DE2410745A1 - STEPPER MOTOR - Google Patents

Description

The invention "relates to a very small stepping motor, which as an electromechanical converter in clocks with quartz, crystals as well as in other clocks can be used.

It has already been proposed a motor of this type, which two stator or stators and a rotor with six Poland has. In this type of motor, however, only two of the six magnetic poles generate effective torque, and the The motor therefore has unused poles. This in turn results in a lower efficiency of the motor. Of the When a pulse is applied, the rotor rotates through an angle of 60 °, but it tends to do so due to its inertia to rotate around a value corresponding to two poles, d. H. by 120 °. In addition, a special magnetizing

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setup required to "cover the six poles of the rotor." magnetize, and it is very difficult to magnetize six poles with the same magnetic assignment.

Still another motor for timepieces has been proposed in which a rotor made of a permanent magnet is disposed directly in a solenoid. However, since a magnetic field generated in a cavity in the solenoid is directly used in a motor of this type, the magnetic flux density or induction cannot possibly be increased, which in turn reduces the? Efficiency is deteriorated.

The object of the invention is therefore to eliminate the aforementioned disadvantages and to create a motor for watches, in which a high output power is obtained with a low power consumption and a low voltage can. This object is achieved according to the invention by the features in the characterizing part of claim 1.

Advantageously, in a stepping motor according to the invention, a rotor with two magnetized poles and a pair of stator or stators are used which enclose substantially the entire circumferential area of the rotor.

Further details and advantages of the invention will become apparent from the following description with reference to FIG the attached drawings are explained in detail. Show it:

1 shows the structure of a small stepping motor according to the invention;

I ¹ Xg. 2 a waveform of pulses applied to a coil:

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lig. 3 the relationship between an equilibrium position of a Rotor and a magnetic potential;

4 and 5 equilibrium positions of a motor and magnetic tracks, over which a magnetic flux flows}

lig. 6 depending on an equilibrium position of a Rotor a variation of a magnetic potential; and

"7 shows a relationship between the diameter of a rotor and its minimum control voltage.

In "Fig. 1 stators 2 and 3 are opposed to one another Rotor 1 arranged with two magnetic poles · These stators are wound on a yoke 5 »around which a coil 4 is wound is fastened by means of screws 6, whereby a pair of stators is created. So that the rotor 1 is only in one Direction rotates is by means of an eccentrically arranged pin 7j with which the clear distance between the rotor

1 and the stators 2 and 3 is adjustable, at least one cylindrical! "laugh of stators 2 and 3 somewhat eccentrically arranged with respect to the center of the rotor 1; the rotor 1 is balanced in the position and in equilibrium in which its magnetic poles (N, S) are inclined or inclined on one side of the stators 2 and towards.

In Fig. 2, a waveform of a control voltage applied to the coil 4 is shown. For example, it has a pulse train of positive and negative pulses, which abut alternately _{NaCN e} i _ner second. The rotor 1 then rotates 180 ° because its magnetic poles N and S exert a magnetic repulsion or attraction force on the magnetic poles If and S of the stators when the voltage is applied

2 and 3 generate. The rotor 1 then continues to rotate accordingly the next pulse by 180 °, since the opposite

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Magnetic poles H and S are generated on the stators 2 and 3. A continuous rotation of the rotor in one direction can then be obtained by the repeated application of the pulses will.

In] fig. 3 is, in graph form, FIG Relationship between the magnetic potential in the free space formed by the rotor and stators and the equilibrium position of the rotor 1 shown «The control voltage of the motor is proportional to the difference between a maximum value Pmax. and a minimum value Pmin. a magnetic potential P, d. H. proportional Pmax.-Pmin .. In order to be able to control and operate the motor with a low voltage, the value Pmax.-Pmin. be as small as possible or reduced to a minimum. Accordingly, is another object of the invention the creation of a method for realizing the above-described condition.

According to the invention, attempts have been made with the following four methods to obtain the aforementioned Pmax.-Pmin. to make it as small as possible or reduce it to a minimum.

1) the rotor 1 has been made smaller to thereby decrease the magnetomotive force of the magnet;

2) the gap 8 between stators 2 and 3 has been reduced to a minimum value;

3) the clearance between rotor 1 and stators 2 and 3 has been increased4

4-) the angle OG at the pointed ends of the stators 2 and 3 was chosen so that the optimal value of the magnetic reluctance is close to the pointed tapered ends can be obtained.

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The above-mentioned methods will now be described in detail.

The miniaturization of the rotor 1 not only makes a decrease in the level difference of the magnetic potential possible, but also results in advantageous dynamic characteristics on the rotor itself. The torque To, which is applied to the circular rotor 1 in the uniform magnetic field is given by the equation:

To- = -4— MoBoDt sin β = KMo (HI) Dt sin 9 .... 1, 2 / to

where Mo is the intensity of the magnetization, 'D is the diameter of the rotor, θ is the angle between the magnetic dipole of the rotor and the magnetic field, _{no is} the permeability in vacuum, Bo is the magnetic flux density or induction, t is the thickness of the rotor, H the Number of turns of the coil and I is the current flowing through the coil.

The moment of inertia Io of the rotor is then given by the equation given:

/ L 4

where f is the density, D is the diameter and t is the thickness of the rotor.

Accordingly, Equation 1 can also be transformed as follows:

To = KMoHI sine

where Vo is the volume of the rotor. From the last equation it can be seen that the torque generated by the

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Magnetic field applied to the rotor is inversely proportional to the square root of the rotor's moment of inertia. The moment of inertia dee JL-to rs is proportional to the fourth power of the Iiutoi'durchmeauer: ,, if the volume of the rotor is assumed to be conotant / <lr-i. Consequently, assuming that dn.3 / oluinen de.u Hotors is constant, the expensive voltage can be reduced and the torque increased if the diameter of the rotor is reduced. As a result of the experiments and studies with the present invention, the in 2 ¹ Ig. 7 is obtained between the diameter of the rotor 1 and the minimum control voltage. The diameter of the rotor was set according to the invention to a value which is greater than or equal to. 2.5 mm is required to operate a watch with sufficient electromotive force or voltage supplied by a battery .3 V ₀ Consequently, two batteries are required when the diameter of the rotor becomes larger than 2.5 mm. Furthermore, a rotor with a diameter of 3 »5 mm can, based on the data in]? Ig. 7 can be created when a lithium battery is used, the electromotive force or voltage of which is 2.5 V and which has been developed in the meantime.

The effect of the gap 8 between the stators 2 and 3 will now be explained below. (The following is simplicity only spoken of gap 8 for the sake of it.). The value Bnax.-Pmin. gradually increases as the gap 8 of zero is gradually increased. As a result, it is desirable and advantageous to make the gap 8 as small as possible to control and drive the motor with low voltage. However, there is a certain gap size required because the torque which is applied to the rotor

ORIGINAL INSPECTED

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the magnetic field is exerted depends mainly on the magnetic flux generated in the vicinity of the gap 8. at the motor according to the invention, the tests and investigations have shown that an adequate dimension of the gap

8 for a rotor 1 with a diameter of 2 mm approximately 0.1 mm.

Next, the influence of the clearance 9 between the rotor and the stators will be explained, i. H. the one in between defined, free space 9 »if the cylindrical surfaces of the stators are arranged concentrically with respect to the rotor 1. (In the following, for the sake of simplicity, the term clear spacing or clear intermediate space 9 is used).

Too great an increase in the clear distance 9 leads to a deterioration in the efficiency, since this affects the rotor

1 torque exerted as a function of that in the vicinity of the Gap 8 generated, magnetic flux decreases, and since the counter electromotive force generated in the coil 4 or the · Back EMF is reduced. Accordingly, the experiments have confirmed that the appropriate dimension - the clearance

9 is 1.0 to 1.5 times the aforementioned gap 8.

The influence of the angle 06 on the tapered ends of the stators 2 and 3 will now be explained. (In the following the For the sake of simplicity, always referred to as the end angle CXi). When the rotor 1 is inserted into the stators 2 and 3, where the clear distance 9 between them is chosen so that it is the same, there are two positions in which the rotor 1 in the Balance is. The rotor 1 is in a position in equilibrium, in which its S and N poles with respect to the stators

2 and 3 are arranged as shown in FIG. The rotor 1 is also in equilibrium in another position, in which its S and N poles are opposite the gap 8 are arranged, as shown in FIG.

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Or in short, the equilibrium position of the rotor is different depending on the end angle &. In detail This means that the rotor 1 is in equilibrium, as shown in Fig. 4-, when the end angle 00 is small, while the rotor 1 is in equilibrium, as shown in Fig. 5, when the end angle 06 is large. The magnetic flux or the induction flux in each of the the two layers described above is shown in FIG. 4 and in FIG. 5, respectively represented by arrow marks.

If the magnetic resistance of the magnetic track 10 in Fig. 4 is indicated by RA and the magnetic reluctance of the magnetic track 11 in Fig. 5 is indicated by RB, then in Fig. 4 the value RB is greater than the value RA, while in 5 the value RB is smaller than the value RA. The magnetic resistance RB in the magnetic path 11 depends on the end angle Qb . In other words, the smaller the end angle 06 , the larger the value RBj or vice versa, the larger the end angle (Xf, the smaller the value RB between the magnetic reluctance RB and the magnetic reluctance RA in the magnetic path including the control coil is determined the rotor 1 is in equilibrium when its magnetic poles are opposite the gap, in which case RB is smaller than RA. The relationship between the magnetic potential and the equilibrium position of the rotor is shown in FIG 6, the solid curve 12 shows the relationship when RA is smaller than RB, while the dashed curve 13 shows the relationship when RA is greater than RB. Curves 12 and 13 become flatter when RA

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is equal to RB o In this case the magnetic potential difference becomes zero and the rotor can be controlled and operated with a very small voltage _o In this case, however, the rotor tends to turn slightly in the opposite direction if any external load is applied it is put on. Consequently, the value of the magnetic potential difference must be determined accordingly. It has been confirmed that the appropriate value of the magnetic potential difference can be obtained by changing the end angle OG by changing the magnetic resistance near the (stator ^ ends. On the other hand, the value of this magnetic resistance changes depending on the thickness of the stator In the case of a rotor and stators which are about half the thickness of the rotor, the rotor is in equilibrium, as shown in FIG. 5, at an end angle 00 of about 60, and the magnetic potential difference has the smallest value at an end angle Oi of about 50. In the practical embodiment, however, the stator 2 is slightly displaced with respect to the rotor 1 and the position of the magnetic poles on the rotor is inclined by about JO °, as shown in FIG and determine «

How easy it is to adjust the stator depends on the relationship between the adjustment angle of the stator and the angular displacement or displacement of the rotor The stator is very difficult to adjust in comparison with the stator, the end angle ty of which is less than 45 ° How easy it is to adjust the stator therefore has an impact

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on the performance as well as the price of the engine.

The end angle OCf was then set in an angle range from 10 ° "to 45 ° with regard to the test and investigation results. In addition, the tests have shown that the most appropriate end angle (/, is around 25 ° o

With the invention, a very small stepping motor is thus created, the rotor diameter of which is 2.5 mm and which can be used in a watch with quartz crystal. The stepping motor according to the invention has the following advantages: the power consumption of the stepping ^{motor is about 5 to 7 u} w "when it is controlled or driven step by step every second, so that the quartz crystal clock can be operated with a battery for one year The output torque of the motor is then more than 4 dynes cm (4.08 mgcm), which guarantees a torque that is about five times the torque required to drive the entire winding wheel in the watch. In addition, since the irregularity of the rotation angle of the rotor is reduced by using the two-pole stepping motor according to the invention, high reliability can be obtained.

Patent claims:

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Claims (3)

Claims ! 1. Small stepper motor, characterized in ^s - et n 'that a rotor (1) consists of a cylindrical permanent magnet, a pair of magnetic poles. and that its diameter is less than 2.5 mm, that two stators (2, 3) have two opposing, cylindrical surfaces which are arranged around the rotor (1) so that its circumference is at least more than 300 ° is enclosed that at least one of the cylindrical surfaces is arranged eccentrically with respect to the rotor axis, and that at least one coil (4) is magnetically connected to the stators (2, 3). 2. Small stepping motor according to claim 1, characterized in that an adjusting device (7) is provided to adjust at least one of the cylindrical surfaces of the stators (2, 3) eccentrically with respect to the rotor axis, in order to thereby establish a GieichgewichtsXage of the rotor (1) and in that the opposite cylindrical surfaces of the stators (2, 3) ■ 1 _t O to 1.5 times as strong as the rotor (1) made of a permanent magnet. 3. Small stepping motor according to claims 1 and 2, characterized in that the stators (2, 3) have an end angle Φ at their tapered ends, and that this end angle 00 is set in an angle * range of 10 ° to 45 ° . 409843/0705 Blank