Internal-combustion engines – Engine speed regulator – Open loop condition responsive
Reexamination Certificate
1999-04-29
2001-03-13
Solis, Erick (Department: 3747)
Internal-combustion engines
Engine speed regulator
Open loop condition responsive
Reexamination Certificate
active
06199536
ABSTRACT:
The invention concerns a method to avoid bucking oscillations during acceleration of vehicles according to the preamble of claim
1
.
BACKGROUND
Bucking oscillations are vehicle longitudinal oscillations caused by introduction of energy into the engine-drive train-body oscillation system, especially during acceleration of the vehicle. The engine torque is transferred to the drive train via a flywheel, which acts as a torsion spring and must initially be distorted under the influence of the engine torque. If this occurs from a rapid torque buildup, overshooting of the flywheel occurs because of the kinetic energy stored in the flywheel, which manifests itself in the aforementioned category of bucking oscillations.
Measures can be taken to avoid bucking oscillations via which the engine torque is influenced in phase-directed fashion so that the longitudinal oscillations of the vehicle are prevented. Ignition angle adjustment, interventions in the fuel injection or deliberate influencing of throttle valve movement are considered as such measures. In the latter the gas pedal movement is ordinarily converted in attenuated fashion to movement of the throttle valve so that the throttle valve is opened with lower speed or time-delayed relative to gas pedal movement. In this procedure the bucking oscillations are reduced, but at the same time the response of the vehicle significantly deteriorates.
The problem underlying the invention is to prevent bucking oscillations reliably without adversely affecting acceleration behavior and exhaust behavior.
This problem is solved according to the inventions with the features of claim
1
.
SUMMARY
To accelerate the vehicle free of bucking, a specific engine torque trend that prevents bucking oscillations is converted by changing the throttle valve setting according to a stipulated function. This type of engine torque trend is achieved in that the trend of the throttle valve setting, starting from an initial closed position, is initially increased briefly to a local maximum, in which the throttle valve is opened. The throttle valve is then moved back to the closed position according to the local minimum in the throttle valve function and finally the target opening position is opened accordingly until the target torque value is reached. The trend of the throttle valve function is essentially independent of the trend of gas pedal movement.
Right after activation of the gas pedal, the throttle valve is acted upon according to the throttle valve function so that dead times between gas pedal movement and throttle valve movement are virtually avoided. An optimized engine torque trend is simulated by the rise to a local maximum and the subsequent fall to a local minimum, during which the drive train is excited by the application of a torque pulse in the prestress direction, oscillates further to the reversal point of the oscillation excursion during the local minimum and is exposed at the reversal point to the target torque value at full prestress. In this manner acceleration free of bucking with almost maximum possible agility can be obtained.
Another advantage lies in the fact that because of brief opening of the throttle valve in the region of the local maximum of the throttle valve trend, a rapid, delay-free filling of the intake tube of the internal combustion engine with intake air is made possible. Moreover, by direct driving of the throttle valve in the region of the local maximum, delays as a result of attenuated conversion of the gas pedal movement and, as a result, inertia of engine and control components, are avoided.
Adjustment of the throttle valve expediently occurs by an electrically operable control element, which is exposed to a current function through which the desired trend of the throttle valve setting is produced. The current function is advantageously designed as a roughly rectangular fiction with time-discrete current intervals that can be simply generated.
The current function preferably has an irregularity with which the local maximum in the trend of the throttle valve setting is simulated and which is designed as a brief rectangular pulse with high amplitude. The irregularity causes a very brief, partial opening of the throttle valve so that a significant rise in intake pressure and engine torque can be achieved. Because of this, the maximum vehicle acceleration is reached in the shortest possible time. 100% current of the throttle valve for 20 ms is already sufficient to open the throttle valve 20% and to achieve 50% of the maximum intake pressure, in which the maximum vehicle acceleration occurs free of bucking after about 180 ms.
In order to achieve the torque fiction responsible for startup free of bucking via the throttle valve setting, the time intervals of the different phases within the throttle valve function can be adjusted to the oscillation period of the bucking oscillation. The time interval between the initial closed position and the target opening position of the throttle valve expediently amounts to about ¼ to ½ of the oscillation time of the bucking oscillation, in which the precise value of this time interval depends on the amplitude and duration of the local maximum in the throttle valve function. If the local maximum is produced roughly as a Dirac pulse, the time interval for distortion of the drive train and bucking-free application of the target torque is reduced to ¼. If, on the other hand, the throttle valve function is stipulated in an easy to accomplish manner as a roughly sloped, continuous torque trend between the local maximum, the local minimum and the target torque value, the time interval rises to ½ of the oscillation period of the bucking oscillation.
In order to recognize an acceleration intention with reference to a gas pedal activation caused by the driver, the speed of the gas pedal is detected and a throttle valve change is preferably triggered for a case in which the gas pedal speed lies above a threshold value that can be determined as a function of different parameters, for example, as a function of the initial position of the gas pedal, the path difference between the initial position and the end position of the gas pedal, the engine speed and the presently engaged gear.
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Flinspach Roland
Haller Andreas
Moser Franz
Rink Günter
Daimler-Chrysler AG
Fuller III Roland A.
Solis Erick
LandOfFree
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