Abstract: An automatic transmission shift control system calibrates a locking speed, which is regulated by a regulating valve and at which locking of a specific frictional element is performed so as to shift an transmission gear mechanism to a specific gear, in accordance with a deviation of an input speed of rotation to the transmission from a specified input speed of rotation while shifting the transmission to the specific gear. The system further varies the calibration according to a transitional period of time which is defined from a completion of shifting to a preceding gear from which the transmission is shifted directly to the specific gear to a commencement of shifting to the specific gear subsequently to the shifting to the preceding gear.

Abstract: A control apparatus for an engine and an automatic transmission controls a starting timing, a terminating timing, or methods of torque reduction of the engine during gear shifts. Using stored information such as a turbine speed signal, a gear shift signal, a degree to which a throttle valve is opened, a vehicle speed, an engine speed and so on, the control apparatus calculates an appropriate torque reduction which is performed by either retarding ignition timing or cutting fuel supplied to fuel injection valves. According to one embodiment of the invention, by detecting a variation ratio or differential value of turbine speed, a period of the torque reduction is started, ended, and kept within a proper timing. According to another embodiment of the invention, based on a "chasing" state of an input torque of the transmission against the variation of engine load, the timing of torque reduction is changed.

Abstract: A control system controls a second to third gear shift of an automatic transmission in an advantageous way. The transmission has a 3-4 clutch, which is locked under hydraulic pressure, and a 2-3 brake provided with a lock pressure chamber and an unlock pressure chamber. The 2-3 brake is locked when a hydraulic pressure is developed in the lock pressure chamber only and is unlocked when a fluid pressure is developed in the unlock pressure chamber and when a hydraulic pressure is released from both the lock pressure chamber and the unlock pressure chamber. Hydraulic pressure is released from the lock pressure chamber so as to unlock the 2-4 brake only when a second to third gear shift is needed for the first time after engine ignition simultaneously with application of pressure to the 3-4 clutch so as to lock the 3-4 clutch.

Abstract: A control apparatus for an engine and an automatic transmission controls a starting timing, a terminating timing, or methods of torque reduction of the engine during gear shifts. Using stored information such as a turbine speed signal, a gear shift signal, a degree to which a throttle valve is opened, a vehicle speed, an engine speed and so on, the control apparatus calculates an appropriate torque reduction which is performed by either retarding ignition timing or cutting fuel supplied to fuel injection valves. According to one embodiment of the invention, by detecting a variation ratio or differential value of turbine speed, a period of the torque reduction is started, ended, and kept within a proper timing. According to another embodiment of the invention, based on a "chasing" state of an input torque of the transmission against the variation of engine load, the timing of torque reduction is changed.

Abstract: A shift control system for an automatic transmission includes a shift gear mechanism for providing a plurality of shift stages of different speed ratios, a plurality of frictional elements, a first valve for controlling a hydraulic fluid supply, a second valve provided in a hydraulic release line to control hydraulic fluid release, a first frictional element included in the plurality of the frictional elements, a second frictional element included in the plurality of the frictional elements, a piston provided in the second frictional element, a timing valve for controlling a supply timing of the hydraulic pressure for the releasing chamber of the second frictional element in response to actuating hydraulic pressure introduced into the first frictional element, an oil temperature detecting device, and a start detecting device for detecting start of engaging operation of the first frictional element.

Abstract: A control system for an automatic transmission includes a main hydraulic line to which hydraulic pressure is introduced when a manual valve takes a reverse range position for reverse movement. First and second hydraulic lines are separated from the main hydraulic line, a first frictional element is connected with the first hydraulic line, and a second frictional element is connected with the second hydraulic line. An accumulator is disposed on the second hydraulic line, a shift valve is disposed on the second hydraulic line closer to the second frictional element than the accumulator, and a first drain port is formed on the manual valve for draining hydraulic fluid from the main hydraulic line when the manual valve is shifted from the reverse range to another range. A spool is disposed in the shift valve for moving to a position to shift the shift valve so that the second line is interrupted by the shift valve and divided between a second frictional element line and an accumulator line.

Abstract: A control system for an automatic transmission has a shift gear mechanism with a plurality of frictional elements, including a low reverse brake which is selectively actuated for switching a power transmitting path to establish a desired shift stage. A hydraulic control circuit controls supply of a hydraulic fluid to and relief of the fluid from an actuator for the frictional element. An accumulator is provided in a hydraulic passage communicated with the low reverse brake for obviating a shock as the low reverse brake is engaged. Back pressure of the accumulator is controlled when a first shift gear stage is established through the engagement of the low reverse brake. A torque shock can be suppressed when the first stage is established in an L-range.

Abstract: An automatic transmission line pressure control system controls line pressure in an automatic transmission equipped with a torque convertor for hydraulically coupling and uncoupling friction coupling elements of the automatic transmission. The automatic transmission line pressure control system regulates line pressure for selectively coupling and uncoupling the friction coupling elements so as to shift the automatic transmission into desired speed gears. The line pressure is forcibly dropped to a level lower than a level present before an occurrence of a manual shift-down operation when a shift-down sensor detects the occurrence of a manual shift-down. The line pressure is then raised as a speed sensor detects an increase in rotational speed transmitted the automatic transmission, thereby shifting the automatic transmission into desired speed gears.

Abstract: A shift control system for an automatic transmission including a shift gear mechanism for providing a plurality of shift stages of different speed ratios, a plurality of frictional elements to be selectively actuated for switching a power transmitting path to establish a desired shift stage, range selecting device for selecting a shift range at least between a forward and a reverse ranges through a manual operation of a driver, control device for providing the shift gear mechanism with a specific shift stage in which an input member and output member of the shift gear mechanism are rotated together with each other in the case where the reverse range is selected during a forward movement and thereafter a forward range is selected again, the specific shift stage being provided for a predetermined time period after the forward range is selected again. A double lock condition of the shift gear mechanism can be avoided.