MXPA06005392A - An improved continuously variable transmission device - Google Patents

Abstract

A continuously variable transmission device has planetary members (23) in rolling contact with radially inner and outer races (12, 14;36, 37) each comprising axially spaced relatively axially movable parts, and control means (18) for determining the axial separation of the parts (12, 14) of one of the two races, in which the planetary members (23) are connected for drive transmission to an input or output member (30) of the transmission device by connection means which allows the radial position of the planets to vary in response to variation in the axial separation of the parts (12, 14) of the said one of the two races (37), and in which the generatrix of the curved surface (70, 71) of at least one of the races (37) and/or planetary members (23) is non-circular.

Description

IMPROVED CONTINUOUSLY VARIABLE TRANSMISSION DEVICE Field of the Invention The present invention relates to an improved continuously variable transmission device.

BACKGROUND OF THE INVENTION In particular the present invention relates to a continuously variable transmission device of the type having planetary members in rolling contact with radially internal and external bearing paths each comprising two axially spaced parts, with control means for selectively varying the axial spacing of the two parts of a bearing path and thus the radial position of the planetary members in rolling contact therewith. Such a transmission device may have torsionally sensitive members applied to one of the two transmission drive transmission members (particularly the input and output shafts) to determine the compensation variation in the separation of the two parts of the transmission. another bearing path and thus the transmission ratio of the device, and also to vary the forces exchanged between the satellites and the normal bearing paths to the interconnection between them. The rolling contact between the planetary members and the bearing paths is lubricated by means of a very thin film of lubricant. It is essential that this thin film of lubricant be present in order to avoid dry friction contact between the members in relative motion, which can lead to premature wear, but also that the film must be extremely thin to avoid relative slippage. In the prior art transmission devices, the rolling contact between the satellites and the bearing paths inevitably requires circular arcs for the rolling contact surfaces, which is the generatrix of the curved surfaces in rolling contact with each other. This is especially true of the rolling contact transmission devices of the toroidal cavity type but also of those of the semi-toroidal cavity type. This means that the tensile coefficient, ie the relationship between the tensile force exerted between the satellite and the rolling path and the contact force between these members can also be controlled by using separate force generators (such as by hydraulic pressure). ) and designs that allow maximum efficiency in different relationships are not available. This has the disadvantage that the contact force between the satellites and the bearing paths is not optimal in all ratios. In a continuously variable rolling contact transmission device of the type defined above, the input to the device can be applied by the radially internal bearing paths and the output of the device taken from the satellites by satellite carriers or a satellite carrier. , with the external bearing path constituting the stationary component. The high transmission ratio is then achieved with the two components of the radially external raceway located in their position of maximum spacing while the parts of the internal raceway are located as close together as possible so that the satellites are "compressed" "effectively to its greater radial position. Such transmission may be referred to as quasi-toroidal rolling contact transmission. It will be appreciated that in such transmission, the roles of the input and output shaft can be reversed and, in the design in question, the roles of the three components, particularly the radially internal bearing paths, the satellites, which in different embodiments include conveyors satellite and satellite carriers, and the radially external bearing paths can all be exchanged in a that either of them can be kept stationary and the other two can be used as the entry or exit member. A configuration with the stationary outer bearing path will be described in greater detail in the following but it will be understood that the invention is not intended to be limited to such a configuration and can equally be applied to others. The present invention is directed to a rolling contact continuously variable transmission device of the type described in the above, in which the contact force between the satellites and the bearing paths generated by the control means to selectively vary the axial separation of the two parts of a bearing path that can be optimized for all ratios. This is achieved, according to the invention, by changing the shape of one or more of the curved contact surfaces (either of the satellites or the bearing paths or both) from a generally spherical configuration to one in which the generatrix of either or both of the satellites and one or both of the bearing paths is not circular, which, in essence, maintains a more favorable contact angle with the position variations. According to one aspect of the present invention, therefore, a continuously variable transmission device of the type having planetary members in rolling contact with the radially internal and external bearing paths each comprising relative and axially movable parts. separate, and control means for determining the axial separation of the parts of one of the two bearing paths, in which the satellites are connected for the drive transmission to an input or ut member of the transmission devices by means of the means of connection that allows the radial position of the satellites to vary in response to the variation in the axial separation of the parts of one of the two bearing paths, and in which the generatrix of the curved surface of at least one of the bearing paths and / or the satellites is not circular. The generatrix of the curved surface of at least one of the bearing paths and / or the satellites may be continuous or discontinuous. In this respect, the term "discontinuous" is not meant to mean that the curve has parts that are lost, but rather that it has particularities, that it has parts or regions that do not conform to the general function that defines the curve. For example, the curved surface may have separate rectilinear portions but sharper curves, or even the continuously curved sections may have sharper curves therebetween. Not only this, satellites can also be provided with an equatorial channel in which a connection is extended for the transmission of the forces in use, and in a composite planetary member, the two individual roller elements of which it can be composed can be joined by an intermediate element to which the connection is connected. The transmission of forces can also be achieved by means of a slotted plate having inclined grooves in a radial line passing through the groove so that, in use, a force which has a radial and a circumferential component is applied. Alternatively, the connection between each planetary body and the satellite carrier may be in the form of a respective input arm for each satellite. The term "entry" is of relevant course in only one direction of the relative rotation. In the other direction of the relative rotation, the "entry" arm becomes an "exit" arm. The forces can be transmitted to and from the satellites satisfactorily through such a configuration because the satellites at the ends of the arms and the connection to the satellite carrier are restricted to follow a circular motion.

As defined in the above, the surface of revolution of each planetary body can be defined by a curvilinear generatrix. This differs from the prior art in that it is not part of a circle. Similarly, the bearing paths can also be defined by a non-circular generator. In one embodiment of the invention, the curvilinear generatrix of each bearing element surface is a spiral. This can be from any of the known spiral curves, such as an Archimedean spiral (for which the polar equation is r = a?) Fermat's spiral (for which the polar equation is r = aL?), Or a hyperbolic spiral or logarithmic spiral (respectively defined by r = a /? and r = aeb). There are other suitable known spirals. However, the generatrix does not need to be a spiral, and other noncircular curves can be chosen. For example, a simple conic section such as a parabola, hyperbola or ellipse can be used as a polynomial curve or a digitally defined curve that has no simple or classical description can do. Obviously, the generatrix will not understand the totality of any curve but rather a part only, which has the appropriate dimensions. In a preferred embodiment of the invention, the satellite carrier has a plurality of arms extending from an axial end of the device substantially parallel to the axis of rotation of the device, and a reinforcing ring that together links the three free ends that it reinforces the free ends of the arms. This reinforcement ring occupies the space between the ends of the arms of the satellite carrier and an end cover of the device, which lies radially externally of the internal bearing paths so as not to interfere with the movement thereof. The radially internal and external bearing paths are located within a fixed housing and one or the other of the bearing paths can be rotated with respect to the housing by the input or output member of the transmission device. In a preferred embodiment of the invention, the radially inner raceway can be rotated with respect to the housing with the input member of the transmission. Likewise, it is preferred that the satellite carrier be rotatable with respect to the housing with the output member of the transmission.

BRIEF DESCRIPTION OF THE DRAWINGS Now several embodiments of the present invention will be described more particularly, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an axial sectional view taken on line II of the Figure , of a rolling contact continuously variable transmission device of the prior art formed as an embodiment of the present invention shown in a low transmission ratio; Figure 2 is an end view of another prior art device similar to that of Figure 1 but having a greater number of satellites; Figure 3 is a partial axial sectional view of a part of a first embodiment of the invention illustrating the components in two different transmission ratios; and Figure 4 is an axial sectional view similar to that of Figure 3, illustrating a second embodiment of the invention, in which the curvilinear generation of the planetary members is reversed with respect to those shown in Figure 3.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings, and particularly to Figures 1 and 2, the transmission device shown comprises a housing generally indicated at 11 within which is located a radially external bearing path 12 formed in two parts. 14 relative and axially displaced coupled together by a so-called "sphere spindle" comprising several helical rows of spheres 15 coupled in corresponding helical notches in the two parts 13, 14 that allows them to rotate with respect to each other on the central longitudinal X-X axis of the device. The sphere spindle has several starts (four in this case), - this results from the need to fill the space available with the spheres (for maximum load capacity) but to avoid using large spheres (which may be required for a single thread) start) with the relatively long advance necessary to balance the axial and circumferential loads. The relative axial displacement between the two parts 13, 14 is achieved by mounting the part 14 on fixed pins 16 which form an Oldham coupling with a pair of pins in the housing for restricting the part 14 of the bearing path against rotational movement while allowing the axial displacement. The Oldham coupling is used herein as a "tolerance accommodation" arrangement that allows radial translation but not rotation. The two pairs of pins in fact do not lie in the same plane, as they appear in the drawing, but are arranged at 90 degrees to each other and the small flat parts indicated by the crosses run in the grooves in Oldham's ring. The part 13 of the rotationally displaceable raceway is maintained in a generally cylindrical carrier 17 which can be rotated on the X-X axis by an adjusting arm 18 rotated by an adjusting actuator 10. The activator 10, seen in extreme in Figure 1 is preferably a spindle activator having a spindle of spheres driven by an electric motor (not shown). By rotating the rotationally displaceable bearing path portion 13 on the axis XX, the latter effectively "twists" in relation to the external bearing path portion 14 axially displaceable by the action of the spindle 14 of spheres, causing it to move axially. along the sliding pins 16 without rotating. In this way, the two rolling path parts 13, 14 move apart or together when the outer rolling path part rotationally displaceable in one direction or the other rotates. The two bearing track parts have curved bearing surfaces 19, 20 curved and coupled by the curved surfaces of the planetary member generally indicated at 21 comprising two approximately hemispherical shields 22, 23 held together by a central pin 24 bearing a bearing or bushing 25 of rolling elements by means of which the planetary member 21 is carried. As can be seen in Figure 2, each bushing 25 engages in a slot in a plate 61 carried on a five-satellite carrying arm 27 of a satellite carrier 28 which is fixedly connected to an output shaft 29 which coaxially surrounds and it is carried in the input shaft 30 by means of a bearing 31. This configuration will be described in greater detail in the following. An additional bearing 32 interconnects the input shaft 30 and the satellite carrier 28, and the seals 33, 34 protect the internal part of the device from ingress of dust, dirt and other contaminating particles, moisture or water. The planetary members 21 also roll on an internal bearing path generally indicated at 35 which comprises an axially movable bearing path portion 36 and an axially displaceable bearing portion 37 carried therein by a sphere spindle 38 similar to that by which the two parts of the radially external bearing path are interconnected. A light precharged torsion spring 40 urges the internal rolling path part 37 axially displaceable towards the planetary member 21 in order to maintain contact. The manner in which the transmission ratios are changed and the torque between the input and output shaft is detected by the radially internally and axially displaceable bearing path part 37 carried by the sphere spindle 38 in the part 36 axially fixed bearing path is fully described in the applicant's previous International Patent Application No. WO 99/35417, description of which is incorporated herein by reference and will not be further described herein. In the previous International Application referred to above, the satellites were solid spherical balls and the forces exerted by their movement between the radially internal and external bearing paths were transmitted by the satellite carriers located between each adjacent pair of satellites. When the parts of the external bearing path move together in order to drive the satellites radially and internally, the radially internal raceway parts were separated with the contact pressure maintained by the torque-sensitive configuration as explained in FIG. that document. When the two radially outer raceway parts approach their closest approach position, the contact patches between the satellites and the bearing paths move radially inward and, by virtue of the shape of the spherical satellites, the normal to the contact surfaces, which passes through the center of the satellite, they are tilted more closely with respect to the rolling axis so that the radially reduced component of the force becomes smaller and the axially reduced component greater. Therefore, a much larger absolute contact in the satellite must be exercised in order to reach the lowest ratios and, of course, it comes at a point where the additional radial displacement available by the additional increase in force becomes relatively minor and the forces become unacceptably high. In addition, the highest and lowest ratio of the contact patches closest to the tread axis of the satellite undergo substantial "rotation" which increases the heating effect of the friction contact generating with this additional heat that needs to be dissipated in order to maintain the device within tolerable limits. As will be described hereafter in relation to Figures 3 and 4, a variation in the contact force for a specific transmission ratio can be designated in the transmission using the inventive principles explained herein. As can be seen in Figure 2, the modality shown is configured to allow the maximum use to be made of the circumferential space so that the largest possible number of satellites can be set in a device of a given size. In Figure 2, as in the embodiment of Figure 1, the same reference numbers are used to indicate the same or corresponding components. This embodiment has five satellites 60 in a transmission of the same dimensions as in the embodiment of Figure 1, which has only four satellites. These satellites 60 are linked to the arms 27 of the satellite carrier by a disk 61 fixed to the arms 27 of the satellite carrier in the middle plane of the ring of the satellites 60. The disk 61 has generally wide radial grooves 62 within which the bushings 63 housing the rolling element bearings 25 in which the satellites roll are housed. The bushings 63 by themselves roll within the slot 62 during the relationship change movements. The grooves can be inclined from the strictly radial orientation shown, and this allows the contact forces in the external bearing path to increase or decrease. This can be a useful design tool. This embodiment is circumferentially very compact and has a high load carrying capacity. The disc 61 is locally widened to provide a wider support for the rollers constituted by the bushings 63. FIGS. 3 and 4 illustrate two different embodiments of the invention utilizing noncircular curvilinear curvature for the internal bearing path and the satellite. Only a part of the rolling path 37 is illustrated in each of Figures 3 and 4, and likewise only a part of the satellite 23. In Figure 3, the curved satellite contact surface, generally indicated at 70 of the path 37 internal bearing is formed as an elliptical curve oriented with the major axis parallel to the X axis of the transmission. In this embodiment, the satellite 23 also has a rolling contact surface 71, which in use, will roll on the rolling path surface 70 and have a generatrix in the form of an elliptical curve with its major axis perpendicular to the X axis of the transmission. The point of contact between the curved surface 71 of the satellite 23 and the surface 70 of the rolling path 37 is indicated at A. In the illustrated position, the transmission is shown in a high ratio position. An alternative position, illustrated in dashed line 23 bis with a contact point B, also illustrates the tangent AT for curve 70 at position A of satellite 23 and the tangent BT to surface 70 in the low-margin position indicated in dashed line inclines at an angle a. The radial difference between the position of the satellite 23 in the high ratio condition and its position in the low relation condition is represented by the radial dimension dR. It will be appreciated that in this embodiment, a relatively large angle, in the region of 52 ° exists between the tangent AT and the BT while the radial difference between the two positions of the satellite is of the order of 5mm. These dimensions are given to the same scale as the drawing, and are not intended to be limiting. For a given radius of the contact point (A or B) of the machine's center line, the tensile force in the contact zone A or B is defined in this sense the tensile force is the torque divided by the radio in which force is considered to be acting. The contact force by the contrast does not depend on the torque or radius but on the axial force and the contact angle (contact force = axial force / sine (contact angle)) where the axial force is substantially proportional to the moment of torsion and the constant of proportionality is determined by the advance of the spindle of internal spheres (or helix angle). The parameter normally of interest to the designer is the tensile coefficient, that is to say the tensile force ratio for the contact force at the point of contact between the satellite and the internal rolling path. This has a greater influence on efficiency. The tensile coefficient is proportional to the radius sine (contact angle). In this way, for any radio, which corresponds to a particular relationship, the designer needs to have control of the contact angle if he is going to have control of the tensile coefficient. The ratio of a contact angle at a radius to another contact angle at an adjacent radius defines the curvature. Therefore, the control of the tensile coefficient over the entire ratio of the transmission requires control of the curvature over the entire surface of the internal raceway (and only on this surface). A circular arc implies no curvature control, resulting in an arbitrary relationship between the tensile coefficient and the ratio. If more or less a constant tensile coefficient is desired over the ratio margin, as can often be the case, ie according to the principles of the present invention, this can be achieved by a non-circular arc. In an alternative embodiment in Figure 4, a structure is shown which, again, has elliptical generatrixes. In this case, the generatrix of the internal rolling path 37 has a major axis perpendicular to the machine's X axis while the major axis of the elliptical generator of satellite 23 is parallel to the machine's X axis. Again, two positions, corresponding approximately to the highest and lowest useful ratio, have been illustrated in the same manner as in the embodiment of Figure 3. In this embodiment, it will be noted that the angle of inclination of the contact point B in the low ratio is much greater than in the modality of Figure 3, as is the AT tangent. The angle α between them, however, is rather less than 35 °, while the radial difference dR between satellite 23 in its high relation position and 23a in its low relation position is much smaller by 18mm (again with reference to the scale of the drawings which is not intended to be limiting). It will be observed, therefore, that by varying the curvature of the satellite as well as the curvature of the bearing path, the difference in curvature between the internal bearing path and the satellite in the area of contact between them can be selected by any radius. This arises as follows: if it is assumed that the internal bearing path has an arbitrary curvature, perhaps determined by the previous process, the curvature of the satellite determines an important parameter in each relation, which is the difference of curvature between the two surfaces of the Contact. For a given contact force, this parameter determines the size of the contact patch and the shape. If the curvature difference is small, the patch will be highly elliptical (with the major axis in the plane of Figures 3 and 4) and will comprise a large area of maximum low contact pressure. These conditions make the load capacity high but low efficiency, the latter due to increased rotation losses with patch area and eccentricity. On the other hand, if the curvature difference is large, the contact patch will be elliptical and smaller in area but with a higher maximum contact pressure. In this case, the efficiency is increased but the load capacity is reduced. With this information, the designer is able to design a satellite profile to optimize the load capacity and efficiency in different relationships, when required. In this case, the rate of curvature change of the satellite is selected to produce the desired ratio of change in curvature difference between the satellite and the internal raceway. With this form of satellite in this fixed mode, the shape of the external bearing path can be defined in the same way, using the difference of local curvature to optimize the efficiency and / or load capacity in particular relations. If the spherical satellites are used, the procedure can still be applied to the external bearing path. In the internal bearing path, however, since the satellite arc is determined and is circular, there is a more complex exchange between the coefficient of traction, the efficiency and the load capacity in each relation.

If the increased torque capacity is required in a particular ratio, this difference in curvature becomes small so that a large contact area is achieved in order to maximize the carrying capacity. On the other hand, if the increased efficiency is the priority, the difference can be large, so that a small contact area is achieved in order to minimize fluid friction losses due to the element of rotation of the movement through the surface. Once the curvature of the satellite has been determined according to the requirements, so that the interconnection of the internal raceway is of course possible for the curvature of the external raceway, it can be optimized using similar considerations.

Claims (10)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and therefore the property described in the following claims is claimed as property. CLAIMS 1. A continuously variable transmission device of the type having planetary members in rolling contact with radially internal and external bearing paths, characterized in that each comprises relative and axially mobile, axially separated parts, and control means for determining the separation of the parts of one of the two bearing paths, in which the satellites are connected for the drive transmission to an input or output member of the transmission device by means of connection that allows the radial position of the satellites vary in response to the variation of the axial separation of the parts of the first of the two bearing paths, and in which the generatrix of the curved surface of at least one of the bearing paths and / or the satellites is not circular .
2. 2. The continuously variable transmission device according to claim 1, characterized in that the generatrix of the curved surface of at least one of the bearing paths and / or the satellites is discontinuous.
3. 3. The continuously variable transmission device according to claim 1 or claim 2, characterized in that at least part of the generatrix of the curved surface of at least one of the bearing paths and / or the satellites is a volute curve. , involute or evolves.
4. The continuously variable transmission device according to any of claims 1 to 3, characterized in that at least part of the generatrix of the curved surface of at least one of the bearing paths and / or the satellites are further curved sharply that at least another part.
5. The continuously variable transmission device according to claim 1 or claim 2, characterized in that the control means includes two adjustment members interengaged by the helical intercoupling means so that the relative rotational movement of one of the members of adjustment results in relative axial displacement between the two adjustment members.
6. The continuously variable transmission device according to any of the preceding claims, characterized in that the connection means between the satellites and a satellite carrier comprises a connector plate having a plurality of slots, having at least one radial component , within which a part of a respective satellite is coupled.
7. The continuously variable transmission device according to claim 6, characterized in that the slots are inclined in a radial line passing through the slot in such a way that the application applies or has applied to it a force having a radial component and one circumferential.
8. The continuously variable transmission device according to any of the preceding claims, characterized in that the radially internal and external bearing paths are located within a fixed housing and one or the other of the bearing paths can be rotated with respect to the accommodation through the input or output tree of the transmission device.
9. 9. The continuously variable contact transmission device for rolling according to any of the preceding claims, characterized in that it has an epicyclic gear of fixed relation in the drive train to an output drive member and / or from its drive member of entering. The continuously variable transmission device according to any of the preceding claims, characterized in that the two parts of the radially external raceway and / or the radially internal raceway are interconnected by means of a helical coupling with the driver element. rolling between the two parts to reduce friction.