Rotary electric machine

In the armature winding of a rotary electric machine, in a series coil portion group, the numbers of turns of conducting wire in the coil portions that have an electrical angular phase difference of θk that satisfies θ1<θkθm are different than the numbers of turns of conducting wire in the θ1 and θm coil portions, and are also different than the numbers of turns of conducting wire in the coil portions that are adjacent to the θk coil portions on two sides in a circumferential direction of the stator core, and phases of the θk coil portions are also different than phases of each of the coil portions that are adjacent to the θk coil portions on the two sides in the circumferential direction.

TECHNICAL FIELD

The present invention relates to a construction of a rotary electric machine, and relates to a rotary electric machine that is used in an automotive electric power steering apparatus, for example.

BACKGROUND ART

Conventionally, in electric motors in which a three-phase electric current is supplied from an inverter to an armature winding that includes coil portions in which conducting wires are wound so as to be housed in plurality of slots that are formed on a stator core so as to be concentrated on a plurality of teeth, electric motors are known in which space factor of the coil portions in the slots is improved by making the number of turns of the conducting wires in the coil portions on adjacent teeth different (see Patent Literature 1 and Patent Literature 2, for example).

In Patent Literature 1 above and Patent Literature 2 above, a rotary electric machine that is characterized in that the number of field poles in the rotor is 12n±2n and the number of slots is 12n, where n is a natural number, and an electric motor that is characterized in that the number of field poles in the rotor is 18n±2n and the number of slots is 18n, where n is a natural number, are disclosed, and these aim for vibration and noise reductions in the electric motors.

CITATION LIST

Patent Literature

SUMMARY OF THE INVENTION

Problem to be Solved by the Invention

However, as described in Patent Literature 1 above and Patent Literature 2 above, in an electric motor that is characterized in that the number of field poles in the rotor is 12n±2n and the number of slots is 12n, where n is a natural number, and an electric motor that is characterized in that the number of field poles in the electric motor is 18n±2n and the number of slots is 18n, where n is a natural number, the constructions are such that coil portions that have identical phase are adjacent in at least one position in a circumferential direction.

As a result thereof, coil portions that are adjacent to coil portions that have a large number of turns of conducting wire, i.e., overwound coil portions, have identical phase, and heat generation is concentrated locally.

In electric motors that are used in automotive electric power steering apparatuses, for example, battery voltage is low, at approximately 12 V generally, and since it is necessary to increase electric current in order to increase output, coil portions are formed that have a lower number of turns using conducting wire that has a larger diameter.

Here, one problem has been that localized heat generation is increased between coil portions that have identical phase where the coil portions that have identical phase are adjacent if the steering wheel position is kept in a constant position and the three-phase electric current is fixed without fluctuating during steering wheel operation under electric power steering, for example.

The present invention aims to solve the above problems and an object of the present invention is to provide a rotary electric machine that can suppress increases in localized heat generation if the number of turns or wire diameter of conducting wires of some coil portions are changed.

Means for Solving the Problem

A rotary electric machine according to the present invention includes:

a stator including:a stator core in which a plurality of slots are formed by a plurality of teeth that extend radially inward from an annular core back so as to leave a spacing in a circumferential direction; andan armature winding that includes a plurality of coil portions that are mounted to the teeth of the stator core; and

a rotor that is disposed inside the stator so as to have a magnetic air gap portion interposed, and that rotates around a rotating shaft,

the number of identical-phase coil portions among the coil portions in the armature winding is n, where n≥3, and in a series coil portion group that includes in of the coil portions that are serially connected, where m≤n), where a largest electrical angular phase difference between two of the coil portions is θm, an electrical angular phase difference of a first of the coil portions that have the largest electrical angle phase difference is θ1=0°, and respective electrical angular phase differences of remaining coil portions relative to the coil portion that has an electrical angular phase difference of θ1are θ2, θ3, etc., through θmin increasing order:the numbers of turns of conducting wire in the coil portions that have an electrical angular phase difference of θkthat satisfies θ1<θk<θm, where k=2, 3, etc., through m−1, are different than the numbers of turns of conducting wire in the coil portions that have electrical angular phase differences of θ1and θm, and are also different than the numbers of turns of conducting wire in the coil portions that are adjacent to the coil portions that have the electrical angular phase differences of θkon two sides in a circumferential direction of the stator core, and phases of the coil portions that have the electrical angular phase differences of θkare also different than phases of each of the coil portions that are adjacent to the coil portions that have the electrical angular phase differences of Ok on the two sides in the circumferential direction; orwire diameters of conducting wire in the coil portions that have the electrical angular phase difference of θkthat satisfies θ1<θ1<θk<θm, where k=2, 3, etc., through m−1, are different than wire diameters of conducting wire in the coil portions that have electrical angular phase differences of θ1and θm, and are also different than wire diameters of conducting wire in the coil portions that are adjacent to the coil portions that have the electrical angular phase differences of θkon two sides in a circumferential direction of the stator core, and phases of the coil portions that have the electrical angular phase differences of θkare also different than phases of each of the coil portions that are adjacent to the coil portions that have the electrical angular phase differences of θkon the two sides in the circumferential direction.

Effects OF THE Invention

According to the rotary electric machine according to the present invention, increases in localized heat generation in specific coil portions can be suppressed if the number of turns or wire diameter of conducting wires of some coil portions are changed.

DESCRIPTION OF EMBODIMENTS

Respective embodiments of the electric motor according to the present invention will now be explained with reference to the drawings, and identical or corresponding members and portions in each of the figures will be explained using identical numbering.

FIG. 1is a configuration diagram that shows an automobile electric power steering apparatus1to which an electric motor7according to Embodiment 1 of the present invention is mounted, andFIG. 2is a cross section that shows an electric driving apparatus13fromFIG. 1.

This electric power steering apparatus includes: an electric motor7that constitutes a rotary electric machine; and an electric driving apparatus13that is constituted by an electronic control unit (ECU)6that is integrated with the electric motor7.

Moreover, in the above electric driving apparatus13, the electric motor7and the ECU6are integrated so as to be disposed in an axial direction of the electric motor7, but are not limited thereto, and the ECU6may be disposed in a radial direction of the electric motor7, or the electric motor7and the ECU6may be separate.

In this electric power steering apparatus1, a driver steers a steering wheel (not shown), and torque therefrom is transmitted to a shaft2by means of a steering column (not shown). Here, torque that is detected by a torque sensor3is converted into electrical signals, which are transmitted through cables (not shown) to the ECU6by means of a first connector4.

At the same time, vehicle information such as vehicle speed is converted to electrical signals, which are transmitted to the ECU6through a second connector5. The ECU6computes the required assisting torque from the above torque and the vehicle information such as the vehicle speed, and supplies electric current through an inverter to the electric motor7that is arranged so as to be parallel to a housing10.

Electric power supply to the ECU6is fed by means of an electric power supply connector8from a battery or an alternator.

Torque that is generated by the electric motor7is made to generate thrust that moves the rack shaft (not shown) inside the housing10in the direction of the arrows X to assist the steering force of the driver by means of a gear box9into which belts (not shown) and ball screws (not shown) are mounted internally.

Tie rods11thereby move, enabling the tires to be steered and the vehicle turned.

As a result, the driver is assisted by the torque of the electric motor7, and can turn the vehicle using a reduced steering force.

Moreover, a rack boot12is disposed so as to prevent foreign matter from entering the apparatus.

The electric motor7includes: a stator22; a cylindrical frame24, the stator22being fixed to an inner wall surface of the cylindrical frame24; a housing23that is fixed by a plurality of bolts60so as to cover an opening portion at one end of the frame24; and a rotor29that is rotatably disposed inside the stator22.

The stator22has: a stator core20that is configured by laminating core sheets of a magnetic body such as electromagnetic steel sheets, etc.; and an armature winding38that is housed in this stator core20.

The rotor29has; a shaft27that constitutes a rotating shaft, two end portions thereof being supported by a first bearing25that is fitted into the housing23and a second bearing26that is fitted into a wall portion28; a rotor core30through which the shaft27passes; fourteen permanent magnets32that are embedded and glued inside this rotor core30at a uniform spacing circumferentially; a pulley61that is fixed to a first end portion of the shaft27; and a sensor permanent magnet31that is fixed to a second end portion of the shaft27so as to face a magnetic sensor14that constitutes a rotational angle sensor that is disposed on a circuit board19.

FIG. 3is a frontal cross section that shows the electric motor7fromFIG. 2.

The stator core20of the stator22has: an annular core back33; and eighteen teeth34that extend radially inward from the core back33, which is a magnetic air gap length direction, slots35being formed between adjacent teeth34.

The armature winding38of the stator22is constituted by a plurality of coil portions in which conducting wires21are respectively wound into concentrated windings on the eighteen teeth34so as to have insulators39interposed, and that are accommodated in the slots35.

The respective coil portions are mounted to each of the teeth34, to which the numbers 1, 2, 3, etc., through 18 are allotted counterclockwise, and are connected to U-phase, V-phase, and W-phase electric power supplies.

There are six coil portions that are included in the V phase, i.e., −V11, +V12, −V13, +V21, −V22, and +V23, six coil portions that are included in the W phase, i.e., −W11, +W12, −W13, +W21, −W22, and +W23, and six coil portions that are included in the U phase, i.e., −U11, +U12, −U13, +U21, −U22, and +U23, which are each connected externally.

As shown inFIG. 3, the respective coil portions correspond to the respective Numbers 1 through 18 of the teeth34, and are disposed so as to line up in order of −V11, −W22, +W23, +U21, +V12, −V13, −W11, −U22, +U23, +V21, +W12, −W13, −U11, −V22, +V23, +W21, +U12, and −U13. Moreover, “+” and “−” indicate winding polarities of the coil portions, “+” and “−” having opposite winding polarities.

FIG. 4is an explanatory diagram for connection of the armature winding38, the armature winding38being constituted by a first armature winding portion36and a second armature winding portion37.

In the first armature winding portion36, the respective coils portions −U11, +U12, and −U13are connected in series, the respective coil portions −V11, +V12, and −V13are connected in series, −W11, +W12, and −W13are connected in series, and connecting portions A1, B1, and C1of respective first identical-phase winding portions of these are connected to constitute a delta connection.

In the second armature winding portion37, the respective coil portions −U21, +U22, and −U23are connected in series, the respective coil portions −V21, +V22, and −V23are connected in series, −W21, +W22, and −W23are connected in series, and connecting portions A2, B2, and C2of respective second identical-phase winding portions of these are connected to constitute a delta connection.

Moreover, the armature winding38, in which the number of parallel arms in each phase is two, may be configured by wye-connecting the first armature winding portion36and the second armature winding portion37, as shown inFIG. 5.

Moreover, hereafter a plurality of coil portions that have identical phase that are connected in series will be called a “series coil portion group”.

Alternatively, as shown inFIG. 6, the armature winding38may be configured into a single set of three-phase delta connections by connecting A, B, and C, which are connecting portions at two end portions of the series coil portion groups of each phase, in which all of the respective coil portions that have identical phase are connected in series.

Alternatively, as shown inFIG. 7, the armature winding38may be configured into a single set of three-phase wye connections by connecting A, B, and C, which are connecting portions at two end portions of the series coil portion groups of each phase, in which all of the respective coil portions that have identical phase are connected in series.

InFIG. 3, cross sections of the conducting wires21that constitute the coil portions in each of the slots35are shown. In this figure, the number of conducting wires21that are adjacent to the first and second side walls that extend in a radial direction of each of the teeth34represents the number of turns of the conducting wires21in the each of the coil portions.

In this figure, if Numbers 2, 3, 5, 6, 8, 9, 11, 12, 14, 15, 17, and 18 of the teeth34are collectively called teeth A, and Numbers 1, 4, 7, 10, 13, and 16 of the teeth34are collectively called teeth B, then the number of turns and the wire diameter of the conducting wires21of the coil portions that are mounted to the teeth B are greater in number and larger than the number of turns and the wire diameter of the conducting wires21of the coil portions that are mounted to the teeth A.

Moreover, in this figure, hatching has been added to indicate the cross sections of the coil portions that are mounted to the teeth B.

Moreover, configuration of the rotor29and construction of the stator22may be different to those ofFIG. 3provided that the electric motor7has fourteen field poles in the rotor29, and the number of slots35and the number of teeth34in the stator22is eighteen.

FIG. 8is a frontal cross section cross section that shows a variation of the electric motor7according to Embodiment 1, and in this electric motor7, fourteen permanent magnets32are embedded in a rotor core30so as to have shapes in which a radial length of the fourteen permanent magnets32is longer than a circumferential length, and facing surfaces of adjacent permanent magnets32are magnetized so as to be mutually identical poles.

FIG. 9is a frontal cross section that shows another variation of the electric motor7according to Embodiment 1, and in this electric motor7, fourteen permanent magnets32are affixed around an outer circumference of the rotor core30at a uniform pitch in a circumferential direction.

Moreover, in this example, an outer side of the permanent magnets32may be covered by a cover in which a nonmagnetic material such as a stainless alloy or aluminum is made into a cylindrical shape to protect and prevent scattering of the permanent magnets32.

In addition,FIG. 10is a frontal cross section that shows yet another variation of the electric motor7according to Embodiment 1, and in this electric motor7, tip portions of each of the teeth34of the stator22are placed in contact at end surfaces in a circumferential direction.

In addition,FIG. 11is a frontal cross section that shows yet another variation of the electric motor7according to Embodiment 1, and in this electric motor7, as can be seen fromFIG. 12, which shows a portion of the stator core20that is ⅙ of a circumference, the stator core20is constituted by: open core blocks41that have openings at tip portions near the rotor29between pairs of adjacent teeth34; and linked core blocks40that are disposed on upper and lower portions of these open core blocks41, and in which tip portions near the rotor29between pairs of adjacent teeth34are linked to each other.

Moreover, the linked core blocks40include those in which two end surfaces at the tip portions near the rotor29between the adjacent teeth34are placed in contact with each other.

FIG. 13is a circuit diagram for the electric motor7and the ECU6.

Details are omitted in the electric motor7, and only the armature winding is shown.

Details of the ECU6are also omitted for simplicity, and only the power circuit portion of the inverter42is shown.

The ECU6is constituted by a circuit of a single inverter42, and three-phase electric current is supplied to the armature winding38from this inverter42.

In the armature winding38, the connecting portions A1and A2, the connecting portions B1and B2, and the connecting portions C1and C2are respectively connected by connecting portions A, B, and C at the connecting portions A1, B1, and C1of the wye-connected first armature winding portion36and the connecting portions A2, B2, and C2of the wye-connected second armature winding portion37that are shown inFIG. 5to configure a circuit in which two arms of each phase are connected in parallel.

Moreover, with regard to the armature winding38that is connected to the inverter42, the first armature winding portion36and the second armature winding portion37that are shown inFIG. 4, which are delta-connected, may alternatively be used.

The armature windings38that are shown inFIGS. 6 and 7, in which the coil portions are each connected in series, are also possible.

A direct-current power source is supplied to the ECU6from a power source43such as a battery, being connected to an electric power supply relay45so as to have a noise reduction coil44interposed.

Moreover, inFIG. 13, the power source43is depicted as if it were inside the ECU6, but in fact electric power is supplied from an external power source such as a battery through a connector.

One electric power supply relay45that is constituted by two MOSFETs is disposed, and operates such that the electric power supply relay45opens during failure, to prevent excessive electric current from flowing.

In this figure, connection is made sequentially in order of the power supply43, the coil44, and the electric power supply relay45, but it goes without saying that the electric power supply relay45may be disposed at a position that is closer to the power supply43than the coil44.

In this figure, this is constituted by a single capacitor46, but it goes without saying that it may be configured by connecting a plurality of capacitors in parallel.

The inverter42is constituted by a bridge that uses six MOSFETs, a first MOSFET47and a second MOSFET48being connected in series, a third MOSFET49and a fourth MOSFET50being connected in series, a fifth MOSFET51and a sixth MOSFET52being connected in series, and these three sets of MOSFETs being further connected in parallel. In addition, a first shunt53, a second shunt54, and a third shunt55that are used in the detection of electric current values are respectively connected to a ground (GND) side of each of the three lower MOSFETs, i.e., the second MOSFET48, the fourth MOSFET50, and the sixth MOSFET52. Moreover, an example is shown in which there are three shunts53,54, and55, but since electric current detection is possible even if there are two shunts or even if there is a single shunt, it goes without saying that such configurations are also possible.

Supply of electric current to the electric motor7, as shown inFIG. 13, is respectively supplied from between the first MOSFET47and the second MOSFET48through a busbar62to a first U-phase winding portion U1, which is a series coil portion group of the first armature winding portion36of the electric motor7, and a second U-phase winding portion U2, which is a series coil portion group of the second armature winding portion37, from between the third MOSFET49and the fourth MOSFET50through a busbar62to a first V-phase winding portion V1, which is a series coil portion group of the first armature winding portion36of the electric motor7, and a second V-phase winding portion V2, which is a series coil portion group of the second armature winding portion37, and from between the fifth MOSFET51and the sixth MOSFET52through a busbar62to a first W-phase winding portion W1, which is a series coil portion group of the first armature winding portion36of the electric motor7, and a second W-phase winding portion W2, which is a series coil portion group of the second armature winding portion37.

Electrically connected positions between the electric motor7and the ECU6are at three positions in total for three phases, but they are connected so as to be divided into the first armature winding portion36and the second armature winding portion37inside the electric motor7.

In the cases of the connections inFIGS. 6 and 7, in which all of the coil portions that have identical phase are connected in series, electric current is respectively supplied from between the first MOSFET47and the second MOSFET48through a busbar62to a U-phase winding portion U, which is a series coil portion group of the armature winding38of the electric motor7, from between the third MOSFET49and the fourth MOSFET50through a busbar62to a V-phase winding portion V, which is a series coil portion group of the armature winding38of the electric motor7, and from between the fifth MOSFET51and the sixth MOSFET52through a busbar62to a W-phase winding portion W, which is a series coil portion group of the armature winding38of the electric motor7.

Next, an electric motor that represents a first reference example will be explained based on the drawings as a comparative example for explaining the effects according to this embodiment.

FIG. 14is a frontal cross section that shows an electric motor of a first reference example, and the only differences from the electric motor according to Embodiment 1 that is shown inFIG. 3are that the number of turns and the wire diameters of the conducting wires21are different, and construction of the stator22, i.e., the armature winding38and the arrangement of the respective coil portions that constitute components thereof are similar or identical to those ofFIG. 3.

FIG. 15is a diagram that shows a manufacturing method for the stator core20of the electric motor that is shown inFIG. 14.

This stator core20is constituted by: an inner core57that includes teeth34but does not include a core back33, in which tip portions of adjacent teeth34are linked to each other; and an outer core56that includes the core back33but does not include the teeth34, and is manufactured by press-fitting the inner core57into the outer core56.

The teeth34of the inner core57before press-fitting are in a state in which there is no core back33, and the coil portions can be mounted from radially outside.

Thus, the stator22is produced by mounting the coil portions onto the inner core57to which insulators39have been mounted, and then press-fitting the outer core56.

In the case of this first reference example, the number of turns of the conducting wires21in the respective coil portions on all of the teeth34is equal.

InFIG. 14, broken lines are shown inside each of the slots35that divide the slots35symmetrically in half in the circumferential direction of the stator22, and the arrangement of the conducting wires21of the coil portions inside the slots35is symmetrical around the teeth34relative to the broken lines shown inside the slots35.

In configurations such as this first reference example, some problems inside each of the slots35have been that gaps increase toward a radially outer side of the stator core20, space factor that is occupied by the coil portions inside the slots35decreases, the ratio of plane cross-sectional area that is occupied by the coil portions relative to the plane cross-sectional area of the slots35is reduced, and resistance of the coil portions is increased, increasing the amount of heat generated.

FIG. 16is a frontal cross section of an electric motor that shows a second reference example.

This electric motor7has ten field poles in a rotor29, and the number of slots35and the number of teeth34in a stator22is twelve, the rotatable rotor29being disposed inside the stator22.

A shaft27that constitutes a rotating shaft is disposed in the rotor29, and a rotor core30outside the shaft27, and ten permanent magnets32are embedded inside the rotor core30at a uniform pitch in a circumferential direction.

The stator22has: a stator core20that is constituted by a magnetic body on which are formed: a core back33; twelve teeth34that are disposed at a uniform pitch, and that protrude outward from the core back33in a magnetic air gap length direction; and twelve slots35that are disposed between the teeth34; and a plurality of coil portions that are respectively mounted to the twelve teeth34of this stator core20in concentrated windings, and that are accommodated in the slots35.

The teeth34onto which the coil portions are mounted are numbered 1, 2, 3, etc., through 12 counterclockwise, the coil portions that are mounted onto the respective teeth34are connected to U-phase, V-phase, and W-phase electric power supplies, and are configured by being respectively connected externally so as to have four coil portions that are included in the V phase, i.e., +V11, −V12, −V21, and +V22, four coil portions that are included in the W phase, i.e., +W11, −W12, −W21, and +W22, and four coil portions that are included in the U phase, i.e., +U11, −U12, −U21, and +U22.

As shown inFIG. 16, the coil portions for each of the phases line up sequentially in order of −U21, +U22, +V11, −V12, −W21, +W22, +U11, −U12, −V21, +V22, +W11, and −W12so as to correspond to each of Numbers 1 through 12 of the teeth34.

Moreover, “+” and “−” indicate winding polarities of the coil portions, “+” and “−” having opposite winding polarities.

In this figure, the number of turns of the conducting wires21in the coil portions that are mounted to Numbers 2, 4, 6, 8, 10, and 12 of the teeth34is greater than the number of turns of the conducting wires21in the coil portions that are mounted to Numbers 1, 3, 5, 7, 9, and 11 of the teeth34, making them overwound coil portions. Cross sections of the overwound coil portions are represented by hatching in the slots35inFIG. 16.

In this figure, there are six positions where a coil portion that is adjacent to an overwound coil portion has identical phase. Thus, there are six slots35in which coil portions for each of the phases are housed. Since the space factor of the slots35in which the overwound coil portions that are mounted to Numbers 2, 4, 6, 8, 10, and 12 of the teeth34are housed improves, the amount of heat generated can be reduced compared to when the number of turns of the conducting wires21of the coil portions on all of the teeth34is equal.

However, since respective coil portions that have identical phase are disposed adjacently in all of the coil portions, heat generated due to the electric current is concentrated between the adjacent identical-phase coil portions, increasing localized heat generation.

Since the amount of localized heat generated in the slots35in which single-phase coil portions are disposed is increased if the steering wheel of the electric power steering is fixed and the three-phase electric current is fixed without fluctuating, one problem has been that this leads to torque reduction due to reductions in magnetic characteristics of the permanent magnets32and to deterioration in performance due to heating of the circuit board19, etc.

FIG. 17Ashows electrical angular phases of the serially connected coil portions +U21, −U22, and +U23in the U phase of the second armature winding portion37(seeFIGS. 4 and 5) according to Embodiment 1 as a vector diagram, vector length representing the strength of the magnetomotive force that the coil portions that are mounted to each of the teeth34generate, and vector angle representing the electrical angular phase of the coil portions that are mounted to each of the teeth34. Since magnetomotive force from the coil portions is proportional to the product of the number of turns and the magnitude of the electric current, vector length in the diagram is proportional to the number of turns.

Here, “electrical angular phase” is an angle when the angle that is formed by a single North-seeking (N) pole and a single South-seeking (S) pole that are adjacent to each other on the rotor29of the electric motor7is converted to 180°. If the winding polarities of the coil portions are different, then the electrical angular phase inverts by 180°.

Taking these into account, in the electric motor7in which the number of field poles is fourteen and the number of slots35in the stator22is eighteen that is shown inFIG. 3, for example, because the angle that is formed by the adjacent N and S poles is 360°/14=25.71°, this angle is converted to 180°.

In this electric motor7, because the angle that is formed by two adjacent teeth34is 360°/18=20°, when this angle is converted to electrical angular phase, it becomes 20°×180/25.71=140°.

Moreover, in contrast to the electrical angular phase, the angle where the angle when the rotor29rotates through one revolution is 360° is called a “mechanical angle” or a “mechanical angular phase” or simply an “angle”.

The electrical angular phases of the coil portions +U21, −U22, and +U23that are shown inFIG. 17Aare 0°, 20°, and 40°, respectively, where the coil portion +U21is the base.

In the vector diagram, where the vector length is the magnetomotive force from the coils and vector angle is the electrical angular phase, electrical angular phase difference is defined as the angle that is formed by two vectors. Consequently, the greatest electrical angular phase difference is an electrical angular phase difference of 40° between −U22and +U23. Here, if the electrical angular phase is set to θ1=0° using +U23as a base, the electrical angular phase of the coil portion +U21is 20°, making θ2=20°, and the electrical angular phase of the coil portion −U22is 40°, making θ3=40°.FIG. 17Ashows this vector diagram, and it can be seen that that θ1<θ2<θ3.

In the examples according to this embodiment, the coil portion +U21, i.e., the coil portion for which the electrical angular phase is θ2, is an overwound coil, in which the number of turns of the conducting wire21is greater than other serially connected identical-phase coil portions, and since the magnetomotive force that is generated is stronger than those of −U22and +U23, the vector length is shown larger than for others.

As a comparative example, magnetomotive force vectors that are generated in coil portions in the U phase of the second armature winding portion37fromFIG. 14, represented by the first reference example, in which the number of turns in all of the coil portions is equal, are shown inFIG. 17B. The magnetomotive force that the U phase generates is expressed by a resultant vector length.

In this comparative example, the magnetomotive forces that are generated by the coil portions +U21, −U22, and +U23are equal.

Consequently, in Embodiment 1, in which the vector where the electrical angular phase that is positioned centrally is increased compared to when the number of turns of the conducting wires21in all of the coil portions is equal, the resultant vector length is increased, enabling magnetomotive force to be increased.

Magnetic flux density is thereby increased in the magnetic air gap portion between the stator22and the rotor29of the electric motor7, enabling torque to be improved.

FIG. 18Bshows, as a vector diagram, electrical angular phases of the coil portions +U21, −U22, and +U23in the second U-phase winding portion U2of the second armature winding portion37when the sum of the number of turns of the conducting wires21in all of the coil portions that are mounted to the teeth34is equal to that of Embodiment 1, which is shown inFIG. 18A, and the number of turns in all of the coil portions is equal.

The sum of the number of turns of the conducting wires21in all of the coil portions that are mounted to the teeth34will be called a “total number of turns”. If the vector length is represented by the number of turns, the magnetomotive force of the configuration in Embodiment 1 by finding the length of the resultant vector is 17+2×14 cos 20°, as shown inFIG. 19A.

The magnetomotive force when the total number of turns is equal to that of Embodiment 1 and the number of turns of the conducting wires21in all of the coil portions is equal, on the other hand, is 15+2×15 cos 20°, as shown inFIG. 19B. The difference in magnetomotive force is 2(1−cos 20°)≅0.1206, that of the configuration in Embodiment 1 being the greater.

In other words, if the total number of turns is kept constant, the configuration according to Embodiment 1 is effective in increasing magnetomotive force, and improving torque compared to configurations in which the number of turns of the conducting wires21in all of the coil portions is equal, as in the first reference example.

Specifically, when an electric motor that outputs torque that has a target value is designed, then since the total number of turns of the conducting wires21in the coil portions can be reduced, the conducting wires21that constitute the coil portions can be made shorter, reducing the resistance of the coil portions, and enabling the amount of heat generated to be reduced.

When an electric motor that outputs torque that has a target value is designed, the length of the resultant vector that represents the magnetomotive force can be adjusted over a range of finer values by adjusting the number of turns of the conducting wire21in the coil portion +U21to make an overwound coil, or alternatively to make an underwound coil in which the number of turns is reduced compared to other coil portions.

Since the torque of the electric motor is proportional to the magnetomotive force, torque can be specified over a range of finer values, effectively improving torque design freedom of the electric motor.

Moreover, in the case of the connections that are shown inFIGS. 6 and 7, if the electrical angular phases of the serially connected U-phase coil portions −U11, +U12, −U13, +U21, −U22, and +U23are represented in a vector diagram, since the vectors of the coil portions −U11and +U21coincide, the vectors of the coil portions +U12and −U22coincide, and the vectors of the coil portions −U13and +U23coincide, the vector arrangements are similar or identical to those ofFIG. 18A, enabling similar or identical effects to be achieved.

In this example, the number of identical-phase coil portions is six, and if the number of serially connected coil portions is three or six, the electrical angular phases of the series coil portion group have the relationship θ1<θ2<θ3, and the effects can be achieved by making the number of turns of the coil portion or portions for which the electrical angular phase is θ2different.

Generalizing this, if n is the number of identical-phase coil portions among the coil portions, where n≥3, in a series coil portion group that includes in of the above coil portions that are serially connected, where m≤n, θmis the largest electrical angular phase difference between two of the above coil portions, θ1=0° is the electrical angular phase difference of a first of the above coil portions that have the largest electrical angular phase difference, and θ2, θ3, etc., through θmare the respective electrical angular phase differences of the remaining coil portions relative to the above coil portion that has an electrical angular phase difference of θ1sequentially in increasing order, then there are electrical angular phase differences of θkthat satisfy θ1<θk<θm, where k=2, 3, etc., through m−1, and in that case, it goes without saying that effects that are similar or identical can be achieved even if the number of turns is made different in the coil portions for which the electrical angular phase is θk.

FIG. 20shows mechanical angular phase in the second U-phase winding portion U2, which is a series coil portion group in the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In this figure, a case is shown in which the coil portions +U21, −U22, and +U23are connected in series. The mechanical angular phase of the tooth34onto which the coil portion +U21is wound is the base, which is φ1=0°. The largest electrical angle phase difference in a counterclockwise direction from the tooth34at Number 4 is the tooth34at Number 9 onto which the coil portion +U23is wound, which is positioned at φ3=100° from the tooth34at Number 4. The tooth34at Number 8 onto which the coil portion −U22is wound is disposed between the teeth34at Numbers 4 and 9, and is positioned at φ2=80° from the tooth34at Number 4.

Here, the tooth34at Number 4 onto which the coil portion +U21is wound is adjacent to the teeth34onto which the coil portion +W23and the coil portion +V12, which are in different phases, are wound.

Since the coil portion +U21is an overwound coil compared to the coil portions −U22, +U23, +W23, and +V12, the conducting wire21that constitutes the coil portion is longer than those of the other coil portions, and resistance is increased, making localized heat generation more likely to concentrate there.

However, in this coil portion +U21, localized heat generation due to identical-phase electric current concentration is suppressed due to the coil portions that are adjacent on two sides thereof in the circumferential direction of the stator22being V-phase and W-phase, and the heat generated can be dispersed.

This is not limited to the electric motor7according to Embodiment 1 that is shown inFIG. 3, and even if the coil portion +U21is an underwound coil compared to the coil portions −U22, +U23, +W23, and +V12, or if the wire diameter of the coil portion +U21is smaller than that of the coil portions −U22, +U23, +W23, +V12, and resistance is increased, since the coil portions that are adjacent on two sides of the coil portion +U21in the circumferential direction have different phases, the heat generated is dispersed and localized heat generation can be suppressed, as in the case of the electric motor7in which the number of field poles in the rotor29is 12n±2n and the number of slots35is 12n, where n is a natural number, and in the case of the electric motor7in which the number of field poles of the rotor29is 18n±2n and the number of slots35is 18n, where n is a natural number, compared to where coil portions that have identical phase are adjacent.

In addition, disposing the identical-phase coil portions so as to be dispersed on the stator22in this manner is effective in preventing the strength of the magnetic field that is generated in the magnetic air gap portion between the stator22and the rotor29from becoming nonuniform in the coil portions of each of the three phase winding portions if decentration occurs in the rotor29.

Mechanical angular phase when coil portions in the tooth34at Numbers 4, 8, and 18 are connected in series is shown inFIG. 21as a first example that has a different connection method for the respective coil portions of the U phase.

Connection diagrams for the armature winding38in this instance are shown inFIGS. 22 and 23.

In the U phase, a series coil portion group is configured in which respective coil portions of −U13, +U21, and −U22are connected in series.

FIG. 24shows a vector diagram of electrical angular phases of respective coil portions of a U-phase series coil portion group in the armature windings that are shown inFIGS. 22 and 23.

Since this figure is similar or identical toFIGS. 17A and 18A, except that the numbers of the teeth34of the respective coil portions that are connected are different than inFIG. 20, the magnetomotive forces that are generated are similar or identical to those ofFIG. 20.

Here, the mechanical angular phase of the tooth34at Number 1 onto which the coil portion −U13is wound is the base, which is φ1=0°. The largest electrical angle phase difference in a counterclockwise direction from the tooth34at Number 18 is the tooth34at Number 8 onto which the coil portion −U22is wound, which is at φ3=160°. When the tooth34at Number 8 is viewed from the tooth34at Number 18, which is the base, the tooth34at Number 4 is disposed between the teeth34at Numbers 18 and 8, and the mechanical angular phase of the tooth34at Number 4 is φ2=160°.

In this case, the tooth34at Number 4 onto which the overwound coil portion +U21is wound is also adjacent to the teeth34onto which the coil portion +W23and the coil portion +V12, which are in different phases, are wound, enabling similar or identical effects to those inFIG. 20to be achieved.

In addition, mechanical angular phase when coil portions in the tooth34at Numbers 4, 9, and 17 are connected in series is shown inFIG. 25as a second example that has a different connection method for the coil portions of the U phase.

Connection diagrams for the armature winding38in this instance are shown inFIGS. 26 and 27.

In the U phase, a series coil portion group is configured in which respective coil portions of +U12, +U21, and −U23are connected in series.

FIG. 28shows a vector diagram of electrical angular phases of coil portions of that constitute a U phase of an armature winding portion36in the connection methods that are shown inFIGS. 26 and 27.

Since this figure is similar or identical toFIGS. 17A and 18A, except that the numbers of the teeth34of the respective coil portions that are connected are different than inFIG. 20, the magnetomotive forces that are generated are similar or identical to those ofFIG. 20.

Here, the mechanical angular phase of the tooth34at Number 17 onto which the coil portion +U12is wound is the base, which is φ1=0°. The largest electrical angle phase difference in a counterclockwise direction from the tooth34at Number 17 is the tooth34at Number 9 onto which the coil portion +U23is wound, which is at φ3=200°. When the tooth34at Number 8 is viewed from the tooth34at Number 17, which is the base, the tooth34at Number 4 is disposed between the teeth34at Numbers 17 and 9, and the mechanical angular phase of the tooth34at Number 4 is φ2=100°.

In this case, the tooth34at Number 4 onto which the overwound coil portion +U21is wound is also adjacent to the teeth34onto which the coil portion +W23and the coil portion +V12, which are in different phases, are wound, enabling similar or identical effects to those inFIG. 20to be achieved.

Cases in which the coil portion +U21is an overwound coil portion or an underwound coil portion compared to the coil portions −U22and +U23have been mentioned above, but the coil portion −U22and the coil portion +U23may be overwound coils or underwound coils compared to the coil portion +U21.

Since the total number of turns can be specified in even more detail, the torque of the electric motor7can be specified in even more detail, enabling torque design freedom of the electric motor to be improved.

Furthermore, as shown inFIG. 3, in the electric motor7according to this embodiment, the coil portion −U22and the coil portion +U23, which are identical in phase, are adjacent.

Resistance can be reduced by making the coil portion −U22and the coil portion +U23overwound coils or underwound coils compared to the coil portion +U21, reducing the amount of heat generated at positions where the identical phases are adjacent, enabling the concentration of generated heat to be suppressed.

As shown inFIG. 3, the number of turns in the coil portions that are adjacent to each of the teeth B that have an overwound coil portion is different than the number of turns on the teeth B. Gaps in the slots35are thereby reduced compared to the configuration inFIG. 14in which the number of turns in all of the coil portions is made equal, enabling space factor of the coil portions to be improved. Consequently, by improving the space factor, the cross-sectional area of the coil portions relative to the area of the slots35is increased, enabling the amount of heat generated to be reduced.

Moreover, if the manufacturing method that was mentioned in the first reference example is adopted in the examples according to this embodiment in which the number of turns is different within the construction of a single stator22, manufacturing is possible by inserting bobbins that are mounted to the teeth A into the inner core57first, and inserting insulators that are mounted to the teeth B afterwards.

In this case, as shown inFIG. 3, the construction is such that coil portions on one side protrude beyond the central broken lines of the slots35.

From the above, it is possible to manufacture the above construction that reduces the gaps in the slots35by adopting the teeth B that have overwound coil portions, enabling reductions in the amount of heat generated to be achieved.

As shown inFIG. 3, the wire diameter of the coil portions that are mounted to the teeth B that have overwound coil portions is larger than the wire diameter of the other identical-phase coil portions that are serially connected to those coil portions.

For example, the coil portions that are connected in series to the coil portion −V11that is mounted to the tooth34at Number 1 are the coil portion +V12that is mounted to the tooth34at Number 5, and the coil portion −V13that is mounted to the tooth34at Number 6, and the wire diameter of the coil portion −V11is larger than that of to the coil portions +V12and −V13.

By making the wire diameter different in this manner, gaps in the slots35are reduced, improving space factor of the coil portions in the slots35, reducing the resistance of the coil portions, and enabling the amount of heat generated to be reduced.

As shown inFIG. 3, the arrangement of the coil portions in each phase in the stator22is identical even if the stator22is rotated by 180° around its center.

The arrangement of the respective number of turns of the conducting wires21in the stator22is also identical even if the stator22is rotated by 180° around its center.

In other words, if the arrangement of the coil portions and the number of turns in each phase in an upper half of the stator22that includes the teeth34at Numbers 1 through 9 is rotated by 180° around the center of the stator22, it is similar to the arrangement of the coil portions and the number of turns in each phase in a lower half of the stator22that includes the teeth34at Numbers 10 through 18.

Here, because the magnetomotive forces that the respective coil portions of the stator22generate are expressed as a product of the respective number of turns and the electric current, distribution of the magnetomotive forces in the stator22is also identical if the stator22is rotated by 180° around its center.

This means that the magnetomotive forces have rotational symmetry by 180°, i.e., rotational symmetry for two iterations.

The examples according to this embodiment have 180° rotational symmetry, but to generalize this, if, when rotated P degrees around the stator22, where P is an integer, the arrangement of the phases and the number of turns is similar or identical to that prior to rotation, then it has rotational symmetry by P degrees, i.e., rotational symmetry for 360/P iterations.

These magnetomotive forces are one factor in the generation of electromagnetic vibrational forces that arise in a radial direction of the stator22, and electromagnetic vibrational forces are known to be proportional to these magnetomotive forces in the armature winding.

The electromagnetic vibrational forces that arise in the radial direction of the stator22are factors of noise and vibration in the electric motor, and spatial first-order electromagnetic vibrational forces in particular give rise to rattling noise in the bearings of an electric motor, making reduction desirable since they are a major source of noise.

Thus, by making the magnetomotive forces that the respective coil portions of the stator22generate rotationally symmetrical by 180°, as described above, it becomes possible to suppress the generation of spatial first-order electromagnetic vibrational forces that constitute a major source of noise.

FIG. 29is a frontal cross section of an electric motor7that shows a configuration in which the number of turns of the conducting wires21is increased in coil portions that are mounted to each of the teeth34at Numbers 1, 3, 5, 7, 9, 11, 13, 15, and 17.

In the configuration that is shown inFIG. 29, coil portions that have a different number of turns are disposed in all of the slots35, further reducing gaps in the slots35compared to those of Embodiment 1, which is shown inFIG. 3, thereby further improving space factor in the slots35.

However, in the configuration that is shown inFIG. 29, the arrangement of the numbers of turns, i.e., the distribution of the magnetomotive forces are not rotationally symmetrical by 180°. Consequently, the configuration in the figure will be called an “asymmetrical magnetomotive force configuration”.

Now, values of spatial first-order electromagnetic vibrational force in the electric motors7according to the first reference example and Embodiment 1 were compared where the spatial first-order electromagnetic vibrational force in an asymmetrical magnetomotive force configuration was set to 1, the results being shown inFIG. 30.

From this figure, whereas spatial first-order electromagnetic vibrational force is generated in the asymmetrical magnetomotive force configuration, it is suppressed in Embodiment 1 so as to be approximately equal to that of the first reference example.

Consequently, by making the arrangement of the coil portions in which the number of turns are made different rotationally symmetrical by 180° relative to the stator22, it is possible to suppress spatial first-order electromagnetic vibrational forces that constitute a noise source from increasing while retaining the above-mentioned effects of making the number of turns different.

In the examples according to this embodiment, the rotational symmetry is by 180°=360°/2, i.e., the rotational symmetry is for two iterations, and since the spatial order components that are present in the magnetomotive forces are second-order or greater, spatial first-order electromagnetic vibrational forces are not generated, but generalizing this, if the distribution of the number of turns is rotationally symmetrical by 360°/L, where L is a natural number that is greater than or equal to two, i.e., rotationally symmetrical for L iterations, then it goes without saying that spatial first-order electromagnetic vibrational forces are not generated since the spatial order components that are present in the magnetomotive forces are greater than or equal to L-th order.

Moreover, there is no problem even if an arrangement that is rotationally symmetrical for L iterations drifts within manufacturing errors (at a mechanical angle of approximately ±10°), since the electromagnetic vibrational forces ofFIG. 30will not increase to the level of the example inFIG. 29.

In the electric motor7in which the number of magnetic field poles is fourteen and the number of teeth34and slots35is eighteen, as described above, the electrical angular phases of the coil portions that constitute the respective series coil portion groups thereof have an arrangement in which three magnetomotive force vectors line up so as to have a phase difference of 20°, as shown inFIGS. 17A and 18A.

Since the distribution of the magnetomotive forces in the example according to this embodiment is rotationally symmetrical by 180°, as described above, a maximum of two sets of three phases can be configured within one 360° lap of the electric motor7.

Consequently, by making the number of parallel arms in the circuits one or two, the number of coils that constitute an identical-phase series coil portion group can be made six or three.

Consequently, by making the coils that correspond to the three magnetomotive force vectors that line up at this electrical angle phase difference of 20° one set, and so as to have identical phase, the total number of turns in each of the series coil portion groups that have identical phase can be made equal, as shown inFIGS. 17A and 18A.

In the examples according to this embodiment, cases in which the number of parallel arms in the circuits is one or two are shown, but if the distribution of the number of turns and the magnetomotive forces mentioned above is rotationally symmetrical by 360°/L, then a maximum of L sets of three phases can be configured within one 360° lap of the electric motor7.

Consequently, by making the number of parallel arms in the circuits equal to L, configurations are possible in which the total number of turns in each of the identical-phase series coil portion groups is made equal.

Here, since the induced voltages that are generated in each of the series coil portion groups of each of the identical-phase series coil portion groups become equal, one effect is that cyclic currents are not generated in the parallel circuits of each of the phases.

The electric motor7according to this embodiment has “concentrated windings”, in which coil portions are mounted so as to be concentrated on the teeth34, also enabling effects to be achieved such as making coil ends small, being compact, reducing copper loss, and having low heat generation and high efficiency.

Because there are (18±4)y field poles and the number of teeth34and slots35is 18y, where y is a natural number, torque can be improved compared to when there are (3±1)y field poles and the number of teeth34or slots35is 3y.

Electromagnetic vibrational forces that arise in spatial second-order stator cores20can be reduced compared to when there are (12±2)y field poles and the number of teeth34or slots35is 12y, enabling effects to be achieved such as enabling vibration noise to be reduced.

Because harmonic winding factors are reduced, particularly the 6f components and 12f components, which are major components of torque ripples, torque ripples can be reduced.

FIG. 31shows a different configuration of the poles and slots35in Embodiment 1.

There are twenty-two field poles and the number of teeth34is eighteen. Since the arrangement of the coil portions in the circumferential direction is similar or identical to that inFIG. 3, it goes without saying that effects that are similar or identical to the above can be achieved.

The field poles are permanent magnets32, but it goes without saying that a reluctance-type rotary electric machine that does use permanent magnets32may be used, or the field poles may be formed by mounting windings to a rotor core and passing an electric current therethrough.

FIGS. 3, 10, and 11are frontal cross sections of electric motors7that shows this embodiment and variations of this embodiment, but those inFIGS. 10 and 11, in particular, in which tip portions of the teeth34that are on a side near the rotor29are linked to the tip portions of adjacent teeth34, can release heat through linking of the tooth34.

Consequently, pathways that transfer heat are formed by the constructions of these variations, enabling temperature increases in the electric motor7to be reduced.

In the electric motor7according to this embodiment, as shown inFIG. 3, the coil portions −V11, +U21, −W11, +V21, −U11, and +W21are equal in wire diameter. These coil portions each belong to separate series coil portion groups and, for example, the coil portion +U21belongs to the series coil portion group that is constituted by the coil portions −U22, +U21, and +U23, as shown inFIGS. 4 and 5.

The coil portion +U21is positioned at an intermediate electrical angular phase between the other two identical-phase series coil portions −U22and +U23.

Similarly, the coil portions −V11, −W11, +V21, −U11, and +W21in each of the series coil portion groups are positioned at intermediate electrical angular phases between the other coil portions.

In other words, if the armature winding38is constituted by parallel circuits that include a first armature winding portion36and a second armature winding portion37, the wire diameters of the coil portions in the series coil portion groups that constitute the parallel circuit are equal to the wire diameters of the coil portions that have equal electrical angular phase in other series coil portion groups.

Because the resistance values of each of the series coil portion groups thereby become equal, one effect is that electric current does not become unbalanced in the respective series coil portion groups when equal voltages are applied to each of the series coil portion groups.

Since the magnetomotive force distribution is disturbed if electric current becomes unbalanced in the respective phases of the circuits of the electric motor7, or in the parallel circuits that constitute the respective phases, one problem has been that torque ripples are increased, but this problem does not arise in the examples according to this embodiment.

Here, a turn ratio is defined as a ratio between the number of turns in the coil portions that are mounted to the teeth A and the number of turns in the coil portions that are mounted to the teeth B, and is given by (the turn ratio)=(the number of turns (ß) in the coil portions that are mounted to the teeth B)/(the number of turns (α) in the coil portions that are mounted to the teeth A).

For example, as shown inFIG. 3of this embodiment, because the number of turns (α) in the coil portions that are mounted to the teeth A is fourteen, and the number of turns (ß) in the coil portions that are mounted to the teeth B is seventeen, the turn ratio is (ß/α)=17/14=1.214.

Turn ratios when the numbers of turns in the coil portions of the teeth A and the teeth B are varied are presented in a table inFIG. 33.

Combinations of numbers of turns have been selected for which the sums of the numbers of turns in all of the coil portions that are mounted to the stator22, i.e., the total numbers of turns, are equal.

For example, whereas the total number of turns when α=12 and ß=12 in this figure is 12×6+12×12=216, the total number of turns when α=11 and ß=14 in this figure is 11×12+14×6=216, which are equal values. The total numbers of turns in a remainder of the combinations are also216.

As in the first reference example that is shown inFIG. 14, the generated torque in an electric motor7in which the number of turns in all of the coil portions is equal is approximately proportional to the product of the electric current value that is applied to the coil portions and the total number of turns.

Consequently, combinations of numbers of turns were selected such that generated torque of the electric motor7became approximately equal by making the total numbers of turns equal to each other and making the applied electric currents equal.

Analytical calculations were performed using the combinations of numbers of turns that are shown inFIG. 33, and the calculated results are shown inFIG. 34represented as relationships between average torque and torque ripples relative to the turn ratio.

The average torque and torque ripples are both represented as ratios for which the value is 1 when α=12 and ß=12.

From this figure, average torque is at a maximum at a turn ratio of 1.60, and torque ripples are at a minimum at a turn ratio of 1.27. If the turn ratio is greater than 1.0 and less than or equal to 2.0, then effects can be achieved by which the average torque is improved and torque ripples are less than or equal to when the turn ratio is 1, which corresponds to the first reference example.

FIG. 35is a frontal cross section that shows an electric motor7according to Embodiment 2 of the present invention.

In the electric motor7according to this embodiment, a circumferential width WBof teeth B onto which overwound coil portions are mounted is greater than a circumferential width WAof teeth A.

A remainder of the configuration is similar or identical to that of the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In this electric motor7, magnetic saturation is less likely to occur in the teeth34to which the overwound coil portions are mounted, enabling torque improvement and reductions in torque ripples to be achieved.

If underwound coil portions are mounted to the teeth B, the width of the slots35in which the coil portions that are mounted to the teeth B are housed can be increased instead by making the width WBsmaller than the width WA, and resistance can be reduced by increasing the wire diameter of the coils that are mounted to the teeth B, enabling reductions in the amount of heat generated to be achieved.

FIG. 36is a frontal cross section that shows an electric motor7according to Embodiment 3 of the present invention.

In the electric motor7according to this embodiment, in addition to increasing a circumferential width of teeth B that have overwound coil portions to make WB>WA, a circumferential width WS2′ of slots35in which the coil portions that are mounted to the teeth B are housed is increased, and a width WS1′ of a remainder of the slots35is reduced compared to those inFIG. 35.

A remainder of the configuration is similar or identical to that of the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In the configuration inFIG. 35, a circumferential width of the slots35in which the coil portions that are mounted to the teeth B are housed is WS2, and a circumferential width of a remainder of the slots35is WS1, but in the configuration inFIG. 36, compared to the respective width values WS1′ and WS2′, WS1′<WS1, and WS2′>WS2.

Gaps are thereby increased in the slots35in which the overwound coil portions −V11, +U21, −W11, +V21, −U11, and +W21are housed compared to the configuration inFIG. 35in which only the circumferential width of the teeth34was changed, enabling a greater number of turns of conducting wire21to be wound onto the teeth34, and improving freedom in selecting the number of turns.

Additionally, one effect is that gaps in a remainder of the slots35in which the overwound coil portions are not housed are reduced, improving space factor.

FIG. 37is a frontal cross section that shows a variation of the electric motor7according to Embodiment 3.

In this variation, an example is shown in which, in addition to the modifications to the width of the teeth34and the modification to the width of the slots35that are shown inFIG. 36, the number of turns of the conducting wires21on the teeth B onto which the overwound coil portions are wound is increased by a single turn. In this figure, the cross sections of the additional single turns of the conducting wires21inside the slots35are hatched.

By making the circumferential widths of the slots35different in this manner, the area of the slots35is used effectively, increasing freedom in selecting the number of turns, and enabling torque performance to be improved.

FIG. 38is a frontal cross section that shows an electric motor according to Embodiment 4.

In this embodiment, a wire diameter of conducting wires21of coil portions that are mounted to teeth B is equal to a wire diameter of the conducting wires21on teeth A.

A remainder of the configuration is similar or identical to that of the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In this embodiment, since the coil portions that are mounted to each of the teeth34can be configured using conducting wires21that have one wire diameter, similar or identical effects to those of Embodiment 1 can also be achieved while increasing manufacturability.

FIG. 39is a frontal cross section that shows an electric motor7according to Embodiment 5.

In this embodiment, the number of turns of conducting wire21in coil portions that are mounted to teeth B is equal to the number of turns of the conducting wire21in coil portions on teeth A, and a wire diameter of conducting wires21of coil portions that are mounted to teeth B is different than a wire diameter of the conducting wires21on teeth A.

In this figure, the cross sections of the coil portions on the teeth34to which the coil portions are mounted in which the wire diameter of the conducting wire21is different are hatched.

A remainder of the configuration is similar or identical to that of the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In a configuration in which the number of turns in all of the coil portions is equal, and in which there are coil portions in which the wire diameter of the conducting wires21is different, as in the electric motor7according to this embodiment, effects such as space factor of the coil portions in the slots35being improved and the amount of heat generated being reduced can also be achieved.

FIG. 40is a frontal cross section that shows an electric motor7according to Embodiment 6.

In this embodiment, rectangular wire that has a rectangular cross section is used in conducting wires that constitute components of coil portions.

In this figure, the number of turns of conducting wires21ain coil portions that are mounted to teeth B is greater than the number of turns of conducting wires21ain coil portions that are mounted to teeth A. In this figure, cross sections of overwound coil portions are hatched.

A remainder of the configuration is similar or identical to that of the electric motor7according to Embodiment 1 that is shown inFIG. 3.

In this embodiment, by using the rectangular conducting wires21a, gaps in the slots35are reduced compared to coil portions that use round conducting wire21, enabling space factor to be improved.

Since a configuration that has different numbers of turns can be achieved in a similar or identical manner to the round wire, as shown in this figure, additional improvements in space factor in the slots35can be achieved in addition to the effects that have been mentioned so far.

Furthermore,FIG. 41is a variation of Embodiment 6, the number of turns and cross-sectional area of conducting wires21ain coil portions that are mounted to teeth B being greater than in a remainder of the coil portions.

In this variation, having different cross-sectional areas corresponds to having different wire diameters in the round wire.

Consequently, by making the cross-sectional areas of the rectangular wires different, space factor in the slots35can be further improved in a similar manner to making the wire diameters different in the electric motor7according to Embodiment 1.

FIG. 42is a circuit diagram for an electric motor7and an ECU6according to Embodiment 7.

In this embodiment, two inverters42drive the electric motor7, a first inverter42A being connected to the connecting portions A1, B1, and C1of the first armature winding portion36of the armature winding38inFIG. 3, and a second inverter42B being connected to the connecting portions A2, B2, and C2of the second armature winding portion37.

For simplicity, only the armature winding is shown in the electric motor7inFIG. 42.

This electric motor winding is constituted by: a first armature winding portion36that is constituted by a first U-phase winding portion U1, a first V-phase winding portion V1, and a first W-phase winding portion W1; and a second armature winding portion37that is constituted by a second U-phase winding portion U2, a second V-phase winding portion V2, and a second W-phase winding portion W2.

Details of the ECU6are also omitted for simplicity, and only the power circuit portions of the first inverter42A and the second inverter42B are shown.

The ECU6is constituted by circuits of the two inverters42A and42B, and three-phase electric current is supplied to the first and second armature winding portions36and37respectively from these inverters42A and42B.

A direct-current power source is supplied to the ECU6from a power source43such as a battery, an electric power supply relay45A being connected so as to have a noise reduction coil44interposed.

Moreover, inFIG. 42, the power source43is depicted as if it were inside the ECU6, but in fact electric power is supplied from an external power source such as a battery through a connector.

There are two electric power supply relays45A and45B that are each constituted by two MOSFETs, and the electric power supply relays45A and45B open during failure, to prevent excessive electric current from flowing.

Moreover, in the figure, the electric power supply relays45A and45B are connected after the power supply43and the coil44, but it goes without saying that the electric power supply relays45A and45B may be disposed at a position that is closer to the power supply43than the coil44.

Moreover, a first capacitor46A and a second capacitor46B are smoothing capacitors.

In the figure, these are each constituted by a single capacitor, but it goes without saying that they may be configured by connecting a plurality of capacitors in parallel.

The first inverter42A is constituted by a bridge that uses six MOSFETs. Specifically, in the first inverter42A, a first MOSFET47A and a second MOSFET48A are connected in series, a third MOSFET49A and a fourth MOSFET50A are connected in series, a fifth MOSFET51A and a sixth MOSFET52A are connected in series, and these three sets of MOSFETs are further connected in parallel. In addition, shunt resistors are respectively connected singly to a ground (GND) side of each of the three lower MOSFETs, i.e., the second MOSFET48A, the fourth MOSFET50A, and the sixth MOSFET52A, and these are the shunts53A,54A, and55A. These shunt resistors are used to detect electric current value. Moreover, an example is shown in which there are three shunts53A,54A, and55A, but since electric current detection is possible even if there are two shunts or even if there is a single shunt, it goes without saying that such configurations are also possible.

Supply of electric current to the electric motor7is such that electric current is respectively supplied from between the first MOSFET47A and the second MOSFET48A through a busbar62, etc., to a first U-phase winding portion U1of the electric motor7, from between the third MOSFET49A and the fourth MOSFET50A through a busbar62, etc., to a first V-phase winding portion V1of the electric motor7, and from between the fifth MOSFET51A and the sixth MOSFET52A through a busbar62, etc., to a first W-phase winding portion W1of the electric motor7.

The second inverter42B is also constituted by a bridge that uses six MOSFETs, in a similar manner to the first inverter42A. Specifically, in the second inverter42B, a first MOSFET47B and a second MOSFET48B are connected in series, a third MOSFET49B and a fourth MOSFET50B are connected in series, a fifth MOSFET51B and a sixth MOSFET52B are connected in series, and these three sets of MOSFETs are further connected in parallel. In addition, shunt resistors are respectively connected singly to a ground (GND) side of each of the three lower MOSFETs, i.e., the second MOSFET48B, the fourth MOSFET50B, and the sixth MOSFET52B, and these are the shunts53B,54B, and55B. These shunt resistors are used to detect electric current value. Moreover, an example is shown in which there are three shunts53B,54B, and55B, but since electric current detection is possible even if there are two shunts or even if there is a single shunt, it goes without saying that such configurations are also possible.

Supply of electric current to the electric motor7is such that electric current is respectively supplied from between the first MOSFET47B and the second MOSFET48B through a busbar62, etc., to a second U-phase winding portion U2of the electric motor7, from between the third MOSFET49B and the fourth MOSFET50B through a busbar62, etc., to a second V-phase winding portion V2of the electric motor7, and from between the fifth MOSFET51B and the sixth MOSFET52B through a busbar62, etc., to a second W-phase winding portion W2of the electric motor7.

The two inverters42A and42B are switched by sending signals from the controlling circuit (not shown) to each of the above MOSFETs that correspond to the angle of rotation that is detected by the magnetic sensor14that constitutes the rotational angle sensor, to supply the desired three-phase electric currents to the first armature winding portion36and the second armature winding portion37.

Moreover, the angle of rotation of the shaft27may be detected using a resolver or a giant magnetoresistive (GMR) sensor instead of the magnetic sensor14.

When driven by the two inverters42A and42B in this manner, torque ripples can be significantly reduced by changing the phases of the electric currents that the two inverters42A and42B supply. By offsetting the phases of the electric currents of the two inverters42A and42B by 30 electrical degrees, mutual electrical angular phase sixth-order torque ripples are canceled out, achieving an effect that reduces P-P values of torque ripples significantly.

In an electric power steering apparatus1, torque ripples not only cause vibration and noise, the driver may also feel the torque ripples, which degrades the steering feel.

However, since torque ripples can be reduced significantly using the configuration according to this embodiment, reducing vibration noise, one effect is that a superior steering feel can be achieved.

In addition, since the first armature winding portion36and the second armature winding portion37, which are each constituted by three phases, are connected to different inverters42A and42B, even in the event of failure of one of the inverters42A and42B or a wire breakage in the connections of one, etc., since three-phase input from the other can continue, one effect is that redundancy that continues driving the electric motor7is achieved.

By using two inverters42A and42B, since the electric current that the inverters42A and42B supply can be reduced to half that of the case of one inverter42, loss in the circuits is reduced, and one effect is that the amount of heat generated is reduced.

Moreover, since the effects according to this embodiment can be combined with the configurations of the electric motor in each of the above embodiments, in addition to the effects that have been mentioned in each of the above embodiments, effects such as reductions in the amount of heat generated, reductions in torque ripples, and imparting redundancy can be added.

Moreover, in each of the above embodiments, an electric motor that has a three-phase armature winding as a rotary electric machine has been explained, but this is one example, and the electric motor may have a multiphase armature winding other than a three-phase one.

An electric motor that is mounted to an electric power steering apparatus is one example, and it may be an electric motor that is used for machining, conveyance, etc.

The present invention can also be applied to generators.