US 5,848,370 AGranted

Hydraulic pressure control apparatus for automatic transmission

AssigneeNippondenso Co., Ltd.

InventorsTetsuji Kozaki, Masami Fujitsuna

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Abstract

In order to precisely determines the time to start feedback control of line pressure during a shifting period, a shift control computer calculates an effective gear ratio Ge=Nt/Nos at the time of an shift instruction based on input shaft rotational speed Nt and detected vehicle speed Nos and then calculates a parameter F=Nos.times.Ge-Nt indicating the point to start feedback control based on the input shaft rotational speed Nt, the detected vehicle speed Nos and the effective gear ratio Ge. By comparing the calculated parameter F with a predetermined value .DELTA.Nt, hydraulic pressure at the start of shift operation is maintained if F<.DELTA.Nt and, if F.gtoreq..DELTA.Nt, feedback control is performed to cause the input shaft rotational speed Nt to vary in a predetermined manner.

Claims9

Dependent claims

A shifting period hydraulic pressure control apparatus for an automatic transmission which selectively operates friction elements of a speed change gear mechanism for gear shift operation by regulating hydraulic line pressure onto the friction elements, the apparatus comprising:

an input shaft rotational speed detector which detects rotational speed of an input shaft of the speed change gear mechanism;
an output shaft rotational speed detector which detects rotational speed of an output shaft of the speed change gear mechanism;
a shift start instructing unit which provides an instruction to start shift operation;
an effective gear ratio calculating unit which calculates an effective gear ratio at a time of providing the shift start instruction based on a ratio between the detected input shaft rotational speed and the detected output shaft rotational speed;
and
a feedback control starting point determining unit which determines a point to start feedback control for a shifting period based on the calculated effective gear ratio.

3 more elements

Dependencies are inferred from the claim text.