Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
1999-04-09
2001-01-23
Herrmann, Allan D. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C384S450000, C384S475000, C384S516000, C384S615000, C476S008000
Reexamination Certificate
active
06176805
ABSTRACT:
GROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an angular bearing which is adaptable to a dual cavity toroidal type continuously variable transmission for use as a transmission for, for example, an automobile and which is disposed in a joint portion between a cam disc constituting a loading cam unit and an end of a torque input shaft to bear a load which is added to the cam disc in a thrust direction.
2. Description of the Related Art
A toroidal type continuously variable transmission which has been developed and researched to serve as a transmission adapted mainly to an automobile incorporates at least one toroidal transmission mechanism. The toroidal transmission mechanism is structured by combining input and output discs and a plurality of rotative power rollers held between the two discs with each other, the input and output discs having opposite surfaces each of which has a cross sectional shape formed into a circular arc recess. The input disc is integrally and rotatively joined to a torque input shaft. Moreover, the input disc is engaged to the torque input shaft to limit movement of the input disc toward the torque input shaft. On the other hand, the output disc is relatively rotatively joined to the torque input shaft. Moreover, the output disc is joined to be opposite to the input disc such that movement of the output disc in a direction apart from the input disc is limited.
When the input disc of the toroidal transmission mechanism is rotated, the output disc is inversely rotated through the power rollers. Therefore, the rotational motion, which is input to the input shaft is, as rotational motion in the inverse direction, transmitted to an output gear joined to the output disc so as to be output from the output shaft. At this time, the outer surfaces of the power rollers are brought into contact with a position adjacent to the outer surface of the input disc and the central portion of the output disc by changing the angle of inclination of the rotational shaft of each power roller. Thus, acceleration from the torque input shaft to the output gear is permitted. Inversely, the outer surfaces of the power rollers are brought into contact with the position adjacent to the central portion of the input disc and the outer surface of the output disc by changing the angle of inclination of each power roller. Thus, deceleration from the torque input shaft to the output gear is permitted. Also intermediate gear ratios between the two gear ratios can be realized in a continuously variable manner by adequately adjusting the angle of inclination of the rotational shaft of each power roller.
To be adaptable to greater input/output torque, a dual cavity toroidal type continuously variable transmission has been disclosed which is constituted by, in parallel, connecting two toroidal transmission mechanisms to each other on the same axis. The parallel-connection dual cavity toroidal type continuously variable transmission incorporates two output discs which are provided for front and rear toroidal transmission mechanisms, respectively. The rear surfaces of the two output discs are connected to each other through one output gear shaft. A loading cam unit, which is capable of enlarging/reducing the pressure corresponding to the magnitude of the input torque and applied in the direction of the torque input shaft, is disposed between either of the input discs and an end of the torque input shaft.
The loading cam unit has two cam surfaces each of which is disposed on either side of the cam disc and the surface of the input disc opposite to the cam disc. Moreover, the loading cam unit has a plurality of rolling elements which are, by a holding plate, held between the foregoing cam surfaces such that rolling is permitted. When the rolling elements are rolled, the cam disc is pressed against the power rollers. Thus, frictional force having appropriate magnitude is always generated between the input disc and the outer surface of each power roller and between the outer surface of each power roller and the output disc. The cam disc is, through an angular bearing, rotatively connected to a projecting jaw portion formed around the outer periphery of the end of the torque input shaft.
The angular bearing has two raceway grooves provided adjacent to the shaft and the disc and a plurality of balls held between the two raceway grooves. Thus, a thrust load applied to the cam disc is borne. The raceway groove located to the shaft side (hereinafter, the shaft-side raceway groove) is formed in the outer surface of the projecting jaw portion formed in the outer periphery of the end of the torque input shaft, the foregoing raceway groove being formed in a circumferential direction of the torque input shaft. On the other hand, the raceway groove located to the disc side (hereinafter, the disc-side raceway groove) is formed in the inner surface of a joining opening formed in the central portion of the cam disc, the disc-side raceway groove adjacent being formed in the circumferential direction of the cam disc. Moreover, a holding unit for disposing the plural balls at appropriate intervals is combined, if necessary.
The parallel-connection dual cavity toroidal type continuously variable transmission has the one output gear which is integrated with the output gear shaft and which is simultaneously rotated by the two output discs from two sides. Thus, reaction force having the same magnitude of the pressure which is directly applied to the input disc adjacent to the loading cam unit is made to simultaneously be exerted to the other input disc through the angular bearing and the torque input shaft. Thus, the magnitude of the torque which is transmitted to each of the two output discs is made to be the same.
A situation will now be-considered in which a defective operation of the angular bearing disposed between the cam disc and the torque input shaft enlarges or reduce the rotation resistance of only either toroidal transmission mechanism. In this case, the equilibrium state of the torque which is transmitted by the four power rollers is lost. Thus, synchronization in the transmission between the front and rear toroidal transmission mechanisms is disordered. Moreover, each power roller encounters hunting and vibrations, causing the overall transmission performance of the toroidal type continuously variable transmission and durability of the same to deteriorate. Further, a portion of the power rollers may bear torque larger than a limit of the designed torque. In the foregoing case, safety of a traction portion against the gross slip deteriorates, causing possibility of occurrence of slips at high temperatures to be raised. To prevent the above-mentioned problems, the angular bearing of the dual cavity toroidal type continuously variable transmission must minimize rotational friction loss in the bearing to make the magnitude of the torque which is transmitted to each of the front and rear toroidal transmission mechanisms to be the same.
If loads in the thrust and radial directions exerting on the cam disc of the toroidal continuously variable transmission are enlarged and, therefore, the load of the angular bearing is enlarged, the angular contact angle of each ball is gradually enlarged. As a result, a point of contact between each ball and each raceway groove approaches a shoulder portion of the raceway groove. Therefore, if a large torque is input to the cam disc, a so-called edge load state occurs in which the contact ellipse of the bearing runs on the shoulder portion of the raceway groove. Thus, the pressure at the point of contact between the balls and each raceway groove is raised excessively. Therefore, there is apprehension that the bearing encounters premature separation. When the large load is input, the cam disc is warped, that is, deformed outwards. Therefore, the shape of the disc-side raceway groove in the inner surface of the joining opening formed in the central portion of the disc is distorted. As a result, the contact ellipse furthermore runs on the should
Fujinami Makoto
Goto Nobuo
Itoh Hiroyuki
Kato Hiroshi
Herrmann Allan D.
NSK Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
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