Refrigeration equipment

Abstract

This disclosure provides a refrigeration system that can easily suppress excessive increases in the discharge refrigerant temperature of the compressor. [Solution] The refrigeration system in this disclosure includes a compressor for compressing a refrigerant, and at startup or when operation begins after an oil recovery operation, the rotational speed of the compressor is gradually increased from a first rotational speed lower than the indicated rotational speed or indicated horsepower rotational speed for the compressor, and the increase in the indicated rotational speed or indicated horsepower is restricted while the rotational speed of the compressor is gradually increased from the first rotational speed.

Description

Technical Field

[0001] The present disclosure relates to a refrigeration device.

Background Art

[0002] Patent Document 1 discloses a conventional control method for a compressor, namely compressor startup control. In this compressor startup control, at the time of starting the compressor, in order to prevent sudden pressure fluctuations in the refrigerant circuit and suppress oil discharge at low outside air temperatures, the rotational speed is gradually increased to a target rotational speed corresponding to the required capacity.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present disclosure provides a refrigeration device that can easily suppress the excessive increase in the discharged refrigerant temperature of the compressor.

Means for Solving the Problems

[0005] The refrigeration device in the present disclosure includes a compressor that compresses refrigerant. At the time of startup or at the start of operation after oil recovery operation, the rotational speed of the compressor is gradually increased from a first rotational speed lower than the rotational speed of the indicated rotational speed or indicated horsepower for the compressor, and while the rotational speed of the compressor is gradually increased from the first rotational speed, the increase in the indicated rotational speed or the indicated horsepower is restricted.

Effects of the Invention

[0006] The refrigeration system in this disclosure can quickly resolve the discrepancy between the compressor's rotational speed and the indicated rotational speed or indicated horsepower of the compressor. Therefore, when the indicated rotational speed or indicated horsepower of the compressor is reduced, the actual rotational speed of the compressor tends to decrease, making it easier to suppress an excessive rise in the refrigerant discharge temperature of the compressor. [Brief explanation of the drawing]

[0007] [Figure 1] Diagram showing the refrigerant circuit of the air conditioning system according to Embodiment 1. [Figure 2] Diagram showing the configuration of the control system for an air conditioning system. [Figure 3] This chart shows the changes in compressor rotational speed, the rotational speed of the indicated horsepower of the compressor, and the discharge refrigerant temperature of the compressor, starting from the time the air conditioning system is started up or from the start of operation after an oil recovery operation. [Modes for carrying out the invention]

[0008] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, the technology was known in the field of refrigeration equipment. In that industry, it was common practice to design products that gradually increased the compressor speed to a target speed during compressor startup in order to prevent rapid pressure fluctuations in the refrigerant circuit and to suppress oil discharge at low ambient temperatures. Under these circumstances, the inventors discovered that while gradually increasing the compressor speed to a target speed during compressor startup could suppress a rapid rise in the refrigerant temperature discharged from the compressor, if the target speed increased while the compressor speed was being gradually increased, the time during which the target speed and the compressor speed were at odds would be prolonged, and the discharged refrigerant temperature would continue to rise during that time. The inventors discovered that even when the discharge refrigerant temperature reaches a predetermined temperature and the target rotational speed is reduced to protect the discharge temperature, if there is a discrepancy between the target rotational speed and the compressor rotational speed, the compressor rotational speed cannot be reduced quickly, and the discharge refrigerant temperature may become excessively high. To solve this problem, the subject matter of this disclosure was established. Therefore, this disclosure provides a refrigeration system that can easily suppress excessive increases in the discharge refrigerant temperature of the compressor.

[0009] The embodiments will be described in detail below with reference to the drawings. However, unnecessary details may be omitted. For example, detailed explanations of already well-known matters or redundant explanations of substantially identical configurations may be omitted. This is to avoid the following explanation becoming unnecessarily verbose and to facilitate understanding for those skilled in the art. The attached drawings and the following description are provided to enable those skilled in the art to fully understand this disclosure and are not intended to limit the subject matter described in the claims.

[0010] (Embodiment 1) Embodiment 1 will be described below with reference to the drawings.

[0011] [1-1. Structure] [1-1-1. Refrigerant Circuit Configuration] Figure 1 shows the refrigerant circuit 1A of an air conditioning system 1 according to Embodiment 1. The air conditioning system 1 includes an indoor unit 2 and an outdoor unit 3. The indoor unit 2 is installed indoors and provides indoor air conditioning by blowing out warm air or cool air. The outdoor unit 3 is installed outdoors and is connected to the indoor unit 2 via refrigerant piping. In this embodiment, the air conditioning system 1 includes a plurality of indoor units 2 and a plurality of outdoor units 3. The number of indoor units 2 and outdoor units 3 can be arbitrarily set to one or more each. The air conditioning system 1 corresponds to an example of a "refrigeration system" in this disclosure.

[0012] The indoor unit 2 has an indoor heat exchanger 21. The indoor heat exchanger 21 is a heat exchanger that exchanges heat between the refrigerant flowing inside and the surrounding air. The indoor heat exchanger 21 is, for example, a finned tube type heat exchanger.

[0013] An indoor gas valve 22 is connected to one of the inlet and outlets of the refrigerant flow path of the indoor heat exchanger 21 via refrigerant piping. The indoor gas valve 22 is a valve connected to the indoor-outdoor connecting gas pipe 4 that connects the indoor unit 2 and the outdoor unit 3. The indoor-outdoor connecting gas pipe 4 is a refrigerant pipe through which gaseous refrigerant flows.

[0014] The indoor unit 2 has an indoor expansion valve 23. The indoor expansion valve 23 is an expansion valve connected via refrigerant piping to the other inlet / outlet of the refrigerant flow path of the indoor heat exchanger 21. In this embodiment, the indoor expansion valve 23 is configured so that its opening degree can be adjusted by control.

[0015] An indoor liquid valve 24 is connected to the indoor expansion valve 23 via refrigerant piping. The indoor liquid valve 24 is connected to the indoor gas valve 22, which is connected to the indoor-outdoor connecting liquid pipe 5 that connects the indoor unit 2 and the outdoor unit 3. The indoor-outdoor connecting liquid pipe 5 is a refrigerant pipe through which liquid refrigerant flows.

[0016] The indoor unit 2 has an indoor blower 25. The indoor blower 25 can be any type of blower, such as a cross-flow fan or a centrifugal fan. The indoor blower 25 takes in indoor air into the housing of the indoor unit 2, exchanges heat with the refrigerant through the indoor heat exchanger 21, and blows the heat-exchanged air back into the room.

[0017] The outdoor unit 3 has a compressor 31. The compressor 31 is a device that compresses the inhaled refrigerant and discharges it through the discharge port. The compressor 31 can be, for example, a compressor of any type such as a scroll type or a rotary type. The compressor 31 is provided with an injection port 31A which is an opening that enables the injection of refrigerant into the intermediate pressure chamber. The intermediate pressure chamber is a chamber in the compressor 31 where the pressure of the refrigerant is the intermediate pressure between the pressure of the inhaled refrigerant and the pressure of the discharged refrigerant. A check valve is provided at the injection port 31A to block the refrigerant flowing back from the intermediate pressure chamber to the injection pipe 50 side described later. The discharge port of the compressor 31 is connected to the discharge pipe 32. The discharge pipe 32 is a refrigerant pipe through which the high-temperature and high-pressure gas refrigerant discharged from the discharge port of the compressor 31 flows. A high-pressure switch HP is provided in the discharge pipe 32. The high-pressure switch HP is a pressure switch that detects whether the pressure of the refrigerant flowing inside the discharge pipe 32 is a predetermined value or more.

[0018] The discharge pipe 32 is connected to an oil separator 33. The oil separator 33 separates and recovers the oil contained in the high-temperature and high-pressure refrigerant flowing in the discharge pipe 32. An oil pipe 33A is connected to the oil side outlet of the oil separator 33. The oil pipe 33A is mainly a pipe through which the oil separated and recovered in the oil separator 33 flows. The oil pipe 33A is connected to the oil separator 33 and to an intermediate portion of the suction pipe 44 described later. An oil recovery valve 33B that can be opened and closed by control is provided in the oil pipe 33A. Also, a check valve 33C that blocks the flow of oil from the oil recovery valve 33B side toward the oil separator 3 is provided in the oil pipe 33A between the oil recovery valve 33B and the oil separator 33. Further, the portion of the oil pipe 33A between the oil recovery valve 33B and the check valve 33C branches and is connected to an oil valve 33D. The oil valve 33D is connected to an oil balance pipe 6. The oil balance pipe 6 is a pipe that connects the oil valves 33D provided in each outdoor unit 3 in parallel. The air conditioner 1 adjusts the distribution of oil between each outdoor unit 3 through the oil balance pipe 6.

[0019] A high-pressure side gas pipe 34 is connected to the refrigerant side outlet of the oil separator 33. The high-pressure side gas pipe 34 is a refrigerant pipe connecting the oil separator 33 and the four-way valve 35. Inside the high-pressure side gas pipe 34, a high-temperature and high-pressure gas refrigerant from which oil has been removed in the oil separator 33 flows. A high-pressure side pressure sensor PS1 for measuring the pressure of the refrigerant inside the high-pressure side gas pipe 34 is provided on the high-pressure side gas pipe 34.

[0020] A check valve 36 is provided on the high-pressure side gas pipe 34. The check valve 36 blocks the flow of the refrigerant in the high-pressure side gas pipe 34 from the four-way valve 35 towards the oil separator 33.

[0021] The four-way valve 35 is a valve capable of switching the refrigerant flow path. An outdoor heat exchanger 37 and an outdoor side gas valve 38 are connected to the four-way valve 35 via refrigerant pipes, respectively. Further, a low-pressure side gas pipe 39 is connected to the four-way valve 35. The four-way valve 35 switches the operation of the air conditioner 1 to the cooling operation by communicating the high-pressure side gas pipe 34 and the outdoor heat exchanger 37 and communicating the outdoor side gas valve 38 and the low-pressure side gas pipe 39. Also, the four-way valve 35 switches the operation of the air conditioner 1 to the heating operation by communicating the high-pressure side gas pipe 34 and the outdoor side gas valve 38 and communicating the outdoor heat exchanger 37 and the low-pressure side gas pipe 39.

[0022] The outdoor heat exchanger 37 is a heat exchanger that exchanges heat between the refrigerant flowing inside and the outside air. The outdoor heat exchanger 37 can be any heat exchanger such as a fin-tube type heat exchanger. Also, an outdoor blower 37A is provided in the outdoor unit 3 to take in the outside air into the housing of the outdoor unit 3 and exchange heat with the refrigerant through the outdoor heat exchanger 37. Among the outdoor heat exchanger 37, the gas side inlet and outlet of the refrigerant flow path are connected to the four-way valve 35 via a refrigerant pipe, and the liquid side inlet and outlet of the refrigerant flow path are connected to the liquid side refrigerant pipe 41 via the outdoor expansion valve 40. In the present embodiment, the outdoor expansion valve 40 is an expansion valve whose opening degree can be adjusted by control.

[0023] The liquid-side refrigerant piping 41 is a refrigerant piping through which refrigerant, mainly in liquid form, flows. The liquid-side refrigerant piping 41 is connected to the outdoor expansion valve 40 and the outdoor liquid valve 42. The outdoor liquid valve 42 is a valve connected to the indoor-outdoor connecting liquid pipe 5. The indoor-outdoor connecting liquid pipe 5 connects the indoor liquid valve 24 of each indoor unit 2 in parallel to the outdoor liquid valve 42. In addition, the indoor-outdoor connecting liquid pipe 5 connects the outdoor liquid valve 42 of each outdoor unit 3 in parallel to the indoor liquid valve 24.

[0024] The outdoor gas valve 38 is a valve connected to the indoor-outdoor connecting gas pipe 4. The indoor-outdoor connecting gas pipe 4 connects the indoor gas valve 22 of each indoor unit 2 in parallel to the outdoor gas valve 38. In addition, the indoor-outdoor connecting gas pipe 4 connects the outdoor gas valve 38 of each outdoor unit 3 in parallel to the indoor gas valve 22.

[0025] The low-pressure gas pipe 39 is a refrigerant pipe connecting the four-way valve 35 and the accumulator 43. The low-pressure gas refrigerant that has evaporated from the indoor heat exchanger 21 and the outdoor heat exchanger 37, which functions as an evaporator, mainly flows through the low-pressure gas pipe 39. The low-pressure gas pipe 39 is equipped with a low-pressure pressure sensor PS2 that measures the pressure of the refrigerant inside the low-pressure gas pipe 39.

[0026] The accumulator 43 allows only the gaseous refrigerant contained in the refrigerant of the low-pressure gas pipe 39 to flow into the suction pipe 44. The suction pipe 44 is a refrigerant pipe that connects the outlet of the gaseous refrigerant in the accumulator 43 to the inlet of the compressor 31. The compressor 31 draws in the gaseous refrigerant that has passed through the accumulator 43 via the suction pipe 44.

[0027] An injection pipe 50 is provided in the refrigerant circuit 1A. The injection pipe 50 is a refrigerant pipe that branches off from the liquid-side refrigerant pipe 41 and is connected to the injection port 31A of the compressor 31. An electronic expansion valve 51 is provided in the injection pipe 50. The electronic expansion valve 51 is an expansion valve whose opening degree can be controlled. The electronic expansion valve 51 reduces the pressure of the refrigerant in the injection pipe 50.

[0028] A subcooled heat exchanger 53 is provided in the refrigerant circuit 1A. The subcooled heat exchanger 53 is a heat exchanger that exchanges heat between the refrigerant flowing inside the injection piping 50 and the refrigerant flowing inside the liquid-side refrigerant piping 41. The subcooled heat exchanger 53 may be, for example, a plate-type heat exchanger. The subcooled heat exchanger 53 is located downstream of the electronic expansion valve 51 in the injection piping 50. In other words, the electronic expansion valve 51 is located in the injection piping 50 between the branching point 41A between the injection piping 50 and the liquid-side refrigerant piping 41 and the subcooled heat exchanger 53.

[0029] A branch pipe 55 is provided in the refrigerant circuit 1A. The branch pipe 55 is a refrigerant pipe that branches off from the injection pipe 50 and is connected to the low-pressure gas pipe 39. Specifically, the branch pipe 55 branches off from the injection pipe 50 between the subcooled heat exchanger 53 and the connection portion to the injection port 31A. An on-off valve 57 is also provided in the branch pipe 55. The on-off valve 57 is a valve that can be switched between an open state and a closed state by control. When the on-off valve 57 is in the open state, it allows the flow of refrigerant in the branch pipe 55, and when it is in the closed state, it blocks the flow of refrigerant in the branch pipe 55.

[0030] When the on-off valve 57 is open, the injection pipe 50 and the low-pressure gas pipe 39 are connected via the branch pipe 55, so the refrigerant pressure in the injection pipe 50 is lower than the refrigerant pressure in the intermediate pressure chamber of the compressor 31. For this reason, when the on-off valve 57 is open, the refrigerant in the injection pipe 50 is not injected into the compressor 31.

[0031] On the other hand, when the on-off valve 57 is closed, the injection piping 50 and the low-pressure gas pipe 39 are not connected via the branch piping 55. Therefore, if the opening of the electronic expansion valve 51 is greater than or equal to a predetermined opening, the pressure of the refrigerant in the injection piping 50 rises and becomes higher than the pressure of the refrigerant in the intermediate pressure chamber of the compressor 31. For this reason, when the on-off valve 57 is closed, the refrigerant in the injection piping 50 can be injected into the compressor 31 via the injection port 31A.

[0032] The outdoor unit 3 is equipped with an outdoor air temperature sensor TS1 that measures the temperature of the outside air. The outdoor air temperature sensor TS1 measures the temperature of the outside air. Specifically, the outdoor air temperature sensor TS1 is installed, for example, near the outside air intake port in the housing of the outdoor unit 3, and measures the temperature of the outside air drawn into the housing by the drive of the outdoor fan 37A.

[0033] The outdoor unit 3 is equipped with a gas-side temperature sensor TS2 and a liquid-side temperature sensor TS3. The gas-side temperature sensor TS2 measures the temperature of the refrigerant flowing near the gas-side inlet and outlet of the outdoor heat exchanger 37. The liquid-side temperature sensor TS3 measures the temperature of the refrigerant flowing near the liquid-side inlet and outlet of the outdoor heat exchanger 37.

[0034] The indoor unit 2 is equipped with an indoor temperature sensor TS4. The indoor temperature sensor TS4 measures the temperature of the refrigerant flowing near the liquid side inlet and outlet of the indoor heat exchanger 21.

[0035] The outdoor unit 3 is equipped with a discharge temperature sensor TS5. The discharge temperature sensor TS5 measures the discharge refrigerant temperature, which is the temperature of the refrigerant discharged by the compressor 31.

[0036] [1-1-2. Control System Configuration] Figure 2 shows the configuration of the control system of the air conditioning unit 1. The air conditioning system 1 has a control unit 70. The control unit 70 is connected to various parts of the air conditioning system 1, such as the compressor 31, and controls these parts to perform various processes in the air conditioning system 1.

[0037] In this embodiment, the control unit 70 comprises a processor and a storage medium, and the processor reads and executes a program stored in the storage medium to perform various processing for the air conditioner 1. The processor that the control unit 70 may include is, for example, a CPU (Central Processing Unit) or an MPU (Micro-Processing Unit). The storage medium that the control unit 70 may include is, for example, a hard disk, flash memory, or optical disc. The control unit 70 may be installed in either the indoor unit 2 or the outdoor unit 3, or it may be installed outside the indoor unit 2 and the outdoor unit 3. Alternatively, the control unit 70 may function through the cooperation of the indoor unit 2, the outdoor unit 3, and a plurality of components, circuits, etc. installed outside them.

[0038] The control unit 70 controls the compressor 31 and adjusts its rotational speed. The control unit 70 is also configured to acquire the current value of the secondary current of the compressor 31. The secondary current is the current flowing through the motor of the compressor 31.

[0039] In this embodiment, the control unit 70 calculates the indicated horsepower, which is the horsepower of the compressor 31 corresponding to the air conditioning load, based on the air conditioning load, such as the cooling load and heating load. The indicated horsepower is larger when the air conditioning load is large and smaller when the air conditioning load is small. Except during special operations such as when the air conditioning system 1 is started up or when operation starts after an oil recovery operation, the control unit 70 operates the compressor 31 at the indicated horsepower. As a result, the compressor 31 rotates at a rotational speed corresponding to the indicated horsepower, i.e., the rotational speed of the indicated horsepower. In contrast to this embodiment, the control unit 70 may also calculate the indicated rotational speed, which is the rotational speed of the compressor 31 corresponding to the air conditioning load, without using the indicated horsepower, and control the compressor 31 to operate at the indicated rotational speed.

[0040] The control unit 70 controls the oil recovery valve 33B and the on / off valve 57, switching them individually between open and closed states. The control unit 70 controls the four-way valve 35, switching the operation of the air conditioner 1 between cooling and heating operation. The control unit 70 controls the indoor expansion valve 23, the outdoor expansion valve 40, and the electronic expansion valve 51, adjusting their respective opening degrees. The control unit 70 controls the rotation speed of the indoor blower 25 and the outdoor blower 37A, adjusting their respective airflow rates.

[0041] The control unit 70 acquires the measured values ​​from the high-pressure side pressure sensor PS1 and the low-pressure side pressure sensor PS2. The control unit 70 acquires the measured value from the high-pressure switch HP. The control unit 70 acquires the measured values ​​from the outside air temperature sensor TS1, the gas side temperature sensor TS2, the liquid side temperature sensor TS3, the indoor side temperature sensor TS4, and the discharge temperature sensor TS5.

[0042] [1-2. Operation] The operation of the air conditioning system 1, configured as described above, will be explained below.

[0043] Figure 3 is a chart showing the changes in the rotational speed of the compressor 31, the rotational speed of the indicated horsepower for the compressor 31, and the discharge refrigerant temperature of the compressor 31, starting from the time of startup of the air conditioning system 1 or the start of operation after an oil recovery operation. In Figure 3, time t0 is the time of startup of the air conditioning system 1 or the start of operation after an oil recovery operation. Graph G1 in Figure 3 shows the rotational speed of the compressor 31. Graph G2 in Figure 3 shows the rotational speed of the indicated horsepower for the compressor 31. Graph G3 in Figure 3 shows the discharge refrigerant temperature of the compressor 31. Note that "startup of the air conditioning system 1" specifically means the time when the compressor 31 is driven from a stopped state. Also, "start of operation after an oil recovery operation" means the time when the air conditioning system 1 returns to normal cooling or normal heating operation after the oil recovery operation has finished. Oil recovery operation is an operation to return oil to the compressor 31 in order to maintain lubrication of the sliding parts of the compressor 31, and is performed before the oil stored in the compressor 31 runs out. Specifically, the control unit 70 performs oil recovery operation during cooling by reducing the rotational speed of the compressor 31 compared to normal cooling operation, opening the oil recovery valve 33B, and slightly increasing the opening of the indoor expansion valve 23 compared to normal cooling operation. During oil recovery operation during cooling operation, the amount of oil discharged from the compressor 31 is reduced by lowering the rotational speed of the compressor 31. In addition, by opening the indoor expansion valve 23, the liquid refrigerant from the indoor heat exchanger 21 is returned to the accumulator 43 along with the oil. This allows the oil to be collected on the outdoor unit 3 side.

[0044] As shown in Figure 3, the control unit 70 controls the rotational speed of the compressor 31 to a first rotational speed N1, which is lower than the rotational speed N2 of the instructed horsepower for the compressor 31 at time t0, when the air conditioner 1 is started up and when operation starts after an oil recovery operation. Furthermore, the control unit 70 controls the rotational speed of the compressor 31 to gradually increase from the first rotational speed N1 after time t0, bringing it closer to the rotational speed of the instructed horsepower shown in graph G2. In this way, by gradually increasing the rotational speed of the compressor 31 from a first rotational speed N1 that is lower than the rotational speed N2 of the instructed horsepower at time t0, a rapid rise in the discharge refrigerant temperature of the compressor 31 can be suppressed. In this embodiment, the control unit 70 gradually increases the rotational speed of the compressor 31 from the first rotational speed N1 by increasing the rotational speed of the compressor 31 in steps. Alternatively, the control unit 70 may continuously increase the rotational speed of the compressor 31.

[0045] Furthermore, the control unit 70 controls the rate of increase of the compressor 31's rotational speed per unit time while gradually increasing the compressor 31's rotational speed from the first rotational speed N1. By performing such control, the time required to start up the air conditioning system 1 can be easily shortened. In this embodiment, the control unit 70 increases the frequency of increases in the compressor 31's rotational speed as the elapsed time from time t0 decreases, and decreases the frequency of increases in the compressor 31's rotational speed as the elapsed time from time t0 increases. Also, the control unit 70 increases the amount of each increase in the compressor 31's rotational speed as the elapsed time from time t0 decreases, and decreases the amount of each increase in the compressor 31's rotational speed as the elapsed time from time t0 increases. Note that either the frequency of increases in rotational speed or the amount of each increase may be a constant value.

[0046] The control unit 70 increases the rotational speed of the compressor 31 until the rotational speed of the compressor 31 matches the rotational speed of the indicated horsepower.

[0047] The control unit 70 restricts the increase in the indicated horsepower while gradually increasing the rotational speed of the compressor 31 from the first rotational speed N1. As a result, while the rotational speed of the compressor 31 is gradually increasing from the first rotational speed N1, the rotational speed of the indicated horsepower is maintained at a value that does not exceed the rotational speed N2. In this way, by keeping the rotational speed of the indicated horsepower at a value that does not exceed the initial value of the rotational speed of the indicated horsepower, the time Δt from time t0 to time t1, when the rotational speed of the compressor 31 matches the rotational speed of the indicated horsepower, can be shortened.

[0048] After time t1, when the rotational speed of the compressor 31 matches the rotational speed of the indicated horsepower, the control unit 70 controls the compressor 31 to match the indicated horsepower and maintains the state in which the rotational speed of the compressor 31 matches the rotational speed of the indicated horsepower. That is, after time t1, if the control unit 70 reduces the indicated horsepower, the rotational speed of the indicated horsepower will decrease, and the rotational speed of the compressor 31 that matches it will also decrease. Furthermore, after time t1, when the rotational speed of the compressor 31 matches the rotational speed of the indicated horsepower, the control unit 70 does not restrict an increase in the indicated horsepower, but allows an increase in the indicated horsepower.

[0049] Furthermore, in this embodiment, as shown in Figure 3, the control unit 70 performs control to reduce the instructed horsepower when the discharge refrigerant temperature of the compressor 31 exceeds a predetermined temperature TA. This prevents the discharge refrigerant temperature of the compressor 31 from becoming excessively high.

[0050] As shown in Figure 3, if the time t2 at which the discharge refrigerant temperature of the compressor 31 exceeds a predetermined temperature TA is later than the time t1 at which the rotational speed of the compressor 31 matches the indicated horsepower, then when the control unit 70 reduces the indicated horsepower at time t2, the rotational speed of the compressor 31, which matches the indicated horsepower, also decreases accordingly. Therefore, the discharge refrigerant temperature of the compressor 31 can be appropriately reduced.

[0051] On the other hand, unlike in Figure 3, if the time t2 at which the discharge refrigerant temperature of the compressor 31 exceeds a predetermined temperature TA is earlier than the time t1 at which the rotational speed of the compressor 31 matches the rotational speed of the instructed horsepower, then the rotational speed of the compressor 31 at time t2 is smaller than the rotational speed of the instructed horsepower. For this reason, the control unit 70 controls the compressor 31 to increase its rotational speed in order to bring it closer to the rotational speed of the instructed horsepower, and even if the control unit 70 reduces the instructed horsepower at time t2, the rotational speed of the compressor 31 may not decrease. In such cases, it is difficult to appropriately lower the discharge refrigerant temperature of the compressor 31.

[0052] In contrast, in this embodiment, as described above, the time Δt from time t0 to time t1 can be shortened, making it easier to prevent the discharge refrigerant temperature of the compressor 31 from exceeding a predetermined temperature TA before time t1, and making it easier for time t2 to occur after time t1. Therefore, it becomes easier to appropriately lower the discharge refrigerant temperature of the compressor 31.

[0053] [1-3. Effects, etc.] As described above, in this embodiment, the air conditioning system 1 is equipped with a compressor 31 that compresses a refrigerant, and at startup or when operation starts after an oil recovery operation, the rotational speed of the compressor 31 is gradually increased from a first rotational speed N1 which is lower than the indicated rotational speed or indicated horsepower rotational speed for the compressor 31, and the increase in the indicated rotational speed or indicated horsepower is restricted while the rotational speed of the compressor 31 is gradually increased from the first rotational speed N1. This makes it easier to quickly resolve the discrepancy between the rotational speed of the compressor 31 and the rotational speed of the indicated rotational speed or indicated horsepower for the compressor. Therefore, when the indicated rotational speed or indicated horsepower of the compressor 31 is reduced, the actual rotational speed of the compressor 31 tends to decrease, making it easier to suppress the discharge refrigerant temperature of the compressor 31 from rising excessively.

[0054] As in this embodiment, the air conditioning system 1 may be configured such that the rotational speed of the compressor 31 is gradually increased from a first rotational speed N1, and after the rotational speed of the compressor 31 matches the indicated rotational speed or indicated horsepower, the increase in the indicated rotational speed or indicated horsepower is not restricted. This ensures that the compressor 31's rotational speed can follow the indicated rotational speed or horsepower, and then allows the indicated rotational speed or horsepower to be freely set. This makes it easier to prevent the discharge refrigerant temperature of the compressor 31 from rising excessively.

[0055] As in this embodiment, the air conditioning system 1 may be configured such that the rate of increase in the rotational speed of the compressor 31 is gradually reduced while the rotational speed of the compressor 31 is gradually increased from the first rotational speed N1. This shortens the time required for the air conditioning system 1 to start up. As a result, it is easier to prevent the discharge refrigerant temperature of the compressor 31 from rising excessively while minimizing any decrease in convenience.

[0056] (Other embodiments) As described above, Embodiment 1 has been explained as an example of the technology disclosed in this application. However, the technology in this disclosure is not limited to this and can be applied to embodiments that have been modified, replaced, added, or omitted. Furthermore, it is possible to create new embodiments by combining the components described in Embodiment 1 above. Therefore, other embodiments are illustrated below.

[0057] In Embodiment 1, an air conditioning system 1 was described as an example of a refrigeration system, but this is merely an example. The refrigeration system may be any refrigeration system having a refrigerant circuit, such as a refrigerator or a display case.

[0058] In Embodiment 1, the indoor expansion valve 23 and the outdoor expansion valve 40 were described as having a configuration in which the opening degree can be adjusted by control, but this is just one example. The indoor expansion valve 23 and the outdoor expansion valve 40 do not have to be expansion valves in which the opening degree can be adjusted by control, and may be, for example, temperature-type expansion valves.

[0059] In Embodiment 1, the control unit 70 was described as including a processor and a storage medium, but this is just one example. The control unit 70 may, for example, use wired logic that cannot be rewritten. Using wired logic in the control unit 70 is effective in improving processing speed. Examples of wired logic include ASICs (Application Specific Integrated Circuits). The control unit 70 may also be implemented by combining a processor and wired logic. Implementing the control unit 70 by combining a processor and wired logic can improve processing speed while increasing the freedom of software design. Furthermore, the control unit 70 and a circuit having a different function from the control unit 70 may be configured with a single semiconductor element. Examples of circuits having a different function include A / D-D / A conversion circuits. The control unit 70 may also be configured with a single semiconductor element or with multiple semiconductor elements. When configured with multiple semiconductor elements, various controls may be implemented with different semiconductor elements. Moreover, the control unit 70 may be configured with a configuration including semiconductor elements and passive components such as resistors or capacitors.

[0060] Since the embodiments described above are for illustrative purposes of the technology described herein, various modifications, substitutions, additions, omissions, etc., can be made within the claims or their equivalents.

[0061] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0062] (Technology 1) A refrigeration system comprising a compressor for compressing a refrigerant, wherein at startup or when operation begins after an oil recovery operation, the rotational speed of the compressor is gradually increased from a first rotational speed lower than the indicated rotational speed or indicated horsepower rotational speed for the compressor, and the increase in the indicated rotational speed or indicated horsepower is restricted while the rotational speed of the compressor is gradually increased from the first rotational speed. This makes it easier to quickly resolve the discrepancy between the compressor's rotational speed and the indicated rotational speed or indicated horsepower for the compressor. Therefore, when the indicated rotational speed or indicated horsepower of the compressor is reduced, the actual rotational speed of the compressor tends to decrease more easily, making it easier to suppress an excessive rise in the compressor's discharge refrigerant temperature.

[0063] (Technology 2) The refrigeration apparatus according to Technology 1, wherein the rotational speed of the compressor is gradually increased from the first rotational speed, and after the rotational speed of the compressor matches the indicated rotational speed or the indicated horsepower, the increase in the indicated rotational speed or the indicated horsepower is not restricted. This allows for the setting of the indicated rotational speed or horsepower freely after ensuring that the compressor's rotational speed can track the indicated rotational speed or horsepower. As a result, it becomes easier to suppress the compressor's discharge refrigerant temperature from rising excessively.

[0064] (Technology 3) The refrigeration apparatus according to Technology 1 or 2, wherein the rate of increase in the rotational speed of the compressor is gradually reduced while the rotational speed of the compressor is gradually increased from the first rotational speed. This reduces the time required for the refrigeration system to start up. As a result, it becomes easier to prevent the compressor's discharge refrigerant temperature from rising excessively while minimizing any decrease in convenience. [Industrial applicability]

[0065] This disclosure is applicable to air conditioning systems. Specifically, this disclosure is applicable to household air conditioning systems or commercial air conditioning systems, etc. [Explanation of Symbols]

[0066] 1. Air conditioning system (refrigeration system) 1A Refrigerant Circuit 2 Indoor unit 3 Outdoor unit 4. Internal and external gas pipes 5. Internal and external connecting liquid pipes 6. Oil balance pipe 21 Indoor heat exchanger 22 Indoor gas valve 23. Indoor expansion valve 24 Indoor liquid valve 25 Indoor fan 31 Compressor 31A Injection Port 32 Discharge pipe 33 Oil Separator 33A Oil pipe 33B Oil recovery valve 33C Check valve 33D Oil Valve 34 High-pressure gas pipe 35 Four-way valve 36 Check valve 37 Outdoor heat exchanger 37A outdoor blower 38 Outdoor gas valve 39 Low-pressure gas pipe 40 Outdoor expansion valve 41 Liquid side refrigerant piping 41A Branch point 42 Outdoor liquid valve 43 Accumulator 44 Suction pipe 50 Injection Piping 51 Electronic expansion valve 53 Cooling heat exchanger 55 Branch piping 57 Shut-off valve 70 Control Unit HP High-Voltage Switch PS1 High-Pressure Side Pressure Sensor PS2 Low-Pressure Side Pressure Sensor TS1 Outdoor Temperature Sensor TS2 Gas-side temperature sensor TS3 Liquid-side temperature sensor TS4 Indoor Temperature Sensor TS5 Discharge Temperature Sensor

Claims

1. Equipped with a compressor to compress the refrigerant, At startup or when operation begins after an oil recovery operation, the rotational speed of the compressor is gradually increased from a first rotational speed lower than the indicated rotational speed or indicated horsepower rotational speed for the compressor. While gradually increasing the rotational speed of the compressor from the first rotational speed, the increase in the indicated rotational speed or the indicated horsepower is restricted. Refrigeration equipment.

2. The rotational speed of the compressor is gradually increased from the first rotational speed, and after the rotational speed of the compressor matches the indicated rotational speed or the indicated horsepower, the increase in the indicated rotational speed or the indicated horsepower is not restricted. The refrigeration apparatus according to claim 1.

3. While gradually increasing the rotational speed of the compressor from the first rotational speed, the rate of increase in the rotational speed of the compressor is gradually reduced. The refrigeration apparatus according to claim 1 or 2.

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