JPH04185249A - Permanent-magnet rotor - Google Patents

Abstract

PURPOSE:To get a well-balanced waveform of a counter electromotive force and to reduce rotational vibrations by uniting in the axis direction at least two yokes which have even-numbered, at least four, magnetic poles, on the outer part so that magnetic poles of one yoke which have a magnet may be laid on top of magnetic poles of the other yoke which have no magnet in the rotational direction and by letting the polarity of the magnetic poles of one yoke agree with that of the other yoke in the axial direction. CONSTITUTION:Slots 19 to be inserted with permanent magnets are made or every other magnetic pole in the outer part of a yoke 16 at nearly equal distance from the center so that the yoke 16 may have even number of, at least four, magnetic poles 18b, 18b and 18d, 18d on the outer part. Permanent magnets 26, 27 are so attached to the slots 19 respectively that they may have the same polarity toward an axis of rotation. A yoke 15 is structured in the same manner as the yoke 16, however, permanent magnets 24, 25 are attached to the yoke 15 with the magnetic poles facing in the opposite direction to that of the permanent magnets 26, 27 attached to the yoke 16. The two yokes are united in the axial direction so that the magnetic poles of one yoke which have a magnet may be laid on top of the magnetic poles of the other yoke which have no magnet in the rotational direction, so the polarity of the magnetic poles of the two yokes agrees with each other in the axial direction.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a rotor of a brushless motor, and in particular has four or more magnetic poles protruding radially on the surface of a yoke, and one of these magnetic poles This relates to a permanent magnet rotor in which permanent magnets are attached so that the same poles face the center of rotation every other time.

[Conventional technology]

Generally, as a rotor of a brushless motor, a yoke is formed by a plurality of laminated silicon steel plates, and this yoke has at least four even numbered magnetic poles on its outer circumference, and these magnetic poles have slots for attaching permanent magnets. Permanent magnets are provided on the outer peripheral surface of the yoke for every other magnetic pole at approximately equal distances from the center, and permanent magnets are attached to these slots so that the side facing the rotation axis has the same magnetism. FIG. 5 schematically shows the structure of a conventional brushless motor having a rotor of permanent magnet type. The brushless motor, designated as a whole by the reference numeral 29, has a motor case 2, which has a cylindrical side wall 3 and a front surface 4 closing both ends of this side wall.
and a rear plate 5. A plurality of drive coils 6 are arranged in a cylindrical shape inside the side wall 3 and fixed to the wall surface. A rotary shaft 8 is concentrically fixed to the center of the permanent magnet rotor 7. The rotary shaft 8 protrudes from both ends of the permanent magnet rotor 7, and one end is supported by a bearing 10 mounted on the rear plate 5 of the motor case 2. The other end of the six rotatable shafts 8 is rotatably supported by a bearing 12 mounted on the front plate 4 of the motor case 2 .

FIG. 6 shows a conventional permanent magnet rotor 7, in which a rotating shaft 8 is inserted into a yoke 30 formed of a plurality of laminated silicon steel plates, and the rotating shaft 8 and yoke 30 are integrally constructed. ing. The outer periphery of the yoke 30 has at least four even-numbered magnetic poles, and slots 19 for attaching permanent magnets to these magnetic poles are provided on the outer periphery of the yoke 30 every other magnetic pole at approximately equal distances from the center. A permanent magnet 31 is attached to the slot 19 so that the surface facing the rotating shaft has the same magnetism.

In this brushless motor 29, the magnetic pole position is detected using the back electromotive force induced in the windings by the magnetic flux of the magnet attached to the rotor when the motor rotates, and the motor is rotated by a control circuit (not shown).

When the rotor is stationary at startup, no back electromotive force is generated, so the position cannot be detected.Therefore, first, the rotor is excited with a current of the current limiter's limit value using a certain pattern of drive signals for a certain period of time. Then, the rotor moves to a position corresponding to the excitation pattern, and the position is determined. Therefore, if a commutation signal is applied with current flowing to switch the output turn, the permanent magnet rotor 7 will rotate continuously.
The rotational force is taken out to the outside of the motor via the rotating shaft 8 as power. As the motor rotates, it exceeds the minimum rotational speed required for sensorless driving, so a commutation signal is obtained by detecting and processing the back electromotive force from the next commutation, and from now on, sensorless driving is performed. Become.

FIG. 7 is a front cross-sectional view showing the lines of magnetic force of a conventional permanent magnet rotor inside a brushless motor. Slots 19 for attaching magnets are provided on the outer peripheral surface of the yoke 30 for every other magnetic pole at approximately equal distances from the center, and permanent magnets are attached to the slots 19 so that the surface facing the rotating shaft has the same magnetism. 31 is attached. Therefore, as shown in the figure, the magnetic flux of the permanent magnet 31 passes through the magnetic pole 18C and the inside of the drive coil 6 from the north pole toward the south pole, and returns to the magnetic pole 18a.

[Problem to be solved by the invention]

However, in the case of a conventional permanent magnet rotor, two permanent magnets are required for a four-pole rotor, and as shown in Figure 7, the magnetic flux flow of the magnetic poles where the magnets are attached to the outer circumference of the yoke. The magnetic flux flows perpendicularly to the slot 19, whereas the magnetic flux direction of the magnetic poles to which no magnet is attached is intensively pulled and bent by the magnetic force of the drive coil, resulting in different magnetic flux flows at each magnetic pole. Therefore, there was a problem in that the waveform of the back electromotive force induced in the windings was disturbed, resulting in poor rotation.

Therefore, an object of the present invention is to provide a permanent magnet rotor that has twice the number of magnetic poles as the number of magnets due to repulsion between the magnetic poles of the permanent magnets, has a well-balanced back electromotive force waveform, and has little rotational vibration. .

[Means to solve the problem]

In order to achieve the above object, the permanent magnet rotor of the present invention is a rotor of a brushless motor having permanent magnets, in which a yoke is formed by a plurality of laminated silicon steel plates, and this yoke has at least It has four even number of magnetic poles, and slots for attaching permanent magnets are provided on every other magnetic pole at approximately the same distance from the center. A permanent magnet is attached so as to have magnetism, and the at least two yokes with the above structure are coupled in the axial direction so that the magnetic pole with the magnet and the magnetic pole without the magnet overlap in the rotating direction, and the magnetic pole in the axial direction are the same.

〔Example〕

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a brushless motor with a permanent magnet rotor according to the invention, the brushless motor, generally designated 1, having a surrounding motor case 2, which has a cylindrical side wall 3. It is composed of a front plate 4 and a rear plate 5. A plurality of drive coils 6 are arranged in a cylindrical shape inside the side wall 3 and fixed to the wall surface.

A rotary shaft 8 is concentrically fixed to the center of the permanent magnet rotor 7. The rotary shaft 8 protrudes from both ends of the permanent magnet rotor 7, and one end is attached to a bearing 1 mounted on the rear plate 5 of the motor case 2.
The other end of the one-rotation shaft 8, which is rotatably supported by the motor case 2, is rotatably supported by a bearing 12 mounted on the front plate 4 of the motor case 2.

In this brushless motor 1, the magnetic pole position is detected using the electric power (hereinafter referred to as back electromotive force) induced in the windings by the magnetic flux of the magnet attached to the rotor when the motor rotates, and a control circuit (not shown) detects the magnetic pole position. When the 0 rotor rotates by , it is stationary and starting, the position cannot be detected because no back electromotive force is generated.Therefore, first, it is excited with the current limit value of the current limiter using a drive signal of a certain pattern for a certain period of time. . Then, the rotor moves to a position corresponding to the excitation pattern, and the position is determined. Therefore, if a commutation signal is applied with current flowing to switch the output cover turn, the permanent magnet rotor 7 will rotate continuously, and the rotational force will be taken out to the outside of the motor via the rotating shaft 8 as motive power. . Since the rotation of the motor exceeds the minimum rotation speed required for sensorless drive, a commutation signal is obtained by detecting and processing the back electromotive force from the next commutation.
From now on, it will be driven without a sensor.

FIGS. 2 and 3 show an exploded perspective view of a permanent magnet rotor and a completed perspective view of a permanent magnet rotor according to an embodiment of the present invention. The yoke 16 of the permanent magnet rotor 7 is made of a plurality of silicon steel plates laminated in the axial direction of the rotating shaft 8, and an adhesive layer is applied to the surface of the steel plates, and the surfaces are fixed by pressure and heat during lamination.

The thickness of the silicon steel plate of the yoke 16 is either 0.35 mm or 0.5 mm, and as shown in FIG. , slots 19 into which permanent magnets are inserted have magnetic poles 18d, 18d, and are provided on the outer circumferential surface of the yoke 16 for every other magnetic pole at approximately equal distances from the center. Permanent magnets 26 and 27 are attached so that they have the same magnetism.

The yoke 15 is constructed in the same manner, but the magnetic poles of the permanent magnets 24 and 25 are opposite to those of the permanent magnets 28 and 27 attached to the yoke 16. and at least 2
The yokes have the same magnetic poles in the axial direction because the magnetic poles with magnets and the magnetic poles without magnets are coupled in the axial direction so as to overlap in the rotational direction.

Figure 3 shows a yoke 15, 16 and a permanent magnet 2 on the rotating shaft.
4, 25, 26, and 27 are respectively inserted and coupled. The figure shows a completed perspective view of the permanent magnet rotor 7, in which the length of the permanent magnet is shorter than the length of the yoke by at least one steel plate, and magnetic flux leaks to the side of the permanent magnet. It has a structure without FIG. 4 shows the flow of magnetic lines of force in the permanent magnet rotor 7 when it is inside the motor. A notch 26 is provided between the S pole 18a and the N pole 18c, and the permanent magnet 24 is The lines of magnetic force coming out from the north pole repel each other in the permanent magnets, come out from the magnetic pole surface of 18c, pass through the inside of the drive coil 6, and reach the south pole. Furthermore, at least two yokes are coupled in the axial direction so that a magnetic pole with a magnet and a magnetic pole without a magnet are overlapped in the rotational direction, and since the magnetic poles in the axial direction are the same, the surface passing through the magnetic poles 18a and 18c The combination of magnetic fluxes becomes equal to each other, and the back electromotive force waveforms also become equal.

In this example, the permanent magnet is a braceodium (P
(r) Cast magnets made from alloys are used, but cast magnets (alnico magnets, braceodium magnets), sintered magnets (ferrite magnets, rare earth magnets), and resin bonded magnets (ferrite magnets, rare earth magnets) are used. can be used. Furthermore, although a silicon steel plate is used as the material of the yoke, any one of sintered alloy, lump iron, and cold rolled steel (SPCC material) can be used.

The permanent magnet is in the form of a plate with a rectangular cross section in which the length of the side that coincides with the axial direction of the rotor is in the range of 2 to 5 times the length of the side that touches the rotational direction of the rotor. It is easier to process than other magnets.

- Since the silicon steel plate of the yoke 16 of the invention is formed by press working, high productivity can be obtained and a rotor with a more precise outer diameter can be obtained.

〔Effect of the invention〕

As is clear from the description of the embodiments above, according to the present invention, four or more magnetic poles are provided radially on the outer periphery of a silicon steel plate, and slots are provided on the outer periphery of the yoke of every other magnetic pole. At least two
The yokes are coupled in the axial direction so that the magnetic pole with a magnet and the magnetic pole without a magnet overlap in the rotating direction, and since the magnetic poles in the axial direction are the same, the rotation with a well-balanced back electromotive force waveform of each magnetic pole is achieved. A permanent magnet rotor with less vibration can be obtained.

Furthermore, the permanent magnet of the present invention has a simple shape and is made of hard material, so it can withstand high-speed rotation.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a brushless motor having a permanent magnet rotor according to the present invention. FIG. 2 is an exploded perspective view of the permanent magnet rotor of the present invention. FIG. 3 is a completed perspective view of the permanent magnet rotor of the present invention. FIG. 4 is a front cross-sectional view showing lines of magnetic force of the dual magnet rotor of the present invention inside the brushless motor. 51st! I. Cross-sectional view of a brushless motor with a conventional permanent magnet rotor. FIG. 6 is a perspective view of a conventional permanent magnet rotor. FIG. 7 is a front sectional view showing lines of magnetic force of a conventional permanent magnet rotor inside a brushless motor. 1... Brushless motor, 7... Permanent magnet rotor,
16 - York, l 8 a, 18
b, 18c, 18d...Magnetic pole, 19...Slot, 24.25, 26.27...Permanent magnet or more Applicant Seiko Epson Corporation Representative Patent Attorney Kizobe Suzuki and 1 other person Figure 4' L9 Figure 6

Claims (1)

[Claims] 1) In the rotor of a brushless motor having permanent magnets, a yoke is formed by a plurality of laminated silicon steel plates, and this yoke has at least four even numbered magnetic poles on its outer periphery. Slots for attaching permanent magnets are provided on the outer circumferential surface of the yoke for every other magnetic pole at approximately the same distance from the center, and the slots have the same magnetic properties on the side facing the rotating shaft. a permanent magnet is attached to the yoke, and the at least two yokes with the above structure are coupled in the axial direction so that the magnetic pole with a magnet and the magnetic pole without a magnet overlap in the rotation direction, and the magnetic poles in the axial direction are the same. A permanent magnet rotor characterized by: 2) Use of any one of cast alnico magnets, cast hot-worked rare earth boron magnets, sintered ferrite magnets, sintered rare earth magnets, resin bonded ferrite magnets, and resin bonded rare earth magnets. A permanent magnet rotor according to claim 1.