Compressor capacity modulation

Abstract

A pulsed modulated capacity modulation system for refrigeration, air conditioning or other types of compressors is disclosed in which suitable valving is provided which operates to cyclically block flow of suction gas to a compressor. A control system is provided which is adapted to control both the frequency of cycling as well as the relative duration of the on and off time periods of each cycle in accordance with sensed system operating conditions so as to maximize the efficiency of the system. Preferably the cycle time will be substantially less than the time constant of the load and will enable substantially continuously variable capacity modulation from substantially zero capacity to the full capacity of the compressor. Additional controls may be incorporated to modify one or more of the motor operating parameters to improve the efficiency of the motor during periods of reduced load.

Description

(shown in FIG. 6) to compress fluid drawn into cylinder 74 through inlet passage 80. Inlet passage 80 is connected to suction fitting 82 provided in shell 56 to provide a supply of suction gas to compressor 54. As thus far described, rotary compressor 54 is typical of rotary type refrigeration and air conditioning compressors.

In order to incorporate the pulse width capacity modulation system of the present invention into rotary compressor 54, a valve assembly 84 is provided being disposed within shell 56 and between suction fitting 82 and suction gas flow path inlet passage 80. Operation of valve assembly 84 is controlled by a control module 86 which receives signals from one or more sensors 88 indicative of the system operating conditions.

Operation of valve assembly 84, control module 86 and sensors 88 will be substantially identical to that described above with valve assembly 84 operating under the control of control module 86 to cyclically open and close to thereby modulate the flow of suction gas into cylinder 74. As with compressor 10, both the cycle frequency as well as the relative duration of the open and closed portions of the cycle may be varied by control module 86 in response to system operating conditions whereby the system efficiency may be maximized and the capacity varied to any desired capacity between zero and full load.

FIG. 7 shows a scroll type compressor 144 which includes a compressor assembly 146 and a driving motor 148 both disposed within hermetic shell 150.

Compressor assembly 146 includes a mean hearing housing 152 secured within and supported by outer shell 150, an orbiting scroll member 154 movably supported on bearing housing 152 and a nonorbiting scroll member 156 axially movably secured to bearing housing 152. Scroll members 154 and 156 each include end plates 158 and 160 from which interleaved spiral wraps 162 and 164 extend outwardly. Spiral wraps 162 and 164 together with end plates 158 and 160 cooperate to define moving fluid pockets 166, 168 which decrease in size as they move from a radially outer position to a radially inner position in response to relative orbital movement between scroll members 154 and 156. Fluid compressed within the moving fluid pockets 166, 168 is discharged through a centrally located discharge passage 170 provided in nonorbiting scroll member 156 into a discharge chamber 172 defined by the upper portion of hermetic shell 150 and muffler plate 174 and thereafter is supplied to the system via discharge fitting 176. An Oldham coupling is also provided acting between scroll members 154 and 156 to prevent relative rotation therebetween.

A drive shaft 180 is also provided being rotatably supported in bearing housing 152 and having one end thereof drivingly coupled to orbiting scroll member 154. A motor rotor 182 is secured to drive shaft 180 and cooperates with motor stator 184 to rotatably drive drive shaft 180. As thus far described, scroll compressor 144 is typical of scroll type compressors and will operate to draw fluid to be compressed flowing into hermetic shell 150 via inlet 186 into the moving fluid pockets via suction inlet 188 provided in nonorbiting scroll member 156, compress same and discharge the compressed fluid into discharge chamber 172.

In order to incorporate the pulse width capacity modulation system into scroll compressor 144, a valve assembly 190 is provided being positioned in overlying relationship to suction inlet 188 so as to be able to selectively control flow of fluid to be compressed into respective moving fluid pockets 166 and 168. Operation of valve assembly 190 is controlled by control module 192 in response to signals received from one or more sensors 194 in substantially the same manner as described above. It should be noted that while the present invention has been shown and described with reference to a scroll compressor in which the hermetic shell is substantially at suction pressure, it may also be easily incorporated in other types of scroll compressors such as those in which the interior is at discharge pressure or in which both scrolls rotate about radially offset axes.

As may now be appreciated, the pulsed capacity modulation system of the present invention is extremely well suited for a wide variety of compressors and is extremely effective in providing a full range of modulation at relatively low costs. It should be noted that if desired the pulsed capacity modulation system of the present invention may also be combined with any of the other known types of capacity modulation systems for a particular application.

In the above embodiments, it is intended that the compressor continue to be driven while in an unloaded condition. Obviously, the power required to drive the compressor when unloaded (no compression taking place) is considerably less than that required when the compressor is fully loaded. Accordingly, it may be desirable to provide additional control means operative to improve motor efficiency during these periods of reduced load operation.

Such an embodiment is shown schematically in FIG. 8 which comprises a motor compressor 90 which may be of the type described above with respect to FIG. 1, FIGS. 5 and 6, or FIG. 7 and includes a solenoid valve assembly connected to a suction line which is operative to selectively block the flow of suction gas to the compressing mechanism. The solenoid valve assembly is intended to be controlled by a control module 92 in response to system conditions sensed by sensors 94. As thus far described, the system represents a schematic illustration of any of the embodiments described above. In order to improve efficiency of the driving motor during reduced load operation, a motor control module 96 is also provided which is connected to the compressor motor circuit via line 98 and to control module 92 via line 100. It is contemplated that motor control module 96 will operate in response to a signal from control module 92 indicating that the compressor is being placed in reduced load operating condition. In response to this signal, motor control module 96 will operate to vary one or more of the compressor motor operating parameters to thereby improve its efficiency during the period of reduced load. Such operating parameters are intended to include any variably controllable factors which affect motor operating efficiency including voltage reduction or varying the running capacitance used for the auxiliary winding of a single phase motor. Once control module 92 signals motor control module 96 that the compressor is being returned to fully loaded operation, motor control module 96 will then operate to restore the affected operating parameters to maximize motor efficiency under full load operation. There may be some time lag between the closing of the solenoid valve assembly and the reduced loading on the compressor which will be primarily dependent upon the volume of suction gas in the area between the solenoid valve assembly and the compression chamber. As a result, it may be desirable to provide for an appropriate time delay before the motor operating parameter is adjusted for the reduced loading. Of course, it is desirable that the solenoid valve assembly be positioned as close as possible to the compression chamber so as to minimize this delayed reaction time.

It should also be noted that while each of the embodiments has been described as incorporating a solenoid valve which operates to control the flow of pressurized discharge gas to the suction gas flow control valve for controlling suction gas flow, it is also possible to substitute other types of valves therefor such as, for example, solenoid valves by themselves or any other suitable valving arrangement. It is, however, believed that the use of a solenoid valve for controlling the flow of a pressurized fluid such as discharge gas to the suction control valve is preferred because it allows for application of greater actuating forces to the suction gas control valve and hence faster operation thereof. An exemplary embodiment of such a valve assembly is shown and will be described with reference to FIG. 9 it being noted that this valve assembly may be used in any of the embodiments described above.

As shown in FIG. 9, valve assembly 102 comprises a solenoid control valve 106 and a pressure actuated valve 104.

Solenoid valve assembly control valve 106 includes a housing 108 within which is provided a valve chamber 110 having a valve member 112 movably disposed therein. A pressurized fluid supply line 114 opens into chamber 110 adjacent one end thereof and a vent passage 116 opens outwardly from chamber 110 adjacent the opposite end thereof. An outlet passage 118 is also provided opening into chamber 110 approximately midway between the opposite ends thereof. Valve member 112 is secured to one end of plunger 120 the other end of which extends axially movably along hermetically sealed bore 121 about which a solenoid coil 122 is positioned. As shown, plunger 120 will be biased into the position shown in which valve member 112 overlies and closes off pressurized fluid supply line 114 and outlet passage 118 is in open communication with vent passage 116. When solenoid coil 122 is energized, shaft plunger 120 will operate to move valve member 112 into a position in which it overlies and closes off vent passage 116 and allows open communication between pressurized fluid supply line 114 and outlet 118. The opposite end of pressurized fluid supply line 114 will be connected to a suitable source of pressurized fluid such as for example discharge gas from the compressor.

Pressure actuated valve assembly 104 includes a housing 124 having a cylinder 126 provided therein within which piston 128 is movably disposed. A shaft 130 has one end connected to piston 128 and extends from cylinder 126 through bore 132 into a chamber 134 provided in housing 124. A valve member 136 is secured to the end of shaft 130, is positioned within chamber 134 and is movable by shaft 130 into and out of sealing engagement with valve seat 138 provided on partition 140 so as to selectively control flow of suction gas from chamber 134 into chamber 142 and then through outlet 144 outlet 145. An inlet 146 inlet 147 is provided for supplying suction gas to chamber 134.

Fluid outlet line 118 opens into one end of cylinder 126 and serves to provide pressurized fluid thereto to bias piston 128 in a direction such that valve 136 moves into sealing engagement with valve seat 138 to thereby interrupt the flow of suction gas from inlet 146 to outlet 144 inlet 147 to outlet 145. A return spring 148 return spring 149 is also provided within cylinder 126 which serves to bias piston 128 in a direction so as to move valve member 136 out of sealing engagement with valve seat 138 in response to venting of the pressurized fluid from cylinder 126.

In operation, when control module 50 determines that capacity modulation is in order, it will operate to energize solenoid control valve 106 thereby moving valve 112 to the right as shown and allowing pressurized fluid to flow through chamber 110 to cylinder 126. This pressurized fluid then operates to move piston 128 in a direction to close valve 136 thereby preventing further flow of suction gas to the compression mechanism. When solenoid control valve 106 is deenergized by control module 50, valve 112 will move into a position to interrupt the supply of pressurized fluid to cylinder 126 and to vent same via passage 116 thereby enabling return spring 148 return spring 149 to move piston 128 in a direction to open valve member 136 such that the flow of suction gas to the compressor is resumed.

It should be noted that valve assembly 102 is exemplary only and any other suitable arrangement may be easily substituted therefor. As noted before, in order to facilitate rapid response to capacity modulation signals, it is desirable that the suction flow shut off valve be located as close to the compression chamber as possible. Similarly, the pressurized fluid supply line and vent passages should be sized relative to the volume of the actuating cylinder being supplied thereby to ensure rapid pressurization and venting of same.

It will be appreciated by those skilled in the art that various changes and modifications may be made to the embodiments discussed in this specification without departing from the spirit and scope of the invention as defined by the appended claims.

Claims

1. A capacity modulated compressor comprising:

a compression mechanism having a compression chamber therein, a suction inlet for supplying suction gas to the compression chamber and a movable member operative to vary the volume of said compression chamber;

a power source operatively connected to effect movement of said movable member to thereby compress gas drawn into said compression chamber through said suction inlet;

a valve provided in the suction gas flow path to said compression mechanism, said valve being operable between open and closed positions to cyclically allow and prevent flow of suction gas into said compression chamber; and

control apparatus for actuating said valve between said open and closed positions, said control apparatus being operative to cycle said valve such that its cycle time is substantially smaller than the time constant of the load on said compressor.

2. A capacity modulated compressor as set forth in claim 1 wherein said valve is positioned in close proximity to said compression chamber.

3. A capacity modulated compressor as set forth in claim 1 wherein said valve is a bidirectional valve.

4. A capacity modulated compressor as set forth in claim 1 wherein at least one of said cycle time and the time duration said valve is in said closed position is varied in response to sensed operating conditions.

5. A capacity modulated compressor as set forth in claim 4 wherein said power source continues to effect movement of said movable member as said valve is cycled between said open and closed positions.

6. A capacity modulated compressor as set forth in claim 4 wherein said cycle time and said time duration are varied in response to said sensed operating condition.

7. A capacity modulated compressor as set forth in claim 1 wherein said valve is actuated by pressurized fluid.

8. A capacity modulated compressor as set forth in claim 7 further comprising a control valve operative to control the flow of pressurized fluid to said valve.

9. A capacity modulated compressor as set forth in claim 8 wherein said control valve is a solenoid actuated valve.

10. A capacity modulated compressor as set forth in claim 7 wherein said pressurized fluid is supplied from said compression mechanism.

11. A capacity modulated compressor as set forth in claim 1 wherein said power source comprises an electric motor.

12. A capacity modulated compressor as set forth in claim 11 wherein said control module operates to vary an operating parameter of said electric motor when said valve is in said closed position so as to thereby improve the operating efficiency of said motor.

13. A capacity modulated compressor as set forth in claim 12 wherein said operating parameter of said motor is varied a predetermined time period after said valve is moved to said closed position.

14. A capacity modulated compressor as set forth in claim 1 wherein said compression mechanism is a reciprocating piston compressor.

15. A capacity modulated compressor as set forth in claim 14 wherein said reciprocating piston compressor includes a plurality of pistons and cylinders, said valve being operative to prevent flow of suction gas to all of said cylinders.

16. A capacity modulated compressor as set forth in claim 15 wherein said valve operates to prevent flow of suction gas to all of said cylinders simultaneously.

17. A capacity modulated compressor comprising:

a hermetic shell;

a compression mechanism disposed within said shell, said compression mechanism including a compression chamber defined in part by a moveable member, said moveable member operating to vary the volume thereof;

a drive shaft rotatably supported within said shell and drivingly coupled to said movable member;

a suction inlet passage for supplying suction gas to said compression chamber from a source remote from said shell;

a valve within said suction inlet passage, said valve being actuable between an open position to allow flow of suction gas through said inlet passage and a closed position to substantially prevent flow of suction gas through said inlet passage;

a controller for cyclically actuating said valve to an open position for first predetermined time periods and to a closed position for second predetermined time periods, the ratio of said first predetermined time period to the sum of said first and second predetermined time periods being less than a given load time constant and determining the percentage modulation of the capacity of said compressor.

18. A capacity modulated compressor as set forth in claim 17 wherein said valve is a bidirectional valve and is actuable to said closed position by pressurized fluid.

19. A capacity modulated compressor as set forth in claim 18 further comprising a solenoid valve actuable by said controller to control flow of said pressurized fluid to said valve.

20. A capacity modulated compressor as set forth in claim 19 wherein said pressurized fluid is discharge gas from said compressor.

21. A capacity modulated compressor as set forth in claim 17 wherein said valve is positioned in close proximity to said compression chamber.

22. A capacity modulated compressor as set forth in claim 17 wherein said compressor is a refrigeration compressor.

23. A capacity modulated compressor as set forth in claim 17 wherein said compressor is an air compressor.

24. A capacity modulated compressor as set forth in claim 17 wherein said compressor is a rotary compressor.

25. A capacity modulated compressor as set forth in claim 17 wherein said compressor is a scroll compressor.

26. A capacity modulated compressor as set forth in claim 17 wherein said sum of said first and second time periods is less than one half of said load time constant.

27. A capacity modulated compressor as set forth in claim 17 further comprising a motor for rotatably driving said drive shaft, said valve being actuable between said open and closed positions while said motor continues to rotatably drive said drive shaft.

28. A capacity modulated compressor as set forth in claim 27 wherein said controller operates to vary an operating parameter of said motor between periods in which said valve is in said closed position and in said open position to thereby improve the operating efficiency of said motor.

29. A method of modulating the capacity of a compressor forming a part of a cooling system to accommodate varying cooling load conditions comprising:

sensing an operating parameter of said cooling system, said parameter being indicative of the system load;

determining a cycle frequency of a maximum duration which will minimize variation in the suction pressure of refrigerant being supplied to said compressor;

determining a first time period during which suction gas will be supplied to said compressor and determining a second time period during which suction gas will be prevented from flowing to said compressor, said first and second time periods being equal to said cycle frequency; and

pulsing a valve between open and closed positions for said first and second time periods respectively to thereby modulate the capacity of said compressor in response to said system operating parameter.

30. A capacity modulated compressor comprising:

a compression mechanism having a compression chamber therein, a suction inlet for supplying suction gas to the compression chamber and a movable member operative to vary the volume of said compression chamber;

a power source operatively connected to effect movement of said movable member to thereby compress gas drawn into said compression chamber through said suction inlet;

a valve provided in the suction gas flow path to said compression mechanism and actuated by pressurized fluid, said valve being operable between open and closed positions to cyclically allow and prevent flow of suction gas into said compression chamber; and

control apparatus for actuating said valve between said open and closed positions, said control apparatus being operative to cycle said valve such that its cycle time is substantially smaller than the time constant of the load on said compressor.

31. A capacity modulated compressor as set forth in claim 30 further comprising a control valve operative to control the flow of pressurized fluid to said valve.

32. A capacity modulated compressor as set forth in claim 31 wherein said control valve is a solenoid actuated valve.

33. A capacity modulated compressor as set forth in claim 30 wherein said pressurized fluid is supplied from said compression mechanism.

34. A capacity modulated compressor comprising:

a compression mechanism having a compression chamber therein, a suction inlet for supplying suction gas to the compression chamber and a movable member operative to vary the volume of said compression chamber;

an electric motor operatively connected to effect movement of said movable member to thereby compress gas drawn into said compression chamber through said suction inlet;

a valve provided in the suction gas flow path to said compression mechanism, said valve being operable between open and closed positions to cyclically allow and prevent flow of suction gas into said compression chamber; and

a control apparatus for actuating said valve between said open and closed positions, said control apparatus being operative to cycle said valve such that its cycle time is substantially smaller than the time constant of the load on said compressor and operable to vary an operating parameter of said electric motor when said valve is in said closed position so as to thereby improve the operating efficiency of said motor.

35. A capacity modulated compressor as set forth in claim 34 wherein said operating parameter of said motor is varied a predetermined time period after said valve is moved to said closed position.

36. A capacity modulated compressor comprising:

a hermetic shell;

a compression mechanism disposed within said shell, said compression mechanism including a compression chamber defined in part by a movable member, said movable member operating to vary the volume thereof;

a drive shaft rotatably supported within said shell and drivingly coupled to said movable member;

a suction inlet passage for supplying suction gas to said compression chamber from a source remote from said shell;

a valve within said suction inlet passage, said valve being actuable between an open position to allow flow of suction gas through said inlet passage and a closed position to substantially prevent flow of suction gas through said inlet passage, said valve being a bidirectional valve actuable to said closed position by pressurized fluid; and

a controller for cyclically actuating said valve to an open position for first predetermined time periods and to a closed position for second predetermined time periods, the ratio of said first predetermined time period to the sum of said first and second predetermined time periods being less than a given load time constant, determining the percentage modulation of the capacity of said compressor.

37. A capacity modulated compressor as set forth in claim 36 further comprising a solenoid valve actuable by said controller to control flow of said pressurized fluid to said valve.

38. A capacity modulated compressor as set forth in claim 37 wherein said pressurized fluid is discharge gas from said compressor.

39. A capacity modulated compressor comprising:

a hermetic shell;

a compression mechanism disposed within said shell, said compression mechanism including a compression chamber defined in part by a movable member, said movable member operating to vary the volume thereof;

a drive shaft rotatably supported within said shell and drivingly coupled to said movable member;

a suction inlet passage for supplying suction gas to said compression chamber from a source remote from said shell;

a valve within said suction inlet passage, said valve being actuable between an open position to allow flow of suction gas through said inlet passage and a closed position to substantially prevent flow of suction gas through said inlet passage;

a controller for cyclically actuating said valve to an open position for first predetermined time periods and to a closed position for second predetermined time periods, the ratio of said first predetermined time period to the sum of said first and second predetermined time periods being less than a given load time constant, determining the percentage modulation of the capacity of said compressor; and

a motor for rotatably driving said drive shaft, said valve being actuable between said open and closed positions while said motor continues to rotatably drive said drive shaft;

wherein said controller operates to vary an operating parameter of said motor between periods in which said valve is in said closed position and in said open position to thereby improve the operating efficiency of said motor.

40. A method of modulating the capacity of a compressor forming a part of a cooling system to accommodate varying cooling load conditions comprising:

sensing an operating parameter of said cooling system, said parameter being indicative of the system load;

determining a cycle frequency of a maximum duration which will minimize variation in the suction pressure of refrigerant being supplied to said compressor;

determining a first time period during which suction gas will be supplied to said compressor and determining a second time period during which suction gas will be prevented from flowing to said compressor, said first and second time periods being equal to said cycle frequency; and

pulsing a valve between open and closed positions for said first and second time periods respectively to thereby modulate the capacity of said compressor in response to said system operating parameter.