Oil free type screw compressor

An oil-free type screw compressor comprising a low pressure stage compressor main body and a high pressure stage compressor main body each having a cooling jacket for the cooling by oil;

• a first passage for supplying the lubrication oil to a bearing and/or a timing gear in each compressor main body;
• a second passage for supplying the lubrication oil to each cooling jacket for cooling the compressor main body;
• an oil sump for accommodating the lubrication oil which has passed through the first or second passage;
• and
• an oil cooler capable of cooling the lubrication oil to two different temperatures wherein the lubrication oil passing through the second passage is introduced into the oil sump without passing through the first passage, wherein the lubrication oil passing through the first passage is introduced into the oil sump without passing through the second passage, and wherein the lubrication oil with the lower-temperature is introduced to the second passage, and the lubrication oil with the higher-temperature is introduced to the first passage.

An oil-free type screw compressor comprising:

• a compressor main body provided with a cooling jacket;
• an electric motor for driving the compressor main body;
• a gear casing for accommodating a gear set which transmits the rotation of the electric motor to the compressor main body while changing the rotational speed, the gear casing having an oil sump formed in the bottom thereof;
• an oil pump for feeding lubrication oil from the oil sump to the cooling jacket;
• an oil cooler for cooling the lubrication oil fed from the oil pump;
• and
• a lubrication pipe branching from a branch portion located between ends of a lubrication oil flow passage in the oil cooler, through which the lubrication oil is supplied to a timing gear and/or a bearing in the compressor main body.

An oil-free type screw compressor comprising:

• a compressor main body provided with a cooling jacket;
• an oil cooler for cooling lubrication oil;
• and
• an oil sump for storing the lubrication oil, from which the lubrication oil is supplied through the oil cooler to a lubrication point in the compressor main body and to the cooling jacket, wherein
• a part of the lubrication oil supplied from the oil sump is supplied to the lubrication point without passing through the oil cooler.