Information
-
Patent Grant
-
6658885
-
Patent Number
6,658,885
-
Date Filed
Wednesday, October 2, 200221 years ago
-
Date Issued
Tuesday, December 9, 200320 years ago
-
Inventors
-
Original Assignees
-
Examiners
-
CPC
-
US Classifications
Field of Search
US
- 062 296
- 062 469
- 062 472
- 181 403
- 417 312
-
International Classifications
-
Abstract
The entire discharge flow in a high side, vertical, hermetic rotary compressor is directed into the oil sump which generates foam for sound attenuation and heats the oil to reduce its viscosity and to drive off refrigerant dissolved in the oil.
Description
BACKGROUND OF THE INVENTION
Commonly assigned U.S. Pat. Nos., 4.900,234; 4,907,414 and 5,077,981 each disclose a low side hermetic compressor in which a portion of the discharge of the compressor is bled into the oil sump. The high pressure gas being bled into the oil sump represents a loss but, because the interior of the compressor shell and the oil sump are at suction pressure, the foam generated by the high pressure gas expanding to suction pressure in the oil provides sound attenuation.
Discharge gas pulsation in the shell cavity beneath the motor in a high side vertical, hermetic rotary compressor has been found to be one of the major noise sources. In current compressor designs, the compressed gas discharges from the pump structure into the muffler cavity and then passes into the lower shell cavity. The discharge gas passes from the lower shell cavity to the discharge at the top of the compressor shell by passing through the gap between the rotor and stator and/or passing through passages between the stator and the compressor shell.
SUMMARY OF THE INVENTION
According to the teachings of the present invention the discharge gas in a high side rotary compressor passes from the pump structure into the muffler cavity and then passes via tubes into the oil sump located beneath the pump structure. Discharging the hot high pressure gas into the oil sump heats the oil and thereby reduces its viscosity. Additionally, the discharging of the high pressure gas into the oil sump, which is also at discharge pressure, generates foam roughly in the volume of the gas discharged from the pump structure. The foam will pass from the oil sump, through the pump structure to the upper part of the lower shell cavity, i.e. the part below the motor. Any foam entering the gap between the rotor and stator will tend to be collapsed and the oil will tend to be centrifugally separated such that it collects on the stator and drains due to gravity.
It is an object of this invention to reduce rotary compressor noise due to discharge gas pulsation.
It is another object of this invention to provide additional attenuation without reducing efficiency.
It is a further object of this invention to improve oil lubrication capability by increasing oil temperature in the sump. These objects, and others as will become apparent hereinafter, are accomplished by the present invention.
Basically, the entire discharge flow in a high side, vertical, hermetic rotary compressor is directed into the oil sump which generates foam for sound attenuation and heats the oil to reduce its viscosity and to drive off refrigerant dissolved in the oil.
BRIEF DESCRIPTION OF THE DRAWINGS
For a fuller understanding of the present invention, reference should now be made to the following detailed description thereof taken in conjunction with the accompanying drawings wherein:
FIG. 1
is a partially sectioned view of a compressor employing the present invention schematically located in a refrigeration circuit;
FIG. 2
is a sectional view taken along line
2
—
2
of
FIG. 1
;
FIG. 3
is a sectional view taken along line
3
—
3
of
FIG. 2
;
FIG. 4
is a partially cutaway view of the discharge muffler of the present invention;
FIG. 5
is an enlarged view of a portion of
FIG. 1
; and
FIG. 6
is a sectional view taken along line
6
—
6
of FIG.
5
.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In
FIGS. 1-3
and
5
, the numeral
10
generally designates a vertical, high side, rolling piston compressor. Compressor
10
is in a refrigeration circuit serially including compressor
10
, discharge line
60
, condenser
70
, expansion valve
80
and evaporator
90
. The numeral
12
generally designates the shell or casing. Suction tube
16
is sealed to shell
12
and provides fluid communication between suction accumulator
14
, which is connected to evaporator
90
, and suction chamber S. Cylinder
20
, piston
22
, pump end bearing
24
, motor end bearing
28
and vane
30
collectively make up the pump structure. Suction chamber S and compression chamber C are defined by bore
20
-
1
in cylinder
20
, piston
22
, bearings
24
and
28
, and vane
30
which separates suction chamber S and compression chamber C.
Eccentric shaft
40
includes a portion
40
-
1
supportingly received in bore
24
-
1
of pump end bearing
24
, eccentric
40
-
2
which is received in bore
22
-
1
of piston
22
, and portion
40
-
3
supportingly received in bore
28
-
1
of motor end bearing
28
. Oil pick up tube
34
extends into sump
36
from a bore in portion
40
-
1
. Stator
42
is secured to shell
12
by a shrink fit, welding or any other suitable means. Commonly there will be passages in the form of slots or grooves
42
-
2
in the outer surface of the stator
42
running its entire length to provide flow paths for refrigerant gas across the motor defined by stator
42
and rotor
44
and for the return flow of oil to oil sump
36
. Rotor
44
is suitably secured to shaft
40
, as by shrink fit, and is located within bore
42
-
1
of stator
42
in a spaced relationship and coacts therewith to define a variable speed motor. Vane
30
is biased into contact with piston
22
by spring
31
.
Discharge port
28
-
2
in motor end bearing
28
is overlain by normally closed valve
29
. Valve
29
is within and opens into muffler
32
. As described so far, compressor
10
is generally conventional. The present invention differs in the details of muffler
32
and the resultant differences in operation of compressor
10
. Referring specifically to
FIGS. 3 and 4
it will be evident that muffler
32
differs from conventional mufflers in that it has two downwardly directed discharge tubes
32
-
1
and
32
-
2
which are blocked at their ends and which have a plurality of ports
32
-
1
a
and
32
-
2
a
, respectively, which are each located within the portion of the 180° perimeter of tubes
32
-
1
and
32
-
2
which is not directed towards the other one of discharge tubes
32
-
1
and
32
-
2
or pick up tube
34
. The reason for these locations of ports
32
-
1
a
and
32
-
2
a
is to avoid discharging gas towards oil pick up tube
34
. Referring specifically to
FIG. 3
, it will be noted that discharge tubes
32
-
1
and
32
-
2
extend into oil sump
36
and that all of ports
32
-
1
a
and
32
-
2
a
are located above the intake of oil pick up tube
34
. This is to prevent the generation of foam from uncovering oil pick up tube
34
and thereby interfering with compressor lubrication.
Although two discharge tubes
32
-
1
and
32
-
2
are illustrated with each having a plurality of ports
32
-
1
a
and
32
-
2
a
, respectively, one discharge tube and any convenient number of ports may be employed. The critical consideration is to avoid unnecessary restrictions. Accordingly, the discharge tubes should have a combined cross section at least equal to that of discharge port
28
-
2
and the ports
32
-
1
a
and
32
-
2
a
should be at least 0.25 inches in diameter and have a total cross sectional area on the order of 1.2 to 1.5 times the area of discharge port
28
-
2
.
As best shown in
FIGS. 1
,
5
and
6
, an oil separator
50
is suitably secured to the top of the interior of shell
12
in a surrounding relationship to discharge line
60
. Referring specifically to
FIGS. 5 and 6
, oil separator
50
includes: (1) a flat portion
50
-
1
facing rotor
44
and having a plurality of ports
50
-
1
a for oil drainage; (2) an inner annular wall member
50
-
2
having a plurality of ports
50
-
2
a
and being welded or otherwise suitably secured to the interior of shell
12
; and, (3) outer annular wall member
50
-
3
having a plurality of ports
50
-
3
a
and being spaced from the interior of shell
12
.
Initially, compressor
10
will be charged with oil up to, or a little above, the top surface of motor end bearing
28
. During operation of compressor
10
, some oil will be carried off to the refrigeration circuit due to the affinity between oil and refrigerant. The generation of foam by the discharge gas will temporarily remove oil from the sump as the foam moves into the space above motor end bearing
28
. Foam will be continuously generated, collapsed and drained back into sump
36
but the oil level will drop due to the removal of oil as foam. To prevent the excess loss of oil due to foam generation, ports
32
-
1
a
and
32
-
2
a
must be located above the inlet of oil pick up tube
34
by a minimum of a quarter of an inch. If the level of oil in sump
36
drops below ports
32
-
1
a
and
32
-
2
a
, no foam is generated and compressor
10
will be noisier but will operate without problems as long as the oil is able to circulate for compressor lubrication.
In operation, rotor
44
and eccentric shaft
40
rotate as a unit and eccentric
40
-
2
causes movement of piston
22
. Oil from sump
36
is drawn through oil pick up tube
34
into bore
40
-
4
which acts as a centrifugal pump. The pumping action will be dependent upon the rotational speed of shaft
40
. As best shown in
FIG. 2
, oil delivered to bore
40
-
4
is able to flow into a series of radially extending passages, in portion
40
-
1
, eccentric
40
-
2
, and portion
40
-
3
exemplified by passage
40
-
5
in eccentric
40
-
2
, to lubricate bearing
24
, piston
22
, and bearing
28
, respectively. The excess oil flows from bore
40
-
4
and either passes downwardly over the rotor
44
and stator
42
to the sump
36
or is carried by the gas flowing from the annular gap between rotor
44
and stator bore
42
-
1
and impinges and collects on the inside of cover
12
-
1
or oil separator
50
before draining to sump
36
.
Piston
22
coacts with vane
30
in a conventional manner such that refrigerant gas is drawn through suction tube
16
and passageway
20
-
2
to suction chamber S. The gas in suction chamber S is compressed after suction chamber S has been cut off from suction tube
16
and has been transformed into a compression chamber C while a new suction chamber is being formed. The hot compressed gas in compression chamber C passes through discharge port
28
-
2
unseating discharge valve
29
and enters into the interior of muffler
32
. The compressed gas divides in muffler
32
with part flowing into tube
32
-
1
and out ports
32
-
1
a
and part flowing into tube
32
-
2
and out ports
32
-
2
a
. The gas, at discharge pressure, passing from muffler
32
via ports
32
-
1
a
and
32
-
2
a
enters oil sump
36
which is also at discharge pressure. Depending upon the oil level in sump
36
and the location of ports
32
-
1
a
and
32
-
2
a
relative to the oil in sump
36
, foam may or may not be generated. The passing of the hot discharge gas into oil sump
36
increases the temperature of the oil in sump
36
and tends to generate foam. Under certain operating conditions, such as those encountered in heat pump operation, the solubility of the refrigerant in the oil could be very high due to low ambient temperature. In such a case, the oil lubrication capability may be compromised but refrigerant solubility will be significantly reduced due to the heating of the oil thereby improving its lubricating effectiveness. Additionally, the discharge of the gas into the oil sump
36
produces a foam which has a greater volume than the oil forming the foam and so tends to flow through the passages defined by recessed portions
20
-
3
and
20
-
4
and the interior of shell
12
, as best shown in FIG.
2
. There will be a tendency for the lower shell, i.e. the portion of shell
12
below rotor
44
and stator
42
to fill with foam. Because the gas/liquid impedance is ineffective for sound transmission and because there is no direct path for sound to travel, the compressor
10
is quieter than conventional compressors. If ports
32
-
1
a
and
32
-
2
a
are located above the surface of the oil in sump
36
, no foam will be generated but the oil will be heated by the hot discharge gas thereby improving the lubricating effectiveness of the oil.
If excessive oil passes from compressor
10
with the discharge gas it can interfere with heat transfer in the refrigeration system and can leave an inadequate amount of oil in oil sump
36
for proper lubrication. The presence of foam greatly increases the amount of oil present with the discharge gas. The discharge gas must however go past the motor and this can only be done by passing through the clearance between rotor
44
and stator bore
42
-
1
or by passing through the slots or grooves
42
-
2
in the outer surface of stator
42
. Because the clearance between rotor
44
and stator bore
42
-
1
is small and because the relative movement of rotor
44
with respect to stator
42
results in a shearing force on any foam bubbles entering the clearance, the foam tends to collapse in passing between the rotor
44
and stator
42
. Additionally, the relative rotation of rotor
44
with respect to stator
42
tends to cause the discharge gas to move in a spiral path that tends to centrifugally remove oil from the gas. The swirling flow tends to persist into the space between rotor
44
and discharge line
60
. Oil separator
50
tends to collect oil and prevents its being entrained with the gas passing from compressor
10
through discharge line
60
to the condenser
70
of the refrigeration circuit. Specifically, refrigerant, oil and any remaining foam passing between rotor
44
and stator
42
tends to be moving in a spiral path which tend to move any oil outward. The refrigerant and any entrained oil will flow either through ports
50
-
3
a
or between wall member
50
-
3
and the interior of shell
12
before passing through ports
50
-
2
a
and the changes in flow direction will tend to separate out entrained oil which will drain through drainage ports
50
-
1
a
. The refrigerant and any entrained oil passing through ports
50
-
2
a
will undergo a change in flow direction prior to flowing into discharge line
60
which will tend to separate out entrained oil which will drain through drainage ports
50
-
1
a
. The oil draining through drainage ports
50
-
1
a
will tend to fall into the swirling flow passing between rotor
44
and stator
42
and will thereby be directed towards the interior of casing
12
. While discharge gas may flow past stator
42
via grooves
42
-
2
, it is more likely to be the location of return oil flow to sump
36
given the fact that there is no pressure gradient so that gravity flow of the oil will take place and because of the centrifugal effect on oil in the gap between rotor
44
and stator bore
42
-
1
.
Although the present invention has been illustrated and described in terms of a vertical, high side, variable speed compressor, other modifications will occur to those skilled in the art. For example, the invention is applicable to both horizontal and vertical compressors. The only significant difference would be the location of the oil sump relative to the muffler and the discharge from the muffler could be straight down into the portion of the oil sump between the pump structure and the stator which would be well removed from the appropriate oil pick up tube. It is therefore intended that the present invention is to be limited only by the scope of the appended claims.
Claims
- 1. In a refrigeration system containing refrigerant and serially including a high side rotary compressor, a condenser, expansion means and an evaporator, said compressor comprising:shell means having a first end and a second end; cylinder means containing pump means including a vane and a piston coacting with said cylinder means to define suction and compression chambers; said cylinder means being fixedly located in said shell means near said first end; first bearing means secured to said cylinder means and extending towards said first end; second bearing means secured to said cylinder means and extending towards said second end; a discharge port in said second bearing means; a normally closed discharge valve controlling flow through said discharge port, an oil sump located at the lowest portion of said shell means and containing oil therein; and muffler means for directing at least a major portion of the discharge flow passing through said discharge port into said oil in said oil sump whereby said oil is heated and foam is generated.
- 2. The compressor of claim 1 wherein:said compressor is a vertical compressor; and said oil sump is located beneath said pump means.
- 3. The compressor of claim 1 wherein said muffler means includes at least one discharge tube having a blocked end and at least one port along its length.
- 4. The compressor of claim 1 further including means for oil separation secured to and located within said shell means at said second end and forming a portion of a discharge flow path leading to said condenser.
US Referenced Citations (7)