Interrelated power delivery controls – including engine control – Transmission control – With clutch control
Reexamination Certificate
2000-11-06
2002-09-24
Marmor, Charles A. (Department: 3747)
Interrelated power delivery controls, including engine control
Transmission control
With clutch control
C477S120000
Reexamination Certificate
active
06454676
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to a control system for an internal combustion engine equipped with an automatic transmission for driving a motor vehicle such as an automobile, car and so forth. More particularly, the present invention is concerned with an automatic-transmission-equipped engine control system which is capable of controlling a driving power at a minimum fuel consumption even in the nonlock-up state of input/output elements of an input clutch (i.e., even when the input clutch which may be constituted by a torque converter including a fluid coupler portion are not in the state where the input element and the output element thereof are directly or straight-forwardly coupled with each other.
2. Description of Related Art
In general, the automatic transmission operatively coupled to an internal combustion engine (hereinafter also referred to simply as the engine) includes an input clutch and a continuously variable transmission (also termed CVT in short) for regulating variably the transmission gear ratio in a stepless manner or continuously.
In the automatic-transmission-equipped engine control system of this type, it is required to optimize the engine operation range with a view to enhancing the fuel-cost performance by resorting to cooperative control of the engine and the continuously variable transmission (CVT) regardless of whether the input clutch is in the nonlock-up state or in a changeover or switching phase intervening between the nonlock-up state and the lock-up state.
As the conventional automatic-transmission-equipped engine control systems known heretofore, there may be mentioned driving power control systems for the motor vehicles such as those described below.
In the first place, reference may be made to Japanese Patent Publication No. 62263/1993. In this publication, there is disclosed such an arrangement of the conventional automatic-transmission-equipped engine control system in which the desired or target driving power demanded by the driver is corrected or modified in dependence on the operating state of the engine, whereon target values of the control parameters for the engine and the automatic transmission are arithmetically determined.
At this juncture, it should be mentioned that the desired or target level or value of the driving power is basically determined on the basis of the accelerator pedal actuation quantity (hereinafter also referred to as the accelerator pedal stroke) and the speed of the motor vehicle on which the engine is mounted. This speed will hereinafter be referred to as the motor vehicle speed or simply as the vehicle speed or car speed. The target value of the driving power thus determined is then corrected in view of the engine operating state such as the rate of change of the accelerator pedal stroke, the slope of a road on which the motor vehicle is running and the running state of the motor vehicle such as the weight of the motor vehicle and the like.
As the target control parameters for the target driving power, there are arithmetically determined the target engine torque and the target transmission gear ratio (target value of the ratio in the rotation speed (rpm) between the input and output shafts of the continuously variable transmission or CVT).
In succession, the engine torque is modified or corrected so that the actual driving power and the target or demanded driving power coincides with each other, while the engine output control unit is so controlled that the transmission gear ratio of the continuously variable transmission (CVT) coincides with the target transmission gear ratio (i.e., target value of the transmission gear ratio).
In this manner, not only the fuel-cost performance of the motor vehicle is improved but also the engine output power control can be realized with enhanced response performance in the transition state of the motor vehicle. Thus, the excellent maneuverability of the motor vehicle can be realized while realizing the target driving power, i.e., driving power demanded by the driver.
Further, Japanese Patent Application Laid-Open Publication No. 332446/1995 (JP-A-7-332446) discloses a speed change control unit for the continuously variable transmission (CVT) in which a speed-change map data prepared with importance being put on to the fuel-cost performance and a speed-change map data prepared with importance being put on the engine power are employed, wherein the transmission gear ratio is determined by interpolating each of the speed-change map data in accordance with a signal bearing correlation to the rate of change of the engine load.
In this way, the speed change control which ensures the most appropriate engine output performance can be carried out in conformance with the acceleration demanded by the driver.
Furthermore, in the continuously variable transmission (CVT) described in Japanese Patent Application Laid-Open Publications Nos. 1135/1999 and 324176/1998, a torque converter or the like is employed as the input clutch, wherein in the state where the input and output shafts of the torque converter are not directly intercoupled (i.e., in the nonlock-up state or in the converter state, so to say), the target transmission gear ratio and the target engine torque are determined.
By way of example, according to the teaching disclosed in Japanese Patent Application Laid-Open Publication No. 1135/1999, the target engine torque is corrected in dependence on the operating state of the mechanism for interrupting intermittently the CVT interrupting mechanism such as the start clutch, torque converter or the like.
Furthermore, according to the teaching disclosed in Japanese Patent Application Laid-Open Publication No. 1135/1999, control of the input shaft power (target driving power) of the automatic transmission (T/M) is realized in the state where the fuel consumption ratio is most preferable at the time point when the stable operation point at which the engine output torque coincides with the absorption torque of the automatic transmission has been reached.
However, with the conventional automatic-transmission-equipped engine control systems (i.e., driving power control systems) in which the input clutch typified by the fluid coupler such as the torque converter, for example, is employed as the intermittently interrupting mechanism of transmission, there arise inconveniences such described below when such a combination of the engine speed (rpm) and the engine torque is selected which can minimize the fuel consumption ratio in the nonlock-up state of the input/output elements of the input clutch.
More specifically, when such target engine speed and target engine torque which can minimize the fuel consumption in the nonlock-up state mentioned above are selected for controlling correspondingly the continuously variable transmission (CVT) and the intake air quantity regulating unit (throttle actuator), the speed ratio between the input and output shafts of the torque converter will become greater than “1” (one) or the engine speed (rpm) becomes greater than the input speed of the continuously variable transmission (CVT), to say in another way. Consequently, even when the continuously variable transmission (CVT) is controlled optimally, control to realize the demanded or target engine speed is impossible, incurring a problem that the target driving power as demanded by the driver can not be met.
For coping with the problem mentioned above, the engine control system described, for example, in Japanese Patent Application Laid-Open Publication No. 1135/1999 is so arranged as to modify or correct the output shaft torque of the continuously variable transmission (CVT) by dividing it by a torque ratio which is based on the speed ratio between the input shaft and the output shaft of the torque converter.
Owing to the arrangement described above, the driving power control accuracy can certainly be enhanced even in the nonlock-up state of the torque converter. Besides, in the engine control system disclosed in the above-mentioned publicat
Date Toshiaki
Ohuchi Hirofumi
Yonezawa Shiro
Marmor Charles A.
Pang Roger
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