A valve gear for an engine includes a camshaft including a cam, a rocker shaft, and a first rocker arm which swings when pressed by the cam. The valve gear includes a spring, which biases the first rocker arm and a second rocker arm which presses an intake valve or an exhaust valve, in a return direction. The valve gear includes a first pin hole of the first rocker arm, a second pin hole and a third pin hole of the second rocker arm, a first switch pin, a second switch pin, a third switch pin, and a switch which switches between a connected state and a non-connected state of the switch pins. The second rocker arm includes a stopper against which the first rocker arm abuts. When the first rocker arm abuts against the stopper, all of the pin holes are located on the same axis.

A mechanical system that forms a cam follower or a rocker arm. The mechanical system includes a support element, a pin extending between two opposite ends along a first axis, and a roller mounted on the pin, movable in rotation relative to the pin around the first axis and adapted to roll on a cam. The support element further comprises an insert having holding members supporting the pin ends, provided with cut-outs having a shape complementary to the shape of the pin-ends, for assembling pin with insert by quarter-turn around the first axis. The pin ends each have a flat surface and an external surface. A first dimension of each pin end, measured perpendicularly to the flat surface, between the flat surface and the external surface of the pin end, is higher than half the outer diameter of the pin ends.

A method for making a valve stem seal, comprising the steps of providing a metal retainer having a top portion and a body portion. The body portion having a first section and a second section. In a first state, the first section of the body portion is cylindrical and the second section of the body portion is cone shaped. Providing a hollow mold. Inserting the metal retainer into the outer mold piece, inserting the inner mold piece into the metal retainer, and then securing the inner and outer mold pieces to each other. Filling a cavity around the top portion of the metal retainer with an elastomeric compound. Removing the metal retainer and the formed rubber sealing element from the mold pieces, and pressing downward over the formed valve stem seal to compress the second section of the body portion radially inwardly.

A rocker arm includes a roller, a support shaft coaxially mounted in the roller and having a first end portion and a second end portion, walls including at least a first wall and a second wall arranged along the rotation axis and opposite each other with having the roller therebetween, the first wall having a first through hole through which the first end portion is inserted and the second wall having a second through hole through which the second end portion is inserted, and plate portions including at least a first plate portion and a second plate portion arranged opposite each other with having the first wall, the second wall and the support shaft therebetween. The first plate portion is in contact with a first end surface of the first end portion and the second plate portion is in contact with a second end surface of the second end portion.

A rocker arm includes a pair of sidewalk disposed along a heightwise direction so as to be opposed to each other. The sidewalk define a space to house a roller and have opposed portions extending in the heightwise direction relative to adjacent portions which are adjacent to the opposed portions. The opposed portions have thinner portions having smaller thicknesses than the adjacent portions.

A method for supplying inert gas into a poppet valve intermediate and an apparatus for supplying inert gas are provided that are capable of properly filling the inert gas without waste into the poppet valve intermediate of any size. After a negative pressure is achieved by suction in an internal space (Win) of a poppet valve intermediate (W) as compared to an ambient pressure (Pa) of the poppet valve intermediate (W), the inert gas is supplied into the internal space (Win) until a pressure (P) of the internal space (Win) reaches the ambient pressure (Ps) of the poppet valve intermediate (W).

An assembling apparatus places a retainer on a valve spring to surround an upper end of a valve stem. The apparatus includes an assembling head, and a moving unit configured to move the assembling head between the supply position of the retainer and an assembling position. The assembling head includes a holding unit configured to hold the retainer, and a push unit configured to push out the retainer. The push unit includes a push member supported to be able to advance/retreat along an elevating direction of the assembling head, and a biasing member configured to bias the push member in an advancing direction.

An assembling apparatus assembles a retainer by engaging a pair of cotter pieces with a valve stem. The apparatus includes an assembling head configured to hold, in a separated state, the pair of cotter pieces in the separated state prepared by a preparation unit and engage the pair of cotter pieces with the upper end of the valve stem. The head includes a storage member including a storage chamber, and a holding unit capable of pressing the pair of cotter pieces stored in the storage chamber against the upper end of the valve stem. The storage member includes first and second abutting portions. The second abutting portion positions the valve stem in the axial direction, and the first abutting portion positions the pair of cotter pieces in the axial direction.

An engine valve and a method of producing the engine valve are provided. The engine valve includes a shaft part and an umbrella part formed at one end of the shaft part. The engine valve opens and closes an intake port or an exhaust port of a combustion chamber of an internal combustion engine. Further, at least a portion of the engine valve that extends from the umbrella part to a position on the shaft part in a longitudinal direction thereof includes a valve body made of steel or nickel alloy, and a core member made of copper or copper alloy and provided inside the valve body.

A method for producing at least one hollow valve for gas exchange may include introducing a bore into a valve shaft and into a valve head to form the at least one hollow valve, measuring a depth of the bore, washing the at least one hollow valve at least once, providing the at least one hollow valve in a retaining device, orienting the retaining device together with the at least one hollow valve with respect to an associated electrode, moving the associated electrode in relation to the at least one hollow valve, inserting the associated electrode into the bore of the at least one hollow valve, enlarging the bore in a region of the valve head by electromechanical machining processes, removing the associated electrode from the at least one hollow valve, rinsing and/or preserving the at least one hollow valve, and measuring a wall thickness of a valve bottom.