Strength analysis of the intermediate shaft of the hypocycloidal fuel pump

Abstract

Diesel engines are currently characterized by very high injection pressure. The high pressure allows to achieve better parameters of the fuel atomization process, thus contributing to the improvement of the engine’s ecological parameters. Achieving such a high pressure is possible thanks to the use of reciprocating positive displacement pumps, enabling the fuel pressure to be increased up to 3000 bar. A common feature of currently produced pumps is the drive of the pressing sections through the camshaft, which is lubricated using fuel. For this reason, cam-driven pumps are very sensitive to the quality of the fuel used, and one of its disadvantageous features is also the generation of lateral force on the piston of the section. For this reason, the authors of the article have developed a pump solution, using a hypocycloid drive, in which the disadvantages of traditional cam-driven pumps have been eliminated. The hypocycloid mechanism used has a separate lubrication system, and due to the generated rectilinear motion only the force parallel to the direction of the movement works on the piston. An important problem in the construction of a hypocycloid pump is the high loads of cooperating elements. The intermediate pump shaft is considered to be the most loaded element due to the complex state of stress. The article presents the methodology and results of simulation tests. Stress states have been determined for the position of the shaft in which it takes the highest load. As a result, it was recognized that the pump shaft was designed properly and despite the high force acting on the piston section, it is possible to ensure its long-term and reliable operation.