Note: Descriptions are shown in the official language in which they were submitted.
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HERMETICALLY SEALED SCROLL TYPE REFRIGERANT
COMPRESSOR WITH AN IMPROVED LUBRICATING MECHANISM
B~C:KGROUND OF THE INVENTION
Field of the Invention
This inventioD relates to a hermetically sealed scroll type
refrigerant compressor, and more particularly to a lubricating mecha-
nism thereof.
Descri~ion of the Prior Art
Japanese Patent Application Publication No. 60-73~0~3 dis-
closes a hermetically sealed scroll type refrigerant compressor which
is designe~ such that the longitudinal axis of ~he drive shaft is gener-
ally perpendicular to a horizontal plane when the compressor is
installed. Therefore, in general, the compressor can b~e called a verti-
cally installed type scroll refrigerant compressor. The compressor
includes a hermetically sealed housing in which a compression mecha-
nism having fixedi and orbiting scrolls, a driving mechanism having a
motor and a motor driven drive shaft, and a rutation preventing
device for preventing rotatioD of the orbiting scroll during orbital
motion are contained. The fixe~ scroll includes a circular end plate
which divides the cavity defined by the housing into suction and dis-
charge chamber sections. The suction chamber section contains the
driving mechanism, the ro~ation preventing mechanism and the spiral
elements of the fixed and orbiting scrolls.
The drive shaft includes an axial condui~. The axis of the con-
duit is radially offset from the axis of ~he drive shaft. The drive shaft
is provided with a centrifugal pump at its lower end. The centrifugal
pump is immersed in a reservoir of lubricating oil which accumulates
at the inner bottom portion of the housing.
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In operation, refrigerant gas flowing from an external îluid
circuit flows into the suction chamber section through an inlet port
disposed through a side wall of the housing. The refrigerant gas is
taken into a pair of outer fluid pockets which are defined by the spiral
elements. The refrigerant gas is compressed inwardly toward a cen-
tral fluid pocket due to orbital motion of the orbiting scroll. As the
refrigerant gas moves towards the central fluid pocket, it undergoes a
volume reduction and compression and is discharged into the dis-
charge chamber section through a hole extending through the circular
end plate of the fixed scroll. The compressed refrigerant gas in the
discharge chamber section flows out of the compressor and to the
external fluid circuit through an outlet port which is disposed through
an upper end of the housing. After circulating through the external
fluid circuit, the refrigerant gas which exits through the outlet port
returns ~o the compressor through the inlet porl.
Furthermore, lubrica~ing oil which accumulates at the inner
bottom end portion of the housing flows upwardly through the axial
conduit by operation of the centrifugal pump. The pump operates
during rotation of the drive shaft. The lubricating oil which has
upwardly passed over the axial conduit flows through other conduits
and into frictional surfaces of the slidable members of the compres-
sor, such as the rotation preventing mechanism and the bearings
rotatably supporting the drive shaft, in order to lubricate them.
As mentioned above, in this prior art, the lubricating oil at the
inner bottom portion of the housing is supplied to the frictional sur-
faces of the slidable members of the compressor through the axial
conduit and the other conduits by use o~ the centrifugal pump. How-
ever, the flow rate of the lubricating oil which has passed through the
axial conduit and the other conduits quadratically increases in accor-
dance with the increase in rotational speed of the drive shaft. This
increase in flow rate occurs because the hydraulic resistance which is
generated at the axial conduit and the other conduits when the lubri-
cating oil passes therethrough is negligible.
Accordingly, when the capability of the centrifugal pump is
designed so as to be able to supply a sufficient amolmt of the
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lubricating oil to the frictional surfaces of the slidable members of
the compressor during low rotational speeds of the drive shaft, an
excessive amount of the lubricating oil is supplied to the fri~tional
surfaces during high rotational speeds of the drive shaft. Therefore,
during high rotational speeds OI the drive shaft, viscous drag of the
lubricating oil generated between the frictional surfaces increases
greatly so that the frictional surfaces do not smoothly slide relative to
each other. In addition, when an excessive amount of the lubricating
oil is supplie~ to the frictional surfaces between the fixed and orbiting
scrolls, an excessive amount of the lubricating oil is taken into the
fluid pockets of the scrolls together with the refrigerant, and exits to
the fluid circuit via a compression and discharge process of the
refrigerant. Therefore, the ratio of the amount of the lubricating oil
to the amount of the refrigerant in the circulation of the fluid circuit
increases. As a result, the heat exchangeability of the evaporator
forming a part of the fluid circuit decreases. On the other hand,
when the capability of the centrifugal pump is designed so as to be
able to supply a sufficient, but not an excessive, amount of lubricating
oil to the frictional surfaces during high rotational speeds of the drive
shaft, an insufficient amount of the lubricating oil is supplied to the
frictional surfaces during low ro~ational speeds of the c!rive shaft.
Therefore, the frictional surfaces may seize in the low rotational
speeds of the drive shaft due to the lack of lubricating oil.
- In order to resolve these defects, Japanese Patent Application
Publication No. 63-90,684 discloses a vertically installed type scroll
refrigerant compressor. A construction of this compressor is substan-
tially similar to the construction of the compressor disclosed in the
Japanese '083 publieation, except for the lubricating oil pumping
device which is disposed at the lower end of the drive shaft. The
pumping device therein includes a centri~ugal pump and a positive-
displacement pump, wherein the displacement linearly increases in
accordance with the increase in rotational speed of the drive shaft.
By a combination of the centrifugal pump and the positive-displace-
ment pump, a sufficient, but not excessive, amount of the lubricating
oil is supplied to the frictional surfaces even though the drive shaft
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rotates at any rotational speed. Accordingly, the above-mentioned
defects can be resolved.
However, in this prior art, the pumping device is comprised of
a large number of component parts. This construction requires a
complicated assembling process and a resultant increased manufac-
turing cost.
SUM~IARY OF THE~ INVENTION
Accordingly, it is an object of the present invention to provide
a hermetically sealed scroll type refrigerant compressor which
includes a simply structured lubricating mechanism for effectively
lubricating the frictional surfaces of the slidable members thereof at
any rotational speed of the drive shaf t.
A scroll type compressor with a hermetically sealed housing
includes fixed and orbiting scrolls disposed within ~he housing. The
fixed scroll comprises a first end plate from which a first spiral ele-
ment extends. The orbiting scroll cornprises a second end plate from
which a second spiral element extends. The first and second spiral
elements interfit at an angular and radial of gset to form a plurality of
line contacts which define at least one pair of sealed off fluid
pockets.
A drive mechanism includes a drive shaft which is rotatably
supported in the housing, and a pin member which is integrated with
one end of the drive shaft. The axis of the pin member is radially
offset from the axis of the drive shaft. The pin member is rotatably
connected to the orbiting scroll to effect orbital motion of the orbit-
ing scroll. A rotation preventing device, such as an Oldham coupling
mechanism, prevents rotation of the orbiting scroll during its orbital
motion. With this con~truction, the volume of the fluid pockets
changes to compress refrigerant fluid within the pockets. The longi-
tudinal axis of the drive shaft is generally perpendicular to a horizon-
tal plane, when the compressor is installed. A motor is associated
with the drive shaft so as to rotate the drive shaft.
An axial bore is formed through the drive shaft. One end of
the axial bore, opposite to the orbiting scroll, is immersed in lubricat-
ing oil which accumulates at an inner bottom portion of the housing.
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A throttling device, such as an orifice tube, penetrates through the
pin member and is fluidly coupled with the a~nal ~ore. A centrifugal
pump which operates during rotation of the drlve shaf t is provided at
the one end of the ax~al bore. The pump operates to conduct the
lubricating oil at the inner bottom portion of the housing to the fric-
tional surfaces of the slidable members of the compressor via an or~-
~ice tube.
BR~ElF DESCRIPTIONQF THE DRAWING
The drawing is a vertical section view of a vertically installed
type scroll refrigerant compressor in accordance with one embodi-
ment of the present invention.
DETAILl~D DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference to the drawing, a vertically installed type scroll
refrigerant compressor in accordance with one embodiment of the
present invention is shown. Compressor 1n includes casing 11 com-
prising cylindrical portion 12 and a pair of shallow cup-shaped por-
tions 13 and 14 hermetically fixecl to both ends of cylindrical portion
12, fixed and orbiting scrolls 20 and 30, inner block member 40 and
motor 50.
Cylindrical portion 12 includes annular flanges 121 and 122
projecting radially outward f rom upper and lower ends thereof,
respectively. Shallow cup~haped portion 13 includes annular ~lange
131 projecting radially outward from an opening end thereof, and
shallow cup~haped portion 14 includes annular flange 141 projecting
radially outward from an opening end thereof. Flange 131 is hermeti-
cally and releasably secured to flange 121 by a plurality of screws 200
and O-ring seal 201. Flange 141 is hermetically and releasably
secured to flange 122 by a plurality of screws 22û and O-ring seal 221.
With this construction, cylindrical portion 12 and the pair of shallow
cup-shaped portions 13 and 14 can be disassembled when necessary.
Cylindrical portion 12 further includes a plurality of projections 123
projecting radially inward from the upper end thereof.
Fixed scroll 20 includes circular end plate 21 and spiral ele-
ment or wrap 22 extending downwardly from the lower end surface of
circular end plate 21. Circular end plate 21 is forcibly inserted into
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an inner peripheral wall OI shallow cup-shaped portion 13. O-ring
seal 210 is disposed between the outer peripheral surface of circular
end plate 21 and the inner peripheral wall of shallow cup-shaped por-
tion 13 to seal the mating surface therebetween. The cavity defined
by casing 11 is thereby divided into first and second cavities 60 and 61
by circular end plate 21 of fixed scroll 20. Axial hole 24 is formed in
circular end plate 21 at the central location to link cavity 60 and a
late~mentioned central fluid pocket 71b. Axial hole 24 is covered by
one way valve 25 disposed on the upper end surface of circular end
plate 21. Curved plate 251 of rigid material, such as steel"s disposed
on one way valve 25 to prevent excessive bending of one way valve
25. Curved plate 251 and one way valve 25 are firmly secured to cir-
cular end plate 21 at their one end by screw 26. Circular end plate 21
is provided with annular wall 211 projecting downwardly frorn the
peripheral end surface thereof. Radial hole 23 is formed in annular
wall 211. Annular Ilange 211a projects radially outward from a lower
end of arlnular wall 211. Orbiting scroll 30 includes circular end plate
31 and spiral element or wrap 32 extending upwardly from one end
surface of circular Pnd plate 31. Spiral element 22 of fixed scroll 20
and spiral element 32 of orbiting scroll 30 interfit at an angular and
radial o~fset to form a plurality of line contacts which define at least
one pair of sealed off fluid pockets ~1 therebetween. Annular projec-
tion 33 projects axially from the other end surface of circular end
plate 31. Shallow depression 34 is also formed at the other end sur-
face of circular end plate 31 at a central location, and is linked to
radial conduit 101 formed in circular end plate 31. Radial conduit 101
extends in one direction to the outer peripheral surface of circular
end plate 31; but the outer radial end ~hereof is blocked by plug 102.
The outer radial portion of conduit 101 is linked through axial short
path 103 to annular groove 104 formed at one end surface of circular
end plate 31 at a peripheral location. Radial conduit 101, axial short
path 103 and annular groove 104 conduct the lubricating oil in shallow
depression 34 to the mating surfaces between annular wall 21 of fixed
scroll 20 and circular end plate 31 of orbiting scroll 30.
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Inner block member 40 includes central portion 41, first axial
annular wall ~12 projecting upwardly from central portion 41 at a
peripheral loca~ion, and secon~ axial annular wall 43 projecting down-
wardly from central portion 41 at a peripheral location. Axial annu-
lar projection 44 projects downwardly from central portion 41 at a
central location. First axial annular wall 42 is secured by a plurality
o~ screws 400 to flange 211a of annular wall 211. A plurality of elon-
gated screws 400a secure flange 211a to a plurality of projections 123
through first axial annular wall 42. Inner block member 40 and fixed
scroll 20 are thereby firmly secured to cylindrical portion 12 of casing
11.
Motor 50 includes stator 51 which is firmly secured to a lower
end of second axial annular wall ~3 by a plurality of screws S00.
Rotor 52 of motor 50 is disposed within stator S1 and is fixed to drive
shaft 15 extending therethrough. Wires 110 from stator 51 are con-
nected with terminals 111 which are connected to an external elec^
tric source (not shown). Hermetic seal base 120 is insulated from ter-
minals 111 and hermetically fi~ed to opening 12g which is formed in
cylindrical portion 12.
Drive shaft 15 exten~s through axial annular projection 4~.
Axial annular projection 44 e~tends within an opening in rotor 52.
Drive shaft 15 is rotatably supported within axial annular projection
44 through upper and lower fixed plain bearings 15a and 15b disposed
between the exterior surface of drive shaft 15 and the interior sur-
face of axial annular projection 44. Driv~ shaft 15 extends through
central portion 41 of inner block member 40. Pin member 16 is inte-
grated with and projects axially from the upper end surface of drive
shaft 15. The axis of pin member 16 is radially offset ~rom the axis of
drive shaft 15. Pin member 16 is rotatably disposed within axial annu-
lar projec~ion 33 of orbiting scroll 30 through fixed plain bearing 16a.
Drive shaft 15 includes axial bore 151 extending from an opening at
the lower end surface of drive shaft 15 and terminating at the lower
end portion of pin member 16. A plurality of radial bores 152 extend
through drive shaft 15 at lncations within annular projection 44.
Centrifugal pump 1~ includes annular cylinder 171 and annular
truncated cone 172. Annular cylinder 171 is firmly secured to the
outer peripheral surface of the lower end portion of drive shaft 15 at
its upper end by welding or by a plurality OI fastening devices, such as
screws (not shown). Annular truncated cone 17~ is integrated with
the lower end of annular cylinder 171 and gradually narrows down-
wardly. Centrifugal pump 17 is immersed in a reservoir of lubricating
oil which accumulates at the inner bottom portion of casing 11.
A throttling device, such as orifice tube 1~, penetrates through
pin member 16 so as to link shallow depression 34 to axial hole 151.
Balance weight 35 is integrated with a lower end portion of pin
member lB and serves to average the torque of drive shaft 15 acting
on pin member 16 during rotation. Balanc~ weight 35 includes annular
disk portion 35a and crescent-shaped portion 35b which is integrated
with the upper surface of annular disk portion 35a. Needle thrust
bearing 81 is disposed between the end surface of axial annular pro-
jection 33 and the upper end surface of annular disk portion 35a.
Needle thrust bearing 82 is disposed b~tween the lower end surface of
annular disk portion 35a and an upper surface of central portion 41 of
inner block member 40. Balance weight 35 is thereby rotatably sup-
ported by bearings 81 and 82.
Rotation preventing device 19, for example an Oldham cou-
pling mechanism, is disposed between the lower peripheral surface of
circular end plate 31, exterior of annular projection 33, and the upper
surface of inner block member 40 to prevent rotation of orbiting
scroll 30 during its orbital motion. Rotation preventing device 19 and
pin member 16, as well as spiral elements 22 and 3~, are all contained
in cavity 61.
In operation, stator 51 generates a magnetic field, causing
rotation of rotor 52 to thereby rotate drive shaft 15. The rotation of
drive shaft 15 is converted into the orbital motion of orbiting scroll 30
by pin member 16. The rotational motion of orbiting scroll 30 is pre-
vented by rotation preventing device 19. Refrigerant gas is intro-
duced into cavity 61 from the external refrigeration circuit through
suction gas inlet pipe 90~ The refrigerant gas is then taken into the
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outer fluid pockets ~la between fixed scroll 20 and orbiting scroll 30
through hole 23, The refrigerant gas is compressed inwardly toward
the central fluid pocket 71b of spiral elements 22 and 32 due to the
orbi~al motion of orbi~ing scroll 30. As the refrigerant gas moves
towards the central fluid pocket 71b, it undergoes a ~olume reduction
and compression. The refrigerant gas is discharged ~rom the central
fluid pocke~ 71b to cavity 60 through hole 24 with the bending of one
way valve 25. Compressed refrigerant gas in cavity 60 flows out of
the cornpressor to the external refrigerant circuit through discharge
gas outlet pipe 91.
Lubricating oil which accumulates at the inner bottom portion
of casing 11 flows upwardly through axial bore 151 by virtue of the
operation of centrifugal pump 17 which operates during rotation of
drive shaft lS. A small part of the lubricating oil which flows
upwardly through axial bore 151 further flows into the gap between
fixed plain bearings 15a9 15b and the exterior surface of drive shaft 15
to lubricate the contact surfaces by virtue of the centrifugal force
generated by rotation of drive shaft 15 during operation of the com-
pressor. A large part of the lubricating oil which flows upwardly
through axial bore 151 further flows through orifice tube 18. The
lubricating oil which has passed through orifice tube 18 is supplied to
fiY~ed plain bearings 16a, needle thrust bearings 81 and 82, and the
mating surfaces between annular wall 211 of fixed scroll 20 and circu-
lar end plate 31 of orbiting scroll 30 in order to lubricate them.
Furthermore, the flow rate of the lubricating oil which flows
through axial bore 151 quadratically incrsases in accordance with the
increase in rotational speed of drive shaft 15. When the lubricating
oil which flows through axial bore 151 further flows through orifice
tube 18, hydraulic ~riction generated at orifice tube 18 quadratically
increases in accordance with increase in flow rate of the lubricating
oil which flows through axial bore 151. Accordingly, the increase in
the flow rate of the lubricating oil which is passed through orifice
tube 18 is sufficiently reduced due to the quadratic increase in
hydraulic friction genera~ed at orifice tube 1~, even though the flow
rate of the lubricating oil which f lows through axial bore 151
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quadratically increases in accordance with increase in the rotational
speed of drive shaft 15. Therefore, if the diameter and length of ori
fice tube 18 are appropriately designed, the flow rate of the lubricat-
ing oil which is passed through orifice tube 1~ varies within a narrow
range of values. This allows the frictional surfaces of the above-
mentioned slidable members of the compressor to receive a sufficient,
but not excessive, amount of the lubricating oil even though drive
shaft 15 rotates at any rotational speed.
Furthermore, in the above embodiment, although orifice tube
18 is used as a throttling device, a porous metal member or an aper-
ture having a throttling portion can also be used as the throttling
device in this invention. Such throttling devices can be positioned at
any location along axial bore 151 of drive shaft 15.
As mentioned above, in this invention, the frictional surfaces
of the slidable members of the compressor can receive an appropriate
amount of the lubricating oil even though the drive shaft rotates at
any rotational speed. Moreover, the lubricating mechanism is struc-
tured by a simple combination of the throttling device and the cen-
trifugal pump. Accordingly, the defects experienced in the compres-
sor of the Japanese '083 and '684 Publications are eliminated.
This invention has been described in detail in connection with
the preferred embodiments. These embodirnents, however, are
merely for example only and the invention is not restricted thereto.
It will be understood by those skilled in the art that other variations
and modifications can easily be made within the scope of thi~s inven-
tion defined by the claims.
