Note: Descriptions are shown in the official language in which they were submitted.
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SCROLL TYPE COMPRESSOR WITH VARL~BLE
DISPLACEMENT MECHANISM
BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to a scroll type compressor, and in
particular, to a scroll type co~ ressor with a variable displacement mech~ni~m
Description of the Prior Art
Scroll type fluid displacement apparatuses are known int he prior art.
For example, U.S. Patent No. 801,182 to Cruex
10 discloses a scroll apparatus which inrl~ldes two scrolls, each having a circular
end plate and a spiroidal or involute spiral element extending from the end
plates. The scrolls are m~int~ined ~n~ rly and radially offset so that both
spiral elements interfit to form a plurality of 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 scrolls shifts the line contacts along the
spiral curved surfaces and, as a result, the volume of the fluid pockets
increased or decreases, depending upon the direction of the orbital motion.
Thus, a scroll type fluid displacement apparatus may be used to compress,
expand or pump fluids.
When conventional scroll type coll~lessors are used in automobile air
conditioners, these compressors usually are driven by the automobile engine
through an electromagnetic clutch. In such automobile air conditioners, when
capacity control mech~ni~m~ are not provided for the colllplessors, thermal
control of the passenger compartment or control of the air conditioner is
generally accomplished by intermittent operation of the compressor through
engagement of the electromagnetic clutch. Although the energy required for
m~int~ining the passenger colllpalllllent at the desired temperature may not
be large once the desired temperature is initially achieved, a relatively large
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force is required to drive the co~ ressor during the initial intermittent
operation thereof, and to a lesser extent, upon each subsequent actuation of
the compressor. This intermittent operation consumes large amounts of
energy.
It is known to provide a scroll type compressor with a displacement or
volume adjusting mech~ni~m to control the col~ression ratio as operation
demands. For example, as disclosed in U.S. Patent No. 4,904,164 issued on
February 27, 1990, to Atsushi Mabe et al.,
A variable di$placement mech~ni.~m for controlling the
10 compression ratio includes a pair of holes formed through the end plate of one
of the scrolls. The pair of holes provides fluid communication between
intermediate fluid pockets formed between the spiral elements and located on
one side of the end plate, and an intermediate pressure chamber which is
located on the opposite side of the end plate. Flow of the fluid through the
15 holes is controlled by valve plates which cover the holes. The intermediate
pressure chamber is linked by a communication channel with the suction
chamber. The opening and closing of the communication channel is controlled
by a valve control meçh~ni~m in response to the suction pressure. The
compressor also includes an axial tip seal element disposed in a groove formed
20 along the axial end of each of the spiral elements. The tip seals m~int~in the
axial sealing between the axial end surface of the spiral element of each scrolland the inner surface of the end plate of the other scroll.
During compressor operation, at high suction pressure, the
communication channel is closed by the valve control m~rh~nicm Fluid
25 compressed to the intermediate pressure level corresponding to the
intermediate fluid pockets, flows into the intermediate pressure chamber and
raises the pressure therein until it is equal to the pressure in the intermediate
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pockets, thereby c~-lcing the valve plates to close the holes and prevent further
flow. In this situation, since no further fluid may escape from the fluid pockets
before being forced into the discharge chamber, the displacement volume or
compression ratio of the colllpressor is m~Yimllm
When the suction pressure is reduced, for example, as the demand on
the system decreases, the communication ch~nn~l is opened by the valve
control mech~ni~m, linking the intermediate pressure chamber with the suction
chamber and thereby reducing the pressure in the intermediate pressure
chamber. Accordingly, the valve plates are opened, and fluid flows from the
10 intermediate fluid pockets to the intermediate pressure chamber thought the
pair of circular holes, and back to the suction chamber through the
communication channel. In this situation, since a portion of the fluid escapes
from the fluid pockets before being forced into the discharge chamber, the
displacement volume is minimllm
The pressure in the intermediate pressure chamber is varied in a range
from the suction pressure to the predetermined intermediate pressure which
~revell~s communication between the sealed-off fluid pockets and the
intermediate pressure chamber. This variance is controlled in accordance with
the opening and closing of the link between the interme~ ted pressure
20 chamber and suction chamber, which is itself dependent upon the suction
pressure. Thus, the compression ratio of the compressor, which depends upon
whether the fluid in the pockets escapes back to the suction chamber, is
controlled in a range from the m~ximllm value, that is, 100~o, to a
predetermined minim~lm value, for example, 305to, generally in dependence
25 upon the suction ~res~ule.
However, if the compressor is operating at a high rotational speed while
the compression ratio is being adjusted to equal the minimllm value, that is,
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when the co,lul,ul~ication channel is opened, the obtainable minimllm value of
the compression ratio is undesirably increased above the predetermined
minim~lm value since the pressure drop of the fluid as it flows through the pairof circular holes is not negligible due to the extreme increase in flow rate of
5 the fluid as it passes through the pair of circular holes. In other words, theflow of fluid though the holes is restricted by the size of the holes, which is not
large enough to accommodate the sudden increase in flow rate when the
communication channel is opened, c?~llcing a greater than desired quantity of
fluid to remain in the fluid pockets and be col,l~ressed. Accordingly, the
10 effectiveness of the displacement control provided by the displacement
adjusting mech~ni~m is ~limini~hed, particularly during operation of the
compressor at high rotational speeds.
In order to resolve the above~ -c~e~l drawback, the radius of the pair
of circular holes can be enlarged so as to be slightly smaller than the thickness
15 of the spiral elements. Thus, the pressure drop through the pair of circular
holes may be reduced to a negligible value. However, during orbital motion,
certain portions of the tip seal on one of the spiral elements will repeatedly
pass over the circular holes. These portions of the tip seal will tend to be bent
into the circular holes due to the plessùre differential and the fact that the
20 support provided behind the tip seal is reduced when enlarged holes are used.As a result, these portions of the axial tip seal element tend to be sandwiched
between the edge of the axial end of the spiral element and an edge of the
circular hole c~llsin~ damage thereto, for example, the tip seal may be cut.
Damaged tip seals reduce the efficiency of the compressor and possibly impair
25 proper functioning, altogether.
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SUMMARY OF THE INVENTION
The present invention is directed to a scroll type fluid compressor
including a housing having a fluid inlet port and a fluid outlet port. A fixed
scroll is fixedly disposed within the housing and has an end plate from which
5 a first spiral wrap extends into the interior of the housing. An orbiting scroll
has an end plate from which a second spiral wrap extends. The first and
second wraps interfit at an ~n~ r and radial offset to form a plurality of line
contacts which define at least one sealed-off fluid pocket. The co~ ressor
further includes an outlet aperture formed through the end plate of one of the
10 scrolls. A driving meçh~ni~m is operatively connected to the orbiting scroll to
effect the orbital motion of the orbiting scroll whereby the volume of the fluidpockets change during orbital motion to conl~less the fluid in the pockets with
the compressed fluid discharged though the outlet aperture. A displacement
adjusting means includes at least one hole formed through the end plate of one
15 of the scrolls to form a first fluid channel between the at least one sealed-off
fluid pocket and the opposite side of the end plate of the one scroll. A
plurality of seal elements are sequentially disposed along the axial end surfaceof the wrap of the other of the scrolls, with the plurality of seal elements
defining at least one spaced portion therebetween on the axial end surface.
20 The spaced portion is positioned so as to cross over the hole during relative orbital motion of the scrolls.
In a further embodiment the colllpressor in~h~des two fluid pockets and
two holes forming the first fluid channel. The plurality of seal elements
includes three seal elements defining two spaced portions on the axial end
25 surface, with each spaced portion positioned to cross over the holes.
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In a further embodiment the holes and fluid pockets are positioned in
pairs such that the spaced portions simlllt~neously cross over the holes during
relative orbital motion of the scrolls.
Accordingly, since no portion of the tip seals of the orbiting scroll
5 crosses over the holes, the diameter of the holes may be enlarged in order to
prevent the undesirable constriction of flow therethrough, without increasing
the possibility of d~m~ging the tip seal. Therefore, the present invention has
the advantage of allowing the displacement adjusting mech~ni~m to more
effectively control the compression ratio at any rotational speed, without
10 increasing the possibility that the tip seal element will be damaged.
Various additional advantages and features of novelty which
characterize the invention are further pointed out in the claims that follow.
However, for a better underst~n~ling of the invention and its advantages,
reference should be made to the accompanying drawings and descriptive
matter which illustrate and describe preferred embodiment of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a vertical longit~ltlin~l sectional view of a scroll type
compressor with a variable displacement mech~ni~m in accordance with a
preferred embodiment of this invention.
Figure 2 is a schematic horizontal perspective view of the scroll type
compressor of Figure 1, as viewed from the right side in Figure 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to Figure 1, a scroll type co~ ressor according to the present
invention is shown. The scroll type co~ ressor in~ ldes compressor housing
10 having front end plate 11 and cup-shaped casing 12 attached to front end
plate 11. Opening 111 is formed through the center of front end plate 11 and
drive shaft 13 is disposed in opening 111. Annular projection 112 projects
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.
rearwardly from front end plate 11. Annular projection 112 faces cup-shaped
casing 12 and is concentric with opening 111. An outer peripheral surface of
projection 112 extends into opening 121 of cup-shaped casing 12. Opening 121
of cup-shaped casing 12 is covered by front end plate 11. O-ring 14 is disposed
5 between the outer peripheral surface of ~nn~ r projection 112 and an inner
wall of opening 121 of cup-shaped casing 12 to seal the mating surface of front
end plate 11 and cup-shaped casing 12.
Annular sleeve 16 longitlltlin~lly projects from the front end surface of
front end plate 11, and defines shaft seal cavity 161. Drive shaft 13 is disposed
10 though sleeve 16 which surrounds and rotatably supports drive shaft 13 through
bearing 17 located within the front end of sleeve 16. Drive shaft 13 inclll~les
disk-shaped rotor 131 formed on its inner end. Rotor 131 is rotatably
supported in opening 111 of front end plate 11 though bearing 15. Shaft seal
assembly 18 is coupled to drive shaft 13 within shaft seal cavity 161 of ~nnlll~r
15 sleeve 16.
Pulley 201 is rotatably supported by ball bearing 19 which is disposed
about the outer peripheral surface of ~nn~ r sleeve 16. Electromagnetic coil
202 is fixed about the outer surface of ~nmll~r sleeve 16 by support plate 204.
Coil 202 is disposed within the inner and outer surfaces of pulley 201. Support
20 plate 204 is fixed to sleeve 16 by a snap ring, and supports coil 202 so as to
allow pulley 201 to freely rotate with respect thereto. Armature plate 203 is
elastically supported on the outer end of drive shaft 13 in a known manner.
Pulley 201, electromagnetic coil 202 and armature plate 203 form
electromagnetic clutch 20. When a current is provided to coil 202, plate 203
25 is attracted into contact with the axial surface of pulley 201, and rotational
motion is transferred from pulley 201 to drive shaft 13. In operation, drive
shaft 13 is driven by an external power source, for exarnple, the engine of an
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automobile, through a rotation tra~ llilling device such as electromagnetic
clutch 20.
Fixed scroll 21, orbiting scroll 22 and rotation preventing/thrust bearing
mech~ni~m 24 are disposed in the interior of housing 10. Fixed scroll 21
5 includes circular end plate 211 and spiral element 212 affixed to or integrally
extending from one end surface of circular end plate 211. Fixed scroll 21 is
fixed within the inner chamber of cup-shaped casing 12 by screws (not shown~
screwed into end plate 211 from the outside of cup-shaped casing 12. Circular
end plate 211 of fixed scroll 21 in~nl~tingly partitions the inner chamber of
10 cup-shaped casing 12 into two chambers, front charnber 27 and rear chamber
28. Front chamber 27 inclllcles suction chamber 271. O-ring 123 is disposed
between an outer peripheral surface of circular end plate 211 and an inner
peripheral wall of cup-shaped casing 12 to increase the in~ul~tion between
front chamber 27 and rear chamber 28. Spiral element 212 of fixed scroll 21
15 is located within front chamber 27. Front chamber 27 is linked to an element
of an external fluid circuit such as an air-conditioning system through inlet
opening 31 formed through casing 12.
Wall 122 longitu(lin~lly projects from the inner rear end surface of cup-
shaped casing 12 and divides rear chamber 28 into discharge chamber 281 and
20 intermediate pressure chamber 282. The axial end surface of wall 122
contracts the rear end surface of circular end plate 211. Discharge chamber
281 is linked to an external element of the air conditioning system through
outlet 32 formed through the rear end surface of casing 12.
Orbiting scroll 22 is located in front chamber 27 and includes circular
25 end plate 221 and spiral element 222 extending from one end surface of
circular end plate 221. Spiral element 222 of orbiting scroll 22 and spiral
element 212 of fixed scroll 21 interfit at an ~n~ r offset of appr- xi~ tely 180~
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and a predetermined radial offset to form sealed spaces or fluid pockets
between spiral element 212 and 222. Bushing 23 is supported on a pin which
projects from the rear end of disc-shaped portion 131 of drive shaft 13. The
pin is offset from the axis of drive shaft 13 such that bushing 23 is eccentric
5 with respect to drive shaft 13. Orbiting scroll 22 is supported on bushing 23
through radial needle bearing 30. Rotation of drive shaft 13 is converted into
orbiting motion of orbiting scroll 22 through the projecting pin and bushing 23.Rotation of orbiting scroll 22 is prevented by convenlional rotation
preventing/thrust bearing m~rh~ni~m 24 which is disposed between ~nmll~r
10 projection 112 of front end plate 11 and circular end plate 221 of orbiting
scroll 22.
A plurality of line contacts are formed between the walls of the spiral
elements to form the fluid pockets between the scrolls. As the orbiting scroll
orbits with respect to the fixed scroll, the line contacts move along the spiral15 elements, casing the volume of the fluid pockets to be decreased, and the
pockets to moved until they open into central fluid pocket 272. Central fluid
pocket 272 also undergoes co,lll)ression as well.
Refrigeration fluid from the external fluid circuit is introduced into
suction chamber 271 through inlet port 31 and flows into the outer fluid
20 pockets formed between spiral elements 212 and 222 through open spaces
between the spiral elements. The outer fluid pockets between the spiral
elements sequentially open and close during the orbital motion of orbiting
scroll ~. When the outer fluid pockets are open, fluid to be compressed flows
into the pockets but no compression occurs. When the pockets are closed, no
25 additional fluid flows into the pockets and colllpression begins. Since the
location of the outer terminal ends of spiral elements 212 and 222 is at a finalinvolute angle, the location of the pockets is directly related to the final
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involute angle. As orbiting motion contin~les, the refrigeration fluid in the
sealed pockets is moved along the walls of the spiral elements and is
compressed as the volume of the pockets is decreased.
The compressed refrigeration fluid llltim~tely flows into central pocket
5 272 and is discharged into discharge chamber 281 through discharge aperture
or port 213 which is formed at the center of circular end plate 211. Valve
plate 231 of spring material is disposed on discharge port 231 and the
compressed fluid is pushed pass valve plate 231 by virtue of a pressure
difference between the central pocket and the discharge ch~mber. Damage or
10 deformation of valve plate 231 is prevented by valve retainer 231a which
receives valve plate 231 to prevent excessive bending thereo~
Referring to Figure 2, a pair of circular holes 214 and 215 are formed
in circular end plate 211 of fixed scroll 21 and are generally symmetrically
placed so that an axial end surface of spiral element 222 of orbiting scroll 22
15 generally simultaneously crosses over both holes. Holes 214, 215 communicate
between intermediated fluid pockets 273 and intermediate pressure chamber
282. The radius of each of holes 214, 215 is designed so as to be slightly
smaller than the thickness of the spiral elements. Circular hole 214 opens
along the inner side wall of spiral element 212. Circular hole 215 opens along
20 the outer side wall of spiral element 212. Both circular hole are formed by
deeply cutting the holes into the wall of spiral element 212 of fixed scroll 21.Therefore, when the radially outer wall of spiral element 222 of orbiting scroll22 contacts the radially inner wall of spiral element 212 of fixed scroll 21 at the
location of circular holes 214, the circular hole is entirely covered by the axial
25 end of spiral element 222 of orbiting scroll 22. Similarly, hole 215 is covered
as well since the inner wall of element 2~ contacts the outer wall of element
212.
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A pair of valve plates 341 (only one valve plate is shown in Figure 1)
are attached by fasteners (not shown) to the rear end surface of circular end
plate 211. Valve plates 341 are made of spring material so that the bias of
valve plate 34 pushes them against a rear end opening of holes 214 and 215 to
5 close each hole. A pair of valve retainers 341a (only one valve retainer is
shown in figure 1) are associated with the valve plates and function to prevent
excessive bending or deforrnation as discussed with respect to valve retainer
231a.
Circular end plate 211 of fixed scroll 21 also includes communicating
10 channel 29 formed at an outer side portion of the terminal end of spiral
element 212. Communication ch~nnel 29 provides communication between
suction chamber 271 and irltermediate pressure chamber 282. Control
mesh~ni~m 36 controls fluid co~w,ication between suction chamber 271 and
intermediate pressure chamber 282, and thus between the intermediate fluid
15 pockets and the suction chamber, to vary the compression ratio of the compressor
as discussed above with reference to aforementioned U.S. Patent No. 4,904,164.
A complete description of the operation of control mech~ni~m 36 also is providedin the '164 patent.
Axial tip seal element 230 is disposed in groove 213 which is formed to
20 extend along the axial end of spiral element 212 of fixed scroll 21. A plurality
of axial tip seal elements 240a, 240b and 240c are disposed in a plurality of
grooves 223a, 223b and 223c, respectively, which are sequentially located along
the axial end of spiral element 222 of orbiting scroll 22. As illustrated in
Figure 2, first spaced portion 241 is defined between axial tip seal elements
25 240a and 240b on the axial end of spiral element 222 of orbiting scroll 22.
Second spaced portion 242 is defined between axial tip seal elements 240b and
240c on the axial end of spiral element 222 of orbiting scroll 22. The axial
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12
surface of spiral element 222 is not provided with a groove at the location of
first and second spaced portions 241 and 242. First and second spaced portions
241 and 242 are located so as to cross over circular holes 214 and 215,
respectively, during the orbital motion of orbiting scroll 22.
Accordingly, since no portion of the tip seals of the orbiting scroll cross
over the circular holes, the diameter of circular holes 214 and 215 may be
enlarged in order to prevent the undesirable constriction of flow therethrough
and corresponding pressure drop during operation of the compressor at high
rotational speeds, without experiencing the drawback of having the axial tip
10 seal element becoming sandwiched between the edge of the axial end of spiral
element 222 and the edge of circular holes 214 and 215. Thus, the possibility
of ~l~m~ging the axial tip seal elements, such as by cutting thereof, is
precluded. Therefore, the effectiveness of the displacement adjusting
meçh~ni~m in controlling the col"pression ratio at any rotational speed is
15 increased without increasing the possibility that the tip seal element will be
damaged. In fact, the provision of spaced portions 241 and 242 reduces the
chance of damage even if the circular holes are not enlarged. Finally, the
effectiveness of the sealing between the axial end surface of spiral element 222or orbiting scroll 22 and the inner surface of circular end plate 211 of fixed
20 scroll 21 which is provided by the use of axial tip seal elements 204a, 240b and
240c is only negligibly decreased as compared with the use of only one tip seal.This invention has been described in detail in connection with the
illustrated preferred embodiment. This embodiment, however, is merely for
example only and the invention is not restricted thereto. It will be easily
25 understood by those skilled in the art that other variations and modifications
can be easily made within the scope of this invention, as defined by the
appended claims.
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