Inverter-integrated driving module and manufacturing method therefor

Phase coils are each configured by winding a conductor wire in a concentrated winding consecutively on three circumferentially consecutive tooth portions, six inverter units of an inverter module are each disposed in close proximity to a motor so as to face each of the phase coils axially, and the motor and the inverter module are electrically connected by connecting an alternating-current output terminals of each of the plurality of inverter units to output wires of the phase coils that face the inverter units axially.

TECHNICAL FIELD

The present invention relates to a driving module in which an inverter is internally mounted and to a manufacturing method therefor.

BACKGROUND ART

In conventional power module-integrated motors, a power module is inserted into and fixed to a power module mount portion that is formed by cutting away a stator axially such that power terminals and controlling terminals project externally, the power terminals are connected to a motor winding, the controlling terminals are connected to an external controlling circuit, and a rotor core is configured so as to rotate by means of switching of the power module by sending signals from the external controlling circuit (see Patent Literature 1, for example).

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

However, in conventional power module-integrated motors, because respective output wires of the motor winding are led around an end surface of the stator to be connected to the power terminals of the power module that is inserted into and fixed to the power module mount portion that is formed by cutting away the radially outer side of the stator axially, one disadvantage has been that wiring length between the power module and the motor is increased, increasing copper loss due to the wiring in question.

In conventional power module-integrated motors, the motor winding includes twelve phase coils that are wound into concentrated windings on each of the tooth portions, and although the arrangement of the twelve phase coils is not described at all, the twelve phase coils are generally arranged so as to line up in order of a U phase, a V phase, a W phase, a U phase, a V phase, etc., through a V phase, and a W phase.

Now, if the motor winding is constituted by two three-phase alternating current windings, then the U-phase coils that constitute each of the three-phase alternating-current windings are configured by connecting two U-phase phase coils in series, the V-phase coils are configured by connecting two V-phase phase coils in series, and the W-phase coils are configured by connecting the two W-phase phase coils in series. Thus, because the number of connections between the phase coils is extremely large, another disadvantage has been that complicated connecting work is increased, giving rise to cost increases.

The present invention aims to solve the above problems and an object of the present invention is to provide an inverter-integrated driving module and a manufacturing method therefor that can reduce copper loss by configuring phase coils by winding a conductor wire into concentrated windings consecutively on a plurality of circumferentially consecutive tooth portions, and by disposing inverter units so as to face the phase coils axially in close proximity, to reduce the number of connections between the phase coils and also to shorten wiring length between an inverter module and a motor.

Means for Solving the Problem

In order to achieve the above object, according to one aspect of the present invention, there is provided an inverter-integrated driving module including: a motor including: a stator in which a stator coil that is constituted by M phase coils (where M is an integer that is greater than or equal to 3) is mounted into an annular stator core; and a rotor that has magnetic poles in which North-seeking (N) poles and South-seeking (S) poles are arranged so as to alternate circumferentially; and an inverter module that includes a plurality of inverter units each including: a positive electrode-side input terminal; a negative electrode-side input terminal; an upper arm switching element of which a positive-electrode side is connected to the positive electrode-side input terminal; a lower arm switching element of which a negative-electrode side is connected to the negative electrode-side input terminal; and an alternating-current output terminal that is connected to a negative-electrode side of the upper arm switching element and a positive-electrode side of the lower arm switching element. Each of the M phase coils is configured into a concentrated winding coil in which a conductor wire is wound into a concentrated winding consecutively on L circumferentially consecutive tooth portions (where L is an integer that is greater than or equal to 2), each of the plurality of inverter units of the inverter module is disposed in close proximity to the motor so as to face each of the M phase coils axially, and the motor and the inverter module are electrically connected by connecting the alternating-current output terminals of each of the plurality of inverter units to output wires of the phase coils that face the inverter units axially.

Effects of the Invention

According to the present invention, because each of the M phase coils is configured into a concentrated winding coil in which a conductor wire is wound into a concentrated winding consecutively on L circumferentially consecutive tooth portions (where L is an integer that is greater than or equal to 2), the number of connections between the phase coils is reduced, reducing complicated connecting work between the phase coils, and enabling costs to be reduced.

Because the inverter module is disposed in close proximity to the motor such that each of a plurality of inverter units faces each of the M phase coils axially, lengths of wiring between the inverter module and the motor are shortened, enabling copper loss to be reduced.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of an inverter-integrated driving module according to the present invention will now be explained using the drawings.

FIG. 1is an exploded perspective that shows an inverter-integrated driving module according to Embodiment 1 of the present invention,FIG. 2is a schematic diagram that explains a configuration of a motor that is used in the inverter-integrated driving module according to Embodiment 1 of the present invention,FIG. 3is a schematic diagram that explains a configuration of a 2-in-1 inverter unit that is used in the inverter-integrated driving module according to Embodiment 1 of the present invention, andFIG. 4is a circuit diagram of the inverter-integrated driving module according to Embodiment 1 of the present invention.

InFIG. 1, an inverter-integrated driving module1includes: a positive electrode electric supply board2and a negative electrode electric supply board3that are connected to an external direct-current (DC) power supply to constitute a DC supply line; an inverter module4that converts the direct-current power that is supplied to the positive electrode electric supply board2and the negative electrode electric supply board3into alternating-current power; and a motor14that is driven to rotate by supplying thereto the alternating-current power that is converted by the inverter module4.

The positive electrode electric supply board2and the negative electrode electric supply board3are each manufactured into a circular ring-shaped flat plate, and are disposed parallelly and coaxially so as to have a predetermined clearance to constitute parallel plate electrodes.

The inverter module4is configured by mounting six 2-in-1 inverter units5concyclically at a uniform angular pitch on a first surface of a circuit board6. As shown inFIG. 3, the 2-in-1 inverter units5include an upper arm switching element7, a lower arm switching element8, a positive electrode input terminal10, a negative electrode input terminal11, and an alternating-current output terminal12. The upper arm switching element7and the lower arm switching element8are resin-sealed by an insulating resin, a first end of the positive electrode input terminal10is connected to a positive-electrode side of the upper arm switching element7and is extended outward from the resin-sealed portion, a first end of the negative electrode input terminal11is connected to a negative-electrode side of the lower arm switching element8and is extended outward from the resin-sealed portion, and a first end of the alternating-current output terminal12is connected to a negative-electrode side of the upper arm switching element7and a positive-electrode side of the lower arm switching element8and is extended outward from the resin-sealed portion. Semiconductor switching elements such as metal-oxide-semiconductor field-effect transistors (MOSFETs), or insulated gate bipolar transistors (IGBTs), for example, can be used for the upper arm switching elements7and the lower arm switching elements8. Moreover, although not shown, a heatsink is disposed on a second surface of the circuit board6so as to enable heat that is generated in the upper arm switching elements7and the lower arm switching elements8to be radiated effectively.

The motor14includes: a rotor16that is manufactured by pressing a magnetic material such as iron, for example, and has: a cylindrical rotor yoke portion17; and a bottom surface portion18that extends inward from a first axial end of the rotor yoke portion17, the bottom surface portion18being fixed to a shaft15at a central axial position of the rotor yoke portion17; permanent magnets19that are fixed to an inner circumferential surface of the rotor yoke portion17; and a stator20that has: a cylindrical stator core21that has: a stator yoke portion22that is manufactured into a cylindrical shape; and tooth portions23that are each disposed so as to project radially outward from an outer circumferential surface of the stator yoke portion22, and that are arranged at a uniform angular pitch circumferentially; and a stator coil24that is wound onto the tooth portions23.

The rotor16is manufactured by press-molding a magnetic material such as iron, for example, but it is not absolutely necessary for the bottom surface portion18to be a magnetic body. Specifically, it is sufficient that at least the rotor yoke portion17of the rotor16be manufactured using a magnetic material. A rotor16that is manufactured in this manner is configured so as to be rotatable by the shaft15being rotatably supported in a housing (not shown).

The permanent magnets19are sintered rare-earth magnets, for example. Sixteen permanent magnets19are arranged at a uniform angular pitch circumferentially such that North-seeking (N) poles and South-seeking (S) poles alternate, and are fixed to the inner circumferential surface of the rotor yoke portion17.

The stator core21is manufactured, for example, by laminating magnetic steel sheets such that eighteen tooth portions23are disposed so as to project from an outer circumferential surface of the stator yoke portion22. The stator coil24is constituted by six phase coils25. Each of the phase coils25is configured by winding a single conductor wire a predetermined number of times onto one tooth portion23, then winding it a predetermined number of times onto the next circumferentially adjacent tooth portion23, and then winding it a predetermined number of times onto the next circumferentially adjacent tooth portion23. In other words, each of the phase coils25is a concentrated winding coil that is configured by winding a single conductor wire consecutively onto three circumferentially adjacent tooth portions23. Thus, as shown inFIG. 2, the six phase coils25are wound onto the stator core21so as to line up circumferentially in order of a U1phase, a V1phase, a W1phase, a U2phase, a V2phase, and a W2phase. Moreover, inFIG. 2, U+(V+, W+) and U−(V−, W−) indicate that the winding direction of the conductor wire relative to the tooth portion23that constitutes the U phase (V phase or W phase) is a reverse direction.

As shown inFIG. 4, a first three-phase alternating-current winding24A that is constituted by star-connected coils is manufactured by connecting together (wye-connecting) winding finish end portions of three phase coils25, namely the U1phase, the V1phase, and the W1phase, and a second three-phase alternating-current winding24B that is constituted by star-connected coils is manufactured by connecting together (wye-connecting) winding finish end portions of three phase coils25, namely the U2phase, the V2phase, and the W2phase.

As shown inFIG. 2, the motor14is configured into an outer-rotor three-phase motor in which the number of poles is sixteen and the number of slots is eighteen by fixing to a housing (not shown) a stator20that is manufactured in this manner so as to be disposed on an inner circumferential side of the rotor16so as to be coaxial to the shaft15.

The inverter module4is manufactured so as to have an outside diameter that is approximately equal to the stator20, and is configured such that radial positions of the 2-in-1 inverter units5are approximately equal to radial positions of the phase coils25in the stator20. The inverter module4is fixed to the housing (not shown) so as to be disposed at a second axial end of the stator20in close proximity to the stator20so as to be coaxial to the shaft15such that the respective 2-in-1 inverter units5face each of the six phase coils25axially. In addition, the positive electrode electric supply board2and the negative electrode electric supply board3are disposed at a second axial end of the inverter module4in close proximity to the inverter module4so as to be coaxial to the shaft15.

As shown inFIG. 4, in an inverter-integrated driving module1that is configured in this manner, the positive electrode electric supply board2and the negative electrode electric supply board3are connected to the external electric power supply30by means of the wiring31, the positive electrode input terminals10of the six 2-in-1 inverter units5are connected to the positive electrode electric supply board2, and the negative electrode input terminals11are connected to the negative electrode electric supply board3. The respective alternating-current output terminals12of the six 2-in-1 inverter units5are connected to respective winding start end portions of the six phase coils25. In addition, a smoothing capacitor32is connected in parallel to an input side of the inverter module4to absorb ripple currents and stabilize input voltage. Moreover, it is preferable to configure the wiring31using stranded wire so as to lower inductance.

In an inverter-integrated driving module1that is configured in this manner, ON/OFF switching of the upper arm switching elements7and the lower arm switching elements8of the six inverter units5is controlled by a controlling apparatus33such that direct-current power that is supplied from the electric power supply30is converted into alternating-current power and is supplied to the stator coil25. A rotating magnetic field is thereby generated in the stator20. Torque is generated by interaction between this rotating magnetic field of the stator20and the magnetic fields from the permanent magnets19, driving the rotor16to rotate.

Because the electric power supply is direct current, this inverter-integrated driving module1can also be used in cases that use a plurality of motors, such as electric trains.

According to Embodiment 1, because the inverter module4is disposed in close proximity to the stator20so as to be coaxial to the shaft15such that the respective 2-in-1 inverter units5face each of the phase coils25axially, lengths of wiring that connects the 2-in-1 inverter units5and the stator coil24can be shortened. Thus, copper loss due to the wiring that connects the 2-in-1 inverter units5and the stator coil24can be reduced. In addition, since impedance of the wiring that connects the 2-in-1 inverter units5and the stator coil24is reduced, the capacity of the smoothing capacitor32can be reduced, enabling reductions in the size of the inverter-integrated driving module1to be achieved.

Because the 2-in-1 inverter units5are arranged concyclically at a uniform angular pitch, heat-generating parts are distributed circumferentially, reducing the density of generated heat. Thus, the 2-in-1 inverter units5can be cooled efficiently, enabling excessive temperature increases to be suppressed.

Because the first and second three-phase alternating-current windings24A and24B are configured by wye-connecting three phase coils25, cyclic currents do not flow through the phase coils25. Thus, copper loss due to cyclic currents is reduced, enabling increased efficiency.

Because the positive electrode electric supply board2and the negative electrode electric supply board3constitute parallel plate electrodes, the positive electrode electric supply board2and the negative electrode electric supply board3act as a smoothing capacitor, shown schematically inFIG. 4as the smoothing capacitor32. In addition, because the positive electrode electric supply board2and the negative electrode electric supply board3are disposed so as to be placed in close axial proximity to the inverter module4, reductions in inductance can be achieved. Thus, looking at the system as a whole, because inductance is reduced, the smoothing capacitor32can be reduced in size, enabling system-wide reductions in size to be achieved.

Because the inductance is low, semiconductor switching elements that have silicon carbide (SiC) elements that enable high-frequency driving can be used in the upper arm switching elements7and the lower arm switching elements8instead of semiconductor switching elements that have silicon (Si) elements. Because silicon carbide (SiC) elements have low inductance, surge voltages can be suppressed. In that case, because the capacity of the smoothing capacitor32can be reduced for high-frequency driving, the smoothing capacitor32can be reduced in size, enabling further system-wide reductions in size to be achieved.

Now, in a comparative example in which twelve phase coils are wound onto a stator core21by winding a single conductor wire into a concentrated winding on each of the tooth portion23in order of a U phase, a V phase, a W phase, a U phase, a V phase, etc., circumferentially, for example, a U-phase coil is manufactured by connecting a winding finish end portion of a phase coil that is wound onto a first tooth portion23and a winding start end portion of a phase coil that is wound onto a fourth tooth portion23, and by connecting a winding finish end portion of the phase coil that is wound onto the fourth tooth portion23and a winding start end portion of the phase coil that is wound onto a seventh tooth portion23, a V-phase coil is manufactured by connecting a winding finish end portion of a phase coil that is wound onto a second tooth portion23and a winding start end portion of a phase coil that is wound onto a fifth tooth portion23, and by connecting a winding finish end portion of the phase coil that is wound onto the fifth tooth portion23and a winding start end portion of the phase coil that is wound onto a eighth tooth portion23, and a W-phase coil is manufactured by connecting a winding finish end portion of a phase coil that is wound onto a third tooth portion23and a winding start end portion of a phase coil that is wound onto a sixth tooth portion23, and by connecting a winding finish end portion of the phase coil that is wound onto the sixth tooth portion23and a winding start end portion of the phase coil that is wound onto a ninth tooth portion23. A first three-phase alternating-current winding is manufactured by connecting winding finish end portions of the U-phase coil, the V-phase coil, and the W-phase coil that are manufactured in this manner. Thus, seven connection points are required in the comparative example to constitute a first three-phase alternating-current winding that is equivalent to that of Embodiment 1.

In Embodiment 1, on the other hand, because the U-phase coil, the V-phase coil, and the W-phase coil are configured by winding a single conductor wire consecutively onto three circumferentially adjacent tooth portions23, the first three-phase alternating-current winding24A can be manufactured simply by connecting the winding finish end portions of the U-phase coil, the V-phase coil, and the W-phase coil. Thus, there is only a single connection point when configuring the first three-phase alternating-current winding24A, enabling connection points to be reduced significantly. Because connection among the phase coils is a complicated operation in which the conductor wire is led onto an end surface of the stator core21, significant reductions in connection points enable complicated connecting operations to be reduced, enabling cost reductions to be achieved. Moreover, significant reductions in connection points can similarly be made with regard to the second three-phase alternating-current winding24B.

Moreover, in Embodiment 1 above, each of the phase coils is configured by winding a single conductor wire into a concentrated winding consecutively on three circumferentially adjacent tooth portions, but from the viewpoint of reducing the number of connections, each of the phase coils need only be configured by winding single conductor wire into concentrated windings consecutively on two or more circumferentially adjacent tooth portions.

In Embodiment 1 above, the stator coil is constituted by two three-phase alternating-current windings, but the stator coil may also be configured into a single three-phase alternating-current winding. In that case, U-phase, V-phase, and W-phase phase coils may also be configured by connecting in series identical-phase phase coils that are configured by winding a single conductor wire into a concentrated winding consecutively on three circumferentially adjacent tooth portions, or U-phase, V-phase, and W-phase phase coils may also be configured by winding a single conductor wire into concentrated windings consecutively on six circumferentially consecutive tooth portions. Then, the inverter module is configured such that three inverter units are disposed concyclically on the front surface of a board so as to face the U-phase, V-phase, and W-phase phase coils.

In Embodiment 1 above, a three-phase motor has been explained, but similar effects can also be achieved if the motor is a polyphase motor that has three or more phases, and particularly if it is a K-phase motor (where K is a prime number that is greater than or equal to 3).

FIG. 5is a circuit diagram of the inverter-integrated driving module according to Embodiment 2 of the present invention.

InFIG. 5, a stator coil26is constituted by a first three-phase alternating-current winding26A and a second three-phase alternating-current winding26B that are each delta-connected. Specifically, the first three-phase alternating-current winding26A is configured into a mesh-connected coil by connecting a winding finish end portion of a U1-phase phase coil25to a winding start end portion of a V1-phase phase coil25, connecting a winding finish end portion of the V1-phase phase coil25to a winding start end portion of a W1-phase phase coil25, and connecting a winding finish end portion of the W1-phase phase coil25to a U1-phase winding start end portion. Similarly, the second three-phase alternating-current winding26B is configured into a mesh-connected coil by connecting a winding finish end portion of a U2-phase phase coil25to a winding start end portion of a V2-phase phase coil25, connecting a winding finish end portion of the V2-phase phase coil25to a winding start end portion of a W2-phase phase coil25, and connecting a winding finish end portion of the W2-phase phase coil25to a U2-phase winding start end portion.

Moreover, Embodiment 2 is configured in a similar or identical manner to that of Embodiment 1 above except that a motor14A into which the stator coil26is mounted is used instead of the motor14.

In an inverter-integrated driving module1A that is configured in this manner, because the first and second three-phase alternating-current windings26A and26B that constitute the stator coil26are configured into mesh-connected coils, connection of a neutral point that is required in a wye connection is no longer required, enabling the connection points to be further reduced.

FIG. 6is a schematic diagram that explains a method for connecting a stator coil in an inverter-integrated driving module according to Embodiment 3 of the present invention. Moreover, a rotor is omitted fromFIG. 6in order to facilitate explanation.

InFIG. 6, a neutral-point lead wire27that is configured using winding finish portions of U1-phase, V1-phase, and W1-phase phase coils25that constitute a first three-phase alternating-current winding is led out at a first axial end of the stator20, in addition, a neutral-point lead wire27that is configured using winding finish portions of U2-phase, V2-phase, and W2-phase phase coils25that constitute a second three-phase alternating-current winding is led out at the first axial end of the stator core21, and is joined by solder, etc., to an annular linking body29that is made of an electrically-conductive material that is disposed at the first axial end of the stator20. Output wires28that are configured using winding start portions of the U1-phase, V1-phase, W1-phase, U2-phase, V2-phase, and W2-phase phase coils25are led out near a second axial end of the stator20, and are respectively joined by solder, etc., to alternating-current output terminals12of inverter units5.

Moreover, the rest of the configuration is configured in a similar or identical manner to that of Embodiment 1 above.

According to Embodiment 3, the neutral-point lead wires27of the phase coils25are connected at the first axial end of the stator20. Thus, because connecting wire portions between the output wires28of the phase coil25and the alternating-current output terminals12are distributed circumferentially at the second axial end of the stator20, wiring lengths of the output wires28can be shortened, enabling reductions in inductance. Capacity of the smoothing capacitor32can thereby be further reduced, enabling reductions in size. In addition, because connection and disconnection between the inverter module4and the motor14is facilitated, the inverter module4and the motor14can be replaced easily when a failure occurs.

FIG. 7is a schematic diagram that explains a configuration of an inverter-integrated driving module according to Embodiment 4 of the present invention,FIG. 8is a schematic diagram that explains a configuration of a motor that is used in the inverter-integrated driving module according to Embodiment 4 of the present invention,FIG. 9is a schematic diagram that explains arrangement of inverter units in inverter modules that are used in the inverter-integrated driving module according to Embodiment 4 of the present invention, andFIG. 10is a circuit diagram of the inverter-integrated driving module according to Embodiment 4 of the present invention.

InFIG. 7, an inverter-integrated driving module1B includes: a motor40; first and second inverter modules50A and50B that are disposed at two axial ends of the motor40; a first parallel plate electrode that is constituted by a first positive electrode electric supply board2aand negative electrode electric supply board3athat are connected to an external electric power supply30ato constitute a DC supply line; and a second parallel plate electrode that is constituted by a second positive electrode electric supply board2band negative electrode electric supply board3bthat are connected to an external electric power supply30bto constitute a DC supply line.

As shown inFIG. 8, the motor40includes: a rotor41that is manufactured by laminating magnetic steel sheets such as iron, for example, into a cylindrical shape, and that is fixed to a shaft15that is inserted through a central axial position thereof; permanent magnets19that are fixed to an outer circumferential surface of the rotor41; and a stator42that has: a cylindrical stator core43that has: a stator yoke portion44that is manufactured into a cylindrical shape; and tooth portions45that are each disposed so as to project radially inward from an inner circumferential surface of the stator yoke portion44, and that are arranged at a uniform angular pitch circumferentially; and a stator coil46that is wound onto the tooth portions45.

Ten permanent magnets19are arranged at a uniform angular pitch circumferentially such that North-seeking (N) poles and South-seeking (S) poles alternate, and are fixed to the outer circumferential surface of the rotor41.

The stator core43is manufactured, for example, by laminating magnetic steel sheets such that twelve tooth portions45are disposed so as to project from an outer circumferential surface of the stator yoke portion44. The stator coil46is constituted by six phase coils47. Each of the phase coils47is configured by winding a single conductor wire a predetermined number of times onto one tooth portion45, and then winding it a predetermined number of times in a reverse direction onto the next circumferentially adjacent tooth portion45. In other words, each of the phase coils47is a concentrated winding coil that is configured by winding a single conductor wire consecutively onto two circumferentially adjacent tooth portions45. Thus, as shown inFIG. 8, the six phase coils47are wound onto the stator core43so as to line up circumferentially in order of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase.

As shown inFIG. 10, a first three-phase alternating-current winding46A that is constituted by star-connected coils is manufactured by connecting together winding finish end portions of three phase coils47, namely the U1phase, the V1phase, and the W1phase, and a second three-phase alternating-current winding46B that is constituted by star-connected coils is manufactured by connecting together winding finish end portions of three phase coils47, namely the U2phase, the V2phase and the W2phase. Moreover, winding finish portions of the phase coils47form neutral-point lead wires, and winding start portions form output wires.

The motor40is configured into a 10-pole 12-slot inner-rotor three-phase motor by disposing the rotor41rotatably such that the shaft15is rotatably supported in a housing (not shown), and by fixing the stator42to the housing so as to be disposed so as to surround the rotor41and so as to be coaxial to the shaft15.

The first inverter module50A is configured by mounting three 2-in-1 inverter units5concyclically at a uniform angular pitch on a first surface of a circuit board6. The first inverter module50A is manufactured so as to have an outside diameter that is approximately equal to the stator42, and is configured such that radial positions of the 2-in-1 inverter units5are approximately equal to radial positions of the phase coils47in the stator42. The first inverter module50A is fixed to the housing (not shown) so as to be disposed at a second axial end of the stator42in close proximity to the stator42so as to be coaxial to the shaft15such that the respective 2-in-1 inverter units5face the respective U1-phase, V1-phase, and W1-phase phase coils47axially. In addition, the first positive electrode electric supply board2aand the first negative electrode electric supply board3aare disposed at a second axial end of the first inverter module50A in close proximity to the first inverter module50A so as to be coaxial to the shaft15.

The second inverter module50B is configured by mounting three 2-in-1 inverter units5concyclically at a uniform angular pitch on a first surface of a circuit board6. The second inverter module50B is manufactured so as to have an outside diameter that is approximately equal to the stator42, and is configured such that radial positions of the 2-in-1 inverter units5are approximately equal to radial positions of the phase coils47in the stator42. The second inverter module50B is fixed to the housing (not shown) so as to be disposed at a first axial end of the stator42in close proximity to the stator42so as to be coaxial to the shaft15such that the respective 2-in-1 inverter units5face the respective U2-phase, V2-phase, and W2-phase phase coils47axially. In addition, the second positive electrode electric supply board2band the second negative electrode electric supply board3bare disposed at a first axial end of the second inverter module50B in close proximity to the second inverter module50B so as to be coaxial to the shaft15.

As shown inFIG. 9, the 2-in-1 inverter units5in the first inverter module50A and in the second inverter module50B are arranged at a uniform angular pitch circumferentially so as to be offset by 60 degrees from each other.

As shown inFIG. 10, in an inverter-integrated driving module1B that is configured in this manner, the first positive electrode electric supply board2aand the first negative electrode electric supply board3aare connected to the external electric power supply30aby means of wiring31a,the positive electrode input terminals10of three 2-in-1 inverter units5are connected to the first positive electrode electric supply board2a, and the negative electrode input terminals11are connected to the first negative electrode electric supply board3a. The respective alternating-current output terminals12of the three 2-in-1 inverter units5are connected to respective winding start end portions of three phase coils47. In addition, a first smoothing capacitor32ais connected in parallel to an input side of the first inverter module50A.

In addition, the second positive electrode electric supply board2band the second negative electrode electric supply board3bare connected to the external electric power supply30bby means of wiring31b, the positive electrode input terminals10of three 2-in-1 inverter units5are connected to the second positive electrode electric supply board2b, and the negative electrode input terminals11are connected to the second negative electrode electric supply board3b. The respective alternating-current output terminals12of the three 2-in-1 inverter units5are connected to respective winding start end portions of three phase coils47. In addition, a second smoothing capacitor32bis connected in parallel to an input side of the second inverter module50B.

In an inverter-integrated driving module1B that is configured in this manner, ON/OFF switching of the upper arm switching elements7and the lower arm switching elements8of the six inverter units5that constitute the first and second inverter modules50A and50B is controlled by a controlling apparatus33such that direct-current power that is supplied from the electric power supplies30aand30bis converted into alternating-current power and is supplied to the stator coil46. A rotating magnetic field is thereby generated in the stator42. Torque is generated by interaction between this rotating magnetic field of the stator42and the magnetic fields from the permanent magnets19, driving the rotor41to rotate.

According to Embodiment 4, because the first and second inverter modules50A and50B are disposed in close proximity to the two axial ends of the motor40such that each of the 2-in-1 inverter units5face each of the phase coils47axially, and electric power is supplied to each of the two three-phase alternating current windings that constitute the stator coil46, lengths of wiring that connects the 2-in-1 inverter units5and the stator coil46can be shortened. Thus, copper loss due to the wiring that connects the 2-in-1 inverter units5and the stator coil46can be reduced.

Because three 2-in-1 inverter units5are arranged concyclically at a uniform angular pitch in each of the first and second inverter modules50A and50B, heat-generating parts are further distributed circumferentially compared to Embodiment 1 above, reducing the density of generated heat even further. Thus, the heat that is generated in the 2-in-1 inverter units5is radiated efficiently, suppressing excessive temperature increases.

Because the first parallel plate electrode, which is constituted by the first positive electrode electric supply board2aand the first negative electrode electric supply board3a, is disposed in close proximity to the first inverter module50A, and the second parallel plate electrode, which is constituted by the second positive electrode electric supply board2band the second negative electrode electric supply board3b, is disposed in close proximity to the second inverter module50B, lengths of wiring between the parallel plate electrodes and the first and second inverter modules50A and50B are shortened. Thus, inductance between first and second inverter modules50A and50B and the motor40is reduced, enabling electric current to be passed to the motor40without the phase of the electric current being delayed even when driven at high-frequencies.

Moreover, in Embodiment 4 above, electric power is supplied to each of the first and second inverter modules independently from two electric power supplies, but electric power may also be supplied to each of the first and second inverter modules by a single electric power supply.

In Embodiment 4 above, the two three-phase alternating current windings of the stator coil are each configured into a star-connected coil that is formed by wye-connecting (alternating-current connecting) three phase coils, but the two three-phase alternating current windings of the stator coil may also each be configured into a mesh-connected coil that is formed by delta-connecting (alternating-current connecting) three phase coils. In that case, because there is no neutral-point connection, connection and disconnection between the first and second inverter modules and the motor are facilitated. Thus, if the first and second inverter modules or the motor fails, the first and second inverter modules or the motor can be replaced easily.

In Embodiment 4 above, a 10-pole 12-slot inner-rotor three-phase motor is used, but the motor is not limited to a 10-pole 12-slot inner-rotor three-phase motor, provided that it is an inner-rotor three-phase motor in which the number of poles is 10N and the number of slots is 12N, or the number of poles is 14 N and the number of slots is 12N (where N is a positive integer).

Arrangement of inverter units in first and second inverter modules that are disposed at two axial ends of a 12N-slot (12±2)N-pole inner-rotor three-phase motors will now be explained.

Phase coils are configured by winding a conductor wire consecutively into a concentrated winding on two consecutive tooth portions. The phase coils are thereby arranged circumferentially such that sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase are repeated for a total of N times. A first three-phase alternating-current winding is constituted by 3N U1-phase, V1-phase, and W1-phase phase coils, and a second three-phase alternating-current winding is constituted by 3N U2-phase, V2-phase, and W2-phase phase coils.

Here, if the N phase coils of identical phase are connected in series, then the three 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of 120 degrees in a similar manner to Embodiment 4 above. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by 60 degrees from each other. In that case, the number of 2-in-1 inverter units is six, and the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is (N−1).

If the N phase coils in each of the phases are connected in parallel, then the 2-in-1 inverter units are disposed so as to face each of the phase coils axially, and electric power must be supplied to the identical-phase phase coils with identical timing. Thus, the 3N 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of (360/3N) degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by (60/N) degrees from each other. In that case, the number of 2-in-1 inverter units is 6N, and the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is zero.

Moreover, in a comparative example in which phase coils are configured by winding conductor wires into concentrated windings on single tooth portions, the phase coils are arranged circumferentially in sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase so as to be repeated for a total of 2N times. A first three-phase alternating-current winding is constituted by 6N U1-phase, V1-phase, and W1-phase phase coils, and a second three-phase alternating-current winding is constituted by 6N U2-phase, V2-phase, and W2-phase phase coils.

In this comparative example, if the 2N phase coils of identical phase are connected in series, then the three 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of 120 degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by 60 degrees from each other. In that case, the number of 2-in-1 inverter units is six, but the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is (2N−1). Thus, the present application can significantly reduce the number of connections between the phase coils compared to the comparative example.

In this comparative example, if the 2N phase coils of identical phase in each of the phases are connected in parallel, then the 2-in-1 inverter units of each of the first and second inverter modules are disposed so as to face each of the phase coils axially, and electric power must be supplied to the identical-phase phase coils with identical timing. Thus, the 6N 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of (360/6N) degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by (30/N) degrees from each other. In that case, the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is zero, but the number of 2-in-1 inverter units is 12N. Thus, the present application can significantly reduce the number of 2-in-1 inverter units compared to the comparative example.

Next, a winding configuration of a stator coil in a 12N-slot (12±2)N-pole inner-rotor three-phase motor will be explained.

Phase coils are configured by winding a conductor wire consecutively into a concentrated winding on two consecutive tooth portions. The phase coils are thereby arranged circumferentially such that sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase are repeated for a total of N times. Then, N three-phase alternating-current windings that are manufactured by connecting winding finish end portions of the U1-phase, V1-phase, and W1-phase phase coils, and N three-phase alternating-current windings that are manufactured by connecting winding finish end portions of the U2-phase, V2-phase, and W2-phase phase coils, are formed respectively. Thus, the stator coil is constituted by 2N three-phase alternating-current windings. The neutral points of the 2N three-phase alternating-current windings are not electrically connected to each other. In other words, the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically. In addition, 2-in-1 inverter units are connected to each of the winding start end portions of the 6N phase coils.

Here, the 2N three-phase alternating-current windings that constitute the stator coil are each manufactured by wye-connecting phase coils in units of a/c poles and b/c slots, where a is the number of poles, b is the number of slots, and c the greatest common divisor of a and b. In other words, because this is a (12±2)N-pole 12N-slot three-phase motor, the respective three-phase alternating-current windings are manufactured by wye-connecting phase coils in units of (6±1) poles and six slots.

If the neutral points of the respective three-phase alternating-current windings are connected to each other electrically, there is a risk that cyclic currents may arise between identical phases due to irregularities in the resistance of the phase coils, irregularities in characteristics of the inverter elements, etc. In the present configuration, because the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically, such cyclic currents do not arise.

If the neutral points of the respective three-phase alternating-current windings are connected to each other electrically, the motor cannot operate if a situation arises in which electric current cannot be passed through the phase coils of one of the three-phase alternating-current windings due to a ground fault, a bridging fault, etc. In the present configuration, because the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically, problems in the phase coils of one of the three-phase alternating-current windings do not affect the phase coils of the other three-phase alternating-current windings, enabling operation of the motor.

In the present configuration, because the magnetic flux is closed in six-slot units, the stator can be assembled by linking 2N (=12N/6) segmented stators that are manufactured in six-slot units, facilitating preparation of the motor. The stator can be manufactured by the following three methods, for example.

In a first manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which an annular stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each two consecutive tooth portions of the segmented stator cores. Next, an annular stator core is manufactured by linking the segmented stator cores of the 2N segmented stators. The stator is then manufactured by connecting the neutral points of the phase coils using an annular connecting board.

In a second manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which a rectangular parallelepiped stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each two consecutive tooth portions of the segmented stator cores. Next, a rectangular parallelepiped stator core is manufactured by linking the segmented stator cores of the 2N segmented stators. Next, an annular stator core is manufactured by bending the rectangular parallelepiped stator core into an annular shape, and abutting and welding tip end portions. The stator is then manufactured by connecting the neutral points of the phase coils using an annular connecting board. Moreover, a “rectangular parallelepiped stator core” is an annular stator core that is cut and opened up and is spread into a single plane from a position at which a plane that includes a central axis intersects it.

In a third manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which an annular stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each two consecutive tooth portions of the segmented stator cores. Next, the neutral points of the phase coils of the segmented stators are connected using circular arc-shaped segmented connecting boards that are manufactured so as to correspond to six slots. An annular stator is then manufactured by linking the segmented stator cores of the 2N segmented stators in which the neutral points of the phase coils are connected.

In the present configuration, because the magnetic circuit is closed in six-slot units, as explained in the third manufacturing method, the phase coils that are wound into the segmented stator cores can be connected using 2N (=12N/6) circular arc-shaped segmented connecting boards that are manufactured so as to correspond to six slots. Because of this, the materials yield of the circuit boards is improved compared to when a single annular connecting board is used.

Moreover, in the first and second manufacturing methods, the phase coils are connected using an annular connecting board after the annular stator core is manufactured, but the phase coils may also be connected using segmented connecting boards instead of an annular connecting board.

Next, the third manufacturing method will be explained in detail usingFIG. 11.FIG. 11is a perspective that explains a method for manufacturing a stator of a 24-slot 20-pole three-phase motor that is used in an inverter-integrated driving module according to the present invention.

As shown inFIG. 11(a), segmented stator cores72are first manufactured by laminating a predetermined number of core segments that are punched from magnetic steel sheets. These segmented stator cores72are manufactured into circular arc-shaped shapes in which an annular stator core71that has twenty-four tooth portions73is divided into four equal sections circumferentially. Next, phase coils47are mounted onto the respective tooth portions73of the segmented stator cores72. The phase coils47are concentrated winding coils that are configured such that a first wound portion47ais manufactured by winding a single conductor wire a predetermined number of times in a first direction and a second wound portion47bis manufactured by subsequently winding the single conductor wire a predetermined number of times in a second direction. The first wound portion47aand the second wound portion47bare mounted onto respective adjacent tooth portions73. Moreover, winding start end portions of the phase coils47project from the first wound portions47ato constitute output wires48, and winding finish end portions project from the second wound portions47bto constitute neutral-point lead wires49.

Next, tip ends of the tooth portions73are plastically deformed so as to project on first and second circumferential sides by pressing the tip ends of each of the tooth portions73from radially inside to manufacture the segmented stators70A, as shown inFIG. 11(b). Flange portions74thereby extend from the tip ends of the tooth portions73on the first and second circumferential sides, preventing dislodging of the first wound portions47aand the second wound portions47bof the phase coils47from the tooth portions73. The segmented stators70A include the circular arc-shaped segmented stator cores72, and the U-phase, V-phase, and W-phase phase coils47that are mounted onto each two adjacent tooth portions73.

Next, as shown inFIG. 11(b), the neutral-point lead wires49of the U-phase, V-phase, and W-phase phase coils47are connected using segmented connecting boards75to form a single three-phase alternating-current winding. The segmented connecting boards75have a circular arc-shaped shape in which an annular connecting board is divided into four equal sections circumferentially, and are configured by forming three penetrating apertures76that correspond to the neutral-point lead wires49, and wiring77that connects the penetrating apertures76electrically, on an insulating circuit board. The neutral-point lead wires49of the U-phase, V-phase, and W-phase phase coils47are inserted into the penetrating apertures76, and are soldered to the wiring77. The three phase coils47that are wound into the segmented stator core72are thereby wye-connected to configure a three-phase alternating-current winding.

Next, four segmented stator cores72are linked and integrated by placing end surfaces of the segmented stator cores72in contact with each other and joining them by welding, etc., to manufacture an annular stator core71. As shown inFIG. 11(c), a stator70is thereby manufactured in which three-phase alternating-current windings are mounted onto each of the segmented stator cores72.

In this case, the respective three-phase alternating-current windings are configured into star-connected coils in which the phase coils are wye-connected, but the respective three-phase alternating-current windings may also be configured into mesh-connected coils in which the phase coils are delta-connected. In that case, operation of the motor is enabled even if one three-phase alternating-current winding fails due to a ground fault or a bridging fault, etc.

If there is a difference in resistance between the coils that are wound onto each of the teeth, or if the timing of passage of electric current to each of the inverters is off, then cyclic currents arise between coils of identical phase when the coils of identical phase are connected in parallel, increasing copper loss, but if the neutral points are separated from each other electrically, such phenomena do not occur.

The neutral points of the respective three-phase alternating-current windings are separated from each other electrically, but the neutral points of the respective three-phase alternating-current windings may also be connected electrically. In that case, because the magnetic flux is closed in six-slot units, preparation of the motor is facilitated.

A 12N-slot (12±2)N-pole inner-rotor three-phase motor has been explained, but the present configuration can also be applied to a 12N-slot (12±2)N-pole outer-rotor three-phase motor.

In addition, in a motor in which a bearing is between the rotor and the inverter module, there is a bearing holding member. Generally, axial length of the motor is lengthened when there are segmented connecting boards, but increases in axial length can be suppressed without dividing the bearing holding member by embedding a portion or all of the segmented connecting boards in the bearing holding member.

FIG. 12is a schematic diagram that explains a configuration of a motor that is used in the inverter-integrated driving module according to Embodiment 5 of the present invention.

InFIG. 12, a motor60includes: a rotor61that is manufactured by laminating magnetic steel sheets such as iron, for example, into a cylindrical shape, and that is fixed to a shaft15that is inserted through a central axial position thereof; permanent magnets19that are fixed to an outer circumferential surface of the rotor61; and a stator62that has: a cylindrical stator core63that has: a stator yoke portion64that is manufactured into a cylindrical shape; and tooth portions65that are each disposed so as to project radially inward from an inner circumferential surface of the stator yoke portion64, and that are arranged at a uniform angular pitch circumferentially; and a stator coil66that is wound onto the tooth portions65.

Sixteen permanent magnets19are arranged at a uniform angular pitch circumferentially such that North-seeking (N) poles and South-seeking (S) poles alternate, and are fixed to the outer circumferential surface of the rotor61.

The stator core63is manufactured, for example, by laminating magnetic steel sheets such that eighteen tooth portions65are disposed so as to project from an outer circumferential surface of the stator yoke portion64. The stator coil66is constituted by six phase coils67. Each of the phase coils67is configured by winding a single conductor wire a predetermined number of times onto one tooth portion65, then winding it a predetermined number of times in a reverse direction onto the next circumferentially adjacent tooth portion65, and then winding it a predetermined number of times in a reverse direction onto the next circumferentially adjacent tooth portion65. In other words, each of the phase coils67is a concentrated winding coil that is configured by winding a single conductor wire consecutively onto three circumferentially adjacent tooth portions65. Thus, the six phase coils67are wound onto the stator core63so as to line up circumferentially in order of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase.

Although not shown, a first three-phase alternating-current winding that is constituted by star-connected coils is manufactured by connecting together winding finish end portions of three phase coils67, namely the U1phase, the V1phase, and the W1phase, and a second three-phase alternating-current winding that is constituted by star-connected coils is manufactured by connecting together winding finish end portions of three phase coils67, namely the U2phase, the V2phase and the W2phase.

The motor60is configured into a 16-pole 18-slot inner-rotor three-phase motor by disposing the rotor61rotatably such that the shaft15is rotatably supported in a housing (not shown), and by fixing the stator62to the housing so as to be disposed so as to surround the rotor61and so as to be coaxial to the shaft15.

An inverter-integrated driving module according to Embodiment 5 is configured in a similar or identical manner to that of Embodiment 4 above except that the motor60is used instead of the motor40.

Thus, the first positive electrode electric supply board2aand the first negative electrode electric supply board3aare connected to the external electric power supply30aby means of wiring31a, the positive electrode input terminals10of three 2-in-1 inverter units5are connected to the first positive electrode electric supply board2a, and the negative electrode input terminals11are connected to the first negative electrode electric supply board3a. The respective alternating-current output terminals12of the three 2-in-1 inverter units5are connected to respective winding start end portions of three phase coils67. In addition, a first smoothing capacitor32ais connected in parallel to an input side of the first inverter module50A.

In addition, the second positive electrode electric supply board2band the second negative electrode electric supply board3bare connected to the external electric power supply30bby means of wiring31b, the positive electrode input terminals10of three 2-in-1 inverter units5are connected to the second positive electrode electric supply board2b, and the negative electrode input terminals11are connected to the second negative electrode electric supply board3b. The respective alternating-current output terminals12of the three 2-in-1 inverter units5are connected to respective winding start end portions of three phase coils67. In addition, a second smoothing capacitor32bis connected in parallel to an input side of the second inverter module50B.

Consequently, similar or identical effects to those in Embodiment 4 above are also exhibited in Embodiment 5.

Moreover, in Embodiment 5 above, electric power is supplied to each of the first and second inverter modules independently from two electric power supplies, but electric power may also be supplied to each of the first and second inverter modules by a single electric power supply.

In Embodiment 5 above, the two three-phase alternating current windings of the stator coil are each configured into a star-connected coil that is formed by wye-connecting (alternating-current connecting) three phase coils, but the two three-phase alternating current windings of the stator coil may also each be configured into a mesh-connected coil that is formed by delta-connecting (alternating-current connecting) three phase coils. In that case, because there is no neutral-point connection, connection and disconnection between the first and second inverter modules and the motor are facilitated. Thus, if the first and second inverter modules or the motor fails, the first and second inverter modules or the motor can be replaced easily.

In Embodiment 5 above, a 16-pole 18-slot inner-rotor three-phase motor is used, but the motor is not limited to a 16-pole 18-slot inner-rotor three-phase motor, provided that it is an inner-rotor three-phase motor in which the number of poles is 16N and the number of slots is 18N, or the number of poles is 20N and the number of slots is 18N (where N is a positive integer).

Arrangement of inverter units in first and second inverter modules that are disposed at two axial ends of an 18N-slot (18±2)N-pole inner-rotor three-phase motors will now be explained.

Phase coils are configured by winding a conductor wire consecutively into a concentrated winding on three consecutive tooth portions. The phase coils are arranged circumferentially such that sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase are repeated for a total of N times. A first three-phase alternating-current winding is constituted by 3N U1-phase, V1-phase, and W1-phase phase coils, and a second three-phase alternating-current winding is constituted by 3N U2-phase, V2-phase, and W2-phase phase coils.

Here, if the N phase coils of identical phase are connected in series, then the three 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of 120 degrees in a similar manner to Embodiment 5 above. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by 60 degrees from each other. In that case, the number of 2-in-1 inverter units is six, and the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is (N−1).

If the N phase coils in each of the phases are connected in parallel, then the 2-in-1 inverter units are disposed so as to face each of the phase coils axially, and electric power must be supplied to the identical-phase phase coils with identical timing. Thus, the 3N 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of (360/3N) degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by (60/N) degrees from each other. In that case, the number of 2-in-1 inverter units is 6N, and the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is zero.

Moreover, in a comparative example in which phase coils are configured by winding conductor wires into concentrated windings on single tooth portions, the phase coils are arranged circumferentially in sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase so as to be repeated for a total of 3N times. A first three-phase alternating-current winding is constituted by 9N U1-phase, V1-phase, and W1-phase phase coils, and a second three-phase alternating-current winding is constituted by 9N U2-phase, V2-phase, and W2-phase phase coils.

In this comparative example, if the 3N phase coils of identical phase are connected in series, then the three 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of 120 degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by 60 degrees from each other. In that case, the number of 2-in-1 inverter units is six, but the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is (3N−1). Thus, the present application can significantly reduce the number of connections between the phase coils compared to the comparative example.

In this comparative example, if the 3N phase coils of identical phase in each of the phases are connected in parallel, then the 2-in-1 inverter units of each of the first and second inverter modules are disposed so as to face each of the phase coils axially, and electric power must be supplied to the identical-phase phase coils with identical timing. Thus, the 9N 2-in-1 inverter units of each of the first and second inverter modules are arranged circumferentially at a pitch of (360/9N) degrees. The 2-in-1 inverter units in the first inverter module and the second inverter module are offset by (20/N) degrees from each other. In that case, the number of connections between the phase coils of identical phase when forming the first and second three-phase alternating-current windings is zero, but the number of 2-in-1 inverter units is 18N. Thus, in the present application, the number of 2-in-1 inverter units can be reduced significantly compared to the comparative example.

Next, a winding configuration of a stator coil in an 18N-slot (18±2)N-pole inner-rotor three-phase motor will be explained.

Phase coils are configured by winding a conductor wire consecutively into a concentrated winding on three consecutive tooth portions. The phase coils are thereby arranged circumferentially such that sequences of a U1phase, a V2phase, a W1phase, a U2phase, a V1phase, and a W2phase are repeated for a total of N times. Then, N three-phase alternating-current windings that are manufactured by connecting winding finish end portions of the U1-phase, V1-phase, and W1-phase phase coils, and N three-phase alternating-current windings that are manufactured by connecting winding finish end portions of the U2-phase, V2-phase, and W2-phase phase coils, are formed respectively. Thus, the stator coil is constituted by 2N three-phase alternating-current windings. The neutral points of the 2N three-phase alternating-current windings are not electrically connected to each other. In other words, the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically. In addition, 2-in-1 inverter units are connected to each of the winding start end portions of the 6N phase coils.

Here, the 2N three-phase alternating-current windings that constitute the stator coil are each manufactured by wye-connecting phase coils in units of a/c poles and b/c slots, where a is the number of poles, b is the number of slots, and c the greatest common divisor of a and b. In other words, in this example, because this is a (18±2)N-pole 18N-slot three-phase motor, the respective three-phase alternating-current windings are manufactured by wye-connecting phase coils in units of (9±1) poles and nine slots.

If the neutral points of the three-phase alternating-current windings are connected to each other electrically, there is a risk that cyclic currents may arise between identical phases due to irregularities in the resistance of the phase coils, irregularities in characteristics of the inverter elements, etc. In the present configuration, because the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically, such cyclic currents do not arise.

If the neutral points of the three-phase alternating-current windings are connected to each other electrically, the motor cannot operate if a situation arises in which electric current cannot be passed through the phase coils of one of the three-phase alternating-current windings due to a ground fault, a bridging fault, etc. In the present configuration, because the neutral points of the 2N three-phase alternating-current windings are separated from each other electrically, problems in the phase coils of one of the three-phase alternating-current windings do not affect the phase coils of the other three-phase alternating-current windings, enabling operation of the motor.

In the present configuration, because the magnetic flux is closed in nine-slot units, the stator can be assembled by linking 2N (=18N/9) segmented stators that are manufactured in nine-slot units, facilitating preparation of the motor. The stator can be manufactured by the following three methods, for example.

In a first manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which an annular stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each three consecutive tooth portions of the segmented stator cores. Next, an annular stator core is manufactured by linking the segmented stator cores of the 2N segmented stators, and the stator is then manufactured by connecting the neutral points of the phase coils using an annular connecting board.

In a second manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which a rectangular parallelepiped stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each three consecutive tooth portions of the segmented stator cores. Next, a rectangular parallelepiped stator core is manufactured by linking the segmented stator cores of the 2N segmented stators. Next, an annular stator core is manufactured by bending the rectangular parallelepiped stator core into an annular shape, and abutting and welding tip end portions, and the stator is then manufactured by connecting the neutral points of the phase coils using an annular connecting board. Moreover, a “rectangular parallelepiped stator core” is an annular stator core that is cut and opened up and is spread into a single plane from a position at which a plane that includes a central axis intersects it.

In a third manufacturing method, a predetermined number of core segments that are punched from magnetic steel sheets, for example, are first laminated to manufacture segmented stator cores that have a shape in which an annular stator core is divided into 2N equal sections. Next, 2N segmented stators are manufactured by winding phase coils onto each three consecutive tooth portions of the segmented stator cores. Next, the neutral points of the phase coils of the segmented stators are connected using circular arc-shaped segmented connecting boards that are manufactured so as to correspond to nine slots. An annular stator is then manufactured by linking the segmented stator cores of the 2N segmented stators in which the neutral points of the phase coils are connected.

In the present configuration, because the magnetic circuit is closed in nine-slot units, as explained in the third manufacturing method, the phase coils that are wound into the segmented stator can be connected using 2N (=18N/9) circular arc-shaped segmented connecting boards that are manufactured so as to correspond to nine slots. Because of this, the materials yield of the circuit boards is improved compared to when a single annular connecting board is used.

Moreover, in the first and second manufacturing methods, the phase coils are connected using an annular connecting board after the annular stator core is manufactured, but the phase coils may also be connected using segmented connecting boards instead of an annular connecting board.

In this case, the respective three-phase alternating-current windings are configured into star-connected coils in which the phase coils are wye-connected, but the respective three-phase alternating-current windings may also be configured into mesh-connected coil in which the phase coils are delta-connected. In that case, operation of the motor is enabled even if one three-phase alternating-current winding fails due to a ground fault or a bridging fault, etc.

If there is a difference in resistance between the coils that are wound onto each of the teeth, or if the timing of passage of electric current to each of the inverters is off, then cyclic currents arise between coils of identical phase when the coils of identical phase are connected in parallel, increasing copper loss, but if the neutral points are separated from each other electrically, such phenomena do not occur.

The neutral points of the respective three-phase alternating-current windings are separated from each other electrically, but the neutral points of the respective three-phase alternating-current windings may also be connected electrically. In that case, because the magnetic flux is closed in nine-slot units, preparation of the motor is facilitated.

A 18N-slot (18±2)N-pole inner-rotor three-phase motor has been explained, but the present configuration can also be applied to a 18N-slot (18±2)N-pole outer-rotor three-phase motor.

In addition, in a motor in which a bearing is between the rotor and the inverter module, there is a bearing holding member. Generally, axial length of the motor is lengthened when there are segmented connecting boards, but increases in axial length can be suppressed without dividing the bearing holding member by embedding a portion or all of the segmented connecting boards in the bearing holding member.

Moreover, in each of the above embodiments, the inverter units are configured by connecting upper arm switching elements and lower arm switching elements in series, but a diode that supplies return current to the motor, which is an inductive load, may be additionally connected in parallel to each of the upper arm switching elements and lower arm switching elements.

In each of the above embodiments, the inverter unit is constituted by single upper arm switching elements and single lower arm switching elements, but an inverter unit may also be constituted by a plurality of upper arm switching elements that are connected to each other in parallel and a plurality of lower arm switching elements that are connected to each other in parallel.