Patent Publication Number: US-2018030972-A1

Title: Electric compressor

Description:
TECHNICAL FIELD 
     The present invention relates to a compressor for a refrigerating cycle which compresses a refrigerant, in particular to an electric compressor provided with an electric motor as a driving source. 
     BACKGROUND ART 
     A compressor used for a refrigerating cycle which sucks a low temperature and low pressure refrigerant and discharges a high temperature and high pressure refrigerant due to compression. Among compressors, there is an electric compressor provided with an electric motor as a driving source of a compression mechanism for the refrigerant. In the electric compressor, a driving circuit which converts direct current provided from a power source into alternating current by an inverter and supplies the alternating current to the electric motor is arranged. 
     The inverter is provided with a power switching element such as an IGBT (Insulated Gate Bipolar Transistor) and a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). 
     The power switching element generates heat by loss in switching (switching loss). When a temperature of the power switching element exceeds a heat resistance temperature by the heat, the power switching element is damaged. Thus, a configuration in which a passage for a low temperature and low pressure suction refrigerant and the power switching element are arranged along respective surfaces of partition walls which define respective housing spaces of the driving circuit and the compression mechanism and the power switching element is cooled by the suction refrigerant through the partition wall is conventionally proposed (see Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     Patent Literature 1: JP 2007-224809 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the conventional technique, during a period in which the electric compressor is stopped, the high pressure refrigerant located at a part of a discharge side flows into a part of a suction side, and thereby when the electric compressor is activated in which heat generation of the power switching element becomes maximum, the high temperature and high pressure refrigerant flowing into the part of the suction side from the part of the discharge side reaches a passage of the suction refrigerant, and therefore the power switching element might not be cooled sufficiently. 
     An object of the present invention is, in consideration of the problem described above, to provide an electric compressor capable of cooling a power switching element sufficiently by a refrigerant in a passage for a suction refrigerant. 
     Solution to Problem 
     In order to achieve the above object, an electric compressor according to an aspect of the present invention is an electric compressor which drives a compression mechanism for a refrigerant driven by the electric motor. The electric compressor includes a main housing housing the compression mechanism and the electric motor, a circuit housing housing a driving circuit of the electric motor, and is partitioned from the main housing by a partition wall, a suction refrigerant passage arranged on one surface of the partition wall exposed to the main housing and formed such that the refrigerant flowing into the suction refrigerant passage from an outside of the main housing through a suction port is sucked to an inside of the main housing through a refrigerant outlet, a check valve arranged in the suction refrigerant passage and configured to prevent the refrigerant from flowing backward from the refrigerant outlet toward the suction port in the suction refrigerant passage, and a power switching element contacted with a contact part in the other surface of the partition wall exposed to the circuit housing, the contact part opposed to a part of the suction refrigerant passage at a side of the suction port with respect to the check valve. 
     The check valve of the electric compressor according to the aspect of the present invention may include a valve body movable along a passing direction of the refrigerant in the suction refrigerant passage, a valve seat member having a valve seat part with which the valve body comes into contact with and separate from the refrigerant outlet side and is fixed to an inner surface of the suction refrigerant passage, and a spring biasing the valve body in a valve closing direction in contact with the valve seat part. The valve seat member may be formed to have a length in the passing direction of the refrigerant such that a part of the inner surface at a side of the suction port with respect to the valve seat member is exposed. 
     The check valve of the electric compressor according to the aspect of the present invention may include a valve body movable along a passing direction of the refrigerant in the suction refrigerant passage, a valve seat member having a valve seat part with which the valve body comes into contact with and separate from the refrigerant outlet side and is fixed to an inner surface of the suction refrigerant passage, and a spring biasing the valve body in a valve closing direction in contact with the valve seat part. The valve seat member may include an opening part which exposes a part of the inner surface at a side of the suction port with respect to the valve seat part. 
     A wall thickness of a part of the partition wall according to the aspect of the present invention where the suction refrigerant passage is arranged may be smaller than a wall thickness of the partition wall at a peripheral part of the suction refrigerant passage. 
     Advantageous Effects of Invention 
     According to the electric compressor according to one aspect of the present invention, the suction refrigerant passage is arranged at the part of the one surface of the partition wall facing the contact part to be contacted with the power switching element on the other surface of the partition wall. At this time, the power switching element contacted with the contact part is cooled via the partition wall by the low temperature and low pressure refrigerant flowing from the suction port and passing in the suction refrigerant passage toward the refrigerant outlet. 
     Here, when the electric compressor is stopped, the high temperature and high pressure refrigerant in the main housing, which tries to flow into the suction refrigerant passage from the refrigerant outlet, is prevented from flowing into the suction refrigerant passage by the check valve. Thus, a low temperature and low pressure refrigerant flowing from the suction port always exists at a part facing the contact part of the suction refrigerant passage to be contacted with the power switching element. 
     Accordingly, during a period in which the electric compressor is stopped, the power switching element, which is contacted with the contact part facing the suction refrigerant passage via the partition wall, is cooled by the low temperature and low pressure refrigerant in the suction refrigerant passage. In this way, the power switching element can be cooled sufficiently by the refrigerant in the suction refrigerant passage. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  illustrates a front view with a partial cross-section of an electric compressor according to one embodiment of the present invention. 
         FIG. 2  illustrates a side view seen from a side of a lid part of an inverter case shown in  FIG. 1 . 
         FIG. 3  illustrates a side view seen from a side of a circuit housing part of the inverter case shown in  FIG. 1 . 
         FIG. 4  illustrates a schematic view of a configuration of a check valve arranged in a suction refrigerant passage shown in  FIG. 2 . 
         FIG. 5  illustrates a side view seen from the side of the lid part of the inverter case shown in  FIG. 1 . 
         FIGS. 6( a ) to 6( c )  illustrate views of the specific configurations of the check valve shown in  FIG. 4 . 
         FIG. 7  illustrates an enlarged cross-sectional view of a main part showing a wall thickness of a partition wall near a suction refrigerant passage shown in  FIG. 2 . 
     
    
    
     DESCRIPTION OF EMBODIMENT 
     Hereinafter, an embodiment of the present invention is described with reference to drawings. 
       FIG. 1  illustrates a front view with a partial cross-section of an electric compressor according to one embodiment of the present invention, and  FIG. 2  and  FIG. 3  illustrate side views of an inverter case shown in  FIG. 1 . An electric compressor  1  of the present embodiment shown in  FIG. 1  is formed to drive a compression mechanism  3  by using an electric motor  5  so as to compress a refrigerant. 
     Further, as shown in  FIG. 1 , the electric compressor  1  of the present embodiment is provided with, in addition to the compression mechanism  3  and the electric motor  5 , a housing  7  (corresponding to a main housing in Claims) in which the compression mechanism  3  and the electric motor  5  are housed, and an inverter case  11  in which an inverter circuit  9  (corresponding to a driving circuit in Claims) formed as a driving circuit of the electric motor  5  is housed. 
     The compression mechanism  3  is provided with a pair of side blocks  3   a ,  3   b , a cylinder block  3   c  intervened by the side blocks  3   a ,  3   b , and a rotor  3   e  having a cylindrical shape housed in a cylinder chamber  3   d  having an oval shape formed in the cylinder block  3   c . A plurality of vanes (not shown) is supported on a peripheral surface of the rotor  3   e  so as to appear and disappear from the peripheral surface. 
     When the rotor  3   e  is rotated in the cylinder chamber  3   d  by the electric motor  5 , each vane of the rotor  3   e  appears and disappears in accordance with an inner surface of the cylinder chamber  3   d . With this, volume of a space formed by the rotor  3   e , two vanes adjacent to each other and the cylinder chamber  3   d  is changed. Further, a lower pressure refrigerant is sucked through a suction port (not shown) formed on the side block  3   a  during a period in which the volume of the space is increased. The suction refrigerant is compressed in accordance with decrease of the volume of the space. The compressed high pressure refrigerant is discharged from a discharge port (not shown) formed on the side block  3   b.    
     The housing  7  is formed in a cylindrical shape with one end being sealed. The compression mechanism  3  is housed in the housing  7 . Further, an inside of the housing  7  is partitioned by the housed compression mechanism  3  into a compression chamber  7   a  sealed and arranged at a sealed side, and a suction chamber  7   b  arranged at an opening side. The side block  3   b  is exposed to the compression chamber  7   a . The side block  3   a  is exposed to the suction chamber  7   b . The electric motor  5  is housed in the suction chamber  7   b . The suction chamber  7   b  is sealed by the inverter case  11  mounted to an opening  7   c  of the housing  7 . 
     The inverter case  11  is provided with a lid part  11   a  which seals the suction chamber  7   b  by covering the opening  7   c  of the housing  7 , and a circuit housing part  11   b  (corresponding to a circuit housing in Claims) arranged at an outside of the suction chamber  7   b  (housing  7 ) sealed by the lid part  11   a . The inverter circuit  9  is housed in the circuit housing part  11   b.    
     As shown in  FIG. 2 , the lid part  11   a  is provided with a suction port  11   c  which communicates the outside of the housing  7  with the suction chamber  7   b  in a state in which the opening  7   c  of the housing  7  is covered, and a partition wall  11   d  which partitions the suction chamber  7   b  and the circuit housing part  11   b . The suction port  11   c  is formed to suck a low temperature and low pressure refrigerant to be compressed by the compression mechanism  3  into the suction chamber  7   b  from an outside of the electric compressor  1  (for example, an evaporator of the refrigerating cycle). The suction port  11   c  is formed integrally with one surface  11   e  (corresponding to one surface in Claims) exposed to the suction chamber  7   b  of the partition wall  11   d.    
     As shown in  FIG. 3 , the circuit housing part  11   b  is formed in a cylindrical shape having a bottom provided by the partition wall  11   d . As shown in  FIG. 1 , a circuit substrate  9   a  of the inverter circuit  9  is fixed to other surface  11   f  (corresponding to other surface in Claims) of the partition wall  11   d  exposed to the circuit housing part  11   b . The circuit housing part  11   b  is sealed by a cap  11   h  mounted to an opening  11   g  of the circuit housing part  11   b.    
     A power switching element  9   b  such as an IGBT and a MOSFET, which form the inverter circuit  9 , is installed on the circuit substrate  9   a . A casing of the power switching element  9   b  is contacted with a contact portion  11   i  (corresponding to a contact part in Claims) having a thick wall formed in the other surface  11   f  of the partition wall  11   d  in a surface contact manner. 
     Further, in the present embodiment, a large gap is provided between the other surface  11   f  of the partition wall  11   d  and the circuit substrate  9   a  so that heat dissipation performance of the circuit substrate  9   a  is improved, and in order to allow the power switching element  9   b  to contact the other surface  11   f  of the partition wall  11   d , the contact portion  11   i  is made to be thicker than other part of the partition wall  11   d . However, the contact portion  11   i  may be made to have the same thickness as other part of the partition wall  11   d  so that the power switching element  9   b  is contacted with the other surface  11   f.    
     A suction refrigerant passage  13  is formed in the one surface  11   e  opposite to the other surface  11   f  on which the contact portion  11   i  of the partition wall  11   d  is formed. The suction refrigerant passage  13  is formed to introduce the refrigerant, which is passed through the suction port  11   c  from the outside of the electric compressor  1  (for example, an evaporator of the refrigerating cycle), into the suction chamber  7   b  sealed by the lid part  11   a.    
     As shown in  FIG. 2 , the suction refrigerant passage  13  is formed such that the refrigerant passed through the suction port  11   c  flows toward an outlet port  13   a  (corresponding to a refrigerant outlet in Claims) opened to the one surface  11   e  of the partition wall  11   d  exposed to the suction chamber  7   b . A check valve  15  is arranged in the suction refrigerant passage  13 . 
     The check valve  15  is formed to prevent the refrigerant from flowing backward in the suction refrigerant passage  13  from the outlet port  13   a  toward the suction port  11   c . As shown by the view in  FIG. 4  schematically, the check valve  15  is provided with a valve body  15   a , a valve seat member  15   b  and a spring  15   d.    
     The valve body  15   a  is formed in a cylindrical shape having an outer diameter smaller than an inner diameter of the suction refrigerant passage  13  and formed in a movable manner along a passing direction A of the refrigerant in the suction refrigerant passage  13  from the suction port  11   c  toward the outlet port  13   a.    
     The valve seat member  15   b  is formed in a cylindrical shape having an inner diameter smaller than the outer diameter of the valve body  15   a . The valve seat member  15   b  is press-fitted into the suction refrigerant passage  13  from a side closer to the suction port  11   c  than the valve body  15   a  such that a center axial direction of the valve seat member  15   b  is matched with the passing direction A of the refrigerant, and the valve seat member  15   b  is fixed to an inner surface  13   b  of the suction refrigerant passage  13  at a position near the outlet port  13   a  at a side of the suction port  11   c . The refrigerant flowing into the suction refrigerant passage  13  from the suction port  11   c  toward the outlet port  13   a  is passed through an inside of the valve seat member  15   b.    
     The spring  15   d  is arranged opposite to the valve seat member  15   b  with respect to the valve body  15   a . The spring  15   d  is formed to bias the valve body  15   a  in a valve closing direction such that the valve body  15   a  is contacted with a valve seat part  15   c  formed by an end surface of the valve seat member  15   b  arranged at a side of the outlet port  13   a  of the suction refrigerant passage  13 . 
     In the check valve  15  formed as described above, the valve body  15   a  is moved against the biasing force of the spring  15   d  so that the check valve  15  is opened when the pressure of the refrigerant in the suction chamber  7   b  is decreased because the refrigerant is sucked into the compression mechanism  3  during a period in which the electric compressor  1  is working. With this, the check valve  15  allows the refrigerant flowing into the suction refrigerant passage  13  from the suction port  11   c  to flow into the suction chamber  7   b  from the outlet port  13   a . At this time, the valve body  15   a  is located at a position shown in  FIG. 2  against the outlet port  13   a  of the suction refrigerant passage  13 . 
     Further, during a period in which the electric compressor  1  is stopped, the valve body  15   a  is contacted with the valve seat part  15   c  of the valve seat member  15   b  by the biasing force of the spring  15   d  so that the check valve  15  is closed. At this time, the valve body  15   a  is located at a position shown by a side view in  FIG. 5  against the outlet port  13   a  of the suction refrigerant passage  13 . 
     Further, during the period in which the electric compressor  1  is stopped, for example, when the pressure in the suction chamber  7   b  is increased due to the high temperature and high pressure refrigerant flowing from the compression chamber  7   a , the pressure in the suction chamber  7   b  acts as force for contacting the valve body  15   a  in a valve closed state with the valve seat part  15   c  of the valve seat member  15   b . Thus, the valve body  15   a  is kept in the valve closed state, and the check valve  15  prevents the high temperature and high pressure refrigerant from flowing backward from the suction chamber  7   b  into the suction refrigerant passage  13  via the outlet port  13   a.    
     Here, in order to perform the function of the check valve  15  described above, it is necessary that the valve seat part  15   c  of the valve seat member  15   b  is fixed at a position near the outlet port  13   a  in the suction refrigerant passage  13  when large force is applied to the valve body  15   a  in the valve closing direction. As a specific configuration to perform the function described above, configurations as shown by views in  FIGS. 6( a ) to 6( c )  can be considered. 
     At first, as shown by the check valve  15  in  FIG. 6( a ) , a configuration in which a length in the center axial direction of the valve seat member  15   b  is set as same as a gap between the valve body  15   a  located at a valve closed position and a distal end  17   a  of a refrigerant tube  17  and the valve seat member  15   b  is pressed by the distal end of the refrigerant tube  17  fixed to the suction port  11   c  may be adopted. 
     Further, as shown by the check valve  15  in  FIG. 6( b ) , a configuration in which a distal end  17   a  of the refrigerant tube  17  is extended into the suction refrigerant passage  13  to contact with the valve seat member  15   b  and the valve seat member  15   b  is pressed by the distal end of the refrigerant tube  17  fixed to the suction port  11   c  may be adopted. 
     Further, as shown by the check valve  15  in  FIG. 6( c ) , a configuration in which a stepped part  13   c  is formed in the middle of the suction refrigerant passage  13  and the valve seat member  15   b  is press-fitted into the suction refrigerant passage  13  from a side (outlet port  13   a  side) opposite to a side of the suction port  11   c  so that the valve seat member  15   b  is abutted on the stepped part  13   c  may be adopted. 
     In such a case, it is necessary that an opening  13   d  for press-fitting the valve seat member  15   b  into the suction refrigerant passage  13  is formed in the suction refrigerant passage  13  and the opening  13   d  is sealed by a sealing member  13   e  after housing the valve seat member  15   b , the valve body  15   a , and the spring  15   d  sequentially in the suction refrigerant passage  13 . 
     It is preferable that a part to which the inner surface  13   b  is exposed is arranged in the suction refrigerant passage  13  in which the check valve  15  having the configuration described above is arranged, at the outlet port  13   a  side with respect to the refrigerant tube  17  fitted with the suction port  11   c . For example, in the check valve  15  shown in  FIG. 4 , the inner surface  13   b  of the suction refrigerant passage  13  can be exposed by shortening the length in the center axial direction of the valve seat member  15   b  such that a large gap is provided between the distal end  17   a  of the refrigerant tube  17  and the valve seat member  15   b.    
     Further, the inner surface  13   b  of the suction refrigerant passage  13  can be also exposed via a penetration window  15   e  by forming the penetration window  15   e  (corresponding to an opening part in Claims) on a peripheral surface of the valve seat member  15   b  as shown by the check valve  15  in  FIG. 6( a ) . Further, in  FIG. 6( a ) , a plurality of the penetration windows  15   e  is formed, however the number of the penetration windows  15   e  may be set to one. 
     When the inner surface  13   b  of the suction refrigerant passage  13  is exposed in this way, the low temperature and low pressure refrigerant flowing into the suction refrigerant passage  13  from the suction port  11   c  and flowing toward the outlet port  13   a  is always contacted with the inner surface  13   b . Even if the high temperature and high pressure refrigerant flows into the suction chamber  7   b  from the compression chamber  7   a , the check valve  15  prevents the refrigerant from flowing into the suction refrigerant passage  13  at a position near the outlet port  13   a , and therefore the high temperature and high pressure refrigerant is not contacted with the inner surface  13   b  of the suction refrigerant passage  13 . 
     Further, in the present embodiment, the check valve  15  shown in  FIG. 4  is arranged in the suction refrigerant passage  13  and the inner surface  13   b  of the suction refrigerant passage  13  is exposed. As shown in  FIG. 3 , an exposed part of the inner surface  13   b  of the suction refrigerant passage  13  is located at a position just behind the contact portion  11   i  on the other surface  11   f  of the partition wall  11   d  with which the power switching element  9   b  is contacted. That is, the power switching element  9   b  is contacted with the contact portion  11   i  facing a part to which the inner surface  13   b  of the suction refrigerant passage  13  is exposed. 
     Accordingly, the power switching element  9   b  is cooled by heat transmitted from the low temperature and low pressure refrigerant, which is passed through the suction refrigerant passage  13  from the suction port  11   c  toward the outlet port  13   a , to the contact portion  11   i  via the inner surface  13   b  of the suction refrigerant passage  13  and the partition wall  11   d.    
     Here, as shown by the enlarged cross-sectional view of the main part of the partition wall  11   d  in a direction perpendicular to the passing direction A of the refrigerant in  FIG. 7 , a wall thickness of a part of the partition wall  11   d  where the suction refrigerant passage  13  is formed, namely a wall thickness x between the inner surface  13   b  of the suction refrigerant passage  13  and the contact portion  11   i  on the other surface  11   f  of the partition wall  11   d , is smaller than a wall thickness y of a peripheral part of the suction refrigerant passage  13  of the partition wall  11   d.    
     That is, strength of the partition wall  11   d  is necessary to endure differential pressure between the suction chamber  7   b  and the circuit housing part  11   b , and therefore the wall thickness y should be set in accordance with the necessity of the strength. In a part in which the suction refrigerant passage  13  is formed, a frame which forms the suction refrigerant passage  13  has a reinforcement function. Accordingly, even if the wall thickness x of the part of the partition wall  11   d  in which the suction refrigerant passage  13  is formed is set to be smaller than the wall thickness y of the peripheral part of the suction refrigerant passage  13 , the necessary strength can be maintained. 
     Further, since the wall thickness x between the inner surface  13   b  of the suction refrigerant passage  13  and the contact portion  11   i  on the other surface  11   f  of the partition wall  11   d  is smaller than the wall thickness y of the peripheral part of the suction refrigerant passage  13  of the partition wall  11   d , heat transmission efficiency from the inner surface  13   b  of the suction refrigerant passage  13  to the contact portion  11   i  of the partition wall  11   d  is enhanced, and therefore cooling efficiency of the power switching element  9   b  is improved. 
     In this way, according to the electric compressor  1  of the present embodiment, the refrigerant is sucked from the suction port  11   c  and passed through the suction refrigerant passage  13 , and thereby the power switching element  9   b  contacted with the contact portion  11   i , which is formed at a back side of the suction refrigerant passage  13 , is cooled. At this time, in the electric compressor  1  of the present embodiment, the check valve  15  prevents the high temperature and high pressure refrigerant, which flows into the suction chamber  7   b  from the compression chamber  7   a , from flowing backward to the suction refrigerant passage  13 . Thus, the low temperature and low pressure refrigerant always exists in the suction refrigerant passage  13  and thereby the power switching element  9   b  can be cooled efficiently by the refrigerant in the suction refrigerant passage  13 . 
     Further, in the present embodiment, a configuration in which the lid part  11   a  which covers the opening  7   c  of the housing  7  is arranged in the inverter case  11  and the suction port  11   c  for sucking the refrigerant into the suction chamber  7   b  and the suction refrigerant passage  13  are arranged in the lid part  11   a  is described as an example. However, a configuration in which one or both of the suction port  11   c  and the suction refrigerant passage  13  are arranged in the housing  7  may be adopted. 
     It should be noted that the present application claims priority to Japanese Patent Application No. 2015-025291, filed on Feb. 12, 2015, and the entire contents of which are incorporated by reference herein. 
     INDUSTRIAL APPLICABILITY 
     The present invention can be used in an electric compressor that drives a compression mechanism for a refrigerant driven by an electric motor. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1  ELECTRIC COMPRESSOR 
               3  COMPRESSION MECHANISM 
               3   a ,  3   b  SIDE BLOCK 
               3   c  CYLINDER BLOCK 
               3   d  CYLINDER CHAMBER 
               3   e  ROTOR 
               5  ELECTRIC MOTOR 
               7  HOUSING (MAIN HOUSING) 
               7   a  COMPRESSION CHAMBER 
               7   b  SUCTION CHAMBER 
               7   c  OPENING (OPENING OF HOUSING) 
               9  INVERTER CIRCUIT (DRIVING CIRCUIT) 
               9   a  CIRCUIT SUBSTRATE 
               9   b  POWER SWITCHING ELEMENT 
               11  INVERTER CASE 
               11   a  LID PART 
               11   b  CIRCUIT HOUSING PART (CIRCUIT HOUSING) 
               11   c  SUCTION PORT 
               11   d  PARTITION WALL 
               11   e  SURFACE OF PARTITION WALL (ONE SURFACE) 
               11   f  SURFACE OF PARTITION WALL (OTHER SURFACE) 
               11   g  OPENING OF CIRCUIT HOUSING PART 
               11   h  CAP 
               11   i  CONTACT PORTION (CONTACT PART) 
               13  SUCTION REFRIGERANT PASSAGE 
               13   a  OUTLET PORT (REFRIGERANT OUTLET) 
               13   b  INNER SURFACE 
               13   c  STEPPED PART 
               13   d  OPENING 
               13   e  SEALING MEMBER 
               15  CHECK VALVE 
               15   a  VALVE BODY 
               15   b  VALVE SEAT MEMBER 
               15   c  VALVE SEAT PART 
               15   d  SPRING 
               15   e  PENETRATION WINDOW (OPENING PART)