Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
2000-11-17
2002-04-30
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S611000, C060S612000, C060S602000, C123S559100
Reexamination Certificate
active
06378307
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of application number 199 55 508.7, filed in Germany, Nov. 18, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention relates to an internal combustion engine with an exhaust gas turbocharger, and an associated method. Preferred embodiments relate to an exhaust gas turbocharger, which comprises an exhaust gas turbine and a compressor for generating compressed boost air, having an additional, air-driven turbine, which is torsionally connected to the compressor and to which combustion air can be supplied via an adjustable shut-off element, a turbine outlet of the air-driven turbine being connected by a connecting duct to the induction path downstream of the compressor and having a closed-loop and open-chain control unit for generating setting signals which adjust the shut-off element.
An exhaust gas turbocharger for an internal combustion engine is known from German Patent Document DE 42 13 047 A1, whose exhaust gas turbine is driven by the exhaust gas back pressure and drives, via a connecting shaft, a compressor for generating increased boost pressure. In order to improve the transient behavior of the exhaust gas turbocharger, compressed air from a pressure reservoir in the compressor inlet can be fed in via an additional duct to support the run-up of the supercharger to higher peripheral speeds; at the same time, a throttle upstream of the compressor inlet is displaced into the shut-off position in order to prevent the compressed air fed in at a positive pressure from escaping to the atmosphere via the intake line.
By means of this exhaust gas turbocharger, it is in fact possible to increase the supercharger rotational speed even at low-load operating points, at which only a small exhaust gas back pressure is built up, by feeding in additional compressed air. In this way, delays in the build-up of pressure, which may be attributed to a delay in the increase in the supercharger rotational speed due to inertia, can be reduced. This advantage must, however, be purchased at the cost of a high level of structural complication. In particular, it is necessary to ensure a sufficiently high positive pressure in the pressure reservoir, for which purpose an additional compressor, including the drive unit necessary for the compressor, is required.
In order to improve the response behavior of exhaust gas turbochargers, the inertia of the superchargers has been previously reduced by a reduction in size and a lighter design by means, in particular, of reducing the turbine impeller diameter. As a result of the smaller mass moment of inertia of the supercharger rotor, the delay in the build-up of boost pressure is reduced and, correspondingly, a higher engine torque can be built up in a shorter time. The reduction in the impeller volume of the supercharger rotor can, however, lead to a deterioration in the efficiency of the exhaust gas turbocharger. A further problem associated with relatively small exhaust gas turbocharger designs is the high supercharger rotational speeds and, in particular, the large rotational speed range which has to be overcome by the supercharger rotor between lower engine load and full load.
A further exhaust gas turbocharger device of the generic type is revealed in Japanese Patent Document JP 10-315 616 A1. Associated with the exhaust gas turbocharger described in this publication is an additional, air-driven turbine, which is seated on the same drive shaft as the exhaust gas turbine and the compressor and is capable of supplying drive power to the compressor. The air-driven turbine is fed with compressed air from a compressed air reservoir and the expanded air at the turbine outlet of the air turbine is combined with the compressed air from the compressor and subsequently introduced into the air inlet of the internal combustion engine.
The compressed-air driven turbine is switched on in the lower load range, during which an exhaust gas back pressure sufficient for driving the exhaust gas turbine is not yet available or is just being built up, so that the rotor of the exhaust gas turbocharger can be accelerated to higher revolutions despite a low exhaust gas back pressure. Although this appliance makes it possible to build up an exhaust gas turbocharger rotor rotational speed sufficient for a build-up of boost pressure over a wide operating range of the internal combustion engine, an additional compressed air reservoir, including the associated drive units, must again be considered as reservations with respect to the appliance as described in this JP 10-315 616 A1.
The invention is based on the problem of improving the efficiency of an exhaust gas turbocharger by simple means.
This problem is solved, in accordance with the invention, by providing an arrangement of the above referred to type, wherein an additional duct is provided between the compressor inlet or a line section opening into the compressor inlet and the air inlet of the air-driven turbine,
wherein the air supply in the additional duct and in the compressor inlet can be adjusted by the shut-off element, and
wherein in a lower load range, in a case where required boost pressure falls below a threshold value, a setting signal is generated in the closed-loop and open-chain control unit, which setting signal adjusts the shut-off element into a position opening the additional duct and reducing the air supply to the compressor inlet.
This problem is also solved by a method of operating an internal combustion engine having an exhaust gas turbocharger with an exhaust gas turbine and a compressor for generating compressed boost air, having an additional, air-driven turbine, which is torsionally connected to the compressor and to which combustion air can be supplied via an adjustable shut-off element, the turbine outlet being connected to a duct section communicating with the compressor outlet, wherein, in a lower load range, in a case where the required boost pressure falls below a threshold value, at least a partial flow of the induced combustion air is guided via the air-driven turbine.
The novel internal combustion engine comprises an exhaust gas turbocharger which has an additional duct between the compressor inlet and the air inlet of the air-driven turbine, it being possible to adjust the air supply to the additional duct and also to the compressor inlet by a shut-off element, as a function of the operating condition of the internal combustion engine. This embodiment offers the advantage that the supply of combustion air to both the compressor and the air-driven turbine can take place via a common induction duct. The feed to the compressor and/or to the air turbine takes place by means of the adjustment of the shut-off element, which is, in particular, arranged in the region where the additional duct branches off from the induction duct and which permits an adjustment of the air flow both through the additional duct and through the induction duct directly into the compressor inlet. As a departure from the prior art, no additional pressure reservoirs and no units generating compressed air are necessary in this embodiment so that the design is substantially simplified.
For the case where, in the lower load range, the required boost pressure determined in a closed-loop and open-chain control unit falls below a threshold value, the shut-off element is adjusted into a position opening the additional duct and reducing, in particular shutting off, the air supply to the compressor inlet. This achieves the effect that, even in the low-load range, the rotor rotational speed of the exhaust gas turbocharger is raised to such an extent that the compressor can generate an appreciable compressor output and the rotational speed can be sufficiently raised within a short time for the desired build-up of boost pressure to be realized. The supercharger rotational speed is held at a comparatively high level, even at low-load operating points, so that the transient behavior of the exhaust gas turbocharger is clearly
Fledersbacher Peter
Sumser Siegfried
Willand Juergen
Wirbeleit Friedrich
Crowell & Moring LLP
Daimler-Chrysler AG
Denion Thomas
Trieu Thai-Ba
LandOfFree
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