GB1588333A - Transmission device - Google Patents

Description

(54) TRANSMISSION DEVICE (71) We VADETEC, S.A., a Swiss body corporate of 7 Chemin des Charmettes, B.P. 3453, 1002 Lausanne, Switzerland do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a transmission device, and more particularly relates to improvements in or modifications of the transmission device claimed in our copending Application 79 15 195, Serial No.

1564825.

In our said co-pending Application are disclosed transmission devices comprising a frame, drive input means, drive output means, and means interconnecting said input and output means including a first element having a first axis fixed relative to the frame, a second element having a second axis intersecting said first axis at a predetermined angle established by supporting means for said second element, said first element having a pair of rolling surfaces disposed about said first axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said first axis, said second element having a pair of rolling surface disposed about said second axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said second axis, means for urging the respective rolling surfaces of the first and second elements into relative rolling engagement at points of contact located on each side of the plane passing through the point of intersection of said axes and perpendicular to the first axis, the rolling surfaces of at least one of said elements being defined by generatrices inclined oppositely with respect to the axis thereof and symmetrically with respect to the point of intersection of said first and second axes, and means for varying the spacing of the points of contact from the said point of intersection so as to give a variable ratio of rolling surface radii.

To provide a larger change in ratio in this arrangement, it has been necessary to vary the positions of the points of contact over a relatively large distance. This is not advantageous in terms of power consumption and the speed with which the transmission ratio can be obtained.

In accordance with the invention therefore, in a transmission device as above described the rolling surfaces of one of the first and second elements are defined by a curved generatrix to be convex in longitudinal section and the rolling surfaces of the other of the elements are defined by a curved generatrix to be convex in longitudinal section and the rolling surfaces of the other of the elements are defined by a curved generatrix to be concave in longitudinal section.

Preferably the respective convex and concave generatrices are arcs having radii of a slightly different value, which radii are substantially larger than the average distance of each rolling surface from its respective axis. Advantageously, the radii are approximately twenty times the value of said average distance.

Preferably the second axis of the second element is capable of moving biconically about the first axis with the apex of the cones of movement being the point of intersection of said axes.

In a preferred embodiment a drive transmitting linkage connecting the second element to another member is adapted and arranged to prevent rotation of the second element relative to the said another member, but to have flexibility in a radial direction to permit the biconical movement of the second member.

Preferably the said drive transmitting linkage is an annular diaphragm having concentric corrugations.

Preferably the inner edge of said annular diaphragm is connected directly to the second element and the outer peripheral edge thereof is connected to the frame.

An embodiment of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Figure I shows a longitudinal section of a transmission in accordance with the invention, on a plane passing through the first and second axes.

Figures 2, 3 and 4 show respectively, in perspective and on a larger scale, three of the components of the transmission of Figure 1 which have been shown in a cutaway perspective view in Figures 2 and 4 in order to make the drawing clearer.

The transmission shown includes a fixed frame having two flanks A, and A2 at each end which are joined by a crank case A3 of a generally cylindrical form. On this frame A, a first element 2 and a second element 3 are mounted by means of bearings.

The first element 2 is rotatable around a first axis 7. This first axis which is the longitudinal axis of the transmission is fixed with respect to the frame A. The first element 2 is composed of two semi-sections 4 and 5 defining two bearing tracks 8 and 9 approximately of the shape of truncated cones and which will be specified further on.

These two semi-sections 4 and 5 are mounted on a shaft 11 (output shaft) that is coaxial with the first axis 7 and are movable axially with respect to each other in the longitudinal direction of the first axis 7.

Keys 22a and 22b fasten the semi-sections 4 and 5 to the shaft 11 so that they may rotate together.

The bearing tracks 8 and 9 are disposed around the first axis 7. They are symmetrically arranged around a plane that is perpendicular to the first axis 7 at a point S of this axis. The two major bases of the semisections 4 and 5 face each other.

The shaft 11 is supported by frame A, at each of its extremities, by a system of bearings consisting of a first series of roller bearings la and ib which are coaxial with the first axis 7.

A support 13 is rotatable around the first axis 7 by means of a system of bearings 25a and 25b inserted between frame A and support 13. The abovementioned bearing ib is itself mounted inside of support 13, approximately within the transversal plane of bearing 25b at one extremity of the transmission so that the first element 2 may turn with respect to support 13 which may itself turn with respect to frame A.

Support 13. which is essentially symmetrical, has as its axis, a second axis 12 inclined with respect to the longitudinal axis 7 of the transmission. It supports the second element 3 by means of roller bearings 26a and 26b. The second element 3 is a solid of revolution, cylindrical in form, disposed about the second axis 12, which passes through point S on the first axis 7 and is inclined at a constant angle a with respect to the latter.

The second element 3 includes two bearing tracks 19 and 20 which are disposed about the second axis 12 and are arranged in a nearly symmetrical fashion with respect to a plane 16 which is perpendicular to this second axis at point S. These bearing tracks are formed by two annular rings 27 and 28 which are movable axially with respect to each other in the longitudinal direction of the second axis 12, inside the body of the second element 3, but are linked to the second element 3 so as to be non-rotatable relative thereto.

A mechanical system urges the two bearing tracks 19 and 20 of the second element 3 axially in such a manner as to apply them, with sufficient force, at two contact points P1 and P2, against the bearing tracks 8 and 9 of the first element 2. The principal patent Application 79 15 195 has described several methods of designing this mechanical system, these methods naturally being applicable in the case of the present improvements. By way of illustration, another method is indicated in Figures 1 to 3.

According to this method, each ring 27 and 28 (Figures 1 and 3) possesses exterior helicoidal ramps, opposite in direction, which make contact with interior helicoidal ramps 121a and 121b borne by rings 122 and 123 which are housed within the second element 3 and are fastened to it. It is clear that the reaction between the helicodial ramps 120a and 120b, on the one hand, and 121a and 121b, on the other hand, has a tendency to separate the semi-sections 4 and 5 from each other and to apply the bearing tracks 8 and 9 against bearing tracks 19 and 20 with a normal force sufficient to transmit the input couple without slipping.

Two annular chambers 14a and 14b are constructed between the interior wall of the two semi-sections 4 and 5 and the exterior surface of shaft 11. These annular chambers communicate with the outside by means of conduits 17a, 17b and 15 which are constructed for this purpose in the body of shaft 11. A cylindrical groove 18, which surrounds shaft 11, permits introducing a fluid into chambers 14a and 14b when shaft 11 rotates on its own axis 7. Sealing joints 21a, 21b, 21c, 21d, 21e and 21f assure tightness of the system of annular chambers and of fluid supply conduits for these annular chambers. The effect of introducing a fluid into the annular chambers 14a and 14b is to simultaneously displace the two semi sections 4 and 5 and their bearing tracks 8 and 9 axially, thus separating them. Thus, the effect of the hydraulic apparatus is to modify the relative positions of contact points P1 and P2 and consequently, the transmission ratio.

Apparatus which shall be described further on prevents the second element 3 from turning around the first axis 7 with respect to frame A. Finally, an input shaft 33 is mounted so as to rotate in support 13. This shaft 33 is coaxial with axis 7.

The transmission which has been described up to this point with reference to Figur 1 is practically identical to the one for which several designs have been described in the principal patent Application. It would be useful to review its method of operation here.

The bearing tracks 8 and 9 of the first element 2 are in rolling frictional contact at P1 and P2 against bearing tracks 19 and 20 of the second element 3. The specific contact pressure is created by ramps 120a, 120b, 121a and 121b. Due to the action of the input couple applied to shaft 33, tracks 19 and 20 are caused to rotate on the one hand, at velocity * around their own axis (the second axis 12) in a rotary reference frame linked to the first axis and to the second axis, and, on the other hand, in a conical motion of apex S, around the first axis 7, at velocity a.

The aforementioned rotational velocities * a and the rotational velocity w of the first element 2 around axis 7 are related to eath other by a kinematic equation depending on the geometry of the bearing tracks. In present case where the velocities a and * are maintained at a constant ratio, there is therefore only one output velocity at which the transmission output shaft 11 will be driven for a given relative position of points P1 and P2.

It should be pointed out that the bearing tracks 8 and 9 of the first element 2 and the bearing tracks 19 and 20 of the second element 3 automatically center themselves symmetrically with respect to point S. In fact, decentering of one of the tracks of the first element would have the effect of correlatively decentering the corresponding track of the second element. Consequently, the pressure at contact points P1 and P2 would be different since one of the tracks would receive less thrust from the helicodial ramps 120a and 120b than the other one.

This would result in a difference of fluid pressure contained in annular chambers 14a and 14b, which is impossible since these chambers are connected. Therefore, dissymetry between the tracks, if it does occur, disappears automatically.

The present improvements concern the mechanical linkage introduced in the case of the special design employed between frame A and the second element 3 in order to prevent the latter from rotating around the second axis 12 in an absolute frame of reference linked to the frame A. (Consequently, a = *) In accordance with these improvements, this linking system is arranged to drive the second element 3 by one of the longitudinal extremities, that is, the left extremity in accordance with Figure 1. Although this system could be designed to use Oldham or similar joint, it is preferably to design it using a transverse component connecting frame A to the second element 3 and offering, on the one hand, sufficient flexibility in the transverse direction to permit concial movement of the second element 3 around point S and, on the other hand, offering practically zero flexibility in the circumferential direction.

In accordance with the preferred design method which is depicted in Figures 1 and 4, the abovementioned transverse component is an annular diaphragm 124 with concentric corrugations whose exterior edge is attached to frame A by means of a first rigid ring 125 and whose interior edge is attached to the second element 3 on one of the extreme transversal faces of the latter by means of a second rigid ring 126. Ring 125 may be axially blocked by flank A1 against the exterior cage of bearing 25a by interposing an annular brace 127 and prevented from rotating by means of keys 128 inserted in exterior slots 129 (Figure 4) of ring 125. As for ring 126, it can be attached to the second element 3 by means of screw 130 which also serves to attach annular ring 122. The operation of diaphragm 124 (or equivalent component) does not need any supplementary explanation. It is obvious that, with respect to the conical gears of the principal patent Application, it facilitates the construction of the transmission by freeing the central portion of the latter and by permitting the entire essentially cylindrical portion of support 13 to be constructed in one piece.

In accordance with the invention, the present improvements concern the shape of the bearing tracks 8 and 9 of the first element 2 and bearing tracks 19 and 20 of the second element 3 and aim to provide tracks of a nature such that a relatively small axial displacement performed by the hydraulic apparatus will result in a relatively large axial displacement of contact points P and P2.

For this purpose, the two couples of these bearing tracks have curved generatrices whose radii of curvature are comparable and are long with respect to the average distance of each track from its axis of revolution 7 or 12. The ratio between these radii of curvature and this average distance is preferably between 10 and 100.

According to the method of construction shown in Figure 1, the generatrices of the two bearing tracks 8 and 9 of one of the couples, that is, those of the first element 2, are concave in form whereas the generatrices of the two bearing tracks 19 and 20 are convex in form. In Figure 1, rl indicates the radius of curvature of one of the two generatrices of bearing track 8 which are located within this plane, these two generatrices being tangents at point P,. Radius r, is slightly larger than radius r2 but is of the same order of magnitude.

It is easy to calculate (generally with the help of a computer) the radii of curvature r1 and r2 as a function of the angle of inclination a so as to obtain the desired result. The latter is a compromise between acceptable efficiency (related to the area of the contact zones) and a large displacement of points P1 and P2 for a relatively small displacement of semi-sections 4 and 5, and, consequently, of rings 27 and 28. Because of this, a variation of transmission ratio is obtained which is not only economical but practically without inertia.

WHAT WE CLAIM IS: 1. A transmission device having a frame, drive input means, drive output means, and means interconnecting said input and output means including a first element having a first axis fixed relative to the frame, a second element having a second axis intersecting said first axis at a predetermined angle established by supporting means for said second element, said first element having a pair of rolling surface disposed about said first axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said first axis, said second element having a pair of rolling surfaces disposed about said second axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said second axis, means for urging the respective rolling surfaces of the first and second elements into relative rolling engagement at points of contact located on each side of the plane passing through the point of intersection of said axes and perpendicular to the first axis, the rolling surfaces of at least one of said elements being defined by generatrices inclined oppositely with respect to the axis thereof and symmetrically with respect to the point of intersection of said first and second axes, and means for varying the spacing of the points of contact from said point of intersection so as to give a variable ratio of rolling surface radii wherein the rolling surfaces of one of the first and second element are defined by a curved generatrix to be convex in longitudinal section and the rolling surfaces of the other of the elements are defined by a curved generatrix to be concave in longitudinal section.

2. A transmission device as claimed in claim 1, wherein the respective convex and concave generatrices are arcs having radii of a slightly different value, which radii are substantially larger than the average distance of each rolling surface from its respective axis.

3. A transmission device as claimed in claim 2, wherein the said radii are approximately twenty times the value of said average distance.

4. A transmission device as claimed in any of claims 1 to 3, wherein said concave generatrix defines the rolling surfaces of said first element and said convex generatrix defines the rolling surfaces of said second element.

5. A transmission device as claimed in any preceding claim wherein the second axis is capable of moving biconically about the first axis with apex of the cones of movements being the point of intersection of said axes.

6. A transmission device as claimed in claim 5, wherein a drive transmitting linkage connecting the second element to another member is adapted and arranged to prevent rotation of the second element relative to said another member, but to have flexibility in a radial direction to permit the biconical movement of the second member.

7. A transmission device as claimed in claim 6, wherein said drive transmitting linkage is an annular diaphragm having concentric corrugations.

8. A transmission device as claimed in claim 7, wherein the inner edge of said annular diaphragm is connected directly to the second element and the outer peripheral edge thereof is connected to the frame.

9. A transmission device substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. is preferably between 10 and 100. According to the method of construction shown in Figure 1, the generatrices of the two bearing tracks 8 and 9 of one of the couples, that is, those of the first element 2, are concave in form whereas the generatrices of the two bearing tracks 19 and 20 are convex in form. In Figure 1, rl indicates the radius of curvature of one of the two generatrices of bearing track 8 which are located within this plane, these two generatrices being tangents at point P,. Radius r, is slightly larger than radius r2 but is of the same order of magnitude. It is easy to calculate (generally with the help of a computer) the radii of curvature r1 and r2 as a function of the angle of inclination a so as to obtain the desired result. The latter is a compromise between acceptable efficiency (related to the area of the contact zones) and a large displacement of points P1 and P2 for a relatively small displacement of semi-sections 4 and 5, and, consequently, of rings 27 and 28. Because of this, a variation of transmission ratio is obtained which is not only economical but practically without inertia. WHAT WE CLAIM IS:

1. A transmission device having a frame, drive input means, drive output means, and means interconnecting said input and output means including a first element having a first axis fixed relative to the frame, a second element having a second axis intersecting said first axis at a predetermined angle established by supporting means for said second element, said first element having a pair of rolling surface disposed about said first axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said first axis, said second element having a pair of rolling surfaces disposed about said second axis one each side of the plane passing through the point of intersection of said axes and perpendicular to said second axis, means for urging the respective rolling surfaces of the first and second elements into relative rolling engagement at points of contact located on each side of the plane passing through the point of intersection of said axes and perpendicular to the first axis, the rolling surfaces of at least one of said elements being defined by generatrices inclined oppositely with respect to the axis thereof and symmetrically with respect to the point of intersection of said first and second axes, and means for varying the spacing of the points of contact from said point of intersection so as to give a variable ratio of rolling surface radii wherein the rolling surfaces of one of the first and second element are defined by a curved generatrix to be convex in longitudinal section and the rolling surfaces of the other of the elements are defined by a curved generatrix to be concave in longitudinal section.

2. A transmission device as claimed in claim 1, wherein the respective convex and concave generatrices are arcs having radii of a slightly different value, which radii are substantially larger than the average distance of each rolling surface from its respective axis.

3. A transmission device as claimed in claim 2, wherein the said radii are approximately twenty times the value of said average distance.

4. A transmission device as claimed in any of claims 1 to 3, wherein said concave generatrix defines the rolling surfaces of said first element and said convex generatrix defines the rolling surfaces of said second element.

5. A transmission device as claimed in any preceding claim wherein the second axis is capable of moving biconically about the first axis with apex of the cones of movements being the point of intersection of said axes.

6. A transmission device as claimed in claim 5, wherein a drive transmitting linkage connecting the second element to another member is adapted and arranged to prevent rotation of the second element relative to said another member, but to have flexibility in a radial direction to permit the biconical movement of the second member.

7. A transmission device as claimed in claim 6, wherein said drive transmitting linkage is an annular diaphragm having concentric corrugations.

8. A transmission device as claimed in claim 7, wherein the inner edge of said annular diaphragm is connected directly to the second element and the outer peripheral edge thereof is connected to the frame.

9. A transmission device substantially as hereinbefore described with reference to the accompanying drawings.