Machine element or mechanism – Gearing – Interchangeably locked
Patent
1989-11-22
1991-11-26
Herrmann, Allan D.
Machine element or mechanism
Gearing
Interchangeably locked
74473R, F16H 536
Patent
active
050673629
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT/EP88/00424 filed 18 May 1988 and based in turn on German application P37 17 935.7 filed 27 May 1987 under the International Convention
FIELD OF THE INVENTION
The invention relates to a control device for a gearbox of group design. More particularly the invention relates to a transmission of group design, primarily for a farm tractor, wherein at least the gears of a standard transmission are changed mechanically by hand according to a standard H shifting pattern and an additional shifting is effected in two forward drive groups and one reverse drive group.
BACKGROUND OF THE INVENTION
Such a device is known from EP 00 52 794. As shown in FIG. 3 of this patent specification, four gears of the standard transmission are shifted mechanically by hand with the manual shift lever 20 from the gearbox according to an H pattern.
Furthermore, via a second gear-shift lever 40, the shifting of two drive gear groups and one reverse drive group takes place.
Such devices, or as shown in FIGS. 1 and 2, with a gear splitting that can be shifted up or down under load of the gears 1 to 4, have proven to be successful in farm tractors.
However, the mechanical two-lever shifting has high space requirements in the driver's cabin, and generally does not satisfy the demands imposed on modern from tractors.
OBJECTS OF THE INVENTION
It is therefore an object of the present invention to provide a control device for a transmission of the aforedescribed type with the simplest possible means.
Another object is to provide such a control system which requires no intervention in the gearbox and which permits the gears of the main gearbox to continue to be shifted mechanically so that it is possible to equip already existing farm tractors with the device.
SUMMARY OF THE INVENTION
This object is attained, according to the invention, in that a road travel gear group (S) and a farming operation group (A), as well as a reverse group (R) are engaged by means of a servo control on the manual gear lever for the gears in the standard transmission.
A gear-shift mechanism is arranged on the gearbox, this mechanism consisting of an electro-hydraulic control unit, a power-assisted servo control for shifting the groups and a transmission system for the gears in the basic transmission shifted manually according to an H-type shifting pattern.
Advantageously the servo control has solenoid valves, and a selector slide is permanently connected with a pressure source and is displaced by the pressure medium into two respective end positions and one middle position. For each position of the servo control and for each position of the selector slide, one of the solenoid valves is assigned. Via the three-position selector slide, a two-position shifting piston for the engagement and disengagement of the road travel group (S) and a three-position shifting piston for the farming operation group (A) and a reverse group (R), as well as a middle- and a zero-position are shifted via a control valve and a shift lever.
A pressure-cutoff valve is assigned to each end position of the two-position shifting piston which also has a command slide valve assigned to it.
To the three-position shifting piston, a command slide valve is assigned and to each end position, a pressure-cutoff valve can be assigned. For venting both piston spaces in the middle position both two-way valves are shifted.
Due to the single-lever shifting, the space requirements in the driver's cabin are reduced and the entire shifting operation is considerably simplified, since the driver need no longer reach from one gearshift lever to the other, in various driving situations. In addition, the shifting of the groups is facilitated. As a result of the combination in one shifting mechanism of all the elements involved in the power-assisted shifting of the groups and the manual shifting of the basic transmission, a simplification of the shifting arrangement results and there is no change in the gearbox, so that transmi
REFERENCES:
patent: 2582895 (1952-01-01), Young
patent: 3757598 (1973-09-01), Van Dest
patent: 4483210 (1984-11-01), Mayuzumi
patent: 4590817 (1986-05-01), Bennett
patent: 4905530 (1990-03-01), Stehle et al.
Dubno Herbert
Herrmann Allan D.
Trousdell William O.
Zahnradfabrik Friedrichshafen AG
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