Abstract:
There is provided a motor-driven compressor including a semiconductor device that comprises a compression mechanism, a motor, a housing, a wall, an electronic component, and a resin member. The motor drives the compression mechanism. The housing accommodates therein the compression mechanism and the motor. The wall extends from an outer surface of the housing so as to surround a part thereof and have an opened end and cooperates with the outer surface of the housing to form a casing. The electronic component is accommodated in the casing and includes a semiconductor module that includes a circuit board connected to the outer surface of the housing and a semiconductor element mounted to the circuit board. The resin member seals an entirety of the electronic component in the casing.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a motor-driven compressor including a semiconductor device that drives a motor of the motor-driven compressor. 
         [0002]    Japanese Patent Application Publication No. 2003-322082 discloses a motor-driven compressor having a compression mechanism, a motor driving the compression mechanism, and a semiconductor device including a drive circuit driving the motor. The semiconductor device has transistor modules that are fixed to a housing of the motor-driven compressor by bolts through a resin insulation sheet. 
         [0003]    A semiconductor device generates heat during its operation. The heat may cause thermal stress which in turn causes peeling at a connection part between a semiconductor element and a circuit board. In order to address such problems of the motor-driven compressor mounting the semiconductor device on the motor-driven compressor, effective measures need to be taken to ensure reliability of the semiconductor device that drives the motor of the motor-driven compressor. 
         [0004]    The present invention, which has been made in light of the above problems, is directed to providing a motor-driven compressor including a semiconductor device that improves its reliability. 
       SUMMARY OF THE INVENTION 
       [0005]    In accordance with an aspect of the present invention, there is provided a motor-driven compressor including a semiconductor device that comprises a compression mechanism, a motor, a housing, a wall, an electronic component, and a resin member. The motor drives the compression mechanism. The housing accommodates therein the compression mechanism and the motor. The wall extends from an outer surface of the housing so as to surround a part thereof and have an opened end and cooperates with the outer surface of the housing to form a casing. The electronic component is accommodated in the casing and includes a semiconductor module that includes a circuit board connected to the outer surface of the housing and a semiconductor element mounted to the circuit board. The resin member seals an entirety of the electronic component in the casing. 
         [0006]    Other aspects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention together with objects and advantages thereof, may best be understood by reference to the following description of the presently preferred embodiments together with the accompanying drawings in which: 
           [0008]      FIG. 1  is a perspective view of a motor-driven compressor having a semiconductor device according to an embodiment of the present invention; and 
           [0009]      FIG. 2  is a longitudinal sectional view of the compressor of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
       [0010]    The following will describe a semiconductor device mounted on a motor-driven compressor according to an embodiment of the present invention with reference to  FIGS. 1 and 2 . Referring to  FIG. 1 , the motor-driven compressor that is designated by reference numeral  10  includes a housing  11 . The housing  11  accommodates therein a compression mechanism  12  compressing refrigerant and discharging refrigerant and a motor  13  driving the compression mechanism  12 . The housing  11  is formed with an inlet  14  through which refrigerant is flowed into the housing  11 . The motor-driven compressor  10  further includes a semiconductor device  15  for driving the motor  13 . The semiconductor device  15  serves as an inverter for converting DC power to AC power and supplying the AC power to the motor  13 . 
         [0011]    The housing  11  has a wall  17  formed integrally with the housing  11  and extending from the outer surface  16  of the housing  11 . In the present embodiment, the wall  17  is formed annularly at one end of the housing  11  adjacent to the motor  13 . The wall  7  has an opened end  18 . Therefore, a circular recess is formed at a part of the outer surface  16  of the housing  11  by the wall  17  and has a bottom that is formed by a part of the outer surface  16  at the one end of the housing  11 . 
         [0012]    As shown in  FIG. 2 , electronic components  19  that form the semiconductor device  15  are accommodated in the recess of the wall  17 . The electronic component  19  includes a semiconductor module  20 . The semiconductor module  20  includes a semiconductor element  21  and a circuit board  22  mounting thereon the semiconductor element  21 . The semiconductor element  21  includes a switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a diode. 
         [0013]    The circuit board  22  includes a ceramic board  23  that serves as an insulating layer, a first metal plate  24  that is connected on the first surface of the ceramic board  23  and serves as a wiring layer, and a second metal plate  25  that is connected on the second surface of the ceramic board  23  that is located on the side of the ceramic board  23  opposite to the first surface and serves as a connection layer. The semiconductor element  21  is soldered to the first metal plate  24  and the second metal plate  25  is connected by brazing directly on the outer surface  16  of the housing  11  of the recess surrounded by the wall  17 . The second metal plate  25  is brazed to the outer surface  16  of the housing  11 . The ceramic board  23  is made of, for example, aluminum nitride. The first metal plate  24  and the second metal plate  25  are made of, for example, pure aluminum such as aluminum for industrial use having 99.0% purity or higher, or copper. 
         [0014]    In the present embodiment, the second metal plate  25  serves as a stress reducing member reducing the stress applied to the connection between the circuit board  22  and the semiconductor element  21  and the connection between the circuit board  22  and the housing  11 . The stress reducing member disperses the thermal stress caused by the difference of linear thermal expansion coefficient among the ceramic board  23 , the first metal plate  24 , the second metal plate  25 , and the housing  11  thereby to reduce thermal stress applied to the above connections, namely the connection between the circuit board  22  and the semiconductor element  21  and the connection between the circuit board  22  and the housing  11 . Though not shown in the drawing, the second metal plate  25  has therein a space in the form of a step, a groove, or a recess forming a part of the second metal plate  25  that is not connected to the housing  11  and hence helps reduce or relieve the thermal stress. 
         [0015]    As described above, the wall  17  of the housing  11  forms a casing  26  housing the electronic components  19  including a semiconductor module  20 . In other words, a space that is defined by the wall  17  and a part of the outer surface  16  of the housing  11  surrounded by the wall  17  serve as a casing for the semiconductor device  15 . 
         [0016]    As shown in  FIG. 2 , the casing  26  is sealed by a resin member  27  with the electronic components  19  housed in the casing  26 . In the present embodiment, the resin member  27  sealing the casing  26  is made of epoxy resin. 
         [0017]    The resin member  27  fills the space surrounded by the wall  17  to the opened end  18  of the wall  17 . Thus, the electronic components  19  housed in the casing  26  are covered entirely by the resin member  27 . The resin member  27  is not covered, but exposed to the atmosphere at the opened end  18  of the wall  17 . 
         [0018]    The following will describe the operation of the semiconductor device  15  for the motor-driven compressor  10 . The semiconductor module  20  housed in the casing  26  is cooled by refrigerant flowing in the housing  11  of the motor-driven compressor  10 . In the present embodiment wherein the circuit board  22  of the semiconductor module  20  is brazed directly to the outer surface  16  of the housing  11 , heat exchange is performed easily between the refrigerant flowing in the housing  11  and the circuit board  22 . Additionally, in the structure wherein the casing  26  is sealed by the resin member  27 , thermal deformation at the connection between the semiconductor element  21  and the circuit board  22  and between the circuit board  22  and the housing  11  is suppressed and hence reduced. 
         [0019]    The present embodiment offers the following advantageous effects. 
         [0020]    (1) Sealing the casing  26  housing therein the electronic component  19  including the semiconductor module  20  by a resin member suppresses the thermal deformation. Therefore, the connection between the semiconductor element  21  and the circuit board  22  and the connection between the circuit board  22  and the housing  11  are prevented from being peeled by thermal stress, so that the reliability of the semiconductor device  15  is improved. 
         [0021]    (2) Additionally, sealing the casing  26  by the resin member  27  improves the connection between the housing  11  and the semiconductor module  20 , so that heat radiation of the semiconductor device  15  is improved. The reliability in the strength of the connection between the semiconductor element  21  and the circuit board  22  and the connection between the circuit board  22  and the housing  11  is improved, with the result that the reliability of the semiconductor device  15  is improved and, therefore, the deterioration of the semiconductor device  15  is suppressed. 
         [0022]    (3) The configuration in which the semiconductor module  20  is connected directly to the housing  11  allows the semiconductor device  15  to be simplified in structure and be made smaller in size. 
         [0023]    (4) The configuration in which the casing  26  is formed by the wall  17  of the housing  11  allows the wall  17  to serve as a jig that regulates the flow of resin when sealing the casing  26  by the resin member  27 . Therefore, no jig need to be prepared for regulating the flow of resin and the sealing operation is made easily. 
         [0024]    (5) The configuration in which the wall  17  forms a casing for the semiconductor device  15  allows the motor-driven compressor  10  to be simplified in structure and be made smaller in size as compared to a case in which a separate semiconductor device having therein the electronic component  19  is mounted on the housing  11 . 
         [0025]    (6) The wall  17  that is formed integrally with the housing  11  when making the housing  11 , so that strength of the semiconductor device  15  including a casing is secured. 
         [0026]    (7) In the semiconductor device  15 , the second metal plate  25  of the circuit board  22  serves as stress reducing member. The provision of this stress reducing member in addition to the resin member  27  helps prevent the connection from being peeled. 
         [0027]    (8) The circuit board  22  is brazed to the housing  11  and therefore the connection between the circuit board  22  and the housing  11  is improved. As a result, heat radiation of the semiconductor device  15  is improved. 
         [0028]    The present embodiment may be modified as follows. For connecting the semiconductor module  20  to the housing  11 , a bolt, pressure welding and so on may be used. 
         [0029]    The layout and the number of the casing  26  may be changed. For example, the casing  26  may be formed extending from the outer peripheral surface of the housing  11  and a plurality of the casings  26  may be disposed. The wall  17  is not limited to an annular or a circular shape, but it may be of a rectangular shape. That is, as far as the wall  17  serves as a jig that regulates the flow of resin when sealing by a resin member, the wall  17  may be formed in any shape. 
         [0030]    As far as the resin member  27  covers the entire electronic component  19  in the casing  26 , the resin member  27  may be formed in any shape. The second metal plate  25  may be made of a metal plate that simply serves as a connection layer. That is, the second metal plate may dispense with thermal stress relieving part such as the aforementioned step, groove or recess.