Browse Topic: Transmission fluids
The acceleration of 800V permanent magnet radial flux e-motors marks a significant leap in the automotive industry. This motor architecture offers increased power density through smaller, lighter designs that spin at higher rpm. However, this advancement brings with it the challenge of efficient thermal management, especially in dissipating heat from the magnet wire within the stator. Effective thermal management is crucial for improving e-motor efficiency. The primary heat sources are the copper-insulated magnet wires, with heat spreading to the slot liners. Engineers have explored various cooling methods, including traditional water jackets using ethylene glycol and water. However, the trend is shifting towards using automatic transmission fluid (ATF) or oilbased fluids for direct cooling, driven by its integration convenience with the e-motor gearbox and inverter systems.
A well-designed cooling system is crucial in construction machines for efficient heat dissipation from vital components, including the Radiator(RAD), Oil Cooler (OC) and Intercooler (IC). The radiator ensures optimal engine performance and longevity by maintaining a stable operating temperature. Oil Coolers preserve hydraulic system efficiency. Inter Coolers optimize engine performance through denser intake air. The robust cooling system enhances system reliability, reduces downtime, avoid overdesigned system, and increases operator safety in demanding construction environments. The size and location of heat exchangers are critical in cooling system design. Using 1D simulation tool KULI for cooling system design offers the benefits of comprehensive system simulation, optimization of thermal management, reduced development time and costs, enhanced system reliability, improved integration with other systems, and real-world testing and validation. The tool enables time and cost-effective 1D heat transfer analysis, facilitating design of experiments. This analysis guides the design process to the next level, where the finalized design can be verified using CFD analysis for the optimal case, avoiding multiple 3D simulations which consume a lot of time & cost. This paper talks about KULI software to analyze the sizing and placement of heat exchangers within given size constraints for a new engine packaging in a construction machine. The approach helped to determine the optimal size and positioning of the heat exchangers while considering heat transfer, fluid flow, pressure drops, and temperature distribution. This data-driven approach allowed to design an efficient cooling system that ensures reliable performance of critical components.
Effective design of the lubrication path greatly influences the durability of any transmission system. However, it is experimentally impossible to estimate the internal distribution of the automotive transmission fluid (ATF) to different parts of the transmission system due to its structural complexities. Hybrid vehicle transmission systems usually consist of different types of bearings (ball bearings, thrust bearings, roller bearings, etc.) in conjunction with gear systems. It is a perennial challenge to computationally simulate such complicated rotating systems. Hence, one-dimensional models have been the state of the art for designing these intricate transmission systems. Though quantifiable, the 1D models still rely heavily on some testing data. Furthermore, HEVs (hybrid electric vehicles) desire a more efficient lubrication system compared to their counterparts (Internal combustion engine vehicles) to extend the range of operation on a single charge. Thus, this paper includes a detailed, transient, three-dimensional CFD analysis of the lubricating oil flow path in an HEV transmission system using the commercial CFD software Simerics-MP+. The modeled transmission system includes scores of bearings, rotating components, and planetary gear systems. Using this modeling framework, we can predict the lubrication state of the various components of the transmission system. Furthermore, this paper reveals the effect of the centrifugal force on the oil distribution and the wetting fraction of different components. Additionally, two different designs of lubricating flow paths inside the roller bearings are explored to study the effect on the wetting of the rollers. The current simulation framework adopts the volume of fluid (VOF) technique to accurately model the two-phase interface development in the rotating systems.
Wet-sump transmissions are widely used in heavy duty and medium duty vehicles. As these transmissions do not have a dedicated forced lubrication system, it is important that the gear train, shafts, and enclosure are designed appropriately so that enough oil splashes to critical locations to ensure sufficient lubrication. The lubrication effectiveness of such transmissions can be studied through detailed tests or numerical simulations. Often, the vehicle, and therefore the transmission, encounters some severe operating conditions, such as climbing on an incline, driving downhill, etc. Studying these conditions through tests is an expensive process and this imposes the need for an analysis first approach. In this paper, the 3D multiphase Volume of Fluid (VOF) method is used to examine two such extreme cases: an 8-degree tilted installation of transmission in a vehicle, and an inclined condition of transmission during a 10-degree uphill climb. By studying the oil volume fraction on gears and splash patterns, inertia and reverse gears in the first case and headset gear in the second case are found susceptible to oil starvation. The effectiveness of a simple and easily deployable solution of increasing the transmission oil level is then assessed. Results show that increasing the oil level improves the lubrication effectiveness in the first case, but only slightly in the second case. However, both cases show higher churning losses. This calls for a trade-off between lubrication effectiveness and power/torque consumption. Present work demonstrates how the developed methodology can help identify oil-starving locations and evaluate potential solutions for extreme cases, eliminating the need for testing multiple prototypes before arriving at a suitable solution.
Gearbox power transfer efficiency is a major factor in overall powertrain efficiency of a passenger vehicle. With rapidly changing emission and fuel efficiency regulations, there is a push to increase the gearbox efficiency to improve the overall fuel economy of the vehicle. In case of an existing gearbox, efficiency can be improved by using the low viscosity lubrication oil. Despite a benefit in increasing the gearbox efficiency, lowering down the viscosity of lubrication oil gives rise to few challenges with respect to its performance. One of these challenges is breather performance which defines that transmission oil should not come out of breather pipe in some pre-defined conditions during gearbox operation. As this validation is being carried out on proto parts when the complete system is ready, failure to satisfy the defined criteria for breather performance can lead to multiple trials. This further leads to extended design cycles for launching new passenger vehicles with better transmission efficiency and fuel economy into the market. Design cycle time can be reduced by using CFD simulation techniques for oil flow simulation to predict the breather performance in the early design stage. Current paper describes a CFD simulation method developed for virtual validation of gearbox lubrication oil breather performance using ParticleWorks software. Simulation model consists of complete gearbox system with all the gears rotating, shift system, oil flow galleries and transmission housings. Input conditions to the CFD Model are as per the actual test conditions. CFD Simulation model is validated by correlating it with the actual oil flow using cut-section into the gearbox housing. Validated model is being used to carry out virtual validation of lubrication breather system of new design.
In electric vehicles (EVs), drivetrain lubricants (EV fluids) are often relied upon to aid in cooling the motors. In such cases, the lubricants must provide high cooling performance. They should also improve the efficiency of the transmissions and reduction gearboxes in EV drivetrains. Both requirements can be met by lowering the viscosity of the fluid. This effectively improves the heat transfer coefficient and also helps increase efficiency by reducing churning loss. However, a viscosity that is too low can negatively affect the fatigue life of mechanical parts such as gears and bearings. To solve the issues associated with lower viscosities, we optimized the anti-wear agents, dispersants, and other additives to develop formulations specially designed for EV drivetrains. The result are lubricants that provide excellent extreme pressure properties and protection for drivetrain components despite their lower viscosities. We evaluated performance of the developed lubricants, and it was confirmed that lower viscosity contributes to better cooling effect and improved helical gear efficiency as expected. In addition, these lubricants have much improved electrical insulation properties and Cu compatibility compared to conventional automatic transmission fluids (ATFs). In summary, we showed it was possible to lower viscosity without sacrificing protection and developed EV fluids that provide excellent motor cooling performance and help increase the range of the vehicle.
The heat generated by an internal combustion engine must be dissipated to maintain acceptable component temperatures throughout the entire powertrain system under all operating conditions. However, under cold start conditions it is beneficial to retain this available heat to achieve faster warm-up in order to reduce fuel consumption. In modern engines there are several components in the coolant circuit that are used to accelerate the warm-up of sub-system fluids such as the engine oil, transmission oil and axle oil. The magnitude of the fuel consumption reduction will depend on how these rapid warm-up devices are arranged, combined and controlled. This paper describes a methodology that was developed to optimize the distribution of coolant heat in the powertrain system during warm-up. A comparative study can be performed to optimize the arrangement of each heat exchanger in any given powertrain system to minimize cost and time early in development. Different thermal strategies or technologies that affect warm-up can also be evaluated using this methodology to assess their effectiveness.
In recent decades, there has been a growing focus on improving overall vehicle efficiency and fuel economy due to growing customer awareness and more stringent environmental regulations. Effort has been placed on improving the engine efficiency and reducing the losses of the transmission and driveline. One essential component of this process is to correctly size the transmission oil pump as it is one of the main energy consumers in the powertrain. Conversely, the oil pump has a critical mission of ensuring reliable and high quality gear shift as well as supplying lubrication and cooling oil to various components in the transmission. This paper outlines a strategy to systematically understand and quantify the main requirements for sizing the oil pump to ensure adequate performance while minimizing the energy consumption of the pump. The proposed framework is a three-legged approach. The first component identifies the main consumers within the automatic transmission and establishes a relationship between the operating parameters, component specific parameters and the specific demand of that particular oil consumer. The second leg looks at various operating conditions and a plethora of load cases are identified. The third leg connects the first two components and proposes the most optimized pump displacement size minimizing the required power to run the pump while meeting the requirements.
In line with Global targets of reducing CO2 Emissions, transportation industry is witnessing a significant shift in focus — from emissions to fuel economy — by regulators, researchers, OEMs, fuels and lubricant manufactures. Improvements in fuel economy can have a significant bottom-line impact for fleets and owner operators alike. There are many paths to take when looking at a program to reduce fuel consumption. These include new engine and transmission designs, new metallurgies, surface finish, coatings, new injection technologies, turbochargers and of course through engine and transmission lubricants. Passenger car engine lubricants are being upgraded time to time and customized for fuel economy and emission compliance benefits as the vehicle technology evolved to meet the emerging regulations. New vehicle technology has shifted surface tribology more towards boundary regime as new designs are compact, offer high operating temperatures and pressures. Fuel Economy (FE) Regulations also require lower viscosity for reducing hydrodynamic friction. Thus, engine oil at reduced viscosity has to face tough challenges of hardware durability by maintaining the right film thickness and better anti wear protection through it’s ingredients, which are base oils and performance additives. Friction Modifiers are key additives in automotive lubricants to take care of boundary friction through adsorption at tribo surface under mild load conditions and plays extremely important role now a days to achieve the required FE targets of original engine manufacturers. Engine oils can play a major role in improving the FE. Nowadays, Frictional torque test is widely used for assessing the frictional performance of engine oils and thereby for optimizing the composition of engine oils for its better fuel economy. There is also a requirement of compatible engine oils for after treatment devices used in new generation engines and this again requires new Low SAPS additive chemistry. Therefore, new generation engine oils for mobility sector has to strike the right balance of base oils and additive components to ensure not only sufficient engine protection, but also to maintain the overall performance & fuel economy requirements besides taking care of latest after treatment systems. Key challenge is to deliver fuel economy along with hardware durability, which requires balanced approach at tribo level by selecting the right screening methodology, high quality base oils, and superior additives chemistries. Friction Torque Test and MIDC Test on Chassis Dyno were carried out on selected candidate oils. Up to 3% efficiency improvement was achieved in SAE 0W-16 grade meeting API SN credentials under MIDC Test Cycle run on Bharat Stage VI passenger car with gasoline engine. This paper presents an effort made by IndianOil R&D in the direction of achieving fuel economy through low viscosity engine lubricants.
Automatic transmissions utilize solenoids to manage the flow of transmission fluid throughout the transmission and engage the appropriate clutches during a gear change. Because of the small clearances between sliding interfaces in a solenoid, compatibility between materials and fluids is essential to long-term functionality. The accumulation of films formed from corrosive species on these components can lead to premature failure. Copper (Cu) corrosion strip tests are found in almost all lubricant specifications; however, they do not necessarily provide assurances in the field. Long-duration, powered solenoid soak tests are undertaken to evaluate the long-term functionality of the transmission. The complexity of oil-based corrosion mechanisms, including the temperature dependence of these processes, can be difficult to evaluate even with this advanced level of testing. In this study, the corrosion rates of two Cu-based alloys relevant to solenoid components were evaluated while immersed in two typical commercial fluids at multiple temperatures. Results from powered solenoid soak tests in heated fluids were compared against a wire corrosion test method. The wire test method allows for real-time monitoring of corrosion rates through resistance measurements of a thin wire immersed in a fluid. Surfaces of solenoid bearings and wires were analyzed using a scanning electron microscope (SEM) and by energy-dispersive X-ray spectroscopy (EDS). The wire test method, which showed good reproducibility between two labs, offers an efficient and cost-effective way to screen fluid chemistries over a range of temperatures for potential corrosion issues with transmission component alloys.
In the present article, structural spring characteristics of two different Belleville springs are analyzed to overcome a failure issue in an automatic shift transmission clutch system. The spring design is evaluated through explicit dynamics analysis by finite element modelling and validated by DIN 2093 standard. Automatic shift transmissions that are used in off-highway vehicles are employed with multi-plate wet clutch system to actuate the planetary gears. These clutches are actuated through automatic transmission fluid that are supplied through flow channels. The clutch piston is moved axially by fluid pressure against the clutch pack and Belleville spring thereby transfers torque. Meanwhile, the clutch piston is retracted by the spring force once the fluid pressure is cut off. The spring is designed in such a way that during the energizing mechanism, positive spring stiffness is maintained. It is noticed that the clutch function is obstructed as the spring is inverted to other side due to unstable negative stiffness characteristic. It stalls the function of clutch system and automatic shift transmission thereby vehicle becomes inoperable. The present study compares two different spring characteristics required to suit the clutch design for proper function of transmission system.
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