Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Reexamination Certificate
1999-07-14
2001-02-06
Ta, Khoi Q. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
C477S046000, C701S054000
Reexamination Certificate
active
06183390
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to speed ratio control of a vehicle continuously variable transmission which is provided with a manual operation mode.
BACKGROUND OF THE INVENTION
A continuously variable transmission for a vehicle which is operated in a manual operation mode as well as in an automatic operation mode is disclosed in Tokkai Hei 9-196156 published in 1997 by the Japanese Patent Office.
The transmission is provided with a speed ratio controller so as to control the speed ratio of the transmission. The speed ratio controller stores a map defining plural fixed target speed ratios corresponding to various speed ratio grade any of which may be selected by a driver via a selector lever.
When in the manual operation mode, the controller looks up this map for finding the target speed ratio corresponding to the selected speed ratio grade and feedback controls the speed ratio of the transmission such that it coincides with the target speed ratio found in the map. With this controller, therefore, the continuously variable transmission may act as a quasi-manual transmission.
SUMMARY OF THE INVENTION
The toroidal continuously transmission is provided with power rollers which vary their gyration angle according to an oil pressure supplied from an oil pressure control valve. The speed ratio of the transmission varies according to the variation of the gyration angle of the power rollers. The variation of the speed ratio is fed back to the oil pressure control valve via a feedback mechanism connected to a trunnion which supports one of the power rollers.
When an output torque of an engine of the vehicle changes, the torque input to the transmission changes accordingly. Due to the change of the input torque, the equilibrium of forces acting on the power roller is affected and the trunnion supporting the power roller suffers deformation.
This deformation of the trunnion introduces an error in the speed ratio fed back via the feedback mechanism to the oil pressure control valve. This error is known as a torque shift error in the toroidal continuously transmission.
Oil pressure in the oil pressure control valve is feedback controlled by the controller so that the deviation of the real speed ratio of the transmission from the target speed ratio derived from the map becomes zero. When the deviation due to the above torque shift error is recognized, therefore, the oil pressure is immediately controlled so as to eliminate the deviation.
However, due to this control, the speed ratio may oscillate before it comes to coincide with the target speed ratio.
In the manual operation mode wherein the speed ratio should be fixed, the driver may experience some discomfort from the oscillation of speed ratio.
It is therefore an object of this invention to suppress oscillation of speed ratio of the toroidal continuously variable transmission in the manual operation mode.
In order to achieve the above object, this invention provides a speed ratio controller for use with a toroidal continuously variable transmission which transmits an input torque from an engine to a drive wheel of a vehicle at an arbitrary speed ratio.
The controller comprises a member for selecting either of an automatic operation mode and a manual operation mode of the transmission, a member for designating a speed ratio grade in the manual operation mode, a sensor for detecting the input torque of the transmission,a sensor for detecting a real speed ratio of the transmission, and a microprocessor programmed to calculate a target speed ratio according to the speed ratio grade designated by the speed ratio grade designating member, feedback control the speed ratio of the transmission such that the real speed ratio coincides with the target speed ratio, and prevent the speed ratio of the transmission from varying irrespective of the target speed ratio, after the input torque is varied.
This invention also provides a method for controlling a speed ratio of a toroidal continuously variable transmission. The toroidal continuously variable transmission transmits an input torque from an engine to a drive wheel of a vehicle at an arbitrary speed ratio, and comprises a member for selecting either of an automatic operation mode and a manual operation mode of the transmission and a member for designating a speed ratio grade in the manual operation mode.
The method comprises detecting the input torque of the transmission, detecting a real speed ratio of the transmission, calculating a target speed ratio according to the speed ratio grade designated by the speed ratio grade designating member, feedback controlling the speed ratio of the transmission such that the real speed ratio coincides with the target speed ratio, and preventing the speed ratio of the transmission from varying irrespective of the target speed ratio, after the input torque is varied.
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: 5997430 (2000-06-01), Tanabe
patent: 6076031 (2000-06-01), Takizawa et al.
patent: 9-196156 (1997-07-01), None
Koga Masato
Minagawa Yuusuke
Narita Yasushi
Takizawa Satoshi
Watanabe Mitsuru
Foley & Lardner
Nissan Motor Co,. Ltd.
Ta Khoi Q.
LandOfFree
Speed ratio controller and control method of toroidal... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Speed ratio controller and control method of toroidal..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Speed ratio controller and control method of toroidal... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2608563