Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
1999-05-05
2001-09-11
Bucci, David A. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C476S048000, C384S618000
Reexamination Certificate
active
06287235
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thrust generating mechanism for a toroidal continuously variable transmission which is provided in an automobile or other vehicle.
BACKGROUND TO THE INVENTION
Toroidal continuously variable transmissions transmit motive power through an arrangement in which a power roller is tightly held between an input disk and an output disk. Rotations from the input disk rotate the power roller which in turn rotates the output disk as a result of frictional contact.
The transmission of motive power under these circumstances depends on the force of frictional contact between the input/output disks and the power roller. The frictional force in turn corresponds to a thrust force which grips (sandwiches) the power roller. U.S. Pat. No. 2,959,063 discloses a mechanism of generating a thrust force which acts on the input/output disks in order to grip the power roller.
The disclosed mechanism consists of arranging a plurality of cam rollers held in a retainer on the same axis as the input/output disks to generate a thrust force so that the power roller which is gripped between the input/output disks is placed under pressure in proportion to the input torque from the input shaft.
The plurality of cam rollers are disposed on the inner side of the retainer at equal intervals in the radial direction. Each cam roller is formed in an approximately conical trapezoid shape and is disposed so that the long radius end faces outwardly. The end face of each cam roller forms a rounded face which is maintained in contact with the inner face of the retainer.
Due to the fact that the long radius end faces are maintained in contact by the retainer, the cam rollers are gripped between a cam flange(input member), which is a member fixed on the input shaft side, and the rear face of the input disk, which can slide with respect to the input shaft. A cam face, the depth of which gradually decreases towards the circumference, is formed on the opposed faces of the input member and rear face of the input disk. When the input member rotates in response to an input torque, the cam roller displaces through a narrow range along the cam face towards the circumference while rotating. The input disk is pressured in the axial direction from the rear face and, in this way, a thrust force is generated. The thrust force allows the input disk to press the power roller onto the output disk and thus to achieve the transmission of rotational torque.
The conical trapezoid shape of the cam roller allows it to be pressured in the radial direction by the rotations of the input member. As a result, a sliding friction is generated on the metal contact face of the long radius end face of the cam roller and the retainer. Surface pressure acting on the cam roller decreases away from the center of the contact point of the rounded long radius end face with the inner face of the retainer. In this way, the moment of the sliding frictional force which impedes the cam roller from rotating can be minimized.
SUMMARY OF THE INVENTION
However the above alignment does not address the residual problem of the frictional force. The size of the frictional force generates a divergence with respect to set values of the thrust force which grips and pressures the power roller.
Reducing the thrust force when input torque is increasing, results in power roller slip and reductions in the torque transmission capacity of the continuously variable transmission. Conversely excessive thrust force when input torque is decreasing reduces the durability of the input/output disks and the power roller.
The object of the present invention is to improve the transmission capacity and durability of a toroidal continuously variable transmission so that the thrust value of the power roller is close to a set value, by reducing frictional forces which are generated by the retainer and the cam roller.
In order to achieve the above object, the present invention provides a toroidal continuously variable transmission which has a power roller which is gripped between an input disk and an output disk arranged on the same axis. The toroidal continuously variable transmission comprises an input shaft which supports the input disk so as to reciprocate freely, a cam member which is disposed in proximity to the input disk and is fixed to the input shaft, a cam roller which is gripped between the cam member and the rear face of the input disk and is provided with a conical rotating face, and a retainer which is stored so that the cam roller faces the radial direction about the input shaft and a long radius end face is disposed so as to form an outer wall. The toroidal continuously variable transmission further comprises a bearing which is interposed at the contact point of said long radius end face with said retainer in the radial direction of said cam roller.
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: 700145 (1902-05-01), Larned et al.
patent: 718110 (1903-01-01), Eveland
patent: 718111 (1903-01-01), Eveland
patent: 2057213 (1936-10-01), Skyiepal
patent: 2956441 (1960-10-01), De Brie Perry
patent: 2978282 (1961-04-01), Fisher
patent: 3163050 (1964-12-01), Kraus
patent: 3163478 (1964-12-01), Pitner
patent: 3240542 (1966-03-01), Jahn
patent: 3778124 (1973-12-01), Alling
patent: 5322735 (1994-06-01), Fridez et al.
patent: 10-331937 (1998-12-01), None
Nanbu Toshikazu
Yamamoto Takeshi
Yasuda Yoshiteru
Bucci David A.
Foley & Lardner
Joyce William C
Nissan Motor Co,. Ltd.
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