A rocker arm assembly for an engine is configured to fit about a pivot shaft that extends along a central axis. The assembly includes an intermediate shaft configured to be rotatably disposed about the pivot shaft. A cam-side arm is pivotable about the central axis and is configured to be driven by a cam. A valve-side arm is pivotable about the central axis and relative to the cam-side arm, and is configured to convert rotation of the rocker arm assembly about the central axis into operation of an engine valve. An annular compressible fluid chamber is disposed between the intermediate shaft and the valve-side arm. When the cam-side arm and the intermediate shaft are engaged, pivoting of the cam-side arm compresses fluid within the chamber, causing corresponding pivoting of the valve-side arm and operation of the valve. The fluid provides hydraulic lash adjustment.

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 p.sub.1, a restoring energy accumulator preferably embodied as a spring (25), and at least one hydraulic basic pressure tank (40) having a lower pressure p.sub.0 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).

In order to ensure a simple, reliable and recuperative operation in a hydraulic drive (10) for accelerating and braking a gas exchange valve (20) of internal combustion engines or other reciprocating engines, it is proposed that a first pressure reservoir (41) for providing a first pressure p.sub.1 comprises a restoring energy accumulator, preferably configured as a spring (25), and at least one hydraulic base pressure reservoir (40), which has a lower pressure p.sub.0 than the first pressure reservoir (41). In a connecting line (48) between the first hydraulic pressure reservoir (41) and the working cylinder (22), a controllable opening (49) of a first valve (46) comprising at least one check valve (47) is arranged upstream or downstream in the flow path, which allows the pressure medium (30) to flow in the direction of working cylinder (22), but prevents a backflow towards the pressure reservoir (41). In order to also initiate the closing movement or to enable the breaking of the gas exchange valve in a hydraulically simple and reliable manner, in a second connecting line (58) between the first pressure reservoir (41) and the working cylinder (22) there is arranged a controllable opening (59) of a second valve (56) comprising a check valve (57), which prevents a flow in the direction of the working cylinder (22), but allows a return flow in the direction of the pressure reservoir (41).

In order to ensure a simple, reliable and recuperative operation in a hydraulic drive (10) for accelerating and braking a gas exchange valve (20) of internal combustion engines or other reciprocating engines, it is proposed that a first pressure reservoir (41) for providing a first pressure p.sub.1 comprises a restoring energy accumulator, preferably configured as a spring (25), and at least one hydraulic base pressure reservoir (40), which has a lower pressure p.sub.0 than the first pressure reservoir (41). In a connecting line (48) between the first hydraulic pressure reservoir (41) and the working cylinder (22), a controllable opening (49) of a first valve (46) comprising at least one check valve (47) is arranged upstream or downstream in the flow path, which allows the pressure medium (30) to flow in the direction of working cylinder (22), but prevents a backflow towards the pressure reservoir (41).

In order to also initiate the closing movement or to enable the breaking of the gas exchange valve in a hydraulically simple and reliable manner, in a second connecting line (58) between the first pressure reservoir (41) and the working cylinder (22) there is arranged a controllable opening (59) of a second valve (56) comprising a check valve (57), which prevents a flow in the direction of the working cylinder (22), but allows a return flow in the direction of the pressure reservoir (41).

A camless valve control system for an internal combustion engine, includes a hydraulic pump, with a rotating shaft timed to the operation of the engine and a hydraulic actuator configured to selectively open and close one of an intake valve and an exhaust valve of the engine. The hydraulic actuator includes a rotating cylindrical pump body and one or more control rings with holes channeling the flow of the hydraulic control fluid to affect the selective opening and closing of the one of the intake value and the exhaust valve. The pump body includes a cylindrical center portion configured to receive torque from the hydraulic pump and at least one channel providing a flow of hydraulic control fluid from the pump.

A camless valve control system for an internal combustion engine, includes a hydraulic pump, with a rotating shaft timed to the operation of the engine and a hydraulic actuator configured to selectively open and close one of an intake valve and an exhaust valve of the engine. The hydraulic actuator includes a rotating cylindrical pump body and one or more control rings with holes channeling the flow of the hydraulic control fluid to affect the selective opening and closing of the one of the intake value and the exhaust valve. The pump body includes a cylindrical center portion configured to receive torque from the hydraulic pump and at least one channel providing a flow of hydraulic control fluid from the pump.

A camshaft adjusting system (1) for a first camshaft (2) and a second camshaft (3) which are arranged concentrically with respect to one another is provided, with the second camshaft (3) being arranged within the first camshaft (2). A hydraulic camshaft adjuster (4) of the vane cell type is set up to adjust the first camshaft (2), and an electric camshaft adjuster (5) is set up to adjust the second camshaft (3). The second camshaft (3) is supported in the axial direction on a stator (6) of the hydraulic camshaft adjuster (4). Further, a camshaft adjusting unit is provided including the camshaft adjusting system (1) and two camshafts (2, 3).

A camshaft adjusting system (1) for a first camshaft (2) and a second camshaft (3) which are arranged concentrically with respect to one another is provided, with the second camshaft (3) being arranged within the first camshaft (2). A hydraulic camshaft adjuster (4) of the vane cell type is set up to adjust the first camshaft (2), and an electric camshaft adjuster (5) is set up to adjust the second camshaft (3). The second camshaft (3) is supported in the axial direction on a stator (6) of the hydraulic camshaft adjuster (4). Further, a camshaft adjusting unit is provided including the camshaft adjusting system (1) and two camshafts (2, 3).

An oil supply control device includes: a memory which stores first master data constituted by predetermined control value; a hydraulic controller which outputs the control value to an adjusting device to cause a hydraulic pressure to coincide with a target hydraulic pressure; and a determination portion which determines whether or not a first difference between an output control value and the control value of the first master data lies within a predetermined allowable range, wherein the hydraulic controller starts to control the adjusting device with use of the control value of the first master data, when the first difference lies within the allowable range, and starts to control the adjusting device with use of the control value of second master data, when the first difference does not lie within the allowable range, the control value of the second master data causing the first difference to lie within the allowable range.

An oil supply control device includes: a memory which stores first master data constituted by predetermined control value; a hydraulic controller which outputs the control value to an adjusting device to cause a hydraulic pressure to coincide with a target hydraulic pressure; and a determination portion which determines whether or not a first difference between an output control value and the control value of the first master data lies within a predetermined allowable range, wherein the hydraulic controller starts to control the adjusting device with use of the control value of the first master data, when the first difference lies within the allowable range, and starts to control the adjusting device with use of the control value of second master data, when the first difference does not lie within the allowable range, the control value of the second master data causing the first difference to lie within the allowable range.