Air Conditioning System

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.

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

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).

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

is a diagram showing a configuration of an air conditioning systemaccording to the present embodiment. The air conditioning systemaccording to the present embodiment is a heat recovery type air conditioning system. The air conditioning systemincludes indoor units,,, and, an outdoor unit, and a branch unitprovided therebetween. With this configuration, the air conditioning systemcan perform a cooling operation and a heating operation for each of the indoor units,,, and

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,,, andare not distinguished from one another, they will be referred to as indoor units.

The outdoor unitincludes a compressor, a plurality of four-way valves (flow path switching mechanisms),, and, an outdoor heat exchanger, an outdoor-side electric expansion valve, and an outdoor fanand has three refrigerant flow paths. Among the plurality of four-way valves,, andprovided in the outdoor unit, the four-way valvesandare connected so that the outdoor heat exchangerselectively communicates with a discharge side or a suction side. Moreover, the four-way valveis connected so that a high/low-pressure gas pipe selectively communicates with the discharge side or the suction side.

The branch unitis connected to the indoor unitby the high/low-pressure gas pipe, the low-pressure gas pipe, and the liquid pipe. The branch unitis connected to the indoor unitby a liquid pipeand a gas pipe. The branch unitis connected to the indoor unitby a liquid pipeand a gas pipe. The branch unitis connected to the indoor unitby a liquid pipeand a gas pipe. The branch unitis connected to the indoor unitby a liquid pipeand a gas pipe

The branch unitincludes a low-pressure gas regulating valve and a high/low-pressure gas regulating valve for each indoor unit. Specifically, the branch unitincludes a low-pressure gas regulating valveand a high/low-pressure gas regulating valvewith respect to the indoor unit. The branch unitincludes a low-pressure gas regulating valveand a high/low-pressure gas regulating valvewith respect to the indoor unit. The branch unitincludes a low-pressure gas regulating valveand a high/low-pressure gas regulating valvewith respect to the indoor unit. The branch unitincludes a low-pressure gas regulating valveand a high/low-pressure gas regulating valvewith respect to the indoor unit

Each indoor unitincludes an indoor-side electric expansion valve, an indoor heat exchanger, and an indoor fan. Specifically, the indoor unitincludes an indoor-side electric expansion valve, an indoor heat exchanger, and an indoor fan. The indoor unitincludes an indoor-side electric expansion valve, an indoor heat exchanger, and an indoor fan. The indoor unitincludes an indoor-side electric expansion valve, an indoor heat exchanger, and an indoor fan. The indoor unitincludes an indoor-side electric expansion valve, an indoor heat exchanger, and an indoor fan

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 systemshown in, an independent cooling operation, an independent heating operation, a simultaneous cooling operation, and a simultaneous heating operation are possible.is a diagram showing ON and OFF of the four-way valves,, andin each operation. In addition, in the following description, for ease of understanding, the four-way valvemay be referred to as four-way valve A. The four-way valvemay be referred to as four-way valve B. The four-way valvemay 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 compressorto the outdoor heat exchangeris defined as an OFF position and a position where communication is established from the outdoor heat exchangerto the suction side of the compressorand the discharge-side refrigerant flow path of the compressoris closed is defined as an ON position. In four-way valve C, a position where the low-pressure gas pipecommunicates with the high/low-pressure gas pipesis defined as an OFF position and a position where communication is established from the discharge side of the compressorto the high/low-pressure gas pipeand the high/low-pressure gas pipeside is closed is defined as an ON position.

As shown in, 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.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.

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.

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.

are diagrams showing the control content of a case where switching is performed only in the first step.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.

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 inwill be described with reference to the drawings.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, 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 compressorflows into the outdoor heat exchangerand is condensed and liquefied. This condensed liquid refrigerant is expanded in the indoor unitto become a low-pressure liquid refrigerant, and the indoor unitcan perform the cooling operation.

In this state, as shown in, 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 compressorhas nowhere to go, and the pressure on the high-pressure side (from the compressorto four-way valves A, B, and C) rises rapidly. Subsequently, as shown in, in the second step, four-way valve C is turned on. Thereby, the compressed gas flows into the indoor unitand the high-pressure-side/low-pressure-side regulating valves of the branch unitalso 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, 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. 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, 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 exchangersis 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 compressoris 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.is a timing chart showing control of a case where four-way valves A, B, and C are all turned on when the compressoris activated.is a timing chart showing control of a case where four-way valves A, B, and C are all turned off when the compressoris activated.

In, 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. Moreover, tdenotes a first step execution timing and tdenotes a second step execution timing. As shown in, after the compressoris 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. 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.

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 compressoris in operation will be described. Specifically, description will be given with reference to.is a timing chart showing the control of a case where four-way valves A, B, and C are all turned on while the compressoris being activated.is a timing chart showing the control of a case where four-way valves A, B, and C are all turned off while the compressoris being activated. The horizontal and vertical axes ofand the like are similar to those of, and therefore description thereof will be omitted.

As shown in, in a state in which the rotational speed of compressoris 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 compressoris 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 compressoris 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, 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 compressoris 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 compressoris activated. It is desirable to reduce the pressure by basically reducing the rotational speed of the compressorto 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 compressoris 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 compressordecreases 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 compressorcan be reused and a four-way valve switching pattern can be simplified. Moreover, before the first step is performed, the rotational speed of the compressormay 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 compressorcan 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 systemdescribed 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.

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