Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1998-07-21
2001-07-10
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C701S059000, C701S061000, C074S824000, C074S824000, C074S824000, C180S233000, C477S043000
Reexamination Certificate
active
06259983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hydraulic control system for an automatic transmission. More specifically, it relates to a hydraulic control system for an automatic transmission which corrects shift controls, including a servo starting control, by learning.
2. Description of the Related Art
Japanese Patent Publication No. 179676/1993 describes a conventional control with learning for starting time of servo control of a clutch which is engaged in a shift. In servo starting control clearance between the friction pads of the clutch is decreased and the clutch is taken to the state just before start of engagement. In this control procedure, turbine rotational speed is detected as an input shaft rotation speed, and the time between a shift control start and start of speed change in input shaft rotation, which is the start of the torque phase, is measured. Then this measured time and a stored basic servo filling time are compared, and the hydraulic pressure applied to the hydraulic servo is corrected so that the measured time comes to equal the basic filling time. That is to say, when the time between shift control start and the start of change in rotational speed of the input shaft is longer than a predetermined basic time, it is determined that the filling of the hydraulic servo for the engagement side clutch (clutch which is engaged in the shift) is not sufficient, and the hydraulic pressure applied to the hydraulic servo for the engagement side clutch is corrected so that the time for starting servo control is increased. Conversely, when the time between the shift control start and the start of change in rotational speed of the input shaft is shorter than the predetermined basic time, it is determined that the filling state of the hydraulic servo is too great, and the hydraulic pressure applied to the hydraulic servo for the engagement side clutch is corrected so that the time for starting the servo control is decreased.
But the phenomenon, in which the time from start of the shift control to the rotational change in speed of the input shaft is longer than the predetermined value, is not limited to the case in which the filling of the hydraulic servo is insufficient. When the rate of increase of the hydraulic pressure for engagement after start of the servo control is too low, the time from the start of shift control to the start of rotational speed change is increased even if the starting of servo control is performed properly. According to the prior art, in this case, it is determined that the filling state of the hydraulic servo is insufficient and the time for starting the servo control is corrected to be longer. Therefore, the hydraulic servo is filled and engagement of the engagement side clutch is started too early. Then, a shift shock occurs because of a tie-up with a disengagement side clutch which is disengaged in the shift.
SUMMARY OF THE INVENTION
Therefore, an object of the invention is to provide a hydraulic control system for an automatic transmission, which solves the aforementioned problem by proper learning control.
In order to achieve the aforementioned object, the hydraulic control system of the present invention provides a novel shift control for a shift to a predetermined gear ratio by engaging a first frictional engagement element and disengaging a second frictional engagement element. The shift control system comprises an input shaft which receives power from an engine output shaft, an output shaft which is connected to vehicle wheels, a plurality of frictional engagement elements for changing the power transmission path between the input shaft and the output shaft, including the first frictional engagement element and the second frictional engagement element, hydraulic servos that engage and disengage the frictional engagement elements, a rotation change start detector which detects start of a change in rotational speed of the input shaft, a rotation change amount detector which detects the amount of rotational change at the start of the rotational speed change, a learning controller which corrects the shift control based on the time period from start of a shift control to the start of rotational speed change detected by the rotation change start detector and the amount of change in the rotational speed detected by the rotation change amount detector at the start of the rotational speed change, and an adjusting device which adjusts at least an engagement side pressure applied to the hydraulic servo for the first frictional engagement element, based on a signal from the learning controller.
The learning controller corrects a servo starting control, in which a piston is advanced by applying a hydraulic pressure to the hydraulic servo for the first frictional engagement element and the frictional engagement element is brought to a state just before torque transmission. Further, the learning controller corrects the torque phase control, which increases the hydraulic pressure in the hydraulic servo for the first frictional engagement element to a target for the engagement pressure just before the start of the rotational speed change. When the time between the start of the shift control start and the rotational speed change start is longer than a predetermined basic time and the amount of rotational change is larger than a predetermined value, it is determined that the filling state for the first frictional engagement element servo is insufficient, and the learning controller corrects so that the time for the servo starting control is increased.
Conversely, when the time period extending from the shift control start (t=O) to the rotation change start (t
ST
) is longer than a predetermined basic time and the amount of rotational change is smaller than a predetermined value, it is determined that the target engagement pressure is too low, and the learning controller corrects so that the target engagement pressure is increased.
The start of change of the rotational speed of the input shaft is preferably detected as a change in the rotational speed of the input shaft relative to the rotational speed of the output shaft, i.e. as related to the beginning of a shift to the predetermined gear ratio.
According to the invention, the learning control is performed based on both (1) the time (t
ST
) from the shift control start to the start of change in the rotational speed of the input shaft and (2) the amount of rotational speed change at that time. Therefore, the shift control is performed properly and undesirable phenomena such as shift shock are reduced.
According to the invention, moreover, when the time (t
ST
) from the shift control start to the start of change in rotational speed of the input shaft is longer than the predetermined basic time and the amount of rotational change at the time of the rotational change start is larger than the predetermined value, the time for the servo starting control is corrected to be longer. Therefore, the servo starting control is properly corrected and a shift shock which would result from a large rotational change at the shift start is prevented.
Moreover, when the time from the shift control start to the start of rotational speed change at the input shaft is longer than the predetermined basic time and the amount of the rotational change at the rotational speed change start is smaller than the predetermined value, the target engagement pressure is increased for correction. Therefore, an erroneous learning correction for the servo starting control is prevented. As a result, the time from the shift control start to the shift start is shortened and sensation of a long shift time is avoided.
Further, the start of rotational change of the input shaft is detected based on the gear ratio. Therefore, the rotational change start is detected by a simple rotational speed detector and the difference relative to the output shaft rotational speed is easily and correctly determined. Moreover, the time of the rotation change detection is regarded as the time of the shift start. Then, the
Kubo Takayuki
Nishida Masaaki
Saito Masao
Tsutsui Hiroshi
Yamamoto Yoshihisa
Aisin Aw Co. Ltd.
Cuchlinski Jr. William A.
To Tuan C
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