CAMLESS ENGINE THEORY

CAMLESS ENGINE THEORY

SINCE THE ORGANIZATION OF THE AUTOMOBILE, THE INTERNAL COMBUSTION ENGINE (ICE) HAS EVOLVED CONSIDERABLY. HOWEVER, ONE CONSTANT HAS REMAINED THROUGHOUT THE DECADES OF INTERNAL COMBUSTION ENGINE DEVELOPMENT. THE CAMSHAFT HAS BEEN THE PRIMARY MEANS OF CONTROLLING THE VALVE ACTUATION AND TIMING, AND THEREFORE, INFLUENCING THE OVERALL PERFORMANCE OF THE VEHICLE.

THE CAMSHAFT IS ATTACHED TO THE CRANKSHAFT OF AN ICE AND ROTATES RELATIVE TO THE ROTATION OF THE CRANKSHAFT. THEREFORE, AS THE VEHICLE INCREASES IS VELOCITY, THE CRANKSHAFT MUST TURN MORE QUICKLY, AND ULTIMATELY THE CAMSHAFT ROTATES FASTER. THIS DEPENDENCE ON THE ROTATIONAL VELOCITY OF THE CRANKSHAFT PROVIDES THE PRIMARY LIMITATION ON THE USE OF CAMSHAFTS.

AS THE CAMSHAFT ROTATES, CAM LOBES, ATTACHED TO THE CAMSHAFT, INTERFACE WITH THE ENGINE’S VALVES. THIS INTERFACE MAY TAKE PLACE VIA A MECHANICAL LINKAGE, BUT THE RESULT IS, AS THE CAM ROTATES IT FORCES THE VALVE OPEN. THE SPRING RETURN CLOSES THE VALVE WHEN THE CAM IS NO LONGER SUPPLYING THE OPENING FORCE.

SINCE THE TIMING OF THE ENGINE IS DEPENDENT ON THE SHAPE OF THE CAM LOBES AND THE ROTATIONAL VELOCITY OF THE CAMSHAFT, ENGINEERS MUST MAKE DECISIONS EARLY IN THE AUTOMOBILE DEVELOPMENT PROCESS THAT AFFECT THE ENGINE’S PERFORMANCE. THE RESULTING DESIGN REPRESENTS A COMPROMISE BETWEEN FUEL EFFICIENCY AND ENGINE POWER. SINCE MAXIMUM EFFICIENCY AND MAXIMUM POWER REQUIRE UNIQUE TIMING CHARACTERISTICS, THE CAM DESIGN MUST COMPROMISE BETWEEN THE TWO EXTREMES.

THIS COMPROMISE IS A PRIME CONSIDERATION WHEN CONSUMERS PURCHASE AUTOMOBILES. SOME INDIVIDUALS VALUE POWER AND LEAN TOWARD THE PURCHASE OF A HIGH PERFORMANCE SPORTS CAR OR TOWING CAPABLE TRUCKS, WHILE OTHERS VALUE FUEL ECONOMY AND VEHICLES THAT WILL PROVIDE MORE MILES PER GALLON.

RECOGNIZING THIS COMPROMISE, AUTOMOBILE MANUFACTURERS HAVE BEEN ATTEMPTING TO PROVIDE VEHICLES CAPABLE OF CYLINDER DEACTIVATION, VARIABLE VALVE TIMING (VVT), OR VARIABLE CAMSHAFT TIMING (VCT). THESE NEW DESIGNS ARE MOSTLY MECHANICAL IN NATURE. ALTHOUGH THEY DO PROVIDE AN INCREASED LEVEL OF SOPHISTICATION, MOST ARE STILL LIMITED TO DISCRETE VALVE TIMING CHANGES OVER A LIMITED RANGE.