Air conditioning system, control method for air conditioning system, and control program for air conditioning system

Abstract

This disclosure provides an air conditioning system that appropriately switches between the operation of the second compressor alone and the combined operation of the first and second compressors. [Solution] An air conditioning system that circulates a refrigerant and performs air conditioning by connecting a first compressor driven by a gas engine and a second compressor driven by a motor in parallel, comprising a control unit that controls the driving of the first compressor and the second compressor, wherein the control unit comprises a first drive control unit that, when the air conditioning system is started, drives only the first compressor for a first period and calculates a first air conditioning load which is the air conditioning load for the first period, and a second drive control unit that, based on the first air conditioning load, decides whether to drive both the first and second compressors or drive only the second compressor, wherein the second drive control unit decides to drive only the second compressor if the suction differential temperature falls below a predetermined threshold during the first period.

Description

Technical Field

[0001] The present disclosure relates to an air conditioner, a control method thereof, and a control program for an air conditioner.

Background Art

[0002] Patent Document 1 discloses an air conditioner including an outdoor unit and an indoor unit, where the outdoor unit includes a gas engine having gas as a driving source, a first compressor that obtains driving force from the gas engine and compresses a refrigerant, and a second compressor having an electric motor as a driving source.

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 an air conditioner, a control method thereof, and a control program for an air conditioner that appropriately switches between the independent operation of the second compressor and the combined operation of the first compressor and the second compressor.

Means for Solving the Problems

[0005] The air conditioning system in this disclosure is an air conditioning system that performs air conditioning by circulating a refrigerant, wherein a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel, and the system includes a control unit that controls the driving of the first compressor and the second compressor, the control unit comprising: a first drive control unit that, when the air conditioning system is started, drives only the first compressor for a first period and calculates a first air conditioning load, which is the air conditioning load for the first period; and a second drive control unit that, based on the first air conditioning load, decides whether to drive both the first and second compressors or only the second compressor, the second drive control unit decides to drive only the second compressor if the suction differential temperature falls below a predetermined threshold during the first period.

[0006] The control method for an air conditioning system in this disclosure is a control method for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel and a refrigerant is circulated to provide air conditioning, and comprises a control unit that controls the driving of the first compressor and the second compressor, wherein when the air conditioning system is started, the control unit performs a first control step of driving only the first compressor for a first period and calculating a first air conditioning load, which is the air conditioning load for the first period, and a second control step of determining whether to drive both the first and second compressors or only the second compressor based on the first air conditioning load, and in the second control step, if the suction differential temperature falls below a predetermined threshold during the first period, it is determined to drive only the second compressor.

[0007] The control program for the air conditioning system is a control program for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel to circulate a refrigerant and provide air conditioning. The processor of the control unit that controls the driving of the first compressor and the second compressor functions as a first drive control unit that drives only the first compressor for a first period when the air conditioning system is started and calculates a first air conditioning load, which is the air conditioning load for the first period, and a second drive control unit that, based on the first air conditioning load, decides whether to drive both the first and second compressors or only the second compressor, and the second drive control unit decides to drive only the second compressor if the suction temperature difference falls below a predetermined threshold during the first period. [Effects of the Invention]

[0008] The air conditioning system, control method for the air conditioning system, and control program for the air conditioning system described in this disclosure can appropriately switch between operation of the second compressor alone and operation of the first and second compressors together. [Brief explanation of the drawing]

[0009] [Figure 1] Refrigerant circuit diagram showing the air conditioning system in Embodiment 1 [Figure 2] Block diagram showing the configuration of the control unit in Embodiment 1 [Figure 3] Graph showing the relationship between air conditioning load and efficiency in Embodiment 1 [Figure 4] Timing chart showing an example of compressor state transitions in Embodiment 1 [Figure 5] Timing chart showing another example of the compressor state transitions in Embodiment 1 [Figure 6] A flowchart showing an example of the processing in the outdoor unit control unit in Embodiment 1. [Modes for carrying out the invention]

[0010] (Knowledge and other information that formed the basis of this disclosure) At the time the inventors conceived of this disclosure, there was an air conditioning system comprising a gas engine powered by gas, a first compressor that compressed a refrigerant using the gas engine as a driving force, and a second compressor powered by an electric motor.

[0011] Furthermore, it has been proposed that, for example, when starting an air conditioning system, only the first compressor is driven during the first period, and the first air conditioning load, which is the air conditioning load during the first period, is calculated. Based on the first air conditioning load, the system appropriately switches between operating the second compressor alone and operating both the first and second compressors together.

[0012] However, in the above air conditioning system, the first compressor has a higher capacity than the second compressor, so the thermostat sometimes shuts off during the first period (for example, 5 minutes). The inventors discovered that when the thermostat shuts off in such a short period, the entire space may not reach the target temperature, which could impair user comfort. To solve this problem, the subject matter of this disclosure was established. This disclosure provides an air conditioning system capable of appropriately switching between standalone operation of the second compressor and combined operation of the first and second compressors, a control method for the air conditioning system, and a control program for the air conditioning system.

[0013] 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.

[0014] (Embodiment 1) Embodiment 1 will be described below with reference to the drawings. [1-1. Configuration, etc.] [1-1-1. Configuration of refrigerant circuit] First, referring to FIG. 1, the refrigerant circuit that constitutes the air conditioner 1 will be described. FIG. 1 is a refrigerant circuit diagram showing the air conditioner 1 in Embodiment 1. As shown in FIG. 1, the air conditioner 1 according to the present embodiment includes an outdoor unit 10 and an indoor unit 30. In FIG. 1, only one indoor unit 30 is installed, but a plurality of indoor units 30 may be installed in parallel with respect to the outdoor unit 10.

[0015] The outdoor unit 10 includes a gas engine 11, a first compressor 12, a motor 13, and a second compressor 14. The gas engine 11 drives the first compressor 12. The first compressor 12 is driven by the gas engine 11 and compresses the refrigerant. The motor 13 drives the second compressor 14. The second compressor 14 is driven by the motor 13 and compresses the refrigerant. The first compressor 12 and the second compressor 14 are connected in parallel.

[0016] In the present embodiment, the first compressor 12 has a higher capacity than the second compressor 14. [[ID=​​​​​​​

[0018] Downwind of the outdoor heat exchanger 17 is a radiator 18 that cools the cooling water for the gas engine 11. Furthermore, an outdoor fan 19 is positioned near the radiator 18 to circulate outside air to the outdoor heat exchanger 17 and the radiator 18. An outdoor expansion valve 20 is provided on one side of the outdoor heat exchanger 17. The outdoor expansion valve 20 is connected to the indoor unit 30 via refrigerant piping.

[0019] The indoor unit 30 comprises an indoor heat exchanger 31, an indoor fan 32, and an indoor expansion valve 33. The refrigerant piping 35 is connected to one end of the indoor heat exchanger 31 via the indoor expansion valve 33. The other end of the indoor heat exchanger 31 is connected to the suction pipes 36 of the first compressor 12 and the second compressor 14 via a four-way valve 16 and an accumulator 21. The indoor unit 30 corresponds to an example of an "indoor unit".

[0020] A bypass pipe 22, connected to the suction side of the first compressor 12 and the second compressor 14, is connected to the refrigerant piping 35 that connects the outdoor heat exchanger 17 and the indoor heat exchanger 31. A waste heat recovery pressure reducing device 23 and a waste heat recovery heat exchanger 24 are provided in the bypass pipe 22.

[0021] Furthermore, one end of the oil return pipe 25 is connected to the lower part of the oil separator 15, and the other end of the oil return pipe 25 is connected to the suction pipes 36 of the first compressor 12 and the second compressor 14. Furthermore, a refrigerant temperature sensor 26 for detecting the temperature of the discharged refrigerant is provided on the discharge side of the first compressor 12 and the second compressor 14.

[0022] [1-1-2. Control Configuration] Next, the control configuration of this embodiment will be described with reference to Figure 2. Figure 2 is a block diagram showing the control configuration of the air conditioning system 1 of this embodiment. As shown in Figure 2, the air conditioning system 1 comprises an outdoor unit control unit 40 and an indoor unit control unit 50. The outdoor unit control unit 40 controls each part of the outdoor unit 10. The indoor unit control unit 50 controls each part of the indoor unit 30. The outdoor unit control unit 40 corresponds to an example of a "control unit".

[0023] First, let's explain the configuration of the outdoor unit control unit 40. The outdoor unit control unit 40 includes an outdoor unit communication circuit 41, an outdoor unit processor 42, and an outdoor unit memory 43. The outdoor unit communication circuit 41 communicates with the indoor unit communication circuit 51 according to instructions from the outdoor unit processor 42. The outdoor unit communication circuit 41 receives a differential temperature signal SG from the indoor unit communication circuit 51. The differential temperature signal SG indicates the intake differential temperature ΔTP of the indoor unit 30.

[0024] The outdoor unit processor 42 is a processor such as a CPU (Central Processing Unit) or MPU (Micro Processing Unit). The outdoor unit processor 42 may consist of a single processor or multiple processors. The outdoor unit processor 42 corresponds to an example of a "processor".

[0025] The outdoor unit memory 43 is a memory that stores programs and data. The outdoor unit memory 43 stores the outdoor unit control program 431. The outdoor unit memory 43 has a non-volatile storage area. The outdoor unit memory 43 may also have a volatile storage area and constitute the work area of ​​the outdoor unit processor 42. The outdoor unit memory 43 is composed of, for example, ROM (Read Only Memory) or RAM (Random Access Memory). Outdoor unit control program 431 corresponds to an example of a "control program".

[0026] The outdoor unit control unit 40 controls the first compressor 12, second compressor 14, outdoor fan 19, outdoor expansion valve 20, etc. of the outdoor unit 10 of the air conditioning system 1. A refrigerant temperature sensor 26 is connected to the outdoor unit control unit 40.

[0027] The outdoor unit processor 42 functions as a first drive control unit 421 and a second drive control unit 422. Specifically, the outdoor unit processor 42 functions as the first drive control unit 421 and the second drive control unit 422 by reading and executing the outdoor unit control program 431 from the outdoor unit memory 43.

[0028] When the air conditioning system 1 is started, the first drive control unit 421 drives only the first compressor 12 during the first period P1 and calculates the first air conditioning load L1, which is the air conditioning load LD for the first period P1. The first period P1 is, for example, 5 minutes.

[0029] In this way, when the air conditioning system 1 is started, only the first compressor 12 is driven, so even if, for example, liquid refrigerant is lying inside the compressor, damage to the compressor can be suppressed. This is because the second compressor 14 is more likely to be damaged when compressing liquid refrigerant compared to the first compressor 12.

[0030] Furthermore, the first drive control unit 421 calculates the first air conditioning load L1 based on, for example, the rated output of the first compressor 12, the rated output of the second compressor 14, the output of the first compressor 12, the output of the second compressor 14, the intake temperature difference ΔTP of the indoor unit 30, etc. The intake temperature difference ΔTP indicates the difference between the target temperature and the intake temperature. The target temperature is set, for example, by the remote control 90. The intake temperature is the temperature of the air drawn in by the indoor unit 30. The intake temperature is detected by the intake temperature sensor 34. The outdoor unit communication circuit 41 receives a signal indicating the intake temperature difference ΔTP from the indoor unit communication circuit 51. The first drive control unit 421 acquires the intake temperature difference ΔTP from the outdoor unit communication circuit 41.

[0031] Furthermore, the second drive control unit 422 determines, based on the first air conditioning load L1, whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14. The second drive control unit 422 decides, for example, to drive both the first compressor 12 and the second compressor 14 when the first air conditioning load L1 is equal to or greater than the first threshold TH1. The second drive control unit 422 also decides, for example, to drive only the second compressor 14 when the first air conditioning load L1 is less than the first threshold TH1. The first threshold TH1 is, for example, 30% of the maximum load. The maximum load is, for example, the sum of the rated capacity of the first compressor 12 and the rated capacity of the second compressor 14.

[0032] Furthermore, the second drive control unit 422 decides to drive only the second compressor 14 if, during the first period P1, the suction differential temperature ΔTP in the indoor unit 30 falls below a predetermined threshold ΔTHA. The intake temperature difference ΔTP indicates the difference between the target temperature and the intake temperature. The target temperature is set, for example, by the remote control 90. The intake temperature is the temperature of the air drawn in by the indoor unit 30. The intake temperature is detected by the intake temperature sensor 34. Furthermore, in the first period P1, when the outdoor unit communication circuit 41 receives a differential temperature signal SG from the indoor unit communication circuit 51, the second drive control unit 422 determines whether the suction differential temperature ΔTP in the indoor unit 30 is less than or equal to a predetermined threshold ΔTHA. The differential temperature signal SG indicates the suction differential temperature ΔTP. The predetermined threshold ΔTHA is, for example, "2°C". The predetermined threshold ΔTHA is set to a value greater than the transition threshold ΔTHB, which will be described later.

[0033] Furthermore, if the intake temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1, the second drive control unit 422 drives only the second compressor 14 during the second period P2 following the first period P1, and calculates the second air conditioning load L2, which is the air conditioning load for the second period P2. The second period P2 is, for example, a period of the same length as the first period P1. In other words, the second period P2 is, for example, "5 minutes".

[0034] The second drive control unit 422 calculates the second air conditioning load L2 based on, for example, the rated output of the first compressor 12, the rated output of the second compressor 14, the output of the first compressor 12, the output of the second compressor 14, the intake temperature difference ΔTP of the indoor unit 30, etc. The outdoor unit communication circuit 41 receives a differential temperature signal SG indicating the intake differential temperature ΔTP from the indoor unit communication circuit 51. The second drive control unit 422 acquires the intake differential temperature ΔTP from the outdoor unit communication circuit 41.

[0035] The second drive control unit 422 then decides, based on the second air conditioning load L2, whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14. The second drive control unit 422 decides to drive both the first compressor 12 and the second compressor 14, for example, when the second air conditioning load L2 is greater than or equal to the second threshold TH2. The second drive control unit 422 also decides to drive only the second compressor 14, for example, when the second air conditioning load L2 is less than the second threshold TH2. The second threshold TH2 is, for example, the same value as the first threshold TH1. In other words, the second threshold TH2 is, for example, 30% of the maximum load. The maximum load is, for example, the sum of the rated capacity of the first compressor 12 and the rated capacity of the second compressor 14.

[0036] Next, the configuration of the indoor unit control unit 50 will be described. The indoor unit control unit 50 includes an indoor unit communication circuit 51, an indoor unit processor 52, and an indoor unit memory 53. The indoor unit communication circuit 51 communicates with the outdoor unit communication circuit 41 according to instructions from the indoor unit processor 52. The indoor unit communication circuit 51 transmits a differential temperature signal SG, etc., to the outdoor unit communication circuit 41. The differential temperature signal SG indicates the intake differential temperature ΔTP.

[0037] The indoor unit processor 52 is a processor such as a CPU or MPU. The indoor unit processor 52 may consist of a single processor or multiple processors.

[0038] The indoor unit memory 53 is a memory that stores programs and data. The indoor unit memory 53 stores the indoor unit control program 531. The indoor unit memory 53 has a non-volatile storage area. Alternatively, the indoor unit memory 53 may also have a volatile storage area and constitute the work area of ​​the indoor unit processor 52. The indoor unit memory 53 is composed of, for example, ROM or RAM.

[0039] The indoor unit control unit 50 controls the indoor fan 32, indoor expansion valve 33, and other components of the indoor unit 30 of the air conditioning system 1.

[0040] The indoor unit processor 52 functions as a drive control unit 521 and a transmission unit 522. Specifically, the indoor unit processor 52 functions as a drive control unit 521 and a transmission unit 522 by reading and executing the indoor unit control program 531 from the indoor unit memory 53.

[0041] The drive control unit 521 controls each part of the indoor unit 30 according to the setting information from the remote control 90. The drive control unit 521 receives instruction information from, for example, the remote control 90 and switches the indoor unit 30 on or off. Furthermore, the drive control unit 521 receives instruction information from, for example, the remote control 90 and controls the operating mode of the indoor unit 30. The operating modes include a heating operation mode, a cooling operation mode, and a fan operation mode. The heating operation mode is an operating mode in which the drive control unit 521 causes the indoor unit 30 to perform heating operation. The cooling operation mode is an operating mode in which the drive control unit 521 causes the indoor unit 30 to perform cooling operation. The fan operation mode is an operating mode in which the drive control unit 521 causes the indoor unit 30 to perform fan operation.

[0042] Furthermore, the drive control unit 521 receives target temperature information from, for example, the remote control 90 and controls each part of the indoor unit 30 based on the target temperature. The drive control unit 521, for example, when performing heating or cooling operation, transitions to fan operation when the intake temperature difference ΔTP falls below the transition threshold ΔTHB. The intake temperature difference ΔTP indicates the difference between the target temperature and the intake temperature. The target temperature is set, for example, by the remote control 90. The intake temperature is the temperature of the air drawn in by the indoor unit 30. The intake temperature is detected by the intake temperature sensor 34. The transition threshold ΔTHB is, for example, "1°C".

[0043] The transmitting unit 522, while the drive control unit 521 is controlling the operating mode of the indoor unit 30, causes the indoor unit communication circuit 51 to transmit a differential temperature signal SG to the outdoor unit communication circuit 41. The differential temperature signal SG indicates the intake differential temperature ΔTP.

[0044] In this embodiment, only one indoor unit 30 is installed in the air conditioning system 1, but multiple indoor units 30 may be installed in the air conditioning system 1. In this case, for example, if the intake differential temperature ΔTP of at least one of the multiple indoor units 30 falls below a predetermined threshold ΔTHA during the first period P1, the second drive control unit 422 decides to drive only the second compressor 14.

[0045] [1-1-3. Relationship between air conditioning load and efficiency] Next, we will explain the relationship between the air conditioning load LD and efficiency EF, referring to Figure 3. Figure 3 is a graph showing the relationship between the air conditioning load LD and efficiency EF. In Figure 3, the horizontal axis represents the air conditioning load (LD), and the vertical axis represents the efficiency (EF).

[0046] Graph G1 shows the relationship between the air conditioning load LD and efficiency EF when only the second compressor 14 is driven. Graph G2 shows the relationship between the air conditioning load LD and efficiency EF when only the first compressor 12 is driven. Graph G3 shows the relationship between the air conditioning load LD and efficiency EF when both the first compressor 12 and the second compressor 14 are driven.

[0047] By comparing graphs G1, G2, and G3, the following can be observed. In other words, when the air conditioning load LD is within the first range LA, the efficiency EF is best when only the second compressor 14 is driven. The first range LA is the range of the first load LD1 or less. Furthermore, when the air conditioning load LD is within the second range LB, the efficiency EF is best when only the first compressor 12 is driven. The second range LB is the range where the first load LD1 or greater and the second load LD2 or less. Furthermore, when the air conditioning load LD is in the third range LC, the efficiency EF is best when both the first compressor 12 and the second compressor 14 are driven. The third range LC is the range of the second load LD2 or higher. The load THL represents the air conditioning load LD at the intersection of graph G1 and graph G3. The first threshold TH1 and the second threshold TH2 are set, for example, based on the load THL.

[0048] Therefore, from the viewpoint of efficiency EF, it is preferable to drive only the second compressor 14 when the air conditioning load LD is in the first range LA, to drive only the first compressor 12 when the air conditioning load LD is in the second range LB, and to drive both the first compressor 12 and the second compressor 14 when the air conditioning load LD is in the third range LC.

[0049] However, since the first compressor 12 is driven by the gas engine 11, it is efficient when driven at medium to high power, but relatively inefficient when driven at low power.

[0050] Therefore, in this embodiment, the second drive control unit 422 determines, based on the first air conditioning load L1, whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14. Furthermore, the second drive control unit 422 determines, based on the second air conditioning load L2, whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14.

[0051] [1-2. Operation, etc.] [1-2-1. Operation of the refrigerant circuit] Next, with reference to Figure 1, the operation of the air conditioning system in the embodiment will be described. (Air conditioning operation) During cooling operation, at least one of the first compressor 12 and the second compressor 14 is driven according to the air conditioning load LD. The four-way valve 16 is set to allow the refrigerant to flow in the direction indicated by the dashed arrow.

[0052] The high-temperature, high-pressure gaseous refrigerant compressed in at least one of the first compressor 12 and the second compressor 14 flows into the oil separator 15. After the oil is separated in the oil separator 15, the gaseous refrigerant passes through the four-way valve 16 and enters the outdoor heat exchanger 17. In the outdoor heat exchanger 17, the gaseous refrigerant exchanges heat with the outside air and dissipates heat, then condenses into a high-pressure liquid refrigerant which passes through the outdoor expansion valve 20 and is supplied to the indoor unit 30.

[0053] The high-pressure liquid refrigerant that enters the indoor unit 30 is depressurized by the indoor expansion valve 33, becoming a gas-liquid two-phase state, and flows into the indoor heat exchanger 31. In the indoor heat exchanger 31, the gas-liquid two-phase refrigerant exchanges heat with the air in the space to be air-conditioned, absorbs heat, evaporates, and flows out of the indoor unit 30 as a gaseous refrigerant. The gaseous refrigerant that flows out from the indoor unit 30 returns to the outdoor unit 10. The gaseous refrigerant that flows into the outdoor unit 10 passes through the four-way valve 16 and the accumulator 21 and returns to at least one of the first compressor 12 and the second compressor 14, and the above process is repeated.

[0054] (Heating operation) During heating operation, both the first compressor 12 and the second compressor 14, or only the second compressor 14, are driven according to the air conditioning load LD. The four-way valve 16 is set to allow the refrigerant to flow in the direction indicated by the solid arrow.

[0055] The high-temperature, high-pressure gaseous refrigerant compressed by both the first compressor 12 and the second compressor 14, or by the second compressor 14 alone, flows into the oil separator 15. The gaseous refrigerant, from which the oil has been separated in the oil separator 15, passes through the four-way valve 16 and is supplied to the indoor unit 30. The high-temperature, high-pressure gaseous refrigerant that enters the indoor unit 30 flows into the indoor heat exchanger 31, exchanges heat with the air in the space being air-conditioned to release heat, then condenses as a liquid refrigerant and flows out of the indoor unit 30 through the indoor expansion valve 33.

[0056] The liquid refrigerant that flows out of the indoor unit 30 returns to the outdoor unit 10. The liquid refrigerant that flows into the outdoor unit 10 is depressurized by the outdoor expansion valve 20 and flows into the outdoor heat exchanger 17 in a gas-liquid two-phase state. The gas-liquid two-phase refrigerant exchanges heat with the outside air in the outdoor heat exchanger 17, absorbs heat, evaporates, becomes a gaseous refrigerant, and returns to both the first compressor 12 and the second compressor 14, or to the second compressor 14, through the four-way valve 16 and the accumulator 21, and the above process is repeated. [1-2-2. Transition of Compressor State] Next, we will explain the state transitions of the compressor with reference to Figures 4 and 5. Figure 4 is a timing chart showing an example of the state transition of the compressor in Embodiment 1. Figure 4 is a timing chart for the case in the first period P1 when the suction differential temperature ΔTP does not fall below a predetermined threshold ΔTHA.

[0057] The upper section of Figures 4-5 shows the on / off changes of the first compressor 12, and the lower section of Figures 4-5 shows the on / off changes of the second compressor 14. In the upper and lower sections of Figures 4-5, the horizontal axis represents time T, and the vertical axis represents on / off.

[0058] As shown in Figure 4, at time T0, the air conditioning system 1 is started, and during the first period P1 from time T0 to time T1, the first drive control unit 421 drives only the first compressor 12. The first drive control unit 421 also calculates the first air conditioning load L1, which is the air conditioning load LD for the first period P1. The second drive control unit 422 then decides to drive only the second compressor 14 if the first air conditioning load L1 is less than the first threshold TH1. Therefore, at time T1, the first compressor 12 is stopped and the second compressor 14 is started.

[0059] On the other hand, if the first air conditioning load L1 is equal to or greater than the first threshold TH1, the second drive control unit 422 decides to drive both the first compressor 12 and the second compressor 14. Therefore, as shown by the dashed line in Figure 4, the first compressor 12 continues to operate at time T1. Also, the second compressor 14 starts operating at time T1. In other words, both the first compressor 12 and the second compressor 14 are operating at time T1.

[0060] Figure 5 is a timing chart showing another example of the state transition of the compressor in Embodiment 1. Figure 5 is a timing chart when the suction differential temperature ΔTP is less than or equal to a predetermined threshold ΔTHA during the first period P1.

[0061] As shown in Figure 5, at time T0, the air conditioning system 1 is started, and during the first period P1 from time T0 to time T1, the first drive control unit 421 drives only the first compressor 12. The first drive control unit 421 also calculates the first air conditioning load L1, which is the air conditioning load LD for the first period P1. Since the suction temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1, the second drive control unit 422 decides to drive only the second compressor 14 at time T1. Therefore, at time T1, the drive of the first compressor 12 is stopped, and the drive of the second compressor 14 is started. Then, during the second period P2 from time T1 to time T2, only the second compressor 14 is driven. Also, during the second period P2, the second drive control unit 422 calculates the second air conditioning load L2, which is the air conditioning load LD for the second period P2.

[0062] Then, if the second air conditioning load L2 is less than the second threshold TH2, the second drive control unit 422 decides to drive only the second compressor 14. Therefore, at time T2, the first compressor 12 remains stopped, and the second compressor 14 continues to operate. In other words, at time T2, only the second compressor 14 is operated.

[0063] On the other hand, if the second air conditioning load L2 is equal to or greater than the second threshold TH2, the second drive control unit 422 decides to drive both the first compressor 12 and the second compressor 14. Therefore, as shown by the dashed line in Figure 5, the first compressor 12 is started to run at time T2. Also, the second compressor 14 continues to run at time T2. In other words, both the first compressor 12 and the second compressor 14 are running at time T2.

[0064] As explained with reference to Figures 4-5, the second drive control unit 422 determines, based on the air conditioning load LD, whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14. Therefore, it is possible to appropriately switch between operating the second compressor 14 alone and operating the first compressor 12 and the second compressor 14 together, depending on the air conditioning load LD.

[0065] [1-2-3. Processing of the outdoor unit control unit] Next, the processing of the outdoor unit control unit 40 will be described with reference to Figure 6. Figure 6 is a flowchart showing an example of the processing of the outdoor unit control unit 40 in Embodiment 1. As shown in Figure 6, first, in step S101, the first drive control unit 421 drives the first compressor 12 when starting the air conditioning system 1. In this way, when the air conditioning system 1 is started, only the first compressor 12 is driven, so even if, for example, liquid refrigerant is lying inside the compressor, damage to the compressor can be suppressed. This is because the second compressor 14 is more likely to be damaged when compressing liquid refrigerant compared to the first compressor 12. Next, in step S103, the first drive control unit 421 calculates the first air conditioning load L1. The first air conditioning load L1 is the air conditioning load LD for the first period P1.

[0066] Next, in step S105, the outdoor unit control unit 40 determines whether or not the first period P1 has elapsed since the air conditioning system 1 was started in step S101. If the outdoor unit control unit 40 determines that the first period P1 has not elapsed (step S105; NO), the process returns to step S103. If the outdoor unit control unit 40 determines that the first period P1 has elapsed (step S105; YES), the process proceeds to step S107.

[0067] Then, in step S107, the second drive control unit 422 determines whether the suction differential temperature ΔTP in the first period P1 has fallen below a predetermined threshold ΔTHA. If the second drive control unit 422 determines that the suction temperature difference ΔTP is below a predetermined threshold ΔTHA (step S107; YES), the process proceeds to step S117. If the second drive control unit 422 determines that the suction temperature difference ΔTP is not below a predetermined threshold ΔTHA (step S107; NO), the process proceeds to step S109.

[0068] Then, in step S109, the second drive control unit 422 determines whether the first air conditioning load L1 is greater than or equal to the first threshold TH1. If the second drive control unit 422 determines that the first air conditioning load L1 is not equal to or greater than the first threshold TH1 (step S109; NO), the process proceeds to step S111. Then, in step S111, the second drive control unit 422 drives the second compressor 14. Next, in step S113, the second drive control unit 422 stops driving the first compressor 12. After that, the process ends.

[0069] If the second drive control unit 422 determines that the first air conditioning load L1 is equal to or greater than the first threshold TH1 (step S109; YES), the process proceeds to step S115. Then, in step S115, the second drive control unit 422 drives the second compressor 14. After that, the process ends.

[0070] If the answer in step S107 is YES, then in step S117, the second drive control unit 422 drives the second compressor 14. Next, in step S119, the second drive control unit 422 stops driving the first compressor 12. Next, in step S121, the second drive control unit 422 calculates the second air conditioning load L2. The second air conditioning load L2 is the air conditioning load LD for the second period P2.

[0071] Furthermore, the processing in steps S107, S117, S119, and S121 provides the following effect to the air conditioning system 1. Specifically, it is possible to suppress the indoor unit 30 from repeatedly switching between thermo-on and thermo-off, especially when the air conditioning load LD is low, thereby preventing a decrease in user comfort.

[0072] Next, in step S123, the outdoor unit control unit 40 determines whether or not the second period P2 has elapsed since the first compressor 12 was stopped in step S119. If the outdoor unit control unit 40 determines that the second period P2 has not elapsed (step S123; NO), the process returns to step S121. If the outdoor unit control unit 40 determines that the second period P2 has elapsed (step S123; YES), the process proceeds to step S125.

[0073] Then, in step S125, the second drive control unit 422 determines whether the second air conditioning load L2 is greater than or equal to the second threshold TH2. If the second drive control unit 422 determines that the second air conditioning load L2 is not equal to or greater than the second threshold TH2 (step S125; NO), the process ends thereafter. If the second drive control unit 422 determines that the second air conditioning load L2 is equal to or greater than the second threshold TH2 (step S125; YES), the process proceeds to step S127. Then, in step S127, the second drive control unit 422 drives the first compressor 12. After that, the process ends.

[0074] Steps S101-S103 correspond to an example of the "first control step". Steps S107-S119 correspond to an example of the "second control step".

[0075] [1-3. Effects, etc.] As described above, the air conditioning system 1 of this embodiment is an air conditioning system 1 that performs air conditioning by circulating a refrigerant, in which a first compressor 12 driven by a gas engine 11 and a second compressor 14 driven by a motor 13 are connected in parallel, and the system includes an outdoor unit control unit 40 that controls the driving of the first compressor 12 and the second compressor 14, and the outdoor unit control unit 40 includes a first drive control unit 421 that, when the air conditioning system 1 is started, drives only the first compressor 12 for a first period P1 and calculates a first air conditioning load L1 which is the air conditioning load LD for the first period P1, and a second drive control unit 422 that, based on the first air conditioning load L1, decides whether to drive both the first compressor 12 and the second compressor 14 or drive only the second compressor 14, and the second drive control unit 422 decides to drive only the second compressor 14 if the suction differential temperature ΔTP in the first period P1 falls below a predetermined threshold ΔTHA.

[0076] This allows the system to determine whether to drive both the first compressor 12 and the second compressor 14, or only the second compressor 14, based on the first air conditioning load L1, which is the air conditioning load LD for the first period P1. Therefore, it is possible to appropriately switch between operating the second compressor 14 alone and operating the first compressor 12 and the second compressor 14 together. Furthermore, if the suction temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1, it is decided to drive only the second compressor 14. Therefore, it is possible to appropriately switch between the operation of the second compressor 14 alone and the combined operation of the first compressor 12 and the second compressor 14.

[0077] Furthermore, in this embodiment, if the intake temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1, the second drive control unit 422 drives only the second compressor 14 during the second period P2, calculates the second air conditioning load L2, which is the air conditioning load LD for the second period P2, and decides whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14, based on the second air conditioning load L2.

[0078] As a result, if the intake temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1, a decision is made based on the second air conditioning load L2, which is the air conditioning load LD for the second period P2, to either drive both the first compressor 12 and the second compressor 14, or drive only the second compressor 14. Therefore, it is possible to appropriately switch between operating the second compressor 14 alone and operating the first compressor 12 and the second compressor 14 together.

[0079] Furthermore, in this embodiment, a plurality of indoor units 30 are provided, and the second drive control unit 422 decides to drive only the second compressor 14 when the suction differential temperature ΔTP of at least one of the plurality of indoor units 30 falls below a predetermined threshold ΔTHA during the first period P1.

[0080] As a result, if the suction temperature difference ΔTP of at least one of the multiple indoor units 30 falls below a predetermined threshold ΔTHA during the first period P1, it is decided to drive only the second compressor 14. Therefore, even when multiple indoor units 30 are provided, it is possible to appropriately switch between the operation of the second compressor 14 alone and the combined operation of the first compressor 12 and the second compressor 14.

[0081] Furthermore, in this embodiment, the second drive control unit 422 decides to drive both the first compressor 12 and the second compressor 14 when the first air conditioning load L1 is equal to or greater than the first threshold TH1, and decides to drive only the second compressor 14 when the first air conditioning load L1 is less than the first threshold TH1.

[0082] As a result, when the first air conditioning load L1 is equal to or greater than the first threshold TH1, it is decided to drive both the first compressor 12 and the second compressor 14, and when the first air conditioning load L1 is less than the first threshold TH1, it is decided to drive only the second compressor 14. Therefore, by setting the first threshold TH1 to an appropriate value, it is possible to appropriately switch between operation of the second compressor 14 alone and operation of the first compressor 12 and the second compressor 14 together.

[0083] Furthermore, in this embodiment, the second drive control unit 422 decides to drive both the first compressor 12 and the second compressor 14 when the second air conditioning load L2 is equal to or greater than the second threshold TH2, and decides to drive only the second compressor 14 when the second air conditioning load L2 is less than the second threshold TH2.

[0084] As a result, when the second air conditioning load L2 is equal to or greater than the second threshold TH2, it is decided to drive both the first compressor 12 and the second compressor 14, and when the second air conditioning load L2 is less than the second threshold TH2, it is decided to drive only the second compressor 14. Therefore, by setting the second threshold TH2 to an appropriate value, it is possible to appropriately switch between operation of the second compressor 14 alone and operation of the first compressor 12 and the second compressor 14 together.

[0085] Furthermore, the control method for the air conditioning system 1 in this embodiment is a control method for an air conditioning system that performs air conditioning by circulating a refrigerant, wherein a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel, and the control method includes a control unit that controls the driving of the first compressor and the second compressor, and when the air conditioning system is started, the control unit performs a first control step of driving only the first compressor for a first period and calculating a first air conditioning load, which is the air conditioning load for the first period, and a second control step of deciding whether to drive both the first and second compressors or only the second compressor based on the first air conditioning load, and in the second control step, if the suction differential temperature ΔTP falls below a predetermined threshold ΔTHA during the first period, it is decided to drive only the second compressor.

[0086] The control method for the air conditioning system 1 in this embodiment provides the same effects and advantages as the air conditioning system in this embodiment.

[0087] Furthermore, the outdoor unit control program 431 of the air conditioning system 1 in this embodiment is an outdoor unit control program 431 of an air conditioning system 1 in which a first compressor 12 driven by a gas engine 11 and a second compressor 14 driven by a motor 13 are connected in parallel and circulate a refrigerant to perform air conditioning, and the outdoor unit processor 42 of the outdoor unit control unit 40 which controls the driving of the first compressor 12 and the second compressor 14 is configured to start the air conditioning system 1 during a first period P1, and only the first compressor 12 is controlled. The first drive control unit 421 drives the compressors and calculates the first air conditioning load L1, which is the air conditioning load LD for the first period P1. The second drive control unit 422, based on the first air conditioning load L1, determines whether to drive both the first compressor 12 and the second compressor 14, or to drive only the second compressor 14. The second drive control unit 422 decides to drive only the second compressor 14 if the suction temperature difference ΔTP falls below a predetermined threshold ΔTHA during the first period P1.

[0088] The outdoor unit control program 431 of the air conditioning system 1 in this embodiment provides the same effects and advantages as the air conditioning system 1 in this embodiment.

[0089] (Other embodiments) Embodiment 1 has been described 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. Therefore, other embodiments are described below as examples.

[0090] In this embodiment, the case where the "control unit" is an outdoor unit control unit 40 is described, but the embodiment is not limited to this. The "control unit" only needs to control the driving of the first compressor 12 and the second compressor 14. The "control unit" may have the functions of, for example, an outdoor unit control unit 40 and an indoor unit control unit 50. That is, the "control unit" may control, for example, each part of the outdoor unit 10 and the indoor unit 30.

[0091] In this embodiment, we describe a case where the second period P2 is, for example, the same length as the first period P1, but the embodiment is not limited to this. The second period P2 may be longer than the first period P1, or the second period P2 may be shorter than the first period P1.

[0092] In this embodiment, we describe the case where a predetermined threshold ΔTHA is "2°C" and a transition threshold ΔTHB is "1°C", but the embodiment is not limited to this. For example, it is sufficient if the predetermined threshold ΔTHA is greater than the transition threshold ΔTHB.

[0093] Furthermore, in this embodiment, we describe a case where the second threshold TH2 is the same value as the first threshold TH1, for example, but the embodiment is not limited to this. The second threshold TH2 may be a value greater than the first threshold TH1, or the second threshold TH2 may be a value less than the first threshold TH1.

[0094] Each of the outdoor unit processor 42 and the indoor unit processor 52 may be hardware programmed to implement the corresponding functional unit. That is, these processors may consist of, for example, an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array).

[0095] The outdoor unit communication circuit 41 and the indoor unit communication circuit 51 may each perform wireless communication. For wireless connection, standards such as Wi-Fi (registered trademark) and WiMAX (registered trademark) may be used.

[0096] In the flowchart shown in Figure 6, the processing steps of the outdoor unit control unit 40 are divided according to the main processing content to facilitate understanding of the operation, and the operation is not limited by the way the processing units are divided or the names of the units. Depending on the processing content, it may be further divided into more steps. Alternatively, it may be divided so that one step unit includes even more processing. Furthermore, the order of the steps may be rearranged as appropriate, as long as it does not impede the intent of this disclosure.

[0097] 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 scope of the claims or equivalents thereof.

[0098] (Note) Based on the above description of embodiments, the following technologies are disclosed.

[0099] (Technology 1) An air conditioning system comprising a first compressor driven by a gas engine and a second compressor driven by a motor, connected in parallel, which circulates a refrigerant to provide air conditioning, the system comprising a control unit that controls the driving of the first compressor and the second compressor, the control unit comprising a first drive control unit that, when the air conditioning system is started, drives only the first compressor for a first period and calculates a first air conditioning load, which is the air conditioning load for the first period, and a second drive control unit that, based on the first air conditioning load, decides whether to drive both the first and second compressors or only the second compressor, the second drive control unit decides to drive only the second compressor if the suction differential temperature falls below a predetermined threshold during the first period, the air conditioning system.

[0100] This configuration allows the system to determine whether to drive both the first and second compressors, or only the second compressor, based on the first air conditioning load, which is the air conditioning load during the first period. Therefore, it is possible to appropriately switch between operating the second compressor alone and operating both the first and second compressors together. Furthermore, if the suction temperature difference falls below a predetermined threshold during the first period, it is decided to operate only the second compressor. Therefore, it is possible to appropriately switch between operating the second compressor alone and operating both the first and second compressors together.

[0101] (Technology 2) The air conditioning system according to Technical 1, wherein the second drive control unit, when the suction differential temperature falls below a predetermined threshold during the first period, drives only the second compressor during the second period, calculates the second air conditioning load which is the air conditioning load during the second period, and determines, based on the second air conditioning load, whether to drive both the first and second compressors or only the second compressor.

[0102] With this configuration, if the intake temperature difference falls below a predetermined threshold during the first period, the system determines whether to drive both the first and second compressors, or only the second compressor, based on the second air conditioning load, which is the air conditioning load for the second period. Therefore, it is possible to appropriately switch between operation of the second compressor alone and operation of both the first and second compressors together.

[0103] (Technology 3) An air conditioning system according to Technology 1 or Technology 2, comprising multiple indoor units, wherein the second drive control unit determines to drive only the second compressor when the intake differential temperature of at least one of the multiple indoor units falls below a predetermined threshold during the first period.

[0104] With this configuration, if the intake temperature difference of at least one of the multiple indoor units falls below a predetermined threshold during the first period, it is decided to drive only the second compressor. Therefore, even when multiple indoor units are installed, it is possible to appropriately switch between the operation of the second compressor alone and the combined operation of the first and second compressors.

[0105] (Technology 4) The air conditioning system according to any one of the technologies 1 to 3, wherein the second drive control unit decides to drive both the first compressor and the second compressor when the first air conditioning load is equal to or greater than a first threshold, and decides to drive only the second compressor when the first air conditioning load is less than the first threshold.

[0106] With this configuration, when the first air conditioning load is above the first threshold, it is decided to drive both the first and second compressors, and when the first air conditioning load is below the first threshold, it is decided to drive only the second compressor. Therefore, by setting the first threshold to an appropriate value, it is possible to appropriately switch between operation of the second compressor alone and operation of both the first and second compressors together.

[0107] (Technology 5) The air conditioning system according to Technical Reference 2, wherein the second drive control unit decides to drive both the first compressor and the second compressor when the second air conditioning load is equal to or greater than a second threshold, and decides to drive only the second compressor when the second air conditioning load is less than the second threshold.

[0108] With this configuration, when the second air conditioning load is above the second threshold, it is decided to drive both the first and second compressors, and when the second air conditioning load is below the second threshold, it is decided to drive only the second compressor. Therefore, by setting the second threshold to an appropriate value, it is possible to appropriately switch between operation of the second compressor alone and operation of the first and second compressors together.

[0109] (Technology 6) A control method for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel to circulate a refrigerant and provide air conditioning, comprising a control unit that controls the driving of the first compressor and the second compressor, wherein when the air conditioning system is started, the control unit performs a first control step of driving only the first compressor for a first period and calculating a first air conditioning load which is the air conditioning load for the first period, and a second control step of deciding whether to drive both the first and second compressors or only the second compressor based on the first air conditioning load, wherein in the second control step, if the suction differential temperature falls below a predetermined threshold during the first period, it is decided to drive only the second compressor.

[0110] This control method for the air conditioning system produces the same effects as the air conditioning system described in Technical 1.

[0111] (Technology 7) A control program for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel to circulate a refrigerant and provide air conditioning, wherein the processor of the control unit that controls the driving of the first compressor and the second compressor functions as a first drive control unit that drives only the first compressor for a first period when the air conditioning system is started and calculates a first air conditioning load which is the air conditioning load for the first period, and a second drive control unit that decides whether to drive both the first and second compressors or only the second compressor based on the first air conditioning load, and the second drive control unit decides to drive only the second compressor if the suction differential temperature falls below a predetermined threshold during the first period.

[0112] According to the control program of this air conditioning system, the same effects and functions as the air conditioning system described in Technology 1 are achieved. [Industrial applicability]

[0113] As described above, the air conditioning system, control method for the air conditioning system, and control program for the air conditioning system according to this disclosure are suitably applicable to an air conditioning system that appropriately switches between the operation of the second compressor alone and the combined operation of the first and second compressors. [Explanation of Symbols]

[0114] 1. Air conditioning system 10 Outdoor Units 11 Gas engine 12. First Compressor 13 Motors 14. Second Compressor 30 Indoor Units (Indoor Units) 31 Indoor heat exchanger 34. Intake temperature sensor 40. Outdoor unit control unit (control unit) 41 Outdoor unit communication circuit 42. Outdoor unit processor (processor) 421 First Drive Control Unit 422 Second Drive Control Unit 43 Outdoor unit memory 431 Outdoor unit control program (control program) 50 Indoor Unit Control Unit 51 Indoor unit communication circuit 52 Indoor Unit Processor 521 Drive Control Unit 522 Transmitter 53 Indoor unit memory 531 Indoor Unit Control Program LD air conditioning load L1 1st air conditioning load L2 2nd air conditioning load P1 Period 1 P2 Second Period TH1 First threshold TH2 Second threshold SG differential temperature signal ΔTHA predetermined threshold ΔTHB transition threshold ΔTP Intake Temperature Difference

Claims

1. An air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by an electric motor are connected in parallel to circulate a refrigerant and perform air conditioning, The system includes a control unit that controls the operation of the first compressor and the second compressor, The control unit, A first drive control unit that, when starting the air conditioning system, drives only the first compressor for a first period and calculates the first air conditioning load, which is the air conditioning load for the first period, A second drive control unit that determines, based on the first air conditioning load, whether to drive both the first compressor and the second compressor, or to drive only the second compressor, Equipped with, An air conditioning system in which the second drive control unit decides to drive only the second compressor when the suction temperature difference falls below a predetermined threshold during the first period.

2. The second drive control unit is, If the suction temperature difference falls below a predetermined threshold during the first period, only the second compressor is driven during the second period, and the second air conditioning load, which is the air conditioning load for the second period, is calculated. Based on the second air conditioning load, it is determined whether to drive both the first and second compressors, or only the second compressor. The air conditioning device according to claim 1.

3. Equipped with multiple indoor units, The second drive control unit determines to drive only the second compressor when, among the plurality of indoor units, the suction differential temperature of at least one indoor unit falls below a predetermined threshold during the first period. The air conditioning device according to claim 1.

4. The second drive control unit is, When the first air conditioning load is equal to or greater than the first threshold, it is decided to drive both the first compressor and the second compressor. If the first air conditioning load is less than the first threshold, it is decided to drive only the second compressor. An air conditioning device according to any one of claims 1 to 3.

5. The second drive control unit is, When the second air conditioning load is equal to or greater than the second threshold, it is decided to drive both the first compressor and the second compressor. If the second air conditioning load is less than the second threshold, it is decided to drive only the second compressor. The air conditioning device according to claim 2.

6. A control method for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by a motor are connected in parallel to circulate a refrigerant and provide air conditioning, The system includes a control unit that controls the operation of the first compressor and the second compressor, The control unit, A first control step in which, when starting the air conditioning system, only the first compressor is driven for a first period and the first air conditioning load, which is the air conditioning load for the first period, A second control step of determining whether to drive both the first compressor and the second compressor, or only the second compressor, based on the first air conditioning load, Execute, In the second control step, if the suction differential temperature falls below a predetermined threshold during the first period, it is decided to drive only the second compressor. A method for controlling an air conditioning system.

7. A control program for an air conditioning system in which a first compressor driven by a gas engine and a second compressor driven by an electric motor are connected in parallel to circulate a refrigerant and provide air conditioning, The processor of the control unit that controls the driving of the first compressor and the second compressor is When the air conditioning system is started, a first drive control unit drives only the first compressor for a first period and calculates the first air conditioning load, which is the air conditioning load for the first period, and A second drive control unit that determines whether to drive both the first compressor and the second compressor, or only the second compressor, based on the first air conditioning load. To make it function as, The second drive control unit decides to drive only the second compressor if the suction differential temperature falls below a predetermined threshold during the first period. Control program for air conditioning system.

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