JPH0130438B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a frost detection device used in a refrigerator cooler, etc., in which a case covering a light-emitting and light-receiving element is made of a resin having light transmission characteristics similar to the spectral distribution of the light-emitting element. This case blocks visible light and allows only the light from the light emitting element to pass through.

Generally, frost adhering to the evaporator of refrigerators and other freezers can be removed by defrosting at fixed intervals by integrating the operating hours of the compressor, or by counting the number of openings and closings of the refrigerator and freezer compartment doors and removing the frost when a fixed number of times is reached. It was meant to cause frost. However, the formation of frost on the evaporator of a refrigerator, etc. is greatly affected by the outside temperature and humidity of the refrigerator, the frequency of opening and closing of the refrigerator and freezer compartment doors, and the contents stored in the refrigerator. There were disadvantages such as defrosting was not carried out when necessary, and defrosting was not carried out even though a large amount of frost formed on the evaporator and the refrigeration capacity was reduced.

In order to overcome these drawbacks, various frost detection devices have been proposed that use light-emitting elements such as light-emitting diodes and light-receiving elements such as hetotransistors as a means of directly detecting frost formation. The element and light-receiving element are housed in a case that has an aperture that allows the light from the element to pass through, or a case that has a lens, etc. in this aperture, and frost or water droplets may adhere to the aperture of the case or the lens, etc. provided in the aperture. It was easy to do so, and there was a risk of malfunction. Furthermore, since the characteristics of the light-emitting element and the light-receiving element are likely to change due to the influence of the external atmosphere, particularly moisture and cooling/heating cycles, there has been a desire for a frost detection device that has a structure that is disconnected from the external atmosphere.

The present invention aims to eliminate such drawbacks, and one embodiment thereof will be described below with reference to the accompanying drawings.

In Figures 1 and 2, 1 is an evaporator of a refrigerator or other refrigerator, 2 is a pipe through which refrigerant passes, and 3
is a fin plate arranged perpendicular to this pipe 2, 4 is a frost detection hole provided in the fin plate 3,
Reference numeral 5 denotes frost detection devices that are provided facing each other through the frost detection hole 4. The frost detection device 5
A U-shaped sealed case 6 made of a visible cut resin such as polycarbonate that blocks visible light and preferentially transmits only light emitting element light, a light emitting diode 7 as a light emitting element, and a phototransistor 8 as a light receiving element. It is composed of a mounting plate 9 for fixing the light emitting diode 7 and the phototransistor 8, and a sealing resin 10 for sealing the mounting plate 9 inside the case 6. The case 6 consists of a pair of storage parts 6a for storing both the elements 7 and 8, and a fixing part 6b for arranging a mounting plate 9 to which both the elements are fixed. FIG. 3 shows an example of the light transmission characteristics of the case 6. In this figure, A is the transmission characteristic when 1 mm thick transparent nylon is used as the molding resin for the case 6, and B is the light transmission characteristic when 1 mm thick polycarbonate is used. Further, FIG. 4 shows an example of the spectral distribution of a light emitting diode and the spectral sensitivity distribution of a phototransistor.

That is, as is clear from this graph, transparent nylon A transmits light with a wider range of wavelengths than the spectral distribution of the light emitting diode 7, but polycarbonate B limits the wavelength of light that can be transmitted.
Only light having a wavelength close to the spectral distribution of the light emitting diode 7 is transmitted. In other words, by not transmitting light with wavelengths in the visible light range, the accuracy of light sensing is greatly improved. Therefore, in the above configuration, since visible cut resin is used for the case 6 of the frost detection device 5, most of the visible light is blocked and only the light from the light emitting diode 7 is preferentially transmitted. Light can be exchanged between the phototransistor 7 and the phototransistor 8 without being affected by disturbance light. Since there is no need for an opening in the housing case that allows light to pass through, unlike in the past, it has become possible to create a completely sealed structure that is cut off from the external atmosphere.

To further summarize the above, since it is not affected by ambient light, the phototransistor 8 senses the ambient light even though the frost detection hole 4 is closed by frost and the light from the light emitting diode 7 is blocked. There is no such situation where frost formation is not detected. In addition, the surrounding conditions in which the frost detection device is used are harsh, with high temperature and humidity during defrosting and extremely low temperatures during cooling operation, but as mentioned above, the case is completely sealed, so it is not affected by moisture. Cold and heat cycle resistance is also improved.

As is clear from the above description, the frost detection device of the present invention has a light emitting element such as a light emitting diode and a light receiving element such as a phototransistor arranged opposite to a frost detection hole provided in an evaporator, and both of the elements The sealed case, which consists of a pair of storage parts for storing the elements and a fixing part for arranging the mounting plate to which both the elements are fixed, is integrally formed of a visible light cut synthetic resin that transmits the light from the light emitting element, so it is water resistant. It has the excellent effect of improving moisture resistance and cold/heat cycle resistance, and preventing malfunctions caused by ambient light.

[Brief explanation of drawings]

FIG. 1 is a plan view of a part of an evaporator having a frost detection device according to an embodiment of the present invention, and FIG. 2 is a perspective view of the same device.
FIG. 3 is a light transmission characteristic diagram of the case, and FIG. 4 is a spectral distribution diagram of the light emitting diode and phototransistor. 4...Frost detection hole, 7...Light emitting diode light emitting element, 8...Phototransistor light receiving element, 6...
Case, 6a... Storage section, 6b... Fixed section, 9...
...Mounting plate.

Claims (1)

[Claims] 1. A light-emitting element and a light-receiving element arranged opposite to each other in a frost detection hole provided in the evaporator, a pair of storage parts for storing the two elements in a sealed state, and a fixing part for arranging the mounting plate to which the two elements are fixed. 1. A frost detection device comprising: a sealed case made of a visible light-cutting synthetic resin having light transmission characteristics similar to the spectral distribution of the light emitting element.