Pre-grinding hob and machining method thereof

Abstract

The invention relates to a pre-grinding hob which comprises front teeth and back teeth. A small tooth is formed at the back portion of a tooth root of each normal tooth of the pre-grinding hob, the small teeth are tooth profiles of tooth tops of the pre-grinding hob, the original normal teeth of the pre-grinding hob are called as the front teeth, and the small teeth formed at the back portions of the tooth roots of the normal teeth of the pre-grinding hob are called as back teeth; the front teeth and the back teeth of the pre-grinding hob are designed on one equally-divided part, and angles of front tooth blade ditches and back tooth blade ditches are different; the pressure angle of the front tooth blade ditches is 20 degrees, the front tooth root transition circular bead R is 0.3 modulus, and tooth profile curves of the tooth tops of the front teeth and the back teeth are oval; and the cross section of the bottom of the tooth profile of the tooth top of each front tooth is an elliptic long shaft, wherein the distance between the center of the long shaft and the tooth top end of the front tooth is a short semi shaft, and the length of the short semi shaft is 0.65 time that of a long semi shaft. Hob materials are subject to cobalt-contained high-speed steel or powder metallurgy, the technology for heating processing is used in cooperation, a TiAlN or TiN coating is adopted for surface processing, and the hob surface hardness is greatly improved on the original basis.

Description

technical field [0001] The invention belongs to the field of special tools for gear machining, in particular to a high-efficiency and high-precision pre-grinding hob. Background technique [0002] In the prior art, circular arc gear transmission is widely used in national defense, medical equipment, precision instruments (such as watches), etc. This type of circular arc gear is characterized by small modulus, high transmission ratio and compact structure. Generally, precision hobs are usually used for hobbing or milling cutters to process ordinary gears. For arc gears, hobs generally have the following characteristics: 1. The hob has an arc tooth shape, and It also adopts small modulus, its diameter is small (about ￠6mm), and the precision requirement is high (tolerance is 0.003mm); 2. This kind of arc-shaped hob is mostly made of YG6X or YT10 hard alloy material , high hardness; 3. The blanks of hobs are mostly pressed and sintered. After the blanks are machined, there is ...

AI Technical Summary

Problems solved by technology

These two kinds of round-end grinding hobs have the following disadvantages: when processing gears with a small number of teeth, the involute of the gear after grinding is extended, which cannot meet the design requirements and affects the meshing coefficient of the gear; Grinding teeth will have grinding steps, resulting in stress concentration, which affects the bending strength of the gear tooth root

Ordinary pre-grinding hobs have low strength due to the small number of blades and grooves, and the service life of the hob is also low

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