JPH01259748A - Stepping motor - Google Patents

Abstract

PURPOSE:To reduce a variation of torque in high resolution, by using three stator cores and by arranging said cores so that the tooth pitch thereof is shifted by 1/3 to the magnetization pitch of a rotor magnet. CONSTITUTION:A rotor is constituted by a cylindrical permanent magnet 1 subjected to multipoler magnetization on many peripheral faces, a yoke 2 fixing said permanent magnet, and a shaft 3. Said rotor is also equipped with a stator core 10, an exciting coil 20, and a bearing 30 and said core 10 have comb teeth corresponding to the magnetization pitch of said permanent magnet 1. Also, a motor is composed of three stator cores 10a-10c, three exciting coils 20a-20c, and the rotor. Further, when the magnetization pitch of said permanent magnets 1a-1c is P, the pitch of each of the comb teeth of said core 10a is 2P and said comb teeth are alternately arranged to constitute a magnetic circuit. On the other hand, the core 10b is arranged so as to be shifted 1/3P from the core 10a. Thus, when said exciting coils 20 are excited by successive addition of electric current, the rotor rotates by 1/3P every time.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to the structure of a stepping motor.

[Synchronization] Conventional stepping motors, for example, are based on US patent no.
, 3238399, the outline of which is shown in Figure 6. A rotor with multi-pole magnetization of a cylindrical permanent magnet, a stator core with comb-shaped teeth facing the rotor, and an excitation boiler inside the stator core. It is equipped with two stator cores, and the teeth of the stator core are 1/1 of the magnetized pitch.
They were arranged so that they were shifted by 2.

[Problems to be Solved by the Invention] However, in the conventional technology as described above, when trying to reduce the step angle of the motor, the step angle (resolution) of the motor is determined by the number of teeth and the magnetization pitch of the stator core. Therefore, in order to obtain a very small stave angle, it is necessary to reduce the magnetization pitch of the permanent magnet and the tooth width of the stator core, but it is difficult to magnetize and process the teeth of the stator core with a width of about 2 mm or less. , for example, if the outer diameter of the motor is 50 mm
In terms of magnetization, the magnetization is 5o poles and the step angle is 3.6', and it is difficult to obtain a step angle smaller than this.

Further, PM stepping motors have problems such as large torque fluctuations due to large torque ripples and loss of synchronization in high-speed ranges, which limits their use in high-speed ranges.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object thereof is to provide a stepping motor with high resolution, less torque fluctuation, and which can be used in a high-speed range.

[Means for Solving the Problems] A stepping motor of the present invention includes a rotor made of a cylindrical permanent magnet whose outer peripheral surface is alternately magnetized with N poles and S poles, and an N pole on the outer peripheral surface of the rotor. or a stator core having teeth arranged opposite to the S pole with a certain gap therebetween;
An excitation coil is wound around the stator core and rotates the rotor by magnetizing the stator core, and the number of stator cores is n, and the magnetization pitch angle of the permanent magnet is P.
In this case, n is 3 or more, and the teeth of the stator core are arranged so as to be shifted by an angle of P/n.

[Example] The present invention will be explained in detail below based on examples.

FIG. 1 is a cross-sectional view of one embodiment of the present invention, in which 1 is a cylindrical permanent magnet whose outer circumferential surface is multipole magnetized, 2 is a yoke for identifying the permanent magnet, and 3 is a shaft. It makes up the rotor. 10 is a stator core, 20 is an exciting coil 30
is a bearing. The stator core 10 has comb teeth corresponding to the magnetization pitch of the permanent magnets, and the motor has 10a,
It consists of a stator core consisting of three pieces, 10b and 10c, and an excitation coil and a rotor, also consisting of three pieces.

FIG. 2 is a diagram showing the relationship between the stator core of the stepping motor of the present invention and the magnetization pitch of the permanent magnets. When the magnetization pitch of the permanent magnet is P, the comb teeth 11a and llb of the stator core 10a are each 2P, and the comb teeth 11a and lb are 2P, respectively.
lb are arranged alternately and constitute a magnetic circuit with permanent magnets and comb teeth. The permanent magnets 1a, 1b, and the IC are magnetized on the same line at the same pitch. On the other hand, the stator core llb has a magnetization pitch P of the permanent magnets with respect to lla.
They are arranged so as to be shifted by 1/3 of the distance. Similarly, the stator core 11C is arranged to be shifted by 1/3P with respect to stator core llb and by 2/3P with respect to stator core lla.

By sequentially applying current to the excitation coils 20a, 20b, and 20c to excite them, the rotor rotates by 1/3P. In this embodiment, the permanent magnet is magnetized with 48 poles, the comb teeth 11a of the stator core are arranged at a pitch of 15 degrees, and lla and llb are set at a pitch of 7.
5° pitch, stator cores 10a and 10b 2.5@,
Similarly, by arranging the stator cores 10a and 10c offset by 5@ (10b and 10c by 2.5'') and sequentially exciting the excitation coils 20a, 20b, and 20c, a stepping motor with a resolution of 144 steps per rotation can be created. In this example, the excitation was performed by three-phase excitation.In this case, the motor drive circuit can be used by simply changing the final output of the three-phase drive circuit for a DC brushless motor to a pulse output. Since there is no need for a dedicated special circuit, it is easily accepted by the world.

FIG. 3 is a diagram showing the torque ripple of the stepping motor of the present invention. For comparison, the torque ripple of a conventional 48-pole magnetized stepping motor is shown in FIG. As can be seen from the figure, the stepping motor of the present invention exhibits smooth torque fluctuations with little variation.

FIG. 5 is a diagram showing the frequency and torque of the stepping motor of the present invention. Note that the above-mentioned stepping motor was used for comparison. It can be seen that the stepping motor of the present invention is capable of high-speed operation without step-out at high frequencies (high-speed range).

[Effects of the Invention] As described above, according to the present invention, three stator cores are used and the pitch of the teeth is shifted by 1/3 from the magnetization pitch of the rotor magnets, thereby achieving high performance. We were able to create a stepping motor that can provide smooth rotation with low torque fluctuations and can be used up to high speeds.

This has the effect of making it possible to respond to the high precision and high speed required for information devices such as printers and magnetic recording devices, and contributing to a highly information-oriented society based on OA.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the present invention. FIG. 2 is a diagram showing the relationship between the teeth of the stator core and the magnets, showing an embodiment of the present invention. FIG. 3 is a diagram showing the torque ripple of the stepping motor of the present invention. FIG. 4 is a diagram showing torque ripple of a conventional stepping motor. FIG. 5 is a diagram showing the frequency and torque of the stepping motor of the present invention. FIG. 6 is a diagram showing a conventional technique. 1...Permanent magnet 2...Yoke 3...Shaft 10...Stator core 11...Comb teeth 20...Exciting coil 30...Bearing Applicant: Seiko Epson Co., Ltd. Attorney Master Kizo Suzuki (1 other person) 1oaJTJ-1 1ob, ';x, child-D7
Figure 1 Figure 2

Claims (1)

[Claims] (1) A rotor consisting of a cylindrical permanent magnet with alternating north and south poles magnetized on its outer circumferential surface, and an N pole on the outer circumference of the rotor.
The stator core has teeth that are arranged opposite to the poles or S poles with a certain gap therebetween, and an excitation coil that is wound within the stator core and rotates the rotor by magnetizing the stator core. A stepping motor characterized in that, where n is a magnetization pitch angle of n permanent magnets, n is 3 or more, and the teeth of a stator core are arranged so as to be shifted by an angle of P/n.