Planetary gear transmission systems or components – Nonplanetary variable speed or direction transmission... – Nonplanetary transmission is friction gearing
Reexamination Certificate
1999-12-14
2001-09-11
Marmor, Charles A (Department: 3681)
Planetary gear transmission systems or components
Nonplanetary variable speed or direction transmission...
Nonplanetary transmission is friction gearing
C475S070000
Reexamination Certificate
active
06287232
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a non-finite speed ratio transmission device for vehicles using a toroidal continuously variable transmission.
BACKGROUND OF THE INVENTION
A non-finite speed ratio transmission device which combines a toroidal continuously variable transmission (CVT), a fixed speed ratio transmission and a planetary gear unit for increasing the speed ratio range of the CVT is disclosed in Tokkai Hei 9-42428 published by the Japanese Patent Office in 1997.
In this device, the engine output is input to both the CVT and a fixed speed ratio transmission. The output shaft of the CVT is joined to a sun gear of the planetary gear unit and an output shaft of the fixed speed ratio transmission is joined to a carrier of planet gears of the planetary gear unit via a power circulation clutch. A ring gear of the planetary gear unit is joined to the drive shaft which drives the wheels. The output shaft of the CVT is also joined to the drive shaft via a direct clutch.
In this device, two power transmission modes are used, i.e., a direct drive mode in which a direct clutch is engaged and a power circulation clutch is disengaged, and a power circulation mode in which the direct clutch is disengaged and the power circulation clutch is engaged.
In the direct mode, the engine output is transmitted to the drive shaft via the CVT. In the power circulation mode, the rotation of the ring gear stops in a position where the rotation of the sun gear which rotates due to the output of the CVT and the rotation of the planet carrier which rotates due to the output of the fixed speed ratio transmission, are balanced. This state is the neutral state where a rotation torque is not transmitted to the drive shaft.
In this case, the ratio of the engine rotation speed and the rotation speed of the drive shaft, i.e., the speed ration of the non-finite speed ratio transmission device, becomes infinite.
This state is called the geared neutral position GNP. Therefore, the rotation direction of the ring gear changes according to whether the speed ratio of the CVT is larger or smaller than the GNP. Forward or reverse motion of the vehicle from stop is therefore performed by increasing or decreasing the speed ratio of the CVT from the GNP.
In this device the speed ratio of the CVT increases as the vehicle speed increases when the vehicle is moving forward in the power circulation mode. Herein the speed ratio of the CVT denotes the ratio of the input rotation speed and output rotation speed of the CVT. When the speed ratio of the CVT has increased to a predetermined speed ratio, the power circulation clutch is disengaged and the direct clutch is engaged.
Hence, there is a change-over from the power circulation mode to the direct mode. In the direct mode, the output of the CVT is directly transmitted to the drive shaft without modification.
Therefore, according to this transmission, all running states including forward and reverse from the stop state of the vehicle, and running at high speed, can be changed over smoothly without using a torque converter. An identical non-finite speed ratio transmission is also disclosed in U.S. Pat. No. 5,935,039.
SUMMARY OF THE INVENTION
The speed ratio of the CVT is changed by moving trunnions which support power rollers in the CVT by an oil Pressure.
A piston of a hydraulic cylinder is joined to each trunnion and the hydraulic pressure is made to act on both ends of the piston, and displacement of the trunnion is performed due to this differential pressure. The differential pressure is controlled by a pressure control valve which is feedback controlled electronically.
When the speed ratio is controlled via pressure control, there is an advantage in that the torque transmitted by the CVT is easily controlled near the geared neutral position GNP of the power circulation mode.
On the other hand, there is a problem in that the response of feedback control of the pressure control valve decreases when the temperature of the oil which transmits hydraulic pressure is low.
Moreover, if there is scatter in the characteristics of the hydraulic cylinders, it is difficult to make the speed ratio of the continuously variable transmission coincide with a target speed ratio with sufficient precision. Specifically, when an input torque of the CVT abruptly changes, a difference between a command value of the differential pressure and a real differential pressure exerted on the piston becomes large, and the precision of speed ratio control declines.
It is therefore an object of this invention to increase the control precision of speed ratio of a non-finite speed ratio transmission device while maintaining desirable transmission torque control characteristics near the geared neutral position GNP of the power circulation mode.
In order to achieve the above object, this invention provides a non-finite speed ratio transmission device for use with a vehicle, comprising a toroidal continuously variable transmission which varies a speed ratio according to a gyration angle of a power roller gripped by an input disk and output disk, a fixed speed ratio transmission which varies a rotation speed of the input disk at a fixed speed ratio, a planetary gear unit having a final output shaft which varies a rotation direction 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, a hydraulic cylinder comprising a first oil chamber and second oil chamber, a direction change-over valve which selectively supplies an oil pressure to the first oil chamber and the second oil chamber according to a displacement position, an actuator which displaces the direction change-over valve, a feedback member which feeds back a displacement of the power roller to the direction change-over valve, and an oil pressure control valve which varies the differential pressure between the first oil chamber and second oil chamber.
The power roller varies the gyration angle according to a displacement of a supporting member which supports the power roller, and the hydraulic cylinder displaces the supporting member according to a differential pressure between the first oil chamber and the second oil chamber. The feedback member connects the supporting member and direction change-over valve, and is arranged to displace the direction change-over valve in a direction opposite to a direction of displacement of the direction change-over valve due to the actuator.
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: 5194052 (1993-03-01), Ueda et al.
patent: 5711741 (1998-01-01), Inoue
patent: 5779591 (1998-07-01), Inoue
patent: 5902207 (1999-05-01), Sugihara
patent: 5935039 (1999-08-01), Sakai et al.
patent: 5980420 (1999-11-01), Sakamoto et al.
patent: 6030311 (2000-02-01), Osumi
patent: 6063002 (2000-03-01), Nobumoto et al.
patent: 63-130954 (1988-06-01), None
patent: 9-42428 (1997-02-01), None
patent: 9-89071 (1997-03-01), None
Nishio Motoharu
Sakai Hiromasa
Foley & Lardner
Ho Ha
Marmor Charles A
Nissan Motor Co,. Ltd.
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