JP2006234320A - Refrigerating machine and its capacity control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a refrigerating machine and its capacity control method capable of keeping a compressor in an operation state of high efficiency corresponding to load, to achieve an energy saving operation of the refrigerating machine. <P>SOLUTION: As shown in Fig. 2, this vapor compression type refrigerating machine comprises an evaporator 10 producing cold water, a condenser 30 radiating heat to cooling water, a restricting mechanism 40 mounted between the condenser 30 and the evaporator 10, the compressor 20, and a motor 50 for driving the compressor 20. The compressor 20 is a centrifugal compressor comprising a suction guide vane 25, an invertor 80 is mounted for driving and controlling the motor 50, and further a control means 70 is mounted to control a capacity of the compressor 20 by controlling opening and closing of the guide vane 25, and a rotational frequency of the compressor 20 by the invertor 80. A cold water temperature detector 90 is mounted for detecting a cold water outlet temperature of the evaporator 10, and the control means 70 controls the rotational frequency of the compressor 20 and the opening and closing of the suction guide vane 25 to control the cold water outlet temperature detected by the cold water temperature detector 90 to a predetermined target value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a refrigerator and a capacity control method thereof.

  Conventionally, an evaporator that produces cold water, a condenser that dissipates the heat taken into the system to the cooling water, a compressor that is a booster required to configure the system, and a throttle that generates a low temperature by reducing the pressure from the condenser There is a vapor compression refrigerator having a mechanism (pressure reduction device) as a basic component. FIG. 1 is an overall schematic configuration diagram showing an example of a conventional vapor compression refrigerator 500 of this type. As shown in the figure, the vapor compression refrigerator 500 includes an evaporator 510, a compressor 520, a condenser 530, and a decompression device 540. In each of these devices, the refrigerant evaporates, presses and compresses, condenses, and The refrigeration cycle is configured by repeating the decompression. That is, this refrigeration cycle manufactures chilled water with a cold heat source obtained by the evaporator 510 to cope with the load, while supplying heat from the evaporator 510 taken into the refrigeration system and the electric motor 521 that drives the compressor 520. The amount of work performed by the compressor 520 is discharged into the cooling water supplied to the condenser 530. On the other hand, a commercial power source 570 is directly connected to the motor 521 via a motor starting means 560. Generally, the motor 521 is started as a current reducing device at the time of starting via a condorfa or a reactor device (not shown). The number rotates substantially in accordance with the frequency of the commercial power source 570, and no means for changing the number of rotations is provided. In addition, as a means for detecting the fluctuation of the load, a cold water temperature detector 513 is installed at the cold water outlet 511 of the evaporator 510, and this measurement signal is taken into the refrigerator operating means 580 and compressed so that the cold water outlet temperature always becomes a target value. The capacity of the machine 520 is controlled. The control method is such that if the cold water outlet temperature rises above a target value, the suction guide vane 525 installed in the compressor 520 is opened to increase the suction capacity of the compressor 520 to increase the capacity of the vapor compression refrigerator 500. This is a simple control method in which the chilled water outlet temperature is brought close to the target value and, on the other hand, if the chilled water outlet temperature falls below the target value, the chilled water outlet temperature is brought close to the target value by the reverse operation.

  As another method for controlling the suction capacity of the compressor 520, there is a method in which a pressure reducing device is provided in the connecting pipe 590 connecting the evaporator 510 and the compressor 520 to adjust the pressure loss. There is nothing superior to the suction guide vane 525 as the suction performance control means.

  However, since the compressor 520 is designed so that a predetermined suction capacity and work can be obtained with the suction guide vane 525 fully opened, if the suction guide vane 525 operates in a direction in which the suction capacity decreases, the compressor 520 naturally. The efficiency of 520 is reduced as compared with the operation in the designed state. As a result, the energy saving operation of the refrigerator 500 cannot be performed.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a refrigerator that can maintain the compressor in a high-efficiency operation state corresponding to a load and can achieve energy-saving operation of the refrigerator, and a capacity control method thereof. There is to do.

  Capacitance control in a refrigerator that has an evaporator, a centrifugal compressor, a condenser, and a decompression device as basic components changes the suction capacity of the compressor so that the chilled water outlet temperature becomes the target value. It is to change the capacity. Therefore, in the present invention, not only the suction guide vane is controlled as in the prior art, but also the electric motor is driven by an inverter to make the rotation speed variable, and the compressor is maintained in a high-efficiency operation region, thereby enabling the energy-saving operation of the refrigerator. I was able to. In this case, it is preferable to take measures to avoid surging specific to a centrifugal compressor. That is, in order to keep the compressor in a highly efficient operation at all times with respect to load fluctuations and cooling water temperature fluctuations, in the present invention, the conventional suction guide vane control is added to the rotational speed control and the control is used in combination. However, since the centrifugal compressor has a unique surging phenomenon, the rotation speed control cannot be continued regardless of the cooling water temperature, and the cooling water temperature rises during operation at the design rotation speed or lower, and the compressor If the required work increases, the surging area will be reached and stable operation of the compressor becomes impossible. And in order to avoid this surging, the limit work to reach the surging of the compressor is increased by increasing the rotation speed. On the other hand, if the increased rotation speed is maintained, the cooling water temperature is reduced. It will be out of the high-efficiency operating range of the machine, and it will not be energy saving operation as a refrigerator. Therefore, in the present invention, the compressor speed control and the guide vane control are used together to maintain the energy saving operation of the refrigerator, and further, the compressor can be stably operated by avoiding the surging peculiar to the centrifugal compressor. I made it.

  That is, the invention described in claim 1 includes an evaporator for producing cold water, a condenser for radiating heat to the cooling water, a decompression device provided between the condenser and the evaporator, a compressor, and an electric motor for driving the compressor. The compressor is constituted by a centrifugal compressor provided with a suction guide vane, an inverter for driving and controlling the electric motor is installed, and the guide vane The refrigerator is provided with control means for controlling the capacity of the compressor by opening and closing and controlling the number of revolutions of the compressor by an inverter.

  The invention according to claim 2 of the present application is provided with a chilled water temperature detector for detecting a chilled water outlet temperature of the evaporator, and the control means has a predetermined target for the chilled water outlet temperature detected by the chilled water temperature detector. The refrigerator according to claim 1, wherein the rotation speed of the compressor and the opening / closing of the suction guide vane are controlled so as to be a value.

  The invention according to claim 3 of the present application includes a cooling water temperature detector for detecting the inlet or outlet temperature of the cooling water, a low pressure side pressure detector for detecting an evaporator pressure or a compressor suction pressure, a condenser pressure or A high pressure side pressure detector for detecting the compressor discharge pressure is installed, and the control means is calculated from the detected inlet or outlet temperature of the cooling water, the detected low pressure value, and the detected high pressure value. The refrigerator according to claim 2, wherein the rotation speed of the compressor and the suction guide vane of the compressor are controlled so that the operation state of the compressor always falls within a predetermined operable range. is there.

  The invention according to claim 4 of the present application is characterized in that a switching device is provided for switching between a case where the electric motor is driven from a commercial power source via the inverter and a case where the motor is driven directly from the commercial power source. 1 in the refrigerator.

  The invention according to claim 5 of the present invention drives an evaporator for producing cold water, a condenser for radiating heat to the cooling water, a decompression device provided between the condenser and the evaporator, a centrifugal compressor, and a compressor. In a method for controlling a vapor compression refrigerator that includes an electric motor that combines the above, a suction guide vane control provided in the compressor is combined with an inverter control of a compressor rotation speed by an inverter that drives and controls the electric motor. Thus, there is provided a control method for a refrigerator, wherein capacity control of the compressor is performed.

  The invention according to claim 6 of the present application detects the temperature of the cold water outlet, and controls the rotation speed of the compressor and the opening / closing of the suction guide vane so that the cold water outlet temperature becomes a predetermined target value. It exists in the control method of the refrigerator of Claim 5.

  The invention according to claim 7 of the present invention includes an inlet or outlet temperature to the condenser of the cooling water, a low pressure side pressure that is the evaporator pressure or a compressor suction pressure, and the condenser pressure or the compressor discharge pressure. Detects a certain high-pressure side pressure, and controls the compressor speed and compressor suction guide vane so that the compressor operating state calculated from these detected values always falls within the predetermined operable range. The method of controlling a refrigerator according to claim 6.

  In the invention according to claim 8 of the present application, when performing the inverter control, the limit work for avoiding the surging of the compressor at the current rotational speed is determined from the detected value of the inlet or outlet temperature of the cooling water. Calculate the theoretical work of the compressor from the detected value of the low-pressure side pressure and the detected value of the high-pressure side pressure, compare the theoretical work and the limit work, and continue the inverter control if the theoretical work is less than the limit work 8. The refrigerator control method according to claim 7, wherein when the theoretical work reaches the limit work, the current rotation speed is fixed or the limit rotation speed is increased to shift to guide vane control.

  The invention described in claim 9 is characterized in that when the cooling water inlet or outlet temperature is higher than the design temperature, the motor is driven directly from a commercial power source without using an inverter. It is in the control method of the refrigerator.

  According to the present invention, in addition to the method of controlling the suction capacity of the compressor with the guide vane, the motor can be controlled by controlling the number of revolutions of the compressor by using a frequency variable inverter drive. Capacity control operation is possible with energy saving.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 2 is an overall schematic configuration diagram showing a refrigerator (vapor compression refrigerator) 1-1 according to the first embodiment of the present invention. As shown in the figure, the refrigerator 1-1 includes an evaporator 10 that produces cold water, a compressor (centrifugal compressor) 20 that raises and raises the temperature of the refrigerant from the evaporator 10 to the condenser 30, and this refrigeration. A condenser 30 for releasing the heat taken into the machine 1-1 to the cooling water, and a throttle mechanism (pressure reduction device) 40 provided between the condenser 30 and the evaporator 10 for reducing the pressure from the condenser 30 to the pressure of the evaporator 10. An electric motor 50 that drives the compressor 20, an electric motor start panel 60 that is used to start and stop the electric motor 50, and an inverter 80 that supplies the electric motor 50 with freely controlled frequency of the power supplied from the commercial power source 75. And a control means 70 for controlling the operation of the refrigerator 1-1 by outputting an inverter control signal indicating the frequency of the power supplied to the electric motor 50 to the inverter 80, and detecting a cold water outlet temperature of the evaporator 10. Cold water temperature sensor , A cooling water temperature detector 100 for detecting the cooling water inlet temperature of the condenser 30, a low pressure side pressure detector 110 for detecting the pressure of the refrigerant (low pressure side pressure) in the evaporator 10, and the condenser 30. And a high pressure side pressure detector 120 for detecting the pressure of the refrigerant inside (high pressure side pressure). The compressor 20 includes a centrifugal single-stage or multi-stage impeller 23 in the casing 21, a guide vane 25 is installed on the suction side, and a gear mechanism or the like is provided between the electric motor 50 and the impeller 23. The speed increasing device 26 is installed. The discharge pipe 27 of the compressor 20 is connected to the condenser 30, and the suction pipe 29 of the compressor 20 is connected to the evaporator 10. The low pressure side pressure detector 110 may be installed on the suction side (suction pipe 29) of the compressor 20 instead of being installed in the evaporator 10, and the suction pressure may be detected, or the high pressure side pressure detector 120. Instead of installing in the condenser 30, it may be installed on the discharge side (discharge pipe 27) of the compressor 20 to detect the discharge pressure. The control means 70 includes a cold water outlet temperature detected by the cold water temperature detector 90, a cooling water inlet temperature detected by the cooling water temperature detector 100, a low pressure side pressure detected by the low pressure side pressure detector 110, and a high pressure side. The high pressure side pressure detected by the pressure detector 120 is input, an inverter control signal is output to the inverter 80 based on these detection signals, and a guide vane control signal for opening and closing is output to the guide vane 25.

  In the refrigerator 1-1 configured as described above, the refrigerant is repeatedly evaporated, pressurized, compressed, condensed, and depressurized in the evaporator 10, the compressor 20, the condenser 30, and the decompression device 40. Composed. That is, in this refrigeration cycle, similarly to the conventional example shown in FIG. 1, cold water is produced by a cold heat source obtained by the evaporator 10 to cope with the load, while from the evaporator 10 taken into the refrigerator 1-1. The amount of heat and the work amount of the compressor 20 supplied from the electric motor 50 are discharged to the cooling water supplied to the condenser 30.

  And in this refrigerator 1-1, the said control means 70 decided to open / close the said guide vane 25, and to control the rotation speed of the electric motor 50 by the inverter 80, and to control the capacity | capacitance of the said compressor 20 by this. As a result, the performance of the refrigerator 1-1 could be greatly improved as compared with the capacity control using only the suction guide vane 525 shown in FIG. That is, as described above, the compressor 20 is designed so that a predetermined suction capacity and work can be obtained when the suction guide vane 25 is fully open, so that the suction capacity is reduced by the suction guide vane 25. Naturally, the efficiency of the compressor 20 is lowered as compared with the operation in the designed state, and as a result, the energy saving operation of the refrigerator 1-1 cannot be performed. FIG. 3 is a diagram showing the performance of the refrigerator 500 when the capacity is controlled only by the guide vane 525 shown in FIG. 1, and the refrigeration capacity (coefficient of performance, that is, COP) obtained with respect to the input power is cooling water. It shows how it changes with temperature. On the other hand, FIG. 4 shows the performance when the rotation speed control of the electric motor 50 and the opening / closing control of the guide vane 25 are used in combination using the refrigerator 1-1. As can be seen from both figures, the control method of the refrigerator 1-1 shown in FIG. 4 is much better in performance and energy saving than the control method of the conventional refrigerator 500 shown in FIG. I understand.

However, since the centrifugal compressor 20 has a unique surging phenomenon, the rotational speed control is limited. FIG. 5 is a diagram showing characteristics (relationship between cooling water inlet temperature and refrigeration capacity ratio) when the capacity of the refrigerator 1-1 is controlled by changing the rotation speed of the compressor 20, and the temperature of the cooling water is decreased. For example, the capacity control operation can be performed by reducing the rotation speed of the compressor 20, but there is a limit value. In other words, if the load decreases under the condition that the cooling water inlet temperature is constant, it is possible to cope with the decrease in the rotation speed of the compressor 20, but eventually the surging limit line shown in the figure is reached and the compressor 20 cannot be stably operated. Enter the realm. For stable operation, it is only necessary to shift to the guide vane control based on the surging limit line. In this embodiment, as a means for determining this boundary, the pressure in the evaporator 10 (or the suction pressure of the compressor 20) is determined. ) And the pressure in the condenser 30 (or the discharge pressure of the compressor 20). In other words, if the work of the compressor 20 is displayed by isothermal work, the work Wc is set to P1 and P2 as the pressures on the low pressure side and the high pressure side, respectively.
Wc = P1 × V1 × Log (P2 / P1) Equation (1)
It becomes. Here, V1 is the specific volume of compressor suction, and the value of P1 × V1 hardly changes during operation except when the refrigerator 1-1 is started. That is, P1 × V1 can be set as a constant if the specifications of the refrigerator 1-1 are determined, and the limit work of the compressor 1-1 can be calculated by detecting two pressures P1 and P2 on the low pressure side and the high pressure side. It is.

  6 that the recommended rotational speed of the compressor 1-1 and the corresponding surging limit line can be simply determined by the cooling water temperature (inlet temperature in this example). The figure shows the relationship between the rotational speed and the relationship between the cooling water inlet temperature and the surging limit work). The linear relationship shown in the figure can be easily derived from the rotational speed on the surging limit line in FIG. 5 showing the capacity control characteristic and the operating state of the compressor at this position. This indicates that the stable operation region of the refrigerator 1-1 can be determined.

  From the above, in this refrigerator 1-1, the control means 70 detects the chilled water outlet temperature by the chilled water temperature detector 90 as a method of performing capacity control by determining increase / decrease in load, and this temperature approaches the target value. In this way, the suction capacity of the compressor 20 is controlled by controlling the guide vane 25. As a means for controlling the suction capacity of the compressor 20, in addition to guide vane control, control by varying the rotational speed of the compressor 20 is added. Further, as a method for avoiding the surging specific to the centrifugal compressor 20, the following method is used. That is, as described above, surging occurs when the rotational speed is reduced to cope with a decrease in load. Therefore, the limit work in the vicinity of surging is determined in advance for each rotational speed, and the current operation is performed. It is easy to avoid surging by examining at any time how much the state can afford for this marginal work. That is, when the limit work is reached, the rotational speed is fixed, and if the subsequent load reduction is dealt with by the guide vane control, stable operation becomes possible. What is necessary is just to calculate by said Formula (1) as a means to determine a limit work.

  On the other hand, the limit work of the compressor 20 varies depending on the rotation speed, and the limit rotation speed of the compressor 20 corresponds to the limit work determined from the system (the cooling water inlet temperature or the outlet temperature) of the refrigerator 1-1. That is, if the temperature of the cooling water is detected, the limit rotational speed of the compressor 20 (minimum rotational speed of the compressor 20) is determined, and if the load is reduced, the control proceeds to guide vane control. In this embodiment, in order to enable this control, in addition to the conventional detection of the chilled water outlet temperature (by the chilled water temperature detector 90), the cooling water inlet temperature (by the chilled water temperature detector 100), the evaporator pressure and the condensation. It is constructed by a system for detecting the vessel pressure (by the low pressure side pressure detector 110 and the high pressure side pressure detector 120). Stable capacity control is also possible with a system that detects the cooling water outlet temperature instead of the cooling water inlet temperature, the compressor suction pressure instead of the evaporator pressure, and the compressor discharge pressure instead of the condenser pressure. is there.

  FIG. 7 is a schematic control explanatory diagram showing a control method of the refrigerator 1-1 by the control means 70. In the figure, when the refrigerator 1-1 is first started (step 1A), the cooling water inlet temperature is detected by the cooling water temperature detector 100 (step 2A), and the inverter 80 is controlled by the inverter control signal, as described above. The rotation speed of the compressor 20 is set to the limit rotation speed (step 3A). Then, the guide vane (GV) 25 is gradually opened by the guide vane control signal (step 4A), and the guide vane 25 is controlled until the cold water outlet temperature reaches a predetermined temperature (step 5A). That is, when the cold water outlet temperature is low, the guide vane 25 is controlled to close (step 6A), and when the cold water outlet temperature is high, the guide vane 25 is fully opened and the rotational speed is increased (step 7A). Then, if the opening degree of the guide vane 25 is stabilized at 100% or less on the step 6A side, it is determined that the load is small, and a routine (step 8A) for controlling the guide vane 25 with the rotation speed fixed is entered. In this case, the cooling water inlet temperature is detected from the cooling water temperature detector 100 at any time (step 9A), and if the cooling water is high, the frequency of the inverter 80 reaches the limit rotational speed of the compressor 20 corresponding to the cooling water temperature. The guide vane 25 is closed until the load is met (step 10A), and the guide vane control is continued (step 8A). On the other hand, if the cooling water inlet temperature is lowered in step 9A, the frequency is lowered to the limit rotational speed and the guide vane 25 is opened to cope with the load (steps 11A and 12A), but the opening degree of the guide vane 25 is 100%. If it reaches, the guide vane 25 is fixed to 100%, and the control shifts to inverter (INV) control (step 13A). Further, if the chilled water outlet temperature does not reach a predetermined temperature at the limit rotational speed set after the start of the refrigerator 1-1 and the opening degree of the guide vane 25 reaches 100%, it is determined that the required load is large and the guide vane 25 is moved. The routine is fixed to 100% and the inverter 80 control routine is entered (steps 7A and 13A). In this routine, the pressures of the evaporator 10 and the condenser 30 are detected by the low-pressure side pressure detector 110 and the high-pressure side pressure detector 120, respectively (Step 14A), and the theoretical work indicating the operation state of the compressor 20 is calculated ( Step 15A) compares this calculated value with the limit work at the current rotational speed given from the cooling water inlet temperature (Step 16A) to determine whether or not it is in the stable operation region (Step 17A). If the theoretical work is less than the limit work, the inverter control is continued (step 13A). If the theoretical work reaches the limit work, the current rotational speed is fixed or the critical rotational speed is increased and the control shifts to guide vane control (step 13A). 10A).

  FIG. 8 is an overall schematic configuration diagram showing a refrigerator (vapor compression refrigerator) 1-2 according to the second embodiment of the present invention. If the frequency is varied by the inverter 80 as in the first embodiment and the conventional control of the guide vane 25 and the rotation speed control of the compressor 20 are used in combination with the load fluctuation of the refrigerator 1-1, the energy saving capacity control is performed. Although it is obvious that a system can be constructed, if the electric motor 50 is driven through the inverter 80, the electric loss of the inverter 80 is naturally added to the system. As a system, even if the loss of the inverter 80 is compensated, an excessive energy saving effect can be obtained. However, the temperature of the cooling water is close to the design condition, the load of the refrigerator 1-1 is large, and the rotational speed of the compressor 20 is 100. When the operation close to% is continued, no merit through the inverter 80 is obtained. That is, in such a case, energy saving can be achieved by switching to a system in which the electric motor 50 is directly driven from the electric motor starting panel 60 without using the inverter 80.

  Therefore, the refrigerator 1-2 is configured such that the driving of the electric motor 50 can be arbitrarily switched between the case where the electric motor 50 is driven via the inverter 80 and the case where the electric motor is driven directly from the electric motor starting panel 60. In the figure, the same parts as those of the refrigerator 1-1 are designated by the same reference numerals, and detailed description thereof is omitted. In this embodiment, the difference from the first embodiment is that an inverter 80 and a switching device 85 that switches a circuit that bypasses the inverter 80 are installed between the motor starting board 60 and the motor 50, and this switching device 85 is driven. The switching signal is transmitted from the control means 70.

  Switching of the driving method of the electric motor 50 is performed by the cooling water inlet temperature (or the cooling water outlet temperature). In other words, when the cooling water inlet temperature is close to the design conditions, the limit rotational speed for shifting to guide vane control is high, so the capacity control range by rotational speed control is narrow, and this range is also compared with guide vane control from the viewpoint of energy saving. Therefore, the superiority of the rotational speed control is not recognized. Conversely, in such a case, driving the electric motor 50 directly from the electric motor starting board 60 can reduce the loss of the inverter 80, thereby enabling more energy saving operation.

  FIG. 9 is a schematic control explanatory diagram showing a control method of the refrigerator 1-2 by the control means 70. This control method is determined based on whether the cooling water inlet temperature is lower or higher than the design temperature as a reference for determining switching of the driving method of the electric motor 50 as described above. That is, this control method detects the cooling water inlet temperature at the time of starting the refrigerator 1-2 (step 1B) (step 2B), and if the detected cooling water temperature is higher than the design temperature, the conventional guide vane is used thereafter. Operation control is performed in a simple mode of only 25, and when the cooling water temperature is lower than the design temperature, the same control method as in the first embodiment, that is, the control of the guide vane 25 and the rotational speed control by the inverter 80 are used in combination. This is a control method in which operation control is performed and operation is continued only in one of the modes until the refrigerator 1-2 is stopped. Specifically, when the cooling water inlet temperature is higher than the design temperature, first, the control means 70 sets the rotation speed to 100% (step 3B), and the motor 50 is directly driven by the motor starting board 60 by the switching device 85. Then, the opening degree of the guide vane 25 is controlled according to the cold water outlet temperature detected by the cold water temperature detector 90 (steps 5B and 6B). Therefore, if the cooling water inlet temperature is equal to or higher than the design temperature immediately after startup, the electric motor 50 is directly driven until the electric motor 1-2 stops. If the cooling water inlet temperature is lower than the design temperature, the inverter is connected to the electric motor 50 until the refrigerator 1-2 stops. Drive through. In the case of this embodiment, the start-up of the refrigerator 1-2 (step 1B) is performed via the inverter 80, but it is also possible to start the motor 50 directly from the motor start panel 60. However, in the case of direct starting, since the starting current becomes large, it is necessary to provide a large power supply facility, and there is no merit of direct driving. In general, since the cooling water temperature is determined by the outside wet bulb temperature, this control system can sufficiently perform energy-saving operation if the change in weather conditions is small.

  When the frequency of starting and stopping of the refrigerator 1-2 is low and there are many continuous operations, it is assumed that the inverter drive and the start panel direct drive are switched during the operation of the refrigerator 1-2, and the control method in this case As a third embodiment, FIG. 10 is a schematic control explanatory diagram. In addition, the structure of the refrigerator used for this embodiment may be the same structure as the refrigerator 1-2 of said 2nd embodiment. That is, in this embodiment, when the cooling water inlet temperature is equal to or higher than the design temperature, the rotational speed is set to 100% (step 3C), and the motor 50 is directly driven by the motor starter panel 60 by the switching device 85. (Step 4C). The operation up to this point is the same as in the second embodiment, but thereafter, the operation control using the same guide vane control and rotation speed control as described in the first embodiment is entered (step 5C), and the cold water outlet temperature is set to a predetermined value. A control operation is performed so as to approach the value of. In step 2C, when the temperature is equal to or higher than the design temperature, in step 5C, the motor 50 is directly driven by the motor start panel 60. In step 2C, if the temperature is lower than the design temperature, the motor 50 is driven via an inverter in step 5C. . In the control method of step 5C and subsequent steps, in the case of this embodiment, when the cooling water inlet temperature is high and the system operated in the direct drive guide vane control routine detects a decrease in the cooling water inlet temperature, the rotational speed is lowered. Although the operation is started (steps 6C and 7C), the rotational speed is checked at this stage, and if it is confirmed that it is 100%, it is possible to switch to inverter driving without any problem and shift to inverter control (step 8C). ). On the other hand, when the inverter control routine is operated and it is determined that the theoretical work exceeds the limit work (step 9C), the rotational speed is increased to shift to the guide vane control as in step 17A of FIG. If it is confirmed that the rotational speed has reached 100% (step 11C), a routine for switching to direct driving (step 12C) is constructed.

It is a whole schematic block diagram which shows an example of the conventional vapor compression refrigerator 500. 1 is an overall schematic configuration diagram showing a refrigerator (vapor compression refrigerator) 1-1 according to a first embodiment of the present invention. It is a figure which shows the performance of the refrigerator 500 at the time of performing capacity | capacitance control only with the guide vane 525 shown in FIG. It is a figure which shows the performance at the time of using together rotation speed control of the electric motor 50, and opening / closing control of the guide vane 25 using the refrigerator 1-1. It is a figure which shows the characteristic at the time of changing the rotation speed of the compressor 20, and controlling the capacity | capacitance of the refrigerator 1-1 (relationship between a cooling water inlet temperature and a refrigerating capacity ratio). It is a figure which shows the relationship between a cooling water inlet temperature-rotational speed of the compressor 20, and a cooling water inlet temperature-surging limit work. FIG. 4 is a schematic control explanatory diagram illustrating a control method of the refrigerator 1-1 by the control means 70. It is a whole schematic block diagram which shows the refrigerator (vapor compression type refrigerator) 1-2 concerning 2nd, 3rd embodiment of this invention. It is a schematic control explanatory drawing which shows the control method of the refrigerator 1-2 by 2nd embodiment. It is schematic control explanatory drawing which shows the control method of the refrigerator 1-2 by 3rd embodiment.

Explanation of symbols

1-1 Refrigerator (vapor compression refrigerator)
10 Evaporator 20 Compressor (centrifugal compressor)
21 casing 23 impeller 25 guide vane 26 speed increasing device 27 discharge pipe 29 suction pipe 30 condenser 40 throttling mechanism (decompression device)
DESCRIPTION OF SYMBOLS 50 Electric motor 60 Electric motor starting board 70 Control means 75 Commercial power supply 80 Inverter 85 Switching apparatus 90 Cold water temperature detector 100 Cooling water temperature detector 110 Low pressure side pressure detector 120 High pressure side pressure detector 1-2 Refrigerator (vapor compression refrigeration Machine)

Claims (9)

A vapor compression type comprising an evaporator for producing cold water, a condenser for radiating heat to the cooling water, a decompression device provided between the condenser and the evaporator, a compressor, and an electric motor for driving the compressor. In the refrigerator,
The compressor is constituted by a centrifugal compressor provided with a suction guide vane, and an inverter for driving and controlling the electric motor is installed.
Furthermore, the refrigerator which installed the control means which controls the capacity | capacitance of the said compressor by opening and closing of the said guide vane and the rotation speed control of the compressor by an inverter. While installing a cold water temperature detector that detects the cold water outlet temperature of the evaporator,
The said control means controls the rotation speed of a compressor and opening / closing of a suction guide vane so that the cold water exit temperature detected with the said cold water temperature detector may become a predetermined target value. Refrigerator. A cooling water temperature detector for detecting the inlet or outlet temperature of the cooling water, a low pressure side pressure detector for detecting an evaporator pressure or a compressor suction pressure, and a high pressure side pressure for detecting a condenser pressure or a compressor discharge pressure. Install the detector and
The control means is such that the operation state of the compressor calculated from the detected inlet or outlet temperature value of the cooling water, the detected low pressure value, and the detected high pressure value is always within a predetermined operable range. The refrigerator according to claim 2, wherein the rotation speed of the compressor and the suction guide vane of the compressor are controlled so as to enter.   The refrigerator according to claim 1, further comprising a switching device that switches between a case where the electric motor is driven from a commercial power source via the inverter and a case where the motor is directly driven from the commercial power source. An evaporator that produces cold water, a condenser that radiates heat to the cooling water, a decompression device provided between the condenser and the evaporator, a centrifugal compressor, and an electric motor that drives the compressor are configured. In the control method of the vapor compression refrigerator,
Control of a refrigerator that controls the capacity of the compressor by combining suction guide vane control provided in the compressor and inverter control of compressor rotation speed by an inverter that drives and controls the electric motor. Method.   6. The refrigerator according to claim 5, wherein the temperature of the cold water outlet is detected, and the rotation speed of the compressor and the opening and closing of the suction guide vane are controlled so that the cold water outlet temperature becomes a predetermined target value. Control method.   Detecting the inlet or outlet temperature to the condenser of the cooling water, the low pressure side pressure that is the evaporator pressure or compressor suction pressure, and the high pressure side pressure that is the condenser pressure or compressor discharge pressure, and The compressor speed and the suction guide vane of the compressor are controlled so that the operation state of the compressor calculated from the detected value is always within a predetermined operable range. The refrigerator control method as described. When performing the inverter control,
From the detected value of the cooling water inlet or outlet temperature, determine the limit work to avoid the surging of the compressor at the current rotational speed,
From the detected value of the low-pressure side pressure and the detected value of the high-pressure side pressure, calculate the theoretical work of the compressor,
Compare the theoretical work with the limit work and if the theoretical work is below the limit work, continue the inverter control, and if the theoretical work reaches the limit work, fix the current speed or increase the speed limit to guide vane control. The method of controlling a refrigerator according to claim 7, wherein the control is performed. 6. The method of controlling a refrigerator according to claim 5, wherein when the cooling water inlet or outlet temperature is higher than the design temperature, the electric motor is driven directly from a commercial power source without using an inverter.

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