Hybrid Engine Stop Control for Smooth Change-of-Mind Restarts

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Solution Overview

Problem

Hybrid vehicles experience driveline torque disturbances during engine restarts due to automatic engine stopping and subsequent changes in operating conditions, as the engine speed reaches zero before restarting, leading to delays in torque availability to the powertrain.

Innovation Solution

Inhibiting automatic engine stopping based on an inhibit engine pull-down torque threshold, which is a function of vehicle driving history, ensuring the electric machine has sufficient torque capacity to restart the engine and maintain expected performance levels, thereby reducing torque disturbances.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If automatic engine stopping is implemented to reduce fuel consumption, then fuel efficiency is improved, but driveline torque disturbances occur during engine restart due to delayed torque availability

Engineering Contradiction:

Improvefuel consumptionVSAvoiddriveline torque stability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system performs preliminary assessment of driver behavior patterns and vehicle operating conditions before initiating engine shutdown. By analyzing driving history and predicting potential torque demands, the system prevents engine stop decisions that would lead to torque disturbances, thereby maintaining both fuel efficiency and driveline stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system continuously monitors driver demand patterns, vehicle operating conditions, and engine restart requirements. This feedback mechanism allows the control system to adjust engine shutdown timing and restart strategies dynamically, ensuring that engine restarts are coordinated with actual torque demands to avoid driveline torque disturbances.

Inventive Principle:

Principle #23Feedback

2Productivity

If engine shutdown time is reduced for faster response, then productivity is improved, but the engine may restart before reaching zero speed causing torque disturbances

Engineering Contradiction:

Improveengine shutdown speedVSAvoiddriveline torque stability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system dynamically adjusts the engine shutdown process based on real-time conditions. Rather than using a fixed shutdown timeline, the system modulates shutdown speed and timing according to predicted driver demands and vehicle operating states, allowing faster shutdown when conditions permit while preventing premature restarts that would cause torque disturbances.

Inventive Principle:

Principle #15Dynamics

3Power

If the driveline disconnect clutch is closed to enable engine restart via integrated starter/generator, then torque availability is improved, but driveline speed reduction and torque disturbances occur

Engineering Contradiction:

Improveengine torque availabilityVSAvoiddriveline torque disturbance

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The system applies preliminary anti-action by predicting potential torque disturbances before they occur. When an engine restart is anticipated, the system pre-coordinates clutch engagement timing and integrated starter/generator torque application to counteract potential driveline speed reductions, thereby maintaining torque availability while preventing harmful torque disturbances.

Inventive Principle:

Principle #9Preliminary anti-action

Data Source

PatentUS11745720B2Methods and system for controlling an engine

Publication Date: 2023.09.05 FORD GLOBAL TECH LLC

AI summary

Systems and methods for operating a hybrid vehicle are described. In one example, the automatic engine stopping may be inhibited so that an engine may be restarted during change of mind conditions without generating a large driveline torque disturbance. The engine stopping may be inhibited based on a inhibit engine pull-down torque threshold.