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In order to show the meshing characteristics of the trimming gear, the basic parameters are: the center distance A=15omm, the number of the gears of the driving gear, the displacement of the shifting gear and the modification of the three types of gears for calculation and comparison. The radius of curvature of the cycloidal profile of each point except the vicinity of the node is greater than the radius of curvature of the involute profile. Since the two tooth profiles of the cycloidal tooth shape are convexly facing the concave surface, the actual contact area when meshing is larger than that of the involute tooth profile. Under the same conditions, the contact stress of the cycloidal tooth segment is small, and as a result, the amount of wear is reduced. Therefore, the wear resistance of the trimming gear is better than that of the involute tooth profile. If the transmission ratio is increased, the wear resistance of the modified gear will be more obvious.
This is extremely detrimental to the wear of the tooth flanks, especially at the root of the tooth. The calculation results also show that the displacement has little effect on the relative sliding coefficient of the gear. The greater the rotation ratio i, the more severe the wear of the gear. This indicates that the wear of the cycloid is evenly worn. At the crest and root, the sliding coefficient of the modified tooth profile is much smaller than the sliding coefficient of the involute profile. Under the same conditions, the larger the absolute value of the sliding coefficient and the larger the transmission ratio i, the more serious the wear. Obviously, the wear resistance of the modified tooth shape is better than that of the involute tooth profile.
The contact stress of the cycloidal profile is always smaller than the standard involute profile. When the meshing point is at the BZ point, the contact stress of the involute tooth profile is 3.87 times that of the cycloidal tooth profile. At point B, it is 2.2 times. This shows that the contact strength of the trimming gear in the cycloidal area is higher than that of the involute gear. It also shows that the modified gears in the closed gear transmission also have considerable advantages. The three calculation results are similar, in which the shape of the modified tooth shape is the smallest, but it is also sufficient to meet the basic requirements of the open gear transmission. The theoretical calculation of the root bending strength and the comparison of the tooth root thickness of the modified tooth shape are compared with the involute curve. The tooth shape is large, so the root of the modified tooth shape has a higher bending strength.
The flexural strength of the modified tooth profile is about 19-23 higher than the involute profile. In the case of severe abrasive wear, when the middle wear is in the middle, the full flank of the involute tooth shape, especially the deeper scratches at the tooth top and the root, is visually observed. The tooth surface of the modified tooth shape is very bright. The plastic flow of the three tooth profiles is not obvious. The wear curve is double-peaked, and the maximum amount of wear occurs at the top of the tooth, between the root and the node. At the top of the tooth, the amount of wear of the modified tooth shape is the least, and the amount of wear of the tooth shape of the shift is the largest and the tip of the tooth is sharpened. During the entire wear process, the amount of trimming tooth wear is smaller and uniform than that of the involute tooth profile. In the case of pinions, the amount of trimming tooth wear is reduced by 2.8 compared to the standard involute tooth profile and the deformed tooth profile, respectively. Similar conclusions have been made for both large gears and spur gears.
When the involute gear transmission ratio reaches i=6, undercutting occurs and the wear of the pinion gear is also very disadvantageous. The trimming gear transmission can work normally, which is very advantageous for the transmission with large modulus and large speed ratio. The experimental study of wear resistance is to simulate the abrasive wear condition, and the hematite powder of an iron ore of Angang is used as the abrasive grain. The hob is machined on a hobbing machine into a standard involute gear, an involute shift gear and a trimming gear. The experimental device is a swing box open type closed power test bench. The wear of the tooth thickness at any tooth height was measured with a universal tool microscope. Eight types were arranged in equal rows on the crest and observed the change of bending stress at the root. It can be seen from the experimental results that the stress of each of the two tooth shapes increases linearly with the increase of the load. The profiled tooth profile is about 21 higher than the involute profile on the root bending strength. Under the same conditions of noise and center distance separation experiment, the working noise of the modified tooth shape is 71-75dB; the involute tooth shape is 80-85dB, which indicates that the work of shaping the tooth shape is more stable and is more conducive to environmental protection. The results of the center distance separation experiment show that there is no significant difference between the modified gear transmission and the involute gear transmission when the center distance changes slightly.
Comparing the two tooth shapes, it is known that the shape of the tooth is better than the involute profile in terms of wear resistance, contact strength, root bending strength, transmission stability, large speed ratio and closed gear transmission. . Especially for low-speed, heavy-duty open transmission, the modified tooth profile is more valuable than the involute tooth profile and the equal-gap displacement tooth profile.
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