Thermal measuring and testing – Transformation point determination
Patent
1998-08-06
2000-07-25
Bennett, G. Bradley
Thermal measuring and testing
Transformation point determination
374 28, 374140, 374149, 374151, 62140, 62156, G01N 2504, G01N 2514, G01K 10008, F25D 2106
Patent
active
060929251
DESCRIPTION:
BRIEF SUMMARY
DETAILED DESCRIPTION OF THE INVENTION
1. Field of the Invention
The present invention relates to a frost deposition detecting device having a temperature sensor, and more particularly to a frost deposition detecting device used in an evaporator or a defrosting device of a heat exchanger for various industrial machines and home refrigerators.
2. Related Art
As is well known, the cooling efficiency of a refrigerator is often reduced due to frost deposited on the surface of the cooling fin of an evaporator or a heat exchanger incorporated into it. If cooling operation is continued in the frosted condition, energy consumption will be unnecessarily increased, resulting in high costs and mechanical breakdown. To solve such problem, there has been a method in which defrosting is performed by energizing the heater to raise the temperature of the cooling fin when the total operation time of the compressor in a temporary operation mode reaches a predetermined value, and the heater is switched off after a predetermined period of time has passed since the defrosting operation.
In the conventional defrosting method, the timing to start defrosting can be controlled. However, controlling the timing is not good enough for a defrosting operation, since frosting conditions may vary depending on the ambient temperature, humidity, frequency of opening and closing the door, and the conditions of the content of the refrigerator. As this defrosting method is not for detecting frosting conditions, defrosting may be performed in a non-frosted state, or no defrosting may be performed at all even in an over-frosted state, which by no means increases energy efficiency in the cooling operation.
To eliminate the above problems, the following methods have been developed. emitted from a light emitting element is reflected from a reflecting surface, and the reflected light is detected by a photodetector. A change in the quantity of light caused by a shift in the refraction index of the light received by the photodetector or the angle of incidence can be detected from the quantity of frost deposited on the reflecting surface. Thus, the deposited frost can also be detected. is detected: The temperature of the cooling machine or the ambient temperature is detected in a non-frosted condition and a frosted condition. Deposited frost can be detected from the detected temperature difference. frequency of the piezoelectric vibrator is detected: This method utilizes the face that frost deposited on the surface of a piezoelectric vibrator changes the resonance frequency. If the resonance frequency (the quantity of deposited frost) is larger than a predetermined value, frost deposition is detected. Information on the total operation time of the compressor, frequency of opening and closing of the door, and the outside temperature is inputted into the microcomputer, which judges whether frost exists or not by accumulating the data. Frost deposition can be detected in accordance with a frost deposition detecting program.
However, with the optical frost deposition detecting method (1), it is difficult to keep the frost deposition detector small, and regular maintenance is necessary to maintain a good detection accuracy as the reflection ratio of the reflecting surface. Also, the circuit structure is complicated, resulting in higher cost.
With the method (2) of detecting from a temperature difference, there are many problems in practical use such as low detection accuracy caused by varied quantity of deposited frost. With the method (3) using a piezoelectric vibrator, there is a problem that dust on the vibrator and vibration both from inside and outside often cause erroneous operation. The problem with the microcomputer-controlled method (4) is that the energy consumption efficiency is low due to the varied quantity of deposited frost depending on the season, weather, and other conditions.
In view of this, the present inventor has disclosed, in Japanese Patent Application No. 6-223482 (or U.S. Pat. No. 5,522,232), an inexpensive frost deposition detect
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Bennett G. Bradley
Ishizuka Electronics Corporation
Verbitsky Gail
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