Idled Drive Unit Heating to Cut Gear Train Losses in BEVs

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Solution Overview

Problem

Battery electric vehicles (BEVs) experience power losses due to idled drive motors, particularly in gear trains, as they continue to rotate without generating torque, leading to inefficiencies in torque delivery on paved roads where less torque is needed.

Innovation Solution

Implementing a system with multiple drive units where waste heat from an active drive unit is used to heat the gear train of an idled drive unit, reducing oil viscosity and minimizing power losses by maintaining the gear train at an optimal temperature.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the drive unit is idled to reduce energy consumption, then energy efficiency is improved, but power losses in the gear train increase due to continued rotation and oil viscosity

Engineering Contradiction:

Improveenergy efficiencyVSAvoidpower losses in gear train

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent applies parameter changes by actively controlling the temperature of the gear train oil through a thermal management system. By maintaining the oil temperature within an optimal range, the viscosity of the lubricant is optimized, which reduces friction and power losses in the gear train while the drive unit is idled, thereby resolving the contradiction between energy efficiency and power losses.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The thermal management system utilizes waste heat from other vehicle components to heat the gear train oil when needed, rather than requiring dedicated energy input. This self-service approach allows the system to maintain optimal operating conditions using otherwise wasted energy resources, reducing overall energy consumption while minimizing power losses.

Inventive Principle:

Principle #25Self-service

2Loss of energy

If the gear train is heated to reduce oil viscosity and power losses, then power efficiency is improved, but energy consumption increases

Engineering Contradiction:

Improvepower lossesVSAvoidenergy consumption for heating

Core Design Contradiction:

Loss of energyVSUse of energy by moving object

Solution Approach 1:

The patent converts waste heat from other vehicle components into a beneficial resource for heating the gear train oil. By capturing and redirecting heat that would otherwise be dissipated, the system reduces power losses in the gear train without requiring additional energy consumption, thus converting a harmful effect (waste heat) into a beneficial one (reduced viscosity and power losses).

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 approach reduces power losses in idled drive units by lowering oil viscosity and maintaining the gear train at an optimal temperature, thereby extending the vehicle's range and improving efficiency during normal driving conditions.

Implementation Method 1

heat generated by a non-idled drive unit is transferred to the gear train of the idled drive unit

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Implementation Method 2

reduces the viscosity of oil lubricating the gear train and thereby reduces power loss

Methodology Applied

Scientific EffectViscosity reduction through heating: Heating

Data Source

PatentUS12117074B1Reducing losses in an idled vehicle drive unit

Publication Date: 2024.10.15 RIVIAN HOLDINGS LLC

AI summary

A vehicle includes first and second drive units, such as drive units that each include an electric motor and a gear train coupling the electric motor to one or more wheels. A first drive unit may be idled while the second drive unit continues to induce movement of the vehicle. Losses within the first drive unit while idled may be reduced by heating the first drive unit, such as with heat generated by the second drive unit. A cooling system is present and may be used to heat the first drive unit by directing fluid exiting the second drive unit into the first drive unit before entering the cooling system or bypassing the cooling system entirely. Oil circulation within the first drive unit may facilitate heating of the gear train by bypassing a heat exchanger receiving the oil and the fluid.