Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
2001-09-18
2004-01-13
Marmor, Charles A (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S117000, C701S064000
Reexamination Certificate
active
06676567
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to control devices for controlling automotive automatic transmissions, and more particularly to control devices of a type that includes a so-called speed change completion degree estimating system that estimates the speed change compression degree assumed by the transmission, particularly estimates, upon selection of a drive range from a non-drive range, the time (or timing) when a friction element needed for the drive range starts its actual engaging operation following completion of piston stroke thereof.
2. Description of Related Art
In an automotive automatic transmission, there are installed a plurality of friction elements, such as clutches and brakes, and a hydraulic actuating means for selectively actuating the friction elements. That is, by actuating the friction elements that are selected, a certain power transmission path is provided to establish a desired gear, and by switching the friction elements that are to be actuated, another power transmission path is provided to establish another gear while carrying out a speed change of the transmission.
The transmission is powered by an engine through a torque converter. That is, the torque inputted to the transmission is outputted therefrom while being subjected to a speed change according to a selected gear.
One of the speed change completion degree estimating systems is described in Japanese Patent First Provisional Publication 6-109130. The system is constructed to estimate, upon selection of a drive range from a non-drive range, the time (or timing) when a friction element needed for the drive range starts its actual engaging operation following completion of piston stroke thereof, by detecting a speed drop from the torque converter to the transmission. That is, before starting of the engaging operation of the friction element, the hydraulic pressure for the element is so controlled as to obtain an optimum piston stroke, and after starting of the engaging operation, the hydraulic pressure is so controlled as to obtain an optimum speed change. That is, the completion of the piston stroke, namely, the timing of starting the actual engaging operation of the friction element is estimated by the drop of rotation speed of input means of the transmission.
Japanese Patent First Provisional Publication 4-366063 describes another system that estimates completion of the piston stroke, namely, the time of starting the actual engaging operation of a friction element. In this system, when, upon selection of a drive range from a non-drive range, a speed ratio between input and output speeds of a torque converter is reduced to indicate a value corresponding a drop of an input means of the transmission, estimation is so made that the friction element has finished the piston stroke, namely, started its actual engaging operation.
SUMMARY OF THE INVENTION
In the above-mentioned known systems, the estimation for completion of the piston stroke is based on the assumption that when, under standstill of an associated motor vehicle, the rotation speed of an output shaft of the transmission is 0 (zero) and when, due to engagement of the friction element, the input and output shafts of the transmission are engaged, the rotation speed of the input shaft is 0 (zero), and even under this condition, the engine is able to keep its operation due to a slip effect of the torque converter.
Accordingly, the above-mentioned systems have the following weak points due to their constructional inherence.
That is, if, during running of a vehicle (viz., transmission output shaft speed>0), the driver moves the shift lever from D-range to N-range by mistake and then noticing the mistake, he or she returns the shift lever back to D-range, there is such a possibility that the rotation speed of the turbine of the torque converter (viz., transmission input shaft speed) increases with progress of the speed change in the transmission. In this case, the estimation to completion of the piston stroke of the friction element (namely, the timing of starting the actual engaging operation of the element) is not achieved.
The above matters will be clearly understood from the following explanation which is made with the aid of
FIGS. 7
to
10
.
That is, as is shown in
FIG. 7
, when, at time “t
1
”, the driver moves the shift lever back to D-range from N-range upon noticing the miss-shifting, a command value “Po” of hydraulic pressure of the friction element is set to instantly increase the pressure to a relatively high level for instantly completing the piston stroke as shown. However, actually, the hydraulic pressure “Pc” fed to the friction element is forced to increase with a certain time lug, as is indicated by a solid curve.
However, during running of the vehicle, it sometimes occurs that with starting of actual engaging operation of the friction element at time “t
2
”, the turbine rotation speed “Nt” (viz., transmission input shaft speed) is increased as shown in
FIG. 7
irrespective of the engine rotation speed “Ne”. In this case, detection of the time “t
2
” when the piston stroke of the friction element is completed (viz., the actual engaging operation starts) is not achieved by the above-mentioned known estimation system because the system is constructed to use the drop of the turbine rotation speed “Nt” as a sign of that completion.
Thus, in reality, upon sensing such sign, it becomes necessary to set the command value “Po” to assume the character as shown by the alternate long and two short dashes line in order that, after the time “t
2
”, the turbine rotation speed “Nt” is smoothly increased to the level “No” of transmission output shaft speed. (In the illustrated example, explanation is based on third gear having a gear ratio of 1:1, and thus, the level is equal to the transmission output shaft speed “No”). Thus, it is necessary to control the actual hydraulic pressure “Pc” in a manner as is indicated by the alternate long and short dash line.
However, actually, due to the above-mentioned reasons, even after the time “t
2
”, the command value “Po” is kept high that is set for controlling the piston stroke.
Accordingly, in the above-mentioned known system, the actual hydraulic pressure “Pc” is forced to increase rapidly toward and finally to the level of the higher command value “Po”, as is indicated by the solid line, so that after the time “t
2
”, the turbine rotation speed “Nt” is rapidly increased to the transmission output shaft speed irrespective of a desired speed acceleration gradient, inducing a possibility of a marked select shock.
Furthermore, as is shown in
FIG. 8
, after the time “t
2
” when the actual engaging operation of the friction element starts following completion of the piston stroke effected by the actual hydraulic pressure “Pc” that is increased to follow the command value “Po” of hydraulic pressure due to the shift back of the shift lever from N-range to D-range at the time “t
1
”, it becomes necessary to increase the command value “Po” of hydraulic pressure in such manner as is indicated by the alternate long and short dash line for the purpose of smoothly effecting the change gear. However, in the known system, for the abovementioned reasons, the timing, viz., the time “t
2
”, of starting the actual engaging operation of the friction element can not be detected because the shifting from N-range to D-range is made under running of the associated vehicle. Thus, in the known system, even after the time “t
2
”, the command value “Po” of hydraulic pressure for the friction element is kept at the value for controlling the piston stroke as is indicated by the solid line, and thus, the actual hydraulic pressure “Pc” is settled to the kept value of the command value “Po” without increasing.
Accordingly, in reality, after the time “t
2
”, with progress of the gear changing operation, it becomes necessary to smoothly bring the turbine rotation speed “Nt” to the transmission output shaft speed as is indicated by the alternate long and short dash li
Abdelnour Dennis
Foley & Lardner
Jatco LTD
Marmor Charles A
LandOfFree
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