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Claims  |
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What is claimed is:
1. A ball polishing apparatus for polishing a ball, comprising:
a lower polishing disk having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, an outer
circumferential portion of said inner disk and an inner circumferential
portion of said outer polishing disk forming a holding portion for
rollably holding the ball;
magnetic holding means for holding said outer disk in a state in which said
outer disk is movable with reference to said inner disk in an axial
direction of said inner disk, said magnetic holding means including a
holding ring provided for a lower surface of said outer disk and a
repulsive ring located in opposition to the holding ring, said holding
ring and said repulsive ring being magnetized and arranged with their
same-polarity portions facing each other, to thereby generate a magnetic
repulsive force by which to hold said outer disk in a floating state;
first driving means for driving said inner disk;
second driving means for driving said outer disk without impairing the
floating state of said outer disk achieved by the magnetic force;
an upper polishing disk opposing said lower polishing disk, for pushing the
ball held by said holding portion; and
third driving means for driving said upper polishing disk.
2. An apparatus according to claim 1, wherein said magnetic holding means
comprises a holding ring, constituted by a permanent magnet provided on a
side of a lower surface of said outer disk, and a repulsive ring, provided
at a location to oppose said holding ring, for generating a magnetic
repulsive force with respect to said holding ring.
3. An apparatus according to claim 1, wherein said upper polishing disk and
said third driving means are integrally provided and are driven by fourth
driving means in a direction to approach and separate from said lower
polishing disk.
4. An apparatus according to claim 3, comprising:
detecting means for detecting a load applied on the ball by said upper
polishing disk; and
control means for driving said fourth driving means by a detection signal
supplied from said detecting means in order to control the load applied on
the ball by said upper polishing disk.
5. An apparatus according to claim 4, wherein said detecting means is a
strain gauge provided on said upper polishing disk.
6. A ball polishing apparatus for polishing a ball, comprising:
a base;
a rotary member constituting a cylindrical member and provided on said base
to be rotatable about an axis of the cylindrical member;
a lower polishing disk having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, and provided in said
rotary member, an outer circumferential portion of said inner disk and an
inner circumferential portion of said outer disk, forming a holding
portion for rollably holding the ball;
magnetic holding means for holding said outer disk in a state where said
outer disk is movable with reference to said inner disk in an axial
direction of said inner disk, said magnetic holding means including a
holding ring provided for a lower surface of said outer disk and a
repulsive ring located in opposition to the holding ring, said holding
ring and said repulsive ring being magnetized and arranged with their
same-polarity portions facing each other, to thereby generate a magnetic
repulsive force by which to hold said outer disk;
first driving means for driving said inner disk;
magnetic coupling means, provided at an inner circumferential portion of
said cylindrical member, for coupling said outer disk with said
cylindrical member in a non-contact manner by a magnetic force;
second driving means for integrally rotating said outer disk and said
cylindrical member through said magnetic coupling means provided to said
cylindrical member by driving said cylindrical member;
an upper polishing disk opposing said lower polishing disk, for pushing the
ball held by said holding portion;
third driving means, being integral with said upper polishing disk, for
driving said upper polishing disk;
fourth driving mean, for driving said upper polishing disk in a direction
to approach and separate from said lower polishing disk;
detecting means for detecting a load which said upper polishing disk
applies to the ball; and
control means for controlling the load which said upper polishing disk
applies to the ball, by driving said fourth driving means in accordance
with a detection signal supplied from said detecting means.
7. An apparatus according to claim 6, wherein said second driving means
comprises an integral gear formed on the inner circumferential surface of
said cylindrical member, a driving gear meshed with said internal gear,
and a power source for driving said driving gear.
8. A polishing method of polishing a ball with upper and lower polishing
disks, comprising the steps of:
holding an outer disk by a magnetic repulsive force and in a state in which
said outer disk is movable with reference to said inner disk in an axial
direction of said inner disk, by using said lower polishing disk
constituted by said inner disk and said outer disk surrounding said inner
disk and coaxial therewith;
supplying a ball to a holding portion formed by an outer circumferential
portion of said inner disk and an inner circumferential portion of said
outer disk;
pushing the ball held by said holding portion by said upper polishing disk
with a predetermined load; and
driving said inner disk, outer disk, and upper polishing disk.
9. A method according to claim 8, wherein said upper polishing disk and
said inner disk of said lower polishing disk are rotated in different
directions, and said outer disk of said lower polishing disk and said
inner disk are rotated in the same direction.
10. A ball polishing apparatus for polishing a ball, comprising:
at least two inner disks vertically spaced apart at a predetermined gap and
arranged coaxial in a horizontal plane, each having a diameter greater
than the immediate lower one; at least two annular outer disks, having
different diameters and surrounding said inner disks and coaxial
therewith, respectively, forming holding portions for holding the ball
with inner circumferential portions thereof and outer circumferential
portions of said inner disk;
magnetic holding means for holding said outer disk in a state in which said
outer disk is movable with reference to said inner disk in an axial
direction of said inner disk, said magnetic holding means including
holding rings provided for lower surfaces of the respective outer disks
and repulsive rings located in opposition to the respective holding rings,
said holding rings and said repulsive rings being magnetized and arranged
with their same-polarity portions facing each other, to thereby generate a
magnetic repulsive force by which to hold said outer disk; and
driving means for driving said inner and outer disks in predetermined
directions, respectively.
11. A ball polishing apparatus for polishing a ball, comprising:
a driving shaft;
first driving means for driving said driving shaft;
a lower polishing disk having a holding portion formed on an upper surface
thereof for rollably holding the ball, and a support shaft provided on a
lower surface thereof;
coupling means for coupling said support shaft to said driving shaft,
allowing said support shaft to move along an axis of said driving shaft
and to swing away from the axis of said driving shaft, and making said
support shaft rotate together with said driving shaft;
magnetic holding means for holding said lower polishing disk in a state
where said outer disk is movable along said axis, said magnetic holding
means including a first ring provided for a lower surface of said lower
polishing disk and a second ring located in opposition to the first ring,
said first ring and said second ring being magnetized and arranged with
their same-polarity portions facing each other, to thereby generate a
magnetic repulsive force by which to hold said lower polishing disk;
an upper polishing disk, arranged above said lower polishing disk and
opposing said lower disk, for pushing the ball held by said holding
portion with a predetermined load; and
second driving means for driving said upper polishing disk.
12. An apparatus according to claim 11, wherein said coupling means
comprises an insertion hole formed in an upper end face of said driving
shaft and having a diameter larger than that of said support shaft, an
engaging groove radially formed in an upper end portion of said driving
shaft intersecting with the insertion hole, an a pin provided at a lower
end portion of said support shaft and engaged in said engaging groove.
13. A ball polishing apparatus for polishing a ball, comprising:
a lower polishing disk, having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, an outer
circumferential portion of said inner disk and an inner circumferential
portion of said outer disk forming a holding portion for rollably holding
the ball;
positioning means for moving at least one of said outer and inner disks in
an axial direction of said outer and inner disks and adjusting the
positions of said outer and inner disks in a horizontal direction
perpendicular to said axial direction;
first driving means for driving said lower polishing disk;
an upper polishing disk, arranged and opposed said lower polishing disk,
for pushing the ball held by said holding portion; and
second driving means for driving said upper polishing disk.
14. An apparatus according to claim 13, wherein said positioning means
regulates a movement of said outer disk in a radial direction thereof and
vertically moves at least one of said outer and inner disks.
15. A ball polishing apparatus for polishing a ball, comprising:
a lower polishing disk, having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, an outer
circumferential portion of said inner disk and an inner circumferential
portion of said outer polishing disk forming a holding portion for
rollably holding the ball;
holding means for moving said outer disk with reference to said inner disk
in an axial direction of said inner disk and holding said inner and outer
disks such that horizontal positions thereof are maintained in a
predetermined state;
first driving means for driving said lower polishing disk;
an upper polishing disk, arranged and opposing said lower polishing disk,
for pushing the ball held by said holding portion; and
second driving means for driving said upper polishing disk. |
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Claims |
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Description |
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Background of the Invention
1. Field of the Invention
The present invention relates to a ball polishing apparatus for polishing a
ball with high shape precision, and a method for the same.
2. Description of the Related Art
To polish a ball, a polishing apparatus as shown in FIG. 1 is
conventionally used. Referring to FIG. 1, reference numeral 1 denotes a
lower polishing disk which is driven to rotate. V-shaped grooves 3 for
rotatably holding a multiple of balls 2, i.e., ceramic balls, as works are
formed in the upper surface of the lower polishing disk 1 in the
circumferential direction.
An upper polishing disk 4 which is driven to rotate in the opposite
direction to that of the lower polishing disk 1 is provided on the upper
surface side of the lower polishing disk 1. The upper and lower polishing
disks 4 and 1 are rotated in the opposite directions while the upper
polishing disk 4 is in tight contact with the balls 2 so as to serve as a
predetermined load. Then, each ball 2 is rotated about its axis and an
axis of each disk so as to be polished by polishing grains which are
externally supplied.
Not only the sphericity but also the diameter of the plurality of balls 2
supplied to the V-shaped grooves 3 of the lower disk 1 during one
polishing, i.e., the balls 2 of one lot vary (the variation in diameter is
called size variation). Thus, when the polishing disks 1 and 4 are rotated
while the balls 2 are pushed with a predetermined pressure by the upper
polishing disk 4, the pressure applied on each ball 2 becomes momentarily
excessive or insufficient due to the variation in sphericity or diameter
of the ball 2.
When an abnormality occurs in the pressure in this manner, galling occurs
between the lower polishing disk 1 and a ball 2, thus damaging the lower
polishing disk 1 or failing to obtain a desired sphericity or size
variation as the shape precision of the ball 2.
The size of a ball 2 which can be polished is determined by the size of the
corresponding V-shaped groove 3 formed in the lower polishing disk 1.
Thus, to polish balls 2 having a different size, the lower polishing disk
1 must be replaced with one in which V-shaped grooves 3 appropriate for
the size of the new balls 2 are formed. However, it is not easy to replace
the lower polishing disk 1, resulting in a cumbersome operation.
Summary of the Invention
It is an object of the present invention to provide a polishing apparatus
which can polish works with high variation-free shape precision without
causing galling between the works and the polishing disks even when the
sizes of the works of one lot vary, and a method for the same.
According to one aspect of the present invention, there is provided a ball
polishing apparatus for polishing a ball, comprising:
a lower polishing disk having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, an outer
circumferential portion of said inner disk and an inner circumferential
portion of said outer polishing disk forming a holding portion for
rollably holding the ball; magnetic holding means for holding said outer
disk in a floating state by a magnetic force and in a predetermined
positional relationship with said inner disk; first driving means for
driving said inner disk; second driving means for driving said outer disk
without impairing the floating state of said outer disk achieved by the
magnetic force; an upper polishing disk opposing said lower polishing
disk, for pushing the ball held by said holding portion; and third driving
means for driving said upper polishing disk.
According to another aspect of the present invention, there is provided a
ball polishing apparatus for polishing a ball, comprising:
a base; a rotary member constituting a cylindrical member and provided on
said base to be rotatable about an axis of the cylindrical member; a lower
polishing disk having a inner disk and an annular outer disk surrounding
said inner disk and coaxial therewith, and provided in said rotary member,
an outer circumferential portion of said inner disk and an inner
circumferential portion of said outer disk, forming a holding portion for
rollably holding the ball; magnetic holding means, provided at a base
portion serving as an interior of said rotary member, for holding said
outer disk in a floating state by a magnetic force and in a predetermined
positional relationship with said inner disk; first driving means for
driving said inner disk; magnetic coupling means, provided at an inner
circumferential portion of said cylindrical member, for coupling said
outer disk with said cylindrical member in a non-contact manner by a
magnetic force; second driving means for integrally rotating said outer
disk and said cylindrical member through said magnetic coupling means
provided to said cylindrical member by driving said cylindrical member; an
upper polishing disk opposing said lower polishing disk, for pushing the
ball held by said holding portion; and third driving means for driving
said upper polishing disk.
According to yet another aspect of the present invention, there is provided
a polishing method of polishing a ball with upper and lower polishing
disks, comprising the steps of:
holding an outer disk in a floating state by a magnetic force and in a
predetermined positional relationship with an inner disk by using said
lower polishing disk constituted by said inner disk and said annular outer
disk surrounding said inner disk and coaxial therewith; supplying a ball
to a holding portion formed by an outer circumferential portion of said
inner disk and an inner circumferential portion of said outer disk;
pushing the ball held by said holding portion by said upper polishing disk
with a predetermined load; and driving said inner disk, outer disk, and
upper polishing disk.
According to another aspect of the present invention, there is provided a
ball polishing apparatus for polishing a ball, comprising:
at least two inner disks vertically spaced apart at a predetermined gap and
opposing each other, each having a diameter greater than the immediate
lower one; at least two of annular outer disks, having different diameters
and surrounding said inner disks and coaxial therewith, respectively,
forming holding portions for holding the ball with inner circumferential
portions thereof and outer circumferential portions of said inner disk;
magnetic holding means for holding said outer disks in a floating state by
a magnetic force and in a predetermined positional relationships with said
inner disks; and driving means for driving said inner and outer disks in
predetermined directions, respectively.
According to yet another aspect of the invention, there is provided a ball
polishing apparatus for polishing a ball, comprising:
a lower polishing disk, having an inner disk and an annular outer disk
surrounding said inner disk and coaxial therewith, an outer
circumferential portion of said inner disk and an inner circumferential
portion of said outer disk forming a holding portion for rollably holding
the ball; positioning means for moving at least one of said outer and
inner disks to adjust a mutual positional relationship therebetween; first
driving means for driving said lower polishing disk; an upper polishing
disk, arranged and opposing said lower polishing disk, for pushing the
ball held by said holding portion; and second driving means for driving
said upper polishing disk.
Additional objects and advantages of the invention will be set forth in the
description which follows, and in part will be obvious from the
description, or may be learned by practice of the invention. The objects
and advantages of the invention may be realized and obtained by means of
the instrumentalities and combinations particularly pointed out in the
appended claims.
Brief Description of the Drawings
The accompanying drawings, which are incorporated in and constitute a part
of the specification, illustrate presently preferred embodiments of the
invention and, together with the general description given above and the
detailed description of the preferred embodiments given below, serve to
explain the principles of the invention.
FIG. 1 shows the arrangement of a conventional polishing apparatus;
FIG. 2 is a sectional view showing the overall arrangement of a polishing
apparatus according to the first embodiment of the present invention;
FIG. 3 is a plan view showing a magnetizing state of driven and driving
rings;
FIG. 4 is a sectional view showing a connecting state between strain gauges
provided on an upper polishing disk, and a controller;
FIG. 5 is a plan view showing the arrangement of the strain gauges provided
on the upper polishing disk;
FIG. 6 is a sectional view showing the overall arrangement of a polishing
apparatus according to the second embodiment of the present invention;
FIG. 7 is a sectional view showing the overall arrangement of a polishing
apparatus according to the third embodiment of the present invention;
FIG. 8 is a sectional view showing the overall arrangement of a polishing
apparatus according to the fourth embodiment of the present invention;
FIG. 9 is a view for explaining a state in which an outer disk is moved
upward;
FIG. 10 is a view for explaining rotation about an axis of a ball and
rotation about an axis of each disk; and
FIG. 11 is a view for explaining moments generated in a ball.
Detailed Description of the Preferred Embodiments
The preferred embodiments of the present invention will be described with
reference to the accompanying drawings.
FIGS. 2 to 5 show a polishing apparatus according to the first embodiment
of the present invention. Referring to FIG. 2, reference numeral 11
denotes a base. A cylindrical rotary member 12 is rotatably provided on
the base 11 through a thrust bearing 13. A first power source 14 is
provided in the rotary member 12. The axis of a driving shaft 15 of the
first power source 14 coincides with the center of rotation of the rotary
member 12.
A lower polishing disk 18 consists of an inner disk 16 and an annular outer
disk 17. The power source 14 drives the inner disk 16 of the lower
polishing disk 18. A shaft portion 16c is provided to extend from the
lower surface of the inner disk 16 and coupled to the driving shaft 15 of
the power source 14.
The outer disk 17 is disposed to surround the inner disk 16 at a
predetermined gap to be coaxial with it, i.e., such that the center of
rotation of the outer disk 17 coincides with that of the inner disk 16.
The outer disk 17 is held in a floating state by a magnetic force. That
is, the outer disk 17 is mounted at the inner side, along the radial
direction, of the upper surface of a holding ring 19 which is surrounding
the inner disk 16. A driven ring 21, which is alternately magnetized to
the N and P poles along its circumferential direction as shown in FIG. 3,
is provided on the outer side, along the radial direction, of the upper
surface of the holding ring 19. A repulsive ring 22, the upper surface of
which is magnetized to the N pole, is disposed below the lower surface of
the holding ring 19 to oppose it at a predetermined gap. The holding ring
19 is magnetized such that its lower surface in the direction of thickness
becomes the N pole.
The opposing surfaces of the repulsive and holding rings 22 and 19 are
magnetized to the same pole. Thus, a magnetic repulsive force is generated
between the rings 22 and 19 to hold the holding ring 19 in the floating
state together with the outer disk 17. The magnetic repulsive force
generated between the holding and repulsive rings 19 and 22 is set to a
magnitude to float the outer disk 17 at substantially the same level with
the inner disk 16.
The repulsive ring 22 is held by a holding mechanism 36 and adjusts the gap
with respect to the holding ring 19 as required, thereby controlling the
magnetic repulsive force generated between the repulsive and holding rings
22 and 19. In other words, the repulsive ring 22 adjusts the floating
height of the holding ring 19.
A stepped portion 23 is formed in the upper portion of the inner
circumferential surface of the rotary member 12. A driving ring 24 is
provided in the stepped portion 23. The driving ring 24 is alternately
magnetized to the N and S poles along its circumferential direction so as
to oppose the opposite poles formed on the driven ring 21, as shown in
FIG. 3. Thus, the driving and driven rings 24 and 21 are coupled to each
other by a magnetic attractive force. In other words, the driving and
driven rings 24 and 21 constitute a magnet coupling.
An internal gear 25 is formed in the upper portion of the inner
circumferential surface of the stepped portion 23. The internal gear 25 is
meshed with a driving gear 27 which is driven by a second power source 26.
The second power source 26 is mounted on a top plate 37 arranged above the
rotary member 12.
Hence, when the second power source 26 is operated to rotate the driving
gear 27 to rotate the rotary member 12 through the internal gear 25, the
driven ring 21 which is coupled to the driving ring 24 by the magnetic
attractive force can be rotated integrally with the rotary member 12.
Accordingly, the outer disk 17 integrally provided with the driven ring 21
is also rotated.
The upper ends of the outer circumferences of the inner and outer disks 16
and 17 form surfaces 16a and 17a, respectively, which are inclined at a
predetermined angle, i.e., 45.degree.. The pair of inclined surfaces 16a
and 17a form a holding portion 28 having a substantially V-shaped section.
A plurality of ceramic balls 29 which are to be polished are rollably held
in the holding portion 28.
An upper polishing disk 31 is arranged above the lower polishing disk 18.
The upper polishing disk 31 comprises a disk portion 32 and a shaft
portion 33, as shown in FIG. 4. The diameter of the disk portion 32 is
larger than that of the inner disk 16 of the lower polishing disk 18, and
a lower end portion of the shaft portion 33 is fitted in a fitting hole
32a formed at the central portion of the disk portion 32. The shaft
portion 33 is inserted in a sleeve 34 and rotatably supported by a bearing
34a. A male thread 35 is formed in the upper portion of the outer
circumferential surface of the sleeve 34, as shown in FIG. 2. The male
thread 35 is threadably engaged with a female thread portion 38 formed in
the top plate 37. A third power source 39 is integrally provided on the
upper end of the sleeve 34, and the shaft portion 33 is rotated by the
power source 39.
A driven gear 41 is provided on the upper end portion of the sleeve 34. The
driven gear 41 is meshed with a driving gear 42. The driving gear 42 is
rotated by a fourth power source 43 provided on the top plate 37. When the
sleeve 35 is rotated by the fourth power source 43 through the driving and
driven gears 42 and 41, the sleeve 35 is moved in the vertical direction
by the threadable engagement of its male thread 35 with the female thread
portion 38. This changes the gap between the lower and upper polishing
disks 18 and 31. In other words, a machining load (polishing load) of the
upper polishing disk 31 against the balls 29 held by the holding portion
38 can be controlled.
The fourth power source 43 is controlled by a controller 44. The polishing
load applied to the upper polishing disk 31 is input to the controller 44.
That is, in the disk portion 32 of the upper polishing disk 31, its
central and peripheral portions 45a and 45b are coupled to each other by
four arms 50 arranged at equal angular intervals of 90.degree. in the
circumferential direction, as shown in FIG. 5. A strain gauge 46 is
mounted at an intermediate portion of the upper surface of each arm 50.
One end of a first lead wire 47 is connected to each strain gauge 46.
The four lead wires 47 are respectively electrically connected to four
conductive zones 49, provided at the lower end portion of the shaft
portion 33, through pins 48 provided on the peripheral portion 45b of the
upper disk 31, as shown in FIG. 4. One end of each brush 51 contacts each
conductive zone 49. The other end portion of each brush 51 is supported by
a bracket 52 provided to extend from the lower end portion of the sleeve
34. One end of each second lead wire 53 is connected to the other end of
the corresponding brush 51. The second lead wires 53 are guided to the
controller 44 and connected such that the four strain gauges 46 form a
bridge circuit (not shown) in the controller 44. An output signal from the
bridge circuit is compared with a preset value set in the controller 44.
When a difference occurs between the output signal and the preset value,
the controller 44 outputs a drive signal to the fourth power source 43.
Then, the sleeve 34 is driven by the power source 43 to move upward or
downward, and the upper polishing disk 31 is interlocked with the movement
of the sleeve 34 to control the gap with respect to the lower polishing
disk 18, i.e., the polishing load.
This control will be described in more detail. When the balls 29 are to be
polished by the upper polishing disk 31, an output from the bridge circuit
constituted by the strain gauges 46 varies depending on the contact force
(polishing load) between the upper polishing disk 31 and the balls 29. For
example, when unmanned coarse polishing of the balls 29 is continued over
a long period of time, the polishing load is decreased as the machining
proceeds. In this case, an output from the bridge circuit becomes close to
zero and a difference between the output and the preset value becomes
large. Then, the upper polishing disk 31 is driven to move downward Thus,
the machining load of the upper polishing disk 31 on the balls 29 is
maintained at a predetermined value.
Inversely, when galling occurs between the upper disk 31 and the balls 29
and an output from the bridge circuit becomes larger than the preset
value, the upper disk 31 is driven to move upward to maintain the
polishing load at the predetermined value. Thus, the upper polishing disk
31 can be prevented from being damaged.
A polishing agent is supplied from a nozzle (not shown) to the holding
portion 28.
The operation of polishing the balls 29 by the polishing apparatus having
the above arrangement will be described.
The outer disk 17 of the lower polishing disk 18 is held at a height by the
magnetic repulsive force generated between the holding and repulsive rings
19 and 22 to keep a predetermined positional relationship with the inner
disk 16. The height of the outer disk 17 can be adjusted by the holding
mechanism 36. The holding portion 28 is caused to hold the multiple of
balls 29. Then, the first to third power sources 14, 26, and 39 are
operated to rotate the inner disk 16 of the lower polishing disk 18 and
the upper polishing disk 31 in the opposite directions and to rotate the
rotary member 12 in the same direction as the inner disk 16 of the lower
polishing disk 18. When the rotary member 12 is rotated, the outer disk 17
is rotated in the same direction as the inner disk 16 by the magnetic
coupling of the driving ring 24 and the driven ring 21. In other words,
the inner disk 16 and the outer disk 17 of the lower disk 18 are rotated
together.
The fourth power source 43 is operated to move the upper polishing disk 31
downward so that the lower surface of the disk portion 32 of the upper
polishing disk 31 is brought into contact with the balls 29, held by the
holding portion 28 defined by the inner and outer disks 16 and 17, with a
predetermined polishing load. Then, the balls 29 are polished as they are
rotated about their axes and the axis of each disk by the three-point
contact among the inclined surfaces 16a and 17b of the holding portion 28
and the disk portion 32 of the upper polishing disk 31. At this time, the
outer disk 17 is moved downward against the magnetic repulsive force.
The shape precision, i.e., sphericity and size, of the multiple of balls 29
supplied to and held by the holding portion 28 varies, and the polishing
load applied on each respective ball 29 is changed in accordance with this
variation. When the polishing load is changed, the outer disk 17 of the
lower polishing disk 18 is moved in accordance with this change against
the magnetic repulsive force with respect to the repulsive ring 22.
For example, assume that the balls 29 have a size variation and a size
difference. For a ball 29 having a large diameter, the outer disk 17 is
moved downward against the magnetic repulsive force with respect to the
repulsive ring 22, and for a ball 29 having a small diameter, the outer
disk 17 is moved upward by the repulsive force received from the repulsive
ring 22. In this manner, if the outer disk 17 is moved by the magnetic
force in accordance with the size variation and diameter difference of the
balls 29, the balls 29 in the holding portion 28 can be prevented from
being applied with an excessive polishing force. Then, galling does not
occur between the balls 29 and the upper and lower polishing disks 31 and
18.
The outer disk 17 is biased by the magnetic repulsive force between the
holding and repulsive rings 19 and 22 to keep a predetermined positional
relationship with the inner disk 16 and upper polishing disk 31.
Therefore, if polishing of the balls 29 is continued until the outer disk
17 has a predetermined positional relationship with the inner disk 16 and
upper polishing disk 31, i.e., until the outer disk 17 is not pushed by
the balls 29 and its height is determined by only the magnetic repulsive
force, the balls 29 held by the holding portion 28 can be precisely
polished to have a uniform shape free from a size difference.
The polishing load of the upper polishing disk 31 on the balls 29 is
detected by each strain gauges 44, input to the controller 44, and
compared with the preset value by the controller 44. When a difference
occurs between the detection signal from each strain gauge 46 and the
preset value of the controller 44, the upper polishing disk 31 is
vertically driven to control the polishing load on the balls 29 by an
in-process such that this difference is eliminated. For this reason, if,
e.g., unmanned coarse polishing is performed over a long period of time,
the polishing load is constantly maintained at an appropriate value even
when machining proceeds, and thus unmanned precision machining is enabled.
In this embodiment, regarding especially a change in diameter of each bal
29 accompanying the progress of polishing and a macroscopic change in load
to the ball 29 caused by the vertical movement of the outer disk 17
because of wear of the upper polishing disk 31, inner, and outer disks 16,
17, the upper polishing disk 31 is vertically moved by the fourth power
source 43 on the basis of the detection signals from the strain gauges 46
to adjust these changes by the in-process such that a predetermined
polishing load can be obtained. Simultaneously, regarding a size variation
(variation in diameter among individual balls of one lot) of the balls 29
and a microscopic change in load which occurs instantaneously due to the
difference in diameter of the individual balls 29, they can be
automatically polished by the magnetic repulsive force between the holding
and repulsive rings 19 and 22 by the in-process. In this manner, because
of the two relative cooperative operations including the macroscopic and
microscopic adjusting operations of the load, the ball machining precision
is greatly improved as compared to a case in which only either the
macroscopic or microscopic adjusting operation of the load is performed.
FIG. 6 shows the second embodiment of the present invention. Referring to
FIG. 6, reference numeral 61 denotes a first bottomed member having an
open upper surface. The upper end of a first hollow shaft 62 is coupled to
the central portion of the bottom portion of the first cylindrical member
61. Thus, the lower end of the first hollow shaft 62 is coupled to a first
power source 63. The first cylindrical member 61 is then rotated.
A second cylindrical member 64 having a similar shape to the cylindrical
member 61 is disposed in the first cylindrical member 61. The upper end of
a second hollow shaft 65 having a diameter smaller than that of the first
hollow shaft 62 is coupled to the central portion of the bottom portion of
the second cylindrical member 64. The second hollow shaft 65 extends
through the first hollow shaft 62, and its lower end portion is coupled to
a second power source 66. The second hollow shaft 65 is rotated in a
direction opposite to that of the first hollow shaft 62.
A first inner disk 67 is provided in the second cylindrical member 64. A
first driving shaft 67a is provided to extend from the lower surface of
the first inner disk 67. The first driving shaft 67a extends through the
second hollow shaft 65, and its lower end is coupled to a third power
source 68. The first driving shaft 67a is driven to rotate in the same
direction as the second hollow shaft 65.
A first annular outer disk 69 is surrounding the first inner disk 67. The
first outer disk 69 is mounted at the radially inner portion of the upper
surface of a first annular holding ring 71, and the lower side of the disk
69 in the direction of thickness is magnetized to the N pole. A first
driven ring 72 which is alternately magnetized to the S and N poles along
its circumferential direction is provided on the radially outer portion of
the upper surface of the holding ring 71.
A first repulsive ring 73 having the upper side, which opposes the first
holding ring 71 and is magnetized to the N pole, is provided on the inner
bottom portion of the second cylindrical member 64. The first outer disk
69 is held in the floating state by the magnetic repulsive force between
the repulsive and holding rings 73 and 71.
The upper ends of the outer and inner circumferences of the first inner and
outer disks 67 and 69 form surfaces 67a and 69a, respectively, which are
inclined at predetermined angles, i.e., 45.degree.. The inclined surfaces
67a and 69a form a first annular holding portion 74 for rollably holding
ceramic balls 29 as the works.
A first driving ring 75, which is magnetized to generate a magnetic
attractive force with respect to the first driven ring 72, is provided at
a location of the upper portion of the inner circumferential surface of
the second cylindrical member 64 to oppose the first holding and driven
rings 71 and 72. In other words, the driving ring 75 and the first holding
and driven rings 71 and 72 are coupled to each other by the magnetic
attractive force. Thus, when the second cylindrical member 64 is rotated
together with the first inner disk 67, the first outer disk 69
magnetically coupled to the first driving ring 75 is rotated in the same
direction.
A second inner disk 76 having a diameter larger than that defined by the
first holding portion 74 is disposed above the first inner disk 67 such
that its lower surface opposes the upper surface of the first inner disk
67 in a parallel manner. A second driving shaft 77 is provided on the
upper surface of the second inner disk 76. The second driving shaft 77 is
rotated by a fourth power source 78 in the direction opposite to the first
inner disk 67.
A second annular outer disk 79 is surrounding the second inner disk 76. The
second outer disk 79 is provided on the radially inner portion of the
upper surface of a second annular holding ring 81, and the upper surface
of the disk 79 in the direction of thickness is magnetized to the N pole.
A second driven ring 82 which is alternately magnetized to the S and N
poles along its circumferential direction is provided on the radially
outer portion of the upper surface of the second holding ring 81.
The outer diameter of the second holding ring 81 is formed to be
substantially the same as that of the second cylindrical member 64. The
second holding ring 81 is held in the floating state by the magnetic
repulsive force generated between the holding ring 81 and a second
repulsive ring 83 provided on the upper end face of the second cylindrical
member 64.
The upper ends of the outer and inner circumferential portions of the
second inner and outer disks 76 and 79 respectively form surfaces 76a and
79a which are inclined at predetermined angles, i.e. 45.degree.. The
inclined surfaces 76a and 79a define a second annular holding portion 84
for rollably holding the balls 29.
A second driving ring 85 is provided at a location of the upper portion of
the inner circumferential surface of the first cylindrical member 61 to
oppose the second holding and driven rings 81 and 82. The second driving
ring 85 is magnetized to generate a magnetic attractive force with respect
to the second holding and driven rings 81 and 82. Thus, when the first
cylindrical member 61 is rotated, the second holding ring 81 is
interlocked with this rotation by the magnetic attractive force.
A third inner disk 86 is disposed above the second inner disk 76 such that
its lower surface is spaced apart to be parallel with the upper surface of
the second inner disk 76. The third inner disk 86 is a circular disk
having a diameter larger than that defined by the second holding portion
84, and a third hollow shaft 87 is provided on the upper surface of the
third inner disk 86. The second driving shaft 77 extends through the third
hollow shaft 87.
The third hollow shaft 87 is coupled to a fifth power source 88. The fifth
power source 88 drives the third inner disk 86 to rotate in the direction
opposite to the second inner disk 76.
The second and third inner disks 76 and 86 can be vertically positioned by
vertical driving mechanisms (not shown).
According to the polishing apparatus having the arrangement described
above, the balls held by the first holding portion 74 are polished by the
polishing load supplied from the second inner disk 76, and the balls 29
held by the second holding portion 84 are polished by the polishing load
supplied from the third inner disk 86.
When the balls 29 held by the holding portions 74 and 84 have a size
difference or a diameter difference, the first and second outer disks 69
and 79 which define the respective holding portions are moved in
accordance with the size difference or diameter difference against the
magnetic repulsive forces with respect to the first and second repulsive
rings 73 and 83. Thus, the balls 29 in the holding portions 74 and 84 can
be prevented from being applied with an excessive polishing force, and no
galling occurs among the inner disks 67, 76, and 86.
If polishing is continued until the first and second outer disks 69 and 79
are set in predetermined floating states by the magnetic repulsive forces
with respect to the repulsive rings 73 and 83, respectively, the balls 29
held by the holding portions 74 and 84 can be uniformly polished with high
precision without causing a size variation.
Since the first and second holding portions 74 and 84 are vertically
formed, if balls 29 having different sizes and materials are supplied to
them, two types of balls 29 can be polished by a single machining and, if
the same type of balls are to be polished, the number of machined balls
can be increased twice or more, thus improving the productivity.
In the second embodiment, the two holding portions are vertically provided.
However, three or more holding portions can be formed by stacking more
inner and outer disks.
In the second embodiment, four strain gauges 46 (only two are shown) are
also provided to the uppermost third inner disk 86 in the same manner as
in the first embodiment. The strain gauges 46 detect the polishing load
applied on the third inner disk 86, and output signals from the strain
gauges 46 are input to a controller 44 of the same type as that shown in
the first embodiment. The controller 44 compares each detection signal
with a preset value set in the controller 44 and vertically controls the
third inner disk 86 such that the comparison value becomes constant.
Hence, the polishing loads of the second and third inner disks 76 and 86
on the balls 29 can always be maintained at constant values.
When the uppermost third inner disk 86 is vertically driven, the second and
first inner disks 76 and 67 below it are interlocked with this vertical
movement, and thus the polishing loads on the balls 29 held by the first
and second holding portions 74 and 84 can be maintained at constant
values.
FIG. 7 shows the third emb | | |
