Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
2001-01-09
2002-02-05
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C427S007000, C427S010000, C427S099300, C123S319000, C123S339140
Reexamination Certificate
active
06345221
ABSTRACT:
INCORPORATION BY REFERENCE
The disclosure of each of Japanese Patent Applications No. HEI 12-017558 filed on Jan. 26, 2000 and No. HEI 12-149088 filed on May 19, 2000, including the specification, drawings and abstract, is incorporated herein by reference in their entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a control apparatus which is provided in a vehicle equipped with a continuously variable transmission (hereinafter, referred to simply as “CVT”) and a control method of the control apparatus. A speed ratio of the CVT is continuously variable, and the CVT is connected to an output side of a power source of the vehicle.
2. Description of Related Art
As a transmission for a vehicle, for example, a belt type or a Troydal type CVT is known. The belt type CVT consists of an input pulley, an output pulley, a belt, and the like. A width of a groove of each pulley is variable. Each portion of the belt which wraps each pulley takes a shape of a partial circle. A radius of the circle of each pulley can be continuously varied by making the groove width of the input pulley smaller and the groove width of the output pulley greater, or vice versa. As a result, a speed ratio of the belt type CVT can be continuously varied. Here, the speed ratio is a ratio of input revolutions per minute against output revolutions per minute of the CVT. Hereinafter, revolutions per minute are referred to simply as “revolutions”.
The Troydal type CVT consists of a pair of disks (that is, an input disk and an output disk), a power roller, and the like. Each disk has a Troydal face, and the power roller is disposed between both disks such that the power roller contacts each Troydal face. By slanting the power roller, an input radius is increased and an output radius is decreased, or vice versa. Here, the input radius is a distance between an axis of the input disk and a point on which the input disk makes contact with the power roller. In the same way, the output radius is a distance between an axis of the output disk and a point on which the output disk makes contact with the power roller. Consequently, the speed ratio of the Troydal type CVT can be continuously changed.
When a vehicle is equipped with one of the above-mentioned CVTs connected to the output side of an engine, engine revolutions can be smoothly controlled by continuously changing the speed ratio on the basis of a driving condition such as a vehicle speed, a required driving force (which is controlled by an accelerator angle, or the like), and the like. One example of a control device in which the lowest fuel consumption of the engine is achieved by effectively using such a characteristic of the CVT is shown in Japanese Laid-Open Patent Application No. 11-78619. In the control device described therein, a target driving force of a vehicle is determined on the basis of the accelerator angle or the like. A target power of the engine to obtain the target driving force is determined. Target output revolutions of the engine are calculated based on the target power, so that the lowest fuel consumption is achieved. The speed ratio of the CVT is controlled so that the actual output revolutions of the engine are equal to the target output revolutions. On the other hand, a target output torque of the engine for generating the above-mentioned target power is calculated by using a known formula, that is, torque multiplied by revolutions is equal to power. The engine is controlled so that an actual output torque of the engine is equal to the target output torque. By the aforementioned control, the fuel economy of the engine can be improved.
Next, a technique which was already known before the aforementioned Japanese Laid-Open Patent Application No. 11-78619 publication, will be described. In this technique, the target output torque of the engine is calculated by using the actual output revolutions of the engine. The target output torque fluctuates in response to the fluctuation of the actual output revolutions of the engine. When the vehicle is running, the engine is connected to wheels of the vehicle. Consequently, torque is not only transmitted from the engine to the wheels, but torque is also transmitted from the wheels to the engine. Force from the road surface is inputted to the wheels, so that torque to the engine is generated. For example, when the vehicle runs on a rough road, the output revolutions of the engine fluctuate, in accordance with the fluctuation of the load inputted to the wheels. Consequently, the target output torque of the engine varies because the output revolutions of the engine vary, although the target power of the engine is maintained constant. Furthermore, the control of the output torque of the engine has an inevitable minute delay. Consequently, when the engine is controlled so that the output torque of the engine is equal to the target output torque, the driving force fluctuates because of a phase difference between the output torque and the output revolutions of the engine. A jerkiness of the vehicle may therefore occur.
In the control apparatus described in the above publication, the target output torque of the engine is calculated by dividing the target power by the target output revolutions. This control prevents the target output torque of the engine from fluctuating.
However, when a driver depresses an accelerator pedal of the vehicle suddenly and strongly, the accelerator angle increases radically. Subsequently, a difference between the target output revolutions and the actual output revolutions of the engine becomes larger because the target output revolutions of the engine are higher in accordance with increasing of the target driving force. When the target output torque of the engine is calculated by using the target output revolutions, the driving force of the vehicle is lower than the driving force required by the driver. The acceleration performance of the vehicle therefore does not satisfy the acceleration performance required by the driver because the engine is controlled only based on minimum fuel consumption. Consequently, the engine performance is lower and the driver may not be satisfied with the drivability of the vehicle.
SUMMARY OF THE INVENTION
It is thus one object of the present invention to solve the aforementioned problems.
Another object of the invention is to restrain the fluctuation of the driving force which is caused by the load to the vehicle from outside.
yet another object is to improve the drivabilty of the vehicle by outputting enough torque from the power source in a transient driving condition of the vehicle.
According to the invention, the above and other objects are achieved by a control apparatus in a vehicle which is equipped with a power source and a continuously variable transmission. The continuously variable transmission is connected to the power source. The apparatus comprises a target power determinator, a target revolutions determinator, determining means, setting means, and a target torque determinator. The target power determinator determines a target power of the power source. The target revolutions determinator determines target revolutions on the basis of the target power. The determining means determines whether or not the vehicle is in a transient driving condition. The setting means sets the target revolutions as the setting revolutions when the determining means determines that the vehicle is not in the transient driving condition. Furthermore, the setting means sets revolutions different from the target revolutions as the setting revolutions when the determining means determines that the vehicle is in the transient driving condition. The target output torque determinator determines a target output torque of the power source on the basis of the target power and the setting revolutions.
When the vehicle is in a stable driving condition, it is determined that the vehicle is not in the transient driving condition and the target output torque of the power source is set on the basis of the target revolutions of the powe
Hattori Yuji
Kono Katsumi
Matsuo Kenji
Tamura Tadashi
Taniguchi Hiroji
Cuchlinski Jr. William A.
Hernandez Olga
Toyota Jidosha & Kabushiki Kaisha
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