CROSS-REFERENCES TO RELATED APPLICATIONS
The present application is a continuation of and claims priority to Chinese Patent Application No. 2010101014022 filed Jan. 27, 2010, U.S. patent application Ser. No. 12703506 filed Feb. 10, 2010, U.S. patent application Ser. No. 12727907 filed Mar. 19, 2010, and Provisional Application No. 61314372 filed Mar. 16, 2010, each of which is hereby incorporated by reference in its entirety.
FIELD OF THE INVENTION
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The present invention relates generally to reciprocating refrigeration compressors and specifically to improving efficiency by improving the structure of the valve plate, piston, and cylinder bore.
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OF THE INVENTION
A reciprocating refrigeration compressor is composed of main parts, including the body, crankshaft, cylinder cover, valve plate, piston, connecting rod, motor, motor cover, bearing housing, bottom plate, and the like. Typically, an electric motor drives the crankshaft, which is connected to a connecting rod and piston. The crankshaft moves the piston upward and downward. A valve plate on the cylinder plane has a suction port and a discharge port. As the piston moves downward on the suction stroke, pressure is reduced in the cylinder. Refrigeration systems use a circulating liquid refrigerant that enters the compressor as a vapor. When the pressure falls below that in the compressor suction line, the pressure differential causes the suction valves to open and forces the refrigerant vapor to flow into the cylinder.
As the piston reaches the bottom of its stroke and starts upward on the compression stroke, pressure is developed in the cylinder, forcing the suction valves closed. The pressure in the cylinder continues to rise as the piston moves upward, compressing the vapor trapped in the cylinder. When the pressure in the cylinder exceeds the pressure existing in the compressor discharge line, the discharge valve is forced open, and the compressed gas flows into the discharge line which is connected to the condenser.
When the piston starts downward, the reduction in pressure allows the discharge valve to close because of the higher pressure in the condenser and discharge line, and the cycle is repeated.
Three main factors affect compressor efficiency: 1) The seating of the valves; 2) the temperature of the cylinder walls (if the cylinder wall are hot and suction gas entering the cylinder on the intake stroke is heated by the cylinder walls, the gas expands, resulting in a reduced weight of gas entering the compressor); and 3) the clearance volume of the cylinder.
The most important factor affecting compressor efficiency is clearance volume. The clearance volume is composed of following five areas: 1) clearance above the piston; 2) clearance for reed thickness; 3) discharge ports on valve plate; 4) clearance between the piston and the cylinder wall; and 5) clearance for the reed opening and stopping.
When the piston starts down on the suction stroke, the residual high pressure gas in the clearance volume expands and its pressure is reduced. No vapor from the suction line can enter the cylinder until the pressure in the cylinder has been reduced below the suction line pressure. Thus, the first part of the suction stroke is actually lost from a capacity standpoint, and as the compression ratio increases, a greater percentage of the suction stroke is occupied by the residual gas.
A problem exists in the efficiency of the compressor. Compressor efficiency is typically effected by the clearance volume, rate of heat transfer, valve and piston leakage, vapor load and the like. For example, in a typical three-cylinder compressor having pistons with a diameter of 65 mm, a high temperature results in a compression ratio from 4-8; a media temperature application in a compression ratio from 7-12, and low temperature application results in a compression ratio from 8-18. Because of the difference between discharge pressure vs. suction pressure, the efficiency effects are 12-19%, 16-28%, 19-41%, respectively. The larger the compression ratio, the more serious the efficiency effect will be.
Regular improvements from many compressor builders are: 1) Mill the reed shape to certain depth (usually is same as reed thickness) on the top of piston; 2) Reduce the thickness of valve plate; and 3) Use a model called discs compressor, which has different valve plate designing to eliminate discharge port clearance volume. All these methods will reduce the clearance volume, thus raising the compressor efficiency to certain level, but the clearance volume issues with high temperature and high pressure still exists. A further difficulty with existing methods is that they require major changes to the design of the compressor. There is a long-standing need for an improvement to compressor efficiency that is simple and does not require major design changes.
BRIEF DESCRIPTION OF THE INVENTION
The present invention is a device and method of improving the efficiency of a reciprocating refrigeration compressor comprising a cylinder body and a piston. The method comprises creating at least one channel in the piston, such that, when a compression stroke is completed the channel transfers a pressure in a clearance volume to a low pressure side of the piston.
In an embodiment, at least one groove is created in a wall of the cylinder body. In addition, each channel has a first end comprising an opening on the exterior diameter of the piston between a pressure ring and an oil ring and a second opening on the low pressure side of the piston. When a compression stroke is completed, each opening of the channel on the exterior diameter of the piston aligns with each groove to transfer a pressure in the clearance volume to the low pressure side of the piston.
In an embodiment, a duct is created in the cylinder body. The duct extends from an opening at the clearance volume side of the cylinder body to a second opening in the wall of the cylinder. When a compression stroke is completed, each channel aligns with each duct and pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.
In an embodiment, each channel comprises a first end comprising a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston. The first end opening has a diameter smaller than a second diameter of the remainder of the channel. Each first end comprises a ball, a spring, and a set screw. The ball has a diameter greater that the first end diameter and less than the second diameter. The ball is held against the opening, which is spherical shaped, by the spring, to seal the first end opening. A portion of the ball extends from the top of the piston into the clearance volume. When the piston moves up and down normally, high pressure does not cause compression of the spring, so that the opening remains sealed by the ball. When the piston completes a compression stroke, the portion of the ball extending from the opening contacts the valve plate. The upward movement of the piston pushes the ball into the valve plate. Contact with the valve plate compresses the spring and moves the ball down into the first end opening, thus opening the channel. High pressure in the clearance volume flows through the channel to the low pressure side of the piston. As the piston continues its cycle and moves downward from the valve plate, the ball is resealed in the opening by energy released from the spring.
The present invention is an improvement for a reciprocating refrigeration compressor, comprising a cylinder body and a piston. The improvement comprises at least one channel in the piston connecting the clearance volume to a low pressure side of the piston.
In an embodiment, the improvement comprises at least one groove in a wall of the cylinder body. In addition, each channel comprises a first end having an opening on a exterior diameter of the piston between the pressure ring and the oil ring and a second opening on the low pressure side of the piston. When a compression stroke is completed, each channel aligns with each groove to transfer pressure in the clearance volume to the low pressure side of the piston.
In an embodiment, the improvement comprises at least one duct in the cylinder body. The duct has an opening extending from the clearance volume to a second opening at a point in a wall of the cylinder. In addition, each channel comprises a first end having an opening on a exterior diameter of the piston between the pressure ring and an oil ring. When a compression stroke is completed, each channel aligns with each duct and pressure in the clearance volume is transferred to the low pressure side of the piston through the ducts and the channels.
In an embodiment, the improvement comprises a channel comprising a first end having a first opening on the clearance volume side of the piston and a second opening on the low pressure side of the piston. The first end opening has a diameter smaller than a second diameter of the remainder of the channel. Each first end comprises a ball, a spring, and a set screw. The ball extends from the first end opening and has a diameter greater that the first end diameter, but less than the second diameter. The ball is held against the opening by the spring with a portion of the ball extending from the top of the piston into the clearance volume to seal the first end opening of the channel. The ball and spring work together to open the channel when the ball is pressed and the spring is compressed, and to close the channel when the spring is extended.
The present invention addressed the issue of high pressure in clearance volume affecting the efficiency of a refrigeration compressor with a new technical method that releases the high pressure simply and in very short time. The present invention provides a substantial improvement in the volumetric efficiency of the compressor by releasing the high pressure from clearance volume of the compressor. Among the advantages of this invention are:
1) Without the high pressure in the clearance volume, the efficiency effect from that will be controlled to about 2% only, thus, the compressor efficiency will be raised dramatically.
2) Without the high pressure, high temperature will be reduced automatically. Without high temperature, the density of vapor will not have extra expansion. Thus, the extra compressor efficiency will be raised.
3) The high pressure will be released to compressor crankcase, which will raise internal pressure. Thus the suction pressure will be raised, and this result will be really helpful to compressor system capacity.
4) High pressure is the main reason for noise. Without high pressure, the compressor will be quieter.
5) Reducing the possibility of “slugging.” Slugging occurs when the compressor vapor condenses to a liquid upon entering the compressor. Because liquid does not compress, slugging leads to failure of the compressor.
As used herein, “approximately” means within plus or minus 25% of the term it qualifies. The term “about” means between ½ and 2 times the term it qualifies. The term “substantially” means that ninety-five percent of the values of the physical property when measured along an axis of, or within a plane of or within a volume of the structure, as the case may be, will be within plus or minus 10% of a mean value.
As used herein, “implementation” is interchangeable with “embodiment.”
As used herein, “top” and “up” mean furthest away from the crankcase, while “bottom” and “down” mean closest to the crankcase.
Numerical ranges as used herein are intended to include every number and subset of numbers contained within that range, whether specifically disclosed or not. Further, these numerical ranges should be construed as providing support for a claim directed to any number or subset of numbers in that range.
The methods of the present invention can comprise, consist of or consist essentially of the essential elements and limitations of the invention described herein, as well as any additional or optional components, or limitations described herein or otherwise useful in compositions and methods of the general type as described herein.
All references to singular characteristics or limitations of the present invention shall include the corresponding plural characteristic or limitation, and vice versa, unless otherwise specified or clearly implied to the contrary by the context in which the reference is made. Definitions used herein are intended to supplement and illustrate, not preclude, the definitions known to those of skill in the art.
All combinations of method or process steps as used herein can be performed in any order, unless otherwise specified or clearly implied to the contrary by the context in which the referenced combination is made.