JPH05196343A - Method and device for starting defrosting operation in refrigerant evaporator - Google Patents

Abstract

PURPOSE:To prevent operator's individual differences from having an influence on the commencement of defrosting operation, and defrosting operation from being periodically started regardless of the amount of frost by a method wherein an expansion valve is controlled by an expansion valve control computer and defrosting operation is automatically started when the maximum valve capacity drops below the set value. CONSTITUTION:A low temperature air cooling apparatus using an ordinal refrigerating cycle is equipped with an expansion valve control computer 1 to control an electronic expansion valve 4, and a pressure sensor 2 and a temperature sensor 3 are mounted on the downstream side of a refrigerant evaporator 9 and connected to the computer 1 by signal wires 12 and 13. A low temperature air cooling apparatus control board 10 which controls the refrigerant evaporator 9 and a defrosting device is connected to the computer 1 by a defrosting signal wire 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low temperature air cooling device for cooling and keeping an object to be cooled by circulating low temperature air,
Moisture in the air adheres to the surface of the refrigerant evaporator as frost and significantly reduces the cooling efficiency of the low temperature air cooling device.Therefore, during cooling operation, the cooling efficiency is sensed and defrosting is started. The present invention relates to a defrost starting method and apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, there are defrosters for refrigerant evaporators that utilize sensible heat or latent heat of sprinkling water, refrigerant hot gas, etc. (1) directly measuring the thickness of frost attached to the refrigerant evaporator, (2) measuring the pressure loss of air passing through the refrigerant evaporator, (3) measuring the increase in blower current consumption, ( 4) There are things such as regularly performed at the set time.

[0003]

Among the conventional defrosting method and apparatus for the refrigerant evaporator, the above-mentioned (1),
In the case of (2) and (3), the start time is set by visually confirming the actual frosted state or by experience, and there is an individual difference in the defrosting person in the setting of the defrost start time. The detection of the optimum defrost start time becomes ambiguous, and defrost is started earlier than the time when the cooling efficiency of the evaporator is not carelessly decreased, or the cooling efficiency of the evaporator is decreased due to excessive frost formation. Notwithstanding the state, defrost started later than that time, and the temperature of the cooling room was raised unnecessarily, and low efficiency long-term operation of the compressor was performed, which not only deteriorates the quality of cold-stored products. There is a drawback that it does not save energy.

In the case of (4), depending on the opening / closing degree of the low temperature compartment door of the refrigerant evaporator, the temperature of the air to be cooled and the humidity of the object to be cooled depending on the amount of storage and removal of the object to be cooled, a certain amount of frost will be present on the refrigerant evaporator. Although there is a variation in the time of defrosting, there is a possibility that defrosting will be performed earlier at some times and later at other times because defrosting is performed regularly at a predetermined time regardless of the amount of frost adhesion, and there is a delay in starting defrosting early. The start-up has the same drawbacks as described above, which means that the compressor operating time is lengthened, its life is shortened, and energy is not saved.

According to the present invention, an expansion valve control computer controls an expansion valve connected to a refrigerant evaporator, detects frost formation on the refrigerant evaporator, detects an optimum defrost start time, and automatically detects when defrost is necessary. Defrosting in a refrigerant evaporator that does not start defrosting at the set time, regardless of individual differences in defrosting person setting the defrosting start time, and regardless of the amount of frost adhesion It is an object to provide a starting method and an apparatus thereof.

[0006]

In order to achieve the above-mentioned object, the present invention provides a temperature sensor and a pressure sensor, each of which is provided with a control of an expansion valve for supplying a refrigerant to a refrigerant evaporator downstream of the evaporator. The expansion valve control computer connected by the signal line is used so that the expansion valve always self-searches and stores the maximum valve capacity adapted to the refrigerating capacity of the evaporator.

Next, when the refrigerant evaporator becomes more frosty, the refrigerating capacity of the refrigerant evaporator decreases. The temperature sensor and pressure sensor attached downstream of the refrigerant evaporator detect the temperature and pressure to control the expansion valve. The maximum valve capacity value is reduced by a computer, and when the maximum valve capacity value becomes equal to or less than a preset set value, defrosting is started as the optimum defrosting start time.

Further, a plurality of refrigerant circulation circuits are provided in the same compressor and condenser, and a temperature sensor and a pressure sensor downstream of the refrigerant evaporator in each of the circuits are used to determine the maximum valve capacity of each of the plurality of expansion valves. Either the maximum value, the minimum value or the average value is used to activate the known defrosting device to start the defrosting.

[0009]

The electronic expansion valve 4 for supplying the refrigerant to the refrigerant evaporator 9 is controlled by the pressure sensor 2 attached downstream of the evaporator 9 for detecting the refrigerant evaporation pressure and the temperature sensor 3 for detecting the refrigerant temperature. Since the expansion valve control computer 1 connected with is used, a value obtained by converting the pressure detected by the refrigerant evaporation pressure sensor 2 in the computer 1 into an evaporation temperature and a temperature sensor attached downstream of the evaporator, that is, on the evaporator refrigerant outlet side It is possible to perform a proportional control of the liquid refrigerant passage amount of the electronic expansion valve 4 by calculating the difference from the temperature detected by 3, ie, the degree of superheat.

When frost forms on the refrigerant evaporator 9, the temperature of the temperature sensor 3 is often lowered beyond the range of the proportional control, and the expansion valve control computer 1 decreases the maximum valve capacity of the electronic expansion valve 4. The capacity of the electronic expansion valve 4 is adjusted so that the refrigerating capacity of the evaporator 9 and the capacity of the electronic expansion valve 4 are balanced.

When there is more frost on the refrigerant evaporator 9, the expansion valve control computer 1 further reduces the maximum valve capacity of the electronic expansion valve 4, and the expansion valve control computer 1 stores the set maximum valve for defrost start. Compared with the capacity, whether the maximum valve capacity is the same as the set maximum valve capacity for defrost start,
Alternatively, the expansion valve control computer 1 sets the low temperature air cooling device control panel 10 as the optimum defrost start time when it falls below
Send a defrost start signal to and start defrost.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A detailed description will be given of the accompanying drawings showing an example of a defrost initiation device in a refrigerant evaporator used for carrying out the present invention. Figure 1 is a piping / wiring diagram when a single refrigerant evaporator is installed in a single cooling chamber, and Figure 2 is a piping / wiring diagram when multiple refrigerant evaporators are installed in a single cooling chamber. 3 is a piping / wiring diagram in the case where a plurality of refrigerant evaporators are installed in a plurality of cooling chambers, and FIG. 4 shows the relationship between the actual valve capacity and the maximum valve capacity with respect to the degree of superheat of the temperature sensor unit. .

Reference numeral 1 is an expansion valve control computer, which is a compressor 5
To a high pressure refrigerant liquid in the condenser 7 via the high pressure gas pipe 15, and the pressure is reduced by the electronic expansion valve 4 via the high pressure liquid pipe 16 and heat is exchanged with the air from the blower 8 in the evaporator 9 in the cooling chamber 17, In the refrigeration cycle that returns to the compressor 5 via the low-pressure gas pipe 14, the pressure sensor 2 that detects the refrigerant evaporation pressure provided in the low-pressure gas pipe 14 downstream of the refrigerant evaporator 9, the temperature sensor 3 that detects the refrigerant evaporation temperature, and the electronic expansion The valve 4 is connected by signal lines 12, 13 and 6, respectively. The difference between the value obtained by converting the refrigerant evaporation pressure detected by the pressure sensor 2 into the evaporation temperature by the computer 1 and the temperature detected by the temperature sensor 3, that is, The degree of superheat is calculated and the amount of liquid refrigerant passing through the electronic expansion valve 4 is proportionally controlled.

Reference numeral 10 is a known defrosting device (not shown).
A low-temperature air-cooling device control panel for controlling the above, which is connected to the expansion valve control computer 1 by the defrost signal line 11, and when the frost on the evaporator 9 increases, the temperature detected by the temperature sensor 3 is often low. , Exceeding the range of proportional control,
The expansion valve control computer 1 senses that the cooling capacity of the refrigerant evaporator 9 has decreased, decreases the maximum valve capacity of the electronic expansion valve 4, and compares it with the set maximum valve capacity for starting defrost stored in the computer 1, When the reduced maximum valve capacity becomes equal to or less than the set maximum valve capacity for starting defrost, the defrost start signal from the computer 1 is received via the defrost signal line 11 as the optimum defrost start time to start defrost. Is.

In FIG. 3, reference numerals 18 and 19 are cooling chambers equipped with blowers 8a and 8b, respectively, and a plurality of electronic expansion valves 4a and 4b are connected to each other by branching a high pressure liquid pipe 16 and connecting refrigerant evaporators 9a and 9b. The installed temperature sensors 3a and 3b are similar to the above temperature sensors installed downstream of the plurality of refrigerant evaporators 9a and 9b, respectively, before the branching portion to the low pressure gas pipe 14.

Reference numerals 6a and 6b respectively denote a plurality of electronic expansion valves 4
a and 4b are expansion valve control signal lines for connecting the expansion valve control computer 1, 12 is a pressure sensor signal line for connecting the pressure sensor 2 installed in the same low-pressure gas pipe 14 and the computer 1, and 13a , 13b are temperature sensor signal lines for connecting the plurality of temperature sensors 3a, 3b and the computer 1, respectively. Similarly to the above, the computer 1 and the defrosting devices of the plurality of evaporators 9a, 9b of the cooling chambers 18, 19 are connected. The low temperature air cooling device control panel 10 to be controlled is connected by the defrost signal lines 11a and 11b.

In FIG. 4, point A is the maximum valve capacity of the initially set expansion valve, and the degree of superheat of the temperature sensors 3, 3a, 3b is in the proportional band range 1 (the degree of superheat of the temperature sensor when the expansion valve starts to open).
The actual valve capacity with respect to the heat load fluctuation is linear IA, I so that it becomes II (the temperature sensor superheat degree at which the expansion valve has the maximum capacity).
Refrigerant evaporators 9 and 9 are successively adjusted on B and IC
When the frost on a, 9b increases, the temperature sensors 3, 3a,
When the degree of superheat of part 3b decreases and becomes less than or equal to the degree of superheat I of the temperature sensor at the beginning of opening the expansion valve, the maximum valve capacity is point A → point B → C
If the maximum planting, minimum value or average value of the valve maximum capacity of the plurality of expansion valves 4a, 4b reaches the D point or lower, the low temperature air is set as the most common defrost start time. Defrost signal line 1 on the cooling device control panel 10
Expansion valve control computer 1 via 1, 11a, 11b
A defrost start signal is sent to start defrost.

[0018]

Since the present invention has the above-described structure, even if the low temperature air cooler of the low temperature air cooler is partially frosted, the refrigerant evaporators 9, 9a and 9b are frosted. Since the defrosting is started at the optimum defrost start time by catching the decrease in the maximum valve capacity of the expansion valves 4, 4a, 4b, there is a change in the state of the cooling air (humidity), a change in the refrigerating capacity of the compressor, and other disturbances. However, the decrease in the expansion valve maximum valve capacity indicates the amount of frost formed on the refrigerant evaporator, and therefore the optimum defrost start time can be grasped with certainty, so that defrosting of the refrigerant evaporators 9, 9a, 9b is started steadily. By doing so, the operating time of the compressor is shortened, the life of the compressor is extended, energy is saved, and the quality of low-temperature stored products is not impaired.

[Brief description of drawings]

FIG. 1 is a piping / wiring diagram schematically showing a case where a single refrigerant evaporator is installed in a single cooling chamber of the present invention.

FIG. 2 is a piping / wiring diagram schematically showing a case where a plurality of refrigerant evaporators are installed in a single cooling chamber.

FIG. 3 is a piping / wiring diagram schematically showing a case where a plurality of refrigerant evaporators are installed in a plurality of cooling chambers.

FIG. 4 is a chart showing the relationship between the actual valve capacity and the maximum valve capacity with respect to the degree of superheat of the temperature sensor unit of the expansion valve.

[Explanation of symbols]

1 Expansion valve control computer 2 Pressure sensor 3,3a, 3b Temperature sensor 4,4a, 4b Electronic expansion valve 5 Compressor 6 Expansion valve control signal line 7 Condenser 8, 8a, 8b Blower 9, 9a, 9b Refrigerant evaporator 10 Low-temperature air cooler control panel 11, 11a, 11b Defrost signal line 12 Pressure sensor signal line 13 Temperature sensor signal line 14 Low pressure gas pipe 15 High pressure gas pipe 16 High pressure liquid pipe 17, 18, 19 Cooling chamber A Initial setting maximum valve capacity B , C Maximum valve capacity after adjustment D Set maximum valve capacity for defrost start I Superheat degree of temperature sensor when expansion valve starts opening II Superheat degree of temperature sensor when expansion valve reaches maximum valve capacity

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor, Yoshiyuki Mada 1-6, 7-703, Ayumagaya Nishi, Minoh City, Osaka Prefecture

Claims (4)

[Claims] 1. A low temperature air cooling apparatus for supplying a refrigerant from an expansion valve connected to a refrigerant evaporator and cooling air by utilizing latent heat of vaporization of the refrigerant, wherein the expansion valve is controlled by an expansion valve control computer. The defrost of the frost generated on the evaporator surface was searched by the computer by detecting the temperature and pressure of the refrigerant evaporator downstream, and the decrease in the maximum capacity of the expansion valve to below the set value was detected and a known defrost device was used. A method for starting defrost in a refrigerant evaporator, comprising: 2. A plurality of expansion valves and a refrigerant evaporator are used for one compressor and a condenser, and the refrigerant is supplied from each expansion valve connected to each refrigerant evaporator to utilize latent heat of vaporization of the refrigerant. In the low temperature air cooling device for cooling air by controlling the expansion valves by the expansion valve control computer, the computer controls the defrosting of frost generated on the surfaces of the refrigerant evaporators. Defrost start in a refrigerant evaporator characterized by starting using a known defrost device using any of the maximum, minimum or average values of the expansion valve capacities retrieved by detecting Method. 3. A low-temperature air cooling device in which a compressor, a condenser, an expansion valve and a refrigerant evaporator are sequentially connected by a pipeline to flow a refrigerant and then circulates back to the compressor to control the expansion valve. A control computer is provided, and a temperature sensor and a pressure sensor in which each signal line is connected to the computer are provided in a pipeline downstream of the evaporator, and a defrosting low-temperature air cooling device control panel for controlling the defrosting of the evaporator is provided in the computer. A defrost start signal is sent to the control panel by detecting the decrease of the maximum capacity of the expansion valve, which is found by the computer detecting the temperature and pressure downstream of the refrigerant evaporator, provided by connecting the signal line. A defrost starting device in a refrigerant evaporator, characterized by inputting and starting defrosting using a known defrosting device. 4. A plurality of expansion valves and a refrigerant evaporator are sequentially connected to a single compressor and a condenser by pipelines to flow the refrigerant,
In the low-temperature air cooling device that returns to the compressor and circulates again, an expansion valve control computer that controls the opening and closing of the expansion valve by connecting a signal line to each of the plurality of expansion valves is provided, and each expansion valve control computer is provided in a pipeline downstream of each evaporator. A temperature sensor and a pressure sensor whose signal lines are connected to the computer are provided, and a low-temperature air cooling device control panel for controlling the defrost of each evaporator is provided to the computer by connecting the defrost signal line. By inputting a defrost start signal to the control panel using any one of the maximum value, the minimum value or the average value of the valve maximum capacities of the plurality of expansion valves searched by detecting the temperature and pressure of A defrost starting device in a refrigerant evaporator, characterized in that the defrosting device is used to start defrosting.