PURPOSE: To eliminate pressure relief of servo oil pressure from a friction engaging element in shifting up an automatic transmission and to prevent engine blow-up due to under lap in speed change.
CONSTITUTION: A hydraulic control device has a B-3 control valve 24 juxtaposed with a creating oil pressure for a 2-3 shift valve 21 and a brake B-3, and a B-2 orifice control valve 25 juxtaposed with a connecting oil passage for the 2-3 shift valve 21 and a 6 brake B-2 and also provided in a pressure governing drain oil passage L7 for the B-3 control valve 24. In 2-3 shift, firstly, the B-3 control valve 24 is switched, forming a return intercommunicating state via the 2-3 shift valve 21, and a 2-3 timing valve 23. Oil pressure exhaust to the B-2 orifice control valve 25 for servo oil pressure exhausted from the B-3 brake is blocked. The B-2 orifice control valve 25 is then switched, preventing drain due to intercommunication at the switching transition of both the valves 24, 25.
FUKATSU AKIRA
YAMAMOTO YOSHIHISA
SUZUKI AKITOMO
TABATA ATSUSHI
HOJO YASUO
KAIGAWA MASATO
OBA HIDEHIRO
KIMURA HIROMICHI
HAMASHIMA TETSUO
TOYOTA MOTOR CORP
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