JP2736487B2 - 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 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 a rotor generated when power is not supplied is as follows.
It is generated by magnetic attraction between the permanent magnet of the rotor and the pole teeth of the stator. When the stator is constituted by two stator sets, and when the stator sets are shifted by π / 2 in electrical angle, the period of the detent torque is π. Are set to a relatively small value.

[0003] Usually, a motor pursuing a high-precision stop position is designed so that the detent torque becomes small because the detent torque becomes a load during rotation (energization). However, depending on the application, a large detent torque is required when the load is reliably stopped by the detent torque when the power is not supplied.

Japanese Patent Application Laid-Open No. Sho 60-43059 discloses that the width of the pole teeth of the stator is made irregular to change the pattern of torque generation in each phase when power is not supplied, thereby improving the detent torque. doing. However, according to the above technology, the unbalanced state of the torque in each phase is uncertain, and it is difficult to secure a constant detent torque in the manufacturing process, and a product as expected cannot be obtained.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the detent torque of the rotor when power is not supplied and to stabilize the permanent magnet type stepping motor of this type.

[0006]

According to the above object, the present invention provides a cylindrical
Centered on the comb-shaped magnetic pole facing the permanent magnet of the rotor
And two upper and lower stators in which the magnetic poles are alternately positioned.
A pair of stators having a coil provided therebetween is connected to the shaft of the rotor.
Caps for stepping motors arranged side by side
The magnetic pole is formed in the case of
One of the three stators is used
At least one outer diameter dimension is formed small, and this small
The outer diameter of the outer diameter stator and the cap-shaped case
A gap is formed between the stator and the circumference.
By differing between sets, between two stator sets
Is set to make the magnetic resistance different.

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 such that the torque does not completely cancel out in the process of combining the two torques. Detent torque can be secured.

[0008]

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

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

The shaft 5 is fixed between the bottom of the case 9 and a lid case 10 for closing the opening of the case 9. The rotation of the pinion 6 is controlled by the gear 1 for reduction.
1, an output shaft 14 via an intermediate gear (not shown) and a gear 13
Is transmitted to The gear 11 is supported from a shaft 15 by a cover case 10 and a partition plate 17 fitted inside the case 9, and the output shaft 14 has a bearing 18 formed on the partition plate 17 and the cover case 10. It is rotatably supported by a bearing 19 fitted in the hole.

The two stator sets 3 and 4 include 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. 37. Each stator 22, 2
Numerals 3 and 24 are annular and have a size to enter the inside of the case 9. As shown in FIG.
9 and 30 are formed.

The magnetic poles 27 and 28 and the magnetic poles 29 and 30
Are the respective stators 21 and 22, the stators 23 and 2
A part of the inner peripheral portion of the rotor 4 is bent at a right angle, and alternately faces the NS pole on the outer periphery of the rotor 2. 2
The three stator sets 3 and 4 are arranged so as to be shifted by π / 2 in electrical angle. Thus, the case 9 also serves as the stator 21 at the bottom.

In particular, in the present invention, three stators 22,
At least one of the stators 23 , 24, for example, the two stators 23 , 24 has a small outer diameter,
Two gaps 31 are formed between the outer diameter portions of the stators 23 and 24 and the inner circumference of the case 9. The two gaps 31 are provided at the joint between the outer peripheral portions of the stators 23 and 24 and the case 9 to increase the magnetic resistance. The outer peripheral portion of the other stator 22 is joined
The portions are fitted in a state in which they are in close contact with the inner peripheral surface of the case 9 so that the magnetic resistance does not increase. Like this
Is different between the two stator sets 3 and 4.
You. As a result, between the two stator sets 3 and 4,
Their magnetoresistance is different.

3 to 6 show a specific example of forming the gap 31 only for the stator 24. FIG. FIG. 3 shows an example in which, for example, four projections 32 are formed on the outer periphery of the stator 24, and the projections 32 are applied to the inner peripheral surface of the case 9 to form the gap 31 of the air gap. . 4, the stator 24 is formed to be smaller than the inner diameter of the case 9, and the hole 33 and the projection 34 of the coil bobbin 37 are fitted to each other to establish a positioning state. Gap 3
1 is an example of forming the same.

In FIG. 5, the stator 24 is configured to have an outer diameter smaller than the inner diameter of the case 9, and a non-magnetic member 3 such as a separate part or outsert molding is formed on the outer peripheral portion.
The outer peripheral portion of the non-magnetic member 35 is
This is an example of positioning by abutting the inner peripheral surface of the device. further,
FIG. 6 shows an example in which the stator 24 is configured to have a small outer diameter, a non-magnetic member 38 is integrally formed on the outer peripheral edge of the bobbin 37, and the stator 24 is fitted into the interior to perform positioning. It is. In these cases, the gap 31 is filled with the non-magnetic members 35 and 38.

In the preferred embodiment, the gap 31 is formed in the portion of the stator set 4 (the stators 23 and 24) as described above. If the gap 31 is formed in the portion of the stator set 3 (the stators 21 and 22), the magnetic resistance in the portion of the case 9 which also serves as the stator 21 increases, and the necessary torque during rotation cannot be obtained. is there. Therefore, the position where the gap 31 is to be formed is closer to the stator set 4 than to the stator set 3. Further, the gap 31 is formed by the stator 23,
24 may be formed only on one of them.

Next, FIGS. 7 and 8 show how the detent torque is generated when one of the stator sets 4 is not energized. The magnetic flux from the N pole of the rotor 2 depends on the rotational position of the rotor 2 as shown in FIG.
9 or 30 to return to the south pole, or as shown in FIG.
And returns to the S pole via the magnetic pole 30. When the magnetic flux passing through only one magnetic pole 29 or the magnetic pole 30 is Φa and the magnetic flux passing through the two magnetic poles 29 and 30, the gap 31 and the case 9 is Φb, the rotor 2 receives the magnetic flux Φa and Φb. The direction and magnitude relationship of the torque are as shown in the following table when viewed at the boundary of the SN pole (the position indicated by ▼ in the drawing).

[0018]

[Table 1]

In the table, CW indicates clockwise rotation, and CCW indicates counterclockwise rotation. here,
If the gap 31 is not formed, the stator set 4
The curve of the combined torque in the portion should appear as the dotted line in (1) of FIG. 9 from the magnitude relation of the torque between the respective rotation phases. However, since a gap 31 is formed between the case 9 and the stators 23 and 24, and the magnetic force is attenuated at that position, the torque due to the magnetic flux Φb is relatively smaller than the torque due to the magnetic flux Φa. As a result, the resultant torque appears as a solid line in (1) of FIG.

On the other hand, since no gap 31 is formed between the stators 21 and 22 and the case 9 in the portion of the stator set 3, the combined torque of the stator set 3 is as shown in FIG. In this case, the waveform of the stator set 4 is substantially the same as that shown by the dotted line. Of course, since the pole teeth 27 and 28 of the stator set 3 are shifted from the pole teeth 29 and 30 of the stator set 4 by π / 2 in electrical angle, the torque curve has an inverted waveform. .

Since the final detent torque generated in the rotor 2 is the sum of the combined torques generated by the stator set 3 and the stator set 4, as shown in a waveform (3) of FIG. It remains as much as the difference. As described above, since the resultant torque between the two stator sets 3 and 4 is not completely canceled out and remains as much as the difference, the detent torque appears larger than that of the related art.

[0022]

According to the present invention, between two stator sets,
Is the magnetic resistance different due to the difference in the amount of gap formation?
Between the two stator sets when no power is applied
The torque is no longer canceled. As a result, the detent torque at the time of non-energization increases, so that even if a force or load in the return direction is applied to the portion driven by the stepping motor, the ability to hold the stop position increases. Moreover,
Since this large detent torque can be easily obtained by the gap between the stator and the case, a stable detent torque can be obtained without variation in characteristics.

[Brief description of the drawings]

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

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

3 to 6 are cross-sectional views of a portion where a gap is formed between a case and a stator.

FIGS. 7 and 8 are explanatory diagrams showing the principle of generation of torque according to the state of generation of magnetic flux in each rotation phase of the rotor.

FIG. 9 is a waveform diagram of a combined torque generated in each stator set and a waveform diagram of a detent torque obtained by the combined torque.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stepping motor 2 Rotor 3 Stator set 4 Stator set 8 Permanent magnet 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 31 Gap

Claims (2)

(57) [Claims] 1. A two-stator set having, at its center, a comb-shaped magnetic pole facing a permanent magnet of a cylindrical rotor, and a coil provided between two upper and lower stators in which the magnetic poles are alternately positioned. the in stepping motor arranged in the axial direction of the rotor, to form a magnetic pole on the cap-shaped case, a cap-shaped case and
It is combined with one of the stator by over scan, the other three stearyl
Reduced to form at least one outer diameter of the chromatography data,
The small outer diameter the clearance formed between the inner periphery of the outer diameter portion and the cap-like casing of the stator, Rukoto made different formation amount <br/> of the gap between the stator assembly, 2 One station
A stepping motor characterized in that the magnetic resistance differs between data sets . 2. A gap is not formed in a stator portion including a cap-shaped case of two stator sets, but is formed between an outer diameter portion of a stator of another stator set portion and an inner periphery of the case. The stepping motor according to claim 1, wherein