Endless belt power transmission systems or components – Pulley with belt-receiving groove formed by drive faces on... – Fluid pressure actuator for adjustment of member
Reexamination Certificate
2002-04-24
2004-03-30
Fenstermacher, David (Department: 3682)
Endless belt power transmission systems or components
Pulley with belt-receiving groove formed by drive faces on...
Fluid pressure actuator for adjustment of member
C474S018000
Reexamination Certificate
active
06712724
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a belt-type continuously variable transmission (CVT), and more particularly to a belt-type CVT whose driving pulley and driven pulley are formed into a two-piston structure.
U.S. Pat. No. 5,295,915 discloses a belt-type CVT whose driving pulley and driven pulley are formed into a two-piston structure.
SUMMARY OF THE INVENTION
However, the belt-type CVT of U.S. Pat. No. 5,295,915 has a problem that it is necessary that a torque cam mechanism for controlling a belt clamping force is disposed at an end of an input shaft. This arrangement increases an axial dimension of the belt-type CVT and generates a considerable loss of a hydraulic pump.
It is therefore an object of the present invention to provide an improved belt-type CVT which ensures a high pump-efficiency without increasing an axial dimension of the CVT.
An aspect of the present invention resides in a belt-type continuously variable transmission which comprises a driving pulley having a driving-side transmission piston chamber and a driving-side clamp piston chamber; a driven pulley having a driven-side transmission piston chamber and a driven-side clamp piston chamber; an endless belt wound around the driving pulley and the driven pulley so as to transmit a driving force from the driving pulley to the driven pulley; and a hydraulic circuit controlling effective pulley diameters of the driving pulley and the driven pulley relative to the belt according to vehicle condition indicative information to continuously vary a transmission ratio of the belt-type continuously variable transmission; wherein at least one of first and second relationships is satisfied, the first relationship being that an effective cross sectional area of the driving-side transmission piston chamber is equal to an effective cross sectional area of the driven-side transmission piston chamber, and the second relationship being that an effective cross sectional area of the driving-side clamp piston chamber is equal to an effective cross sectional area of the driven-side clamp piston chamber; wherein one of third and fourth relationships is satisfied, the third relationship being that a common passage of the hydraulic circuit fluidly communicates the driving-side transmission piston chamber and the driven-side transmission piston chamber, the fourth relationship being that the common passage fluidly communicates the driving-side clamp piston chamber and the driven-side clamp piston chamber.
REFERENCES:
patent: 5295915 (1994-03-01), Friedmann
patent: 6050911 (2000-04-01), Feuchter et al.
patent: 6336878 (2002-01-01), Ehrlich et al.
patent: 6336880 (2002-01-01), Agner
patent: 6394920 (2002-05-01), Morlok
patent: 2001/0031678 (2001-10-01), Schmid et al.
patent: 2001/0044350 (2001-11-01), Nishigaya et al.
Fenstermacher David
JATCO LTD
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