Abstract: A concentric camshaft arrangement comprises an inner shaft, an outer tube concentrically arranged around the inner shaft and rotatably supported in a cylinder head. A first set of lobes is fixed for rotation with the outer tube and a second set of lobes is rotatably supported by bearing journals on the outer tube and connected for rotation with the inner shaft. The outer tube is supported in the cylinder head by means of a roller bearing and an oil feed is provided for supplying oil for lubricating the bearing journals of the second set of cam lobes. At least part of the oil feed is defined by a radial clearance between the outer surface and an inner surface of the cylinder head that is sealed at its axial ends, the radial clearance being larger than any radial clearance at the roller bearing so that loads on the camshaft are supported at least predominantly by the roller bearing.

Abstract: A spool valve for controlling a twin phaser for coupling a drive member to two driven members and to enable the phase of the two driven members to be varied independently includes a bore operably associated with the twin phaser, fluid channels opening into the bore, and a spool. The spool is received in and is moveable relative to the bore so as to selectively open and close the fluid channels in a predetermined manner, thereby providing a fluid communication between the spool and the twin phaser, and varying a phase of output members relative to an input member. The spool and the fluid channels are configured so that an axial displacement of the spool relative to the bore serves to control a phase of a first output member, and a rotation of the spool relative to the bore serves to control a phase of a second output member.

Abstract: An engine valve system comprises two cams (10,12) mounted coaxially, a summation rocker (14) coupled to followers (16,18) of both cams and movable in proportion to the instantaneous sum of the lifts of the respective cams, and a valve actuating rocker (20) pivotably coupled to the summation rocker (14) and operative to open an engine valve (22) in dependence upon the movement of the summation rocker (14). In the invention, the actuating rocker (20) rests on a hydraulic lash adjuster (24). A control spring (136) is provided to urge the summation rocker (14) in a direction to compress the hydraulic lash adjuster (24). A stop (138) associated with the control spring (136) limits the movement of the summation rocker (14) towards the lash adjuster (24) so as to set the clearance in the valve system when the valve (22) is closed and the cam followers (16,18) are on the base circles of the two cams (10,12).

Abstract: A spool valve for controlling a twin phaser for coupling a drive member to two driven members and to enable the phase of the two driven members to be varied independently includes a bore operably associated with the twin phaser, fluid channels opening into the bore, and a spool. The spool is received in and is moveable relative to the bore so as to selectively open and close the fluid channels in a predetermined manner, thereby providing a fluid communication between the spool and the twin phaser, and varying a phase of output members relative to an input member. The spool and the fluid channels are configured so that an axial displacement of the spool relative to the bore serves to control a phase of a first output member, and a rotation of the spool relative to the bore serves to control a phase of a second output member.