Air conditioner and method for controlling air conditioner

Abstract

To provide an air conditioner which hardly disturbs air conditioning before and after a specific section in which indoor temperature easily fluctuates, and a method for controlling an air conditioner.SOLUTION: An air conditioner 1 includes a compressor, a condenser, an expansion valve 30 and an evaporator, and includes a refrigerant circuit part for performing air conditioning of the interior of a railroad vehicle, a position identification part 56 for periodically determining the position of the railroad vehicle within a route, an overheat degree information acquisition part 57 for periodically acquiring overheat degree information of refrigerant in the evaporator, and an expansion valve control part 58 for controlling the opening of the expansion valve 30 to be a constant opening in the case that the position determined by the position identification part 56 is determined to be a start point of a specific section in which indoor temperature easily changes, and changing the constant opening of the expansion valve 30 from the constant opening to an opening based on the overheat degree information of the refrigerant acquired by the overheat degree information acquisition part 57 in the case that it is determined to be an end point of the position identification section determined by the position identification part 56.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to an air conditioner and a method for controlling the air conditioner. [Background technology]

[0002] 2. Description of the Related Art Some air conditioners are installed in railway vehicles and perform air conditioning in the interior of the railway vehicle using feedforward control.

[0003] For example, Patent Document 1 discloses an air conditioner that is equipped with various sensors that detect the temperature and humidity inside and outside a railway vehicle, as well as the passenger occupancy rate, predicts sensible heat load and latent heat load based on the output of these sensors, and performs feedforward control of the refrigeration cycle based on the predicted sensible heat load and latent heat load. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-312474 Summary of the Invention [Problem to be solved by the invention]

[0005] In railway vehicles, the interior temperature can change significantly in specific sections, such as sections where the power supply is cut off, or sections where the vehicle is stopped at the platform where passengers get on and off.

[0006] In particular, in sections where there is no electricity, the power supply is cut off, which causes the compressors in air conditioners to stop, causing large changes in the indoor temperature. Also, in sections where trains are stopped, the indoor air and outside air mix together as passengers get on and off, causing large changes in the indoor temperature.

[0007] In the case of the feedforward control performed by the air conditioner described in Patent Document 1, if such a change in indoor temperature occurs in a specific section, the air conditioning of the indoor air will be disrupted for a while after the railway vehicle passes through the specific section, and the air conditioning will not be stable.

[0008] The present disclosure has been made to solve the above-mentioned problems, and aims to provide an air conditioner and a control method for an air conditioner that are less likely to disrupt air conditioning before and after specific sections where indoor temperatures are prone to fluctuate. [Means for solving the problem]

[0009] To achieve the above object, an air conditioner according to the present disclosure includes a refrigerant circuit unit, a position identification unit, a superheat degree information acquisition unit, and an expansion valve control unit. The refrigerant circuit unit includes a compressor that compresses a refrigerant, a condenser that condenses the refrigerant compressed by the compressor, an expansion valve that opens to expand the refrigerant condensed by the condenser, and an evaporator that evaporates the refrigerant expanded by the expansion valve, and air-conditions the interior of a railway vehicle. The position identification unit periodically identifies the position of the railway vehicle within a route. The superheat degree information acquisition unit periodically acquires information on the superheat degree of the refrigerant in the evaporator. The expansion valve control unit sets the aperture of the expansion valve to a constant aperture when it determines that the position identified by the position identification unit is the start point of a specific section in which the interior temperature is likely to fluctuate, and changes the aperture of the expansion valve from the constant aperture to an aperture based on the refrigerant superheat degree information acquired by the superheat degree information acquisition unit when it determines that the position identified by the position identification unit is the end point of the specific section. The specific section is a section where the train stops for passengers to get on and off the platform, and in the train stop section, the compressor operates using power supplied to the refrigerant circuit section. Furthermore, when the position identifying section determines that the position identified by the position identifying section is the start point of the train stop section, the expansion valve control section changes the opening degree of the expansion valve to an opening degree that is larger by a certain value than the opening degree at the start point of the train stop section, and maintains that opening degree. [Effects of the Invention]

[0010] According to the configuration of the present disclosure, when the position identified by the position identification unit is determined to be the start point of a specific section where the indoor temperature is likely to fluctuate, the expansion valve control unit sets the expansion valve to a constant opening, and when the position identified by the position identification unit is determined to be the end point of the specific section, the expansion valve control unit changes the opening of the expansion valve from the constant opening to an opening based on the refrigerant superheat information acquired by the superheat information acquisition unit. Therefore, the air conditioner is likely to return to its original air conditioning state after the railroad vehicle passes through the specific section. As a result, the air conditioner is less likely to experience disruptions in air conditioning before and after the specific section. [Brief explanation of the drawings]

[0011] [Figure 1] Refrigerant circuit diagram of an air conditioner according to a first embodiment of the present disclosure. [Figure 2] PH diagram showing the refrigerant state of the refrigeration cycle performed by the air conditioner according to embodiment 1 [Figure 3] A pH diagram showing an example of the refrigerant state of the refrigeration cycle performed by a normal air conditioner when a train equipped with a normal air conditioner is in a dead section. [Figure 4] Hardware configuration diagram of a control unit included in an air conditioner according to embodiment 1 [Figure 5] Block diagram of a control unit included in the air conditioner according to the first embodiment. [Figure 6] FIG. 10 is a diagram showing an example of operation chart data stored in a storage device provided in a control unit of the air conditioner according to the first embodiment. [Figure 7] FIG. 10 is a diagram showing an example of valve opening data stored in a storage device included in the control unit of the air conditioner according to the first embodiment. [Figure 8] 1 is a flowchart of an expansion valve control process performed by a control unit included in the air conditioner according to the first embodiment. [Figure 9] Graph showing an example of a change in the opening degree of an expansion valve provided in the air conditioner according to the first embodiment. [Figure 10] A pH diagram showing an example of the refrigerant state of the refrigeration cycle performed by a normal air conditioner when a train equipped with a normal air conditioner is in a train stop section. [Figure 11]FIG. 10 is a diagram showing an example of valve opening data stored in a storage device included in an air conditioner according to a second embodiment. [Figure 12] Graph showing an example of a change in the opening degree of an expansion valve provided in an air conditioner according to embodiment 2. [Figure 13] A pH diagram showing an example of the refrigerant state of the refrigeration cycle performed by a conventional air conditioner when a train equipped with a conventional air conditioner is in a tunnel section. [Figure 14] FIG. 10 is a diagram showing an example of valve opening data stored in a storage device included in an air conditioner according to Embodiment 3. [Figure 15] Graph showing an example of a change in the opening degree of an expansion valve provided in an air conditioner according to embodiment 3. DETAILED DESCRIPTION OF THE INVENTION

[0012] An air conditioner and a method for controlling the air conditioner according to an embodiment of the present disclosure will be described in detail below with reference to the drawings, in which the same or equivalent parts are designated by the same reference numerals.

[0013] (Embodiment 1) The air conditioner according to the first embodiment is an air conditioner installed in a train car that runs on electricity. In this air conditioner, the opening degree of the expansion valve is kept constant when the train enters a section without power, in order to prevent disruptions to the air conditioning after the section without power. First, the configuration of the air conditioner will be explained with reference to Figures 1 to 3. Additionally, a control method for the air conditioner will be explained using an example in which the air conditioner cools the interior of a train.

[0014] Fig. 1 is a refrigerant circuit diagram of an air conditioner 1 according to embodiment 1. For ease of understanding, a four-way valve is omitted from Fig. 1. Also shown are a control unit 50, a pressure sensor 60, and a temperature sensor 70 electrically connected to the components of the air conditioner 1.

[0015] 1, the air conditioner 1 includes a compressor 10 that compresses a refrigerant, an outdoor heat exchanger 20 that exchanges heat between the refrigerant and the air outside the railway vehicle, i.e., the outside air, an expansion valve 30 that expands the refrigerant, an indoor heat exchanger 40 that exchanges heat between the refrigerant and the indoor air of the railway vehicle, and a control unit 50 that controls the operation of the compressor 10 and the expansion valve 30. The compressor 10, outdoor heat exchanger 20, expansion valve 30, and indoor heat exchanger 40 are connected in this order to form a refrigerant circuit unit 2.

[0016] The compressor 10 is a device that compresses low-pressure refrigerant and converts it into high-pressure refrigerant by the rotational movement of a rotor. Specifically, the compressor 10 has an intake port and a discharge port (not shown), and draws in low-pressure refrigerant through the intake port. The compressor 10 compresses the drawn refrigerant to a desired pressure by controlling the rotation speed of the rotor (not shown) with a control unit 50. The high-pressure refrigerant is then discharged from the discharge port.

[0017] The compressor 10 has an intake port and an outlet port connected to a four-way valve (not shown). The outdoor heat exchanger 20 and the indoor heat exchanger 40 are connected to the four-way valve (not shown) via refrigerant pipes. The four-way valve is electrically connected to a control unit 50, and under the control of the control unit 50, directs refrigerant flowing from either the outdoor heat exchanger 20 or the indoor heat exchanger 40 to the intake port of the compressor 10. The four-way valve also directs high-pressure refrigerant discharged from the compressor 10 to either the outdoor heat exchanger 20 or the indoor heat exchanger 40. In this way, the four-way valve switches the flow direction of the refrigerant in the refrigerant circuit unit 2, thereby switching the air conditioner 1 between a cooling operation state and a heating operation state. For example, the four-way valve directs refrigerant flow in the direction of arrow A in FIG. 1 to place the air conditioner 1 in a cooling operation state. The configuration of each part of the air conditioner 1 will be described below assuming the cooling operation state.

[0018] The outdoor heat exchanger 20 is, for example, a fin-and-tube heat exchanger, and exchanges heat between the outside air and the refrigerant flowing through the tubes. Specifically, the outdoor heat exchanger 20 includes tubes and fins attached to the tubes (not shown). The high-pressure refrigerant compressed by the compressor 10 flows through the tubes, transferring heat from the refrigerant to the fins. Meanwhile, a fan (not shown) blows outside air onto the fins. As a result, the outdoor heat exchanger 20 exchanges heat between the refrigerant and the outside air. This causes the outdoor heat exchanger 20 to release heat to the outside air, condensing the refrigerant. As a result, the outdoor heat exchanger 20 functions as a condenser. The outdoor heat exchanger 20 discharges the condensed refrigerant to the expansion valve 30.

[0019] The expansion valve 30 shown in Fig. 1 is, for example, a solenoid valve or an electric valve, and includes a valve element that opens and closes the refrigerant flow path. The expansion valve 30 is electrically connected to the control unit 50, and the valve element adjusts the opening degree of the flow path according to the output of the control unit 50. This controls the degree of decompression of the refrigerant. As a result, the expansion valve 30 reduces the pressure of the refrigerant to a pressure according to the output of the control unit 50 and expands it. The expansion valve 30 flows the expanded refrigerant to the indoor heat exchanger 40.

[0020] Like the outdoor heat exchanger 20, the indoor heat exchanger 40 is, for example, a fin-and-tube heat exchanger, and exchanges heat between the indoor air of the train and the refrigerant flowing through the tubes. More specifically, like the outdoor heat exchanger 20, the indoor heat exchanger 40 includes tubes and fins (not shown). In the indoor heat exchanger 40, the refrigerant expanded by the expansion valve 30 flows through the tubes, and as a result, the tubes transfer the heat of the refrigerant to the fins. Meanwhile, a fan (not shown) blows indoor air onto the fins. As a result, the indoor heat exchanger 40 exchanges heat between the refrigerant and the indoor air, evaporating the refrigerant. This allows the indoor heat exchanger 40 to function as an evaporator. As a result, the indoor heat exchanger 40 cools the indoor air. This allows the indoor heat exchanger 40 to cool the interior of the train. The indoor heat exchanger 40 then returns the evaporated refrigerant to the compressor 10.

[0021] In this way, the air conditioner 1 performs cooling operation to cool the indoor air by switching the four-way valve. The state of the refrigerant at this time is shown in FIG.

[0022] Figure 2 is a pH diagram showing the state of the refrigerant in the refrigeration cycle of the air conditioner 1. In Figure 2, the horizontal axis represents the enthalpy per unit mass of the refrigerant, and the vertical axis represents the refrigerant pressure. To facilitate understanding, Figure 2 also shows a saturated liquid line 3 and a saturated vapor line 4.

[0023] First, the refrigerant is compressed by the compressor 10, becoming a high-pressure, high-temperature gas as shown by the path from point A0 to point B0 in FIG. 2, and flows into the outdoor heat exchanger 20. The refrigerant that flows into the outdoor heat exchanger 20 is condensed and changes from a gas state to a single-phase liquid state as shown by the path from point B0 to point C0 in FIG. 2. The single-phase liquid refrigerant then flows into the expansion valve 30, where it changes from the single-phase liquid state to a low-pressure two-phase gas-liquid state as shown by the path from point C0 to point D0 in FIG. 2. As a result, the low-pressure refrigerant is supplied to the indoor heat exchanger 40. In the indoor heat exchanger 40, the refrigerant exchanges heat with outside air and is reduced in pressure. As shown by the path from point D0 to point A0 in FIG. 2, the refrigerant changes from a two-phase gas-liquid state to a gaseous refrigerant and flows into the compressor 10.

[0024] In the air conditioner 1, in order to cool the interior of the train to a desired temperature, the control unit 50 controls the rotation speed of the rotor of the compressor 10, the rotation speed of the fan (not shown), and the opening degree of the expansion valve 30. At this time, the control unit 50 controls the opening degree of the expansion valve 30 based on the outputs of the pressure sensor 60 and the temperature sensor 70 shown in Fig. 1 so that the degree of superheat SH shown in Fig. 2 falls within a certain range.

[0025] Specifically, as shown in FIG. 1, the air conditioner 1 includes a pressure sensor 60 that detects the pressure of the low-pressure refrigerant discharged from the indoor heat exchanger 40, and a temperature sensor 70 that detects the temperature of the refrigerant. The control unit 50 acquires refrigerant pressure data and temperature data from the pressure sensor 60 and temperature sensor 70, converts the refrigerant pressure from the acquired pressure data into a saturated value to determine the evaporation temperature, and then subtracts the determined evaporation temperature from the refrigerant temperature value from the acquired temperature data to determine the degree of superheat SH. The control unit 50 then adjusts the position of the valve element of the expansion valve 30 to an opening degree that causes the determined degree of superheat SH to fall within a certain numerical range. In this way, the control unit 50 efficiently cools the interior of the train to the desired temperature.

[0026] However, train lines have sections where there is no power supply. In such sections, the power supply is stopped, i.e., an instantaneous power outage occurs, causing the compressor 10 to temporarily stop operating and preventing sufficient refrigerant compression. In such cases, it becomes difficult to control the superheat degree SH described above. For a more detailed explanation, FIG. 3 shows the refrigerant state during an instantaneous power outage in a typical air conditioner that does not include the control unit 50 of the first embodiment.

[0027] Figure 3 is a pH diagram showing an example of the refrigerant state of the refrigeration cycle operated by a normal air conditioner when a train equipped with the normal air conditioner is in a section where there is no electricity. To make it easier to understand, the refrigerant state of the refrigeration cycle when the train is running in a normal section where there is electricity is displayed as a solid line A0B0C0D0 in Figure 3.

[0028] When an instantaneous power outage occurs, the rotation speed of the compressor 10 temporarily decreases. As a result, in the refrigeration cycle of a typical air conditioner, as shown by dotted line B1C1 in FIG. 3, the refrigerant compressed by the compressor 10 becomes high-pressure, but at a lower pressure than when a train is traveling on a normal section. Also, as shown by point A1 in FIG. 3, the low-pressure gas refrigerant drawn into the compressor 10 becomes high-pressure than when a train is traveling on a normal section. As a result, the superheat degree SH takes an unstable value during the instantaneous power outage, and as a result, the superheat degree SH remains unstable even immediately after the power outage when the supply of power is resumed. This makes it difficult to adjust the opening of the expansion valve 30 immediately after the instantaneous power outage, disrupting air conditioning.

[0029] Therefore, in the air conditioner 1 according to the first embodiment, in order to suppress disruptions in air conditioning after a dead section, the control unit 50 determines whether the train is entering a dead section, and if it determines that the train is entering a dead section, it maintains the opening degree of the expansion valve 30 at a constant opening degree without varying it depending on the value of the superheat degree SH. Next, the configuration of the control unit 50 will be described with reference to Figures 4 to 6.

[0030] Fig. 4 is a hardware configuration diagram of the control unit 50 provided in the air conditioner 1. Fig. 5 is a block diagram of the control unit 50. Fig. 6 is a diagram showing an example of operation chart data 542 stored in a storage device 54 provided in the control unit 50. Fig. 7 is a diagram showing an example of valve opening data 543 stored in the storage device 54. For ease of understanding, Figs. 4 and 5 also show the expansion valve 30, pressure sensor 60, and temperature sensor 70, which are connected to the control unit 50.

[0031] 4, the control unit 50 includes a computer including an MPU (Micro Processing Unit) 51, a ROM (Read-Only Memory) 52, and a RAM (Random Access Memory) 53, a storage device 54, a pressure sensor 60 that detects the pressure of the refrigerant discharged from the indoor heat exchanger 40, a temperature sensor 70 that detects the temperature of the refrigerant, and an I / O port (Input / Output Port) 55 that is electrically connected to components such as the expansion valve 30 and a fan (not shown).The control unit 50 reads out various programs stored in the ROM 52 or the storage device 54 into the RAM 53 and executes them, thereby performing various processes to control components of the air conditioner 1, such as the expansion valve 30 and a fan (not shown) connected to the I / O port 55.

[0032] For example, the control unit 50 reads and executes an expansion valve control program stored in the ROM 52 to perform expansion valve control processing that determines whether the train is in a dead power section and controls the opening degree of the expansion valve 30. To perform the expansion valve control processing, the control unit 50 includes various blocks configured as software shown in FIG. 5. In detail, the control unit 50 includes a position identification unit 56, a superheat degree information acquisition unit 57, and an expansion valve control unit 58.

[0033] The position identification unit 56 periodically acquires the current time to identify the train's position within the line. More specifically, the control unit 50 includes a clock unit (not shown), and the position identification unit 56 reads the current time from the clock unit. The position identification unit 56 then transmits the time to the expansion valve control unit 58 as data identifying the train's position within the line. The position identification unit 56 periodically acquires the current time and transmits the acquired time data to the expansion valve control unit 58.

[0034] Meanwhile, the superheat degree information acquisition unit 57 acquires refrigerant pressure data from the pressure sensor 60. It also acquires refrigerant temperature data from the temperature sensor 70. The storage device 54 stores data related to a refrigerant pH diagram, including data such as an isotherm and a saturated vapor line, i.e., refrigerant data 541. The superheat degree information acquisition unit 57 reads the refrigerant data 541 from the storage device 54 and calculates the evaporation temperature from the read refrigerant data 541 and the refrigerant pressure data acquired from the pressure sensor 60. The superheat degree information acquisition unit 57 then calculates the degree of superheat SH by subtracting the calculated evaporation temperature from the value of the refrigerant temperature data acquired from the temperature sensor 70. The superheat degree information acquisition unit 57 periodically calculates the degree of superheat SH, similar to the position identification unit 56. The superheat degree information acquisition unit 57 transmits the calculated degree of superheat SH to the expansion valve control unit 58 each time it calculates the degree of superheat SH.

[0035] When the expansion valve control unit 58 receives the time data from the position identification unit 56, it determines from the time data whether the train has advanced to just before the section where there is no electricity.

[0036] More specifically, the memory device 54 stores train operation chart data 542 in which multiple points that the train passes through, as shown in Fig. 6, are associated with the times at which the train passes through those points. The points that the train passes through in the operation chart data 542 include the entrances and exits of sections with no electricity, as well as the positions just before and just after the sections with no electricity. The expansion valve control unit 58 reads the operation chart data 542 from the memory device 54, and determines whether the train has reached the position just before the section with no electricity, based on the read operation chart data 542 and the time data received from the position identification unit 56.

[0037] The expansion valve control unit 58 receives data on the degree of superheat SH from the superheat degree information acquisition unit 57. When the expansion valve control unit 58 determines that the train has not reached a position immediately before the dead section, it adjusts the position of the valve element of the expansion valve 30 to an opening degree such that the degree of superheat SH received from the superheat degree information acquisition unit 57 falls within a certain numerical range. In this way, the expansion valve control unit 58 cools the inside of the train to a desired temperature.

[0038] Meanwhile, the storage device 54 stores valve opening data 543 shown in FIG. 5. As shown in FIG. 7, the valve opening data 543 associates a section in which the expansion valve 30 is to be opened to a specific opening and a fluctuation value of the opening of the expansion valve 30 in that section. Specifically, the valve opening data 543 associates a dead section in which the expansion valve 30 is to be fixed to a specific opening and a fluctuation value of the opening indicating how much the opening of the expansion valve 30 is to be changed and fixed in that dead section. When the expansion valve control unit 58 determines that the train has reached a position just before the dead section, it reads the valve opening data 543 from the storage device 54 and fixes the opening of the expansion valve 30 to the opening based on the read valve opening data 543. Specifically, because the fluctuation of the opening shown in FIG. 7 is zero, the expansion valve control unit 58 maintains the opening of the expansion valve 30 at the opening of the expansion valve 30 at the time of determination. This facilitates control of the opening of the expansion valve 30 when power supply is resumed after an instantaneous power outage. This also suppresses disruptions to air conditioning.

[0039] Next, the above processing performed by the position identification unit 56, the superheat degree information acquisition unit 57, and the expansion valve control unit 58 will be described in more detail with reference to Figures 8 and 9. Note that the following description will also be given using an example in which the air conditioner 1 is performing cooling operation.

[0040] Fig. 8 is a flowchart of the expansion valve control process performed by the control unit 50 provided in the air conditioner 1. Fig. 9 is a graph showing an example of the change in the opening degree of the expansion valve 30 provided in the air conditioner 1.

[0041] First, the power switch and operation mode selection button (not shown) are pressed to start the air conditioner 1, and when cooling operation is selected, the expansion valve control program is executed by the MPU 51 provided in the control unit 50, and as a result, the expansion valve control processing flow is started.

[0042] In the flow of the expansion valve control process, first, as shown in Fig. 8, the expansion valve control unit 58 acquires current time data (step S1). In detail, the position identification unit 56 periodically transmits current time data to the expansion valve control unit 58. The expansion valve control unit 58 receives the data to acquire the current time data.

[0043] Next, the expansion valve control unit 58 reads out the operation chart data 542 from the storage device 54, thereby acquiring the operation chart data 542 (step S2).

[0044] The operation chart data 542 includes times T1, T2, T3, and T4 at which the train passes each of the positions just before, at the entrance, at the exit, and just after the dead power section. The expansion valve control unit 58 determines whether or not the train is at a position just before the dead power section based on the acquired current time data and the operation chart data 542 (step S3). In detail, the expansion valve control unit 58 determines whether or not the current time is time T1 at which the train passes the position just before the dead power section shown in Fig. 9, for example, whether or not the current time is within a range of several seconds before or after the time T1 at which the train passes the just before position.

[0045] When the expansion valve control unit 58 determines that the train is located just before the dead section (Yes in step S3 shown in FIG. 8), it reads the valve opening data 543 from the storage device 54 to acquire the valve opening data 543 (step S4). The valve opening data 543 shown in FIG. 7 stores data indicating how much the opening of the expansion valve 30 should be changed from the opening at the time of the determination in step S3, i.e., from the opening at the position just before the dead section. The expansion valve control unit 58 sets the opening of the expansion valve 30 to the opening at the position just before the dead section based on the acquired valve opening data 543. This is because such an opening is specified in the valve opening data 543, and because setting the opening of the expansion valve 30 at such an opening and not changing it reduces disruption of air conditioning after an instantaneous power outage. Furthermore, the expansion valve control unit 58 determines the period for which the opening of the expansion valve 30 should remain at the opening at the position just before the dead section based on the operation chart data 542 shown in FIG. 6. For example, the expansion valve control unit 58 determines the period for which the opening degree is maintained at the position immediately before the dead section as the period obtained by subtracting T1, which is the time when the position immediately before the dead section is passed from T4, which is a fixed period later than the time T3, which is the time when the train passes the exit of the dead section shown in FIG. 9. This is because, during this period, the opening degree of the expansion valve 30 can be maintained at the opening degree at the time of determination until the operation of each part of the air conditioner 1 stabilizes after the power supply is resumed. Then, the expansion valve control unit 58 maintains the opening degree of the expansion valve 30 at a fixed opening degree for the specified period (step S5 shown in FIG. 8). This prevents disruptions to air conditioning when the train passes the dead section and power supply is resumed. After the specified period has elapsed, the expansion valve control unit 58 proceeds to step S6.

[0046] On the other hand, if the expansion valve control unit 58 determines that the train is not immediately before the dead section (No in step S3), it determines whether the train is outside the dead section (step S6). Specifically, the expansion valve control unit 58 treats the dead section not as a narrow section from the entrance to the exit, but as a broad section from the immediately preceding position to the immediately succeeding position, and determines whether the train is outside this broad section. Specifically, the expansion valve control unit 58 determines whether the current time is before time T1 at which the train passes the position immediately before the dead section shown in FIG. 9, or whether the current time is after time T4 at which the train passes the position immediately succeeding the dead section. As a result, the expansion valve control unit 58 determines whether it is possible to control the opening degree of the expansion valve 30 based on the superheat degree SH.

[0047] When it is determined that the train is not in a dead section (Yes in step S6), the expansion valve control unit 58 acquires data on the degree of superheat SH from the above-mentioned superheat degree information acquisition unit 57 (step S7). As described above, the superheat degree information acquisition unit 57 periodically transmits data on the degree of superheat SH calculated to the expansion valve control unit 58. The expansion valve control unit 58 receives this data and thereby acquires the data on the degree of superheat SH.

[0048] When the expansion valve control unit 58 acquires the data on the degree of superheat SH, it sets the opening degree of the expansion valve 30 to an opening degree that brings the degree of superheat SH into a certain numerical range (step S8). As a result, the expansion valve control unit 58 controls the opening degree of the expansion valve 30 based on the acquired data on the degree of superheat SH. By controlling the expansion valve 30 at such an opening degree, the expansion valve control unit 58 cools the inside of the train cabin to a desired temperature.

[0049] After determining the opening degree in step S8, the expansion valve control unit 58 returns to step S1, thereby preparing for the train passing through a section with no power.

[0050] The control unit 50 repeats the flow of steps S1-S8 above until the power switch and operation mode selection button are pressed again. When the power switch is pressed again and the operation of the air conditioner 1 stops, the control unit 50 forcibly terminates the expansion valve control process. Alternatively, when the operation mode selection button is pressed and an operation mode other than cooling operation is selected, the control unit 50 forcibly terminates the expansion valve control process.

[0051] The outdoor heat exchanger 20 described in the first embodiment is an example of a condenser as defined in the present disclosure. The indoor heat exchanger 40 is an example of an evaporator as defined in the present disclosure. The superheat degree SH is an example of superheat degree information as defined in the present disclosure.

[0052] Furthermore, the section from the position immediately before the dead section to the position immediately after the dead section is an example of a specific section in which the indoor temperature is likely to fluctuate as defined in the present disclosure. Sections other than the position immediately before the dead section to the position immediately after the dead section are examples of sections other than the specific section as defined in the present disclosure. The position immediately before the dead section is an example of the start point of a specific section or the start point of a dead section as defined in the present disclosure. The position immediately after the dead section is an example of the end point of a specific section as defined in the present disclosure. Note that the above specific section may be a dead section in the narrow sense from the entrance to the exit of the dead section, or a dead section in the broad sense from the position immediately before the dead section to the position immediately after the dead section.

[0053] Furthermore, while the above-mentioned step S6 determines whether the train has just passed the position immediately preceding the dead section or whether the train has just passed the position immediately following the dead section, if it is determined in step S3 that the train is just preceding the dead section, it may instead determine whether the train is just following the dead section. In particular, it may determine whether the current time is time T4 at which the train will pass the position just following the dead section, for example, whether the current time is within a range of several seconds before or after the time T4 at which the train passes the position just following the dead section.

[0054] As described above, in the air conditioner 1 according to the first embodiment, when the expansion valve control unit 58 determines that the train is immediately before a dead section, i.e., when it determines that the train is entering the dead section, it maintains the opening degree of the expansion valve 30 at the opening degree at the time of the determination. Furthermore, when the expansion valve control unit 58 determines that the train is not in a dead section, i.e., when it determines that the train is leaving the dead section, it sets the opening degree of the expansion valve 30 to an opening degree based on the refrigerant superheat degree SH acquired by the superheat degree information acquisition unit 57. As a result, in the air conditioner 1, when the train leaves the dead section, the opening degree of the expansion valve 30 simply changes from a fixed opening degree to an opening degree based on the superheat degree SH. Therefore, after the train passes through the dead section, when power is supplied to the compressor 10 and the compression degree returns to the original level, the original air conditioning state is easily restored. As a result, in the air conditioner 1, air conditioning is less likely to be disrupted before and after the dead section.

[0055] (Embodiment 2) In the air conditioner 1 according to the first embodiment, when the expansion valve control unit 58 determines that the train is entering a dead section, the expansion valve control unit 58 maintains the opening degree of the expansion valve at a constant opening degree. Furthermore, when the expansion valve control unit 58 determines that the train has left the dead section, the expansion valve control unit 58 changes the opening degree of the expansion valve 30 from the constant opening degree to an opening degree based on the refrigerant superheat degree SH. However, the expansion valve control unit 58 is not limited to this. The expansion valve control unit 58 may maintain the opening degree of the expansion valve at a constant opening degree when it determines that the train is entering a specific section where the indoor temperature is prone to fluctuate. Furthermore, when it determines that the train has left the specific section, the expansion valve control unit 58 may change the opening degree of the expansion valve 30 from the constant opening degree to an opening degree based on the refrigerant superheat degree SH.

[0056] In the air conditioner 1 according to the second embodiment, the specific section described above is a vehicle stop section, for example, a section of a station platform where a railroad vehicle stops. The air conditioner 1 according to the second embodiment will be described below with reference to Figures 10 to 12. The description of the second embodiment will focus on the configuration that differs from the first embodiment.

[0057] Fig. 10 is a pH diagram showing an example of the refrigerant state of the refrigeration cycle performed by a normal air conditioner when a train equipped with the normal air conditioner is in a train stop section. Fig. 11 is a diagram showing an example of valve opening data 543 stored in a storage device 54 provided in an air conditioner 1 according to embodiment 2. Fig. 12 is a graph showing an example of the change in opening of an expansion valve 30 provided in an air conditioner 1 according to embodiment 2.

[0058] First, we will discuss the issues that arise when a train is stopped in a section where the train is stopped. When a train is stopped in a section where the train is stopped, the doors open and close, and passengers get on and off. This causes outside air to enter the room, resulting in a mixture of the outside air and the room air. This can result in significant changes in the room temperature. For example, the room temperature can rise significantly during cooling operation. In this case, in a typical air conditioner, the rotation speed of the compressor 10 increases suddenly, and as shown by the dotted line B2C2 in Figure 10, the high-pressure refrigerant discharged from the compressor 10 becomes higher in pressure than when the train is traveling in a normal section. Furthermore, as shown by point A2 in Figure 10, the low-pressure refrigerant drawn into the compressor 10 becomes lower in pressure than when the train is traveling in a normal section. As a result, the superheat degree SH takes an unstable value when the train is stopped in the section where the train is stopped, and the superheat degree SH remains unstable even after the train departs from the section where the train is stopped. This makes it difficult to adjust the opening of the expansion valve 30 after the train departs, resulting in disrupted air conditioning.

[0059] Therefore, in the air conditioner 1 according to the second embodiment, the expansion valve control unit 58 determines whether or not a train is about to enter a vehicle stop section, for example, a section where a station platform is located, and if it determines that a train is about to enter a section where a platform is located, it keeps the opening of the expansion valve 30 at a constant opening.

[0060] More specifically, in the case of the second embodiment, although not shown, the train passing points in the train operation chart data 542 stored in the storage device 54 include data on the entrances and exits of the platform section and the positions just before and just after these sections, and the times at which these points are passed are stored. The expansion valve control unit 58 receives current time data from the position identification unit 56 and reads out the train operation chart data 542 from the storage device 54. Then, based on the received current time data and the train operation chart data 542 read out from the storage device 54, the expansion valve control unit 58 determines whether the train has proceeded to a position just before entering the platform section.

[0061] When the expansion valve control unit 58 determines that the train has proceeded to a position immediately before entering the platform section, it reads out the valve opening data 543 shown in Fig. 11 from the storage device 54. In the second embodiment, the valve opening data 543 is associated with platform section data and an opening fluctuation value indicating how much the opening of the expansion valve 30 is to be fluctuated and fixed in that section. Since the valve opening data 543 shown in Fig. 11 indicates that the fluctuation value of the opening of the expansion valve 30 in the platform section Pq-Pr is +X, the expansion valve control unit 58 increases the opening of the expansion valve 30 by X from the opening of the expansion valve 30 at the time of determination based on the read-out valve opening data 543, and maintains the increased opening until the train leaves the platform section and travels a certain distance. In other words, the expansion valve control unit 58 maintains the opening of the expansion valve 30 at a value X larger than the opening of the expansion valve 30 at the time of determination for a period obtained by subtracting the time T1 at which the train reaches the position immediately preceding the platform section from the time T4 at which the train passes the position immediately following the platform section, which is a certain period later than the time T3 at which the train passes the exit of the platform section shown in FIG. 12 . Generally, after the train leaves the platform section, the effects of outside air flowing into the room remain for a while. By maintaining the opening of the expansion valve 30 at this opening, the expansion valve control unit 58 makes it easier for the train to return to its original cooling state after leaving the platform section, thereby suppressing disruptions to the air conditioning at that time. Note that the above X in the valve opening data 543 is a constant.

[0062] On the other hand, if it is determined that the train has not yet reached a position immediately before entering the platform section, the expansion valve control unit 58 controls the opening degree of the expansion valve 30 based on the data on the superheat degree SH received from the superheat degree information acquisition unit 57. In detail, the position of the valve element of the expansion valve 30 is adjusted to an opening degree such that the superheat degree SH received from the superheat degree information acquisition unit 57 falls within a certain numerical range. In this way, the expansion valve control unit 58 cools the inside of the train to a desired temperature.

[0063] After determining that the train has reached a position immediately before entering the platform section, the expansion valve control unit 58 determines whether the train has reached a position immediately after the platform section. If the expansion valve control unit 58 determines that the train has reached the position immediately after the platform section, it controls the opening degree of the expansion valve 30 based on the data of the superheat degree SH described above. This allows the train interior to be cooled to a desired temperature.

[0064] As described above, in the air conditioner 1 according to the second embodiment, when it is determined that the train has proceeded to a position immediately before entering the platform section, in other words, when it is determined that the train is entering a section where the train is stopping, the expansion valve control unit 58 sets the opening degree of the expansion valve 30 to a higher opening degree than the opening degree at the time of determination, and maintains that opening degree. This makes it easier for the air conditioner 1 to return to the original air conditioning state when the train leaves the section where the train is stopping, thereby suppressing disruptions to the air conditioning inside the train.

[0065] The section from the immediately preceding position to the immediately succeeding position including the platform section described in embodiment 2, in other words, the section from the immediately preceding position to the immediately succeeding position including the vehicle stop section, is an example of a specific section in which the interior temperature is likely to fluctuate as defined in the present disclosure. Sections other than the immediately preceding position to the immediately succeeding position are examples of non-specific sections as defined in the present disclosure. The position immediately preceding the vehicle stop section is an example of the start point of a specific section or the start point of a vehicle stop section as defined in the present disclosure. The position immediately succeeding the vehicle stop section is an example of the end point of a specific section as defined in the present disclosure. The above specific section may be a vehicle stop section in the narrow sense from the entrance to the exit of the platform, or a vehicle stop section in the broad sense from the immediately preceding position to the immediately succeeding position.

[0066] (Embodiment 3) In the air conditioner 1 according to the second embodiment, when the expansion valve control unit 58 determines that the train is entering a vehicle stop section, the opening degree of the expansion valve is kept constant, but the section determined by the expansion valve control unit 58 is not limited to the vehicle stop section. As described above, the section determined by the expansion valve control unit 58 may be any specific section where the indoor temperature is likely to fluctuate.

[0067] In the air conditioner 1 according to the third embodiment, the specific section described above is a tunnel section through which a railway vehicle travels. The air conditioner 1 according to the third embodiment will be described below with reference to Figures 13 to 15. The description of the third embodiment will focus on the configuration that differs from the first and second embodiments.

[0068] Fig. 13 is a pH diagram showing an example of the refrigerant state of the refrigeration cycle performed by a normal air conditioner when a train equipped with the normal air conditioner is in a tunnel section. Fig. 14 is a diagram showing an example of valve opening data 543 stored in a storage device 54 provided in an air conditioner 1 according to embodiment 3. Fig. 15 is a graph showing an example of the change in opening of an expansion valve 30 provided in an air conditioner 1 according to embodiment 3.

[0069] First, we will explain the issues surrounding tunnel sections. In summer, the temperature in tunnel sections, i.e., sections of railway tracks located inside tunnels, is lower than that outside the tunnels. As a result, the temperature of the air contacting the outdoor heat exchanger 20, i.e., the condenser, is lower during cooling operation. In the cooling / heating cycle shown in Figure 13, the refrigerant is at a lower pressure, as indicated by the dotted line B3C3, than when a train is running on a normal section. As a result, as indicated by point B3 in Figure 13, the refrigerant enters the indoor heat exchanger 40, i.e., the evaporator, with a lowered quality factor. As a result, the refrigerant does not evaporate sufficiently in the evaporator, and a two-phase refrigerant flows into the compressor 10, as indicated by point A3 in Figure 13. This can lead to a decrease in lubricating oil concentration, potentially causing the rotor shaft of the compressor 10 to seize.

[0070] Therefore, in the air conditioner 1 according to embodiment 3, the expansion valve control unit 58 determines whether the train is about to enter a tunnel section, and if it determines that the train is about to enter a tunnel section, the opening of the expansion valve 30 is kept small.

[0071] In detail, in the air conditioner 1 according to the third embodiment, although not shown, train operation chart data 542 including data associating each point in the tunnel section, such as the tunnel entrance and exit, and the positions just before and just after the tunnel, with the time at which these points will be passed is stored in the storage device 54. The expansion valve control unit 58 receives current time data from the position identification unit 56 and reads out this train operation chart data 542 from the storage device 54. Then, based on the received current time data and the train operation chart data 542 read out from the storage device 54, the expansion valve control unit 58 determines whether the train has proceeded to a position just before entering the tunnel section.

[0072] In the third embodiment, valve opening data 543 is stored in the storage device 54. The valve opening data 543 associates section data of the tunnel section with a fluctuation value of the opening that indicates how much the opening of the expansion valve 30 is to be varied and fixed in this section, as shown in FIG. 14 . When the expansion valve control unit 58 determines that the train has proceeded to a position immediately before entering the tunnel section, it reads out the valve opening data 543 from the storage device 54. Since the fluctuation value of the opening of the expansion valve 30 in the tunnel section Ps-Pt is −Y in the read valve opening data 543 shown in FIG. 14 , the expansion valve control unit 58 reduces the opening of the expansion valve 30 by Y compared to the opening of the expansion valve 30 at the time of determination. The opening is then maintained at that value until the train travels a certain distance from the position immediately before entering the tunnel and exits the tunnel. More specifically, the expansion valve control unit 58 maintains the opening of the expansion valve 30 at a small opening from time T1 when the train passes the immediately preceding position in the tunnel section shown in Figure 15, through time T2 when the train enters the tunnel, until time T4, a certain period of time after the time T2. This prevents the refrigerant in a gas-liquid two-phase state from flowing into the compressor 10, which could cause the rotor shaft of the compressor 10 to seize. Note that the above Y in the valve opening data 543 is a constant.

[0073] On the other hand, if the expansion valve control unit 58 determines that the train has not yet reached a position immediately before entering the tunnel section, it controls the opening of the expansion valve 30 based on the data on the superheat degree SH received from the superheat degree information acquisition unit 57. That is, it adjusts the position of the valve element of the expansion valve 30 to an opening that causes the superheat degree SH to fall within a certain numerical range. In this way, the expansion valve control unit 58 cools the inside of the train to a desired temperature.

[0074] After determining that the train has reached a position immediately before the tunnel section, the expansion valve control unit 58 determines whether the train has reached a position immediately after the tunnel section. If the expansion valve control unit 58 determines that the train has reached a position immediately after the tunnel section, it controls the opening degree of the expansion valve 30 based on the data of the superheat degree SH described above. This allows the interior of the train to be cooled to a desired temperature.

[0075] As described above, in the air conditioner 1 according to the third embodiment, when the expansion valve control unit 58 determines that the train has reached a position immediately before entering a tunnel section, it reduces the opening of the expansion valve 30 to a smaller opening than the opening at the time of the determination, and maintains that opening. This prevents problems such as the compressor 10 burning out in the air conditioner 1. Furthermore, as a result of the compressor 10 operating smoothly, the air conditioning inside the train is less likely to be disrupted.

[0076] The section from the position immediately before the tunnel section to the position immediately after the tunnel section described in embodiment 3 is an example of a specific section in which the indoor temperature is likely to fluctuate, as defined in the present disclosure. Sections other than the position immediately before the tunnel section to the position immediately after the tunnel section are examples of sections other than the specific section, as defined in the present disclosure. The position immediately before the tunnel section is an example of the start point of a specific section or the start point of a tunnel section, as defined in the present disclosure. The position immediately after the tunnel section is an example of the end point of a specific section, as defined in the present disclosure. The specific section may be a tunnel section in the narrow sense, from the entrance to the exit of the tunnel, or a tunnel section in the broad sense, from the position immediately before the tunnel section to the position immediately after the tunnel.

[0077] In addition, in the third embodiment, when it is determined that the train has reached a position immediately before entering a tunnel section, the expansion valve control unit 58 reduces the opening degree of the expansion valve 30 from the opening degree at the time of the determination, but the opening degree of the expansion valve 30 in this case is not limited to this. The opening degree of the expansion valve 30 in this case may be a normal opening degree, for example, a constant opening degree that is smaller than the average normal opening degree.

[0078] Furthermore, when the expansion valve control unit 58 determines that the train has reached a position just before entering a tunnel section, the period for reducing the opening of the expansion valve 30 may be from the time the train enters the tunnel section until the time the train leaves the tunnel section and travels a certain distance.

[0079] The air conditioner 1 and the control method for the air conditioner 1 according to the embodiment of the present disclosure have been described above, but the air conditioner 1 and the control method for the air conditioner 1 are not limited to this.

[0080] For example, in embodiments 1-3, the position identifying unit 56 acquires the current time to identify the position of the train within the line. However, the position identifying unit 56 is not limited to this. The position identifying unit 56 may be any unit that identifies the position of the railway vehicle within the line. For example, the position identifying unit 56 may include a receiver for a satellite positioning system, and the position of the train may be identified by the receiver. Also, in embodiments 1-3, the expansion valve control unit 58 identifies the position of the train within the line based on the train schedule data 542 and the current time acquired by the position identifying unit 56, but the position identifying unit 56 may also identify the position of the train within the line based on the train schedule data 542 and the current time.

[0081] In the second and third embodiments, the vehicle on which the air conditioner 1 is installed is a train. However, the vehicle is not limited to this. In the second and third embodiments, the vehicle may be any railroad vehicle.

[0082] As described above, the air conditioner 1 and the control method for the air conditioner 1 are not limited to the above-described embodiment, and various modifications and substitutions can be made. Various embodiments of the present disclosure are described below as appendices.

[0083] (Appendix 1) a refrigerant circuit section for air-conditioning an interior of a railway vehicle, the refrigerant circuit section including: a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed by the compressor; an expansion valve for expanding the refrigerant condensed by the condenser by opening a valve; and an evaporator for evaporating the refrigerant expanded by the expansion valve; a position identification unit that periodically identifies a position of the railway vehicle within a line; a superheat degree information acquisition unit that periodically acquires information about the superheat degree of the refrigerant in the evaporator; an expansion valve control unit that sets the opening degree of the expansion valve to a constant opening degree when it is determined that the position identified by the position identifying unit is the start point of a specific section in which the indoor temperature is likely to fluctuate, and that changes the opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired by the superheat degree information acquiring unit when it is determined that the position identified by the position identifying unit is the end point of the specific section; An air conditioner equipped with: (Appendix 2) the railway vehicle is a train that runs on a supply of electric power, The specific section is a dead section where no power is supplied to the train, When the position identified by the position identifying unit is determined to be the start point of the dead zone, the expansion valve control unit fixes the opening degree of the expansion valve to the opening degree at the start point of the dead zone. 1. An air conditioner as described in Appendix 1. (Appendix 3) the specific section is a vehicle stop section for passengers of the railroad vehicle to get on and off at a platform, When the position identified by the position identifying unit is determined to be the start point of the vehicle stop section, the expansion valve control unit changes the opening degree of the expansion valve to an opening degree that is larger by a certain value than the opening degree at the start point of the vehicle stop section, and maintains the opening degree. 1. An air conditioner as described in Appendix 1. (Appendix 4) the specific section is a tunnel section in which the railway vehicle runs inside a tunnel, When the position identified by the position identifying unit is determined to be the start point of the tunnel section, the expansion valve control unit changes the opening degree of the expansion valve to an opening degree that is smaller by a certain value than the opening degree at the start point of the tunnel section, and maintains the opening degree. 1. An air conditioner as described in Appendix 1. (Appendix 5) When it is determined that the position identified by the position identifying unit is outside the specific section, the expansion valve control unit controls the opening degree of the expansion valve based on the superheat degree information of the refrigerant acquired by the superheat degree information acquiring unit to an opening degree such that the superheat degree of the refrigerant in the evaporator falls within a certain numerical range. 5. An air conditioner according to any one of claims 1 to 4. (Appendix 6) A control method for an air conditioner for air-conditioning a passenger compartment of a railway vehicle, the air conditioner comprising: a compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve that opens to expand the refrigerant condensed by the condenser; and an evaporator that evaporates the refrigerant expanded by the expansion valve, the method comprising: a position determination step of determining a position of the rail vehicle within a line; a superheat degree information acquisition step of acquiring information about the superheat degree of the refrigerant in the evaporator; a first expansion valve control step of setting the opening degree of the expansion valve to a constant opening degree when it is determined that the position identified in the position identification step is a start point of a specific section in which the indoor temperature is likely to fluctuate; a second expansion valve control step of changing an opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired in the superheat degree information acquisition step when it is determined that the position identified in the position identification step is an end point of the specific section; A control method for an air conditioner comprising: [Explanation of symbols]

[0084] 1 air conditioner, 2 refrigerant circuit section, 3 saturated liquid line, 4 saturated vapor line, 10 compressor, 20 outdoor heat exchanger, 30 expansion valve, 40 indoor heat exchanger, 50 control section, 51 MPU, 52 ROM, 53 RAM, 54 storage device, 55 I / O port, 56 location identification section, 57 superheat information acquisition section, 58 expansion valve control section, 60 pressure sensor, 70 temperature sensor, 541 refrigerant data, 542 operation chart data, 543 valve opening data, SH superheat.

Claims

1. A refrigerant circuit section for air-conditioning the interior of a railway vehicle, the refrigerant circuit section comprising: a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed by the compressor; an expansion valve for expanding the refrigerant condensed by the condenser by opening a valve; and an evaporator for evaporating the refrigerant expanded by the expansion valve; a position identification unit that periodically identifies a position of the railway vehicle within a line; a superheat degree information acquisition unit that periodically acquires information about the superheat degree of the refrigerant in the evaporator; an expansion valve control unit that sets the opening degree of the expansion valve to a constant opening degree when it is determined that the position identified by the position identifying unit is the start point of a specific section in which the indoor temperature is likely to fluctuate, and that changes the opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired by the superheat degree information acquiring unit when it is determined that the position identified by the position identifying unit is the end point of the specific section; Equipped with The specific section is a vehicle stop section where passengers of the railway vehicle get on and off at a platform, and in the vehicle stop section, the compressor is operated by supplying power, When the expansion valve control unit determines that the position identified by the position identification unit is the start point of the vehicle stop section, the air conditioner changes the opening degree of the expansion valve to an opening degree that is a certain value larger than the opening degree at the start point of the vehicle stop section and maintains that opening degree.

2. A refrigerant circuit section for air-conditioning the interior of a railway vehicle, the refrigerant circuit section comprising: a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed by the compressor; an expansion valve for expanding the refrigerant condensed by the condenser by opening a valve; and an evaporator for evaporating the refrigerant expanded by the expansion valve; a position identification unit that periodically identifies a position of the railway vehicle within a line; a superheat degree information acquisition unit that periodically acquires information about the superheat degree of the refrigerant in the evaporator; an expansion valve control unit that sets the opening degree of the expansion valve to a constant opening degree when it is determined that the position identified by the position identifying unit is the start point of a specific section in which the indoor temperature is likely to fluctuate, and that changes the opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired by the superheat degree information acquiring unit when it is determined that the position identified by the position identifying unit is the end point of the specific section; Equipped with The specific section is a tunnel section in which the railway vehicle runs inside a tunnel, and in the tunnel section, the compressor is operated by supplying electric power, When the expansion valve control unit determines that the position identified by the position identification unit is the start point of the tunnel section, the air conditioner changes the opening of the expansion valve to an opening that is a certain value smaller than the opening at the start point of the tunnel section and maintains that opening.

3. When it is determined that the position identified by the position identifying unit is outside the specific section, the expansion valve control unit controls the opening degree of the expansion valve based on the superheat degree information of the refrigerant acquired by the superheat degree information acquiring unit to an opening degree such that the superheat degree of the refrigerant in the evaporator falls within a certain numerical range.

3. The air conditioner according to claim 1 or 2.

4. A control method for an air conditioner for air-conditioning a passenger compartment of a railway vehicle, the air conditioner comprising: a compressor that compresses a refrigerant; a condenser that condenses the refrigerant compressed by the compressor; an expansion valve that opens to expand the refrigerant condensed by the condenser; and an evaporator that evaporates the refrigerant expanded by the expansion valve, the method comprising: a position determination step of determining a position of the rail vehicle within a line; a superheat degree information acquisition step of acquiring information about the superheat degree of the refrigerant in the evaporator; a first expansion valve control step of setting an opening degree of the expansion valve to a constant opening degree when it is determined that the position identified in the position identification step is a start point of a specific section in which the indoor temperature is likely to fluctuate; a second expansion valve control step of changing an opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired in the superheat degree information acquisition step when it is determined that the position identified in the position identification step is an end point of the specific section; Equipped with The specific section is a vehicle stop section where passengers of the railway vehicle get on and off at a platform, and in the vehicle stop section, the compressor is operated by supplying power, In the first expansion valve control step, if it is determined that the position identified in the position identification step is the start point of the vehicle stop section, the opening degree of the expansion valve is changed to an opening degree that is a certain value larger than the opening degree at the start point of the vehicle stop section, and that opening degree is maintained.

5. A method for controlling an air conditioner for air-conditioning the interior of a railway vehicle, the air conditioner comprising: a compressor for compressing a refrigerant; a condenser for condensing the refrigerant compressed by the compressor; an expansion valve for expanding the refrigerant condensed by the condenser by opening a valve; and an evaporator for evaporating the refrigerant expanded by the expansion valve, a position determination step of determining a position of the rail vehicle within a line; a superheat degree information acquisition step of acquiring information about the superheat degree of the refrigerant in the evaporator; a first expansion valve control step of setting an opening degree of the expansion valve to a constant opening degree when it is determined that the position identified in the position identification step is a start point of a specific section in which the indoor temperature is likely to fluctuate; a second expansion valve control step of changing an opening degree of the expansion valve from the constant opening degree to an opening degree based on the superheat degree information of the refrigerant acquired in the superheat degree information acquisition step when it is determined that the position identified in the position identification step is an end point of the specific section; Equipped with The specific section is a tunnel section in which the railway vehicle runs inside a tunnel, and in the tunnel section, the compressor is operated by supplying electric power, In the first expansion valve control step, if it is determined that the position identified in the position identification step is the start point of the tunnel section, the opening degree of the expansion valve is changed to an opening degree that is a certain value smaller than the opening degree at the start point of the tunnel section, and that opening degree is maintained.

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