Range Of Gear Ratios Research Articles

STRUCTURAL DESIGN OF NON-STANDARD GEAR TRANSMISSION

Non-standard gear transmissions are increasingly finding their applications in practice, primarily being designed for various applications. While standard circular gears are designed for a constant gear ratio, non-standard gears have a variable gear ratio that changes. This paper addresses the issue of designing non-circular gears for a specific range of gear ratios. An elliptical shape for the gears was chosen. The uniqueness of the proposed solution lies in selecting an ellipse as the evolute for creating the involute curve of the gear tooth.

Research on the efficiency analysis method of 9AT transmission planetary gear system based on power loss

As the core element of power transmission in Automatic Transmission (AT), the planetary gear system has advantages in the gear ratio range, load carrying capacity and transmission efficiency, and its transmission efficiency analysis is an important link in the design of automatic transmission.This paper proposes a method to analyze the transmission efficiency of planetary gear system of 9AT transmission considering power losses. Firstly, based on the hypergraph theory to establish the power transmission roadmap of each gear of the transmission (9AT) and the triangular hypergraph of the four-row planetary gear system, as well as the power flow model of the four-row planetary gear system without considering the power losses, and then the rotational speed, torque, and power change of each gear of the gear system are analyzed through the power spectrum. Secondly, a power flow model considering power losses and circulating power was established to analyze the influence law of different operating parameters (speed, torque, viscosity, gear meshing friction coefficient), and structural parameters (characteristic coefficients of each planetary row) on the transmission efficiency of the system. Finally, the equivalent planetary gear system transmission efficiency experimental bench considering losses is established to measure the transmission efficiency of the two-row planetary gear system at different speeds and torques, and the results of the experimental tests have the same trend with the theoretical calculations, which provides an analytical method to improve the transmission efficiency of the planetary gear system of the 9AT transmission.

ГЕОМЕТРИЧЕСКИЙ АНАЛИЗ И ТЕОРЕТИЧЕСКАЯ ОЦЕНКА КПД ПЛОСКО-КОНИЧЕСКОГО ЗАЦЕПЛЕНИЯ СФЕРИЧЕСКОЙ РОЛИКОВОЙ ПЕРЕДАЧИ

The study objective was to assess the influence of friction factors and geometric parameters of a spherical rolling screw motion drive on its efficiency. The load is transferred by means of a cone-and-plate engagement of two rows of rollers mounted on a satellite with fixed and driven plate central gears. With the help of a spherical rolling screw motion drive, it is possible to realize a wide range of gear ratios (16...200) and reduce the material capacity of the gearbox, ensuring the ratio of its mass to the nominal transmitted torque of less than 0.1 kg/(N•m). The main task of this research is to find out the ascent angle of the spatial closed center curves with the help of which the surfaces of the central wheel teeth are formed. The research methods are based on the application of the classical mechanics laws and computer modeling algorithms in NX system. The novelty of the research is in the novelty of the technical object under study, its low level of being studied, the lack of detailed methods of its calculation and design. As a result, based on the analysis of the geometric satellite model, the equations of the center curves are obtained and an algorithm for determining the ascent angle of the center curve in the middle section of the central wheel teeth is developed, which allows power analysis of the motion drive. The applicability of the formula for calculating the average ascent angle of a piecewise helical curve located on a cylindrical surface for spherical motion drives is evaluated and the necessity of its adjustment taking into account a given gear ratio and the inclination angle of the drive shaft crank is found out. An algorithm is developed for the theoretical study of the efficiency of spherical roller gears at the design stage.

Design and Analysis of Six Speed Constant Mesh Gearbox using Al 7075 Alloy as Gear Material

Abstract: A design concept for a 6-speed constant mesh gearbox utilizing Al 7075 as the material for helical gears. The objective of this design is to enhance the performance and durability of the transmission system while reducing weight and improving overall efficiency. Al 7075 is chosen as the material for the helical gears due to its excellent strength-to-weight ratio and high fatigue resistance. These properties make it suitable for handling the demanding operating conditions and torque loads experienced in a gearbox. The helical gear configuration offers advantages such as smoother and quieter operation compared to other gear types, reducing noise and vibration levels. The gearbox is designed with six speeds to provide a wide range of gear ratios, enabling optimal engine performance at various vehicle speeds. The constant mesh design ensures quick and seamless gear shifting, enhancing the driving experience and minimizing power losses during gear changes

Investigation of energy characteristics of the electromechanical control system of 4-drive electric vehicle

Purpose. To determine for the developed electromechanical control system of a 4-drive electric vehicle, the power of the drives and the coefficients of the gearboxes that ensure the minimum energy consumption during acceleration from 0 to 100 km / h in 5 s. Research methods. Mathematical analysis and modeling. Findings. The proposed solution is to determine, for a given vehicle dynamics (acceleration from 0 to 100 km / h in 5 s), by mathematical modeling, values of drive powers and gear ratios, which increase the efficiency of the electromechanical system. The condition for increasing the efficiency is to minimize the consumption of electrical energy for acceleration. The developed computer model of the electromechanical control system of the 4 - drive electric vehicle allows to carry out researches on definition of electromechanical parameters of the control system providing the minimum energy consumption at dispersal from 0 to 100 km / h for 5 s. The current consumed by the drives was determined by studying the energy characteristics of the drives obtained on a previously developed laboratory stand. Gear ratios and drive power have been found to provide minimum power consumption when accelerating a 4-wheel drive electric vehicle. From the obtained data it is seen that for each power studied there are minima in the range of gear ratios 1-3,4. Also in the course of the research it was found that among the studied powers of 30-160 kW there is a drive that uses less energy. For the studied electric vehicle, these are four drives of 75 kW with a reduction factor of 3,3. The presence of minima in the interval between the gear ratios and the interval of the studied drive powers is explained by the variability of the engine efficiency in the load ranges varying from 0.3 to 2 times and the engine shaft speed of 0-3000 rpm, due to varying degrees of loss impact, the dynamic modes of the drive. Originality. The study of energy characteristics based on the developed control system for a 4-wheel drive vehicle makes it possible to find the electromechanical parameters of the system that provide a minimum of energy consumption during acceleration from 0 to 100 km/h in 5 s. Practical value. The electromechanical parameters of the control system of the 4-drive electric vehicle obtained as a result of research allow to receive economy of electric energy at dispersal from 0 to 100 km / h for 5 s in 2-3% within one experimental nominal power of the engine.

Results of research of the combined seeder for strip sowing of grasses into sod

The development of ecological agriculture has aroused interest to the technology of increasing the productivity of natural forage lands, which consists in strip sowing of grasses with mechanical tillage in the sod of strips, the size of which ensures the successful development of seedlings without the use of chemicals. Several models of seeders SDK have been developed and mass-produced to implement this technology. A further development of this type of machines is the creation of a mounted seeder SDK-2.8M, intended for direct strip sowing of grass seeds into sod with the application of a starting dose of mineral fertilizers. To evaluate the efficiency of the seeder SDK-2.8M in the autumn of 2022, stand and field tests were carried out in the fields of the North-East Federal Research Center. Stand tests on sowing seeds of meadow fescue and red clover showed that the range of gear ratios of the seeder from 0.104 to 0.900 allows to set the seeding rate in the interval of 2.5-140.4 kg/ha. The sowing part ensures uniform distribution of seeds over the feed rolls and the stability of sowing by each feed roll in accordance with agrotechnical requirements. The deviation of the actual seeding rate from preassigned (6.0 kg/ha) for sowing fescue is 2.6%, clover – 2.3%; uneven seeding between feed rolls for fescue – 3.61%, for clover – 5.36%; seeding instability for fescue – 4.83%, for clover – 6.03%. Field tests revealed that the seeder stably performs tillage and clover sowing, maintains the working width and the installation depth of tillage. The average tillage depth was equal to 68 mm, the crumbling of the soil (fraction up to 25 mm) – 85.1%, the average depth of seeding – 16.4 mm, density after rolling – 1.1 g/cm3 .The use of a frame of the original design made it possible to reduce the number of assembly units of the tillage part and auxiliary mechanisms, which reduced the mass of the seeder by 640 kg, in comparison with SDKP-2.8M, while maintaining agrotechnical performance indicators.

A High Efficiency Transmission Architecture for Electric Vehicles

<div class="section abstract"><div class="htmlview paragraph">A Dual Power Split Electronic Continuously Variable Transmission (DPS-ECVT) with an input-split, output coupled, split-power-path configuration is proposed for improving overall system efficiency and range for electric vehicles. By modulating the power split ratio between the mechanical (planetary gear meshes) and electrical (Motor Generator Units) driveline components, a continuous range of gear ratios operating at higher efficiency is obtained. The proposed concept leverages two power-split units that lead to significantly reduced power flow through the electrical drivelines (compared with single speed EV transmissions as well as single power-split E-CVTs) while providing the same overall ratio spread for transmission operation. A multi-layered optimization is performed, first an inner layer optimization on the operational control strategy to maximize the end-of-cycle SOC (State of Charge) of the battery for a given set of transmission design parameters, and then subsequently an outer layer optimization on the design parameters to maximize the overall efficiency over multiple configurations of the given architecture. The performance of the architecture is bench-marked using simulation models derived from a Chevy Bolt baseline that are simulated on the EPA highway (HWFET) and the urban (UDDS) driving cycles. An effective gain of 13.6 percent in the range is demonstrated. A stick-diagram schematic realization of the optimized configuration is also presented.</div></div>

Self-braking harmonic drives in mechanisms of mining machines

The conditions of self-braking in harmonic drives with a flexible wheel made in the form of a bushing chain are considered. A special feature of the harmonic drive is the design that has a dual generator and a double-crowned sprocket. This design allows to avoid skewing the chain under load. The criteria for self-braking in chain harmonic drives are defined. It is found that for chain harmonic drives in the range of gear ratios above 30, the effect of self-braking is provided. In the range of gear ratios up to 30, extra-centroid gearing is required to achieve the effect of self-braking.

Preliminary modelling of power losses in roller chain drive: application to single speed cycling

A quasi-static chain drive model is proposed. This model, consistent with single speed cycling application, applies to simple two sprocket drives. The kinematics of the transmission is determined, including the capture and release positions of the rollers and the influence of the polygonal effect. The tensions into the links and the contact forces (between rollers and sprocket) are then calculated based on the results of the kinematic analysis. Both chain strands are assumed to be straight and their tension are considered as imposed. An estimate of the roller displacement is proposed using existing studies on the relationship between loading conditions and roller positions along the sprocket tooth profile. The presented model, is then used to assess the contribution of both meshing and roller motion on the global efficiency of the drive. Calculations show that the magnitude of both loss sources is similar for a wide range of gear ratios and loading conditions. According to the presented results, the relative motion between the rollers and the sprocket tooth profile should be considered in future studies dedicated to chain drive efficiency.

Dynamic behaviour of a planetary reducer with double planet gears

Abstract. Planetary reducers have a wide and significant application in modern machine industry. They are extremely compact and reliable, and they can achieve a wide range of gear ratios as well as high efficiency. Since they often operate in extremely changeable working conditions, such as often starting and stoping, it is both interesting and desirable to study their dynamic behaviour. This paper presents a dynamic model of a planetary reducer with double planet gears created by applying Lagrange's equations of the second kind. After a planetary gear reducer has been designed and a CAD model created, the dynamic model was made. Most of characteristic values needed for solution of the equations are taken from the CAD model. Due to their complexity, the equations are solved in math simulation software. A lot of interesting results concerning the dynamic behaviour of the model are obtained, which can be helpful in understanding the dynamic occurrences in the inside of a planetary gearbox. At the end of the paper, conclusions are drawn, and further research directions in this area are given.

Методика расчета и проектирования сферических роликовых передач с двухрядным сателлитом

The article presents a method for calculating and designing spherical roller gears with a double-row pinion. The studied gears are analogs of planetary gears with a double-wheel pinion. They make it possible to implement a wide range of gear ratios. The advantages of spherical roller gears include small dimensions, low material consumption, and layout properties. A special feature of the proposed calculation algorithm is the search for optimal geometric gears parameters according to the criteria of maximum efficiency coefficient taking into account maximum load capacity for a given maximum radial dimensions. The main criterion of strength is fatigue endurance. The method includes design and verification calculations. It makes it possible to develop the small-sized speed reducers for low-speed drives for various purposes.

Optimization of Coaxial Magnetic Gear Design and Magnet Material Grade at Different Temperatures and Gear Ratios

Magnetic gears, like mechanical gears, transform power between different speeds and torques; however, magnetic gears' contactless nature provides inherent potential benefits over mechanical gears. A genetic algorithm was used to optimize magnetic gears at different temperatures across a range of gear ratios. Using different magnet material grades on the different rotors and for the tangentially and radially magnetized magnets can slightly increase the specific torque relative to designs with a single magnet material. The high pole count rotor requires a magnet material with higher coercivity than that of the low pole count rotor magnet material, especially for designs with a large gear ratio. While increasing the temperature produces an exponential decay in the achievable specific torque, with a compounding reduction of about 0.4% for each degree Celsius, the temperature does not significantly affect the optimal geometric parameters and primarily affects the optimal materials. The gear ratio significantly affects the optimal geometric parameters and can impact the optimal magnet materials. Additionally, the genetic algorithm was employed to characterize the impact of stack length using 3D finite element analysis. Designs with shorter stack lengths favored thinner magnets and higher pole counts and may be able to use magnet materials with lower coercivities.

Improving energy performance of hydraulic torque converters

Torque converters are widely used in the transmissions of self-propelled vehicles for various purposes on wheeled and tracked chassis. A significant drawback of torque converters compared to mechanical transmissions is their relatively low efficiency. Therefore, the task of ensuring high efficiency values of torque converters in the entire range of gear ratios has been of importance since the invention of these hydraulic machines. Torque converters have the lowest efficiency values in the torque transformation mode among low and medium gear ratios from 0 to 0.7. In addition, the nature of the change in efficiency for an integrated torque converter in automatic transition to the fluid coupling mode also usually decreases sharply. This article discusses a number of motor and tractor torque converter designs aimed at obtaining high values of efficiency in the range of small or medium gear ratios. The considered technical solutions are associated with a reduction in energy losses when the working fluid enters the pump wheel of the torque converter.

Mechanical Stepless Self-Regulating Transmission for Vehicles

The article discusses a mechanical stepless transmission capable of self-control in a wide range of gear ratios depending on the traction load of the vehicle. Mechanical stepless transmission is based on using angular oscillations of freewheel mechanisms (FWM) and elastic linkages (torsion shafts) enabling multiflow transformation of mechanical power, ensuring the automatic increase of torque on the output shaft of the transmission with a reduction in its frequency or smooth increase of its frequency with concurrent reduction of torque. The article gives basic mathematical dependencies and makes computer simulation of transmission operation. The article shows a Simulink design model that includes an engine block to create an incoming flow of torque and power, a transmission block with parallel branches of freewheels modules for smoothing and converting torque, and a block for determining torque, power, and efficiency at the output of the transmission. The graphs show that the use of parallel freewheel mechanisms allows us to smooth the flow of output torque and power, and greatly reduces the inertial performance of the transmission at the starting moment. The results of the calculations and their analysis show that the proposed self-controlled mechanical stepless transmission has a high torque ratio and ensures the continuous transfer of power to the output shaft with high efficiency. The obtained characteristics tell us that the proposed transmission has an advantage over mechanical transmissions because of the quick response at the moment of vehicle start and the ability to continuously deliver power and torque flow to the output shaft or drive wheels.

A Model-Based Approach to the Estimation and Control of a Continuously Variable Transmission

The Van Doorne continuously variable transmission (CVT) provides a continuous range of gear ratios (GRs) compared to a common discrete transmission, offering a potential improvement in driveline and vehicle efficiency. However, poor understanding of the dynamics of slip inherent to the CVT can lead to conservative control designs unable to realize the benefits. This brief presents a control architecture with the goal of estimating and controlling the CVT using recently developed models, given only sensors likely to be included on a production vehicle. The current state of the transmission and the disturbance torque from the driveline shaft are estimated by an extended Kalman filter (EKF). A model predictive controller (MPC) uses these estimates to optimize a feedback control sequence defined over a receding horizon to improve drivability and efficiency while enforcing safety constraints on the slip. The control scheme is validated through nonlinear simulations of a CVT, which demonstrate the ability to track both GR and slip set points while enforcing constraints.

Development of the positive engagement continuously variable transmission design with the application of graph theory

Various designs of CVTs were explored from two points of view: analysis of the design itself and analysis of the methods and techniques, used in the process of creation of the CVT. To solve the problem of finding new designs of mechanisms, the graph transformation method was developed. It includes the following heuristic techniques: a decrease in the number of graph nodes at simplification of a design or to remove non-essential elements; a change in location of graph edges and comparison of a new location of edges and necessary changes in a design; a search for all possible options for location of the parts that correspond to the same graph; introduction to the graph of the nodes, corresponding to the property, for implementation of which a part (a node) can be added to a design or, vice versa, can be removed from a design, and the property it implemented will be implemented by other parts. The original design of the CVT, in which load is transmitted by gear engagement without using friction disks and flexible sections, was developed. A continuously variable of transition ratio is ensured by a gear wheel with a variable pitch. The gear wheel consists of three gear sectors, two of which are involved in meshing. The third unloaded sector performs a turn with angular velocity that is higher than velocity of rotation of the output shaft until it takes a position before coming into engagement. The CVT does not have such drawback as fluctuations of transmission ratio. Based on the analysis of the bond-graphs, efficiency was determined, which depending on velocity of the output shaft is in the range of 95…97 %. The disadvantage of the developed design is an insufficiently wide gear ratio range R=1.5…1.6, which is limited by transverse contact ratio e α

Theoretical and Experimental Research of Spherical Roller Transmissions

Передачи с промежуточными телами качения в настоящее время используются для решения специальных инженерных задач. Они имеют низкую материалоемкость и высокую нагрузочную способность, так как передача мощности осуществляется по нескольким параллельным потокам, число которых равно числу тел качения. К недостаткам многих конструкций, препятствующих широкому использованию в промышленности, относят низкий КПД и недостаточную надежность. В статье рассмотрены вопросы расчета и проектирования передач, у которых траектории центров масс тел качения расположены на сферических поверхностях. Ролики взаимодействуют со сферическими кулачками, образующими пространственные замкнутые периодические беговые дорожки. Преимуществами являются небольшие осевые и радиальные габариты, возможность объединения в конструкции одного механизма редукторного узла и угловой муфты. Рассмотрены конструкции сферических роликовых передач, проведен сравнительный анализ двух- и трехзвенных механизмов, представлены результаты силового анализа и произведена теоретическая оценка потерь мощности. Приведены результаты экспериментальных исследований КПД и шумовых характеристик разработанных редукторов. Обосновывается вывод о конкурентоспособности сферических роликовых передач как передач общемашиностроительного назначения в диапазонах передаточных отношений 3…15, частот вращения валов не более 3000 мин-1.

Planetary Gear of K-V-V Type

Рассмотрены конструктивные варианты новой зубчатой планетарной передачи. Эта передача содержит неподвижное колесо с внутренними зубьями и расположенные внутри него сателлиты наружной и центральной групп. Наибольший сателлит наружной группы является ведомым. Ведущим может быть любой другой сателлит. Приводятся реализуемый диапазон передаточных чисел и соответствующие ему расчетные значения КПД новой передачи. Отсутствие водила существенно упрощает конструкцию и удешевляет изготовление таких передач.

Stuck in gear: age-related loss of variable gearing in skeletal muscle.

Skeletal muscles power a broad diversity of animal movements, despite only being able to produce high forces over a limited range of velocities. Pennate muscles use a range of gear ratios, the ratio of muscle shortening velocity to fiber shortening velocity, to partially circumvent these force-velocity constraints. Muscles operate with a high gear ratio at low forces; fibers rotate to greater angles of pennation, enhancing velocity but compromising force. At higher forces, muscles operate with a lower gear ratio; fibers rotate little so limiting muscle shortening velocity, but helping to preserve force. This ability to shift gears is thought to be due to the interplay of contractile force and connective tissue constraints. In order to test this hypothesis, gear ratios were determined in the medial gastrocnemius muscles of both healthy young rats, and old rats where the interaction between contractile and connective tissue properties was assumed to be disrupted. Muscle fiber and aponeurosis stiffness increased with age (P<0.05) from 19.1±5.0 kPa and 188.5±24.2 MPa, respectively, in young rats to 39.1±4.2 kPa and 328.0±48.3 MPa in old rats, indicating a mechanical change in the interaction between contractile and connective tissues. Gear ratio decreased with increasing force in young (P<0.001) but not old (P=0.72) muscles, indicating that variable gearing is lost in old muscle. These findings support the hypothesis that variable gearing results from the interaction between contractile and connective tissues and suggest novel explanations for the decline in muscle performance with age.

Optimal Gear Ratio Planning for Flywheel-Based Kinetic Energy Recovery Systems in Motor Vehicles

An efficient computational methodology is proposed for optimal gear ratio planning in motor vehicle kinetic energy recovery systems (KERS) using a flywheel and continuously variable transmission (CVT). Initial modeling of a clutch-less KERS, comprising an input wheel, CVT, flywheel, and bearings, shows that the “least effort” or “minimum energy loss” optimal control problem can be formulated in two ways: one being a conventional two-state formulation involving input wheel angular velocity and CVT gear ratio, for which least effort control can be solved in simple cases with Pontryagin's maximum principle. The second formulation involves a single-state CVT gear ratio equation for which the input wheel angular velocity and acceleration appear as unknown time-dependent parameters. A novel multiparameter optimization methodology is proposed using the single-state formulation to find optimal CVT gear ratios by adopting two discrete time scales: one being a small time scale for numerical integration of the model, and the second involving discrete transitions, hundreds of times larger. Using Chebyshev polynomial expansions (CPEs) to initially generate sets of zero-energy-loss least effort kinematics for use as the time-dependent parameters in the CVT gear ratio equation, two solution approaches are developed. The first involves a single large discrete time transition, which only requires discretization of the input wheel angular acceleration at the start and end-of-transition. The second approach involves multiple large-scale discrete time transitions as a generalization of the first, but additionally needing discretization of the input wheel angular velocity, and the CVT gear ratio, plus dynamic programming to find the optimum. Both approaches are tested using the clutchless KERS model by assuming a “super CVT” gear ratio range (but with no restrictions for use with slipping clutches). Comparison with least effort control via Pontryagin's maximum principle shows that the single transition approach is in practice far superior. The single transition approach is then used to compare a minimum energy loss clutchless KERS gear ratio plan, with one obtained using constant input wheel angular acceleration as a benchmark. This comparison, involving power losses throughout the KERS, shows the very clear benefits of adopting an optimal gear ratio plan.