Rotational driving apparatus for disks having a magnet disposed on a motor mounting base surface to absorb radial deflections

A rotational driving apparatus for disks includes a motor mounting base, a motor attached to the motor mounting base, a turn table made of a non-magnetic material and attached to a rotational shaft of the motor, for supporting a disk thereon, a turn table magnet disposed on the turn table, for absorbing the disk placed on the turn table, and a magnetic plate member disposed on the motor mounting base and under the turn table, thereby generating a transverse force exerted on the rotational motor shaft due to a magnetic force of the turn table magnet which acts on the magnetic plate member so as to tilt the rotational motor shaft.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a rotational driving apparatus used for 
disks, for recording and/or replaying an information signal using an 
optical disk, a magneto-optic disk, or the like. More particularly, it 
relates to a rotational driving apparatus for disks which can absorb 
radial deflections of a rotational driving motor used for disks. 
2. Description of the Prior Art 
Referring now to FIG. 9, it illustrates a perspective view showing a prior 
art rotational driving apparatus for disks. Furthermore, FIG. 10 shows a 
plan view of FIG. 9, and FIG. 11 shows a cross-sectional view taken along 
the line D--D of FIG. 10. In the figures, reference numeral 1 denotes a 
motor mounting base shaped like a base plate, 2 denotes a motor used for 
rotationally driving a disk, which is mounted and secured to the motor 
mounting base 1, and 3 denotes a rotational motor shaft, which extends 
vertically through and above the motor mounting base 1. 
Furthermore, reference numeral 4 denotes a turn table on which a disk is 
placed, which is secured to an upper end of the rotational motor shaft 3, 
and 5 denotes a turn table magnet shaped like a planar disk, which is 
mounted on the turn table 4. Opposite surfaces of the turn table magnet 5 
in the direction of the rotational motor shaft 2 are magnetized, so that a 
disk placed on the turn table 4 can stick firmly onto the turn table 4. 
Reference numeral 9 denotes a helical spring for preventing radial 
deflections of the rotational motor shaft 3, and 10 denotes a fixing pin 
mounted on the motor mounting base 1. The helical portion of the spring 9 
is engaged with the pin. Furthermore, reference numeral 11 denotes a 
stopper mounted on the motor mounting base 1 for securing an end of the 
spring 9 to the motor mounting base 1. The other end of the spring 9 
presses the rotational motor shaft 3 transversely. 
Reference numeral 21' denotes an urging force of the spring 9 transversely 
pressing the rotational shaft 3 of the motor. The urging force 21' tilts 
the rotational shaft 3 of the motor in the direction indicated by the 
arrow b in FIG. 11 at all times. Reference numeral 22 and 23 denotes 
radial deflections produced in the rotational shaft 3 of the motor when 
the urging force 21' does not act on the rotational shaft 3 rotating. 
Next, a description will be made as to the operation of the prior art 
rotational driving apparatus. Since the urging force 21' of the spring 9 
tilts the rotational shaft 3 of the motor at all times, the radial 
deflections designated by the reference numerals 22 and 23, which are 
produced when the rotational shaft 3 of the motor rotates, can be 
prevented. Thus, the deflections of a disk which is placed on the turn 
table 4 and rotates together with the turn table 4 can be suppressed to a 
minimum. 
Although such a prior art rotational driving apparatus having the structure 
mentioned above effects the purpose of suppressing the deflections of a 
disk, which is placed on the turn table 4 and rotates together with the 
turn table 4, to a minimum, it suffers from disadvantages that the spring 
9 which abuts on the rotational shaft 3 of the motor wears out, and the 
friction between the spring 9 and the rotational motor shaft 3 causes an 
increase in the driving force of the motor 2. 
JP-A 1/253864 is one of references which disclose such a prior art 
technique. A disk supporting apparatus of a disk player disclosed in the 
reference is adapted to prevent surface vibrations in a direction of 
surface deflection of a disk on a turn table by forming a projecting 
portion shaped like an annular ring on a peripheral part of a damper for 
holding the disk between itself and the turn table, and mounting an 
annular magnet within the annular-shaped projecting portion, but the 
apparatus cannot prevent the radial deflections of the rotational motor 
shaft. 
SUMMARY OF THE INVENTION 
The present invention is made to overcome the aforementioned problem. More 
precisely, it is an object of the present invention to provide a 
rotational driving apparatus for disks with a high degree of reliability, 
which can prevent radial deflections of a rotational motor shaft 
efficiently by using a magnetic force of a turn table magnet without the 
use of a spring for tilting the rotational motor shaft, thereby 
suppressing deflections of a disk placed on a turn table to a minimum 
without having to increase a motor driving force. 
It is another object of the present invention to provide a rotational 
driving apparatus for disks with a high degree of reliability, which can 
prevent radial deflections of a rotational motor shaft more efficiently, 
thereby suppressing deflections of a disk placed on a turn table to a 
minimum more effectively. 
In accordance with the present invention, there is provided a rotational 
driving apparatus for disks, including a motor mounting base; a motor 
attached to the motor mounting base; a turn table made of a non-magnetic 
material and attached to a rotational shaft of the motor, for placing a 
disk thereon; a turn table magnet disposed on the turn table, for 
adsorbing a disk placed on the turn table; and a magnetic plate member 
disposed on the motor mounting base and under the turn table, for 
generating a magnetic force in cooperation with the turn table magnet so 
as to exert a transverse force on the turn table, the transverse force 
finally acting on the rotational motor shaft, thereby tilting the 
rotational motor shaft at a certain angle. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member is constructed of a magnetic material which is not 
integral with the motor mounting base, and the magnetic plate member is 
mounted on and secured to the motor mounting base. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member is formed integrally as a part of the motor mounting 
base and is located under the turn table. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member forms a planar projecting portion which protrudes 
from an upper surface of the motor mounting base so as to get closer to a 
lower surface of the turn table. 
In accordance with a preferred embodiment of the present invention, there 
is provided a rotational driving apparatus for disks, including a motor 
mounting base; a motor attached to the motor mounting base; a turn table 
made of a non-magnetic material and attached to a rotational shaft of the 
motor, for placing a disk thereon; a turn table magnet disposed on the 
turn table, for adsorbing the disk placed on the turn table; and a magnet 
disposed on the motor mounting base and under the turn table, for 
preventing deflections of the rotational motor shaft, and for generating 
an adsorption or repulsion force in cooperation with the turn table magnet 
so as to exert a transverse force on the turn table, the transverse force 
finally acting on the rotational motor shaft, thereby tilting the 
rotational motor shaft at a certain angle. 
In accordance with a preferred embodiment of the present invention, the 
magnet for preventing deflections of the rotational motor shaft is a 
magnet shaped like a planar projecting portion which protrudes from an 
upper surface of the motor mounting base so as to get closer to a lower 
surface of the turn table. 
Further objects and advantages of the present invention will be apparent 
from the following description of the preferred embodiments of the 
invention as illustrated in the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A description will be made as to an embodiment of the present invention. 
FIG. 1 shows a perspective view of a rotational driving apparatus for disks 
according to the first embodiment of the present invention, FIG. 2 shows a 
plan view of FIG. 1, and FIG. 3 shows a cross-sectional view taken along 
the line III--III of FIG. 2. In the figures, reference numeral 1 denotes a 
motor mounting base made of a magnetic material or a non-magnetic 
material, 2 denotes a motor used for rotationally driving a disk, which is 
mounted and secured to the motor mounting base 1, and 3 denotes a 
rotational motor shaft, which extends vertically through and above the 
motor mounting base 1. 
Furthermore, reference numeral 4 denotes a turn table made of a 
non-magnetic material for placing a disk thereon, which is secured to an 
upper end of the rotational motor shaft 3, and 5 denotes a turn table 
magnet shaped like a planar and annular ring, which is mounted on the turn 
table 4. The turn table magnet 5 is adapted to stick a disk placed on the 
turn table 4 onto the turn table 4. 
Reference numeral 6 denotes a magnetic planar plate which is disposed on 
the motor mounting base 1. The magnetic planar plate 6 is constructed of a 
magnetic plate which is not integral with the motor mounting base 1 and is 
mounted on the motor mounting base 1, thereby forming a planar projection 
on the motor mounting base 1, which is located under the turn table 4. 
In the rotational driving apparatus for disks so constructed, an adsorption 
force designated by the arrow 25 shown in FIG. 3 acts on the magnetic 
plate member 6, and this results in causing a transverse force 21 exerted 
on the rotational motor shaft 3 in the turn table 4, thereby tilting the 
rotational motor shaft 3 at all times. 
Next, a description will be made as to the operation of the rotational 
driving apparatus of the first embodiment. The adsorption force 25 between 
the turn table magnet 5 and the magnetic plate member 6 causes the 
transverse force 21 exerted on the turn table 4. Thus, the force 
transversely acts on the rotational motor shaft 3. This results in tilting 
the rotational motor shaft 3. Also, while the rotational motor shaft 3 is 
rotating, the transverse force 21 caused by the adsorption force 25 of the 
turn table magnet 5 acts on the rotational motor shaft 3 so as to tilt it 
at a certain angle and keep it in balance. As a result, radial deflections 
of the rotational motor shaft 3 can be prevented. 
Accordingly, deflections of a disk placed on the turn table 4 can be 
reduced to a minimum and the reliability of rotational driving for disks 
can be increased. Furthermore, since the magnetic plate member 6 which 
forms the planar projection on the motor mounting base, as previously 
mentioned, protrudes from the upper surface of the motor mounting base 1 
so as to get closer to the lower surface of the turn table 4, the 
adsorption force 25 exerted on the magnetic plate member 6 by the magnetic 
force of the turn table magnet 5 can be generated more effectively. 
Referring now to FIG. 4, it illustrates a plan view of a rotational driving 
apparatus for disks according to a second embodiment of the present 
invention. Furthermore, FIG. 5 shows a cross-sectional view taken along 
the line V--V of FIG. 4. 
In accordance with the first embodiment mentioned above, the magnetic plate 
member 6 which is not integral with the motor mounting base 1 is mounted 
on and secured to the motor mounting base 1 and is located under the turn 
table 4. On the contrary, the magnetic plate member 6 according to the 
second embodiment is formed integrally on the motor mounting base 1, as 
shown in FIG. 5. That is, the magnetic plate member 6 is a projecting 
portion of the motor mounting base, which protrudes from the upper surface 
of the motor mounting base 1 so as to get closer to the lower surface of 
the turn table 4. Thus, the second embodiment provides the advantages that 
it is not necessary to use another magnetic member which is not integral 
with the motor mounting base 1 and the mounting process of the magnetic 
plate member can be omitted, as well as the same advantage as that offered 
by the first embodiment. 
In the first and second embodiments, the magnetic plate member 6 is formed 
as a planar projection. Alternatively, the magnetic plate member 6 of a 
rotational driving apparatus according to a third embodiment of the 
present invention can be constructed of a magnetic material such as a 
corrugated magnetic material, for only causing an adsorption force 25 as 
shown in FIG. 3 due to the magnetic force of the turn table magnet 5, 
which results in generating a transverse force 21 exerted on the 
rotational motor shaft 3. In this case, the same advantages as those 
offered by the first and second embodiments can be provided. 
FIG. 6 shows a perspective view of a rotational driving apparatus for disks 
according to a fourth embodiment of the present invention, FIG. 7 shows a 
plan view of FIG. 6, and FIG. 8 shows a cross-sectional view taken along 
the line VIII--VIII of FIG. 7. 
In accordance with the aforementioned first and second embodiments, the 
magnetic plate member 6 is disposed on the motor mounting base 1. On the 
contrary, according to the fourth embodiment, a magnet 7 for preventing 
deflections of the motor shaft is disposed on the motor mounting base 1, 
instead of the magnetic plate member 6. The magnet 7 for preventing 
deflections of the motor shaft forms a planar projecting member which 
protrudes from the upper surface of the motor mounting base 1 so as to get 
closer to the lower surface of the turn table 4. 
Next, a description will be made as to the operation of the rotational 
driving apparatus of the fourth embodiment. An adsorption force 25 or a 
repulsion force is generated between the turn table magnet 5 and the 
magnet 7 for preventing deflections of the motor shaft, and this results 
in causing a transverse force 21 which acts on the turn table 4 and hence 
the rotational shaft 3. Thus, the transverse force 21 tilts the rotational 
motor shaft 3 towards the direction designated by the arrow a in FIG. 8. 
Even when the rotational motor shaft 3 so tilted rotates, the adsorption 
force 25 or repulsion force by the turn table magnet 5 also acts on the 
magnet 7 for preventing deflections of the motor shaft to generate the 
transverse force 21 which holds the rotational motor shaft 3 tilted at a 
certain angle and keeps it in balance. As a result, radial deflections of 
the rotational motor shaft 3 can be prevented. Thus, deflections of a disk 
perpendicular to the direction of the rotational motor shaft 3 can be 
reduced to a minimum more effectively than in the aforementioned first and 
second embodiments. 
Next, a description will be made as to a fifth embodiment of the present 
invention. In accordance with the fourth embodiment mentioned above, the 
magnet 7 for preventing deflections of the motor shaft which is not 
integral with the motor mounting base 1 is mounted on and secured to the 
motor mounting base 1. On the contrary, the magnet 7 for preventing 
deflections of the motor shaft according to the fifth embodiment is formed 
integrally on the motor mounting base 1 instead of the magnetic plate 
member, as shown in FIG. 5. The magnet 7 can be formed by magnetizing a 
projecting portion of the motor mounting base 1, which protrudes from the 
upper surface of the motor mounting base 1 so as to get closer to the 
lower surface of the turn table 4. Thus, the fifth embodiment provides the 
same advantages as those offered by the fourth embodiment. 
In the fourth and fifth embodiments, the magnet 7 for preventing 
deflections of the motor shaft is formed on the motor mounting base 1 as a 
planar projection. Alternatively, the magnet 7 for preventing deflections 
of the motor shaft of the present invention can be constructed of a 
magnetic in any shape if it can generate an adsorption force 25 or a 
repulsion force due to the magnetic force of the turn table magnet 5, 
which results in generating a transverse force 21 which acts on the turn 
table 4 and hence the rotational motor shaft 3. In this case, the same 
advantages as those offered by the fourth and fifth embodiments can be 
provided. 
As previously mentioned, the present invention offers the following 
advantages. 
In accordance with a preferred embodiment of the present invention, a 
magnetic plate member disposed on a motor mounting base and under a turn 
table is provided and adapted to generate a transverse force exerted on a 
rotational motor shaft by virtue of a magnetic force of a turn table 
magnet which acts on the magnetic plate member, thereby tilting the 
rotational motor shaft. Therefore, since the rotational driving apparatus 
does not need a spring used for tilting the rotational motor shaft, it can 
prevent wear in the spring, and an increase in the driving force of the 
motor caused by a friction between the spring and the rotational motor 
shaft while preventing radial deflections of the rotational motor shaft by 
using the magnetic force of the turn table magnet, thereby reducing 
deflections of a disk placed on the turn table to a minimum and hence 
improving the reliability. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member constructed of a magnetic material which is not 
integral with the motor mounting base is mounted on and secured to the 
motor mounting base. Therefore, radial deflections of the rotational motor 
shaft can be prevented by only attaching the magnetic plate member onto 
the motor mounting base. Accordingly, deflections of a disk placed on the 
turn table can be reduced to a minimum, and hence the reliability of the 
apparatus can be improved. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member is formed integrally with the motor mounting base. 
Therefore, radial deflections of the rotational motor shaft can be 
prevented without having to use another magnetic material which is not 
integral with the motor mounting base. Accordingly, deflections of a disk 
placed on the turn table can be reduced to a minimum, and hence the 
reliability of the apparatus can be improved. 
In accordance with a preferred embodiment of the present invention, the 
magnetic plate member forms a planar projecting portion which protrudes 
from an upper surface of the motor mounting base so as to get closer to a 
lower surface of the turn table. Therefore, radial deflections of the 
rotational motor shaft can be prevented more effectively by using the 
magnetic force of the turn table magnet more efficiently. 
In accordance with a preferred embodiment of the present invention, a 
magnet disposed on the motor mounting base and under the turn table for 
preventing deflections of the rotational motor shaft is provided instead 
of the magnetic plate member and adapted to generate a transverse force 
exerted on the rotational motor shaft by virtue of an adsorption force or 
a repulsion force between the turn table magnet and the magnet, thereby 
tilting the rotational motor shaft. Therefore, since the rotational 
driving apparatus does not need a spring used for tilting the rotational 
motor shaft, it can prevent wear in the spring, and an increase in the 
driving force of the motor caused by a friction between the spring and the 
rotational motor shaft while preventing radial deflections of the 
rotational motor shaft by using an adsorption force or a repulsion force 
between the turn table magnet and the magnet for preventing deflections of 
the rotational motor shaft, thereby reducing deflections of a disk placed 
on the turn table to a minimum and hence improving the reliability of the 
apparatus. 
In accordance with a preferred embodiment of the present invention, the 
magnet for preventing deflections of the rotational motor shaft forms a 
planar projecting portion which protrudes from an upper surface of the 
motor mounting base so as to get closer to a lower surface of the turn 
table. Therefore, radial deflections of the rotational motor shaft can be 
prevented more effectively by using an adsorption force or a repulsion 
force between the turn table magnet and the magnet for preventing 
deflections of the rotational motor shaft. 
Many widely different embodiments of the present invention may be 
constructed without departing from the spirit and scope of the present 
invention. It should be understood that the present invention is not 
limited to the specific embodiments described in the specification, except 
as defined in the appended claims.