JP3428612B2 - Stepping motor - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor having a rotor that rotates within a stator.

[0002]

2. Description of the Related Art Conventionally, various stepping motors have been proposed and disclosed in, for example, Japanese Unexamined Patent Publication No. 1-126146. In a stepping motor, the pole teeth of a yoke having a plurality of exciting coils and the magnetic poles (N pole and S pole) of a rotor are opposed to each other, and a pulse current is supplied to each exciting coil in a fixed order so that the rotor is rotated by a fixed angle. It is rotated one by one.

[0003]

As shown in FIG. 6, the rotor 1 is formed by molding a plastic magnet, and the rotor 1 is provided integrally with the rotary shaft 2. The peripheral surface 3 of the rotor 1 is magnetized with N poles and S poles alternately at a predetermined pitch. The upper and lower end surfaces 4, 5 of the rotor 1 are provided with recesses 6, 6, respectively.
7 are formed, and the moment of inertia of the rotor 1 is reduced by the recesses 6 and 7. That is, the recesses 6, 7
By thinning the peripheral walls 8 and 9 formed on the periphery,
The moment of inertia of the rotor 1 is reduced to improve the responsiveness of the stepping motor. However, conventionally, since the thickness of the peripheral walls 8 and 9 has not been particularly taken into consideration, the peripheral walls 8 and 9 are excessively thinned, and the rotor 1 cannot be magnetized with sufficient strength. There was a fear that the detent torque was insufficient. The present invention provides a stepping motor capable of reducing the inertia moment of the rotor and obtaining a sufficient detent torque.

[0004]

In order to solve the above problems, the present invention provides an inner yoke and an outer yoke having a plurality of pole teeth alternately arranged in the circumferential direction, and an excitation magnet mounted between these yokes. A stepping motor comprising a plurality of stators each including a coil in the axial direction, coaxially arranged in the stator, and having a rotor in which N poles and S poles are alternately arranged at a predetermined pitch on a peripheral surface, the rotor has a peripheral wall having a predetermined thickness is formed around at the recess and recess provided on at least one axial end face, the
The rotor has a groove portion of a predetermined depth in the axially central portion of the peripheral surface.
However, the predetermined thickness of the peripheral wall is half the predetermined pitch.
1 and the predetermined depth of the groove is
It is larger than half of the switch.

Further, in the present invention, the predetermined depth is larger than the predetermined thickness.

Further, according to the present invention, the rotor is formed by molding a plastic magnet.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Recesses 28, 29 are provided on at least one of upper and lower end surfaces 26, 27 (end surfaces in the axial direction) of a rotor 22, and thickness W of peripheral walls 30, 31 formed around the recesses 28, 29. Is set to ½ or more of the magnetization pitch P (predetermined pitch), the moment of inertia of the rotor 22 can be reduced, a sufficient magnetic flux density can be obtained, and the detent torque can be improved.

Further, a groove portion 32 is formed in the central portion in the axial direction of the peripheral surfaces 24 and 25 of the rotor 22, and the depth D of the groove portion 32 is made larger than one half of the magnetizing pitch P. Rotor
It is possible to reduce the moment of inertia of 22 and reduce magnetic interference between the stators 10 and 11 through the vicinity of the central portion in the axial direction, thereby improving smoothness and stationary angle accuracy.

Further, the depth D of the groove 32 is preferably larger than the thickness W of the peripheral walls 30 and 31, so that magnetic interference can be further mitigated.

If the rotor 22 is molded with a plastic magnet, the number of parts can be reduced and the rotor 22 can be manufactured at low cost.

[0011]

An embodiment of the present invention will be described below with reference to the accompanying drawings. 1 to 3 are views showing a first embodiment.

Reference numerals 10 and 11 denote stators, and two of these stators 10 and 11 are arranged in the axial direction. Stator 10,
Reference numeral 11 is a coil in which exciting coils 16 and 17 are mounted between the inner yokes 12 and 13 and the outer yokes 14 and 15, respectively. Inner yoke 12,
The outer yoke 13 and the outer yokes 14 and 15 each have a plurality of pole teeth 18, 19, 20, and 21 arranged alternately in the circumferential direction. 22 is a rotor, and this rotor 22 is a molded plastic magnet. The rotor 22 is provided integrally with the rotating shaft 23 and is coaxially arranged in the stators 10 and 11. N poles and S poles are alternately arranged at a magnetizing pitch P (predetermined pitch) on the peripheral surfaces 24 and 25 of the rotor 22 (see FIG. 2). The magnetizing pitch P is the distance between the adjacent N and S poles on the peripheral surfaces 24 and 25. The rotor 22 rotates the rotary shaft 23 by the magnetic action of the magnetic poles magnetized on the peripheral surfaces 24 and 25 and the magnetic paths generated in the stators 10 and 11 according to the pulse signals supplied to the exciting coils 16 and 17. Let

As shown in FIG. 3, the rotor 22 has an upper end surface 26.
(Axial end surface) and lower end surface 27 (axial end surface) are provided with recessed portions 28 and 29, respectively, and peripheral walls 30 and 31 formed around the recessed portions 28 and 29 are provided. . The thickness W (predetermined thickness) of the peripheral walls 30, 31 is larger than one half of the magnetizing pitch P. That is, as shown in FIG.
If the thickness W is larger than ½ of the magnetic pitch P, a substantially constant magnetic flux density can be obtained, but the thickness W of the peripheral walls 30, 31 is smaller than ½ of the magnetic pitch P. It was found from the experiments conducted by the inventors of the present application that the magnetic flux density is reduced even when the coercive force is sufficient. That is, a sufficient magnetic flux density can be obtained by making the thickness W of the peripheral walls 30, 31 larger than one half of the magnetizing pitch P.

Reference numeral 32 denotes a groove portion, which is formed at the center of the rotor 22 in the axial direction. The depth D (predetermined depth) of the groove 32 is larger than the thickness W of the peripheral walls 30 and 31, and is larger than half the magnetizing pitch P.

According to the first embodiment described above, the rotor 22
Since the recesses 28 and 29 and the groove 32 are provided in the rotor 22,
The moment of inertia of can be reduced. Further, by setting the thickness W of the peripheral walls 30 and 31 to be ½ or more of the magnetizing pitch P, a sufficient magnetic flux density can be obtained and the detent torque can be improved as compared with the conventional case. Further, by making the depth D of the groove portion 32 larger than one half of the magnetizing pitch P, magnetic interference between the respective stators 10 and 11 through the vicinity of the central portion in the axial direction is mitigated, and smoothness and smoothness are improved. The stationary angle accuracy can be improved.

In the first embodiment, the upper end surface 26 of the rotor 22 is
And the lower end surface 27 is provided with recesses 28 and 29, respectively.
The recesses 28 and 29 may be provided in at least one of the rotors 22, and the same effect can be expected. Also, the rotor 22 may be composed of the magnet holder 22a and the ferrite magnet 22b as in the second embodiment shown in FIG. 5, but if the rotor 22 is molded with a plastic magnet as in the first embodiment, the number of parts is reduced. Can be manufactured at low cost.

[0017]

According to the present invention, a plurality of stators each having an inner yoke and an outer yoke having a plurality of pole teeth alternately arranged in the circumferential direction and an exciting coil mounted between these yokes are provided in the axial direction. In a stepping motor having a rotor arranged coaxially in the stator and having N poles and S poles arranged alternately on a peripheral surface at a predetermined pitch, the rotor is provided on at least one of axial end faces. And a peripheral wall having a predetermined thickness formed around the concave portion, and the rotor has a predetermined depth in a central portion in the axial direction of the peripheral surface.
And the predetermined thickness of the peripheral wall is
The predetermined depth of the groove, which is larger than one half of the
Is larger than one half of the predetermined pitch,
Reduce the rotor's moment of inertia and ensure sufficient magnetic flux density.
It is possible to obtain the degree and from the axial center near
It reduces the magnetic interference of magnetic flux entering each yoke,
Uneven tent torque can be prevented.

Further, in the present invention, the predetermined depth is larger than the predetermined thickness, and magnetic interference can be further mitigated.

Further, according to the present invention, the rotor is formed by molding a plastic magnet, and the number of parts can be reduced and the rotor can be manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of the present invention.

FIG. 2 is a front view of the rotor of the above embodiment.

FIG. 3 is a cross-sectional view of the rotor of the above embodiment.

FIG. 4 is a diagram showing the relationship between the thickness of the peripheral wall and the magnetic flux density in the above embodiment.

FIG. 5 is a sectional view of a rotor showing a second embodiment of the present invention.

FIG. 6 is a sectional view of a rotor showing a conventional example.

[Explanation of symbols]

10, 11 stator 12 and 13 inner yoke 14,15 Outer yoke 16, 17 Excitation coil 18, 19, 20, 21 pole teeth 22 rotor 24, 25 circumference 26 Upper end surface (axial end surface) 27 Lower end surface (axial end surface) 28, 29 recess 30, 31 perimeter wall 32 groove P Magnetization pitch (predetermined pitch) W thickness (predetermined thickness) D depth (predetermined depth)

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-7-203645 (JP, A) JP-A-1-126146 (JP, A) Actually open 6-36380 (JP, U) Actually open 59- 191875 (JP, U) Actual Kaihei 7-11889 (JP, U) Actual Kohei 1-39105 (JP, Y2) (58) Fields investigated (Int.Cl. ⁷ , DB name) H02K 37/00 H02K 1 / 27 501

Claims (3)

(57) [Claims] 1. A plurality of stators each comprising an inner yoke and an outer yoke having a plurality of pole teeth arranged alternately in the circumferential direction and an exciting coil mounted between these yokes are provided in the axial direction, and the stator is provided. A stepping motor having a rotor arranged coaxially therein and having N-poles and S-poles arranged alternately on a peripheral surface at a predetermined pitch, wherein the rotor has a concave portion provided on at least one of axial end faces, and The rotor has a peripheral wall of a predetermined thickness formed in the periphery of the recess, and the rotor has a groove portion of a predetermined depth in the axial center of the peripheral surface.
And the predetermined thickness of the peripheral wall is one half of the predetermined pitch.
And the predetermined depth of the groove is the predetermined pitch.
Stepping characterized by being greater than one half of
motor. 2. The stepping motor according to claim 1, wherein the predetermined depth is larger than the predetermined thickness. 3. The stepping motor according to claim 1, wherein the rotor is a molded plastic magnet.