Abstract:
There is provided an inverter device that is small in size and has high durability against long-term use with vibration. A power substrate  20  is placed at a bottom portion of a box-shaped module case  11 , and a control substrate  30  forms a lid of an opening in the module case  11 , and thus an inverter device  10  of the present invention is modularized, thereby reducing a height of the inverter device  10 . In the inverter device  10 , a capacitor  22  is provided between the power substrate  20  and the control substrate  30 , and the capacitor  22  is covered with a resin mold layer  12  and fixed in the module case  11 . The capacitor  22  is fixed in the module case  11  by the resin mold layer  12 , which provides higher durability against vibration than that by conventional fastening with a screw.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to an inverter device, and, for example, relates to an inverter device suitable for constituting an electric compressor integrally with a compression mechanism and an electric motor that drives the compressor mechanism. 
       BACKGROUND ART 
       [0002]    An on-vehicle air conditioner in an electric car or a fuel-cell car without an engine includes a compressor including an electric motor as a power supply for compressing and circulating a refrigerant. The compressor includes an inverter device that converts DC power supplied from a battery that is an on-vehicle power supply into three-phase AC power and supplies the AC power to the electric motor. From a desire for space saving, there is an integral electric compressor including an inverter device incorporated into one housing together with a compression mechanism and an electric motor. 
         [0003]    To the inverter device, a smoothing capacitor for preventing changes in DC power is electrically connected in parallel. 
         [0004]    For mounting of a smoothing capacitor, for example, Patent Document 1 proposes that positive and negative laminated input conductor plates connected to input terminals of a switching module including a radiating base substrate, an insulating substrate, and a semiconductor device are bent to three-dimensionally place a smoothing capacitor and a control circuit board with respect to the switching module. 
         [0005]    Patent Document 2 discloses an inverter device in which a smoothing capacitor for preventing changes in DC power is placed above a power semiconductor device in a module case. 
       CITATION LIST 
     Patent Document 
       [0006]    Patent Document 1: Japanese Patent Laid-Open No. 9-308265 ( FIG. 1 ) 
         [0007]    Patent Document 2: Japanese Patent Laid-Open No. 2004-335625 ( FIG. 1 ) 
       DISCLOSURE OF THE INVENTION 
     Problems to be solved by the Invention 
       [0008]    Patent Document 1 can reduce a mounting area of an inverter device to effectively use space. However, the inverter device in Patent Document 1 has a structure in which one end of the cylindrical smoothing capacitor is fixed to the control circuit board provided vertically to the switching module. Thus, if the inverter device in Patent Document 1 is mounted in a car and vibrated, the control circuit board may be horizontally bent and displaced to cause the smoothing capacitor to oscillate around a fixed end (on the control circuit board side), which may provide insufficient durability. 
         [0009]    In the inverter device in Patent Document 2, the control circuit board is placed in parallel with a bottom floor of the module case, and thus higher durability against vibration than that in Patent Document 1 is provided. However, in the inverter device in Patent Document 2, a terminal of the smoothing capacitor is fastened by a screw to the module case to fix the smoothing capacitor, which may also provide insufficient durability under a severe vibration condition of a car. In Patent Document 2, a fixed base protruding in a cantilevered manner in the module case supports an end of the smoothing capacitor from below, but the fixed base increases a height of the inverter device, which prevents a reduction in size, particularly, height of the inverter device. 
         [0010]    In view of the above-described background, the present invention has an object to provide an inverter device that is small in size and has durability against long-term use with vibration. 
       Solution to Problem 
       [0011]    An inverter device of the present invention is based on modularization for a size reduction. Specifically, the inverter device of the present invention includes two substrates: a power substrate that converts DC power supplied from a high voltage power supply into AC power and applies the AC power to an electric motor; and a control substrate that controls the application of the AC power to the electric motor. The power substrate is placed at a bottom of a box-shaped module case, and the control substrate forms a lid of an opening in the module case, and thus the inverter device of the present invention is modularized. In the inverter device of the present invention, the smoothing capacitor is provided on the power substrate, a resin mold layer is filled into the module case from the power substrate to a position covering the smoothing capacitor to fix the smoothing capacitor in the module case. The smoothing capacitor is fixed in the module case by the resin mold layer, which provides higher durability against vibration than that by conventional fastening with a screw. 
         [0012]    In the present invention, a film capacitor can be used as a smoothing capacitor. Generally, a film capacitor covered with resin is distributed, but in the present invention, a film capacitor element can be used without a protective layer of resin. This can reduce a thickness of the smoothing capacitor, and thus reduce a height of the inverter device. 
         [0013]    The smoothing capacitor comprised of the film capacitor includes a laminated body and an electrode, and is electrically connected to the power substrate via the electrode. However, in the present invention, the power substrate and the film capacitor may be electrically connected via an electrode of the film capacitor and a lead wire connected to the electrode. 
         [0014]    A conductive pattern electrically connected to the electrode of the smoothing capacitor needs to be placed on the power substrate correspondingly to the electrode of the smoothing capacitor. However, this limits circuit design of the power substrate. On the other hand, the conductive pattern of the power substrate and the electrode of the smoothing capacitor are connected via the lead wire, and thus the conductive pattern can be provided in any position, thereby increasing flexibility in circuit design of the power substrate. 
         [0015]    When the conductive pattern of the power substrate and the electrode of the smoothing capacitor are connected via the lead wire, a first resin mold layer is formed with the conductive pattern of the power substrate and the lead wire being connected. At the time when the first resin mold layer is formed, a tip of the lead wire connected to the electrode of the smoothing capacitor is exposed from an upper surface of the first resin mold layer. Then, with the tip of the lead wire and the electrode of the capacitor being connected, a second resin mold layer may be formed to cover the smoothing capacitor. 
       ADVANTAGEOUS EFFECTS OF INVENTION 
       [0016]    According to the present invention, the power substrate and the control substrate are modularized, thereby reducing a size of the inverter device. In the inverter device of the present invention, the smoothing capacitor is fixed in the module case by the resin mold layer, which provides higher durability against vibration than that by conventional fastening with a screw. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0017]      FIG. 1  is a partial sectional view of an inverter device according to a first embodiment. 
           [0018]      FIG. 2  is a schematic view showing a circuit configuration of a power substrate according to the first embodiment. 
           [0019]      FIGS. 3A and 3B  are views showing a capacitor according to the first embodiment. 
           [0020]      FIGS. 4A and 4B  are partial sectional views of an inverter device according to a second embodiment. 
           [0021]      FIG. 5  is a view showing essential parts of an inverter device according to a third embodiment. 
           [0022]      FIG. 6  is another view showing essential parts of the inverter device according to the third embodiment. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
       [0023]    Hereinafter the present invention will be described in detail based on embodiments shown in the accompanying drawings. 
         [0024]    An embodiment of an inverter device according to the present invention will be described with reference to  FIGS. 1 to 3 . 
         [0025]    An inverter device  10  is mounted in an electric vehicle such as an electric car that uses an electric motor as a drive source of the vehicle, or a hybrid car that uses an engine that is an internal combustion engine and an electric motor as a drive source of the vehicle, and is an electric power conversion device that converts DC power supplied from a battery that is an on-vehicle power supply into three-phase AC power and supplies the AC power to the electric motor. 
         [0026]    The inverter device  10  includes a module case  11 , a power substrate  20  provided at a bottom of the module case  11 , and a control substrate  30  that closes an opening in the module case  11 . 
         [0027]    The power substrate  20  coverts DC power supplied from a high voltage power supply  40  into AC power, applies the AC power to an electric motor  50  according to control by the control substrate  30  to rotationally drive the electric motor  50 . 
         [0028]    The control substrate  30  controls the application of the AC power converted by the power substrate  20  to the electric motor  50 . 
         [0029]      FIG. 2  is a schematic view showing a circuit configuration of the power substrate  20 . Electric power of high voltage, for example, 300 V is supplied from the high voltage power supply  40  to the power substrate  20 . A switching element  21  comprised of a plurality of IGBTs and a gate circuit (not shown) are mounted on the power substrate  20 . 
         [0030]    A microcomputer that controls an operation of the switching element  21  is provided on the control substrate  30 . When a control signal of the microcomputer is transmitted from the control substrate  30  to the power substrate  20  to drive the gate circuit, and input to the switching element  21 , the switching element  21  is operated. Thus, DC power of high voltage supplied from the high voltage power supply  40  is converted into a three-phase AC and applied to the electric motor  50  to rotationally drive the electric motor  50 . The electric motor  50  is an alternator such as an induction motor or a synchronous motor. 
         [0031]    A smoothing capacitor (hereinafter simply referred to as a capacitor)  22  that smoothens pulsing of the DC power is electrically connected to the power substrate  20  in parallel. A snubber capacitor for removing noise in a high frequency band may be provided on the power substrate  20 , but may be omitted because the capacitor  22  is provided on the power substrate  20  to also remove the noise in the high frequency band. 
         [0032]    In the circuit configuration described above, the electric power is supplied from the high voltage power supply  40  to the power substrate  20  via an input/output terminal  23 , and the input/output terminal  23  is comprised of pin-shaped PN terminals  23   a  and  23   b  mounted on the power substrate  20 . 
         [0033]    To the PN terminals  23   a  and  23   b , for example, a busbar (wire for applying a voltage to the power substrate  20 )  24  is connected from a side of the high voltage power supply for electrical conduction. 
         [0034]    As shown in  FIG. 1 , the inverter device  10  includes the box-shaped module case  11  having an opening in an upper portion and a rectangular plane. The module case  11  is produced, for example, by injection molding of resin, and a wire comprised of a busbar or the like, a terminal, and the like that are not shown are embedded in a side wall and a bottom floor. 
         [0035]    The power substrate  20  is placed on the bottom floor in the module case  11 . On the power substrate  20 , other electronic components  25  to  28  are provided in addition to the capacitor  22 . In this example, the power substrate  20  is placed on the bottom floor, but a configuration in which the capacitor  22  and the other electronic components  25  to  28  are directly provided on the bottom floor of the module case  11  and the bottom floor functions as the power substrate  20  is covered by the present invention. 
         [0036]    The capacitor  22  that is the film capacitor includes a laminated body  221  and an electrode  222  as shown in  FIG. 3 . The rectangular parallelepiped laminated body  221  is configured, for example, by laminating resin films with aluminum deposited on surfaces thereof in a comb shape. The electrode  222  is placed on each of opposite sides in a width direction of the laminated body  221 . The electrode  222  is electrically connected to a conductive pattern (not shown) provided on the power substrate  20 . 
         [0037]    The capacitor  22  is covered with a resin layer  223  around the laminated body  221  and at a part of each electrode  222  as a general sales configuration as shown by the dotted line in  FIG. 3 . This is because the laminated body  221  is formed of a thin resin film, and without being covered with resin or the like, the resin film may be delaminated or damaged to impair the function of the capacitor  22 . Generally, the resin layer  223  has a thickness of about 1 to 2 mm, and without the resin layer  223 , the height of the inverter device  10  can be reduced for the thickness. In the present invention, a capacitor  22  covered with a resin layer  223  or a film capacitor element  22  that is not covered with a resin layer  223  may be used. In the present invention, even if the resin layer  223  is provided, the laminated body  221  may be partially covered as shown in  FIG. 3  rather than entirely covered. 
         [0038]    As shown in  FIG. 1 , the control substrate  30  is placed at the upper end of the side wall of the module case  11  to close the upper opening in the module case  11 . As shown in  FIG. 1 , a CPU (Central Processing Unit)  31  that comprises the microcomputer, and other electronic components  32  and  33  are provided on an upper surface of the control substrate  30 . An electronic component  34  is provided on a lower surface of the control substrate  30 . 
         [0039]    As shown in  FIG. 1 , a region surrounded by the module case  11  and the control substrate  30  in the inverter device  10  is filled with a resin mold layer  12  formed of epoxy resin or other resin. The resin mold layer  12  can be formed as described below. The power substrate  20  is placed in a predetermined position on the bottom floor of the module case  11 , then a resin composition before cured is poured into the module case  11 , and then the resin composition is cured with the control substrate  30  being placed on the predetermined position. The resin mold layer  12  firmly fixes the power substrate  20  to the module case  11 , and further fixes the capacitor  22  to the power substrate  20 . 
         [0040]    The above-described inverter device  10  provides advantages described below. 
         [0041]    In the inverter device  10 , the power substrate  20  is provided at the bottom of the module case  11 , the control substrate  30  functions as the lid of the module case  11 , and the capacitor  22  is housed in the module case  11 . This can reduce the size, particularly, the height of the inverter device  10 . 
         [0042]    The capacitor  22  provided on the power substrate  20  is covered with the resin mold layer  12  and fixed in the module case  11 . Thus, even if the inverter device  10  is mounted in a car and used for a long period, the capacitor  22  is firmly fixed on the power substrate  20  by the resin mold layer  12  filled in the module case  11 , and thus the capacitor  22  is reliably connected to the power substrate  20 . 
         [0043]    In the inverter device  10 , the capacitor  22  is placed immediately above the switching element  21  of the power substrate  20 , thereby reducing an induction component and preventing a surge due to resonance phenomena. 
       Second Embodiment 
       [0044]    If the electrode  222  of the capacitor  22  is aligned with the conductive pattern of the power substrate  20 , the electrode  222  and the conductive pattern can be directly connected. However, the present invention is not limited to this, and the electrode  222  of the capacitor  22  and the conductive pattern of the power substrate  20  can be connected via a lead wire. A second embodiment shows an example thereof. In the inverter device  10 , the resin mold layer  12  is filled from the bottom of the module case  11 , that is, the power substrate  20  to the lower surface of the control substrate  30 , but the advantages of the present invention can be obtained if the resin mold layer  12  is filled to a position covering the capacitor  22 . 
         [0045]    In the second embodiment, as shown in  FIG. 4A , a first resin mold layer  13  is provided so that a lower end of a lead wire L is connected to a conductive pattern (not shown) and an upper end of the lead wire L is exposed from an upper surface of the first resin mold layer  13 . At this time, the capacitor  22  is not yet placed in a predetermined position. 
         [0046]    After the first resin mold layer  13  is cured, the capacitor  22  is placed in a position where the electrode  222  of the capacitor  22  and the lead wire L can be connected on the first resin mold layer  13 , and the electrode  222  of the capacitor  22  and the lead wire L are connected ( FIG. 4B ). 
         [0047]    Then, epoxy resin is further poured into the module case  11  and hardened to provide a second resin mold layer  14 . The capacitor  22  is firmly fixed in the module case  11  by the second resin mold layer  14 . 
         [0048]    The inverter device  100  of the second embodiment provides the same advantages as in the first embodiment, and also provides an advantage described below. Specifically, the electrode  222  of the capacitor  22  and the conductive pattern are connected via the lead wire L, and thus the conductive pattern can be provided in any position. Thus, higher flexibility in circuit design of the power substrate  20  is provided as compared with the conductive pattern formed correspondingly to a mounting position of the electrode  222  of the capacitor  22 . 
       Third Embodiment 
       [0049]    To confirm whether a capacitor is not damaged during assembly of an inverter device, a withstand voltage test is conducted after the assembly of the inverter device is completed. In conducting the withstand voltage test, the capacitor covered with a resin mold layer needs to be electrically disconnected from a high voltage power supply, and after the withstand voltage test is finished, the capacitor needs to be electrically connected to the high voltage power supply. A third embodiment proposes a configuration for satisfying the needs. 
         [0050]    As shown in  FIG. 5 , a capacitor  60  according to the third embodiment includes electrodes  62 P and  62 N on opposite sides of a laminated body  61 . The electrodes  62 P and  62 N have terminals  621  to  624  at opposite ends in a longitudinal direction bent outward into an L shape. 
         [0051]    Support pins  71  to  74  corresponding to the terminals  621  to  624  are provided at four corners of a box-shaped module case  11  housing the capacitor  60 . 
         [0052]    Among the support pins  71  to  74 , the support pin  71  is a component of a busbar  70 P including a terminal  75  electrically connected to the high voltage power supply, and a ribbon-shaped conductor  77  electrically connected to a conductive pattern CP 1  of a power substrate  20  as shown in  FIG. 6 . Similarly, the support pin  72  is a component of a busbar  70 N including a terminal  76  electrically connected to the high voltage power supply, and a ribbon-shaped conductor  78  electrically connected to a conductive pattern CP 2  of the power substrate  20 . The support pins  73  and  74  are members that mechanically support the capacitor  60  in an inverter device. However, the support pin  74  has a U-shaped support portion  741  that supports the terminal  624 , and also a probe contact portion  742  with which a probe of a test device is brought into contact in a withstand voltage test. 
         [0053]    A surrounding wall  11   c  having an L-shaped plane section surrounding the support pin  71  is formed around the support pin  71 . The surrounding wall  11   c  is integrally formed with the module case  11 . A gap is provided between a tip of the surrounding wall  11   c  and a side wall  11   s  of the module case  11 , and through the gap, a tip of the terminal  621  of the capacitor  60  can be brought into contact with the support pin  71  in the surrounding wall  11   c.    
         [0054]    The terminals  621  to  624  are supported by the corresponding support pins  71  to  74 , and the capacitor  60  is placed in a predetermined position in the module case  11 . At this time, an insulating sheet IS is provided between the terminal  621  of the capacitor  60  and the support pin  71  to electrically disconnect the terminal  621  from the support pin  71 , that is, disconnect the capacitor  60  from the high voltage power supply. 
         [0055]    Then, resin such as epoxy is poured into the module case  11 , and curing of a resin mold layer is waited for. The gap between the tip of the surrounding wall  11   c  and the side wall  11   s  of the module case  11  is narrow, and the terminal  621  of the capacitor  60  is inserted into the gap, thereby preventing the poured resin from entering inside the surrounding wall  11   c . After the resin is cured, the probe of the test device is brought into contact with the probe contact portion  742  of the support pin  74 , and a predetermined voltage is applied to conduct a withstand voltage test. 
         [0056]    After the withstand voltage test is finished, the insulating sheet IS provided between the terminal  621  and the support pin  71  is removed. Since the resin does not enter inside the surrounding wall  11   c , the insulating sheet IS can be easily removed. 
         [0057]    As described above, according to the third embodiment, even for the inverter device in which the capacitor  60  is covered with the resin mold layer, a withstand voltage test can be easily conducted. 
         [0058]    Instead of the insulating sheet IS, as shown in  FIG. 5 , a probe  90  including an insulator  91  placed on a side of the support pin  71  and a conductor  92  placed on a side of the terminal  621  may be provided between the terminal  621  of the capacitor  60  and the support pin  71 , and the conductor  92  and the test device are connected, and then the probe  90  can function as a probe of the test device. In this case, the probe contact portion  742  of the support pin  74  is not needed. 
       DESCRIPTION OF SYMBOLS 
       [0000]    
       
           10 ,  100  inverter device 
           11  module case 
           12  resin mold layer 
           13  first resin mold layer 
           14  second resin mold layer 
           20  power substrate 
           21  switching element 
           22  capacitor 
           30  control substrate 
           40  high voltage power supply 
           50  electric motor 
           60  capacitor 
         L lead wire