A method of operating an internal combustion engine having an electrical circuit that includes a connection closed by abutment between two distinct parts, one of which is mounted to a rocker arm of a rocker arm assembly and another that is mounted to a part distinct from the rocker arm. The connection is structured such that the movement of the rocker arm causes relative motion between the surfaces of the distinct parts that close the connection. The relative motion causes the circuit resistance to transition between values within a first range and values within a second range. The transitions of resistance between those ranges are detected and their presence, absence, or timing used for purposes of providing diagnostic feedback or control.

A valve timing adjustment device includes a vane rotor and a hydraulic oil control valve. The vane rotor is fixed to an end portion of one of a drive shaft and a driven shaft and defines a through hole. The hydraulic oil control valve includes a sleeve and a spool. The sleeve includes a body portion in the through hole and a fixing portion fixed into a shaft fixing hole defined in the one. At least a portion of the through hole is sealed by the body portion. A difference between a radial dimension of the shaft fixing hole and a radial dimension of the fixing portion is greater than a total of a predetermined coaxiality between the through hole and the shaft fixing portion and a predetermined coaxiality between the body portion and the fixing portion.

A hydraulic oil control valve is coaxially disposed with a rotational axial of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve, a spool slidably moving in an axial direction within the sleeve, and a filter member configured to capture foreign matters contained in the hydraulic oil. The sleeve includes an inner sleeve and an outer sleeve defining therein an axial hole extending in the axial direction. A space between the axial hole and the inner sleeve in a radial direction serves as a hydraulic oil supply passage. The filter member is disposed in the space to overlap with at least one of internal members in the inner sleeve when viewed in the radial direction.

A hydraulic oil control valve, which is placed along a rotational axis of a valve timing adjusting device, includes a sleeve and a spool configured to slide in an axial direction on an inner side of the sleeve in a radial direction. The sleeve includes: an inner sleeve that has an opening in which a distal end portion of the spool is inserted; and an outer sleeve. In a state where the spool is positioned farthest from an actuator, the distal end portion projects from the opening toward a side that is opposite to the actuator.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device for adjusting valve timing of a valve. The valve is selectively opened or dosed by a drive shaft receiving a driving force from a drive shaft. The hydraulic oil control valve includes a tubular sleeve and a spool that is slidably moved within the sleeve. The sleeve includes an inner sleeve and an outer sleeve that is fixed to an end portion of one of the drive shaft and the driven shaft with an axial force. When the axial force is not applied, a minimum clearance between the outer sleeve and the inner sleeve in a radial direction is larger than a minimum clearance between the inner sleeve and the spool in the radial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve, a spool, a movement restricting portion, a fixing member. The sleeve includes an inner sleeve and an outer sleeve. The fixing member is fixed to an end portion of the outer sleeve facing the actuator. The fixing member is configured to restrict the inner sleeve from moving in a circumferential direction relative to the outer sleeve and to restrict the inner sleeve and the spool from coming off from the outer sleeve toward the actuator in the axial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve and a spool that is slidably moved in an axial direction within the sleeve in a radial direction. The sleeve includes an inner sleeve disposed radially outside of the spool and an outer sleeve defining an axial hole extending in the axial direction. The inner sleeve is inserted into the axial hole. The outer sleeve is fixed to an end portion of one shaft when an axial force is applied to the outer sleeve in the axial direction. An inner sleeve end portion of the inner sleeve in the axial direction away from the actuator protrudes from the outer sleeve away from the actuator in the axial direction.

A hydraulic oil control valve is coaxially disposed with a rotational axis of a valve timing adjustment device. The hydraulic oil control valve includes a sleeve and a spool sliding in an axial direction within the sleeve. The spool has an inner space serving as a drain passage through which the hydraulic oil discharged from a phase shifting portion flows. The spool defines a drain inlet that guides the hydraulic oil discharged from the phase shifting portion into the drain passage. At least one of the sleeve or the spool defines an opening through which the hydraulic oil in the drain passage is discharged from the hydraulic oil control valve. A protrusion is formed between the drain inlet and the opening to extend radially inward beyond the drain inlet.

A gas exchange valve for an internal combustion engine may include a valve stem and a wear resistance improving functional layer. The valve stem may extend in an axial direction and may transition into a valve plate in the axial direction. The functional layer may include nickel and tungsten. The functional layer may be arranged in a coating area on an outer circumference of the valve stem and may at least partially define a sliding surface.

An electromagnetic switching valve includes: a sleeve; a spool; an electromagnetic actuator, including a plunger having a through passage and a stator exerting a magnetomotive force on the plunger; and a transmission member of a tubular shape, interposed between the plunger and the spool and transmitting a driving force. The stator includes an insertion hole through which the transmission member is inserted. The transmission member includes: a facing wall facing the through passage; a first internal passage formed closer to the plunger than the facing wall and communicating with the through passage; a first opening formed closer to the plunger than the insertion hole and opening the first internal passage in a radial direction; second internal passages formed closer to the spool than the facing wall; and second openings formed closer to the spool than the insertion hole and opening the second internal passages in the radial direction.