JP7467827B2 - Air conditioners - Google Patents

Description

The present invention relates to an air conditioner.

In an air conditioner having an outdoor unit and an indoor unit, generally, when the indoor temperature detected by the indoor unit during cooling operation falls below a predetermined temperature, for example 1°C, below the set temperature that is the target value for this indoor temperature, or when the indoor temperature during heating operation exceeds the set temperature by a predetermined temperature, for example 1°C, the compressor mounted in the outdoor unit is stopped and the indoor fan mounted in the indoor unit is stopped, thereby stopping the air conditioning operation of the air conditioner in a so-called thermo-off state. Then, when the indoor temperature rises above the set temperature during cooling operation, or when the indoor temperature falls below the set temperature during heating operation, the compressor and indoor fan are restarted, and the air conditioning operation of the air conditioner is resumed in a so-called thermo-on state (see, for example, Patent Document 1).

JP 2009-79847 A

In the air conditioner that goes into the thermo-off state or thermo-on state during the above-mentioned air conditioning operation, even if the compressor speed is set to the minimum speed, that is, even if the indoor unit is only exerting the minimum air conditioning capacity, if the load of the room in which the indoor unit of the air conditioner is installed (hereinafter referred to as the air conditioning load) is small, the air conditioning capacity exerted may be greater than the air conditioning load. If the compressor speed is set to the minimum speed but the air conditioning capacity exerted is greater than the air conditioning load, the indoor temperature during cooling operation is likely to fall below the specified temperature rather than the set temperature, or the indoor temperature during heating operation is likely to exceed the specified temperature rather than the set temperature, so the thermo-off state and the thermo-on state are frequently repeated. In this way, if the thermo-off state and the thermo-on state are frequently repeated, the compressor is stopped and restarted repeatedly each time, and there is a problem that the energy saving performance of the air conditioner is deteriorated due to the increased power consumption of the compressor at the time of restart. In addition, if the compressor is stopped and restarted frequently, there is a risk that the life of the compressor will be shortened.

The present invention aims to solve the problems mentioned above and provide an air conditioner that does not frequently alternate between the thermo-off state and the thermo-on state.

In order to solve the above problems, the air conditioner of the present invention has a refrigerant circuit formed by connecting a compressor, a four-way valve, an outdoor heat exchanger, a main expansion valve, and an indoor heat exchanger with refrigerant piping, an indoor temperature sensor that detects the indoor temperature, which is the temperature of the air-conditioned space, and a heat exchange amount adjustment means provided in the refrigerant circuit and adjusts the heat exchange amount in the indoor heat exchanger. Furthermore, the heat exchange amount adjustment means is formed by a first branch pipe, a second branch pipe, a first sub-expansion valve, a second sub-expansion valve, and an internal heat exchanger, one end of the first branch pipe is connected to the refrigerant piping connecting the four-way valve and the outdoor heat exchanger so as to bypass the outdoor heat exchanger, and the other end is connected to the refrigerant piping connecting the outdoor heat exchanger and the main expansion valve , and the second branch pipe is connected to the refrigerant piping connecting the main expansion valve and the indoor heat exchanger so as to bypass the indoor heat exchanger, and the other end is connected to the refrigerant piping connecting the indoor heat exchanger and the four-way valve . Then, during heating operation of the air conditioner, when the indoor temperature is rising toward the set temperature, which is a target value for the indoor temperature, and the temperature difference obtained by subtracting the indoor temperature from the set temperature is smaller than a predetermined value, and the compressor rotation speed is lower than a predetermined value; or, during cooling operation, when the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is smaller than a predetermined value, and the compressor rotation speed is lower than the predetermined value, the first sub-expansion valve adjusts the amount of refrigerant flowing through the first branch pipe, the second sub-expansion valve adjusts the amount of refrigerant flowing through the second branch pipe, and the internal heat exchanger exchanges heat between the refrigerant flowing through the first branch pipe and the refrigerant flowing through the second branch pipe.

The air conditioner of the present invention configured as described above does not frequently alternate between the thermo-off state and the thermo-on state, preventing a deterioration in energy efficiency and a shortened compressor lifespan.

FIG. 1 is a refrigerant circuit diagram according to a first embodiment of the present invention. 4 is a sub-expansion valve opening degree table according to the first embodiment of the present invention. FIG. 4 is a refrigerant circuit diagram according to a second embodiment of the present invention. FIG. 11 is a refrigerant circuit diagram according to a third embodiment of the present invention. 13 is a sub-expansion valve opening degree table according to the third embodiment of the present invention. FIG. 11 is a refrigerant circuit diagram according to a fourth embodiment of the present invention. FIG. 13 is a refrigerant circuit diagram according to a fifth embodiment of the present invention.

The following describes in detail an embodiment of the present invention with reference to the attached drawings. As an embodiment, an air conditioner in which one outdoor unit and one indoor unit are connected by two refrigerant pipes is taken as an example. Note that the present invention is not limited to the following embodiment, and various modifications are possible without departing from the spirit of the present invention.

As shown in FIG. 1, the air conditioner 1 in this embodiment includes an outdoor unit 2 installed outdoors, and an indoor unit 3 installed indoors and connected to the outdoor unit 2 by a liquid pipe 4 and a gas pipe 5. In detail, the shutoff valve 25 of the outdoor unit 2 and the liquid pipe connection part 33 of the indoor unit 3 are connected by the liquid pipe 4. In addition, the shutoff valve 26 of the outdoor unit 2 and the gas pipe connection part 34 of the indoor unit 3 are connected by the gas pipe 5. The above forms the refrigerant circuit 10 of the air conditioner 1.

<Outdoor unit configuration>
First, the outdoor unit 2 will be described. The outdoor unit 2 includes a compressor 21, a four-way valve 22, an outdoor heat exchanger 23, an internal heat exchanger 24a, a stop valve 25 to which one end of the liquid pipe 4 is connected, a stop valve 26 to which one end of the gas pipe 5 is connected, a main expansion valve 27, a first sub-expansion valve 28a, a second sub-expansion valve 29a, and an outdoor fan 30. These devices except for the outdoor fan 30 are connected to each other by refrigerant pipes described in detail below to form an outdoor unit refrigerant circuit 10a that forms part of the refrigerant circuit 10.

Compressor 21 is a variable-capacity compressor whose operating capacity can be changed by controlling the rotation speed with an inverter (not shown). The refrigerant discharge side of compressor 21 and port a of four-way valve 22 are connected by discharge pipe 61. In addition, the refrigerant suction side of compressor 21 and port c of four-way valve 22 are connected by suction pipe 66.

The four-way valve 22 is a valve for switching the direction of refrigerant flow, and has four ports a, b, c, and d. As described above, port a is connected to the refrigerant discharge side of the compressor 21 by a discharge pipe 61. Port b is connected to one of the refrigerant inlets and outlets of the outdoor heat exchanger 23 by a refrigerant piping 62. As described above, port c is connected to the refrigerant suction side of the compressor 21 by a suction pipe 66. And port d is connected to the shutoff valve 26 by an outdoor unit gas pipe 64.

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 30 described below. One refrigerant inlet/outlet of the outdoor heat exchanger 23 is connected to port b of the four-way valve 22 by a refrigerant piping 62 as described above, and the other refrigerant inlet/outlet is connected to the shutoff valve 25 by an outdoor unit liquid pipe 63. The outdoor heat exchanger 23 functions as a condenser when the air conditioner 1 is operating in cooling mode, and as an evaporator when operating in heating mode.

The main expansion valve 27 is an electronic expansion valve and is provided in the outdoor unit liquid pipe 63. By adjusting the opening degree of the main expansion valve 27, the discharge temperature, which is the temperature of the refrigerant discharged from the compressor 21, is set to a target discharge temperature determined based on the air conditioning capacity required by the indoor unit 3. The first sub-expansion valve 28a is an electronic expansion valve and is provided between the outdoor heat exchanger 23 and the main expansion valve 27 in the outdoor unit liquid pipe 63. By adjusting the opening degree of the first sub-expansion valve 28a, the amount of refrigerant flowing through the first branch pipe 67a described later is adjusted. The second sub-expansion valve 29a is an electronic expansion valve and is provided in the outdoor unit gas pipe 64. By adjusting the opening degree of the second sub-expansion valve 29a, the amount of refrigerant flowing through the second branch pipe 68a described later is adjusted.

The internal heat exchanger 24a is, for example, a double-pipe heat exchanger, and the first branch pipe 67a and the second branch pipe 68a are connected to exchange heat between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a. Here, the first branch pipe 67a is connected at one end between the outdoor heat exchanger 23 and the first sub-expansion valve 28a in the outdoor unit liquid pipe 63, and at the other end between the first sub-expansion valve 28a and the main expansion valve 27 in the outdoor unit liquid pipe 63. In other words, the first branch pipe 67a is connected to the outdoor unit refrigerant circuit 10a so as to bypass the first sub-expansion valve 28a. In addition, the second branch pipe 68a is connected at one end between the stop valve 26 and the second sub-expansion valve 29a in the outdoor unit gas pipe 64, and at the other end between the second sub-expansion valve 29a and the four-way valve 22 in the outdoor unit gas pipe 64. In other words, the second branch pipe 68a is connected to the outdoor unit refrigerant circuit 10a so as to bypass the second sub-expansion valve 29a.

The internal heat exchanger 24a, the first sub-expansion valve 28a, the second sub-expansion valve 29a, the first branch pipe 67a, and the second branch pipe 68a described above form the heat exchange amount adjustment means of the present invention.

The outdoor fan 30 is made of a resin material and is disposed near the outdoor heat exchanger 23. The outdoor fan 30 is rotated by a fan motor (not shown) to take in outside air from an intake port (not shown) of the outdoor unit 2 into the interior of the outdoor unit 2, and releases the outside air that has exchanged heat with the refrigerant in the outdoor heat exchanger 23 to the outside of the outdoor unit 2 from an outlet port (not shown) of the outdoor unit 2.

In addition to the configuration described above, the outdoor unit 2 is provided with various sensors. As shown in FIG. 1, the discharge pipe 61 is provided with a discharge pressure sensor 71 that detects the pressure of the refrigerant discharged from the compressor 21, and a discharge temperature sensor 73 that detects the temperature of the refrigerant discharged from the compressor 21. The suction pipe 66 is provided with a suction pressure sensor 72 that detects the pressure of the refrigerant sucked into the compressor 21, and a suction temperature sensor 74 that detects the temperature of the refrigerant sucked into the compressor 21.

A heat exchanger temperature sensor 75 is provided in the middle of the refrigerant flow path (not shown) of the outdoor heat exchanger 23 to detect the temperature of the refrigerant flowing through the middle of the refrigerant flow path, i.e., the temperature of the outdoor heat exchanger 23. An outdoor air temperature sensor 76 is provided near the air intake (not shown) of the outdoor unit 2 to detect the temperature of the outdoor air flowing into the outdoor unit 2, i.e., the outdoor air temperature.

<Indoor unit configuration>
Next, the indoor unit 3 will be described with reference to Fig. 1. The indoor unit 3 includes an indoor heat exchanger 31, an indoor fan 32, a liquid pipe connection part 33 to which the other end of the liquid pipe 4 is connected, and a gas pipe connection part 34 to which the other end of the gas pipe 5 is connected. These devices except for the indoor fan 32 are connected to each other by refrigerant pipes described in detail below to configure an indoor unit refrigerant circuit 10b that is a part of the refrigerant circuit 10.

The indoor heat exchanger 31 exchanges heat between the refrigerant and the indoor air taken into the indoor unit 3 from an intake port (not shown) of the indoor unit 3 by the rotation of the indoor fan 32 described later. One refrigerant inlet/outlet is connected to the liquid pipe connection part 33 and the indoor unit liquid pipe 91, and the other refrigerant inlet/outlet is connected to the gas pipe connection part 34 and the indoor unit gas pipe 92. The indoor heat exchanger 31 functions as an evaporator when the air conditioner 1 is in cooling operation, and functions as a condenser when the air conditioner 1 is in heating operation. The refrigerant pipes are connected to the liquid pipe connection part 33 and the gas pipe connection part 34 by welding, flare nuts, etc.

The indoor fan 32 is made of a resin material and is located near the indoor heat exchanger 31. The indoor fan 31 is rotated by a fan motor (not shown) to draw indoor air into the indoor unit 3 from an intake port (not shown) of the indoor unit 3, and blows the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 31 out into the room from an outlet port (not shown) of the indoor unit 3.

In addition to the configuration described above, the indoor unit 3 is provided with various sensors. The indoor unit liquid pipe 91 is provided with a liquid-side temperature sensor 81 that detects the temperature of the refrigerant flowing into or out of the indoor heat exchanger 31. The indoor unit gas pipe 92 is provided with a gas-side temperature sensor 82 that detects the temperature of the refrigerant flowing out of or into the indoor heat exchanger 31. A room temperature sensor 83 is provided near the 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.

<Operation of the refrigerant circuit>
Next, the flow of refrigerant in the refrigerant circuit 10 and the operation of each part during air conditioning operation of the air conditioner 1 in this embodiment will be described. The air conditioner 1 in this embodiment can perform air conditioning operation without operating the heat exchange amount adjustment means, and air conditioning operation with the heat exchange amount adjustment means operating. In the following description, the heating operation and cooling operation without operating the heat exchange amount adjustment means are referred to as normal heating operation and normal cooling operation, respectively, and the heating operation and cooling operation with the heat exchange amount adjustment means operating are referred to as controlled heating operation and controlled cooling operation, respectively, and the operation of the refrigerant circuit 10 will be described using FIG. 1 as an example of normal heating operation and controlled heating operation.

<Normal heating operation>
When the air conditioner 1 performs normal heating operation, the four-way valve 22 shown in Fig. 1 is switched to the state shown by the solid lines, i.e., so that ports a and d of the four-way valve 22 communicate with each other, and so that ports b and c of the four-way valve 22 communicate with each other. As a result, refrigerant circulates in the direction shown by the solid arrows in the refrigerant circuit 10, and the refrigerant circuit 10 becomes a heating cycle in which the outdoor heat exchanger 23 functions as an evaporator and the indoor heat exchanger 31 functions as a condenser. During normal heating operation, the first sub-expansion valve 28a and the second sub-expansion valve 29a are each fully open.

When the compressor 21 is driven with the refrigerant circuit 10 in the heating cycle, the high-pressure refrigerant discharged from the compressor 21 flows through the discharge pipe 61 and into the four-way valve 22, then flows from the four-way valve 22 through the outdoor unit gas pipe 64, passes through the second sub-expansion valve 29a which is fully open, and flows out into the gas pipe 5 through the stop valve 26. The refrigerant flowing through the gas pipe 5 flows into the indoor unit 3 through the gas pipe connection part 34.

The refrigerant that flows into the indoor unit 3 flows through the indoor unit gas pipe 92 and into the indoor heat exchanger 31, where it exchanges heat with the indoor air drawn into the indoor unit 3 by the rotation of the indoor fan 32, and is condensed. In this way, the indoor heat exchanger 31 functions as a condenser, and the indoor air that has exchanged heat with the refrigerant in the indoor heat exchanger 31 is blown out into the room from an air outlet (not shown), heating the room in which the indoor unit 3 is installed.

The refrigerant flowing out from the indoor heat exchanger 31 flows through the indoor unit liquid pipe 91 and flows out into the liquid pipe 4 through the liquid pipe connection part 33. The refrigerant that flows through the liquid pipe 4 and flows into the outdoor unit 2 through the stop valve 25 flows through the outdoor unit liquid pipe 63 and is reduced in pressure when passing through the main expansion valve 27, the opening of which is adjusted so that the discharge temperature detected by the discharge temperature sensor 73 becomes the target discharge temperature. The refrigerant that has passed through the main expansion valve 27 passes through the first auxiliary expansion valve, which is fully open, and flows into the outdoor heat exchanger 23, where it exchanges heat with the outside air taken into the outdoor unit 2 by the rotation of the outdoor fan 30, and evaporates. The refrigerant that flows out from the outdoor heat exchanger 23 to the refrigerant piping 62 flows through the four-way valve 22 and the suction pipe 66, is sucked into the compressor 21, and is compressed again.

<Adjustable heating operation>
The state and operation of the refrigerant circuit 10 when the air conditioner 1 performs the controlled heating operation is the same as that during normal heating operation, except that the heat exchange amount adjustment means operates. When the indoor temperature during normal heating operation is rising toward the set temperature, for example, between the start of heating operation and the time when the indoor temperature reaches the set temperature, if the temperature difference obtained by subtracting the indoor temperature detected by the indoor temperature sensor 81 from the set temperature is less than a predetermined value, and the compressor 21 is operating at a predetermined rotation speed or less at this time, the heat exchange amount adjustment means is operated to perform the controlled heating operation.

Here, the above-mentioned specified rotation speed of the compressor 21 is a predetermined value, for example, a rotation speed that is a predetermined value (for example, 10 rps) higher than the minimum allowable rotation speed in terms of the performance of the compressor 21, and it has been found that when the compressor 21 is driven at or below this specified rotation speed, the heating capacity exerted by the indoor unit 3 is the minimum capacity. In addition, the above-mentioned specified value of the temperature difference is also a value determined in advance through testing, etc., and it has been found that if the compressor 21 is driven at or below the specified rotation speed when the indoor temperature is rising toward the set temperature and the temperature difference between the set temperature and the indoor temperature is less than this specified value, the heating capacity exerted by the indoor unit 3 is excessive, and if the heating operation is continued in this state, the air conditioner 1 will be thermo-off. The value of the temperature difference is, for example, 4°C.

As described above, when the indoor temperature is rising toward the set temperature during normal heating operation and the temperature difference between the set temperature and the indoor temperature is below a predetermined value, the compressor 21 is operating at a predetermined rotation speed or less, i.e., the heating capacity exerted by the indoor unit 3 is at its minimum capacity, the heating capacity exerted is excessive for the air conditioning load due to reasons such as a small air conditioning load in the room in which the indoor unit 3 is installed. If normal heating operation is continued in this state, there is a risk that the indoor temperature will reach a predetermined temperature, for example a temperature 1°C or more higher than the set temperature (hereinafter sometimes referred to as the thermo-off temperature), causing the air conditioner 1 to enter the thermo-off state, and then the indoor temperature will fall below the set temperature, causing the thermo-on state, and then the thermo-off state will be repeated.

In the air conditioner 1 of this embodiment, when the indoor temperature is rising toward the set temperature during normal heating operation and the temperature difference obtained by subtracting the indoor temperature from the set temperature falls below a predetermined value, if the compressor 21 is operating at a rotation speed equal to or lower than a predetermined rotation speed, an adjusted heating operation is performed to operate the heat exchange amount adjustment means. Specifically, the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are adjusted according to the temperature difference between the set temperature and the indoor temperature, using the sub-expansion valve opening degree table 300a shown in FIG. 2.

The sub-expansion valve opening table 300a is determined in advance and is stored, for example, in a storage unit (not shown) of the outdoor unit 2. As shown in FIG. 2, the sub-expansion valve opening table 300a determines the opening of the first sub-expansion valve 28a and the opening of the second sub-expansion valve 29a according to the temperature difference between the set temperature and the indoor temperature for each of the controlled heating operation and the controlled cooling operation described below. In the sub-expansion valve opening table 300a, the opening of each expansion valve is expressed as a percentage, with 100% being fully open and 0% being fully closed.

More specifically, during controlled heating operation in the sub-expansion valve opening table 300a, if the temperature difference obtained by subtracting the indoor temperature from the set temperature is 4°C or more, that is, if the indoor temperature is 4°C or more lower than the set temperature, the air conditioner 1 performs normal heating operation rather than controlled heating operation, so the opening of the first sub-expansion valve 28a and the opening of the second sub-expansion valve 29a are each 100% (fully open). Generally, the internal heat exchanger 24a, which is a double-pipe heat exchanger, has a large flow resistance, so if the opening of the first sub-expansion valve 28a and the opening of the second sub-expansion valve 29a are both fully open, almost no refrigerant flows through the first branch pipe 67a or the second branch pipe 68a.

In addition, when the temperature difference obtained by subtracting the indoor temperature from the set temperature is -1°C or more and less than 0°C, that is, when the indoor temperature is higher than the set temperature and lower than the thermo-off temperature, the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are each 0% (fully closed). In this way, if the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are each fully closed, the amount of refrigerant flowing through the first branch pipe 67a and the second branch pipe 68a is maximized, and the amount of heat exchange between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a in the internal heat exchanger 24a is maximized. As a result, the amount of heat exchange between the refrigerant and the indoor air in the indoor heat exchanger 31 is minimized, and the heating capacity exerted by the indoor unit 3 is also minimized, so that it is possible to prevent the indoor temperature from rising and the air conditioner 1 from entering the thermo-off state.

And, when the temperature difference obtained by subtracting the indoor temperature from the set temperature is 0°C or more and less than 4°C, the temperature difference is divided into regions in increments of 1°C, and the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are set so that the opening degree decreases in increments of 20% from 80% to 20% as the temperature difference moves from the high temperature difference region to the low temperature difference region. In this way, by changing the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a according to the temperature difference, the amount of refrigerant flowing through the first branch pipe 67a and the second branch pipe 68a changes, respectively, and the amount of heat exchange between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a in the internal heat exchanger 24a changes. As a result, the amount of heat exchange between the refrigerant and the indoor air in the indoor heat exchanger 31 changes, and the heating capacity exhibited by the indoor unit 3 can also be changed. In addition, during controlled cooling operation in the sub-expansion valve opening table 300a, the opening of the first sub-expansion valve 28a and the opening of the second sub-expansion valve 29a corresponding to each temperature difference are the same, except that the temperature difference is the indoor temperature minus the set temperature compared to controlled heating operation, so detailed explanations are omitted.

When the regulated heating operation is performed, the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are adjusted according to the temperature difference by referring to the item for regulated heating operation in the above-mentioned sub-expansion valve opening degree table 300a. By making the opening degree of the first sub-expansion valve 28a smaller than the fully open state according to the temperature difference, a part of the refrigerant (amount of refrigerant corresponding to the opening degree of the first sub-expansion valve 28a) that passes through the main expansion valve 27 and flows through the outdoor unit liquid pipe 63 flows through the first branch pipe 67a. On the other hand, by making the opening degree of the second sub-expansion valve 29a smaller than the fully open state according to the temperature difference, a part of the refrigerant (amount of refrigerant corresponding to the opening degree of the second sub-expansion valve 28a) that flows out of the four-way valve 22 and flows through the outdoor unit gas pipe 64 flows through the second branch pipe 68a. In FIG. 1, the flow of the refrigerant in the first branch pipe 67a and the flow of the refrigerant in the second branch pipe 68a are respectively indicated by dashed arrows.

The refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a exchange heat in the internal heat exchanger 24a. At this time, the amount of heat exchanged between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a in the internal heat exchanger 24a is determined by the amount of refrigerant flowing through the first branch pipe 67a and the amount of refrigerant flowing through the second branch pipe 68a. In other words, the amount of heat exchanged in the internal heat exchanger 24a is determined by the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a.

As described above, the internal heat exchanger 24a exchanges heat between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a, and changes the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a according to the temperature difference obtained by subtracting the indoor temperature from the set temperature. The more the amount of heat exchange between the refrigerant flowing through the first branch pipe 67a and the refrigerant flowing through the second branch pipe 68a in the internal heat exchanger 24a increases, the less the amount of heat exchange in the indoor heat exchanger 31 decreases. In this way, by operating the heat exchange amount adjustment means during the adjusted heating operation, the amount of heat exchange in the indoor heat exchanger 31 is reduced to reduce the heating capacity exerted by the indoor unit 3, thereby suppressing the rise in the indoor temperature and keeping the indoor temperature below the thermo-off temperature, and thus preventing the air conditioner 1 from frequently repeating the thermo-off state and the thermo-on state.

When the air conditioner 1 is in normal cooling operation or adjusted refrigerant operation, the four-way valve 22 shown in FIG. 1 is switched to the state shown by the dashed lines, that is, so that ports a and b of the four-way valve 22 are in communication with each other, and so that ports c and d of the four-way valve 22 are in communication with each other, and the refrigerant circuit 10 is in a cooling cycle in which the outdoor heat exchanger 23 functions as a condenser and the indoor heat exchanger 31 functions as an evaporator.

During normal cooling operation, the first sub-expansion valve 28a and the second sub-expansion valve 29a are fully opened. During normal cooling operation, when the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, if the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the heat exchange amount adjustment means is operated to operate the heat exchange amount adjustment means to perform the adjusted cooling operation. Specifically, the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are adjusted by referring to the item for the adjusted cooling operation in the sub-expansion valve opening degree table 300a shown in FIG. 2, that is, the heat exchange amount adjustment means is operated to reduce the heat exchange amount in the indoor heat exchanger 31, thereby reducing the cooling capacity exerted by the indoor unit 3. The adjusted cooling operation may be performed if the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed during normal cooling operation and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value.

As described above, when the air conditioner 1 of this embodiment is performing air conditioning operation, if the indoor temperature is rising or falling toward the set temperature and the temperature difference between the indoor temperature and the set temperature is less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or lower than a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform regulated heating operation or regulated cooling operation. This prevents the air conditioner 1 from frequently repeatedly switching between the thermo-off state and the thermo-on state, thereby preventing a deterioration in energy efficiency and a shortened lifespan of the compression region 21 due to frequent stopping and restarting of the compressor 21.

Next, a second embodiment of the present invention will be described mainly with reference to FIG. 3. The air conditioner 1 of this embodiment is the same as the first embodiment, except that the heat exchange amount adjustment means is different from that of the first embodiment. For this reason, detailed explanations of the operation of the refrigerant circuit 10 during normal heating operation, controlled heating operation, normal cooling operation, and controlled cooling operation will be omitted, and only the configuration and function of the heat exchange amount adjustment means will be described.

The heat exchange amount adjustment means of this embodiment is formed by the internal heat exchanger 24b, the first sub-expansion valve 28b, the second sub-expansion valve 29a, the first branch pipe 67a, and the second branch pipe 68a shown in FIG. 3.

The first sub-expansion valve 28b is an electronic expansion valve and is provided between the main expansion valve 27 and the shutoff valve 25 in the outdoor unit liquid pipe 63. The amount of refrigerant flowing through the first branch pipe 67b (described later) is adjusted by adjusting the opening degree of the first sub-expansion valve 28b. The second sub-expansion valve 29b is an electronic expansion valve and is provided in the refrigerant pipe 62. The amount of refrigerant flowing through the second branch pipe 68b (described later) is adjusted by adjusting the opening degree of the second sub-expansion valve 29b.

The internal heat exchanger 24b is, for example, a double-pipe heat exchanger, in which the first branch pipe 67b and the second branch pipe 68b are connected to exchange heat between the refrigerant flowing through the first branch pipe 67b and the refrigerant flowing through the second branch pipe 68b. Here, the first branch pipe 67b is connected at one end between the main expansion valve 27 and the first sub-expansion valve 28b in the outdoor unit liquid pipe 63, and at the other end between the first sub-expansion valve 28b and the stop valve 25 in the outdoor unit liquid pipe 63. In other words, the first branch pipe 67b is connected to the outdoor unit refrigerant circuit 10a so as to bypass the first sub-expansion valve 28b. In addition, the second branch pipe 68b is connected at one end between the four-way valve 22 and the second sub-expansion valve 29b in the refrigerant piping 62, and at the other end between the second sub-expansion valve 29b and the outdoor heat exchanger 23 in the refrigerant piping 62. In other words, the second branch pipe 68b is connected to the outdoor unit refrigerant circuit 10a so as to bypass the second sub-expansion valve 29b.

The heat exchange amount adjustment means described above is operated when the air conditioner 1 of this embodiment performs regulated heating operation or regulated cooling operation. Specifically, the sub-expansion valve opening degree table 300a shown in FIG. 2 is used to adjust the opening degrees of the first sub-expansion valve 28b and the second sub-expansion valve 29b according to the temperature difference between the set temperature and the room temperature.

When the air conditioner 1 is performing normal heating operation, if the indoor temperature is rising toward the set temperature and the temperature difference obtained by subtracting the indoor temperature from the set temperature is less than a predetermined value, if the compressor 21 is operating at a rotation speed equal to or lower than a predetermined rotation speed, the air conditioner 1 performs controlled heating operation to operate the heat exchange amount adjustment means. Specifically, the items for controlled heating operation in the sub-expansion valve opening table 300a shown in FIG. 2 are referenced, and the opening of the first sub-expansion valve 28b and the opening of the second sub-expansion valve 29b are adjusted according to the temperature difference. As a result, the amount of refrigerant flowing through the first branch pipe 67b and the second branch pipe 68b is adjusted, and the refrigerant flowing through the first branch pipe 67b and the refrigerant flowing through the second branch pipe 68b exchange heat in the internal heat exchanger 24b, thereby reducing the amount of heat exchanged in the indoor heat exchanger 31, and the heating capacity exerted by the indoor unit 3 is reduced, thereby suppressing the rise in the indoor temperature. In FIG. 3, the flow of refrigerant in the first branch pipe 67b and the flow of refrigerant in the second branch pipe 68b are indicated by dashed arrows, respectively.

On the other hand, when the air conditioner 1 is performing normal cooling operation, if the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs a controlled cooling operation in which the heat exchange amount adjustment means is operated. Specifically, the items for controlled cooling operation in the sub-expansion valve opening table 300a shown in FIG. 2 are referenced, and the opening degree of the first sub-expansion valve 28b and the opening degree of the second sub-expansion valve 29b are adjusted according to the temperature difference. As a result, the amount of refrigerant flowing through the first branch pipe 67b and the second branch pipe 68b is adjusted, and the refrigerant flowing through the first branch pipe 67b and the refrigerant flowing through the second branch pipe 68b exchange heat in the internal heat exchanger 24b, thereby reducing the amount of heat exchange in the outdoor heat exchanger 23, and thus reducing the amount of heat exchange in the indoor heat exchanger 31. This reduces the cooling capacity exerted by the indoor unit 3, thereby suppressing the decrease in the indoor temperature.

As described above, when the air conditioner 1 of this embodiment is performing air conditioning operation, if the indoor temperature is rising or falling toward the set temperature and the temperature difference between the indoor temperature and the set temperature is below a predetermined value, and the compressor 21 is operating at a rotation speed below a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform regulated heating operation or regulated cooling operation. This prevents the air conditioner 1 from frequently repeatedly switching between the thermo-off state and the thermo-on state, thereby preventing a deterioration in energy efficiency and a shortened lifespan of the compression region 21 due to frequent stopping and restarting of the compressor 21.

In the first embodiment, a part of the refrigerant flowing from the outdoor unit 2 to the indoor unit 3 during the controlled heating operation is caused to flow to the second branch pipe 68a, and is heat exchanged with the refrigerant flowing through the first branch pipe 67a in the internal heat exchanger 24a, thereby reducing the amount of heat exchanged in the indoor heat exchanger 31 functioning as a condenser during the heating operation. In other words, the first embodiment works better during the controlled heating operation than during the controlled cooling operation. In contrast, in the present embodiment, a part of the refrigerant flowing to the outdoor heat exchanger 23 functioning as a condenser during the controlled cooling operation is caused to flow to the second branch pipe 68a, and is heat exchanged with the refrigerant flowing through the first branch pipe 67a in the internal heat exchanger 24a, thereby reducing the amount of heat exchanged in the outdoor heat exchanger 23 functioning as a condenser during the cooling operation, and thus reducing the amount of heat exchanged in the indoor heat exchanger 31. For this reason, the present embodiment works better during the controlled cooling operation than during the controlled heating operation.

Next, a third embodiment of the present invention will be described with reference to Figures 4 and 5. In the first and second embodiments, the heat exchange amount adjustment means reduces the heat exchange amount in the indoor heat exchanger 31 to prevent the indoor temperature from reaching the temperature at which the air conditioner 1 turns off. In contrast, in the air conditioner 1 of this embodiment, the heat exchange amount adjustment means reduces the amount of refrigerant circulating in the refrigerant circuit 10 to reduce the heat exchange amount in the indoor heat exchanger 31.

The air conditioner 1 of this embodiment is the same as the first embodiment, except that the heat exchange amount adjustment means is different from that of the first embodiment. For this reason, detailed explanations of the operation of the refrigerant circuit 10 during heating operation and cooling operation will be omitted, and only the configuration and function of the heat exchange amount adjustment means will be explained.

The heat exchange amount adjustment means of this embodiment is formed by the first sub-expansion valve 28c and the high-low pressure bypass pipe 69 shown in FIG. 4. One end of the high-low pressure bypass pipe 69 is connected to the discharge pipe 61, and the other end is connected to the suction pipe 66. In other words, the high-low pressure bypass pipe 69 bypasses the refrigerant discharge side and the refrigerant suction side of the compressor 21. The first sub-expansion valve 28c is an electronic expansion valve provided in the high-low pressure bypass pipe 69, and by adjusting the opening degree thereof, the amount of refrigerant discharged from the compressor 21 to the discharge pipe 61 that corresponds to the opening degree of the first sub-expansion valve 28c is allowed to flow to the high-low pressure bypass pipe 69.

The heat exchange amount adjustment means described above is operated when the air conditioner 1 of this embodiment performs regulated heating operation or regulated cooling operation. Specifically, the opening of the first sub-expansion valve 28c is adjusted according to the temperature difference between the set temperature and the room temperature using the sub-expansion valve opening table 300b shown in FIG. 5.

The sub-expansion valve opening table 300b is determined in advance and is stored, for example, in a storage unit (not shown) of the outdoor unit 2. As shown in FIG. 5, the sub-expansion valve opening table 300b determines the opening of the first sub-expansion valve 28c according to the temperature difference between the set temperature and the indoor temperature during both regulated heating operation and regulated cooling operation (described later). In the sub-expansion valve opening table 300b, the opening of the first sub-expansion valve 28c is expressed as a percentage, with 100% being fully open and 0% being fully closed.

More specifically, during controlled heating operation in the sub-expansion valve opening table 300b, if the temperature difference obtained by subtracting the indoor temperature from the set temperature is 4°C or more, in other words, if the indoor temperature is 4°C or more lower than the set temperature, the air conditioner 1 performs normal heating operation rather than controlled heating operation, and the opening of the first sub-expansion valve 28c is 0% (fully closed). In this way, by fully closing the opening of the first sub-expansion valve 28c, no refrigerant flows through the elevation difference bypass pipe 69, so the amount of refrigerant circulating through the refrigerant circuit 10 does not decrease during normal heating operation.

In addition, when the temperature difference obtained by subtracting the indoor temperature from the set temperature is -1°C or more and less than 0°C, that is, when the indoor temperature is higher than the set temperature and lower than the thermo-off temperature of the air conditioner 1, the opening degree of the first sub-expansion valve 28c is set to 100% (fully open) to prevent the indoor temperature from rising and the air conditioner 1 from entering the thermo-off state. In this way, by fully opening the first sub-expansion valve 28c, a large amount of refrigerant flows through the elevation difference bypass pipe 69, so that the amount of refrigerant circulating through the refrigerant circuit 10 is reduced during normal heating operation, and the amount of heat exchanged in the indoor heat exchanger 31 is reduced. In FIG. 4, the flow of refrigerant through the high and low pressure bypass pipe 69 is indicated by dashed arrows.

When the temperature difference obtained by subtracting the indoor temperature from the set temperature is 0°C or more and less than 4°C, the temperature difference is divided into regions in increments of 1°C, and the opening degree of the first sub-expansion valve 28a and the opening degree of the second sub-expansion valve 29a are set so that the opening degree increases in increments of 20% from 20% to 80% as the temperature difference moves from the high temperature difference region to the low temperature difference region. In this way, by changing the opening degree of the first sub-expansion valve 28a according to the temperature difference, the amount of refrigerant flowing through the elevation difference bypass pipe 69 changes, and thus the amount of refrigerant flowing to the indoor heat exchanger 31 changes, so that the heating capacity exerted by the indoor unit 3 can also be changed. Note that during the regulated cooling operation in the sub-expansion valve opening degree table 300b, the opening degree of the first sub-expansion valve 28c according to each temperature difference is the same as during the regulated heating operation, except that the temperature difference is the indoor temperature minus the set temperature compared to the regulated heating operation, so a detailed description is omitted.

When the air conditioner 1 is performing normal heating operation, if the indoor temperature is rising toward the set temperature and the temperature difference obtained by subtracting the indoor temperature from the set temperature becomes equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs a controlled heating operation in which the heat exchange amount adjustment means is operated. When the controlled heating operation is performed, the items for controlled heating operation in the sub-expansion valve opening table 300b described above are referenced, and the opening of the first sub-expansion valve 28c, which was fully closed during normal heating operation, is adjusted according to the temperature difference. By increasing the opening of the first sub-expansion valve 28c according to the temperature difference, of the refrigerant discharged from the compressor 21 to the discharge pipe 61, an amount of refrigerant according to the opening of the first sub-expansion valve 28c flows into the high-low pressure bypass pipe 69. As a result, the amount of refrigerant flowing from the outdoor unit 2 to the indoor unit 3 is reduced, and the amount of heat exchanged in the indoor heat exchanger 31 is reduced, so that the heating capacity exerted by the indoor unit 3 is reduced and the rise in the indoor temperature can be suppressed.

On the other hand, when the air conditioner 1 is performing normal cooling operation, if the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs a controlled cooling operation in which the heat exchange amount adjustment means is operated. When the controlled cooling operation is performed, the items for controlled heating operation in the above-mentioned sub-expansion valve opening table 300b are referenced, and the opening degree of the first sub-expansion valve 28c, which was fully closed during normal heating operation, is adjusted according to the temperature difference. By increasing the opening degree of the first sub-expansion valve 28c, of the refrigerant discharged from the compressor 21 to the discharge pipe 61, an amount of refrigerant corresponding to the opening degree of the first sub-expansion valve 28c flows into the high-low pressure bypass pipe 69. As a result, the amount of refrigerant flowing from the outdoor unit 2 to the indoor unit 3 is reduced, and the amount of heat exchanged in the indoor heat exchanger 31 is reduced, so that the cooling capacity exerted by the indoor unit 3 is reduced and the drop in the indoor temperature can be suppressed.

As described above, when the air conditioner 1 of this embodiment is performing air conditioning operation, if the indoor temperature is rising or falling toward the set temperature and the temperature difference between the indoor temperature and the set temperature is below a predetermined value, and the compressor 21 is operating at a rotation speed below a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform regulated heating operation or regulated cooling operation. This prevents the air conditioner 1 from frequently repeatedly switching between the thermo-off state and the thermo-on state, thereby preventing a deterioration in energy efficiency and a shortened lifespan of the compression region 21 due to frequent stopping and restarting of the compressor 21.

In the first and second embodiments, each heat exchange amount adjustment means is formed of an internal heat exchanger, two sub-expansion valves, and two branch pipes. In contrast, the heat exchange amount adjustment means of this embodiment is formed of only one sub-expansion valve (first sub-expansion valve 28c) and one refrigerant pipe (high/low pressure bypass pipe 69). In other words, in this embodiment, fewer components are required to form the heat exchange amount adjustment means compared to the first and second embodiments, so the heat exchange amount adjustment means can be realized at low cost. In addition, since the number of sub-expansion valves to be controlled is smaller than in the first and second embodiments, the heat exchange amount in the indoor heat exchanger 31 can be adjusted with simple control.

Next, a fourth embodiment of the present invention will be described with reference to FIG. 6. In the third embodiment, the amount of refrigerant flowing into the indoor unit 3 is reduced by returning a portion of the refrigerant discharged from the compressor 21 to the refrigerant intake side of the compressor 21 by the heat exchange amount adjustment means, and the amount of heat exchange in the indoor heat exchanger 31 is reduced, so that the indoor temperature does not reach the temperature at which the air conditioner 1 turns off the thermostat. In contrast, in the air conditioner 1 of this embodiment, the heat exchange amount adjustment means returns a portion of the refrigerant flowing through the outdoor unit liquid pipe 63 to the refrigerant intake side of the compressor 21, thereby reducing the amount of refrigerant flowing into the indoor unit 3 and reducing the amount of heat exchange in the indoor heat exchanger 31.

The air conditioner 1 of this embodiment is the same as the third embodiment, except that the heat exchange amount adjustment means is different from that of the third embodiment. For this reason, detailed explanations of the operation of the refrigerant circuit 10 during heating operation and cooling operation will be omitted, and only the configuration and function of the heat exchange amount adjustment means will be explained.

As shown in FIG. 6, the receiver 200, the first sub-expansion valve 28d, and the outflow pipe 70 constitute the heat exchange amount adjustment means of this embodiment. The receiver 200 is a cylindrical sealed container and is disposed between the outdoor heat exchanger 23 and the main expansion valve 27 in the outdoor unit liquid pipe 63. The receiver 200 and the outdoor unit gas pipe 64 are connected by the outflow pipe 70, and the first sub-expansion valve 28d is provided on the outflow pipe 70. The first sub-expansion valve 28d is an electronic expansion valve, and by adjusting the opening degree thereof, the amount of refrigerant remaining in the receiver 200 that corresponds to the opening degree of the first sub-expansion valve 28c is caused to flow to the outdoor unit gas pipe 64.

The heat exchange amount adjustment means described above is operated when the air conditioner 1 of this embodiment performs regulated heating operation or regulated cooling operation. Specifically, the opening of the first sub-expansion valve 28d is adjusted according to the temperature difference between the set temperature and the room temperature using the sub-expansion valve opening table 300b shown in FIG. 5. Note that in FIG. 5, the flow of refrigerant from the receiver 200 to the outflow pipe 70 is indicated by dashed arrows.

When the air conditioner 1 is performing normal heating operation, if the indoor temperature is rising toward the set temperature and the temperature difference obtained by subtracting the indoor temperature from the set temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs controlled heating operation to operate the heat exchange amount adjustment means. When controlled heating operation is performed, the items for controlled heating operation in the sub-expansion valve opening table 300b described above are referenced, and the opening of the first sub-expansion valve 28d, which was fully closed during normal heating operation, is adjusted according to the temperature difference. By increasing the opening of the first sub-expansion valve 28d, an amount of refrigerant that corresponds to the opening of the first sub-expansion valve 28d flows through the outflow pipe 70 to the outdoor unit gas pipe 64 from the refrigerant that is retained in the receiver 200. As a result, the amount of refrigerant that flows from the outdoor unit 2 to the indoor unit 3 is reduced, and the amount of heat exchanged in the indoor heat exchanger 31 is reduced, so that the heating capacity exhibited by the indoor unit 3 is reduced and the rise in the indoor temperature can be suppressed.

On the other hand, when the air conditioner 1 is performing normal cooling operation, if the indoor temperature is rising toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs a controlled cooling operation in which the heat exchange amount adjustment means is operated. When the controlled cooling operation is performed, the items for controlled cooling operation in the above-mentioned sub-expansion valve opening table 300b are referenced, and the opening of the first sub-expansion valve 28d, which was fully closed during normal heating operation, is adjusted according to the temperature difference. By increasing the opening of the first sub-expansion valve 28d, an amount of refrigerant that corresponds to the opening of the first sub-expansion valve 28d flows through the outflow pipe 70 to the outdoor unit gas pipe 64 from the refrigerant that remains in the receiver 200. As a result, the amount of refrigerant that flows from the outdoor unit 2 to the indoor unit 3 is reduced, and the heat exchange amount in the indoor heat exchanger 31 is reduced, so that the cooling capacity exhibited by the indoor unit 3 is reduced and the drop in the indoor temperature can be suppressed.

As described above, when the air conditioner 1 of this embodiment is performing air conditioning operation, if the indoor temperature is rising or falling toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform regulated heating operation or regulated cooling operation. This prevents the air conditioner 1 from frequently repeatedly switching between the thermo-off state and the thermo-on state, thereby preventing a deterioration in energy efficiency and a shortened lifespan of the compression region 21 due to frequent stopping and restarting of the compressor 21.

In the first and second embodiments, the heat exchange amount adjustment means is formed of an internal heat exchanger, two sub-expansion valves, and two branch pipes. In contrast, the heat exchange amount adjustment means of this embodiment is formed of only one sub-expansion valve (first sub-expansion valve 28c), one receiver (receiver 200), and one refrigerant pipe (outlet pipe 70). In other words, in this embodiment, fewer components are required to form the heat exchange amount adjustment means compared to the first and second embodiments, so the heat exchange amount adjustment means can be realized at low cost. In addition, since the number of sub-expansion valves to be controlled is smaller than in the first and second embodiments, the heat exchange amount in the indoor heat exchanger 31 can be adjusted with simple control.

Next, the fifth embodiment of the present invention will be described with reference to FIG. 7. In the first and second embodiments, the heat exchange amount adjustment means during controlled heating or controlled cooling operation exchanges heat between the refrigerant flowing into the heat exchanger functioning as a condenser (the indoor heat exchanger 31 during heating operation, and the outdoor heat exchanger 23 during cooling operation) and the refrigerant decompressed by the main expansion valve 27 in the internal heat exchanger 24a or 24b, thereby reducing the heat exchange amount in the indoor heat exchanger 31. In the third and fourth embodiments, the heat exchange amount adjustment means during controlled heating or controlled cooling operation reduces the amount of refrigerant flowing through the indoor heat exchanger 31, thereby reducing the heat exchange amount in the indoor heat exchanger 31.

In contrast to each of the above-mentioned embodiments, when the air conditioner 1 of this embodiment performs regulated heating operation or regulated cooling operation, the heat exchange amount adjustment means formed by the refrigerant piping that bypasses the outdoor heat exchanger 23, the refrigerant piping that bypasses the indoor heat exchanger 31, and the internal heat exchanger that exchanges heat with the refrigerant flowing through each of these refrigerant piping is operated to reduce the heat exchange amount in the indoor heat exchanger 31.

The fifth embodiment of the present invention will be described below mainly with reference to FIG. 7. The air conditioner 1 of this embodiment is the same as the first to fourth embodiments except that the heat exchange amount adjustment means is different from the first to fourth embodiments. For this reason, detailed explanations of the operation of the refrigerant circuit 10 during normal heating operation, controlled heating operation, normal cooling operation, and controlled cooling operation will be omitted, and only the configuration and function of the heat exchange amount adjustment means will be described.

The heat exchange amount adjustment means of this embodiment is formed by the internal heat exchanger 24c, the first sub-expansion valve 28e, the second sub-expansion valve 29e, the first branch pipe 67c, and the second branch pipe 68c shown in FIG. 7.

The first branch pipe 67c has one end connected to the refrigerant piping 62, and the other end connected to the outdoor unit liquid pipe 63 between the outdoor heat exchanger 23 and the main expansion valve 27. In other words, the first branch pipe 67c is connected to the outdoor unit refrigerant circuit 10a so as to bypass the outdoor heat exchanger 23. The second branch pipe 68c has one end connected to the outdoor unit liquid pipe 63 between the main expansion valve 27 and the stop valve 25, and the other end connected to the outdoor unit gas pipe 64. In other words, the second branch pipe 68c is connected to the outdoor unit refrigerant circuit 10a so as to bypass the indoor heat exchanger 31.

The internal heat exchanger 24c is, for example, a double-pipe heat exchanger, and exchanges heat between the refrigerant flowing through the first branch pipe 67c and the refrigerant flowing through the second branch pipe 68c. The first sub-expansion valve 28e is an electronic expansion valve, and is provided in the first branch pipe 67c between the internal heat exchanger 24c and the outdoor unit liquid pipe 63 side of the first branch pipe 67c. The amount of refrigerant flowing through the first branch pipe 67c is adjusted by adjusting the opening degree of the first sub-expansion valve 28e. The second sub-expansion valve 29b is an electronic expansion valve, and is provided in the second branch pipe 68c between the internal heat exchanger 24c and the outdoor unit gas pipe 64 side of the second branch pipe 68c. The amount of refrigerant flowing through the second branch pipe 68c is adjusted by adjusting the opening degree of the second sub-expansion valve 29e.

The heat exchange amount adjustment means described above is operated when the air conditioner 1 of this embodiment performs regulated heating operation or regulated cooling operation. Specifically, the opening degree of each of the first sub-expansion valve 28e and the second sub-expansion valve 29e is adjusted according to the temperature difference between the set temperature and the room temperature, using the sub-expansion valve opening degree table 300a shown in FIG. 2.

When the air conditioner 1 is performing normal heating operation, if the indoor temperature is rising toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the air conditioner 1 performs an adjusted heating operation in which the heat exchange amount adjustment means is operated. Specifically, the items for adjusted heating operation in the sub-expansion valve opening table 300a shown in FIG. 2 are referenced, and the opening degree of the first sub-expansion valve 28e and the opening degree of the second sub-expansion valve 29e are adjusted according to the temperature difference. As a result, the refrigerant flows through the first branch pipe 67c and the second branch pipe 68c, and the refrigerant flowing through the first branch pipe 67c and the refrigerant flowing through the second branch pipe 68c exchange heat in the internal heat exchanger 24c, reducing the amount of heat exchange in the indoor heat exchanger 31. This reduces the heating capacity exerted by the indoor unit 3, thereby suppressing the rise in the indoor temperature.

On the other hand, when the air conditioner 1 is performing normal cooling operation, if the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, if the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform a controlled cooling operation. Specifically, the items for controlled cooling operation in the sub-expansion valve opening table 300a shown in FIG. 2 are referenced, and the opening degree of the first sub-expansion valve 28e and the opening degree of the second sub-expansion valve 29e are reduced according to the temperature difference. As a result, the refrigerant flows through the first branch pipe 67c and the second branch pipe 68c, and the refrigerant flowing through the first branch pipe 67c and the refrigerant flowing through the second branch pipe 68c exchange heat in the internal heat exchanger 24c, reducing the amount of heat exchange in the outdoor heat exchanger 23, and thus reducing the amount of heat exchange in the indoor heat exchanger 31. This reduces the cooling capacity exerted by the indoor unit 3, thereby suppressing the decrease in the indoor temperature.

As described above, when the air conditioner 1 of this embodiment is performing air conditioning operation, if the indoor temperature is rising or falling toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is equal to or less than a predetermined value, and the compressor 21 is operating at a rotation speed equal to or less than a predetermined rotation speed, the heat exchange amount adjustment means is operated to perform regulated heating operation or regulated cooling operation. This prevents the air conditioner 1 from frequently repeatedly switching between the thermo-off state and the thermo-on state, thereby preventing a deterioration in energy efficiency and a shortened lifespan of the compression region 21 due to frequent stopping and restarting of the compressor 21.

As described above, the heat exchange amount adjustment means provided in the air conditioner 1 of the first embodiment works better during regulated heating operation, and the heat exchange amount adjustment means provided in the air conditioner 1 of the second embodiment works better during regulated cooling operation. In contrast, the heat exchange amount adjustment means provided in the air conditioner 1 of this embodiment exchanges heat in the internal heat exchanger 24c between the refrigerant flowing through the first branch pipe 67c bypassing the outdoor heat exchanger 23 and the refrigerant flowing through the second branch pipe 68c bypassing the indoor heat exchanger 31. Therefore, it works in the same way during regulated heating operation and regulated cooling operation, and the heat exchange amount in the indoor heat exchanger 31 can be reduced.

REFERENCE SIGNS LIST 1 Air conditioner 2 Outdoor unit 3 Indoor unit 10 Refrigerant circuit 21 Compressor 22 Four-way valve 23 Outdoor heat exchanger 24a to 24c Internal heat exchanger 27 Main expansion valve 28a to 28e First auxiliary expansion valve 29a, 29b, 29e Second auxiliary expansion valve 31 Indoor heat exchanger 67a to 67c First branch pipe 68a to 68c Second branch pipe 69 Bypass pipe 70 Outlet pipe 300a, 300b Auxiliary expansion valve opening degree table

Claims (1)

a refrigerant circuit formed by connecting a compressor, a four-way valve, an outdoor heat exchanger, a main expansion valve, and an indoor heat exchanger with a refrigerant piping;
an indoor temperature sensor for detecting an indoor temperature, which is the temperature of an air-conditioned space;
a heat exchange amount adjusting means provided in the refrigerant circuit and adjusting a heat exchange amount in the indoor heat exchanger;
having
the heat exchange amount adjusting means is formed by a first branch pipe, a second branch pipe, a first sub-expansion valve, a second sub-expansion valve, and an internal heat exchanger,
the first branch pipe is connected at one end to a refrigerant pipe connecting the four-way valve and the outdoor heat exchanger so as to bypass the outdoor heat exchanger, and is connected at the other end to a refrigerant pipe connecting the outdoor heat exchanger and the main expansion valve ;
the second branch pipe has one end connected to a refrigerant pipe connecting the main expansion valve and the indoor heat exchanger so as to bypass the indoor heat exchanger, and the other end connected to a refrigerant pipe connecting the indoor heat exchanger and the four-way valve ;
During heating operation, when the indoor temperature is rising toward a set temperature, which is a target value of the indoor temperature, and a temperature difference obtained by subtracting the indoor temperature from the set temperature becomes smaller than a predetermined value, if the rotation speed of the compressor is lower than a predetermined rotation speed,
or,
During cooling operation, when the indoor temperature is decreasing toward the set temperature and the temperature difference obtained by subtracting the set temperature from the indoor temperature is smaller than a predetermined value, if the rotation speed of the compressor is lower than a predetermined rotation speed,
The first sub-expansion valve adjusts the amount of refrigerant flowing through the first branch pipe,
The second sub-expansion valve adjusts the amount of refrigerant flowing through the second branch pipe,
The internal heat exchanger exchanges heat between the refrigerant flowing through the first branch pipe and the refrigerant flowing through the second branch pipe.
An air conditioner characterized by the above.

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