CAMLESS ENGINE
In internal
combustion engine with pistons the camshaft is used to operate poppet valve. It
consists of a cylindrical rod running the length of the cylinder bank with
a number of oblong lobes protruding from it, one for each valve. The
cam lobes force the valves open by pressing on the valve, or on some
intermediate mechanism, as they rotate. The cam has been an integral part of the IC engine
from its invention. The cam controls the “breathing channels” of the IC
engines, that is, the valves through which the fuel air mixture (in SI engines)
or air (in CI engines) is supplied and exhaust driven out. Besieged by demands
for better fuel economy, more power, and less pollution, motor engineers around
the world are pursuing a radical “camless” design that promises to deliver the
internal – combustion engine’s biggest efficiency improvement in years. The aim
of all this effort is liberation from a constraint that has handcuffed
performance since the birth of the internal-combustion engine more than a
century ago.
Camless
engine technology is soon to be a reality for commercial vehicles. In the
camless valve train, the valve motion is controlled directly by a valve
actuator – there’s no camshaft or connecting mechanisms. Precise
electrohydraulic camless valve train controls the valve operations, opening,
closing etc., its general features and benefits over conventional engines. The engines powering today’s vehicles,
whether they burn gasoline or diesel fuel, rely on a system of valves to admit
fuel and air to the cylinders and let exhaust gases escape after combustion.
Rotating steel camshafts with precision-machined egg-shaped lobes, or cams, are
the hard-tooled “brains” of the system. They push open the valves at the proper
time and guide their closure, typically through an arrangement of pushrods,
rocker arms, and other hardware. Stiff springs return the valves to their closed
position. In an overhead-camshaft engine, a chain or belt driven by the
crankshaft turns one or two camshafts located atop the cylinder head.
A single overhead camshaft (SOHC) design
uses one camshaft to
To eliminate the cam,
camshaft and other connected mechanisms, the Camless engine makes use of three
vital components – the sensors, the electronic control unit and the actuator
Mainly five sensors are used in connection with the valve operation. One for
sensing the speed of the engine, one for sensing the load on the engine,
exhaust gas sensor, valve position sensor and current sensor. The sensors will
send signals to the electronic control unit.
The electronic control unit
consists of a microprocessor, which is provided with a software algorithm. The
microprocessor issues signals to the solid-state circuitry based on this
algorithm, which in turn controls the actuator, to function according to the
requirements.
An electro hydraulic camless valve train was developed
for a camless engine. Initial development confirmed its functional ability to
control the valve timing, lift, velocity, and event duration, as well as to
perform selectively variable deactivation in a four-valve multicylinder engine.
The system employs the hydraulic pendulum principle, which contributes to low
hydraulic energy consumption. The electro hydraulic valve train is integral
with the cylinder head, which lowers the head height and improves the engine
packaging. Review of the benefits expected from a camless engine points to
substantial improvements in performance, fuel economy, and emissions over and
above what is achievable in engines with camshaft-based valve trains.
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