JPH05236687A - Brushless dc motor - Google Patents

Abstract

PURPOSE:To simplify the constitution of a rotor by widening the width of the space made in a rotor core. CONSTITUTION:Space 2c, which extends in radial direction from the end of a permanent magnet 2d to the vicinity of the outer end of a rotor core 2a, is made to prevent the short circuit of the magnetic flux generated by adjacent permanent magnets 2b. This space 2c is made wide so that one margin may continue to the outer margin of the end face of the permanent magnet 2b, and that the other end may continue to the specified position inner from the inner margin of the end face of the permanent magnet 2b, which prevents the section of the rotor core 2a, which forms the flow of a magnetic flux between it and an armature 1, from widening. And, the rotor 2 is divided in radial direction into a plurality of divisions, and it is in such condition that each division is rotated by a specified skew angle from adjacent division. Hereby, the skew angle per division can be enlarged, and the number of division of the rotor 2 can be lessened, so the constitution of the rotor 2 can be simplified.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless DC motor including an armature having an armature winding wound around an armature core and a rotor having a permanent magnet embedded in the rotor core.

[0002]

2. Description of the Related Art Conventionally, a motor has been adopted as a drive source for a compressor or the like, paying attention to advantages such as easy electric control. In addition, although there are various types of motors, at present, it is possible to easily obtain a rotating magnetic field by using a three-phase AC power supply, a commutator is not required, and it is robust, low-priced, and easy to handle. The three-phase induction motor is most commonly used because of its advantages. However, in the induction motor, not only is the armature winding wound around the armature core, but the rotor winding is also wound around the rotor core.
Since current also flows through the rotor winding during operation, even if it is assumed that there is no mechanical loss, the output is more than the input due to the secondary copper loss due to the current flowing in the rotor winding. It can be reduced and efficiency cannot be increased so much.

Focusing on this point, instead of winding the rotor winding around the rotor core, a permanent magnet is attached to the rotor core to reduce the secondary copper loss to 0, and a brushless system capable of achieving high operating efficiency. DC motors have been proposed. This brushless DC
The motor has a structure in which at least one pair of permanent magnets is provided on the outer periphery of the rotor core (hereinafter referred to as a surface magnet structure), and a structure in which at least one pair of permanent magnets is embedded inside the rotor core. (Hereinafter, referred to as an embedded magnet structure).

In the surface magnet structure, a permanent magnet is simply attached to the surface of the rotor core,
When the rotor is rotated at a high speed, the permanent magnet is likely to peel off, and the rotor cannot be rotated at a high speed. On the other hand, in the case of the embedded magnet structure, since the permanent magnet is embedded inside the rotor core, peeling of the permanent magnet can be prevented, and it is possible to cope with higher speed rotation than that of the surface magnet structure. Further, since the permanent magnet is embedded, the inductance can be increased, and the torque component due to the inductance can be increased, which is suitable for driving a high torque load. Therefore, a brushless DC motor having an embedded magnet structure is adopted for applications that require high-speed rotation and high-torque load driving.

Further, in any of the above structures,
Since a slot ripple is generated under the influence of the armature slot (see FIG. 13), a method of skewing the armature core to reduce the slot ripple is known, but the armature core slot is slanted. However, there is a problem that the automatic winding work becomes difficult. Therefore, a method of skewing the rotor core has been proposed (JP-A-63-140).
645).

FIGS. 11A and 11B are schematic views for explaining a method of skewing the rotor core, in which three pairs of permanent magnets 82 are embedded in the rotor core 81 so as to face the radial direction. At the same time, the rotor core 81 is divided into a plurality of pieces in the axial direction, and the divided portions 81a are pressed into the rotating shaft in a state of being sequentially rotated by a predetermined angle to be integrated. In addition, 83
Is an air gap located on an extension line of the permanent magnet 82 for preventing a short circuit of magnetic flux.

[0007]

In the case of adopting the skew structure of the rotor cores described above, if the gaps 83 of the adjacent divided portions 81a do not at least partially overlap each other in the entire length range, the rotor cores will be separated from each other. The partial contact causes a short circuit of the magnetic flux through the contact portion (see FIG. 12). Therefore, the rotation angle must be set so that the voids 83 of the adjacent divided portions 81a overlap at least partially in the entire length range {see FIG. 11 (B)}. As a result, one divided part 8
Since the skew angle per 1a cannot be set too large, the number of divided portions 81a required to electrically skew by 360 ° becomes remarkably large, the rotor structure becomes complicated, and manufacturing becomes difficult. At the same time, there is an inconvenience of increasing costs. Specifically, if the number of slots is S, the number n of the divided portions 81a must satisfy the following equation. (360 / S) × k = αn where k is a constant indicating the ratio of the skew angle to the angle of one slot, and α is the skew angle per one divided portion.

In order to eliminate such inconvenience and increase the skew angle per divided portion, the permanent magnet 82 is used.
Although it is conceivable to increase the thickness of the magnet, not only will the cost be increased due to the increase in the size of the permanent magnet 82, but also a new inconvenience will occur in that performance will be deteriorated such as torque reduction. Become. Although the rotor having the permanent magnets 82 embedded in the radial direction has been described above as an example, a rotor having the permanent magnets embedded in the direction perpendicular to the radial direction has a wider gap width. Because it becomes narrower
The inconvenience becomes more remarkable.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to increase the skew angle per divided portion, simplify the structure of the rotor, and simplify the manufacturing work. An object of the present invention is to provide a brushless DC motor having a magnet structure.

[0010]

In order to achieve the above object, a brushless DC motor according to a first aspect of the present invention is provided with a permanent magnet having a predetermined thickness and oriented in a direction perpendicular to a radial direction at a predetermined position of a rotor core. In addition, a gap is formed that extends from the end face position of each permanent magnet to a predetermined position near the outer circumference of the rotor core to prevent short circuit of magnetic flux, and the width of the gap is set to be larger than the thickness of the permanent magnet. Furthermore, the rotor core is divided into a plurality of parts in the axial direction, and the adjacent divided parts are positioned in a relatively rotated state so that the air gaps overlap at least partially over the entire length range. There is one.

According to another aspect of the brushless DC motor of the present invention, one edge of the air gap is continuous with the outer edge of the end surface of the permanent magnet, and the other edge is inside the inner edge of the end surface of the permanent magnet. It is continuous to the predetermined position. According to another aspect of the brushless DC motor of the present invention, one edge of the air gap is continuous with the outer edge of the corresponding end surface of one of a pair of adjacent permanent magnets, and the other edge of the other permanent magnet. It is continuous with the outer edge of the corresponding end face.

A brushless DC motor according to a fourth aspect of the present invention has a shape in which the air gap extends linearly in the radial direction of the rotor core.
In the brushless DC motor of claim 5, the width of the air gap is gradually expanded in the radial direction of the rotor core.

[0013]

In the brushless DC motor according to the first aspect of the present invention, since the width of the air gap formed at a predetermined position of the rotor core for preventing the short circuit of the magnetic flux is widened, the limit skew angle which does not cause the short circuit of the magnetic flux is set. Since the size of the rotor core can be increased, and as a result, the number of divisions of the rotor core can be reduced, the structure of the rotor can be simplified and the manufacturing can be facilitated. Further, since the thickness of the permanent magnet is not increased even if the width of the gap is widened, it is possible to reliably prevent disadvantages such as cost increase and performance deterioration.

According to the brushless DC motor of the second aspect, when the width of the air gap is widened, the surface area of the rotor core portion which achieves the flow of magnetic flux with the armature is not reduced. Therefore, the deterioration of the performance of the brushless DC motor can be reliably prevented. Brushless D according to claim 3
In the case of the C motor, the width of the air gap can be significantly widened as compared with the case where the air gap is formed corresponding to the end face of each permanent magnet.
Since the limit skew angle can be remarkably increased, the number of divisions of the rotor core can be remarkably reduced, and remarkably simplification of the configuration can be achieved.

According to the brushless DC motor of the fourth aspect, it is possible to prevent the inconvenience that the flow of the magnetic flux in the rotor core is disturbed by the air gap, and to exhibit good performance as the brushless DC motor. According to the brushless DC motor of the fifth aspect, since the width of the air gap is gradually widened toward the outer peripheral side, the skew angle per divided portion can be increased.

[0016]

Embodiments will now be described in detail with reference to the accompanying drawings showing embodiments. 5 is a vertical sectional view showing an embodiment of the brushless DC motor of the present invention, FIG. 2 is a perspective view showing the structure of the rotor, and FIG. 1 is a vertical sectional view showing the structure of the rotor. As shown in FIG. 5, the brushless DC motor has an armature 1 in which armature windings are wound around a plurality of slots formed on the inner surface of a substantially cylindrical armature core, and slightly smaller than the inner diameter of the armature 1. The rotor 2 having at least one pair (two pairs in the illustrated embodiment) of permanent magnets 2b is embedded inside a rotor core 2a having an outer diameter.

The rotor 2 shown in FIGS. 1 and 2 has a permanent magnet 2b embedded in a direction perpendicular to the radial direction of the rotor 2,
In order to prevent a short circuit of the magnetic flux generated by the adjacent permanent magnets 2b, a magnetic flux short circuit preventing gap 2c extending radially from the end of the permanent magnet 2b to the vicinity of the outer end of the rotor core 2a.
Has been formed. The rotor 2 is divided into a plurality of divided portions 21 in the axial direction, and each divided portion 2
1 is rotated by a predetermined skew angle with respect to the adjacent divided portions 21. The gap 2c is filled with an adhesive filler made of a non-magnetic material, and the portion remaining outside the gap 2c is the magnetic flux short circuit portion 2e. Further, since the rotor core 2a is formed by laminating silicon steel plates and the like, if necessary, pins, bolts and the like (not shown) may be passed through to solidify the whole. Further, instead of the pin, the bolt, or the like, or in addition to the pin, the bolt, or the like, a tube body (for example, SUS tube) made of a non-magnetic material having an inner diameter substantially equal to the outer diameter of the rotor core 2a is used, and the tube body is rotated. The child iron core 2a may be inserted.

As the adhesive filler, only an adhesive represented by an epoxy adhesive or an acrylic adhesive can be used, and the adhesive strength is reduced with respect to this adhesive. It is possible to use a material in which a solid substance that can be solidified without being mixed is mixed. When the void 2c has a relatively narrow width, it is preferable to use only the adhesive, and when the void 2c has a relatively wide width, a solid mixture is used in the adhesive to complete the solidification required time. It is preferable to prevent a significant increase in A ferrite magnet can be used as the permanent magnet 2b, but a rare earth magnet is preferably used.

Generally, r1: radius of rotor t1: thickness of magnetic flux short-circuited portion α: skew angle per divided portion Lm: thickness of permanent magnet Lg: width of air gap, conventional brushless DC motor In, Lg = Lm / 2 ^1/2 . On the other hand, the condition for overlapping the voids is (r1-t1) tan α <Lg α <tan ⁻¹ {Lg / (r1-t1)}. Here, in order to increase the skew angle α, (1) the width Lg of the gap is increased.

(2) The radius r1 of the rotor is reduced. (3) Increase the thickness t1 of the magnetic flux short circuit portion. Although the methods of (2) and (3) are considered, the performance of the brushless DC motor is deteriorated. Therefore, the method (1) is adopted in the present invention.
More specifically, as shown in FIG. 3, one end of the void 2c is continuous with the outer end of the end face of the permanent magnet 2b, and the other end of the gap 2c is the end face of the permanent magnet 2b. ． The rotor core portion, which is formed wider than the conventional brushless DC motor so as to continue at a predetermined position inward of the inner edge, forms a magnetic flux flow with the armature 1 in a narrow width. Is prevented from becoming. The relative position of each divided portion 21 with respect to the axis of the rotor 2 is, as shown in FIG. 4, the total length range of the voids 2c of one of the divided portions 21 with respect to the entire length range of the voids 2c of the adjacent divided portions 21. It is set to always overlap regardless of the amount. Specifically, if the thickness of the permanent magnet 2b is Lm, the distance between the outer ends of the pair of facing voids 2c is Lga, and the distance between the inner ends of the pair of facing voids 2c is Lgb, then 2Lm /
Since 2 ^1/2 <(Lga-Lgb), the width of the gap 2c can be widened without impairing the characteristics of the brushless DC motor. It is preferable to set the relative position such that the outermost ends of the voids 2c slightly overlap each other (so that the upper limit value satisfies the above equation), and the skew angle α of one divided portion 21 is preferably set. Can be maximized.

With the brushless DC motor having the above structure, the skew angle α can be set larger than that of the conventional brushless DC motor, so that the number of divisions of the rotor 2 can be reduced, and the structure can be simplified and manufactured. Can be achieved. Although the width of the air gap 2c is set to be large, the size of the portion where the flow of magnetic flux is formed between the armature 1 and the armature 1 is the same as that of the conventional brushless DC motor. it can. Further, when the number of divisions is set to be the same as that of the conventional brushless DC motor, the overlapping range of the gaps 2c of the adjacent divided portions 21 can be increased, so that high performance of the brushless DC motor can be achieved.

FIG. 6 is a diagram showing the state of each divided portion 21 when the rotor 2 is divided into five and the skew angle α is set to 3.75 °, and the rotor 2 is divided into five divided portions 21. Then, by setting the skew angle for each, a skew of 15 ° can be achieved as a whole. FIG. 7 is a diagram showing a change in the gap magnetic flux density corresponding to the position of the rotor in the brushless DC motor incorporating the rotor 2 skewed as described above, and the slot ripple is significantly reduced. I know that Also, electromagnetic noise can be significantly reduced.

[0023]

[Embodiment 2] FIG. 8 is a schematic view showing the structure of a rotor incorporated in another embodiment of the brushless DC motor of the present invention. The difference from the above embodiment is that each permanent magnet is separated by a predetermined distance. Only the point that a void 2c having an integrated shape is formed instead of the void formed in the above.

Therefore, in the case of this embodiment, 2L
The width of the void 2c can be widened so as to satisfy m / 2 ^1/2 <Lg (where Lg is the width of the void 2c in this embodiment). That is, the skew angle α can be further increased and the number of divisions of the rotor 2 can be further reduced as compared with the case of the first embodiment.

[0025]

[Embodiment 3] FIG. 9 is a schematic view showing the structure of a rotor incorporated in still another embodiment of the brushless DC motor of the present invention. The difference from the embodiment of FIG. 1 is that the width of the air gap 2c is the radius. The point is that the both ends of the gap 2c are made to substantially coincide with the centrifugal direction of the rotor core 2a.

Therefore, in the case of this embodiment, FIG.
In the embodiment of the above, since the gap portion (the outermost edge portion of the gap) where the overlap is first eliminated when the skew is applied to each of the divided portions 21 is formed into one wide portion, The skew angle per part can be increased (Fig. 9
Therefore, the number of divisions of the rotor 2 can be reduced.

[0027]

[Fourth Embodiment] FIG. 10 is a schematic view showing the structure of a rotor incorporated in a further embodiment of the brushless DC motor of the present invention. The difference from the embodiment of FIG. 8 is that the width of the air gap 2c is the radius. The point is that the both ends of the gap 2c are made to substantially coincide with the centrifugal direction of the rotor core 2a.

Therefore, in the case of this embodiment, FIG.
In the embodiment of the above, since the gap portion (the outermost edge portion of the gap) where the overlap is first eliminated when the skew is applied to each of the divided portions 21 is formed into one wide portion, The skew angle per part can be increased (Fig. 1
The number of divisions of the rotor 2 can be reduced.

[0029]

As described above, according to the invention of claim 1, the skew angle per division can be increased and the number of divisions of the rotor can be reduced, so that the structure of the rotor can be simplified and the manufacturing work can be simplified. It has the unique effect of being able to do it. In addition to the effect of claim 1, the invention of claim 2 can prevent the decrease of the range in which the flow of the magnetic flux is formed with the armature, so that the characteristic deterioration of the brushless DC motor can be reliably prevented. Produce an effect.

According to the invention of claim 3, the skew angle can be increased and the number of divisions of the rotor can be reduced, so that the structure of the rotor can be simplified and the manufacturing work can be simplified, and moreover, it can be connected to the armature. Since it is possible to prevent a decrease in the range where the flow of magnetic flux is formed, it is possible to reliably prevent characteristic deterioration of the brushless DC motor. Claim 4
Since the invention of (1) can prevent the flow of magnetic flux from being disturbed by the air gap, it has a unique effect of reliably preventing characteristic deterioration of the brushless DC motor.

According to the fifth aspect of the invention, since the width of the gap is gradually expanded in the radial direction, there is a unique effect that the skew angle per divided portion can be further increased.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing the structure of a rotor in an embodiment of a brushless DC motor of the present invention.

FIG. 2 is a perspective view showing a rotor in one embodiment of the brushless DC motor of the present invention.

FIG. 3 is an enlarged view showing a main part of a rotor.

FIG. 4 is a schematic diagram illustrating a skew angle between adjacent divided portions.

FIG. 5 is a vertical sectional view schematically showing an embodiment of the brushless DC motor of the present invention.

FIG. 6 is a diagram showing a state of each divided portion when the rotor is divided into five and the skew angle per division is set to 3.75 °.

FIG. 7 is a diagram showing slot ripples corresponding to rotational positions of a rotor.

FIG. 8 is a vertical cross-sectional view showing the structure of a rotor in another embodiment of the brushless DC motor of the present invention.

FIG. 9 is a vertical cross-sectional view showing the structure of a rotor in yet another embodiment of the brushless DC motor of the present invention.

FIG. 10 is a vertical cross-sectional view showing the structure of a rotor in yet another embodiment of the brushless DC motor of the present invention.

FIG. 11 is a diagram illustrating a rotor skew method.

FIG. 12 is a diagram illustrating an inconvenience when the skew angle is too large.

FIG. 13 is a diagram illustrating slot ripple when skew is not applied to either the rotor or the armature.

[Explanation of symbols]

1 armature 2 rotor 2a rotor core 2
b Permanent magnet 2c Air gap 21 Divided part

Claims (5)

[Claims] 1. An armature (1) formed by winding an armature winding around an armature core, and a permanent magnet (2b) around a rotor core (2a).
A brushless DC motor including a rotor (2) in which a permanent magnet (2b) having a predetermined thickness and oriented in a direction perpendicular to a radial direction is provided at a predetermined position of a rotor core (2a). In addition, a gap (2c) is formed to extend from the end face position of each permanent magnet (2b) to a predetermined position near the outer circumference of the rotor core (2a) to prevent a short circuit of magnetic flux, and the width of the gap (2c). Is set to be larger than the thickness of the permanent magnet (2b), and the rotor core is divided into a plurality of parts in the axial direction, and the gap (2
The brushless DC motor according to (c) is characterized in that the adjacent divided portions (21) are positioned in a relatively rotated state so that at least a part thereof overlaps over the entire length range. 2. One end of the void (2c) is continuous with the outer end of the end face of the permanent magnet (2b), and the other end of the gap is closer to the inner end of the end face of the permanent magnet (2b). The brushless D according to claim 1, wherein the brushless D is also continuous at a predetermined inner position.
C motor. 3. One end of the void (2c) is continuous with the outer end of the corresponding end of one pair of adjacent permanent magnets (2b), and the other end is the other end. Magnet (2
The brushless DC motor according to claim 1, which is continuous with the outer edge of the corresponding end surface of b). 4. The brushless DC motor according to claim 1, wherein the air gap (2c) has a shape that extends linearly in the radial direction of the rotor core (2a). 5. The rotor core (2a) having a width of the air gap (2c).
The brushless DC motor according to claim 4, wherein the brushless DC motor gradually expands in the radial direction.