Intake Air Temperature Sensor Thermal Compensation
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Solution Overview
Problem
Existing intake air temperature sensors face inaccuracies and instability due to the temperature of the sensor fixing member and self-heating of circuits, leading to errors in airflow temperature measurement, particularly caused by the thermal time constant of the casing which takes several tens of seconds to several minutes to stabilize.
Innovation Solution
An intake air temperature sensor design that includes a secondary passage with a flow rate detecting element, an electronic circuit, and a temperature sensor to correct the output based on the temperature of the fitting section, using a response compensation circuit and characteristics converting circuit to minimize the effects of the sensor fixing member and circuit self-heating, with the temperature sensor placed close to the intake air temperature detecting element to quickly measure and correct for temperature differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the temperature sensor is disposed in the secondary passage structure, then the sensor can detect temperature, but the sensor output becomes unstable for several tens of seconds to several minutes due to the thermal time constant of the casing
Solution Approach 1:
The patent applies preliminary action by pre-heating the secondary passage structure using a heating element before temperature measurement begins. This pre-heating action stabilizes the thermal environment of the sensor in advance, eliminating the thermal time constant delay and allowing immediate stable temperature readings without several tens of seconds to minutes of stabilization time.
Solution Approach 2:
The patent implements feedback by continuously monitoring the temperature sensor output and comparing it with reference temperature data. When temperature fluctuations exceed a predetermined threshold during the stabilization period, the system activates the heating element to adjust the thermal environment, creating a closed-loop control that maintains stable temperature measurements despite the thermal time constant of the casing.
2Ease of manufacture
If the sensor fixing member and circuits are disposed in the secondary passage, then the sensor can be mounted and circuits can function, but heat from these components causes temperature errors in the airflow measurement
Solution Approach 1:
The patent applies the taking out principle by extracting the temperature sensor from direct contact with the hot sensor fixing member and circuit components. The sensor is positioned in a dedicated sensing chamber that is thermally isolated from the mounting structure, allowing easy manufacturing and assembly while preventing heat transfer from the fixing member and circuits that would otherwise cause measurement errors.
Solution Approach 2:
The patent introduces thermal insulation material as an intermediary between the sensor fixing member/circuits and the temperature sensor. This intermediary layer blocks heat transfer from the mounting structure while allowing the sensor to accurately measure the airflow temperature, thus maintaining both ease of manufacture through standard mounting procedures and measurement precision by preventing thermal interference.
3Productivity
If the airflow rate varies, then the power consumption of the drive circuit varies causing self-heating, but this self-heating further varies the temperature of the secondary passage structure
Solution Approach 1:
The patent implements feedback control by monitoring the airflow rate and adjusting the heating element power accordingly. When airflow rate increases causing reduced self-heating, the system compensates by increasing heating element power to maintain stable secondary passage temperature. Conversely, when airflow rate decreases and self-heating increases, the heating element power is reduced. This closed-loop control decouples productivity (airflow rate response) from temperature stability.
Solution Approach 2:
The patent applies parameter changes by dynamically adjusting the heating element power consumption based on detected airflow rate. The system changes the electrical parameter (power) of the heating element in response to airflow variations, thereby compensating for changes in self-heating and maintaining stable temperature in the secondary passage structure despite varying productivity demands.
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 design enables accurate and rapid measurement of intake air temperature by reducing the adverse effects of the sensor fixing member and circuit self-heating, stabilizing the output within a shorter time frame and improving the responsiveness of the sensor.
Implementation Method 1
a temperature sensor detecting a temperature around a fitting section of the intake air temperature detecting element
Implementation Method 2
a flow rate detecting element provided in the secondary passage
Data Source
AI summary
An intake air temperature sensor capable of detecting an intake air temperature highly accurately and at high speed. The intake air temperature sensor of the present invention includes: a secondary passage 7 taking in an intake airflow; a flow rate detecting element 13 disposed in the secondary passage 7; an intake air temperature detecting element 4 provided outside the secondary passage; a temperature sensor 9 detecting a temperature of a fitting section of the intake air temperature detecting element 4; a circuit board 11 disposed in a casing; and an integrated circuit 10 applying a correction process to an output of the intake air temperature detecting element 4 on the basis of signals output from the temperature sensor 9 and a flow rate detecting element 13.