US20080184733A1

US20080184733A1 - Scroll compressor with refrigerant injection system

Info

Publication number: US20080184733A1
Application number: US11/671,073
Authority: US
Inventors: Robin G. Skinner
Original assignee: Tecumseh Products Co
Current assignee: Tecumseh Products Co
Priority date: 2007-02-05
Filing date: 2007-02-05
Publication date: 2008-08-07
Also published as: CA2618414A1

Abstract

A scroll compressor including a refrigerant injection system. The refrigerant injection system includes an injection inlet conduit which is disposed at least partially within the suction pressure chamber of the scroll compressor, and includes one end sealingly fitted into an opening in the non-orbiting scroll member which is disposed within the suction pressure chamber. The non-orbiting scroll member includes a pair of transfer passages at least partially formed in a side thereof which faces the discharge pressure chamber, as well as injection ports for injecting refrigerant from the transfer passages into the working pockets defined between the non-orbiting and orbiting scroll members. A cover plate, disposed in the discharge chamber of the compressor, is secured to the base plate of the non-orbiting scroll via a gasket and a plurality of fasteners to enclose and seal the transfer passages from the discharge pressure chamber. A discharge valve assembly is secured to the cover plate and is operable to selectively open and close the discharge port of the non-orbiting scroll member.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to scroll compressors and, in particular, to a scroll compressor which includes a refrigerant injection system.
2. Description of the Related Art
Scroll compressors include a housing having a suction inlet in communication with a suction pressure chamber, and a discharge outlet in communication with a discharge pressure chamber. A motor-compressor unit is disposed within the housing, and a portion of the motor-compressor unit typically separates the suction pressure chamber from the discharge pressure chamber. The motor-compressor unit includes an electric motor for rotating a crankshaft that is rotatably supported by a crankcase which is secured with respect to the compressor housing. The crankshaft includes an eccentric portion which orbitally drives an orbiting scroll member with respect to a non-orbiting or fixed scroll member.
The orbiting scroll member and the non-orbiting scroll member include intermeshing spiral wraps which define a plurality of variable volume working pockets therebetween. During operation of the compressor, refrigerant at suction pressure is drawn into an inlet into the working pockets defined between the scroll members and is thereafter compressed as the refrigerant is moved toward the central portion of the scroll members before the refrigerant is discharged through a discharge port in the non-orbiting scroll member into the discharge chamber of the compressor.
Refrigerant injection systems for scroll compressors are generally known, in which liquid and/or vapor refrigerant is tapped from a selected location of the refrigeration system externally of the compressor, and is injected into the working pockets between the fixed and orbiting scroll members of the scroll compressor. The injected refrigerant is typically at an intermediate pressure, and is injected into low and/or intermediate pressure working pockets of the scroll compressor in order to cool the scroll members as necessary and/or to increase the efficiency of operation of the scroll compressor.
Many known refrigerant injection systems include an injection inlet conduit which is at least partially disposed within, or which passes through, the discharge pressure chamber of the scroll compressor. In one known arrangement, the injection inlet conduit extends through the discharge chamber between a first fitting in the top cap of the compressor and a second fitting in the non-orbiting scroll member. The first and second fittings are each disposed in the discharge chamber. Therefore, this arrangement requires very robust seals between the injection conduit and the compressor housing, as well as between the injection conduit and the non-orbiting scroll member because the refrigerant injected through the injection inlet conduit is at an intermediate pressure while the discharge chamber is at a much higher discharge pressure.
Other refrigerant injection systems include porting arrangements for injecting refrigerant through the orbiting scroll member and/or are operable in combination with pressure biasing arrangements by which the non-orbiting scroll member is pressure biased against the orbiting scroll member. These systems require very precise machining of components and are otherwise typically expensive and/or difficult to manufacture.
What is needed is a refrigerant injection system for a scroll compressor which is an improvement over the foregoing.

SUMMARY OF THE INVENTION

The present invention provides a scroll compressor including a refrigerant injection system. The refrigerant injection system includes an injection inlet conduit which is disposed at least partially within the suction pressure chamber of the scroll compressor, and includes one end sealingly fitted into an opening in the non-orbiting scroll member which is disposed within the suction pressure chamber. The non-orbiting scroll member includes a pair of transfer passages at least partially formed in a side thereof which faces the discharge pressure chamber, as well as injection ports for injecting refrigerant from the transfer passages into the working pockets defined between the non-orbiting and orbiting scroll members. A cover plate, disposed in the discharge chamber of the compressor, is secured to the base plate of the non-orbiting scroll via a gasket and a plurality of fasteners to enclose and seal the transfer passages from the discharge pressure chamber. A discharge valve assembly is secured to the cover plate and is operable to selectively open and close the discharge port of the non-orbiting scroll member.
Advantageously, the present refrigerant injection system includes an injection inlet conduit disposed at least partially in the suction pressure chamber of the compressor, such that the connections between the compressor housing and injection inlet conduit, and between the injection inlet conduit and non-orbiting scroll member, are more effectively sealed. Additionally, the cover plate includes a gasket disposed between the cover plate and the base plate of the non-orbiting scroll member which, together with a plurality of fasteners securing the cover plate to the base plate of the non-orbiting scroll member with the gasket captured therebetween, provides a robust seal around the transfer passages to seal the transfer passages from the discharge pressure chamber.
In one form thereof, the present invention provides a scroll compressor, including a housing including a suction pressure chamber and a discharge pressure chamber; a motor-compressor unit disposed within the housing, including a crankcase and a stator, rotor, and drive shaft assembly, the drive shaft rotatably supported by the crankcase; a first scroll member fixed with respect to the housing, the first scroll member including a base plate; a first wrap extending from the base plate; and a second scroll member coupled to the drive shaft for orbital movement, the second scroll member including a second wrap intermeshed with the first wrap to define a plurality of variable-volume working pockets; and a refrigerant injection system, including an inlet conduit; at least a pair of passages at least partially formed in the base plate of the first scroll member, the passages in fluid communication with the inlet conduit; at least a pair of injection ports in the base plate of the first scroll member, the injection ports in fluid communication with respective the passages and with the working pockets; and a cover plate secured to the base plate of the first scroll member and enclosing the passages, the cover plate disposed within the discharge pressure chamber.
In another form thereof, the present invention provides a scroll compressor, including a housing including a suction pressure chamber and a discharge pressure chamber; a motor-compressor unit disposed within the housing, including a crankcase and a stator, rotor, and drive shaft assembly, the drive shaft rotatably supported by the crankcase; a first scroll member fixed with respect to the housing, the first scroll member including a base plate separating the housing into the suction and discharge pressure chambers; a first wrap extending from the base plate; and a second scroll member coupled to the drive shaft for orbital movement, the second scroll member including a second wrap intermeshed with the first wrap to define a plurality of variable-volume working pockets; and a refrigerant injection system, including an inlet conduit disposed at least partially within the suction pressure chamber and including an end sealingly fitted to the first scroll member on a side of the first scroll member which is disposed within the suction pressure chamber; at least one passage at least partially formed in the base plate of the first scroll member, the passage in fluid communication with the inlet conduit; at least one injection port in the base plate of the first scroll member, the injection port in fluid communication with the passage and with at least one of the working pockets.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a schematic view of an exemplary refrigeration system including a scroll compressor having a refrigerant injection system in accordance with the present invention;

FIG. 2 is a longitudinal sectional view of the scroll compressor of FIG. 1;

FIG. 3 is a fragmentary sectional view of a portion of the scroll compressor, taken along a section plane different from that of FIG. 2;

FIG. 4 is an exploded view showing the non-orbiting scroll member, cover plate, gasket, and discharge valve assembly;

FIG. 5 is a first end view of the base plate of the non-orbiting scroll member without the cover plate attached thereto; and

FIG. 6 is a second end view of the non-orbiting scroll member showing the spiral wrap, discharge port, and injection ports.

Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrates one embodiment of the invention, in one form, and such exemplification is not to be construed as limiting the scope of the invention any manner.

DETAILED DESCRIPTION

Referring to FIG. 1, an exemplary refrigeration system 10 is shown, including a scroll compressor 12 having a refrigerant injection system in accordance with the present invention. Refrigeration system 10 generally includes, in series, scroll compressor 12, condenser 14, economizer 16, expansion valve 18, and evaporator 20. Refrigeration system 10 includes a primary or main circuit or line 22 and a refrigerant injection or bypass circuit or line 24 connected to main line 22 between condenser 14 and economizer 16. Injection line includes a control valve 26, such as an on/off solenoid valve, for example, for controlling the injection of refrigerant into scroll compressor 12 as described in further detail below. Optionally, depending on the thermodynamic requirements of system 10, injection line 24 may be connected to main line 22 at other locations on main line 22.
In use, when scroll compressor 12 is running, high pressure refrigerant at discharge pressure exits the discharge outlet 28 of scroll compressor 12 and passes to condenser 14 where heat is removed from the refrigerant in a known manner via the heat exchangers (not shown) of condenser 14. A first or main portion of the refrigerant passes from the outlet of condenser 14 through first heat exchanger 30 of economizer 16 and thence through expansion valve 18 where the refrigerant is flashed to vapor. Then, the refrigerant passes through evaporator 20 where heat is extracted from the surrounding environment in a known manner via the heat exchangers (not shown) of evaporator 20, and the suction pressure refrigerant is returned to scroll compressor 12 via suction inlet 32.
As is known, the economizer 16 may be used to increase the capacity of the system, particularly with higher ambient temperatures. In particular, a second or auxiliary portion of the high pressure refrigerant downstream of the outlet of condenser 14 passes through injection line 24 and through an expansion valve 34 where the refrigerant is at least partially flashed to a vapor before passing through second heat exchanger 36 of economizer 16, which is disposed in heat exchange relationship with first heat exchanger 30 of economizer 16 to thereby cool the main flow of refrigerant in line 22. The refrigerant in injection line 24 then passes through control valve 26 when control valve 26 is open and thence into injection inlet 38 of scroll compressor 12 for injection into the variable-volume working pockets between the scrolls of scroll compressor 12, as described in further detail below.
Referring to FIG. 2, scroll compressor 12 is shown, which includes main housing 40, bottom cap 42 including base 43 secured to the lower end thereof, and a top cap 44. Main housing 40 includes suction inlet 32 and top cap 44 includes discharge outlet 28. Bottom and top caps 42 and 44 are each secured to their respective ends of housing 40 by welding or brazing, for example, to define an enclosed hermetic housing in which the motor-compressor unit 46 of compressor 10 is disposed. Motor-compressor unit 46 generally includes a first, non-orbiting or fixed scroll member 48, a second, orbiting scroll member 50, as well as crankcase 52, drive shaft 54, stator 56, rotor 58, and outboard bearing assembly 60. Non-orbiting scroll member 48 rests on the upper end of housing 40 and is secured around its perimeter to the interior of top cap 44 by welding or brazing, for example, and divides the interior of housing 12 into a suction chamber 62 in fluid communication with suction inlet 32 in housing 12, and discharge chamber 64 in fluid communication with discharge outlet 32 in top cap 44. Non-orbiting scroll member 48 may also include a sealing member, such as O-ring 49 disposed in a groove around the perimeter of non-orbiting scroll member 48, to provide a seal between the exterior surface of non-orbiting scroll member 48 and the interior surface of top cap 44.
Non-orbiting scroll member 48 includes base plate 66 having first side 68 facing discharge chamber 64 and second side 70 facing suction chamber 62, and an involute wrap 72 extending from base plate 66. Non-orbiting scroll member 48 further includes a plurality of mount flanges 74 (FIG. 4) spaced radially around base plate 66 and extending from second side 70, and a plurality of bolts 75 (FIG. 5) extend through mount flanges 74 into crankcase 52 for securing non-orbiting scroll member to crankcase 52. Further details of non-orbiting scroll member 48 are described below.
Crankcase 52 includes main bearing 76 in which the upper portion of drive shaft 54 is rotatably supported. Stator 56 is fixed within housing 12 by a plurality of bolts (not shown) which pass through outboard bearing assembly 60, stator 56, and into crankcase 52. Further details regarding the structure of motor-compressor unit 46 and the manner in which same is mounted within compressor housing 12 are set forth in U.S. patent application Ser. No. 11/039,552, filed on Jan. 20, 2005, assigned to the assignee of the present invention, the disclosure of which is expressly incorporated herein by reference. Drive shaft 54 is secured to rotor 58 in a suitable manner, and outboard bearing assembly 60 includes outboard bearing 78 which supports a lower end of drive shaft 54. The upper portion of drive shaft 54 includes an eccentric end mounted within annular hub 80 extending downwardly from base plate 82 of orbiting scroll member 50. Orbiting scroll member 50 additionally includes an involute wrap 84 extending upwardly from base plate 82 thereof, which is in meshing relationship with wrap 72 of non-orbiting scroll member 48. Oldham coupling 86 is operatively coupled between orbiting scroll member 50 and crankcase 52 to prevent rotational movement of orbiting scroll member 50, as is known.
In operation, electrical energization of stator 56 rotatably drives rotor 58 and drive shaft 54 to move orbiting scroll member 50 in an orbiting manner with respect to non-orbiting scroll member 48. Refrigerant at suction pressure is drawn from suction chamber 62 into a suction inlet (not shown) defined between non-orbiting and orbiting scroll members 48 and 50, and is compressed within the plurality of variable volume, working pockets which are defined between wraps 72 and 84 of non-orbiting and orbiting scroll members 48 and 50, respectively, as orbiting scroll member 48 orbits. The compressed refrigerant is then discharged through discharge port 88 in base plate 66 of non-orbiting scroll member 48 and through discharge check valve assembly 90 described below, into discharge chamber 64 at a discharge pressure.
Referring to FIGS. 3-6, the details of refrigerant injection system of scroll compressor 12 will now be described. Referring to FIG. 3, injection inlet conduit 92 includes a first end having an inlet fitting 94 sealingly connected to housing 40 of scroll compressor 12 in a suitable manner, such as by welding or brazing. A suitable coupling (not shown) may be used to attach injection line 24 of refrigeration system 10 to inlet fitting 94 of injection inlet conduit 92. Injection inlet conduit 92 is at least partially disposed within suction pressure chamber 62 and, as shown in the embodiment of FIG. 3, extends through suction pressure chamber 62 through a gap provided between compressor housing 40 and crankcase 52. A second, opposite end of injection inlet conduit 92 is fitted within an opening 96 of base plate 66 of non-orbiting scroll member 48 in second side 70 of non-orbiting scroll member 48 which faces suction pressure chamber 62. A suitable sealing element, such as O-ring 98 captured within groove 100 around opening 96 of non-orbiting scroll member 48, provides a seal between injection inlet conduit 92 and opening 96 in base plate 66 of non-orbiting scroll member 48.
Referring to FIG. 4, base plate 66 of non-orbiting scroll member 48 includes transfer passage 102 formed at least partially within second side 70 of non-orbiting scroll member 48 which faces discharge chamber 64. Transfer passage 102 is in fluid communication with opening 96 as described above, and branches into a pair of transfer passages 102 a and 102 b which each terminate in end portions 104 disposed generally on respective opposite sides of discharge port 88 of non-orbiting scroll member 48. Transfer passage 102 may be formed in non-orbiting scroll member 48 by machining or by being cast into base plate 66 of non-orbiting scroll member 48. Each end portion 104 includes at least one injection port 106 such as, for example, a set of three individual injection ports 106 as shown in FIGS. 5 and 6, which pass through base plate 66 of non-orbiting scroll member 48 and are in fluid communication with respective variable-volume working pockets defined between the wraps 72 and 84 of non-orbiting and orbiting scroll members 48 and 50, respectively. Injection ports 106 may be in fluid communication with low, intermediate, or high pressure working pockets defined between scroll members 48 and 50 and, in the embodiment described herein, injection ports 106 are in fluid communication with intermediate pressure working pockets.
Referring to FIG. 4, cover plate 108 is secured to first side 68 of base plate 66 of non-orbiting scroll member 48 which faces discharge chamber 64 via a plurality of fasteners 110, with gasket 112 captured and compressed between cover plate 108 and base plate 66. Gasket 112 and cover plate 108 each include a plurality of holes 114 and 116, respectively, through which fasteners 110 may pass, and base plate 66 of non-orbiting scroll member 48 includes a corresponding number of holes 118 into which fasteners 110 may be secured, such as by a threading engagement or by another suitable manner. Gasket 112 includes an opening 120 therein corresponding to the shape or outline of transfer passage 102. Cover plate 108 is disposed within discharge chamber 64 and gasket 112, together with fasteners 110, provides a robust seal between cover plate 108 and base plate 66 of non-orbiting scroll member 48 to enclose and seal transfer passages 102 at intermediate pressure from the high pressure within discharge chamber 64.
Still referring to FIG. 4, discharge valve assembly 90 generally includes a flapper-type discharge valve 122 made of spring steel, for example, which is secured along with a curved valve stop or backer 124 to cover plate 108 via fastener 126. Cover plate 108 includes a recessed area 128 for receiving valve 122 and valve stop 124, as well as opening 130 aligned with discharge port 88 in non-orbiting scroll member 48, and valve 122 normally rests against the annular edge of discharge port 88, as shown in FIG. 3.
Control valve 26 of refrigeration system 10 is operated to in turn control the injection of refrigerant into the working pockets of scroll members 48 and 50 of scroll compressor 12. A temperature sensor (not shown) may be associated with discharge chamber 64, discharge outlet 28 or main line 22 of refrigerant system between scroll compressor 12 and condenser 14, to determine the temperature of the discharge pressure refrigerant. If the temperature is within an acceptable range, a suitable controller, such as a computer processor controller (not shown) may place control valve 26 in a closed position such that no refrigerant is injected into scroll compressor 12. If the detected temperature of the discharge pressure refrigerant is higher than a predetermined temperature, the controller may open control valve 26 to allow refrigerant to be injected from injection line 24 into scroll compressor 12 to cool non-orbiting and orbiting scroll members 48 and 50 and/or to increase the efficiency of operation of scroll compressor 12.
More specifically, opening control valve 26 allows refrigerant at intermediate pressure, typically in the form of a vapor or a liquid/vapor mixture, to pass from injection line 24 into scroll compressor 12 and thence through injection inlet conduit 92, transfer passages 102 a and 102 b, and injection ports 106 into intermediate pressure working pockets defined between non-orbiting and orbiting scroll members 48 and 50. Typically, the pressure of the injected refrigerant is slightly higher than the pressure of the refrigerant within the intermediate pressure working pockets, such that refrigerant cannot escape in a reverse direction from the intermediate pressure working pockets back through the refrigerant injection system, i.e., refrigerant is only injected into the intermediate pressure working pockets. The injection of intermediate pressure refrigerant into the working pockets defined between non-orbiting scroll member 48 and orbiting scroll member 50 functions to cool the scrolls and/or to increase the efficiency of operation of scroll compressor 12.
Advantageously, the present vapor injection system includes an injection inlet conduit 92 disposed at least partially within, or disposed completely within, the suction pressure chamber 62 of compressor 12, such that the connections between the injection inlet conduit 92 and the compressor housing 40 and/or non-orbiting scroll member 48 are more easily sealed. Additionally, a robust seal around transfer passages 102 is provided by the capture and compression of gasket 112 between cover plate 108 and base plate 66 of non-orbiting scroll member 48 by fasteners 110 to seal transfer passages 102 from the high pressures within discharge pressure chamber 64. Other embodiments, or modifications of, the present injection system are possible. For example, liquid refrigerant from immediately downstream of the condenser may be injected into the working pockets between the scrolls for cooling the scrolls.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. A scroll compressor, comprising:

a housing including a suction pressure chamber and a discharge pressure chamber;

a motor-compressor unit disposed within said housing, including a crankcase and a stator, rotor, and drive shaft assembly, said drive shaft rotatably supported by said crankcase;

a first scroll member fixed with respect to said housing, said first scroll member comprising:

a base plate separating an interior of said housing into said suction and discharge pressure chambers;

a first wrap extending from said base plate; and

a second scroll member coupled to said drive shaft for orbital movement, said second scroll member including a second wrap intermeshed with said first wrap to define a plurality of variable-volume working pockets; and

a refrigerant injection system, comprising:

an inlet conduit disposed in said suction pressure chamber, said inlet conduit separate from said first scroll member and including a first end connected to an injection inlet fitting in said housing and a second end connected to a fitting in said first scroll member, each said fitting disposed within said suction pressure chamber;

at least a pair of passages at least partially formed in said base plate of said first scroll member, said passages in fluid communication with said inlet conduit;

at least a pair of injection ports in said base plate of said first scroll member, said injection ports in fluid communication with respective said passages and with said working pockets; and

a cover plate secured to said base plate of said first scroll member and enclosing said passages, said cover plate disposed within said discharge pressure chamber.

2. (canceled)

3. (canceled)

4. (canceled)

5. The scroll compressor of claim 1, wherein a plurality of said injection ports are associated with each said passage.

6. The scroll compressor of claim 1, wherein said cover plate further comprises a discharge opening therein, said discharge opening aligned with a discharge port in said first scroll member.

7. The scroll compressor of claim 1, further comprising a discharge valve assembly including a discharge valve and a valve stop each secured to said cover plate, said discharge valve operable to open and close a discharge port of said first scroll member.

8. The scroll compressor of claim 1, further comprising a gasket disposed between said cover plate and said base plate of said first scroll member, and a plurality of fasteners securing said cover plate to said base plate with said gasket captured between said cover plate and said base plate.

9-15. (canceled)