Hydraulic servo-control of a servo-controlled gearbox
A hydraulic servo-control of a servo-controlled gearbox comprises hydraulic actuators defining chambers, a storing tank containing control fluid used by the actuators at room pressure, a hydraulic accumulator containing control fluid under pressure, a motor pump drawing the fluid from the tank and feeding it under pressure to the accumulator, and solenoid valves selectively connecting the chambers to the tank and accumulator. The accumulator includes an outer housing defining an inner cylindrical surface defining a first diameter, a piston arranged and axially slidable and mobile inside the housing and defining there a first variable-volume chamber for a gas and second variable-volume chamber for the fluid under pressure, and a limit stopper arranged at an open end of the housing, acting as a striker for the piston, and having an annular circlip defining an opening and overall second diameter approximating by excess the first diameter of the surface of the housing.
1. A hydraulic servo-control of a servo-controlled gearbox, the servo-control comprising:
a plurality of hydraulic actuators defining respective chambers;
a storing tank containing control fluid used by the hydraulic actuators;
a hydraulic accumulator containing control fluid under pressure and comprising an outer housing having a cup-shaped body with cylindrical symmetry, such that it defines an axis (X) and an upper wall, a lateral cylindrical wall coaxial to the axis (X) and an inner cylindrical surface having a first diameter (W); and a piston having a lateral cylindrical wall and a base wall with a diameter less than that of said lateral cylindrical wall, which is arranged inside the outer housing, and which is axially sliding and mobile inside the outer housing itself, and suited to define, inside the outer housing, a first variable-volume chamber (C 1 ) for a gaseous material and a second variable-volume chamber (C 2 ) for the control fluid under pressure and a limit stop, which is arranged at an open end of the outer housing, and acts as a striker element for the piston; wherein the outer overall diameter of the piston approximates the first diameter (W) of the inner cylindrical surface of the outer housing;
a motor pump that draws the control fluid from the storing tank and feeds the control fluid under pressure to the hydraulic accumulator;
a plurality of solenoid valves that selectively connect the chambers of the hydraulic actuators to the storing tank and hydraulic accumulator;
said limit stop having a annular circlip defining an opening and overall second diameter (Z) that approximates the first diameter (W) of the inner surface of the outer housing; wherein, in the condition in which the ends of the circlip defining the opening are arranged in contact with each other, the second overall diameter (Z) approximates the first diameter (W) of the inner cylindrical surface of the outer housing, wherein a stop limit is adapted to engage the circlip and wherein the circlip is housed in a seat of the inner cylindrical surface of the outer housing spaced longitudinally from the base wall of the piston so as to project toward the inside of the outer housing.
2. The servo-control as set forth in claim 1 , wherein a size of the opening of the circlip is no greater than about 1 mm.