Internal-combustion engines – Engine speed regulator – Having condition responsive means with engine being part of...
Reexamination Certificate
1999-04-29
2001-04-24
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Having condition responsive means with engine being part of...
C123S406500, C123S492000
Reexamination Certificate
active
06220221
ABSTRACT:
BACKGROUND
Bucking oscillations are vehicle longitudinal oscillations produced by energy introduction into the oscillation system engine-drive train-body, especially during acceleration of the vehicle. The engine torque is transferred via a flywheel to the drive train, which acts as a torsion spring and initially must be distorted under the influence of the engine torque. If this occurs by a rapid torque buildup, because of the kinetic energy stored in the flywheel, overshooting of the flywheel occurs, which manifests itself in the aforementioned category of bucking oscillations.
Prevention of bucking oscillations is known from DE 40 13 943 C2, in which the engine torque is influenced by controlled fuel injection as a function of the oscillation time of the bucking oscillation. An attempt is made to avoid longitudinal movements caused by bucking by a deliberate reduction or increase of engine torque in the corresponding phases of the bucking oscillation.
The method known from DE 40 13 943 C2 presumes that the oscillation period of the bucking oscillation is initially recorded. The engine torque curve is then influenced via fuel injection in counterphase to the bucking oscillation. This procedure has the drawback that, to record the oscillation period, the first bucking oscillation having the highest amplitude must be waited for before the bucking-attenuating measures can be taken, so that driving comfort is not improved to the desired extent. Another shortcoming is that the torque curve is countercontrolled to the bucking movement, which makes necessary rapid, consecutive buildup and reduction of the engine torque. This multiple torque change adversely affects the basic acceleration of the vehicle and causes a deterioration in exhaust behavior of the internal combustion engine.
A method to prevent interfering load change impacts in a vehicle internal combustion engine is also known from DE 37 38 719 C2. According to the method known from this document, to avoid vehicle longitudinal oscillations, the adjustment command given by the driver via the gas pedal is to be transferred in delayed fashion for a power control element, in which the delay is limited to the range of the zero passage of the torque curve. During abrupt load changes, the driver's desires are transferred with a delay to the engine control.
The method known from DE 37 38 719 C2 is only suitable to minimize load change impacts because of intervention in the region of the zero passage of the torque curve, but not to avoid bucking oscillations that ordinarily occur in the exclusively positive or exclusively negative torque region without zero passage.
The underlying problem of the invention is to reliably prevent bucking oscillations without adversely affecting the acceleration behavior and exhaust behavior.
This problem is solved according to the invention with the features of claim
1
.
SUMMARY
The torque curve is divided into two sections between the lower torque value and the upper torque value: a first section connected with the lower torque value with the local maximum and a second section adjacent to the upper torque value with the local minimum. In the first section, the drive train, starting from the lower torque value, is initially prestressed at the local maximum with a defined torque pulse or a first step. In the second section, the torque drops to the local minimum. The engine torque is further reduced during oscillation of the drive train from the local torque maximum to the local torque minimum; because of inertia of the drive train, this is prestressed, despite the already reduced torque. At the reversal point of the oscillation excursion, the engine torque reaches the upper torque value from the local minimum. The drive train is statically prestressed because of this at the moment of application of the upper torque value, and no or only strongly reduced bucking oscillations occur.
Another advantage is that acceleration of the vehicle is built up almost the same as during a torque step function, so that high agility is reached, but without the bucking oscillations that occur in a step function.
In an expedient modification the time interval between the lower torque value (in the case of a positive vehicle acceleration, the initial value) and the upper torque value (the target value) amounts to about ¼ to ½ of the oscillation time of the bucking oscillation, so that optimal oscillation compensation is achieved. This interval varies as a function of the selected function of the local maximum and is divided into a period of maximum and a period of minimum engine torque. If a rectangular pulse in the approximate form of a Dirac pulse is chosen as oscillation excitation to prestress the drive train as local maximum, the entire time interval for the maximum and the minimum can be shortened to ¼ of the oscillation time of the bucking oscillation. This curve has the advantage that the rise from the lower to the upper torque value is achieved in the shortest possible time, while avoiding bucking oscillations.
The local minimum connected to the local maximum can also have a rectangular curve. The amplitude can have a small value greater than zero, or can also be equal to zero.
If the time interval for the local maximum is increased, the amplitude of the maximum is preferably simultaneously reduced. With equal level of the local minimum, the duration of the minimum must be simultaneously short. Overall, the entire interval for the maximum and the minimum is increased to a maximum to half the oscillation time of the bucking oscillation. This variant has the advantage that it is sufficient to apply a lower level for the torque maximum; the bucking oscillations can nevertheless be equalized.
If the interval for the local maximum with the same amplitude is increased, the amplitude and time of the local minimum are reduced.
Instead of a rectangular function, a continuous function can also be chosen for the torque curve. It is particularly advantageous to provide a sloped curve with an intermediate point minimum between the maximum and the minimum and between the minimum and the upper torque value. The two slopes can be designed with different steepness, in which the slope between the local minimum and the upper torque value is steeper than the slope between the local maximum and the local minimum.
In the continuous curve no torque jumps occur; it can therefore be easily implemented technically.
Additional advantages and expedient variants can be gathered from the other claims, the description of the figure and the drawings. In the drawings:
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Flinspach Roland
Haller Andreas
Moser Franz
Daimler-Chrysler AG
Fuller III Roland A.
Solis Erick
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