Browse Topic: Wet disc clutches
As a newly designed hybrid transmission, DHT (Dedicated Hybrid Transmission) owns the advantages of compact structure, multi-modes and excellent comprehensive performance. Compared with the traditional add-on hybrid transmission with one single motor, DHT uses one independent generator for engine starting and speed adjusting which can be largely improve the driving performance in the mode changing process. Based on the series-parallel DHT with wet clutch for power coupling, this paper firstly analyses the power coupling clutch device functionalities from the power flow viewpoint under normal and limp home condition. And for the changing process from series to parallel mode, a clutch coordination control strategy is designed by combining generator fast speed adjusting with clutch accurately pressure controlling to fulfill the fast driver intension response and clutch protection. And target torques of power sources are designed by a model-based method and two PID closed-loop algorithms
Advanced features in automotive systems often necessitate the management of complex interactions between subsystems. Existing control strategies are designed for certain levels of robustness, however their performance can unexpectedly deteriorate in the presence of significant uncertainties, resulting in undesirable system behaviors. This limitation is further amplified in systems with complex nonlinear dynamics. Hydro-mechanical clutch actuators are among those systems whose behaviors are highly sensitive to variations in subsystem characteristics and operating environments. In a P2 hybrid propulsion system, a wet clutch is utilized for cranking the engine during an EV-HEV mode switching event. It is critical that the hydro-mechanical clutch actuator is stroked as quickly and as consistently as possible despite the existence of uncertainties. Thus, the quantification of uncertainties on clutch actuator behaviors is important for enabling smooth EV-HEV transitions. In this paper, a
Accurate determination of driveshaft torque is desired for robust control, calibration, and diagnosis of propulsion system behaviors. The real-time knowledge of driveshaft torque is also valuable for vehicle motion controls. However, online identification of driveshaft torque is difficult during transient drive conditions because of its coupling with vehicle mass, road grade, and drive resistance as well as the presence of numerous noise factors. A physical torque sensor such as a strain-gauge or magneto-elastic type is considered impractical for volume production vehicles because of packaging requirements, unit cost, and manufacturing investment. This paper describes a novel online method, referred to as Virtual Torque Sensor (VTS), for estimating driveshaft torque based on Machine-Learning (ML) approach. VTS maps a signal from Inertial Measurement Unit (IMU) and vehicle speed to driveshaft torque. The unique advantage is that VTS does not explicitly rely on the first principles
Multi-speed transmissions can improve power and economy performance of battery electric vehicles (BEVs), thus becoming an inevitable trend in automotive industry. A two-speed dedicated electric transmission (2DET), which can realize switching of two gear ratios through two wet clutches, is explained firstly. Secondly, 2DET is developed and a prototype is assembled in a BEV of Beijing Electric Vehicle Co. Ltd. (BJEV). Thirdly, the differences of new European driving cycle (NEDC) and China light duty vehicle test cycle passenger (CLTC-P) are compared. Fourthly, the parameters of battery cell are tested and a simulation model of the whole vehicle with 2DET is built. Finally, vehicle economy performance under NEDC and CLTC-P is simulated, and the results are validated in bench tests. Comparison shows that the economy simulation results match the test results, and the vehicle economy under CLTC-P is better than NEDC, with an increase of 1.16%.
Hybrid powertrains have become many original equipment manufacturers (OEMs)’ choice to meet ever-stringent fuel consumption regulations. A P2 powertrain technology is widely adopted by automotive OEMs to reuse existing engines and transmission production capacity and reduce investment. A standalone P2 module of an integrated e-motor with an engine decoupling wet clutch is developed and applied in a transverse-mounted P2 hybrid powertrain system. A P2 hybrid powertrain controller has been developed to test and validate the P2 module and control strategy. This P2 powertrain system with a decoupling clutch capable of slipping control enables the vehicle launch or low-speed drive in engine direct-drive mode. A control algorithm that controls the clutch slipping to transmit the desired cranking torque from P2 e-motor to fast-start the engine during the drive mode change from Electric drive to Parallel drive has been developed and validated. The proposed engine slip-start with clutch
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
This paper focuses on modeling of the heavy-duty vehicle drivetrain with automatic transmission by using dual clutch scheme. The planetary gear set in the automatic transmission is complicated structure and difficult to understand. The advantage of the dual clutch scheme is that it can be used to represent the complex planetary gear set intuitively, which is a great help to understand the gear shifting process. It is also suitable for being used in the controller due to its low order. Some conditions are required to convert the planetary gear set to the dual clutch model. The heavy-duty vehicle driveline can be converted to the dual clutch model due to its heavy engine and vehicle inertia. This paper also proposes system parameter estimation methods to represent the driveline model. The main parameters are lumped inertia, lumped gear efficiency, output shaft compliance and friction coefficient of clutches. First, a method for estimating lumped inertia and lumped gear efficiency is
This study aims to solve the problem of impact in a parallel hybrid electric system based on the continuously variable transmission (CVT) during switching from pure electric mode to engine-driven, power-generating mode. Taking into account the torque response characteristics of the engine and motor and the dynamic characteristics of the wet clutch hydraulic control system, the mode switching process is divided into six stages, namely, pure electric mode, wet-clutch free travel, engine start-up, engine speed synchronization, clutch combination, and engine intervention drive. A coordination control strategy is developed based on the model predictive control algorithm to ensure smooth mode switching. The effectiveness of the control algorithm is verified using Matlab/Simulink and the AMESim co-simulation platform. Results show that with the mode switching coordination control strategy, the components of the system work harmoniously. The maximum impact is reduced by 52.0% at the speed
The dual clutch transmission is one of the possible choices for electric vehicle drivelines. The basic principle and control mode of shifting of wet dual clutch transmission are introduced, and the dynamic process of shifting of wet double clutch transmission is studied. Combined with the dynamic model of the wet clutch engagement process, the difference between the dynamic characteristics of the dual clutch transmission modeling using the Coulomb friction model and the dual-clutch transmission model using the average flow model and the micro-convex contact theory is analyzed. The shift control strategy of the dual clutch transmission proposes a correction method to improve the shifting smoothness. Studies have shown that the torque response of the wet clutch has significant hysteresis, and the improved control algorithm can significantly improve the shifting smoothness of the wet dual clutch transmission. Based on the dynamic model of the wet clutch, the torque interruption of the
The wet clutch system (WCS) is a complex combination of friction plates, separator plates and fluid (lubricant). The basic function of the WCS is to transfer torque under various operating conditions such as slipping, shifting, start/launch and/or torque converter clutch (TCC) operation. Under these conditions the slope of the coefficient of friction (ÎĽ or COF) versus slip speed (ÎĽ-v) curve must be positive to prevent shudder of the WCS, a highly undesirable condition in the lubricated friction system. An extended durability duty cycle test procedure is required to evaluate the WCS during which the ÎĽ-v curve is monitored for a negative slope, a condition indicating the potential for shudder. The friction plates, separator plates, and lubricant must be tested together and remain together during the test to be properly evaluated as a WCS. This paper describes a new test procedure which builds on the basics of the SAE J2964 - Low Speed Continuous Slip ÎĽPVT Procedure [1] by adding a
Engine start while driving is one of the most typical and frequent work conditions for hybrid vehicles. Engine start has very significant impact on the driving comfort. Engine start, especially a dynamical engine start, have high control requirements regarding control time, torque output and riding comfort. In some hybrid transmissions such as P2, engine is cranked and synchronized through wet clutch slipping. Because clutch pressure control has time-varying delay and estimation precision of engine torque by ECU (Engine Control Unit) is poor, conventional PID controller is unable to meet the high requirements of control quality. A new control algorithm is proposed in this paper to cope with all these challenges. The new control algorithm is based on LADRC (Linear Active Disturbance Rejection Controller) and is improved through combination with Smith predictor and Adaline network. LADRC is adopted to reduce negative effects of poor precision of engine torque. Smith predictor is
A wet clutch model is required in automotive propulsion system simulations for enabling robust design and control development. It commonly assumes Coulomb friction for simplicity, even though it does not represent the physics of hydrodynamic torque transfer. In practice, the Coulomb friction coefficient is treated as a tuning parameter in simulations to match vehicle data for targeted conditions. The simulations tend to deviate from actual behaviors for different drive conditions unless the friction coefficient is adjusted repeatedly. Alternatively, a complex hydrodynamic model, coupled with a surface contact model, is utilized to enhance the fidelity of system simulations for broader conditions. The theory of elastic asperity deformation is conventionally employed to model clutch surface contact. However, recent examination of friction material shows that the elastic modulus of surface fibers significantly exceeds the contact load, implying no deformation of fibers. This article
In this SAE Recommended Practice, attention will be given to passenger cars and light trucks (through Class III).
In this SAE Recommended Practice, attention will be given to passenger cars and light trucks (through Class III).
The objective of this glossary is to establish uniform definitions of parts and terminology for engine cooling systems.
This SAE Recommended Practice defines the principal terms and equations pertaining to automotive automatic transmission clutch plate, band, or other wet-friction systems. The terms apply directly to friction-system testing as is typically conducted on inertia-stop test equipment. Some terms can be directly applied to the analysis of friction in the transmission or brake assembly and other friction-test equipment. The glossary presents terms used to describe the set-up, testing, and results of tests as shown in Figure 1, which were taken on a clutch SAE No. 2 machine. The glossary is intended to provide a collection of definitions in the hope of eliminating confusion in terminology and a common set of terms for improving the state-of-the-art of friction-system development and their application to passenger cars and trucks. This document focuses on the terminology of friction-system testing. References for this type of testing are shown in Section 2.
The objective of this glossary is to establish uniform definitions of parts and terminology for engine cooling systems.
This SAE Recommended Practice is prepared as a guideline to improve and maintain the quality of remanufactured automotive products. Installation of remanufactured or rebuilt products is often an economical way to repair a vehicle even though they may not fully be equivalent to original equipment parts. Before processing any part, a remanufacturer should determine if the original design and present condition of the core are suitable for remanufacturing, so as to provide durable operation of the part as well as acceptable performance when installed in a vehicle. The remanufacturer should also carefully consider the safety aspects of the product and any recommendations of the original manufacturer related to remanufacturing or rebuilding their product.
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