Scroll compressor with oil pickup tube in oil sump

In a high side scroll compressor, the motor is located above the scrolls and the oil sump and discharge gas are isolated from each other. The compressor can be used in an orientation that can range between vertical and at least 20.degree. of horizontal.

BACKGROUND OF THE INVENTION 
Scroll machines can be used to compress, expand or pump fluids and include 
two scroll members each of which has a circular end plate and a spiral or 
involute wrap. The scroll members are maintained angularly and radially 
offset so that both wraps interfit to make either a plurality of line 
contacts or are spaced by minimum clearances between the wraps to thereby 
define at least one pair of fluid pockets or chambers. One scroll member 
is stationary and the other orbits through an eccentric shaft and an 
antirotation coupling. The relative orbital motion of the two scroll 
members shifts the line contacts or minimum clearances along the curved 
surfaces of the wraps so that the trapped volumes in the fluid pockets 
change in volume. The trapped volumes can increase or decrease depending 
upon the direction of orbiting motion. Because several trapped volumes 
generally exist at the same time, several line contact or minimum 
clearance points also exist at the same time with each moving along the 
wraps with movement being towards the center or discharge port in the case 
of a compressor. In the case of a compressor, the compressed gas produces 
a force tending to axially separate the scroll members resulting in high 
thrust loads and tip leakage. Additionally, different designs are normally 
required for horizontal and vertical units. The inherent configuration of 
scroll machines is tall/long and thin. Thus, from the system unit size and 
packaging configurations, it is generally desirable to mount the scroll 
machines horizontally. 
Conventionally, in vertical scroll compressors, the motor is mounted 
beneath the scroll mechanism with the following results: a slightly longer 
shell; a basic centrifugal pump which requires high lift in order to cross 
the motor and lubricate the highly loaded bearings; a gravity oil 
separation mechanism which is orientation sensitive to return the oil to 
the sump; and a finely metered oil injection system with limited sealing 
capabilities. 
SUMMARY OF THE INVENTION 
In the preferred embodiment, a high side scroll compressor is sealed by a 
combination of close tolerance control and oil injection. It is therefore 
necessary to provide effective oil separation from the discharge gas since 
the oil provides a lubrication function in addition to sealing. The oil 
sump is isolated and the oil pumping action takes place due to the 
centrifugal pumping action of the crankshaft and due to the pressure 
differential between the oil sump which is at compressor discharge 
pressure and the interstage pressure(s) at which oil injection into the 
scrolls takes place. In a vertical orientation, the motor is mounted on 
top of the scroll which permits the taking advantage of the vortex created 
at the entry of the discharge tube for centrifugal separation of the oil. 
In a generally horizontal orientation, the device still operates 
satisfactorily and the weight bias of the motor is reduced. An angle of at 
least 15.degree.-20.degree. from horizontal is necessary for a gravity 
return of the oil to the sump. 
It is an object of this invention to provide an orientation insensitive 
scroll compressor. 
It is another object of this invention to provide a scroll compressor in 
which the oil sump and discharge gas are isolated from each other. These 
objects, and others as will become apparent hereinafter, are accomplished 
by the present invention. 
Basically, a high side scroll compressor uses oil injection for sealing, 
for supplying a back pressure bias for offsetting axial loading and for 
providing lubrication. The oil sump is isolated and at discharge pressure 
so that a pressure differential provides the motive force for supplying 
the oil to the bearing surfaces and thereafter to the points of injection. 
In the vertical orientation, the motor is located above the scroll members 
and its weight acts in concert with the back-pressure bias to offset axial 
loading.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
In FIGS. 1-4, the numeral 20 generally indicates the fixed scroll having a 
wrap 22 and the numeral 21 generally indicates the orbiting scroll having 
a wrap 23. The chambers labeled A-M and 1-12 each serially show the 
suction, compression and discharge steps with chamber M being the common 
chamber formed at discharge 25 when the device is operated as a 
compressor. It will be noted that chambers 4-11 and D-K are each in the 
form of a helical crescent or lunette approximately 360.degree. in extent 
with the two ends being points of line contact or minimum clearance 
between the scroll wraps. If, for example, point X in FIG. 1 represents 
the point of line contact or of minimum clearance separating chambers 5 
and 9 it is obvious that there is a tendency for leakage at this point 
from the high pressure chamber 9 to the lower pressure chamber 5 and that 
any leakage represents a loss or inefficiency. To minimize the losses from 
leakage, it is conventionally necessary to maintain close tolerances, use 
a positive mechanical tip seal and to run at high speed. However, the 
present invention uses oil injection to achieve a sealing function. Again 
referring to FIGS. 1-4, it will be noted that there is a symmetry in that 
chambers 1-12 correspond to chambers A-L with a difference being that they 
are on opposite sides of the wraps 22 and 23. 
Referring now to FIGS. 5-8, fixed scroll 20 is generally disc shaped with a 
spiral shape portion removed to define wrap 22. Two diametrically spaced 
recessed areas 20-1 and 2, approximately 30.degree. in circumferential 
extent, are formed in the circumference of fixed scroll 20 so as to leave 
ledges 20-3 and 4, respectively. As best shown in FIG. 7, diametrical bore 
20-5 is fluidly connected to discharge 25 so as to form a part of the 
discharge flow path and extends between spaced recess areas 20-1 and 2. 
Bore 20-6 receives the suction tube and serves as an inlet. Bore 20-6 has 
an internal groove 20-7 formed therein for receiving an O-ring as will be 
described below. Counterbored axial bores 20-8 are provided for receiving 
assembly bolts. Axial bore 20-9 receives the oil pickup tube and forms a 
portion of the lubricant flow path. Axial bores 20-10 form a portion of 
the oil return flow. 
Referring now to FIGS. 9-12, orbiting scroll 21 has a boss 21-1 on the side 
opposite to wrap 23. Axial bore 21-2 is formed in boss 21-1. Radial bore 
21-3 terminates in bore 21-2 and is plugged at the other end by a set 
screw 26, or other suitable structure. Axial bore 21-4 intersects annular 
groove 21-14 and terminates in bore 21-3 and together therewith form a 
portion of the lubricant flow path. Diametrically opposed bores 21-5 and 6 
are intersected by axial bores 21-7 and 21-8, respectively. Radial bore 
21-9 is formed in boss 21-1 and is intersected by axial bore 21-10. Axial 
bore 21-11 extends through orbiting scroll 21. Axial bores 21-7, 8, 10 and 
11 each terminate at wrap 23 to provide a flow path for the lubricant 
which provides a seal between wraps 22 and 23. More specifically, bores 
21-7 and 8 provide oil between the wraps at lower intermediate pressure 
and bores 21-10 and 11 provide oil between the wraps at upper intermediate 
pressure thereby creating a pressure differential with the oil sump. 
Additionally, this oil at the lower and upper intermediate pressure 
levels, prior to being supplied between the wraps, acts on the back of 
orbiting scroll 21 to balance the axial forces tending to separate scrolls 
20 and 21. Radial grooves 21-12 and 13 coact with the Oldham coupling in a 
conventional manner. Diametrically located V-grooves 21-15 provide a 
lubrication path across boss 21-1 which provides a thrust face for the 
crankshaft. 
Crankshaft 30, as best shown in FIG. 16, serially includes reduced shaft 
portion 30-1, main shaft portion 30-2, flange portion 30-3 and eccentric 
30-4. Generally axial bore 30-5 terminates in diametrical bore 30-6. Bores 
30-5 and 6 form part of the lubricant flow path and define a centrifugal 
pump. In assembly, crankshaft 30 is received in bearing head 32 which is 
best illustrated in FIGS. 13-15. 
Main shaft portion 30-2 of crankshaft 30 is supportedly received in bore 
32-1 of bearing head or crankcase 32 while reduced shaft portion 30-1 
extends outwardly therefrom. Bore 32-1 is located in tubular portion 32-5 
and transitions into bore 32-4 with annular shoulder 32-2 and annular 
recess 32-3 defined therebetween. Shoulder 32-2 controls the upward axial 
motion of crankshaft 30 which may occur during start up (electromagnetic 
force) or due to unbalanced gas forces during abnormal operation. Radial 
slots 32-6 and 7 are formed in annular recess 32-8 in face 32-9 and coact 
with the Oldham coupling in a conventional manner. Tubular portion 32-5 is 
surrounded by and coaxial with sleeve portion 32-10 and together therewith 
forms an annular recess 32-11 for collecting the oil which then drains 
through passages 32-12. As best shown in FIGS. 13 and 14, the bottom 
portion of recess 32-11 is separated into four portions by webs 32-20 
which are at an angular spacing of 90.degree. and provide rigidity. An 
annular shoulder 32-13 is formed on the inner wall of sleeve portion 32-10 
and supports the stator of the motor. Annular recess 32-14 is formed in 
bore 32-1 and defines an oil galley providing an oil volume for 
lubricating the crankshaft and journal surfaces. Diametrically spaced, 
axially extending, recessed areas 32-15 and 16 are formed in the outer 
wall of sleeve portion 32-10 and correspond to spaced recessed areas 20-1 
and 2 of fixed scroll 20. Radial notches 32-17 and 18 extend through 
sleeve portion 32-10 at recessed areas 32-15 and 16, respectively. 
Threaded axial bores 32-21 receive bolts 40. Counterweight 34 which is 
illustrated in FIG. 17 is secured to flange 30-3 of crankshaft 30 in any 
suitable fashion and offsets the dynamic unbalance due to the eccentric 
30-4, orbiting scroll 21 and Oldham coupling 36. 
Referring now to FIGS. 18-20, the numeral 14 generally designates a scroll 
compressor which has a three-piece shell 15 made up of top shell 15-1, 
middle shell 15-2 and bottom shell 15-3. Shells 15-1 to 3 are welded 
together such that top shell 15-1 and bottom shell 15-3 are partially 
within middle shell 15-2 and their ends define shoulders which serve to 
hold the compressor structure in place as will be explained below. Suction 
tube 16 and discharge tube 17 extend through and are suitably sealed to 
middle shell 15-2 and top shell 15-1, respectively, as by welding. Suction 
tube 16, additionally, is received in bore 20-6 of fixed scroll 20 and is 
sealed from the interior of shell 15 by O-ring 18 which is located in 
internal groove 20-7 in bore 20-6. 
Eccentric 30-4 of crankshaft 30 is received in bore 21-2 of tubular boss 
21-1 of orbiting scroll 21 and as shown in FIGS. 18-20, the end of 
eccentric 30-4 is in an enlarged portion of bore 21-2 and not in contact 
therewith so that edge effects are avoided. Crankshaft 30 and orbiting 
scroll 21 move as a unit with flange 30-3 and counterweight 34 in bore 
32-4 while boss 21-1 is held to the orbiting motion of orbiting scroll 21. 
Flange 30-3 which is located between shoulder 32-2 and tubular boss 21-1 
also serves as a thrust surface. Oldham coupling 36 is located in annular 
recess 32-8, radial grooves 21-12 and 13, and radial slots 32-6 and 7 so 
that Oldham coupling 36 coacts with orbiting scroll 21 and bearing head 32 
in a conventional fashion to limit movement of orbiting scroll 21 to an 
orbiting motion. Spacer ring 38 is bolted between fixed scroll 20 and 
bearing head 32 by a plurality of assembly bolts 40 which have bolt seals 
41 to prevent leakage along the threads of bolts 40. Spacer ring 38 
prevents the tightening of bolts 40 to such an extent that movement of 
orbiting scroll 21 and Oldham coupling 36 is interfered with. As best 
shown in FIG. 19, spacer ring 38 has a pair of diametrically spaced, 
axially extending, recessed areas 38-1 and 2. If desired, spacer ring 38 
may be made as part of bearing head 32 or fixed scroll 20. However, for 
manufacturing purposes, a separate spacer ring 38 is preferred since its 
thickness can be selected depending upon the thickness of the plate or 
disk of the orbiting scroll 21. 
With shaft 30, bearing head 32, orbiting scroll 21, spacer ring 38, Oldham 
coupling 36 and fixed scroll 20 bolted together by bolts 40 into the 
assembly described above, stator 44-1 of motor 44 is shrink fit into the 
bearing head 32 such that stator 44-1 engages angular shoulder 32-13 and 
is properly positioned thereby. As stator 44-1 is being fit into place, 
rotor 44-2 is shrink fit onto reduced shaft portion 30-1 of crankshaft 30. 
It will be noted that rotor counterweights 44-3 and 4 are provided on 
rotor 44-2 to offset the inertial forces and moment produced by the 
driving of orbiting scroll 21 and eccentric 30-4. It should be noted that 
orbiting scroll 21 is balanced so that its center of gravity is located 
along the axis of bore 21-2. 
Oil pickup tube 50 is inserted into axial bore 20-9 in fixed scroll 20. The 
assembly of shaft 30, bearing head 32, orbiting scroll 21, spacer ring 38, 
Oldham coupling 36, fixed scroll 20 pickup tube 50 and motor 44 is then 
inserted in middle shell 15-2. Suction tube 16 is inserted through opening 
15-4 in shell 15-2 past O-ring 18 into bore 20-6 and is then welded or 
otherwise suitably secured in place. A gasket 19 is placed upon the 
machined lower surface of fixed scroll 20 and lower shell 15-3 is then 
inserted into middle shell 15-2 until it squeezes gasket 19 between shell 
15-3 and fixed scroll 20 and is then welded or otherwise suitably secured 
to middle shell 15-2. Top shell 15-1 is then inserted into middle shell 
15-2 until it engages sleeve portion 32-10 of bearing head 32 and is then 
welded or otherwise suitably secured to middle shell 15-2. Gasket 19 
ensures the isolation of the discharge gas and lubrication oil. When 
assembly takes place as described, the internal compressor structure is 
secured and located in a manner easily executed in a manufacturing 
process. 
In operation gaseous refrigerant is drawn into scroll compressor 14 via 
suction tube 16 and passes via bore 20-6 into the space surrounding wraps 
22 and 23 as best shown in FIGS. 5 and 18. The gaseous refrigerant is 
compressed in the manner illustrated in FIGS. 1-4. Referring now to FIGS. 
7 and 19, the compressed gaseous refrigerant is forced through discharge 
25 into bore 20-5 where the flow divides. A first portion of the flow 
passes from bore 20-5 serially into the flow passage defined by the 
interior of middle shell 15-2 and recessed areas 20-1, 38-1 and 32-15 from 
which it passes through radial notch 32-17 and passes over stator 44-1 
into discharge tube 17 which delivers the compressed refrigerant to the 
system. Similarly, the second portion of the flow passes from bore 20-5 
serially into the flow passage defined by the interior of middle shell 
15-2 and recessed areas 20-2, 38-2 and 32-16 from which it passes through 
radial notch 32-18 and passes over stator 44-1 into discharge tube 17. 
Since the middle shell has a large surface area exposed to ambient, this 
circulation of the compressed refrigerant in contact with shell 15 prior 
to discharge from the shell 15 effectively reduces the discharge gas 
temperature and thereby provides efficient cooling. Because the flow path 
requires flow over the rotating rotor 44-2, the gas and oil mist is 
effectively subjected to a centrifugal separation which removes oil from 
the compressed refrigerant gas delivered to discharge tube 17. The flow of 
refrigerant is indicated by the arrows in FIGS. 18 and 19. The 
centrifugally separated oil flows downwardly, as indicated by the arrows 
in FIG. 20, through the holes in the motor 44 (not illustrated) and the 
arc passages (not illustrated) on the outer diameter of stator 44-1 and 
the inner wall of sleeve portion 32-10 to recess 32-11. 
Since the interior of shell 15 is at compressor discharge pressure this 
pressure can be used in combination with the centrifugal pump defined by 
bores 30-5 and 6 in crankshaft 30 to deliver the lubricant. Specifically 
oil sump 48 which is defined by bottom shell 15-3 is at discharge pressure 
and oil pickup tube 50 extends beneath the surface of the oil. As long as 
this is true, oil will be delivered through tube 50 if it is connected to 
a region at less than discharge pressure. This also requires that the 
location of the inlet of the pickup tube be considered when the unit is 
located in other than an essentially vertical position. For example the 
inlet of the tube may have to be located at one side of the shell 15 which 
is the bottom when the compressor 14 is 20.degree. from horizontal. 
Referring specifically to FIGS. 10 and 20, compressor discharge pressure 
acting on the oil in oil sump 48 forces oil into pickup tube 50 from which 
the oil serially passes through axial bore 20-9, axial bore 21-4 and 
radial bore 21-3 into the bottom of axial bore 21-2, beneath eccentric 
30-4. Because of the movement of orbiting scroll 20, the bore 21-4 will be 
moving relative to bore 20-9 but they will remain in registration such 
that the oil flow path established therebetween continually exists. 
Additionally, bore 21-4 intersects annular groove 21-14 which provides 
lubrication for thrust bearing lubrication between fixed scroll 20 and 
orbiting scroll 21. Due solely to the pressure differential between the 
back of orbiting scroll which is at less than discharge pressure and 
discharge pressure acting on the sump, or in combination with centrifugal 
force of bore 30-6 a portion of the oil flows up bore 30-5 into bore 30-6 
which acts as a centrifugal booster pump and then passes at increased head 
into the annular chamber defined by annular recess 32-14 and crankshaft 30 
at a higher than compressor discharge pressure thereby providing a seal 
from the discharge gas. Oil flows upwardly and downwardly from the annular 
recess 32-14 to lubricate the crankshaft 30. Oil flowing upwardly flows 
through passages in the eccentric shaft and out of bearing head 32 and 
passes down the tubular portion 32-5 into annular recess 32-11 where it 
joins oil flowing by gravity after being centrifugally separated from the 
discharge gas as described above. The oil drains from annular recess 32-11 
due to gravity via one or more oil drains 32-12 which are each serially 
connected through a bore 38-3 in spacer ring 38 and a bore 20-10 in fixed 
scroll 20 back to the oil sump 48. It should be noted that this is the 
only return path to the sump 48 and the compressed refrigerant passing 
through bore is prevented by gasket 19 from leaking into sump 48. Gasket 
19 also prevents the leakage of oil back into the discharge passages if, 
for example, the oil sump level reached the rotor such as when there is 
refrigerant entrainment in the oil. Hence this compressor will safely 
operate fully submerged in oil. 
The oil flowing downwardly from the annular recess 32-14 between crankshaft 
30 and the eccentric shaft journal defined by bore 32-1 flows into upper 
intermediate pressure chamber which is at less than discharge pressure and 
is defined by bore 32-4 in which eccentric 30-4 and counterweight 34 
rotate and boss 21-1 orbits. A portion of the oil supplied into the bottom 
of axial bore 21-2 flows through the oil clearance between eccentric 30-4, 
bore 21-2 and V-grooves 21-15 into the upper intermediate pressure chamber 
defined by bore 32-4. Oil entering the upper intermediate pressure chamber 
"flashes off" any entrained refrigerant. The upper intermediate pressure 
chamber defined by bore 32-4 is in a restricted fluid communication with 
annular lower intermediate pressure chamber defined by spacer ring 38 and 
annular recess 32-8 in which Oldham coupling 36 moves and orbiting scroll 
21 orbits. The restriction between the chambers is defined by the coaction 
of face 32-9 with orbiting scroll 21. The oil in the upper intermediate 
pressure chamber defined by bore 32-4 serves to lubricate shoulder 32-2 
flange 30-3 and counterweight 34 as it enters the chamber while providing 
a seal. If the thrust forces are properly balanced, shoulder 32-2 will not 
be loaded. Oil and the flashed refrigerant from the upper intermediate 
stage pressure chamber defined by bore 32-4 passes through bores 21-9 and 
10 to be delivered to the wraps at one point and via bore 21-11 to be 
delivered to the wraps at a second point such that the oil provides a seal 
between the wraps 22 and 23 which confine compressed gaseous refrigerant 
at a pressure less than discharge. Oil also leaks between and thereby 
lubricates the contact area of face 32-9 and orbiting scroll 21 as it 
flows to the chamber defined by spacer ring 38 and annular recess 32-8 but 
the pressure is reduced from upper intermediate to lower intermediate 
pressure in going between the chambers. The lower intermediate pressure 
oil in the chamber defined by spacer ring 38 and annular recess 32-8 
lubricates the Oldham coupling 36 and is delivered via bores 21-7 and 21-8 
to the wraps at different points such that the oil provides a seal between 
the wraps which confine compressed gaseous refrigerant at a pressure less 
than the pressure at which oil is delivered via bores 21-10 and 11. 
Because bores 21-7,8,10 and 11 are in fluid communication with the gas 
being compressed between the wraps but which is at less than discharge 
pressure, this establishes a pressure differential with the oil sump which 
is at discharge pressure and provides the pressure differential necessary 
for oil flow. 
Although the present scroll compressor 14 is operational when a single 
level of back pressure acts on orbiting scroll 21, by using dual back 
pressure chambers, the rotating action of counterweight 34 agitates the 
oil and thereby removes the refrigerant saturated in the oil. As a result 
of centrifugal force, oil moves away from the center of rotation and thus 
the separated gaseous refrigerant can be injected back into the scrolls 
along with the oil and thereby increase the efficiency. The remainder of 
the oil passes between the sealing surfaces defined by face 32-9 and 
orbiting scroll 21 into the lower intermediate pressure chamber defined by 
spacer ring 38 and annular recess 32-8 thereby lubricating the thrust 
surface and the Oldham coupling. The oil then passes into bores 21-5 and 
6, and is injected into the scroll elements via bores 21-7 and 8, 
respectively. Since the axial forces are balanced by dual back pressures 
in the respective chambers, the pressure at the lower intermediate 
pressure is lower than the case where the whole back chamber is exposed to 
a single intermediate pressure. This reduces the pressure differential 
between the suction plenum and the lower intermediate back chamber and 
thereby reduces the tendency to leak. 
Although a preferred embodiment of the present invention has been 
illustrated and described, other modifications will occur to those skilled 
in the art. It is, therefore, intended that the present invention is to be 
limited only by the scope of the appended claims.