Shu Qifu once put forward the concept of “equivalent blank” to study the influence of taper on the forming process of helical gear forming die forging, but the helical gear blank he discussed does not contain tooth profile. Therefore, it is necessary to study the influence of taper on the forming process of helical gear blank.
In the process of studying the influence of tooth shape on the hot die forging process of driven helical gear, it is found that the tooth shape of helical gear blank is not formed at the same time: after the tooth height direction is formed to a certain extent, the material first flows to the outer diameter direction to form the tooth shape at the outer diameter of helical gear, and then reverses the direction to form the tooth shape at the inner diameter of helical gear. This leads to metal accumulation in the local area of the large end when the small end tooth at the inner diameter is formed. In order to eliminate this influence as much as possible, the small end of the helical gear blank should first contact the die, so that the filling process of the large and small ends of the tooth profile can be completed synchronously, that is, the taper of the helical gear blank β It shall be less than the cone angle of tooth die root α。
The schematic diagram of bevel gear blank taper is shown in the figure, where β Is the tooth surface angle (taper) of helical gear blank, γ Is the base angle of helical gear blank, and H is the height of helical gear blank. In order to maintain the principle of constant volume before and after deformation, the height h of helical gear blank should be reduced with the increase of taper.
| Scheme I | Scheme II | Scheme III | |
| Gear blank taper β | α-1° | α-3° | α-5° |
In order to determine the appropriate taper of hot die forging helical gear blank, the following three schemes are designed. Tooth shaped die root cone α For reference, reduce a certain angle respectively. The specific scheme is shown in the table.