Patent Application
20140132092
1. Field of the Invention
The present invention relates to a rotating electrical machine, such as a small electric motor and generator.
2. Description of the Related Art
In the market, there has been a strong demand for miniaturization and thinning of rotating electrical machines which are small-sized to medium-sized electric motors or generators having output power of about 1 kW or less. Further, in recent years, high-efficiency and energy-saving electric motors have been required as a global warming countermeasure. Also, in generators, as a result of reviewing the use of natural energy as an alternative of nuclear power, the demand for a small wind power generator for home use has also been growing. In the case of wind power generation, the rotational speed of a wind turbine is low, and hence the rotational speed is increased by gears, and the like, so as to rotate a generator. Further, lower cost is also strongly demanded from the market. Therefore, for use in such applications, multipolar permanent magnet type generators have been attracting attention. One of the forms of such rotating electrical machines is a hybrid-type stepping motor (hereinafter abbreviated as HBSTM). Also, the demand for HBSTMs has been increasing because of its original function of facilitating the positioning control, and because of its use as a so-called direct drive motor which is a multi-pole synchronous motor (of about 100 poles) having low speed and high torque characteristics and which can eliminate the use of a mechanical moderator by taking advantage of the characteristics. However, further improvements in torque and efficiency have been required because of the above-described reasons.
The rotating electrical machine is classified into a radial gap type rotating electrical machine and an axial gap type rotating electrical machine. The radial gap type rotating electrical machine has been widely used as a general purpose machine because of the advantages that the size of air gap can be reduced, and that the area facing the air gap can be increased in the rotary shaft direction of the rotating electrical machine. Further, the axial gap type rotating electrical machine, which is formed to have a thin shape, is advantageous for obtaining higher output power as compared with the radial gap type rotating electrical machine. Therefore, the axial gap type rotating electrical machine has been used in applications and fields in which a rotating electrical machine having a special shape is required. However, because of the above-described reasons, further improvements in torque and efficiency have been required for both the radial gap type rotating electrical machine and the axial gap type rotating electrical machine.
Rotating electrical machines are disclosed, for example, in “Method for Using Stepping Motor” (written by Masafumi Sakamoto, published by Ohmsha, Ltd.) p 44, FIG. 2.32.
In order to improve torque and efficiency characteristics of an HBSTM, it is effective to reduce the air gap g between the stator and the rotor or to increase the facing area S between the stator teeth and rotor teeth. The permeance P of the air gap between the stator teeth and rotor teeth is expressed by the following expression (1) in which μ0 is permeability of vacuum.
P=μ
0
S/g (1)
That is, torque and efficiency characteristics of HBSTMs can be improved by increasing the permeance P. However, in the case of HBSTMs, the air gap g is already as small as about 0.05 mm, and hence it is difficult to further reduce the air gap g.
As a device for further reducing the air gap g of HBSTMs, there is an inner spigot structure of a rotating electrical machine, as illustrated in the right figure of FIG. 2.32 of “Method for Using Stepping Motor” described above. The structure shown in this figure adopts a structure, referred to as an “inner spigot” structure, in which a part of each of front and rear brackets is not fitted into a part of an outer peripheral portion of the stator but is directly fitted into a part of an inner peripheral portion of the stator to guide to secure the air gap. This figure discloses front and rear brackets, a stator configured by a laminated portion of silicon steel sheets and a winding provided at the laminated portion, and a rotor inserted into the stator. In such structure in which the stator is formed by laminating silicon steel sheets, even when the air gap is set to about 0.05 mm, the air gap can be sufficiently secured in mass production. Such structure has been widely adopted for HBSTMs. However, as can be seen from the right figure of FIG. 2.32 of “Method for Using Stepping Motor”, the structure has a problem that, since the length of the rotor in the rotary shaft direction becomes shorter than the lamination length of the stator, the stator cannot be effectively used over the entire lamination length of the stator, and hence the facing area S of the air gap portion is reduced. This results in a problem that the permeance P expressed by expression (1) is not increased so much.
The present invention is realized by the following devices. Note that the components for realizing the following devices are respectively denoted by reference numerals for reference purposes, but are not limited to these denoted by the reference numerals.
“Device 1”
A rotating electrical machine including a stator (100), a rotor (200), and a rotary shaft (10), the rotating electrical machine being realized by a device wherein:
the stator (100) is provided with a stator core (1) including an annular yoke portion (110) and n winding poles (120) radially extending from the annular yoke portion (110), and a winding (4) concentrically wound around each of the winding poles (120);
a winding axis of the winding (4) is perpendicular to the rotary shaft (10);
the stator core (1) is divided into two portions each having a thickness substantially half the thickness of the stator core (1) in a rotary shaft direction, and is also circumferentially divided into n portions each including each of the winding poles (120);
each of the n winding poles (120) includes, at a distal end portion (121) thereof, a circumference portion (122) having small teeth substantially in parallel with the rotary shaft, and an end surface portion (123) having small teeth substantially perpendicular to the rotary shaft;
the rotor (200) includes a permanent magnet (8) magnetized in the rotary shaft direction, and two rotor cores (7) holding the permanent magnet therebetween;
the rotor core (7) includes a circumference portion (72) having small teeth substantially in parallel with the rotary shaft (10), and an end surface portion (73) having small teeth substantially perpendicular to the rotary shaft;
the circumference portion (122) of the winding pole (120) in the stator (100) and the circumference portion (72) of the rotor core (7) in the rotor (200) face each other via an air gap to provide a radial gap, and the end surface portion (123) of the winding pole (120) in the stator (100) and the end surface portion (73) of the rotor core (7) in the rotor (200) face each other via an air gap to provide an axial gap; and
n is an integer of 2 or more.
“Device 2”
The rotating electrical machine as described in “device 1”, the rotating electrical machine being realized by a device wherein:
brackets (5, 6) and bearings (9) are provided on an outer side of the rotor (200) in the rotary shaft direction; and
in a state where the stator core (1) is divided into n portions, the winding (4) is concentrically wound around each of the winding poles (120), and the divided portions of the stator core (1) are combined and assembled with each other by being inserted from the outer side in the direction perpendicular to the rotary shaft by using the brackets (5, 6) and the bearings (9) as guides.
“Device 3”
A rotating electrical machine including a stator (300), a rotor (200), and a rotary shaft (10), the rotating electrical machine being realized by a device wherein:
the stator (300) includes a stator core (14) provided with an annular yoke portion (15) and n winding poles (120) radially extending in a state of being in contact with an inner circumference of the annular yoke portion (15), and a winding (4) concentrically wound around each of the winding poles (120);
a winding axis of the winding (4) is perpendicular to the rotary shaft (10);
the stator core (14) is divided, except the annular yoke portion (15), into two portions each having a thickness substantially half the thickness of the stator core (14) in a rotary shaft direction and is also circumferentially divided into n portions each including each of the winding poles (120);
each of the n winding poles (120) includes, at a distal end portion (121) thereof, a circumference portion (122) having small teeth substantially in parallel with the rotary shaft, and an end surface portion (123) having small teeth substantially perpendicular to the rotary shaft;
the rotor (200) includes a permanent magnet (8) magnetized in the rotary shaft direction, and two rotor cores (7) holding the permanent magnet therebetween;
the rotor core (7) includes a circumference portion (72) having small teeth substantially in parallel with the rotary shaft (10), and an end surface portion (73) having small teeth substantially perpendicular to the rotary shaft;
the circumference portion (122) of the winding pole (120) in the stator (300) and the circumference portion (72) of the rotor core (7) in the rotor (200) face each other via an air gap to provide a radial gap, and the end surface portion (123) of the winding pole (120) in the stator (300) and the end surface portion (73) of the rotor core (7) in the rotor (200) face each other via an air gap to provide an axial gap; and
n is an integer of 2 or more.
“Device 4”
The rotating electrical machine as described in “device 3”, the rotating electrical machine being realized by a device wherein:
brackets (17) and bearings (9) are provided on an outer side of the rotor (200) in the rotary shaft direction; and
in a state where the stator core (14), except the annular yoke portion (15), is divided into n portions, the winding (4) is concentrically wound around each of the winding poles (120), and the divided portions of the stator core (14) are combined and assembled with each other in such a manner that the divided portions are assembled from the outer side in the direction perpendicular to the rotary shaft and the annular yoke portion (15) is successively inserted from the rotary shaft direction by using the brackets (17) and the bearings (9) as guides.
“Device 5”
The rotating electrical machine as described in one of “device 1” to “device 4”, the rotating electrical machine being realized by a device wherein:
a rotary-shaft-direction thickness of a groove for winding in each of the winding poles (120) of the stator (100, 300) is reduced from a center toward an outer side of the stator (100, 300).
“Device 6”
A rotating electrical machine including a stator (400), a rotor (200), and a rotary shaft (10), the rotating electrical machine being realized by a device wherein:
the stator (400) is provided with two stator cores (18) each including a disk-like yoke portion (410) and n winding poles (420) extending from the disk-like yoke portion (410) in parallel with the rotary shaft (10), and a winding (19) concentrically wound around each of the winding poles (420), and is configured by combining the two stator cores (18) with each other in a state where the winding poles (420) face each other in a rotary shaft direction;
a winding axis of the winding (19) is in parallel with the rotary shaft (10);
each of the two stator cores (18) has a thickness substantially half the thickness of the stator (400) in the rotary shaft direction;
each of the n winding poles (420) includes, at a distal end portion (120) thereof, a circumference portion (422) having small teeth substantially in parallel with the rotary shaft (10), and an end surface portion (423) having small teeth substantially perpendicular to the rotary shaft (10);
the rotor (200) includes a permanent magnet (8) magnetized in the rotary shaft direction, and two rotor cores (7) holding the permanent magnet (8) therebetween;
the rotor core (7) includes a circumference portion (72) having small teeth substantially in parallel with the rotary shaft (10), and an end surface portion (73) having small teeth substantially perpendicular to the rotary shaft;
the circumference portion (122) of the winding pole (420) in the stator (400) and the circumference portion (72) of the rotor core (7) in the rotor (200) face each other via an air gap to provide a radial gap, and the end surface portion (123) of the winding pole (420) in the stator (400) and the end surface portion (73) of the rotor core (7) in the rotor (200) face each other via an air gap to provide an axial gap; and
n is an integer of 2 or more.
“Device 7”
The rotating electrical machine as described in one of “device 1” to “device 6”, the rotating electrical machine being realized by a device wherein:
the stator core (1, 14, 18) is configured by a dust core or a sintered core.
“Device 8”
The rotating electrical machine as described in one of “device 1” to “device 7”, the rotating electrical machine being realized by a device wherein:
the rotor core (7) is configured by a dust core or a sintered core.
“Device 9”
The rotating electrical machine as described in one of “device 7” and “device 8”, the rotating electrical machine being realized by a device wherein:
the dust core or the sintered core configuring one of or both of the stator core (1, 14, 18) and the rotor core (7) is subjected to one of or both of resin coating treatment and resin impregnation treatment.
(1) A portion facing an air gap is provided at the axial gap portion in addition to the radial gap portion. Therefore, even when, due to the elimination of the inner spigot structure, the air gap length is slightly increased as compared with the prior art, the increase in the area of the portion facing the air gap is much larger, and hence the torque can be significantly increased.
(2) The rotary-shaft-direction thickness of the groove portion of the core of the winding portion is reduced from the center toward the outer side of the stator core, so that the space factor of the winding can be further increased, and hence the efficiency of the rotating electrical machine can be improved.
(3) The stator is configured by split cores, so that the winding space factor can be significantly improved, and hence higher torque can be obtained.
(4) A dust core is used, and thereby it is possible to obtain a highly efficient rotating electrical machine which has almost no eddy current loss and in which in particular, the iron loss at the time of high speed rotation is small.
(5) In the case of the present invention in which the winding axis is set in parallel with the rotary shaft direction, the outer diameter of the permanent magnet can be increased, and hence the interlinkage magnetic flux can be increased, which is advantageous for obtaining higher torque.
In the following, embodiments according to the present invention will be described with reference to the accompanying drawings.
In
Reference numeral 3 denotes an insulator, such as resin. Each of reference numerals 5 and 6 denotes a bracket made of an aluminum material, or the like, and serves to secure the air gap between the rotor core 7 and the stator core 1 via a bearing 9. Each of the brackets 5 and 6 is provided with a cylindrical portion formed concentrically to an inner diameter portion into which the bearing 9 is fitted. The outer diameter portion of the cylindrical portion of each of the brackets 5 and 6 is fitted with the inner diameter portion of a flange-like guide portion denoted by reference numeral 2, so that the air gap is secured. Reference numeral 8 denotes the permanent magnet, such as a neodymium magnet, magnetized in the rotary shaft direction. In the conventional HBSTM, the magnetic field of the permanent magnet in the rotary shaft direction is bent into the direction perpendicular to the rotary shaft direction, so as to pass through the air gap in the radial direction. In this way, in the HBST, the permanent magnet is magnetized in the rotary shaft direction, and hence the magnetic flux of the permanent magnet easily leaks in the rotary shaft direction. The present invention is featured in that the magnetic field in the rotary shaft direction is also effectively utilized. Reference numeral 10 denotes the rotary shaft. Reference numeral 11 denotes a bolt. The brackets 5 and 6 are tightened and fixed to each other by the bolts 11 so as to hold the stator core 1 therebetween.
(1) The rotor 200 configured by the rotor core 7 and the permanent magnet 8 is fixed to the rotary shaft 10. Then, spacers 12 are arranged on both sides of the rotor 200, and the brackets 5 and 6 are combined with each other so as to sandwich the rotor 200 together with the spacers.
(2) By using the brackets 5 and 6 and the bearings 9 as guides, six sets of two stator cores 1, which are combined back to back with each other in the rotary shaft direction and around which a winding is wound, are radially inserted from the outer side to the inner side so as to reach concentric guides respectively provided on the brackets 5 and 6.
(3) The brackets 5 and 6, and the stator cores 1 are fixed by the bolts 11. Next, the permanent magnet 8 may be magnetized in the rotary shaft direction.
Next, the structure of the rotor core will be described.
When the stator core 1 shown in
The rotor core 7 of the prior art is made by laminating silicon steel sheets, but the rotor core 7 may be formed of a dust core. In the case of the HBSTM, the magnetic flux of the permanent magnet passes through a part of the rotor and of the stator in the rotary shaft direction. Therefore, even when the permeability of compacted powder is lower than the permeability of silicon steel sheet, it can be expected that the interlinkage magnetic flux of the HBSTM is increased in spite of the lower permeability. In particular, the rotor core used in the present invention has teeth in both the radial direction and the axial direction, and hence the teeth can be manufactured more easily and inexpensively in the case where a dust core or a sintered core is used. As described above, in the case of the HBSTM, its characteristics are equivalent to or better than the characteristics in the case where silicon steel sheets are used. Therefore, from the viewpoint of manufacturing and also the viewpoint of characteristics, it is convenient to adopt a dust core or a sintered core for the rotor core of the present invention.
The dust core is manufactured in such a manner that, by mixing soft magnetic iron powder with a small amount of resin as a lubricant or binder, the iron power particles are coated with the resin so that electrical insulation between the iron powder particles is increased to reduce eddy current, and that the mixture is compressed and molded and then sintered. In a rotating electrical machine using the dust core, the core can be formed into a complicated three-dimensional shape, while, in a rotating electrical machine using a core formed by laminating silicon steel sheets, the core has a simple two-dimensional shape. Further, the core formed of the dust core has a characteristic that eddy current loss, which is a part of iron loss, is close to zero. The dust core described above has a disadvantage that the magnetic flux density is lower than that of the core formed by laminating silicon steel sheets. However, the dust core can be made suitable for increasing the efficiency of the rotating electrical machine in such a manner that the dust core is formed into a so-called overhang shape in which the end surface portion of the rotor can be additionally made to face the stator core so as to increase the area in which the stator and the rotor face each other. When the dust core is used, it is possible to easily form the overhang shape, or the like, of the rotating electrical machine, which shape is difficult to be formed by using the method of laminating silicon steel sheets. A sintered core is a metal body which is formed in such a manner that iron powder is pressed and heat-treated at high temperature so that the particles of the iron powder are combined with each other. Unlike the dust core, in the sintered core, the resin binder is not interposed between the particles of the iron powder. Therefore, in the sintered core, the eddy current loss is larger than that of the dust core, but the mechanical strength is larger than that of the dust core. For this reason, the sintered core is used for a rotating electrical machine in which the current frequency and the rotation speed are relatively low. The divided members of the stator core 1 are manufactured by simultaneously compressing and molding the compacted powder using a same mold.
The structure of a stator core 14 according to the present embodiment is the same as the structure shown in
An example of assembly sequence of the structure shown in
(1) A rotor 200 configured by a rotor core 7 and a permanent magnet 8 is fixed to a rotary shaft 10. Then, spacers 12 are arranged on both sides of the rotor 200, and brackets 17 are combined with each other so as to sandwich the rotor 200 together with the spacers.
(2) By using the brackets 17 and bearings 9 as guides, six sets of two stator cores 14, which are combined back to back with each other in the rotary shaft direction and around which the winding 4 is wound, are radially inserted from the outer side to the inner side so as to reach concentric guides respectively provided on the brackets 17.
(3) The annular yoke 15 is fitted to the outer periphery of the stator core 14. While a lead 16 is taken out from the annular yoke 15, the brackets 17 are combined with each other and are fixed to each other with screws (not shown) or the like as required. Next, the permanent magnet 8 may be magnetized in the rotary shaft direction.
Note that the inner rotor type HBSTM is described above with reference to
A rotor core 7, a permanent magnet 8, a bearing 9, a rotary shaft 10, and a spacer 12 of a rotating electrical machine according to the present embodiment are the same as those of the rotating electrical machine of
The embodiment shown in
Note that, when the stator core and the rotor core described above are configured by the dust core, it is preferred that the dust core is subjected to one of or both of resin coating treatment and resin impregnation treatment in order to improve the strength and durability thereof. Here, when the treatment is performed, the specific method of the treatment is not limited in particular, and any method can be adopted as long as the method enables the surface of the dust core to be coated with resin and enables resin to be impregnated into the dust core. Specifically, examples of the treatment include electro-deposition coating, electrostatic coating, dipping, and the like. Note that the resin used here is not limited in particular, and various resin can be suitably selected and used. Further, when the dipping is performed, it is possible to use a generally used dipping liquid which contains liquid adhesive or varnish.
The structure shown in
The rotating electrical machine according to the present invention can be used for an electric motor or generator and is very practical and suitable for obtaining a less expensive, robust, small and light electric motor or generator, high torque and high efficiency. Therefore, it is expected that the present invention will make a great industrial contribution.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
The entire disclosure of Japanese Patent Application No. 2012-250053 filed on Nov. 14, 2012 including the specification, claims, drawings and summary is incorporated herein by reference in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2012-250053 | Nov 2012 | JP | national |
