1.  Field of the Invention
The present invention relates to an eccentric rotor used as a silent call device for a mobile communications apparatus, a compact vibrator motor having the rotor and a method of manufacturing the rotor, and more particularly, to an improvement of assembly and structure of an eccentric rotor which does not require an eccentric weight. 
2.  Description of the Related Art
Referring to FIG.  21, as a silent call device for a pager or a mobile phone, an eccentric weight W made of tungsten alloy is coupled to an output shaft S of a cylindrical DC motor M. When the motor M rotates, vibrations are generated due to the difference in centrifugal force of the eccentric weight W.
However, as the above addition of the eccentric weight W to the output shaft S requires a space for rotation of the eccentric weight W in an apparatus such as a pager, there is a limit in designing the apparatus.  Also, use of the expensive tungsten alloy increases the production costs. 
The present applicant have suggested a cylindrical coreless vibrator motor in Japanese Patent Application No.  Hei 2-309070 and the corresponding U.S. Pat.  No.  5,107,155, in which a built-in rotor itself is made eccentric excluding an output shaft.  The above motor having no output shaft and no eccentric weight is favorably noticed by the market as there is no limit in design, use thereof is easy and there is no danger during rotation.  However, as the motor requires three cylindrical coreless coils, the number of parts or processing steps increases, thus increasing the production costs. 
In order to make a rotor with a core itself vibrate instead of the cylindrical coreless coil type, the present applicant has suggested removing one of three salient pole type cores as shown in FIG.  4 of Japanese Patent Publication No.  Hei 6-81443.  The above two salient pole type cores where one pole in three phases is missing are preferable in the case of a motor such as a massager needing a relatively large amount of output.  However, for a portable apparatus such as a portable terminal using a low voltage, as the portable apparatus is small, movement of the center of mass is little and the amount of vibrations is insufficient. 
Also, as disclosed in U.S. Pat.  No.  5,341,057, the present applicant has suggested a compact vibrator motor having an eccentric armature iron core which is formed by arranging three salient poles made of magnetized material at one angular side with respect to a rotor to face a field magnet having four alternate north and south pole sections.  Also, the same technical concept has been disclosed in Japanese Laid-open Patent Application No.  9-261918.  However, as the three armature iron cores made of magnetized material are distributed at one angular side and cogging torque (a force of being absorbed by a field magnet) increases in the case of the motor, pores needs to be enlarged and the diameter of the motor itself cannot be reduced. 
The above motor having a built-in type eccentric rotor becomes a shaft-fixed type as it does not need an output shaft.  As the size of the above motor is reduced, the distance between armature coils decreases.  Thus, connection of the end portion thereof to the commutator without damage to the armature coil is very difficult.  Particularly, when a printed circuit board is used as a flat panel commutator as it is, where the end portion of the armature coil is directly welded thereon, welding of the end portion is not easy as the end portion is easily detached from a printed pattern due to elasticity of the end portion. 
To solve the above problems, it is the first objective of the present invention to provide a structure of a built-in type non-mold eccentric rotor to obtain vibrations with only an eccentric rotor in which each end portion of an armature coil can be easily connected to a commutator. 
It is the second objective of the present invention to provide the structure in which the armature coil can be easily fixed although arranged to be inclined. 
It is the third objective of the present invention to provide an eccentric rotor having a resin bearing portion, without using a sintered oil-storing bearing, which has advantages in that a mechanical noise can be reduced, the number of parts can be reduced as the commutator functions as a bearing, and the production costs can be saved. 
It is the fourth objective of the present invention to secure a sufficient maintenance intensity using a printed wiring commutator device in arranging a guide for determining the position of a resin holder having a bearing portion and an air-core coil when a non-molding type flat rotor is configured to solve the problems of the conventional mold type. 
It is the fifth objective of the present invention to provide an eccentric rotor in which the nature of sliding and the amount of eccentricity coexist. 
It is the sixth objective of the present invention to solve the problems of the conventional mold type or loss of properties, without sacrifice of the thickness, by forming a printed wiring coil at the eccentric printed wiring commutator device constituting a non-mold type flat rotor. 
It is the seventh objective of the present invention to provide a low-postured eccentric rotor, that is, a thin vibrator motor. 
It is the eighth objective of the present invention to provide a method of manufacturing a non-mold type flat rotor which can be subject to mass production due to the property of a printed wiring commutator device. 
Accordingly, to achieve the above objects, there is provided an eccentric rotor which includes a printed wiring commutator device where a hole for shaft installation is formed at the center thereof and a plurality of segment patterns are formed at the periphery of one surface thereof, a winding type armature coil integrally formed in a non-mold manner so as to be eccentric toward the other surface of the printed wiring commutator device, an end connection portion installed at such a position at the outer circumferential portion of the printed wiring commutator device that latching an end portion of the winding type armature coil is possible within a range of not deviating from the turning circumference during rotation and simultaneously electrical connection with the segment patterns is possible, and also at the position of not overlapping the winding type armature coil viewed from a plane, a resin bearing holder inserted in the shaft installation hole so that part thereof protrudes toward the segment pattern and simultaneously the other part thereof is extended toward the other surface of the printed wiring commutator device, and a resin eccentric weight exhibiting density of over 3 installed at the printed wiring commutator device. 
It is preferred in the present invention that the resin bearing holder exhibits a feature of sliding of a mobile friction coefficient equal to or less than 0.4 (1.5 kg/cm2) and is installed in a bearing hole located at the center to be capable of directly rotating to the shaft. 
It is preferred in the present invention that a compact vibrator motor includes a printed wiring commutator device where a hole for shaft installation is formed at the center thereof and a plurality of segment patterns are formed at the periphery of one surface thereof, a winding type armature coil configured in a non-mold manner by being wound around two magnetized salient poles, which become a winding type armature coil position determination guide, facing each other and by making an open angle of wiring of a blade receiving magnetic flux of a field magnet eccentric, at the other surface of the printed wiring commutator device, an eccentric rotor having an eccentricity accentuating non-magnetized salient pole simultaneously used as a resin holder and an eccentric weight made of sliding, high density resin exhibiting density of equal to or more than 3 and a mobile friction coefficient of equal to or less than 0.4 (1.5 kg/cm2), and arranged such that the thickness thereof is within a thickness in the axial direction of the winding type armature coil, by being inserted in the shaft installation hole, to maintain the magnetized salient poles, between two magnetized salient poles, a shaft supporting the eccentric rotor to be capable of rotating, and a housing accommodating the eccentric rotor and a magnet for applying magnetic force to the eccentric rotor. 
It is preferred in the present invention that the compact vibrator motor further comprises an eccentric rotor configured by winding a third armature coil around the non-magnetic salient pole. 
To achieve the above objects, there is provided an eccentric rotor including a printed wiring commutator device formed to be eccentrically as an expanded fan viewed from a plane, in which a hold for shaft installation is formed at the center thereof and a plurality of segment patterns are formed at the periphery of one surface thereof, a winding type air-core armature coil incorporated in an air-core armature coil position determination guide in a non-mold manner, which protrudes and is formed to be eccentric at the other surface of the printed wiring commutator device, an end connection portion installed at such a position at the outer circumferential portion of the printed wiring commutator device that latching an end portion of the winding type armature coil is possible within a range of not deviating from the turning circumference during rotation and simultaneously electrical connection with the segment patterns is possible, and also at the position of not overlapping the winding type armature coil viewed from a plane, a resin bearing holder inserted in the shaft installation hole so that part thereof protrudes toward the segment pattern and simultaneously the other part thereof is extended toward the other surface of the printed wiring commutator device, and a resin eccentric weight exhibiting density of over 3 installed at a fan-like arc-shaped portion of the printed wiring commutator device. 
It is preferred in the present invention that the air-core armature coil position determination guide and the eccentric weight are connected by a resin passing portion installed at the printed wiring commutator device for reinforcement. 
It is preferred in the present invention that the resin bearing holder, the air-core coil position determination guide and the arc-shaped eccentric weight are connected together by the same resin. 
It is preferred in the present invention that, in forming conductive bodies electrically connecting predetermined segment patterns of the printed wiring commutator device through through holes, the through holes are used as a resin passing portion when the resin bearing holder is formed integrally. 
To achieve the above objects, there is provided a compact vibrator motor including an eccentric rotor; a shaft supporting the eccentric rotor for rotating; and a housing accommodating the eccentric rotor, and a magnet for applying a magnetic force to the eccentric rotor. 
It is preferred in the present invention that an eccentric rotor includes an eccentric printed wiring commutator device formed as an expanded fan viewed from a plane, in which a hole for shaft installation is formed at the center thereof, a plurality of segment pieces are exposed toward the periphery of one surface thereof, at least one armature coil is formed in a printed wiring manner at at least one surface, a winding type armature coil installation guide is eccentrically incorporated, and an end connection portion for each coil is arranged in the turning outer circumference during rotation, a winding type air-core coil incorporated in the air-core position determination guide in a non-mold manner and the end portion is connected to the end connection portion, a resin bearing holder inserted in the shaft installation hole so that part thereof protrudes toward the segment pattern and simultaneously the other part thereof is extended toward the other surface of the printed wiring commutator device, and a resin eccentric weight exhibiting density of over 3 installed at a fan-like arc-shaped portion of the printed wiring commutator device. 
It is preferred in the present invention that a printed wiring commutator device is provided in which an armature coil formed by the printed wiring is formed at both surfaces, the device functioning as one coil through a through hole. 
It is preferred in the present invention that, in forming bodies electrically connecting predetermined segment patterns of the printed wiring commutator device through the through holes, the through holes are used as a resin passing portion when the resin bearing holder is formed integrally. 
It is preferred in the present invention that resin holder, air-core coil position determination resin guide and eccentric weight are integrally formed at the printed wiring commutator device using the same sliding resin exhibiting density of equal to or more than 3 and a mobile friction coefficient of equal to or less than 0.4 (1.5 kg/cm2). 
To achieve the above objects, there is provided a method of manufacturing an eccentric rotor which includes the steps of (a) forming a hold for shaft installation at the center thereof and at least a plurality of segment patterns at the periphery of one surface thereof, installing an end connection portion at the outer circumference thereof, and installing a plurality of printed wiring commutator devices where a resin passing portion is formed through a connection portion arranged at the outer circumference thereof, (b) integrally forming a resin bearing holder with resin exhibiting a sliding property and a mobile friction coefficient of equal to or less than 0.4 (1.5 kg/cm2) by setting the printed wiring commutator device to an injection mold, (c) integrally installing a winding type armature coil to be eccentric by separating from each connection portion or as it is, in a non-mold manner, and (d) configuring an eccentric rotor by connecting an end portion of the winding type armature coil to the end connection portion. 
It is preferred in the present invention that, when the resin bearing holder is integrally molded in the step (b), the air-core coil position determination guide and the eccentric weight are formed concurrently, that the method further includes a step of injection-molding at least an eccentric weight portion with resin exhibiting density over 3, after the step (b), and that, as a means for installing a winding type armature coil of the step (c) of claim 45, the air-core armature coil determination guide is heated and extended.