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Diesel Generator sets
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What are the types of tappets for diesel generator sets?
June 25, 2022
A tappet driven by the camshaft is an integral part of the valve train. The valve tappet, also called a tappet, is used to follow the contour of the cam on the camshaft for movement. The valve tappet is driven directly by the camshaft and transforms the rotational motion of the camshaft into a reciprocating motion to open and close the valve. At present, diesel generator set tappets include integral sliding tappet, cam follower (roller tappet), roller arm type and hydraulic tappet.
Integral sliding tappet
Integral tappet transmits motion in the form of an integral part, more commonly found in small generators. To reduce the weight of the pushrod and inertia of movement, some integral tappets are designed as hollow tubes, while others are designed as solid ones. Integral tappet is mainly used in older engines or some high performance engines. One of its disadvantages is that it is noisy and has a particular knocking sound.
Integral tappet engines are required to have measures to adjust the valve lash. The valve is exposed to high temperature gas, the valve is heated and expands, elongating along the valve stem, the longer the valve stem, the greater the expansion. If there is no clearance between tappet and valve foot or rocker arm and valve foot in the transmission process, the internal combustion engine will work soon and the valve will leak air due to poor closing.
Roller type tappet
Roller tappets are fitted with a small roller at the lower end so that the roller rolls on the curve of the cam tip when the cam tops the roller, reducing direct wear between the tappet or cam, they are mainly used in high compression ratio engines, they are very similar to integral tappets, the only difference is that the cam follower rolls on the camshaft through the roller instead of sliding through the metal, the cam follower reduces friction, and the load is distributed more evenly. And the load is distributed more evenly.
Roller arm tappet
Instead of a tappet, a rocker arm with a roller is used between the cam and tappet, called a roller arm, and one end of the roller arm is set on a shaft parallel to the camshaft, which is called the roller shaft. By replacing the tappet with a roller arm, the lateral pressure of the camshaft on the tappet and the reciprocating inertia force of the tappet can be reduced.
Hydraulic tappet (column) can reduce noise and control valve lash: Hydraulic tappet keeps valve lash to zero by oil pressure. Hydraulic tappet mainly consists of tappet housing, oil hole, plunger spring, spring seat, spring, one-way ball, plunger, metering valve, tappet seat and lock ring.
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