Conductive Grease for Electric Drive Unit Grounding

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Solution Overview

Problem

Conventional grounding solutions for electric vehicle drivetrains are ineffective in consistently grounding rotor shaft voltage, leading to severe electrically induced bearing and gear damage due to asymmetric magnetic fields and common mode voltage.

Innovation Solution

A conductive grease formulation comprising a base oil, organic lubricant additives for enhanced lubrication, and conductive additives for increased electrical conductivity and thickening, specifically including ionic and inorganic lubricant additives, is developed to improve electrical conductivity and protect drivetrain components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional conductive grease is used, then lubrication is provided, but electrical conductivity is insufficient to effectively ground rotor shaft voltage

Engineering Contradiction:

Improvegrounding effectivenessVSAvoidelectrical induced bearing damage

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the electrical conductivity parameter of the grease by incorporating conductive additives (graphite, metal particles, carbon nanotubes) into the base grease formulation. This changes the electrical properties of the grease from insulating to conductive, enabling effective grounding of rotor shaft voltage while maintaining lubrication functions.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite grease material by combining conventional lubricant base oil with conductive additives such as graphite, metal particles, or carbon nanotubes. This composite formulation simultaneously provides lubrication and electrical conductivity, resolving the contradiction between mechanical protection and electrical grounding effectiveness.

Inventive Principle:

Principle #40Composite materials

2Reliability

If conventional grounding solutions are used, then cost is reduced, but service frequency increases and protection effectiveness decreases

Engineering Contradiction:

Improveprotection effectivenessVSAvoidservice frequency

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The conductive grease performs self-grounding function continuously during operation without requiring external grounding systems or periodic intervention. The grease inherently provides both lubrication and electrical conductivity, eliminating the need for separate grounding maintenance and reducing service frequency while improving protection effectiveness.

Inventive Principle:

Principle #25Self-service

3Strength

If grease viscosity is increased for better lubrication, then film strength improves, but electrical conductivity decreases

Engineering Contradiction:

Improvelubrication film strengthVSAvoidelectrical conductivity

Core Design Contradiction:

StrengthVSReliability

Solution Approach 1:

The patent uses composite material formulation where conductive additives (graphite flakes, metal particles, carbon nanotubes) are dispersed in the grease matrix. These additives provide electrical conductivity pathways that are independent of the base oil viscosity, allowing high viscosity grease for strong lubrication films while maintaining effective electrical conductivity for grounding.

Inventive Principle:

Principle #40Composite materials

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 conductive grease formulation effectively minimizes voltage differences between the rotor shaft and chassis, allowing safe current flow and reducing the risk of electrical discharges, thereby extending bearing life and preventing premature failure.

Implementation Method 1

a conductive additive for increasing electrical conductivity and thickening of the base oil, the conductive additive comprising ionic lubricant additives and/or inorganic lubricant additives

Methodology Applied

Scientific EffectElectrical conduction: Conduction (electrical)

Implementation Method 2

a conductive additive for increasing electrical conductivity and thickening of the base oil

Methodology Applied

Scientific EffectThickening:

Implementation Method 3

an organic lubricant additive for enhancing lubrication of the base oil

Methodology Applied

Scientific EffectLubrication: Lubrication

Data Source

PatentUS20250171705A1Conductive grease formulations and grounding solutions for electric drive unit

Publication Date: 2025.05.29 TESLA INC

AI summary

A conductive grease comprising a base oil, an organic lubricant additive for enhancing lubrication of the base oil, and a conductive additive for increasing electrical conductivity and thickening of the base oil. The conductive additive comprising ionic lubricant additives and/or inorganic lubricant additives. A testing method to quantitatively measure the effectiveness of conductive grease and a grounding solution utilizing the conductive grease.