Zahnradfabrik Friedrichshafen, Ag.

Robert Marion

Hansjorg Dach

Horst Furtner

To control the changeover between different speed ratios in an automotive transmission, with the aid of hydraulically actuatable clutches and brakes, a 1-2 shift valve (70) and a 2-3 shift valve (90) responsive to a speed-dependent fluid pressure are subjected to a countervailing load-dependent fluid pressure generated by a throttle valve (40), under the control of the vehicular accelerator, above a predetermined intermediate point of the load range. Fluid for the actuation of the clutches and brakes, under a pressure rising in the lower part of the load range and remaining constant in its upper part, is delivered by a modulating valve (340) in cascade with the throttle valve, provided with a limitedly displaceable slider, or by cascaded modulating and limiting valves (350, 357).

Hydraulic gear-shift control for automotive transmission systems

Two concurrently operated hydraulic brakes of an automotive transmission, actuated in an intermediate-speed ('second gear') position, are filled under the control of a slide valve whose slider in a normal position admits fluid at high rate to both brakes and thereafter assumes an unstable throttling position in which the fluid pressure gradually builds up in them to a value causing an associated plunger to return the slider to normal. One of the brakes, which is only unidirectionally effective, remains actuated also upon an upshift into a high-speed position ('third gear') whereas the other, bidirectionally effective brake is released upon such upshift under the control of a shift valve which cuts off the fluid flow to the latter brake and establishes a drainage path therefor by passing the slide valve.

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Lindau, Germany

Robert Marion