The crankshaft is the most important component in the engine. It receives the force from the connecting rod and converts it into torque that is output through the crankshaft and drives other accessories on the engine to work. The crankshaft is subject to the combined effects of centrifugal force of the rotating mass, gas inertia force with periodic changes, and reciprocating inertia force, so that the crankshaft is subjected to bending and torsional loads. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the surface of the journal needs to be wear-resistant, uniform in work and good in balance.
For crankshaft rough machining, CNC lathes, CNC internal milling machines, CNC lathes and other advanced equipment will be widely used for CNC turning, internal milling, turning-broaching of the main journal and connecting rod journal to effectively reduce the deformation of crankshaft machining. For crankshaft finishing, CNC-controlled crankshaft grinders are widely used for precision grinding of their journals. This kind of grinding machine will be equipped with automatic requirements of grinding wheel dynamic balancing device, center frame automatic tracking device, automatic measurement, automatic compensation device, automatic dressing of grinding wheel, constant linear speed and other functional requirements to ensure stable grinding quality. The status of high-precision equipment dependence on imports is estimated to remain unchanged in the short term.
The most important part in the engine. It receives the force from the connecting rod and converts it into torque that is output through the crankshaft and drives other accessories on the engine to work. The crankshaft is subject to the combined effects of centrifugal force of the rotating mass, gas inertia force with periodic changes, and reciprocating inertia force, so that the crankshaft is subjected to bending and torsional loads. Therefore, the crankshaft is required to have sufficient strength and rigidity, and the surface of the journal needs to be wear-resistant, uniform in work and good in balance.
In order to reduce the mass of the crankshaft and the centrifugal force generated during the movement, the crankshaft journal is often made hollow. There are oil holes in the surface of each journal so that oil can be drawn in or out to lubricate the journal surface. In order to reduce stress concentration, the transition point of the main journal, the crank pin and the crank arm are connected by a transition arc.
The function of the crankshaft balance weight (also called counterweight) is to balance the rotational centrifugal force and its moment, and sometimes it can also balance the reciprocating inertia force and its moment. When these forces and moments themselves reach equilibrium, the counterweight can also be used to reduce the load on the main bearing. The number, size, and placement of counterweights should be considered based on factors such as the number of cylinders in the engine, the arrangement of the cylinders, and the shape of the crankshaft. The balance weight is generally integrated with the crankshaft by casting or forging. The high-power diesel engine balance weight is manufactured separately from the crankshaft and then bolted together.