Abstract: An apparatus for controlling a turbocharger includes a compressor and a turbine coupled to the compressor and comprises a variable capacity device for varying the flow rate of an exhaust gas introduced into the turbine in the low speed state of an engine connected to the turbocharger, an exhaust gas bypass device bypassing the variable capacity device and the turbine to control the flow rate of the exhaust gas in the high speed state of the engine, and an overboost device for detecting the accelerating state of the engine and controlling the operation of the exhaust gas bypass device such that the exhaust gas bypass device reduces the flow rate of the exhaust gas introduced into the turbine only when the supercharging pressure has reached a predetermined pressure in the accelerating state of the engine.

Abstract: A variable-capacitance radial turbine has a swingable tongue member which is swingably mounted in an inlet throat portion of a scroll fluid passage of the turbine and which is swingable on a pivot shaft parallel to the turbine wheel axis. The right and left scroll side walls are formed with right and left seat surfaces, and the tongue member is formed with right and left sealing surfaces on both sides. The right and left seat surfaces and sealing surfaces are not perpendicular to the turbine wheel axis, and they are so shaped that when the tongue member is in a predetermined limit position, the right and left sealing surfaces are in contact with the right and left seat surfaces respectively so as to seal the clearances between the tongue member and the scroll side walls over the full length of the tongue member.

Abstract: A turbine scroll passage of a turbine is divided into first and second scroll passages extending in parallel to each other along the scroll passage. The first passage is formed with a side aperture for directing the fluid in the scroll passage to a turbine wheel. The second passage is isolated from the side aperture by a partition wall separating the second passage from the first passage. The partition wall is formed with a longitudinally extending opening for providing a fluid communication between the first and second passages. The opening extends longitudinally through about 360 degrees around the axis of the turbine, and has a constant width over its length. In the secondary passage, there is disposed a valve of a swing, rotary or other type, for closing the secondary passage. When the turbine is a part of a turbocharger connected with an internal combustion engine, the secondary passage is closed by the valve in a low engine speed range.

Abstract: A diffuser for a fluid impelling device such as a radial or axial turbine, comprising outer and inner casing members radially spaced apart from each other and thereby forming therebetween a diffuser chamber having annular cross-section which gradually increases in area toward the gas outlet end of the diffuser, wherein a flow throttling element is provided or the inner casing member is shaped to have a flow throttling portion so that the diffuser chamber is throttled at the gas outlet end for precluding separation of gas flow from an inner surface of the outer casing member.