Air Fuel Ratio Sensor Half Activated State Detection
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Solution Overview
Problem
Existing air/fuel ratio sensors for internal combustion engines take a long time to activate, leading to delayed air/fuel ratio feedback control, and current methods for determining the half-activated state are inaccurate due to variations in the gaseous atmosphere, resulting in potential errors in air/fuel ratio detection.
Innovation Solution
A sensor control apparatus with a differential voltage detection system that compares voltages generated when a current is turned on and off to determine the half-activated state of the sensor, allowing for earlier air/fuel ratio feedback control by using a pair of electrodes on a solid electrolyte, a current source, and voltage detecting sections to accurately assess the sensor's state without being influenced by the gaseous atmosphere.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a pump current type or limiting current-type oxygen sensor is used to detect oxygen concentration over a wide range, then the sensor can provide linear output for accurate air/fuel ratio control, but it takes a long time (over ten seconds to tens of seconds) for the sensor to become activated
Solution Approach 1:
The patent applies partial action by introducing the concept of a 'half-activated state' that occurs before full sensor activation. During this partial activation period, the sensor can still provide sufficient signal quality for lambda (rich/lean) determination, enabling earlier air/fuel ratio feedback control without waiting for complete activation. This resolves the contradiction by allowing useful measurement function at a partial level of activation.
Solution Approach 2:
The patent implements preliminary action by detecting the half-activated state and enabling lambda determination functionality before the sensor reaches full activation. The control apparatus prepares the feedback control system in advance by switching to lambda determination mode when the half-activated state is detected, rather than waiting for full activation. This preliminary engagement of control functionality reduces the effective delay in air/fuel ratio control.
2Loss of time
If the integrated value of output voltage is used to estimate the half-activated state, then activation progress can be tracked, but the judgment is largely influenced by the gaseous atmosphere to which the sensor is exposed, leading to inaccurate detection
Solution Approach 1:
The patent introduces an intermediary approach by using a differential amplifier to compare the output voltage with a reference voltage. This differential measurement method acts as an intermediary that eliminates the influence of gaseous atmosphere variations, as both the sensor output and reference voltage are equally affected by atmospheric conditions. The comparison reveals only the activation state information, filtering out atmospheric interference.
Solution Approach 2:
The patent employs copying by introducing a reference voltage that replicates the expected output characteristics under known conditions. By comparing the actual sensor output against this reference copy, the system can identify deviations caused by activation state while canceling out common-mode variations due to gaseous atmosphere. The reference voltage serves as a template against which activation progress is measured.
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
Enables accurate detection of the half-activated state, allowing for rapid air/fuel ratio feedback control even before the sensor reaches full activation, reducing errors caused by atmospheric variations and enabling continuous feedback control until full activation is achieved.
Implementation Method 1
a sensor cell having a pair of electrodes on the opposite sides of a solid electrolyte (e.g., ZrO2) so as to utilize such a phenomenon that an electromotive force is produced when the ambient gases on the opposite sides of the sensor cell are different in oxygen concentration and oxygen ion moves between the opposite sides through the solid electrolyte
Implementation Method 2
Such a phenomenon is not attained unless the solid electrolyte is heated and activated
Data Source
AI summary
A sensor control apparatus comprising an air/fuel ratio sensor having a sensor cell with a pair of electrodes, a current source capable of supplying a predetermined current between the electrodes, a current control section that turns on/off the current source, a voltage detecting section that detects voltages generated between the electrodes at respective times when the current source is turned on and off, a differential voltage detecting section that detects a differential voltage between the voltages that are generated at the respective times when the current source is turned on and off, a first voltage comparing section that compares the differential voltage with a first threshold voltage, and a half-activated state determining section that determines that the sensor cell has reached a half-activated state when the differential voltage is lower than the first threshold voltage. A sensor control method is also provided.