Constant evaporator pressure slide valve modulator for screw compressor refrigeration system
First Claim
1. In a closed loop refrigeration system for conditioning a space, said system comprising a positive displacement compressor, a condenser, and an evaporator, conduit means carrying a condensible refrigerant working fluid and connecting said compressor, condenser and evaporator in closed loop series and including expansion means upstream of said evaporator, said compressor including a shiftable slide valve for movement between a first position to effect full unloading of the compressor and a second position to effect full loading of the compressor, and vice versa, a fluid motor for shifting said slide valve between said first and second positions, said fluid motor comprising a movable member operatively coupled to said slide valve, means defining with said movable member a first sealed chamber remote from said slide valve and a second sealed chamber proximate to said slide valve on respective sides of said movable member, means for subjecting said second chamber to compressor discharge pressure;
- the improvement comprising;
restricted passage means connecting said first chamber to said second chamber such that said first chamber tends to be at discharge pressure with zero pressure differential across said movable member,means normally venting said first chamber to compressor suction pressure, thereby overriding said restricted passage means, andmeans for selectively activating the venting of said first chamber to compressor suction pressure in response to fall of suction pressure below a predetermined value, thereby preventing a serious reduction in evaporator temperature caused by either a reduction in load on the evaporator, an increase in speed of the compressor or both.
5 Assignments
0 Petitions
Accused Products
Abstract
A space conditioning closed loop refrigeration system, particularly a vehicle air conditioning system utilizing a positive displacement compressor having a slide valve for varying the capacity and shiftable between full load and full unload positions and vice versa and driven therebetween by a linear fluid motor having a movable member coupled to the slide valve and forming a first chamber which is normally dumped via a slide valve modulator to compressor suction pressure and a second chamber open to compressor discharge pressure. A restricted passage between chambers tends to cause the first chamber to reach compressor discharge pressure absent that chamber dumping to suction. The slide valve modulator selectively activates the venting of the first chamber to compressor suction pressure in response to fall of suction pressure below a predetermined value to prevent a serious reduction in evaporator temperature caused by either a reduction in load on the evaporator, an increase in speed of the compressor, or both. A temperature unloader in the form of a normally closed valve is connected within a bypass passage by passing the slide valve modulator to insure dumping of the first chamber to suction in response to a predetermined drop in temperature of the space to be conditioned, irrespective of the level of compressor suction pressure.
81 Citations
9 Claims
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1. In a closed loop refrigeration system for conditioning a space, said system comprising a positive displacement compressor, a condenser, and an evaporator, conduit means carrying a condensible refrigerant working fluid and connecting said compressor, condenser and evaporator in closed loop series and including expansion means upstream of said evaporator, said compressor including a shiftable slide valve for movement between a first position to effect full unloading of the compressor and a second position to effect full loading of the compressor, and vice versa, a fluid motor for shifting said slide valve between said first and second positions, said fluid motor comprising a movable member operatively coupled to said slide valve, means defining with said movable member a first sealed chamber remote from said slide valve and a second sealed chamber proximate to said slide valve on respective sides of said movable member, means for subjecting said second chamber to compressor discharge pressure;
- the improvement comprising;
restricted passage means connecting said first chamber to said second chamber such that said first chamber tends to be at discharge pressure with zero pressure differential across said movable member, means normally venting said first chamber to compressor suction pressure, thereby overriding said restricted passage means, and means for selectively activating the venting of said first chamber to compressor suction pressure in response to fall of suction pressure below a predetermined value, thereby preventing a serious reduction in evaporator temperature caused by either a reduction in load on the evaporator, an increase in speed of the compressor or both. - View Dependent Claims (2, 3, 4, 5, 6, 7)
- the improvement comprising;
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8. A climate control system for controlling the temperature of air in a controlled area, said system including a compressor operable over a varying load level, said system being capable of at least a cooling mode, wherein said compressor is activated to reduce said air temperature said control system comprising:
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temperature sensing means for monitoring said air temperature, further sensing means for sensing at least one operating parameter of said climate control system other than said air temperature, said climate control system including an evaporator coupled to said compressor and over which said air is passed to remove heat from said air while evaporating a working fluid, said further sensing means comprising means for sensing the compressor suction pressure of the working fluid returned from said evaporator to said compressor and said system further comprising means responsive to said means for sensing said compressor suction pressure for maintaining constant the pressure of said working fluid at said evaporator, means responsive to said air temperature sensing means for overriding said further sensing means and for effecting full unload operation of said compressor, irrespective of the compressor suction pressure, and means responsive to said air temperature for turning on and off said compressor.
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9. A control system for controlling the temperature of air in a controlled area, said system including a compressor operable over a varying load level, said system being capable of at least a cooling mode, wherein said compressor is activated to reduce said air temperature said control system comprising:
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temperature sensing means for monitoring said air temperature, further sensing means for sensing at least one operating parameter of said climate control system other than said air temperature, said climate control system including an evaporator coupled to said compressor and over which said air is passed to remove heat from said air while evaporating a working fluid, said further sensing means comprising means for sensing the compressor suction pressure of the working fluid returned from said evaporator to said compressor and said system further comprising means responsive to said means for sensing said compressor suction pressure for maintaining constant the pressure of said working fluid at said evaporator, and means responsive to said temperature sensing means for monitoring said air temperature for overriding said further sensing means and for effecting full unload operation of said compressor, irrespective of the compressor suction pressure.
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Specification