JP3791293B2 - Cooling device for vehicle controller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a cooling device for an electronic device, and more particularly to a cooling device for a vehicle controller.
[0002]
[Prior art]
As a motor controller for vehicles, there are devices that convert power supply current from direct current to alternating current with semiconductor switching elements (inverters), or conversely, devices that convert alternating current into direct current (converters). A cooling device is required to generate heat with loss during conversion. As this cooling device, a natural convection type, a forced convection type, or a heat sink using a heat pipe is used according to the heat generation amount of the device.
[0003]
For example, Japanese Patent Laid-Open No. 6-165524 discloses a structure of an inverter device that is cooled by a heat sink using a heat pipe.
[0004]
[Problems to be solved by the invention]
All the cooling devices for converters and inverters as described above remove the heat generated in the semiconductor element by air cooling, and the cooling performance fluctuates because the temperature of the cooling air fluctuates depending on the surrounding conditions where the vehicle travels. Resulting in.
[0005]
For example, the temperature of air used for cooling fluctuates due to changes in temperature due to changes in the climate and altitude, or due to changes in wind speed or temperature due to the wind being blocked by structures such as tunnels and platforms. The temperature may rise abnormally compared to when traveling.
[0006]
When using an air-cooling type cooling device, the amount of heat that can be cooled is proportional to the temperature difference between the semiconductor element and the cooling air. That is, when a cooler having a certain cooling capacity is used and the heat generation amount of the semiconductor element is constant, if the cooling air temperature rises, the temperature of the semiconductor element rises accordingly. Accordingly, when a situation in which the cooling air temperature rises is assumed, the cooler must be designed so that the temperature of the semiconductor is below the allowable limit even when the cooling air reaches the maximum temperature.
[0007]
However, since the temperature of the cooling air is relatively low under normal driving conditions, the performance required for the cooler in that case is smaller than the required performance when the environmental temperature rises abnormally. The difference in required performance depends on the air temperature rise, but it is also possible that the required performance of the cooler differs several times between normal driving and abnormal environmental temperature rise. In that case, it is necessary to mount a cooler having a performance several times the required performance during normal driving.
[0008]
In order to increase the performance of the cooler, the size of the heat sink must be increased and the capacity of the blower for sending cooling air must be increased, which increases the cost. In other words, when the environmental temperature is expected to rise abnormally, if the cooler is designed to meet the required cooling performance when the temperature rises, the cooler will be manufactured compared to the case where the cooler is designed with the required performance during normal driving. Cost becomes high.
[0009]
It is an object of the present invention to provide a required specification of an air cooling device for cooling a controller when the cooling device for the controller of the vehicle is used in an environment where the temperature of the cooling air fluctuates. It is to relax the required performance below and to provide a method of constructing an air cooling device with a smaller air cooling heat sink and blower blower, thereby reducing the cost of the air cooling device.
[0010]
[Means for Solving the Problems]
The above object is to provide a cooling device in which a heating element including a semiconductor switching element in a block having good heat conduction, an air cooling radiator, and a thermosyphon using water as a working fluid are attached by the air cooling radiator during normal operation. When cooling, and when the temperature of the block exceeds the boiling point of water due to a temporary increase in temperature of the cooling air, heat is transferred to the tank containing water provided above the block by the thermosyphon, This is accomplished by keeping the block below a certain temperature .
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of the present invention. The figure shows a motor control device for a locomotive having a structure in which a diesel engine is mounted to generate electric power using the engine power, and the motor is driven by the current. A semiconductor element 1 such as a gate insulating bipolar transistor (IGBT) constituting a converter or an inverter is mounted on a substrate 2. The substrate 2 is covered with a container and filled with an insulating material to form a sealed module 3. Furthermore, the module 3 is mounted on a block 4 made of metal such as aluminum.
[0013]
The IGBT module 3 controls the power supply current of the motor in accordance with the operation status of the vehicle. At this time, the logic control unit 5 controls the operation of the converter or the inverter. When the converter or inverter performs control, heat is generated due to current loss, but during normal driving, the heat is dissipated into the cooling air by the heat sink 6 attached to the back surface of the block 4. In this embodiment, since the case where the heat generation amount of the IGBT module is relatively large is considered, a blower 7 is provided to send cooling air to the heat sink 6. The blower 7 takes in cooling air from the lower part of the side surface and sends it to the heat sink, and the warmed air after cooling is discharged to the outside from the ceiling.
[0014]
In this embodiment, the motor control device for the locomotive is targeted, and unlike the passenger car, as shown in FIG. 2, the control device 18 can be installed in front of the engine 17, so that the control shown in FIG. The size of the device can occupy a space of about 2 m × 2 m × 3 m.
[0015]
FIG. 3 shows an example of temperature conditions in the first embodiment. During normal driving, the cooling air temperature of the controller is considered to be equal to the outside air temperature, so it is about 40 ° C. at the maximum. Further, as a case where the environmental temperature rises abnormally, consider a situation where the cooling air temperature temporarily becomes extremely high as shown in FIG.
[0016]
At this time, as shown in the figure, the difference between the temperature obtained by subtracting the heat conduction resistance of the block 4 and the base portion of the heat sink 6 from the allowable limit of the semiconductor element and the cooling air temperature is the temperature difference that can be used for cooling the heat sink 6. . That is, in the example shown here, when the environmental temperature rises abnormally, the temperature difference that can be used for cooling the heat sink 6 becomes about 1/5 of that during normal running.
[0017]
In the forced convection cooling device, when the temperature difference that can be used for cooling is about 1/5 as described above, if the same amount of heat is to be removed, the temperature rise of the cooling air and the heat transfer resistance of the heat sink are both 1 / Must be lowered to 5. To reduce the temperature rise, the air flow must be increased by a factor of five. At that time, the heat transfer resistance also decreases as the wind speed increases. However, since it does not decrease linearly, it is necessary to increase the number of fins of the heat sink. Further, if the air volume is increased by a factor of 5, the pressure loss increases with the square of the air volume, so a blower having a discharge pressure of 25 times must be prepared. That is, if the cooling capacity is covered only by the heat sink and the blower when the environmental temperature rises, the cost of the cooler will be considerably increased.
[0018]
Therefore, in the present invention, as shown in FIG. 1, a plurality of water flow paths 8 are provided inside the block 4, and are connected to water tanks 9 installed at the upper part of the IGBT module 3. Moreover, the lower end side of each flow path 8 is connected to a pipe 14 from the water tank 9 and is piped so as to form a loop.
[0019]
Details of the IGBT module 3, the block 4, and the heat sink 6 are shown in FIG. FIG. 4 is a horizontal sectional view. The IGBT module 3 is fixed to the block 4 with a bolt 10 or the like. Fins 11 are attached to the back surface of the block 4 to constitute the heat sink 6. Further, it is preferable to fill the gap between the substrate 2 and the block 4 with thermal conductive grease 12 in order to reduce the thermal conductive resistance. In this embodiment, flat fins such as aluminum are used as the fins 11, and the fixing method is a structure in which the fins 11 are directly fixed to the back surface of the block 4 by a method such as brazing. As the shape of the fin, one having a slit may be used, or a heat sink in which the base and the fin are integrated can be fixed to the block with a bolt.
[0020]
An example of the change in the temperature of the block 4 when this structure is adopted is shown in FIG. The heat sink is designed so that the block temperature can be cooled to about 80 ° C. during normal driving. At this time, the required cooling capacity is determined based on a heat sink heat radiation temperature difference larger than that at the time when the environmental temperature is abnormally increased as shown in FIG. 3, so that the cost of the cooler can be reduced.
[0021]
FIG. 6 shows a longitudinal sectional view of the heat sink 6. FIG. 6 shows a state where the block temperature exceeds 100 ° C. During normal driving, water is warmed in the block 4 and circulates gently by buoyancy, but contributes little to cooling. When the ambient temperature rises abnormally, the inflow air temperature of the cooler rises and the block temperature rises accordingly. However, when the block temperature exceeds the boiling point of water 100 ° C., boiling starts in the water flow path 8 and beyond. The temperature rise of the block is suppressed. If the inner surface of the water flow path 8 formed inside the block 4 has a grooved shape as shown in FIG. 4, it is effective for improving the boiling limit heat flux. The groove in the tube may be formed directly in the block, or a cylindrical hole may be made in the block, and the grooved tube may be inserted into the block and fixed with solder or the like. Vapor generated by boiling in the flow path 8 is discharged into the water tank 9 through the pipe and condensed in water. Moreover, since water is supplied to the block internal flow path 8 through the piping from the water tank 9, boiling continues and a so-called thermosiphon is formed. Since heat is transported from the block 4 to the water tank 9 by the thermosyphon, the temperature of the block 4 can be kept constant until the water in the water tank 9 reaches 100 ° C.
[0022]
The capacity of water in the tank is (water capacity) x (specific heat of water) x (boiling point of water-water temperature during normal driving)> (heat generation amount of semiconductor) x (time during which the ambient temperature rises abnormally) You can decide. For example, when the module heat generation amount is 5 kW, the environmental temperature rises abnormally for 10 minutes, and the water temperature during normal driving is considered to be 50 ° C. or less, the tank capacity needs to be 18 l or more per module. Therefore, a space of about 10 cm is required above the semiconductor module. However, in the case of the locomotive shown as the present embodiment, there is a sufficient space, so that a space for installing the tank can be secured without any problem.
[0023]
In the present embodiment, the water tank 9 is not actively cooled, but if the water temperature during normal running is high, the necessary tank capacity increases as described above. Therefore, the thermal resistance between the surrounding structure is small to some extent, and it is more efficient that the heat escapes so that the water temperature is within the outside air temperature + 10 ° C. By the way, as described above, it is considered that water circulates gently between the block 4 and the water tank 9 even during normal traveling. However, the buoyancy, which is the driving force for circulation, is much smaller than when boiling occurs in the flow path 8, and the amount of heat transported is small. Therefore, the balance between the heat leaked to the water tank 9 side during normal driving and the heat conduction resistance from the tank to the surrounding members allows the heat to escape to the surroundings with a temperature difference of about 10 ° C. or less. What is necessary is just to decide the connection method.
[0024]
In order to prevent the temperature of the block 4 from rising when boiling occurs inside the flow path 8, it is necessary to prevent the pressure inside the water tank 9 and the piping system from rising. If a flexible tube with elasticity is used for piping, the increase in volume due to steam can be released to some extent even when the water temperature rises. If this is still insufficient, the water tank 9 may be equipped with a pressure adjustment mechanism or a pressure adjustment valve using a bellows or the like. Further, in order to suppress an increase in the volume of water, it is necessary to quickly condense the water vapor inside the water tank 9. For this purpose, it is effective to make the steam flowing from the flow path 8 side into bubbles as fine as possible in the water tank 9. Thus, as shown in FIG. 6, it is effective to cover the inlet from the steam pipe 13 to the water tank 9 with a wire mesh 15 so that the steam passes through the hole in the wire mesh and becomes fine bubbles before going out into the water. It is.
[0025]
A second embodiment of the present invention is shown in FIG. FIG. 7 is a partial vertical sectional view of the second embodiment. In the second embodiment, a heat pipe type heat sink is used for cooling the module. At this time, the block 4 is installed so as to protrude in half to the module side and the cooling air flow path side, and the heat pipe 16 is provided on the cooling air flow path side and the water flow path 8 is provided on the module side. The water flow path 8 and the heat pipe 16 communicate with each other at the lower end as in FIG. A fin 10 is attached in the vicinity of the tip of the heat pipe 16 and is cooled by cooling air. In order to increase the heat transport capability, it is effective to use water as the working liquid of the heat pipe 16. In this case, heat is transported by boiling inside the heat pipe during normal traveling, and heat is transported mainly by boiling inside the water flow path 8 when the cooling air temperature rises abnormally. This is done automatically based on the following principle. That is, since the internal volume of the heat pipe is constant, the boiling point of water changes according to the ambient temperature by changing the internal pressure. On the other hand, since the internal pressure is equal to the atmospheric pressure in the thermosiphon system on the flow path 8 side, the operating temperature is fixed at the boiling point of water in the atmospheric pressure. Therefore, only the heat pipe is operating while the block temperature is low, and when the temperature exceeds 100 ° C., the thermosyphon starts to operate and transports heat toward the water tank 9.
[0026]
As described above, in this embodiment, a cooling device that is small and can be efficiently cooled can be realized by performing a heat pipe operation at a low temperature and a thermosiphon operation at a high temperature.
[0027]
【The invention's effect】
By taking the structure of the present invention and cooling the semiconductor with a thermosiphon only when the cooling air temperature rises abnormally, the cooling performance of the air cooling heat sink can be designed based on the outside air temperature during normal running, The size of the heat sink can be reduced and the number of fins can be reduced. Moreover, since the thing with the small capacity | capacitance of the blower for ventilation of cooling air can be selected, the manufacturing cost of a cooling device can be made small.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an embodiment of the present invention.
FIG. 2 is a view showing a locomotive using the first embodiment of the present invention.
FIG. 3 is a diagram illustrating an example of a change over time in cooling air temperature.
FIG. 4 is a horizontal sectional view showing an embodiment of the present invention.
FIG. 5 is a diagram showing an example of temporal changes in cooling air temperature and block temperature.
FIG. 6 is a vertical sectional view showing an embodiment of the present invention.
FIG. 7 is a vertical sectional view showing a second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Semiconductor element, 2 ... Board | substrate, 3 ... IGBT module, 4 ... Aluminum block, 5 ... Logic control part, 6 ... Heat sink, 7 ... Blower, 8 ... Flow path, 9 ... Water tank, 10 ... Bolt, 11 ... Fin DESCRIPTION OF SYMBOLS 12 ... Thermal conductive grease, 13 ... Steam piping, 14 ... Liquid return piping, 15 ... Wire mesh, 16 ... Heat pipe, 17 ... Engine, 18 ... Control apparatus.

Claims (1)

In a cooling device in which a heating element including a semiconductor switching element in a block having good heat conduction, an air-cooling radiator, and a thermosyphon using water as a working fluid are attached.
During normal operation, cooling is performed by the air-cooling radiator, and when the temperature of the block exceeds the boiling point of water due to a temporary increase in cooling air, the heat is placed in a tank containing water provided above the block. A cooling device for a heating element, wherein heat is transported by a siphon and the block is kept at a constant temperature or lower.

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