JP3497438B2 - Showcase cooling system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a showcase cooling device for cooling a plurality of showcases installed in a store by a common refrigerator.

[0002]

2. Description of the Related Art Conventionally, in this type of showcase cooling device, the refrigerant is circulated by a single compressor (or a small number of compressors) for many showcases to keep each showcase cool. Considering that many showcases are operated at the same time, the capacity of the compressor is considerably large so that the cooling capacity is not impaired even when all the showcases are in operation. Further, since the load of each showcase is small in winter and large in summer, the refrigerating capacity of the compressor is set according to the summer when the load becomes large.

However, if a compressor having such a large refrigerating capacity is operated with the same capacity even in winter, the operating efficiency is lowered and it is disadvantageous in terms of energy saving. Also,
A showcase cooling device that allows switching between summer cooling capacity and winter cooling capacity and switches it manually has been proposed, but switching at every season change is also disadvantageous in terms of maintenance. Is.

Therefore, in order to solve such a problem, a showcase cooling device disclosed in Japanese Patent Laid-Open No. 9-217974 has been proposed.

This showcase cooling device sets a target suction pressure of the compressor on the basis of the operating rate of the electromagnetic valve of the showcase, and rotates the compressor on the basis of the deviation between the target suction pressure and the actual suction pressure. It is configured to control the number.
That is, since the operating rate of the solenoid valve is high when the load is large and is low when the load is small, energy saving can be achieved based on this operating rate. Further, this showcase cooling device discloses a configuration for determining the temperature drop rate of the showcase, a configuration for determining the average on / off period of the solenoid valve of the showcase, etc., but these configurations also aim to save energy. Have the same effect.

[0006]

However, in the latter showcase cooling device, the special operation information of the showcase such as the operating rate of the solenoid valve, the temperature drop rate, or the average on / off period of the solenoid valve is collected and calculated. Therefore, it is inevitable that the control system will be large-scaled and complicated,
It was disadvantageous in terms of manufacturing cost.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a showcase cooling device which can save energy without increasing the size and complexity of the control system.

[0008]

In view of the above-mentioned conventional problems, the invention of claim 1 circulates a refrigerant by a common compressor in a plurality of showcases arranged in a store and sets the compressor. In the showcase cooling device that controls the rotation speed of the compressor based on the suction pressure, the control means that controls the rotation speed of the compressor includes an in-store enthalpy calculation unit that calculates the in-store enthalpy from the in-store temperature and humidity and an in-store enthalpy calculation. Based on the difference between the target suction pressure setting calculation unit that sets the target suction pressure of the compressor based on the enthalpy calculated in the section, and the target suction pressure calculated by the target suction pressure setting calculation unit and the actual suction pressure of the compressor possess a rotational speed command computation unit for commanding the rotational speed of the compressor, the target suction pressure setting operation unit, the store
Enthalpy calculated by the internal enthalpy calculation section and show
Set the target suction pressure of the compressor based on the set temperature inside the case.
It is configured to be set.

According to the first aspect of the present invention, noting that the load of the showcase is affected not only by the temperature in the store but also by the humidity in the store, the load of the showcase is determined by the enthalpy in the store consisting of the temperature and the humidity in the store. . Then, the target suction pressure of the compressor is set based on the calculated in-store enthalpy, and the rotation speed of the compressor is obtained from the target suction pressure and the actual suction pressure. Also, target inhalation
The pressure setting calculation unit was calculated by the in-store enthalpy calculation unit.
The pressure is based on the enthalpy and the set temperature inside the showcase.
It is configured to set the target suction pressure of the compressor. that's all
According to the invention of claim 1, the special case of the showcase
Proper compressor speed without collecting operating data
In addition to setting in, store enthalpy and in-store setting
Set the target suction pressure of the compressor from the temperature and
The accuracy of force values is improved.

[0010]

[0011]

According to the invention of claim 2 , a plurality of the inventions are arranged in the store.
Refrigerant is circulated by a common compressor in the showcase
In addition, the compressor speed is controlled based on the set suction pressure of the compressor.
The rotation speed of the compressor in the showcase cooling device
The control means for controlling the store is based on the store temperature and store humidity.
In-store enthalpy calculator that calculates in-store enthalpy
Compress based on the enthalpy calculated by the enthalpy calculator
Target suction pressure setting calculator that sets the target suction pressure of the machine
And the target suction pressure calculated by the target suction pressure setting calculator
Of the compressor based on the deviation between the compressor and the actual suction pressure of the compressor
The target suction pressure setting calculation unit compresses based on the enthalpy calculated by the in-store enthalpy calculation unit and the deviation between the showcase internal temperature and the actual internal temperature. It is configured to set the target suction pressure of the machine.

According to the present invention, the target suction pressure is set based on the deviation between the set temperature in the store and the actual temperature in the store in addition to the enthalpy in the store. When it is significantly higher than the set value), the target suction pressure is slightly low, while when the deviation is small, the target suction pressure is high.

According to a third aspect of the present invention, a refrigerant is circulated by a compressor common to a plurality of showcases arranged in a store, and the showcase cooling device controls the number of revolutions of the compressor based on a suction pressure set by the compressor. In, the control means for controlling the compressor, the in-store enthalpy calculation unit that calculates the in-store enthalpy from the temperature and humidity in the store, and the temporary target suction pressure of the compressor based on the enthalpy calculated by the in-store enthalpy calculation unit. A temporary target suction pressure setting calculation unit to be set,
A suction pressure correction calculation unit that corrects the actual suction pressure of the compressor based on the deviation between the temporary target suction pressure calculated by the temporary target suction pressure setting calculation unit and the preset target suction pressure, and a suction pressure correction calculation unit It has a structure including a rotation speed command calculation unit that commands the rotation speed of the compressor based on the deviation between the suction pressure calculated and corrected in step S1 and the preset target suction pressure.

According to the present invention, the actual suction pressure is corrected based on the provisional target suction pressure and the set target suction pressure set by the in-store enthalpy, and the corrected suction pressure and the preset target suction pressure are set. The rotation speed of the compressor is determined based on the deviation of. Since the number of revolutions is determined without changing the preset target suction pressure value in this way, it can be applied to a compressor that does not have the function of externally changing the setting of the target suction pressure, making it a versatile one. There is.

In the invention of claim 4 , the temporary target intake pressure setting calculation unit adds the set temperature of the showcase to the enthalpy of the store, and in the invention of claim 5 , the set temperature of the showcase and the actual set temperature. The deviation of and is also added to improve the accuracy of the target suction pressure value.

In the first to fifth aspects, the rotation speed of the compressor is controlled based on the suction pressure. However, the rotation speed is controlled based on the evaporation temperature of the refrigerant instead of the suction pressure. Good.

[0018]

1 to 6 show a first embodiment of a showcase cooling device according to the present invention, in which FIG. 1 is a refrigerant pipeline diagram between a showcase and a refrigerator in a store, and FIG. Is a block diagram showing a drive circuit of the showcase cooling device, FIG.
Is a graph showing monthly changes in in-store temperature, humidity and enthalpy, FIG. 4 is a table showing the relationship between in-store temperature and in-store humidity and enthalpy, and FIG. 5 is a relationship between in-store enthalpy and showcase evaporation temperature / intake pressure. The table shown in FIG. 6 is a graph for explaining the operation of the showcase cooling device.

First, the refrigerant piping system between the showcase and the refrigerator in the store, which constitutes the showcase cooling device, will be described with reference to FIG. A large number of showcases 1 are arranged in the store, and an evaporator 11 for cooling the inside of the store is installed in these showcases 1. Further, these evaporators 11 are connected to the condenser 21 and the compressor 22 of the refrigerator 2 in parallel with each other via the expansion valve 12 and the electromagnetic valve 13. Here, each solenoid valve 13 regulates the refrigerant flow to each evaporator 11, and opens when the refrigerant flows to cool the inside of the refrigerator, while it closes when the inside cooling is unnecessary to block the refrigerant inflow. regulate.

The showcase 1 is arranged in a store, and the temperature and humidity inside the store are controlled by a store air conditioner (not shown). When the store temperature, store humidity and store enthalpy were investigated (store in Kawagoe City, Saitama Prefecture), the results shown in FIG. 3 were obtained.

That is, the temperature inside the store is 21.8 ° C. to 26 ° by month.
Although the temperature does not change so much, the in-store humidity is 50% RH in July-September, while it is around 35% RH in January and February, and as a result, it is 8 in the month with a small enthalpy (January). 0.67 kcal / kg, 12.7 in the big month (August)
It was 2 kcal / kg, and it was found that the two were changed about 1.5 times when compared. The enthalpy based on the in-store temperature and in-store humidity is shown in a table as shown in FIG. That is, when the temperature is 14 ° C. and the humidity is 30% RH, the enthalpy is 5.14 kcal / kg, while the temperature is 30 ° C. and the humidity is 80%.
At RH, the enthalpy becomes 20.14 kcal / kg, and the enthalpy changes greatly depending on the temperature and humidity.

Further, the relationship between the suction pressure / evaporation temperature of the showcase and the enthalpy was tested in a multi-stage open type showcase in which the internal temperature was set to 5 ° C. The results shown in FIG. 5 were obtained in this experiment.

That is, the enthalpy is 10 kcal / kg, the suction pressure is 3.64 kg / cm ² , and the enthalpy is 20 kca.
It was found that the suction pressure was 2.58 kg / cm ² at 1 / kg, and the suction pressure decreased as the enthalpy increased.

In order to obtain the optimum number of revolutions of the compressor 22 corresponding to the change of the suction pressure, from the relation between the store temperature and the store humidity and the enthalpy and the relation between the enthalpy and the suction pressure of the showcase as described above. The present embodiment constitutes the drive circuit shown in FIG.

That is, the in-store temperature sensor 31 for detecting the temperature inside the store 3 (outside the showcase 1) and the in-store humidity sensor 32 for detecting the in-store humidity (outside the showcase 1).
Has been installed. In addition, the control device 4 that drives and controls the compressor 22 based on the detection signals from the sensors 31 and 32.
have.

The control device 4 has an in-store enthalpy calculating section 41 for calculating the in-store enthalpy from the detected temperature and detected humidity of each sensor 31, 32. The in-store enthalpy calculation unit 41 stores the data shown in the table of FIG. 4, and calculates the in-store enthalpy based on this.

The in-store enthalpy calculated by the in-store enthalpy calculation unit 41 is input to the target suction pressure setting calculation unit 42. The target suction pressure setting calculation unit 42 sets an optimum target suction pressure corresponding to the in-store enthalpy. For example, in the above-mentioned multi-stage open type showcase 1 (set temperature 5 ° C.), the data shown in the table of FIG. The target suction pressure is stored and the optimum target suction pressure is set for this in-store enthalpy.

In this embodiment, the inside temperature setting unit 43 for inputting the set temperature is provided, and the inside temperature setting unit 43 is provided.
Although the set temperature is input from the above, when the set temperature of each showcase 1 is the same, the target suction pressure corresponding to the set temperature may be stored in advance. It becomes unnecessary.

The target suction pressure calculated by the target suction pressure setting calculation section 42 is input to the rotation speed command calculation section 25 of the refrigerator 2. The actual suction pressure of the compressor 22 detected by the suction pressure sensor 23 is input to the rotation speed command calculation unit 25, and the rotation speed of the compressor 22 is based on the deviation between the actual suction pressure and the target suction pressure. Is calculated.

The rotation speed signal of the rotation speed command calculation section 25 is output to the compressor 22 through the inverter 24. Then, the suction pressure of the compressor 22 is detected by the suction pressure sensor 23, fed back to the rotation speed command calculation unit 25, and converged so as to gradually approach the target suction pressure, and the optimum rotation speed is obtained.

As described above, the in-store enthalpy calculation unit 41, the target suction pressure setting calculation unit 42, the inside temperature setting unit 43 of the control device 4, and the rotation speed command calculation unit 2 of the refrigerator 2 are described.
5 constitutes a control means for controlling the rotation speed of the compressor 22.

The feedback control such as the rotation speed command calculation unit 25 → the inverter 24 → the compressor 22 → the suction pressure sensor 23 → the rotation speed command calculation unit 25 is disclosed in Japanese Patent Application Laid-Open No. 9-217974 described above. It has the same structure as the showcase cooling device.

The operation based on the above configuration will be described with reference to the graph of FIG. That is, when the rotation speed of the compressor 22 is high, the power consumption and the refrigerating capacity are naturally high, while when the rotation speed is low, the power consumption and the refrigerating capacity are low. Further, when the in-store enthalpy is high, the suction pressure is low, while when the in-store enthalpy is low, the suction pressure is high.

In such a situation, when the temperature inside the refrigerator is kept constant, the refrigerating capacity of the compressor 22 increases as the enthalpy in the store increases, while the refrigerating capacity of the compressor 22 decreases as the enthalpy in the store decreases. Good. Here, when the showcase load is shown in the graph by taking the case where the number of operating showcases is large and the case where the number of operating showcases is small as an example, it is a straight line of two stages of lower right and lower in FIG.

As can be seen from FIG. 6, the rotation speed of the compressor 22 corresponding to the in-store enthalpy can be selected, that is, the high rotation speed is selected when the in-store enthalpy is high, while the low rotation speed is selected when the in-store enthalpy is low. The number is selected. Also, when the number of operating showcases changes from “many” to “minority”, and vice versa, from “minority” to “many”
When it changes to, the number of rotations corresponds to the in-store enthalpy, as shown by the double-headed arrow in FIG.

As described above, according to the showcase cooling device of this embodiment, the rotation speed of the compressor 22 is controlled based on the enthalpy in the store corresponding to the temperature and the humidity in the store. Information is unnecessary as data, and energy saving can be achieved.

7 and 8 show a second embodiment of the showcase cooling device according to the present invention. In this embodiment, the inside temperature sensor 1 built in the showcase 1 is replaced with the inside temperature setting unit 43 according to the first embodiment.
4, an inside temperature setting device 15 for setting the inside temperature, and an inside temperature deviation calculation unit 45. That is,
The internal temperature deviation calculation unit 45 calculates the deviation between the internal temperature and the internal set temperature, and inputs this deviation to the target suction pressure setting calculation unit 42. Then, the target suction pressure setting calculation unit 42 sets the target suction pressure based on the in-store enthalpy and this deviation. By setting the target suction pressure in this way, the optimum rotational speed of the compressor 22 is obtained as in the first embodiment. The other configurations are the same as those of the first embodiment.
The description is omitted because it is similar to the embodiment.

The operation of the second embodiment will be described with reference to the graph of FIG. That is, when the rotation speed of the compressor 22 is high, the refrigeration capacity is naturally high, while when the rotation speed is low, the refrigeration capacity is low. Further, when the in-store enthalpy is high, the suction pressure is low, while when the in-store enthalpy is low, the suction pressure is high.

In such a situation, when the in-store temperature is kept constant, the refrigerating capacity of the compressor 22 is increased as the in-store enthalpy increases, while the refrigerating capacity of the compressor 22 is reduced as the in-store enthalpy decreases. Good. Here, if the change is shown when the deviation is large and when it is small, it is a straight line in two steps, downward and downward in FIG.

As can be seen from FIG. 8, the rotation speed of the compressor 22 corresponding to the in-store enthalpy can be selected, that is, the high rotation speed is selected when the in-store enthalpy is high, while the low rotation speed is selected when the in-store enthalpy is low. The number is selected. Also, when the deviation changes from "large" to "small", and vice versa, when it changes from "small" to "large",
As shown by the double-headed arrow in FIG. 8, the number of rotations is changed to correspond to the in-store enthalpy.

As described above, the showcase cooling device according to this embodiment is different from the first embodiment in that the rotation speed of the compressor 22 is controlled based on the enthalpy in the store corresponding to the temperature and humidity in the store. Similarly, the target suction pressure setting condition also includes the difference between the internal cold storage temperature and the internal cold storage temperature, so that the internal cold storage condition of the showcase 1 is also taken into consideration, and a more optimal compression is achieved. The number of rotations of the machine 22 is obtained.

Further, since the inside temperature sensor 14 and the inside temperature setting device 15 are always installed in the general-purpose showcase 1, it is also necessary to prepare special equipment for realizing the present embodiment. Absent.

FIG. 9 shows a third embodiment of the showcase cooling device according to this embodiment. In the first embodiment, the target suction pressure is immediately calculated from the in-store enthalpy and the set temperature of the inside temperature setting section. On the other hand, in the present embodiment, the temporary target suction pressure calculation unit 46 calculates the temporary target suction pressure from the in-store enthalpy and the set temperature. Then, the suction pressure correction calculation unit 47 calculates the deviation between the temporary target suction pressure and the preset target suction pressure (fixed target pressure) preset in the compressor 22, and corrects the suction pressure of the compressor 22. Then, the rotation speed command calculation unit 25 determines the rotation speed of the compressor 22 based on the deviation between the corrected suction pressure and the set target pressure described above. The set target suction pressure is set on the basis of when the showcase load (in-store enthalpy) is high (summer season).

Based on this corrected suction pressure, the optimum rotational speed of the compressor 22 is obtained as in the first embodiment. The rest of the configuration is the same as that of the first embodiment, so its explanation is omitted.

The operation of the third embodiment will be described with reference to the graph of FIG. That is, when the rotation speed of the compressor 22 is high, the refrigeration capacity is naturally high, while when the rotation speed is low, the refrigeration capacity is low. Further, when the in-store enthalpy is high, the suction pressure is low, while when the in-store enthalpy is low, the suction pressure is high.

In such a situation, when the in-store temperature is constant, the refrigerating capacity of the compressor 22 is increased as the in-store enthalpy increases, while the refrigerating capacity of the compressor 22 is decreased as the in-store enthalpy decreases. Good.

As can be seen from FIG. 10, there is a deviation (ΔP in FIG. 10) between the set target suction pressure set in the state where the in-store enthalpy is high and the temporary target suction pressure, and the optimum value is based on this deviation. The compressor 22 is operated at the rotation speed.

As described above, according to the showcase cooling device of this embodiment, since the suction pressure is corrected to determine the rotation speed, the compressor which does not have the function of externally changing the setting of the target suction pressure. It can also be applied to and is general-purpose.

As in the first embodiment, when the set temperatures of the respective showcases 1 are the same, the temporary target suction pressure corresponding thereto may be stored in advance. Is unnecessary.

FIG. 11 shows a fourth embodiment of the showcase cooling device according to the present invention. In this embodiment, instead of the inside temperature setting unit 43 according to the third embodiment, the inside temperature sensor 14 built in the showcase 1 and the inside temperature are set as in the second embodiment. The inside temperature setting device 15 and the inside temperature deviation calculation unit 45 are provided. That is, the internal temperature deviation calculation unit 45 calculates the deviation between the internal temperature and the internal set temperature, and inputs this deviation to the temporary target intake pressure setting calculation unit 46. And
The temporary target suction pressure setting calculation unit 46 sets the temporary target suction pressure based on the in-store enthalpy and the deviation. By setting the temporary target suction pressure in this way, the optimum rotational speed of the compressor 22 is obtained as in the third embodiment. The rest of the configuration is the same as that of the third embodiment, so the description thereof is omitted.

As described above, according to the showcase cooling device of this embodiment, the rotation speed of the compressor 22 is controlled based on the enthalpy in the store corresponding to the temperature and humidity in the store, as in the second embodiment. Is the same as that of the third embodiment, but since the setting condition of the temporary target suction pressure is also the condition of the deviation between the inside temperature and the inside set temperature, the inside temperature situation of the showcase 1 is also taken into consideration. As a result, a more optimal rotation speed of the compressor 22 can be obtained.

Further, since the inside temperature sensor 14 and the inside temperature setting device 15 are always installed in the general-purpose showcase 1, it is necessary to specially prepare equipment in order to realize this embodiment. Absent.

In the first to fourth embodiments, the rotation speed of the compressor 22 is controlled under the condition of the in-store enthalpy and the suction pressure. However, as shown in FIG. The temperature also has a correlation like the suction pressure. Therefore, the rotation speed of the compressor 22 may be controlled under the conditions of the in-store enthalpy and the evaporation temperature. In this case, the first
The suction pressure sensor 23 of the fourth embodiment may be replaced with the evaporation temperature sensor, the suction pressure with the evaporation temperature, the target suction pressure with the target evaporation temperature, and the temporary target suction pressure with the temporary target evaporation temperature.

[0054]

As described in the foregoing, according to claim 1 invention 及
According to the invention of claim 2 and claim 2, the compressor can be set to an appropriate rotation speed based on the enthalpy of the store without collecting special operation data of the showcase, and the control system becomes large-scale and complicated. It is possible to save energy without turning it on. Also, when calculating the target suction pressure,
The deviation between the set temperature or the set temperature in the refrigerator and the actual temperature in the refrigerator is added.
Taste to improve the accuracy of the target suction pressure.
You can

[0055]

According to the third aspect of the invention, it can be applied to a compressor that does not have the function of changing the setting of the target suction pressure from the outside, and it is general-purpose.

According to the invention of claim 4 and the invention of claim 5 , when the target suction pressure is calculated, the temperature set in the cold storage or the deviation between the set temperature in the cold storage and the actual cold storage temperature is taken into consideration. The accuracy of the target suction pressure of the invention of Item 3 can be improved.

[Brief description of drawings]

[Figure 1] Refrigerant pipeline diagram between showcase and refrigerator in the store

FIG. 2 is a block diagram showing a drive circuit of the showcase cooling device according to the first embodiment.

[Fig. 3] Graph showing monthly changes in temperature, humidity, and enthalpy in the store

FIG. 4 is a table showing a relationship between an in-store temperature and an in-store humidity and an enthalpy.

FIG. 5 is a table showing the relationship between the enthalpy in the store and the evaporation temperature / suction pressure of the showcase.

FIG. 6 is a graph illustrating the operation of the showcase cooling device according to the first embodiment.

FIG. 7 is a block diagram showing a drive circuit of a showcase cooling device according to a second embodiment.

FIG. 8 is a graph illustrating the operation of the showcase cooling device according to the second embodiment.

FIG. 9 is a block diagram showing a drive circuit of a showcase cooling device according to a third embodiment.

FIG. 10 is a graph illustrating the operation of the showcase cooling device according to the third embodiment.

FIG. 11 is a block diagram showing a drive circuit of a showcase cooling device according to a fourth embodiment.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Showcase, 2 ... Refrigerator, 3 ... Store, 4 ... Control device, 14 ... Warehouse temperature sensor, 15 ... Warehouse temperature setter, 2
2 ... Compressor, 23 ... Suction pressure sensor, 25 ... Rotation speed command calculation unit, 31 ... Store temperature sensor, 32 ... Store humidity sensor, 41 ... Store enthalpy calculation unit, 42 ... Target suction pressure setting calculation unit, 43 ... Warehouse Internal temperature setting unit, 45 ... Internal temperature deviation calculation unit, 46 ... Temporary target suction pressure calculation unit, 47 ... Suction pressure correction calculation unit.

Claims (6)

(57) [Claims] 1. A showcase cooling device in which a refrigerant is circulated by a compressor common to a plurality of showcases arranged in a store, and the rotation speed of the compressor is controlled based on a suction pressure set by the compressor. The control means for controlling the number of revolutions is to set the target suction pressure of the compressor based on the in-store enthalpy calculation unit that calculates the in-store enthalpy from the in-store temperature and in-store humidity, and the enthalpy calculated in the in-store enthalpy calculation unit. Target suction pressure setting calculation unit, and a rotation speed command calculation unit that commands the rotation speed of the compressor based on the deviation between the target suction pressure calculated by the target suction pressure setting calculation unit and the actual suction pressure of the compressor. The target suction pressure setting calculation unit calculates the target suction pressure of the compressor based on the enthalpy calculated by the in-store enthalpy calculation unit and the set temperature inside the showcase. Showcase cooling apparatus characterized by a constant. 2. A showcase cooling device in which a refrigerant is circulated by a compressor common to a plurality of showcases arranged in a store, and the rotation speed of the compressor is controlled based on a suction pressure set by the compressor. The control means for controlling the number of revolutions is to set the target suction pressure of the compressor based on the in-store enthalpy calculation unit that calculates the in-store enthalpy from the in-store temperature and in-store humidity, and the enthalpy calculated in the in-store enthalpy calculation unit. Target suction pressure setting calculation unit, and a rotation speed command calculation unit that commands the rotation speed of the compressor based on the deviation between the target suction pressure calculated by the target suction pressure setting calculation unit and the actual suction pressure of the compressor. The target suction pressure setting calculation unit is configured to calculate the pressure based on the enthalpy calculated by the in-store enthalpy calculation unit and the difference between the showcase internal temperature and the actual internal temperature. Showcase cooling apparatus characterized by setting the target suction pressure of the machine. 3. A showcase cooling device in which a refrigerant is circulated by a compressor common to a plurality of showcases arranged in a store, and the rotation speed of the compressor is controlled based on a suction pressure set for the compressor. The control means for controlling the number of rotations is an in-store enthalpy calculation unit that calculates the in-store enthalpy from the temperature and humidity in the store, and a temporary target suction pressure of the compressor based on the enthalpy calculated by the in-store enthalpy calculation unit. And a temporary target suction pressure setting calculation unit for setting the actual suction pressure of the compressor based on a deviation between the temporary target suction pressure calculated by the temporary target suction pressure setting calculation unit and a preset target suction pressure. The suction pressure correction calculation unit for correction, and the rotation speed of the compressor are indicated based on the deviation between the suction pressure calculated and corrected by the suction pressure correction calculation unit and the preset target suction pressure. Showcase cooling device and having a rotational speed command computation unit for. 4. The temporary target suction pressure setting calculation unit according to claim 3 sets the temporary target suction pressure of the compressor based on the enthalpy calculated by the in-store enthalpy calculation unit and the set temperature inside the showcase. Showcase cooling device characterized by: 5. The temporary target suction pressure setting calculation unit according to claim 3, wherein the compressor is based on the enthalpy calculated by the in-store enthalpy calculation unit and the deviation between the showcase internal set temperature and the actual internal temperature. The showcase cooling device is characterized by setting a temporary target suction pressure of. 6. A showcase cooling device characterized in that the suction pressure according to any one of claims 1 to 5 is replaced with an evaporation temperature of a refrigerant.