Patent Publication Number: US-8118564-B2

Title: Motor-driven compressor

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates generally to a motor-driven compressor, and more particularly to a motor-driven compressor having an inverter for driving an electric motor. 
     The motor-driven compressor has an electric motor for driving a compression mechanism of the compressor and an inverter for controlling and driving the electric motor. The motor-driven compressor is often installed and used in a vehicle and has a problem of vibration developed by an internal combustion engine. 
     If any frequency spectrum of the vibration developed by the internal combustion engine encompasses the resonance frequency of the inverter substrate, the substrate resonates with the vibration of the internal combustion engine and the stress of a solder or the like on the substrate is increased. If the stress on the solder is increased, problems occur so that cracks are generated in the leads (or pins) which are connected to the substrate by the solder. 
     To prevent the above problems, a gel material is enclosed for damping or suppressing the vibration in a conventional inverter type motor-driven compressor. That is, an inverter chamber of the motor-driven compressor is filled with vibration-damping gel thereby to fix and seal the inverter and its elements. Thus, the inverter and the substrate are fixed, so that the vibration is restrained. The motor-driven compressor having such an inverter is disclosed in the Japanese Patent Application Publication No. 2003-322082. 
     However, the inverter whose chamber is filled with the gel is undetachably fixed. Therefore, the use of the vibration-damping gel is not suitable to a motor-driven compressor having such an inverter that needs to be removed as required. 
     Furthermore, since substantially the entire space of the inverter chamber should be filled with the gel, the inverter with such a chamber becomes heavier. Additionally, the need of high-temperature treatment for curing the gel requires large-sized equipment for raising the inverter chamber temperature, with the result that the production cost is increased and harmful load is inevitably applied to electronic components due to the high-temperature treatment. 
     The present invention is directed to a motor-driven compressor which is capable of reducing the vibration of an inverter substrate without filling inverter chamber with vibration-damping gel. 
     SUMMARY OF THE INVENTION 
     In accordance with an aspect of the present invention, a motor-driven compressor includes a compression mechanism for compressing a refrigerant gas, an electric motor, an inverter assembly and an inverter chamber. The electric motor drives the compression mechanism. The inverter assembly converts direct-current power into polyphase alternating-current power to supply to the electric motor and controls a rotational speed of the electric motor. A substrate having an electric circuit and an electronic component connected to the substrate are provided in the inverter assembly. The inverter chamber detachably accommodates the inverter assembly. A vibration damping member is arranged in the inverter assembly. 
     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 
       The features of the present invention that are believed to be novel are set forth with particularity in the appended claims. 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: 
         FIG. 1  is a longitudinal cross sectional view of a motor-driven compressor according to a first embodiment of the present invention, 
         FIG. 2  is a fragmentary view showing an inverter assembly of the motor-driven compressor of  FIG. 1 ; and 
         FIG. 3  is a fragmentary view showing an inverter assembly of the motor-driven compressor of  FIG. 1  according to an alternative embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following will describe a motor-driven compressor of a first preferred embodiment according to the present invention with reference to  FIG. 1  through  FIG. 3 .  FIG. 1  shows a motor-driven compressor  10  according to the first preferred embodiment. The motor-driven compressor  10  includes a first housing  24  and a second housing  25 , which are fixed to each other by a plurality of bolts  16 . The first housing  24  is formed in a cylindrical shape, including a cylindrical portion  24   f  and a closed bottom portion  24   g . An annular shaft support portion  24   h  extends from the internal end face of the bottom portion  24   g  of the first housing  24 . 
     In  FIG. 1 , the right side of the drawing or the side of the second housing  25  corresponds to the front side of the motor-driven compressor  10 , and the left side of the drawing or the side of the first housing  24  to the rear side of the motor-driven compressor  10 . 
     The motor-driven compressor  10  has a fixed scroll member  11  and a movable scroll member  12  which cooperate to define therebetween a compression chamber  13 . The fixed scroll member  11  has a fixed base plate  11   a  with a disk shape, a fixed scroll wall  11   b  having a spiral shape and extending from the fixed base plate  11   a  and an outermost fixed scroll wall  11   c . The fixed base plate  11   a  has a discharge port  47  formed therethrough and at the center thereof. The fixed scroll member  11 , the movable scroll member  12  and the compression chamber  13  cooperate to form a compression mechanism of the motor-driven compressor  10  for compressing a refrigerant gas. 
     The movable scroll member  12  has a movable base plate  12   a  with a disk shape and a movable scroll wall  12   b  having a spiral shape and extending toward the front of the motor-driven compressor  10  from the movable base plate  12   a . The movable scroll member  12  is formed with an annular boss  12   c  extending toward the rear of the motor-driven compressor  10  from the center of the movable base plate  12   a  for holding therein a ball bearing  17 . 
     The motor-driven compressor  10  has a crank mechanism  19  through which the movable scroll member  12  performs an orbital motion with respect to the fixed scroll member  11  and pins  20  for preventing the movable scroll member  12  from rotating. The pins  20  are mounted to a shaft support member  15  and loosely fitted in an annular recess  12   d . The crank mechanism  19  includes the boss  12   c , a crank pin  22   a  of the drive shaft  22  and the ball bearing  17  for supporting the crank pin  22   a  through a bushing  18 . 
     The drive shaft  22  is disposed in the motor-driven compressor  10 , extending through the electric motor  26  at the center thereof. The electric motor  26  used for driving the compression mechanism is a three-phase synchronous motor. The electric motor  26  includes the drive shaft  22 , a rotor  28  fitted on the drive shaft  22  and a stator  30  located outside the rotor  28  and having a coil  29  wound therearound. 
     The first housing  24  has an Inverter chamber  101  formed in the outer periphery adjacent to the rear end thereof in the form of a recess. An inverter assembly  100  is accommodated in the inverter chamber  101 . It is noted that  FIG. 1  shows only the base  110  of the inverter assembly  100  for the sake of simplicity of illustration, but the inverter assembly  100  will be described in detail in later part hereof with reference to  FIG. 2 . 
     The inverter assembly  100  is electrically connected to the electric motor  26  through an airtight terminal  122  provided in the first housing  24  (which will be described later with reference to  FIG. 2 ). The inverter assembly  100  is operable to convert direct-current power supplied from an external device into polyphase alternating-current power, then supply the power to the electric motor  26  and control a rotational speed of the electric motor  26 . 
     The first housing  24  has a cover  150  mounted thereon for covering the inverter assembly  100  and separating the Inverter chamber  101  from the outside of the first housing  24 . A part of the outer wall of the motor-driven compressor  10  is provided by the cover  150 . That is, the cover  150 , the first housing  24  and the second housing  25  cooperate to separate the inside of the motor-driven compressor  10  from the outside of the first housing  24 . The cover  150  and the first housing  24  cooperate to define the outer wall of the Inverter chamber  101 . The inverter assembly  100  is disposed at the top of the first housing  24  above the drive shaft  22 , as seen in  FIG. 1 , when the motor-driven compressor  10  is used. 
     The drive shaft  22  is supported at the front end thereof adjacent to the crank mechanism  19  by the shaft support member  15  through a ball bearing  22   e  and at the opposite rear end thereof by a shaft support portion  24   h  of the first housing  24  through a ball bearing  22   f . A seal member  22   g  is provided behind the ball bearing  22   e  for sealing between the drive shaft  22  and the shaft support member  15 . 
     Fluid as a refrigerant gas flows in a space covered by the first housing  24  and the second housing  25 . In this space, the first housing  24  and the shaft support member  15  cooperate to define a motor chamber  27 , and the first housing  24 , the second housing  25  and the shaft support member  15  also cooperate to define a crank chamber  21 . The motor chamber  27  is connected to the crank chamber  21  through a suction passage (not shown). 
     The fixed scroll member  11  and the second housing  25  cooperate to define a discharge chamber  32  on the opposite side of the compression chamber  13  relative to the discharge port  47 . Refrigerant gas is compressed in the compression chamber  13 , and then flowed into the discharge chamber  32  through the discharge port  47 . A reed valve  34  and a retainer  36  are provided in the discharge chamber  32  for preventing backflow of the refrigerant gas, that is, a flow of the refrigerant gas from the discharge chamber  32  toward the discharge port  47 . The discharge chamber  32  has an outlet  32   a  which provides fluid communication between the discharge chamber  32  of the motor-driven compressor  10  and the external refrigeration circuit out of the motor-driven compressor  10 . 
     In the motor-driven compressor  10  having the above structure, refrigerant gas to be compressed flows from the suction side of the external refrigeration circuit into the motor chamber  27  through a suction port (not shown). Then, the refrigerant gas flows from the motor chamber  27  into the crank chamber  21  through a suction passage (not shown) and the compression chamber  13  in communication with the crank chamber  21 . In the compression chamber  13 , the refrigerant gas is compressed by orbital movement of the movable scroll member  12  in accordance with the rotation of the drive shaft  22  and the compressed refrigerant gas flows through the discharge port  47  into the discharge chamber  32 . Subsequently, the refrigerant gas is discharged out of the motor-driven compressor  10  through the outlet  32   a.    
       FIG. 2 , which is a fragmentary cross sectional view taken along the line II-II of  FIG. 1 , shows the inverter assembly  100  and peripheral structure thereof. 
     A gasket  120  is interposed between the cover  150  and the first housing  24  for sealing the inverter chamber  101 . The gasket  120  is made of a metal plate as a base plate surrounded by rubber. 
     The inverter assembly  100  includes a substrate  112  having an electric circuit and the base  110  for supporting the substrate  112 . The substrate  112  is fixed to the base  110  by screws  128 . 
     The cover  150 , the base  110  and the first housing  24  are fastened together by screws  118 . It is noted that the screws  118  are located at positions different from the illustration of  FIG. 2 , so that only the heads of the screws  118  are shown in the drawing and the portions of the inverter assembly  100  fastened by the screws  118  are not shown. The inverter assembly  100  includes various electronic components such as a capacitor  114 , a coil  116 , an airtight terminal  122 , an IGBT (insulated gate bipolar transistor)  124  and a varistor (not shown) which are connected to the substrate  112 . 
     The substrate  112  has at the center thereof a damper weight  140  made of a potting material with a certain weight and serving as a vibration damping member for reducing the vibration produced in the substrate  112 . The damper weight  140 , which is not a member for fixing the substrate  112  to the other components such as the cover  150  and the base  110  to support such components, may be so mounted on the substrate  112  that it is not in contact with the above components. In addition, the damper weight  140  is not in contact with the outer wall of the inverter chamber  101 . The resonance frequency when the substrate  112  and the damper weight  140  are vibrated together is shifted by mounting the damper weight  140  on the substrate  112 . The weight of the damper weight  140  is determined such that due to this shift the resonance frequency is out of the range of the frequency spectrum of the vibration produced in the internal combustion engine. Alternatively, the weight of the damper weight  140  is determined such that the resonance frequency shifts at least to the frequency range with smaller amplitude of the vibrations produced by the internal combustion engine. 
     Since the damper weight  140  is not intended to directly suppress the deformation of the substrate  112 , the damper weight  140  is used neither like a gel to fill the spaces between the substrate  112  and cover  150  and between the substrate  112  and the base  110 , nor to cover the entire substrate  112 . 
     In mounting the damper weight  140  on the substrate  112 , the semifluid potting material is put on the substrate  112  and then allowed to be solidified and adhered to the substrate  112  over time. 
     The capacitor  114  is provided by an electrolytic capacitor with a lead  114   a  which is soldered to the substrate  112  to electrically connect the capacitor  114  to the electric circuit of the substrate  112 . The capacitor  114  is fixed to the substrate  112  by the lead  114   a  and solder around the lead  114   a  (not shown) and adhered fixedly to the base  110  by resin adhesive  114   b.    
     The coil  116  has a lead  116   a  which is soldered to the substrate  112  to electrically connect the coil  116  to the electric circuit of the substrate  112 . The coil  116  is fixed to the substrate  112  by the lead  116   a  and solder around the lead  114   a  (not shown) and adhered fixedly to the base  110  by resin adhesive  116   b.    
     The IGBT  124  has a lead  124   a  which is soldered to the substrate  112  to electrically connect the IGBT  124  to the electric circuit of the substrate  112 . The IGBT  124  is fixed to the base  110  by screws  126 . 
     The airtight terminal  122  has a lead  122   a  which is soldered to the substrate  112  to electrically connect the airtight terminal  122  to the electric circuit of the substrate  112 . The airtight terminal  122  is fixed to the base  110 . Though not shown in the drawing, the airtight terminal  122  electrically connects the inverter assembly  100  to the electric motor  26  (refer to  FIG. 1 ) in the first housing  24  and air-tightly separates the inverter chamber  101  from the motor chamber  27  which accommodated therein the electric motor  26 . 
     A refrigerant passage (not shown) is formed between the first housing  24  and the stator  30  ( FIG. 1 ). The refrigerant gas flowing in this passage cools the inverter assembly  100  through the first housing  24  and also cools the electric motor  26  through the stator  30 . 
     The inverter assembly  100  is assembled with the substrate  112 , the capacitor  114  and the coil  116  supported by the base  110 . As described above, the base  110  is fastened to the first housing  24  by the screws  118  and, therefore, the inverter assembly  100  is fastened to the first housing  24 . Thus, the inverter assembly  100  is detachably mounted to the first housing  24  by means of the screws  118 . 
     In assembling the motor-driven compressor  10 , firstly the inverter assembly  100  is completed, for example, by firstly installing various electronic parts on the base  110 , fastening the substrate  112  to the base  110  by the screws  128  and then connecting various electronic parts to the substrate  112 . 
     After assembling the inverter assembly  100  has been thus completed, the inverter assembly  100  is mounted to the motor-driven compressor  10 . The cover  150 , the base  110  and the first housing  24  are fastened together by the screws  118 . 
     Because the inverter chamber  101  is not filled with gel, the base  110  may be removed from the first housing  24  by taking out the screw  118 , so that the inverter assembly  100  can also be removed from the first housing  24 . Thus, the integral-type inverter assembly  100  is of a cartridge-type and it is detachably accommodated in the inverter chamber  101  of the motor-driven compressor  10 . 
     The inverter assembly  100  of the motor-driven compressor  10  operates to suppress the vibration of the substrate  112  as follows. 
     The damper weight  140  mounted on the substrate  112  increases the weight of a portion of the substrate  112  which is vibrated together with the substrate  112 . This shifts the resonance frequency of the substrate  112  to a higher range that is out of the frequency spectrum of the vibration produced by the internal combustion engine. Thus, the substrate  112  does not resonate with the vibration of the internal combustion engine and vibration energy of the substrate  112  is decreased, accordingly. Therefore, the stress applied to the solder and the leads for electronic component such as the leads  114   a ,  116   a ,  122   a  and  124   a  is decreased. If the resonance frequency does not shift out of the above range, the resonance frequency shifts to a spectrum which has a smaller amplitude, at least the stress is reduced. 
     The damper weight  140 , which is made of a potting material, is soft after solidification and deformable adequately by the vibration, thus absorbing vibration energy to decrease the vibration level. 
     According to the inverter assembly  100  and the motor-driven compressor  10  of the first preferred embodiment wherein the damper weight  140  is mounted on the substrate  112  to reduce the vibration of the substrate  112 . Therefore, the vibration of the substrate  112  is reduced by the damper weight  140  without using gel in the inverter chamber  101 . 
     Because the inverter chamber  101  is not filled with gel, the inverter assembly  100  is detachable from the first housing  24  of the motor-driven compressor  10  by removing the screw  118 . 
     The damper weight  140  is mounted at the center of the substrate  112  where the amplitude of vibration of the substrate  112  is large. Thus, the reduction of vibration and the shift of resonance frequency are done effectively at the position where the vibration energy is large. 
     The inverter of the motor-driven compressor  10  of the present embodiment differs from conventional motor-driven compressor in that the inverter chamber  101  is not filled with gel. The damper weight  140  is made of a resin and its volume is much smaller than that of the inverter chamber  101 , so that the overall weight of the motor-driven compressor  10  can be reduced. 
     According to the motor-driven compressor  10  of the first preferred embodiment, having no gel in the inverter chamber  101 , high temperature treatment for consolidating gel can be dispensed with. Thus, a large-sized equipment for the treatment is unnecessary, so that the production cost is reduced and the treatment placing the electronic components under a load of high temperature can be avoided. 
     The damper weight  140  does not need to be in direct contact with the other components such as the cover  150  or the base  110  and, therefore, the damper weight  140  may be mounted on the substrate  112  at any time before the cover  150  is mounted on the motor-driven compressor  10 . Additionally, such arrangement of the damper weight  140  helps to increase the freedom in shape and mounting position of the damper weight  140 . 
     In the first preferred embodiment, the damper weight  140  is made of a potting material or a resin. According to the present invention, the damper weight  140  may be made of any other suitable non-conducting material. The material of the damper weight  140  does not necessarily contain resin. Additionally, the damper weight  140  may have any other shape or structure, or it may be mounted in any other way, if the damper weight  140  performs the function as a vibration damping member for reducing the vibration of the substrate  112  or shifting a resonance frequency of the substrate  112  to a high range. 
     The damper weight  140  is mounted at the center of the substrate  112 , as shown in  FIG. 2 . The position of mounting the damper weight  140  is not limited to the above center position, but it may be mounted at any other position or mounted at dispersed plural positions. For example, the damper weight  140  may be mounted at any position where amplitude of the substrate  112  in vibrating is large. The position where the amplitude becomes large includes a position where the amplitude is locally maximized. This is determined depending on the shape of the substrate  112 , the position and the number of the screw  128  and the conditions of each of the electronic components such as the weight, the mounting position and the fixed condition of the capacitor  114 . 
     The damper weight  140  may be mounted to any member of the inverter assembly  100  other than the substrate  112 . For example, the damper weight  140  may be mounted on the base  110  to reduce vibration of the base  110  as shown in  FIG. 3 , thereby to reduce the vibration transmitted from the base  110  to the substrate  112 . 
     In the first preferred embodiment, the motor-driven compressor  10  has been described as a scroll type compressor. However, the motor-driven compressor  10  is not limited to the scroll type compressor, but it may be of any type compressor having a compression mechanism for compressing a fluid. 
     Therefore, the present examples and embodiments are to be considered as illustrative and not restrictive, and the invention is not to be limited to the details given herein but may be modified within the scope of the appended claims.