Hydraulic control system for controlling line pressure based on backtorque and throttle rate in an automatic transmission

A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that

• said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:
• wherein said correction means determines the amount by which the target hydraulic pressure set by the target hydraulic pressure setting means is increased according to the kind of the back torque upshift as well as to the said parameter indicative of the engine load and the rotational speed of the driving system.

A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that

• said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:
• wherein said rotational speed detecting means detects the rotational speed of a turbine of a torque convertor as the rotational speed of the driving system and said correction means increases the target hydraulic pressure only when the engine load is in a predetermined range.

A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that

• said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and load on the engine of a vehicle, an engine load detecting means which detects a parameter indicative of the engine load and another parameter indicative of the rate of change in the engine load a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in said another parameter indicative of the rate of change in the engine load by a predetermined amount, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the engine load and the rotational speed of the driving system:
• wherein said correction means increases the target hydraulic pressure only when the engine load is in a predetermined range.

A hydraulic control system for an automatic transmission including a multi-speed transmission gear mechanism having an input shaft, an output shaft and a plurality of friction coupling elements, the hydraulic control system being for selectively applying and releasing the friction coupling elements to cause the transmission gear mechanism to shift to a speed which is determined according to a predetermined shift pattern, and comprising a hydraulic circuit for supplying a hydraulic pressure to the friction coupling elements and applying the friction coupling elements and a control means which controls the hydraulic circuit, characterized in that

• said control means is provided with a target hydraulic pressure setting means which sets a target hydraulic pressure to be applied to the friction coupling elements according to a kind of shift to be effected and a degree of opening of a throttle valve for an engine throttle valve detecting means which detects a parameter indicative of the degree of opening of the throttle valve and another parameter indicative of the rate of change in the degree of opening of the throttle valve, a back torque shift detecting means which detects that the transmission gear mechanism is to make a back torque upshift due to a reduction in of said another parameter indicative of the rate of change in the degree of opening of the throttle valve the degree of opening of the throttle valve at a rate not less than a predetermined rate, a rotational speed detecting means which detects a rotational speed of a driving system which drives the input shaft of the transmission gear mechanism, and a correcting means which, when the back torque shift detecting means detects that the transmission gear mechanism is to make said back torque upshift increases the target hydraulic pressure set by the target hydraulic pressure setting means by an amount which is determined according to said parameter indicative of the degree of opening of the throttle valve and the rotational speed of the driving system, and does not correct the target hydraulic pressure when the back torque upshift is not detected.