Hypoid Gears Research Articles

Software System SPDIAL

Spiroid gears are direct competitors to traditional technical solutions - worm and hypoid gears; and they have proven themselves in a large number of specific technical applications, providing greater strength, smaller size, and easier production. However, their design process is much less subject to being typical and standard and to resulting in simple engineering techniques. In fact, effective solutions can be obtained only by actually researching the space of parameters. An indispensable tool for this is a computer-aided design and research system. The paper presents the summary of such a system SPDIAL+ for worm-type gears (worm, QN-gears, spiroid) developed at Izhevsk scientific school in the field of gears and gearboxes. In particular, the possibilities of designing a conjugated gear, choice of gearwheel cutting parameters, analysis of gears under the action of errors and loads are considered. The role and results of applying the program as the main tool for research, design and innovations like new varieties of gears, their new properties in specific applications, new methods and techniques of tooth machining are shown.

Influence of meshing stiffness variation on the vibration characteristics of main reduction gears

Abstract The meshing stiffness of the main and passive gears of the main reducer of the rear axle of a commercial vehicle is taken as the object of this study, aiming to optimize the influence of the meshing stiffness of the main and passive gears on the vibration and noise, enhance the meshing performance of the gear teeth, reduce the vibration and noise of the main reducer, and improve the vibration performance of the main reducer. Through UG 3D modeling software and ADAMS dynamics simulation, the dynamics characteristics of hypoid gears under different gear tooth meshing stiffness coefficients are analyzed and simulated. It is concluded that under the meshing stiffness coefficients of 0.8 to 0.9 times, the translational vibration acceleration and angular acceleration of the passive gears are smaller, the translational vibration and torsional vibration are smoother, and it can improve the performance of the meshing vibration of the gear system of the main gear reducer.

Efficiency of Bevel and Hypoid Gears—Test Rig Development and Experimental Investigations

The efficiency of bevel and hypoid gears is, alongside load capacity, one of their most important design criteria. To consider the efficiency of bevel and hypoid gears during the development and design process, validated calculation methods based on experimental investigations are necessary. However, the isolated experimental investigation of the load-dependent power losses of bevel and hypoid gears has not been adequately investigated, as most of the experimental investigations consider the complete gearbox. This paper presents a test rig that allows for the experimental investigation of the efficiency of bevel and hypoid gears with a measurement uncertainty of the efficiency of ∆η≤±0.08% according to the Guide to the Expression of Uncertainty in Measurement (GUM). Using the developed test rig, experimental investigations on the efficiency behavior of bevel and hypoid gears regarding the influence of the axial offset, driving direction, and microgeometry are carried out for different operating points varying in circumferential speed and load. This paper discusses the methodology and the first experimental results of a study on the efficiency of bevel and hypoid gears in detail.

Failure Analysis of Off-Highway Hypoid Gear Due to Non-metallic Inclusion

Failure Analysis of Off-Highway Hypoid Gear Due to Non-metallic Inclusion

Optimization of machine tool settings for Spirac hypoid gears by controlling symmetry of contact paths

A novel optimization method to control the symmetry of contact paths on the concave and convex tooth surfaces of the gear then improves the meshing quality was proposed. By modifying the angular setting of the head cutter when cutting the pinion, the direction angles of the two contact paths are equated to estimate their symmetry. The relation between the direction angles is formulated precisely, the influence of the angular setting on the contact paths is investigated, and the equations for obtaining the values of the machine tool settings are derived. The proposed method is applied to a numerical example of a Spirac hypoid gear pair, and the results reveal that the contact paths on the concave and convex tooth surfaces are approximately symmetrical and the transmission errors of both sides are comparable.

Improving Machined Accuracy Under a Constant Feed Speed Vector at the End-Milling Point by Estimating Machining Force in Tool Approach

A five-axis machining center (5MC) is capable of synchronous control, which makes it a feasible tool for quickly and accurately machining complicated three-dimensional surfaces, such as propellers and hypoid gears. Recently, the necessity of improving both the machined shape accuracy and the machined surface roughness of free-form surfaces is growing. Therefore, in our previous study, we aimed to maintain the feed speed vector at the end-milling point by controlling two linear axes and a rotary axis of the 5MC to improve the quality of the machined surface. Additionally, we developed a method for maintaining the feed speed vector at the end-milling point by controlling the three axes of the 5MC to reduce the shape error of the machined workpieces (referred to as the shape error herein), considering the approach path of the tool determined via calculation. However, a high machining force at the start of the workpiece cutting was observed and the factor contributing to this phenomenon was not determined, although this phenomenon leads to a shape error to a certain degree according to the machining condition. In this study, the main objective is to suggest a method to reduce the machining force at the start of the workpiece cutting and shape error. Hence, we develop a theoretical method to estimate the machining force by using an instantaneous cutting force model, which considers the synchronized motion of two linear axes and a rotary axis of the 5MC. Subsequently, we determine the most suitable approach path of the tool considering the prediction of the machining force. The results of this study indicate that the machining force can be estimated by applying an instantaneous cutting force using the feed per tooth and machining angle, and that both a high machining force at the start of the workpiece cutting and shape error reduction can be realized by using the proposed approach path of the tool.

Rear Axle Whine Reduction by Gear Contact Patch Optimization

In-cab whine is a highly annoying phenomena in all the category of vehicles. The in-cab noise of passenger vehicle with Rear Wheel Drive ( RWD) considered for this study consist of axle whine noise. The whine noise is heard at multiple speeds during Wide Open Throttle (WOT) as well as coasting. To resolve the issue of whine noise, series of measurement are carried out to identify the source and transfer path of the whine. The noise measurement revealed that rear axle pinion mesh order is responsible for in-cab whine. It is confirmed through measurement that the whine is structure borne. The order based operational deflections shapes of rear axle show excessive vibration on differential nose in affected speed zones. It is thus learnt that whine is due to poor contact pattern of pinion and crown wheel of the rear axle. The three resonances in operation range amplify this mesh order resulting in whine. It is decided to work on noise source i.e. gear rather than transfer path. The hypoid gear design is optimized through Tooth Contact Analysis (TCA). The lapping and heat treatment processes of gear manufacturing are modified. The contact pattern of optimized gear is identified on gear tester machine. Significant improvement is observed in contact pattern. The in-cab noise measurement is carried out with optimized hypoid gear and it is found that the whine is completely eliminated.
 Keywords: Rear axle, Whine reduction, Gear contact, Patch optimization, Rear Wheel Drive, Whine Source, Vibration on Transfer Paths, Noise Generation, Hypoid Gear, Heat Treatment

Forecasting model for hypoid gear elastohydrodynamic lubrication considering entrainment effect

In full consideration of time-varying meshing performance and oil film characteristics, entrainment effect on elastohydrodynamic lubrication (EHL) is developed for establishing accurate forecasting model of the complex hypoid gears. Firstly, dynamic loaded tooth contact analysis (DLTCA) is employed to determine the meshing interface kinematics, load distribution and entrainment speed under dynamic load condition. Then, entrainment speed is introduced into the EHL governing equation and accurate forecasting model is established. With accurate discretization of EHL governing equation, discrete convolution and fast Fourier transformation (DC-FFT) method is employed to compute the flank elastic deformation. Finally, a hypoid gear set in automotive industrial application is exercised to verify entrainment effect on EHL assessment in the proposed model.

An exact system of generation for face-milled hypoid gears with uniform depth taper: Application to hypoid gear drives with high gear ratio

An exact system of generation for face-milled hypoid gears with uniform depth taper is proposed. This system defines the location of pinion and wheel, their respective cutting (or grinding) cutters, and the relations of motion in their respective reference coordinate systems attached to the cutting machine. As a result, the grinding cutter geometric parameters and basic machine-tool settings are analytically determined without the need of any further optimization process. The appropriate selection of the mean cutter radius is addressed following the recommendations of the Information Sheet AGMA ISO 22849-A12. The tooth contact analysis of the gear drive shows a localized bearing contact with no unloaded transmission errors in the absence of misalignments. A lower sensitivity of the contact pattern to errors of alignment is observed as the mean cutter radius is decreased. Stress analysis shows that only the application of a tip relief is needed to avoid edge contacts at the tip of the gear tooth surfaces, being the point width of the cutting blades a key parameter to balance bending stresses in the pinion and the wheel.

Research on noise reduction of drive axle hypoid gear based on tooth surface mismatch modification

In order to reduce the transmission noise of drive axle hypoid gear, a method of tooth surface mismatch modification was proposed. Firstly, on the basis of establishing the grinding mathematical model of hypoid gear with cutter tilt, the theoretical tooth surface equation was derived, and the numerical tooth surface was calculated by dividing the grid points on tooth surface. Secondly, the pinion tooth surface which was full conjugated with gear tooth surface was constructed, and the tooth surface mismatch topography was established and decomposed into the first order and second order mismatch coefficients. According to the modification requirements, the pinion target surface was constructed by modifying the tooth surface mismatch coefficients, and the pinion modified machine setting parameters were acquired by establishing the pinion processing parameters corrected mathematical model. Finally, the loaded tooth contact analysis with finite element simulation and drive axle NVH (Noise, Vibration, Harshness) simulation were carried out for a pair of hypoid gear, therefore the loaded tooth contact areas, transmission errors curves, and noise simulation curves were obtained, and the simulation results show that after modification the tooth contact stress, loaded transmission errors amplitude, and NVH simulation curves value are all reduced. The road test results indicate that the drive axle hypoid gear howling phenomenon under the high speed operation can be eliminated, so the effectiveness of tooth surface modification method and NVH simulation method were verified.

An analytical prediction methodology of the correlation between transmission error and tooth pitch error for face-hobbed hypoid gears

An analytical prediction methodology of the correlation between transmission error and tooth pitch error for face-hobbed hypoid gears

Fundamental study on estimation of tooth contact area based on combined image from temperature monitor images of tooth surface with a high-speed-camera thermography and on meshing vibration for high reduction ratio hypoid gear with a three-tooth pinion

Fundamental study on estimation of tooth contact area based on combined image from temperature monitor images of tooth surface with a high-speed-camera thermography and on meshing vibration for high reduction ratio hypoid gear with a three-tooth pinion

Process and tool design optimization for hypoid gears with the help of the manufacturing simulation BevelCut

Catastrophic tool wear, active clearance sides of the tool and resulting fins at the tooth’s root are among the undesirable phenomena that can occur when cutting bevel gears. So far, these obstacles to manufacturing could not be predicted during the design phase. This paper presents an approach to identify critical process and tool designs using the manufacturing simulation BevelCut. Based on the simulation results, the occurrence of cutting phenomena is correlated to the characteristic values and corrective measures are deduced. Finally, the effectiveness of the corrective measures is assessed by comparing the characteristic values of the original and optimized design

Investigating the Tooth Contact Based on a High-speed Thermography Monitoring Conducted Under High-reduction Hypoid Gears Meshing Condition

Investigating the Tooth Contact Based on a High-speed Thermography Monitoring Conducted Under High-reduction Hypoid Gears Meshing Condition

Sustainability-oriented dry cutting tool collaborative optimization model for face-hobbing hypoid gears

Dry cutting as an important sustainability manufacturing technology is enhancing ever-higher levels of hypoid gear production. To improve economic and environmental attributes of sustainability manufacturing, a new data-driven dry cutting tool collaborative optimization model considering both geometric accuracy and loaded contact performances is established for face-hobbing hypoid gears. Where, an innovative ease-off tooth contact analysis (e-TCA) method is proposed to establish accurate relations between ease-off flank and loaded contact performance evaluations. Then, for the initial design flank from arc-shaped tool, Top-Rem tool modification is applied to establish the collaborative optimization model. By fine-modifying the ease-off flank relating to Top-Rem tool parameters, the current design flank can get an adaptive approximation to the target flank requiring the loaded contact performance evaluations. Moreover, in addition to the accuracy and efficiency of dry cutting at its own, the cutting gear number of per hour, cutting gear number of per tool and cutting power consumption are used the main assessment items on sustainability. The numerical and experimental examples are provided to verify that the proposed tool collaborative optimization model will significantly improve sustainability in terms of economic and environmental assessments.

An efficient vectorization solution to cutting dynamics modeling for face-hobbing of hypoid gears

The cutting vibration generated by cutting forces is critical to the accuracy and efficiency of face-hobbed hypoid gears. However, few relevant works are currently on cutting dynamics modeling for the face-hobbing process due to its complex spatial relationships. This study developed an efficient cutting dynamics model considering comprehensive characteristics of the non-generated face-hobbed hypoid gear machining process. A concise and efficient analytical solution to cutting dynamics modeling for face-hobbing of hypoid gears is obtained by using a vectorization method to characterize chip regenerating mechanisms. The machine tool vibration caused by cutting forces is predicted and validated according to an industrial case study. The proposed cutting dynamic model is 36.11% more efficient than the semi-analytical dynamic model derived from other cutting force prediction methods, and its accuracy is also improved with an error of less than 15%. Furthermore, the proposed vectorization solution to face-hobbing cutting dynamics modeling will be a practicable and effective method for analyzing the chatter in the machining of complex surfaces.

Consideration of the influences of the driving direction within the calculation of the pitting load-carrying capacity of bevel and hypoid gears

Pitting is, besides scuffing, tooth flank fracture and the phenomenon micropitting, one of the primary failure modes of the flank load-carrying capacity of bevel and hypoid gears. The international standard ISO 10300-2:2014 is widely used for the estimation of the flank load-carrying capacity of bevel and hypoid gears based on operational data and the macrogeometry of the gear set. The calculated safety factors against pitting often show similar values for pinion and wheel. Due to similar safety factors against pitting, the gear is expected to fail as often as the pinion. However, investigations in the field do not confirm this. Initial experimental investigations show an influence of the driven and driving part of the gear set. Within this paper, the phenomenon regarding the driven and driving part of the gear set will be discussed for the first time and the influence parameter will be clarified. Because of the potential for recuperation in electrified agricultural tractors, railroad trains, hybrid and electrical vehicles, this topic is of great importance. In this context an actual calculation approach based on the standard calculation method of the ISO 10300-2:2014 will be presented and verified with test results.

A Numerical Gear Rolling Test Method for Face-Hobbed Hypoid Gears

A numerical gear rolling test (NGRT) method for actual tooth surfaces was proposed. The non-uniform rational B-spline (NURBS) fitting method was adapted to reconstruct the actual tooth surface, and the instant meshing point as well as the transmission error of two meshing gears were solved. The instant contact ellipse boundary of each meshing point can be accurately searched, and then the contact pattern formed by a series of contact ellipses on the actual tooth surface can be obtained. Finally, the rolling test experiment for a pair of hypoid gears was conducted to verify the feasibility of the proposed method. The result shows that the contact pattern obtained is consistent with the actual rolling test result, the relative errors of the transmission error amplitudes were only 4.5% and 5.3% for the drive and coast sides, respectively, and the contact ellipse of the actual tooth surface is not necessarily a standard ellipse and the instant contact path is not necessarily a straight line. This NGRT method helps to reduce equipment and time costs in closed-loop gear manufacturing, which is of great significance for mass production.

Thermal lubrication characteristics of hypoid Gear with non-Newtonian fluids considering roughness

Based on Hertz contact theory and EHL, the model of elliptic contact elastohydrodynamic lubrication considering load, speed, roughness, thermal effect, and shear-thinning effect of non-Newtonian fluids is established. The variation trend of oil film pressure, thickness, and temperature with load, entrainment velocity, and the slide-roll ratio is analyzed. Then, several lubrication states considering roughness, the thermal effect, and the characteristics of non-Newtonian fluid are compared. Compared with the smooth surface, the roughness when RMS is 0.15 μm increases the maximum film pressure (P max) by 8.34%, increases the maximum film temperature (T max) by 7.18%, and reduces the minimum film thickness (H min)by 9.13%. The pressure and temperature are more sensitive to light load. The results are approximate to that of the smooth surface when the entrainment velocity is big enough. The pressure and thickness decrease with the increasing slide-roll ratio. The decreasing speed of the oil film thickness becomes faster as a result of the thermal effect. The roughness and the characteristics of non-Newtonian fluid have a significant impact on temperature.

Transferability of the scuffing load capacity of gear oils determined on spur gears to hypoid gears

AbstractThe scuffing load carrying capacity is a decisive design criterion in the development of gears. In addition to the gear geometry, the entire tribological system of the gearbox must also be taken into account. Besides the loads and speeds occuring during the operation of the gears, the lubricant used and its additives have a significant influence on the scuffing load carrying capacity. In particular, hypoid gears show an unfavorable combination of high sliding velocities and high contact stresses in tooth contact with regard to the failure mode scuffing. To ensure safe operation, highly additivated gear oils are generally used in hypoid transmissions. Since it is generally not possible to determine the influence of the lubricant on the load carrying capacity of gears on the basis of physical or chemical oil data alone, experimental test methods are necessary. Due to the high scuffing load carrying capacity of highly additivated hypoid oils, the limits of many test methods are reached. In order to ensure testing highly additivated hypoid oils as close as possible to their application a new hypoid scuffing test was developed. However, since spur gear scuffing test methods can be carried out more quickly and with less resource and effort, the applicability of the spur gear scuffing test S‑A10/16.6R/90 to high additivated hypoid oils is investigated. The comparability of the two test methods and the transferability of the scuffing load carrying capacity of a gear oil determined on spur gears to hypoid gears is evaluated in scope of this paper.