Analysis of Cummins engine valves

Cummins engines comply with ISO3046 standards and adopt SAE standard flywheel housing. Relying on its reliable stability, start-up performance and low emission standards, the country has guaranteed three guarantees, creating a world brand in the engine and generator set industry, and are deeply trusted by the majority of users. The Sino-US joint venture Dongfeng Cummins and Chongqing Cummins generator sets have small size, light weight, low fuel consumption, high power, reliable work, and easy to supply and repair. It adopts an electronic speed regulator, which has protection functions such as excessive cooling water temperature, low oil pressure, speed alarm and automatic parking.
[Brief description]
The valve mechanism of the engine is an important part of the entire air distribution system. Its function is to ensure that the engine can absorb as much gas mixture or air as possible during the engine's intake phase, and at the same time, it is reliably sealed during the engine compression and work phases. Because the valve mechanism withstands high temperatures from the engine when combustion and is cooled from the intake, its working environment is extremely harsh. Valve mechanisms vary greatly in structure depending on the type of engine. For a four-stroke engine, the valve mechanism has different types because of the different engine speeds. In addition, due to the effect of temperature during combustion, the valve stems are thermally expanded due to direct heating of the gas. Therefore, in order to ensure reliable sealing of the valve in any case, even when the engine is overheated, the gap must be reserved at the valve head so that the valve and its transmission mechanism can still fit tightly when the valve is extended due to heat. Currently, the size of valve clearance is mainly determined by experience methods. If the gap is too small, the engine may be closed tightly when heated, resulting in air leakage, resulting in a decrease in engine power and deterioration of performance. If the gap is too large, it will cause impacts between the parts of the transmission system, accelerating wear, and at the same time, the valve opening time is reduced, resulting in insufficient charge and reducing the engine power. Therefore, it is very important to determine the valve clearance.
However, with the continuous advancement of engine technology, various valve mechanisms have emerged one after another, so the requirements for valve clearance are also different. For example, some engine air distribution mechanisms require valve clearance, while some do not, some engines give cold gaps, some give hot gaps, and some give hot gaps at the same time. Various different regulations often cause inconvenience to actual work. This article will explain the relationship between the valve mechanism and the valve gap according to different valve mechanisms.
【Type】
1. The camshaft of the side-mounted valve
side-mounted valve mechanism is high. The valve is driven by the cam, and then the valve is pushed by the tappet. The transmission chain of this mechanism is short, has a simple structure and has a good power response. In the past, FAW's CA10B gasoline engine used this system. However, because the intake duct angle of this type of engine is too large and the flame propagation distance is long, which is not conducive to improving engine performance, except for small lawn mowers and snow sweepers, high-power and high-speed gasoline engines no longer use this structure.
2.
The driving method of the overhead valve mechanism with a camshaft with a high-mounted camshaft with a high-mounted overhead valve mechanism is to drive the push rod, push rod and rocker arm by the cam, and then the valve is pushed by the rocker arm. This kind of mechanism is used by FAW and II Automobile. The transmission chain of this mechanism is long and is not suitable for high-speed engines.
3. Camshaft overhead valve
camshaft overhead valve mechanism is a camshaft that drives the crankshaft directly through a toothed belt or chain. Therefore, the valve mechanism has good rigidity and is suitable for high-speed engines. It is also a commonly used type of light vehicle and sedan engines. Its working methods generally include the following: (1) cam direct drive type; (2) cam rocker pressing arm, rocker pressing valve type; (3) cam top rocker pressing arm, rocker pressing valve type.