Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2000-08-28
2002-03-19
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S084000, C701S087000, C477S155000
Reexamination Certificate
active
06360154
ABSTRACT:
BACKGROUND AND SUMMARY OF THE INVENTION
This application claims the priority of German Application 19940703.7, filed Aug. 27, 1999, the disclosure of which is expressly incorporated by reference herein.
The invention concerns a process and a device for engine and transmission control.
In motor vehicles with internal combustion engines, the speed and torque range of the engine is reproduced in the speed and torque range of the wheels through a transmission.
In older vehicles, an accelerator is connected directly with the throttle of a vehicle, so that an engine torque corresponding to the application of the accelerator results. This torque is transferred to the drive wheels according to the gear ratio. If a stepped automatic transmission is used between the propulsion engine and the drive wheels, then in this embodiment a step-shaped trace of the transmission output torque resulting from gear shifting is produced.
However, mechanically decoupling the accelerator from the throttle is also known. In U.S. Pat. No. 4,893,526, for example, a desired value for a transmission output torque is determined from the longitudinal speed of the vehicle and the position of the accelerator pressed by the driver. Thus, the accelerator position does not directly indicate the engine output torque, but rather ends up determining an output torque on the wheels which is directly dependent on the desired transmission output torque.
According to U.S. Pat. No. 4,893,526, a desired engine speed is determined depending on this transmission output torque, which is set by the adjustment of a continually adjustable vehicle transmission. The motor and the transmission are thus operated by an engine control or a transmission control, respectively.
A control is known from the VDI [German Engineering Society] Magazine, special issue “Abtriebstechnik” [Drive Technology], issue 134, March 1992, pp. 26-49, which determines a desired engine speed dependent on the throttle angle, and also sets that speed by adjustment of a continually adjustable transmission.
A system for setting a gear ratio is described in German Patent DE 196 26 936 A1, in which first a desired speed of the engine is determined, and the gear ratio of the transmission is adjusted depending on this desired speed. At least one of the dimensions influencing or representing the driving situation and/or the driving conditions is then determined and the determination of the desired speed of the motor is performed according to this dimension.
A process and a device for control of the drivetrain of a vehicle is known from German Patent DE 197 03 863 A1. While driving, a desired value for the output torque of the vehicle or for the transmission output torque, respectively, is preset. The different operating points of the drivetrain are characterized by output torques of the propulsion unit and speed gear ratios which differ as little as possible. Assessment dimensions are then determined for possible operating points while driving. An optimal operating point is then selected, and the transmission is set correspondingly. As an alternative to setting the gear ratio, the output speed of the propulsion unit corresponding to the operating point selected can also be set by an alteration of the gear ratio.
All of the above-mentioned technical literature is similar in that an engine speed is set by adjustment of the transmission. It is thereby possible to realize continuous wheel torque traces (e.g. hyperbolic traces of equal propulsion performance). In stepped automatic transmissions, this type of adjustment is not possible without further measures due to the discrete gear ratio changes.
In any case, a type of adjustment is also sought for stepped automatic transmissions that, in addition to other designs, allows the wheel output torque (wheel torque) to be changed continuously at a constant accelerator position over the vehicle speed. This relationship is shown in FIG.
7
. The black dashed lines indicate the relationship between the driving speed and the wheel torque at each fixed gear ratio (1
st
gear-5
th
gear) and maximum accelerator angle (engine full load). The solid black line shows the wheel torque trace when using a stepped automatic transmission with normal control at partial accelerator position (engine partial load). The white dashed line shows the physical maximum limit curve with decoupling of the throttle (engine full load) from the accelerator position (partial accelerator position). The hyperbolic gray solid line represents a wheel torque/vehicle speed trace for partial accelerator position as desired for reasons of drivability and driving performance (desired trace). Such a trace represents a continuous traction trace, for which essentially no discontinuities occur in the output torque trace if gear shifting is not considered.
The goal of the present invention is to reproduce this type of behavior with stepped automatic transmissions as well.
A further goal is to realize any desired wheel torque and/or transmission output torque which deviates from the hyperbolic shape without discontinuities. It is particularly noted that the wheel torque and the transmission output torque essentially correspond—apart from a multiplication factor.
The present invention provides drive management based on torque coordination. A torque of the drive wheels desired by the driver (wheel torque and/or transmission output torque) is realized, in that during, as well as outside of, a gear shift of the stepped automatic transmission, desired engine torques and consequently engine torque defaults, namely desired engine torque defaults affecting the filling and ignition, are calculated. These desired engine torques or engine torque defaults, respectively, are calculated by the totality of the torque coordinator, engine control, and transmission control and are converted within the bounds of physical limits. The actual transmission output torque is determined from the torque actually realized from the motor within the bounds of physical limits. Discontinuities are essentially avoided by the permanent realization of this transmission output torque, even during gear shifting.
When the stepped automatic transmission is not shifting gears, the desired torque is attained by calculating, depending on the gear ratio and the default transmission output torque, at least an engine torque default affecting the filling M_IND_ACC and/or an engine torque default affecting the ignition M_IND_GS. A definite engine torque should thereby be attained which, while shifting between the known gear ratios, provides exactly the default transmission output torque. The engine torque defaults M_IND_ACC and M_IND_GS are transmitted to the engine control and are realized by way of the control of the filling and ignition. In so doing, other parameters could possibly be included in the calculation and/or conversion of the engine torques in the controls (engine control and transmission control).
Within the physical limits of the engine, the torque defaults are generally fulfilled; the transmission output torque
10
is thus, except for shifting gears, adjusted. If the engine cannot achieve the torque default, a transmission output torque and/or wheel torque resulting from the realizable engine torque M_IND and the corresponding gear ratios is produced which deviates from the default.
During gear shifting of the stepped automatic transmission, the realization of the transmission output torque essentially occurs via a friction element provided in the stepped automatic transmission. A specific torque is transmitted corresponding to the control variable selected for the friction element. Therefore, the control variable is set during gear shifting so that exactly the desired transmission output torque is attained.
However, the load on the friction element during gear shifting from the friction output produced by slip can be problematic. To increase the service life of the friction element, it is therefore advisable to keep the friction output within a preset level. This type of adjustme
Krenn Helmut
Wolf Lothar
Bayerische Motoren Werke Aktiengesellschaft
Nguyen Tan
LandOfFree
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