Analyzing Cummins engine valves

Cummins engines comply with ISO3046 standards and use SAE standard flywheel housings. Relying on their reliable stability, starting performance and low emission standards, they have a nationwide three-guarantee, creating a brand-new engine andGenerator setA world-class brand in the industry and deeply trusted by users. Sino-US joint ventures Dongfeng Cummins and Chongqing CumminsGenerator setIt has small size, light weight, low fuel consumption, high power, reliable operation, and convenient parts supply and maintenance. It adopts electronic speed regulator and has protection functions such as excessive cooling water temperature, low oil pressure, overspeed alarm and automatic parking.
【Brief description】
The engine's valve train is an important part of the entire valve system. Its function is to ensure that the engine can inhale as much gas mixture or air as possible during the intake stage while the engine is working, and to reliably seal during the engine compression and power stages. Because the valve train withstands the high temperatures from engine combustion and is cooled by the intake air, its working environment is extremely harsh. The structure of the valve train varies greatly depending on the engine type. For four-stroke engines, the types of valve trains are also different because of the different engine speeds. In addition, due to the effect of temperature during combustion, the valve stem is directly heated by the gas and causes thermal expansion. Therefore, in order to ensure that the valve can be reliably sealed under any circumstances, even when the engine is overheated, a gap must be reserved at the valve head. , so that the valve and its transmission mechanism can still fit tightly when the valve and its transmission mechanism are stretched by heat. Currently, manufacturers mainly rely on empirical methods to determine the size of the valve clearance. If the gap is too small, the engine may not close tightly when heated, causing air leakage, resulting in reduced engine power and worsened performance. If the gap is too large, collisions will occur between the parts of the transmission system, accelerating wear, and the opening time of the valve will be reduced, resulting in insufficient charging and a decrease in engine power. Therefore, the determination of valve clearance is very important.
However, with the continuous advancement of engine technology, various valve mechanisms emerge in endlessly, so the requirements for valve clearance are also different. For example, some engine valve trains require valve clearance, while others do not. Some engines provide cold clearance, some provide hot clearance, and some provide both hot and cold clearance. Various regulations often bring inconvenience to practical work. This article will explain the relationship between the valve mechanism and valve clearance based on different valve mechanisms.
【type】
1. Side-mounted valve
The camshaft of the side-mounted valve train is mounted high. The valve is driven by a cam that drives the tappet, which then pushes the valve. The transmission chain of this mechanism is short, the structure is simple, and the dynamic response is good. In the past, my country's FAW's CA10B gasoline engine used this system. However, because the inlet angle of this type of engine is too large and the flame propagation distance is long, it is not conducive to improving engine performance. Therefore, except for the engines of small lawn mowers and snowplows, high-power and high-speed gasoline engines have basically This structure is no longer used
2. Overhead valve with high camshaft
The overhead valve mechanism with a high camshaft is driven by the cam driving the tappets, push rods and rocker arms, and then the rocker arms push the valves. The CA141 and EQ6100 of my country's FAW and Second Automobile Works use this mechanism. The transmission chain of this mechanism is relatively long and is not suitable for high-speed engines.
3. Camshaft overhead valve
The overhead camshaft valve mechanism is a crankshaft that directly drives the camshaft 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 presses the rocker arm, and the rocker arm presses the valve type; (3) cam presses the rocker arm, and the rocker arm presses the valve type.