Scroll compressor oil pumping system

A scroll machine has a cover plate attached to the lower bearing housing which is adjacent the lower motor windings of the scroll machine. The cover plate has a plurality of grooves which work in conjunction with a lower counterweight of the scroll machine to circulate the lubricating oil located in the sump around the lower motor winding to cool the motor.

FIELD OF THE INVENTION 
The present invention generally relates to scroll-type machinery. More 
particularly, the present invention relates to a scroll type machine which 
includes a lower housing which is adapted to prevent lower counterweight 
oil pumping power loss and to provide additional motor cooling. 
BACKGROUND AND SUMMARY OF THE INVENNTION 
Scroll machinery for fluid compression or expansion is typically comprised 
of two upstanding interfitting involute spirodal wraps or scrolls which 
are generated about respective axes. Each respective scroll is mounted 
upon an end plate and has a tip disposed in contact or near contact with 
the end plate of the other respective scroll. Each scroll further has 
flank surfaces which adjoin, in moving line contact or near contact, the 
flank surfaces of the other respective scroll to form a plurality of 
moving chambers. Depending upon the relative orbital motion of the 
scrolls, the chambers move from the radially exterior ends of the scrolls 
to the radially interior ends of the scroll for fluid compression, or from 
the radially interior ends of the scrolls to the radially exterior ends of 
the scrolls for fluid expansion. The scrolls, to accomplish the formation 
of the chambers, are put in relative orbital motion by a drive mechanism. 
Either one of the scrolls may orbit or both may rotate eccentrically with 
respect to one another. 
A typical scroll machine, according to the design which has a non-orbiting 
scroll, includes an orbiting scroll which meshes with the non-orbiting 
scroll, a thrust bearing to take the axial loads on the orbiting scroll, 
and a lubricant supply system for lubricating the various moving 
components of the machine including the thrust bearing. 
The typical lubricant supply system incorporates a lubricant sump in the 
lower or bottom portion of the housing into which the drive shaft extends 
so as to pump lubricant therefrom to the various portions of the 
compressor requiring lubrication. In addition, the lubricant also often 
acts to aid in the removal of heat from the various components of the 
compressor. In order to insure that sufficient lubricating oil is 
contained within the sump to assure adequate lubrication and/or cooling of 
the moving parts while also minimizing the overall height of the housing, 
it is sometimes necessary that the lubricant level within the housing 
extend above the rotating lower end of the rotor. The higher viscosity of 
the lubricant as compared to refrigerant gas can create an increased drag 
on rotation of the portion of the rotor submersed in lubricant, thus 
resulting in increased power consumption. This problem can be further 
aggravated in scroll-type compressors which employ a counterweight secured 
to the lower end of the rotor and thus also submersed in the lubricant. 
U.S. Pat. No. 4,895,496 discloses a cup-shaped shield member which projects 
above the oil level in the sump and is positioned in surrounding 
relationship to the lower end of the rotor via a close fit with the drive 
shaft whereby the oil level in the area within the shield is reduced by 
the initial rotation of the rotor upon startup and return oil flow into 
this area is greatly restricted. Thus, the oil induced drag on the rotor 
and the resulting increased power consumption of the motor is greatly 
reduced. In one embodiment, a rotation inhibiting projection is provided 
on the shield while in another embodiment the shield is allowed to rotate 
with the drive shaft although the speed of rotation thereof will be 
substantially less than that of the drive shaft due to the drag exerted 
thereon by the lubricant. In both embodiments, however, the power 
consumption of the motor is greatly reduced thus resulting in significant 
improvement in the operating efficiency of the compressor. 
While the above described shield does reduce motor power consumption by 
substantially eliminating the viscous drag of the lubricant on the rotor, 
it also eliminates or significantly reduces the amount of lubricant being 
circulated across the lower end turns of the stator. In some applications, 
it may be desirable to achieve the advantages of this higher operating 
efficiency while also maintaining a substantial flow of lubricant across 
the stator end turns for cooling of same. 
U.S. Pat. No. 5,064,356 discloses a shield which is carried by the drive 
shaft and allowed to freely rotate therewith. This shield incorporates a 
generally flat circular disk or flange positioned in close proximity to 
the lower end of the rotor which serves to restrict return flow of oil to 
the area of the rotating rotor and/or counterweight but still enables some 
circulation of oil across the adjacent stator end turns. This increase in 
lubricant circulation results in improved cooling of the stator end turns 
without any substantial effect on the overall operating efficiency of the 
compressor. 
While the above described shield in the U.S. Pat. No. 5,064,356 does allow 
for the increase in circulation of oil across the adjacent stator end 
turns, this approach, similar to the approach taken in the U.S. Pat. No. 
4,895,496 completely isolates the lower counterweight from the oil sump. 
The lower counterweight due to its rotation within the compressor has a 
large pumping capacity. This pumping capacity could be utilized to improve 
the oil circulation in the area surrounding the motor stator to improve 
motor cooling. 
The present invention provides an oil circulation system which does not 
isolate the lower counterweight but restricts the oil circulation around 
the lower end of the motor stator in such a way that it controls the oil 
circulation's net effect on motor cooling as well as power loss versus the 
oil level within the lubrication sump. 
Other advantages and objects of the present invention will become apparent 
to those skilled in the art from the subsequent detailed description, 
appended claims and drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
While the present invention is suitable for incorporation into many 
different types of scroll machines, for exemplary purposes it will be 
described herein incorporated into a scroll compressor. Referring now to 
the drawings in which like reference numerals designate like or 
corresponding parts throughout the several views, there is shown in FIG. 1 
a vertical sectional view of a scroll compressor 10 incorporating the 
lubrication system according to the present invention. Generally speaking, 
compressor 10 comprises a generally cylindrical hermetic shell 12 having 
welded at the upper end thereof a cap 14. Cap 14 is provided with a 
refrigerant discharge fitting 16 optionally having the usual discharge 
valve therein (not shown). Other elements affixed to cylindrical shell 12 
include a transversely extending partition 18 which is welded about its 
periphery at the same point cap 14 is welded to shell 12, a lower bearing 
housing 20 which is affixed to shell 12 at a plurality of points by 
methods known well in the art, and a suction gas inlet fitting 22. 
Lower bearing housing 20 locates and supports within shell 12 a main 
bearing housing 24, a motor stator 26, a lower bearing 28 and a 
non-orbiting scroll member 30. A crankshaft 32 having an eccentric crank 
pin 34 at the upper end thereof is rotatably journaled in lower bearing 28 
in lower bearing housing 20 and in an upper bearing 36 in main bearing 
housing 24. Crankshaft 32 has at its lower end the usual relatively large 
diameter oil-pumping concentric bore 38 which communicates with a smaller 
diameter bore 40 extending upwardly therefrom to the top of crankshaft 32. 
The lower portion of cylindrical shell 12 is filled with lubricating oil 
in the usual manner. Pumping bore 38 at the bottom of crankshaft 32 is the 
primary pump acting in conjunction with bore 40 to pump lubricating fluid 
to all the various portions of the compressor which require lubrication as 
will be described later herein. 
Crankshaft 32 is rotatably driven by an electric motor including motor 
stator 26 having motor windings 42 passing therethrough, and a motor rotor 
44 press fit on crankshaft 32 and having a lower counterweight 46 and an 
upper counterweight 48. 
Main bearing housing. 24 includes a bearing cage 50 and an upper bearing 
housing 52. Bearing cage 50 has a generally cylindrical shaped central 
portion 54 within which the upper end of crankshaft 32 is rotatably 
supported by means of bearing 36. An upstanding annular projection 56 is 
provided on bearing cage 50 adjacent the outer periphery of central 
portion 54 and includes an accurately machined radially outwardly facing 
surface 58, an accurately machined radially inwardly facing surface 59 and 
an upwardly facing locating surface 60. A plurality of radially 
circumferentially spaced supporting arms 62 extend generally radially 
outwardly from central portion 54 and include axially extending portions 
adapted to engage and be supported on lower bearing housing 20. A step 64 
is provided on the terminal end of the axially extending portion of each 
of the supporting arms 62 for engaging lower bearing housing 20. Step 64 
is designed to mate with a corresponding recess provided on the abutting 
portion of lower bearing housing 20 for aiding in radially positioned 
bearing cage 50 with respect to lower bearing housing 20. 
Upper bearing housing 52 of main bearing housing 24 is generally cup-shaped 
including an upper annular guide ring portion 66 integrally formed 
therewith, an annular axial thrust bearing surface 68 disposed below ring 
portion 66, and a second annular supporting bearing surface 70 positioned 
below and in radially outwardly surrounding relationship to axial thrust 
bearing surface 68. Axial thrust bearing surface 68 serves to axially 
movably support an orbiting scroll member 72, and supporting bearing 
surface 70 provides support for an Oldham coupling 74. The lower end of 
upper bearing housing 52 includes an annular recess defining radially 
inwardly and axially downwardly facing surfaces 76, 78 respectively which 
are designed to mate with surfaces 58 and 60 respectively of bearing cage 
50 to aid in axially and radially positioning bearing cage 50 and upper 
bearing housing 52 relative to each other. Additionally, a cavity 80 is 
designed to accommodate rotational movement of upper counterweight 48 
secured to crankshaft 32 at the upper end thereof. The provision of this 
cavity enables counterweight 48 to be positioned in closer proximity to 
orbiting scroll member 72 thus enabling the overall size thereof to be 
reduced. 
Annular integrally formed guide ring 66 is positioned in surrounding 
relationship to a radially outwardly extending flange portion 84 of 
non-orbiting scroll member 30 and includes a radially inwardly facing 
surface 86 adapted to abut a radially outwardly facing surface 88 of 
flange portion 84 so as to radially and axially position non-orbiting 
scroll member 30. 
Non-orbiting scroll member 30 has a centrally disposed discharge passageway 
94 communicating with an upwardly open recess 96 which is in fluid 
communication via an opening 98 in partition 18 with a discharge muffler 
chamber 100 defined by cap 14 and partition 18. Non-orbiting scroll member 
30 further has in the upper surface thereof an annular recess 102 having 
parallel coaxial side walls in which is sealingly disposed for relative 
axial movement an annular floating seal 104 which serves to isolate the 
bottom of recess 102 from the presence of gas under suction and discharge 
pressure so that it can be placed in fluid communication with a source of 
intermediate fluid pressure by means of a passageway (not shown). 
Non-orbiting scroll member 30 is thus axially biased against orbiting 
scroll member 72 by the forces created by discharge pressure acting on the 
central portion of non-orbiting scroll member 30 and those created by 
intermediate fluid pressure acting on the bottom of recess 102. This axial 
pressure biasing, as well as other various techniques for supporting 
scroll member 30 for limited axial movement, are disclosed in much greater 
detail in assignee's U.S. Pat. No. 4,877,382, the disclosure of which is 
hereby incorporated herein by reference. 
Relative rotation of the scroll members is preferably prevented by the 
usual Oldham coupling 74 of the type disclosed in the above referenced 
U.S. Pat. No. 4,877,382, however, the coupling disclosed in assignee's 
copending application Ser. No. 591,443 entitled "Oldham Coupling for 
Scroll Compressor" filed Oct. 1, 1990, now U.S. Pat. No. 5,320,506, the 
disclosure of which is hereby incorporated herein by reference, may be 
used in place thereof. 
The compressor is preferably of the "low side" type in which suction gas 
entering via gas inlet 22 is allowed, in part, to escape into shell 12 and 
assist in cooling the motor. So long as there is an adequate flow of 
returning suction gas the motor will remain within desired temperature 
limits. When this flow drops significantly, however, the loss of cooling 
will eventually cause a temperature sensor to signal the control device 
and shut the machine down. 
The scroll compressor as thus far broadly described is either now known in 
the art or is the subject matter of other pending applications for patent 
by applicant's assignee. The details of construction which incorporate the 
principles of the present invention are those which deal with a unique 
lubrication circulation system, indicated generally at 200. 
Lower counterweight 46 and a portion of motor windings 42 of motor stator 
26 extend below the oil level 202 located within the lower portion of 
cylindrical shell 12. Lower counterweight 46 and approximately one-half of 
motor windings 42 of motor stator 26 are completely covered by a 
cylindrical cover plate 210. Cover plate 210 is an integral part of lower 
bearing housing 20 and is located a distance "h" below the bottom of motor 
windings 42. Cover plate 210 restricts but does not isolate oil 
circulation to lower counterweight 46. Lower counterweight 46 has a large 
pumping capacity but since its suction area is, highly restricted, large 
scale cavitation is created all around lower counterweight 46. This large 
scale cavitation reduces the power consumed by lower counterweight 46 as 
it rotates within the lubricant sump, but it still allows for some oil 
circulation which promotes motor cooling heat transfer by convection into 
the circulating oil. The oil in turn is cooled by suction gas convection. 
The space 212 between the lower end turn of motor windings 42 and cover 
plate 210 is full of oil and cavitation bubbles swirling at some 
tangential velocity Vz during operation of compressor 10 as shown by the 
arrow in FIG. 3. The magnitude of Vz is limited by viscous friction in the 
space 212 and the plurality of ribs 214 of lower housing 20. A radial 
pressure gradient develops due to this swirling rotation and some radial 
flow, Vr shown by the arrows in FIG. 2, exists due to the vertically 
offset position of lower counterweight 46. In order to encourage 
additional radial flow in a controlled way, a plurality of formed radial 
slots 216 are incorporated into lower cover plate 210. Radial slots 216 
will also resist the swirling action on the lower side of space 212. The 
radial pressure gradient is therefore reduced on the side of space 212 
adjacent cover plate 210. This difference in the radial pressure gradient 
causes a radial circulating flow F.sub.R Of Oil as shown by the arrows in 
FIG. 2. This oil flow is small enough that it does not consume a 
significant amount of power, but it is large enough to significantly 
reduce motor temperature, especially at the high load low voltage 
operating conditions. This flow of oil is essentially insensitive to the 
oil level within the lubrication sump as long as the oil level is 
maintained within normal operating limits. The amount of flow can easily 
be controlled by selecting the appropriate depth of radial slots 216. 
Radial slots 216 may be incorporated into lower bearing housing 20 during 
its manufacture, thus reducing or eliminating any costs associated with 
the machining of radial slots 216. The incorporation of radial slots 216 
into lower bearing housing 20 thus eliminates the need for any type of 
auxiliary shield along with the assembly and durability issues arising 
from the use of the auxiliary shield. 
The present invention thus prevents any significant lower counterweight oil 
pumping power loss, it provides additional motor cooling due to the 
controlled amount of radial oil circulation and it makes the lower 
counterweight oil pumping power loss essentially insensitive to the oil 
level within the lubrication sump. In addition, the undesirable general 
swirling of the oil within the lubrication sump is also reduced by the 
incorporation of the above described lubricant circulation system. 
While the above detailed description describes the preferred embodiment of 
the present invention, it should be understood that the present invention 
is susceptible to modification, variation and alteration without deviating 
from the scope and fair meaning of the subjoined claims.