Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-09-23
2001-04-10
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C092S136000, C092S033000
Reexamination Certificate
active
06212889
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of turbochargers and, more particularly, to an improved pneumatic actuator for use with a turbocharger variable nozzle turbine.
BACKGROUND OF THE INVENTION
Turbochargers for gasoline and diesel internal combustion engines are known devices used in the art for pressurizing or boosting the intake air stream, routed to a combustion chamber of the engine, by using the heat and volumetric flow of exhaust gas exiting the engine. Specifically, the exhaust gas exiting the engine is routed into a turbine housing of a turbocharger in a manner that causes an exhaust gas-driven turbine to spin within the housing. The exhaust gas-driven turbine is mounted onto one end of a shaft that is common to a radial air compressor impeller mounted onto an opposite end of the shaft. Thus, rotary action of the turbine also causes the air compressor impeller to spin within a compressor housing of the turbocharger that is separate from the exhaust housing. The spinning action of the air compressor impeller causes intake air to enter the compressor housing and be pressurized or boosted a desired amount before it is mixed with fuel and combusted within the engine combustion chamber.
The amount by which the intake air is boosted or pressurized is controlled by regulating the amount of exhaust gas that is passed through the turbine housing by a wastegate, and/or by selectively opening or closing an exhaust gas channel or passage to the turbine running through the turbine housing, and/or by adjusting the position of one or more vanes within the turbine housing to vary the gas flow velocity of exhaust gas to the turbine. For example, the use of adjustable vanes within a turbine housing can be used as one way of reducing turbo lag, i.e., the lag time between the time that the vehicle is accelerated from idle and sufficient pressure is developed by the turbocharger compressor to effect an appreciable increase in engine power, by reducing the flow area within the turbine housing to provide the necessary power to quickly accelerate the turbine wheel. As the volumetric flow rate of exhaust gas increases with increasing engine RPM, the vanes are adjusted to increase the flow area within the turbine housing to enable the exhaust gas to generate the appropriate power to compress the necessary quantity of inlet air.
Turbochargers constructed having such an adjustable member within the turbine housing are referred to in industry as variable geometry turbines (VGTs). The movable member within such VGTs, in the form of vanes, nozzles or the like, is positioned in the turbine housing between an exhaust gas inlet or volute and the turbine. The movable member is activatable from outside of the turbine housing by suitable actuating mechanism to increase or decrease the exhaust gas flow within the turbine housing to regulate the air intake boost pressure as called for by the current engine operating conditions, as explained above.
VGTs known in the art can be actuated by using a pneumatic activating means, i.e., by using compressed air or the like or by hydraulic activating means, i.e., by using a pressurized fluid such as oil or the like. An example hydraulically activated actuator includes one comprising a combined piston and rack and pinion assembly. The piston in such actuator assembly is reciprocated within a cylinder by pressurized oil that is passed through a dedicated oil passage within the turbocharger. The oil is passed to the piston at a particular pressure using a valve. A rack and pinion assembly is used with the piston to convert reciprocating piston movement into rotary movement that ultimately actuates the movable member within the turbine, e.g., a VGT vane or nozzle.
A concern with the above-described design is that, due to spatial constraints, the use of a combined piston and rack and pinion assembly requires that the oil passage through the turbocharger be limited in diameter, thereby reducing the response of the actuator assembly to oil pressure. Additionally, the use of such combined piston and rack and pinion assembly requires additional space for proper assembly operation, thereby precluding packaging the assembly in a compact manner to both conserve space around the turbocharger unit and to minimize assembly exposure to radiant heat transfer caused by the intrusion of one or more component to the outline limits of the turbocharger.
It is, therefore, desired that an actuator assembly for a VGT be constructed in a manner that both improves actuator response to an activating means, and improves movable member response to the actuator, i.e., provides a more direct actuator movement to movable member movement. It is desired that such actuator assembly also be constructed having a compact size, when compared to conventional VGT actuators, to both increase available space around the turbocharger and minimize or eliminate exposure to undesirable heat effects.
SUMMARY OF THE INVENTION
A Turbocharger for internal combustion engines employing the present invention incorporates a turbocharger housing in which an actuator assembly is integrated for operating a movable member in the housing. The actuator assembly includes an actuator cylinder disposed within the housing and a main shaft positioned axially within the cylinder. the main shaft is rotatably mounted in the cylinder and has a set of helical splines disposed along an outside diameter surface section and the main shaft also has an end that extends through the cylinder that is connected to an actuating lever. A cylindrical collar is disposed concentrically around a section of the main shaft and is axially movable thereon. The collar includes an annular seal disposed along an inside diameter to form a leak-tight seal between the collar and the main shaft. The collar has a set of helical splines disposed along an outside diameter surface and a set of helical splines disposed along an inside diameter surface that complements and engages the set of helical splines on the main shaft. A sealing sleeve is attached to the collar adjacent an end of the collar with an outside diameter greater than the collar. The sealing sleeve includes an annular seal disposed along an outside diameter to form a leak-tight seal between the sealing sleeve and a cylinder wall surface. A stationary sleeve is disposed concentrically around the collar and fixedly mounted within the cylinder a sufficient distance from the sealing sleeve to permit a desired degree of axial sealing sleeve and collar displacement within the cylinder and the stationary sleeve has a set of helical splines disposed along an inside diameter that complements and engages the collar outside diameter helical splines to rotate the collar within the cylinder as the collar is displaced axially therethrough.
In operation, rotation of the collar and stationary sleeve causes the main shaft to be rotated within the cylinder by engagement between the set of helical splines disposed along the collar inside diameter and the set of helical gears disposed along the main shaft. The engaged sets of helical splines disposed along the collar inside diameter and along the main shaft are designed to rotate the main shaft in the same direction as the collar and to an extent greater than the collar. Hydraulic pressure activates the actuator assembly to provide axial and rotational motion.
REFERENCES:
patent: 3090244 (1963-05-01), Davis
patent: 4313367 (1982-02-01), Weyer
patent: 4508016 (1985-04-01), Weyer
patent: 4804316 (1989-02-01), Fluery
patent: 5447095 (1995-09-01), Weyer
patent: 5487273 (1996-01-01), Elpern et al.
patent: 4111340 A1 (1992-10-01), None
patent: 297 16 199 U1 (1997-11-01), None
patent: 2033007A (1980-05-01), None
patent: 2164099A (1986-03-01), None
Allied-Signal Inc.
Denion Thomas
Fischer Felix L.
Langton Grant T.
Trieu Thai-Ba
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