An Oldham coupling includes: a driven Oldham flange that is formed at a drive-side rotor; a drive Oldham flange that is formed at a planetary rotor; and an Oldham intermediate that is configured to synchronize rotation of the driven Oldham flange and rotation of the drive Oldham flange. A thrust section is formed at a rotor plate portion which is a portion other than the Oldham coupling. The thrust section is configured to limit tilting of the planetary rotor relative to the driven Oldham flange when the thrust section contacts the planetary rotor in an axial direction. There is satisfied a relationship of θ2>θ1 where: θ1 is a maximum tilt amount of the planetary rotor relative to the driven Oldham flange; and θ2 is a maximum tilt amount of the planetary rotor in a clearance formed at the Oldham coupling.

An object of the present invention is to provide a chain guide mechanism that can readily integrate all the components in a simple structure and enhance work efficiency during assembly or maintenance. The chain guide mechanism of the present invention is configured to be able to integrally support, on a frame, components including a plurality of sprockets, a chain, a fixed chain guide, and a pivoting chain guide. The frame includes a pivoting chain guide holding part that holds a mounting boss of the pivoting chain guide in a state of a loose fit. The pivoting chain guide holding part is configured to allow the mounting boss to be fitted therethrough from one side.

This invention describes a variable valve timing mechanism which may be fitted to an internal combustion engine to provide precise control over timing of the valve opening and closing events of the camshaft relative to the crankshaft. Various methods for its application are described to provide settable valve timing at either predetermined angle selected by the operator, or automatic variable valve timing as governed by parameters of the operating engine. Said mechanism comprised of oppositely located idler rollers, whereas not bound to a single yoke or carrier, are driven by a cam to achieve independent movement of the rollers, which bear against both tension and slack sides of the belt between the crankshaft and camshaft pulleys causing predictable and repeatable variation in valve timing. Thus, this invention, whereby coordinated but non-uniform movements of the idler rollers is achieved by the mechanical appurtenances described herein, including a specially developed cardioid cam to actuate said idler rollers, produces precise changes in camshaft phase angle.

An object of the present invention is to provide a chain guide mechanism that can readily integrate all the components in a simple structure and enhance work efficiency during assembly or maintenance. The chain guide mechanism of the present invention is configured to be able to integrally support, on a frame, components including a plurality of sprockets, a chain, a fixed chain guide, and a pivoting chain guide. The frame includes a pivoting chain guide holding part that holds a mounting boss of the pivoting chain guide in a state of a loose fit. The pivoting chain guide holding part is configured to allow the mounting boss to be fitted therethrough from one side.

A method of two-step variable valve lift (VVL) malfunction avoidance learning control may include: in a two-step VVL system which is operated with a main lift and a secondary lift, verifying, by an electronic control unit (ECU), an operation avoidance area based on locking of a lock pin of a cam follower ; performing VVL operation learning, in which a failure of occurrence of the second lift is determined on the basis of a locking failure of the cam follower due to an initially set value of the operation avoidance area; and reflecting the operation avoidance area to the two-step VVL system with a corrected set value which is obtained through the VVL operation learning.

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.

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.

A synchronous belt drive system having: a synchronous belt with a tensile cord of high-modulus fiber such as glass, carbon, PBO, or aramid; a driver sprocket and at least one driven sprocket, at least one of which is an obround sprocket; and a tensioner having: a base having a cylindrical portion extending axially with a radially outer surface and a receiving portion, an eccentric arm pivotally engaged with the radially outer surface, a torsion spring disposed within the receiving portion, the torsion spring applying a biasing force to the eccentric arm, and a pulley journalled to the eccentric arm. Preferably, no one of the eccentric arm, pulley, or torsion spring is axially displaced along an axis A-A from the others. The obround sprocket has a toothed surface and at least one linear portion disposed between two arcuate portions having a constant radius, the linear portion having a predetermined length.

An Oldham coupling includes: a driven Oldham flange that is formed at a drive-side rotor; a drive Oldham flange that is formed at a planetary rotor; and an Oldham intermediate that is configured to synchronize rotation of the driven Oldham flange and rotation of the drive Oldham flange. A thrust section is formed at a rotor plate portion which is a portion other than the Oldham coupling. The thrust section is configured to limit tilting of the planetary rotor relative to the driven Oldham flange when the thrust section contacts the planetary rotor in an axial direction. There is satisfied a relationship of θ2>θ1 where: θ1 is a maximum tilt amount of the planetary rotor relative to the driven Oldham flange; and θ2 is a maximum tilt amount of the planetary rotor in a clearance formed at the Oldham coupling.

In a hollow exhaust poppet valve including a fillet increasing in diameter toward a leading end, a stem, and a head and having a coolant within a hollow part formed from the head to the stem, the stem includes a first stem part on a base end side, and a second stem part integrated with the first stem part via a step part and integrated with the fillet, and the hollow part includes a first hollow part formed inside the first stem part, and a second hollow part formed inside the second stem part, the fillet, and the head in such fashion as to have a constant inner diameter greater than the first hollow part and formed so as to be continuous with the first hollow part via a tapered part or a curved part.