Hybrid Engine Stop Control via Negative Torque

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Solution Overview

Problem

In hybrid electric vehicles, when the clutch is disengaged and fuel supply to the internal combustion engine is stopped, the engine's rotation slows due to friction resistance, causing discomfort and noise as it takes time to stop, which affects the driver and passengers.

Innovation Solution

A drive control device with a sensor and programmable controller that decreases the engine's rotation speed to a predetermined level above the resonance frequency band by stopping fuel supply and applying negative torque from the electric motor, then disengages the clutch and controls the variable valve timing mechanism to quickly stop the engine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of time

If the fuel supply to the internal combustion engine stops under a state in which the clutch is disengaged, then the engine stops rotating, but it takes time until the rotation stops which causes discomfort to driver and passengers

Engineering Contradiction:

Improvetime required for engine to stopVSAvoiddiscomfort to driver and passengers

Core Design Contradiction:

Loss of timeVSObject-affected harmful factors

Solution Approach 1:

The electric motor applies negative torque to the internal combustion engine before the clutch is disengaged, actively counteracting the engine's rotation and creating a preliminary opposing force that accelerates the stopping process and prevents discomfort to occupants

Inventive Principle:

Principle #9Preliminary anti-action

Solution Approach 2:

The fuel supply is stopped and negative torque is applied to the engine before the clutch disengagement is completed, preparing the engine for rapid deceleration and ensuring the rotation stops quickly without causing discomfort

Inventive Principle:

Principle #10Preliminary action

2Speed

If the clutch is disengaged before stopping fuel supply, then the engine can stop, but the rotation speed decreases slowly due to internal friction resistance

Engineering Contradiction:

Improveengine rotation speedVSAvoidtime until rotation stop

Core Design Contradiction:

SpeedVSLoss of time

Solution Approach 1:

The fuel supply is stopped and negative torque is applied to the engine before the clutch is disengaged, preparing the engine for rapid deceleration. This preliminary action ensures that when the clutch disengages, the engine rotation speed decreases quickly rather than slowly

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The electric motor changes the torque parameter from positive (driving) to negative (retarding), creating a controlled deceleration force that rapidly reduces engine rotation speed without relying solely on internal friction resistance

Inventive Principle:

Principle #35Parameter changes

3Speed

If negative torque is applied to the internal combustion engine from the electric motor via the clutch in an engaged state, then the rotation speed decreases to predetermined level, but the clutch must be disengaged afterward

Engineering Contradiction:

Improveengine rotation speedVSAvoidclutch disengagement operation

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The patent combines the functions of engine deceleration and clutch disengagement into a coordinated control sequence. The negative torque application and clutch disengagement are merged into a single integrated operation that achieves rapid engine stop while managing the complexity of the clutch transition

Inventive Principle:

Principle #5Merging (Combining)

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 solution reduces the time required for the internal combustion engine to stop, minimizing discomfort and noise by controlling the engine's speed through the electric motor and clutch, ensuring smoother transitions and preventing resonance-related noise.

Implementation Method 1

exerting a negative torque to the internal combustion engine from the electric motor via the clutch in an engaged state

Methodology Applied

Scientific EffectNegative torque: Torque

Implementation Method 2

control the variable valve timing mechanism to return to a predetermined position

Methodology Applied

Scientific EffectVariable valve timing:

Data Source

PatentUS9951709B2Drive control device and drive control method for hybrid electric vehicle

Publication Date: 2018.04.24 NISSAN MOTOR CO LTD

AI summary

A hybrid electric vehicle comprises an internal combustion engine and an electric motor/generator connected via a first clutch. In response to a system stop request in a vehicle stop state, a rotation speed of the internal combustion engine is decreased to a predetermined rotation speed higher than a predetermined resonance frequency band by a negative torque applied to the internal combustion engine from the electric motor/generator via the first clutch. Then, the disengagement of the first clutch starts. The rotation speed of the engine falls below the predetermined resonance frequency band within a predetermined period from the start of the disengagement. As a consequence, the required period from a stopping operation of the internal combustion engine until actual operation stop thereof in a vehicle stationary state is reduced.