JPH03195337A - Step motor and manufacture thereof - Google Patents

Abstract

PURPOSE:To facilitate manufacture of a motor having high torque and high output by burying a permanent magnet having high coercive force in the groove at the core tooth section of the motor and employing a permanent magnet having low coercive force as the main flux field magnet. CONSTITUTION:Magnetic rotor steel boards are laminated to produce rotor core blocks 6a, 6b, non magnetized rare earth permanent rod magnets 16a, 16b are inserted into the groove in a rotor tooth 7 and secured in place, then the outer circumference thereof is polished. The permanent rod magnet 16a is magnetized radially and the permanent rod magnet 16b is magnetized in different direction. A non-magnetized Alnico disc permanent magnet is then sandwiched between two rotor cores provided with permanent rod magnets and fixed to a rotary shaft 11 thus assembling a rotor. Thus assembled rotor is then placed in a ceramics and subjected to a magnetic field in the axial direction thus magnetizing the permanent disc magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a stepping motor and a method for manufacturing the same.

(Prior Art) In recent years, there has been a demand for the development of small, lightweight motors with high output density (motor torque/motor weight) as actuators for drive mechanisms of precision control equipment for OA and FA.

A stepping motor having an inductor is generally used as a motor that generates high torque.

Since the stepping motor has a large number of teeth (inductors) on the air gap surface, the air gap magnetic flux density changes as the magnetic resistance changes depending on the rotor position. This changes the magnetic energy and produces torque.

However, if the air gap length is narrowed or the magnetic loading/electrical loading is increased, the torque will not increase much and the motor will become larger due to magnetic saturation of the core teeth and leakage of magnetic flux to the tooth sides.

Therefore, the following stepping motor has been developed to improve this drawback.

10 and 11 show a conventional high-torque/high-output chipping motor. The motor has a structure in which a plurality of stator pole teeth 2 are provided in the circumferential direction of a stator core 1, and each A polyphase winding 4 is wound around the stator pole teeth 2,
A plurality of stator small teeth 3 are provided on the inner circumferential surface of each stator pole tooth 2, and a stator with a rod-shaped permanent magnet 5 fixed in a radial direction magnetized in the groove of the stator small teeth 3, A plurality of rotor teeth 7 are provided on the outer circumferential surface of the rotor core 6 facing each other, and the rotor teeth 7 are divided into two in the axial direction, and each rotor tooth 7 is divided into 1/2.
The tooth pitch is shifted, a disc-shaped permanent magnet 8 magnetized in the axial direction is provided in the divided part, and a rod-shaped permanent magnet 9 magnetized in the radial direction is fixed in the groove of the rotor teeth 7. The polarity of the permanent magnet 5 and the rod-shaped permanent magnet 9 of the rotor is set in a direction that cancels out the main magnetic flux generated by the disk-shaped permanent magnet 8, thereby achieving high torque and high output. Note that the reference numeral 11 indicates a rotation axis.

(Problems to be Solved by the Invention) In the stepping motor rotor shown in FIGS. 10 and 11, the rod-shaped permanent magnets 9 and the disc-shaped permanent magnets 8 embedded in the grooves of the rotor teeth 7 are formed in a closed magnetic path. The direction of the magnetic flux is opposite. Therefore, if both magnets are magnetized after assembly, the permanent magnet that was magnetized first may be affected by the reverse magnetic field when the remaining permanent magnets are magnetized later, and may be demagnetized.

Therefore, when manufacturing the rotor of the high-torque, high-output chipping motor described in "-", after magnetizing the disc-shaped permanent magnet 8 in the rotor, the magnetized bar-shaped permanent magnet 9 is magnetized. Insert and fix into the groove of the rotor tooth 7. However, the polarity of the disk-shaped permanent magnet 8 and the rod-shaped permanent magnet 9 is opposite, and the rod-shaped permanent magnet 9 is connected to the rotor tooth 7.
When inserted into the groove, the magnet receives a repulsive force, resulting in poor workability and may damage the magnet. Furthermore, if the outer diameter of the rotor is polished after the entire assembly, the polished iron powder will adhere to the magnetized rotor surface and become clogged between the motor gaps 10, making it impossible to drive.

Therefore, the present invention provides a high-torque, high-power product that is easy to manufacture by embedding a permanent magnet with a high coercive force in the groove of the motor core teeth and using a permanent magnet with a low coercive force as the main flux field magnet. The present invention aims to provide a stepping motor and a method for manufacturing the same.

[Structure of the invention]

(Means for Solving the ill! Problem) The present invention provides a plurality of stator pole teeth in the circumferential direction of a stator core, and winds a polyphase winding around each stator pole tooth, and A stator comprising a plurality of small stator teeth and a first rod-shaped permanent magnet with a high coercive force magnetized in the radial direction fixed in the groove of the small stator teeth, and an outer circumferential surface of a rotor core facing the small stator teeth. The rotor is divided into two parts in the axial direction, the rotor teeth are shifted by 1/2 tooth pitch, and a low coercive force disc-shaped permanent magnet magnetized in the axial direction is provided in the divided part. It consists of a rotor in which a rod-shaped permanent magnet with a high coercive force magnetized in the radial direction is fixed in the tooth groove, and the polarity of the first rod-shaped permanent magnet and the second rod-shaped permanent magnet is generated by the disk-shaped permanent magnet. The direction is to cancel the magnetic flux.

In addition, the present invention involves inserting and fixing bar-shaped, unmagnetized rare earth permanent magnets into the grooves of the rotor teeth, polishing the outer periphery, and in this state, removing the two rotor cores magnetized in the radial direction. After assembling the rotor by sandwiching and attaching a disk-shaped permanent magnet with a low coercive force to the rotating shaft, the disk-shaped permanent magnet is placed inside a thin cylinder of magnetic material and magnetized in the axial direction to manufacture the rotor. This is what I did.

(Function) A permanent magnet with a low coercive force does not have a large saturation magnetizing magnetic field, so even if a magnetized permanent magnet with a high coercive force is applied with a saturating magnetizing magnetic field in a reverse magnetic field, a high coercive force permanent magnet will not be demagnetized. .

Therefore, after assembling the rotor with the permanent magnets unmagnetized, first the bar-shaped permanent magnets can be magnetized in the radial direction, and then the disk-shaped permanent magnets can be magnetized in the axial direction. Manufacturing becomes easy.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a vertical sectional view showing one embodiment of the present invention, and FIG.
The figure is a cross-sectional view taken along line A-A in Figure 1;
FIG. 3(a) is a sectional view taken along line XX in FIG. 1, and FIG. 3(b) is a sectional view taken along line Y-Y in FIG. 1.

First, the configuration of the stepping motor will be explained.

As shown in FIGS. 1 and 2, the stator 12 has eight stator pole teeth 2 disposed circumferentially on the inner circumferential side of the stator core 1.
Five stator small teeth 3 are formed on the inner circumferential surface of the stator pole tooth 2, and each stator pole tooth 2 is provided with a two-phase winding 4.

The rotor 13 also has two rotor cores 6 on the rotating shaft 11.
A disk-shaped permanent magnet 14, which is an alnico permanent magnet with a low coercive force, is sandwiched in the axial direction. Therefore, on the outer peripheral surface of the rotor core 6, there are 5
Zero rotor teeth 7 are provided, and the two rotor cores 6 are fixed to the rotating shaft 11 at positions offset from each other in the circumferential direction by 1/2 of the rotor tooth pitch. Further, the disk-shaped permanent magnet 14 is magnetized in the axial direction.

On the other hand, rod-shaped permanent magnets 15a, 15b, which are rare earth permanent magnets with high coercive force, are embedded in the grooves of the stator small teeth 3, and two rod-shaped permanent magnets 15a, 15b are inserted into one groove.
15b is arranged at an arbitrary distance from the center of the stator core 1 so as to be magnetically divided into two parts, and the magnetization direction is in the radial direction, and the magnetic flux generated by the disk-shaped permanent magnet 14 of the rotor 13 is struck. The direction is to erase. In the same state, rod-shaped permanent magnets are placed in the grooves of all the small stator teeth 3 in the circumferential direction],
5a and 15b are embedded.

Further, in the grooves of the rotor teeth 7 of the two rotor cores 6, there are bar-shaped permanent magnets 16a, 1, which are rare earth permanent magnets with high coercive force.
6b is embedded. This rod-shaped permanent magnet 16a,
The magnetization direction of magnet 1.6b is the direction that cancels the magnetic flux generated by the disk-shaped permanent magnet 14 provided on the rotor 13, and is the radial direction.

In addition, in this embodiment, the air gap surface of the rod-shaped permanent magnet 16a of the rotor 13 becomes the south pole on the X-X cross section side, and the air gap surface of the rod-shaped permanent magnet 16b of the rotor 13 becomes the north pole on the Y-Y cross section side. . In the same state, rod-shaped permanent magnets 16a and 16b are embedded in the grooves of all the rotor teeth 7 in the circumferential direction.

Next, a method of manufacturing the stepping motor configured as described above, particularly a method of manufacturing the rotor thereof, will be described.

(1) First manufacturing method First, two block-shaped rotor cores 6 are made by laminating rotor magnetic steel plates, and rod-shaped permanent magnets, which are unmagnetized rare earth permanent magnets, are placed in the grooves of each rotor tooth 76. The magnet 16 is inserted and fixed, and the outer periphery is polished. Next, with one of the two rod-shaped permanent magnets 16 attached to the rotor core 6 as shown in FIG. The rod-shaped permanent magnet 16 is magnetized. Further, the bar-shaped permanent magnet 16 is magnetized in the same manner by changing the magnetization direction of the other magnet. Next, the disk-shaped permanent magnet 14, which is a disk-shaped non-magnetized alnico permanent magnet, is sandwiched between two rotor cores with rod-shaped permanent magnets and is attached to the rotating shaft 11, and the rotor is assembled, as shown in FIG. The rotor 1 is made of a thin cylinder 22 made of magnetic material.
3 is placed in a magnetizer 23 formed in a cylindrical shape with a non-magnetic material, and 3kO is applied in the axial direction by an axial magnetizing coil 24.
The disk-shaped permanent magnet 14 is magnetized by applying a magnetic field of e.

■Second manufacturing method Similarly to the first manufacturing method described above, after rotor assembly and outer periphery polishing, the rod-shaped permanent magnet 16 is magnetized, and the disc-shaped permanent magnet 1 is magnetized.
4, after assembling the motor in an unmagnetized state, put the motor into a magnetizer and apply 3k to the entire motor using an axial magnetizing coil.
The disk-shaped permanent magnet 14 is magnetized by applying an axial magnetic field of Oe.

■ Third manufacturing method Insert an unmagnetized bar-shaped permanent magnet 16 into the groove of the rotor tooth 7.
The unmagnetized disk-shaped permanent magnet 14 is sandwiched between two rotor cores with rod-shaped permanent magnets that have been fixed and polished on their outer peripheries, and are attached to the rotating shaft 11 to assemble the rotor. First, the rotor is assembled using a magnetizer shown in FIG. Radial magnetizing coil 2 attached to magnetizing yoke 25
6a, 26b, and 26c apply a radial magnetic field of 20 kOe to magnetize the rod-shaped permanent magnets 16 of the rotor 13.

Next, the rotor 13 is covered with the thin cylinder 22 described above, and the fifth
Using the magnetizer 23 shown in the figure, an axial magnetic field of 3 kOe is applied to the disk-shaped permanent magnet 14 by an axial magnetizing coil 24.
magnetize.

(a) Fourth manufacturing method After rotor assembly and rotor outer periphery polishing are completed by the third manufacturing method described in 1, first, the radial magnetizing coils 26a, 26b, 26c are made using the magnetizer shown in FIG. By 2
A radial magnetic field of 0 kOe is applied to magnetize the rod-shaped permanent magnets 16 of the rotor 13. Next, after assembling the motor, use the magnetizer shown in FIG.
4, the disk-shaped permanent magnet 14 is magnetized by applying an axial magnetic field of 3 kOe.

(fifth manufacturing method) In the stepping motor having the above-described structure and its manufacturing method, the bar-shaped permanent magnet is a rare earth plastic permanent magnet.

(6) Sixth manufacturing method In each of the second to fifth manufacturing methods described above, the rod-shaped permanent magnet is formed by placing rare earth permanent magnet powder into grooves of iron core teeth and molding with resin.

Next, the operation of this embodiment will be explained. FIG. 7 shows the characteristics of the permanent magnet used in this example. Disc-shaped permanent magnet 14
The magnetic properties of alnico permanent magnets used in
C=6000e, residual magnetic flux density Br=1.3T, magnetizing magnetic field Hm=3kOe, and the magnetic properties of the rare earth permanent magnet used for the bar-shaped permanent magnet 16 are coercive force BHC:
9kOe, residual magnetic flux density Br=1. OT, magnetizing magnetic field Hm
= 20kOe.

First, as described above, after polishing the outer periphery of the rod-shaped permanent magnet 16 attached to the groove of the rotor 1 iron core 6, it is magnetized by applying a magnetic field of 20 kOe in the radial direction using a magnetizer shown in FIG. 4 or FIG. . However, the magnetization directions of the rod-shaped permanent magnets inserted and fixed in the grooves of the two rotor cores 6 are opposite.

Next, the two rotor cores 6 sandwich the disk-shaped permanent magnet 14 and attach it to the rotating shaft 11, and the disk-shaped permanent magnet 14 is magnetized by applying a magnetic field of 3 kOe in the axial direction using the magnetizer shown in FIG. do. At this time, the magnetization direction of the bar-shaped permanent magnet] 6 is the radial direction, which is perpendicular to the axial magnetic field, which is the magnetization direction of the disk-shaped permanent magnet 14, so it is not easily affected by the axial magnetizing magnetic field. .

Assuming that a maximum reverse magnetic field of 3 kOe is applied to the bar-shaped permanent magnet 16, during that time, the operating point is in the second quadrant and not in the third quadrant, as shown in FIG. Therefore, it can be seen that when the temporal reverse magnetic field disappears, it is possible to return to near the original operating point and no demagnetization occurs.

In addition, the thin cylinder 22 used in the first manufacturing method described above is produced by increasing the permeance coefficient of the bar-shaped permanent magnet 16 and setting the operating point of the magnet to a region with a small magnetic field. , - prevent demagnetization in temporal reverse magnetic fields. Furthermore, demagnetization of the disk-shaped permanent magnet 14 having a small coercive force is prevented.

Note that the present invention is not limited to the embodiments described in 1. The rod-shaped permanent magnets 15 and 16 inserted into each groove of the rotor teeth 7 may be either the grooves of the small stator teeth 3 or the grooves of the rotor teeth 7.

Further, the same can be done when the disc-shaped permanent magnet 14 is provided in the stator 12, and the method for manufacturing the rotor 13 can be used as the method for manufacturing the stator 12, and the same effect can be obtained. Furthermore, since a stepping motor is one type of inductor type electric machine, it is natural that similar effects can be obtained by applying the present invention to other inductor type motors/generators (including linear motors).

〔Effect of the invention〕

As explained above, according to the present invention, since the permanent magnets are magnetized after attaching the rod-shaped permanent magnets to the rotor or after assembling the rotor and polishing the outer periphery, manufacturing can be facilitated.

[Brief explanation of drawings]

Figure 1 is a longitudinal cross-sectional view showing one embodiment of the stepping motor of the present invention, Figure 2 is a cross-sectional view taken along line A-A in Figure 1, and Figure 3 is an enlarged cross-sectional view (a). is a cross-sectional view taken along line X-X in FIG. 2, (b) is a cross-sectional view taken along line Y-Y in FIG. 2, and FIG. 4 is a rod-shaped permanent magnet in the first manufacturing method of the present invention. 5 is an explanatory diagram showing a method for magnetizing a disk-shaped permanent magnet in the first manufacturing method of the present invention. FIG. 6 is an explanatory diagram showing a method for magnetizing a disk-shaped permanent magnet in the first manufacturing method of the present invention. Fig. 7 is an explanatory diagram showing a method different from Fig. 4 for rod-shaped permanent magnets in the method, Fig. 7 is a line diagram showing demagnetization curves of rare earth magnets and alnico permanent magnets used in the examples of the present invention, and Fig. 8 is a diagram showing the demagnetization curves of the rare earth magnets and alnico permanent magnets used in the examples of the present invention. Explanatory diagram showing the movement of the demagnetization curve of a bar-shaped permanent magnet when the maximum reverse magnetic field is applied to the bar-shaped permanent magnet due to the magnetization of the disc-shaped permanent magnet used in the embodiments of the invention. Figure 9 is an explanatory diagram showing the operating point on the demagnetization curve of a rod-shaped permanent magnet when the rotor is placed in a thin magnetic cylinder in the second manufacturing method of the present invention, and Figure 10 is an explanatory diagram showing the operating point on the demagnetization curve of a rod-shaped permanent magnet when the rotor is placed in a thin magnetic cylinder in the second manufacturing method of the present invention. FIG. 11 is a vertical sectional view of a stepping motor; and FIG. 11 is a conventional cross-sectional view of a high output stepping motor. ]・Stator core 3・Stator small teeth 7・Rotor teeth 11・Rotating shaft 13・Rotors 15a, 15b, 16a. 20... Magnetizing yoke 22... Magnetic cylinder 24... Axial magnetizing coil 2... Stator pole teeth 4... Winding 8... Rotor core 12... Stator 14... Disc-shaped permanent Magnet 16b... Rod-shaped permanent magnet 21... Radial magnetizing coil z3... Magnetizer

Claims (2)

[Claims] (1) A plurality of stator pole teeth are provided in the circumferential direction of the stator core, a polyphase winding is wound around the stator pole teeth, and a plurality of stator small teeth are provided on the inner peripheral surface. a stator comprising a first bar-shaped permanent magnet having a high coercive force magnetized in the radial direction fixed in a tooth groove; and a plurality of rotor teeth provided on the outer peripheral surface of the rotor core opposite to the stator small teeth, and It is divided into two parts in the axial direction, and each rotor tooth is
/2 tooth pitch shifted, a disc-shaped permanent magnet with a low coercive force magnetized in the axial direction is provided in the divided part, and a second bar-shaped permanent magnet with a high coercive force magnetized in the radial direction is provided in the groove of the rotor teeth. and a fixed rotor, wherein the polarity of the first bar-shaped permanent magnet and the second bar-shaped permanent magnet is in a direction that cancels the field main magnetic flux generated by the disc-shaped permanent magnet. motor. (2) After inserting and fixing rod-shaped, unmagnetized rare earth permanent magnets into the grooves of the rotor teeth, the outer periphery is polished, and in this state, the two rotor cores magnetized in the radial direction are A magnetic disc-shaped permanent magnet is sandwiched and attached to a rotating shaft to assemble the rotor, and then the disc-shaped permanent magnet is placed in a thin cylinder made of magnetic material so that the disc-shaped permanent magnet is magnetized in the axial direction. A method for manufacturing a stepping motor according to claim 1.