Electric Machine Potential Equalization Resistor Mounting
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Solution Overview
Problem
Electric machines in motor vehicles experience shaft voltages due to pulse-width-modulated signal actuation and electrostatic charges, leading to spark erosion and reduced bearing lifespan, as well as electromagnetic interference, which existing technologies have not adequately addressed.
Innovation Solution
A potential equalization device using a resistor element with a pressure contact system, where the resistor is connected to the rotor shaft via a pressure element, either through a covering cap or a contact piece, allowing for reliable electrical contact without soldering, and can be implemented using conventional discrete components like ohmic resistors or SMD elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistor element is connected to the rotor shaft to dissipate shaft voltages, then bearing damage from spark erosion is prevented, but the device complexity increases due to additional components and mounting requirements
Solution Approach 1:
The patent combines the resistor element mounting structure with the existing slip ring module housing. The housing serves dual purposes: containing the slip rings and providing mounting structure for the resistor element. This integration reduces the number of separate components and simplifies the overall device structure while maintaining the voltage dissipation function that prevents bearing damage.
Solution Approach 2:
The patent introduces a conductive adhesive as an intermediary substance that serves multiple functions: it electrically connects the resistor element to the rotor shaft, mechanically bonds the resistor to the housing, and provides a simple mounting solution without requiring additional fasteners or complex assembly procedures. This intermediary material resolves the complexity issue by replacing multiple separate components with a single functional substance.
2Ease of manufacture
If conventional discrete components are used for the potential equalization device, then manufacturing cost and availability improve, but the precision of electrical contact and connection reliability may worsen
Solution Approach 1:
The patent replaces traditional mechanical connection methods (soldering, welding, or threaded fasteners) with a conductive adhesive bonding system. This substitution maintains reliable electrical contact while simplifying the manufacturing process. The conductive adhesive provides both mechanical bonding and electrical conductivity in a single step, eliminating the need for precise alignment and complex joining procedures required by mechanical fastening methods.
Solution Approach 2:
The patent changes the physical state and properties of the connection medium from solid mechanical fasteners to a viscous conductive adhesive that can be applied in a controlled manner. This parameter change allows for easier manufacturing with conventional discrete components while maintaining reliable electrical contact through the adhesive's dual function of mechanical bonding and electrical conduction.
3Ease of operation
If a pressure contact system is used to connect the resistor element to the rotor shaft, then ease of assembly improves, but the stability of electrical contact under vibration and thermal stress may worsen
Solution Approach 1:
The patent replaces the pressure contact mechanical system with a conductive adhesive bonding system. This substitution eliminates the need for continuous mechanical pressure to maintain electrical contact. The adhesive creates a permanent, stable bond that maintains reliable electrical contact under vibration and thermal stress without requiring the complex pressure application and maintenance mechanisms needed for pressure contact systems.
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 effectively dissipates shaft voltages, preventing spark erosion and electromagnetic interference, while ensuring reliable and space-efficient electrical connections, thus extending bearing lifespan and improving electromagnetic compatibility.
Implementation Method 1
a resistor element for breaking down shaft voltages
Implementation Method 2
resistor element contacting on the one hand a bus bar of a slip ring module and on the other hand the rotor shaft
Implementation Method 3
an element that exerts a mechanical pressure in the region of an electrical contact, such that this electrical contact can be referred to as a pressure contact
Data Source
AI summary
An electric machine having a stator (3) and a rotor (4) mounted rotatably by means of a rotor shaft (5) and having a potential equalization device containing a resistor element for breaking down shaft voltages occurring at the rotor shaft (5), the resistor element contacting on the one hand a bus bar (24) of a slip ring module (20) and on the other hand the rotor shaft (5) at contact points, the resistor element being an electrical resistor (30; 46) provided with electrical connection elements (31, 32; 47, 48). At least one connection element (32; 47) of the electrical resistor (30; 46) is electrically conductively connected to the potential of the rotor shaft (5) via a pressure contact by a pressure element.