Air conditioning system

Abstract

In an air-conditioning system according to an embodiment, a flow path switching valve is switched in stages by a first stage in which the flow path switching valve is switched on the basis of a threshold value of a high-pressure pressure and a pressure difference between the high-pressure pressure and a low-pressure pressure, and a second stage in which the flow path switching valve is switched on the basis of a threshold value of an alert time from implementation of the first stage.

Description

Technical Field

[0001] The present invention relates to the technology of air conditioning systems. Background Art

[0002] There is an air conditioning system including a plurality of flow path switching valves (see, for example, Patent Document 1).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-224830 Summary of the Invention

[0006] Technical problem to be solved by the invention

[0007] In an air-conditioning system equipped with multiple flow switching valves, when switching from cooling operation to heating operation, or from heating operation to cooling operation, problems such as excessive pressure and poor circuit closure may occur depending on the switching timing of the multiple flow switching valves.

[0008] In view of the above circumstances, an object of the present invention is to provide a technology for suppressing the occurrence of switching failures.

[0009] Solutions for solving the above technical problems

[0010] An air conditioning system according to an embodiment includes an outdoor unit, multiple indoor units, and one or more branch units. The outdoor unit includes a compressor, multiple flow path switching mechanisms, an outdoor heat exchanger, an outdoor electric expansion valve, and an outdoor fan, and has three refrigerant flow paths. The indoor unit includes an indoor electric expansion valve and an indoor heat exchanger. The branch unit is equipped with a high- and low-pressure gas regulating valve and a low-pressure gas regulating valve. The air-conditioning system is characterized in that the branch unit and the outdoor unit are connected by high- and low-pressure gas pipes, low-pressure gas pipes and liquid pipes, the branch unit and the indoor unit are connected by gas pipes and liquid pipes, and among the multiple flow switching valves equipped with the outdoor unit, at least one is connected in a manner that can selectively connect the outdoor heat exchanger to the discharge side and the suction side, and at least one is connected in a manner that can selectively connect the high- and low-pressure gas pipes to the discharge side and the suction side, and the flow switching valve is switched in stages through the first stage and the second stage. In the first stage, the switching is performed based on the threshold of either the high pressure or the pressure difference between the high pressure and the low pressure, and in the second stage, the switching is performed based on the threshold of the time elapsed since the implementation of the first stage.

[0011] Effects of the Invention

[0012] According to the present invention, it is possible to provide a technique for suppressing the occurrence of switching failures. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a diagram showing the configuration of an air conditioning system.

[0014] Figure 2 It is a diagram showing the opening (ON) and closing (OFF) of the four-way valve during each operation.

[0015] Figure 3 This is a diagram showing the contents of switching control when switching from cooling-only operation to heating-only operation.

[0016] Figure 4 This is a diagram showing the contents of switching control when switching from heating-only operation to cooling-only operation.

[0017] Figure 5 This is a diagram showing the contents of switching control when switching from the cooling-only operation to the simultaneous cooling operation.

[0018] Figure 6 This is a diagram showing the control details when switching only in the first stage.

[0019] Figure 7 This is a diagram showing the control details when switching only in the first stage.

[0020] Figure 8 This is a diagram showing the state of the four-way valve when switching from cooling only to heating only.

[0021] Figure 9 This is a diagram showing the state of the four-way valve when switching from cooling only to heating only.

[0022] Figure 10 This is a diagram showing the state of the four-way valve when switching from cooling only to heating only.

[0023] Figure 11 This is a timing chart showing control when all four-way valves A, B, and C are opened at the time of startup of the compressor.

[0024] Figure 12 This is a timing chart showing control when all four-way valves A, B, and C are closed at the time of startup of the compressor.

[0025] Figure 13 This is a timing chart showing control when all four-way valves A, B, and C are opened during startup of the compressor.

[0026] Figure 14 This is a timing chart showing control when all four-way valves A, B, and C are closed during startup of the compressor. DETAILED DESCRIPTION

[0027] Hereinafter, an air conditioning system according to an embodiment will be described with reference to the drawings.

[0028] Figure 1 This figure shows the configuration of an air conditioning system 100 according to this embodiment. The air conditioning system 100 according to this embodiment is a heat recovery type air conditioning system. The air conditioning system 100 includes indoor units 31a, 31b, 31c, and 31d, an outdoor unit 30, and a branch unit 32 interposed between them. This configuration enables the air conditioning system 100 to independently perform cooling and heating operations in the indoor units 31a, 31b, 31c, and 31d.

[0029] In addition, although four indoor units are described, any number of indoor units is sufficient. In the following description, when the indoor units 31a, 31b, 31c, and 31d are not distinguished from each other, they are referred to as indoor units 31.

[0030] The outdoor unit 30 includes a compressor 1, multiple four-way valves (flow switching mechanisms) 9, 10, and 11, an outdoor heat exchanger 2, an outdoor electric expansion valve 4, and an outdoor fan 3, and has three refrigerant flow paths. Of the multiple four-way valves 9, 10, and 11 included in the outdoor unit 30, four-way valves 9 and 10 are connected so that the outdoor heat exchanger 2 can be selectively connected to the discharge side or the suction side. Furthermore, four-way valve 11 is connected so that high- and low-pressure gas pipes can be selectively connected to the discharge side or the suction side.

[0031] The branch unit 32 is connected to the indoor unit 31 via the high- and low-pressure gas pipes 17, the low-pressure gas pipe 16, and the liquid pipe 18. The branch unit 32 is connected to the indoor unit 31a via the liquid pipe 18a and the gas pipe 19a. The branch unit 32 is connected to the indoor unit 31b via the liquid pipe 18b and the gas pipe 19b. The branch unit 32 is connected to the indoor unit 31c via the liquid pipe 18c and the gas pipe 19c. The branch unit 32 is connected to the indoor unit 31d via the liquid pipe 18d and the gas pipe 19d.

[0032] The branch unit 32 is equipped with a low-pressure gas regulating valve and a high- and low-pressure gas regulating valve for each indoor unit 31. Specifically, the branch unit 32 is equipped with a low-pressure gas regulating valve 14a and a high- and low-pressure gas regulating valve 15a for the indoor unit 31a. The branch unit 32 is equipped with a low-pressure gas regulating valve 14b and a high- and low-pressure gas regulating valve 15b for the indoor unit 31b. The branch unit 32 is equipped with a low-pressure gas regulating valve 14c and a high- and low-pressure gas regulating valve 15c for the indoor unit 31c. The branch unit 32 is equipped with a low-pressure gas regulating valve 14d and a high- and low-pressure gas regulating valve 15d for the indoor unit 31d.

[0033] Each indoor unit 31 includes an indoor electric expansion valve, an indoor heat exchanger, and an indoor fan. Specifically, the indoor unit 31a includes an indoor electric expansion valve 5a, an indoor heat exchanger 6a, and an indoor fan 7a. The indoor unit 31b includes an indoor electric expansion valve 5b, an indoor heat exchanger 6b, and an indoor fan 7b. The indoor unit 31c includes an indoor electric expansion valve 5c, an indoor heat exchanger 6c, and an indoor fan 7c. The indoor unit 31d includes an indoor electric expansion valve 5d, an indoor heat exchanger 6d, and an indoor fan 7d.

[0034] The system to which the present invention can be applied is not limited to the configuration of the air conditioning system described above, and refrigeration cycle components such as solenoid valves and expansion valves may be added as needed. Furthermore, in this embodiment, the expansion valve is conceived as a branch unit high- and low-pressure gas adjustment valve / low-pressure gas adjustment valve, but this is not necessarily limited to this. Furthermore, a subcooling heat exchanger or a pressure relief valve may be added to the branch unit as needed, and refrigeration cycle components may also be added if necessary. Furthermore, in the present invention, a four-way valve is used as a flow path switching valve, and by closing one of the connection ports, it can be used as a three-way valve, but this is not necessarily limited to this.

[0035] Figure 1 The air conditioning system 100 shown is capable of performing a cooling-only operation, a heating-only operation, a simultaneous cooling operation, and a simultaneous heating operation. Figure 2 : This diagram shows the opening and closing of four-way valves 9, 10, and 11 during various operations. In the following description, for ease of understanding, four-way valve 9 is sometimes referred to as four-way valve A. Four-way valve 10 is sometimes referred to as four-way valve B. Four-way valve 11 is sometimes referred to as four-way valve C.

[0036] Regarding opening and closing, four-way valves A and B are closed in the position connecting the discharge side of compressor 1 to the outdoor heat exchanger 2, and open in the position connecting the discharge side of compressor 1 to the suction side of outdoor heat exchanger 2 and blocking the refrigerant flow path on the discharge side of compressor 1. Four-way valve C is closed in the position connecting the low-pressure gas pipe 16 and the high- and low-pressure gas pipes 17, and open in the position connecting the discharge side of compressor 1 to the high- and low-pressure gas pipes 17 and blocking the high- and low-pressure gas pipes 17.

[0037] like Figure 2 As shown, in cooling-only operation, four-way valves A, B, and C are all closed. In heating-only operation and simultaneous heating operation, four-way valves A, B, and C are all open. In simultaneous cooling operation, four-way valves A and C are open, and four-way valve B is closed.

[0038] On this basis, the opening and closing control of the four-way valve during operation switching will be described below. In this embodiment, the four-way valve is switched in stages through a first stage and a second stage. Figure 3 This diagram illustrates the switching control details when switching from cooling-only operation to heating-only operation. In cooling-only operation, four-way valves A, B, and C are all closed. In this state, in the first stage, four-way valves A and B are opened. Then, in the second stage, four-way valve C is opened. As a result, four-way valves A, B, and C are all open, switching to heating-only operation.

[0039] Figure 4 This diagram illustrates the switching control details when switching from heating-only operation to cooling-only operation. In heating-only operation, four-way valves A, B, and C are all open. In this state, four-way valve C is closed in the first stage. Then, in the second stage, four-way valves B and C are closed. This completes the process of closing four-way valves A, B, and C, switching to cooling-only operation.

[0040] Figure 5 This diagram illustrates the switching control details when switching from cooling-only operation to simultaneous cooling operation. In cooling-only operation, four-way valves A, B, and C are all closed. In this state, four-way valve A is opened in the first stage. Then, four-way valve C is opened in the second stage. This results in both four-way valves A and C being open, while four-way valve B remains closed, switching to simultaneous cooling operation.

[0041] Figure 6 、 Figure 7 This is a diagram showing the control details when switching only in the first stage. Figure 6 This diagram illustrates the switching control details when switching from simultaneous cooling operation to simultaneous heating operation. In simultaneous cooling operation, four-way valves A and C are both open, and four-way valve B is closed. In this state, four-way valve B is opened in the first stage. This opens four-way valves A, B, and C, switching to simultaneous heating operation.

[0042] Figure 7 This diagram illustrates the switching control details when switching from simultaneous heating operation to simultaneous cooling operation. In simultaneous heating operation, four-way valves A, B, and C are all open. In this state, four-way valve B is closed in the first stage. This allows four-way valves A and C to remain open, while four-way valve B is closed, switching to simultaneous heating operation.

[0043] Use the attached figure to explain the above control contents from Figure 3 The control contents of switching from cooling alone to heating alone are explained. Figure 8 、 Figure 9 、 Figure 10 : is a diagram showing the state of the four-way valve when switching from cooling only to heating only. Figure 8As shown, in the case of cooling-only operation, four-way valves A, B, and C are all closed. In this case, the high-pressure refrigerant compressed by the compressor 1 flows into the outdoor heat exchanger 2, where it condenses and liquefies. The condensed liquid refrigerant expands in the indoor unit 31 to become a low-pressure liquid refrigerant, allowing the indoor unit 31 to perform cooling operation.

[0044] In this state, if Figure 9 As shown in the figure, in the first stage, the four-way valves A and B are opened. As a result, the discharge side refrigerant flow path is closed, the discharge gas compressed by the compressor 1 has nowhere to go, and the pressure on the high-pressure side (from the compressor 1 to the four-way valves A, B, C) rises sharply. Figure 10 As shown, the four-way valve C is opened in the second stage. This allows compressed gas to flow into the indoor unit 31, and the high-pressure / low-pressure regulating valve of the branch unit 32 also operates appropriately in conjunction with the switching of these four-way valves, thereby enabling heating operation.

[0045] As described above, by intentionally forming a closed portion in the first stage and rapidly increasing the pressure on the high-pressure side, the high pressure can be maintained, allowing smooth switching of the four-way valve in the second stage. Since switching of the four-way valve requires a pressure difference, this operation allows all four-way valves to be switched without problems even in an air conditioning system having multiple flow path switching valves such as four-way valves.

[0046] In addition, Figure 4 When switching from heating operation alone to cooling operation alone as described in the previous section, the operation is reversed. Figure 10 、 Figure 9 、 Figure 8 It goes without saying that all four-way valves can be switched without any problem by switching in the order of

[0047] In this case, the condition for transitioning from the first stage to the second stage is based on the time elapsed since the first stage. This time elapsed is preferably as short as possible to prevent a sudden increase in high pressure. However, if it is too short, the switching of four-way valves A and B and the switching of four-way valve C may be reversed, resulting in unexpected switching failures. Therefore, it is best to initiate the second stage within at least 3 seconds (e.g., 1 second) from the first stage.

[0048] While the above description explains that simultaneous switching of the flow path switching valves, namely, four-way valves A and B, connected to the outdoor heat exchanger 2, allows for seamless four-way valve switching, there are also operating modes in which one side of the outdoor heat exchanger 2 functions as a condenser and the other as an evaporator. In heat recovery air conditioning systems, for example, there is an operating mode in which four-way valve A is opened (low-pressure position) and four-way valve B is closed (high-pressure position) to achieve simultaneous cooling and heating. In this case, one of the four-way valves does not switch, and thus the high-pressure circuit cannot be closed, potentially leading to switching problems.

[0049] Therefore, especially when the compressor 1 is started, the four-way valve switching action is not performed until the pressure on the high-pressure side reaches a predetermined value or the pressure difference between the pressure on the high-pressure side and the pressure on the low-pressure side reaches a predetermined value. Figure 11 、 Figure 12 Provide explanation. Figure 11 This is a timing chart showing control when all four-way valves A, B, and C are opened at the start of the compressor 1. Figure 12 This is a timing chart showing control in the case where all four-way valves A, B, and C are closed at the start of the compressor 1.

[0050] exist Figure 11 、 Figure 12 In FIG, the horizontal axis shows time, and the vertical axis shows the opening and closing of the four-way valves A, B, and C and the speed of the compressor 1. In addition, t1 shows the execution timing of the first stage, and t2 shows the execution timing of the second stage. Figure 11 、 Figure 12 As shown, after the compressor 1 is started, switching control is started, and after the rotation speed increases to a certain level, the first stage is performed, the second stage is performed, and then after the switching control is completed, the rotation speed is increased to a predetermined Hz.

[0051] The magnitude of the pressure difference, not the magnitude of the pressure, is required for switching the four-way valve. Therefore, when switching the four-way valve at startup of the compressor 1, it is desirable to determine the switching based on the pressure difference. By performing the first and second stages while ensuring a predetermined pressure difference in this manner, a certain degree of high pressure can be maintained even after switching either of the four-way valves A and B, and all four-way valves can be switched without problems.

[0052] In this case, it is recorded that in order to prevent a sudden increase in high pressure, the transition from stage 1 to stage 2 is preferably about 1 second, but in order to maintain high pressure, the time is preferably as short as possible, preferably within about 3 seconds, or about 1 second.

[0053] As described above, by performing the above-described switching control at the time of startup of the compressor 1 , it is possible to realize highly reliable switching of the four-way valve while simplifying the switching control.

[0054] As another example of the effect of the present invention, the operation when switching from cooling operation to heating operation during the operation of the compressor 1 will be described. Figure 13 、 Figure 14 Provide explanation. Figure 13 This is a timing chart showing control when all four-way valves A, B, and C are opened during startup of the compressor 1 . Figure 14 This is a timing chart showing control when all four-way valves A, B, and C are closed during startup of the compressor 1 . Figure 13 、 Figure 14 The horizontal and vertical axes are Figure 11 、 Figure 12 The same, so the description is omitted.

[0055] like Figure 13 、 Figure 14 As shown, when the speed of the compressor 1 becomes the specified rps, the switching control is started. After the speed is reduced to a certain level (upper speed limit A), the speed is further reduced (upper speed limit B), the first stage is performed, the second stage is performed, and then after the switching control is completed, the speed is increased to the specified rps.

[0056] When compressor 1 is started, pressure is typically low. Therefore, in the first stage of four-way valve switching, switching is performed when the pressure differential exceeds a specified value. However, during compressor operation, pressure is typically high. Therefore, if the first stage is performed as usual, the pressure on the high-pressure side could rise sharply, potentially causing the system to shut down due to high-pressure protection. Therefore, when switching the four-way valve while compressor 1 is operating, switching control must be performed using a separate four-way valve switching logic.

[0057] Furthermore, during startup of compressor 1, the first stage is implemented when the pressure differential exceeds a predetermined value. However, as described above, the compressor is in a high-pressure state during operation. Therefore, the four-way valve switching during operation of compressor 1 is implemented when the pressure on the high-pressure side or the pressure differential falls below a predetermined value. In this case, the parameter to be considered for high-pressure protection is not the pressure differential but the high-pressure pressure. Therefore, unlike during startup of compressor 1, the high-pressure side pressure can be used as the threshold for implementation of the first stage. To reduce the pressure on the high-pressure side, it is generally desirable to reduce the rotational speed of compressor 1. However, if there is a valve that bypasses high and low pressures, the high-pressure side pressure can also be reduced by opening it.

[0058] In addition, depending on the external air conditions, the pressure on the high-pressure side may not reach the specified value no matter how much the speed of the compressor 1 is reduced. In such a case, after a specified time has passed since the switching action began and pressure monitoring began, the first stage is carried out to switch the four-way valve. The specified time at this time can be a time that can only be implemented after the speed of the compressor 1 is sufficiently reduced to a level that does not affect the switching of the four-way valve. By having sufficient time like this, even if the first stage is carried out when the pressure on the high-pressure side is higher than the specified value, the rapid rise of the high pressure can be suppressed to a certain extent, and reliable four-way valve switching can be implemented.

[0059] By adopting this switching control, the first and second stages of compressor 1 startup can be used consistently, simplifying the four-way valve switching pattern. Furthermore, before the first stage, the high-pressure side pressure monitoring can be initiated by reducing the compressor 1's speed to a certain level. Since pressure fluctuations occur with four-way valve switching, it is desirable to perform switching at a speed below which the compressor 1 can operate stably.

[0060] As described above, in the above-described compressor operation of this embodiment, by adopting the above-described switching mode, highly reliable four-way valve switching can be achieved while simplifying the switching control. Furthermore, in this embodiment, cooling operation is achieved when all four-way valves A, B, and C are closed, while heating operation is achieved when all four-way valves A, B, and C are open. However, this is not limiting. For example, even if the four-way valves are connected so that cooling operation is achieved when all four-way valves A and B are closed and four-way valve C is open, and heating operation is achieved when all four-way valves A and B are open, this does not deviate from the scope of the present invention, as is apparent from the foregoing.

[0061] The various functions performed by the air conditioning system 100 described above are implemented by, for example, a hardware processor such as a CPU (Central Processing Unit) executing a program (software). Some or all of these components may be implemented using hardware (circuitry; including circuitry) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a GPU (Graphics Processing Unit), or through a combination of software and hardware. The program may be pre-stored on a storage device (a storage device with a non-transitory storage medium) such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory, or it may be stored on a removable storage medium (a non-transitory storage medium) such as a DVD or CD-ROM and installed by attaching the storage medium to a drive.

[0062] As described above, according to the present embodiment, it is possible to provide a technique for suppressing the occurrence of switching failures.

[0063] While the embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to the embodiment and includes designs and the like within the scope of the present invention.

[0064] Industrial Applicability

[0065] The present invention can be applied to an air conditioning system including a plurality of flow path switching valves.

[0066] Description of Reference Numerals

[0067] 1 compressor

[0068] 2 Outdoor heat exchanger

[0069] 3 outdoor fans

[0070] 4. Outdoor electric expansion valve

[0071] 5a, 5b, 5c, 5d indoor electric expansion valve

[0072] 6a, 6b, 6c, 6d indoor heat exchangers

[0073] 7a, 7b, 7c, 7d indoor fans

[0074] 9, 10, 11 four-way valve

[0075] 14a, 14b, 14c, 14d low-pressure gas regulating valve

[0076] 15a, 15b, 15c, 15d high and low pressure gas regulating valves

[0077] 16 low-pressure gas pipe

[0078] 17 High and low pressure gas pipes

[0079] 18, 18a, 18b, 18c, 18d liquid pipes

[0080] 19a, 19b, 19c, 19d gas pipes

[0081] 30 outdoor units

[0082] 31, 31a, 31b, 31c, 31d indoor units

[0083] 32 branch units

[0084] 100 air conditioning system.

Claims

1. An air conditioning system, characterized in that: have: The outdoor unit includes a compressor, multiple flow path switching mechanisms, an outdoor heat exchanger, an outdoor electric expansion valve, and an outdoor fan, and has three refrigerant flow paths; Multiple indoor units with indoor electric expansion valves and indoor heat exchangers; More than one branch unit is equipped with high and low pressure gas regulating valves and low pressure gas regulating valves. The branch unit and the outdoor unit are connected through high and low pressure gas pipes, low pressure gas pipes and liquid pipes. The branch unit and the indoor unit are connected via gas pipes and liquid pipes. Among the plurality of flow path switching valves provided in the outdoor unit, at least one is connected in a manner that enables the outdoor heat exchanger to be selectively connected to the discharge side and the suction side, and at least one is connected in a manner that enables the high-pressure and low-pressure gas pipes to be selectively connected to the discharge side and the suction side. The flow path switching valve is switched in stages through the first stage and the second stage. In the first stage, the switching is performed based on the threshold of either the high pressure or the pressure difference between the high pressure and the low pressure. In the second stage, the switching is performed based on the threshold of the time elapsed from the implementation of the first stage.

2. The air conditioning system according to claim 1, wherein: When the high-pressure and low-pressure gas pipes become the high-pressure side after the second-stage switching, the flow path switching valve provided in the outdoor heat exchanger is switched in the first stage. When the high- and low-pressure gas pipes become the low-pressure side after the second-stage switching, the flow path switching valves provided in the high- and low-pressure gas pipes are switched in the first stage.

3. The air conditioning system according to claim 2, wherein: A plurality of the outdoor heat exchangers are provided, each of which is provided with a flow path switching valve. When all the flow path switching valves provided in the plurality of outdoor heat exchangers are switched, the switching is performed by simultaneously switching the flow path switching valves provided in all the outdoor heat exchangers in the first stage or the second stage. When any one of the flow path switching valves included in the plurality of outdoor heat exchangers is switched, only the flow path switching valve included in the target outdoor heat exchanger is switched in the first stage or the second stage.

4. The air conditioning system according to claim 1, wherein: Perform stage 2 within at least 3 seconds of performing stage 1.

5. The air conditioning system according to claim 1, wherein: When the compressor is started and when the compressor is running, the threshold value used as a reference in the first stage is different. When the flow path switching valve is switched at compressor startup, the first stage is performed when either the pressure difference between the high pressure and the low pressure is greater than a predetermined value. When the flow path switching valve is switched during compressor operation, the first stage is performed when either the high pressure or the pressure difference between the high pressure and the low pressure is equal to or less than a predetermined value.

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