Patent Grant
7374406
The present invention relates generally to multi-capacity compressors having disengageable eccentric structures. More specifically, the present invention relates to a system and method for reducing noise in a multi-capacity compressor caused by a disengageable eccentric structure.
Compressor capacity in refrigerant compressors may be varied, especially in multi-cylinder refrigerant compressors, by providing a two position eccentric cam rotatably mounted on the crankpin. The cam is angularly adjustable in response to reversing the direction of rotation of the crankpin by the crankshaft drive motor. One direction of rotation results in the positioning of the eccentric cam having a more eccentric rotation path to provide compression in a corresponding cylinder, while the opposite direction of rotation results in the position of the eccentric cam having a circular rotational path to provide a different amount of compression or no compression in the cylinder. The use of the two position eccentric cam (i.e., the disengageable eccentric cam) allows the compressor to have variable capacity by effectively removing compression in one of the cylinders for one direction of rotation and allows the compressor to maintain efficiency, while under varying load requirements.
One type of eccentric cam is described in U.S. Pat. No. 4,479,419, hereinafter the '419 Patent. The angular positioning of the cam (i.e., the eccentric cam) on the crankpin is accomplished by providing a pair of drive stops which are angularly spaced on a portion of the crankpin, and a dog provided on the cam. These stops and the dog are angularly positioned with respect to each other such that upon rotation of the crankshaft in one direction a first stop will engage one side of the dog and rotate the cam to a first prescribed angular position on the crankpin to produce one piston stroke length. Conversely, reversing the rotation of the crankshaft disengages the dog from the first stop and causes the cam to rotate and engage the opposite side of the dog to a second stop, which also rotates the cam to a second prescribed angular position on the crankpin to produce another piston stroke length.
A compressor operates by drawing gas into a chamber and compressing the gas during a compression cycle. The end of the compression cycle is when the discharge of gas from the compression chamber ends and drawing of the gas into the chamber begins. Reciprocating compressors having disengageable eccentric structures typically include a piston that compresses gas inside a compression cylinder or chamber. A protrusion on the eccentric cam, called a dog, engages a stop on the crankshaft to facilitate rotation of eccentric cam structure. At the completion of the compression cycle, the compressed gas is discharged from the compression cylinder through a discharge valve in a valve plate at one end of the cylinder. The end of the compression cycle in a reciprocating compressor corresponds approximately to the top dead center position of the piston (i.e., the maximum length the piston extends into the compression cylinder). A volume of gas, commonly referred to as reexpansion gas, is not discharged from the compression cylinder and remains in the clearance space of the cylinder (i.e., the space between the valve plate and piston) at the completion of the compression cycle. The reexpansion gas remaining in the cylinder exerts force on the piston. In reciprocating compressors using a disengageable eccentric cam, a force on the piston from the reexpansion gas transfers through the piston assembly to the disengageable eccentric cam. The eccentric cam is accelerated to a rotational velocity greater than the velocity of the crankpin, which results in a slight disengagement of the disengageable eccentric cam's dog from the stop on the crankpin. The crankpin continues to rotate and the eccentric portion returns to the same velocity as the crankpin. The eventual reengagement of the stop on the crankpin with the dog on the disengageable eccentric cam occurs with substantial momentum and impact, thus producing noise, commonly referred to as chatter. Chatter is a metallic clacking or clicking noise generated by the rapid and forceful reengagement of the stop and dog.
Rotary compressors having disengageable eccentric structures are also susceptible to noise in the form of chatter. Rotary compressors include a roller having an eccentric crank mounted on a crankshaft. A protrusion on the eccentric crank, called a dog, engages a stop on the crankpin to facilitate rotation of the roller structure. The roller compresses gas inside a compression cylinder. At the completion of the compression cycle, the compressed gas is discharged from the compression cylinder through a discharge valve positioned along the inner surface of the cylinder. Like in the reciprocating compressor, a volume of reexpansion gas is not discharged from the compression cylinder and remains in the cylinder at the completion of the compression cycle. The reexpansion gas remaining in the cylinder exerts force on the roller, causing the roller and eccentric crank to accelerate to a rotational velocity greater than the crankpin. The crankpin continues to rotate and the roller and eccentric crank return to the same velocity as the crankshaft. The eventual reengagement of the stop on the crankpin with the dog on the disengageable eccentric crank occurs with substantial momentum and impact, thus producing the chatter.
The problem of chatter is not limited to reciprocating and rotary compressors. Any type of compressor having a disengageable eccentric structure may be susceptible to the problem of chatter.
One attempt to address the problem of disengagement and reengagement of the stop and dog includes placing locking mechanisms for the disengageable eccentric structure on the disengageable eccentric cam. For example, U.S. Pat. No. 6,092,993, herein incorporated by reference, utilizes various latching mechanisms that mechanically hold the disengageable eccentric cam and the crankpin stop together while the crankpin is rotating. However, the latching means requires additional components and/or machining on the rotating crankpin and disengageable eccentric cam to maintain engagement. Also shown in U.S. Pat. No. 6,092,993, is the attempt to address the problem of disengagement and reengagement of the stop and dog using inertial mass to hold disengageable eccentric structure against the crankpin stops. The addition of mass to the eccentric cam shifts the center of gravity of the eccentric cam and acts to provide additional force to maintain engagement while the crankpin is rotating. However, cam inertia is generally ineffective to prevent disengagement, particularly from the force against the disengageable cam caused by reexpansion gas.
What is needed is a method and/or system for reducing noise and chatter in variable capacity compressors with disengageable eccentric structures resulting from reexpansion gas remaining in the cylinder at the completion of the compression cycle.
The present invention is directed to a method and system for reducing noise in multi-capacity compressors having disengageable eccentric structures. The noise created by rapid engagement and disengagement of the disengageable eccentric structure with the crankpin is reduced or eliminated by decreasing the amount of reexpansion gas present in the compression chamber of the compressor at or near the completion of the compression cycle.
The present invention includes a multi-capacity fluid compressor including a compression chamber having a discharge end and an inner surface. The compressor also includes a compression member having a disengageable eccentric structure allowing the compressor to provide a plurality of discrete compression capacities. A valve portion is disposed adjacent to the discharge end of the compression chamber and is arranged and disposed to discharge a compressed fluid when the compression member has completed a compression cycle. A discharge arrangement is arranged and disposed to discharge at least a portion of fluid remaining in the compression chamber at the completion of the compression cycle by the compression member. The discharge of at least a portion of the fluid remaining in the compression chamber reduces or eliminates forces on the disengageable eccentric structure to limit rotational acceleration of the disengageable eccentric structure.
Another embodiment of the present invention includes a multi-capacity fluid compressor including a compression chamber having a discharge end and an inner surface. The compressor further includes a compression member having a disengageable eccentric structure allowing the compressor to provide a plurality of discrete compression capacities. The compression member is arranged and disposed to travel along a portion of the inner surface to vary the volume of the compression chamber. A valve portion is disposed adjacent to the discharge end of the compression chamber and is arranged and disposed to discharge a compressed fluid when the compression member has completed a compression cycle. An opening is disposed in one of the components selected from the group consisting of the valve portion, the compression member, the inner surface and combinations thereof. The opening is configured to discharge at least a portion of fluid remaining in the compression chamber at the completion of the compression cycle by the compression member. The discharge of at least a portion of fluid remaining in the compression chamber reduces or eliminates forces on the disengageable eccentric structure to limit rotational acceleration of the disengageable eccentric structure.
A method for reducing chatter in multi-capacity compressors comprising the steps of providing a multi-capacity compressor having a compression chamber having a discharge end and an inner surface. The compressor further includes a compression member having a disengageable eccentric structure that allows the compressor to provide a plurality of discrete compression capacities. The compression member is arranged and disposed to travel along a portion of the inner surface to vary the volume of the compression chamber. A valve portion is disposed adjacent to the discharge end of the cylinder and is arranged and disposed to discharge compressed fluid. An opening is disposed in one of the components selected from the group consisting of the valve portion, the compression member, the inner surface and combinations thereof. The method further includes compressing a fluid by decreasing the volume of the compression chamber with the compression member. A volume of compressed fluid is discharged from the valve portion when the compression member has completed compressing the fluid. Thereafter at least a portion of fluid remaining in the compression chamber is removed through the opening to reduce or eliminate forces on the disengageable eccentric structure to prevent rotational acceleration of the disengageable eccentric structure.
The method and/or system according to the present invention may be utilized with any type of compressor having a portion of the compression mechanism disengageable from the driving member during operation susceptible to chatter. In particular, the present invention is suitable for use with a multi-capacity reciprocating compressor or a multi-capacity rotary compressor.
The method and/or system according to the present invention reduces noise in a compressor having a disengageable eccentric structure without additional noise reducing components and/or machining of the rotating crankpin and disengageable eccentric structure. Further, the system according to the present invention is capable of reducing noise in a compressor having a disengageable eccentric structure with little or no loss in efficiency.
The method and/or system according to the present invention also reduces the number of disengagement and reengagements of the dog on the disengageable eccentric structure and the stop on the crankpin, decreasing the wear on the components and increasing the operational life of the system.
Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.
A system to which the invention may be applied is illustrated, by means of example, in
The compressor 101 compresses a refrigerant vapor and delivers it to the condenser 103. The compressor 101 is preferably a reciprocating compressor, however the compressor according to the present invention is not limited to a reciprocating compressor. Any type of compressor that uses a portion of the compression mechanism disengageable from the driving member during operation (i.e., a disengageable eccentric cam structure) may utilize the present invention. Other suitable compressor types include, but are not limited to, rotary compressors, scotch yoke compressors, and scroll compressors. The refrigerant vapor delivered by the compressor 101 to the condenser 103 enters into a heat exchange relationship with a fluid, e.g., air or water, and undergoes a phase change to a refrigerant liquid as a result of the heat exchange relationship with the fluid. The condensed liquid refrigerant from condenser 103 flows though an expansion device 105 to an evaporator 107. The liquid refrigerant in the evaporator 107 enters into a heat exchange relationship with another fluid, e.g. air or water, to remove heat from the air or water. The refrigerant liquid in the evaporator 107 undergoes a phase change to a refrigerant vapor as a result of the heat exchange relationship with the air or water. The vapor refrigerant in the evaporator 107 exits the evaporator 107 and returns to the compressor 101 by a suction line to complete the cycle. It is to be understood that any suitable configuration of condenser 103 and evaporator 107 can be used in the system 100, provided that the appropriate phase change of the refrigerant in the condenser 103 and evaporator 107 is obtained.
The capacity of compressor 101 directly affects the amount of cooling provided by the refrigerant in the evaporator 107. For example, when a two-stage reciprocating compressor is operated in a maximum capacity mode, compressor 101 operates at full capacity and provides maximum cooling in the evaporator 107. When the two-stage reciprocating compressor is operated in a reduced capacity mode, the amount of cooling provided in the evaporator 107 is similarly reduced.
The multi-capacity gas compressor according to the invention includes a plurality of compression chambers, where each of the compression chambers has a discharge end, an inner surface, and a compressing component (e.g. a piston or compression roller). The compressing component is positioned in the compression chamber adjacent to the inner surface and is mounted to allow travel within the compression chamber, either axially or circumferentially. The position of the compressing component determines the volume of the compression chamber. Accordingly, the travel of the piston or roller increases or decreases the volume of the compression chamber. A reexpansion gas discharge system is positioned adjacent to the discharge end of the compression chamber, e.g., a cylinder. The reexpansion gas discharge can include an opening in the discharge end, the compressing component, the inner surface, or any combination thereof. The opening allows discharge of at least a portion of gas remaining in the compression chamber (i.e., reexpansion gas) after the compression cycle is complete.
The discharge of reexpansion gas 309 from the compression chamber either takes place through an opening in the compression chamber or through a valve activated at or near the completion of the compression cycle. The opening in the chamber according the present invention includes openings that allow constant passage of at least some gas, or openings that allow passage of gas only at predetermined positions of the compressing component in the compression cycle.
In one embodiment having an opening allowing the constant passage of at least some gas, the gas is permitted to discharge from the compression chamber to either an opening in the valve plate 307, as illustrated in
In one embodiment having an opening that allows passage of gas only at predetermined positions of the compression member, the piston assembly 300 may include a passage in the piston head 301 that aligns with a passage in the cylinder wall, as illustrated in
In accordance with one embodiment, the present invention is directed to a reciprocating compressor. The compressor includes a reversible motor for rotating in a forward and a reverse direction and a block with a plurality of cylinders and the associated compression chambers each having a single piston. One or more of the pistons include a disengageable eccentric cam system between the motor and the piston or pistons for driving the piston or pistons at a full stroke between a bottom position and a top dead center position when the motor is operated in the forward direction. The piston with the disengageable eccentric cam is driven at a reduced stroke between an intermediate position and the bottom position when the motor is operated in the reverse direction. The structure supporting the cylinders includes an opening for the appropriate cylinders that allows the discharge of reexpansion gas at or near the completion of the compression cycle (i.e., at or near the top dead center position of the stroke). Alternatively, the structure supporting the cylinders may include a valve 601 that is opened for the appropriate cylinders at or near the end of the compression cycle to discharge at least a portion of the reexpansion gas.
In accordance with another embodiment of the present invention, the invention is directed to a two-stage reciprocating compressor. In this embodiment, the compressor includes a reversible motor for rotating in either a forward or a reverse direction and a structure for supporting one or more cylinders having a single cylinder, an associated single compression chamber, and a single piston. A mechanical system is provided between a motor and the single piston for driving the piston within the cylinder between a bottom position and a top dead center position when the motor is operated in the forward direction. The space formed within the cylinder by the piston is the compression chamber. When a reduced capacity is desired, the piston is driven at a reduced stroke between an intermediate position and the top dead center position by operating the motor in a reverse direction. In order to discharge reexpansion gas, an opening is provided in the structure supporting the cylinders permitting discharge of reexpansion gas at or near the completion of the compression cycle (i.e., at or near the top dead center position of the stroke). Alternatively, the structure having the cylinder may include a valve 601 that is opened at or near the end of the compression cycle to discharge at least a portion of the reexpansion gas 309.
In accordance with still another embodiment of the present invention, the invention is directed to a rotary compressor. The compressor includes a reversible motor for rotating in a forward and a reverse direction and a plurality of compression chambers and associated compression rollers. One or more of the compression rollers are mechanically connected to a disengageable eccentric structure driven by the crankpin and the motor. The disengageable eccentric system includes a compression roller or rollers that provide a small clearance when the motor is operated in one direction and a larger clearance when operated in the opposite direction. The rotary compressor operates at a larger capacity (i.e., compresses a greater quantity of gas) when the roller or rollers provide a small clearance and a smaller capacity (i.e., compresses a smaller quantity of gas) when the roller or rollers provide a larger clearance. The cylinders containing the compression rollers include an opening that allows the discharge of reexpansion gas remaining in the cylinder at or near the completion of the compression cycle (i.e., at or near the point where the discharge of gas is complete and the drawing in of gas begins). Alternatively, the structure that includes the cylinder may include a valve 601 that is opened at or near the end of the compression cycle to discharge at least a portion of the reexpansion gas 309.
The compressor according to the present invention is not limited to reciprocating compressors or rotary compressors. Any type of compressor that uses a portion of compression mechanism disengageable from the driving member during operation (i.e., a disengageable eccentric structure) may utilize the present invention. Other suitable compressor types include, but are not limited to, scotch yoke compressors, and scroll compressors.
In accordance with a further embodiment of the present invention, the compressor having the system for reducing the amount of reexpansion gas in the compression chamber at or near the end of the compression cycle may be used in a variety of commercial or residential applications utilizing a refrigeration cycle. For example, the present invention may be utilized in a heating, ventilating, and air conditioning (“HVAC”) system to condition air within an enclosure. The HVAC system includes a two-stage compressor having an opening in a compression cylinder and/or compression component to discharge reexpansion gas. The compressor is operable at either a first stage with a first capacity or at a second stage with a second, reduced capacity.
According to another embodiment, the invention is directed to a refrigerator appliance that includes a two-stage compressor having an opening in the compression cylinder and/or compression component to discharge reexpansion gas. The compressor is operable at either a first stage with a first capacity or at a second stage with a second, reduced capacity. Preferably, the compressor is continuously operated in the reduced capacity mode until a high cooling demand, such as opening the door or introducing a load of relatively warm perishables, is placed on the refrigerator. When high demand is required, the compressor may be switched to the first, increased, capacity to compensate for the increased demand.
While the invention has been described with reference to a preferred embodiment, 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 disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims.
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