Composition of Valve Transmission Mechanism for Diesel Generator Unit

The valve transmission mechanism of the diesel generator set is used to transmit the lifting force of the camshaft to the valve assembly. It mainly consists of three parts: the tappet, push rod, and rocker arm driven by the camshaft. As the temperature of the engine increases during operation, the parts of the valve mechanism will expand due to heat. So, there must be a clearance inside the valve mechanism, which is called the valve clearance. All valve mechanisms of engines must consider this clearance. But now some engines use zero clearance valve mechanisms, which actually use technologies (such as hydraulic) that do not require adjusting valve clearance.

1. Strut

There are several types of tappets on diesel generator sets, including integral sliding tappets, cam follower tappets (roller tappets), roller arm tappets, and hydraulic tappets. When the camshaft rotates, in order to avoid the lateral force of the cam convex tip when moving the valve, which directly acts on the valve foot and causes one-way wear of the valve stem, resulting in loose valve closure, valve tappets are installed between the valve and the camshaft. Used to follow the contour of the cam on the camshaft for movement. The valve tappet is directly driven by the camshaft, converting the rotational motion of the camshaft into reciprocating motion to open and close the valve.

2. Push rod

The push rod is a transmission rod between the valve tappet and the rocker arm group, usually made of aluminum alloy (or steel). In order to reduce motion inertia, the push rod is often made hollow. The two ends of the aluminum alloy push rod are embedded with heat-treated steel material to increase wear resistance. Some machines have oil injection holes in the middle of the push rod to lubricate the rocker arm. Some push rods have small convex balls at the top, which roll inside the tappet and rocker arm.

Only diesel engines with a camshaft built into the cylinder block use push rods, while top mounted camshaft engines do not require push rods.

The push rod may be solid or hollow. On some engines, there is a small hole in the center of the push rod that allows oil to flow through the hydraulic tappet to the upper part of the cylinder head. The push rod of the integral strut does not have convex balls at both ends, but uses concave surfaces.

3. Swing arm

The rocker arm has two functions: one is to change the direction of the lifting force of the cam; The second is to provide a certain mechanical efficiency during the valve lifting process. When the tappet and push rod move upwards, the rocker arm rotates around the central pivot point, causing a change in the direction of movement on one side of the valve. This change in direction causes the valve to open downwards.

The rocker arm is mounted on the rocker arm shaft of the cylinder head and made of carbon steel or alloy steel. One end of it is made into a long arm, and the other end is made into a short arm. The long arm end is in contact with the pneumatic foot, the upper part of the short arm end has an adjustment screw, and the lower part is connected to the valve push rod. The distance from the rocker arm shaft to both ends of the rocker arm is not equal. The advantage of making one end of the rocker arm into a long arm is that it can reduce the size of the cam without reducing the lift of the valve.

There are various ways to design and install rocker arms. Some are installed on the rocker arm shaft, and in this assembly form, springs, washers, various rocker arms, and bolts are required. Some rocker arms are directly installed on cylinder heads using bolts.

The above is the introduction of the three major components of the valve transmission mechanism of diesel generator sets by Dingbo Electric Power: the strut, push rod, and rocker arm. We hope it can be helpful to you. Dingbo Electric Power was established in 2006 and is a diesel generator set manufacturer that integrates diesel generator set design, supply, commissioning, and maintenance. Our company has advanced process equipment, reliable product quality, and a sound service network. We welcome customers and friends to visit and consult us. If any question please feel free to visit our website https://www.dieselgeneratortech.com/ or send email to sales@dieselgeneratortech.com.