JP7516285B2 - Air conditioning equipment for railway vehicles - Google Patents

Description

The present invention relates to a technology that realizes the function of cleaning the surface of a heat exchanger by repeatedly frosting and defrosting the heat exchanger in the refrigeration cycle of a railway vehicle air conditioning system, which requires a particularly high level of reliability.

Technology for maintaining the cleanliness of heat exchangers in home air conditioners is as shown in Patent Document 1. The technology described in Patent Document 1 uses a refrigeration cycle to cause frost or freezing on the heat exchanger surface, and then thaws it to effectively clean dirt from the heat exchanger surface. On the other hand, technology for creating a highly reliable refrigeration cycle for railway vehicles is as shown in Patent Document 2.

Patent No. 6417073

The equipment that makes up the refrigeration cycle of a railway vehicle air conditioning system needs to ensure a high level of reliability. In this regard, there is room for improvement in the technology of Patent Document 1. In other words, to perform frosting and thawing operations, an additional mechanism is required to adjust the amount of refrigerant circulating and to temporarily reduce pressure different from that in normal operation, but the challenge is to suppress the increase in failure rate caused by this additional mechanism.

The present invention was made in consideration of the above problems, and its purpose is to provide an air conditioner for railway vehicles that can maintain reliability even when a mechanism is added to temporarily change the flow pattern of the refrigeration cycle (heat pump cycle) in order to intentionally frost or freeze and thaw the surface of a heat exchanger that is the subject of frost cleaning in order to clean it.

The present invention, which solves the above problems, is an air conditioning system for railway vehicles equipped with a heat pump cycle, and includes a compressor, an indoor heat exchanger, an outdoor heat exchanger, and a first pressure reducing means. The compressor, the indoor heat exchanger, the outdoor heat exchanger, and the first pressure reducing means form a cycle in one path from the start to the end, and a second pressure reducing means is provided in a flow path separate from the cycle, and frost is formed on the target heat exchanger to be cleaned by operating the second pressure reducing means.

The present invention provides a railway vehicle air conditioner that can maintain reliability even when a mechanism is added to temporarily change the flow pattern of the refrigeration cycle in order to clean the heat exchanger that is the subject of frost cleaning by intentionally forming frost or freezing and thawing the surface.

1 is a cycle system diagram of a railway vehicle air conditioning system according to a first embodiment of the present invention (the system of the first embodiment). This is a cycle system diagram for cooling only of a basic railway vehicle air conditioning system (basic system) capable of frost cleaning operation. FIG. 4 is a cycle system diagram of a railway vehicle air conditioning system according to a second embodiment of the present invention (second embodiment system). FIG. 11 is a cycle system diagram of a railway vehicle air conditioning system according to a third embodiment of the present invention (the system of the third embodiment). FIG. 11 is a cycle system diagram of a railway vehicle air conditioning system according to a fourth embodiment of the present invention (the system of the fourth embodiment). FIG. 11 is a cycle system diagram of a railway vehicle air conditioning system according to a fifth embodiment of the present invention (the system of the fifth embodiment). FIG. 11 is a cycle system diagram for explaining the flow of refrigerant when the indoor heat exchanger is subjected to frost cleaning during cooling operation in a railway vehicle air conditioning system according to a sixth embodiment of the present invention (the system of the sixth embodiment). FIG. 8 is a cycle system diagram for explaining the flow of refrigerant when the exterior heat exchanger is subjected to frost cleaning during heating operation in the railway vehicle air conditioning system of FIG. 7. FIG. 13 is a cycle system diagram of a railway vehicle air conditioning system according to a seventh embodiment of the present invention (the system of the seventh embodiment). FIG. 13 is a cycle system diagram of a railway vehicle air conditioning system according to an eighth embodiment of the present invention (the system of the eighth embodiment). FIG. 13 is a cycle system diagram of a railway vehicle air conditioning system according to a ninth embodiment of the present invention (the system of the ninth embodiment).

Figure 1 is a cycle system diagram of the device of Example 1. Figure 2 is a cycle system diagram of the basic device for cooling only. Note that the operations of heating and cooling are explained in Example 6 (Figures 7 and 8) and Example 7 (Figure 9). Other than that, Examples 1 to 5 (Figures 1 to 6), Example 8 (Figure 10), and Example 9 (Figure 11) exemplify an air conditioner for cooling only, and the explanations relate only to the cooling operation. However, the present invention is not limited to these examples.

The device of Example 1 shown in FIG. 1 is a device dedicated to cooling operation, and its main parts are composed of an outdoor unit, an indoor unit, a flow control valve 31, and a bypass flow path 32 including the same. The outdoor unit has a compressor 1, an outdoor heat exchanger 11, an outdoor fan 12, an outdoor heat exchanger gas header 13, an outdoor capillary tube 14, and an outdoor liquid distributor 15. In addition, a device called an accumulator (not shown) is arranged just before the suction side of the compressor 1. This accumulator temporarily holds the liquid phase of the refrigerant flowing into the compressor 1, and prevents a large amount of liquid refrigerant from flowing into the compressor 1, thereby improving the reliability of the air conditioner, and is applied to all examples described in this specification. However, such an accumulator is a basic component of the refrigeration cycle and is common, so its description will be omitted below.

The indoor unit has an indoor capillary tube 24 and an indoor liquid distributor 25, which are the first pressure reducing means, as well as an indoor heat exchanger 21, an indoor fan 22, an indoor heat exchanger gas header 23, an indoor temperature sensor 41, and an indoor heat exchanger temperature sensor 42. Note that the terms indoor unit and outdoor unit are merely names used to simplify the explanation, and do not strictly distinguish which distribution each element belongs to.

The device of Example 1 has a heat pump cycle (hereinafter also simply referred to as "cycle") formed by a single (unicursus) path of piping including a compressor 1, an indoor heat exchanger 21, an outdoor heat exchanger 11, and first pressure reducing means 24, 25 from the start end to the end end. In this way, the first pressure reducing means 24, 25 are inserted into the piping of one path forming the cycle. Second pressure reducing means 31, 32 are disposed in a path separate from this cycle. The second pressure reducing means 31, 32 consists of a flow control valve 31 and a bypass path 32.

Next, the refrigerant flow during cooling in the device of Example 1 will be explained element by element. Compressor 1 is a machine that sucks in refrigerant at a low temperature and low pressure, and discharges it at a high temperature and high pressure, and is driven to rotate by an electric motor. For compressor 1 in a railway vehicle air conditioning device, a simple constant speed drive method in which the rotation speed is fixed is preferable from the standpoint of reliability, as it reduces the failure rate by the amount that an inverter, etc. can be omitted, and is robust.

The discharge side of the compressor 1 is connected to the outdoor heat exchanger gas header 13 of the outdoor heat exchanger 11 by piping. The gas refrigerant discharged from the compressor 1 flows to the outdoor heat exchanger gas header 13, where it is divided into refrigerant paths within the outdoor heat exchanger 11. The outdoor heat exchanger 11 is cooled by outdoor air using the outdoor fan 12. Inside the outdoor heat exchanger 11, the gas refrigerant flowing in from the outdoor heat exchanger gas header 13 is condensed and partially or completely liquefied. The cooled refrigerant passes through the outdoor capillary tube 14 for each path and is collected by the outdoor liquid distributor 15.

The refrigerant leaving the outdoor liquid distributor 15 flows through piping to the indoor liquid distributor 25. The indoor liquid distributor 25 is designed to split the refrigerant inside, and the split refrigerant flows into the indoor heat exchanger 21 via the indoor capillary tubes 24 for each path. The indoor capillary tubes 24 are made of small tubes with an inner diameter of 4 mm or less, preferably 1 to 3 mm. In the small tubes, the refrigerant is decompressed and cooled by the action of fluid resistance.

The refrigerant, which has been decompressed and cooled by the indoor capillary tube 24, flows into each refrigerant path in the indoor heat exchanger 21. Indoor air is blown into the indoor heat exchanger 21 by the indoor fan 22. Because the indoor air is hotter than the refrigerant inside, the liquid refrigerant inside the indoor heat exchanger 21 evaporates and gasifies, absorbing heat from the air passing through. As a result, the air that has passed through the indoor heat exchanger 21 becomes cold and is blown into the room, cooling the room.

At this time, the heat exchange efficiency is reduced due to factors such as the fact that the air blown by the indoor fan 22 is not uniform throughout the indoor heat exchanger 21. For example, if the refrigerant flows uniformly through each refrigerant path of the indoor heat exchanger 21, the amount of heat exchange is large in areas with a large air volume, the refrigerant gasifies quickly, and a superheated gas region occurs. Conversely, the amount of heat exchange is small in areas with a small air volume, leaving a large amount of liquid refrigerant behind, resulting in unevenness.

The heat exchanger section in the superheated gas region, where only gas refrigerant is present inside the refrigerant piping, becomes wider. In this superheated gas region, heat is exchanged between the air and the single-phase refrigerant gas, which has a low heat transfer coefficient, and the heat exchange efficiency decreases. Conversely, if the proportion of liquid phase in the refrigerant returned to the compressor exceeds a certain ratio, this can cause the compressor to break down. To avoid this, during normal cooling operation, the refrigerant leaving the indoor heat exchanger 21 is designed to be at a temperature higher than the saturation temperature of the outlet pressure.

However, if there is a path where a large amount of liquid refrigerant remains, it is necessary to produce excess superheated gas in the remaining paths in order to gasify this remaining liquid refrigerant. This also causes the superheated gas area inside the heat exchanger to expand.

For this reason, the fluid resistance of the indoor capillary tube 24 may be designed to be small for the capillaries connected to paths with a large amount of heat exchange and large for the capillaries connected to paths with a small amount of heat exchange, thereby adjusting the amount of refrigerant flowing through each path and reducing the superheated gas area generated within the indoor heat exchanger 21.

The refrigerant evaporated by the indoor heat exchanger 21 joins the indoor heat exchanger gas header 23 and flows from there to the suction side of the compressor 1. The refrigerant is then heated and pressurized again by the compressor 1, forming a refrigeration cycle for cooling.

In the device of Example 1, the combined indoor liquid distributor 25 and indoor capillary tube 24 form the first pressure reduction means 24, 25. By reducing the pressure while distributing it to each path in this way, even if one of the capillary tubes becomes clogged, the remaining capillary tubes can reduce the pressure, meaning that cooling operation can continue.

The first pressure reducing means 24, 25 are designed so that the refrigerant evaporation temperature in the indoor heat exchanger 21 does not exceed freezing during normal cooling operation, making it suitable for normal cooling operation. The reason for this is that if frost forms on the fin surfaces of the indoor heat exchanger 21, the frost will fill the air passages between the fins, obstructing the air flow, making it impossible to maintain the efficiency of heat exchange required for normal cooling operation.

However, if the design remains suitable only for normal cooling operation, it will not be possible to achieve the frost cleaning operation that provides the cleaning effect of frosting the indoor heat exchanger 21, instantly melting the frost, freezing the water to lift off dirt, and quickly cleaning the dirt with a large amount of melted water. To achieve this, the device of Example 1 is equipped with second pressure reduction means 31, 32.

Here, the configuration of a basic device that is a dedicated cooling device and has the minimum functions required to enable frost cleaning operation will be described with reference to Fig. 2. The basic device in Fig. 2 has the same configurations of the indoor and outdoor units as the device in Example 1 shown in Fig. 1, but does not have the bypass flow path 32 as the second pressure reducing means 31, 32 and the flow control valve 31 inserted therein, and an electronic expansion valve 51 is provided in the middle of the refrigerant piping connecting the discharge side of the outdoor liquid distributor 15 and the suction side of the indoor liquid distributor 25.

The electronic expansion valve 51 has a built-in stepping motor and the like, and the valve opening degree inside the valve body can be precisely adjusted by servo control, thereby changing the fluid resistance. In the basic device of FIG. 2, the electronic expansion valve 51, together with the indoor capillary tube 24, is a part of the function of the first pressure reducing means 24, 25 that belongs to one path that forms the cycle of the heat pump, and does not correspond to the second pressure reducing means 31, 32 formed by providing a flow path separate from the cycle in the first embodiment of FIG. 1.

The indoor capillary tube 24, which is a part of the first pressure reducing means 24, 25, only needs to have the effect of roughly suppressing the flow rate of the refrigerant flowing into the indoor heat exchanger 21. In the basic device of FIG. 2, when performing frost cleaning operation, the valve opening of the electronic expansion valve 51 is reduced so that the refrigerant evaporation temperature inside the indoor heat exchanger 21 is below freezing, and the amount of pressure reduction of the refrigerant is increased.

However, in a cycle using the electronic expansion valve 51, if the valve element inside the electronic expansion valve 51 becomes clogged or if the electrical circuit for precisely adjusting the valve opening degree breaks down, there is a concern that normal cooling operation may be hindered. From the standpoint of reliability and availability, the basic configuration of FIG. 2 leaves room for improvement compared to the configuration of Example 1 shown in FIG. 1.

In the device of Example 1, in order to perform frost cleaning operation while maintaining a simple basic configuration without using an electronic expansion valve 51, a bypass flow path 32 is provided that connects the piping on the discharge side of the compressor 1 to the piping between the outdoor liquid distributor 15 and the indoor liquid distributor 25, and a flow control valve 31 is provided midway along this bypass flow path 32.

In the device of Example 1, the bypass flow path 32 can be blocked by fully closing the flow control valve 31, enabling normal cooling operation. When the refrigerant evaporation temperature in the indoor heat exchanger 21 is lowered below the freezing point for frost cleaning operation, the flow control valve 31 is opened, and the high-temperature gas refrigerant discharged from the compressor 1 is merged with the refrigerant flowing to the indoor liquid distributor 25.

In the device of Example 1, the refrigerant in a liquid or liquid-rich state that is cooled by the outdoor heat exchanger 11 and flows out of the outdoor liquid distributor 15 is partly warmed by the high-temperature gas refrigerant and gasified. This gas refrigerant itself merges, and the gas phase ratio of the refrigerant flowing to the indoor liquid distributor 25 increases compared to when the flow control valve 31 is fully closed. This increases the flow rate of the refrigerant flowing through the indoor capillary tube 24 and increases the pressure loss of the refrigerant in the capillary tube, so the refrigerant is significantly reduced in pressure and the pressure in the indoor heat exchanger 21 decreases, making it possible to lower the evaporation temperature below freezing.

In the device of Example 1, the flow rate control valve 31 has a complex configuration because it has a built-in stepping motor like the electronic expansion valve 51 and the opening degree of the internal valve can be adjusted. There are concerns about the electronic expansion valve 51 becoming clogged inside the valve or the electrical circuit that controls it failing. However, even if the flow rate control valve 31 does become clogged, this is a failure within the bypass flow path 32, so the refrigerant piping circuit necessary for cooling operation outside the bypass flow path 32 is maintained, allowing cooling operation to continue.

In the device of Example 1, in order to cause frost to form on the fin surfaces of the indoor heat exchanger 21 during frost cleaning operation, it is necessary to flow the refrigerant so that the amount of heat exchange is large when the temperature of the air flowing into the indoor heat exchanger is high, and conversely, the amount of heat exchange is small when the air temperature is low.

This is because when the temperature of the air flowing into the indoor heat exchanger 21 is high, if the amount of heat exchange is insufficient, the water condensed by the air that flows in will not freeze and form frost, even if the temperature of the fin surface is below freezing.

In addition, when the inflow air temperature is low, even if a large amount of liquid refrigerant flows inside the indoor heat exchanger 21, it is possible that the liquid refrigerant cannot be sufficiently evaporated because it cannot remove a large amount of heat from the air. This can cause a large amount of liquid refrigerant to flow into the compressor 1, which can lead to a malfunction.

For this reason, in the first embodiment, when the indoor air temperature is high, the opening of the flow control valve 31 is reduced, and the amount of gas refrigerant flowing through the bypass passage 32 is reduced. As a result, most of the refrigerant discharged from the compressor 1 flows to the outdoor heat exchanger 11 and is cooled, and most of the cooled refrigerant flows to the indoor heat exchanger 21, so that the heat exchange amount can be maintained large.

When the indoor air temperature is low, the flow control valve 31 is opened wider, and the amount of gas refrigerant flowing through the bypass flow path 32 is increased. This reduces the amount of refrigerant flowing to the outdoor heat exchanger 11, and the refrigerant cooled in the outdoor heat exchanger 11 is also heated by the high-temperature refrigerant that joins from the bypass flow path 32. This increases the enthalpy of the refrigerant, making it easier for the refrigerant to gasify while reducing the amount of heat that can be exchanged by the indoor heat exchanger 21.

When the indoor air temperature is high, it is likely that the outdoor air temperature is also high. This means that the refrigerant temperature leaving the outdoor liquid distributor 15 is not low enough, meaning that the subcooling amount cannot be achieved and there is a high possibility that the refrigerant is in a two-phase gas-liquid state including gas refrigerant. In such a case, even if the amount of gas flowing through the bypass flow path 32 for frost cleaning is small, sufficient pressure reduction can be achieved in the indoor capillary tube 24.

Conversely, if the indoor air temperature is low, the outdoor air temperature is likely to be low as well. In this case, the amount of heat that can be dissipated by the outdoor heat exchanger 11 increases, so the temperature of the refrigerant leaving the outdoor liquid distributor 15 is low, meaning the amount of subcooling is likely to be large.

In this case, the refrigerant leaving the outdoor liquid distributor 15 is completely in liquid phase, and in order to perform frost cleaning operation, it is necessary to increase the amount of gas refrigerant flowing through the bypass flow path 32, improve the gas quality of the refrigerant flowing through the indoor capillary tube 24, and ensure a pressure reduction amount so that the temperature inside the indoor heat exchanger 21 is below freezing.

To perform these controls using the flow rate control valve 31, in Example 1, an indoor temperature sensor 41 is provided to measure the indoor intake air temperature, and an indoor heat exchanger temperature sensor 42 is provided to monitor the evaporation temperature in the indoor heat exchanger 21.

In this way, the device of Example 1 provides a bypass flow from the compressor 1 to the first pressure reducing means 24, 25 that can adapt to the temperature of each part. By narrowing the bypass flow when the intake air temperature of the heat exchanger 21 that causes frost is high, and increasing the bypass flow when the intake air temperature is low, it is possible to suppress heat shortages and excessive cooling during frosting operation while using the compressor 1 at a constant rotation speed.

As described above, the device of Example 1 shown in FIG. 1 uses a simple and robust constant-speed drive motor as the compressor 1, and is configured with first pressure reducing means 24, 25 for cooling operation and second pressure reducing means 31, 32 for frost cleaning operation. The first pressure reducing means 24, 25 are multiple capillary tubes 24 with redundancy, and the second pressure reducing means 31, 32 are a bypass flow path 32 and a flow control valve 31 inserted therein. The device of Example 1 configured in this way can maintain reliability even if a mechanism for temporarily changing the flow pattern of the refrigeration cycle is added to clean the surface of the heat exchanger 21 that is the target of frost cleaning by intentionally forming frost or freezing and thawing it.

Figure 3 is a cycle system diagram of the device of Example 2. The device of Example 2 is also a device dedicated to cooling operation, and is configured with an outdoor unit and an indoor unit, similar to the device of Example 2 shown in Figure 2. The device of Example 2 shown in Figure 3 is arranged between the discharge side of the outdoor liquid distributor 15 and the suction side of the indoor liquid distributor 25 so as to replace the electronic expansion valve 51 in the basic device shown in Figure 2 with a frosting capillary tube 33, which is the second pressure reducing means 33, and a pipe having a bypass valve 34 in parallel.

In this configuration, during normal cooling operation, the refrigerant coming out of the outdoor liquid distributor 15 branches off into a pipe with a frost prevention capillary tube 33 installed and a pipe with a bypass valve 34 installed, but since the flow path with the bypass valve 34 has a smaller pressure loss than the piping path with the frost prevention capillary tube 33, most of the refrigerant flows through the bypass valve 34 side. Furthermore, the first pressure reducing means consisting of the indoor liquid distributor 25 and the indoor capillary tube 24 reduces the pressure to an appropriate temperature for cooling the indoor heat exchanger 21.

In addition, during frost cleaning operation, by closing the bypass valve 34, the refrigerant coming out of the outdoor liquid distributor 15 passes only through the pipe in which the frost capillary tube 33 is installed, so the flow rate in the capillary tube 33 increases and a large pressure reduction can be achieved. This makes it possible to lower the fin surface temperature of the indoor heat exchanger 21 below freezing point.

The bypass valve 34 is a valve that only closes and opens the internal valve by turning the current on and off, and since it is simple and does not have any internal structure to adjust the flow resistance, there is little risk of clogging. This bypass valve 34 does not require a servo function to adjust the opening degree, and the failure rate of the simplified control electrical circuit is also low.

The device of Example 2 employs a bypass valve 34 that closes when power is turned on, and is controlled to close only during frost cleaning operation. In this control mode, the valve is open during normal cooling operation as well as when operation is stopped. Therefore, even in the unlikely event that the electrical circuit controlling the bypass valve 34 fails, the valve is opened when power is turned off, allowing normal cooling operation to continue and improving availability.

Moreover, even if frost cleaning operation is performed frequently, it is only five minutes to an hour a day, which is a short time for the valve to be blocked compared to when the unit is not in operation or during normal cooling operation. Therefore, even if some factor causes the valve to become stuck in a blocked position, the probability of this occurring is expected to be extremely low.

On the other hand, the frosting capillary tube 33 is more likely to become clogged with foreign matter than a stuck solenoid valve. Even in this case, however, the refrigerant flows through the piping in which the bypass valve 34 is located, so normal cooling operation can continue. However, in this case, pseudo-frosting operation may occur unintentionally, and efficiency may decrease compared to normal cooling operation.

The pseudo-frosting operation state is a state in which the refrigerant flow rate at the bypass valve 34 increases and the amount of pressure reduction increases by the amount of refrigerant that does not flow through the pipe in which the frosting capillary tube 33 is placed, so that the refrigerant evaporation temperature of the indoor heat exchanger 21 becomes lower than before the frosting capillary tube 33 is blocked. To avoid this, it is necessary to design the first pressure reduction means so that the refrigerant evaporation temperature does not fall below freezing.

In the present invention, it is defined that the second pressure reducing means 33 is operated during frost cleaning operation. Also, in the device of Example 2, the bypass valve 34 is energized and closed during frost cleaning operation. The flow path in which the bypass valve 34 is inserted is the main refrigerant circuit including the first pressure reducing means for normal cooling operation. This gives the impression that the first pressure reducing means is operated during frost cleaning operation.

Although this expression is misleading, it is the frost capillary tube 33, which is the second pressure reducing means 33, that actually starts to operate as the pressure reducing means during the frost cleaning operation. In other words, the only thing that is operated to enhance the function of the second pressure reducing means 33 is the bypass valve 34 on the same refrigerant piping as the first pressure reducing means, so there is no essential contradiction between the definition of the present invention and the explanation of the embodiment.

Figure 4 is a cycle system diagram of the device of Example 3. The device of Example 3 is also dedicated to cooling, and in addition to the device of Example 2 shown in Figure 3, an auxiliary bypass valve 35 is added and piped in parallel with the bypass valve 34 arranged between the discharge side of the outdoor liquid distributor 15 and the suction side of the indoor liquid distributor 25.

In the device of Example 3 configured as described above, during normal cooling operation, the bypass valve 34 and auxiliary bypass valve 35 are opened, and the refrigerant coming out of the outdoor liquid distributor 15 branches off and flows into a pipe in which the frost prevention capillary tube 33 is installed and into a pipe in which the bypass valve 34 and auxiliary bypass valve 35 are installed, and is reduced in pressure by the flow resistance of the refrigerant in each pipe. The refrigerant is further reduced in pressure to a temperature appropriate for cooling the indoor heat exchanger 21 by the first pressure reducing means composed of the indoor liquid distributor 25 and the indoor capillary tube 24.

In addition, in the device of Example 3, during frost cleaning operation, by closing both the bypass valve 34 and the auxiliary bypass valve 35, the refrigerant coming out of the outdoor liquid distributor 15 passes only through the piping in which the frost capillary tube 33 is installed, so the flow rate in the capillary tube increases and a large pressure reduction can be achieved. This makes it possible to lower the fin surface temperature of the indoor heat exchanger 21 below freezing point.

In the device of Example 3, even if either the bypass valve 34 or the auxiliary bypass valve 35 fails, one of the valves is reliably open, making it possible to continue normal cooling operation. If either the bypass valve 34 or the auxiliary bypass valve 35 is blocked, the flow resistance of the refrigerant in the remaining piping increases, and the amount of pressure reduction may increase slightly. However, even in such a case, if the first pressure reduction means is designed so that the amount of refrigerant evaporation in the indoor heat exchanger 21 does not drop below freezing, normal cooling operation will be possible.

Figure 5 is a cycle system diagram of a railway vehicle air conditioning system according to Example 4 of the present invention (hereinafter, also referred to as "the system of Example 4"). The railway vehicle air conditioning system of Example 4 shown in Figure 5 is also dedicated to cooling, and in addition to the railway vehicle air conditioning system of Example 2, a bypass flow path 32 that connects the discharge side of the compressor to a pipe in which a capillary tube for frosting is arranged, and a flow control valve 31 are provided on this bypass flow path 32. In particular, in Example 4, the bypass flow path 32 is connected between the outdoor liquid distributor 15 and the capillary tube for frosting 33.

The configuration of Example 4 is the same as that of Example 1, except that a capillary tube 33 for frost formation is added when the refrigerant evaporation temperature of the indoor heat exchanger 21 does not fall below freezing during frosting operation, or when it is particularly desired to lower the frost temperature on the fin surface.

In the configuration of Example 4, the bypass valve 34 is opened during normal cooling operation. As a result, the refrigerant coming out of the outdoor liquid distributor 15 branches off and flows into a pipe in which a frost prevention capillary tube 33 is installed, and into a pipe in which a bypass valve 34 and an auxiliary bypass valve 35 are installed. The refrigerant is reduced in pressure by the resistance of each refrigerant flow. Furthermore, the refrigerant is reduced in pressure to a temperature appropriate for cooling the indoor heat exchanger 21 by the first pressure reducing means constituted by the indoor liquid distributor 25 and the indoor capillary tube 24.

In the configuration of the fourth embodiment, during frost cleaning operation, the bypass valve 34 is closed, the flow rate control valve 31 is opened, and the high-temperature gas refrigerant discharged from the compressor 1 is merged with the refrigerant flowing to the indoor liquid distributor 25. As a result, the refrigerant in a liquid or liquid-rich state that is cooled by the outdoor heat exchanger 11 and flows out of the outdoor liquid distributor 15 is partly warmed and gasified by the high-temperature gas refrigerant, and the gas refrigerant itself merges, so that the gas phase ratio of the refrigerant flowing to the indoor liquid distributor 25 increases compared to when the flow rate control valve 31 is fully closed.

As a result, the flow rate of the refrigerant flowing through the frosting capillary tube 33 and the indoor capillary tube 24 increases, and the pressure loss of the refrigerant in the capillary tube also increases, so the refrigerant is significantly reduced in pressure and the pressure in the indoor heat exchanger 21 decreases, making it possible to lower the evaporation temperature below freezing point.

In addition, when the indoor air temperature is high, the opening of the flow control valve 31 is reduced, and when the indoor air temperature is low, the opening of the flow control valve 31 is increased, thereby achieving a heat exchange amount that allows appropriate frost formation on the indoor heat exchanger 21 according to the indoor air temperature.

Figure 6 is a cycle system diagram of the device of the fifth embodiment of the present invention. The railroad vehicle air conditioning device of the fifth embodiment is also dedicated to cooling, and is configured with an outdoor unit and an indoor unit, similar to the device of the second embodiment shown in Figure 2. The device of the fifth embodiment shown in Figure 6 is arranged between the discharge side of the outdoor liquid distributor 15 and the suction side of the indoor liquid distributor 25 so as to replace the electronic expansion valve 51 in the basic device shown in Figure 2 with the pipe heating unit 36 as the second pressure reducing means.

The pipe heating unit 36 may be constructed by heating the refrigerant with hot water by providing an electric heater on the surface of the pipe or by using a plate heat exchanger to heat the refrigerant. In other words, the heating structure of the pipe heating unit 36 heats the refrigerant from outside the flow path. In the device of Example 5, the pipe heating unit 36 does not perform heating operation during normal cooling operation. Therefore, in the cycle of the device of Example 5, the refrigerant flows in the same way as in normal piping, and is depressurized to an appropriate temperature for cooling the indoor heat exchanger 21 by the first depressurization means composed of the indoor liquid distributor 25 and the indoor capillary tube 24.

In addition, the device of Example 5 heats the refrigerant in the pipe heating unit 36 during frost cleaning operation. As a result, the refrigerant that has been cooled in the outdoor heat exchanger 11 and is in a liquid or liquid-rich state that flows out of the outdoor liquid distributor 15 is warmed and gasified by the pipe heating unit 36. As a result, the gas phase ratio of the refrigerant flowing to the indoor liquid distributor 25 increases compared to before heating by the pipe heating unit 36.

As a result, in the device of Example 5, the flow rate of the refrigerant flowing through the indoor capillary tube 24 is increased, and the pressure loss of the refrigerant in the capillary tube 24 is also increased, so the refrigerant is significantly reduced in pressure and the pressure in the indoor heat exchanger 21 decreases, making it possible to lower the evaporation temperature below freezing point.

Figure 7 is a cycle diagram for explaining the flow of refrigerant when the indoor heat exchanger 21 is frost-cleaned during cooling operation in the device of Example 6. Figure 8 is a cycle diagram for explaining the flow of refrigerant when the outdoor heat exchanger 11 is frost-cleaned during heating operation in the device of Example 6.

The device of Example 6 shown in Figures 7 and 8 is a dual-purpose device equipped with both cooling and heating functions, whereas the device of Example 4 shown in Figure 5 was a dedicated cooling device. The indoor and outdoor units are the same, but there are differences in the various pipes connecting them and the elements inserted into them.

The difference is that a four-way valve 2 is attached to the compressor 1 located between the outdoor heat exchanger gas header 13 and the indoor heat exchanger gas header 23, making it possible to change the direction of the one-way flow from the compressor 1 depending on whether heating or cooling is selected. In addition, as a second pressure reducing means common to the devices of Examples 2 to 4 and 6, capillary tubes 33, 37 and 38 are provided in parallel to the piping having the bypass valve 34 that is piped between the outdoor liquid distributor 15 and the indoor liquid distributor 25, but the form differs for each of the devices of Examples 2 to 4 and 6.

In the device of Example 6, a first frosting capillary tube 37 and a second frosting capillary tube 38 are connected in parallel to the path of the bypass valve 34 as the second pressure reducing means. The bypass flow path 32 extends in a T-shape from the midpoint where the first and second frosting capillary tubes 37, 38 are connected in series, and is connected to the discharge side of the compressor 1 with a flow control valve 31 inserted therebetween, and also serves as the second pressure reducing means.

Next, the refrigerant flow during cooling in Example 6 will be explained element by element. The refrigerant discharged from the compressor 1 flows through the four-way valve 2 to the outdoor heat exchanger gas header 13 of the outdoor unit. Four pipes are connected to the four-way valve 2: the suction side of the compressor 1, the discharge side of the compressor 1, the outdoor heat exchanger 11 side, and the indoor heat exchanger 21 side.

This four-way valve 2 switches the flow path so that the gas discharged from the compressor 1 flows to the outdoor heat exchanger 11 during cooling as shown in FIG. 7, and to the indoor heat exchanger during heating as shown in FIG. 8. At the same time, the flow path is switched so that the refrigerant from the indoor heat exchanger 21 flows to the suction side of the compressor 1 during cooling, and the refrigerant from the outdoor heat exchanger 11 flows to the suction side of the compressor 1 during heating.

The gas refrigerant that flows into the outdoor heat exchanger gas header 13 is divided into separate refrigerant paths within the outdoor heat exchanger 11. The outdoor heat exchanger 11 is cooled by outdoor air using the outdoor fan 12, and inside the outdoor heat exchanger 11, the gas refrigerant that flows in from the outdoor heat exchanger gas header 13 condenses and is partially or completely liquefied. The cooled refrigerant passes through the outdoor capillary tube 14 for each path and is collected by the outdoor liquid distributor 15.

Part of the refrigerant coming out of the outdoor liquid distributor 15 flows into the flow path consisting of the first frosting capillary tube 37 and the second frosting capillary tube 38, while the majority flows into the flow path containing the bypass valve 34. The refrigerant, which is slightly depressurized due to the fluid resistance of these two flow paths, flows into the indoor liquid distributor 25.

The indoor liquid distributor 25 is designed to split the refrigerant inside, and the split refrigerant flows into the indoor heat exchanger 21 via the indoor capillary tubes 24 for each path. The indoor capillary tubes 24 are made of thin tubes with an inner diameter of 4 mm or less, preferably 1 to 3 mm. Fluid resistance acts on the thin tubes inserted in the indoor liquid distributor 25, reducing the pressure of the refrigerant to a low temperature.

The refrigerant, which has been decompressed and cooled by the indoor capillary tube 24, flows into each refrigerant path in the indoor heat exchanger 21. Indoor air that is hotter than the refrigerant inside is blown into the indoor heat exchanger 21 from the indoor fan 22, so the liquid refrigerant inside the indoor heat exchanger 21 evaporates and gasifies, removing heat from the air. The air that passes through the indoor heat exchanger 21 becomes cold and is blown into the room to cool it down.

The refrigerant evaporated by the indoor heat exchanger 21 joins the indoor heat exchanger gas header 23, and from there flows through the four-way valve 2 to the suction side of the compressor 1. The refrigeration cycle for cooling is completed by raising the temperature and pressure again by the compressor. Next, the refrigerant flow during heating in Example 6 will be explained element by element. The high-temperature, high-pressure gas refrigerant discharged from the compressor 1 flows to the outdoor heat exchanger gas header 23 of the indoor heat exchanger 21 through the four-way valve 2 that has been switched for heating.

The gas refrigerant that flows into the indoor heat exchanger gas header 23 is divided into separate refrigerant paths within the indoor heat exchanger 21. Indoor air is circulated through the indoor heat exchanger 21 by an indoor fan 22. The gas refrigerant that flows in from the indoor heat exchanger gas header 23 inside the indoor heat exchanger 21 is cooled by this indoor air, condensing and partially or completely liquefying. Conversely, the indoor air is warmed by the refrigerant and returns to the room to provide heating.

The cooled refrigerant passes through the indoor capillary tube 24 for each path and is collected by the indoor liquid distributor 25. Some of the refrigerant that leaves the indoor liquid distributor 25 flows into the flow path consisting of the first frosting capillary tube 37 and the second frosting capillary tube 38, while the majority flows into the flow path containing the bypass valve 34. The refrigerant, whose pressure is slightly reduced due to the fluid resistance of these two flow paths, flows into the outdoor liquid distributor 15.

The outdoor liquid distributor 15 is designed to split the refrigerant inside, and the split refrigerant flows into the outdoor heat exchanger 11 via the indoor capillary tubes 14 for each path. The outdoor capillary tubes 14 are made of small tubes with an inner diameter of 4 mm or less, preferably 1 to 3 mm. The small tubes that make up the outdoor liquid distributor 15 have a fluid resistance that reduces the pressure of the refrigerant so that it becomes colder.

The refrigerant, which has been reduced in pressure by the outdoor capillary tube 14 and reduced in temperature, flows into each refrigerant path in the outdoor heat exchanger 11. The outdoor fan 12 blows outdoor air, which is hotter than the refrigerant inside, into the outdoor heat exchanger 11. When the liquid refrigerant inside the outdoor heat exchanger 11 evaporates and gasifies, it takes heat from the air, so the air that passes through the outdoor heat exchanger 11 becomes cold and is released outside.

The refrigerant evaporated by the outdoor heat exchanger 11 joins the outdoor gas header 13, and from there flows through the four-way valve 2 to the suction side of the compressor 1. The compressor then raises the temperature and pressure again, completing the refrigeration cycle for heating.

In this configuration, if the flow control valve 31 provided in the bypass flow path 32 connecting the discharge side of the compressor 1 with the first frosting capillary tube 37 and the second frosting capillary tube 38 is closed and the bypass valve 34 is open, most of the refrigerant passes through the flow path with the bypass valve 34, rather than through the flow path consisting of the first frosting capillary tube 37 and the second frosting capillary tube 38, whether in cooling or heating mode.

Most of the pressure reduction under each condition is borne by the indoor capillary tube 24 in cooling mode and the outdoor capillary tube 14 in heating mode, allowing normal operation for both cooling and heating modes.

In addition, to perform frost cleaning operation on either the indoor heat exchanger 21 or the outdoor heat exchanger 11, the flow control valve 31 provided in the bypass flow path 32 is opened, and the discharge gas from the compressor is merged into the connection point between the first frost capillary tube 37 and the second frost capillary tube 38.

This improves the gas quality of the refrigerant that is cooled, condensed, and liquefied in one of the heat exchangers, and by increasing the gas flow rate inside the capillary tube, the pressure loss inside the tube is increased, allowing the refrigerant to be reduced in pressure to an evaporation temperature below freezing on the heat exchanger surface that is subject to frost.

Specifically, when the indoor heat exchanger 21 is in frost cleaning operation, the four-way valve 2 is switched to the cooling operation state, the bypass valve 34 is closed, the discharge gas of the compressor 1 is condensed in the outdoor heat exchanger 11, and the discharge gas discharged directly from the compressor 1 is merged with the condensed liquid refrigerant. At that time, the opening of the flow control valve 31 is appropriately adjusted, and the refrigerant whose gas quality has been improved by the merger of the discharge gas is depressurized by the second frost capillary tube 38, further improving the gas quality.

Then, the pressure is further reduced by passing through the indoor liquid distributor 25 and the indoor capillary tube 24, and the evaporation temperature reaches a temperature that can cause the indoor heat exchanger 21 to drop below freezing. At this time, the opening degree of the flow control valve 31 is controlled based on information from the indoor temperature sensor 41 and the indoor heat exchanger temperature sensor 42.

When the outdoor heat exchanger 11 is in frost cleaning operation, the four-way valve 2 is switched to the heating operation state, the bypass valve 34 is closed, the discharge gas from the compressor 1 is condensed in the indoor heat exchanger 21, and the discharge gas discharged directly from the compressor 1 is merged with the condensed liquid refrigerant.

At that time, the opening of the flow control valve 31 is appropriately adjusted, and the refrigerant, whose gas quality has been improved by the merging of the discharge gas, is depressurized by the first frosting capillary tube 37, further improving the gas quality. The refrigerant then passes through the outdoor liquid distributor 15 and the indoor capillary tube 14, and is further depressurized, reaching an evaporation temperature that can lower the outdoor heat exchanger 11 below freezing.

At this time, the opening degree of the flow control valve 31 is controlled based on information from the outdoor temperature sensor 43 and the outdoor heat exchanger 11 temperature sensor 44. Since the refrigerant coming out of the outdoor liquid distributor 15 passes only through the pipe in which the frost prevention capillary tube 33 is installed, the flow rate in the capillary tube increases, and a large reduction in pressure can be achieved. This makes it possible to lower the fin surface temperature of the indoor heat exchanger 21 below freezing point.

Figure 9 is a cycle system diagram of the device of Example 7. The device of Example 7 is also a dual-purpose device with both heating and cooling functions, and shows the flow of refrigerant during cooling operation. Like Example 6, Example 7 is also capable of heating operation by using the four-way valve 2. The device of Example 7 is configured such that, compared to the device of Example 6, the piping with the bypass valve 34 and the second pressure reducing means consisting of the first frosting capillary tube 37 and the second frosting capillary tube 38 are removed.

The purpose of the first frosting capillary tube 37 and the second frosting capillary tube 38 in the device of Example 6 is that they can significantly reduce the refrigerant evaporation temperature during frost cleaning operation without ensuring a large pressure loss between the outdoor capillary tube 14 and the indoor capillary tube 24.

Therefore, if sufficient pressure loss can be obtained by the outdoor capillary tube 14 and the indoor capillary tube 24 even during freeze cleaning operation, the first frosting capillary tube 37 and the second frosting capillary tube 38 are not necessary.

In this way, if the first frosting capillary tube 37 and the second frosting capillary tube 38 are not necessary, the bypass valve 34 is also not necessary, and with only the configuration shown in Figure 9, not only normal cooling and heating operation but also frost cleaning operation for the indoor heat exchanger 21 and the outdoor heat exchanger 11 are possible.

Figure 10 is a cycle system diagram of the device of Example 8. The device of Example 8 is also for cooling only, and the heat pump cycle is similar to that of the device of Example 1 shown in Figure 1. In addition to the components of the device of Example 1, the device of Example 8 is composed of a drainage tray 61 below the indoor heat exchanger 21 that can receive and store condensed water 62 condensed in the indoor heat exchanger 21, a pump 63, a condensed water return flow path 64, and a spray nozzle 65 that sprays spray water 66 onto the indoor heat exchanger 21.

According to the device of Example 8, condensation water 62, which is moisture in the air that condenses on the fin surface of the indoor heat exchanger 21 during cooling operation, is received in a drainage tray 61 arranged below the indoor heat exchanger 21, some of which is stored and then sucked up by a pump 63 and sprayed onto the indoor heat exchanger 21 by a condensation water return flow path 64 and a spray nozzle 65.

In the device of Example 8, when the frost cleaning operation is performed, the more moisture that frosts or freezes on the fin surface, the more water flows over the fin surface when the frost and ice melt, so a high cleaning effect can be achieved.

According to the device of Example 8, condensation water 62 generated during operation prior to the frosting operation can be stored in the drainage tray 61 and sprayed onto the heat exchanger to be cleaned during the frosting cleaning operation. This can increase the amount of water that frosts or freezes on the fin surface, improving the cleaning effect of the frosting cleaning.

In FIG. 10, the condensed water 62 condensed by the indoor heat exchanger 21 is sprayed onto the indoor heat exchanger 21 as the target of the frost cleaning operation. However, if the unit is capable of both heating and cooling and heating operation, it goes without saying that the condensed water spraying method can be applied to the outdoor heat exchanger 11 during heating operation. Although not shown in FIG. 10, the drain pans of the outdoor heat exchanger 11 and the indoor heat exchanger 21 may be connected, and the condensed water 62 captured by both can be supplied to the condensed water return flow path 64.

Conventionally, condensation water 62 generated in the indoor heat exchanger 21 during cooling has been sprayed onto the outdoor heat exchanger 11 to improve heat dissipation efficiency and improve cooling performance. For a different purpose, in the device of Example 8, it is also possible to use the water generated by melting the frost and ice after performing the frost cleaning operation as condensation water 62. In this case, it is preferable to perform control so that the frost cleaning operation is repeated two or more times in succession.

Figure 11 is a cycle system diagram of the device of Example 9. The device of Example 9 is also dedicated to cooling, and a second bypass valve 39 is added and inserted so as to be connected in series to the frosting capillary tube 33, which is the second pressure reducing means 33 in the device of Example 2 shown in Figure 3.

During normal cooling operation, the device of Example 9 opens the bypass valve 34 and closes the second bypass valve 39. As a result, the refrigerant coming out of the outdoor liquid distributor 15 flows only through the pipe in which the bypass valve 34 is installed, and is further reduced in temperature to an appropriate temperature for cooling the indoor heat exchanger 21 by the first pressure reducing means 24, 25 consisting of the indoor liquid distributor 25 and the indoor capillary tube 24.

In addition, in the device of Example 9, during frost cleaning operation, the bypass valve 34 is closed and the second bypass valve 39 is opened, so that the refrigerant coming out of the outdoor liquid distributor 15 passes only through the pipe in which the frost capillary tube 33 is installed, increasing the flow rate in the capillary tube and achieving a large pressure reduction. This makes it possible to lower the fin surface temperature of the indoor heat exchanger 21 below freezing.

In the device of Example 9, during cooling, the bypass valve 39 is closed, so that the refrigerant does not flow through the piping in which the frost prevention capillary tube 33 is arranged. Therefore, unlike the device of Example 2, the device of Example 9 can be designed so that the evaporation temperature of the refrigerant in the indoor heat exchanger 21 is appropriate by reducing the pressure in the indoor capillary tube 24.

In the device of Example 9, the main refrigerant circuit that performs cooling operation, including the first pressure reducing means 24, 25, is the flow path that passes through the bypass valve 34. The bypass valve 34 on the same refrigerant piping as the first pressure reducing means 24, 25 is turned on as a control during frost cleaning operation. With this control, it is the frost capillary tube 33, which is the second pressure reducing means, that actually begins to operate as the pressure reducing means 33.

The railway vehicle air conditioning system according to the embodiment of the present invention (hereinafter, also referred to as "the system") can be summarized as follows.
[1] In this device, a heat pump cycle is formed with one path from the start point to the end point. This cycle includes a compressor 1, an indoor heat exchanger 21, an outdoor heat exchanger 11, and first pressure reducing means 14, 15, 24, and 25.

The first pressure reducing means 14, 15, 24, 25 are inserted into one path that forms the cycle of the heat pump. The second pressure reducing means 31, 33, 36-38 are configured in a flow path that is arranged separately from this cycle. By operating the second pressure reducing means 31, 33, 36-38, frost is formed on one of the heat exchangers 21, 11 to be cleaned.

The target heat exchanger 21, 11 refers to the heat exchanger that is cooled during normal heating and cooling operation, and is the indoor heat exchanger 21 during cooling operation and the outdoor heat exchanger 11 during heating operation. By operating the second pressure reduction means, this device can achieve a situation that cannot be achieved by the first pressure reduction means alone, that is, a pressure reduction amount of the refrigerant that can reduce the temperature to a level that causes frost to form on the heat exchanger surface.

In this device, the second pressure reducing means 31, 33, 36-38 are arranged to minimize the possibility of disrupting the cycle that is essential for cooling operation, in which the refrigerant discharged from the compressor circulates to the compressor 1 via the outdoor heat exchanger 11, the first pressure reducing means 14, 15, 24, 25, and the indoor heat exchanger 21 during cooling. Therefore, even if the second pressure reducing means 31, 33, 36-38 fail, cooling operation is possible, and the reliability of the air conditioning device for railway vehicles can be improved. Therefore, this device can maintain its reliability even if a mechanism is added that temporarily changes the flow pattern of the refrigeration cycle to intentionally frost or freeze and thaw the surface of the heat exchanger that is the target of frost cleaning to clean it.

[2] In the above [1], the operating state of the compressor 1 is either an operating state at a specified rotation speed or a stopped state. In this way, the motor only requires a simple control function of ON/OFF. In other words, since no other inverter circuit for variable speed control is required, reliability against failures is significantly higher.

[3] In the above [1], the first pressure reducing means is composed of small diameter tubes 14, 24. These are configured to be suitable for normal heating and cooling operation without any forced frosting or freezing.

[4] In the above [1], the second pressure reducing means is composed of a thin pipe flow path consisting of thin pipes 33, 37, 38 arranged in parallel, each having an inner diameter of 4 mm or less, and a thick pipe having an inner diameter of 4 mm or more in parallel with the thin pipe flow path, and solenoid valves 34, 35 are inserted in the flow path of the thick pipe, and frost is formed by closing the solenoid valves 34, 35. The additional components with such a configuration are much more reliable against failures than variable speed motor control devices that require an inverter circuit or the like.

[5] In the above [1], the second pressure reducing means is composed of a bypass flow path 32 that branches off from the piping near the discharge side of the compressor 1 and merges with the high pressure side of the first pressure reducing means, and a flow control valve 31 provided midway along the bypass flow path 32. This device causes frosting by opening the flow control valve 31. This configuration of the device requires only a few additional elements compared to conventional devices, and can be easily achieved by simply changing the connections of the piping.

[6] As in the device of Example 3 shown in Fig. 4, the second pressure reducing means is composed of a small diameter tube 33, a plurality of pipes are arranged in parallel with the second pressure reducing means 33, and solenoid valves 34, 35 are inserted in the flow paths of the plurality of pipes. In the device of Example 3, frost is formed by closing the solenoid valves 34, 35. The configuration of the device of Example 3 requires relatively few elements to be added or replaced compared to the conventional device, can be easily realized, and has high reliability against failures.

[7] As in the device of Example 9 shown in FIG. 11, the second pressure reducing means is composed of a thin pipe 33, one or more bypass pipes are arranged in parallel with the thin pipe 33, and a solenoid valve 34 is inserted in each of the flow paths on the bypass pipe side, and a solenoid valve 39 is also inserted in the flow path in which the thin pipe 33 is arranged.

The device of Example 9 causes frosting by closing the solenoid valve 34 inserted in the flow path on the bypass piping side and opening the solenoid valve 39 inserted in the flow path on the small diameter tube 33 side. The device of Example 9 also requires relatively few elements to be added or replaced compared to conventional devices, is easy to implement, and is highly reliable against breakdowns.

[8] As in the device of Example 5 shown in FIG. 6, a pipe superheating unit 36 for heating the refrigerant in the pipe between the condensation side heat exchanger 11 and the first pressure reducing means 24, 25 may be provided as a second pressure reducing means. In the device of Example 5, during frost cleaning operation, the refrigerant is heated and gasified by the pipe heating unit 36, and the gas phase ratio of the refrigerant flowing to the indoor liquid distributor 25 is increased compared to before heating by the pipe heating unit 36.

This increases the flow rate of the refrigerant passing through the indoor capillary tube 24, lowering the pressure inside the indoor heat exchanger 21 and making it possible to lower the evaporation temperature below the freezing point. Therefore, the device of Example 5 can also temporarily frost and freeze the surface of the indoor heat exchanger 21 to be cleaned, and can reliably perform the frost cleaning operation.

[9] As shown in Fig. 10, the device of Example 8 may further include a drain pan 61 disposed below the target heat exchanger 21 to receive condensed liquid droplets, and a condensed water return flow path 64 for spraying condensed water 62 stored in the drain pan 61 onto the upper part of the target heat exchanger 21. The device of Example 8 may perform a frosting operation during or after spraying the condensed water 62 onto the target heat exchanger 21 to cause frost to form, and then perform a thawing operation to thaw the frost. Such a device of Example 8 may provide a cleaning effect using a larger amount of cleaning water.
[supplement]

As shown in FIG. 2, railroad car air conditioning systems use a constant-speed compressor 1, and the pressure reducing device often uses capillary tubes 14, 24 made of multiple long, thin tubes. The pressure reducing effect of the capillary tubes 14, 24 is achieved by circulating the refrigerant through a tube with a long, thin inner diameter, increasing the flow rate of the refrigerant, and causing friction between the refrigerant and the tube wall. The capillary tubes 14, 24 cannot change their opening independently, so the flow rate control range is not large.

Frost cleaning operation is a temporary maintenance operation that keeps the fin surfaces clean by repeating frost and thaw operations. This frost cleaning operation is performed by adjusting the amount of refrigerant circulating and temporarily generating a larger reduction in pressure in the target heat exchanger than in normal operation. To perform frost operation while keeping the rotation speed of the compressor 1 constant, it was necessary to ensure a flow control range that could reduce pressure significantly using an electronic expansion valve 51 such as that arranged in the device in Figure 2. However, the electronic expansion valve 51 requires a complex control device and is prone to malfunctions, leaving room for improvement.

The objective of the present invention is to add a mechanism equivalent to an electronic expansion valve 51 that allows frosting and freezing on the surfaces of the heat exchangers 11, 21 through the refrigeration cycle in order to maintain the cleanliness of the heat exchangers 11, 21, without lowering the inherent reliability of the heat exchangers. For example, the means for achieving this are, first, to omit the inverter circuit used for variable speed control of the compressor 1. Second, to pipe a simple variable pressure reduction mechanism in place of the electronic expansion valve 51 (Figure 2), which requires a control unit capable of controlling the opening degree.

The means for solving this problem are as follows. The compressor 1, the indoor heat exchanger 21, the outdoor heat exchanger 11, and the first pressure reducing means 24, 25 form a heat pump cycle in one path. In other words, the cycle is formed by flow paths connected in a single line. A second pressure reducing means is provided as a variable pressure reducing mechanism on a separate flow path from this single-line cycle. By operating this second pressure reducing means, frost is formed on the heat exchanger that is the target of frost cleaning.

Specifically, the variable pressure reducing mechanism, which is the second pressure reducing means, is configured as a variable pressure reducing mechanism that combines flow rate adjustment valve 31 (Fig. 1), which has a relatively simple structure and control method, solenoid valves 34, 35 (Fig. 4), 39 (Fig. 11), which can be simply opened and closed, and capillaries 33 (Fig. 3), 37, 38 (Fig. 7). This simplification reduces the failure rate.

The device may be realized by including a computer having a memory that stores a program including operation patterns that adapt to environmental temperature and other various conditions for valve operation during frost cleaning operation, an arithmetic processing unit (CPU) that reads the contents of the memory and executes it, an interface that inputs and outputs operation commands to the computer, and an actuator or servo mechanism that is connected to the interface and executes the operation commands. The above-mentioned computer may be a one-chip microcomputer, or it may be part of a computer for other purposes. The device may also be realized by replacing the above-mentioned computer with hardware of equivalent function.

1 Compressor, 2 Four-way valve, 11 Outdoor heat exchanger, 12 Outdoor fan, 13 Outdoor heat exchanger gas header, 14 Outdoor capillary tube, 15 Outdoor liquid distributor, 21 Indoor heat exchanger, 22 Indoor fan, 23 Indoor heat exchanger gas header, 24 Indoor capillary tube, 25 Indoor liquid distributor, 31 Flow control valve, 32 Bypass flow path, 33 Frost capillary tube, 34 Bypass valve, 35 Auxiliary bypass valve, 36 Pipe heating section, 37 First frost capillary tube, 38 Second frost capillary tube, 39 Second bypass valve, 41 Indoor temperature sensor, 42 Indoor heat exchanger temperature sensor, 43 Outdoor temperature sensor, 44 Outdoor heat exchanger temperature sensor, 51 Electronic expansion valve 51, 61 Drain pan, 62 Condensed water, 63 Pump, 64 Condensation water return flow path, 65 spray nozzle, 66 spray water

Claims (5)

A railway vehicle air conditioning device equipped with a heat pump cycle,
The refrigerant coolant supply system includes a compressor, an indoor heat exchanger, an outdoor heat exchanger, and a first pressure reducing means,
the compressor, the indoor heat exchanger, the outdoor heat exchanger, and the first decompression means form the cycle in one path from a starting point to a terminal point,
a second pressure reducing means is provided in a flow path separate from the cycle;
the second pressure reducing means is composed of a small-diameter pipe flow path made up of small-diameter pipes arranged in parallel, a bypass flow path branching off from a pipe near the discharge side of the compressor and merging with a high-pressure side of the small-diameter pipe flow path, and a flow rate regulating valve provided midway through the bypass flow path,
a pipe having a larger diameter than the thin tube and disposed in parallel with the thin tube flow path;
A solenoid valve is inserted in the flow path of the thick pipe,
By closing the solenoid valve and opening the flow rate control valve, frost is formed on the heat exchanger to be cleaned.
Air conditioning equipment for railway vehicles. The operating state of the compressor is selected from a state of operation at a predetermined rotation speed and a state of stop.
2. A railroad vehicle air conditioning system according to claim 1. The first pressure reducing means is constituted by a thin tube.
2. A railroad vehicle air conditioning system according to claim 1. The air conditioning device for railway vehicles according to claim 1, wherein the small diameter tube has an inner diameter of 4 mm or less. a drain pan disposed below the target heat exchanger for receiving condensed liquid;
A condensation water return flow path for spraying the condensation water accumulated in the drain pan onto an upper portion of the target heat exchanger;
and
The condensation water is sprayed on the target heat exchanger, or after the frost is formed, and then
A thawing operation is performed to thaw the formed frost.
The air conditioning device for a railway vehicle according to any one of claims 1 to 4 .

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