Power converter

Abstract

To provide a power conversion device capable of reducing pump power of a cooling system and achieving cost reduction.SOLUTION: In a power conversion device 1, a heat transfer block of a heat receiving unit 12 has a semi-conductor module 11 mounted on one main surface and a plurality of fins 31b formed on the other main surface. A porous body 32 is provided in the heat transfer block. A liquid-phase working refrigerant 100 flows through a first flow path 35. A second flow path 36 has a plurality of vapor discharge units 36a formed between a plurality of fins of the heat transfer block, and a gas-phase working refrigerant 101 flows therethrough. A reservoir tank stores the working refrigerant. A heat exchange unit is connected to the second flow path and the reservoir tank. A check valve is disposed between the heat exchange unit and the reservoir tank and regulates movement of the working refrigerant from a reservoir tank side to a heat exchange unit side. A pump is connected to the first flow path and the reservoir tank, and delivers the working refrigerant in the reservoir tank to the first flow path.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] Embodiments of the present invention relate to a power conversion device.

Background Art

[0002] Techniques using a power conversion device in a railway vehicle or the like are known. Such a power conversion device applies a circulation water cooling system, which is a circulation method, to the cooling method of a system including a semiconductor module. The circulation water cooling system of this power conversion device has, for example, a circulation water cooling system including a heat receiving part, a heat exchanger, a reservoir tank, and a pump. The heat receiving part has a heat sink block on which a semiconductor module is mounted and cooled. The pump supplies internal fluid from the reservoir tank to the heat receiving part and the heat exchanger, and returns it from the heat exchanger to the reservoir tank.

[0003] Such a circulation water cooling system can maintain stable cooling performance because it circulates a working refrigerant with a constant flow rate. However, among power electronics devices, in applications where load fluctuations are large, if the flow rate is circulated constantly, the semiconductor elements may be overcooled, and the temperature change of the semiconductor elements may increase. In addition, the temperature fluctuation of the cooling water cooling system with respect to the load fluctuation of the power conversion device system increases. In addition, a high heat flux is required for the circulation water cooling system. However, in order to increase the heat flux of the circulation water cooling system, it is necessary to increase the flow rate, and an increase in pump power due to pressure loss becomes an issue.

[0004] For example, as a cooling system corresponding to a high heat flux, a boiling cooling method that uses the latent heat of vaporization due to a phase change of a working refrigerant or the like is also known. However, the cooling system of the boiling cooling method has a problem in the cooling responsiveness (stability) with respect to a steep load. In particular, it is difficult to configure a plurality of modules in parallel and increase the capacity.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Patent No. 6407542 [Patent Document 2] Patent No. 6693476 [Patent Document 3] Patent No. 6760214 [Patent Document 4] Patent No. 6461361 [Overview of the project] [Problems that the invention aims to solve]

[0006] The problem that this invention aims to solve is to provide a power conversion device that can reduce the pump power of a cooling system and reduce costs. [Means for solving the problem]

[0007] The power conversion device of this embodiment comprises a semiconductor module, a heat transfer block, a porous body, a first channel, a second channel, a reservoir tank, a heat exchange section, and a pump. The heat transfer block has a semiconductor module attached to one main surface and a plurality of fins formed on the other main surface. The porous body is provided on the heat transfer block. , in contact with the plurality of fins The first flow path carries a liquid-phase working refrigerant. The second flow path carries a gaseous working refrigerant, which has multiple vapor outlets formed between the multiple fins of the heat transfer block. A reservoir tank stores the working refrigerant. A heat exchange unit is connected to the second flow path and the reservoir tank. A pump is connected to the first flow path and the reservoir tank and delivers the working refrigerant from the reservoir tank to the first flow path. [Brief explanation of the drawing]

[0008] [Figure 1] A schematic diagram illustrating the configuration of a power conversion device according to the first embodiment. [Figure 2] A schematic diagram illustrating the configuration of the cooling system of a power converter according to the first embodiment. [Figure 3]A schematic diagram illustrating the configuration of the cooling system of a power converter according to the first embodiment. [Figure 4] A schematic diagram illustrating the configuration of the heat receiving section of a power conversion device according to the first embodiment. [Figure 5] A perspective view showing an exploded view of the heat receiving section according to the first embodiment. [Figure 6] A cross-sectional view showing the configuration of the heat receiving section according to the first embodiment. [Figure 7] A cross-sectional view showing an enlarged view of the configuration of the heat receiving section according to the first embodiment. [Figure 8] A cross-sectional view showing a part of the heat receiving section according to the first embodiment. [Figure 9] A diagram illustrating the gas-liquid separation conditions of the heat receiving section according to the first embodiment. [Figure 10] A cross-sectional view showing the configuration of the heat receiving section of a power conversion device according to the second embodiment. [Figure 11] A cross-sectional view showing an enlarged view of the configuration of the heat receiving section according to the second embodiment. [Figure 12] A cross-sectional view showing the configuration of the heat receiving section of a power conversion device according to the third embodiment. [Figure 13] A cross-sectional view showing an enlarged view of the configuration of the heat receiving section according to the third embodiment. [Figure 14] A cross-sectional view showing the configuration of the heat receiving section of a power conversion device according to the fourth embodiment. [Figure 15] A cross-sectional view showing the configuration of the heat receiving section of a power conversion device according to the fourth embodiment. [Figure 16] A cross-sectional view showing the configuration of the heat receiving section of a power conversion device according to the fourth embodiment. [Modes for carrying out the invention]

[0009] The power conversion device 1 according to this embodiment will be described below with reference to Figures 1 to 9. In each figure, for the sake of clarity, the scale of each component will be appropriately changed, and some parts will be omitted or simplified in the description.

[0010] FIG. 1 is an explanatory diagram schematically showing the configuration of a power conversion device 1 according to an embodiment. FIG. 2 is an explanatory diagram showing the configuration of the cooling system 2 of the power conversion device 1 and schematically showing the flow of the working refrigerant when boiling occurs. FIG. 3 is an explanatory diagram showing the configuration of the cooling system 2 of the power conversion device 1 and schematically showing the flow of the working refrigerant when not boiling.

[0011] FIGS. 4 to 7 schematically show the configuration of the heat receiving part 12 of the power conversion device 1. FIG. 4 is an explanatory diagram of the heat receiving part 12, FIG. 5 is an exploded perspective view of the heat receiving part 12, and FIGS. 6 and 7 are cross-sectional views of the heat receiving part 12. FIG. 8 is a cross-sectional view showing the configuration of the first flow path 35 formed in the porous body 32 of the heat receiving part 12, and the heat receiving part inlet 37 and the heat receiving part outlet 38 provided in the first flow path 35. FIG. 9 is an explanatory diagram of the gas-liquid separation conditions of the heat receiving part 12.

[0012] The power conversion device 1 is provided, for example, in a railway vehicle such as an electric locomotive. The power conversion device 1 converts, for example, DC power supplied from an overhead line via a pantograph into AC power.

[0013] As shown in FIG. 1, the power conversion device 1 includes a semiconductor module 11, a heat receiving part 12, a heat exchange part 13, a reservoir tank 14, a pump 15, a blower 16, a check valve 17, a pipe 18, a temperature sensor 19, a pressure sensor 20, and a control part 21. As shown in FIGS. 2 and 3, the heat receiving part 12, the heat exchange part 13, the reservoir tank 14, the pump 15, and the check valve 17 of the power conversion device 1 are connected by the pipe 18 to constitute the cooling system 2.

[0014] Such a power conversion device 1 is fluidly connected to the heat receiving part 12, the heat exchange part 13, the reservoir tank 14, and the pump 15 by the pipe 18. As a specific example, the heat receiving part 12 is fluidly connected to the heat exchange part 13, the reservoir tank 14, and the pump 15 via the pipe 18. The heat exchange part 13 is fluidly connected to the reservoir tank 14 via the check valve 17. The reservoir tank 14 is fluidly connected to the pump 15 via the pipe 18. The pump 15 is fluidly connected to the heat receiving part 12.

[0015] As shown in Figures 2 and 3, the liquid-phase working refrigerant stored in the reservoir tank 14 is pumped out by the pump 15 and circulates through the heat receiving section 12, the heat exchange section 13, and the reservoir tank 14. Also, as shown in Figure 2, the working refrigerant, which has undergone a phase change from liquid to gas due to the temperature of the heat receiving section 12, is separated from the liquid-phase working refrigerant in the heat receiving section 12, moves to the heat exchange section 13, where it condenses and undergoes a phase change from gas to liquid, and is sent to the reservoir tank 14. The working refrigerant should preferably have high latent heat of vaporization, surface tension, density, and a low viscosity coefficient, assuming it is within the saturation temperature operating range applied to the power conversion device. Furthermore, the working refrigerant should preferably have a low ozone depletion potential and global warming potential, demonstrating environmental friendliness. When applying this cooling system, the working refrigerant can be set as appropriate.

[0016] The semiconductor module 11 can be attached to one heat receiving section 12, for example, in one or more units. The semiconductor module 11 may be, for example, a module containing multiple semiconductor elements in a single package, or a module that includes a control circuit, drive circuit, and protection circuit in addition to semiconductor elements. Furthermore, the semiconductor module 11 may be configured so that the semiconductor elements are directly attached to the heat receiving section 12, or it may be configured so that the semiconductor elements are attached to the heat receiving section 12 via other components. In other words, as long as the semiconductor module 11 is configured to be able to be cooled by the heat receiving section 12 when it generates heat, the arrangement and mounting method of the components can be set as appropriate.

[0017] The heat receiving section 12 allows the liquid-phase working refrigerant 100 to pass through. The heat receiving section 12 separates the liquid-phase working refrigerant 100 from the working refrigerant 101, which is a gaseous state formed when a portion of the liquid-phase working refrigerant 100 undergoes a phase change due to the heat of the attached semiconductor module 11. The heat receiving section 12 sends the liquid-phase working refrigerant 100 to the reservoir tank 14 and the gaseous working refrigerant 101 to the heat exchange section 13. For example, as shown in Figure 1, multiple heat receiving sections 12 are provided.

[0018] As shown in Figures 4 to 7, the heat receiving section 12 comprises, for example, a pair of heat transfer blocks 31, a porous body 32, and a header member 33. The heat receiving section 12 also has a first flow path 35 provided within the porous body 32 through which liquid-phase working coolant 100 flows in a single-phase flow, and a second flow path 36 through which gas-phase working coolant 101 flows in a single-phase flow within the header member 33 from the gap between the pair of heat transfer blocks 31 and the porous body 32. The heat receiving section 12 also has a heat receiving section inlet 37 and a heat receiving section outlet 38 that connect the first flow path 35 to the piping 18.

[0019] The heat transfer block 31 is formed in a flat plate shape, with one main surface formed in a planar shape and the other main surface formed in a comb-fin shape. The heat transfer block 31 has a plurality of grooves 31a extending in one direction, formed on the surface (the other main surface) facing the porous body 32. In addition, for example, the heat transfer block 31 has a porous layer 31c formed on each surface of the plurality of grooves 31a. The heat transfer block 31 is formed from a material with high thermal conductivity, such as aluminum. The porous body 32 is provided between the opposing main surfaces of the pair of heat transfer blocks 31. In addition, the semiconductor module 11 is attached to the outer surface, which is the main surface opposite to the opposing main surface of the pair of heat transfer blocks 31. As a specific example, the semiconductor module 11 is attached to one of the main surfaces (outer surface) of each of the pair of heat transfer blocks 31.

[0020] The groove 31a extends in one direction. The groove 31a has a rectangular cross-sectional shape perpendicular to its longitudinal direction. Multiple grooves 31a are arranged at equal intervals in a direction perpendicular to the direction in which the groove 31a extends. For example, the groove 31a extends in the vertical direction when the heat receiving section 12 is attached. With multiple grooves 31a formed on one side, the heat transfer block 31 is formed in a fin shape, with multiple rectangular fins 31b extending in one direction formed on the surface facing the porous body 32.

[0021] The porous layer 31c is bonded to the surface of the groove 31a. In other words, the porous layer 31c is formed around the fin 31b. The porous layer 31c formed on the surface of the groove 31a does not fill the groove 31a, but forms a space inside it. That is, the porous layer 31c formed in the groove 31a forms a steam discharge section 36a inside it, which is a steam discharge channel (gas phase region) that discharges steam and constitutes part of the second flow channel 36, covered with a porous body 32. The porous layer 31c has multiple holes formed in it that allow the working coolant 100 of the liquid tank that has passed through from the heat transfer block 31 to pass through. The porous layer 31c is a sintered body, foam body, or lotus type of resin or metal fibers / particles, etc., and has appropriate thermal conductivity and appropriate porosity.

[0022] The porous body 32 is formed in the shape of a flat plate and is placed between a pair of heat transfer blocks 31. The porous body 32 has a first channel 35 through which the liquid phase working coolant 100 flows. The porous body 32 also covers the grooves 31a of the heat transfer blocks 31, thereby forming a plurality of vapor outlets 36a between the pair of heat transfer blocks 31. The porous body 32 also has a plurality of holes that allow a portion of the liquid phase working coolant 100 flowing through the first channel 35 to pass through, and the differential pressure level between the liquid phase of the first channel 35 and the gas phase of the vapor outlets 36a, with the porous body 32 in between, is within a range that is below the maximum capillary force inside the porous body 32. As a result, as shown in Figure 6, the porous body 32 allows the liquid phase working coolant 100 to pass through the first channel 35, and through the plurality of holes formed inside, allows a portion of the liquid phase working coolant 100 to pass from the first channel 35 through the interior to the outer surface. Furthermore, the porous body 32 prevents the liquid phase of the working refrigerant 100 from moving to the vapor discharge section 36a and moves the liquid working refrigerant 100 from the liquid tank to the porous layer 31c. The porous layer 31c and the porous body 32 then perform gas-liquid separation of the working refrigerant 100 at the interface between the porous body 32 in contact with the heat transfer block 31 and the joint between the porous layer 31c and the groove 31a of the heat transfer block 31, allowing the gaseous working refrigerant 101 to pass through the multiple vapor discharge sections 36a, which constitute the second flow path 36.

[0023] The conditions for achieving gas-liquid separation in the porous layer 31c and porous body 32 are as follows. Let Pv be the pressure (atmospheric pressure) on the gas phase side, Pl be the pressure on the liquid phase side, σ [N / m] be the surface tension of the working medium, and r [m] be the average pore radius of the porous body 32. Here, the pressure Pv on the gas phase side is the vapor pressure in the vapor discharge section 36a, and the pressure Pl on the liquid phase side is the pressure of the working refrigerant 100 flowing through the first channel 35 formed in the porous body 32. In this case, the conditions for achieving gas-liquid separation are: Pv-Pl<2σ / r This is how it works. In order to satisfy the conditions for successful gas-liquid separation, the cooling system is configured based on, for example, the porosity and pore shape of the porous body 32, as well as the heat generated by the semiconductor module 11, the flow rate from the pump 15, the type of working medium, etc. Furthermore, the pump 15 is driven and controlled by the control unit 21 to satisfy the conditions for successful gas-liquid separation.

[0024] The porous body 32 is, for example, a sintered body, foam, or lotus-shaped body made of resin or metal fibers or particles, and has appropriate thermal conductivity and appropriate porosity.

[0025] Furthermore, the porous body 32 may be molded integrally with the pair of heat transfer blocks 31, or it may be formed separately from the pair of heat transfer blocks 31, and a portion of it may come into contact with the pair of heat transfer blocks 31 to be assembled or joined together.

[0026] The header member 33 is positioned above the heat receiving section 12 when the heat receiving section 12 is positioned on a railway vehicle or the like. The header member 33 covers the upper ends of the multiple steam discharge sections 36a and together with the multiple steam discharge sections 36a, constitutes the second flow path 36. The header member 33 has an opening 33a to which the piping 18 is connected.

[0027] The first flow path 35 is, for example, located inside the porous body 32. The first flow path 35 is a flow path through which the liquid-phase working coolant 100 flows in a single phase. As shown in Figure 8, one end of the first flow path 35 is connected to the heat receiving section inlet 37, and the other end is connected to the heat receiving section outlet 38. The first flow path 35 is set to a predetermined flow path width in order to obtain a predetermined flow path length, and has a flow path shape that bends at multiple points. Alternatively, the first flow path 35 may be a chamber that is fluidly continuous with the heat receiving section inlet 37 and heat receiving section outlet 38 without bending at multiple points.

[0028] The second flow path 36 is a flow path through which gaseous refrigerant flows in a single phase. The second flow path 36 is composed of multiple vapor outlets 36a formed by the porous layer 31c and the internal space of the porous body 32 provided in the multiple grooves 31a of the heat transfer block 31. The second flow path 36 is a flow path through which gaseous working refrigerant 101, separated from the porous layer 31c provided in the multiple grooves 31a and the porous body 32 in contact with the multiple fins 31b, flows from the multiple vapor outlets 36a to the internal space of the upper header member 33. In the second flow path 36, to prevent gaseous working refrigerant 101 from flowing from the vapor outlets 36a to any space other than the internal space of the header member 33, each side of the porous body 32 other than the surface facing the heat transfer block 31 and the header member 33, and the lower end of the vapor outlets 36a are closed by covers or the like.

[0029] The heat exchange section 13 allows the gaseous working refrigerant to pass through its interior and, through heat exchange, condenses the gaseous working refrigerant, causing it to undergo a phase change into a liquid working refrigerant.

[0030] The reservoir tank 14 stores the liquid phase working refrigerant. The reservoir tank 14 delivers the liquid phase working refrigerant to the heat receiving section 12 and also recovers the liquid phase working refrigerant that has passed through the heat receiving section 12 and the liquid phase working refrigerant that has condensed in the heat exchange section 13.

[0031] Pump 15 increases the liquid phase working refrigerant in the reservoir tank 14 to a predetermined pressure and pumps it to the heat receiving unit 12. Pump 15 can also adjust the flow rate (pressure) of the working refrigerant it discharges.

[0032] The blower 16 blows outside air from the power converter 1 to the heat exchange section 13. For example, the blower 16 takes in outside air from the wind tunnel duct 16a. By blowing air to the heat exchange section 13, the blower 16 performs heat exchange between the outside air and the gaseous working refrigerant flowing through the heat exchange section 13.

[0033] The check valve 17 prevents backflow of the working refrigerant from flowing from the reservoir tank 14 to the heat exchange section 13. In other words, the check valve 17 allows the flow of working refrigerant from the heat exchange section 13 to the reservoir tank 14, and restricts the flow of working refrigerant from the reservoir tank 14 to the heat exchange section 13.

[0034] The piping 18 connects the various components of the cooling system and constitutes a flow path for the working refrigerant. As a specific example, as shown in Figures 1 to 3, the piping 18 includes a heat receiving section inlet pipe 18a, a heat receiving section outlet pipe 18b, a steam flow pipe 18c, and a liquid return pipe 18d.

[0035] The heat receiving section inlet pipe 18a connects the reservoir tank 14 and the primary side of the first flow path 35 of the multiple heat receiving sections 12 via the pump 15. Specifically, the heat receiving section inlet pipe 18a connects the reservoir tank 14 and the pump 15, as well as the pump 15 and the heat receiving section inlets 37 of the multiple heat receiving sections 12. For example, the heat receiving section inlet pipe 18a is a branch pipe connected to the multiple heat receiving section inlets 37 on the secondary side of the pump 15.

[0036] The heat receiving section outlet pipe 18b connects the secondary side of the first flow path 35 of the multiple heat receiving sections 12 and the reservoir tank 14. Specifically, the heat receiving section outlet pipe 18b connects the heat receiving section outlets 38 of the multiple heat receiving sections 12 and the reservoir tank 14. The heat receiving section outlet pipe 18b is a confluence pipe that merges on the secondary side of the multiple heat receiving section outlets 38.

[0037] The steam flow pipe 18c connects the second flow paths 36 of the multiple heat receiving sections 12 to the heat exchange section 13. For example, the same number of steam flow pipes 18c are provided as the number of heat receiving sections 12. The multiple steam flow pipes 18c are each connected to the openings 33a of the header members 33 of the heat receiving sections 12, forming a flow path for the gaseous working refrigerant into the heat exchange section 13. Note that the steam flow pipe 18c may be a single confluence pipe instead of multiple pipes, but in such a configuration, it is configured to prevent movement from the second flow path 36 of one heat receiving section 12 to the second flow path 36 of another heat receiving section 12.

[0038] The liquid reflux pipe 18d connects the heat exchange section 13 and the reservoir tank 14. A check valve 17 is positioned in the middle of the liquid reflux pipe 18d.

[0039] The temperature sensor 19 detects, for example, the temperature of the heat receiving section 12. For example, the temperature sensor 19 outputs an output signal, which is a voltage value corresponding to the detected temperature, to the control unit 21. The temperature sensor 19 may be provided on each of the multiple heat receiving sections 12, or it may be provided on any one of the heat receiving sections 12.

[0040] The pressure sensor 20 detects the pressure in the flow path through which the gaseous working medium flows. The pressure sensor 20 is installed, for example, in the steam flow pipe 18c. The pressure sensor 20 may also be installed in the second flow path 36. Furthermore, the pressure sensor 20 may be installed in each steam flow pipe 18c, or in any of the steam flow pipes 18c.

[0041] The control unit 21 controls the pump 15 to satisfy the conditions for successful gas-liquid separation in the porous body 32, for example, based on the temperature detected by the temperature sensor 19 and / or the pressure of the gas phase working medium detected by the pressure sensor 20.

[0042] For example, the control unit 21 includes an input unit 41, a display unit 42, a communication unit 43, an interface 44, a storage unit 45, and a processor 46. For example, the control unit 21 may be a control panel or a processing terminal.

[0043] The input unit 41 is a device that accepts user input, such as an operation panel including buttons, a touch panel, a keyboard, or a mouse. The display unit 42 is a display device, such as a liquid crystal display or an organic EL display. The communication unit 43 is an arbitrary communication interface controlled by the processor 46 that can communicate with external terminals such as personal computers or management systems using wired or wireless communication technology.

[0044] Interface 44 is a terminal or circuit that can be connected to external devices. For example, interface 44 is connected to a temperature sensor 19 and a pressure sensor 20.

[0045] The storage unit 45 includes memory and storage. The storage unit 45 stores various types of data. For example, the storage unit 45 stores the control program and control data for the pump 15. The storage unit 45 also stores temperature and pressure information detected by the temperature sensor 19 and the pressure sensor 20. The storage unit 45 may store this temperature and pressure information in association with the date and time, as well as the identification number of the heat receiving unit 12.

[0046] Such a memory unit 45 includes, for example, EEPROM (Electrically Erasable Programmable Read-Only Memory) (registered trademark), ROM (Read Only Memory), RAM (Random Access Memory), NAND flash memory, SSD (Solid State Drive), etc.

[0047] The processor 46 includes processing circuits. The processor 46 includes, for example, a CPU (Central Processing Unit). The processor 46 may also be a microcontroller, FPGA (Field Programmable Gate Array), DSP (Digital Signal Processor), GPU (Graphics Processing Unit), or other general-purpose or dedicated processors. Furthermore, the processor 46 may be singular or plural and is mounted on a circuit board such as a motherboard.

[0048] The processor 46 controls the pump 15 based, for example, on control programs and control data stored in the memory unit 45, and temperature and pressure information detected by the temperature sensor 19 and pressure sensor 20. The processor 46 controls the pump 15 to drive it in a manner that satisfies the conditions for successful gas-liquid separation in the porous layer 31c and the porous body 32.

[0049] Next, the operation of the power converter 1 configured in this way will be explained. In the following explanation, an example in which the power converter 1 is installed in a railway vehicle will be used. For example, when power is supplied from the pantograph to enable a railway vehicle to run, the processor 46 of the control unit 21 drives the pump 15. The liquid-phase working coolant stored in the reservoir tank 14 passes through the first channel 35 of the heat receiving unit 12, which is sent from the pump 15, and is recovered into the reservoir tank 14. In addition, a portion of the liquid-phase working coolant 100 flowing through the first channel 35 permeates into the porous body 32 by capillary force. Furthermore, the semiconductor module 11 attached to the heat receiving unit 12 generates heat due to the operation of the power converter.

[0050] In this case, when a railway vehicle is running, the semiconductor module 11 rises to a temperature at which the liquid-phase working coolant 100 boils inside the heat receiving section 12. As a result, heat from the semiconductor module 11 is transferred from the pair of heat transfer blocks 31 of the heat receiving section 12 to the porous body 32. Then, in the porous layer 31c and the porous body 32, the liquid-phase working coolant 100 near the multiple vapor outlets 36a, specifically, as shown in Figure 7, near the joints between the multiple grooves 31a and the porous layer 31c, and near the joints between the tip surfaces of the multiple fins 31b and the porous body 32, turns into vapor. That is, the liquid-phase working coolant 100 undergoes a phase change to the gaseous working coolant 101. This induces vapor in the vapor outlets 36a.

[0051] At this time, if the pressure difference between the pressure Pv of the gaseous working refrigerant 101 in the vapor discharge section 36a and the pressure Pl of the liquid working refrigerant 100 flowing through the first channel 35 of the porous body 32 is less than or equal to the maximum capillary head (2σ / r) in the porous body 32, the pressure balance between the supply of working refrigerant to the joint between the heat transfer block 31 and the porous body 32 and the evaporation is maintained. As a result, the gaseous and liquid phases of the working refrigerant are separated by the porous body 32. For example, the control unit 21 drives the pump 15 based on the temperature detected by the temperature sensor 19 and the pressure detected by the pressure sensor 20 so as to maintain the pressure balance between the supply of working refrigerant and the evaporation.

[0052] As shown in Figure 2, the steam (gaseous working refrigerant) generated in the steam discharge section (gas phase region) 36a is sent to the header member 33 at the top of the heat receiving section 12, and is sent to the heat exchange section 13 via the steam flow pipe 18c. A blower 16 installed in the heat exchange section 13 blows in outside air, and heat exchange is performed in the heat exchange section 13, causing the gaseous working refrigerant inside the heat exchange section 13 to condense and release heat. The condensed working refrigerant undergoes a phase change from gas to liquid and is sent to the reservoir tank 14 via the liquid reflux pipe 18d.

[0053] At this time, the check valve 17 prevents the liquid phase working refrigerant in the reservoir tank 14 from flowing back into the heat exchange section 13 due to pressure fluctuations between the heat exchange section 13 and the reservoir tank 14. In addition, the liquid phase working refrigerant, which has been separated into gas and liquid form via the porous body 32, is sent into the reservoir tank 14 via the heat receiving section outlet pipe 18b.

[0054] The liquid-phase working coolant flowing through the heat-receiving outlet pipe 18b receives and transports heat due to sensible heat other than the latent heat of vaporization in the porous layer 31c and porous body 32, which can result in a low degree of subcooling. In order to maintain the thermal balance of the cooling system 2, the piping for this heat loss and the heat capacity of the reservoir tank 14 are necessary.

[0055] Thus, when the semiconductor module 11 is subjected to a high thermal load, such as when a railway vehicle is in operation, the cooling system is maintained to function normally by separating the working coolant into a liquid phase and a gas phase within the heat receiving section 12, and circulating the working coolant by recirculating each phase, as shown in Figure 2.

[0056] Furthermore, when the railway vehicle is stopped, the semiconductor module 11 rises to a temperature where the liquid-phase working coolant inside the heat-receiving section 12 does not boil. Therefore, the liquid-phase working coolant does not undergo a phase change to the gas phase in the heat-receiving section 12. Consequently, the liquid-phase working coolant is sent into the reservoir tank 14 via the heat-receiving section outlet pipe 18b of the porous body 32. In this way, when the semiconductor module 11 is under low heat load, such as when the railway vehicle is stopped, the cooling system functions normally by circulating the working coolant by recirculating the liquid-phase working coolant that has passed through the heat-receiving section 12, as shown in Figure 3.

[0057] As described above, in this embodiment, the power converter 1 uses a pump 15 to circulate the liquid-phase working refrigerant to the heat receiving section 12, but it is not necessary to circulate the liquid-phase working refrigerant to the heat exchange section 13. Since there is no pressure loss in the heat exchange section 13, the power of the power converter 1 can be reduced. Therefore, the power converter 1 can contribute to miniaturization and energy saving of the pump 15. In addition, since the temperature difference can be reduced by liquefying the working refrigerant from a gaseous state rather than dissipating heat with a single-phase liquid flow, when compared under the same heat dissipation conditions, the volume of the heat exchange section 13 in the power converter 1 of this embodiment can be reduced compared to the volume of the heat exchange section of a conventional circulating water-cooled heat exchange section. Therefore, as the power converter 1 is miniaturized, the degree of freedom in installing the heat exchange section 13 can be improved and the weight of the cooling system can be reduced.

[0058] Furthermore, in normal operation when the liquid-phase working refrigerant boils, the power converter 1 utilizes the latent heat of vaporization due to boiling cooling, thus enabling high heat flux. Even when the liquid-phase working refrigerant does not boil at low flow rates, heat transport and heat dissipation are possible with low pump power. Therefore, the cooling system of the power converter 1 can reduce fluctuations in heat load caused by supercooling resulting from conventional circulating water cooling systems and overshoot resulting from conventional boiling cooling systems. As a result, the power converter 1 can suppress and level out temperature fluctuations, thereby extending the lifespan of the semiconductor elements used in the semiconductor module 11.

[0059] Furthermore, the vapor discharge section 36a through which the gaseous working refrigerant passes is formed by a space surrounded by multiple grooves 31a of the heat transfer block 31 and porous layers 31c formed in each of these grooves 31a. Therefore, as shown in Figure 5, by making the porous body 32 placed inside the heat receiving section 12 a simple plate shape and the heat transfer block 31 fin-shaped, liquid supply pressure loss can be suppressed, the manufacturing cost of the porous body 32 can be reduced, and as a result, the cost of the heat receiving section 12 can be reduced. In addition, by providing porous layers 31c around the fins 31b of the heat transfer block 31 (on the surface of the grooves 31a), the liquid supplied by capillary force can be captured, and drying out of the heat transfer surface can be suppressed.

[0060] As described above, the power conversion device 1 of this embodiment enables gas-liquid separation of the working refrigerant in the heat receiving section 12, and recirculates the liquid and gas phases of the working refrigerant when it boils, and recirculates the liquid phase of the working refrigerant when it is not boiling. In addition, a porous layer 31c is provided in the groove 31a of the heat transfer block 31, and the porous body 32 is made into a plate shape. Therefore, the power conversion device 1 can reduce the pump power of the cooling system pump 15 and reduce costs.

[0061] The embodiments are not limited to the examples described above. For example, the material of the porous layer 31c and porous body 32, the optimal porosity, pore size, etc. will differ depending on the applicable working refrigerant and the thermal load conditions of the semiconductor module 11. Therefore, as shown in Figures 10 and 11, the heat receiving section 12A according to the second embodiment may be configured such that both the heat transfer block 31 and the porous body 32 are arranged in a fin shape and interlocked alternately, thereby optimizing the manufacturing and molding costs of the heat transfer block 31 and the porous body 32. The heat receiving section 12A used in the power converter 1 according to the second embodiment will be described below with reference to Figures 10 and 11. In the configuration of the heat receiving section 12A according to the second embodiment, components that are the same as those in the heat receiving section 12 according to the first embodiment described above will be denoted by the same reference numerals, and their detailed explanation will be omitted.

[0062] The heat receiving section 12A comprises a pair of heat transfer blocks 31, a porous body 32A, and a header member 33. The heat receiving section 12A also has a first flow path 35 provided within the porous body 32A through which liquid-phase working coolant flows in a single-phase flow, and a second flow path 36 through which gas-phase working coolant flows in a single-phase flow within the header member 33 from the gap between the pair of heat transfer blocks 31 and the porous body 32A. The heat receiving section 12A also has a heat receiving section inlet 37 and a heat receiving section outlet 38 that connect the first flow path 35 to the piping 18.

[0063] The heat transfer block 31 is formed in a flat plate shape. The heat transfer block 31 has a plurality of grooves 31a extending in one direction, formed on the surface facing the porous body 32A. For example, the heat transfer block 31 does not have a porous layer 31c.

[0064] The groove 31a extends in one direction. The cross-sectional shape of the groove 31a perpendicular to the longitudinal direction of the groove 31a is formed in a rectangular shape. Multiple grooves 31a are arranged at equal intervals in a direction perpendicular to the extension direction of the groove 31a. The groove 31a extends in the vertical direction, for example, when the heat receiving section 12 is attached. With multiple grooves 31a formed on one side, the surface of the heat transfer block 31 facing the porous body 32 is formed in a fin shape with multiple rectangular fins 31b extending in one direction. The width in the direction perpendicular to the longitudinal direction of the groove 31a, in other words, the spacing between adjacent fins 31b, is set to a width that allows for the placement of two steam discharge sections 36a of the second flow path 36 and the fins 32a of the porous body 32A, which will be described later.

[0065] The porous body 32A is provided between a pair of heat transfer blocks 31. The porous body 32A is formed in the shape of a flat plate, and its main surfaces facing the pair of heat transfer blocks 31 are porous fins formed in the shape of fins. The porous body 32A has a first channel 35 through which a liquid-phase working coolant flows. The porous body 32A also has a plurality of rectangular fins 32a extending in one direction on each of the pair of main surfaces facing the heat transfer blocks 31.

[0066] Each fin 32a is positioned in the center in the width direction of each groove 31a of the heat transfer block 31 and joined to the inner surface of the groove 31a. As a result, the multiple fins 31b of the heat transfer block 31 and the multiple fins 32a of the porous body 32A are arranged alternately, and a steam discharge section 36a is formed between adjacent fins 31b and fins 32a. The multiple fins 31b of the heat transfer block 31 are joined to the main surface of the porous body 32A (the groove between adjacent fins 32a), and the multiple fins 32a of the porous body 32A are joined to the bottom surface on the central side in the width direction of the multiple grooves 31a of the heat transfer block 31.

[0067] In this heat receiving section 12A, the heat transfer block 31 and the porous body 32A are shaped so that multiple fins 31b and 32a of both are interlocked (arranged) alternately, thereby forming steam discharge sections 36a between adjacent fins 31b and 32a. Then, gas-liquid separation of the working refrigerant 100 occurs at the interface where the heat transfer block 31 and the porous body 32A are in contact, that is, at the interface of the joint between the fins 31b of the heat transfer block 31 and the porous body 32A, and between the fins 32a of the porous body 32A and the heat transfer block 31. Then, the gas phase working refrigerant 101 passes through the multiple steam discharge sections 36a, which are the second flow path 36. As a result, the heat receiving section 12A has the same effect as the heat receiving section 12A according to the first embodiment described above.

[0068] Furthermore, the heat receiving section 12A has a porous body 32A on a plate with multiple fins 32a on its main surface. The pitch (spacing) of the multiple fins 32a can be such that they are positioned between the multiple fins 31b of the heat transfer block 31, and together with the multiple fins 31b of the heat transfer block 31, they can form a steam discharge section 36a. Therefore, the number and spacing of the multiple fins 32a can be reduced compared to a configuration in which multiple fins of the porous body are placed next to each other to form a steam discharge section 36a. Thus, the power conversion device 1 can reduce the pump power of the cooling system's pump 15 and reduce costs.

[0069] Furthermore, the embodiments are not limited to the examples described above. For example, as shown in Figures 12 and 13, the heat receiving section 12B according to the third embodiment may be configured such that the porous layer 31c provided on the heat transfer block 31 of the heat receiving section 12 according to the first embodiment is provided in a plurality of grooves 31a of the heat transfer block 31 of the heat receiving section 12A according to the second embodiment. The heat receiving section 12B may be configured such that a porous body 32A is provided between a pair of heat transfer blocks 31 having such porous layer 31c.

[0070] Furthermore, as shown in the heat receiving section 12 of the fourth embodiment shown in Figures 14 to 16, for example, in the porous body 32 of the first to third embodiments, the porosity of the porous body 32 near the contact interface where the porous body 32 and the heat transfer block 31 come into contact may be increased. Since steam generation due to boiling becomes significant near the contact interface between the porous body 32 and the heat transfer block 31, if the steam is not properly discharged, it will lead to a rapid deterioration of heat transfer due to dry-out. Therefore, as shown in each example in Figures 14 to 16, by providing a porous layer 32b with a higher porosity than the porosity of the porous body 32 near the contact interface where the porous body 32 comes into contact with the heat transfer block 31, the pressure loss due to steam escaping can be reduced and steam discharge can be promoted.

[0071] Any power conversion device configured as described above can reduce the pump power of the cooling system's pump 15 and also reduce costs.

[0072] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. The following is a description equivalent to the invention described in the original claims of this application. [1] Semiconductor modules and, A heat transfer block having a semiconductor module attached to one main surface and a plurality of fins formed on the other main surface, a heat receiving section comprising a porous body provided on the heat transfer block, a first flow path through which a liquid-phase working coolant flows, and a second flow path through which a gas-phase working coolant flows, having a plurality of vapor discharge sections formed between the plurality of fins of the heat transfer block, A reservoir tank for storing the aforementioned working refrigerant, The heat exchange section connected to the second flow path and the reservoir tank, A check valve is positioned between the heat exchange section and the reservoir tank to restrict the movement of the working refrigerant from the reservoir tank side to the heat exchange section side. A pump connected to the first flow path and the reservoir tank, which sends the working refrigerant from the reservoir tank to the first flow path, A power conversion device equipped with the following features. [2] The power conversion device according to [1], wherein the heat transfer block has a porous layer provided on the surface of a plurality of grooves formed between the plurality of fins. [3] The heat transfer blocks are provided in pairs, The power conversion device according to [1], wherein the semiconductor module is provided on each of the main surfaces of the pair of heat transfer blocks. [4] The porous body is provided between the pair of heat transfer blocks and has the first flow channel formed inside it, The power conversion device according to [2], wherein the plurality of steam discharge sections are formed between the plurality of fins. [5] The porous body has a plurality of fins, The power conversion device according to [1] or [2], wherein the plurality of fins formed on the heat transfer block and the plurality of fins formed on the porous body are arranged alternately with the steam discharge section formed between them. [6] A temperature sensor for detecting the temperature of the heat receiving section, A pressure sensor for detecting the pressure in the second flow path, or the flow path connecting the second flow path and the heat exchange section, The power conversion device according to [1], comprising a control unit that controls the flow rate of the working refrigerant based on temperature information detected by the temperature sensor and pressure information detected by the pressure sensor. [7] The power conversion device according to [1], further comprising a blower for supplying air to the heat exchange section. [Explanation of Symbols]

[0073] 1...Power converter, 2...Cooling system, 11...Semiconductor module, 12, 12A, 12B...Heat receiving section, 13...Heat exchange section, 14...Reservoir tank, 15...Pump, 16...Blower, 16a...Wind tunnel duct, 17...Check valve, 18...Piping, 18a...Heat receiving section inlet pipe, 18b...Heat receiving section outlet pipe, 18c...Steam flow pipe, 18d...Liquid reflux pipe, 19...Temperature sensor, 20...Pressure sensor, 21...Control unit, 31...Heat transfer block, 31a... Groove, 31b...fin, 31c...porous layer, 32, 32A...porous body, 32b...porous layer, 32a...fin, 33...header member, 33a...opening, 35...flow channel, 36...flow channel, 36a...steam discharge section, 37...heat receiving section inlet, 38...heat receiving section outlet, 41...input section, 42...display section, 43...communication section, 44...interface, 45...storage section, 46...processor, 100...working refrigerant (liquid phase), 101...working refrigerant (gas phase).

Claims

1. Semiconductor modules and A heat transfer block having a semiconductor module attached to one main surface and a plurality of fins formed on the other main surface, a heat receiving section provided on the heat transfer block and having a porous body in contact with the plurality of fins, a first flow path through which a liquid-phase working coolant flows, and a second flow path through which a gas-phase working coolant flows, having a plurality of vapor discharge sections formed between the plurality of fins of the heat transfer block, A reservoir tank for storing the aforementioned working refrigerant, The heat exchange section connected to the second flow path and the reservoir tank, A pump connected to the first flow path and the reservoir tank, which sends the working refrigerant from the reservoir tank to the first flow path, A power conversion device equipped with the following features.

2. The power conversion device according to claim 1, wherein the heat transfer block has a porous layer provided on the surface of a plurality of grooves formed between the plurality of fins.

3. The heat transfer blocks are provided in pairs, The power conversion device according to claim 1, wherein the semiconductor module is provided on each of the main surfaces of the pair of heat transfer blocks.

4. The porous body is provided between the pair of heat transfer blocks and has the first flow channel formed inside it. The power conversion device according to claim 2, wherein the plurality of steam discharge sections are formed between the plurality of fins.

5. The porous body has a plurality of fins, The power conversion device according to claim 1 or claim 2, wherein the plurality of fins formed on the heat transfer block and the plurality of fins formed on the porous body are arranged alternately with the steam discharge section formed between them.

6. A temperature sensor for detecting the temperature of the heat receiving section, A pressure sensor for detecting the pressure in the second flow path, or the flow path connecting the second flow path and the heat exchange section, The power conversion device according to claim 1, further comprising a control unit that controls the flow rate of the working refrigerant based on temperature information detected by the temperature sensor and pressure information detected by the pressure sensor.

7. The power conversion device according to claim 1, further comprising a blower for supplying air to the heat exchange section.

8. The power conversion device according to claim 1, further comprising a check valve disposed between the heat exchange section and the reservoir tank, which restricts the movement of the working refrigerant from the reservoir tank side to the heat exchange section side.

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