Air conditioner and air conditioner control method
Patent Information
- Application Number
- ES2022923771T
- Authority / Receiving Office
- ES · ES
- Patent Type
- Patents
- Current Assignee / Owner
- Filing Date
- 2022-01-26
- Publication Date
- 2026-08-31
- Estimated Expiration
- 2042-01-26
Smart Images
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Abstract
Description
Air conditioner and air conditioner control method Technical field The present invention relates to an air conditioning apparatus and to a method for controlling an air conditioning apparatus. Previous technique Some air conditioning units include an internal heat exchanger that cools the refrigerant outlet from an external heat exchanger during a cooling operation. For example, patent literature 1 discloses an air conditioning apparatus comprising compressors that compress refrigerant, a branch provided to a high-pressure liquid line through which the refrigerant outlet from an outdoor heat exchanger flows, and an internal heat exchanger disposed between the compressors and the branch. The internal heat exchanger performs heat exchange between the refrigerant separated at the branch and cooled through decompression by an expansion device and the refrigerant freshly separated at the branch during a cooling operation, thereby cooling the freshly separated refrigerant at the branch, and then returning the refrigerant to the high-pressure liquid line. The internal heat exchanger of the air conditioning unit described in patent literature 1 cools the refrigerant outlet of the outdoor heat exchanger during cooling operation. This air conditioning unit has improved cooling performance. The air conditioning unit also includes two indoor heat exchangers, one of which functions as an evaporator and the other as a condenser. During a room heating operation involving the other indoor heat exchanger, the air conditioning unit closes a switching valve provided between the compressors and the branch, allowing the internal heat exchanger to serve as a reservoir for excess refrigerant. Therefore, the air conditioning unit has improved heating performance.WO 2016 / 047506 A1 also discloses an air conditioning unit with a closed refrigerant circuit comprising an outdoor heat exchanger, an expansion valve, an indoor heat exchanger, a compressor, and a four-way reversible switching mechanism. The system further includes a dual-channel internal heat exchanger in which the refrigerant in a return channel and the refrigerant in a bypass-controlled liquid channel exchange heat. A control valve selectively connects the second channel to the expansion valve, enabling specific control of the internal heat exchange operation. List of appointments Patent literature Patent literature 1: Publication of unexamined Japanese patent application no. H4-257661. Patent literature 2: Document WO2016 / 047506 A1 describing a gas-liquid separator. Patent literature 3: Document US2014 / 123689 describing a heat pump and water heating circuit for a structure. Summary of the invention Technical problem However, the air conditioning apparatus described in patent literature 1 has a complicated structure due to the expansion device included in the internal heat exchanger to decrease the refrigerant pressure. An objective of the present invention, which has been achieved to solve the above problem, is to provide an air conditioning apparatus that has improved cooling performance and improved heating performance with a simple structure, and a method for controlling the air conditioning apparatus. Solution to the problem In order to achieve the above objective, an air conditioning apparatus according to the present invention comprises the features of claim 1. Advantageous effects of the invention According to the present invention, the controller switches the second switching mechanism so that the second channel is connected to the first expansion valve, thereby causing the refrigerant, after heat exchange by the internal heat exchanger, to flow to the first expansion valve. This process causes the internal heat exchanger to cool the indoor air. The refrigerant flowing through the first expansion valve to the internal heat exchanger is therefore at a lower temperature. This configuration can thus improve the cooling performance of the air conditioning unit. Furthermore, the controller switches the second switching mechanism so that the second channel is disconnected from the first expansion valve, thus stopping the flow of refrigerant from the second channel to the first expansion valve. This prevents the indoor heat exchanger from heating the indoor air. The refrigerant that entered the second channel during the heating process remains in that channel. This configuration prevents the refrigerant circuit from becoming overcharged during heating operation. Therefore, this configuration can improve the heating performance of the air conditioning unit. In addition, the internal heat exchanger has a second channel leading to a branch and a second switching mechanism. The branch is located within a refrigerant line that connects the outdoor heat exchanger to the first expansion valve. The second switching mechanism is positioned on the refrigerant line closer to the first expansion valve than to the branch and is configured to switch the direction of refrigerant flow. In other words, the controller can connect or disconnect the second channel to or from the refrigerant line simply by switching this second mechanism. This configuration can improve both the cooling and heating performance of the air conditioning unit.Therefore, the air conditioning unit can achieve improved cooling performance and improved heating performance with a simple structure. Brief description of the drawings Figure 1 illustrates a refrigerant circuit of an air conditioning apparatus according to an embodiment of the present invention; Figure 2 illustrates a hardware configuration of a controller included in the air conditioning appliance according to the embodiment; Figure 3 illustrates the refrigerant circuit with refrigerant flows during a cooling operation in the air conditioning unit according to the embodiment; and Figure 4 illustrates the refrigerant circuit with refrigerant flows during a heating operation in the air conditioning unit according to the embodiment. Description of achievements The following describes an air conditioning apparatus and a method for controlling an air conditioning apparatus according to an embodiment of the present invention in detail with reference to the accompanying drawings. In the drawings, identical or corresponding components are provided with the same reference symbol. The air conditioning unit, according to the embodiment, is designed to condition the interior air of a railway vehicle. This air conditioning unit includes, in addition to an interior heat exchanger and an exterior heat exchanger, an internal heat exchanger intended to improve cooling performance. The air conditioning unit also includes a controller that switches three-way valves, thereby allowing refrigerant to flow to the internal heat exchanger during cooling operation. The air conditioning unit to be controlled by the controller is described below with reference to Figure 1. Figure 1 illustrates a refrigerant circuit of an air conditioning unit 1 according to one embodiment. Figure 1 also shows, in addition to the individual components of the air conditioning unit 1, electrical connections between a controller 80 and the individual components with dashed lines for clarity. As illustrated in Figure 1, the air conditioning unit 1 includes a compressor 10 that compresses refrigerant, three-way valves 21 and 22 that switch the directions of the refrigerant flows, an outdoor heat exchanger 30 that performs heat exchange between the refrigerant and the outdoor air, expansion valves 41 and 42 that expand the refrigerant, and an indoor heat exchanger 50 that performs heat exchange between the refrigerant and the indoor air. The compressor 10, the three-way valves 21 and 22, the outdoor heat exchanger 30, the expansion valves 41 and 42, and the indoor heat exchanger 50 are connected in sequence and constitute a refrigerant circuit 2. Compressor 10 compresses low-pressure refrigerant, converting it into high-pressure refrigerant. Compressor 10 has an inlet and an outlet, which are not shown. Compressor 10 draws in low-pressure refrigerant through the inlet and discharges high-pressure refrigerant through the outlet. The inlet is connected to an internal heat exchanger 60, described below. The outlet is connected to the three-way valve 21 via a check valve 11, which allows refrigerant to flow from compressor 10 to the three-way valve 21 and prevents it from flowing in the opposite direction. Three-way valves 21 and 22 are connected in parallel. Specifically, three-way valve 21 has three ports. These ports include a first port connected to a branch pipe of refrigerant line 31 leading to the outdoor heat exchanger 30. A second port is connected to a refrigerant line 12 extending from the compressor 10. A third port is connected to a branch pipe of refrigerant line 51 leading to the indoor heat exchanger 50. The three-way valve 22 also has a first port, a second port, and a third port. The first port is connected to another branch pipe of the refrigerant line 31. The second port is connected to a refrigerant line 63 that extends from the internal heat exchanger 60. The third port is connected to another branch pipe of the refrigerant line 51. Three-way valves 21 and 22 are each either a solenoid valve or a motorized valve, for example. Three-way valves 21 and 22 are electrically coupled to controller 80, which is described below. In response to a switching operation by controller 80, three-way valves 21 and 22 direct the refrigerant entering from compressor 10 through refrigerant line 12 to refrigerant line 31, which leads to the outdoor heat exchanger 30. Three-way valves 21 and 22 also direct the refrigerant exiting from the indoor heat exchanger 50 through refrigerant line 51 to refrigerant line 63, which leads to the indoor heat exchanger 60. In this way, three-way valves 21 and 22 switch the operating mode of air conditioning unit 1 to cooling mode. In addition, three-way valves 21 and 22 direct the refrigerant introduced from compressor 10 to refrigerant pipe 51, which leads to the indoor heat exchanger 50, in response to another switching operation by controller 80. Three-way valves 21 and 22 direct the refrigerant outlet from the outdoor heat exchanger 30, through refrigerant pipe 31, to refrigerant pipe 63, which leads to the indoor heat exchanger 60. Three-way valves 21 and 22 thus switch the operating mode of air conditioning unit 1 to a heating mode. That is, the three-way valves 21 and 22 switch the directions of the refrigerant flows in the refrigerant circuit 2, and thus achieve the cooling mode or the heating mode of the air conditioning unit 1. The three-way valves 21 and 22 accordingly guide the refrigerant compressed by the compressor 10 to the outdoor heat exchanger 30 or to the indoor heat exchanger 50. The outdoor heat exchanger 30 has a finned-tube structure. Specifically, the outdoor heat exchanger 30 has multiple fins and tubes, which are not shown. The fins are supplied with outside air by a fan, which is also not shown. The tubes allow refrigerant from compressor 10 to flow through them during cooling operation, or allow refrigerant from an expansion valve 41 to flow through them during heating operation. The outdoor heat exchanger 30 with this structure performs heat exchange between the outside air supplied to the fins and the refrigerant flowing through the tubes, and condenses the refrigerant during cooling operation, or evaporates the refrigerant during heating operation.The outdoor heat exchanger 30 therefore functions as a condenser during cooling operation, or as an evaporator during heating operation. During cooling operation, the outdoor heat exchanger 30 sends the refrigerant to an expansion valve 42, illustrated in Figure 1, or to three-way valves 21 and 22 during heating operation. Expansion valves 41 and 42 each have a valve body, not shown, for adjusting the opening of a refrigerant flow path. Expansion valves 41 and 42 are each either a solenoid valve or a motorized valve, for example. Expansion valves 41 and 42 are electrically connected to the controller 80 shown in Figure 1, and they adjust the valve body openings that define the flow paths according to the output of controller 80. Expansion valves 41 and 42 decrease the refrigerant pressure by means of the valve body openings. Expansion valves 41 and 42 decrease the refrigerant pressure to a pressure that depends on the output of controller 80 and thus expand the refrigerant. Expansion valves 41 and 42 are intended to expand refrigerant during heating and cooling operations, respectively. Expansion valve 41 is connected in parallel with a check valve 68, so that expansion valve 41 is used only during heating operation and not during cooling operation. The check valve 68 allows refrigerant to flow from a refrigerant line 32, which has a branch between expansion valve 41 and the outdoor heat exchanger 30, to either the indoor heat exchanger 60 or the indoor heat exchanger 50, and does not allow refrigerant to flow in the opposite direction. Expansion valve 42 is connected in parallel with a check valve 46, so that expansion valve 42 is used only during cooling operation and not during heating operation.The check valve 46 allows the refrigerant to flow in the direction from the indoor heat exchanger 50 to the outdoor heat exchanger 30, and does not allow the refrigerant to flow in the opposite direction. Expansion valves 41 and 42 are controlled by controller 80, so the openings of the individual valve bodies are adjusted depending on whether the current mode is cooling or heating. In cooling mode, expansion valve 42 expands the refrigerant and sends the expanded refrigerant to the indoor heat exchanger 50. In heating mode, expansion valve 41 expands the refrigerant and sends the expanded refrigerant to the outdoor heat exchanger 30. The indoor heat exchanger 50 has a finned-tube structure, similar to the outdoor heat exchanger 30. Specifically, the indoor heat exchanger 50 has fins, which are not shown, just like the outdoor heat exchanger 30. The fins are supplied with indoor air by a fan, which is not shown. The indoor heat exchanger 50 also has tubes, which are not shown. These tubes allow the refrigerant expanded by the expansion valve 42 to flow through them during cooling operation, or they allow the refrigerant compressed by the compressor 10 to flow through them during heating operation. The indoor heat exchanger 50, with this structure, performs heat exchange between the supplied indoor air and the refrigerant flowing through the tubes.This indoor heat exchanger 50 functions as an evaporator, absorbing heat from the indoor air and evaporating the refrigerant during cooling operation, or as a condenser, discharging heat to the indoor air and condensing the refrigerant during heating operation. The indoor heat exchanger 50 cools the indoor air accordingly during cooling operation, or heats the indoor air during heating operation. During cooling operation, the indoor heat exchanger 50 returns the refrigerant to the three-way valves 21 and 22, or sends the refrigerant to the expansion valve 41, or to the expansion valve 41. These components constitute refrigerant circuit 2, which allows air conditioning unit 1 to perform either cooling or heating operations. These operations essentially require the condenser to discharge the heat absorbed from the air by the evaporator and the incoming heat generated by compression. The condenser must therefore have a higher heat exchange efficiency than the evaporator. The refrigerant contains a naturally occurring material, which is environmentally friendly. Specifically, the refrigerant is made of carbon dioxide, or CO2. CO2 never liquefies, even in a supercritical state at pressures exceeding the supercritical point. The outdoor heat exchanger 30, which acts as a condenser during cooling operation, therefore preferably has a large volumetric capacity, similar to a gas chiller. Given this, the outdoor heat exchanger 30 is designed to have a refrigerant volumetric capacity even greater than that of the indoor heat exchanger 50, compared to that of an air conditioning unit using condensable refrigerant. If the amount of refrigerant used in refrigerant circuit 2 is appropriately determined for the volumetric capacity of the outdoor heat exchanger 30, which acts as a condenser during cooling operation, the indoor heat exchanger 50, which has a smaller volumetric capacity than the outdoor heat exchanger 30 and acts as a condenser during heating operation, will suffer from excess refrigerant. This excess refrigerant unintentionally increases the temperature and pressure of the refrigerant flowing through the indoor heat exchanger 50 during heating operation, thereby impairing the heating performance of the air conditioning unit 1.If such deterioration of the heating performance of air conditioning appliance 1 is reduced by the indoor heat exchanger 50 designed to have a volumetric capacity that is greater than the outdoor heat exchanger 30, this indoor heat exchanger 50 requires a greater amount of refrigerant and results in an increase in the size of air conditioning appliance 1. To address these issues, the air conditioning unit 1 further includes an internal heat exchanger 60 designed to enhance cooling performance, and a three-way valve 70 that switches the direction of refrigerant flow to the internal heat exchanger 60, thereby allowing the internal heat exchanger 60 to store excess refrigerant during heating operation. The internal heat exchanger 60 has a shell-and-tube structure for heat exchange between two types of refrigerant in different states. Specifically, the internal heat exchanger 60 comprises multiple interconnected tubes 61 and a hollow cylindrical shell 62 with a cylindrical shaft extending longitudinally from and housing the tubes 61 within it. The tubes 61 are connected to the refrigerant pipe 63, which leads to the second port of the three-way valve 22, described above, for introducing refrigerant that will undergo heat exchange. Specifically, this is for introducing the low-temperature refrigerant flowing from the indoor heat exchanger 50 during cooling operation, or for introducing the low-temperature refrigerant flowing from the outdoor heat exchanger 30 during heating operation. The tubes 61 are also connected to a refrigerant pipe 64, which leads to the compressor 10, for discharging the introduced refrigerant. Conversely, the casing 62 is connected to a refrigerant pipe 65 to introduce the high-temperature refrigerant that will undergo heat exchange after condensing in the outdoor heat exchanger 30 during cooling operation. The refrigerant pipe 65 is connected to a branch 33 provided on the refrigerant pipe 32, which connects the outdoor heat exchanger 30 to the expansion valve 41. The refrigerant pipe 65 is fitted with a filter 67 to remove water and contaminants from the refrigerant. The casing 62 is also connected to a refrigerant pipe 66 to discharge the introduced refrigerant. This refrigerant pipe 66 is connected to the junction between a refrigerant pipe 43 extending from the expansion valve 41 and a refrigerant pipe 44 extending from the expansion valve 42. The refrigerant pipe 65 is fitted with a check valve 68, which allows refrigerant to flow from the refrigerant pipe 32 into the housing 62 and prevents flow in the opposite direction, thus defining the refrigerant flow direction described above. The refrigerant pipe 65 has an intermediate section 651 running longitudinally. This intermediate section 651 is connected to a refrigerant pipe 45 that branches off from the refrigerant pipe 43 leading to the expansion valve 41, introducing the existing refrigerant adjacent to the expansion valve 41.The refrigerant pipe 45 is provided with a check valve 69, which allows the refrigerant to flow in the direction from the refrigerant pipe 43 to the housing 62 and does not allow the refrigerant to flow in the opposite direction, to prevent the occurrence of a reverse flow of refrigerant from the refrigerant pipe 65 to the expansion valve 41. The shell 62 of the internal heat exchanger 60 has an internal space in which the tubes 61 are spaced between them and against the inner wall of the shell 62. The tubes 61 are made of a metal, such as aluminum, that has high thermal conductivity. When the coupling relationship described above causes low-temperature refrigerant to enter the tubes 61 from the internal heat exchanger 50 and high-temperature refrigerant to enter the shell 62 from the external heat exchanger 30 during cooling operation, these refrigerants exchange heat with each other. This heat exchange cools the refrigerant that entered the shell 62 from the external heat exchanger 30. The cooled refrigerant is then sent to the refrigerant line 66 extending from the shell 62.The refrigerant pipe 66 is fitted with the three-way valve 70 to control whether to supply the outlet refrigerant to the indoor heat exchanger 50. The three-way valve 70 leads to the refrigerant pipe 66 connected to the housing 62 of the internal heat exchanger 60, the refrigerant pipe 43 connected to the expansion valve 41, and the refrigerant pipe 44 connected to the expansion valve 42. The three-way valve 70 is a solenoid valve or a motorized valve, similar to three-way valves 21 and 22. The three-way valve 70 is electrically connected to the controller 80. In response to a switching operation by the controller 80, the three-way valve 70 directs the cooled refrigerant, which flows from the housing 62 to the refrigerant pipe 66 during the cooling operation, to the refrigerant pipe 44, thus supplying the refrigerant to the expansion valve 42. The refrigerant to be expanded by the expansion valve 42 is therefore at an even lower temperature.Therefore, the indoor heat exchanger 50 has an even greater efficiency in cooling indoor air. To perform such switching operations of the three-way valve 70 depending on the cooling mode or the heating mode, the air conditioning unit 1 includes the controller 80. The following describes a configuration of the controller 80 and a method for controlling the air conditioning unit 1 executed by the controller 80, with reference to Figures 2 to 4. Figure 2 illustrates a hardware configuration of controller 80 included in air conditioning unit 1. Figure 3 illustrates the refrigerant circuit with refrigerant flows during a cooling operation in air conditioning unit 1. Figure 4 illustrates the refrigerant circuit with refrigerant flows during a heating operation in air conditioning unit 1. Figure 2 also illustrates the components electrically connected to controller 80 for clarity. Figures 3 and 4 include arrows indicating the directions of refrigerant flows along some segments of refrigerant circuit 2. Figures 3 and 4 do not illustrate controller 80 or the electrical connections between controller 80 and individual components. As illustrated in Figure 2, the controller 80 includes an inlet / output (I / O) port 81. The I / O port 81 is electrically connected to the compressor 10, the three-way valves 21, 22 and 70 and the expansion valves 41 and 42 to be controlled by the controller 80, in order to achieve the refrigerant flows described above. The I / O port 81 is also electrically connected to pressure sensors 91 and 92 and a switch 93, which are illustrated not in Figure 2 but in Figures 1, 3, and 4. Pressure sensor 91 measures the refrigerant pressure and determines whether the detected pressure is significantly low, indicating a refrigerant leak, during the activation and deactivation of air conditioning unit 1. Pressure sensor 92 measures the refrigerant pressure and determines whether the detected pressure is high enough to exceed the permissible limit during the activation of air conditioning unit 1. Switch 93 deactivates air conditioning unit 1 when the refrigerant pressure is high enough to exceed the permissible limit. Controller 80 has a computer that includes a central processing unit (CPU) 82, a read-only memory (ROM) 83, and a random-access memory (RAM) 84, as illustrated in Figure 2. The CPU 82, ROM 83, and RAM 84 are electrically connected to the I / O port 81.The CPU 82 loads several programs stored in ROM 83 into RAM 84 and executes the programs, so that the controller 80 runs several processes to control the individual components of the air conditioning unit 1. For example, when the CPU 82 executes a control program stored in ROM 83, the controller 80 operates the compressor 10 electrically connected to the I / O port 81 described above, and opens or closes the three-way valves 21, 22 and 70 and the expansion valves 41 and 42 or adjusts their openings. These procedures are described in more detail below. In response to a push action on a power button, not shown, and a push action on a mode selection button, also not shown, to select cooling operation, controller 80 operates compressor 10. Controller 80 switches the coupling ratio between the individual ports of three-way valves 21 and 22, thereby connecting refrigerant pipe 12 extending from compressor 10 to refrigerant pipe 31 leading to the outdoor heat exchanger 30, as shown in Figure 3. Controller 80 also connects refrigerant pipe 51 extending from the indoor heat exchanger 50 to refrigerant pipe 63 leading to the tubes 61 of the indoor heat exchanger 60.Controller 80 switches the coupling ratio between the individual ports of the three-way valve 70, thereby connecting the refrigerant pipe 66 extending from the housing 62 of the internal heat exchanger 60, to the refrigerant pipe 44 leading to the expansion valve 42. In addition, controller 80 closes the expansion valve 41 and opens the expansion valve 42. Controller 80 controls these three-way valves 21, 22, and 70 and the expansion valves 41 and 42, thereby circulating refrigerant through compressor 10, three-way valve 21, outdoor heat exchanger 30, check valve 68, filter 67, housing 62 of the indoor heat exchanger 60, three-way valve 70, expansion valve 42, indoor heat exchanger 50, three-way valve 22, tubes 61 of the indoor heat exchanger 60, and compressor 10 in sequence, as illustrated by the arrows in Figure 3. Controller 80 thus causes the outdoor heat exchanger 30 to function as a condenser and the indoor heat exchanger 50 to function as an evaporator. These functions achieve cooling operation to cool the indoor air. During the cooling operation, the high-temperature refrigerant condensed by the external heat exchanger 30 enters the shell 62 of the internal heat exchanger 60 through the refrigerant pipe 65. The low-temperature refrigerant evaporated by the internal heat exchanger 50 enters the tubes 61 of the internal heat exchanger 60 through the refrigerant pipe 63. The high-temperature refrigerant flowing through the shell 62 and the low-temperature refrigerant flowing through the tubes 61 thus exchange heat with each other in the internal heat exchanger 60. This heat exchange cools the high-temperature refrigerant flowing through the shell 62. The refrigerant that exits the shell 62 into the refrigerant pipe 66 and is fed to the expansion valve 42 is therefore at an even lower temperature.Furthermore, the refrigerant that expands through expansion valve 42 and is fed to the indoor heat exchanger 50 is at an even lower temperature. Therefore, the indoor heat exchanger 50 has an even greater efficiency in cooling the indoor air, resulting in a higher cooling efficiency for air conditioning unit 1. Conversely, in response to a push manipulation of the mode selection button, not illustrated, to select the heating operation, the controller 80 switches the coupling ratio between the individual ports of the three-way valves 21 and 22, thereby connecting the refrigerant pipe 12 extending from the compressor 10 to the refrigerant pipe 51 leading to the indoor heat exchanger 50, illustrated in Figure 4. The controller 80 also connects the refrigerant pipe 31 extending from the outdoor heat exchanger 30 to the refrigerant pipe 63 leading to the tubes 61 of the indoor heat exchanger 60. Controller 80 switches the coupling ratio between the individual ports of the three-way valve 70, thereby disconnecting the refrigerant pipe 66 extending from the housing 62 of the internal heat exchanger 60, from the refrigerant pipe 44 leading to the expansion valve 42, and connecting the refrigerant pipe 44 to the refrigerant pipe 43 leading to the expansion valve 41. In addition, controller 80 opens the expansion valve 41 and closes the expansion valve 42. Controller 80 controls these three-way valves 21, 22, and 70 and the expansion valves 41 and 42, and thus circulates refrigerant through compressor 10, three-way valve 21, indoor heat exchanger 50, check valve 46, three-way valve 70, expansion valve 41, outdoor heat exchanger 30, three-way valve 22, the tubes 61 of the indoor heat exchanger 60, and compressor 10 in sequence, as illustrated by the arrows in Figure 4. Controller 80 therefore causes the outdoor heat exchanger 30 to function as an evaporator and the indoor heat exchanger 50 to function as a condenser. These functions accomplish the heating operation to warm the indoor air. During the heating operation, the three-way valve 70 closes the end adjacent to refrigerant pipes 43 and 44 of refrigerant pipe 66, which extends from the shell 62 of the internal heat exchanger 60. This isolates refrigerant pipe 66 from refrigerant pipes 43 and 44. This arrangement prevents refrigerant within refrigerant pipe 66, in region A1 illustrated in Figure 4, from reaching refrigerant pipes 43 and 44. The arrangement also prevents refrigerant within the shell 62 from reaching refrigerant pipes 43 and 44 via refrigerant pipe 66. The refrigerant pipe 65 leading to the casing 62 is provided with the check valve 68 which prevents the refrigerant from flowing in the direction from the casing 62 to the refrigerant pipe 32 leading to the outdoor heat exchanger 30. The refrigerant pipe 45 coupled to the intermediate portion 651 of the refrigerant pipe 65 is provided with the check valve 69 which prevents the refrigerant from flowing in the direction from the refrigerant pipe 65 to the refrigerant pipe 43 which extends from the refrigerant pipe 45 and leads to the expansion valve 41. This structure can prevent the refrigerant within the refrigerant pipe 65 and a portion of the refrigerant pipe 45 within region A2 illustrated in Figure 4 from reaching the refrigerant pipes 32 and 43.The structure can also prevent the coolant inside housing 62 from reaching coolant pipes 32 and 43 through coolant pipe 65. That is, the shell 62 of the internal heat exchanger 60 is isolated from the coolant pipes 32, 43, and 44 during the heating operation. Coolant flow from the shell 62 to the coolant pipes 32, 43, and 44 is prevented. The coolant that entered the shell 62 during the cooling operation is thus trapped inside the shell 62. The shell 62 therefore stores the excess coolant caused by the difference in the amount of coolant required between the heating and cooling operations. In other words, the excess coolant is stored in the internal heat exchanger 60.This reserve can prevent excess refrigerant from inducing a temperature increase and a pressure increase in the refrigerant in the indoor heat exchanger 50 during heating operation, resulting in a reduction in the deterioration of the heating performance of the air conditioning unit 1. During the heating operation, the low-temperature refrigerant evaporated by the outdoor heat exchanger 30 enters the tubes 61 of the indoor heat exchanger 60. This low-temperature refrigerant cools the refrigerant inside the housing 62, thus lowering its pressure. When the refrigerant flowing through the refrigerant lines 32 and 43 has a higher pressure than the refrigerant inside the housing 62, the higher-pressure refrigerant flows through check valves 68 and 69 into the refrigerant line 65 and the housing 62 connected to the refrigerant line 65. The housing 62 thus stores a larger quantity of refrigerant. By storing a larger quantity of excess refrigerant during the heating operation, the housing 62 further reduces the deterioration in the heating performance of the air conditioning unit 1. To end the cooling or heating operation, a user of air conditioner 1 presses the power button again, which is not shown. Controller 80 then forcibly shuts down the process described above, followed by the deactivation of air conditioner 1. The expansion valve 42 in the embodiment described above is an example of a first expansion valve in the present invention. The expansion valve 41 is an example of a second expansion valve in the present invention. The three-way valves 21, 22, and 70, which switch the directions of the refrigerant flows, are also referred to as switching mechanisms. The three-way valves 21 and 22 are an example of a first switching mechanism in the present invention. The three-way valve 70 is an example of a second switching mechanism in the present invention. The refrigerant pipe 63, the tubes 61, and the refrigerant pipe 64 are an example of a first channel included in the internal heat exchanger 60 of the present invention. The refrigerant pipe 65, the casing 62, and the refrigerant pipe 66 are an example of a second channel included in the internal heat exchanger 60 of the present invention. The refrigerant pipe 45 is an example of a branch pipe in the present invention. The check valve 46 is an example of a first check valve in the present invention. The check valve 69 is an example of a second check valve in the present invention. The check valve 68 is an example of a third check valve in the present invention.As described above, the controller 80 of the air conditioning unit 1, according to the embodiment, switches the three-way valve 70 during cooling operation, thereby connecting the refrigerant pipe 66 extending from the housing 62 of the internal heat exchanger 60 to the refrigerant pipe 44 leading to the expansion valve 42. The refrigerant cooled through the heat exchanger in the housing 62 is thus directed to the expansion valve 42. The refrigerant flowing through the expansion valve 42 to the internal heat exchanger 50 consequently has a lower temperature. This internal heat exchanger 50 has a higher efficiency in cooling the indoor air, resulting in improved cooling performance of the air conditioning unit 1. Furthermore, controller 80 switches the three-way valve 70 during the heating operation, thereby disconnecting the refrigerant line 66 from the refrigerant line 44 and stopping the flow of refrigerant from the housing 62 to the expansion valve 42. The refrigerant that entered the housing 62 during the cooling operation is thus retained in the housing 62 during the heating operation. This reserve can reduce the excess refrigerant in the refrigerant circuit 2 during the heating operation. In other words, the refrigerant, which is in a gaseous or supercritical state during the cooling operation, is transformed into a liquid state during the heating operation, and the housing 62 can retain an amount of refrigerant corresponding to the density difference between the two states.This reserve can prevent excess refrigerant from inducing a pressure increase and a temperature increase in the refrigerant in the indoor heat exchanger 50. Therefore, the air conditioning unit 1 has improved heating performance. Since the reservoir prevents excess refrigerant from inducing a pressure increase during the heating operation, the refrigerant discharged from compressor 10 has a lower temperature. Compressor 10 therefore has a higher compression efficiency. Controller 80 can improve the cooling performance of air conditioner 1 during cooling operation and improve the heating performance of air conditioner 1 during heating operation, simply by switching the three-way valve 70. In other words, air conditioner 1 can achieve improved cooling and heating performance with a simple structure. Such air conditioner 1 can be easily manufactured. The air conditioning unit 1 preferably performs a heating operation for at least a short period after the cooling operation has finished. This heating operation allows a larger quantity of refrigerant to be stored in the internal heat exchanger 60, and thus prevents the refrigerant from becoming liquid and remaining in the compressor 10 during the deactivation of the air conditioning unit 1. The air conditioning apparatus 1 and the method of controlling the air conditioning apparatus 1 according to the embodiment of the present invention described above are mere examples. Although the refrigerant in this implementation is CO2, this is merely an example. The refrigerant can be any other refrigerant commonly used in air conditioning units. The refrigerant simply needs to have a difference in volume between the cooling and heating operations, resulting in excess refrigerant because the air conditioning unit stores excess refrigerant in the internal heat exchanger during heating. For example, the refrigerant can be a material that has different volumes depending on whether the temperature is high or low. Although the three-way valves 21 and 22 switch the directions of refrigerant flow in the refrigerant circuit 2 in this embodiment, the air conditioning unit 1 may have a different configuration. The three-way valves 21 and 22 in the air conditioning unit 1 may be other switching mechanisms for changing the directions of the refrigerant flows compressed by the compressor 10. For example, the three-way valves 21 and 22 may be replaced by a four-way valve. Although the internal heat exchanger 60 has a shell-and-tube structure in its embodiment, this internal heat exchanger 60 is merely an example. The internal heat exchanger 60 only needs to have a structure to perform heat exchange between the coolant flowing through the first channel and the coolant flowing through the second channel. For example, the internal heat exchanger 60 can have a double-pipe structure, in which one pipe houses another pipe within it. The internal heat exchanger 60 can also have a spiral structure made of a plate bent into a spiral. Alternatively, the internal heat exchanger 60 can have a stacked structure made of a stack of plates. Although air conditioning unit 1 is designed to condition the interior air of a railway vehicle in the embodiment, this air conditioning unit 1 is merely an example. The present invention can be applied to any general air conditioning unit. For example, air conditioning unit 1 can be designed to condition the interior air of a building. Although the control program is stored in ROM 83 in the embodiment, the control program can also be stored on a non-transient, computer-readable recording medium, such as a floppy disk, a compact disc (CD-ROM), a digital versatile disc (DVD), or a magneto-optical (MO) disk, and distributed. In this case, the control program stored on the non-transient recording medium can be installed on a computer to configure the controller 80 that executes the control process. The control program can also be stored on a disk drive included in a server device on a communication network, such as the Internet, and can be downloaded to a computer by superimposing it onto a carrier wave, for example. The foregoing describes some example embodiments for illustrative purposes. Accordingly, the specification and drawings should be considered illustrative rather than restrictive. Therefore, this detailed description should not be taken in a limiting sense, and the scope of the invention is defined solely by the included claims, together with the full range of equivalents to which those claims are entitled. List of reference signs 1 Air conditioning unit 2 Coolant circuit 10 Compressor 11 Check valve 12 Refrigerant piping 21, 22 Three-way valve 30 Outdoor heat exchanger 31, 32 Refrigerant piping 33 Bifurcation 41, 42 Expansion valve 43, 44, 45 Refrigerant piping 46 Check valve 50 Indoor heat exchanger 51 Refrigerant piping 60 Internal heat exchanger 61 Tube 62 Housing 63-66 Coolant piping 67 Filter 68, 69 Check valve 70 Three-way valve 80 Controller 81 I / O Port 82 CPU 83 ROM 84 RAM 91, 92 Pressure sensor 93 Switch 651 Intermediate portion A1, A2 Region
Claims
1. An air conditioning apparatus (1), comprising: a refrigerant circuit (2) including - an outdoor heat exchanger (30) for heat exchange between the refrigerant and outdoor air, - a first expansion valve (42) for expanding the refrigerant, - an indoor heat exchanger (50) for heat exchange between the refrigerant and indoor air, - a compressor (10) for compressing the refrigerant, and - a first switching mechanism (21, 22) for switching the direction of a refrigerant flow, the outdoor heat exchanger (30), the first expansion valve (42), the indoor heat exchanger (50), and the first switching mechanism (21, 22) being coupled to each other in sequence, the compressor (10) being coupled to the first switching mechanism (21, 22); an indoor heat exchanger (60) including - a first channel (61, 63,64) leading to the first switching mechanism (21, 22) and the compressor (10), and - a second channel (62, 65, 66) leading to a branch (33) and a second switching mechanism (70), the branch (33) being included in a refrigerant pipe (32, 43, 44) that couples the outdoor heat exchanger (30) to the first expansion valve (42), the second switching mechanism (70) being disposed in a position in the refrigerant pipe (32, 43, 44) more adjacent to the first expansion valve (42) than to the branch (33) and configured to switch one direction of a refrigerant flow, the indoor heat exchanger (60) being configured to perform heat exchange between the refrigerant flowing through the first channel (61, 63, 64) and the refrigerant flowing through the second channel (62, 65, 66); a first check valve (46) coupled in parallel to the first expansion valve (42),the first check valve (46) being configured to allow the refrigerant to flow in one direction from the indoor heat exchanger (50) to the outdoor heat exchanger (30) and to prevent the refrigerant from flowing in the opposite direction; a second expansion valve (41) disposed in a position on the refrigerant piping (32, 43, 44) more adjacent to the outdoor heat exchanger (30) than to the second switching mechanism (70), and configured to expand the refrigerant; a branch pipe (45) branching from a position on the refrigerant piping (32, 43, 44) between the second switching mechanism (70) and the second expansion valve (41), the branch pipe (45) leading to the second channel (62, 65, 66); a second check valve (69) provided on the branch pipe (45),the second check valve (69) being configured to allow the refrigerant to flow in one direction into the second channel (62, 65, 66) and to prevent the refrigerant from flowing in the opposite direction; and a controller (80) for (i) switching the second switching mechanism (70) such that the second channel (62, 65, 66) is connected to the first expansion valve (42), and thereby causing the refrigerant after the heat exchange performed by the internal heat exchanger (60) to flow to the first expansion valve (42), and (ii) closing the second expansion valve (41) and opening the first expansion valve (42), and thereby causing the refrigerant flowing through the first expansion valve (42) to expand, in a process of causing the internal heat exchanger (50) to cool the indoor air, and (i) switching the second switching mechanism (70) such that the second channel (62, 65,66) is disconnected from the first expansion valve (42), thereby stopping the flow of refrigerant from the second channel (62, 65, 66) to the first expansion valve (42), and (ii) closing the first expansion valve (42) and opening the second expansion valve (41), thereby causing the refrigerant flowing through the second expansion valve (41) to expand, in a process of causing the indoor heat exchanger (50) to heat the indoor air.
2. The air conditioning apparatus (1) according to claim 1, wherein the outdoor heat exchanger (30) has a volumetric capacity for holding the refrigerant that is greater than the volumetric capacity of the indoor heat exchanger (50) for holding the refrigerant.
3. The air conditioning apparatus (1) according to claim 1 or 2, wherein the second channel (62, 65,66) includes a third check valve (68) adjacent to the branch (33), the third check valve (68) being configured to permit refrigerant to flow in one direction from the branch (33) to the second switching mechanism (70).
4. The air conditioning apparatus (1) according to any one of claims 1 to 3, wherein the first switching mechanism (21, 22) includes two three-way valves (21, 22) coupled in parallel with each other.
5. The air conditioning apparatus (1) according to any one of claims 1 to 3, wherein the first switching mechanism (21, 22) includes a four-way valve.
6. The air conditioning apparatus (1) according to any one of claims 1 to 5, wherein the controller (80) switches the first switching mechanism (21, 22) such that the first switching mechanism (21,22) guides the refrigerant compressed by the compressor (10) to the outside heat exchanger (30) and guides the refrigerant leaving the inside heat exchanger (50) to the first channel (61, 63, 64), and thus causes the inside heat exchanger (50) to cool the inside air, and switches the first switching mechanism (21, 22) in such a way that the first switching mechanism (21, 22) guides the refrigerant compressed by the compressor (10) to the inside heat exchanger (50) and guides the refrigerant leaving the outside heat exchanger (30) to the first channel (61, 63, 64), and thus causes the inside heat exchanger (50) to heat the inside air.
7. A method for controlling an air conditioning appliance (1), the air conditioning appliance (1) including a refrigerant circuit (2) comprising an outdoor heat exchanger (30) for effecting heat exchange between refrigerant and outdoor air,- a first expansion valve (42) for expanding the refrigerant, - an indoor heat exchanger (50) for performing heat exchange between the refrigerant and indoor air, and - a first switching mechanism (21, 22) for switching one direction of a flow of the refrigerant compressed by a compressor (10), the outdoor heat exchanger (30), the first expansion valve (42), the indoor heat exchanger (50) and the first switching mechanism (21, 22) being coupled to each other in sequence, an indoor heat exchanger (60) including - a first channel (61, 63, 64) leading to the first switching mechanism (21, 22) and the compressor (10), and - a second channel (62, 65, 66) leading to a branch (33) and a second switching mechanism (70), the branch (33) being included in a refrigerant pipe (32, 43,44) coupling the outdoor heat exchanger (30) to the first expansion valve (42), the second switching mechanism (70) being disposed in a position on the refrigerant piping (32, 43, 44) more adjacent to the first expansion valve (42) than to the branch (33) and configured to switch one direction of a refrigerant flow, the indoor heat exchanger (60) being configured to perform heat exchange between the refrigerant flowing through the first channel (61, 63, 64) and the refrigerant flowing through the second channel (62, 65, 66), a first check valve (46) coupled in parallel to the first expansion valve (42), the first check valve (46) being configured to allow refrigerant to flow in one direction from the indoor heat exchanger (50) to the outdoor heat exchanger (30) and to prevent refrigerant from flowing in one direction opposite,a second expansion valve (41) disposed in a position on the refrigerant piping (32, 43, 44) more adjacent to the outdoor heat exchanger (30) than to the second switching mechanism (70), and configured to expand the refrigerant, a branch pipe (45) branching from a position on the refrigerant piping (32, 43, 44) between the second switching mechanism (70) and the second expansion valve (41), the branch pipe (45) leading to the second channel (62, 65, 66), and a second check valve (69) provided on the branch pipe (45), the second check valve (69) being configured to permit refrigerant to flow in one direction into the second channel (62, 65, 66) and to prevent refrigerant from flowing in the opposite direction, the method comprising: causing the indoor heat exchanger (50) to cool the indoor air by switching the first switching mechanism (21,22) such that the first switching mechanism (21, 22) guides the refrigerant compressed by the compressor (10) to the outside heat exchanger (30) and guides the refrigerant leaving the inside heat exchanger (50) to the first channel (61, 63, 64); and causing the indoor heat exchanger (50) to heat the indoor air by switching the first switching mechanism (21, 22) such that the first switching mechanism (21, 22) directs the refrigerant compressed by the compressor (10) to the indoor heat exchanger (50) and directs the refrigerant leaving the outdoor heat exchanger (30) to the first channel (61, 63, 64), wherein causing the indoor heat exchanger (50) to cool the indoor air includes (i) switching the second switching mechanism (70) such that the second channel (62, 65, 66) is connected to the first expansion valve (42),and thus guiding the refrigerant after the heat exchange performed by the internal heat exchanger (60) to the first expansion valve (42), and (ii) closing the second expansion valve (41) and opening the first expansion valve (42), and thus causing the refrigerant flowing through the first expansion valve (42) to expand, and causing the internal heat exchanger (50) to heat the internal air includes (i) switching the second switching mechanism (70) such that the second channel (62, 65, 66) is disconnected from the first expansion valve (42), and thus stopping the flow of refrigerant from the second channel (62, 65, 66) to the first expansion valve (42), and (ii) closing the first expansion valve (42) and opening the second expansion valve (41), and thus causing the refrigerant flowing through the second expansion valve (41) to expand.