Automated drive train for a motor vehicle and method of controlling a drive train

Abstract

An automated drive train is provided for a motor vehicle comprising a single friction clutch, which is actuatable by a first actuator. A step transmission connected to the output side of the friction clutch comprises wheel sets to engage and disengage forward gears. A plurality of partial load positive gear shift clutches are provided which each include a synchronization means and which are actuatable by means of second actuators for engaging and disengaging the gears. A controller is provided for controlling the actuators such that the drive train is controlled to carry out a gear change under one of the three possible modes (A, B, C) depending on the conditions of the gear change to be made, wherein the three possible modes (A, B, C) of gear changes take place with an opened (C), a closed (B) or with a slipping (A) friction clutch (FIG. 6).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation of, and claims the benefit of U.S. patent application Ser. No. 09 / 737,898 filed Dec. 15, 2000, the contents of which are herein incorporated by reference.BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] The present invention relates to an automated drive train for a motor vehicle comprising a single friction clutch, which is actuated by an actuator and is connected at the input side to the motor of the vehicle, and a step transmission connected to the output side of the clutch. The transmission comprises a first plurality of wheel sets for engaging and disengaging corresponding forward gears and a corresponding plurality of positive gear shift clutches, each having synchronization means. The gear shift clutches can be actuated for engaging and disengaging the gears by a second plurality of second actuators. A controller coordinates the control of the first actuator with the second actuators. [00...

AI Technical Summary

Benefits of technology

[0023] With suitable configuration of the gear shift clutches, shifting can take place such that when the gear to be disengaged is initially still engaged the torque is completely transferred to the gear shift clutch of the gear to become engaged. This results in a condition of substantially no load for a short time on the gear shift clutch of the gear to be disengaged, so that this gear is easily disengaged in this short time interval. In the following synchronizing phase of the gear changer for the gear to be engaged, the input side friction clutch remains at least partially closed, so that the torque from the motor is transferred via the friction clutch working in slip operation and via the synchronization means for the gear to be engaged to the drive wheel of the vehicle.

[0043] Finally it is preferred in modes A, B that the torque input to the shift transmission, after having disengaged the previously engaged gear, is reduced for a short time, after reaching the synchronization speed and during the engagement of the gear to be engaged. This reduces or completely avoids differences in rotary speed when transferring the torque from the synchronizer to the idler of the associated wheel set.

Problems solved by technology

While the traction force decrease when changing gears by manual shifting is considered to be not particularly unpleasant, the associated “nicking” of the automobile is considered to be less comfortable when the step transmission is automated.

The traction force interruption is found to be uncomfortable, because with an automated step transmission, the driver is not occupied during gear changing.

However, when shifting in the lower gears, a considerable traction force decrease still occurs because the torque of the sixth gear is considerably less than that of the lower gears.

In the transmission of DE 44 01 812, the construction is comparatively complicated due to the double clutch arrangement at the input side.

Further, the traction force support can only maximally transmit the torque of the sixth gear to the drive wheels.

The complexity of DE 29 24 656 is also considerable, in particular due to the free wheel for the first gear.

The true double clutch transmission, as disclosed in DE 38 123 27 requires not only constructive complexity due to the two clutches, a comparatively long hollow shaft construction is necessary which makes the transmission expensive.

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