Filter Degradation Estimation Using Evaporator Temperature Change Rate
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Solution Overview
Problem
Existing filter-clogging detection mechanisms in vehicular air conditioners are inaccurate when air temperature varies, as they rely on stable environmental conditions and cannot determine filter degradation effectively when the temperature of air drawn into the air conditioner case changes.
Innovation Solution
A filter-degradation estimating device that includes an intake air temperature detecting section, an evaporator temperature detecting section, a temperature change rate calculating section, a standard change rate calculating section, and a degradation degree calculating section, which calculates the degradation degree of the filter based on temperature change rates and standard change rates, even when air temperature varies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing filter-clogging detection mechanisms are used, then the device can detect filter clogging under stable environmental conditions, but the detection accuracy deteriorates when air temperature varies
Solution Approach 1:
The patent changes the detection parameter from static temperature difference to dynamic temperature change rate. By calculating how quickly the evaporator temperature changes over time (dT/dt), the system can detect filter degradation regardless of the absolute air temperature. This transforms the detection approach from being sensitive to environmental temperature conditions to being insensitive to them, thereby resolving the contradiction between measurement precision and adaptability.
Solution Approach 2:
The patent replaces the conventional mechanical/thermal equilibrium-based detection method with a dynamic rate-of-change detection method. Instead of relying on steady-state temperature differences that depend on environmental conditions, the system uses the rate of temperature change during compressor operation, which provides a universal indicator of filter degradation across all temperature conditions.
2Measurement precision
If blower and compressor operations are altered to improve filter degradation detection, then detection accuracy improves, but air conditioning control performance deteriorates
Solution Approach 1:
The patent maintains continuous air conditioning control by using temperature change rate data collected during normal compressor operation. The system continuously monitors dT/dt without interrupting or altering blower and compressor operations, ensuring both accurate filter degradation detection and stable air conditioning performance simultaneously.
Solution Approach 2:
The system uses feedback from the evaporator temperature sensor to calculate the temperature change rate, which then feeds into the filter degradation estimation. This closed-loop approach allows the system to detect filter status without disrupting the primary air conditioning control loop, maintaining ease of operation while improving measurement precision.
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 estimation of filter degradation without affecting air conditioning control, allowing for precise prediction of filter replacement needs and preventing changes in air temperature and airflow caused by altering blower and compressor operations.
Implementation Method 1
an evaporator configured to cool the air drawn into the air conditioner through evaporation of a refrigerant
Data Source
AI summary
A filter monitoring system for a filter in a vehicle air conditioner includes a first temperature sensor to detect an air temperature of intake air drawn into an air conditioner case through the filter, a second temperature sensor to detect an evaporator temperature of the evaporator, and a processor coupled to the first and second temperature sensors and coupled to a memory. The processor is configured to calculate an actual change-rate of the evaporator temperature while a compressor is in operation, calculate an expected change-rate of the evaporator temperature based on the air temperature and operation levels of a blower and the compressor by using predetermined data with a properly functioning filter, calculate a degradation degree of the filter by comparing the actual change-rate to the expected change-rate, and output a signal indicating degradation of the filter upon determining that the degradation degree is out of an acceptable range.