JP2008175442A - Cooling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cooling device capable of quickly bringing an inside temperature of a showcase to a set temperature in a pull-down operation after termination of a defrosting operation. <P>SOLUTION: This cooling device where a cycle from the start of the pull-down operation to the next pull-down operation through a normal operation, is regarded as one cycle, comprises a valve opening control means 30 for setting an upper limit value of an opening of an electronic expansion valve in the next cycle on the basis of a prescribed valve opening of the electronic expansion valve during the normal operation in the cooling operation of the previous cycle. By changing the upper limit value of the opening of the electronic expansion valve according to a load of the showcase, the inside temperature of the showcase can be quickly brought to the set temperature in performing the pull-down operation after the termination of a defrosting operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a cooling device that controls the supply of refrigerant to an evaporator by adjusting the opening of an electronic expansion valve so that the inside of a container is in a desired temperature state.

  For example, in a showcase that displays and sells products in a cooled state, an evaporator and an electronic expansion valve are provided in the showcase, and a compressor and a condenser are provided outside the showcase. The container is maintained at a desired temperature state by circulating and supplying the refrigerant to the condenser, the electronic expansion valve, and the evaporator. Specifically, the opening degree of the electronic expansion valve is reduced when the internal temperature of the container is lower than the set temperature, while the electronic expansion valve is reduced when the internal temperature of the container is higher than the set temperature. The opening is enlarged so that the inside of the container is in a desired temperature state (see, for example, Patent Document 1).

JP-A-2005-180815

  By the way, in this kind of cooling device, normally, in order to remove the frost adhering to the evaporator, the supply of the refrigerant is periodically stopped to defrost the evaporator. Since the internal temperature rises due to this defrosting operation, in the pull-down operation after the completion of the defrosting operation, the opening degree of the electronic expansion valve must be increased for a relatively long time in order to rapidly cool the internal temperature. I must. However, if the opening of the electronic expansion valve is increased too much immediately after starting the compressor, the refrigerant flow rate will increase and the degree of superheat will decrease, but there will be no difference between the refrigerant liquid temperature and the internal temperature. The inside may not cool. In order to prevent this, the opening degree of the electronic expansion valve is set to an appropriate upper limit value (hereinafter referred to as “upper limit valve opening degree”).

  However, since the load on the showcase varies depending on the number of connected showcases and the season, for example, when pull-down operation is performed during periods when the load on the showcase is high, such as in summer, continuous operation at the same upper valve opening as in winter However, since the refrigerant flow rate is insufficient, it takes time for the internal temperature to reach the set value, resulting in a problem that the freshness of the product is lowered.

  In view of the above circumstances, an object of the present invention is to provide a cooling device that can quickly bring the temperature in the storage case of the showcase to the set temperature when performing the pull-down operation after the completion of the defrosting operation. To do.

  In order to achieve the above object, the cooling device according to claim 1 of the present invention controls the supply of the refrigerant to the evaporator by adjusting the opening of the electronic expansion valve to bring the inside of the container into a desired temperature state. In the cooling device, the cycle from the start of the pull-down operation to the start of the pull-down operation again after the normal operation is defined as one cycle, and the opening degree of the electronic expansion valve at the predetermined time during the normal operation in the cooling operation of the previous cycle is the predetermined valve opening degree. And a valve opening degree control means for setting an upper limit value of the opening degree of the electronic expansion valve in the next cycle based on the predetermined valve opening degree.

  The cooling device according to claim 2 of the present invention is the cooling device according to claim 1, wherein the valve opening control means is configured to detect the time when the liquid back is generated when the liquid back is generated during the normal operation of the previous cycle. The opening degree obtained by subtracting a certain pulse from the opening degree of the electronic expansion valve is set as a predetermined valve opening degree, and the upper limit value of the opening degree of the electronic expansion valve in the next cycle is set based on the predetermined valve opening degree. And

  The cooling device according to claim 3 of the present invention is the cooling device according to claim 1, wherein the valve opening degree control means sets the opening degree of the electronic expansion valve when the normal operation of the previous cycle is finished as a predetermined valve opening degree. The upper limit value of the opening degree of the electronic expansion valve in the next cycle is set based on the predetermined valve opening degree.

  A cooling device according to a fourth aspect of the present invention is the cooling device according to any one of the first to third aspects, wherein the valve opening degree control means is configured to open the predetermined valve of the electronic expansion valve during normal operation of the previous cycle. A value increased by a predetermined amount from the degree is set as an upper limit value of the opening degree of the electronic expansion valve in the next cycle.

  According to the cooling device of the present invention, by setting the upper limit valve opening degree of the electronic expansion valve of the next cycle based on the predetermined valve opening degree of the electronic expansion valve during the normal operation of the previous cycle, The valve opening degree control that follows the fluctuation can be performed. As a result, when performing pull-down operation after the completion of the defrosting operation, the temperature in the showcase cabinet can be quickly reached the set temperature, and the freshness of the products stored in the cabinet can be improved. Can do.

  Hereinafter, preferred embodiments of a cooling device according to the present invention will be described in detail with reference to the accompanying drawings as appropriate.

(Embodiment 1)
FIG. 1 conceptually shows the configuration of a cooling device according to an embodiment of the present invention. The cooling device illustrated here is applied to an open showcase 11 that displays and sells products stored in the storage 10 in a cooled state, and includes an evaporator 12 and an electronic expansion valve in each of the multiple open showcases 11. 13 are individually provided, and one condenser 14 and one compressor (compressing means) 15 are provided outside the open showcase 11.

  The electronic expansion valve 13 is for adiabatically expanding the liquid refrigerant discharged from the condenser 14 and supplying the liquid refrigerant to the evaporator 12. In the present embodiment, when the opening degree command is given, the electronic expansion valve 13 is applied which can change the opening degree according to the opening degree command and adjust the flow rate of the refrigerant passing therethrough. The electronic expansion valve 13 is configured to adjust the refrigerant flow rate by moving the valve body in the axial direction in accordance with the rotation angle of the pulse motor to increase or decrease the opening.

  The compressor 15 is for compressing the low-temperature and low-pressure gas refrigerant discharged from the evaporator 12 and supplying the compressed refrigerant to the condenser 14 as a high-temperature and high-pressure gas refrigerant. The condenser 14 cools, condenses, and liquefies the gas refrigerant compressed by the compressor 15. The evaporator 12 evaporates the refrigerant liquid adiabatically expanded by the electronic expansion valve 13.

  In this cooling device, an evaporator 12 and an electronic expansion valve 13 provided in each open showcase 11 are connected in parallel to the condenser 14 and the compressor 15 to constitute a refrigeration cycle. That is, the high-temperature and high-pressure gas refrigerant discharged from the compressor 15 dissipates heat in the condenser 14 and becomes a high-temperature and high-pressure liquid refrigerant. This high-temperature and high-pressure liquid refrigerant is branched and supplied to the electronic expansion valve 13 of each storage 10 and is adiabatically expanded to become a cold / low-pressure gas-liquid two-phase refrigerant and supplied to the evaporator 12 of the storage 10. The low-temperature and low-pressure gas-liquid two-phase refrigerant supplied to the evaporator 12 exchanges heat by blowing the air inside the container 10 around the evaporator 12 by a blower fan (not shown), absorbs heat, and absorbs low-temperature and low-pressure gas. The container 10 is cooled by becoming a refrigerant. The low-temperature and low-pressure gas refrigerant that has passed through the evaporator 12 joins outside the open showcase 11, is sucked into the compressor 15, is compressed, and is again supplied to the condenser 14 as high-temperature and high-pressure gas refrigerant.

  In each open showcase 11, refrigerant temperature sensors 20 and 21 are provided in the refrigerant supply pipe 16 connected to the inlet and outlet of the evaporator 12, respectively. The inlet portion refrigerant temperature sensor 20 and the outlet portion refrigerant temperature sensor 21 detect the temperature of the refrigerant passing through the respective refrigerant supply pipes 16 and give a detection result to a valve opening degree control means 30 described later. The difference between the inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21 is the degree of superheat in the evaporator, which is an index of cooling efficiency.

  A blown air temperature sensor 22 is provided in the vicinity of a cold air outlet (not shown) opened in the upper front of the open showcase 11. This blown air temperature sensor 22 detects the temperature of the cold air blown into the housing from the cold air outlet and gives a detection result to a valve opening degree control means 30 described later.

  FIG. 2 is a graph schematically showing changes in the opening degree of the electronic expansion valve 13 with respect to changes in the blowing air temperature detected by the blowing air temperature sensor 22 (hereinafter, the opening degree of the electronic expansion valve 13 is expressed as “valve opening”). Called "degree"). As shown in FIG. 2, the cycle of the cooling operation by the cooling device includes a pull-down operation (rapid cooling operation), a normal operation, and a defrosting operation. In the present embodiment, the cycle of one cooling operation is started from the start of pull-down operation (ie, the end of the defrosting operation of the previous cycle) until the end of the defrosting operation through the normal operation (ie, the pull-down operation of the next cycle). (Until the start)

  The pull-down operation is an operation for rapidly cooling the internal temperature that has been raised by the defrosting operation to the set temperature. In the present embodiment, the control of the valve opening in the pull-down operation is performed based on the deviation between the detected superheat degree and the superheat degree target value as will be described later. The normal operation is an operation for maintaining the temperature in the storage at the set temperature after the temperature in the storage reaches the set temperature by the pull-down operation. In the present embodiment, control of the valve opening degree in normal operation is performed based on the deviation between the detected blowing temperature and the blowing temperature set value, as will be described later. In the defrosting operation, the valve opening is set to zero, supply of the refrigerant is stopped, and a heater installed in the vicinity of the evaporator 12 is energized to remove frost attached to the evaporator. This defrosting operation is forcibly performed every time a certain time elapses (for example, every 6 hours, such as 3:00, 9:00, 15:00, 21:00). The defrosting operation is terminated when a temperature sensor (not shown in FIG. 1) installed in the vicinity of the evaporator detects that the temperature has exceeded a certain temperature. And one cycle of operation is completed.

  The cooling device having the above configuration includes the valve opening degree control means 30 as its control system. As shown in FIG. 1, in this embodiment, each open showcase 11 is provided with individual valve opening control means 30. The valve opening degree control means 30 adjusts the opening degree of the electronic expansion valve 13 based on the detection results of the inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21 or the blown air temperature sensor 22 described above. A degree comparison unit 31, a blown air temperature comparison unit 32, a valve opening setting unit 33, and an upper limit valve opening setting unit 34.

  The superheat degree comparison unit 31 stores the superheat degree target value of the refrigerant in the evaporator 12, and is the temperature difference between the superheat degree target value and the refrigerant detected by the inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21. The deviation from the degree of superheat is calculated, and the calculation result is given to the valve opening setting unit 33. In the present embodiment, the superheat degree target value is set to 5 ° C., for example.

  The blown air temperature comparison unit 32 stores the set value of the blown air temperature, calculates the deviation between this set value and the detected temperature of the blown air temperature sensor 22, and gives the calculation result to the valve opening setting unit 33. It is. In the present embodiment, the blown air temperature set value is set to −5 ° C., for example.

  The valve opening setting unit 33 sets the valve opening based on the calculation result in the superheat degree comparison unit 31 or the calculation result in the blown air temperature comparison unit 32. In the valve opening setting unit 33, two operation modes of the normal operation and the pull-down operation described in FIG. 2 are set in advance, and after the defrosting operation is completed, the pull-down operation is performed. When the blown air temperature detected by has reached a desired blown air temperature set value, the operation is shifted to normal operation. More specifically, when the temperature detected by a temperature sensor (not shown) installed near the evaporator at the end of the defrosting operation exceeds a preset upper threshold (for example, + 10 ° C.), defrosting is performed. Is completed, the defrosting operation is terminated, and the valve opening setting unit 33 selects the pull-down operation mode. On the other hand, when the blown air temperature reaches the lower threshold (for example, −5 ° C.) by performing the pull-down operation, the valve opening setting unit 33 selects the normal operation mode.

  In the pull-down operation mode, the superheat degree comparison unit 31 reads out the superheat degree target value, obtains the superheat degree from the detection results of the inlet refrigerant temperature sensor 20 and the outlet refrigerant temperature sensor 21, and calculates the superheat degree target value and the detected superheat degree. The calculation result of the deviation is given to the valve opening setting unit 33. The valve opening degree setting unit 33 sets the valve opening degree based on the deviation between the superheat degree target value and the detected superheat degree, the time change rate of the deviation, and the like, and gives the setting information to the electronic expansion valve 13 as an opening degree command. .

  On the other hand, in the normal operation mode, the blown air temperature comparison unit 32 reads the blown air temperature set value, and calculates the deviation calculation result between the detected temperature of the blown air temperature sensor 22 and the blown air temperature set value. 33. The valve opening setting unit 33 sets the valve opening based on the deviation between the blown air temperature set value and the detected temperature, the time change rate of the deviation, and the like, and gives the setting information to the electronic expansion valve 13 as an opening command. .

  The upper limit valve opening setting unit 34 sets an upper limit value of the valve opening (hereinafter referred to as “upper valve opening”) based on the valve opening set by the valve opening setting unit 33. . In the present embodiment, when the degree of superheat becomes zero during normal operation of the previous cycle and the liquid back phenomenon occurs in which the refrigerant in the gas-liquid two-phase state is discharged from the evaporator 12, An opening obtained by subtracting a certain pulse from the valve opening is set as a predetermined valve opening, and an upper limit valve opening in the next cycle is set based on the predetermined valve opening. Hereinafter, an example of setting the upper limit valve opening will be described with reference to FIG.

  As shown in FIG. 2, when the pull-down operation of the nth cycle is started (that is, at the end of the defrosting operation of the previous cycle), the opening degree of the electronic expansion valve 13 is set to zero by the immediately preceding defrosting operation. Immediately after starting the pull-down operation, the detected superheat degree becomes larger than the superheat degree target value. For this reason, the valve opening degree a is enlarged and set in order to rapidly reduce the blown air temperature T. When the blown air temperature T reaches the set value, the pull-down operation is terminated and the normal operation is started.

During normal operation, the blown air temperature T is maintained at a substantially set value, and the valve opening degree a is also maintained at a substantially constant value. On the other hand, even if the blown air temperature T is maintained at a constant value, the degree of superheat decreases as the load on the showcase decreases. Therefore, if the normal operation is continued with almost no change in the valve opening (that is, without changing the refrigerant flow rate), the degree of superheat becomes zero at time t ₁ and the refrigerant in the gas-liquid two-phase state is discharged from the evaporator 12. The liquid back phenomenon discharged from the liquid occurs. Let the valve opening at this time be a (t ₁ ). When the liquid back occurs, the valve opening degree a is reduced as shown in FIG. 2, and the valve opening degree a is increased when the degree of superheat is restored to the target value. At this time, the valve opening degree a (t ₂ ) at the time t ₂ when the superheat degree is restored to the target value is obtained by subtracting a predetermined pulse (for example, 5 pulses) from the valve opening degree a (t ₁ ) when the liquid back is generated. The value a (t ₁ ) −5 pulses is set. By performing such setting, it is possible to prevent the liquid back from being continuously generated. The valve opening (a (t ₁ ) −5 pulses) at this time is stored as a predetermined valve opening.

Once again superheat at the later time t ₃ may zero the result liquid back occurs, that is reducing the valve opening a in the same manner as during the first liquid back, the degree of superheat is restored to the target value, the valve opening Enlarge degree a. The valve opening a (t ₄ ) at time t ₄ when the degree of superheat is restored to the target value is a value a () obtained by subtracting a predetermined pulse (for example, 5 pulses) from the valve opening a (t ₃ ) at the time when the liquid back occurs. t ₃₎ is set to -5 pulse. The valve opening (a (t ₃ ) −5 pulses) at this time is stored as a predetermined valve opening.

After the normal operation is completed, the valve opening is set to zero and the supply of the refrigerant is stopped to perform the defrosting operation. Here, a value a (t ₄ ) +150 pulses obtained by adding a predetermined pulse (for example, 150 pulses) to the valve opening degree a (t ₄ ) at time t ₄ is set as the upper limit valve opening degree of the (n + 1) th cycle. At the same time as the defrosting operation is finished and the nth cycle is finished, the pull-down operation of the (n + 1) th cycle is started. In the pull-down operation of the (n + 1) th cycle, control is performed with the valve opening not exceeding a (t ₄ ) +150 pulse which is the value set above.

  As shown in FIG. 2, during normal operation, the valve opening a is maintained at a substantially constant value, but this constant value varies depending on the load on the showcase. For example, in the summer when the load on the showcase is high, the valve opening is large, and in the winter when the load on the showcase is low, the valve opening is small. Therefore, the value of the valve opening degree in a state where the blowing temperature is stable during normal operation is a material for determining the load on the showcase. By reflecting this in the upper limit valve opening of the next cycle, the upper limit valve opening can be changed according to the load of the showcase.

  FIG. 3 is a flowchart showing the contents of the valve opening control process of the electronic expansion valve performed by the valve opening control means 30 shown in FIG. In FIG. 3, only the processing related to the control of the upper limit valve opening degree is shown for easy understanding. Hereinafter, the control performed by the valve opening degree control means 30 will be described with reference to FIG.

  First, in the defrosting operation of the (n-1) th cycle, when the defrosting operation is completed (step S101: YES), the valve opening degree control means 30 selects the pull-down operation mode through the valve opening degree setting unit 33, and n Start the cooling operation for the second cycle. The valve opening degree control means 30 calculates the deviation between the superheat degree and the superheat degree target value through the superheat degree comparison unit 31, and gives this calculation result to the valve opening degree setting unit 33. Next, the valve opening degree control means 30 sets the valve opening degree of the electronic expansion valve based on the calculation result through the valve opening degree setting unit 33, and sets the set valve opening degree and the upper limit valve opening degree setting unit 34. The stored upper limit valve opening is compared. When the set valve opening is smaller than the upper limit valve opening, this set value is given to the electronic expansion valve 13 as an opening command. On the other hand, when the set valve opening is larger than the upper limit valve opening, the upper limit valve opening is given to the electronic expansion valve 13 as an opening command (step S102). Accordingly, the valve opening in the pull-down operation does not exceed the value stored in the upper limit valve opening setting unit 34.

  Next, the valve opening control means 30 determines whether or not the blown air temperature detected by the blown air temperature sensor 22 has reached a set value (−5 ° C.) (step S103). When the blown air temperature detected by the blown air temperature sensor 22 reaches the set value (step S103: YES), the valve opening degree control means 30 switches from the pull-down operation to the normal operation through the valve opening degree setting unit 33. In normal operation, the valve opening degree control means 30 calculates the deviation between the detected temperature and the blown air temperature set value through the blown temperature comparison unit 32 and gives the calculation result to the valve opening degree setter 33. Next, the valve opening degree control means 30 sets the valve opening degree of the electronic expansion valve based on the calculation result through the valve opening degree setting unit 33, and gives this setting information to the electronic expansion valve 13 as an opening degree command (step). S104).

The valve opening control means 30 sets the valve opening based on the calculation result of the deviation between the detected temperature from the blowing temperature setting unit 32 and the set value, and monitors the superheat degree through the superheat degree comparison unit 31. Then, it is determined whether the degree of heating has become zero, that is, whether a liquid back has occurred (step S105). When the superheat degree becomes zero in the superheat degree comparison unit 31, that is, when a liquid back phenomenon occurs (step S <b> 105: YES), the valve opening degree control means 30 passes through the valve opening degree setting unit 33 and the electronic expansion valve. At the same time as the opening degree of 13 is reduced, the valve opening degree a (t ₁ ) when the degree of superheat becomes zero, that is, when the liquid back occurs is stored (step S106). When the degree of superheat is restored to the target value by reducing the valve opening and reducing the refrigerant flow rate, the valve opening control means 30 passes through the valve opening setting unit 33 and starts a predetermined pulse from the valve opening a (t ₁ ). A value a (t ₁ ) −5 pulses subtracted (for example, 5 pulses) is set, and this value is given to the electronic expansion valve 13 as an opening degree command (step S107). Further, the valve opening (a (t ₁ ) −5 pulses) at this time is stored as a predetermined valve opening.

  Next, the valve opening degree control means 30 determines whether it is time to perform the defrosting operation (step S108). When it is not time to perform the defrosting operation (step S108: NO), the above processing steps S104 to S107 are repeated.

When it is time to perform the defrosting operation (step S108: YES), the valve opening degree control means 30 closes the electronic expansion valve 13 through the valve opening degree setting unit 33 and supplies the refrigerant to the evaporator 12. Is stopped (step S109). Next, the valve opening degree control means 30 subtracts a predetermined pulse (for example, 5 pulses) from the predetermined valve opening degree set in step S107, that is, the valve opening degree a (t ₃ ) at the time when the liquid back is finally generated. a (t ₄ ) is transmitted to the upper limit valve opening setting unit 34. Next, the valve opening degree control means 30 uses the upper limit valve opening degree setting unit 34 to obtain a value a (t ₄ ) +150 obtained by adding 150 pulses to the upper limit valve opening degree of the (n + 1) th cycle to the predetermined valve opening degree a (t ₄ ). The pulse is set and stored (step S110), and the process returns to step S101.

When a certain time (for example, 6 hours) elapses, the operation is switched from the normal operation to the defrosting operation, and when the temperature near the evaporator reaches a certain set value or more during the defrosting operation (step S101: YES), the valve opening degree The control means 30 determines that the defrosting has been completed, selects the pull-down operation mode through the valve opening setting unit 33, and starts the pull-down operation of the (n + 1) th cycle. The valve opening control means 30 sets the valve opening through the valve opening setting unit 33, the set valve opening, and the upper limit valve opening a (t ₄ ) +150 stored in the upper valve opening setting unit 34. Compare the pulse. When the set valve opening is smaller than the upper limit valve opening, this setting information is given to the electronic expansion valve 13 as an opening command, whereas when the set valve opening is larger than the upper limit valve opening, The a (t ₄ ) +150 pulse that is the upper limit valve opening degree is given to the electronic expansion valve 13 (step S102). The above processing is repeated individually for each open showcase 11.

  As described above, according to the cooling device of the present embodiment, the upper limit valve opening degree of the electronic expansion valve of the next cycle is set based on the opening degree of the electronic expansion valve at a predetermined time during the normal operation of the previous cycle. By doing so, it is possible to perform valve opening control following the fluctuation of the load on the showcase. As a result, when performing pull-down operation after the completion of the defrosting operation, the temperature in the showcase cabinet can be quickly reached the set temperature, and the freshness of the products stored in the cabinet can be improved. Can do.

  In the embodiment described above, when a liquid back occurs during normal operation of the previous cycle, the valve opening at the time when the liquid back occurs is stored, and a value obtained by subtracting a predetermined pulse from this valve opening, that is, Although the upper limit valve opening of the next cycle is set based on the predetermined valve opening, the present invention is not limited to this. For example, there may be a case where liquid back does not occur during normal operation. In this case, the valve opening (that is, the valve opening immediately before entering the defrosting operation) at the time when the normal operation is finished is set as the predetermined valve opening, and the upper limit valve opening of the next cycle is based on the predetermined valve opening. May be set.

Regardless of whether or not a liquid back has occurred, the valve opening after a predetermined time has elapsed after the start of the cooling operation of the nth cycle (for example, if one cycle is 6 hours, 5 hours from the start of operation) The valve opening at the time when the valve has passed is defined as a predetermined valve opening a (t ₁ ), and a value a (t ₁ ) +150 obtained by adding a predetermined pulse (for example, 150 pulses) to the predetermined valve opening is set as the upper limit valve of the next cycle. You may make it set to an opening degree.

  Furthermore, in embodiment mentioned above, although the blowing air temperature sensor 22 was arrange | positioned in the vicinity of the cold air outlet, and it comprised so that a blowing air temperature might be detected, it is not limited to this. For example, the temperature sensor 22 may be provided on a shelf displaying goods in a storage case of a showcase, and the above-described control may be performed based on the temperature detected by the temperature sensor 22. Further, a temperature sensor 22 may be provided in the vicinity of the evaporator 12 and the above-described control may be performed by detecting the temperature of the air after passing through the evaporator 12.

  Moreover, although embodiment mentioned above has illustrated the cooling device which applied the storage provided with a plurality of open showcases individually, it does not necessarily need to be a plurality of storages.

FIG. 1 is a conceptual diagram showing a configuration of a cooling device according to an embodiment of the present invention. FIG. 2 is a graph showing changes in the opening of the electronic expansion valve with respect to changes in the blown air temperature. FIG. 3 is a flowchart showing the contents of the expansion valve opening degree control process performed by the valve opening degree control means shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Container 11 Showcase 12 Evaporator 13 Electronic expansion valve 14 Condenser 15 Compressor 16 Refrigerant supply line 20 Inlet part refrigerant | coolant temperature sensor 21 Outlet part refrigerant | coolant temperature sensor 22 Outlet air temperature sensor 30 Valve opening degree control means 31 Superheat degree Comparison part 32 Blowing air temperature comparison part 33 Valve opening degree setting part 34 Upper limit valve opening degree setting part

Claims (4)

In the cooling device that controls the supply of the refrigerant to the evaporator by adjusting the opening of the electronic expansion valve, and makes the inside of the container a desired temperature state,
The cycle from the start of pull-down operation to normal operation and re-entering pull-down operation is defined as one cycle.
In the cooling operation of the previous cycle, the opening degree of the electronic expansion valve at a predetermined time during normal operation is set as the predetermined valve opening degree, and the upper limit value of the opening degree of the electronic expansion valve of the next cycle is set based on this predetermined valve opening degree A cooling device comprising valve opening control means. The valve opening control means is
When a liquid back occurs during normal operation of the previous cycle, the opening obtained by subtracting a certain pulse from the opening of the electronic expansion valve at the time when the liquid back occurs is defined as the predetermined valve opening. The cooling device according to claim 1, wherein an upper limit value of the opening degree of the electronic expansion valve in the next cycle is set based on the above. The valve opening control means is
The opening degree of the electronic expansion valve at the time when the normal operation of the previous cycle is finished is set as a predetermined valve opening degree, and the upper limit value of the opening degree of the electronic expansion valve in the next cycle is set based on the predetermined valve opening degree. The cooling device according to claim 1. The valve opening control means is
2. A value that is increased by a predetermined amount from the predetermined valve opening degree of the electronic expansion valve during normal operation of the previous cycle is set as an upper limit value of the opening degree of the electronic expansion valve of the next cycle. 4. The cooling device according to any one of items 1 to 3.

Images