Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Reexamination Certificate
2000-09-29
2002-02-05
Nguyen, Tan (Department: 3661)
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
C701S051000, C477S037000, C477S046000, C477S044000, C477S045000, C477S048000
Reexamination Certificate
active
06345226
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to speed ratio control of a vehicle equipped with a slip control system and a continuously variable transmission (CVT).
BACKGROUND OF THE INVENTION
When slip control systems, such as an anti-lock brake system (ABS) or a traction control system (TCS), are operating, a braking force or drive force fluctuates and a sensor detected vehicle speed (=drive wheel speed) fluctuates. Therefore, if speed ratio control is performed based on the sensor detected vehicle speed, a speed ratio may vary suddenly. If the speed ratio varies suddenly during operation of a slip control system, the effectiveness of slip suppression by the slip control system will decline.
In JP-A-H2-234851 published by the Japanese Patent Office in 1990, a technique is disclosed of preventing a sudden change of speed ratio so as to prevent the decline of slip suppression by performing speed ratio control based not on the sensor detected vehicle speed, but on an estimated vehicle speed (=driven wheel speed).
SUMMARY OF THE INVENTION
However, in the aforesaid speed change control device, if the estimated vehicle speed becomes abnormal because of:
an incorrect estimation of the vehicle speed due to a failure of a sensor, etc.,
a communication error due to a break in a harness, or
a running on a chassis dynamometer (estimated vehicle speed is zero as driven wheels are on a free roller and do not rotate),
the speed ratio changes suddenly when the vehicle speed used for speed ratio control changes over from the sensor detected vehicle speed to the estimated vehicle speed, or from the estimated vehicle speed to the sensor detected vehicle speed according to the operating state of a slip control system. Also, the speed ratio will vary abruptly if the estimated vehicle speed varies abruptly when the slip control system operates and speed ratio control is performed based on the estimated vehicle speed. If the speed ratio varies suddenly, a shift shock will occur or the slip will recur.
Moreover, as the estimated vehicle speed is always zero when running on the chassis dynamometer, if the slip control system operates and the estimated vehicle speed is used for speed ratio control instead of the sensor detected vehicle speed, the speed ratio will suddenly change to the maximum speed ratio.
It is therefore an object of this invention to prevent the speed ratio from varying suddenly even if the estimated vehicle speed becomes abnormal, and to prevent slip with shift shock from recurring.
In order to achieve the above object, the present invention provides a speed ratio control device used with a vehicle comprising a continuously variable transmission and a slip control system for suppressing a slip of a drive wheel by controlling either of braking force and drive force. The device comprises a sensor which detects a vehicle speed, an actuator which varies a speed ratio of the transmission, and a microprocessor programmed to estimate the vehicle speed based on a running state, compute a target speed ratio of the transmission based on the sensor detected vehicle speed when the slip control system is not operating, compute the target speed ratio of the transmission based on the estimated vehicle speed when the slip control system is operating, and control the actuator so that the speed ratio of the transmission approaches the target speed ratio. The microprocessor is further programmed to determine whether the estimated vehicle speed is abnormal, and prohibit use of the estimated vehicle speed in speed ratio control when it is determined that the estimated vehicle speed is abnormal.
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: 5109962 (1992-05-01), Sato
patent: 5240094 (1993-08-01), Suzuki
patent: 5383125 (1995-01-01), Hibi
patent: 6146307 (2000-11-01), Takizawa et al.
patent: 6157884 (2000-12-01), Narita et al.
patent: 6165101 (2000-12-01), Takizawa et al.
patent: 6183390 (2001-02-01), Koga et al.
patent: 43 01 591 (1993-07-01), None
patent: 0 373 865 (1990-06-01), None
patent: 2-234851 (1990-09-01), None
patent: 403079852 (1991-04-01), None
Akanuma Masatoshi
Koga Masato
Shimanaka Shigeki
Takayama Junya
Takizawa Satoshi
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