Abstract: A torque converter clutch control system has a plurality of operating modes among them an off mode wherein torque coupling is fluidic, a controlled capacity mode wherein the torque coupling is fluidic and mechanical during period of positive engine torque, an apply mode for smoothly transitioning from the OFF mode to the controlled capacity mode, and a release mode for smoothly transitioning from the controlled capacity mode to the off mode. Additionally, a lock mode is provided wherein torque coupling is mechanical via the torque converter clutch and a coast mode wherein torque coupling is mechanical and fluidic during periods of negative torque.

Abstract: A hydraulically-actuated multi-step transmission is adapted to prevent the occurrence of engagement shocks of a direct-coupled or lock-up clutch associated with a torque converter. Downshifting is carried out once with the direct-coupled clutch (8) engaged when the vehicle is slowed toward a stop. This is followed by a further downshift with the accelerator released and the direct-coupled clutch disengaged.

Abstract: An rpm-changing engaging device of a motor vehicle is controlled during an engaging process in such fashion that a curve is selected according to which the rpm difference based on the input rpm of the engaging device is adjusted between the input rpm of the engaging device and its output rpm by the engaging device indirectly or directly, corresponding to the value, determined prior to the engaging process or before the stopping of the motor vehicle, of a driving activity. A precondition is that the rpm difference, based on the input rpm of the engaging device and its output rpm. The curve is selected from a family of several engaging devices.

Abstract: An air-fuel ratio control system controls the air-fuel ratio of a mixture supplied to an internal combustion engine. The engine is installed on an automotive vehicle having an automatic transmission provided with a locking-up device. The air-fuel ratio control system controls the air-fuel ratio to a predetermined air-fuel ratio leaner than a stoichiometric air-fuel ratio when the locking-up device is engaged. The air-fuel ratio control system sets the predetermined air-fuel ratio to a value depending on whether the locking-up device is fully engaged or partially engaged.

Abstract: A shift valve of a hydraulic control system for an automatic transmission system, which ensures safety by maintaining a standard shifting operation when an electronic control system is out of order.

Abstract: In an electronically controlled transmission adapted to control operation of a torque converter clutch in softlock and hardlock modes, a test to determine whether the clutch is operating with an acceptable slip magnitude in a control region or whether it is operating with a high level of slip or instability outside the control region. The test distinguishes periods of instability associated with deterioration of the clutch from transients associated with normal operating conditions and background noise. An instability counter, interval clock and warm-up cycle counter are used to determine an appropriate point for discounting prior events and reentering the control test. Continuous slip mode of operation of the clutch is disabled entirely after a predetermined number of verified unstable events have occurred.

Abstract: In an automatic transmission provided with a hydraulic lockup clutch which can directly and mechanically engage an input shaft with an output shaft of a torque converter, input torque of the above torque converter is detected and an working oil pressure supplied to said lockup clutch is detected. And a target oil pressure for said lockup clutch is set based on said input torque, supply of the oil pressure is feedback controlled so that an actual working oil pressure gets close to said target oil pressure, and said lockup clutch is controlled to the semi-clutch state.