JP5055180B2 - Cooling storage - Google Patents

Description

  The present invention relates to a cooling storage provided with a refrigerant circuit having an evaporator and an expansion valve, and more particularly to opening degree control of the expansion valve.

Conventionally, stores such as supermarkets have been installed with low-temperature showcases such as refrigerated or frozen open showcases for displaying and selling products, and showcases with doors, and prefabricated cooling storages for storing products in the backyard. ing. The refrigeration cycle provided in such a cooling storage is, for example, as shown in Patent Document 1, by connecting a compressor, a condenser, a liquid electromagnetic valve, an expansion valve, an evaporator, and the like in a ring shape with a refrigerant pipe. Was composed.
JP-A-5-296614

  In this case, an expansion valve is provided on the inlet side of the evaporator, and the superheat degree of the refrigerant in the evaporator is adjusted to an optimum value. This expansion valve may be of the temperature type (mechanical type), and this is because the bellows adjusts the valve opening according to the refrigerant temperature on the outlet side of the evaporator, so only the degree of superheat is adjusted. Played a role. Therefore, since it was difficult to fully close, a liquid electromagnetic valve or the like that can fully close the refrigerant pipe was provided in the vicinity of the expansion valve.

  On the other hand, in recent years, an electronic expansion valve (or an electric expansion valve) using a driving device such as a stepping motor has been developed. According to such an electronic expansion valve, fine control of the valve opening degree can be realized, and Pipes can be fully closed.

  Therefore, it is conceivable to realize highly accurate cooling control by replacing the mechanical expansion valve employed in the conventional cooling storage with an electronic expansion valve. However, since the control device in the conventional cooling storage is based on the premise that a mechanical expansion valve is provided, it does not have a function of controlling the opening degree of the expansion valve.

  In such a case, an expansion valve control means for separately controlling the opening degree of the expansion valve is provided, and expansion is performed based on temperature control ON / OFF data (thermo signal), a defrosting signal, and a non-cooling signal input from an existing control device. While controlling the opening and closing of the valve, the opening degree of the expansion valve is controlled based on the degree of superheat calculated from the refrigerant inlet temperature and the refrigerant outlet temperature of the evaporator input to the expansion valve control means.

  When the defrosting operation is performed in the cooling storage, the temperature of the evaporator rises after the completion of the defrosting, so that the operation of the fan for the cooler is delayed for a certain period of time in order to suppress the increase in the internal temperature. In this case, in the existing control device, when the defrost signal is not input to each expansion valve control device, each expansion valve control device executes the superheat degree control of the expansion valve on the assumption that the cooling operation is started.

  However, when the degree of superheat control of the expansion valve is executed in a state where the cooler blower is stopped, the valve opening may increase, and in such a case, liquid refrigerant stays in the evaporator. There is a problem that causes liquid back.

  The present invention has been made to solve the conventional technical problems, and while using an existing control device, the opening degree of the expansion valve is controlled by a control device provided in each expansion valve, and an appropriate cooling operation is performed. A cooling storage can be provided.

  The cooling storage of the present invention comprises a refrigerant circuit having an evaporator and an expansion valve, and is formed by circulating cool air exchanged with the evaporator into a storage chamber by means of a blower, the refrigerant inlet temperature and refrigerant outlet of the evaporator A controller for controlling the opening degree of the expansion valve based on the temperature and a predetermined superheat setting value, and the controller sets the superheat setting value during the start delay period of the blower after the defrosting of the evaporator. It is characterized by raising.

  According to the present invention, in a cooling storage unit that includes a refrigerant circuit having an evaporator and an expansion valve and circulates cold air heat-exchanged with the evaporator into a storage chamber by a blower, the refrigerant inlet temperature and the refrigerant outlet temperature of the evaporator And a controller for controlling the valve opening degree of the expansion valve based on a predetermined superheat degree set value, and the controller increases the superheat degree set value during the start-up delay period of the blower after completion of defrosting of the evaporator. Therefore, based on the refrigerant inlet temperature and refrigerant outlet temperature and the predetermined superheat setting value of the evaporator that has been heated to high temperature by defrosting, the controller starts the blower after defrosting without expanding the valve opening of the expansion valve. During the delay period, the opening degree of the expansion valve can be controlled to be reduced based on the raised superheat setting value.

  As a result, it is possible to avoid inconvenience that the liquid refrigerant stays in the evaporator and causes liquid back.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a refrigerant circuit diagram of a cooling storage 1 to which the present invention is applied, and FIG. 2 is a schematic electrical block diagram of a main controller C and expansion valve controllers 15 and 16. The cooling storage 1 of the present embodiment is a refrigerated open showcase installed in a store such as a supermarket, for example. Here, two (but not limited to) a plurality of showcases 2 and 3 are connected. is set up.

  The cooling device R that cools the cooling storage 1 includes a refrigerator 4 installed outside the store, and a refrigerant circuit 5 extends between the refrigerator 4 and the showcases 2 and 3 installed in the store. Piping is connected.

  The refrigerant circuit 5 includes a compressor 7 installed on the refrigerator 4 side, a condenser 8 as a radiator, an evaporator 9 set in the showcase 2 to cool the inside of the storage chamber 2A, and an inside of the showcase 3 From the evaporator 11 for cooling the interior of the storage chamber 3A, the electronic expansion valves 10 and 12 as pressure reducing devices for controlling the amount of refrigerant flowing into the evaporators 9 and 11, and a dryer or accumulator (not shown). Composed.

  The discharge side of the compressor 7 is connected to the inlet of the condenser 8, and the outlet of the condenser 8 is branched through a three-way valve, and one branched pipe is connected to the electronic expansion valve 10 of the showcase 2. The outlet of the electronic expansion valve 10 is connected to the inlet of the evaporator 9 that cools the interior of the storage chamber 2A. The other branched pipe is connected to the inlet side of the electronic expansion valve 12 of the showcase 3, and the outlet of the electronic expansion valve 12 is connected to the inlet of the evaporator 11 that cools the interior of the storage chamber 3A. Then, the outlets of the evaporators 9 and 11 merge and are connected to the suction side of the compressor 7.

  In the figure, reference numeral 21 denotes an evaporator blower which is provided in the vicinity of the evaporator 9 and circulates the cold air exchanged heat with the evaporator 9 into the storage chamber 2A of the showcase 2, and 22 is provided in the vicinity of the evaporator 11. It is a blower for evaporators.

  The electronic expansion valves 10 and 12 are expansion valves whose valve opening can be adjusted with high accuracy by a stepping motor. Each of the electronic expansion valves 10 and 12 can be adjusted in predetermined steps by a predetermined step between fully closed and fully opened by expansion valve controllers 15 and 16 described later in detail.

  A temperature sensor 17 for detecting the refrigerant inlet temperature is provided on the refrigerant inlet side of the pipe of the evaporator 10, and a temperature sensor 18 for detecting the refrigerant outlet temperature is provided on the refrigerant outlet side of the pipe of the evaporator 10. Is provided. Similarly, the evaporator 12 is also provided with a temperature sensor 19 for detecting the refrigerant inlet temperature and a temperature sensor 20 for detecting the refrigerant outlet temperature. These temperature sensors 19 and 20 are connected to an expansion valve controller 16 that controls the electronic expansion valve 12.

  In the figure, C is a main controller constituted by a general-purpose microcomputer. On the input side of the main controller C, a control panel for inputting a main temperature sensor 30 for detecting the temperature in the storage chamber 2A of one showcase 2 constituting the cooling storage 1 and the set temperatures of the storage chambers 2A and 2B. 27 is connected, and the compressor 7 of the cooling storage 1 and the condenser fans 21 and 22 are connected to the output side. The main controller C is connected to signal lines 23 and 24 for transmitting thermo ON / OFF data, a defrosting signal, and a non-cooling signal to the expansion valve controllers 15 and 16, respectively.

  The expansion valve controller 15 is constituted by a general-purpose microcomputer, and on its input side, a signal line 23 for inputting thermo ON / OFF data, a defrost signal, and a non-cooling signal from the main controller C, and an evaporator 9 are connected to temperature sensors 17 and 18 for detecting the refrigerant inlet temperature and the refrigerant outlet temperature, and an expansion valve temperature sensor 25 for detecting the temperature of the region in the storage chamber 2A cooled by the evaporator 9.

  Similarly, the expansion valve controller 16 is constituted by a general-purpose microcomputer, and a signal line 24 for inputting thermo ON / OFF data, a defrosting signal, and a non-cooling signal from the main controller C on the input side thereof. The temperature sensors 19 and 20 for detecting the refrigerant inlet temperature and the refrigerant outlet temperature of the evaporator 11 are connected to the expansion valve temperature sensor 26 for detecting the temperature of the region in the storage chamber 3A cooled by the evaporator 11. Yes.

  These expansion valve controllers 15 and 16 calculate the degree of superheat of the refrigerant in the evaporator 9 or 11 by subtracting the refrigerant inlet temperature detected by the temperature sensors 17 and 19 from the refrigerant outlet temperature detected by the temperature sensors 18 and 20. .

(Normal cooling control)
With the above configuration, the main controller C can set the set temperature (for example, 5 ° C. or the like) set by the control panel 27 based on the internal temperature detected by the main temperature sensor 30 provided in the area in the one storage chamber 2A. When the upper limit temperature (ON point) set above the refrigeration temperature is reached, the compressor 7 is started, and when the temperature drops to the set temperature (OFF point), the compressor 7 is stopped. At this time, when the internal temperature detected by the main temperature sensor 30 reaches the upper limit temperature, the main controller C transmits a thermo-ON signal to each of the expansion valve controllers 15 and 16, and the detected internal temperature is set. When the temperature is reached, a thermo OFF signal is transmitted to each of the expansion valve controllers 15 and 16.

  When the compressor 7 is started, the refrigerant gas that has been compressed and becomes high temperature dissipates heat in the condenser 8 and is liquefied. The expansion valve controllers 15 and 16 open the electronic expansion valves 10 and 12 by transmitting the thermo-ON signal from the main controller C to the expansion valve controllers 15 and 16. As a result, the liquid refrigerant that has passed through the condenser 8 is throttled by the electronic expansion valves 10 and 12, and then flows into the evaporators 9 and 11 to evaporate. The evaporators 9 and 11 exhibit a cooling effect by the endothermic action at this time.

  Since the cold air heat-exchanged with the evaporators 9 and 11 is circulated in the storage chambers 2A and 3A by the respective evaporator fans 21 and 22, the inside of the cooling storage 1 (the storage chambers 2A and 3A) has the same setting. Maintained cooling to temperature. Then, the refrigerant exiting each of the evaporators 9 and 11 is again sucked into the compressor 7 and compressed.

  Here, the expansion valve controllers 15 and 16 control the electronic expansion valves 10 and 12 based on the temperature control ON / OFF data, the defrost signal, and the non-cooling signal transmitted from the main controller C through the signal line 23 or 24, respectively. Controls whether it is fully closed or opened. That is, when any one of the thermo OFF signal, the defrost signal, and the non-cool signal is transmitted from the main controller C to the expansion valve controllers 15 and 16, the expansion valve controllers 15 and 16 fully close the electronic expansion valves 10 and 12. And stop cooling. On the other hand, when a thermo-ON signal is transmitted from the main controller C, the superheat degree of the evaporator 9 or 11 calculated from the refrigerant inlet temperature and the refrigerant outlet temperature detected by each temperature sensor 17, 18, or 19, 20 is refrigerated. The valve openings of the electronic expansion valves 10 and 12 are adjusted so that the target value is optimal for the cycle.

  In this case, if the opening degree of the electronic expansion valves 10 and 12 is too small, the degree of superheat increases and the refrigerant completely evaporates before leaving the evaporators 9 and 11, so the cooling effect in the evaporators 9 and 11 is descend. On the other hand, if the valve openings of the electronic expansion valves 10 and 12 are too large, the degree of superheat will be negative, and a so-called liquid back phenomenon will occur in which unvaporized refrigerant flows out of the evaporators 9 and 11 and is sucked into the compressor 7. become.

  Each expansion valve controller 15, 16 adjusts the valve opening of each electronic expansion valve 10, 12 to an optimum target value for the operation of the refrigeration cycle so that such a problem does not occur. PID control is used. This PID control includes proportional control (determining a control amount in a direction that eliminates the deviation e from the target value), integral control (determining a control amount in a direction that eliminates the steady deviation e), and differential control (determining a change in the deviation e. The final control amount of the valve opening of the electronic expansion valves 10 and 12 is determined from the sum of the control amounts by determining the control amount in the direction of elimination, in which case the proportional coefficient KP, the integral coefficient KI, and the differential coefficient KD is required.

  Each of the expansion valve controllers 15 and 16 has at least two types determined in advance by experiment, that is, a proportional coefficient KP, an integral coefficient KI, and a differential coefficient KD that are adopted at the time of pull-down, and a normal cooling operation (during a thermocycle). The proportional coefficient KP, the integral coefficient KI, and the differential coefficient KD employed in FIG.

  Therefore, each expansion valve controller 15, 16 indicates which proportional coefficient K P, integral coefficient KI and differential coefficient KD is used, the expansion valve temperature sensor 25 connected to each of the expansion valve controllers 15, 16, 26 is determined based on the detected temperature by 26, and these are switched to determine the control amount of the valve opening of each expansion valve 10, 12.

  And each expansion valve controller 15 and 16 performs PID control using each coefficient, determines the valve opening degree of each electronic expansion valve 10 and 12, and makes superheat degree correspond with a target value. As a result, the superheat degree control with high accuracy can be realized by the electronic expansion valves 10 and 12.

(Control when the first cooling failure occurs)
When executing the cooling control, the expansion valve controllers 15 and 16 determine whether or not the abnormal control condition is satisfied at regular time intervals. In this embodiment, the abnormal control condition is (1) that the refrigerant inlet temperature detected by the temperature sensor 17 or 19 is a predetermined set temperature, for example, 0 ° C. or more. (2) Calculated by the expansion valve controllers 15 and 16. Further, the degree of superheat is equal to or less than a predetermined abnormal value, for example, −3.0 ° C. or less. (3) The valve opening degree of the electronic expansion valves 10 and 12 is set to a preset lower limit value.

  That is, although the refrigerant inlet temperature is equal to or higher than the predetermined set temperature and the valve opening degree of the electronic expansion valve is the lower limit value, the superheat degree in the evaporator is equal to or lower than the predetermined value, that is, lower than the refrigerant inlet temperature. When the refrigerant outlet temperature is lower than the actual value, it is determined that an abnormal state in which the degree of superheat is calculated to be lower than the actual value and the valve opening is too narrow has occurred.

  As a cause of the occurrence of the abnormal state, temperature sensors 17 and 19 for detecting the refrigerant inlet temperature of the evaporator due to the influence of heat from the other evaporator that is transmitted through the refrigerant pipe in which the evaporators 9 and 11 are provided. It is conceivable that the temperature sensors 18 and 20 that detect the refrigerant outlet temperature temporarily detect a temperature lower than the actual refrigerant temperature.

  In this case, the expansion valve controllers 15 and 16 calculate the degree of superheat lower than the actual value, and the expansion valve controllers 15 and 16 open the expansion valves 10 and 12 regardless of the conditions for causing the liquid back. I will narrow down the degree. Thereby, sufficient refrigerant | coolant is no longer supplied to the evaporator 9 or 11 concerned, and a cooling failure generate | occur | produces.

  In the present embodiment, the expansion valve controllers 15 and 16 that determine whether or not the abnormal state as described above has occurred and determine that the abnormal control condition is satisfied are the valves of the expansion valve 10 or 12. It opens to the direction which expands an opening, for example, the predetermined | prescribed upper limit of valve opening.

  As a result, the occurrence of an abnormal state due to an apparent liquid back occurring in the evaporator 9 or 11 is sufficient for the evaporator 9 or 11 by expanding the valve opening of the electronic expansion valve 10 or 12. It becomes possible to supply a refrigerant and to improve cooling failure.

  Accordingly, appropriate superheat control can be realized by the expansion valve controllers 15 and 16 that control the valve openings of the electronic expansion valves 10 and 12, and a smooth cooling operation can be executed.

(Control when second cooling failure occurs)
Further, in this embodiment, the opening control of the expansion valve 12 of the evaporator 11 that cools the respective expansion valve controllers 15 and 16, particularly, the region where the main temperature sensor 30 is not provided (the storage chamber 3 </ b> A in this embodiment). The expansion valve controller 16 that performs the above operation is the storage chamber 3A detected by the expansion valve temperature sensor 26 used for the PID control connected to the expansion valve controller 16 when the cooling control is executed. The temperature in the inner area is compared with the temperature adjustment ON / OFF data transmitted from the main controller C.

  Specifically, the expansion valve controller 16 includes a cooling state in the storage chambers 2 </ b> A and 3 </ b> A ascertained from temperature control ON / OFF data transmitted from the main controller C, and a storage chamber detected by the expansion valve temperature sensor 26. The cooling state of the area within 3A is compared.

  When these cooling states are different, for example, when an OFF signal is transmitted from the main controller C to the expansion valve controller 16, and the temperature detected by the expansion valve temperature sensor 26 is higher than the upper limit temperature (ON point). The expansion valve controller 16 executes the superheat control based on the expansion valve temperature sensor 26 without fully closing the electronic expansion valve 12.

  Thereby, the electronic expansion valve 12 of the evaporator 11 that cools the region in the storage chamber 3A at a position separated from the main temperature sensor 30 can be appropriately controlled to open and close, and the cooling failure in the region can be avoided in advance. Is possible.

  Similarly, when an ON signal is transmitted from the main controller C to the expansion valve controller 16, and the temperature detected by the expansion valve temperature sensor 26 is lower than the set temperature (OFF point), the expansion valve controller 16 Does not execute superheat control, but fully closes the electronic expansion valve 12 based on the expansion valve temperature sensor 26.

  Accordingly, the electronic expansion valve 12 of the evaporator 11 that cools the region in the storage chamber 3A at a position separated from the main temperature sensor 30 can be appropriately controlled to open and close, and the region can be prevented from being overcooled. Is possible.

  Therefore, it is possible to suppress the unevenness of the cooling state in the storage chambers 2A and 3A cooled by the plurality of evaporators 9 and 11, and to cool the whole uniformly and appropriately.

(Control when changing temperature setpoint)
Next, with reference to FIGS. 3 and 4, the control when the set temperature in the storage chambers 2A and 3A is changed by the control panel 27 will be described. FIG. 3 is a timing chart with respect to temperature change, and FIG.

  The expansion valve controllers 15 and 16 of this embodiment are not connected to the main controller C that sets the set temperatures in the storage chambers 2A and 3A by communication lines, and temperature control ON / OFF data transmitted from the main controller C The valve opening degree of the electronic expansion valves 10 and 12 is controlled by the defrosting signal and the non-cooling signal and the refrigerant temperature of each evaporator. Therefore, even when the set temperature in the storage chambers 2A and 3A is changed by the control panel 27 in the main controller C, the valve opening degree of the expansion valves 10 and 12 in the expansion valve controllers 15 and 16 is directly determined. Not reflected in control.

  However, as described above, each coefficient used based on the temperature detected by the expansion valve temperature sensors 25 and 26 in the PID control is changed. Since this change is also made based on the temperature set values in the storage chambers 2A and 3A, the expansion valve controllers 15 and 16 need to grasp the change of the temperature set values.

  Therefore, in this embodiment, the temperature set value is corrected by the expansion valve controllers 15 and 16 as follows. First, the expansion valve controllers 15 and 16 (1) that the defrosting signal and the non-cooling signal are not transmitted from the main controller C. (2) The temperature control ON / OFF data changes from the thermo ON signal to the thermo OFF signal. The temperature detected by the expansion valve temperature sensors 25 and 26 connected to the expansion valve controller 15 or 16 is stored in a built-in memory on the condition that a predetermined delay time d has elapsed. In addition, the thing by the thermo OFF signal based on a defrosting signal and a non-cooling signal can be excluded reliably by making it the conditions that predetermined | prescribed delay time d passed after changing to the thermo OFF signal.

  Then, as shown in FIG. 4, the chamber internal temperature detected by the expansion valve temperature sensors 25 and 26 stored in the memory is monitored every predetermined sampling period T (for example, 2 hours) and stored in the memory. Store. The temperature after change set in the main controller C for a certain time, for example, every integral multiple of the sampling period T (here, 24 hours), the minimum value of the internal temperature for each sampling period T stored in the memory Estimating the set value, the temperature set value held by the expansion valve controllers 15 and 16 is corrected to the estimated value.

  At this time, as shown in FIG. 4, in the cooling operation for one day, so-called night setback (NSB; energy saving operation such as nighttime) or so-called demand setback (DSB. Energy saving operation according to demands in business hours, etc.) ) Furthermore, there is a temperature change due to the influence of the disturbance (error TP2) due to customer traffic. In addition, since the attachment positions of the main temperature sensor 30 connected to the main controller C and the expansion valve temperature sensors 25 and 26 (particularly the temperature sensor 26 provided in the storage chamber 3A) are separated from each other, the attachment positions depend on these attachment positions. An error (TP1) occurs.

The minimum value of the internal temperature for each sampling period T stored in the memory excluding the influence of NSB, DSB, disturbance error (TP2), mounting error (TP1), etc., is the current temperature setting value in the main controller C. Since the expansion valve controllers 15 and 16 estimate that there is something, the expansion valve controllers 15 and 16 obtain an estimated value on condition that the following expression is satisfied.
| Estimated value−Current set value | ≧ | TP1 | + | TP2 |

  When the estimated values are obtained as described above, the expansion valve controllers 15 and 16 correct the currently set temperature set value to the estimated value obtained this time. Thereafter, the superheat degree control of the electronic expansion valves 10 and 12 is executed according to the corrected temperature setting value.

  As a result, it is possible to realize optimal superheat degree control of the electronic expansion valves 10 and 12 according to the temperature state in the cabinet without directly connecting the main controller C and the expansion valve controllers 15 and 16 by communication lines. It becomes possible.

  In particular, in this embodiment, a defrosting signal and a non-cooling signal are transmitted as the internal temperature detected by the expansion valve temperature sensors 25 and 26 and stored in the memory at every sampling period T for obtaining an estimated value. In other words, the temperature at the time of the thermo OFF when the cooling operation by the thermo cycle is performed, which is estimated based on the temperature data excluding NSB and DSB, and also mounting error and disturbance error Is used.

  Thereby, the set temperature (OFF point) appropriately controlled by the main controller C is estimated more accurately from the temperatures detected by the expansion valve temperature sensors 25 and 26 connected only to the expansion valve controllers 15 and 16. It becomes possible. Therefore, even when the conventional mechanical expansion valve is replaced with an electronic expansion valve, it is possible to realize optimum superheat degree control by the electronic expansion valve without changing the existing main controller C. .

(Control at the end of defrosting)
When the cooling operation as described above is performed, frost grows on the evaporators 9 and 11, so that the main controller C performs the defrosting operation of the evaporators 9 and 11 when the cooling operation elapses for a predetermined time. Here, a description will be given with reference to a diagram showing changes in the valve opening degree and the superheat degree set value of the expansion valves 10 and 12 in FIG. In this embodiment, the defrosting signal is transmitted to the expansion valve controllers 15 and 16 until the defrosting operation time and the predetermined draining time have elapsed by the main controller C, and the expansion valve controllers 15 and 16 Based on this, the electronic expansion valves 10 and 12 are fully closed (left side in the figure). At this time, the main controller C stops the operation of the evaporator fans 21 and 22 in order to prevent the temperature in the storage chambers 2A and 3A from rising.

  As a result, the high-temperature and high-pressure gas refrigerant discharged from the compressor 7 passes through the defrosting pipe provided with an electronic valve (not shown) and bypasses the electronic expansion valves 10 and 12 in the bypass pipes in the evaporators 9 and 11. Flow into. The refrigerant flowing into the evaporators 9 and 11 is condensed by dissipating a part of the latent heat or sensible heat there, and the evaporators 9 and 11 are heated by the heat dissipation at this time and grow into the evaporators 9 and 11. The frost melts.

  Then, the main controller C ends the defrosting operation after the predetermined defrosting operation time and the draining operation time have ended. At this time, the main controller C delays the activation of the evaporator fans 21 and 22 for a predetermined time immediately after the end of the defrosting operation because the temperatures of the evaporators 9 and 11 are high. After completion of the defrosting operation, the main controller C cancels the defrosting signal to the expansion valve controllers 15 and 16.

  The expansion valve controllers 15 and 16 return the superheat degree control of the expansion valves 10 and 12 by releasing the defrost signal. At this time, the expansion valve controllers 15 and 16 are preliminarily set with data related to the start delay period of the blower after completion of the defrosting operation, and during the predetermined delay period after the end of the defrosting signal, normal cooling is performed. The superheat degree set value is increased by a predetermined value from the superheat degree set value used for superheat degree control during operation (center of FIG. 5).

  Therefore, after completion of the defrosting operation, the expansion valve controllers 15 and 16 first maximize the openings of the electronic expansion valves 10 and 12 for valve cleaning. Thereafter, the expansion valve controllers 15 and 16 perform superheat degree control of the electronic expansion valves 10 and 12 using a superheat degree set value higher than the superheat degree set value in the cooling operation as described above.

  Then, after the startup delay period of the blowers 21 and 22 has elapsed, the expansion valve controllers 15 and 16 return to the superheat setting value in the cooling operation, and execute superheat control of the electronic expansion valves 10 and 12 (right side of FIG. 5). ).

  Thus, during the start-up delay period of the blowers 21 and 22 after the defrosting operation is completed, the expansion valve controllers 15 and 16 increase the superheat degree set value during the normal cooling operation to increase the electronic expansion valves 10 and 12. Therefore, the expansion valve controllers 15 and 16 are connected to the electronic expansion valve 10 on the basis of the refrigerant inlet temperature and refrigerant outlet temperature of the evaporators 9 and 11 and the predetermined superheat degree set value, which are increased by defrosting. The opening degree of the electronic expansion valves 10 and 12 can be controlled to be reduced based on the raised superheat setting value without expanding the opening degree of the 12 valves.

  Therefore, it is possible to avoid the disadvantage that the liquid refrigerant stays in the evaporators 9 and 11 and causes liquid back.

  The superheat degree control of the electronic expansion valves 10 and 12 in which the superheat degree setting value after the defrosting operation is changed is particularly effective in a prefabricated refrigerator or the like.

It is a refrigerant circuit figure of the cooling storage of a present Example. It is a schematic electrical block diagram of the main controller and each expansion valve controller. It is a timing chart with respect to a temperature change. It is a figure which shows the estimation conditions of a temperature setting value. It is a figure which shows the change of the valve opening degree of an expansion valve, and a superheat degree setting value.

Explanation of symbols

C Main controller 1 Cooling storage 2, 3 Showcase 4 Refrigerator 5 Refrigerant circuit 7 Compressor 8 Condenser 9, 11 Evaporator 10, 12 Electronic expansion valve 15, 16 Expansion valve controller 17, 19 Temperature sensor (refrigerant inlet temperature)
18, 20 Temperature sensor (refrigerant outlet temperature)
21, 22 Blower for evaporator 23, 24 Signal line 25, 26 Temperature sensor for expansion valve 27 Control panel 30 Main temperature sensor

Claims (1)

In a cooling store comprising a refrigerant circuit having an evaporator and an expansion valve, and circulating cold air exchanged with the evaporator into a storage chamber by a blower,
A controller for controlling the opening degree of the expansion valve based on the refrigerant inlet temperature and the refrigerant outlet temperature of the evaporator and a predetermined superheat setting value;
The controller increases the superheat setting value during a startup delay period of the blower after completion of defrosting of the evaporator.