The tooth profile design of spiral bevel gear forging is an important step in the design of gear forging die. The tooth profile parameters of forging can guide the subsequent die tooth profile design, and the tooth profile parameters of forging are determined according to the tooth profile parameters of finished spiral bevel gear parts and forging process requirements.
As shown in the figure, it is a tooth of the equivalent gear of CA141 driven spiral bevel gear forging, and gives the relationship between the tooth profile of the forging and the part. Since the tooth profile of the equivalent gear is consistent with that of the spiral bevel gear on the back cone, the modulus and pressure angle of the equivalent gear are equal to that of the big end of the spiral bevel gear. According to the involute parallel theorem, the curve parallel to a given involute is also an involute, and the curve is the same as the base circle of the given involute, that is, it is known that the tooth profile curve of the finished spiral bevel gear part is an involute. Since the tooth profile curve of the spiral bevel gear forging is parallel to the finished spiral bevel gear, the tooth profile curve of the spiral bevel gear forging is also an involute, Due to the existence of oxide scale in the precision forging process of spiral bevel gear and considering the cutting allowance of subsequent finish machining, it is necessary to leave unilateral normal machining allowance for the tooth profile of forging Δ。 Since there are many parameters involved in the calculation of tooth profile parameters, in order to avoid confusion, the parameter codes of spiral bevel gear used below are listed in the table.
| Parameter name | Tooth profile of finished gear | Gear forging tooth profile | Tooth profile of hot forging die |
| Modulus of large end face | m | m’ | m” |
| Radius of addendum circle | ra | r’a | r”a |
| Radius of tooth root circle | rf | r’f | r”f |
| Dividing circle radius | r | r’ | r” |
| Normal tooth angle | α | α’ | α” |
| Number of teeth | Z | Z | Z |
| Split cone angle | δ | δ | δ |
| Equivalent gear addendum circle radius | rav | r’av | r”av |
| Equivalent gear root circle radius | rfv | r’fv | r”fv |
| Equivalent gear indexing circle radius | rv | r’v | r”v |
| Equivalent gear base circle radius | rbv | r’bv | r”bv |
As can be seen from the figure, because, i.e Δ/ RB < 0.01 is far less than the radius of the base circle, so we can get:
The pitch circle radius and normal tooth angle inv of the large end of the tooth profile of the spiral bevel gear part α′ vr α Substituting into the formula, the obtained value can be obtained by looking up the involute function table α′。
From the geometric relationship between spiral bevel gear forging and finished gear:
The module M ‘of spiral bevel gear forging is:
Since the dimensions of tooth tip circle and tooth root circle of precision forged spiral bevel gear forging can fully meet the requirements of parts, the following can be obtained:
