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| United States Patent | 5613841 |
| Link to this page | http://www.wikipatents.com/5613841.html |
| Inventor(s) | Bass; Mark (Sidney, OH);
Doepker; Roy J. (Lima, OH);
Caillat; Jean-Luc M. (Dayton, OH);
Warner; Wayne R. (Piqua, OH) |
| Abstract | A scroll-type machine is disclosed which is particularly well suited for
use as a compressor in refrigeration and air conditioning systems and
incorporates a unique arrangement for modulating the capacity thereof. In
one group of embodiments the capacity of the scroll-type machine is
modulated by relative axial movement between the scroll members so as to
form a leakage path across the wrap tips and opposed end plates. In
another group of embodiments, modulation is achieved by reducing the
orbital radius of one of the scroll members to thereby form a leakage path
across the flank surfaces of the wraps. Both types of scroll separation
may be accomplished in a time pulsed manner to thereby enable a full range
of modulation with the duration of the loading and unloading periods being
selected to maximize the efficiency of the overall system. A motor control
arrangement is also disclosed which may be used with either of the
modulation methods mentioned above to increase the efficiency of the motor
during periods of reduced load. Additionally, either of the modulation
arrangements mentioned above may be combined with a delayed suction form
of capacity modulation with or without the motor control feature to
thereby achieve better operating efficiency under certain conditions. |
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Title Information  |
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Drawing from US Patent 5613841 |
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Capacity modulated scroll machine |
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| Publication Date |
March 25, 1997 |
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Title Information |
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Description |
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BACKGROUND AND SUMMARY OF THE INVENTION
The present invention is related to capacity modulation of compressors and
more particularly to capacity modulation of scroll-type compressors.
Capacity modulation is often a desirable feature to incorporate in air
conditioning and refrigeration compressors in order to better accommodate
the wide range of loading to which the systems may be subjected. Many
different approaches have been utilized for providing this capacity
modulation feature ranging from controlling of the suction inlet to
bypassing discharge gas back to the suction inlet. With scroll-type
compressors, capacity modulation has often been accomplished via a delayed
suction approach which comprises providing ports at various positions
which, when opened, allow the compression chambers formed between the
intermeshing scroll wraps to communicate with the suction gas supply
thereby delaying the point at which compression of the suction gas begins.
This method of capacity modulation actually reduces the compression ratio
of the compressor. While such systems are effective at reducing the
capacity of the compressor, they are only able to provide a predetermined
amount of compressor unloading, the amount of unloading being dependent
upon the positioning of the unloading ports along the wraps. While it is
possible to provide multiple step unloading by incorporating a plurality
of such ports at different locations, this approach becomes costly and
requires additional space to accommodate the separate controls for opening
and closing each set of ports.
The present invention, however, overcomes these deficiencies in that it
enables virtually a continuous range of unloading from 100 percent or full
capacity down to virtually zero capacity utilizing only a single set of
controls. Further, the system of the present invention enables the
operating efficiency of the compressor and/or refrigeration system to be
maximized for any degree of compressor unloading desired.
In the present invention, compressor unloading is accomplished by
cyclically effecting axial or radial separation of the two scroll members
for predetermined periods of time during the operating cycle of the
compressor. More specifically, the present invention provides an
arrangement wherein one scroll member is moved axially or radially toward
and away from the other scroll member in a pulsed fashion to cyclically
provide a leakage path across the tips or flanks of the wraps from higher
pressure compression pockets defined by the intermeshing scroll wraps to
lower pressure pockets and ultimately back to suction. By controlling the
relative time between sealing and unsealing of the scroll wrap tips or
flanks, virtually any degree of compressor unloading can be achieved with
a single control system. Further, by sensing various conditions within the
refrigeration system, the duration of compressor loading and unloading for
each cycle can be selected for a given capacity such that overall system
efficiency is maximized. For example, if it is desired to operate the
compressor at 50 percent capacity, this can be accomplished by operating
the compressor alternately in a loaded condition for five seconds and
unloaded for five seconds or loaded for seven seconds and unloaded for
seven seconds, one or the other of which may provide greater efficiency
for the specific operating conditions being encountered.
The various embodiments of the present invention described below provide a
wide variety of arrangements by which one scroll member may be axially or
radially reciprocated with respect to the other to accommodate a full
range of compressor unloading. The ability to provide a full range of
capacity modulation with a single control system as well as the ability to
select the duration of loaded and unloaded operation cooperate to provide
an extremely efficient system at a relatively low cost.
Additionally, in order to even further improve system efficiency in some
applications, it may be desirable to combine a delayed suction type of
capacity modulation with the pulsed unloading approach mentioned above.
For example, when operating conditions are such that system pressures just
downstream of the discharge valve are at a level below the full load
design level, the compression ratio of the compressor will result in
pressure of the compressed fluid as it is discharged from the compression
chamber being too high, a condition known as over-compression. The most
efficient way to reduce capacity under these conditions is to reduce the
compression ratio of the compressor and hence the pressure of the
compressed fluid exiting the compression chamber such that it is equal to
or only slightly above the system pressure just downstream of the
discharge valve thus eliminating the lost work due to over-compression.
However, if a further reduction in capacity is indicated by system
condition once the over-compression condition has been eliminated, the use
of a pulsed type of capacity modulation will be more efficient as it will
avoid creation of a condition known as under-compression, that being a
situation where the pressure of the compressed fluid as it leaves the
compression chamber being below that of the system just downstream of the
discharge valve. Thus, the present invention also includes a system in
which both pulsed and delayed suction capacity modulation approaches are
combined which result in even greater efficiencies for systems likely to
encounter such operating conditions than could be achieved by either of
the two capacity modulation approaches alone.
Additionally, the present invention may also incorporate a motor control
module which will operate to control various operating parameters thereof
to enhance its operating efficiency during periods when the motor load is
reduced due to unloading of the compressor.
Additional advantages and features of the present invention will become
apparent from the subsequent description and the appended claims taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a section view of a scroll-type refrigeration compressor in
accordance with the present invention;
FIG. 2 is a fragmentary section view of a scroll-type refrigeration
compressor showing another embodiment of the present invention;
FIG. 3 is a view similar to that of FIG. 2 but showing the compressor in an
unloaded condition;
FIG. 4 is a fragmentary section view of a scroll-type refrigeration
compressor showing a further embodiment of the present invention;
FIG. 5 is an enlarged view of the valve arrangement incorporated in the
embodiment shown in FIG. 4;
FIG. 6 is also a fragmentary section view of a scroll-type refrigeration
compressor showing another embodiment of the present invention;
FIGS. 7 through 15 are all fragmentary section views of refrigeration
compressors in accordance with the present invention in which the orbiting
scroll member is axially reciprocated to accomplish compressor unloading;
FIGS. 16 through 22 are all fragmentary section views of refrigeration
compressors in accordance with the present invention in which the
non-orbiting scroll member is axially reciprocated to accomplish
compressor unloading;
FIGS. 23 through 28 are all fragmentary section views of refrigeration
compressors in accordance with the present invention in which the scroll
members are co-rotating;
FIGS. 29 through 30 are both fragmentary section views of additional
embodiments of refrigeration compressors all in accordance with the
present invention in which the non-orbiting scroll member is reciprocated;
and
FIG. 31 is a section view of yet another embodiment of a scroll-type
compressor in accordance with the present invention adapted to be driven
by an external power source;
FIGS. 32 through 34 are fragmentary section view of additional embodiments
of scroll-type compressors in accordance with the present invention;
FIG. 34A is an enlarged fragmentary view of the valving arrangement shown
in FIG. 34 and enclosed within circle 34A;
FIG. 35 is a fragmentary section view of a further embodiment of a
scroll-type compressor in accordance with the present invention;
FIG. 36 is also a fragmentary section view of yet a further embodiment of
the present invention showing an arrangement for radially unloading of the
compressor in accordance with the present invention;
FIG. 37 is a section view of the crank pin and drive bushing employed in
the embodiment of FIG. 36, the section being taken along lines 37--37
thereof;
FIG. 38 is a section view of the embodiment shown in FIG. 36, the section
being taken along lines 38--38 thereof;
FIG. 39 is a view similar to that of FIG. 36 but showing the compressor in
an unloaded condition;
FIG. 40 is a fragmentary section view showing a modified version of the
embodiment of FIG. 36, all in accordance with the present invention;
FIG. 41 is a fragmentary section view showing a portion of a scroll-type
compressor incorporating another embodiment of the radial unloading
arrangement of FIG. 36, all in accordance with the present invention;
FIG. 42 is a section view similar to that of FIG. 38 but showing the
embodiment of FIG. 41;
FIG. 43 is a fragmentary section view showing yet another embodiment of the
present invention;
FIG. 44 is a view of a portion of the embodiment shown in FIG. 43 in an
unloaded condition;
FIG. 45 is a schematic showing a means for reducing motor power consumption
during periods when the compressor is operating in an unloaded condition
in accordance with the present invention; and
FIG. 46 is a section view of a compressor incorporating both cyclical
scroll wrap separation and delayed suction unloading, all in accordance
with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring now to the drawings and in particular to FIG. 1, there is shown a
hermetic scroll compressor in accordance with the present invention
indicated generally at 10. Scroll compressor 10 is generally of the type
described in assignee's U.S. Pat. No. 5,102,316, the disclosure of which
is incorporated by reference, and includes an outer shell 12 within which
is disposed a driving motor including stator 14 and rotor 16, a crankshaft
18 to which rotor 16 is secured, upper and lower bearing housings 20, 22
for rotatably supporting crankshaft 18 and compressor assembly 24.
Compressor assembly 24 includes an orbiting scroll member 26 supported on
upper bearing housing 20 and drivingly connected to crankshaft 18 via
crank pin 28 and drive bushing 30. A second non-orbiting scroll member 32
is positioned in meshing engagement with scroll member 26 and axially
movably secured to upper bearing housing 20 by means of a plurality of
bolts 34 and associated sleeve members 36. An Oldham coupling 38 is
provided which cooperates between scroll members 26 and 32 to prevent
relative rotation therebetween.
A partition plate 40 is provided adjacent the upper end of shell 12 and
serves to define a discharge chamber 42 at the upper end thereof.
In operation, as orbiting scroll member 26 orbits with respect to scroll
member 32, suction gas is drawn into shell 12 via suction inlet 44 and
thence into compressor 24 through inlet 46 provided in non-orbiting scroll
member 32. The intermeshing wraps provided on scroll members 26 and 32
define moving fluid pockets which progressively decrease in size and move
radially inwardly as a result of the orbiting motion of scroll member 26
thus compressing the suction gas entering via inlet 46. The compressed gas
is then discharged into discharge chamber 42 via discharge port 48
provided in scroll member 32 and passage 50. A suitable pressure
responsive discharge valve 51 is preferably provided seated within
discharge port 48.
Scroll member 32 is also provided with an annular cylindrical recess 52
formed in the upper surface thereof. One end of a generally irregularly
shaped cylindrical member 54 within which passage 50 is provided projects
into cylinder 52 and divides same into upper and lower chambers 56 and 58.
The other end of cylindrical member 54 is sealingly secured to partition
plate 40. An annular ring 60 is secured to the upper end of scroll member
32 and includes an axially extending flange 62 slidingly engageable with
cylinder member 54 to thereby seal off the open upper end of chamber 56.
Cylindrical member 54 includes a passage 64 having one end which opens into
upper chamber 56. A fluid line 66 is connected to the other end of passage
64 and extends outwardly through shell 12 to a solenoid operated valve 68.
A second fluid line 70 extends from valve 68 to suction line 72 connected
to suction inlet 44 and a third fluid line 74 extends from valve 68 to a
discharge line 76 extending outwardly from discharge chamber 42.
In order to bias scroll member 32 into sealing engagement with scroll
member 26 for normal fully loaded operation, a bleed hole 78 is provided
in scroll member 32 communicating between chamber 58 and a compression
pocket at an intermediate pressure between suction and discharge pressure.
Thus, chamber 58 will be at an intermediate pressure which together with
the discharge pressure acting on the upper surface of scroll member 32 in
the area of discharge port 48 will exert a biasing force on scroll member
urging it axially into sealing engagement with orbiting scroll member 26.
At the same time, solenoid valve 68 will be in a position so as to place
upper chamber 56 in fluid communication with suction line 72 via fluid
lines 66 and 70.
In order to unload compressor 24, solenoid valve 68 will be actuated in
response to a signal from control module 80 to interrupt fluid
communication between lines 66 and 70 and to place fluid line 66 in
communication with discharge line 76 thus increasing the pressure within
chamber 56 to that of the discharge gas. The biasing force resulting from
this discharge pressure will overcome the sealing biasing force thereby
causing scroll member 32 to move axially upwardly away from orbiting
scroll member 26. This axial movement will result in the creation of a
leakage path between the respective wrap tips and end plates of scroll
members 26 and 32 thereby substantially eliminating continued compression
of the suction gas. When unloading occurs, discharge valve 51 will move to
a closed position thereby preventing the back flow of high pressure fluid
from discharge chamber 42 or the downstream system. When compression of
the suction gas is to be resumed, solenoid valve 68 will be actuated to a
position in which fluid communication between upper chamber 56 and
discharge line 76 via lines 66 and 74 is interrupted and upper chamber 56
is placed in communication with suction line 72 via fluid lines 66 and 70
thereby relieving the axially directed separating force. This then allows
the cooperative action of the intermediate pressure in chamber 58 and
discharge pressure acting in passage 50 to again move scroll member 32
into sealing engagement with scroll member 26.
Preferably, control module 80 will have one or more appropriate sensors 82
connected thereto to provide the required information for control module
80 to determine the degree of unloading required for the particular
conditions existing at that time. Based upon this information, control
module 80 will send appropriately timed sequential signals to solenoid
valve 68 to cause it to alternately place fluid line 66 in communication
with discharge line 76 and suction line 72. For example, if conditions
indicate that it is desirable to operate compressor 24 at 50 percent of
full capacity, control module 80 may actuate solenoid valve to a position
to place fluid line 66 in communication with suction line 72 for a period
of say 10 seconds whereupon it is switched to place fluid line 66 in fluid
communication with discharge line 76 for a like period of 10 seconds.
Continued switching of solenoid valve 68 in this manner will result in
compression occurring during only 50 percent of the operating time thus
reducing the output of compressor 24 to 50 percent of its full load
capacity. As the sensed conditions change, control module will vary the
relative time periods at which compressor 24 is operated in a loaded and
unloaded condition such that the capacity of compressor 24 may be varied
between fully loaded or 100 percent capacity and completely unloaded or 0
percent capacity in response to varying system demands.
FIGS. 2 and 3 show an axial unloading scroll compressor 34 similar to that
of FIG. 1 with the primary exception being the arrangement for placing
upper chamber 56 in fluid communication with suction and discharge lines.
Accordingly, like portions have been indicated by the same reference
numbers. As shown therein, passage 64 has been replaced by a passage 86
provided in annular member 60 which opens at one end into upper chamber 56
and at the other end through a radially outwardly facing sidewall. A
flexible fluid line 88 extends from the outer end of passage 86 to a
fitting 90 extending through shell 12 with a second line 92 connecting
fitting 90 to solenoid valve 68. As with FIG. 1, solenoid valve 68 has
fluid lines 70 and 74 connected to suction line 72 and discharge line 76
and is controlled by control module 80 in response to conditions sensed by
sensor 82 to effect movement of non-orbiting scroll member 32 between the
positions shown in FIGS. 2 and 3 in the same manner as described above
with respect to the embodiment of FIG. 1. While this embodiment eliminates
the need for an extra fitting extending outwardly from the high pressure
discharge chamber 42, it requires that fluid conduit 88 be flexible so as
to accommodate axial movement of scroll member 32 and associated annular
member 60. It should also be noted that in this embodiment cylindrical
member 54 is sealingly secured to partition plate 40 by means of nut 55
which threadedly engages the upper end thereof. Also in this embodiment,
discharge valve 51 has been replaced by a discharge check valve 93 secured
to the outer shell. It should be noted that the provision of a check valve
some place along the discharge flowpath is highly desirable in order to
prevent back flow of compressed gas from the system when the compressor is
in an unloaded condition.
FIGS. 4 and 5 show another embodiment 94 of the present invention in which
axial unloading separating pressure fluid is provided directly from the
discharge gas exiting the compressor. In this embodiment, a tubular member
96 is suitably secured to partition member 40 and includes a radially
outwardly extending flange 98 which is positioned in and separates
cylindrical recess into upper and lower chambers 56 and 58. Tubular member
96 also defines passage 50 for directing compressed discharge gas from
port 48 to discharge chamber 42. An axial extending bore 100 is provided
in tubular member which opens outwardly through the upper end thereof and
is adapted to receive a fluid conduit 102. Fluid conduit 102 extends
outwardly through the top of shell 12 and is connected to solenoid valve
68. Solenoid valve also has fluid conduits 70 and 74 connected to
respective suction and discharge lines 72, 76 and is controlled by control
module 80 in response to signals from appropriate sensors 82 in the same
manner as described above.
A valve member 104 is axially movably disposed within bore 100. Valve
member 104 includes a reduced diameter portion 106 operative to place
radially extending passages 108 and 110 provided in member 96 in fluid
communication when in a first position so as to vent upper chamber 56 to
suction and to place radial fluid passage 110 in fluid communication with
radial fluid passage 112 when in a second position so as to admit
discharge gas from discharge flowpath 50 to upper chamber 56. A vent
passage 113 is also provided which communicates between the bottom of bore
100 and passage 50 to vent gas from the area below valve 104 during
operation thereof. A spring 114 is also provided which serves to aid in
biasing valve 104 into its second position whereas pressurized discharge
fluid entering bore 100 via passage 112 and passage 113 serves to bias
valve member 104 into its first position.
As shown, valve member 104 and solenoid valve 68 are both in a position for
fully loaded operation wherein solenoid valve 68 is in position to place
fluid conduit 102 in communication with the suction line 72 and valve
member 104 is in a position to vent upper chamber 56 to the interior of
shell 12 which is at suction pressure. When it is desired to unload the
compressor, solenoid valve 68 will be actuated to a position to place
fluid line 102 in communication with fluid line 74 thereby enabling
pressurized discharge fluid to act on the upper end of valve member 104.
This pressurized fluid together with spring 114 will cause valve member
104 to move downwardly thereby closing off communication of radial passage
110 with radial passage 108 and opening communication between radial
passage 110 and radial passage 112. Discharge pressure fluid will then
flow into upper chamber 56 thus overcoming the intermediate pressure
biasing force resulting from the communication of chamber 58 with a
compression chamber at intermediate pressure via passage 78 and causing
scroll member 32 to move axially upwardly away from orbiting scroll member
26. It should be noted that the relatively short flowpath for supplying
discharge pressure fluid to upper chamber 56 ensures rapid unloading of
the compressor.
FIG. 6 shows a modified embodiment similar to that of FIGS. 4 and 5 except
that solenoid valve 68 is positioned within shell 12. This embodiment
eliminates the need for an additional fluid conduit through the high
pressure portion of the shell, requiring only an electrical feed for
actuating solenoid valve 68. In all other respects, construction and
operation of this embodiment is substantially the same as that described
above with respect to the embodiment shown in FIGS. 4 and 5 and
accordingly corresponding portions are indicated by the same reference
numbers.
While the previously described embodiments have been directed to unloading
arrangements wherein the non-orbiting scroll has been moved axially away
from the orbiting scroll, it is also possible to apply these same
principles to the orbiting scroll. FIGS. 7 through 15 described below
illustrate such a series of embodiments.
Referring now to FIG. 7, a scroll compressor 140 is shown which is similar
to the scroll compressors described above except that non-orbiting scroll
member 142 is non-movably secured to bearing housing 144 and orbiting
scroll member 146 is axially movable. It is also noted that compressor 140
is a high side machine, that is, the suction inlet 149 is directly
connected to the non-orbiting scroll member 142 and the interior of the
shell 12 is at discharge pressure. In this embodiment, orbiting scroll
member 146 is axially movable and is biased into engagement with
non-orbiting scroll 142 by means of a pressure chamber 148 defined between
orbiting scroll member 146 and main bearing housing 144. An annular recess
150 is provided in main bearing housing 144 in which is disposed a
suitable annular resilient seal member 152 which sealingly engages the
lower surface of orbiting scroll member 146 so as to prevent fluid
communication between chamber 148 and the interior of shell 12 which is at
discharge pressure. A second annular seal 154 is provided on main bearing
housing 144 surrounding shaft 18 to prevent fluid leakage therealong. A
small passage 156 is provided through the end plate of orbiting scroll
member 146 to place chamber 148 in fluid communication with a compression
chamber at a pressure intermediate suction and discharge pressure.
Additionally, a passage 158 in main bearing housing extends outwardly from
chamber 148 and has one end of fluid line 160 connected thereto. The other
end of fluid line 160 extends outwardly through shell 12 and is connected
to solenoid valve 162. A second fluid line 164 extends between solenoid
valve 162 and suction line 148.
In operation, chamber 148 will be supplied with fluid at intermediate
pressure to thereby bias orbiting scroll 146 into sealing engagement with
non-orbiting scroll 142. At this time, solenoid valve 162 will be in a
position to prevent fluid communication between lines 160 and 164. In
order to unload compressor 140, solenoid valve 162 is actuated to a
position to place line 160 in fluid communication with fluid line 164
thereby venting the intermediate pressure in chamber 148 to suction. The
pressure within the compression pockets will then cause orbiting scroll
member 146 to move axially downwardly as shown compressing resilient seals
152 and thereby forming a leakage path across the respective wrap tips and
associated end plates of the orbiting and non-orbiting scroll members 146,
142. While passage 156 may continue to provide fluid at a pressure
somewhat higher than suction pressure to chamber 148, the relative sizing
of passage 158, fluid lines 160 and 164 and passage 158 will be such that
there will be insufficient pressure in chamber 148 to bias orbiting scroll
member 146 into sealing engagement with non-orbiting scroll member 142 so
long as solenoid valve 162 is in a position to maintain fluid
communication between suction line 149 and chamber 148. Solenoid valve 162
will be cycled between open and closed positions so as to cyclically load
and unload compressor 140 in substantially the same manner as described
above.
FIG. 8 shows a modified version 140a of the embodiment of FIG. 7 wherein a
plurality of springs 166 are provided. Springs 166 are seated in recesses
168 provided in bearing housing 144a and bear against the end plate of
orbiting scroll 146 so as to assist in urging orbiting scroll into sealing
engagement with non-orbiting scroll 142. Springs 166 serve primarily to
provide an initial biasing force for orbiting scroll member 146 on initial
start up of compressor 140a but will also assist in providing more rapid
loading of compressor 140a upon closing of solenoid valve 162 during
operation.
FIG. 9 shows a further modification 140b of the embodiments of FIGS. 7 and
8. In this embodiment shell 12 is provided with a partition member 170 to
separate the interior thereof into a high pressure discharge chamber 172
to which discharge port 174 is connected via conduit 176 and a low suction
pressure chamber therebelow within which the compressor is disposed.
Additionally, in this embodiment shaft seal 154 has been replaced with a
second annular seal 178 positioned radially inwardly and concentric with
seal 150b. Thus the area in which crank pin 28 and drive bushing 30 are
located will be at suction pressure to thereby avoid any problems
associated with providing lubrication thereto from the oil sump which is
also at suction pressure. It should be noted that the oil sump in the
embodiments of FIGS. 7 and 8 was at discharge pressure and hence do not
present any problems with respect to supplying of lubricant to these drive
components.
The embodiment 140c of FIG. 10 is substantially identical to that of FIG. 9
with the exception that in addition to the biasing force resulting from
intermediate fluid pressure in chamber 148b, a plurality of springs 180
are also provided being positioned between orbiting scroll member 156 and
main bearing housing 144 and functioning primarily to assist during start
up but also to assist in reloading of compressor 140c similar to that
described above with reference to FIG. 8.
In the embodiment of FIG. 11, non-orbiting scroll member 182 is provided
with an annular recess 184 within which an annular ring-shaped piston
member 186 is movably disposed. The lower surface of annular piston member
186 bears against a radially outwardly extending portion 187 of end plate
189 of orbiting scroll member 146 and radially inner and outer annular
seals 188, 190 are provided thereon which sealingly engage radially inner
and outer walls of recess 184. A radially extending passage 192 provided
in non-orbiting scroll member 182 communicates with the upper portion of
recess 184 and has fluid conduit 194 connected to the outer end thereof.
Fluid conduit 194 extends outwardly through shell 12 to solenoid valve
196. A second fluid conduit 198 connects solenoid valve 196 to suction
line 200 whereas a third fluid conduit 202 connects solenoid valve 196 to
discharge line 204.
Under normal fully loaded operating conditions, orbiting scroll member 146
will be axially biased into sealing engagement with non-orbiting scroll
member 182 by intermediate fluid pressure in chamber 206 admitted thereto
via bleed passage 208. At this time, the area of recess 184 disposed above
annular piston member 186 will be vented to suction via solenoid valve 196
and conduits 194 and 198. When conditions indicate partial unloading of
the compressor is desirable, solenoid valve 196 will be actuated to place
fluid conduit 194 in fluid communication with discharge line 204 via
conduit 202. The area above annular piston 186 will then be pressurized by
fluid at discharge pressure thereby causing orbiting scroll member 146 to
be biased axially downwardly as shown. As noted above, cyclical switching
of solenoid valve 196 will result in repetitive loading and unloading of
the compressor with the degree of unloading being determined by associated
sensors and control module (not shown). It should be noted that in this
embodiment, the compressor is shown as a high side machine and thus
suction inlet 200 is directly connected to the suction inlet of
non-orbiting scroll 182.
The embodiment 208 of FIG. 12 represents a combination of the axial
unloading arrangement of FIG. 11 and the orbiting scroll biasing
arrangement of FIG. 9 both described above. Accordingly, elements
corresponding to like elements shown in and described with reference to
FIGS. 9 and 11 are indicated by the same reference numbers. In this
embodiment, the intermediate pressure axial biasing chamber 148b for the
orbiting scroll is completely separate from the unloading discharge
pressure biasing chamber defined by recess 184 and annular piston 186.
In like manner, the embodiment 210 of FIG. 13 represents a combination of
the intermediate pressure biasing arrangement of FIG. 8 described above
and the axial unloading pressure biasing arrangement of FIG. 11.
Accordingly, corresponding elements have been indicated by the same
reference numbers used in these respective figures.
FIG. 14 shows an embodiment 212 wherein shell 12 includes an upper chamber
214 at discharge pressure and a lower portion 216 at a pressure
intermediate suction and discharge. Accordingly, suction line 234 is
directly connected to non-orbiting scroll member 224. Additionally, a
suitable annular seal 225 may be provided between orbiting scroll 222 and
non-orbiting scroll 224 around the outer periphery thereof. Orbiting
scroll 222 is biased into sealing relationship with non-orbiting scroll
224 by intermediate pressure in chamber 216 supplied via passage 226. In
order to unload compressor 212, a solenoid valve 228 is provided having a
first fluid line 230 extending through shell 12 and being connected to one
end of a passage 231 provided in lower bearing housing 233. A second fluid
line 232 is connected between the suction inlet 234 and solenoid valve
228. When solenoid valve 228 is opened, the intermediate pressure acting
on the lower surface of orbiting scroll 222 will be vented to suction via
passage 231, fluid line 230, solenoid valve 228 and fluid line 232.
Because passage 231, fluid lines 230 and 232 and solenoid valve 228 will
be sized to provide a flow volume greater than that through passage 226
plus the leakage into the area defined between the bearing housing and end
plate of orbiting scroll 222, the biasing force acting on orbiting scroll
222 will be relieved thus allowing the force of the fluid within the
compression chamber to move orbiting scroll 222 axially away from
non-orbiting scroll 224. As soon as solenoid valve 228 is closed, leakage
flow of intermediate pressure fluid within lower portion 216 of shell 12
combined with flow from passage 226 will quickly restore the | | |
