JPS5851183B2 - Defrost control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defrosting control device for a cold storage, etc., and includes a first defrost sensor that detects the surface temperature of a coil of a cooler, and a defrost control device that detects the temperature of the air inside the refrigerator that is cooled by the cooler. It has a second temperature sensor that detects temperature, and controls the temperature inside the refrigerator based on the signal from the second temperature sensor, and starts and ends defrosting of the cooler based on the signal from the first temperature sensor. Features.

Conventionally, temperature control for the internal temperature of a cold storage box and defrost control for the cooler are performed using two thermostats, a temperature control thermostat and a defrost thermostat, respectively, but by digitizing these, one control is possible. The purpose is to realize two functions of temperature control and defrosting control using a circuit.

The present invention will be described below with reference to embodiments shown in the drawings.

First, the cold storage is equipped with a cooler (not shown) inside the refrigerator, an electric compressor 1 outside the refrigerator that constitutes a refrigeration cycle together with the cooler, and a defrosting device in the cooler. A defrosting heater 2 is installed as a defrosting heater.

The electric compressor 1 and the defrosting heater 2 constitute a series circuit with respect to an AC power source as shown in FIG. A relay contact 3a is connected, and the electric compressor 1 and the discharge heater 2 are operated alternately by opening and closing the relay contact 3a.

Further, as shown in FIG. 2, the electric compressor 1 and the defrosting heater 2 may be alternately connected to the AC power source by the relay contact 3a of the electromagnetic relay 3 to obtain the same function.

Next, a control circuit for controlling the electromagnetic relay will be explained based on FIG. 3.

In the figure, EB is a DC power supply, R1 and RTl are a first temperature sensor that detects the surface temperature of the cooler, and R1 and RTl are connected in series between the DC power supply 880 and include a first bias resistor and a thermistor, and R2 is a second temperature sensor. A resistor VR is a first variable resistor, R3 is a third resistor, and these are connected in series between the DC power source EB.

OP is a first operational amplifier whose terminals are connected to the DC power supply EB, and the positive input terminal and negative input terminal of the amplifier are connected to a first variable resistor ■R1, the first resistor R1, and a first temperature sensor RT1.
At the same time, a fourth resistor R4 for hysteresis is connected between the output terminal and the positive input terminal to set the temperature difference between the defrosting start temperature and the return temperature of the cooler. ing.

R,, RT2 are a fifth resistor for bias connected in series between the DC power supply EB and a second temperature sensor for detecting the air temperature in the refrigerator, R6 is a sixth resistor, VR2 is a second variable resistor, R
A seventh resistor 7 is connected in series between the direct power source EB and the resistor Q.

OP2 is a second terminal whose terminal is connected between the DC power supplies 880.
The positive input terminal and the negative input terminal of the operational amplifier are connected to the second
A variable resistor vR2 is connected to the intermediate point between the fifth resistor R1 and the second temperature sensor RT2, and is connected between the output terminal and the positive input terminal for setting the on-off temperature difference of the electric compressor 10. An eighth resistor R8 for hysteresis is connected.

TR1 is a first transistor for relay control, and its collector is connected to the positive side of the DC power supply EB via the relay coil 3b of the electromagnetic relay 3, its emitter is connected to the negative side of the DC power supply EB, and its base is connected to the ninth It is connected to the output terminal of the second operational amplifier OP2 via a resistor R0 and a Zener diode DZ.

TR2 is a second transistor whose collector and emitter are connected to a ninth resistor R0 and a zener diode D.
2 and the negative side of the DC power supply EB, and its base is connected to the output terminal of the first operational amplifier OP1.

Further, the first variable resistor VR1 and the second variable resistor R2 are interlocked by a double variable resistor.

The operation of the above circuit configuration will be explained, but first we will explain the relationship between the amount of frost on the cooler and the temperature, and the set temperature inside the refrigerator T2.
and the defrosting start cooler temperature TtK.

and the return temperature TtF are as shown in Figure 4 and the following table, respectively.In other words, the defrosting return temperature TI is determined regardless of the set internal temperature T2.
For example, F may be kept constant at +5° C., or may be changed depending on the preset temperature inside the refrigerator and the defrosting start temperature TIK.

Next, to explain the operation, first, the first operational amplifier OP
A bias voltage set by the first variable resistor VR1 and the second variable resistor vR2 is applied to the positive input terminals of the first and second operational amplifiers OP2.

When the temperature inside the refrigerator is high and the resistance value of the second temperature sensor RT2 is small, the output of the second operational amplifier OP2 becomes bi-level, and the first transistor TR1 is turned on to turn on the electromagnetic relay 3.
A current flows through the relay coil 3b, the relay contact 3a is energized, and the electric compressor 1 is turned on, refrigerant is circulated through the cooler and the inside of the refrigerator is cooled.

When the temperature inside the refrigerator reaches the set temperature, the second temperature sensor R
The resistance value of T2 becomes large, the output of the second operational amplifier OP2 becomes low level, the first transistor TR1 is turned off, the electric compressor 1 is turned off, and the defrosting heater 2 is turned on.

While this operating state is repeated alternately, frost (including the amount of water) accumulates in the cooler, and during the cooling operation, the second temperature sensor RT2
When the first temperature sensor RT1 detects a set temperature lower than that and reaches a state requiring defrosting, the first temperature sensor RT1
increases, the output of the first operational amplifier OP2 becomes bi-level, and the second transistor TR2 is turned on.

As a result, the first transistor TR1, which is in the on state, is turned off, and the current to the relay coil 3b of the electromagnetic relay 3 is cut off, and the relay contact 3a is deenergized, so that the electric compressor 1
is in the OFF state, the defrosting heater 2 is in the ON state, and defrosting of the cooler starts.0 Then, when the defrosting of the cooler is completed, the first temperature sensor RT1
When the voltage reaches the recovery temperature, the voltage at the negative input terminal of the first operational amplifier OP1 becomes higher than the bias voltage at the positive input terminal, the output of the first operational amplifier OP1 becomes low level, and the first transistor TR1 is turned off.

At the defrost return temperature, the temperature inside the refrigerator also rises, so the resistance value of the second temperature sensor RT2 is small.
Since the voltage at the cutting end of the operational amplifier OP2 is at a high level, the first transistor TR1 returns to the on state at the same time as the second transistor TR2 is turned off, and the electric compressor 1 resumes operation to cool the inside of the refrigerator.

In the above circuit configuration, the cooling operation by the electric compressor 1 and the defrosting operation by the defrosting heater 2 are performed alternately, so that cycle defrosting is possible with a small amount of frost formation.

It is also possible to use a hot gas defrost method using a solenoid valve as a defrosting device instead of the defrosting heater 2, but in this case, the electrical connections in Figures 1 and 2 only need to be partially changed. The control circuit does not require any modifications.

As mentioned above, the defrosting control device according to the present invention replaces the temperature regulating thermostat with an electronic thermostat, and can realize the two functions of temperature regulating control and defrosting control with one control circuit whose main parts are electronic. It has a practically beneficial effect.

Furthermore, according to the present invention, the operation switching means for the electric compressor and the defrosting device can be configured with, for example, a single relay device, which simplifies the circuit configuration and reduces malfunctions due to aging.

[Brief explanation of the drawing]

Figures 1 and 2 are operational circuit diagrams of different embodiments controlled by the device of the present invention, Figure 3 is a control circuit diagram of the device of the present invention, and Figure 4 is a characteristic diagram showing the relationship between frost formation amount and temperature. It is.

Claims (1)

[Claims] 1 A first temperature sensor that detects the surface humidity of the cooler, and a second temperature sensor that detects the temperature inside the refrigerator cooled by the cooler.
a temperature sensor, an electric compressor that forms a refrigeration cycle together with the cooler, a defrosting device that defrosts the cooler, and a temperature sensor that controls the electric compressor at a predetermined internal temperature based on the second temperature sensor. The control circuit includes a control circuit that generates an operating output and operates the defrosting device to maintain a desired internal temperature in a state where there is no operating output, and the first temperature sensor detects the second temperature sensor. A defrosting control device characterized in that the mechanism disables the operating output when a temperature lower than the set temperature is sensed.