Vehicle Hill Hold Control During Idling Stop
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Solution Overview
Problem
Vehicles with idling stop technology face deteriorated hill start performance due to lack of creep torque during engine idling stop, as existing hill hold control systems cancel braking force application when engine rotation speed exceeds a certain threshold, leading to insufficient braking force and delayed engine restart.
Innovation Solution
A control device that prohibits cancellation of hill hold control when the engine is being stopped through idling, allowing continued braking force application and autonomous engine restart when possible, and adjusts cancellation conditions based on engine rotation speed and restart command history to maintain hill start performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If hill hold control is cancelled when engine rotation speed exceeds a certain threshold, then fuel economy is improved through idling stop, but hill start performance deteriorates due to insufficient braking force
Solution Approach 1:
The control device dynamically adjusts the hill hold control cancellation timing based on engine rotation speed trends. Instead of using a fixed threshold, the system monitors whether the engine rotation speed is increasing or decreasing to determine the optimal moment to cancel hill hold control, ensuring both fuel economy and hill start performance
Solution Approach 2:
The control device uses feedback from engine rotation speed sensors to continuously monitor engine state and adjust hill hold control accordingly. By detecting the trend of engine rotation speed change, the system provides feedback-based control that prevents premature cancellation of braking force while enabling fuel-efficient idling stop operation
2Device complexity
If hill hold control is cancelled based on engine rotation speed threshold, then control simplicity is maintained, but hill start performance deteriorates when engine restart is delayed
Solution Approach 1:
The control device performs preliminary assessment of engine rotation speed trend before canceling hill hold control. By checking whether the engine rotation speed is increasing or decreasing, the system takes preliminary action to ensure braking force is maintained until the appropriate moment, preventing delayed engine restart issues without significantly increasing control complexity
Data Source
AI summary
Hill hold control for a vehicle that is executed in response to idling stop of an engine is cancelled on the condition that a command to restart the engine for recovery from the idling stop is issued and an engine rotation speed is higher than or equal to a predetermined determination value; whereas, cancellation of the hill hold control is prohibited when the engine is in process of being stopped through the idling stop.