Patent Publication Number: US-7898200-B2

Title: Controller of electric motor

Description:
FIELD OF THE INVENTION 
     The present invention relates to a controller of an electric motor of an axial air-gap type. 
     BACKGROUND ART 
     The electric motor of the axial air-gap type having a rotor having a permanent magnet, two stators arranged on both sides of the rotor in a rotation axis direction of the rotor, and an armature winding mounted to each stator is formerly known (e.g., see Japanese Patent Laid-Open No. 10-271784 and Japanese Patent Laid-Open No. 2001-136721). In accordance with such an electric motor of the axial air-gap type, relatively high output torque can be generated while the axial length of the rotor of the electric motor is shortened. 
     In electric conducting control of the electric motor of the axial air-gap type, an electric current is conducted to the armature windings of both the stators arranged on both the sides of the rotor in the technique described in the above publications. Thus, leakage of a magnetic flux in the armature of the stator is reduced and output torque of the electric motor can be increased. 
     Now, an idea that the electric motor of the axial air-gap type is also operated as an electricity generator to perform a driving operation and an electricity generating operation may come up. However, in the cited documents 1 and 2, there is no description about a construction where the electric motor of the axial air-gap type is also operated as the electricity generator. Therefore, an object of the present invention is to provide a controller able to efficiently operate the electric motor of the axial air-gap type as the electric motor and the electricity generator. 
     SUMMARY OF THE INVENTION 
     The present invention is made to achieve the above object, and relates to a controller of an electric motor of an axial air-gap type comprising a rotor having a permanent magnet, and a first stator and a second stator oppositely arranged through the rotor in a rotation axis direction of the rotor. 
     The controller comprises a first current conducting control means for supplying a driving electric current from a first power source to an armature winding of the first stator in order to rotate the rotor; and a second current conducting control means for charging a second power source by electric power generated in an armature winding of the second stator when the rotor is rotated by the supply of the driving electric current to the armature winding of the first stator. 
     In accordance with such a present invention, while the electric motor is rotated by the armature winding of the first stator and the rotor, the electric motor can be operated as an electricity generator by combining the armature winding of the second stator and the rotor. In this case, a compact package can be set by integrating the electric motor and the electricity generator in comparison with a case in which the electric motor and the electricity generator are set to different bodies. Further, when request torque with respect to the electric motor is small and there is a margin in the output of the electric motor, the second power source can be efficiently charged by electric power generated in the second stator by the second current conducting control means. 
     Further, characteristics of the armature winding of the first stator and the armature winding of the second stator are set such that an induced voltage caused in the armature winding of the second stator by rotating the rotor becomes lower than a predetermined voltage when the predetermined voltage is applied to the armature winding of the first stator by the first current conducting control means and the driving electric current is supplied thereto. 
     In accordance with such a present invention, the induced voltage caused in the armature winding of the second stator becomes lower than the voltage applied to the armature winding of the first stator. Therefore, a charging circuit of the second power source connected to the armature winding of the second stator can be set to a low withstand voltage specification. Thus, the charging circuit can be made compact. 
     Further, the second current conducting control means switches between an electricity generating mode for charging the second power source by electric power generated in the armature winding of the second stator, and a driving mode for supplying the driving electric current from the second power source to the armature winding of the second stator in accordance with request torque of the electric motor. 
     In accordance with such a present invention, when the request torque of the electric motor is high, the second current conducting control means supplies the driving electric current from the second power source to the armature winding of the second stator. Thus, a magnetic flux generated by the driving electric current supplied to the armature winding of the first stator is swept by the driving electric current supplied to the armature winding of the second stator, and the output torque of the electric motor can be raised. On the other hand, when the request torque of the electric motor is low, the second current conducting control means charges the second power source by electric power generated in the armature winding of the second stator. Thus, when the request torque of the electric motor is small, a charging amount of the second power source can be secured. 
     Further, the controller comprises a charging state detecting means for detecting a charging state of the second power source, and the second current conducting control means switches between the electricity generating mode and the driving mode, in accordance with the request torque of the electric motor and the charging state of the second power source. 
     In accordance with such a present invention, the electricity generating mode and the driving mode can be switched by the second current conducting control means in consideration of a balance of the request torque of the electric motor and the charging state of the second power source. 
     Further, the controller comprises a charging state detecting means for detecting a charging state of the second power source; and a change-over switch for switching connection between the armature winding of the second stator and a driving circuit of the armature winding of the second stator to a conducting state and an interrupting state; and the second current conducting control means switches between an electricity generating mode for charging the second power source by electric power generated in the armature winding of the second stator, a driving mode for supplying the driving electric current from the second power source to the armature winding of the second stator, and an interruption mode for setting a portion between the armature winding of the second stator and a driving circuit of the armature winding of the second stator to the interrupting state by the change-over switch, in accordance with request torque of the electric motor and the charging state of the second power source. 
     In accordance with such a present invention, when it is a state other than the electricity generating mode and the driving mode, the portion between the armature winding of the second stator and the driving circuit of the armature winding of the second stator is interrupted as the interruption mode. Thus, it is avoided that the induced voltage is caused in the armature winding of the second stator, and rotation load of the rotor can be reduced. 
     Further, the controller comprises a charging state detecting means for detecting a charging state of the second power source; and in accordance with request torque of the electric motor and the charging state of the second power source, the second current conducting control means switches between an electricity generating mode for charging the second power source by electric power generated in the armature winding of the second stator, a driving mode for supplying the driving electric current from the second power source to the armature winding of the second stator, and an interruption mode in which both a first switching element for switching conduction and interruption on a high electric potential side of an input section of the armature winding of each phase, and a second switching element for switching conduction and interruption on a low electric potential side of the input section of the armature winding of each phase are set to an off state, wherein the first switching element and the second switching element constitute a driving circuit of the second stator and are arranged for each phase of the second stator. 
     In accordance with such a present invention, when it is a state except for the electricity generating mode and the driving mode, both the first switching element and the second switching element are set to the off state as the interruption mode so that the electric current generated in the armature winding of the second rotor by the rotation of the rotor is reduced, and rotation load of the rotor can be reduced. 
     Further, the controller comprises a rotational speed detecting means for detecting a rotational speed of the electric motor; and in the interruption mode, the second current conducting control means sets each first switching element and each second switching element to the off state when the rotational speed of the electric motor is less than a predetermined rotational speed, and sets each first switching element to an on state and sets each second switching element to the off state, or sets each first switching element to the off state and sets each second switching element to the on state, when the rotational speed of the electric motor is the predetermined rotational speed or more. 
     In accordance with such a present invention, when the rotational speed of the electric motor is high, each first switching element is set to the on state and each second switching element is set to the off state, or each first switching element is set to the off state and each second switching element is set to the on state. Thus, the electric current generated in the armature winding of the second rotor by the rotation of the rotor is further reduced, and rotation load of the rotor can be reduced. 
     Further, magnetic circuit cross sections of the first stator and the second stator are set to the same. 
     In accordance with such a present invention, matching property of magnetic resistance in the armature of the first stator and magnetic resistance in the armature of the second stator is raised in the driving mode, and magnetic fluxes generated by the armature winding of the first stator and the armature winding of the second stator can be further strengthened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a constructional view of a vehicle to which a controller of an electric motor of the present invention is mounted. 
         FIG. 2  is an explanatory view of the structure of the electric motor of an axial air-gap type. 
         FIG. 3  is an explanatory view of a mounting mode of armature windings in a first stator and a second stator. 
         FIG. 4  is a block diagram showing a functional construction of the controller of the electric motor. 
         FIG. 5  is a constructional view of a driving circuit of the electric motor. 
         FIG. 6  is an explanatory view of operation states of a both-side stator driving mode and a one-side stator driving mode. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the present invention will be explained with reference to  FIGS. 1 to 6 . 
     First, the schematic construction of a vehicle mounting an electric motor of this embodiment will be explained with reference to  FIG. 1 .  FIG. 1  is a view showing the schematic construction of this vehicle. 
     The vehicle  1  of this embodiment is a hybrid vehicle of a parallel type, and has an internal combustion engine (engine)  2  as a main propulsive force generating source of the vehicle  1 , and also has an electric motor  3  as an auxiliary propulsive force generating source. The electric motor  3  is an electric motor of an axial air-gap type having a rotor  11 , a first stator  12   a  and a second stator  12   b  although the electric motor  3  will be described later. A resolver  14  as a rotation angle detecting means for detecting a rotation angle of the rotor  11  of the electric motor  3  is arranged in the electric motor  3 . 
     An output shaft  2   a  of the internal combustion engine  2  is coaxially directly connected to a rotating shaft  3   a  rotatable integrally with the rotor  11  of the electric motor  3 . The output shaft  2   a  of the internal combustion engine  2  and the rotating shaft  3   a  of the electric motor  3  may be also connected through a power transmitting mechanism such as a speed reducer or the like. These output shaft  2   a  and rotating shaft  3   a  are connected to the input side of a transmission  5  through a clutch  4 . An output side of the transmission  5  is connected to drive wheels  7 ,  7  of the vehicle  1  through a differential gear unit  6 . 
     In this vehicle  1 , output torque of the internal combustion engine  2 , or torque provided by adding output torque (power torque) of the electric motor  3  to this output torque is transmitted to the drive wheels  7 ,  7  as propulsive force of the vehicle  1  through the clutch  4 , the transmission  5  and the differential gear unit  6 . Thus, running of the vehicle  1  is performed. The electric motor  3  can also perform a regenerative operation in which the electric motor  3  generates electricity by kinetic energy of the vehicle  1  transmitted from the drive wheels  7 ,  7  side to the electric motor  3  and this electric power generation energy is charged to an unillustrated storage battery as an electric source of the electric motor  3 . Regenerative torque generated by the electric motor  3  during a regenerative operation functions as braking force of the vehicle  1 . 
     Further, the vehicle  1  has a controller  8  for controlling the operation of the electric motor  3 . A detection value θm_s of the rotation angle of the rotor  11  is inputted from the above resolver  14  to this controller  8 . A torque command value Tr_c as a request value of the output torque of the electric motor  3  is also inputted to the controller  8 . The torque command value Tr_c is determined by an unillustrated vehicle operation controller performing centralized operation control of the vehicle  1  in accordance with a manipulation amount of an accelerator pedal of the vehicle  1 , a manipulation amount of a brake pedal, a vehicle speed or the like. 
     The controller  8  controls conducting electric currents of armature windings of the first stator  12   a  and the second stator  12   b  so as to generate the output torque of torque command value Tr_c in the electric motor  3 . 
       FIGS. 2(   a ) and  2 ( b ) are perspective views showing the structure of the rotor  11  of the electric motor  3 , the first stator  12   a  and the second stator  12   b .  FIG. 2(   a ) shows the rotor  11 , the first stator  12   a  and the second stator  12   b  in an assembled state of the electric motor  3 .  FIG. 2(   b ) shows the rotor  11 , the first stator  12   a  and the second stator  12   b  in a disassembled state of the electric motor  3 . 
     The rotor  11  is constructed from a frame body  14  formed by a non-magnetic material, and a plurality of permanent magnets  15  assembled into this frame body  14 . The frame body  14  is constructed by integrally forming a base body  16  of a disk shape, a circular ring-shaped body  17  spaced from an outer circumferential face of this base body  16  in a diametrical direction and coaxially arranged around the base body  16 , and a plurality of partition plates  18  connecting these base body  16  and ring-shaped body  17 . As shown by a virtual line in  FIG. 2(   a ), the rotating shaft  3   a  is coaxially attached to the base body  16 . 
     The plurality of partition plates  18  are radially extended between the outer circumferential face of the base body  16  and an inner circumferential face of the ring-shaped body  17 , and are arrayed at an equal angle interval around the axis of the rotor  11 . In each space surrounded by the outer circumferential face of the base body  16 , the inner circumferential face of the ring-shaped body  17 , and the partition plates  18 ,  18  adjacent to each other in the circumferential direction of the rotor  11 , the permanent magnet  15  of the same shape as this space (fan plate shape) is fitted. Thus, the plurality of permanent magnets  15  are arrayed at an equal angle interval around the axis of the rotor  11  between the base body  16  and the ring-shaped body  17 . 
     Each permanent magnet  15  is a magnet in which one face in its thickness direction (the axial direction of the rotor  11 ) is the north pole and the other face is the south pole. As described in each permanent magnet  15  of  FIG. 2(   b ), the permanent magnets  15 ,  15  adjacent to each other in the circumferential direction of the rotor  11  are set such that their magnetic poles of faces of the same side in the thickness direction are different from each other. In other words, the plurality of permanent magnets  15  arranged in the rotor  11  are arrayed such that the orientations (orientations in the axial direction of the rotor  11 ) of magnetic fluxes of the permanent magnets  15 ,  15  adjacent in the circumferential direction of the rotor  11  are mutually reverse. In the illustrated example, the number of permanent magnets  15  is  12 , and a number of pole-pairs of the rotor  11  is  6 . 
     Additionally, the permanent magnets may be also arrayed respectively separately on one face side and the other face side of the axial direction of the rotor  11 . 
     The first stator  12   a  and the second stator  12   b  have the same construction except that the first stator  12   a  and the second stator  12   b  are different in thickness. As shown in  FIG. 2(   b ), a plurality of teeth  20   a ,  20   b  respectively projected in the axial direction of ring-shaped base bodies  19   a ,  19   b  from one face among both end faces in the axial direction of the base bodies  19   a ,  19   b  are arrayed at an equal angle interval around the axis of the base bodies  19   a ,  19   b . The base bodies  19   a ,  19   b  and the teeth  20   a ,  20   b  are integrally formed by a magnetic material. In the illustrated example, the numbers of teeth  20   a ,  20   b  of the first stator  12   a  and the second stator  12   b  are respectively  36 . 
     In the first stator  12   a  and the second stator  12   b , as shown in  FIGS. 2(   b ) and  3 , an armature winding  22   a  is mounted to a slot  21   a  as a groove between the teeth  20   a ,  20   a  adjacent to each other in the circumferential direction, and an armature winding  22   b  is mounted to a slot  21   b  as a groove between the teeth  20   b ,  20   b .  FIG. 3  is a cross-sectional view of the first stator  12   a  and the second stator  12   b.    
     In this embodiment, the armature winding  22   a  mounted to the first stator  12   a  and the armature winding  22   b  mounted to the second stator  12   b  have three phases (U-phase, V-phase and W-phase). Further, the armature winding  22   a  in the first stator  12   a  and the armature winding  22   b  in the second stator  12   b  are mutually mounted in the same manner. 
     For example, when the armature winding  22   a  of each phase of the first stator  12   a  is seen in the axial direction of the first stator  12   a , this armature winding  22   a  is mounted to the first stator  12   a  such that a winding loop in number equal to the number of permanent magnets  15  of the rotor  11  is formed at an equal angle interval in the circumferential direction of the first stator  12   a . The armature winding  22   b  of the second stator  12   b  side is also similarly mounted. 
     Further, a winding pattern of the armature winding  22   a  of the first stator  12   a  side and a winding pattern of the armature winding  22   b  of the second stator  12   b  side are the same, and a winding number of times of the armature winding  22   b  is set to be smaller than that of the armature winding  22   a . Thus, when a predetermined driving voltage is applied to the armature winding  22   a  of the first stator  12   a  and the rotor  11  is rotated, a voltage generated in the armature winding  22   b  of the second stator  12   b  is set to be lower than the predetermined voltage. 
     Further, a wire diameter of the armature winding  22   a  of the first stator  12   a  is larger than that of the armature winding  22   b  of the second stator  12   b  so that the thickness of the second stator  12   b  is thinner than that of the first stator  12   a.    
     As shown in  FIG. 2(   a ), the first stator  12   a  and the second stator  12   b  are arranged coaxially with the rotor  11  on both sides of the axial direction of the rotor  11  in an assembled state of the electric motor  3  so as to sandwitch the rotor  11  between the first stator  12   a  and the second stator  12   b , and are fixed to an unillustrated housing of the electric motor  3 . In this case, tip faces of the tooth  20   a  of the first stator  12   a  and the tooth  20   b  of the second stator  12   b  are opposed in proximity to the rotor  11 . 
     Further, in this embodiment, the first stator  12   a  and the second stator  12   b  are assembled into the electric motor  3  such that the position (an angular position around the axis) of each tooth  20   a  of the first stator  12   a  and the position (an angular position around the axis) of each tooth  20   b  of the second stator  12   b  are conformed when the electric motor  3  is seen in the axial direction of the rotor  11  in the assembled state of the electric motor  3 . 
     Namely, the individual tooth  20   a  of the first stator  12   a  and the individual tooth  20   b  of the second stator  12   b  are arranged in direct opposing positions and are assembled in the axial direction of the rotor  11 . The armature winding  22   a  of each phase of the first stator  12   a  and the armature winding  22   b  of the second stator  12   b  of the same phase as this armature winding  22   a  are mounted to the first stator  12   a  and the second stator  12   b  such that the winding loop of the armature winding  22   a  of the first stator  12   a  and the winding loop of the armature winding  22   b  of the second stator  12   b  are opposed to each other in the axial direction of the rotor  11  for each phase (such that the winding loop of the first stator  12   a  side and the winding loop of the second stator  12   b  side are mutually located in the same angular position when these armature windings are seen in the axial direction of the rotor  11 ). 
     Accordingly, when the electric current of the same phase is conducted to the armature winding  22   a  of each phase of the first stator  12   a  and the armature winding  22   b  of the second stator  12   b  of the same phase as this armature winding  22   a , a magnetic flux generated by the armature winding  22   a  of the first stator  12   a  and a magnetic flux generated by the armature winding  22   b  of the second stator  12   b  attain a state mutually strengthened to its maximum extent in the axial direction of the rotor  11  for each phase. In this embodiment, the first stator  12   a  and the second stator  12   b  have the same structure except that the first stator  12   a  and the second stator  12   b  are different in thickness. Accordingly, magnetic circuit cross sections (cross sections of magnetic paths) for each phase of the first stator  12   a  and the second stator  12   b  are mutually the same. 
     Next, the construction of the controller  8  will be explained in detail with reference to  FIG. 4 .  FIG. 4  is a block diagram showing the functional construction of the controller  8 . The controller  8  is constructed by an electronic circuit unit including a microcomputer and the like. In the following explanation, as shown in  FIG. 4 , reference numeral  13   a  is given to the armature winding of each phase mounted to the first stator  12   a , and reference numeral  13   b  is given to the armature winding of each phase mounted to the second stator  12   b.    
     First, the summary of control processing of the electric motor  3  using the controller  8  will be explained. In this embodiment, conducting electric currents (phase electric currents) of the armature windings  13   a ,  13   b  of each phase of the first stator  12   a  and the second stator  12   b  of the electric motor  3  are controlled by so-called d-q vector control. Namely, the controller  8  converts the armature windings  13   a ,  13   a ,  13   a  of the three phases of the first stator  12   a , and the armature windings  13   b ,  13   b ,  13   b  of the three phases of the second stator  12   b  into equivalent circuits in a d-q coordinate system of a two-phase direct current, and treats these armature windings. 
     The equivalent circuits corresponding to the first stator  12   a  and the second stator  12   b  respectively have an armature on a d-axis (hereinafter called a d-axis armature), and an armature on a q-axis (hereinafter called a q-axis armature). The d-q coordinate system is a rotating coordinate system in which a field magnet direction provided by the permanent magnet  15  of the rotor  11  is the d-axis, and a direction perpendicular to the d-axis is the q-axis and this rotating coordinate system is rotated integrally with the rotor  11  of the electric motor  3 . 
     The controller  8  then controls the electric currents of the respective phases of the armature winding  13   a  of the first stator  12   a  and the armature winding  13   b  of the second stator  12   b  of the electric motor  3  such that the torque of torque command value Tr_c given from the exterior is outputted from the rotating shaft  3   a  of the electric motor  3 . 
     In this case, in this embodiment, control for switching between a “both-side stator driving mode” and a “one-side stator driving mode” are switched in accordance with the magnitude of torque command value Tr_c. In the “both-side stator driving mode”, a driving electric current is conducted to both the armature winding  13   a  of the first stator  12   a  and the armature winding  13   b  of the second stator  12   b , and the electric motor  3  is driven. In the “one-side stator driving mode”, the driving electric current is conducted to only the armature winding  13   a  of the first stator  12   a  (the supply of the driving electric current to the armature winding  13   b  of the second stator  12   b  is stopped), and the electric motor  3  is driven. 
     Further, in the “one-side stator driving mode”, the controller  8  performs control for switching between an “electricity generating mode” for charging a battery by electric power generated in the armature winding  13   b  of the second stator  12   b  by rotating the rotor  11 , and an “interruption mode” for interrupting connection between the armature winding  13   b  of the second stator  12   b  and its driving circuit. 
     The controller  8  has a first electric current command determining section  30  as its functional construction. The first electric current command determining section  30  determines a d-axis electric current command value Id_c 1  as a command value of the electric current (hereinafter called a d-axis electric current) of the d-axis armature of the first stator  12   a , and a q-axis electric current command value Iq_c 1  as a command value of the electric current (hereinafter called a q-axis electric current) of the q-axis armature. The first electric current command determining section  30  also switches between the “both-side stator driving mode” and the “one-side stator driving mode”, and switches between the “electricity generating mode” and the “interruption mode” in the “one-side stator driving mode”. 
     Further, the controller  8  has a first electric current control section  40   a  for determining a d-axis voltage command value Vd_c 1  as a command value of the voltage (hereinafter called a d-axis voltage) of the d-axis armature of the first stator  12   a , and a q-axis voltage command value Vq_c 1  as a command value of the voltage (hereinafter called a q-axis voltage) of the q-axis armature, in accordance with d-axis electric current command value Id_c 1  and q-axis electric current command value Iq_c 1  of the first stator  12   a.    
     Further, the controller  8  has electric current sensors  33   a ,  34   a  as an electric current detecting means for detecting the respective phase electric currents of the armature windings  13   a ,  13   a  of two phases, e.g., the U-phase and the W-phase, of the armature windings  13   a ,  13   a ,  13   a  of the three phases of the first stator  12   a . The controller  8  also has a dq converting section  36   a  for calculating a d-axis electric current detection value Id_s 1  as a detection value (estimated value) of the d-axis electric current of the first stator  12   a  and a q-axis electric current detection value Iq_s 1  as a detection value (estimated value) of the q-axis electric current from an electric current detection value Iu_s 1  of the U-phase armature winding  13   a  of the first stator  12   a  and an electric current detection value Iw_s 1  of the W-phase armature winding  13   a  obtained by passing the outputs of these electric current sensors  33   a ,  34   a  through a BP (Band Pass) filter  35   a . The BP filter  35   a  is a filter of bandpass characteristics for removing a noise component from the outputs of the electric current sensors  33   a ,  34   a.    
     The dq converting section  36   a  calculates the d-axis electric current detection value Id_s 1  and the q-axis electric current detection value Iq_s 1  by coordinate-transforming the electric current detection value Iu_s 1  of the U-phase armature winding  13   a  of the first stator  12   a , the electric current detection value Iw_s 1  of the W-phase armature winding  13   a , and an electric current detection value Iv_s 1  (=−Iu_s 1 −Iw_s 1 ) of the V-phase armature winding  13   a  calculated from these electric current detection value Iu_s 1  and electric current detection value Iw_s 1  by the following expression (1) in accordance with an electric angle θe of the rotor  11  (calculated by multiplying a detection value θm_s of the rotation angle of the rotor  11  using the resolver  14  by the number of pole-pairs of the rotor  11 ). 
     
       
         
           
             
               
                 
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     The first electric current control section  40   a  has a subtracting section  41   a  for calculating an error ΔId 1  (=Id_c 1 −Id_s 1 ) between the d-axis electric current command value Id_c 1  and the d-axis electric current detection value Id_s 1 . The first electric current control section  40   a  also has a d-axis electric current PI control section  42   a  for calculating a basic command value Vd 1 _c 1  of the d-axis voltage by feedback control using a PI (proportion-integration) control law so as to dissolve the error ΔId 1  (bring the error ΔId 1  close to zero). The first electric current control section  40   a  also has a subtracting section  45   a  for calculating an error ΔIq 1  (=Iq_c 1 −Iq_s 1 ) between the q-axis electric current command value Iq_c 1  and the q-axis electric current detection value Iq_s 1 . The first electric current control section  40   a  also has a q-axis electric current PI control section  46   a  for calculating a basic command value Vq 1 _c 1  of the q-axis voltage by the feedback control using the PI (proportion-integration) control law so as to dissolve the error ΔIq 1  (bring the error ΔIq 1  close to zero). The first electric current control section  40   a  further has a non-interference control section  44   a  for calculating a correction amount Vd 2 _c 1  of the d-axis voltage and a correction amount Vq 2 _c 1  of the q-axis voltage for canceling speed electromotive forces interfering with each other between the d-axis and the q-axis. 
     The non-interference control section  44   a  calculates the correction amount Vd 2 _c 1  of the d-axis side from the q-axis electric current command value Iq_c 1  and a rotor angular velocity (calculated by differentiating the detection value θm_s of the rotor angle), and calculates the correction amount Vq 2 _c 1  of the q-axis side from the d-axis electric current command value Id_c 1  and the rotor angular velocity. 
     Further, the first electric current control section  40   a  has an adding section  43   a  for adding the correction amount Vd 2 _c 1  to the basic command value Vd 1 _c 1  of the d-axis voltage and calculating the final d-axis voltage command value Vd_c 1 , and an adding section  47   a  for adding the correction amount Vq 2 _c 1  to the basic command value Vq 1 _c 1  of the q-axis voltage and calculating the final q-axis voltage command value Vq_c 1 . 
     Further, the controller  8  has a three-phase converting section  31   a  for calculating phase voltage command values Vu_c 1 , Vv_c 1 , Vw_c 1  of the armature winding  13   a  of the respective U-phase, V-phase and W-phase of the first stator  12   a  from the d-axis voltage command value Vd_c 1  and the q-axis voltage command value Vq_c 1 . The controller  8  also has a first PDU (Power Drive Unit)  32   a  for conducting an electric current to the armature winding  13   a  of each phase of the first stator  12   a  in accordance with these phase voltage command values Vu_c 1 , Vv_c 1 , Vw_c 1 . The controller  8  further has a battery  38   a  (corresponding to a first power source of the present invention) for supplying electric power to the first PDU  32   a.    
     The three-phase converting section  31   a  calculates the above phase voltage command values Vu_c 1 , Vv_c 1 , Vw_c 1  by coordinate-transforming the d-axis voltage command value Vd_c 1  and the q-axis voltage command value Vq_c 1  by the following expression (2) in accordance with the electric angle θe of the rotor  11 . A(θe) T  within expression (2) is a transposition matrix of matrix A(θe) defined in the provision of the above expression (1). 
     
       
         
           
             
               
                 
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     A first current conducting control means of the present invention is constructed by the first electric current command determining section  30 , the first electric current control section  40   a , the three-phase converting section  31   a , the first PDU  32   a , the battery  38   a , the electric current sensors  33   a ,  34   a , the bandpass filter  35   a , and the dq converting section  36   a.    
     Further, the controller  8  has a second electric current control section  40   b  for determining a d-axis voltage command value Vd_c 2  and a q-axis voltage command value Vq_c 2  of the second stator  12   b  in accordance with a d-axis electric current command value Id_c 2  and a q-axis electric current command value Iq_c 2  of the armature winding  13   b  of the second stator  12   b . The controller  8  also has electric current sensors  33   b ,  34   b  for detecting the respective phase electric currents of the armature windings  13   a ,  13   a  of the U-phase and the W-phase among the armature windings  13   b ,  13   b ,  13   b  of the three phases of the second stator  12   b . The controller  8  further has a dq converting section  36   b  for calculating a d-axis electric current detection value Id_s 2  and a q-axis electric current detection value Iq_s 2  of the second stator  12   b  from an electric current detection value Iu_s 2  of the U-phase armature winding  13   b  and an electric current detection value Iw_s 2  of the W-phase armature winding  13   b  of the second stator  12   b  obtained by passing the outputs of these electric current sensors  33   b ,  34   b  through the BP filter  35   a.    
     Similar to the above-mentioned first electric current control section  40   a , the second electric current control section  40   b  has a subtracting section  41   b  for calculating an error ΔId 2  (=Id_c 2 −Id_s 2 ) between the d-axis electric current command value Id_c 2  and the d-axis electric current detection value Id_s 2 . The second electric current control section  40   b  also has a d-axis electric current PI control section  42   b  for calculating a basic command value Vd 1 _c 2  of the d-axis voltage by feedback control using a PI (proportion-integration) control law so as to dissolve the error ΔId 2  (bring the error ΔId 2  close to zero). The second electric current control section  40   b  also has a subtracting section  45   b  for calculating an error ΔIq 2  (=Iq_c 2 −Iq_s 2 ) between the q-axis electric current command value Iq_c 2  and the q-axis electric current detection value Iq_s 2 . The second electric current control section  40   b  also has a q-axis electric current PI control section  46   b  for calculating a basic command value Vq 1 _c 2  of the q-axis voltage by the feedback control using the PI (proportion-integration) control law so as to dissolve the error ΔIq 2  (bring the error ΔIq 2  close to zero). The second electric current control section  40   b  further has a non-interference control section  44   b  for calculating a correction amount Vd 2 _c 2  of the d-axis voltage and a correction amount Vq 2 _c 2  of the q-axis voltage for canceling speed electromotive forces interfering with each other between the d-axis and the q-axis. 
     Further, the second electric current control section  40   b  has an adding section  43   b  for adding the correction amount Vd 2 _c 2  to the basic command value Vd 1 _c 2  of the d-axis voltage and calculating the final d-axis voltage command value Vd_c 2 , and an adding section  47   b  for adding the correction amount Vq 2 _c 2  to the basic command value Vq 1 _c 2  of the q-axis voltage and calculating the final q-axis voltage command value Vq_c 2 . 
     Further, the controller  8  has a three-phase converting section  31   b  for calculating phase voltage command values Vu_c 2 , Vv_c 2 , Vw_c 2  of the armature winding  13   b  of the respective U-phase, V-phase and W-phase of the second stator  12   b  from the d-axis voltage command value Vd_c 2  and the q-axis voltage command value Vq_c 2 . The controller  8  also has a second PDU  32   b  for conducting an electric current to the armature winding  13   b  of each phase of the second stator  12   b  in accordance with these phase voltage command values Vu_c 2 , Vv_c 2 , Vw_c 2 . The controller  8  also has a battery  38   b  (corresponding to a second power source of the present invention) for supplying electric power to the second PDU  32   b  and charged by output electric power of the second PDU  32   b . The controller  8  further has a charging state detecting section  39  (corresponding to a charging state detecting means of the present invention) for outputting an electricity generating torque command value Trb according to output voltage Vbat of the battery  38   b  (corresponding to a charging state of the present invention) to the first electric current command determining section  30 . 
     The charging state detecting section  39  increases the electricity generating torque command value Trb as a charging amount of the battery  38   b  decreases. The charging state detecting section  39  sets the electricity generating torque command value Trb to zero when the battery  38   b  is in a full charging state. 
     The d-axis electric current command value Id_c 2  and the q-axis electric current command value Iq_c 2  of the second stator  12   b  are determined by a second electric current command determining section  37 . The second electric current command determining section  37  determines d-axis electric current command value Id_c 2  and q-axis electric current command value Iq_c 2  by applying torque command value Tr 2 _c with respect to the second stator  12   b  determined by the first electric current command determining section  30  to a corresponding map (data of the corresponding map are stored to an unillustrated memory) of preset torque Tr_ 2  and the d-axis electric current Id and the q-axis electric current Iq. 
     In this case, when torque command value Tr 2 _c is positive, the “driving mode” for supplying the driving electric current to the armature winding  13   b  of the second stator  12   b  is attained. When torque command value Tr 2 _c is negative, the “electricity generating mode” for charging the battery  38   b  by electric power generated in the armature winding  13   b  of the second stator  12   b  by rotating the rotor  11  is attained. 
     Further, when torque command value Tr 2 _c is zero, the “interruption mode” for turning-off the switch of each phase of the change-over switch  50  (opening state) and interrupting connection between the second PDU  32   b  and the armature winding  13   b  of the second stator  12   b  is attained. In the “driving mode” and the “electricity generating mode”, the switch of each phase of the change-over switch  50  is turned on and the second PDU  32   b  and the armature winding  13   b  of the second stator  12   b  are set to a current conducting state. 
     Further, the first electric current command determining section  30  applies torque command value Tr_c and electricity generating torque command value Trb to a corresponding map (data of the corresponding map are stored to an unillustrated memory) between torque command value Tr_c with respect to the electric motor  3  set in advance and electricity generating torque command value Trb according to a charging state of the battery  39   b , and d-axis electric current Id, q-axis electric current Iq of the first stator  12   a  and torque command value Tr 2 _c with respect to the second stator  12   b , and determines torque command value Tr 2 _c with respect to the second stator  12   b , and d-axis electric current command value Id_c 1  and q-axis electric current command value Iq_c 1  of the first stator  12   a.    
     Here,  FIG. 6  is a graph showing the relation of output torque Tr and conducting electric current I of the electric motor  3 . In this figure, the axis of ordinate is set to output torque Tr, and the axis of abscissa is set to conducting electric current I. Reference numeral a in this figure shows the “both-side stator driving mode” for supplying a driving electric current to both the first stator  12   a  and the second stator  12   b , and reference numeral b shows the “one-side stator driving mode” for conducting the driving electric current to only the first stator  12   a.    
     As can be seen from  FIG. 6 , an upper limit of the output torque of the electric motor  3  can be expanded by setting the “both-side stator driving mode” and changing the output characteristics of the electric motor  3  to a high torque specification. Further, in a low torque area of Tr&lt;Tr 1  within this figure, the difference in output torque between the “both-side stator driving mode” and the “one-side stator driving mode” with respect to the same conducting electric current is reduced. 
     Therefore, in the above corresponding map in the first electric current command determining section  30 , the “one-side stator driving mode” is set when torque command value Tr_c is a preset threshold value Tr 1  or less. When torque command value Tr_c exceeds the threshold value Tr 1 , the “both-side stator driving mode” is set. Thus, in the low torque area, the “one-side stator driving mode” is attained and the output characteristics of the electric motor  3  become a low torque specification. Therefore, it is possible to avoid electric power loss on the second stator  12   b  side and improve operation efficiency of the electric motor  3 . 
     Here, in the “both-side stator driving mode”, positive torque command value Tr 2 _c is outputted from the first electric current command determining section  30  to the second electric current command determining section  37 . Thus, the driving electric current is supplied to both the armature winding  13   a  of the first stator  12   a  and the armature winding  13   b  of the second stator  12   b , and the output torque of the electric motor  3  is increased. 
     Further, in the above corresponding map in the first electric current command determining section  30 , when electricity generating torque command value Trb is outputted in the “one-side stator driving mode”, d-axis electric current command value Id_c 1  and q-axis electric current command value Iq_c 1  of the first stator  12   a  are determined such that total torque of torque command value Tr_c and electricity generating torque command value Trb is generated by the supply of the driving electric current to the armature winding  13   a  of the first stator  12   a.    
     Torque command value Tr 2 _c outputted to the second electric current command determining section  37  is then set to correspond to electricity generating torque command value Trb. Thus, the above “electricity generating mode” for charging the battery  38   b  through the second PDU  32   b  by electric power generated in the second stator  12   b  by rotating the rotor  11  is attained. 
     Here, as mentioned above, when a predetermined voltage is applied to the armature winding  13   a  of the first stator  12   a  and the rotor  11  is rotated, an induced voltage caused in the armature winding  13   b  of the second stator  12   b  becomes lower than the predetermined voltage. Therefore, a withstand voltage specification of the second PDU  32   b  can be set to be lower than that of the first PDU  32   a . Thus, the second PDU  32   b  can be made compact and reduced in cost. 
     Further, the output of the battery  38   b  of the second stator  12   b  side becomes lower than that of the battery  38   a  of the first stator  12   a  side. Namely, the electric motor  3  can be set to function as an alternator, and the battery  38   b  can be used as an electric power source for a device of a low voltage specification. 
     Further, when electricity generating torque command value Trb is zero, torque command value Tr 2 _c outputted from the first electric current command determining section  30  to the second electric current command determining section  37  also becomes zero. Thus, the switch of each phase of the change-over switch  50  is turned off, and the above “interruption mode” is attained. In this case, the above “one-side stator driving mode” for supplying the driving electric current to only the armature winding  13   a  of the first stator  12   a  is attained, and no induced voltage is caused in the armature winding  13   b  of the second stator  12   b  when the rotor  11  is rotated. Therefore, rotation load of the rotor  11  is reduced. 
     Next,  FIG. 5  is a view showing the construction of an inverter  60   a  arranged in the first PDU  32   a , and an inverter  60   b  arranged in the second PDU  32   b . The first PDU  32   a  has the inverter  60   a  in which a switching circuit  61   a  is arranged for armature winding  13   a  of each phase. The switching circuit  61   a  has a transistor  62   a  for conducting/interrupting an input section of the armature winding  13   a  of each phase of the first stator  12   a  on a high electric potential side (a side shown by Hi within this figure), and a transistor  63   a  for conducting/interrupting this input section on a low electric potential side (Lo within this figure). The first PDU  32   a  changes an electric current conducting amount of each armature winding  13   a  by switching on/off of the transistor  62   a  and the transistor  63   a  of each switching circuit  61   a  by PWM control. 
     Similarly, the second PDU  32   b  has an inverter  60   b  having a switching circuit  61   b  for armature winding  13   b  of each phase. The switching circuit  61   b  has a transistor  62   b  (corresponding to a first switching element of the present invention) for conducting/interrupting each armature winding  13   b  of the second stator  12   b  on a high electric potential side, and a transistor  63   b  (corresponding to a second switching element of the present invention) for conducting/interrupting each armature winding  13   b  of the second stator  12   b  on a low electric potential side. 
     In this embodiment, in the “interruption mode”, the switch of each phase of the change-over switch  50  is turned off and the portion between the second PDU  32   b  and the armature winding  13   b  of each phase of the second stator  12   b  is interrupted. However, all transistors  62   b ,  63   b  of the inverter  60   b  shown in  FIG. 6  may be also turned off (gate off) without arranging the change-over switch  50 . Further, when the rotational speed of the electric motor  3  exceeds a predetermined rotational speed, all transistors  62   b  of the high electric potential side of the inverter  60   b  shown in  FIG. 6  are turned on and all transistors  63   b  of the low electric potential side are turned off, or all the transistors  63   b  of the low electric potential side of the inverter  60   b  are turned on and all the transistors  62   b  of the low electric potential side are turned off, so that a so-called three-phase short-circuit state is set. Thus, the current conducting amount of each armature winding  13   b  of the second stator  12   b  is further reduced and electric power loss can be reduced. 
     The rotational speed of the electric motor  3  can be detected by differentiating detection value θm_s of the rotation angle of the rotor  11  by the resolver  14 . The construction for detecting the rotational speed of the electric motor  3  in this way corresponds to a rotational speed detecting means of the present invention. 
     In this embodiment, in the “electricity generating mode”, the characteristics of the armature winding  13   a  and the armature winding  13   b  are set such that the induced voltage caused in the armature winding  13   b  of the second stator  12   b  becomes lower than a voltage applied to the armature winding  13   a  of the first stator  12   a . However, the effects of the present invention can be also obtained even when such characteristics are not set. 
     Further, in this embodiment, the “driving mode” and the “electricity generating mode” are switched in accordance with torque command value Tr_c with respect to the electric motor  3  and the charging state of the battery  38   b  of the second stator  12   b  side. However, the “driving mode” and the “electricity generating mode” may be also switched in accordance with only torque command value Tr_c with respect to the electric motor  3 . 
     Further, in this embodiment, when torque command value Tr 2 _c with respect to the second stator  12   b  is zero, the “interruption mode” for interrupting the portion between the second PDU  32   b  and the armature winding  13   b  of the second stator  12   b  is set. However, the effects of the present invention can be also obtained even when no “interruption mode” is set.