Exhaust-gas turbocharger for the two-stage supercharging of an internal-combustion engine with a device to prevent losses of lubricant

Claim 1

An exhaust gas turbocharger for the two-stage supercharging of an internal combustion engine comprising a low-pressure exhaust gas turbocharger, a high pressure exhaust gas turbocharger and a device to prevent loss of lubricants, the high-pressure exhaust gas turbocharger and the low-pressure exhaust gas turbocharger including compressors connected with each other by a low pressure charging air line, a compressor housing, an exhaust gas turbine, a turbine housing, a housing for bearings of the compressor and exhaust gas turbine, an oil collecting means, means for limiting the escape to atmosphere of oil mist formed in the oil collecting means, said means for limiting including the low-pressure charging air line communicating with said oil collecting means, a means for delivering oil from the oil collecting means to the bearing housing, the bearing housing positioned between the high-pressure exhaust gas turbine and the high pressure compressor, the bearing housing connected by an oil return line with the lubricating oil collecting means and the low pressure charging air line, said oil return line being a conducting connection between the oil collecting means and an inner space of the bearing housing, an equalizing line between the oil collecting means and the lower pressure charging air lines; the bearing housing surrounded by an outer housing spaced from the bearing housing, the space between the bearing housing and the outer housing defining an annular air barrier channel therebetween, the channel connected to the high-pressure compressor to receive leakage air from the high pressure compressor, vent means for connecting the low pressure charging air line and the equalizing line to the channel, and means for maintaining a minimal pressure difference between the bearing housing and the compressor and turbine, said means for maintaining including a blocking air duct communicating with a blocking air ring surrounding said bearing housing.