AIR CONDITIONING SYSTEM

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application No. PCT/JP2023/006993, filed Feb. 27, 2023, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to a technology for air conditioning systems.

BACKGROUND ART

There is an air conditioning system including a plurality of flow path switching valves (see, for example, Japanese Unexamined Patent Application, First Publication No. 2015-224830).

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 A diagram showing a configuration of an air conditioning system.

FIG. 2 A diagram showing ON/OFF of a four-way valve in each operation.

FIG. 3 A diagram showing switching control content of a case where an operation is switched from an independent cooling operation to an independent heating operation.

FIG. 4 A diagram showing switching control content of a case where the operation is switched from the independent heating operation to the independent cooling operation.

FIG. 5 A diagram showing switching control content of a case where the operation is switched from the independent cooling operation to a simultaneous cooling operation.

FIG. 6 A diagram showing control content of a case where switching is performed only in a first step.

FIG. 7 A diagram showing control content of a case where switching is performed only in the first step.

FIG. 8 A diagram showing a state of the four-way valve when the operation is switched from independent cooling to independent heating.

FIG. 9 A diagram showing a state of the four-way valve when the operation is switched from the independent cooling to the independent heating.

FIG. 10 A diagram showing the state of the four-way valve when the operation is switched from the independent cooling to the independent heating.

FIG. 11 A timing chart showing control of a case where four-way valves A, B, and C are all turned on when a compressor is activated.

FIG. 12 A timing chart showing control of a case where four-way valves A, B, and C are all turned off when the compressor is activated.

FIG. 13 A timing chart showing control of a case where four-way valves A, B, and C are all turned on while the compressor is being activated.

FIG. 14 A timing chart showing control of a case where four-way valves A, B, and C are all turned off while the compressor is being activated.

DESCRIPTION OF EMBODIMENTS

Hereinafter, an air conditioning system of an embodiment will be described with reference to the drawings.

FIG. 1 is a diagram showing a configuration of an air conditioning system 100 according to the present embodiment. The air conditioning system 100 according to the present 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 provided therebetween. With this configuration, the air conditioning system 100 can perform a cooling operation and a heating operation for each of the indoor units 31a, 31b, 31c, and 31d.

Although four indoor units are shown in the drawing, a plurality of indoor units may be used. In the following description, when the indoor units 31a, 31b, 31c, and 31d are not distinguished from one another, they will be referred to as indoor units 31.

The outdoor unit 30 includes a compressor 1, a plurality of four-way valves (flow path switching mechanisms) 9, 10, and 11, an outdoor heat exchanger 2, an outdoor-side electric expansion valve 4, and an outdoor fan 3 and has three refrigerant flow paths. Among the plurality of four-way valves 9, 10, and 11 provided in the outdoor unit 30, the four-way valves 9 and 10 are connected so that the outdoor heat exchanger 2 selectively communicates with a discharge side or a suction side. Moreover, the four-way valve 11 is connected so that a high/low-pressure gas pipe selectively communicates with the discharge side or the suction side.

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

The branch unit 32 includes a low-pressure gas regulating valve and a high/low-pressure gas regulating valve for each indoor unit 31. Specifically, the branch unit 32 includes a low-pressure gas regulating valve 14a and a high/low-pressure gas regulating valve 15a with respect to the indoor unit 31a. The branch unit 32 includes a low-pressure gas regulating valve 14b and a high/low-pressure gas regulating valve 15b with respect to the indoor unit 31b. The branch unit 32 includes a low-pressure gas regulating valve 14c and a high/low-pressure gas regulating valve 15c with respect to the indoor unit 31c. The branch unit 32 includes a low-pressure gas regulating valve 14d and a high/low-pressure gas regulating valve 15d with respect to the indoor unit 31d.

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

A system to which the present invention can be applied is not limited to the above-described configuration of the air conditioning system and refrigeration cycle parts such as solenoid valves and expansion valves may be added as necessary. Although an expansion valve is assumed to be the high/low-pressure gas regulating valve/low-pressure gas regulating valve of the branch unit in the present embodiment, the present invention does not need to be limited thereto. Moreover, refrigeration cycle parts such as a supercooling heat exchanger and a pressure relief valve may be added to the branch unit as necessary. Although a four-way valve is used as a flow path switching valve and one of connection ports is blocked to use it as a three-way valve in the present invention, the present invention does not need to be limited thereto.

In the air conditioning system 100 shown in FIG. 1, an independent cooling operation, an independent heating operation, a simultaneous cooling operation, and a simultaneous heating operation are possible. FIG. 2 is a diagram showing ON and OFF of the four-way valves 9, 10, and 11 in each operation. In addition, in the following description, for ease of understanding, the four-way valve 9 may be referred to as four-way valve A. The four-way valve 10 may be referred to as four-way valve B. The four-way valve 11 may be referred to as four-way valve C.

Moreover, in relation to ON and OFF, in four-way valves A and B, a position where communication is established from the discharge side of the compressor 1 to the outdoor heat exchanger 2 is defined as an OFF position and a position where communication is established from the outdoor heat exchanger 2 to the suction side of the compressor 1 and the discharge-side refrigerant flow path of the compressor 1 is closed is defined as an ON position. In four-way valve C, a position where the low-pressure gas pipe 16 communicates with the high/low-pressure gas pipes 17 is defined as an OFF position and a position where communication is established from the discharge side of the compressor 1 to the high/low-pressure gas pipe 17 and the high/low-pressure gas pipe 17 side is closed is defined as an ON position.

As shown in FIG. 2, in the case of the independent cooling operation, four-way valves A, B, and C are all turned off. In the case of the independent heating operation and the simultaneous heating operation, four-way valves A, B, and C are all turned on. In the case of the simultaneous cooling operation, four-way valves A and C are turned on and four-way valve B is turned off.

Based on this, the ON/OFF control of the four-way valve during operation switching will be described below. In the present embodiment, the four-way valve is switched by a first step and a second step step by step. FIG. 3 is a diagram showing the switching control content of a case where the operation is switched from the independent cooling operation to the independent heating operation. In the independent cooling operation, four-way valves A, B, and C are all turned off. In this state, in the first step, four-way valves A and B are turned on. Subsequently, in the second step, four-way valve C is turned on. Thereby, four-way valves A, B, and C are all turned on and the operation is switched to the independent heating operation.

FIG. 4 is a diagram showing the switching control content of a case where the operation is switched from the independent heating operation to the independent cooling operation. In the case of the independent heating operation, four-way valves A, B, and C are all turned on. In this state, in the first step, four-way valve C is turned off. Subsequently, in the second step, the four-way valves A and B are turned off. Thereby, all four-way valves A, B, and C are turned off and the operation is switched to the independent cooling operation.

FIG. 5 is a diagram showing the switching control content of a case where the operation is switched from the independent cooling operation to the simultaneous cooling operation. In independent cooling operation, four-way valves A, B, and C are all turned off. In this state, in the first step, four-way valve A is turned on. Subsequently, in the second step, four-way valve C is turned on. Thereby, both four-way valves A and C are turned on and four-way valve B remains in the OFF state, such that the operation is switched to the simultaneous cooling operation.

FIGS. 6 and 7 are diagrams showing the control content of a case where switching is performed only in the first step. FIG. 6 is a diagram showing the switching control content of a case where the operation is switched from the simultaneous cooling operation to the simultaneous heating operation. In the simultaneous cooling operation, four-way valves A and C are all turned on and four-way valve B is turned off. In this state, four-way valve B is turned on in the first step. Thereby, four-way valves A, B, and C are all turned on and the operation is switched to the simultaneous heating operation.

FIG. 7 is a diagram showing the switching control content of a case where the operation is switched from the simultaneous heating operation to the simultaneous cooling operation. In the simultaneous heating operation, four-way valves A, B, and C are all turned on. In this state, in the first step, four-way valve B is turned off. Thereby, four-way valves A and C remain in the ON state and four-way valve B is turned off, such that the operation is switched to the simultaneous cooling operation.

Within the above-described control content, the control content for switching from the independent cooling to the independent heating shown in FIG. 3 will be described with reference to the drawings. FIGS. 8, 9, and 10 are diagrams showing the state of the four-way valve when the operation is switched from the independent cooling to the independent heating. As shown in FIG. 8, in the case of the independent cooling operation, four-way valves A, B, and C are all turned off. In this case, the high-pressure refrigerant compressed by the compressor 1 flows into the outdoor heat exchanger 2 and is condensed and liquefied. This condensed liquid refrigerant is expanded in the indoor unit 31 to become a low-pressure liquid refrigerant, and the indoor unit 31 can perform the cooling operation.

In this state, as shown in FIG. 9, in the first step, four-way valves A and B are turned on. Thereby, the discharge-side refrigerant flow path is blocked, 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 four-way valves A, B, and C) rises rapidly. Subsequently, as shown in FIG. 10, in the second step, four-way valve C is turned on. Thereby, the compressed gas flows into the indoor unit 31 and the high-pressure-side/low-pressure-side regulating valves of the branch unit 32 also operate appropriately in conjunction with the switching operations of these four-way valves, such that the heating operation can be performed.

As described above, a high pressure can be maintained by creating a blocked portion in the first step and rapidly increasing the pressure on the high-pressure side and the four-way valve can be switched smoothly in the second step. Because a pressure difference is required to switch the four-way valve, it is possible to switch all four-way valves without any problems even in an air conditioning system in which a plurality of flow path switching valves such as four-way valves are provided by performing this operation.

Moreover, when the operation is switched from the independent heating operation to the independent cooling operation as described in FIG. 4, the operation is reversed. In other words, it goes without saying that it is possible to switch all four-way valves without any problem by switching in the order of FIGS. 10, 9, and 8. In this case, a condition for performing the second step from the first step is based on an elapsed time after the first step is performed. This elapsed time should be as short as possible to prevent a sudden increase in the high pressure. However, if the elapsed time is too short, the switching of four-way valves A and B and the switching of four-way valve C may be reversed, which is likely to cause unexpected switching problems. Therefore, it is only necessary to perform the second step within at least 3 sec (for example, 1 sec) after the first step is performed.

Although the case where the four-way valve can be switched without any problems by simultaneously switching the flow path switching valves connected to each outdoor heat exchanger 2, i.e., four-way valves A and B, has been described above, there is also an operation mode in which one of the outdoor heat exchangers 2 is used as a condenser and the other is used as an evaporator. In a heat recovery type air conditioning system, for example, there is an operation mode in which four-way valve A is turned on (at a low-pressure position) and four-way valve B is turned off (at a high-pressure position) to perform the simultaneous cooling/heating operations. In this case, because one of the four-way valves does not perform the switching operation, the high-pressure circuit cannot be closed, which is likely to cause a switching failure.

Therefore, when the compressor 1 is activated particularly, the four-way valve switching operation 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. Specifically, description will be given with reference to FIGS. 11 and 12. FIG. 11 is a timing chart showing control of a case where four-way valves A, B, and C are all turned on when the compressor 1 is activated. FIG. 12 is a timing chart showing control of a case where four-way valves A, B, and C are all turned off when the compressor 1 is activated.

In FIGS. 11 and 12, the horizontal axis represents time and the vertical axis represents ON/OFF of four-way valves A, B, and C and a rotational speed of the compressor 1. Moreover, t1 denotes a first step execution timing and t2 denotes a second step execution timing. As shown in FIGS. 11 and 12, after the compressor 1 is activated, switching control is started. After the rotational speed increases to a certain level, the first step is performed and the second step is performed. Subsequently, after the end of the switching control, the rotational speed is increased to a predetermined Hz value.

Because what is required for switching the four-way valve is a magnitude of a pressure difference instead of a magnitude of the pressure, it is desirable to perform the determination based on the pressure difference when the four-way valve is switched at the activation of the compressor 1. When the first and second steps are performed after a predetermined pressure difference is secured in this way, a certain degree of high pressure can be maintained even after one of four-way valves A and B is switched and all four-way valves can be switched without any problems.

In this case, it is shown that the time for the transition from the first step to the second step is preferably approximately 1 sec in the sense of preventing a sudden increase in the high pressure. However, in the sense of maintaining the high pressure, this time should be as short as possible and it is preferable to perform the transition for approximately 1 sec within approximately 3 sec.

As described above, it is possible to implement highly reliable four-way valve switching after simplifying the switching control by performing the above-described switching control at the activation of the compressor 1.

As another example of the effect of the present invention, an operation when the operation is switched from the cooling operation to the heating operation while the compressor 1 is in operation will be described. Specifically, description will be given with reference to FIGS. 13 and 14. FIG. 13 is a timing chart showing the control of a case where four-way valves A, B, and C are all turned on while the compressor 1 is being activated. FIG. 14 is a timing chart showing the control of a case where four-way valves A, B, and C are all turned off while the compressor 1 is being activated. The horizontal and vertical axes of FIGS. 13 and 14 and the like are similar to those of FIGS. 11 and 12, and therefore description thereof will be omitted.

As shown in FIGS. 13 and 14, in a state in which the rotational speed of compressor 1 is at a predetermined rps, switching control is started. After the rotational speed is decreased to a certain level (upper limit speed regulation A), the rotational speed is further decreased (upper limit speed regulation B), the first step is performed, and the second step is performed. Subsequently, after the end of the switching control, the rotational speed is increased to the predetermined rps.

Because the pressure is usually low when the compressor 1 is activated, the switching operation is performed when the pressure difference is greater than or equal to a predetermined value in the first step of the four-way valve switching. However, because the pressure is usually high in most cases while the compressor is in operation, if the first step is performed as usual, the pressure on the high-pressure side may rise rapidly and there is a possibility that the system will stop due to high-pressure protection. Therefore, when the four-way valve is switched while the compressor 1 is in operation, it is necessary to perform the switching control using a different four-way valve switching logic.

Moreover, at the activation of the compressor 1, the first step is performed when the pressure difference reaches a predetermined value or more. However, because the pressure is high while the compressor is in operation as described above, the four-way valve switching during the operation of the compressor 1 is performed when the high-pressure-side pressure or the pressure difference is less than or equal to a predetermined value. At this time, because a parameter to be noted for the high-pressure protection is the high-pressure pressure instead of the pressure difference, it is preferable to perform the first step with the pressure on the high-pressure side as a threshold value, unlike when the compressor 1 is activated. It is desirable to reduce the pressure by basically reducing the rotational speed of the compressor 1 to reduce the pressure on the high-pressure side. However, if there is a valve that bypasses high and low pressures, the pressure on the high-pressure side may be reduced by opening the valve.

Moreover, according to the outside air condition, the pressure on the high-pressure side may not reach a predetermined value no matter how much the rotational speed of the compressor 1 is reduced. In this case, it is only necessary to perform the first step and switch the four-way valve when a predetermined time has elapsed after the switching operation began and pressure monitoring started. In this case, it is preferable for the predetermined time to be the time that allows the operation to be performed after the rotational speed of the compressor 1 decreases sufficiently to a level that does not affect the switching of the four-way valve. By allowing the sufficient time in this way, even if the first step is performed when the pressure on the high-pressure side is higher than the predetermined value, a sudden increase in the high-pressure is suppressed to some extent and the four-way valve switching can be performed reliably.

By controlling the switching in this way, the first and second steps at the activation of the compressor 1 can be reused and a four-way valve switching pattern can be simplified. Moreover, before the first step is performed, the rotational speed of the compressor 1 may be reduced to a certain extent and then monitoring of the high-pressure side pressure may be started. Because pressure fluctuations occur due to the switching of the four-way valve, it is desirable to perform the switching at a rotational speed at which the compressor 1 can operate stably or lower.

As described above, in the present embodiment, it is possible to implement highly reliable four-way valve switching after simplifying the switching control using the above-described switching pattern while the compressor is in operation. Although four-way valves A, B, and C are all turned off for the cooling operation and all turned on for the heating operation in the present embodiment, the present invention is not limited thereto. For example, it goes without saying that a case where the four-way valves are connected so that four-way valves A and B are turned off and four-way valve C is turned on for the cooling operation and four-way valves A and B are turned on and four-way valve C is turned off for the heating operation does not depart from the scope of the present invention.

Each function executed by the air conditioning system 100 described above is implemented, for example, by a hardware processor such as a central processing unit (CPU) executing a program (software). Some or all of these constituent elements may be implemented by hardware (including a circuit; circuitry) such as a large-scale integration (LSI) circuit, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or a graphics processing unit (GPU) or may be implemented by software and hardware in cooperation. The program may be pre-stored in a storage device (a storage device including a non-transitory storage medium) such as a hard disk drive (HDD), a solid-state drive (SSD), or a flash memory or may be stored in a removable storage medium (the non-transitory storage medium) such as a DVD or a CD-ROM and installed when the storage medium is mounted on a drive device.

As described above, according to the present embodiment, it is possible to provide technology for suppressing the occurrence of switching failures.

Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to the present embodiment and various designs and the like are included without departing from the scope and spirit of the present invention.

INDUSTRIAL APPLICABILITY

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