Analysis Of Failure Of Ball Plug Type Inner Curve Hydraulic Motor And The Radial Unbalanced Force

Low speed high torque hydraulic motor has been widely used in a variety of mobile hydraulics because of its characteristics as follows: high power density, high start torque and stability under low speed condition. Ball plug type inner curve hydraulic motor is especially used in a number of mobile hydraulics for merits of compact size, simple construction, low price and so on. However, some issues were found during the time it worked, including short lifetime, sharp declination in efficiency after a period of time.Force analysis and failure analysis of the ball plug type inner curve hydraulic motor, concentrating deformation and abrasion of the plunger as well as fracture and spot corrosion of the rail , were made in the paper. For the design calculation of ball plug type inner curve hydraulic motor, constant pressure of returning oil is generally applied which was showed distinct in different chamber enclosed between rotor housing and plunger by CFD technique and force analysis method. Eventually a radial unbalanced force of the rotor was concluded. The result that the radial unbalanced force of rotor was obtained while the relationship between radial unbalanced force and fracture of the rail was also presented.The main content of this paper is as follows:In chapter 1, the purpose, significance and background of the research were expounded. Research status of the inner curve hydraulic motor both at home and abroad was summarized. Main contents of the research were summarized.In chapter 2, the structure and operation principle of the ball plug type inner curve hydraulic motor were elaborated. PROE was applied for accurate modeling of ball plug type inner curve hydraulic motor's rail. Based on the common theory of inner curve hydraulic motor, MATLAB is used to analyse kinematical and mechanical characteristics of ball plug type inner curve hydraulic motor so as to lay a foundation for the further study.In chapter 3, force analysis and failure analysis of the ball plug type inner curve hydraulic motor, concentrating deformation and abrasion of the plunger as well as fracture and spot corrosion of the rail , were made in this chapter. Spot testing was made to show a drastic fluctuation in pressure of the hydraulic system.The solution of failure in ball plug type inner curve hydraulic motor's rail was put forward by means of installing a accumulator in the system or optimizing the performance of relief valve to reduce the pressure fluctuation.In chapter 4, working process of ball plug type inner curve hydraulic motor was analysed and pressure of returning oil was showed distinct in different chamber enclosed between rotor housing and plunger by CFD technique and force analysis method. Eventually a radial unbalanced force of the rotor was concluded. The result that the radial unbalanced force of rotor was obtained while the relationship between radial unbalanced force and fracture of the rail was also presented. The fact that additional torque pulsation brought by variation in pressure of returning oil, which exists in the separate chamber formed by rotor and all plungers, was found. The fact that periodic oil whirl would appear in the clearance formed between the rotor and the pintle under the condition of a radial unbalanced force which occurs in the rotor was also pointed out.