Linear actuators are disclosed. The linear actuator comprises a thruster and a stator. The thruster includes a thruster winding, and the stator includes a stator winding. The stator is disposed about the thruster. The linear actuator also includes a sheath disposed about the stator and the thruster. The thruster is configured to translate within the sheath relative to the stator upon application of an electrical current to the stator winding, the thruster winding, or a combination thereof. The stator winding and the thruster winding each comprise a nonpermanent magnet.

A head assembly for an internal combustion engine includes an electromagnetic valve actuation system. The head has an intake or exhaust passage defined therein. A valve is disposed in the passage and is operable to selectively open and close the passage. The head has a cooling passage defined therein for passage of a cooling fluid. An electromagnetic actuator has a piston in mechanical communication with the valve and a coil in fluid communication with the cooling passage. The electromagnetic actuator is operable to move the valve between a closed and an open position.

An apparatus includes a valve and an actuator. The valve has a portion movably disposed within a valve pocket defined by a cylinder head of an engine. The valve is configured to move relative to the cylinder head a distance between a closed position and an opened position. The portion of the valve defines a flow opening that is in fluid communication with a cylinder of an engine when the valve is in the opened position. The actuator is configured to selectively vary the distance between the closed position and the opened position.

An electrical system including a linear motor in which energized forcer and thruster coils are used for the field and armature elements, respectively. In accordance with various exemplary embodiments, one or more thruster coils may be provided on a reciprocating shaft with opposing single or multiple fixed forcer coils. Using coils as the electromagnets for both forcer and thruster coils advantageously provides necessary power while also minimizing system weight and decreases in magnetism typically encountered with permanent magnets with rising temperature, resulting in higher and more controllable magnetic forces over varying temperatures. A ferrous system housing and open ferrous containers for the thruster coils may be further included to advantageously focus the magnetic forces. Additionally, multiple forcer and thruster coils may be disposed in various arrangements along the reciprocating shaft. Exemplary applications include use of such a system for controlling oscillations of a poppet valve in an internal combustion engine.

A valve-timing control apparatus includes an electric motor; a speed-reduction mechanism configured to reduce a rotational speed of the output shaft of the electric motor; a slip ring provided on a surface of a tip portion of the electric motor; a cover member provided to cover at least a part of the surface of the tip portion of the electric motor; a power-feeding brush disposed in the cover member and being in contact with the slip ring; and an angle sensing mechanism configured to sense a rotational angle of the output shaft of the electric motor. The angle sensing mechanism includes a detected portion attached to the output shaft of the electric motor, and a detecting portion attached to the cover member and opposed to the detected portion. The power-feeding brush is located so as not to overlap with the detected portion in a vertically-upper direction from the detected portion.