U.S. patent application number 09/978406 was filed with the patent office on 2003-04-17 for scroll compressor with condition responsive back pressure chamber valve.
Invention is credited to Barito, Thomas R., Sun, Zili.
Application Number | 20030072663 09/978406 |
Document ID | / |
Family ID | 25526061 |
Filed Date | 2003-04-17 |
United States Patent
Application |
20030072663 |
Kind Code |
A1 |
Sun, Zili ; et al. |
April 17, 2003 |
SCROLL COMPRESSOR WITH CONDITION RESPONSIVE BACK PRESSURE CHAMBER
VALVE
Abstract
A scroll compressor includes first and second scroll members
having wraps interfitting to define compression chambers. As is
known, a back pressure chamber is defined to hold the two scroll
members in contact with each other. A valve is positioned to
selectively block flow of refrigerant into the back pressure
chamber, but is condition responsive to change the flow of
refrigerant into the back pressure chamber dependent on conditions
within the compressor. In one embodiment, the valve normally blocks
a second tap which communicates with discharge pressure. If an
elevated temperature is reached the valve moves to an open position
and refrigerant can flow from the discharge pressure chamber into
the back pressure chamber. In another embodiment, the valve
selectively closes a lower pressure tap.
Inventors: |
Sun, Zili; (Arkadelphia,
AR) ; Barito, Thomas R.; (Arkadelphia, AR) |
Correspondence
Address: |
CARLSON, GASKEY & OLDS, P.C.
400 WEST MAPLE ROAD
SUITE 350
BIRMINGHAM
MI
48009
US
|
Family ID: |
25526061 |
Appl. No.: |
09/978406 |
Filed: |
October 16, 2001 |
Current U.S.
Class: |
418/55.5 ;
418/57 |
Current CPC
Class: |
F04C 27/005
20130101 |
Class at
Publication: |
418/55.5 ;
418/57 |
International
Class: |
F04C 018/04 |
Claims
1. A scroll compressor comprising: a first scroll member having a
base and a generally spiral wrap extending from its base; a second
scroll member having a base and a generally spiral wrap extending
from its base, said wraps of said first and second scroll members
intermitting to define compression chambers; said second scroll
member being driven to orbit relative to said first scroll member
to entrapped refrigerant in said compression chambers to become
compressed; and a back pressure chamber defined behind a base of
one of said first and second scroll members, and a tap for
delivering a refrigerant to said back pressure chamber, and a
condition responsive valve operable upon said compressor reaching a
particular condition to change the flow of refrigerant being
delivered to said back pressure chamber.
2. A scroll compressor as recited in claim 1, wherein said valve
includes a bi-metal member which is movable between two positions,
and has a trigger temperature causing it to move to an actuated
position, and said valve moving to said actuated position when a
trigger temperature is reached to cause said change in the flow of
refrigerant to said back pressure chamber.
3. A scroll compressor as recited in claim 2, wherein said valve is
normally biased to a position blocking flow through a tap, and said
bi-metal element moving to its actuated position allowing
refrigerant to flow from said tap into said back pressure chamber
when an elevated temperature is reached.
4. A scroll compressor as recited in claim 3, wherein there are a
pair of taps with said valve closing off the tap to a higher
pressure location, with a first tap being normally opened and
communicating with a location at a lower pressure than said first
tap.
5. A scroll compressor as recited in claim 4, wherein said valve is
normally spring biased to close said second tap, with said bi-metal
element snapping to an actuated position causing said valve to move
away from said tap and allow flow of said second higher pressure
refrigerant into said back pressure chamber.
6. A scroll compressor as recited in claim 2, wherein said valve is
normally held away from said tap but is movable to selectively
close said tap if said bi-metal element reaches its trigger
temperature.
7. A scroll compressor as recited in claim 6, wherein said valve
closes said tap throughout the orbiting cycle of said second scroll
member.
8. A scroll compressor as recited in claim 2, wherein said valve is
positioned such that it only blocks flow of refrigerant from said
tap into said back pressure chamber at lower pressure locations in
an orbiting cycle of said orbiting scroll member.
9. A scroll compressor as recited in claim 1, wherein said back
pressure chamber is defined behind said second scroll member.
10. A scroll compressor as recited in claim 1, wherein there are a
pair of taps, with a first tap communicating with a lower pressure
location in said compression chambers and a second tap
communicating with a higher pressure location and there being a
pair of valves with a first valve selectively moving to close said
first tap when an elevated temperature is reached and a second
valve selectively moving to open said second tap when said elevated
temperature is reached.
11. A scroll compressor comprising: a first scroll member having a
base and a generally spiral wrap extending from its base; a second
scroll member having a base and a generally spiral wrap extending
from its base, said wraps of said first and second scroll members
interfitting to define compression chambers; said second scroll
member being driven to orbit relative to said first scroll member
to entrapped refrigerant in said compression chambers to become
compressed; and a pair of taps extending through one of said first
and second scroll members to deliver a refrigerant into a back
pressure chamber defined behind a base of one of said first and
second scroll members, a first of said tap communicating with a
lower pressure compression chamber, and a second of said taps
communicating with the higher pressure compression chamber, a
condition responsive valve selectively opening or closing said
second tap, and said condition responsive valve being movable upon
an elevated temperature being reached within said compressor to
open said second tap.
12. A scroll compressor as recited in claim 11, wherein said taps
extend through second scroll member.
13. A scroll compressor as recited in claim 12, wherein said back
pressure chamber is defined behind said second scroll member.
14. A scroll compressor as recited in claim 11, wherein said valve
includes a bi-metal member which is movable between two positions,
and has a trigger temperature causing it to move to an actuated
position, and said valve moving to said actuated position when a
trigger temperature is reached to cause said change in the flow of
refrigerant to said back pressure chamber.
15. A scroll compressor as recited in claim 14, wherein said valve
is normally biased to a position blocking flow through a tap, and
said bi-metal element moving to its actuated position allowing
refrigerant to flow from said tap into said back pressure chamber
when an elevated temperature is reached.
16. A scroll compressor as recited in claim 15, wherein said valve
is normally spring biased to close said second tap, with said
bi-metal element snapping to an actuated position causing said
valve to move away from said tap and allow flow of said second
higher pressure refrigerant into said back pressure chamber.
Description
BACKGROUND OF THE INVENTION
[0001] This application relates to a scroll compressor wherein
valves are selectively actuated based upon adverse conditions in a
scroll compressor to change the back pressure chamber tapped
fluid.
[0002] Scroll compressors are becoming widely utilized in
refrigerant compression applications. In a scroll compressor a
first scroll member includes a base with a generally spiral wrap
extending from its base. A second scroll member has a base with a
generally spiral wrap extending from its base. The wraps of the two
scroll members interfit to define compression chambers. The second
scroll member is caused to orbit relative to the first scroll
member, and as the two wraps orbit relative to each other an
entrapped refrigerant is compressed. Scroll compressors are widely
utilized due to efficiency and other advantages. However, they also
raise challenges to a scroll compressor designer. One challenge
relates to resisting a so-called "separating force". As the
refrigerant is compressed between the two relatively orbiting
scroll members, a force is created by the compressed refrigerant
tending to separate the two scroll members. To resist this force,
compressed refrigerant is tapped to a back pressure chamber behind
one of the two scroll member bases. This back pressure force
resists the separating force and holds the two scroll members in
contact with each other.
[0003] There are challenges with regard to providing an optimum
back pressure chamber force. The back pressure chamber force which
is optimum will vary with varying conditions within the compressor.
There are situations wherein the compressor will be operating under
adverse conditions, and it is difficult to address those conditions
while at the same time providing a desirable back pressure force
for normal operating conditions.
[0004] As an example, scroll compressors may sometimes operate at a
high pressure ratio condition. If there is a loss of charge or an
indoor fan failure, then very high pressure ratio conditions can be
created. The stability of the scroll compressor is effected by the
back pressure chamber force. A desired back pressure chamber force
to obtain optimum stability increases as the pressure ratio
increases. Thus, a desirable back pressure chamber to obtain
optimum stability at normal operating ranges would be undesirably
low at high pressure ratio operation.
[0005] It is thus desirable to provide a scroll compressor having a
condition responsive control of the pressure in a back pressure
chamber.
SUMMARY OF THE INVENTION
[0006] In the disclosed embodiment of this invention, a back
pressure tap from an intermediate pressure chamber delivers an
intermediate pressure fluid to a back pressure chamber in a scroll
compressor. A second selective tap communicates discharge pressure
chamber to the back pressure chamber. A valve is biased to close
this second tap. The valve is conditioned responsive, such that if
conditions within the scroll compressor indicate a higher pressure
would be desirable within the back pressure chamber, the valve
moves to an open position and discharge pressure refrigerant is
delivered to the back pressure chamber. In one preferred
embodiment, a bi-metal snap valve is utilized which is normally
biased to close the second discharge pressure tap, but is movable
to a position at which it allows flow from the second discharge
pressure tap into the back pressure chamber when an elevated
temperature is experienced in the scroll compressor.
[0007] In another embodiment, it is the intermediate pressure tap
which is closed by a valve upon certain conditions. In this
embodiment, the valve is normally open and allows flow into the
back pressure chamber under normal conditions. However, if an
elevated temperature is reached, then the valve is moved to a
position at which it will block flow of at least intermediate
pressure fluid to the back pressure chamber. In one embodiment,
this valve will block the flow of any refrigerant into the back
pressure chamber. In such condition, the back pressure chamber will
quickly move to a suction pressure and the two scroll members will
move out of contact with each other. This will eliminate any
resultant damage which may otherwise be experienced if the scroll
compressor was operated at a high pressure ratio condition. In a
third embodiment the valve which selectively closes off the
intermediate pressure tap only will close portions of the tap at a
lower pressure range. The tap will be free to deliver refrigerant
into the back pressure chamber through a portion of the orbiting
cycle of the orbiting scroll associated with higher pressure
refrigerant.
[0008] In sum, the present invention provides a scroll compressor
wherein the pressure of refrigerant delivered to a back pressure
chamber is controlled by a condition responsive valve. The
invention thus allows a scroll compressor designer to ensure safe
operation of the scroll compressor at a variety of extreme
conditions, and across a variety of otherwise undesirable operating
conditions.
[0009] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross-sectional view of a prior art
compressor.
[0011] FIG. 2 is a cross-sectional view of a first embodiment of
this invention.
[0012] FIG. 3A shows the first embodiment in a normal state.
[0013] FIG. 3B shows the first embodiment in an actuated state.
[0014] FIG. 4 shows a second embodiment.
[0015] FIG. 5 shows a third embodiment.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0016] A prior scroll compressor 20 is illustrated in FIG. 1 having
a non-orbiting scroll 22 with a generally spiral wrap 23. An
orbiting scroll 24 has wrap 25. The wraps interfit to define
compression chambers 34 as known. A tap 26 taps refrigerant from
one of the compression chambers 34 to a back pressure chamber 32
defined by seals 28 and 39. While the back pressure chamber 32 is
shown behind the base of the orbiting scroll 24, it should be
understood that back pressure chambers are also provided behind the
base of the non-orbiting scroll 22. The features of this invention
would extend fully to such a scroll compressor.
[0017] One problem encountered with scroll compressors occurs at
extreme operational ranges of the compressor. If a problem exists
in the system, such as a lower charge of refrigerant within the
refrigerant cycle than is desirable, or if another system component
such as the indoor fan fails, then conditions within the scroll
compressor can reach undesirable extremes. One such extreme relates
to the pressure ratio, which is the ratio of the discharge pressure
to the suction pressure across the compressor. If the pressure
ratio increases to an undesirably high level, then there can be
damage to the scroll compressor. Moreover, the scroll compressor
often will operate in an unstable and noisy manner.
[0018] Scroll compressor designers attempt to select the pressure
delivered to the back pressure chamber 32 in such a way that it
will ideally meet the required back pressure force for the normal
operating conditions of the compressor 20. However, upon certain
conditions, such as high pressure ratio operation, the normal back
pressure chamber force which is desirable will be too low.
[0019] As shown, a discharge pressure chamber 33 communicates with
a discharge port 35 formed through the non-orbiting scroll. As is
also known, a motor selectively 120 selectively drives a shaft 122
to cause the orbiting scroll 24 to orbit. The suction tube 124
delivers the suction refrigerant into a chamber 126 surrounding the
motor to cool the motor.
[0020] FIG. 2 shows a first embodiment 50 of the present invention
which addresses the above discussed problem. The orbiting scroll 52
in the first embodiment 50 includes the normal passage 54
communicating with a tap 56 to an intermediate pressure chamber 58.
The passage 54 also communicates with a tap 60 which delivers
refrigerant to a back pressure chamber 62 defined between two seals
63 and 66. As is mentioned above, while the present embodiment is
illustrated with a back pressure chamber behind the orbiting scroll
52, the aspects of this invention would also apply to the type of
scroll compressor having its back pressure chamber behind the
non-orbiting scroll. A worker in this art would understand how to
apply the goals and benefits of this invention to such a scroll
compressor.
[0021] As also shown, a second passage 64 communicates with a
discharge pressure chamber 66. The passage 64 communicates with the
tap 68 to the back pressure chamber 62. Plugs 70 close the passages
54 and 64, as known.
[0022] A condition responsive valve 72 selectively closes the tap
68.
[0023] As shown in FIG. 3A, the valve assembly 72 includes a valve
plate 74 normally spring biased 76 to a position at which it closes
the tap 68. A bi-metal two-position snap member 78 is shown in its
relaxed position. Member 78 is attached to plate 74. Such bi-metal
elements are known, and snap between two portions when a trigger
temperature is reached. The member 78 will remain in this position
unless the conditions within the scroll compressor are such that
the temperature adjacent to the snap member 78 increases beyond a
"trigger" temperature. A pin 80 moves with the snap member 78.
[0024] As shown in FIG. 3B, conditions within the scroll compressor
have changed such that the temperature has increased beyond the
"trigger point" of the snap element 78. The snap element now
assumes a distinct configuration from that shown in FIG. 3A. The
pin 80 is now forced against the rear of the base of the orbiting
scroll 52, and the plate 74 is forced away from the tap 68. In this
position, refrigerant from the passage 64 which is at discharge
pressure, is delivered into the back pressure chamber 62. In this
way, should the conditions be indicative of a high pressure ratio
operation, a higher pressure of refrigerant is delivered to the
back pressure chamber. The problems discussed above are thus
reduced or even eliminated.
[0025] FIG. 4 shows another embodiment 90. In embodiment 90, it is
the tap 92 to the intermediate pressure chamber 94 which is
selectively opened or closed by the valve element 99. Seals 96 and
98 define the back pressure chamber, as known. The valve 99
includes a valve plate member 100 which selectively closes the tap
92. The bi-metal snap member 102 is shown in a position such that
it snaps to bias the valve 100 to close the tap 92 when the
elevated temperature is reached. In a relaxed position, the snap
element 102 would be more generally flat, and the plate 100 is
moved away from the position closing the tap 92. In this position,
refrigerant can flow through the tap 92 into the back pressure
chamber. However, should elevated temperatures be reached, the snap
member 102 will snap to the illustrated position and the valve 100
closes the tap 92.
[0026] In this embodiment, the valve 100 will close all
communication with tap 92, once the condition has been reached.
Eventually, refrigerant from the suction pressure chamber 126 will
leak around the seals 96 and 98 such that the back pressure chamber
will move to suction pressure. At that time, the orbiting scroll
member 95 will be able to move away from the non-orbiting scroll
member. This will also eliminate the damages discussed above in
that the two scrolls will no longer be held in contact with each
other, and much of the ill effect of high pressure ratio operation
will be avoided. Further, this embodiment could be utilized with
the type of embodiment having the discharge pressure tap which is
selectively opened. That is, the FIG. 4 and 3 embodiments could be
utilized in combination.
[0027] FIG. 5 shows yet another embodiment which is similar to the
FIG. 4 embodiment. However, the valve assembly 112 is positioned
such that it blocks the tap 106 at positions such as shown at 108.
Refrigerant at the location of the position 108 will not be
delivered into the back pressure chamber 110 when the snap member
114 is moved to this actuated position. However, a second position
116 is shown in phantom at which the tap will no longer be aligned
with the valve 112. It should be understood that the tap 106 will
move through an orbiting cycle during the orbiting movement of the
orbiting scroll 118. When the tap reaches the position 116, then
refrigerant can be delivered into the back pressure chamber 110. In
this way, the scroll compressor designer can eliminate lower or
intermediate pressure refrigerant from entering the back pressure
chamber 116, while still allowing the flow of discharge pressure
refrigerant through the positions 116. This will also address the
high pressure ratio operation issues in a manner similar to the
FIG. 3A embodiment.
[0028] Although preferred embodiments of this invention have been
disclosed, a worker in this art would recognize that many
modifications would come within the scope of this invention. For
that reason, the following claims should be studied to determine
the true scope and content of this invention.
* * * * *