Abstract:
A motor rotor equipped with a cylindrical rotor core formed by stacking multiple electromagnetic steel plates, end plates and balance weights stacked at both ends of the rotor core, and multiple headed swaging pins penetrating and integrally connecting the rotor core, the end plates, and the balance weights, wherein spacers or washers formed of a harder material than the swaging pins are interposed between the seating surface of the balance weights and the heads of the swaging pins. Thus, resistance of the motor rotor to excessive excitation force can be increased and a decrease in fastening strength can easily be prevented without changing the structure integrally fastened together by the swaging pins.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a motor rotor which cylindrically stacks a plurality of electromagnetic steel plates and integrally fastens the plurality of electromagnetic steel plates by swaging pins, and a motor and an electric compressor using the same. 
       BACKGROUND ART 
       [0002]    In a rotor of a motor used in an electric compressor, a plurality of electromagnetic steel plates are cylindrically stacked so as to configure a rotor core, a magnet is embedded to the inside of the rotor core, end plates are stacked on both ends of the rotor core, balance weights are stacked on both end surfaces, and the rotor core, the end plates, and the balance weights are integrally fastened by a plurality of headed swaging pins (also referred to as rivets) or bolts and nuts which are inserted from one side (for example, refer to PTLs 1 to 3). 
         [0003]    In this motor rotor, in general, a ferrous base material is used as the material of the swaging pin, a brass material, a zinc material, a stainless material, or the like is used as the material of the end plats in order to prevent a leakage of magnetic flux, and a brass material, a steel material, a stainless material, or the like which is a metal having a high specific weight is used as the material of the balance weight. In addition, in order to integrally fasten the plurality of electromagnetic steel plates including balance weights and the end plates, bolts and nuts described in PTL 3 are used. However, economically, as shown in PTLs 1 and 2, the end plates and/or balance weights are integrally fastened simultaneously by the swaging pins. 
       CITATION LIST 
     Patent Literature 
       [0004]    [PTL 1] Japanese Unexamined Patent Application Publication No. 2009-124821 
         [0005]    [PTL 2] Japanese Unexamined Patent Application Publication No. 2000-116080 
         [0006]    [PTL 3] Japanese Unexamined Patent Application Publication No. 2007-198335 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    In the motor rotor having the above-described configuration, in most cases, the ferrous base material is mainly used as the material of the swaging pin, and a brass material is used as the materials of the balance weight and the end plate for the sake of the functions. However, the present inventors assumed an overload operation under an excitation condition in which an excessive load was applied to the motor rotor and performed an excitation test (excitation test in X, Y, and Z axial directions). As a result, the seating surface of the balance weight which was stacked and disposed on the head side of the swaging pin was depressed by setting due to the contact with the swaging pin head, rattling occurred due to a decrease in fastening strength, and there was a concern that damages occurred. 
         [0008]    The above-described problems are likely to be more and more conspicuous as a load applied to a motor increase and the motor rotates a high speed, and measures are necessary in a motor to which the motor rotor haying the above-described configuration is applied and an electric compressor or the like to which the motor is applied. 
         [0009]    The present invention is made in consideration of the above-described circumstance, and an object thereof is to provide a motor rotor in which a resistance with respect to an excessive excitation force of the motor rotor can be increased without changing an integral fastening structure formed by the swaging pin and a decrease in fastening strength can be easily prevented, and a motor and an electric compressor using the motor rotor. 
       Solution to Problem 
       [0010]    In order to achieve the above-described object, a motor rotor of the present invention and a motor and an electric compressor using the motor rotor adopt the following means. 
         [0011]    That is, according to an aspect of the present invention, there is provided a motor rotor, including: a cylindrical rotor core which is formed by stacking a plurality of electromagnetic steel plates; end plates and balance weights which are stacked on both ends of the rotor core; and a plurality ox headed swaging pins which penetrate and integrally fasten the rotor core, the end plates, and the balance weights, in which a washer or a spacer which is formed of a harder material than materials of the swaging pins is interposed between a head of each swaging pin and a seating surface of each balance weight. 
         [0012]    According to the present invention, in the motor rotor in which the end plates and the balance weights are stacked on both ends of the rotor core which is formed by stacking the plurality of electromagnetic steel plates and the rotor core, the end plates, and the balance weights are integrally fastened so as to be swaged by the plurality of headed swaging pins, the washer or the spacer which is formed of a harder material than the material of the swaging pin is interposed between the head of the swaging pin and the seating surface of the balance weight. Accordingly, even under an excitation condition in which an excessive load is applied to the motor rotor, since the seating surface of the balance weight which is stacked and disposed on the head side of the swaging pin is in contact with the swaging pin head via the washer or the spacer formed of a harder material than that of the swaging pin, depression in the seating surface due to contact with the swaging pin head is not generated, it is possible to maintain fastening strength. 
         [0013]    Meanwhile, a swaging piece of the swaging pin can be rigidly swaged so as to be bitten to the end plate or the balance weight which is stacked and disposed on the swaging portion side of the swaging pin. Accordingly, since the fastening strength of the balance weight performed by the swaging pin increases and resistance with respect to an excessive excitation force is improved, it is possible to decrease risk of the fastening strength of the balance weight decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor so as to secure reliability of the motor. 
         [0014]    In addition, in the motor rotor of the present invention, in the above-described motor rotor, a counterbore which causes the washer or the spacer to be interposed is provided on the seating surface of the balance weight. 
         [0015]    According to the present invention, since a counterbore which causes the washer or the spacer to be interposed is provided on the seating surface of the balance weight, the washer or the spacer can be interposed between the swaging pin head and the seating surface of the balance weight via the counterbore. Accordingly, it is possible to stabilize seating of the washer or the spacer, and it is possible to further increase the fastening strength of the balance weight. 
         [0016]    In addition, in the motor rotor of the present invention, in any one of the above-described motor rotors, a diameter of the washer or the spacer is larger than a diameter of a head of the swaging pin. 
         [0017]    According to the present invention, since the diameter of the washer or the spacer is larger than the diameter of the head of the swaging pin, it is possible to reliably decrease a surface procedure applied to the seating surface of the balance weight by allowing the diameter of the washer or the spacer which is in contact with the seating surface of the balance weight to be larger than the diameter of the head of the swaging pin, and it is possible to prevent depression due to setting of the seating surface. Accordingly, it is possible to increase fastening strength of the balance weight and it is possible to reliably improve the resistance with respect to an excessive excitation force. 
         [0018]    Moreover, in the motor rotor of the present invention, in any one of the above-described motor rotors, a swaging pin is formed of a ferrous base material, the balance weight is formed of a brass material, and the washer or the spacer is formed of a stainless material. 
         [0019]    According to the present invention, since the swaging pin is formed of a ferrous base material, the balance weight is formed of a brass material, and the washer or the spacer is formed of a stainless material, the inexpensive washer or spacer is interposed in a state where a brass material which has lower hardness than that of the swaging pin and is cheaper than a stainless material or the like is used as the balance weight, and it is possible to secure the fastening strength of the balance weight. Accordingly, it is possible to increase the fastening strength of the balance weight while preventing an increase in cost, and it is possible to improve the resistance with respect to an excessive excitation force. 
         [0020]    In addition, according to another aspect of the present invention, there is provided a motor, including: a motor rotor; and a motor stator, in which the motor rotor is any one of the above-described motor rotors. 
         [0021]    According to the motor of the present invention, since the motor rotor is any one of the above-described motor rotors, it is possible to improve fastening strength of the end plates and the balance weights which are staked on both ends of the motor rotor and are integrally fastened via the swaging pins, Accordingly, since the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the motor rotor, it is possible to decrease risk of the fastening strength of the end plate and the balance weight decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor so as to secure reliability of the motor. 
         [0022]    In addition, according to still another aspect of the present invention, there is provided an electric compressor, including: a compression mechanism; and a motor which drives the compression mechanism via a driving shaft, in which the motor is the above-described motor. 
         [0023]    According to the electric compressor of the present invention, since the motor which drives the compression mechanism, via the driving shaft is the above-described motor, the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the rotor of the motor which drives the compression mechanism, and if is possible to decrease risk of the fastening strength of the end plate and the balance weight decreasing, rattling occurring, and damage occurring. Accordingly, it is possible to further improve a vibration-proof performance at the time of the overload operation of the electric compressor so as to increase reliability of the electric compressor. 
       Advantageous Effects of Invention 
       [0024]    According to the motor rotor of the present invention, even under an excitation condition in which an excessive load is applied to the motor rotor, since the seating surface of the balance weight which is stacked and disposed on the head side of the swaging pin is in contact with the swaging pin head via the washer or the spacer formed of a harder material than that of the swaging pin, depression in the seating surface due to contact with the swaging pin head is not generated, it is possible to maintain fastening strength. Meanwhile, the swaging piece of the swaging pin can be rigidly swaged so as to be bitten to the end plate or the balance weight which is stacked and disposed on the swaging portion side of the swaging pin. Accordingly, since the fastening strength of the balance weight performed by the swaging pin increases and resistance with respect to an excessive excitation force is improved, it is possible to decrease risk of the fastening strength of the balance weight decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor so as to secure reliability of the motor. 
         [0025]    According to the motor of the present invention, it is possible to improve fastening strength of the end plates and the balance weights which are staked on both ends of the motor rotor and are integrally fastened via the swaging pins. Accordingly, since the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the motor rotor, it is possible to decrease risk of the fastening strength of the end plate and the balance weight decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor so as to secure reliability of the motor. 
         [0026]    According to the electric compressor of the present invention, since the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the rotor of the motor which drives the compression mechanism, and it is possible to decrease risk of the fastening strength of the end plate and the balance weight decreasing, rattling occurring, and damage occurring. Accordingly, it is possible to further improve a vibration-proof performance at the time of the overload operation of the electric compressor so as to increase reliability of the electric compressor. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]      FIG. 1  is a longitudinal sectional view of an electric compressor according to a first embodiment of the present invention. 
           [0028]      FIG. 2  is a longitudinal sectional view of a motor rotor in the electric compressor. 
           [0029]      FIG. 3  is an enlarged sectional corresponding view of an A portion of the motor rotor. 
           [0030]      FIG. 4  is an enlarged sectional corresponding view of the A portion in  FIG. 2  of a motor rotor according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0031]    Hereinafter, embodiments according to the present invention will be described with reference to the drawings. 
       First Embodiment 
       [0032]    Hereinafter, a first embodiment of the present invention will be described with reference to  FIGS. 1 to 3 . 
         [0033]      FIG. 1  is a longitudinal sectional view of an electric compressor according to a first embodiment of the present invention.  FIG. 2  is a longitudinal sectional view of a motor rotor, and  FIG. 3  is an enlarged sectional corresponding view of an A portion. 
         [0034]    Here, the electric compressor  1  is an inverter integrated electric compressor  1  in which an inverter  25  driving a motor  1  is integrally incorporated to a housing  2  of the electric compressor  1 . However, the present invention can be similarly applied to the electric compressor  1  in which the inverter  25  is not provided, or the inverter  25  is separately installed. 
         [0035]    The inverter integrated electric compressor  1  includes a cylindrical housing  2 , one end side of the housing  2  is sealed by a compressor-side end housing  3 , and the other end side of the housing  2  is sealed by a motor-side end housing  4 . A known scroll compression mechanism (compression mechanism)  7  configured of a pair of fixed scroll  5  and turning scroll  6  is incorporated into one end side of the cylindrical housing  2 , and a high-pressure refrigerant gas which is compressed by the compression mechanism  7  is ejected into an ejection chamber  10  via an ejection port  8  and an ejection valve  9  and is ejected to a refrigerating cycle from the ejection chamber  10 . 
         [0036]    The fixed scroll  5  configuring the scroll compression mechanism  7  is fixed to the compressor-side end housing  3  by a bolt  11 , and the turning scroll  6  is swingably supported by a thrust bearing  12  via rotation blocking means such as an Oldham link  13 . The fixed scroll  5  and the turning scroll  6  engage with each other as well known so as to form a compression chamber  14 , the compression chamber  14  is moved by revolution turning driving of the turning scroll  6  while the volume of the compression chamber  14  is decreased from the outer circumferential side to the center side so as to perform the compression operation. 
         [0037]    A motor  17  configured of a motor stator (stator)  15  and a motor rotor (rotor)  16  is incorporated into the other end side of the cylindrical housing  2 , and a driving shaft  18  is integrally connected to the motor rotor  16  of the motor  17 . The driving shaft  18  is rotatably supported by a bearing  20  which is installed around the center inside the housing  2  and a bearing  21  which is provided in the inner surface of the motor-side end housing  4 , a crank pin  19  provided on one end of the driving shaft  18  is connected to the turning scroll via a drive bush  22  and a turning bearing  23 , and the turning scroll  6 , that is, the scroll compression mechanism  7  can be driven. 
         [0038]    Meanwhile, an inverter accommodation portion  24  is integrally formed on the outer surface side of the motor-side end housing  4 , and the inverter  25  which drives the motor  17  is installed and accommodated inside the inverter accommodation portion  24 . The inverter  25  converts DC power supplied from an external battery or the like into three-phase AC power having a desired frequency, the three-phase alternating power is applied to the motor  17  via a hermetic terminal (not shown) which penetrates the motor-side end housing  4 , and the motor  17  is driven. 
         [0039]    For example, the inverter  25  is configured of a power substrate on which a switching circuit having multiple power transistors such as IGBT which is a power semiconductor switching element is mounted, a control substrate on which a control communication circuit having an element which is operated at a low voltage such as a GPO which controls the switching circuit and others based on a control signal input from the outside is mounted, a smoothing capacitor which is configured of a filter circuit for removing noise, and an electric component such as a coil, and since the inverter  25  itself is well known, the detail descriptions are omitted. 
         [0040]    As described above, the motor  17  which is driven via the inverter  25  is configured of the motor stator (stator)  15  and the motor rotor (rotor)  16 . The motor stator (stator)  15  includes a stator core  26  which is configured by stacking a required number of electromagnetic steel plates which are annularly punched, and winding coils (not shown) are collectively wound around tooth portions provided on the inner circumferential side of the stator core  26  via an insulating bobbin  21 . 
         [0041]    Meanwhile, as shown in  FIG. 2 , the motor rotor (rotor)  16  which is rotatably provided on the inner circumference of the motor stator  15  via a predetermined motor gap includes a cylindrical rotor core  28  which is configured by laminating a required number of thin punched electromagnetic steel plates, and a through hole  29  which is fitted to the driving shaft  18  axially penetrates at the center portion of the rotor core  28 . In the rotor core  28 , magnetic embedded holes having the number corresponding to the number of motor poles are provided along the outer circumference portion of the rotor core  28  so as to surround the through hole  29 , and a permanent magnet (not shown) (hereinafter, simply referred, to as a magnet) is incorporated into each magnet embedded hole. 
         [0042]    In addition, end plates  30  and  31  are stacked on both end surfaces of the rotor core  28  formed by stacking a plurality of electromagnetic steel plates so as to prevent slipping out of the magnets and prevent a leakage of magnetic flux, and balance weights  32  and  33  for balancing a rotating system are stacked and disposed on the outer surfaces of the end plates  30  and  31 . The rotor core  28 , the end plates  30  and  31 , the balance weights  32  and  33  are integrally fastened via a plurality of (four in the present embodiment) headed swaging pins (also referred to as rivets)  34 . 
         [0043]    A head  35  is provided on one end side of each of the headed swaging pins  34 , and a swaging portion  36  is provided on the other end side thereof. The headed swaging pins  34  are inserted into through holes (not shown) provided in the rotor core  28 , the end plates  30  and  31 , and the balance weights  32  and  33  from the balance weights  32  and  33  sides, and the swaging portions  36  is swaged to the end plates  31  and  30  or the balance weights  33  and  32  of the other end sides by a swage tool. Accordingly, the rotor core  28 , the end plates  30  and  31 , and the balance weights  32  and  33  are rigidly and integrally fastened. 
         [0044]    In addition, as described above, in the present embodiment, even in a case where the motor rotor (rotor)  16 , in which the rotor core  28 , the end plates  30  and  31 , and the balance weights  32  and  33  are integrally fastened via the headed swaging pins  34 , is repeatedly operated under an excitation condition in which an excessive load is applied to the motor rotor  16  due to an overload operation or the like, in order to prevent fastening strength of the balance weights  32  and  33  fastened toy the swaging pins  34  from decreasing and prevent occurrence of rattling and damages, the following configuration is adopted. 
         [0045]    As a result of an excitation test, as described above, it is found out that the reason why the fastening strength with respect to the balance weights  32  and  33  decreases is because the seating surfaces of the balance weights  32  and  33  laminated and disposed on the head  35  side of the swaging pin  34  are depressed by setting due to contact with the head  35  of the swaging pin  34 , the fastening strength decreases, and rattling occurs. It is considered that the above-described problems occur because a brass material which is a high specific weight metal is used as the materials of the balance weights  32  and  33  and the hardness of the brass material is lower than that of a ferrous base material which is mainly used as the material of the swaging pin. 
         [0046]    Accordingly, in the present embodiment, for example, washers  37  are interposed between the heads  35  of the swaging pins  34  which integrally fastens the balance weights  32  and  33  to the rotor core  28  and the seating surfaces of the balance weights  32  and  33 , and the washers  3  axe formed of a material, for example, a stainless material which is harder than the materials of the swaging pins  34  which use a ferrous base material in most cases, and integrally fasten the balance weights  32  and  33 . Accordingly, even when an excessive load is applied to the head  35  sides of the swaging pins  34 , depression due to setting of the seating surfaces of the balance weights  32  and  33  does not occur. 
         [0047]    That is, in general, for example, the swaging pin  34  is formed of a ferrous base material such as cold heading carbon steel (JIS-G- 3507 - 2 ) , the end plates  30  and  31  are formed of a non-magnetic material such as aluminum so as to prevent a leakage of a magnetic flux, and the balance weights  32  and  33  are formed of a brass material, a stainless material, or the like which has high specific weight. In the present embodiment, among the materials, each of the swaging pins  34  is formed of a ferrous base material, each of the washers  37  formed of a stainless material having higher hardness than that of the swaging pin  34  is interposed therebetween in a state where a brass material which is a metal having high specific weight and is cheaper than the stainless material or the like is used as the material of each of the balance weights  32  and  33  which are in contact with the heads  35  of the swaging pins  34 , and the above-described condition is satisfied. 
         [0048]    In addition, as described above, when the configuration is adopted, in which the washer  37  is interposed between the head  35  of the swaging pin  34  and the seating surface of each of the balance weights  32  and  33 , a diameter φ 1  of the washer  37  is larger than a diameter φ 2  of the head of the swaging pin  34  (φ 1 &gt;φ 2 ) and a counterbore  38  is provided on the seating surface of each of the balance weights  32  and  33  so as to stabilize seating of the washer  37 . However, the counterbore  38  is not indispensable and may be omitted. 
         [0049]    According to the above-described configuration, the present embodiment exerts the following effects. 
         [0050]    In the electric compressor  1 , DC power supplied from an external power source is converted into three-phase AC power having a desired frequency by an inverter  25 , the three-phase AC power is applied to the motor  17 , the motor  17  is rotationally driven, and the scroll compression mechanism  7  is driven. According to driving of the motor  17  and the scroll compression mechanism  7 , a low-pressure refrigerant gas is sucked into the housing  2  from a refrigerating cycle side, and the low-pressure refrigerant gas flows to the scroll compression mechanism  7  side along the inner surface side of the housing  2  and is sucked into the scroll compression mechanism  7  so as to be compressed to a high-temperature and high-pressure gas. The high-pressure gas is ejected to the outside via the ejection chamber  10 . 
         [0051]    During this, power having a frequency suitable for the load is applied to the motor  17  via the inverter  25 , and during a high load operation, an excessive load is applied to the motor rotor  16  and a large excitation force is applied to the motor rotor  16 . Meanwhile, in the present embodiment, in the motor rotor  15  in which the rotor core  28  formed by stacking the plurality of electromagnetic steel plates, the end plates  30  and  31  and the balance weights  32  and  33  are integrally fastened by the plurality of headed swaging pins  34 , the washers  37  formed of a harder material than the material of the swaging pins  34  are interposed between the heads  33  of the swaging pins  34  and the seating surfaces of the balance weights  32  and  33 . 
         [0052]    Accordingly, even under an excitation condition which an excessive load is applied to the motor rotor  16 , since the seating surface of each of the balance weights  32  and  33  on the head  35  side of the swaging pin  34  is in contact with the swaging pin head  35  via the washer  37  formed of a harder material than that of the swaging pin  34 , depression in the seating surface due to contact with the swaging pin head  35  is not generated, it is possible to maintain fastening strength. Meanwhile, since the swaging portion  36  side of the swaging pin  34  is rigidly swaged such that the swaging pieces is bitten to the end plates  30  and  31  or the balance weights  32  and  33 , it is possible to improve fastening strength by the swaging pin  34 . 
         [0053]    Accordingly, since the fastening strength of the balance weights  32  and  33  performed by the swaging pin  34  increases and resistance with respect to an excessive excitation force is improved, it is possible to decrease risk of the fastening strength of the balance weight  32  and  33  decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor  17  so as to secure reliability of the motor  17 . 
         [0054]    In addition, when the washer  37  is interposed between the seating surface of each of the balance weights  32  and  33  and the swaging pin bead  35 , since the counterbore  38  is provided on the seating surface of each of the balance weights  32  and  33 , the washer  37  can be interposed between the swaging pin head  35  and the seating surface of each of the balance weights  32  and  33  via the counterbore  38 . Accordingly, it is possible to stabilize seating of the washer  37 , and it is possible to further increase the fastening strength of the balance weights  32  and  33 . 
         [0055]    Moreover, since the diameter φ 1  of the washer  37  is larger than the diameter φ 2  of the head of the swaging pin  34 , it is possible to reliably decrease a surface pressure applied to the seating surface of the balance weights  32  and  33  by allowing the diameter φ 1  of the washer  37  which is in contact with the seating surface of each of the balance weights  32  and  33  to be larger than the diameter φ 2  of the head of the swaging pin  34 , and it is possible to prevent depression due to setting of the seating surface. Accordingly, it is possible to increase fastening strength of the balance weights  32  and  33  and it is possible to reliably improve the resistance with respect to an excessive excitation force. 
         [0056]    In the present embodiment, since the swaging pin  34  is formed of a ferrous base material, the balance weights  32  and  33  are formed of a brass material, and the washer  37  is formed of a stainless material, the inexpensive washer  37  is interposed in a state where a brass material which has lower hardness than that of the swaging pin  34  and is cheaper than a stainless material or the like is used as the balance weights  32  and  33 , and it is possible to secure the fastening strength of the balance weights  32  and  33 . Accordingly, it is possible to increase the fastening strength of the balance weights  32  and  33  while preventing an increase in cost, and it is possible to improve the resistance with respect to an excessive excitation force. 
         [0057]    In the motor  17  according to the present embodiment, since the motor rotor  16  thereof is the above-described motor rotor  16 , it is possible to improve fastening strength of the balance weights  32  and  33  which are staked on both ends of the meter rotor  16  and are integrally fastened by the swaging pins  34 . Accordingly, since the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the motor rotor  16 , it is possible to decrease risk of the fastening strength of the balance weights  32  and  33  decreasing, rattling occurring, and damage occurring, and it is possible to enhance quality of the motor  17  so as to secure reliability of the motor  17 . 
         [0058]    Similarly, in the electric compressor  1  according to the present embodiment, since the motor  17  which drives the compression mechanism  7  via the driving shaft  18  is the above-described motor  17 , the resistance with respect to the excessive excitation force increases even under an excitation condition in which an excessive load is applied to the motor rotor  16  of the motor  17  which drives the compression mechanism  7 , and it is possible to decrease risk of the fastening strength of the balance weights  32  and  33  decreasing, rattling occurring, and damage occurring. Accordingly, it is possible to further improve a vibration-proof performance at the time of the overload operation of the electric compressor  1  so as to increase reliability of the electric compressor  1 . 
       Second Embodiment 
       [0059]    Next, a second embodiment of the present invention will be described with reference to  FIG. 4 . 
         [0060]    The present embodiment is different from the first embodiment in that a spacer  39  is interposed therebetween instead of the washer  37 . Since other matters are similar to the first embodiment, descriptions thereof are omitted. 
         [0061]    As shown in  FIG. 4 , in the present embodiment, the spacer  39  having a ring  39 A is interposed between the head  35  of the swaging pin  34  and the seating surface of each of the balance weights  32  and  33 , and the spacer  39  is formed of a material, for example, a stainless material which is harder than the swaging pin  34  formed of a ferrous base material and integrally fastens the balance weights  32  and  33 . Accordingly, even when an excessive load is applied to the head  35  side of the swaging pin  34 , depression duet to setting of the seating surface of each of the balance weights  32  and  33  does not occur. 
         [0062]    In addition, similarly to the first embodiment, when the spacer  39  is interposed between the head  35  of the swaging pin  34  and the seating surface of each of the balance weights  32  and  33 , the counterbore  38  is provided on the seating surface ox each of the balance weights  32  and  33  and a diameter φ 3  of the ring  39 A of the spacer  39  is larger than the diameter of the swaging pin head  35  (φ 3 &gt;φ 2 ). 
         [0063]    According to this configuration, it is possible to obtain effects similar to those of the first embodiment. 
         [0064]    In addition, the present invention is not limited to the above-described embodiments, and can be appropriately modified. For example, in the above-described embodiments, specific materials of the swaging pin  34  and the balance weights  32  and  33  are exemplified. However, the present invention is not limited to the materials, and materials other than the exemplified materials may be used as long as they satisfy a condition with respect to hardness specified by claim  1 . 
         [0065]    In addition, the shape, the size, or the like of each of the balance weights  32  and  33  is not particularly limited as long as it satisfies each function, and whether the sides to which the swaging portion  36  side of the swaging pin  34  is to be swaged are the balance weights  32  and  33  or the end plates  30  and  31  is determined according to the shape or the size. In addition, the compression mechanism is not limited to the scroll compression mechanism  7  and may be any compression mechanism. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1 : electric compressor 
           7 : scroll compression mechanism (compression mechanism.) 
           15 : motor stator (stator) 
           16 : motor rotor (rotor) 
           17 : motor 
           18 : driving shaft 
           28 : rotor core 
           30 ,  31 : end plate 
           32 ,  33 : balance weight 
           34 : swaging pin (rivet) 
           35 : head 
           36 : swaging portion 
           37 : washer 
           38 : counterbore 
           39 : spacer 
           39 A: ring 
         φ 1 : diameter of washer 
         φ 2 : diameter of swaging pin bead 
         φ 3 : diameter of ring of spacer