Machine element or mechanism – Rotary member or shaft indexing – e.g. – tool or work turret – Preselected indexed position
Patent
1988-10-26
1990-01-30
Wright, Dirk
Machine element or mechanism
Rotary member or shaft indexing, e.g., tool or work turret
Preselected indexed position
74867, B60K 4116
Patent
active
048965685
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an electric-hydraulic control for an automatic transmission.
THE RELATED ART
Electric-hydraulic controls are known, particularly for transmissions having only one primary shaft, wherein the output of a driving engine is directed over a hydrodynamic unit and this can be bridged with, for instance, a converter coupling. Pressure-and switch valves are therein arranged to insure that in emergency, such as a failure of the electric system, driving can continue. Normally, system failures present no insurmountable problem; since the drive in all speeds takes place over the hydrodynamic unit, it is possible to stop and then again to start, without turning off or throttling the engine.
However, more difficult problems arise when the output flow is directed over the hydrodynamic unit only in some of the speeds, for instance where Speed 1, 2 and R, and 4 is transmitted purely mechanically and Speed 3 by power split, which means partially purely mechanically and partially over the hydrodynamic unit.
It is therefore the object of the invention to further improve an electro-hydraulic control for a transmission with two primary shafts, so that in case of current-supply failure it is possible to continue to drive at a certain speed, to stop and to start again or even to drive in reverse.
SUMMARY OF THE INVENTION
An electro-hydraulic control for an automatic transmission is provided comprising:
a hydrodynamic unit having a turbine;
a driving unit having a driving shaft and delivering a driving output;
a first and second primary shaft, the shafts being respectively connected to the turbine and to the driving shaft;
a stepped-down planetary coupling gear receiving the driving output, the received output dependent upon a means selected from the group consisting of separate gear speeds and power-split gear speeds;
a selecting slide for choosing a neutral gear position, a drive gear position and a reverse gear position;
an electronic device communicating with the selecting slide with a plurality of solenoid valves kept in a zero position by a spring means communicating with the electronic device;
a hydraulic pressure means including a pressure source, pressure-and switch valves, and dampers for actuating speed shift couplings and brakes; and
an emergency valve designed as a stop valve capable of operating in mutual relationship the solenoid valves and shift couplings controlling a highest speed gear and reverse gear.
By providing an emergency valve between the solenoid valve and the shifting couplings, once for the mechanical speed and once for the R-speed, it is possible to actuate these couplings via the selecting lever, even when the solenoid valves fail. The coupling, commonly known as a clutch, which under normal operation conditions is used only for the R-speed, in the drive position of the selecting slide, can also be used for driving in connection with the hydrodynamic unit. As a result, starting in drive or reverse is also possible with the corresponding position change of the selecting slide.
Upon a current supply failure while the transmission is in drive gear, the shift coupling for the highest speed is actuated by hydraulic pressure to allow purely mechanical transmission through the second shaft to continue drive operation. A change in position of the selecting slide into a neutral gear position and again back into the drive gear position causes a repositioning of the emergency valve. Thereby it becomes possible through a drive coupling to drive over the hydrodynamic unit, the first primary shaft and also to start.
The emergency valve can comprise a recess sleeve valve having three control pistons on one end thereof with the same diameters, a control piston at a second end thereof with a larger diameter than that of the control pistons and a stop pin on the second end. A recessed cylindrical bore may be present wherein the sleeve valve is supported in an axially slidable fashion, the bore being provided with annular spaces cooperating with the control pistons.
REFERENCES:
patent: 4351206 (1982-09-01), Lemieux et al.
patent: 4393732 (1983-07-01), Suzuki et al.
patent: 4494423 (1985-01-01), McCarthy et al.
Dubno Herbert
Wright Dirk
Zahnradfabrik Friedrichshafen AG
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