Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1998-07-24
2001-01-30
Kamen, Noah P. (Department: 3747)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
Reexamination Certificate
active
06178748
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an altitude compensating wastegate control system for a turbocharger which automatically compensates for decreased air density and barometric pressure at high altitudes by bleeding off, in preselected steps, the pressure in an air line supplying intake manifold pressure to an actuator of the turbocharger wastegate, thereby raising the intake manifold pressure level required before the wastegate of the turbocharger opens. The preselected steps are selected by the control system in response to sensed barometric pressure to produce different bleed configurations without requiring a dedicated feedback circuit.
THE PRIOR ART
Although the intake manifold pressure requirements of a turbocharged engine are fairly constant across the engine speed range at full load, the output pressure is highly dependent on engine speed because the compressor of the turbocharger is driven by a turbine powered by flow from the exhaust manifold. Inasmuch as a turbocharger must produce an adequate manifold pressure in the engine at lower speeds, a turbocharger wastegate is used to maintain an upper limit on intake manifold pressure of the engine at higher engine speeds by bypassing a portion of the exhaust flow around the turbocharger turbine to avoid engine damage due to excessive cylinder pressure. Operation of the wastegate is controlled by a spring controlled actuator which is fed pressurized air from the intake manifold, so that pressurized air fed to the actuator will cause the normally-closed wastegate to open as the spring force is overcome.
However, the low altitude parameters for controlling wastegate operation are not desirable for controlling engines at higher altitudes, where air density is lower because there will be less oxygen per piston stroke available for combustion resulting in less power and poor combustion. In fact, higher intake manifold pressure and increased mass air flow are desirable.
Previously, various altitude compensation systems for controlling turbocharger wastegate operation at high altitudes have been taught. Such systems are disclosed, for example, in U.S. Pat. Nos. 3,195,805, 4,476,682, 4,492,519, 4,790,139, 4,848,086, and 5,036,663.
As an example, U.S. Pat. No. 4,476,682 includes a bleed valve comprising an evacuated bellows exposed to atmospheric pressure and located in an intake manifold pressure sensing line. The bellows expands as altitude increases and releases pressure from the sensing line to atmosphere, reducing pressure in the sensing line and, thereby raising the intake manifold pressure at which the wastegate opens so that turbocharger operation does not decrease.
The electronic systems disclosed in the other references require feedback for operation, requiring the presence of a separate circuit and/or sensor for providing such feedback.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the invention to provide an altitude compensating wastegate control system for a turbocharger that does not require feedback or a separate circuit and/or sensor.
This object, as well as others, is met by the wastegate actuator control system of the present invention which utilizes available input from a barometric pressure sensor for operating a bleed-off valve system associated with the air supply line from the intake manifold which controls the operation of the wastegate actuator. The control system conFIG.s the bleed-off valve system in one of a plurality of predefined stepped settings, to compensate for altitude effects, the altitude being derived from sensed barometric air pressure.
REFERENCES:
patent: 3195805 (1965-07-01), Cholvin et al.
patent: 4283912 (1981-08-01), Cholvin
patent: 4442672 (1984-04-01), Fischer
patent: 4468928 (1984-09-01), Suzuki
patent: 4476682 (1984-10-01), McInerney
patent: 4492519 (1985-01-01), Owen et al.
patent: 4703625 (1987-11-01), Caldwell
patent: 4790139 (1988-12-01), Roach
patent: 4848086 (1989-07-01), Inoue et al.
patent: 5036663 (1991-08-01), Akagi et al.
patent: 5755101 (1998-05-01), Free et al.
Calfa Jeffrey P.
Hernandez Gilberto
Kamen Noah P.
Navistar International Transportation Corp.
Sullivan Dennis Kelly
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