JPH03117871A - Temperature controller for open display case - Google Patents

Abstract

PURPOSE:To maintain the temperature of food constant by varying signals to be output from a second amplifier and a comparator upon change of the atmospheric temperature, and controlling chilled gas temperature to be supplied inversely proportionally to the atmospheric temperature. CONSTITUTION:A low temperature open display case 1 is composed of an adiabatic box 3 having a commodity containing and removing opening 2 at its upper surface. A first temperature sensor 16 detects the temperature of supplied chilled gas heat-exchanged by a heat exchanger 8 or an evaporator, and a second temperature sensor 19 detects the atmospheric temperature. First, second amplifiers 18, 20 respectively amplify signals from both the sensors 16, 19. A controller 28 controls a comparator 27A which receives the outputs from the amplifiers 18, 20 and compares them, and the supply of liquid refrigerant to the exchanger 8 based on the output from the comparator 27A. As the atmospheric temperature changes, the signals from the amplifier 20 and the comparator 27A are varied, and the temperature of chilled gas to be supplied is controlled inversely proportionally to the atmospheric temperature based on the change of the output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a temperature control device for a low temperature showcase, particularly an oven showcase.

(b) Prior art U.S. Patent No. 2,148,643 specification and drawings (hereinafter referred to as 1st prior art example), U.S. Patent No. 2,186.984 specification and drawings (hereinafter referred to as 2nd prior art example), Special Public Service 1977
In Publication No. 23713 (hereinafter referred to as the 3rd conventional example), a temperature sensing device filled with gas is installed outside the warehouse such as a machine room, and a temperature sensing part of this temperature sensing device is installed in the evaporator, and the temperature sensing device is installed in the evaporator to detect changes in temperature. So-called on-off operation control is performed in which the electric contact mechanism is closed and opened to operate and stop the compressor based on changes in the gas pressure within the temperature sensing section.

Also, U.S. Patent No. 4.585.165 and drawings (
(hereinafter referred to as the fourth conventional example) discloses a configuration in which the temperature of multiple radiators is controlled using both a hot water temperature measurement sensor and an outside air temperature sensor, and the temperatures detected by each are amplified and compared to finalize the final result. The output of the comparator is used to turn on and off transistors and relays to open and close switches.

(c) Problems to be Solved by the Invention In the first to third conventional examples described above, since the temperature sensing device is mechanical and is placed in a position exposed to the outside air, it is difficult to detect changes in the outside temperature. Since there is a time delay (operation lag) in the operation, we try to compensate for this operation lag, but heating control is a temperature control of a sealed refrigerator, so it is not affected by radiant heat, and the stored food itself Since the control does not take into account the influence of outside air on the temperature, if such a temperature sensing device is used in an oven-type showcase, there will be a large temperature difference between the cold air temperature and the stored food, leading to a decline in the quality of the stored food. There was an issue.

Furthermore, in the fourth conventional example, the temperature at two locations is detected, the detected values are amplified and compared, and then the circuit to be controlled is operated using a switching transistor and a relay. When used in an oven-type showcase, the same problems as the first to third conventional examples described above will occur.

The present invention aims to solve the above problems,
Specifically, the purpose is to maintain the temperature of the food constant by changing the temperature of the supplied cold air that forms the air curtain in response to the increase or decrease in radiant heat that enters the storage chamber through the opening.

(2) Means for Solving the Problems As a means for solving the above problems, the present invention provides an open showcase in which an air curtain of cold air is formed in an opening for storing and taking out products formed on one side. A first temperature sensor detects the temperature of the supplied cold air heat exchanged with the heat exchanger serving as the evaporator, and a second temperature sensor detects the outside air temperature.
A temperature sensor, first and second amplifier circuits that amplify signals from the first and second temperature sensors, respectively, and a comparison circuit that receives and compares the outputs of the first and second amplifier circuits. , and a control circuit that controls the supply of liquid refrigerant to the heat exchanger serving as an evaporator based on the output of the comparison circuit, and the control circuit that controls the supply of liquid refrigerant to the heat exchanger serving as an evaporator based on the output of the comparison circuit, A configuration was adopted in which the supplied cold air temperature is controlled in inverse proportion to the outside air temperature based on the change in the output signal.

(E) Effect According to the above means, during cooling operation, the signal output from the second amplifier circuit to the comparison circuit is changed in accordance with the change in outside air temperature, and the temperature of the supplied cold air is made inversely proportional to the change in this output signal. When the outside air temperature drops or rises, the supplied cold air temperature is automatically raised or lowered to maintain the inside of the refrigerator within a predetermined temperature range.

(F) Example Hereinafter, an example of the present invention will be described in detail based on FIGS. 1 to 3.

Figure 2 (1) is a low-temperature open showcase with an insulating box (3) that has an opening (2) on the top for storing and taking out products.
A partition plate (5) is arranged in the refrigerator interior (4) defined by the insulation box (3), and the interior is divided into a storage room (6) and a passage (7). The opposite vertical areas of this passage (7) are provided with plate-fin type first and second heat exchangers (8) and (9), and the bottom area is provided with an axial flow type heat exchanger that can be rotated forward and backward. A blower (10) is provided respectively. Further, below the insulation box (3), a compressor (11) and a condenser (1
A machine room (13) is formed in which equipment such as 2) is installed.

Further, (15A) and (15B) are the first and second passage frontages above the first and second heat exchangers (8) and (9), respectively,
The first passageway frontage (15A> acts as a blowout port during cooling operation and blows out the cold air cooled by the first heat exchanger (8), and at this time, the solid line points towards the second passageway frontage (15B) which becomes the suction port. Cold air flows as shown by the arrow, and a cold air curtain is formed in the opening (2).Furthermore, when the first heat exchanger (8) is in heavy duty operation, the refrigerant flows to the second heat exchanger (9) to perform cooling operation. The second passageway frontage (15B) acts as a blow-off port and blows out cold air, and the first passageway frontage (15B) serves as a suction port.
The cold air flows toward A) as indicated by the chain arrow, and a cold air curtain is formed at the opening (2>).

FIG. 1 shows a schematic temperature control circuit of the low-temperature open showcase, and (16) indicates the first and second power supply lines (Ll
), (t,,), the first temperature sensor is disposed near the storage chamber (6) side of the first passage frontage (15A), and is connected between the first heat exchanger (8) It has a negative characteristic that detects the temperature of the cool air that has undergone heat exchange and is blown out from the first opening (15A). Also, (R1) to (R6
) are first to fifth bias resistors that constitute the first amplifier circuit (18) together with the first amplifier (17).

Here, in case cooling operation is performed using the second heat exchanger (9), a first
A temperature sensor (16) is provided. (19> is, for example, a second temperature sensor with a negative characteristic that detects the outside air temperature, which is disposed near the outside air inlet side of the condenser (12); (20) is a second amplifier circuit; (R6) to (R1, ) are the 6th to 10th bias resistors for the second amplifier (21), (R, , ) to (R.

4) is a third amplifier that further amplifies the output of the second amplifier (21).
These are the 11th to 14th bias resistors for the amplifier (22). Further, (23) is the first diode connected to the output terminal of the third amplifier (22), and is used as a constant current element to keep the potential difference between both ends of the variable resistor (24) constant for setting the temperature inside the refrigerator. . Further, (25) is a fine adjustment resistor for finely adjusting the potential of the variable resistor (24), and (26) is a bias resistor of the first diode (23).

Further, (27) is a comparator which inputs the output of the first amplifier (17) and also inputs the output of the third amplifier (24) via a variable resistor (24), (Rts), (R11)
constitutes a comparison circuit (27A) together with a comparator (27),
The 15th and 16th resistors are used to provide hysteresis to the output of the comparator circuit (27A), and (Rxt) is the comparator (27).
and the operation control circuit (28) of the compressor (11).
) is the 17th resistor connected between the . The operation control circuit (28) includes an NPN transistor (29) to which a 17th resistor (R, ?) is connected to the base, and a compressor operation control relay (29) connected to this transistor (29).
30) excitation filter (30C) and the second diode (30C).
1) and a relay switch (305) of the relay (30), the relay switch (305) is normally closed, normally closed contact (3QS+>, (305,) and changeover contact (305,).
05,), and the compressor (11) is operated when the switching contact (305,) is closed to the normally closed contact (305,).

The operation of the temperature control device will be explained below.

Normal temperature condition (20″C) with almost no change in outside temperature
In this case, the supplied cold air temperature is maintained at approximately 0°C, and at this time, the resistance value of the second temperature sensor (19) and the second
The output of the amplifier circuit (20) also hardly changes, and the potential input from the variable resistor (24) to the comparator (27) is approximately constant, and the comparator (27) receives an H (high) level signal. When the transistor (29) is on and the excitation coil (3
When the relay switch (30S) is turned off, the compressor (11) stops and the first heat exchanger (8) becomes an evaporator.
), when liquid refrigerant is not being supplied to the refrigerator, the temperature inside the refrigerator rises and the temperature of the cold air blown out from the first passage opening (15A) also rises, the resistance value of the first temperature sensor (16) decreases, and the temperature of the first temperature sensor (16) decreases. 1
When the input potential of the + (plus) input terminals of the amplifier (17) decreases, the output of the first amplifier (17) decreases, and the input of the + side input terminal of the comparator (27) also decreases. When the temperature of the supplied cold air rises and the potential of the + side input terminal becomes lower than the potential of the - (minus) input terminals, the comparator (27)
outputs an L (low) level signal instead of an H level signal, turns off the transistor (29), and turns off the relay coil (30).
C) becomes de-energized, the switching contact (305m) of the relay switch (305) closes to the normally closed contact (305,), the compressor (11) starts operating, and the first heat exchanger that becomes the evaporator (
8) is supplied with liquid refrigerant. Thereafter, when the temperature inside the refrigerator decreases due to the operation of the compressor (11), the resistance value of the first temperature sensor (16) increases, and the output of the first amplifier (17) increases, the positive side of the comparator (27) increases. The input at the input terminal also increases.゛Then, when the supplied cold air temperature decreases and the potential of the + side input terminal of the comparator (27) becomes higher than the - input terminal, the comparator (27) outputs an H level signal and the transistor (29)
) is turned on, the relay fill (30C) is energized, the relay switch (305) is switched, and the compressor operation is stopped. Thereafter, the above operation is repeated, and the compressor (11) is repeatedly operated and stopped, and as shown in FIG. 3(A), the temperature of the supplied cold air is, for example, between -0.5°C and 0.5°C. By changing the temperature, the inside of the refrigerator is maintained at the set supply cold air temperature.

In addition, when the cooling operation is being performed as described above, the temperature of the outside air, for example, the air inside the store such as a supermarket where the open showcase (1) is installed, changes during the day, the crowding of customers, and seasonal changes. When changed due to etc.,
For example, when the outside temperature rises to, for example, 25°C, the resistance value of the second temperature sensor (19) decreases and the second amplifier (
The input potential of the - input terminals of 21) increases, the output potential of the second amplifier (21) decreases, and the output potential of the third amplifier (22) reverses and increases. And variable resistor (24)
The potential of the comparator (27) also rises, and the input potential of the - input terminals of the comparator (27) also rises. Here, when the compressor (11) is in a stopped state and the temperature of the supplied cold air gradually rises and the output of the first amplifier (17) gradually decreases, the comparator (27) before the outside air temperature rises is at L level. The comparator (
The input potential of the + side input terminal becomes lower than the - input terminal of 27), the comparator (27) outputs an L level signal, the transistor (29) is turned off, and the excitation coil (30C) is de-energized. , the relay switch (30S) switches,
The compressor (11) starts operating.

When the compressor (11) continues to operate and the temperature of the supplied cold air gradually decreases, the voltage between the terminals of the first temperature sensor (16) gradually increases, the output of the first amplifier (17) increases, and the comparator ( The potential of the + side input terminal of 27) rises, and before the outside air temperature rises, the supplied cold air temperature becomes lower than the temperature at which the comparator (27) outputs an H level signal, and for example, the comparison is made at -1.5°C. When the potential of the positive input terminal of the device (27) becomes higher than the negative input terminal, the comparator (27) outputs an H level signal, the relay switch (30S) is switched, and the compressor (
11) stops operation.

Thereafter, by repeatedly operating and stopping the compressor (11), that is, supplying and stopping the liquid refrigerant to the heat exchanger that serves as the evaporator, the temperature of the supplied cold air changes to the outside air temperature as shown in Figure 3 (B). is controlled lower than before (A), and the thermocycle becomes shorter. Therefore, the temperature of the stored products in the warehouse is maintained within the same predetermined temperature range as before the outside temperature rose. In addition, the supplied cold air temperature will be approximately 0.2°C when the outside air temperature increases by 1°C.
It is controlled in inverse proportion to the outside air temperature so that the outside temperature is lowered.

Further, when the outside temperature drops to, for example, 15°C, the voltage between the terminals of the second temperature sensor (19) increases, the potential of the − input terminals of the second amplifier (21) decreases, and the voltage between the terminals of the second amplifier (21) decreases. 21) increases, and the output of the third amplifier (22) decreases. Then, from the variable resistor (26) to the comparator (27
) decreases. Here, when the compressor (11) is not operating and the supplied cold air temperature is rising, the voltage between the terminals of the first temperature sensor (16) gradually decreases, and the output of the first amplifier (17) gradually decreases. The potential of the + side input terminal of the comparator (27) gradually decreases. And the comparator (27) before the outside temperature drops
When the supplied cold air temperature rises above the temperature at which outputs an L level signal, for example, +1°5°C, the potential of the + side input terminal of the comparator (27) becomes lower than that of the - input terminal, and the comparator (27) outputs an L level signal.
27) outputs an L level signal instead of an H level signal,
The relay switch (305) switches the compressor (11)
starts driving.

When the compressor (11) continues to operate and the temperature of the supplied cold air gradually decreases, the voltage between the terminals of the first temperature sensor (16) gradually increases, the output of the first amplifier (17) increases, and the comparator ( The potential of the + side input terminal of 27) increases, and before the temperature of the supplied cold air decreases to the temperature at which the comparator (27) outputs an H level signal before the outside air temperature decreases, for example, +0.5
°C, the potential of the + side input terminal of the comparator (27) becomes higher than the - input terminal, the comparator (27) outputs an H level signal instead of an L level signal, and the relay switch (305)
is switched and the compressor (11) stops operating. From now on,
By repeatedly starting and stopping the compressor (11), the temperature of the supplied cold air is controlled to be higher than that shown in (A) before the outside air temperature rises, as shown in Figure 3 (C), and the thermocycle becomes longer. . Therefore, the temperature of the stored products in the warehouse is maintained within the same predetermined temperature range as before the outside air temperature decreased. In addition, the supplied cold air temperature decreases by approximately 0.2° when the outside air temperature decreases by 1°C, for example.
It is controlled in inverse proportion to the outside air temperature so that C becomes higher.

Therefore, due to a change in the outside temperature, the second amplifier circuit (20)
The output of the comparator (27) changes, and the potential of the − input terminals of the comparator (27) changes, and the temperature of the supplied cold air that the comparator (27) outputs by switching between an H level signal and an L level signal is equal to the outside air temperature. The supply cold air temperature, that is, the upper limit of the set temperature, at which the compressor (11) starts operating when the outside air temperature rises, and the supply cold air temperature, that is, the set temperature, at which the compressor (11) stops operating. Since both lower limit values are automatically lowered, the temperature inside the refrigerator is controlled within a temperature range that is approximately the same as before the outside air temperature rises, and the thermocycle is shortened. As a result, the outside air temperature rises and the air curtain is closed. Even if the radiant heat that passes through and reaches the stored food in the storage room (6) from the opening (2) increases, the temperature of the stored food follows the internal temperature and hardly changes with respect to the increase in radiant heat. Moreover, when the outside air temperature drops, both the upper and lower limits of the set temperature automatically rise, so the supplied cold air temperature is controlled to be higher than before the outside air temperature dropped, and as a result, the outside air temperature decreases. Even if the radiant heat from the opening (2) to the stored food in the storage room (6) decreases, the temperature of the stored food follows the internal temperature and there is almost no temperature change in response to the decrease in radiant heat. Therefore, the temperature of the stored food can be kept almost constant regardless of seasonal changes in the outside temperature or changes in the temperature inside the store during the day. can maintain good quality over a long period of time.

(G) Effects of the Invention Since the present invention is an operation control device for an open showcase configured as described above, the temperature of the supplied cold air and the outside air temperature are detected by the first and second temperature sensors, and the respective temperature sensors Since the compressor operation is controlled by amplifying the signals from the outside and comparing them with a comparator, this change is caused by changes in the outside temperature and the temperature of the stored products inside the warehouse due to radiant heat. A temperature control signal that is inversely proportional to the outside air temperature is output from the comparison circuit to automatically change the set temperature of the supplied cold air to maintain the food temperature within a predetermined temperature range, that is, to improve the followability of the food product temperature to changes in outside air temperature. As a result, it is possible to effectively control the temperature of foods that have a narrow storage temperature range, such as ice-cold foods.

[Brief explanation of the drawing]

1 to 3 show one embodiment of the present invention, FIG. 1 is a schematic circuit diagram of a temperature control device, FIG. 2 is a schematic vertical cross-sectional view of an open showcase, and FIG. It is a characteristic diagram of the supplied cold air temperature shown. (1)...Open showcase, (2)...Opening, (8), (9)...First and second heat exchangers, (
11)...Compressor, (16)...First temperature sensor, (18)...First amplifier circuit, (19)...Second temperature sensor, (20)... Second amplification circuit, (2
7A)... Comparison circuit, (28)... Operation control circuit.

Claims (1)

[Claims] 1. In an open showcase in which an air curtain of cold air is formed in the opening for storing and taking out products formed on one side, the first step detects the temperature of the supplied cold air that has been heat exchanged with a heat exchanger serving as an evaporator. A temperature sensor, a second temperature sensor that detects outside temperature, first and second amplification circuits that amplify signals from both the first and second temperature sensors, and each of these first and second amplification circuits. A comparison circuit inputs and compares the output, and a control circuit that controls the supply of liquid refrigerant to the heat exchanger, which is an evaporator, based on the output of the comparison circuit. A temperature control device for an open showcase that changes signals output from a second amplifier circuit and a comparison circuit, and controls the temperature of supplied cool air in inverse proportion to the outside air temperature based on changes in the output signals.