Refrigeration cycle apparatus

The present invention has an object to provide a refrigeration cycle apparatus. A refrigeration cycle apparatus according to the present invention includes: a compressor; and a control apparatus configured to calculate a rotation number command of the compressor. The control apparatus includes a capacity controller configured to calculate the rotation number of the compressor as a capacity rotation number, a protection controller configured to calculate the rotation number of the compressor as a protection rotation number and a rotation number selection unit configured to select any one of the capacity rotation number and the protection rotation number as the rotation number command of the compressor. The rotation number command of the compressor is calculated so that at least any one of causing the current capacity value to approach the capacity target value and causing the protection variable to approach the protection target value is satisfied.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is based on PCT filing PCT/JP2019/009660, filed Mar. 11, 2019, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a refrigeration cycle apparatus using a vapor compression refrigeration cycle, and more particularly to a refrigeration cycle apparatus including a compressor whose rotation number is a variable.

BACKGROUND ART

A control apparatus of a refrigeration cycle apparatus as follows has hitherto been disclosed: specifically, the control apparatus calculates a speed command of an inverter motor adapted for a load by using PI control or the like, and in order to reduce high pressure of refrigerant to an allowable value, calculates an upper limit speed of the speed command of the inverter motor in reference to a graph, based on a limited value of the high pressure and detected pressure on the high pressure side (for example, see Patent Document 1).

PRIOR ART DOCUMENTS

Patent Documents

SUMMARY

Problem to be Solved by the Invention

The control apparatus disclosed in Patent Document 1 does not consider the fact that the upper limit speed for reducing the high pressure of refrigerant to an allowable value changes from moment to moment due to influences such as changes in an ambient environment, variation of performance of devices constituting the refrigeration cycle apparatus, and aging of the refrigeration cycle apparatus. Thus, depending on an operation condition of the refrigeration cycle apparatus, the upper limit speed of the speed command of the inverter motor calculated by the control apparatus may be much faster or much slower than the original upper limit speed. As a result, there is a problem in that, when the upper limit speed of the speed command of the inverter calculated by the control apparatus exceeds the original upper limit speed, failure is more likely to occur in the devices constituting the refrigeration cycle apparatus. Further, there is a problem in that, when the upper limit speed of the speed command of the inverter calculated by the control apparatus falls below the original upper limit speed, capacity of the refrigeration cycle apparatus deteriorates.

The present invention is made in order to solve the problems as described above, and has an object to provide a refrigeration cycle apparatus that can optimally control capacity.

Means to Solve the Problem

In order to solve the problems described above, a refrigeration cycle apparatus according to the present invention includes: a compressor whose rotation number is a variable; and a control apparatus configured to calculate a rotation number command of the compressor for handling the rotation number of the compressor. The control apparatus includes a capacity controller configured to calculate the rotation number of the compressor as a capacity rotation number in order to cause a current capacity value indicating current capacity of the refrigeration cycle apparatus to be a capacity target value being determined at suitable time, a protection controller configured to calculate the rotation number of the compressor as a protection rotation number in order to cause a protection variable being a variable related to a limitation item including protection of the refrigeration cycle apparatus to be a protection target value being determined at suitable time, and a rotation number selection unit configured to select any one of the capacity rotation number calculated by the capacity controller and the protection rotation number calculated by the protection controller as the rotation number command of the compressor. The rotation number command of the compressor is calculated so that at least any one of causing the current capacity value to approach the capacity target value and causing the protection variable to approach the protection target value is satisfied.

Effects of the Invention

According to the present invention, the refrigeration cycle apparatus includes the compressor whose rotation number is a variable, and the control apparatus that calculates the rotation number command of the compressor for handling the rotation number of the compressor. The rotation number command of the compressor is calculated so that at least any one of causing the current capacity value to approach the capacity target value and causing the protection variable to approach the protection target value is satisfied. Therefore, the capacity of the refrigeration cycle apparatus can be optimally controlled.

DESCRIPTION OF EMBODIMENTS

First Embodiment

FIG.1is a schematic diagram illustrating an example of a configuration of an air conditioning apparatus1according to the first embodiment of the present invention.

As illustrated inFIG.1, the air conditioning apparatus1being a refrigeration cycle apparatus includes a control apparatus2, a compressor3, a four-way valve4, an outdoor heat exchanger5, an electric expansion valve6, and an indoor heat exchanger7. The compressor3, the four-way valve4, the outdoor heat exchanger5, the electric expansion valve6, and the indoor heat exchanger7are connected with piping, and refrigerant flows inside the piping.

The air conditioning apparatus1includes, as necessary, a compressor temperature sensor10, a discharge temperature sensor11, an outdoor heat exchanger temperature sensor12, an indoor heat exchanger temperature sensor13, a room temperature sensor14, a high pressure sensor15, a low pressure sensor16, and a current sensor17.

The control apparatus2controls the rotation number of the compressor3, based on various pieces of sensor information or external input. Here, the rotation number of the compressor3is similar in meaning to the speed of an inverter motor constituting the compressor3.

Note that an accumulator may be connected to a suction side of the compressor3. Further, a receiver may be connected between the outdoor heat exchanger5and the electric expansion valve6, and another electric thermal expansion valve that is different from the electric expansion valve6may be connected between the receiver and the outdoor heat exchanger5.

A cooling cycle of the air conditioning apparatus1will be described. The refrigerant that has been brought into a high temperature and high pressure state through compression of the compressor3is discharged from the compressor3. Subsequently, the refrigerant passes through the piping indicated by the solid line of the four-way valve4, has its heat dissipated to an outdoor space with the outdoor heat exchanger5, and liquefies under high pressure. The refrigerant that has passed through the outdoor heat exchanger5has its pressure reduced by the electric expansion valve6to be brought into a low-temperature two-phase state, absorbs heat from an indoor space with the indoor heat exchanger7, and vaporizes under low pressure. The refrigerant that has vaporized in the indoor heat exchanger7is sucked into the compressor3and is compressed. Through the repetition of such an operation as described above, the refrigeration cycle of the air conditioning apparatus1is implemented.

A heating cycle of the air conditioning apparatus1will be described. The refrigerant in the high temperature and high pressure state that is discharged from the compressor3passes through the piping indicated by the broken line of the four-way valve4, has its heat dissipated to an indoor space with the indoor heat exchanger7, and liquefies under high temperature. The refrigerant that has liquefied in the indoor heat exchanger7has its pressure reduced by the electric expansion valve6to be brought into a low-temperature two-phase state, absorbs heat from an outdoor space with the outdoor heat exchanger5, and vaporizes. The refrigerant that has vaporized in the outdoor heat exchanger5is sucked into the compressor3and is compressed. Through the repetition of such an operation as described above, the heating cycle of the air conditioning apparatus1is implemented.

FIG.2is a block diagram illustrating an example of a configuration of the control apparatus2.

As illustrated inFIG.2, the control apparatus2includes a capacity controller101, a protection controller102, a rotation number selection unit103, and an upper and lower limiter104.

The capacity controller101includes a PI controller being a dynamic controller including an integrator. The capacity controller101defines room temperature acquired from the room temperature sensor14as a current capacity value indicating the current capacity and set room temperature determined at suitable time as a capacity target value, and calculates a capacity rotation number that is a rotation number command of the compressor3necessary for causing the room temperature to asymptotically approach or match the set room temperature.

The protection controller102calculates a protection rotation number being a rotation number command of the compressor3necessary for causing protection variables being predetermined variables necessary for protecting devices constituting the air conditioning apparatus1to asymptotically approach or match their protection target values that are determined at suitable time or in advance. Here, the predetermined variables are compressor temperature, discharge temperature, condensation temperature, evaporation temperature, high pressure, low pressure, and current. The compressor temperature is temperature detected by the compressor temperature sensor10. The discharge temperature is temperature detected by the discharge temperature sensor11. The condensation temperature is temperature detected by the outdoor heat exchanger temperature sensor12in a case of the cooling cycle, and temperature detected by the indoor heat exchanger temperature sensor13in a case of the heating cycle. The evaporation temperature is temperature detected by the indoor heat exchanger temperature sensor13in a case of the cooling cycle, and temperature detected by the outdoor heat exchanger temperature sensor12in a case of the heating cycle. The high pressure is pressure detected by the high pressure sensor15. The low pressure is pressure detected by the low pressure sensor16. The current is current detected by the current sensor17. Further, the protection target values are a compressor temperature upper value, a discharge temperature upper value, a condensation temperature upper value, an evaporation temperature lower value, a high pressure upper value, a low pressure lower value, and a current upper value.

The protection controller102includes a PI controller for each protection variable described above, and calculates the protection rotation number for each protection variable.

Note that the protection variables described above merely illustrate examples of typical variables necessary for protecting the devices, and variables other than those described above may be adopted as the protection variables. Note that the protection variable to be adopted has the following characteristics: for the protection variable whose protection target value increases when the rotation number of the compressor3increases, an upper value of the protection variable is used, whereas for the protection variable whose protection target value reduces when the rotation number of the compressor3increases, a lower value of the protection variable is used.

The rotation number selection unit103includes a minimum rotation number selection unit105. The minimum rotation number selection unit105selects the minimum rotation number out of the capacity rotation number output from the capacity controller101and the protection rotation numbers output from the protection controller102as a control rotation number.

All of the protection variables illustrated inFIG.2have characteristics of changing so as to depart from respective limitations when the rotation number of the compressor3increases. For example, when the rotation number of the compressor3is increased, the discharge temperature increases and changes so as to exceed the discharge temperature upper value. Thus, when the minimum rotation number selection unit105selects the minimum rotation number out of the capacity rotation number output from the capacity controller101and the protection rotation numbers output from the protection controller102, all of the protection variables can be controlled within their upper and lower limits.

The upper and lower limiter104stores a predetermined rotation number upper value Rmax and rotation number lower value Rmin. When the control rotation number selected by the rotation number selection unit103is the rotation number lower value Rmin or lower, the upper and lower limiter104outputs the rotation number lower value Rmin, when the control rotation number is the rotation number upper value Rmax or higher, the upper and lower limiter104outputs the rotation number upper value Rmax, and in other cases, the upper and lower limiter104outputs the control rotation number as it is. The compressor3operates according to the rotation number output from the upper and lower limiter104. The rotation number output from the upper and lower limiter104is fed back to the capacity controller101and the protection controller102, and is used for calculation in a reset function of integrated values.

<Reset Function of Integrated Value>

FIG.3is a block diagram illustrating an example of a configuration of a PI controller111being a controller that performs proportional (P)-integral (I) control. Note that the PI controller111corresponds to the PI controller included in each of the capacity controller101and the protection controller102illustrated inFIG.2.

The PI controller111includes two inputs and one output. Parameters are a proportional gain112(Kp), an integral gain113(Ki), and a constant114(Ka).

First, a value a is calculated, which is obtained by multiplying, by a constant114, a value obtained by subtracting input2defined as the rotation number of the compressor3from output being output of the PI controller111. Note that although the constant114is a set parameter, a reciprocal of the proportional gain112is often used in PI control.

Next, a value ε is calculated, which is obtained by subtracting a from input1being deviation information. Finally, a value obtained by adding a value obtained by multiplying input1by the proportional gain112and a value obtained by multiplying an integrated value of ε by the integral gain113and a control period Ts is output as output.

To put the above description in an expression, the following expression (1) is obtained, where k represents the number of steps in repeated calculation.

According to the method described above, integrated values stored in an integrator115are not diverged. The reset function of the integrated values is continuous processing, and when the control period Ts becomes smaller, it approaches behavior of a continuous system.

FIGS.4to6are each a diagram for illustrating operation of the air conditioning apparatus1. Here, as an example, heating operation including the compressor temperature as the protection variable will be described.

As illustrated inFIG.4, the set room temperature being the capacity target value is set to be 22° C. from 0 min to 30 min, 27° C. from 30 min to 60 min, and 22° C. from 60 min to 90 min. Note that the solid line inFIG.4denotes the room temperature.

As illustrated inFIG.5, the compressor temperature upper value being the protection target value for the compressor temperature is set to be 100° C. Note that, inFIG.5, the solid line denotes the compressor temperature.

As illustrated inFIG.6, the capacity rotation number is below the protection rotation number from 0 min to 30 min, and the rotation number selection unit103selects the capacity rotation number. As a result, the room temperature asymptotically approaches the set room temperature, the compressor temperature becomes smaller than the compressor temperature upper value, and the air conditioning apparatus1operates within limitations. Further, owing to the reset function of the integrated value, the protection rotation number avoids divergence without continuing to increase, in spite of the fact that a difference between the compressor temperature and the compressor temperature upper value is not zero.

When the set room temperature is changed to 27° C. at the time point of 30 min, the protection rotation number falls below the capacity rotation number, and thus the rotation number selection unit103selects the protection rotation number. As a result, the compressor temperature asymptotically approaches the compressor temperature upper value, the room temperature becomes smaller than the set room temperature, and the air conditioning apparatus1operates within limitations. Further, owing to the reset function of the integrated value, the protection rotation number and the capacity rotation number are not significantly deviated, and thus when an operation condition of the air conditioning apparatus1changes, the control rotation number is instantaneously switched, and high-accuracy control of the rotation number of the compressor3can be implemented.

Note that, in a time period when the compressor temperature asymptotically approaches the compressor temperature upper value, the room temperature does not reach the set room temperature and the capacity is smaller than requested. However, if the rotation number is increased in order to further increase the capacity, the compressor temperature undesirably exceeds the compressor temperature upper value. Thus, the operation state in which the compressor temperature asymptotically approaches the compressor temperature upper value is the operation state in which performance of the devices constituting the air conditioning apparatus1is continuously exerted at the maximum and the capacity of the air conditioning apparatus1is maximized.

When the set room temperature is changed to 22° C. again at the time point of 60 min, the capacity rotation number immediately falls below the protection rotation number, and the rotation number selection unit103selects the capacity rotation number. As a result, the room temperature asymptotically approaches the set room temperature, the compressor temperature becomes smaller than the compressor temperature upper value, and the air conditioning apparatus1operates within limitations.

The above has described a case in which seven protection variables are defined. However, this is not restrictive, and the protection variable(s) may be selected according to the devices constituting the air conditioning apparatus1and the operation condition of the air conditioning apparatus1. For example, only the compressor temperature may be used as the protection variable, or two variables, namely the compressor temperature and the discharge temperature, may be used as the protection variables. When the protection variables are limited, sensors corresponding to the variables not to be limited may be excluded from the configuration of the air conditioning apparatus1.

The air conditioning apparatus1need not include pressure sensors such as the high pressure sensor15and the low pressure sensor16. In this case, high pressure calculated based on the condensation temperature and low pressure calculated based on the evaporation temperature may be adopted as the protection variables. When the high pressure is calculated, the condensation temperature upper value may not be adopted as the protection variable. When the low pressure is calculated, the evaporation temperature lower value may not be adopted as the protection variable.

The capacity controller101and the protection controller102are not limited to the PI controllers, and are only required to include a dynamic controller including at least an integrator, and for example, a proportional-integral-differential (PID) controller, an integral (I) controller, or the like may be used.

The above has described a position-type PI controller, but a speed-type PI controller may be used.

The modification of the first embodiment described above can also be similarly applied to other embodiments to be described later.

According to the first embodiment, influences such as changes in an ambient environment, variation of performance of the devices constituting the refrigeration cycle apparatus, and aging of the refrigeration cycle apparatus can be reduced, and any one of the room temperature, the compressor temperature, the discharge temperature, the condensation temperature, the evaporation temperature, the high pressure, the low pressure, and the current can be caused to asymptotically approach a target value. For example, when the room temperature asymptotically approaches a target value, the compressor temperature is the compressor temperature upper value or lower, the discharge temperature is the discharge temperature upper value or lower, the condensation temperature is the condensation temperature upper value or lower, the evaporation temperature is the evaporation temperature lower value or higher, the high pressure is the high pressure upper value or lower, and the low pressure is the low pressure lower value or higher. Specifically, it is guaranteed regarding the air conditioning apparatus1that all of the protection variables operate within limitations. When one of the protection variables asymptotically approaches the protection target value, it is guaranteed that all of the other protection variables are within limitations.

When the protection variable asymptotically approaches the protection target value, although the room temperature does not necessarily asymptotically approach the set room temperature, the compressor3operates at the largest rotation number within limitations. Thus, the capacity of the air conditioning apparatus1is maximized, and deviation between the room temperature and the set room temperature is minimized. Specifically, nearly maximum performance of the devices constituting the air conditioning apparatus1can be exerted. In a situation in which the protection variables change due to the reset function of the integrated value, the control rotation number selected by the rotation number selection unit103is switched automatically, immediately, and smoothly, and an air conditioning system that enables continuous protection of the devices constituting the air conditioning apparatus1can be implemented.

The capacity target value and the protection target value may be set from the outside as variable values. For example, for the sake of energy saving, an upper system that changes the set room temperature at predetermined time may be used in cooperation, and the set room temperature output from the upper system may be defined as the capacity target value. Further, for example, when the upper system makes a request of limiting the current to a determined value or less at suitable time (as appropriate, at predetermined appropriate time), by defining a current value corresponding to the request as the protection target value, operation of the air conditioning apparatus1in compliance with electricity regulations or the like can be implemented. Alternatively, if a system incorporating a wattmeter is used, an air conditioning system that can comply with the request of limiting power from the upper system to a predetermined value or less can be implemented.

Second Embodiment

FIG.7is a block diagram illustrating an example of a configuration of the control apparatus2according to the second embodiment.

As illustrated inFIG.7, in the control apparatus2according to the second embodiment, the protection controller102includes a PI controller corresponding to a discharge superheat degree, and the rotation number selection unit103includes a maximum rotation number selection unit106. Other configurations and operations are similar to those of the first embodiment, and thus detailed description thereof is herein omitted.

As illustrated inFIG.7, in the second embodiment, the discharge superheat degree is included as the protection variable, and a discharge superheat degree lower value is included as the protection target value. Note that, although the compressor temperature, the discharge temperature, the condensation temperature, the evaporation temperature, the high pressure, the low pressure, and the current included in the protection variables described in the first embodiment depart from limitations when the rotation number of the compressor3is increased, the discharge superheat degree departs from limitations when the rotation number of the compressor3is reduced. For example, when the rotation number of the compressor3is increased, the discharge temperature increases and changes so as to exceed the discharge temperature upper value, whereas when the rotation number of the compressor3is reduced, the discharge superheat degree reduces and changes so as to fall below the discharge superheat degree lower value. Thus, it is desirable that the rotation number of the compressor3be larger than the protection rotation number calculated by the PI controller corresponding to the discharge superheat degree.

The rotation number selection unit103according to the second embodiment includes a maximum rotation number selection unit106and a minimum rotation number selection unit105. The maximum rotation number selection unit106compares the capacity rotation number calculated by the capacity controller101and the protection rotation number calculated by the PI controller corresponding to the discharge superheat degree, and outputs the larger rotation number as a selected rotation number. The minimum rotation number selection unit105compares the selected rotation number output from the maximum rotation number selection unit106and the protection rotation number calculated by the PI controllers corresponding to the protection variables other than the discharge superheat degree, and selects the minimum rotation number as the control rotation number.

Based on the above, according to the second embodiment, the compressor3is controlled at the rotation number for causing the discharge superheat degree to asymptotically approach the discharge superheat degree lower value or a higher rotation number. Accordingly, liquid refrigerant can be arranged not to flow into the compressor3, and a long life of the devices constituting the air conditioning apparatus1can be implemented.

Note that the above has described a case in which the discharge superheat degree is adopted as the protection variable. However, variables other than the discharge superheat degree may be adopted as the protection variables.

A plurality of protection rotation numbers may be input to the maximum rotation number selection unit106. Note that the protection variable corresponding to the protection rotation numbers input to the maximum rotation number selection unit106has the following characteristics: for the protection variable whose protection target value increases when the rotation number of the compressor3increases, a lower value of the protection variable is used, whereas for the protection variable whose protection target value reduces when the rotation number of the compressor3increases, an upper value of the protection variable is used.

In a temperature condition in a case of operation of the air conditioning apparatus1or in a transitional state of actual operation of the air conditioning apparatus1, the protection rotation number corresponding to the discharge superheat degree may be larger than the protection rotation numbers corresponding to the protection variables other than the discharge superheat degree. In the limitations of the discharge superheat degree, occurrence of a problem immediately after the departure is relatively infrequent. Thus, in such a case, other protection variables need to be preferentially put within limitations by setting the discharge superheat degree to the discharge superheat degree lower value or lower. In order to implement the operation as described above, in the rotation number selection unit103, arithmetic of the minimum rotation number selection unit105is performed after arithmetic of the maximum rotation number selection unit106. By adopting the configuration as described above, an air conditioning system in which the order of priority is provided for the protection variables can be implemented.

Third Embodiment

FIG.8is a block diagram illustrating an example of a configuration of the control apparatus2according to the third embodiment.

As illustrated inFIG.8, in a case of heating operation, the control apparatus2according to the third embodiment defines the condensation temperature as the current capacity value, defines a condensation temperature target value as the capacity target value, and calculates the rotation number of the compressor3for causing the condensation temperature to asymptotically approach the condensation temperature target value. Other configurations and operations are similar to those of the second embodiment, and thus detailed description thereof is herein omitted.

As the condensation temperature, temperature detected by the indoor heat exchanger temperature sensor13may be used. Further, as the condensation temperature, temperature obtained through conversion using a calculation expression for obtaining saturation temperature based on pressure detected by the high pressure sensor15may be used.

As the condensation temperature target value, a predetermined constant may be used. Further, the condensation temperature target value is a value that is successively calculated based on the room temperature and the set room temperature, and a variable having such characteristics as to have a larger value when the room temperature is lower than the set room temperature and have a smaller value when the room temperature is higher than the set room temperature may be used. Alternatively, for the sake of energy saving, an upper system that changes the condensation temperature target value at each time is used in cooperation, and the condensation temperature target value output from the upper system may be defined as the capacity target value.

Based on the above, according to the third embodiment, influences received due to disturbance for a detected value of the room temperature can be reduced, and an air conditioning system having small abrupt changes can be implemented. Further, by adopting a configuration of not using room temperature information for the condensation temperature target value, the capacity of the air conditioning apparatus1can be controlled even without the room temperature sensor14. In addition, by adopting a configuration of obtaining the condensation temperature based on the pressure detected by the high pressure sensor15, the air conditioning apparatus1can be controlled with information of only and outdoor unit even without information of an indoor unit. Thus, an air conditioning system in which the outdoor unit can be independently controlled without receiving influences of limitations such as communication can be implemented.

Fourth Embodiment

FIG.9is a block diagram illustrating an example of a configuration of the control apparatus2according to the fourth embodiment.

As illustrated inFIG.9, in a case of cooling operation, the control apparatus2according to the fourth embodiment defines the evaporation temperature as the current capacity value, defines an evaporation temperature target value as the capacity target value, and calculates the rotation number of the compressor3for causing the evaporation temperature to asymptotically approach the evaporation temperature target value. Other configurations and operations are similar to those of the second embodiment, and thus detailed description thereof is herein omitted.

As the evaporation temperature, temperature detected by the indoor heat exchanger temperature sensor13may be used. Further, as the evaporation temperature, temperature obtained through conversion using a calculation expression for obtaining saturation temperature based on pressure detected by the low pressure sensor16may be used.

As the evaporation temperature target value, a predetermined constant may be used. Further, the evaporation temperature target value is a value that is successively calculated based on the room temperature and the set room temperature, and a variable having such characteristics as to have a larger value when the room temperature is lower than the set room temperature and have a smaller value when the room temperature is higher than the set room temperature may be used. Alternatively, for the sake of energy saving, an upper system that changes the evaporation temperature target value at each time is used in cooperation, and the evaporation temperature target value output from the upper system may be defined as the capacity target value.

Based on the above, according to the fourth embodiment, influences received due to disturbance for a detected value of the room temperature can be reduced, and an air conditioning system having small abrupt changes can be implemented. Further, by adopting a configuration of not using room temperature information for the evaporation temperature target value, the capacity of the air conditioning apparatus1can be controlled even without the room temperature sensor14. In addition, by adopting a configuration of obtaining the evaporation temperature based on the pressure detected by the low pressure sensor16, the air conditioning apparatus1can be controlled with information of only and outdoor unit even without information of an indoor unit. Thus, an air conditioning system in which the outdoor unit can be independently controlled without receiving influences of limitations such as communication can be implemented.

Fifth Embodiment

FIG.10is a schematic diagram illustrating an example of a configuration of an air conditioning apparatus20according to the fifth embodiment of the present invention.

As illustrated inFIG.10, the air conditioning apparatus20is a water air conditioning system. Specifically, the air conditioning apparatus20includes a water refrigerant heat exchanger21and a water-type indoor heat exchanger22. Other configurations and operations are similar to those of the air conditioning apparatus1according to the second embodiment, and thus detailed description thereof is herein omitted.

The water refrigerant heat exchanger21and the water-type indoor heat exchanger22are connected with piping, and water flows inside the piping. The water refrigerant heat exchanger21performs heat exchange between refrigerant and water, and the water that has been subjected to heat exchange circulates in the piping. Further, at an outlet of the water refrigerant heat exchanger21, an outlet water temperature sensor32is provided. The outlet water temperature sensor32measures outlet water temperature of the water refrigerant heat exchanger21. In addition, a water refrigerant heat exchanger temperature sensor31is provided in the water refrigerant heat exchanger21. The water refrigerant heat exchanger temperature sensor31measures temperature of the water refrigerant heat exchanger21.

FIG.11is a block diagram illustrating an example of a configuration of the control apparatus2included in the air conditioning apparatus20.

As illustrated inFIG.11, in the fifth embodiment, the outlet water temperature is included as the protection variable, an outlet water temperature upper value is included as the protection target value in a case of heating, and an outlet water temperature lower value is included as the protection target value in a case of cooling.

Based on the above, according to the fifth embodiment, in a situation in which the outlet water temperature is required to be protected, the outlet water temperature is included as the protection variable, the outlet water temperature upper value is included as the protection target value in a case of heating, and the outlet water temperature lower value is included as the protection target value in a case of cooling. Then, in a case of heating, the rotation number of the compressor3is controlled so that the outlet water temperature asymptotically approaches the outlet water temperature upper value, and in a case of cooling, the compressor3is controlled at the rotation number for causing the outlet water temperature to asymptotically approach the outlet water temperature lower value or a lower rotation number. Accordingly, the outlet water temperature can be arranged not to become excessively high temperature in a case of heating, and freezing of water in a case of cooling can be arranged not to occur.

Further, some water air conditioning systems make a stop request to the compressor3when the outlet water temperature departs from a permitted range. For such the system as described above, by setting the protection target value corresponding to the outlet water temperature to be within permitted limitations, unnecessary stop requests for the compressor3can be arranged not to be made, and high-efficiency operation of the water air conditioning system can be implemented.

Sixth Embodiment

FIG.12is a block diagram illustrating an example of a configuration of the control apparatus2according to the sixth embodiment.

As illustrated inFIG.12, in a case of heating operation, the control apparatus2according to the sixth embodiment defines the condensation temperature as the current capacity value, defines a condensation temperature target value as the capacity target value, and calculates the rotation number of the compressor3for causing the condensation temperature to asymptotically approach the condensation temperature target value. Other configurations and operations are similar to those of the fifth embodiment, and thus detailed description thereof is herein omitted.

As the condensation temperature, temperature detected by the water refrigerant heat exchanger temperature sensor31may be used. Further, as the condensation temperature, temperature obtained through conversion using a calculation expression for obtaining saturation temperature based on pressure detected by the high pressure sensor15may be used.

As the condensation temperature target value, a predetermined constant may be used. Further, the condensation temperature target value is a value that is successively calculated based on the room temperature and the set room temperature, and a variable having such characteristics as to have a larger value when the room temperature is lower than the set room temperature and have a smaller value when the room temperature is higher than the set room temperature may be used. Alternatively, for the sake of energy saving, an upper system that changes the condensation temperature target value at each time is used in cooperation, and the condensation temperature target value output from the upper system may be defined as the capacity target value.

Based on the above, according to the sixth embodiment, influences received due to disturbance for a detected value of the room temperature can be reduced, and a water air conditioning system having small abrupt changes can be implemented. Further, by adopting a configuration of not using room temperature information for the condensation temperature target value, the capacity of the air conditioning apparatus1can be controlled even without the room temperature sensor14. In addition, by adopting a configuration of obtaining the condensation temperature based on the pressure detected by the high pressure sensor15, the air conditioning apparatus20can be controlled with information of only and outdoor unit even without information of an indoor unit. Thus, a water air conditioning system in which the outdoor unit can be independently controlled without receiving influences of limitations such as communication can be implemented.

Seventh Embodiment

FIG.13is a block diagram illustrating an example of a configuration of the control apparatus2according to the seventh embodiment.

As illustrated inFIG.13, in a case of cooling operation, the control apparatus2according to the seventh embodiment defines the evaporation temperature as the current capacity value, defines an evaporation temperature target value as the capacity target value, and calculates the rotation number of the compressor3for causing the evaporation temperature to asymptotically approach the evaporation temperature target value. Other configurations and operations are similar to those of the fifth embodiment, and thus detailed description thereof is herein omitted.

As the evaporation temperature, temperature detected by the water refrigerant heat exchanger temperature sensor31may be used. Further, as the evaporation temperature, temperature obtained through conversion using a calculation expression for obtaining saturation temperature based on pressure detected by the low pressure sensor16may be used.

As the evaporation temperature target value, a predetermined constant may be used. Further, the evaporation temperature target value is a value that is successively calculated based on the room temperature and the set room temperature, and a variable having such characteristics as to have a larger value when the room temperature is lower than the set room temperature and have a smaller value when the room temperature is higher than the set room temperature may be used. Alternatively, for the sake of energy saving, an upper system that changes the evaporation temperature target value at each time is used in cooperation, and the evaporation temperature target value output from the upper system may be defined as the capacity target value.

Based on the above, according to the seventh embodiment, influences received due to disturbance for a detected value of the room temperature can be reduced, and a water air conditioning system having small abrupt changes can be implemented. Further, by adopting a configuration of not using room temperature information for the evaporation temperature target value, the capacity of the air conditioning apparatus1can be controlled even without the room temperature sensor14. In addition, by adopting a configuration of obtaining the evaporation temperature based on the pressure detected by the low pressure sensor16, the air conditioning apparatus20can be controlled with information of only and outdoor unit even without information of an indoor unit. Thus, a water air conditioning system in which the outdoor unit can be independently controlled without receiving influences of limitations such as communication can be implemented.

Eighth Embodiment

FIG.14is a block diagram illustrating an example of a configuration of the control apparatus2according to the eighth embodiment.

As illustrated inFIG.14, the control apparatus2according to the eighth embodiment defines the outlet water temperature as the current capacity value, defines an outlet water temperature target value as the capacity target value, and calculates the rotation number of the compressor3for causing the outlet water temperature to asymptotically approach the outlet water temperature target value. Other configurations and operations are similar to those of the fifth embodiment, and thus detailed description thereof is herein omitted.

As the outlet water temperature, temperature detected by the outlet water temperature sensor32may be used.

As the outlet water temperature target value, a predetermined constant may be used. The constant may be set by a user. Further, the outlet water temperature target value is a value that is successively calculated based on the room temperature and the set room temperature, and a variable having such characteristics as to have a larger value when the room temperature is lower than the set room temperature and have a smaller value when the room temperature is higher than the set room temperature may be used. Alternatively, for the sake of energy saving, an upper system that changes the outlet water temperature target value at each time is used in cooperation, and the outlet water temperature target value output from the upper system may be defined as the capacity target value.

Based on the above, according to the eighth embodiment, influences received due to disturbance for a detected value of the room temperature can be reduced, and a water air conditioning system having small abrupt changes can be implemented.

Ninth Embodiment

In the PI controller or the PID controller included in the capacity controller101and the protection controller102according to the first to eighth embodiments, the reset function of the integrated value may be executed with a method using non-continuous processing. The method is, for example, implemented as in the following expression (2).

Here, I is an integrated value stored in the integrator115. A reset method of the integrated value may be different depending on a controller.

The method of reset of the integrated value using the continuous processing described in the first embodiment is a method that is effective when the control period is sufficiently short. Thus, when the control period is short, the continuous processing may be executed, whereas when the control period is long, the non-continuous processing may be executed. For example, when the control period is shorter than Ti=Kp/Ki (Ti: integral time period), the continuous processing may be executed, whereas when the control period is the integral time period or longer, the non-continuous processing may be executed.

Note that the implementation method of the reset function of the integrated value using the non-continuous processing is not limited to the above. Any implementation method may be used, in so far as output of the controller and output of the upper and lower limiter104are compared, and processing different from usual integral operation is executed when the values are different.

Based on the above, according to the ninth embodiment, even when the control periods are different in the controllers, the controllers have an appropriate reset function of the integrated value. As a result, when the protection variables are switched due to change in an operation state of the air conditioning apparatus1or20, the controller that generates the protection rotation number to be input to the rotation number selection unit103is immediately switched, and the operation of the air conditioning apparatus1or20can be continued stably without departing from the limitations.

Note that, in the present invention, each embodiment can be freely combined, and each embodiment can be modified or omitted as appropriate within the scope of the invention.

While the invention has been shown and described in detail, the foregoing description is in all aspects illustrative and not restrictive. It is therefore understood that numerous unillustrated modifications can be devised without departing from the scope of the present invention.

Explanation of Reference Signs