Air-Fuel Ratio Control via Brake Booster Inflow Compensation
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Solution Overview
Problem
The existing air-fuel ratio control methods fail to accurately reflect the fresh air component flowing into the intake manifold from a brake booster, leading to deviations in air amount modeling and misfire phenomena due to the positioning of Mass Air Flow (MAF) sensors, which cannot recognize the large air inflow during repeated brake applications.
Innovation Solution
An air-fuel ratio control method that measures absolute pressure in the intake manifold using a MAP sensor, compares it with a model pressure, determines if the deviation is caused by brake operation, and corrects the intake air amount based on the brake inflow flow rate using a map, ensuring accurate air-fuel ratio control by calculating the cylinder intake air amount and adjusting fuel injection accordingly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a MAF sensor is installed at the front end of the throttle valve to directly measure the amount of air, then the air amount can be directly measured, but the air flowing into the intake manifold from the brake booster cannot be recognized, leading to large deviation between actual air amount and modeled air amount
Solution Approach 1:
The patent uses the MAP sensor as an intermediary to indirectly detect the brake booster air inflow. By measuring the absolute pressure in the intake manifold and comparing it with model pressure, the system can detect deviations caused by brake booster air inflow, thereby compensating for the MAF sensor's inability to directly measure this air flow.
Solution Approach 2:
The patent implements a feedback mechanism where the MAP sensor continuously monitors the intake manifold pressure, compares it with the model pressure, and uses the deviation information to correct the air amount calculation. This feedback loop enables the system to dynamically adjust for brake booster air inflow effects.
2Ease of operation
If the brake booster is connected to the intake manifold to boost master cylinder force, then brake operation is enabled, but fresh air flows into the intake manifold during brake application, causing deviation in air-fuel ratio control
Solution Approach 1:
The MAP sensor serves as an intermediary device that indirectly measures the effect of brake booster air inflow on the intake manifold pressure. By detecting pressure deviations, the system can infer the amount of air introduced during brake operation and compensate for its effect on air-fuel ratio control.
Solution Approach 2:
The patent replaces direct mechanical measurement of brake booster air flow with a pressure-based detection system. Instead of mechanically measuring the air flow from the brake booster, the system uses MAP sensor pressure measurements and mathematical modeling to substitute for the direct measurement, achieving accurate air-fuel ratio control.
3Reliability
If lambda control is used to compensate for lean combustion state, then misfire can be prevented when air inflow is small, but feedback control stops when air-fuel ratio exceeds predetermined limit value, making it difficult to prevent misfire
Solution Approach 1:
The patent applies preliminary action by proactively detecting and compensating for brake booster air inflow before it causes lean combustion conditions. By using MAP sensor data to predict and adjust for the air inflow, the system prevents the air-fuel ratio from exceeding limits in the first place, rather than attempting to correct the problem after lambda control becomes ineffective.
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 method allows for stable air-fuel ratio control, preventing misfires by accurately accounting for air inflow from the brake booster, reducing the likelihood of lean combustion states and ensuring proper engine operation.
Implementation Method 1
measuring, by a manifold absolute pressure (MAP) sensor, an absolute pressure of an intake manifold of a vehicle
Implementation Method 2
the brake booster 4 is connected to the intake manifold 13 formed with a negative pressure to use the negative pressure of the intake manifold
Data Source
AI summary
An air-fuel ratio control method reflecting a brake booster inflow flow rate includes: determining a deviation between an actually measured pressure of an intake manifold and a model pressure of the intake manifold is equal to or greater than a predetermined value; determining that the deviation is caused by a brake operation; correcting an intake air amount by reflecting a flow rate flowing into the intake manifold from a brake booster; and performing an air-fuel ratio control based on the corrected intake air amount.