Infinite speed ratio continuously variable transmission

Details Infinite speed ratio continuously variable transmission Infinite speed ratio continuously variable transmission

2001-03-30

2003-12-09

Lavinder, Jack (Department: 3683)

Planetary gear transmission systems or components

Nonplanetary variable speed or direction transmission...

Plural power paths to planetary gearing

C475S215000, C475S208000, C477S039000

Reexamination Certificate

active

06659901

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to improvement of an infinite speed ratio continuously variable transmission used in vehicles, etc.
BACKGROUND OF THE INVENTION
Examples of vehicle transmissions known in the art are belt type or toroidal type continuously variable transmissions. An infinite speed ratio continuously variable transmission (hereafter referred to as IVT) is also known wherein a fixed speed ratio transmission and planetary gear set are combined with a continuously variable transmission (hereafter referred to as CVT) to enlarge the speed change region of the CVT, and a speed ratio can be varied up to infinity, as disclosed for example in Tokkai Hei 10-325459 published by the Japanese Patent Office in 1998.
In such the IVT, torque transmission and speed ratio are controlled by a differential pressure acted on a piston of a hydraulic actuator which drives a trunnion. As shown in
FIG. 17
, by engaging a power recirculation mode clutch and releasing a direct mode clutch, a power recirculation mode can be selected wherein a unit speed ratio (hereafter referred to as IVT ratio ii, unit input shaft rotation speed/unit output shaft rotation speed) is varied continuously from a negative value to a positive value including infinity (=geared neutral point), according to the difference of speed ratio of the CVT and fixed speed ratio transmission. Alternatively, by releasing the power recirculation mode clutch and engaging the direct mode clutch, a direct mode can be selected wherein speed change control is performed according to the speed ratio of the CVT (hereafter referred to as CVT ratio ic).
If the change-over between the power recirculation mode and direct mode is performed at or in the vicinity of the rotation synchronous point RSP (
FIG. 17
) where the IVT ratio ii coincides in the power recirculation mode and direct mode, the change-over between the power recirculation mode clutch and direct mode clutch can be made while suppressing shock.
SUMMARY OF THE INVENTION
However, in the aforesaid prior art, except when a change-over of running mode was performed, the power recirculation mode clutch and direct mode clutch were engaged and released based on independently controlled clutch pressures, and if there was a fault in the control unit or a valve stick occurred, there was a possibility that both clutches would simultaneously engage.
For example, when the vehicle is traveling in the power recirculation mode, if the direct mode clutch is engaged due to a fault, the IVT ratio ii must take a value corresponding to the rotation synchronous point RSP, so the CVT ratio ic is forced to vary towards the rotation synchronous point RSP as shown by the dot-and-dash line of FIG.
17
.
Conversely, when the vehicle is traveling in the direct mode, if the power recirculation mode clutch is engaged due to a fault, the IVT ratio ii must again take a value corresponding to the rotation synchronous point RSP as described above, so the CVT ratio ic is forced to vary towards the rotation synchronous point RSP. In both modes, when a fault occurs, a speed change ratio may vary.
It is therefore an object of this invention, which was conceived in view of the above problem, to prevent a speed change from varying towards the rotation synchronous point RSP due to a fault in a control device.
In order to achieve above object, this invention provides a toroidal continuously variable transmission comprising an infinite speed ratio continuously variable transmission, comprising a continuously variable transmission which can vary speed ratio continuously, a fixed speed ratio transmission, a unit input shaft which connects to input side of the continuously variable transmission and the fixed speed ratio transmission, a unit output shaft which connects to output side of the continuously variable transmission and the fixed speed ratio transmission via a planetary gear set, a first clutch device interposed between the fixed speed ratio transmission and the planetary gear set, which sets a power recirculation mode, a second clutch device interposed between the continuously variable transmission and the unit output shaft, which sets a direct mode, and a clutch control unit which controls the power recirculation mode and the direct mode by selectively engaging the clutches of the first and second clutch devices according to the running state, wherein at least one of the first clutch device and the second clutch device provides a one way clutch, a first clutch interposed in series to the one way clutch and a second clutch which is provided in parallel to the one way clutch, and the clutch control unit only permits engaging one of the first clutch device and the second clutch device when both the first clutch device and the second clutch device can transmit torque in both directions.
This invention further provides an infinite speed ratio continuously variable transmission, comprising a continuously variable transmission which can vary speed ratio continuously, a fixed speed ratio transmission, a unit input shaft which connects to input side of the continuously variable transmission and the fixed speed ratio transmission, a unit output shaft which connects to output side of the continuously variable transmission and the fixed speed ratio transmission via a planetary gear set, a first clutch device interposed between the fixed speed ratio transmission and the planetary gear set, which sets a power recirculation mode, a second clutch device interposed between the continuously variable transmission and the unit output shaft, which sets a direct mode, at least one of the first clutch device and the second clutch device can select a state from a engaging state which transmit torque in at least one direction, a engaging state which transmit torque in both direction, and a release state which does not transmit torque, and a clutch control unit which controls the power recirculation mode and the direct mode by selectively engaging the clutches of the first and second clutch devices according to the running state, wherein the clutch control unit only permits engaging one of the first clutch device and the second clutch device when both the first clutch device and the second clutch device can transmit torque in both directions.


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patent: 7-139608 (1995-05-01), None
patent: 10-325459 (1998-12-01), None

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