JP2008057873A - Refrigerating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in a refrigerating device comprising a variable-speed compressor and a constant-speed compressor, and inhibiting the start and stop of the constant-speed compressor to prevent wastage of the constant-speed compressor caused by repeating of its start and stop, that excess and deficiency in output is found when the stop and start of the constant-speed compressor is excessively inhibited. <P>SOLUTION: An inhibition signal from a start/stop inhibition device is canceled out when a predicted value of low pressure of the refrigerating device is over an upper limit value of a prescribed range, and the signal for inhibiting the start/stop of the constant-speed compressor is output from the start/stop inhibition device, thus the low pressure can be controlled within the prescribed range even when the start/stop inhibition signal is output. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to suppression of start and stop of a constant speed compressor in a refrigeration apparatus including an inverter compressor (variable speed compressor) having a variable operating frequency and a constant speed compressor having a constant operating frequency.

  A conventional refrigeration system increases or decreases the operating frequency and the number of operating units of a compressor based on the measured values of the refrigerant temperature, the low pressure of the compressor, and the high pressure, and compares the measured value with a preset threshold value. Thus, the increase / decrease range of the operating frequency and the number of operating units were determined.

For example, there is a control method for reducing the operating frequency of the compressor when the refrigerant discharge temperature is equal to or higher than a set value and the compression ratio obtained from the low pressure and the high pressure is equal to or higher than the set value (see Patent Document 1).
Japanese Patent Laid-Open No. 5-10608

  In the conventional refrigeration system operation control method, the control is performed by comparing the measured values such as the discharge temperature and the low pressure and the calculated values such as the compression ratio calculated from the measured low pressure and high pressure with a threshold value. Since it becomes control, the value obtained is discontinuous.

  FIG. 3 shows an example in which the output control of the compressor is performed so that the low pressure of the compressor approaches the target value in a refrigeration apparatus equipped with an inverter compressor and a constant speed compressor. The horizontal axis represents time, and the vertical axis represents low pressure. Zone control is performed in which four regions from region A to region D are set, and the boundary between region B and region C is set as a target value. This zone control will be described in detail.

  When the low pressure is located in the region A, since the low pressure is very large as compared with the target value, it is considered that the refrigerating capacity is insufficient, so the output of the compressor is greatly increased. When the low pressure is located in the region B, since the low pressure is larger than the target value, it is considered that the refrigerating capacity is insufficient, so the output of the compressor is increased by a small amount. Next, when the low-pressure pressure is located in the region C, since the low-pressure pressure is smaller than the target value, the refrigerating capacity is sufficient, so the output of the compressor is reduced. When the low-pressure pressure is located in the region D, since the low-pressure pressure is very small compared to the target value, the refrigerating capacity is excessive, so that the output of the compressor is greatly reduced.

  In order to control the output of the compressor in this way, control corresponding to the region C is performed when the low pressure is in the state A, the state A, or the state C. In the state A and the state A, the value of the low-pressure pressure is the same, but the change in the low-pressure pressure is the same control regardless of whether it is a downward trend or an upward trend and the opposite. Moreover, although the tendency of the change of the low pressure is the same in the state A and the state C, the same control is performed although the value of the low pressure is different. Further, in the state A and the state C, although the value of the low pressure and the tendency of the change in the low pressure are different, the same control is performed.

  As described above, in the conventional control method (zone control, etc.) for controlling the operation of the compressor by comparing the measured value or the calculated value obtained from the measured value with the threshold value, the state of the refrigeration apparatus is accurately grasped. It is difficult to control the operation of the compressor so that the necessary refrigeration capacity can be output efficiently.

  As described above, since the output of the required refrigeration apparatus fluctuates due to the fluctuation of the low pressure, the constant speed compressor is frequently started and stopped. In order to prevent the constant speed compressor from being remarkably consumed due to repeated start and stop, a start / stop suppression device for suppressing start and stop of the constant speed compressor is provided. However, if the start of the constant speed compressor is excessively suppressed, the output of the refrigeration apparatus is insufficient, and if the stop of the constant speed compressor is excessively suppressed, the output of the refrigeration apparatus becomes excessive. It has occurred.

  The invention described in claim 1 includes at least one variable speed compressor having a variable operating frequency, at least one constant speed compressor having a constant operating frequency, and pressure disposed on the low pressure side of these compressors. In a refrigeration system comprising a detector and a control device that controls the operating frequency and the number of operating units according to the load of the compressor, the low pressure is measured by the pressure detector, and the current low pressure and the past low pressure are measured. The reference low pressure is calculated from the reference low pressure, the reference low pressure is not less than the upper limit value or less than the lower limit value of the predetermined range, and the control device outputs a signal for increasing the number of operating the constant speed compressors by two or more. In this case, the number of operating units of the constant speed compressor is increased to one unit, and the operating frequency of the variable speed compressor is maximized.

  The invention according to claim 2 includes at least one variable speed compressor having a variable operating frequency, at least one constant speed compressor having a constant operating frequency, and pressure disposed on the low pressure side of these compressors. In a refrigeration system comprising a detector and a control device that controls the operating frequency and the number of operating units according to the load of the compressor, the low pressure is measured by the pressure detector, and the current low pressure and the past low pressure are measured. The reference low pressure is calculated from the reference low pressure, the reference low pressure is not less than the upper limit value or less than the lower limit value of the predetermined range, and a signal for reducing the number of operating constant speed compressors by two or more is output from the control device. In this case, the number of reduced operation units of the constant speed compressor is reduced to one, and the operation frequency of the variable speed compressor is minimized.

  According to a third aspect of the present invention, there is provided at least one variable speed compressor having a variable operating frequency, at least one constant speed compressor having a constant operating frequency, and pressure disposed on a low pressure side of these compressors. In a refrigeration apparatus comprising a detector, a control device that controls the operating frequency and the number of operating units according to the load of these compressors, and a start / stop suppression device that suppresses repeated start / stop of the constant speed compressor, A low pressure is measured by the pressure detector, a reference low pressure is calculated from a current low pressure and a past low pressure, the reference low pressure is not less than an upper limit value within a predetermined range, and from the start / stop suppression device. When a signal for suppressing the start / stop of the constant speed compressor is output, the suppression signal from the start / stop suppression device is invalidated.

  According to a fourth aspect of the present invention, there is provided at least one variable speed compressor having a variable operating frequency, at least one constant speed compressor having a constant operating frequency, and pressure disposed on a low pressure side of these compressors. In a refrigeration apparatus comprising a detector, a control device that controls the operating frequency and the number of operating units according to the load of these compressors, and a start / stop suppression device that suppresses repeated start / stop of the constant speed compressor, A low pressure is measured by the pressure detector, a reference low pressure is calculated from a current low pressure and a past low pressure, the reference low pressure is not more than a lower limit value of a predetermined range, and from the start / stop suppression device. When a signal for suppressing the start / stop of the constant speed compressor is output, the suppression signal from the start / stop suppression device is invalidated.

  According to the first aspect of the present invention, an output signal that predicts that the low-pressure pressure of the refrigeration apparatus is out of the predetermined range and that increases the number of operating the constant speed compressors by two or more is output. When the output is performed, the refrigeration capacity of the refrigeration apparatus is ensured while suppressing the start of the constant speed compressor by setting the increased operation number to one and maximizing the operation frequency of the variable speed compressor. Can do.

  According to the second aspect of the present invention, an output signal that predicts that the low-pressure pressure of the refrigeration apparatus is out of the predetermined range, and that the control apparatus reduces the number of operating constant-speed compressors by two or more is provided. When outputting, by reducing the operating frequency of the variable speed compressor and minimizing the operating frequency of the variable speed compressor, the refrigeration capacity of the refrigeration apparatus is reduced while suppressing the stop of the constant speed compressor, Energy saving operation can be performed.

  According to invention of Claim 3, the signal which suppresses the start / stop of the said constant speed compressor from the said start / stop suppression apparatus when the predicted value of the low pressure of the said freezing apparatus exceeds the upper limit of the said predetermined range. When the signal is output, the suppression signal from the start / stop suppression device is invalidated so that the low pressure can be controlled to be within the predetermined range even when the start / stop suppression signal is output.

  According to invention of Claim 4, the signal which suppresses the start / stop of the said constant speed compressor from the said start / stop suppression apparatus when the estimated value of the low pressure of the said freezing apparatus is less than the lower limit of the said predetermined range. When the signal is output, the suppression signal from the start / stop suppression device is invalidated to control the low pressure to be within the predetermined range even when the start / stop suppression signal is output, and energy saving operation is performed. be able to.

  Hereinafter, the implementation method of this invention is demonstrated in detail using drawing.

  FIG. 1 is a refrigerant circuit diagram of a refrigeration apparatus to which the present invention is applied. This refrigeration apparatus includes one inverter scroll compressor (inverter compressor) 10 that can control the rotation speed by an inverter. In the present invention, the compressor is applicable to either a hermetic type or a semi-hermetic type regardless of the type of compression method such as a reciprocating type, a screw type, or a rotary type.

  In this embodiment, an HFC refrigerant is assumed as the refrigerant to be used, but the same effect can be obtained by using other refrigerants such as a CFC refrigerant, an HCFC refrigerant, and a natural refrigerant.

  The inverter compressor 10 sucks and compresses the low-temperature and low-pressure gaseous refrigerant and discharges it as a high-temperature and high-pressure refrigerant. The discharged high-temperature and high-pressure refrigerant flows into the oil separator 13. In the oil separator 13, the lubricating oil contained in the refrigerant is separated and stored.

  The separated lubricating oil flows into the strainer 27 through the service valve 26, and contaminants in the lubricating oil are removed by the strainer 27. The lubricating oil from which the contaminants have been removed is returned to the compressor 10 via the electromagnetic valve 28. At this time, the amount of lubricating oil in the compressor is measured by the float switch 23 installed in the compressor, and the electromagnetic valve 28 is opened and closed so that the amount of lubricating oil in the compressor becomes constant.

  In addition, when liquid refrigerant is included in the lubricating oil returned to the compressor, there is a possibility that the compression mechanism in the compressor may be insufficiently lubricated and become defective, so the pressure is reduced in the capillary tube 29 and the refrigerant is completely vaporized. Yes. By evaporating the refrigerant with the capillary tube 29, there is also an effect of cooling the lubricating oil.

  The refrigerant from which the lubricating oil has been removed in the oil separator 13 flows into the condenser 14, and the high-temperature and high-pressure refrigerant is cooled by the cooling fan 63 and condensed and liquefied. In this embodiment, an air-cooled condenser is used, but a water-cooled or evaporative condenser may be used. In this embodiment, an integrated refrigerator in which the condenser and the compressor are disposed in the same casing is assumed. However, the present invention is not limited to this, and the refrigerator and the condensing unit are separately provided. A separate installation type may be used.

  The refrigerant liquefied in the condenser 14 flows out of the condenser 14 and is stored in the receiver tank 15. The receiver tank 15 has a fusible plug 46 as a safety device when a defect occurs in the refrigeration apparatus and the pressure and temperature inside the refrigerant circuit become very high.

  As the high pressure of the compressor, the refrigeration apparatus measures the pressure in the receiver tank 15 and controls the compressor and the like. The receiver tank 15 is connected to a high pressure sensor 58 via a capillary tube 57, and the high pressure sensor 58 measures the high pressure of the compressor. The receiver tank 15 is connected to a high pressure gauge 62 via capillary tubes 57 and 61 in order to observe the high pressure of the compressor as needed. Note that the high pressure may be measured directly from the discharge port of the compressor 10 instead of the receiver tank 15.

  In order to increase the refrigerating capacity of the liquid refrigerant, the liquid refrigerant stored in the receiver tank 15 is supercooled by the air cooling by the cooling fan 63 in the supercooler 16 again. In the present embodiment, the condenser 14 and the supercooler 16 are integrated, but the condenser and the supercooler may be provided separately.

  The supercooled liquid refrigerant flows into the filter dryer 17 through the service valve 48. The moisture in the refrigerant is removed by the filter dryer 17, and after confirming the amount of moisture by the moisture indicator 18, the liquid refrigerant flows out to an evaporator (not shown) such as a showcase installed in the store.

  In this embodiment, a liquid injection mechanism is used to cool the compressor. For this reason, a liquid injection circuit is provided from the receiver tank 15 to the compressor 10 via the service valve 34, the strainer 35, the electric valve 36, and the electromagnetic valve 37.

  The liquid refrigerant from which contaminants have been removed by the strainer 35 is decompressed by the motor-operated valve 36 to cool the compressor 10. The degree of opening and closing of the electromagnetic valve 37 and the degree of opening and closing of the electric valve 36 are adjusted by the operating state of the compressor 10 and the temperature of the compressor 10. When the high pressure of the compressor 10 becomes very large, the compressor is urgently stopped by a high pressure switch 52 disposed in the compressor 10 via the capillary tube 51.

  Since the refrigerant that has been vaporized and cooled in the evaporator and has reached low temperature and low pressure may return to the refrigeration system including the liquid refrigerant (liquid back), the refrigerant and the gaseous refrigerant are allowed to flow into the accumulator 19 once and then the liquid refrigerant and the gaseous refrigerant are To separate. Possible causes of the liquid back include a defective expansion valve and clogging of the evaporator filter. The liquid refrigerant enters the case of the compressor 10 due to the liquid back, breakage of the compression mechanism due to liquid compression, liquid refrigerant When a large amount of lubricating oil is discharged together, there may be a lack of lubrication.

  In the accumulator 19, the liquid refrigerant is stored, and only the gaseous refrigerant flows out and is sucked into the compressor 10 through the strainer 20. In this embodiment, since the pressure of the refrigerant returned from the evaporator is used as the low pressure of the compressor 10, the inlet side of the accumulator 19 is connected to the low pressure sensor 59 by piping. The low pressure may be measured directly from the suction port of the compressor 10 instead of from the accumulator 19.

  Next, the control flow of the inverter compressor 10 in the present embodiment will be described with reference to FIGS. 1, 4, and 5. In this control method, the target operating frequency TCF of the compressor required by the refrigeration system is obtained from the current low pressure LP and operating frequency CF and the target low pressure TLP, and the inverter is compressed so that the obtained target operating frequency TCF is obtained. It controls the operating frequency of the machine.

  FIG. 4 is a flowchart for calculating the target operating frequency TCF. First, at the stage where calculation of the target operating frequency TCF is started (S100), the low pressure LP is measured. Since the target low pressure TLP is a value unique to the refrigeration apparatus, the target low pressure TLP is set to a low pressure that can supply the refrigeration capacity required by the refrigeration system because the object to be cooled is set to the target temperature through experiments.

  The target operating frequency TCF is obtained by integrating the output change rate K with the current operating frequency CF. This operation change rate K includes a proportional component KP, a differential component KD, and an integral component KI. The proportional component KP is calculated from Equation 1 below (S101). With the proportional component KP, it is possible to obtain an operating frequency that can output the refrigeration capacity required by the refrigeration system at the current low pressure LP.

  Measurement of the low pressure LP of the inverter compressor 10 by the low pressure sensor 59 is performed several tens of times per second. However, the measurement value is sampled every predetermined time TS, and the predetermined measurement measured immediately before the current measurement is performed. Using the low pressure PLP and the low pressure LP before the time TS, the change rate GLP of the low pressure is calculated from the following formula 2 (S102).

  Using the obtained low pressure change rate GLP, the target low pressure TLP, and the differential component adjustment coefficient CD, the differential component KD of the output change rate K is calculated from Equation 3 below (S102). The differential component adjustment coefficient CD is a constant adjusted according to the installation environment of the refrigeration apparatus. Based on the differential component KD, it is possible to obtain an operating frequency that can output the refrigeration capacity required by the refrigeration system at the low pressure when the low pressure LP changes minutely at the current low pressure change rate GLP.

  Using the current low pressure LP, the target low pressure TLP, and the integral component adjustment coefficient CI, the integral component KI of the output change rate K is calculated from Equation 4 below (S103). The integral component adjustment coefficient CI is a constant adjusted according to the installation environment of the refrigeration apparatus. The integral component KI is a value obtained by accumulating the past integral component PKI and the difference between the current low-pressure pressure LP and the target low-pressure pressure TLP, and an operation frequency that can correct the offset between the target low-pressure pressure TLP and the low-pressure pressure LP can be obtained. it can.

  Since the current integral component KI obtained by Equation 4 corresponds to the past integral component PKI in the next step, the past integral component PKI is replaced with the current integral component KI according to Equation 5 below.

  Note that the accumulation of the integral component KI and the past integral component PKI needs to be reset every predetermined time CT (S106), and therefore is counted by the accumulation time ITIME (S103). Although the mathematical formula shown in step S103 in FIG. 4 is different from the mathematical formula 4, this has the same meaning as executing the mathematical formula 4 and the mathematical formula 5 in order. In step S107, the past integral component PKI is not used because it is not used.

  When the operation frequency CF is less than the maximum operation frequency MAXCF, which is the maximum value of the inverter compressor operation frequency (S104), no offset due to saturation of the operation frequency CF has occurred, so the integral component KI and the accumulated time ITIME are reset. (S107).

  When the low pressure LP is equal to or lower than the target low pressure TLP (S105), the integral component KI and the accumulated time ITIME are reset (S107) because there is no offset causing the refrigeration capacity shortage.

  Using the proportional component KP, the differential component KD, and the integral component KI obtained from the above, the output change rate K is calculated from the following Equation 6 (S108).

  In the case where the current low pressure change rate GLP is maintained, the reference low pressure after the reference time CG is calculated from Equation 7 below (S109).

  When the obtained reference low pressure is within the range around the target low pressure TLP (upper limit HLP and lower limit LLP) (S109), it is sufficient to continue the operation with the current operation frequency CF, so the output change rate K is set to 1. (S110).

  Using the current operating frequency CF and the output change rate K, the target operating frequency TCF is calculated from the following formula 8 (S111).

  Next, the target operation frequency TCF is adjusted so that the obtained target operation frequency TCF becomes an appropriate value. At this time, in this embodiment, an energy saving mode for saving energy consumption of the refrigeration apparatus is installed, and the target operating frequency is adjusted simultaneously in the normal mode or the energy saving mode. The flow for adjusting the target operating frequency TCF is shown in FIG.

  When the current operation frequency CF is smaller than the minimum operation frequency MINCF, which is the minimum operation frequency capable of stably operating the inverter compressor (S201), that is, when the inverter compressor is stopped, the target operation The frequency TCF is set to the minimum operating frequency MINCF (S204).

  When the target operating frequency TCF is smaller than the minimum operating frequency MINCF (S202) and in the energy saving mode (S205), the target operating frequency TCF is set to 0 and the compressor is stopped (S206). When not in the energy saving mode, the target operating frequency TCF is set to the minimum operating frequency MINCF in order to stably operate the inverter compressor (S204).

  When the target operating frequency TCF is higher than the maximum operating frequency MAXCF (S203), the target operating frequency TCF is set to the maximum operating frequency MAXCF in order to operate the inverter compressor normally (S207).

  As described above, it is possible to obtain the target operating frequency TCF that can realize the low pressure TLP that can output the refrigeration capacity required by the refrigeration system. In this control method, adjustment of the constants CD, CI, and CG is necessary at the beginning of installing the refrigeration apparatus, but unlike the conventional zone control, no threshold is required. In zone control, excessive operation was necessary to ensure the necessary refrigeration capacity, but this control method always calculates the necessary refrigeration capacity and controls the inverter compressor's operating frequency as needed. The refrigeration capacity can be output more quickly and energy-saving operation with better operating efficiency is possible.

  FIG. 2 is a refrigerant circuit diagram of a refrigeration apparatus to which the present invention is applied. This refrigeration apparatus is composed of three compressors, 10 is an inverter scroll compressor (inverter compressor) whose rotation speed can be controlled by an inverter, and 11 and 12 are constant speed scroll compressors (constant constant) operated by commercial power. Fast compressor). In the present invention, these compressors are applicable to either a hermetic type or a semi-hermetic type regardless of the type of compression method such as a reciprocating type, a screw type, and a rotary type.

  In this embodiment, an HFC refrigerant is assumed as the refrigerant to be used, but the same effect can be obtained by using other refrigerants such as a CFC refrigerant, an HCFC refrigerant, and a natural refrigerant.

  The compressors 10, 11, and 12 are connected in parallel to both the discharge port and the suction port. Each compressor sucks and compresses a low-temperature and low-pressure gas refrigerant and discharges it as a high-temperature and high-pressure refrigerant. The discharged high-temperature and high-pressure refrigerant merges and flows into the oil separator 13. In the oil separator 13, the lubricating oil contained in the refrigerant is separated and stored.

  The separated lubricating oil flows into the strainer 27 through the service valve 26, and contaminants in the lubricating oil are removed by the strainer 27. The lubricating oil from which the contaminants have been removed branches and is returned to the compressors 10, 11, 12 via the solenoid valves 28, 30, 32. At this time, the amount of lubricating oil in each compressor is measured by the float switches 23, 24, 25 installed in each compressor, and the solenoid valve 28 is set so that the amount of lubricating oil in each compressor becomes more than the required amount. , 30, 32 are opened and closed.

  In addition, when liquid refrigerant is included in the lubricating oil returned to the compressor, the compression mechanism in the compressor may be insufficiently lubricated and may be defective. Therefore, the pressure is reduced in the capillary tubes 29, 31, and 33, and the refrigerant is completely discharged. Vaporize. By evaporating the refrigerant with the capillary tubes 29, 31, 33, there is also an effect of cooling the lubricating oil.

  The refrigerant from which the lubricating oil has been removed in the oil separator 13 flows into the condenser 14, and the high-temperature and high-pressure refrigerant is cooled by the cooling fan 63 and condensed and liquefied. In this embodiment, an air-cooled condenser is used, but a water-cooled or evaporative condenser may be used. In this embodiment, an integrated refrigerator in which the condenser and the compressor are disposed in the same casing is assumed. However, the present invention is not limited to this, and the refrigerator and the condensing unit are separately provided. A separate installation type may be used.

  The refrigerant liquefied in the condenser 14 flows out of the condenser 14 and is stored in the receiver tank 15. The receiver tank 15 has a fusible plug 46 in order to prevent an explosion when a defect occurs in the refrigeration apparatus and the pressure and temperature inside the refrigerant circuit become extremely high.

  As the high pressure of the compressor, the refrigeration apparatus measures the pressure in the receiver tank 15 and controls the compressor and the like. The receiver tank 15 is connected to a high pressure sensor 58 via a capillary tube 57, and the high pressure sensor 58 measures the high pressure of the compressor. The receiver tank 15 is connected to a high pressure gauge 62 via capillary tubes 57 and 61 in order to observe the high pressure of the compressor as needed.

  In order to increase the refrigerating capacity of the liquid refrigerant, the liquid refrigerant stored in the receiver tank 15 is supercooled by the air cooling by the cooling fan 63 in the supercooler 16 again. In the present embodiment, the condenser 14 and the supercooler 16 are integrated, but the condenser and the supercooler may be provided separately.

  The supercooled liquid refrigerant flows into the filter dryer 17 through the service valve 48. The moisture in the refrigerant is removed by the filter dryer 17, and after confirming the amount of moisture by the moisture indicator 18, the liquid refrigerant flows out to an evaporator (not shown) such as a showcase installed in the store.

  In this embodiment, a liquid injection mechanism is used to cool the compressor. For this reason, from the receiver tank 15 to the compressors 10, 11, 12 via the service valves 34, 38, 42 and the strainers 35, 39, 43 and the motorized valves 36, 40, 44 and the electromagnetic valves 37, 41, 45, respectively. A liquid injection circuit is provided. In the pressure reduction operation of the liquid injection circuit, the pressure may be reduced by a capillary tube or an expansion valve.

  The liquid refrigerant from which contaminants have been removed by the strainers 35, 39, 43 is decompressed by the motor-operated valves 36, 40, 44, and the compressors 10, 11, 12 are cooled. The degree of opening / closing of the electromagnetic valves 37, 41, 45 and the degree of opening / closing of the electric valves 36, 40, 44 are adjusted by the operating state of the compressor and the temperature of the compressor. When the high pressure of the compressor becomes very large, the compressors are urgently stopped by the high pressure switches 52, 54, 56 provided in the compressors 10, 11, 12.

  Since the refrigerant that has been vaporized and cooled in the evaporator and has reached low temperature and low pressure may return to the refrigeration system including the liquid refrigerant (liquid back), the refrigerant and the gaseous refrigerant are allowed to flow into the accumulator 19 once and then the liquid refrigerant and the gaseous refrigerant are To separate. Possible causes of liquid back include expansion valve defects and clogged evaporator filters. Liquid refrigerant enters the cases of the compressors 10, 11, and 12 due to liquid back, and the compression mechanism is damaged by liquid compression. In addition, there is a possibility of insufficient lubrication due to a large amount of lubricating oil being discharged together when the liquid refrigerant is discharged.

  In the accumulator 19, the liquid refrigerant is stored, and only the gaseous refrigerant flows out, and is sucked into the compressors 10, 11, and 12 through the strainers 20, 21, and 22, respectively. In this embodiment, since the pressure of the refrigerant returned from the evaporator is used as the low pressure of the compressor, the inlet side of the accumulator 19 is connected to the low pressure sensor 59 by piping.

  Next, the operation control method of the inverter compressor 10 and the constant speed compressors 11 and 12 in the present embodiment will be described with reference to FIGS. 2 and 6 to 9. In this embodiment, since a plurality of compressors are mounted, operation control of the compressor is performed using the total operation frequency SCF of the entire refrigeration apparatus. In this control method, the target total operation frequency TSCF required by the refrigeration system is obtained from the current low pressure LP, total operation frequency SCF, and target low pressure TLP. The target operation frequency TCF and the target operation number TNC are obtained from the obtained target total operation frequency TSCF, and the operation frequency of the inverter compressor and the operation number of the constant speed compressor are controlled so as to become the target operation frequency TCF and the target operation number TNC. To do.

  FIG. 6 is a flowchart for calculating the target total operation frequency TSCF. First, at the stage where calculation of the target total operation frequency TSCF is started (S300), the low pressure LP is measured. Since the target low pressure TLP is a value unique to the refrigeration apparatus, the target low pressure TLP is set to a low pressure at which the refrigeration capacity required by the refrigeration system can be stably supplied by performing experiments in advance.

  The total operating frequency SCF is calculated from Equation 9 below using the operating frequency CF of the inverter compressor 10 and the operating number NC of the constant speed compressors 11 and 12 (S301).

  Here, the constant speed conversion frequency CCF is an operation frequency of the inverter compressor that has a discharge amount equal to the discharge amount when one constant speed compressor is operated at the power supply frequency. The constant speed conversion frequency CCF is determined by the combination of the inverter compressor and the constant speed compressor mounted on the refrigeration apparatus and the power supply frequency of the constant speed compressor.

  In the compressor used in the present embodiment, the discharge amount of a 10 horsepower constant speed compressor operating at a power frequency of 50 Hertz is equal to the discharge amount of a 10 horsepower inverter compressor operating at an operating frequency of 60 Hertz. I have confirmed. From this, the operating frequency of the operating constant speed compressor is converted to an operating frequency of 60 Hz of the inverter compressor, and the total operating frequency of the entire refrigeration apparatus is calculated.

  It has been confirmed that the discharge amount of a 10-horsepower constant speed compressor operating at a power frequency of 60 Hz is equal to the discharge amount of a 10-horsepower inverter compressor operating at an operating frequency of 72 Hz. When using this refrigeration system in the Hertz region, CCF is converted to 72 Hertz.

  In order to verify the validity of this method, the total operating frequency of the entire refrigeration system calculated in the refrigeration system with the valve opening of the expansion valve fixed, and when the refrigeration system is in a steady state at the total operating frequency at that time FIG. 10 shows the relationship with the low pressure. As the total operating frequency increases, the low-pressure pressure decreases almost uniformly, indicating that the controllability of the refrigeration apparatus is good. Moreover, since the same tendency is shown irrespective of the difference in power supply frequency, there is no difference in controllability depending on the power supply frequency in the area where the refrigeration apparatus is installed.

  The target total operation frequency TSCF is obtained by integrating the output change rate K with the current total operation frequency SCF. This output change rate K includes a proportional component KP, a differential component KD, and an integral component KI. The proportional component KP is calculated from Equation 1 (S302). With the proportional component KP, it is possible to obtain a total operating frequency that can output the refrigeration capacity required by the refrigeration system at the current low pressure LP.

  The low pressure sensor 59 measures the low pressure LP of the compressors 10, 11, and 12 every predetermined time TS, and uses the low pressure PLP and the low pressure LP before the predetermined time TS measured immediately before the current measurement. Then, the change rate GLP of the low pressure is calculated from Equation 2 (S303).

  Using the obtained low pressure change rate GLP, target low pressure TLP, and differential component adjustment coefficient CD, the differential component KD of the output change rate K is calculated from Equation 3 (S303). The differential component adjustment coefficient CD is a constant adjusted according to the installation environment of the refrigeration apparatus. Based on the differential component KD, it is possible to obtain an operating frequency that can output the refrigeration capacity required by the refrigeration system at the low pressure when the low pressure LP changes minutely at the current low pressure change rate GLP.

  Using the current low pressure LP, the target low pressure TLP, and the integral component adjustment coefficient CI, the integral component KI of the output change rate K is calculated from Equation 4 (S304). The integral component adjustment coefficient CI is a constant adjusted according to the installation environment of the refrigeration apparatus. The integral component KI is a value obtained by accumulating the past integral component PKI and the difference between the current low-pressure pressure LP and the target low-pressure pressure TLP, and an operation frequency that can correct the offset between the target low-pressure pressure TLP and the low-pressure pressure LP can be obtained. it can.

  Since the current integral component KI obtained by Equation 4 corresponds to the past integral component PKI in the next step, the past integral component PKI is replaced with the current integral component KI according to Equation 5 below.

  Note that the accumulation of the integral component KI needs to be reset every predetermined time CT (S307), and therefore is counted by the accumulation time ITIME (S304). Note that the mathematical formula shown in step S304 in FIG. 4 is different from the mathematical formula 4, but this has the same meaning as executing the mathematical formula 4 and the mathematical formula 5 in order. In step S308, the past integral component PKI is not used because it is not used.

  If the operating frequency CF is less than the maximum operating frequency MAXCF, which is the maximum value of the inverter compressor operating frequency (S305), the offset due to saturation of the operating frequency CF has not occurred, so the integral component KI and the accumulated time ITIME are reset. (S308).

  Further, when the low pressure LP is equal to or lower than the target low pressure TLP (S306), the offset that causes the refrigeration capacity shortage has not occurred, so the integral component KI and the accumulated time ITIME are reset (S308).

  Using the proportional component KP, differential component KD, and integral component KI obtained from the above, the output change rate K is calculated from the equation 6 (S309).

  When the current low pressure change rate GLP is maintained, the reference low pressure after the reference time CG is calculated from Equation 7 (S310).

  When the obtained reference low pressure is within the range around the target low pressure TLP (upper limit HLP and lower limit LLP) (S310), it is sufficient to continue the operation with the current total operation frequency SCF. It is set to 1 (S311).

  Using the current total operating frequency SCF and the output change rate K, the target total operating frequency TSCF is calculated from the following formula 10 (S312).

  Next, the target operation frequency TCF of the inverter compressor and the target operation number TNC of the constant speed compressor are calculated from the obtained target total operation frequency TSCF (S400). In this embodiment, an energy saving mode for saving energy consumption of the refrigeration apparatus is installed, and the target operating frequency TCF is adjusted simultaneously in the normal mode or the energy saving mode. FIG. 7 is a flowchart for calculating the target operating frequency TCF and the target operating number NC from the target total operating frequency TSCF.

  When the current total operating frequency SCF is smaller than the minimum operating frequency MINCF, which is the minimum operating frequency at which the inverter compressor can be stably operated (S401), that is, when the inverter compressor is stopped, the target The number of operating units TNC is set to 0, and the target operating frequency TCF is set to the minimum operating frequency MINCF (S406).

  When the target total operation frequency TSCF is smaller than the minimum operation frequency MINCF (S402) and in the energy saving mode (S407), the target operation number TNC is set to 0 and the target operation frequency TCF is set to 0 (S408). When not in the energy saving mode, the target operation frequency TCF is set to MINCF and the target operation number TNC is set to 0 in order to give priority to cooling (S406).

  When both the total operation frequency SCF and the target total operation frequency TSCF are greater than the minimum operation frequency MINCF, the target operation number is calculated from the following formula 11 (S403). Here, MAXCF is the maximum value (maximum operating frequency) of the operating frequency at which the inverter compressor can operate, and INT represents the maximum integer value that does not exceed the numerical value in parentheses.

  From the obtained target operation number TNC and the target total operation frequency TSCF, the target operation frequency TCF is calculated from the following Equation 12 (S404).

  From the above, the target operation frequency TCF and the target operation number TNC are obtained. Here, in order to prevent the constant speed compressor from starting before the operating frequency CF of the inverter compressor reaches the maximum operating frequency MAXCF, the start of the constant speed compressor is suppressed (S500). Further, in this embodiment, a high freshness mode for keeping the output of the refrigeration apparatus high is installed, and the target operating frequency in the normal mode or the high freshness mode is adjusted simultaneously. FIG. 8 shows a flowchart of the constant speed compressor start suppression.

  When the operating number NC is larger than the target operating number TNC (S501), the constant speed compressor does not start, so start suppression control is not performed. When the operating number NC is larger than the target operating number TNC and in the high freshness mode (S502), and the target operating frequency TCF is lower than the predetermined operating frequency LCF (S503), the target operating number TNC is set to TNC-1, and the target The operation frequency is set to the maximum operation frequency MAXCF (S504). That is, the output is increased by operating the inverter compressor at the maximum operating frequency MAXCF, and the start of the constant speed compressor is suppressed.

  When the operating number NC is larger than the target operating number TNC and not in the high freshness mode (S502), and the target operating frequency TCF is lower than the predetermined operating frequency HCF (S505), the target operating number TNC is set to TNC-1, and the target The operation frequency is set to the maximum operation frequency MAXCF (S504). That is, the output is increased by operating the inverter compressor at the maximum operating frequency MAXCF, and the start of the constant speed compressor is suppressed. Note that the predetermined operating frequency LCF is set to a value smaller than the predetermined operating frequency HCF, and in the high freshness mode, priority is given to the refrigeration capacity, so starting of the constant speed compressor is less likely to be suppressed than in the normal mode. .

  Next, in order to prevent deterioration of the constant speed compressor due to repeated start and stop of the constant speed compressor, the start and stop of the constant speed compressor is suppressed (S600). However, if the constant speed compressor is excessively suppressed, the low pressure LP greatly fluctuates due to excessive or insufficient refrigeration capacity, so that the low pressure LP is within the range around the target low pressure TLP. Need to control. In this embodiment, the upper limit value of this range is HLP2, and the lower limit value is LLP2. In addition, since excessive or insufficient refrigeration capacity is generated by suppressing the start / stop of the constant speed compressor for a long time regardless of the low pressure LP, a time limit is continuously set for the start / stop suppression.

  FIG. 9 shows a flowchart of the start / stop suppression of the constant speed compressor. When the target operating number TNC is equal to the operating number NC (S601), since it is not necessary to suppress the start / stop, the target operating frequency TCF and the target operating number TNC are not changed. The time during which the start / stop of the constant speed compressor is suppressed is measured by the start / stop suppression count RC (S602).

  The reference low pressure obtained from Equation 7 is calculated, and when the reference low pressure is equal to or higher than the upper limit value HLP2 (S603), the start / stop suppression count RC is replaced with the start / stop suppression limit CRC + 1 (S604). By replacing the start / stop suppression count RC in this way, it is possible to invalidate the start / stop suppression even when the start / stop suppression count RC is less than the start / stop suppression limit CRC.

  When the reference low pressure is not the upper limit value HLP2 and not more than the lower limit value LLP2 (S605), the start / stop suppression count RC is replaced with the start / stop suppression limit CRC + 1. By replacing the start / stop suppression count RC in this way, it is possible to invalidate the start / stop suppression even when the start / stop suppression count RC is less than the start / stop suppression limit CRC.

  When the reference low pressure is not higher than the upper limit HLP2 and not lower than the lower limit LLP2, the start / stop suppression count RC is not changed. Therefore, the start / stop suppression is not invalidated when the start / stop suppression count RC is less than the start / stop suppression limit CRC.

  When the start / stop suppression count RC is smaller than the start / stop suppression limit CRC (S606) and the target operation number TNC is larger than the operation number NC (S607), the target operation number TNC is replaced with the operation number NC, and the target operation frequency TCF is replaced with maximum operating frequency MAXCF (S608). In this way, the output of the refrigeration system is secured by maximizing the output of the inverter compressor without increasing the number of operating constant speed compressors, and the frequency of starting and stopping of the constant speed compressor is suppressed. .

  When the start / stop suppression count RC is smaller than the start / stop suppression limit CRC and the target operation number TNC is smaller than the operation number NC, the target operation number TNC is replaced with the operation number NC, and the target operation frequency TCF is replaced with the minimum operation frequency MINCF. (S609). Thus, without increasing the number of operating constant speed compressors, the output of the refrigeration system is reduced by minimizing the output of the inverter compressor, and the frequency of starting and stopping of the constant speed compressor is suppressed. .

  When the start / stop suppression count RC is larger than the start / stop suppression limit CRC, the start / stop suppression count RC is reset to 0 (S610), and control for starting and stopping the constant speed compressor is performed.

  Here, when the target operating number TNC is larger than the operating number NC + 2 (S611), the target operating number TNC is replaced with the operating number NC + 1, and the target operating frequency TCF is replaced with the maximum operating frequency MAXCF (S612). In this way, it is possible to suppress the increase in the number of operating constant speed compressors by two or more at one time, keep the increase by one, and ensure the output of the refrigeration system by maximizing the output of the inverter compressor to ensure constant speed compression. The frequency of starting and stopping the machine has been reduced. When the target operating number TNC is smaller than the operating number NC-2 (S613), the target operating number TNC is replaced with the operating number NC-1, and the target operating frequency TCF is replaced with the minimum operating frequency MINCF (S614). In this way, it is possible to suppress the decrease in the number of operating constant-speed compressors by two or more at a time, and to keep the decrease in one unit, to reduce the output of the refrigeration system by minimizing the output of the inverter compressor and to keep The frequency of the start and stop of the high-speed compressor is suppressed.

  When the target operation number TNC is smaller than the operation number NC + 2 and the target operation number TNC is larger than the operation number NC-2, the target operation frequency TCF and the target operation number TNC are not changed.

  From the above, in the refrigeration apparatus in which a plurality of compressors are mounted, the target operating frequency TCF and the target operating number TNC that can supply the refrigeration capacity required by the refrigeration system can be obtained.

  In this embodiment, the constant speed compressors 11 and 12 use the same output compressors. However, when using compressors having different outputs, the constant speed conversion frequency CCF is obtained for each compressor and operates. The total operating frequency SCF can be obtained from the following Equation 13 by obtaining the sum of the constant speed conversion frequencies CCF corresponding to the constant speed compressor. Si represents the operating state of the constant speed compressor i, which is 1 when operating and 0 when stopped. CCFi is a constant speed conversion frequency of the constant speed compressor i.

  In both the first and second embodiments, the low pressure LP fluctuates with a certain range, so that the average value within the predetermined time TS is used to stabilize the compressor operation control. Is desirable.

  In addition, in order to prevent large fluctuations in the target operating frequency and the target total operating frequency, the target operating frequency and the target total operating frequency obtained by the calculation, the average value of the current operating frequency and the total operating frequency are set as the new target operating frequency. Further, control may be performed so that the target total operation frequency is obtained.

It is a refrigerant circuit diagram of the refrigerating device in which one compressor to which the present invention is applied is mounted. It is a refrigerant circuit diagram of a refrigerating device in which a plurality of compressors to which the present invention is applied are mounted. It is the figure which showed the example regarding the time change of a low pressure pressure. It is a flowchart figure at the time of calculating target operation frequency TCF in the refrigerating device carrying one inverter compressor to which the present invention is applied. It is a flowchart figure at the time of adjusting target operation frequency TCF in the refrigerating device carrying one inverter compressor to which this invention is applied. It is a flowchart figure at the time of calculating the target operation frequency TCF and the target operation number TNC in the refrigeration apparatus equipped with a plurality of compressors to which the present invention is applied. It is a flowchart figure at the time of preparing target operation frequency TCF and target operation number TNC in the refrigerating device in which a plurality of compressors to which the present invention is applied are mounted. It is a flowchart figure at the time of suppressing starting of a constant speed compressor in the refrigerating device in which a plurality of compressors to which the present invention is applied are mounted. It is a flowchart figure at the time of suppressing the start and stop of a constant speed compressor in the refrigerating device in which a plurality of compressors to which the present invention is applied are mounted. It is a graph showing the relationship between the total operation frequency to which this invention is applied, and low pressure pressure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Inverter scroll compressor 11, 12 Constant speed scroll compressor 13 Oil separator 14 Condenser 15 Receiver tank 16 Subcooler 17 Filter dryer 18 Moisture indicator 19 Accumulator 20, 21, 22, 27, 35, 39, 43 Strainers 23, 24, 25 Float switch 26, 34, 38, 42, 47, 48 Service valve 28, 30, 32, 37, 41, 45 Solenoid valve 29, 31, 33, 49, 51, 53, 55, 57, 61 Capillary tube 36, 40, 44 Electric valve 46 Soluble plug 50 Low pressure switch 52, 54, 56 High pressure switch 58 High pressure sensor 59 Low pressure sensor 60 ECC board 62 High pressure gauge 63 Cooling fan

Claims (4)

At least one variable speed compressor with a variable operating frequency, at least one constant speed compressor with a constant operating frequency, a pressure detector disposed on the low pressure side of these compressors, In a refrigeration apparatus comprising a control device that controls the operating frequency and the number of operating units according to the load,
Low pressure is measured by the pressure detector,
The reference low pressure is calculated from the current low pressure and the past low pressure,
When the reference low pressure is not less than the upper limit value or less than the lower limit value of the predetermined range and a signal for increasing the number of operating constant speed compressors by two or more is output from the control device,
A refrigerating apparatus characterized in that the number of increased operating speeds of the constant speed compressor is one and the operating frequency of the variable speed compressor is maximized. At least one variable speed compressor with a variable operating frequency, at least one constant speed compressor with a constant operating frequency, a pressure detector disposed on the low pressure side of these compressors, In a refrigeration apparatus comprising a control device that controls the operating frequency and the number of operating units according to the load,
Low pressure is measured by the pressure detector,
The reference low pressure is calculated from the current low pressure and the past low pressure,
When the reference low pressure is not less than the upper limit value or less than the lower limit value of the predetermined range, and a signal for reducing the number of operating constant speed compressors by two or more is output from the control device,
A refrigerating apparatus characterized in that the number of operating units of the constant speed compressor is reduced and the operating frequency of the variable speed compressor is minimized. At least one variable speed compressor with a variable operating frequency, at least one constant speed compressor with a constant operating frequency, a pressure detector disposed on the low pressure side of these compressors, In a refrigeration apparatus comprising a control device that controls an operating frequency and the number of operating units according to a load, and a start / stop suppression device that suppresses repeated start / stop of the constant speed compressor,
Low pressure is measured by the pressure detector,
The reference low pressure is calculated from the current low pressure and the past low pressure,
When the reference low pressure is not less than the upper limit value of a predetermined range and a signal for suppressing on / off of the constant speed compressor is output from the on / off suppressing device,
A refrigeration apparatus, wherein a suppression signal from the start / stop suppression apparatus is invalidated. At least one variable speed compressor with a variable operating frequency, at least one constant speed compressor with a constant operating frequency, a pressure detector disposed on the low pressure side of these compressors, In a refrigeration apparatus comprising a control device that controls an operating frequency and the number of operating units according to a load, and a start / stop suppression device that suppresses repeated start / stop of the constant speed compressor,
Low pressure is measured by the pressure detector,
The reference low pressure is calculated from the current low pressure and the past low pressure,
When the reference low pressure is not more than a lower limit value of a predetermined range and a signal for suppressing on / off of the constant speed compressor is output from the on / off suppressing device,
A refrigeration apparatus, wherein a suppression signal from the start / stop suppression apparatus is invalidated.