Papers by Keyword: Helical Gear

Abstract: This research aims to investigate micro-crack on a failed for helical gear transmission which was to adjust the engine to increased horsepower. The helical gears made are from chromium steel JIS-SCr 420. The spectrophotometer test machine was used to detect chemical composition, Mechanical properties were evaluated by Vickers hardness and microstructural analysis with an optical microscope, which the crack of the surface layer and energy dispersive spectroscopy using a scanning electron microscope. The results showed that the fracture characteristic of the helical gear’s surface was expected to beach marks and break away. It can be seen that the mixing failure area of oxide inclusion with carbide surrounding before the liquid state of material will be solidified which caused the failure cause of this helical gear. The summary analysis results can be accorded with the assumption of this research and which help prolong service life of the component.

Abstract: The gear honing is the most economical way for hard finishing an involute helical gear after hobbing and heat treatment or after shaving and heat treatment. The gear honing can also be applied to the modification of gear tooth surfaces to compensate for the distortions that occur during heat treatment process. Most published papers on the technology of gear honing describes on the principle of generated gear surface. However, the longitudinal tooth flank crowning of a helical gear with honing has not been investigated yet. Therefore, in this paper, we proposed a novel method for longitudinal tooth flank crowning of work gear surfaces by setting a crossed angle between the honing cutter and work gear axes as a linear function of honing cutter's traverse feed in the honing process. A mathematical model for the tooth profile of work gear honed by a standard honing cutter is also established. Three numeral examples are presented to illustrate and verify the merits of the proposed gear honing method in longitudinal crowning.

Abstract: Based on comprehensive considerations the influences of stiffness excitation, deviation excitation, meshing impact excitation, friction of tooth surface, and other kinds of nonlinear factors, it established a nonlinear coupled vibration model of bending-torsion-axial-swing coupled helical gear transmission system by applying the Lumped Mass Method. After transformed the model to dimensionless form, it used Runge-Kutta method to solve the nonlinear vibration model of the system, and then the time domain chart, spectrum chart, phase chart, Poincare chart, and FFT chart were obtained; it discussed the influence of system parameters on its dynamic characteristics.

Abstract: The article demonstrates one of the ways to reduce uneven load distribution along the width of the gear wheels which can be used in place of expensive modifications of the tooth flanks (crowning). This can be achieved by appropriate selection of the shape of the gear wheels for example the disk shape. The presented numerical example illustrates the above possibility taking into account deformability of the wheel body.

Abstract: The paper presents an analytical investigation of the effect of the tooth wear on the dynamic transmission error of helical gear pairs with small number of pinion teeth. Firstly, the dynamic analysis is conducted to investigate only the effect of the time-varying mesh stiffness on the variation of dynamic transmission error along the line of action. Then, the tooth wear effect on the dynamics of helical gear with small number of pinion teeth is being researched. In the analysis, instantaneous dynamic contact analysis is used in wear depth calculations. A comparative study was performed to investigate the relation between total contact ratio, mesh stiffness and dynamic transmission error of helical gear pairs with small number of teeth.

Abstract: This study presents a dynamic model of helical gears for analyzing the effect of pinion-shaft flexibility on the dynamic behavior of helical gears. In the analysis, the time-varying mesh stiffness is determined in relation with the geometry of the gear pair and incorporates the deflection of the pinion–shaft. A comparison analysis is presented for the dynamic transmission error response of gear pairs supported with a rigid and a flexible shaft system. The results show that the pinion-shaft deflection must be included in the dynamic analysis since they can strongly affect the dynamic characteristics of helical gear pairs.

Abstract: To solve noise and vibration problem and other problems of helical gears, to improve its reliability and safety, this paper uses transmission of helical gear as the research object and makes an analysis of dynamic characteristics of time-varying contact wire and time-varying friction after giving the length of the contact wire, time-varying friction and fast Algorithm for the friction torque. The results of experiment show that the fluctuations of time-varying contact wire is an important cause of tooth surface friction and tooth surface friction torque fluctuations. Time-varying contact wire length, tooth surface friction and friction torque fluctuations are smallest at twenty centigrade degrees, which provide a theoretical basis for the parameter design of gears and engineering optimization.

Abstract: Swept method is a commonly used parametric modeling method for helical gears. For the problem of tooth profiles distortion and parameters loss in parametric design, the symmetric equations that used to establish involutes and dedendum transition curves are proposed. The boundaries between teeth and the starting and ending angles of tooth profile curve are precisely calculated. Feature-based swept methods are applied as solutions. Instance modeling results demonstrate the accuracy of the methods and also reflect their preciseness and convenience.

Abstract: Involute helical gears, with advantages of large carrying capacity, smooth transmission and long life, etc., are widely used in automotive, mining, helicopters and other high-speed and heavy-load transmission system. Poor working conditions lead to fatigue crack and other faults of gear key parts such as tooth root and tooth face. To identify the root causes of gear faults, strain monitoring methods are often used to monitor the stress changes of gear key parts so as to work out individualized improvement plants. Good test results can be obtained using real-time wireless data collection technology when the gear is in low-speed and light loading condition, and we can get important data such as speed, torque and dynamic strain on tooth root, etc. However, involute helical gears tend to work in high-speed and heavy harsh conditions, especially when the gear speed reaches a large value (eg. 10000r/min above), gear strain measurement device will suffer big centrifugal force and the impact of shear force which may results partial bonded adhesive failure (cracks, erosion, etc.) and even whole peeling of strain gages, thus inaccurate and even error results will be obtained. Transient finite element analysis method is used in this paper to study the relationship between rotation velocity and test accuracy of strain gauge as well as the process of the bonded adhesive failure, which may provide effective guidance for the fault diagnoses of gear meshing.

Abstract: The utilization of tooth contact pattern in a gear meshing model for estimation of sliding loss in a spur and helical gear pair is presented in this paper. The photo of tooth contact pattern taken after the gear operation is used as the database to generate the simplified tooth contact pattern. Then the simplified contact pattern is used along with the gear meshing model to estimate the sliding loss of a gear pair. Experiments are done to verify the results. The estimated results from the presented method agree well with the experimental results. The presented method is able to estimate the effect of the helix angle on the sliding loss correctly whereas the estimation without using the data of tooth contact pattern cannot.