Takayuki Aoyama

Analysis of noise occurrence by cavitation in the main bearing of diesel engine

Abstract This paper presents an analysis of noise occurrence at the 7th main bearing of an inline six cylinder diesel engine. From experimental results of the engine, it seems that cavitation in the bearing oil film is a major factor for this noise, and the noise occurs with a combination of the following conditions; (1) cavitation exists in oil film at the main bearing, (2) main journal is unstable and (3) excitation force acts at this moment. This assumption is analyzed using engine vibration analysis, EHL analysis and stability analysis. The results agree with the condition of the noise occurrence.

Design Method for Optimizing Contact Ratio of Hypoid Gears

Innumerable solutions can be obtained when the pitch surface of a hypoid gear is solved from the requirements of two cones. The pitch angle is determined by the Gleason method based on the idea that the tooth lengthwise curvature corresponds to the cutter radius. This study proposes a new design method that can optimize the contact ratio using the pitch angle, using the new tooth geometry advocated by Honda. The balance of the contact ratios of the convex and concave sides of a gear can be optimized by designing the pitch angle. By optimizing the contact ratio, noise and vibration performance can be improved. In addition, highly efficient gear design can be achieved by decreasing the spiral angle.The effectiveness of this optimized design method is confirmed by measuring transmission errors under load. Design examples of a highly efficient gear by reducing the spiral angle and a gear which ensures high noise and vibration performance are shown. Using this proposed method expands the design freedom of hypoid gears.© 2013 ASME

Flexible Multibody Dynamics Analysis of Automobile Engine

The calculation method of dynamics behavior on automobile engine is getting more important as computer-aided engineering technique to design optimized mechanisms and structures for lighter weight, lower mechanical friction and lower noise. Engine system consists of deformable moving components and several kinds of mechanical joints, such as an oil lubricated bearing. Dynamics problem includes various kinds of noise and vibration phenomena in wide frequency range. Therefore, it is crucial to analyze precisely the coupling behavior between rigid motion and elastic deformation of moving components considering nonlinear dynamic effect of mechanical joint. In this study, we formulated equations of motion for the flexible multibody dynamics system and developed a computer software specialized for internal combustion engines. In the formulation, both rigid motion and elastic deformation are simply expressed by eigen modes on a local observer frame in order to calculate efficiently many deformation modes up to higher frequency range. In addition, several kinds of force elements are formulated to express the nonlinear forces of mechanical joints and the boundary conditions. The developed program has been verified by the experiments under running condition and applied to the real engine design.Copyright

Calculation Method for Coupled Vibration Between Tooth Contact and Nonlinear Structural Components Under Running Conditions

The purpose of this study was to develop a numerical calculation method for gear system vibration, which changes depending on nonlinear structural components such as bearing clearance and spline contact. The numerical calculation method uses multibody dynamics simulation with the following features: a) the use of theoretical tooth shapes and stiffness to represent the tooth contact of gear pairs, b) the use of finite element models to express the gear system, including the nonlinear structural components causing the variation, c) consideration of the coupled vibration between the tooth contact and gear system. The numerical calculation method allowed the prediction of the variation tendency due to changes in some clearances and spline contacts.Copyright

Influence of Bearing Clearance on Load Sharing in Planetary Gears

Load sharing among plural pinions in planetary gears should be equal to reduce gear noise and to secure the strength of the gears and bearings. This study investigates the influence of bearing clearance on load sharing using multibody dynamics analysis. One of the characteristics of this analysis is its capability to calculate dynamic gear meshes and bearing clearance nonlinearity. Contact analysis of the gears defines the tooth surface expressed by numerical formula involving modified surface geometry. Moreover, nonlinear stiffness is used to express the bearing clearance. The numerical method is verified by experiments that measure bearing loads on pinions using strain gauges. Subsequently, the influence of bearing clearance is examined numerically. The results confirm that the clearance of the carrier is dominant. In addition, unequal loads arise from reductions in the bearing loads and inclination of the carrier. Finally, this paper suggests an appropriate clearance for well-balanced load sharing.© 2011 ASME