Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-09-07
2001-10-02
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C060S280000, C060S295000
Reexamination Certificate
active
06295817
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of 198 40 629.0-13, filed Sep. 5, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a drive assembly for a vehicle having an internal-combustion engine for delivering driving energy, an exhaust gas turbocharger which has a turbine and a compressor, with the turbine being driven by exhaust gases of the internal-combustion engine and the compressor being driven by the turbine, and an air guiding system which feeds fresh air to the compressor in which it is compressed to form charge air. The air guiding system guides the charge air from the compressor to the internal-combustion engine.
In known drive assemblies, an exhaust gas turbocharger is normally used for increasing the power of an internal-combustion engine. This exhaust gas turbocharger has a turbine driven by exhaust gases of the internal-combustion engine and a compressor driven by the turbine. Fresh air, which is normally taken in from the atmospheric environment of the vehicle via an air filter, is compressed to form charge air which is then supplied from a compressor to the internal-combustion engine for the combustion. As the result of the compression, a larger flow rate is obtained which permits an increase of the power of the internal-combustion engine.
Because the exhaust gas turbocharger of a drive assembly is normally designed for the full-load operation at high rotational engine speeds, the exhaust gas turbocharger can cause only a relatively low compression of the fresh air at low rotational engine speeds. In such a low rotational speed range of the internal-combustion engine, a power increase can hardly be achieved with the exhaust gas turbocharger. The compressor will generate a sufficient supercharging only at higher rotational speeds. By way of the increased air flow rate and the correspondingly enlarged fuel flow rate, this supercharging causes, on one hand, a power increase of the internal-combustion engine and, on the other hand, an increased exhaust gas temperature and a raised exhaust gas pressure, whereby the power output of the turbine is considerably increased. Because of this feedback, the internal-combustion engine can rapidly supply a high power as soon as the turbocharger “responds”; i.e., as soon as a sufficient supercharging takes place by the compressor. Normally, a so-called “turbohole” exists at low rotational speeds until the turbocharger responds.
In order to improve the efficiency of a supercharged internal-combustion engine also in the range of low rotational speeds, a large number of different suggestions have been made.
For example, U.S. Pat. No. 3,673,797 describes a drive assembly in which the driving power of an internal-combustion engine is increased by a turbine driven by the exhaust gases of the internal-combustion engine. The turbine feeds its driving power into a differential gearing which interacts with the transmission line of the internal-combustion engine. In this manner, the driving power of the internal-combustion engine is increased directly by the driving power of the turbine. This turbine also has, however, a turbohole at low rotational speeds of the internal-combustion engine.
In addition, in this drive assembly, a second differential gearing is arranged in the transmission line driven by the internal-combustion engine and the turbine. By way of the second differential gearing, a compressor is driven which compresses fresh air and feeds it as charge air to the internal-combustion engine. The compressor, which is mechanically driven in this manner, therefore indirectly also increases the driving power of the internal-combustion engine. Such a mechanically driven compressor has no very pronounced turbohole like that associated with an exhaust gas turbocharger so that, also at lower rotational speeds, a power increase can be achieved here by supercharging the engine.
Furthermore, the known drive assembly has another compressor which is driven by the turbine and compresses fresh air which is then supplied either in series to the other compressor or in parallel thereto to the internal-combustion engine. A drive assembly constructed in this manner can be implemented only at very high expenditures.
SUMMARY OF THE INVENTION
An object of the present invention is to overcome the problems associated with the known drive assembly in a constructively simple manner such that the efficiency of an associated internal-combustion engine is increased in the low rotational speed range.
According to the invention, this object has been achieved by a drive assembly in which an additional compressor is provided to generate compressed fresh air which, as a function of the requirements, can be fed to the air guiding system upstream of the internal-combustion engine. A compressor which already exists in the vehicle for different purposes can be used as the additional compressor.
The invention is based on the recognition of the advantages of using an air compression device already contained in the vehicle for basically any purpose, such as a compressor or a blower, for increasing the pressure level of the air supplied to the internal-combustion engine for the combustion.
By way of the measure suggested according to the present invention, with existing drive assemblies, only constructively simple changes have to be made which, in addition, can be carried out in a low-cost and simple manner to arrive at the drive assembly according to the invention.
The invention utilizes the recognition that even a relatively low rise of the pressure level of the fresh air supplied to the internal-combustion engine is sufficient for causing a response of the turbocharger at low rotational speeds. The reason is that even a slightly raised pressure results in an increased rate of air flow and thus in an increased fuel supply, whereby the exhaust gas temperature and the exhaust gas pressure and thus the exhaust gas enthalpy are increased so that the turbine can immediately transmit more power to the compressor. This feedback will then rapidly build up so that the exhaust gas turbocharger will respond. In this manner, the turbohole is shifted to lower rotational speeds, in the direction of an idling speed.
Corresponding to an advantageous embodiment, the compressed fresh air generated by the additional compressor is fed into the air guiding system in front of the compressor so that a raised pressure level is already supplied to the compressor. This has the result that the pressure raise caused by the additional compressor does not have an additive but a multiplicative effect on the charge air pressure generated by the compressor. Thereby, the exhaust gas turbocharger responds at still lower rotational speeds.
According to the invention, the use of any compression device which is already contained for another purpose in the vehicle is usable for generating compressed fresh air. Such compression devices are, for example, a compressed-air pump of a level control system, a compressed-air pump of a pneumatic spring system and the like. The use of such an air compression device already existing in the vehicle is, among other reasons, also possible because, on one hand, only a slight raising of the pressure level is required for achieving the desired effect. On the other hand, the above-mentioned air compression devices are typically not required by the pertaining vehicle systems (such as the level control system, the pneumatic spring system, etc.) in operating phases in which a power increase is to be achieved by way of these air compression devices. In addition, such pneumatic systems of the vehicle normally have compressed-air storage devices so that the pertaining air compression device can also take over a different function in the vehicle for a short time.
Corresponding to a particularly advantageous embodiment of the drive assembly according to the invention, a secondary air compressor is used for the precompression. This secondary air compressor is used in the case of an internal-combustion
Abthoff Joerg
Pfaff Ruediger
Wiltschka Joachim
Crowell & Moring , L.L.P.
Daimler-Chrysler AG
Denion Thomas
Trieu Thai-Ba
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