US 5,630,772 A · Control method and control system for automatic transmission

Abstract

A system and method for controlling an automatic transmission in a vehicle drive train including an engine, the automatic transmission and a fluid coupling for transmitting the rotation of the engine to the transmission. The transmission includes a clutch applied when a forward running range is selected; a second one-way clutch which is applied, when the first clutch is applied, to establish a forward 1st speed; and a brake for locking the one-way clutch, when applied, to block the reverse rotation of the output shaft of the transmission. A first hydraulic servo receives a first oil pressure for applying the first clutch and a second hydraulic servo receives a second oil pressure for applying the brake. When a forward running range is selected, with the vehicle stopped, the engine idling and a foot brake engaged, the oil pressure of the first hydraulic servo is lowered from the oil pressure at the 1st speed whereas the oil pressure of the second hydraulic servo is raised to a modulated pressure. The modulated pressure is set to generate, against the reverse force on the vehicle facing up an incline, a resistance corresponding to the forward driving force generated when the engine is idling in 1st speed.

Claims10

Dependent claims

A method for controlling an automatic transmission in a drive train of a vehicle including an engine, the automatic transmission having an output shaft, a fluid coupling for transmitting rotation from the engine to the transmission, a first clutch applied when a forward running range is selected, a second, one-way clutch which is applied when the first clutch is applied, to establish a forward let speed;

a brake for locking the one-way clutch, when applied, to block reverse rotation of the output shaft of the transmission, a first hydraulic servo for receiving oil pressure to apply the first clutch;
and a second hydraulic servo for receiving oil pressure to engage the brake, said method comprising:
responsive to selection of a forward running range with the vehicle stopped, throttle opening for the engine at idle and a foot brake engaged, lowering oil pressure to the first hydraulic servo to a pressure below the oil pressure received by the first hydraulic servo at 1st speed and raising oil pressure of the second hydraulic servo to a modulated pressure, said modulated pressure generating, against the reverse force on the vehicle facing uphill on an incline, a resistance force corresponding to the forward driving force of the engine idling in 1st speed, thereby establishing a neutral control state with hill-holding.

A control system for an automatic transmission in a vehicle drive train including an engine, the transmission having an output shaft and a fluid coupling for transmitting the rotation of the engine to the transmission, the control system comprising:

a first clutch applied responsive to selection of a forward running range;
a second, one-way clutch applied when said clutch is applied, to establish a forward 1st speed;
a brake for locking said one-way clutch, when applied, to block reverse rotation of the output shaft of said transmission;
a first hydraulic servo for receiving a first oil pressure and for applying said clutch responsive to the first oil pressure;
a second hydraulic servo for receiving a second oil pressure to apply said brake;
and
a hydraulic control unit for feeding said first and second oil pressures, respectively, to said first and second hydraulic servos, said hydraulic control unit comprising:
pressure-reducing means for lowering said first oil pressure to said first hydraulic servo to lower than oil pressure at 1st speed in the forward running range, when the vehicle is stopped, the engine is idling and a foot brake is engaged;
and
oil pressure feeding means for feeding said second oil pressure to said second hydraulic servo at a level to generate, against the reverse force on the vehicle when facing up an incline, a resistance force corresponding to the forward driving force generated when the engine is idling in 1st speed.

7 more elements

Dependencies are inferred from the claim text.

Control method and control system for automatic transmission

Life of this patent

Control method and control system for automatic transmission

Life of this patent

Abstract

Claims10