Gear Characteristics Research Articles

Lubrication characteristics of double involute gears under the tribo-dynamic condition

PurposeThe purpose of this paper is to study the lubrication characteristics of double involute gear (DIG), compare its lubrication differences under quasi-static and tribo-dynamic conditions and study the influence of different factors on its lubrication characteristics under the tribo-dynamic condition.Design/methodology/approachAccording to the meshing characteristics of DIG and elastohydrodynamic lubrication (EHL) theory, a tribo-dynamic model of DIG is established based on the “subsection method.” The Runge-Kutta method and the multigrid method are integrated to solve the model, and the dynamic analytical model of lubricating oil is established in the iterative solution.FindingsThe load and the transmission error fluctuate obviously under the tribo-dynamic condition, which is not conducive to the lubrication of DIG. The influence of rotational speeds and torque on the lubrication properties of DIG has obvious differences under tribo-dynamic and quasi-static conditions.Originality/valueThis research can provide a theoretical basis for improving the lubrication performance, reducing the loss of mechanical efficiency and improving the bearing capacity and service life of DIG.

Study on Structural Vibration Characteristics of L-Shaped Flexible Ring Gear and Establishment of System Coupling Vibration Model

L-shaped flexible ring gear is a new solution to the non-uniform load distribution of planetary transmission systems. At present, the research on L-shaped flexible ring gear is still focused on its meshing characteristics and dynamic load sharing performance, and its structural vibration characteristics and dynamic coupling vibration characteristics with the system are not involved. Considering that the structural flexibility of the L-shaped flexible ring gear is significantly higher than that of the traditional ring gear, the structural vibration will obviously affect the load sharing and dynamic load factor performance of the transmission system, as well as the safety and reliability of the mechanism. Due to its strong structural flexibility and structural particularity, the existing dynamic analysis model is difficult to meet the requirements of analysis and design. In this paper, the coupling vibration model of L-shaped flexible ring gear planetary transmission systems is established, and the structural vibration characteristics of L-shaped flexible ring gear and its influence on the dynamic performance of the systems are deeply analyzed. The model foundation and theoretical guidance are provided for the design of L-shaped flexible ring gear and the analysis of the dynamic characteristics of flexible ring gear systems.

ПОСТРОЕНИЕ РАЦИОНАЛЬНЫХ ПЛАНЕТАРНЫХ МЕХАНИЗМОВ НА ОСНОВЕ МАТРИЧНОГО МЕТОДА СТРУКТУРНОГО АНАЛИЗА

The study objective is to show the possibilities of the matrix approach in solving problems of analyzing structural properties and developing efficient structures of mechanisms.
 The task to which the paper is devoted is to define the structural characteristics of planetary gears with one external and one internal engagement and to improve their structures.
 Research methods. The paper uses a matrix method for analyzing the structural properties of the mechanism and modifying its structure, which is based on describing the mobility of kinematic pairs, links, kinematic chains, mechanisms using mobility matrices and the use of matrix equations. 
 The novelty of the work. Matrix equations are proposed that make it possible to conduct a structural analysis of independent closed circuits of complex mechanisms consistently. In contrast to the algebraic method, using a matrix approach, it is possible not only to find local and general mobility, determine the number of redundant connections, but also to find which mobility is missing.
 Study results. The analysis showed that the planetary gears under consideration have redundant connections and mobility in the gears, leading to point contact of the teeth and uneven load distribution in planetary pinions. Proposals have been developed to eliminate redundant connections identified in the mechanisms.
 Conclusions. The study conducted on the example of planetary gears shows that the matrix method of structural analysis is an effective means of identifying redundant connections and a tool that simplifies the search for technical solutions to eliminate them.

Structure design method of new balanced vibration reduction gear for the three cylinder engine.

Aiming at the engineering requirements of reducing the volume and improving the vibration characteristics of gears in the three-cylinder engine balanced system, a design and optimization method of gear structure is proposed based on the Design of Experiments (DOE) and proxy models. The paper analyzes the structure improvement process based on the gear design model and technical index requirements. By designing the plane characteristics of the weight-increasing module, the weight-reducing module and the elastic module, the calculation model of balance performance indices such as mass, moment of inertia and unbalance of new balanced vibration reduction gear are constructed. Then, a more efficient design method is proposed based on dynamic simulation and multidisciplinary optimization design platform (Isight). The results show that the new design method of gear structure can effectively reduce the structure improvement cycle. At the same time, the improved structure can reduce the thickness of the weight-increasing module by 6.3 mm and the vibration attenuation by more than 90%.

Research on Axial Modification of Traction Gear

When locomotive traction gear is meshed in transmission, unbalanced loading is easily formed due to various factors such as deformation and error. The research shows that axial modification can avoid this problem. In order to meet the design requirements of axial modification on different types of traction gear, the idea of parameterization can effectively reduce the development cycle. In this paper, on the premise of clarifying the structural form of locomotive driving device, the working characteristics of traction gear are introduced, the force analysis of motor shaft and axle is carried out in consideration of various aspects, the deflection deformation of each part is computed and superposed according to material mechanics, and the mathematical model of axial modification is established by combining the driving direction of motor comprehensively. The calculation model of load distribution is determined according to the actual error. Taking a certain type of locomotive traction gear as an example, the feasibility of the algorithm is verified by comparing the theoretical calculation value with the measured data and load distribution patterns before and after modification, and the results show that this method has guiding significance for axial modification.

Torque Ripple according to The Number of Permanent Magnet Poles of Magnetic Gear

The power transmission of magnetic gears, based upon the at-tractive force of magnets, does not involve direct contact between the power transmission shafts. Thus, vibration or noise, due to friction, can be reduced. However, magnets and iron cores, which are the main components of magnetic gears, generate cogging torque. This increases torque ripples that are the cause of the noise and vibration of permanent-magnet (PM) machines. In this study, a torque ripple reduction method, using the combination of number of poles and number of pole pieces was proposed. This method uses the structural characteristics of magnetic gears only. This method was suggested instead of the existing torque ripple reduction methods for PM machines to reduce the torque ripples of magnetic gears. Furthermore, the correlation between the numbers of poles, pole pieces, and torque ripples was analyzed. From this analysis, a design guideline that minimizes torque ripples in the initial design of magnetic gears was proposed.

Failure analysis of nylon gears made by additive manufacturing

Additive manufacturing enables fast manufacturing of polymer gears directly from a 3D model. Failed polymer gears can be replaced easily and quickly using many different materials. Mechanical and thermal characteristic of gears manufactured using additive manufacturing are mostly dependent on selected manufacturing parameters and material. In this research, the influence of the most important manufacturing parameter (infill percentage) on failure types and service life of additive manufactured nylon gears is experimentally investigated. The experimental tests were carried out using a custom-made gear testing device. Samples with 20, 40, 60, 80 and 100% of infill volume were tested. Infill type, shell thickness, and manufacturing speed were the same for all samples. Service life of gears was tested and failure types were characterized.

Design of Active Continuous Variable Transmission Control System with Planetary Gear

Planetary gearboxes have been employed in various applications due to their advantages of maintaining a high speed-reduction ratio, such as in wind power applications which have now become a prevailing green energy resource. A traditional power transmission machine of the wind turbine has a fixed gear-ratio mechanical gearbox for speed-increasing transmission. The purpose of this study is to propose an active continuous variable transmission (ACVT) control system with a planetary gear to apply to the wind turbine. The planetary gear holds three terminals, i.e., the ring gear, the planet carrier, and sun gear, and the motions of three terminals can be controlled purposely by the servomotors to achieve ACVT. The three different transmission types of the proposed ACVT can be operated. The dynamic characteristic of the planetary gear is expressed in block diagram form, and a pseudo derivative feedback feed-forward controller of the velocity control loop is designed for the required performance. The results can be used to verify the effect of the proposed ACVT with the planetary gear.

Influence of Misalignment on Beveloid Gear Tooth Contact and Dynamic Characteristics in Transfer Case Transmission of AWD Vehicle

Beveloid gears are usually employed to transfer motion of small shaft angle, but the assembly errors or misalignment can affect the gear tooth contact and dynamic performance. A dynamic model and tooth contact analysis model of the intersecting beveloid gear pair are established, the defects of the theoretical tooth surface in the meshing are analyzed, and a microgeometry modification method to improve the meshing performance is proposed. At the same time, the effects of system misalignment and manufacturing errors on its meshing characteristics are considered. By studying the sensitivity of the static and dynamic characteristics of beveloid gear on different misalignment components, the influence laws of misalignment on the contact pattern, transmission error, mesh stiffness, and dynamic excitation force are obtained, which give suggestions for tooth surface modification and support structural stiffness design of beveloid gear with a good NVH performance.

Pattern Classification and Gear Design of Spatial Noncircular Gear Continuously Variable Transmission

Noncircular gear and curve face gear are collectively referred to as spatial noncircular gear. Combined with the transmission characteristics of spatial noncircular gear, a new classification design method of spatial noncircular gear continuously variable transmission (CVT) pattern was proposed, including two categories named addition type and multiplication type, with a total of five subcategories. Through the combination of the transmission ratio changing mechanism and transmission selection mechanism, it can realize the CVT. The overall transmission ratio depends on the phase angle between the spatial noncircular gear pairs and is independent of the input rotation angle. Firstly, the CVT principle and transmission ratio characteristics of each pattern were analyzed. Then the tooth profile classification design of spatial noncircular gear was carried out, and the general parametric design equations of the tooth surface with different tooth profiles were obtained. Finally, through simulation, the overall transmission ratio of each pattern was compared between theory and simulation, which verified the correctness of the CVT classification design method. The advantages and disadvantages of the two categories were analyzed. Moreover, through the transmission experiments of curve face gear pairs with different tooth profiles, the transmission ratios were compared between theory and experiment. Considering the influencing factors such as machining error, assembly error and measurement error, the experimental error is within a reasonable error range, which verified the correctness of the tooth profile classification design method. This study provides a new idea for the further research and application of spatial noncircular gear CVT.

An analytical framework of the kinematic geometry for general point-contact gears from contact path

Based on the idea that the relative curvature relationships along total contact path will better reflect the contact characteristics of gears, this study attempts to develop an analytical framework for the kinematic geometry of point-contact gears from the contact paths. First, a general method for obtaining the contact path of a gear from a pinion is proposed. Second, a normal curvature and geodesic torsion calculation method in the contact path direction is developed. Then, based on the linearly dependent condition of the tangent vectors of the two contact paths, two relative normal curvature analysis methods are proposed by applying the fundamental form theory. Finally, a sample case is presented to show the application and complete the verification of the kinematic geometry methods. The sample case agrees with the analytical model.

Study on the Lubrication Characteristics of Spur Gear Pairs With Low Sliding Ratio Under Mixed Elastohydrodynamic Lubrication

Abstract The relative sliding at the meshing point directly affects the contact and lubrication characteristics of the gear pair and is an important factor of gear wear and power loss. In this study, for investigation of a new type of low sliding ratio (LSR) gear pair whose tooth profile is constructed by a cubic function, a three-dimensional (3D) mixed elastohydrodynamic lubrication (EHL) line contact model was established with consideration of the effect of tooth profile geometry, transient motion characteristics, load distribution, and machining roughness. The distribution of the center film thickness of the LSR gear along the meshing line was predicted through an example the result of which was compared with a typical line contact EHL formula to verify the model. In addition, the difference was investigated in film thickness distribution of friction coefficient and temperature rise between LSR spur gears and involute spur gears. Hence, the effect of 3D rough tooth surface on the contact lubrication characteristics of LSR gears was discussed. The results demonstrated that the minimum center film thickness of the LSR gear appeared at the alternating point of the concave and convex tooth surfaces. At the same time, compared with the involute gear, the LSR gear significantly increased the film thickness at the start and ending points of the meshing and reduced the friction coefficient and the flash temperature rise.

Fracture Failure Analysis and Optimal Design of Transmission Gear

In a special vehicle gearbox planetary transmission mechanism, the sun gear was broken under high-torque and high-speed operating conditions. This paper conducts chemical composition detection, hardness detection, non-metallic inclusion detection, part fracture scanning and other failure causes detection for the failed sun gear, and analyzes the main factors that cause the failure according to the failure characteristics of the sun gear, and proposes improvement measures, which has certain guidance significance.

Dynamic characteristics of helical gears incorporating the effects of coupled sliding friction

Dynamic characteristics of helical gears incorporating the effects of coupled sliding friction

Using abrasive flow finishing process to reduce noise and vibrations of cylindrical and conical gears

This paper reports on reduction of noise and vibrations of cylindrical and conical gears through simultaneous reduction in their microgeometry errors, functional parameters, and surface roughness by finishing them with abrasive flow finishing (AFF) process. Previously identified optimum values of AFF medium viscosity and finishing time were used during AFF of the chosen gears. Noise and vibrations characteristics of the unfinished gears and the AFF finished gears were studied by varying motor speed and applied load at four levels each. An indigenously developed test rig was used for spur and straight bevel gears whereas drivetrain diagnostic simulator was used for helical gears. Indigenously developed dual flank roll tester was used to evaluate functional parameters of the unfinished and the best finished gears by AFF process. It was found that AFF process simultaneously reduced microgeometry errors, functional parameters, maximum and average values of surface roughness of spur, helical, and straight bevel gears. It reduced noise and vibration by 5.2 dBA and 5.3 m/s2 for spur gears, by 3.4 dBA and 7.5 m/s2 for helical gears, and by 4.6 dBA and 4 m/s2 for straight bevel gears. This study proves that AFF is an easy-to-operate and effective process for reducing noise and vibrations of cylindrical and conical gears through simultaneous reduction in their microgeometry errors, functional parameters, and surface roughness values. Outcome of this work will be helpful for various manufactures and users of different types of gears.

Influence of floating support on the dynamic characteristics of compound planetary gear set

Due to a large number of components, complex meshing relations and high requirements for assembly accuracy, the dynamic characteristic of compound planetary gear, such as vibration, impact, periodic motion and load sharing, are more easily affected by internal excitation than those of simple planetary gear set and parallel shafting gear set. To improve the load sharing behavior and the resistance of Chaos motions in the compound planetary gear set, in this work, by introducing the floating support into the center gear and planet gear, a lumped-parameter dynamic model of the compound planetary gear set is built based on the lumped parameter method and Lagrange kinematics equation. The steady response is calculated by numeric method to investigate the influence of floating support from different components on loading sharing behavior and periodic motion. The results indicate that, the increase of the floating value of all components improves the instantaneous load-sharing behavior, and single floating of planet gear reduces the load sharing behavior. To avoid the system being in quasi-periodic motion and Chaos motions under the condition of floating support, the input speed should be avoided away from the range of 3201 r/min-5069 r/min.

A new method for estimating length-dependent capture modes in gillnets: a case study in the Danish cod (Gadus morhua) fishery

Abstract Gillnets are used world-wide for harvesting groundfish and pelagic species at sea and in freshwater. Little consideration has been given to how fish are caught in gillnets, even though the capture mode provides valuable information for understanding gear catchability. This paper describes a new method of estimating the length-dependent fish capture modes in gillnets. Using this method, we investigated the length-dependent capture modes for cod (Gadus morhua) in commercial monofilament nylon gillnets. Cod is a target species for several fisheries in the Northern Atlantic. This is the first time the capture mode was formally related to fish size with a direct representation of the experimental observations. The results demonstrated that gillnets are clearly designed for gilling. However, capture modes were size dependent, with small fish being caught by the mouth and larger fish by the maxillary. The application of the method is relevant when used by gear technologists to evaluate different gear characteristics to improve size or species selectivity. Changing the hanging ratio, for instance, or replacing nylon twine by thicker biodegradable material may considerably change the capture modes and their effect on gear efficiency.

Fracture characteristics of asymmetric high contact ratio spur gear based on strain energy release rate

Variations in design parameters and methodology have a significant effect on the fracture characteristics of spur gear. Furthermore, the geometry and load acting on the spur gear affect the propagation of fractures and the bending fatigue life. In comparison with conventional gear design, the direct design strategy is a highly efficient method for improving fracture resistance. This study attempts to investigate the fracture properties of a direct designed asymmetric high contact ratio (AHCR-DD) spur gear subjected to the mix-mode of crack failures. The stress intensity factor (SIF) and the shape factor are compared to conventional normal and high contact ratio spur gears. In addition, the fracture properties of conventional design symmetric HCR (SHCR-CD), direct design symmetric HCR (SHCR-DD), and AHCR-DD spur gears are compared. When compared to other gears, the AHCR-DD spur gear has a higher fracture resistance. A parametric study of the fracture properties of the AHCR-DD spur gear is also carried out to provide useful information for designing such gears. Variations in the contact ratio, rim thickness, number of teeth, and addendum pressure angle are used to assess fracture performance. It is observed that using a direct design technique significantly reduces the SIF. This investigative study provides valuable guidelines in the future for developing non-standard spur gears such as AHCR-DD.

About the characteristics of gear and devices for winter amateur fishing on the Dniprovske (Zaporizhske) reservoir

About the characteristics of gear and devices for winter amateur fishing on the Dniprovske (Zaporizhske) reservoir

Generation of Artificial Learning Data to Train Functional Meta-Models of Micro Gears

The complexity of products increases considerably and key functions can often only be realized by using high-precision components. As a result, the requirements of high-precision components reach technological manufacturing limits. This is of particular importance for micro components, such as micro gears, where the manufacturing deviations are relatively large compared to the component size and therefore have a large influence on the functional characteristics of the assembled product. A potential solution is to develop a meta-model with machine learning (ML) methods, which enables the real-time prediction of functional characteristics of micro gears in terms of kinematic transmission error (KTE), based on optical in-line measurements of the entire topography of the gear. To train a suitable ML model large amounts of data are needed. This poses a challenge because real measurements cannot cover the entire spectrum of all deviations and also require a large amount of resources in terms of time, material and costs. In this paper, an approach for the generation of learning data on the basis of virtual and deviated gear models is developed with the help of Skin Model Shapes. The objective is to generate gear data that reflects the nominal shape as well as the process-related manufacturing deviations and the random scatter. For validation, the artificially generated gears are compared with a reference dataset both geometrically and functionally. Therefore, both the standard deviations and the KTE are calculated for both data sets.