CVVD Engine Coasting Regeneration Control for Drag Torque Reduction

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Solution Overview

Problem

Mild hybrid electric vehicles (MHEV) with continuously variable valve duration (CVVD) engines face limitations in regenerative braking efficiency due to engine drag torque, which reduces energy recovery and increases deceleration, limiting fuel efficiency and power generation capacity.

Innovation Solution

A coasting regeneration control method and device that uses an engine control unit (ECU) to determine and enter a coasting regeneration mode, maximizing intake air and CVVD target duration to increase power generation torque of the belt-driven motor by fully opening the throttle valve and delaying intake valve closure, thereby reducing pumping loss and drag torque.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If power generation torque of BDM is increased in coasting regeneration, then energy recovery amount is increased, but vehicle deceleration becomes larger causing driving difference

Engineering Contradiction:

Improveenergy recovery amountVSAvoidvehicle deceleration

Core Design Contradiction:

Loss of energyVSSpeed

Solution Approach 1:

The patent converts the harmful engine drag torque into a beneficial effect by operating the engine in a controlled coasting regeneration mode where the drag torque is optimized to be small, allowing the BDM to generate power while minimizing negative impacts on vehicle deceleration and driver comfort

Inventive Principle:

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

Solution Approach 2:

The patent changes operating parameters including throttle valve opening degree, intake air amount, and CVVD target duration to optimize the balance between BDM power generation torque and engine drag torque, enabling energy recovery while controlling vehicle deceleration

Inventive Principle:

Principle #35Parameter changes

2Ease of manufacture

If BDM is connected to crankshaft through belt in MHEV, then system cost is reduced compared to full hybrid, but engine acts as resistor decreasing regenerative braking efficiency

Engineering Contradiction:

Improvesystem costVSAvoidregenerative braking efficiency

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The patent dynamically controls the engine operation mode during regenerative braking, switching between normal operation and coasting regeneration mode based on vehicle conditions, allowing the connected BDM system to achieve good regenerative braking efficiency while maintaining cost-effectiveness

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes engine operating parameters including throttle valve opening, intake air amount, and valve duration to reduce engine drag torque during coasting regeneration, enabling the BDM to generate power efficiently despite being mechanically connected to the crankshaft

Inventive Principle:

Principle #35Parameter changes

3Reliability

If brake lights are turned on when deceleration is 1.3 m/s2 or more, then safety regulation is satisfied, but amount of power generation of BDM is limited in regenerative braking

Engineering Contradiction:

Improvesafety regulation complianceVSAvoidpower generation amount

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent dynamically adjusts the coasting regeneration control based on vehicle deceleration conditions, optimizing the balance between meeting brake light activation requirements and maximizing BDM power generation within regulatory constraints

Inventive Principle:

Principle #15Dynamics

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 enhances fuel efficiency by reducing engine drag torque and increasing energy recovery during coasting regeneration without requiring additional mechanical devices, improving the overall fuel efficiency of MHEV systems.

Implementation Method 1

a closing time of the intake valve is delayed after a start point of time of a compression stroke (LIVC, Late Intake Valve Closure), thereby decreasing pumping loss and increasing power generation torque of the BDM

Methodology Applied

Scientific EffectPumping loss reduction through valve timing control:

Implementation Method 2

a belt driven motor (BDM) can assist engine power

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS11654885B2Coasting regeneration control method and device of vehicle with continuously variable valve duration engine

Publication Date: 2023.05.23 HYUNDAI KEFICO CORP

AI summary

A coasting regeneration control method of a vehicle equipped with a continuously variable valve duration (CVVD) engine includes: determining, by an engine control unit (ECU), whether a current state of the vehicle satisfies coasting regeneration conditions; and entering, by the ECU, a coasting regeneration mode and performing regenerative braking when the current state of the vehicle satisfies the coasting regeneration conditions, in which when the coasting regeneration mode is entered, a throttle valve is fully opened so that the amount of intake air of the engine is maximized, a CVVD target duration is controlled to be maximized, and a closing time of an intake valve is delayed after a start point of time of a compression stroke, thereby decreasing pumping loss of the engine.