Abstract: A hydraulic control system for a power train including a shift speed mechanism, a frictional element for switching a shift characteristic of the shift speed mechanism, a hydraulic control mechanism for controlling a hydraulic pressure, a target shift time setting device for setting a target shift time based on an input speed difference of the shift speed mechanism through the shift operation and an input torque introduced to the shift speed mechanism, an angular acceleration calculator for calculating an angular acceleration of an input member of the shift speed mechanism based on the target shift time obtained through the target shift time setting device and the input speed change of the shift speed mechanism through the shift operation, an inertia hydraulic pressure setting device for setting an inertia hydraulic pressure for coping with a moment force due to a moment of inertia of a power transmitting system to the shift speed mechanism based on the angular acceleration of the input member of the shift spe

Abstract: A shift control system for an automatic power transmission is capable of optimizing operation timing of a timing valve and whereby eliminate a shift-shock and occurrence of racing.

Abstract: An electronic transmission coastdown shift control method in which the transmission controller has the capacity to predict timing of apply element application. The control method of the present invention improves the shift sequence by accurately prefilling the apply element. The transmission controller vents the release element when apply element application is imminent and controls the application of the oncoming element to achieve a controlled element exchange for a smooth coastdown shift. A duty cycle is then applied to complete the oncoming element application with a soft yet quick application and control the engagement of the oncoming element. The identification of the application point of the oncoming element enables the apply element fill volume to be learned during coastdown shifts. It also enables the calculation of a line pressure correction factor necessary in accurately predicting application of the apply element. Anticipation of a coastdown tip-in condition is also provided.

Abstract: A method for controlling shifting of a powershift transmission of an agricultural vehicle in accordance with a boost pressure developed by a turbocharger of an engine associated with said vehicle. The turbocharger generates a turbo boost pressure which is indicative of the engine torque being produced by the engine at a given time. The turbo boost pressure is monitored by a sensor which generates a boost pressure signal in accordance with the sensed boost pressure. This signal is then modified in accordance with the sensed engine speed of the vehicle to produce a compensated turbo boost signal. The compensated turbo boost signal is compared against predetermined full-load and no-load turbo boost values to determine the percentage value of full-load boost pressure, and thus the load on the engine, at a given time.

Abstract: In an arrangement for automatically changing gear in an epicyclic change-speed gearbox from a previous gear, in which a first frictional connection (clutch or brake) is engaged, into another gear, in which a second frictional connection is engaged, the working pressure for engaging the first frictional connection is switched off when the working pressure for engaging the second frictional connection reaches a significant pressure value. The pressure value is determined by comparison with a reference parameter which depends on the load torque.

Abstract: A speed change control method and apparatus for a vehicular automatic transmission having a first-speed clutch for establishing a first speed and a second-speed clutch for establishing a second speed, includes subjection of at least a duty ratio Dr of a second-speed solenoid valve for supplying oil pressure to the second-speed clutch to feedback control, so that the first-speed clutch is engaged while disengaging the second-speed clutch. This thereby increases a turbine rotational speed Nt toward the first-speed synchronous rotational speed. Further, an upper limit value Dmax of the duty ratio Dr is set, and the duty ratio Dr is subject to feedback control within a resultant duty ratio range. This thereby prevents the duty ratio Dr from being set at an excessive value caused by a delay in the rise of the oil pressure. As a result, even if a depression of an accelerator pedal is suddenly increased during a downshifting process, an interlock problem can be prevented, thereby ensuring smooth speed change.

Abstract: A shift control system for obtaining a smooth shift feeling in a shifting necessitating redeployment of friction elements. The shift control system is comprised of a sensor which detects a state that disengagement pressure of a friction element to be disengaged almost becomes zero during shifting. In reply to the detection of the sensor, a controller adjusts engagement pressure of the other friction element to be engaged at a predetermined value determined according to input torque and gear ratio.

Abstract: The present invention relates to technology wherein the torque input to an automatic transmission is estimated using an intake flow rate corrected by eliminating an intake flow rate friction component, the invention enabling the intake flow rate at the time of cool down to be accurately corrected. The characteristics of warm-up intake flow rate friction component versus engine rotational speed are pre-stored, and a warm-up intake flow rate friction component retrieved from an actual engine speed. A ratio for when the automatic transmission is in a non driving range, between the actual intake flow rate and the retrieved warm-up intake flow rate friction component is then obtained to set a correction coefficient. The warm-up intake flow rate friction component is then corrected by the most recently set correction coefficient, and this becomes the intake flow rate friction component.

Abstract: An electrohydraulic control system for an automatic transmission includes planetary gearsets, clutch and brakes that control the condition of the gear components, hydraulically actuated solenoid control valves, electronic sensors connected to a microprocessor, a gear selector mechanism and an overdrive cancel switch. The extent to which a gear ratio change is completed, as represented by the ratio of the current operating gear ratio and the gear ratio associated with gear ratio at the completion of the gear shift, is used as a variable in algorithms executed by the microprocessor to schedule change in state of solenoid operated valve. The state determines the engaged and disengaged condition of friction elements that produce the gear shift.

Abstract: In a certain speed stage shifting of an automatic transmission of a vehicle including a speed change gear mechanism including rotary members such as gears and gear carriers and hydraulically operated friction engaging brakes and clutches adapted to provide various speed stages according to selective engagement and disengagement of the friction engaging brakes and clutches, the servo oil pressure of a first friction engaging brake is immediately lowered down to a stand-by pressure marginally higher than a threshold pressure bordering non sliding and sliding of the first friction engaging brake at the start of a change-over of a second friction engaging brake is and then, when a substantial change-over of the second friction engaging means started, the servo oil pressure is further lowered across the threshold pressure and thereafter periodically lowered by a decrement the magnitude of which may desirably be increased along with a lapse of time.

Abstract: In a computer-based control, pressure is progressively decreased in an off-going clutch for gradual release while pressure is progressively increased in an on-coming clutch. Positive off-going clutch slip and the rate of slip change are monitored to detect the onset of turbine flare. A control calculates a compensation pressure which is added to the on-coming clutch pressure to reduce the slip and thus the flare. The control calculates a term proportional to slip and an integral term when the slip and slip rate are positive. When the slip rate goes negative, the control calculates a negative integral term. All the calculated terms are combined to produce the compensation pressure value.