Aisin Aw Co., Ltd.

Takahiro Inoue

Masahiro Hayabuchi

Masaaki Nishida

Kenichi Tsuchida

Akitomo Suzuki

Takayuki Hisano

A hydraulic control apparatus for an automatic transmission including a hydraulic pressure source, hydraulic paths, hydraulic servos for operating friction elements which are coupled with the hydraulic source an the hydraulic paths, a control device arranged on the hydraulic paths for operating engagement release through supply/removal of hydraulic pressure to the hydraulic servos and valves which are arranged on the hydraulic path for cutting off hydraulic pressure from the hydraulic pressure source to the hydraulic servo with hydraulic pressure in the downstream side of the control device as signal pressure.

Hydraulic control apparatus for an automatic transmission

To make it possible to maintain speeds during failures in an automatic transmission that does not have exclusive friction elements corresponding to the attainment of each speed. The hydraulic control apparatus of an automatic transmission, provided with control means for supplying regulated pressure to each of the hydraulic servos that are first through fourth friction elements to which hydraulic pressure is supplied from the oil path L , and provided with switching valves ( )-( ) for cutting off the supply of hydraulic pressure to friction elements other than the friction elements that engage in each speed, on the upstream side of the supply paths L , L , L , L and L . Each switching valve is switched by hydraulic pressure (C -C , B pressures) regulated by the control means that achieve regulated pressure operating conditions during failures, and selective application of signal pressure (Sol, SolB, SoIC pressures) output by the control means as operating means. In a speed that has been attained, the supply path to friction elements that are not to be engaged is cut off. Through this, even during failures the regulated pressure action of the control means corresponding to friction elements that are not to be engaged is ineffective, so the speed that has been attained is fixed.

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Anjo, Japan

Takahiro Inoue