Patent ID: 6780140
Filing Date: 2004-08-24
Classification: F16H,Y10T

Abstract:
A lockup control system of an automatic transmission with a torque converter having a lockup clutch, comprising:an operating condition detector that detects an operating condition on an engine and an automotive vehicle, the operating condition including at least a throttle opening and a vehicle speed; a controller that controls a transmission ratio and an engaging state of the lockup clutch, responsively to an operating point determined based on the throttle opening and the vehicle speed; the controller pre-storing a predetermined lockup control map including at least a predetermined coast slip lockup area, within which the lockup control system executes a slip lockup control mode under a vehicle's coasting condition that torque is transferred from drive wheels to the engine, so that a speed difference between input and output speeds of the torque converter is brought closer to a predetermined value; the controller determining whether (i) a first transition from a vehicle's driving condition under which torque is transferred from the engine to the drive wheels to the predetermined coast slip lockup area occurs in a release mode of the lockup clutch or (ii) a second transition from the vehicle's coasting condition to the predetermined coast slip lockup area occurs in the release mode of the lockup clutch; and the controller controlling the lockup clutch depending on whether the first transition occurs or the second transition occurs, so that the lockup clutch is conditioned in the slip lockup control mode when the first transition occurs, and that the lockup clutch is conditioned in the release mode when the second transition occurs.