Grounding Ring Sealing Structure for Rotor Voltage Discharge

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Solution Overview

Problem

In electric motors, internal rotor voltage buildup can degrade components due to improper grounding, leading to performance issues and noise, vibration, and harshness (NVH), particularly in oil-cooled environments where oil films interfere with grounding paths.

Innovation Solution

A grounding ring with stacked lips is disposed on the shaft, making electrical contact with the rotor while preventing oil from contacting the grounding path, ensuring effective discharge of rotor voltage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a grounding component contacts the rotor to ground it in an oil-cooled motor, then the rotor voltage can be discharged, but an oil film develops between the grounding components and the rotating rotor increasing resistance to the electrical path

Engineering Contradiction:

Improvegrounding path reliabilityVSAvoidelectrical contact resistance

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The grounding ring is divided into multiple lips (first lip, second lip, third lip) stacked along the longitudinal axis. The first lip provides electrical contact with the rotor for grounding, while the second and third lips provide sealing functions. This segmentation allows each lip to perform its specific function independently, preventing oil from compromising the electrical contact of the first lip.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second lip acts as an intermediary barrier between the cooling oil and the first lip. By positioning the second lip between the oil and the electrical contact surface, it prevents direct contact between oil and the grounding path, maintaining low electrical resistance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If grounding components are used to discharge rotor voltage, then internal rotor voltage can be prevented from building up, but the components may not properly provide a low resistance path to ground due to oil film interference

Engineering Contradiction:

Improvevoltage discharge effectivenessVSAvoidoil film interference

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The harmful oil film is extracted or excluded from the electrical contact interface by using sealed lips. The sealing lips create a barrier that removes oil from the vicinity of the electrical contact, ensuring that the grounding path remains free from oil contamination.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Different regions of the grounding ring have different properties: the first lip has high electrical conductivity for voltage discharge, while the second and third lips have sealing properties to exclude oil. This local differentiation of properties ensures that each region performs its intended function effectively.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If multiple lips are stacked along the longitudinal axis of the rotor and shaft, then sealing and grounding functions can be integrated, but device complexity increases

Engineering Contradiction:

Improvemulti-functionality of grounding ringVSAvoidnumber of lips in grounding ring

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple functions (grounding and sealing) are merged into a single grounding ring component. By stacking lips with different functions on the same ring, the design integrates voltage discharge and oil sealing capabilities in one element, reducing the need for separate components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The grounding ring is designed as a universal component that performs multiple functions: the first lip provides electrical grounding, while the second and third lips provide sealing against cooling oil. This multi-functional design eliminates the need for separate grounding and sealing components.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 prevents rotor voltage buildup, maintaining motor performance and reducing NVH by providing a reliable grounding path that is resistant to oil interference.

Implementation Method 1

The first lip can provide an electrical path to discharge a voltage from the rotor

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

The second lip can provide a seal between the first lip and the cooling liquid

Methodology Applied

Scientific EffectSealing:

Data Source

PatentUS12506375B2System and method of discharging rotor voltage

Publication Date: 2025.12.23 RIVIAN HOLDINGS LLC

AI summary

Systems and method to control rotor voltage of a liquid cooled motor are provided. A system can include a rotor, a shaft, and a ring. The ring can be disposed on the shaft. The ring can include a first lip in contact with an inner surface of the rotor and a second lip in contact with the inner surface of the rotor and a cooling liquid. The first lip can provide an electrical path to discharge a voltage from the rotor. The second lip can provide a seal between the first lip and the cooling liquid.