Gear-shift device for a change-speed gearbox

In a gear-shift device for a change-speed gearbox, a shift actuator, a selection actuator, an actuator which is arranged such that it can be displaced exclusively axially with regard to a housing, an auxiliary transmission for converting a rotary motion into a reciprocating motion, a brake which is connected to the selection actuator and an engageable and disengageable locking device are arranged in terms of their action in such a manner that two of the three actuators are arranged fixed in terms of movement with respect to one another and are connected to the third actuator by the auxiliary transmission, and the selection actuator is fixed either in a rotationally fixed or axially undisplaceable manner with regard to the housing.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application claims the priority of German application 196 35 866.3-14 
filed in Germany on Sep. 4, 1996, the disclosure of which is expressly 
incorporated by reference herein. 
The invention relates to a gear-shift device for a change-speed gearbox of 
the type having multiple actuators A gear-shift device of the general type 
mentioned at the outset forms the subject-matter of pending U.S. 
application Ser. No. 08/818,358 filed Mar. 17, 1997 (based on 
corresponding German Patent Application 196 10 104.2-14), which is not a 
prior publication. 
In this gear-shift device, a selection control sleeve is arranged 
concentrically to a shift control shaft and is connected to the latter by 
the auxiliary transmission in the form of a gate/gate pin arrangement, the 
shift control shaft being connected, by a rod-like actuator, to a 
pressure-medium servomotor of the axial-piston design, while an 
electromagnet is used for actuating the brake acting on the selection 
control sleeve. The selection control sleeve is fixed immovably with 
regard to the housing in the longitudinal directions of the central axis, 
while the shift control shaft is latched by a latching device in its 
significant rotation-angle positions assigned to a respective shift gate 
for shifting one or two gears. In this gear-shift device according to the 
older patent application, it is already possible to shift gear from a 
current gear into a new gear while skipping at least one intermediate gear 
by causing the shift control shaft to execute a linear actuation motion 
which oscillates about the middle significant position and thus 
alternately engaging and disengaging the brake of the actuation control 
sleeve when passing through the middle significant position. In order, 
when skipping gears, to avoid an impact between the synchronization 
devices assigned to these gears by means of the shift control shaft, a 
certain free travel is provided for the shift control shaft. 
German Patent Document DE 41 37 142 A1 has disclosed a gear-shift device of 
another type, in which an electric motor is connected, by means of a 
helical gear mechanism for converting a rotary motion into a reciprocating 
motion, to a gear-shift rod which is mounted rotatably and axially 
displaceably in a housing and can be fixed with regard to the housing by 
means of an engageable and disengageable brake device in such a manner 
that the gear-shift rod is arranged to be exclusively axially displaceable 
in the engaged position of the brake, but in the disengaged position of 
the brake is arranged to be both axially displaceable and rotatable with 
regard to the housing. The gear-shift rod is directly connected to the 
motor shaft of the electric motor by means of a coupling which can be 
engaged and disengaged in opposite directions to the brake. When changing 
between selecting and shifting, both coupling and brake have to be 
reversed and the electric motor stopped. 
German Patent Document DE 43 09 027 A1 has disclosed a further gear-shift 
device of another type, in which a gear-shift shaft, which is arranged 
rotatably and axially displaceably with regard to a pressure-medium 
cylinder, can be moved by a first axial piston of the pressure-medium 
cylinder directly in the directions of the gear-shift shaft axis for 
shifting the gears. 
A second axial piston of the pressure-medium cylinder, with the aid of an 
auxiliary transmission for converting a reciprocating motion into a rotary 
motion with regard to the gear-shift shaft axis, causes the gear-shift 
shaft to perform rotary movements for selecting the shift gates. 
An object of the invention is to allow a gear-shift device of the type 
mentioned at the outset likewise to skip at least one intermediate gear 
when shifting from a current gear into a new gear, while dispensing with 
or largely avoiding special free travel for the shift actuator. 
The above-mentioned object is advantageously achieved according to the 
invention by providing a gear shift device for a change-speed gearbox, 
comprising: 
a housing, 
a shift actuator which is arranged rotatably and axially displaceably with 
respect to a central axis of the housing, 
a selection actuator which is coaxial with respect to the central axis and 
is arranged rotatably relative to the housing, the selection actuator 
being fixed with regard to the housing in the longitudinal directions of 
the central axis, 
an axial actuator which is coaxial with respect to the central axis and is 
arranged such that it can be displaced exclusively axially relative to the 
housing, 
an engageable and disengageable brake for fixing the selection actuator 
with regard to the housing in the circumferential directions of the 
central axis, and 
an auxiliary transmission for converting a reciprocating motion into a 
rotary motion, 
wherein two of the three actuators are both arranged such that they are 
fixed in terms of movement with respect to one another, at least in the 
longitudinal directions of the central axis, and are connected to the 
third actuator by the auxiliary transmission, 
wherein an engageable and disengageable locking device is connected in 
terms of action both to the selection actuator and to the brake in such a 
manner that the selection actuator can be fixed with regard to the housing 
alternately either exclusively in the circumferential directions or 
exclusively in the longitudinal directions of the central axis, and 
wherein the selection actuator is connected by the auxiliary transmission 
to the actuator which is arranged such that it can be displaced 
exclusively axially with regard to the housing. 
According to the invention, the shift actuator, when actuated into the 
rotation-angle position associated with the new gear, remains fixed 
immovably by the fixing device in the longitudinal directions of the 
central axis of the housing, so that special free travel for the shift 
actuator--in order to avoid impact between synchronization devices during 
this actuation--are not required, because the linear movement required for 
selecting the new rotation-angle position is performed only by the third 
actuator which is arranged such that it can be displaced exclusively 
axially with regard to the housing.

DETAILED DESCRIPTION OF THE INVENTION 
The following arrangement is common to the three embodiments of FIGS. 1 to 
5 of the gear-shift device according to the invention, and includes the 
following elements arranged coaxially with a central axis 7--7 of a 
housing 8 (not shown in more detail) of a change-speed gearbox (likewise 
not shown in more detail). 
(i) a shift actuator 9, in the form of a shaft, 
(ii) a selection actuator 10, in the form of a hollow shaft or sleeve, 
(iii) a rod-like actuator 11, and 
(iv) a pressure-medium servomotor 28 with a double-acting axial piston 29. 
The shift actuator 9 is designed to be fixed in terms of movement with 
regard to the selection actuator 10, or is integral therewith. The 
selection actuator 10 is connected, by means of an auxiliary transmission 
14 in the form of a helical gear mechanism for converting a reciprocating 
motion into a rotary motion, to the actuator 11 which is arranged such 
that it can be displaced exclusively axially with regard to the housing 8 
and is for its part connected fixedly in terms of movement to the axial 
piston 29. 
The shift actuator 9 can be actuated into a significant rotation-angle 
position (FIG. 3), in which an axial groove 21 on the outer circumference 
of the selection actuator 10 lies in a reference plane 30--30 of the 
housing 8, which plane contains the central axis 7--7. The axial groove 21 
is assigned to the shift gate 3-4 for optionally engaging forward gears 3 
and 4 in such a manner that by actuating the shift actuator 9 in the 
significant rotation-angle position in the directions of the central axis 
7--7 the forward gear 3 or 4 is either engaged or disengaged. 
The shift actuator 9 can be actuated into a further significant 
rotation-angle position (FIG. 3), in which an axial groove 22 on the outer 
circumference of the selection actuator 10 lies in the reference plane 
30--30. The axial groove 22 is assigned to the shift gate 1-2 for 
optionally shifting the forwards gears 1 and 2 in such a manner that by 
actuating the shift actuator 9, which is in the significant rotation-angle 
position, in the directions of the central axis 7--7 the forward gear 1 or 
2 is either engaged or disengaged. 
The shift actuator 9 can be actuated into a third significant 
rotation-angle position (FIG. 3), in which an axial groove 23 on the outer 
circumference of the selection actuator 10 lies in the reference plane 
30--30. The axial groove 23 is assigned to the shift gate 5-6 for 
optionally shifting the forward gears 5 and 6 in such a manner that by 
actuating the shift actuator 9, which is in the significant rotation-angle 
position, in the directions of the central axis 7--7 the forward gear 5 or 
6 is either engaged or disengaged. 
To actuate the shift actuator 9 into the respective significant 
rotation-angle position, the selection actuator 10 is fixed with regard to 
the housing 8, in the directions of the central axis 7--7, by means of an 
engageable and disengageable locking device 12, a locking engagement 
member 19 being engaged in a circumferential groove 20 on the outer 
circumference of the selection actuator 10 in such a manner that the 
selection actuator 10 is fixed so as to be undisplaceable exclusively 
axially. 
To actuate the shift actuator 9 in the directions of the central axis 7--7 
for the purpose of shifting the gears, the locking device 12 is disengaged 
and a brake 13, which is connected to the selection actuator 10, is 
engaged, a brake engagement member 18 passing into the axial groove 21 or 
22 or 23 which is respectively situated in the reference plane 30--30 in a 
rotationally fixed but axially displaceable manner relative to the 
selection actuator 10. 
The axial piston 29 has a significant stroke position 16, in which the 
shift actuator 9, in the unactuated position, adopts a rest position 16*, 
which is centered by return springs, at the transition between the shift 
gate 3-4 and a neutral selection gate 0--0 of the shift diagram of FIG. 6. 
In the rest position 16*, the shift actuator 9 is situated in the 
significant rotation-angle position of the switch gate 3-4, the brake 
engagement member 18 passing into the associated axial groove 21. 
In order to ensure that the locking device 12 and the brake 13 can be 
actuated only in the significant stroke position 16 of the axial piston 
29, a displacement sensor 15, which indicates the stroke position 16, is 
connected to a device which controls a servomotor 17 of the brake 13 but 
is not shown in more detail. 
In the first embodiment of the gear-shift device according to the invention 
in accordance with FIG. 1, the circumferential groove 20 of the locking 
device 12 is offset with regard to the axial grooves 21 to 23 of the brake 
13 in the longitudinal directions of the central axis 7--7, the brake 
engagement member 18 being connected to the locking engagement member 19 
by means of a differential lever 24 which is articulated with regard to 
the housing 8 in its middle region. 
In the second embodiment of the gear-shift device according to the 
invention in accordance with FIG. 2 and 3, the circumferential groove 20 
of the locking device 12 is arranged diametrically opposite, with regard 
to the central axis 7--7, to the axial grooves 21 to 23 of the brake 13, 
the brake engagement member 18 and the locking engagement member 19 being 
connected to one another by at least one hoop-like linkage 25 and/or 26, 
which surrounds the selection actuator 10, and the linkages being 
displaceably guided parallel to the reference plane 30--30 in a frame-like 
guide 31 which is fixed in terms of movement to the housing 8. 
In the third embodiment of the gear-shift device according to the invention 
in accordance with FIGS. 4 and 5, both the circumferential groove 20 of 
the locking device 12 and the axial grooves 21 to 23 of the brake 13 are 
arranged centrically with respect to a reference plane 27--27 of the 
selection actuator 10, which plane lies perpendicular to the central axis 
7--7. The axial grooves 21 to 23 lie within the rotation-angle region 
covered by the circumferential groove 20, the position 32* indicating a 
chord length corresponding to the dimension of the curve of the 
rotation-angle range. 
The circumferential groove 20 is situated in a radial bulge 33 of the 
selection actuator 10 and radially outwardly with respect to the axial 
grooves 21 to 23. The brake engagement member 18 of the brake 13 and the 
locking engagement member 19 of the locking device 12 are structurally 
combined to form a common engagement member 18 (19), which can alternately 
be engaged in the circumferential groove 20, on the one hand, or one of 
the axial grooves 21 to 23, on the other hand, by means of a linkage 4, 
which is connected in a manner not illustrated in more detail to the 
servomotor 17 of the brake 13. 
In all three embodiments of the gear-shift device, the linkage-coupling 
between locking device 12, brake 13 and servomotor 17 is made such that 
the selection actuator 10 is arranged to be either exclusively axially 
immovable or exclusively rotationally fixed with regard to the housing 8. 
The method of operation of the gear-shift device according to the invention 
is explained below with reference to a gear-shift sequence. 
When shifting up from second gear into third gear, the shift actuator 9 
initially adopts that rotation-angle position in which the axial groove 22 
assigned to the switch gate 1-2 is situated in the reference plane 30--30 
and accommodates the brake engagement member 18. By actuating the 
servomotor 28 into its significant stroke position 16, second gear is 
disengaged and the shift actuator 9 is moved into the shift gate 0--0 in 
the direction of the central axis 7--7. 
On reaching the significant stroke position 16, the displacement sensor 15 
reverses the servomotor 17 of the brake 13, so that the selection actuator 
10 is fixed in the longitudinal directions of the central axis 7--7 with 
regard to the housing 8 by the locking device 12. A subsequent controlled 
actuation of the actuator 11 by the servomotor 28 leads to a rotary 
movement of the shift actuator 9 into that significant rotation-angle 
position in which the axial groove 21 assigned to the switch gate 3-4 lies 
in the reference plane 30--30. When the shift actuator 9 reaches this 
rotation-angle position, the servomotor 17 is reversed again, as a result 
of which the brake engagement member 18 engages in the axial groove 21 and 
the locking engagement member 19 disengages from the circumferential 
groove 20. When the servomotor 17 reaches this position, the shift 
actuator 9 is actuated further by the servomotor 28, in the directions of 
the central axis 7--7, beyond the selection gate 0--0 and as a result 
third gear is engaged. 
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.