JPH0453182Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a synchronous motor, and more particularly to improvements in its rotor assembly unit.

A small synchronous motor used as a drive source for a timer, etc. generally has a case consisting of a container-shaped main body and a lid, and a plurality of synchronous motors integrally formed with the main body and the lid so as to be arranged circumferentially within the case. The rotor assembly unit is composed of two stator pieces, a coil located on the outer periphery of the stator pieces and disposed inside the case, and a rotor assembly unit bearing between the case body and the lid at a position inside the stator. There is. The rotor assembly is constructed by insert-molding magnets, whose circumferential surfaces are alternately magnetized with different polarities around the rotating shaft, into a bearing bush.

By the way, this type of synchronous motor is small,
There is a strong demand for thinning, but since both end faces of the magnet are held by the flange of the bearing bushing, it has been difficult to reduce the thickness of this flange. That is, if the thickness of the flange is too thin, the flange portion may curl up when cutting the gate after molding. Of course, if the gate is located on the end face of the flange part, the above-mentioned problem when cutting the gate will not occur, but since the end face of the flange part is in sliding contact with the bearing, problems such as poor rotation due to gate marks may occur. This is undesirable.

In view of these circumstances, the present invention provides a small and thin synchronous motor without almost changing the basic specifications of conventional synchronous motors.It provides a counterbore in the end face of the magnet and an outer part of the flange of the bearing bush. The diameter and thickness are approximately the same as the inner diameter and depth of this counterbore, and a protrusion with a slightly smaller diameter is formed on the end face of this flange, and the gate is located on a part of the circumferential surface of this protrusion. It is. The present invention will be explained in detail below with reference to embodiments shown in the drawings.

FIG. 1 is a partially cutaway front view of an example synchronous motor.
FIG. 2 shows an exploded perspective view. In these figures, reference numeral 1 denotes a case composed of a main body 2 formed generally in the shape of a container, and a lid 3 assembled to cover this opening. The main body 2 and the lid 3 are each provided with stator pieces 4 and 5 which are cut and raised in the shape of tongues and arranged alternately in the circumferential direction.
is provided. A coil 6 is arranged around the outer periphery of these stator pieces 4, 5, and a rotor assembly unit 10 is arranged inside. The rotor assembly unit 10 includes a rotating shaft 11 and a cylindrical magnet 12, which are rotatably supported by bearings 7 and 8 fitted with their axes aligned with the center positions of the main body 2 and the lid 3.
and a bearing bush 13.
The upper end of the rotating shaft 11 protrudes upward from the bearing 8 of the case lid 3, and an output gear 9 is fixed to this protruding end. The magnet 12 has different polarities alternately magnetized in the circumferential direction on its circumferential surface, and counterbores 14 and 15 are respectively provided in the upper and lower end surfaces in the axial direction. The bearing bush 13 into which the magnet 12 is insert-molded has a substantially pincushion shape as a whole, and flanges 16 and 17 that fit with the counterbores 14 and 15 of the magnet are integrally formed on the upper and lower end surfaces in the axial direction. There is. In other words, the bearing bush 13 is integrally formed with a pair of flanges 16 and 17 that clamp the magnet 12, and the outer diameter of the flanges 16 and 17 is the same as the inner diameter of the counterbores 14 and 15 provided in the magnet 12. and its thickness is approximately equal to the depth of the counterbore. The reason why the magnet 12 is attached to the rotating shaft 11 via the bearing bush 13 is that it is difficult to press-fit and fix the magnet 12 made of sintered ferrite or the like directly onto the rotating shaft 11. A protrusion 18 having a diameter slightly smaller than the outer diameter of the flange 16 is integrally provided on the end face of the bearing bush 13 . A gate portion 19 is provided on a part of the circumferential surface of this protrusion 18 . Therefore, the thickness of the protrusion 18 is set to a size necessary for providing the gate 19.

According to the synchronous motor of the embodiment configured as above, the height dimension of the rotor assembly unit 10 is
The thickness is approximately equal to the thickness of the magnet 12. However, the thickness of the flanges 16 and 17 of the bearing bush 13 that clamps the magnet 12 is equal to the depth of the counterbores 14 and 15, ensuring sufficient rigidity. Therefore, even when the molded body is separated from the runner of the mold after the insert molding process, there is no problem such as warping of the flanges 16 and 17. Also, flange 1
6 and 17, the magnet 12 is held securely. Furthermore, since the protrusion 18 is formed on the end face of the flange 16 and the gate part 19 is provided on a part of the peripheral surface of this protrusion, the rotor assembly unit 10
There are no gate marks on the sliding contact surface between the bearing 8 and the bearing 8, and no subsequent processing is required.

As described in detail above, according to the present invention, the overall dimensions of the rotor assembly unit can be made approximately equal to the thickness dimension of the magnet, and a small and thin synchronous motor can be obtained. In addition, the post-processing process for cutting the gate portion of the bearing bushing in which the magnet is insert-molded can be streamlined, which has the effect of reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view of a synchronous motor according to the present invention, and FIG. 2 is an exploded perspective view of the same. 1...Case, 2...Main body, 3...Lid, 4,
5... Stator piece, 6... Coil, 7, 8... Bearing, 9... Output gear, 10... Rotor assembly unit, 11... Rotating shaft, 12... Magnet, 13
...Bearing bush, 14,15...Spot face, 1
6, 17...flange, 18...protrusion, 19...
Gate section.

Claims (1)

[Scope of utility model registration request] A plurality of stator pieces are integrally formed with the case so as to be arranged circumferentially within the case, a coil is arranged on the outer periphery of the stator pieces, and a coil is arranged on the inner side of the stator piece. A synchronous motor is constructed of a rotor assembly unit formed by insert-molding a cylindrical magnet into a bearing bush around a rotary shaft that is rotatably supported by a pair of bearings provided in a case. A counterbore is provided on both end faces of the bearing bushing, and flanges having an outer diameter and thickness approximately equal to the inner diameter and depth of the counterbore are integrally provided at both ends of the bearing bush, and the bearing bush is provided with a counterbore on the end face of one flange. A synchronous motor characterized by having a rather small protrusion that comes into sliding contact with the protrusion, and a gate provided on a part of the circumferential surface of the protrusion.