Rotor for rotary electric machine

A rotor (1) for a rotary electric machine includes a rotor core (2) including a first core portion (20) having a plurality of core pieces (5, 6) joined together through caulking portions (2a) and a hollow first lightening portion (20a), and a second core portion (21) having a plurality of core pieces (7, 8) joined together through caulking portions (2a) and a press-fit portion (21b). A radial magnetic path width of a ring-shaped outer circumferential portion formed by laminating the first core portion (20) and the second core portion (21) changes along a circumferential direction of the rotor core (2). Therefore, a weight and an inertia can be reduced.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a National Stage of International Application No. PCT/JP2013/078582, filed Oct. 22, 2013, the contents of which are incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a rotor for a rotary electric machine, including a rotor core on which a plurality of permanent magnets are arranged, which are each extended in an axial direction of the rotor core and are fixed along a circumferential direction of the rotor core.

BACKGROUND ART

In recent years, a lightweight low-inertia motor is demanded for various purposes of use.

For example, focusing on a motor for an electric power steering device to be mounted in a vehicle, a higher torque, a lighter weight, and a lower inertia are strongly demanded.

The higher torque is demanded for the purpose of employing the electric power steering device for a large-sized vehicle, the lighter weight is for the purpose of improving fuel efficiency of an automobile, and the lower inertia is for the purpose of improving steering responsiveness.

A high-torque motor has an increased motor body size. Along with this, a weight and an inertia of a rotor also increase.

To cope with this, as a rotor including permanent magnets firmly fixed to an outer circumferential surface of a rotor core, there is known a rotor including lightening portions formed in portions except for an outer circumferential portion that is held in contact with the permanent magnets to reduce the weight and the inertia of the rotor so as to improve the responsiveness (see, for example, Patent Literature 1).

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, although the lightening portions are formed in the rotor core so that a dimension of a magnetic path width (in a radial direction of the rotor core) of the outer circumferential portion of the rotor core, which is held in contact with the permanent magnets, becomes uniform along a circumferential direction of the rotor core, the rotor having the configuration described above has a problem of insufficient reduction in weight and inertia.

The present invention has been made to solve the problem described above, and therefore has an object to provide a rotor for a rotary electric machine, which is capable of further reducing a weight and an inertia.

Solution to Problem

According to one embodiment of the present invention, there is provided a rotor for a rotary electric machine, including:

a shaft;

a rotor core through which the shaft passes, for rotating integrally with the shaft; and

a plurality of permanent magnets, each being extended in an axial direction of the rotor core and being fixed to the rotor core along a circumferential direction of the rotor core,

in which the rotor core includes:a first core portion including a plurality of core pieces joined together through caulking portions, and a hollow first lightening portion separated away from the shaft in a radial direction of the rotor core; anda second core portion including a plurality of core pieces joined together through caulking portions, and a press-fit portion held in close contact with the first core portion, into which the shaft is press-fitted, and

in which a radial width of a magnetic path of a ring-shaped outer circumferential portion formed by laminating the first core portion and the second core portion changes along the circumferential direction.

Advantageous Effects of Invention

According to the rotor for a rotary electric machine of the one embodiment of the present invention, the radial magnetic path width of the outer circumferential portion changes along the circumferential direction. Therefore, the weight and the inertia can be reduced.

DESCRIPTION OF EMBODIMENTS

Now, embodiments of the present invention are described referring to the drawings. In each of the drawings, the same or corresponding components and parts are denoted by the same reference symbols for description.

First Embodiment

FIG. 1is a front view of a rotor1for a motor according to a first embodiment of the present invention,FIG. 2is a side sectional view ofFIG. 1,FIG. 3is a sectional view taken along the line III-III ofFIG. 2, andFIG. 4is a sectional view taken along the line IV-IV ofFIG. 2.

The rotor1includes a shaft3, a rotor core2fixed to the shaft3so as to be rotatable integrally therewith, and a plurality of permanent magnets4which are each extended in an axial direction of the rotor core2and are fixed equiangularly to an outer circumferential surface of the rotor core2.

The rotor core2includes a pair of cover pieces9each being formed of a thin steel plate and having a doughnut-like shape, and first core portions20and second core portions21alternately arranged in a portion between the pair of cover pieces9.

Each of the first core portions20is formed by alternately laminating first core pieces5each formed of a thin steel plate illustrated inFIG. 5, and second core pieces6each formed of a thin steel plate illustrated inFIG. 6.

Each of the first core portions20has a hollow first lightening portion20aso as to be separated away from the shaft3in a radial direction of the rotor core2. Each of the second core portions21has a press-fit portion21binto which the shaft3is press-fitted and a plurality of second lightening portions21aformed equiangularly around the press-fit portion21b.

Each of the first core pieces5and each of the second core pieces6respectively have a lightening hole5aand a lightening hole6aeach formed to have an inner diameter sufficiently larger than an outer diameter D3of the shaft3, caulking portions2aformed equiangularly at five positions, and a ring-shaped outer circumferential piece portion5band a ring-shaped outer circumferential piece portion6bformed at outer circumferential portions.

The lightening holes5aand6aare components of the first lightening portion20a.

The first core piece5has an outer diameter dimension D5afor the lightening hole5a, a minimum dimension W5aand a maximum dimension W5bfor a magnetic path width (in the radial direction) of the outer circumferential piece portion5bhaving a regular decagonal shape, and a dimension D2between a center of the first core piece5and each of the caulking portions2a.

The second core piece6has an outer diameter dimension D6afor the lightening hole6a, a minimum dimension W6aand a maximum dimension W6bfor a magnetic path width (in the radial direction) of the outer circumferential piece portion6bhaving a regular decagonal shape, and a dimension D2between the center of the second core piece6and each of the caulking portions2a.

The magnetic path width of the outer circumferential piece portion5bof the first core piece5is smaller over an entire circumference than the magnetic path width of the outer circumferential piece portion6bof the second core piece6. Therefore, the minimum dimension W5aand the maximum dimension W5bof the magnetic path width of the outer circumferential piece portion5bof the first core piece5are smaller throughout the circumference than the minimum dimension W6aand the maximum dimension W6bof the magnetic path width of the outer circumferential piece portion6bof the second core piece6.

Each of the second core portions21is formed by alternately laminating first core pieces7each formed of a thin steel plate illustrated inFIG. 7, and second core pieces8each formed of a thin steel plate illustrated inFIG. 8.

Each of the first core pieces7and each of the second core pieces8respectively have a press-fit piece portion7cand a press-fit piece portion8ceach having the same diameter as the outer diameter D3of the shaft3, into which the shaft3is press-fitted, and caulking portions2aformed equiangularly at five positions.

Further, the first core piece7and the second core piece8respectively have lightening holes7aand lightening holes8awhich each have a polygonal shape and are formed equiangularly, and a ring-shaped outer circumferential piece portion7band a ring-shaped outer circumferential piece portion8bformed at outer circumferential portions.

The lightening holes7aand8aare components of the second lightening portion21a, whereas the press-fit piece portions7cand8care components of the press-fit portion21b.

The first core piece7has a dimension D7abetween outer circumferential sides of the pair of opposing lightening holes7a, a minimum dimension W7aand a maximum dimension W7bfor a magnetic path width (in the radial direction) of the outer circumferential piece portion7bhaving a regular decagonal shape, and a distance D2between a center of the first core piece7and each of the caulking portions2a.

The second core piece8has a dimension D8abetween outer circumferential sides of the pair of opposing lightening holes8a, a minimum dimension W8aand a maximum dimension W8bfor a magnetic path width (in the radial direction) of the outer circumferential piece portion8bhaving a regular decagonal shape, and a distance D2between the center of the second core piece8and each of the caulking portions2a.

The magnetic path width of the outer circumferential piece portion7bof the first core piece7is smaller over an entire circumference than the magnetic path width of the outer circumferential piece portion8bof the second core piece8. Therefore, the minimum dimension W7aand the maximum dimension W7bof the magnetic path width of the outer circumferential piece portion7bof the first core piece7are smaller throughout the circumference than the minimum dimension W8aand the maximum dimension W8bof the magnetic path width of the outer circumferential piece portion8bof the second core piece8.

The outer circumferential piece portions7band8bof the second core portion21and the outer circumferential piece portions5band6bof the first core portion20have the same outer circumferential shape, and are components of the outer circumferential portion of the rotor core2.

In the first core portion20, the first core pieces5and the second core pieces6are alternately laminated by the caulking portions2alocated at the distance D2from the center of the first core portion20. In the second core portion21, the first core pieces7and the second core pieces8are alternately laminated by the caulking portions2alocated at the distance D2from the center.

The caulking portions2aof the first core portion20are formed in inner projecting portions of the outer circumferential piece portions5band6b, whereas the caulking portions2aof the second core portion21are formed in connecting portions between the outer circumferential piece portion7band the press-fit piece portion7cand connecting portions between the outer circumferential piece portion8band the press-fit piece portion8cso as to be formed coaxially with the caulking portions2aof the first core portion20.

In the rotor core2, after the first core portions20and the second core portions21are laminated alternately, both sides of the rotor core2are covered with the cover pieces9.

The rotor core2has an inner circumferential wall surface having a convex and concave shape along the axial direction and an outer circumferential surface having a regular decagonal shape. On each part of the outer circumferential surface, the permanent magnet4is fixed.

At a portion immediately below the permanent magnet4, the magnetic path widths of the core pieces5,6,7, and8respectively have the dimensions W5a, W6a, W7a, and W8a. At a portion between the adjacent permanent magnets4, that is, at a corner of each part of the outer circumferential surface of the rotor core2, the magnetic path widths of the core pieces5,6,7, and8respectively have the dimensions W5b, W6b, W7b, and W8b. The magnetic path widths of the core pieces5,6,7, and8in the portion between the adjacent permanent magnets4are larger than those in the portion immediately below the permanent magnet4.

Note that, each of the permanent magnets4has a width dimension W4(in the circumferential direction) and a thickness dimension T4(in the radial direction).

The thickness dimension T4of each of the permanent magnets4, the width dimension W4of each of the permanent magnets4, and the sizes W5aand W5bof the magnetic path width of the first core piece5of the first core portion20have a relationship of W5a<T4<W5b<W4.

The thickness dimension T4of each of the permanent magnets4, the width dimension W4of each of the permanent magnets4, and the sizes W6aand W6bof the magnetic path width of the second core piece6of the first core portion20have a relationship of W6a<T4<W6b<W4.

The thickness dimension T4of each of the permanent magnets4, the width dimension W4of each of the permanent magnets4, and the sizes W7aand W7bof the magnetic path width of the first core piece7of the second core portion21have a relationship of W7a<T4<W7b<W4.

The thickness dimension T4of each of the permanent magnets4, the width dimension W4of each of the permanent magnets4, and the sizes W8aand W8bof the magnetic path width of the second core piece8of the second core portion21have a relationship of W8a<T4<W8b<W4.

According to the rotor1configured as described above, in the first core portion20, by laminating the first core pieces5each having the lightening hole5a, and the second core pieces6each having the lightening hole6a, the first lightening portion20ais formed.

Therefore, the rotor1is reduced in inertia and weight, which enables the improvement of responsiveness of the motor and the reduction in weight of the motor.

Further, the rotor core2having the surface onto which the permanent magnets4are fixed is press-fitted over the shaft3. The lightening hole5aof each of the first core pieces5and the lightening hole6aof each of the second core pieces6are set to have the dimensions sufficiently larger than the dimension D3of the shaft3. Therefore, the press-fit portions21bof the second core portions21and the cover pieces9are press-fitted over and fixed to the shaft3, whereas the first core portions20are not press-fitted over and fixed to the shaft3.

Therefore, the total number of core pieces to be press-fitted and fixed is reduced. As a result, a press-fitting force at the time of press-fitting the shaft3into the rotor core2is reduced to suppress deformation, bending, and axial center runout of the shaft3. Accordingly, the rotor1with high accuracy can be obtained.

Further, the lightening holes7aand8aare respectively formed in each of the first core pieces7and each of the second core pieces8of the second core portion21to be press-fitted over the shaft3. Therefore, the inertia and the weight of the rotor1can be reduced.

Further, the rotor core2includes the cover pieces9and the second core portions21each having the press-fit portion21bon both sides thereof. Therefore, a tilt of the rotor core2to be press-fitted over the shaft3at the time of the press-fitting is corrected. As a result, the rotor1with high accuracy, in which the axial core runout of the shaft3and the rotor core2is suppressed, can be obtained.

In the first core portion20, the magnetic path widths of the outer circumferential piece portion5bof the first core piece5and the outer circumferential piece portion6bof the second core piece6respectively have the dimensions W5aand W6ain the vicinity of a portion on a pole center line of each of the permanent magnets4and the dimensions W5band W6bin the vicinity of an inter-pole portion of the permanent magnets4. Therefore, the magnetic path widths have different values along the circumferential direction.

Each of the permanent magnets4has a smaller magnetic flux density in the vicinity of the portion on the pole center line. Therefore, the portions of the first core portion20corresponding to the above-mentioned portions of the permanent magnets4can be set to have the small dimensions W5aand W6a. Specifically, the lightening hole5aof the first core piece5and the lightening hole6aof the second core piece6can be radially enlarged, and the rotor1can be correspondingly reduced in weight and inertia.

Note that, the outer circumferential piece portion5bof the first core piece5and the outer circumferential piece portion6bof the second core piece6of the first core portion20have a large magnetic flux density in the portions between the adjacent permanent magnets4, and the dimensions W5band W6bthereof are set larger than the dimensions W5aand W6awithin a range in which magnetic saturation does not occur. In this manner, increase in cogging torque is suppressed.

Similarly to the above, also in the second core portion21, the outer circumferential piece portion7bof the first core piece7and the outer circumferential piece portion8bof the second core piece8have a large magnetic flux density in the portions between the adjacent permanent magnets4, and the dimensions W7band W8bthereof are set larger than the dimensions W7aand W8awithin a range in which magnetic saturation does not occur. In this manner, the increase in cogging torque is suppressed.

A relationship of the dimensions W5aand W5bof the magnetic path width of the outer circumferential piece portion5bof the first core piece5, a relationship of the dimensions W6aand W6bof the outer circumferential piece portion6bof the second core piece6, a relationship of the dimensions W7aand W7bof the outer circumferential piece portion7bof the first core piece7, and a relationship of the dimensions W8aand W8bof the magnetic path width of the outer circumferential piece portion8bof the second core piece8with respect to the width dimension W4of each of the permanent magnets4are set to W5a<(½)·W4<W5b<W4, W6a<(½)·W4<W6b<W4, W7a<(½)·W4<W7b<W4, and W8a<(½)·W4<W8b<W4, respectively.

As described above, the width dimension W4of each of the permanent magnets4is larger than any of the dimensions of the magnetic path widths of the first core piece5and the second core piece6of the first core portion20and the first core piece7and the second core piece8of the second core portion21.

The reason is as follows. The magnetic flux generated from each of the permanent magnets4is split into two directions toward two permanent magnets4adjacent thereto in the circumferential direction. Therefore, the magnetic flux density in the outer circumferential portion of the rotor core2at a portion between the permanent magnets4becomes smaller than that inside the permanent magnets4. Therefore, the dimensions W5b, W6b, W7b, and W8bof the magnetic path widths of the outer circumferential piece portion5b,6b,7b,8bcan be set smaller than the width dimension W4of each of the permanent magnets4. As a result, for the dimensions W5a, W6a, W7a, and W8aof the magnetic path widths in the vicinity of the center of each of the permanent magnets4where the magnetic flux density is smaller than that in the portion between the adjacent permanent magnets4, the magnetic path widths can be further reduced.

By setting the magnetic path widths W5b, W6b, W7b, and W8bat the portion between the permanent magnets4larger than (½)·W4to avoid the magnetic saturation, the increase in cogging torque can be suppressed.

Further, the lightening holes7aand8acan be enlarged to appropriate sizes. Therefore, the weight and the inertia can be reduced.

Further, the lightening holes7aof the first core piece7and the lightening holes8aof the second core piece8of the second core portion21are formed equiangularly so that each of the numbers thereof is the same as the number of poles of the permanent magnets4(ten in this embodiment).

Therefore, the magnetic flux in the outer circumferential portion of the rotor core2has a distribution regularly changed at each predetermined angle. Therefore, the cogging torque can be reduced.

Further, each of the magnetic path widths of the outer circumferential piece portion5bof the first core piece5and the outer circumferential piece portion6bof the second core piece6of the first core portion20and the magnetic path widths of the outer circumferential piece portion7bof the first core piece7and the outer circumferential piece portion8bof the second core piece8of the second core portion21is set to be different at each predetermined angle for the number of the poles of the permanent magnets4. The magnetic flux in the outer circumferential portion of the rotor core2has a distribution regularly changed at each predetermined angle. Therefore, the cogging torque can be reduced.

Further, in the first core portion20, the first core pieces5and the second core pieces6are arranged so as to be alternately laminated one by one in the axial direction. Further, the magnetic path width of the outer circumferential piece portion5bof the first core piece5is smaller over the entire circumference than the magnetic path width of the outer circumferential piece portion6bof the second core piece6.

Therefore, the first core portion20has the concave and convex shape along the axial direction and alternately different inner-diameter dimensions. By arranging the first core pieces5each having the smaller magnetic path width of the outer circumferential piece portion5b, the first core portion20can be reduced in weight. Further, by arranging the second core pieces6each having the larger magnetic path width of the outer circumferential piece portion6b, the magnetic path that is insufficient only with the arrangement of the first core pieces5is compensated for. As a result, the increase in cogging torque due to magnetic saturation can be prevented.

The same effects can be obtained even when a set of a plurality of the core pieces5and a set of a plurality of the core pieces6are laminated instead of the arrangement in a one-by-one manner.

Further, also in the second core portion21, the first core pieces7and the second core pieces8are arranged so as to be alternately laminated one by one in the axial direction. Further, the magnetic path width of the outer circumferential piece portion7bof the first core piece7is smaller over the entire circumference than the magnetic path width of the outer circumferential piece portion8bof the second core piece8.

Therefore, the second core portion21has the concave and convex shape along the axial direction and alternately different inner-diameter dimensions. By arranging the first core pieces7each having the smaller magnetic path width of the outer circumferential piece portion7b, the second core portion21can be reduced in weight. Further, by arranging the second core pieces8each having the larger magnetic path width of the outer circumferential piece portion8b, the magnetic path that is insufficient only with the arrangement of the first core pieces7is compensated for. As a result, the increase in cogging torque due to magnetic saturation can be prevented.

The same effects can be obtained even when a set of a plurality of the core pieces7and a set of a plurality of the core pieces8are laminated instead of the arrangement in a one-by-one manner.

Further, the rotor core2includes the cover pieces9on both sides, for covering the interior. Therefore, scrap metal that is generated due to bite occurring when the rotor core2covered with the cover pieces9is press-fitted over the shaft3and internally adhering scrap can be kept inside the rotor core2. In this manner, the scrap generated inside the rotor core2can be prevented from being caught in a clearance between the rotor1and a stator (not shown).

The caulking portions2aare formed in portions of the core pieces5,6,7, and8, which are located between the permanent magnets4and where the magnetic path width of the outer circumferential portion of the rotor core2is large.

In this manner, the lightening holes5a,6a,7a, and8aof the core pieces5,6,7, and8, which are located at the portions immediately below the permanent magnets4where the magnetic flux density is smaller can be increased without being disturbed by the caulking portions2a. Therefore, the inertia and the weight of the rotor1can be reduced.

Further, when the distance between each of the caulking portions2aof the rotor core2and the center of the rotor core2is defined as D2, the inner-diameter dimension of the press-fit portion21bof the second core portion21(radial dimension of the shaft3) is defined as D3, the radial dimension of the lightening hole5aof the first core piece5is defined as D5a, the radial dimension of the lightening hole6aof the second core piece6is defined as D6a, the largest distance between the pair of opposing lightening holes7aof the first core piece7is defined as D7a, and the largest distance between the pair of opposing lightening holes8aof the second core piece8is defined as D8a, a value of D2is larger than a half value of D3but is smaller than a value of half of each of the other dimensions D5a, D6a, D7a, and D8a.

In this manner, the caulking portions2aare arranged so as not to be present in the outer circumferential portion of the rotor2, that is, so as not to interfere with the magnetic path. As a result, the magnetic flux distribution is uniformized over the entire rotor core2to reduce the cogging torque.

Second Embodiment

FIG. 9is a front view of a rotor1for a motor according to a second embodiment of the present invention, andFIG. 10is a side sectional view ofFIG. 9.

In this embodiment, the shaft3passing through a center axis line of the first lightening portions20aof the first core portions20each being interposed between the second core portions21on both sides is surrounded by rings10through gap portions10atherebetween instead of the cover pieces9. Each of the rings10is interposed between the press-fit portions21bof the pair of second core portions21adjacent to each other.

The rings10serve as a substitute for the cover pieces9of the first embodiment.

The remaining configuration is the same as that of the rotor1of the first embodiment.

According to the rotor1of this embodiment, the scrap metal or the like generated due to bite occurring when the rotor core2is press-fitted over the shaft3can be kept in the gap portions10aof the rings10. In this manner, the scrap metal or the like can be prevented from being caught in the clearance between the rotor1and the stator (not shown).

Further, the rings10can prevent radially inner-side portions of the second core portions21from being deformed in the axial direction along with the press-fitting of the shaft3when the rotor core2is press-fitted over the shaft3by end surfaces that come into contact with the radially inner-side portions. As a result, the rotor1with high accuracy can be obtained.

Third Embodiment

FIG. 11is a front view of a rotor1for a motor according to a third embodiment of the present invention, andFIG. 12is a side sectional view ofFIG. 11.

In this embodiment, the first core portion20is formed by laminating the first core pieces5having the same shape, whereas the second core portion21is formed by laminating the first core pieces7having the same shape. Specifically, the outer circumferential piece portion5bof the first core piece5of the first core portion20and the outer circumferential piece portion7bof the first core piece7of the second core portion21have the same width dimension. Therefore, a magnetic-path width dimension W2of the outer circumferential portion of the rotor core2is the same along the axial direction.

The remaining configuration is the same as that of the rotor1of the second embodiment.

When the permanent magnets4are magnetized by a magnetizing device, the magnetic path width of the outer circumferential portion is narrowed with the reduction of the rotor core2in weight. As a result, magnetic flux passages for the magnetization of the permanent magnets4are narrowed, which requires a larger magnetic field.

On the other hand, according to the rotor1of this embodiment, a bar-like iron core can be smoothly inserted into an inner circumferential portion of the rotor core2for the magnetization of the permanent magnets4. Further, the magnetization of the permanent magnets4is facilitated because of the iron core serving as a magnetic path for the passage of the magnetic flux.

Fourth Embodiment

FIG. 13is a front view of a rotor1for a motor according to a fourth embodiment of the present invention,FIG. 14is a side sectional view ofFIG. 13,FIG. 15is a sectional view taken along the line XV-XV ofFIG. 14, andFIG. 16is a sectional view taken along the line XVI-XVI ofFIG. 15.

In this embodiment, the caulking portions2aare formed in the outer circumferential portion of the rotor core2.

The remaining configuration is the same as that of the rotor1of the first embodiment.

As described above, by forming the caulking portions2ain the magnetic path in the outer circumferential portion of the rotor core2, the rotor1that is reduced in weight and inertia by integrating the outer circumferential portion serving as the magnetic path and the caulking portions2acan be obtained.

Fifth Embodiment

FIG. 17is a front view of a rotor1for a motor according to a fifth embodiment of the present invention,FIG. 18is a side sectional view ofFIG. 17,FIG. 19is a sectional view taken along the line XIX-XIX ofFIG. 18, andFIG. 20is a sectional view taken along the line XX-XX ofFIG. 18.

In this embodiment, the caulking portions2aof the second core portions21are formed in press-fit piece portions7cand8cof the press-fit portions21bof the second core portions21. The caulking portions2aof the first core portions20are formed in the first core pieces5and the second core pieces6on the same axis lines as the caulking portions2aof the second core portions21.

The remaining configuration is the same as that of the rotor1of the first embodiment.

By forming the caulking portions2aof the second core portion21in the press-fit portion21bas described above, the rotor1that is reduced in weight and inertia by integrating the first core pieces7and the second core pieces8through the press-fit portions21bin the second core portion21can be obtained.

Sixth Embodiment

FIG. 21is a front view of a rotor1for a motor according to a sixth embodiment of the present invention, andFIG. 22is a side sectional view ofFIG. 21.

In this embodiment, both sides of the second core portion21interposed between the first core portions20are covered with the cover pieces9.

The remaining configuration is the same as that of the rotor1of the first embodiment.

This rotor1can provide the same effects as those of the rotor of the first embodiment in which the cover pieces9are provided on both sides thereof.

Seventh Embodiment

FIG. 23is a front view of a rotor1for a motor according to a seventh embodiment of the present invention,FIG. 24is a side sectional view ofFIG. 23,FIG. 25is a sectional view taken along the line XXV-XXV ofFIG. 24, andFIG. 26is a sectional view taken along the line XXVI-XXVI ofFIG. 24.

The rotor1of this embodiment is an IPM-type rotor in which the permanent magnets4are embedded.

Although the arrangement of the permanent magnets4is different from that of the rotor1of the first embodiment, the remaining configuration is the same as that of the rotor1of the first embodiment.

Note that, any of the rotors1according to the second to sixth embodiments described above may be applied to the IPM type rotor, and the same effects as those of the rotor1of the first embodiment can be obtained for each rotor.

Eighth Embodiment

FIG. 27is a front view of a rotor1for a motor according to an eighth embodiment of the present invention,FIG. 28is a side sectional view ofFIG. 27,FIG. 29is a sectional view taken along the line XXIX-XXIX ofFIG. 28, andFIG. 30is a sectional view taken along the line XXX-XXX ofFIG. 28.

The rotor1of this embodiment is a consequent-pole rotor in which the N-poles of the permanent magnets4are all oriented outward.

The rotor of this embodiment also has the same configuration as that of the rotor1of the first embodiment.

Note that, any of the rotors1according to the second to sixth embodiments described above may be applied to the consequent-pole rotor, and the same effects as those of the rotor1of the first embodiment can be obtained for each rotor.

Note that, although the rotor1for a motor is described as the rotor for a rotary electric machine in each of the embodiments described above, the present invention is also applicable to a rotor for a power generator. In this case, the effects of improving power generation efficiency can be obtained by reducing the weight and the inertia.

REFERENCE SIGNS LIST