Experiment and result analysis of helical gear meshing transmission

After the transmission test bench is assembled, the contact spot detection experiment of helical gear is carried out below. Because the tooth surface equation of helical gear is generated by meshing with helical cylindrical gear, the meshing state of the two gears should be good in theory.

The specific steps of contact spot detection of helical gear are as follows: firstly, thoroughly clean the measured helical gear, secondly, apply a layer of red lead powder on single or more teeth of helical cylindrical gear, the coating shall be thin and uniform, and the coating thickness shall be about 5um. After applying red lead powder on the small helical cylindrical gear, rotate the small helical cylindrical gear, The purpose is to mesh the gear of the small helical cylindrical gear coated with red lead powder with the tooth surface of the helical gear. After several revolutions, remove the helical gear and observe the contact marks on the tooth surface. Figure 1 shows contact spot detection.

After completing the contact spot detection of the helical gear, calculate the size of the contact trace on the helical gear tooth surface (as shown in Figure 2). That is, the percentage along the tooth length direction and tooth height direction of helical gear.

Percentage along the tooth length direction of helical gear: the ratio of the length ‘B of contact trace (remove the broken part C greater than the modulus value) to the working length’ B.

Percentage along the tooth height direction of helical gear: the ratio of the average height H ‘of contact trace to the working height H’.

According to the experimental analysis of the distribution of contact spots in Figure 1, the erythema area on the tooth surface of helical gear is unevenly distributed along the direction of tooth width, increasing from outside to inside. According to the table analysis, the highest erythema area along the direction of tooth height and tooth length is less than 50%, indicating that the accuracy of face gear is less than Grade 7. There is a certain gap between the tooth profile of helical gear machined by actual hobbing and the theoretical meshing tooth profile. Analyze the reasons for this gap:

Firstly, based on the principle of gear hobbing, there are differences between the actual helical gear hobbing and the theoretical modeling model. The main reason for this difference is that when hobbing helical gears, the requirements for hobs are very high. In order to avoid the difference, a special hob should be designed and modified to meet the requirements of hobbing helical gear.

Second, the error of tool setting before gear hobbing has a great impact on the gear profile. During gear hobbing, the center of the gear blank is determined first, and then the center line of the hob is determined by marking the center of the gear blank to mesh with the center line of the gear blank to complete tool setting. The error caused by tool setting is finally reflected in the tooth profile of face gear by gear hobbing. Although it is impossible to completely eliminate the error during tool setting, the error should be minimized.

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