Hydraulic Drive for Accelerating and Braking Dynamically Moving Components

Abstract

The aim of the invention is to ensure that a hydraulic drive (10) for accelerating and braking a gas exchange valve (20) of internal combustion engines or other reciprocating engines operates in a simple, reliable and recuperative manner. To this end, a first pressure tank (41) for providing a first pressure p1, a restoring energy accumulator preferably embodied as a spring (25), and at least one hydraulic basic pressure tank (40) having a lower pressure p0 than the first pressure tank (41) are provided. A controllable opening (49) of a first valve (46) is arranged with at least one non-return valve (47) located upstream or downstream of the opening in the flow path, in a connection line (48) between the first hydraulic pressure tank (41) and the working cylinder (22), said non-return valve allowing the pressure medium (30) to flow towards the working cylinder (22) but preventing it from flowing back towards the pressure tank (41). In order to also initiate the closing movement or the braking of the gas exchange valve in a hydraulically simple and reliable manner, a controllable opening (59) of a second valve (56) is arranged in a second connection line (58) between the first pressure tank (41) and the working cylinder (22), with a non-return valve (57) that prevents flow towards the working cylinder (22) but allows backflow towards the pressure tank (41).

What is claimed is: 
     
         1 . A hydraulic drive for accelerating and braking dynamically moving components, in particular valves in gas exchange controls of internal combustion engines and other reciprocating engines, wherein the hydraulic drive comprises the following:
 at least one component to be driven, in particular a valve, preferably a gas exchange valve or a plurality of gas exchange valves which can be actuated jointly via a valve bridge, of an internal combustion engine or another reciprocating engine;   a working cylinder with comprising a pressure acting surface of a drive piston,   at least one first pressure reservoir for providing a first pressure p 1  of a hydraulic pressure medium,   at least one restoring energy accumulator with a biasing force F Fv , preferably configured as a spring, which engages at the component or at the gas exchange valve, respectively,   at least one hydraulic base pressure reservoir, which has a lower pressure p 0  than than that of the first pressure reservoir,   characterized in that   in a first connecting line between the first hydraulic pressure reservoir and the working cylinder there is provided a controllable opening of a first valve comprising at least one, preferably spring-loaded, check valve, which is arranged serially in the flowpath upstream, within or downstream, allowing the pressure medium to flow in a direction towards the working cylinder but preventing a backflow in a direction towards the pressure reservoir.   
     
     
         2 . The hydraulic drive according to  claim 1 , characterized in that in a second connecting line between the first pressure reservoir and the working cylinder there is provided a controllable opening of a second valve comprising at least one, preferably spring-loaded check valve, which is arranged serially in the flowpath upstream, within or downstream, preventing a flow in a direction towards the working cylinder, but allowing a backflow in a direction towards the pressure reservoir. 
     
     
         3 . The hydraulic drive according to  claim 2 , characterized in that the drive comprises at least a second pressure reservoir with a pressure p 2 , and that the controllable opening of the second valve is connected with this second pressure reservoir instead of with the first pressure reservoir, wherein the pressure (p 2 ) of the second pressure reservoir is preferably between the pressure of the hydraulic base pressure reservoir p 0  and the first pressure p 1  and is preferably chosen so low that the gas exchange valve can reliably swing back onto the valve seat during the closing process. 
     
     
         4 . The hydraulic drive according to  claim 1 , characterized in that the biasing force F Fv , of the restoring energy accumulator is adjustable. 
     
     
         5 . The hydraulic drive according to  claim 1 , characterized in that the restoring spring accumulator is configured with a progressive spring characteristic. 
     
     
         6 . The hydraulic drive according to  claim 1 , characterized in that at least the controllable opening of the first valve and the controllable opening of the second valve are combined to form a valve unit with a mutual actuator, wherein the combined valve unit is preferably configured as a 3/2-way valve or as a 4/2-way valve. 
     
     
         7 . The hydraulic drive according to  claim 1 , characterized in that in a connecting line between the working cylinder and the base pressure reservoir there is arranged a third controllable opening of a third valve, wherein a—preferably adjustable—throttle is arranged in the flow path upstream, within or downstream of the third valve. 
     
     
         8 . The hydraulic drive according to  claim 1 , characterized in that the controllable opening of the third valve opens in a time-controlled manner shifted by a predetermined time after opening of the second valve, the time preferably being selected such that the second check valve at this time has already closed again and keeps the gas exchange valve fixed in this position. 
     
     
         9 . The hydraulic drive according to  claim 8 , characterized in that the third valve has a closed intermediate position and that during the opening of the second valve the resetting movement of the third valve, which is preferably driven by a spring, is unlocked and started, whereby pressure medium is displaced via a pressure acting surface of the valve and driven through a throttle so that the intermediate position of the valve is traversed only slowly and the cross-section opens only after a desired delay time. 
     
     
         10 . The hydraulic drive according to  claim 6 , characterized in that the third valve is configured as controllable by pressure only or as controllable by pressure in addition to another actuation, namely by the pressure in the working cylinder, in such manner that it opens below a switching pressure level and closes above this pressure level, wherein this pressure level is preferably slightly higher than the pressure in the base pressure reservoir and significantly lower than the pressures in the first or second pressure reservoir. 
     
     
         11 . The hydraulic drive according to  claim 7 , characterized in that the transition cross section from the working cylinder into the connecting line is configured in such manner that upon approaching the gas exchange valve to the valve seat it is reduced by a control edge of the drive piston, whereby the gas exchange valve is braked and touches down gently on the valve seat. 
     
     
         12 . The hydraulic drive according to  claim 7 , characterized in that the connecting line splits up into two connections at the working cylinder, whereby, when the gas exchange valve approaches the valve seat, the first connection is cut off by the control edge of the drive piston whereas the second connection is guided by means of a fixed or adjustable throttle in such manner that the gas exchange valve is braked and touches down gently on the valve seat. 
     
     
         13 . The hydraulic drive according to  claim 1 , characterized in that the first valve and/or the second valve and/or the third valve is configured as a rotary slide valve, wherein the rotary slide valve or the rotary slide valves is/are synchronously driven at a fixed rotational speed ratio relative to the working cycle frequency of the reciprocating engine or of the internal combustion engine. 
     
     
         14 . The hydraulic drive according to  claim 13 , characterized in that the phase angle, at which the rotary slide valve opens, is adjustable with respect to a reference point in the working cycle of the reciprocating engine or of the internal combustion engine. 
     
     
         15 . The hydraulic drive according to  claim 2 , characterized in that the biasing force F Fv  of the restoring energy accumulator is adjustable. 
     
     
         16 . The hydraulic drive according to  claim 3 , characterized in that the biasing force FFv of the restoring energy accumulator is adjustable. 
     
     
         17 . The hydraulic drive according to  claim 2 , characterized in that the restoring spring accumulator is configured with a progressive spring characteristic. 
     
     
         18 . The hydraulic drive according to  claim 3 , characterized in that the restoring spring accumulator is configured with a progressive spring characteristic. 
     
     
         19 . The hydraulic drive according to  claim 4 , characterized in that the restoring spring accumulator is configured with a progressive spring characteristic.