Hiroki Maruyama

Noise Comparison of Polyacetal Gears Based on Differences of Gear Processing Methods

The mass production of plastic gears by injection molding has many advantages ; however, hobbing has been used in cases where injection molding could not be applied due to economical problems of mold shrinkage in the small-volume production of a wide variety of gears and technical problems in the processing of large-sized thick gears. It has been said that there are differences in the magnitude of noises between injection-molded plastic gears and hobbed plastic gears causing a difference in acoustic characteristics based on the difference of crystallinity of their gear surfaces. In this study, by using a polyacetal gear, and by measuring noises of both gears at each point of time when the properties of their gear surfaces were changed by the wear during a long period of operation, the difference of noises based on the difference of plastic gear processing methods was verified quantitatively based on experimental results.

Water Lubrication characteristics of Polyacetal Gears Filled with Carbon Fiber.

For a polyacetal with high strength and rigidity, we should select a composite polyacetal filled with, for example, carbon fiber. However, this may not be true in the case when this kind of composite polyacetal is used in water. That is, it is considered that the sliding characteristics might decrease because water enters into the bonding space of carbon fibers and polyacetal and of carbon fibers with each other. In this study, operation tests of a polyacetal gear filled with carbon fiber in water and with water drops were examined and the wear of the gear and the change of the tooth profile were determined. By comparing these results with those of an unfilled polyacetal gear, we investigated the usefulness of polyacetal gears filled with carbon fiber in water or steamy environments.

Term of life and wear of plastic intermediate gears.

The plastic gears used for driving paper-drying drums in paper-making machines and others are used at a gear ratio of 1:1 by putting several gears in a row. Accordingly, the intermediate gears undergo loading on both tooth surfaces, but at present, the operational characteristics of the plastic gears being used in this way have not been elucidated at all. Therefore, in this study, the operation test applying alternating loads was carried out using MC nylon gears and such things as the operational term of life, the wear of teeth, and the state of change of tooth profile were examined.