1. Field of the Invention
The present invention relates to an exhaust valve, in particular, capable of correctly opening an outlet port of a cylinder while maximizing compression efficiency.
2. Description of the Related Art
Generally in a cooling cycle, fluid having a large amount of heat is sucked and then exhausted after loosing heat through compressing, condensing, expanding and evaporating processes.
A cooling apparatus for performing the above processes may comprise a compressor, a condenser, expansion valves and an evaporator. The compressor sucks and compresses coolant evaporated in the evaporator to raise the pressure thereof so that coolant may be converted into a state liquefiable at a relatively high temperature.
In general, the compressor is divided into a reciprocating compressor, a revolving compressor, a scrolling compressor and the like according to application policies thereof. The reciprocating compressor can compress coolant through processes of sucking, compressing and exhausting coolant gas as a piston reciprocates inside a cylinder. The reciprocating compressor has a suction valve for sucking coolant, a cylinder for compressing coolant introduced through the suction valve and an exhaust valve for exhausting coolant compressed in the cylinder.
FIG. 1 is a schematic perspective view illustrating a conventional reciprocating compressor.
Referring to FIG. 1, the reciprocating compressor comprises a column-shaped cylinder 11, a piston 12 for being inserted into one side of the cylinder 11 and performing a linear reciprocating motion inside the cylinder 11 to compress fluid, suction and exhaust valves 14 and 15 arranged in opposition to the front of the piston 12 for sucking and exhausting fluid, a valve plate 13 arranged between the suction valve 14 and the exhaust valve 15 for supporting the suction and exhaust valves 14 and 15 and a head cover 16 having channels for fluid which is introduced into the cylinder 11 and exhausted from the same.
The reciprocating compressor further comprises a connecting rod 17 connected to the rear of the piston 12 and a crank shaft 18 connected to the rod 17 and rotated by a motor (not shown).
Briefly describing the operation of the reciprocating compressor, the motor (not shown) is driven to rotate the crank shaft 18 so that the connecting rod 17 connected to the crank shaft 18 may move in a circle in cooperation with the connecting rod 17. The movement of the connecting rod 17 causes the piston 12 connected thereto to perform a linear reciprocating motion so that fluid is sucked into the cylinder 11, compressed therein, and then exhausted therefrom.
In the above operation, the suction and exhaust valves 14 and 15 perform sucking and exhausting procedures as follows and have the following structures.
FIGS. 2A to 2D are schematic plan views illustrating a head cover (FIG. 2A), an exhaust valve (FIG. 2B), a valve plate (FIG. 2C) and a suction valve (FIG. 2D), respectively, in a conventional reciprocating compressor. Seen from the front of the piston in FIG. 1, the cylinder may be sequentially coupled with the inlet valve, the valve plate, the outlet valve and the head cover in the order of description, i.e. from the inlet valve to the head cover.
Referring to FIGS. 2A to 2D, the valve plate 13 includes a suction port 13a for sucking fluid and an exhaust port 13b for exhausting fluid as a member for supporting the suction valve 14 and the exhaust valve 15.
The suction valve 14 is a member arranged between the valve plate 13 and the cylinder 11, and has a suction plate 14a at a position corresponding to the suction port 13a of the valve plate 13 and an exhaust port 14b at a position corresponding to the exhaust port 13b of the valve plate 13.
Further, the exhaust valve 15 is a member arranged between the valve plate 13 and the head cover 16, and has an exhaust plate 15a at a position corresponding to the exhaust port 13b of the valve plate 13 and a suction port 15b at a position corresponding to the suction port 13a of the valve plate 13.
The head cover 16 is a member for defining the channels of fluid sucked and exhausted into/from the cylinder, and has a suction tube 16a at a position corresponding to the suction port 13a of the valve plate and an exhaust tube 16b at a position corresponding to the exhaust port 13b. 
Description will be made about the operation of the conventional reciprocating compressor including the suction valve 14, the valve plate and the exhaust valve 15 having the above configuration. When the piston 12 moves backward inside the cylinder 11 due to the circular motion of the crank shaft, the pressure within the cylinder 11 is lowered to fold the suction plate of the suction valve. Therefore, fluid is sucked into the cylinder via the folded suction plate 14a after passing through the suction tube 16a, the suction port 15b and the suction port 13a of the valve plate.
Fluid sucked as above is compressed as the piston 12 moves forward due to the circular motion of the crank shaft. Fluid compressed like this passes through the exhaust port 14b of the suction valve and the exhaust port 13b of the valve plate, and then flows out via the exhaust tube 16b of the head cover pushing out the exhaust plate 15a of the exhaust valve which is supported by a spring and the like.
FIGS. 3A and 3B schematically illustrate the operation of the exhaust valve in the conventional reciprocating compressor, in which the suction valve is not shown for the convenience""s sake of description.
Describing a process of exhausting fluid from the cylinder in reference to FIGS. 3A and 3B, fluid compressed via forward movement of the piston is exhausted via the exhaust port 13b of the valve plate, i.e. out of the cylinder pushing out the exhaust plate 15a of the exhaust valve. Preferably, the exhaust plate of the exhaust valve is made of a material capable of resisting a certain amount of pressure.
After fluid is exhausted, the piston moves backward due to the circular motion of the crank shaft accordingly lowering the pressure within the cylinder so that the exhaust pate 15a is shut due to its own elasticity to prevent further exhaustion of fluid.
The above process continuously takes place as the crank shaft continuously performs the circular motion while the piston connected thereto repeatedly performs the reciprocating motion.
However, according to the operation of the exhaust valve in the above reciprocating compressor, it can be seen that the exhaust plate 15a of the exhaust valve is folded for a certain degree instead of being completely folded in an exhausting process. Since the exhaust plate 15a is not completely folded as above, fluid is obstructed in exhaustion along a proceeding direction thereby preventing smooth exhaustion.
Further, the above valve is opened according to the fluid pressure inside the cylinder so that the exhaust valve is opened later than a desired time point thereby resulting in overshooting as a problem.
Further, when the exhaust valve 15a is shut in a sucking process, the entire portion of the exhausting valve 15a contacting to the valve plate 13 hits the valve plate 13 to produce noise. Heavy noise also takes place from vibration of the valve and fluid leakage through a gap which is produced by the valve folded in exhaustion.
The above phenomena not only degrade the entire efficiency of the reciprocating compressor but also provide users with displeasure due to heavy noise.
The present invention has been made in conjunction with the above problems and it is therefore an object of the invention to provide an exhaust valve capable of elevating compression efficiency by correctly opening an exhaust port.
It is another object of the invention to provide a reciprocating compressor having the above exhaust valve.
According to an aspect of the invention to obtain the above objects, it is provided an exhaust apparatus comprising: a guide connected in parallel to an exhaust port of a cylinder; a needle valve provided inside the guide for opening/shutting the exhaust port while moving in cooperation with the guide; and an electromagnet provided in the rear of the guide for controlling the needle valve.
In the exhaust apparatus, the needle valve is preferably a permanent magnet.
Preferably, the exhaust apparatus further comprises metallic materials having magnetism at both sides of the exhaust port for opening the exhaust port of the cylinder for a predetermined range, in which the predetermined range means a range where the electromagnet has a flux density larger than a critical flux density, and the critical flux density is determined from the attraction between the metallic materials and the needle valve.
In the exhaust apparatus, the guide is connected in perpendicular to the exhaust port of the cylinder, and the electromagnet is provided in the rear of the guide when the guide is provided perpendicular to the exhaust port of the cylinder.
According to another aspect of the invention to obtain the above objects, it is provided a reciprocating compressor comprising: a cylinder having a predetermined internal space; a piston for linearly reciprocating inside the cylinder; and exhaust means for exhausting fluid which is compressed due to linear reciprocation of the piston according to opening/shutting means moving corresponding to the flux density of an electromagnet.
In the reciprocating compressor, the exhaust means may comprise: a guide connected in parallel or perpendicular to an exhaust port of the cylinder; and the electromagnet provided in the rear of the guide for controlling the opening/shutting means.
In the reciprocating compressor, the opening/shutting means is preferably a permanent magnet.
Preferably, the reciprocating compressor may further comprise an exhaust tube on one side of the guide for exhausting fluid and metallic materials having magnetism at both sides of the exhaust port of the cylinder for maintaining the attraction with the opening/shutting means when the guide is parallel to the exhaust port of the cylinder.
Preferably, the reciprocating compressor may further comprise an exhaust tube parallel to the exhaust port of the cylinder and a metallic material having magnetism at one end of the guide for maintaining the attraction with the opening/shutting means when the guide is perpendicular to the exhaust port of the cylinder.
In the reciprocating compressor, the intensity of the flux density of the electromagnet is varied proportionally to the displacement of the piston, and the flux density of the electromagnet takes place according to a current applied to the electromagnet.
According to still another aspect of the invention to obtain the above objects, it is provided an exhaust apparatus comprising: a guide penetrating in parallel an exhaust port connected in parallel to an exhaust port of a cylinder; a needle valve provided inside the guide for opening/shutting the exhaust port while moving in cooperation with the guide; and an electromagnet provided in the rear of the guide for controlling the needle valve.