Small Modulus Spiral Bevel Gear Manufacturers: Design Basis and Selection of Preheat Treatment Methods for Small Modulus Spiral Bevel Gears

Generally speaking, the selection principles of the design benchmark of small modulus spiral bevel gear include: the principle of datum coincidence, the principle of datum unification, the principle of self-datum, the principle of mutual datum, the principle of easy clamping, etc. In general, bevel gear design will be developed and designed in strict accordance with these principles. After the design basis is determined, manufacturing will proceed. Today we mainly discuss the preheat treatment of bevel gear blanks in the manufacturing process.

Proper preheating of the bevel gear blank can not only obtain a more uniform organization, but also eliminate the stress during heat treatment and reduce deformation.

1. The normalizing high temperature tempering process is suitable for high hardenability low carbon medium alloy steel, such as 22CrMnMo, 20CrNiMo, 18crniwa, 20crni3, etc. The hardness is 170-228hbw, and the metallographic structure is tempered sorbite, distributed on ferrite and ferrite matrix.

2. The simple isothermal normalizing process equipment adopts two trolley-type resistance furnaces. The process route is as follows: the gear blank is heated at high temperature (940-960 ℃)-discharged after heat preservation-air cooling for appropriate time-entering No.2 furnace for isothermal temperature (550-650 ℃)-exhaust cooling. The isothermal temperature and isothermal time were determined according to the austenite isothermal transformation curve of gear billet steel, and the normal normalizing structure was obtained. This process is suitable for steels with high hardenability and easy to produce granular bainite, such as cr2ni4mo 18, 20cr2ni4, 20CrMnTiH, 20mncr5, 16MnCr5 and 22CrMoH steels. The hardness is 156-200hbw, and the metallographic structure is pre-eutectoid F pseudo-eutectoid P, but the effect of eliminating the banded structure is not ideal.

After installation, the rack and pinion cannot be put into use immediately. We need to adjust them first. The following are the adjustment items after rack and pinion installation:

First, check whether the gear and rack are correctly assembled.

Second, check whether the tooth surface contact is biased to one end. After running, it needs to be continuously debugged. Smooth operation.

Third, it must be observed whether there is proper side clearance.

Fourth, we need to lubricate the gears and racks before operation.

During the installation process, we can use small tripod to fix the rack. Rack and pinion fit should be included in the selection of zero backlash tolerance. How to select zero backlash tolerance for rack and pinion fit? The following is a brief description of the selection of zero backlash tolerance for rack and pinion fit:

The design of small module spiral bevel gear should not achieve zero backlash fit by selecting tolerances in the design, but only by designing adjustment mechanisms (adjusting center distance). This requires the assembler to judge whether zero backlash fit is achieved according to various inspection methods or experience of gear backlash and actual assembly conditions. Generally speaking, gear-related fit cannot achieve zero backlash fit, the practical significance is not great (because the gears are in line contact during the torque transmission process, and there will be a certain amount of wear after a period of operation). It is possible to design mechanisms such as eccentric shafts (wheels) and adjustable gear seats to adjust or compensate for backlash.