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).

Even in the case where, due to distortion (undulation) or the like of an end surface of an adjusting screw abutting on a valve stem end, there exists a non-linear undulation movement amount in a movement amount of the end surface with respect to a rotation return angle of the adjusting screw, the undulation movement amount is continuously measured, and a screw return movement amount based on a screw pitch and on the rotation return angle is continuously calculated, and, when a total movement amount of the undulation movement amount and the screw return movement amount has attained a prescribed clearance, return rotation is ended.

A valve arrangement is provided for supplying air to a combustion chamber of an internal combustion engine, the valve arrangement including a first valve, the first valve including a first valve head, a first valve stem and an internal cavity, which is partly located in the first valve stem and open towards a lower surface of the first valve head, a valve guide arranged to surround a portion of the first valve stem such that the first valve stem is movable in the valve guide along a longitudinal direction between an upper, closed position of the valve, and a lower, open position, in which open position air may be supplied to the combustion chamber past the first valve head, the valve guide including an air passage allowing supply of additional air to the combustion chamber via the internal cavity in the first valve, when the first valve is in its closed position. The valve arrangement includes a guide leakage preventing means for preventing liquid from leaking from a region externally of the first valve stem to the valve guide air passage.

In the coil spring of the present invention, a helical space defined by a space between coils has a first end region whose space is increased as it extends towards the other side in the axial direction from a first reference point where the space is zero, a reference region whose space is set at a reference value L (L>0), and a second end region whose space becomes narrow as it extends toward the other side in the axial direction and zero at a second reference point. The first end region has a first end outer part and a first end inner end. In a case where a pitch angle of the space between coils that causes the displacement of the space between coils per turn of the helical space to be L is a reference pitch angle Pa, the pitch angle in the first end outer part is set at Pa while the pitch angle in the first end inner part is set at Pb (Pb>Pa).

An internal combustion engine switches valve operation states, reduces or prevents wear of a cam and a rocker arm, and reduces the size of the cylinder head to ensure a sufficient valve lift amount. A valve spring retainer includes a cylindrical portion including a first through hole with an inner diameter decreases from the first end portion toward the second end portion, a cone-shaped portion including a second through hole with an inner diameter increases as it extends away from the second end portion of the cylindrical portion, and a flange portion extending radially outward from the cone-shaped portion. An outer diameter of the cylindrical portion is constant from the first end portion to the second end portion, and an outer diameter of the cone-shaped portion increases as it extends away from the second end portion.

A decompression shaft (56) of a decompression device (50) includes an engagement pin (53) that is guided by a guide groove (51a) formed in a decompression weight (51), a decompression cam (54) that is provided on one cam surface of an intake valve cam (25c) and an exhaust valve cam (25b) so as to advance and retreat, and a connection portion (55) that connects the engagement pin (53) and the decompression cam (54). The decompression weight (51) is formed with a rotation restricting groove (51e) that restricts rotation of the decompression shaft (56) when a force acts in a direction in which the decompression cam (54) moves on the decompression shaft (56) from an advanced position to a retracted position when an engine (E) is stopped and that is continuous with the guide groove (51a).

The present invention concerns a method and a device for electrically controlling a valve actuator in a two-stroke or four-stroke combustion engine where the actuator comprises a solenoid (A), a plunger (5) and a spring (6), wherein the engine has at least one cylinder (1) with at least one freely controllable engine valve disc (10) with corresponding valve stem (11) and a valve spring (4), where a distance (7) is provided between the lower end of the plunger and the upper end of the valve stem and where air is supplied, or exhaust gases are evacuated from, a combustion chamber (3) past a lower part of the valve stem with the valve disc via at least one channel (2) in the cylinder, wherein the valve actuator is activatable to open the engine valve. The invention is characterized in that the opening of the engine valve is initiated after activation of the solenoid, wherein the following acceleration of the plunger brings its lower end to strike the upper end of the valve stem for initial opening of the valve.

An internal combustion engine includes, as a lost motion spring that urges a rocker arm toward a cam, a compression coil spring supported on a cylinder head. A shaft is located on an inner side of the compression coil spring and extends along a winding axis of the compression coil spring. The internal combustion engine significantly reduces or prevents a decrease in the fuel efficiency and an increase in the size of the variable valve mechanism, while surging is unlikely to occur while running at a high speed, and it is possible to reduce the size or the weight of the rocker arm.

A modular cylinder head is configured for use with combustion engine block configurations each having different valvetrain oiling pathways. Thus, when used with “LA-style” engine blocks, oil receiving/delivery ports provided by the cylinder head are compatibly interfaced with an oil outlet port provided by the engine block, thus allowing oil to pass from the engine block into the head for delivery to a valvetrain carried thereby. Alternatively, when the head is used with “Magnum-style” engine blocks, the oil receiving/delivery ports of the head are not used. Rather, a pushrod and lifter having internal ports are used by the cylinder head to allow oil to pass from the engine block, through the internal ports of the lifter and pushrod, and into the valvetrain.

A valve seat insert includes a top convex arcuate blend for improving fluid flow, and a valve seating surface for slowing down valve recession. The valve seating surface includes a radially outer convex arcuate segment defining an outer radius of curvature forming a first wear crown for contacting the valve at an early wear state, a radially inner convex arcuate segment defining an inner radius of curvature forming a second wear crown for contacting the valve at a later wear state, and a linear segment extending between the radially outer convex arcuate segment and the radially inner convex arcuate segment.