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Selection of main parameters of the gear pair In order to more clearly analyze the influence degree of each parameter, the influence trend and the influence sensitivity, each factor selects three levels. Pressure angle: The gear pair is the high gear of the transmission, which requires high noise, so the pressure angle cannot be increased. The primary selection is 17.5°, 18.5° and 20°. The full cone bearing heavy transmission is usually used in the high gear. The helix angle is 16°~26°. The helix angle is selected as 16°, 20° and 26°; the height of the tooth tip is initially selected as 1, 1.25 and 1.5, and the final tooth height coefficient is selected according to the tooth thickness of the tooth tip.
Experimental Design This test is a three-factor three-level, and orthogonal table L9 (34) is selected. The A factor is the pressure angle α, the B factor is the helix angle β, and the C factor is the crown height coefficient K. Test index: bending strength safety factor Sb, contact strength safety factor Sc; strength calculation using GB3480. Record the test plan and test results , analysis of variance analysis of test results.
Gear Strengthening Test Scheme and Test Results Test Scheme Test Results Test No. A (pressure angle α) B (helix angle b) C (tooth height coefficient b) A factor indicator map is drawn based on the analysis results. The medium thick line represents the influence of each factor on the bending strength, and the thin line represents the influence of each factor on the contact strength. It shows the influence of each factor on the bending strength and contact strength. According to the specific use conditions of the gear pair, the weighted average method is used to analyze the combined effects of each factor on the bending strength and contact strength.
Conclusion: (1) For the contact strength, the degree of influence from high to small is the pressure angle, the helix angle and the height of the crown. The influence sensitivity from large to small is the helix angle, the pressure angle, and the height of the tip. (2) For the bending strength, the degree of influence from the largest to the smallest is the pressure angle, the height of the tip, and the helix angle. The influence sensitivity from large to small is the tip height coefficient, the helix angle, and the pressure angle.
(3) The gear pair is the high gear of the transmission, the speed is high, the noise is high, and there should be a large contact strength; in actual use, the broken teeth appear, which is insufficient bending strength. Comprehensive considerations, the results of the weighted score calculation results, the degree of influence from large to small is the pressure angle, the tip height coefficient, the helix angle. The influence sensitivity from large to small is the helix angle, the tip height coefficient, and the pressure angle.
(4) The pressure angle, the helix angle, and the tip height coefficient are proportional to the gear contact strength and bending strength. In fact, through the comparative analysis of the low gear pair, it can be known that the above conclusions (1), (2) and (4) are true for all transmission gear pairs in terms of single contact strength or bending strength.
The optimization result uses the above conclusions to strengthen the gear pair. In addition to considering the ideal influence degree and influence sensitivity of each parameter, it is also necessary to comprehensively consider the actual situation of the gear pair, such as the tooth top when the tooth height coefficient is 1.5. Over the top and other factors. The final optimization parameters are: pressure angle 20°, helix angle 26°, driving wheel tip height factor 1.4, driven wheel tooth tip height factor 1.3.
It can be seen that in the case where the modulus and the tooth width are not changed, the contact strength can be increased by 18 and the bending strength can be increased by 25 by changing the pressure angle, the helix angle and the height of the tooth tip, and the strengthening effect is very obvious. The key issue after reinforcement is to find the best tip trim and tooth profile modification through bench test to achieve the best load carrying capacity.