Hydraulic tappet

Hydraulic tappet

The reciprocating piston petrol engine

Published in M.J. Nunney, Light and Heavy Vehicle Technology, 2007

In more recent American engine designs there has been a revival of interest in the roller type of sliding cam follower, the roller being used at the foot of a hydraulic tappet (this type of tappet is described later). The roller is provided with needle rolling bearings at its pivot and operates against a nodular iron camshaft with modern cam forms. Careful design is necessary to ensure that the roller is of optimum size to minimize contact stress. Also, the roller track may require a crowned profile, so as to compensate for any slight misalignment between the roller and its cam. Apart from conferring greater durability on the valve train, it is claimed by one manufacturer that this arrangement reduces friction by about 8 per cent and is therefore a contributory factor in improving the all-important fuel economy. A roller may similarly be applied to the pivoting rocker of an overhead camshaft installation, as described earlier.

Experimental study on the energy consumption of gasoline engine lubricating pumps in standardized driving cycles

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Journal Information

Published in Mechanics Based Design of Structures and Machines, 2023

Zhongmin Liu, Xin Zhai

Principally, the sliding bearing’s lubricating pressure of gasoline engine gradually increases with the increase of engine speed. In the hydraulic system of engine, such as Variable Valve Timing controller (VVT), hydraulic tappet, and piston jet cooling, working pressure steps up at certain speeds, shown in Figure 1.

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The reciprocating piston petrol engine

Experimental study on the energy consumption of gasoline engine lubricating pumps in standardized driving cycles