Hybrid Engine Pull-Down Threshold Adjustment for Fuel Efficiency

Solution Overview

Problem

Hybrid electric vehicles face inefficiencies in fuel usage due to hysteresis in engine pull-up and pull-down thresholds, leading to unnecessary engine operation when power demand is steady within the thresholds, and the existing methods do not effectively address situations where the battery is near full charge and unable to accept regenerative braking, resulting in suboptimal fuel economy.

Innovation Solution

The engine pull-down threshold is adjusted by raising it to an adjusted level based on the duration and rate of driver demand within the hysteresis region, allowing for engine shutdown when the demand remains below the pull-up threshold, and the engine is commanded to operate unfueled during battery overcharge to assist in deceleration, optimizing fuel efficiency by relying on electric power when possible.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by moving object

If the engine is maintained on using standard EPU and EPD thresholds, then the engine can respond to power requests, but fuel efficiency deteriorates when driver demand is steady within the hysteresis region

Engineering Contradiction:

Improvefuel efficiencyVSAvoidengine response reliability

Core Design Contradiction:

Use of energy by moving objectVSReliability

Solution Approach 1:

The patent applies dynamics by making the pull-down threshold adjustable rather than fixed. The controller dynamically raises the pull-down threshold when driver demand remains steady within the hysteresis region for a predetermined duration, enabling the system to adapt to sustained low-demand conditions and shut down the engine appropriately, thereby improving fuel efficiency while maintaining reliable engine response capability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the pull-down threshold from a fixed value to a dynamically adjustable value. By raising the threshold under specific conditions (steady demand within hysteresis region), the system modifies the operational parameters to enable engine shutdown when appropriate, resolving the contradiction between maintaining engine readiness and improving fuel efficiency.

Inventive Principle:

Principle #35Parameter changes

2Use of energy by moving object

If the pull-down threshold is raised to enable engine shutdown, then fuel efficiency improves, but the engine may shut down inappropriately when rapid power demand increases occur

Engineering Contradiction:

Improvefuel efficiencyVSAvoidengine response speed

Core Design Contradiction:

Use of energy by moving objectVSSpeed

Solution Approach 1:

The patent applies preliminary action by monitoring driver demand continuously and identifying when it remains steady within the hysteresis region for a predetermined duration before raising the pull-down threshold. This preliminary monitoring and timing mechanism ensures that engine shutdown decisions are made only when appropriate, preventing inappropriate shutdowns during rapid power demand increases while still enabling fuel-efficient shutdowns during sustained low-demand conditions.

Inventive Principle:

Principle #10Preliminary action

3Use of energy by moving object

If the engine is pulled up unfueled to assist deceleration when battery is near full charge, then regenerative braking efficiency improves, but the engine may remain on unnecessarily when steady power demand is below EPU threshold

Engineering Contradiction:

Improveregenerative braking efficiencyVSAvoidfuel consumption

Core Design Contradiction:

Use of energy by moving objectVSLoss of energy

Solution Approach 1:

The patent applies dynamics by making the pull-down threshold adjustable rather than fixed. The controller dynamically raises the pull-down threshold when driver demand remains steady within the hysteresis region for a predetermined duration, enabling the system to adapt to sustained low-demand conditions and shut down the engine appropriately, thereby improving fuel efficiency while maintaining reliable engine response capability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the parameter of the pull-down threshold from a fixed value to a dynamically adjustable value. By raising the threshold under specific conditions (steady demand within hysteresis region), the system modifies the operational parameters to enable engine shutdown when appropriate, resolving the contradiction between maintaining engine readiness and improving fuel efficiency.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS11273819B2Systems and methods for controlling stop/start events for a hybrid electric vehicle

Publication Date: 2022.03.15 FORD GLOBAL TECH LLC

AI summary

Methods and systems are provided for controlling engine operation in a hybrid electric vehicle equipped with stop/start capabilities under conditions where requested power or torque is in a hysteresis region between an engine pull up threshold and an engine pull down threshold. In one example, a method comprises obtaining an adjusted engine pull down threshold upon the requested power or torque remaining in the hysteresis region for more than a threshold duration, and commanding the engine deactivated in response to the adjusted engine pull down threshold being equivalent to the requested power or torque. In this way, a motor/generator may be used to meet the requested torque response rather than the engine under such conditions, which may improve fuel economy.