Patent ID: 12244181

DETAILED DESCRIPTION

Hereinafter, embodiments of the motor according to the present disclosure will be described with reference to the drawings.

First Embodiment

FIG.1is a vertical cross-sectional view showing a first embodiment of the motor according to the present disclosure.FIG.2is a transverse cross-sectional view of a rotor120and a stator130in the cross section perpendicular to a rotary shaft110of a motor100shown inFIG.1. In the following descriptions, the direction parallel to the rotary shaft110is expressed as an axial direction. The direction parallel to the diameter of the circumference around the rotary shaft110is expressed as a radial direction. The direction along the circumference around the rotary shaft110is expressed as a circumferential direction.

The motor100of the present embodiment is an IPM (Interior Permanent Magnet) motor that is mounted on vehicles, such as hybrid vehicles, electric vehicles, or hydrogen vehicles, for example, and generates a driving force for traveling the vehicles. The motor100includes, for example, a rotary shaft110, a rotor120fixed to the rotary shaft110, a stator130disposed around the rotor120, and a housing140for housing the rotor120and the stator130.

The rotor120has a cylindrical shape, for example. The stator130has an annular or cylindrical shape, for example, and is disposed on the outside of the rotor120in the radial direction so as to surround the rotor120. The rotor120and the stator130are disposed coaxially with each other, and the outer circumferential surface of the rotor120and the inner circumferential surface of the stator130face each other in the radial direction. A predetermined air gap is formed between the outer circumferential surface of the rotor120and the inner circumferential surface of the stator130.

The housing140includes a pair of housing members141,142having a closed-bottomed cylindrical shape, for example. The pair of housing members141,142is fastened and integrated with each other by a fastening member such as a bolt143, for example, in a state where their openings are bonded together. The housing140has bearings144,145for rotatably supporting the rotary shaft110and the rotor120.

As shown inFIG.2, the rotor120includes, for example, a plurality of magnet slots121, a plurality of main magnets122housed in the plurality of magnet slots121, and a plurality of auxiliary magnets123housed in the plurality of magnet slots121together with each of the main magnets122. More specifically, the rotor120includes a rotor core124fixed to the rotary shaft110, and the plurality of magnet slots121are disposed in the rotor core124.

The rotor core124is formed in a substantially cylindrical shape by stacking a large number of electromagnetic steel plates, and has a through-hole125at its center. The rotary shaft110is fitted into the through-hole125of the rotor core124, whereby the rotor core124is fixed to the rotary shaft110. More specifically, the large number of electromagnetic steel plates forming the rotor core124are fixed to the rotary shaft110by, for example, swaging, welding, an adhesive, a projection and recess structure such as a key and keyway, spline, etc., or press-fitting or the like.

The stator130includes a cylindrical stator core131including the large number of stacked electromagnetic steel plates, for example. The stator core131includes a plurality of slots132evenly spaced in the circumferential direction. The slot132penetrates the stator core131in the axial direction. In the slot132, a 3-phase stator winding133is wound and disposed, for example. In the present embodiment, for example 48 slots132are evenly spaced in the circumferential direction such that the 3-phase stator windings133corresponding to the number of magnetic poles of the rotor120are housed therein.

As will be described in detail later, the motor100according to the present embodiment is characterized in that at least one of a first condition or a second condition is satisfied. The first condition is that the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets. The second condition is that magnetization directions of the main magnet122and the outer magnet123aincluded in the auxiliary magnet123that are housed in the same magnet slot121intersect outside in the radial direction so as to define an acute angle.

FIG.3is an enlarged view of the rotor120shown inFIG.2. It should be noted thatFIG.3shows an example in which the motor100satisfies only the above-described first condition and does not satisfy the above-described second condition. The rotor120includes a plurality of pairs121P of the magnet slots121, a plurality of pairs122P of the main magnets122, and a plurality of auxiliary magnets123.

The plurality of pairs121P of the magnet slots121, each pair121P of the magnet slots121being arranged in a V-shape opening outward in the radial direction of the rotor120, are evenly spaced in the circumferential direction of the rotor120. Each magnet slot121has a rectangular shape as viewed in the axial direction of the rotary shaft110and includes extended portions121aat the opposite ends thereof in the circumferential direction of the rotor120. The extended portion121aextends in the longitudinal direction and the transverse direction of the rectangular magnet slot121, for example.

The plurality of pairs122P of the main magnets122are housed in the plurality of pairs121P of the magnet slots121with their polarities alternately reversed in the circumferential direction so that the north pole and the south pole alternately face outward in the radial direction. The pair122P of the main magnets122having the north pole facing outward in the radial direction is disposed asymmetrically with respect to the north pole center line Nc extending in the radial direction of the rotor120. The pair122P of the main magnets122having the south pole facing outward in the radial direction is disposed asymmetrically with respect to the south pole center line Sc extending in the radial direction of the rotor120. The main magnets122are permanent magnets. Examples of the main magnets122may include rare-earth sintered magnets, such as neodymium magnets or samarium magnets, ferrite magnets, FCC magnets, or alnico magnets.

The plurality of auxiliary magnets123are housed in the extended portions121aof the magnet slots121, for example. The plurality of auxiliary magnets123include a plurality of outer magnets123ahoused in the outer ends in the circumferential direction in each pair121P of the magnet slots121. In addition, in the example shown inFIG.3, the plurality of auxiliary magnets123include a plurality of inner magnets123bhoused in the inner ends in the circumferential direction in each pair121P of the magnet slots121.

Furthermore, in the example shown inFIG.3, the plurality of auxiliary magnets123are bonded magnets. That is, in the example shown inFIG.3, the motor100satisfies the above-described first condition that the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets. Here, the bonded magnet is prepared by filling a mixture of magnetic particles or powder with a binder, such as a resin, into the magnet slot121and then curing the mixture, for example.

In addition, in the example shown inFIG.3, the main magnet122and the outer magnet123ahoused in the same magnet slot121are magnetized in the same direction. That is, in the example shown inFIG.3, the motor100does not satisfy the above-described second condition that the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle.

Here, the magnetization direction of the bonded magnet can be controlled by filling a mixture of magnetic particles or powder and a binder, such as a resin, into the magnet slot121and then curing the mixture while applying a magnetic field in a direction equal to the magnetization direction, for example. It should be noted that a method for controlling the magnetization direction of the bonded magnet is not particularly limited as long as the magnetization direction of the bonded magnet can be controlled in a desired direction. For example, the bonded magnet may be formed into the shape of the magnet slot121beforehand and magnetized in a predetermined direction, and then inserted into the magnet slot121.

In the example shown inFIG.3, the bonded magnets as the auxiliary magnets123are filled into all of the extended portions121aof the magnet slots121and cured, such that they are housed in all of the extended portions121aof the magnet slots121. However, the bonded magnets as the auxiliary magnets123may be housed in part of the extended portions121aof the magnet slots121.

FIG.4is an enlarged view of the rotor120illustrating Modification 1 of the motor100according to the first embodiment ofFIG.3. In Modification 1 of the motor100, the bonded magnets as the auxiliary magnets123are housed only in the extended portions121aof the magnet slots121located on the opposite sides of the rectangular main magnets122in the longitudinal direction as viewed in the direction parallel to the axial direction of the rotary shaft110.

In other words, in Modification 1 of the motor100shown inFIG.4, the bonded magnets as the auxiliary magnets123are housed only in the inner ends and the outer ends in the circumferential direction in each V-shaped pair121P of the magnet slots121. That is, in Modification 1 of the motor100, the bonded magnets housed in each magnet slot121are only the outer magnet123aand the inner magnet123bforming the auxiliary magnets123.

FIG.5is an enlarged view of the rotor120illustrating Modification 2 of the motor100according to the first embodiment ofFIG.3. In Modification 2 of the motor100, the bonded magnets as the auxiliary magnets123are housed only in the extended portions121aof the magnet slots121located on the outer side in the circumferential direction in the pair122P of the main magnets122arranged in a V-shape as viewed in a direction parallel to the axial direction of the rotary shaft110.

In other words, in Modification 2 of the motor100shown inFIG.5, the bonded magnets as the auxiliary magnets123are housed only in the outer ends in the circumferential direction in each V-shaped pair121P of the magnet slots121. That is, in Modification 2 of the motor100, the bonded magnet housed in each magnet slot121is only the outer magnet123aforming the auxiliary magnet123.

FIG.6is an enlarged view of the rotor120illustrating Modification 3 of the motor100according to the first embodiment ofFIG.3. In Modification 3 of the motor100, the motor100satisfies both of the above-described first and second conditions. That is, in the example shown inFIG.6, the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets, and the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle θ.

FIG.7is a graph showing the comparison of the average torque of the motor according to a comparative example and the average torques of the motors100according to the first embodiment and Modification 3. Here, the motor according to the comparative example has the same configuration as that of the motor100shown inFIG.1toFIG.3except that the motor according to the comparative example does not have the auxiliary magnet123as a bonded magnet. In addition, the motor100of the first embodiment includes the rotor120having the configuration shown inFIG.3and the motor100of Modification 3 includes the rotor120having the configuration shown inFIG.6. It should be noted that in the motors according to the comparative example, the first embodiment, and Modification 3, the rotor cores124have the same lamination thickness, that is, the laminations of the electromagnetic steel plates have the same thickness.

As shown inFIG.7, since the motor100according to the first embodiment satisfies the first condition that the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets, the standardized average torque is about 17% higher than that of the motor according to the comparative example not including the auxiliary magnet123. In addition to the first condition, the motor100according to Modification 3 satisfies the second condition that the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle θ. Consequently, the standardized average torque of the motor100according to Modification 3 is about 19% higher than that of the motor according to the comparative example.

FIG.8is a graph showing the comparison of lamination thicknesses between the motor of the comparative example and the motor100of the present embodiment. It should be noted thatFIG.8shows standardized lamination thicknesses required for the motors of the comparative example, the first embodiment, and Modification 3 to output the same torque. As shown inFIG.8, since the motor100according to the first embodiment satisfies the above-described first condition, the standardized lamination thickness is about 15% less than that of the motor according to the comparative example not including the auxiliary magnet123. In addition to the first condition, since the motor100according to Modification 3 satisfies the second condition, the standardized lamination thickness is about 16% less than that of the motor according to the comparative example.

FIG.9is a graph showing standardized rates of an average torque to a magnet amount (average torque/magnet amount) obtained by the division of the average torques of the motors100according to the first embodiment shown inFIG.3, Modification 1 shown inFIG.4, and Modification 2 shown inFIG.5by their respective magnet amounts. As shown inFIG.9, suppose that the rate of the average torque to the magnet amount of the motor100according to the first embodiment is 1.0, the rate of the average torque to the magnet amount of the motor100according to Modification 1 is 1.03 and the rate of the average torque to the magnet amount of the motor100according to Modification 2 is 1.03, both of which are higher than that of the motor100according to the first embodiment.

As shown inFIG.9, the first embodiment, Modification 1, and Modification 2 are listed in increasing order of contribution of the magnet amount of the auxiliary magnets123to the torque of the motor100. That is, the outer magnets123aof the motor100of Modification 2 shown inFIG.5have the largest contribution to the torque of the motor100. The inner magnets123bof the motor100of Modification 1 shown inFIG.4have the second largest contribution to the torque of the motor100. The auxiliary magnets123housed in the extended portions121aon the opposite sides in the transverse direction of the main magnet122of the motor100of the first embodiment shown inFIG.3have the smallest contribution to the torque of the motor100.

Hereinafter, the functions of the motor100according to the present embodiment and the motors100according to its Modification 1 to Modification 3 will be described.

The motor100of the present embodiment includes the rotor120and the stator130disposed around the rotor120. The rotor120includes the plurality of pairs121P of the magnet slots121, the plurality of pairs122P of the main magnets122, and the plurality of auxiliary magnets123. The plurality of pairs121P of the magnet slots121, each pair121P of the magnet slots121being arranged in a V-shape opening outward in the radial direction of the rotor120, are evenly spaced in the circumferential direction of the rotor120. The plurality of pairs122P of the main magnets122are housed in the plurality of pairs121P of the magnet slots121with their polarities alternately reversed in the circumferential direction so that the north pole and the south pole alternately face outward in the radial direction. The plurality of auxiliary magnets123include the outer magnets123ahoused in the outer ends in the circumferential direction in each pair121P of the magnet slots121. The motor100of the present embodiment satisfies at least one of the first condition that the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets or the second condition that the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle θ.

The motors100according to the first embodiment and Modification 1 to Modification 3 satisfying the first condition can omit a resin mold for fixing the main magnet122, and can fix the main magnet122by filling a bonded magnet into the magnet slot121instead of using the resin mold. That is, since the motor100satisfying the first condition replaces the resin mold with the bonded magnet, the rotor120does not need to be thinner or larger in size for the arrangement of the auxiliary magnets123. Therefore, while suppressing an increase in the physical size of the motor, the motor100satisfying the first condition can increase a magnetic torque as compared to the motor according to the comparative example not including the auxiliary magnet123as shown inFIG.7.

In addition, the motor100according to Modification 3 satisfying the second condition can increase a magnetic torque as compared to the motor100according to the first embodiment not satisfying the second condition as shown inFIG.7. That is, by defining the magnetization directions of the main magnet122and the auxiliary magnet123, the motor100satisfying the second condition can increase a magnetic torque without increasing a magnet amount as compared to the motor not satisfying the second condition. Therefore, the motor100satisfying the second condition can increase a magnetic torque while suppressing an increase in the physical size of the motor.

In addition, in the motor100according to Modification 3 satisfying the second condition, the plurality of auxiliary magnets123include the plurality of inner magnets123bhoused in the inner ends in the circumferential direction in each pair121P of the magnet slots121as shown inFIG.6. In the motor100according to Modification 3, the main magnet122and the inner magnet123bhoused in the same magnet slot121are magnetized in the same direction.

With such a configuration, the motor100according to Modification 3 can increase a magnetic torque with the inner magnets123bas shown inFIG.7. In addition, the motor100according to Modification 3 satisfies the first condition as well. Therefore, the motor100according to Modification 3 can fix the main magnet122by filling the bonded magnet into the magnet slot121instead of using the resin mold, and increase a magnetic torque while suppressing an increase in the physical size of the motor, as described above.

In addition, in the motors100according to the first embodiment, Modification 1, and Modification 2 satisfying only the first condition, the main magnet122and the outer magnet123ahoused in the same magnet slot121are magnetized in the same direction as shown inFIG.3toFIG.5.

In the motors100according to the first embodiment, Modification 1, and Modification 2, the outer magnet123adisposed at the outer end in the circumferential direction in each pair121P of the magnet slots121has a larger contribution to the torque as compared to the auxiliary magnet123disposed in a different position. Therefore, even if the main magnet122and the outer magnet123aare magnetized in the same direction, the motors100according to the first embodiment, Modification 1, and Modification 2 can increase a magnetic torque while suppressing an increase in the physical size of the motor by replacing the resin mold with the bonded magnet.

In addition, in the motors100according to the first embodiment and Modification 1, the plurality of auxiliary magnets123include the plurality of inner magnets123bhoused in the inner ends in the circumferential direction in each pair121P of the magnet slots121as shown inFIG.3andFIG.4. The main magnet122and the inner magnet123bhoused in the same magnet slot121are magnetized in the same direction.

With such a configuration, the motors100according to the first embodiment and Modification 1 can increase a magnet amount and increase a magnetic torque while suppressing an increase in the physical size of the motor by replacing the resin mold with the inner magnet123bthat is the bonded magnet.

In addition, in the motors100according to the first embodiment and Modification 1 to Modification 3, each magnet slot121includes the extended portions121aat its opposite ends in the circumferential direction, and the auxiliary magnets123that are bonded magnets are housed in at least part of the extended portions121aas shown inFIG.3toFIG.6.

With such a configuration, the motors100according to the first embodiment and Modification 1 to Modification 3 can fill the bonded magnets into the spaces of the extended portions121aor replace the resin mold to be filled into the extended portion121awith the bonded magnet. This can increase a magnetic torque while suppressing an increase in the physical size of the motor100. In addition, since an uncured bonded magnet can be filled into the extended portion121a, the auxiliary magnet123can be housed, without a gap, in the extended portion121ahaving a complex shape.

As described above, according to the present embodiment and its modifications, it is possible to provide the motor100capable of increasing a torque while suppressing an increase in the physical size of the motor.

Second Embodiment

Hereinafter, with reference toFIG.10toFIG.14and also toFIG.1andFIG.2, a second embodiment of the motor according to the present disclosure will be described. The motor100of the present embodiment is different from the motor100according to Modification 3 of the foregoing first embodiment shown inFIG.6mainly in that the auxiliary magnet123is not a bonded magnet. Since the other configurations of the motor100of the present embodiment are equal to those of the motor100according to Modification 3 of the foregoing first embodiment, like reference numerals designate like parts to omit their redundant explanations.

FIG.10is an enlarged view of the rotor120of the motor100according to the second embodiment, corresponding toFIG.3illustrating the foregoing first embodiment.FIG.11andFIG.12are enlarged views of the rotors120of the motors100according to Modification 1 and Modification 2 of the second embodiment shown inFIG.10, respectively.FIG.13is an enlarged view of the rotor120of the motor according to the comparative example, which is not included in the motor according to the present disclosure.

In the motors100according to the second embodiment and its Modifications 1 and 2 shown inFIG.10toFIG.12and the motor according to the comparative example shown inFIG.13, the auxiliary magnets123are not bonded magnets, but, for example, sintered magnets like the main magnets122. Therefore, these motors100do not satisfy the first condition that the main magnets122are sintered magnets and the auxiliary magnets123are bonded magnets.

Meanwhile, the motor100according to the second embodiment and the motors100according to Modification 1 and Modification 2 of the second embodiment shown inFIG.10toFIG.12satisfy the second condition. The second condition is that the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle θ1, θ2, or θ3. More specifically, the acute angles θ1, θ2, and θ3shown inFIG.10toFIG.12are, for example, 10°, 20°, and 30°, respectively.

In contrast, the motor according to the comparative example shown inFIG.13satisfies neither the first condition nor the second condition. More specifically, in the motor according to the comparative example shown inFIG.13, the main magnet122and the outer magnet123ahoused in the same magnet slot121are magnetized in the same direction, and the angle defined by the magnetization directions of the main magnet122and the outer magnet123ais 0°.

In addition, in the motors100according to the second embodiment and its Modifications 1 and 2 shown inFIG.10toFIG.12and the motor according to the comparative example shown inFIG.13, the auxiliary magnets123include the outer magnets123aand the inner magnets123b. Here, in these motors, the main magnet122and the inner magnet123bhoused in the same magnet slot121are magnetized in the same direction. It should be noted that these motors100may not include the inner magnet123b.

FIG.14is a graph showing an example of the relation between the angle θ defined by the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121and a standardized average torque of the motor. As shown inFIG.14, the motors100according to the second embodiment and its Modifications 1 and 2, in which the magnetization directions of the main magnet122and the outer magnet123ahoused in the same magnet slot121intersect outside in the radial direction so as to define an acute angle) (0°<θ<90°, have a higher average torque than that of the motor according to the comparative example (θ=0°).

Therefore, according to the motors100according to the second embodiment and its Modifications 1 and 2, satisfying the second condition can increase a torque while suppressing an increase in the physical size of the motor as compared to the motor according to the comparative example which does not satisfy the second condition.

Although the embodiments of the motors according to the present disclosure have been described in detail above with reference to the drawings, specific structures are not limited thereto, and any design changes that fall within the spirit and scope of the present disclosure are encompassed by the scope of the present disclosure.

DESCRIPTION OF SYMBOLS

100Motor120Rotor130Stator121Magnet slot121aExtended portion121P Pair of magnet slots122Main magnet122P Pair of main magnets123Auxiliary magnet123aOuter magnet123bInner magnetθ Acute angleθ1Acute angleθ2Acute angleθ3Acute angle