Clutch torque point learning method and clutch control method

Abstract

The present invention aims to enable the accurate learning of a true torque point in a wet friction clutch ( ), prevent the clutch connection shock by absorbing the response delay upon an ordinary clutch connection control, and to successfully combine the time lag and shock. In the present invention, the value (D) itself of the duty ratio of the duty pulse output from the ECU ( ) is learned as the torque point (Dm). In a power transmission device of a vehicle having a fluid coupling ( ) and the wet friction clutch ( )provided in series between the engine (E) and transmission (T/M), the value (Dm) of the duty ratio at the time when the clutch input side revolution (Nt) decreases to a value lower than the engine revolution (Ne) by a prescribed revolution (Nm) during the process of gradually connecting the clutch is learned as the torque point. Preferably, learning is conducted after the elapse of a prescribed waiting time (&Dgr;t ). During an ordinary clutch connection control, a prescribed start duty (Dst ) for connecting the clutch ( ) broadly up to a point close to the torque point (Dtb) is initially output from the ECU ( ), and a gradual duty (Dk) is output after retaining such start duty (Dst ) for a prescribed time (&Dgr;t ). Preferably, a first gradual duty (Dk ) for gradually connecting the clutch quickly is output, and a second gradual duty (Dk ) for gradually connecting the clutch slowly is output thereafter.