Interrelated power delivery controls – including engine control – Transmission control – Transmission controlled by engine
Reexamination Certificate
1997-12-29
2001-07-03
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Transmission controlled by engine
C477S154000, C477S110000
Reexamination Certificate
active
06254512
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of Japanese application number 08-347103, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to an apparatus for controlling the oil pressure in an automatic transmission of a vehicle when changing a transmission speed (a gear ratio), and more particularly to a control apparatus and a method for engaging and disengaging a clutch by directly and electrically controlling the oil pressure acting on the clutch (friction coupling device).
An apparatus disclosed in Japanese Patent Application Un-examined laid-open No. JP-A-63-263248 is a widely known example of apparatus for engaging and disengaging the clutch by electrically controlling the clutch operating oil pressure. This Japanese Patent Unexamined Publication described a system in which when controlling the oil pressure acting on the disengaging clutch to change the transmission speed, the revolution speed of the transmission input shaft (turbine revolution speed) is controlled to follow up the preset target value of the revolution speed of the transmission input shaft. This invention proposes a method for performing stable control of the disengaging clutch, realized by feedback control of the operating oil pressure of the disengaging clutch according to the change in the input shaft revolution speed which changes with the engaging state of the engaging clutch.
According to the above-mentioned well-known example, the operating oil pressure of the disengaging clutch is controlled by feedback of the transmission input shaft revolution speed. However, there is a difficulty in discriminating between the change in the input shaft revolution speed caused by an increase of the engine torque due to pressing down on the accelerator pedal, and the change of the input shaft revolution speed attending on the disengagement of the disengaging clutch. This difficulty results in the degradation of the controllability of the operating oil pressure control. Accordingly, a great shock at gear change is inevitable, which arises from a shift in disengaging timing of the disengaging clutch when changing the gears.
SUMMARY OF THE INVENTION
The present invention has as its object to provide a good speed change characteristic by clearly discriminating between the change in the input shaft revolution speed due to the increase of the engine torque, and the change in the input shaft revolution speed attending on the disengagement of the disengaging clutch, and accurately controlling the operating oil pressure of the disengaging clutch.
It is becoming increasingly important to establish a transmission control system which eliminates the one way clutch for the purposes of down-sizing, weight reduction, and improved controllability of the automatic transmission, and directly and electrically controlling the clutch operating oil pressure for engaging and disengaging the clutch. In the above system, it is indispensable to control with high accuracy the clutch operating oil pressure for a period from when a speed change start command signal is issued until the gears are actually changed. In real motor vehicles, however, many man-hours have been spent for matching which is required according to individual differences among the transmissions attributable to mass-production, the wear of the clutch due to secular change, the change of the clutch operating oil pressure accompanying the changes in oil temperature, etc. Therefore, it is essential to detect changes in the clutch operating oil pressure by using some sensor signal, and perform feedback control based on detection results.
However, when the above-mentioned feedback control is executed according to only one piece of data on revolution speed, it is impossible to discriminate between the change in the input shaft revolution speed caused by the rise in the engine torque due to pressing down on the accelerator pedal or the change in the input shaft revolution speed attending on the disengagement of the disengaging clutch. The resulting inadequate controllability of the operating oil pressure control invariably gives rise to a great shock in changing gears.
The above problem is solved by control apparatus as follows. The present invention provides a hydraulic control apparatus of an automatic transmission, which has a pressure-adjust command generating unit for changing a transmission speed by engaging and disengaging a specified friction coupling device in the automatic transmission connected to an engine, and adjusting an oil pressure acting on the friction coupling device and varying a pressure adjusting characteristic when changing the speed, comprising:
a speed change command signal generating unit for generating speed change command signals representing a speed change ratio;
a transmission output shaft revolution speed detecting unit for detecting revolution speed of an output shaft of the automatic transmission;
a transmission input shaft revolution speed detecting unit for detecting revolution speed of an input shaft of the automatic transmission;
a revolution ratio calculating unit for calculating an output shaft revolution ratio of the transmission by using two revolution speeds obtained by the two revolution speed detecting units; and
a target revolution ratio setting unit for storing or calculating a target value of the revolution ratio,
wherein there is further provided an oil pressure correction value calculating unit for correcting an oil pressure acting on the friction coupling device so that an actual revolution ratio, calculated by the revolution ratio calculating unit, follows up the target revolution ratio when a signal is generated by the speed change command signal generating unit.
Preferably, the hydraulic control apparatus of an automatic transmission further comprises an initial oil pressure command value storing unit for setting a target oil pressure command value for a specified period just after a signal is generated by the speed change command signal, wherein an initial oil pressure command value output from the storing unit is calculated by using a transmission input shaft torque and a transmission input shaft revolution speed as parameters.
Preferably, the hydraulic control apparatus of an automatic transmission further comprises a target engine torque calculating unit for controlling the engine torque so that an actual revolution ratio, calculated by the revolution ratio calculating unit, follows up the target revolution ratio when the signal is generated by the speed change command signal generating unit.
Preferably, the hydraulic control apparatus of an automatic transmission further comprises a hydraulic pressure changing (updating) unit for inputting the oil pressure command value, after control has been performed so that an actual revolution ratio calculated by the revolution ratio calculating unit follows up the target revolution ratio, into the initial oil pressure command value storing unit to update the stored value of the initial oil pressure command value storing unit.
REFERENCES:
patent: 4680988 (1987-07-01), Mori
patent: 5163342 (1992-11-01), Pollack
patent: 5251509 (1993-10-01), Pollack et al.
patent: 5267491 (1993-12-01), Sumimoto
patent: 63-263248 (1988-10-01), None
Minowa Toshimichi
Ochi Tatsuya
Estremsky Sherry
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
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