The steering knuckle is a reciprocating mechanism in the cylinder block of an automobile engine. The basic structure of the steering knuckle can be divided into the top, head and skirt. The top of the steering knuckle is the main part of the combustion chamber, and its shape is related to the selected combustion chamber form. Gasoline engines mostly use flat-topped steering knuckles, which has the advantage of small heat absorption area. Diesel engine steering knuckles often have a variety of pits on the top, and their specific shape, position and size must be compatible with the diesel engine's mixture formation and combustion requirements.
The The whole steering knuckle can be divided into three parts: steering knuckle crown, steering knuckle head and steering knuckle skirt.
The main role of the steering knuckle is to withstand the combustion pressure in the cylinder and transmit this force to the crankshaft through the steering knuckle pin and connecting rod. In addition, the steering knuckle also forms a combustion chamber with the cylinder head and cylinder wall.
The steering knuckle crown is an integral part of the combustion chamber, so it is often made in different shapes. Most of the gasoline engine steering knuckle crowns use flat or concave roofs to make the combustion chamber compact in structure, small in heat dissipation area, and simple in manufacturing process.
All parts below the steering knuckle ring groove are called steering knuckle skirts. Its role is to guide the steering knuckle to reciprocate in the cylinder and withstand side pressure. When the engine is working, due to the pressure of the gas in the cylinder, the steering knuckle will be bent and deformed. After the steering knuckle is heated, because the steering knuckle pin has more metal, its expansion is greater than elsewhere. In addition, the steering knuckle will also squeeze and deform under the action of side pressure. The combined result of the above-mentioned deformation makes the section of the steering knuckle skirt become an ellipse with the long axis in the direction of the steering knuckle pin. In addition, due to the uneven temperature and mass distribution of the steering knuckle along the axis, the thermal expansion of each section is up and down.
The steering knuckle works under the conditions of high temperature, high pressure, high speed and poor lubrication. The steering knuckle is in direct contact with high-temperature gas, and the instantaneous temperature can reach more than 2500K. Therefore, the heat is severe and the heat dissipation conditions are very poor. Therefore, the temperature of the steering knuckle is very high during operation, and the top is up to 600-700K, and the temperature distribution is very uneven; The gas pressure is very large, especially the power stroke pressure is the largest, the gasoline engine is as high as 3 to 5MPa, and the diesel engine is as high as 6 to 9MPa, which causes the steering knuckle to impact and bear the side pressure; the steering knuckle is at a high speed in the cylinder (8 ~12m/s) Reciprocating motion, and the speed is constantly changing, which generates a large inertial force, so that the steering knuckle is subjected to a large additional load. Working under such harsh conditions, the steering knuckle will deform and accelerate wear, and it will also generate additional loads and thermal stresses, and at the same time be affected by the chemical corrosion of the gas.
steering knuckle inspection is mainly the measurement of the diameter of the skirt, the height of the steering knuckle ring groove and the size of the steering knuckle pin seat hole:
① The selection of the steering knuckle should be determined according to the repair size of the cylinder. Generally, the increased size is marked on the top of the steering knuckle;
②In the same series of fish delivery, the structure of the steering knuckle is not necessarily the same, so when choosing a steering knuckle, you must choose the corresponding type of steering knuckle according to the type of engine. On the same engine, you should choose the same brand, the same group or steering knuckles of the same product code; steering knuckles of the same product code must be used for the same model, to ensure that the difference in diameter and quality of the steering knuckle does not exceed the range specified by the original factory. Otherwise, it will cause poor engine combustion, rough work, economic and dynamic performance and other failures Therefore, when selecting a steering knuckle, the corresponding type of steering knuckle must be selected according to the type of engine.