Abstract:
A first inverter circuit ( 3 A) and a second inverter circuit ( 3 B) are formed on a substrate ( 25 ). The first inverter circuit ( 3 A) outputs a first three-phase alternating current generated by a first group of switching elements (SW 1,  SW 2,  SW 3,  SW 4,  SW 5,  SW 6 ) via a first output busbar ( 28 UA), a second output busbar ( 28 VA), and a third output busbar ( 28 WA). A second inverter circuit ( 3 B) outputs a second three-phase alternating current generated by a second group of switching elements (SW 7,  SW 8,  SW 9,  SW 10,  SW 11,  SW 12 ) via a fourth output busbar ( 28 UB), a fifth output busbar ( 28 VB), and a sixth output busbar ( 28 WB). The fourth output busbar ( 28 UB) is in close proximity to the first output busbar ( 28 UA), the fifth output busbar ( 28 VB) is in close proximity to the second output busbar ( 28 VA) and the sixth output busbar ( 28 WB) is in close proximity to the third output busbar ( 28 WA). The first group of switching elements (SW 1,  SW 2,  SW 3,  SW 4,  SW 5,  SW 6 ) and second group of switching elements (SW 7,  SW 8,  SW 9,  SW 10,  SW 11,  SW 12 ) are arranged so that the direction of the current in the fourth output busbar ( 28 UB) is opposite to the direction of the current in the first output busbar ( 28 UA), the direction of the current in the fifth output busbar ( 28 VB) is opposite to the direction of the current in the second output busbar ( 28 VA), and the direction of the current in the sixth output busbar ( 28 WB) is opposite to the direction of the current in the third output busbar ( 28 WA).

Description:
[0001]    This application claims the benefit of priority of prior U.S. application Ser. No. 09/599,547, filed Jun. 23, 2000, and Japanese Application 11-178899, filed Jun. 24, 1999. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The entire contents of both of these applications is incorporated herein by reference.  
           [0003]    This invention relates to a power module of an inverter circuit which supplies electric power to an alternating current motor.  
         BACKGROUND OF THE INVENTION  
         [0004]    A technique is known whereby a direct current is converted to an alternating current of a predetermined frequency and a predetermined voltage by an inverter in order to obtain an alternating current which drives an alternating current motor. The direct current is obtained by supplying it from battery current or by rectifying alternating current with a converter or a rectifier circuit.  
         SUMMARY OF THE INVENTION  
         [0005]    When an alternating current is generated in the inverter, a magnetic field is also formed around the current flow. Such a magnetic field may adversely affect to the electronic parts in the vicinity when it becomes large.  
           [0006]    It is therefore an object of this invention to suppress the formation of the magnetic field in the inverter.  
           [0007]    It is another object of this invention to make an inverter circuit more compact.  
           [0008]    It is yet another object of this invention to make the space occupied by an alternating current motor and an inverter circuit which drives the alternating current motor, smaller.  
           [0009]    In order to achieve the above objects, this invention provides a power module for an inverter which converts a direct current from a direct current power supply source to two types of three-phase alternating current.  
           [0010]    The power module comprises a substrate, a first inverter circuit formed on the substrate, and a second inverter circuit formed on the substrate.  
           [0011]    The first inverter circuit comprises a first group of switching elements, a first output busbar, a second output busbar and a third output busbar, wherein the first output busbar, second output busbar and third output busbar output a first three-phase alternating current generated by the first group of switching elements.  
           [0012]    The second inverter circuit comprises a second group of switching elements, a fourth output busbar disposed in close proximity to the first output busbar, a fifth output busbar disposed in close proximity to the second output busbar and a sixth output busbar disposed in close proximity to the third output busbar, wherein the fourth output busbar, the fifth output busbar and sixth output busbar output a second three-phase alternating current generated by the second group of switching elements.  
           [0013]    The first group of switching elements and second group of switching elements, are disposed so that the current flowing in the fourth output busbar and the current flowing in the first output busbar are in opposite directions, and the current flowing in the fifth output busbar and the current flowing in the second output busbar are in opposite directions, and the current flowing in the sixth output busbar and the current flowing in the second output busbar are in opposite directions.  
           [0014]    The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]    [0015]FIG. 1 is a circuit diagram of an inverter using a power module according to this invention and an alternating current motor which the inverter drives.  
         [0016]    [0016]FIG. 2 is a table showing the switching state of switching elements of the power module, and the direction of the current between phase U, phase V and phase W phase coils of the alternating current motor.  
         [0017]    [0017]FIG. 3 is a circuit diagram of the inverter comprising a plan view of the power module.  
         [0018]    [0018]FIG. 4 is a diagram describing the current flow within the power module in a switching period of 0 to 60 degrees.  
         [0019]    [0019]FIG. 5 is a diagram describing the current flow within the power module in a switching period of 60-120 degrees.  
         [0020]    [0020]FIG. 6 is a diagram describing the current flow within the power module in a switching period of 120-180 degrees.  
         [0021]    [0021]FIG. 7 is a diagram describing the current flow within the power module in a switching period of 180-240 degrees.  
         [0022]    [0022]FIG. 8 is a diagram describing the current flow within the power module in a switching period of 240-300 degrees.  
         [0023]    [0023]FIG. 9 is a diagram describing the current flow within the power module in a switching period of 300-360 degrees.  
         [0024]    [0024]FIG. 10 is a perspective view of a power module and an alternating current motor connected to the power module according to a second embodiment of this invention.  
         [0025]    [0025]FIG. 11 is a plan view of the power module and of extended parts according to the second embodiment of this invention.  
         [0026]    [0026]FIG. 12 is a rear view of the power module and the alternating current motor according to the second embodiment of this invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0027]    Referring to FIG. 1 of the drawings, a stator of a three-phase alternating current motor  4  comprises a stator coil A and stator coil B wound in parallel with phase U, phase V and phase W. The three-phase alternating current from a switching circuit  3 A of an inverter  3  is supplied to the stator coil A. The three-phase alternating current from a switching circuit  3 B of the inverter  3  is supplied to the stator coil B.  
         [0028]    The switching signals S 1  (S 4 ), S 2  (S 5 ) and S 3  (S 6 ) have phase differences of a hundred and twenty degrees. As a result, the inverter circuit  3 A supplies U phase current, V phase current and W phase current with phase differences of a hundred and twenty degrees to the phase U, phase V and phase W of the stator coil A. The inverter circuit B supplies U phase current, V phase current and W phase current with phase differences of a hundred and twenty degrees to the phase U, phase V and phase W of the stator coil B.  
         [0029]    A control unit  10  outputs a square wave signal to the switching elements SW 1 -SW 12  in sixty degree units, as shown in the table of FIG. 2. ON is represented by “H” and OFF is represented by “L.” The switching elements SW 1 -SW 2  perform ON/OFF switching operations according to this signal. In the following description, this section divided every sixty degrees is called a switching period.  
         [0030]    For the phase U, the control unit  10  outputs the same signal S 1  to switching elements SW 1 , SW 8 .  
         [0031]    A signal S 4  having a phase difference of a hundred and eighty degrees from the signal S 1  to the switching elements SW 1 , SW 8  is output to the switching elements SW 2 , SW 7 . For the phase W, the control unit  10  outputs the same signal S 2  to the switching elements SW 3 , SW 10 .  
         [0032]    A signal S 5  having a phase difference of a hundred and eighty degrees from the signal S 2  to the switching elements SW 3 , SW 10  is output to the switching elements SW 4 , SW 9 . For the phase V, the control unit  10  outputs the same signal S 3  to the switching elements SW 5 , SW 12 .  
         [0033]    A signal S 6  having a phase difference of a hundred and eighty degrees from the signal S 3  to the switching elements SW 5 , SW 12  is output to the switching elements SW 6 , SW 11 .  
         [0034]    As a result of the above signal outputs, currents having a phase difference of sixty degrees to each other flow from the switching circuit  3 A to the phase U, phase V and phase W of the stator coil A. Also, currents respectively having opposite phase to the currents flowing from the switching circuit  3 A to the stator coil A flow from the switching circuit  3 B to the phase U, phase V and phase W of the stator coil B.  
         [0035]    In order to realize the above circuit configuration of the inverter  3 , the inverter  3  comprises a power module  21  in which the switching elements SW 1 -SW 6  and switching elements SW 7 -SW 12  are installed on one substrate  25  as shown in FIG. 3.  
         [0036]    The power module  21  has the following construction.  
         [0037]    At a center part of the substrate  25 , a positive electrode busbar  26 P and a negative electrode busbar  26 N are disposed in proximity and parallel with each other.  
         [0038]    Positive electrode busbar branches  27 P 1 ,  27 P 2 ,  27 P 3 ,  27 P 4  extending in a perpendicular direction, are formed in the positive electrode busbar  26 P. The switching elements SW 1  and SW 8  are arranged between the positive electrode busbar branches  27 P 1  and  27 P 2 . The switching elements SW 3  and SW 10  are arranged between the positive electrode busbar branches  27 P 2  and  27 P 3 . The switching elements SW 5  and SW 12  are arranged between the positive electrode busbar branches  27 P 3  and  27 P 4 .  
         [0039]    A collector C of the switching element SW 1  shown in FIG. 1 is connected to the positive electrode busbar branch  27 P 1 . Collectors C of the switching element SW 8  and the switching element SW 3  shown in FIG. 1 are connected to the positive electrode busbar branch  27 P 2 , respectively. Collectors C of the switching elements SW 10  and SW 5  shown in FIG. 1 are connected to the positive electrode busbar branch  27 P 3 , respectively. The collector C of the switching element SW 12  shown in FIG. 1 is connected to the positive electrode busbar branch  27 P 4 .  
         [0040]    Negative electrode busbar branches  27 N 1 ,  27 N 2 ,  27 N 3 ,  27 N 4  are formed extending in a perpendicular direction in the negative electrode busbar  26 N. The negative electrode busbar branches  27 N 1 ,  27 N 2 ,  27 N 3 ,  27 N 4  project from the negative electrode busbar  26 N in opposite directions to the positive electrode busbar branches  27 P 1 ,  27 P 2 ,  27 P 3  and  27 P 4 , respectively.  
         [0041]    SW 2  and SW 7  are disposed between the negative electrode busbar branches  27 N 1  and  27 N 2 . The switching elements SW 4  and SW 9  are disposed between the negative electrode busbar branches  27 N 2  and  27 N 3 . The switching elements SW 6  and SW 11  are disposed between the negative electrode busbar branches  27 N 3  and  27 N 4 .  
         [0042]    The collector C of the switching element SW 2  shown in FIG. 1 is connected to the negative electrode busbar branch  27 N 1 . The collectors C of the switching elements SW 7  and SW 4  shown in FIG. 1 are respectively connected to the negative electrode busbar branch  27 N 2 . The collectors C of the switching elements SW 9  and SW 6  shown in FIG. 1 are respectively connected to the negative electrode busbar branch  27 N 3 . The collector C of the switching element SW 11  shown in FIG. 1 is connected to the negative electrode busbar branch  27 N 4 .  
         [0043]    Further, output bus bars  28 UA,  28 VA,  28 WA are arranged perpendicular to the positive electrode busbar  26 P and negative electrode busbar  26 N, and supply a current to the phase U, phase V and phase W of the stator coil A in the state where they are insulated from the positive electrode busbar  26 P and negative electrode busbar  26 N. The output busbar  28 UA is arranged between the switching elements SWI, SW 2 , and switching elements SW 8 , SW 7 . The output busbar  28 VA is arranged between the switching elements SW 3 , SW 4 , and switching elements SW 10 , SW 9 . The output busbar  28 WA is arranged between the switching elements SW 5 , SW 6 , and switching elements SW 12 , SW 11  .  
         [0044]    An emitter E of the switching element SW 1  and the collector C of the switching element SW 2  shown in FIG. 1 are connected to the output busbar  28 UA. An emitter E of the switching element SW 3  and the collector C of the switching element SW 4  shown in FIG. 1 are connected to the output busbar  28 VA. An emitter E of the switching element SW 5  and the collector C of the switching element SW 6  shown in FIG. 1 are connected to the output busbar  28 WA.  
         [0045]    The output bus bars  28 UB,  28 VB,  28 WB which supply current to the phase U, phase V and phase W of coil B are disposed respectively parallel and in close proximity to the output bus bars  28 UA,  28 VA,  28 WA. The output bus bars  28 UB,  28 VB,  28 WB are also arranged in a state of insulation with respect to all of the positive electrode busbar  26 P, negative electrode busbar  26 N and output bus bars  28 UB,  28 VB, and  28 WB.  
         [0046]    In FIG. 3 of the drawings, the output bus bars  28 UA,  28 VA,  28 WA and the output bus bars  28 UB,  28 VB,  28 WB are drawn staggered to the left and right for convenience of description, but the output bus bars  28 UA,  28 VA,  28 WA, and output bus bars  28 UB,  28 VB,  28 WB, actually overlap.  
         [0047]    An emitter E of the switching element SW 8  and the collector of the switching element SW 7  shown in FIG. 1 are connected to the output busbar  28 UB. An emitter E of the switching element SW 10  and the collector C of the switching element SW 9  shown in FIG. 1 are connected to the output busbar  28 VB. An emitter E of the switching element SW 12  and the collector C of the switching element SW 11  shown in FIG. 1 are connected to the output busbar  28 WB.  
         [0048]    A drive signal is output from the control unit  10  to the pair of switching elements SW 1  and SW 8  which synchronously perform ON/OFF operation, the pair of switching elements SW 2  and SW 7 , the pair of switching elements SW 3  and SW 10 , the pair of switching elements SW 4  and SW 9 , the pair of switching elements SW 5  and SW 12 , and the pair of switching elements SW 6  and SW 11 , respectively. For this purpose, a base B of the switching element of each pair shown in FIG. 1 is connected to the control unit  10  by a common bus.  
         [0049]    The positive electrode busbar  26 P is connected with the battery  1  shown in FIG. 1, which is a direct current power supply source, and with the positive electrodes of the electrolytic capacitor  2 . The negative electrode busbar  26 N is connected with the battery  1  and the negative electrodes of the electrolytic capacitor  2 .  
         [0050]    Referring to FIG. 3, an upper end of the output busbar  28 UA is connected to the phase U of the coil A of the alternating current motor  4 . An upper end of the output busbar  28 VA is connected to the phase V of the coil A of the alternating current motor  4 . An upper end of the output busbar  28 WA is connected to the phase W of the coil A of the alternating current motor  4 . The output bus bars  28 UA,  28 VA,  28 WA therefore correspond to three-phase alternating current output terminals of the switching circuit  3 A.  
         [0051]    Likewise, a lower end of the output busbar  28 UB is connected to the phase U of the coil B of the alternating current motor  4 . An lower end of the output busbar  28 VB is connected to the phase V of the coil B of the alternating current motor  4 . An lower end of the output busbar  28 WB is connected to the phase W of the coil B of the alternating current motor  4 . The output bus bars  28 UB,  28 VB,  28 WB therefore correspond to three-phase alternating current output terminals of the switching circuit  3 B.  
         [0052]    Thus, the inverter  3  can be made compact by storing all of the switching elements on one substrate  25 .  
         [0053]    Moreover, as the positive electrode busbar  26 P and negative electrode busbar  26 N are arranged in parallel, and the output busbar  28 UA,  28 VA,  28 WA, and output busbar  28 UB,  28 VB,  28 WB are respectively arranged parallel, the magnetic fields produced around the bus bars by the currents are mutually negated.  
         [0054]    The interaction of this field will be described with reference to FIGS.  4 - 9 .  
         [0055]    [0055]FIG. 4 shows the current flow in the switching period 0-60 degrees shown in the table of FIG. 2.  
         [0056]    In the switching period 0-60 degrees, a current flow is set up toward the phase V from the phase W and the phase U, and in the power module  21 , current is output from the output bus bars  28 UA,  28 UB,  28 WA,  28 WB and input into the output bus bars  28 VA,  28 VB. Consequently, the direction of the current is reversed in part of the output busbar  28 UA and part of the adjoining output busbar  28 UB, and in this part, the fields due to the current are mutually canceled out. The same is true of a part of the output busbar  28 VA and a part of the adjoining output busbar  28 VB. The same is true of a part of the output busbar  28 WA and a part of the adjoining output busbar  28 WB.  
         [0057]    Further, there is no section where current flows in the same direction between adjoining output bus bars. Therefore, the currents which flow in the output bus bars do not form a strong field.  
         [0058]    In part of the positive electrode busbar  26 P and part of the negative electrode busbar  26 N, currents are formed in opposite directions as shown by hatching in the figure. In this part, the fields formed by the current are mutually canceled out. In other parts also, there is no section where current flows in the same direction. Therefore, the currents which flow through the positive electrode busbar  26 P and negative electrode busbar  26 N do not form a strong field.  
         [0059]    Likewise, FIGS.  5 - 9  show the current flow through the power module  21  at 60-90 degrees, 90-120 degrees, 120-180 degrees, 180-240 degrees, 240-300 degrees, and 300-360 degrees of the switching period. As is clear from these figures, in every switching period, currents flow in opposite directions in all adjoining output bus bars, and there is no section in which current flows in the same direction. Moreover, currents always flow in opposite directions in part of the positive electrode busbar  26 P and negative electrode busbar  26 N, and here too there is no section in which currents flow in the same direction.  
         [0060]    As described above, according to the inverter  3  using this power module  21 , as the current in the power module  21  does not form a strong field, undesirable effects of the field on surrounding electronic parts are prevented.  
         [0061]    Next, a second embodiment of this invention will be described referring to FIGS.  10 - 12 .  
         [0062]    This embodiment relates to the fixing of the inverter  3  using the power module  21  shown in FIGS.  1 - 3  to the alternating current motor  4 .  
         [0063]    The circuit configuration of the inverter  3 , power module  21  and alternating current motor  4  are the same as those of the first embodiment. The power module  21  is disposed at the bottom of a case  31  of the inverter  3 . Horizontally extending parts  29 UA,  29 VA,  29 WA are joined to the output bus bars  28 UA,  28 VA,  28 WA of the power module  21 , respectively. Likewise, horizontally extending parts  29 UB,  29 VB,  29 WB are joined to the output bus bars  28 UB,  28 VB,  28 WB of the power module  21 , respectively. The length of the power module  21  including the extended parts  29 UA,  29 VA,  29 WA and the extended parts  29 UB,  29 VB,  29 WB is set longer than the length of a case  41  of the alternating current motor  4  in the same direction. Also, the dimensions of the case  31  in the direction of an axis of rotation  43  is set to a length which can accommodate the extended parts  29 UA,  29 VA,  29 WA, and the extended parts  29 UB,  29 VB,  29 WB.  
         [0064]    Referring to FIG. 10, external terminals  42 UA, 42 VA, 42 WA connected to the phase U, phase V, and phase W of the stator coil A of FIG. 1 are attached to a front face  41 A of the case  41  of the alternating current motor  4  so that they project above the case  41 .  
         [0065]    Referring to FIG. 12, external terminals  42 UB,  42 VB,  42 WB connected to the phase U, phase V and phase W of the stator coil B are attached to the rear face  41 B of the case  41  of the alternating current motor  4  so that they project above the case  41 .  
         [0066]    Holes through which these external terminals  42 UA,  42 VA,  42 WA, and the external terminals  42 UB,  42 VB,  42 WB penetrate are formed beforehand in the base of the case  31  of the inverter  3 . By fitting the case  31  at a predetermined position on the case  41 , the external terminals  42 UA,  42 VA,  42 WA, and the external terminals  42 UB,  42 VB,  42 WB respectively penetrate the case  31  and are joined to the ends of the extended parts  29 UA,  29 VA,  29 WA, and the extended parts  29 UB,  29 VB,  29 WB, respectively. Various methods may be used to effect the join of the external terminals to the extended parts, such as pressure clamping, welding, screwing and clamping.  
         [0067]    The external wiring connected to the alternating current motor and power module  21  generates fields which do not cancel each other out mutually. By providing the extending parts  29 UA,  29 VA,  29 WA and the extending parts  29 UB,  29 VB,  29 WB which match the external terminals  42 UA,  42 VA,  42 WA and the external terminals  42 UB,  42 VB,  42 WB in the power module  21 , as in this embodiment, the length of external wiring which connects the alternating current motor  4  to the power module  21  can be shortened. Shortening of external wiring has a desirable effect in suppressing generation of magnetic fields. Moreover, since the alternating current motor  4  and inverter  3  form one piece by the above arrangement of the power module  21 , space required for installation of the inverter  3  and the alternating current motor  4  can also be saved.  
         [0068]    The contents of Tokugan Hei 11-178899, with a filing date of Jun. 24, 1999 in Japan, are hereby incorporated by reference.  
         [0069]    Although the invention has been described above by reference to certain embodiments of the invention, the invention is not limited to the embodiments described above. Modifications and variations of the embodiments described above will occur to those skilled in the art, in light of the above teachings.  
         [0070]    The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows: