U.S. patent application number 09/729701 was filed with the patent office on 2001-05-10 for vibration type driving aparatus.
Invention is credited to Chiba, Ichiro, Kai, Takashi, Maruyama, Yutaka.
Application Number | 20010000940 09/729701 |
Document ID | / |
Family ID | 26547305 |
Filed Date | 2001-05-10 |
United States Patent
Application |
20010000940 |
Kind Code |
A1 |
Maruyama, Yutaka ; et
al. |
May 10, 2001 |
Vibration type driving aparatus
Abstract
In a vibration type driving apparatus comprising a vibration
member of which the vibration is excited, and a contacting member
contacting with the vibration member, the contacting member and the
vibration member being moved relative to each other by the
vibration of the vibration member, a friction member is provided on
the contacting portion of at least one of the vibration member and
the contacting member, and the friction member is formed with a
contacting surface smoothed by the pressing of a mold.
Inventors: |
Maruyama, Yutaka; (Tokyo,
JP) ; Kai, Takashi; (Tokyo, JP) ; Chiba,
Ichiro; (Yokohama-shi, JP) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154
US
|
Family ID: |
26547305 |
Appl. No.: |
09/729701 |
Filed: |
December 6, 2000 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
09729701 |
Dec 6, 2000 |
|
|
|
09162378 |
Sep 28, 1998 |
|
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Current U.S.
Class: |
310/326 ;
310/323.08; 310/323.11 |
Current CPC
Class: |
H02N 2/0065 20130101;
H02N 2/163 20130101; Y10T 29/42 20150115; H02N 2/007 20130101 |
Class at
Publication: |
310/326 ;
310/323.08; 310/323.11 |
International
Class: |
H01L 041/04 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 30, 1997 |
JP |
9-266107 |
Dec 12, 1997 |
JP |
9-362371 |
Claims
What is claimed is:
1. A vibration type driving apparatus comprising: a vibration
member of which the vibration is excited; and a contacting member
contacting with said vibration member, said contacting member and
said vibration member being moved relative to each other by the
vibration of said vibration member; wherein a friction member is
provided on the contacting portion of at least one of said
vibration member and said contacting member, and said friction
member is formed with a contacting surface smoothed by the pressing
of a mold.
2. A vibration type driving apparatus according to claim 1, wherein
the formation of said contacting surface by the pressing of said
mold is effected with heating.
3. A vibration type driving apparatus according to claim 1, wherein
the formation of said contacting surface by the pressing of said
mold is effected by a press forming method.
4. A vibration type driving apparatus according to claim 1, wherein
the formation of said contacting surface by the pressing of said
mold is effected by an ultrasonic working method.
5. A vibration type driving apparatus according to claim 1, wherein
said friction member is a material including a resin material.
6. A vibration type driving apparatus according to claim 2, wherein
said friction member is a material including a resin material.
7. A vibration type driving apparatus according to claim 3, wherein
said friction member is a material including a resin material.
8. A vibration type driving apparatus according to claim 1, wherein
said friction member is set so that the ridgeline portion of the
contacting portion of a partner side contacting said friction
member is in non-contact with said friction member.
9. A vibration type driving apparatus according to claim 8, wherein
said friction member is formed with a depressed portion, and is in
non-contact with said ridgeline portion of the contacting portion
of said partner side.
10. A vibration type driving apparatus according to claim 8,
wherein said friction member is formed with a protruding portion,
and is in non-contact with said ridgeline portion of the contacting
portion of said partner side.
11. A vibration type driving apparatus according to claim 9,
wherein said depressed portion of said friction member is formed at
the same time by the pressing of said contacting surface by said
mold.
12. A vibration type driving apparatus according to claim 10,
wherein said protruding portion of said friction member is formed
at the same time by the pressing of said contacting surface by said
mold.
13. An apparatus for driving an object to be driven by using the
vibration type driving apparatus according to claim 1 as a drive
source.
14. A vibration type driving apparatus comprising: a vibration
member of which the vibration is excited; and a contacting member
contacting with said vibration member, said contacting member and
said vibration member being moved relative to each other by the
vibration of said vibration member; wherein a friction member is
provided on the contacting portion of at least one of said
vibration member and said contacting member, and said friction
member is formed of a resin composition containing heat-resisting
resin and mesophased pitch carbon fiber.
15. A vibration type driving apparatus according to claim 14,
wherein said mesophased pitch carbon fiber is carbonic.
16. A vibration type driving apparatus according to claim 14,
wherein said mesophased pitch carbon fiber comprises short
fiber.
17. A vibration type driving apparatus according to claim 14,
wherein the content of said mesophased pitch carbon fiber is 10 to
30% by weight.
18. A vibration type driving apparatus according to claim 14,
wherein said heat-resisting resin includes fluororesin.
19. A vibration type driving apparatus according to claim 14,
wherein said heat-resisting resin includes polyimide resin.
20. A vibration type driving apparatus according to claim 14,
wherein said resin composition contains molybdenum disulfide.
21. A vibration type driving apparatus according to claim 14,
wherein said resin composition contains polyimide powder.
22. An apparatus for driving an object to be driven by using the
vibration type driving apparatus according to claim 14 as a drive
source.
Description
BACKGROUND OF THE INVENTION
1. 1. Field of the Invention
2. This invention relates to a vibration type driving apparatus in
which a vibration member of which the vibration is excited and a
contacting member contacting with the vibration member move
relative to each other.
3. 2. Related Background Art
4. An already proposed vibration type driving apparatus is
constructed as shown, for example, in FIG. 6 of the accompanying
drawings. This vibration type driving apparatus has a ring-like
vibration member 61 and a moving member (contacting member) 74.
5. The vibration member 61 is comprised of an elastic member 63, a
group of piezoelectric elements 64 adhesively secured to the
underside of the elastic member 63, and a friction member 66
adhesively secured to the upper surface (contacting surface) of the
comb-tooth-like portion of the elastic member 63, and the underside
of the moving member 74 is brought into pressure contact with the
upper surface (sliding surface) of the friction member 66 by
pressing means, not shown.
6. In the vibration type driving apparatus thus constructed, when a
periodic signal is applied to the group of piezoelectric elements
64, a travelling wave in which elliptical motions having a
plurality of time phase differences are combined together is
excited in the surface particles of the vibration member 61 (the
elastic member 63 and the friction member 66), and the moving
member 74 is frictionally driven and rotated. Accordingly, the
frictional contact state between the vibration member 61 and the
moving member 74 is a factor which determines various kinds of
performance such as the output torque, the number of revolutions,
the energy efficiency and the life of the driving apparatus.
7. So, heretofore, polishing work (see Japanese Patent Application
Laid-Open No. 2-211074) or grinding work (see Japanese Patent
Application Laid-Open No. 1-286783) has been done to make the
flatness and surface roughness of the sliding surface of the
friction member 66 fall within a predetermined range. There is also
a case where the portion around the sliding surface of the friction
member 66 is worked into a predetermined shape by cutting work (see
Japanese Patent Application Laid-Open No. 6-46580).
8. In the polishing work and the grinding work, however, the
handling of the friction member 66 is inconvenient and requires a
long working time and a high cost. Also, in the polishing work and
the grinding work, irregularity is liable to occur to the finished
state of the sliding surface, and this is considered to directly
affect the irregularity of the performance of the vibration type
driving apparatus.
9. Also, the cutting work requires many steps and moreover, the
work must be done individually for each member, and in addition, to
finish the cut shape between workpieces uniformly, it is necessary
to strictly effect the custody of a parameter such as a working
force, and this is inconvenient and takes a long working time.
10. Further, the friction member 66 popular in the vibration type
driving apparatus, as shown in FIG. 7 of the accompanying drawings
(a cross-sectional view taken along the line 7--7 of FIG. 6), is
formed of a hard additive 84 and relatively soft binder resin 85
and therefore, when it is cut by a cutting tool, cutting resistance
increases in the portion of the additive and decreases in the
portion of binder resin. Therefore, the cut surface becomes an
uneven surface in which the additive protrudes from the binder
resin, and a suitable smooth surface is difficult to obtain.
11. As regards other material of the friction member, for example,
in Japanese Patent Application Laid-Open No. 5-239442 and Japanese
Patent Application Laid-Open No. 4-49872, a resin material
containing carbon fiber is disclosed as a material being good in
abrasion property and suitable as a frictional material for a
vibration wave motor from the long durability life and the
stability of the coefficient of friction thereof.
12. However, when the evaluation of the performance of the
vibration wave driving apparatus under various environments has
been effected in the various uses of the vibration wave driving
apparatus, it has been found that the abrasion resistance of a
frictional material, i.e., the abrasion loss of the frictional
material, is remarkably changed by the influence of a change
particularly in humidity. Therefore, it has been found that the
life of the vibration wave driving apparatus depends greatly on the
durability life of the frictional material and is greatly changed
under the influence of a change in the humidity particularly in the
environment of use.
13. A frictional material for a vibration wave driving apparatus
stable against the influence of a change in humidity under an
environment of low humidity or high humidity or under an
environment in which there are changes in humidity is desired.
SUMMARY OF THE INVENTION
14. One aspect of the invention is to provide a friction member on
the sliding portion of at least one of a vibration member and a
contacting member which are the constituent members of a vibration
wave driving apparatus, and smoothly working the sliding surface of
the friction member by the pressing of a mold, thereby obtaining
the sliding surface which can be worked more easily and in a
shorter time than by cutting in the prior art and which is free of
irregularity and assumes proper flatness and proper surface
roughness.
15. One aspect of the invention is to provide a friction member on
the sliding portion of at least one of a vibration member and a
contacting member which are the constituent members of a vibration
wave driving apparatus, the friction member being formed of a resin
composition containing heat resisting resin and carbon fiber of the
mesophase pitch origin, and stable driving can be realized even
under an environment of low humidity or high humidity.
BRIEF DESCRIPTION OF THE DRAWINGS
16. FIG. 1A is a cross-sectional view showing the construction of a
vibration type motor which is a first embodiment of the present
invention, and FIG. 1B is an enlarged view of the sliding portion
of the motor.
17. FIG. 2 is an enlarged view of the sliding portion of a
vibration type motor which is a fourth embodiment of the present
invention.
18. FIG. 3 is an enlarged view of the sliding portion of a
vibration type motor which is a fifth embodiment of the present
invention.
19. FIGS. 4A and 4B are illustrations showing a method of working
the friction member of the motor of the fourth embodiment.
20. FIGS. 5A and 5B are illustrations showing a method of working
the friction member of the motor of the fifth embodiment.
21. FIG. 6 is a perspective view of a vibration type motor
according to the prior art.
22. FIG. 7 is an enlarged view of the sliding portion of the
vibration type motor according to the prior art.
23. FIG. 8 is a cross-sectional view showing another embodiment of
the vibration wave motor of the present invention.
24. FIG. 9 is a graph showing the relation between the abrasion
loss and humidity of a frictional material consisting of
fluororesin containing carbon fiber according to a sixth embodiment
of the present invention.
25. FIG. 10 is a graph showing the relation between the abrasion
loss and humidity of a frictional material consisting of polyimide
resin containing carbon fiber according to a seventh embodiment of
the present invention.
26. FIG. 11 is a schematic view of an instrument having the
vibration wave motor shown in FIG. 8 as a drive source.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
27. First Embodiment
28. FIG. 1A shows a ring type vibration type motor (vibration type
driving apparatus) which is a first embodiment of the present
invention. In FIG. 1A, the reference numeral 3 designates a
ring-like elastic member formed of a metal or the like. A group of
piezoelectric elements 4 as electromechanical energy conversion
elements comprising two groups of piezoelectric elements
alternately polarized and disposed in a ring-like shape are
concentrically adhesively secured to the underside of the elastic
member 3. Also, the upper portion of the elastic member 3 is formed
into a comb-tooth-like shape to enlarge vibration amplitude, and a
friction member 6 is concentrically adhesively secured to the upper
surface of this comb-tooth-like portion. The elastic member 3, the
group of piezoelectric elements 4 and the friction member 6
together constitute a vibration member 1. Also, the inner
peripheral portion of the elastic member 3 is attached to a base
member 10 by a screw 13, and the entire vibration member 1 is fixed
to the base member 10.
29. The reference numeral 14 denotes a moving member (contacting
member). This moving member 14 has a ring portion 2 and a disc-like
spring portion 5 having its inner peripheral boss portion 7
spline-coupled to a motor output shaft 11, and the ring portion 2
is brought into pressure contact with the vibration member 1
(friction member 6) by the pressing force of the spring portion 5.
The spring portion 5 is elastically deformed by the inner
peripheral boss portion 7 being pushed axially downwardly of a
motor by the upper bearing 9 of the motor output shaft 11 and
produces the above-mentioned pressing force.
30. In the thus constructed vibration type motor, when two high
frequency signals differing in phase from each other are applied to
the group of piezoelectric elements 4, a circumferential travelling
wave is created in the elastic member 3 and the friction member 6.
Therefore, the moving member 14 which is in pressure contact with
the friction member 6 is rotatively driven while sliding relative
to the friction member 6 by the friction thereof with this friction
member 6, and this rotation is transmitted to the motor output
shaft 11 through the spring portion 5 and the boss portion 7 and is
taken out as a motor output, and is used as a drive force for an
object to be driven in an apparatus (for example, the
photosensitive drum of a copying apparatus).
31. The moving member 14 in the present embodiment is formed of
aluminum containing 3% by weight of silicon particles having an
average particle diameter of the order of 3 .mu.m. Also, the
surface of contact with the friction member 6 on the moving member
14 (ring portion 2) is worked to the range of flatness of 10 .mu.m
or less and surface roughness Rmax of 0.2 to 2 .mu.m suitable for
motor driving by polishing.
32. On the other hand, as the friction member 6, use is made of 80%
by weight of PTFE resin and 20% by weight of carbon fiber uniformly
dispersed by a mixer, and press-formed, and thereafter heat-treated
at 380.degree. C.
33. However, as the materials of the moving member and the friction
member in the present invention, use may be made of other materials
than the materials in the present embodiment, for example, a
metallic material or a ceramic material as the material of the
moving member, and other resin than fluororesin as the base
material of the friction member 6.
34. FIG. 1B shows the sliding portion of the motor of the present
embodiment on an enlarged scale. The friction member 6 is in
pressure contact with the moving member 14 (ring portion 2) on the
surface (sliding surface) of the sliding portion (contact portion)
15 thereof.
35. In the present embodiment, the surface of the sliding portion
15 is pressed by a method of pressing a mold. Specifically, the
flat portion of a punch which is a metallic mirror surface is
pressed against the entire surface of the sliding portion 15 of the
friction member 6 by pressure of the order of 4.times.10.sup.7
N/m.sup.2, and is held for 60 seconds and is smoothed.
36. Thereby, the surface of the sliding portion 15 is worked into a
smooth surface which is a surface suitable for motor driving and in
which carbon fiber and PTFE resin are constructed substantially on
the same surface and which is free of waviness, specifically a
surface having flatness of 10 .mu.m or less and surface roughness
Rmax within a range of 5 .mu.m or less.
37. Accordingly, it becomes possible to efficiently transmit minute
displacement created on the surface of the sliding portion 15 by
the group of piezoelectric elements 4 to the moving member 14 and
moreover, it is possible to work workpieces more easily and within
a shorter time than in the working by grinding or polishing and
without any irregularity between the workpieces. Further, it is
possible to obtain the above-described smooth surface to thereby
obtain the stable output of the vibration type motor which has been
impossible by the cutting work alone.
38. Second Embodiment
39. While the first embodiment has been described with respect to a
case where a mold is simply pressed to thereby work the surface of
the sliding portion 15 of the friction member 6, the surface of the
sliding portion 15 may be worked by an ultrasonic working method.
The construction of the vibration type motor and the shape of each
constituent member in this embodiment are similar to those in the
first embodiment.
40. Specifically, the flat portion of an ultrasonic working horn
which is a metallic mirror surface member is pressed against the
entire surface of the sliding portion 15 with pressure of the order
of 3.times.10.sup.7 N/m.sup.2 and ultrasonic vibration is applied
thereto, and the flat portion is held for 10 seconds in a state in
which the temperature of the sliding portion 15 is of the order of
200 to 300.degree. C., and is subjected to smoothing work.
41. Thereby, the surface of the sliding portion 15 is worked into a
smooth surface which is a surface suitable for motor driving and in
which carbon fiber and PTFE resin are constructed substantially on
the same surface and which is free of waviness, specifically a
surface having flatness of 5 .mu.m or less and surface roughness
Rmax within a range of 3 .mu.m or less.
42. Accordingly, it becomes possible to more efficiently transmit
minute displacement created on the surface of the sliding portion
15 by the group of piezoelectric elements 4 to the moving member 14
than in the case of the first embodiment and moreover, it is
possible to work workpieces more easily and within a shorter time
than in the working by grinding or polishing and without any
irregularity between the workpieces. Further, it is possible to
obtain the stable output of the vibration type motor which has been
impossible by the cutting work alone.
43. Third Embodiment
44. While the first embodiment has been described with respect to a
case where a mold is simply pressed to thereby work the surface of
the sliding portion 15 of the friction member 6, the surface of the
sliding portion 15 may be worked by a press molding method. The
construction of the vibration type motor and the shape of each
constituent member in this embodiment are similar to those in the
first embodiment.
45. Specifically, the flat portion of a metal mold which is a
heated mirror surface member is pressed against the entire surface
of the sliding portion 15 with pressure of the order of
3.times.10.sup.7 N/m.sup.2 and is held for 20 seconds in a state in
which the temperature of the sliding portion 15 is of the order of
200.degree. C., and effects smoothing and pressing.
46. Thereby, as in the second embodiment, the surface of the
sliding portion 15 is worked into a smooth surface having flatness
of 5 .mu.m or less and surface roughness Rmax within a range of 3
.mu.m or less.
47. Accordingly, it becomes possible to more efficiently transmit
minute displacement created on the surface of the sliding portion
by the group of piezoelectric elements 4 to the moving member 14
than in the case of the first embodiment and moreover, it is
possible to work workpieces more easily and within a shorter time
than in the working by grinding or polishing and without any
irregularity between the workpieces. Further, it is possible to
obtain the stable output of the vibration type motor which has been
impossible by the cutting work alone.
48. Fourth Embodiment
49. FIG. 2 shows the sliding portion of a vibration type motor
which is a fourth embodiment of the present invention on an
enlarged scale. The construction of the vibration type motor and
the shape of each constituent member in this embodiment are
basically similar to those in the first embodiment and therefore,
common constituents are given the same reference characters as
those in the first embodiment and need not be described.
50. In the present embodiment, the moving member 14 and a friction
member 6' are made of the same materials as in the first
embodiment, but the sliding portion 16 of the friction member 6' is
formed into a bank type having ring-like grooves on the outer
peripheral side and inner peripheral side thereof, and the surface
(sliding surface) of this bank type sliding portion 16 is in
pressure contact with the moving member 14 (ring portion 2).
51. The inner diameter side ridgeline 16a of the bank type sliding
portion 16 is located more diametrally outside than the inner
diameter side ridgeline 2a of the ring portion 2, and the outer
diameter side ridgeline 16b of the bank type sliding portion 16 is
located more diametrally inside than the outer diameter side
ridgeline 2b of the ring portion 2. Therefore, the surface of the
bank type sliding portion 16 is in non-contact with the ridgelines
2a and 2b of the ring portion 2.
52. Thereby, the hard and sharp ridgelines 2a and 2b of the ring
portion 2 made of aluminum containing silicon can be prevented from
bearing against the bank type sliding portion 16 at a certain angle
even if the ring portion 2 is deformed by vibration. Accordingly,
it is possible to prevent the concentration of stress in the bank
type sliding portion 16 by the bearing against the ridgelines 2a
and 2b of the ring portion 2, sudden abrasion caused thereby, and
further a reduction in the starting torque and the instability of
the output of the motor due to the unstable contact between the
ridgelines 2a, 2b and the bank type sliding portion 16.
53. Also, in the present embodiment, the bank type sliding portion
16 is formed by an ultrasonic working method. Specifically, as
shown in FIG. 4A, a bank type ultrasonic working horn 19 made of a
metal is pressed against the upper surface of the friction member
6' with pressure of the order of 5.times.10.sup.7 N/m.sup.2 and
ultrasonic vibration is applied thereto, whereby the friction
member 6' is held for 10 to 30 seconds in a state in which the
temperature of the friction member 6' is 200 to 300.degree. C.,
thereby forming a bank type sliding portion 16 of a height of 50 to
200 .mu.m.
54. Subsequently, as shown in FIG. 4B, a flat type ultrasonic
working horn 20 which is a mirror surface member made of a metal is
pressed against the surface 17 of the bank type sliding portion 16
with pressure of the order of 3.times.10.sup.7 N/m.sup.2, and
ultrasonic vibration is applied thereto, whereby the bank type
sliding portion 16 is held for 10 seconds in a state in which the
temperature of the bank type sliding portion 16 is of the order of
200 to 300.degree. C., thereby effecting the smoothing of the
surface 17.
55. Thereby, the surface 17 of the bank type sliding portion 16,
like the surface of the sliding portion 15 described in the second
embodiment, is worked into a smooth surface which is suitable for
motor driving and in which carbon fiber and PTFE resin are
constructed substantially on the same surface and which is free of
waviness.
56. Accordingly, it becomes possible to efficiently transmit minute
displacement created on the surface 17 of the bank type sliding
portion 18 by the group of piezoelectric elements 4 to the moving
member 14 and moreover, it is possible to work workpieces more
easily and within a shorter time than in the working by grinding or
polishing and without any irregularity between the workpieces.
Further, it is possible to obtain the stable output of the
vibration type motor which has been impossible by the cutting work
alone.
57. As a method of working what provides the same shape, flatness
and surface roughness as those of the bank type sliding portion 16
in the present embodiment, it is also possible to use a press
molding method. Also in a method of pressing a mold, it is possible
to give an appropriate condition such as heating to thereby work
substantially the same shape as that of the bank type sliding
portion 16.
58. Fifth Embodiment
59. FIG. 3 shows the sliding portion of a vibration wave motor
which is a fifth embodiment of the present invention on an enlarged
scale. The construction of the vibration type motor and the shape
of each constituent member in this embodiment are basically similar
to those in the first embodiment and therefore, common constituents
are given the same reference characters as those in the first
embodiment and need not be described.
60. In the present embodiment, the moving member 14 and a friction
member 6" are made of the same materials as those in the first
embodiment, but the sliding portion 18 of the friction member 6" is
formed into a bank type having a ring-shaped cut-away on the inner
peripheral side thereof, and the surface (sliding surface) of this
bank type sliding portion 18 is in pressure contact with the moving
member 14 (ring portion 2).
61. The inner diameter ridgeline 18a on the surface of the bank
type sliding portion 18 is located more diametral outside than the
inner diameter side ridgeline 2a of the ring portion 2, and the
outer diameter ridgeline 18b of the bank type sliding portion 18 is
also located more diametral outside than the outer diameter
ridgeline 2b' of the ring portion 2. That is, the outer diameter
ridgeline 2b' of the ring portion 2 is on the bank type sliding
portion 18 of the friction member 6".
62. However, the outer diameter ridgeline 2b' of the ring portion 2
is formed into a rounded shape and therefore does not directly
contact with the bank type sliding portion 18. Thus, the upper
surface of the bank type sliding portion 18 is in non-contact with
the ridgelines 2a and 2b' of the ring portion 2.
63. Thereby, the hard and sharp ridgelines 2a and 2b' of the ring
portion 2 made of aluminum containing silicon can be prevented from
bearing against the bank type sliding portion 18 at a certain angle
even if the ring portion 2 is deformed by vibration. Accordingly,
it is possible to prevent the concentration of stress in the bank
type sliding portion 18 by the bearing against the ridgelines 2a
and 2b' of the ring portion 2 and sudden abrasion caused thereby
and further, a reduction in the starting torque and the instability
of the output of the motor due to the unstable contact between the
ridgelines 2a, 2b' and the bank type sliding portion 18.
64. Also, in the present embodiment, the bank type sliding portion
18 is formed by an ultrasonic working method. Specifically, as
shown in FIG. 5A, a bank type ultrasonic working horn 22 made of a
metal is first pressed against the surface of the friction member
6" with pressure of the order of 5.times.10.sup.7 N/m.sup.2 and
ultrasonic vibration is applied thereto, whereby the friction
member 6" is held for 10 to 30 seconds in a state in which the
temperature of the friction member 6" is 200 to 300.degree. C.,
thereby forming a bank type sliding portion 18 of a height of 50 to
200 .mu.m. Subsequently, as shown in FIG. 5B, a flat type
ultrasonic working horn 23 which is a mirror surface member made of
a metal is pressed against the surface 21 of the bank type sliding
portion 18 with pressure of the order of 3 .times.10.sup.7
N/m.sup.2, and ultrasonic vibration is applied thereto, whereby the
bank type sliding portion 18 is held for 10 seconds in a state in
which the temperature of the bank type sliding portion 18 is 200 to
300.degree. C., thereby effecting the smoothing of the surface
21.
65. Thereby, the surface 21 of the bank type sliding portion 18,
like the sliding portion 15 described in the second embodiment, is
worked into a smooth surface which is suitable for motor driving
and in which carbon fiber and PTFE resin are constructed
substantially on the same surface and which is free of
waviness.
66. Accordingly, it becomes possible to efficiently transmit minute
displacement created on the surface 21 of the bank type sliding
portion 18 by the group of piezoelectric elements 4 to the moving
member 14 and moreover, it is possible to work workpieces more
easily and within a shorter time than in the working by grinding or
polishing and without any irregularity between the workpieces.
Further, it is possible to obtain the stable output of the
vibration type motor which has been impossible by the cutting work
alone.
67. As a method of working what provides the same shape, flatness
and surface roughness as those of the bank type sliding portion 18
in the present embodiment, it is possible to use a press molding
method. Also, in a method of pressing a mold, it is possible to
give an appropriate condition such as heating to thereby work
substantially the same shape as that of the bank type sliding
portion 18.
68. Also, each of the above embodiments has been described with
respect to a case where the vibration member is provided with a
friction member, but the present invention can also be applied to a
vibration type driving apparatus in which the moving member
(contacting member) is provided with a friction member or both of
the vibration member and the moving member are provided with
friction members.
69. Further, the present invention can also be applied to a
vibration type driving apparatus having a friction member having
other sliding portion shape than the shapes in the above-described
embodiments.
70. Also, the present invention can be applied to other vibration
type driving apparatus (for example, of a linear type) than the
ring-like vibration type motor described in each of the above
embodiments.
71. As described above, in the above-described embodiments, design
is made such that the sliding surface of the friction member is
worked by pressing a mold and therefore, it is possible to obtain a
sliding surface having all of suitable flatness, surface roughness
and shape more easily and within a shorter time than in the case of
the prior-art working method of effecting the cutting work or the
polishing work, and further without any irregularity between
workpieces.
72. If the friction member is heated and thermoplastically deformed
when the mold is pressed, a sliding surface free of irregularity
can be obtained more easily and within a shorter time than when the
mold is simply pressed.
73. Also, if the sliding surface of the friction member is worked
by a press molding method or an ultrasonic working method, a
sliding surface free of irregularity can be obtained more easily
and within a shorter time than when the mold is simply pressed in a
high atmosphere.
74. Further, if the sliding surface of the friction member is
formed into a shape which is in non-contact with at least one
ridgeline portion on the sliding portion of a partner member to be
contacted (for example, a contacting member made of aluminum or the
like), the friction member can be prevented from being shaved by
the hard and sharp ridgeline portion of the partner member, or a
reduction in the starting torque and the instability of the output
of the driving apparatus by unstable contact can be prevented.
75. Other example of the friction member will now be described.
76. Another friction member for the vibration wave motor is
characterized by the use of a material comprising a resin
composition containing heat-resisting resin and mesophased pitch
carbon fiber.
77. That is, this friction member is characterized in that the kind
of the carbon fiber contained in the material thereof is a resin
material limited to mesophased pitch carbon fiber, whereby the
change in the abrasion loss of the friction member relative to a
temperature change is made as small as possible.
78. As the heat-resisting resin contained in the resin composition
used for the friction member, mention may be made of one or more
kinds of resin chosen from among fluororesin, polyimide resin,
alkyd resin, polyester resin, acryl resin, amino resin, polyamide
resin, epoxy resin, phenol resin, urea resin, polyurethane resin,
polyamide imide resin, polyether imide resin and silicone resin. Of
these resins, fluororesin and polyimide resin are preferable, and
fluororesin is particularly preferable. These resins have high
durability, heat resistance and hydrophobic property and therefore
provide a friction characteristic suitable for a vibration wave
motor (vibration type driving apparatus). Also, other additive, for
example, organic, inorganic or like fiber can be added to
heat-resisting resin to thereby achieve an improvement in
durability. Besides, another effect can be expected in reducing and
adding a solid lubricant.
79. As the mesophased pitch carbon fiber contained in the resin
composition used for the friction member of the present invention,
use is made of mesophased pitch carbon fiber in pitch carbon
fiber.
80. That is, generally carbon fiber has its property greatly
influenced by the starting raw material and is often distinguished
by the name of the raw material. At present, commercially available
on the industrial scale are two kinds, i.e., PAN carbon fiber using
acryl fiber (polyacrylonitrile, hereinafter referred to as "PAN")
as the starting raw material, and pitch carbon fiber made from a
pitch obtained by polymerizing tar obtained during the dry
distillation of coal or the residual oil of the distillation or
heat decomposition of crude oil by heat treatment, and PAN carbon
fiber overhelmingly occupies the share, but pitch carbon fiber is
commercially most available as inexpensive and universal carbon
fiber. It is further classified into what was subjected to
graphitic treatment and became graphitic fiber, and carbonic fiber
which is not subjected to graphitic treatment.
81. Pitch carbon fiber is further divided into two, and carbon
fiber made from mesophased pitch producing liquid crystal phase
(mesophase) optically exhibiting anisotropy when pitch is heated
and changes from the liquid phase to the solid phase is called
mesophased pitch carbon fiber, and what does not produce mesophase
and is made from optically isotropic pitch is called isotropic
pitch carbon fiber, and these two are distinguished from each
other. This difference between anisotropy and isotropy is
remarkable in the orientation of the minute texture (crystal) of
the carbon material and the degree thereof, and greatly changes the
property of carbon fiber. Above all, the mesophased pitch is noted
as a characteristic of the material because the minute texture of
carbon fiber has remarkable orientation in the axial direction or
the cross-sectional direction thereof and as the result, it is
possible to make the mechanical properties thereof, e.g., tensile
modulus of elasticity, compressive strength, etc. great.
82. However, it is very difficult to foresee the phenomenon of
general frictional abrasion as well as the phenomenon of special
frictional abrasion in the vibration wave motor from these
mechanical properties of carbon fiber, and by actually making
various kinds of materials and evaluating them by the use of a
vibration wave motor, and examining the difference therebetween, it
has been found that when the environment of use such as the
humidity condition of the vibration wave motor changes, mesophased
pitch carbon fiber is suitable as a material difficult to be
affected by humidity.
83. As specific examples of mesophased pitch carbon fiber used in
the present invention, trade name MC-249, produced by Osaka Gas
Co., Ltd., is mentioned for carbonic fiber, and trade name MG
II-249, produced by Osaka Gas Co., Ltd., is mentioned for graphitic
fiber subjected to graphitic treatment.
84. The content of mesophased pitch carbon fiber in the
aforementioned resin composition in the present invention is
usually 2 to 50% by weight, preferably 5 to 40% by weight, and more
preferably 10 to 30% by weight. For less than 2% by weight, the
friction member is liable to be affected by humidity, and when 50%
by weight is exceeded, the strength of the resin composition drops
and this is not preferable.
85. Besides the above-mentioned components, other additives can be
further added to the aforementioned resin composition in the
present invention. As the additives, mention may be made, for
example, of solid lubricants such as molybdenum trisulfide, carbon
powder and PTFE powder, high molecular materials such as polyimide
powder and other highly heat-resisting material powder, and
alumina, silicon carbide and other inorganic material powder. If
these additives are added, durability, the stability of frictional
abrasion and other various characteristics can be improved and this
is preferable.
86. The vibration wave motor of the present embodiment is a
vibration wave motor having a vibration member forming vibration,
and a contacting member frictionally contacting with this vibration
member and moved relative to the vibration member by the vibration,
characterized in that a friction member formed of a resin
composition containing the above-mentioned heat-resisting resin and
mesophased pitch carbon fiber is provided on the frictional
contacting portion of at least one of the vibration member and the
contacting member.
87. FIG. 8 is a cross-sectional view showing an embodiment of the
vibration wave motor of the present invention. In FIG. 8, the
reference numeral 101 designates a vibration member comprising
piezoelectric elements 104 as two groups of ring-like
electromechanical energy conversion elements polarized into a
plural portion and secured to one end surface of a ring-like
metallic elastic member 103 formed of stainless steel by a
heat-resisting epoxy resin adhesive agent, and a friction member
105 likewise secured to the other end surface of the metallic
elastic member 103.
88. On the other hand, a friction member 106a is provided on the
frictional sliding surface of a ring-like contacting member 106
formed of an aluminum alloy on a moving member 102 side. The
contacting member 106 is mounted on a support member 108 through a
rubber ring 107, and the support member 108 is fixed to an output
shaft 112 by a screw 111. The friction member 105 of the vibration
member 101 and the friction member 106a of the contacting member
106 are in contact with each other to thereby form a frictional
sliding surface, and are axially pressed by a pressing leaf spring
116 with a load of 5 kgf in total. The reference numeral 109
denotes a bearing, the reference numeral 113 designates a disk
plate for fixing the vibration member 101, reference numeral 118
designates a cover, the reference numerals 114 and 115 denote
pressure-giving collars, and the reference numeral 117 designates a
collar fixed to the output shaft 112 by a screw 111a.
89. Showing an example of the shape of the friction member 105, a
circumferential level difference 105a is provided on the friction
member 105, and the height C thereof is 0.15 mm. Also, the width a
of the portion of contact (sliding surface) between the friction
members 105 and 106a of FIG. 8 is 0.8 mm, and the diameter b of the
portion of contact (sliding surface) is 30 mm.
90. When an AC voltage of a frequency inherent to the vibration
member 101 is applied to the two groups of piezoelectric elements
104 alternately polarized in the direction of thickness thereof,
the vibration member 101 causes resonance and a travelling
vibration wave is created in the circumferential direction thereof,
and a frictional force acts on the friction member 106a through the
friction member 105, and the moving member 102 is rotatively
driven.
91. The friction member may be used as both or one of the friction
members 105 and 106a. When the friction member of the present
invention is used as one of them, an ordinary friction member can
be used as the other. As the ordinary friction member, mention may
be made of an aluminum-silicon alloy, hardened steel, ceramics, a
super hard alloy or the like which is hard and has toughness and is
almost free from abrasion.
92. As described above, in the construction of the present
invention, a friction member formed of a resin composition
containing heat-resisting resin and mesophased pitch carbon fiber
is used as the frictionally contacting friction member of at least
one of the contacting member and the vibration member of the
vibration wave motor and therefore, the vibration wave motor can be
driven stably against the influence of any change in humidity under
an environment of low humidity or high humidity and an environment
having changes in humidity, and the stabilization of the life of
the vibration wave motor also becomes possible, and the reliability
of the vibration wave motor can be more enhanced.
93. Also, the present invention can be used in various kinds of
apparatuses with a vibration wave motor provided with the
above-described friction member as a drive source, and as specific
examples of the apparatuses, mention may be made of optical
apparatuses such as cameras, business machines such as printers and
copying apparatuses, and automobile-related apparatuses such as
power windows and active suspensions.
94. Sixth Embodiment
95. The friction member was made in the following manner.
96. Carbon fiber (short fiber) shown in Table 1 and 20% by weight
of carbon fiber (short fiber) subjected to graphitic treatment were
uniformly dispersed in and mixed with 80% by weight of
polytetrafluoroethylene (hereinafter referred to as PTFE) resin
powder, whereafter they were pressed with pressure of 500
kg/cm.sup.2 to thereby make a molded body having a diameter of 8
cm, an inner diameter of 1 cm and a height of 10 cm, and it was
baked at a temperature of 360.degree. C. for 3 hours to thereby
obtain a cylindrical baked member. The cylindrical baked member was
cut by a cutting apparatus to thereby make a cylindrical sheet
having a thickness of 0.5 mm. The sheet was punched and was used as
the ring-like friction member 105 of FIG. 8.
97. The dimensions of the short fiber used were a diameter of about
10 .mu.m to 13 .mu.m and a length of about 100 .mu.m to 130
.mu.m.
1TABLE 1 Sample No. kind of carbon fiber 1 mesophased pitch
(carbonic) 2 mesophased pitch + graphitic treatment (graphitic) 3*
isotropic pitch (carbonic) 4* isotropic pitch + graphitic treatment
(graphitic) 5* polyacrylonitrile (carbonic)
98. (Note 1) In Table 1, Nos. 1 and 2 show embodiments and Nos. 3,
4 and 5 (mark *) show comparative examples.
99. (Note 2) In Table 1, the mesophased pitch carbon fiber of
sample No. 1 is trade name MC-249 produced by Osaka Gas Co.,
Ltd.
100. The mesophased pitch+graphitic treatment of sample No. 2 is
trade name MG II-249 produced by Osaka Gas Co., Ltd.
101. The isotropic pitch carbon fiber of sample No. 3 is trade name
SG-249 produced by Osaka Gas Co., Ltd.
102. The isotropic pitch+graphitic treatment of sample No. 4 is
trade name LXX-941 produced by Osaka Gas Co., Ltd.
103. The polyacrylonitrile carbon fiber of sample No. 5 is trade
name Toreka MLD-300 produced by Toray Industries, Inc.
104. In Table 1, Nos. 1, 3 and 5 are fiber which was carbonized and
became carbonic after each raw material was insolubilized or
stabilizing-treated (treated at 800 to 1200.degree. C. in
inactivated ambient gas) after fiber forming, and Nos. 2 and 4 are
fiber which was further subjected to graphitic treatment at 2000 to
3000.degree. C. in inactivated ambient gas and became carbonic.
105. The shape of the friction member 105, as shown in FIG. 8, is
such that the friction member 105 is provided with a
circumferential level difference 105a, the height of which is 0.15
mm. Also, the width a of the portion of contact (sliding surface)
between the friction members 105 and 106a is 0.8 mm and the
diameter b of the portion of contact (sliding surface) is 30
mm.
106. The friction member 105 was fixed to a metallic elastic member
103 formed of stainless steel by an adhesive agent (of the epoxy
thermosetting type), and as the friction member 106a of the
contacting member 106 formed of aluminum, use was made of one
formed of tungsten carbide containing cobalt by thermal spraying to
make the vibration wave motor shown in FIG. 8.
107. The evaluation of the friction member described below is
obtained as a value obtained by the vibration wave motor being
driven at 300 rpm in rotating speed and torque of 300 g-cm for 100
hours on end. The result is shown in FIG. 9.
108. FIG. 9 shows the abrasion loss of the friction member 105
formed of PTFE material containing the carbon fiber of Table 1
after 100 hours of driving when the humidity was changed to 1% to
95% at a temperature of 40.degree. C. The abrasion loss is a value
obtained by measuring the height of the level difference 105a of
FIG. 8 by a height gauge, and subtracting the height after driving
in advance from the height of the level difference 105a before
driving.
109. As can be seen from FIG. 9, the friction members of Nos. 1 and
2, as compared with the friction members of Nos. 3 to 5, are very
small in the change (increase) in abrasion at both low humidity and
high humidity, as compared with humidity of 40 to 70%.
110. Also, No. 2, as compared with No. 1, is generally great in
abrasion loss. No. 2 is graphitic and relatively soft and its
abrasion loss seems to have become relatively great.
111. Seventh Embodiment
112. As in Embodiment 6, by the use of the carbon fibers of Nos. 1
to 5 shown in Table 1, the resin material was made into polyimide
resin, and as in Embodiment 6, 88% by weight of polyimide resin
powder and 12% by weight of carbon material were uniformly
dispersed and mixed together and a cylindrical baked member
obtained by pressing and heating the mixture at 350.degree. C. for
10 minutes while molding it into a cylindrical shape having a
diameter of 8 cm, an inner diameter of 1 cm and a height of 10 cm
with molding pressure of 2000 kgf/cm.sup.2 was cut to thereby make
a sheet having a thickness of 0.5 mm. The sheet was punched, and
was used as the ring-like friction member 105 of FIG. 8 in a
vibration wavemotor, and evaluation similar to that in Embodiment 6
was done. The result is shown in FIG. 10. In FIG. 10, Nos. 1 and 2
show the embodiments, and Nos. 3, 4 and 5 show comparative
examples.
113. As shown in FIG. 10, the abrasion loss of the friction member
is generally greater than in the aforedescribed Embodiment 6, and
this shows that polyimide resin is affected by humidity, and at low
humidity and high humidity, as compared with humidity of 40% to
70%, the tendency of abrasion loss becoming greater as in
Embodiment 6 is seen. It seems that the change in the abrasion loss
due to the influence of humidity is basically attributable to the
difference between the kinds of carbon fiber. However, as the
phenomenon of frictional abrasion, the difference between the resin
materials appears in Embodiments 6 and 7, and for example, the
coefficient of friction of polyimide resin is about 0.4 and is
greater than 0.2 which is the coefficient of friction of
fluororesin and therefore, correspondingly, the torque of the motor
becomes greater and the performance of the motor becomes better,
but the fluctuation of the coefficient of friction of polyimide
resin becomes as great as about .+-.0.1, and as compared with about
.+-.0.03 of fluororesin, the fluctuations of the torque and
rotation of the motor are correspondingly increased.
114. Also, as a small quantity of additive material, it is possible
to add a solid lubricant such as molybdenum disulfide, a high
molecular material such as polyimide power or an inorganic material
such as alumina to the resin of Embodiments 6 and 7 to thereby give
durability, the stability of frictional abrasion and other various
characteristics. Above all, the material having molybdenum
disulfide or polyimide powder added thereto exhibited lower
abrasion loss than No. 1 of FIG. 9 and No. 1 of FIG. 10.
115. In both of Embodiments 6 and 7, the friction member 106a which
is the partner member of the resin material is a hard film, and it
is judged that little or no abrasion occurs thereto and the
evaluation is not affected thereby. The use of other hard material,
e.g. ceramics, also led to a similar result.
116. The friction member of the present invention can be used as
one of the friction member 105 and the friction member 106a, and in
Embodiments 6 and 7, the friction member 105 and the friction
member 106a may be interchanged with each other, and the friction
member of the present invention may be used as the friction member
106a of the contacting member 106, and a hard film or the like may
be used as the friction member 105 of the metallic elastic member
103. Also, the friction of the present invention may be used as
each of the friction member 105 and the friction member 106a.
117. In the above-described embodiments, there has been shown an
example in which the friction member is applied to the disc-like
vibration wave motor shown in FIG. 8, but besides it, a frictional
contacting surface provided with the above-described friction
member may be formed on a bar-like vibration wave motor by a
similar method.
118. FIG. 11 is a schematic view of an apparatus having the
vibration wave motor shown in FIG. 8 as a drive source. The
reference numeral 123 designates a gear having a large gear 123a
and a small gear 123b, and the large gear 123a is in meshing
engagement with a gear 120 on the vibration wave motor side. The
reference numeral 124 denotes a driven member, for example, a lens
barrel, and the small gear 123b of the gear 123 is in meshing
engagement with a gear 124a provided on the outer peripheral
portion of the lens barrel, and is rotated by the driving force of
the motor. On the other hand, an encoder slit plate 125 is mounted
on the gear 123, and the rotation of the gear 123 is detected by a
photocoupler 126, and the rotation and stoppage of the motor are
controlled, for example, for auto-focusing.
119. As described above, according to the sixth and seventh
embodiments, mesophased pitch carbon fiber is used as the carbon
fiber contained in the resin which is the friction member, whereby
the long-term use of the vibration wave motor under an environment
of low humidity or high humidity becomes possible and in addition,
the stabilization of the life of the vibration wave motor under an
environment having a humidity change also becomes possible, and the
reliability of the vibration wave motor is more enhanced.
120. Also, there can be provided an apparatus using a vibration
wave motor excellent in the friction characteristic to the
above-mentioned humidity change.
* * * * *