air conditioner

Abstract

To provide an air conditioner that can maintain comfort and suppress increases in power consumption when starting low-temperature outdoor heating. [Solution] An air conditioner according to one embodiment of the present invention comprises a primary refrigerant circuit, a secondary refrigerant circuit, an indoor fan, a supply temperature sensor, and a control device. When the control device determines that there is a heating means for heating the secondary refrigerant at the start of heating operation, it executes a first low-temperature control mode in which, after the circulation pump of the secondary refrigerant circuit is started and the detected value of the supply temperature sensor is less than a threshold, the indoor fan is rotated at a first rotational speed after the compressor of the primary refrigerant circuit starts operating. When the control device determines that there is no heating means, it executes a second low-temperature control mode in which, after the circulation pump is started and the detected value of the supply temperature sensor is less than a threshold, the indoor fan is rotated at a second rotational speed lower than the first rotational speed until the compressor starts operating.

Description

Technical Field

[0001] The present invention relates to an air conditioner including a primary refrigerant circuit and a secondary refrigerant circuit.

Background Art

[0002] Conventionally, there is known a technique of reducing the rotational speed of an outdoor fan (blower) that forms an air flow in an outdoor heat exchanger that functions as an evaporator when starting heating in an intermediate expansion system (see, for example, Patent Document 1). By this, since an increase in the evaporation pressure can be suppressed, it is possible to suppress a decrease in reliability and comfort that may occur due to continuous operation for a long time in a state where the compressor cannot secure a pressure difference (outside the operating range).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the above technique, a pressure difference is secured by suppressing an increase in the evaporation pressure, but a pressure difference can also be secured by suppressing a decrease in the condensation pressure. For example, when starting heating in an intermediate expansion system under conditions where the outside air temperature is low, in order to suppress a decrease in the condensation pressure of the refrigerant in the water-cooled refrigerant heat exchanger, water, which is the heat exchange target of the high-pressure refrigerant, is heated, for example, by heat absorption from indoor air or an auxiliary heat source, and then the compressor is operated.

[0005] However, the method of heating water by absorbing heat from the indoor air has the problem that it takes time for the refrigerant temperature to rise because it takes time for the heat to be absorbed from the indoor air, thus reducing comfort. In this case, the absorption of heat from the indoor air can be promoted by rotating the indoor fan. On the other hand, the method of heating water by absorbing heat from an auxiliary heat source has the problem that the time it takes to heat the water is prolonged because the rotation of the indoor fan promotes the dissipation of heat into the indoor air, thus increasing the power consumption of the auxiliary heat source.

[0006] In view of the above circumstances, the object of the present invention is to provide an air conditioner that can suppress increases in comfort and power consumption when low-temperature outdoor heating is started. [Means for solving the problem]

[0007] An air conditioner according to one embodiment of the present invention comprises a primary refrigerant circuit, a secondary refrigerant circuit, an indoor fan, a supply temperature sensor, and a control device. The primary refrigerant circuit includes an outdoor unit having a compressor and an outdoor heat exchanger, and a refrigerant-to-refrigerant heat exchanger that exchanges heat between the primary refrigerant and the secondary refrigerant, through which the primary refrigerant circulates. The secondary refrigerant circuit includes an indoor unit connected to the refrigerant heat exchanger and having an indoor heat exchanger, and a circulation pump, through which the secondary refrigerant circulates. The indoor fan forms an airflow that passes through the indoor heat exchanger. The supply temperature sensor detects the temperature of the secondary refrigerant supplied to the indoor heat exchanger. The control device has a heater determination unit that determines whether or not there is a heating means for heating the secondary refrigerant, and controls the compressor, the circulation pump, and the indoor fan. The control device performs heating operation by causing the inter-refrigerant heat exchanger in the primary refrigerant circuit to function as a condenser, and by operating the circulation pump and the indoor fan. When it is determined that the heating means is present at the start of the heating operation, if the detected value of the supply temperature sensor is below a threshold after the circulation pump has started, a first low-temperature control mode is executed in which the indoor fan is rotated at a first rotational speed after the compressor has started operating. If it is determined that the heating means is not present, if the detected value of the supply temperature sensor is below a threshold after the circulation pump has started, a second low-temperature control mode is executed in which the indoor fan is rotated at a second rotational speed lower than the first rotational speed until the compressor starts operating.

[0008] The above-mentioned air conditioner rotates the indoor fan at a first rotational speed after the compressor starts operating in the first low-temperature control mode, and rotates the indoor fan at a second rotational speed until the compressor starts operating in the second low-temperature control mode. Therefore, it is possible to suppress increases in comfort and power consumption when starting low-temperature outdoor heating.

[0009] The outdoor unit may further include an outside temperature sensor for detecting the temperature of the outside air. The control device may execute the first low-temperature control mode or the second low-temperature control mode when the value detected by the outside temperature sensor is less than or equal to a predetermined value.

[0010] The control device may include an outdoor control device installed on the outdoor unit and an indoor control device installed on the indoor unit that controls the indoor fan.

[0011] The control device may further include an input unit for inputting information regarding the presence or absence of the heating means. The heater determination unit may determine the presence or absence of the heating means based on the information input to the input unit.

[0012] The first rotational speed may be set according to the operating load of the indoor unit. The second rotational speed may be set to a rotational speed lower than the minimum value of the first rotational speed.

[0013] The air conditioner may further include a return temperature sensor that detects the temperature of the secondary refrigerant flowing into the refrigerant intermediate heat exchanger. In the first low-temperature control mode, the control device may start the compressor when the detection value of the return temperature sensor reaches a first specified value.

[0014] In the second low-temperature control mode, the control device may start the compressor when the detection value of the return temperature sensor reaches a second specified value that is lower than the first specified value.

[0015] The indoor unit may further include a room temperature sensor that detects the indoor temperature. The control device may set the second specified value based on the detection value of the room temperature sensor.

Advantages of the Invention

[0016] According to the present invention, it is possible to suppress an increase in comfort and power consumption during startup of low-outdoor-temperature heating.

Brief Description of the Drawings

[0017] [Figure 1] It is a refrigerant-water circuit diagram of an air conditioner according to an embodiment of the present invention. [Figure 2] It is a block diagram showing the configuration of a control device. [Figure 3] It is a diagram showing an example of the timing chart of the operations of the compressor, indoor fan, and heater and the time change of the temperature of water (water temperature) circulating in the water circuit when the first low-temperature control mode is executed. [Figure 4] It is a diagram showing an example of the timing chart of the operations of the compressor and indoor fan and the time change of the temperature of water (water temperature) circulating in the water circuit when the second low-temperature control mode is executed. [Figure 5] It is a flowchart showing an example of the processing procedure at the start of heating operation executed in the control device. [Figure 6] It is a flowchart showing an example of the processing procedure of the first low-temperature control mode executed in the control device. [Figure 7]It is a flowchart showing an example of the processing procedure of the second low-temperature control mode executed in the control device.

Embodiments for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0019] FIG. 1 is a refrigerant-water circuit diagram of an air conditioner 100 according to an embodiment of the present invention. The air conditioner 100 of this embodiment is an air conditioning device of an indirect expansion system including an outdoor unit 2, a plurality (three in this embodiment) of indoor units 3a, 3b, 3c (hereinafter collectively referred to as indoor unit 3 unless otherwise individually described), a relay unit 50, and a control device 90. Further, the outdoor unit 2 and the relay unit 50 constitute a heat source module 55 in the air conditioner 100.

[0020] (Outdoor Unit) The outdoor unit 2 has a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an expansion valve 24, and an accumulator 25. By connecting these devices to each other with pipes and the relay unit 50 described later, a refrigerant circuit 20 (primary refrigerant circuit) in the refrigerant-water circuit of the air conditioner 100 is formed.

[0021] The compressor 21 is a variable-capacity compressor whose operating capacity can be varied by controlling the rotation speed with an inverter (not shown). The refrigerant discharge side of the compressor 21 is connected to port a of the four-way valve 22 by a discharge pipe 61. Also, the refrigerant suction side of the compressor 21 is connected to the refrigerant outflow side of the accumulator 25 by a suction pipe 65.

[0022] The four-way valve 22 is a valve for switching the direction of refrigerant flow and has four ports a, b, c, and d. Port a is connected to the refrigerant discharge side of the compressor 21 by the discharge pipe 61, as described above. Port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 23 by the refrigerant piping 62. Port c is connected to the refrigerant inlet side of the accumulator 25 by the refrigerant piping 66. And port d is connected to the gas refrigerant inlet and outlet 51b of the water refrigerant heat exchanger 51 in the relay unit 50, which will be described later, by the outdoor unit gas pipe 64.

[0023] The outdoor heat exchanger 23 exchanges heat between the refrigerant and the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 29, which will be described later. One of the refrigerant inlets and outlets of the outdoor heat exchanger 23 is connected to port b of the four-way valve 22 by refrigerant piping 62, as described above, and the other refrigerant inlet and outlet is connected to the liquid refrigerant inlet and outlet 51a of the water refrigerant heat exchanger 51 (inter-refrigerant heat exchanger) in the relay unit 50, which will be described later, by the outdoor unit liquid pipe 63.

[0024] The expansion valve 24 is, for example, an electronic expansion valve. The expansion valve 24 is located in the outdoor unit liquid pipe 63 and its opening can be adjusted to reduce the pressure of the refrigerant passing through it.

[0025] The outdoor fan 29 is made of resin and is located near the outdoor heat exchanger 23. The outdoor fan 29 is driven by a fan motor (not shown) and takes in outside air from an intake port (not shown) of the outdoor unit 2, and releases the outside air, which has exchanged heat with the refrigerant in the outdoor heat exchanger 23, to the outside of the outdoor unit 2 from an outlet (not shown) of the outdoor unit 2.

[0026] (indoor unit) Each indoor unit 3 has an indoor heat exchanger 31, an indoor fan 32, and an on / off valve 33. Each indoor unit 3a to 3c has the same configuration and, when connected to the relay unit 50, forms the water circuit 30 (secondary refrigerant circuit) in the refrigerant-water circuit of the air conditioner 100. The water circuit 30 has a circulation pump 34 that circulates water as a secondary refrigerant between the relay unit 50 and each indoor unit 3a to 3c.

[0027] The indoor heat exchanger 31 is a water-air heat exchanger that exchanges heat between water and outside air taken into the indoor unit 3 by the rotation of the indoor fan 32. The inlet side of the indoor heat exchanger 31 is connected to the outlet 51d of the water-refrigerant heat exchanger 51 of the relay unit 50 by the first water pipe 11 and the first water branch pipe 111 that branches off from the first water pipe 11. The outlet side of the indoor heat exchanger 31 is connected to the inlet 51c of the water-refrigerant heat exchanger 51 by the second water pipe 12 and the second water branch pipe 121 that branches off from the second water pipe 12. The circulation pump 34 is located in the second water pipe 12.

[0028] The indoor fan 32 is made of resin and is located near the indoor heat exchanger 31. The indoor fan 32 is driven by a fan motor (not shown) and takes in indoor air from an intake port (not shown) of the indoor unit 3, and blows the air, which has exchanged heat with water in the indoor heat exchanger 31, into the room from an outlet (not shown) of the indoor unit 3. The indoor fan 32, together with the indoor heat exchanger 31, constitutes a fan coil unit (FCU).

[0029] The shut-off valve 33 is located in the first water branch piping 111 and is a shut-off valve capable of blocking the flow of water from the outlet 51d of the water refrigerant heat exchanger 51 to the indoor heat exchanger 31. The opening and closing of the shut-off valve 33 is controlled individually for each indoor unit 3a to 3c, and the shut-off valve 33 of the indoor unit 3 that is stopped (or will be stopped) is switched to the closed state.

[0030] Alternatively, a flow control valve whose opening degree can be arbitrarily adjusted may be used instead of the on / off valve 33. In this case, the flow rate of water flowing through the indoor heat exchanger 31 can be controlled according to the opening degree of the flow control valve. As a result, the flow rate of water flowing into the indoor heat exchanger 31 can be adjusted for each indoor unit 3, improving responsiveness to required capacity and enhancing comfort.

[0031] (Relay unit) The relay unit 50 has a water refrigerant heat exchanger 51 and is connected to the outdoor unit 2. In this embodiment, as shown in Figure 1, the relay unit 50 is described as being installed outside the outdoor unit 2, but the relay unit 50 may also be installed inside the outdoor unit 2.

[0032] The water-refrigerant heat exchanger 51 is, for example, a double-tube heat exchanger or a plate-type heat exchanger, and has a refrigerant-side flow path 511, a water-side flow path 512, a liquid refrigerant inlet / outlet 51a, a gas refrigerant inlet / outlet 51b, a water inlet 51c, and a water outlet 51d.

[0033] One end of the refrigerant-side flow path 511 is connected to the liquid refrigerant inlet / outlet 51a, and the other end is connected to the gaseous refrigerant inlet / outlet 51b. The water-side flow path 512 is connected to the water inlet 51c, and the other end is connected to the water outlet 51d. In the water-refrigerant heat exchanger 51, heat exchange occurs between the refrigerant flowing through the refrigerant-side flow path 511 and the water flowing through the water-side flow path 512.

[0034] The liquid refrigerant inlet / outlet 51a is connected to the other refrigerant inlet / outlet of the outdoor heat exchanger 23 by the outdoor unit liquid pipe 63. The gas refrigerant inlet / outlet 51b is connected to port d of the four-way valve 22 by the outdoor unit gas pipe 64. The water inlet 51c is connected to the indoor heat exchanger 31 of each indoor unit 3 by the second water pipe 12 and the second water branch pipe 121. The water outlet 51d is connected to the indoor heat exchanger 31 of each indoor unit 3 by the first water pipe 11 and the first water branch pipe 111.

[0035] The circulation pump 34 is a variable-capacity pump driven by a motor (not shown). When the circulation pump 34 is driven, water flows out from the outlet 51d of the water-refrigerant heat exchange unit 51 to the first water pipe 11, and then flows into the inlet 51c of the water-refrigerant heat exchange unit 51 via the first water branch pipe 111, the indoor heat exchanger 31, the second water branch pipe 121, and the second water pipe 12, thus circulating the water.

[0036] The relay unit 50 further includes a receiving unit 53 that receives input instructions from the user. The receiving unit 53 may be an input operation unit that receives input instructions from the user, or it may be a receiving device that receives an input signal corresponding to the input instructions generated by the input operation unit. The input instructions include, for example, an instruction value relating to the set temperature of each indoor space in which the indoor unit 3 is installed, or the temperature of the water circulating in the water circuit 30 (the temperature of the water flowing out from the water refrigerant heat exchanger 51). When the receiving unit 53 of the relay unit 50 receives the input instructions, it transmits a message to the control device 90 to that effect.

[0037] The flow rate of water circulating through the circulation pump 34 is controlled by the rotation speed of the motor mentioned above. This ensures that water is supplied to each indoor unit 3 at the same flow rate. In the example shown in Figure 1, the circulation pump 34 is located in the second water pipe 12, but it may be located in the first water pipe 11 instead, or inside the relay unit 50.

[0038] The water circuit 30 may be equipped with an auxiliary heat source, such as a heater 36, as a heating means for heating the secondary refrigerant (water) circulating in the water circuit 30. The heater 36 is installed, for example, in the first water piping 11. The heater 36 may be located inside the relay unit 50.

[0039] The heater 36 is not limited to being installed in the first water pipe 11, but may also be installed in the second water pipe 12, the first water branch pipe 111, or the second water branch pipe 121. In addition to the heater, a burner or the like can be used as a heating means. Furthermore, the installation of a heating means is optional, and the air conditioner 100 does not need to be equipped with a heating means.

[0040] (Sensors) The air conditioner 100 is equipped with various sensors. In the outdoor unit 2, the discharge pipe 61 is equipped with a high-pressure sensor 71 for detecting the pressure of the refrigerant discharged from the compressor 21 and a discharge temperature sensor 72 for detecting the temperature of the refrigerant discharged from the compressor 21. The suction pipe 65 is equipped with a low-pressure sensor 73 for detecting the pressure of the refrigerant drawn into the compressor 21 and a suction temperature sensor 74 for detecting the temperature of the refrigerant drawn into the compressor 21.

[0041] The outdoor heat exchanger 23 is equipped with a heat exchanger temperature sensor 75 for detecting the temperature of the refrigerant flowing through the outdoor heat exchanger 23. Furthermore, an outside air temperature sensor 76 is provided near the intake port (not shown) of the outdoor unit 2 for detecting the temperature of the outside air flowing into the outdoor unit 2, i.e., the outside air temperature.

[0042] The indoor unit 3 may be equipped with a room temperature sensor 77 that detects the temperature of the air flowing into the indoor unit 3 (room temperature). The room temperature sensor 77 corresponds to a detection means for detecting the indoor load. The indoor load is calculated based on the difference between the temperature of the room in which the indoor unit 3 is installed (room temperature) and the set temperature of the indoor unit 3 (target room temperature). The room temperature sensor 77 may be provided only in some of the indoor units 3a to 3c, or it may not be provided in any of the indoor units 3a to 3c.

[0043] The water circuit 30 is equipped with a supply temperature sensor 78 and a return temperature sensor 79. The supply temperature sensor 78 is installed in the first water pipe 11 connected to the outlet 51d of the water refrigerant heat exchanger 51 and detects the temperature of the water supplied to the indoor heat exchanger 31. The return temperature sensor 79 is installed in the second water pipe 12 connected to the inlet 51c of the water refrigerant heat exchanger 51 and detects the temperature of the water flowing into the water refrigerant heat exchanger 51.

[0044] (Control device) The control device 90 is, for example, an outdoor control device provided in the outdoor unit 2, and is mounted on a control board housed in an electrical component box (not shown) of the outdoor unit 2.

[0045] Figure 2 is a block diagram showing the configuration of the control device 90. As shown in the figure, the control device 90 includes a CPU 91, a storage unit 92, a communication unit 93, a sensor input unit 94, and a rotation speed detection unit 95.

[0046] The memory unit 92 is a non-volatile memory such as flash memory, and stores the control program and control parameters of the outdoor unit 2, detected values ​​corresponding to detection signals from various sensors, the control status of the compressor 21 and outdoor fan 29, the rotation speed of the indoor fan 32 acquired via the communication unit 93, and the control status of each indoor unit 3a to 3c, including the operating mode entered by the user.

[0047] The communication unit 93 is an interface for communication with the indoor unit 3 and the relay unit 50. The sensor input unit 94 takes in the detection results from various sensors of the outdoor unit 2 and outputs them to the CPU 91. The rotation speed detection unit 95 detects the rotation speed of the compressor 21 motor 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 motor's drive shaft, or it 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.

[0048] 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 memory unit 92. The program is installed in the control unit 90, for example, via various storage media. Alternatively, the program may be installed via the internet or the like.

[0049] The CPU 91 receives the detection results from each sensor of the outdoor unit 2 described above via the sensor input unit 94. Furthermore, the CPU 91 receives control signals transmitted from the indoor unit 3 and the relay unit 50 (receiving unit 53) via the communication unit 93. The control signals transmitted from the indoor unit 3 include the required operating capacity requested by the indoor unit 3 (total indoor load of indoor units 3a to 3c). The control signals transmitted from the relay unit 50 (receiving unit 53) include instruction values ​​regarding the temperature of the water circulating in the water circuit 30 (temperature of the water flowing out of the water refrigerant heat exchanger 51) and user input instructions. The control signals transmitted from the relay unit 50 may also include the control signals transmitted from the indoor unit 3 described above.

[0050] Based on the received detection results and control signals, the CPU 91 controls the drive of the compressor 21, outdoor fan 29, indoor fan 32, and circulation pump 34, for example, by setting the indicated rotational speed at which these devices are driven. The CPU 91 also controls the switching of the four-way valve 22 based on the received detection results and control signals. Furthermore, the CPU 91 controls the opening degree of the expansion valve 24 and the opening and closing of the on-off valve 33, etc., based on the received detection results and control signals.

[0051] The CPU 91 also has a heater determination unit 911 as one of its functional blocks, which determines the presence or absence of the heater 36. The heater determination unit 911 determines the presence or absence of the heater 36 when the air conditioner 100 is installed, and the determination result is pre-set in the storage unit 92.

[0052] The heater determination unit 911 may determine the presence or absence of the heater 36 based on an input operation by the worker installing the air conditioner 100, or it may determine the presence or absence of the heater 36 based on the detection result of whether or not there is a connection between the heater drive circuit mounted on the relay unit 50 and the heater 36. The determination result of the presence or absence of the heater 36 is basically not changed after the air conditioner 100 is installed. However, if the heater 36 is added later or removed, the determination result may be changed based on the determination method described above.

[0053] In addition to the control device 90 installed on the outdoor unit 2, indoor control devices 38 may be installed on each indoor unit 3a to 3c. The indoor control device 38 may be equipped with a thermostat for controlling the airflow (rotation speed) of the indoor fan 32 and the opening and closing of the on-off valve 33. The indoor control device 38 may perform the above-mentioned various controls based on control commands from the control device 90, or independently of the control device 90.

[0054] [Basic operation of an air conditioner] Next, we will explain the basic operation of the air conditioner 100. The operation of the air conditioner 100 during cooling and heating operations will be described below.

[0055] (Air conditioning operation) When the air conditioner 100 is in cooling operation, the four-way valve 22 is switched to the state shown by the solid line in Figure 1, that is, port a and port b are in communication, and port c and port d are in communication, and the compressor 21 and circulation pump 34 are driven. When the compressor 21 is driven, refrigerant circulates in the refrigerant circuit 20, and when the circulation pump 34 is driven, water circulates in the water circuit 30. As a result, the outdoor heat exchanger 23 functions as a condenser, and the water-refrigerant heat exchanger 51 functions as an evaporator.

[0056] The rotational speed of the compressor 21 and the flow rate of the circulation pump 34 are determined according to information regarding the indoor load or the heat load of the water circuit 30. Here, "indoor load" refers to the load calculated based on the detection results of various sensors in the indoor units 3a to 3c. Also, "heat load" refers to the load calculated based on the detection results of various sensors in the water circuit 30. Here, we will explain using the example where all indoor units 3 are performing indoor cooling.

[0057] The refrigerant, compressed by the compressor 21 to a high temperature and high pressure, is discharged from the compressor 21, flows through the discharge pipe 61, enters the four-way valve 22, flows from the four-way valve 22 into the refrigerant piping 62, and enters the outdoor heat exchanger 23. The refrigerant that enters the outdoor heat exchanger 23 condenses by exchanging heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 29.

[0058] The refrigerant flowing out from the outdoor heat exchanger 23 flows through the outdoor unit liquid pipe 63 and is depressurized as it passes through the expansion valve 24. Here, the opening of the expansion valve 24 is set so that the superheat (degree of superheating) of the refrigerant drawn into the compressor 21 reaches the target superheat, which is necessary to achieve the set temperature during cooling operation in the room where the indoor unit 3 is installed.

[0059] The refrigerant that passes through the expansion valve 24 and flows through the outdoor unit liquid pipe 63 flows into the liquid refrigerant inlet / outlet 51a of the water refrigerant heat exchanger 51. The refrigerant that flows into the liquid refrigerant inlet / outlet 51a passes through the refrigerant-side flow path 511 and exchanges heat with the water flowing through the water-side flow path 512, evaporating and flowing into the outdoor unit gas pipe 64 from the gas refrigerant inlet / outlet 51b of the water refrigerant heat exchanger 51. The refrigerant that flows into the outdoor unit gas pipe 64 flows through the four-way valve 22, refrigerant piping 66, accumulator 25 and suction pipe 65, and is drawn into the compressor 21 and compressed again.

[0060] Meanwhile, the water cooled as it flows through the water-side channel 512 flows out from the outlet 51d of the water refrigerant heat exchanger 51 into the first water pipe 11. The water that flows into the first water pipe 11 flows into the indoor heat exchanger 31 of each indoor unit 3 via the first water branch pipe 111 and the open on-off valve 33, and the rotation of the indoor fan 32 cools the indoor air passing through the indoor heat exchanger 31. This cools the room in which the indoor unit 3 is installed.

[0061] Water flowing out of the indoor heat exchanger 31 of each indoor unit 3 joins the second water pipe 12 via the second water branch pipe 121 and is drawn into the circulation pump 34. The water drawn into the circulation pump 34 is sent to the inlet 51c of the water-refrigerant heat exchanger 51, passes through the water-side flow path 512, is cooled again by the refrigerant flowing through the refrigerant-side flow path 511, and then flows out from the outlet 51d towards the indoor unit 3.

[0062] (Heating operation) When the air conditioner 100 is operating in heating mode, the four-way valve 22 is switched to the state shown by the dashed line in Figure 1, that is, port a and port d are in communication, and port b and port c are in communication, and the compressor 21 and circulation pump 34 are driven. When the compressor 21 is driven, refrigerant circulates in the refrigerant circuit 20, and when the circulation pump 34 is driven, water circulates in the water circuit 30. As a result, the outdoor heat exchanger 23 functions as an evaporator, and the water-refrigerant heat exchanger 51 functions as a condenser.

[0063] The rotational speed of the compressor 21 and the flow rate of the circulation pump 34 are determined according to information regarding the indoor load or the heat load of the water circuit 30. Here, we will explain using the example where all indoor units 3 are performing indoor heating.

[0064] The refrigerant, compressed by the compressor 21 to a high temperature and high pressure, is discharged from the compressor 21, flows through the discharge pipe 61, enters the four-way valve 22, flows from the four-way valve 22 to the outdoor unit gas pipe 64, and enters the gas refrigerant inlet / outlet 51b of the water refrigerant heat exchanger 51. The refrigerant that enters the gas refrigerant inlet / outlet 51b passes through the refrigerant-side flow path 511 and heats the water flowing through the water-side flow path 512. The refrigerant that has condensed through heat exchange with the water flowing through the water-side flow path 512 flows out of the liquid-side inlet / outlet 51a of the water refrigerant heat exchanger 51 into the outdoor unit liquid pipe 63.

[0065] The refrigerant that flows out into the outdoor unit liquid pipe 63 is depressurized as it passes through the expansion valve 24. Here, the opening of the expansion valve 24 is set so that the subcooling (degree of supercooling) of the refrigerant flowing out from the water-refrigerant heat exchanger 51 becomes the target subcooling, which is necessary to achieve the set temperature during heating operation in the room where the indoor unit 3 is installed.

[0066] The refrigerant that passes through the expansion valve 24 and flows through the outdoor unit liquid pipe 63 flows into the outdoor heat exchanger 23. The refrigerant that flows into the outdoor heat exchanger 23 exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 29 and evaporates. The refrigerant that flows out of the outdoor heat exchanger 23 flows through the refrigerant piping 62 and is drawn into the compressor 21 via the four-way valve 22, refrigerant piping 66, accumulator 25 and suction pipe 65, where it is compressed again.

[0067] Meanwhile, the water heated as it flows through the water-side channel 512 flows out from the outlet 51d of the water-refrigerant heat exchanger 51 into the first water pipe 11. The water that flows into the first water pipe 11 flows into the indoor heat exchanger 31 via the first water branch pipe 111 and the open-off valve 33, and the rotation of the indoor fan 32 heats the indoor air passing through the indoor heat exchanger 31. This provides heating to the room in which the indoor unit 3 is installed.

[0068] The water flowing out of the indoor heat exchanger 31 joins the second water pipe 12 via the second water branch pipe 121 and is drawn into the circulation pump 34. The water drawn into the circulation pump 34 is sent to the inlet 51c of the water-refrigerant heat exchanger 51, passes through the water-side flow path 512, is heated again by the refrigerant flowing through the refrigerant-side flow path 511, and then flows out from the outlet 51d toward the indoor unit 3.

[0069] For example, when starting up the heating system under low ambient temperature conditions, if the temperature of the water exchanging heat with the refrigerant in the water-refrigerant heat exchanger, which functions as a condenser, is low, the condensation pressure (condensation temperature) will not rise easily. If the condensation pressure of the refrigerant in the water-refrigerant heat exchanger is too low, the reliability and comfort of the compressor may decrease, which can occur if the compressor continues to operate outside its operating range. The operating range of the compressor refers to the range of pressure difference (compression ratio) between the high-pressure and low-pressure sides that is predetermined as part of the compressor specifications from a reliability standpoint.

[0070] Therefore, in order to suppress the decrease in condensation pressure of the water refrigerant heat exchanger when the heating system is started, one possible method is to heat the water, which is the target of heat exchange with the high-pressure refrigerant, by means of heat absorption from, for example, indoor air or an auxiliary heat source, before operating the compressor.

[0071] However, the method of heating water by absorbing heat from the indoor air has the problem that it takes time for the refrigerant temperature to rise because it takes time for the heat to be absorbed from the indoor air, thus reducing comfort. In this case, the absorption of heat from the indoor air can be promoted by rotating the indoor fan. On the other hand, the method of heating water by absorbing heat from an auxiliary heat source has the problem that the time it takes to heat the water is prolonged because the rotation of the indoor fan promotes the dissipation of heat into the indoor air, thus increasing the power consumption of the auxiliary heat source.

[0072] To resolve these issues, the control device 90 optimizes the compressor startup timing and the indoor fan speed according to the presence or absence of an auxiliary heat source when the operating conditions at the start of heating operation meet predetermined conditions, thereby suppressing a decrease in comfort and an increase in power consumption. The details of the control device 90 will be described below.

[0073] [Control device details] In this embodiment, when the control device 90 determines that there is an auxiliary heat source (heater 36) at the start of heating operation, it executes the first low-temperature control mode described later, and when it determines that there is no auxiliary heat source, it executes the second low-temperature control mode described later.

[0074] (First low-temperature control mode) Figure 3 shows an example of the timing chart of the operation of the compressor 21, indoor fan 32, and heater 36 during the execution of the first low-temperature control mode, as well as the time change of the water temperature (water temperature) circulating in the water circuit 30. For the sake of explanation, the room temperature is shown as a constant value here.

[0075] When heating operation starts at time t0, the circulation pump 34 is activated to circulate the water in the water circuit 30. If the water circuit 30 is equipped with a heater 36, the heater 36 is activated together with the circulation pump 34 to heat the water in the water circuit 30. By raising the water temperature in advance before starting the compressor 21 in this way, the water temperature can be brought closer to the recommended lower limit temperature for starting the compressor 21 (for example, 20°C). Here, the recommended lower limit temperature for starting the compressor 21 is the water temperature set in order to suppress the decrease in refrigerant condensation pressure (and consequently the decrease in compressor reliability) that occurs when the water temperature flowing into the water-refrigerant heat exchanger 51 is low.

[0076] On the other hand, if the indoor fan 32 is operated before the compressor 21 is started, when the water temperature is higher than the room temperature (during the period t1-t2 indicated by arrow A in Figure 3), heat is released from the water into the indoor air. This prolongs the time it takes for the water temperature to reach the recommended lower limit temperature for starting the compressor 21, resulting in reduced comfort and increased power consumption of the heater 36.

[0077] Therefore, when the control device 90 determines that the heater 36 is present at the start of heating operation, after the circulation pump 34 is started, if the value detected by the supply temperature sensor 78 is less than a threshold (Th1), it executes a first low-temperature control mode in which the compressor 21 starts operating and the indoor fan 32 rotates at a first rotational speed (R1).

[0078] The threshold value (Th1) is not particularly limited as long as it is higher than the recommended lower limit temperature for starting the compressor 21, and can be set according to the specifications of the compressor 21. In this embodiment, for example, it is set to 22°C.

[0079] Furthermore, the first rotational speed (R1) mentioned above is the rotational speed of the indoor fan 32, which is set according to the operating load of the indoor unit 3, and is not particularly limited as long as it is within the set range.

[0080] In the case where the water circuit 30 has a heater 36, by operating the indoor fan 32 after the compressor 21 starts operating (and not operating the indoor fan 32 until the compressor 21 starts operating), the rise in water temperature can be accelerated compared to when the indoor fan 32 is operated before the compressor 21 starts. This helps to suppress a decrease in comfort and also suppress an increase in the power consumption of the heater 36.

[0081] The control device 90 may execute the first low-temperature control mode when the value detected by the outside air temperature sensor 76 is below a predetermined value (Th2). When starting heating under low outside temperatures, the time required for the compressor 21 to reach the lower limit of the compression ratio in its operating range is longer, so adopting the first low-temperature control mode when the outside air temperature is below a predetermined value (Th2) is highly effective. The predetermined value (Th2) is, for example, 2°C.

[0082] The timing for starting the operation of the indoor fan 32 may be at the same time as the start of operation of the compressor 21, or it may be after a predetermined time has elapsed since the start of operation of the compressor 21. Similarly, the timing for stopping the operation of the heater 36 may be at the same time as the start of operation of the compressor 21, or it may be after a predetermined time has elapsed since the start of operation of the compressor 21.

[0083] The indoor fan 32 may be controlled by the outdoor control device 90, or it may be controlled by the indoor control device 38 based on control commands from the control device 90.

[0084] On the other hand, the timing for starting the operation of the compressor 21 may be determined based on the temperature of the water flowing into the water refrigerant heat exchanger 51. In this embodiment, the control device 90 starts the compressor 21 when the value detected by the return temperature sensor 79 reaches a predetermined first specified value (T1).

[0085] The first specified value (T1) is preferably the recommended lower limit temperature for starting the compressor 21, for example, 20°C. This allows the heat source to be switched from the heater 36 to the heat source module 55 (Figure 1) at an appropriate timing, thereby suppressing an increase in the power consumption of the heater 36 and preventing a decrease in the reliability of the compressor 21.

[0086] (Second low-temperature control mode) Figure 4 shows an example of the timing chart of the operation of the compressor 21 and the indoor fan 32, and the time change of the water temperature (water temperature) circulating in the water circuit 30 during the execution of the second low-temperature control mode. For the sake of explanation, the room temperature is shown as a constant value here.

[0087] If the water circuit 30 does not have a heater 36, operating the indoor fan 32 together with the circulation pump 34 causes the water in the water circuit 30 to absorb heat from the indoor air, raising the water temperature. By raising the water temperature in advance before starting the compressor 21 in this way, the water temperature can be brought closer to the recommended lower limit temperature for starting the compressor 21 (for example, 20°C).

[0088] On the other hand, if the rotation speed of the indoor fan 32 is too high, the indoor air (cool air) that has been cooled by the water will be blown back into the room, reducing comfort.

[0089] Therefore, when the control device 90 determines that there is no heater 36 at the start of heating operation, after the circulation pump 34 is started, if the detected value of the supply temperature sensor is less than the threshold (Th1), it executes a second low-temperature control mode in which it rotates the indoor fan 32 at a second rotational speed (R2) lower than the first rotational speed (R1) until the compressor 21 starts operating.

[0090] The threshold (Th1) is the same as the threshold (Th1) used in the first low-temperature control mode, but it is more preferable to set it based on the detection value of the room temperature sensor 77, and is set to a temperature, for example, 3°C lower than the room temperature. By making the threshold (Th1) variable according to the temperature of the indoor air that is the object of heat absorption, heat dissipation from water to the indoor air can be suppressed.

[0091] Furthermore, the second rotational speed (R2) is not particularly limited as long as it is a rotational speed that can suppress the decrease in comfort of the indoor space. For example, it is set to a rotational speed such that cool air does not reach the indoor space in which the indoor unit 3 is installed, that is, a rotational speed lower than the lower limit of the rotational speed set according to the operating load of the indoor unit 3 (the minimum value of the first rotational speed (R1)).

[0092] In the case where there is no heater 36 in the water circuit 30, the indoor fan 32 can be rotated at a second speed until the compressor 21 starts operating, allowing the water to absorb heat from the indoor air and promoting a rise in water temperature. This helps to suppress a decrease in comfort.

[0093] Similarly, in the second low-temperature control mode, the indoor fan 32 may be controlled by the control device 90, which is an outdoor control device, or it may be controlled by the indoor control device 38 based on control commands from the control device 90.

[0094] The control device 90 may also execute the second low-temperature control mode when the value detected by the ambient temperature sensor 76 is less than or equal to a predetermined value (Th2), similar to the first low-temperature control mode described above. In this case as well, the effectiveness of adopting the second low-temperature control mode can be increased.

[0095] On the other hand, the timing for starting the operation of the compressor 21 may be determined based on the temperature of the water flowing into the water refrigerant heat exchanger 51, similar to the first low-temperature control mode. In this embodiment, the control device 90 starts the compressor 21 when the value detected by the return temperature sensor 79 reaches a predetermined second specified value (T2).

[0096] The second specified value (T2) is preferably the recommended lower limit temperature for starting the compressor 21, but it is often difficult to raise the water temperature to the recommended lower limit temperature for starting by the operation of the indoor fan 32 alone. For this reason, the second specified value (T2) is set to a lower temperature than the first specified value (T1), and its value is not particularly limited as long as it is a temperature that does not impair the reliability of the compressor 21 (a temperature that does not prolong the operating period outside the operating range of the compressor 21), for example, 9°C.

[0097] Alternatively, the control device 90 may set a second specified value (T2) based on the value detected by the room temperature sensor 77. By making the second specified value (T2), which is the starting condition for the compressor 21, variable according to the temperature of the room air to be absorbed, it is possible to reliably start the compressor 21 while maximizing the amount of heat absorbed from the room temperature. More specifically, the second specified value (T2) can be set to a temperature, for example, 3°C lower than the room temperature.

[0098] Alternatively, after operating the outdoor fan 32 at a second rotational speed (R2), the compressor 21 may be started when the rate of change over time (slope) of the value detected by the supply temperature sensor 78 falls below a predetermined level. In this case, the control device 90 acquires the value detected by the supply temperature sensor 78 at a predetermined period (e.g., 0.5 seconds) and stores it in the storage unit 92. The compressor 21 is started when the slope of the supply temperature calculated using the current supply temperature and the past supply temperature (e.g., 60 seconds ago) stored in the storage unit 92 falls below a predetermined level (e.g., 1°C / minute or less).

[0099] After the compressor 21 is started, the control device 90 sets the rotational speed of the indoor fan 32 from the second rotational speed (R2) to the first rotational speed (R1), that is, to an airflow rate corresponding to the indoor load.

[0100] Figure 5 is a flowchart showing an example of the processing procedure performed by the control device 90 when heating operation starts.

[0101] When heating operation begins, the control device 90 operates the circulation pump 34 to circulate water in the water circuit 20 (ST101).

[0102] The control device 90 determines whether the value detected by the supply temperature sensor 78 is less than a threshold (Th1) (ST102). If the detected value is equal to or greater than the threshold (Th1) (No in ST102), it starts the compressor 21 and begins normal heating operation without executing either the first low-temperature control mode or the second low-temperature control mode (ST107). On the other hand, when the control device 90 determines that the value detected by the supply temperature sensor 78 is less than a threshold (Th1) (Yes in ST102), it determines whether the value detected by the outside air temperature sensor 76 is less than or equal to a predetermined value (Th2) (ST103).

[0103] When the control device 90 determines that the value detected by the outside air temperature sensor 76 exceeds a predetermined value (Th2) (No in ST103), it starts the compressor 21 and begins normal heating operation without executing either the first low-temperature control mode or the second low-temperature control mode (ST107). On the other hand, when the control device 90 determines that the value detected by the outside air temperature sensor 76 is less than or equal to the predetermined value (Th2) (Yes in ST103), it determines whether or not a heater 36 is installed in the water circuit 30 (ST104).

[0104] Note that the order of ST102 and ST103 may be reversed, and ST103 may be omitted.

[0105] When the control device 90 determines that the heater 36 is installed (Yes in ST104), it executes the first low-temperature control mode (ST105), and when it determines that the heater 36 is not installed (No in ST104), it executes the second low-temperature control mode (ST106).

[0106] Figure 6 is a flowchart showing an example of the processing procedure for the first low-temperature control mode executed in the control device 90.

[0107] In the first low-temperature control mode, the control device 90 activates the heater 36 (ST201). After a predetermined time (e.g., 60 seconds) has elapsed (Yes in ST202), the control device 90 determines whether the value detected by the return temperature sensor 79 is equal to or greater than the first specified value (T1) (ST203). If the value detected by the return temperature sensor 79 is less than the first specified value (T1) (No in ST203), the control device 90 returns to ST202. If it is equal to or greater than the first specified value (T1) (Yes in ST203), the control device 90 starts the compressor 21 (ST204) and then operates the indoor fan 32 at a first rotational speed (R1). This ends the first low-temperature control mode, and the system transitions to normal heating operation.

[0108] Figure 7 is a flowchart showing an example of the processing procedure for the second low-temperature control mode executed in the control device 90.

[0109] In the second low-temperature control mode, the control device 90 operates the indoor fan 32 at a second rotational speed (R2) (ST301). After a predetermined time (for example, 60 seconds) has elapsed (Yes in ST203), the control device 90 determines whether the value detected by the return temperature sensor 79 is equal to or greater than the second specified value (T2) (ST303). If the value detected by the return temperature sensor 79 is less than the second specified value (T2) (No in ST303), the control device 90 returns to ST302. If it is equal to or greater than the second specified value (T2) (Yes in ST303), the compressor 21 is started (ST304), and then the indoor fan 32 operates at a first rotational speed (R1). This ends the second low-temperature control mode, and the system transitions to normal heating operation.

[0110] Although embodiments of the present invention have been described above, it goes without saying that the present invention is not limited to the embodiments described above and can be modified in various ways.

[0111] For example, in the above embodiment, the number of indoor units 3 connected to the relay unit was set to 3, but this is not limited to this; it is sufficient to have at least one indoor unit connected.

[0112] Furthermore, although the above embodiments have described an air conditioner equipped with a secondary refrigerant circuit using water as the secondary refrigerant as an example, the secondary refrigerant may be a refrigerant other than water. [Explanation of symbols]

[0113] 2…Outdoor unit 3(3a~3c)…Indoor unit 20…Refrigerant circuit (primary refrigerant circuit) 21... Compressor 23…Outdoor heat exchanger 30...Water circuit (secondary refrigerant circuit) 31…Indoor heat exchanger 32…Indoor fan 34…Circulation pump 36... Heater 38... Indoor control unit 51…Water-refrigerant heat exchanger (inter-refrigerant heat exchanger) 76... Outdoor temperature sensor 77... Room temperature sensor 78... Supply temperature sensor 79...Return temperature sensor 90...Control device (outdoor control device) 100... Air conditioner

Claims

1. An outdoor unit having a compressor and an outdoor heat exchanger, and a refrigerant-to-refrigerant heat exchanger that exchanges heat between a primary refrigerant and a secondary refrigerant, and a primary refrigerant circuit through which the primary refrigerant circulates, The indoor unit includes an indoor unit connected to the aforementioned refrigerant heat exchanger and having an indoor heat exchanger, and a circulation pump, and a secondary refrigerant circuit through which the secondary refrigerant circulates. An indoor fan that forms an airflow through the indoor heat exchanger, A supply temperature sensor for detecting the temperature of the secondary refrigerant supplied to the indoor heat exchanger, A control device that controls the compressor, the circulation pump, and the indoor fan, having a heater determination unit that determines whether or not there is a heating means for heating the secondary refrigerant, Equipped with, The control device is In the primary refrigerant circuit, the interrefrigerant heat exchanger is made to function as a condenser, and the circulation pump and the indoor fan are operated to perform heating operation. At the start of the aforementioned heating operation, When it is determined that the heating means is present, after the circulation pump is started, if the detected value of the supply temperature sensor is less than the threshold, a first low-temperature control mode is executed in which the compressor starts operating and the indoor fan rotates at a first rotational speed. If it is determined that there is no heating means, after the circulation pump is started, if the detected value of the supply temperature sensor is below the threshold, a second low-temperature control mode is executed in which the indoor fan is rotated at a second rotational speed lower than the first rotational speed until the compressor starts operating. Air conditioner.

2. An air conditioner according to claim 1, The outdoor unit further includes an outside temperature sensor for detecting the temperature of the outside air. The control device executes the first low-temperature control mode or the second low-temperature control mode when the value detected by the ambient temperature sensor is less than or equal to a predetermined value. Air conditioner.

3. An air conditioner according to claim 1, The control device comprises an outdoor control device installed on the outdoor unit and an indoor control device installed on the indoor unit that controls the indoor fan. Air conditioner.

4. An air conditioner according to claim 1, The control device further includes an input unit for inputting information regarding the presence or absence of the heating means, The heater determination unit determines the presence or absence of the heating means based on the information input to the input unit. Air conditioner.

5. An air conditioner according to claim 1, The first rotational speed is set according to the operating load of the indoor unit. The second rotational speed is set to a rotational speed lower than the minimum value of the first rotational speed. Air conditioner.

6. An air conditioner according to claim 1, The system further includes a return temperature sensor for detecting the temperature of the secondary refrigerant flowing into the refrigerant heat exchanger, In the first low-temperature control mode, the control device starts the compressor when the value detected by the return temperature sensor reaches a first specified value. Air conditioner.

7. An air conditioner according to claim 6, In the second low-temperature control mode, the control device starts the compressor when the value detected by the return temperature sensor reaches a second specified value that is lower than the first specified value. Air conditioner.

8. An air conditioner according to claim 7, The indoor unit further includes a room temperature sensor for detecting the indoor temperature. The control device sets the second specified value based on the value detected by the room temperature sensor. Air conditioner.

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