JP2004159448A - Stator structure of coaxial motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stator structure which lessens iron loss, in a coaxial motor which has three-layer structure. <P>SOLUTION: The coaxial motor has a stator (1), an inner rotor (2) inside the above stator (1), and an outer rotor (3) outside the above stator (1) where the above inner rotor (2) and the above outer rotor (3) rotate around a common rotating shaft (5). The stator (1) is equipped with a plurality of split cores (4) which are arranged cylindrically at equal angle intervals around the rotating shaft (5). Here, each split core (4) is arranged apart from an adjacent split core (4), the internal perimeter (43) of each split core (4) is semicircular, and further the periphery (41) of each split core (4) is semicircular. In each split core, the two side faces (45 and 47) coupled with the periphery and the internal perimeter are constituted of plane surfaces, and besides they are arranged roughly symmetrically about the center face (51) extending in the radial direction of the stator. The iron loss of the rotor and the stator decreases due to the split core in such form. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a motor stator structure in which a plurality of rotors are coaxially arranged on a stator.
[0002]
[Prior art]
JP-A-2000-224836 and JP-A-2000-14103 disclose a coaxial motor in which two rotors and one stator are coaxially arranged in a three-layer structure. In these coaxial motors, the stator has a yoke for passing magnetic flux to an inner rotor disposed inside the stator or an outer rotor disposed outside the stator.
[0003]
[Patent Document 1]
JP 2000-224836 A [Patent Document 2]
Japanese Patent Application Laid-Open No. 2000-14103
[Problems to be solved by the invention]
When the magnetic flux of each of the two rotors passes through the stator, iron loss occurs in the stator in proportion to the magnetic flux density and the magnetic flux frequency. In the case of a structure having a yoke on the stator as in the prior art, the relative permeability at the tip of the yoke changes rapidly from the relative permeability of 1 in the air gap to about 10000 in the steel plate of the yoke. Therefore, there is a problem that the magnetic field changes greatly and iron loss increases.
[0005]
An object of the present invention is to provide a stator structure for reducing iron loss in a coaxial motor having a three-layer structure.
[0006]
[Means for Solving the Problems]
The present invention provides a stator including a plurality of split cores arranged at intervals around a rotation axis and a coil wound on the plurality of split cores, and is arranged coaxially with the stator inside the stator. A coaxial motor having an inner rotor and an outer rotor disposed coaxially with the stator outside the stator, wherein the inner rotor and the outer rotor rotate around a common rotation axis; The core has an inner peripheral surface facing the inner rotor, and a side surface connecting the outer peripheral surface facing the outer rotor is formed of a flat surface, and an interval between adjacent split cores is narrower on the inner rotor side, It is characterized in that the width gradually increases toward the outer rotor side. Preferably, the two side surfaces of the split core are arranged substantially in parallel.
[0007]
[Action / Effect]
According to the present invention, each of the divided cores is arranged at a distance from an adjacent divided core, and a side surface connecting the inner peripheral surface facing the inner rotor and the outer peripheral surface facing the outer rotor is formed as a flat surface. At the same time, the interval between adjacent split cores is narrower on the inner rotor side and gradually increases toward the outer rotor side. Thus, since each of the divided cores does not have a sharp end, iron loss generated in each of the divided cores is reduced. In addition, due to the shape of each of the divided cores, the magnetic fields of the inner and outer rotors pass through the inside of the opposed rotor, and the generated magnetic field and the opposed rotor magnetic field are inside the rotor. A magnetic field of the difference frequency will flow. As a result, the frequency of the iron loss generated in the rotor is also reduced, so that the iron loss in the rotor is also reduced.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0009]
FIG. 1 schematically shows a coaxial motor having the stator structure of the present invention. The coaxial motor has a three-layer structure in which a stator 1, an inner rotor 2 located inside the stator 1, and an outer rotor 3 located outside the stator 1 are coaxially arranged. The stator 1, the inner rotor 2, and the outer rotor 3 all have a substantially cylindrical shape. Stator 1 is sandwiched between inner rotor 2 and outer rotor 3 via an air gap. The case 8 that houses the stator 1, the inner rotor 2, and the outer rotor 3 supports and fixes the stator 1 with a stator support 17. The inner rotor 2 is rotatably supported on the case 8 via a bearing 33, the outer rotor 3 is rotatably supported on the shaft 7 of the inner rotor 2 via a bearing 35, and via a bearing 37. The case 8 is rotatably supported. The three-layer structure of such a coaxial motor is disclosed in detail in JP-A-2000-14103. FIG. 1 is merely an example of a three-layer structure of a coaxial motor, and the method of supporting the stator 1, the inner rotor 2, and the outer rotor 3 may be different from that in FIG.
[0010]
Referring to FIG. 2, a single stator winding including a plurality of coils 9 is formed on stator 1, and the single stator winding has an alternating current for driving an outer rotor and an alternating current for driving an inner rotor. A composite current obtained by combining the currents flows. Thus, in the coaxial motor, the same number of rotating magnetic fields as the number of rotors are generated, and the inner rotor 2 and the outer rotor 3 rotate around the common rotation axis 5. Further, the AC current for driving the inner rotor 2 is supplied from an inverter (not shown) so as to apply a rotational torque only to the inner rotor 2 and the AC current for driving the outer rotor 3 to apply a rotational torque only to the outer rotor. Each rotor rotates in synchronization with the corresponding rotating magnetic field, and is independently controlled. For example, the driving current of each rotor is set by a current setting method disclosed in Japanese Patent Application Laid-Open No. H11-275826.
[0011]
Permanent magnets 12 extending in parallel to the rotation axis direction are arranged at predetermined intervals of 60 degrees in the inner rotor 2 so that the magnetic poles facing the stator alternately become S poles and N poles. Here, in the present embodiment, a single magnetic pole of the inner rotor 2 is configured by two magnets 12 a and 12 b symmetrically arranged with respect to one radial plane of the inner rotor 2. Permanent magnets 11 extending in parallel to the rotation axis direction are arranged on the outer rotor 3 at predetermined intervals of 30 degrees so that the S pole and the N pole are arranged with respect to one pole of the inner rotor 2. When the magnets are arranged on the inner rotor 2 and the outer rotor 3, the rotation of one rotor does not affect the rotation of the other rotor.
[0012]
The stator structure according to the present invention will be described with reference to FIG. The stator 1 includes a plurality of divided cores 4 (stator pieces) arranged in a cylindrical shape at equal angular intervals around a rotor rotation shaft 5, a coil 9 wound around teeth of each divided core 4, and an adjacent divided core 4. And a spacer 14 disposed between them. The spacer 14 is made of an insulator such as a resin, and magnetically and electrically separates the divided core 4 from an adjacent divided core. That is, a magnetic gap equivalent to the air gap exists between the split cores 4. In the present embodiment, 18 split cores 4 are arranged on the stator 1 at every 20 degrees. FIG. 4 shows six split cores 4 of the whole.
[0013]
The plurality of split cores 4 extend radially in the radial direction with respect to the rotation shaft 5 and are housed in a stator case 21 which is a thin insulator having a cylindrical shape with the rotation shaft 5 as a central axis. The stator case 21 may be configured such that the axial length is longer than the axial length of the divided cores 4 so that the stator case 21 has an opening having the same shape as the outer peripheral surface 41 of each of the divided cores 4. By doing so, the outer peripheral surface 41 of each split core 4 can directly face the outer rotor 3.
[0014]
The outer peripheral surface 41 of each split core 4 facing the outer rotor 3 has a semi-cylindrical shape and is arranged so as to be included in one cylindrical surface 53 having the rotation shaft 5 as an axis. Therefore, in FIG. 2, the cross section of the outer peripheral surface 41 perpendicular to the axial direction is arc-shaped. This cylindrical surface 53 corresponds to the outer peripheral surface of the stator 1. Similarly, the inner peripheral surface 43 of each split core 4 facing the inner rotor 2 has a semi-cylindrical shape, and is arranged so as to be included in one cylindrical surface 55 having the rotating shaft 5 as a central axis. I have. This cylindrical surface 55 corresponds to the inner peripheral surface of the stator 1. Therefore, the cross section of the inner peripheral surface 43 perpendicular to the axial direction has an arc shape.
[0015]
Further, the two side surfaces 45 and 47 of each split core 4 are planes which are connected to the outer peripheral surface 41 and the inner peripheral surface 43. Therefore, in FIG. It has become. The two side surfaces 45 and 47 of each split core 4 are arranged substantially symmetrically with respect to the center plane 51 of the split core 4 extending along the radial direction of the stator. Furthermore, in the present embodiment, the side surfaces 45 and 47 are arranged substantially parallel to the center plane 51, and as shown in FIG. 1, a cross section of the split core 4 along the center plane 51 (left half of FIG. 1). Is rectangular. As described above, when the width L of the divided core 4, that is, the distance between the side surfaces 45 and 47 is small, the three-dimensional shape of the divided core 4 is substantially a rectangular parallelepiped. The width L between the two side surfaces 45 and 47 is substantially constant in the radial direction because the two side surfaces 45 and 47 are substantially parallel.
[0016]
The split core 4 of the stator 1 is formed by laminating grain-oriented electromagnetic steel sheets. By using a grain-oriented electrical steel sheet having a high magnetic permeability in one direction, the saturation magnetic flux density is increased. Conventionally, it was not possible to use a steel sheet with high magnetic permeability in one direction because it was necessary to consider the yoke part, but by using the above-described stator structure of the present invention, it is possible to use directional magnetic steel sheets. It becomes.
[0017]
Next, a structure for fixing the split core 4 will be described.
[0018]
One annular flat plate 31 is arranged on a plurality of divided cores 4 arranged in a cylindrical shape, and is arranged in contact with one end face 59 of each divided core 4. Two long-axis bolts 16 penetrate the annular flat plate 31 except for the head, and are installed between the divided cores 4. The divided cores 4 are fixed by the bolts 16 tightening the divided cores 4 in the axial direction. Here, the screw portion of the bolt 16 is screwed with a screw hole 25 provided in the stator support portion 17, and the annular flat plate 31 uniformly presses the divided cores 4 by tightening the bolt 16.
[0019]
A cooling path 61 defined by the stator case 21, the coil 9, and the spacer 14 is provided between adjacent split cores 4, that is, in a slot. The stator case 21 closes the space between the adjacent split cores 4 in the radial direction from the outer rotor 3 side, and the spacer 14 closes the space between the adjacent split cores 4 in the radial direction from the inner rotor 2 side. . Therefore, the stator case 21 and the spacer 14 function as a closing member for forming the cooling path 61. One of the bolts 16 is disposed in the cooling path 61 and one is embedded in the spacer 14. By providing the cooling path 61 in contact with the coil, the coil that generates a large amount of heat can be preferentially cooled, and the cooling efficiency is improved.
[0020]
The cooling path 61 is supplied with a cooling liquid such as oil from a cooling liquid port 19 that penetrates the case 8 that houses the stator 1, the inner rotor 2, and the outer rotor 3. The groove 65 connecting the adjacent cooling passages 61 is formed at the end face of the split core such that the cooling liquid flowing into the cooling passage 61 from the cooling liquid outlet 19 flows into the adjacent cooling passage 61 and is discharged from the adjacent cooling liquid outlet 19. 59. The configuration relating to such a cooling path is not described in detail because it departs from the subject matter of the present invention, but is disclosed in detail in JP-A-2000-14103 (published on January 14, 2000).
[0021]
A second embodiment of the stator structure of the present invention will be described with reference to FIG.
[0022]
In the first embodiment described above, since the two side surfaces 45 and 47 are substantially parallel, the width L between the two side surfaces 45 and 47 of the split core 4 is substantially constant in the radial direction. In the embodiment, the width L of the split core 4 increases radially outward. That is, the width L2 of the divided core 4 on the outer peripheral surface 53 of the stator 1 is set to be larger than the width L1 of the divided core 4 on the inner peripheral surface 55 of the stator 1. In this way, even when the width of the magnet 11 of the outer rotor 3 in the circumferential direction is large or the magnet 11 of the outer rotor 3 has a strong magnetic force, magnetic saturation in the split core 4 can be prevented. In the second embodiment as well, the two side surfaces 45 and 47 of each split core 4 are arranged substantially symmetrically with respect to the center plane 51 extending along the radial direction of the stator.
[0023]
Further, even when the width of the divided cores 4 is increased on the outer peripheral side, the interval D between the adjacent divided cores is set to increase radially outward in order to secure the passage area of the cooling passage 61. . By setting the interval between adjacent divided cores to be a narrow interval D1 on the inner peripheral side and a wide interval D2 on the outer peripheral side, an area between the stators can be secured, and a coil area and a cooling area wound around the stator can be secured. Can be secured. As a result, the coil area can be increased, and copper loss can be reduced. In addition, the cooling efficiency is improved by increasing the cooling area.
[0024]
A third embodiment of the stator structure of the present invention will be described with reference to FIG.
[0025]
In the present embodiment, the width L of the split core 4 decreases radially outward. That is, the width L1 of the divided core 4 on the inner peripheral surface 55 of the stator 1 is set to be larger than the width L2 of the divided core 4 on the outer peripheral surface 53 of the stator 1. By doing so, the passage area of the cooling passage 61 can be made very large.
[0026]
Next, the effect of using the stator structure according to the first, second, and third embodiments will be described with reference to FIGS.
[0027]
The magnetic flux passing through the stator 1, the inner rotor 2 and the outer rotor 3 is typically as shown by a curve 71, and differs depending on the positional relationship between the inner rotor 2 and the outer rotor 3.
[0028]
When the magnetic poles of the inner rotor 2 and the outer rotor 3 are opposite to each other, the magnetic flux from the magnet 12 of the inner rotor passes through the magnet 11 of the outer rotor 3 radially facing the magnet 12, Then, it goes to the outer rotor magnet 11 'next to the magnet 11, and returns to the inner rotor. When the magnetic poles of the inner rotor and the outer rotor face each other with the same polarity, the magnetic flux from the magnet 12 of the inner rotor 2 is repelled by the magnet 11 of the outer rotor 3 which faces the magnet 12 in the radial direction. It returns through the magnet 11 'next to 11 and back to the inner rotor.
[0029]
The direction of the magnetic flux varies depending on the magnetic pole position of the inner rotor 2 and the magnetic pole position of the outer rotor 3. In any case, the magnetic flux of the inner rotor 2 flows through the outer rotor 3 due to the effect of the shape of the split core 4 according to the present invention. And the magnetic flux 3 of the outer rotor passes through the inner rotor 2.
[0030]
Therefore, the frequency of the magnetic flux of each rotor is the difference between its own magnetic flux frequency and the magnetic flux frequency of the counterpart rotor (self magnetic flux frequency-magnetic flux frequency of the counterpart rotor). The frequency of the magnetic flux is obtained by multiplying the number of rotations of the rotor by the number of pole pairs of the rotor. As described above, the frequency of the magnetic flux decreases as compared with the case where the magnetic flux rotates alone, and the iron loss decreases. Further, since the split core 4 has no portion where the magnetic field changes suddenly and concentrates, the core loss of the split core 4 also decreases.
[0031]
It is apparent that the present invention is not limited to the above-described embodiment, and that various changes can be made within the scope of the technical idea.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an axial section of a coaxial motor having a stator according to the present invention. Specifically, the left half is a cross section taken along the line IO in FIG. 2, and the right half is a cross section taken along the line I′-O in FIG.
FIG. 2 is a partial cross-sectional view showing a cross section perpendicular to the axial direction of the coaxial motor having the stator of the first embodiment.
FIG. 3 is a partial cross-sectional view illustrating a cross section perpendicular to an axial direction of a stator according to a second embodiment.
FIG. 4 is a partial sectional view showing a section perpendicular to the axial direction of a stator according to a third embodiment.
FIG. 5 is a partial sectional view of a coaxial motor perpendicular to an axial direction schematically showing a magnetic field generated in a coaxial motor having a stator structure according to the present invention; However, this is a case where the magnetic poles of the outer rotor and the inner rotor that face each other in the radial direction are different poles.
FIG. 6 is a partial cross-sectional view of a coaxial motor perpendicular to an axial direction schematically showing a magnetic field generated in a coaxial motor having a stator according to the present invention. However, this is a case where the magnetic poles of the outer rotor and the inner rotor that face each other in the radial direction are the same.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stator 2 Inner rotor 3 Outer rotor 4 Split core 5 Rotating shaft 9 Coil 11 Outer rotor magnet 12 Inner rotor magnet 14 Spacer 16 Bolt 41 Outer peripheral surface 43 of divided core Inner peripheral surface 45, 47 of divided core Side surface 51 of divided core Core central surface 53 Stator outer peripheral surface 55 Stator inner peripheral surface

Claims (4)

A stator including a plurality of split cores arranged at intervals around the rotation axis and a coil wound on the plurality of split cores,
An inner rotor arranged coaxially with the stator inside the stator,
Having an outer rotor disposed coaxially with the stator outside the stator,
In a coaxial motor in which the inner rotor and the outer rotor rotate around a common rotation axis,
The plurality of split cores, an inner peripheral surface facing the inner rotor, and a side surface that couples an outer peripheral surface facing the outer rotor are formed by a plane,
The distance between adjacent split cores is narrower on the inner rotor side and gradually increases toward the outer rotor side. The stator structure of a coaxial motor according to claim 1, wherein the two side surfaces are substantially parallel. The stator has a first closing member that radially closes a space between adjacent split cores from an outer rotor, and a second closing member that radially closes a space between adjacent split cores from an inner rotor. With a closing member,
The cooling path defined by the first and second closing members and the coil, and bolts for fixing the individual divided cores are arranged in a space between adjacent divided cores. The stator structure of the coaxial motor according to 1. The stator structure of a coaxial motor according to claim 1, wherein the divided cores of the stator are formed by laminating grain-oriented electromagnetic steel sheets.

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