A harmonic drive (1), including a wave generator (8), a flexible, externally toothed gear component (14), in particular in the form of a flex ring, which can be deformed by said wave generator, and at least one internally toothed gear component (4, 5) that meshes with the flexible, externally toothed gear component (14). The flexible, externally toothed gear component (14) has a non-circular basic shape in relation to its mechanically non-loaded state.

Methods and systems are provided for adjusting engine cranking. In one example, a method for an engine cold start may include extending engine cranking at least based on one or more engine cold start conditions, where extending engine cranking may increase an engine oil pressure in a plurality of camshaft phaser cavities of a variable camshaft timing (VCT) phaser. In some examples, the method may further include, after engine cranking, enabling fueling. In this way, fuel efficiency considerations may be balanced with increases to the engine oil pressure such that components of the VCT phaser may be actuated and/or lubricated.

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 timing adjusting device includes an intake variable valve mechanism and an exhaust variable valve mechanism. The exhaust variable valve mechanism includes an exhaust electric driving portion and an exhaust phase shifting portion including an input shaft. The exhaust phase shifting portion is disposed in a rotation transmission path between an exhaust camshaft and a crankshaft and configured to shift a rotation phase of the exhaust camshaft. The input shaft rotates in a rotational direction opposite to a rotational direction of the crankshaft when advancing the rotation phase. A phase of the exhaust phase shifting portion is configured to be shifted to a most advanced angle phase when the exhaust electric driving portion is de-energized or fails and when the exhaust phase shifting portion receives a torque in a forward rotational direction.

A coil spring of this invention includes a first end coil part with a first bearing surface facing to the first side in the axial direction, a second end coil part with a second bearing surface facing to the second side in the axial direction and a central coil part connecting the first and second end coil parts. A displacement length in the axial direction from the outer end portion until the inner end portion of the first end coil part is a thickness of a spring wire forming the coil spring so that a space between the outer end portion of the first end coil part and an inner end portion of the central coil part is zero, and a displacement length in the axial direction between the outer end portion of the first end coil part and a point away along the circumferential direction from the outer end portion toward the inner end portion of the first end coil part by a half of turn around the axial line is less than a half of the thickness of the spring wire.

An engine valve includes a stem, a head comprising an outer lip surface, a seating surface extending from the outer lip surface toward the stem, and a combustion surface extending from the outer lip surface on the opposite side of the head as compared to the seating surface. The combustion surface includes a first convex arcuate surface spaced away from the outer lip surface, at least partially forming a raised ring, and a first concave arcuate surface spaced away from the outer lip surface, at least partially forming a dimple.

An engine head assembly includes a valve seat insert having a valve seating surface defining a center axis, and each of an inner peripheral surface and an outer peripheral surface extending circumferentially around the valve seat center axis. The outer peripheral surface includes an upper section interference-fitted with the engine head, and a lower section. A stiffness relief channel is formed by a relief cutout in the valve seat insert, and extends radially between the lower section of the outer peripheral surface and the engine head. The stiffness relief channel permits flexing of the valve seat insert to cushion valve seating to prolong engine valve and valve seat insert service life.

A camshaft phaser is provided that includes a stator, a rotor having a plurality of vanes that form fluid chambers with the stator, and a timing wheel attached to the rotor. The rotor includes an axial fastening interface with an annular groove for receiving an annular protrusion of the timing wheel.

An opposed-piston engine includes an engine block, at least two intake valves, and at least two exhaust valves. The engine block includes a first center section and a second center section. The first center section defines a first cylinder half bore having a first longitudinal axis and a first open end. The second center section defines a second cylinder half bore having a second longitudinal axis and a second open end. The second longitudinal axis is offset from the first longitudinal axis. The first and second open ends overlap to form and opening therebetween that places the first and second cylinder half bores in fluid communication with one another to form a single cylinder. The intake valves are arranged at the first open end of the first cylinder half bore. The exhaust valves are arranged at the second open end of the second cylinder half bore.