Oil feeding device for scroll fluid apparatus

An oil feeding device for plain bearings supporting a crankshaft connected to an orbital scroll member in a scroll fluid apparatus, including axially extending oil flow passages formed on the outer peripheral surface of the crankshaft at portions journaled by the plain bearings but displaced from the lines of action of lateral loads caused by fluid pressure in the sealed space between two scroll members, thereby generating bearing oil film reactions commensurate with the lateral loads, so as to produce an optimum oil film pressure distribution for the bearings at all times.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to scroll fluid apparatus suitable for use as 
compressors, expanders, liquid pumps, etc. and, more particularly, to an 
oil feeding device for the scroll fluid apparatus of the aforementioned 
type. 
2. Description of the Prior Art 
A scroll fluid apparatus of the type disclosed, for example, in U.S. Pat. 
No. 3,884,599 usually comprises an orbiting scroll member including an end 
plate, and a wrap in the form of an involute or any other curve similar 
thereto which is located on the end plate in upstanding position; a fixed 
scroll member including an end plate, a wrap in the form of an involute or 
any other curve similar thereto which is located on the end plate in 
upstanding position, and a discharge port formed in the end plate; a 
housing formed with a suction port and containing the orbiting scroll 
member and the fixed scroll member maintained in pressing engagement with 
each other at the surface of the respective end plates with the wraps 
facing inwardly against the end plates of the opposed scroll members; an 
Oldham's ring interposed between the orbiting scroll member and the 
housing or the fixed scroll member for preventing the rotation of the 
orbiting scroll member on its own axis; and a crankshaft maintained in 
engagement with the orbiting scroll member to enable the orbiting scroll 
member to move in orbiting movement by the action of the crankshaft while 
the orbiting scroll member does not rotate apparently on its own axis, 
whereby the fluid within sealed spaces defined by the two scroll members 
can be allowed to perform a pumping action or a pressure fluid can be 
supplied through the discharge port to expand the pressure fluid to cause 
a drive force for rotating the crankshaft to be generated. 
In scroll fluid apparatus of the aforementioned type, the crankshaft is 
usually of a vertical type and its shaft portion is journaled by two plain 
bearings or upper and lower plain bearings while its crank portion is in 
engagement with a plain bearing mounted at the orbiting scroll member. Oil 
feeding devices for feeding lubricating oil to the plain bearings 
journaling the shaft portion of the vertical crankshaft are disclosed, for 
example, in U.S. Pat. No. 4,065,279 and Japanese patent Application 
Laid-Open No. 125386/80. The oil feeding devices of the prior art 
disclosed in these documents include oil feeding grooves extending along 
the axis of the shaft portion or the crank portion. One disadvantage of 
the oil feeding devices of the prior art referred to hereinabove would 
appear to be the lack of ingenuity in design with which each bearing is 
caused to generate an oil film reaction capable of coping with a load 
applied on the bearing by the fluid pressure in the sealed spaces defined 
by the two scroll members and by the tilting of the crankshaft in the 
bearings. 
SUMMARY OF THE INVENTION 
This invention has been developed for the purpose of obviating the above 
noted disadvantage of the prior art. Accordingly, the object of the 
present invention is to provide an oil feeding device for a scroll fluid 
apparatus capable of causing an optimum oil film pressure to be generated 
in a plain bearing at all times to avoid wear and seizure that might 
otherwise occur in the bearing. 
According to the invention, there is provided an oil feeding device for a 
scroll fluid apparatus including a fixed scroll member and an orbiting 
scroll member arranged in combination, a crankshaft connected at its crank 
portion to said orbiting scroll member through a first bearing and second 
and third bearings for journaling said crankshaft, at least one of said 
bearings comprising a plain bearing, characterized in that an oil feeding 
means is provided on the outer peripheral surface of a portion of said 
crankshaft journaled by said plain bearing at a position which is spaced 
apart from the line of action of lateral load which is caused by fluid 
pressure in sealed spaces defined by the two scroll members, so as to 
cause a bearing oil film reaction to be generated corresponding to the 
lateral load. 
Additional and other objects, features and advantages of the present 
invention will become apparent from the description set forth hereinafter 
when considered in conjunction with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings wherein like reference numerals are used 
throughout the various views to designate like parts and, more 
particularly, to 
FIGS. 1-3, according to these figures, a scroll fluid apparatus 
functioning, for example, as a compressor and incorporating therein oil 
feeding device of the invention includes a housing 1A defining a chamber 1 
in which a fixed scroll member generally designated by the reference 
numeral 2 and an orbiting scroll member generally designated by the 
reference numeral 3 are disposed. The fixed scroll member 2 and the 
orbiting scroll member 3 include end plates 4 and 5 and wraps 6 and 7 of 
vortical form located in upstanding position on the respective end plates 
4 and 5. The fixed scroll member 2 and the orbiting scroll member 3 are 
maintained in pressing engagement with each other with the wraps 6 and 7 
facing inwardly. The orbiting scroll member 3 has mounted on an underside 
therein a plain bearing 8 in engagement with a crank portion 9b of a 
crankshaft generally designated by the reference numeral 9 which is off 
center with respect to a shaft portion 9a of the crankshaft 9 journaled by 
an upper plain bearing 11 and a lower plain bearing 12 mounted on a frame 
10. The crankshaft 9 is driven for rotation by an electric motor 13. As 
the crankshaft 9 rotates, the orbiting scroll member 3 moves in orbiting 
movement through an Oldahm's ring 14 and an Oldham's key 15, but is 
prevented from apparently rotating on its own axis. Fluid or gas to be 
compressed is sucked into sealed spaces defined between the fixed scroll 
member 2 and the orbiting scroll member 3 through a suction pipe 16 and 
compressed by the orbiting movement of the orbiting scroll member 3, and 
the compressed gas is discharged through an outlet 17 into the chamber 1 
from which it is released through a discharge pipe 18. As the fluid sealed 
between the two scroll members 2 and 3 is compressed, the pressure of the 
fluid applies a lateral force on the orbiting scroll member 3. This 
lateral force is applied to the crank portion 9b through the plain bearing 
8 and then transmitted to the shaft portion 9a which is borne by the plain 
bearings 11 and 12. Thus, due to the fluid pressure in the sealed spaces 
between the two scroll members, lateral or radial loads are applied on the 
plain bearings 8, 11 and 12, respectively. The crankshaft 9 is formed 
therein with an off-center oil feeding passageway 19 whose eccentricity 
with respect to the shaft portion 9a increases in a vertical direction. 
The off-center oil feeding passageway 19 draws, by suction, the oil on the 
bottom of the chamber 1 and feeds the same to the bearings 11 and 12 by 
centrifugal pumping action as the crankshaft 9 rotates. 
The oil feeding device for the bearings 8, 11, and 12 will be described in 
detail by referring to FIG. 2. In this figure, oil is fed to the plain 
bearing 8 of the orbiting scroll member 3 as will be presently described. 
The oil on the bottom of the chamber 1 is drawn by suction by the 
centrifugal pumping action of the off-center oil feeding passageway 19 and 
introduced into an oil chamber 20 defined by the upper end of the crank 
portion 9b of the crankshaft 9, plain bearing 8 and orbiting scroll member 
3. The oil introduced into the oil chamber 20 in this way is passed 
through a recessed oil flow passage 21 formed axially on the outer 
peripheral surface of the crank portion 9b of the crankshaft 9 to 
lubricate the plain bearing 8 of the orbiting scroll member 3 and the 
crank portion 9b. The oil that has lubricated the plain bearing 8 is 
discharged into an intermediate chamber 25 defined by the frame 10 and the 
orbiting scroll member 3 after flowing through an annular groove 23 formed 
in the connection between the crank portion 9b and a balance weight 22 to 
lubricate a thrust bearing 24 formed in the lower portion of the plain 
bearing 8 as a unit therewith. 
Feed of oil to the upper plain bearing 11 journaling the shaft portion 9a 
of the crankshaft 9 is effected by feeding the oil drawn by suction by the 
off-center oil feeding passageway 19 to an oil feeding aperture 26 and a 
recessed oil flow passage 27 formed axially on the outer peripheral 
surface of the shaft portion 9a and communicating with the oil feeding 
aperture 26. The oil that has lubricated the plain bearing 11 flows 
through an annular groove 28 formed in the connection between the shaft 
portion 9a and the balance weight 22 to a thrust bearing 29 formed in the 
upper portion of the bearing 11 as a unit therewith, to lubricate the 
thrust bearing 29 before being discharged into the intermediate chamber 
25. Part of the oil that has lubricated the upper plain bearing 11 is 
discharged into an oil discharging chamber 30 defined by the shaft portion 
9a, frame 10, plain bearing 11 and plain bearing 12 through the lower end 
of the plain bearing 11, to be discharged into the chamber 1 through an 
oil discharging aperture 31 formed in the frame 10. 
The oil discharged into the intermediate chamber 25 is supplied through 
small openings 32 formed in the orbiting scroll member 3 to portions of 
the two scroll members 2 and 3 in engagement with one another. Thus, an 
intermediate pressure which is between the discharge pressure and the 
suction pressure prevails in the intermediate chamber 25. This enables oil 
to be fed to the upper plain bearing 11 and the plain bearing 8 of the 
orbiting scroll member 3 by the differential pressure between the 
discharge pressure and the intermediate pressure and the centrifugal 
pumping action of the off-center oil feeding passageway 19. 
Feeding of oil to the lower plain bearing 12 journaling the shaft portion 
9a of the crankshaft 9 is effected by feeding the oil drawn by suction by 
the off-center feeding passageway 19 to an oil feeding aperture 33 
communicating with the off-center oil feeding passageway 19 and a recessed 
oil flow passage 34 formed axially on the outer peripheral surface of the 
shaft portion 9a and communicating with the oil feeding aperture 33. The 
oil that has lubricated the lower plain bearing 12 is discharged into the 
chamber 1 from the upper end of the plain bearing 12 through the oil 
discharging chamber 30 and oil discharging aperture 31 and at the same 
time discharged into the chamber 1 through the lower end of the plain 
bearing 12. 
One of the features of the present invention is that oil feeding means for 
supplying lubricant oil between the plain bearings and the crankshaft 9, 
such as the axially extending oil flow passages 21, 27 and 34 or oil 
feeding apertures 26 and 33, are provided on the outer peripheral surfaces 
of the crankshaft 9. More specifically, the axially extending oil flow 
passages 21, 27 and 34 are provided by forming recessed portions on the 
outer peripheral surfaces of the crankshaft 9. The oil feeding apertures 
26 and 33 have openings at the outer peripheral surfaces of the crankshaft 
9. The inner peripheral surfaces of the plain bearings are not provided 
with axially extending grooves at all. Thus, the oil feeding means rotate 
with the crankshaft 9. In the embodiment shown, the oil flow passages 21, 
27 and 34 are defined by recessed flat portions of the crankshaft 9. The 
flat portions may be replaced by axially extending grooves formed on the 
outer peripheral surfaces of the crankshaft 9. 
Another feature of the present invention is that the oil feed means are 
located at positions spaced apart from the lines of action of lateral 
loads applied on the bearings. In the embodiment shown, the axially 
extending oil flow passages 21, 27 and 34 and the oil feeding apertures 26 
and 33 are located such that, as shown in FIG. 3, they are disposed on a 
line X connecting the center S of the shaft portion 9a of the crankshaft 9 
and the center C of the crank portion 9b thereof. As noted above, the 
fluid compressed in the sealed spaces between the two scroll members 2 and 
3 applies a lateral force P on the orbiting scroll member 3, which is 
transmitted to the crank portion 9b of the crankshaft 9. It has been found 
that the direction of the force P is substantially perpendicular to the 
line X as shown in FIG. 3, at all times and moves in synchronism with the 
rotation of the crankshaft 9. The force P can be resolved into a component 
of force P.sub.x in the direction of line X and a component of force 
P.sub.1 perpendicular to the line X. In magnitude, the components of force 
P.sub.x and P.sub.1 are in the ratio P.sub.x :P.sub.1 =approximately 1:8. 
Thus, the force P can be regarded as substantially equal to the component 
of force P.sub.1 in magnitude and direction. 
Since the oil flow passages 21, 27 and 34 are located on the line X, it can 
be said that the oil flow passage 21 is located at a position which is 
advanced for an extent of 90 degrees in the direction of rotation of the 
crankshaft 9 with respect to the force P, the oil flow passage 27 is 
located at a position which is displaced for an extent of 180 degrees with 
respect to the oil flow passage 21, and the oil flow passage 34 is located 
at a position which is displaced for an extent of 180 degrees with respect 
to the oil flow passage 27. The above noted positional arrangement of the 
oil flow passages 21, 27 and 34 is intended to locate each of them at a 
position which is advanced for an extent of 90 degrees in the direction of 
rotation of the crankshaft 9 with respect to a line of action of a lateral 
load and to effectively cause a bearing oil film reaction to be generated. 
The reason why the oil film reaction is generated will be described later. 
The above described positional arrangement of the oil flow passages 21, 27 
and 34 is also intended to facilitate forming of the oil feeding apertures 
26 and 33 which are connected to the off-center oil feeding passageway 19 
which is positioned on the line X as viewed from above. 
In operation the electric motor 13 is actuated to rotate the crankshaft 9 
in the direction of an arrow A or clockwise in FIG. 4. This makes the 
orbiting scroll member 3 move in orbiting movement with respect to the 
fixed scroll member 2, so as to compress gas drawn by suction through the 
suction pipe 16 between the two scroll members 2 and 3 and discharge the 
compressed gas via the discharging pipe 18. During this compression 
stroke, the gas in sealed spaces defined by the two scroll members 2 and 3 
applies the force or load P.sub.1 on the crank portion 9b of the 
crankshaft 9 through the orbiting scroll member 3 and the plain bearing 8. 
This makes the crankshaft 9 tilt between the upper plain bearing 11 and 
the lower plain bearing 12. As a result, a load P.sub.2 acts on the upper 
plain bearing 11 and a load P.sub.3 acts on the lower plain bearing 12. 
FIGS. 5-7 illustrates the relationship between the positions of the oil 
flow passages 21, 27 and 34 and the directions in which the loads act that 
are established at this time. In these figures, the force P caused by the 
fluid pressure is expressed as its component of force P.sub.1 for the 
convenience of explanation. As can be clearly seen in FIGS. 5-7, the oil 
flow passages 21, 27 and 34 are located in positions which are advanced 
clockwise for an extent of 90 degrees with respect to the lines of actions 
of the loads P.sub.1, P.sub.2 and P.sub.3 respectively. It will also be 
clearly seen that the loads P.sub.1, P.sub.2 and P.sub.3 move in 
synchronism with the rotation of the crankshaft 9. Thus, the oil supplied 
through the oil flow passages 21, 27 and 34 to the bearing gaps of the 
plain bearings 8, 11 and 12 generates oil film reactors F.sub.1, F.sub.2 
and F.sub.3 corresponding to the loads P.sub.1, P.sub.2 and P.sub.3 
respectively, as shown in FIGS. 5-7. As described hereinabove, the 
positional relations between the lines of actions of the loads P.sub.1, 
P.sub.2 and P.sub.3 and the oil flow passages 21, 27 and 34, respectively, 
are constant for the respective bearings, so that the oil film pressure 
generated in each bearing is substantially similar. The oil film pressure 
distribution formed between the plain bearing 8 and the crank portion 9b 
shown in FIG. 5 will be described in some detail. 
The crank portion 9b has its center C1 displaced by the load from the 
center B1 of the plain bearing 8. A minimum gap position Za.sub.1 is 
formed on a side of the line Y.sub.1 connecting the centers C.sub.1 and 
B.sub.1 together on which the load P.sub.1 acts, and a maximum gap 
position Za.sub.2 is formed on the opposite side. The oil introduced from 
the oil flow passage 21 under the oil supply pressure is withdrawn to the 
bearing gap between the crank portion 9b and the plain bearing 8 by the 
rotation of the crank portion 9b as well as the oil supply pressure, and 
forcibily fed into the region of bearing gap which is narrowing with 
respect to the direction of rotation of the crank portion 9b. That is, 
what is generally referred to as a wedging action occurs. By virtue of the 
wedging action, the oil film pressure rises starting at the maximum gap 
position Za.sub.2 and is maximized before the minimum gap position 
Za.sub.1 is reached, thereby generating an oil film pressure F.sub.1 
corresponding to the load P.sub.1. Thereafter the oil film pressure drops 
and substantially reaches an intermediate pressure at the minimum gap 
position Za.sub.1. In the region of widening bearing gap from the minimum 
gap position Za.sub.1 formed along the direction of rotation of the crank 
portion 9b, the oil film pressure begins to drop starting at the minimum 
gap position Za.sub.1 and becomes lower than the intermediate pressure. 
Thereafter the oil film pressure rises again after reaching the maximum 
value, until it reaches the oil supply pressure at the oil flow passage 
21. Since the bearing gap is widening between the oil flow passage 21 and 
the maximum gap position Za.sub.2 with respect to the direction of 
rotation of the crank portion 9b, the oil film pressure drops and then 
gradually rises again until it substantially reaches the intermediate 
pressure level at the maximum gap position Za.sub.2. 
As described hereinabove, the oil film pressures F.sub.1 -F.sub.3 can be 
produced continuously and optimally on the bearings 8, 11 and 12, 
respectively, which are sufficiently high to bear the loads P.sub.1 
-P.sub.3 on their sliding surfaces. The oil film pressures F.sub.1 
-F.sub.3 act in a manner to reduce the tilting of the crankshaft 9 within 
the respective bearings that might otherwise be increased by the loads 
P.sub.1 -P.sub.3. As a result, the crankshaft 9 is prevented from 
contacting the bearings 8, 11 and 12 at one side only, thereby avoiding 
wear and seizure of the bearings 8, 11 and 12. Also, since the oil flow 
passages 21, 27 and 34 are located at all times in positions which are 
displaced from the minimum gap positions of the bearings, the oil flow 
passages 21, 27 and 34 never scratch the portions of the crankshaft 9 that 
might tend to contact the bearings at one side only. Moreover, the 
arrangement that the oil flow passages 21 and 37 open in the intermediate 
chamber 25 and the oil flow passage 34 opens in the chamber 1 enables the 
avoidance of a malfunctioning in oil feeding that might otherwise occur 
due to precipitation as gas bubbles of the gas dissolved in the oil and 
collection thereof in the oil feeding passageways. This is conducive to 
prevention of a reduction in the volume of oil fed to the bearings. Also, 
since the oil flow passages 21, 27 and 34 rotate with the crankshaft 9, 
fresh oil is supplied to the bearing surfaces at all times, thereby 
enabling the bearings to be effectively cooled. 
In order to increase the effects achieved in producing the oil film 
pressures and cooling the bearings, annular grooves 35 and 36 may be 
formed on the outer circumferential surface of the shaft portion 9a in 
positions corresponding to the positions in which the oil feeding 
passageways 26 and 33 communicating with the off-center oil feeding 
passageway 19 open in the oil flow passages 27 and 34, respectively, as 
shown in FIGS. 8 and 9. By this arrangement, it is possible to feed oil 
not only through the oil flow passages 27 and 34 but also through the 
annular grooves 35 and 36. This is conducive to increased volume of the 
oil fed to the bearings and increased oil film pressures as well as 
improved cooling of the bearings. The positions of the annular grooves 35 
and 36 are not limited to those described hereinabove, and they may be 
formed on the bearing side. 
In the embodiments shown and described hereinabove, feeding of oil to the 
plain bearing 8 is effected by feeding oil in the oil chamber 20 above the 
crank portion 9b through the oil below passage 21 to the bearing 8. 
However, an oil feeding passageway communicating the off-center feeding 
passageway 19 with the oil flow passage 21 may be additionally formed in 
the crank portion 9b. To more suitably supply oil to the lower plain 
bearing 12 journaling the shaft portion 9a than to any other bearings, as 
shown in FIG. 10, an off-center oil passageway 37 and an oil feeding 
aperture 38 may be formed for the bearing 12 in the shaft portion 9a. It 
is to be understood that the present invention can have application in 
cases where any one of the bearings 8, 11 and 12 is a roller bearing. In 
the description set forth hereinabove, the oil flow passages 21, 27 and 34 
have been described as being located in positions which are advanced in 
the rotational direction of the crankshaft for an extent of 90 degrees 
with respect of the lines of actions of the loads P.sub.1, P.sub.2 and 
P.sub.3 respectively. However, the positions of the passages 21, 27 and 34 
are not limited to those described in the above embodiment and may be 
changed to any positions which are spaced apart from the lines of action 
of the loads P.sub.1 -P.sub.3 so that generation of oil film pressures 
F.sub.1, F.sub.2 and F.sub.3 corresponding to the loads P.sub.1, P.sub.2 
and P.sub.3 due to the wedging action would not significantly be affected 
by the oil flow passages. The oil flow passage is preferably located in 
the region which are advanced in the rotational direction of the 
crankshaft from 45 degrees to 315 degrees with respect to the line of 
action of the load P.sub.1, P.sub.2 or P.sub.3. In addition, the 
directions of the loads P.sub.1, P.sub.2 and P.sub.3 are influenced and 
varied by the centrifugal force exerting on the orbiting scroll member 3, 
which acts in a direction opposite to the direction in which the component 
of the force P.sub.x acts in FIG. 3. Thus, the oil flow passages 21, 27 
and 34 are preferably located in positions which are out of this variation 
zone. 
From the foregoing description, it will be appreciated that in the prefered 
embodiment, an oil film reaction within each plain bearing is produced at 
all times, though the fluid pressure between the two scroll members 
applied a lateral load on the crank portion of the crankshaft and causes 
tilting of the crankshaft in the plain bearings, whereby wear and seizure 
of the bearings can be prevented from taking place.