Brushless Motor Circuit Board Integration for Handheld Power Tools
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Solution Overview
Problem
Handheld power tools with brushless electric motors face issues of increased volume, reliability concerns due to multiple circuit boards, and excessive heat generation from capacitors and power switches, leading to susceptibility to connection failures.
Innovation Solution
A compact handheld grinder design featuring a single circuit board with integrated components such as a rectifier, DC bus capacitors, motor switches, and a power switch, which minimizes inter-board connections, reduces heat generation, and enhances reliability by soldering these components directly onto the board.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple circuit boards are used to support capacitor, power switch and control circuitry, then the power tool can perform required functions, but the volume of the power tool increases and connections between boards become susceptible to wearing out or breaking
Solution Approach 1:
The patent consolidates multiple circuit boards into a single integrated circuit board that houses all electronic components including the rectifier, capacitor, power switch, and control circuitry. This merging eliminates inter-board connections, reducing the risk of connection failure while maintaining compact dimensions suitable for handheld power tools.
2Power
If capacitor and power switch are used to control current flow, then the brushless electric motor can be driven, but undesirable heat is generated
Solution Approach 1:
The patent introduces a pulse width modulation (PWM) controller as an intermediary between the power switch and the brushless electric motor. This PWM controller efficiently switches current delivery to the motor, significantly reducing heat generation compared to traditional linear control methods while maintaining full motor drive capability.
3Ease of manufacture
If several circuit boards are used to support electronic components, then the power tool can be assembled with separate functional modules, but the device complexity increases and connections are more susceptible to failure
Solution Approach 1:
The patent integrates all electronic components including rectifier, capacitor, power switch, and control circuitry onto a single circuit board, eliminating the need for multiple separate functional modules. This reduces device complexity while maintaining ease of manufacture through standardized PCB assembly processes.
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 solution results in a more compact, reliable, and less heat-generating power tool with reduced susceptibility to connection failures, improving overall performance and user experience.
Implementation Method 1
a rectifier configured to receive power from an alternating current (AC) power source and operable to convert an alternating current to a direct current
Implementation Method 2
a capacitor connected electrically between the rectifier and the switching arrangement, wherein the capacitor is coupled in parallel across the rectifier
Implementation Method 3
a brushless electric motor operable to rotate an output shaft in response to the direct current
Data Source
AI summary
A power tool comprising a housing, a motor, and a circuit board residing in the housing is provided. A rectifier that receives an alternating current and converts the alternating current to a direct current, a switching arrangement having a plurality of motor switches connected electrically between the rectifier and the motor, and a capacitor connected electrically between the rectifier and the switching arrangement, are mounted on a rear portion of a planar surface of the circuit board. A switching arrangement and at least one heat sink in thermal communication therewith are mounted on a front portion of the planar surface of the circuit board.