Hydraulic control device for lockup clutch

Abstract

A hydraulic control device for a lockup clutch prevents stagnation and accumulation of air bubbles in a torque converter when a vehicle is at a stop at low oil temperature, preventing impairment of vehicle drive performance caused by insufficient transmission torque at the time of start of the vehicle. It occurs sometimes that air-mixed hydraulic oil is supplied into a torque converter (32) from a second oil path (132) when a vehicle is at a stop, with a transmission set to a drive range such as a D range, at a low oil temperature in a time, for example, immediately after an engine (30) is started. In such a case, when a lockup clutch is disengaged, in which a second line hydraulic pressure (PL2) is supplied from the second oil path (132) to the lockup clutch (28), a third oil path (134) is interrupted (closed) to prohibit discharge of the hydraulic oil. As a result, despite large pipe path resistance due to high viscosity, the hydraulic oil in the torque converter (32) is reliably discharged from a first oil path (130) to an oil cooler (142) via a cooler oil path (140). Thus, air bubbles in the torque converter (32) are reduced with the discharge of the hydraulic oil.

Description

technical field [0001] The present invention relates to an oil pressure control device for a lock-up clutch, in particular to a technique for improving the driving performance of a vehicle which is damaged by air mixing to reduce the transmission torque of a fluid transmission device at low oil temperature. Background technique [0002] One type of hydraulic control device for a lock-up clutch includes a device including a lock-up clutch, a first oil passage, a second oil passage, and a third oil passage. Among them, the lock-up clutch is provided in a fluid transmission device such as a torque converter or a fluid coupling, and is engaged and disengaged by hydraulic pressure. The first oil passage communicates with an engagement-side oil chamber of the lock-up clutch, and supplies engagement oil pressure to the engagement-side oil chamber when the lock-up clutch is engaged. The second oil passage communicates with a disengagement-side oil chamber of the lock-up clutch, and...

AI Technical Summary

Problems solved by technology

[0010] The present invention is made against the background of the above-mentioned situation, and its purpose is to improve the driving performance of the vehicle due to the fact that the air bubbles remain and accumulate in the fluid transmission device when the vehicle is stopped at low oil temperature, and sufficient transmission torque cannot be obtained when starting. Damaged situation

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