Power plants – Fluid motor means driven by waste heat or by exhaust energy... – With supercharging means for engine
Reexamination Certificate
1999-09-29
2001-04-24
Denion, Thomas (Department: 3748)
Power plants
Fluid motor means driven by waste heat or by exhaust energy...
With supercharging means for engine
C123S322000, C415S158000, C415S164000
Reexamination Certificate
active
06220032
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of 198 44 573.3-13, filed Sep. 29, 1998, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an engine braking process or operation for a supercharged internal-combustion engine, and more particularly, to an engine braking operation in which the engine has an exhaust gas turbocharger with a turbine with a variable turbine geometry which can be adjusted between a ram position with the smallest possible turbine cross-section and an opening position with the largest possible turbine cross-section.
DE 196 37 999 A1 discloses an internal-combustion engine which has an exhaust gas turbocharger having a turbine geometry which is variably adjustable by adjustable guide baffles. The guide baffles comprise guide blades which can be adjusted by an actuator to change the effective turbine cross-section of the turbine. As a result, depending on the operating condition of the internal-combustion engine, exhaust back pressures of different intensities can be implemented in the section between the cylinders and the turbine. Thereby, the power of the exhaust gas turbocharger can be adjusted according to the system requirements.
In order to achieve an engine braking effect in the braking operation of the internal-combustion engine, the guide baffles are changed into a ram position in which the turbine cross-section is reduced, whereby a high exhaust back pressure is built up. The exhaust gas flows at a high flow rate through the ducts between the guide blades and acts at a high impulse upon the turbine wheel. The turbine power is transmitted to the compressor. Thereupon, the combustion air fed to the engine is subjected to an increased charge pressure by the compressor.
As a result, the cylinder is acted upon on the input side by an increased pressure. On the output side, an increased exhaust back pressure exists between the cylinder outlet and the exhaust gas turbocharger. This exhaust back pressure counteracts the blowing-off of the air compressed in the cylinder into the exhaust gas pipe system. In the engine braking operation, during the compression stroke and push-out stroke, the piston must carry out compression work against the high excess pressure in the exhaust gas pipe system, whereby a strong braking effect is achieved.
SUMMARY OF THE INVENTION
An object of the present invention is to influence the action of the engine brake by simple measures so that a braking is possible which is adapted to different situations.
According to the present invention, this object has been achieved by a method in which in the engine braking operation, a permissible turbine cross-section band width within the range between the ram position and the opening position is defined for the adjustment of the variable turbine geometry. The turbine cross-section band width is bounded by a hard braking adjustment and a soft braking adjustment, which represent definable limit values. The hard braking adjustment is situated between the ram position and a drive starting position assigned to the fired drive operating mode, wherein the soft braking adjustment is situated between the drive starting position and the opening position, in the drive starting position. The turbine geometry in the fired drive operating mode assumes its smallest cross-section, in the hard braking adjustment, the engine braking power maximum is reached.
By defining two braking adjustments or braking positions of the variable turbine geometry, a band width is determined for the movement of the component influencing the effective turbine cross-section. Within this band width, the variable turbine geometry can take up different positions as a function of the actually existing situation. The hard and the soft braking adjustment mark limit values within the maximally possible positions, which are characterized by the ram position with a minimal turbine cross-section and the opening position with a maximal turbine cross-section.
The band width marked by the hard and the soft braking adjustment represents a cutout within the maximally possible positions of the turbine geometry limited by stops. In the hard braking adjustment, the effective turbine cross-section is further reduced than in the soft braking adjustment. Thereby, in the hard braking adjustment, a higher exhaust back pressure arises in the exhaust gas pipe system upstream of the turbine and a higher engine braking power can also be generated than in the softer braking adjustment. Arbitrary adjustments of the variable turbine geometry are conceivable between the two braking adjustments.
The hard braking adjustment and the soft braking adjustment are in a defined relationship with a starting position of the turbine geometry assigned to the fired driving operating mode. In the case of the fired drive, the turbine geometry assumes its smallest cross-section in the starting position in this operating mode. This cross-section, beginning from the starting position, is opened further with an increasing load or rotational speed. The turbine cross-section is normally opened further in the starting position than in the ram position.
According to the invention, the hard braking adjustment is now situated between the ram position with the smallest possible turbine cross-section and the starting position, and the soft braking adjustment is situated between the starting position and the opening position with the largest possible turbine cross-section. The two braking adjustments are therefore situated on this side and on the other side of the starting position for the fired operation.
As a result, on one hand, a sufficiently wide motion band is determined for the variable turbine geometry. This permits the generation of sufficiently high braking powers in the range of the hard braking adjustment. In addition, smaller engine braking powers in the range of the soft braking adjustment are permitted. On the other hand, the range of the adjusting path adjusting the variable turbine geometry is considerably reduced. It is sufficient to vary the adjustment of the variable turbine geometry in a smaller range which, however, includes the most important engine braking power sections. This has the advantage that a small adjusting path for the variable turbine geometry allows large changes of the engine braking power.
Because only relatively small adjusting paths must be applied, the turbine geometry can be adjusted between the different braking positions with low expenditures and within a short time. As a result, it is possible to rapidly react to new driving situations and influence the dynamic behavior of the vehicle.
If, for example, the turbine geometry is in the hard braking adjustment with a correspondingly high engine braking power, the charger will exhibit a fast response behavior. If the turbine geometry is in the soft braking adjustment with a correspondingly lower engine braking power, a uniform soft starting of the engine brake takes place, which results in lower forces onto the braked wheels and in smaller speed changes. In the case of a softer adjustment of the engine brake, a destabilizing wheel slip is avoided. In the case of a harder adjustment, maximal engine braking powers can be achieved. The change from the hard adjustment to the soft adjustment and vice-versa can be implemented with short adjusting paths and the lowest possible delay.
The starting position is expediently in the range of the largest gradient of the engine braking power—adjusting path curve. Slight changes in the adjusting path of the variable turbine geometry cause a maximal change in the engine braking power. The hard braking adjustment and the soft braking adjustment are situated on both sides of this point in the area with the high gradient, so that a large engine braking power spectrum can be covered by a short adjusting path.
The hard braking adjustment is situated in the engine braking power maximum which is situated close to the ram position while the opening of the turbine geometry is small. In the engine
Schmidt Erwin
Sumser Siegfried
Daimler-Chrysler AG
Denion Thomas
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Trieu Thai-Ba
LandOfFree
Engine braking process for a supercharged... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Engine braking process for a supercharged..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Engine braking process for a supercharged... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2435656