Spindle motor

A spindle motor adapted to be loaded with a disk provided with an attracted plate and to rotate the disk is provided which comprises a turn table having a flange portion on a front surface of which the disk is to be mounted and on a back surface of which a rotor yoke is supported, and a cylindrical portion a distal end of which is to be opposed to the attracted plate, the turn table being supported on a housing of a stator through a rotational shaft; an attraction magnet fixed to the distal end of the cylindrical portion of the turn table, and an aligning member an inner periphery of which is engaged with an outer periphery of the cylindrical portion and an outer periphery of which is to be brought into contact with an inner periphery of a center hole of the disk to align the disk; and an urging member interposed between the aligning member and the flange portion of the turn table to urge the aligning member by restoration force, wherein the urging member is comprised of an annular spring material with a plurality of peaks in wave shape.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spindle motor, for example, loaded with an optical disk such as a mini disk (MD) or the like and operating to drive it.

2. Related Background Art

FIG. 4is a longitudinal sectional view showing an example of a conventional spindle motor loaded with a disk of relatively large diameter (Φ120) such as a CD, a DVD, or the like, and this spindle motor20is composed of a stator section21as a fixed section, and a rotor section22supported as rotatable relative to the stator section21and loaded with the optical disk.

Among these, the stator section21is composed of a stator board23as a fixture member of this spindle motor20, a cylindrical housing24a lower end of which is fixed in an insert hole in the central region of the stator board23, a laminated iron core25fitted on the outer periphery of the housing24, a plurality of coils26wound on the laminated iron core25, a sliding bearing27pressed into the housing24, a thrust receiver24ainserted and fixed in the lower end of the housing24, and so on.

On the other hand, the rotor section22is generally composed of a rotational shaft28which is inserted in the sliding bearing27and the lower end of which is supported by the thrust receiver24a,a turn table29of approximate disk shape having a longitudinal section of approximately anastatic () shape in which the upper half of the rotational shaft28is pressed in the center of a cylindrical portion29a,a rotor yoke30of an approximately anastatic section engaged with a projection formed in the lower center of the turn table29, the projection being caulked at its outer periphery, an aligning member32and an attraction magnet35set on the cylindrical portion29aof the turn table29, and so on.

Among these components, the rotor yoke30is provided with a cylindrical rotor magnet (permanent magnet)31the periphery of which is fixed to the inner periphery of the cylindrical portion of the rotor yoke30with an adhesive, and this rotor magnet31is opposed with a predetermined gap to the outer periphery of the aforementioned laminated iron core25.

A compression coil spring33of a material of a rectangular section is set in a groove formed in a lower surface of the aligning member32, and the lower end of this compression coil spring33is supported by a bottom surface of a groove formed around the lower end of the cylindrical portion29aof the turn table29, whereby this compression coil spring33is maintained in a compressed state inFIG. 4.

Further, a stopper34of annular shape on a plan view is pressed and secured onto a stepped portion formed in an outer peripheral portion at the upper end of the cylindrical portion29aof the turn table29, and the annular attraction magnet35is set in an annular groove formed at the upper end of the cylindrical portion29aand is secured with an adhesive.

When the optical disk36, indicated by chain lines, is mounted on the upper surface of the cylindrical portion29aof the turn table29, an inner lower edge of a center hole36aof the disk is guided in contact with a slant face32aformed on the outer periphery of the aligning member32, whereby the optical disk36is aligned with the turn table29and the rotational shaft28through the aligning member32.

The attraction magnet35attracts an attracted plate38supported at its outer periphery by a holder37mounted on the upper surface of the optical disk36, whereby the optical disk36is maintained in a mounted state while being urged against the turn table29.

In the spindle motor of this structure, the rotor section22is rotated by interaction of magnetic fields generated by energization of the coils26and magnetic fields established by the rotor magnet31and the rotor yoke30.

In conjunction therewith, the optical disk36is rotated together with the turn table29in synchronism with the rotor section22, while being maintained in the urged state against the turn table29by the stopper37.

In recent optical disk apparatuses equipped with this spindle motor, however, there are demands for further decrease in size and thickness, as is the case with a portable MD or the like, and demands for higher accuracy of positioning of the optical disk in correspondence with increase in density of the optical disk.

SUMMARY OF THE INVENTION

The present invention provides a spindle motor capable of meeting the demands for the higher accuracy of positioning of the optical disk while achieving the decrease in size and thickness.

An example of the spindle motor according to the present invention is as follows.

A spindle motor is adapted to be loaded with a disk provided with an attracted plate and to rotate the disk, and comprises:

a turn table having a flange portion on a front surface of which the disk is to be mounted and on a back surface of which a rotor yoke is supported, and a cylindrical portion a distal end of which is to be opposed to the attracted plate, the turn table being supported on a housing of a stator through a rotational shaft;

an attraction magnet fixed to the distal end of the cylindrical portion of the turn table, and an aligning member an inner periphery of which is engaged with an outer periphery of the cylindrical portion and an outer periphery of which is to be brought into contact with an inner periphery of a center hole of the disk to align the disk; and

an urging member interposed between the aligning member and the flange portion of the turn table to urge the aligning member by a restoration force;

wherein the urging member is comprised of an annular spring member with a plurality of peaks in a wave shape.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the spindle motor according to the present invention will be described below with reference to the drawings.FIG. 1is a longitudinal sectional view showing a first embodiment of the present invention, and the spindle motor of the present embodiment is different from that described in Related Background Art withFIG. 4, in that the outside diameter of the motor is as small as approximately half, and is particularly different in the shape and function of the turn table10and the aligning member13.

First, this spindle motor1is constructed in structure in which the laminated-iron-core-fitting portion of the housing5, the lower end of which is inserted and fixed in the stator board4of the stator section2, is smaller in diameter and longer in length. As a result, the inside and outside diameters of the laminated iron core6are also smaller, and the upper portion of the housing5extends up into the turn table10. Reference symbol5adesignates a thrust receiver as in the conventional motor, numeral7coils, and numeral8a sliding bearing, this sliding bearing8having a larger ratio of fitting length to shaft diameter than the conventional sliding bearing.

The upper part of the rotational shaft9fitted in this sliding bearing8is pressed into the turn table10, the turn table10has a large cylindrical portion10bbelow a small cylindrical portion10aformed at the upper end, a clearance groove10cof wedge shape formed around the outer periphery of the lower part of the large cylindrical portion10b,a flat portion10dformed on the outer peripheral side of the clearance groove10c,and a clearance groove10eformed continuously outside the flat portion10d.

Among these, the inner peripheral surface of the large cylindrical portion10bserves as a guide portion while the upper portion of the housing5is inserted into the large cylindrical portion10b.A groove portion10fof trapezoid shape is formed on the lower surface side of the flat portion10dand opposite to the upper portions of the coils7, and a groove portion10gis formed further on the outer periphery side of the groove portion10f.An upper end of annular rotor yoke11is inserted and fixed in the groove portion10g,and the rotor magnet12is fixed to the inner periphery of the rotor yoke11in a state in which the upper end thereof is in close fit with the lower surface of the turn table10.

As a result, the rotor portion3is attracted downward by the magnetism of the rotor magnet12, so that the lower end of the rotational shaft9is always in contact with the thrust receiver5a.

The aligning member13is set as vertically movable on the outer periphery of the large cylindrical portion10bof the turn table10, and the aligning member13has an annular claw portion13avertically formed in the lower part on the inner periphery side. This claw portion13ais opposed to the clearance groove10cformed in the turn table10, and a groove portion13bof trapezoid shape and a projecting portion13care formed continuously outside a flat portion on the outer periphery side of the claw portion13a.The projecting portion13cis opposed to the clearance groove10eof the turn table10.

In this structure, the urging member14, which will be detailed hereinafter withFIGS. 2A–2C, is interposed between the groove portion13band the flat portion10dof the turn table10, and the position of the urging member14is regulated by the inner peripheral side of the groove portion13b.In the outer peripheral region of the aligning member13, a slant face portion13eforming the projecting portion13cat the lower end is provided as continuous from an arcuate curved portion, and this slant face portion13eserves as a guide face while the optical disk16is mounted as described later.

A stepped portion13dis formed at the upper end and on the inner periphery side of the aligning member13, and a wide, thin attraction magnet15of annular shape on a plan view (not shown) is fitted between the stepped portion13dand the outer periphery of the small cylindrical portion10aof the turn table10. The inner periphery of the attraction magnet15is bonded to the small cylindrical portion10awith an adhesive. As a result, the aligning member13is urged against the lower surface of the attraction magnet15via the stepped portion13dby resilient restoration force of the urging member14, and the attraction magnet15also functions as a stopper for the aligning member13.

FIG. 2Ais a plan view showing the aforementioned urging member14, andFIG. 2Ba right side view ofFIG. 2A. This urging member14is made of a phosphor bronze sheet for thin spring by punching and press working and in annular and wave shape with three peaks (valleys)14aat equal intervals. These peaks (valleys)14aeach are in contact with the flat portion10dof the turn table10and the groove portion13bof the aligning member13. The reason why the nonmagnetic phosphor bronze sheet is employed herein as a material of the urging member14is that it does not affect the magnetic fields generated by the coils7and the rotor magnet12. Therefore, the urging member14may be made of any material for spring, such as inexpensive stainless steel SUS304 or the like, as long as it causes little influence on the magnetic fields.FIG. 2Cwill be described later in the second embodiment.

The following will describe the action in mounting and holding an optical disk on the spindle motor1of the structure as described above, including the longitudinal sectional view ofFIG. 3.

While the inner periphery of the center hole16ais guided by the slant face portion13eformed in the outer periphery of the aligning member13, the lower end face of the optical disk16comes to be coaxially mounted on the turn table10, and the attracted plate16bof the optical disk16is attracted by the attraction magnet15, whereby the optical disk is maintained in the mounted state.

During the mounting process in conjunction with the attracting action, the aligning member13is moved down together with the optical disk16thereby, and the claw portion13ais guided by the large cylindrical portion10bof the turn table10to be fitted into the groove10cof the turn table10, whereupon the urging member14is compressed.

This urging member14can be formed in a profile lower than that of the conventional urging member and it is possible to select an arbitrary spring constant, flexure amount, urging force, etc., by changing the dimensions of thickness and inside and outside diameters at arbitrary positions of the turn table10and the aligning member13. In addition, since the aligning member13is urged at the three points of the peaks (valleys)14aof wide span, the urging force can be uniformly exerted on the aligning member13during the mounting operation of the optical disk16, so as to ensure smooth motion while suppressing fluctuation during the down motion.

Namely, since the degree of freedom is large in designing of the urging member14and the attraction surface of the attraction magnet15is wide enough to increase the attracting force, it is feasible to facilitate setting of the mutual delicate force relation selected under the condition of the attracting force between the attraction magnet15and the attracted plate16a>the repulsive force of the urging member14in the mounting process and in the holding state of the optical disk16, to enhance the alignment performance for the optical disk16moved down while being guided by the slant face portion13eof the aligning member13, and to increase the holding force after the mounting operation.

In addition, since the degree of freedom is increased in the designing of the urging member14and the flexure amount is decreased, it is feasible to decrease the vertical stroke of the aligning member13and to decrease the thickness of the spindle motor1in correlation with the turn table10and the rotor yoke11and the shape of the attraction magnet15.

Further, since the engaging portions of the sliding bearing8and the rotational shaft9with the housing5are long and the housing5extends into the large cylindrical portion10bof the turn table10, the engagement length of the sliding bearing8and the rotational shaft9is set large relative to the shaft diameter and the fluctuation of the rotational shaft8and the turn table10is decreased thereby. As a result, the fluctuation of the aligning member13is also suppressed, whereby the alignment accuracy of the optical disk16is improved.

Further, the radial position of the urging member14can be readily regulated by the groove portion13bof the aligning member13. This regulating portion is provided in the aligning member13in the embodiment of the present invention, but it may also be provided in the turn table10. Since the regulation is effected by regulating either the inside or the outside of the urging member14, the degree of freedom is large in designing.

Further, since the stopper24shown inFIG. 4in the conventional motor does not have to be used herein, the assembly time can also be decreased.

FIG. 2Ccited previously shows the second embodiment of the spindle motor according to the present invention, in which the urging member17replaces the urging member14shown inFIGS. 2A and 2Band is constructed in structure in which projections17aof an arcuate section and spherical outer periphery are formed at the tops of the respective peaks (valleys)14a.

In this case, the vertices of the small projections17aare brought into contact with the flat portion10dof the turn table10and the groove portion13bof the aligning member13, which can suppress the fluctuation of the aligning member13relative to the turn table10and ensure smoother vertical motion of the aligning member, as compared with the line or surface contact case by means of the urging member14.

As described above, the present invention offered the configuration wherein the urging member was constructed of the single annular spring material with the three peaks of wave shape at equal intervals, and thus has permitted the provision of the spindle motor capable of meeting the demands for higher accuracy of positioning of the optical disk while achieving the decrease in size and thickness, as compared with the conventional motors, in correlation with the housing, the turn table, the rotor yoke, the aligning member, and so on.