JPH04366382A - Cold temperature cabinet - Google Patents

Abstract

PURPOSE:To provide a low temperature cabinet which is capable of maintaining the cooling effect in a storage chamber even when there occurs an operation failure of a cold accumulating agent temperature sensor. CONSTITUTION:A compressor 8 is operated based on the output of a cold accumulating agent operation sensor 17 throughout the operation which ranges from cold accumulation operation which freezes a cold accumulating agent 6 to an in-cabinet cooling operation which cools a storage chamber 2. A DC fan motor 14 is operated based on the output of an in-cabinet temperature sensor 18. Over the period ranging from the cold accumulation operation to the in-cabinet cooling operation, the compressor 8 and the DC fan motor are operated based on the output of an in-cabinet temperature sensor 18 when the cold accumulating agent temperature sensor 17 is subjected to a failure.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-temperature refrigerator that uses a cold storage agent to keep a storage room at a low temperature.

0002

2. Description of the Related Art The applicant previously applied for a low-temperature warehouse for transportation in which a cold storage agent is frozen in advance using a cooling device, and then the interior of the storage chamber is cooled by the latent heat of melting of the cold storage agent.
The application was filed as No. 307926.

According to this application, during a cold storage operation to freeze a cold storage agent, a compressor of a cooling device is operated to freeze the cold storage agent based on the output of a cold storage agent temperature sensor that detects the temperature of the cold storage agent, and after freezing, During the internal cooling operation that cools the storage room,
In addition to controlling the operation of the compressor, the blowing means is operated based on the output of the internal temperature sensor that detects the temperature of the storage room to supply cold air from the cold storage agent to the storage room, thereby cooling the inside of the storage room to a predetermined level. It is kept at a low temperature.

0004

[Problems to be Solved by the Invention] Here, in the process of changing from a thawing state to freezing and from a frozen state to thawing, the cold storage agent changes from normal temperature to an extremely low temperature of -30°C or less, and frost formation etc. occur. There is a high risk that failures such as disconnections and short circuits will occur in cold storage agent temperature sensors.

[0005] When such a failure occurs, it is impossible to ascertain the frozen status of the refrigerant, so it is impossible to make a decision to start the refrigerator cooling operation, and conventionally, the operation of the entire system has been stopped. Therefore, in the past, it has been impossible to cool the inside of the storage room due to the stoppage of the system.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a low-temperature refrigerator that ensures cooling within the storage chamber even if the cool storage agent temperature sensor fails.

[0007]

[Means for Solving the Problems] A low-temperature refrigerator R of the present invention is a cooling device having a storage chamber 2 for storing articles, a cold storage agent 6, a cooler 10 for cooling the cold storage agent 6, and a compressor 8. 7, a blowing means (DC fan motor) 14 that sends cold air from the cold storage agent 6 to the storage room 2, a cold storage agent temperature sensor 17 that detects the temperature of the cold storage agent 6, and an internal temperature sensor that detects the temperature of the storage room 2. The sensor 18 and the cool storage agent temperature sensor 1 are connected to each other from the cold storage operation that freezes the cold storage agent 6 to the internal cooling operation that cools the storage room 2.
The compressor 8 is operated based on the output of the refrigerator 7, and the DC fan motor 1 is operated based on the output of the refrigerator interior temperature sensor 18 during the refrigerator cooling operation.
The cool storage agent temperature sensor 1 is equipped with a control device (microcomputer) 46 that operates the cold storage agent temperature sensor 1 during the cold storage operation, during the refrigerator cooling operation, or during the period from the cold storage operation to the refrigerator cooling operation.
7 is out of order, the microcomputer 46 detects the internal temperature sensor 18.
The compressor 8 and the DC fan motor 14 are operated based on the output.

[0008]

[Operation] According to the present invention, when a failure such as a disconnection or a short circuit occurs in the cold storage agent temperature sensor 17, the DC fan motor is controlled by the internal temperature sensor 18 instead of the operation control of the compressor 8 by the sensor. The microcomputer 46 switches to control the operation of the compressor 14 and the compressor 8. Thereby, the inside of the storage chamber 2 is cooled to at least the set temperature.

[0009]

Embodiments Next, embodiments of the present invention will be explained based on the drawings. FIG. 1 is a block diagram of an electric circuit, and FIG. 2 is a longitudinal sectional view of the low-temperature refrigerator R.

The low-temperature refrigerator R includes a main body 1 made of a heat-insulating box, a storage chamber 2 formed in the main body 1 for storing articles,
A door 3 that opens and closes the storage room 2, a cold storage room 4 that communicates with the storage room 2 via a duct 5, a cold storage agent 6 stored in the cold storage room 4, and a cooling device 7 that cools the cold storage agent 6. It is configured. Here, the cold storage agent 6 has a freezing and melting temperature Ts of -
Use one at 25°C.

The cooling device 7 includes a compressor 8, an accumulator 9, a cooler 10 disposed in the cold storage chamber 4 so as to be in close thermal contact with the cold storage agent 6, and a capillary tube 11.
It is composed of a condenser 12 and a condenser blower 13. Further, the cold air cooled by the cool storage agent 6 is sent to the storage room 2 via the duct 5 by a DC fan motor 14 as a blowing means.

The air in the storage chamber 2 is supplied to the cold storage chamber 4 from the suction port 15.
The cold air from the cold storage chamber 4 is blown out from the outlet 16 of the duct 5 into the storage chamber 2. A cool storage agent temperature sensor 17 is attached to the cool storage agent 6 as a temperature detection means for detecting the temperature thereof. Further, the air outlet 16 is provided with an internal temperature sensor 1 that detects the temperature of the cold air blown into the storage room 2.
8 is provided. Furthermore, the temperature of the condenser 12 is detected by a condenser temperature sensor 19.

Casters 20 are attached to the bottom of the main body 1, and bumpers 21 are attached to the upper and lower ends of the outer peripheral surface of the main body 1. Further, a machine room 22 is formed in the rear corner of the lower part of the main body 1, and a compressor 8, a storage battery, etc., which will be described later, are housed therein. still,
In this embodiment, in order to obtain sufficient cooling capacity, two cooling devices 7 and two DC fan motors 14 each of the same size are installed.

In FIG. 1, a rectifier circuit 31 as a power supply circuit is connected to the a contact point of a switching relay 36, and the output of a storage battery 32 connected to a charging circuit 33 is connected to a relay coil Ry.
It is connected to the B contact of the switching relay 36 via the contact No. 6. The switching relay 36 connects the power source of a microcomputer (hereinafter referred to as a microcomputer) 46 as a control device constituting the control unit to an AC power source (AC200V) and a storage battery 3.
It functions as a switching means for switching between 2 and 2. That is, the common contact c of the switching relay 36 is connected to the microcomputer 46,
When AC power is connected, the contact is closed to contact A, and when AC power is disconnected, it is closed to contact B. As a result, the microcomputer 46 operates using the AC power source when the AC power source is connected, and uses the storage battery 32 as the power source when the AC power source is disconnected.

The storage battery 32 includes a resistor 3 as a current sensor.
4 are connected in series and output a voltage proportional to the charging current. Further, a voltage monitoring circuit 35 for monitoring the voltage of the storage battery 32 is connected to the common contact c of the switching relay 36.
The output is input to the microcomputer 46. The voltages generated by the cool storage agent temperature sensor 17, the internal temperature sensor 18, the condenser temperature sensor 19, and the resistor 34, which are composed of transistor sensors, are amplified by amplifier circuits 37, 38, 39, and 40, respectively, and are all sent to the microcomputer 46. is input. Furthermore, the output of the negative phase detection circuit 41 that detects the connection state of the connected three-phase AC power source is also input to the microcomputer 46.

Compressor motor 42 of two compressors 8
, 43 and the reverse phase detection circuit 41, the relay coils 44 and 45 switch contacts (not shown) to bring the AC power supply into a normal connection state, and are respectively relay coils Ry2.
, Ry3, Ry4, and Ry5 to the AC power source. The DC fan motors 14, 14 are connected to a common contact c of a switching relay 36 via a contact of a relay coil Ry1. These relay coils Ry1, Ry2
, Ry3, Ry4, Ry5, and Ry6 are connected to the output of the microcomputer 46, and the microcomputer 46 opens and closes each contact by controlling energization of these, and controls the operation and stopping of the compressor 8 and DC fan motor 14 as described later. do. Similarly, the microcomputer 46 also controls switching between normal phase and negative phase, and discharge control of the storage battery 32.

Here, like the microcomputer 46, when the DC fan motor 14 is connected to an AC power source, it operates using the AC power source via the rectifier circuit 31 and the switching relay 36, and when the AC power source is disconnected, it operates using the storage battery 32 as a power source. . That is, during the cold storage operation to freeze the cold storage agent 6, the DC fan motor 14 uses the output of the rectifier circuit 31 as a power source, and the storage battery 32 and charging circuit 33 are not used.

Further, a switch input line from an operation panel 47 provided with input means for inputting signals to the microcomputer 46 and various display means and a display output line to the operation panel 47 are connected to the microcomputer 46 . Furthermore, the output of the rectifier circuit 31 is connected to the microcomputer 4 via a power signal line 49.
6, and based on this, the microcomputer 46 determines whether or not there is an AC power source.

Next, the operation will be explained. When the low-temperature refrigerator R is connected to an alternating current power source (AC200V) and the microcomputer 46 is powered on for the first time, the setting operation states of switches SW1 to SW4, which are input means provided on the operation panel 47, are read. Here, the operation panel 47 is provided with a refrigerator switch SW for instructing the start of internal cooling.
1. Temperature selection switch SW2 that selects the internal temperature to +5°C, which is the refrigeration temperature; Temperature selection switch SW3, which selects the freezing temperature to 0°C; and Temperature selection switch SW4, which selects the freezing temperature to -18°C. LED4 to LED6,
A display section 48 consisting of two 7-segment LEDs, S
When any one of SW2 to SW4 is operated, the microcomputer 46 lights up the LED4 to LED6 corresponding to the selected temperature. Further, the microcomputer 46 detects that the low-temperature refrigerator R is connected to the AC power source based on the output from the power signal line 49.

FIG. 3 shows the temperature changes and operations of each part during operation, and FIG. 4 shows the microcomputer 4 from cold storage operation to refrigerator cooling operation.
6 shows a flowchart of the control program of No. 6. At the delivery base, when the low-temperature warehouse R is connected to an alternating current power source (AC200V), charging of the storage battery 32 is started. Further, it is assumed that SW4 is operated on the operation panel 47 and -18° C. is designated as the internal temperature Tc. The rectifier circuit 31 is connected to the microcomputer 46 via the a contact of the switching relay 36.
The process starts at the same time as the power is supplied, and in step 50 it is determined whether or not the cool storage agent temperature sensor 17 is short-circuited. If it is not short-circuited, the cool storage agent temperature sensor 17 is disconnected in step 51. Determine whether or not. If there is no failure in any of them, step 52 indicates that the compressor 8 is currently in use.
It is determined whether or not it is running, and since it is stopped, step 53
In step 54, it is determined whether the temperature of the cool storage agent 6 is -35° C. or higher, and since the temperature is high at the start of operation, the compressor 8 is operated in step 54. As a result, the cool storage operation shown in FIG. 3 is started. Note that a short circuit or disconnection of the cool storage agent temperature sensor 17 can be determined by an abnormality in the output potential from the sensor. In other words, if the output generated by the cool storage agent temperature sensor 17 is an output corresponding to a temperature of +80°C or higher, it means that there is a short circuit, and conversely -5
If the output corresponds to a temperature of 0° C. or lower, the microcomputer 46 can determine that there is a disconnection.

If the compressor 8 is in operation in step 52, it is determined in step 55 whether the temperature of the refrigerant 6 is below -37°C, and if it is below, the compressor 8 is operated in step 56.
stop. As long as the cool storage agent temperature sensor 17 is normal and the AC power source (AC 200V) is connected, the compressor 8 is repeatedly operated and stopped under the above control.

In step 57, a subroutine for determining the completion of freezing of the cool storage agent 6 and the completion of charging of the storage battery 32 is executed. That is, there are two freezing determination conditions for the cold storage agent 6 here. One is that the temperature of the cold storage agent 6 based on the output of the cold storage agent temperature sensor 17 is -29 degrees Celsius lower than the freezing and melting temperature of -25 degrees Celsius. ℃ or below for more than 9 hours,
The other is -3, where the temperature of cold storage agent 6 is 7°C lower than -25°C.
This means that the temperature remained below 2°C for 10 minutes or more. If either one of these two conditions is satisfied, freezing of the cold storage agent 6 is considered to have been completed.

The charging state of the storage battery 32 is determined by inputting the voltage generated by the resistor 34 and calculating the charging current flowing through the storage battery 32 from that value. Consider it completed. When all of these steps are completed, the microcomputer 46 turns on the LED 2 to indicate that the cold storage operation is ready.

Next, in step 58, the refrigerator switch S
It is determined whether W1 has been pressed or not, and if it has not been pressed, it is determined in step 59 whether the freezing and charging have been completed, and since neither freezing nor charging has been completed since the power has just been turned on here, step 64 At this point, the DC fan motor 14 is stopped.

The conventional cold storage operation operation will be explained based on FIG. 3. The temperature of the cold storage agent 6 rapidly decreases due to the operation of the compressor 8, and the freezing temperature of the cold storage agent 6 reaches Ts about 3.5 hours after the start of operation. It reaches -25°C. However, due to the supercooling phenomenon of the cool storage agent 6, the cool storage agent 6 does not freeze immediately, and its temperature continues to fall further. Then, the temperature of the cold storage agent 6 is about -
Freezing begins when the temperature reaches 31°C, and the temperature of the cold storage agent 6 is approximately -
Return to 25°C. While the cold storage agent 6 is frozen, its temperature is -25
The temperature remains constant at ℃, but once the freezing ends, the temperature starts to drop again and becomes lower than -32℃.

In the process of the above-described operation, when the freezing and charging completion determination conditions of step 57 are satisfied, the process proceeds from step 59 to step 60, where it is determined whether the DC fan motor 14 is currently operating, and since it is not, step 61 is performed. The temperature of the storage compartment 2 based on the internal temperature sensor 18 is the set temperature Tc.
It is determined whether the temperature is +1°C or higher, and since the temperature of the storage chamber 2 is high here, the DC fan motor 14 is operated in step 63.
The cool storage operation is ended and the refrigerator internal cooling operation is started. This DC
By operating the fan motor 14, latent heat of fusion of the cool storage agent 6 or cold air cooled by the cooler 10 is circulated into the storage chamber 2, thereby cooling the storage chamber 2.

When the temperature of the storage chamber 2 based on the internal temperature sensor 18 reaches the set temperature Tc by this cooling, the process proceeds from steps 60 and 62 to step 64, and the DC fan motor 14 is stopped. In this way, DC fan motor 1
4 is repeatedly operated and stopped, and the temperature of storage room 2 is -18
Maintained around ℃.

Here, when the refrigerator switch SW1 is pressed during the cold storage operation, the cold storage agent 6 freezes or the storage battery 32 freezes.
Step 58
The process then proceeds to step 60, so that the cold storage operation is shifted to the internal cooling operation. This is performed when it is necessary to cool the food in the storage room 2 while freezing the cold storage agent 6.

[0029] Also, during the above-mentioned cold storage operation or refrigerator cooling operation, in step 50 or 51, the cold storage agent temperature sensor 17 is
If a failure is discovered, the process proceeds to step 65. In step 65, it is determined whether or not the DC fan motor 65 is in operation. If it is not in operation, in step 66, the temperature of the storage compartment 2 based on the internal temperature sensor 18 is set to the set temperature Tc + 1°C.
(i.e. -17°C) or higher, and if the temperature is higher than that, the compressor 8 and the DC fan motor 14 are
is operated, and when the temperature of the storage compartment 2 based on the internal temperature sensor 18 reaches the set temperature Tc due to this cooling, step 6
Step 5 and step 67 proceed to step 69, where the compressor 8 and DC fan motor 14 are stopped.

That is, if a failure such as a short circuit or disconnection occurs in the cold storage agent temperature sensor 17, it will be impossible to determine whether the freezing of the cold storage agent 6 is complete, but even in that case, instead of stopping the entire system, the compressor 8 and the DC fan motor 14 are automatically controlled by comparing the temperature of the storage compartment 2 based on the internal temperature sensor 18 and the set temperature Tc, that is, the control of general refrigerator operation is performed. The DC fan motor 14 is repeatedly operated and stopped, and the temperature of the storage chamber 2 is maintained at around -18° C., which is the set temperature Tc. Therefore, although the temperature of the cold storage agent 6 is not controlled, even if the foods are stored in the storage chamber 2, at least the preservation of these foods is achieved.

Here, the microcomputer 46 displays the temperature inside the storage chamber 2 and the set temperature on the display section 48 during normal operation.
When a failure occurs in the cool storage agent temperature sensor 17, an alarm such as E5 is displayed in the case of a disconnection, and E6 is displayed in the case of a short circuit. This notifies the user of the occurrence of a failure. In addition, in the above embodiment, a failure of the cool storage agent temperature sensor 17 is handled during the entire period from the cold storage operation to the refrigerator cooling operation, but the failure of the cold storage agent temperature sensor 17 can be handled only during the cold storage operation or depending on the usage pattern. The problem may be dealt with only during internal cooling operation.

After or during the cold storage operation and refrigerator cooling operation as described above, articles such as food are stored in the low-temperature refrigerator R, disconnected from the AC power source, and loaded onto a delivery vehicle. When the AC power supply to the low-temperature refrigerator R disappears (AC power is turned off)
Next, a cold storage operation is started in which the storage chamber 2 is cooled by the latent heat of fusion of the cold storage agent 6. During the cold storage operation, the microcomputer 46 and the DC fan motor 14 are supplied with power by discharging the storage battery 32 by switching the changeover switch 36 to the b contact. Further, the DC fan motor 14 is controlled by the microcomputer 46, and is operated when the temperature of the storage chamber 2 measured by the internal temperature sensor 18 rises to the set temperature Tc+1° C., and is stopped when the temperature falls to Tc. As a result, the inside of the storage chamber 2 is maintained at around -18°C. It is assumed that the contacts of the relay switch Ry6 are closed.

[0033] This cold storage operation ends five hours after the AC power supply is turned off, and thereafter the DC fan motor 14 also stops, resulting in a complete stop. These five hours are determined as enough time for the delivery vehicle to complete the delivery.

[0034]

According to the present invention, when a failure such as a disconnection or a short circuit occurs in the cold storage agent temperature sensor, instead of controlling the operation of the compressor using the sensor, the air blowing means and the compressor are controlled using the internal temperature sensor. Since the control device switches over to control the operation of the machine, even if such a failure occurs, the inside of the storage chamber is maintained cooled at least at the set temperature. Therefore, cooling of the items in the storage chamber is ensured, so that even if food items etc. must be stored during the above-mentioned period, it is possible to prevent these foodstuffs from spoiling.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an electric circuit.

FIG. 2 is a longitudinal cross-sectional view of the low-temperature refrigerator.

FIG. 3 is a characteristic diagram showing temperature changes and operations during operation.

FIG. 4 is a flowchart of a control program.

[Explanation of symbols]

2 Storage room 6 Cold storage agent 7 Cooling device 8 Compressor 10 Cooler 14 DC fan motor 17 Cool storage agent temperature sensor 18 Internal temperature sensor 46 Microcomputer R Low temperature storage

Claims (1)

[Claims] [Claim 1] A storage room for storing articles, a cold storage agent,
a cooling device having a cooler and a compressor for cooling the cold storage agent; and a blowing means for sending cold air from the cold storage agent to the storage room;
A cold storage agent temperature sensor that detects the temperature of the cold storage agent, an internal temperature sensor that detects the temperature of the storage chamber, and a cold storage operation that freezes the cold storage agent to an internal cooling operation that cools the storage chamber. a control device that operates the compressor based on the output of the cool storage agent temperature sensor, and operates the air blowing means based on the output of the indoor temperature sensor during the indoor cooling operation, and during the cool storage operation, Alternatively, if the cold storage agent temperature sensor fails during the refrigerator cooling operation, or during the period from the cold storage operation to the refrigerator cooling operation, the control device controls the compressor and the air blowing means based on the output of the refrigerator temperature sensor. A low-temperature refrigerator characterized by operating.