Piston operated bypass valve for a screw compressor

摘要

A screw compressor includes a valve hole formed at a discharge side end surface of a discharge casing and at a position opening to a compression work chamber; a bypass flow path having the valve hole and a discharge chamber communicate with each other; and a valve body arranged in the valve hole. The screw compressor also includes cylinder chambers provided on a rear surface side of the valve body; a piston reciprocally moving in the cylinder chambers; a rod connecting the piston and the valve body; communication paths for introducing a fluid on a discharge side into the cylinder chamber on a side opposite to a valve body side of the piston and on the valve body side; a pressure discharge path; a plurality of valve means; and a controller controlling the plurality of valves means.

主权项

1. A screw compressor including:
a male rotor and a female rotor rotating while engaging with each other with rotation axes thereof that are substantially parallel to each other; a main casing having a bore arranging the male rotor and the female rotor; and a discharge casing abutting a discharge side end surface of the main casing in a rotor axial direction to cover an opening of the bore; a discharge chamber or a discharge flow path where compressed gas is discharged from a compression work chamber formed by the male rotor and the female rotor via an outlet port formed in at least one of the main casing and the discharge casing; a valve hole formed near the outlet port at an end surface of the discharge casing on at least one of sides of the male rotor and the female rotor and at a position opening to the compression work chamber; a bypass flow path having the valve hole and the discharge chamber or the discharge flow path communicate with each other; and a valve body arranged in the valve hole, the screw compressor comprising: cylinder chambers provided on a rear surface side of the valve body; a piston reciprocally moving in the cylinder chambers; a rod connecting together the piston and the valve body; a communication path for introducing a fluid on a discharge side of the compressor into the cylinder chambers on a side opposite to a valve body side of the piston and on the valve body side; a pressure discharge path for discharging to a suction side of the compressor the fluid introduced into the cylinder chambers on the side opposite to the valve body side of the piston and on the valve body side; a plurality of valve means provided at the pressure discharge path or the communication path, the valve means changing pressure in the cylinder chambers on the side opposite to the valve body side of the piston and on the valve body side; and a controller detecting whether or not over-compression is occurring in the compression work chamber, the controller controlling the plurality of valve means to open the valve body upon detecting the over-compression and close the valve body upon not detecting the over-compression; wherein the communication path includes a first communication path connecting together inside of the cylinder chamber on the side opposite to the valve body side of the piston and the discharge side of the compressor and a second communication path connecting together inside of the cylinder chamber on the valve body side of the piston and the discharge side of the compressor; wherein the pressure discharge path includes a first pressure discharge path connecting together the inside of the cylinder chamber on the side opposite to the valve body side of the piston and a low pressure space of the compressor and a second pressure discharge path connecting together the inside of the cylinder chamber on the valve body side of the piston and the low pressure space of the compressor; wherein the plurality of valve means includes a first valve means provided at the first pressure discharge path for opening and closing the pressure discharge path and a second valve means provided at the second pressure discharge path for opening and closing the pressure discharge path; wherein the controller controls the first and second valve means to open the valve body upon detecting the occurrence of the over-compression and close the valve body upon not detecting the occurrence of the over-compression; and wherein the controller obtains a pressure ratio during operation based on suction pressure to the compressor and discharge pressure of the compressor, compares the pressure ratio with a set pressure ratio previously stored, judges that the over-compression has occurred when the pressure ratio during operation has become smaller than the set pressure ratio, and controls the first and second valve means to open the valve body.