JP4276394B2 - Showcase cooling system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a showcase cooling apparatus that cools a plurality of showcases installed in a store with a common refrigerator.
[0002]
[Prior art]
Conventionally, in this type of showcase cooling device, the refrigerant is circulated by one (or a small number) of compressors for a large number of showcases, and each showcase is kept cold. The capacity of the compressor is quite large so that the cooling capacity is not impaired when the case is operated simultaneously. In addition, since the load on each showcase decreases during the winter and increases during the summer, the refrigeration capacity of the compressor is set in accordance with the summer when the load increases.
[0003]
However, operating a compressor having a large refrigeration capacity with the same capacity even in winter is disadvantageous in terms of energy saving because of a reduction in operating efficiency. In addition, a showcase cooling system has been proposed that enables switching between the cooling capacity in summer and the cooling capacity in winter, and switching this manually. However, switching at each turn of the season is also disadvantageous in terms of maintenance. It is a thing.
[0004]
In order to solve such problems, the applicant has proposed a showcase cooling apparatus according to Japanese Patent Application No. 2000-88104.
[0005]
This showcase cooling device calculates the enthalpy in the store based on a temperature sensor that detects the temperature in the store and a detection signal from the humidity sensor that detects the humidity in the store, and then a compressor that appropriately corresponds to the enthalpy and the set temperature in the store The target suction pressure is set, and then the rotational speed of the compressor is varied based on the deviation between the target suction pressure and the actual suction pressure.
[0006]
As a result, the refrigeration capacity is controlled so as to cope with the in-store enthalpy (showcase load) regardless of the winter season or summer season, and a showcase cooling device excellent in energy saving is realized.
[0007]
[Problems to be solved by the invention]
By the way, the load on the showcase does not only change due to the enthalpy in the store, but also changes depending on the amount of the cold food in the showcase, for example. For this reason, in the showcase cooling apparatus in which the target suction pressure is set based only on the in-store enthalpy, when there are some showcases in which a large amount of products that are not expected are continuously displayed, If there is a showcase in which only a few products are displayed, the COP of the entire cooling device becomes low, and a sufficient energy saving effect cannot be obtained.
[0008]
Also, when the characteristics of each showcase are the same and the set temperature inside the cabinet is exactly the same, there is no problem because all the required evaporation temperatures of the inside heat exchanger are the same. When some showcases with different characteristics are connected, for example, when showcases that have the same set temperature in the cabinet but require a lower evaporation temperature than others are connected, There is a risk that the cold will become sweet. On the other hand, when a showcase with a higher evaporation temperature than the others is connected even if the internal set temperature is the same, the COP of the entire cooling device is lowered, and a sufficient energy saving effect cannot be obtained.
[0009]
In addition, when the showcase is different in the presence or absence of doors, internal volume, internal fan air flow, installation environment, etc., the evaporation temperature of the internal heat exchanger required to maintain the internal temperature at the same temperature Will also be different. For this reason, the minimum required evaporation temperature of the heat exchanger, which changes depending on the in-store enthalpy, also changes for each showcase. The evaporating temperature of the heat exchanger corresponds to the operating low pressure (suction pressure) of the refrigerator, and in order to set the optimal target suction pressure for this changing evaporation temperature, the target suction pressure setting unit is set for each showcase. A pressure formula must be created. In other words, when a showcase with different characteristics comes out due to a difference in installation environment or the like, a new calculation formula for setting the target suction pressure has to be recreated.
[0010]
Furthermore, as described above, the conventional showcase cooling device has a configuration in which the rotational speed of the compressor is varied based only on the deviation between the target suction pressure and the actual suction pressure, where the actual suction pressure is Since it always fluctuates even if it is minute, the deviation from the target suction pressure also always fluctuates. This makes it necessary to recalculate the target suction pressure frequently in a few time intervals, and the control means has a large calculation capacity. If you do not have it, the process will not be in time. In addition, the actual suction pressure fluctuates greatly when the compressor is turned on and off, but if the low pressure value data is collected for a certain period and the average is not taken, the target suction pressure fluctuates severely and cannot be controlled. It was.
[0011]
In view of the above-mentioned conventional problems, the object of the present invention is to correct the target suction pressure based on the suction pressure data of the compressor and the temperature data of the showcase, and to maintain the product in the warehouse at an appropriate product temperature. It is an object of the present invention to provide a showcase cooling apparatus that can increase COP and reliably obtain an energy saving effect, and can further prevent a compressor from being shortened.
[0012]
[Means for Solving the Problems]
  In view of the above-described conventional problems, the present invention provides a showcase cooling device that circulates refrigerant in a compressor common to a plurality of showcases arranged in a store and controls the number of revolutions of the compressor. , In-store enthalpyas well asShowcase chamber set temperatureEvery timeThanCompressorThe target suction pressure setting calculator that calculates the target suction pressure and the average value of the actual suction pressure of the compressor per unit timeA plurality of corresponding pressure levels are set, it is determined which of the pressure levels the average value is, and the correction value corresponding to the determined pressure level is adjusted to the target suction pressure. To correct the target suction pressureCorrection calculationPartAnd correction calculationPartAnd a rotation speed command calculation unit that determines the rotation speed of the compressor based on the deviation between the target suction pressure and the actual suction pressure that have been corrected and calculated in (1).
[0014]
  The invention according to claim 2 is a showcase cooling apparatus for circulating refrigerant in a compressor common to a plurality of showcases arranged in a store and controlling the rotation speed of the compressor.as well asShowcase chamber set temperatureEvery timeThanCompressorA target suction pressure setting calculation unit for calculating and setting a target suction pressure;A setting unit that sets the upper and lower limits of the suction pressure of the compressor within a predetermined range, and the operating ratio of the total time exceeding the upper limit, which is the sum of the times when the suction pressure of the compressor exceeds the upper limit per unit time. Any one of the operating ratio of the total time exceeding the lower limit totaling the time exceeding the lower limit value of the pressure or the operating ratio of the total offset time obtained by offsetting the total time exceeding the upper limit and the total time exceeding the lower limit mutually. Set multiple operation ratio levels corresponding to the operation ratio, determine which operation ratio level the operation ratio is, and adjust the correction value corresponding to the determined operation ratio level to the target suction pressure. A correction calculation unit for correcting the target suction pressure;Correction calculationPartAnd a rotation speed command calculation section for determining the rotation speed of the compressor based on the deviation between the target suction pressure corrected and calculated in step S3 and the actual suction pressure of the compressor.
[0016]
  The invention of claim 3 is a showcase cooling apparatus for circulating refrigerant in a compressor common to a plurality of showcases arranged in a store and controlling the rotation speed of the compressor.as well asShowcase chamber set temperatureBy degreeRCompressorA target suction pressure setting calculator for calculating the target suction pressure;A setting unit that sets the upper and lower limits of the suction pressure of the compressor within a predetermined range, the upper limit total number of times that the suction pressure of the compressor has exceeded the upper limit value per unit time, and the lower limit of the suction pressure The number of times corresponding to any one of the total number of cancellations obtained by offsetting the total number of times exceeding the lower limit or the total number of times exceeding the upper limit and the total number of times exceeding the lower limit mutually. A correction calculation unit that determines which number level the total number of times is, and corrects the target suction pressure by adjusting a correction value corresponding to the determined number of times to the target suction pressure;Correction calculationPartAnd a rotation speed command calculation section for determining the rotation speed of the compressor based on the deviation between the target suction pressure corrected and calculated in step S3 and the actual suction pressure of the compressor.
[0018]
  According to a fourth aspect of the present invention, there is provided a showcase cooling apparatus for circulating a refrigerant with a compressor common to a plurality of showcases arranged in a store and controlling the rotation speed of the compressor.as well asShowcase chamber set temperatureBy degreeRCompressorThe target suction pressure setting calculation unit that calculates the target suction pressure, and the average value of the internal temperature of each showcase per unit timeSet a plurality of corresponding internal temperature levels, determine which of the internal temperature levels the average value is, and set the correction value corresponding to the determined temperature level as the target inhalation Adjust target suction pressure by adjusting to pressureCorrection calculationPartAnd correction calculationPartAnd a rotation speed command calculation section for determining the rotation speed of the compressor based on the deviation between the target suction pressure corrected and calculated in step S3 and the actual suction pressure of the compressor.
[0020]
  The invention of claim 5 provides at least two correction operations of claims 1 to 4.PartAnd each correction calculationPartPriority order is set for each correction operation according to this priority order.PartIt has the structure which has the control means which performs.
[0021]
  According to the invention of claim 5, a plurality of types of correction calculationPartCompensation calculation corresponding to the showcase loadPartCan be selected arbitrarily, and multiple correction operationsPartAre set at the same time, the correction calculation is performed according to the priority order.PartIs selected
[0022]
Note that the actual suction pressure is much higher during showcase defrosting operation than during steady operation (cooling operation when the internal temperature is stable), and it is a time period during which the target suction pressure does not need to be corrected. The pull-down operation performed following the defrosting operation is a transient cooling operation for shifting to the steady operation, and is a time zone in which the target suction pressure is not required to be corrected. According to the sixth aspect of the invention, the correction calculation of the target suction pressure is not performed in such a time zone where correction is unnecessary. Further, by forcibly correcting the target suction pressure during the pull-down operation, the transition to the steady operation is performed in a short time (Claim 7).
[0023]
DETAILED DESCRIPTION OF THE INVENTION
1 to 7 show a first embodiment of a showcase cooling apparatus according to the present invention. FIG. 1 is a refrigerant conduit diagram between a showcase and a refrigerator in a store, and FIG. 2 is a drive of the showcase cooling apparatus. 3 is a block diagram showing a circuit, FIG. 3 is a graph showing monthly changes in store temperature, humidity and enthalpy, FIG. 4 is a table showing the relationship between store temperature, store humidity and enthalpy, and FIG. 5 is evaporation of store enthalpy and showcase. Table showing relationship between temperature and suction pressure, FIG. 6 is a graph showing changes in actual suction pressure and corrected target suction pressure, and FIG. 7 is a graph showing changes in refrigeration capacity and compressor rotation speed accompanying changes in actual suction pressure. It is.
[0024]
First, the overall configuration of the showcase cooling apparatus will be described with reference to FIG. A large number of showcases 1 are arranged in the store, and these showcases 1 are provided with an evaporator 11 for cooling the inside of the store. These evaporators 11 are connected to the condenser 21 and the compressor 22 of the refrigerator 2 in parallel via the expansion valve 12 and the electromagnetic valve 13. Here, each solenoid valve 13 regulates the refrigerant flow to each evaporator 11 and is opened when the refrigerant is flowed to cool the inside of the cabinet. On the other hand, when the inside cooling is unnecessary, the solenoid valve 13 is closed to prevent the refrigerant from flowing. regulate.
[0025]
The showcase 1 is disposed in a store, and the temperature and humidity in the store are controlled by a store air conditioner (not shown). When this in-store temperature, in-store humidity, and in-store enthalpy were investigated (store in Kawagoe City, Saitama Prefecture), the results shown in FIG. 3 were obtained.
[0026]
That is, the temperature in the store is 21.8 ° C-26 ° C by month, but the change is not so great, but the humidity in the store is 50% RH from July to September, while it is around 35% RH in January and February. As a result, it became 8.67 kcal / kg in the month of small enthalpy (January) and 12.72 kcal / kg in the large month (August). FIG. 4 shows the enthalpy based on the in-store temperature and the in-store humidity in a table. That is, when the temperature is 14 ° C. and the humidity is 30% RH, the enthalpy is 5.14 kcal / kg, whereas when the temperature is 30 ° C. and the humidity is 80% RH, the enthalpy is 20.14 kcal / kg. To do.
[0027]
In addition, the relationship between the suction pressure / evaporation temperature of the showcase and the enthalpy was tested in a multistage open showcase in which the internal temperature was set at 5 ° C. In this experiment, the result shown in FIG. 5 was obtained.
[0028]
That is, the suction pressure is 3.64 kg / cm at an enthalpy of 10 kcal / kg.² The suction pressure is 2.58 kg / cm at an enthalpy of 20 kcal / kg.² It was found that the suction pressure decreased as the enthalpy increased.
[0029]
Based on the relationship between store temperature and store humidity and enthalpy as described above, and the relationship between enthalpy and suction pressure (or evaporation temperature), first, the target suction pressure is set, and then this target suction pressure is corrected. In order to obtain the optimum rotational speed of the compressor 22 based on the corrected suction pressure, the present embodiment constitutes a drive circuit shown in FIG.
[0030]
That is, an in-store temperature sensor 31 for detecting the temperature in the store (outside of the showcase 1) and an in-store humidity sensor 32 for detecting the humidity in the store (outside of the showcase 1) are installed in the store 3. Moreover, it has the control apparatus 4 which drive-controls the compressor 22 based on the detection signal from each of these sensors 31 and 32.
[0031]
The control device 4 includes an in-store enthalpy calculation unit 41 that calculates an in-store enthalpy from the detected temperature and detected humidity of each sensor 31 and 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 data.
[0032]
The in-store enthalpy calculated by the in-store enthalpy calculating unit 41 is input to the target suction pressure setting calculating unit 42. The target suction pressure setting calculation unit 42 sets an optimal target suction pressure corresponding to the in-store enthalpy. For example, in the above-described multistage open type showcase 1 (set temperature 5 ° C.), the data shown in the table of FIG. It is stored and the target suction pressure optimum for this in-store enthalpy is set. The set temperature is input by the internal temperature setting unit 33.
[0033]
The above configuration is not different from the showcase cooling apparatus shown by the applicant in the patent application related to Japanese Patent Application No. 2000-88104. As shown in FIG. 2, the showcase cooling device according to the present invention is that the target suction pressure correction calculation unit 43 corrects the target suction pressure calculated by the target suction pressure setting calculation unit 42.
[0034]
That is, the target suction pressure correction calculation unit 43 includes a target suction pressure P calculated by the target suction pressure setting calculation unit 42._AIs input, the suction pressure value set by the suction pressure width setting unit 34 is input, the operation signal from the operation state output unit 44 is input, and the actual suction pressure data of the compressor 22 is input from the suction pressure sensor 23. It has become so.
[0035]
Here, the suction pressure width setting unit 34 includes an upper limit value P of the suction pressure._HAnd lower limit P_LAre arbitrarily set (or fixed values obtained in advance by experiments, etc.), and this upper limit value P_HAnd lower limit P_LIs input to the target suction pressure correction calculation unit 43. Further, the target suction pressure correction calculation unit 43 has an upper limit value P._HAnd lower limit P_LBased on
Upper level P_H1, P_H2(P_H2> P_H1> P_H)When
Lower level P_L1, P_L2(P_L2<P_L1<P_L)When
Are set respectively.
[0036]
The operating state output unit 44 inputs whether each showcase 1 is in the defrosting operation, the pull-down operation, or the steady operation to the target suction pressure correction calculation unit 43, and at the time of the defrosting operation or the subsequent pull-down operation In this case, the target suction pressure correction calculation unit 43 does not perform calculation processing.
[0037]
As shown in FIG. 6, the target suction pressure correction calculation unit 43 monitors the actual suction pressure detected by the suction pressure sensor 23, and whether or not all of the showcases 1 installed in a plurality are in steady operation. Monitoring. Here, when all the showcases 1 start a steady operation, a correction calculation process is executed. In this correction calculation process, first, the average value P of the suction pressure per unit time (per 2 hours in the experiment)_MAsk for. Next, as shown below, the average value P_MIs at which level, and based on this determination, the target suction pressure P_AFor example, the correction value is adjusted in seven steps.
[0038]
P_M≧ P_H2            → P_A+ 3α (α; correction value (positive))
P_H2> P_M≧ P_H1      → P_A+ 2α
P_H1> P_M≧ P_H       → P_A+ Α
P_H> P_M> P_L        → P_A
P_L≧ P_M> P_L1       → P_A-Α
P_L1≧ P_M> P_L2      → P_A-2α
P_L2≧ P_M            → P_A-3α
If this is described based on the graph of FIG. 6, the target suction pressure is set based on the in-store enthalpy during the defrosting operation and the subsequent pull-down operation. When this pull-down operation is finished and the operation is shifted to the steady operation, the average value P of the suction pressure over 2 hours of the steady operation is obtained._MAsk for. Where the average value P_MFor example, P_H1> P_M≧ P_HWhen the target suction pressure P_AIs added with a correction value α to set a new target suction pressure. As a result, in the subsequent correction calculation, the correction is further updated based on the new target suction pressure. FIG. 6 shows the displacement of the target suction pressure when there is a correction and the target suction pressure when there is no correction (conventional control), and the target suction pressure correction processing according to this embodiment is performed. It can be understood that it varies according to the showcase load.
[0039]
The target suction pressure corrected by the target suction pressure correction calculation unit 43 as described above is input to the rotation speed command calculation unit 24. The rotational speed command calculation unit 24 determines the rotational speed of the compressor 22 based on the deviation between the corrected target suction pressure and the actual suction pressure, and varies the rotational speed of the compressor 22 through the inverter 25.
[0040]
According to this embodiment, the average value P of the actual suction pressure during operation._MThis average value P_MIs a suction pressure value within a predetermined range (upper limit value P_HAnd lower limit P_L), That is, when the load fluctuation of the showcase is large, the target suction pressure P_ATherefore, as shown by the bidirectional arrow in FIG. 7, the rotation speed of the compressor 22 is switched to correspond to the showcase load.
[0041]
8 and 9 show a second embodiment of the showcase cooling apparatus according to the present invention. The showcase cooling apparatus according to the second embodiment has a time measurement high and low suction pressure setting section 35 instead of the suction pressure width setting section 34 of the first embodiment, and the target suction is based on the setting signal. The target suction pressure P is calculated by the pressure correction calculation unit 45._AIs to be corrected.
[0042]
That is, the high / low suction pressure setting unit 35 for measuring time includes an upper limit value P of the suction pressure._HAnd lower limit P_LAre arbitrarily set (or fixed values obtained in advance by experiments, etc.), and this upper limit value P_HAnd lower limit P_LIs input to the target suction pressure correction calculation unit 45.
[0043]
As shown in FIG. 8, the target suction pressure correction calculation unit 45 monitors the actual suction pressure detected by the suction pressure sensor 23 and installs a plurality of units as in the showcase cooling apparatus according to the first embodiment. It is monitored whether or not all the showcases 1 are in steady operation. Here, when all the showcases 1 start a steady operation, a correction calculation process is executed. In this correction calculation process, first, the unit time T₀The suction pressure is the upper limit P (per 2 hours in the experiment)_HAnd lower limit P_LThe time that exceeds is measured. For example, as shown in FIG._HElapsed time T exceeding₁~ T_N(T in FIG. 9₁~ T₈)
T₁+ T₂... T_N-1+ T_N= T_S(Total time of each elapsed time)
Is calculated. In calculation, the upper limit P_HElapsed time T exceeding_NIs determined as plus time, while lower limit P_LElapsed time T exceeding_NIs calculated as a minus time. Therefore, the unit time T₀Upper limit P during_HAnd lower limit P_LWhen the suction pressure changes over both, the total time is calculated so as to cancel each other, and the upper limit value P_HElapsed time T exceeding_NWhen is long, plus total time (+) T_SIs calculated and the lower limit P_LElapsed time T exceeding_NWhen is long, minus total time (-) T_SIs calculated.
[0044]
After the calculation of this total time, the total time (±) T_SUnit time T₀The percentage of
T_S÷ T₀× 100 = (±) T_M(%) (Percentage of operation outside the upper / lower limit range)
Ask for.
[0045]
Next, this operating ratio T_MIn determining which level is, the target suction pressure correction calculation unit 45 includes an operation ratio level.
T_H1, T_H2, T_H, T_L, T_L1, T_L2
(T_H2> T_H1> T_H> T_L> T_L1> T_L2)
Is set, and the driving rate T_MIs determined at which level, and based on this determination level, the target suction pressure P_AFor example, the correction value is adjusted in seven steps.
[0046]
T_M≧ T_H2            → P_A+ 3α (α; correction value (positive))
T_H2> T_M≧ T_H1      → P_A+ 2α
T_H1> T_M≧ T_H       → P_A+ Α
T_H> T_M> T_L        → P_A
T_L≧ T_M> T_L1       → P_A-Α
T_L1≧ T_M> T_L2      → P_A-2α
T_L2≧ T_M            → P_A-3α
The target suction pressure corrected by the target suction pressure correction calculation unit 45 as described above is input to the rotation speed command calculation unit 24. The rotational speed command calculation unit 24 determines the rotational speed of the compressor 22 based on the deviation between the corrected target suction pressure and the actual suction pressure, and varies the rotational speed of the compressor 22 through the inverter 25.
[0047]
According to this embodiment, the load fluctuation of the showcase is determined from the operation ratio outside the upper / lower limit value range, and the target suction pressure P_AIs corrected to an appropriate value.
[0048]
In the present embodiment, the upper limit value P_HAnd lower limit P_LBoth of these values are set, but one of the values P_H, P_LAnd set the target suction pressure P_AMay be corrected. Since other configurations and operations are the same as those of the first embodiment, illustration and description thereof are omitted.
[0049]
10 and 11 show a third embodiment of the showcase cooling apparatus according to the present invention. The showcase cooling apparatus according to the third embodiment has a high / low suction pressure setting unit 36 for counting the number of times in place of the time measurement high / low suction pressure setting unit 35 of the second embodiment. Based on the target suction pressure correction calculation unit 46, the target suction pressure P_AIs to be corrected.
[0050]
That is, the high / low suction pressure setting unit 36 for counting time includes an upper limit P of the suction pressure._HAnd lower limit P_LAre arbitrarily set (or fixed values obtained in advance by experiments, etc.), and this upper limit value P_HAnd lower limit P_LIs input to the target suction pressure correction calculation unit 46.
[0051]
As shown in FIG. 8, the target suction pressure correction calculation unit 46 monitors the actual suction pressure detected by the suction pressure sensor 23 and installs a plurality of units as in the showcase cooling apparatus according to the first embodiment. It is monitored whether or not all the showcases 1 are in steady operation. Here, when all the showcases 1 start a steady operation, a correction calculation process is executed. In this correction calculation process, first, the unit time T₀The suction pressure is the upper limit P (per 2 hours in the experiment)_HAnd lower limit P_LMeasures the number of times exceeding. For example, as shown in FIG._HThe number N of times exceeding (8 times in FIG. 11) is counted. In addition, the upper limit value P is counted._HThe number of times that exceeds is determined as a positive number, while the lower limit P_LThe number of times exceeding is determined as a minus number. Therefore, the unit time T₀Upper limit P during_HAnd lower limit P_LWhen the suction pressure changes across both, the number N is calculated so as to cancel each other, and the upper limit value P_H(+) N is calculated and the lower limit value P is exceeded._L(−) N is calculated when there are a large number of times exceeding.
[0052]
Next, in determining which level the number N is at, the target suction pressure correction calculation unit 46 receives the number level.
N_H1, N_H2, N_H, N_L, N_L1, N_L2
(N_H2> N_H1> N_H> N_L> N_L1> N_L2)
Is set, and it is determined at which level the number of times N is, and the target suction pressure P is determined based on this determination level._AFor example, the correction value is adjusted in seven steps.
[0053]
N ≧ N_H2            → P_A+ 3α (α; correction value (positive))
N_H2> N ≧ N_H1      → P_A+ 2α
N_H1> N ≧ N_H       → P_A+ Α
N_H> N> N_L        → P_A
N_L≧ N> N_L1       → P_A-Α
N_L1≧ N> N_L2      → P_A-2α
N_L2≧ N → P_A-3α
The target suction pressure corrected by the target suction pressure correction calculation unit 46 as described above is input to the rotation speed command calculation unit 24. The rotational speed command calculation unit 24 determines the rotational speed of the compressor 22 based on the deviation between the corrected target suction pressure and the actual suction pressure, and varies the rotational speed of the compressor 22 through the inverter 25.
[0054]
According to this embodiment, the load fluctuation of the showcase 1 is determined from the number of operations outside the upper / lower limit value range, and the target suction pressure is corrected to an appropriate value.
[0055]
In the present embodiment, the upper limit value P_HAnd lower limit P_LBoth of these values are set, but one of the values P_H, P_LAnd set the target suction pressure P_AMay be corrected. Since other configurations and operations are the same as those of the second embodiment, illustration and description thereof are omitted.
[0056]
FIG. 12 shows a fourth embodiment of the showcase cooling apparatus according to the present invention. The showcase cooling apparatus according to the fourth embodiment has an internal temperature range setting unit 37 instead of the intake pressure range setting unit 34 of the first embodiment, and this setting signal is used as a target intake pressure correction calculation unit. 47 is input. In the first embodiment, the detected pressure of the suction pressure sensor 23 is input to the target suction pressure correction calculation unit 47. In the present embodiment, the detected temperature data from the internal temperature sensor 38 of each showcase 1 is used. This is input to the target suction pressure correction calculation unit 47.
[0057]
Here, the internal temperature range setting unit 37 includes an upper limit value K of the internal temperature._HAnd lower limit K_LAre arbitrarily set (or fixed values obtained in advance by experiments, etc.), and this upper limit value K_HAnd lower limit K_LIs input to the target suction pressure correction calculation unit 47. Further, in the target suction pressure correction calculation unit 47, an upper limit value K_HAnd lower limit K_LBased on
Upper level K_H1, K_H2(K_H2> K_H1> K_H)When
Lower level K_L1, K_L2(K_L2<K_L1<K_L)When
Are set respectively.
[0058]
The operation state output unit 44 inputs whether each showcase 1 is in the defrosting operation, the pull-down operation, or the steady operation to the target suction pressure correction calculation unit 47, and during the defrosting operation or the subsequent pull-down operation In this case, the target suction pressure correction calculation unit 47 does not perform calculation processing.
[0059]
The target suction pressure correction calculation unit 47 monitors the internal temperature detected by the internal temperature sensor 38 and also monitors whether or not all of the plurality of showcases 1 installed are in steady operation. . Here, when all the showcases 1 start a steady operation, a correction calculation process is executed. In this correction calculation process, first, the average value K of the internal temperature per unit time (per 2 hours in the experiment)_MAsk for. Next, the average value K_MIs at which level, and based on this determination, the target suction pressure P_AFor example, the correction value is adjusted in seven steps.
[0060]
K_M≧ K_H2            → P_A+ 3α (α; correction value (positive))
K_H2> K_M≧ K_H1      → P_A+ 2α
K_H1> K_M≧ K_H       → P_A+ Α
K_H> K_M> K_L        → P_A
K_L≧ K_M> K_L1       → P_A-Α
K_L1≧ K_M> K_L2      → P_A-2α
K_L2≧ K_M            → P_A-3α
The target suction pressure P corrected by the target suction pressure correction calculation unit 47 as described above._AIs input to the rotation speed command calculation unit 24. The rotational speed command calculation unit 24 determines the rotational speed of the compressor 22 based on the deviation between the corrected target suction pressure and the actual suction pressure, and varies the rotational speed of the compressor 22 through the inverter 25.
[0061]
According to this embodiment, the average value K of the inside temperature during operation_MThis average value K_MIs the internal temperature value of the predetermined width (upper limit K_HAnd lower limit K_L), That is, when the load fluctuation of the showcase 1 is large, the rotational speed of the compressor 22 is switched to correspond to the showcase load.
[0062]
13 and 14 show a fifth embodiment of the showcase cooling apparatus according to the present invention. In this embodiment, all the correction controls of the showcase cooling apparatus according to the first to fourth embodiments are provided.
[0063]
Further, the correction processing according to the first embodiment is the first correction processing mode, the correction processing according to the second embodiment is the second correction processing mode, the correction processing according to the third embodiment is the third correction processing mode, and the fourth embodiment. When the correction processing according to the embodiment is set to the fourth correction processing mode, the first to fourth correction processing modes have the first correction processing mode as the highest priority, and the second to fourth correction processing modes are sequentially set in priority order. . If this is shown by a flowchart, control is performed as shown in FIG.
[0064]
That is, is the pressure range set by the suction pressure range setting unit 34 (S1), or the time measurement high and low suction pressure setting unit 35 is the time measurement upper limit value P?_HAnd lower limit P_LIs set (S2), or the upper limit P for counting the number of times in the high / low suction pressure setting unit 36 for counting the number_HAnd lower limit P_LIs set (S3), and whether the temperature range is set by the internal temperature range setting unit 37 (S4) is sequentially determined. Here, when the condition of step S1 is satisfied, the first correction processing mode is executed (S5). When the condition of step S1 is not satisfied and the condition of step S2 is satisfied, the second correction processing mode is executed (S6). If neither of the conditions of steps S1 and S2 is satisfied and the condition of step S3 is satisfied, the third correction processing mode is executed (S7). When none of the conditions of steps S1, S2, and S3 is satisfied and the condition of step S4 is satisfied, the fourth correction processing mode is executed (S8).
[0065]
The priority order is not limited to this, and the priority order may be set from the fourth correction processing mode to the first correction processing mode, contrary to the above. In addition, when all of the first to fourth correction processing modes are not provided, that is, when at least two correction processing modes are provided, the priority is similarly given and controlled.
[0066]
In the first to fifth embodiments, the target suction pressure P is used during the defrosting operation and the pull-down operation._ACorrection processing is prohibited. This is because the actual suction pressure is much higher during the defrosting operation of the showcase 1 than during the steady operation (during the cooling operation in a state where the inside temperature is stable), and the target suction pressure P_AThe pull-down operation performed after the defrosting operation is a transient cooling operation for shifting to the steady operation, and the target suction pressure P_AThis is a time zone that does not require correction. However, since the pull-down operation is an operation in which rapid cooling is performed as described above, the target suction pressure may be forcibly lowered.
[0067]
Furthermore, in the first to fifth embodiments, the target suction pressure P_AIs set based on in-store enthalpy, but is not limited to this. For example, although it is already known technology, the target suction pressure P based on the operating rate of the solenoid valve 13 of the showcase 1_AThe target suction pressure P based on the temperature drop rate of the showcase 1_AAnd the target suction pressure P based on the average on / off cycle of the solenoid valve 13 of the showcase 1_ATarget suction pressure P_ACan be applied to any showcase cooling device as long as it is set in advance.
[0068]
【The invention's effect】
As described above, according to the present invention, it is set according to the enthalpy in the store, the set temperature inside the showcase, etc. even when the showcase has a load change or when a showcase having different characteristics is connected. Since the target suction pressure is corrected to an appropriate pressure, the cooling of the showcase is not reduced, or the COP of the entire showcase cooling device is not lowered.
[0069]
In addition, in order to detect the operating state and correct the target suction pressure as needed, create a calculation formula for the target suction pressure for each showcase model, or change the formula every time the connected model is changed. Not only is it unnecessary, but it is not necessary to create a new calculation formula even when a new showcase with different characteristics appears depending on the installation environment.
[0070]
Further, the correction value for the target suction pressure has two upper and lower threshold values for the suction pressure value and the internal temperature value, and the correction value is obtained by calculating over the operation unit time whether or not the threshold value is exceeded. The calculation means does not require a large calculation capability, and can sufficiently exhibit the control capability even during operation in which the suction pressure varies greatly, such as when the compressor is turned on and off.
[Brief description of the drawings]
FIG. 1 Refrigerant pipeline diagram between a showcase and a refrigerator in a store
FIG. 2 is a block diagram showing a drive circuit of the showcase cooling apparatus according to the first embodiment.
FIG. 3 is a graph showing monthly changes in store temperature, humidity and enthalpy.
FIG. 4 is a table showing the relationship between store temperature and store humidity and enthalpy.
FIG. 5 is a table showing the relationship between in-store enthalpy and the evaporation temperature and suction pressure of a showcase.
FIG. 6 is a graph showing changes in actual suction pressure and corrected target suction pressure of the showcase cooling apparatus according to the first embodiment.
FIG. 7 is a graph showing changes in refrigeration capacity and compressor rotation speed with changes in actual suction pressure.
FIG. 8 is a block diagram showing a drive circuit of the showcase cooling apparatus according to the second embodiment.
FIG. 9 is a graph showing changes in actual suction pressure and corrected target suction pressure of the showcase cooling apparatus according to the second embodiment.
FIG. 10 is a block diagram showing a drive circuit of a showcase cooling apparatus according to a third embodiment.
FIG. 11 is a graph showing changes in actual suction pressure and corrected target suction pressure of the showcase cooling device according to the third embodiment.
FIG. 12 is a block diagram showing a drive circuit of a showcase cooling device according to a fourth embodiment.
FIG. 13 is a block diagram showing a drive circuit of a showcase cooling device according to a fifth embodiment.
FIG. 14 is a flowchart showing priority control in the correction processing mode of the showcase cooling apparatus according to the fifth embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Showcase, 2 ... Refrigerator, 3 ... Store, 4 ... Control apparatus, 22 ... Compressor, 23 ... Suction pressure sensor, 24 ... Rotation speed command calculating part, 34 ... Suction pressure width setting part, 35 ... Time measurement High / low suction pressure setting unit, 36... High / low suction pressure setting unit for counting, 37 .. chamber internal temperature range setting unit, 38 .. chamber internal temperature sensor, 42... Target suction pressure setting unit, 43, 45, 46, 47, 48 ... Target suction pressure correction calculation unit.

Claims (7)

In the showcase cooling device that circulates the refrigerant with a compressor common to a plurality of showcases arranged in the store and controls the rotation speed of the compressor,
A target suction pressure setting calculation unit for calculating a target suction pressure of more compressor-chamber set temperature of the store enthalpy and showcases,
A plurality of pressure levels corresponding to the average value of the actual suction pressure of the compressor per unit time are set, and it is determined which pressure level the average value is among the pressure levels. A correction calculation unit that corrects the target suction pressure by adjusting a correction value corresponding to the determined pressure level to the target suction pressure ;
Wherein the correction showcase cooling device and having an arithmetic unit and a rotational speed command computation unit for determining the rotational speed of the compressor based on the deviation between the corrected calculated target suction pressure and the actual suction pressure. In the showcase cooling device that circulates the refrigerant with a compressor common to a plurality of showcases arranged in the store and controls the rotation speed of the compressor,
A target suction pressure setting calculating unit for calculating sets the target suction pressure of more compressor-chamber set temperature of the store enthalpy and showcases,
A setting unit for setting an upper limit value and a lower limit value of the suction pressure of the compressor within a predetermined range;
Operation ratio of the total time exceeding the upper limit totaling the time when the suction pressure of the compressor exceeds the upper limit value per unit time, operation of the total time exceeding the lower limit totaling the time exceeding the lower limit value of the suction pressure While setting a plurality of operation ratio levels corresponding to any one operation ratio among the operation ratios of the offset total time obtained by canceling the ratio or the total time exceeding the upper limit and the total time exceeding the lower limit mutually, A correction calculation unit that determines which driving rate level the driving rate is, and corrects the target suction pressure by adjusting a correction value corresponding to the determined driving rate level to the target suction pressure;
A showcase cooling apparatus, comprising: a rotation speed command calculation section that determines a rotation speed of the compressor based on a deviation between a target suction pressure corrected by the correction calculation section and an actual suction pressure of the compressor. In the showcase cooling device that circulates the refrigerant with a compressor common to a plurality of showcases arranged in the store and controls the rotation speed of the compressor,
A target suction pressure setting calculation unit for calculating a target intake pressure of the compressor Ri by the storage room set temperature of the store enthalpy and showcases,
A setting unit for setting an upper limit value and a lower limit value of the suction pressure of the compressor within a predetermined range;
The total number of times exceeding the upper limit, the total number of times that the suction pressure of the compressor has exceeded the upper limit value per unit time, the total number of times exceeding the lower limit, the total number of times exceeding the lower limit value of the suction pressure, or the total number of times exceeding the upper limit And a total number of offsets obtained by canceling each other over the lower limit, a plurality of count levels corresponding to any one total number of times are set, and the total number of times becomes any number level. A correction calculation unit that corrects the target suction pressure by adjusting a correction value corresponding to the determined number of times to the target suction pressure;
A showcase cooling apparatus, comprising: a rotation speed command calculation section that determines a rotation speed of the compressor based on a deviation between a target suction pressure corrected by the correction calculation section and an actual suction pressure of the compressor. In the showcase cooling device that circulates the refrigerant with a compressor common to a plurality of showcases arranged in the store and controls the rotation speed of the compressor,
A target suction pressure setting calculation unit for calculating a target intake pressure of the compressor Ri by the storage room set temperature of the store enthalpy and showcases,
A plurality of internal temperature levels corresponding to the average value of the internal temperature of each showcase per unit time are set, and which of the internal temperature levels the average value is set to A correction calculation unit that determines and corrects the target suction pressure by adjusting a correction value corresponding to the determined temperature level to the target suction pressure ;
A showcase cooling apparatus, comprising: a rotation speed command calculation section that determines a rotation speed of the compressor based on a deviation between a target suction pressure corrected by the correction calculation section and an actual suction pressure of the compressor. Together comprising at least two correction operation unit of the claims 1 to 4, prioritize respective correction calculation unit, and wherein the control means executes the correction calculation unit according to this priority Showcase cooling system to do. The show according to any one of claims 1 to 5, wherein at least one showcase includes a control unit that prohibits execution of the correction calculation unit during a defrosting operation and a subsequent pull-down operation. Case cooling device. The showcase cooling device according to any one of claims 1 to 6, further comprising correction means for correcting the target suction pressure to be low during the pull-down operation.

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