DC Motor Brush Holder Shielding Cap for EMC
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Solution Overview
Problem
Existing interference suppression devices for DC motors are complex and difficult to integrate, especially in geared motors, as they require intricate designs and additional components to effectively shield the commutation system from radiated and conducted electromagnetic interference.
Innovation Solution
A shielding cap designed as a conductive bent sheet metal part covers the brush holder and commutation system, incorporating ceramic feedthrough capacitors and inductive components, which act as filters and seals, reducing interference without additional effort or cost by forming a prefabricated structural unit with the brush holder.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a printed circuit board with conductor surfaces and hollow-cylindrical shielding device is used to shield the commutation device, then good shielding effect is achieved, but the technical design becomes complex and difficult to integrate into a motor
Solution Approach 1:
The patent combines the shielding function with the existing motor housing structure. The housing itself is designed to provide shielding by positioning the commutation device within the conductive housing, eliminating the need for separate shielding components like printed circuit boards or hollow-cylindrical devices. This merging of shielding function into the housing structure reduces design complexity while maintaining shielding effectiveness.
Solution Approach 2:
The motor housing serves multiple functions: it provides structural support, contains internal components, and simultaneously acts as an electromagnetic shield. By making the housing conductive and strategically positioning the commutation device within it, the housing performs both mechanical and electromagnetic shielding functions, simplifying the overall design.
2Object-affected harmful factors
If a conductive metallic shielding can is used to surround the brush device, then shielding is improved, but additional components and complexity are introduced
Solution Approach 1:
Instead of adding a separate shielding can around the brush device, the patent integrates shielding functionality into the existing motor housing. The housing is designed with conductive properties and specific geometric features that create shielding zones around the commutation device and brushes, eliminating the need for additional shielding components.
Solution Approach 2:
The motor housing itself provides the shielding function without requiring external shielding components. By designing the housing with appropriate conductive materials and geometric configurations, the housing serves its own shielding needs, making the system self-sufficient and reducing component count.
3Object-affected harmful factors
If feedthrough capacitors are inserted in openings for connection lines through the shielding part, then conducted interference is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent uses simple, inexpensive feedthrough capacitors that can be easily integrated into the housing openings. These basic capacitive elements provide effective interference suppression without requiring complex filtering circuits or expensive components, maintaining manufacturing simplicity while reducing conducted interference.
Solution Approach 2:
Feedthrough capacitors are placed at the openings where connection lines pass through the conductive housing. These capacitors act as intermediaries that block high-frequency interference while allowing DC and low-frequency signals to pass, effectively reducing conducted interference without complicating the overall manufacturing process.
4Object-affected harmful factors
If the shielding part is designed as a cap covering the brush holder, then shielding effectiveness is improved, but device complexity increases
Solution Approach 1:
The patent integrates the shielding cap design directly into the motor housing structure. The housing includes integrated cap portions that cover the brush holder and commutation device, combining the shielding function with the housing itself rather than using separate shielding components. This reduces structural complexity while maintaining shielding effectiveness.
Solution Approach 2:
The housing is segmented into different functional zones, with specific portions designed as integrated caps that cover the brush holder and commutation device. This segmentation allows the housing to provide localized shielding where needed while maintaining overall structural simplicity and avoiding the need for separate shielding components.
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 solution effectively eliminates radiated and conducted electromagnetic interference with minimal effort and low additional cost, ensuring interference-free operation by integrating shielding components directly into the motor housing and gear flange, enhancing electromagnetic compatibility.
Implementation Method 1
In terms of reducing line-bound interference, it is advantageous if the shielding cap has recesses in which ceramic feedthrough capacitors for the connection lines are seated
Implementation Method 2
A shielding cap designed as a conductive bent sheet metal part covers the brush holder and commutation system, incorporating ceramic feedthrough capacitors and inductive components, which act as filters and seals, reducing interference
Data Source
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AI summary
The invention relates to a suppressor for the commutating system (14, 16; 18) of a DC motor (10), the commutator discs thereof working together with a brush support arrangement (54) having at least two brushes (14, 16) that can be connected to a DC voltage supply (30, 32) by means of connecting cables (20, 28), wherein the connecting cables are connected to each other and/or to ground by means of at least one capacitance (38). The commutating system (14, 16; 18) is thereby partially shielded by an electrically conductive part (52) having pass-through openings for connecting cables (20, 28) of the brushes (14, 16) capacitively connected to the housing of the motor in a region not shielded by the housing (46) of the motor (10) and/or by a flange-mounted gearbox (44), whereby the electromagnetic compatibility (EMC) of the drive arrangement is significantly improved with little additional effort.