TRANSMISSION OF CONTINUOUS VARIABLE TYPE OF ROLLING BEARING TRACTION ORUIDAL RING
This invention relates to continuously variable ratio ("CVTs") transmissions of the toroidal rolling ring bearing type and especially with elements to control the orientation of the rollers in the variators. This is a simplified representation of part of a known variator, seen in a direction perpendicular to the common N axis of the two discs G and J. A single roller A, which the practice will be of a set of three arranged at equal angular intervals around the N axis. It transmits traction between partially toroidal F and H race rings and G and J discs respectively, and is mounted inside a car C to rotate around a center and axis (B) both of which are defined by and fixed in relation to the car. A rod P connects the carriage C to a piston D which is free to move axially within a fixed cylinder E, and also to tilt slightly as it does without losing the seal. Said inverter has been found to work efficiently in a CVT of the so-called "controlled torque" where a pressure generated hydraulically (by means not
REF: 26429 shown) in the cylinder E exerts a force on the piston D, which for balance must balance the reaction force resulting from the resulting torque in the contact between the roller A and the rolling rings F and H. Roller A changes its orientation angle (or "tilt angle"), and thus the ratio it transmits between discs G and J, tipping around the rod axis P, and it has been found that each position of the center of piston D, within its scale of axial movement inside the cylinder E, correlates with a unique angle of inclination of the roller A. In other words, each angle of balance inclination of the roller is defined uniquely by just three points, a say, the contact locations of the roller A with the rolling rings F and H and the location of the center of the piston D. Said variator, and the CVT of which it is a part, is described and shown in greater detail in the EP-B Patent -0444086. As is well known in this art, the center of the roller at all times is restricted to following the central circle of the bull to which the rolling rings F and H are made. That central circle must be in the middle plane M of the bull. The rod P, which, as already observed, defines the axis of inclination of the roller, is inclined to that plane at an angle L ", known as the angle of castor.The advantages of operation of a variator of ring of rolling toroidal with a degree Substantial beaver angle, say of the order of 15a, are well known in the art It will be seen that in the apparatus of Figure 1, as is typical in the prior art, the axis of motion of the component that applies the reaction force (the piston D) and the axis of inclination (the rod P) coincide in the third of the three points whereby each angular establishment of the roller is uniquely defined.This coincidence imposes restrictions on the placement and orientation of certain components, particularly the cylinder E, and thus on the total dimensions of the variator, for example, because the cylinder axis E is inclined to the median plane M transverse by the castor angle L, the radius or to which the cylinder is positioned relative to the disk N axis exceeds the radius of the discs themselves. If I did not; a corner of the cylinder endangering it to damage the disc 1. In accordance with the present invention, these restrictions are decreased, thereby providing greater freedom to place the equivalent of the cylinder E in order to minimize the overall dimensions of the variator, separating the functions of generation of reaction force and control of inclination in order to avoid that the two axes coincide in the third point, in the manner just described. This separation also occurs in the unusual CVT described in Patent Specification US-A-3933054, but there the tilt control of each roller is achieved by a configured slot, in which a pin is fastened to the roller bearings and which it is projected in a coaxial direction with the roller itself. This construction has two particular disadvantages. First of all, any pin and groove coupling is inherently prone to wear and friction. Secondly, the orientation and minimum length of the pin, in relation to the roller, is such that whenever the two discs tend to move slightly al. in any direction along its common axis, as they tend to do it continually in use under varying loads, the consequence effect of the pin and groove coupling will cause the roller to "lead" to a new angle of inclination, changing from this way the transmitted relationship even if the change has not been requested. The present invention is based on a different inclination control mechanism, which does not require pin and groove connection and which is inherently less prone to cause any ratio change in response to the axial movements of the discs. The present invention is defined by the claims, the contents of which are to be read as included within the description of this specification, and the invention will now be described by way of example with reference to the following additional figures of diagrammatic drawings, in which: 2 shows a roller control mechanism, seen along the axis of the roller; Figure 3 is a partial view in the direction of arrow III in Figure 2; Figure 4 is another partial view, in the direction of arrow IV in Figure 2; and Figure 5 shows part of another embodiment of the invention. Figure 2 shows a source 1 d connected hydraulic power, through ducts 3, 4 and a central programmed control system 2 of a proper class to control torque, to opposite ends of a cylinder 5 containing a piston 6. The roller 7 is rotatably mounted inside a carriage 8, which is fixed to the piston 6 through a rod 9. Articles 7, 8, 9 and 6 corresponding to articles A, C, P and D in the Figure 1 to the extent that the hydraulic forces generated within the cylinder 5 are controlled so as to balance the reaction forces of torque generated in the contacts between the roller 7 and the discs 10 and 11, thus bringing the CVT to equilibrium with the roller the angle of inclination appropriate to that reaction of torque. In Figure 1, however, both the center of the roller A and its axis of rotation were fixed relative to the carriage C. In Figure 2, as will be further explained, the carriage 8 determines only the center of rotation of the roller. This axis of rotation, and thus also the perpendicular inclination axis around which it is inclined to change the ratio, is determined by a rod 13 that can slide through, but is radially constrained by, an opening 14 formed in a member. 15 which is either fixed to or part of the fixed structure of the CFT. In Figures 2 and 3 the cylinder 5 is shown fixed. Figure 3 shows that the piston 6 comprises a two-part cylindrical sleeve 17, the ends 18, 19 of which pass through sealed openings in the opposite end walls of the body. cylinder 5. The sleeve 17 also has a central portion 20 of amplified diameter, which bears a seal 21 and thus moves like a piston inside the central chamber 22 of the cylinder 5, inside the central part 20 of the sleeve 17 is adjusted a ring.25, in the middle of which a member 26 is free to rotate in the shape of a spherical bearing. The rod 9 is fixed to the member 26. This piston shape essentially in this manner is of a kind shown in greater detail in the patent publication W092 / 11475 and has the advantage that the rod 9 is free to rotate through a tapered angle but it is out of contact with the hydraulic fluid in cylinder 5. thus avoiding the need for flexible seals around the rod if it were attached to a conventional piston, and therefore was exposed to cylinder fluid . As also shown in Figure 3, the carriage 8 supports the roller 7 through a rod 28 to which the inner half 29 of a spherical bearing is fixed. In this way, as already mentioned, the carriage 8 fixes only the center and not also the axis of rotation of the roller 7. As shown in Figures 3 and 4, the outer half 30 of the spherical bearing is retained by the inner wall of a sleeve 31 which is fixed (through a second carriage 16 that fits with good clearance within the jaws of the carriage 8) both to the rod 13 and to a ball rolling ring 32 around which the roller 7 rotates Due to the two ball joints in 25/26 and
29/30 the piston / cylinder combination 5/6, which can be considered as a first part of the roller operating mechanism, can exert thrust on the roller 7 to balance the reaction forces against the discs 10 and 11, but can not define the angle of relation adopted by the roller. In contrast, the rod 13 and associated parts, which together constitute a second part of the operating mechanism, can exert not this thrust, but define both the axis around which the roller is tilted to change the ratio and the angle (the "angle"). of beaver "36) that makes that axis with the flat 35 medium of bull. In terms of explanation of the operation of a torque controlled CVT given in the third paragraph of this specification, in Figure 2 each equilibrium inclination angle of the roller 7 now correlates with a single triangle of which the fixed aperture 14 is always the vertex, but the placements of the two roller / disc contacts and the distances between each of these contacts and the vertex are unique. It should also be noted that the axes of the rod 13 and roller 7 are coplanar and intersect in the center of the roller, thereby minimizing any driving effect that the rod imposes on the roller in response to axial movements of the discs. , 11 under load. In Figure 2, the cylinder axis 5 is shown aligned with the median plane of the bull: alternatively, it could, for example, be deviated from that plane, but parallel thereto. Because the cylinder axis is no longer aligned with the roll tilt axis (as is, for example, in the detailed embodiments of EP-B-0444086) the structure of the cylinder 5 can now be placed more freely, and notably at a substantially lower radius relative to the common axis of the discs, and the relative simplicity of the rod 13 and the other parts defining the axis of inclination allow them to be placed at a still lower radius. Possibly, as indicated in Figure 2, the entire structure of the cylinder 5, the rod 13 and the member 15 can be accommodated within the imaginary cylinder of which 10 and 11 constitute the end walls. In the alternative construction shown in delineation in Figure 5, the opening 14, instead of being formed in a member 15 fixed to the structure of the CFT as an integer, is now formed in a flange 40 formed in the front tip of the end 18 of the sleeve 17. The opening 14 therefore moves with the piston 6, and each angle of equilibrium inclination of the roller 7 (not shown in Figure 5) correlates with a trio of unique locations, namely, the two roller / disc contacts and instantaneous placement of the aperture 14, which of course now reflects the position within its stroke of the piston 6. With this embodiment, it is necessary to ensure that the aperture 14 follows a predetermined trajectory as the piston 6 It moves back and forth. This would not be ensured if the piston 6 were conventional, of circular delineation and free to rotate, as well as to move axially, with respect to the cylinder 5. This rotation can be prevented, and the predetermined movement of the opening 14 therefore ensures , by a guide pin 41 which projects axially forwardly from the structure of the cylinder 5 and which passes through a second opening 42 in the flange 40. Alternatively, the rotation could be prevented by making the end 18 of the delineation sleeve 17 not circular where it passes through the front wall of cylinder 5.