In addition to the gas pressure, inertial force, and centrifugal force, the crankshaft is subjected to additional loads due to torsional vibration. It is an important moving part on the diesel engine, which has complicated processing technology, high processing precision and high cost.
Due to the limitation of the length and width of the locomotive, the diesel engine of the locomotive is generally 4~6m in length and 2.5~3m in width. Therefore, the crankshaft of the diesel engine is generally about 4m. Depending on the power of the diesel engine, the diameter of the main journal of the crankshaft is φ190mm, φ220mm, φ230mm, φ250mm, etc., and the crank pin (also called the connecting rod neck) is correspondingly smaller.
The crankshaft is mounted on each spindle bearing of the crankcase of the diesel engine body. The crank pin is movably connected with the piston-linkage group, the output end drives the traction engine through the coupling, and the free end drives the camshaft, the oil pump, etc. through the transmission gear, and borrows The cardan shaft drives the auxiliary device.
In addition to the gas pressure, inertial force, and centrifugal force, the crankshaft is subjected to additional loads due to torsional vibration. It is an important moving part of the diesel engine with high strength (susceptibility to fatigue damage), large cross-section change (easy to cause stress concentration), poor structural rigidity (easy to cause deformation and vibration); its processing technology is complicated (to prevent deformation of the clamp, Heat treatment deformation, etc.), high processing precision (many dimensions and dimensional tolerances are required and interchangeable, etc.), and the cost is expensive.
The speed of locomotive diesel engines is generally between medium and high speed, so the crankshaft must also be balanced.
The crankshaft of the locomotive diesel engine is divided into its billet material and its formation. It is also divided into a cast ductile iron crankshaft and an all-fiber extruded alloy steel crankshaft. The processing technology of the two is also very different. The following is an example of the alloy steel crankshaft with full fiber extrusion, and introduces the process of the crankshaft of the locomotive diesel engine (Fig. 1).
Processing technology of locomotive diesel engine crankshaft
Crankshaft blanks are usually roughed and then tempered for good mechanical properties, followed by semi-finished and precision axles. In addition, it is necessary to process each hole system, such as: internal cavity oil passage - oblique oil hole, main oil hole, weight reduction hole, straight oil hole, etc., and the working environment of the crankshaft in the diesel engine is relatively bad, the journal The surface needs to be strengthened. Generally, there are two methods of surface intermediate frequency quenching and nitriding. In addition, some details must be dealt with, such as round roll rolling strengthening and shot peening. In addition, dynamic balance and oil pump oil test must be done.
The typical machining process of the locomotive diesel crankshaft is as follows:
Roughing and roughing of the spindle neck and connecting rod neck quenching and tempering process hole quenching and tempering (performance test) Dash semi-finishing spindle neck and connecting rod neck flange hole roughing processing stress finishing finishing spindle neck and connecting rod neck finishing Kinds of holes (oil holes, balance block mounting faces, weight reduction holes, inclined oil holes, flange holes, etc.)
Rough grinding spindle neck and connecting rod neck nitriding fine grinding spindle neck and connecting rod neck polishing spindle neck and connecting rod neck rounding rolling strengthening treatment and other assembly pump oil dynamic balance oiling anti-rust delivery.
Early crankshaft production line machining equipment and its characteristics
Around the 1980s, the machining equipment for crankshaft production was ordinary machine tools, such as: C61125, V1000 lathe and M1380 cylindrical grinder for machining the main journal; C8210 flying cutter lathe for processing the connecting rod neck and German crankshaft grinder; Z3080 rock wall drilling machines of various types of holes and XA2112 gantry milling machines for milling the plane and bevel of the crankshaft; as well as some homemade special machine tools, in addition to special tooling and tools.
Whether domestic or foreign, the professional production of early crankshafts is based on the crankshaft process to build a production line and configure multiple units. The characteristics of the crankshaft production line thus configured are: production according to the process flow, reducing the round-trip transportation of the crankshaft, the layout of the machine tool is relatively reasonable, and the lines are relatively clear, and different crankshaft types can be produced according to this process.
Advanced equipment for modern crankshaft production and its selection
After entering the 21st century, with the development of computer numerical control and the advancement of machine tool equipment manufacturing precision, the production of diesel engine crankshafts is dominated by three types of equipment: turning and milling machining center, boring and milling machining center and crankshaft driven grinding machine. The equipment is high precision, flexible and adaptable equipment).
The turning and milling center is represented by Austrian WFL (Fig. 2), Germany's NILES-SIMONS and Wohlenberg, and Spain's BOST. The crankshaft is from Germany's NAXOS (Fig. 3), Italy's AZ and BERCO, and Japan's Karatsu. The company, the British Landis company as the representative; the milling center with the Spanish Nicholas company, Germany MATEC company and SHW company, Czech Dows. The Vasdorf company is represented. These devices, in general, can cover the processing of the locomotive diesel engine crankshaft, the difference is that the difference in accuracy and price is relatively large. In the selection, the overall balance should be based on the accuracy, batch size and price tolerance of the production crankshaft.
After 2007, the company introduced WFL's turning and milling machining center and NAXOS's follow-up crankshaft grinding machine. After the introduction of advanced equipment, the manufacturing precision of the product has been considerably guaranteed. In the past, the manufacturing precision that was grasped by the operator has been replaced by equipment. In addition, the combined machining technology such as turning and milling has realized relatively concentrated machining processes, reduced the number of repeated loading and unloading and positioning of the workpiece, shortened the machining auxiliary time, and improved the machining accuracy of the workpiece. And the production efficiency, the number of equipment is significantly reduced, the production area of ​​the production line is saved, the output per unit area is greatly improved, and the labor intensity of the workers is also reduced (of course, the cultural and technical quality of the workers needs to be improved). A turning and milling center replaces the machining functions of turning, milling, drilling, expanding and reaming that were previously required by six or seven machine tools, including all machining of the main journal, connecting rod neck and crank of the crankshaft, and flange holes. Machining, keyway machining, threaded hole machining, main oil hole and oblique oil hole processing, etc., reduce the number of clamping times, improve product accuracy, and at the same time greatly reduce the tooling preparation for the trial production of new products, and the processing flexibility of the machine tool is greatly reduced. In the same way, a crankshaft follower grinder replaces the original ordinary large cylindrical grinder and connecting rod crankshaft grinder. One device has the effect of two grinders, and the space is only one grinder.
After the introduction of advanced equipment, the layout of the machine tools is suitable for cluster layout. In addition, the environmental requirements are also correspondingly improved, and the workshop building should be more suitable for fully enclosed air conditioning.
According to the comprehensive measurement, some domestic equipment can be equipped according to the complexity and batch size of the specific crankshaft production. The domestic milling equipment center (such as the Shenyang Machine Tool Group) and some ordinary machine tools, and the servo grinding machine of Shanghai Machine Tool Plant In recent years, there has also been great progress, which is a very good choice for the overall plan of the production line. The main difference between domestically produced equipment and imported equipment is in accuracy and reliability, but there is a great advantage in price, and there is no problem with semi-finishing or rough grinding of the crankshaft. This is more cost-effective in terms of efficiency and cost accounting.
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