EP0113786A1

EP0113786A1 - Scroll type compressor with displacement adjusting mechanism

Info

Publication number: EP0113786A1
Application number: EP82306702A
Authority: EP
Inventors: Masaharu Hiraga; Atsushi Mabe; Yuji Yoshii
Original assignee: Sanden Corp
Current assignee: Sanden Corp
Priority date: 1982-12-15
Filing date: 1982-12-15
Publication date: 1984-07-25
Also published as: AU9152782A; AU561950B2

Abstract

A scroll type compressor including a housing, a fixed scroll which is joined to the housing and including a first end plate (271) from which a first wrap (272) extends and an orbiting scroll which includes a second end plate (281) from which a second wrap (282) extends. The wraps interfit at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed off luid pockets. The first end plate is formed with a plurality of pairs of holes (279, 276), the holes of each pair of holes being placed at symmetrical positions. The most inwardly placed hole is placed at a location defined by involute angles within the area defined by Φend-2(n-l)π>Φl>Φend-2n, where Φend is the final involute angle of the wrap which extends from the end plate having the holes, ΦI is the involute angle at which the hole is placed and n is the amount of pairs of holes. The most outwardly placed hole is placed at a location defined by involute angles within the area defined by Φn-l + 2x > Φn > Φend-2π. The intermediate holes are located within an area defined by Φk-l + 2π > Φk > Φk+ 1-2n, where Φk is the involute angle at which hole kth from the most inwardly placed hole is located. A control mechanism (372) controls the opening and closing of the holes to thereby control the capacity or displacement volume of the compressor.

Description

BACKGROUND OF THE INVENTION

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.
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.
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.
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.
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 ₃₅6,6₄8, filed on March 9, ₁₉8₂. 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

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.
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.
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.
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.
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.
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.
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

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

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.
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.
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.
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.
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.
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.
Orbiting scroll ₂8, which is located in first chamber ₂₉, includes circular end plate 281 and a wrap or spiral element ₂8₂ affixed to or extending from one side surface of end plate ₂8₁. Spiral elements ₂₇₂ and ₂8₂ interfit at an angular offset of ₁8₀° and a predetermined radial offset. The spiral elements define at least a pair of sealed off fluid pockets between their interfitting surfaces.
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.
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 ₂8₁ 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 ₂8₁, and a plurality of bearing elements, stch as balls ₃₃₃ placed between pockets _33Ia, ₃₃₂a formed through rings 3₃1 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.
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 ₂8₂. 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.
In operation, fluid generally is taken into the fluid pockets formed between spiral elements ₂₇₂ and ₂8₂ 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 ₂8₂ is at the final involute angle, therefore, the location of these open spaces is directly related to the final involute angle.
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 ₂8₂ 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 2₇₉ communicate between suction chamber ₃₀₁ and the other fluid pocket A'.
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 ₂8₂ of orbiting scroll ₂8.
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 ₂8₂ of orbiting scroll ₂8.
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 ₂8₂ 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 ₂8₂ remains completely in contact with end plate ₂₇₁ when spiral element ₂8₂ completely overlaps the holes, while the size of holes ₂₇₅, ₂₇6, ₂₇8 and ₂₇₉ are kept sufficiently large.
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 2₇₅, ₂₇6, ₂₇8 and ₂₇₉; and (₂) annular shaped electromagnetic coil ₃₇₂ attached to the outer surface of partition wall ₂₇₃.
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 2₇₅, 2₇6, 2₇8 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, 2₇6, 2₇8 and 2₇₉. Deactivating coil ₃₇₁ permits the valve plates to again seal the openings to the holes because of their inherent spring tendency.
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 37₂a.
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, ₂8₂ 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.
When valve member ₃₇₁ is opened by magnetic coil ₃₇₂, each hole 275, 2₇6, 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 ₂8₂ 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 ₂8₂, 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 ₂8₂ 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 ₂8₂ 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. ,
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.
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.

Claims

i. In a scroll type compressor including a pair of scrolls each having ar: end plate and a wrap extending from one side surface of said end plate, said wraps interfitting at an angular and radial offset to make a plurality of line contacts between said wraps to define at least one pair of sealed off fluid pockets, and a driving mechanism operatively connected to one of said scrolls for orbiting said one scroll relative to the other one of said scrolls while preventing rotation of said one scroll to thereby change the volume of the fluid pockets, the improvement comprising:
one end plate having at least two pairs of holes in fluid communication with a suction chamber, said holes of each pair of holes being located at symmetrical locations along the wrap which extends from said one end plate so that said other wrap simultaneously crosses over both of said holes in each pair of holes, the most inwardly placed hole of said pairs of holes being located within an are defined by φend-2(n-1)π>φ1>φend-2n , where φ end is the final involute angle of said wrap which extends from said one end plate, φ is the involute angle at which said most inwardly placed hole is located and n is the number of pairs of holes, the most outwardly placed hole of said pairs of holes being located within an area defined by φn-1+2π> φn>φ end-2Tr, and the intermediate holes of said pairs of holes being located within an area defined by φk-I+2π>φk>φk+I-2π, where φk is the involute angle at which the kth hole from the most inwardly placed hole is located; and

control means for selectively opening and closing said pairs of holes to permit fluid communication therethrough to said suction chamber to thereby selectively control the displacement volume of said compressor.
₂. The scroll type compressor of claim i wherein said control means includes a valve member and an electromagnetic device, said valve member being attached to the end surface of said end plate and covering the opening of each of said holes, said electromagnetic device being supported adjacent said valve member to move said valve member toward and away from said end surface to open and close said holes.
₃. The scroll type compressor of claim ₂ wherein said valve member comprises a separate flat plate attached adjacent each of said holes.
₄. The scroll type compressor of claim ₁ wherein said holes extend into a portion of said wrap which extends from said one end plate.
₅. The scroll type compressor of claim ₂ wherein said holes extend into a portion of said wrap which extends from said one end plate.
6. The scroll type compressor of claim ₃ wherein said holes extend into a portion of said wrap which extends from said one end plate.