Vehicle Start-Stop System Gradient-Based Threshold Control
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Solution Overview
Problem
Existing start-stop systems in vehicles often inadvertently shut down or restart the engine when driving on inclines due to drivers overestimating brake pressure, leading to inefficient operation and increased emissions.
Innovation Solution
The system determines first and second threshold brake values based on functions of the road gradient, allowing for more intuitive engine control by varying the difference between these values with the gradient, thereby reducing inadvertent engine shutdowns and restarts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the threshold brake pressure is increased to prevent inadvertent engine shutdowns on inclines, then engine reliability is improved, but fuel efficiency deteriorates due to increased idling time
Solution Approach 1:
The patent applies dynamics by making the threshold brake pressure variable rather than fixed. The threshold dynamically adjusts based on detected road gradient conditions - increasing on inclines to prevent inadvertent shutdowns and using lower values on flat surfaces to maximize fuel efficiency. This dynamic adaptation resolves the contradiction by optimizing the threshold for each operating condition.
Solution Approach 2:
The patent changes the parameter of threshold brake pressure based on road gradient. By detecting the gradient and adjusting the threshold accordingly, the system adapts to different operating conditions - using higher thresholds on inclines to maintain reliability and lower thresholds on flat surfaces to improve fuel efficiency, thus resolving the contradiction between these two objectives.
2Use of energy by moving object
If the start-stop system is made more sensitive to brake pressure changes, then fuel efficiency is improved through more frequent shutdowns, but driver control deteriorates due to inadvertent engine stops
Solution Approach 1:
The patent changes the sensitivity parameter of the start-stop system based on road gradient. On flat surfaces, the system uses lower thresholds for greater sensitivity and frequent shutdowns to improve fuel efficiency. On inclines, the system reduces sensitivity by using higher thresholds, preventing inadvertent shutdowns when the driver applies normal braking force, thus maintaining driver control while still allowing fuel-efficient operation when appropriate.
3Device complexity
If a fixed threshold brake pressure is used for engine shutdown, then system complexity is reduced, but adaptability deteriorates due to inadequate performance on varying road gradients
Solution Approach 1:
The patent transforms the fixed threshold system into a dynamic one that adapts to road gradient conditions. The system detects gradient information and adjusts the threshold brake pressure accordingly, enabling it to perform adequately on both flat surfaces and inclines. This dynamic adaptation improves versatility without significantly increasing system complexity, as the adjustment logic follows clear gradient-based rules.
Data Source
AI summary
Systems and methods are provided for a vehicle including a start-stop system configured to shut down and restart an engine of the vehicle automatically based on a brake value of a brake system. In one example, the method may include determining a first threshold brake value as a first function of a gradient of a surface on which the vehicle is positioned, determining a second threshold brake value as a second function of the gradient, wherein a difference between the first and second threshold brake values varies as a function of the gradient, shut down the engine when the brake value exceeds the first threshold brake value, and restart the engine when the brake value drops below the second threshold brake value. In this way, an incidence of inadvertent engine shut downs and restarts when the vehicle is stopped on an incline may be decreased.