JPH0759322A - Small sized dc motor - Google Patents

Abstract

PURPOSE:To provide a small sized DC motor that can be mounted on a printed circuit board without an angle member and the like, along with good efficiency by enlarging a coefficient of permeance. CONSTITUTION:A small DC motor has a four-pole field magnet magnetized with N- and S-poles alternately. A case 1 for holding a field magnet 2 has a square shape in cross section, and the center of the magnetic pole is formed at each corner. The field magnet 2 is made of plastic magnet and molded integrally with the case 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compact DC motor having a box shape, which is used for a wireless calling device (pager) as a silent alarm source.

[0002]

2. Description of the Related Art Cylindrical coreless motors as shown in FIG. 4 are known as cylindrical compact DC motors used as silent notification sources such as pagers and alarms. In order to use the motor as a vibration source, the output shaft S of the motor
A high density eccentric weight W made of a tungsten alloy is arranged on the shaft to generate a vibration by centrifugal force during rotation.

[0003]

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

The present invention has a cylindrical type on the equipment side,
Even though it is a square tube type, we have focused on the fact that the occupied layout space is almost the same and can be mounted on a printed wiring board etc. without the need for a mounting angle, etc. It is intended to provide a compact DC motor having a mold shape.

[0005]

According to the present invention, in a small direct current motor having a quadrupole field magnet magnetized in N and S alternately, a case holding the field magnet has a substantially square cross section. The magnetic field is formed and magnetized so that the center of the magnetic pole comes to the corner of a square. This field magnet is preferably made of a plastic magnet and molded integrally with the case.

[0006]

By doing so, since it is a square type, it can be fixed to a printed wiring board or the like by adhesion with a double-sided adhesive tape. Since the square corners of the field magnet are thick, the substantial permeance coefficient is large. If the field magnet is made of a plastic magnet and integrally molded with the case, the number of processing steps such as bonding can be reduced.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is applied to a square tube type slotless vibration motor, and is shown in a sectional view showing the features of the present invention. Reference numeral 1 is a case having a square tube shape and a square cross section, and a field magnet 2 made of a rare earth plastic is integrally formed therein. The field magnet 2 is magnetized into four equal poles alternately in N and S so that the center of the magnetic pole is at the corner of the case. Three
Is an eccentric slotless iron core formed by laminating silicon steel plates arranged inside this field magnet 2 with a gap therebetween, and has six armature coils 5 with a shaft 4 in the center and a thin insulator 5a on the outer periphery. To form a rotor R. 3a
Is a through hole that emphasizes the amount of eccentricity.

FIG. 2 shows a case where the motor is mounted on a printed wiring board 6 by means of a double-sided adhesive tape 7, and terminals 9 and 9 projecting from the bracket side 8 are provided on the printed wiring board 6 in a predetermined manner. Power is supplied by connecting to the patterns 6a and 6b.

The structure shown in FIG. 3 is applied to a salient pole rotor 10, in which the lower half of the iron core consisting of 6 salient poles is cut out and 3 poles are eccentrically arranged on one side. In this case, since the angle of the field magnet 2 is thick, the sine curve magnetization curve is obtained and the cogging torque is reduced while the permeance coefficient is increased.

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

[0011]

As described above, according to the present invention, since the square tube having a substantially square cross section is used as described above, the device can be easily fixed to the printed wiring board with the double-sided adhesive tape. Moreover, since the corners are thick, the permeance coefficient becomes large, and high efficiency can be obtained, and as if a sine curve magnetization curve is obtained, the cogging torque can be reduced.

[Brief description of 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 example of a mounting structure of the motor.

FIG. 3 is a lateral cross-sectional view of a main part of the other embodiment.

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

[Explanation of symbols]

 1 case 2 field magnet 3 eccentric slotless iron core 4 axis 5 armature

Claims (2)

[Claims] 1. A small direct current motor comprising a four-pole field magnet magnetized by alternating N and S magnets, wherein a case for holding the field magnet is formed to have a substantially square cross section, and the center of the magnetic pole is A small DC motor magnetized so that it is almost at the corner. 2. The small DC motor according to claim 1, wherein the field magnet is made of a plastic magnet and is integrally molded with the case.