Pressure reservoir for exerting pressure on a hydraulic system, with which preferably a gas exchange valve of an internal combustion engine is actuated

A hydraulic system (10) for actuating a gas exchange valve (12) of an internal combustion engine (14), the system including a fluid reservoir (34), a fluid pump (36), a fluid line (38, 42, 44, 54, 60), a pressure reservoir (62) that communicates with the fluid line (38, 42, 44, 54, 60) and has a housing (64, 68) and a piston (72) prestressed in operation by prestressing means (88, 90), and an actuating device (16), which communicates via a valve device (48, 56) with the fluid line (38, 42, 44, 54, 60) and actuates the gas exchange valve (12), the prestressing means (88, 90) having a characteristic force-travel curve, in one range of motion of the piston (72), that has a slope which differs from the slope in a different range of motion of the piston (72), and including at least two series-connected springs (88, 90), the stiffness of at least one spring (88) differing from that of at least one other spring (90), wherein the pressure reservoir (62) further comprises an elongated part (80) with two end portions (82, 84) and one support portion (86), which is disposed between the end portions (82, 84) and has a larger outer dimension than the end portions (82, 84) and on which two adjacent springs (88, 90) are braced, the at least one spring (88) being tightened in operation between one side of the support portion (86) and the piston (72), and the at least one other spring (90) being tightened between the other side of the support portion (86) and a housing portion (68).