JPH07241051A - Rotor for internal rotation type brushless motor - Google Patents

Abstract

PURPOSE:To obtain a rotor for internal rotation type brushless motor suitable for high speed rotation in which the magnetic force of a magnet can be utilized efficiently. CONSTITUTION:The rotor for internal rotation type brushless motor comprises a rotor yoke having a continuous ring-like outer peripheral wall 37, and even number of arcuate segment magnets 33 disposed in the yoke, wherein each magnet 3 is built in along the outer peripheral surface of the rotor yoke. The outer peripheral wall 37 of rotor yoke for supporting each magnet 33 which touching the outer side face 33a thereof has maximum thickness at the central position 37c corresponding to the lateral center C along the arc of the magnet 33 and the thickness decreases gradually toward the opposite end positions 37e corresponding to the opposite end parts in the lateral direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor for an inversion type brushless motor, in which a rotor magnet incorporated in a rotor yoke is formed of a plurality of segment type magnets.

[0002]

2. Description of the Related Art In Japanese Utility Model Laid-Open No. 5-4742, short-circuit magnetic flux between adjacent segment type magnets is limited,
A rotor for an inversion type brushless motor is described that can increase the effective magnetic flux that contributes to rotation and guarantee the strength of the outer peripheral wall of the rotor yoke that the outer peripheral surface of each magnet contacts so that the magnets do not scatter during rotation. ing.

That is, as shown in FIG. 6, in the above-mentioned publication, an even number of segment type magnets 3 are installed inside the rotor yoke 2 of the rotor along the outer peripheral surface of the rotor yoke 2, and the rotor yoke 2 is attached to the magnet 3. Formed by a yoke main body 8 inside, a ring-shaped outer peripheral wall 9 outside the magnet 3 for holding the magnet 3, and a connecting portion 10 connecting the yoke main body 8 and the outer peripheral wall 9. A rotor having a structure in which a fine thermal strain is applied to a part of the outer peripheral wall 9 close to 10 by heat treatment (irradiation of a laser beam) is shown. In addition, the arrow in FIG. 6 has shown the laser beam irradiated.

Further, in the above-mentioned publication, as shown in FIG. 7, instead of the heat treatment, a part of the outer peripheral wall 9 adjacent to the connecting portion 10 is provided with a corrugated mechanical strain by press working. The rotor is also listed.

In such a conventional technique, thermal distortion or mechanical distortion is provided on the outer peripheral wall of the rotor yoke 2 between adjacent magnets 3 to reduce the magnetic permeability of that portion. . As a result, the short-circuit magnetic flux between the adjacent segment type magnets 3 can be limited, and the outer peripheral wall 9 of the rotor yoke 2 can be continuously made into a ring shape without a break, so that the outer peripheral wall for limiting the short-circuit magnetic flux is cut. The strength of the outer peripheral wall 9 can be assured as compared with the configuration in which the magnet 3 is provided, and thus, the scattering of the magnet 3 at high speed rotation can be prevented.

[0006]

The centrifugal force that acts on each segment type magnet 3 when the rotor rotates is
Virtually, it acts on the center portion in the width direction along the arc of the magnet 3. Further, this centrifugal force is supported by the portion of the outer peripheral wall 9 in contact with each magnet 3 that corresponds to the center portion in the width direction along the arc of the magnet 3.

However, in the above-mentioned conventional structure, since the thickness of each portion of the outer peripheral wall 9 for supporting the magnet 3 in contact with its outer surface is the same, the rotation speed of the rotor is increased, for example, 10,000 rpm or more. In that case, the entire outer peripheral wall 9 must be thickened in order to withstand the centrifugal force that increases accordingly.

Then, not only the weight of the rotor is increased, but also the centrifugal force acting on the outer peripheral wall 9 is increased. In addition, since the thickness of the portion that limits the short-circuit magnetic flux increases and the magnetic path cross-sectional area increases, it becomes easier for the magnetic flux to pass through this portion, and the magnetic force of the magnet 3 that is the purpose of Japanese Utility Model Laid-Open No. 5-4742. There is a problem in that the point of efficiently using is impaired.

Further, in the conventional technique shown in FIG. 6, it is necessary to irradiate a laser beam after assembling the rotor, so that there is a problem that there are many manufacturing steps. Further, in the conventional technique shown in FIG. 7, since the corrugation is formed on the outer peripheral surface of the rotor yoke 2, the air gap between the stator core and the corrugated portion of the outer peripheral wall 9 becomes uneven. Therefore, there is a problem that the rotational torque fluctuation of the rotor becomes large.

An object of the present invention is to obtain a rotor for an inversion type brushless motor which is suitable for high speed rotation and which can efficiently utilize the magnetic force of a magnet.

[0011]

In order to achieve the above object, a rotor for an inversion type brushless motor according to the present invention has a rotor yoke having an outer peripheral wall continuous in a ring shape without a break, and a rotor yoke inside the yoke. In a rotor for an inversion type brushless motor, which is provided with a plurality of arc-shaped segment magnets, each magnet being incorporated along the outer peripheral surface of the rotor yoke, The rotor yoke supporting the outer peripheral wall of the rotor yoke in contact with each magnet, the maximum thickness of the central position corresponding to the central portion in the width direction along the arc of the magnet, and the width from the central position. It is characterized in that the thickness is gradually reduced toward both end positions corresponding to both end portions in the direction.

[0012]

In the rotor of the present invention, the thickness of each part of the ring-shaped outer peripheral wall of the rotor yoke which is continuous without interruption is maximized at the center position corresponding to the center part in the width direction along the arc of each magnet. Since the thickness is gradually reduced from the center position to the both end positions corresponding to the both end portions in the width direction, the centrifugal force acting on each magnet at the maximum thickness portion does not have to be evenly thickened over the entire outer peripheral wall. By supporting the respective forces, it is possible to prevent the outer wall from being deformed or damaged by centrifugal force.

As described above, since it is not necessary to increase the thickness of the outer peripheral wall to withstand the centrifugal force, the weight of the rotor as a whole is not increased and the centrifugal force can be suppressed accordingly.

As described above, the rotor of the present invention is suitable for a high-speed inner rotation type brushless motor because it is lightweight and has a large centrifugal force resistance.

Further, the outer peripheral wall portion corresponding to both ends in the width direction along the arc of each adjacent magnet is thinner than the other outer peripheral wall portions, and therefore, the magnetic path cross-sectional area is the smallest. Due to the magnetic saturation of the portion, the short-circuit magnetic flux that short-circuits between the segment magnets adjacent to each other through the portion can be limited.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to FIGS. 1 and 2 show the structure of an inner-rotating brushless motor including a rotor according to the present embodiment. Reference numeral 21 in these drawings denotes a stator including a stator core 22 and a stator coil 23.

The stator core 22 is a magnetic material, and is formed by stacking laminated steel plates (core plates) punched by a press die into a shape as shown in FIG. 2 and fastening them with a plurality of caulking pins (not shown). However, the stator core 22 may be formed of another magnetic material and is not limited to the laminated structure. The stator core 22 has, for example, six substantially T-shaped magnetic poles 22a on its inner peripheral surface,
A stator coil 23 is wound around each of the magnetic poles 22a with an insulating layer (not shown) interposed therebetween.

As shown in FIG. 1, the stator 21 is sandwiched by a pair of light metal motor frames 24 arranged on both sides in the thickness direction thereof. Each motor frame 24 has, for example, a circular shape having a larger diameter than the stator 21, and is connected via a plurality of connecting bolts (not shown) penetrating the stator 21 and nuts screwed to these. Ball bearings 25 are attached to the central portions of the respective stators 21 as shown in FIG.

Inside the stator 21, a rotor (rotor) 31 according to this embodiment is arranged. The rotor 31 is
A rotor yoke (rotor core) 32, an even number of, for example, four segment magnets 33, and a light metal rotating shaft 3
4 and. This rotor 31 has its rotary shaft 34
Are rotatably supported and attached to the respective ball bearings 25. One end of the rotary shaft 34 is provided so as to penetrate a ball bearing 25 attached to one motor frame 24, and this one end is used as an output end connected to a load (not shown).

As shown in FIGS. 2 and 3, the rotor yoke 32 having the same thickness as the stator core 22 is a magnetic material, and is a laminated steel sheet punched by a press die into a shape as shown in FIGS. 3 and 4, for example. It is formed by stacking (core plates) and fastening with a plurality of caulking pins 35, but the rotor yoke 32 may be formed of another magnetic material,
The laminated structure is not limited.

The rotor yoke 32 is located inside the magnet 33 and has a yoke main body 36 having a central hole 36a through which the rotary shaft 34 penetrates, and a magnet 33 located outside the magnet 33. Is formed by an outer peripheral wall 37 that supports the outer peripheral surface of the yoke, and a connecting portion 38 that integrally connects the yoke main body portion 36 and the outer peripheral wall 37. A peripheral portion of the rotor yoke 32 is surrounded by a yoke body portion 36, an outer peripheral wall 37, and a connecting portion 38.
Individual magnet mounting holes 39 are formed. These mounting holes 3
Reference numeral 9 corresponds to the shape of the magnet 33 and has an arc shape in a plan view.

The yoke body 36 forms a magnetic path inside the magnet 33. The outer peripheral wall 37, which is continuous in a ring shape without breaks, forms a magnetic path outside the magnet 33, and contacts the outer surface of the magnet 33 to support it from the outside to prevent the magnet 33 from scattering during rotation. is doing. The connecting portion 38 connects the yoke main body portion and the outer peripheral wall 37 to secure the structural strength of the rotor yoke 32.

Each magnet 33 is made of a so-called plastic magnet made by mixing powder particles of a magnetic material into a synthetic resin, and has an arc shape in plan view as shown in FIG. 3 and the like, and as shown in FIG. The rotor yoke 32 has the same thickness as that of the rotor yoke 32. These magnets 3
3 is inserted into each magnet mounting hole 39. Therefore, the magnets 33 are incorporated along the outer peripheral surface of the rotor yoke 32 and are discontinuously provided by being separated from each other by the connecting portion 38.

As shown in FIG. 3, four magnets 3
Outer surface 33a is magnetized to the N pole and the inner side surface is magnetized to the S pole, and the other two are magnetized to the S pole and the inner surface are the N pole. These magnets 33 are inserted into the respective magnet mounting holes 39 so as to have N-pole and S-pole polarities alternately in the circumferential direction of the outer peripheral surface of the rotor 31, so that the rotor 31 alternates in the circumferential direction. It has magnetic pole portions showing the polarities of N pole and S pole. Incidentally, instead of the above arrangement,
The magnets 33 may be arranged so that the rotor 21 has magnetic pole portions that exhibit the polarities of two adjacent N poles and two adjacent S poles in the circumferential direction.

As shown in FIG. 4, the outer peripheral wall 37 is
The outer peripheral surface 37a is an outer peripheral wall forming a perfect circle. Then, the thickness of the magnet contact portion of the outer peripheral wall 37 in contact with the outer surface 33a of each magnet 33 is such that the center position 37c corresponding to the center portion C in the width direction along the arc of the magnet 33 is the maximum and It is gradually thinned from 37c to both end positions 37e corresponding to both ends E in the width direction. Therefore, the outer peripheral wall 37
When the radius of the outer peripheral surface 37a of A is A and the radius of the outer surface 33a of the magnet 33, in other words, the radius of the inner peripheral surface 37b of the outer peripheral wall 37 which is in contact with the outer surface 33a of the magnet 33, is B> It is formed so as to satisfy the relationship of A. The center OA of the radius A is the same as the center of the rotor yoke 32, but the center OB of the radius B is slightly displaced from the center of the rotor yoke 32.

In FIG. 1, 40 is fitted to the rotary shaft 34,
In addition, it is a spacer such as a sleeve or a washer that is interposed between the inner ring of the ball bearing 25 and the yoke body 36 of the rotor yoke 32.

In the above structure, the effective magnetic flux that effectively contributes to the rotational drive of the rotor 31 extends from the N pole outside the magnet 33 to the external space of the rotor 31, that is, the stator 22.
Air gap g between the tip surface of the magnetic pole 22a (see FIG. 1).
Crossing the stator 21 and passing through the other magnetic pole 2 again.
2a to reach the S pole outside the magnet 33 through the air gap g. Such an effective magnetic flux interacts with the magnetic flux generated in the magnetic pole 22a of the stator 21 to give a rotational torque to the rotor 31, and thereby the rotor 31 can be rotationally driven.

By the way, the outer peripheral wall 37 of the rotor yoke 32 is
Has a continuous ring shape without a joint, so that a part of the magnetic flux passes through the outer peripheral wall 37 and short-circuits between the adjacent magnets 33. This short circuit magnetic flux does not contribute to the rotational drive of the rotor 31.

However, in the rotor 31 of this embodiment,
An outer peripheral wall portion between both end positions 37e corresponding to the end portions E in the width direction along the arcs of the adjacent magnets 33 on the outer peripheral wall 37, in other words, a portion 37d near the connecting portion 38 of the outer peripheral wall 37 (FIG. 4). (See) is formed as the thinnest in the outer peripheral wall 37 and forms a short circuit magnetic flux limiting portion having the smallest magnetic path cross-sectional area.

Therefore, the portion 37d is easily magnetically saturated, and the magnetic saturation can limit the short-circuit magnetic flux which short-circuits the adjacent magnets through the portion 37d. And since the short circuit magnetic flux can be reduced in this way,
It is possible to secure a large amount of the effective magnetic flux and improve the efficiency of using the magnetic force of each magnet 33.

Moreover, in order to increase the effective magnetic flux, the portion 3 in the vicinity of the connecting portion 38 in the outer peripheral wall 37 as described above.
Since the magnetic path cross-sectional area of 7d is made narrower than other portions to reduce the short-circuit magnetic flux between the adjacent magnets 33, a laser beam is irradiated after the rotor 31 is assembled to lower the magnetic permeability of the vicinity portion. Compared with the technique of limiting the short-circuit magnetic flux, there is no need to specially reduce the magnetic permeability, so that there is an advantage that the number of manufacturing processes can be reduced.

In the rotor 31 having the above-mentioned structure, the thickness of each part of the ring-shaped outer peripheral wall 37 which is continuous without a break is such that the centrifugal force acting on each magnet 33 acts, that is, the width along the arc of the magnet 33. The central position 37c corresponding to the central portion C in the direction is thicker, and is between the magnet non-opposing portions between the adjacent magnets 33, in other words, the both end positions 37e corresponding to the widthwise both end portions E along the arc of the adjacent magnets 11. Centrifugal force non-acting point (the vicinity 3
Since the outer peripheral wall 37 does not have to have a uniform thickness, the centrifugal force acting on the magnet 33 is supported at the maximum thickness portion (center position 37c portion), It is possible to prevent the outer wall 37 from being deformed or damaged by centrifugal force.

In addition, the entire outer peripheral wall 37 is not thickened to have a uniform thickness to withstand the centrifugal force, but as described above, the action point of the centrifugal force acting on the magnet 33 is changed from the action point of the centrifugal force to the non-action point side of the centrifugal force. Since the thickness of the rotor 31 is made as thin as possible to hold the magnet 33, the total weight of the rotor 31 is not increased, and the centrifugal force generated can be suppressed accordingly.

Therefore, since the above-mentioned weight reduction is realized and the centrifugal force resistance is large, it is suitable for a high speed rotation (10,000 rpm or more) inversion type brushless motor. Of course, since the inertia is reduced by the weight reduction, the startability is also improved.

Further, the rotor 31 for the inversion type brushless motor according to this embodiment has a rotor yoke 32 having an outer peripheral wall 37 which is continuous in a ring shape without a break, and the yoke 32.
And a plurality of arc-shaped segment magnets 33 provided inside, and each magnet 33 is incorporated along the outer peripheral surface 37a of the rotor yoke 32.
The outer peripheral wall 37 of the rotor yoke 32, which supports the magnets 33 in contact with the outer surface thereof, is attached to the outer peripheral surface 3 thereof.
7a is an outer peripheral wall 37 forming a perfect circle, and the outer peripheral wall 3
7, the thickness of the portion in contact with each of the magnets 33 is the center portion C in the width direction along the arc of the magnet 33.
The maximum position of the center position 37c corresponding to the above is provided, and the center position 37c is gradually thinned from the center position 37c to both end positions 37e corresponding to the both end portions E in the width direction.

Therefore, in addition to the above-described effects, since the outer peripheral surface 37a of the outer peripheral wall 37 is a perfect circle, the outer peripheral surface of the rotor 31, that is, the air gap g between the outer peripheral surface 37a and the stator core 22 is reduced. There is also an advantage that the respective portions are made uniform and the fluctuation of the rotation torque of the rotor 31 can be reduced.

FIG. 5 shows a second embodiment of the present invention.
This embodiment differs from the first embodiment only in the points described below, and the rest of the configuration is described in the first embodiment shown in FIGS. 1 to 4 including parts not shown in FIG. Since it has the same structure as the rotor of the inner rotor type brushless motor, the same components are designated by the same reference numerals as in the first embodiment, and the description of the configuration and the description of the action and effect based thereon will be omitted. However, this same portion also constitutes a part of the configuration of the rotor of this embodiment.

The second embodiment differs from the first embodiment in the structure of the outer peripheral wall 37 of the rotor yoke 32. Specifically, a curved surface drawn with a radius A starting from a point OB slightly displaced from the center of the rotor yoke 32 is formed with outer peripheral surfaces 37a of four magnet contacting portions of the outer peripheral wall 37 which are in contact with the respective magnets 33. . Along with this, a curved surface drawn with a radius B starting from the center OA of the rotor yoke 32 forms an outer peripheral surface 33a of each magnet 33, in other words, an inner peripheral surface 37b portion of the outer peripheral wall 37 in contact with the outer peripheral surface 33a of each magnet 33. Has been done. The two radii A and B satisfy the relation of B> A.

As a result, the thickness of each magnet contact portion in contact with each magnet 33 on the outer peripheral wall 37 is maximum at the center position 37c corresponding to the center portion C in the width direction along the arc of the magnet 33, and from this center position 37c. The thickness is gradually reduced toward both end positions 37e corresponding to the both end portions E in the width direction.

It is needless to say that the intended purpose of the present invention can be achieved also in the configuration of the second embodiment.

[0041]

As described in detail above, according to the rotor for an inner rotor type brushless motor according to the present invention, it is possible to uniformly thicken the entire ring-shaped outer peripheral wall of the rotor yoke without interruption. The centrifugal force acting on each magnet is supported by its maximum thickness part, and the deformation or damage of the outer peripheral wall due to the centrifugal force can be prevented, and the increase in the weight of the entire rotor is small, and the centrifugal force generated is small. Since the force can be suppressed to a small level, it is suitable for a high-speed inner rotation type brushless motor. Further, the outer peripheral wall has a minimum magnetic path cross-sectional area portion at a portion corresponding to both ends in the width direction along the arc of each adjacent magnet, and due to magnetic saturation of this portion, a gap between adjacent segment type magnets is generated. Since the short-circuit magnetic flux can be limited and the effective magnetic flux that contributes to the rotational driving of the rotor can be increased, the magnetic force of the magnet can be efficiently used.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an inner rotation type brushless motor including a rotor according to a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line ZZ in FIG.

FIG. 3 is a perspective view showing a rotor according to the first embodiment with a part thereof disassembled.

FIG. 4 is a plan view showing a rotor according to the first embodiment.

FIG. 5 is a plan view showing an inner rotor type brushless motor rotor according to a second embodiment of the invention.

FIG. 6 is a cross-sectional view showing a cross section orthogonal to the rotation axis of a conventional rotor.

FIG. 7 is a perspective view showing a part of a steel plate forming a rotor yoke of a conventional rotor.

[Explanation of symbols]

 31 ... Rotor, 32 ... Rotor yoke, 33 ... Magnet, 33a ... Outer surface of magnet, 37 ... Outer peripheral wall of rotor yoke, 37a ... Outer peripheral surface of outer peripheral wall, 37c ... Center position of magnet contact portion, 37d ... Magnet on outer peripheral wall Contact part, 37e ... Edge position of magnet contact part, C ... Center part in width direction of magnet, E ... End part in width direction of magnet.

Claims (1)

[Claims] 1. A rotor yoke having an outer peripheral wall which is continuous in a ring shape without interruption, and a plurality of arc-shaped segment magnets provided inside the yoke, wherein each magnet comprises a rotor yoke. In a rotor for an adder-type brushless motor incorporated along an outer peripheral surface, a thickness of a portion of the outer peripheral wall of the rotor yoke that supports the magnets in contact with the outer surface thereof is in contact with the magnets. An adderless brushless characterized in that the center position corresponding to the center portion in the width direction along the arc is maximized and gradually decreased from this center position to both end positions corresponding to both ends in the width direction. Rotor for motor.