Easy-to-assemble structure of power converter

An easy-to-assemble structure of a power converter includes a control circuit board, semiconductor modules with power terminals and control terminals extending therefrom, and a capacitor to smooth voltage to be applied to the semiconductor modules. The capacitor includes capacitor devices coupled to the power terminals and voltage measuring terminals joined to electrodes of the capacitor devices. The control terminals and the voltage measuring terminals extend in a direction normal to the surface of the control circuit board. This permits the connections of the voltage measuring terminals and the control terminals with the control circuit board to be achieved simultaneously by bringing them close to the control circuit board from the normal direction.

CROSS REFERENCE TO RELATED DOCUMENT

The present application claims the benefit of priority of Japanese Patent Application Nos. 2011-117630 and 2012-52397 filed on May 26, 2011 and Mar. 9, 2012, disclosures of which are incorporated herein by reference.

BACKGROUND

1. Technical Field

This application relates generally to a power converter equipped with a semiconductor module and a capacitor working to smooth the voltage applied to the semiconductor module.

2. Background Art

FIG. 43illustrates a conventional power converter9, as taught in Japanese Patent First Publication No. 2010-119274, which works to perform power conversion between DC power and AC power. The power converter consists of a plurality of semiconductor modules92in which semiconductor devices are installed and a cooling pipe which dissipates thermal energy from the semiconductor modules92.

Each of the semiconductor modules92includes a plurality of power terminals98and control terminals921. The power terminals98are broken down into a positive terminal98ato be connected to a positive electrode of a dc power supply (not shown), a negative terminal98bto be connected to a negative electrode of the dc power supply, and ac terminals98cto be coupled to an ac load (not shown). The control terminals921are coupled to a control circuit board94. The control circuit board94works as a controller to control operations of the semiconductor modules92to translate a dc voltage applied to the positive terminal98aand the negative terminal98binto an ac voltage which is to be outputted from the ac terminals98c.

The power terminals98ato98care coupled to bus bars99(i.e., a positive bus bar99a, a negative bus bar99b, and an ac bus bar99c). Specifically, the power terminals98aand98bare joined to the dc power supply through the positive terminal98aand the negative terminal98b. The ac terminal98cis joined to the ac load. A smoothing capacitor97is connected to the positive bus bar99aand the negative bus bar99b.

The control circuit board94has fabricated thereon a voltage detector which monitors the voltage developed at the smoothing capacitor97. The monitored voltage is used for controlling the operation of the ac load. The smoothing capacitor97is coupled to the voltage detector through wires95and an electric connector96.

The power converter9, however, faces the problem that the assembling of the power converter9requires two discrete steps: one is to join the semiconductor modules92to the control circuit board94, and the other is to connect the smoothing capacitor97to the control circuit board94.

Specifically, the production of the power converter9needs two connecting steps of putting the control terminals921into connector holes93formed in the control circuit board94and then drawing the wires95from the smoothing capacitor97to joint them to the connector96.

SUMMARY

It is therefore an object of this disclosure to provide an improved structure of a power converter which is designed to connect semiconductor modules and a capacitor to a control circuit board in a decreased number of steps.

According to one aspect of an embodiment, there is provided a power converter which may be employed in automotive vehicles such as electric cars or hybrid cars. The power converter comprises: (a) a control circuit board; (b) a plurality of semiconductor modules each of which includes a main unit in which semiconductor devices are fabricated, the main unit having power terminals and control terminals extending therefrom; (c) a capacitor working to smooth voltage to be applied to the semiconductor modules, the capacitor including capacitor devices coupled to the power terminals and voltage measuring terminals coupled to electrodes of the capacitor devices; (d) a control circuit disposed on the control circuit board to control switching operations of the semiconductor devices of the semiconductor modules; and (e) a voltage detector disposed on the control circuit board to measure voltages applied to the capacitor devices. The control terminals extend in a direction normal to a surface of the control circuit board in connection with the control circuit. The voltage measuring terminals extend in a direction normal to the surface of the control circuit board in connection with the voltage detector. Therefore, in assembling of the power converter, the connections of the voltage measuring terminals and the control terminals with the control circuit board may be achieved simultaneously by bringing the voltage measuring terminals and the control terminals close to the control circuit board from the normal direction. This eliminates the need for two discrete steps of connecting the voltage measuring terminals to the control circuit board and connecting the control terminals to the control circuit board, thus resulting in a decrease in number of steps of assembling the power converter.

Additionally, the connection of the capacitor to the voltage detector is achieved without need for an additional step of, for example, drawing wires from the capacitor, as illustrated inFIG. 43. The wires are usually flexible. It is, thus, difficult to draw the wires from the capacitor and connect them to a connector automatically. In contrast, the voltage measuring terminals are not flexible, thus facilitating the ease with which the capacitor is joined to the voltage detector.

All of the voltage measuring terminals may be laid to overlap the control circuit board, as viewed from the direction normal to the surface of the control circuit board. In other words, the voltage measuring terminals are all disposed inside the control circuit board, as viewed from the normal direction, thus permitting the power converter to be reduced in size.

The capacitor and the semiconductor modules may be arrayed adjacent each other in a direction parallel to the major surface of the control circuit board. This permits the capacitor and the semiconductor modules to be located as close to each other as possible, thus allowing bus bars connecting the capacitor and the semiconductor modules to be decreased in length.

Each of the voltage measuring terminals may be made up of a first section joined to one of the capacitor devices and a second section made to be separate from the first section. The second section is secured to the first section and couple with the voltage detector. This results in a decrease in production cost of the power converter. Usually, it is necessary to make the voltage measuring terminal to integrally include a portion which is to be in electric contact with the electrode of the capacitor device. The voltage measuring terminal is made of, for example, a metal strip. If the voltage measuring terminal is made of a one-piece strip, it will be longer than each of the first and second sections. For instance, when the measuring terminal is cut out, as illustrated inFIG. 42, from the metal plate70into an L-shape, it produces the large useless portion72. The structure of the voltage measuring terminal is designed to eliminate such a problem. The voltage measuring terminal is, as described above, made up of two discrete parts: the first and second sections, thus permitting the first section to be decreased in length to increase the area of the useless portion72. This results in a decrease in production cost of the voltage measuring terminals.

The second section may be made of a one-piece member of a combination of a plurality of discrete members.

The second section may have a portion extending parallel to the major surface of the control circuit board. A joint of the second section to the first section may be located away from a joint of the second section to the voltage detector, as viewed from the direction normal to the major surface of the control circuit board. In other words, a portion of the first section of the voltage measuring terminal extending outside the capacitor may be located away from the voltage detector, thereby resulting in an increase in freedom of arrangement of the voltage detector on the surface of the control circuit board.

The power converter may also include a terminal module in which the second sections of all of the voltage measuring terminals are disposed inside a sealed capsule. This facilitates the ease with which the first and second sections are aligned with each other and joined together.

Either of the first and second sections may have a protrusion at which the first and second sections are welded. The second section may have a width which is greater than a tolerance for misalignment of the first section in a width-wise direction of the second section. The welding of the first and second sections may, thus, be achieved by pressing the tip of the protrusion against the surface of the second section, in other words, established at a small contact area between the first and second sections, thus resulting in a decreased amount of thermal energy, as generated by the resistance welding, which facilitates the ease of welding operation.

The width of the second section is, as described above, is selected to be greater than the tolerance for misalignment of the first section in the width-wise direction of the second section during the assembling of the capacitor, thereby ensuring the stability in contact, that is, welding between the first and second sections at the protrusion even when the first section is misaligned in the width-wise direction of the second section.

The capacitor may have a casing in which the capacitor devices are disposed and has an opening through which the capacitor devices are to be installed. The capacitor is retained or fixed with the opening facing the semiconductor modules. This permits bus bars connecting the capacitor and the semiconductor modules to be decreased in length. This results in a decrease in inductance L of the bus bars, which leads to a reduction in surge voltage V (=Ldi/dt) which occurs when the semiconductor modules are turned on or off.

The casing may have positioning grooves in which the voltage measuring terminals are fit. This facilitates the ease with which the voltage measuring terminals are positioned relative to the control circuit board and joined thereto in assembling of the power converter.

Each of the positioning grooves may have formed on an inner wall thereof a pair of protrusions which create a nip through which a corresponding one of the voltage measuring terminals extends. This improves the resistance of the voltage measuring terminal to mechanical vibration and the accuracy in positioning the voltage measuring terminal. This facilitates the ease with which the voltage measuring terminals are positioned relative to the control circuit board and joined thereto in assembling of the power converter.

The control circuit board may be designed to have a high-voltage region to which voltage to be developed at the power terminals is applied and a low-voltage region to which the voltage lower than the voltage to be developed at the power terminals is applied. The voltage detector is disposed on a peripheral area of the low-voltage region. This permits an available area of the control circuit board where electronic parts are to be mounted to be increased. Since the higher voltage is applied to the high-voltage region, an insulating region needs to be provided between the high-voltage region and the low-voltage region. Similarly, since the higher voltage is applied to the voltage detector, an insulation region (i.e., a detector insulating region needs to be disposed around the voltage detector. It is impossible to mount the electronic parts over the insulating region and the detector insulating region. If the voltage detector is disposed in the center of the low-voltage region, a need will arise for increasing the size of the detector insulating region, so that an area of the low-voltage region occupied by the detector insulating region is increased, thus resulting in a decrease in available area of the control circuit board. The voltage detector in this disclosure is, however, disposed on the peripheral area of the low-voltage region, thus decreasing the area of the low-voltage region occupied by the detector insulating region. The detector insulating region may be laid to overlap the insulating region partially, so that such an overlap serves as both a portion of the insulating region and a portion of the detector insulating region, thus resulting in a decreased area of the low-voltage region occupied by the detector insulating region, that is, an increased available area of the control circuit board.

The control circuit board may have an insulating region which delimits and electrically insulates between the high-voltage region and the low-voltage region. The voltage detector is disposed in abutment with a side edge of the control circuit board and the insulating region. This enables the insulating region and the detector insulating region to overlap each other partially, so that the overlap may be functionally shared by the insulating region and the detector insulating region. This results in a decreased area of the control circuit board occupied only by the detector insulating region. The area of the voltage detector may extend until the side edge of the control circuit board. This eliminates the need for the detector insulating region to surround the entire periphery of the voltage detector, thereby further decreasing the area of the control circuit board occupied only by the detector insulating region, thus resulting in an increase in available area of the control circuit board.

A portion of the control terminals of each of the semiconductor modules works as a low-potential terminal coupled electrically to low-potential electrodes of the capacitor devices. The voltage measuring terminals is coupled electrically to high-potential electrodes of the capacitor devices. The voltage detector is disposed adjacent to the low-potential terminals and uses the low-potential terminals and the voltage measuring terminals to measure the voltage developed at the capacitor. In other words, the power converter is designed to use a portion of the control terminals of the semiconductor modules to measure the voltages appearing at the capacitor devices, thus permitting the number of the voltage measuring terminals to be decreased.

The casing may be designed to have an outer wall on which terminal holders are formed. Each of the terminal holders is made up of a pair of protrusions which hold a portion of one of the voltage measuring terminals in contact therewith. A contact of one of the pair of protrusions with the one of the voltage measuring terminals is located closer to the opening of the casing than the other of the pair of protrusions. This ensures the enhanced stability in retaining the voltage measuring terminal on the casing, which improves the accuracy in positioning the voltage measuring terminal to facilitate the ease with which the voltage measuring terminal is joined to the control circuit board. The casing may be made of resin and have the advantage that it is insusceptible to breakage. If the contacts of the protrusions with the voltage measuring terminal are arrayed in alignment with each other in a direction in which the voltage measuring terminal is held, it will result in a decreased linear interval therebetween. This requires the need for using resin-molding dies in which projections for forming the contacts are located close to each other to make the casing. The decreasing of the linear interval requires the projections of the resin-molding die to have a decreased width, which will be subjected to breakage during use. In contrast, the contacts of the protrusions of the terminal holder with the voltage measuring terminal are offset from each other to increase the liner interval therebetween, thus enabling the distance between the projections of the resin-molding dies to be increased to avoid the breakage thereof in the course of forming the casing.

A given number of the terminal holders are provided to hold each of the voltage measuring terminals. In other words, the terminal holders are broken down into a plurality of groups each for one of the voltage measuring terminals. The terminal holders of each group are broken down into two types: a projection terminal holder and a flat face terminal holder. The protrusions of the projection terminal holder have projections which form a grip through which one of the voltage measuring terminals passes. The protrusions of the flat face terminal holder have flat faces which are placed in surface contact with the one of the voltage measuring terminals. The flat face terminal holder is located closer to the control circuit board than the projection terminal holder.

In short, the projection terminal holder serves to retain the voltage measuring terminal firmly, thus enhancing the resistance of the voltage measuring terminal to the mechanical vibration.

The contacts of the protrusions of each of the terminal holders with the voltage measuring terminal are shifted from each other, in other words, arranged out of alignment with each other in the direction perpendicular to the length of a corresponding one of the voltage measuring terminals. The holding of the voltage measuring terminal by the contacts may, therefore, result in bending thereof, which increases the difficulty in joining the voltage measuring terminals to the control circuit board. In order to alleviate this problem, each of the groups of the terminal holders has at least the one flat face terminal holder to hold the voltage measuring terminal by the flat faces placed in direct contact therewith, thereby enhancing the accuracy in orienting or positioning the voltage measuring terminal on the casing to facilitate the ease with which the voltage measuring terminal is joined to the control circuit board.

Each of the voltage measuring terminals may be designed to have reinforcement ribs which are placed in contact with a corresponding one of the terminal holders and extend substantially parallel to an outer wall of the casing.

Each of the reinforcement ribs works to increase the mechanical strength of the voltage measuring terminal, which increases the resistance of the voltage measuring terminal to bending thereof when inserted and held between the protrusions of the terminal holder. This results in improvement of stability of orientation of the voltage measuring terminal, thereby facilitating the ease with which the voltage measuring terminal is joined to the control circuit board.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings, wherein like reference numbers refer to like parts in several views, particularly toFIGS. 1 and 2, there is shown a power converter1which may be mounted in automotive vehicles such as electric vehicles or hybrid vehicles. The power converter1is equipped with a plurality of semiconductor modules2, a capacitor3, and a control circuit board4. Each of the semiconductor modules2includes a main unit22in which semiconductor devices23, as illustrated inFIGS. 5 and 6, are fabricated. The main unit22has power terminals20and control terminals21extending therefrom.

The capacitor3is, as illustrated inFIG. 2, equipped with a plurality of capacitor devices30(four capacitor devices30in this embodiment) connecting with the power terminal20, a housing or casing31in which the capacitor devices30are disposed, and voltage measuring terminals32connecting with electrodes38of the capacitor devices30.

The control circuit board4has disposed thereon a control circuit43, as illustrated inFIG. 4, which works to control switching operations of the semiconductor modules2and a voltage detector42which works to measure the voltage applied to the capacitor devices30.

The control terminals21extend in a direction (i.e., the Z-direction inFIG. 2) normal to the major surface of the control circuit board4and connect with the control circuit43.

The voltage measuring terminals32extend in a direction (i.e., the Z-direction) normal to the major surface of the control circuit board4and connect with the voltage detector42.

The control terminals21and the voltage measuring terminals32, as can be seen fromFIG. 2, have end portions extending in the Z-direction. The control circuit board4, as illustrated inFIG. 4, has formed therein a plurality of through holes44and45opening in the Z-direction. To the holes44and45, the ends of the control terminals21and the voltage measuring terminals32are inserted from the Z-direction. The control terminals21are connected electrically to the control circuit board4. The voltage measuring terminals32are connected electrically to the control circuit board4.

Each of the semiconductor modules2is, as can be seen fromFIG. 2, equipped with a plurality of power terminals20. The power terminals20include positive terminals20awhich, as illustrated inFIG. 5, connect with a positive electrode of a dc (direct current) power supply19, negative terminals20bwhich connect with a negative electrode of the dc power supply19, and ac (alternating current) terminals20cwhich connect with an ac load60. The control circuit board4is, as described above, joined to the control terminals21of the semiconductor modules2and works to control the switching operations of the semiconductor modules2to convert the dc voltage, as developed between the positive terminals20aand the negative terminals20binto the ac voltage which is, in turn, outputted from the ac terminals20c.

The semiconductor modules2and the capacitor3are, as illustrated inFIG. 2, located adjacent each other in a direction parallel to the major surface48of the control circuit board4.

The semiconductor modules2and a plurality of cooling pipes12are laid to overlap each other to form a semiconductor stack10. The cooling pipes12have formed therein coolant paths11through which a cooling medium or coolant16flows.

The cooling pipes12, as clearly illustrated inFIG. 3, extend in a longitudinal direction of the semiconductor module1, that is a direction in which the semiconductor modules2are stacked (i.e., the X-direction). Every adjacent two of the cooling pipes12are joined together at ends thereof opposed to each other in the Y-direction through a pair of connecting pipes18. The outermost one of the cooling pipes12in the X-direction, that is, the cooling pipe12ais joined to an inlet pipe14through which the coolant16is loaded into the cooling paths11and an outlet pipe15through which the coolant16is discharged from the cooling paths11. After entering the cooling paths11from the inlet pipe14, the coolant16is distributed to the cooling paths11, respectively, and flows out of the outlet pipe15, thereby absorbing the thermal energy, as produced by the semiconductor modules2, to cool the whole of the semiconductor stack10.

The power converter1is equipped with a metallic frame13which is of a substantially rectangular shape. A spring17is, as illustrated inFIGS. 1 and 3, disposed between one of the cooling pipes12which is located at the end of the semiconductor stack10, that is the leftmost cooling pipe12band an inner end wall131of the frame13. The spring17urges the semiconductor stack10elastically against the inner end wall131of the frame13to bring the cooling pipes12into constant abutment with the semiconductor modules2and also to retain the semiconductor stack10within the frame13.

The spring17may alternatively be disposed between the leftmost cooling pipe12aand an inner end surface of the frame13to urge the semiconductor stack10into constant abutment with the inner end wall131of the frame13.

The frame13, as illustrated inFIG. 3, has formed therein a chamber S in which the capacitor13is retained. The frame13also has formed therein a plurality of mount holes361with internal threads360. In assembling of the power converter1, the capacitor3is, as illustrated inFIG. 1, installed in the mount chamber S, after which bolts36secured to the capacitor3are fastened into the mount holes361to fix the capacitor3to the frame13.

To the positive terminals20aof the semiconductor modules2, a positive bus bar7ais welded. Similarly, to the negative terminals20bof the semiconductor modules2, a negative bus bar7bis welded. The negative bus bar7bis partially covered with a resinous insulator73. The positive bus bar7ais placed on the surface of the insulator73. The positive bus bar7a, the negative bus bar7b, and the insulator73are united to form a bus module74.

The capacitor3is made up of the capacitor devices30, the casing31in which the capacitor devices30are disposed, and a resinous capsule33by which the capacitor devices30are sealed within the casing31. The plurality of capacitor devices30are, as described above inFIG. 1, retained within the casing31. The casing31has formed therein an opening310through which the capacitor devices30are to be installed in the casing31. The capacitor3is secured to the frame13with the opening310of the casing31facing the semiconductor modules2.

Each of the capacitor devices30has ends38which are opposed to each other in the X-direction in which the power terminals20extend. The ends38serve as electrodes38aand38bconnecting electrically with the power terminals20.

The electrodes38aand38bof each of the capacitor devices30have metallic connecting plates39which will also be indicated by39aand39bbelow. Each of the connecting plates39is bent within the casing31to have ends390extending outside the capsule33. The ends390extend parallel to the Y-direction at heights substantially equal to that of the ends200of the power terminals20. In other words, the ends390are oriented substantially in alignment with the ends200of the power terminals20in the Y-direction and secured to the positive bus bar7athrough bolts395.

The capacitor3is also equipped with the voltage measuring terminals32, as described above. The voltage measuring terminals32extend from the connecting plates39boutside the capsule33toward the semiconductor modules2in the Y-direction, bent at right angles toward the control circuit board4in the Z-direction, and then connect with the voltage detector42on the control circuit board4. The voltage measuring terminals32are each made of a metallic plate and have a given degree of rigidity. Each of the connecting plates39and a corresponding one of the voltage measuring terminals32are made of a one-piece member.

The whole of the voltage measuring terminals32is, as can be seen fromFIGS. 1 and 2, laid to overlap with the control circuit board4, as viewed from the Z-direction. In other words, as viewed from the Z-direction, the voltage measuring terminals32are all disposed inside the control circuit board4.

The capacitor3is, as described inFIG. 1, made up of the capacitor devices30. Two of the capacitor devices30work as a filter capacitor device30a, as illustrated inFIG. 5, to smooth the voltage at the dc power supply19before being stepped up. The other capacitor devices30work as a main capacitor device30bto smooth the voltage after being stepped up. These two types of capacitor devices30aand30bare connected electrically at the lower potential electrodes38thereof to the common connecting plate39, while they are connected electrically at the higher potential electrodes38to the connecting plates39, respectively.

Referring back toFIG. 1, the power converter1is equipped with the three voltage measuring terminals32. One of the voltage measuring terminals32serves as a first voltage measuring terminal32awhich is connected to the lower potential electrodes38of the capacitor devices30aand30b. One of the voltage measuring terminals32serves as a second voltage measuring terminal32bwhich is connected to the higher potential electrode38of the filter capacitor device30a. The other voltage measuring terminal32serves as a third voltage measuring terminal32cwhich is connected to the higher potential electrode38of the main capacitor device30b. The voltage measuring terminals32a,32b, and32care used to measure the voltage VLat the dc power supply19before being stepped up and the voltage VHat the dc power supply19after being stepped up. The voltages VLand VHare used to control the operation of the ac load60.

The circuit structure of the power converter1will be described with reference toFIG. 5. The power converter1is equipped with a step-up circuit (e.g., a step-up transformer)61which works to step-up the dc voltage developed at the dc power supply19and an inverter62which works to translate the step-upped voltage into an ac voltage. The step-up circuit61is made up of two semiconductor devices23(e.g., IGBTs) and a choke coil63. Each of the semiconductor devices23has a freewheel diode24connected parallel thereto in a backward direction.

The step-up circuit61consists of the semiconductor devices23which are broken down into upper-arm semiconductor devices23awhich are connected at collectors thereof (i.e., the positive terminals20a) to the positive bus bar7aand lower-arm semiconductor devices23bwhich are connected at emitters thereof to the negative bud bar7b. Each of the semiconductor modules2has one of the upper-arm semiconductor devices23aand one of the lower-arm semiconductor devices23bwhich are sealed therein. The emitter of the upper-arm semiconductor device23aand the collector of the lower-arm semiconductor device23bare connected electrically to the ac terminal20cwithin the semiconductor module2.

Each of the semiconductor modules2is, as illustrated inFIG. 6, equipped with the ten control terminals21. The control terminals21include temperature-sensing cathodes K for use in measuring the temperature of the semiconductor module2, temperature-sensing anodes A for use in measuring the temperature of the semiconductor module2, gates G of the semiconductor devices23(IGBTs) inFIG. 6, current-sensing emitters SE for use in taking out a portion of emitter current, and kelvin emitters KE at which a reference potential is developed for the gates G. A set of the temperature-sensing cathode K, the temperature-sensing anode A, the gate G, the current-sensing emitter SE, the kelvin emitter KE is provided for each of the upper-arm and lower-arm semiconductor devices23aand23b.

The control circuit board4has, as clearly illustrated inFIG. 4, disposed thereon the control circuit43working to control the switching operations of the semiconductor modules2and the voltage detector42working to measure the voltage appearing across the semiconductor devices30. The control circuit43(i.e., the control circuit board4) includes a high-voltage region40to which the voltages VLand VHdeveloped at the semiconductor modules2(i.e., the power terminals20) are applied and a low-voltage region41to which the voltage lower than the voltage VHis applied. The voltage detector42is disposed on a peripheral area of the low-voltage region41.

The high-voltage region40and the low-voltage region41are delimited by an insulating region46to electrically insulate therebetween. The voltage detector42is disposed in direct contact with the insulating region46and also embraced by an insulating region which will also be referred to as a detector insulating region47below. The detector insulating region47is, as clearly illustrated inFIG. 4, laid to overlap the insulating region46partially. An overlap471between the detector insulating region47and the insulating region46serves to insulate the voltage detector42from the high-voltage region40. A remaining L-shaped portion470of the detector insulation region47which does not overlap the insulating region46is made up of two sides: one extending from the insulating region46in the Y-direction, and the other extending from the former side in the X-direction until a side edge400of the control circuit board4. The L-shaped portion470serves to insulate the voltage detector43from the low-voltage region41.

In the high-voltage region40, through holes44are formed for insertion of the control terminals21. Electronic parts (not shown) are fabricated in the high-voltage region40to make a gate driver which drives the semiconductor modules2.

Similarly, in the low-voltage region41, electronic parts (not shown) such as a microcomputer or resistors are installed to make an electric circuit working to a signal to the gate driver in the high-voltage region40. To the low-voltage region41, a voltage of, for example, several volts required to activate the electronic parts is applied.

The voltage detector42has formed therein through holes45through which the voltage measuring terminals32ato32care inserted. The voltage detector42may be made of a voltage divider to measure the before-stepped up voltage VLand the after-stepped up voltage VH, as produced by the dc power supply19(seeFIG. 5).

The casing31of the capacitor3has, as described above, the opening310. An opening edge315of the casing31, as illustrated inFIG. 7, projects outside the surface of the resinous capsule33toward the semiconductor stack10(seeFIG. 2). The opening edge315has formed therein positioning grooves34in which the voltage measuring terminals32are fit.

The beneficial advantages of the structure of the power converter1will be described below.

The power converter1has, as described above, the voltage measuring terminals32disposed in the capacitor3. The voltage measuring terminals32are oriented to extend in the Z-direction to establish electric connections with the voltage detector42on the control circuit board. Similarly, the control terminals21of the semiconductor modules2are oriented to extend in the Z-direction to establish electric connections with the control circuit43on the control circuit board4. Therefore, in assembling of the power converter1, the connections of the voltage measuring terminals32and the control terminals21with the control circuit board4may be achieved simultaneously by bring the voltage measuring terminals32and the control terminals21close to the control circuit board4from the Z-direction. This eliminates the need for two discrete steps of connecting the voltage measuring terminals32to the control circuit board4and connecting the control terminals21to the control circuit board4, thus resulting in a decrease in step of assembling the power converter1.

The connection of the capacitor3to the voltage detector41is achieved without need for an additional step of, for example, drawing the wires95from the capacitor97, as discussed inFIG. 43. The wires95are usually flexible. It is, thus, difficult to draw the wires95from the capacitor97and connect them to the connector96automatically. In contrast, the voltage measuring terminals32are not flexible, thus facilitating the ease with which the capacitor3is joined to the voltage detector42.

The whole of the voltage measuring terminals32is, as already described inFIGS. 1 and 2, laid to overlap with the control circuit board4, as viewed from the Z-direction. In other words, as viewed from the Z-direction, the voltage measuring terminals32are all disposed inside the control circuit board4, thus permitting the power converter1to be reduced in size.

The capacitor3and the semiconductor modules2are, as clearly illustrated inFIG. 2, disposed adjacent each other in the direction parallel to the major surface48of the control circuit board4, thus permitting them to be arrayed as close to each other as possible, which allows the bus bars7aand7bconnecting the capacitor3and the semiconductor modules2to be decreased in length.

The casing31, as illustrated inFIG. 2, has the opening310through which the capacitor devices30are to be installed within the casing31. The capacitor3is fixed with the opening310facing the semiconductor modules2, thus permitting the bus bars7aand7bconnecting the capacitor3and the semiconductor modules2to be decreased in length. This results in a decrease in inductance L of the bus bars7aand7b, which leads to a reduction in surge voltage V (=Ldi/dt) which occurs when the semiconductor modules2are turned on or off.

The opening edge315of the casing31, as illustrated inFIG. 7, has formed therein the positioning grooves34in which the voltage measuring terminals32are fit. Specifically, the voltage measuring terminals32are firmly fixed in the positioning grooves34, so that they are positioned at a desired orientation accurately. This facilitates the ease with which the voltage measuring terminals32are positioned relative to the control circuit board4and joined thereto in assembling of the power converter1.

The control circuit43, as described above, has the high-voltage region40and the low-voltage region41. The voltage detector42is disposed on the peripheral area of the low-voltage region41. In other words, the voltage detector42is located adjacent the insulating region46. This permits an available area of the control circuit board4where the electronic parts are to be mounted to be increased. Since the higher voltage is applied to the high-voltage region40, the insulating region46is provided between the high-voltage region40and the low-voltage region41. Similarly, since the higher voltage is applied to the voltage detector42, the detector insulating region47is disposed around the voltage detector42. It is impossible to mount the electronic parts over the insulating region46and the detector insulating region47. If the voltage detector42is disposed in the center of the low-voltage region41, a need will arise for increasing the size of the detector insulating region47, so that an area of the low-voltage region41occupied by the detector insulating region47is increased, thus resulting in a decrease in available area of the control circuit board4. The voltage detector42in this embodiment is, however, disposed on the peripheral area of the low-voltage region41, thereby decreasing the area of the low-voltage region41occupied by the detector insulating region47. Specifically, the detector insulating region47is, as clearly illustrated inFIG. 4, laid to overlap the insulating region46partially, so that the overlap471serves as both a portion of the insulating region46and a portion of the detector insulating region47, thus resulting in a decreased area of the low-voltage region41occupied by the detector insulating region47, that is, an increased available area of the control circuit board4.

The voltage detector42is, as can be seen inFIG. 4, located adjacent both the side edge400of the control circuit board4and the insulating region46, thereby enabling the insulating region46and the detector insulating region47to overlap each other partially, so that the overlap471may be functionally shared by the insulating region46and the detector insulating region47. This results in a decreased area of the control circuit board4occupied only by the detector insulating region47. The area of the voltage detector42extends until the side edge400of the control circuit board4. This eliminates the need for the detector insulating region47to surround the entire periphery of the voltage detector42, thereby further decreasing the area of the control circuit board4occupied only by the detector insulating region47, thus resulting in an increase in available area of the control circuit board4.

The cooling pipes12within in which the cooling paths12are formed are placed in abutment with the semiconductor modules2, but however, the cooling paths12may alternatively be formed so that the coolant16flows in direct contact with the semiconductor modules2.

The power converter1of the second embodiment will be described below which is different in number of the voltage measuring terminals32and structure of the control circuit board4from the first embodiment.

Each of the semiconductor modules2is, like in the first embodiment, equipped with the plurality of control terminals21(seeFIG. 6). One of the control terminals21(i.e., the kelvin emitter KE of the lower-arm semiconductor device23b) is at the same potential as the negative terminal20b. The kelvin emitter KE (i.e., a lower-potential terminal210) is, thus, connected to the lower-potential electrodes38bof the capacitor devices30through the negative bus bar7b, as illustrated inFIG. 2.

The capacitor3has the two voltage measuring terminals32one of which is coupled to the high potential electrode38aof the filter capacitor device30a, as illustrated inFIG. 5, and the other of which is coupled to the high potential electrode38aof the main capacitor30b.

The control circuit board4, as clearly illustrated inFIG. 8, has formed therein two holes45(45a,45b) through which the above two voltage measuring terminals32of the capacitor3pass.

The high-voltage region40of the control circuit board4, like in the first embodiment, has a plurality of through holes44formed therein. The low-potential terminal210(i.e., the kelvin emitter KE of the lower-arm semiconductor device23bof each of the semiconductor modules2) is inserted into a terminal connector49that is one of the holes44.

The voltage detector42is, like in the first embodiment, disposed adjacent the terminal connector49. The voltage detector42is also located on a peripheral area of the low-voltage region41.

At least one of the terminal connectors49and the voltage detector42are coupled through wire (not shown). The voltage detector42is implemented by a voltage divider which measures voltages developed across the one of the terminal connectors49and the holes45. Specifically, the voltage divider uses the low-potential terminal210inserted into the terminal connector49and the voltage measuring terminals32inserted into the holes45to monitor the before-stepped up voltage VLand the after-stepped up voltage VH, as appearing at the capacitor devices30. All of the terminal connectors49may be coupled electrically to the voltage detector42.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The structure of the power converter1of the second embodiment is, as discussed above, designed to use a portion of the control terminals21(i.e., the low-potential terminals210) of the semiconductor modules2to measure the voltages appearing at the capacitor devices30, thus permitting the number of the voltage measuring terminals32to be decreased as compared with the first embodiment equipped with the three voltage measuring terminals32.

The voltage detector42is disposed adjacent or close to the low-potential terminals210, thus permitting the length of wire used to connect the voltage detector42and the low-potential terminals210to be shortened on the control circuit board4.

The power converter1of the third embodiment will be described below with reference toFIG. 9which is different in configuration of the capacitor3from the first embodiment.

The opening edge315of the capsule33has, like in the first embodiment, formed therein positioning grooves34in which the voltage measuring terminals32are retained. Each of the positioning grooves34has a pair of ridge-like protrusions35formed on opposed inner side walls340of the groove34. The protrusions35face each other across the width of the positioning groove34and serve to create a tight grip through which a corresponding one of the voltage measuring terminals32passes.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The structure of the power converter1of the third embodiment is, as discussed above, designed to have the protrusions35formed on each of the positioning grooves34to hold the width of the voltage measuring terminal32without any play, thereby improving the resistance of the voltage measuring terminal32to mechanical vibration and the accuracy in positioning the voltage measuring terminal32. This facilitates the ease with which the voltage measuring terminals32are positioned relative to the control circuit board4and joined thereto in assembling of the power converter1. The power converter1of the third embodiment also offers the same other advantages as in the first embodiment.

The power converter1of the fourth embodiment will be described below with reference toFIGS. 10 to 15which is different in configuration of the capacitor3from the first embodiment.

The casing31has the opening310, as can be seen inFIG. 11, formed in one of the ends thereof opposed in the Z-direction. Specifically, the opening310faces in a direction opposite the control circuit board4. Each of the voltage measuring terminals32is, as illustrated inFIGS. 12 to 15, made up of a first section321leading to the capacitor device30and a second section322as a discrete member separate from the first section321. The second section322is welded to the first section321and joined to the control circuit board4.

The first section321is, as illustrated inFIG. 14, connected to the electrode38of the capacitor device30. The first section321has a plurality of bends. Specifically, the first section321is of a substantially L-shape and extends from a capacitor connecting portion71in the Z-direction. The capacitor connecting portion71is joined to the electrode38of the capacitor device30. The first section321also projects outside the opening310of the casing31, extends, as clearly illustrated inFIG. 12, in the Y-direction toward the semiconductor modules2, and then is bent toward the control circuit board4in the Z-direction. The first section321has an end326is located near the opening edge315of the casing31. The end326is welded to the second section322to join the first and second sections321and322together. The second section322, as illustrated inFIGS. 14 and 15, extends straight in the Z-direction and connects at an end thereof with the control circuit board4. The first section321and the second section322are each made of a metallic plate or strip.

The casing31has, as illustrated inFIGS. 14 and 15, an outer wall311on which terminal holders5are formed. Each of the terminal holders5also works as a terminal mount and is made up of a pair of protrusions50which hold a portion of the voltage measuring terminal32(i.e., the second section322) firmly therebetween. The protrusions50of each of the terminal holders5are, as can be seen inFIG. 15, offset from each other in the Z-direction. Specifically, the protrusions50of each of the terminal holders5are upper and lower protrusions50xand50ywith projections or salients51xand51ywhich will be generally denoted by reference number51. The salients51xand51yare formed on opposed surfaces of the upper and lower protrusions50xand50yand arrayed out of alignment with each other in the X-direction. In other words, the salient51xis located closer to the opening310of the casing31than the salient51y. The salients51xand51yare placed in direct abutment with the voltage measuring terminal32.

The outer wall311of the casing31has the three terminal holders5for each of the voltage measuring terminals32in this embodiment. The terminal holders5are, as can be seen fromFIGS. 14 and 15, broken down into two types: one is a projecting terminal holder5aand the other is a flat face-terminal holder5b. The two projecting terminal holders5aand the one flat face-terminal holder5bare disposed on the outer wall311for each of the voltage measuring terminal32. Each of the projecting terminal holders5ais, as described above, made of the upper and lower protrusions50xand50ywith the salients51xand51ywhich create a nip through which the second section322of the voltage measuring terminal32passes. The flat face-terminal holder5bis made up of the upper and lower protrusions50xand50ywith flat faces55placed in direct surface contact with the second section322of the voltage measuring terminal32. The area of the flat face-terminal holder5bwhich is in contact with the voltage measuring terminal32is, thus, greater than those of the projecting terminal holders5a, thereby ensuring the stability in orientation of the voltage measuring terminal32. The flat face-terminal holder5bis closer to the control circuit board4than the projecting terminal holders5a.

The second section322of each of the voltage measuring terminals32is, as clearly illustrated inFIG. 13, of a rectangular shape in cross section. The two protrusions50of each of the terminal holder5work to nip the width of the second section322in the X-direction, thereby retaining the voltage measuring terminal32firmly on the outer surface of the casing31.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The structure of the power converter1of the fourth embodiment has the beneficial advantages as discussed below.

Each of the voltage measuring terminals32is, as already described with reference toFIGS. 13 to 15, made up of two parts: the first section321and the second section322which are welded together. This results in a decrease in production cost of the power converter1. Specifically, it is necessary to make the voltage measuring terminal32to integrally include a portion (i.e., the capacitor connecting portion71) which is to be in electric contact with the electrode of the capacitor device30. If the voltage measuring terminal32is made of a one-piece strip, it will be longer than each of the first and second sections321and322. For instance, when the measuring terminal32is cut out, as illustrated inFIG. 42, from a metal plate70into an L-shape, it produces a large useless portion72. The structure of the voltage measuring terminal32in this embodiment is designed to eliminate such a problem. The voltage measuring terminal32is, as described above, made up of two discrete parts: the first and second sections321and322, so that the length of the first section will be shorter than an overall length of the voltage measuring terminal32. The second section322may be made using a separate strip member. It is, thus, possible to minimize the area of the useless portion72. This results in a decrease in production cost of the voltage measuring terminals32.

The casing31has, as illustrated inFIG. 15, formed on the outer wall311of the casing31the terminal holders5each made up of the pair of protrusions50. The pair of protrusions50has the salient51xand51yor the flat faces55to retain the voltage measuring terminal32(i.e., the second section322) firmly on the casing31. One of the salients51xand51yof the protrusions50of each of the terminal holders5is offset or staggered from the other one of the salient51xand51yin the lengthwise direction of the voltage measuring terminal32, thereby ensuring the enhanced stability in retaining the voltage measuring terminal32on the casing31, which improves the accuracy in positioning the voltage measuring terminal32to facilitate the ease with which the voltage measuring terminal32is joined to the control circuit board4. The casing31is made of resin and has the advantage that it is insusceptible to breakage. If the salients51xand51yare arrayed in alignment with each other in the X-direction, it will result in a decreased linear interval therebetween. This requires the need for using resin-molding dies in which projections for forming the salient51xand51yare located close to each other to make the casing31. The decreasing of the linear interval between the salient51xand51yrequires the salient-forming projections to have a decreased width, which will be subjected to breakage during use. In contrast, the salient51xand51yof the protrusions50of the terminal holder5are offset from each other in the Z-direction to increase the liner interval therebetween, thus enabling the distance between the salient-forming projections of the resin-molding dies to be increased to avoid the breakage thereof in the course of forming the casing31.

The terminal holders5are, as already described inFIG. 15, broken down into two types: the projecting terminal holder5aand the flat face-terminal holder5b. The flat face-terminal holder5bis made up of the upper and lower protrusions50xand50ywith the flat faces55placed in direct surface contact with the second section322of the voltage measuring terminal32and located closer to the control circuit board4than the projecting terminal holders5a. The area of the flat face-terminal holder5bwhich is in contact with the voltage measuring terminal32is greater than those of the projecting terminal holders5a, thereby ensuring the stability in orientation of the voltage measuring terminal32and enhancing the resistance thereof to the mechanical vibration.

The salients51xand51yof the terminal holder5are shifted from each other, in other words, arranged out of alignment with each other in the direction perpendicular to the length of a corresponding one of the voltage measuring terminals32. The holding of the voltage measuring terminal32by the salients51xand51ymay, therefore, result in bending thereof. In order to alleviate this problem, each of the sets of the terminal holders5has at least the one flat face-terminal holder5bto hold the voltage measuring terminal32by the flat faces55placed in direct contact therewith, thereby enhancing the stability in retaining and the accuracy in positioning the voltage measuring terminal32on the casing31to facilitate the ease with which the voltage measuring terminal32is joined to the control circuit board4.

The power converter1of the fourth embodiment also offers the same other advantages as in the first embodiment.

The power converter1of the fifth embodiment will be described below with reference toFIGS. 16 and 17which is different in configuration of the voltage measuring terminals32from the first embodiment.

Each of the voltage measuring terminals32is equipped with reinforcement ribs323formed on portions thereof retained by the terminal holder5. The reinforcement ribs323extend substantially parallel to the outer wall311of the casing31. The voltage measuring terminal32, as clearly illustrated inFIG. 16, has the reinforcement ribs323one for each of the terminal holders5(i.e., the pair of protrusions50). Each of the reinforcement ribs323is formed by a tab extending from the second section322of the voltage measuring terminal32perpendicular to the length of the second section322. The two of the reinforcement ribs323for each of the terminal holders5extend in opposite directions. The reinforcement ribs323are, as can be seen inFIG. 17, placed in direct contact with outer surfaces500of the protrusions50.

Each of the reinforcement ribs323works to increase the mechanical strength of the voltage measuring terminal32, which increases the resistance of the voltage measuring terminal32to bending thereof when inserted and held between the protrusions50of the terminal holder5. This results in improvement of stability of orientation of the voltage measuring terminal32, thereby facilitating the ease with which the voltage measuring terminal32is joined to the control circuit board4.

The power converter1of the sixth embodiment will be described below with reference toFIGS. 18,19, and20which is different in structure of the voltage measuring terminals32from the first embodiment.

Each of the voltage measuring terminals32is, like in the fourth embodiment, made up of two parts: the first section321and the second section322. The first section321has formed therein a cut-out hole37in which an end of the second section322is fit to establish electrical connection between the first section321and the second section322.

The casing31of the capacitor3has formed therein a hole316through which the second section322passes. The second section322has a flange325. The casing31has a hook or claw317which locks the flange325of the second section322to hold the second section322firmly.

The cut-out hole37of the first section321of the voltage measuring terminal32has, as can be seen inFIGS. 19 and 20, arc-shaped inner walls371and four inner tabs or protrusions372each of which extends inwardly radially from between adjacent two of the arc-shaped inner walls371. The second section322has formed on an end thereof a flange head327which has an outer diameter smaller than the distance between diametrically opposed two of the inner protrusions372of the first section321. The mechanical/electrical joint between the first and second sections321and322is achieved by inserting the flange head327into the center of the cut-out hole37and then thrusting it while elastically pushing the inner protrusions372until the inner protrusion372are snap fit on the jaw of the flange head327of the second section322.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The structure of the voltage measuring terminal32of this embodiment establishes the mechanical/electrical connection of the first and second sections321and322without use of welding techniques, thus facilitating the ease of assembling of the voltage measuring terminal32, and permits, like in the third embodiment, the first section321to be decreased in length to increase the area of the useless portion72. This results in a decrease in production cost of the voltage measuring terminals32.

The power converter1of the sixth embodiment also offers the same other advantages as in the first embodiment.

The power converter1of the seventh embodiment will be described below with reference toFIGS. 21 and 22which is different in configuration of the voltage measuring terminals32from the sixth embodiment.

Specifically, the first section321of the voltage measuring terminal32has formed therein the cut-out hole37in which the end of the second section322is fit to establish electrical connection between the first section321and the second section322. The cut-out hole37is, as can be seen inFIG. 21, implemented by a spiral groove or slit to form a scroll spring370. The second section322has a cone-shaped end, as illustrated inFIG. 22, which is to be thrust against the scroll spring370to establish the electrical connection of the first and second sections321and322.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The power converter1of the eighth embodiment will be described below with reference toFIGS. 23 and 24which is different in structure of the voltage measuring terminals32from the sixth embodiment.

The first section321of the voltage measuring terminal32has formed therein the cut-out hole37in which the end of the second section322is fit to establish electrical connection between the first section321and the second section322.

The cut-out hole37is, as can be seen inFIG. 23, implemented by a cross-shaped groove or slit extending from a center circular hole373to form four triangular shaped elastic springs374. The second section322has, like in the sixth embodiment, formed on the end thereof the flange head327which is greater in diameter than the center circular hole373of the first section321. The mechanical/electrical joint between the first and second sections321and322is achieved by pushing the flange head327against the center hole373of the first section321while elastically thrusting the spring374until the springs374are snap fit on the jaw of the flange head327of the second section322.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The power converter1of the ninth embodiment will be described below with reference toFIGS. 25 and 26which is different in structure of the voltage measuring terminals32from the sixth embodiment.

The first section321of the voltage measuring terminal32has a center hole375, a pair of inner arc-shaped slits376, and a pair of outer arc-shaped slits377formed therein. The inner arc-shaped slits376extend substantially parallel to the length of the first section321and are symmetric with respect to the center hole375. Similarly, the outer arc-shaped slits377extend substantially parallel to the width of the first section321and are symmetric with respect to the center hole375. The outer arc-shaped slits377are located outside the inner arc-shaped slits376in the lengthwise direction of the first section321. The inner and outer arc-shaped slits376and377form a flat spring378around the center hole375.

The second section322has a small-diameter portion328extending from the end of a major portion thereof. The electrical joint between the first and second sections321and322is achieved by inserting the small-diameter portion328into the center hole375and then pushing the second section322while elastically thrusting the flat spring378until the flat spring378are in direct abutment with a shoulder328(i.e., an annular end surface of the major portion of the second section322).

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The power converter1of the tenth embodiment will be described below with reference toFIGS. 27 to 30which is different in structure of the voltage measuring terminals32from the first embodiment.

Each of the voltage measuring terminals32is equipped with two terminal hooks8for use in retaining the voltage measuring terminal32on the casing31. Each of the terminal hooks8functions as a male hook and is made up of three parts: a first protrusion81extending from the body of the voltage measuring terminal32in the X-direction, a second protrusion82extending from an end of the first protrusion81in the Z-direction, and a third protrusion83extending diagonally from the second protrusion82parallel to the body of the voltage measuring terminal32. The first, second, and third protrusions81,82, and83will also be referred to below as a first upright stud, a horizontal lug, and a diagonal lug, respectively.

The casing31of the capacitor3, as clearly illustrated inFIGS. 29 and 30, has two terminal holders5formed therein. Each of the terminal holders5is made up of a pair of female hooks52and53. The female hook53is, as clearly illustrated inFIG. 30, made up of two parts: a first protrusion53aextending from the body of the casing31in the Y-direction and a second protrusion53bextending from an end of the first protrusion53ain the Z-direction. The first and second protrusions53aand53bwill also be referred to below as an upright stud and a horizontal lug, respectively. The upright stud53a, the horizontal stud53b, and the outer wall of the casing31define a groove or recess S1into which the diagonal lug83of the voltage measuring terminal32is fit. The fitting of the diagonal lug83into the recess S1is achieved by inserting the voltage measuring terminal32into grooves between the female hooks52and53of the terminal holders5in a direction perpendicular to the surface of the casing31while allowing the diagonal lugs83to be deformed elastically and snapping the diagonal lugs83into the recesses S1, respectively. This establishes the mechanical joint of the voltage measuring terminal32to the casing31.

The voltage measuring terminal32is held by the female hooks52and53of each of the terminal holders5from being moved in the X-direction (i.e., the width-wise direction of the voltage measuring terminal32). The diagonal lugs83of the terminal hooks8are locked firmly in the recesses S1of the female hooks53from being moved in the Z-direction (i.e., the lengthwise direction of the voltage measuring terminal32). The movement of the voltage measuring terminal32in the Y-direction is stopped by the abutment of the diagonal lugs83of the terminal hooks8with the horizontal studs53bof the female hooks53.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The movements of the voltage measuring terminal32in three directions: the X-, Y-, and Z-directions are locked by the snap-fit features (i.e., the combinations of the terminal holders5and the terminal hooks8), thus ensuring the stability of the joint of the voltage measuring terminal32to the casing32and the orientation thereof, thereby facilitating the ease with which the voltage measuring terminal32is coupled to the control circuit board4.

The power converter1of the tenth embodiment also offers the same other advantages as in the first embodiment.

The power converter1of the eleventh embodiment will be described below with reference toFIGS. 31 to 34which is different in location where the second section322of each of the voltage measuring terminals32is joined to the control circuit board4from the first embodiment. The same reference numbers, as employed in the first embodiment, will refer to the same parts, and explanation thereof in detail will be omitted here.

Specifically, the joint of the first section321and the second section322of each of the voltage measuring terminals32is, as can be seen inFIGS. 31 to 34, located away from that of the second section322and the voltage detector42, as viewed from the Z-direction (i.e., direction normal to the major surface48of the control circuit board4).

The power converter1is, as illustrated inFIGS. 33 and 34, equipped with the three voltage measuring terminals32. The second section322of each of the voltage measuring terminals32is made of a metallic strip whose surface is metal-plated (e.g., solder-plated). The first section321is not metal-plated. The second sections322of all the voltage measuring terminals32are encapsulated by a resinous mold335as a terminal module330. The terminal module330is secured to the surface of the casing31of the capacitor3.

The resinous mold335is of a substantially parallelogram as viewed from the Z-direction. The second section322is of a substantially C-shape and made up of three parts: a terminal-joining portion392, a board-joining portion393, and a connecting portion391which connects the terminal-joining portion392and the board-joining portion393together. The connecting portion391is partly encapsulated by the resinous mold335. The terminal-joining portion392and the board-joining portion393extend, as illustrated inFIG. 31, from ends of the connecting portion391parallel to each other toward the control circuit board4in the Z-direction.

The second section322is so oriented, as can be seen inFIG. 32, as to have the connecting portion391extending parallel to the major surface48of the control circuit board4. The connecting portion391is, as described above, disposed inside the resinous mold335working as a sealed capsule. The resinous mold335is fixed on the surface319of the casing31which faces the major surface48of the control circuit board4.

The first section321of each of the voltage measuring terminals32, as illustrated inFIGS. 32 and 34, has a protrusion345formed on the surface thereof facing the terminal-joining portion392of the second section322. The protrusion345has a tip which is placed in contact with and resistance-welded to the surface of the terminal-joining portion392to make a mechanical/electrical joint of the first and second sections321and322.

The terminal-joining portion392, as clearly illustrated inFIG. 33, has a width W extending in the X-direction. The width W is greater than that of a pin-like top portion of the board joining portion393. The top portion of the board-joining portion393is fit in a corresponding one of the holes45which are, as illustrated inFIG. 38, formed in the control circuit board4. The width W of the terminal-joining portion392is determined to be greater than a tolerance for misalignment of the first section321in the X-direction.

The connecting portion391of the second section322of each of the voltage measuring terminals32extends, as clearly illustrated inFIG. 34, parallel to the side surface399of the resinous mold336which extends diagonally with respect to the length of the casing31of the capacitor3. Outer two of the second sections322have module-mounting tabs336which extend outside the resinous mold335. The module-mounting tabs336have holes337for mounting the terminal module330on the casing3.

The mounting of the terminal module330on the casing31will be described below in detail. Specifically, the terminal module330is secured to the casing31using thermoplastic staking techniques (also called heat staking or thermal caulking). The casing31, as illustrated inFIG. 35, includes mount tables351(only one is shown for the brevity of illustration) and studs339protruding from the mount tables351in the Z-direction. Each of the mount table351is formed on the surface319of the casing31which is, as illustrated inFIG. 32, farther away from the control circuit board4. The casing31is made of a thermoplastic resin.

The joining of the terminal module330to the casing31is achieved, as illustrated inFIG. 36, by placing the terminal module330on the casing31, inserting the studs339into the holes337of the module-mounting tabs336, pressing heated compression probes (not shown) on the tops of the studs339while softening them to form large-diameter heads on the studs339, as illustrated inFIG. 37. The head of each of the studs339and the mount table form a grip in the Z-direction in which the module mounting tab336is retained.

Like in the first embodiment, the control circuit board4, as illustrated inFIG. 38, has the high-voltage region40, the low-voltage region41, and the insulating region46to electrically insulate the high-voltage region40and the low-voltage region41from each other. The voltage detector42is disposed on an area of the control circuit board4which extends from the side edge400to the insulating region46.

Other arrangements are identical with those in the first embodiment, and explanation thereof in detail will be omitted here.

The structure of the power converter1of the eleventh embodiment has beneficial advantages, as discussed below.

The joint300of the first section321and the second section322of each of the voltage measuring terminals32is, as can be seen inFIGS. 31 and 34, separate from the joint of the second section322to the control circuit board42in the Y-direction. In other words, a portion of the first section321of the voltage measuring terminal32extending outside the capacitor3is located away from the voltage detector42, thereby resulting in an increase in freedom of arrangement of the voltage detector42on the surface of the control circuit board4.

The second sections322of all the voltage measuring terminals32are, as illustrated inFIG. 33, disposed inside the sealed capsule335as the terminal module330. This facilitates the ease with which the first and second sections321and322are aligned with each other and joined together.

The terminal module330in which the second sections322are disposed is mounted on the casing31through the thermoplastic staking techniques. This eliminates the need for fasteners such as bolts or nuts to secure the terminal module330to the casing31, thus resulting in a decrease in production cost of the power converter1.

The surface of the second section322of each of the voltage measuring terminals32is plated or coated with the metal layer (e.g., the solder layer), thus facilitating the joining of the second section322to the control circuit board4. Specifically, when the second section322is soldered to the control circuit board4, the metal layer on the second section322enhances the solder wettability on the surface of the second section322.

If each of the voltage measuring terminals32is made of a one-piece member, it is necessary to form the metal layer over the entire surface of the voltage measuring terminal32. In contrast, the voltage measuring terminal32is made up of two parts: the first section321and the second section322, thus permitting an area of the voltage measuring terminal32which is to be coated with the metal layer to be minimized. This also results in a decrease in production cost of the voltage measuring terminals32.

The first section321of each of the voltage measuring terminals32, as already described inFIG. 34, has the protrusion345formed on the surface thereof. The first section321and the second section322are welded together at the tip of the protrusion345. The welding of the first and second sections321and322may be achieved by pressing the tip of the protrusion345against the surface of the second section322(i.e., the terminal-joining portion392), in other words, established at a small contact area between the first and second sections321and322, thus resulting in a decreased amount of thermal energy, as generated by the resistance welding, which facilitates the ease of welding operation.

The width W of the terminal-joining portion392of each of the voltage measuring terminals32is selected to be greater than the tolerance for misalignment of the first section321in the X-direction, thereby ensuring the stability in contact, that is, welding between the first and second sections321and322at the protrusion345even when the first section321is misaligned in the X-direction.

Particularly, the structure of the power converter1of this embodiment is, as clearly illustrated inFIG. 31, designed not to position the capacitor devices30within the casing31, but only to arrange them hermetically within the resinous capsule33, thus causing the capacitor devices30to be misaligned greatly, which will lead to great misalignment of the first sections321of the voltage measuring terminals32. The width W of the second sections322absorbs such a misalignment.

The voltage detector42is, as illustrated inFIG. 38, disposed on the area of the control circuit board4which is located in abutment with the side edge400and the insulating region46, thereby permitting, like in the first embodiment, the insulating region46and the detector insulating region47to be laid to overlap each other to have a common area or a portion of the detector insulating region47to be omitted. This minimizes an area of the control circuit board4occupied only by the detector insulating region47, which results in an increased area of the control circuit board4available for installation of electronic parts.

As apparent from the above discussion, the structure of the power converter1of this embodiment enables the voltage detector42to be disposed within the low voltage region43regardless of the locations of the first portions321of the voltage measuring terminals32(i.e., the joint300of the first section321and the second section322inFIG. 31) which extend outside the capacitor3.

The power converter1of the eleventh embodiment also offers the same other advantages as in the first embodiment.

The voltage detector42, as illustrated inFIG. 39, may alternatively be disposed on an area of the control circuit board4which is located in abutment with only the insulating region46. The insulating region46is laid to overlap the detector insulating region47partially, thus resulting in a decrease in area of the control circuit board4occupied only by the detector insulating region47, which results in an increased area of the control circuit board4available for installation of electronic parts.

The voltage detector42, as illustrated inFIG. 40, may alternatively be disposed on an area of the control circuit board4which is located in abutment with only the side edge400of the control circuit board4. This also permits the part of the detector insulating region47to be omitted, like in the above embodiments, thus resulting in an increased area of the control circuit board4available for installation of electronic parts.

The sealed capsule335of the terminal module330is, as can be seen inFIG. 33, substantially a parallelogram as viewed from the Z-direction, but may be, as illustrated inFIG. 41, of a rectangular shape.

The terminal-joining portion392of the second section322of each of the voltage measuring terminals32may alternatively be shaped to have a protrusion such as the protrusion345. The protrusion345on the first section321may be omitted.