Title of Invention

"A SYNCHRONISING RING FOR A GEARBOX SYNCHRONISER"

Abstract

"A SYNCHRONISING RING FOR A GEARBOX SYNCHRONIZER" A synchronising ring for a gearbox synchroniser, of the type comprising at least one frustoconical working surface adapted to cooperate by friction with a complementary working surface of another component, wherein the frustoconicel working surface is a surface of a layer of material, in particular of friction material, which is applied on a body of generally annular frustoconical form fabricated from a sheet metal blank, characterised in that the layer of material is formed by moulding it in place on the fabricated body, and in that the layer of material is a layer of mouldable friction material adapted to cooperate with a friction surface in a liquid environment.

Full Text

The present invention relates to synchronising rings for synchronisers of synchromesh gearboxes. During a gear changing operation in a multi-ratio gearbox, the synchronisation which is necessary between the selector sleeve, which rotates at the same speed as the output shaft, and the corresponding pinion is obtained by means of a synchromesh device which is a system for synchronising the two speeds using friction effects. In one known example of a design of such a synchronising device, the latter is equipped with a hub or sleeve which is coupled through a splined coupling with the secondary shaft. The selector sleeve is mounted on this hub for axial sliding movement with respect to the latter. On each side, the hub is provided with a synchronising ring, which has, for example, an internal friction cone. The cone of the synchronising ring and the complementary external cone on the pinion together constitute a conical coupling or cone clutch, which produces the required synchronisation by mutual frictional contact, that is to say it causes the roving pinion to be driven in rotation in such a way that the corresponding gear ratio is then engaged smoothly. The teeth and friction surfaces of the gears of the gearbox are of treated steel, and they are for example coated with molybdenum. In one known design of synchronising rings, the latter are made in the form of solid metal elements which are machined, the internal cones and the rings being for example of bronze, aluminium alloy or sintered steel. This design of solid synchronising ring made in one piece has a number of disadvantages. First of all, the ring is relatively heavy and has a relatively high inertia. The manufacture of the rings by machining calls for numerous steps in which machining is repeated, and is therefore particularly time-consuming and costly. Finally, the rigidity which is needed in each synchronising ring leaves no scope for reduction in its dimensions or weight. An object of the present invention is to provide a novel design for a synchronising ring which overcomes the above mentioned drawbacks. According to the invention, a synchronising ring for a gearbox synchroniser, of the type comprising at least one frustoconical bearing or working surface adapted to cooperate by friction with a complementary working surface of another component, is characterised in that the frustoconical working surface is a surface of a layer of a material, in particular a friction material, which is applied on a body of generally annular frustoconical form fabricated from a sheet metal blank. Some other preferred, and/or alternative, features of the invention are as follows: - Preferably, the frustoconical sheet metal body defines at least one frustoconical lateral face which is coated with a layer of the said material and which has a substantially constant thickness; - The external frustoconical lateral face of the body is preferably coated with a layer of the said friction material; - Alternatively or in addition, the internal frustoconical lateral face of the body may be coated with a layer of the said material, so that in the latter case there are two working surfaces, i.e. a double cone; - Preferably, the or each layer of the said material is formed by moulding it on the fabricated body; - Preferably, the or each said working surface includes a set of grooves, which are oriented substantially axially and which are formed by moulding within the thickness of the layer of friction material; - The frustoconical fabricated annular body, being delimited axially by two opposite terminal edges, preferably includes at least one additional working portion, press-formed integrally with the body and projecting from one of its said terminal edges; - The said additional working portion may be a substantially radially oriented collar portion; - The collar portion may extend radially outwards and include teeth at its periphery; the collar portion then preferably extends radially outwards from the terminal edge of the frustoconical annular body having the larger diameter; - Alternatively, the collar portion may extend radially inwardly, and include means for fastening the frustoconical annular body on to another element, and in particular on means for driving the synchronising ring in rotation; - Preferably, where the collar portion extends radially inwardly, it extends from the terminal edge of the frustoconical annular body having the larger diameter; however, the collar portion may instead extend radially inwardly from the terminal edge of the frustoconical annular body having the smaller diameter; - Preferably, the said additional working portion includes at least one substantially axially oriented lug; - Preferably, the or each said axial lug extends axially substantially along the external frustoconical lateral face of the fabricated body, so as to constitute an abutment and axial positioning element of the synchronising ring; - The said additional working portion preferably comprises at least one radially oriented lug; the or each radial lug is then preferably a driving lug for driving the synchronising ring in rotation, and projects from the terminal edge of the frustoconical annular body having the smaller diameter, towards the axis of the synchronising ring; - The frustoconical annular body is preferably fabricated by blanking, stamping and/or drawing of a flat blank of steel plate; - Preferably, the layer of the said material is a layer of a mouldable friction material adapted to cooperate with a friction surface in a liquid environment; - A layer of adhesive or bonding material is preferably interposed between the frustoconical annular body and the said layer of material. The invention not only enables the above mentioned problems to be overcome, but also has" additional advantages. In this connection, known synchronising rings, being rigid, call for a very high finish in order to ensure good contact with the material of the component with which they make frictional contact. In addition, any deformation of the known types of synchronising ring, which may be mechanical in origin or due to heat, can give rise to rapid deterioration in the friction surfaces, and lead to seizing up of the synchronising device. The invention eliminates this danger, because the friction material applied on one or both of the lateral faces of the synchronising ring is to some extent deformable. The invention also enables improved synchronising efficiency to be obtained, because on engagement of the synchronising ring according to the invention with the material of the element with which it makes frictional contact, the oil film is broken more rapidly. Accordingly, the present invention relates to a synchronising ring (20) for a gearbox synchroniser, of the type comprising at least one frustoconical working surface (26) adapted to cooperate by friction with a complementary working surface of another component, wherein the frustoconical working surface (26) is a surface of a layer of material (38), in particular of friction material, which is applied on a body (23) of generally annular frustoconical form fabricated from a sheet metal blank, characterised in that the layer of material (38) is formed by moulding it in place on the fabricated body, and in that the layer of material (38) is a layer of mouldable friction material adapted to cooperate with a friction surface in a liquid environment. Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of some preferred embodiments "of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings, in which: - Figure 1 is a perspective view of a first embodiment of a synchronising ring in accordance with the invention; - Figure 2 is an axial end view of the synchronising ring shown in Figure 1 ; - Figure 3 is a view in cross section taken on the line 3-3 in Figure 2; - Figure 4 is a view on an enlarged scale of the detail indicated in Figure 2 at D4; - Figure 5 is a view on an enlarged scale of the detail shown in Figure 2 at D5; - Figure 6 is a view on an enlarged scale of the detail indicated in Figure 3 at D6, with the plane of cross section passing through one of the grooves in the layer of friction material; - Figure 7 is a perspective view of a synchronising ring with a double cone, made in accordance with the invention; - Figure 8 is an axial end view of the synchronising ring shown in Figure 7; - Figure 9 is a view in cross section taken on the line 9-9 in Figure 8; - Figure 10 is a view on an enlarged scale in cross section taken on the line 10-10 in Figure 8; - Figure 11 is a perspective view of a third embodiment of a synchronising ring in accordance with the invention; - Figure 12 is an axial end view of the synchronising ring shown in Figure 11; - Figure 1 3 is a view in cross section taken on the line 13-13 in Figure 12; - Figure 14 is a view on an enlarged scale, in cross section taken on the line 14-14 in Figure 12; - Figure 1 5 is a view on an enlarged scale of the detail indicated in Figure 13 at D 15; - Figures 16A, 16B and 16C are scrap views in cross section to enable comparison to be made between two embodiments of the synchronising ring shown in Figures 11 to 15 and a solid ring in accordance with the current state of the art; - Figure 17 is a partial front view of the body fabricated from metal plate on which is shown one version of the peripheral teeth; - Figure 1 8 is a view in cross section taken on the line 18-18 in Figure 17; - Figure 1 9 is a partial rear view of the body fabricated in metal plate, on which is shown one embodiment of the engagement and axial positioning lugs of the sleeve; and - Figure 20 is a view in cross section taken on the line 20-20 in Figure 19. Referring first to Figures 1 to 6, these Figures show a synchronising ring which is to some extent of a generally known design. The synchronising ring, denoted by the reference numeral 20, consists essentially of a generally frustoconical portion 22 which has a frustoconical bearing surface 26, and a complementary portion, or additional working portion, for driving the ring 20 in rotation. This additional working portion is in the form of an external radial collar 24 in this embodiment. In accordance with the invention, the synchronising ring 20 consists essentially of a generally annular frustoconical body 28 which is fabricated from steel plate by means of known fabricating techniques, in particular by blanking, drawing and stamping. The generally frustoconical form of the body 28 defines an axis X-X, and is delimited axially by an axial terminal edge 30 of smaller diameter and an axial terminal edge 32 of larger diameter. The frustoconical annular body 28 also has a conical outer lateral or side face 34 and a conical inner lateral or side face 36. In the embodiment shown in Figures 1 to 6, and in accordance with the present invention, it is the conical inner side face 36 of the body 28 that is provided with a layer 38 of friction material. The frustoconical inner peripheral surface of this layer 38 constitutes the frictional bearing surface 26, also referred to as the friction cone, of the synchronising ring 20. This friction cone is adapted to cooperate with a complementary convex conical surface which is for example formed on the roving pinion of the synchroniser of the gearbox in which the synchronising ring 20 is incorporated. In accordance with a feature of the invention, the layer of friction material 38 is for example formed by moulding it on to the metallic body 28. The precise geometry of the frustoconical engagement surface 26 is obtained by moulding, that is to say it does not depend on the precision with which the annular body 28, which constitutes an insert in the mould, is made. Rather, the surface geometry depends only on the accuracy of the mould itself. The friction material which is used for forming the friction cone 26 must be a friction material which is capable of being moulded and which is able to work in oil. One example of a friction material and its method of manufacture is described and shown in the patent specification W095/26473. In order to improve the adherence of the moulded layer of friction material on the sheet steel annular body 28, it is possible to carry out an initial deposition of a resin on the body 28 or on the friction material, before the operation of applying the latter by moulding is carried out. This initial deposition may be achieved by immersion of the metal component in a bath of resin, or by projecting the resin on to the surface which is to be coated with the layer of material 28, or by any other suitable method of deposition, for example by means of a roller. In a manner which is already known for friction cones, the concave frustoconical engagement surface 26 may include a set of substantially axially oriented grooves 40. In this example, the grooves 40 are formed integrally by moulding with the layer of friction material 38. The drive collar 24 is formed integrally by blanking and stamping with the frustoconical annular body 28, and it extends radially outwardly from the axial terminal edge 32 of the latter having the larger diameter. The peripheral edge 44 of the collar portion 24 includes teeth 46 which are arranged to cooperate with complementary teeth of the selector sleeve of the synchroniser. The abutment and axial positioning elements of the synchronising sleeve 20 are also formed integrally with the frustoconical annular body 28. In this example, there are three of these elements, made here in the form of axial lugs 28 which project from the large-diameter terminal edge 32 of the frustoconical annular body 28 of the synchronising sleeve 20. These lugs 48 are bent back at substantially 1 80 degrees so that they extend axially along the outer frustoconical surface 34 of the annular body 28. To this end, the elements 48 are press-formed by blanking, stamping and bending, that is to say no additional machining operation is necessary in order to form the abutment and axial positioning elements 48. The synchronising ring 20 shown in Figures 1 to 6 can be made inexpensively. Its weight and its inertia are greatly reduced as compared with known types of synchronising ring of solid form, and its manufacture calls for no machining operation at all. In addition, because the hardness of drawn steel is greater than that of sintered steel or that of the brasses which are used in the manufacture of solid synchronising rings, it is possible to reduce the number of teeth 46. In addition, the fact that the grooves 40 are formed in the moulding operation opens the way, if necessary, to numerous possible variations in their dimensions, forms and orientations. Reference is now made to Figures 7 to 10, showing a synchronising ring having a double friction cone. In this connection, and in accordance with a known design, the ring 20 has two frustoconical bearing surfaces 26 which are two surfaces having a common axis X-X. The two surfaces 26 are substantially parallel to each other. In accordance with features of the invention, the two frustoconical surfaces or friction cones, namely an inner friction cone and an outer friction cone, are defined by the peripheral surfaces of two layers 38 of friction material, both of which are formed by moulding them on a frustoconical annular body 28 which is itself fabricated from a piece of sheet metal or metal plate. The inner and outer surfaces 26 are formed with axial grooves 40 formed integrally by moulding with the layers 38. This method of making a friction cone by moulding a friction material around a metallic insert 28, enables the working or bearing surfaces 26 to be given the greatest possible geometrical precision without any machining operation, and without any repeated machining after moulding. In this example, the synchronising ring 20 has four driving lugs 50 for driving the ring in rotation. These lugs 50 are formed integrally by press-forming with the frustoconical annular body 28. Each driving lug 50 projects axially from the axial terminal edge 30 of the body 28 having the smaller diameter, towards the axis X-X, and, in the embodiment shown in the drawings, has a conical orientation which is substantially the same as that of the body 28 itself. In another version (not shown), each lug 50 projects axially from the other terminal edge 32 of the ring, i.e. that having the larger diameter. Each lug 50 is joined to the axial terminal edge 30 through a pair of rounded reliefs 52 which increase the shear strength of the lugs 50 by preventing the occurrence of points of high stress. The double cone synchronising ring shown in Figures 7 to 10 has the advantages mentioned above, which are inherent in the design according to the invention using a body fabricated from metal plate, with friction cones which are formed by moulding in a friction material. The use of moulding which enables very precise geometries and concentricities of the two frustoconical surfaces 26 to be obtained is of particular advantage when it is compared with the state of the art in which the ring 20 is solid, and in which the two surfaces 26 have to be made by machining. In the third embodiment of the invention shown in Figures 11 to 15, the synchronising ring 20 is a ring in which the friction cone 26 is external. In accordance with features of the invention, this external friction cone 26 is formed integrally by moulding a layer 38 of friction material on to the frustoconical outer side face 34 of a frustoconical annular body 28 press-formed from sheet or plate metal. In the further embodiment shown in Figures 11 to 15, the drive means for driving the synchronising ring 20 in rotation consist of a radial collar portion 24 which extends radially inwardly towards the axis X-X from the axial terminal edge 32 of the annular body 28 having the larger diameter. In this example, the collar portion 24 is formed with three axially oriented holes 60 by which the synchronising ring 20 can be riveted on to axial bars 62, as shown in Figure 16B. Each bar 62 has a stepped axial end portion, the cylindrical portion 64 of which, having a reduced diameter, is received through a respective one of the holes 60. The portion 64 can then be upset axially so as to constitute a rivet head 66 which secures the collar portion 24 axially with respect to the axial bar 62. Figure 16A shows a synchronising ring 20 in accordance with the current state of the art, in which the body 28' of the ring 20 is a solid body formed by machining, which defines a frustoconical engagement surface, or cone, 26', which is again a machined surface. If Figure 16A is now compared with Figure 16B, it will be seen that the synchronising ring 20 made in accordance with the present invention can be used in place of the synchronising ring of Figure 1 6A without any modification of the axial bars 62 being necessary. The synchronising ring 20, press-formed from sheet metal, has a very high rigidity while at the same time having very precise geometrical features, especially as regards the friction cone surface 26. With reference to Figure 16C, this shows another version of the synchronising ring 20 shown in Figures 11 to 15 and in Figure 16B. In this version, the internal radial collar portion 24 extends radially from the axial terminal edge 30 of smaller diameter of the frustoconical annular body 28. This version is easier to make as regards the press-forming of the annular body 28 with its collar portion 24, because the re-entrant flange in the peripheral portion of the body, seen for example in Figure 16B, is replaced by an outwardly divergent flange in Figure 16C. However, with this version it is necessary either to modify the bars 62 or to use spacers as indicated at 63. In addition, the synchronising ring 20 is slightly less rigid than that in the embodiment shown in Figures 11 to 1 5. In the embodiment shown in Figures 17 and 18, the driving teeth 46 for driving the synchronising ring 20 in rotation are fabricated during the blanking and forming operations on the sheet metal body 28. These teeth are profiled, that is to say their side face 43 which faces axially towards the apex of the cone defined by the frusto-conical body is of pointed form having two flat facets 45 separated by a radially oriented working edge 47. Finally, in the embodiment shown in Figures 1 9 and 20, each of the lugs 48 which constitutes an abutment and axial positioning element for the synchronising ring 20 consists of two parallel lugs 48, between which a positioning lug 49 extends radially outwards. Like the axially oriented lugs 48, the lugs 49 are press-formed during the fabrication of the body 20. We Claim; 1. A synchronising ring (20) for a gearbox synchroniser, of the type comprising at least one frustoconical working surface (26) adapted to cooperate by friction with a complementary working surface of another component, wherein the frustoconical working surface (26) is a surface of a layer of material (38), in particular of friction material, which is applied on a body (23) of generally annular frustoconical form fabricated from a sheet metal blank, wherein the layer of material (38) is formed by moulding it in place on the fabricated body and in that the layer of material (38) is a layer of mouldable friction material adapted to cooperate with a friction surface in a liquid environment. 2. A synchronising ring as claimed in claim 1, wherein the frustoconical sheet metal body (28) defines at least one frustoconical lateral face (34, 36) which is coated with a layer of material (38) and which is of substantially constant thickness. 3. A synchronising ring as claimed in claim 1 and 2, wherein the external frustoconical lateral face (34) of the body (28) is coated with a layer of material (38). 4. A synchronising ring as claimed in claim 2 and 3, wherein the internal frustoconical lateral face (36) of the body (28) is coated with a layer of material (38). 5. A synchronising ring as claimed in anyone of the preceding claims, wherein the said working surface (26) includes a set of grooves (40), oriented substantially axially and formed by moulding within the thickness of the layer of material (38). 6. A synchronising ring as claimed in anyone of the preceding claims, wherein the annular frustoconical sheet metal body (28) is delimited axially by two terminal edges (30, 32), and in that it includes at least one additional working portion (24,48,50), formed integrally with the body and projecting from one of its terminal edges (30, 32). 7. A synchronising ring as claimed in claim 6, wherein the said working portion is a substantially radially oriented collar portion (24). 8. A synchronising ring as claimed in claim 7, wherein the collar portion (24) extends radially outwards and includes teeth (46) at its periphery (44). 9. A synchronising ring as claimed in any of the preceding claims, wherein the collar portion (24) extends radially outwards from the terminal edge (32) of the frustoconical annular body (28) having the larger diameter. 10. A synchronising ring as claimed in claim 7, wherein the collar portion (24) extends radially inwards, and includes means (60) for fastening the frustoconical annular body (28) on another element, and in particular on means (62) for driving the ring (20) in rotation. 11. A synchronising ring as claimed in claim 10, wherein the collar portion (24) extends radially inwards from the terminal edge (32) of the frustoconical annular body (26) having the larger diameter. 12. A synchronising ring as claimed in claim 10, wherein the collar portion (24) extends radially inwards from the terminal edge (30) of the frustoconical annular body (28) having the smaller diameter. 13. A synchronising ring as claimed in claim 6, wherein the said working portion includes at least one substantially axially oriented lug (48, 50). 14. A synchronising ring as claimed in any of the preceding claims, wherein the said lug (43) extends axially substantially along the external frustoconical lateral face (34) of the sheet metal body (28), so as to constitute a boss element for abutment and axial positioning of the ring (20). 15. A synchronising ring as claimed in claim 6, wherein the said working portion comprises at least one radially oriented lug (49). 16. A synchronising ring as claimed in any of the preceding claims, wherein the lug is a driving lug for driving the ring (20) in rotation, the lug projecting from the terminal edge (30) of the frustoconical annular body (28) having the smaller diameter and towards the axis of revolution (X-X) of the synchronising ring. 17. A synchronising ring as claimed in anyone of the preceding Claims, wherein the frustoconical annular body (28) is formed from steel plate by blanking, stamping and/or drawing of a flat blank. 18. A synchronising ring as claimed in any one of the preceding Claims, wherein a layer of adhesive, or glue, is interposed between the frustoconical annular body (28) and the layer of material (38). 19. A synchronising ring (20) for a gearbox synchroniser substantially as herein described with reference to and as illustrated in the accompanying drawings.

Documents:

1948-del-1997-abstract.pdf

1948-del-1997-claims.pdf

1948-del-1997-correspondence-others.pdf

1948-del-1997-correspondence-po.pdf

1948-del-1997-description (complete).pdf

1948-del-1997-drawings.pdf

1948-del-1997-form-1.pdf

1948-del-1997-form-13.pdf

1948-del-1997-form-19.pdf

1948-del-1997-form-2.pdf

1948-del-1997-form-3.pdf

1948-del-1997-form-4.pdf

1948-del-1997-form-6.pdf

1948-del-1997-petition-137.pdf