valve train

valve train

[′valv ‚trān]
(mechanical engineering)
The valves and valve-operating mechanism for the control of fluid flow to and from a piston-cylinder machine, for example, steam, diesel, or gasoline engine.

Valve train

The valves and valve-operating mechanism by which an internal combustion engine takes air or fuel-air mixture into the cylinders and discharges combustion products to the exhaust. See Valve

Mechanically, an internal combustion engine is a reciprocating pump, able to draw in a certain amount of air per minute. Since the fuel takes up little space but needs air with which to combine, the power output of an engine is limited by its air-pumping capacity. The flow through the engine should be restricted as little as possible. This is the first requirement for valves. The second is that the valves close off the cylinder firmly during the compression and power strokes. See Internal combustion engine

In most four-stroke engines the valves are the inward-opening poppet type, with the valve head ground to fit a conical seat in the cylinder block or cylinder head. The valve is streamlined and as large as possible to give maximum flow, yet of low inertia so that it follows the prescribed motion at high engine speed.

Engine valves are usually opened by cams that rotate as part of a camshaft, which may be located in the cylinder block or cylinder head. Riding on each cam is a cam follower or valve lifter, which may have a flat or slightly convex surface or a roller, in contact with the cam. The valve is opened by force applied to the end of the valve stem. A valve rotator may be used to rotate the valve slightly as it opens. In engines with the camshaft and valves in the cylinder head, the cam may operate the valve directly through a cup-type cam follower. To ensure tight closing of the valve even after the valve stem lengthens from thermal expansion, the valve train is adjusted to provide some clearance when the follower is on the low part of the cam. See Cam mechanism

References in periodicals archive ?
The design is available in either a packaged or semi-packaged format--which reflects the growing importance of installation versatility--including pre-piped, modulating gas valve train and control panel options that can be attached to the burner mounting plate or supplied separately.
ANS will use the investment proceeds to put its ongoing customer projects into high-volume series production, initially in automotive applications such as valve train components, cylinder liners and connecting rods.
Deep investigations were carried out during initial design and development phase by simulating the whole thermodynamic cycle, valve train simulation, engine cooling and lubrication circuit flow simulations.
Rane (Madras) is part of Rane Group, a global supplier of steering and suspension systems, friction materials, valve train components, occupant safety systems, diecasting products and aerospace-grade wiring harnesses.
The FXX K offers LaFerrari's V12 engine with new camshafts, a redesigned intake manifold and a modified valve train with mechanical rather than hydraulic lifters which bring the power up to 848bhp.
I particularly enjoyed developing the valve train to run at more than 20,000rpm, and designing the cylinder head architecture on the Cosworth 1999 CK engine project," he says.
These new outboards are heralded as the industry's easiest to maintain, with an exclusive lifetime maintenance-free valve train, no-mess oil-change system, no tools-required fuel filter, colour-coded maintenance locators and an up-front freshwater valve flush system.
And on those nights when you toss and turn, restlessly worrying that sludge is somehow building up inside your valve train, get up and change the oil, then go back to bed.
These are next-generation compact engines that combine a base engine with a newly designed framework, the VTEC variable valve train system with thoroughly reduced friction, a turbocharger with a low moment of inertia and high responsiveness, and direct injection technology to achieve good balance between high output and torque, above those of conventional naturally-aspirated engines, along with excellent fuel economy.
Scorpion Racing Products are well known for their superior quality valve train products produced through state-of-the-art, automated robotic manufacturing techniques, but don't think that they've taken the human element out of the equation.
crankcase, valve train, fuel injection and ignition systems, filters), and prevention of combustion engine damage.
The study tested eight types of recent-model vehicles of various engine configurations, sizes, valve train types, and fuel efficiency with different ethanol-gasoline blends.