Cooling apparatus

A cooling apparatus includes a case in which a refrigerant passage through which a refrigerant flows is formed inside, and an element module partially disposed within the refrigerant passage and including an element provided inside. A portion of the element module in contact with the refrigerant is formed of an insulating material.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2011/055589 filed Mar. 10, 2011, the contents of all of which are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to a cooling apparatus, and particularly to a cooling apparatus in which an element module is disposed within a refrigerant passage.

BACKGROUND ART

Various types of cooling apparatuses for cooling elements have been conventionally proposed.

The semiconductor device described in Japanese Patent Laying-Open No. 2006-339239, for example, includes a semiconductor module containing a heat generating element and a cooling jacket holding a refrigerant therein. The refrigerant is an insulating material, and the heat generating element is directly immersed in the refrigerant.

The cooling jacket is provided with a pump for forced circulation of the refrigerant in the cooling jacket, and a heat exchanger for cooling the refrigerant. The heat exchanger for cooling the refrigerant in the cooling jacket is formed such that radiator coolant or a refrigerant for an air conditioner of an automobile circulates therein.

The semiconductor element described in Japanese Patent Laying-Open No. 2010-177529 includes a heat sink for cooling a transistor, wherein the transistor is mounted on the heat sink.

The power converting apparatus described in Japanese Patent Laying-Open No. 2006-166604 includes a water passage cover, and a power semiconductor module provided on the water passage cover, wherein a liquid coolant circulates in the water passage cover.

The immersed-type double-sided heat radiating power module described in Japanese Patent Laying-Open No. 2005-57212 includes a power element, a first electrode joined to one surface of the power element, a second electrode joined to the other surface of the power element with a heat sink interposed therebetween, a third electrode joined to the power element through a wire, and a box-like package.

The power element, the first, second, and third electrodes, and the heat sink are housed within the package, and the first, second, and third electrodes are in close contact with an inner surface of the package with a thermally conductive insulating layer interposed therebetween. Moreover, part of the space inside the package other than the part in which the power element is located is charged with a sealant made of a silicone gel, an epoxy resin, or the like.

The cooling apparatus described in Japanese Patent Laying-Open No. 2008-283067 includes cooling pipes provided on opposing main surfaces of a semiconductor module.

The stacked-type cooling apparatus described in Japanese Patent Laying-Open No. 2005-191527 includes cooling pipes disposed on opposing surfaces of an electronic component.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

The semiconductor device described in Japanese Patent Laying-Open No. 2006-339239 has a problem in that since an electrode of the heat generating element is in direct contact with the refrigerant, no refrigerant other than an insulating refrigerant can be adopted.

In the semiconductor element described in Japanese Patent Laying-Open No. 2010-177529, since the transistor is disposed on the heat sink, the cooling efficiency is lower than a case where the transistor is immersed in a refrigerant.

Similarly, in the power converting apparatus described in Japanese Patent Laying-Open No. 2006-166604, the power semiconductor module is not immersed in the liquid coolant, so that the cooling efficiency is lower than a case where the power semiconductor module is immersed in the liquid coolant.

In the immersed-type double-sided heat radiating power module described in Japanese Patent Laying-Open No. 2005-57212, the package in contact with the coolant water is not formed of an insulating material. It is thus necessary to adopt a thermally conductive insulating layer with a large film thickness, or increase the distance between the power element and an inner wall surface of the package. Consequently, the size of the heat radiating module increases.

In the cooling apparatus described in Japanese Patent Laying-Open No. 2008-283067, the semiconductor module disposed between the cooling pipes and the cooling pipes have thermal expansion coefficients different from each other, so that the semiconductor module may be damaged if it is heated to an elevated temperature. On the other hand, if a gap is formed between the semiconductor module and each cooling pipe, the cooling efficiency of the semiconductor module significantly decreases.

A similar problem to that with the above-described cooling apparatus also occurs in the stacked-type cooling apparatus described in Japanese Patent Laying-Open No. 2005-191527.

The present invention was made in view of the problems as described above, and an object of the invention is to provide a cooling apparatus that can adopt various types of refrigerants, and is also small in size and exhibits high cooling performance.

Solution to Problem

A cooling apparatus according to the present invention includes a case in which a refrigerant passage through which a refrigerant flows is formed, and an element module partially disposed within the refrigerant passage and including an element provided inside. A portion of the element module in contact with the refrigerant is formed of an insulating material. The element includes a first unit element and a second unit element that generates an amount of heat greater than that generated by the first unit element. A distance between the second unit element and an inner wall surface of the refrigerant passage is smaller than a distance between the first unit element and the inner wall surface of the refrigerant passage.

Preferably, the element module includes a first insulating substrate in contact with the refrigerant, a second insulating substrate facing the first insulating substrate and disposed at a distance from the first insulating substrate, and being in contact with the refrigerant, and a resin portion charged between the first insulating substrate and the second insulating substrate and formed of an insulating material. The element is provided between the first insulating substrate and the second insulating substrate, and disposed within the resin portion.

Preferably, the first insulating substrate includes a first inner surface facing the second insulating substrate, and a first outer surface positioned opposite to the second insulating substrate with respect to the first inner surface. The second insulating substrate includes a second inner surface facing the first insulating substrate, and a second outer surface positioned opposite to the first insulating substrate with respect to the second inner surface. The resin portion reaches the first outer surface and the second outer surface from a portion between the first insulating substrate and the second insulating substrate, and is formed to cover a portion of the second outer surface. A first cooling surface uncovered by the resin portion and in contact with the refrigerant is formed on the first outer surface. A second cooling surface uncovered by the resin portion and in contact with the refrigerant is formed on the second outer surface. When the first insulating substrate, the second insulating substrate, and the element are seen in a direction in which the first insulating substrate and the second insulating substrate are arranged, the element is disposed within the first cooling surface and the second cooling surface.

Preferably, the resin portion is formed from the portion between the first insulating substrate and the second insulating substrate toward portions of the first outer surface and the second outer surface, and is formed to cover the portions of the first outer surface and the second outer surface, and includes an edge extending along outer peripheries of the first insulating substrate and the second insulating substrate. The first cooling surface is formed on a portion of the first outer surface uncovered by the edge, and the second cooling surface is formed on a portion of the second outer surface uncovered by the edge. A receiving portion that receives a portion of the edge is formed on an inner surface of the refrigerant passage.

Preferably, the first insulating substrate includes a plurality of first cooling fins protruding from the first cooling surface. The second insulating substrate includes a plurality of second cooling fins protruding from the second cooling surface. Preferably, the first insulating substrate and the second insulating substrate are formed of a ceramic. Preferably, the first insulating substrate includes a first inner surface facing the second insulating substrate, and a first outer surface positioned opposite to the second insulating substrate with respect to the first inner surface. The second insulating substrate includes a second inner surface facing the first insulating substrate, and a second outer surface positioned opposite to the first insulating substrate with respect to the second inner surface. The first unit element is provided in a position closer to the first inner surface than the second inner surface, and the second unit element is provided in a position closer to the second inner surface than the first inner surface.

A distance between the second outer surface and an inner wall surface of the refrigerant passage is smaller than a distance between the first outer surface and the inner wall surface of the refrigerant passage. Preferably, at least one of a plurality of depressions or a plurality of projections are formed on an inner surface of the refrigerant passage. Preferably, the case is integrally formed by resin molding.

Advantageous Effects of Invention

The cooling apparatus according to the present invention can adopt various types of refrigerants, and is also small in size and exhibits high cooling efficiency.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described hereinafter. Note that identical or corresponding parts are denoted by identical reference signs, and description thereof may not be repeated. Moreover, in the below-described embodiments, unless otherwise stated, when reference is made to a number, an amount, or the like, the scope of the present invention is not necessarily limited to that number, amount, or the like. Furthermore, unless otherwise stated, where there are a plurality of embodiments hereinbelow, it is originally intended to combine features of the various embodiments, as appropriate.

FIG. 1is a circuit diagram showing the configuration of main portions of a PCU to which the cooling apparatus for a semiconductor element according to one embodiment of the present invention is applied. It is noted that PCU100shown inFIG. 1represents a “control device for a rotating electric machine that drives a vehicle”.

Referring toFIG. 1, PCU100includes a converter110, inverters120,130, a control device140, and capacitors C1, C2. Converter110is connected between a battery B, and inverters120,130, and inverters120,130are connected to motor generators MG1, MG2, respectively.

Converter110includes power transistors Q13, Q14, diodes D13, D14, and a reactor L. Power transistors Q13, Q14are connected in series, and each power transistor receives a control signal from control device140at its base. Diodes D13, D14are connected between the collector and the emitter of power transistors Q13and Q14, respectively, so as to allow current to flow from the emitter toward the collector of power transistors Q13and Q14, respectively. A reactor L has its one end connected to a power supply line PL1, which is connected to a positive electrode of battery B, and its other end connected to a connection point between power transistors Q13and Q14.

Converter110boosts a DC voltage received from battery B using reactor L, and supplies the boosted voltage to a power supply line PL2. Converter110reduces the DC voltage received from inverters120,130, and charges battery B.

U-phase arm121U includes two power transistors Q1, Q2connected in series. Similarly, each of U-phase arm131U, V-phase arms121V,131V, and W-phase arms121W,131W includes two of power transistors Q3to Q12connected in series. Diodes D3to D12are connected between the collector and the emitter of power transistors Q3to Q12, respectively, so as to allow current to flow from the emitter toward the collector.

An intermediate point of the arm of each phase of inverters120,130is connected to an end of each phase of the coil of each phase of motor generators MG1, MG2, respectively. Motor generators MG1, MG2are configured such that one ends of the three coils of the U-, V- and W-phases are connected in common to the intermediate point.

Capacitor C1is connected across power source lines PL1and PL3to smooth the voltage level of power source line PL1. Capacitor C2is connected across power source lines PL2and PL3to smooth the voltage level of power source line PL2.

Inverters120,130convert a DC voltage from capacitor C2to an AC voltage based on a driving signal from control device140to drive motor generators MG1, MG2.

Control device140calculates a voltage of the coil of each phase of motor generators MG1, MG2based on a motor torque command value, a current value of each phase of motor generators MG1, MG2, and input voltages of inverters120,130, and, based on the calculation result, generates a PWM (Pulse Width Modulation) signal for turning on/off power transistors Q1to Q11, and outputs the signal to inverters120,130.

Control device140also calculates a duty ratio of power transistors Q12, Q13for optimizing the input voltages of inverters120,130based on the above-mentioned motor torque command value and a motor speed, and based on the calculation result, generates a PWM signal for turning on/off power transistors Q12, Q13, and outputs the signal to converter110.

Furthermore, control device140controls the switching operation of power transistors Q1to Q14in converter110and inverters120,130, in order to convert AC electric power generated by motor generators MG1, MG2to DC electric power for charging battery B.

During operation of PCU100, heat is generated by power transistors Q1to Q14and diodes D1to D14that constitute converter110and inverters120,130. It is thus necessary to provide a cooling apparatus for promoting cooling of these semiconductor elements.

FIG. 2is a circuit diagram schematically showing cooling circuit10that cools inverter120. As shown inFIG. 2, cooling circuit10includes a heat exchanger11provided in a radiator of a vehicle, a pump12, a cooling apparatus13, and a refrigerant pipe14in which a refrigerant15flows inside.

Heat exchanger11cools refrigerant15using ambient air. The cooled refrigerant15is supplied to cooling apparatus13with pump12, and cooling apparatus13cools each element of inverter120provided inside. Refrigerant15discharged from cooling apparatus13is supplied to heat exchanger11and cooled therein.

FIG. 3is a cross-sectional view of cooling apparatus13, andFIG. 4is a side cross-sectional view of cooling apparatus13. As shown inFIG. 3, cooling apparatus13includes a case20in which refrigerant15flows, and a plurality of element modules21,22,23,24,25, and26provided inside case20.

Case20includes a plurality of partition plates32,33disposed at a distance from each other inside case20, and partition plates32,33form a plurality of refrigerant passages34,35, and36inside case20. Refrigerant passages34,35, and36are connected in series.

A supply port30and a discharge port31are formed in a peripheral wall portion of case20, with supply port30and refrigerant passage34communicating with each other, and discharge port31and refrigerant passage36communicating with each other. Refrigerant15that has entered refrigerant passage34through supply port30thus flows sequentially through refrigerant passage34, refrigerant passage35, and refrigerant passage36, and discharged through discharge port31.

As shown inFIG. 4, case20includes a case main body41whose upper surface is open, an upper wall portion42that covers the opening in case main body41, and a potting material43that paves upper wall portion42. Each of case main body41and upper wall portion42is formed of an insulating material, for example. Partition plates32and33are formed integrally with a bottom surface of case main body41, and protrude upward from the bottom surface of case main body41.

Refrigerant passage36is formed between a side wall portion of case main body41and partition plate33, and refrigerant passage35is formed between partition plates33and32. Refrigerant passage34is formed between partition plate32and the side wall portion of case main body41.

Each of refrigerant passages34,35, and36is filled with refrigerant15to an upper end thereof.

A receiving portion44that receives a lower end of element module21and a receiving portion47that receives an upper end of element module21are formed in refrigerant passage34. A receiving portion45that receives a lower end of element module24and a receiving portion48that receives an upper end of element module24are formed in refrigerant passage35. A receiving portion46that receives a lower end of element module25and a receiving portion49that receives an upper end of element module25are formed in refrigerant passage36.

Receiving portions44,45, and46are formed by providing recesses in the bottom surface of case main body41, and receiving portions47,48, and49are through-holes formed in upper wall portion42. The lower ends of element modules21,24, and25are fitted into receiving portions44,45, and46, and the upper ends of element modules21,24, and25are fitted into receiving portions47,48, and49.

Element modules21,24, and25are positioned with the upper ends of element modules21,24, and25being fitted into receiving portions47,48, and49, and receiving portions44,45, and46are formed to be slightly wider than the lower ends of element modules21,24, and25. An electrode wiring protrudes from an upper end surface of each of element modules21,24, and25, and the electrode wiring penetrates potting material43.

A portion located between the upper end and lower end of each of element modules21,24, and25is disposed within each of refrigerant passages34,35, and36, and the portion of each of element modules21,24, and25is in direct contact with refrigerant15.

By bringing each element module into contact with refrigerant15as described above, the cooling efficiency of the element in cooling apparatus13is increased.

All of element modules21to26are substantially identical in structure. The structure of element module21is now described as a representative example.

FIG. 5is a side view of element module21, and, as shown inFIGS. 5 and 3, diode D1and power transistor Q1are arranged in a direction in which refrigerant15circulates. In the example shown inFIG. 5, diode D1is disposed upstream from power transistor Q1in the direction in which refrigerant15circulates; however, power transistor Q1may be disposed upstream from diode D1in the direction in which refrigerant15circulates.

Generally, power transistor Q1generates an amount of heat greater than that generated by diode D1. Power transistor Q1is therefore disposed upstream in the direction in which refrigerant15circulates, so that it can be cooled with refrigerant15that has not been warmed by diode D1. This allows power transistor Q1to be cooled well.

Insulating substrate51and insulating resin52are each formed of an insulating material such as a ceramic, alumina (aluminum oxide (Al2O3)), aluminum nitride (aluminum nitride (AlN)) or the like.

Insulating substrate50includes an outer surface53and an inner surface54facing insulating substrate51. Outer surface53is disposed opposite to insulating substrate51with respect to inner surface54, and a portion of outer surface53is in contact with refrigerant15.

Insulating substrate51includes an outer surface55and an inner surface56facing insulating substrate50. Outer surface55is disposed opposite to insulating substrate50with respect to inner surface56, and a portion of outer surface55is in direct contact with refrigerant15.

Electrode plate58is provided on inner surface56of insulating substrate51, and electrode plate57is provided on inner surface54of insulating substrate50. As shown inFIG. 7, an electrode wiring74is formed on the upper end of electrode plate57, and an electrode wiring73is formed on the upper end of electrode plate58.

InFIG. 6, power transistor Q1is fixed to electrode plate58, and one main surface of power transistor Q1is fixed to electrode plate58by solder60. The other main surface of power transistor Q1is fixed to a base of electrode plate57by solder61.

Diode D1is fixed to electrode plate57, and one main surface of diode D1is fixed to electrode plate57by solder62. The other main surface of diode D1is fixed to a base of electrode plate58by solder63.

Power transistor Q1and diode D1are located between insulating substrates50and51, and insulating resin52is charged between insulating substrates50and51.

Power transistor Q1and diode D1are thus located within insulating resin52, which prevents contact of power transistor Q1and diode D1with refrigerant15.

Insulating resin52is formed of an insulating material, for example, a thermosetting resin such as BMC (Bulk Molding Compound), an epoxy resin, or the like, or an insulating thermoplastic resin such as PPS (Polyphenylene Sulfide), PBT (Polybutylene Terephthalate), or the like.

Referring toFIGS. 6 and 7, insulating resin52reaches outer surface53of insulating substrate50and outer surface55of insulating substrate51from a portion between insulating substrates50and51, and includes an edge70that is formed to cover portions of outer surfaces53and55. Edge70is formed with an annular shape along outer peripheral edges of insulating substrates50and51.

Edge70includes an upper edge portion70aformed along upper edge portions of insulating substrates50,51, a lower edge portion70bformed along lower edge portions of insulating substrates50,51, and a side edge portion70cextending along side edge portions of insulating substrates50,51.

InFIGS. 7 and 5, upper edge portion70aand lower edge portion70bpass between insulating substrates50and51and along peripheral edge portions of insulating substrates50,51to reach outer surfaces53,51. Upper edge portion70aand lower edge portion70bare formed to cover portions of outer surfaces53and55. As shown inFIGS. 6 and 5, side edge portion70cis formed to be flush with outer surfaces53and55. A cooling surface71is formed on a portion of outer surface53uncovered by edge70, and a cooling surface72is also formed on a portion of outer surface55uncovered by edge70.

An upper surface of upper edge portion70ais positioned above an upper surface of upper wall portion42, and positioned outside refrigerant passage34. Electrode wirings73,74protrude upward from the upper surface of upper edge portion70a, which prevents contact of electrode wirings73,74with refrigerant15.

On the other hand, a portion of element module21positioned within refrigerant passage34and in contact with refrigerant15is formed of an insulating material.

Therefore, a refrigerant other than an insulating refrigerant can be adopted as refrigerant15, for example, an LLC (Long Life Coolant). This also allows cooling circuit10shown inFIG. 1to be incorporated into a cooling circuit generally mounted on a vehicle, thus making equipment mounted on the vehicle more compact.

When element module21is seen in a direction in which insulating substrates50,51are arranged, power transistor Q1and diode D1are positioned within cooling surface72of insulating substrate51, as shown inFIG. 5. Similarly, when insulating substrate50of element module21is seen two-dimensionally, power transistor Q1and diode D1are positioned within cooling surface71.

Thus, power transistor Q1and diode D1are cooled well by direct contact of refrigerant15with cooling surfaces71and72.

Furthermore, the number of components is reduced by fixing element module21to case20by means of upper edge portion70a, which is a portion of insulating resin52.

In cooling apparatus13according to the first embodiment, element modules21,24, and25are positioned with their upper edge portions70abeing fitted into receiving portions47,48, and49. Upper ends of insulating substrates50,51are separated below from receiving portion47. Thus, even if thermal stress is produced between an inner wall surface of receiving portion47and upper edge portion70a, the application of great thermal stress to insulating substrates50,51is prevented, which prevents damage to insulating substrates50,51.

FIG. 8is a cross-sectional view showing a fabrication step when charging an insulating resin52of the element module. As shown inFIG. 8, at the time of charging insulating resin52, an element module in which insulating resin52has not been formed is placed in a resin molding apparatus80.

Resin molding apparatus80includes a mold81and a mold82, which define a cavity83within resin molding apparatus80. A supply port85, which communicates with cavity83and through which resin material84is supplied, is formed in mold81.

Then, at the time of forming insulating resin52, the element module is placed within cavity83first. Insulating substrate50of the element module is brought into contact with an inner wall surface of mold81, and insulating substrate51is brought into contact with mold82.

A portion of the outer surface of insulating substrate50in contact with mold81is to become cooling surface71, and a portion of the outer surface of insulating substrate51in contact with mold82is to become cooling surface72.

Resin material84is charged into cavity83while insulating substrates50,51are in contact with the inner wall surfaces of molds81,82.

At the time, if a small gap is formed between the inner wall surfaces of molds81,80and the outer surfaces of insulating substrates50,51, a small amount of resin will be formed in cooling surfaces71,72.

In cooling apparatus13according to this embodiment, since refrigerant15is brought into contact with substantially the entire surfaces of cooling surfaces71,72, even if a thin film of resin is formed in a portion of cooling surfaces71,72, the cooling efficiency of power transistor Q1and diode D1will show substantially no decrease.

Thus, in the step of forming insulating resin52, it is not necessary to apply an excessive load on insulating substrates50,51, and the load applied to insulating substrates50,51can be kept low.

Consequently, damage to insulating substrates50,51can be prevented during the manufacturing process of the element module, leading to an improved yield.

InFIG. 4, case main body41is formed with a box shape that is open upward, and partition plates32,33are formed to extend upward from the bottom surface of case main body41. Case main body41and partition plates32,33can be integrally resin-molded easily by injection molding, which leads to a reduced number of manufacturing steps of cooling apparatus13.

Second Embodiment

Cooling apparatus13according to the second embodiment will be described usingFIGS. 9 to 11, andFIG. 3, as needed. Among the components shown inFIGS. 9 to 11, components identical or corresponding to those shown inFIGS. 1 and 8above may be denoted by identical numerals, and description thereof may not be repeated.

FIG. 9is a cross-sectional view showing element module21mounted on cooling apparatus13according to the second embodiment. Element module21shown inFIG. 9includes a plurality of cooling fins91provided on cooling surface71and a plurality of cooling fins90provided on cooling surface72. The plurality of cooling fins90,91are formed in a height direction at a distance from one another.

FIG. 10is a side view of element module21shown inFIG. 9. As shown inFIG. 10, each cooling fin90extends in a width direction of element module21. In other words, each cooling fin90extends in the direction in which refrigerant15circulates. This prevents resistance to circulation of refrigerant15from becoming excessively high due to cooling fin90. Cooling fin91is also formed to extend in the direction in which refrigerant15circulates, as with cooling fin90.

FIG. 11is a side view of element module21showing a modification of cooling fin90. In the example shown inFIG. 11, each cooling fin90is formed to extend in an oblique direction. Each cooling fin90is thus disposed to intersect with the direction in which refrigerant15circulates, which disturbs the flow of refrigerant15to promote creating turbulence while refrigerant15flows between cooling fins90. The efficiency of cooling with refrigerant15can be improved by creating turbulence in the flow of refrigerant15. In the example shown inFIG. 11, cooling fins91are formed in the same manner as with cooling fins90. Cooling fins90,91can thus adopt various shapes.

Third Embodiment

Cooling apparatus13according to a third embodiment will be described usingFIG. 12, andFIG. 6above.FIG. 12is a cross-sectional view of cooling apparatus13according to the third embodiment.

Now referring toFIG. 6, diode D1is provided in a position closer to inner surface54of insulating substrate50than inner surface56of insulating substrate51, and power transistor Q1is provided in a position closer to inner surface56of insulating substrate51than inner surface54of insulating substrate50.

Turning back toFIG. 12, in the case of element module21, refrigerant15flows between insulating substrate50and the inner wall surface of element module21, and between insulating substrate51and partition plate32.

A flow path width W2of a flow path formed between the outer surface of insulating substrate51and partition plate32is smaller than a flow path width W1of a flow path formed between the outer surface of insulating substrate50and the inner wall surface of case20.

Hence, the flow velocity of refrigerant15flowing between insulating substrate51and partition plate32is higher than that of refrigerant15flowing between insulating substrate50and the inner wall surface of case20. This allows power transistor Q1that generates an amount of heat greater than that generated by diode D1to be cooled well, which prevents power transistor Q1from being heated to an elevated temperature.

It is noted that element module22is disposed in the same manner as with element module21, and power transistor Q2of element module21is cooled well.

Element modules23,24are disposed such that a distance between element modules23,24and partition plate33is smaller than a distance between element modules23,24and partition plate32. Hence, the flow velocity of refrigerant15flowing between partition plate33and element modules23,24is higher than that of refrigerant15flowing between partition plate32and element modules23,24, so that power transistors Q3, Q4can be cooled well. It is noted that power transistors Q3, Q4are disposed in positions closer to the insulating substrate facing partition plate33than the insulating substrate facing partition plate32.

Element modules25,26are disposed such that a distance between the inner wall surface of case20and element modules25,26is smaller than a distance between element modules25,26and partition plate33. Hence, the flow velocity of refrigerant15flowing between the inner wall surface of case20and element modules25,26is higher than that of refrigerant15flowing between partition plate33and element modules25,26.

Since power transistors Q5, Q6are disposed in positions closer to the inner wall surface of case20than partition plate33, they are cooled well with refrigerant15having a higher flow velocity.

Fourth Embodiment

Cooling apparatus13according to a fourth embodiment will be described usingFIG. 13.FIG. 13is a cross-sectional view of cooling apparatus13according to the fourth embodiment.

As shown inFIG. 13, a plurality of projections95and depressions96are formed on an inner surface of case20, a surface of partition plate32, and a surface of partition plate33.

The formation of the plurality of projections95and depressions96on inner surfaces of refrigerant passages34,35,36allows turbulence to be created in the flow of refrigerant15flowing in refrigerant passages34,35,36. Each of the elements is thus cooled well. While the example shown inFIG. 13describes the case where the plurality of projections and depressions are formed, depressions or projections may also be formed alone.

Fifth Embodiment

Cooling apparatus13according to a fifth embodiment will be described usingFIGS. 14 and 15.

FIG. 14is a side view showing element module21mounted on cooling apparatus13according to the fifth embodiment. As shown inFIG. 14, power transistor Q1and diode D1are arranged in a height direction of element module21. In the example shown inFIG. 14, power transistor Q1is disposed above diode D1.

FIG. 15is a cross-sectional view of cooling apparatus13according to the fifth embodiment. InFIG. 15, insulating substrate51of element module21is disposed to face partition plate32, and insulating substrate50is disposed to face the inner wall surface of case main body41.

Similarly, insulating substrate51of element module24is disposed to face partition plate33, and insulating substrate50of element module21is disposed to face partition plate32.

Insulating substrate50of element module25is disposed to face the inner wall surface of case main body41, and insulating substrate51of element module25is disposed to face partition plate33.

A bulging portion97that protrudes toward element module21is formed in a portion of partition plate32facing power transistor Q1of element module21. A bulging portion98that protrudes toward element module24is formed in a portion of partition plate33facing power transistor Q4of element module24. A bulging portion99that protrudes toward element module25is formed in a portion of the inner wall surface of case20facing power transistor Q5of element module25.

Hence, the flow velocity of refrigerant15flowing between bulging portions97,98, and99and element modules21,23, and25is higher than that of refrigerant15flowing in other portions of refrigerant passages34,35, and36. Consequently, power transistors Q1, Q4, and Q5can be cooled well.

While the foregoing first to fifth embodiments have described the cooling apparatus for inverter120shown inFIG. 1, needless to say, the present invention can also be applied to a cooling apparatus for inverter130or a cooling apparatus that cools converter110. Alternatively, the elements of inverters120,130, and converter110may be cooled with a single cooling apparatus.

Furthermore, when the cooling apparatus that cools inverter120, the cooling apparatus that cools inverter130, and the cooling apparatus that cools converter110are connected to one another, they are connected in series in the direction in which refrigerant15circulates. Specifically, as shown inFIG. 16, cooling circuit10includes a cooling apparatus13A that cools the elements of inverter120, a cooling apparatus13B that cools the elements of inverter130, and a cooling apparatus13C that cools the elements of converter110. Refrigerant pipe14connects cooling apparatus13A, cooling apparatus13B, and cooling apparatus13C in series.

INDUSTRIAL APPLICABILITY

The present invention can be applied to cooling apparatuses that cool elements.

REFERENCE SIGNS LIST