Study On High Pressure Common Rail Pump Floating Bearing Capability

High pressure pump is the core component of Common Rail System whose function is to supply adequate fuel quantity in order to set up rail pressure. In high pressure pump, roller tappet plays an important role which transfers energy from camshaft to plunger thus determines pump capability. A so called floating ring bearing is composed of roller, bushing and pin which can be divided into two kinds of bushing bearing, one is inner bearing which is composed of pin and bushing, another one is outer bearing which is composed of bushing and roller. Roller is drived by pump camshaft then transfers energy to bushing and makes it roll. As a result, the inner bearing which is composed of bushing and pin will be the weaker point due to bushing lower rotation speed. So our strategy is to study inner bearing capability in all conditions then to combine outer bearing together to study the whole floating ring bearing capability.A normal way of bushing bearing research is to study Reynolds equation. In this thesis, we also follow such a traditional method to study floating ring bearing capability. Firstly, we make up normal Reynolds equation from flow consistence equation and transfer it into a round bearing style. Then the equation is solved by a numerical method Finite Differential Method (FDM), program is coded in MATLAB M file language. Based on Reynolds equation and FDM program, we study all parameters which impact bearing capability such as bearing length to diameter rate ,eccentricity, bearing deformation under heavy duty, oil film viscosity relationship with pressure. Rough surface is also taken into consideration by solving so called average flow quantity Reynolds equation. At last, inner bearing and outer bearing is considered together through the method: floating ring will be balanced both by force and by torque in stable working condition. So influence of inner to outer clearance rate, inner to outer radius rate to bearing capability is considered. Endurance tests have also been proceeded to validate different inner to outer clearance rate influence on floating ring bearing capability. Both theoretical and experimental result shows that inner to outer clearance rate has a great influence on floating ring bearing capability.