Method and apparatus for hydraulic control of automatic transmission

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 including first and second frictional units respectively, having fluid operated actuating means which are to be selectively made operative and inoperative for producing a plurality of gear ratios between the 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 throttle 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 throttle pressure approximates torque output of the engine,
• means for generating a governor fluid pressure variable with vehicle speed,
• a pressure regulator valve communicating with said modified pressure generating means for generating a line pressure variable with said modified throttle fluid 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 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 first and second frictional units,
• a gear shift valve provided operatively between said gear position selector valve and the actuating means of said first frictional unit, said gear shift valve being connected for communication with said governor pressure and said 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 and said first frictional unit, said gear position selector valve having a valve member movable to a position providing communication through said gear position selector valve between said pressure regulator valve and the actuating means of said second frictional unit, and providing communication between the pressure regulator valve and said gear shift valve, said gear shift valve, in turn, having a valve member movable between positions establishing open and closed conditions of said gear shift valve and providing communication between said pressure regulator valve and said actuating means of the first frictional unit through the gear shift valve when the gear shift valve is open, and
• a pressure reducing valve provided operatively between the actuating means of said first frictional unit and said gear position selector valve and having a valve member movable into a position providing communication between the actuating means of the first frictional unit and said gear position selector valve through said gear shift valve, the pressure reducing valve communicating with said throttle pressure generating means and being responsive to said throttle pressure for producing a friction unit actuating 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 to which the one 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.

A hydraulic control system for an automatic transmission for an automotive vehicle having an engine, the transmission being adapted for shifting between different gear ratios according to a shift pattern, the transmission having a plurality of frictional units for effecting shifting, at least one of which includes driving and driven elements which are frictionally engageable under conditions which at least at certain points along the shift pattern involve a speed differential between the driving and driven elements, the control system comprising:

• a fluid source,
• means communicating with said fluid source for generating a first fluid pressure which is variable in a first pattern corresponding approximately to the pattern of torque output of the vehicle engine, said first fluid pressure generating means being adapted to supply said first fluid pressure to a frictional unit other than the one frictional unit to operate such other frictional unit,
• means for changing said first pattern of variation of said first fluid pressure to a second pattern corresponding approximately to a combination of the pattern of engine torque output and the pattern of differential speed between the driving and driven elements of said one frictional unit at the time of engagement of the elements, said changing means generating a second fluid pressure which varies in said second pattern, said first pressure generating means being coupled for communication with said changing means, said changing means being adapted to supply said second fluid pressure to said one frictional unit to operate such one frictional unit,
• whereby said second fluid pressure reaching said one frictional unit is sufficient to meet torque reaction requirements and differential speed compensation requirements of the one frictional unit at all shift points and is sufficiently low to avoid substantial shocks in effecting shifting by the one frictional unit.

A hydraulic control system for an automatic transmission for an automotive vehicle having an engine with a throttle which opens in degrees, the transmission being adapted for shifting between different gear ratios and having a plurality of friction units with fluid pressure operated servos to effect shifting between gear ratios, the control system comprising:

• a fluid source,
• means communicating with said fluid source for generating a line pressure which varies approximately linearly with the degree of engine throttle opening from low to medium degrees of opening and which is approximately constant from medium to high degrees of throttle opening, said line pressure generating means being adapted to supply line pressure to the servo of one of the friction units,
• means, communicating with said fluid source, for generating a non-servo actuating throttle pressure which is proportional to the degree of throttle opening over most of the throttle opening range,
• means, connected for communication with both said line pressure and non-servo actuating throttle pressure generating means, for generating a reduced servo actuating pressure which is proportional to the degree of throttle opening over most of the throttle opening range by reducing said line pressure under the influence of said non-servo actuating throttle pressure, said reduced servo pressure actuating means being adapted to supply said reduced servo actuating pressure to the servo of another of the friction units other than the one friction unit,
• whereby said reduced servo actuating pressure is sufficient to actuate the one friction unit so as to provide an effective grip for shifting but at the same time is not so high as to create substantial shocks during shifting under the influence of another friction unit.

A hydraulic control system for an automatic transmission for an automotive vehicle having an engine with a throttle which opens in degrees, the automotive vehicle having an operating range extending from a state in which conditions such as the carburetor throttle opening, vehicle speed, torque and the engine speed are at or near their minimums to states in which such conditions are at or near their maximums, the transmission being adapted for shifting between different gear ratios and having a pluality of friction units each with at least one fluid pressure operated actuator to effect shifting between gear ratios, the control system comprising:

• a source of fluid,
• means connected with said fluid source for generating one fluid pressure which is continuously variable over a majority of the vehicle operating range,
• means connected with said fluid source for generating another fluid pressure which is always greater than the one pressure and which varies in a generally discontinuous manner over the same operating range over which the one pressure varies continuously,
• means for changing the other pressure under the action of the one pressure to provide a reduced servo-actuating pressure which is continuously variable over approximately the same range over which the one pressure is continuously variable, said one pressure generating means and said other pressure generating means both being coupled for communication with said changing means, said changing means also being coupled for communication with an actuator of one of the friction units to selectively supply said reduced servo-actuating fluid pressure to the one friction unit to effect actuation thereof,
• whereby said reduced servo actuating pressure is sufficiently high to actuate the one friction unit so as to provide an effective grip for shifting but at the same time is not so high as to create substantial shocks during shifting of the transmission under the influence of the one friction unit.

A method of hydraulically controlling an automatic transmission for an automotive vehicle having an engine, the transmission being adapted for shifting between different gear ratios according to a shift pattern, the transmission having a plurality of friction units for effecting shifting, at least one of which includes driving and driven elements which are frictionally engageable conditions which at least at certain points along the shift pattern involve a speed differential between the driving and driven elements, the method comprising the steps of:

• generating a first fluid pressure which is variable in a first pattern corresponding approximately to the pattern of torque output of the vehicle engine,
• supplying said first fluid pressure to a friction unit other than the one friction unit to operate such other friction unit,
• changing said first pattern of variation of said fluid pressure to a second pattern corresponding approximately to a combination of the pattern of 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,
• directing said second fluid pressure to said one friction unit to operate such one friction unit,
• whereby said second fluid pressure reaching said one friction unit is sufficient to meet torque reaction requirements and differential speed compensation requirements of the one friction unit at all shift points and is sufficiently low to avoid substantial shocks in effecting shifting by the one friction unit.

A method of hydraulically controlling an automatic transmission for an automotive vehicle having an engine with a throttle which opens in degrees, the transmission being adapted for shifting between different gear ratios and having a plurality of friction units with fluid pressure operated servos to effect shifting between gear ratios, the method comprising the steps of:

• generating a line pressure which varies approximately linearly with the degree of engine throttle opening from low to medium degrees of opening and which is approximately constant from medium to high degrees of throttle opening,
• supplying said line pressure to one of the friction units,
• providing a non-servo actuating throttle pressure which is proportional to the degree of throttle opening over most of the throttle opening range,
• producing, in response to and under the influence of said non-servo actuating throttle pressure, a reduced servo actuating pressure which is proportional to the degree of throttle opening over most of the throttle opening range by reducing said line pressure,
• supplying said reduced servo actuating pressure to the servo of one of the friction units,
• whereby said reduced servo actuating pressure is sufficient to actuate the one friction unit so as to provide an effective grip for shifting but at the same time is not so high as to create substantial shocks during shifting under the influence of the one friction unit.

A method of hydraulically controlling an automatic transmission for an automotive vehicle having an engine with a throttle which opens in degrees, the automotive vehicle having an operating range extending from a state in which conditions such as the carburetor throttle opening, vehicle speed, torque and the engine speed are minimums to states in which such conditions are at or near their maximums, the transmission being adapted for shifting between different gear ratios and having a plurality of friction units each with at least one fluid pressure operated servo to effect shifting between gear ratios, the control system, the method comprising the steps of:

• providing one fluid pressure which is continuously variable over a majority of the vehicle operating range,
• generating another fluid pressure which is always greater than the one pressure and which varies in a discontinuous mannner over the same operating range over which the one pressure varies continuously,
• changing the other fluid pressure under the action of the one pressure to provide a reduced servo-actuating pressure which is continuously variable over approximately the same range over which the one pressure is continuously variable,
• selectively supplying said reduced servo-actuating fluid pressure to the servo-actuator of the one friction unit to effect actuation thereof,
• whereby said reduced servo-actuating pressure is sufficiently high to actuate the one friction unit so as to provide an effective grip for shifting but at the same time is not so high as to create substantial shocks during shifting of the transmission under the influence of the one friction unit.

A hydraulic control system for an automatic transmission for an automotive vehicle having an engine with a throttle which opens in degrees, the transmission being adapted for shifting between different gear ratios and having a plurality of friction units with fluid pressure operated servos to effect shifting between gear ratios, the control system comprising:

• a fluid source;
• means, communicating with said fluid source, for generating a non-servo actuating throttle pressure which is proportional to the degree of throttle opening over most of the throttle opening range;
• means for generating a modified throttle pressure, said modified throttle pressure generating means being coupled with said non-servo actuating throttle pressure generating means and including means for eliminating any increase in throttle pressure produced by said non-servo actuating throttle pressure generating means beyond a medium degree of throttle opening, whereby said modified throttle pressure increases continuously from low to medium degrees of throttle opening and remains constant from medium to high degrees of throttle opening;
• means, communicating with said fluid source, for generating a line pressure, said line pressure generating means communicating with said modified throttle pressure generating means to be acted thereby, whereby said line pressure varies approximately linearly with the degree of engine throttle opening from low to medium degrees of engine throttle opening and which remains approximately constant from medium to high degrees of engine throttle opening, the line pressure being always greater than the modified throttle pressure;
• means, communicating with said fluid source, for generating a modulated throttle pressure, said modulated throttle pressure generating means communicating with said throttle pressure generating means to be acted thereby, whereby said modulated throttle pressure remains approximately constant from low to medium degrees of engine throttle opening and linearly increases with the degree of engine throttle opening from medium to high degrees of engine throttle opening;
• means, communicating with said fluid source, for generating a governor pressure which varies with the vehicle speed of the automotive vehicle;
• gear shift valve means, communicating with said modulated throttle pressure and governor pressure generating means and also communicating with said line pressure generating means, for supplying said line pressure to the servo of one of the friction units in response to said modulated throttle pressure and said governor pressure;
• means, connected for communication with said line pressure generating means via said gear shift valve means when said modulated throttle pressure and said governor pressure satisfy a predetermined relationship and connected for communication with said non-servo actuating throttle pressure generating means, for generating a reduced servo actuating pressure which is proportional to the degree of engine throttle opening over most of the throttle opening range by said line pressure under the influence of said non-servo actuating throttle pressure, said reduced servo generating means being adapted to supply said reduced servo actuating pressure to the servo of another of the friction units other than the one friction unit,
• whereby said reduced servo actuating pressure is sufficient to actuate another of the friction units so as to provide an effective grip for shifting but at the same time not so high as to create substantial shocks during shifting under the influence of the another friction unit.

An automatic transmission for an automatic vehicle having an engine with a throttle which opens in degrees, the transmission being shiftable between a plurality of gear ratios, the transmission comprising:

• a high-and-reverse friction unit with driving and driven elements which may operate with a speed differential at the time of shifting between gear ratios,
• said high-and-reverse friction unit including a fluid actuator, said high-and-reverse friction unit and its actuating means cooperating to contribute to a shifting between gear ratios,
• a pair of planetary gear sets which are operatively coupled together and which provide a plurality of transmission drive conditions including a plurality of forward drive gear ratios, including a lowest drive ratio, and including a reverse drive ratio,
• a forward drive friction unit having a fluid actuator which cooperates with said planetary gear sets to provide a forward drive condition of the transmission in all forward gear ratios,
• a low-and-reverse friction unit, having a fluid actuator, said high-and-reverse friction unit cooperating with said planetary gear sets to establish, when actuated and when the low-and-reverse friction unit is deactuated, a forward drive gear ratio other than the lowest forward drive gear ratio and to establish, when actuated in combination with the low-and-reverse friction unit, a reverse drive condition;
• a gear position selector valve communicating with each of said friction units for selectively supplying pressurized fluid to the actuators of said friction units to contribute to selection of the drive condition of the transmission, said gear position selector valve having a valve member movable between at least a forward drive position and a reverse position,
• a pair of passageway branches establishing the communication between the gear position selector valve and the high-and-reverse friction unit, one of said branches being connected with said gear position selector valve so as to establish communication with the high-and-reverse friction unit when the gear position selector valve member has been moved to the reverse position, the other branch establishing communication between the gear selector valve and the high-and-reverse friction unit when the gear position selector valve member has been moved to the forward drive position and other conditions are met for actuating the high-and-reverse friction unit,
• means for generating an actuating fluid pressure which is approximately linearly proportional to the degree of throttle opening,
• said means for generating a linearly proportional actuating pressure being interposed in said other branch between the high-and-reverse friction unit and said gear position selector valve,
• whereby a reduced fluid pressure is fed to said high-and-reverse friction unit only when said gear position selector valve member is in the forward drive position and other conditions are met for actuating the high-and-reverse friction unit and whereby said linearly proportional fluid pressure reaching said high-and-reverse friction unit is sufficient to meet torque reaction requirements and differential speed compensation requirements of the high-and-reverse friction unit at all shift points and is sufficiently low to avoid substantial shock in effecting shifting by the high-and-reverse friction unit.

An automatic transmission, for an automotive vehicle having an engine with a throttle which opens in degrees, the transmission being shiftable between a plurality of gear ratios, the transmission comprising:

• a friction unit with driving and driven elements which may operate with a speed differential at the time of shifting between gear ratios,
• said friction unit including a fluid actuator, said friction unit and its actuating means cooperating to contribute to a shifting between gear ratios,
• means for generating an actuating fluid pressure which is approximately linearly proportional to the degree of throttle opening, said means for generating a linearly proportional actuating pressure including a pressure reducing valve,
• a conduit extending from said pressure generating means to said fluid actuator of said friction unit to selectively apply said linearly proportional fluid pressure thereto,
• whereby said linearly proportional fluid pressure reaching said friction unit is sufficient to meet torque reaction requirements and differential speed compensation requirements of the friction unit at all shift points and is sufficiently low to avoid substantial shock in effecting shifting by the one friction unit.

An automatic transmission, for an automotive vehicle having an engine with a throttle which opens in degrees, the transmission being shiftable between a plurality of gear ratios, the transmission comprising:

• a friction unit with driving and driven elements which may operate with a speed differential at the time of shifting between gear ratios,
• said friction unit including a fluid actuator, said friction unit and its actuating means cooperating to contribute to a shifting between gear ratios,
• means for generating an actuating fluid pressure which is approximately linearly proportional to the degree of throttle opening,
• a conduit extending from said pressure generating means to said fluid actuator of said friction unit to selectively apply said linearly proportional fluid pressure thereto,
• means for effecting a kickdown condition in the hydraulic control system of the automatic transmission, said kickdown effecting means providing a downshift tendency at very high degrees of throttle opening,
• said kickdown effecting means being operatively coupled with said means for generating a linearly proportional actuating pressure to render said means for generating a linearly proportional actuating pressure ineffective during said kickdown condition,
• whereby said linearly proportional fluid pressure reaching said friction unit is sufficient to meet torque reaction requirements and differential speed compensation requirements of the friction unit at all shift points and is sufficiently low to avoid substantial shock in effecting shifting by the one friction unit.