Lock-up clutch control device for a torque converter

Abstract

A supplying port connecting to a supplying-side hydraulic pressure is arranged in a lock-up control valve. When the lock-up relay valve is switched ON (right half position), a supplying hyraulic pressure is supplied to a second oil chamber through an oil passage, led to a first oil chamber through an orifice and drained to a draining hydraulic oil passage through the oil passage. At this state in the lock-up control valve an inner pressure of the first oil chamber operates on a chamber through the oil passage, while an inner pressure of the second oil chamber operates on a chamber through the oil passage, and a controlling pressure from a linear solenoid valve operates on the controlling chamber. When the controlling pressure from the controlling chamber decreases by a deceleration of a vehicle speed, a valve closes a draining oil port and a drain port and increases an inner pressure of the first oil chamber. At this state when the hydraulic pressure of the second oil chamber increases by the contraction of the outer configuration of a torque convertor by a decrease of the centrifugal force, the draining oil port is connected to the supplying port and the hydraulic pressure is supplied to the first oil chamber to increase the hydraulic pressure of the chamber.