Refrigeration cycle device

Abstract

A refrigeration cycle device according to one embodiment of the present invention comprises: a heat storage circuit including a bypass flow path that connects the discharge side of a compressor to refrigerant piping between an outdoor heat exchanger and a main expansion valve, an auxiliary heat exchanger that is positioned in the bypass flow path and has a heat storage material capable of exchanging heat with some of the refrigerant discharged from the compressor, a first bypass expansion valve that is positioned in the bypass flow path between the compressor and the auxiliary heat exchanger, and a second bypass expansion valve that is positioned in the bypass flow path between the auxiliary heat exchanger and the refrigerant piping; and a control unit that controls the opening degree of the first bypass expansion valve on the basis of the rate of change of a detection value from a pressure sensor for detecting the pressure of the refrigerant on the discharge side of the compressor in a heat storage heating operation mode.

Description

Refrigeration cycle equipment

[0001] The present invention relates to a refrigeration cycle device equipped with a heat storage circuit.

[0002] A refrigeration cycle apparatus that defrosts an outdoor heat exchanger by utilizing heat stored in a heat storage material is known. This type of refrigeration cycle apparatus includes a refrigerant circuit including a compressor, an outdoor heat exchanger, an indoor heat exchanger, and an expansion valve, as well as a heat storage circuit including a bypass flow path connecting the discharge side of the compressor to a liquid refrigerant pipe between the outdoor heat exchanger and the expansion valve, a heat storage tank disposed in the bypass flow path, and two bypass expansion valves disposed upstream and downstream of the heat storage tank (see, for example, Patent Document 1).

[0003] The heat storage tank contains a heat storage material capable of exchanging heat with a portion of the refrigerant discharged from the compressor. During heating operation, a portion of the refrigerant discharged from the compressor is introduced into the heat storage tank to store the heat of the refrigerant (hereinafter also referred to as heat storage heating operation). During defrosting operation, the indoor and outdoor heat exchangers function as condensers, and the heat stored in the heat storage material is used to cause the heat storage tank to function as an evaporator. This allows the defrosting operation of the outdoor heat exchanger (hereinafter also referred to as defrost heating operation) to be performed without stopping the heating operation, thereby minimizing the decline in heating capacity even during defrosting operation.

[0004] JP 2016-17738 A

[0005] Commonly known methods for controlling the opening of an expansion valve include feedback control (FB control) and feedforward control (FF control). Examples of FB control include target discharge temperature control, which is used to adjust the flow rate of the entire refrigerant circuit, and target subcool control, which is used to adjust the flow rate according to the capacity of the indoor unit. FF control, on the other hand, is a control aimed at improving tracking and is performed primarily based on the compressor rotation speed. For example, the compressor rotation speed increases as the heating capacity required by the indoor unit increases. In FF control, the expansion valve opening is increased in response to the rate of increase in the compressor rotation speed to prevent the temperature of the refrigerant discharged from the compressor from becoming too high.

[0006] However, while Patent Document 1 describes opening each bypass expansion valve during heat storage heating operation, it does not describe how to control the opening of each bypass expansion valve when the heating capacity demand from the indoor unit changes during heat storage heating operation. Therefore, in the heat storage heating operation described in Patent Document 1, if the bypass expansion valve opening is controlled using the FF control described above, increasing the compressor rotation speed in response to an increase in the heating demand increases the bypass expansion valve opening. This results in excessive refrigerant being supplied to the heat storage tank. This reduces the amount of refrigerant supplied to the indoor heat exchanger (the user-side heat exchanger) below the amount required by the increase in heating demand, potentially resulting in a decrease in heating capacity (comfort). Furthermore, to prevent this decrease in heating capacity, the compressor rotation speed must be excessively increased, which increases power consumption.

[0007] In view of the above circumstances, an object of the present invention is to provide a refrigeration cycle device that can suppress a decrease in comfort and an increase in power consumption even when the required heating capacity changes during heat storage heating operation.

[0008] a heat storage circuit including: a bypass flow path connecting a discharge side of the compressor to a refrigerant pipe between the outdoor heat exchanger and the main expansion valve; an auxiliary heat exchanger arranged in the bypass flow path and having a heat storage material capable of exchanging heat with a portion of the refrigerant discharged from the compressor; a first bypass expansion valve arranged in the bypass flow path between the compressor and the auxiliary heat exchanger; and a second bypass expansion valve arranged in the bypass flow path between the auxiliary heat exchanger and the refrigerant pipe; a pressure sensor detecting a pressure of the refrigerant on the discharge side of the compressor; and a control unit controlling openings of the main expansion valve, the first bypass expansion valve, and the second bypass expansion valve, In a heat storage heating operation mode in which the indoor heat exchanger and the auxiliary heat exchanger function as condensers and the outdoor heat exchanger functions as an evaporator, the control unit controls the opening degree of the first bypass expansion valve based on the rate of change of the detection value of the pressure sensor.

[0009] In the heat storage heating operation mode, the control unit may control the opening degree of the first bypass expansion valve to decrease the opening degree of the first bypass expansion valve when the rate of change of the detection value of the pressure sensor is a positive value, and may control the opening degree of the first bypass expansion valve to increase the opening degree of the first bypass expansion valve when the rate of change of the detection value of the pressure sensor is a negative value.

[0010] The control unit may be configured to control the opening degree of the first bypass expansion valve based on the detection value of the pressure sensor when the heat-storage heating operation mode is started.

[0011] The control unit may be configured to control the opening degree of the second bypass expansion valve in the heat-storage heating operation mode so that the subcooling level of the refrigerant flowing out of the auxiliary heat exchanger reaches a preset target subcooling level.

[0012] The control unit may calculate a theoretical discharge temperature, which is the discharge temperature when the refrigerant sucked into the compressor is saturated vapor, and control the opening degree of the main expansion valve so that the temperature of the refrigerant discharged from the compressor becomes the theoretical discharge temperature.

[0013] According to the present invention, even if the required heating capacity changes during the heat storage heating operation, it is possible to suppress a decrease in comfort and an increase in power consumption.

[0014] 1 is a refrigerant circuit diagram of a refrigeration cycle device according to an embodiment of the present invention; 2 is a block diagram showing the configuration of a control device in the refrigeration cycle device; 3 is a flowchart showing an example of a processing procedure for a heat storage heating operation mode executed by the control device; 4 is a timing chart showing the operation or state of each part of the refrigeration cycle device at the start of the heat storage heating operation mode; and 5 is a timing chart showing the operation or state of each part of the refrigeration cycle device during execution of the heat storage heating operation mode.

[0015] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0016] 1 is a refrigerant circuit diagram of a refrigeration cycle apparatus 100 according to one embodiment of the present invention. The refrigeration cycle apparatus 100 of this embodiment is an air conditioner including an outdoor unit 2 and an indoor unit 3. Details of the refrigeration cycle apparatus 100 will be described below.

[0017] [Configuration of Refrigeration Cycle Apparatus] The outdoor unit 2 includes a compressor 21 and an outdoor heat exchanger 22. The indoor unit 3 includes an indoor heat exchanger 23. The outdoor unit 2 and the indoor unit 3 are connected by a gas pipe 12 and a liquid pipe 13. The refrigeration cycle apparatus 100 includes a refrigerant circuit 20, a heat storage circuit 50, and a control device 90.

[0018] (Refrigerant Circuit) The refrigerant circuit 20 includes a compressor 21 , an outdoor heat exchanger 22 , an indoor heat exchanger 23 , and a main expansion valve 24 disposed between the outdoor heat exchanger 22 and the indoor heat exchanger 23 .

[0019] The compressor 21 is a variable capacity compressor whose operating capacity can be varied by being driven by a motor (not shown) whose rotation speed is controlled by an inverter. The discharge side of the compressor 21 is connected to port a of a first four-way valve 41 (described later) via a discharge pipe 11. The suction side of the compressor 21 is connected to the outlet side of the accumulator 25 via a suction pipe 16.

[0020] As the outdoor heat exchanger 22 and the indoor heat exchanger 23, various types of heat exchangers can be used, such as a parallel flow heat exchanger, a fin tube heat exchanger, or a plate fin heat exchanger, which can exchange heat between air and refrigerant.

[0021] One refrigerant inlet / outlet of the outdoor heat exchanger 22 is connected to port e of a second four-way valve 42 (described later) by a refrigerant pipe 14. The other refrigerant inlet / outlet of the outdoor heat exchanger 22 is connected to one refrigerant inlet / outlet of the indoor heat exchanger 23 by a liquid pipe 13 via a main expansion valve 24. The outdoor heat exchanger 22 functions as a condenser during cooling operation and defrost heating operation, and as an evaporator during heating operation and heat storage heating operation, depending on the switching of the first four-way valve 41 and the second four-way valve 42. An outdoor fan (not shown) for blowing air through the outdoor heat exchanger 22 may be arranged near the outdoor heat exchanger 22.

[0022] One refrigerant inlet / outlet of the indoor heat exchanger 23 is connected to port b of a first four-way valve 41 (described later) via a gas pipe 12. The other refrigerant inlet / outlet of the indoor heat exchanger 23 is connected to the other refrigerant inlet / outlet of the outdoor heat exchanger 22 via the main expansion valve 24 via a liquid pipe 13, as described above. By switching the first four-way valve 41 and the second four-way valve 42, the indoor heat exchanger 23 functions as an evaporator during cooling operation and as a condenser during heating operation, heat storage heating operation, and defrost heating operation. An indoor fan (not shown) for blowing air through the indoor heat exchanger 23 may be arranged near the indoor heat exchanger 23.

[0023] The main expansion valve 24 is an electronic expansion valve whose opening is controlled based on the number of pulses given to a stepping motor (not shown), and is disposed in the liquid pipe 13 connecting the outdoor heat exchanger 22 and the indoor heat exchanger 23. The main expansion valve 24 is a pressure reducing valve that reduces the pressure of the refrigerant flowing through the liquid pipe 13. The opening of the main expansion valve 24 is adjusted according to the heating capacity required by the indoor unit 3 during heating operation, and according to the cooling capacity required by the indoor unit 3 during cooling operation.

[0024] The first four-way valve 41 and the second four-way valve 42 are flow path switching valves for switching the direction of refrigerant flow in the refrigerant circuit 20. The first four-way valve 41 and the second four-way valve 42 switch the connection of one refrigerant inlet / outlet of the outdoor heat exchanger 22 to the refrigerant discharge port or the refrigerant suction port of the compressor 21.

[0025] The first four-way valve 41 has four ports a, b, c, and d. Port a is connected to the discharge side of the compressor 21 via a discharge pipe 11. Port b is connected to one refrigerant inlet / outlet of the indoor heat exchanger 23 via a gas pipe 12. Port c is connected to the inlet side of the accumulator 25 via a refrigerant pipe 15. Port d is connected to a junction B with the first bypass pipe 54 of the heat storage circuit 50 via a check valve 43 and a refrigerant pipe 17. The check valve 43 is a directional control valve that allows refrigerant to flow from port d toward the junction B and prohibits refrigerant from flowing in the opposite direction.

[0026] As will be described later, during heating operation, heat storage heating operation, and defrost heating operation, the first four-way valve 41 is in a first state in which port a communicates with port b and port c communicates with port d, as shown by solid lines in Fig. 1. During cooling operation, the first four-way valve 41 is in a second state in which port a communicates with port d and port b communicates with port c, as shown by dashed lines in Fig. 1.

[0027] The second four-way valve 42 has four ports e, f, g, and h. Port e is connected to one refrigerant inlet / outlet of the outdoor heat exchanger 22 via a refrigerant pipe 14. Port f is connected to a branch point A of the discharge pipe via a first bypass pipe 54. Branch point A is provided between the discharge side of the compressor 21 and port a of the first four-way valve 41. Port g is connected to one refrigerant inlet / outlet of the auxiliary heat exchanger 53 via a second bypass pipe 55. Port h is connected to a junction point C of the refrigerant pipe 15. Junction point C is provided between port c of the first four-way valve 41 and the suction side of the accumulator 25.

[0028] As will be described later, during heating operation and heat-storage heating operation, the second four-way valve 42 is in a first state in which port e communicates with port h and port f communicates with port g, as shown by solid lines in Fig. 1. During cooling operation and defrosting heating operation, the second four-way valve 42 is in a second state in which port e communicates with port f and port g communicates with port h, as shown by dashed lines in Fig. 1.

[0029] The inflow side of the accumulator 25 is connected to the port c of the first four-way valve 41 by the refrigerant piping 15, and the outflow side is connected to the suction side of the compressor 21 by the suction piping 16. The accumulator 25 separates the refrigerant that has flowed in into gas refrigerant and liquid refrigerant, and allows only the gas refrigerant to be sucked into the compressor 21.

[0030] (Heat Storage Circuit) The heat storage circuit 50 includes a first bypass expansion valve 51 , a second bypass expansion valve 52 , and an auxiliary heat exchanger 53 disposed between the first bypass expansion valve 51 and the second bypass expansion valve 52 .

[0031] The first bypass expansion valve 51 and the second bypass expansion valve 52 are electronic expansion valves whose opening degrees are controlled based on the number of pulses applied to a stepping motor (not shown). The first bypass expansion valve 51 is disposed in a first bypass pipe 54 between a branch point A of the discharge pipe 11 and a junction B with the refrigerant pipe 17. The second bypass expansion valve 52 is disposed in a third bypass pipe 56 connecting the other refrigerant inlet / outlet of the auxiliary heat exchanger 53 and a junction D with the liquid pipe 13.

[0032] The first bypass pipe 54, the second bypass pipe 55, and the third bypass pipe 56 form a bypass flow path of the present invention that connects the discharge side of the compressor 21 to the refrigerant pipe (junction D of the liquid pipe 13) between the outdoor heat exchanger 22 and the main expansion valve 24.

[0033] The auxiliary heat exchanger 53 is disposed in the second bypass pipe 55. One refrigerant inlet / outlet of the auxiliary heat exchanger 53 is connected to the port g of the second four-way valve 42 by the second bypass pipe 55, and the other refrigerant inlet / outlet of the auxiliary heat exchanger 53 is connected to the junction D of the liquid pipe 13 via the second bypass expansion valve 52 by the third bypass pipe 56.

[0034] The auxiliary heat exchanger 53 has a heat storage material 57 capable of exchanging heat with a portion of the refrigerant discharged from the compressor 21. The heat storage material 57 is, for example, a block made of a metal with excellent thermal conductivity, such as copper or aluminum. Alternatively, a liquid or slurry phase change substance capable of storing heat by heat exchange with the refrigerant flowing through the auxiliary heat exchanger 53 may be used as the heat storage material. Furthermore, the amount of heat stored in the heat storage material 57 is not particularly limited as long as it can store enough heat to evaporate the refrigerant flowing from the outdoor heat exchanger 22 and the indoor heat exchanger 23 in the auxiliary heat exchanger 53 during the defrosting heating operation described below.

[0035] Various sensors are provided in the outdoor unit 2. In this embodiment, as shown in Fig. 1 , the discharge pipe 11 is provided with a discharge pressure sensor 71 that detects the discharge pressure, which is the pressure of the refrigerant discharged from the compressor 21, and a discharge temperature sensor 73 that detects the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 21. The suction pipe 16 is provided with a suction pressure sensor 72 that detects the suction pressure, which is the pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 74 that detects the suction temperature, which is the temperature of the refrigerant sucked into the compressor 21.

[0036] The outdoor heat exchanger 22 is provided with an outdoor heat exchanger temperature sensor 75 that detects the outdoor heat exchanger temperature, which is the temperature of the outdoor heat exchanger 22. An outdoor air temperature sensor 76 that detects the temperature of the outdoor air flowing into the housing (not shown) of the outdoor unit 2, i.e., the outdoor air temperature, is provided near an air inlet (not shown) of the outdoor unit 2.

[0037] Meanwhile, in the indoor unit 3, a gas-side temperature sensor 77 is provided on one refrigerant inlet / outlet side of the indoor heat exchanger 23 of the gas pipe 12, and a liquid-side temperature sensor 78 is provided on the other refrigerant inlet / outlet side of the indoor heat exchanger 23 of the liquid pipe 13. A room temperature sensor 79 is provided near an air intake (not shown) of the indoor unit 3 to detect the temperature of the indoor air flowing into the indoor unit 3, i.e., the room temperature.

[0038] Furthermore, the heat storage circuit 50 is provided with a heat storage circuit temperature sensor 80 that detects the temperature of the heat storage material 57 .

[0039] (Control Device) The control device 90 is, for example, an outdoor unit control device provided in the outdoor unit 2, and is mounted on a control board stored in an electrical component box (not shown) of the outdoor unit 2. The control device 90 corresponds to the control unit of the present invention.

[0040] 2 is a block diagram showing the configuration of the control device 90. As shown in the figure, the control device 90 has a CPU 91, a storage unit 92, a communication unit 93, a sensor input unit 94, and a rotation speed detection unit 95.

[0041] The memory unit 92 is a non-volatile memory such as a flash memory, and stores the control program and control parameters of the outdoor unit 2, detection values ​​corresponding to detection signals from various sensors, the control state of the compressor 21 and outdoor fan, etc., the rotation speed of the indoor fan obtained via the communication unit 93, the control state of the indoor unit 3 including the operating mode set and input by the user, etc.

[0042] The communication unit 93 is an interface for communicating with the indoor unit 3. The sensor input unit 94 takes in detection results from various sensors in the outdoor unit 2 and outputs them to the CPU 91. The rotation speed detection unit 95 detects the rotation speed of the motor of the compressor 21 and outputs it to the CPU 91. The rotation speed detection unit 95 may be configured to directly detect the rotation speed of the motor using an encoder or the like attached to the drive shaft of the motor, or may be configured to detect the rotation speed of the motor from the drive current supplied to the motor. In the following description, the rotation speed of the compressor 21 refers to the rotation speed of the motor.

[0043] The CPU 91 is a control unit that controls the operation of each part of the outdoor unit 2, including the compressor 21, by executing a program stored in the storage unit 92. The program is installed in the control device 90, for example, via various recording media. Alternatively, the program may be installed via the Internet or the like.

[0044] The CPU 91 receives the detection results of the sensors in the outdoor unit 2 via the sensor input unit 94. Furthermore, the CPU 91 receives control signals transmitted from the indoor unit 3 via the communication unit 93. The control signals transmitted from the indoor unit 3 include the required operating capacity (thermal load of the indoor unit 3) required by the indoor unit 3c. Based on the received detection results and control signals, the CPU 91 controls the operation of the compressor 21, the outdoor fan, and the indoor fan, for example, setting the indicated rotation speeds at which these are driven. Based on the received detection results and control signals, the CPU 91 also controls the switching of the first four-way valve 41 and the second four-way valve 42. Based on the received detection results and control signals, the CPU 91 also controls the rotation speeds of the compressor 21 and the outdoor fan, and the opening degrees of the main expansion valve 24, the first bypass expansion valve 51, and the second bypass expansion valve 52.

[0045] [Basic Operation of Refrigeration Cycle Apparatus] Next, a description will be given of the basic operation of the refrigeration cycle apparatus 100. The refrigeration cycle apparatus 100 (controller 90) of this embodiment can perform the four operation modes shown in Table 1.

[0046]

[0047] (1: Cooling Operation) In the cooling operation mode, the first four-way valve 41 is switched to the second state (a-d communication, b-c communication), and the second four-way valve 42 is switched to the second state (e-f communication, g-h communication). The opening of the main expansion valve 24 is feedback controlled so that the temperature of the refrigerant discharged from the compressor 21 becomes a target discharge temperature. The first bypass expansion valve 51 is fully open, and the second bypass expansion valve 52 is fully closed. In the cooling operation mode, the outdoor heat exchanger 22 functions as a condenser, and the indoor heat exchanger 23 functions as an evaporator.

[0048] Here, the target discharge temperature refers to the theoretical discharge temperature, which is the discharge temperature when the refrigerant drawn into the compressor 21 is saturated vapor. The theoretical discharge temperature is calculated based on the discharge pressure and the suction pressure and is the discharge temperature when the refrigerant drawn into the compressor 21 is saturated vapor (with a quality fraction of 1), and refers to the discharge temperature when adjusted to an ideal refrigeration cycle. Calculation parameters for the theoretical discharge temperature may include the rotation speed of the compressor 11 in addition to the discharge pressure and the suction pressure. By controlling the aperture of the main expansion valve 24 so that the temperature of the refrigerant drawn into the compressor 21 becomes the theoretical discharge temperature, the quality fraction of the refrigerant drawn into the compressor 21 can be adjusted to 1 in accordance with changes in the rotation speed of the compressor 21, thereby preventing a decrease in the reliability of the compressor.

[0049] The high-pressure gas refrigerant discharged from the compressor 21 is divided at branch point A of the discharge pipe 11 into a refrigerant flowing to the first four-way valve 41 and a refrigerant flowing to the first bypass pipe 54 via the first bypass expansion valve 51. The high-pressure gas refrigerant that has flowed to the first four-way valve 41 merges into the first bypass pipe 54 via the refrigerant pipe 17, the check valve 43, and the junction B, and flows into the refrigerant pipe 14 via the second four-way valve 42. The high-pressure gas refrigerant that has flowed into the refrigerant pipe 14 exchanges heat with outside air in the outdoor heat exchanger 22, which functions as a condenser, to condense into high-pressure liquid refrigerant, which flows into the liquid pipe 13. Note that, normally, the first bypass expansion valve 51 is fully opened to prevent backflow; however, when the check valve 43 is provided in the refrigerant pipe 17 as in this embodiment, the first bypass expansion valve 51 may be fully closed.

[0050] The intermediate-pressure liquid refrigerant that flows into the liquid pipe 13 is decompressed by the main expansion valve 24 to become low-pressure liquid refrigerant, which flows into the indoor heat exchanger 23. Because the second bypass expansion valve 52 is fully closed, the liquid refrigerant is prevented from flowing into the heat storage circuit 50 from the junction D of the liquid pipe 13. The low-pressure liquid refrigerant that flows into the indoor heat exchanger 23, which functions as an evaporator, evaporates by exchanging heat with the indoor air and becomes low-pressure gas refrigerant, which flows into the gas pipe 12. This cools the room in which the indoor unit 3 is installed. The low-pressure gas refrigerant that flows into the gas pipe 12 flows into the accumulator 25 via the first four-way valve 41 and the refrigerant pipe 15, and is then drawn into the compressor 21 via the suction pipe 16.

[0051] (2: Heating Operation) In the heating operation mode, the first four-way valve 41 is switched to the first state (a-b communication, c-d communication), and the second four-way valve 42 is switched to the first state (e-h communication, f-g communication). The opening of the main expansion valve 24 is feedback controlled so that the temperature of the refrigerant discharged from the compressor 21 becomes a target discharge temperature. The first bypass expansion valve 51 is fully closed, and the second bypass expansion valve 52 is opened to a small degree that prevents refrigerant from accumulating in the heat storage circuit 50. In the heating operation mode, the outdoor heat exchanger 22 functions as an evaporator, and the indoor heat exchanger 23 functions as a condenser.

[0052] The high-pressure gas refrigerant discharged from the compressor 21 flows into the indoor heat exchanger 23 via the discharge pipe 11, the first four-way valve 41, and the gas pipe 12. Because the first bypass expansion valve 51 is fully closed, the gas refrigerant is prevented from flowing from branch point A of the discharge pipe 11 into the heat storage circuit 50. The high-pressure gas refrigerant that flows into the indoor heat exchanger 23, which functions as a condenser, condenses through heat exchange with the indoor air, becoming high-pressure liquid refrigerant and flowing into the liquid pipe 13. This provides heating for the room in which the indoor unit 3 is installed.

[0053] The intermediate-pressure liquid refrigerant that has flowed into the liquid pipe 13 is decompressed by the main expansion valve 24 to become low-pressure liquid refrigerant, which then flows into the outdoor heat exchanger 22. The pressure of the refrigerant remaining in the heat storage circuit 50 is higher than the pressure of the refrigerant at the junction D of the liquid pipe 13 downstream of the main expansion valve 24, so it passes through the second bypass expansion valve 52, which has been adjusted to the above-mentioned predetermined opening due to this pressure difference, and joins at the junction D of the liquid pipe 13. The low-pressure liquid refrigerant that has flowed into the outdoor heat exchanger 22, which functions as an evaporator, evaporates by exchanging heat with outside air, becoming low-pressure gas refrigerant, which then flows into the refrigerant pipe 14. The low-pressure gas refrigerant that has flowed into the refrigerant pipe 14 flows into the accumulator 25 via the second four-way valve 42 and the refrigerant pipe 15, and is drawn into the compressor 21 via the suction pipe 16.

[0054] (3: Heat Storage Heating Operation) In the heat storage heating operation mode, the first four-way valve 41 is switched to a first state (a-b communication, c-d communication), and the second four-way valve 42 is switched to a first state (e-h communication, f-g communication). The aperture of the main expansion valve 24 is feedback-controlled so that the temperature of the refrigerant discharged from the compressor 21 reaches a target discharge temperature. The aperture of the first bypass expansion valve 51 is controlled so that the temperature difference between the temperature of the refrigerant flowing through the auxiliary heat exchanger 53 and the temperature of the heat storage material 57 reaches a predetermined temperature difference. In this embodiment, as described below, the aperture is controlled in response to changes in the pressure (high pressure) on the inlet side of the first bypass expansion valve when the required heating capacity is changed. The aperture of the second bypass expansion valve 52 is either fixed or feedback-controlled so that the subcooling (degree of supercooling) of the refrigerant flowing out of the auxiliary heat exchanger 53 reaches a target subcooling. In the heat storage heating operation mode, the outdoor heat exchanger 22 functions as an evaporator, and the indoor heat exchanger 23 and the auxiliary heat exchanger 53 function as condensers.

[0055] The high-pressure gas refrigerant discharged from the compressor 21 is divided at branch point A of the discharge pipe 11 into refrigerant flowing to the first four-way valve 41 and refrigerant flowing to the first bypass pipe 54 via the first bypass expansion valve 51. The high-pressure gas refrigerant that has flowed to the first four-way valve 41 flows into the indoor heat exchanger 23, which functions as a condenser, via the gas pipe 12, and condenses by exchanging heat with the indoor air, becoming high-pressure liquid refrigerant, which then flows into the liquid pipe 13. This provides heating for the room in which the indoor unit 3 is installed. The intermediate-pressure liquid refrigerant that has flowed into the liquid pipe 13 is decompressed by the main expansion valve 24, becoming low-pressure liquid refrigerant, and flows into the outdoor heat exchanger 22.

[0056] On the other hand, the high-pressure gas refrigerant that has flowed into the first bypass pipe 54 flows into the auxiliary heat exchanger 53 via the second four-way valve 42 and the second bypass pipe 55. The auxiliary heat exchanger 53 functions as a condenser, and the high-pressure gas refrigerant that has flowed into the auxiliary heat exchanger 53 condenses by exchanging heat with the heat storage material 57, becoming high-pressure liquid refrigerant, and flows into the third bypass pipe 56. As a result, heat is stored in the heat storage material 57. The intermediate-pressure liquid refrigerant that has flowed into the third bypass pipe 56 is decompressed by the second bypass expansion valve 52 and becomes low-pressure liquid refrigerant. The low-pressure liquid refrigerant decompressed by the second bypass expansion valve 52 merges with the low-pressure liquid refrigerant decompressed by the main expansion valve 24 at a junction D of the liquid pipe 13, and flows into the outdoor heat exchanger 22.

[0057] The outdoor heat exchanger 22 functions as an evaporator, and the low-pressure liquid refrigerant that flows into the outdoor heat exchanger 22 evaporates by exchanging heat with outside air, becoming low-pressure gas refrigerant, which flows into the refrigerant pipe 14. The low-pressure gas refrigerant that has flowed into the refrigerant pipe 14 flows into the accumulator 25 via the second four-way valve 42 and the refrigerant pipe 15, and is then drawn into the compressor 21 via the suction pipe 16.

[0058] The heat storage heating operation mode is an operation mode in which heat from the refrigerant is stored in the heat storage material 57 while maintaining the indoor heating function so that the auxiliary heat exchanger 53 functions as a heat source-side heat exchanger in a defrost heating operation mode, which will be described later. The heat storage heating operation mode is typically automatically switched from the heating operation mode depending on the outdoor air temperature, etc. For example, when the outdoor air temperature is low enough to cause frost formation on the outdoor heat exchanger 22, the operation mode is switched to the heat storage heating operation mode. On the other hand, when the outdoor air temperature rises to a level where frost formation is no longer a risk during the heat storage heating operation, the operation mode may be automatically switched to the heating operation mode.

[0059] Furthermore, when it is determined during the heat storage heating operation that the heat storage material 57 has reached a preset temperature that is deemed to be a sufficient amount of heat for performing the defrost heating operation based on the detected value of the heat storage circuit temperature sensor 80, the operation mode may be automatically switched from the heat storage heating operation mode to the heating operation mode. Alternatively, when it is determined that the amount of heat stored in the heat storage material 57 has decreased during the heating operation and the temperature of the heat storage material 57 has fallen below the above temperature by at least a predetermined temperature, the operation mode may be automatically switched from the heating operation mode to the heat storage heating operation mode.

[0060] (4: Defrosting and Heating Operation) In the defrosting and heating operation mode, the first four-way valve 41 is switched to a first state (a-b communication, c-d communication), and the second four-way valve 42 is switched to a second state (e-f communication, g-h communication). The opening of the main expansion valve 24 is feedback controlled so that the temperature of the refrigerant discharged from the compressor 21 becomes a target discharge temperature. The opening of the first bypass expansion valve 51 is fixed to a predetermined opening that ensures a flow rate of refrigerant necessary to complete defrosting of the outdoor heat exchanger 22, and the second bypass expansion valve 52 is fully open. In the defrosting and heating operation mode, the outdoor heat exchanger 22 and the indoor heat exchanger 23 function as condensers, and the auxiliary heat exchanger 53 functions as an evaporator.

[0061] The high-pressure gas refrigerant discharged from the compressor 21 is divided at branch point A of the discharge pipe 11 into refrigerant that flows to the first four-way valve 41 and refrigerant that flows to the first bypass pipe 54 via the first bypass expansion valve 51. The high-pressure gas refrigerant that has flowed to the first four-way valve 41 flows into the indoor heat exchanger 23, which functions as a condenser, via the gas pipe 12, and condenses into high-pressure liquid refrigerant by exchanging heat with the indoor air, which then flows into the liquid pipe 13. This provides heating for the room in which the indoor unit 3 is installed. The intermediate-pressure liquid refrigerant that has flowed into the liquid pipe 13 is reduced in pressure by the main expansion valve 24 and becomes low-pressure liquid refrigerant.

[0062] On the other hand, the high-pressure gas refrigerant that has flowed into the first bypass pipe 54 flows into the outdoor heat exchanger 22, which functions as a condenser, via the second four-way valve 42 and the refrigerant pipe 14. The high-pressure gas refrigerant that has flowed into the outdoor heat exchanger 53 exchanges heat with frost adhering to the outdoor heat exchanger 22, condenses into high-pressure liquid refrigerant, and flows into the liquid pipe 13. As a result, the frost adhering to the outdoor heat exchanger 22 is melted and removed by the heat of the refrigerant. The intermediate-pressure liquid refrigerant that has flowed into the liquid pipe 13, together with the low-pressure liquid refrigerant decompressed by the main expansion valve 24, flows from the confluence D of the liquid pipe 13 via the third bypass pipe 56 and the second bypass expansion valve 52 into the auxiliary heat exchanger 53.

[0063] The auxiliary heat exchanger 53 functions as an evaporator, and the low-pressure gas-liquid two-phase refrigerant that has flowed into the auxiliary heat exchanger 53 evaporates by exchanging heat with the heat stored in the heat storage material 57, becoming low-pressure gas refrigerant and flowing into the second bypass piping 55. The low-pressure gas refrigerant that has flowed into the second bypass piping 55 flows into the accumulator 25 via the second four-way valve 42 and the refrigerant piping 15, and is then drawn into the compressor 21 via the suction piping 16.

[0064] In the defrosting heating operation mode, the defrosting operation of the outdoor unit can be performed without stopping the heating operation, so that the deterioration of the indoor heating function can be suppressed during the defrosting operation.

[0065] [Issues in the heat storage heating operation mode] In a refrigeration cycle apparatus equipped with the heat storage heating operation mode, when the above-described heat storage heating operation mode is executed, the method of controlling the first bypass expansion valve 51 that adjusts the flow rate of the refrigerant flowing through the heat storage circuit 50 has the following issues.

[0066] Generally, two types of expansion valve control are known: feedback control (FB control) and feedforward control (FF control). FB control compares a current value with a target value and attempts to match the current value with the target value. Examples of such control include target discharge temperature control, which is used to adjust the flow rate of the entire refrigerant circuit, and target subcooling control, which is used to adjust the flow rate according to the capacity of the indoor unit. FF control, on the other hand, aims to improve tracking and is primarily performed based on the compressor speed. For example, when the compressor speed is increased in response to an increase in the heating capacity required by the indoor unit, FF control increases the opening of the expansion valve in response to the rate of increase in the compressor speed, preventing the temperature of the refrigerant discharged from the compressor from becoming too high.

[0067] If the opening degree of the first bypass expansion valve 51 is controlled by the FF control as described above, when the rotation speed of the compressor 21 is increased in response to an increase in the required heating capacity, the opening degree of the first bypass expansion valve 51 is controlled to be larger, which may result in an excessive supply of refrigerant to the auxiliary heat exchanger 53, which is a heat storage tank, and the amount of refrigerant supplied to the indoor heat exchanger 23, which is a user-side heat exchanger, being less than the amount of refrigerant required by the increase in the required heating capacity, resulting in a decrease in heating capacity (comfort). Furthermore, in order to prevent such a decrease in heating capacity, it is necessary to excessively increase the rotation speed of the compressor 21, which poses a problem of increased power consumption.

[0068] [Details of this embodiment] In this embodiment, in order to suppress a decrease in comfort and an increase in power consumption even when the required heating capacity changes during the heat storage heating operation, the first bypass expansion valve 51 is controlled as follows. Details of the processing executed by the control device 90 in the heat storage heating operation mode will be described below. Here, the case where the heating operation mode is switched to the heat storage heating operation mode will be described as an example.

[0069] Fig. 3 is a flowchart showing an example of a processing procedure for the heat-storage heating operation mode executed by the control device 90. Fig. 4 is an example of a timing chart showing the operation or state of each part of the refrigeration cycle apparatus 100 at the start of the heat-storage heating operation mode, in which (A) shows the rotation speed of the compressor 21, (B) shows the condensing pressure of the refrigerant in the indoor heat exchanger 23 (high pressure in the refrigerant circuit 20), and (C) shows the opening (pulse number) of the first bypass expansion valve 51. Fig. 5 is an example of a timing chart showing the operation or state of each part of the refrigeration cycle apparatus 100 during execution of the heat-storage heating operation mode, in which (A) shows the rotation speed of the compressor 21, (B) shows the condensing pressure of the refrigerant in the indoor heat exchanger 23 (high pressure in the refrigerant circuit 20), (C) shows the opening (pulse number) of the first bypass expansion valve 51, (D) shows the pressure of the refrigerant in the auxiliary heat exchanger 53 (high pressure in the heat-storage circuit 50), (E) shows the flow rate of the refrigerant flowing through the indoor unit 3, and (F) shows the flow rate of the refrigerant flowing through the heat-storage circuit 50.

[0070] When the heat-storage heating operation mode is executed, the control device 90 adjusts the opening degree of the first bypass expansion valve 51 based on the pressure of the refrigerant on the discharge side of the compressor 21. Here, the pressure of the refrigerant on the discharge side of the compressor 21 means the pressure on the high-pressure side in the refrigerant circuit 20 or the pressure of the refrigerant in the auxiliary heat exchanger 53 in the heat-storage circuit 50, and in this embodiment, it is the discharge pressure, which is the pressure on the inlet side of the first bypass expansion valve 51. This pressure value is detected by the discharge pressure sensor 71. Hereinafter, the pressure of the refrigerant on the discharge side of the compressor 21 will also be simply referred to as the "high pressure refrigerant."

[0071] As shown in FIG. 4, when the heat storage heating operation mode is started at time T1, the control device 90 detects the current high pressure of the refrigerant (ST101), and calculates an opening control amount for setting the opening of the first bypass expansion valve 51 based on the detected high pressure of the refrigerant (ST102).

[0072] In normal control of the opening degree of the first bypass expansion valve 51, the opening degree is adjusted so that the temperature difference between the temperature of the refrigerant flowing through the auxiliary heat exchanger 53 and the temperature of the heat storage material 57 becomes a predetermined temperature difference. However, when the first bypass expansion valve 51 is opened, the amount of refrigerant flowing from the compressor 21 to the indoor heat exchanger 23 decreases, which may temporarily significantly reduce the heating capacity of the indoor unit 3 when the heat storage heating operation starts.

[0073] Therefore, in this embodiment, in order to suppress a decrease in indoor comfort (heating capacity) at the start of the heat storage heating operation, the current high pressure of the refrigerant is detected before opening the first bypass expansion valve 51, and the opening control amount of the first bypass expansion valve is corrected based on the detected value (ST102). Specifically, for example, when the high pressure of the refrigerant is equal to or higher than a preset threshold, the opening control amount of the first bypass expansion valve 51 is calculated so that the opening is set to a preset value corresponding to the rotation speed of the compressor 21 without correcting the opening control amount. When the high pressure of the refrigerant is lower than the threshold, the opening control amount of the first bypass expansion valve 51 is calculated so that the corrected opening is smaller than the opening before correction (i.e., without correction). The correction amount of the opening control amount may be a fixed value or may be variably set based on the detected high pressure.

[0074] Next, the control device 90 adjusts the aperture of the first bypass expansion valve 51 using the calculated aperture control amount (ST103). As a result, the first bypass expansion valve 51 opens (time T2 in FIG. 4), and the aperture gradually increases toward the target aperture determined by the calculated aperture control amount. As the aperture of the first bypass expansion valve 51 increases, the refrigerant pressure (condensing pressure) in the indoor heat exchanger 23 also decreases, but it is possible to ensure a pressure that provides the heating capacity necessary to maintain indoor comfort.

[0075] Next, the control device 90 determines at predetermined time intervals whether there has been a change in the required operating capacity (hereinafter also referred to as the required heating capacity) requested by the indoor unit 3 (ST104). When an instruction to change the required heating capacity from the indoor unit 3 is confirmed (Yes in ST104), the control device 90 changes the rotation speed of the compressor 21 to a rotation speed corresponding to the changed required heating capacity. In this embodiment, the control device 90 calculates the rate of change in the high pressure of the refrigerant before and after changing the rotation speed of the compressor 21. The rate of change in the high pressure of the refrigerant is calculated based on the rate of change in the value detected by the discharge pressure sensor 71.

[0076] When there is no instruction to change the required heating capacity (No in ST104), the opening of the first bypass expansion valve 51 is controlled so that the difference between the refrigerant temperature on the inlet side of the first bypass expansion valve 51 (detection value of the discharge temperature sensor 73) and the temperature of the heat storage material 57 (detection value of the heat storage circuit temperature sensor 80) is constant.

[0077] As shown in Figure 5, when an instruction to change the required heating capacity is received at time T3, the control device 90 detects the current (time T3) high pressure of the refrigerant before the rotation speed of the compressor 21 is changed, and stores it in the memory unit 92 (ST105).

[0078] Next, at time T4, the control device 90 changes the rotation speed of the compressor 21 so that it becomes the target rotation speed corresponding to the changed required heating capacity (ST106). Here, an example will be described in which the required heating capacity increases, and in this case, the rotation speed of the compressor 21 is increased so that it becomes the rotation speed corresponding to the increase (or increase rate) of the required heating capacity. Note that if the required heating capacity decreases, the rotation speed of the compressor 21 is decreased so that it becomes the rotation speed corresponding to the decrease (or decrease rate).

[0079] As the rotation speed of the compressor 21 increases, the discharge pressure of the compressor 21 increases, and therefore the flow rate and pressure of the refrigerant flowing through the indoor heat exchanger 23 and the flow rate and pressure of the refrigerant flowing through the heat storage circuit 50 all increase (see FIGS. 5B, 5D to 5F). When the rotation speed of the compressor 21 reaches the target rotation speed, the control device 90 detects the current (time T5) high pressure of the refrigerant after the rotation speed of the compressor 21 has been changed, and stores this in the memory unit 92 (ST107).

[0080] Next, the control device 90 calculates the opening control amount of the first bypass expansion valve 51 based on the rate of change of the high pressure of the refrigerant detected in ST105 and ST107 (ST108). Here, if the detected value of the high pressure before the change in the rotation speed of the compressor 21 detected in ST105 is P1, and the detected value of the high pressure after the change in the rotation speed of the compressor 21 detected in ST107 is P2, the value calculated by the formula (P2-P1) / P1 is defined as the rate of change of the high pressure.

[0081] Here, the detection timing of the detected value P1 is, for example, when it is determined in ST104 that an instruction to change the required heating capacity has been issued. The detection timing of the detected value P2 is, for example, after a predetermined period of time has elapsed since control to change the rotation speed of the compressor 21 was started, which is required for the rotation speed of the compressor 21 to reach the target rotation speed. However, this is not limited to this, and the detection value of the discharge pressure sensor 71 may be obtained at predetermined intervals (for example, one minute). In this case, the detection value obtained immediately after control to change the rotation speed of the compressor 21 was started is set to P1, and the detection value obtained immediately after the rotation speed of the compressor 21 has reached the target rotation speed is set to P2.

[0082] When the rate of change in the detected value of the high pressure is a positive value, the control device 90 calculates the opening amount of the first bypass expansion valve 51 so as to reduce the opening of the first bypass expansion valve 51. In the example shown in Fig. 5, the high pressure increases due to an increase in the rotation speed of the compressor 21, so the rate of change in the detected value of the high pressure is positive, and therefore the opening of the first bypass expansion valve 51 is controlled so as to reduce the opening of the first bypass expansion valve 51 (ST109, time T6).

[0083] This reduces the amount and pressure of the refrigerant flowing into the heat storage circuit 50 (see FIGS. 5(D) and 5(G)). As a result, the flow rate and pressure of the refrigerant flowing to the indoor heat exchanger 23 increase (see FIGS. 5(B) and 5(E)), thereby preventing a decrease in indoor comfort due to insufficient heating capacity.

[0084] When the required heating capacity decreases, the rotation speed of the compressor 21 decreases, causing the rate of change of the detected high pressure value to become negative, and in this case, the opening of the first bypass expansion valve 51 is controlled to increase. As a result, the amount and pressure of refrigerant flowing into the heat storage circuit 50 increase, and the flow rate and pressure of refrigerant flowing to the indoor heat exchanger 23 decrease.

[0085] Thereafter, by repeatedly executing the processes of ST104 to ST109 at a predetermined interval, it is possible to continue to supply the necessary amount of refrigerant to the heat storage circuit 50 while suppressing a decrease in indoor comfort during the heat storage heating operation.

[0086] As described above, according to this embodiment, in the heat storage heating operation mode, the opening degree of the first bypass expansion valve 51 is controlled based on the rate of change of the high pressure of the refrigerant detected by the discharge pressure sensor 71, so that a decrease in comfort can be suppressed even if the required heating capacity changes during the heat storage heating operation. Furthermore, even if the required heating capacity increases during the heat storage heating operation, a sufficient amount of refrigerant can be supplied to the indoor heat exchanger 23 to suppress a decrease in comfort, so that there is no need to excessively increase the rotation speed of the compressor 21, thereby suppressing an increase in power consumption.

[0087] Although the embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the above-described embodiments and that various modifications can be made.

[0088] For example, in the above embodiment, a refrigeration cycle device in which one indoor unit 3 is connected to an outdoor unit 2 has been described as an example, but this is not limited to this, and the present invention can also be applied to a refrigeration cycle device in which multiple indoor units 3 are connected to an outdoor unit 2.

[0089] In addition, in the above embodiment, the discharge pressure sensor 71 is used to detect the high pressure of the refrigerant, but instead, a sensor capable of detecting the pressure (condensation pressure) of the refrigerant flowing through the indoor heat exchanger 23 may be used, or a sensor capable of detecting the pressure of the refrigerant flowing through the auxiliary heat exchanger 53 may be used.

[0090] DESCRIPTION OF SYMBOLS 2... Outdoor unit 3... Indoor unit 20... Refrigerant circuit 21... Compressor 22... Outdoor heat exchanger 23... Indoor heat exchanger 24... Main expansion valve 41... First four-way valve 42... Second four-way valve 50... Heat storage circuit 51... First bypass expansion valve 52... Second bypass expansion valve 53... Auxiliary heat exchanger 54... First bypass piping (bypass flow path) 55... Second bypass piping (bypass flow path) 56... Third bypass piping (bypass flow path) 57... Heat storage material 71... Discharge pressure sensor (pressure sensor) 90... Control device (control unit) 100... Refrigeration cycle device

Claims

1. A heat storage circuit including: a refrigerant circuit including a compressor, an outdoor heat exchanger, an indoor heat exchanger, and a main expansion valve arranged between the outdoor heat exchanger and the indoor heat exchanger; a bypass flow path connecting the discharge side of the compressor to a refrigerant pipe between the outdoor heat exchanger and the main expansion valve; an auxiliary heat exchanger arranged in the bypass flow path and having a heat storage material capable of exchanging heat with a portion of the refrigerant discharged from the compressor; a first bypass expansion valve arranged in the bypass flow path between the compressor and the auxiliary heat exchanger; and a second bypass expansion valve arranged in the bypass flow path between the auxiliary heat exchanger and the refrigerant pipe; a pressure sensor that detects the pressure of the refrigerant on the discharge side of the compressor; and a control unit that controls the openings of the main expansion valve, the first bypass expansion valve, and the second bypass expansion valve, respectively, in a heat storage heating operation mode in which the indoor heat exchanger and the auxiliary heat exchanger function as condensers and the outdoor heat exchanger functions as an evaporator, and the control unit controls the opening of the first bypass expansion valve based on a rate of change in the detection value of the pressure sensor. Refrigeration cycle equipment.

2. A refrigeration cycle apparatus as described in claim 1, wherein, in the heat storage heating operation mode, the control unit controls the opening of the first bypass expansion valve to decrease the opening degree of the first bypass expansion valve when the rate of change of the detection value of the pressure sensor is a positive value, and controls the opening of the first bypass expansion valve to increase the opening degree of the first bypass expansion valve when the rate of change of the detection value of the pressure sensor is a negative value.

3. A refrigeration cycle apparatus according to claim 1, wherein the control unit controls the opening of the first bypass expansion valve based on the detection value of the pressure sensor when the heat-storage heating operation mode is started.

4. A refrigeration cycle apparatus as claimed in any one of claims 1 to 3, wherein the control unit controls the opening of the second bypass expansion valve in a heat storage heating operation mode so that the subcooling of the refrigerant flowing out of the auxiliary heat exchanger reaches a preset target subcooling.

5. A refrigeration cycle device according to any one of claims 1 to 3, wherein the control unit calculates a theoretical discharge temperature, which is the discharge temperature when the refrigerant sucked into the compressor is saturated vapor, and controls the opening of the main expansion valve so that the temperature of the refrigerant discharged from the compressor becomes the theoretical discharge temperature.

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