Abstract: An angular position of a lever with which a rocker arm contacts to define a fulcrum therebetween is varied by rotation of a cam which is installed in a manner to be rotatable relative to its cam shaft and drivingly connected through a spring to the cam shaft or to an output shaft of a driving system.

Abstract: The present invention features a variable valve timing arrangement having a zero valve clearance maintaining device which takes the form of either a springy finger-like extension provided on a valve timing control lever, which extension biases a rocker arm which operates the valve, against the valve stem until the rocker arm has been cammed to pivot by a predetermined amount; or an eccentric bush on which the control lever is mounted and a telescopic hydraulic cylinder arrangement which rotates the bush to press the lever against the rocker arm with a predetermined force adequate for maintain a zero valve clearance.

Abstract: An internal to be at engine is provided with an engine cooling system by which the amount of cooling water introduced to a radiator is changed in accordance with engine load, so that the temperature of the cooling water is controlled to be at lower levels during a high engine load mode operation than during a low engine load mode operation. Additionally, an ignition timing control system of the engine is arranged to retard the ignition timing for a time period immediately after engine operation is shifted to the high engine load mode, thereby effectively preventing engine knock from arising when the engine operation is shifted to the high engine load mode.

Abstract: The present invention features a valve train for inducing reciprocative motion in a valve which includes a lever pivotally mounted at one end thereof, a rocker arm which engages the lever to define a fulcrum point therebetween, and which engages a valve at one end thereof, a first cam which engages the other end of the rocker arm, a second cam which engages the top of the lever and a mechanism which guidingly interconnects the rocker arm, at a point intermediate of the ends thereof, with the lever for preventing relative slip therebetween and for ensuring that a cam following portion of the rocker arm smoothly follows the first cam.

Abstract: A reaction member located above an angled rocker arm induces the latter to pivot once a telescopically extendible hydraulic tappet, under the influence of a cam, has lifted the rocker arm sufficiently to engage an apex thereof against the reaction member. The tappet includes a piston which defines therein a variable volume chamber into which hydraulic fluid may be readily introduced via a solenoid control valve, but only slowly discharged. The degree of extension of the tappet controls the valve lift induced by the rocker arm.

Abstract: A valve operating mechanism of an internal combustion engine comprises a first cam rotatable about an axis in timed relation to the engine speed, a rocker arm operatively engaged with the valve of the engine and rockable to open and control closing of said valve, a second cam rockable about an axis parallel to the axis of said first cam and interposed between the first cam and the rocker arm to provide an operative connection therebetween, the first and second cams having mating cam faces which taper axially thereof, and means for shifting one of the first and second cams axially thereof relative to the other thereby varying the angular position of the second cam independently of that of the first cam in response to variation of the engine operating condition whereby valve lift, valve timing and the period during which the valve is open are varied in accordance with the varying operating conditions of the engine.