Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Patent
1997-10-27
2000-10-17
Wright, Dirk
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
F16H 6104, B60K 4106, F02D 2902
Patent
active
061323349
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a control system for an automatic transmission, and more particularly to a system for controlling hydraulic pressure for use in so-called clutch-to-clutch shift or direct pressure control in accordance with control of a power source, such as an engine or a motor.
BACKGROUND ART
Since shift of the gear stage in an automatic transmission involves change in the rotations of a plurality of rotative elements, the inertia forces of the rotative elements must be absorbed to make the torque shift to be performed smoothly in order to prevent shift shock. Control for preventing the shift shock has been performed by controlling engaging pressure or releasing pressure for frictional engagement units, such as clutches and brakes, for performing the shift so as to absorb the inertia forces (energy) attributable to sliding of the frictional engagement units.
Change in the rotations of the engine which occurs when shift is performed becomes different between a power-on state in which the accelerator pedal has been depressed and a power-off state contrary to the power-on state. Therefore, when clutch-to-clutch shift is performed in which the states of engagement of two frictional engagement units are simultaneously changed, the engaging pressure for the on-coming frictional engagement unit is made adaptable to the state of revolution of the engine when the shift is performed.
When shift down, which is clutch-to-clutch shift, is performed, the engaging pressure for the on-coming frictional engagement unit is gradually raised (swept up) after rise in the engine revolving speed to the synchronized revolving speed at the gear stage set by the shift down because the engine revolving speed is attempted to be raised in the power-on state. In the power-off state, the engine revolving speed is undesirably lowered if the frictional engagement unit which has realized the gear stage is released. Therefore, the engaging pressure for the on-coming frictional engagement unit is enlarged in an early stage to raise the engine revolving speed to the synchronized revolving speed at the gear stage set by the shift down. That is, the engaging pressure for the frictional engagement unit is controlled to be adaptable to the tendency of the change in the revolving speed of the engine when the shift is performed.
When the clutch-to-clutch shift is performed, learning control is performed such that the hydraulic pressure is corrected in accordance with the state of fuel injection in the engine and the tied-up state when the previous shift has been performed and the shift is performed with the corrected hydraulic pressure when the next shift is performed.
That is, the clutch-to-clutch shift is performed such that the hydraulic pressure for at least one of the frictional engagement unit of the frictional engagement units for performing the shift is successively changed to correspond to the state of progress of the shift to prevent shock attributable to rapid change of the output torque. In this case, change in the revolving speed (the engine revolving speed) input to the automatic transmission is affected by the input torque, the friction coefficient of the frictional member or the change rate of the hydraulic pressure. Thus, there arises a possibility that fuel injection in the engine is undesirably performed excessively or a tied-up state occurs on the contrary.
Therefore, the foregoing problems have been prevented by correcting the controlled value of the hydraulic pressure in accordance with the detected state when the shift has been performed and the next clutch-to-clutch shift is controlled in accordance with the corrected controlled value. Since the foregoing control is able to use the individual difference in the automatic transmission and the factor such as the change of the frictional engagement unit as the time lapses in the control of the shift, control of the shift suitable for each case can be performed. Therefore, shift shock occurring when the clutch-to-clutch shift is performed can
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Kaigawa Masato
Tabata Atsushi
Takahashi Nobuaki
Toyota Jidosha & Kabushiki Kaisha
Wright Dirk
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