Friction gear transmission systems or components – Friction gear includes idler engaging facing concave surfaces – Toroidal
Reexamination Certificate
1998-09-30
2001-01-30
Fenstermacher, David M. (Department: 3682)
Friction gear transmission systems or components
Friction gear includes idler engaging facing concave surfaces
Toroidal
C384S127000, C384S903000
Reexamination Certificate
active
06179744
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a trunnion support for supporting a power roller of a toroidal continuously variable transmission.
BACKGROUND OF THE INVENTION
In a toroidal continuously variable transmission, power rollers are supported by trunnions as disclosed for example by Tokkai Sho 57-47060 published by the Japanese Patent Office in 1982. A piston is fixed to these trunnions respectively. When a piston is driven hydraulically and the trunnions are displaced at right angles to a rotation shaft of an input disk and output disk, the gyration angle of the power roller varies, and a rotation ratio (drive ratio) of the input disk and output disk holding the power rollers varies.
The upper ends and lower ends of these trunnions are respectively fitted to a link so that they can displace in synchronism. Each trunnion is joined to the link via a needle bearing and a spherical joint so as to permit it to rotate freely and incline through a very small range.
When the power roller is inclined, a load acts on the trunnion in a direction other than the anal direction.
This load is absorbed by the relative displacement of the spherical joint and a link. Since there is a small clearance between the needle bearing and the trunnion and between the needles, some needles may incline relative to the trunnion in this case. The inclined needles, however, exert an axial force on the trunnion when it rotates. According to an analysis, about 10% of the force of a radial load supported by the needle bearing acts on the trunnion in the axial direction.
As a result, there is an excess or deficiency of the drive force exerted by the piston on the trunnion, and this results in scatter of torque transmitted by the power rollers.
SUMMARY OF THE INVENTION
It is therefore an object of this invention to prevent the inclined needles from exerting an external force on the trunnion.
In order to achieve the above object, this invention provides a trunnion supporting structure of a continuously variable transmission. The transmission comprises an input disk and output disk arranged facing each other on a rotation axis, power rollers for transmitting a torque between the disks, trunnions supporting the power rollers, and a link connecting the trunnions, wherein a gyration angle of the power rollers is varied by driving the trunnions along a trunnion axis at right angles to the rotation axis.
The supporting structure comprises a needle bearing, a spherical joint, a first member, a second member and a third member.
The needle bearing comprises plural rolling pasts which roll along a circular path. The first member is disposed inside, the circular path and the second member is disposed outside the circular path. The needle bearing allows relative rotation between the first member and the second member. The third member prevents the relative inclination of the first member and the second member.
It is preferable that the trunnion comprises a shoulder part extending at right angles to the trunnion axis, the first member is the trunnion, the second member is the spherical joint, the third member is supported by the trunnion, and the spherical joint is fitted between the shoulder part and the third member such that a displacement of the spherical joint in a direction of the trunnion axis is limited by the shoulder part and the third member.
It is further preferable that the spherical joint is fitted in a throughole formed in the link.
It is also preferable that the third member comprises an annular retainer supported via a snap ring fitted to the trunnion.
In this case, It is further preferable that the supporting structure further comprises a spacer filling a gap between the shoulder part and the spherical joint.
When the spacer is provided, it is further preferable that a contact area between the spacer and the shoulder part is set larger than a contact area between the spacer and the spherical joint.
It is also preferable that the supporting structure further comprises a spring interposed between the snap ring and the retainer.
It is also preferable that the third member is a nut which screws into the trunnion, and the supporting structure further comprises a thrust needle bearing interposed between the spherical joint and the shoulder part, and a thrust needle bearing interposed between the spherical joint and the nut.
When the toroidal continuously variable transmission comprises a wire for synchronizing the rotation of the plural trunnions, it is preferable that the third member comprises a pulley supported by the trunnion around which the wire is looped.
In this case, it is further preferable that the supporting structure further comprises a spacer filling a gap between the shoulder part and the spherical joint.
In this case, it is further preferable that a contact area between the spacer and the shoulder part is set larger than a contact area between the spacer and the spherical joint.
It is also preferable that the supporting structure further comprises a spring pushing the pulley towards the spherical joint.
It is also preferable that the pulley is fixed to the trunnion by a nut, and the supporting structure further comprises a thrust needle bearing interposed between the spherical joint and the shoulder part, and a thrust needle bearing interposed between the spherical joint and the pulley.
It is also preferable that the first member comprises a cylindrical member, the second member comprises a wall of a throughole formed in the link, the spherical joint is fitted between an outer circumference of the trunnion and an inner circumference of the cylindrical member, and the third member is supported by the link.
In this case, it is further preferable that the link comprises an anvil part extending into the throughole, the third member comprises an annular retainer supported in the throughole via a snap ring by the link, and the cylindrical member is fitted between die anvil part and the retainer such that a displacement of the cylindrical part in a direction of the trunnion axis is limited by the anvil part and the retainer.
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: 4968289 (1990-11-01), Nakano
patent: 5187995 (1993-02-01), Nakano
patent: 5885185 (1999-03-01), Kidokoro et al.
patent: 5893815 (1999-04-01), Nakano
patent: 57-47060 (1982-03-01), None
Nakano et al.; “Dynamic Characteristics of Speed Ratio Control of the Halt Toroidal CVT for Passenger Cars”; The Engineering Society for Advancing Mobility Land Sea Air and Space; Sep. 1990; pp. 24-32.
Fenstermacher David M.
Foley & Lardner
Nissan Motor Co,. Ltd.
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