JP2000134893A - Brushless motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a high efficiency brushless motor containing no cogging torque and having a simple structure wherein the stator is constructed by winding an armature winding around tees and the rotor is constructed by applying magnets on the surface of a yoke such that the relationship between the pole pitch and the circumferential length at the magnetized part of a magnet falls within a specified range. SOLUTION: Magnets 3 of identical shape and magnetization are arranged at a constant pole pitch to a rotor iron 4 and pasted thereto. Polarity of the magnets is alternated and the intensity of magnetization is equalized for all magnets and made uniform on the magnet surface. The pole pitch τp and the circumferential length τm of the magnet 3 satisfy a relationship τm<τp. Teeth 6 are arranged at constant pitch on the stator and a coil 5 is wound concentrically around the teeth. Opening of a slot receiving the coil 5 is limited in order to prevent spring out of the coil and to reduce harmonic field at the gap part. According to the arrangement, a high efficiency brushless motor containing no cogging torque and having a simple structure can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a brushless motor, and more particularly to a permanent magnet type brushless motor used for an elevator or the like, which is required to have a relatively large and low torque ripple.

[0002]

2. Description of the Related Art In general, a concentrated winding brushless motor is D
Widely used for micro motors such as VD. The structure is such that coils are intensively wound around a rotor in which a ring-shaped integral magnet, which is magnetized alternately N and S at equal intervals, is attached to a rotor core, and teeth arranged at equal pitches. Consists of a stator. Electrically, two poles and three teeth or four poles and three teeth are basic units, and by repeating the same, motors having eight poles and 12 teeth and 12 poles and 9 teeth are widely used. However, this motor has a large cogging torque, which must be reduced by a method such as skew.

On the other hand, Japanese Unexamined Patent Publication No. 62-110468 discloses a motor having 10 poles to 12 teeth and a motor having 14 poles to 12 teeth. The frequency is reduced by increasing the frequency of cogging torque. A method has been proposed.

[0004]

However, even in the above method, the cogging torque may not be sufficiently small depending on the use of the motor. For example, in a machine such as an elevator in which the number of revolutions of the motor changes continuously, it is inevitable that the vibration frequency of the cogging torque overlaps with the resonance point of the mechanical system at a certain number of revolutions. If there is, torque ripple will increase.

[0005] To solve this problem, the most common conventional countermeasure is to perform skew. However, the skew complicates the structure of the motor, thereby reducing manufacturability and deteriorating motor characteristics. There is. As another method, there is a method in which a groove is provided at the tip of the tooth. However, this is also inferior in manufacturability, a magnetic gap is widened, and motor characteristics are deteriorated. As another method, there is a method in which the magnetization of the magnet is magnetized in a sine wave shape.However, when a large motor with a diameter of about several tens of centimeters is used, the magnet cannot be made as an integral body. Since neodymium magnets are extremely expensive and account for the largest percentage of the total cost of the motor, it is desirable that the magnets have a shape that is easy to process and have a simple magnetization.

In view of the above problems, an object of the present invention is to provide a highly efficient brushless motor having a simple structure and no cogging torque, and an application product thereof.

[0007]

The feature of the present invention to achieve the above object is that the stator has a structure in which armature windings are intensively wound around each of 12 teeth, and the rotor has a structure in which 10 teeth are provided.
Attach a pole or 14 pole magnet to the yoke surface,
The pole pitch τp and the circumferential length τm of the magnetized portion of the magnet
Is set to fall within a predetermined range. The predetermined range is “τm <τp” or “τm / τp ≒ 0.8
7 "," τm / τp ≒ 0.72 ”. As will be described later, the number of poles may be multiplied by a natural number.

Another feature of the present invention resides in that the magnet is fixed by a jig by utilizing the gap between the magnets generated by this structure.

Another feature of the present invention is that in the abduction type motor comprising a plurality of repetitions of the electric unit, the outer side of each magnet is cut along the inner circumference of the rotor iron, and the magnetic gap is reduced. The side is to be plane.

Another feature of the present invention is that a rotor having 10n poles or 14n poles magnets attached to the yoke surface, where n is an integer of 1 or more, a core composed of 12n teeth, and each tooth are provided. In a brushless motor having a stator with intensively wound armature windings, the pole pitch τp
And the circumferential length τm of the magnetized portion of the magnet is “τm <
τp ”.

Another feature of the present invention is that a rotor having a magnet of 10n poles or 14n poles bonded to the yoke surface, where n is an integer of 1 or more, a core composed of 12n teeth, and each tooth are provided. In a brushless motor having a stator with intensively wound armature windings, the pole pitch τp
And the circumferential length τm of the magnetized portion of the magnet falls within a predetermined range, and the predetermined range is “τm / τp ≒ 0.87”.
Alternatively, a brushless motor characterized in that “τm / τp ≒ 0.72”.

Another feature of the present invention is that, in the brushless motor described above, when one pole is constituted by one magnet, each magnet is connected to a rotor by using a jig in a gap generated between the magnets. It is fixed to.

Another feature of the present invention is that in the above-described brushless motor, an axle-type motor in which a rotor having one pole formed of one magnet is located outside a stator, and each magnet has an outer periphery. The side is cut along the circumference of the rotor core,
The inner peripheral side is a plane.

Another feature of the present invention is that the brushless motor according to any one of claims 1 to 4 is used as a hoist motor in an elevator apparatus including a hoist, a car, a rope, and a counterweight. is there.

The above and other features of the present invention will be apparent from the following description.

[0016]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows an embodiment of the present invention. FIG. 1 shows a sectional structure of a brushless motor according to an embodiment of the present invention. This motor is a so-called external rotation type motor in which the rotor 1 is located outside the stator 2. The rotor 1 is provided with ten fan-shaped magnets 3 each having the same shape and the same magnetization, all of which are arranged at equal intervals of a pole pitch 9 on the rotor iron 4 and bonded to the rotor iron 4. The polarity of the magnet is such that the magnetization direction is alternately N and S adjacent to the axis center, and the magnetization intensity is the same for all magnets and uniform on the magnet surface. The magnet 3 is configured such that the ratio of the circumferential length τm to the pole pitch τp is 0.87. Therefore, a gap of 0.13 in pole pitch ratio is formed between the magnets.
By utilizing this, for example, a magnet holder 8 as shown in FIG.
The magnet 3 can be fixed with the metal fitting. If there is no gap between the magnets, it is difficult to fix the magnets, but this method can easily fix them. On the other hand, the stator has twelve teeth 6 arranged at equal pitches, and the coils 5 are wound around each tooth intensively. The space in which the coil 5 enters is called a slot. As shown in FIG. 1, the opening of the slot is narrowed, which aims to prevent the coil from popping out and reduce the harmonic magnetic field in the gap.
It is well known that it is generally better not to widen the slot opening.

The cogging torque is a torque pulsation peculiar to the brushless motor, and is generally evaluated by a torque waveform when the motor is forcibly turned from the outside without energizing the armature winding. The cycle of the cogging torque is determined by the number of teeth and the least common multiple of the number of magnetic poles. Since the motor of FIG. 1 has 10 poles and 12 teeth, pulsation occurs due to 60 times of cogging torque per rotation of the motor. This motor has an electrical angle of one rotation
Since it is 0π, the cycle of the cogging torque is 1 /
6π.

FIG. 2 shows the results of analysis and calculation of the waveform of the cogging torque. In the analysis, the rotor is rotated little by little without energizing the armature winding, the torque is calculated each time, and the waveform obtained by summing up the results is the waveform shown in FIG. The horizontal axis in FIG. 2 is the rotation angle of the motor in electrical angle, and the vertical axis is the magnitude of the torque. Further, eight types of motors were analyzed, and the ratio τm / τp of the pole pitch τp and the length τm in the magnet circumferential direction in the motor structure of FIG. 1 was varied from 1.00 to 0.70. Since these motors have the same pole pitch τp, they are motors which differ only in the circumferential length of the magnet.
As can be seen from the waveforms in FIG. 2, the waveforms of all the motors are sinusoidal, have almost no harmonics, and have the same phase. Therefore, only the amplitude of the cogging torque depends on the circumferential length τp of the magnet.

Therefore, in order to make this easier to understand, FIG. 3 shows a relationship diagram based on FIG. 2, in which τm / τp is plotted on the horizontal axis and the cogging torque amplitude is plotted on the vertical axis. As is clear from FIG. 3, in the state of τm <τp, the cogging torque is more surely reduced than in the case of τm = τp.
It can be seen that there is almost no cogging torque when .tau.p = 0.87 and near 0.72. τm / τp
2 is between 0.72 and 0.87, the amplitude is negative because the phase of the cogging torque is 180 in FIG.
反映 It reflects something that has changed. The amplitude reaches the maximum value in the opposite phase when τm / τp = 0.80. According to FIG. 3, the amplitude of the cogging torque is “τm / τ
It changes almost sinusoidally with respect to "p".

By the way, looking only at the cogging torque, τ
Also in the case of m / τp ≒ 0.72, the cogging torque becomes small. Also, in the case of τm / τp ≒ 0.87, the amount of magnets is larger than in the case of τm / τp ≒ 0.72, so that the torque can be increased. This is desirable because the motor output can be increased in density.

The values of 0.87 and 0.72 are 10
The following shows that the values are almost universal for a motor having 12 teeth of poles. Since the number of poles and the number of slots are determined in the motor according to the invention, there are countless other combinations having different motor sizes, gap lengths, armature windings, magnet shapes, and teeth shapes. However, in a motor having a simple tooth shape and a simple magnet as shown in FIG. 1, only the gap length and the slot opening determine the magnitude of the cogging torque.

FIG. 4 shows that the values of .87 and 0.72, which are the values of .tau.m / .tau.p, hardly depend on the gap between the stator and the rotor. FIG. 4 shows the eight types of motors used in the calculation of FIG.
The cogging torque waveform was analyzed for a total of 24 types of motors, which were changed to 5 mm and 2 mm, and the amplitude and “τm /
τp ”. As can be seen from FIG. 4, changing the gap changes the absolute value of the amplitude of the cogging torque, but the trend of this waveform is not different from that of FIG. Therefore, τm at which the amplitude is almost eliminated
It can be seen that the value that / τp is 0.87 or 0.72 does not depend on the gap.

FIG. 5 shows the value of .tau.m / .tau.
The value of 87 or 0.72 slightly changes depending on the width of the slot opening. FIG.
Analyzes the cogging torque waveforms for a total of 24 types of motors in which the slot openings are changed to 4 mm, 6 mm, and 8 mm from the eight types of motors used in the calculation of FIG. 2, and the amplitude and “τm / τp Is summarized. According to FIG. 5, τm = τ has the largest amplitude.
In the case of p, the time when the waveform of the cogging torque is in the opposite phase and has the largest amplitude is when τm / τp = 0.80. This tendency is exactly the same as in FIG. However, in FIG. 5, the ratio between the positive maximum value and the negative maximum value of the amplitude is slightly different depending on the width of each slot opening.
There is a difference in the degree. However, as is apparent from FIG. 5, it is certain that there is a value where the amplitude becomes zero between τm / τp = 1.0 and 0.8, and the value is 0.85 to 0. Between .90. Therefore, there is τm / τp where the cogging torque disappears between 0.85 and 0.90 even if the waveform slightly changes as shown in FIG.
It can be seen that the present invention is effective between 0. Similarly, the cogging torque disappears even when τm / τp is between 0.70 and 0.75. Thus, in the present invention, the cogging torque can be eliminated by a very simple means of setting the width of the magnet to a predetermined value.

Next, a concentrated winding motor of a comparative example will be described. The structure is the same as the basic structure of FIG.
The number of poles and teeth is 12. The motor of the structure of this comparative example is electromagnetically a repetitive structure of a basic unit of two poles and three teeth, and is a rotationally symmetric motor including the winding method of the teeth. The cycle of cogging torque is 2 which is the least common multiple of 8 poles and 12 teeth.
4, since the electric angle of this motor is 8π per rotation, the period of the cogging torque is 1 / 3π.

FIG. 6 shows the waveforms of cogging torques of the motor of the comparative example, which are calculated and analyzed for five types of motors in which only the circumferential length of the magnet is changed. It can be seen that the waveform in FIG. 6 includes a cogging component having a 1 / 6π period in addition to the above-described component having a 1 / 3π period. τm / τp = 0.87
In the case of (1), the component of the 1 / 6π period seems to have almost disappeared, but it can be seen that the component of the 1 / 3π period has hardly changed. Therefore, the cogging torque cannot be eliminated regardless of the value of τm / τp.

As can be seen from the above, the present invention is particularly effective for a motor having 10 poles and 12 slots.
However, the effect is small compared to the electromagnetically basic motor having two poles and three teeth. Also, there is a motor having a repeating structure of an electromagnetic basic unit of 4 poles and 3 teeth such as 12 poles and 9 teeth. Even in such a motor, the waveform of the cogging torque is very similar to the waveform of FIG. , The cogging torque is 1 / 3π cycle component and 1/6
It has two components of π period. Therefore, the present invention has a small effect even with a motor having a repeating structure of an electromagnetic basic unit having four poles and three teeth.

A feature of the present invention is that a completely excellent effect can be obtained even with a motor having 14 magnets while keeping the structure of FIG. 1 as it is. FIG. 7 shows the waveform of the cogging torque analyzed and calculated by this motor. This waveform has almost the same tendency as the motor having 10 poles and 12 teeth shown in FIG. 2. When τm / τp = 1.0, the amplitude is maximum, when τm / τp = 0.80, the amplitude is maximum in the opposite phase, τm / τp. = 0.87, the amplitude almost disappears. Therefore, even in a motor having 14 poles and 12 teeth, the cogging torque can be eliminated with a value of τm / τp = 0.87 or 0.72.

A motor having a pole / slot ratio of 10/12, such as 20 poles 24 teeth, 30 poles 36 teeth, etc., in which the electromagnetic structure of the motor of the 10 pole 12 tooth basic unit is repeated, or 14 28 poles 24 teeth, 42 repeating the electromagnetic structure of poles 12 teeth
The features of the present invention provide the same effect for a motor having a ratio of the number of poles such as 36 teeth and slots to 14/12.

The above is an embodiment in which one pole on the rotor side is constituted by one magnet and its width is kept within a predetermined range. However, a plurality of poles of the rotor are constituted by one magnet, and The same effect as described above can be obtained by taking a magnetizing method such as keeping the magnetic range within the above-mentioned predetermined range or weakening the magnetization between the poles in the predetermined range.

Although the above embodiment is directed to an external rotation type motor, it is also effective for an internal rotation type brushless motor.

FIG. 8 shows another embodiment of the present invention. The magnet is an external rotation type motor having 40 poles and 48 teeth, and is electrically four times the structure of the above-described 10 poles and 12 teeth motor. This embodiment is characterized in the magnet shape, and the outer peripheral side of the magnet that is in close contact with the rotor iron 4 is cut into an arc shape along the inner circumference of the rotor iron 4, thereby improving the stability of fixing the magnet. On the other hand, the inner peripheral side of the magnet is not scraped off to have an arc shape, but a flat surface. In a brushless motor using an expensive neodymium-based magnet, the cost of the magnet material and processing is the largest share of the cost. Regarding the processing cost, in processing a magnet, it is easy to cut the corners of the magnet to round it into a convex shape, but it is difficult to cut the inside of the magnet to round it into a concave shape. Therefore, if the outer peripheral side of the magnet is made convex and the inner peripheral side is made flat, processing can be simplified and the cost can be reduced. In FIG. 8, since the inner peripheral side of the magnet is a plane, the cross-sectional shape is drawn as a straight line, but it is hardly apparently distinguished from an arc. Therefore, since it is apparent that there is almost no change in the magnetic circuit, the feature of the present invention that the circumferential length is set to 0.87 of the pole pitch is effective as it is.

FIG. 9 is a schematic view showing an embodiment of an elevator apparatus using a motor according to the present invention. The hoisting motor 9 directly drives the sheave 10, the force of which is transmitted to the rope 12, and the car 11 moves along the guide rail 14.
Both ends of the rope 12 are fixed to the ceiling, and the car 11 and the counterweight 13 are suspended via the pulley 16. Since the torque of the motor is transmitted to the car 11 via the rope, the car vibrates if there is a torque pulsation such as cogging torque, and the riding comfort is deteriorated. Rope 12 and counterweight 1
Due to the configuration of the elevator 3 and the car 11, it is unavoidable to have a mechanical system resonance frequency of several Hz, so even a slight torque ripple of the motor amplifies the car vibration and degrades ride comfort. The use of the motor according to the present invention eliminates the cogging torque, thereby realizing an elevator having a comfortable ride. Further, in the motor of the present invention, since the armature winding is wound around each of the teeth, there is an advantage that the coil end is smaller than that of the motor having the normal distributed winding. Therefore, it is effective for reducing the size of the motor, especially for reducing the thickness. By arranging this thin motor in the gap between the cage and the wall in the hoistway 15 as shown in FIG. 9, an elevator without a rooftop machine room can be realized while suppressing an increase in the cross-sectional area of the hoistway.

As described above, according to the present invention, a magnet having a simple shape and magnetization is used, and the width of the magnet is set to 0.8, which is the pole pitch.
Simple structure of 7 or 0.72, 10 poles 1
The cogging torque of a brushless motor of 2 teeth or 14 poles and 12 teeth can be eliminated, and the efficiency does not deteriorate as compared with before the measures are taken.

If the magnet width is reduced and a magnet is fixed in this gap by using a jig, the fixing method is simplified.

Also, in an epimotor using this structure, the outer peripheral surface of the magnet is formed into an arc shape and the inner peripheral surface is made flat, thereby facilitating machining of the magnet and eliminating cogging torque with a simpler shape. be able to.

Further, by using the motor of the present invention for an elevator hoist, it is possible to obtain an elevator apparatus having good ride comfort and having no roof-top machine room having a small hoistway cross-sectional area.

[0037]

According to the present invention, a highly efficient brushless motor having a simple structure and no cogging torque, and an application product thereof can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a structure of a brushless motor according to an embodiment of the present invention.

FIG. 2 is a diagram showing a cogging torque waveform of the motor according to the embodiment of the present invention.

FIG. 3 is a diagram showing the relationship between the amplitude of cogging torque and τm / τp.

FIG. 4 is a diagram showing the gap dependence of the relationship between the amplitude of the cogging torque and τm / τp.

FIG. 5 is a diagram showing the slot opening dependence of the relationship between the amplitude of the cogging torque and τm / τp.

FIG. 6 is a diagram showing a waveform of a cogging torque of a motor having a 2-pole-3 teeth structure of a comparative example.

FIG. 7 is a diagram illustrating a cogging torque waveform of a motor according to another embodiment of the present invention.

FIG. 8 is a view illustrating a motor structure according to another embodiment of the present invention.

FIG. 9 is a diagram showing an embodiment of an elevator apparatus using the motor of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotor, 2 ... Stator, 3 ... Permanent magnet, 4 ... Rotor iron, 5 ... Coil, 6 ... Teeth, 7 ... Shaft, 8 ... Magnet holding, 9 ... Hoisting motor, 10 ... Sheave, 11 ... Basket, 1
2 ... rope, 13 ... counterweight, 14 ... guide rail, 15 ... hoistway, 16 ... pulley.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Motoya Ito 7-1-1, Omikacho, Hitachi City, Ibaraki Prefecture Within Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Fumio Tajima 7-1 Omikacho, Hitachi City, Ibaraki Prefecture No. 1 Inside Hitachi, Ltd.Hitachi Research Laboratories (72) Inventor Suetaro Shibukawa 2520 Oji Takaba, Hitachinaka City, Ibaraki Prefecture Inside Hitachi Ltd. Automotive Equipment Division (72) Inventor Kenji Kuniya Hitachika City, Ibaraki Prefecture 2520 Co., Ltd.Hitachi, Ltd.Automotive Equipment Division (72) Inventor Hideki Nihei 1070 Ma, Hitachinaka-shi, Ibaraki Pref.Hitachi, Ltd.Mito Plant, Hitachi Ltd. (72) Inventor Takanori Nakata 1070, Mo, Hitachinaka-shi, Ibaraki Stock F-term in the Mito Plant of Hitachi, Ltd. (reference) 5H019 AA03 CC03 CC04 CC07 CC 08 CC09 DD01 DD10 EE01 FF01 5H621 AA02 BB10 GA01 HH01 JK01 JK15

Claims (5)

[Claims] 1. A rotor in which n is an integer of 1 or more, and a 10n-pole or 14n-pole magnet is attached to a yoke surface,
In a brushless motor having a stator made of 12n teeth and a stator in which armature windings are intensively wound around each tooth, the relationship between the pole pitch τp and the circumferential length τm of the magnetized portion of the magnet is expressed as “τm <Τp ”. 2. A rotor in which n is an integer of 1 or more, and a 10n-pole or 14n-pole magnet is attached to a yoke surface;
In a brushless motor having a core made of 12n teeth and a stator having armature windings intensively wound on each tooth, the relationship between the pole pitch τp and the circumferential length τm of the magnetized portion of the magnet is predetermined. The predetermined range is “τm / τp ≒ 0.87” or “τm / τp ≒ 0.7.
2 ", a brushless motor. 3. The brushless motor according to claim 1, wherein each magnet is fixed to a rotor by using a jig in a gap formed between the magnets when one pole is constituted by one magnet. Brushless motor characterized in that: 4. A brushless motor according to claim 1, wherein a rotor having one pole formed by one magnet is located outside the stator, and each magnet is A brushless motor characterized in that the outer peripheral side is cut along the circumference of the rotor core and the inner peripheral side is flat. 5. An elevator apparatus comprising a hoist, a car, a rope, and a counterweight, wherein the brushless motor according to claim 1 is used as a hoist motor.