JPH04347570A - Stepping motor - Google Patents

Abstract

PURPOSE:To alleviate a holding torque to realize driving with a small electrical power by causing pole sections of a first yoke and a second yoke to show poles in different polarities due to a permanent magnet while the power source is not supplied. CONSTITUTION:A permanent magnet 31 is provided between an upper first yoke 29 and a lower second yoke 30 with the upper surface defined as N-pole while the lower surface as S-pole. In the case of supplying no electrical power to a stepping motor, poles of different polarities appear at the pole end of the first yoke 1 and that of the second yoke 30 due to the operation of the permanent magnet 31. Therefore, a rotor 21 receives a repulsive force against the one yoke and an attractive force for the other yoke. A holding torque thereof is reduced due to simultaneous effect of the repulsion and attraction. When electrical power is supplied to the stepping motor, electromagnets 25 to 28 are energized, magnetizing the first and second yokes in the same direction to rotate the rotor 21.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a stepping motor that is compact and highly efficient, and is used, for example, in a camera lens barrel to drive the movement of the lens barrel or to drive shuttering. This invention relates to a stepping motor.

0002

2. Description of the Related Art FIG. 6 shows a conventional example of a stepping motor. The rotor 11 of this stepping motor is in the form of a short column having four magnetic poles of N, S, N, and S on its rotating surface, and its rotating shaft 12 is rotatably supported. Further, the stator is composed of a first electromagnet 13 and a second electromagnet 14 arranged on both sides of the rotor 11. When the excitation coil 15 is supplied with power, the first electromagnet 13 generates a magnetic pole at the magnetic pole part of the yoke 16,
The second electromagnet 14 generates a magnetic pole at the magnetic pole portion of the yoke 18 when the excitation coil 17 is supplied with power.

[0003] This stepping motor has a first electromagnet 1
3 and the second electromagnet 14 are alternately supplied with power and driven to rotate. For example, when the excitation coil 15 of the first electromagnet 13 is supplied with power, the magnetic pole portion of the yoke 16 is magnetized as shown in the figure.
Therefore, the magnetic poles of the rotor 11 are subjected to a magnetic action by the stator magnetic poles, and the rotor 11 moves in the direction of the arrow shown in the figure. Subsequently, the excitation coil 17 of the second electromagnet 14 is supplied with power, and the magnetic pole generated in the yoke 18 causes the rotor 11 to advance in the same manner as described above. In this way, each time the first electromagnet 13 and the second electromagnet 14 are alternately supplied with power, the rotor 11 repeats the step and the rotor 11 rotates.

0004

[Problem to be Solved by the Invention] In the stepping motor as described above, when no power is supplied, the magnetic poles of the rotor 11 exert an attractive action on the yokes 16 and 18, so that the holding torque ( (also called holding torque or detent torque). That is, in the case of non-power feeding, the stator forms a magnetic circuit with the rotor 11 as shown by the dotted line 19 in the figure, so that a holding torque is generated by seeking the minimum reluctance.

As a result, in order to rotate the rotor, it is necessary to generate a rotational torque that overcomes the holding torque, and it is necessary to supply a correspondingly large amount of electric power. For this reason,
The ratio of power output to electrical input, ie, efficiency, decreases, and this effect is particularly noticeable when intermittent operation is performed.

SUMMARY OF THE INVENTION In view of the above-mentioned circumstances, it is an object of the present invention to develop a highly efficient stepping motor that can be driven with low electric power by reducing the holding torque.

[0007]

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a rotor having magnetic poles polarized on a rotating surface, and a rotor between a first yoke and a second yoke. In addition to providing a permanent magnet, at least two electromagnets equipped with excitation coils that generate magnetic flux in the same direction are provided in these two yokes, and the magnetic pole portions of the first and second yokes are connected to the rotation of the stator. A stepping motor is proposed, which is characterized by having a rotor having electromagnets arranged in two stages along the axial direction.

[0008]

[Operation] When power is not supplied to the stepping motor, the magnetic pole part of the first yoke of each electromagnet is exposed to either the N or S magnetic pole by the permanent magnet, and the magnetic pole part of the second yoke represents the other magnetic pole. That is, the magnetic poles of different polarities appearing on the magnetic pole portions of the first and second yokes oppose the magnetic poles of the rotor. Therefore, between the first and second yokes and the rotor, the magnetic poles with the same polarity repel and the magnetic poles with different polarity attract, so the holding torque decreases due to the simultaneous action of repulsion and attraction. do.

When power is supplied to a stepping motor,
Because the first and second yokes are magnetized in the same direction by the excitation action of the excitation coil, the magnetization of either the first or second yoke increases, and the magnetization of the other increases. The magnetization of the yoke decreases. From this, the rotor rotates with high efficiency by supplying power to each electromagnet according to predetermined conditions so that the magnetic pole of the yoke with increased magnetization acts magnetically on the magnetic pole of the rotor.

0010

[Embodiment] Next, an embodiment of the present invention will be described with reference to the drawings. Figure 1 is a perspective view of a stepping motor, Figure 2
1 is a simplified diagram of the same motor showing the arrangement of the stator magnetic pole portion and the rotor magnet magnetic pole.

The rotor 21 has a short column shape and is rotatably supported by a rotating shaft 22, and the rotating shaft 22 is provided with a pinion gear 23 for driving output. This rotor 21
has six magnetic poles polarized in the order of N, S, N, S, N, S on the outer peripheral surface (rotating surface).

The stator 24 is composed of a first electromagnet 25, a second electromagnet 26, a third electromagnet 27, and a fourth electromagnet 28. These electromagnets 25 to 28 have a common first yoke 29 on the upper side, a second yoke 30 on the lower side, and a permanent magnet 31 provided between these yokes 29 and 30. It is provided as a component of It should be noted that the permanent magnet 31 is magnetized to have an N pole on its upper surface and an S pole on its lower surface.

The first yoke 29 and the second yoke 30 have the same shape, and as shown in the figure, are plate-shaped bodies with bifurcated legs formed in straight lines from both sides of a substantially semicircular part. There is. The permanent magnet 31 is shaped like an arcuate plate, and is fixed so as to be inserted between the semicircular portions of the first yoke 29 and the second yoke 30.

An excitation coil 25c of the first electromagnet 25 and an excitation coil 28c of the fourth electromagnet 28 are provided on the bifurcated legs at one end of the first yoke 29 and the second yoke 30. That is, the excitation coil 25c is provided around the outer legs of the first and second yokes, and the tips of these outer legs are used as magnetic pole parts 25a and 25b.
An excitation coil 28c is provided around the inner legs of the first and second yokes, and the tips of these inner legs serve as magnetic pole parts 28a and 28b.

Similarly, an excitation coil 26c of the second electromagnet 26 and an excitation coil 27c of the third electromagnet 27 are provided for the bifurcated legs on the other end side of the first yoke 29 and the second yoke 30. The tips of the inner legs are magnetic pole parts 26a, 26b, and the tips of the outer legs are magnetic pole parts 27a, 27b.

[0016] The first electromagnet 25 and the second electromagnet 26 are connected in series to supply power at a voltage V1, and the third electromagnet 27 and the fourth electromagnet 28 are connected in series to supply power at a voltage V2. , the fourth electromagnets 26 and 28 are connected to the first
, the third electromagnets 25 and 27 are configured to generate magnetic poles of opposite polarity.

The magnetic pole parts 25a, 25b of the first electromagnet 25,
Magnetic pole parts 26a, 26b of the second electromagnet 26, third electromagnet 2
7 magnetic pole parts 27a, 27b, and the magnetic pole part 2 of the fourth electromagnet 28
8a and 28b are arranged with respect to the magnet poles of the rotor 21 as shown in FIG. In addition, in this figure, 2
Reference numerals 1a and 21b indicate the upper and lower halves of the rotor 21, and the excitation coil and yoke are shown divided into two parts for convenience of illustration.

Next, the principle of operation of the above-mentioned stepping motor will be explained with reference to FIG. (A) in Figure 3;
(B) and (C) are simplified diagrams showing the first electromagnet 25 as an example. When the first electromagnet 25 is not powered as shown in FIG. 3A, a magnetic flux φ1 is generated as shown in the figure, so the magnetic pole part 25a has an N pole, and the magnetic pole part 25b has an S pole. appear. As a result, the magnet magnetic pole (S) of the rotor 21 is attracted to the N pole of the magnetic pole part 25a, and
Since it is repelled by the S pole of b, the holding torque of the rotor 21 is halved due to the simultaneous action of attraction and repulsion.

As shown in FIG. 3B, when a supply voltage +V is applied to the first electromagnet 25, a current I flows in the direction shown in the excitation coil 25c, and magnetic fluxes φ2 and φ3 as shown are generated. . That is, magnetic fluxes φ2 and φ3 in the same direction are simultaneously generated in the first yoke 29 and the second yoke 30. As a result, the magnetic flux generated only by the excitation coil 25c is reduced to φ20
Then, φ2 = φ20 + φ1, φ3 = φ20 - φ1, the strength of the magnetic pole (N) of the magnetic pole part 25a increases due to the addition of magnetic flux, and the strength of the magnetic pole (S) of the magnetic pole part 25b increases due to the cancellation of magnetic flux. Decrease. That is, if configured so that φ20=φ1, the magnetic pole portion 25a becomes a twice as strong magnetic pole, and the magnetic pole portion 25b becomes a non-magnetic pole. Therefore, the magnetic pole of the magnetic pole portion 25a increased in this way further increases the rotational torque of the rotor 21.

As shown in FIG. 3C, when a voltage -V is applied to the first electromagnet 25, a current I is applied to the exciting coil 25c.
flows in the direction of the arrow shown in the figure, and the magnetic fluxes φ4 and φ5 as shown in the figure
occurs. As a result, for the same reason as described above, the magnetization of the magnetic pole (N) of the magnetic pole part 25a decreases due to magnetic flux cancellation, and the strength of the magnetic pole (S) of the magnetic pole part 25b increases.

The above-mentioned principle is not limited to the first electromagnet 25, but also applies to the second to fourth electromagnets 26, 27, and 28. When no power is supplied, the holding torque is halved, and when power is supplied, the magnetic pole of the magnetic pole part is Strength increases.

Next, the operation of the above-mentioned stepping motor will be explained with reference to FIGS. 4 and 5. In addition, FIG. 4 is a time chart of the supply voltage V, and (A) in FIG.
-(E) are simplified diagrams showing the rotation process of the rotor 21, and 21a and 21c indicate the upper half and lower half of the rotor 21. Note that (A) to (E) shown in FIG.
This is written in correspondence with the rotor rotation mode shown in .

When the rotor 21 is in the rotational position shown in FIG.
If power is supplied with positive pulse voltages V11 and V21 at time T1 in FIG. 4, the magnetic pole portion 2 of the first electromagnet 25
5a is the north pole, the magnetic pole part 25b is non-magnetized, the magnetic pole part 26a of the second electromagnet 26 is non-magnetized, and the magnetic pole part 26b is the south pole. Moreover, the magnetic pole part 27a of the third electromagnet 27 is N pole, the magnetic pole part 27b is non-magnetized, and the magnetic pole part 28 of the fourth electromagnet 28 is
a is non-magnetized, and the magnetic pole portion 28b is the S pole. As a result, the rotor 21 enters the rotation mode shown in FIG. 5(A).

At time T2, only the supply voltage V21 becomes the negative pulse voltage V22, so as shown in FIG. The magnetic pole part 28a of the fourth electromagnet 28 changes to the S pole.
becomes the N pole, and the magnetic pole portion 28b becomes non-magnetized. Than this,
Due to the magnetic action of each magnetic pole part, the rotor 21 continues to move forward in the direction of the arrow in the figure and rotates to the position shown in FIG. 5(B).

At time T3, the power supply voltage V1 becomes the negative pulse voltage V12, so the magnetic poles of the first electromagnet 25 and the second electromagnet 26 change magnetically as shown in FIG.
The data 21 continues to advance. Similarly, when moving to time T4, the negative pulse voltage becomes V23, so the third and fourth
The magnetic pole parts of the electromagnets 27 and 28 change their magnetic properties as shown in FIG. The magnetism changes as shown in (E), causing the rotor 21 to move forward. In this way, the rotor 21 is driven to rotate each time the power supply voltages V1 and V2 change to positive and negative pulse voltages.

In the explanation of FIG. 5, the magnetic pole portion where the magnetic flux cancels out is unmagnetized, but in reality, the permanent magnet 3
Since there is a difference between the magnetic flux of No. 1 and the magnetic flux of the excitation coil, the magnetic flux of the excitation coil becomes a magnetic pole portion with reduced magnetic pole strength due to cancellation.

Furthermore, the stepping motor of the present invention can be operated with a 1-phase excitation drive method or a 1-2 phase excitation drive method, but if the power feeding interval is set, a holding torque is generated by the stator magnetic poles, and the rotor is Because we cannot expect smooth progress,
It is preferable to supply power using a two-phase excitation drive system as shown in FIG. Furthermore, when implementing the present invention, it is not necessarily necessary to use the first to fourth electromagnets, and the number can be increased or decreased as desired.

[0028]

Effects of the Invention As described above, in the stepping motor according to the present invention, when no power is supplied, the magnetic pole portions of the first yoke and the second yoke of each electromagnet have different polarities due to permanent magnets. Since the holding torque is reduced by the magnetic action of the magnetic poles, the motor can be driven satisfactorily with small electric power.

Furthermore, since the magnetic pole portion of each electromagnet is magnetized by the magnetic flux from the permanent magnet and the magnetic flux from the excitation coil, the strength of the magnetic pole is increased. As a result, a highly efficient stepping motor with a large rotational torque is obtained, and a stepping motor suitable for sensitive control is obtained.

[Brief explanation of drawings]

FIG. 1 is a perspective view of a stepping motor showing an embodiment of the present invention.

FIG. 2 is a simplified diagram of the motor showing the arrangement of the magnetic poles of the rotor and the magnetic poles of the stator.

[Figure 3] Rotor and stay for explaining the principle of the present invention
(A) shows the state in which the electromagnets forming the rotor are not powered, (B) shows the state in which the electromagnets are powered with positive voltage, and (C) shows the state in which the electromagnets are powered with negative voltage. It is a figure showing each state.

FIG. 4 is a time chart showing the power supply voltage of the stepping motor.

FIG. 5 is an explanatory diagram for explaining the rotor rotation operation of the stepping motor.

FIG. 6 is a simplified diagram of a stepping motor shown as a conventional example.

[Explanation of symbols]

21 Rotor 23 Pinion gear 24 Stator 25-28 Electromagnet 25a-28a, 25b-28b Magnetic pole part 25c-2
8c Excitation coil 29 First yoke 30 Second yoke 31 Permanent magnet

Claims (1)

[Claims] Claim 1: A permanent magnet is provided between a rotor having magnetic poles polarized on the rotating surface, a first yoke, and a second yoke, and a permanent magnet is provided between these two yokes in the same direction. At least two or more electromagnets equipped with excitation coils that generate magnetic flux are provided, and each electromagnet is arranged so that the magnetic pole portions of the first and second yokes are positioned in two stages along the rotational axis direction of the rotor. A stepping motor characterized by having a more structured stator.