Friction gear transmission systems or components – Fluid control – Of toroidal transmission
Patent
1997-12-19
2000-06-06
Graysay, Tamara L.
Friction gear transmission systems or components
Fluid control
Of toroidal transmission
476 40, F16H 1538
Patent
active
060712090
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to continuously-variable ratio transmissions ("CVT's") of the toroidal-race rolling-traction type and especially to means for controlling the orientation of the rollers in the variators, that is to say the ratio-varying components, of such CVT's.
FIG. 1 is a simplified representation of part of one known variator, viewed in a direction perpendicular to the common axis N of the two discs G and J. A single roller A, which will in practice be one of a set of three disposed at equal angular intervals around the axis N, transmits traction between part-toroidal races F and H in discs G and J respectively, and is mounted within a carriage C to rotate about a center and axis (B) both of which are defined by and fixed relative to the carriage. A rod P connects the carriage C to a piston D which has freedom to move axially within a fixed cylinder E, and also to tilt slightly as it does so without losing seal.
Such a variator has been found to work efficiently in a so-called "torque-controlled" CVT where a pressure generated hydraulically (by means not shown) in cylinder E exerts a force on piston D, which for equilibrium must balance the reaction force resulting from the resultant torque at the contact between the roller A and the races F and H. Roller A changes its angle of orientation (or "tilt angle"), and thus the ratio it transmits between discs G and J, by tilting about the axis of rod P, and it has been found that each position of the center of piston D, within its range of axial movement within cylinder E, correlates with a unique tilt angle of the roller A. In other words, each equilibrium tilt angle of the roller is uniquely defined by just three points, namely the locations of contact of the roller A with races F and H and the location of the centre of the piston D. Such a variator, and the CVT of which it is part, is described and shown in more detail in Patent EP-B-0444086.
As is well known in this art, the center of the roller is at all times constrained to follow the center circle of the torus to which races F and H conform. That center circle must lie in the mid-plane M of the torus. Rod P, which as already noted defines the tilt axis of the roller, is inclined to that plane at an angle L, known as the castor angle. The advantages of operating a toroidal-race variator with a substantial degree of castor angle, say of the order of 15.degree., are well known in the art.
It will be seen that in the apparatus of FIG. 1, as is typical in the prior art, the axis of movement of the component which applies the reaction force (the piston D) and the axis of tilt (the rod P) coincide at the third of the three points by which each angular setting of the roller is uniquely defined. This coincidence imposes constraints upon the location and orientation of certain components, particularly the cylinder E, and thus on the overall dimensions of the variator. For example, because the axis of cylinder E is inclined to the transverse mid-plane M by the castor angle L, the radius at which the cylinder is located relative to the disc axis N exceeds the radius of the discs themselves. If it did not, a corner of the cylinder would be at risk of fouling the disc J.
SUMMARY OF THE INVENTION
According to the present invention such constraints are diminished, thus providing greater freedom to locate the equivalent of cylinder E so as to minimise the overall dimensions of the variator, by separating the functions of reaction force generation and tilt control so as to avoid the two axes coinciding at the third point, in the manner just described. Such separation occurs also in the unusual CVT described in U.S. Pat. No. 3,933,054, but there the tilt control of each roller is achieved by a shaped slot, in which runs a pin fixed to the roller bearings and projecting in a direction coaxial with the roller itself. Such a construction has two particular disadvantages. Firstly that any pin-and-slot engagement is inherently liable to wear and friction. Secondly that the orientation an
REFERENCES:
patent: 1999543 (1935-04-01), Madle
patent: 2125999 (1938-08-01), Erban
patent: 2446409 (1948-08-01), Chilton
patent: 3153938 (1964-10-01), Brie Perry
patent: 3267756 (1966-08-01), Brie Perry et al.
patent: 3823613 (1974-07-01), Abbott
patent: 3993054 (1976-11-01), Iseman
patent: 4281559 (1981-08-01), Sharpe
patent: 5395292 (1995-03-01), Fellows et al.
patent: 5564993 (1996-10-01), Robinson
Graysay Tamara L.
Joyce William C.
Torotrak (Development) Limited
LandOfFree
Continuously-variable-ratio transmission of the toroidal-race-ro does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Continuously-variable-ratio transmission of the toroidal-race-ro, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Continuously-variable-ratio transmission of the toroidal-race-ro will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2209803