Oxygen Sensor Heater Control via Dynamic Target Resistance
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Solution Overview
Problem
Oxygen sensors in internal-combustion engines face degradation issues, leading to increased internal resistance, which affects temperature control and further degrades the sensor, as existing feedback control methods can excessively heat the detection element, exacerbating degradation.
Innovation Solution
An oxygen sensor controlling apparatus that monitors the degree of degradation and gas atmosphere by obtaining a degradation index and using it to adjust the target resistance value for the heater, ensuring appropriate energization control to maintain a constant temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If feedback control is performed to decrease element impedance, then element impedance approaches target impedance, but element temperature rises excessively causing further degradation
Solution Approach 1:
The patent changes the control parameter from fixed target impedance to dynamic target impedance that varies with degradation index. As degradation increases, the target impedance value is adjusted to account for the inverted V-shaped relationship between sensor output and internal resistance, preventing excessive temperature rise while maintaining adequate measurement precision.
Solution Approach 2:
The patent implements feedback control that incorporates the degradation index into the target impedance calculation. The controller continuously monitors sensor output and degradation index, adjusting the target impedance value accordingly to maintain element temperature within safe limits while achieving adequate impedance control.
2Reliability
If heater energization is increased to compensate for degradation, then element impedance decreases, but element temperature rises causing accelerated degradation
Solution Approach 1:
The patent dynamically adjusts the target impedance parameter based on the degradation index and sensor output state. By accounting for the inverted V-shaped relationship between sensor output and internal resistance, the system maintains appropriate heater energization levels that prevent both insufficient performance and excessive temperature rise that would accelerate degradation.
Solution Approach 2:
The patent makes the target impedance value dynamic rather than fixed. The target impedance varies with degradation index and sensor output state, allowing the system to adapt heater control to current operating conditions and prevent premature sensor failure while maintaining adequate performance.
3Ease of operation
If target impedance is kept constant, then control is simple, but element temperature becomes unstable due to degradation
Solution Approach 1:
The patent changes the target impedance parameter from constant to variable based on degradation index and sensor output. This dynamic adjustment maintains element temperature stability despite degradation while adding manageable complexity to the control system through structured parameter modification.
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 approach allows for effective heater control based on the sensor's degradation and gas atmosphere, preventing excessive heating and prolonging the sensor's lifespan by maintaining optimal operating conditions.
Implementation Method 1
a heater that heats the detection element
Implementation Method 2
The solid electrolyte that forms the detection element shows excellent oxygen ion conductivity in a high temperature state
Data Source
AI summary
An oxygen sensor controlling apparatus includes: a controller configured to obtain a degradation index of a detection element; obtain a sensor output; detect an internal resistance of the detection element by causing a temporary change between electrodes of the detection element; successively obtain a target resistance value corresponding to the internal resistance using a first sensor output that is a value of the sensor output obtained at a time before or after a period when the temporary change occurs and the degradation index; and feedback control energization of the heater so that the internal resistance becomes the target resistance value.