Browse Topic: Clutches
High-speed wet clutches may experience dynamic instability between the friction plates, leading to rattling vibrations and a significant increase in drag torque. This study employs a homogeneous flow model to characterize the gas-liquid two-phase flow within a high-speed clutch. It establishes a dynamic model for the angular oscillation of friction plates. Finite-element numerical simulations and stability analyses were conducted. The results indicate that as the clutch speed difference increases, the density and viscosity of the two-phase flow decrease rapidly, leading to a sharp reduction in fluid stiffness and damping. Consequently, the friction plates become more susceptible to angular oscillation. The stability of angular oscillation is determined by two key parameters: dimensionless comprehensive stiffness and critical frequency ratio. Higher dimensionless comprehensive stiffness and a lower critical frequency ratio enhance oscillation stability. Numerical evaluations of various groove types reveal that as rotational speed and friction plate clearance increase, the fluid stiffness coefficient, damping coefficient, dimensionless comprehensive stiffness, and critical moment of inertia all decrease, thereby reducing angular oscillation stability. Among the tested groove geometries, enclosed grooves and spiral grooves exhibit superior stability due to their strong hydrodynamic effects, yielding the highest dimensionless comprehensive stiffness. The critical frequency ratio for the self-excited angular oscillation of friction plates is approximately 0.5, termed the half-frequency oscillation characteristic. Experimental data validate the proposed angular oscillation model and its frequency response, providing a theoretical foundation for performance prediction and stability optimization in high-speed clutch design.
High-temperature hydraulic control in a Formula 1 drivetrain requires dimensional stability, controlled sealing force, and resistance to wear under sustained pressure cycling. Inside the limited-slip differential, the sealing architecture plays a defined mechanical role in maintaining consistent torque management under race conditions. In Formula 1, drivetrain reliability and performance are closely linked. The limited-slip differential (LSD) governs torque distribution between the rear wheels, allowing controlled transfer of power to the wheel with greater available grip. By limiting speed difference across the rear axle, the differential contributes directly to traction and cornering behavior, particularly where grip levels vary across the vehicle. At the center of this assembly is a hydraulic actuator that clamps a friction clutch inside the differential. The actuator modulates clutch engagement to redirect torque as grip levels change through corner entry, mid-corner load transfer, and acceleration on exit. Its performance depends on precise hydraulic control, which in turn depends on sealing integrity. Within this system, seal integrity is paramount, as significant leakage could cause a catastrophic loss of system function and force the team to retire the car.
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.
Model Based Design (MBD) uses mathematical modelling to create, test and refine systems in simulated environment, primarily applied in control system development. This paper discusses an approach to control gear shifting using shift logic on vehicle level for twin clutch transmission using prototype controller. Twin clutch transmission is a concept with two clutches, one at input end of the transmission called primary clutch and the other at output end of the transmission called secondary clutch. This concept is proposed to counter the challenges with conventional transmission which include increased gear shift time and effort in lower gears, potential rollback of vehicle in uphill condition and chance of missed shifts. The advantages of this concept include reduced gear shift effort and improved synchronizer life with potential for reducing the size of the synchro pack. This paper proposes a methodology to develop shift logic, integrate hardware with software, flashing and calibration on vehicle using prototype controller. The shift logic is implemented using state machines in ASCET. The state machine uses vehicle speed, accelerator pedal position, gear shifter input, shift maps and current gear to determine most optimal gear shift in real-time. This control logic is then converted into c-code and integrated with hardware using INTECRIO, which is a build environment where inputs and outputs are mapped accordingly for shift actuation. In the next step, .a2l and .cod files are generated, which are flashed onto rapid prototyping hardware from ETAS using INCA. The same is used to actuate shift solenoids of transmission to change the gear. Use of rapid prototyping hardware has significantly reduced the number of iterations required for integrating software with ECU from specific supplier, thus reducing overall development time. Final vehicle level calibration is done using INCA, followed by validation process to ensure optimal performance.
This study presents a simulation-based approach to estimate the dog clutch engagement probability maps under different vehicle operating conditions. The developed probability function incorporates multiple critical parameters including initial speed differential between engaging components, application of countershaft brake, number of tooth in dog clutch, friction coefficients at tooth interfaces, applied actuation force, dog tooth geometry, and component inertia. Using MATLAB and Simulink, comprehensive simulation models were developed to analyze engagement dynamics and produce detailed probability maps at different vehicle speeds. The present work effectively outlines optimal operational zones for successful engagement while identifying critical regions prone to tooth clash and engagement failure. The effect of tooth geometry on engagement probability has been investigated to study its effect on the optimal mismatch speeds. The resulting engagement maps serve as valuable diagnostic tools for identifying potential system limitations, such as inadequate actuation forces or excessive speed differentials during shifting operations. Additionally, these simulations provide a cost-effective method for validating design innovations before physical prototyping, substantially reducing development time and resource expenditure.
Puddling is a crucial process in rice cultivation, involving the preparation of the soil in a flooded field to create a soft, muddy seedbed. There are two classifications for puddling: full cage and half cage. Full cage puddling involves replacing the rear wheels of the tractor with steel paddle wheels, which are used to till the rice paddies directly without any additional implement. In the half cage puddling, the rear wheels remain on the tractor, and a smaller cage or paddle wheel is attached to the outside. Considering the field size, the operator often releases the clutch very quickly after a speed or direction change. This generates torque spikes, which are harmful to Transmission Gears and Clutches. This can lead to gear teeth bending fatigue failure due to repeated higher bending stresses. In this paper, a study related to how to reduce overall product development time by simulating bending fatigue failure of gear in lab environment is presented. A systematic approach is used to understand the field application, data acquisition, Data analysis, new test stand development and replication of failure mode in lab environment. This approach resulted in significant time savings. Multiple design iterations with minimal variation can be executed. This eliminates dependency on field, environmental conditions, and different variabilities. Finally, it supports timely decision-making based on the outcomes.
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.
This paper describes an optimal control method utilizing a Linear Quadratic Regulator (LQR) to control the torque during the gear shift on a multispeed electrified transmission to optimize for clutch actuator durability and shift performance. The dynamic state-space model of the system has been obtained using System-Identification. An LQR controller is formulated to minimize driveline oscillations and transmission-input-torque using the model by manipulating the electrical torque applied by the traction motor at the transmission input. The LQR controller is implemented in a simulation framework wherein the impact of vehicle parameters on the shift quality metrics is also assessed. Subjective and objective requirements are considered in the tuning process for the LQR controller. The LQR controller is utilized to generate profiled torque table calibrations. These calibrations are then deployed onto a production ready Transmission Control Unit and experimentally validated on a Class-8 Heavy Duty vehicle retrofitted with an electrified multispeed transmission. Experimental validation is performed at multiple Gross-Combination-Vehicle Weight (GCVW) configurations. Significant reduction of clutch actuation effort, shift time while maintaining adherence to subjective and objective shift quality metrics has been demonstrated compared to traditional S-Shaped torque profiling.
In cost- effective P2 hybrid vehicles with low voltage electric machines connected to the engine, an interesting control problem arises during the transition to a locked driveline state. This occurs when the engine connects to the wheels via a separation clutch. The two primary torque sources, the engine and the clutch, are traditionally imperfect estimators of applied and transferred torques. The Hybrid Supervisor’s feedforward constraints model relies on these imperfect inputs to determine torque and acceleration limits for the engine’s desired acceleration profiles and to specify engine feedforward commands, aiming for synchronization speed. Due to the inaccuracies in the torque estimates of the engine and clutch, the Hybrid Supervisor is susceptible to control windup, increased jerk to the driveline during synchronization, and inaccurate computation of its target acceleration profile, speed, and torque targets for the engine to achieve synchronization speed. This paper presents a disturbance estimation strategy to minimize control windup in the development of the Hybrid Supervisor’s speed trajectory, engine feedforward torque commands, and acceleration commands for transitioning a low voltage P2 Hybrid from EV Mode to Hybrid Mode. Simulation and vehicle results indicating the profiled engine speed remains within +- 5 to 8% of its target with minimal overshoot till we get to synch speed, are provided to demonstrate the strategy’s effectiveness.
This paper explores the application of a modeled torque converter in the real-time control of a hybrid electric powertrain. The study aims to determine the optimal gear selection and engine speed target required to meet driver demands. It also delves into the concept of torque converter input inertia compensation, particularly during open, open-to-close, and close-to-open states. The primary objective is to achieve the intended driver torque while minimizing torque sag and bumps during these transitions. This approach ensures improved powertrain response and maintains system integrity within the operational limits of the battery, motors, and engine.
Clutch wear is a significant factor affecting vehicle performance and maintenance costs, and understanding its dynamics is crucial for original equipment manufacturers (OEMs) to enhance product reliability and customer satisfaction. It is important to predict clutch wear to enable customers to understand the condition of their clutch and the remaining clutch life, to avoid sudden vehicle breakdowns. This paper explains the approach of measuring the clutch wear profile on an actual vehicle and simulating the same conditions on a powertrain test bench, with the establishment of a correlation in clutch wear profiles.
Cooling system for an IC engine, consisting of the Water pump (WP), Radiator and Fan, plays an important role in maintaining thermal efficiency of the engine and protects the engine from overheating. Based on the vehicle application requirement, Fan will be mounted directly either on Crankshaft or WP pulley. But wherever increase in Fan speed ratio are in demand, it is preferred to mount the Fan on WP pulley. So it important to understand the WP housing structural strength with respect to vibration loads contributed from Radiator Fan assembly. This paper presents investigation of Failure of WP Housing during engine validation at engine test bed with Electronic Viscous Fan, based on the different operating conditions of the engine and fan as per the validation cycle. While the accessories are loading and the corresponding stresses are high when the fan is engaged. But in the current case, the failure of WP housing happened only during Fan clutch disengaged condition. Experimental Frequency Response Function (FRF) were carried out to identify the mode shapes and resonant frequencies. Vibration on WP housing were compared with Fan engaged and disengaged condition to identify the critical frequency ranges that minimize vibrational impacts on the WP housing. The results indicate a significant correlation between Fan Blade Pass Frequency (FBPF) and vibrational amplitude on WP housing. By optimizing FBPF, it is successfully mitigated high vibration levels, thereby enhancing the structural integrity and operational reliability of the WP housing. In addition, the results of crack initiation points, strain gauge measurements, structural and modal analyses are examined to enhance the WP housing strength.
The definitions and illustrations in this SAE Recommended Practice are intended to establish common nomenclature and terminology for automotive transmission one-way clutches.
Wysong USA has been manufacturing industrial press brakes, hydraulic shears, and mechanical shears for sheet metal and plastics for nearly 120 years. Like many companies, their motto was “if it ain’t broke, don’t fix it,” so their product had remained essentially the same. But during a customer visit that motto clashed with another company saying, “the customer is always right.” This customer had replaced the dry clutch brake for an oil shear clutch brake that was more accurate. “The customer is always right” won, so Wysong updated their product line and increased accuracy while reducing costs, making it a win all around.
In torque converters, a lockup clutch is used for direct torque transfer from the engine to the gearbox. Nowadays, earlier lockup engagement is necessary to reduce fuel consumption. It introduces noise and vibration issues in the transmission that are solved by clutch slipping. However, the clutch experiences much heat because of earlier engagement, which needs to be adequately dissipated by ATF oil. To overcome this issue, multi-plate clutches are commonly used for efficient torque transfer and clutch slipping. On the other side, packaging space for torque converters is reducing at the vehicle level, especially in hybrid vehicles, which reduces the efficient cooling of clutches. So, accurate modeling of clutch slipping is necessary to improve the clutch performance and durability of the product. Clutch slipping is a transient phenomenon that involves conjugate heat transfer and rotational flow modeling. There are different ways to model clutch slipping in CFD simulations. One of the modeling methods is applying the power loss as heat flux in clutch facings. However, heat flux is a vector quantity, and its direction is defined. That means the model introduces the approximation in heat transfer direction and reduces calculation accuracy. In this paper, power loss is applied as an energy source, which is a scalar quantity, and modeling methodology is explained. With this methodology, CFD calculation results are correlated well with test measurement, allowing to match the clutch design with the challenging packaging constraints.
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