초록 ▼

A fluid pressure control system for controlling an automatic transmission which includes a gear transmission mechanism and several fluid pressure actuated friction engaging mechanisms, selective engagement of which provides various speed stages from the gear transmission mechanism. A line pressure v

A fluid pressure control system for controlling an automatic transmission which includes a gear transmission mechanism and several fluid pressure actuated friction engaging mechanisms, selective engagement of which provides various speed stages from the gear transmission mechanism. A line pressure valve produces a line pressure which increases from a base pressure by an amount proportional to engine load. A throttle pressure valve produces a throttle pressure which is proportional to engine load. A shift valve selectively switches supply of an actuating pressure to one of the friction engaging mechanisms via a passage, according to the operational condition of the vehicle. The actuating pressure is supplied by a fluid pressure control system which receives supply of line pressure and which outputs a pressure which, when engine load is medium, is approximately equal to line pressure, but which, when engine load is small or is large, is substantially lower than line pressure. Thereby, the performance of the actuating pressure for cushioning over abrupt engagement of the friction engaging mechanism is more suitably tailored to the torque characteristics of the engine of the vehicle, and gear shift shock is accordingly reduced.

대표청구항 ▼

For an automatic transmission for an automotive vehicle, comprising a gear transmission mechanism and a plurality of fluid pressure actuated friction engaging mechanisms, a plurality of speed stages being provided by said gear transmission mechanism according to selective actuation of said friction

For an automatic transmission for an automotive vehicle, comprising a gear transmission mechanism and a plurality of fluid pressure actuated friction engaging mechanisms, a plurality of speed stages being provided by said gear transmission mechanism according to selective actuation of said friction engaging mechanisms; a fluid pressure control system, comprising: (a) a line fluid pressure control valve which produces a line fluid pressure which increases from a predetermined base pressure approximately proportionally to a quantity representative of engine load; (b) a throttle fluid pressure control valve which produces a throttle fluid pressure which is approximately proportional to said quantity representative of engine load; (c) a means for controlling fluid pressure, which receives supply of said line pressure and said throttle pressure and outputs an output fluid pressure, and which comprises; a first fluid pressure modulation valve, which is supplied with the throttle pressure, and which outputs a throttle modulator fluid pressure which is the same as throttle pressure when the throttle pressure is below a first predetermined level, and is equal to said first predetermined level when the throttle pressure is greater than said first predetermined level; and a second fluid pressure modulation valve, which receives said line fluid pressure and said throttle modulator fluid pressure, and which produces, as said output of said fluid pressure control means, a fluid pressure which, when the line pressure is lower than a second predetermined pressure, is less than line pressure, but increases faster with increasing engine load than does said line pressure; when said line pressure is between said second predetermined pressure and a third predetermined pressure, is substantially equal to line pressure; and, when line pressure is greater than said third predetermined pressure, is substantially equal to said predetermined pressure; (d) a shift valve which receives said output fluid pressure and which, according to the operational conditions of the vehicle, selectively supplies it as an actuating fluid pressure to one of said friction engaging mechanisms; whereby the overall shape of a graph of said output fluid pressure of said fluid pressure control means as the ordinate, and engine load as the abscissa, is convex upwards; whereby said shift valve is provided with a pressure to supply to said friction engaging mechanism as an actuating fluid pressure, the variation of which with respect to engine load is of the same general nature, as is the variation of engine torque with respect to engine load.