Brush Assembly EMI Suppression Circuit Board for Power Tools
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Power tools face challenges in effectively suppressing Electromagnetic Interference (EMI) generated by brushed motors, particularly at the commutator and brush contact points, due to the difficulty in mounting and grounding EMI suppression components, especially in frameless motors.
Innovation Solution
The integration of EMI suppression components, including X and Y capacitors, on a circuit board or rear bearing retainer, electrically coupled to the brushes and armature shaft, providing effective grounding and electrical connectivity to reduce EMI through strategic mounting and routing configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If EMI suppression components are mounted near the motor commutator and brushes, then EMI suppression effectiveness is improved, but device complexity and mounting difficulty increase
Solution Approach 1:
The patent combines multiple EMI suppression components (X capacitors and Y capacitors) and their mounting structure into an integrated circuit board assembly. This merging approach maintains the effectiveness of EMI suppression by keeping components near the commutator and brushes while reducing overall mounting complexity through integration.
Solution Approach 2:
The patent introduces a circuit board as an intermediary structure that facilitates the mounting of EMI suppression components near the motor commutator and brushes. This intermediary provides a standardized platform for component installation, simplifying the mounting process while maintaining proximity to the EMI source.
2Object-affected harmful factors
If EMI suppression components are mounted near the motor commutator and brushes, then EMI suppression effectiveness is improved, but ease of manufacture decreases
Solution Approach 1:
The patent performs preliminary action by pre-assembling the EMI suppression components on the circuit board before final installation into the motor assembly. This preliminary mounting on a standardized circuit board simplifies the manufacturing process, as the EMI suppression subsystem can be prepared independently and then integrated into the motor.
3Object-affected harmful factors
If EMI components are properly grounded to reduce emissions, then EMI suppression effectiveness is improved, but device complexity increases in frameless motors
Solution Approach 1:
The patent makes the circuit board serve multiple functions: it provides mechanical support for the EMI suppression components, establishes electrical connections between components, and provides the grounding path to the motor frame or chassis. This multi-functionality eliminates the need for separate grounding structures, reducing complexity while maintaining effective EMI suppression.
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 effectively minimizes EMI emissions by grounding Y capacitors to the armature shaft and connecting X capacitors between brushes, reducing both symmetrical and asymmetrical interference, thus meeting regulatory requirements with a cost and space-efficient solution.
Implementation Method 1
two Y capacitors having first terminals electrically coupled to the two brushes and second terminals electrically coupled to a point of substantially zero potential
Implementation Method 2
an X capacitor having terminals electrically coupled to the two brushes
Data Source
AI summary
A power tool is provided including a housing and an electric motor disposed within the housing, where the electric motor includes a stator and an armature rotatably received within the stator, and the armature includes an armature shaft on which a commutator is mounted. The power tool includes a brush assembly disposed around the commutator. The brush assembly includes at least two brushes in contact with the commutator and a circuit board mounted on the brush assembly and in electrical contact with the brushes. The circuit board includes at least one electromagnetic interference (EMI) suppression component electrically mounted thereon, the EMI suppression component being electrically coupled to the brushes.