Hydro-mechanical Transmission Research Articles

Configuration of the Power Reflux Hydro-Mechanical Transmission System

The hydro-mechanical transmission system (HMTS) operates either in power split transmission mode (PSTM) or power reflux transmission mode (PRTM). Although PRTM is often ignored as a transition mode, this study reveals that the HMTS operating in the PRTM can accumulate the power input from the power source in the form of reflux power (in some references, scholars also refer to the reflux power as circulating power), thereby enabling the HMTS to exhibit a similar transmission performance as hydrodynamic transmission systems. Accordingly, this study applies the PRTM to the starting of construction vehicles and refers to the HMTS operating only in the PRTM as the power reflux hydro-mechanical transmission system (PHTS). By analyzing the internal relationship between the configuration and the power flow, transmission characteristics, energy storage mechanism, and energy loss mechanism of the PHTS, the optimal PHTS configuration suitable for construction vehicles was explored. The results indicate that reasonable configurations can enable the PHTS to significantly improve the efficiency of the construction vehicle transmission system, reducing energy consumption while ensuring power performance. Expanding the displacement ratio control range of the hydraulic speed regulation mechanism and combining the PRTM with the PSTM in an orderly manner can widen the high-efficiency range of the vehicle transmission system without increasing the number of vehicle gears.

Hydromechanical Transmission IC2OC: Component Sizing and Optimization

The IC2OC transmission is a continuous transmission whose layout can change from simple IC to simple OC configuration and vice versa. It was proposed to cover a wider range of vehicle speeds without adding gears. Its sizing can lead to higher efficiencies than those of the IC and OC layouts. Therefore, this work deals with the sizing methodologies of this transmission. Two methodologies are proposed and discussed: the first uses the functional and constitutive equations of the transmission; the second is based on a mathematical programming problem. Both methodologies start from the choice of the full mechanical point speeds. The comparison between the two methods is carried out on the transmission of a commercially available 230 kW reach stacker. The comparison shows that the functional method, leaner and faster, can provide results very close to those obtained with the heavy and time-consuming optimization, provided that the values of the two full mechanical point speeds are the optimal ones for the two basic transmissions taken individually.

ACTIVE MONITORING OF COMPLEX ELEMENTS OF HYDROMECHANICAL TRANSMISSIONS
 OF MOBILE MACHINES

The issues of active monitoring and diagnosing the technical condition of a mobile machine equipped with a hydromechanical
 transmission are reflected. The factors influencing the decrease in machine efficiency and the deterioration
 of transmission performance are considered. It is noted that the main processes contributing to the loss of performance
 of a hydromechanical transmission are friction and wear of the working surfaces of parts and their interfaces;
 fatigue processes in parts subject to variable loads; aging of materials The causes of defects and the nature of their
 manifestation in hydromechanical transmissions are given, as well as measures for continuous and active monitoring of
 faults in automatic transmissions. It is noted that in order to carry out active monitoring of automated mechanical and
 hydromechanical transmissions that have complex elements of gear interaction, it is necessary to obtain interdependencies
 between diagnostic parameters and criteria for assessing the technical condition in order to implement this information
 in monitoring and diagnostic algorithms for mobile applications.

Shifting quality analysis of unmanned tractor equipped with series hydro-mechanical transmission

The series hydro-mechanical transmission (HMT) can improve the power performance and fuel economy of unmanned tractors at a lower cost. However, its shifting impact problem needs to be solved before it can be applied in practice. In this study, the control parameters of the HMT power-shift system were optimized from the perspectives of energy loss and driving comfort to improve the shifting quality of the transmission. First, the powertrain of the HMT was introduced. Second, a shifting dynamics model of the HMT was established and experimentally validated. Third, based on the single-factor simulation results, the influence of each factor on the shifting quality of the tractor was analyzed. Finally, a matching strategy for shifting parameters was proposed, and related simulation analysis was conducted on the shifting quality under plowing conditions. Compared to the standard parameters, the results show that the optimized shift parameters reduce the sliding friction work of the clutch under 9 operating conditions as well as the peak acceleration of the tractor under 12 operating conditions. In summary, the parameter-matching method proposed in this study was effective and provided theoretical and methodological support for the development of HMT and its control system for unmanned tractors.

РАЗРАБОТКА СПЕЧЕННОГО ФРИКЦИОННОГО МАТЕРИАЛА ДЛЯ ГИДРОТРАНСФОРМАТОРА ГМП САМОСВАЛОВ БЕЛАЗ

The torque converter is designed to transmit mechanical energy from the engine through a circulating fluid flow and automatically steplessly changes, within certain limits, the angular speed and transmitted torque depending on the load on the dump truck wheels. The torque converter makes it possible to achieve low speeds of the dump truck with increased traction on the drive wheels, ensures stable engine operation when the load changes, and also helps reduce dynamic loads in the dump truck transmission. The paper presents the results of a study of the effect of iron-chromium alloy powder ПХ30 (PKh30) on increasing the performance properties of sintered friction material for use in the torque converter locking clutch of a hydromechanical transmission. This is achieved due to the high physical and mechanical properties of PKh30, and the Cr23C6 layer formed during the sintering process with a thickness of up to 6 μm. It is established that the introduction of 10–40 vol.% of PKh30 powder helps to increase the friction coefficient from 0.042 to 0.075, with the maximum content being 28 %. Based on the data obtained, the composition of the composite friction material ФМ-15 (FM-15) was developed and patented. The manufactured friction discs, installed and operated in the hydromechanical transmission torque converter of the BELAZ-7555E mining dump truck with a load capacity of 60 tons, showed high performance properties. The developed composition of the friction material is also used in the friction clutches of the loading and hauling machine MoAZ-40751 with a load capacity of 16 tons and the loading and transport mine machine MoAZ-75851 with a load capacity of 50 tons with an electronic-hydraulic automatic control system. The study of tribological properties was carried out on a friction machine ИМ 58 (IM 58). The morphology of the friction surface was studied on a scanning electron microscope MIRA (Czech Republic) with an INCA 350 micro-X-ray spectral attachment from Oxford Instruments (United Kingdom). Phase composition was determined on an Ultima IV X-ray diffractometer of Rigaku Company (Japan) in CuKα radiation at an X-ray tube voltage of 40 kV, anode current of 40 mA.

Design considerations about the hydromechanical transmission IC2OC

The hydromechanical transmission IC2OC operates as an Input Coupled transmission at low speeds and as an Output Coupled transmission at high speeds; a series of clutches allows the shift between two layouts. In this way the transmission speed range can be almost doubled.The design of this transmission requires the full mechanical speed value for both basic layouts. Since these values heavily influence transmission performance, their choice must be made carefully.In this paper two choice criteria for these two speeds are proposed and discussed: the first one refers to the optimal choice for each basic layout; the second sets these speeds in correspondence with the speed of the maximum energy processed in a working cycle.The effectiveness of these two criteria, applied to an off-road vehicle transmission, demonstrates that the former guarantees greater efficiency than the latter, despite its good assumptions.

Integrated transmission vibration reduction technology based on the “isolating-reducing-optimizing” method

Hydro-mechanical transmission devices that can transfer power from the engine to the action mechanism are widely used in heavy-duty vehicles. It has many components, and the operating conditions are complex and changeable. Multi-source excitations and load disturbances easily aggravate vehicle vibrations, which has an adverse impression on the running quality of the whole vehicle. Therefore, it is necessary to carry out research on the vibration problems caused by multiple excitation sources. Thus, in this paper, a new vibration reduction method of “isolating-reducing-optimizing” for hydro-mechanical transmission devices is proposed to optimize such devices in multiple dimensions to improve their dynamic responses. This novel method optimized the coupling stiffness to isolate the vibration caused by the engine fluctuating torque. Moreover, the vibration energy decoupling method and optimization method are used to decouple the rigid body vibration of the mounting system, and gear profile modification method based on a dynamic model is used to attenuate the internal high frequency vibration caused by the gear meshing excitation. Finally, the steady-state conditions and cycle conditions vibration tests of the transmission system before and after optimization are carried out. The time and frequency domain vibration responses of the transmission system before and after optimization are compared to verify the effectiveness of the optimization method.

Гидромеханические трансмиссии лесотранспортных машин: технологическая связь с воздействием на почвенно-растительную среду

Reducing the negative impact on the forest soil and vegetation environment of wheeled propellers of biaxial articulated forest transport vehicles, along with changing the parameters of the propellers themselves, can be effectively carried out by redistributing the power flow in the hydromechanical transmission. In order to ensure high traction performance and cross-country capability through single obstacles (root systems) in the conditions of a cutting area, it is necessary to take into account the rational parameters of the components and assemblies of the hydromechanical transmission based on new scientifically sound technical solutions. A review of the designs of hydromechanical transmissions of domestic and foreign-made forest transport vehicles revealed their advantages and disadvantages that affect the effectiveness of their use in the conditions of forest exploitation. The primary transportation of trees, which occupies a significant volume during logging, is effectively handled by forest transport vehicles with high energy saturation. The use of a promising torque converter design as part of a hydromechanical transmission unit for the separate drive of the drive axles of wheeled articulated timber vehicles will compensate for the effect of external forces and reactions to the wheel mover, as well as minimize the phenomenon of power circulation in a closed loop "wheel mover – bearing surface", which will contribute to an increase in traction performance. The technological relationship from the use of different powertrain designs is characterized by moderate differentiation (p < 0.05) according to the criteria of impact on the soil environment, based on the use of the median method in the statistical analysis of similarities and differences. Future research will answer the following questions: how will the level of loss of useful power in the hydromechanical transmission of a wheeled forest transport vehicle equipped with a new torque converter change in conditions of constantly changing external influences? How and how closely will the transmission parameters with the new torque converter affect the performance and patency of the forest transport vehicle, taking into account the characteristics of the soil and plant environment?

A compact hydro-mechanical transmission solution to wheel loader propulsion system and its control strategy

Given the need for high efficiency to wheel loader powertrain, hydro-mechanical transmission is a promising solution to wheel loader propulsion system since it enables efficient engine operations owing to its continuously variable transmission function. The current hydro-mechanical transmission consists of planetary gear set and two hydrostatic units, making it bulky and complex in controls. This study proposes a simple and compact hydro-mechanical transmission solution to wheel loader powertrain. It improves vehicle acceleration performance by providing hydraulic torque assistance at low vehicle speed. The steady-state characteristics of the proposed hydro-mechanical transmission are analyzed, and the mathematical models of proposed wheel loader powertrain are constructed. An optimization strategy is developed as a reference for the design of an engine-speed based control strategy. The simulation results of the key components of proposed powertrain are analyzed. Furthermore, the engine-speed based control strategy is evaluated by the optimization strategy in different forms of the loading cycles. The results demonstrate the effectiveness of proposed wheel loader powertrain and its control strategy.

Comprehensive lumped parameter and multibody approach for the dynamic simulation of agricultural tractors with tyre–soil interaction

AbstractModern agricultural tractors are complex systems, in which multiple physical (and technological) domains interact to reach a wide set of competing goals, including work operational performance and energy efficiency. This complexity translates to the dynamic, multi‐domain simulation models implemented to serve as digital twins, for rapid prototyping and effective pre‐tuning, prior to bench and on‐field testing. Consequently, a suitable simulation framework should have the capability to focus both on the vehicle as a whole and on individual subsystems. For each of the latter, multiple options should be available, with different levels of detail, to properly address the relevant phenomena, depending on the specific focus, for an optimal balance between accuracy and computation time. The methodology proposed here by the authors is based on the lumped parameter approach and integrates the models for the following subsystems in a modular context: internal combustion engine, hydromechanical transmission, vehicle body, and tyre–soil interaction. The model is completed by a load cycle module that generates stimulus time histories to reproduce the work load under real operating conditions. Traction capability is affected by vertical load on the wheels, which is even more relevant if the vehicle is travelling on an uncompacted soil and subject to a variable drawbar pull force as it is when ploughing. The vertical load is, in turn, heavily affected by vehicle dynamics, which can be accurately modelled via a full multibody implementation. The presented lumped parameter model is intended as a powerful simulation tool to evaluate tractor performance, both in terms of fuel consumption and traction dynamics, by considering the cascade phenomena from the wheel–ground interaction to the engine, passing through the dynamics of vehicle bodies and their mass transfer. Its capabilities and numerical results are presented for the simulation of a realistic ploughing operation.

ПРОГНОЗИРОВАНИЕ РЕСУРСА ГЛАВНОЙ ПЕРЕДАЧИ САМОСВАЛА БЕЛАЗ НА СТАДИИ ПРОЕКТИРОВАНИЯ

The purpose of the research is to improve the method for calculating the lifetime of bevel gears with a circular tooth of the driving axle of the BELAZ dump truck with a hydromechanical transmission. An analysis of domestic and foreign calculation methods showed that when determining the contact stresses in the gearing, the influence of the modification of the side surfaces of the teeth on the magnitude of internal dynamic loads is not taken into account, which leads to a significant overestimation of the calculated lifetime of gears during their design. The solution to the problem is the introduction of refinement coefficients into the calculation methods traditionally used in OJSC “BELAZ”, the values of which are determined according to the recommendations of the Gleason company (USA), the supplier of gear-cutting equipment to OJSC “BELAZ”. Comparison of the actual value of the lifetime of the gear wheels of the main gear, established according to the results of the career operation of the BELAZ dump truck with a carrying capacity of 90 t with a hydromechanical transmission (about 142,000 km of run), with the results of calculating the lifetime using the proposed (134,000 km of run) and traditional (167,000 km of run) methods showed that the relative error in estimating the lifetime of the bevel gears of the drive axle of the dump truck, calculated by the proposed method, is about 6 %, and by the traditional one — 15.5%.

Optimal Matching Method of Structural Parameters of Hydro-mechanical Transmission Device

In this paper, for the hydro-mechanical transmission device with constant speed input and variable speed output, an optimization model is constructed, which takes the structural parameters of the fixed gear train, the rotating gear train, and the circular diameter of the torque converter as the design variables and the weighted comprehensive efficiency as the objective function. The optimization model considers the influence of the change of the stator opening on the original characteristics of the torque converter, and limits the value of the structural parameters of the planetary gear train by the reference value of the transmission ratio of the planetary gear train given in the mechanical design manual, and gives the steps to solve the optimization model by using the search algorithm. The value range of the hydraulic torque converter is limited by reversely calculating the circulation circle diameter of the hydraulic torque converter within the speed range, so as to improve the search efficiency. The optimization model and solution method are verified by taking a boiler feed pump of a thermal power plant as the load.

ОЦЕНКА ЭКСПЛУАТАЦИОННОГО РЕСУРСА ПЛАНЕТАРНОЙ КОРОБКИ ПЕРЕДАЧ ГМТ КАРЬЕРНОГО САМОСВАЛА ПО РЕЗУЛЬТАТАМ ФОРСИРОВАННЫХ СТЕНДОВЫХ ИСПЫТАНИЙ

The aim of this work is to assess the compliance of the estimated lifetime of the planetary gearbox of hydromechanical transmission of a BELAZ mining dump truck with the actual operational one based on the results of accelerated (forced) bench tests. Preliminary strength calculations were carried out for the two most stressed modes of movement of a mining dump truck in a quarry on the rise, where the most significant damage to gear trains takes place: for maximum productivity (power) and maximum torque. Investigations showed that the gears limiting the lifetime of the gearbox are the sun gear and satellites of the 3rd planetary series. As a result of the tests, the estimated operating time of the planetary gearbox on the bench was achieved, which guarantees an operational life of at least 400,000 km of the dump truck run.

Аналіз конструктивних особливостей різних типів коробок перемикання передач автомобілів

One of the important components of the car design is the gearbox, which is part of the transmission. It is the gearbox that is responsible for changing the direction of the car and its speed. This affects traction and dynamic properties in general. The purpose of this article is to analyze the design features of various types of car gearboxes. The work analyzes the design features of various types of car gearboxes. The purpose of the gearbox, the effect on the traction-speed properties, which are a set of properties that determine the possible speed ranges and the maximum intensity of acceleration when the car is moving in the traction mode in various operating conditions, are given, as well as the main requirements that it should provide. The peculiarities of the construction of mechanical gearboxes, their structure, the principle of operation and the possibility of placement in a car are considered. The structure and main elements of the hydromechanical transmission (HMT) design are presented. It consists of three main parts: a torque converter, a manual gearbox and a control system. The design features of the gearbox with V-belt and toroid variators are considered. The principle of operation of variators, which ensures a stepless change of the gear ratio within the established limits, is presented. The design of the gearbox with a double clutch is considered, which ensures uninterrupted transmission of the power flow to the drive wheels. The gearbox is controlled by an electronic control unit, which receives information from sensors located in the box and is connected by a high-speed bus to the engine's electronic control unit. The main advantages and disadvantages of each type of considered gearboxes are highlighted. The mechanical gearbox has proven itself as a unit that is simple in design and reliable in operation. The prospects for the development of the gearbox are the development of new electronic control systems, the use of modern materials with high performance indicators and the use of high-performance methods of mechanical processing.

Design procedures for hybrid hydromechanical transmissions

Hybrid hydromechanical transmissions are particularly suitable for heavy vehicle and have the potential to provide better efficiencies than other hybrid architectures. However, their study must be carried out with care, since there are many possible transmission configurations and there is not one superior to the others for all applications. The particular complexity of these transmissions requires that design be treated as an optimization problem.In this paper, the optimization procedures of the “non-optimal” type are compared with the “optimal” ones, which are more precise than the former, but much heavier in terms of calculation time. The former consist of two sections. The first one is dedicated to the simultaneous optimization of the layout and components of the non-hybrid hydromechanical transmission; the second one is dedicated to the accumulator only, which can be optimized by means of simple physical laws or by means of a “Design of Experiments “procedure.The “optimal” procedures, on the other hand, proceed with the sizing of the entire hybrid transmission through a mathematical programming problem that can be single or multi-objective. It will be demonstrated that the DOE “non-optimal” procedure provides results very close to those derived from the “optimal” procedures, with considerable savings in calculation times.

Energy efficiency optimization of a compound coupled hydro-mechanical transmission for heavy-duty vehicles

The concept of carbon neutrality makes scholars not only intensify their exploration on the utilization of new energy, but also further optimizing the utilization of traditional energy by improving energy management. Nearly half of energy losing among traditional internal combustion vehicle is due to energy delivering and operation. The CCHMT prototype enabled the vehicle to run smoothly and efficiently under harsh conditions. However, the large number of parameters makes the optimization of energy management system difficult, which adds a lot of troubles to the subsequent product serialization. Thus, after finishing research on CCHMT-3, a comprehensive optimization algorithm based on NSGA-II&SA is constructed to optimize the transmission characteristic parameters of CCHMT-4. By using the algorithm-optimized parameters, the AMEsim model simulation with CCHMT-4 shows better static speed regulation characteristics, efficiency characteristics and load stiffness characteristics. Furthermore, the dynamic characteristics of CCHMT-4 are simulated by DP dynamic programming algorithm, and the result shows that under the operation condition of JN1015, the fuel consumption rate is reduced by 13.9% compared with CCHMT-3. Subsequently, CCHMT-4 prototype processing and test-bed construction were carried out to verify the relevant characteristics of CCHMT-4. The experiment results show that the actual efficiency of CCHMT-4 is 80.6%–86.0%, the experimental data of fuel consumption is 0.701 kg, which shows better operation performance than CCHMT's former research.

Energy Saving Performance of Agricultural Tractor Equipped with Mechanic-Electronic-Hydraulic Powertrain System

Tractors are usually applied in field operations, road transport, and other operations. Modern agriculture has higher design requirements for tractor powertrains due to the complicated working environments and various operations. To meet the driving requirements of the tractor under multiple operations, a mechanic-electronic-hydraulic powertrain system (MEH-PS) for tractors has been designed according to the characteristics of the hydro-mechanical composite transmission and electromechanical hybrid system. The principle of multiple driven and transmission modes of MEH-PS are introduced, the speed regulation characteristic curve of hydro-mechanical transmission (HMT) is given, and the related power element model, tractor model, and efficiency model are established. The HMT optimal economy transmission ratio control strategy and hybrid rule-based optimization energy management strategy were developed. Take three typical tractor operations for analysis: ploughing, harvesting, and transport. The results show that the engine operating points are mainly distributed in the higher load area, the tractor maintains high system efficiency, and the relative error between simulated and tested fuel consumption is within 5%, which further proves the reliability of the model. The solution also showed lower fuel consumption in all three operations compared to DLG’s announced PowerShift tractors and CVT tractors. Thus, the powertrain system can meet the tractor’s drive requirements under complex operating conditions and maintain high efficiency and is therefore suitable for tractors that need to operate frequently in the field and on the road.

MODERN TRENDS OF DESIGN, RESEARCH AND USE OF HYDRAULIC MACHINES IN DRIVES OF MECHANISMS AND TRANSMISSIONS (REVIEW ARTICLE)

The work is devoted to an overview of modern trends in the design, research and use of hydraulic machines in the drives of mechanisms and transmissions. The analysis of the use of hydromechanical transmissions has been carried out. The advantages and disadvantages of hydromechanical transmissions in comparison with mechanical ones are described. A brief overview of modern approaches to the design of new products, taking into account the existing information technologies, is carried out. We have analyzed modern software products designed to support the project at different stages of the product life cycle. It has been found that at the present time the appearance of individual variants of highly specialized software with a modern interface for synthesizing the structure of a designed product does not make it possible to solve the problems of synthesis and structural analysis of hydro-mechanical transmissions. A review of the analysis of operational factors affecting the fault tolerance and operating parameters of hydrostatic transmissions in general and hydromechanical transmission in particular is carried out. We have also considered the examples of technical solutions that allow to reduce the number of failures associated with the influence of one factor or another, as well as allow to reduce its influence on the parameters of the mechanism. The analysis of sources with information on the study of the parameters of hydrostatic transmissions using field tests or the mathematical apparatus developed by the authors is carried out. The ways of solving problems arising at the stages of design research are outlined. Keywords: design, hydrostatic transmission, hydromechanical transmission, influence of operational factors, synthesis

Test oil grade "A"

The article analyzes the results of the performance test oil grade "A" for hydromechanical transmission.

Novel design of compound coupled hydro-mechanical transmission on heavy-duty vehicle for energy recycling

How to efficiently transmit power and reuse/recover energy has been the subjects of heated discussion in the high-power transmission field. Regarding heavy-duty vehicles, they used to be equipped with a gearbox as a typical type of high-power transmission to deliver power to the wheel. However, a gearbox transmission has quite complex mechanical structure for realizing a large speed-regulating range, and it has an inevitable drawback of weighing too much. In addition, it cannot reuse/recover energy. In this study, a novel design of a compound coupled hydro-mechanical transmission (CCHMT) is proposed to realize energy reuse/recovery on heavy-duty vehicles. The CCHMT has an optimal structure coupled with hydraulic and mechanical components, which makes its speed change continuously and keep the engine running with a high fuel economy. Moreover, compared with both hybrid and battery electric vehicles, vehicle with CCHMT has higher power density. To validate the transmission's feasibility and operational efficiency, simulation modeling and experiments are conducted. The CCHMT can transform unstable energy under a wide speed-regulation range, reuse/recover a vehicle's excess energy at an efficiency of 82.30%/62.94%, and provide a stable driving torque with a high efficiency of 76%, which shows a good energy management performance on heavy-duty vehicle's hydraulic system.