JPH0484090A - Defrosting control device for low temperature show-case - Google Patents

Abstract

PURPOSE:To perform a positive defrosting and maintain a temperature within a refrigerator when a defrosting operation is carried out by a method wherein a main evaporator for maintaining an inside part of the refrigerator at a predetermined temperature, an auxiliary evaporator of which cooling operation is carried out when the main evaporator performs a defrosting operation, and a cold air circulating fan are disposed within a cooling chamber and then the auxiliary evaporator is turned ON/OFF in response to a temperature of air flow. CONSTITUTION:During a normal cooling operation, a first relay 34 is not operated, a contact point 34A is changed over to a side (a), a refrigerant supplying solenoid valve 26 is opened or closed in response to ON/OFF of a thermostat 35 (TH), a supplying of refrigerant for a main evaporator 8 is stopped and then the main evaporator 8 is controlled under a thermostatic operation. During a defrosting operation, a defrosting timer 33 is operated and the first relay 34 is operated under a closed state of a contact point 33A. The contact point 34A is changed over to a side (b), an operation of the main evaporator 8 is stopped and the second relay 38 is operated and a defrosting heater 21 generates heat under a closed state of a contact point 38A so as to perform a defrosting operation of the main evaporator 8. A refrigerant supplying solenoid valve 28 is opened and an auxiliary evaporator 12 performs a cooling operation. A fan motor 36 continues to rotate and then a protection air flow A2 is circulated by a fan 14. A thermostat 22 turns ON/OFF in response to a temperature of the protection air flow and a thermo-operation of the auxiliary evaporator 12 is controlled.

Description

[Detailed description of the invention] (b) Industrial application field The present invention relates to a defrosting control device for a low temperature showcase.

(b) Conventional technology Today, a variety of food and beverages are stored in warehouses at low temperatures.

Low-temperature showcases from which customers can freely take out items are widely installed in supermarkets, convenience stores, and the like.

In this low-temperature showcase, an evaporator and a blower for circulating cold air are placed in a cooling room that is separated from the storage room, and the cold air cooled by the evaporator is used to form an air curtain on the open surface of the storage room. Then, the air is blown out from one outlet of this open surface, sucked in from the other outlet, and returned to the cooling chamber.
By circulating the air again, the inside of the refrigerator is thermally isolated from the outside world and maintained at a constant low temperature. By the way, when a customer takes out a product from a warehouse, the air curtain is disturbed and outside air enters. As a result, cold air containing moisture from the outside air circulates, and as the cooling operation continues, frost gradually forms on the evaporator, reducing the cooling effect of the evaporator. Therefore, it is necessary to periodically stop the cooling operation and defrost the air.

The cooling operation is stopped by means such as closing a refrigerant supply solenoid valve disposed in the refrigerant pipe so that the refrigerant does not flow into the evaporator. On the other hand, in order to perform effective defrosting, two evaporators are used, and when one evaporator is being defrosted, the other is operated for cooling so that an air curtain is always formed at the opening of the storage room. Japanese Unexamined Patent Publication No. 57-47176 discloses a refrigerated showcase that prevents the temperature inside the refrigerator from rising during defrosting.

(c) In terms of the problem to be solved by the invention, the cooling device shown in the above publication uses the heat of the high temperature liquefied refrigerant liquefied in the condenser to defrost one of the evaporators, On the other hand, the low-temperature liquefied refrigerant after passing through the evaporator,
The cooling effect is performed by evaporation in other evaporators, but as defrosting approaches the end of defrosting in the evaporator (for example 9a) during defrosting, the amount of heat spent on defrosting decreases.
The remaining heat is passed through the cold air circulation path by the blower and passes through the other evaporator 9b which is currently being cooled. Therefore, there arises a drawback that the cooling effect in the evaporator 9b is reduced.

The present invention has been made in view of the above points, and provides a defrosting control device for a low-temperature showcase that can perform reliable defrosting and prevent the internal temperature from fluctuating during defrosting. The purpose is to provide.

(d) Means for Solving the Problems The present invention has a storage room with one side open so that customers can take out stored products from the opening, and a cooling room that is separated from the storage room. In a low-temperature showcase in which a cold air circulation fan and an evaporator are arranged in the cooling chamber to form a cold air curtain in the open part of the chamber, the temperature inside the chamber is detected and the ON/OF depending on detected temperature
A main evaporator that maintains the inside of the refrigerator at a predetermined temperature under F operation control;
and an auxiliary evaporator that is operated for cooling when the main evaporator is defrosted.

A constantly operating cold air circulation fan is disposed in each of the cooling chambers, and a control means is provided for turning the auxiliary evaporator ON/OFF depending on the temperature of the air flowing through it. be.

(e) Operation When the time comes for defrosting the main evaporator, the auxiliary evaporator enters cooling operation, depending on the temperature of the circulating air flow passing through it.
Controlled to stop and restart cooling operation.

If the circulating airflow becomes too low, the auxiliary evaporator shuts down to ensure defrosting and to avoid starvation of the heat source used to defrost the main evaporator. Even during defrosting, a protective airflow is created in place of an air curtain, preventing the quality of products inside the warehouse from deteriorating.

(F) EXAMPLES The present invention will now be described in detail with reference to the accompanying drawings.

FIGS. 1(a) and 1(b) are structural cross-sectional views of the low-temperature showcase according to the present invention, and FIG. 1(a) shows the main evaporator forming an inner air curtain on the open surface of the storage room during cooling. Figure (b) shows a state in which the auxiliary evaporator is operated in place of the main evaporator during defrosting, thereby forming an outer layer air curtain, and the showcase body l
has a machine room 2 in its lower part that houses a compressor, a condenser, etc., and above this is separated from a storage room 3 to form a cooling room 4, and the storage room 3 has its upper part open, The customer can insert his/her hand through this upper surface opening 5 and take out various items displayed and stored in the storage room 3.

At the back of the storage compartment 3, a main cold air passage 6 and a protective air flow passage 7 are vertically partitioned and formed, and a main evaporator 8 is disposed within the main cold air passage 6. Furthermore, cold air discharge ports 9 are provided at the tips of the main cold air passage 6 and the protective air flow passage 7. IO is provided, and an inner layer air curtain A□ is formed from the cold air discharge port 9 toward the cold air suction port 11 during cooling, and during defrosting, the cold air discharge port 10
Outer layer air curtain A2 toward the colder air intake port 11
is starting to form. Note that 35 is a thermostat arranged in front of the cold air discharge port 9 to detect the cold air temperature after the main evaporator 8 and to control the ON/OFF movement of the main evaporator 8.

In the cooling chamber 4, an auxiliary evaporator 12 is arranged on the side near the cold air suction port 11, and behind it, as shown in FIG. Cool air circulation fans 13a, 13a and a protective airflow fan 14 for circulating the protective airflow through the protective airflow passage 7 are arranged.

Cold air circulation fans 13a, 13a and protective airflow fan 14
are separated from each other by partition plates 16 and 16 in the fan case 15 and are arranged independently. And each fan 13a.

13a, 14, the cold air inlet 17.17 and the protective air flow port 18 are opposed to each other, and the main cold air passage 6 and the protective air flow passage 7 are made to oppose each other.
A main cold air duct 19 and a protective airflow duct 20, which respectively communicate with each other, are divided into sections. Further, a defrosting heater 21 is disposed in front of the main evaporator 8 (on the windward side). Therefore, when the cold air circulation fans 13a, 13a are driven and rotated, the cold air circulates according to the solid arrow shown in FIG.
The inside is thermally isolated from the outside world and maintained at a constant low temperature. During defrosting, the operation of the main evaporator 8 is stopped, but the auxiliary evaporator 12 is operated instead.
According to the solid arrow shown in FIG. 3(b), the protective airflow circulates to form an outer layer air curtain, thereby suppressing fluctuations in the temperature inside the storage room 3. Further, the defrosting heater 21 is energized, and the main evaporator 8 is defrosted.

By operating the auxiliary evaporator 12, a protective airflow is formed in the upper opening 5 of the storage compartment 3 to maintain a low temperature inside the storage compartment. Heat is removed and the heat source becomes insufficient, resulting in insufficient defrosting of the main evaporator 8, which may result in residual frost.

Therefore, the present invention performs cooling operation and stopping of the auxiliary evaporator 12, that is, ON/OFF control, depending on the temperature of the air flow flowing through the auxiliary evaporator 12, thereby ensuring reliable defrosting and cooling. The temperature inside the refrigerator has been maintained.

Therefore, the thermostat 2 is installed on the windward side of the auxiliary evaporator 12.
2, and this thermostat 22 controls the auxiliary evaporator 12.
A solenoid valve for refrigerant supply arranged in the refrigerant circuit (described later)
The auxiliary evaporator 12 is ON/OFF controlled by closing or opening.

Fig. 3 shows the refrigerant piping diagram, and the gas refrigerant discharged from the compressor (not shown) is liquefied through the condenser (not shown), and the liquefied refrigerant is divided into two systems, and is connected to each pipe line 24 and 25. flows. The main evaporator 8 is disposed in the conduit 24, and a refrigerant supply solenoid valve 26 and an expansion valve 27 are disposed on the inlet side thereof. Similarly, the auxiliary evaporator 12 and a refrigerant supply solenoid valve 28 and an expansion valve 29 are disposed on the inlet side of the auxiliary evaporator 12 in the conduit 25. Here, the refrigerant supply solenoid valve 26 is controlled to open and close by a thermostat 35 provided inside the refrigerator, while the refrigerant supply solenoid valve 2
8 is controlled to open and close by the thermostat 22 mentioned above.

Figure 4 shows the overall control circuit diagram, where 30 is an AC power supply;
A compressor (CM) 1 is connected in series with a low pressure switch 32.

A defrosting timer 33 closes a contact 33A when a set defrosting time has elapsed, and excites a first relay 34 (LX) connected in series to the contact 33A. 34A is a relay contact of the first relay 34, which is normally closed to the a side and switches to the b side when the first relay 34 is energized.

And arranged in the main cooling passage 6 on this a side,
Thermostat 35 (TH
) and the above-mentioned refrigerant supply solenoid valve 26 (SV engineering) are connected in series. Therefore, when the temperature inside the refrigerator reaches the set upper limit, the thermostat 35 closes and opens the refrigerant supply solenoid valve 26 to allow the refrigerant to flow into the main evaporator 8 for a cooling effect.When the temperature inside the refrigerator reaches the lower limit temperature, the thermostat 35 is opened, the refrigerant supply solenoid valve 26 is closed, the refrigerant supply is stopped, and the main evaporator 8 is stopped. In addition, AC power supply 30
A fan motor 36 (FM) for driving the cold air circulation fans 13a, 13a and the protective airflow fan 14 is connected to the fan motor 36 (FM), and these fan motors are constantly rotated. On the other hand, the above-mentioned thermostat 22 (HT
H) and a refrigerant supply solenoid valve 28 (SV, ) are connected in series. Therefore, during defrosting, the refrigerant supply solenoid valve 28 is energized and opened by switching the contact 34A.
A cooling operation is performed by flowing the refrigerant into the auxiliary evaporator 12, and the rotation of the protective airflow fan 14 causes the protective airflow to flow through the top opening 5 of the storage compartment 3.
At the same time, the thermostat 22 detects the temperature of this protective air flow, and when it becomes too cold to reach the set lower limit temperature (±0 degrees Celsius), it turns 0FF (closed circuit), and the temperature rises to reach the upper limit temperature (±5 degrees Celsius). ℃), it turns ON (opens), opens and closes the refrigerant supply solenoid valves 28, respectively, and controls the operation and stop of the auxiliary evaporator 12.

Reference numeral 21 denotes a defrosting heater (DI()), which is connected in series with the relay contact 38A of the second relay 38 (2X) connected to the b side and generates heat when energized during defrosting. A frost heater heating preventer 39 is connected, and when it becomes heated, the circuit opens and the defrosting heater 21 is cut off from the power supply for safety protection.

40 is a dew-proof heater.

Next, the operation of the above configuration will be explained.

During normal cooling operation, the first relay 34 is inactive and the contact 34A is switched to the a side and held. Therefore, the refrigerant supply solenoid valve 26 turns on the thermostat 35 (TH).
/OFF opens and closes to stop the supply of refrigerant to the main evaporator 8, and the main evaporator 8 is under thermo-operation control. When the defrosting time comes, the defrosting timer 33 operates and the 43
3A is closed, the first relay 34 is operated, and the contact 34A is closed.
is switched to the b side, the operation of the main evaporator 8 is stopped, and the second relay 38 is operated to open the contact 38A, causing the defrosting heater 21 to generate heat and defrosting the main evaporator 8.

Further, the refrigerant supply solenoid valve 28 is opened, and the auxiliary evaporator 12 enters the cooling operation.

The fan motor 36 (FM) continues to rotate, and the cold air ring fan 14 operates to circulate and form a protective airflow A2.

The thermostat 22 then adjusts the temperature to the temperature of the protective air stream.
By turning on/off, the auxiliary evaporator 12 is also thermo-controlled, and the auxiliary evaporator 12 is operated without taking away the heat from the defrosting heater 21.
It is possible to prevent frost from remaining on the storage compartment 3, and protect the inside of the storage room 3 from being affected by the temperature of the outside world with the protective airflow, thereby preventing damage to the products.

The operating states of the main circuit components shown in FIG. 4 are shown in the table below.

(g) Effects of the invention As described above, according to the present invention, the main evaporator, which normally forms an air curtain in the open part of the storage room to control cooling of the inside of the storage room to a predetermined temperature, is not operated during defrosting. An auxiliary evaporator is installed to prevent damage to stored products by forming a protective airflow similar to an air curtain, and this auxiliary evaporator is controlled to turn ON/OFF at the temperature of the protective airflow. Heat is removed from the defrosting heat source of the main evaporator in the frost by the low-temperature protective air current, preventing the heat source from becoming insufficient and causing no residual frost. Therefore, reliable defrosting and prevention of deterioration of stored products during defrosting can be appropriately achieved.

[Brief explanation of the drawing]

Fig. 1(a) is a schematic structural diagram of the low temperature showcase of the present invention showing a state in which the main evaporator is operated to form an inner layer air curtain, and Fig. 1(b) shows the main evaporator during defrosting. Schematic structural diagram of the same low-temperature showcase showing a state in which a protective airflow is formed in the auxiliary evaporator operated in place of the second one.
The figure shows the structure of a duct installed in a cooling chamber in which cold air and protective airflow passages are formed independently, and the related configuration of a cold air circulation fan and a protective airflow fan placed at the entrance of the duct. A perspective view, Figure 3 is a main part diagram of the refrigerant piping, Figure 4
The figure is a control circuit diagram. 3... Storage room, 4... Cooling room, 8... Main evaporator, 1
2... Auxiliary evaporator, 13a, 13a... Cool air circulation fan, 14... Protective airflow fan, 21... Defrosting heater, 22... Thermostat (HTH).

Claims (1)

[Claims] (1) It has a warehouse with one side open so that customers can take out stored products from the open part, and a cooling room that is separated from this warehouse, and a fan for circulating cold air is installed in the cooling room. In a low-temperature showcase in which a refrigerator and an evaporator are arranged to form a cold air curtain in an open part of the warehouse, the temperature inside the warehouse is detected and ON/OFF operation is controlled according to the detected temperature. A main evaporator that maintains the inside of the refrigerator at a predetermined temperature, an auxiliary evaporator that operates to cool the main evaporator during defrosting, and a cold air circulation fan that operates constantly are arranged in the cooling chamber, and the auxiliary evaporator A defrosting control device for a low-temperature showcase, comprising a control means for turning on/off an evaporator according to the temperature of an air flow flowing through the evaporator.