Vehicle Free-Run Control for Deceleration and Fuel Efficiency
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Solution Overview
Problem
During inertia running, vehicles experience poor deceleration feeling and fuel efficiency when the power transmission between the engine and drive wheels is uniformly interrupted, especially at lower speeds with small running resistance, leading to a strange feeling for the driver.
Innovation Solution
A vehicle running control device that determines a target vehicle deceleration based on speed and road gradient, estimates the expected deceleration during free-run control, and adjusts the engine and electric motor torque to match the target deceleration, allowing for smoother and more efficient engine shutdown during inertia running.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power transmission between the engine and drive wheels is uniformly interrupted during inertia running, then fuel efficiency is improved, but the deceleration feeling becomes poor and strange at lower vehicle speeds
Solution Approach 1:
The patent applies local quality by differentiating the control strategy based on vehicle speed conditions. At lower speeds with small running resistance, the system maintains power transmission to preserve engine brake effect, while at higher speeds it interrupts power transmission to improve fuel efficiency. This localized adaptation to different operating conditions resolves the contradiction between fuel efficiency and deceleration feeling.
Solution Approach 2:
The system dynamically adjusts the power transmission state based on real-time vehicle speed and running resistance conditions. The control device continuously monitors vehicle state and switches between maintaining and interrupting power transmission, making the system adaptable to changing conditions rather than using a fixed uniform interruption strategy.
2Loss of energy
If the engine is stopped during inertia running, then fuel consumption is reduced, but the vehicle deceleration may not match driver expectations
Solution Approach 1:
The control device performs preliminary estimation of vehicle deceleration before stopping the engine. By calculating the expected deceleration based on running resistance and comparing it with target deceleration, the system determines in advance whether engine stoppage is appropriate, ensuring that deceleration control requirements are met before committing to the fuel-saving action.
Solution Approach 2:
The system uses feedback by comparing estimated vehicle deceleration with target vehicle deceleration. This closed-loop control ensures that the actual deceleration matches driver expectations, and only when the comparison indicates suitability does the system proceed with engine stoppage to reduce fuel consumption.
Data Source
AI summary
A vehicle running control device in a vehicle includes a power connecting/disconnecting device interrupting power transmission between an engine and drive wheels, the vehicle running control device providing free-run control of interrupting the power transmission with the power connecting/disconnecting device and stopping the engine during inertia running, the vehicle running control device being configured to determine a target vehicle deceleration at the start of the free-run control based on a vehicle speed and to estimate an estimated vehicle deceleration when the free-run control is started, before starting the free-run control, and when the estimated vehicle deceleration is closer to the target vehicle deceleration at the start of the free-run control, the free-run control being more easily provided.