Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Reexamination Certificate
1999-06-11
2001-01-16
Estremsky, Sherry (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
C477S046000
Reexamination Certificate
active
06174261
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to suppression of noise accompanying high engine rotation speed in a vehicle.
BACKGROUND OF THE INVENTION
In a continuously variable transmission (CVT), the variation of speed ratio when an accelerator pedal is fully depressed is set for example as follows.
First, the speed ratio is changed to a maximum value, i.e., the speed ratio at which an output rotation speed is lowest relative to an input rotation speed. Second, the engine rotation speed is increased to a maximum region, and a running speed is then increased by decreasing the speed ratio.
In this speed ratio control, the engine rotation speed remains in the maximum region for a long period from when the accelerator pedal is depressed to when the vehicle speed reaches the speed desired by the driver, and this causes a large noise outside the vehicle.
In order to solve this noise problem, Tokkai Hei 5-126239 published by the Japanese Patent office in 1993 discloses a method wherein a transient target speed ratio is set so that the engine rotation speed increases gradually for a sudden operation of the accelerator pedal.
According to this method, when the accelerator pedal is depressed, the engine rotation speed increases gradually due to the fact that the speed ratio changes to the maximum value comparatively slowly. In the period required to reach the vehicle speed depending on depression of the accelerator pedal, the time during which the engine rotation speed is in the maximum region is short, so vehicle noise due to acceleration is less.
SUMMARY OF THE INVENTION
However, when the time constant of the speed ratio variation is changed, the time required for the engine rotation speed to reach the maximum region is long, and as a result, there is less bodily perception of acceleration.
It is therefore an object of this invention to suppress noise outside a vehicle without affecting the bodily perception of acceleration.
In order to achieve the above object, this invention provides a speed ratio controller for use with a vehicle which runs under a drive force of an engine via a continuously variable transmission. The controller comprises a sensor for detecting a running condition of the vehicle, a sensor for detecting a vehicle speed, and a microprocessor programmed to calculate a first final target input rotation speed of the continuously variable transmission based on the running condition, calculate a second final target input rotation speed by limiting an upper limit of the first final target input rotation speed with a predetermined value, calculate a second final target speed ratio from the vehicle speed and second final target input rotation speed, calculate a first final target speed ratio from the vehicle speed and first final target input rotation speed, calculate a time constant of a speed ratio variation based on the first final target input rotation speed, set a transient target speed ratio from the second final target speed ratio and the time constant, and control a speed ratio of the continuously variable transmission to be equal to the transient target speed ratio.
This invention also provides a speed ratio control method for a vehicle which runs under a drive force of an engine via a continuously variable transmission. The method comprises detecting a running condition of the vehicle, detecting a vehicle speed, calculating a first final target input rotation speed of the continuously variable transmission based on the running condition, calculating a second final target input rotation speed by limiting an upper limit of the first final target input rotation speed with a predetermined value, calculating a second final target speed ratio from the vehicle speed and second final target input rotation speed, calculating a first final target speed ratio from the vehicle speed and first final target input rotation speed, calculating a time constant of a speed ratio variation based on the first final target input rotation speed, setting a transient target speed ratio from the second final target speed ratio and the time constant, and controlling a speed ratio of the continuously variable transmission to be equal to the transient target speed ratio.
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.
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Koga Masato
Minagawa Yuusuke
Narita Yasushi
Takizawa Satoshi
Watanabe Mitsuru
Estremsky Sherry
Foley & Lardner
Nissan Motor Co,. Ltd.
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