JP3107118B2 - Small DC motor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small DC motor having a rectangular shape used for a radio alerting device (pager) silent sound source or the like.

[0002]

2. Description of the Related Art A cylindrical coreless motor as shown in FIG. 4 is known as a small DC motor having a cylindrical shape used as a silent information source such as a pager or an alarm clock. In order to use the motor as a vibration source, the output shaft S of the motor is required.
And a high-density eccentric weight W made of a tungsten alloy is arranged in the center to generate vibration by centrifugal force during rotation.

[0003]

However, such a cylindrical type has a drawback in that it is inconvenient to handle the device when mounting it on a device and has to be separately mounted on a printed wiring board or the like via a mounting angle or the like. In the case of a flat motor, it can be directly fixed to a printed wiring board or the like via a double-sided adhesive tape on the bottom surface or the upper surface. Some recent double-sided pressure-sensitive adhesive tapes reach 2 kg per 1 cm of adhesive strength, and are sufficiently practical.

According to the present invention, a cylindrical type is used on the device side,
Focusing on the fact that the occupied space is almost the same even with the square tube type, it can be mounted on a printed wiring board, etc. without the need for mounting angles, etc., the permeance coefficient is increased, and the square tube is aimed at high efficiency It is an object of the present invention to provide a compact DC motor having a shape.

[0005]

SUMMARY OF THE INVENTION The present invention provides a small DC motor having a quadrupole field magnet magnetized alternately with N and S, in which a case holding the field magnet is formed to have a substantially square cross section. It is formed and magnetized so that the center of the magnetic pole is at the corner of the square. This field magnet is preferably made of a plastic magnet and molded integrally with the case.

[0006]

In this way, since it is square, it can be fixed to a printed wiring board or the like by bonding with a double-sided adhesive tape. Since the corners of the square of the field magnet become thick, the substantial permeance coefficient becomes large. If the case magnet is formed integrally with the field magnet by using a plastic magnet, the number of processing steps such as bonding can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a feature of the present invention, which is applied to a rectangular tube type slotless vibration motor. Reference numeral 1 denotes a case having a square cylindrical shape and a square cross section, in which a field magnet 2 made of a rare earth plastic is integrally formed. The field magnet 2 is alternately magnetized into N and S equally into four poles such that the center of the magnetic pole is at the corner of the case. 3
Is an eccentric slotless iron core formed by laminating a silicon steel plate disposed inside the field magnet 2 with a gap therebetween. The armature coil 6 includes a shaft 4 at the center and a thin insulator 5a at the outer periphery. Are arranged to form the rotor R. 3a
Is a through hole that emphasizes the amount of eccentricity.

FIG. 2 shows, as an example of mounting the motor, a case in which the motor is fixed to a printed wiring board 6 with a double-sided adhesive tape 7 therebetween. The power is supplied by connecting to the patterns 6a and 6b.

FIG. 3 shows an application to the salient pole type rotor 10, in which a lower half of an iron core comprising six salient poles is cut out and three poles are eccentrically arranged on one side. In this case, since the angle of the field magnet 2 is large, it is possible to obtain a sine curve magnetization curve and increase the cogging torque while increasing the permeance coefficient.

Although the above is an embodiment applied to a vibration motor having an eccentric rotor, it goes without saying that it can also be applied to a normal rotary type.

[0011]

As described above, since the present invention has a rectangular tube shape having a substantially square cross section as described above, the device can be easily fixed to a printed wiring board with a double-sided adhesive tape. In addition, since the corner portions are thick, the permeance coefficient becomes large, high efficiency is obtained, and a sine curve magnetization curve is obtained, so that the cogging torque can be reduced even with a general cored motor.

[Brief description of the drawings]

FIG. 1 is a sectional view of a small DC motor of an eccentric slotless vibration type as one embodiment of the present invention.

FIG. 2 is a perspective view of an embodiment of the mounting structure of the motor.

FIG. 3 is a cross-sectional view of a main part of another embodiment.

FIG. 4 is a perspective view of a conventional small cylindrical DC motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Case 2 Field magnet 3 Eccentric slotless iron core 4 Axis 5 Armature

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02K 23/04 H02K 7/075

Claims (2)

(57) [Claims] 1. A square tube-shaped case having a substantially square cross section, and a case which is stored inside the case and has a cylindrical space inside, so that the center of the magnetic pole comes to a corner of the square tube-shaped case. A magnet whose poles are alternately magnetized N and S, a rotor stored in the cylindrical space of the magnet via a radial gap, and one side of the case so as to be placed horizontally on a printed wiring board and used. A small DC motor comprising a power supply terminal drawn out of the motor. 2. The magnet according to claim 1, wherein the magnet is made of a plastic magnet and is integrally formed with the case.
2. A small DC motor according to item 1.