GEAR-SHIFT DEVICE FOR MOTOR-VEHICLE GEARBOXES (PNEUMATIC GEAR-SHIFT SERVO DEVICE)

摘要

The invention concerns a gear-shift device (10) for, in particular, the gearboxes of motor vehicles. A control rod (20) in the shift device (10) can be moved longitudinally inside a piston rod (22) and operates, via a rod system (6, 8, 16, 18), together with a shift lever (4). Mounted on the piston rod (22) is a piston (114) on both sides of which a pressure medium can act, and the piston rod (22) operates in conjunction with means (24, 26, 28, 32) for shifting the gears in the gearbox. Moving the control rod (20) longitudinally in the piston rod causes control valves (100, 102, 106, 108) to be actuated by means of actuator pistons (92, 94). The gear-shift force exerted by the lever (4) and rod system (6, 8, 16, 18) on the control rod (20) is transmitted proportionally by the piston rod (22) to the means (24, 26, 28, 32) for shifting the gears in the gearbox. The two sides of the gear-shift device produce different forces, thus enabling different gears to be engaged using different gear-shift forces. These different forces are produced by different valve characteristic curves, the differences in the characteristic curves being due to differences in the areas of the actuator pistons (92, 94) and/or differences in the dimensions of the two opposite faces of the piston (114).