Tomio Koyama

Noise and life of helical timing belt drives

A new helical timing belt has been developed to reduce noise. In the present study, three belts, each having a curvilinear tooth profile and helix angles of 3 deg, 5 deg and 10 deg, respectively, were designed. The noise and life of the helical timing belt under a constant transmission force are compared with those of a conventional timing belt, in which the helix angle is zero. The noise level of the new helical belts having helix angles of 5 deg or 10 deg was found to be around 5 dB(A) lower than the conventional belt. The belt life was found to be almost identical for each type when the installation tension was set while the slack side tension for the transmission force was lowest. The results of the present study showed that helical belts should be selected for applications in which noise is a crucial factor.

A Study on Jumping Characteristics in Synchronous Belt Drives: Experimental Results and FE Analysis at Driven Pulley Jumping

The jumping characteristics at the driven pulley of L type synchronous belt drives are experimentally and analytically discussed. The number of the driving and the driven pulley teeth is the same and the wrapping angle of the belt on both pulleys is π radian. In this paper, the meshing state of belts on both of the driving and driven pulleys just before jumping is analyzed using the Finite Element analysis. Standardized L type synchronous belts and pulleys are used for analysis and experiments of the meshing states between belt and pulley, load distribution stress analysis and jumping torque. A 337L075 trapezoidal tooth profile synchronous belt and a 36L075 synchronous pulley are used in the analysis and the experiments. The wrapping angle of belt on both the driving and the driven pulley is equal to π radian. “ABAQUS/Standard” is used for the simulation and analysis of the belt. The simulation of the FE analysis of the wrapping angle of the belt on the driven pulley is almost the same with the experimental result. FE analysis of the load distribution just before jumping on the driven pulley agrees well with the experimental results.Copyright

Side Tracking in Helical Synchronous Belt Drives Under Torque: Influence of Pulley Flange on Axial Belt Movement

When helical synchronous belt drives operate under a torque, the belt experiences side tracking, which results in an offset between the position of the belt on the driving pulley and that on the driven pulley. Side tracking causes the belt from running off the pulley. The general countermeasure is to fit a flange either to the driving pulley, to both the driving and driven pulleys, or to one side of the driving pulley and the opposite side on the driven pulley. In this study, the axial movement of helical synchronous belts under torque was investigated when the pulley flange attaches to either the driving pulley or driven pulley. In addition, fatigue tests were conducted in order to ascertain the damage to the side face of the belt. It was found that the offset is effectively reduced when a flange is installed on the driving pulley, on the side that affects the direction of the moved belt, even if a flange is not fitted to the same side of the driven pulley. When a flange is fitted solely on the driven pulley, there is a large offset, but the force of the belt pushing against the flange is reduced. As a result, the damage to the side face of the belt is mitigated.Copyright

Transmission Error in Helical Synchronous Belt Drives in Bidirectional Operation: Influence of Pulley Flange Under No Load

Helical synchronous belt drives are more effective than conventional synchronous belt drives with respect to reducing noise and transmission error per single pitch of the pulley. However, the helix angle of the tooth trace causes axial belt movement. Therefore, a flanged pulley is used in a helical synchronous belt drive. In the present study, the transmission error in a helical synchronous belt drive using a flanged pulley under installation tension was investigated both theoretically and experimentally for the case where the pulley was rotated in bidirectional operation. The computed transmission error agrees well with the experimental results, thereby confirming the applicability of the proposed theoretical analysis for transmission error. In this case, transmission error is found to be generated by the difference in axial belt movement between the driving and driven sides, and by a change in the state of contact between the belt and pulley teeth flanks. The transmission error is reduced when the installation tension is set higher than the tension that causes a change in contact direction between the tooth flanks. In addition, transmission error does not occur when the driving and driven pulleys are of equal outside diameter and have no pulley alignment error.Copyright