Browse Topic: Clutch components
For brake and clutch components of aircraft vehicles which require higher mechanical strength and wear resilient, light-weight aluminium composites were developed infusing solid lubricant. In this study, hybrid composites were developed using powder metallurgy route with aluminum alloy AA356 and various amounts of zirconium oxide (ZrO2) (0, 5, 10, 15, and 20 wt.%) as reinforcements. A solid lubricant hexagonal boron nitride (hBN) at a fixed 5 wt.% is considered. Following the appropriate ASTM guidelines, the specimens were mechanically characterized by measuring their density, porosity, micro-hardness, compression strength, impact strength, and flexural strength, among other properties. The findings showed that the composites' mechanical and physical behaviour were greatly affected by the inclusion of ZrO2. Porosity increased as a result of particle clustering and interfacial voids, while density increased gradually as ceramic content increased. Consistently increasing ZrO2 addition led to micro-hardness improvements; at 20 wt.% reinforcement, values reached their maximum, indicating that the hard ceramic phase contributed to better surface resistance. The best balance between particle reinforcement and matrix continuity was suggested by the compression and flexural strengths peaking at 15 wt.% ZrO2. However, when the addition was raised to 20 wt.%, brittleness and porosity began to marginally deteriorate. Unreinforced and lower ZrO2 composites had superior toughness in impact, whereas materials with a higher content had a poorer energy absorption capacity. The 5 wt.% hBN improved fracture arresting capabilities and helped load transmission over the interface. Inclusion of hBN provides solid-lubricating tribofilm formation that enhances the tribological performance. This study reveals that AA356/ZrO2-hBN hybrid composites have good hardness and compressive strength improvements, with 15 wt.% ZrO2 being the best composition with good strength, toughness, and wear resistance.
The torque transfer response to rider throttle operation contributes to vehicle control in motorcycles equipped with a DCT (Dual Clutch Transmission). The clutch response is a key parameter to enhance torque transfer response. We have developed three new ECU (Electric Control Unit) control methods to enhance the clutch response on the DCT. The DCT clutch transfers torque by controlling the contact force between the clutch discs and the clutch plates. It is desirable to measure the hydraulic pressure value directly from the clutch piston chamber to control the contact force. However, since the clutch piston is a rotating body, it is impractical to place a hydraulic pressure sensor on it. Therefore, the hydraulic pressure sensor is placed along the clutch control oil line at the existing DCT system. Consequently, when oil flows in the oil line, pressure loss in the oil line causes a deviation between the hydraulic pressure sensor value and the clutch piston chamber pressure value, which limits the enhancement of clutch response. To enhance clutch response, we have studied the estimation of the hydraulic pressure value in the clutch piston chamber using the existing hydraulic pressure sensor value at the oil line. This estimation is based on the reaction force characteristics of the clutch piston and Bernoulli’s principle. By using the estimated hydraulic pressure, half-clutch control can be identified, which allows the application of higher feedback gain to enhance clutch response. We also implement correction of clutch control oil viscosity fluctuations based on the hydraulic pressure variations of the clutch control oil. With these technologies applied, the clutch response time is reduced 45% as reference compared to the existing DCT clutch control. This also reduces torque transfer response time, ultimately allowing for smoother vehicle control.
One of the top problems that every Indian automobile manufacturer struggles to manage is the clutch early failure less than 30000 Km. This is mainly due to the extreme heating of the friction lining due to the real-world user profile in the Indian market and users inappropriate driving behaviors like Overloading the goods more than the manufacturer’s recommendation, non-recommended attachments and increased wheel size, Thick traffic leading to high level of clutch modulation and Clutch riding while running and launching the vehicle at higher gears. Although many simulation and testing are done during the development phase, above listed real world user profile and customer driving habits are inevitable by any automobile manufacturer. Hence the prime goal of this experimental research is to indicate or alert the user on the clutch thermal condition due to the driving habit and to encourage the user on right driving habits. This objective is met through a standalone electronic system that consists of a set of thermocouples, a micro controller unit (ECU) and a digital LCD display. Analog output of the thermocouple is fed into the ECU which contains the wear calculation logic to convert the temperature input to the heat energy dissipated through flywheel surface during every clutch engagement. ECU then estimates the friction lining temperature caused due to the heat energy and calculates the wear of the friction lining. Finally, the percentage of facing lining worn due to the launch events along with the clutch housing temperature will be displayed through the LCD display which is fixed in the instrument panel. Hence, by using this system, it is expected that the user awareness with respect to the right driving behavior can be improved and thereby the clutch facing life, hence the reduced cost of warranty incurred by the manufacturer.
Dual mass flywheel (DMF) is an excellent solution to improve the noise, vibration, and harshness (NVH) characteristic of any vehicle by isolating the driveline from the engine torsional vibrations. For the same reason, DMF’s are widely used in high power-density diesel and gasoline engines. However, the real-world usage conditions pose a lot of challenges to the robustness of the DMF. In the present work, by capturing the Real-World Usage Profile (RWUP) conditions, a new methodology is developed to evaluate the robustness of a DMF fitted in a Sports utility vehicle (SUV). Ventilation holes are provided on clutch housing to improve convective heat transfer. Improvement in convective heat transfer will increase the life and will reduce clutch burning concerns. Cities like Mumbai, Chennai, Bangalore, roads will have clogged waters during rainy season. When the vehicle was driven in such roads, water enters inside the clutch housing through ventilation holes. Prolonged usage of vehicle in this condition results in water entering inside the DMF. DMF has grease over the springs to reduce friction. Water entering inside the DMF will reduce the viscosity of grease and subsequently leads to erosion of grease from DMF. This will result in metallic noise concern in Engine ON condition. In the present work, author presents test methodology that shall be used to reproduce the metallic noise concern during development phase. The methodology is the combination of water wading test carried out at 500 mm of water level and subsequently subjecting the vehicle to city drive and high drive profile test of 1000 km. The co-relation was also established with real world failures. Authors also propose design alternatives that shall address metallic noise concern due to water entry. Based on the results of this proposed methodology, the robustness of the DMF could be improved. The paper explains the typical robustness measures needed inside the DMF to avoid real-world NVH failures and the test methodology to evaluate the same.
In emerging markets like India, manual transmission vehicles are still most preferred & contributes to 85% of passenger vehicle sales due to its cost benefit. However, customer expects good NVH behavior for comfortable driving experience in the vehicle to maneuver effortlessly in the highly congested traffic conditions in India. Clutch & its hydraulic release system in manual transmission of IC engines are the significant components which affects the NVH behavior & maneuverability of the vehicle and the driver comfort significantly. This paper focuses on the clutch pedal vibration & groan noise concern observed during clutch pedal actuation in high power density SUV vehicle developed for Indian market. The vehicle had highly efficient & light weight engine which has high engine axial vibrations. Axial vibrations are caused due to engine firing impulses & crankshaft bending causes flywheel axial movement. This movement in turn leads to vibrations in clutch cover diaphragm fingers which are transmitted to clutch pedal through hydraulic fluid pulsation via clutch release system which comprises of CSC, bleeder, clutch high pressure pipe & CMC. Engine vibrations which are transferred through clutch system to clutch pedal is felt on driver foot and causing discomfort during clutch pedal actuation/modulations while launching, creeping and for shifting of the gears in the vehicle. During pedal actuations at higher rpm for shifting gears, low frequency vibrations becomes high frequency and heard as groan noise inside the passenger cabin which results in uneasiness to driver and passengers. This paper describes the literature available, root cause analysis of the concern, effect of clutch disc, cover assembly, hydraulic release system design variables and the optimum solution which does not affect the other performance of the clutch function while reducing the clutch pedal vibration & groan noise concern through simulation & vehicle measurement results.
Agricultural Tractors consisting of a conventional manual transmission and dry friction clutch are mostly assembled with a mechanical type of clutch release mechanism where a defined amount of free play needs to be maintained between the clutch and Release Mechanism. A defined free play is required for efficient operation of clutch, Release Bearing as well as to ensure the durability of the system. As the clutch disc wears the free play between diaphragm spring or levers (as the case may be) and the release bearing is reduced. The rate at which the clutch disc wears is dependent on many factors like working condition of the tractor, grade of the friction lining material, experience of the driver, etc. This makes it very difficult to predict the exact timeline when the free play needs to be adjusted even though an approximate indication is given in instruction manuals. In today’s situation the adjustment of the free play is carried out manually and approximately. Many times, the adjustment activity is neglected, and this leads to early failures of the clutch release bearings and / or clutch. The purpose of this solution is to ensure that the free play adjustment is automatically carried out ensuring longer life of components. The system used for automation consists of a sensorized bearing, smart logic controller, and an actuator motor. As the adjustment would be carried out digitally, it would check and ensure the required free play is always available in the system, as well as eliminate manual intervention. The same can be extended to other areas of applications like commercial vehicles etc. where a mechanical release system is used. This paper describes the innovative ways to automatically maintain a fixed value of free play between the Diaphragm Spring fingers and the clutch release bearing at any point of time as well as to automate this process without manual intervention.
During the vehicle launch (i.e. moving the vehicle from “0” speed), the clutch would be slowly engaged by the Driver or Transmission Control Unit (in Automatic Transmission/Automatic Manual Transmission vehicle) for smooth torque transfer between engine and transmission. The clutch is designed to transfer max engine torque with min heat generation. During the clutch engagement, the difference in flywheel and gearbox input shaft speed is called the clutch slipping phase which then leads to a huge amount of energy being dissipated in terms heat due to friction. As a result, clutch surface temperature increases consistently, when the surface temperature crosses the threshold limit, the clutch wears out quickly or burns spontaneously. Hence it is crucial to predict the energy dissipation and temperature variation in various components of clutch assembly through virtual simulation. During the development process of the vehicle, the clutch is tested over many duty cycles to ensure the temperature, wear rate does not exceed the material thresholds. However, performing these tests for every prototype and for every variant can be expensive and time consuming. In this paper we have proposed a simulation methodology to replicate the vehicle test cycle (Hill- Fade test,) i.e. launching the vehicle on 15% grade followed by a cooling cycle and repeated over 150 cycles in the developed virtual simulation methodology using GT-SUITE application to accurately calculate the dissipated energy and the heat transfer through the components in the clutch housing. The developed simulation model can predict the surface temperature of clutch over the defined cycle, can predict the clutch life and can perform a Design Of Experiments analysis to optimize the vehicle or clutch parameter to meet the required customer targets. With the developed simulation model results and real-world vehicle testing results has been validated. The predicated simulation results have 90% correlation with the vehicle test data.
Downsizing and Light weighting is the latest trend in the automotive industry to achieve more fuel efficient, compact and cost effective design of vehicles. Powertrain components compromise of more than 45% of the total vehicle weight. Automakers are putting significant efforts to reduce the weight of power train components. Integrated design of aluminum Engine Head and Intake manifold has been successfully implemented. Now currently we have identified the gear box housings for downsizing in light duty trucks i.e. Existing light duty trucks Cast Iron transmission. This design has been successfully modified with integrated clutch housing and transmission housing, using lightweight aluminum as the new material, using simulation tools. This lead to weight savings of up to 30% and cost savings of 20-25% as compared to existing cast iron designs. Using an integrated design reduces the assembly cost, makes the design more compact and gives better weight balance. From an emissions perspective, it is estimated that every 50 Kg of weight reduced from an average 1,500 Kg vehicle cuts CO2 emissions by 4 ~ 5 grams. This feat is achieved using simulation tools and experimental verification in three steps. First step is comparing the stiffness values of existing cast iron design with the new aluminum integrated design, step two is to optimize the design using topology optimization tool to achieve the most optimum weight of the housing. Step three is to analyses the housings strength in static, dynamic and fatigue loading conditions. The same is being backed by conducting experimental verification and these results has been correlated with the simulation results. The stiffness tests at the test rig have been successfully completed and the stiffness vales have matched with 98% accuracy with the CAE simulation results. The same housing is checked with RLDA tests and has been successfully completed all the requirements. Accelerated Endurance Test is also done on the vehicle with new housing to verify the design in running conditions as well. The FE simulation tools have helped us in selecting the right parameters for the design and ensure first time right design at the development phase. For future this can be implemented on light duty buses as well. The design and ensure first time right design at the development phase.
In modern automotive vehicles, there is a major concern for noise and vibrations generating from drivetrain. These noise and vibrations affect the passenger comfort and drivetrain parts life. Engine generates fluctuating torque and causes angular acceleration that results into torsional vibrations. These vibrations are transmitted to powertrain. Clutch disc consists damper springs and hysteresis which aids reducing these torsional vibrations. Based on the damper spring stiffness, one can control the resonance speed range and shift the resonance rpm out of driving speed range of engine. The resonance should not happen within driving speed range of vehicle to avoid large amplitude torsional vibration. But here limitation is put on the torque transmission capability of clutch for meeting vehicle requirements. As, low stiffness of damper spring requires large wind-up angle so, it is critical to decide its stiffness. The present work is related to resolving the issues of clutch damper spring failures by incorporating adequate design parameters. The vehicle model was built in AMESIM for simulation of clutch twist angle during operating condition. The damper spring can undergo full compression and hit stopper pin which is termed as spring saturation. Due to saturation, damper spring can break down if the stress generated exceeds its threshold material strength. Damper spring design was optimized based on simulation results, by proper selecting the stiffness values, to overcome saturation phenomenon. From simulation, it is concluded that new designed values are meeting requirements.
The automotive world has seen an increase in customer demands for vehicles having low noise and vibrations. One of the most important source of noise and vibrations associated with vehicles is the vibration of driveline systems. For commercial vehicles, the refinement of drivelines from NVH point of view is complex due to the cost and efficiency constraints. The typical rear wheel drive configuration of commercial vehicles mostly amplifies the torsional vibrations produced by engine which results into higher noise in the vehicle operating speed range. Theoretically, there are various options available for fine tuning the torsional vibration performance of the vehicle drive train. The mass moments of inertia and stiffness of the drivetrain components play significant role in torsional vibration damping, however, except minor changes to flywheel mass, it is hardly possible to change other components, subject to design limitations. Considering this, clutch disc torque twist characteristics plays an important role in mitigating the NVH concerns. The drive train represents a vibration system with several resonance frequencies which can be calculated using various simulation tools. With the help of simulation tools like 1D or multi body dynamics, optimized solution for the driveline fine tuning can be obtained which can reduce vehicle level noise. In this paper, 1D simulation model is used for the prediction of torsional vibration performance of the vehicle. Theoretical model of drivetrain component engine, clutch, gearbox etc. were built considering mass, inertia and stiffness values. Clutch damper parameters are optimized based on the simulation results and effect is validated by vehicle level noise and torsional vibration measurements.
In this current fast-paced world, releasing a defect free product on time is of utmost importance in the automotive domain. The automobile powertrain is designed with a fine balance of weight and power. Clutch, an intermediate part between engine & transmission in manual transmission vehicle plays crucial role for vehicle smooth drive & functionality. Hydraulic clutch slave cylinder (CSC) which is a part of clutch release system was observed with one failure mode in one of the vehicles during internal road validation. It facilitates to actuate the clutch diaphragm in order to disengage the clutch when clutch pedal is pressed and to re-engage the clutch back when the clutch pedal is released. CSC failure directly disconnects the response of leg to clutch and thus driver may lose vehicle control and can possibly cause a severe vehicle crash. After investigation and dismantling the failed part, wear marks were observed on anti-rotation pin (which locks CSC hydraulic chamber against plastic body) and on elliptical O-ring, which locks oil flow to the plastic chamber. Unique in the industry, a component-level test setup was developed for validation and improved CSC design. Few samples were successfully tested for failure simulation and results were very encouraging. For strengthening of the CSC, design modification was done, and the new designed parts were tested on the same component-level test setup for validation. The sample passed the component-level test, and subsequently vehicle level test, and was approved for production. The component-level test methodology helped to test multiple design iterations and samples within a postulated time and cost. This methodology can be used as a part of front-loading support for all future projects.
The main components present in the clutch disc assembly are friction facing, metallic disc, damper spring, drive plate, retainer plate, washers and hub. Among the parts, metallic disc is the weakest component present in the clutch system and moreover it is subjected to higher fatigue load during the vehicle operating condition. Hence it is necessary to make the design as more robust to withstand the worst loading conditions. The metallic disc is subjected to axial load, torque, speed and axial misalignment during vehicle operating condition. Through bench test, it was observed that higher severity in metallic disc was due to axial misalignment. Initially, metallic disc was tested for axial misalignment condition up to failure through bench test and the number of cycles were determined. Structural simulation was simulated as the same as bench test using ANSYS workbench 19.2. From this better correlation arrived between FEA and bench test. To make FEA result more robust, tolerance study was done using six sigma methodology. Therefore, this Numerical method was useful to obtain a sturdy design of metallic disc without investing much time through bench test. Optimization study was performed on metallic disc by considering all the possible design parameters without affecting the functionality of the component. A Novel Y shaped design profile was introduced in the metallic disc to increase the life cycle of the component, which is the main novelty of the current research work. This design pointed 15% and 20% reduction in stress and 10% and 62% least stiffness when equated with the initial design for gearbox side (GBS) and flywheel side (FWS) respectively. Hence the Novel Y shaped design was considered as robust design for the current disc assembly of the automotive application.
Vehicles with manual transmission are still the most preferred choice in emerging markets like India due to their benefits in cost, simplicity and fuel economy. However, the ever-increasing vehicle population and traffic congestion demand a smooth clutch operation and a comfortable launch behaviour of any manual transmission vehicle. In the present work, the launch performance of a sports-utility vehicle (SUV) equipped with dual mass flywheel (DMF) and self-adjusting technology (SAT) clutch could be improved significantly by optimizing the clutch system. The vehicle was observed to be having a mild judder during clutch release (with 0% accelerator pedal input) in a normal 1st gear launch in flat road conditions. An extensive experimental measurement at the vehicle level could reveal the launch judder is mainly due to the 1st order excitation forces created by the geometrical inaccuracy of the internal parts of the clutch system. Moreover, the forces are amplified by the resonance of the complete driveline with the first eigen mode at 8 to 12 Hz. A detailed study in the 1-dimensional torsional simulation model revealed that the eigen mode frequency of the real-wheel drive architecture is mainly driven by several parameters (mass, inertia, torsional stiffness) of the driveline components. Hence, the 1st order excitation forces were needed to be controlled to improve the launch performance. Based on the detailed design of experiments (DOE), it was evident that the cushion disc stiffness and clutch disc parallelism are the significant contributors to the excitation forces. The launch performance of the vehicle could be significantly improved by reducing the cushion disc stiffness at lower axial load (300 N) and by controlling the clutch disc parallelism within a tight tolerance range. The effect of these modifications on different launch conditions is also explained in detail in the present work. The paper gives a holistic view of improving the launch performance of any vehicle without compromising any other parameter.
Gear rattle is due to impact noise of unloaded gears in transmission having freedom to move in backlash region. Engine order vibrations in the presence of backlash in meshing pairs induce the problem. It is a system behavior wherein flywheel torsional vibrations, the pre-damper characteristics and transmission drag torque plays a vital role in an engine idle condition (hot & cold). Idle rattle is a severe issue, which is highly noticeable in cold condition or after 1st engine crank. Gear rattling observed in idle condition is idle gear rattle or neutral gear rattle, specifically in cold condition is a “Cold idle rattle” and this is one of the critical noise parameters considered for entire vehicle NVH. Damper mechanism in the clutch, is used to serve better isolation (by reducing the input excitation to transmission parts) of vibrations between engine and transmission their by reducing gear rattle intensity. Engine firing order, engine downsizing, down speeding (means high peak torque at low engine speed) and other unbalance masses plays leading role in fluctuation of output torque. Clutch parameters like pre-damper stiffness, hysteresis and wind up angle affects more to the cold idle rattle phenomenon. The gear-rattle phenomenon is also depends on vehicle operating temperatures. Temperature variation affects the frictional drag of transmission, which is a most crucial parameter in clutch Pre-damper characteristics design (input parameter) to address rattle. Through experiments, the effect of temperature variation on transmission drag torque and its effect on clutch pre-damper characteristics, which is sensitive to rattle phenomenon, was established. Clutch designer need to understand the requirements and accordingly optimum pre-damper characteristics need to be defined which would result into acceptable idle rattle. This was demonstrated with the experiments considering different pre-damper characteristics on same powertrain. These experiments will help clutch designers to define correct selection / design of pre-damper in the clutch disc.
Automotive clutches are rotary components which transmits the torque from the engine to the transmission. During the engagement, due to the difference in speed of the shafts the friction lining initially slips until it makes a complete engagement. Enormous amount of heat is generated due to the slippage of the friction lining, leading to poor shift quality and clutch failure. Depending on the road & traffic conditions, and frequency of engagement and disengagement of the clutch, it generates transient heating and cooling cycles. Hill fade test with maximum GVW conditions being the worst case scenario for the clutch. A test was conducted to understand the performance of the clutch, in which clutch burning was observed. The clutch lining got blackened and burning smell was perceived. The friction coefficient drops sharply to a point until it cannot transmit the torque required to encounter the slope. This further worsen clutch slippage and lead to more severe temperature rise. The major reason attributed to the burning was inefficient cooling and less thickness of the flywheel & pressure plate. To address this issue transient CFD simulation is performed. Co-simulation methodology is applied to study how the solid temperature influences the air temperature at different time interval of the cycle. The temperature & convective heat transfer co-efficient data exchange happens across the domains after a fixed time interval mentioned in simulation. The heat generated in the solid components are mapped to the air and cooling effect of the fresh air from the ventilation holes are mapped on the solid. To replicate the exact test scenario varying launch energy, convective heat transfer coefficient and rpm is applied on the frictional discs as compared to the conventional steady state simulation approach where constant heat is applied on the frictional disc neglecting the cyclic variation of heating and cooling. A physical test on vehicle was conducted for hill fade condition by inserting the thermocouples in the clutch housing close to the friction lining to measure the air temperature. The measured air temperature shows good trend of correlation with the predicted temperature.
The present work is focussed on the real-world challenges of a dual mass flywheel (DMF) equipped vehicle in the Indian market. DMFs are widely used to isolate the drivetrain from the high torsional vibrations induced by the engine. While DMFs can significantly improve noise, vibration and harshness (NVH) characteristics of a vehicle, there are multiple challenges experienced in real-world operating conditions when compared with the single mass flywheel (SMF). The present work explains the challenges of using a DMF in a high power-density diesel powertrain for a multi-purpose vehicle (MPV) application in the Indian market. Measurements on the flat-road operating conditions revealed that the DMF vehicle is very sensitive for launch behaviour and requires a higher clutch modulation. Vibration measurements at the driver’s seat confirm that the SMF vehicle could be launched more comfortably at the engine idle speed of 850 RPM. However, the DMF vehicle needs a "launch assist" of an additional 100 RPM to meet the acceptable vibration levels in line with that of the SMF. Further, the gradient launch performance of the vehicle is compared for different gradients (6%, 8%, 12%, 18% and 28%) and the results confirmed that the slip time and launch energy of the DMF variant is ~50% higher than the SMF. Moreover, the DMF vehicle could be launched comfortably only up to 12% gradient whereas the SMF variant could negotiate up to 18% gradient easily. Furthermore, the higher launch energy requirement of the DMF is also responsible for the higher temperature of the clutch system by 33% as confirmed by the temperature measurements inside the clutch housing. The increased temperatures pose a major threat to the robustness and useful life of the clutch system parts. Subjective evaluations reveal that the DMF vehicle is prone to frequent engine stalling in speed-breaker and pot-hole manoeuvres. This is mainly due to the requirement of a fuel cut-off strategy which is usually implemented to avoid DMF spring resonance at low engine speeds. However, the requirement of fuel cut-off strategy is not required for the SMF vehicle and hence it could negotiate varying road conditions without any stalling concern. The present work gives a holistic insight into the mentioned challenges with the detailed objective and subjective evaluation data.
In recent years, the automotive engine strategies are forced on downsizing and down speeding to enhance fuel economy and reduce the emission. These make torque increase significantly in order to improve the vehicle performance, especially in diesel engines. At this time, the torsional damper performs the most important role in the driveline NVH of the manual transmission system. The clutch disk with torsional dampers is not easy to be applicable to the high torque of low speed RPM range. And* DMF with sufficient isolation of vibrations of driving system includes disadvantages of the expensive cost, delayed response, and engine NVH aspect deteriorated due to increase of angular acceleration of engine. This paper presents that the Centrifugal Pendulum Absorber (CPA) is applied to maximize the isolation and to compensate for the disadvantages of DMF and SMF system. Furthermore, CPA was developed for the first time in the world on SMF clutch discs in manual transmission.
ABSTRACT Thermal management systems (TMS) of armored ground vehicle designs are often incapable of sustained heat rejection during high tractive effort conditions and ambient conditions. The use of a latent heat energy storage system that utilizes Phase Change Materials (PCMs) is an effective way of storing thermal energy and offers key advantages such as high-energy storage density, high heat of fusion values, and greater stability in temperature control. Military vehicles frequently undergo high-transient thermal loads and often do not provide adequate cooling for powertrain subsystems. This work outlines an approach to temporarily store excess heat generated by the transmission during high tractive effort situations through use of a passive PCM retrofit thereby extending the operating time, reducing temperature transients, and limiting overheating. A numerical heat transfer model has been developed based around a conceptual vehicle transmission TMS. The model predicts the transmission fluid temperature response with and without a PCM retrofit. The developed model captures the physics of the phase change processes to predict the transient heat absorption and rejection processes. The model will be used to evaluate the effectiveness of proposed candidate implementations and provide input for TMS evaluations. Parametric studies of the heat transfer model have been conducted to establish desirable structural morphologies and PCM thermophysical properties. Key parameters include surface structural characteristics, conduction enhancing material, surface area, and PCM properties such as melt temperature, heat of fusion, thermal conductivity, etc. To demonstrate proof-of-concept, a passive PCM enclosure has been designed to be integrated between a transmission bell housing and torque converter. This PCM-augmented module will temporarily strategically absorb and release heat from the system at a controlled rate. This allows surging fluid temperatures to be clamped below the maximum effective fluid temperature rating thereby increasing component life, reliability, and performance. This work outlines cooling system boundary conditions, mobility/thermal loads, model details, enclosure design characteristics, potential PCM candidates, design considerations, performance data, cooling system impacts, conclusions, and potential future work.
The following schematic diagrams exemplify the SAE recommended method of illustrating automotive transmission arrangements. They were developed to standardize industry practice and facilitate a clear understanding of the functional interrelations of the gearing, clutches, hydrodynamic drive unit, and other transmission components. Two variations of diagrams are used: transmission in neutral and in gear. For illustrative purposes, some typical transmissions are shown.
The following schematic diagrams exemplify the SAE recommended method of illustrating automotive transmission arrangements. They were developed to standardize industry practice and facilitate a clear understanding of the functional interrelations of the gearing, clutches, hydrodynamic drive unit, and other transmission components. Two variations of diagrams are used: Transmission in neutral and in gear. For illustrative purposes, some typical transmissions are shown.
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