Hybrid Engine Control for Brake Force During Battery Overcharge

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Solution Overview

Problem

Hybrid electric vehicles face challenges in protecting the main battery from overcharging and securing adequate brake force when the battery is fully charged or in a charging-limiting state, as regenerative braking is unavailable, leading to safety issues and the need for increased engine brake force.

Innovation Solution

An engine control method that detects the state of charge of the main battery and performs an engine fuel cut, maximizing engine load by adjusting the throttle valve to a minimum open position and the cam to maximum retard, thereby ensuring maximum engine load and discharge, even if it reduces efficiency, to prevent overcharging and secure engine brake force.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If regenerative braking is used to secure brake force, then energy efficiency is improved, but when the main battery is fully charged or in charging-limiting state, the battery cannot accept more charge causing safety problems and loss of braking capability

Engineering Contradiction:

Improveenergy efficiencyVSAvoidbraking capability

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

Instead of using regenerative braking to charge the battery (normal operation), the patent inverts the energy flow by using the motor to discharge the battery and drive the engine during fuel cut conditions. This allows the system to maintain braking capability when the battery is fully charged by reversing the charging/discharging direction.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the operational parameters of the motor and battery system. When the battery reaches full charge state, the system transitions from regenerative charging mode to motor-driven engine mode, changing the battery's state from charging to discharging, and the motor's role from generator to motor.

Inventive Principle:

Principle #35Parameter changes

2Force

If the engine is operated to maximize engine load for securing engine brake force, then brake force is improved, but fuel efficiency deteriorates due to increased energy loss

Engineering Contradiction:

Improvebrake forceVSAvoidfuel efficiency

Core Design Contradiction:

ForceVSUse of energy by moving object

Solution Approach 1:

The patent converts the harmful effect of energy loss during engine braking into a beneficial function. By intentionally operating the engine at maximum load during fuel cut, the energy loss that would normally be wasted is converted into useful engine brake force, which is then utilized for vehicle deceleration.

Inventive Principle:

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

Solution Approach 2:

The engine is designed to perform multiple functions: normally it provides propulsion, but during fuel cut conditions with full battery charge, it simultaneously serves as a braking device. This multi-functionality allows the same component to provide both drive force and brake force depending on operational conditions.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS11091144B2Engine control method and system of hybrid electric vehicle

Publication Date: 2021.08.17 HYUNDAI MOTOR CO LTD

AI summary

An engine control method of a hybrid electric vehicle is provided. The method includes detecting a state of charge (SOC) of a main battery of the hybrid electric vehicle and detecting whether a brake requires operation when the main battery is in a fully-charged state or a charging-limiting state. An engine fuel cut of the hybrid electric vehicle is executed when a request for the engine brake is generated and an engine is operated to maximize an engine load of the hybrid electric vehicle.