Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Patent
1992-07-14
1994-05-24
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
F16H 6108
Patent
active
053138562
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to multistage transmissions and to processes for shifting multistage transmissions.
In conventional multistage transmissions having an input shaft and an output shaft arranged so that the output shaft is axially parallel to the input shaft and can be connected to the input shaft by a pair of gear wheels, the flow of torque from the drive engine through the transmission to the motor vehicle wheels must be interrupted when shifting into a new gear. The length of this interruption in driving force is determined by the period of time needed to synchronize the transmission gears which are to be engaged after shifting.
European Published Application No. 01 73 117 discloses a process for shifting a multistage transmission in which the driving torque of the engine is transmitted to the motor vehicle wheels through a temporary engageable gear stage during the interruption in driving force that occurs during the process of shifting to a higher gear. The temporary gear engagement takes place simultaneously with the interruption in driving force so that the driving torque of the engine is transferred in sequence first from the lower gear stage to the temporary gear stage and then to the higher gear stage in order to transmit a driving force during the shift-up process.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a process for shifting a multistage transmission which overcomes the disadvantages of the prior art.
Another object of the invention is to provide an improved shifting process for a multistage transmission in which the torque available for driving the motor vehicle during shifting has an especially favorable characteristic.
These and other objects of the invention are attained by partially engaging a temporary gear stage while the original gear stage is still engaged, disengaging the original gear stage while the temporary gear stage is at least partially engaged, and controlling the speed of the transmission input shaft as a function of an operating characteristic of the vehicle engine to synchronize the gears of the next gear stage to be engaged.
Thus, a gear stage for initiating the process of shifting up is engaged when the original gear stage is still engaged and the driving torque is divided in two paths in the multistage transmission. In other words, a portion of the torque is still transmitted through the original gear stage while the rest of the driving force is transmitted to the drive train through another gear stage. Finally, when the original gear stage is disengaged, e.g., after the driving torque transmitted through the path drops below a given level, only the other gear stage transmits the driving torque. Because of this branching of the driving torque, the torque available for driving the motor vehicle has an especially favorable characteristic.
At the same time, a change in the speed of the transmission input shaft is produced because of the driving torque transmitted through the additional gear stage. During this process, the transmission input shaft speed changes to a certain extent and this change has, for example, a negative speed gradient during the process of shifting up. As a result, a suitable driving torque is available at the transmission output even during the process of changing gears.
The process of shifting down is carried out similarly. In contrast to shifting up, the change in the speed of the transmission input shaft is positive because the input shaft turns at a faster speed in a lower gear than in a higher gear at the same driving speed. Accordingly, the change in speed has a positive gradient.
It is advantageous to provide feedback and control of this gradient for revising or adjusting the transmission input shaft speed. Deviation of the gradient from a given set point is thus minimized.
The gradient set point can be predetermined as a function of several other parameters. One of these parameters is the torque transmitted through the transmission input shaft before initiati
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Klarhoefer Christian
Schneider Arthur
Volkswagen AG
Wright Dirk
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