Drive Motor Locked-Rotor Cooling Using an Engine Oil Pump

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Solution Overview

Problem

In hybrid vehicles without an electric oil pump, a locked rotor of the driving motor in electric vehicle mode leads to low rotational speed of the wheel end oil pump, making it impossible to provide sufficient coolant, which reduces the service life or causes the motor to burn out.

Innovation Solution

A method and device that utilizes the engine end oil pump, connected via a cooling flow path, to drive coolant to the driving motor when a locked rotor condition is detected, with controls to manage engine start, fan speed, and spill valve operation to optimize cooling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the vehicle uses a wheel end oil pump driven by wheel rotation for cooling, then the cooling system is simpler and does not require an electric oil pump, but when the driving motor experiences a locked rotor in electric vehicle mode, the wheel end oil pump rotational speed becomes too low to provide sufficient coolant

Engineering Contradiction:

Improvecooling system structureVSAvoidcooling effectiveness

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The control unit detects locked rotor conditions in advance and proactively increases engine speed to drive the engine end oil pump at a higher rotational speed, ensuring sufficient coolant flow is established before the motor overheats. This preliminary action prevents the cooling deficiency from manifesting as actual damage.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The engine end oil pump serves as an intermediary cooling mechanism that activates when the primary wheel end oil pump is insufficient. By using the engine-driven pump as a backup or supplemental cooling source, the system resolves the contradiction between simple structure and reliable cooling performance.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the engine is started to cool the driving motor during locked rotor conditions, then sufficient coolant can be provided to the motor, but the engine starts and consumes fuel and increases system complexity

Engineering Contradiction:

Improvemotor cooling assuranceVSAvoidfuel consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Instead of fully starting the engine for other functions, the system performs a partial start by increasing engine speed only to the level required to drive the engine end oil pump at sufficient rotational speed for cooling. This excessive action relative to minimum cooling needs ensures reliable cooling while minimizing fuel consumption compared to a full engine start.

Inventive Principle:

Principle #16Partial or excessive action

Solution Approach 2:

The system changes the engine operating parameter (rotational speed) dynamically based on cooling needs. During locked rotor conditions, the engine speed is increased from idle or off-state to a specific range that provides adequate coolant flow, then reduced or stopped when cooling is no longer needed, optimizing the balance between cooling effectiveness and fuel consumption.

Inventive Principle:

Principle #35Parameter changes

3Use of energy by moving object

If the auxiliary cooling starting temperature is set high, then the engine starts later saving energy, but the driving motor may overheat before the engine starts cooling

Engineering Contradiction:

Improveengine start timingVSAvoidmotor temperature

Core Design Contradiction:

Use of energy by moving objectVSTemperature

Solution Approach 1:

The control unit continuously monitors motor temperature and locked rotor status, using this feedback to dynamically adjust the auxiliary cooling starting temperature threshold. When a locked rotor is detected, the system lowers the temperature threshold to trigger earlier engine activation, ensuring the motor is cooled before reaching dangerous temperatures while optimizing engine start timing to minimize fuel consumption.

Inventive Principle:

Principle #23Feedback

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

Ensures sufficient coolant supply to the driving motor, preventing overheating and extending its service life by actively cooling the motor during locked rotor conditions.

Implementation Method 1

the engine end oil pump of the vehicle drives a coolant in a cooling flow path to cool the driving motor

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentEP4438367B1Drive motor stalling cooling method and apparatus for vehicle, and vehicle

Publication Date: 2026.01.21 BYD CO LTD

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AI summary

Provided is a method for cooling a locked rotor driving motor of a vehicle. The vehicle (500) includes a driving motor (501), an engine (502), an engine end oil pump (503), and a cooling flow path (504). The engine (502) is configured to drive the engine end oil pump (503) to run, and the cooling flow path (504) connects the engine end oil pump (503) to the driving motor (501). The method includes: controlling, if a driving mode of the vehicle (500) is an electric vehicle mode, the vehicle (500) meets a preset locked rotor motor activation condition, and a current temperature of the driving motor (501) is greater than an auxiliary cooling starting temperature of the engine, the engine (502) of the vehicle (500) to start, to cause the engine end oil pump (503) of the vehicle (500) to drive a coolant in the cooling flow path (504) to cool the driving motor (501).