JPH0678513A - Stepping motor - Google Patents

Abstract

PURPOSE:To increase and stabilize the detent torque of a rotor at the time of non-conduction by setting the total of the areas of the magnetic poles of stator pairs on the interior side and the total of the areas of the magnetic poles of stator pairs on this side so as to be made to differ. CONSTITUTION:A stepping motor 1 is set so that the total of the areas of the stators 21, 22 of stator pairs 3 on the interior side in a cap-shaped case 9 is made smaller than that of the areas of the magnetic poles 29, 30 of the stators 23, 24 of stator pairs 4 on the inlet side of a case 9. When magnetic flux closed while being passed through only one of magnetic poles 27, 28, 29, 30 is represented by PHIa and magnetic flux passed through two of them and a case 9 by PHIb, the detent torque of a rotor 2 takes a large value by the addition of two torque because magnetic flux PHIa is made larger than another magnetic flux PHIb in the wide magnetic poles 29, 30 of the stator pairs 4 and magnetic flux PHIb is made larger than another magnetic flux PHIa in the narrow magnetic poles 27, 28 of the stator pairs 3 in detent torque at the time of non- conduction. There is no dispersion on characteristics.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of a permanent magnet type stepping motor having a large detent torque.

[0002]

2. Description of the Related Art In a permanent magnet type stepping motor, the detent torque of the rotor generated when the power is not supplied is
It is generated by the magnetic attraction between the permanent magnets of the rotor and the pole teeth of the stator. When the stator is composed of two stator sets, and the stator sets are deviated by an electrical angle of π / 2, the detent torque has a period of π. They cancel each other out and are set to relatively small values.

Usually, in a motor that pursues a highly accurate stop position, the detent torque becomes a load during rotation (energization), so that the detent torque is designed to be small. However, depending on the application, a large detent torque is required to reliably stop the load due to the detent torque when power is not supplied.

Japanese Unexamined Patent Publication No. 60-43059 discloses that the width of pole teeth of the stator is made uneven so that the pattern of torque generation in each phase when not energized is changed to improve the detent torque. is doing. However, according to the above technique, the unbalanced state of the torque in each phase is uncertain, it is difficult to secure a certain detent torque in the manufacturing process, and the expected product cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the detent torque of the rotor in a non-energized state in a permanent magnet type stepping motor of this type to a large or appropriate level and to stabilize it.

[0006]

To achieve the above object, the present invention has a comb-teeth-shaped magnetic pole facing a permanent magnet of a cylindrical rotor in a central portion thereof, and an upper stator and a lower stator having these magnetic poles alternately positioned. In a stepping motor in which a coil is provided to form a stator set, and two stator sets are arranged in the axial direction of the rotor and arranged in a cap-shaped case at a predetermined phase, magnetic poles are formed at the bottom of the cap-shaped case. Also serves as a stator, and this stator and the stator that overlaps via the coil form a stator set on the back side, that is, the bottom side of the cap-shaped case, and the total area of the magnetic poles of the stator set on the back side and the front side, that is, The total area of the magnetic poles of the stator set on the opening side of the cap-shaped case is set to be different. In the preferred embodiment, in order to increase the detent torque, the width of the magnetic poles is narrowed so that the total area of the magnetic poles of the stator set on the back side is smaller than the total area of the magnetic poles of the stator set on the front side. It

According to the above configuration, the torque curve between each stator set and the rotor of the permanent magnet changes, and the torque is set in a state where the torques are added in the process of combining the two torques.
This ensures the necessary detent torque.

[0008]

1 shows a stepping motor 1 according to the present invention. The stepping motor 1 is composed of a cylindrical permanent magnet rotor 2 and two stator sets 3 and 4 surrounding the outer circumference of the rotor 2.

The rotor 2 is rotatably supported on the shaft 5 by a rotating body 7 which also serves as a pinion 6. An annular permanent magnet 8 is combined with the outer circumference of the rotating body 7. Here, as shown in FIGS. 7 and 8, the permanent magnet 8 has N poles and S poles alternately formed in the outer circumferential direction.

The shaft 5 is a cap-shaped case 9
Is fixed between the bottom of the case and the lid case 10 that closes the opening surface of the case 9. The rotation of the pinion 6 is transmitted to the output shaft 14 via a reduction gear 11, an intermediate gear (not shown), and a gear 13. The gear 11 is rotatably supported by the shaft 15. This shaft 15 is used for the lid case 10.
And a partition plate 17 fitted inside the case 9, and the output shaft 14 is rotatable by a bearing portion 18 formed in the partition plate 17 and a bearing 19 fitted in a hole of the lid case 10. Supported by.

The two stator sets 3 and 4 are respectively composed of annular stators 21, 22, 23 and 24 and coils 25 and 26 and coil bobbins 36, which are incorporated between the stators 21 and 22 and between the stators 23 and 24, respectively. It is assembled by 37. Each stator 22, 2
Reference numerals 3 and 24 are annular and have a size that fits inside the case 9, and magnetic poles 27, 28, 29, and 30 are formed in the inner peripheral portion facing the rotor 2 together with the stator 21.

These magnetic poles 27, 28 and magnetic poles 29, 30
Are the respective stators 21, 22, 23, 2
A part of the inner peripheral portion of the rotor 4 is bent at a right angle and alternately faces the outer peripheral NS pole of the rotor 2. Two
The two stator sets 3 and 4 are arranged in a state of being shifted by an electric angle of π / 2. Thus, the bottom of the case 9 also serves as the stator 21.

In particular, in the present invention, as shown in FIG. 2, the total area of the magnetic poles 27, 28 of the stators 21, 22 of the stator set 3 on the inner or bottom side of the cap-shaped case 9 is the case 9. Inlet side, that is, the opening side stator set 4
It is set to be smaller than the total area of the magnetic poles 29 and 30 of the stators 23 and 24. The reverse is also possible. That is, the total area of the magnetic poles 27 and 28 of the stators 21 and 22 of the stator set 3 on the bottom side of the case 9 is larger than the total area of the magnetic poles 29 and 30 of the stators 23 and 24 of the stator set 4 on the opening side of the case 9. It may be set to be. In this embodiment, the widths of the magnetic poles 27 and 28 are smaller than the widths of the magnetic poles 29 and 30, and are set to about 1/2, so that the total area of the magnetic poles 27 and 28 is the magnetic pole 2.
It is smaller than the total area of 9 and 30.

Next, FIGS. 3 and 4 show how the stator sets 3 and 4 generate detent torque when power is not supplied. Depending on the rotational position of the rotor 2, the magnetic flux from the N pole of the rotor 2 passes through only one of the magnetic poles 27, 28, 29, 30 and returns to the S pole, or passes through the opposing magnetic pole 28. To the case 9 and then to the S pole through the magnetic pole 27, to the case 9 through the opposing magnetic pole 27 and to the S pole through the magnetic pole 28, or to the case 9 through the opposing magnetic pole 30. To the S pole via the magnetic pole 29, or to the case 9 through the opposing magnetic pole 29, and then to the S pole via the magnetic pole 30. The magnetic flux that closes through only one of the magnetic poles 27, 28, 29, 30 is Φa, and the magnetic poles 27, 28, 29,
When the magnetic flux passing through the two of 30 and the case 9 is represented by Φb,
These magnetic fluxes Φa and Φb generate CW (clockwise) or CCW (counterclockwise) torque in the rotor 2.

In the wide magnetic poles 29 and 30 of the stator set 4, the magnetic flux Φa becomes larger than the other magnetic flux Φb as shown in FIG. 3, so that the rotor 2 stops at the position shown in the drawing and the torque at that time is stopped. The direction and the magnitude of are as shown in the graph of FIG. The points where the torque curve goes downward to the right and crosses the line with zero torque are electrical angles θ = 0, π, 2π, 3π.
・ It becomes. On the other hand, the narrow magnetic poles 27, 2 of the stator set 3
At 8, the magnetic flux Φb becomes larger than the other magnetic flux Φa as shown in FIG. 4, so the rotor 2 stops at the position where this magnetic flux Φb is formed. Therefore, as shown in FIG. 6, the points where the torque curve goes downward to the right and cross the line of the torque 0 are the electrical angles θ = 0, π, 2π, 3π. As a result,
The combined torque of the stator sets 3 and 4, that is, the detent torque of the rotor 2 becomes a large value by adding the above two torque curves. In FIG. 6, the dotted torque curve shows a case where the widths of the magnetic poles 27 and 28 are wide.

Here, in order to obtain a large detent torque, since the case 9 is a one-cap type, the area of the magnetic poles 27, 28 of the stator set 3 on the far side (bottom of the case 9) is in front of the case 9 ( Magnetic pole 29 of the stator set 4 on the (opening) side,
It must be configured to be smaller than the area of 30. The reason is that in the stator set 3 on the back side, the stator 21 and the case 9 are integrated, and there is only one contact portion in the path of the magnetic flux Φb, so the magnetic resistance in that path is small, and the value shown in FIG. This is because the torque curve of On the other hand, in the phase on the inlet side of the one-cap type case 9, both of the two stators 23 and 24 of the stator set 4 have a contact portion with the outer case 9, and the magnetic path closed through the outer case 9 is closed. This is because if the resistance is large and the widths of the magnetic poles 29 and 30 are narrowed, the torque curve having the value shown in FIG. 6 cannot be obtained, and it becomes difficult to obtain a desired function.

7, 8 and 9 show the total area of the magnetic poles 27 and 28 of the stator set 3 on the rear side and the total area of the magnetic poles 29 and 30 of the stator set 4 on the front side in order to obtain a large detent torque. It shows another means of making it smaller than. 7 is an example in which only the magnetic pole 28 of the stator 22 is configured to have a narrow width, and the one in FIG. 8 is
This is an example in which only a part of the magnetic pole 27 of the stator 21 is configured to have a narrow width.
This is an example in which the magnetic poles 27, 28, 29 of 1, 22, 23 have the same width and only a part of the magnetic pole 30 of the other stator 24 has a wide width. Of course, these magnetic poles 27, 28, 29, 30 may have a rectangular shape or another shape instead of the trapezoidal shape.

10 and 11 show another structure of the cap-shaped case 9. In the structure shown in FIG. 10, a raised portion is formed on the outer peripheral portion of the bottom of the cylindrical case 9, the stator 21 is configured as a separate member, and the two are brought into contact with each other in a large area by press-fitting or the like, thereby magnetically contacting each other. This is an example of improving the coupling, and the example of FIG. 11 is an example in which the contact portion is applied to the outer surface of the stator 21 and fixed by welding or the like. Also in these examples, the case 9 is finally cap-shaped together with another member.

Next, in the embodiment of FIG. 12, the coil bobbin 2
Two stators 2 placed back to back between 5 and 26
In the configuration in which the total area of the one pole teeth 27, 28 of 2, 2 and the total area of the other pole teeth 29, 30 are made different, the areas of the three pole teeth 27, 28, 30 are made the same. The other pole teeth 29 are formed to have a small area. This structure has a structure shown in FIG.
This is equivalent to a case where the stators 22 and 23 of the concrete example are replaced. Therefore, there is an effect that two different detent torques can be selected by simply exchanging the assembled positions of the two stators 22 and 23, and it is possible to appropriately cope with the use of the motor.

[0020]

According to the present invention, the detent torque when not energized is increased and the holding capability of the stop position is increased.
Even if a force or load in the returning direction is applied to the portion driven by the stepping motor, it does not start turning. Moreover, since this large detent torque is easily obtained due to the difference in magnetic flux formation, there is no variation in characteristics and a stable detent torque can be obtained.

In particular, in the present invention, the detent torque is ensured by adding the torques of the respective phases by utilizing the difference in the formation method of the magnetic flux loops. Therefore, a large detent torque can be reliably secured.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a stepping motor of the present invention.

FIG. 2 is an exploded view of an arrangement of magnetic poles of two stator sets.

FIG. 3 is an explanatory diagram showing a torque generation state due to a magnetic flux generation state in each rotation phase of the rotor.

FIG. 4 is an explanatory diagram showing a torque generation state due to a magnetic flux generation state in each rotation phase of the rotor.

FIG. 5 is a waveform diagram of a torque curve generated in each stator set.

FIG. 6 is a waveform diagram of a torque curve generated in each stator set.

FIG. 7 is a development view of magnetic poles in another embodiment.

FIG. 8 is a development view of magnetic poles in another embodiment.

FIG. 9 is a development view of magnetic poles in another embodiment.

FIG. 10 is a partial cross-sectional view of the bottom portion of the case.

FIG. 11 is a partial cross-sectional view of the bottom portion of the case.

FIG. 12 is a development view of magnetic poles according to still another embodiment.

[Explanation of symbols]

 1 Stepping Motor 2 Rotor 3 Stator Set 4 Stator Set 9 Case 21 Stator 22 Stator 23 Stator 24 Stator 25 Coil 26 Coil 27 Magnetic Pole 28 Magnetic Pole 29 Magnetic Pole 30 Magnetic Pole

Claims (3)

[Claims] 1. A rotor set comprising two stator sets having a comb-shaped magnetic pole facing a permanent magnet of a cylindrical rotor in a central portion, and a coil provided between upper and lower stators in which the magnetic poles are alternately positioned. In the stepping motors arranged in the axial direction, the magnetic poles are formed in the cap-shaped case so that the stator also serves as a stator, and the stator and the stator that overlaps with each other through the coil form a stator group on the rear side. A stepping motor, characterized in that the total area of the magnetic poles of the pair is different from the total area of the magnetic poles of the stator group on the front side. 2. The stepping motor according to claim 1, wherein the total area of the magnetic poles of the stator set on the back side is smaller than the total area of the magnetic poles of the stator set on the front side. 3. The stepping motor according to claim 2, wherein the area of the magnetic pole is reduced by narrowing the width of the magnetic pole.