Air-Fuel Ratio Sensor Voltage Control for Exhaust Gas Detection
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Solution Overview
Problem
Existing air-fuel ratio sensors struggle to accurately detect absolute air-fuel ratios in internal combustion engines, especially when the ratio is not stoichiometric, due to variations in sensor output characteristics and aging, leading to inconsistent measurements.
Innovation Solution
A control system for internal combustion engines that utilizes an air-fuel ratio sensor with a diffusion regulating layer and a specific voltage application strategy to differentiate between stoichiometric and non-stoichiometric air-fuel ratios, ensuring accurate detection of air-fuel ratios by setting a constant voltage within defined voltage regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional air-fuel ratio sensor is used to detect exhaust gas, then the stoichiometric air-fuel ratio can be accurately detected, but the absolute value of non-stoichiometric air-fuel ratio cannot be accurately detected due to sensor output characteristic variations and aging
Solution Approach 1:
The patent applies parameter changes by varying the applied voltage across different operating ranges. For stoichiometric detection, a first applied voltage is used, while for non-stoichiometric detection, a second applied voltage is used. This voltage parameter change enables the sensor to accurately detect absolute air-fuel ratio values across different conditions, resolving the contradiction between measurement precision and reliability.
Solution Approach 2:
The control system dynamically adjusts the applied voltage based on the operating conditions. The system switches between first and second applied voltages depending on whether the air-fuel ratio is stoichiometric or non-stoichiometric. This dynamic adaptation ensures consistent and accurate detection across different sensor states and time periods.
2Ease of manufacture
If the same model of air-fuel ratio sensor is used, then manufacturing cost is reduced, but detection accuracy varies between individual sensors and over time due to production tolerances and aging
Solution Approach 1:
The patent compensates for sensor variations by changing the applied voltage parameter. By using different applied voltages for different detection scenarios, the system maintains accurate detection across individual sensors with different output characteristics and over time as sensors age, while still using standardized sensor models.
Solution Approach 2:
The control system uses feedback from the sensor output to determine the appropriate applied voltage. By monitoring the sensor response and adjusting the applied voltage accordingly, the system maintains detection accuracy despite variations between individual sensors and over time.
3Device complexity
If a fixed applied voltage is used in the air-fuel ratio sensor, then the sensor structure is simplified, but the ability to detect both stoichiometric and non-stoichiometric air-fuel ratios accurately is compromised
Solution Approach 1:
The patent implements dynamic voltage adjustment where the control system switches between first and second applied voltages based on the detection requirements. This dynamic approach enables accurate detection of both stoichiometric and non-stoichiometric air-fuel ratios while maintaining relatively simple sensor hardware structure.
Solution Approach 2:
The detection range is segmented into stoichiometric and non-stoichiometric regions, with different applied voltages used for each segment. This segmentation allows the sensor to optimize its performance for different detection scenarios without requiring a completely complex sensor design.
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
The system effectively detects absolute air-fuel ratios, even when they are not stoichiometric, by using a diffusion regulating layer and precise voltage control, enhancing the accuracy and reliability of air-fuel ratio measurements.
Implementation Method 1
a solid electrolyte layer of zirconia, etc., which is arranged between the first electrode and second electrode
Implementation Method 2
a diffusion regulating layer which is arranged between the exhaust passage and the first electrode
Data Source
Figure 1
Figure 2~3
Figure 4(A)~4(C)
AI summary
This control device for an internal combustion engine is equipped with: an air/fuel ratio sensor; and an engine control device that controls the internal combustion engine according to the output of the air/fuel ratio sensor. The air/fuel ratio sensor is configured so that the applied voltage at which the output current reaches zero varies according to the exhaust air/fuel ratio, and the output current increases if the applied voltage is increased at the air/fuel ratio sensor when the exhaust air/fuel ratio is the stoichiometric air/fuel ratio. When the air/fuel ratio of exhaust gas is to be detected by the air/fuel ratio sensor, the applied voltage at the air/fuel ratio sensor is fixed at a constant voltage, said constant voltage being different to the voltage at which the output current reaches zero when the exhaust air/fuel ratio is the stoichiometric air/fuel ratio, and being the voltage at which the output current reaches zero when the exhaust air/fuel ratio is different to the stoichiometric air/fuel ratio. Thus provided is a control device for an internal combustion engine that uses an air/fuel ratio sensor capable of detecting an absolute value for the air/fuel ratio of exhaust gas even if the air/fuel ratio of the exhaust gas is not the stoichiometric air/fuel ratio.