Brushed Motor Power Circuit Integration for Thermal and EMC Management
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Solution Overview
Problem
Existing brushed electric motors for automotive applications face limitations in operating temperature, electromagnetic compatibility, and cooling efficiency due to inadequate space for filters and the use of traditional inductors, as well as challenges with brush wear and assembly complexity.
Innovation Solution
The design incorporates a compact electric motor with a power supply circuit using surface mount technology (SMT) and a thermally conductive cover for enhanced heat dissipation, along with shielded inductors and capacitors for improved electromagnetic compatibility, and multipurpose springs for brush contact and pressure, eliminating the need for a braided connection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional inductors and basic filters are used in the power supply circuit, then the motor can operate with simple structure, but electromagnetic compatibility is poor and operating temperature is limited to 80°-85°C
Solution Approach 1:
The patent combines the power supply circuit, filter components (inductors and capacitors), and brush holder into a single integrated assembly. The inductors are positioned within the brush holder structure, and capacitors are mounted on the cover, merging multiple functions into one compact unit. This integration improves electromagnetic compatibility through proper component placement and shielding while avoiding the complexity of separate distributed components.
Solution Approach 2:
The patent introduces a metallic shield between the commutator and the power supply circuit components. This shield acts as an intermediary that blocks electromagnetic interference from affecting the commutator and brush contact, thereby improving electromagnetic compatibility without requiring complete redesign of the power supply circuit.
2Reliability
If the motor is sealed to protect internal components, then reliability improves, but heat removal becomes difficult and operating temperature is limited
Solution Approach 1:
The patent extracts the main heat generation sources (inductors and capacitors) from the sealed motor housing and positions them on the external cover. The inductors are mounted on the inner surface of the cover, and capacitors are positioned on the outer surface, allowing them to dissipate heat to the external environment. This extraction enables the motor to be sealed for protection while the power supply components remain thermally accessible.
3Ease of manufacture
If a braided conductor is used to connect brushes to power supply circuit, then electrical connection is achieved, but assembly complexity increases and soldering is required
Solution Approach 1:
The patent replaces the traditional braided conductor with spring contacts that provide both mechanical pressure and electrical connection. The springs are positioned to contact the brushes directly, eliminating the need for separate braided conductors and soldering operations. This mechanical-electrical integration simplifies assembly while maintaining reliable electrical connection.
4Reliability
If springs are used to push brushes towards commutator, then electrical contact is maintained, but brush wear increases due to continuous pressure
Solution Approach 1:
The patent modifies the spring pressure parameters by optimizing the spring stiffness and pre-load forces. The springs are designed with specific force characteristics that provide sufficient contact pressure for reliable electrical connection while minimizing excessive wear. The spring force is tuned to achieve the optimal balance between contact reliability and brush longevity.
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 allows the motor to operate effectively at higher temperatures (up to 120°-125°C) with improved electromagnetic compatibility and simplified assembly, while reducing brush wear and enhancing durability.
Implementation Method 1
a cover (10) for sealing the casing (2) and wherein the board (9) is fixed to the cover (10) in such a way as to maximize the heat exchange surface between the board (9) and the cover (10)
Implementation Method 2
noise is suppressed by simple inductors connected in series with the brushes
Implementation Method 3
a filter (13) for suppressing electromagnetic noise generated by operation of the motor (1) and by the power supply circuit (8)
Implementation Method 4
The circuit (8) also comprises capacitors (C1, C2, C3) for filtering electromagnetic noise
Implementation Method 5
brushes (15) mounted in suitable holder sleeves (14) along which they are pushed towards the commutator (7) by springs (17)
Implementation Method 6
shielded inductors and capacitors for improved electromagnetic compatibility
Data Source
Figure 1
Figure 2~4
Figure 5~7
AI summary
An electric motor (1) comprises a casing (2), a stator housed in the casing (2), a sealing cover (10), a rotor (6) rotatable inside the casing (2) and equipped with a commutator (7), a circuit (8) for powering the commutator (7) comprising two brushes (15) in sliding contact with the commutator (7); the motor (1) comprises two brush holder sleeves (14) in which the brushes (15) slide and two springs (17) operating between the brush holder sleeves (14) and the respective brushes (15) in such a way as to push the latter towards the commutator (7); both the sleeves (14) and the springs (17) form part of the circuit (8) for powering the brushes (15).