Rotary expansible chamber devices – Working member has planetary or planetating movement – Helical working member – e.g. – scroll
Reexamination Certificate
1999-11-02
2001-02-20
Denion, Thomas (Department: 3748)
Rotary expansible chamber devices
Working member has planetary or planetating movement
Helical working member, e.g., scroll
C418S151000
Reexamination Certificate
active
06190147
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a rotation balancing mechanism for balancing orbiting scrolls of scroll-type compressors.
FIGS. 9 and 10
show a prior art scroll-type compressor. The scroll type compressor includes a motor housing
15
for a motor
12
and a compressor housing
31
for a compression mechanism
13
. A support frame
16
is attached to the front of the motor housing
15
. The compressor housing
31
is fixed to the support frame
16
. The motor
12
includes a drive shaft
18
. The compression mechanism
13
includes a fixed scroll
32
and an orbiting scroll
33
, which includes a base plate
36
. A crankshaft
51
is located between the drive shaft
18
and the orbiting scroll
33
to cause the orbiting scroll
33
to orbit. Bearing sleeves
63
are formed on the support frame
16
. Bearing sleeves
66
are formed on the rear and peripheral surface of the base plate
36
of the orbiting scroll
33
. Follower crankshafts
61
arc located between the bearing sleeves
63
and the outer bearing sleeves
66
. The follower crankshafts
61
permit orbital movement of the orbiting scroll
33
and prevent rotation about its own axis of the orbiting scroll
33
.
The orbiting scroll
33
orbits with the crank shaft
51
while rotation about its own axis of the orbiting scroll
33
is prevented by the follower crankshafts
61
. This movement draws refrigerant gas from a suction chamber
39
, compresses the gas in a compression chamber
38
, and discharges the gas to an external refrigerant circuit through a discharge port
41
. The compression chamber
38
is defined by the fixed scroll
32
and the orbiting scroll
33
.
The center of gravity of the orbiting scroll
33
is located at an axis O
2
of an eccentric pin
53
. When the orbiting scroll
33
orbits during the operation of the compressor, a centrifugal force is applied to the eccentric pin
53
. The centrifugal force is based on the moment of inertia about the axis O
1
of the crankshaft
51
(drive shaft
18
). That is, centrifugal force FT (WT*R
1
*&ohgr;
2
) is applied to the eccentric pin
53
. R
1
represents the distance between the axis O
1
of the drive shaft
18
and the axis O
2
of the eccentric pin
53
, which is the orbiting radius of the orbiting scroll
33
. The mass of the orbiting scroll
33
that orbits the axis O
2
is represented by WT. The orbiting speed (angular velocity) of the orbiting scroll
33
is represented by &ohgr;. Therefore, a central balance weight
57
, which has a mass W, is integrally attached to the crankshaft
51
. The balance weight is located on the opposite side of crankshaft
51
from the eccentric pin
53
with respect to the axis O
1
. The central balance weight
57
achieves dynamic balancing, that is, the net centrifugal force applied to the crankshaft
51
is null.
In the prior art scroll-type compressor shown in
FIGS. 9 and 10
, since the central balance weight
57
is attached only to the crankshaft
51
, the following problem occurs. As shown in
FIG. 10
, to offset the centrifugal force FT of the orbiting scroll
33
with the single central balance weight
57
, the center of gravity G
1
of the central balance weight
57
must be radially spaced from the axis O
1
of the drive shaft
18
and the central balance weight
57
cannot be compact. Therefore, the central path C
1
, which is the path of the periphery of the central balance weight
57
, is relatively large.
On the other hand, the peripheral surfaces of the outer bearing sleeves
66
, which support the eccentric pins
65
of the follower crankshafts
61
, must not interfere with the central path C
1
. As a result, journal shafts
62
of the follower crankshafts
61
and outer bearing sleeves
66
are obliged to be located to extend radially from peripheral rim of the base plate
36
of the orbiting scroll
33
as shown in FIG.
10
. Accordingly, to avoid interference between the outer paths C
2
, which are the paths of the peripheral surfaces of the outer bearing sleeves
66
, and the inner surface of the housing
31
, projections
31
a
must be formed on the housing
31
. This increases radial size of the compressor housing
31
.
Japanese Unexamined Utility Model Publication No. 1-61480 shows a compressor that is similar to the compressor of
FIGS. 9 and 10
. As shown in
FIG. 11
, the follower crankshafts
61
of the compressor shown in the publication include balance weights
81
, which compensate for the mass imbalance of the crankshafts
61
when orbiting. In this case, since each balance weight
81
is formed perpendicular to a corresponding eccentric pin
65
, trim weights
82
, which nullify the centrifugal force of the corresponding follower crankshaft
61
, are attached to the follower crankshafts
61
. Therefore, the journal shafts
62
are rearwardly extended by the trim weights
82
.
In the above scroll-type compressor of
FIG. 11
, only the balance weight that is attached to the drive crankshaft opposes the centrifugal force caused by the mass of the orbiting scroll. Therefore, the follower crankshafts
61
and the outer bearing sleeves
66
extend radially outward from the base plate
36
of the orbiting scroll
33
, which increases the size of the compressor housing
31
. In addition, the trim weights
82
complicate the structure and increase the mass of the compressor.
SUMMARY OF THE INVENTION
A first objective of the present invention is to provide a rotation balancing mechanism of an orbiting scroll for a scroll-type compressor that reduces the size of the compressor.
A second objective of the present invention is to provide a rotation balancing mechanism for an orbiting scroll that simplifies the structure and reduces the mass.
A third objective of the present invention is to provide a rotation balancing mechanism for an orbiting scroll that that enables smooth orbital movement of the orbiting scroll with a drive crankshaft.
To achieve the above objectives, the present invention provides a scroll type compressor structured as follows. The compressor includes a housing, a fixed scroll, and an orbiting scroll. The fixed scroll is fixed to the housing. The fixed scroll has a base and a spiral portion formed on the base. The orbiting scroll has a base and a spiral portion formed on the base to engage the fixed scroll. The orbiting scroll has a center axis offset from that of the fixed scroll. A driving crankshaft is connected to the base of the orbiting scroll to produce orbital motion. Follower crankshafts are connected to the housing and the base of the orbiting scroll to follow the motion of the orbiting scroll and to prevent the orbiting scroll from rotating about its own axis. Balance weights for balancing a moment of inertia of the orbiting scroll about the driving crankshaft. The balance weights are located on at least the follower crankshafts.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.
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patent: 5556269 (1996-09-01), Suzuki et al.
patent: 5690480 (1997-11-01), Suzuki et al.
patent: 5842842 (1998-12-01), Callens et al.
patent: 5951271 (1999-09-01), DuMoulin et al.
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Ban Takashi
Kimbara Masahiko
Denion Thomas
Kabushiki Kaisha Toyoda Jidoshokki Seisakusho
Morgan & Finnegan L.L.P.
Trieu Theresa
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