| dc.description.abstract | Bevel gears are wildly applied to angular transmission. Traditionally, bevel gears are manufactured by different dedicated gear machines according to the corresponding gearing system. Consequently, the bevel gears manufactured by different gearing system are not interchangeable due to different gearing parameters. Therefore, the design of flank modification on machined bevel gears will be more complicated. Therefore, the purpose of this research is to propose a lead crowning method with hyperbolic curve for spherical involute bevel gears. This design approach is intuitive and suitable for moulded gears. Loaded and unloaded tooth contact of bevel gear pairs under assemblely errors are analyzed to verify the feasibility of the proposed approach. Finally, test bevel gears are also manufactured for the measurement of tooth contact patterns and the fatigue tests.
The tooth contact analysis (TCA) proposed in the thesis is based on the contact conditions which are determined by the spherical involute geometric characteristics, so as to simplify the solving procedure. With aid of this approach, the influence of the flank modification parameters on the contact positions and transmission errors were analyzed for the gear pairs under different assembly errors. The results show that the contact position of the tooth pair due to the offset error is the most sensitive, the next is due to the mounting distance errors of the gear and the pinion. The shaft angle error does not affect the contact position in the direction of the face-width, but only the direction of the tooth profile. The curve of unloaded transmission error (TE) due to the offset error is similar to parabolic curve, the others due to the mounting distance errors are discontinuous linear curve. The shaft angle error affects no transmission error.
The loaded tooth contact analysis (LTCA) approach is based on the influence coefficient method to determine tooth contact stress, load sharing and loaded transmission errors. The results show that contact stress at the contact begin is the highest, and the concentrated contact stress occurs at the contact begin and the contact end. The loaded transmission error (LTE) will be shifted to a certain lag angle when the input torque is increased. At the inner and outer point of single contact tooth pair, a significant jump of the discontinuous LTE curve is also increased with a larger input torque, independ on presence of assembly errors.
The contact positions under various assembly errors simulated by the proposed TCA model are validated by measurement of contact pattern of test gears and interference analysis in CAD porgram. The results show that the TCA model is in good agreement with the contact pattern measurement and CAD simulation.
The gear fatigue test was conducted on a power close-loop test rig. Two kinds of test gears, each with non-modifided and modifided flanks, were tested under different loads for 5*10^5 cycles. The ratios of the tooth surface damage area of different cases are compared. The experimental results show that pitting damage on modified flanks is less than non-modifided under the same conditions.
Additionally, the vibration of the test gears was also measured during the test. It is found from the analysis results of the frequency spectrum that the vibration of the non-modifided gears due to the edge contact and the eccentric error was more serious after occurrence of the pitting on the flanks. The tooth wear has significant effect on thr vibration of the modified gears. Further more, the total amplitude values of vibration on the modifided gears are significantly lower than other cases, if the compensation of the shaft deformation is considered
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