JP2002263575A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin motor for a pager which is simple in production, high in output, easy of handling, and small in size. SOLUTION: A magnet which is formed cylindrically, at least the peripheral surface of which is divided in the circumferential direction, and which is magnetized alternately to be different in polarity and can rotate around the rotational center is provided. A coil is arranged in the axial direction of the magnet. An outside magnetic pole part which is excited by the coil and faces the outside surface of the magnet, a hollow column-shaped inside magnetic pole part which is excited by the coil and faces the inside surface of the magnet, and a weight which is rotated integrally with the magnet, constituted in a shape to be unbalanced in mass with regard to the rotational center, and arranged in the space of the inside diameter part of the hollow cylinder part of the inside magnetic pole part are provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-small, thin coin-shaped motor.

[0002]

2. Description of the Related Art As a pager incorporated in a cellular phone or the like, there is a type in which a weight having an imbalanced mass with respect to the center of rotation is attached to an output shaft of a motor to convert the rotation of the motor into vibration. The demand for use as a means or a signal generating means is increasing. Further, in response to a demand for downsizing of a device, further downsizing of a pager motor is desired.

[0003] Conventionally, there is a brushless type suitable for a small motor. As a brushless type motor having a simple drive circuit, there is a step motor using a permanent magnet described below.

FIG. 6 shows a small cylindrical step motor. Stator coil 1 on bobbin 101
05 is concentrically wound, the bobbin 101 is sandwiched and fixed in the axial direction by two stator yokes 106, and stator teeth 106a and 106b are alternately arranged on the stator yoke 106 in the circumferential direction of the inner diameter surface of the bobbin 101. Placed in
Case 103 includes stator teeth 106a or 106b
Is fixed to the stator 1 and the stator 1
02 is configured. A flange 115 and a bearing 108 are fixed to one of the two cases 103, and another bearing 108 is fixed to the other case 103. The rotor 109 is a rotor magnet 11 fixed to a rotor shaft 110.
1 and the rotor magnet 111 forms a radial gap with the stator yoke 106a of the stator 102.
The rotor shaft 110 is rotatably supported between the two bearings 108.

[0005] As a step motor driven by one coil, there is one shown in FIG. 8 which is often used in a timepiece. 201 is a rotor made of permanent magnets, 202 and 203
Is a stator, and 204 is a coil.

[0006]

However, the conventional small stepping motor shown in FIG. 6 has a case 103, a bobbin 101, a stator coil 105,
Since the stator yoke 106 is arranged concentrically, there is a disadvantage that the outer dimensions of the motor become large. Further, as shown in FIG. 7, the magnetic flux generated by energizing the stator coil 105 mainly passes through the end face 106a1 of the stator tooth 106a and the end face 106b1 of the stator tooth 106b, so that the magnetic flux does not effectively act on the rotor magnet 111. There is a disadvantage that the output does not increase.

[0008] Also in FIG. 8, the magnetic flux generated by energizing the coil concentrates in a place where the gap between the stator 203 and the stator 204 is small, and does not effectively act on the magnet.

[0008] In a pager motor for converting a rotation of the motor into vibration by attaching a weight having an imbalanced mass with respect to the center of rotation to the output shaft of the motor, since the weight is attached to the outside of the motor body, the lead of the apparatus is used. There is a drawback that careful attention is required in assembling such that wires and flexible printed circuit boards do not enter the rotation locus of the weight, and handling is difficult.

As small motors, there are ordinary brush-type cored DC motors and coreless DC motors. However, since there are many components, if the motors are made very small, it is difficult to manufacture and assemble each component, resulting in an increase in cost. . Further, since the weight having the eccentric mass is rotated, vibration is transmitted to the brush portion via the rotating shaft, and the contact of the brush portion is deteriorated, and the durability is poor.

[0010] Further, when a pencil-shaped cylindrical motor is used for a pager incorporated in a cellular phone or the like, it is necessary to reduce the diameter of the motor and the diameter of the weight to reduce the thickness of the device. In such a case, the output of the motor is reduced and the eccentric mass of the weight is also reduced, so that the generated vibration is reduced and the signal cannot be sufficiently transmitted to the user. Also, the motor itself has the disadvantage that the parts are reduced in size, manufacturing becomes difficult, and the cost increases.

Further, there is a coin type brushless motor. For example, JP-A-7-213041 and JP-A-2000-5060
As shown in FIG. The coil is composed of a plurality of coils (301, 302, 303) and a disk-shaped magnet (304). The coil is a thin coin shape as shown in the figure, and its axis is arranged parallel to the axis of the magnet. I have. On the other hand, the disc-shaped magnet is magnetized in the axial direction of the disc, and the magnetized surface of the magnet and the axis of the coil are arranged so as to face each other. In this case, the magnetic flux generated from the coil does not completely and effectively act on the magnet as shown by the arrow in FIG. 10, and the center of the rotational force generated by the magnet is located at a position away from the outer diameter of the motor by L. Therefore, the generated torque is small for the size of the motor.

Further, since the center of the motor is occupied by a coil or a magnet, it is difficult to arrange another component in the motor. Furthermore, since a plurality of coils are required, there are disadvantages that the control of energization of the coils becomes complicated and costs increase.

It is an object of the first and second aspects of the present invention to provide a small and thin pager motor which is easy to manufacture, has a high output and is easy to handle.

[0014]

Means for Solving the Problems In order to achieve the above object, the invention according to claim 1 of the present application has a cylindrical shape and at least an outer peripheral surface divided in a circumferential direction and alternately arranged with different poles. An outer magnetic pole portion which is magnetized and is rotatable about a center of rotation, a coil is arranged in an axial direction of the magnet, and which is excited by the coil and is opposed to an outer peripheral surface of the magnet; and A hollow column-shaped inner magnetic pole portion opposed to the inner peripheral surface of the magnet, and a space formed inside the hollow cylindrical portion of the inner magnetic pole portion, the inner magnetic pole portion being configured to rotate integrally with the magnet and to have an imbalanced mass with respect to the center of rotation. And a weight arranged at the end.

[0015] In the above configuration, the diameter of the motor is determined by the outer magnetic pole facing the outer peripheral surface of the magnet, and the axial length of the motor is determined by arranging the coil and the magnet in this order, thereby making the motor extremely small. Things that can do things. In addition, the magnetic flux generated by the coil crosses the magnet between the outer magnetic pole and the inner magnetic pole, so that it works effectively.
Since the weight rotating integrally with the magnet is arranged in the inner diameter portion of the inner pole portion having the hollow column shape, the size of the motor itself does not increase.

Further, since the weight itself is located at a position surrounded by parts of the motor, there is no danger of contact from the outside and the handling becomes very easy. Further, a portion of the magnet which generates torque is a large torque because the outer diameter of the magnet is large.

[0017] In order to achieve the above object, the invention according to claim 4 of the present application is arranged so that at least the outer peripheral surface is divided into N in the circumferential direction and magnetized alternately at different poles so that the center of rotation is formed. A comb-shaped outer side provided with a magnet rotatable around the center, a coil arranged in the axial direction of the magnet, and energized by the coil and provided on the outer peripheral surface of the magnet so as to face each other at a predetermined angle A degrees Magnetic pole
And an inner magnetic pole portion which is excited by the coil and faces the inner circumferential surface of the magnet and has a hollow columnar shape, and the inner magnetic pole portion which is configured to rotate integrally with the magnet and have an unbalanced mass with respect to the center of rotation. And a weight disposed in the space of the inner diameter of the hollow cylindrical portion, and each of the comb teeth of the outer magnetic pole portion facing the outer peripheral portion of the magnet has a comb-tooth-shaped facing angle A degree, and the outer diameter dimension D1 of the magnet. A> (248.4 / N) -58.86 where D2 is the inner diameter of the magnet.
× (D1−D2) / (D1 × π).

In the above configuration, the diameter of the motor is determined by the outer magnetic pole facing the outer peripheral surface of the magnet, and the length of the motor in the axial direction is determined by arranging the coil and the magnet in this order, so that the motor is extremely reduced in size. Things that can do things. In addition, the magnetic flux generated by the coil crosses the magnet between the outer magnetic pole and the inner magnetic pole, so that it works effectively.
Since the weight rotating integrally with the magnet is arranged in the inner diameter portion of the inner pole portion having the hollow column shape, the size of the motor itself does not increase.

Further, since the weight itself is located at a position surrounded by the motor components, there is no possibility of contact from the outside and the handling becomes very easy. Further, a portion of the magnet which generates torque is a large torque because the outer diameter of the magnet is large.

Further, since the outer magnetic pole portion is formed in a comb-like shape provided at a predetermined angle A degrees to the outer peripheral portion of the magnet, the outer magnetic pole portion is formed in a radial direction compared to a case where the outer magnetic pole portion is formed by unevenness in the radial direction. The dimensions can be made thin. As a result, the outer diameter of the magnet can be made large, so that the torque of the motor can be increased. Assuming that each angle A of the comb teeth of the outer magnetic pole portion facing the outer peripheral portion of the magnet, the outer diameter dimension D1 of the magnet, and the inner diameter dimension D2 of the magnet are A> (248.4 / N) −58.86. × (D1-D2)
By setting / (D1 × π), the boundary between the magnetized pole of the magnet and the pole is located at the center of the comb teeth of the outer magnetic pole portion, and when the motor is stopped, the coil is initially energized. The force of the generated magnetic flux acting on the magnet does not go to the center of rotation of the magnet, so that the rotation can be started stably.

Further, since the magnet and the outer magnetic pole are used as a means for setting the initial position of the magnet to a position where rotation can be started stably, the magnet can be constructed at a low cost.

[0022]

1 to 3 show a step motor according to a first embodiment of the present invention. FIG. 1 is an exploded perspective view of the step motor, and FIG. 3 is an axial sectional view of FIG.
It is sectional drawing in the -A line.

In FIG. 1 to FIG. 3, reference numeral 1 denotes a cylindrical magnet constituting a rotor. The magnet 1, which is a rotor, has its outer peripheral surface divided into n parts in the circumferential direction. Then> the S pole and the N pole are alternately magnetized. Assuming that the magnetized portions are 1a, 1b, 1c and 1d, the magnetized portions 1a and 1c are magnetized to the S pole, and the magnetized portions 1b and 1d are
Polarized. The magnet 1 is made of a plastic magnet material formed by injection molding. Thus, the thickness of the cylindrical shape in the radial direction can be made very thin. Also magnet 1
Has a fitting portion 1e at the center. Cover 2 described later
0 pin 20b so as to be slidable and rotatable.

In particular, as a material of the magnet 1, a plastic magnet formed by injection molding a mixture of a Nd-Fe-B-based rare earth magnetic powder and a thermoplastic resin binder such as polyamide is used. Thus, the bending strength of the compression molded magnet is 500
Against kgf / cm ² degree of, for example, a polyamide resin 800 kgf / cm ² or more bending strength can not be a compression molding obtained when used as a binder material, it can be formed a thin cylindrical shape. The thin cylindrical shape enables the distance between the inner magnetic pole and the outer magnetic pole of the stator 18 to be set short, and a magnetic circuit having a small magnetic resistance therebetween. Thereby, when the coil 2 is energized, a large amount of magnetic flux can be generated even with a small magnetomotive force, thereby improving the performance of the motor.

Further, the shape can be made free and the strength of the fitting portion 1e can be obtained sufficiently. Magnet 1
The slidable fitting portion 1e is formed integrally with the magnet 1 so that the coaxial accuracy of the magnet portion with respect to the center of rotation is improved, vibration is reduced, and the gap distance between the magnet and the stator portion is reduced. It is possible to obtain a sufficient output torque of the motor.

[0026] In addition, the injection molded magnet has a thin resin film formed on the surface, so that the generation of rust is significantly less than that of the compression magnet, so that rust prevention treatment such as painting can be eliminated. In addition, the quality can be improved without the adhesion of magnetic powder, which is a problem with the compression magnet, and the surface swelling that is likely to occur during rust prevention coating.

Reference numeral 2 denotes a cylindrical coil. The coil 2 is arranged concentrically with the magnet 1 and arranged side by side in the axial direction of the magnet 1. The outer diameter of the coil 2 is substantially the same as the outer diameter of the magnet 1. It is.

Reference numeral 18 denotes a stator made of a soft magnetic material, which comprises an outer cylinder and a hollow cylindrical inner cylinder. Stator 18
The coil 2 is provided between the outer cylinder and the inner cylinder, and the coil 18 is energized to excite the stator 18.
The outer cylinder and the inner cylinder of the stator 18 have outer magnetic poles 18a, 18b whose distal ends face the outer peripheral surface of the magnet 1 and inner magnetic poles 18c, 18 which face the inner peripheral surface of the magnet 1.
d, the outer magnetic pole 18a and the outer magnetic pole 18
b is 360 / <n / 2> degrees, that is, 1 so as to be in phase with each other with respect to the magnetized pole of the magnet.
The inner magnetic pole 18c and the inner magnetic pole 18d are formed so as to have the same phase with each other.
The outer magnetic pole 18a is formed so as to be shifted by <n / 2> degrees, that is, 180 degrees, and the outer magnetic pole 18a is arranged to face the inner magnetic pole 18c, and the outer magnetic pole 18b is arranged to face the inner magnetic pole 18d. The outer magnetic poles 18a and 18b of the stator 18 are formed by cutout holes and comb teeth extending in a direction parallel to the axis.

With this configuration, it is possible to form the magnetic poles while minimizing the diameter of the motor. In other words, if the outer magnetic pole is formed by irregularities extending in the radial direction, the diameter of the motor will increase accordingly. However, in this embodiment, the outer magnetic pole is formed by a notch hole and a comb tooth shape extending in a direction parallel to the axis. , The diameter of the motor can be minimized.

In the present embodiment, the inner magnetic pole is formed in a comb shape like the outer magnetic pole by partially cutting out the hollow cylindrical shape. However, only the inner magnetic pole may be simply a hollow cylindrical shape. If the outer magnetic pole is formed in the above-described comb shape, the magnetic flux passing between the inner magnetic pole and the outer magnetic pole is the inner shape obtained by projecting the shape of the comb-shaped outer magnetic pole and the outer magnetic pole onto the cylindrical inner magnetic pole. The shape of the inner magnetic pole may be a simple hollow cylindrical shape to pass between the positions on the magnetic pole. In this embodiment, the outer magnetic pole is 360 / <n / 2> degrees, that is, 1
Although two are formed with a shift of 80 degrees, 360 / <n /
2> It may be an integer multiple of degrees. That is, the number may be one. In the present embodiment, the number of poles of the magnet is four, but if this is, for example, ten, the outer magnetic pole is 360 /
<N / 2> degrees, that is, five teeth may be formed with a shift of 72 degrees, or one tooth may be deleted and four teeth, that is, 72 degrees, 72 degrees, 72 degrees, and 1 tooth may be formed.
It may be formed every 44 degrees. Similarly, in the case of three teeth, it may be formed at every 72 degrees, 144 degrees, and 144 degrees.

The outer magnetic poles 18a and 18b and the inner magnetic poles 18c and 18d of the stator 18 are provided so as to sandwich one end of the magnet 1 so as to face the outer peripheral surface and the inner peripheral surface at one end of the magnet 1. One end of the output shaft 7 is rotatably fitted in the hole 18e of the stator 18. Therefore, the magnetic flux generated by the coil 2 is the outer magnetic pole 18a,
Since it crosses the magnet 1, which is a rotor, between the inner pole 18b and the inner magnetic poles 18c, 18d, it effectively acts on the magnet, which is a rotor, to increase the output of the motor.

The magnet 1 is made of a plastic magnet material formed by injection molding as described above, so that the thickness of the cylindrical shape in the radial direction can be made extremely thin.

[0033] Therefore, the outer magnetic poles 18a, 18 of the stator 18 are provided.
The distance between b and the inner magnetic poles 18c and 18d can be made very small, and the magnetic resistance of the magnetic circuit formed by the coil 2 and the first stator can be made small. As a result, a large amount of magnetic flux can be generated with a small current, so that the output of the motor can be increased, the power consumption can be reduced, and the size of the coil can be reduced.

Numeral 7 denotes a weight which is formed integrally with the magnet 1 so as to have an unbalanced mass with respect to the center of rotation, and which is arranged in the space inside the hollow cylindrical portion of the inner magnetic pole portion. The weight 7 is adhered to the magnet 1 and rotates integrally with the magnet 1.

Reference numeral 20 denotes a cover as a cylindrical member made of a non-magnetic material. Outer magnetic poles 18a and 18b of the stator 18 are fitted to the inner diameter of the cover 20 and fixed with an adhesive or the like. Also, the pin 20b is used for the fitting portion 1 of the magnet 1
e is slidably fitted.

FIG. 2 is a sectional view of the step motor, and FIG.
(a), (b), (c), and (d) are cross-sectional views taken along line AA of FIG. Q1 in FIG. 3 is the outer magnetic pole 1 of the stator 18.
Q2 represents the center of the outer magnetic pole 18b of the stator 18, and Q3 represents the center of rotation of the magnet 1.

FIG. 4 shows the rotational position of the magnet and the state in which the magnet is attracted by the outer magnetic pole when there is no power supply to the coil. The vertical axis represents the magnetic force generated between the magnet and the stator 18 acting on the magnet, and the horizontal axis represents the rotation phase of the magnet. In this figure, the point indicated by point E exerts a negative force when trying to rotate, tries to return to the original position, and when trying to return, a force acts in the direction to advance,
This is the coking position to be returned to the original position, that is, to be stably positioned at the point E by the magnetic force between the magnet and the outer magnetic pole. Point F is a stop position that is an unstable equilibrium state in which a driving force acts on the position of point E before and after even a slight shift. When the coil is not energized, it does not stop at point F but stops at point E due to vibration or changes in posture.

As a result of a numerical simulation by the finite element method, the relationship between the outer magnetic poles 18a and 18b and the magnet 1 when no current is supplied to the coil is obtained due to the relationship between the angle of the magnetized pole and the angle of the outer magnetic pole opposed to it. It became clear that the state of the suction state changed. According to this, the coking position of the magnet changes depending on the angle of the outer magnetic pole facing the magnet. That is, when the angle of the outer magnetic pole facing the magnet is larger than a certain value, the boundary between the pole of the magnet and the pole is stably held at a position facing the center of the outer magnetic pole. The point E in FIG. 4 is a position where the boundary between the poles of the magnet is opposed to the center of the outer magnetic pole. Conversely, when the angle of the outer magnetic pole facing the magnet is smaller than a certain value, the center position of the pole of the magnet is stably held at the position facing the center of the outer magnetic pole. Solid E in Fig. 4
The point is the position where the center of the pole of the magnet faces the center of the outer magnetic pole.

FIG. 5 shows this state in detail. The abscissa represents (magnet thickness / peripheral length per magnet pole), and the ordinate represents (facing angle to magnet per outer magnetic pole / angle per magnet pole). For example, when the outer diameter of the magnet is 10 mm, the inner diameter is 9 mm, and the number of poles is 20, the thickness of the magnet is (outer diameter−inner diameter) / 2, and the outer peripheral length per pole of the magnetic pole is 10 × π / 20. Therefore, the value of (magnet thickness / peripheral length per magnet pole) on the horizontal axis is 0.318
Becomes Further, assuming that the angle of facing the magnet per one outer magnetic pole is 15 degrees, the angle per magnet is 1 unit.
Since the angle is 8 degrees, the vertical axis (the angle facing the magnet per outer magnetic pole / the angle per magnet) is 0.8.
33.

Each point in FIG. 5 has almost zero coking torque.
FIG. 9 is a plot of (a facing angle to a magnet per one outer magnetic pole / an angle per magnet) of a model as follows. Assuming that the vertical axis is Y and the horizontal axis is X, these points can be approximated by a straight line Y = 0.327X + 0.69.
If Y> −0.327X + 0.69, the boundary between the poles of the magnet is stably held at the position facing the center of the outer magnetic pole, and if Y <−0.327X + 0.69, the center position of the magnet pole is the outer magnetic pole. Is stably held at a position facing the center of the.

That is, Y> −0.327X + 0.69 is expressed as follows. Assuming that each of the outer magnetic poles has a facing angle A with respect to the magnet, an outer diameter D1 of the magnet, and an inner diameter D2 of the magnet, A> (248.4 / N) −58.86 × (D
1−D2) / (D1 × π). A> (248.4 / N)-
If it is set to be 58.86 × (D1−D2) / (D1 × π), the boundary between the poles of the magnet is stably held at a position facing the center of the outer magnetic pole.

In the case of the present embodiment, the number N of magnetized poles is 4, so if, for example, the outer diameter D1 of the magnet is 10 mm and the inner diameter D2 of the magnet is 9 mm, (248.4 / N)-
58.86 × (D1−D2) / (D1 × π) = 60.23 degrees, and if each of the opposite angles A of the outer magnetic poles with respect to the magnet exceeds 60.23 degrees, then Y> −0.327X + 0.
69 conditions will be applied. In the present embodiment, the angle A of each outer magnetic pole with respect to the magnet is 90 degrees, so that the boundary between the poles of the magnet and the pole is stably held at a position facing the center of the outer magnetic pole. -ing

When the boundary between the magnetized poles of the magnet is located at a position facing the center of the comb teeth of the outer magnetic pole portion, the coil is energized to excite the comb teeth of the outer magnetic pole portion. Is turned on and starts up. However, if the center of the magnetized pole of the magnet is located at a position facing the center of the comb teeth of the outer magnetic pole portion, the magnet 1 will remain Smooth startup is not performed because no rotational force is generated.

In this embodiment, the angle A of the outer magnetic poles 18a and 18b facing the magnet 1, the outer diameter D1 of the magnet,
Assuming that the inner diameter of the magnet is D2, A> (248.4 /
(N) −58.86 × (D1−D2) / (D1 × π), which corresponds to the case above the portion shown by the straight line shown in FIG. Therefore, when the coil is not energized, the point E is stably stopped at this position because the boundary between the magnetized poles of the magnet is located at a position facing the center of the comb teeth of the outer magnetic pole portion. are doing. When the coil is energized from this state to excite the comb teeth of the outer magnetic pole portion, the magnet 1 always generates a rotational force, and smooth start-up is performed. When the outer magnetic pole is configured as described above, the magnet 1 is not energized when the coil is not energized.
The center of each pole of the magnetized portion functions as a holding means for holding the center at a position deviated from a straight line connecting the center of the outer magnetic pole and the rotation center of the magnet.

Next, the operation of the step motor will be described. A>
(248.4 / N) -58.86 × (D1-D2) / (D1 ×
π), the outer magnetic pole portions 18a and 18b have the center of each pole of the magnetized portion of the magnet 1 as the center of the outer magnetic pole when the coil is not energized. When the coil 2 is not energized, the magnet 1 can be used as a holding means for holding the coil at a position deviated from the straight line connecting the rotation center of the magnet.
3A, where the boundary between the magnetized portions of FIG. 3 faces the center of the outer magnetic poles 18a and 18b.

When the coil 2 is energized from the state shown in FIG. 3A to make the outer magnetic poles 18a and 18b of the stator 18 N poles and the inner magnetic poles 18c and 18d are excited to S poles,
When the magnets 1a and 18b and the inner magnetic poles 18c and 18d are excited, the magnet 1 always receives the electromagnetic force in the rotating direction, and the magnet 1 as the rotor starts to rotate smoothly counterclockwise. Then, the power supply to the coil 2 is cut off at the timing when the state shown in FIG. Since the state shown in FIG. 3B is point F in FIG. 4, the rotor further rotates counterclockwise from the state shown in FIG. Then, a state shown in FIG. 3C stabilized by the coking force is obtained.

Next, the power supply to the coil 2 is reversed, and the stator 1
8, the outer magnetic poles 18a and 18b are S poles, and the inner magnetic pole 18
When c and 18d are excited to the N pole, the magnet 1, which is the rotor, further rotates counterclockwise, and rotates toward the state shown in FIG.

Thereafter, by sequentially switching the energizing direction to the coil 2 in this manner, the magnet 1 as a rotor rotates to a position corresponding to the energizing phase.

Numeral 23 denotes a weight member fixed to the output shaft 7, and rotates integrally with the output shaft 7 and the magnet 1. Weight member 2
Reference numeral 3 denotes a shape having an unbalanced mass with respect to the center of rotation, and generates vibration by rotation of the output shaft 7 and the magnet 1.

The weight member 23 is disposed at the inner diameter of the hollow cylindrical inner magnetic pole, and is protected by the cover 20 and the stator 18 from being accidentally touched from the outside. In addition, since the weight member is disposed at the inner diameter of the hollow cylindrical inner magnetic pole, the external dimensions of the motor are not increased by the weight member 23.

Here, a description will be given of the fact that the step motor having such a configuration is the most suitable configuration for miniaturizing the motor. The basic configuration of the step motor is as follows. First, the magnet is formed in a hollow cylindrical shape, and second, the outer peripheral surface of the magnet is divided into n in the circumferential direction and magnetized alternately at different poles. Third, the coils are arranged side by side in the axial direction of the magnet, and fourth, the outer and inner magnetic poles of the stator, which are excited by the coils, face the outer and inner peripheral surfaces of the magnet. Fifth, the outer magnetic pole is constituted by a notch hole and a tooth extending in a direction parallel to the axis. Sixth, when the coil is not energized, the center of the pole of the magnet is rotated by the center of the outer magnetic pole and the rotation of the magnet. It is provided with holding means for holding at a position shifted from a straight line connecting the center. The diameter of this step motor only needs to be large enough to make the magnetic pole of the stator oppose the diameter of the magnet, and the length of the step motor is the length of the magnet plus the length of the coil. That would be good. Therefore, the size of the step motor is determined by the diameter and length of the magnet and coil.
If the diameters and lengths of the magnet and the coil are made very small, the step motor can be made very small.

At this time, if the diameter and length of the magnet and the coil are made extremely small, it is difficult to maintain the accuracy as a step motor. However, this is because the magnet is formed in a hollow cylindrical shape, The problem of the accuracy of the step motor is solved by a simple structure in which the outer magnetic pole and the inner magnetic pole of the stator are opposed to the outer peripheral surface and the inner peripheral surface of the cylindrical magnet. At this time, if not only the outer peripheral surface of the magnet but also the inner peripheral surface of the magnet is divided and magnetized in the circumferential direction, the output of the motor can be further increased.

In particular, when used for a pager incorporated in a cellular phone or the like, a thin coin-shaped motor can be used as shown in this embodiment, which does not hinder the thinning of the device.
In addition, since the torque is large and the eccentric mass of the weight can be increased, large vibration can be generated.

Each angle A of the comb teeth of the outer magnetic pole portion facing the outer peripheral portion of the magnet, the outer diameter of the magnet
If D1 and the inner diameter of the magnet are D2, A> (248.4
/N)−58.86×(D1−D2)/(D1×π), so that the boundary between the magnetized poles of the magnet is located at the center of the comb teeth of the outer magnetic pole portion. When the motor is stopped and the coil is first energized after the motor is stopped, the magnetic flux generated from the coil acts on the magnet without being directed to the center of rotation of the magnet, so that the rotation can be started stably. Since the magnet and the outer magnetic pole are used as means for setting the initial position of the magnet to a position at which rotation can be started stably, the configuration can be made at a low cost.

Since one coil is used, the control circuit for energization is simplified, and the cost can be reduced.

[0056]

As described above in detail, according to the present invention,
A magnet formed in a cylindrical shape and having at least an outer peripheral surface divided in a circumferential direction and alternately magnetized to different poles and rotatable about a rotation center, and a coil disposed in an axial direction of the magnet; An outer magnetic pole portion which is excited by the magnet and faces the outer peripheral surface of the magnet; an inner magnetic pole portion which is excited by the coil and faces the inner circumferential surface of the magnet and which has a hollow columnar shape; The motor has a completely new configuration that is different from the conventional one because it has a weight that is configured in a shape that results in an unbalanced mass and is disposed in the space of the inner diameter of the hollow cylindrical portion of the inner magnetic pole portion. This makes it possible to obtain an optimal configuration for miniaturizing the motor.

The diameter of the motor only needs to be large enough to make the magnetic pole of the stator oppose the diameter of the magnet, and the length of the motor is a length obtained by adding the length of the coil to the length of the magnet. That would be good. For this reason, the size of the motor is determined by the diameters and lengths of the magnets and coils. If the diameters and lengths of the magnets and coils are made very small, the stepping motor can be made very small. In addition, since the torque is large and the eccentric mass of the weight can be increased, large vibration can be generated.

The weight member 23 is disposed at the inner diameter of the hollow cylindrical inner magnetic pole, and is prevented from being accidentally touched by the cover 20 and the stator 18 from the outside. In addition, since the weight member is disposed at the inner diameter of the hollow cylindrical inner magnetic pole, the external dimensions of the motor are not increased by the weight member 23. Since a single coil is used, the control circuit for energization is simplified and the cost can be reduced.

A magnet is formed in a cylindrical shape, and at least the outer peripheral surface is divided into N parts in the circumferential direction and is alternately magnetized to different poles and is rotatable about the center of rotation. A comb-shaped outer magnetic pole portion which is arranged, is excited by the coil, is provided at an angle of an integral multiple of (720 / N) degrees apart from the outer peripheral surface of the magnet and is opposed to each other by a predetermined angle A; The inner magnetic pole portion which is excited by the coil and faces the inner peripheral surface of the magnet and has a hollow columnar shape, and has a shape which rotates integrally with the magnet and has an unbalanced mass with respect to the center of rotation, and has a hollow inner magnetic pole portion. And a weight disposed in the space of the inner diameter portion of the cylindrical portion, and further, each of the comb-tooth-shaped opposing angles A degrees of the outer magnetic pole portion facing the outer peripheral portion of the magnet,
Assuming that the outer diameter D1 of the magnet and the inner diameter D2 of the magnet are A> (248.4 / N) −58.86 × (D1−D
2) Since it is set to be / (D1 × π), it is possible to make an optimal configuration for miniaturizing the motor.

That is, the diameter of the motor only needs to be large enough to allow the magnetic pole of the stator to face the diameter of the magnet.
The length of the motor should be long enough to add the length of the coil to the length of the magnet. For this reason, the size of the motor is determined by the diameters and lengths of the magnets and coils. If the diameters and lengths of the magnets and coils are made very small, the stepping motor can be made very small. In addition, since the torque is large and the eccentric mass of the weight can be increased, large vibration can be generated. The weight member 23 is disposed at the inner diameter of the hollow cylindrical inner magnetic pole, and is protected from being accidentally touched by the cover 20 and the stator 18 from the outside.

The external weight of the motor is not increased by the weight member 23 because the weight member is arranged at the inner diameter of the hollow columnar inner magnetic pole. Since a single coil is used, the control circuit for energization is simplified and the cost can be reduced. The boundary between the magnetized poles of the magnet and the pole is located at the center of the comb teeth of the outer magnetic pole portion, and the magnetic flux generated from the coil acts on the magnet when the motor is stopped and when the coil is first energized. The rotation can be started stably without going to the center of rotation of the magnet. As described above, since the magnet and the outer magnetic pole are used as means for setting the initial position of the magnet to a position where rotation can be started stably, the structure can be inexpensively configured.

The magnet 1 is made of a plastic magnet material formed by injection molding as described above, so that the thickness of the cylindrical shape in the radial direction can be made extremely thin. Therefore, the outer magnetic poles 18a, 18b of the stator 18 and the inner magnetic poles 18c, 1
8d can be made very small, and the magnetic resistance of the magnetic circuit formed by the coil 2 and the stator can be made small. As a result, a large amount of magnetic flux can be generated with a small current, so that the output of the motor can be increased, the power consumption can be reduced, and the size of the coil can be reduced.

In particular, as a material of the magnet 1, a plastic magnet formed by injection molding a mixture of a Nd-Fe-B-based rare earth magnetic powder and a binder material of a thermoplastic resin such as polyamide is used. Thus, the bending strength of the compression molded magnet is 500
Against kgf / cm ² degree of, for example, a polyamide resin 800 kgf / cm ² or more bending strength can not be a compression molding obtained when used as a binder material, it can be formed a thin cylindrical shape. The thin cylindrical configuration can shorten the distance between the outer magnetic pole and the inner magnetic pole, and can generate a large amount of magnetic flux with a small magnetomotive force, thereby improving the performance of the motor. In addition, the shape could be made free, and the shape for fixing the rotor shaft, which cannot be obtained by compression molding, could be integrated, and sufficient rotor shaft fixing strength could be obtained. Further, since the rotor shaft is excellent in strength, it does not break even when the rotor shaft is press-fitted.

In addition, the injection molded magnet has a thin resin film formed on the surface, so that the generation of rust is significantly less than that of the compression magnet, so that rust prevention treatment such as painting can be eliminated. In addition, the quality can be improved without the adhesion of magnetic powder, which is a problem with the compression magnet, and the surface swelling that is likely to occur during rust prevention coating.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a motor according to the present invention.

FIG. 2 is a sectional view of the motor shown in FIG. 1 in an assembled state.

FIG. 3 is an explanatory diagram of a rotation operation of a rotor of the motor shown in FIG. 2;

FIG. 4 is a graph showing a state of a coking torque.

FIG. 5 is a diagram showing the width and coking torque of the outer magnetic pole,
It is a graph showing the relationship of a magnet dimension.

FIG. 6 is a sectional view of a conventional step motor.

FIG. 7 is a sectional view showing a state of a stator of a conventional step motor.

FIG. 8 is a plan view of another conventional step motor.

FIG. 9 is a perspective configuration diagram of a conventional brushless motor.

FIG. 10 is a sectional view of a conventional brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnet 2 Coil 7 Weight 18 Stator 20 Cover

Claims (9)

[Claims] 1. A magnet formed in a cylindrical shape and having at least an outer peripheral surface divided in a circumferential direction and alternately magnetized to different poles and rotatable around a rotation center, wherein a coil is provided in an axial direction of the magnet. An outer magnetic pole portion arranged and excited by the coil and facing the outer circumferential surface of the magnet; an inner magnetic pole portion excited by the coil and facing the inner circumferential surface of the magnet and having a hollow columnar shape; and integrally formed with the magnet. A motor configured to rotate so as to have an unbalanced mass with respect to the center of rotation, and to have a weight disposed in a space of an inner diameter portion of the hollow cylindrical portion of the inner magnetic pole portion. 2. A magnet formed in a cylindrical shape and having at least an outer peripheral surface divided in a circumferential direction and alternately magnetized to different poles and rotatable about a rotation center, and a coil is provided in an axial direction of the magnet. An outer magnetic pole portion arranged and excited by the coil and facing the outer circumferential surface of the magnet; an inner magnetic pole portion excited by the coil and facing the inner circumferential surface of the magnet and having a hollow columnar shape; and a center of the pole of the magnet. Holding means for holding at a position deviated from a straight line connecting the center of the outer magnetic pole and the rotation center of the magnet, and a shape which is integrally rotated with the magnet and has an unbalanced mass with respect to the rotation center. A motor provided with a weight disposed in a space inside the hollow cylindrical portion of the magnetic pole portion. 3. The apparatus according to claim 2, wherein the holding means holds the center of the pole of the magnet at a position on a straight line connecting a pole between the poles of the outer magnetic pole and a center of rotation of the magnet. Motor as described. 4. A magnet formed in a cylindrical shape and having at least an outer peripheral surface divided by N in a circumferential direction and alternately magnetized to different poles and rotatable about a rotation center, and a coil in an axial direction of the magnet. And a comb-shaped outer magnetic pole portion which is excited by the coil and is provided to face the outer peripheral surface of the magnet by a predetermined angle A.
And an inner magnetic pole portion which is excited by the coil and faces the inner circumferential surface of the magnet and has a hollow columnar shape, and the inner magnetic pole portion which is configured to rotate integrally with the magnet and have an unbalanced mass with respect to the center of rotation. And a weight placed in the space of the inner diameter of the hollow cylindrical portion, and each of the comb teeth of the outer magnetic pole portion facing the outer peripheral portion of the magnet has a comb-tooth-shaped opposing angle A degree, and the outer diameter dimension D1 of the magnet. A> (248.4 / N) -58.86 where D2 is the inner diameter of the magnet.
A motor characterized by the setting of × (D1−D2) / (D1 × π). 5. The motor according to claim 1, wherein the magnet is formed by injection molding. 6. The motor according to claim 5, wherein the magnet is formed of a mixture of a Nd—Fe—B rare earth magnetic powder and a thermoplastic resin binder. 7. The motor according to claim 1, wherein said magnet and said coil have substantially the same outer shape. 8. The motor according to claim 1, wherein the weight has a shape lacking a part of a disk shape. 9. The motor according to claim 8, wherein the weight has a shape lacking substantially half of a disk shape.