Interrelated power delivery controls – including engine control – Transmission control – Continuously variable friction transmission
Reexamination Certificate
1999-12-14
2001-11-06
Bonck, Rodney H. (Department: 3681)
Interrelated power delivery controls, including engine control
Transmission control
Continuously variable friction transmission
Reexamination Certificate
active
06312357
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to control of a non-finite speed ratio transmission device for vehicles using a toroidal continuously variable transmission.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 5,935,039 discloses a non-finite speed ratio transmission device which combines a toroidal continuously variable transmission, a fixed speed ratio transmission and a planetary gear unit in order to obtain a speed ratio range larger than the toroidal continuously variable transmission. Tokkai Hei 10-267117 published by the Japanese Patent Office in 1997 discloses a controller which controls the creep torque applied to a drive wheel at low vehicle speed according to the operating state of the brake in such an non-finite speed ratio transmission device.
This controller assigns a step number obtained by subtracting or adding a fixed amount from a step number corresponding to a geared neutral position GNP to a step motor, and increases or decreases a difference of oil pressure acting on a trunnion from two directions using a relief valve.
The geared neutral position GNP is a rotating position of the step motor at which the output rotation speed of the non-finite speed ratio transmission device becomes zero.
SUMMARY OF THE INVENTION
The response characteristics of oil pressure control generally decline when the temperature of the oil transmitting the oil pressure decreases.
As a result, the precision with which this controller controls creep torque is low at low temperatures.
It is therefore an object of this invention to increase the precision of creep torque control at low temperatures of a non-finite speed ratio transmission device.
In order to achieve the above object, this invention provides a speed ratio controller for use with a non-finite speed ratio transmission device of a vehicle. The transmission device comprises a toroidal continuously variable transmission which causes a speed ratio to vary according to a gyration angle variation of a power roller gripped between an input disk and output disk. The power roller vares the gyration angle according to a displacement of a supporting member which supports the power roller. The transmission device further comprises a fixed speed ratio transmission which varies a rotation speed of the input disk with a fixed speed ratio, and a planetary gear unit which varies a rotation direction of a final output shaft according to a relation between a rotation output speed of the toroidal continuously variable transmission and a rotation output speed of the fixed speed ratio transmission.
The speed ratio controller comprises a hydraulic cylinder which displaces the supporting member according to a supplied hydraulic pressure, a control valve which supplies a hydraulic pressure to the hydraulic cylinder according to a displacement position thereof, an actuator which displaces the control valve according to a command signal, a feedback member which connects the supporting member and control valve and feeds back the displacement of the supporting member to the control valve by causing the control valve to displace in the reverse direction to the displacement direction due to the actuator, a sensor which detects a running state of the vehicle, a sensor which detects the speed ratio of the toroidal continuously variable transmission, and a microprocessor. The microprocessor is programmed to determine whether or not the vehicle running state corresponds to a predetermined state, calculate a new command signal based on a predetermined creep torque and the speed ratio of the toroidal continuously variable transmission when the vehicle running state corresponds to the predetermined state, and output the new command signal to the actuator.
This invention also provides a method for controlling a speed ratio of a non-finite speed ratio transmission device of a vehicle. The transmission device comprises a toroidal continuously variable transmission which causes a speed ratio to vary according to a gyration angle variation of a power roller gripped between an input disk and output disk, the power roller varying the gyration angle according to a displacement of a supporting member which supports the power roller, a hydraulic cylinder which displaces the supporting member according to a supplied hydraulic pressure, a control valve which supplies a hydraulic pressure to the hydraulic cylinder according to a displacement position thereof, an actuator which displaces the control valve according to a command signal, a feedback member which connects the supporting member and control valve and feeds back the displacement of the supporting member to the control valve by causing the control valve to displace in the reverse direction to the displacement direction due to the actuator, a fixed speed ratio transmission which varies a rotation speed of the input disk with a fixed speed ratio, and a planetary gear unit which varies a rotation direction of a final output shaft according to a relation between a rotation output speed of the toroidal continuously variable transmission and a rotation output speed of the fixed speed ratio transmission.
The method comprises detecting a running state of the vehicle, detecting the speed ratio of the toroidal continuously variable transmission, determining whether or not the vehicle running state corresponds to a predetermined state, calculating a new command signal based on a predetermined creep torque and the speed ratio of the toroidal continuously variable transmission when the vehicle running state corresponds to the predetermined state, and outputting the new command signal to the actuator.
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patent: 10-267117 (1998-10-01), None
Kuramoto Hiroaki
Nishio Motoharu
Sakai Hiromasa
Bonck Rodney H.
Foley & Lardner
Nissan Motor Co,. Ltd.
Pang Roger
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