Arrangement for actuating a change-speed gearbox shift mechanism and for engaging and disengaging a main clutch

An arrangement actuates the shift mechanism of a change-speed gearbox and engages and disengages a main clutch via a common servomotor. The shift mechanism, with the interposition of an auxiliary clutch which can be engaged and disengaged by a servomotor, can be actuated independently of the main clutch.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application claims the priority of German application 196 35 867.1, 
the disclosure of which is expressly incorporated by reference herein. 
The present invention relates to an arrangement for actuating the shift 
mechanism of a change-speed gearbox and for engaging and disengaging a 
main clutch arranged upstream of the change-speed gearbox in the flow of 
force. In particular, an auxiliary mechanism transforms a rotary motion of 
a mechanism input member into a reciprocating motion of a mechanism output 
member allocated to the main clutch, and an auxiliary mechanism transforms 
a rotary motion of a mechanism input member into a reciprocating motion of 
a mechanism output member allocated to the shift mechanism. A device 
drives the mechanism input members of the two auxiliary mechanisms by a 
common servomotor, and a device couples and uncouples the mechanism output 
member allocated to the shift mechanism with regard to its drive 
connection relative to the device for driving the mechanism input members. 
In an earlier arrangement of the foregoing type known to the applicants, an 
electric motor is in drive connection. with the worm of a worm gear unit. 
The worm wheel is arranged in a Notionally fixed manner relative to the 
two mechanism input members used in the form of one eccentric each. The 
one eccentric interacts with a clutch disengaging lever of the main clutch 
and the other eccentric interacts with a fork-shaped link on the one lever 
arm of a differential lever. The other lever arm has a toothed segment 
which engages in a rack profile of a shift rod of the shift mechanism. 
Consequently, the clutch disengaging lever and the shift rod are in such a 
fixed kinematic allocation to one another that, during a gear shift, the 
main clutch is first always completely disengaged, then the instantaneous 
gear is disengaged, subsequently the shift lane of the new gear is 
selected (with a separate selecting device), then in further sequence the 
new gear is engaged, and finally the main clutch is re-engaged. This 
sequential progression of the actuations of the main clutch and shift 
mechanism leads in each case to a long shift time during the gear shifts. 
DE 43 36 446 A1 discloses an arrangement for actuating a main clutch to be 
provided in the flow of force between a drive motor and a change-speed 
gearbox. An electric motor is connected by a worm gear unit to an 
eccentric disc of an auxiliary mechanism for transforming a rotary motion 
into a reciprocating motion and the output member of the latter acts on 
the main clutch. The eccentric disc is also coupled to a spring-energy 
accumulator for assisting the clutch actuation. 
EP 0 527 389 A1 discloses a further arrangement for shifting a two-stage 
axle drive of a utility vehicle. A spring-energy accumulator, as a 
function of the position of a device (e.g., a clutch) controls the flow of 
force of the drive torque to the drive axle and can be connected in the 
shift-force transmission between the shift mechanism at the axle drive and 
an electric shift motor. Thereby, the shift is carried out only when the 
flow of force to the drive axle is interrupted. The electric motor acts on 
a worm gear unit, the worm wheel of which has an eccentric which engages 
in a slotted-link guide of the input member of the spring-energy 
accumulator for transforming a rotary motion into a reciprocating motion. 
An object of the present invention is to shorten the shift time in such an 
arrangement. This object is advantageously achieved according to the 
invention by providing that the two mechanism input members are connected 
to one another by an auxiliary clutch used as the device for coupling and 
uncoupling the mechanism output member allocated to the shift mechanism, 
and in that the auxiliary clutch, irrespective of the position of the 
mechanism output member allocated to the main clutch, can be engaged and 
disengaged by a clutch final control element derivable by a servomotor. 
In one embodiment of the arrangement according to the present invention, 
the basic configuration of the mechanical change-speed gearbox is not 
altered, but all shift and control elements can be adaptively arranged at 
the periphery of the surrounding zone of the gearbox. The shift times can 
be markedly reduced by activating the control functions at the same time 
or at overlapping times (declutching and shifting as parallel function 
steps). By the use of only one actuator and a few control elements, the 
overall complexity and thus the costs can be kept down without functional 
disadvantages having to be tolerated. 
In automated change-speed gearboxes, the problem may arise that, due to 
shifts always being associated with an interruption in tractive force on 
account of the gearbox design, a lack of comfort as a result of the 
occurrence of vehicle longitudinal vibrations may be felt in certain 
operating states (e.g. accelerating actions) due to the interruption of 
the drive moment. In the arrangement according to the present invention, 
therefore, it is of particular advantage that critical shift manoeuvres 
take place in a short time sequence. Declutching and shifting into neutral 
can be carried out at the same time in order to achieve the desired 
shift-time gain, in which case electronic engine management may be 
incorporated in the control. 
However operating states, e.g. driving downhill, also occur in which a 
sequential progression of the actuations of main clutch and shift 
mechanism is necessary from the functional point of view. In this respect, 
too, the arrangement according to the present invention provides the 
precondition for variable use of the individual functions in the control 
of the gear shift. 
In the arrangement according to the invention, a worm gear unit can be 
driven via an actuator (servomotor in electromechanical or hydraulic basic 
configuration). The worm gear unit activates, via an eccentric, the 
engagement and disengagement of the main clutch and, in sequence therewith 
or parallel thereto, the shifting and selecting action. Unlike a prior 
arrangement known to applicants, the shifting and selecting function in 
the arrangement according to the present invention can be initiated via a 
frictional or positive auxiliary clutch, which can be engaged and 
disengaged by a clutch final control element driven by a servomotor, such 
that an optimum operating sequence results. All basic functions performed 
here may be realized in a modular type of construction, including an 
electronic control unit for the shift sequence. 
In the arrangement according to the present invention, the shifting and 
selecting operations may be carried out in a manner previously described 
in U.S. patent application Ser. No. 08/818,358, filed Mar. 17, 1997 or 
according to German Application Serial No. 196 35 866.3-14. The relevant 
function units may likewise be accommodated in the drive module.

DETAILED DESCRIPTION OF THE DRAWINGS 
A change-speed gearbox shift mechanism 6 and a main clutch 7 arranged 
upstream of the change-speed gearbox in the flow of force are actuated by 
a common electric servomotor 15. The servomotor 15, via a rotary speed 
reducer device 14, acts with an output-side intermediate shaft 25 on a 
first auxiliary mechanism 8 for transforming a rotary motion into a 
reciprocating motion for engaging and disengaging the main clutch 7 and on 
a second auxiliary mechanism 11 for transforming a rotary motion into a 
reciprocating motion for actuating the shift mechanism 6. 
As seen in FIG. 2, the servomotor 15 is in direct drive connection with a 
coaxial worm 22 of a worm gear unit 21, the worm wheel 20 of which, like 
the one clutch half 23 of an auxiliary clutch 16, is arranged in an 
equally rotationally fixed manner relative to a coaxial intermediate shaft 
25. 
In FIGS. 2 and 3, the auxiliary mechanism 8 has a mechanism input member in 
the form of a cam plate 9, which is arranged in a rotationally fixed 
manner with regard to worm wheel 20 and intermediate shaft 25 and 
interacts with a follower in the form of a roller 26 which is rotatably 
mounted on the one end of a mechanism output member in the form of a 
linkage 10 performing reciprocating motions. The linkage 10 is operatively 
connected to the clutch disengaging lever of the main clutch 7. 
The other clutch half 24 of the auxiliary clutch 16, arranged with its 
clutch axis in alignment with the rotational axis 19--19 of the worm wheel 
20 and the intermediate shaft 25, is arranged in a Notionally fixed manner 
or in one piece with regard to an eccentric disc which is used as 
mechanism input member 12 of the second auxiliary mechanism 11 and has a 
crank pin 27. The latter (i.e., crank pin 27) is arranged eccentrically 
relative to the rotational axis 19--19 and is connected via a uniaxial 
joint 28 to a coupling rod 29. The coupling rod 29, in turn, is 
operatively connected via a further uniaxial joint 30 to the one linkage 
end of a linkage performing reciprocating motions as mechanism output 
member 13 of the auxiliary mechanism 11, in which case the linkage 13 can 
be used as a final control element of the shift mechanism 6 as described 
in aforementioned U.S. patent application Ser. No. 08/818,358, the 
disclosure of which is incorporated by reference herein. The final control 
element is arranged to be displaceable solely in the axial direction 
relative to a housing. 
The other clutch half 24 of the auxiliary clutch 16 can be disengaged from 
the one clutch half 23 by at least one disengaging spring 31 and, via a 
sleeve-shaped clutch final control element 18 which can be driven by an 
electromagnet 17, can be engaged relative to the one clutch half 23, 
irrespective of the particular position of the mechanism output member 10, 
allocated to the main clutch 7, relative to the rotational axis 19--19. 
It can be seen from the diagram of FIG. 4 that. a sequential progression, 
that is, a successive actuation of main clutch (cam train 7.sub.-- (4)), 
and shift mechanism (cam train 6.sub.-- (4)), was characteristic in a 
previous arrangement. If a shift signal, for example for a downshift from 
fifth gear to fourth gear, is activated at time t.sub.-- 0, first of all a 
time interval t.sub.-- 0-t.sub.-- 2, which is required for disengaging the 
main clutch, passes. An actuation of the shift mechanism begins at time 
t.sub.-- 2 to the effect that first of all the fifth gear is disengaged, 
in the course of which a time interval t.sub.-- 2-t.sub.-- 4 passes. A 
selecting motion for selecting the shift lane of the fourth gear is 
carried out at time t.sub.-- 4. This shift lane is reached at time 
t.sub.-- 6, so that the engaging of the fourth gear can be started, which 
is finally engaged at time t.sub.-- 8, and is followed by a last time 
interval t.sub.-- 8-t.sub.-- 9 for the re-engagement of the main clutch. 
Thereby, the shift time for the downshift "5-4" in the case of the prior 
art is equal to the time interval t.sub.-- 0-t.sub.-- 9. 
In contrast, a considerable shift-time gain 32 is obtained in the 
arrangement according to the invention for the same downshift from fifth 
gear to fourth gear according to FIG. 5. When the shift signal appears at 
time t.sub.-- 0, not only is the disengagement of the main clutch 7 
according to the cam train 7.sub.-- (5) activated but so too is the 
disengagement of the fifth gear via the shift mechanism 6 according to the 
cam train 6.sub.-- (5). 
The disengagement of the fifth gear need not necessarily start at time 
t.sub.-- 0 but may also take place earlier or later, but always still 
before time t.sub.-- 2, at which the disengaging action for the main 
clutch 7 has ended. Consequently, the fifth gear is also already 
disengaged at time t.sub.-- 1, i.e., also still before time t.sub.-- 2. 
The subsequent selection of the shift lane for the fourth gear has already 
ended at time t.sub.-- 3, so that the following engagement of the fourth 
gear has likewise ended very early, i.e. at time t.sub.-- 5, which is 
substantially earlier than the corresponding time t.sub.-- 8 in previous 
arrangements. If an equal time interval t.sub.-- 8-t.sub.-- 9=t.sub.-- 
5-t.sub.-- 7 for the re-engagement of the main clutch is taken as a basis 
in both cases, the shift-time gain 32 mentioned at the beginning for the 
"5-4" shift is obtained in the arrangement according to the invention. 
Instead of a cone clutch, other known frictional clutches, such as multiple 
disc clutches, electrodynamic (induction) clutches, or even known positive 
clutches, such as dog clutches, toothed clutches, driving-key clutches, 
etc., can also be used for the auxiliary clutch within the scope of the 
present invention. Likewise, instead of an eccentric mechanism, a crank 
mechanism or a rack-and-pinion arrangement can also be used for the 
auxiliary mechanism 11 in the arrangement according to the present 
invention. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.