TW202407269A - Two-stage refrigeration apparatus - Google Patents

Abstract

A two-stage refrigeration apparatus 1 comprises: a low-stage side refrigeration cycle 10; a high-stage side refrigeration cycle 20; and a control device 30. The control device 30: reduces the rotational speed of a low-stage side motor 11b when the low-stage side suction pressure is lower than a first lower limit pressure; increases the rotational speed of the low-stage side motor 11b when the low-stage side suction pressure exceeds a first upper limit pressure; and maintains the rotational speed of the low-stage side motor 11b and executes control in accordance with the following low-stage side differential pressure, when the low-stage side suction pressure is not less than the first lower limit and not more than the first upper limit pressure. That is, the rotational speed of a high-stage side motor 21a is reduced when the low-stage side differential pressure is lower than a second lower limit pressure, the rotational speed of the high-stage side motor 21a is increased when the low-stage side differential pressure exceeds a second upper limit pressure, and the rotational speed of the high-stage side motor 21a is maintained when the low-stage side differential pressure is not less than the second lower limit and not more than the second upper limit pressure.

Description

Binary freezing device

The present invention relates to a binary refrigeration device.

A binary refrigeration device in which a low-side refrigeration cycle and a high-side refrigeration cycle are thermally connected through a series heat exchanger is known (for example, see Patent Document 1). In the binary refrigeration device of Patent Document 1, in the low-side refrigeration cycle, CO2 (carbon dioxide) is used as the low-side refrigerant, and a scroll-type low-side compressor is used. The purpose of Patent Document 1 is to obtain a highly efficient binary refrigeration device. [Prior technical literature] [Patent Document]

[Patent Document 1] Japanese Patent Application Publication No. 2012-112615

[Problem to be solved by the invention]

Rotary low-side compressors such as scroll type or screw type have bearings. If CO2 is used as the low-side refrigerant and a rotary low-side compressor is used, a very high pressure load will be generated on the bearings. Therefore, there is a risk that the long service life of the bearing cannot be ensured.

The present invention is directed to a binary refrigeration device that uses CO2 as the low-side refrigerant and uses a spiral low-side compressor, and ensures a long service life of the bearings of the low-side compressor. [Technical means to solve problems]

The present invention provides a binary freezing device, which has: The low-side refrigeration cycle has a spiral low-side compressor. The low-side compressor uses CO2 as the low-side refrigerant and has a spiral rotor rotatably supported by a bearing and drives the aforementioned spiral rotor. The low-end side motor compresses the aforementioned low-end side refrigerant; A high-stage side refrigeration cycle, which includes a high-stage side compressor. The high-stage side compressor has a high-stage side motor and compresses the high-stage side refrigerant; a first pressure sensor that measures the suction pressure of the aforementioned low-stage compressor, that is, the low-stage suction pressure; a second pressure sensor that measures the discharge pressure of the low-side compressor, that is, the low-side discharge pressure; and A control device that receives the low-stage suction pressure from the first pressure sensor and the low-stage discharge pressure from the second pressure sensor, and calculates the low-stage discharge pressure and the low-stage suction pressure. The difference is the differential pressure on the low side, The low-stage refrigeration cycle and the high-stage refrigeration cycle share a series capacitor, and the series capacitor functions as a condenser for condensing the low-stage refrigerant in the low-stage refrigeration cycle, and also functions as a condenser for condensing the low-stage refrigerant in the high-stage refrigeration cycle. The side refrigeration cycle functions as an evaporator for evaporating the high-stage refrigerant, and performs heat exchange between the low-stage refrigeration cycle and the high-stage refrigeration cycle. The aforementioned control device system When the low-stage suction pressure is less than the first lower limit pressure, the rotation speed of the low-stage electric motor is reduced. When the low-stage suction pressure exceeds the first upper limit pressure, the rotation speed of the low-stage electric motor is increased. Increase, when the low-stage suction pressure is equal to or greater than the first lower limit pressure and less than the first upper limit pressure, the rotation speed of the low-stage electric motor is maintained, and the following control is performed in response to the low-stage differential pressure, that is, When the low-stage differential pressure is less than the second lower limit pressure, the rotation speed of the high-stage motor is reduced. When the low-stage differential pressure exceeds the second upper limit pressure, the rotation speed of the high-stage motor is increased. When the low-stage differential pressure is greater than the second lower limit pressure and less than the second upper limit pressure, the rotation speed of the high-stage motor is maintained.

According to this structure, since the low-side suction pressure can be adjusted between the first lower limit pressure and the first upper limit pressure, the cooling amount of the low-side refrigeration cycle can be adjusted to an ideal range. In addition, since the low-side differential pressure can be adjusted between the second lower limit pressure and the second upper limit pressure, the pressure load on the bearing can be adjusted, ensuring a long service life of the bearing. If the rotation speed of the low-side motor is increased, the cooling amount of the low-side refrigeration cycle increases and the cooling temperature decreases. Therefore, in the low-stage refrigeration cycle, since the evaporation temperature decreases, the evaporation pressure (that is, the low-stage suction pressure) decreases. On the contrary, when the rotation speed of the low-stage electric motor is reduced, the evaporation pressure (that is, the low-stage suction pressure) increases. In this way, the low-side suction pressure can be adjusted. In addition, if the rotation speed of the high-stage motor is increased, the cooling amount of the high-stage refrigeration cycle increases and the cooling temperature decreases. Therefore, the evaporation temperature of the high-side refrigeration cycle decreases, and the condensation temperature of the low-side refrigeration cycle thermally connected by the series capacitor decreases. Therefore, the condensation pressure of the low-side refrigeration cycle (that is, the low-side discharge pressure) decreases. On the contrary, if the rotation speed of the high-stage motor is reduced, the condensation pressure of the low-stage refrigeration cycle (that is, the low-stage discharge pressure) increases. In this way, the low-side discharge pressure can be adjusted. Therefore, the low-side differential pressure that affects the bearing can be adjusted to an ideal range. In addition, CO2 used as the low-side refrigerant has a GWP (global warming coefficient) of 1 and has excellent environmental performance. In addition, since the low-side compressor is a spiral type, even if CO2 solidifies (turns into dry ice) due to low temperature, it can be crushed by the spiral rotor. Therefore, compared with other rotary types such as scroll type, Few bad effects.

The difference between the second upper limit pressure and the second lower limit pressure may be 0.4 MPa or less. For example, the second lower limit pressure may be 0.6 MPa, and the second upper limit pressure may be 1.0 MPa.

According to this structure, the low-side differential pressure can be specifically adjusted to an ideal range, ensuring a long service life of the bearing.

The aforementioned high-side refrigerant may also be R1234yf.

Based on this structure, R1234yf used as the high-side refrigerant has a GWP of 1 and has excellent environmental performance.

The aforementioned binary refrigeration device may also be equipped with: a first temperature sensor that measures the temperature of the aforementioned low-side motor; and a second temperature sensor that measures the temperature of the aforementioned high-side motor, The aforementioned control device system The temperature of the low-side motor is received from the first temperature sensor, and the temperature of the high-side motor is received from the second temperature sensor, Before the temperature of the low-side motor becomes lower than the upper limit value, the standby operation increases the rotation speed of the low-side motor. The rotation speed of the high-stage motor is increased by waiting until the temperature of the high-stage motor becomes equal to or lower than the upper limit value.

According to this structure, the temperatures of the low-side motor and the high-side motor can be suppressed below the upper limit value. Therefore, the load applied to the low-side motor and the high-side motor can be suppressed below a certain level.

The aforementioned binary refrigeration device may also be equipped with: a first current sensor that measures the current of the aforementioned low-side motor; and a second current sensor that measures the current of the aforementioned high-voltage side motor, The aforementioned control device system The current of the low-side motor is received from the first current sensor, and the current of the high-side motor is received from the second current sensor, Before the current of the low-side motor becomes below the upper limit value, the standby increases the rotation speed of the low-side motor, The rotation speed of the high-stage motor is increased by waiting until the temperature of the high-stage motor becomes equal to or lower than the upper limit value.

According to this structure, the currents of the low-side motor and the high-side motor can be suppressed below the upper limit value. Therefore, the load applied to the low-side motor and the high-side motor can be suppressed below a certain level.

The aforementioned binary refrigeration device may also be equipped with: a first rotational speed sensor, which measures the rotational speed of the aforementioned low-side motor; and a second rotational speed sensor that measures the rotational speed of the aforementioned high-end motor, The aforementioned control device system The rotation speed of the low-side motor is received from the first rotation speed sensor, and the rotation speed of the high-side motor is received from the second rotation speed sensor, Before the rotation speed of the low-side motor becomes below the upper limit value, the standby operation increases the rotation speed of the low-side motor, The rotation speed of the high-stage motor is increased by waiting until the rotation speed of the high-stage motor becomes equal to or lower than the upper limit value.

According to this structure, the rotation speeds of the low-side motor and the high-side motor can be suppressed below the upper limit value. Therefore, the load applied to the low-side motor and the high-side motor can be suppressed below a certain level. [Effects of the invention]

According to the present invention, for a binary refrigeration device using CO2 as the low-side refrigerant and using a spiral low-side compressor, the long service life of the bearings of the low-side compressor can be ensured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) Referring to FIG. 1 , a binary refrigeration device 1 according to the first embodiment includes a low-stage refrigeration cycle 10 , a high-stage refrigeration cycle 20 , and a control device 30 .

In the low-stage refrigeration cycle 10, CO2 (carbon dioxide) is used as the low-stage refrigerant. The low-side refrigeration cycle 10 includes a low-side compressor 11 , an oil recovery device 12 , a series capacitor 5 , an expansion valve 13 and an evaporator 14 .

Referring to Figure 2 at the same time, the low-stage compressor 11 is a spiral type and is used to compress the low-stage refrigerant. The low-stage compressor 11 includes a spiral rotor 11a, a low-stage electric motor 11b that drives the spiral rotor 11a, and a casing 11c that houses these components. The spiral rotor 11a is rotatably supported by a bearing (rolling bearing) 11d, and is mechanically connected to the low-side motor 11b via a connector 11e.

The low-side motor 11b includes a stator 11b1 fixed to the housing 11c and a rotary member 11b2 arranged inside the stator 11b1 and rotatably supported by a bearing (rolling bearing) 11f. The rotation speed of the low-side motor 11b can be adjusted by the inverter 11g.

In this embodiment, the low-stage compressor 11 is an oil-cooling type. Between the helical rotor 11a and the low-end motor 11b, a shaft sealing device 11h is provided adjacent to the coupling 11e. The shaft seal device 11h prevents the passage of oil.

The low-stage compressor 11 sucks the low-stage refrigerant (CO2) from the suction port 11i, compresses it internally, and discharges it from the discharge port 11j. The discharged CO2 contains oil, and is sent to the oil recovery device 12 to recover the oil. The recovered oil is supplied to the low-side compressor 11, that is, recycled. The CO2 after oil separation is sent to the series condenser 5 in the oil recovery device 12 .

The series capacitor 5 is shared by the low-side refrigeration circuit 10 and the high-side refrigeration circuit 20 . In the series capacitor 5 , heat exchange is performed between the low-side refrigeration cycle 10 and the high-side refrigeration cycle 20 . The series capacitor 5 functions as a condenser that cools and condenses the low-side refrigerant in the low-side refrigeration circuit 10 .

The low-side refrigerant condensed in the series capacitor 5 is expanded by the expansion valve 13 and is sent to the evaporator 14 . The expansion valve 13 is, for example, a pressure regulating valve.

In the evaporator 14 , the low-stage refrigerant expanded by the expansion valve 13 evaporates, and the evaporated low-stage refrigerant is sent to the low-stage compressor 11 .

The low-stage refrigeration cycle 10 is provided with a first pressure sensor 15a that measures the suction pressure of the low-stage compressor 11, that is, the low-stage suction pressure, and a first pressure sensor 15a that measures the discharge pressure of the low-stage compressor 11, that is, the low-stage suction pressure. The second pressure sensor 15b of side discharge pressure.

In the high-stage refrigeration cycle 20, for example, HFO (hydrofluoroolefin), HFC (hydrofluorocarbon), or NH3 (ammonia) is used as the high-stage refrigerant. In this embodiment, R1234yf, a type of HFO, is used as the high-side refrigerant. The high-stage refrigeration cycle 20 includes: a high-stage compressor 21 , an oil recovery unit 22 , a condenser 23 , an expansion valve 24 and a series capacitor 5 .

The high-stage compressor 21 compresses the high-stage refrigerant. The high-stage compressor 21 may be, for example, a spiral type, a scroll type, a reciprocating type, or the like. The high-stage compressor 21 has a high-stage electric motor 21a that serves as a drive source. The rotation speed of the high-end motor 21a can be adjusted through the inverter 21b.

The high-stage compressor 21 sucks the high-stage refrigerant from the suction port 21c, compresses it internally, and discharges it from the discharge port 21d. The discharged high-stage refrigerant contains oil, and is sent to the oil collector 22 to recover the oil. The recovered oil is supplied to the high-stage compressor 21, that is, recycled. The high-stage refrigerant whose oil has been separated by the oil recovery device 22 is sent to the condenser 23 .

In the condenser 23, the high-stage refrigerant is cooled and condensed. The high-stage refrigerant condensed in the condenser 23 expands through the expansion valve 24 and is sent to the series capacitor 5 . The expansion valve 24 is, for example, a pressure regulating valve.

The series capacitor 5 functions as an evaporator that cools and condenses the high-side refrigerant in the high-side refrigeration circuit 20 . In the series capacitor 5 , the high-stage refrigerant expanded by the expansion valve 24 evaporates, and the evaporated high-stage refrigerant is sent to the high-stage compressor 21 .

The control device 30 performs calculation processing and controls the entire device. The control device 30 includes, for example, a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) that coordinates with software to achieve predetermined functions. The control device 30 may be composed of a hardware circuit such as a dedicated electronic circuit or a reconfigurable electronic circuit designed to realize a predetermined function, or may be composed of various semiconductor integrated circuits. Examples of various semiconductor integrated circuits include, in addition to CPUs and MPUs, microcomputers, DSP (Digital Signal Processor), FPGA (Field Programmable Gate Array), and ASIC (Application Specific Integrated Circuit). In addition, the control device 30 may also include memory devices such as RAM (Random Access Memory) and ROM (Read Only Memory). Specifically, the control device 30 can be configured as an information processing device such as a desktop computer, a notebook computer, a workpiece station, or a tablet terminal, or a printed circuit board having the same function.

The control device 30 reads the stored data, programs, etc. and performs various calculation processes to achieve predetermined functions. The program executed by the control device 30 can be provided from the outside using a communication unit that communicates according to a predetermined communication standard, or can be stored in a portable recording medium.

Referring to FIG. 3 , the control device 30 has a reception unit 31 , a calculation unit 32 , a low-side rotation speed control unit 33 , and a high-side rotation speed control unit 34 as functional structures. This can be achieved through the coordination of the aforementioned hardware and software. In addition, these can be understood as corresponding circuits.

The receiving unit 31 receives the low-stage suction pressure from the first pressure sensor 15a and receives the low-stage discharge pressure from the second pressure sensor 15b.

The calculation unit 32 calculates the difference between the low-stage discharge pressure and the low-stage suction pressure, that is, the low-stage differential pressure.

The low-side rotation speed control unit 33 controls the rotation speed of the low-side electric motor 11b via the inverter 11g in accordance with the flowcharts of FIGS. 4 to 6 . Similarly, the high-stage side rotation speed control unit 34 controls the rotation speed of the high-stage side motor 21a via the inverter 21b according to the flowcharts of FIGS. 4 to 6 .

Referring to Fig. 4 , the control device 30 starts the operation of the two-stage refrigeration device 1, starts the high-stage compressor 21 (step S4-1), and starts the low-stage compressor 11 (step S4-2). Then, the rotation speed of the low-stage motor 11b is controlled (step S4-3), and the rotation speed of the high-stage motor 21a is controlled (step S4-4). That is, the speed control of the low-side motor 11b (step S4-3) and the speed control of the high-side motor 21a (step S4-4) are not performed when the high-side compressor 21 and the low-side compressor 11 are started. (that is, when the operation starts), but after the high-stage compressor 21 and the low-stage compressor 11 are started.

Referring to FIG. 5 , during the rotation speed control of the low-stage electric motor 11 b (step S4 - 3 in FIG. 4 ), determination of the low-stage suction pressure P1 is performed (step S5 - 1 ). When the low-stage suction pressure P1 is less than the first lower limit pressure P11 (A: step S5-1), the rotation speed of the low-stage electric motor 11b is reduced (step S5-2). Then, the determination regarding the low-stage suction pressure P1 is performed again (step S5-1). In addition, when the low-stage suction pressure P1 exceeds the first upper limit pressure P12 (B: step S5-1), the rotation speed of the low-stage electric motor 11b is increased (step S5-3). Then, the determination regarding the low-stage suction pressure P1 is performed again (step S5-1). In addition, when the low-stage suction pressure P1 is not less than the first lower limit pressure P1 and not more than the first upper limit pressure P12 (C: step S5-1), the rotation speed of the low-stage electric motor 11b is maintained (step S5-4). Then, the rotation speed control of the low-side electric motor 11b is completed (step S4-3 in Fig. 4).

Referring to FIG. 6 , during the rotation speed control of the high-stage motor 21 a (step S4 - 4 in FIG. 4 ), determination of the low-stage differential pressure P2 is performed (step S6 - 1 ). When the low-stage differential pressure P2 is less than the second lower limit pressure P21 (A: step S6-1), the rotation speed of the high-stage electric motor 21a is reduced (step S6-2). Then, the determination regarding the low-side differential pressure P2 is performed again (step S6-1). In addition, when the low-stage differential pressure P2 exceeds the second upper limit pressure P22 (B: step S6-1), the rotation speed of the high-stage electric motor 21a is increased (step S6-3). Then, the determination regarding the low-side differential pressure P2 is performed again (step S6-1). In addition, when the low-stage differential pressure P2 is equal to or greater than the second lower limit pressure P21 and equal to or less than the second upper limit pressure P22 (C: step S6-1), the rotation speed of the high-stage electric motor 21a is maintained (step S6-4). Then, the rotation speed control of the high-stage motor 21a is completed (step S4-4 in FIG. 4).

According to the binary refrigeration device 1 of this embodiment, the low-side suction pressure P1 can be adjusted between the first lower limit pressure P11 and the first upper limit pressure P12. Therefore, the cooling of the low-side refrigeration cycle 10 can be achieved. Adjust the amount to the ideal range. In addition, since the low-side differential pressure P2 can be adjusted between the second lower limit pressure P21 and the second upper limit pressure P22, the pressure load on the bearing 11d can be adjusted, ensuring a long service life of the bearing 11d. When the rotation speed of the low-stage motor 11b is increased, the cooling amount of the low-stage refrigeration cycle 10 increases and the cooling temperature decreases. Therefore, in the low-stage refrigeration cycle 10, since the evaporation temperature decreases, the evaporation pressure (that is, the low-stage suction pressure P1) decreases. On the contrary, when the rotation speed of the low-stage electric motor 11b is reduced, the evaporation pressure (that is, the low-stage suction pressure P1) increases. In this way, the low-side suction pressure P1 can be adjusted. In addition, when the rotation speed of the high-stage motor 21a is increased, the cooling amount of the high-stage refrigeration cycle 20 increases and the cooling temperature decreases. Therefore, the evaporation temperature of the high-side refrigeration cycle 20 decreases, and the condensation temperature of the low-side refrigeration cycle 10 thermally connected through the series capacitor 5 decreases. Therefore, the condensation pressure (that is, the low-side discharge pressure) of the low-side refrigeration cycle 10 decreases. On the contrary, when the rotation speed of the high-stage motor 21a is reduced, the condensation pressure of the low-stage refrigeration cycle 10 (that is, the low-stage discharge pressure) increases. In this way, the low-side discharge pressure can be adjusted. Therefore, the low-side differential pressure P2 that affects the bearing can be adjusted to an ideal range. In addition, CO2 used as the low-side refrigerant has a GWP (global warming coefficient) of 1 and has excellent environmental performance. In addition, since the low-stage compressor 11 is a spiral type, even if CO2 solidifies (turns into dry ice) due to low temperature, it can be crushed by the spiral rotor 11a. Therefore, compared with other rotary compressors such as the scroll type, formula, less bad effects.

In addition, R1234yf used as the high-side refrigerant has a GWP of 1 and has excellent environmental performance.

Ideally, the difference between the second upper limit pressure P21 and the second lower limit pressure P22 is 0.4 MPa or less. For example, the second lower limit pressure P21 is 0.6MPa, and the second upper limit pressure P22 is 1.0MPa. If the differential pressure on the low-end side is 0.6 MPa or more, the load on the bearing 11d will be greater than the necessary minimum load, so that scratches on the bearing 11d can be avoided and a long service life can be ensured. If the differential pressure on the low-end side is within 1.0MPa, overload on the bearing 11d can be avoided and a long service life can be ensured. Thereby, the low-side differential pressure P2 can be specifically adjusted within an ideal range, thereby ensuring a long service life of the bearing 11d.

(Second Embodiment) The binary refrigeration device 1 of the second embodiment shown in FIG. 7 has the same structure as that of the first temperature sensor 15c, the second temperature sensor 15d, and the control device 30. Parts other than these are essentially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

In this embodiment, the low-stage refrigeration cycle 10 is provided with a first temperature sensor 15c that measures the temperature of the low-stage motor 11b (for example, a coil temperature), and a first temperature sensor 15c that measures the temperature of the high-stage motor 21a (for example, a coil temperature). temperature) second temperature sensor 15d.

Referring to FIG. 8 , in this embodiment, the receiving unit 31 of the control device 30 not only receives the low-stage suction pressure and the low-stage discharge pressure as in the first embodiment, but also receives the low-stage pressure from the first temperature sensor 15 c. The temperature of the side motor 11b and the temperature of the high-side motor 21a are received from the second temperature sensor 15d.

In this embodiment, the control performed by the control device 30 is the same as that of FIG. 4 of the first embodiment, but the flowcharts of FIGS. 5 and 6 of the first embodiment are replaced with the flowcharts of FIGS. 9 and 10 respectively.

Referring to FIG. 9 , during the rotation speed control of the low-stage electric motor 11 b (step S4 - 3 in FIG. 4 ), determination of the low-stage suction pressure P1 is performed (step S9 - 1 ). When the low-stage suction pressure P1 is less than the first lower limit pressure P11 (A: step S9-1), the rotation speed of the low-stage electric motor 11b is reduced (step S9-2). Then, the determination regarding the low-stage suction pressure P1 is performed again (step S9-1). In addition, when the low-stage suction pressure P1 exceeds the first upper limit pressure P12 (B: step S9-1), a determination regarding the temperature of the low-stage electric motor 11b is performed (step S9-3). When the temperature of the low-stage motor 11b is below the upper limit value (Y: step S9-3), the rotation speed of the low-stage motor 11b is increased (step S9-4), and the low-stage suction pressure P1 is executed again. Determination (step S9-1). When the temperature of the low-stage electric motor 11b is less than or equal to the upper limit value (N: step S9-3), the rotation speed of the low-stage electric motor 11b is reduced (step S9-2), and the low-stage suction pressure P1 is performed again. Determination (step S9-1). In addition, when the low-stage suction pressure P1 is equal to or greater than the first lower limit pressure P1 and equal to or less than the first upper limit pressure P12 (C: step S9-1), determination regarding the temperature of the low-stage electric motor 11b is performed (step S9-5 ). When the temperature of the low-stage electric motor 11b is less than or equal to the upper limit value (N: step S9-5), the rotation speed of the low-stage electric motor 11b is reduced (step S9-2), and the low-stage suction pressure P1 is performed again. Determination (step S9-1). When the temperature of the lower-side motor 11b is below the upper limit value (Y: step S9-5), the rotation speed of the lower-side motor 11b is maintained (step S9-6), and the rotation speed control of the lower-side motor 11b is completed (Fig. 4 step S4-3).

That is, in this embodiment, in addition to the control of the first embodiment, the control device 30 waits to increase the rotation speed of the low-side motor 11b until the temperature of the low-side motor 11b becomes lower than the upper limit value.

Referring to FIG. 10 , during the rotation speed control of the high-stage electric motor 21 a (step S4 - 4 in FIG. 4 ), determination regarding the low-stage differential pressure P2 is performed (step S10 - 1 ). When the low-stage differential pressure P2 is less than the second lower limit pressure P21 (A: step S10-1), the rotation speed of the high-stage motor 21a is reduced (step S10-2). Then, the determination regarding the low-side differential pressure P2 is performed again (step S10-1). In addition, when the low-stage differential pressure P2 exceeds the second upper limit pressure P22 (B: step S10-1), a determination regarding the temperature of the high-stage electric motor 21a is performed (step S10-3). When the temperature of the high-stage motor 21a is equal to or less than the upper limit (Y: step S10-3), the rotation speed of the high-stage motor 21a is increased (step S10-4). Then, the determination regarding the low-side differential pressure P2 is performed again (step S10-1). When the temperature of the high-stage motor 21a is less than or equal to the upper limit value (Y: step S10-3), the rotation speed of the high-stage motor 21a is reduced (step S10-2). Then, the determination regarding the low-side differential pressure P2 is performed again (step S10-1). In addition, when the low-stage differential pressure P2 is equal to or greater than the second lower limit pressure P21 and equal to or less than the second upper limit pressure P22 (C: step S10-1), the temperature of the high-stage electric motor 21a is determined (step S10-4). . When the temperature of the high-stage motor 21a is less than or equal to the non-upper limit value (N: step S10-5), the rotation speed of the high-stage motor 21a is reduced (step S10-2). Then, the determination regarding the low-side differential pressure P2 is performed again (step S10-1). When the temperature of the high-stage motor 21a is below the upper limit value (Y: step S10-5), the rotational speed of the high-stage motor 21a is maintained (step S10-6), and the rotational speed control of the high-stage motor 21a is completed ( Step S4-4 in Figure 4).

That is, in this embodiment, in addition to the control in the first embodiment, the control device 30 waits to increase the rotation speed of the high-stage motor 21a until the temperature of the high-stage motor 21a reaches the upper limit or lower.

The upper limit value of the temperature of the low-stage motor 11b and the upper limit value of the temperature of the high-stage motor 21a may differ depending on the type of the motor. For example, the upper limit value of type F may be set to 155°C, the upper limit value of type B may be set to 130°C, and the upper limit value of type E may be set to 120°C.

According to this embodiment, the temperatures of the low-stage motor 11b and the high-stage motor 21a can be suppressed to be below the upper limit value. Therefore, the load applied to the low-stage motor 11b and the high-stage motor 21a can be suppressed below a certain level.

Various modifications can be considered for the control in response to the temperature of the low-side motor 11b and the high-side motor 21a.

Referring to FIGS. 7 and 8 , as a first modification, the first temperature sensor 15 c may be replaced by a first current sensor 15 e that measures the current of the low-side motor 11 b. Similarly, the second temperature sensor 15d may be changed to the second current sensor 15f that measures the current of the high-side motor 21a.

Referring to FIGS. 11 and 12 , the temperature of the low-side motor 11 b can also be changed to the current of the low-side motor 11 b (steps S11-3 and S11-5). Similarly, the temperature of the high-stage motor 21a can also be changed to the current of the high-stage motor 21a (steps S12-3, S12-5). That is, in this modification, in addition to the control of the first embodiment, the control device 30 waits until the current of the low-side motor 11b becomes below the upper limit value to increase the rotation speed of the low-side motor 11b. The rotation speed of the high-stage motor 21a is increased in standby mode until the current of the primary-side motor 21a becomes equal to or less than the upper limit value.

The upper limit value of the current of the low-side motor 11b and the upper limit value of the current of the high-side motor 21a are set to the rated current values specified for the motors.

According to the first modification, the currents of the low-side motor 11b and the high-side motor 21a can be suppressed to be below the upper limit value. Therefore, the load applied to the low-stage motor 11b and the high-stage motor 21a can be suppressed below a certain level.

Referring to FIGS. 7 and 8 , as a second modification, the first temperature sensor 15 c may be replaced by a first rotation speed sensor 15 g that measures the rotation speed of the low-side electric motor 11 b. Similarly, the second temperature sensor 15d can also be changed to the second rotation speed sensor 15h that measures the rotation speed of the high-end motor 21a.

Referring to FIGS. 13 and 14 , the temperature of the low-side motor 11 b can also be changed to the rotation speed of the low-side motor 11 b (steps S13-3 and S13-5). Similarly, the temperature of the high-stage motor 21a may be changed to the rotation speed of the high-stage motor 21a (steps S14-3, S14-5). That is, in this modification, in addition to the control of the first embodiment, the control device 30 waits until the current of the low-side motor 11b becomes below the upper limit value to increase the rotation speed of the low-side motor 11b. The rotation speed of the high-stage motor 21a is increased in standby mode until the current of the primary-side motor 21a becomes equal to or less than the upper limit value.

The upper limit of the rotation speed of the low-side motor 11b and the upper limit of the rotation speed of the high-side motor 21a can be set taking into account the allowable rotation speeds of the rotating parts and bearings used in the motors. For example, the upper limit value can be set to 6000 rpm.

According to the second modification, the rotation speeds of the low-side motor 11b and the high-side motor 21a can be suppressed to be below the upper limit value. Therefore, the load applied to the low-side motor and the high-side motor can be suppressed below a certain level.

As described above, the specific embodiments and modifications of the present invention are described. However, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention. For example, the content of each embodiment may be appropriately combined as an embodiment of the present invention.

The present invention discloses the following aspects. (Pattern 1) The low-side refrigeration cycle has a spiral low-side compressor. The low-side compressor uses CO2 as the low-side refrigerant and has a spiral rotor rotatably supported by a bearing and drives the aforementioned spiral rotor. The low-end side motor compresses the aforementioned low-end side refrigerant; A high-stage side refrigeration cycle, which includes a high-stage side compressor. The high-stage side compressor has a high-stage side motor and compresses the high-stage side refrigerant; a first pressure sensor that measures the suction pressure of the aforementioned low-stage compressor, that is, the low-stage suction pressure; a second pressure sensor that measures the discharge pressure of the low-side compressor, that is, the low-side discharge pressure; and A control device that receives the low-stage suction pressure from the first pressure sensor, receives the low-stage discharge pressure from the second pressure sensor, and calculates the low-stage discharge pressure and the low-stage suction pressure. The difference in pressure is the differential pressure on the low side, The low-stage refrigeration cycle and the high-stage refrigeration cycle share a series capacitor. The series capacitor functions as a condenser for condensing the low-stage refrigerant in the low-stage refrigeration cycle, and also functions as a condenser for condensing the low-stage refrigerant in the high-stage refrigeration cycle. The side refrigeration cycle functions as an evaporator for evaporating the high-stage refrigerant, and performs heat exchange between the low-stage refrigeration cycle and the high-stage refrigeration cycle. The aforementioned control device system When the low-stage suction pressure is less than the first lower limit pressure, the rotation speed of the low-stage electric motor is reduced. When the low-stage suction pressure exceeds the first upper limit pressure, the rotation speed of the low-stage electric motor is increased. Increase, when the low-stage suction pressure is equal to or greater than the first lower limit pressure and less than the first upper limit pressure, the rotation speed of the low-stage electric motor is maintained, and the following control is performed in response to the low-stage differential pressure, When the low-stage differential pressure is less than the second lower limit pressure, the rotation speed of the high-stage motor is reduced. When the low-stage differential pressure exceeds the second upper limit pressure, the rotation speed of the high-stage motor is increased. If the low-stage differential pressure is greater than the second lower limit pressure and less than the second upper limit pressure, the rotation speed of the high-stage motor is maintained. (Pattern 2) In the binary refrigeration device of aspect 1, the difference between the second upper limit pressure and the second lower limit pressure is 0.4 MPa or less. (Pattern 3) Such as the binary refrigeration device of aspect 2, wherein the aforementioned second lower limit pressure is 0.6MPa, The aforementioned second upper limit pressure is 1.0MPa. (Pattern 4) A binary refrigeration device according to any one of aspects 1 to 3, wherein the high-side refrigerant is R1234yf. (Mode 5) The binary refrigeration device according to any one of aspects 1 to 4, further comprising: a first temperature sensor that measures the temperature of the low-side motor; and a second temperature sensor that measures the temperature of the aforementioned high-side motor, The aforementioned control device system The temperature of the low-side motor is received from the first temperature sensor, and the temperature of the high-side motor is received from the second temperature sensor, Before the temperature of the low-side motor becomes lower than the upper limit value, the standby operation increases the rotation speed of the low-side motor. Before the temperature of the high-stage motor becomes lower than the upper limit value, the rotation speed of the high-stage motor is increased by waiting. (Mode 6) The binary refrigeration device according to any one of aspects 1 to 5, wherein the first current sensor measures the current of the low-side motor; and a second current sensor that measures the current of the aforementioned high-voltage side motor, The aforementioned control device system The current of the low-side motor is received from the first current sensor, and the current of the high-side motor is received from the second current sensor, Before the current of the low-side motor becomes below the upper limit value, the standby increases the rotation speed of the low-side motor, Before the temperature of the high-stage motor becomes lower than the upper limit value, the rotation speed of the high-stage motor is increased by waiting. (Mode 7) The binary refrigeration device according to any one of aspects 1 to 6, wherein the first rotation speed sensor measures the rotation speed of the low-side motor; and a second rotational speed sensor that measures the rotational speed of the aforementioned high-end motor, The aforementioned control device system The rotation speed of the low-side motor is received from the first rotation speed sensor, and the rotation speed of the high-side motor is received from the second rotation speed sensor, Before the rotation speed of the low-side electric motor becomes below the upper limit value, the waiting period increases the rotation speed of the low-end electric motor. The rotation speed of the high-stage motor is increased by waiting until the rotation speed of the high-stage motor becomes equal to or lower than the upper limit value.

This case claims the priority of the basic application of Japanese Patent Application No. 2022-090252, which has a filing date of June 2, 2022. It is incorporated into this specification with reference to Japanese Patent Application No. 2022-090252.

1: Binary freezing device 5: Series capacitor 10: Low side freezing cycle 11: Low side compressor 11a: Spiral rotor 11b: Low side motor 11b1: Fixtures 11b2: Rotating parts 11c: Shell 11d:Bearing 11e: connector 11f:Bearing 11g:Inverter 11h: Shaft seal device 11i: suction port 11j: spit out 12:Oil recovery device 13:Expansion valve 14:Evaporator 15a: 1st pressure sensor 15b: 2nd pressure sensor 15c: 1st temperature sensor 15d: 2nd temperature sensor 15e: 1st current sensor 15f: 2nd current sensor 15g: 1st speed sensor 15h: 2nd speed sensor 20: High-end side freezing cycle 21:High-end side compressor 21a:High side motor 21b:Inverter 21c: Suction port 21d: spit out 22:Oil recovery device 23:Condenser 24:Expansion valve 30:Control device 31: Receiving Department 32:Operation Department 33: Low unit side speed control part 34:High-end side speed control part

[Fig. 1] is a refrigerant circuit diagram of the binary refrigeration device according to the first embodiment of the present invention. [Fig. 2] is a cross-sectional view showing the inside of the low-stage compressor. [Fig. 3] is a block diagram of the control device of the first embodiment. [Fig. 4] is a flowchart showing control by the control device. [Fig. 5] is a flowchart corresponding to step S4-3 of Fig. 4 of the rotation speed control of the low-side electric motor in the first embodiment. [Fig. 6] is a flowchart corresponding to step S4-4 of Fig. 4 of the rotation speed control of the high-level motor in the first embodiment. [Fig. 7] is a refrigerant circuit diagram of the binary refrigeration device according to the second embodiment of the present invention. [Fig. 8] is a block diagram of the control device of the second embodiment. [Fig. 9] is a flowchart corresponding to step S4-3 of Fig. 4 of the rotation speed control of the low-side electric motor in the second embodiment. [Fig. 10] It is a flowchart corresponding to step S4-4 of Fig. 4 of the rotation speed control of the high-level motor in the second embodiment. [Fig. 11] A flowchart of rotation speed control of the low-side electric motor in the first modification of the second embodiment corresponding to step S4-3 in Fig. 4. [Fig. [Fig. 12] A flowchart of the rotation speed control of the high-stage motor in the first modified example of the second embodiment corresponding to step S4-4 in Fig. 4. [Fig. [Fig. 13] A flowchart of rotation speed control of the low-side electric motor in the second modification of the second embodiment corresponding to step S4-3 in Fig. 4. [Fig. [Fig. 14] A flowchart of rotation speed control of a high-level motor in a second modification of the second embodiment corresponding to step S4-4 in Fig. 4. [Fig.

1: Binary freezing device

5: Series capacitor

10: Low side freezing cycle

11: Low side compressor

11b: Low side motor

11g:Inverter

11i: suction port

11j: spit out

12:Oil recovery device

13:Expansion valve

14:Evaporator

15a: 1st pressure sensor

15b: 2nd pressure sensor

20: High-end side freezing cycle

21:High-end side compressor

21a:High side motor

21b:Inverter

21c: Suction port

21d: spit out

22:Oil recovery device

23:Condenser

24:Expansion valve

30:Control device

Claims (7)

A binary refrigeration device with: The low-side refrigeration cycle has a spiral low-side compressor. The low-side compressor uses CO2 as the low-side refrigerant and has a spiral rotor rotatably supported by a bearing and drives the aforementioned spiral rotor. The low-end side motor compresses the aforementioned low-end side refrigerant; A high-stage side refrigeration cycle, which includes a high-stage side compressor. The high-stage side compressor has a high-stage side motor and compresses the high-stage side refrigerant; a first pressure sensor that measures the suction pressure of the aforementioned low-stage compressor, that is, the low-stage suction pressure; a second pressure sensor that measures the discharge pressure of the low-side compressor, that is, the low-side discharge pressure; and A control device that receives the low-stage suction pressure from the first pressure sensor and the low-stage discharge pressure from the second pressure sensor, and calculates the low-stage discharge pressure and the low-stage suction pressure. The difference is the differential pressure on the low side, The low-stage refrigeration cycle and the high-stage refrigeration cycle share a series capacitor, and the series capacitor functions as a condenser for condensing the low-stage refrigerant in the low-stage refrigeration cycle, and also functions as a condenser for condensing the low-stage refrigerant in the high-stage refrigeration cycle. The side refrigeration cycle functions as an evaporator for evaporating the high-stage refrigerant, and performs heat exchange between the low-stage refrigeration cycle and the high-stage refrigeration cycle. The aforementioned control device system When the low-stage suction pressure is less than the first lower limit pressure, the rotation speed of the low-stage electric motor is reduced. When the low-stage suction pressure exceeds the first upper limit pressure, the rotation speed of the low-stage electric motor is increased. Increase, when the low-stage suction pressure is equal to or greater than the first lower limit pressure and less than the first upper limit pressure, the rotation speed of the low-stage electric motor is maintained, and the following control is performed in response to the low-stage differential pressure, that is, When the low-stage differential pressure is less than the second lower limit pressure, the rotation speed of the high-stage motor is reduced. When the low-stage differential pressure exceeds the second upper limit pressure, the rotation speed of the high-stage motor is increased. When the low-stage differential pressure is greater than the second lower limit pressure and less than the second upper limit pressure, the rotation speed of the high-stage motor is maintained. The binary refrigeration device of claim 1, wherein the difference between the second upper limit pressure and the second lower limit pressure is 0.4 MPa or less. The binary refrigeration device of claim 2, wherein the aforementioned second lower limit pressure is 0.6MPa, The aforementioned second upper limit pressure is 1.0MPa. The binary refrigeration device according to any one of claims 1 to 3, wherein the high-side refrigerant is R1234yf. The binary refrigeration device according to any one of claims 1 to 3, further comprising: a first temperature sensor that measures the temperature of the low-side motor; and a second temperature sensor that measures the temperature of the aforementioned high-side motor, The aforementioned control device system The temperature of the low-side motor is received from the first temperature sensor, and the temperature of the high-side motor is received from the second temperature sensor, Before the temperature of the low-side motor becomes lower than the upper limit value, the standby operation increases the rotation speed of the low-side motor. The rotation speed of the high-stage motor is increased by waiting until the temperature of the high-stage motor becomes equal to or lower than the upper limit value. The binary refrigeration device according to any one of claims 1 to 3, further comprising: a first current sensor that measures the current of the low-side motor; and a second current sensor that measures the current of the aforementioned high-voltage side motor, The aforementioned control device system The current of the low-side motor is received from the first current sensor, and the current of the high-side motor is received from the second current sensor, Before the current of the low-side motor becomes below the upper limit value, the standby increases the rotation speed of the low-side motor, The rotation speed of the high-stage motor is increased by waiting until the temperature of the high-stage motor becomes equal to or lower than the upper limit value. The binary refrigeration device according to any one of claims 1 to 3, further comprising: a first rotational speed sensor that measures the rotational speed of the low-side motor; and a second rotational speed sensor that measures the rotational speed of the aforementioned high-end motor, The aforementioned control device system The rotation speed of the low-side motor is received from the first rotation speed sensor, and the rotation speed of the high-side motor is received from the second rotation speed sensor, Before the rotation speed of the low-side motor becomes below the upper limit value, the standby operation increases the rotation speed of the low-side motor, The rotation speed of the high-stage motor is increased by waiting until the rotation speed of the high-stage motor becomes equal to or lower than the upper limit value.

Images