Generally, a compressor is a device for compressing fluid. The compressor is divided into a rotary compressor, a scroll compressor and a reciprocating compressor according to compressing methods.
The reciprocating compressor includes a motor unit for generating a linear reciprocating driving force and a compression unit for receiving the driving force of the motor unit and compressing gas.
In the reciprocating compressor, as a current is applied to the motor unit, the linear reciprocating driving force generated at the motor unit is transmitted to the compression unit, thereby sucking, compressing, and discharging refrigerant in the compression unit.
FIG. 1 is a view illustrating one example of the compression unit of the reciprocating compressor. As shown in FIG. 1, the compression unit of the reciprocating compressor includes a cylinder 10 provided with a through hole 11 therein which makes a compression space P therein; a piston 20 inserted to the through hole 11 of the cylinder 10 for a linear movement and provided with a hollow channel F therein; and a discharge valve assembly 30 engaged to an end portion of the cylinder 10 for covering the through hole 11.
The piston 20 includes a head portion at one side of a body portion 21 having a predetermined length, and a connecting portion 23 connected to the motor unit at the other side of the body portion 21.
Also, the piston 20 is provided with a hollow channel F formed to penetrate the piston 20 for making the refrigerant flow, and the hollow channel F includes a gas passage 24 having a predetermined depth at a center of the body portion 21 and a suction hole 25 penetrating the head portion 22 to be connected to the gas passage 24.
Also, a suction valve 40 is mounted at a front end surface S of the piston head portion 22 for controlling the refrigerant flowing to the hollow channel F by opening and closing the suction hole 25.
The discharge valve assembly 30 includes a discharge cover 31 engaged to cover an end portion of the cylinder 10, a discharge valve 32 inserted in the discharge cover for opening and closing a compression space P formed by the piston 20 and a through hole of the cylinder 10, and a valve spring 33 for elastically supporting the discharge valve 32.
In the compression unit of the reciprocating compressor, a linear driving force of the motor unit is transmitted to the piston 20, so that the piston 20 has a linear reciprocation in the cylinder 10.
In said process, as shown in FIG. 2, if the piston 20 moves towards a lower dead point a, the discharge valve 32 is in contact to the end portion of the cylinder 10 by a pressure difference to close the compression space P, and the suction valve 40 engaged to the piston 20 is bent to open the suction hole 25. According to this, refrigerant flows through the hollow channel F of the piston 20 and is sucked to the compression space P of the cylinder 10.
Then, if the piston 20 moves from the lower dead point a to an upper dead point b, the suction valve 40 is straightened by a pressure difference as it was, and compresses the refrigerant sucked in the compression space P of the cylinder 10 under a state that the suction hole 25 of the hollow channel is blocked. Subsequently, if the piston 20 reaches to the upper dead point b, the discharge valve 32 is opened, thereby discharging the compressed refrigerant. The said process is continuously repeated to compress gas.
In the meantime, the suction valve 40 mounted to the front end portion S of the piston 20 for opening and closing the hollow channel F by repeating curving and straightening by a pressure difference due to a movement of the piston 20 should have an excellent responsiveness of a valve to suck and compress the refrigerant, and should minimize a stress concentration to prevent damage.
As an example of the suction valve 40 of the reciprocating compressor currently being developed, as shown in FIG. 3, the suction valve 30 formed as a thin circle plate corresponding to the front end portion S of the head portion 22 of the piston includes a fixation point 41 formed at the center of the circle plate and a cut off C having a predetermined width in the circle plate as an opened curved line to bend a part of the circle plate on the basis of the fixation point 41.
The cut off C of the opened curved line includes an inner circular curved line portion makes a circle form to surround the fixation point 41, and an outer circular curved line portion 43 prolonged from the inner circular curved line portion 42 and to be opened outwardly.
The suction valve is composed of a fixation part 44 corresponding to the fixation point 41 side by the inner circular curved line portion 42 and the outer circular curved line portion 43, and an open/close part 45 of the opposite side of the fixation part 44.
The open/close part 45 has a cantilever shape and a width thereof becomes narrower towards an inner end portion of the inner circular curved line portion 42.
Under a state that the open/close part 45 of the suction valve 40 is located at an end surface of the piston 20 to block the hollow channel F of the piston 20, the fixation point 41 thereof is welded to the front end surface S of the piston and fixed-engaged to the piston 20.
The engaged suction valve 40 opens and closed the hollow channel F by the open/close part 45 which is bent and straightened under a state that the fixation point 41 is fixed by a pressure difference as the piston 20 reciprocates.
However, in the process that the open/close part 45 is bent and straightened, since the open/close part 45 of the suction valve for opening and closing the hollow channel F of the piston 20 is formed as a cantilever form, as shown in FIG. 4, a stress is concentrated to a neck portion of the open/close part 45, that is, an inner end portion of the cut off C for forming the open/close part 45. According to this, when the opening and closing operations are continuously performed or the open/close part 45 is opened, the valve is destroyed.