is mounted on the first surface (91) so as to face the second sensor magnet (MG2).