Straight bevel gears are widely used in the plant of large-sized power generation when the gears have large size. The purpose of this study is to manufacture the large-sized straight bevel gears with equi-depth teeth on a multitasking machine. The manufacturing method has the advantages of arbitrary modification of the tooth surface and machining of the part without the tooth surface. For this study, first, the mathematical model of straight bevel gears by complementary crown gears considering manufacture on multitasking machine is proposed, and the tooth contact pattern and transmission errors of these straight bevel gears with modified tooth surfaces are analyzed in order to clarify the meshing and contact of these gears. Next, the numerical coordinates on the tooth surfaces of the bevel gears are calculated and the tooth profiles are modeled using a 3D-Computer-Aided Design (CAD) system. Five-axis control machines were utilized. The gear-work was machined by a swarf cutting using a coated carbide end mill. After rough cutting, the gear-work was heat-treated, and it was finished based on a Computer-Aided Manufacturing (CAM) process through the calculated numerical coordinates. The pinion was also machined similarly. The real tooth surfaces were measured using a coordinate measuring machine and the tooth flank form errors were detected using the measured coordinates. As a result, the obtained tooth flank form errors were small. In addition, the tooth contact pattern of the manufactured large-sized straight bevel gears was compared with those of tooth contact analysis. The data showed good agreement.
For moderating the edge contact of gear tooth surfaces on load, a new concept has been proposed on designing worm gearing. As a first step of research, restricting a field of application of the designing concept, a few methods for generating tooth surface of hourglass worm gearing having a small lead angle have been devised.
This paper tries to apply this designing concept to wider general use — an hourglass worm gearings with a large lead angle. First, the worm axis displacement relative to the wheel axis is roughly calculated by means of elastic deformation theory. And, this idea is applied to the gear designs using two kinds of hourglass worm gearings. As a result, validity of this design concept is substantiated also in the case of large lead angle of worm gearing.
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