Integrated Variable Resistor for Bidirectional Motor Control
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Solution Overview
Problem
Conventional electric power tools require multiple discrete variable resistor units for controlling motor direction, which complicates the circuit board structure and increases manufacturing costs.
Innovation Solution
A simplified circuit board design where a single variable resistor unit, formed by non-printed resistive elements like diodes and resistors, is used, with electrodes arranged in distinct regions for each operation direction, allowing a movable contact to generate a voltage signal based on the rotation angle of a manually-operated member, thereby controlling a DC motor under PWM for normal and reverse rotation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple discrete variable resistor units are used for controlling motor direction, then the motor control function is achieved, but the circuit board structure becomes complex
Solution Approach 1:
The patent combines multiple discrete variable resistor units into a single integrated variable resistor unit. The circuit board includes one variable resistor unit with multiple electrodes (first electrode, second electrode, third electrode, fourth electrode) that collectively perform the functions previously requiring separate resistor units. This merging reduces component count and simplifies the overall circuit board structure while maintaining bidirectional motor control capability.
Solution Approach 2:
The single variable resistor unit is designed to perform multiple functions simultaneously. It provides resistance elements for both clockwise and counterclockwise rotation directions, and includes electrodes that can detect rotation angle information across the full range of motion. This multi-functional design eliminates the need for separate dedicated resistor units for each control function.
2Adaptability or versatility
If multiple discrete variable resistor units are used for controlling motor direction, then the motor control function is achieved, but manufacturing cost increases
Solution Approach 1:
The patent merges multiple discrete variable resistor units into a single integrated unit, reducing the total number of components that need to be sourced, assembled, and tested. This consolidation directly reduces manufacturing costs by eliminating redundant components and simplifying the assembly process.
Solution Approach 2:
The invention eliminates the need for multiple separate variable resistor units, effectively discarding the redundant components. By recovering the control functionality into a single unified structure, the patent reduces material costs, assembly labor, and quality inspection requirements.
3Device complexity
If a single variable resistor unit is used, then the circuit board structure is simplified, but the ability to control motor in both directions may be compromised
Solution Approach 1:
The single variable resistor unit is designed with multiple electrodes (first, second, third, fourth electrodes) that enable it to perform multiple control functions. The electrodes are arranged and connected to provide resistance elements for both clockwise and counterclockwise rotation directions, allowing bidirectional motor control from a single component.
Solution Approach 2:
The variable resistor unit is segmented into multiple functional electrodes that can be independently connected to different circuit nodes. This segmentation within the unified structure allows the single unit to provide differentiated control signals for opposite rotation directions while maintaining physical integration.
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 reduces the complexity and cost of the circuit board by integrating multiple functions into a single variable resistor unit, enhancing manufacturing efficiency and maintaining effective motor control in both rotation directions.
Implementation Method 1
The movable contact is arranged to make sliding contact with the circuit board and contacts one of the plurality of electrodes depending on the operation amount of the manually-operated member
Implementation Method 2
A plurality of resistive elements forms the variable resistor unit. The plurality of resistive elements includes at least one diode
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
An electric power tool (10) includes a manually-operated member (14) and a circuit board (15). A first subset of electrodes (P1a-PZa) is arranged in a first region of the circuit board (15) corresponding to a first operation direction (ND) of the manually-operated member (14), A second subset of electrodes (P1b-PZb) is arranged in a second region of the circuit board (15) corresponding to the second operation direction (OD) of the manually-operated member (14). The electrodes of the first and second subsets are electrically connected in common to a variable resistor unit (16).