JP5111535B2 - Permanent magnet type rotating electric machine - Google Patents

Description

  The present invention relates to a permanent magnet type rotating electrical machine (DC motor with brush) having a field magnet arranged on the outer peripheral side of an armature and having a characteristic field structure.

  Conventionally, a permanent magnet rotor having an even number of poles (the number of magnetic poles) P of 4 or more and a stator having a slot number S that is not a multiple of P, the magnet angle at which the permanent magnet stretches with respect to the rotor center is about 67. .5 ° and the number of cogging torques per round is an integral multiple of twice or more the least common multiple LCM of the number of poles P and the number of slots S, so that the cogging torque can be remarkably reduced. A rotating electrical machine has been proposed (see, for example, Patent Document 1).

JP 2003-134772 (paragraph number [0013], FIG. 2 etc.)

  In recent years, there has been a tendency for cost reduction and quality improvement in permanent magnet type rotating electrical machines that are increasingly applied to various products. Especially in automobiles with many production units and a large number of components, there are many examples of using permanent magnet type rotating electrical machines for electric power steering devices, exhaust gas circulation devices, etc. In addition to lowering the cost of the components themselves, steering The cogging reduction is also demanded at the same time from the viewpoint of performance and device operability.

As means for reducing cogging, the following are well known.
(1) Means for smoothing magnetic flux density distribution (strictly speaking, distribution of square of magnetic flux density) by field magnet skew (step skew, skew magnetization), field magnet end cut, arc shape, etc .;
(2) Means for smoothing the permeance distribution, such as installing a dummy slot at the tip of the armature tooth and cutting the end.

  Further, when distributed winding is used and the number of armature slots is large, the order of cogging becomes high, and therefore cogging tends to be smaller than when concentrated slots are used and the number of slots is small.

  However, the means (1) for smoothing the magnetic flux density distribution tends to increase the magnet cost due to an increase in the number of parts and a complicated magnetizing device.

  Further, as in Patent Document 1, the permanent magnet is stretched with respect to the rotor center so that the cogging number is twice or more the least common multiple LCM of the number of slots S and the number of poles (number of magnetic poles) P of the armature core. There is a possibility that the cogging torque cannot be sufficiently reduced in an armature core (for example, when the slot opening is wide) with a relatively large change in permeance only by setting the angle.

  Further, the means for smoothing the permeance distribution of (2) described above is that the equivalent gap is increased by the dummy slot and the end cut, and the magnetic flux when the armature and the field are incorporated is reduced. There was a tendency for the characteristics to fall. Furthermore, although the dummy slot is effective in reducing the cogging component of a specific order, when the harmonic distribution of the magnetic flux density on the field side is diversified, the total cogging (pp (peak・ To-peak)) may not be reduced.

  In addition, reduction of cogging variation due to product size variation is also an important issue for such products. In the case of a permanent magnet, variations in the width and thickness of the magnet and the mounting position, and in the armature core, variations in the position and dimensions of the dummy slot have affected cogging variations.

  The present invention has been made to solve the above-described problems, and is a permanent magnet type rotating electric machine having a field magnet that can suppress cogging variations due to product variations while minimizing each component of cogging. I will provide a.

A permanent magnet type rotating electrical machine according to the present invention is a permanent magnet type rotating electrical machine having an armature and a field provided on the outer peripheral side or inner peripheral side of the armature via a gap,
The field is
A yoke having a substantially cylindrical cross section;
Provided on the inner peripheral surface or outer peripheral surface of the yoke, provided with permanent magnets for the number of magnetic poles,
The permanent magnet has a magnetic pole angle α viewed from the central axis of the armature of 130 to 135 ° in electrical angle,
Further, the permanent magnet has a chamfered portion of a predetermined shape at the corner on the armature facing the armature at the circumferential end of the permanent magnet so that the magnet surface angle β on the armature facing surface is about 125 °. It is formed.

  In the permanent magnet type rotating electric machine according to the present invention, the magnetic pole angle α viewed from the armature central axis of the permanent magnet is 130 to 135 ° in electrical angle, and the magnet surface angle β on the side facing the armature of the permanent magnet. Since the chamfered portion of a predetermined shape is formed at the corner on the surface facing the armature at the circumferential end of the permanent magnet so that the angle is about 125 °, each component of the cogging torque is minimized. In addition, variation in cogging torque due to variation in product dimensions can be suppressed.

FIG. 3 shows the first embodiment and is a cross-sectional view of the permanent magnet type rotating electric machine 100. FIG. 2 is a cross-sectional view of the field 10 of FIG. FIG. 5 shows the first embodiment and is an enlarged view of a permanent magnet 11. The A section enlarged view of FIG. FIG. 3 is a cross-sectional view of the yoke 12 of FIG. 2. The B section enlarged view of FIG. FIG. 5 shows the first embodiment, and is a cross-sectional view of a yoke 112 according to a modification. FIG. 3 is a cross-sectional view of the armature 30 of FIG. 1. FIG. 9 is a cross-sectional view of the armature core 31 in FIG. 8. FIG. 10 shows the first embodiment and is an enlarged view of the slot 33 of FIG. 9. FIG. 5 shows the first embodiment and shows changes in cogging component and magnetic flux amount with respect to magnetic pole angle α (electrical angle). FIG. 5 is a diagram illustrating the first embodiment and is a diagram illustrating a relationship between the length L of the first chamfer side and the cogging component (amplitude) when the magnetic pole angle α (electrical angle) is 130 ° and the chamfer angle θ is 30 °. . FIG. 5 is a diagram illustrating the first embodiment and is a diagram illustrating a relationship between the length L of the first chamfer side and the cogging component (amplitude) when the magnetic pole angle α (electrical angle) is 130 ° and the chamfer angle θ is 45 °. . The figure which shows Embodiment 1 and is a figure which shows the shape of the chamfer part 11d used as the angle where the magnetic pole angle (alpha) (electrical angle) is 130 degrees and the magnet surface angle (beta) becomes the minimum cogging. The figure which shows Embodiment 1, and is a figure which shows the shape of the chamfer part 11d used as the angle where the magnetic pole angle (alpha) (electrical angle) is 135 degrees and the magnet surface angle (beta) becomes the minimum cogging. FIG. 5 shows the first embodiment, and shows B (magnetic flux density) ^ 2 in each cogging component with or without a magnetic body portion 13a.

Embodiment 1 FIG.
In this embodiment, an inner rotor type brushed DC motor (permanent magnet type rotating electric machine) whose armature is a rotor (rotor) and whose field is a stator (stator) is an object (provided that the armature is A stator (stator) and a DC motor with a brush of an outer rotor type whose field is a rotor (rotor) may be used).

  1 to 10 show the first embodiment. FIG. 1 is a cross-sectional view of the permanent magnet type rotating electric machine 100, FIG. 2 is a cross-sectional view of the field 10 of FIG. 1, and FIG. 4 is an enlarged view of a portion A in FIG. 3, FIG. 5 is a transverse sectional view of the yoke 12 in FIG. 2, FIG. 6 is an enlarged view of a portion B in FIG. 8 is a cross-sectional view of the armature 30 of FIG. 1, FIG. 9 is a cross-sectional view of the armature core 31 of FIG. 8, and FIG. 10 is an enlarged view of the slot 33 of FIG.

The permanent magnet type rotating electrical machine 100 of the present embodiment is, for example, a brushed DC motor having the following specifications.
(1) Output: 10-20W;
(2) Outer diameter: φ50 [mm];
(3) Permanent magnet thickness: 4 [mm];
(4) Number of poles: 4 poles;
(5) Number of armature slots: 6.

  The configuration of the permanent magnet type rotating electrical machine 100 will be described with reference to FIGS. The permanent magnet type rotating electric machine 100 includes at least a field magnet 10 and an armature 30 disposed inside the field magnet 10 through a gap.

  The field magnet 10 includes a yoke 12 having a substantially cylindrical cross section, and arc-shaped permanent magnets 11 provided at substantially equal intervals in the circumferential direction along the inner peripheral surface of the yoke 12. A method for fixing the permanent magnet 11 to the yoke 12 is adhesion, resin molding, or the like.

  One permanent magnet 11 with one magnetic pole is provided. Since the example of FIG. 2 is a four-pole field 10, four permanent magnets 11 are used.

Since the permanent magnet type rotating electrical machine 100 of the present embodiment is a low output (10 to 20 W) brushed DC motor, a ferrite sintered magnet is used for the permanent magnet 11. Ferrite sintered magnet is a magnet with excellent cost performance manufactured by powder metallurgy using Fe ₂ O ₃ (ferric oxide) and BaCO ₃ (barium carbonate) or SrCO ₃ (strontium carbonate) as main raw materials. It is.

  The permanent magnet 11 is a segment (divided, here divided into four) magnet having a concentric circular arc, and is oriented or magnetized in the radial direction. As shown in FIG. 3, the inner peripheral surface 11a of the permanent magnet 11 has an arc in cross section, and the outer peripheral surface 11b of the permanent magnet 11 has an arc concentric with the arc of the inner peripheral surface 11a. The side surface 11c (circumferential end surface) of the permanent magnet 11 faces the radial direction (radial direction).

  The magnetic pole angle of the permanent magnet 11 (angle seen from the center of the field 10) is α. As will be described later, in the present embodiment, the magnetic pole angle α is set to 130 to 135 ° in electrical angle (the mechanical angle is 65 to 67.5 deg if there are four poles).

  Further, the magnetic pole surface angle (inner peripheral surface 11a) of the permanent magnet 11 is β. As will be described later, in this embodiment, the magnetic pole surface angle β is set to about 125 ° in electrical angle (the mechanical angle is about 62.5 ° in the case of 4 poles).

  Further, in order to satisfy the condition that the magnetic pole angle α is 130 to 135 ° in electrical angle and the magnetic pole surface angle β is approximately 125 ° in electrical angle, the angle on the inner peripheral surface 11a side of the side surface 11c of the permanent magnet 11 is set. The chamfered portion is formed by chamfering.

  You may make it form the chamfer 11d of the both ends of the permanent magnet 11 at the time of metal mold | die shaping | molding, for example.

  Moreover, you may make it form the chamfer 11d of the both ends of a permanent magnet by the additional process after sintering.

  As shown in FIG. 4, the chamfering angle of the chamfered portion 11d is θ, and the length of the chamfered first side is L. The chamfering angle θ of the chamfered portion 11d is an angle formed by the chamfered portion 11d and an extension line of the side surface 11c of the permanent magnet 11. The chamfered first side is a side on an extension line of the side surface 11 c of the permanent magnet 11.

  The other edges of the permanent magnet 11 are all chamfered or rounded to prevent cracking and chipping, but may be C chamfered (45 deg).

  As shown in FIG. 5, the yoke 12 is, for example, a substantially cylindrical shape made of a steel plate (which may be a magnetic material), and a convex portion that is recessed (projected) by a predetermined length between the permanent magnets 11. 13 are formed at substantially equal intervals in the circumferential direction. Both ends in the circumferential direction of the convex portion 13 are in contact with (adjacent to) the permanent magnet 11. This portion is referred to as a magnetic body portion 13a.

  In the case of FIG. 5, the two magnetic body parts 13 a that are between the poles are formed integrally with the convex part 13. However, like the yoke 112 of the modified example shown in FIG. The two magnetic body parts 113a may be formed by bending a separately formed steel plate into a cylindrical shape. In this case, if the field 10 is 4 poles, the magnetic body part 113a is provided in 8 places.

  The protrusion amount N (see FIG. 6) of the magnetic part 13a in the radial direction is preferably about half the thickness M of the permanent magnet 11 (see FIG. 6). This is for suppressing the leakage magnetic flux at the end of the permanent magnet 11.

  The yoke 12 is formed by, for example, winding a thin plate (for example, a steel plate having a thickness of about 2 mm) in a ring shape, and welding the end portion or fitting a dovetail groove provided in advance.

  On the other hand, as shown in FIG. 8, the armature 30 includes at least an armature core 31, an armature winding 34 inserted into the slot 33 via an insulating material (not shown), a rotating shaft 35, Is provided. Note that commutators, brushes, and the like are omitted.

  As shown in FIG. 9, the armature core 31 is formed with six slots 33 that are arranged at substantially equal intervals in the circumferential direction along the outer peripheral edge. Between the slots 33, this is called a tooth 32 in the iron core. The teeth 32 are formed so that the circumferential width is substantially constant in the radial direction. Since there are six slots 33, the number of teeth 32 formed therebetween is also six. The six teeth 32 are connected to an annular core back 36 inside the armature core 31. A shaft hole 37 into which the rotary shaft 35 is fitted is provided inside the core back 36.

  As shown in FIG. 10, the slot 33 opens at the outer peripheral edge of the armature core 31. This portion is called a slot opening 33a (slot opening). The armature winding 34 is inserted into the slot 33 provided with an insulating material (not shown) from the slot opening 33a.

  FIG. 11 is a diagram showing the first embodiment and is a diagram showing changes in the cogging component and the magnetic flux amount with respect to the magnetic pole angle α (electrical angle). In FIG. 11, for the cogging component, 12 harmonics, 24 harmonics, 36 harmonics, and 48 harmonics are illustrated. The amount of magnetic flux is 100% when the magnetic pole angle α (electrical angle) is 180 °.

  As shown in FIG. 11, the cogging component is minimized when the magnet surface angle β (the magnetic pole angle α of the surface facing the armature 30 is distinguished as the magnet surface angle β) is approximately 125 ° (electrical angle). Therefore, if the magnetic pole angle α of the permanent magnet 11 is set to 125 ° (electrical angle), the cogging component can be reduced. On the other hand, the amount of magnetic flux of the permanent magnet 11 decreases as the magnetic pole angle α decreases.

  Therefore, the magnetic pole angle α of the permanent magnet 11 is set to 130 ° to 135 ° (electrical angle) at which the amount of magnetic flux does not decrease so much. However, when the magnetic pole angle α is 130 ° to 135 ° (electrical angle), as shown in FIG. 11, the magnetic surface angle β deviates from the target value of approximately 125 ° (electrical angle), and the cogging component is large. Become. This tendency is conspicuous at low-order 12th harmonics and 24th harmonics.

  In the permanent magnet type rotating electrical machine 100 of the present embodiment, the magnetic pole angle α of the permanent magnet 11 is set to 130 ° to 135 ° (electrical angle) that can secure the amount of magnetic flux, and the inner peripheral surface of the side surface 11c of the permanent magnet 11 is set. By chamfering the corner on the 11a side to form the chamfered portion 11d, the magnet surface angle β facing the armature 30 is brought close to approximately 125 ° (electrical angle), which is the target value of the magnet surface angle β. I have to. At this time, the chamfering angle θ of the chamfered portion 11d is preferably about 30 °.

  12 and 13 show the first embodiment, and FIG. 12 shows the length L of the first chamfered side and the cogging component when the magnetic pole angle α (electrical angle) is 130 ° and the chamfering angle θ is 30 °. FIG. 13 is a diagram showing the relationship with (amplitude). FIG. 13 shows the relationship between the length L of the chamfer first side and the cogging component (amplitude) when the magnetic pole angle α (electrical angle) is 130 ° and the chamfer angle θ is 45 °. It is a figure which shows a relationship.

  As shown in FIG. 12, for example, when the magnetic pole angle α (electrical angle) is 130 ° and the chamfer angle θ is 30 °, the length L of the first side of the chamfer is about 0.75 mm, and the cogging component (amplitude) Is minimized. Further, even when the length L of the chamfered first side becomes long, even in the low-order cogging components (12 harmonics and 24 harmonics), the cogging component (amplitude) even if the length L of the chamfered first side is 2.0 mm. ) Is about 0.01. That is, the cogging variation due to the dimensional variation of the chamfered portion 11d can be reduced.

  On the other hand, as shown in FIG. 13, when the magnetic pole angle α (electrical angle) is 130 ° and the chamfering angle θ is 45 °, the length L of the chamfered first side is about 0.5 mm, and the cogging component (Amplitude) is minimized. When the length L of the first side of the chamfer is greater than 1.0 mm, the cogging component (amplitude) increases particularly in the low-order cogging components (12 harmonics and 24 harmonics), and the chamfer angle θ in FIG. For example, the cogging component (amplitude) of the 12th harmonic is twice as long as the length L of the chamfered first side is about 2.0 mm. Therefore, it can be said that the chamfering angle θ of the chamfered portion 11d is preferably about 30 °.

  14 and 15 are diagrams showing the first embodiment, and FIG. 14 is a diagram showing the shape of the chamfered portion 11d in which the magnetic pole angle α (electrical angle) is 130 ° and the magnet surface angle β is an angle that minimizes cogging. FIG. 15 is a diagram showing the shape of the chamfered portion 11d where the magnetic pole angle α (electrical angle) is 135 ° and the magnet surface angle β is an angle at which cogging is minimized.

As shown in FIG. 14, the magnetic pole angle α (electrical angle) is 130 ° and the magnet surface angle β (electrical angle) is set to an angle (about 125 °) at which cogging is minimized. As shown in.
(1) Chamfer angle θ = 30 °;
(2) Chamfered first side length L = 0.75 mm.

Further, as shown in FIG. 15, the shape of the chamfered portion 11 d is such that the magnetic pole angle α (electrical angle) is 135 ° and the magnet surface angle β (electrical angle) is an angle (about 125 °) that minimizes cogging. As shown below.
(1) Chamfer angle θ = 30 °;
(2) Chamfered first side length L = 1.5 mm.

  FIG. 16 is a diagram showing the first embodiment, and is a diagram showing B ^ 2 (the square of magnetic flux density) in each cogging component with or without the magnetic body portion 13a. In FIG. 16, the horizontal axis is the cogging component (12 harmonics, 24 harmonics, 36 harmonics, 48 harmonics, 60 harmonics, 72 harmonics), and the vertical axis is the square of the magnetic flux density (B ^ 2 (FFT ( (Fast Fourier Transform, fast Fourier transform) amplitude).

  By providing the magnetic body portions 13a and 113a (see FIGS. 6 and 7) so as to be adjacent to both ends of the permanent magnet 11, the magnetic path near the side surface 11C of the permanent magnet 11 is directed to the outer angle from the radial orientation. Magnetic flux density distribution becomes smoother and each component of cogging can be further reduced.

  As described above, in the permanent magnet type rotating electrical machine 100 of the present embodiment, cogging occurs in a number that is an integral multiple of the least common multiple LCM of the number S of slots 33 and the number of magnetic poles P per round of the field 10 (for example, In the case of 6 slots and 4 poles, the components 12, 24, 36, 48... Ensure the motor characteristics (magnetic flux amount) by setting the magnetic pole angle α of the permanent magnet 11 to 130 ° to 135 °. However, by setting the angle β of the magnet surface to 125 ° by chamfering the chamfered edge (the chamfered portion 11d) of the permanent magnet 11, each cogging component (for example, 12, 24, 36, 48,...) Are minimum (see FIG. 11).

  By setting the chamfering angle θ of the chamfered portion 11d at the end of the permanent magnet 11 to about 30 °, variation in cogging due to variation in chamfer dimensions can be reduced (see FIGS. 12 and 13).

  By providing the magnetic parts 13a and 113a so as to be adjacent to both ends of the permanent magnet 11, the magnetic path in the vicinity of the side surface 11c of the permanent magnet 11 faces more outward than the radial orientation, so that the air gap magnetic flux density distribution becomes smoother. Each component of cogging can be further reduced.

  The amount M of the magnetic body portions 13a and 113a protruding inward in the radial direction can be reduced to about half of the thickness N of the permanent magnet 11, whereby the leakage magnetic flux at the end of the permanent magnet 11 can be suppressed.

  The length L of the chamfered first side of the end of the permanent magnet 11 with an angle of 30 ° is set to 1.5 mm when the magnet angle α is 135 °, and about 0.75 mm when the magnet angle α is 130 °. Thus, the magnet surface angle β at which the magnet surface angle β becomes an angle at which cogging is minimized can be set to about 125 °.

  10 field magnet, 11 permanent magnet, 11a inner peripheral surface, 11b outer peripheral surface, 11c side surface, 11d chamfered portion, 12 yoke, 13 convex portion, 13a magnetic body portion, 30 armature, 31 armature iron core, 32 teeth, 33 slot , 33a Slot opening, 34 Armature winding, 35 Rotating shaft, 36 Core back, 100 Permanent magnet type rotating electrical machine, 112 Yoke, 113a Magnetic body part.

Claims (6)

In a permanent magnet type rotating electrical machine having an armature and a field provided on the outer peripheral side or inner peripheral side of the armature via a gap,
The field is
A yoke having a substantially cylindrical cross section;
A permanent magnet provided on the inner peripheral surface or the outer peripheral surface of the yoke, the permanent magnet for the number of magnetic poles,
In the permanent magnet, the magnetic pole angle α formed by the sides of the permanent magnet viewed from the armature central axis is 130 to 135 ° in electrical angle,
Further, the permanent magnet has an armature at an end portion in the circumferential direction of the permanent magnet such that a magnet surface angle β, which is an angle formed by both ends of the arc on the side facing the armature , is 125 ° in electrical angle. A permanent magnet type rotating electrical machine, wherein a chamfered portion having an angle of 30 ° with respect to a side surface of the permanent magnet is formed at a corner on the opposite surface side. The yoke is provided with a magnetic part that protrudes from the inner diameter of the yoke to the inner peripheral side at a portion adjacent to both side surfaces of the permanent magnet, and the amount of protrusion N in the radial direction of the magnetic part is determined by the amount of the permanent magnet. permanent magnet rotating electric machine according to claim 1, half, characterized in der Rukoto thickness M. The permanent magnet, the permanent magnet rotating electric machine according to claim 1 or 2, characterized in that it is radially aligned or radially magnetized. The permanent magnet type rotating electric machine according to claim 2 , wherein the yoke and the magnetic body portion are integrally formed. 5. The permanent magnet type rotating electric machine according to claim 4, wherein the magnetic body portion is provided on a convex portion formed by recessing a portion between the permanent magnets of the yoke toward an inner diameter side. The yoke according to claim 5, characterized in that it is constituted by by recessed portions of the plate-like magnetic material to form the convex portion, joining the ends and further formed into a ring Permanent magnet type rotating electric machine.

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