JP2019184115A - Refrigerating machine controller, refrigerating machine, control method of refrigerating machine, and control program of refrigerating machine - Google Patents

Abstract

To provide a refrigerating machine controller capable of protecting a discharged refrigerant temperature while suppressing capacity degradation, and to provide a refrigerating machine, and a control method of the refrigerating machine, and a control program of the refrigerating machine.SOLUTION: A controller 10 of a refrigerating machine includes: a compressor 2 compressing a refrigerant; a condenser 3 condensing the compressed refrigerant; an expansion valve 5 expanding a liquid refrigerant, and having an opening controlled by evaporator outlet overheat degree control of controlling a refrigerant overheat degree of the outlet of an evaporator 6 to a value in a first prescribed range; and the evaporator 6 evaporating the refrigerant. The controller stops the evaporator outlet overheat degree control, and controls the opening of the expansion valve 5 in an opening direction by discharged refrigerant temperature protection control of controlling a discharged refrigerant temperature to a value in a second prescribed range, when a discharged refrigerant temperature exceeds a first threshold value, and stops the discharged refrigerant temperature protection control, and controls the opening of the expansion valve 5 by the evaporator outlet overheat degree control, when a discharged refrigerant temperature is lower than a second threshold value smaller than the first threshold value, and a refrigerant overheat degree of the outlet of the evaporator 6 is equal to or more than a third threshold value.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a refrigerator control device, a refrigerator, a refrigerator control method, and a refrigerator control program.

It is known that the refrigerator has a larger pressure ratio between the low pressure and the high pressure during operation than the air conditioner. In operation with a high pressure ratio (high pressure ratio operation) as in a refrigerator, the discharge refrigerant temperature of the compressor is likely to rise, and the operation is such that the discharge refrigerant temperature exceeds the allowable temperature of the compressor. Protective action to lower
For example, as a protection method for lowering the discharge refrigerant temperature (discharge refrigerant temperature protection method), a method for reducing the pressure ratio by lowering the number of revolutions of the compressor, or by bypassing a part of the liquid refrigerant to the suction side of the compressor A method of cooling the compressor is used.

Patent Document 1 discloses that the opening degree of the expansion valve is controlled in the opening direction until the refrigerant discharge temperature of the compressor reaches the target discharge temperature.
Further, in Patent Document 2, when the degree of superheat of the refrigerant is high, the opening of the expansion valve is increased to increase the refrigerant flow rate, and the refrigerant recovery operation is terminated when the discharged refrigerant temperature reaches a predetermined set value. It is disclosed.

International Publication No. 2015/174054 JP 2000-39237 A

However, the invention disclosed in the above that lowers the rotational speed of the compressor and the invention that bypasses the liquid refrigerant has a problem that the refrigerating capacity is greatly reduced.
In particular, when the liquid refrigerant is bypassed, the liquid refrigerant is returned to the compressor, so that the oil in the compressor is diluted, which may affect the lubricity. Furthermore, since the liquid return amount changes due to the pressure difference between the low pressure and the high pressure, it is difficult to always control the liquid return amount to the optimum amount.

Moreover, in the invention disclosed in Patent Document 1, the termination condition in the expansion valve opening degree control is not disclosed, and it is difficult to control the refrigerator only with the invention disclosed in Patent Document 1.
On the other hand, the invention disclosed in Patent Document 2 is not an invention for the purpose of protecting the discharge refrigerant temperature of the compressor, but an invention for increasing the refrigerant by increasing the degree of superheat and taking out the excess refrigerant stored in the accumulator.

  Furthermore, the inventions disclosed in Patent Documents 1 and 2 are both inventions in air conditioners. The refrigerator is operated with a large pressure ratio between the low pressure and the high pressure compared to the air conditioner. For this reason, the control of the air conditioner cannot be applied to the control of the refrigerator as it is, and it is difficult to apply the inventions disclosed in Patent Documents 1 and 2 to the control of the refrigerator.

  The present invention has been made in view of such circumstances, and has a refrigerator control device, a refrigerator, a refrigerator control method, and a refrigerator capable of protecting the discharged refrigerant temperature while suppressing a decrease in capacity. The purpose is to provide a control program.

In order to solve the above-described problems, a refrigerator control device, a refrigerator, a refrigerator control method, and a refrigerator control program according to the present disclosure employ the following means.
A control device for a refrigerator according to an aspect of some embodiments of the present disclosure includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and the condenser. An expansion valve whose degree of opening is controlled by an evaporator outlet superheat degree control that expands the liquid refrigerant and controls the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range, and a refrigerant derived from the expansion valve A control device for a refrigerator including the evaporator, wherein when the refrigerant discharge refrigerant temperature exceeds a first threshold, the evaporator outlet superheat control is stopped, and the refrigerant discharge The opening degree of the expansion valve is controlled in the opening direction by discharge refrigerant temperature protection control for controlling the temperature to a value within a second predetermined range, and the discharge refrigerant temperature of the compressor is less than a second threshold value that is smaller than the first threshold value. And the degree of superheat of the refrigerant at the outlet of the evaporator For more third threshold value, to stop the discharge refrigerant temperature protection control, controls the opening of the expansion valve by the evaporator outlet superheat degree control.

According to the present disclosure, the discharged refrigerant temperature is controlled to be equal to or lower than the first threshold value, and continuous operation is possible without substantially stopping the compressor.
Moreover, since the refrigerant | coolant thermal energy of the refrigerant | coolant supplied to the evaporator excessively is collect | recovered, the fall of refrigerating capacity can be suppressed very small.
Further, since the compressor can maintain the suction of the refrigerant gas, the liquid refrigerant is not sucked and the oil is not diluted, so that the lubricity of the compressor is not affected.
Further, since the refrigerant flow rate can be finely controlled by the expansion valve, it is possible to control the minimum liquid return amount necessary for maintaining the discharged refrigerant temperature below the first threshold value, and stable operation is possible.

Further, when the refrigerant discharge refrigerant temperature is lower than the second threshold value, which is smaller than the first threshold value, and the refrigerant superheat degree at the outlet of the evaporator is equal to or greater than the third threshold value, the discharge refrigerant temperature protection control is stopped. Since the opening degree of the expansion valve is controlled by the evaporator outlet superheat degree control, after confirming that the refrigerant superheat degree at the outlet of the evaporator is secured, the discharge refrigerant temperature protection control is terminated and Shifting to the evaporator outlet superheat degree control, the discharge refrigerant temperature of the compressor that has decreased too much by the discharge refrigerant temperature protection control can be raised.
Further, the end condition of the discharge refrigerant temperature protection control is clear, and the control can be ended correctly.

  In the above aspect, when the discharge refrigerant temperature of the compressor is a value lower than the second threshold and the refrigerant superheat degree at the outlet of the evaporator is a value lower than the third threshold, the discharge The refrigerant temperature protection control may be stopped, and the opening degree of the expansion valve may be controlled in the closing direction by the evaporator outlet superheat degree control.

  According to the present disclosure, when the discharge refrigerant temperature of the compressor is a value lower than the second threshold value, and the refrigerant superheat degree at the outlet of the evaporator is a value lower than the third threshold value, The discharge refrigerant temperature protection control is stopped, and the opening degree of the expansion valve is controlled in the closing direction by the evaporator outlet superheat degree control. The discharge refrigerant temperature of the compressor is lowered by the discharge refrigerant temperature protection control, and a liquid back may occur in the compressor when the refrigerant superheat degree at the outlet of the evaporator falls below the lower limit value to be ensured. However, according to the present disclosure, since the opening degree of the expansion valve is controlled in the closing direction, it is possible to increase the refrigerant superheat degree at the outlet of the evaporator and further increase the discharge refrigerant temperature of the compressor.

  In the above aspect, when the discharge refrigerant temperature of the compressor is not less than the second threshold value and not more than the first threshold value, the opening degree of the expansion valve is maintained by the discharge refrigerant temperature protection control. It may be controlled.

  According to the present disclosure, when the discharge refrigerant temperature of the compressor is a value that is greater than or equal to the second threshold value and less than or equal to the first threshold value, control is performed to maintain the opening degree of the expansion valve by the discharge refrigerant temperature protection control. To do. Thereby, in the discharge refrigerant temperature protection control, the discharge refrigerant temperature of the compressor is controlled so as to be within the second predetermined range not less than the second threshold and not more than the first threshold. Can be continued. In addition, the capacity of the refrigerator can be secured and maintained.

  In the above aspect, when a predetermined time or more has elapsed since the opening degree of the expansion valve was controlled by the discharge refrigerant temperature protection control, it is determined whether or not the discharge refrigerant temperature of the compressor has exceeded the first threshold value. It may be done.

  According to the present disclosure, whether or not the discharge refrigerant temperature of the compressor has exceeded the first threshold value when a predetermined time or more has elapsed since the opening degree of the expansion valve was controlled by the discharge refrigerant temperature protection control. Make a decision. Thereby, since the refrigerant | coolant discharge refrigerant | coolant temperature of a compressor is determined after predetermined time passes and the refrigerant circuit of a refrigerator will be in a steady state, it can determine correctly.

  In the above aspect, the third threshold value may be a value smaller than a target refrigerant superheat degree in the evaporator outlet superheat degree control.

  According to the present disclosure, since the third threshold value is smaller than the target refrigerant superheat degree in the evaporator outlet superheat degree control, the minimum refrigerant superheat degree at the outlet of the evaporator is ensured, and the compressor liquid The occurrence of back can be suppressed.

  A refrigerator according to an aspect of some embodiments of the present disclosure includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and a liquid refrigerant guided from the condenser. An expansion valve whose degree of opening is controlled by an evaporator outlet superheat degree control that controls the degree of refrigerant superheat at the outlet of the evaporator to a value within a first predetermined range, and the refrigerant introduced from the expansion valve evaporates The evaporator to be operated, and any one of the control devices described above.

  A method of controlling a refrigerator according to an aspect of some embodiments of the present disclosure is provided with a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and the condenser. An expansion valve whose degree of opening is controlled by an evaporator outlet superheat degree control for expanding the liquid refrigerant and controlling the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range, and led from the expansion valve A control method of a refrigerator comprising the evaporator for evaporating a refrigerant, and when the discharge refrigerant temperature of the compressor exceeds a first threshold, the evaporator outlet superheat degree control is stopped, and the discharge A step of controlling the opening of the expansion valve in the opening direction by discharge refrigerant temperature protection control for controlling the refrigerant temperature to a value within a second predetermined range; and a second threshold value at which the discharge refrigerant temperature of the compressor is lower than the first threshold value. Before the evaporator outlet. If the refrigerant superheating degree is equal to or greater than the third threshold value, to stop the discharge refrigerant temperature protection control, and a step of controlling an opening degree of the expansion valve by the evaporator outlet superheat degree control.

  A control program for a refrigerator according to an aspect of some embodiments of the present disclosure is derived from a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, and the condenser. An expansion valve whose degree of opening is controlled by an evaporator outlet superheat degree control for expanding the liquid refrigerant and controlling the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range, and led from the expansion valve A control program for a refrigerator comprising the evaporator for evaporating the refrigerant, and when the discharge refrigerant temperature of the compressor exceeds a first threshold, the evaporator outlet superheat degree control is stopped and the discharge A step of controlling the opening of the expansion valve in the opening direction by discharge refrigerant temperature protection control for controlling the refrigerant temperature to a value within a second predetermined range; and a second threshold value at which the discharge refrigerant temperature of the compressor is smaller than the first threshold value. And a value below When the refrigerant superheat degree at the outlet of the generator is equal to or greater than a third threshold, the discharge refrigerant temperature protection control is stopped, and the opening degree of the expansion valve is controlled by the evaporator outlet superheat degree control. .

According to the present disclosure, when the discharge refrigerant temperature exceeds the first threshold value, the evaporator outlet superheat degree control is stopped, and the opening degree of the expansion valve is controlled by the discharge refrigerant temperature protection control. Can be implemented.
Also, when the refrigerant discharge refrigerant temperature is lower than the second threshold value and the refrigerant superheat degree at the evaporator outlet is equal to or higher than the third threshold value, the discharge refrigerant temperature protection control is stopped and the evaporator outlet overheat is stopped. Since the degree of opening of the expansion valve is controlled by the degree control, the end condition of the discharged refrigerant temperature protection control is clear and can be stopped correctly.

It is the schematic block diagram which showed the one aspect | mode of the refrigerating cycle of the refrigerator which concerns on some embodiment. It is the flowchart which showed control of the control apparatus of the refrigerator which concerns on some embodiment. It is the schematic block diagram which showed the refrigerating cycle of the refrigerator as a reference example. It is the graph which showed the change of the discharge refrigerant | coolant temperature in the refrigerator as a reference example. It is the graph which showed the change of the discharge refrigerant | coolant temperature in the refrigerator which concerns on some embodiment. It is the graph which showed the change of the refrigerating capacity in the refrigerator as a reference example. It is the graph which showed the change of the refrigerating capacity in the refrigerator concerning some embodiments. It is a pressure-enthalpy diagram in the refrigerator as a reference example. It is a pressure-enthalpy diagram in the refrigerator concerning some embodiments.

Hereinafter, embodiments of a refrigerator control device, a refrigerator, a refrigerator control method, and a refrigerator control program according to some embodiments of the present disclosure will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of one aspect of a refrigeration cycle of a refrigerator according to some embodiments of the present disclosure.
As shown in FIG. 1, a refrigeration cycle 1 of a refrigerator includes a compressor 2 that compresses a refrigerant gas introduced from an evaporator 6, and a high-temperature and high-pressure refrigerant compressed by the compressor 2 that is sent from the compressor 2. The condenser 3 that condenses the gas by heat exchange with the outside air, and the gas-liquid internal heat that supercools the liquid refrigerant condensed in the condenser 3 sent from the condenser 3 with the gas refrigerant from the evaporator 6. An exchanger (heat exchanger) 4, an expansion valve 5 for expanding the supercooled liquid refrigerant guided from the gas-liquid internal heat exchanger 4, and the expanded refrigerant and air are heat-exchanged to evaporate the refrigerant. The evaporator 6 is connected to the evaporator pipe 8 in this order. The evaporator 6 is used for cooling the inside of the freezer.

  The refrigeration cycle 1 is provided with a discharge refrigerant temperature sensor 7 that detects a refrigerant temperature (discharge refrigerant temperature) discharged from the compressor 2, and a detection value of the discharge refrigerant temperature sensor 7 is input to the control device 10. It is comprised so that.

The control device 10 has a function of adjusting the opening degree of the expansion valve 5 so as to control the refrigerant superheat degree at the outlet of the evaporator 6 to a value within a first predetermined range including the target refrigerant superheat degree.
By securing the refrigerant superheat degree at the outlet of the evaporator 6, the evaporator 6 can be used efficiently. Therefore, a target refrigerant superheat degree that is a control target value of the refrigerant superheat degree is set. The control device 10 performs control so that the refrigerant superheat degree at the outlet of the evaporator 6 becomes a value in a first predetermined range including the target refrigerant superheat degree.
Control of the degree of refrigerant superheat is performed by the control device 10 adjusting the opening of the expansion valve 5. For example, when increasing the degree of refrigerant superheat, the opening of the expansion valve 5 is controlled in the closing direction. When the refrigerant superheat degree is lowered, the opening degree of the expansion valve 5 is controlled in the opening direction.
For example, the target refrigerant superheat degree is 7 ° C.

  The control device 10 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), and a computer-readable non-transitory storage medium. A series of processes for realizing various functions is stored in a storage medium or the like in the form of a program as an example, and the CPU reads the program into a RAM or the like to execute information processing / arithmetic processing. As a result, various functions are realized. The program is preinstalled in a ROM or other storage medium, provided in a state stored in a computer-readable storage medium, or distributed via wired or wireless communication means. Etc. may be applied. The computer-readable storage medium is a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, a semiconductor memory, or the like.

The refrigerator is said to have a larger pressure ratio between the low pressure and the high pressure during operation than the air conditioner. In such a high pressure ratio operation with a large pressure ratio, the discharge refrigerant temperature of the compressor 2 is likely to rise.
On the other hand, the compressor 2 has an upper limit on the temperature at which the compressor 2 can be operated, and this is set as the compressor allowable temperature upper limit. Therefore, when the operating condition is such that the discharged refrigerant temperature measured by the discharged refrigerant temperature sensor 7 exceeds the compressor allowable temperature upper limit value of the compressor 2, a protection operation for lowering the discharged refrigerant temperature is required.

  Here, when the discharged refrigerant temperature reaches the upper limit value of the compressor allowable temperature, the compressor 2 may not only stop operation but also cause failure. Therefore, a discharge refrigerant temperature control upper limit value (first threshold value) lower by a predetermined temperature than the compressor allowable temperature upper limit value is provided. When the discharge refrigerant temperature reaches the discharge refrigerant temperature control upper limit, it is assumed that discharge refrigerant temperature protection control is performed in some embodiments of the present disclosure. The discharge refrigerant temperature control upper limit value is, for example, the compressor allowable temperature upper limit value −15 ° C.

  In addition, a discharge refrigerant temperature control lower limit value is provided as a second threshold value that is smaller than the discharge refrigerant temperature control upper limit value. The discharge refrigerant temperature control lower limit value is, for example, the discharge refrigerant temperature control upper limit value −35 ° C. The discharge refrigerant temperature control lower limit value is a temperature that is a guideline for determining that the temperature of the compressor 2 is too low when the discharge refrigerant temperature falls below the discharge refrigerant temperature control lower limit value, and increasing the temperature of the compressor 2.

  The discharge refrigerant temperature protection control is to control the discharge refrigerant temperature to be a value in the second predetermined range. The second predetermined range is a range not less than the discharge refrigerant temperature control lower limit (second threshold) and not more than the discharge refrigerant temperature control upper limit (first threshold). The control device 10 controls the opening degree of the expansion valve 5 so that the discharge refrigerant temperature measured by the discharge refrigerant temperature sensor 7 falls within a second predetermined range. Here, the discharge refrigerant temperature control lower limit value is a value smaller than the discharge refrigerant temperature control upper limit value.

Below, control of the refrigerator concerning some embodiments of this indication is explained.
FIG. 2 is a flowchart showing the control of the refrigerator control device according to some embodiments of the present disclosure.
When the control of the control device 10 is started, it is determined whether or not the compressor discharge refrigerant temperature (Td) protection control is being performed (S201). When it is determined that the compressor discharge refrigerant temperature protection control is being performed, the process proceeds to step S202, and when it is determined that the compressor discharge refrigerant temperature protection control is not being performed, the process proceeds to step S208.

In step S202, it is determined whether or not a predetermined time has elapsed since the opening of the expansion valve 5 was changed in the previous process. When the opening degree of the expansion valve 5 is changed, a time lag occurs until the refrigerant circuit of the refrigeration cycle 1 reaches a steady state. Therefore, the time when the refrigerant circuit is predicted to be in a steady state is set to a predetermined time, and it is determined whether or not the predetermined time has elapsed.
When the predetermined time or more has elapsed after the opening degree change, the process proceeds to step S203, and when the predetermined time has not elapsed, the process is once ended and the process is performed again from the beginning.

  If it is determined in step S202 that a predetermined time or more has elapsed after the opening degree of the expansion valve 5 is changed, the compressor discharge refrigerant temperature detected by the discharge refrigerant temperature sensor 7 is set to the discharge refrigerant temperature control upper limit value (first value). It is determined whether or not the threshold value is exceeded (S203).

  When it is determined in step S203 that the compressor discharge refrigerant temperature exceeds the discharge refrigerant temperature control upper limit value, the process proceeds to step S210. On the other hand, when it is determined that the compressor discharge refrigerant temperature is equal to or lower than the discharge refrigerant temperature control upper limit value, the process proceeds to step S204.

  If it is determined in step S203 that the compressor discharge refrigerant temperature exceeds the discharge refrigerant temperature control upper limit, the opening of the expansion valve 5 is increased by a predetermined amount (S210). That is, the control device 10 controls the opening degree of the expansion valve 5 in the opening direction by a predetermined amount. Thereby, the refrigerant | coolant flow volume which circulates through the refrigerating cycle 1 increases, and the compressor discharge refrigerant temperature falls. In this case, the refrigerant superheat degree at the outlet of the evaporator 6 also decreases.

  When the opening degree of the expansion valve 5 is increased by a predetermined amount in step S210, the process is once ended, and the process is performed again from the beginning.

  On the other hand, if it is determined in step S203 that the compressor discharge refrigerant temperature is equal to or lower than the discharge refrigerant temperature control upper limit value, it is determined whether or not the compressor discharge refrigerant temperature is equal to or higher than the discharge refrigerant temperature control lower limit value (second threshold value). Is performed (S204).

  In step S204, when it is determined that the compressor discharge refrigerant temperature is equal to or higher than the discharge refrigerant temperature control lower limit value, the process is temporarily terminated while the control is performed so as to maintain the opening degree of the expansion valve 5, and again, Processing is performed from the beginning.

  On the other hand, when it is determined in step S204 that the compressor discharge refrigerant temperature is lower than the discharge refrigerant temperature control lower limit value, the process proceeds to step S205.

When the compressor discharge refrigerant temperature is lower than the discharge refrigerant temperature control lower limit value, it is necessary to increase the compressor discharge refrigerant temperature. Here, in step S205, the degree of refrigerant superheat at the outlet of the evaporator 6 is determined. When it is determined that the refrigerant superheat degree at the outlet of the evaporator 6 is equal to or higher than the refrigerant superheat degree control lower limit (third threshold value), the process proceeds to step S206. On the other hand, when it determines with a refrigerant | coolant superheat degree being less than a refrigerant | coolant superheat degree control lower limit, it changes to step S211.
Here, the refrigerant superheat degree control lower limit value (third threshold value) is a value that should be secured at least in the refrigerant superheat degree at the outlet of the evaporator 6 in order to use the evaporator 6 efficiently. The refrigerant superheat degree control lower limit value is a value smaller than the target refrigerant superheat degree, for example, a target refrigerant superheat degree of −2 ° C. is set.

When it is determined that the compressor discharge refrigerant temperature is lower than the discharge refrigerant temperature control lower limit value (NO in S204) and the refrigerant superheat degree at the outlet of the evaporator 6 is equal to or higher than the refrigerant superheat degree control lower limit value (YES in S205) ) Needs to increase the refrigerant discharge refrigerant temperature, but since the refrigerant superheat degree is secured, the compressor discharge refrigerant temperature protection control is terminated (S206), and the evaporator outlet superheat degree control is performed (S207). ).
When the evaporator outlet superheat degree control is started in step S207, the process is once ended, and the process is performed again from the beginning.

On the other hand, when it is determined that the compressor discharge refrigerant temperature is lower than the discharge refrigerant temperature control lower limit value (NO in S204) and the refrigerant superheat degree at the outlet of the evaporator 6 is lower than the refrigerant superheat degree control lower limit value (S205). NO) needs to increase the compressor discharge refrigerant temperature and the degree of refrigerant superheat. When the opening degree of the expansion valve 5 is increased, the refrigerant superheat degree at the outlet of the evaporator 6 may not be applied. At this time, since a liquid back may occur in the compressor 2, it is necessary to ensure the degree of refrigerant superheat. Therefore, the opening degree of the expansion valve 5 is decreased by a predetermined amount (S211). That is, the control device 10 controls the opening degree of the expansion valve 5 in the closing direction by a predetermined amount. Thereby, the refrigerant | coolant flow rate which circulates through the refrigerating cycle 1 reduces, and the refrigerant | coolant discharge refrigerant | coolant temperature and the refrigerant | coolant superheat degree in the exit of the evaporator 6 rise.
When the opening degree of the expansion valve 5 is decreased by a predetermined amount in step S211, the process is once ended and the process is performed again from the beginning.
The compressor discharge refrigerant temperature protection control is performed as described above.

  If it is determined in step S201 that the compressor discharge refrigerant temperature protection control is not performed, the compressor discharge refrigerant temperature detected by the discharge refrigerant temperature sensor 7 is the discharge refrigerant temperature control upper limit value (first value). It is determined whether or not the threshold value is exceeded (S208).

  When it is determined in step S208 that the compressor discharge refrigerant temperature exceeds the discharge refrigerant temperature control upper limit value, the process proceeds to step S209. On the other hand, when it is determined that the compressor discharge refrigerant temperature is equal to or lower than the discharge refrigerant temperature control upper limit value, the process proceeds to step S207.

  If it is determined in step S208 that the compressor discharge refrigerant temperature exceeds the discharge refrigerant temperature control upper limit, compressor discharge refrigerant temperature protection control is started (S209), and the opening degree of the expansion valve 5 is increased by a predetermined amount. (S210). That is, the control device 10 controls the opening degree of the expansion valve 5 in the opening direction by a predetermined amount. Thereby, the refrigerant | coolant flow volume which circulates through the refrigerating cycle 1 increases, and the compressor discharge refrigerant temperature falls. In this case, the refrigerant superheat degree at the outlet of the evaporator 6 also decreases.

  When the opening degree of the expansion valve 5 is increased by a predetermined amount in step S210, the process is once ended, and the process is performed again from the beginning.

On the other hand, when it is determined in step S208 that the compressor discharge refrigerant temperature is equal to or lower than the discharge refrigerant temperature control upper limit value, the evaporator outlet superheat degree control is performed (S207).
When the evaporator outlet superheat degree control is started in step S207, the process is once ended, and the process is performed again from the beginning.
As described above, when normal evaporator outlet superheat control is performed, the process proceeds in the order of step S201, step S208, and step S207 in the flowchart of FIG.

  Below, compared with the refrigerator as a reference example, control by the control device of the refrigerator concerning some embodiments of this indication is explained. The refrigeration cycle 51 of the refrigerator as a reference example includes a liquid bypass line 59 that connects the outlet side of the condenser 53 and the inlet side of the compressor 52, as shown in FIG. The refrigerating machine as a reference example is configured to bypass the liquid refrigerant to the inlet side of the compressor 52 when the discharge refrigerant temperature of the compressor 52 measured by the discharge refrigerant temperature sensor 57 exceeds the discharge refrigerant temperature control upper limit value. The compressor 52 is cooled by performing bypass control.

Other configurations of the refrigerator as a reference example are the same as those of the refrigerator according to some embodiments of the present disclosure, and the compressor 2 and the compressor 52, the condenser 3 and the condenser 53, and the gas-liquid internal heat, respectively. The exchanger 4 and the gas-liquid internal heat exchanger 54, the expansion valve 5 and the expansion valve 55, the evaporator 6 and the evaporator 56, the discharge refrigerant temperature sensor 7 and the discharge refrigerant temperature sensor 57, the refrigerant pipe 8 and the refrigerant pipe 58, Each corresponds.
The control device 50 performs liquid bypass control.

FIG. 4 is a graph showing changes in the discharged refrigerant temperature in a refrigerator as a reference example.
In FIG. 4, the vertical axis represents the temperature of refrigerant discharged from the compressor 52, and the horizontal axis represents time. Moreover, in discharge refrigerant temperature, a shows liquid bypass control end temperature mentioned later, b shows discharge refrigerant temperature control upper limit, c shows compressor allowable temperature upper limit.

  When time elapses from time 0 in FIG. 4, the discharge refrigerant temperature of the compressor 52 rises, and reaches the discharge refrigerant temperature control upper limit b at time t1. When the discharge refrigerant temperature reaches the discharge refrigerant temperature control upper limit b, the liquid bypass control is started by the control device 50 and the liquid bypass line 59 is opened. Since there is a time lag for the discharge refrigerant temperature of the compressor 52 to start decreasing after the liquid bypass control is started, the discharge refrigerant temperature starts to decrease after a lapse of a certain time after the time t1. An end temperature is set for the liquid bypass control, and this is set as the liquid bypass control end temperature a. When the discharged refrigerant temperature reaches the liquid bypass control end temperature a at time t2, the liquid bypass line 59 is closed, and the liquid bypass control ends.

  Since there is a time lag even when the discharge refrigerant temperature of the compressor 52 starts to rise after the liquid bypass control is finished, the discharge refrigerant temperature starts to rise after a lapse of a certain time after the time t2. Thereafter, the liquid bypass control is started when the discharge refrigerant temperature reaches the discharge refrigerant temperature control upper limit b at time t3, and the liquid bypass control is ended when the liquid bypass control end temperature a is reached at time t4. The start and end of control are performed alternately and continuously.

  As shown in FIG. 4, when the liquid bypass control is performed, the temperature change of the discharged refrigerant temperature is large. Therefore, the discharge refrigerant temperature frequently reaches the discharge refrigerant temperature control upper limit b and the liquid bypass control end temperature a, and the control is switched in a short time. Further, since the liquid refrigerant is bypassed from the outlet of the condenser 53 to the inlet of the compressor 52, the amount of refrigerant flowing into the evaporator 56 is reduced and does not contribute to the refrigeration function by the reduced amount of refrigerant.

FIG. 5 is a graph showing changes in the discharged refrigerant temperature in refrigerators according to some embodiments of the present disclosure.
In FIG. 5, the vertical axis represents the temperature of refrigerant discharged from the compressor 52, and the horizontal axis represents time. Moreover, in discharge refrigerant temperature, d shows the discharge refrigerant temperature control lower limit (second threshold value) mentioned later, b shows discharge refrigerant temperature control upper limit (first threshold), and c shows compressor allowable temperature upper limit.

  At time 0 in FIG. 5, the evaporator outlet superheat degree control is performed. When time elapses from time 0, the discharge refrigerant temperature of the compressor 2 rises and reaches the discharge refrigerant temperature control upper limit b at time t7. When the discharge refrigerant temperature reaches the discharge refrigerant temperature control upper limit b, the evaporator outlet superheat degree control is stopped and the discharge refrigerant temperature protection control is started.

  As described above, the discharged refrigerant temperature protection control controls the discharged refrigerant temperature to a value within the second predetermined range. The discharge refrigerant temperature measured by the discharge refrigerant temperature sensor 7 is set to a value within a second predetermined range that is a range from the discharge refrigerant temperature control lower limit (second threshold) d to the discharge refrigerant temperature control upper limit (first threshold) b. Furthermore, the control device 10 controls the opening degree of the expansion valve 5.

When the discharged refrigerant temperature protection control is started at time t7, the opening degree of the expansion valve 5 is controlled in the opening direction. Since there is a time lag when the discharge refrigerant temperature of the compressor 2 starts to decrease after the opening degree of the expansion valve 5 is controlled in the opening direction, the discharge refrigerant temperature starts to decrease after a lapse of a certain time after the time t7.
By performing the control shown in the flowchart of FIG. 2 in the discharge refrigerant temperature protection control, the discharge refrigerant temperature of the compressor 2 is controlled such that a large fluctuation is suppressed and the temperature changes within the second predetermined range. . Therefore, according to some embodiments of the present disclosure, stable operation can be continued.

  Further, in the refrigerator as a reference example, the difference between the liquid bypass control end temperature a and the discharge refrigerant temperature control upper limit b is increased in order to avoid frequent switching of the liquid bypass control. On the other hand, in the refrigerator according to some embodiments of the present disclosure, the refrigerant flow rate can be finely controlled by the expansion valve 5. Therefore, it is possible to control to the minimum liquid return amount necessary to maintain the discharged refrigerant temperature below the compressor allowable temperature upper limit value. Thereby, the difference between the discharged refrigerant temperature control lower limit d and the discharged refrigerant temperature control upper limit b can be reduced. Since the level of the discharged refrigerant temperature is proportional to the level of the capacity of the refrigerator, changing the discharged refrigerant temperature at a high value also changes the capacity of the refrigerator at a high value.

FIG. 6 is a graph showing changes in the refrigeration capacity in a refrigerator as a reference example.
In FIG. 6, the vertical axis represents the refrigeration capacity of the refrigerator, and the horizontal axis represents the intake air temperature of the condenser. The intake air temperature of the condenser is approximately equal to the outside air temperature. In the refrigerating capacity, R1 is the refrigerating capacity when switching from the evaporator outlet superheat degree control to the discharge refrigerant temperature protection control (in this case, liquid bypass control) at the suction air temperature T1, and R2 is the suction air temperature T2. Shows the refrigerating capacity. The solid line indicates the relationship between the refrigerating capacity and the intake air temperature of the condenser, and the alternate long and short dash line indicates the transition of the refrigerating capacity that is assumed when normal evaporator outlet superheat control is performed.

  In the refrigerator as a reference example, the refrigerating capacity R2 when the intake air temperature rises and becomes the intake air temperature T2 is compared with the refrigerating capacity R1 when the liquid bypass control is started at the intake air temperature T1. The refrigerating capacity is greatly reduced. That is, when the intake air temperature is high, the discharge refrigerant temperature protection control must always be performed, and the liquid bypass line 59 is always opened.

FIG. 7 is a graph showing changes in the refrigeration capacity in the refrigerator according to some embodiments of the present disclosure.
In FIG. 7, the vertical axis represents the refrigeration capacity of the refrigerator, and the horizontal axis represents the intake air temperature of the condenser. Further, in the refrigerating capacity, R1 indicates the refrigerating capacity when switching from the evaporator outlet superheat degree control to the discharge refrigerant temperature protection control at the intake air temperature T1, and R3 indicates the refrigerating capacity at the intake air temperature T2. The solid line indicates the relationship between the refrigerating capacity and the intake air temperature of the condenser, and the alternate long and short dash line indicates the transition of the refrigerating capacity that is assumed when normal evaporator outlet superheat control is performed.

  In the refrigerator according to some embodiments of the present disclosure, the intake air temperature is increased compared to the refrigerating capacity R1 when the discharge refrigerant temperature protection control is started at the intake air temperature T1, and the intake air temperature T2 In this case, the refrigeration capacity R3 is decreased, but the decrease in the refrigeration capacity is small. This is because, as shown in FIG. 5, the discharge refrigerant temperature decreases little. Here, R3 is a value larger than R2.

FIG. 8 is a pressure-enthalpy diagram in a refrigerator as a reference example.
In FIG. 8, the vertical axis represents pressure and the horizontal axis represents enthalpy. A thick solid line shows the refrigerating cycle at the time of evaporator outlet superheat control, and a thick broken line shows the isothermal curve in that case. The solid line shows the refrigeration cycle during the liquid bypass control, and the broken line shows the isothermal curve in that case. Moreover, a dashed-dotted line shows a saturation curve.

In the refrigerating cycle shown in FIG. 8 at the time of evaporator outlet superheat control in the refrigerator as a reference example, h1 is the outlet of the gas refrigerant of the gas-liquid internal heat exchanger 54, h3 is the liquid of the gas-liquid internal heat exchanger 54 The refrigerant inlet, h4 indicates the liquid refrigerant outlet of the gas-liquid internal heat exchanger 54, and h6 indicates the gas refrigerant inlet of the gas-liquid internal heat exchanger 54.
In the refrigeration cycle shown in FIG. 8 at the time of liquid bypass control, h1 ′ is the gas refrigerant outlet of the gas-liquid internal heat exchanger 54, h3 ′ is the liquid refrigerant inlet of the gas-liquid internal heat exchanger 54, h4 ′. Is the liquid refrigerant outlet of the gas-liquid internal heat exchanger 54, and h6 'is the gas refrigerant inlet of the gas-liquid internal heat exchanger 54.

FIG. 9 is a pressure-enthalpy diagram in a refrigerator according to some embodiments of the present disclosure.
In FIG. 9, the vertical axis represents pressure, and the horizontal axis represents enthalpy. A thick solid line shows the refrigerating cycle at the time of evaporator outlet superheat control, and a thick broken line shows the isothermal curve in that case. A solid line indicates a refrigeration cycle during discharge refrigerant temperature protection control, and a broken line indicates an isothermal curve in that case. Moreover, a dashed-dotted line shows a saturation curve.

In the refrigeration cycle shown in FIG. 9 at the time of evaporator outlet superheat control in a refrigerator according to some embodiments of the present disclosure, h1 is the gas refrigerant outlet of the gas-liquid internal heat exchanger 54, and h3 is the gas-liquid internal The liquid refrigerant inlet of the heat exchanger 54, h4 is the liquid refrigerant outlet of the gas-liquid internal heat exchanger 54, and h6 is the gas refrigerant inlet of the gas-liquid internal heat exchanger 54.
In the refrigeration cycle shown in FIG. 9 at the time of liquid bypass control, h1 ″ is the gas refrigerant outlet of the gas-liquid internal heat exchanger 54, h3 ″ is the liquid refrigerant inlet of the gas-liquid internal heat exchanger 54, and h4 ″. Is the liquid refrigerant outlet of the gas-liquid internal heat exchanger 54, and h6 ″ is the gas refrigerant inlet of the gas-liquid internal heat exchanger 54.

In the refrigerator as a reference example, when the control is switched from the normal evaporator outlet superheat degree control to the liquid bypass control, the discharge refrigerant temperature and the refrigeration capacity decrease.
Further, in the refrigerator according to some embodiments of the present disclosure, when the control is switched from the normal evaporator outlet superheat degree control to the discharge refrigerant temperature protection control, the discharge refrigerant temperature and the refrigerating capacity are similarly reduced. .

  In a refrigerator as a reference example, when the control is switched from normal evaporator outlet superheat control to liquid bypass control, an isothermal curve (thick broken line) indicating the discharge refrigerant temperature in the evaporator outlet superheat control is liquid bypass control. It moves to the isothermal curve (broken line) which shows the discharge refrigerant temperature in this, and this movement distance appears as a temperature difference of discharge refrigerant temperature.

On the other hand, in the refrigerators according to some embodiments of the present disclosure, when the control is switched from normal evaporator outlet superheat control to discharged refrigerant temperature protection control, an equal temperature indicating the discharged refrigerant temperature in the evaporator outlet superheat control. The curve (thick broken line) moves to an isothermal curve (broken line) indicating the discharged refrigerant temperature in the discharged refrigerant temperature protection control, and this moving distance appears as a temperature difference between the discharged refrigerant temperatures.
As described above, according to the refrigerators according to some embodiments of the present disclosure, the discharge refrigerant temperature of the compressor 2 can be limited to the temperature decrease necessary to maintain the compressor allowable temperature upper limit value or less. .
Therefore, compared with liquid bypass control, the fall of discharge refrigerant temperature can be suppressed.

Further, in the refrigerator as the reference example, when the control is switched from the normal evaporator outlet superheat degree control to the liquid bypass control, the refrigerant evaporating temperature is changed from h1 to h1 'or from h6 to h6', the difference x ' Only rise. Therefore, the refrigerating capacity corresponding to the difference x ′ decreases.
Further, when the liquid bypass control is performed, the liquid refrigerant is bypassed from h3 ′ to h1 ′, so that the refrigerating capacity corresponding to the difference y (the two-dot chain line portion) between h3 ′ and h1 ′ is lowered.
From the above, in the refrigerator as a reference example, the refrigeration capacity corresponding to x ′ + y is lowered.

On the other hand, in the refrigerator according to some embodiments of the present disclosure, when the control is switched from normal evaporator outlet superheat control to discharged refrigerant temperature protection control, the refrigerant evaporation temperature is changed from h1 to h1 ″ or from h6. The difference x ″ increases to h6 ″. Therefore, the refrigerating capacity corresponding to the difference x ″ decreases.
As described above, the decrease in the refrigerating capacity of the refrigerators according to some embodiments of the present disclosure is less than the decrease in the capacity during the liquid bypass control. Therefore, according to the refrigerator according to some embodiments of the present disclosure, it is possible to suppress a decrease in the refrigerating capacity.

As described above, according to the refrigerator control device, the refrigerator, the refrigerator control method, and the refrigerator control program according to the present embodiment, the following operational effects can be obtained.
According to the present disclosure, since the discharge refrigerant temperature is controlled to be equal to or lower than the discharge refrigerant temperature control upper limit value, the compressor 2 can be continuously operated without substantially stopping.
Moreover, since the refrigerant | coolant thermal energy of the refrigerant | coolant supplied to the evaporator 6 excessively is collect | recovered by the gas-liquid internal heat exchanger 4, the fall of refrigerating capacity can be suppressed very small.
Further, since the compressor 2 can maintain the refrigerant gas suction, the liquid refrigerant is not sucked and the oil is not diluted, so that the lubricity of the compressor 2 is not affected.
Further, since the refrigerant flow rate can be finely controlled by the expansion valve 5, it is possible to control to the minimum liquid return amount necessary to maintain the discharge refrigerant temperature below the upper limit value of the discharge refrigerant temperature control, and stable operation is possible. .

  Further, the discharge refrigerant temperature of the compressor 2 is a value lower than the discharge refrigerant temperature control lower limit value d smaller than the discharge refrigerant temperature control upper limit value b, and the refrigerant superheat degree at the outlet of the evaporator 6 is equal to or higher than the refrigerant superheat degree control lower limit value. In this case, the discharge refrigerant temperature protection control is stopped, and the opening degree of the expansion valve 5 is controlled by the evaporator outlet superheat degree control. After confirming that the refrigerant superheat degree at the outlet of the evaporator 6 is secured, the discharge refrigerant temperature protection control is finished and the routine is shifted to the normal evaporator outlet superheat degree control. The refrigerant temperature discharged from the compressor 2 can be raised.

  Further, according to the present disclosure, the discharge refrigerant temperature of the compressor 2 is a value lower than the discharge refrigerant temperature control lower limit value d, and the refrigerant superheat degree at the outlet of the evaporator 6 is lower than the refrigerant superheat degree control lower limit value. In this case, the discharge refrigerant temperature protection control is stopped, and the opening degree of the expansion valve 5 is controlled in the closing direction by the evaporator outlet superheat degree control. The discharge refrigerant temperature of the compressor 2 is lowered by the discharge refrigerant temperature protection control, and a liquid back may occur in the compressor 2 when the refrigerant superheat degree at the outlet of the evaporator 6 falls below the lower limit value to be ensured. is there. However, according to the present disclosure, the degree of refrigerant superheating at the outlet of the evaporator 6 can be increased because the opening degree of the expansion valve 5 is controlled in the closing direction. Furthermore, the discharge refrigerant temperature of the compressor 2 can be raised.

  Further, according to the present disclosure, when the discharge refrigerant temperature of the compressor 2 is not less than the discharge refrigerant temperature control lower limit value d and not more than the discharge refrigerant temperature control upper limit value b, the expansion valve 5 is controlled by the discharge refrigerant temperature protection control. Control to maintain the opening. Thereby, in the discharge refrigerant temperature protection control, in order to control the discharge refrigerant temperature of the compressor 2 to be within the second predetermined range of the discharge refrigerant temperature control lower limit d or more and the discharge refrigerant temperature control upper limit b or less, There is little fluctuation in the discharged refrigerant temperature, and stable operation can be continued. In addition, the capacity of the refrigerator can be secured and maintained.

  Further, according to the present disclosure, whether or not the discharge refrigerant temperature of the compressor 2 has exceeded the discharge refrigerant temperature control upper limit b when a predetermined time or more has elapsed since the opening of the expansion valve 5 was controlled by the discharge refrigerant temperature protection control. Judgment is made. Thus, since the refrigerant temperature discharged from the compressor 2 is determined after a predetermined time has elapsed and the refrigerant circuit of the refrigerator has reached a steady state, the determination can be made correctly.

  Further, according to the present disclosure, the refrigerant superheat degree control lower limit value is a value smaller than the target refrigerant superheat degree in the evaporator outlet superheat degree control. The occurrence of liquid back in the machine 2 can be suppressed.

1, 51 Refrigeration cycle 2, 52 Compressor 3, 53 Condenser 4, 54 Gas-liquid internal heat exchanger (heat exchanger)
5, 55 Expansion valve 6, 56 Evaporator 7, 57 Discharge refrigerant temperature sensor 8, 58 Refrigerant piping 10, 50 Control device 59 Liquid bypass line

Claims (8)

A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve whose opening is controlled by an evaporator outlet superheat degree control that expands the liquid refrigerant guided from the condenser and controls the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range;
The evaporator for evaporating the refrigerant led from the expansion valve, and a control device for a refrigerator comprising:
When the discharge refrigerant temperature of the compressor exceeds the first threshold, the evaporator outlet superheat degree control is stopped, and the expansion is performed by discharge refrigerant temperature protection control for controlling the discharge refrigerant temperature to a value within a second predetermined range. Control the opening of the valve in the opening direction,
When the discharge refrigerant temperature of the compressor is lower than a second threshold value that is smaller than a first threshold value, and the refrigerant superheat degree at the outlet of the evaporator is equal to or greater than a third threshold value, the discharge refrigerant temperature protection The control apparatus of the refrigerator which stops control and controls the opening degree of the said expansion valve by the said evaporator exit superheat degree control.   When the discharge refrigerant temperature of the compressor is lower than the second threshold value and the refrigerant superheat degree at the outlet of the evaporator is lower than the third threshold value, the discharge refrigerant temperature protection control The refrigerator control device according to claim 1, wherein the opening degree of the expansion valve is controlled in the closing direction by controlling the degree of superheat of the evaporator outlet.   The control is performed to maintain the opening degree of the expansion valve by the discharge refrigerant temperature protection control when the discharge refrigerant temperature of the compressor is not less than the second threshold and not more than the first threshold. The control apparatus of the refrigerator of Claim 1 or Claim 2.   2. A determination is made as to whether or not the discharge refrigerant temperature of the compressor has exceeded the first threshold when a predetermined time or more has elapsed since the opening of the expansion valve was controlled by the discharge refrigerant temperature protection control. The control apparatus of the refrigerator in any one of Claim 3.   The control apparatus for a refrigerator according to any one of claims 1 to 4, wherein the third threshold value is a value smaller than a target refrigerant superheat degree in the evaporator outlet superheat degree control. A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve whose opening is controlled by an evaporator outlet superheat degree control that expands the liquid refrigerant guided from the condenser and controls the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range;
The evaporator for evaporating the refrigerant guided from the expansion valve;
A refrigerator comprising: the control device according to any one of claims 1 to 5. A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve whose opening is controlled by an evaporator outlet superheat degree control that expands the liquid refrigerant guided from the condenser and controls the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range;
A method of controlling a refrigerator comprising: the evaporator that evaporates the refrigerant guided from the expansion valve;
When the discharge refrigerant temperature of the compressor exceeds the first threshold, the evaporator outlet superheat degree control is stopped, and the expansion is performed by discharge refrigerant temperature protection control for controlling the discharge refrigerant temperature to a value within a second predetermined range. Controlling the opening of the valve in the opening direction;
When the discharge refrigerant temperature of the compressor is lower than a second threshold value that is smaller than a first threshold value, and the refrigerant superheat degree at the outlet of the evaporator is equal to or greater than a third threshold value, the discharge refrigerant temperature protection And a step of controlling the opening degree of the expansion valve by controlling the degree of superheat of the evaporator outlet. A compressor for compressing the refrigerant;
A condenser for condensing the refrigerant compressed by the compressor;
An expansion valve whose opening is controlled by an evaporator outlet superheat degree control that expands the liquid refrigerant guided from the condenser and controls the refrigerant superheat degree at the outlet of the evaporator to a value within a first predetermined range;
A control program for a refrigerator comprising the evaporator for evaporating the refrigerant guided from the expansion valve,
When the discharge refrigerant temperature of the compressor exceeds the first threshold, the evaporator outlet superheat degree control is stopped, and the expansion is performed by discharge refrigerant temperature protection control for controlling the discharge refrigerant temperature to a value within a second predetermined range. Controlling the opening of the valve in the opening direction;
When the discharge refrigerant temperature of the compressor is lower than a second threshold value that is smaller than a first threshold value, and the refrigerant superheat degree at the outlet of the evaporator is equal to or greater than a third threshold value, the discharge refrigerant temperature protection A control program for the refrigerator, comprising: stopping control and controlling the opening degree of the expansion valve by the evaporator outlet superheat degree control.

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