Gas Sensor Element Temperature Profile to Prevent Cracks
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Solution Overview
Problem
Conventional methods for heating sensor elements in gas sensors often result in a lengthy light-off time due to excessive temperature rising rates, which can cause cracking from thermal stress, and lack optimization for preventing cracks while reducing this time.
Innovation Solution
A method for setting a temperature rising profile involves rapid temperature increases, Weibull plotting to determine a crack occurrence failure rate, and establishing a temperature-rising-rate upper limit curve to ensure the profile does not exceed this limit, allowing for quick heating while preventing cracks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the temperature rising rate is increased to reduce light-off time, then the light-off time is shortened, but cracks occur in the sensor element due to thermal stress
Solution Approach 1:
The patent applies dynamics by transitioning from a static constant temperature rising rate to a dynamic variable temperature rising rate profile. The temperature rising rate is adjusted based on the current temperature of the sensor element, being higher at lower temperatures and lower at higher temperatures. This dynamic adjustment allows the system to achieve short light-off time while preventing cracks by adapting the heating rate to the thermal stress承受能力 of the sensor element at different temperature stages.
Solution Approach 2:
The patent changes the parameter of temperature rising rate from a constant value to a variable value that depends on temperature. Specifically, the temperature rising rate is set to be inversely related to the current temperature - higher when temperature is low, and lower when temperature is high. This parameter change resolves the contradiction by allowing rapid initial heating to reduce light-off time while reducing the rate at higher temperatures to prevent thermal stress cracks.
2Reliability
If a constant temperature rising rate is used to prevent cracks, then sensor element integrity is maintained, but light-off time becomes excessively long
Solution Approach 1:
The patent transforms the static constant temperature rising rate into a dynamic variable rate profile that adapts to the current temperature condition. By making the temperature rising rate variable rather than constant, the system can be aggressive (high rate) when it's safe (low temperature) and conservative (low rate) when risk is high (high temperature), thus achieving both short light-off time and crack prevention.
Solution Approach 2:
The patent implements periodic action by dividing the heating process into stages with different temperature rising rates. The heating cycle alternates between rapid heating phases and controlled heating phases based on temperature thresholds, creating a periodic pattern of high and low heating rates that optimizes both speed and safety throughout the light-off process.
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 enables a quick temperature rise of the sensor element while reliably preventing or reducing the occurrence of cracks, thereby optimizing the light-off time and ensuring the sensor's integrity.
Implementation Method 1
the temperature of a sensor element needs to be increased to a predetermined operating temperature by a heater included in the element
Data Source
AI summary
A method for setting a temperature rising profile of a sensor element in the activation of a gas sensor is capable of quickly increasing the temperature of the sensor element while reliably preventing or reducing the occurrence of a crack. The method includes Weibull plotting a failure rate that is a cumulative frequency at which a crack occurs as a result of the rapid temperature rising of the sensor element, identifying a temperature-rising-rate upper limit from the plotting results, determining, based on the temperature-rising-rate upper limit, a temperature-rise upper limit curve, and determining, as an appropriate function, a temperature rising profile in a range in which a temperature rising rate at an appropriate temperature does not exceed values on the temperature-rising-rate upper limit curve for the temperature.