Digital scroll condensing unit controller Number:6,745,584 from the United States Patent and Trademark Office (PTO) owispatent A cooling system controller controls the capacity of a variable capacity compressor based upon the temperature of a housing being cooled, the suction pressure of the compressor or both of these criteria. The cooling system controller is capable of controlling either single-evaporator or multiple-evaporator refrigeration systems. The multiple-evaporator systems can have evaporators of similar temperatures or of mixed temperatures. The controller also allows the use of one or more condenser fans that are operated in a lead/lag fashion to control the cooling capability of the system.<H controller, condensing, Digital, scroll, , 6745584.html, Patent, pto, 6745584

Title: Digital scroll condensing unit controller

Abstract: A cooling system controller controls the capacity of a variable capacity compressor based upon the temperature of a housing being cooled, the suction pressure of the compressor or both of these criteria. The cooling system controller is capable of controlling either single-evaporator or multiple-evaporator refrigeration systems. The multiple-evaporator systems can have evaporators of similar temperatures or of mixed temperatures. The controller also allows the use of one or more condenser fans that are operated in a lead/lag fashion to control the cooling capability of the system.

Patent Number: 6,745,584 Issued on 06/08/2004 to Pham, et al.

Inventors: Pham; Hung M. (Dayton, OH), Vogh, III; Richard P. (Marietta, GA), Jayanth; Nagaraj (Sidney, OH)
Assignee: Copeland Corporation (Sidney, OH)

Appl. No.: 10/270,972

Filed: October 15, 2002

Related U.S. Patent Documents


Application Number	Filing Date	Patent Number	Issue Date
811092	Mar., 2001	6601397

Current U.S. Class: 62/228.3 ; 62/505

Current International Class: F04C 23/00 (20060101); F04C 29/04 (20060101); F25B 49/02 (20060101); F25B 1/04 (20060101); F04C 18/02 (20060101); F25B 5/00 (20060101); F25B 5/02 (20060101)

Field of Search: 62/505,229,181,228.3,164

References Cited [Referenced By]

U.S. Patent Documents


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Primary Examiner: Wayner; William
Attorney, Agent or Firm: Harness, Dickey & Pierce, P.L.C.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No. 09/811,092 filed on Mar. 16, 2001 now U.S. Pat. No. 6,601,397. The disclosure of the above application is incorporated herein by reference.

Claims

What is claimed is:

1. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing; and a vapor injection system for injecting vapor into said compressor at a position intermediate a suction pressure and a discharge pressure, said system controller being coupled to said vapor injection system for controlling injection of said gas.

2. The cooling system according to claim 1, further comprising a temperature sensor for sensing a temperature of gas at said discharge pressure, said system controller being coupled to said temperature sensor for controlling injection of said vapor based on said temperature of said gas at said discharge pressure.

3. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; and a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing.

4. The cooling system according to claim 3, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.

5. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing to maintain a specified temperature in said housing; and a first and a second condenser fan, said controller being coupled to said condenser fans to control said fans based upon a temperature sensed by said temperature sensor, percent duty cycle, and a calculated minimum pressure differential.

6. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a compressor coupled in fluid communication with said evaporator and said condenser, said compressor being a pulse-width modulated variable capacity compressor, wherein said compressor compresses a gas between a suction pressure and a discharge pressure; a temperature sensor disposed in said housing, said temperature sensor operable to read a temperature within said housing; a pressure sensor for sensing said suction pressure; and, a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said housing and said suction pressure to maintain a specified temperature in said housing.

7. The cooling system according to claim 6, wherein said compressor is a scroll compressor.

8. The cooling system according to claim 6, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another.

9. The cooling system according to claim 8, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.

10. The cooling system according to claim 6, wherein said system controller determines an average suction pressure over a specified period of time within each control cycle time.

11. A cooling system comprising: a plurality of housings each having a respective evaporator disposed therein; a condenser coupled in fluid communication with said evaporators; a compressor coupled in fluid communication with said evaporators and said condenser, said compressor being a pulse-width modulated variable capacity compressor; a temperature sensor disposed in at least one of said housings, said temperature sensor operable to read a temperature within said at least one of said housings; and a system controller responsive to said temperature sensor and coupled to said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on said temperature within said at least one of said housings to maintain a specified temperature in said plurality of housings.

12. A cooling system comprising: a plurality of housings, each having an evaporator, an evaporator controller, and a temperature sensor in each of said plurality of housings, each said temperature sensor operable to read a temperature and connected to said evaporator controller in said each of said plurality of housings; a condenser coupled in fluid communication with said evaporators; a compressor coupled in fluid communication with said evaporators and said condenser, said compressor being a pulse-width modulated variable capacity compressor; and a system controller coupled to said evaporator controller and said compressor for providing a variable duty cycle control signal to said compressor, whereby said compressor is modulated between a first capacity state and a second capacity state while operating to thereby adjust the operating capacity of said compressor based on temperature sensor and demand loading state values communicated to said system controller by said evaporator controller.

13. A cooling system comprising: a housing: an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a vapor injection system for injecting vapor into said compressor at a position intermediate a suction pressure and a discharge pressure, said system controller being coupled to said vapor injection system for controlling injection of said gas.

14. The cooling system according to claim 13, further comprising a temperature sensor for sensing a temperature of gas at said discharge pressure, said system controller being coupled to said temperature sensor for controlling injection of said vapor based on said temperature of said gas at said discharge pressure.

15. The cooling system according to claim 13, wherein said compressor is a scroll compressor.

16. The cooling system according to claim 13, wherein said compressor is a scroll compressor.

17. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another; a temperature sensor disposed in said housing and operable to read a temperature within said housing; and a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor.

18. The cooling system according to claim 17, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.

19. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a first and a second condenser fan, said controller being coupled to said condenser fans to control said fans based upon a temperature sensed by said temperature sensor, percent duty cycle, and a calculated minimum pressure differential.

20. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser, wherein said compressor compresses a gas between a suction pressure and a discharge pressure, and said cooling system further comprises a pressure sensor for sensing said suction pressure, said system controller being coupled to said pressure sensor for controlling said capacity of said compressor based on said suction pressure and said temperature within said housing a temperature sensor disposed in said housing and operable to read a temperature within said housing; and a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor.

21. The cooling system according to claim 20, wherein said compressor is a scroll compressor.

22. The cooling system according to claim 20, wherein said compressor has two mechanical elements separated by a seal, said mechanical elements being movable relative to one another to develop fluid pressure and wherein said compressor includes mechanism to selectively break said seal in response to said control signal to thereby alter said fluid pressure developed while allowing said mechanical elements to maintain substantially constant relative movement with one another.

23. The cooling system according to claim 22, wherein said compressor is a scroll compressor and said two mechanical elements are scroll members.

24. The cooling system according to claim 20, wherein said system controller determines an average suction pressure over a specified period of time within each control cycle time.

25. A cooling system comprising: a housing: an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a plurality of housings each having a respective evaporator disposed therein, said temperature sensor being disposed in at least one of said housings.

26. A cooling system comprising: a housing; an evaporator disposed in said housing; a condenser coupled in fluid communication with said evaporator; a pulse-width modulated variable capacity compressor coupled in fluid communication with said evaporator and said condenser; a temperature sensor disposed in said housing and operable to read a temperature within said housing; a system controller including a manual operating mode and an automatic operating mode, said system controller receiving an input from said temperature sensor and providing a variable duty cycle control signal to said compressor; and a plurality of housings, each having an evaporator, an evaporator controller, and a temperature sensor in each of said plurality of housings, each said temperature sensor connected to said evaporator controller in said each of said plurality of housings, each said evaporator controller communicating temperature sensor and demand loading state values to said system controller.

Description

FIELD OF THE INVENTION

The present invention relates generally to a controller for a condensing unit for a refrigeration system or for other cooling systems. More particularly, the present invention relates to a condensing unit employing a variable capacity compressor which is controlled by pulse width modulation using a variable duty cycle signal derived from one or more system sensors. The condensing unit controller is capable of controlling a single evaporator or multiple evaporators of similar or mixed temperatures.

BACKGROUND AND SUMMARY OF THE INVENTION

The present invention is being described associated with a refrigeration system. It is to be understood that the condensing unit of the present invention could be utilized for any other cooling system if desired.

Conventionally, refrigeration systems for refrigeration cases have employed air-cooled or water-cooled condensers fed by a rack of compressors. The compressors are coupled in parallel so that they may be switched on and off in stages to adjust the system cooling capacity to the demands of the load. Typically, the compressors and condensers are located outside of the building on the roof or in a machine room adjacent the area where the refrigeration cases are located.

Within each refrigeration case is an evaporator fed by refrigerant lines from the condensers through which the expanded refrigerant circulates to cool the case. Typically, a closed-loop control system regulates refrigerant flow through the evaporators to maintain the desired case temperatures. Proportional-Integral-Derivative (PID) closed loop control systems are popular for this purpose, with temperature and/or pressure sensors providing the sensed condition inputs.

It is common practice with retail outlets to use separate systems to supply different individual cooling temperature ranges; low temperature (for frozen foods, ice cream, nominally -25/F); medium temperature (for meat, dairy products, nominally +20/F); and high temperature (for floral, produce, nominally +35/to +40/F). The separate low, medium and high temperature systems are each optimized to their respective temperature ranges. Normally, each will employ its own rack of compressors and its own set of refrigerant conduits to and from the compressors, condensers and evaporators.

The conventional arrangement, described above, is very costly to construct and maintain. Much of the cost is associated with the long refrigerant conduit runs. Not only are long conduit runs expensive in terms of hardware and installation costs, but the quantity of refrigerant required to fill the conduits is also a significant cost factor. The longer the conduit run, the more refrigerant required. Adding to these added costs are environmental factors. Eventually fittings leak, allowing the refrigerant to escape to the atmosphere. Invariably, long conduit runs involve more conduit joints that may potentially leak. When a leak does occur, the longer the conduit run, the more refrigerant lost.

One solution to the above described problems is disclosed in Assignee's U.S. Pat. No. 6,047,557, the disclosure of which is incorporated herein by reference. The solution presented in the above patent is a distributed refrigeration system in which the condenser is disposed on the refrigeration case and serviced by a special pulse-width modulated compressor that may be also disposed within the case. If desired, the condenser and compressor can be coupled to service a group of adjacent refrigerant cases, each case having its own evaporator. Further, multiple compressors with at least one pulse-width modulated compressor can be used to handle large evaporator load line-up. Also, the condenser can be disposed in a housing with the evaporator to provide a self-contained package, or can be disposed remotely, as in a split system. The pulse-width modulated compressor is driven by a control system that supplies a variable duty cycle control signal based on measured system load.

While the above described pulse-width modulated compressor and refrigeration system have performed satisfactorily, the continued development of these systems has been directed toward controlling the capacity of the compressor, the condenser and other components within the condensing unit.

Other advantages and objects of the present invention will become apparent to those skilled in the art from the subsequent detailed description, appended claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings which illustrate the best mode presently contemplated for carrying out the present invention:

FIG. 1 is a system block diagram of a prior art refrigeration system configuration;

FIG. 2 is a system block diagram of a condensing unit or cooling system in accordance with the present invention;

FIG. 3 is a cross-sectional view of an embodiment of a pulse-width modulated compressor shown in the loaded state;

FIG. 4 is a cross-sectional view of the compressor of FIG. 3, shown in the unloaded state;

FIG. 5 is a vertical cross-sectional view of the piston assembly shown in FIGS. 3 and 4;

FIG. 6 is a cross-sectional top view of the non-orbiting scroll shown in FIGS. 3 and 4;

FIG. 7 is another embodiment of a condensing unit or cooling system in accordance with the present invention;

FIG. 8 is a schematic view illustrating the controller shown in FIG. 7;

FIG. 9 is a flow diagram for the control system of the present invention;

FIG. 10 is a plan view of the controls for the controller shown in FIGS. 7 and 8;

FIG. 11 is a schematic view illustrating a case controller and system controller in accordance with the present invention; and

FIG. 12 is a system block diagram of a condensing unit or cooling system in accordance with an alternative embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in which like reference numerals designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a conventional refrigeration system that is identified generally by reference numeral 10. Refrigeration system 10 includes a plurality of compressors 12 and a condenser 14 located remote from a plurality of refrigeration cases 16. In this illustration, compressors 12 are configured in a parallel bank located in a machine room or on a roof 18 of a building. Compressors 12 supply condenser 14 that may be air cooled or water cooled. Condenser 14 supplies liquid refrigerant to a receiver 20. Receiver 20, in turn, supplies refrigerant to the individual refrigeration cases 16, which are connected in parallel, as illustrated. In most implementations, a liquid line solenoid valve 22 is used to regulate the flow of refrigerant to the associated evaporator 24. The refrigerant is supplied to evaporator 24 through a suitable expansion device such as expansion valve 26. Expansion valve 26 provides a restricted orifice that causes the liquid refrigerant to atomize into liquid droplets that are introduced into the inlet side of evaporator 24. Evaporator 24, located within refrigerant case 16, extracts heat from case 16 and its contents by vaporization of the liquid droplets into a gas. Compressors 12 extract this gas by suction and compress the gas. The high-temperature compressed gas is then cooled by condenser 14 into the liquid state and returned to receiver 20, whereupon the cycle continues.

To match cooling capacity to the load, compressors 12 may be switched on and off individually or in groups as required. In a typical retail outlet installation, there may be several independent systems, each configured as shown in FIG. 1, to handle different operating temperature ranges. Note that a liquid line 28 and a suction line 30 may each need to be quite lengthy (e.g., up to 150 feet) to span the distance from refrigeration cases 16 to a machine room or roof 18.

FIG. 2 shows a condensing unit or cooling system 40 configured in accordance with the principles of the present invention. Cooling system 40 includes a refrigeration case 42, a compressor 44, a condenser 46, a first expansion valve 48, an economizer 50, a second expansion valve 52 and an evaporator 54. While cooling system 40 is being illustrated in conjunction with refrigeration case 42, it is within the scope of the present invention to use cooling system 40 in conjunction with other cooling devices if desired.

Condenser 46 and compressor 44 are both disposed within case 42 or attached thereto. Evaporator 54 and the associated expansion valves 48 and 52 are likewise disposed within case 42. Condenser 46 includes a heat removal mechanism 56 by which heat is transferred to ambient. Heat removal mechanism 56 can be a water jacket connected to suitable plumbing for carrying waste heat to a water cooling tower located on the building roof or elsewhere exterior to the building. Alternately, heat removal mechanism 56 can be a forced-air cooling system or a passive convection-air cooling system. Cooling system 40 also uses a liquid-line shut off valve 58 for controlling the flow of refrigerant to evaporator 54. Valve 58 communicates with control sensors to supply the refrigerant to evaporator 54 on demand.

FIG. 12 shows an alternative embodiment of a condensing unit or cooling system 240 configured in accordance with the principles of the present invention. Cooling system 240 includes a series of refrigeration cases 242a, 242b and 242c, as well as a group of compressors 244a, 244b, 244c and 244d. The group of compressors 244a-d includes at least one pulse-width modulated compressor 244d. Cooling system 240 is a split system wherein compressors 244a-d are on a roof or in a machine room 18 of a building, while refrigeration cases 242a-c are disposed in a retail area of the building. In machine room 18 along with compressors 244a-d are a condenser 246, a first expansion valve 248, and an economizer 250. Along with the refrigeration cases 242a-c, cooling system 240 includes a second expansion valve 252 and an evaporator 254. While cooling system 240 is illustrated in FIG. 12 in conjunction with refrigeration cases 242a-c, it is within the scope of the present invention to use cooling system 240 in conjunction with other cooling devices it desired.

Condenser 246 includes a heat removal mechanism 256 by which heat is transferred to ambient. Heat removal mechanism 256 can be a water jacket connected to suitable plumbing for carrying waste heat to a water cooling tower located on the building roof or elsewhere exterior to the building. Alternatively, heat removal mechanism 256 can be a forced-air cooling system or a passive convection-air cooling system. Cooling system 240 also uses a liquid-lined shut-off valve 258 for controlling the flow of refrigerant to each evaporator 254. Valve 258 communicates with control sensors to supply the refrigerant to evaporator 254 on demand.

Cooling system 240, like cooling system 40, employs the compressor controller 60 to supply a pulse-width modulated control signal on a capacity signal line 62 to a capacity solenoid valve 64 for compressor 244d. Again, controller 60 adjusts the pulse width of the control signal for valve 64 using an algorithm described below. While only one pulse-width modulated compressor 244d is shown in FIG. 12, more compressors can include a capacity solenoid valve 64 for pulse-width modulation by controller 60. Further, while not shown in FIG. 12, controller 60 may also supply a pulse-width modulated vapor-injection signal on an injection signal line to an injection solenoid valve for any of compressors 244a-d. Controller 60 adjusts the pulse width of the control signal for the injection solenoid valve using an algorithm described below.

Cooling system 40 employs a condensing unit or system controller 60 that supplies a pulse-width modulated control signal on a capacity signal line 62 to a capacity solenoid valve 64 for compressor 44. Controller 60 adjusts the pulse width of the control signal for valve 64 using an algorithm described below. Controller 60 also supplies a pulse-width modulated vapor-injection signal on an injection signal line 66 to an injection solenoid valve 68 for compressor 44. Controller 60 adjusts the pulse width of the control signal for valve 68 using an algorithm described below.

FIGS. 3 and 4 show the details of compressor 44. Scroll compressor 44 comprises an outer shell 70 within which is disposed a driving motor including a stator 72 and a rotor 74, a crankshaft 76 to which rotor 74 is secured, an upper bearing housing 78 and a lower bearing housing 80 for rotatably supporting crankshaft 76 and a compressor assembly 82.

Compressor assembly 82 includes an orbiting scroll member 84 supported on upper bearing housing 78 and drivingly connected to crankshaft 76 via a crankpin 86 and a drive bushing 88. A non-orbiting scroll member 90 is positioned in meshing engagement with orbiting scroll member 84 and is axially movably secured to upper bearing housing 78 by means of a plurality of bolts (not shown) and associated sleeve members (not shown). An Oldham coupling 92 cooperates with scroll members 84 and 90 to prevent relative rotation therebetween. A partition plate 94 is provided adjacent the upper end of shell 70 and serves to divide the interior of shell 70 into a discharge chamber 96 at the upper end thereof and a suction chamber 98 at the lower end thereof.

In operation, as orbiting scroll member 84 orbits with respect to scroll member 90, suction gas is drawn into suction chamber 98 of shell 70 via a suction fitting 100. From suction chamber 98, suction gas is sucked into compressor 82 through an inlet 102 provided in non-orbiting scroll member 90. The intermeshing scroll wraps provided on scroll members 84 and 90 define moving pockets of gas that progressively decrease in size as they move radially inwardly as a result of the orbiting motion of scroll member 84, thus compressing the suction gas entering via inlet 102. The compressed gas is then discharged into discharge chamber 96 via a discharge port 104 provided in non-orbiting scroll member 90 and a passage 106 formed in partition 94. A pressure responsive discharge valve 108 is preferably seated within discharge port 104.

Non-orbiting scroll member 90 is also provided with an annular recess 110 formed in the upper surface thereof. A floating seal 112 is disposed within recess 110 and is biased by intermediate pressurized gas against partition 94 to seal suction chamber 98 from discharge chamber 96. A passage 114 extends through non-orbiting scroll member 90 to supply the intermediate pressurized gas to recess 110.

A capacity control system 120 is shown in association with compressor 44. Control system 120 includes a discharge fitting 122, a piston 124, a shell fitting 126 and solenoid valve 64. Discharge fitting 122 is threadingly received or otherwise secured within discharge port 104. Discharge fitting 122 defines an internal cavity 130 and a plurality of discharge passages 132. Discharge valve 108 is disposed below fitting 122 and below cavity 130. Thus, pressurized gas overcomes the biasing load of discharge valve 108 to open discharge valve 108 and allowing the pressurized gas to flow into cavity 130, through passages 132, and into discharge chamber 96.

Referring now to FIGS. 3, 4 and 5, the assembly of discharge fitting 122 and piston 124 is shown in greater detail. Discharge fitting 122 defines an annular flange 134. Seated against flange 134 is a lip seal 136 and a floating retainer 138. Piston 124 is press fit or otherwise secured to discharge fitting 122 and piston 124 defines an annular flange 140 that sandwiches seal 136 and retainer 138 between flange 140 and flange 134. Discharge fitting 122 defines a passageway 142 and an orifice 144 that extends through discharge fitting 122 to fluidically connect discharge chamber 96 with a pressure chamber 146 defined by discharge fitting 122, piston 124, seal 136, retainer 138 and shell 70. Shell fitting 126 is secured within a bore defined by shell 70 and slidingly receives the assembly of discharge fitting 122, piston 124, seal 136 and retainer 138. Pressure chamber 146 is fluidically connected to solenoid 64 by a tube 148 and with suction fitting 100 and thus suction chamber 98 through a tube 150. The combination of piston 124, seal 136 and floating retainer 138 provides a self-centering sealing system to provide accurate alignment with the internal bore of shell fitting 126. Seal 136 and floating retainer 138 include sufficient radial compliance such that any misalignment between the internal bore of fitting 126 and the internal bore of discharge port 104 within which discharge fitting 122 is secured is accommodated by seal 136 and floating retainer 138.

In order to bias non-orbiting scroll member 90 into sealing engagement with orbiting scroll member 84 for normal full-load operation, solenoid valve 64 is deactivated (or it is activated) by controller 60 to block fluid flow between tube 148 and tube 150. In this position, chamber 146 is in communication with discharge chamber 96 through passageway 142 and orifice 144. The pressurized fluid at discharge pressure within chambers 96 and 146 will act against opposite sides of piston 124, thus allowing for the normal biasing of non-orbiting scroll member 90 towards orbiting scroll member 84 to sealingly engage the axial ends of each scroll member with the respective end plate of the opposite scroll member. The axial sealing of the two scroll members 84 and 90 causes compressor 44 to operate at 100% capacity.

In order to unload compressor 44, solenoid valve 64 will be actuated (or it will be deactuated) by controller 60 to the position shown in FIG. 4. In this position, suction chamber 98 is in direct communication with chamber 146 through suction fitting 100, tube 150, solenoid valve 64 and tube 148. With the discharge pressure pressurized fluid released to suction from chamber 146, the pressure difference on opposite sides of piston 124 will move non-orbiting scroll member 90 upward to separate the axial end of the tips of each scroll member with its respective end plate and the higher pressurized pockets will bleed to the lower pressurized pockets and eventually to suction chamber 98. Orifice 144 is incorporated to control the flow of discharge gas between discharge chamber 96 and chamber 146. Thus, when chamber 146 is connected to the suction side of the compressor, the pressure difference on opposite sides of piston 124 will be created. A wave spring 152 is incorporated to maintain the sealing relationship between floating seal 112 and partition 94 during modulation of non-orbiting scroll member 90. When a gap 154 is created between scrolls 84 and 92, the continued compression of the suction gas will be eliminated. When this unloading occurs, discharge valve 108 will move to its closed position, thereby preventing the backflow of high pressurized fluid from discharge chamber 96 on the downstream refrigeration system. When compression of the suction gas is to be resumed, solenoid valve 64 will be deactuated (or it will be actuated) to again block fluid flow between tubes 148 and 150 allowing chamber 146 to be pressurized by discharge chamber 96 through passageway 142 and orifice 144.

Referring now to FIGS. 3, 4 and 6, a fluid injection system 158 for compressor 44 is shown in greater detail. Compressor 44 includes the capability of having fluid injected into the intermediate pressurized moving chambers at a point intermediate suction chamber 98 and discharge chamber 96. A fluid-injection fitting 160 extends through shell 70 and is fluidically connected to an injection tube 162, which is in turn fluidically connected to an injection fitting 164 secured to non-orbiting scroll member 90. Non-orbiting scroll member 90 defines a pair of radial passages 166, each of which extend between injection fitting 164 and a pair of axial passages 168. Axial passages 168 are open to the moving chambers on opposite sides of non-orbiting scroll member 90 of compressor assembly 82 to inject the fluid into these moving chambers as required by controller 60.

FIG. 2 illustrates vapor injection system 158, which provides the fluid for the fluid injection system of compressor 44. Compressor 44 is shown in a cooling system including condenser 46, first expansion valve or throttle 48, economizer 50, a second expansion valve or throttle 52, an evaporator 54 and a series of piping interconnecting the components as shown in FIG. 2. Compressor 44 is operated by the motor to compress the refrigerant gas. The compressed gas is then liquefied by condenser 46. The economizer 50 can be a flash-tank or heat-exchanger type economizer. As shown, the liquefied refrigerant passes through expansion valve 48 to flash-tank type economizer 50 where it is separated into gas and liquid. The gaseous refrigerant further passes through additional piping to be introduced into compressor 44 through fitting 160. On the other hand, the remaining liquid refrigerant further expands in expansion valve 52, is then vaporized in evaporator 54 and is again taken into compressor 44.

Referring again to FIG. 2, the incorporation of flash-tank economizer 50 and the remainder of the vapor injection system allows the capacity of the compressor 44 to increase above the fixed capacity of compressor 44. Typically, at standard refrigeration conditions, the capacity of the compressor 44 can be increased by approximately 30% to provide a compressor with 130% of its capacity. In order to be able to control the capacity of compressor 44, solenoid valve 68 is positioned between economizer 50 and fitting 160. The increased capacity of compressor 44 can be controlled by controller 60, which operates solenoid valve 68 either in a pulse width injection or continuous injection mode. Solenoid valve 68, when operated in a pulse width modulation mode, in combination with capacity control system 120 of compressor 44 allows the capacity of compressor 44 to be positioned anywhere between 0% and 130% of its fixed capacity to accommodate faster load pull down.

Referring to FIG. 7, a single compressor 44 and condenser 46 can service several distributed refrigeration cases or several distributed cooling units in a heating and cooling (HVAC) system. In FIG. 7, the refrigeration cases or cooling system housings are shown as dashed boxes designated 42a, 42b and 42c. Conveniently, compressor 44 and condenser 46 may be disposed within or attached to one of the refrigeration cases or housings, such as refrigerant case or housing 42a or disposed remotely, such as in a split system as shown in FIG. 12, wherein the compressor 46 and condenser 44 are in a machine room or in a building roof 18. Each refrigeration case or housing has its own evaporator and associated second expansion valve as illustrated at 54(a, b, c) and 52(a, b, c) as well as a liquid line shut off valve 58(a, b, c) and a thermostat 172(a, b, c), which controls a respective liquid line shut off valve 58(a, b, c). In addition, one of the refrigeration cases or housings, typically the lowest temperature case or housing, may have a temperature sensor 174 as illustrated for refrigeration case or housing 42a. When temperature sensor 174 is included, it supplies output information to controller 60 as described below. Finally, a pressure sensor 176 can be included which monitors the pressure of the refrigerant entering suction fitting 100. Pressure sensor 176 supplies this information to controller 60 as described below.

Alternatively, each evaporator 54 can have its own case controller 300 to perform defrost, fan, and electronic expansion valve control based on the case temperature and case outlet pressure, as shown in FIGS. 2, 7 and 11. Referring specifically to FIG. 11, a group of refrigeration cases 42a, 42b, 42c each included a case controller 300a, 300b, 300c, respectively. Temperature sensors 174a, 174b and 174c and pressure sensors 176a, 176b and 176c provide temperature and case outlet pressure measurements to the respective case controllers 300a, 300b and 300c. The case controllers 300a, 300b and 300c are connected via a digital two-way communication path 310 to the system controller 60, whereby temperature and pressure sensor values and case demand loading state (1 or 0) can be provided to system controller 60 by case controllers 300a, 300b and 300c. Further, each case controller 300a, 300b and 300c performs defrost, electronic expansion valve, and fan control locally based on the receive temperature and pressure sensor values.

The multiple case or multiple cooling unit embodiment of FIG. 7 shows how a single compressor 44 can be pulse-width modulated for capacity control and vapor injection by controller 60 to supply the instantaneous demand for cooling. Temperature sensor 174 and/or pressure sensor 176 provide an indication of the load on the system. Controller 60 adjusts the pulse width modulation of both the capacity control system 120 and the vapor injection system to modulate the compressor between its high capacity and low capacity states to meet the instantaneous demand for refrigerant as described below.

Controller 60 is capable of controlling the capacity of compressor 44 by using pulse width modulation of solenoid valve 64. The capacity of compressor 44 can be controlled from 0% to 100% but for this embodiment, the capacity is modulated from 10% to 100% by pulse width modulation operation. In addition, the capacity of compressor 44 can be increased anywhere from 100% to approximately 130% by pulse width modulation of solenoid valve 68, which controls the vapor injection system of the present invention. It is also possible for controller 60 to operate solenoid valve 68 in an on/off manner if desired. The operational characteristics and algorithms incorporated into controller 60 are detailed below.

Controller 60 is capable of controlling either single-evaporator (FIG. 2) or multi-evaporator (FIG. 7) refrigeration systems. The multi-evaporator systems could have evaporators at similar temperatures or at mixed temperatures by employing electronic pressure regulators in the higher temperature evaporators.

Referring now to FIGS. 7 and 8, controller 60 is shown in greater detail. Controller 60 controls an alarm output 200 that will remain on during any alarm condition. Alarm output 200 will reset itself when all alarm conditions are gone.

Controller 60 controls the operation of a first condenser fan 202 and a second condenser fan 204. Cooling system 40 includes two condenser fan motors and fans for condenser 46. Controller 60 controls the operation of the motor for compressor 44 as shown at 206, it controls the operation of vapor injection solenoid valve 68 as shown at 208 and it controls the operation of capacity control solenoid valve 64 as shown at 210.

Various inputs are provided to controller 60. These inputs include control power at 212, an optional suction pressure input from pressure sensor 176 at 214, an optional load case temperature input from temperature sensor 174 at 216, the temperature of refrigerant at the mid-coil or the coil return of condenser 46 from a temperature sensor 218 at 220 and the temperature of the discharge gas of compressor 44 from a temperature sensor 222 at 224. Using the various inputs, controller 60 can control the capacity of compressor 44 based on either case air temperature, compressor suction pressure, or both as detailed below. Controller 60 and the various terminal blocks are housed in an enclosure (not shown) suitable for mounting on cooling system 40.

While not specifically detailed, cooling system 40 also includes a low pressure cutout electromechanical switch to stop compressor 44 at very low suction pressure for vacuum protection; and a high head pressure cutout electromechanical switch to stop compressor 44 at very high discharge pressure, if such protection is required. As detailed above, each evaporator 54(a, b, c) has associated with it their own liquid line solenoid valve 58(a, b, c), their own temperature sensors 172(a, b, c) and their own thermostatic expansion valve 52(a, b, c). None of these valves or sensors are in communication with controller 60. The only communication with controller 60 is through lead case temperature sensor 174 and/or suction pressure sensor 176. Finally, controller 60 is capable of being switched between refrigerants, including, but not limited to, R-404A, R-407C, R-22, R-134a and R-410A as detailed below.

Compressor Capacity Control Algorithms (FIG. 9).

Controller 60 modulates the capacity of compressor 44 through pulse width modulation control of solenoid valve 64 and/or solenoid valve 68. There are two different Proportional-Integral-Derivative control loops. Controller 60 can be set to use suction pressure control using sensor 176, lead case temperature control using sensor 174 or a combination of lead case temperature control with suction control backup using sensors 174 and 176. Each will be described in turn.

Suction Pressure Control: During suction pressure control, compressor 44 will be operated with the loading time adjusted to maintain an average suction pressure at a suction pressure set point 230. Determining the average suction pressure will be done by taking many samples of suction pressure during each load/unload cycle time of compressor 44 and then filtering this suction pressure data using a digital filter 232. The digital filter will produce a useful average pressure for control purposes by removing almost all of the pressure fluctuations caused by the loading and unloading of compressor 44. Preferably, the sampling rate of the digital filter will be inversely proportional to the pulse-width-modulation (PWM) cycle time so that regardless of the PWM cycle time selected, the digital filter will operate with twenty samples during each PWM cycle. The filtering thus achieved will have appropriate timing to match the PWM cycle time selected. Control of the suction pressure is by PID algorithm. The suction pressure set point is settable at controller 60 as described below. The signal from suction pressure sensor 176 is first routed through the digital filter and then to the suction pressure PID algorithm. If suction pressure control is chosen, then the lead case temperatur