STUDY FOR BEARING CONTACT, MANUFACTURING AND ASSEMBLY OF ROLLER GEAR CAM
|關鍵字:||滾齒凸輪;接觸特性;空間凸輪;過切條件;組裝;roller gear cams;bearing contact;spatial cams;undercutting condition;assembly|
Roller gear cams are widely used in the industry for indexing. Compared with conventional indexing cams, roller gear cams require less space and provide accurate, high-speed motions. To date, most studies have been devoted to develop generation models based on the ideal condition of line contact between the cylindrical type of cutters and cam surfaces. However, due to manufacturing and assembly errors, contacts of a roller gear cam become point contacts rather than line contacts. The bearing contact, the undercutting condition and the assembly tolerance were studied based on the realistic of point contact model in this study. The capability of a cam mechanism for an acceptable lifecycle deeply depends on the stress distribution in the practical contact. When two elastic bodies with curved surface transmit loads from one to the other at the point or line contact, contact area can be developed, and accompanied by compressive contact stress, which may effect the lubrication property, even more, may cause fatigue damages on both of the engaged surfaces. For the idea to study of bearing contact properties, the principal directions and curvatures of the cam surface, the contact ellipse and the Hertzian contact stress are studied in sequence based on gearing theory. Undercutting is very detrimental to the kinematic and dynamic performance. Up to now, most studies on the undercutting condition of the roller gear cam were case by case. A mathematical model for the surface profile of the roller gear cams in dimensionless space is proposed. According to this model, the conditions for non-undercutting are generated with procedure to determine the feasible condition region that is free from undercutting is developed in the dimensionless space. This result can be employed with the design approach to determine the feasible region of design parameters. An integrity and robustness of optimization approach is developed that made engineers take account of all aspect of design, possibly and easily. The studies in this thesis can help engineers to improve the design and manufacturing with higher accuracy and quality of roller gear cam mechanisms. Finally, the concept of the robust assemble condition under the minimum variations caused by manufacturing errors is used to achieve the robust tolerance design. The tolerance algorithm is constructed based on the 3-D assembly model, the tooth contact analysis (TCA) technique and the condition number for the theory of matrix. The investigated results demonstrated in, but not limit to, understanding of the assembly nature of the roller gear cam, and can be easily employed for other type of tolerance design. The results are most helpful to the design and manufacturing of the roller gear cam mechanisms with high accuracy and quality.