초록 ▼

A transmission includes a plurality of friction units to effect shifting between gear ratios, one of which includes driving and driven elements which may operate with a speed differential at the time of shifting between gear ratios. A first or line pressure is generated which is variable in a first

A transmission includes a plurality of friction units to effect shifting between gear ratios, one of which includes driving and driven elements which may operate with a speed differential at the time of shifting between gear ratios. A first or line pressure is generated which is variable in a first pattern corresponding approximately to the pattern of torque output of the vehicle engine. This pressure is supplied to a friction unit other than the one friction unit to operate such other friction unit. A second pressure is generated which is variable in a second pattern corresponding approximately to a combination of the pattern of the engine torque output and the pattern of differential speed between the driving and driven elements of said one friction unit at the time of engagement of the elements. The second pressure is directed to said one friction unit to operate such one friction unit.

대표청구항 ▼

A hydraulic control system for an automatic power transmission mechanism including a driving member operatively connected to the input shaft of an engine of an automotive vehicle, which engine has a throttle which opens in degrees, a driven member, and frictional units each having fluid operated act

A hydraulic control system for an automatic power transmission mechanism including a driving member operatively connected to the input shaft of an engine of an automotive vehicle, which engine has a throttle which opens in degrees, a driven member, and frictional units each having fluid operated actuating means which are selectively operative and inoperative for producing a plurality of gear ratios between driving and driven members, comprising: means for generating a throttle fluid pressure which is proportional to the degree of throttle opening over most of the throttle opening range, means, communicating with said throttle pressure generating means, for generating a modified fluid pressure which increases in proportion to the degree of throttle opening from low to medium degrees of throttle opening and remains constant from medium to high degrees of throttle opening, whereby said modified fluid pressure approximates the characteristics of torque output of the engine, means for generating a governor fluid pressure which is approximately variable with vehicle speed of the automotive vehicle, a pressure regulator valve, communicating with said modified pressure generating means, for producing a line pressure varible with said modified throttle fluid pressure, said line pressure being always greater than said modified throttle pressure, means, communicating with said throttle pressure generating means and with said pressure regulator valve, for generating a modulated throttle pressure which remains constant from low to medium degrees of throttle opening and increases in proportion to the degree of throttle opening and increases in proportion to the degree of throttle opening from medium to high degrees of throttle opening, a gear position selector valve provided operatively between said pressure regulator valve and the respective actuating means of said frictional units, said gear position selector valve having a valve member movable between a plurality of positions for providing communication between the pressure regulator valve and the actuating means of at least one of the frictional units, a gear shift valve provided operatively between said gear position selector valve and the actuating means of at least one of the frictional units and connected for communication with said governor pressure and modulated throttle pressure generating means and responsive to said governor pressure and said modulated throttle pressure to provide communication between said gear position selector valve means and the actuating means of the another frictional unit, and a pressure reducing valve provided operatively between the actuating means of the one frictional unit and said gear position selector valve, said pressure reducing valve having a valve member movable into a position providing communication between the one frictional unit and said gear position selector valve through said gear shift valve, the pressure reducing valve being connected with said throttle pressure generating means and being responsive to said throttle pressure for producing a fluid pressure which is not higher than said line pressure by a value variable with said throttle pressure, said valve member of said pressure reducing valve including a first pressure acting area which is selectively exposed to the same fluid pressure to which another frictional unit is selectively exposed and a second pressure acting area, opposite to said first pressure acting area, which is selectively exposed to said throttle pressure.