Machine element or mechanism – Gearing – Interchangeably locked
Patent
1996-12-12
1998-08-25
Marmor, Charles A.
Machine element or mechanism
Gearing
Interchangeably locked
477906, F16H 5900
Patent
active
057972940
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A transmission control of a powershift transmission of this kind has, in general, two forward clutches and two reverse clutches. The corresponding clutch is controlled by a reversing slide or a slide valve having a forward, a reverse and a neutral position. The operation of the slide valve by mechanical devices is already known. Therefore, rotary fingers are provided, for example, by which the slide valve is moved linearly. The rotary finger can be activated by the driver via a Bowden cable.
One disadvantage of the known mechanical solutions, however, is that they are relatively costly to actuate and that, in general, there is no other possibility of affecting or engaging the displacement of the slide valve.
Therefore, the problem on which this invention is based is to provide a shift valve of the kind mentioned above which is easier to actuate and in which, in addition to the normal kind of actuation of the main function, other kinds of actuation are possible when required.
The slide valve is now electro-hydraulically displaced according to the invention. The Bowden cable known for actuating the slide valve is not needed. The initiation or actuation is instead effected electrically such as by magnetic valves. The magnetic valves act, for example, when operating pressure lines, in the sense of raising the pressure by which the desired reversal or linear displacement of the slide valve is obtained.
This manner of actuation can be designated as a basic function. Very few parts are needed for this. In particular, mechanical communication with the driver is no longer required, since the magnetic valves can be easily activated by an electric control connection.
According to the invention, in addition to the above mentioned basic function, a second actuation system can be activated, for example, for emergency operation. In case of failure or interruption of the electro-hydraulic actuation, this system comes into force, according to the invention, in a manner such that if the normal control fails, the slide valve concerned can be correspondingly actuated by the centering piston. This means that it is possible, during an emergency situation, to bring the slide valves to a desired position. In this manner it can be prevented that in case of failure of the normal control, the vehicle, such as a tractor in which the transmission according to the invention has been installed, is no longer movable. If, for example, a displacement in the forward position is effected by an emergency actuation of the slide valve by the centering pistons, the vehicle can be adequately moved. By said emergency actuation, it is possible to continue the work of the tractor or to drive the tractor by its own force back to a yard or to a workshop. It is likewise possible to bring the slide valve to a neutral position by shutting off the engine. Thereby, it is possible, in the case of failure of the electro-hydraulic actuation, to preserve the blocked position of the valve. When the motor is restarted the transmission is assuredly in neutral.
BRIEF DESCRIPTION OF THE DRAWINGS
Advantageous developments and designs of the invention can be seen from the embodiments described herebelow in principle with the aid of the drawings. In the drawings:
FIG. 1 is a flow diagram of one embodiment;
FIG. 2 is the structural design of the shift valve according to the invention in section along line II--II in FIG. 3 of the first embodiment;
FIG. 3 is a section through the shift valve along line III--III in FIG. 2;
FIG. 4 is the structural design of the shift valve of the invention in section along line IV--IV in FIG. 5 of a second embodiment; and
FIG. 5 is a section of the shift valve along line V--V in FIG. 4 of the second embodiment.
DESCRIPTION OF PREFERRED EMBODIMENTS
In FIG. 1 only a simplified flow diagram is shown, since its design is basically known. Only the parts essential to the invention are described in detail there. In the structural embodiments shown in FIGS. 2/3 and 4/5, the same numerals are used for the same pa
REFERENCES:
patent: 3199647 (1965-08-01), Staab
patent: 3772933 (1973-11-01), Prenzel et al.
patent: 4041983 (1977-08-01), Bianchetta
patent: 4046165 (1977-09-01), Rose, Sr. et al.
Bohner Ulrich
Fideler Winfried
Charles Marcus
Marmor Charles A.
ZF Friedrichshafen AG
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