U.S. patent number RE36,604 [Application Number 08/494,148] was granted by the patent office on 2000-03-07 for scroll type compressor having curved surface portions between the shaft and bearing means.
This patent grant is currently assigned to Mitsubishi Denki Kabushiki Kaisha. Invention is credited to Norihide Kobayashi, Toshiyuki Nakamura, Hiroshi Ogawa, Masahiko Oide, Keiju Sakaino, Fumiaki Sano, Yoshinori Shirafuji, Takashi Yamamoto.
United States Patent |
RE36,604 |
Sano , et al. |
March 7, 2000 |
Scroll type compressor having curved surface portions between the
shaft and bearing means
Abstract
A scroll type compressor comprising: a crankshaft having an
eccentric shaft portion formed thereon; an orbiting scroll which is
given torque by the crankshaft through the eccentric shaft portion;
and bearing means for rotatably supporting the crankshaft; wherein
at least one of the eccentric shaft portion and the bearing means
is constituted by a rotatably engaged bushing and a curved surface
portion.
Inventors: |
Sano; Fumiaki (Shizuoka,
JP), Oide; Masahiko (Shizuoka, JP),
Nakamura; Toshiyuki (Shizuoka, JP), Kobayashi;
Norihide (Shizuoka, JP), Ogawa; Hiroshi
(Shizuoka, JP), Shirafuji; Yoshinori (Shizuoka,
JP), Yamamoto; Takashi (Shizuoka, JP),
Sakaino; Keiju (Shizuoka, JP) |
Assignee: |
Mitsubishi Denki Kabushiki
Kaisha (Tokyo, JP)
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Family
ID: |
26376160 |
Appl.
No.: |
08/494,148 |
Filed: |
June 23, 1995 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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Reissue of: |
834220 |
Feb 12, 1992 |
05222881 |
Jun 29, 1993 |
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Foreign Application Priority Data
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Mar 4, 1991 [JP] |
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3-37055 |
Aug 27, 1991 [JP] |
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3-214997 |
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Current U.S.
Class: |
418/55.1;
403/121; 464/106; 418/57; 418/55.5; 418/151; 418/182; 403/124 |
Current CPC
Class: |
F04C
18/0215 (20130101); F04C 29/0057 (20130101); F16D
3/20 (20130101); F01C 21/02 (20130101); Y10T
403/32647 (20150115); F04C 2240/601 (20130101); Y10T
403/32622 (20150115); F16C 2360/42 (20130101); F04C
23/008 (20130101); F04C 2240/807 (20130101) |
Current International
Class: |
F04C
18/02 (20060101); F04C 29/00 (20060101); F01C
21/00 (20060101); F16D 3/20 (20060101); F16D
3/16 (20060101); F01C 21/02 (20060101); F04C
018/04 (); F16C 011/02 (); F16C 032/00 (); F16D
003/10 () |
Field of
Search: |
;418/55.1,55.5,55.6,57,151,182 ;464/106,147 ;403/121,124 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 192 351 |
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Aug 1986 |
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EP |
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0 317 270 |
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May 1989 |
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EP |
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84 34 234 |
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May 1986 |
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DE |
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58-172402 |
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Oct 1983 |
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JP |
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62-143002 |
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Sep 1987 |
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JP |
|
2149784 |
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Jun 1990 |
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JP |
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Other References
Patent Abstracts of Japan, vol. 8, No. 9 (M-268), Jan. 14, 1984, JP
58-172402, Oct. 11, 1983. .
Patent Abstracts of Japan, vol. 8, No. 224 (M-331), Oct. 13, 1994,
JP 59-105987, Jun. 19, 1984. .
Patent Abstracts of Japan, vol. 14, No. 395 (M-1016), Aug. 27,
1990, JP 2-149784, Jun. 8, 1990..
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Primary Examiner: Vrablik; John J.
Attorney, Agent or Firm: Oblon, Spivak, McClelland, Maier
& Neustadt, P.C.
Claims
We claim:
1. A scroll type compressor comprising:
a rotatable crankshaft having an eccentric shaft portion formed
thereon;
a fixed scroll;
an orbiting scroll cooperable with said fixed scroll to compress
gas; and
bearing means rotatably connecting said orbiting scroll to said
eccentric shaft portion so as to orbitally drive said orbiting
scroll, wherein said bearing means comprises:
a) a bushing having an outer periphery fitted in said orbiting
scroll, and
b) a non-rotatable connection between said bushing and said
eccentric shaft portion, said non-rotatable connection including a
portion curved in the direction of the axis of rotation of the
crankshaft.
2. The scroll type compressor of claim 1 wherein said non-rotatable
connection further comprises cooperating flat surfaces on said
bushing and said eccentric shaft portion.
3. A scroll type compressor according to claim 2,
.Iadd.wherein said crankshaft further comprises a main shaft
portion and a sub shaft portion, .Iaddend.further comprising:
an upper balance weight and a lower balance weight placed on the
opposite ends of .[.the.]. .Iadd.a .Iaddend.rotor to be balanced
against a centrifugal force which is generated by an orbiting
movement of the orbiting scroll; and
.[.a.]. .Iadd.the .Iaddend.rotor coupled to said crankshaft for
driving said crankshaft;
.[.the bearing means comprising.]. bearing devices which are
provided in a main frame and a sub frame to support the crankshaft
at .[.its.]. .Iadd.said .Iaddend.main shaft portion and .Iadd.said
.Iaddend.sub shaft portion via further bushings;
wherein in order to prevent partial contact from occurring due to
flexture-deformation of the crankshaft in the bearing .[.parts for
supporting the main shaft and sub shaft portions of the
crankshaft.]. .Iadd.devices.Iaddend., at least one of the main
shaft portion and the sub shaft portion has a central portion
provided with a barrel shaped band portion to present a convex
surface in the entire peripheral direction, the band portion has a
peripheral portion engaged with the further bushings through a
minute gap.
4. A scroll type compressor according to claim 2, .Iadd.wherein
said crankshaft further comprises a main shaft portion and a sub
shaft portion, .Iaddend.further comprising:
an upper balance weight and a lower balance weight placed on the
opposite ends of .[.the.]. .Iadd.a .Iaddend.rotor to be balanced
against a centrifugal force which is generated by an orbiting
movement of the orbiting scroll; and
.[.the bearing means comprising.]. bearing devices which are
provided in a main frame and a sub frame to support the crankshaft
at .[.its.]. .Iadd.said .Iaddend.main shaft portion .Iadd.via a
bushing .Iaddend.and .Iadd.at said .Iaddend.sub shaft portion
.[.via further bushings.].;
wherein in order to prevent partial contact from occurring due to
flexture-deformation of the crankshaft .[.in the bearing devices.].
.Iadd.at said main shaft portion.Iaddend., the main shaft portion
has a central portion provided with a barrel shaped band portion to
present a convex surface in the entire peripheral direction, the
band portion has a peripheral portion engaged with the
.[.further.]. bushing .Iadd.at said main shaft portion
.Iaddend.through a minute gap, and the .[.further.]. bushing
.Iadd.of said main shaft portion .Iaddend.is coupled to the
crankshaft by a pin in terms of a rotational direction; and
wherein the bearing device for supporting the sub shaft portion of
the crankshaft is constructed by a rolling bearing to prevent
partial contact from occurring in the bearing device due to
flexture-deformation of the crankshaft.
5. A scroll type compressor comprising:
a main frame;
a sub frame.Iadd.; .Iaddend.
a crankshaft rotatably mounted in said main frame and said sub
frame via bushings, said crankshaft having an eccentric shaft
portion formed thereon, wherein the main frame and sub frame are
mutually spaced along the axis of the crankshaft;
a fixed scroll;
an orbiting scroll cooperable with the fixed scroll to compress
gas, said orbiting scroll being drivingly mounted on said eccentric
shaft portion;
.[.a.]. .Iadd.an .Iaddend.electric motor mounted between said main
frame and said sub frame and having a rotor coupled to said
crankshaft for driving said crankshaft; upper and lower balance
weights placed at opposite ends of said rotor for balancing
orbiting movement of said orbiting scroll;
a pin rotatably coupling at least one of the bushings to .[.a
respective one of the main frame and.]. the .[.sub frame.].
.Iadd.crankshaft.Iaddend.; and
a circumferentially continuous barrel shaped band portion
presenting a convex surface and formed on said crankshaft to engage
at least one of the bushings through a minute gap.
6. A scroll type compressor comprising:
a main frame;
a sub frame;
a crankshaft rotatably mounted in said main frame and said sub
frame via bushings, said crankshaft having an eccentric shaft
portion formed thereon, wherein the main frame and sub frame are
spaced along the axis of the crankshaft;
a fixed scroll;
an orbiting scroll operable with the fixed scroll to compress gas,
said orbiting scroll being drivingly mounted on said eccentric
shaft portion;
.[.a.]. .Iadd.an .Iaddend.electric motor mounted between said main
frame and said sub frame and having a rotor coupled to said
crankshaft for driving said crankshaft;
upper and lower balance weights placed at opposite ends of said
rotor for balancing orbiting movement of said orbiting scroll;
and
two couples formed between said crankshaft and the bushing of said
main frame, each of said couples comprising a flat surface on one
of said crankshaft and said bushing, and a surface curved in the
direction of the axis of rotation of the crankshaft and engaged
with said flat surface. .Iadd.
7. A scroll type compressor comprising:
a rotatable crankshaft having an eccentric shaft portion formed
thereon, wherein said crankshaft further comprises a main shaft
portion and a sub shaft portion;
a fixed scroll;
an orbiting scroll cooperable with said fixed scroll to compress
gas;
bearing means rotatable connecting said orbiting scroll to said
eccentric shaft portion so as to orbitally drive said orbiting
scroll, wherein said bearing means comprises:
a) a bushing having an outer periphery fitted in said orbiting
scroll, and
b) a non-rotatable connection between said bushing and said
eccentric shaft portion, said non-rotatable connection including a
portion curved in the direction of the axis of rotation of the
crankshaft;
an upper balance weight and a lower balance weight placed on the
opposite ends of a rotor to be balanced against a centrifugal force
which is generated by an orbiting movement of the orbiting scroll;
and
the rotor coupled to said crankshaft for driving said
crankshaft;
bearing devices which are provided in a main frame and a sub frame
to support the crankshaft at said main shaft portion and said sub
shaft portion via further bushings;
wherein in order to prevent partial contact from occurring due to
flexure-deformation of the crankshaft in the bearing devices, at
least one of the main shaft portion and the sub shaft portion has a
central portion provided with a barrel shaped band portion to
present a convex surface in the entire peripheral direction, the
band portion has a peripheral portion engaged with the further
bushings through a minute gap. .Iaddend..Iadd.
8. A scroll type compressor comprising:
a rotatable crankshaft having an eccentric shaft portion formed
thereon, wherein said crankshaft further comprises a main shaft
portion and a sub shaft portion;
a fixed scroll;
an orbiting scroll cooperable with said fixed scroll to compress
gas;
bearing means rotatably connecting said orbiting scroll to said
eccentric shaft portion so as to orbitally drive said orbiting
scroll, wherein said bearing means comprises:
a) a bushing having an outer periphery fitted in said orbiting
scroll, and
b) a non-rotatable connection between said bushing and said
eccentric shaft portion, said non-rotatable connection including a
portion curved in the direction of the axis of rotation of the
crankshaft;
an upper balance weight and a lower balance weight placed on the
opposite ends of a rotor to be balanced against a centrifugal force
which is generated by an orbiting movement of the orbiting scroll;
and
bearing devices which are provided in a main frame and a sub frame
to support the crankshaft at said main shaft portion via a bushing
and at said sub shaft portion;
wherein in order to prevent partial contact from occurring due to
flexure-deformation of the crankshaft at said main shaft portion,
the main shaft portion has a central portion provided with a barrel
shaped band portion to present a convex surface in the entire
peripheral direction, the band portion has a peripheral portion
engaged with the bushing at said main shaft portion and the bushing
is coupled to the crankshaft by a pin in terms of a rotational
direction; and
wherein the bearing device for supporting the sub shaft portion of
the crankshaft is constructed by a ball bearing to prevent partial
contact from occurring in the bearing device for supporting the sub
shaft portion of the crankshaft due to flexure-deformation of the
crankshaft. .Iaddend..Iadd.
9. The scroll type compressor of claim 4 wherein said rolling
bearing comprises a ball bearing. .Iaddend.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a scroll type compressor, and more
particularly to a scroll type compressor which is utilized in
refrigeration and air conditioning systems.
A conventional scroll type compressor, which has been disclosed in
e.g. Japanese Unexamined Patent Publication No. 80088/1988, is
constructed as shown in FIG. 17. In FIG. 17, reference numeral 1
designates a fixed scroll. Reference numeral 2 designates an
orbiting scroll. Reference numeral 3 designates a crankshaft.
Reference numeral 4 designates a driving bushing which is rotatably
mounted in a bearing part 2a formed in the orbiting scroll 2.
Reference numeral 5 designates an Oldham's ring. Reference numeral
6 designates a main frame. Reference numeral 6a designates a main
bearing which is formed in the main frame 6. Reference numeral 7
designates an electric motor stator. Reference numeral 8 designates
an electric motor rotor. Reference numeral 9 designates a sub
frame. Reference numeral 9a designates a sub bearing which is
formed in the sub frame 9. Reference numeral 10 designates a
hermetic shell. Reference numeral 11 designates an intake tube
which directs a refrigerant from outside. Reference numeral 12
designates a discharge tube. Reference numeral 13 designates a
lubricating oil which is stored in a bottom part of the hermetic
shell. The crankshaft 3 has an eccentric shaft portion 3a formed at
an upper portion. The eccentric shaft portion 3a is fitted into the
bearing part 2a through the driving bushing 4, the bearing part 2a
being formed on a base plate undersurface of the orbiting scroll 2.
The crankshaft 3 has a main shaft portion 3b and a sub frame shaft
portion 3c formed on its upper end and lower end, respectively, so
that the main shaft portion 3b is supported by the main bearing 6a
of the main frame 6 and the sub shaft part 3c is supported by the
sub bearing 9a of the sub frame 9. Reference numerals 14 and 15
designate an upper balance weight and a lower balance weight,
respectively, which are attached on the opposite sides (in the
vertical direction) of the electric motor rotor 8.
Now, the operation of the conventional scroll type compressor of
FIG. 17 will be explained. Torque which is generated by the
electric motor is transmitted by the crankshaft 3 which is
shrinkage fitted into the rotor 8. The torque is further
transmitted to the orbiting scroll 2 through the eccentric shaft
portion 3a and the driving bushing 4. The Oldham's ring 5 which
works as a rotation preventing mechanism causes the orbiting scroll
2 to carry out such a revolution movement that the orbiting scroll
moves along a circular orbit. The revolution movement changes the
volume of a compression chamber formed between the fixed scroll 1
and the orbiting scroll 2 to compress the refrigerant.
The refrigerant enters the hermetic shell 10 from an outer
refrigeration cycle through the intake tube 11. The refrigerant is
compressed in the compression chamber to have a high pressure, and
then flows out in the outer refrigeration cycle through the
discharge tube 12. By the way, a thrust direction force of
compressive loads of the refrigerant which are applied to the
orbiting scroll 2 is supported by a thrust bearing surface 6b on an
upper end surface of the main frame 6. On the other hand, a radial
direction force F.sub.g of the compressive loads is transmitted to
the crankshaft 3 through the driving bushing 4 as shown in FIG. 18.
The crankshaft 3 is supported by the main bearing 6a formed in a
lower boss of the main frame 6, and by the sub bearing 9a formed in
the sub frame 9.
The upper balance weight 14 and the lower balance weight 15 which
are mounted on the opposite ends of the rotor 8 are arranged to be
balanced against a centrifugal force F.sub.c1 which is generated by
the revolution movement of the orbiting scroll 2. Centrifugal
forces F.sub.c2 and F.sub.c3 which are generated by the upper
balance weight 14 and the lower balance weight 15 are also
supported by the main bearing 6a and the sub bearing 9a. The
lubricating oil 13 which is stored in the bottom part of the
hermetic shell 10 is fed to sliding parts such as the bearing parts
and the compression chamber by a centrifugal force caused by the
rotation of the crankshaft 3.
In the conventional scroll type compressor, the radial direction
force F.sub.9 which is applied to the orbiting scroll in the
compression stroke is exerted on the eccentric shaft portion 3a
which is at the upper end of the crankshaft 3, as explained.
However, because the eccentric shaft portion 3a as the exerting
point projects from the main bearing 6a of the main frame 6 in the
direction remote from the bearing 9a, the compressive load F.sub.g
causes the crankshaft 3 to be flexture-deformed as shown in FIG.
19. When the crankshaft 3 is flexure-deformed, the eccentric shaft
portion 3a is inclined in the bearing part 2a of the orbiting
scroll 2, the main shaft portion 3b is inclined in the main bearing
6a of the main frame 6, or the sub shaft part 3c is inclined in the
sub bearing 9a of the sub frame 9. This creates e.g. a problem in
that load carrying capacities of the respective bearing parts can
deteriorate to wear or seize the bearing parts.
In particular, recently, the application of a variable speed
operation to a compressor under an inverter control is accompanied
by extension of the operating range of the compressor from a low
speed to a high speed in e.g. air conditioning systems. In a low
speed operating area, an oil film is difficult to be formed in the
bearings. In a high speed operating area, the centrifugal forces
F.sub.c1, F.sub.c2 and F.sub.c3 which are generated by the orbiting
scroll 2, the upper balance weight 14 and the lower balance weight
15 are increased to further enlarge the flexture-deformation of the
crankshaft 3, making the problem more noticeable, which is demanded
to be solved.
SUMMARY OF THE INVENTION
It is an object of the present invention to solve the problem, and
to provide a ,highly reliable scroll type compressor capable of
preventing a bearing part from being damaged due to wear, seize or
the like even if a crankshaft is flexture-deformed by a radial
direction force in compressive loads which are exerted to an
orbiting scroll during a compression stroke.
According to a first aspect of the present invention, there is
provided a scroll type compressor comprising a crankshaft having an
eccentric shaft portion formed thereon; an orbiting scroll which is
given torque by the crankshaft through the eccentric shaft portion;
and bearing means for rotatably supporting the crankshaft; wherein
at least one of the eccentric shaft portion and the bearing means
is constituted by a rotatably engaged bushing and a curved surface
portion.
According to a second aspect of the present invention, there is
provided a scroll type compressor comprising a crankshaft having an
eccentric shaft portion formed thereon; an orbiting scroll which is
given torque by the crankshaft through the eccentric shaft portion,
the bearing means comprising bearing devices which are provided in
a main frame and a sub frame to support the crankshaft at its main
shaft portion and sub shaft portion.
In the second aspect, it is advisable that the scroll type
compressor further comprises an electric motor rotor arranged at an
intermediate position in an axial direction; and an upper balance
weight and a lower balance weight placed on the opposite ends of
the rotor to be balanced against a centrifugal force which is
generated by an orbiting movement of the orbiting scroll; wherein
in order to prevent partial contact from bringing about due to
flexture-deformation of the crankshaft in the bearing devices, at
least one of the main shaft portion and the sub shaft portion has a
central portion provided with a barrel shaped band portion to
present a convex surface in the entire peripheral direction, the
band portion has a peripheral portion engaged with the bushing
through a minute gap, and the bushing is coupled to the crankshaft
by a pin in terms of a rotational direction.
In the second aspect, it is also advisable that the scroll type
compressor further comprises an electric motor rotor arranged at an
intermediate position in an axial direction; and an upper balance
weight and a lower balance weight placed on the opposite ends of
the rotor to be balanced against a centrifugal force which is
generated by an orbiting movement of the orbiting scroll; wherein
in order to prevent partial contact from bringing about due to
flexture-deformation of the crankshaft in the bearing devices, the
main shaft portion has a central portion provided with a barrel
shaped band portion to present a convex surface in at least one of
a reactive force direction of a compressive load generated in a
compression chamber formed between the orbiting scroll and the
fixed scroll, and a reactive force direction of a centrifugal load
generated by a revolution movement of the orbiting scroll and
rotary movements of the upper and lower balance weights, and the
main shaft portion is engaged with a cylindrical bushing through a
minute gap.
In the first aspect, it is advisable that the scroll type
compressor further comprises an electric motor rotor arranged at an
intermediate position in an axial direction; and the bushing
engaged with the eccentric shaft portion and rotatably mounted in a
bearing part of the orbiting scroll; wherein in order to prevent
partial contact from arising due to flexture-deformation of the
crankshaft in the bearing part, two couples of oppositely engaged
surface portions are formed on the eccentric shaft portion and the
bushing, one of the couples are constituted by flat surfaces,
either of the oppositely engaged surface portions in the other
couple is constituted by a curved surface which is curved along an
axial direction, and the other engaged surface portion is
constituted by a flat surface.
It is further advisable that the scroll type compressor further
comprises an upper balance weight and a lower balance weight placed
on the opposite ends of the rotor to be balanced against a
centrifugal force which is generated by an orbiting movement of the
orbiting scroll; and the bearing means comprising bearing devices
which are provided in a main frame and a sub frame to support the
crankshaft at its main shaft- portion and sub shaft portion;
wherein in order to prevent partial contact from bringing about due
to flexture-deformation of the crankshaft in the bearing parts for
supporting the main shaft and sub shaft portions of the crankshaft,
at least one of the main shaft portion and the sub shaft portion
has a central portion provided with a barrel shaped band portion to
present a convex surface in the entire peripheral direction, the
band portion has a peripheral portion engaged with the bushing
through a minute gap.
It is still further advisable that the scroll type compressor
comprises an upper balance weight and a lower balance weight placed
on the opposite ends of the rotor to be balanced against a
centrifugal force which is generated by an orbiting movement of the
orbiting scroll; and the bearing means comprising bearing devices
which are provided in a main frame and a sub frame to support the
crankshaft at its main shaft portion and sub shaft portion; wherein
in order to prevent partial contact from bringing about due to
flexture-deformation of the crankshaft in the bearing devices, the
main shaft portion has a central portion provided with a barrel
shaped band portion to present a convex surface in the entire
peripheral direction, the band portion has a peripheral portion
engaged with the bushing through a minute gap, and the bushing is
coupled to the crankshaft by a pin in terms of a rotational
direction; and wherein the bearing device for supporting the su-b
shaft portion of the crankshaft is constructed by a rolling bearing
to prevent partial contact from bringing about in the bearing
device due to flexture-deformation of the crankshaft.
In the first aspect, it is advisable that the scroll type
compressor further comprises the bushing engaged with the eccentric
shaft portion and rotatable mounted in the orbiting scroll; wherein
the eccentric shaft portion has a flat surface formed on a part of
its peripheral surface, and a curved surface formed on a location
at the side opposite to the flat surface to be curved along an
axial direction, the bushing has an inner peripheral surface
engageable with the eccentric shaft portion, and the inner
peripheral surface has flat surfaces formed on locations
corresponding to the flat surface and the curved surface.
In the first aspect, it is also advisable that the scroll type
compressor further comprises the bushing engaged with the eccentric
shaft portion and rotatably mounted in the orbiting scroll; wherein
the eccentric shaft portion has two flat surfaces formed on its
peripheral surface at opposite sides with respect to the center
thereof, the driving bushing has an inner peripheral surface
engageable with the eccentric shaft portion, the inner peripheral
surface has a flat surface formed thereon at a location
corresponding to one of the eccentric shaft portion flat surfaces
and a curved surface formed thereon at a location corresponding to
the other eccentric shaft portion flat surface, the curved surface
being curved along an axial direction.
In the first aspect, it is further advisable that the scroll type
compressor further comprises the bushing engaged with the eccentric
shaft portion and rotatably mounted in the orbiting scroll; wherein
the eccentric shaft portion has a flat surface formed on a part of
its peripheral surface, and a curved surface formed on a location
at the side opposite to the flat surface to be curved along an
axial direction, the bushing has an inner peripheral surface
engageable with the eccentric shaft portion, and the inner
peripheral surface has a curved surface formed thereon at a
location corresponding to the eccentric shaft portion curved
surface and a flat surface formed thereon at a location
corresponding to the eccentric shaft portion flat surface.
In the scroll type compressor according to the present invention, a
radial direction force is exerted on the orbiting scroll during a
compression stroke, and the force is applied to the eccentric shaft
portion which is provided on top of the crankshaft. As a result,
the crankshaft is subject to flexture-deformation. In accordance
with the present invention, the scroll type compressor is provided
with such bearing means that the eccentric shaft portion, the main
shaft portion or the sub shaft portion of the crankshaft has a
curved surface, or has a central portion provided with a barrel
shaped band portion to present a convex surface in the entire
peripheral direction. The curved surface or the band portion allows
a driving bushing or a cylindrical bushing to be in touch with the
curved surface or the barrel shaped surface so as to be axially
rotatable and movable. Such an arrangement can drive the crankshaft
in a parallel state with respect to each bearing. As a result,
partial contact can be prevented from bringing about in each
bearing, thereby avoiding occurrence of wear and seize. In
addition, a bearing load capacity can be prevented from
deteriorating, providing a highly reliable scroll type compressor
capable of preventing a bearing from being damaged.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal sectional view showing a first embodiment
of a scroll type compressor according to the present invention;
FIG. 2 is a top plan view showing an eccentric shaft portion on top
of a crankshaft in the scroll type compressor of FIG. 1, the
eccentric shaft portion having a driving bushing fitted
thereon;
FIG. 3 is a sectional view taken along the line III--III of FIG. 2
wherein the driving bushing which is fitted thereon in the
embodiment of FIG. 2 is mounted in a bearing part of an orbiting
scroll;
FIG. 4 is a cross sectional view showing a state wherein the
crankshaft is inclined in a bearing structure of the crankshaft
eccentric shaft portion according to the embodiment of FIG. 3;
FIG. 5 is a perspective view showing another structure of the
bearing for the crankshaft eccentric shaft portion;
FIG. 6 is a perspective view showing another structure of the
bearing for the crankshaft eccentric shaft portion;
FIG. 7 is a cross sectional view showing another structure of the
bearing for the crankshaft eccentric shaft portion;
FIG. 8 is a cross sectional view showing another bearing structure
of the crankshaft eccentric shaft portion;
FIG. 9 is a cross sectional view showing a bearing structure for
supporting a main shaft portion of the crankshaft in accordance
with a second embodiment of the scroll type compressor;
FIG. 10 is a cross sectional view showing another structure of the
bearing for the crankshaft main shaft portion;
FIG. 11 is an exploded and perspective view showing another
structure of the bearing for the crankshaft main shaft portion;
FIG. 12 is a cross sectional view showing a bearing structure for
supporting the crankshaft sub bearing portion in accordance with
another embodiment of the scroll type compressor;
FIG. 13 is a cross sectional view schematically showing a state
wherein the crankshaft is inclined in the bearing structure of the
crankshaft sub shaft part of FIG. 12;
FIG. 14 is a cross sectional view showing another structure of the
bearing for the crankshaft sub shaft portion;
FIG. 15 is a cross sectional view showing another structure of the
bearing for the crankshaft sub shaft portion;
FIG. 16 is a cross sectional view schematically showing a state
wherein the crankshaft is inclined in the bearing structure of the
crankshaft sub shaft portion of FIG. 15;
FIG. 17 is a longitudinal sectional view showing a conventional
scroll type compressor;
FIG. 18 is a schematic view showing the directions of compressive
loads and centrifugal forces of balance weights which are exerted
on a crankshaft in the conventional scroll type compressor; and
FIG. 19 is a schematic view showing how the crankshaft is inclined
in the conventional scroll type compressor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The scroll type compressor according to the present invention will
be described in detail, referring to embodiments shown in the
accompanying drawings. In FIG. 1, there is shown the scroll type
compressor 20 according to a first embodiment of the present
invention. In FIG. 1 showing the scroll type compressor 20 of the
first embodiment, similar or corresponding parts are indicated by
the same reference numerals as the conventional scroll type
compressor shown in FIG. 17, and explanation of those parts will be
omitted for the sake of simplicity.
The scroll type compressor 20 of the embodiment includes a
crankshaft 21 which has an electric motor rotor 8 fixed by
shrinkage fit at an intermediate portion thereof in its axial
direction. The crankshaft 21 has an upper portion formed integrally
with an eccentric shaft portion 22 which is fitted into a bearing
part 2a of an orbiting scroll 2 to give torque directly to the
orbiting scroll 2. The crankshaft has a main shaft portion 23
formed thereon at a lower position than the eccentric shaft portion
and a sub shaft portion 24 formed thereon at a lower end, the main
shaft portion 23 being supported by a main shaft bearing 6a of a
main frame 6, and the sub shaft portion 24 being supported by a sub
bearing 9a of a sub frame 9. Bearing devices, i.e. bearing
structures for supporting the eccentric shaft portion 22, the main
shaft portion 23 and the sub shaft portion 24 formed on the
crankshaft 21 will be explained one after another.
In FIGS. 2 and 3, there are shown cross sectional views which
schematically show a bearing structure of the eccentric shaft
portion 22 formed on the upper end of the crankshaft 21 in the
scroll type compressor 20 in accordance with the first embodiment.
As can be clearly seen in FIG. 2, the eccentric shaft portion 22
has an external shape that is formed to be based on a circle whose
center O.sub.2 lies at a location shifted by a predetermined length
with respect to the center O.sub.1 of the crankshaft 21. When the
line connecting the two centers O.sub.1 and O.sub.2 is defined as
Y--Y, and a line perpendicular to the line Y--Y is defined as X--X,
the eccentric shaft portion 22 has a flat surface 22a formed on a
peripheral surface thereof in the direction along the line Y--Y.
The eccentric shaft portion 22 also has a curved surface 22b formed
on the peripheral surface at the side opposite the flat surface
22a, the curved surface 22b presenting a convex surface outwardly
along an axial direction.
On the other hand, the eccentric shaft portion 22 has a driving
bushing 25 engaged thereon in such a manner that the driving
bushing 25 is rotatably mounted in the bearing part 2a of the
orbiting scroll 2. The driving bushing 25 has a bore formed therein
to be engageable with the eccentric shaft portion 22. The inner
peripheral surface of the bore is formed with flat surfaces 25a and
25b at locations which correspond to the flat surface 22a and the
curved surface 22b of the eccentric shaft portion 22, respectively.
The eccentric shaft portion 22 is put into the bore of the driving
bushing 25 with a predetermined gap therebetween as shown in FIG.
3. Even if the eccentric shaft portion 22 is as shown in FIG. 4
when the eccentric shaft portion 22 having such a structure causes
the orbiting scroll 2 to carry out an orbiting movement through the
driving bushing 25, the driving bushing 25 can rotate with a
parallel position to the bearing in the bearing part 2a of the
orbiting scroll 2, without being inclined with the eccentric shaft
portion 22. This is because the curved surface 22b is in touch with
the corresponding flat surface 25b of the driving bushing 25 to be
rotatable and movable in the axial direction. This arrangement can
eliminate partial contact from occurring in the bearing part 2a of
the orbiting scroll 2, prevent bearing performance from
deteriorating, decrease wear and be free from seizure.
Referring now to FIG. 5, there is shown a perspective view of
another embodiment of the eccentric shaft portion which is formed
on the top end of the crankshaft 21. In this embodiment, the
eccentric shaft portion is indicated by reference numeral 26. The
eccentric shaft portion 26 is basically similar to the eccentric
shaft portion 22 shown in FIG. 2. The eccentric shaft portion 26
has an outer shape which is formed based on a circle with the
center O.sub.2. The center O.sub.2 is shifted at a predetermined
distance from the center O.sub.1 of the crankshaft 21. The
eccentric shaft portion 26 includes an eccentric pin 21a which has
a flat surface 26a formed on a peripheral surface at a location
which extends along the line connecting between the two centers
O.sub.1 and O.sub.2. The eccentric pin 21a has the peripheral
surface formed with a cutout 26b on the side opposite the flat
surface 26a, the cutout being U-shaped as viewed from the top.
Into the cutout 26b is inserted a separate coupling member 27 from
upward, the coupling member having a front end formed with a curved
surface 27a and a rear end formed with a flat surface 27b as
clearly shown in FIG. 5. The coupling member 27 has such a shape
which is obtained by cutting off a part of the peripheral portion
of a cylindrical body in its longitudinal direction. The coupling
member 27 is mounted into the cutout 26b of the eccentric shaft
portion 26 in such a manner that the curved surface 27a projects to
be convex in an outward direction along the axial direction of the
eccentric shaft portion 26. By this arrangement, the eccentric
shaft portion 26 can have a substantially same structure as the
eccentric shaft portion 22 shown in FIG. 2. A driving bushing which
is identical to the one shown in FIG. 2 can be used to be engaged
with the eccentric shaft portion 26, and explanation of the driving
bushing for the eccentric shaft portion 26 will be omitted for the
sake of simplicity.
Referring now to FIG. 6, there is shown another embodiment of the
driving bushing which is mounted onto the eccentric shaft portion
formed on the top of the crankshaft 21. The driving bushing of this
embodiment is indicated by reference numeral 28. The driving
bushing 28 has a bore 28a formed therein to be basically engageable
with the basic circle of the eccentric shaft portion like the
driving bushing 25 shown in FIG. 2. The bore 28a has a flat surface
28b and a cutout 28c formed on an inner peripheral surface thereof
in such a manner that the flat surface 28b is perpendicular to a
diametrical center line of the bore and the cutout 28c is opposite
to the flat surface 28b. Into the cutout 28c is inserted a separate
coupling member whose shape is identical to the coupling member 27
shown in FIG. 5. The coupling member 27 is mounted in such a manner
that the curved surface 27a projects to be convex in an inward
direction with respect to the axial direction of the driving
bushing 28. When the driving bushing 28 is used, the eccentric
shaft portion which has the driving bushing 28 engaged with and
mounted to it is different from the eccentric shaft portion shown
in FIG. 2 in that the outer peripheral surface on the side opposite
one of the flat surfaces 22a is not curved but a flat surface. It
means that the eccentric shaft portion and the driving bushing have
such a relation that two couples of oppositely engaged portions are
formed on the opposite peripheral surfaces (the outer peripheral
surface of the eccentric shaft portion and the inner peripheral
surface of the driving bushing) at locations along the line
connecting between the center O.sub.1 of the crankshaft and the
center O.sub.2 of the eccentric shaft portion, that one of the
couples is constituted by flat surfaces (e.g. the flat surfaces 22a
and 25a as shown in FIG. 2), and that either of the oppositely
engaged surface portions in the other couple is constituted by a
curved surface as stated above, and the other engaged surface
portion is constituted by a flat surface.
When the separate coupling member 27 is prepared and is mounted
into the cutout formed in the eccentric shaft portion or the
driving bushing as shown in FIGS. 5 and 6, it is possible to
eliminate difficulty which is involved by working in a direct and
precise manner the curved surface which curves in a direction along
the axis of the eccentric shaft portion outer peripheral surface of
the crankshaft. It is also possible to eliminate similar difficulty
with respect to the inner peripheral surface of the engaged bore of
the driving bushing. In addition, such a solution can not only
improve processability and processing precision but also decrease a
processing cost. The concept of the curved surface which is formed
on either of the one couple of oppositely engaged surface portions
between the eccentric shaft portion and the driving bushing
includes such an arrangement that the eccentric shaft portion has a
groove 29 formed therein to be perpendicular to the axial direction
thereof, and the groove 29 has a cylindrical roller 30 inserted
therein.
In the case of FIG. 7, the cylindrical roller 30 which is a general
purpose part can be used to remarkably improve processability,
thereby allowing a processing cost to be lowered. As shown in FIG.
8, the other couple of oppositely engaged surface portions can have
a highly hard member 31 such as a hardened steel arranged between
the curved surface (e.g. the curved surface 22b of the eccentric
shaft portion 22) and the corresponding flat portion (e.g. the flat
surface 25b of the driving bushing 25) to ensure enough hardness on
both contact portions. In this case, the driving bushing can be
made from a material having relatively lower hardness, such as a
sintered material. Such an arrangement can offer an advantage in
that reliability is ensured while a processing cost is
decreased.
Referring now to FIG. 9, there is shown a bearing structure which
supports the main shaft portion 23 of the crankshaft 21 at the main
bearing part 6a of the main frame 6 in the scroll type compressor
20. The main shaft portion 23 has a central portion provided with a
barrel shaped band portion 32 to present a convex surface in the
entire peripheral direction. The maximum projected portion which
lies at the central portion of the barrel portion 32 has a
cylindrical bushing 33 engaged on the periphery thereof with a
minute gap. The cylindrical bushing 33 is seated on a seat surface
21a which is formed at a lower portion of the main shaft portion of
the crankshaft 21.
The cylindrical bushing 33 is rotatably within the main bearing
part 6a of the main frame 6, and rotates together with the
crankshaft 21. To accomplish this, a bottom surface 33a of the
cylindrical bushing and the seat surface 21a are formed with holes
in the axial direction, and a connecting pin 34 is press fit into
each of the holes. This arrangement allows the cylindrical bushing
33 to rotate together with the crankshaft 21. Either of the holes
which the connecting pin 34 is press fit into is formed as an
elongated hole which is elongated in a radial direction because the
crankshaft 21 is inclined with respect to the cylindrical bushing
33 when the crankshaft 21 receives a compressive load F.sub.g.
Although in the case of FIG. 9 the hole which is formed in the
sheet surface 21a is elongated, the hole which is formed in the
bottom surface 33a of the cylindrical bushing 33 may be
elongated.
In accordance with the bearing structure which is constituted by
the main shaft portion 23 of the crankshaft 21 having the central
portion provided with the barrel shaped band portion to present the
convex surface in the entire peripheral direction, and the
cylindrical bushing 33 arranged in the main bearing part 6a of the
main frame 6, the contacting points between the curved surface on
the band portion 32 of the main shaft portion 23 and the
cylindrical bushing 33 can move following a flexing direction and a
flexing magnitude of the crankshaft 21 though the compressive load
F.sub.g and centrifugal loads F.sub.c1, F.sub.c2 and F.sub.c3 which
are applied on the crankshaft 21 are substantially rectangular in
their directions, and their magnitudes vary depending on the
operating conditions of the compressor to change the flexing
direction of the crankshaft 21. Irrespectively of the operating
conditions of the compressor, the cylindrical bushing 33 can rotate
while constantly maintaining a parallel state to the main bearing
part 6a of the main frame 6 (maintaining such a state that the
central rotating axis of the cylindrical bushing 33 corresponds to
the central axis of the main bearing part 6a).
Such an arrangement can offer a highly reliable bearing structure
which prevents a bearing load carrying capacity from falling and is
free of wear, seizure or the like in the bearing.
By the way, when the cylindrical bushing 33 has moved its
contacting point on the curved surface of the band portion on the
main shaft portion 23 of the crankshaft 21, a gap is apt to be
formed between the sheet surface 21a and the bottom surface 33a of
the cylindrical bushing 33. However, the gap can be minimized by
selecting suitable curvature of the curved surface of the band
portion 32. In this manner, an oil for lubricating the cylindrical
bushing 33 can be prevented from flowing out of the gap.
Although in the bearing structure of the crankshaft main shaft
portion 23 stated above, the seat surface 21a to the cylindrical
bushing 33 is formed on the crankshaft 21, the seat surface may be
an upper surface 14a of an upper balance weight 14 as shown in FIG.
10. In this case, the crankshaft 21 can have the outer diameter
formed in a size smaller than the main shaft portion outer diameter
throughout its entire length, thereby improving machinability of
the crankshaft.
As shown in FIG. 11, the main shaft portion 23 of the crankshaft 21
may be formed in such a manner that two surfaces which are located
in a reactive force direction of the compressive load direction
F.sub.g and in a reactive force direction of centrifugal loads
F.sub.c1, F.sub.c2 and F.sub.c3 (F.sub.c3 is not shown in FIG. 11
but is understood to be the same as shown in FIG. 18) have curved
surfaces 23a and 23b formed on central portions thereof to present
convex surfaces, that a cylindrical bushing 35 which has flat
surfaces 35a and 35b formed on the inner peripheral surface thereof
at locations corresponding to the curved surfaces 23a and 23b, and
that the main shaft portion 23 has the cylindrical bushing 35
engaged therewith. Such an arrangement allows the cylindrical
bushing 35 to follow flexure-deformation of the crankshaft 21 due
to the compressive load F.sub.g, and the centrifugal loads
F.sub.c1, F.sub.c2 and F.sub.c3, and to move its contacting points
on the curved surfaces 23a and 23b of the main shaft portion 23 of
the crankshaft 21. As a result, the cylindrical bushing can be
rotated, maintaining a parallel state to the main bearing part 6a
of the main frame 6, and can offer an advantage similar to the
bearing structure stated above. In this case, the two curved
surfaces 23a and 23b can also work to connect the crankshaft 21 and
the cylindrical bushing 35 in a circumferential direction to need
no connecting pin.
Referring now to FIG. 12, there is shown a bearing structure which
supports the crankshaft 21 by a sub bearing part 9a in a sub frame
9 in a scroll type compressor 20. In the bearing structure, a sub
shaft portion 24 of the crankshaft 21 has a central portion
provided with a barrel shaped band portion 36 to present a convex
surface like the bearing structure for supporting the main shaft
portion 23 of the crankshaft 21 in the main bearing part 6a of the
main frame 6 stated above. The bearing structure is constituted by
engaging a cylindrical bushing 37 with the sub shaft portion 24
with a minute gap around the outer circumference of the band
portion.
In order that the cylindrical bushing 37 can rotate with the
crankshaft 21 as one unit, a connecting pin 38 has one end press
fit into a hole formed in the cylindrical bushing in a radial
direction, and has the other end engaged in an elongated hole 24a
which is formed in the crankshaft 21 to be long in the axial
direction. In this manner, the cylindrical bushing and the
crankshaft are interconnected in the circumferential direction. In
FIGS. 1 and 12, reference numeral 16 designates an oil supply pump,
and reference numeral 17 designates a cover for the oil supply
pump.
In accordance with such an bearing structure wherein the sub shaft
portion 24 of the crankshaft 21 is supported by the sub bearing
part 9a in the sub frame 9, when the crankshaft 21 has
flexture-deformation caused therein as shown in FIG. 13, the
contacting points between the sub shaft portion 24 of the
crankshaft 21 and the cylindrical bushing 37 arranged around the
outer circumference of the sub shaft portion 24 moves on the barrel
shaped band portion which presents the convex surface in the
central portion of the sub shaft portion 24. As a result, the
cylindrical bushing 37 can rotate while maintaining a parallel
state to a boss of the sub frame 9, i.e. the sub bearing part 9a.
Such an arrangement can prevent a bearing load carrying capacity
from lowering, and offer a highly reliable bearing structure which
is free from wear, seizure or the like in the bearing.
Although in the bearing structure for supporting the sub shaft
portion 24 of the crankshaft 21 stated above, the sub shaft portion
24 of the crankshaft 21 has the central portion provided with the
barrel shaped band portion 36 to present the convex surface, and
the cylindrical bushing 37 is engaged on the outer circumference of
the band portion 36, the bearing structure may be constituted by a
cylindrical bushing 39 whose inner peripheral surface has a central
portion provided with a barrel shaped band portion 39a to present a
convex surface, and which is engaged with the crankshaft 21 as
shown in FIG. 14.
Although the connecting pin 38 which have the one end press fit
into the hole in the cylindrical bushing 37 is engaged in the
elongated hole 24a formed in the crankshaft 21 to offer a
connecting mechanism for the crankshaft 21 and the cylindrical
bushing 37 in their rotary direction in the embodiment described
earlier, such an arrangement wherein an elongated hole is formed in
the cylindrical bushing 39, a hole is formed in the sub shaft
portion 24 of the crankshaft 21, and the connecting pin 38 has one
end press fit into the hole in the sub shaft portion 24 and the
other end engaged in the elongated hole may be adopted.
Although in the bearing structure for supporting the sub shaft
portion 24 of the crankshaft 21 as stated earlier, the sub shaft
portion 24 or the cylindrical bushing 39 has the central portion
provided with the barrel shaped band portion to present the convex
surface, the sub shaft portion 24 of the crankshaft 21 may be
supported by the sub bearing part 9a by use of a rolling bearing as
shown in FIG. 15 because a compressive load and a centrifugal load
which are applied on the sub bearing part 9a of the sub frame 9 are
generally smaller than those applied to the eccentric shaft portion
22 and the main shaft portion 23. When the rolling bearing 40 (deep
groove ball bearing in FIG. 15) is used, an inner ring 40a is
mounted to the crankshaft 21 by clearance fit because the scroll
type compressor is subjected to a load fixed to an inner ring (a
load direction rotates, the inner ring rotates and an outer ring is
standstill).
When a load is applied to the crankshaft 21 in a bearing structure
for supporting the shaft portion 24 of the crankshaft 21 by means
of the rolling bearing 40, the inner ring 40a is inclined with
respect to a load direction as shown in FIG. 16 to follow the
inclination of the crankshaft 21. The inclination of the crankshaft
21 does not damage a load carrying capacity or reliability of the
rolling bearing 40. Even if the crankshaft 21 is inclined, a load
carrying capacity or reliability of the bearing is prevented from
lowering.
Although in the scroll type compressor according to the embodiment
shown in FIG. 1, the bearing structure for supporting the eccentric
shaft portion 22, the main shaft portion 23 and the sub shaft
portion 24 of the crankshaft 21 are constituted by arranging the
driving bushing 25 or the cylindrical bushing 33 or 37, and forming
the bearing surfaces of the respective shaft portions in such
convex curved surfaces that the respective bearing surfaces work as
parallel bearings to the respective bushing, at least one of the
eccentric shaft portion, the main shaft portion and the shaft
portion of the crankshaft 21 can be supported by the bearing
structure stated above to prevent a bearing load carrying capacity
in the shaft portion from lowering.
* * * * *