Friction gear transmission systems or components – With lubrication
Reexamination Certificate
1999-07-23
2001-05-08
Estremsky, Sherry (Department: 3681)
Friction gear transmission systems or components
With lubrication
C476S010000
Reexamination Certificate
active
06227996
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an oil pressure control device of toroidal continuously variable transmission for a vehicle.
BACKGROUND OF THE INVENTION
A toroidal continuously variable transmission comprises power rollers between an input disk and output disk, and a rotation of the input disk is transmitted to the output disk via the power rollers. When trunnions supporting the power rollers are displaced vertically in mutually opposite directions by hydraulic actuators, the power rollers incline, and the ratio of the rotation speed of the input disk to the rotation speed of the output disk, i.e., a speed ratio, varies.
Tokkai Hei 2-163562 published by the Japanese Patent Office in 1990 discloses an oil pressure control device of the toroidal continuously variable transmission comprising a first valve and a second valve for operating the actuators which displace the trunnions. The actuators are operated by the first valve during forward running of the vehicle wherein the speed ratio varies widely, and by the second valve during reverse running of the vehicle.
SUMMARY OF THE INVENTION
A change-over between the first valve and the second valve is performed by a change-over valve. The change-over valve comprises a spool displaced by an arm which swings according to the running direction of the vehicle, and the first valve and second valve are selectively connected to the actuators according to the displacement of the spool.
In such a change-over valve, however, the contact point of the arm and the spool tend to suffer wear.
It is therefore an object of this invention to reduce wear between an arm and a spool due to a change-over operation of the change-over valve.
In order to achieve the above object, this invention provides an oil pressure control device of a toroidal continuously variable transmission for a vehicle, the transmission comprising a toroidal unit, and a hydraulic actuator for driving the toroidal unit. The device comprises a first valve and a second valve for operating the actuator, an arm which changes a rotation direction according to a running direction of the vehicle, and a change-over valve comprising a spool in contact with the arm. The change-over valve selectively connects the first valve and the second valve to the actuator according to a rotational displacement of the arm. The arm comprises an arc part in contact with the spool, and a locus of the center of curvature of the arc part, when the spool is displaced, intersects with a perpendicular line dropped from the rotation center of the arm to the center axis of the spool.
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: 2774376 (1956-12-01), Young
patent: 4469061 (1984-09-01), Ajiki et al.
patent: 4558667 (1985-12-01), Inagaki et al.
patent: 5542890 (1996-08-01), Nakano et al.
patent: 5993349 (1999-11-01), Sugihara
patent: 6086505 (2000-07-01), Sakai
patent: 0 373 649 (1990-06-01), None
patent: 2 643 676 (1990-08-01), None
patent: 2-163562 (1990-06-01), None
Estremsky Sherry
Foley & Lardner
Lewis Tisha D.
Nissan Motor Co,. Ltd.
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