Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2001-12-21
2003-06-03
Beaulieu, Yonel (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S093000, C180S170000
Reexamination Certificate
active
06574543
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the automatic control of the running speed of a vehicle.
BACKGROUND OF THE INVENTION
Tokkai Hei 8-295155 published by the Japanese Patent Office in 1996 discloses a fixed running speed control device for a vehicle (cruise control device). The fixed speed control device is a device which maintains a vehicle speed set by a driver. When the driver operates a switch, the vehicle speed at that time is detected by a vehicle speed sensor and is stored in an engine controller as a target vehicle speed. Thereafter, the engine controller performs feedback control on the throttle opening of the engine to make the actual vehicle speed coincide with the target vehicle speed.
For a vehicle equipped with an automatic transmission, the gear ratio is generally determined by an accelerator pedal depression and a vehicle speed. However, the gear ratio cannot be controlled by the accelerator pedal depression since the accelerator pedal depression becomes zero when using the cruise control device. Therefore, the cruise control device firstly determines a throttle opening based on the target automatic transmission output torque and the vehicle speed to achieve a target vehicle speed. Then, the gear ratio is controlled by the determined throttle opening.
SUMMARY OF THE INVENTION
This cruise control device is provided with a disturbance compensator that compensates for the disturbances such as a road gradient. When the engine torque reaches an upper limit before reaching the target output torque for the automatic transmission, the vehicle cannot realize the target vehicle speed. When this situation continues, a disturbance estimation value is increased and the target output torque of the engine also increases as a result. The throttle opening increases as the target output torque of the engine increases, and the automatic transmission performs a downshift when the throttle opening reaches a specific value. This type of downshift causes a sharp increase in the automatic transmission output torque and as a result causes a torque shock.
Suppressing the increase in the target engine torque may prevent such a downshift, but the target vehicle speed will not be achieved if the increase in the target engine torque is suppressed.
It is therefore an object of this invention to provide a cruise control device which advances a downshift performed by the automatic transmission when engine output torque reaches an upper limit.
In order to achieve the above objects, this invention provides a cruise control device used in a vehicle to maintain a vehicle speed at a predetermined vehicle speed, the vehicle being provided with an automatic transmission connected to an engine, and a transmission controller performing gear shift of the automatic transmission in response to a target throttle opening and a vehicle speed.
The cruise control device comprises a sensor which detects a vehicle speed, a sensor which detects a gear ratio of the automatic transmission, and a programmable controller.
The programmable controller is programmed to calculate a target transmission output torque of the automatic transmission which causes the vehicle speed to coincide with the fixed speed; calculate an output torque of the engine by using the target transmission output torque and the gear ratio; determine whether or not a transmission output torque is under a predetermined condition wherein the transmission output torque is impossible to increase; limit the target transmission automatic transmission output torque if the transmission output torque is under the predetermined condition; control the output torque of the engine based on a limited target transmission output torque; calculate the target throttle opening based on the limited target transmission output torque; and output the sum of the target throttle opening value and a predetermined correction value as a throttle opening command value to the transmission controller.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.
REFERENCES:
patent: 6374173 (2002-04-01), Ehlbeck
patent: 8-295155 (1996-11-01), None
Beaulieu Yonel
Foley & Lardner
Nissan Motor Co,. Ltd.
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