Electric Machine Brush With Lateral Braid Attachment
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Solution Overview
Problem
The high operational cycles of 'stop and start' systems in motor vehicle starters lead to significant wear on electric machine brushes, necessitating an increase in the functional distance to enhance their lifespan.
Innovation Solution
The design of a brush for electric machines featuring a body with two bearing surfaces and a braid attachment zone located between these surfaces, allowing for balanced spring forces and improved current distribution, which maximizes the functional distance and service life of the brush.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If the brush body is extended to increase functional distance, then brush lifespan is improved, but brush structural complexity increases
Solution Approach 1:
The brush body is segmented into functionally distinct zones: a front face for commutator contact, a rear face with bearing surfaces, and lateral faces with braid attachment zones. This segmentation allows each zone to be optimized independently, extending the functional distance between front and rear faces to increase lifespan while maintaining manageable structural complexity through clear functional separation.
Solution Approach 2:
The invention utilizes the lateral dimension of the brush body by positioning braid attachment zones on lateral faces rather than only on the front or rear faces. This dimensional redistribution allows the functional distance to be extended along the front-to-rear axis while maintaining compactness in other dimensions, resolving the contradiction between lifespan extension and structural complexity.
2Reliability
If spring force is increased to improve brush contact pressure, then contact reliability is improved, but wear on commutator increases
Solution Approach 1:
The bearing surfaces on the rear face are designed with specific local properties (material composition, surface finish, geometry) that optimize the distribution of spring force. This localized optimization ensures reliable contact pressure is applied uniformly across the commutator contact surface, preventing concentrated stress points that would accelerate wear while maintaining overall contact reliability.
3Duration of action of moving object
If braid attachment zone is moved to maximize functional distance, then brush lifespan is improved, but current distribution may be affected
Solution Approach 1:
The lateral faces of the brush body are specifically designed with optimized material properties and surface characteristics at the braid attachment zones. This local optimization ensures that even though the braid is attached away from the front face, the electrical current is effectively distributed across the entire front face contact area, maintaining current distribution reliability while maximizing functional distance.
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 facilitates better sliding and pressure on the commutator, increases the brush's lifespan, and enhances efficiency by distributing current evenly across the brush's surface.
Implementation Method 1
a spring intended to exert a force on the brush in the direction of the collector
Implementation Method 2
a face, called the front face, intended to rub against a commutator
Implementation Method 3
an electrically conductive element called a braid... ensures the power supply to one of the brushes
Data Source
Figure 1~2
Figure 3a~3c
Figure 4a~5b
AI summary
The invention relates to a brush (25) for an electric machine comprising a body (34) having a surface, referred to as front surface (35), intended for rubbing against a collector (27) of an electric machine rotor and a surface, referred to as the rear surface (38), opposite the front surface, comprising at least one bearing surface (39) for a spring intended for exerting a force on the brush toward the collector (27). The brush also comprises an area (44) for attaching a connection braid to the body (34) of the brush. According to the invention, the area (44) for attaching the connection braid is located, when viewed from above, at least at the rear of said bearing surface (39) on the side of the rear surface (38) of the body of the brush. Said body (34) comprises two bearing surfaces (39), the area (44) for attaching the braid being located between the two bearing surfaces (39). The invention also relates to the corresponding electric machine brush-holder.