Automated manual transmissions based on dry clutch are wide spreading in modern automotive transmissions because of the possible improvements in performance and comfort with respect to manual transmissions. A key issue for an efficient control of electro-actuated dry clutch transmissions is the knowledge of the clutch torque transmitted during the engagement. The torque transmitted by the clutch can be directly measured by means of setups which are difficult to be implemented in commercial products. Therefore it is fundamental to define an accurate torque transmissibility model to be exploited for the estimation of the clutch torque. A possible estimator is based on the inversion of the driveline dynamic model like showed by Gliemo et al. (2006) and by Amari et al. (2009), but the robustness of this type of estimation drastically depends on the availability of the system parameters and on clutch disk acceleration and engine torque measurements. As proposed by Vasca et al. (2008), a possible alternative consists in using an analytical model describing the friction phenomena and providing the torque transmitted by the clutch starting from the throwout bearing position. Unfortunately, the nominal characteristic (torque vs position) is influenced by several variables. Some of them, such as friction pads wear and diaphragm spring fatigue, have a “long term” effect, like showed by Mauro et al. (2002). Other variables have a direct influence also on each engagement maneuver. These variables, such as slipping speed, pressure, slipping acceleration and temperature affect the friction coefficient, as tested by Senatore et al. (2011), Feng et al. (2010) and by LuK (1996), and the normal force (D’Agostino et al., 2012) (Cappetti et al., 2012). The difficulties in representing the contributions of the different variables in the clutch torque transmissibility characteristic lead to the definition of corresponding lumped models, so as in the works of Myklebust et al. (2012;2013). In this paper a temperature dependent torque transmissibility model for dry clutch transmissions is proposed. The model estimates the clutch torque by considering separately the influence of the slipping speed and temperature on the friction coefficient and the influence of the temperature on the normal force determined by the flat spring. In order to estimate the temperatures of interest, two thermal models of a dry dual clutch transmission with a central disk are proposed. The temperatures estimated by means of the proposed thermal models are then used for the analysis of open loop and closed loop operating conditions in a realistic dry dual clutch transmission.

THERMAL MODELS FOR FRICTIONAL TORQUE CHARACTERISTIC IN DRY DUAL CLUTCH TRANSMISSIONS

SENATORE, ADOLFO;
2014

Abstract

Automated manual transmissions based on dry clutch are wide spreading in modern automotive transmissions because of the possible improvements in performance and comfort with respect to manual transmissions. A key issue for an efficient control of electro-actuated dry clutch transmissions is the knowledge of the clutch torque transmitted during the engagement. The torque transmitted by the clutch can be directly measured by means of setups which are difficult to be implemented in commercial products. Therefore it is fundamental to define an accurate torque transmissibility model to be exploited for the estimation of the clutch torque. A possible estimator is based on the inversion of the driveline dynamic model like showed by Gliemo et al. (2006) and by Amari et al. (2009), but the robustness of this type of estimation drastically depends on the availability of the system parameters and on clutch disk acceleration and engine torque measurements. As proposed by Vasca et al. (2008), a possible alternative consists in using an analytical model describing the friction phenomena and providing the torque transmitted by the clutch starting from the throwout bearing position. Unfortunately, the nominal characteristic (torque vs position) is influenced by several variables. Some of them, such as friction pads wear and diaphragm spring fatigue, have a “long term” effect, like showed by Mauro et al. (2002). Other variables have a direct influence also on each engagement maneuver. These variables, such as slipping speed, pressure, slipping acceleration and temperature affect the friction coefficient, as tested by Senatore et al. (2011), Feng et al. (2010) and by LuK (1996), and the normal force (D’Agostino et al., 2012) (Cappetti et al., 2012). The difficulties in representing the contributions of the different variables in the clutch torque transmissibility characteristic lead to the definition of corresponding lumped models, so as in the works of Myklebust et al. (2012;2013). In this paper a temperature dependent torque transmissibility model for dry clutch transmissions is proposed. The model estimates the clutch torque by considering separately the influence of the slipping speed and temperature on the friction coefficient and the influence of the temperature on the normal force determined by the flat spring. In order to estimate the temperatures of interest, two thermal models of a dry dual clutch transmission with a central disk are proposed. The temperatures estimated by means of the proposed thermal models are then used for the analysis of open loop and closed loop operating conditions in a realistic dry dual clutch transmission.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/4504262
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