Abstract:
An object is to increase portions (increase the amount of correction), where the rotational balance of a rotary shaft of a turbocharging device incorporating an electric motor is adjusted, and to maintain sufficient motor driving force even under a high temperature condition. In a balance adjusting structure for the turbocharging device incorporating an electric motor, a rotor core  5  formed by laminating electromagnetic steel plates  51  is interposed between rotor blades provided on one end or both ends, a rotational balance adjusting member made of iron (magnetic induction member) having a thickens larger than the thickness of each electromagnetic steel plate  51  is disposed on an end of the laminated electromagnetic steel plates  51 , or between the laminated layers.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a structure and a method for adjusting rotational balance of a rotor of a turbocharging device incorporating an electric motor turbocharging suction air to an internal combustion. Herein, the turbocharging device incorporating an electric motor includes a turbo charger incorporating a motor generator, a turbo charger incorporating an electric motor, an electric supercharger, and the like. 
       BACKGROUND ART 
       [0002]    Turbo chargers for compressing and turbocharging suction air by driving with exhaust gas of an internal combustion has been widely used, in order to improve output of the internal combustion. 
         [0003]    There has been used a turbo charger incorporating a motor generator that improves acceleration responsiveness by incorporating an electric motor in a rotary shaft of the turbocharging device and assisting the acceleration of rotation of a compressor impeller, and collects energy by converting exhaust gas energy into electric energy. In a case where exhaust gas energy is not utilized and a turbine is omitted, the turbo charger incorporating a motor generator is an electric supercharger that rotates a compressor impeller by only an electric motor. 
         [0004]      FIG. 6  is a schematic configuration diagram of an engine  01  mounted with a turbo charger  03  incorporating a motor generator disclosed in Japanese Patent Application Laid-open No. H8-182382 (Patent Document 1). A turbine wheel  031  of the turbo charger incorporating a motor generator  03  is driven by exhaust gas from an exhaust manifold  011  of the engine  01 . A compressor impeller  032  coaxially connected to the turbine wheel  031  is driven, so that suction air from an air cleaner (not shown) is supplied to the engine  01  via a suction manifold  012 . 
         [0005]    A motor rotor  05  for assisting rotation (driving) of the compressor impeller  032  is disposed on the intermediate-portion of a shaft  041  for connecting the turbine wheel  031  and the compressor impeller  032 . 
         [0006]    As shown in  FIG. 7 , the motor rotor  05  is axially rotatably supported on a pair of bearing support parts provided in a housing (not shown) of the turbo charger incorporating a motor generator  03  via bearings  049 . 
         [0007]    Reference numeral  06  denotes an engine control unit (ECU), which controls operation of the engine  01 , flows a current to a stator  033  depending on the operation status of the engine  1 , and also controls operation of the turbo charger incorporating a motor generator  03 . Reference numeral  07  denotes a battery, which is a power supply of a controller. 
         [0008]      FIG. 7  is a schematic configuration diagram of a conventional motor rotor. 
         [0009]    A motor rotor  05  has a step part  044  that is a narrow shaft part on a side closer to a compressor impeller  043 , on an intermediate part in the thrust direction of a shaft  041  having an end mounted with a turbine wheel  042 . A nut  046 , which is screwed with a screw part formed on the end of the narrow shaft part, through a thrust bush  056 , a rotor  051 , an oil seal accessory  054 , and the compressor impeller  043  which are fitted with (fitted onto) the narrow shaft part, presses and positions these components with respect to the step part  044 . 
         [0010]    A magnet  052  (permanent magnet) is fitted onto the narrow shaft part of the shaft  041 , a sleeve  057  is further fitted onto the outer peripheral part of the magnet  052  to be fixed to the narrow shaft part of the shaft  041 , thereby forming the rotor  051 . 
         [0011]    In this case, the sleeve  057  needs to be fitted onto the outer peripheral part of the magnet arranged on the rotor  051 , in order to prevent breakage and scattering of the magnet. 
         [0012]    A stator  033  for rotating and driving the shaft  041  by utilizing magnetism of the magnet of the rotor  051  is arranged on the housing side of the turbo charger incorporating a motor generator  03 , facing the rotor  051 . 
         [0013]    As a technology related to such a turbo charger incorporating a motor generator, Japanese Patent Application Laid-open No. 2000-145468 (Patent Document 2) is known.
   Patent Document 1: Japanese Patent Application Laid-open No. H8-182382   Patent Document 2: Japanese Patent Application Laid-open No. 2000-145468   
 
         [0016]    However, since the turbo charger incorporating a motor generator is used under a high temperature environment resulting from exhaust gas, performance of a motor that utilizes a magnet significantly deteriorates with rise in temperature, and such a motor is not suitable. 
         [0017]    To cope with this, there is a magnetic inductor type motor as one of motors that do not use a magnet. 
         [0018]    The magnetic inductor type motor is configured that a rotor made of laminated electromagnetic steel plates and iron, or laminated electromagnetic steel plates are driven by a stator arranged around the rotor. 
         [0019]    However, since the rotor rotates at a high speed in a state of being arranged between a turbine wheel and a compressor impeller, it is important to adjust the rotational balance (dynamic balance) of the rotor made of the laminated electromagnetic steel plates and iron, or the laminated electromagnetic steel plates for balancing. Therefore, the adjustment of the rotational balance on a conventional adjustment part (e.g., a nut part for fastening the compressor impeller to a rotary shaft of the turbo charger) can not cope with increase in an adjustment amount, or fine adjustment. 
       DISCLOSURE OF THE INVENTION 
       [0020]    The present invention has been conceived in order to solve such problems, and an object thereof is to provide a structure and a method for adjusting balance of a turbo charger incorporating a motor generator capable of achieving increase in adjustment parts (increase in an adjustment amounts and ensuring fine adjustment) for adjusting the rotational balance of a rotary shaft of the turbo charger, and preventing performance deterioration while maintaining sufficient motor driving force even under a high temperature condition. 
         [0021]    According to the present invention, in order to attain this object, a balance adjusting structure for a turbocharging device incorporating an electric motor includes: at least one rotor blade disposed in a housing; a shaft connected to the rotor blade; a bearing formed in the housing, and configured to rotatably axially support the shaft; a rotor core penetrated by the shaft; and a stator disposed at a position facing the rotor core in the housing, and configured to rotate and drive the rotor core together with the shaft by a magnetic field, wherein the rotor core has a sleeve fitted onto the shaft, a plurality of electromagnetic steel plates laminated in an axial direction of the sleeve and fitted onto the sleeve, and a rotational balance adjusting member disposed on a part of the electromagnetic steel plates in a laminating direction, and having a thickness larger than a thickness of each electromagnetic steel plate, and the rotational balance adjusting member is processed to adjust rotational balance. 
         [0022]    With such a configuration, although heretofore, rotational balance has been adjusted by cutting a nut for fastening a shaft on a compressor impeller being a rotor blade of the turbocharging device incorporating an electric motor, the rotational balance adjusting member enabling balance adjustment is added in addition to the nut part, so that the number of portions where the rotational balance is adjusted increases, thereby enabling higher accurate rotational balance adjustment. 
         [0023]    Additionally, the rotational balance adjusting member is made of a magnetic material, for example, iron, and hence magnetic force resulting from magnetic induction is strengthened. This contributes to improvement of performance as a turbo charger with improvement of performance as an electric motor. 
         [0024]    In the present invention, the rotor core is preferably configured such that the rotational balance adjusting member is interposed on an intermediate part in the laminating direction of the laminated electromagnetic steel plates. 
         [0025]    The rotational balance adjusting member is interposed on the intermediate part in the laminating direction of the laminated electromagnetic steel plates, particularly on a central part is referred to as a center ring. 
         [0026]    Thus, the rotational balance adjusting member that is interposed on the intermediate part in the laminating direction of the laminated electromagnetic steel plates, particularly on the central part, and hence magnetic induction on the both sides of the rotational balance adjusting member is uniformed, thereby improving output as a motor. 
         [0027]    In the present invention, the rotor core preferably includes the sleeve fitted onto the shaft, the plurality of electromagnetic steel plates fitted onto the sleeve, and arranged as a lamination, and a rotational balance adjusting member fixed to both ends of the sleeve, and configured to fix and sandwich the plurality of electromagnetic steel plates. 
         [0028]    With such a configuration, it is possible to form the rotor core in a cartridge-type, and facilitate assembly to the shaft. Additionally, the rotational balance adjustment portions are fixed to the both ends of the sleeve, and the number of the adjustment portions are increased, and hence an adjustment capacity in final rotational balance adjustment after the assembly to the rotor increases, and fine adjustment is possible. Consequently, high accurate rotational balance adjustment is possible. 
         [0029]    In the present invention, the rotor core preferably includes a rotational balance adjusting member fitted onto the sleeve, and interposed on an intermediate part in the laminating direction of the plurality of electromagnetic steel plates that are arranged as a lamination, and a rotational balance adjusting member configured to fix and sandwich both ends of the laminated electromagnetic steel plates, and fixed to both ends of the sleeve. 
         [0030]    With such a configuration, it is possible to form the rotor core in a cartridge-type, and facilitate assembly to the shaft. Additionally, the rotational balance adjustment portions are fixed to the both ends and the intermediate part of the sleeve, and the number of the adjustment portions increases. Therefore, even when rotational balance adjustment singly using the rotor core that requires a large number of steps is omitted, and merged into final rotational balance adjustment after the assembly of the rotor, an adjustment amount can be greatly expanded. Consequently, high accurate rotational balance adjustment is possible. 
         [0031]    In the present invention, at least one balance adjustment member of the balance adjustment members is preferably configured by assembling laminated layers of the same magnetic material as the electromagnetic steel plates of the rotor core. 
         [0032]    With such a configuration, as the rotational balance adjusting member interposed on the intermediate part in the laminating direction of the laminated electromagnetic steel plates, particularly on the central part, the center ring is made of, for example, an electromagnetic steel plate being a magnetic material or iron, and hence magnetic force resulting from magnetic induction is strengthened. This enables contribution to improvement of performance as a turbocharging device incorporating an electric motor with improvement of performance as an electric motor. Furthermore, the electromagnetic steel plate is used for the center ring, and hence assembly of the center ring is completed in a step of assembling the electromagnetic steel plates of the rotor core. Consequently, the number of assembly steps can be further reduced. 
         [0033]    In the present invention, the turbocharging device incorporating an electric motor is preferably either a turbo charger incorporating a motor generator that is mounted with a turbine wheel, which is a rotor blade for utilizing exhaust gas energy on an end of the shaft penetrated by the rotor core and the bearing, and that is mounted with a compressor impeller, which is a rotor blade for compressing inlet air on other end thereof, or an electric supercharger that does not have the turbine wheel and that is mounted with a compressor impeller for compressing inlet air only on one end of the shaft. 
         [0034]    Furthermore, according to the present invention, a rotational balance adjusting method for a rotor of a turbo charger incorporating a motor generator includes the steps of: performing rotational balance adjustment by singly using a rotor blade, for example, such as a turbine wheel, and a compressor impellor; assembling a rotor including the turbine wheel, the compressor impellor, and a rotor core having a rotational balance adjusting member made of a magnetic material; measuring a balance amount by rotating the rotor; and adjusting and processing rotational balance by using an compressor fastening nut, the rotational balance adjusting member of the rotor core, or both of the compressor fastening nut and the rotational balance adjusting member, on the basis of a result of measurement. 
         [0035]    With such a configuration, the compressor fastening nut and the rotational balance adjusting member of the rotor core enable the rotational balance adjustment portions, and increase in the number of the adjustment portions and fine adjustment are possible. Consequently, even when rotational balance adjustment singly using the rotor core that requires a large number of steps is omitted, and merged into final rotational balance adjustment after the assembly of the rotor, high accurate rotational balance adjustment is possible. 
         [0036]    In the present invention, a step of adjusting rotational balance by singly using the rotor core before the step of assembling the rotor may be further added. 
         [0037]    Thus, the step of adjusting rotational balance by singly using the rotor core is further added, and hence it is possible to obtain the rotor with higher accurate rotational balance. 
         [0038]    According to the present invention, although heretofore, rotational balance has been adjusted by cutting a nut for fastening a shaft on a compressor impeller, the rotational balance adjusting member enabling balance adjustment is added to the rotor core in addition to the nut part, so that the number of portions where the rotational balance is adjusted increases, thereby enabling higher accurate rotational balance adjustment. 
         [0039]    Additionally, the rotational balance adjusting member is made of a magnetic material, for example, iron, and hence magnetic force resulting from magnetic induction is strengthened. This contributes to improvement of performance as a turbo charger with improvement of performance as an electric motor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0040]      FIG. 1  is a schematic structure diagram of a turbine rotor according to a first embodiment of the present invention; 
           [0041]      FIG. 2  is a schematic structure diagram of a turbine rotor according to a second embodiment of the present invention; 
           [0042]      FIG. 3  is a schematic structure diagram of a turbine rotor according to a third embodiment of the present invention; 
           [0043]      FIG. 4  is a flowchart of processes of rotational balance adjustment work of the turbine rotor according to the first embodiment of the present invention; 
           [0044]      FIG. 5  is a flowchart of processes of another rotational balance adjustment work of the turbine rotor according to the first embodiment of the present invention; 
           [0045]      FIG. 6  shows a schematic configuration diagram of an engine mounted with a conventional turbo charger incorporating a motor generator; and 
           [0046]      FIG. 7  shows a schematic explanatory diagram of a conventional turbine rotor. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0047]    Hereinafter, embodiments of the present invention will be described in detail with reference to the figures. 
         [0048]    As specific names of a rotor blade, a turbine wheel, and a compressor impeller are used in the description of these embodiments. Additionally, as long as not stated specifically in particular, size, quality of materials, shape, relative arrangement of components described in these embodiments are not intended to limit the scope of the invention, but merely exemplary examples. 
       First Embodiment 
       [0049]    A turbine rotor according to a first embodiment of the present invention will be described with reference to  FIG. 1 . 
         [0050]    A turbine rotor  1  includes a shaft  4 , a turbine wheel  2  disposed on one end of the shaft  4 , a compressor impeller  3  disposed on the other end thereof, two bearings  7  disposed between the turbine wheel  2  and the compressor impeller  3  at intervals, and a rotor core  5  that serves as an electric rotor, and is disposed between the two bearings  7 , and the rotor core  5  is mounted on the shaft  4  via a sleeve  53 . 
         [0051]    The present invention is applicable to both of a case where the respective bearings  7  are arranged on both outer ends of the rotor core  5  as described above, and a case where the two (pair of) bearings  7  are arranged between the turbine wheel  2  and the rotor core  5  at intervals. 
         [0052]    The shaft  4  is a solid shaft, has a stepped part  44  narrowed from an intermediate part, and is a rotary shaft having a thick portion  41  on one end and a narrow portion  42  on the other end. The turbine wheel  2  that is driven by exhaust gas is fixed to the end of the thick portion  41  of the shaft  4 . The bearing  7  fixed to a bearing support part formed in a turbine housing (not shown) is disposed on a back surface side of the turbine wheel  2  via a first seal ring  43  formed integrally with the shaft  4 . 
         [0053]    The rotor core  5  that incorporates the sleeve  53  is fitted onto the narrow portion  42  of the shaft  4  by employing, as a stopper, the stepped part  44  being a stopper part. The rotor core  5  is configured such that a plurality of electromagnetic steel plates  51  having circular circumference are inserted around the sleeve  53  to be laminated in the plate thickness direction of the electromagnetic steel plates  51 . A center ring  52  that is a rotational balance adjusting member, and is made of an electromagnetic steel plate being a magnetic material, or iron is interposed between the electromagnetic steel plates on the intermediate part, particularly the central part, in the laminating direction of the laminated electromagnetic steel plates  51 . 
         [0054]    On a side closer to the compressor impeller  3  of the rotor core  5 , sleeve  45  fitted onto the narrow portion  42  of the shaft  4  abuts. On the other end of the shaft  4 , the compressor impeller  3  is fixed with a nut  31  for fastening via a second seal ring  46 . 
         [0055]    Accordingly, the rotor core  5  has a structure of regulating relative movement in the rotational direction with the shaft  4  by application of proper pressing by the second seal ring  46  interposed between the nut  31  and the rotor core  5 . 
         [0056]    The bearings  7  disposed between the rotor core  5  and the compressor impeller  3  is fitted onto the sleeve  45 . 
         [0057]    With such a configuration, the center ring  52  serves as an adjustment cut part of the rotational balance of the turbine rotor  1 , in addition to the nut  31 , thereby increasing an adjustment range of the rotational balance. 
         [0058]    Additionally, the center ring  52  has a diameter larger than that of the nut  31 , and hence effects of the balance adjustment of the center ring  52  is larger even if the cutting amount is unchanged, and high accurate adjustment is possible in a wide range. Furthermore, fine adjustment is possible. 
         [0059]    Moreover, the rotational balance adjusting member made of an electromagnetic steel plate or iron is disposed on the intermediate part, particularly on the central part, of the laminated electromagnetic steel plates  51 , and hence magnetic induction amounts on the both sides of the rotational balance adjusting member are uniformed, thereby exerting an effect of improving output as a motor. 
         [0060]    In this embodiment, the center ring  52  that serves as the rotational balance adjusting member is disposed on the intermediate part, particularly on the central part, in the laminating direction of the electromagnetic steel plates  51 . However, also in a case where the center ring  52  is disposed on any portion in the laminating direction other than the central part, an action effect as the rotational balance adjusting member can be obtained. 
         [0061]    The correction portion for adjusting the rotational balance of the turbine rotor  1  has been described. Now, description will cover a flow of processes of a rotational balance adjusting method of the turbine rotor  1  shown in  FIG. 4 . 
         [0062]    Step S 1  of setting the turbine wheel  2  in the balance measurement device, measuring a rotational balance amount, and performing balance adjustment of the single turbine wheel  2  on the basis of a result of the measurement. 
         [0063]    Next, Step S 2  of setting the compressor impeller  3  in the balance measurement device, and performing balance adjustment of the single compressor impeller  3  similarly to Step S 1 . 
         [0064]    The rotational balance adjustment of the turbine wheel  2  and the compressor impeller  3  is performed (cut) on the rear side of the rear side (X part (see  FIG. 1 )) of the turbine wheel  2  and on the rear side of the rear side (Y part (see  FIG. 1 )) of the compressor impeller  3 . 
         [0065]    Step S 3  of assembling the turbine rotor  1  by mounting the turbine wheel  2 , the compressor impeller  3 , the rotor core  5 , the bearings  7 , the sleeve  45 , and the like on the shaft  4 . 
         [0066]    Step S 4  of setting the assembled turbine rotor  1  in the balance measurement device, and measuring a balance amount of the whole of the turbine rotor  1 . 
         [0067]    Step S 5  of performing balance adjustment by cutting work of a balance adjustment part A of the nut  43  for fastening the compressor impeller or cutting work of a balance adjustment part B of the outer peripheral part of the center ring  52 , on the basis of a result of measurement. 
         [0068]    Furthermore, in Step S 5 , the cutting work order as to which cutting work is first performed, the cutting work of the nut  31  or the cutting work of the center ring  52  may be determined every time the cutting work is performed. 
         [0069]    Then, the turbine rotor  1  is set in the balance measurement, device again, the balance adjustment is terminated by Step S 6  of confirming the balance of the turbine rotor  1 . 
         [0070]    In a case where the result of measurement in Step S 6  is not an arbitrary balance amount or less, Step S 5  and Step S 6  are repeatedly performed. 
         [0071]    Since various balance measurement devices are disclosed in patent documents (e.g., Japanese Patent Application Laid-open Nos. 2008-58008 and 2008-8219) and the like, description of the balance measurement device will be omitted in this embodiment. 
         [0072]    According to the flow of the processes of the rotational balance adjusting method of the turbine rotor  1  of this embodiment, the adjustment portions for rotational balance of the assembled turbine rotor  1  are the balance adjustment A of the nut  31 , and the balance adjustment B of the center ring  52 , and hence the balance adjustment amount is increases with increase in the balance adjustment portions, and high accurate balance adjustment is possible in a wide range. Furthermore, fine adjustment is also possible. 
         [0073]    Moreover, the center ring  52  has a diameter lager than that of the nut  31 , and hence the effects of the balance adjustment of the center ring  52  are larger even if the cutting amount is unchanged. Accordingly, the cutting work of the nut  31  can be sometimes omitted by first performing the adjustment cutting of the center ring  52 , and reduction in the number of processes can be expected. 
         [0074]    Now, a flow of processes of another rotational balance adjusting method of the turbine rotor  1  will be described with reference to  FIG. 5 . 
         [0075]    Step S 10  of setting the turbine wheel  2  in the balance measurement device, measuring a rotational balance amount, and performing balance adjustment of the single turbine wheel  2  on the basis of a result of the measurement. 
         [0076]    Next, Step S 11  of setting the compressor impeller  3  in the balance measurement device, and performing balance adjustment of the single compressor impeller  3  similarly to Step S 10 . 
         [0077]    Then, Step S 12  of setting the rotor core  5  in the balance measurement device, and performing balance adjustment of the single rotor core  5  similarly to Step S 10 . 
         [0078]    The rotational balance adjustment of the turbine wheel  2  and the compressor impeller  3  is performed on the rear side (X part) of the turbine wheel  2  and on the rear side (Y part) of the compressor impeller  3 . 
         [0079]    Step S 13  of assembling the turbine rotor  1  by mounting the turbine wheel  2 , the compressor impeller  3 , the rotor core  5 , the bearings  7 , the sleeve  45 , and the like on the shaft  4 . 
         [0080]    Step S 14  of setting the assembled turbine rotor  1  in the balance measurement device, and measuring a balance amount of the whole of the turbine rotor  1 . 
         [0081]    Step S 15  of performing balance adjustment by cutting work of the balance adjustment part A of the nut  43  for fastening the compressor impeller or cutting work of the balance adjustment part B of the outer peripheral part of the center ring  52 , on the basis of a result of measurement. 
         [0082]    In Step S 15 , the cutting work order as to which cutting work is first performed, the cutting work of the nut  31  or the cutting work of the center ring  52  may be determined every time the cutting work is performed. 
         [0083]    Then, the turbine rotor  1  is set in the balance measurement device again, the balance adjustment is performed by Step S 16  of confirming the balance of the turbine rotor  1 . 
         [0084]    In a case where the result of measurement in Step S 16  is an arbitrary balance amount or more, Step S 15  and Step S 16  are repeatedly performed. 
         [0085]    In this embodiment, according to the flow of the processes of the rotational balance adjusting method of the turbine rotor  1 , rotational balance adjustment of the single rotor core  5  that is the heaviest among the components is performed, and hence the rotational balance adjustment amount of the assembled turbine rotor  1  is reduced, and balance adjustment performed after the turbine rotor  1  is assembled is facilitated. 
       Second Embodiment 
       [0086]    In this second embodiment, components that are identical with those of the first embodiment are denoted by the same reference numerals, and description thereof will be omitted. 
         [0087]    As shown in  FIG. 2 , a rotor core  8  is configured such that a plurality of electromagnetic steel plates  51  are disposed on a sleeve  81  fitted onto a narrow portion  42  of a shaft  4 . 
         [0088]    The sleeve  81  is formed with a flange part  82  radially from an open edge on one end side of the sleeve  81 . 
         [0089]    On the outer peripheral part of the sleeve  81 , the electromagnetic steel plates  51  are fitted onto the sleeve  81  so as to be laminated in the thrust direction of the sleeve  81 . 
         [0090]    On the other end side of the sleeve  81 , a pressing ring  83  is fitted onto the outer peripheral part of the sleeve  81  to be fixed in caulking to the sleeve  81  in a state of pressing the electromagnetic steel plates  51  in the thrust direction. 
         [0091]    Additionally, a center target  55  having an outer diameter substantially identical with that of the electromagnetic steel plates  51 , and a thickness larger than that of each electromagnetic steel plate  51  is disposed between the electromagnetic steel plates  51  and the flange part  82 . The center target  55  is a part of a revolution speed detection unit used in a case where the revolution speed of the turbine rotor  1  is controlled. In a case where the revolution speed does not need to be detected, the center target  55  is unnecessary. 
         [0092]    The rotor core  8  is pressed against a stepped part  44  via a compressor impeller  3  and a sleeve  45  by a nut  43 , thereby preventing slip in the rotational direction with respect to the shaft  4 . 
         [0093]    The flange part  82  and the pressing ring  83  each have an outer diameter substantially identical with that of each electromagnetic steel plate  51 , and have an action as a rotational balance adjusting member. 
         [0094]    The processes of a rotational balance adjusting method is similar to those of the first embodiment, and therefore description thereof will be omitted. 
         [0095]    The electromagnetic steel plates  51  are fitted onto the sleeve  81  in a laminated manner, and the both sides of the electromagnetic steel plates  51  are sandwiched between the flange part  82  and the pressing ring  83 , thereby facilitating assembly of the shaft  4  and improving the quality of the assembly. 
         [0096]    Furthermore, a balance adjustment part C of the flange part  82 , and a balance adjustment part D of the pressing ring  83  serve as rotational balance adjustment portions, in addition to a balance adjustment part A of the nut  43 , thereby increasing an adjustment amount of the rotational balance, and enabling fine adjustment. 
       Third Embodiment 
       [0097]    In this third embodiment, components that are identical with those of the first and second embodiments are denoted by the same reference numerals, and description thereof will be omitted. 
         [0098]    As shown in  FIG. 3 , a rotor core  9  is configured such that a plurality of electromagnetic steel plates  51  and a center ring  52  being a rotational balance adjusting member are disposed on a sleeve  81  fitted onto a narrow portion  42  of a shaft  4 . 
         [0099]    The sleeve  81  is formed with a flange part  82  radially from an open edge on the one end side of the sleeve  81 . 
         [0100]    On the outer peripheral part of the sleeve  81 , the electromagnetic steel plates  51  are fitted onto the sleeve  81  so as to be laminated in the thrust direction of the sleeve  81 . The center ring  52  being a rotational balance adjusting member is disposed on the intermediate part of the laminated electromagnetic steel plates  51  in the thrust direction of the sleeve  81 , particularly on the central part. On the other end side of the v sleeve  81 , a pressing ring  83  is fitted onto the outer peripheral part of the sleeve  81  to be fixed in caulking to the sleeve  81  in a state of pressing the electromagnetic steel plates  51  in the thrust direction. 
         [0101]    The processes of a rotational balance adjusting method is similar to those of the first embodiment, and therefore description thereof will be omitted. 
         [0102]    The electromagnetic steel plates  51  are fitted onto the sleeve  81  in a laminated manner, and the both sides of the electromagnetic steel plates  51  are sandwiched between the flange part  82  and the pressing ring  83 , thereby forming the rotor core  8  in a cartridge-type, facilitating assembly to the shaft  4 , and improving the quality of the assembly. Additionally, both sides of the electromagnetic steel plates  51  are sandwiched between the flange part  82  and the pressing ring  83 , thereby regulating relative movement of the electromagnetic steel plates  51  and the sleeve  81  during rotation, and easily forming the rotor core  8  in a cartridge type. 
         [0103]    Furthermore, the center ring  52  is interposed on the intermediate part (central part) of the laminated electromagnetic steel plates  51 , and hence magnetic induction is uniformed, thereby improving output as a motor. 
         [0104]    Moreover, a balance adjustment part C of the flange part  82 , a balance adjustment part D of the pressing ring  83 , and a balance adjustment part B of the center ring  52  serve as rotational balance adjustment portions, in addition to a balance adjustment part A of a nut  43 , thereby increasing an adjustment amount of the rotational balance, and enabling fine adjustment. 
       INDUSTRIAL APPLICABILITY 
       [0105]    In order to improve the output of an internal combustion, a motor generator is incorporated in a rotary shaft of a turbo charger that is driven by exhaust gas of the internal combustion, and compresses and turbocharges supply air, and the rotation of a compressor impeller is assisted for acceleration, thereby improving acceleration responsiveness. Additionally, the turbo charger incorporating a motor generator is suitable for use in an internal combustion that is capable of converting exhaust gas energy into electric energy.