JPS6044790A - Controller for defrostation of refrigerator, etc. - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a defrosting control device that optically detects frost adhering to a cooler such as a refrigerator and issues a defrosting command.

Conventional Structure and Problems Generally, this type of defrosting control device is constructed by disposing a frost detector in a cooling chamber in which a cooler is installed in order to detect the amount of frost on the cooler. The frost detector is a frost detector 2 on the cooler plate, which serves as a frost forming plate.A light emitting element and a light receiving element are installed facing each other through the holes. The amount of frost is detected by detecting changes in the amount of light passing through the frost. However, with conventional defrosting control devices, if the light emitting element or light receiving element fails, the amount of transmitted light disappears, or the transmitted light becomes unable to be detected, and the double voltage output from the frost detector is determined by the frost state of the cooler. Regardless of the defrost signal, the defrost operation is always in operation and the defrost heater is continuously energized, so the internal temperature of the refrigerator, etc. continues to rise, not only causing damage to the stored food, but also causing damage to the stored food. This may lead to an unsafe situation such as a fire, which has been a major drawback of optical defrost detection devices. Conventionally, it has been considered to install multiple light emitting elements and light receiving elements as a measure against element failure, but this has not been adopted due to lack of practicality in terms of cost.

Purpose of the Invention Therefore, the present invention eliminates the need for continuous defrosting operation due to a failure of the light emitting element or light receiving element of the frost detector, prevents the temperature inside the refrigerator from becoming too high, and improves the safety of stored products and equipment. The purpose of the present invention is to provide a defrosting control device that can ensure the following.

Structure of the Invention In order to achieve this object, the present invention detects abnormalities in the output signal of the frost detector and detects malfunctions in the light emitting element, light receiving element, etc. of the frost detector. The device is kept inactive and maintains cooling operation to ensure the safety of stored items and equipment.

Description of examples An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a plan view of a refrigerator (cooling chamber A of a refrigerator) equipped with a defrosting control device according to an embodiment of the present invention.

In this figure, reference numeral 1 denotes a cooler consisting of fins 2 and refrigerant pipes 4 passing through end plates 3 on both sides of the fins 20, and constitutes a well-known refrigeration cycle together with an electric compressor 12, which will be described later. 5 is a fan motor for forcibly circulating air in the cooler 1, and 6 is a frost detector attached to a part of the end plate 3.

The cooler 1 is equipped with a cooler defrosting heater 11, which will be described later.
is provided.

The frost detector 6 will be explained in detail in FIG. frost detector 6
A light-emitting element 6a and a light-receiving element 6b facing each other are housed in a case 6c through a frost detection small hole 3b provided in a notch 3a of an end plate 3 of the cooler 1. , the amount of frost is detected by detecting a change in the amount of light passing through the small holes 3b as frosting progresses.

Next, an electric circuit as a defrosting control device will be explained with reference to FIG. Reference numeral 7 denotes a commercial AC power source, and 8 indicates an internal temperature regulator which opens when the internal temperature falls below a predetermined temperature.

9 is a relay that is switched by a signal from a defrosting control circuit 1o, which will be described later, and a normally closed contact 9a is connected to a defrosting heater 1 of the cooler 1.
1 are connected in series, and the normally closed contact 9b is connected to the electric compressor 12.
are connected in series, and the aforementioned fan motor 6 is further connected in parallel with the compressor 12.

Next, the defrosting control circuit 10 will be described. 13 is a power transformer, 14 is a rectifying diode, and 15 is a constant voltage diode, which constitute a DC constant voltage circuit. 16 is a current limiting resistor for the light emitting element 6a of the frost detector 6;
A is connected in series with the DC constant voltage circuit. 1 is a frost detection comparator, which outputs a frost detection type output a determined by the amount of light received by the light receiving element 6b of the frost detector 6 to a non-inverting input terminal 17a, and outputs the frost detection type output a determined by the amount of light received by the light receiving element 6b of the frost detector 6 to the non-inverting input terminal 17a. The defrosting start set voltage determined by the voltage is connected to the inverting input terminal 17b, and the frost detection type output a is compared with the defrosting start set voltage and an output signal is outputted from the output terminal 17c. A feedback resistor 21 is provided between the output terminal 17c and the inverting input terminal 17b. 22 is a failure detector (comparator), in which the frost detection type output a is sent to an inverting input terminal 22a, and an abnormality detection setting voltage determined by the series combined resistance of resistors 18 and 19 and the partial voltage of a resistor 2o is sent to a non-inverting input terminal 22b. The frost detection type output a and the abnormality detection voltage are compared and an output signal is output from the output mAH element 22c. Note that the abnormality detection voltage is sufficiently lower than the defrost start setting voltage, and the light emitting element 6a.

The voltage is set to a very low level at which a failure of the light receiving element 6b can be detected. Reference numeral 23 denotes an AND gate that performs an AND operation between the signal at the output terminal 17a of the frost detection comparator 17 and the signal at the output terminal 22c of the failure detector 22, and 24 drives the relay 9 by the output 23a of the AND gate 23. It is a transistor that

The operation of the above configuration will be explained with reference to the graph of FIG. When the frost on the cooler 1 progresses and the frost detection small holes 3b are blocked by the frost, the amount of light received by the light receiving element 6b decreases, and as a result, the frost detection word output voltage a decreases, and the frost detection comparator 1T When T1 is lower than the defrosting start voltage, a frost detection signal (“H” level) is input from the output terminal 17c of the frost detection comparator 17 to the AND gate 23.

At this time, if the light emitting element 6a and the light receiving element 6b are not malfunctioning, the frost detection type output a is higher than the abnormality detection voltage and the failure signal ("L" level) Ii is not output from the output terminal 22c of the failure detector 22, and the AND gate 23, a normal signal of co H18 level is input.

Therefore, the frost detection comparator 17 causes the frost detection signal to be A.
When the signal is input to the ND gate 23, a defrosting execution signal ("H" level) is output from its output terminal 23a, the transistor 24 is turned on, and the relay 9 is activated. That is, the normally closed contact 9b opens and the normally open contact 9a closes, and the AC power source 7
The electric compressor 12 is disconnected from the compressor to stop the cooling operation, and the cooler defrosting heater 11 is connected to the power source. and cooler 1
When the defrosting progresses and the frost that was shielding the frost detection small holes 3b disappears, the frost detection output a increases, and the differential voltage generated by the feedback resistor 21 of the frost detection comparator 17 is added to the defrost start voltage. When the voltage becomes higher than the voltage, the output terminal 17C,1 of the frost detection comparator 17 does not output the frost signal ("H" level), and as a result, the AND gate 23a1'1 outputs the defrost prohibition signal (
'°L'' level), the transistor 24 becomes non-conductive, the relay 9 is deenergized, the electric compressor 12 is connected to the power supply again, and cooling operation is started.

On the other hand, if a failure occurs such as the light emitting element 6a stopping emitting light or the light receiving sensitivity decreasing of the light receiving element 6b (Fig. 4 p), the frost detection type output a decreases significantly and the reference voltage of the failure detector 22 becomes abnormal. When the detection voltage goes up, a failure signal (°"L I+ level) is output from its output terminal 22c, and the output of the AND gate 23 is a defrosting prohibition signal (°"L" level) regardless of the output of the frost detection comparator 17. From then on, cooling operation continues.

Therefore, when the light-emitting element 6a or the light-receiving element 6b breaks down, the defrosting operation starts regardless of whether or not there is frost on the cooler 1, and the defrosting heater 11 is continuously energized, eliminating the problem of the temperature inside the refrigerator becoming abnormally high. The safety of stored items and equipment can be ensured by continuously being put into cooling operation. Moreover, this embodiment uses a light-emitting element, which is a conventional failure detection method.
It is highly practical as there is no need to preliminarily provide a plurality of light-receiving elements, and failure detection can be realized with a simple circuit and a few additional parts.

In addition to this embodiment, this failure detection also makes it possible to display an abnormality display on the outside of the device to warn the user, or to easily switch to a timer set defrosting mode.

Effects of the Invention As is clear from the above description, the present invention comprises a cooler, a frost detector provided in a cooling chamber in which the cooler is arranged, and optically detects the amount of frost on the cooler, and the frost detector. A defrost control circuit that performs defrosting operation based on an output signal from a Failures such as a significant drop in light emitting quantity or a drop in light receiving sensitivity of the light receiving element can be detected reliably and easily (at low cost) by abnormalities in the power value of the frost detector that normally detects frost formation.
This eliminates the problem of the defrost heater going into defrosting mode regardless of whether or not there is frost on the cooler, causing the temperature inside the refrigerator to rise abnormally. The safety of stored items and equipment can be ensured. It has been further developed to use the failure detector to display an abnormality display on the outside of the device to warn the user, and it has also become possible to easily switch to defrosting with a timer, which has great practical effects.

10, -1-2

[Brief explanation of the drawing]

FIG. 1 is a plan view of a cooler equipped with a defrosting control device according to an embodiment of the present invention, FIG. 2 is a partial sectional view of a frost detector of the same device, and FIG. 3 is an electric circuit diagram of the same device. FIG. 4 is a time chart showing the operation of the device. 6...Frost detector, 10...Defrost control circuit, 22...Failure detector.

Claims (1)

[Claims] a cooler, a frost detector provided in a cooling chamber in which the cooler is placed and optically detects the amount of frost on the cooler, and a defrost control circuit that performs a defrosting operation based on an output signal from the frost detector; A defrosting control device for a refrigerator or the like, comprising a failure detector that detects an abnormality in the output signal and prohibits the defrosting control circuit from starting a defrosting operation.