BACKGROUND OF THE INVENTION
[0001] This invention relates to a compressor, and more particularly, to a scroll type compressor
for an air conditioning apparatus which includes a mechanism for adjusting the displacement
of the compressor.
[0002] Scroll type fluid displacement apparatus are well known in the prior art. For example,
U.S. Patent No. 801,182 (Creux) discloses a device including two scrolls each having
a circular end plate and a spiroidal or involute spiral element. These scrolls are
maintained angularly and radially offset so that both spiral elements interfit to
make 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 changes. Since the volume of the fluid
pockets increases or decreases dependent on the direction of the orbital motion, this
scroll type fluid displacement apparatus is applicable to compress, expand or pump
fluids.
[0003] Scroll type fluid displacement apparatus are suitable for use as refrigerant compressors
in air conditioners. In such air conditioners, thermal control in the room or control
of the air conditioner is generally accomplished by intermittent operation of the
compressor. Once the temperature in the rcom has been cooled to a desired temperature,
the refrigerant capacity of the air conditioner for supplemental cooling, because
of further temperature changes in the room, or for keeping the room at the desired
temperature, generally need not be very large. However, since prior art air conditioners
do not have capacity control mechanisms, after the room has been cooled to the desired
temperature, the output of the compressor is controlled by. intermittent operation
of the compressor. Thus, the relatively large load which is required to drive the
compressor is intermittently applied to the driving source.
[0004] When prior art scroll compressors are used in automotive air conditioners, they are
driven by the automobile engine through an electromagnetic clutch. Once the passenger
compartment reaches a desired temperature, control of the output of the compressor
is accomplished by intermittent operation of the compressor through the electromagnetic
clutch. Thus, the relatively large load which is required to drive the compressor
is intermittently applied to the automobile engine.
[0005] Therefore, it is desirable to provide a scroll compressor with a displacement or
volume adjusting mechanism which controls the compression ratio as occasion demands.
In a scroll type compressor, the adjustment of the displacement can be easily accomplished
by controlling the volume of the sealed off fluid pockets. A displacement adjusting
mechanism is disclosed in our co-pending application Serial Number
356,6
48, filed on March 9,
198
2. This latter application discloses a mechanism including a pair of holes formed through
one of the end plates of one of the scrolls. The holes are placed in symmetrical positions
so that the wrap of the other scroll simultaneously crosses over the holes. In this
compressor, the holes are placed within an area between φ end and φ end-2π , where
ϕ end is the final involute angle of the wrap. Because of the location of these holes
in the area between the end of the wrap and φend-2π , part of the fluid in the sealed
off fluid pockets leaks to the suction chamber through the holes. As a result, no
compression takes place until the fluid pockets pass the hole at location defined
ϕ end-2 π. However, when the holes are placed within the area between ϕ end and ϕ
end-2π, the volume reduction ratio or capacity adjustment capability is limited.
SUMMARY OF THE INVENTION
[0006] It is a primary object of this invention to improve a scroll type compressor by incorporating
a mechanism for changing the compression ratio of the compressor as occasion demands
without the loss of energy consumption.
[0007] It is another object of this invention to provide a scroll type compressor in which
the volume reduction ratio of the fluid pocket is freely selected as occasion demands
without useless operation of the compressor.
[0008] It is still another object of this invention to provide a scroll type compressor
in which sealing of the fluid pockets is maintained while achieving the above objects.
[0009] It is a further object of this invention to provide a scroll type compressor which
is simple in construction and can be simply and reliably manufactured.
[0010] A scroll type compressor according to this invention includes a pair of scrolls.
Each scroll includes an end plate and a wrap extending from one side surface of the
end plate. The wraps interfit at an angular and radial offset to make a plurality
of line contacts and define at least one pair of sealed off fluid pockets. One of
the scrolls (an orbiting scroll) is driven in orbital motion by the rotation of a
drive shaft, while the rotation of the orbiting scroll is prevented. The fluid pockets
shift along the spiral curved surface of the wrap, which changes the volume of the
fluid pockets. One of the end plates has at least two pair of holes formed through
it. The holes of each pair of holes are placed in symmetrical positions so that the
wrap of the other scroll simultaneously crosses over the holes. The most inwardly
placed pair of holes is placed within an area between ϕ end-27T and φend-4π, where
φ end is the final involute angle of the wrap which extends from the end plate having
the holes. A further pair of holes is placed within an area between wend and φend-2π.
[0011] A control device controls the opening and closing of the holes to control the displacement
volume of the fluid pockets. When the holes are closed, compression operates normally
and the displacement volume is not changed. When the holes are opened by the control
device, fluid in the sealed off pockets flows back into the suction chamber through
the holes until the spiral element of the other scroll crosses over the inwardly placed
pair of holes. The displacement volume in the fluid pockets is thereby reduced, and
compression starts at an intermediate stage.
[0012] Further objects, features and other aspects of this invention will be understood
from the detailed description of the preferred embodiments of this invention with
reference to the annexed drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013]
Figure I is a vertical sectional view of a scroll type compressor unit according to
an embodiment of this invention;
Figure 2 is a front end view of the fixed scroll member used in the compressor of Figure I;
Figure 3 is a sectional view of the spiral elements illustrating the hole extending into one
of the spiral elements;
Figure 4 is a perspective view of a magnetic coil used in the compressor of Figure i;
Figure 5 is a front end view of a snap ring used in the compressor of Figure I; and
Figures 6a-6d are schematic views illustrating the operation of the volume or displacement
adjusting mechanism utilizing a pair of holes.
DETAILED DESCRIPTION OF THE INVENTION
[0014] Referring to Figure
1, a refrigerant compressor in accordance with an embodiment of the present invention,
in particular, a scroll type refrigerant compressor i, is shown. Compressor i includes
compressor housing 10 having front end plate 11 and cup shaped casing
12 which is attached to an end surface of front end plate 11. Opening III is formed
in the center of front end plate 11 for the penetration or passage of drive shaft
13. Annular projection 112 is formed in a rear end surface of front end plate 11. Annular
projection
112 faces cup shaped casing
12 and is concentric with opening 111. An outer peripheral surface of annular projection
112 extends into an inner wall of the opening of cup shaped casing
12. Thus, cup shaped casing
12 is covered by front end plate 11. An 0-ring
14 is placed between the outer peripheral surface of annular projection
112 and the inner wall of the opening of cup shaped casing
12 to seal the mating surfaces of front end plate 11 and cup shaped casing
12.
[0015] Annular sleeve 15 projects from the front end surface of front end plate 11 which
surrounds drive shaft
13 and defines a shaft seal cavity. In the embodiment shown in Figure 1, sleeve 15 is
separate from front end plate 11. Therefore, sleeve 15 is fixed to the front end surface
of front end plate 11 by screws
16. An O-ring is placed between the end surface of front end plate 11 and the end surface
of sleeve 15 to seal the mating surfaces of front end plate 11 and sleeve 15. Alternatively,
sleeve
15 may be integral with front end plate 11.
[0016] Drive shaft 13 is rotatably supported by sleeve
15 through bearing
18 located within the front end of sleeve 15. Drive shaft
13 has disk
19 at its inner end which is rotatably supported by front end plate
11 through bearing
20 Icoated within opening 111 of front end plate 11. Shaft seal assembly
21 is coupled to drive shaft
13 within the shaft seal cavity of sleeve 15.
[0017] Pulley
22 is rotatably supported by bearing
23 which is carried on the outer surface of sleeve
15. Electromagnetic coil
24 is fixed about the outer surface of sleeve 15 by support plate 25 and is received
in an annular cavity of pulley
22. Armature plate
26 is elastically supported on the outer end of drive shaft
13 which extends from sleeve 15. Pulley
22, magnetic coil
24 and armature plate
26 form a magnetic clutch. In operation, drive shaft
13 is driven by an external power source, for example the engine of an automobile, through
a rotation transmitting device such as the above explained magnetic clutch.
[0018] A number of elements are located within the inner chamber of cup shaped casing
12 including fixed scroll
27, orbiting scroll
28, a driving mechanism for orbiting scroll
28 and a rotation preventing/thrust bearing device for orbiting scroll
28. The inner chamber of cup shaped casing
12 is formed between the inner wall of cup shaped casing
12 and the rear end surface of front end plate 11.
[0019] Fixed scroll
27 includes circular end plate
271, a wrap or spiral element
272 affixed to or extending from one side surface of end plate
271. Partition wall
273 axially projects from the opposite side surface of circular end plate
271. An axial end surface of partition wall
273 is seated against and connected to an inner surface of end plate 121 of cup shaped
casing
12 by fasteners (not shown). Circular end plate
271 of fixed scroll
27 partitions the inner chamber of cup shaped casing
12 into first chamber
29 and second chamber
30. Seal ring 31 is disposed within a circumferential groove of circular end plate
271 to form a seal between the inner wall of cup shaped casing
12 and the outer wall of circular end plate 271. Spiral element
272 of fixed scroll
27 is located within first chamber
29 and partition wall
273 is located within second chamber
30. Partition wall
273 further divides - second chamber
30 into suction chamber 301 and discharge chamber
302.
[0020] Orbiting scroll
28, which is located in first chamber
29, includes circular end plate 281 and a wrap or spiral element
28
2 affixed to or extending from one side surface of end plate
28
1. Spiral elements
272 and
28
2 interfit at an angular offset of
18
0° and a predetermined radial offset. The spiral elements define at least a pair of
sealed off fluid pockets between their interfitting surfaces.
[0021] Orbiting scroll
28 is rotatably supported by bushing
31 through bearing
32 placed on the outer peripheral surface of bushing
31. Bushing
31 is connected to an inner end of disk
19 at a point radially offset or eccentric of the axis of drive shaft
13.
[0022] Rotation preventing/thrust bearing device
33 is placed between the inner end surface of front end plate 11 and the end surface
of end plate
28
1 which faces the inner end surface of front end plate 11. Rotation preventing/thrust
bearing device
33 includes fixed ring
331 attached to the inner end surface of front end plate member 11, orbiting ring
332 attached to the end surface of end plate
28
1, and a plurality of bearing elements, stch as balls
333 placed between pockets
33Ia,
332a formed through rings 3
31 and
332. The rotation of orbiting scroll
28 during its orbital motion is prevented by the interaction of balls
333 with rings
331,
332; and the axial thrust load from orbiting scroll
28 is supported on front end plate 11 through balls 333.
[0023] Cup shaped casing
12 has an inlet port
34 and outlet port
35 for connecting the compressor unit with an external fluid circuit. Fluid is introduced
from the external circuit into suction chamber
301 through inlet port
34 and flows into chamber
29 through a connecting hole formed through end plate
271 at a position near its outer peripheral surface. The fluid in chamber
29 is taken into the fluid pockets formed between spiral elements
272 and
28
2. As orbiting scroll
28 orbits, the fluid in the fluid pockets moves to the center of the spiral elements
and is compressed. The compressed fluid is discharged into discharge chamber
302 from the fluid pockets in the general area of the center of the spiral elements through
hole
274 formed through circular end plate
271. The compressed fluid then is discharged to the external fluid circuit through outlet
port
35.
[0024] In operation, fluid generally is taken into the fluid pockets formed between spiral
elements
272 and
28
2 through two open spaces. Each open space is defined between the outer terminal end
of one of the spiral elements and the outer wall surface of the outer spiral element.
The entrance to these open spaces sequentially open and close during the orbital motion
of orbiting scroll
28. While the entrance to these open spaces remain open, fluid to be compressed flows
into them, but no compression occurs. After the entrance to these open spaces closes,
the sealed off fluid pockets are formed, no additional fluid flows into the pockets,
and compression begins. The location of the outer terminal end of each spiral element
272 and
28
2 is at the final involute angle, therefore, the location of these open spaces is directly
related to the final involute angle.
[0025] Referring to Figure
2, the final involute angle (φ end) at the end of spiral element
272 of fixed scroll
27 is greater than
4π . At least two pair of holes
275,
276,
278 and
279 are formed in end plate
272 of fixed scroll
27. The holes of each pair of holes are placed at symmetrical positions so that an axial
end surface of spiral element
28
2 of orbiting scroll
28 simultaneously crosses over the pair of holes. Holes
275 and
278 communicate between suction chamber 301 and one of the fluids pockets A, and holes
276 and 2
79 communicate between suction chamber
301 and the other fluid pocket A'.
[0026] Hole 275 of the first pair of holes is placed at a position defined by the involute
angle φ1 and opens along the inner side wall of spiral element
272. The other hole
276 is placed at a position defined by the involute angle ( φI-π) and opens along the
outer side wall of spiral element
272. The preferred area in which to place the first pair of holes
275 and
276, as defined by the involute angles, is given by φend-2π>φI>φend-4π. Thus, the holes
275 and
276 are simultaneously closed by spiral element
28
2 of orbiting scroll
28.
[0027] Hole
278 of the second pair of holes is placed at a position defined by the involute angle
φ2 and opens along the inner side wall of spiral element
272. The other hole
279 is placed at a position defined by the involute angle (φ2-π) and opens along the
outer side wall of spiral element
272. The preferred area within which to place the second pair of holes
278 and
279, as defined by the involute angles, is given byφ1+2π>φ2>φend-2π. Thus, the second
pair of holes along the spiral element
272, and are simultaneously closed by spiral element
28
2 of orbiting scroll
28.
[0028] Holes
275,
276,
278 and
279 are formed by drilling into end plate
271 from the side opposite from spiral element
272. Holes
275 and
278 are drilled at a position which overlaps with the inner wall of spiral element
272, so that a portion of the inner wall of spiral element
272 is removed. Holes
276 and
279 are drilled at a position which overlaps the outer wall of spiral element
272 so that a portion of the outer wall of spiral element
272 is removed. This overlapping of hole
275 is shown in detail in Figure
3. In this arrangement, the axial end surface of each spiral element is provided with
a seal
36 which forms an axial seal between the spiral element and the facing end plate. Holes
275,
276,
278 and
279 are positioned so that they do not connect with the fluid pockets between the spiral
elements when spiral element
28
2 completely overlaps the holes. This is accomplished by extending a portion of each
hole into spiral element
272 with the result that seal element
36 in spiral element
28
2 remains completely in contact with end plate
271 when spiral element
28
2 completely overlaps the holes, while the size of holes
275,
276,
278 and
279 are kept sufficiently large.
[0029] Control mechanism
37, which is located in suction chamber
301, is connected to the outer peripheral surface of partition wall
273. Control mechanism
37 includes: (i) a valve member having a plurality of valve plates
371 which are attached to the end surface of end plate
271 at each hole 2
75,
276,
278 and
279; and (
2) annular shaped electromagnetic coil
372 attached to the outer surface of partition wall
273.
[0030] Each valve plate
371 is made of a spring type magnetic material, and is attached to the end surface of
end plate
271 by a fastener, such as screw
38. Magnetic coil
37 is fitted into groove
277 formed on the outer peripheral surface of partition wall
273, and is held therein against axial movement by a snap ring
39, as shown in Figure
5. The inherent spring tendency of each valve plate
371 pushes it against the opening of a respective hole 2
75, 2
76, 2
78 and
279 to thus close the opening of each hole. Valve plates
371 are controlled by the operation of magnetic coil
372. By activating coil
372, the valve plates
371 are bent away from the openings in holes
275, 2
76, 2
78 and 2
79. Deactivating coil
371 permits the valve plates to again seal the openings to the holes because of their
inherent spring tendency.
[0031] Magnetic coil
372 is provided with contact portions
372a at its end surface facing the valve plates
371. When valve plates
371 are drawn away from holes
275,
276,
278 and
279 by magnetic coil
372, they contact portions 37
2a.
[0032] Referring to Figures 6a-6d, the operation of the mechanism for changing the displacement
volume of the fluid pockets, i.e., the volume of the sealed off fluid pockets at the
time compression begins, will be described. When, during orbital motion, the terminal
end portion of both spiral elements
272,
28
2 are in contact with the opposite side wall of the other spiral element, a pair of
fluid pockets A, A, which are defined between line contacts A-B and line contacts
E-F, are sealed off and simultaneously formed at symmetrical locations, as shown in
Figure 6a. If holes
275,
276,
278 and
279 are closed by valve member
371, compression of the fluid taken into the fluid pockets through the open space between
the spiral elements begins. The fluid in these fluid pockets moves toward the center
of the spiral elements during orbital motion of the orbiting scroll which results
in volume reduction and compression as shown in Figures 6a-6d. This fluid eventually
is discharged into discharge chamber
302 through hole
274. In the above operative mode, compression operates normally and the displacement
volume of the sealed off fluid pockets is determined when the terminal ends of the
spiral elements first contact the opposite side wall of the other spiral element.
[0033] When valve member
371 is opened by magnetic coil
372, each hole 275, 2
76,
278 and
279 is opened. As shown in Figure 6b, even though the sealed off fluid pockets have been
formed by contact of the terminal ends of the spiral elements with the opposite spiral
elements, fluid which has been taken into the sealed off fluid pockets A and A' leaks
from the sealed off fluid pockets A, A' back to suction chamber
301 through the second pair of holes
278 and
279 as orbiting scroll
28 orbits. During the orbital motion of orbiting scroll
28, the axial end surface of spiral element
28
2 of orbiting scroll
28 simultaneously crosses over the two holes
278 and
279. As shown in Figure 6c, this blocks fluid communication between the fluid pockets
A, A' and suction chamber
301 through holes
277 and
278. How-' ever, before the second pair of holes
278 and
279 are simultaneously closed by the axial end surface of spiral element
28
2, the fluid pockets A, A' are connected to suction chamber 301 through the first pair
of holes
275 and
276, which are inwardly located relative to the pair of holes
278 and
279. Therefore, the leakage of fluid in the fluid pockets A, A' continues until the axial
end surface of spiral element
28
2 of orbiting scroll
28 crosses over and closes holes
275 and
276. This latter state, which is shown in Figure 6d, prevents compression. As a result,
the actual compression stroke of fluid pockets A, A' starts after the spiral element
28
2 or orbiting scroll
28 crosses over holes 275 and
276. The volume of the fluid pockets A, A' at the time these pockets are sealed from
suction chamber
301, and compression actually begins, is thereby reduced. In this manner, the capacity
of the compressor is reduced. ,
[0034] In this construction, the involute angle location of the first pair of holes
275 and
276 is placed within the area between φend-2π and φend-4π. The second pair of holes
278 and
279 is placed within the area between Oend and φend-2π. Accordingly, a large reduction
of the displacement volume is realized without performing a useless compression operation.
If the inward hole
276 is placed at φend-4π , the larger the reduction of displacement volume, i.e., the
capacity difference between the normal operation and the displacement or volume adjustment
operation will be larger. Conversely, if the inward hole
276 is placed at φ end-2π, the consequent reduction of displacement volume is smaller.
[0035] This invention has been described in detail in connection with a preferred embodiment
but this embodiment is merely for example only and this invention is not restricted
thereto. It will be easily 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.