Title of Invention	"DRY FRICTION LINING FOR THE FRICTION DEVICE OF A DRY CLUTCH FOR A MOTOR VEHICLE, A DRY FRICTION DEVICE, A DRY FRICTION CLUTCH AND A MOULD FOR MOULDING A FRICTION LINING"
Abstract	Said dry friction lining (10) comprises a friction surface (12) for interacting with a clutch pressure or reaction plate (14), wherein said friction surface (12) comprises projections (16) whose heights (H) are substenlially identical. The heights of projections extend between substantially parallel top (18) and lower (20) planes. The surface area of the assembly parts (22) of the top plane (18) intersecting the projection (16) is equal to or less than 60 % the surface area of the part (24) of the lower plane (20) intersecting the lining (10). A dry friction device comprising said friction lining, a dry clutch comprising said device and a mould whose moulding surface is shaped in such a way that it is complementary to the friction surface (12) of the friction lining (10) are also disclosed.

Title of Invention

"DRY FRICTION LINING FOR THE FRICTION DEVICE OF A DRY CLUTCH FOR A MOTOR VEHICLE, A DRY FRICTION DEVICE, A DRY FRICTION CLUTCH AND A MOULD FOR MOULDING A FRICTION LINING"

Abstract

Said dry friction lining (10) comprises a friction surface (12) for interacting with a clutch pressure or reaction plate (14), wherein said friction surface (12) comprises projections (16) whose heights (H) are substenlially identical. The heights of projections extend between substantially parallel top (18) and lower (20) planes. The surface area of the assembly parts (22) of the top plane (18) intersecting the projection (16) is equal to or less than 60 % the surface area of the part (24) of the lower plane (20) intersecting the lining (10). A dry friction device comprising said friction lining, a dry clutch comprising said device and a mould whose moulding surface is shaped in such a way that it is complementary to the friction surface (12) of the friction lining (10) are also disclosed.

Full Text	DRY FRICTION LINING FOR A FRICTION DEVICE OF A MOTOR VEHICLE DRY CLUTCH, A DRY FRICTION DEVICE, A DRY CLUTCH AND A MOULD FOR MOULDING THE FRICTION LINING The present invention concerns a dry friction lining for a friction device for a motor vehicle dry clutch, a dry friction device comprising such a friction lining, a dry clutch comprising such a friction device, as well as a mould for moulding the friction lining and a method of bedding in such a friction lining. A motor vehicle clutch is intended to transmit a torque between an engine flywheel of the motor vehicle and an input shaft of a gearbox. To this end, the clutch comprises a mechanism, rotationally fixed to the engine flywheel, and a friction device rotationally fixed to the gearbox shaft. Dry friction linings intended to equip a dry clutch ("dry clutch" in English) are usually differentiated from wet friction linings intended to equip a wet clutch ("wet clutch" in English). Dry linings function in an air environment, unlike wet linings, which function in a wet environment, in particular oil. Though both types of friction lining and associated devices make it possible to transmit a torque, there nevertheless exist significant differences in the choice of the type of lining, in particular the choice of materials and their shaping according to the environment in which they are called on to work. The mechanism of a dry clutch comprises a pressure plate and a reaction plate intended each to cooperate with a respective friction lining of the friction device. Each friction lining is carried by at least one support, normally of revolution in shape overall, generally referred to as a friction disc. There is already known, in the prior art, a friction lining for a friction device of a motor vehicle clutch, of the type comprising a friction surface intended to cooperate with a pressure or reaction plate of the clutch. The optimum functioning of a clutch friction device is generally obtained only after a period of bedding in this clutch. This is because, before bedding in, any surface defects or lack of parallelism in the friction lining and plate with which the lining cooperates limits the area of contact of the complementary friction surfaces and therefore the efficacy of functioning of the clutch. However, during bedding in, these defects are attenuated until they eventually disappear because essentially of the wear on the lining. Lack of comfort, known by the term "chattering", may appear during the bedding-in period. The bedding-in period may be relatively long. It may sometimes take approximately 8000 disengagement/engagement cycles before the functioning of the friction device is optimal. The aim of the invention is in particular to reduce the bedding-in time for the lining. To this end, an object of the invention is a dry friction lining of the aforementioned type, where the friction surface comprises projections with substantially identical heights, these projections extending in terms of height between substantially bottom and top planes, the area of all the parts of the top plane intersecting the projections being less than or equal to 60% of the area of the part of the bottom plane intersecting the lining. The projections being arranged so that the area of all the parts of the top plane intersecting these projections is less than or equal to 60% of the area of the part of the bottom plane intersecting the lining, the friction lining according to the invention wears relatively rapidly at the start of life, generally until the projections disappear. Any surface defects and lack of parallelism on the complementary friction surfaces of the lining and of the corresponding plate attenuate relatively quickly, so that the bedding-in period necessary for the optimisation of the functioning of the friction device is shorter than for a conventional friction device. It should be noted that there are known from the prior art linings intended to work in oil (for a wet clutch) whose friction surface has projections. It should be noted that the functioning of such linings differs from that of the linings according to the invention, in particular because the function of the projections on the wet lining surfaces is to improve the cooling of the lining by an optimised circulation of oil, and that these projections are preserved throughout the entire life of the lining. A dry friction lining according to the invention can also comprise one or more of the following characteristics: - at least one projection has a roughly cylindrical shape with an axis substantially perpendicular to the bottom plane; - at least one projection has a roughly conical or frustoconical shape converging towards the top plane; - the friction lining comprises at least two projections provided with contiguous bases; - the ratio of the height of the projections to a height of the friction lining including the projections is between 2% and 10%; - the height of the projections is between 0.1 and 0.3 mm; - the friction lining has a height, excluding the projections, of between 2.5 and 4 mm. Another object of the invention is a dry friction device for a motor vehicle dry clutch that comprises a dry friction lining as defined above, as well as the use of such a lining for a dry friction device. Optionally, the dry friction device according to the invention comprises two movable supports connected together by axial damping means, each support carrying a friction lining as defined above. The invention also concerns a motor vehicle dry clutch that comprises a dry friction device as defined above, as well as the use of the aforementioned linings for equipping a dry clutch. Another object of the invention is a mould for moulding a friction lining that is provided with a moulding surface with a shape complementary to the friction surface of a friction lining as defined above. Finally an object of the invention is a method of bedding in a friction lining where a lining according to the invention is chosen and where the bedding in takes place by abrasion of at least part, or even all, of the projections on the said lining. The invention will be better understood from a reading of the following description, given solely by way of example and made with reference to the accompanying drawings, in which: - figure 1 is a schematic view in section of a new dry friction lining according to a first embodiment of the invention; - figure 2 is a view similar to figure 1 of the friction lining during bedding in; - figure 3 is a view similar to figure 1 of the friction lining after bedding in; - figure 4 is a graph depicting the change in an area of contact of complementary friction surfaces of the friction lining of figure 1 and of a corresponding pressure or reaction plate, according to the wear on the friction linings; - figure 5 is a view similar to figure 1 of a friction lining according to a second embodiment of the invention; - figure 6 is a graph similar to that in figure 4, showing the change in contact area of complementary friction surfaces of the friction lining of figure 5 and a corresponding pressure or reaction plate, according to the wear on the friction lining; - figure 7 is a view similar to figure 1 of a friction lining according to a third embodiment of the invention; - figure 8 is a graph similar to that in figure 4, showing the change in contact area of complementary friction surfaces of the friction lining of figure 7 and a corresponding pressure or reaction plate, according to the wear on the friction lining. Figure 1 depicts a dry friction lining according to a first embodiment of the invention. This lining, designated by the general reference 10, is intended to equip a friction device of a motor vehicle clutch. The friction lining 10 is provided with a friction surface 12, intended to cooperate with a complementary friction surface 13 of a pressure or reaction plate 14 of the clutch, in order to rotationally connect the friction device and a clutch mechanism comprising the plate 14. Preferably, the dry friction device comprises two movable supports, connected together by axial damping means, each support carrying a friction lining 10 cooperating respectively with the pressure plate and the reaction plate. Figure 1 depicts a slight lack of parallelism between the friction lining 10 and the plate 14, as such exists in certain cases. In order to reduce the bedding-in time for the lining 10, the friction surface 12 is provided with projections 16. In the first embodiment of the invention, the projections 16 have roughly cylindrical shapes, with axes perpendicular to the friction surface 12 and substantially identical heights H. In general, the minimum distance D between two projections 16 is 0.3 mm. Preferably, the ratio of the height H of the projections 16 to a height E of the friction lining 10 excluding the projections is between 2% and 10%, preferably between 4% and 7%. For example, the height H of the projections 16 is 0.2 mm, and the height E of the friction lining 10 (measured excluding the projections) is 3.5 mm. The projections 16 extend in height between substantially parallel top 18 and bottom 20 geometric planes. When the lining 10 is new, parts 22 of the top plane 18 intersecting the projections 16 are intended to cooperate with the plate 14. In order to effectively reduce the bedding-in time, the area of all the parts 22 of the top plane 18 intersecting the projections 16 is less than or equal to 60% of the area of a part 24 of the bottom plane 20 intersecting the friction lining 10. Figures 2 and 3 depict the friction lining 10 of figure 1, respectively during and after bedding in. In figure 2, it can be seen that the projections 16 cooperating with the plate 14 wear progressively during bedding in. It will be noted that the perforated contact surface formed by the projections 16 is easier to use than a solid contact surface. Thus, during bedding in, an optimum area of contact between the plate 14 and the friction lining 10 is obtained more rapidly. Figure 3 depicts the friction lining 10 cooperating with the plate 14 after bedding in, all the projections 16 having been worn. Figure 4 is a graph showing the change in the area of contact of the complementary friction surfaces 12, 13 of the friction lining 10 and of the plate 14 (denoted A on the graph) according to the wear on the friction lining 10 (denoted U on the graph). On this graph, it can be seen that, during the bedding-in period, the contact area, equal to the area of the whole of the parts 22, remains substantially constant, until the wear is of the same magnitude as the height H of the projections The contact area A is then at a maximum. In figures 5 to 8, the elements similar to those in the previous figures are designated by identical references. In the second embodiment of the invention depicted in figure 5, the projections have a roughly frustoconical shape converging towards the top plane 18. In this case, as depicted on the graph in figure 6, the area of contact A of the complementary friction surfaces 12, 13 increases progressively until the wear U is of the same magnitude as the height H of the projections 16. When the wear U is of the same magnitude as the height H of the projections 16, the contact area A reaches its maximum value, because the contact area is no longer solely distributed over the projections 16 but over all the part 24. In the third embodiment of the invention depicted in figure 7, the projections 18 have a roughly conical shape converging towards the top plane 18 and are provided with contiguous bases. In this case, as depicted on the graph in figure 8, the area of contact A of the complementary friction surfaces 12, 13 increases progressively until it reaches its maximum value when the wear U has the same magnitude as the height H of the projections 16. Preferably, the lining 10 according to the invention is obtained by moulding by means of a mould provided with a moulding surface with a shape complementary to the friction surface 12. It should be noted that the invention is not limited to the embodiments described above. This is because it is possible to provide other forms or combination of forms for the projections 16. Comparative examples will reveal the advantages of the present invention. A reference lining was manufactured by injection, with two parallel flat surfaces denoted Ex1 hereinafter. A lining according to the invention was manufactured by injection with a mould having hollow shapes on one face in order to obtain a lining with a flat face and a face with projections. The projections are square pyramids in shape, approximately 0.1 mm high and with sides of 0.1 mm. This lining is denoted Ex2 hereinafter. They are distant by approximately 0.4 mm (centre to centre). These two linings, Ex1 and Ex2, each have outside diameters of 200 mm and 137 mm respectively and a thickness of 3.5 mm. The same material was injected to fabricate Ex1 and Ex2. The composition comes from the teachings of FR 2 822 208 and comprises more precisely, in percentage by weight: 16% unsaturated polyester resin, 8% thermo-rubber additive, 0.5% catalyst, 28.5% barium sulphate, 2% zinc stearate and 25% glass fibre approximately 25 mm long. The corresponding injection method is described in the patent application FR 2 836 970, The two linings Ex1 and Ex2 were tested on a bench that makes it possible to know the mechanical response of the linings, in particular the first stages of life of the linings corresponding to bedding in. Such a bench makes it possible in particular to reveal parameters that are related to phenomena of chattering on a clutch The bench comprises a clutch mechanism rotationally connected to an electric motor and a clutch friction member coupled to one of the ends of a torsion bar, the other end of this torsion bar being fixed with respect to the frame of the bench. The linings to be tested equip the clutch friction member. The clutch is calibrated at one third of its nominal value in order to simulate the normal starting of a vehicle. The clutch is then driven in rotation, which drives the friction member and twists the torsion bar to the torque corresponding to the first sliding between the linings the plates of the clutch. At the start of the sliding, the torque supplied by the torsion bar is greater than the clutch sliding torque, and consequently the rotation of the friction member changes direction in order to turn in the opposite direction. This change in direction of rotation causes a reduction in the torque supplied to the friction member by the torsion bar. When the friction torque becomes greater than the torque supplied by the torsion bar, the friction is accelerated in the direction of rotation of the clutch as far as the torque of the torsion bar corresponding to the second sliding between the linings the plates of the clutch. The cycle described above is repeated and corresponds to a vibratory mode whose dynamic coefficient (in newton metre seconds) is calculated. The friction damps the chattering if the dynamic coefficient is less than zero and on the other hand increases the propensity for chattering if the dynamic coefficient is greater than zero. It has been possible to find experimentally that a coefficient of friction greater than or equal to 0 05 N.m.s leads to a significant risk of chattering on a clutch. It is therefore sought to obtain friction linings whose coefficient of friction is less than 0.05 N m.s at the end of a number of cycles that is as small as possible. The dynamic coefficient of friction of the linings Ex1 and Ex2 was measured in accordance with the above test, at 120°C and 140°C, temperature conditions representing the functioning of a dry clutch. The following table sets out the dynamic coefficient of friction (N.m.s.) measured after 0, 150, 2000, 4000 cycles for each of the temperatures. (Table Removed) It is found that the lining Ex1 makes it possible to achieve a dynamic coefficient of friction of around 0.05 N.m.s. at 120°C or 140°C only after 4000 cycles, whilst the lining Ex2 according to the invention makes it possible to obtain dynamic coefficients of friction very significantly less than 0.05 N.m.s. at 120°C or 140°C as from the first cycles. It is deduced from this that a clutch equipped with a lining with projections according to the invention will present a risk of chattering that is greatly reduced compared with a standard lining of the same composition whose surfaces are flat CLAIMS 1. Dry friction lining (10) for a friction device of a motor vehicle dry clutch, of the type comprising a friction surface (12) intended to cooperate with a pressure or reaction plate (14) of the clutch, characterised in that the friction surface (12) comprises projections (16) with substantially identical heights (H), these projections (16) extending in height between substantially parallel top (18) and bottom (20) planes, the area of all the parts (22) of the top plane (18) intersecting the projections (16) being less than or equal to 60% of the area of the part (24) of the bottom plane (20) intercepting the lining (10). 2. Friction lining (10) according to claim 1, characterised in that at least one projection (16) has a roughly cylindrical shape with an axis substantially perpendicular to the bottom plane (20). 3. Friction lining (10) according to claim 1 or 2, characterised in that at least one projection (16) has a roughly conical or frustoconical shape converging towards the top plane (18). 4. Friction lining (10) according to any one of the preceding claims, characterised in that the friction lining comprises at least two projections (16) provided with contiguous bases. 5. Friction lining (10) according to any one of the preceding claims, characterised in that the ratio of the height (H) of the projections (16) to a height (E) of the friction lining (10) including the projections is between 2% and 10%. 6. Friction lining (10) according to any one of the preceding claims, characterised in that the height (H) of the projections is between 0.1 and 0.3 mm. 7. Friction lining (10) according to any one of the preceding claims, characterised in that this friction lining (10) has a height (E), excluding the projections, of between 2.5 and 4 mm. 8. Dry friction device for a motor vehicle dry clutch, characterised in that it comprises a friction lining (10) according to any one of the preceding claims. 9. Friction device according to claim 8, characterised in that it comprises two movable supports connected together by axial damping means, each support carrying a friction lining (10) according to any one of claims 1 to 7. 10. Motor vehicle dry clutch, characterised in that it comprises a friction device according to claim 8 or 9. 11. Mould for moulding a friction lining (10), characterised in that it is provided with a moulding surface with a shape complementary to the friction surface (12) of a friction lining (10) according to any one of claims 1 to 7. 12. Method of bedding in a dry friction lining (10) for a friction device of a motor vehicle dry clutch of the type comprising a friction surface (12) intended to cooperate with a pressure or reaction plate (14) of the clutch, where the said lining is chosen according to the characteristics of claim 1 and where bedding in takes place by abrasion of at least part, or even the whole, of the projections (16) of the said lining.

Full Text

DRY FRICTION LINING FOR A FRICTION DEVICE OF A MOTOR VEHICLE
DRY CLUTCH, A DRY FRICTION DEVICE, A DRY CLUTCH AND A MOULD
FOR MOULDING THE FRICTION LINING
The present invention concerns a dry friction lining for a friction device for a motor vehicle dry clutch, a dry friction device comprising such a friction lining, a dry clutch comprising such a friction device, as well as a mould for moulding the friction lining and a method of bedding in such a friction lining.
A motor vehicle clutch is intended to transmit a torque between an engine flywheel of the motor vehicle and an input shaft of a gearbox. To this end, the clutch comprises a mechanism, rotationally fixed to the engine flywheel, and a friction device rotationally fixed to the gearbox shaft.
Dry friction linings intended to equip a dry clutch ("dry clutch" in English) are usually differentiated from wet friction linings intended to equip a wet clutch ("wet clutch" in English).
Dry linings function in an air environment, unlike wet linings, which function in a wet environment, in particular oil. Though both types of friction lining and associated devices make it possible to transmit a torque, there nevertheless exist significant differences in the choice of the type of lining, in particular the choice of materials and their shaping according to the environment in which they are called on to work.
The mechanism of a dry clutch comprises a pressure plate and a reaction plate intended each to cooperate with a respective friction lining of the friction device. Each friction lining is carried by at least one support, normally of revolution in shape overall, generally referred to as a friction disc.
There is already known, in the prior art, a friction lining for a friction device of a motor vehicle clutch, of the type comprising a friction surface intended to

cooperate with a pressure or reaction plate of the clutch.
The optimum functioning of a clutch friction device is generally obtained only after a period of bedding in this clutch. This is because, before bedding in, any surface defects or lack of parallelism in the friction lining and plate with which the lining cooperates limits the area of contact of the complementary friction surfaces and therefore the efficacy of functioning of the clutch. However, during bedding in, these defects are attenuated until they eventually disappear because essentially of the wear on the lining.
Lack of comfort, known by the term "chattering", may appear during the bedding-in period. The bedding-in period may be relatively long. It may sometimes take approximately 8000 disengagement/engagement cycles before the functioning of the friction device is optimal.
The aim of the invention is in particular to reduce the bedding-in time for the lining.
To this end, an object of the invention is a dry friction lining of the aforementioned type, where the friction surface comprises projections with substantially identical heights, these projections extending in terms of height between substantially bottom and top planes, the area of all the parts of the top plane intersecting the projections being less than or equal to 60% of the area of the part of the bottom plane intersecting the lining.
The projections being arranged so that the area of all the parts of the top plane intersecting these projections is less than or equal to 60% of the area of the part of the bottom plane intersecting the lining, the friction lining according to the invention wears relatively rapidly at the start of life, generally until the projections disappear.
Any surface defects and lack of parallelism on the complementary friction surfaces of the lining and of the corresponding plate attenuate relatively quickly, so that the bedding-in period necessary for the optimisation of the

functioning of the friction device is shorter than for a conventional friction device.
It should be noted that there are known from the prior art linings intended to work in oil (for a wet clutch) whose friction surface has projections.
It should be noted that the functioning of such linings differs from that of the linings according to the invention, in particular because the function of the projections on the wet lining surfaces is to improve the cooling of the lining by an optimised circulation of oil, and that these projections are preserved throughout the entire life of the lining.
A dry friction lining according to the invention can also comprise one or more of the following characteristics:
- at least one projection has a roughly cylindrical shape with an axis
substantially perpendicular to the bottom plane;
- at least one projection has a roughly conical or frustoconical shape
converging towards the top plane;

- the friction lining comprises at least two projections provided with contiguous
bases;
- the ratio of the height of the projections to a height of the friction lining
including the projections is between 2% and 10%;
- the height of the projections is between 0.1 and 0.3 mm;
- the friction lining has a height, excluding the projections, of between 2.5 and
4 mm.
Another object of the invention is a dry friction device for a motor vehicle dry clutch that comprises a dry friction lining as defined above, as well as the use

of such a lining for a dry friction device.
Optionally, the dry friction device according to the invention comprises two movable supports connected together by axial damping means, each support carrying a friction lining as defined above.
The invention also concerns a motor vehicle dry clutch that comprises a dry friction device as defined above, as well as the use of the aforementioned linings for equipping a dry clutch.
Another object of the invention is a mould for moulding a friction lining that is provided with a moulding surface with a shape complementary to the friction surface of a friction lining as defined above.
Finally an object of the invention is a method of bedding in a friction lining where a lining according to the invention is chosen and where the bedding in takes place by abrasion of at least part, or even all, of the projections on the said lining.
The invention will be better understood from a reading of the following description, given solely by way of example and made with reference to the accompanying drawings, in which:
- figure 1 is a schematic view in section of a new dry friction lining according to
a first embodiment of the invention;
- figure 2 is a view similar to figure 1 of the friction lining during bedding in;
- figure 3 is a view similar to figure 1 of the friction lining after bedding in;
- figure 4 is a graph depicting the change in an area of contact of
complementary friction surfaces of the friction lining of figure 1 and of a
corresponding pressure or reaction plate, according to the wear on the friction
linings;

- figure 5 is a view similar to figure 1 of a friction lining according to a second
embodiment of the invention;
- figure 6 is a graph similar to that in figure 4, showing the change in contact
area of complementary friction surfaces of the friction lining of figure 5 and a
corresponding pressure or reaction plate, according to the wear on the friction
lining;
- figure 7 is a view similar to figure 1 of a friction lining according to a third
embodiment of the invention;
- figure 8 is a graph similar to that in figure 4, showing the change in contact
area of complementary friction surfaces of the friction lining of figure 7 and a
corresponding pressure or reaction plate, according to the wear on the friction
lining.
Figure 1 depicts a dry friction lining according to a first embodiment of the invention. This lining, designated by the general reference 10, is intended to equip a friction device of a motor vehicle clutch.
The friction lining 10 is provided with a friction surface 12, intended to cooperate with a complementary friction surface 13 of a pressure or reaction plate 14 of the clutch, in order to rotationally connect the friction device and a clutch mechanism comprising the plate 14.
Preferably, the dry friction device comprises two movable supports, connected together by axial damping means, each support carrying a friction lining 10 cooperating respectively with the pressure plate and the reaction plate.
Figure 1 depicts a slight lack of parallelism between the friction lining 10 and the plate 14, as such exists in certain cases.
In order to reduce the bedding-in time for the lining 10, the friction surface 12

is provided with projections 16. In the first embodiment of the invention, the projections 16 have roughly cylindrical shapes, with axes perpendicular to the friction surface 12 and substantially identical heights H. In general, the minimum distance D between two projections 16 is 0.3 mm.
Preferably, the ratio of the height H of the projections 16 to a height E of the friction lining 10 excluding the projections is between 2% and 10%, preferably between 4% and 7%. For example, the height H of the projections 16 is 0.2 mm, and the height E of the friction lining 10 (measured excluding the projections) is 3.5 mm.
The projections 16 extend in height between substantially parallel top 18 and bottom 20 geometric planes. When the lining 10 is new, parts 22 of the top plane 18 intersecting the projections 16 are intended to cooperate with the plate 14.
In order to effectively reduce the bedding-in time, the area of all the parts 22 of the top plane 18 intersecting the projections 16 is less than or equal to 60% of the area of a part 24 of the bottom plane 20 intersecting the friction lining 10.
Figures 2 and 3 depict the friction lining 10 of figure 1, respectively during and after bedding in.
In figure 2, it can be seen that the projections 16 cooperating with the plate 14 wear progressively during bedding in.
It will be noted that the perforated contact surface formed by the projections 16 is easier to use than a solid contact surface. Thus, during bedding in, an optimum area of contact between the plate 14 and the friction lining 10 is obtained more rapidly.
Figure 3 depicts the friction lining 10 cooperating with the plate 14 after bedding in, all the projections 16 having been worn.

Figure 4 is a graph showing the change in the area of contact of the complementary friction surfaces 12, 13 of the friction lining 10 and of the plate 14 (denoted A on the graph) according to the wear on the friction lining 10 (denoted U on the graph).
On this graph, it can be seen that, during the bedding-in period, the contact area, equal to the area of the whole of the parts 22, remains substantially constant, until the wear is of the same magnitude as the height H of the projections The contact area A is then at a maximum.
In figures 5 to 8, the elements similar to those in the previous figures are designated by identical references.
In the second embodiment of the invention depicted in figure 5, the projections have a roughly frustoconical shape converging towards the top plane 18.
In this case, as depicted on the graph in figure 6, the area of contact A of the complementary friction surfaces 12, 13 increases progressively until the wear U is of the same magnitude as the height H of the projections 16.
When the wear U is of the same magnitude as the height H of the projections 16, the contact area A reaches its maximum value, because the contact area is no longer solely distributed over the projections 16 but over all the part 24.
In the third embodiment of the invention depicted in figure 7, the projections 18 have a roughly conical shape converging towards the top plane 18 and are provided with contiguous bases.
In this case, as depicted on the graph in figure 8, the area of contact A of the complementary friction surfaces 12, 13 increases progressively until it reaches its maximum value when the wear U has the same magnitude as the height H of the projections 16.

Preferably, the lining 10 according to the invention is obtained by moulding by means of a mould provided with a moulding surface with a shape complementary to the friction surface 12.
It should be noted that the invention is not limited to the embodiments described above. This is because it is possible to provide other forms or combination of forms for the projections 16.
Comparative examples will reveal the advantages of the present invention.
A reference lining was manufactured by injection, with two parallel flat surfaces denoted Ex1 hereinafter.
A lining according to the invention was manufactured by injection with a mould having hollow shapes on one face in order to obtain a lining with a flat face and a face with projections. The projections are square pyramids in shape, approximately 0.1 mm high and with sides of 0.1 mm. This lining is denoted Ex2 hereinafter. They are distant by approximately 0.4 mm (centre to centre).
These two linings, Ex1 and Ex2, each have outside diameters of 200 mm and 137 mm respectively and a thickness of 3.5 mm. The same material was injected to fabricate Ex1 and Ex2. The composition comes from the teachings of FR 2 822 208 and comprises more precisely, in percentage by weight: 16% unsaturated polyester resin, 8% thermo-rubber additive, 0.5% catalyst, 28.5% barium sulphate, 2% zinc stearate and 25% glass fibre approximately 25 mm long.
The corresponding injection method is described in the patent application FR 2 836 970,
The two linings Ex1 and Ex2 were tested on a bench that makes it possible to know the mechanical response of the linings, in particular the first stages of life of the linings corresponding to bedding in. Such a bench makes it possible in particular to reveal parameters that are related to phenomena of

chattering on a clutch
The bench comprises a clutch mechanism rotationally connected to an electric motor and a clutch friction member coupled to one of the ends of a torsion bar, the other end of this torsion bar being fixed with respect to the frame of the bench. The linings to be tested equip the clutch friction member. The clutch is calibrated at one third of its nominal value in order to simulate the normal starting of a vehicle.
The clutch is then driven in rotation, which drives the friction member and twists the torsion bar to the torque corresponding to the first sliding between the linings the plates of the clutch. At the start of the sliding, the torque supplied by the torsion bar is greater than the clutch sliding torque, and consequently the rotation of the friction member changes direction in order to turn in the opposite direction. This change in direction of rotation causes a reduction in the torque supplied to the friction member by the torsion bar. When the friction torque becomes greater than the torque supplied by the torsion bar, the friction is accelerated in the direction of rotation of the clutch as far as the torque of the torsion bar corresponding to the second sliding between the linings the plates of the clutch. The cycle described above is repeated and corresponds to a vibratory mode whose dynamic coefficient (in newton metre seconds) is calculated.
The friction damps the chattering if the dynamic coefficient is less than zero and on the other hand increases the propensity for chattering if the dynamic coefficient is greater than zero.
It has been possible to find experimentally that a coefficient of friction greater than or equal to 0 05 N.m.s leads to a significant risk of chattering on a clutch.
It is therefore sought to obtain friction linings whose coefficient of friction is less than 0.05 N m.s at the end of a number of cycles that is as small as possible.

The dynamic coefficient of friction of the linings Ex1 and Ex2 was measured in accordance with the above test, at 120°C and 140°C, temperature conditions representing the functioning of a dry clutch.
The following table sets out the dynamic coefficient of friction (N.m.s.) measured after 0, 150, 2000, 4000 cycles for each of the temperatures.

(Table Removed) It is found that the lining Ex1 makes it possible to achieve a dynamic coefficient of friction of around 0.05 N.m.s. at 120°C or 140°C only after 4000 cycles, whilst the lining Ex2 according to the invention makes it possible to obtain dynamic coefficients of friction very significantly less than 0.05 N.m.s. at 120°C or 140°C as from the first cycles.
It is deduced from this that a clutch equipped with a lining with projections according to the invention will present a risk of chattering that is greatly reduced compared with a standard lining of the same composition whose surfaces are flat

CLAIMS
1. Dry friction lining (10) for a friction device of a motor vehicle dry clutch, of the type comprising a friction surface (12) intended to cooperate with a pressure or reaction plate (14) of the clutch, characterised in that the friction surface (12) comprises projections (16) with substantially identical heights (H), these projections (16) extending in height between substantially parallel top (18) and bottom (20) planes, the area of all the parts (22) of the top plane (18) intersecting the projections (16) being less than or equal to 60% of the area of the part (24) of the bottom plane (20) intercepting the lining (10).
2. Friction lining (10) according to claim 1, characterised in that at least
one projection (16) has a roughly cylindrical shape with an axis
substantially perpendicular to the bottom plane (20).
3. Friction lining (10) according to claim 1 or 2, characterised in that at
least one projection (16) has a roughly conical or frustoconical shape
converging towards the top plane (18).
4. Friction lining (10) according to any one of the preceding claims,
characterised in that the friction lining comprises at least two
projections (16) provided with contiguous bases.

5. Friction lining (10) according to any one of the preceding claims,
characterised in that the ratio of the height (H) of the projections (16) to
a height (E) of the friction lining (10) including the projections is
between 2% and 10%.
6. Friction lining (10) according to any one of the preceding claims,
characterised in that the height (H) of the projections is between 0.1
and 0.3 mm.

7. Friction lining (10) according to any one of the preceding claims,
characterised in that this friction lining (10) has a height (E), excluding
the projections, of between 2.5 and 4 mm.
8. Dry friction device for a motor vehicle dry clutch, characterised in
that it comprises a friction lining (10) according to any one of the
preceding claims.

9. Friction device according to claim 8, characterised in that it
comprises two movable supports connected together by axial damping
means, each support carrying a friction lining (10) according to any one
of claims 1 to 7.
10. Motor vehicle dry clutch, characterised in that it comprises a
friction device according to claim 8 or 9.
11. Mould for moulding a friction lining (10), characterised in that it is
provided with a moulding surface with a shape complementary to the
friction surface (12) of a friction lining (10) according to any one of
claims 1 to 7.
12. Method of bedding in a dry friction lining (10) for a friction device of
a motor vehicle dry clutch of the type comprising a friction surface (12)
intended to cooperate with a pressure or reaction plate (14) of the
clutch, where the said lining is chosen according to the characteristics
of claim 1 and where bedding in takes place by abrasion of at least
part, or even the whole, of the projections (16) of the said lining.

Documents:

http://ipindiaonline.gov.in/patentsearch/GrantedSearch/viewdoc.aspx?id=XRroRZXI6ca5bPlnmwJ2qg==&loc=+mN2fYxnTC4l0fUd8W4CAA==

« Previous Patent

Next Patent »

Patent Number

268884

Indian Patent Application Number

2453/DELNP/2007

PG Journal Number

39/2015

Publication Date

25-Sep-2015

Grant Date

21-Sep-2015

Date of Filing

02-Apr-2007

Name of Patentee

VALEO MATERIAUX DE FRICTION

Applicant Address

RUE THIMONIER, F-87020 LIMOGES, FRANCE

Inventors:

#	Inventor's Name	Inventor's Address
1	MICHEL MARCHISSEAU	33 RUE CONDORCET, F-87100 LIMOGES, FRANCE
2	LOIC ADAMCZAK	LEYRAUD, F-87140 ROUSSAC, FRANCE

PCT International Classification Number

F16D 65/092

PCT International Application Number

PCT/FR2005/050866

PCT International Filing date

2005-10-18

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	0452354	2004-10-18	France