Refrigeration and air conditioning systems are commonly configured with means for system capacity control, thereby allowing the systems to improve temperature control accuracy, reliability, and energy efficiency.
Currently the most common means of refrigerant system capacity control is accomplished by unit cycling (turning the compressor on and off in response to fluctuations in temperature or system pressure). However, unit cycling does not allow for tight temperature control, and therefore, commonly creates discomfort and/or undesired temperature variations in the conditioned/refrigerated space.
A suction modulation valve located on a suction line downstream of the compressor is another means commonly utilized for system capacity control. However, suction modulation valves are expensive and are inefficient for system capacity control.
A hot gas bypass unloader valve integral to the compressor can be used to control compressor capacity, and hence, refrigeration and air conditioning system capacity. The bypass unloader valve operates to re-circulate refrigerant vapor from the discharge plenum back to the suction plenum. Thus, there is no compression generated flow of refrigerant out of the cylinder when the bypass unloader valve is actuated. Unfortunately, bypass unloader valves only control compressor (and system) capacity in distinct increments or modes. For example, in a four cylinder compressor with two pairs of cylinders, a fifty percent capacity reduction is achieved by actuating the bypass unloader valve adjacent one of the two pairs of cylinders. However, a capacity reduction of, for example, twenty five percent could not be achieved in the four cylinder compressor with the bypass unloader valve. Thus, optimal control of compressor capacity, and hence, the refrigerated or air conditioned environment cannot be achieved with current bypass unloader valve technology.
A reciprocating compressor includes a cylinder block, a cylinder head, and a bypass unloader valve assembly. The cylinder block has a cylinder disposed therein. The cylinder head is secured to the cylinder block overlying the cylinder and has a suction plenum and a discharge plenum in selective fluid communication with the cylinder. The bypass unloader valve assembly is in operable communication with the cylinder head and is responsive to control signals to rapid cycle to allow for fluid communication of a refrigerant between the discharge plenum and the suction plenum.
The reciprocating compressor 10 has bypass unloader valve assemblies 14 which interconnect with the cylinder heads 16. The housing 18 of the compressor 10 has an upper portion of which forms the cylinder block 20. The cylinder block 20 is divided into one or more cylinder banks 22, as the compressor 10 is illustrated as a multi-cylinder compressor. The cylinder block 20 defines cylinders 23 which extend therethrough to adjacent the cylinder head 16. Each cylinder head 16 is secured to the cylinder block 20 and overlays the cylinders 23 in each cylinder bank 22. Each cylinder bank 22 has at least one cylinder 23 and may include multiple cylinders 23 as illustrated in
The pistons 24 are disposed in the cylinders 23 and are reciprocally movable therein. The pistons 24 interconnect with the connecting rods 26 which extend internally within the compressor 10 to interconnect with an eccentric portion of the crankshaft 28. The crankshaft 28 is rotatably disposed internally in the compressor 10 and extends through the oil sump 29. The suction manifold 30 and discharge manifold 32 are defined by the cylinder block 20. The check valve 34 extends from the cylinder block 20 into the discharge manifold 32.
Each of the cylinder heads 16 define a suction plenum 36 and discharge plenum 38 which selectively communicate with one another by virtue of actuation of the bypass unloader valve assembly 14. The suction manifold 30 communicates with the oil sump 29 or directly with a suction line (not shown). The suction manifold 30 extends to the cylinder heads 16 to fluidly communicate with the suction plenum 36. The discharge manifold 32 selectively fluidly communicates with the discharge plenum 38 through ports adjacent the check valves 34. The discharge manifold 32 also selectively fluidly communicates with the suction plenum 36 by virtue of actuation of the bypass unloader valve assembly 14.
In one embodiment, when the compressor 10 is in a loaded mode of operation, i.e. the bypass unloader valve assemblies 14 are deactivated and are not cycling, a low pressure refrigerant enters the compressor 10 from the suction line (not shown) through an inlet port (not shown). The reciprocating movement of the pistons 24 within the cylinders 23 draws the refrigerant from the suction line (not shown) through the oil sump 29. The refrigerant is drawn into the suction manifold 30 formed by the cylinder block 28 and into the suction plenum 36 in the cylinder head 16. From the suction plenum 36 the refrigerant passes into the cylinders 23 where it is compressed by the pistons 24. Reed valves (not shown) are positioned above the cylinders 23 to control the flow of refrigerant thereto. After leaving the cylinders 23, the high pressure vapor refrigerant is discharged through the reed valves (not shown) into the discharge plenum 38. In the loaded mode, the discharge pressure of the refrigerant forces open the check valves 34 to permit the passage of the refrigerant to the discharge manifold 32. From the discharge manifold 32 the high pressure vapor refrigerant passes through an outlet port (not shown) to other components of the heating or cooling system.
When the compressor 10 is in an unloaded mode of operation, i.e. the bypass unloader valve assemblies 14 are fully activated or deactivated and are not cycling, the compressor 10 operates as described above up until the point at which the refrigerant is discharged from the cylinders 23 into the discharge plenum 38. Because the bypass unloader valve assemblies 14 are activated, a portion of the bypass unloader valve assemblies 14 is drawn back allowing the discharge plenum 38 to communicate directly with the suction plenum 36. Thus, the refrigerant passes to the suction plenum 36 from the discharge plenum 38 because of the pressure differential therebetween, and a pressure sufficient to open the check valves 34 does not develop. Additionally, when the bypass unloader valve assemblies 14 are activated a second portion of the valve assemblies 14 is withdrawn from a blocking arrangement allowing the discharge manifold 32 to fluidly communicate with the suction plenum 36. Thus, the refrigerant passes to the suction plenum 36 from the discharge manifold 32 because of the pressure differential therebetween, and substantially no high pressure vapor refrigerant passes through an outlet port (not shown) to other components of the heating or cooling system.
As will be discussed in greater detail subsequently, one or all of the bypass unloader valve assemblies 14 can be operated in rapid cycle (for example by pulse width modulation) to provide for a continuously variable capacity (partial load mode) between the capacity achieved by the compressor 10 when the bypass unloader valve assemblies 14 are in the unloaded position, and the capacity achieved by the compressor 10 when the bypass unloader valve assemblies 14 are in the loaded position. The bypass unloader valve assemblies 14 achieve the partial load mode by cycling each or all of the bypass unloader valve assemblies 14 between the loaded position and the unloaded position with a period that is between 1 cycle/second and 1 cycle/180 seconds. This cycle period is short enough to account for the inertia of the reaction of the refrigeration or air conditioning system. Thus, only small temperature fluctuations occur in the evaporator (not shown), these temperature fluctuations do not impair precise regulation of unit being refrigerated or conditioned.
While the compressor 10 is shown as a four cylinder single stage compressor having two cylinder banks 22 of paired cylinders 23, it is understood that additional cylinder banks or cylinders may be provided. Some or all of the cylinders in the cylinder banks 22 may be provided with bypass unloader valve assemblies 14. Alternatively, the compressor 10 can be a multi-stage compressor having dedicated staged cylinder banks or staged cylinders with the banks or cylinders provided with bypass unloader valve assemblies 14.
In
Bypass port 52 extends through the valve plate 40 and communicates with the channel 58 which extends through the casing of the cylinder head 16 and stator casing portion of the bypass unloader valve assembly 14 to connect to the high pressure chamber 60 through a bleed orifice (not shown do to the cross sectional view selected in
In
The channel 58 extends from the discharge manifold 32 (through bypass port 52) to the high pressure chamber 60 to allow refrigerant to communicate therewith. In the loaded position illustrated in
In the unloaded position illustrated in
As discussed previously, the bypass unloader valve assemblies 14 can be operated in a rapid cycle to provide a continuously variable capacity (partial load mode) between the capacity achieved by the compressor 10 when the bypass unloader valve assembly 14 is in the unloaded mode, and the capacity achieved by the compressor 10 when the bypass unloader valve assembly 14 is in the loaded position. More specifically, the solenoid 64 can be activated by the controller 12 to operate in a rapid cycle and provide for a continuously variable capacity by blocking and unblocking the channel 58A in rapid fashion to allow/disallow communication between the discharge manifold 32 and the suction plenum 36 (and to cause valve piston 66 to move and block/unblock opening 74 between the discharge plenum 38 and the suction plenum 36). The solenoid 64 can cycle between the loaded position of
Pulse width modulation of the solenoid 64 of the bypass unloader valve assembly 14 allows for greater compressor 10 capacity control, thereby allowing the bypass unloader valve assembly 14 to rapid cycle and dial in on a desired compressor 10 capacity. Greater compressor 10 capacity control allows the refrigeration or air conditioning system to achieve improved temperature control accuracy, reliability, and energy efficiency.
While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2010/035896 | 5/24/2010 | WO | 00 | 1/5/2012 |
Publishing Document | Publishing Date | Country | Kind |
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WO2011/005367 | 1/13/2011 | WO | A |
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