Electric power converter

The present invention provides a highly reliable electric power converter reduced in parasitic inductance.An electric power converter that includes a capacitor module which has a DC terminal, an inverter which coverts a direct current into an alternating current, and heat release fins which cool the inverter, is constructed so that: the inverter has a power module including a plurality of power semiconductor elements; the power module further has a metallic base, a dielectric substrate provided on one face of the metallic base, a power semiconductor element fixed to the dielectric substrate, and a DC terminal; the metallic base has the heat release fins on the other face; the DC terminal in the power module and the DC terminal in the capacitor module are each formed by stacking flat plate conductors via an insulator; the two positive and negative DC terminals have respective front ends bent in opposite directions; a plane including the bent sections is used as a surface for connecting the power module and the capacitor module; and the insulators overlap each other at the connection surface.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electric power converter adapted to convert direct-current power into alternating-current power, or vice versa.

2. Description of the Related Art

Electric power converters that supply alternating-current (AC) power to or receive AC power from a rotating electric machine operating as a motor or a power generator, may be used under severe environments. For example, when mounted in automobiles, electric power converters (hereinafter, referred to simply as power converters) may be used under severe environments such as a high-temperature environment. In addition, the power that power converters convert tends to be augmented in energy level. For example, power converters are likely to be used under the situation that a current of several hundreds of amperes flows.

Techniques relating merely to reducing inductance are disclosed in JP-A Nos. 2001-268942 and 2001-332688. Also, a technique relating merely to cooling is disclosed in JP-A-2005-259748 (FIG. 1).

SUMMARY OF THE INVENTION

The power converter used under a severe environment needs to maintain high reliability. When the power converter is mounted and used in an automobile, in particular, failures in the power converter during use in a high-temperature environment or during processing of power as high as several hundreds of amperes in current level could induce serious automobile accidents. This is why high reliability is required.

To enhance the reliability of a power converter, it is important to avoid using the power converter at unusual operating temperatures of its electric circuit components, and hence to conduct improvements concerning the temperature of the power converter. To protect the power converter from an unusual high-temperature state, it is important to bestow excellent cooling structure on the converter. It is also important that the converter be constructed to suppress the generation of heat.

An inverter that generates a large amount of heat is included in power converters, so it is necessary to construct the power converters so that each suppresses the generation of heat and so that each can efficiently cool the inverter. Since the inverter generates a large amount of heat during switching, the amount of heat generated can be controlled by shortening the switching time. This, however, tends to increase the amount of current to be processed. For example, if a current of several hundreds of amperes is conducted or cut off for a short time period, since inductance will cause a voltage increase, merely shortening the switching time will result in the deterioration of reliability due to a high voltage. For this reason, it has been difficult to shorten the switching time.

Accordingly, reducing the inductance is desired from the viewpoints of cooling the power converter efficiently and reducing the amount of heat generated. The reliability of the power converter can thus be enhanced.

In order to solve the foregoing problems, one feature of an electric power converter according to the present invention is that: the power converter includes on one face of a metallic base a power semiconductor chip constituting an inverter, uses a first wide conductor and a second wide conductor to establish electrical connection between a direct-current terminal of the inverter and a direct-current terminal of a capacitor module, and has the first and second wide conductors formed into a stacked structure.

The above power converter also has a lot of other features, which will be detailed in the description of embodiments, given below.

The present invention makes it possible to provide a highly reliable, electric power converter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In each of the embodiments described below, an electric power converter includes heat release fins in a semiconductor module and is constructed to cool the semiconductor module efficiently by means of the heat release fins. Also, temperature increases of a smoothing capacitor module are minimized since the power converter is constructed to be efficiently cooled by cooling water. In addition, the amount of heat generated is minimized since the power converter is constructed so that inductance of an electric circuit formed between the inverter and the capacitor module is reduced. That is to say, reducing the inductance of the above circuit makes it possible to reduce a switching time, especially, the operating time required when a power module constituting the inverter changes from a conducting state to a cutoff state. The reduction in the operating time, in turn, makes it possible to reduce the amount of heat generated.

In each of the embodiments described below, there are advantageous effects in that planarity of a heat release substrate forming a metallic base of the semiconductor module can be maintained with high accuracy and that the heat release substrate can be easily manufactured. In addition, a plurality of dielectric substrates each having a plurality of semiconductor chips can be bonded onto one metallic base during manufacture of the dielectric substrates. Furthermore, bonding reliability of each dielectric substrate is high and heat-releasing efficiency of the semiconductor module can be improved.

In each of the embodiments described below, inductance between the capacitor module and a semiconductor power module can be reduced to a low level. Since a conductor between the capacitor module and the semiconductor power module can be reduced in inductance, a terminal connection between the capacitor module and the semiconductor power module can also be reduced in inductance. In addition, a DC terminal section of the semiconductor power module can be reduced in inductance. Efficient reduction of these sections in inductance can be structurally implemented. Furthermore, internal inductance of the capacitor module can be reduced.

In the first and second embodiments, a cooling medium and the semiconductor module are high in heat transfer efficiency, even more reliable cooling is possible, and reduction in the amount of heat generated and efficient release of the heat can be achieved with high reliability.

In first and second embodiments, cooling water for an engine can be used as the cooling medium, device mountability in a vehicle is improved, and a total drive system configuration is simplified. In each of the embodiments described below, a structural relationship between a cooling water pathway and the heat release fins is improved to make the engine cooling water usable. The cooling water pathway and installation of a smoothing capacitor are also structurally improved.

According to the first and second embodiments relating to an electric power converter which has a function that controls two rotating electric machines, a configuration of the entire device is simplified and even higher cooling efficiency can be obtained. In addition, the device is constructed so that it can be easily manufactured.

First Embodiment

FIG. 1is a block diagram showing an embodiment of a hybrid type electric vehicle having an electric power converter according to the present invention. The power converter200according to the present invention can be applied to both a pure electric vehicle and a hybrid type electric vehicle. However, hereinafter, an embodiment of the hybrid type electric vehicle is described below as a representative of both types.

The hybrid type electric vehicle100has an engine120, a first rotating electric machine130, a second rotating electric machine140, and a battery180that supplies high-voltage DC power to the first rotating electric machine130and the second rotating electric machine140. The vehicle100also has a battery to supply low-voltage DC power (14-volt power) to the control circuit described below. This battery is not shown.

Torques based on the engine120, on the first rotating electric machine130, and on the second rotating electric machine140, are transmitted to a transmission150and a differential gear160, and then transferred to front wheels110.

A transmission controller154for controlling the transmission150, an engine controller124for controlling the engine120, the rotating electric machine control circuit disposed on a rotating electric machine control circuit board700to control an electric power converter200, a battery controller184for controlling the battery180such as a lithium ion battery, and an integrated controller170are each connected to a communications line174.

The integrated controller170is a lower-level control device. This controller receives information that indicates states of the transmission controller154, the engine controller124, the power converter200, and the battery controller184, from these controllers via the communications line174. Based on the information, control commands addressed to the four controllers are computed by the integrated controller170and transmitted therefrom to each controller via the communications line174. The battery controller184, for example, reports to the integrated controller170a discharge status of the battery180which is a lithium ion battery, and states of unit cells which constitute the lithium ion battery. After judging from the reported states that the battery180requires recharging, the integrated controller170delivers a power-generating operation instruction to the power converter200. Also, the integrated controller170manages output torques of the engine120, the first rotating electric machine130, and the second rotating electric machine140, arithmetically processes an overall torque or torque distribution ratio of the output torques of the engine120, the first rotating electric machine130, and the second rotating electric machine140, and transmits appropriate control commands to the transmission controller154, the engine controller124, and the electric power converter200, according to particular processing results. In accordance with a torque command, the power converter200controls the first rotating electric machine130and the second rotating electric machine140so that the torque output or power generation specified in the command will be implemented using either one of the rotating electric machines or both thereof.

In order to operate the first rotating electric machine130and the second rotating electric machine140, the power converter200controls switching actions of power semiconductor chips, pursuant to the command from the integrated controller170. The power semiconductor chips each constitute an inverter. The first rotating electric machine130and the second rotating electric machine140are operated as motors or power generators by the switching actions of the power semiconductor chips.

For operation as a motor, direct-current power from the high-voltage battery180is applied to an inverter of the power converter200, then the DC power is converted into a three-phase alternating current by controlling the power semiconductor chip constituting the inverter, and the alternating current is supplied to the rotating electric machine130or140. For operation as a power generator, the rotating electric machine130or140has its rotor rotated by an external torque, and in accordance with this torque, generates three-phase AC power in a stator coil of the rotating electric machine. The generated three-phase AC power is converted into DC power by the power converter200and supplied to the high-voltage battery180, which is then recharged with the DC power.

As shown inFIG. 1, the power converter200includes a capacitor module300containing a plurality of smoothing capacitors to suppress voltage fluctuation of the DC power supply, a power module500containing a plurality of power semiconductors, a switching driver board600with a switching driver for controlling a switching action of the power module500, and a rotating electric machine control circuit board700having a rotating electric machine control circuit for generating a signal which determines a time width of the switching action, that is, a pulse width modulation (PWM) control signal. The high-voltage battery180is a secondary battery such as a lithium ion battery or nickel-hydrogen battery, and outputs high-voltage DC power of 250-600 volts or more.

FIGS. 2,3, and4are exploded perspective views of the above-described power converter200, schematically showing a total configuration thereof.FIGS. 2,3, and4are exploded perspective views of the power converter200when the converter is seen from different directions.

The power converter200has a box-shaped housing210, at the bottom of which is disposed a cooling water channel formation220internally having a cooling water channel216as a cooling pathway for cooling water to circulate therethrough. At the bottom of the housing210, an inlet pipe212for supplying the cooling water to the cooling water channel216, and an outlet pipe214protrude outward from the housing210. The cooling water channel formation220has a function that forms a cooling pathway. Engine-cooling water is used as a cooling medium in the present embodiment, wherein the constituent element220functions as the cooling water channel formation.

The power module500inFIG. 1is constituted by a first power module502and a second power module504, both arranged next to each other in the housing210. The first power module502and the second power module504each have heat release fins506,507for cooling. The cooling water channel formation220has openings218,219. Fixing the first power module502and the second power module504to the cooling water channel formation220makes the cooling heat release fins506,507project from the openings218,219to the inward of the water channel216. The openings218,219are blocked with peripheral metallic walls of the heat release fins506,507. This forms cooling water channels and prevents the cooling water from leaking.

The first power module502and the second power module504are arranged at left and right positions of a virtual line segment orthogonal to a sidewall on which the cooling water inlet pipe212and outlet pipe214are formed. The cooling water channel formed in the water channel formation220extends from one end of the cooling water inlet pipe212to the other end in a longitudinal (longer-side) direction of the housing bottom, is bent into a U-character shape at the other end, and is re-routed to extend to the outlet pipe214in the longitudinal direction of the housing bottom. Thus, two sets of water channels parallel in the longitudinal direction are formed in the water channel formation220, and the openings218,219shaped to penetrate the water channels are also formed in the water channel formation220. The first power module502and the second power module504are fixed to the water channel formation220, along the water channels. The heat release fins provided in the first power module502and the second power module504project to the inward of the water channel216, thus implementing efficient cooling. In addition, heat release surfaces of the first power module502and the second power module504come into firm contact with the metallic water channel formation220, thus implementing efficient heat-releasing construction. Furthermore, since the openings218,219are blocked with the heat release surfaces of the first power module502and the second power module504, compact construction is realized and a cooling effect is improved.

A first driver circuit board602and a second driver circuit board604are arranged next to each other in stacked form above the first power module502and the second power module504, respectively. The first driver circuit board602and the second driver circuit board604constitute the switching driver circuit board600described inFIG. 1.

In planar view, the first driver circuit board602disposed above the first power module502is formed to be slightly shorter than the first power module502. In planar view, the second driver circuit board604disposed above the second power module504is likewise formed to be slightly shorter than the second power module504.

The cooling water inlet pipe212and outlet pipe214are provided on a sideface of the housing210, a hole260is formed on this sideface, and a connector282for a signal is disposed at the hole260. A noise reduction board560fixed adjacently to the connector282, and a second electrical discharge board520are arranged at the disposing position of the connector282, inside the housing210. The noise reduction board560and the second electrical discharge board520are installed so that respective installation surfaces are parallel to those of the first power module502and the second power module504.

A capacitor module300with a plurality of smoothing capacitors is disposed above the driver circuit boards602and604. The capacitor module300also has a first capacitor module302and a second capacitor module304, and the first capacitor module302and the second capacitor module304are arranged above the first driver circuit board602and the second driver circuit board604, respectively.

Above the first capacitor module302and the second capacitor module304, a planar retaining plate320is fixedly disposed with its periphery brought into firm contact with an inner wall surface of the housing210. In addition to supporting the first capacitor module302and the second capacitor module304from above, the retaining plate320retains and immobilizes the rotating electric machine control circuit board700from the underside thereof, as shown inFIG. 2. The retaining plate320constructed of a metallic material releases heat from the capacitor modules302,304and the rotating electric machine control circuit board700by discharging the heat towards the housing210.

As described above, the power module500, the switching driver circuit board600, the noise reduction board560, the second electrical discharge board520, the capacitor module300, the retaining plate320, and the rotating electric machine control circuit board700are stored within the housing210, and an opening that forms an upper section of the housing210is blocked with a metallic cover290.

In addition, if the sidewall of the housing210that has the cooling water inlet pipe212and outlet pipe214routed through the housing is regarded as a front panel, a terminal box800is installed and disposed on the sidewall, that is, the front panel. The terminal box800has DC power terminals812through which to receive the DC power supplied from the battery180, a DC power terminal block810provided internally to the terminals812, AC terminals822connecting to the first rotating electric machine130and the second rotating electric machine140, and an AC terminal block820provided internally to the terminals822.

The DC power terminals810are electrically connected to electrodes of the first capacitor module302and the second capacitor module304via a bus bar, and the AC terminal block820is electrically connected via another bus bar to terminals of the power modules502and504constituting the power module500.

The terminal box800is constructed so that its assembly will be completed when a bottom plate844with the DC power terminal block810disposed thereon, and a cover846are installed on a main unit840of the terminal box. This construction facilitates the assembly of the terminal box800. The power converter200is of a compact shape, as shown inFIG. 5.

<<Constituent Members of the Power Converter200>>

Next, a detailed configuration of the power converter200shown inFIGS. 2 to 7is described below.

A section taken along line I-I ofFIG. 5is shown inFIG. 8. The housing210is approximately a rectangular box structure made of a metallic material, for example, aluminum. The housing210, at the bottom thereof, has a water channel formation220fitted with a cooling water channel, and is open atop. At a section opposite to an inlet and outlet port, the water channel in the bottom of the housing210is bent over to form two cooling water channels next to each other, so that cooling water circulates through the water channels. The cooling water channel bent over includes the water channel formation220constructed into a double structure with a space sandwiched centrally therein so that the cooling water flows through the space. An upper plate of the water channel formation220is formed with openings218and219along the water channels, as shown.

In a lower section of the housing210, one pair of power modules consisting of a first power module502and a second power module504are arranged, which are arranged and immobilized at independent positions above the water channel formation220. The housing210has a large number of heat release fins506,507arranged next to one another on respective heat release surfaces of the first power module502and the second power module504. The heat release fins506,507protrude to the inward of the openings218and219in the water channel formation220. Additionally, each of these openings is blocked with the heat release surfaces of the power modules502and504, formed around the heat release fins506and507. This prevents water leakage and forms an enclosed water channel216.

Such construction efficiently cools the first power module502and the second power module504. In addition, since the housing210is constructed so that the heat release fins506and507of the first power module502and the second power module504are inserted along the openings218and219, the housing210has an advantageous effect in that the first power module502and the second power module504can be accurately positioned with respect to the housing.

In the housing210, a relatively small hole262and a hole264with a relatively large area are sequentially formed next to each other (seeFIG. 3). On a sidewall of the housing210is disposed the terminal box800, with its internal DC power terminal block810being electrically connected to the internal first capacitor module302and second capacitor module304of the housing210via the hole262, and with the internal AC terminal block820of the terminal box800being electrically connected to the internal first capacitor module302and second capacitor module304of the housing210via the hole264by bus bars860and862. Part of the bus bars is disclosed inFIG. 8.

FIG. 9is a plan view showing a state in which the power module500and the switching driver circuit board600are arranged inside the housing210.

The first power module502and second power module504constituting the power module500are arranged closer to the cooling water channels than to the rotating electric machine control circuit board700and the capacitor modules502and504, inside the housing210. The first power module502and the second power module504are arranged in parallel to each other along the cooling water channels.

Geometrically, the first power module502and the second power module504are also of the same construction with respective DC terminals IT1and IT2and AC terminals OT1and OT2arranged to be oriented in the same direction. In this construction, if one of the two power modules (e.g., the first power module502) is disposed in 180-degree rotated form with respect to the other power module (e.g., the second power module504), the respective DC terminals IT1, IT2are arranged to face each other centrally between both. Also, the AC terminals OT1and OT2are both arranged at a sidewall side of the housing210. The first power module502and the second power module504are arranged at positions slightly offset with respect to each other in a longitudinal (longer-side) direction, since the respective DC terminals IT1, IT2opposite in polarity are arranged in close proximity to each other.

InFIG. 9, the DC terminals IT1, IT2and the AC terminals OT1, OT2are shown at both sides of the switching driver circuit boards602and604in a lateral direction thereof, since the first power module502and the second power module504are arranged overlapping the switching driver circuit boards602and604, respectively.

The DC terminals IT1, IT2of the first power module502and those of the second power module504are electrically connected to various terminals of the capacitor modules302and304. The AC terminals OT1, OT2of the first power module502and those of the second power module504are connected to the AC terminal block820within the terminal box800.

The AC terminal OT1of the first power module502includes terminals OT1u, OT1v, OT1wassociated with a U-phase, a V-phase, and a W-phase, respectively. At a sidewall234of the housing210, there are bus bars860u,860v, and860wdirected upward after being routed from layout positions of the terminals OT1u, OT1v, OT1walong one lateral side of each of the power modules502and504arranged next to each other. The terminals OT1u, OT1v, OT1wconnect, via the bus bars860u,860v, and860w, to lead terminals OL1u, OL1v, OL1wprojecting through the hole264formed in major sidewall234of the housing210. The bus bars860u,860v, and860win the present embodiment are routed through a side opposite to the inlet and outlet ports of the water channels.

The AC terminal OT2of the second power module504includes terminals OT2u, OT2v, OT2wassociated with the U-phase, the V-phase, and the W-phase, respectively. There are bus bars862u,862v, and862wdirected upward at the sidewall234of the housing210after being routed from layout positions of the terminals OT2u, OT2v, OT2w. The terminals OT2u, OT2v, OT2wconnect, via the bus bars862u,862v, and862w, to lead terminals OL2u, OL2v, OL2wprojecting through the hole264.

The first capacitor module302, the second capacitor module304, and the rotating electric machine control circuit board700are arranged above the first power module502, the second power module504, and the switching driver circuit boards602and604.

The power modules502and504have screw holes in respective peripheral sections and are fixed to the water channel formation220at the bottom of the housing through the screw holes by means of screws SC1. Also, the driver circuit boards602and604above the power modules502and504are fixed thereto by means of screws SC2.

InFIG. 9, as described above, the first driver circuit board602and the second driver circuit board604are constructed as circuit boards to supply switching signals to the first power module502and the second power module504, respectively. The first driver circuit board602and the second driver circuit board604each have a harness HN routed outward via a connector CN provided on a main surface of the circuit board, and the harness HN is connected to the rotating electric machine control circuit board700.

FIG. 10is a plan view showing a state in which the capacitor module300with a plurality of smoothing capacitors is disposed inside the housing210. The capacitor module300includes the first capacitor module302and the second capacitor module304, which are each formed with five or six film capacitors (capacitor cells) stored within a rectangular parallelepiped casing created from a resin material, for example.

As shown inFIGS. 8 and 10, the first capacitor module302and the second capacitor module304are arranged in parallel to each other, the former being disposed above the first driver circuit board602and the latter above the second driver circuit board604. The first capacitor module302and the second capacitor module304are electrically connected at junctions JN (inclusive of JN1and JN2) to the DC terminals of the first power module502and the second power module504.

The first capacitor module302and the second capacitor module304are constructed so that in the power module500, each is connected to one pair of DC terminals in a U-phase arm, one pair of DC terminals in a V-phase arm, and one pair of DC terminals in a W-phase arm. As shown inFIG. 10, therefore, the first power module502and the second power module504are electrically connected at six positions to the first capacitor module302and the second capacitor module304, respectively, and the connection between the power module and the capacitor module is established in a stacked structure of both with a wide insulator interposed between wide metal conductors. This structure makes it possible to reduce inductance of an electric circuit formed between the power module and the capacitor module. Reducing the inductance yields an effect in that a temporary rise in voltage due to switching of the power module can be suppressed and makes it possible to correspondingly shorten a switching time and hence to realize control that reduces the amount of heat generated.

InFIG. 10, the first capacitor module302and the second capacitor module304have one pair of electrodes TM1and TM2, respectively, that are connected to the DC power terminal block810, and the two capacitor modules are connected to an external DC power supply via the electrodes. The electrodes TM1and TM2of the first capacitor module302and the second capacitor module304are all arranged at the water channel inlet and outlet side of the housing210. That is to say, since these electrodes are arranged at the same side as that having the DC power terminal block810in the terminal box800, electrical wiring to the high-voltage battery that is the external DC power supply becomes easy and working efficiency improves.

InFIG. 10, fixing holes FH1and FH2each with an embedded nut are formed at respective four corners of the first capacitor module302and the second capacitor module304, and these capacitor modules are fixed to the retaining plate320by means of screws SC4(seeFIG. 11) that are threaded into fixing holes FH1, FH2of the retaining plate320through holes associated with the fixing holes FH1, FH2. That is to say, the first capacitor module302and the second capacitor module304are fixed in a suspended condition to the retaining plate320.

FIG. 11is a plan view of the rotating electric machine control circuit board700existing when it is mounted on the retaining plate320disposed inside the housing210. The retaining plate320is constructed as a control circuit board bracket having the rotating electric machine control circuit board700, and is fixed to the housing210, above the capacitor module300.

A plurality of almost equally spaced projections PR (seeFIGS. 9 and 10) are formed peripherally on an inner surface of the housing210. The retaining plate320is supported from its periphery by upper edges of the projections PR and fixed using the screws SC4threaded into the upper edges of the projections PR through the screw holes formed on the periphery of the retaining plate320.

Since the retaining plate is supported by the large number of peripheral projections with an upper wide area, the housing210and the retaining plate320are placed in a favorable, thermal conducting state. As with the housing210, the retaining plate320is formed of a metallic material of high heat conductivity, such as aluminum, in order to improve mechanical strength of the retaining plate. Also, the retaining plate320is formed with patterned depressions and projections on the mounting surface for the rotating electric machine control circuit board700.

The depressions in the retaining plate320are formed at sections opposed to an electrical wiring layer or other regions on the face of the rotating electric machine control circuit board700that is closer to the retaining plate320. Such layout of the depressions makes it possible to prevent the wiring layer or other regions from coming into contact with the retaining plate320, and hence to prevent electrical short-circuiting of the wiring layer or the like. Particularly the sections at which the AC terminals OT1and OT2of the power modules502and504, respectively, are provided have a concave shape. A concave section is also formed at the DC power supply connections. In the depressed sections on the face of the retaining plate320that is directed towards the rotating electric machine control circuit board700, a plurality of bosses BS are formed in scattered form as shown inFIG. 3, and at these bosses, the rotating electric machine control circuit board700is fixed to the retaining plate320by means of screws SC6(seeFIG. 16) that are threaded into the screw holes formed in the rotating electric machine control circuit board700.

As described above, the first capacitor module302and second capacitor module304arranged below the retaining plate320are fixed thereto using the screws SC4threaded into the fixing holes FH1, FH2at the four corners of both capacitor modules through the screw holes in the retaining plate320.

Since the first capacitor module302and the second capacitor module304are thus constructed to be fixed to the retaining plate320that abuts the housing210, the capacitor modules302and304produce an excellent heat-releasing effect in that the heat stemming from both capacitor modules will be easily conducted into the housing210through the retaining plate320. Also, since the housing210is cooled by the cooling water channels, temperature rises of the capacitor modules302and304can be minimized.

(Rotating Electric Machine Control Circuit Board700)

FIG. 11is a plan view of the rotating electric machine control circuit board700with the retaining plate320mounted thereon inside the housing210. Electronic components for small signals are mounted with a connector CN on the rotating electric machine control circuit board700. This connector CN is connected via a harness HN to connectors CN mounted on, for example, the switching driver circuit boards602and604. The rotating electric machine control circuit board700has screw holes formed in various regions at four corners of its periphery and in a central region exclusive of the periphery. The central region detours a region in which components are mounted, and a region in which an electrical wiring layer for connecting the components is formed. The rotating electric machine control circuit board700is constructed so that it can be fixed to the retaining plate320by the screws SC6threaded thereinto through the above screw holes. This construction of the rotating electric machine control circuit board700, compared with, for example, a construction in which the control circuit board is fixed at its marginal portions only to a frame, makes it possible to avoid the adverse event that a middle section of the board deflects or warps for reasons such as vibration. As described above, since the rotating electric machine control circuit board700is constructed to be mounted on the retaining plate320that abuts the housing210, the rotating electric machine control circuit board700produces an excellent heat-releasing effect in that the heat stemming therefrom will be easily conducted into the housing210through the retaining plate320.

The cover290includes a cover member that blocks the opening in the housing210after sequential storage of the first power module502, the second power module504, the switching driver circuit boards602,604, the first capacitor module302, the second capacitor module304, and the retaining plate320, and the rotating electric machine control circuit board700into the housing210.

(Cooling Structure of the Power Modules502and504)

As described above, cooling water channels are formed at a bottom section of the power converter200, near one face thereof.FIG. 12is a bottom structural view of the housing210, showing a water channel retaining member902that is one part of a water channel formation220forming the bottom of the housing. The water channel retaining member902includes a peripheral section904formed to install a bottom plate934which serves as another water channel formation220, and the peripheral section904has a large number of holes SC9for screw locking. The reference number is assigned only to some of the holes, and others are shown without the number. The peripheral section904has a sealing groove906inside to prevent water leakage, and the water channel retaining member902internal to the sealing groove906has an outer region912at both sides. In addition, a first water channel922, a second water channel926, and a central section908are provided, the water channels922and926being the cooling water channels216described inFIG. 8. Fitting an O-ring or a sealing member such as rubber into the sealing groove and then locking each screw hole SC9with a screw provides a sealing function to the sealing groove. Cooling water is supplied to an inlet port916of the water channel922(described earlier as216), and the cooling water flows through the first water channel922in a direction of an arrow. The flow of the cooling water changes into a U-shape inside a bent pathway924, then the cooling water flows through the second water channel926in a direction of an arrow, and the cooling water is discharged from an outlet port918of the water channel926. The first water channel922and the second water channel926are holed as openings218and219, respectively. Installing the bottom plate934described below perFIG. 13forms the water channels922and926.

The central section908between the first water channel922and the second water channel926, and the outer regions912between the first water channel922and the peripheral section904and between the second water channel926and the peripheral section904, each have dents932to reduce aluminum-diecasting thickness.

The bottom plate934for blocking up the bottom of the housing210, shown inFIG. 12, is shown inFIGS. 13A and 13B. The bottom plate934and the water channel retaining member902constitute the water channel formations provided to form the water channels. Inside the water channels, water flows as indicated by arrows inFIG. 13A. The bottom plate934has a lot of screw holes SC9and is screwed down via the screw holes SC9in the peripheral section904of the water channel retaining member902. The bottom plate934also has a first convex935and a second convex936, the first convex935is inserted into the water channel922, and the second convex936is inserted into the water channel926. Dents938are provided to reduce the aluminum-diecasting thickness.

A sectional view of the water channel922, taken along line II-II inFIG. 12, is shown inFIG. 14. The water channel926is also of much the same shape. The water channel retaining member902inFIGS. 12,13, and14includes the water channels922and926arranged in parallel to each other. Cooling water is introduced from the inlet pipe212(omitted fromFIG. 12) into the inlet port916. The inlet port916of the water channel includes a ceiling882formed using metal members integrated with the housing210, and both sides of the water channel include other metal members integrated with the housing210. The latter metal members are sidewalls988and990shown inFIG. 15. As shown inFIG. 14, at a section internal to the inlet pipe, the water channel is progressively increased in width, whereas the water channel is progressively reduced in depth. This structure creates a smooth flow of cooling water, makes swirling less prone to occur, and reduces fluid resistance. The water, once passed through the inlet port, is introduced into the water channel having an opening. When the convex935shown inFIG. 13is provided at the bottom of the water channel having an opening, the bottom of the water channel will correspondingly rise and depth thereof will be greater than height of the heat release fins. The height of the heat release fins ranges from 6 millimeters to 8 millimeters, and the depth of the water channel is up to 10 millimeters, desirably, up to 9 millimeters.

The opening218is disposed at a side opposite to the convex935of the water channel formation220, and the power module502is fixed to the opening218by means of the screws SC1so that the heat release fins506provided on a metallic base944of the power module502jut out towards the opening218. The power module504, although not shown, is fixed to the opening in the water channel formation220forming the other water channel926disposed in parallel to the above water channel922. This method of fixing both power modules improves heat exchange efficiency between the heat released from the heat release fins, and the water that is a cooling medium. In addition, at the bends of the juxtaposed water channels922,926that are connections therebetween, the depth of the water channels is greater than at where the heat release fins506jut out, so that fluid resistance is reduced and the flow of the cooling water is improved.

The power module504has essentially the same structure as that of the power module502, and is also fixed in almost the same way, so the power module502is described in detail below as a representative. A plurality of heat release fins506(in the present embodiment, three units) jut out from the opening218, towards the water channel922. The heat release fins506are provided on one face of the metallic base944, and semiconductor chips are provided on another face of the metallic base944. The semiconductor chips are hermetically sealed in a resin casing946. This construction is also the same in a relationship between the power module504and the water channel926.

As shown inFIGS. 9 and 14, the power module502is fixed together with a metal plate982via the screws SC1to the water channel formation that forms the water channel. In the present embodiment, the power module502is fixed to the water channel cover882formed integrally with the housing210. Screw locking of the power module502blocks the opening218of the water channel922, at the heat release surface of the power module502. A hermetic sealing member, for example, an O-ring986is provided between the heat release surface of the water channel922and the water channel formation around the opening. This forms the structure that makes it possible to prevent water leakage.

A heat release plate984made of a metal or of a relatively soft resin material excellent in heat conductivity is provided facing the metal plate982, and the driver circuit board602is provided facing the heat release plate984. Heat from the driver circuit board602is transmitted to the water channel formation via the heat release plate984and then transferred to the cooling water. Increases in the temperature of the driver circuit board602are minimized. The above construction, operation, and advantageous effects also apply to the power module504and the driver circuit board604.

FIG. 15is a partial, enlarged view of section III-III inFIG. 14. The water channel220adapted to form the water channel922includes the bottom plate934at bottom. Both sides of the water channel922are formed by side plates988and990integrated with the housing210. Hermetic sealing of connections between the side plates988,990and a lower section of the water channel formation220, is accomplished by disposing a hermetic sealing member, for example, a sealing member986formed by an O-ring or a gasket wider than the O-ring. Also, as described above, the heat release surface of the metallic base944of the power module502serves to hermetically seal the opening218in the water channel922. A hermetic sealing member, for example, the sealing member986formed by an O-ring, a gasket, or the like, is provided to seal the above opening. A plurality of semiconductor chips are fixed to the face opposite the above-mentioned face of the metallic base944, and are hermetically sealed by the resin casing946. Above the power module502, as described above, the driver circuit board602is fixed by the screws SC2, with the heat release plates982and984interposed between the circuit board and the screws.

In the above description, as shown inFIG. 14, the water channel is deep at the inlet, outlet, and bends thereof, and the section where the heat release fins are inserted is shallower than these sections of the water channel. That is to say, the depth of the water channel at the insertion section of the fins is slightly greater than the height thereof. In the present embodiment, as described above, the height of the fins ranges from 6 millimeters to 8 millimeters and the depth of the water channel is up to 10 millimeters, desirably, up to 9 millimeters. The above construction, operation, and advantageous effects also apply to the power module504and the water channel formation including the water channel.

FIG. 17shows the power module502or504existing when viewed from the fins.FIG. 16shows the power module502or504whose resin casing946is removed. Section IV-IV inFIG. 16is shown inFIG. 18. Although three semiconductor chips will be shown in an actual sectional view, one semiconductor chip only is shown in enlarged form inFIG. 16. As shown inFIG. 17, three sets of heat release fins,506A,506B, and507C, are provided on the heat release surface of the metallic base944. On this heat release surface, an O-ring or a gasket is provided as a sealing member86to prevent cooling water leakage from the water channel. Pressing the heat release surface of the metallic base944firmly against the opening in the water channel922(216) or926(216) by using screws or the like makes it possible to block the opening with the metallic base944, thus preventing the cooling water from the water channel.

As shown inFIG. 18, the heat release fins are fixed using a brazing material948. Brazing with this material is conducted at a temperature from 600 to 700 degrees Centigrade. On one face of the metallic base944, an electrical dielectric substrate is bonded via a second soldering layer962for each of the three sets of heat release fins, as shown inFIG. 18.

The metallic base944is formed of an alloy that uses copper as its principal constituent and contains an impurity. After brazing, the heat release fins506are, desirably, at least HV50 in hardness and at least 200 W/mK in heat conductivity. The thickness of the metallic base944ranges from 2 millimeters to 4 millimeters. Also, a departure from planarity of the metallic base section under the associated dielectric substrate or between the fixing screw holes978is desirably within ±0.2 mm, and optimally, within ±0.1 mm. In addition, errors in planarity under the six dielectric substrates that are the semiconductor chips constituting the inverters are desirably ±0.4 mm, and optimally, within ±0.3 mm. If an impurity harder than copper is mixed with copper, hardness will increase with each increase in mixing ratio. The heat conductivity of the entire metallic base, however, will decrease since the above impurity is typically lower than copper in heat conductivity. The above hardness and heat conductivity values, therefore, are desirably maintained by adjusting a rate of the impurity. Besides, the metallic base is desirably nickel-plated to a thickness of about 3-9 μm. As shown inFIG. 18, one face of the metallic base has a brazed heat release fin506and another face has a soldered dielectric substrate956that uses a semiconductor chip. In this case, surface roughness of the metallic base can be properly maintained by providing appropriate plating thickness to the metallic base that may be damaged on the surface of the copper. In the present embodiment, the surface roughness of the metallic base sections in at least a mounting region of the dielectric substrate and in a contact region of the O-ring desirably satisfies “Ra=3.2” (Ra: roughness average).

(Manufacture of the Semiconductor Modules)

As shown inFIG. 18, the base plate of a copper-based alloy that satisfies the above conditions has a metallic heat release fin506brazed at a temperature from 600 to 700 degrees Centigrade. The brazing temperature is likely to reach 800 to 900 degrees in some cases. If the metallic base is too soft, the brazing operation will deteriorate planarity, making subsequent bonding of the dielectric substrate956difficult. After-brazing characteristics of at least HV50 in hardness and at least 200 W/mK in heat conductivity can be achieved by selecting an appropriate impurity content. As shown inFIG. 16, three heat release fins,506A to506C, are brazed.

In another processing step, a semiconductor chip952is bonded onto each dielectric substrate956by hot soldering. A first solder layer958, the layer created in this step, is used to fasten the semiconductor chip952and the dielectric substrate together. This hot solder layer is not melted by cold solder bonding with a second solder layer962. As shown inFIG. 16, three diode chips954and three IGBP chips952are bonded onto one dielectric substrate956. In order to avoid the complexity of illustration, one dielectric substrate956only is shown with a reference number, and others are shown without numbering. When two opposed dielectric substrates, each with three diode chips954and three IGBP chips952, are arranged in parallel to each other, one of three phases (U, V, W) is formed for one fin that has been bonded onto a reverse face of the metallic base944. The metallic base944inFIG. 16includes three sets of dielectric substrates of the above opposed parallel arrangement in order to constitute inverters for the three phases. Each dielectric substrate is of the same structure.

After the above processing step, the six dielectric substrates956each with three bonded semiconductor chips952, and the metallic base944with three heat release fins506are bonded with the cold solder962so as to establish the positional relationship shown inFIGS. 16 and 17. That is to say, bonding is conducted to obtain the positional relationship with one fin brazed onto the opposite face of the metallic base944for two dielectric substrates. Of all sections shown inFIG. 18, the section between the heat release fin506and the metallic base944is the highest in bonding temperature, and this section is bonded using a brazing material. The section between the semiconductor chip952and the dielectric substrate956is next highest in bonding temperature, and this section is bonded using hot solder. The section between the dielectric substrate956and the metallic base is the lowest in bonding temperature, and this section is bonded using cold solder. Since the bonding temperature of the heat release fin506brazed is high, the metallic base944uses a metal harder than pure copper. Otherwise, brazing will deteriorate the planarity of the opposite face of the metallic base944and make the dielectric substrate difficult to bond. If the metal added as the impurity is increased in content, the planarity will be easier to maintain, as described above. However, heat conductivity will decrease and the dielectric substrate956will decrease in cooling effect. Both characteristics can be simultaneously obtained using the foregoing after-brazing characteristics conditions of at least HV50 in hardness and at least 200 W/mK in heat conductivity. A departure from the planarity of the metallic base section under the region of each dielectric substrate956is desirably within ±0.2 mm, and optimally, within ±0.1 mm. In addition, an area on the metallic base944where the six dielectric substrates are bonded is desirably able to maintain high planarity, and a departure from the planarity of the metallic base section in the bonding area for all six dielectric substrates is desirably within ±0.4 mm, and optimally, within ±0.3 mm.

In other perspective, the departure from the planarity of the metallic base944in the area sectioned by the fixing screw holes978is desirably within ±0.2 mm, and optimally, within ±0.1 mm.

The present embodiment includes a plurality of dielectric substrates956arranged on the metallic base944, and maintains a layout relationship in which a plurality of semiconductor chips are arranged on each of the dielectric substrate956so as to be able to withstand a high voltage. For the dielectric substrates956thus arranged so that each has a plurality of semiconductor chips to receive, for example, DC power of 300 volts or more and convert the DC power into AC form, since the dielectric substrates increase in surface area, the departure from the planarity in the area where each dielectric substrate956is bonded is desirably within ±0.2 mm, and optimally suppressed to be within ±0.1 mm.

The three sets of semiconductor chips bonded onto one dielectric substrate inFIG. 16are, in the present embodiment, IGBT (Insulated Gate Bipolar Transistor) chips and diode chips, and the chip952inFIG. 18is one of the IGBT chips. Also, in order to form essentially the same structure as that shown inFIG. 18, the diode chips954adjacent to the IGBT chips inFIG. 16are bonded onto the dielectric substrate956by using essentially the same manufacturing method as used inFIG. 18. There is a difference in that the semiconductor chip952is replaced by diode chip954. Three IGBT chips952and three diode chips954are bonded onto each dielectric substrate, and six dielectric substrates956each having the six chips are bonded onto the metallic base944by cold soldering in order to obtain the array shown inFIG. 16.

While the above embodiment has used IGBT chips as the semiconductor chips952, MOS transistor chips may be used instead, in which case, the diode chips954become unnecessary.

The holes978inFIGS. 16,17, and18are screw holes for fixing the semiconductor module to the water channel formation220.

FIG. 19shows another example ofFIG. 18, and the present example uses pin-shaped heat release fins506. Similarly to the wave-shaped heat release fins506inFIG. 18, the pin-shaped heat release fins506are brazed onto a metallic base944using a brazing material. The metallic base plate and the pin-shaped fins are bonded using the brazing material948. In the present example, height of the heat release pins above the base surface ranges from 6 mm to 8 mm. The depth of the position at which the heat release fins are inserted in the water channels inFIG. 4is 10 mm or less, and desirably, 9 mm or less. The number of fins in the areas of each fin and in the area of the heat release fin506A inFIG. 17is from 300 to 700. A diameter of the pins is from 3 to 5 mm at the brazed section, height thereof is from 0.5 mm to 1.5 mm, and a diameter of a section even higher than the brazed section is from 2 mm to 3 mm. These pins are arranged in zigzag form.

FIGS. 20A to 20Care external views of power module502or504.FIG. 20Ais a plan view of the power module502or504,FIG. 20Bis a side view thereof, and20C is a front view thereof. As described in the above example, in the power module structural views ofFIGS. 16 and 17, the resin casing of the power module inFIG. 20is removed from the module. In the plan view ofFIG. 20A, AC terminals OT1u, OT1v, OT1wthat connect to a rotating electric machine are provided at one end of the power module502or504. Three sets of DC terminals IT1N and IT1P that connect to a DC power supply are provided at the other end. These terminals are arranged as inFIG. 9, and are connected to capacitor terminals. The IT1N terminals are connected to a negative side of the DC power supply, and the IT1P terminals, to a positive side of the DC power supply. When the three sets of DC terminals IT1N and IT1P inFIGS. 20A,20C are electrically connected, parallel connections are conducted between positive terminals and between negative terminals.

Reference pins992are provided for positioning the driver circuit boards602and604fixed to the power module502or504.

FIG. 21shows a relationship in position between the power modules502and504existing when the respective heat release fins are fixed so as to protrude towards an opening218or219in a water channel922. Arrows indicate directions of a flow of water in the water channel. The two power modules502and504are arranged in parallel and so that the DC terminals are positioned internally. This arrangement makes the module terminals connectible at a central section to the capacitor terminals, thus simplifying a total device structure. The arrangement also makes it possible to connect capacitor modules302and304in a stacked structure with short electrical wiring and with the DC positive and negative sides facing each other. In addition, it becomes possible to reduce inductance of the electrically wired section and to suppress increases in voltage due to switching between the power modules502and504.

In this device, the power modules have their DC positive terminals IT1P and IT2P connected to one another and have their DC negative terminals IT1N and IT2N connected to one another. Arranging the power module502or504in slightly offset form in parallel, as shown inFIG. 21, makes it possible for a power module of the same shape to be used as the other power module502or504. Such arrangement is also effective for reducing a connection distance and hence, the above inductance. It is possible to arrange the negative N-terminals of the power module502or504adjacently to one another, and arrange the positive P-terminals adjacently to one another. Thus, connection lines are arranged into a neat relationship, and productivity-associated electrical wiring efficiency improves. Additionally, the inductance can be reduced.

Since the AC terminals OT1and OT2that connect to rotating electric machines are arranged outside the parallel-arranged power modules502and504, bus bars for connecting the AC terminals OT1and OT2to terminals of different rotating electric machines can be easily arranged in this structure. The above arrangement also simplifies the structure of the entire device and improves working efficiency.

(Description of Electrical Circuit)

FIG. 22is a circuit diagram of the electric power converter200in the present example. The power converter200includes: a first power module502constituting a first inverter; a second power module504constituting a second inverter; a capacitor module300; a driver circuit92mounted on a first driver circuit board602of the first inverter; a driver circuit94mounted on a second driver circuit board604of the second inverter; a control circuit93mounted on a rotating electric machine control circuit board700; a connector73mounted on a connector board72; a driver circuit91driving a discharge circuit (not shown) of the capacitor module300; and current sensors95and96.

The first power module502and the second power module504each constitute a power converter main circuit of the associated inverter and have a plurality of switching power semiconductor elements. The first power module502and the second power module504operate in accordance with driving signals output from the associated driver circuits92and94, convert DC power supplied from a high-voltage battery180, into three-phase AC power, and supply the power to armature coils of associated rotating electric machines130and140. The main circuit that is the three-phase bridge circuit shown inFIG. 22includes series circuits for three phases, and the series circuits are electrically connected in parallel to one another between positive and negative sides of the battery180. The series circuits are constituted by the semiconductor chips952bonded onto the dielectric substrates956arranged facing each other inFIG. 16. Semiconductor chips of the first power module502and second power module504shown inFIG. 22are arranged as shown inFIG. 16.

(Description of the Second Power Module504)

The first power module502and the second power module504are of the same circuit composition, as shown inFIG. 22, and the second power module504is described below as a representative. The present example uses IGBTs (Insulated Gate Bipolar Transistors)21as the switching power semiconductor elements. Each IGBT21has a collector electrode, an emitter electrode, and a gate electrode. A diode38is electrically connected between the collector electrode and emitter electrode of the IGBT21, and the diode38has a cathodic electrode and an anodic electrode. In order that a direction from the emitter electrode of the IGBT21, towards the collector electrode thereof, is a forward direction, the cathodic electrode and the anodic electrode are electrically connected to the collector electrode and emitter electrode, respectively, of the IGBT21. The IGBT21that is a chip is associated with the semiconductor chip952shown inFIG. 16,18, or19, and the diode38is associated with the diode chip954shown therein. As described in the above example, the switching power semiconductor elements may be MOSFETs (Metal-Oxide Semiconductor Field-Effect Transistors). Each MOSFET has a drain electrode, a source electrode, and a gate electrode. Since the MOSFET includes, between the source electrode and the drain electrode, a parasitic diode in which a direction from the drain electrode, towards the source, is a forward direction, such independent diode as added to each IGBT is not required in the MOSFET.

Arms of each phase are constructed with the source electrodes and drain electrodes of associated IGBTs21electrically connected in series. In the present example, although one IGBT only is shown for an upper or lower arm of each phase, since a capacity of a current to be controlled is large, it is to be assumed that a plurality of IGBTs are electrically connected in parallel. In the present example ofFIG. 22, the upper and lower arms of each phase are each constructed of three IGBTs. The drain electrodes of the IGBTs21constituting the upper arms of each phase are electrically connected to the positive side of the battery180, and the source electrodes of the IGBTs21, to the negative side of the battery180. The terminals of power modules502and504that are to be connected to the positive side of the battery180are shown as IT1P or IT2P inFIGS. 20 and 21. Also, the terminals of power modules502and504that are to be connected to the negative side of the battery180are shown as IT1N or IT2N inFIGS. 20 and 21.

A neutral point in the arms of each phase (i.e., a connection between the source electrode of the upper-arm IGBT and the drain electrode of the lower-arm IGBT) is electrically connected to the armature coil of the associated phase of the associated rotating electric machine130or140. These neutral points are shown as terminals OT1u, OT1v, OT1w, OT2u, OT2v, OT2w, inFIGS. 20 and 21.

The driver circuit92,94constitutes a driver of the associated inverter, and in accordance with a control signal output from the control circuit93, generates the driving signal for driving the IGBT21. The driving signal that has been generated in the circuit92or94is output to the associated first power module502or second power module504. The driver circuit92,94is constructed of one circuit into which the plurality of circuits associated with the upper and lower arms of each phase are integrated, that is, the driver circuit is composed of the integrated circuit in which the circuits for driving the six IGBTs are stored into one block. The circuits associated with the upper and lower arms of each phase include interface circuits, gate circuits, abnormality detection circuits, and so on.

The control circuit93constitutes a controller of the associated inverter, and is constructed of a microcomputer that computes control signals (control data) adapted to operate (turn on/off) a plurality of switching power semiconductor elements. Torque command signals (torque command values) from a host controller, and signals (sensor outputs) from the current sensors95,96, and from rotation sensors mounted in the rotating electric machines130,140, are input to the control circuit93. The control circuit93computes control data from these input signals, and outputs switching timing control signals to the driver circuits92,94.

The connector73for electrical connection between the power converter200and an external controller exchanges information with other devices via a communications line174(seeFIG. 1).

Capacitor module300including the capacitor modules302and304shown inFIG. 10constitutes a smoothing circuit to suppress DC voltage fluctuations caused by switching operation of the IGBT21, and is electrically connected in parallel to the DC terminals of the first power module502and second power module504. The driver circuit91drives the discharge circuit (not shown) that is provided to release a stored charge from the capacitor module300.

Second Embodiment

Next, a second embodiment is described below usingFIGS. 23 to 28. The second embodiment is essentially the same as the first embodiment in terms of the basic concept relating to circuit composition (seeFIG. 22), power module structure (seeFIGS. 16 to 21), and cooling water channel structure (seeFIGS. 12 to 15), and in terms of operation and advantageous effects. One difference exists in that whereas the first embodiment has cooling water channels922and926at the bottom of an inverter200, the second embodiment has cooling water channels at a middle stage of an inverter200. In the second embodiment, electrical components to be cooled, such as power modules502,504and capacitor modules302,304, can be mounted on both upper and lower faces of a cooling water channel formation, and both the upper and lower faces can be used for cooling. For example, the second embodiment can be constructed so that the semiconductor modules mounted as the power modules502,504on one face of the cooling water channel formation will be cooled and so that the capacitor modules302,304mounted on the other face of the cooling water channel formation will be cooled.

The second embodiment of the power converter is described in detail below. In the power converter200, a second base12is stacked on a lower casing13, a first base11on the second base12, and an upper casing10on the first base11, and each is fixed in the particular state. The housing, or inverter200, with the above elements stacked in fixed form on one another, has a round-cornered, rectangular parallelepiped shape as a whole. Constituent components of the housing are formed using a material excellent in heat conductivity, such as aluminum. This housing basically having functions equivalent to those of the housing210described in the first embodiment include the upper casing10and the lower casing13. A water channel formation including the first base11and the second base12is fixed to a central section of the housing that includes the upper and lower casings, and electrical components of the power modules and capacitor modules described below are mounted on both faces of the water channel formation.

The above housing has its entire surface (sidewalls, upper wall, and lower wall) surrounded with a material excellent in heat conductivity, such as aluminum, and the cooling water channel including the first base11and the second base12is fixed in an appropriate heat-conductive structure to the housing, so the housing itself is appropriately cooled. The cooling water channel including the first base11and the second base12forms a cooling water channel in the housing, and forms a room at both upper and lower sections of the water channel formation in the housing. The water channel formation includes two channels,922and926, that are arranged in parallel to each other to allow cooling water as a cooling medium to flow through. The two rooms in this structure are thermally separated by the cooling water channels so that thermal impacts of heat transfer from one room to the other room can be suppressed. In addition, the two rooms and walls thereof are cooled.

As shown inFIG. 24, in the upper room of the water channel formation, a first power module502and a second power module504are arranged next to each other in a longitudinal (longer-side) direction of the housing. The cooling water channels922and926have openings218and219, respectively, as described inFIGS. 12 and 13, and heat release fins of the power modules502and504protrude from the openings into the water channels. Also, the openings218and219are blocked with heat release surfaces of the first power module502and the second power module504, and thus, both power modules are efficiently cooled. In addition, thermal impacts of heat transfer from the power modules502and504to the lower room can be suppressed.

As shown inFIG. 27, the housing has, on one side face thereof in the longitudinal direction, an inlet pipe212and outlet pipe214communicating with the cooling water channels922and926, respectively. The cooling water channels922and926extend in parallel to the longitudinal direction of the housing, are bent into a U-shape at opposite longitudinal ends of the housing, and communicate with each other at the opposite longitudinal ends. The water channels in the second embodiment are essentially of the same shape as that of the water channels described inFIGS. 12-14.

As described above, the cooling water channels922and926of the first base11have the openings218and219, respectively, the heat release fins of the power modules502and504protrude from the openings into the water channels, and the openings218and219are blocked with metallic bases23of the power modules502and504. The fins are directly cooled by the cooling medium, and the metallic bases23are cooled efficiently by the cooling medium flowing through the water channels922and926.

The metallic bases23are of the same shape, operation and advantageous effects as those of the metallic base944described inFIGS. 18 and 19, and are constructed of a highly heat-conductive metallic material based on copper, and the heat release fins protruding into the water channels922and926are provided on a face thereof that is close to flow routes of the cooling medium. The heat release fins have the same structure as that of the heat release fins506and507described inFIGS. 18 and 19, an essential cooling area by the cooling medium increases, and a cooling effect by the cooling medium can be improved.

As described inFIG. 14, in the second embodiment, a depth of the first water channel922also increases at its inlet port formed to receive the cooling water supplied from the inlet pipe212, and then decreases at where the heat release fins506protrude. At the water channel bends where the first water channel922and the second water channel924are connected, the water channel922is once again deeper than at the protruding section of the heat release fins506, and is shallow at where the heat release fins507in the second water channel926protrude. At an outlet port of the second water channel926, the water channel is deeper than at where the heat release fins protrude, and connects to the outlet pipe214. These water channels have the same shape and same operation and advantageous effects as those described inFIGS. 12,13, and14, and are constructed so that at where the heat release fins protrude, the heat released therefrom will be exchanged with the entire cooling water as efficiently as possible, and so that sections free from the fins are minimized in fluid resistance. Cooling efficiency of the entire cooling system consequently improves.

The metallic bases23of the power modules502and504are provided so as to block the openings in the respective water channels, and upper faces of the metallic bases23have essentially the same resin casing24as that shown inFIGS. 15 to 21. The resin casing24shown inFIGS. 23-27is the same as the resin casing946shown inFIGS. 14,15, and20. InFIGS. 23 and 24, an upper lid originally provided on the resin casing24of the first power module502is intentionally omitted for a better understanding of the inside of the power module502. Also, of all semiconductor chips (and wiring structures) present in bonded form on the six dielectric substrates of the first power module502that are arrayed in a row inFIG. 24, only two in the middle of the array are shown in detail and details of the other four semiconductor elements are omitted.

On sidewalls of the first power module502and the second power module504each, these sidewalls extending in a longitudinal (longer-side) direction of the resin casing and being positioned at an opposed side of both power modules, a DC positive module terminal26(seeFIG. 24) and a DC negative module terminal33(also, seeFIG. 24) are provided for each storage room. The DC positive module terminal26and the DC negative module terminal33protrude upward from a side of the resin casing24. A side thereof that is opposite to the protruding side of the DC positive module terminal26and DC negative module terminal33extends into the associated storage room, and the surface thereof is exposed to face the surface of the resin casing24. This forms a DC positive module electrode36and a DC negative module electrode37in each storage room. The terminal26is the same as the IT1P and IT2P shown inFIGS. 20 and 21for the first embodiment, and the terminal33is the same as the IT1N and IT2N shown inFIGS. 20 and 21.

In addition, the first power module502and the second power module504each have AC module terminals27(seeFIG. 24) on the respective sidewalls extending in the longitudinal direction of the resin casing and positioned at sides opposite to the opposed sides of the power modules. The AC module terminals27protrude upward from a sidewall of the resin casing24. A side thereof that is opposite to the protruding side of the AC module terminals27extends into the associated storage room, and the surface thereof is exposed to face the surface of the resin casing24. This forms an AC module electrode35in each storage room. The AC terminals27have the same shape and same operational effects as those of the terminals OT1u, OT1v, OT1w, OT2u, OT2v, and OT2wshown inFIGS. 20 and 21for the first embodiment.

On the upper face of the metallic base23of each storage room, two dielectric substrates22are arranged next to each other in the longitudinal direction of the housing. On an upper face of each dielectric substrate22, two plate-like wiring members39(seeFIG. 24) are arranged next to each other in the longitudinal direction of the housing. One of the two wiring members39provided on one of the two dielectric substrates22of each storage room is electrically connected to the DC positive module electrode36. One of the two wiring members39on the other dielectric substrate22of the storage room is electrically connected to the DC negative module electrode37. The other wiring member39on the other dielectric substrate22of the storage room is electrically connected to the AC module electrode35. These electrical connections are each conducted using an electroconductive wire29.

As shown, on an upper face of either of the wiring members39provided on the two dielectric substrates22of each storage room, three pairs of IGBTs21and diodes38lined up in one direction of the housing are mounted next to one another to face in another direction of the housing. This constitutes upper and lower arms of each phase. The IGBTs21and the diodes38are electrically connected to the wiring member39electrically connected to the AC module electrode35. Gate electrodes of the IGBTs21are electrically connected to a connector25. These electrical connections are each conducted using the electroconductive wire29. The connector25is provided on each of the four sidewalls of the resin casing that form three regions of the upper face of the metallic base23. The above IGBTs21and diode chips38are arranged under the same positional relationship as that described inFIG. 16. Each dielectric substrate22in the second embodiment is the same as the dielectric substrate956in the first embodiment, and has the same operation and same advantageous effects as those of the dielectric substrate956.

The resin casing has a plate-like module casing lid34at its upper section. The module casing lid34constitutes an upper wall to shroud an upper opening in the resin casing and block the storage room, and is molded from the same dielectric resin as used in the resin casing. An upper face of the module casing lid34has a wiring sheet31and a wiring connector32electrically connected thereto. The wiring sheet31is electrically connected to the connector25protruding upward from a through-hole in the module casing lid34. The wiring connector32is electrically connected to driver circuits of a first driver circuit board70and a second driver circuit board71via wiring not shown. The driver circuits are the same as the driver circuits92and94shown inFIG. 22, and are the same as the circuits formed on the driver circuit boards602and604of the first embodiment.

In a cooling room formed at a lower section of the housing is disposed a capacitor module300, which includes two capacitor modules,302and304, and is the same as the capacitor module300used in the first embodiment and in the circuit composition ofFIG. 22.

The capacitor module300is disposed so that its electrical terminals are positioned below a central section of the second base12(i.e., a region enclosed in two legs of a π shape) to ensure proximate arrangement with the DC terminals of the first power module502and the second power module504. The capacitor module300includes four electrolytic capacitors whose sectional shape in a height direction of the housing is rectangular. In order for a longer side of each to face in the longitudinal direction of the housing, the four electrolytic capacitors are arranged in groups of two, one group in the longitudinal direction of the housing and the other group in a lateral (shorter-side) direction thereof, and stored in a capacitor casing51via a retaining band52. The capacitor casing51is a heat-conductive container with an open upper end, and a flange on this casing is in contact with lower ends of the π-shaped legs of the second base12. This makes it possible to connect the capacitor module300and the water channels922and926thermally in a highly heat-conductive condition and to sufficiently cool the capacitor module300.

Each electrolytic capacitor has a positive capacitor terminal57and a negative capacitor terminal56, both of which penetrate a capacitor lid54that blocks the opening in the upper section of the capacitor casing53. The positive capacitor terminal57and the negative capacitor terminal56are plate-shaped and laterally face each other, and a dielectric member55formed integrally with the capacitor lid54is laterally inserted between the terminals. The capacitor terminals are provided such that when the four electrolytic capacitors are stored into the capacitor casing53, the capacitors laterally adjacent to each other will differ in longitudinal position.

The first driver circuit board70is disposed below the second base12at the first power module502, and more specifically, in a region enclosed between one of the π-shaped legs of the second base12and a flange section thereof. The second driver circuit board71is disposed below the second base12at the second power module504, and more specifically, in a region enclosed between the other π-shaped leg of the second base12and a flange section thereof. The first driver circuit board70and the second driver circuit board71are thermally connected to the respective second bases12. Thus, the cooling medium flow channels and the driver circuit boards70and71can be thermally connected and the driver circuit boards70and71can be cooled using the cooling water that is the cooling medium.

A rotating electric machine control circuit board74is provided so as to be opposed to one lateral side of the capacitor casing53that faces the second power module504. The rotating electric machine control circuit board74is thermally connected to the second base12. This makes it possible to arrange the water channels922and926and the rotating electric machine control circuit board74in a highly heat-conductive condition and to efficiently cool the rotating electric machine control circuit board74by means of the cooling medium.

A connector board72is provided so as to be opposed to the other lateral side of the capacitor casing53that faces the first power module502. The connector board72is thermally connected to the second base12. This makes it possible to thermally connect the cooling medium flow channel28and the connector board72and to cool the connector board72by means of the cooling medium. The connector73protrudes outward from the other longitudinal edge of the housing.

The capacitor module300, the first power module502, and the second power module504are electrically connected through a DC connection conductor40. The DC connection conductor40is a rectangular hole penetrating a central portion of the first base11and that of the second base12, and the conductor40extends in the longitudinal direction of the housing and leads to the upper and lower cooling rooms via a through-hole penetrating in the height direction of the housing.

The DC connection conductor40is a wiring member of a stacked structure in which: a plate-like DC positive bus bar45and a plate-like DC negative bus bar44, both extending in the longitudinal direction of the housing, are stacked in the lateral direction thereof, a DC positive module terminal42and a positive capacitor terminal46are integrally formed on the DC positive bus bar45, and a DC negative module terminal41and a negative capacitor terminal47are integrally formed on the DC negative bus bar44.

Employing this structure makes it possible to reduce inductance between the first power module502, the second power module504, and a capacitor module50, and reduce temporary rises in voltage during the switching operation of the IGBT21. Temporary rises in voltage can also be reduced, even at higher switching speeds. Faster switching is therefore possible, so a release of heat from the power modules during switching can be suppressed.

The DC positive module terminal42extends upward from an upper section of the DC positive bus bar45, at where the DC positive module terminal33protrudes upward from the resin casing. The above terminal42is fixed to the DC positive module terminal33by means of a screw or any other appropriate fixture so as to face the DC positive module terminal33, in the lateral direction of the housing. In this way, the DC positive module terminal42is electrically connected to the DC positive module terminal33. The DC negative module terminal41extends upward from an upper section of the DC negative bus bar44, at where the DC negative module terminal26protrudes upward from the resin casing. The above terminal41is fixed to the DC negative module terminal26by means of a screw or any other appropriate fixture so as to face the DC negative module terminal26, in the lateral direction of the housing. In this way, the DC negative module terminal41is electrically connected to the DC negative module terminal26.

The positive capacitor terminals46and the negative capacitor terminals47extend downward from lower sections of the DC positive bus bar45and DC positive bus bar44, at where the above capacitor terminals protrude. The capacitor terminals46,47are each sandwiched from the lateral direction of the housing so as to face in the lateral direction thereof, and one capacitor terminal46,47is fixed to the other capacitor terminal46,47of the same polarity by means of a screw or any other appropriate fixture. In this way, one capacitor terminal is electrically connected to the other capacitor terminal. In this wiring structure, since wiring sections extending from the DC positive bus bar45and the DC negative bus bar44to each capacitor terminal can also be opposed with the same polarity, wiring members with further reduced inductance can be obtained and temporary rises in voltage during the switching operation of the IGBT21can be reduced. Since temporary rises in voltage can also be reduced at higher switching speeds, even if a rise to one voltage level is allowed, faster switching is possible, so the release of heat from the semiconductors during switching can be suppressed.

In the above embodiment, it is possible to arrange the cooling water channels in parallel, provide openings in interstitial regions between the water channels, and connect the terminals of the capacitor module300and the DC terminals of the power modules502and504that are semiconductor modules, through the above openings, and thus to implement the improvement of cooling efficiency and the reduction in inductance.

A DC terminal80is provided at the other longitudinal end of the housing. The DC terminal80includes: a DC positive bus bar84that connects a DC positive external terminal82, a DC negative external terminal81, a DC positive connection terminal86, a DC negative connection terminal85, a DC positive external terminal82, and a DC positive connection terminal86; and a DC negative bus bar83that connects the DC negative external terminal81and the negative connection terminal85.

The DC positive external terminal82and the DC negative external terminal81are electrically connected to external cables extending via connectors mounted in through-holes17provided at the other longitudinal edge of the housing. The DC positive bus bar84and the DC negative bus bar83extend towards the first power module502and the second power module504so as to face each other in the lateral direction of the housing. The DC positive connection terminal86is electrically connected to the DC positive module terminal33,42, and the DC negative connection terminal85to the DC negative module terminal26,41.

Holes18in the upper face of the upper casing10are used for connecting external cables to the DC positive external terminal82and the DC negative external terminal81. The holes18are blocked with a lid, except during the connecting operations.

AC bus bars60for three phases are arranged in both lateral ends of the housing. The AC bus bars60extend from the lower room of the cooling water to the upper room thereof via through-holes provided in a vertical direction (height direction of the housing) at an end of each of the first base11and the second base12. An AC module terminal61is formed at one end of the AC bus bar60, located in the upper room of the water channel. The AC module terminal61faces an AC module terminal27, in the lateral direction of the housing, is opposed to the AC module terminal27, and is fixed thereto by means of a fixture such as a screw. In this way, the AC module terminal61is electrically connected to the AC module terminal27. External connection terminals62for connection to the external cables extending to the rotating electric machines130,140are formed at the other end of the AC bus bar60, located in the lower room of the water channel, and the external connection terminals62are held by a terminal holder63.

Reference number14denotes fitting legs adapted to fix the housing of the power converter200to a housing of a transmission105or to an engine104and the housing of the transmission105. The fitting legs14employ stainless steel or any other appropriate rigid material to ensure strength. The fitting legs14are also formed into a U-shape to have resilience for minimum vibration from the transmission105and the engine104.

The first and second embodiments described above improve cooling efficiency since the cooling water channels that are cooling medium passageways have an opening, since heat release fins protrude from the openings into the water channels, and since the cooling water that is the cooling medium cools directly the heat release fins.

In the first and second embodiments described above, in addition to direct cooling of the heat release fins by the cooling water, a structure formed to block each of the above openings with a metallic base plate for bonding the heat release fins improves cooling efficiency and simplifies the structure of the entire device.

In the first and second embodiments described above, in addition to direct cooling of the heat release fins by the cooling water, the fact that DC terminals of power modules with the heat release fins which contain switching semiconductors to constitute inverters are arranged at one side of each of the power modules simplifies capacitor module connection structure and reduces inductance.

In the first and second embodiments described above, the cooling water channels are arranged in parallel, the openings in the cooling water channels are arranged in parallel, and cooling fins protrude towards the openings, whereby the heat release fins are directly cooled. In addition, the fact that the DC terminals of the power modules with the heat release fins which contain the switching semiconductors to constitute inverters are lined up at inner sides of the parallel-arranged water channels simplifies capacitor module connection structure and reduces inductance. Furthermore, since capacitor modules are arranged in parallel in a plurality of split rows and since capacitor module terminals are positioned internally to the parallel arrangement, it is possible to reduce inductance of a DC circuit as well as to improve cooling efficiency and simplify the configuration of the entire device.

In the above power modules, a copper material that contains another metal is used to increase the hardness of the metallic base plates which retain the semiconductor elements and the heat release fins. This makes it possible to suppress the disturbance of planarity due to fin brazing and facilitates subsequent bonding of a dielectric substrate having a plurality of semiconductor chips. In addition, the above dielectric substrate can be easily bonded onto a plurality of positions of one metallic base, and reliability thereof can be maintained over a long period of time.

Next, a semiconductor power module applied to both power converters of the first and second embodiments will be described in detail below with reference being made toFIGS. 28-36.

FIG. 28is a view showing an internal structure of the semiconductor power module described in the above embodiments. The figure shows the internal structure, inclusive of the connections between semiconductor chips and terminals thereof.FIGS. 29A and 29Bare partial enlarged views from which the casing shown inFIG. 28is omitted.FIG. 29Cis a sectional view of DC terminals. The semiconductor chips are fixed to one side of a metallic base944and hermetically sealed with a resin casing946. In the present embodiment, IGBTs952and diodes954, somewhat differently from those described above, are connected in parallel, for composing this parallel circuit increases currents to be controlled. The DC positive terminal IT1P and the DC negative terminal IT1N form a stacked structure in an opposed arrangement, and are connected to the above chips by bonding in the parallel arrangement. These chips constitute a U-phase upper arm of an inverter. The two rows of chips located to the left of the above chips constitute a lower arm of the inverter.

Inductance is reduced to a low level since the DC terminals form the stacked structure that has wide, opposed conductors arranged with an insulator sandwiched therebetween. Terminal GTUU is a gate terminal of the IGBT which controls a U-phase lower arm of the inverter.

The IGBTs952and the diodes954are mounted on a dielectric substrate956formed from aluminum nitride (AlN). Aluminum nitride (AlN) is favorably used because of its excellent heat conductivity. Silicon nitride (SiN) can be used instead of aluminum nitride (AlN). High toughness of silicon nitride (SiN) allows thin formation of the dielectric substrate956.

A full-surface pattern of nickel-plated copper or the like is formed on the metallic base side of the dielectric substrate956, and an electrical wiring pattern of nickel-plated copper or the like is formed on the chip side of the dielectric substrate956. The dielectric substrate956has a metal attached to both sides thereof to allow soldering between the chip952and the metallic base944and to construct the dielectric substrate956into a metals-sandwiched structure. This construction prevents deformation due to a difference in thermal expansion coefficient between the above two metals when temperature changes. As a result of this sandwiched structure being adopted, thinning down the dielectric substrate956induces a greater amount of eddy current into the full-surface pattern on the metallic base side of the substrate according to a particular change in a flow rate of a switching current into the wiring pattern on the chip side of the substrate. This results in the wiring pattern of the dielectric substrate956being reduced in parasitic inductance and contributes to reduction in power module inductance.

For ease in the description of the terminal structure,FIG. 29Bshows the power module, from which the resin casing946shown inFIG. 29Ais removed. The positive terminal IT1P and the negative terminal IT1N have a wide structure and are arranged in an opposed condition with respect to each other.FIG. 30Ashows the terminal structure, in which reference numbers1012and1014denote conductor-side connections on the positive terminal IT1P and the negative terminal IT1N, respectively, with ends of the connections being bent in opposite directions. Reference numbers1022and1024denote intermediate conductors of the positive terminal IT1P and the negative terminal IT1N, respectively, and form a stacked structure with a sheet insulator interposed between the intermediate conductors.

Reference numbers1032and1034denote chip-side connections on the positive terminal IT1P and the negative terminal IT1N, respectively, and both connections are bent in the same direction. The chip-side connections1032and1034differ from each other in length because the connections are later connected in parallel to the conductors electrically connected to the semiconductor chip. InFIG. 29A, wire bondings are arranged in a parallel-like fashion, which reduces inductance. InFIG. 29A, terminal OT1U is a U-phase terminal of the terminals formed to output three-phase power. InFIG. 29C, nuts1112and1114are embedded in the resin casing in order to facilitate terminal connection to the conductor terminals, and as shown inFIG. 30, the conductor-side connections have a screw insertion hole for fastening with screws.

Reference numbers1032and1034denote the chip-side connections on the positive terminal IT1P and the negative terminal IT1N, respectively, and both connections are bent in the same direction. The chip-side connections1032and1034differ from each other in length because the connections are later connected in parallel to the conductors electrically connected to the semiconductor chip. The chip-side connections on the flat-plate-like positive and negative terminal conductors stacked via an insulator in this manner are bent in the same direction to constitute the two stacked flat-plate conductor planes. This allows a wiring pattern to be formed in parallel to the edge side of the dielectric substrate that is the closest to the terminals. This, in turn, makes it possible to miniaturize the dielectric substrate without creating a superfluous space thereon. InFIG. 29A, wire bondings are arranged in a parallel-like fashion, and directions of the currents flowing into the wire bondings connected to the positive and negative terminals will be opposite to each other. Consequently, inductance will decrease since the magnetic fields created by the currents will counteract each other. InFIG. 29A, terminal OT1U is a U-phase terminal of the terminals formed to output three-phase power. InFIG. 29C, the nuts1112and1114are embedded in the resin casing in order to facilitate terminal connection to the conductor terminals, and as shown inFIG. 30, the conductor-side connections have a screw insertion hole for fastening with screws. At these connections, as described above, the directions of the currents flowing into the capacitor terminal connections and the power module terminal connections will be opposite to each other. Accordingly, inductance will decrease since the magnetic fields created by the currents will counteract each other.

FIGS. 31A and 31Bshow yet another example, which employs a terminal structure in which the positive terminal IT1P and the negative terminal IT1N are arranged at different heights to increase an electrical withstand pressure between the two terminals. Changing the layout height extends a creeping distance and increases dielectric strength. Layout height of the capacitor terminals, as with that of the above power module terminals, is changed to fit the particular power module connections. This ensures an appropriate dielectric creeping distance for the capacitors. In addition, when the power module terminals and the capacitor module terminals are connected, the directions of the currents flowing into the connections will be opposite to each other. Consequently, inductance can be reduced since the magnetic fields created by the currents will counteract each other. In the flat plate conductors elongated when the layout height of the power module and capacitor terminals, the directions of the currents flowing into the conductors will be opposite to each other. Consequently, parasitic inductance can be reduced since the magnetic fields created by the currents will counteract each other.

FIG. 32Bis a detailed sectional view of the connections between the DC terminal pair formed at the power module side, and the DC terminal pair formed at the capacitor side. The DC terminal pair at the power module side is constituted by stacking a positive terminal IT1P and a negative terminal IT1N as flat plate conductors via an insulator1288. The positive terminal IT1P and the negative terminal IT1N are bent in opposite directions to each other at respective front ends. The bent ends serve as the connection planes electrically connected to the positive terminal IT1P and negative terminal IT1N forming the DC terminal pair at the capacitor side. The DC terminal pair at the power module side and the DC terminal pair at the capacitor side are fixed to the connection planes by means of screws.

The DC terminal pair at the capacitor side is constituted by stacking a positive terminal1424P and a negative terminal1424N as flat plate conductors via a sheet insulator1289. An insulator1288for the DC terminal pair at the power module side is formed so as to protrude above the peripheral resin section in order to ensure a creeping distance. For this reason, the insulator1288at the power module side and the sheet insulator1289at the capacitor side overlap each other at respective front ends.

FIGS. 32C to 32Gshow different, further examples of the connection structure shown inFIG. 32B. In each of these examples, the construction of the insulator1288and that of the sheet insulator1289are appropriately modified to ensure the creeping distance.

FIG. 32Cshows a structure that has two protrusions at the front end of the insulator1288for the power module. The sheet insulator1289for the capacitor is disposed between the two protrusions of the insulator1288. That is to say, in this case, the insulator1288at the power module side and the sheet insulator1289at the capacitor side also overlap each other at the respective front ends.

Flow routes of switching currents in the terminals are shown as a broken line inFIG. 32C. As shown therein, currents of the same polarity counteract each other at the terminal connection, whereas currents different in polarity counteract each other at the stacked section having an insulator inserted therein. The magnetic fluxes created by the currents will therefore counteract each other, which will make it possible to reduce parasitic inductance of the terminal connection.

FIG. 32Dshows a construction in which the power module insulator1288has its front end bent towards the positive terminal IT1P. In order for the positive terminal IT1P to accommodate the vent insulator1288, the terminal IT1P has a planar region, except at where the terminal comes into contact with the positive terminal1424P at the capacitor side. A front end of the vent insulator1288is accommodated in the planar region. In addition, the insulator has a face positioned internally to the connection plane. Adopting this structure makes it possible to avoid deterioration due to cracking or other unusual events associated with application of stresses to the insulator during connection.

The sheet insulator1289at the capacitor side also has a front end bent towards the positive terminal1424P. As a result, the insulator1288at the power module side and the sheet insulator1289at the capacitor side overlap each other at the respective front ends. The two insulators overlap during connection, thus double-ensuring adequate insulating characteristics during the connection.

FIG. 32Eshows a construction in which the front ends of the positive terminal IT1P and negative terminal IT1N at the power module side are changed in height. In this figure, the negative terminal IT1N is constructed to be higher than the positive terminal IT1P. Accordingly, the front end of the insulator1288protrudes at the negative terminal IT1N. Also, the sheet insulator1289at the capacitor side extends to a bent section of the positive terminal1424P, and the sheet insulator1289has a front end positioned at the positive terminal IT1P free from the insulator1288. As a result, the insulator1288at the power module side and the sheet insulator1289at the capacitor side overlap each other at the respective front ends. The internal insulator of the capacitor terminal pair and that of the power module terminal pair are formed so that total thickness of the two insulators existing when overlapped on each other will be smaller than maximum thickness of the capacitor terminal or power module terminal pair's insulator, whichever is the larger. It becomes possible, by doing so, to avoid deterioration due to cracking or other unusual events associated with insulator stressing during connection. Such deterioration can also be avoided in a polarity-inversed construction.

FIG. 32Fshows a construction in which the front end of the insulator1288at the power module side is formed at a position higher than the peripheral resin section. At the negative terminal IT1N, the front end of the insulator1288extends to a position higher than the peripheral resin section, whereas, at the positive terminal IT1P, the front end is located at a position lower than the peripheral resin section. Also, the sheet insulator1289at the capacitor side extends to the positive terminal1424P for the power module. As a result, the insulator1288at the power module side and the sheet insulator1289at the capacitor side overlap each other at the respective front ends. This can also be realized in a polarity-inversed construction.

InFIG. 32G, although the construction of the power module terminal insulator is the same as that shown inFIG. 32D, the construction of the capacitor terminal insulator differs from that shown inFIG. 32D. InFIG. 32G, the sheet insulator1289has a front end bent towards the negative terminal IT1N, that is, in a direction opposite to the bending direction of the insulator1288. In this case, the insulator1288at the power module side and the sheet insulator1289at the capacitor side also overlap each other at the respective front ends. This can also be realized in a polarity-inversed construction.

In addition, while the insulator1288is formed from essentially the same resin as used in the peripheral resin section, the insulator is not limited to this kind of material and can use, instead of resin, essentially the same sheet insulator material as that used at the capacitor side. In that case, the sheet insulator will protrude from the terminal pair. When the sheet insulator is used, parasitic inductance can be further reduced since the distance between the stacked conductors will be shorter than that of the paired terminals formed using the stacked conductors that have a molded insulator such as resin.

It is possible to embed terminals and a sheet insulator in resin and then form a resin casing integrally with the resin-embedded terminals and sheet insulator. Alternatively, it is realizable to create the resin casing beforehand and then insert the terminals and the sheet insulator. In the latter case, when solder is used to connect the terminals to a wiring pattern on a dielectric substrate or when ultrasonic, welding, or any other bonding method is used to directly bond the metals of the terminals and the metal of the wiring pattern on the dielectric substrate, height adjustment of the connection surface becomes easy since the resin casing and the terminals are independent of each other.

FIG. 33Ashows a further example employing a structure in which the power module500, the water channel formation220, and the capacitor module300are integrated. The power module500and the capacitor module300are arranged at opposite sides of the water channel formation220, and a conductor1502of a stacked structure, inclusive of a wide conductor and a sheet insulator, is formed to connect DC terminals.FIG. 33Bshows the integrated structure, with the stacked conductor being positioned next to the water channel formation220, and with the DC terminals being connected in that state.FIG. 33Cis a sectional view of a power converter including the stacked structure. Since the water channel formation for cooling is sandwiched between the power module and the capacitor module, reliability of both improves since highly efficient release of heat and reduction in the amount of heat, based on inductance reduction, become possible. The capacitor module300includes a wired capacitor element302on a flat plate conductor301having two stacked flat plate conductors with an insulator therebetween. Terminals of the capacitor module300are formed by bending an end of the flat plate conductor301with the stacked conductors remaining therein, and then bending both ends in opposite directions.

FIG. 34shows a further example of terminals of the power module500, with each of the chip-side connections1032and1034being constructed into a plurality of leads. Front ends of the chip-side connections1032and1034are bent in opposite directions and connected by soldering or the like.

FIGS. 35A and 35Bshow further examples. In both of the examples, a positive wide conductor IT1P and a negative wide conductor IT1N form a stacked structure with an insulator1288sandwiched therebetween. The chip-side connections1032and1034on these terminals are constructed as a plurality of leads, and are connected to chip-side conductors by solder connection or ultrasonic connection. Although somewhat different in form of terminal bending, the examples shown inFIGS. 35A and 35Bare the same in operational effectiveness.

FIGS. 36A and 36Bare respectively a perspective view and exploded view showing a further example of a DC terminal pair for a power module. The DC terminal pair in these figures has a sheet insulator1289′ interposed between a positive terminal IT1P and a negative terminal IT1N. If, as shown in the figures, essentially the same sheet insulator1289′ as that used at the capacitor module side is also applied to the DC terminal pair used at the power module side, a distance between the positive terminal IT1P and the negative terminal IT1N can be narrowed down in comparison with using an insulator1288made of a resin material. Accordingly, inductance in the power module can be further reduced.

FIG. 36Cis a sectional view of section C-C′ inFIG. 36A. Forming a positive terminal IT1P and a negative terminal IT1N by die punching results in a sagging surface1300and a burred surface1400being generated. Since the burred surface has a sharp edge, sheet insulator1289′ is likely to be damaged. For this reason, each terminal preferably has a sagging surface positioned near the sheet insulator1289′. This prevents the sheet insulator1289′ from being damaged at the burred surface, even if either terminal shifts in position. In that case, reliability of insulating characteristics in the positive/negative DC terminal pair can be enhanced as a result.

If the sheet insulator1289′ is to be contained in the power module casing molded, the sheet insulator is preferably a highly heat-resistant sheet insulator such as polyamideimide highly durable at high temperature. This prevents the insulator from being fused by heat as high as about 300° C. during molding. If the sheet insulator is to be inserted between terminals following completion of power module molding, the insulator can be a relatively inexpensive, meta-based aramid fiber capable of withstanding at least a maximum semiconductor junction temperature of 150° C. (preferably, up to 260° C.).

If the associated terminals are of an internally bent structure, adhesion of the sheet insulator1289′ with respect to the terminals at the bends thereof can be improved by thinning down the sheet insulator to 50 μm or less.

Adopting any one of the above structures makes it possible to reduce below 30 nH the main circuit inductance with the modules and capacitors combined. Also, using a thin dielectric substrate such as that of silicon nitride allows the inductance to be further reduced below 20 nH, for example. Accordingly, an increase rate of voltage can be controlled to stay within its permissible range, even if, for example, an on-to-off switching time of the semiconductor chip of the inverter is reduced below 2.0 μs, or further below 1.2 μs, or further below 1.0 μs. The normal DC voltage attained at that time ranges from 300 V to 600 V. Consequently, the device can be operated, even at a maximum current variation (di/dt) of 2 kA/μs, preferably, 4 kA/μs or more.

Speeding up the switching of the semiconductor chip in this manner to shorten the switching time makes it possible to reduce the amount of switching heat generated and released from the semiconductor chip. A less expensive inverter with a smaller silicon area on a semiconductor chip can be consequently realized.