Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Transmission control
Reexamination Certificate
1999-06-23
2001-09-18
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Transmission control
C477S068000
Reexamination Certificate
active
06292730
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to speed ratio control of a continuously variable transmission of a vehicle.
BACKGROUND OF THE INVENTION
Tokkai Hei 8-270772 published by the Japanese Patent Office in 1996 discloses a speed ratio control device of a toroidal continuously variable transmission which transmits an output torque of an engine to drive wheels of a vehicle at an arbitrary speed ratio. This prior art specifically discloses feedback correction of the speed ratio of the transmission as well as a torque shift error correction. The torque shift error is a speed ratio error due to a deformation of trunnions supporting power rollers of the transmission when the output torque of the engine, or in other words, the input torque of the transmission varies.
SUMMARY OF THE INVENTION
Feedback control of the speed ratio is performed based on a deviation of a real speed ratio from a target speed ratio. Herein, the real speed ratio is obtained by dividing an input rotation speed of the transmission by an output rotation speed. For this purpose, a control device is provided with an input rotation speed sensor and an output rotation speed sensor.
With respect to the torque shift error correction, the engine output torque is estimated from an engine rotation speed and a throttle opening. For this purpose, the control device is provided with an engine rotation speed sensor and a throttle opening sensor.
In both feedback correction and torque shift error correction, when rotation sensors related to the correction do not function correctly, there is a possibility that the control device will output a command signal exceeding a hardware operation limit of the transmission. Such a command signal, however, adversely affects the precision and response time of the speed ratio control.
It is therefore an object of this invention to prevent an extraordinary speed ratio control from being performed when an abnormality is detected in any of the rotation speed sensors.
In order to achieve the above object, this invention provides a speed ratio control device for use with a continuously variable transmission transmitting an output torque of an engine to a drive wheel of a vehicle at an arbitrary speed ratio. The device comprises a sensor for detecting a rotation speed of the engine, a sensor for detecting an input rotation speed of the transmission, a sensor for detecting an output rotation speed of the transmission, and a microprocessor programmed to control the speed ratio of the transmission within a predetermined speed ratio range based on output signals from the sensors, perform a determination if any of the sensors has abnormality based on the output signals from the sensors, and correct the predetermined speed ratio range to be narrower when any of the sensors has been determined to have abnormality.
This invention also provides a speed ratio control method of a continuously variable transmission transmitting an output torque of an engine to a drive wheel of a vehicle at an arbitrary speed ratio. The method comprises detecting a rotation speed of the engine from an output signal from an engine rotation speed sensor, detecting an input rotation speed of the transmission from an output signal from an input rotation speed sensor, detecting an output rotation speed of the transmission from an output signal from an output rotation speed sensor, controlling the speed ratio of the transmission within a predetermined speed ratio range based on the output signals from the sensors, performing a determination if any of the sensors has abnormality based on the output signals from the sensors, and correcting the predetermined speed ratio range to be narrower when any of the sensors has been determined to have abnormality.
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: 4764156 (1988-08-01), Ohkumo
patent: 4819187 (1989-04-01), Yasue et al.
patent: 4823644 (1989-04-01), Ohkumo
patent: 5074392 (1991-12-01), Hasegawa et al.
patent: 5287772 (1994-02-01), Aoki et al.
patent: 5682866 (1997-11-01), Shimizu et al.
patent: 5897056 (1999-04-01), Morikawa et al.
patent: 6073072 (2000-06-01), Ishii et al.
patent: 5-294175 (1993-11-01), None
patent: 8-270772 (1996-10-01), None
Koga Masato
Takizawa Satoshi
Watanabe Mitsuru
Foley & Lardner
Nguyen Tan
Nissan Motor Co,. Ltd.
Tran Dalena
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