Note: Descriptions are shown in the official language in which they were submitted.
~L~82385
AXIAI, SEALING MECHANISM FOR A SClROLL
TYPE FLUID DISPLACEP~ENT APPARATUS
B~CKGROUND OF l~IE: INVENTION
This invention relates to a fluid displacement
apparatus, and more parti~ularly, to an axial sealing
mechanism for a scroll type fluid displacement
apparatus.
Scroll type fluid displacement apparatus are well
known in the prior art. For example, U.S. Patent
801,182 issued to Creux discloses apparatus including
two scroll members each having a circular end plate and
a spiroidal or involute spiral element. These scroll
members are maintained angularly and radially offset so
that both spiral elements interfit to make a plurality
o~ line contacts between their spiral curved surfaces to
thereby seal off and define at least one pair of fluid
pockets. The relative orbital motion of the two scroll
members shifts the line contacts along the spiral curved
sur~aces and7 therefore, the fluid pockets change in
volume. Since the volume of the fluid pockets increases
or decreases dependent on the direction of the orbiting
motion, this scroll type fluid displacement apparatus is
applicable to compress, expand or pump ~luids.
In compaxison with conventional compressors of the
~iston ~ype, a scroll type compressor has certain
advantages, such as ~ewer parts and continuous
compression of fluid. However, one of the problems
encountered in prior art scroll type compressor has been
ineffective sealing of the fluid pockets. Axial and
radial sealing of the fluid pockets must be maintained
in a scroll type compressor in order to achieve
efficient operation. The fluid pockets in a scroll type
compressor are defined by line contacts between the
interfitting spiral elements and axial contacts between
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the axial end surfaces of the spiral elements and the
inner surface of the end plates.
In prior scroll-type apparatus, as shown in
Figures 1 and 2, the end surface of each spiral element
1 which faces end plate 2 of the other scroll member is
provided with groove 3 formed along the spiral. Seal
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element 4 is closely fitted within groove 3. Seal element
4 has an axial dimension greater than -the depth of groove 3
so that, before spiral element I is placed in an inter-
fitting position with another spiral element, seal element
4 projects from spiral element I by predetermined amount "y".
Since predetermined amount "y" is greater than axial gap "t"
between the axial end surface of spiral element I and end
plate 2' of the other scroll member, when both spiral
elements I are placed in their interfitting positions as
shown in partial cross-section in Figure 2, seal element 4
maintains contact with the facing end plate 2' of the
opposing scroll member without the use of any axial force
urging device.
A disadvantage of t~e above construction is that
I5 seal element 4 should be urged toward the facing scroll
member by a greater fo~ce to accomplish effective sealing.
In the above construction o~ the axial sealing mechanism,
the seal element should be deformed by compression of the
facing end plate to absorb the cumulative error of assembly
of the scroll members and to accomplish effective axial
sealing along the length of the seal element. As a
resultr the seal element in thir, prior construction must
be formed of very soft material to enable the deformation
of the seal element in accordance with the charge of axial
gap "t" between the spiral element and the facing end plate.
SUMMARY OF THE INVENTION
It is an object of an aspect of this invention to
provide an improved scrolI type fluid displacement apparatus
with high volumetric efficiency and a high energy efficiency
ratio.
It is an object of an aspect of this invention to
provide a scroll type fluid displacement apparatus wherein
abnormal wear of the 2xial seal element is prevented to
achie~e long life and axial sealing of ~he fluid pocket is
enhanced along t~e length of the seal element.
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It is an object of an aspect of this invention to
provide a scroll type fluid displacement apparatus which
is simple in construction and simple to manufacture,
while achieving the above objects.
An aspect of the invention is as follows:
In a scroll type fluid displacement apparatus
including a pair of scrolls each having an end plate and
a spiral wrap extending from ona side of said end plate,
said spiral wrap having a groove formed in its axial end
surface along the spiral curve, said spiral wraps inter-
fitting at an angular and radial offset to make a
plurality of line contacts which define at least one pair
of fluid pockets~ a driving mechanism operatively connect-
ed to one of said scrolls to orbit said one scroll
relative to the other scroll while preventing rotation
of said one scroll to thereby change the volume of the
fluid pockets,.the impxovement comprising a plurality
of projections formed wit~in the bottom surface of said
groove at a predetermined spacing,.a seal element
disposed on said projection along said groove~ said seal
element having a thickness greater than the depth of said
groove minus the depth of said projections so that said
seal element partly e~tends from said groove to contact
and be compressed by the opposing circular end plate
along its entire length to t~ereby axially seal the
fluid pockets.
By way of added explanation, a scroll type fluid
displacement apparatus accordin~ to t~is invention
includes a pair of scrolls each comprising a circular end
3Q plate and a spiral wrap extending from one side of the
circular end plate. A groove is formed in the axial
end surface of each spiral wrap and extends along the spiral
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curve of the wrap. Plural projections are formed in the bottom surface of
'the groove at a predetermined spacing. A seal element is fitted in the
groove having a tllickness greater than the depth of the groove minus the
height of each pro,jection.
Further objects, features and other aspects of this invention will be
understood from the detailed description of the preferred embodiment of
this invention referring to the annexed drawings.
BRIEF DESCRIPTION OF THE DRAWINCS
Figure I iS a perspective view of a known scroll member and seal
element.
Figure 2(a~ is a cross-sectional view of a portion of a scroll member
illustrating placement of the seal element in an axial end portion of the
spiral element and Figure 2(b) is a cross-sectional view of a portion of both
interfitting scroll members.
Figure 3 is a vertical sectional view of a compressor type fluid
displacement apparatus according to one embodiment of this invention.
Figure 4 is a perspective view of one scroll member of the embodi-
ment of Figure 3.
Figure 5 is a partly enlarged perspective view illustrating one of the
projections in Figure 4.
Figure 6 is a sectional view taken along line 6-6 in Figure 5.
Figure 7 is a cross-sectional view illustrating the relationship between
the seal element and the facing end plate in accordance with the present
~5 invention.
DETAILED DESCRlPTION OF THE PREFERRED EMBODIMENTS
Referring to Figure 3, a fluid displacement apparatus in accordance
with the present invention is shown which consists of a, scroll type refrig-
erant compressor. The compressor includes compressor housing IO having
front end plate II and cup shaped casing I2 fastened to an end surface-o
front end plate II. An opening III iS formed in the center of front end
plate II for supporting drive shaft I3. An annular proJection II2, con-
centric with opening III, iS formed on the rear end surface of front end
plate II facing cup shaped casing I2. An outer peripheral surface of
annular projection II2 bites into an inner wall of the opening of cup shaped
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casing I2. Cup shaped casing I2 iS fixed on the rear end surface of front
end plate II by a fastening device, such as bolts and nuts, so that the
opening of cup shaped casing I2 iS covered by front end plate II. An 0-
ring I4 iS placed between the outer peripheral surface of annular projection
II2 and the inner wall of cup shaped casing I2. Front end plate II has
annular sleeve IS projecting from the front end surface thereof; this sleeve
IS surrounds drive shaft I3 to define a shaft seal cavity. As shown in
Figure 3, sleeve IS iS attached to the front end plate II by screws I6, one
of which is shown in Figure 3. An O-ring I7 iS placed between the front
end surface of front end plate II and an end surface of sleeve IS ~CO seal
the mating surface of front end plate II and sleeve I5. Alternatively,
sleeve Ij may be formsd integral with front end plate II.
Drive shaft I3 iS rotatably supported by sleeve IS through bearing I8
disposed within the front end of sleeve IS. Drive shaft I3 has disk shaped
rotor I9 at its inner end; disk shaped rotor I9 iS rotatabiy supported by
front end plate II through bearing ~o disposed within opening III o front
end plate II. A shaft seal assembly 2I iS assembled on drive shaft I3
within the shaft seal cavity of sleeve IS.
A pulley 22 iS rotatably supported by bearing 23 on the outer surface
of sleeve I5. An electromagnetic coil ~4, which is received in an annular
cavity of pulley 22, iS mounted on the outer surface of sleeve I5 by
supported plate 2~I. An armature plate 25 is elastically supported on the
outer end of drive shaft I3 which extends from sleeve IS. A magnetic
clutch is formed by pulley 2a, magnetic coil 24 and armature plate 25.
Thus, drive shaft I3 iS driven by an external power source, for example,
an engine of a vehicle, through a rotatinn transmitting device, such as the
abo~e described magnetic clutch.
A number of elements are located within the inner chamber of cup
shaped casing I2 including fixed scroll 26, orbiting scroll 27, a driving
mechanism for orbiting scroll ~7, and rotation preventing/thrust bearing
device 28 for orbiting scroll Z7. The inner chamber of Cllp shaped casing
I2 iS formed between the inner wall of cup shaped casing I2 and front end
plate I I.
Fixed scroll ~6 includes circular end plate 26I, wrap or spiral element
262 affixed to or extending from one end surface of circular end plate 26I,
and a plurality of internal bosses 263 axially projecting from the end surface
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of circular end plate 26I on the side opposite spiral element 262. The end
surface of each boss 263 is seated on the inner surface of end plate portion
I2I of CUp shaped casing I2 and is fixed to end plate portion I2I by a
plurality of bolts 29, one of which is shown in Figure 3. Hence, fixed scroll
26 iS fixedly disposed within cup shaped cas;ng I2. C:ircular end plate 26I
of fixed scroll 26 partitions the inner chamber of Cllp shaped casing I2 into
rear chamber 3o having bosses 2t;3, and front chamber 3I, in which spiral
element 252 of fixed scroll 26 iS located. A sealing member 32 iS disposed
within circumferential groove 2~54 of çircular end plate 26I for sealing the
outer peripheral surface of circular end plate 26I and the inner wall of cup
shaped casing I2. A hole or discharge port 265 iS formed through circular
end plate 26I at a position near the center of spiral element 262; discharge
port 265 connects the fluid pockets at the center of spiral element 262 and
rear chamber 30.
Orbiting scroll 27, which is disposed in front chamber 3I, includes
circular end plate 27I and wrap or spiral element 272 affixed to or
extending from one end surface of circular end plate 272. The spiral
elements 262 and 272 interfit at an angular offset of I800 and a pre-
determined radial offset. The spiral elements define at least a pair of
fluid pockets between their interfitting sutfaces. Orbiting scroll 27 iS
connected to the driving mechanism and rotation preventing/thrust bearing
device 28. The driving mechanism and rotation preventing/thrust bearing
deYiCe 28 effect orbital motion of orbiting scroll 27 by the rotation of
drive shaft I3 to thereby compress fluid passing ~hrough the compressor.
Ro~ation preventing/th~ust bearing device 28 is placed between the
inner end surface of front end plate II and the end surface of circular end
plate ~-7I which faces the inner end surface of front end plate II, as shown
in Figure 3. Rotation preventing/thrust bearing device 28 includes fixed
ring 28I, which is fastened against the axial end surface of annular pro-
jection II2, orbiting ring 282, which is fastened against the end surface of
circular end plate 272 by a fastening device, and a bearing element, such
as a plurality of spherical balls 283. Rings 28I and 28~ have a plurality
of indentations 28~ and 285 and one of the spherical balls 283 is retained
between each of these indentations 284 and 285o Therefore, the rotation
of orbiting scroll 27 iS prevented by balls 283, which interact with the
edges of indentations 284 and 285 to prevent rotation. Also, these balls
283 carry the axial thrust load from orbiting scroll 27. Therefore, orbiting
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scroll 27 orbits while maintaining its angular orientation to fixed scroll 26.
As orbiting scroll 27 orbits, the line contacts between spiral elements
262 and 272 shift toward the center of the spiral elements along the surfaces
of the spiral elements. The fluid pockets defined by the line contacts
between spiral elements 262 and 27~ move toward the center with a
consequent reduction of volume to thereby compress the fluid in the fluid
pockets. Therefore, fluid or refrigerant gas introduced into front chamber
3I from an external fluid circuit through inlet port 35 mounted on the
outside of cup shaped casing I2 iS taken into the fluid pockets formed at
0 the outer portion of spiral çlements 262 and 27Z. As orbiting scroll 27
orbits, the fluid in the fluid pockets is compressed as the pockets move
toward the center of the spiral element. Finally, the compressed fluid is
discharged into rear chamber 3O through hole 265, and thereafter, the fluid
is discharged to the external fluid circuit through outlet port 36 formed on
cup shaped casing I2.
Referring to Figure 4, each spiral element 262 and 272 is provided
with a groove 37 formed in its axial end surface along the spiral curve of
the spiral element. Groove 37 extends from the inner end portion of the
spiral element to a position close to thç ~erminal end o~ the spiral element.
As shown in Figures 4, 5 and 6, ~roove 37 iS provided with a plurality
of projections 38 on its bottom surface at a predetermined spacing. Groove
37 has depth "d" and each projection 38 has height "P". When seal element
39 having thickness "t" greater than depth "d" of ~roove 37 minus height
"P~ of projection 38 is disposed within groove 37, part of seal element 39
corresponding ~o projection 3~ of groove 37 extends from the upper opening
of groove 37. When the scroll members with seal element 39 are assembled
in their interfitting position as shown in Figure 7, the extended portion of
seal element 39 is compressed by opposite end plate 27I and projections
38. The urging force for urging the seal element toward end plate 27I of
the opposite scroll member is partly provided by projections 38. Therefore,
the deformation of seal element 39 is easily accomplished and the gap
between seal element 3~ and opposite end plate 271 is effectively sealed.
This invention has been described in detail in connection with a
preferred embodiment. However, this embodiment is merely for example
only and the invention is not restricted thereto. It will be easily under-
stood by those skilled in the art that other variations and modifications
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can be easily made within the scope of this invention, as defined by the
appended claims.
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