EP2625637A2 - Method for designing a mould and a tyre - Google Patents

Abstract

The invention relates to a method for designing a mould for vulcanising a tyre, which includes at least one audible wear indicator, comprising the following steps (200-210): defining an initial population, including a mould module having at least one feature relating to the indicator; generating a modified population, including a mould module having at least one feature relating to the indicator obtained by modifying at least one feature of at least one mould model of the initial population; determining at least one performance indicator of every mould model of an assessment population including at least one mould model of the modified population, according to at least one feature of each mould model of the assessment population; selecting one or more mould models from the assessment population according to the performance indicator(s).

Description

 . .

Method of designing a mold and a tire

The present invention relates to a method of designing a mold or a tire.

 A tire of a first type is known comprising a tread provided with a sculpture. The sculpture includes several carving elements such as grooves, furrows or cuts. When rolling the tire, it emits a rolling noise generated by the interaction of this sculpture with the ground. In the case where the sculpture is defined from a periodic pattern, the rolling sound includes a siren due to the periodic interaction of this pattern with the ground. Thus, in order to minimize rolling noise, the tread pattern usually comprises several distinct circumferential portions. Each circumferential portion bears a pattern selected from a group of several distinct patterns, typically three or four patterns. The sculpture thus consists of a non-periodic arrangement of these patterns so as to avoid the sirenation of the tire.

 Also known is a tire of a second type comprising a tread comprising sound wear indicators. These lamps are distributed over the tread so as to emit a characteristic noise beyond a predetermined wear threshold. The characteristic noise is in particular a function of the predetermined distribution.

 However, the integration of the audible wear indicators of the tire of the second type on a tire of the first type poses the problem of the compatibility of the sculpture of the tire of the first type with the predetermined distribution of the sound wear indicators of the tire of the first type. pneumatic second type. Indeed, in the case where a wear indicator is located at the same position as an element of the sculpture such as a seal between two patterns or a notch, the witness does not emit any noise and therefore does not allow detect wear. If the predetermined distribution is respected, it is difficult, if not impossible, to empirically design a tire in which the wear indicators are not located in the same position as the elements of the sculpture. If we position the wear indicators by avoiding the positions of these elements of the sculpture, we do not respect the predetermined distribution. The indicators do not emit the characteristic noise and therefore do not detect the wear of the tire.

 The invention aims to provide a method for easily designing a mold and a tire comprising sound wear indicators.

For this purpose, the subject of the invention is a method for designing a mold of . vulcanizing a tire comprising at least one sound wear indicator, comprising the following steps A to D:

 A - an initial population is defined comprising at least one mold model having at least one characteristic relating to the control,

 B - a modified population is generated comprising at least one mold model having at least one control characteristic obtained by modifying at least one characteristic of at least one mold model of the initial population, C - at least one an indicator of performance of each mold model of an assessment population comprising at least one mold model of the modified population, based on at least one characteristic of each mold model of the assessment population,

 D - one or more mold models of the evaluation population are selected from the performance indicator (s).

 The method according to the invention makes it possible to generate, preferably in an automated manner, populations of model molds and makes it possible to check easily, thanks to the performance indicator, whether the discriminant characteristics relating to the control of a selected mold model satisfy predetermined performance conditions. Thus, it can easily be verified whether the selected mold model makes it possible to manufacture a tire in which the sound wear indicator (s) have the desired distribution and emit the characteristic wear noise of the tire.

 The method according to the invention can use a genetic algorithm. Thus, during step B, modification operators are used that mimic the biological phenomena of combination and / or mutation of the discriminant characteristics. Alternatively, the method according to the invention can use other algorithms of the heuristic or meta-heuristic type. In these cases, during step B, the modification operators are random or semi-random.

 In addition, the method according to the invention makes it possible to very quickly select a mold model satisfying the predetermined performance conditions. Indeed, through the use of a computer program on a conventional personal computer, a mold model can be generally selected in less than 2 minutes. In this case, all the steps are performed by automated means. Alternatively, one or more steps are performed through automated means.

In one embodiment, each indicator comprises a sound cavity shaped so that, beyond a predetermined radial wear threshold, the sound cavity opens radially outwardly of the tire and is shaped so as to be closed by the soil in a watertight manner as it passes through the area of the . . tire contact with the ground.

 When the tire is worn beyond the wear threshold that is considered as a warning threshold, one or more sound cavities appear on the tread.

 These cavities have a particular shape that gives them sound properties, that is to say that these cavities cause a characteristic noise during the rolling of the worn tire.

 Indeed, because the cavity is shaped so as to be closed by the ground substantially sealed, it temporarily traps air during its passage in the contact area of the tire with the ground. However, under the effect of the deformation of the tire in the contact area, the air trapped in the cavity compresses and then suddenly relaxes at the exit of the contact area when the tread leaves the contact with the ground at the rear of the tire and that consequently the cavity opens.

 This expansion of the air lasts about a few milliseconds and causes a specific noise, sometimes called hissing or pumping noise, a function in particular of the shape and volume of the cavity.

 This characteristic noise, which only appears when the tire is worn beyond a certain threshold, thus forms a sound wear indicator. Thus, even if the driver does not visually and regularly inspect the surface condition of his tires, he will be informed of the excessive wear of his tires when, while driving, he will hear this characteristic hiss.

 Preferably, the shape and the volume of the sound cavity are determined so that the frequency and the intensity of the noise produced by the passage of the cavity in the contact area makes this noise audible by the driver from the passenger compartment of the vehicle. vehicle.

 To detect this hissing, it is also possible to use one or more microphones for detecting rolling sounds, connected to a computer capable of detecting the hissing noise of the rolling noise and to inform the driver of the wear of his tires.

Since this phenomenon of hissing occurs only when air is compressed in the cavity and then expanded by escaping from the cavity, it is important that this cavity is sealed substantially by the ground during its passage in the contact area. Indeed, a cavity whose top would be covered by the ground but which, moreover, would include transverse channels in fluid communication with the outside air, would not be sound because the air it contains could not be compressed. This is particularly the case with regard to tread patterns of tires of the state of the art which are generally . . formed by a network of channels communicating the different cavities with each other and with the outside air.

 Similarly, a cavity whose dimensions are too large to be completely covered by the ground during its passage in the contact area, for example a cavity whose length is greater than the length of the contact area, does not could not form a sound cavity within the meaning of the invention.

 In an optional manner, each characteristic relating to the sound wear indicator is chosen from the group comprising at least one characteristic relating to the number of witnesses, at least one characteristic relating to the total volume of the cavities, the volume of each sound cavity being defined when the predetermined radial wear threshold is reached, at least one characteristic relating to the circumferential distribution of the controls and at least one characteristic relating to a dimension of each control.

 The group defined above makes it possible to define the characteristics of the witnesses so that they are audible and can be integrated in a tire.

 The characteristic relating to the circumferential distribution of the witnesses and the characteristic relating to the geometry of each witness make it possible to ensure that each cavity is closed in a substantially watertight manner by the ground during its passage in the contact area and is not not open, for example by a sculpture element opening into the cavity or through the cavity.

 The characteristic relating to the circumferential distribution of the witnesses and the characteristic relating to the number of witnesses make it possible to ensure that the characteristic noise emitted by all the witnesses will be in accordance with the noise sought during the detection of the wear.

 The number of witnesses characteristic and the total cavity volume characteristic make it possible to ensure that the characteristic noise can be detected. Below a predetermined volume, the characteristic noise emitted by the witnesses does not have a spectral level, that is to say a frequency intensity, sufficient to be robustly distinguished from parasitic elementary frequency components, corresponding, for example the noise of the engine and the kinematic chain associated therewith.

 According to other optional features of the method according to the invention:

 The characteristics relating to the circumferential distribution comprise the equi-distribution of the controls and a reference angle of positioning of at least one control. Alternatively, the indicators may be distributed according to an irregular predetermined distribution. In this case, the characteristics relating to the circumferential distribution comprise a positioning angle of each control.

Each witness comprising two ribs formed at the bottom of a groove of . . pneumatic, the characteristic relating to the dimension comprises the thickness of each rib of each witness in the circumferential direction.

 Advantageously, the performance indicator or indicators are determined from the total volume of the sound cavities. The higher the volume of the cavities, the higher the spectral level, ie the frequency intensity, of the characteristic noise. Thus, the higher the volume of the cavities, the more reliable the detection of tire wear. Thus, a mold is preferably sought for which the total volume of the cavities is maximum.

 Each control comprising two ribs formed at the bottom of a groove of the tire, the performance indicator or indicators are determined from at least one indicator of interpenetration between each rib and at least one predetermined zone of the mold model, so-called prohibited .

 The prohibited areas of the mold are such that, if ribs are located in these prohibited areas, the cavities do not function as a sound cavity, for example because there is an air leak. Thus, a mold is preferably sought for which the interpenetration between each rib and the prohibited areas of the mold model is minimal or even zero.

 In one embodiment, a plurality of axially adjacent circumferential bands are determined on each mold model of the evaluation population and at least one interpenetration indicator between each rib and each forbidden zone is determined for each band.

 Each forbidden zone of each band and therefore of each groove is defined. Thus, instead of determining each interpenetration indicator for the entire axial dimension of the tire, each indicator is determined for each band which has a reduced axial dimension. In this embodiment, the forbidden zones have a dimension in the reduced circumferential direction, which gives the process more flexibility, in particular for positioning the controls. This improves the speed of selection of a mold model satisfying the predetermined performance conditions.

 Any number of circumferential bands can be defined. Each band may, depending on the mold model, have a constant or fixed axial dimension. Each band being delimited by two circumferential edges, the edges may be parallel to the circumferential direction or may extend in a path zig-zag or sinusoid. In addition, the strips may, depending on the mold model, for a predetermined angular position, have the same axial dimension or several axial dimensions.

According to other optional features of the method: . .

Since the mold model comprises a plurality of distinct molding matrices of circumferential portions distinct from the tire, the prohibited zones comprise two end zones of each matrix. Indeed, the end zones are fragile so that it is avoided to place molding elements of the control ribs near the circumferential end zones of each matrix.

 The forbidden zone comprises a zone traversed by a molding blade of a tread element so that a sound cavity located in the corresponding forbidden zone of the tire is not closed by the ground in a sealed manner during its passage through the tread. area of tire contact with the ground. Indeed, such a sculpture element would cause an air leak of the sound cavity, which would prevent compression and relaxation of the air contained in this cavity. However, an area comprising a sculpture element connecting two cavities arranged so that these cavities are closed substantially simultaneously by the ground in a substantially watertight manner when they pass through the area of contact of the tire with the ground does not constitute a prohibited zone. .

 Advantageously, the tire comprising a legal wear indicator, the one or more performance indicators are determined from at least one inclusion indicator of at least one legal wear indicator in at least one sound cavity.

 When a legal wear indicator is included in a cavity, it can act, according to the value of the predetermined threshold, as one of the ribs of the cavity and separate the cavity into two contiguous cavities. On the one hand, this results in the destruction of the predetermined distribution of the witnesses and, on the other hand, the decrease of the total volume of the cavities.

 Thus, a mold is preferably sought for which the inclusion of the legal wear indicators in the sound cavities is minimal or even zero.

 Preferably, several axially adjacent circumferential bands are determined on the mold model and at least one inclusion indicator of each lawful wear indicator in each sound cavity is determined for each band.

 Thus, instead of determining each inclusion indicator for the entire width of the tire, each indicator is determined for each band. The process is then given more flexibility, in particular for positioning the witnesses. This improves the speed of selection of a mold model satisfying the predetermined performance conditions.

In one embodiment, each indicator comprises a rib extending radially from the bottom of a circumferential groove of the tire and arranged to contact the ground as it passes through the contact area of the tire. . . pneumatic with the ground beyond a predetermined radial wear threshold of the tire.

 The ribs, without necessarily forming a cavity, may be sufficient to cause a characteristic noise during the rolling of the tire once the wear threshold of the tire reaches. The inventors advance the hypothesis according to which this noise is generated by at least two distinct physical phenomena having a synergistic effect. On the one hand, once the wear threshold is reached, the noise is generated by the impact of the rib on the ground. On the other hand, once the wear threshold is reached, when the tire rolls on the ground, an air plug is likely to form in the groove upstream of the rib because of the significant relative speed between the tire. tire and the air into which the tire enters. Air is thus trapped temporarily in a space between this cap and the rib during the passage of this space in the contact area of the tire with the ground. Under the effect of the deformation of the tire in the contact area, this air trapped in this space compresses and then slackens abruptly at the exit of the contact area when the tread leaves the contact with the ground at the same time. rear of the tire.

 Due to the reduced number of ribs, the design of the tire and its mold is also made simpler because, since each indicator does not form a closed cavity, it is not necessary to avoid the positioning of a rib in an area. forbidden crossed by a lamella.

 Preferably, the ribs are arranged so that, irrespective of the wear of the tire, two circumferentially successive ribs of the same groove and the groove delimit a space which remains open to air during the passage of the two ribs in the groove. tire contact area with the ground.

 Optionally, each characteristic relating to the sound wear indicator is chosen from the group comprising at least one characteristic relating to the number of witnesses, at least one characteristic relating to the circumferential distribution of the controls and at least one characteristic relating to a dimension of each witness.

 According to other optional features of the method according to the invention:

 The characteristics relating to the circumferential distribution comprise the equi-distribution of the controls and a reference angle of positioning of at least one control.

 The dimension characteristic includes the thickness of each rib of each indicator in the circumferential direction.

Advantageously, the performance indicator or indicators are determined from at least one interpenetration indicator between each rib and at least one zone. . - predetermined mold model, called prohibited.

 The prohibited areas of the mold are such that, if ribs are located in these prohibited areas, the ribs are likely to have molding defects and therefore do not generate sufficient noise by striking the ground. Thus, a mold is preferably sought for which the interpenetration between each rib and the prohibited areas of the mold model is minimal or even zero.

 In one embodiment, a plurality of circumferentially adjacent circumferential bands are determined on the mold model and at least one interpenetration indicator between each rib and each forbidden zone is determined for each band.

 According to another optional feature of the method, the mold model comprising a plurality of distinct molding matrices of circumferential portions distinct from the tire, the prohibited zones comprise two end zones of each matrix.

 Advantageously, the tire comprising a legal wear indicator, the one or more performance indicators are determined from at least one overlapping indicator of at least one legal wear indicator with a rib.

 A mold is preferably sought for which the covering of the legal wear indicators with the ribs is minimal or even zero.

 Preferably, a plurality of circumferentially adjacent circumferential bands are determined on each mold model of the evaluation population and at least one overlap indicator of each legal wear indicator with each rib is determined for each band.

 Optionally, each mold model of the evaluation population is selected, each performance indicator of which satisfies a predetermined performance condition associated with the performance indicator.

 Advantageously, the tire comprising N grooves with N> 1 and comprising several sets of witnesses equi-distributed circumferentially, the controls of each set being substantially axially aligned with each other, each mold model of the evaluation population is selected in each case. which, for each set, at least one number N1 interpenetration indicator (s) satisfy a predetermined performance condition associated with the interpenetration indicator with N> N1.

By "circumferentially equi-distributed set of witnesses" is meant that each witness of a set is situated substantially at the same angular distance of the witnesses of the sets which are adjacent to it, whether the witnesses are arranged in the same groove or not. In other words, the equi-distributed sets have two . . to two, the same angular difference. In the case of a single set, this single set is considered circumferentially equi-distributed. Indeed, in this case, the adjacent sets are formed by the set itself.

 For each set, it is thus possible to delete at most N-N1 controls which would have an interpenetration with the forbidden zones. This improves the flexibility and speed of the mold model selection process whose performance indicators satisfy the predetermined performance conditions.

 Preferably, after step A and before step B, the mold models of the initial population are classified and a part of the initial population is selected.

 This avoids proceeding to subsequent steps with mold models that are presumed that they will not generate mold models whose indicators meet all predetermined performance conditions.

 Advantageously, as long as each indicator does not satisfy a predetermined performance condition, steps B and C are repeated generating a new modified population by at least one modification of at least one characteristic of at least one mold model of the population. evaluation form constituting a new initial population.

 It acts by successive iteration so as to converge the discriminant characteristics of each mold model of each evaluation population to a mold model whose indicator (s) satisfy the predetermined predetermined performance conditions.

 Preferably, the mold models of the assessment population are classified and a portion of the assessment population is selected, the selected portion of the assessment population then forming at least a portion of the new initial population.

 This avoids the following iterations with mold models of the evaluation population that are assumed to be unable to generate mold models whose indicators satisfy all of the predetermined performance conditions.

 Advantageously, each characteristic of each model of the initial population and / or of the modified population and / or of the evaluation population satisfies at least one predetermined constraint.

 Thus, it is avoided to define or generate mold models including outliers. Consequently, the convergence of the method according to the invention is favored.

The mold being the negative of the tire and, respectively, the tire - - being the positive of the mold, it is also possible to implement the invention by applying steps A to D to tires comprising at least one sound wear indicator.

 Thus, the subject of the invention is also a method for designing a tire comprising at least one sound wear indicator, comprising the following steps A to D:

 A - an initial population is defined comprising at least one tire model having at least one characteristic relating to the control,

 B - generating a modified population comprising at least one tire model having at least one characteristic relating to the control obtained by modifying at least one characteristic of at least one tire model of the initial population,

 C - at least one performance indicator of each tire model of an evaluation population comprising at least one tire model of the modified population is determined from at least one characteristic of each tire model of the population devaluation,

 D - one or more tire models of the evaluation population are selected from the one or more performance indicators.

 The invention also relates to a computer program comprising code instructions able to control the execution of the steps of one of the methods defined above when it is executed on a computer.

 Another object of the invention is a data recording medium comprising, in registered form, a program as defined above. The invention relates to a provision of a program as defined above on a telecommunication network for download.

 The subject of the invention is a method for manufacturing a mold for vulcanizing a tire, in which a mold design method as defined above is implemented and the mold is produced from one of the selected models.

 The subject of the invention is a method for manufacturing a mold, in which a method of tire design as defined above is implemented, the mold is deduced from one of the selected tires and the mold.

 The subject of the invention is a mold for vulcanizing the tire, in which the mold is manufactured by implementing one of the mold manufacturing methods as defined above.

The subject of the invention is a method for manufacturing a tire, in which a mold is manufactured by implementing one of the mold manufacturing methods as defined above and vulcanizing a green preform in the mold. - -

The subject of the invention is a tire, in which the tire is manufactured by implementing a tire manufacturing method as defined above.

 The invention will be better understood on reading the description which follows, given solely by way of example and with reference to the drawings in which:

 FIG. 1 illustrates a tread of a new tire according to a first embodiment comprising sound wear indicators; FIG. 2 illustrates a tread of the tire of FIG. 1, in a worn state;

 FIG. 3 illustrates details of the tread of the tire of FIG. 1;

 FIG. 4 illustrates a vulcanization mold of the tire of FIG. 1 designed by implementing the method according to a first embodiment of the invention;

 - Figure 5 is a view similar to that of Figure 3 illustrating prohibited areas for the location of sound wear indicators;

 FIG. 6 illustrates a vulcanization mold of the tire of FIG. 1 devoid of sound wear indicators;

 Figures 7 to 9 illustrate the prohibited areas incompatible with the positioning of sound wear indicators of the tire of Figure 1; FIGS. 10 to 12 illustrate zones for positioning legal wear indicators that are incompatible with the positioning of sound wear indicators of the tire of FIG. 1;

 Figure 13 schematically illustrates the method according to the first embodiment of the invention;

 Figure 14 illustrates a Pareto diagram of several molds of an initial population;

 Figure 15 schematically illustrates a step of modifying the molds of the initial population;

 FIG. 16 illustrates a Pareto diagram of several molds of an evaluation population;

 FIG. 17 illustrates a mold designed thanks to the implementation of the method according to the first embodiment of the invention;

 FIG. 18 illustrates a tread of a new tire according to a second embodiment comprising indicators of sound wear;

Fig. 19 illustrates a tread of the tire of Fig. 18 in a worn state; . FIG. 20 illustrates a mold for vulcanizing the tire of FIG. 18 designed by implementing the method according to a second embodiment of the invention;

 Fig. 21 illustrates a tread of a new tire according to a third embodiment including sound wear indicators;

 Figure 22 is an axial sectional view in a plane passing through a groove of a tread of the tire of Figure 21 in a worn state; FIG. 23 illustrates a vulcanization mold of the tire of FIG. 21 designed by virtue of the implementation of the method according to a third embodiment of the invention;

 FIG. 24 illustrates a tread of a new tire according to a fourth embodiment comprising sound wear indicators.

 FIGS. 1 and 2 show a tire according to a first embodiment designated by the general reference 10. The tire 10 comprises a tread 12 of substantially cylindrical shape, the outer surface 13 of which is provided with tread elements 14. In particular, the tread 12 comprises two circumferential and parallel grooves 16, hollowed on the surface of the tire, of predetermined depth when the tire 10 is new. For example, the depth of these grooves 16 is of the order of 8 mm for a passenger vehicle tire and 14 to 25 mm for a truck tire. The tire 10 also comprises sound wear indicators 18.

 Each audible wear indicator 18 comprises two ribs 20 formed at the bottom of the grooves 16 and extending transversely to the grooves 16. The height of the ribs 20 is predetermined when the tire is new. For example, the height of these ribs is substantially equal to 1, 6 mm. Each groove 16 comprises four controls 18 equi-distributed circumferentially along each groove 16, two controls 18 of each groove being substantially axially aligned. Two witnesses substantially aligned axially form a set of witnesses. Thus, in total, the tread 12 comprises four sets of two sound wear indicators 18, ie eight controls 18. Alternatively, the tire may comprise from 1 to 16 sets of indicators 18.

 The volume defined by a groove 16 and two adjacent ribs 20 forms a cavity 22 opening radially outwardly of the tire 10.

When the tire 10 is new, as shown in FIG. 1, the height of the ribs 20 is smaller than the depth of the grooves 16 so that two adjacent cavities 22 comprise a fluidic communication passage situated above the ribs 20. Thus, even when the tread 12 is in _ - contact with soil, the soil does not completely close the cavities 22 because the top of the ribs 20 is not in contact with the ground. In this case, the different cavities 22 adjacent are in fluid communication with each other by a throttling channel delimited by the top of the ribs and the soil covering the cavities 22.

 FIG. 2 shows the tire 10 of FIG. 1 in a worn state in which the tread 12 has been progressively leveled to the point of losing a few millimeters of radial thickness, of the order of 5 mm.

 In this case, the wear of the tread 12 of the tire 10 shown in Figure 2 is of the order of 6 millimeters, that is to say greater than the distance between, when the tire is new, the top of the ribs 20 of the surface 13. Given this pronounced wear, the top of the ribs 20 is at the same level as the surface 13. Thus, the mouth of each cavity 22 is defined by a substantially planar contour formed on the tread 12 and the cavities 22 are separate and separate from each other.

 Each cavity 22 has a length of the order of 10 to 50 millimeters corresponding to the circumferential gap between two adjacent ribs 20 and a depth less than or equal to the initial height of the rib 18.

Thus, the total volume of the cavities 22 is greater than or equal to 2 cm ³ , preferably 5 cm ³ .

 Because the mouth of each cavity 20 is defined by a substantially planar contour, it is able to be closed perfectly and hermetically by a smooth and flat floor during rolling. In other words, when the tire 10 is worn, each cavity 22 is shaped so as to be closed by the ground in a substantially watertight manner as it passes through the contact area of the tire 10 with the ground.

 Such a cavity 20 formed on the surface of the tread 10 of a tire which, on the one hand, opens out radially towards the outside of the tire and, on the other hand, is shaped to be hermetically closed during its passage in the contact area, is called "sound".

 In a tire according to the first embodiment of the invention, such sound cavities only appear when the tire is worn beyond a predetermined radial wear threshold and are non-existent below this threshold, especially when the tire is new.

During the rolling of the tire, a given sound cavity 22 occupies successively an upstream position with respect to the contact area of the tire with the ground in which it is open, then a position located in the contact area in which it is closed because covered by the ground, then finally a position . . downstream of the contact area of the tire with the ground in which it is opened again and in which it is no longer covered by the ground.

 In other words, the rotation of the tire causes, for a given cavity, the admission of air inside the cavity, the compression of the air contained in the cavity when it is closed by the ground in the contact area, then the expansion of the air contained in the cavity during the opening thereof by separating the tread 12 from the ground.

 This succession of admission / compression / expansion steps is at the origin of a characteristic noise, sometimes called hissing or pumping noise resulting from the expansion of the compressed air contained in the cavity.

 The problem to be solved by the invention is to design a vulcanization mold of a tire comprising sound wear indicators and, for example, tire wear indicators of FIGS. 1 and 2. The design process is obviously not limited to the design of a tire vulcanization mold of FIGS. 1 and 2.

 FIG. 3 shows an enlargement of the tread 12 of the tire of FIGS. 1 and 2. The tread 12 is delimited by two shoulders 24, 26.

 The shoulders 24, 26 and the grooves 16 delimit circumferential bands 28A-28C of rubber. In this case, the band 28A is delimited axially by the shoulder 24 and a groove 16, the band 28B by the grooves 16, the band 28C by the other groove 16 and the shoulder 26. Each band 28A, 28B, 28C respectively comprises carving elements 30A, 30B, 30C.

 The carving elements 30A, 30C respectively comprise a secondary groove 16A, 16C extending in a generally circumferential direction, formed in the rubber of the tread 12. The tread elements 30A, 30C respectively comprise tread elements. extending in a generally axial direction from each minor groove 16A, 16C.

 The tread also includes legal wear indicators 38 disposed at the bottom of each groove 16A, 16C. Each legal wear indicator 38 comprises a rib 40 whose height is less than the depth of each groove 16A, 16C when the tire 10 is new. Thus, when the tread 12 is worn beyond a predetermined threshold, called legal, corresponding to grooves having a depth of 1, 6 mm, the ribs 40 are flush with the surface of the tread 12. Controls 38 are thus also called legal wear indicators.

By way of illustration, the tread 12 of FIG. 3 is cut into circumferential portions. Each circumferential portion carries a pattern of elements of _ - sculpture. Each sculpture element pattern belongs to a group of at least three distinct patterns. Here, the group consists of the patterns A ', B', C and ΙΓ. In FIG. 3, two circumferentially adjacent portions are delimited by a dotted line extending between the shoulders 24, 26. The circumferential portions circumferentially follow one another in a predetermined order in order to avoid the siren phenomenon mentioned above.

 FIG. 4 is a schematic representation of a mold 100 for vulcanizing the tire 10. The vulcanization mold 100 is substantially of revolution about an axis X and has a plurality of distinct radial sectors S1-S8 distributed circumferentially around the axis X on angular widths substantially equal. In this case, the mold 100 comprises eight sectors S1 -S8. Each sector S1-S8 comprises a plurality of molding dies of the tread 12. The mold dies of each sector S1-S8 are selected from a group of at least four separate dies. Here, the group consists of matrices of type A, B, C and U. Each matrix A, B, C and U allows the molding respectively of each circumferential portion A ', B', C and U '.

 The matrices A, B and C carry molding elements respectively of the circumferential portions A ', B' and C of the tire 10. The matrix U carries molding elements of the pattern of the circumferential portion U comprising molding elements 38 38. Each matrix A, B, C and U comprises two circumferential end portions making it possible to join the two adjacent matrices circumferentially. In Figure 4, the junction between two matrices is represented by a solid line. Some dies comprise molding elements 18 'of the controls 18 comprising molding elements 20' of each rib 20.

 The mold 100 comprises zones ZI, said prohibited, predetermined mold in which the molding elements 18 'of the witnesses 18, in particular the molding elements 20' of the ribs 20, must not be positioned, for the reasons explained above . Each matrix of the mold 100 comprises two forbidden zones ZI, in this case the two end zones of the matrix. Each forbidden end zone of each matrix has a circumferential length substantially equal to 2 mm. Thus, at the junction of two matrices, the forbidden zone has a circumferential length substantially equal to 4 mm. In FIG. 4, the zones ZI are grayed out. FIG. 5 shows the forbidden zones ZI 'of the tire 10 corresponding to the zones ZI of the mold.

In a variant, the prohibited zones ZI also comprise an area traversed by a molding blade of a sculpture element so that a cavity located . - In said area is not closed by the ground substantially sealed during its passage in the area of contact of the tire with the ground.

 The mold 100 also comprises zones ZTUL comprising the molding elements 38 'of the controls 38 in which the molding elements 18' of the controls 18, in particular the molding elements 20 'of the ribs 20, must not be positioned either for the reasons explained above.

 The invention proposes to determine the mold by avoiding that the molding elements 18 'are located in a prohibited zone ZI or a control 38 is located in a cavity 22 of the tire manufactured by the mold.

 FIG. 6 illustrates a mold 100 'identical to the mold 100 of FIG. 4 but without the elements 18 for molding the witnesses 18 of the tire 10.

 FIG. 7 shows a schematic representation of the mold

100 'on which the white portions indicate the position of the prohibited areas ZI. Conversely, the black areas indicate the position of authorized zones ZA where it is possible to add molding elements 18 'of witnesses 18. FIG. 8 shows a developed schematic representation of an imaginary mold 100 " comprising only the molding elements 18 'of the witnesses 18. In this representation, the white portions indicate the position of the molding elements 20' of the ribs

20. We have distinguished here the elements 20'.1 to 20'.16. Finally, there is illustrated in FIG. 9 a mold 100 '' resulting from the superposition of the molds 100 'and 100 ". We note that the elements

20 'of the ribs 20'.3, 20'.6, 20'.8, 20M 2 and 20M 6 are superimposed with certain zones ZI which makes the manufacture of the tire 10 impossible with the mold 100 "'.

 FIG. 10 shows a schematic representation of the mold 100 'on which the white portions indicate the position of the molding elements 38' of the witnesses 38. FIG. 11 shows a schematic representation of the imaginary mold 100 "on which white portions indicate the molding elements 18 'of the witnesses 18, in this case cavities 22.

Finally, FIG. 12 illustrates the superposition of the molds 100 'and 100 ". It is noted that all the white portions of the mold 100' are superimposed on the black portions of the mold 100". Thus, the mold 100 "'thus satisfies the condition that no witness 38 is located in a cavity 22.

We will now describe a method of designing the mold of FIG. 4 according to a first embodiment of the invention generally illustrated in FIG. 13. . .

Step A: enumeration of an initial population

 In a first step 200, there is enumerated an initial population PP1 comprising a predetermined number of individuals, in this case mold models Pi. Each mold model Pi of the initial population PP1 is characterized by discriminating characteristics.

 This initial population PP1 is called the parent population. The PP1 parent population is randomly generated and includes twenty mold models. The discriminant characteristics comprise a characteristic relating to the number of witnesses, here the total number NTUS of set of witnesses 18, a characteristic relating to the total volume of the sound cavities, here the total volume VTUS of the sound cavities 22, characteristics relating to the distribution circumferential witnesses, here the equi-distribution of sets of witnesses 18 and a reference position aTUS of one set of witnesses 18 and finally a characteristic relating to a dimension of each control, here the ETUS thickness in the circumferential direction of each rib 20 delimiting the sound cavities 22.

Each discriminant feature satisfies at least one predetermined constraint defined by the desired characteristic noise. In the example, each discriminant characteristic belongs to a constraint interval. Here, NTUS 6 [6; 9], VTUS C [0 cm ³ ; 20 cm ³ ], aTUS C [0 °; 360 °] and ETUS C [4 mm; 6 mm].

Table 1 below illustrates the "genotype" of each mold model Pi, i.e., the discriminant characteristics of each mold model Pi of the parent population PP1.

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 Table 1: Discriminant characteristics of each Pi mold model of the PP1 population

In a step 202, the Pi mold models are classified and the best Pi mold models of the PP1 population are selected. For this purpose, one or more indicators, called performance indicators, of the parent population PP1 are determined from the discriminant characteristics of each mold model Pi of the population PP1.

In the present case, the performance indicators comprise the total volume of the VTUS sound cavities, an interpenetrating indicator, between each rib 20 and at least one prohibited zone ZI, and an indicator, referred to as the inclusion indicator, of at least a legal wear indicator in at least one sound cavity. The interpenetration indicator comprises an overlap length LJI between the length of each sound cavity 22 and each forbidden zone ZI. In a variant, the interpénétration indicator comprises a volume VJI substantially equal to the total volume of the sound cavities 22 located in each forbidden zone ZI. The inclusion indicator comprises an LTUL inclusion length of a control 38 in a sound cavity 22. As a variant, the second inter-penetration indicator comprises a volume VTUL substantially equal to the total volume of the witnesses 38 located in each sound cavity 20. In another variant, the performance indicators also include the number NTUS of set of witnesses 18.

 We are trying to generate mold models whose indicators VTUS, LJI = 0 and

LTUL satisfy all predetermined performance conditions. In this case, the predetermined performance conditions are VTUS 6 [0 cm3; 20 cm3] and LJI = 0 and LTUL = 0.

 The first and second interpenetration indicators were concatenated with the data in Table 1 in Table 2 below.

 Table 2: Discriminant characteristics and performance indicators of each Pi mold model of the PP1 population

In a first substep of classification, each mold model Pi of the population PP1 is classified. Each mold model Pi is therefore classified according to VTUS and the first indicator LJI. In FIG. 14, the mold models Pi belonging to the plane VTUS = [0; 20], LJI = [50 cm ³ ; 450 cm ³ ] and LTUL = 0 in a Pareto diagram with VTUS on the abscissa and LJI on the ordinate. Then, we classify the models of mold Pi according to ranks PO to the problem of optimality of Pareto. Thus, the Pi mold models corresponding to the set of solutions of the Pareto optimality problem, that is to say the Pi ^* mold models, are selected . no other mold model Pi exists such that VTUS (Pi) ≤VTUS (Pi ^* ) and LJI (Pi) ≥LJI (Pi ^* ) and such that there is no VTUS or LJI such as VTUS ( Pi) <VTUS (Pi ^* ) and LJI (Pi)> LJI (Pi ^* ). The selected mold models are mold models that provide solutions to the PO PO Pareto optimality problem of 1. In this case, these are the P11, P1, P7, P18, P8 and P20. Then, we subtract from the population PP1, the models of mold PO = 1 and we select the models of mold Pi remaining corresponding to the set of solutions of the problem of optimality of Pareto. The selected mold models are mold models that provide solutions to the Pareto optimality problem of PO = 2 rank. In this case, these are the mold models P13, P17, P2, P16, P12, P9, P6 and P10. Finally, we subtract from the PP population the mold models of PO = 1 and Rank PO = 2 and we select the remaining Pi model models corresponding to the set of solutions to the Pareto optimality problem. The selected mold models are mold models that provide solutions to the Pareto optimality problem of PO = 3 rank. In this case, these are the mold models P15, P4, P3, P19, P5 and P14. In the general case, the selection and retrenchment steps are repeated as many times as necessary in order to assign a PO rank to each of the Pi mold models.

In a second substep of classification, a modified Rank rank ^* determined from the rank PO and predetermined performance conditions not fulfilled by each of the mold models Pi is determined. In the present case, for the mold models Pi of which the indicator LTUL = 0, we add to the PO rank of the mold model Pi the highest PO rank plus one, here 4. For Pi mold models whose second indicator LTUL ≠ 0, we add to the PO rank of the model of mold Pi the corresponding Rank ^* for a mold model Pi of the same rank PO but for which LTUL = 0 and the highest PO rank plus one, here 5 + 4 = 9 for a mold model Pi of rank PO = 1, 6 + 4 for a mold model Pi of rank PO = 2 and 7 + 4 for a mold model Pi of rank PO = 3.

The ranks PO and Rang ^* were concatenated with the data in Table 2 in Table 3 below. - -

Table 3: Discriminant characteristics, performance indicators, PO rank and Rank ^* of each Pi model of the parent population PP1

Then, in a third substep of selection, we select a part of the mold models Pi of the parent population PP1. In this case, half of the Pi model models of the PP1 parent population with the lowest Rank ^* performance indicator, ie the mold models P11, P1, P7, P18, are selected. P13, P17, P2, P15, P4 and P3. These mold models Pi constitute a selected parent population PP1 'comprising the molds P'11 = P11, P'1 = P1, P'7 = P7, P'18 = P18, P'13 = P13, P'17 = P17 , P'2 = P2, P'4 = P4 and P'3 = P3.

Step B: Generation of a modified population

In a subsequent step 204, a modified population PF1 of mold models Fi is generated with i 6 [0; 20] from the mold models Pi 'of the selected parent population PP1' obtained in the previous optional selection step. This step 204 is illustrated in FIG. 15. The modified population PF1 is called the daughter population. Each mold model Fi of the modified population PF is characterized by the same discriminating characteristics as those of the parent population PP1. These discriminant characteristics are obtained by modifying at least one discriminating characteristic of at least one mold model Pi 'of the parent population PP1'. - -

In the described embodiment, a portion of the PF model molds of the population PF1 is generated by means of a combination algorithm AC of at least one discriminant characteristic of two mold models Fi of the PPV population and another part Fi model models of the PF1 population using an AM mutation algorithm of a mold model P'i of the PPV population. As a variant, all the Fi mold models of the population Fi are generated by means of a combination algorithm. In another variant, all the Fi mold models of the population Fi are generated by means of a mutation algorithm.

We will now describe the combination algorithm. In this case, it is an SBX (Simulated Binary Crossover) type algorithm. Two mold models P'i, P'j of the PPV parent population are selected. The selection is made randomly. In a variant, the mold model P'i is selected randomly and the mold model P'j is selected according to predetermined parental selection criteria. In another variant, the mold models P'i, P'j are selected according to predetermined parental selection criteria. Then, we generate a random root u 6 [0; 1]. Then, a crossover operator β is calculated. If u <then β = with r | c = 20, r) _c being the index of

distribution. For each discriminating characteristic H = NTUS, VTUS, aTUS or ETUS, we then define two models of son Fi, Fj such that H (Fi) = 1/2. [(1 +3) .H (P'i) + (1 -3) .H (P'j)] and H (Fj) = 1/2. [(1 -β) .Η (ΡΊ) + (1-3) .H (P'j)].

We will now describe the mutation algorithm. In this case, it is a polynomial mutation algorithm. A mold model P'k of the PPV parent population is selected. The selection is made randomly. In a variant, the mold model P'k is selected according to predetermined parental selection criteria. Then, we generate a random root v 6 [0; 1]. Then, we compute a - 1 _> otherwise δ = 1 - [2 (l - For each discriminating characteristic H = NTUS, VTUS, aTUS or ETUS, we then define a model of a child mold Fk such that H (Fk) = H (P'k) + (Hmax-Hmin). where Hmax and Hmin are respectively the upper and lower limits of the stress intervals of each discriminant characteristic H.

The Fi mold models of the PF1 daughter population thus generated as well as the mold models P'i of the selected PPV parent population constitute a PE1 mold model evaluation population Ei. Alternatively, the evaluation population consists only of mold models Fi of the PF1 daughter population. - -

The discriminant characteristics of each mold model Fi satisfy the predetermined constraints, here Here, NTUS 6 [6; 9], VTUS 6 [0 cm ³ ; 20 cm ³ ], aTUS 6 [0 °; 360 °] and ETUS 6 [4 mm; 6 mm]. Step C: Determination of performance indicators

 In a step 206, the performance indicators VTUS, LJI and LTUL of each mold model Ei of the evaluation population PE1 are then determined from the discriminant characteristics of each mold model Ei of the evaluation population PE1.

 Table 4: Discriminant characteristics and performance indicators of each Ei mold in the PE1 assessment population

 Step D: Selection of the mold (s)

 Then, in a step 208, each performance indicator VTUS, LJI, and LTUL is compared to a predetermined performance condition associated with each performance indicator. In this case, the predetermined conditions are VTUS 6 [0 cm3; 20 cm3] and LJI = 0 and LTUL = 0.

 None of the Ei mold models in the PE1 population have indicators

VTUS, LJI and LTUL satisfying predetermined performance conditions. Also, no model of mold Ei of the population PE1 is selected. The Ei mussels of the PE1 population thus constitute the Pi mussels of a parent or initial PP2 population.

Also, one classifies and selects the mold models Pi of the population . -

PP2 in a manner similar to the ranking performed for Pi mold models of population PP1 in step 202.

In a first substep of classification, each mold model Pi of the PP21 population is classified. Each mold model Pi of the population PP2 is thus classified according to VTUS and the first indicator LJI. In FIG. 16, the mold models Pi of the population PP2 belonging to the plane VTUS = [0; 20], LJI = [0 cm ³ ; 450 cm ³ ] and LTUL = 0 in a Pareto diagram with VTUS on the abscissa and LJI on the ordinate. Then, the Pi model models of the PP2 population are classified according to PO ranks to the Pareto optimality problem. Thus, the mold models Pi of the PP2 population corresponding to the set of solutions of the Pareto optimality problem are successively selected as in a similar way to the selection made for the Pi mold models. The Pi mold models of the selected PP2 population constituting the solutions to the Pareto optimality problem are the mold models E28 = P28, E11 = P11 for the rank PO = 1, E1 = P1, E7 = P7, E23 = P23, E29 = P29 for the rank PO = 2, E13 = P13, E17 = P17, E22 = P22, E25 = P25, E26 = P26 for the rank PO = 3, E21 = P21, E27 = P27, E30 = P30 for the rank PO = 4, E24 = P24, E2 = P2, E15 = P15 for rank PO = 5, E18 = P18, E4 = P4, E3 = P3 for rank PO = 6, E30 = P30, E24 = P24 for rank PO = 7 and E3 = P3, E4 = P4 for the rank PO = 8.

 In a second sub-step of classification, the modified rank is determined

Rank ^* determined from PO Rank and performance conditions not met by each Pi mold model.

The ranks PO and Rang ^* were concatenated with the data in Table 4 in Table 5 below.

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Table 5: Discriminant Characteristics, Performance Indicators, PO Ranks and Ranks ^* of Each Pi Mold Model of the PP2 Parent Population

Then, in a third substep of selection, a part of the mold models Pi of the population PP2 is selected. In this case, half of the Pi mold models of the PP2 population with the lowest Rank ^* performance indicator, ie the mold models P11, P28, P1, P7, P23, are selected. , P13, P17, P22, P25 and P21. These mold models Pi constitute a selected parent population PP2 'mold Pi'.

 Steps B and C are then repeated by generating a new modified population or daughter PF2 of molds Fi by modifying at least one discriminating characteristic of at least one mold model Pi 'of the selected parent population PP2', each characteristic discriminant satisfying at least one predetermined constraint. A new PE2 assessment population consisting of the Fi molds of the new modified population or daughter PF2 and the Ei mussels of the selected parent population PP2 'are thus determined. In general, the PEk assessment population consists of the mussels Pk 'of the selected parent population PPk' and the molds Fk of the modified population or daughter PFk.

If none of the mold models Ei of the PE2 population have VTUS, LJI and LTUL indicators satisfying predetermined performance conditions, a portion of the mold models Ei of the . PE2 population in order to generate a selected parent population PP3 'and steps B and C are repeated as before and so on until a population PEn is obtained comprising at least one mold model whose indicators satisfy the associated predetermined conditions.

 If the indicators of one or more models Ei satisfy the predetermined conditions, in a last step 210, the mold model (s) of the evaluation population is selected from the performance indicators in the PEn population. In this case, we select the model or mold models Ei whose indicators meet all the predetermined performance conditions.

 If several mold models are selected from the performance indicators, the choice of mold model to be selected is made on the basis of additional criteria such as, for example, the largest number of NTUSs or the largest ETUS thickness.

FIG. 4 schematically illustrates the mold 100 on which the molding elements 18 'of the sound wear indicators 18 have been positioned by means of the method according to the first embodiment of the invention. The mold indicators 100 are VTUS = 13.0457 cm ³ and LJI = LTUL = 0 and thus satisfy the predetermined performance conditions. The discriminant characteristics of the mold 100 are VTUS = 13.0457 cm ³ , NTUS = 6, aTUS = 228.334 ° and ETUS = 4.8 mm and each satisfy the associated predetermined stress, ie NTUS 6 [6; 9], VTUS 6 [0 cm ³ ; 20 cm ³ ], aTUS 6 [0 °; 360 °] and ETUS € [4 mm; 6 mm].

FIG. 17 diagrammatically illustrates a vulcanization mold 102 of a MICHELIN ENERGY SAVER tire comprising audible wear indicators 18. The elements 18 'have been positioned in the mold by means of the method according to the first embodiment of FIG. the invention. For the mold 102, the predetermined stresses for each discriminant characteristic are NTUS 6 [4; 8], VTUS 6 [10 cm ³ ; 20 cm ³ ], aTUS 6 [0 °; 360 °] and ETUS 6 [3 mm; 4 mm]. In a similar manner to the mold 100, the mold indicators 102 are VTUS = 14.7241 cm ³ and LJI = LTUL = 0 and thus satisfy the predetermined performance conditions. The discriminant characteristics of the mold 102 are VTUS = 14.7241 cm ³ , NTUS = 4, αTUS = 65.2739 ° and ETUS = 3.1 mm and each satisfy the associated predetermined stress.

 Once the mold 100 of Figure 4 has been selected, the mold is produced by conventional mold manufacturing methods. Once the mold 100 has been manufactured, the tire 10 is manufactured by vulcanizing a green preform in the mold 100.

A tire and a method according to a second embodiment of the invention will now be described with reference to FIGS. Elements similar to those shown in the preceding figures are designated by references . - identical.

 Each control 18 comprises, here consists of a rubber rib 20 arranged transversely to the bottom of the groove 16 in which it is located and extending radially from the bottom of the groove 16. When the tire is new, each rib 20 has a predetermined height substantially equal to the difference between the depth of the grooves 16 and the predetermined radial wear threshold. The ribs 20 are equi-distributed circumferentially on the tire 10. The tire 10 comprises N = 3 grooves 16.

 Each rib 20 is circumferentially separated from each rib 40. In other words, the ribs 20 and 40 do not touch each other.

 When the tire 10 is new, as shown in FIG. 18, the height of the ribs 20, 40 is smaller than the depth of the grooves 16 so that each indicator 18, 38 includes a space above the ribs 20 , 40, that is to say at the top of the ribs 20, 40. Thus, even when the tread is in contact with a flat and smooth ground, the soil does not come into contact with the ribs 20, 40 .

 The ribs 20, 40 are arranged so that, irrespective of the radial wear of the tire 10, two circumferentially successive ribs 20, 40 of the same groove 16 and the groove 16 define a space which remains open to air during their passage in the area of contact of the tire 10 with the ground. According to the distribution of the controls 18, 38, the pairs of ribs 20, 40 concerned comprise two ribs 20, two ribs 40 or a rib 20 and a rib 40. In this case, the distance separating two circumferentially successive ribs 20, 40 the same groove 16 is greater than a predetermined distance, here the length of the contact area, so that, even beyond the predetermined radial wear threshold and / or legal, the ribs 20, 40 and the groove 16 form a space that remains open to air during their passage in the area of contact of the tire 10 with the ground.

 FIG. 19 shows the tire 10 of FIG. 18 worn beyond the predetermined radial wear threshold.

The wear of the tread 12 is greater than the predetermined radial wear threshold, ie greater than the distance separating, when the tire 10 is new, the top of the ribs 20 of the surface of the tread 12. due to the wear greater than the threshold, the top of the ribs 20 is at the same level as the surface of the tread 12. The wear of the tire is below the legal wear threshold, ie less than the distance separating, when the tire 10 is new, the top of the ribs 40 of the surface of the tread 12. The top of the ribs 40 is at a lower level than that of the tread . - rolling at this stage of wear.

 When the tire 10 is worn beyond the predetermined radial wear threshold, each rib 20 is arranged to come into contact with the ground as it passes through the contact area of the tire 10 with the ground. She then emits a sound.

 A second embodiment of the method for designing a mold will now be described.

 Unlike the design method according to the first mode, each characteristic relating to the sound wear indicator 18 is chosen from the group comprising at least one characteristic relating to the number of witnesses, here the total number NTUS of control set 18, at least one characteristic relating to the circumferential distribution of the controls 18, here the equi-distribution of the control sets 18 and a reference position aTUS of one of the control sets 18 and at least one characteristic relating to a dimension of each control here the thickness ETUS in the circumferential direction of each rib 20.

 Unlike the method according to the first mode, on each model of mold Ei of the evaluation population PE1, several axially adjacent circumferential bands are determined, in this case three bands B1, B2, B3 each comprising a groove 16. Thus, each prohibited zone ZI of each band B1 -B3 and therefore of each groove 16 is defined. The zones ZTUL of each band B1-B3 and therefore of each groove 16 are also defined. Each band B1-B3 extends over the entire circumference of the Ei model.

 Prior to step 206, for each band B1-B3, an interpenetration indicator LJIp is determined between each rib 20p of each control 18 and each forbidden zone ZI and an LTULp indicator of recovery of each control 38 with each rib 20p. Thus, if a tire model P1 comprises two witnesses 18p per set and four sets, that is NTUS = 4, eight interpenetration indicators LJIp and eight recovery indicators LTULp are determined, p varying from 1 to 8. .

 The performance indicators of the method according to the second embodiment therefore comprise the LJIp interpenetration indicators between at least one rib 20p and each forbidden zone ZI and an LTULp indicator covering each legal wear indicator 38 with a rib 20p.

 In step 208, each indicator LJIp and LTULp are compared to a predetermined performance condition associated with each performance indicator, here LJIp = 0 and LTULp = 0.

If, for each set of witnesses 18, at least N1 = 2 interpenetration indicators LJIp satisfy the predetermined performance condition associated with . the interpenetration indicator, here LJIp = 0 and if the indicator LTULp also satisfies the predetermined performance condition associated with it, the model Ei is selected.

 Alternatively, N = 2 and N 1 = 1. In another variant, N = 4 and N1 = 2.

 The other characteristics of the method according to the second mode are mutatis mutandis of those of the method according to the first mode.

 FIG. 20 diagrammatically illustrates the mold 100 on which the molding elements 18 'of the sound wear indicators 18 have been positioned by means of the method according to the second embodiment of the invention. The mold indicators 100 are LJIp = LTULp = 0 and thus satisfy the predetermined performance conditions. The discriminant characteristics of the mold 100 are NTUS = 8, aTUS = 104.13 and ETUS = 4.85 mm and each satisfy the associated predetermined stress, ie NTUS 6 [6; 9], ALL6 [0 °; 360 °] and ETUS 6 [4 mm; 6 mm]. The mold comprises molding elements of two sets of three witnesses 18 in which the witnesses are positioned in the strips B1, B2 and B3 and six sets of two witnesses 18 in which the witnesses 18 are positioned in the strips B1 and B2 for one and in the B2 and B3 bands for the other five.

 A tire and a method according to a third embodiment of the invention will now be described with reference to FIGS. Elements similar to those shown in the preceding figures are designated by identical references.

 Unlike the tire according to the first embodiment, each legal wear indicator is attached to a rib 20 of each control 18. Referring to FIGS. 21 and 22 on which the tire 10 according to the third embodiment is shown. with wear corresponding to the predetermined radial wear threshold, the two indicators 18 and 38 therefore form a single wear indicator comprising, here consisting of two ribs 42, 44 arranged at the bottom of the groove 16. The rib 42 has a general shape in step and comprises first and second gum portions 46, 48 respectively forming one of the ribs 20 of the control 18 and the rib 40 of the control 38. The rib 44 forms the other rib 20 of the control 18.

 A third mode of implementation of the mold design process will now be described.

Unlike the method according to the first mode, the discriminant characteristics comprise characteristics relating to the dimensions of each control. These features include the ETUS1 thickness in the circumferential direction of the rib 42 and the ETUS2 thickness in the direction . - circumferential rib 44. The stress interval of ETUS1 is [5 mm; 7 mm] to account for rib 40, and that of ETUS2 is [2 mm; 4 mm]. In addition, the inclusion indicator of legal wear indicators in a sound cavity is suppressed.

 Furthermore, unlike the method according to the first embodiment and in a similar manner to the method according to the second embodiment, on each mold model Ei of the evaluation population PE1, a plurality of circumferential bands, in this case three B1 bands, is determined. B2, B3 each comprising a groove 16. Thus, each forbidden zone ZI of each band B1 -B3 and therefore of each groove 16 is defined. The zones ZTUL of each band B1-B3 and therefore of each groove 16 are also defined.

 Then, prior to step 206, for each band B1 -B3, an interpenetration indicator LJIp is determined between each rib 20p of each control 18 and each forbidden zone ZI and an LTULp indicator of inclusion of each control. 38 in each sound cavity 22p.

 The other characteristics of the method according to the third mode are mutatis mutandis of those of the method according to the first and second modes.

FIG. 23 schematically illustrates the mold 100 on which the molding elements 18 'of the sound wear indicators 18 have been positioned by means of the method according to the second mode. The mold indicators 100 are LJIp = LTULp = 0 and thus satisfy the predetermined performance conditions. The discriminant characteristics of the mold 100 are NTUS = 5, AT = 264.96 °, VTUS = 0.935 cm ³ , ETUS 1 = 5.76 mm and ETUS 2 = 2.76 mm each satisfy the associated predetermined stress, ie NTUS € [6; 9], VTUS € [0 cm ³ ; 20 cm ³ ], aUS € [0 °; 360 °], ETUS1 € [5 mm; 7 mm] and ETUS2 6 [2 mm; 4 mm]. Each set comprises two witnesses 18. The mold 100 comprises three sets in which the witnesses 18 are positioned in the strips B1 and B3 and two sets in which the witnesses 18 are positioned in the strips B1 and B2. In addition, the circumferential order of each rib 42, 44 may vary from one control to another.

 A tire and a method according to a fourth embodiment of the invention will now be described with reference to FIG. Elements similar to those shown in the preceding figures are designated by identical references.

Unlike the tire according to the second embodiment, each rib 20 of each control 18 is contiguous to a rib 40 of a control 38. Referring to FIG. 24 on which the tire according to the fourth embodiment is represented. with a wear corresponding to the predetermined radial wear threshold, the two indicators 18 and 38 therefore form a single wear indicator comprising, here consisting of a single rib 50 arranged at the bottom of the groove 16. . . rib 50 has a general staircase shape and comprises first and second gum portions 52, 54 respectively forming the ribs 20, 40.

 Unlike the method according to the second mode, the ETUS stress interval is [7 mm; 9 mm] to account for rib 40.

 The other characteristics of the method according to the fourth mode are mutatis mutandis of those of the processes according to the second and third modes.

 The invention is not limited to the embodiment previously described.

 Indeed, the method according to the invention is not limited to the tire mold and tire for tourism type vehicle. The invention applies to molds and tires for vehicles of any type, for example heavyweight, for aircraft, for two wheels or for civil engineering machinery.

 In addition, although the previously described design method applies to mold model populations, it is also possible to implement the invention by applying steps A to D to pneumatic model populations. In the present case, once the tire 10 has been selected, the mold 100 is drawn from the tire 10, for example by reverse engineering, and the tire 10 is manufactured by vulcanizing a green preform in the mold 100.

 All or part of the method according to the invention may be implemented by means of code instructions able to control the execution of the steps of the method when it is executed on a computer. The instructions may come from computer programs recorded on a data recording medium, for example of the hard disk or flash memory type, CD or DVD. It may be provided to make such a program available for download on a telecommunications network such as the Internet or a wireless network. Program updates can thus be sent by this network to the computers connected to the network.

 Note that the characteristics of the different embodiments can be combined with each other as long as they are compatible with each other.

 In addition, we can consider other types of sound wear indicators than those described above. One can thus provide a sound wear indicator combining the effects of the first and third embodiments and comprising a rib comprising a sound cavity formed in the rib itself.

Claims

1. A method of designing a mold (100) for vulcanizing a tire (10) comprising at least one sound wear indicator (18), characterized in that it comprises the following steps A to D:

 A - an initial population (PP) comprising at least one mold model (Pi) having at least one characteristic (VTUS, NTUS, aTUS, ETUS) relating to the control (18),

 B - generating a modified population (PF) comprising at least one mold model (Fi) having at least one characteristic (VTUS, NTUS, aTUS, ETUS) relative to the control (18) obtained by modification of at least one characteristic ( VTUS, NTUS, ALL, ETUS) of at least one mold model (Pi) of the initial population (PP),

 C - at least one indicator (NTUS, VTUS, LJI, LTUL) of the performance of each mold model (Ei) of an evaluation population (PE1) comprising at least one mold model (Fi) of the population is determined modified (PF), from at least one characteristic (VTUS, NTUS, aUS, ETUS) of each mold model of the evaluation population (PE1),

 D - one or more mold models (Ei) of the evaluation population (PE1) are selected from the performance indicator or indicators (NTUS, VTUS, LJI, LTUL).

 2. The method of claim 1, wherein each indicator (18) comprises a sound cavity (22) shaped such that, beyond a predetermined radial wear threshold, the sound cavity (22) opens radially to the outside. outside the tire (10) and is shaped so as to be sealed by the ground during its passage in the area of contact of the tire (10) with the ground.

 3. Method according to claim 2, wherein each characteristic (VTUS, NTUS, aTUS, ETUS) relating to the sound wear indicator (18) is chosen from the group comprising at least one characteristic relating to the number of witnesses (NTUS), at least one characteristic relating to the total volume of the cavities (VTUS), the volume of each sound cavity (22) being defined when reaching the predetermined radial wear threshold, at least one characteristic relating to the circumferential distribution of the witnesses (aTUS ) and at least one characteristic relating to a dimension of each control (ETUS).

4. The method of claim 3, wherein the characteristics relating to the circumferential distribution comprise the equi-distribution of the controls and a reference angle (aTUS) of positioning at least one control.

5. The method of claim 3 or 4, wherein, each control (18) comprising two ribs (20) formed at the bottom of a groove (16) of the tire, the characteristic relating to a dimension comprises the thickness (ETUS) each rib (20) of each indicator (18) in the circumferential direction.

 6. Method according to any one of claims 2 to 5, wherein the one or more performance indicators (NTUS, VTUS, LJI, LTUL) are determined from the total volume (VTUS) of the sound cavities (22).

 7. Method according to any one of claims 2 to 6, wherein, each control (18) comprising two ribs (20) formed at the bottom of a groove (16) of the tire (10), the one or more indicators is determined. of performance (NTUS, VTUS, LJI, LTUL) from at least one indicator (LJI) interpenetration between each rib (20) and at least one predetermined zone (ZI) of the mold model (100), so-called prohibited .

 8. Method according to the preceding claim, wherein is determined on each mold model (Ei) of the evaluation population (PE1) several axially adjacent circumferential bands and determined for each band (B1 -B3), at least one interpenetration indicator between each rib (20) and each forbidden zone (ZI).

 The method according to claim 7 or 8, wherein, the mold model (100) comprising a plurality of distinct die-molding dies (A, B, C, U) (Α ', Β', C, U ' ) circumferential distinct from the tire (10), the prohibited areas (ZI) comprise two end zones of each matrix (A, B, C, U).

 The method according to any one of claims 7 to 9, wherein the forbidden zone (ZI) comprises a zone traversed by a molding blade of a sculpture element (30A-30C) so that a sound cavity ( 22) located in the corresponding prohibited zone (ΖΓ) of the tire (10) is not closed by the ground in a sealed manner during its passage in the area of contact of the tire (10) with the ground.

 1 1. A method according to any one of claims 2 to 10, wherein, the tire (10) comprising a legal wear indicator (38), determines the performance indicator (s) (NTUS, VTUS, LJI, LTUL) from at least one indicator (LTUL) for including at least one legal wear indicator (38) in at least one sound cavity (22).

12. Method according to the preceding claim, wherein is determined on the mold model several axially adjacent circumferential bands and determined for each band (B1-B3), at least one inclusion indicator of each lawful wear indicator ( 38) in each sound cavity (22).

The method of claim 1, each control (18) comprises a rib (20) extending radially from the bottom of a circumferential groove (16) of the tire (10) and arranged to contact the tire. ground during its passage in the contact area of the tire (10) with the ground beyond a predetermined radial wear threshold of the tire (10).

 14. Method according to the preceding claim, wherein the ribs (20) are arranged so that, regardless of the wear of the tire, two ribs (20) circumferentially successive of the same groove (16) and the groove (16). ) delimit a space which remains open to the air during the passage of the two ribs (20) in the contact area of the tire (10) with the ground.

 15. The method of claim 13 or 14, wherein each characteristic (NTUS, aTUS, ETUS) relating to the sound wear indicator (18) is selected from the group comprising at least one characteristic relating to the number of witnesses (NTUS), at least one characteristic relating to the circumferential distribution of the controls (aTUS) and at least one characteristic relating to a dimension of each control (ETUS).

 The method according to claim 15, wherein the characteristics relating to the circumferential distribution comprise the equi-distribution of the controls and a reference angle (aTUS) of positioning at least one control.

 The method of claim 15 or 16, wherein the dimension feature comprises the thickness (ETUS) of each rib (20) of each indicator (18) in the circumferential direction.

 18. A method according to any one of claims 13 to 17, wherein the one or more performance indicators (NTUS, LJI, LTUL) are determined from at least one indicator (LJI) interpenetration between each rib (20). ) and at least one predetermined zone (ZI) of the mold model (100), called forbidden.

 19. Method according to the preceding claim, wherein the plurality of circumferentially adjacent circumferential bands is determined on the mold model and for each band (B1-B3) at least one interpenetration indicator is determined between each rib (20) and each prohibited area (ZI).

 The method of claim 18 or 19, wherein, the mold pattern (100) comprising a plurality of distinct die-casting dies (A, B, C, U) (Α ', Β', C, U ' ) circumferential distinct from the tire (10), the prohibited areas (ZI) comprise two end zones of each matrix (A, B, C, U).

21. A method according to any one of claims 13 to 20, wherein, the tire (10) comprising a legal wear indicator (38), determining the performance indicator (s) (NTUS, LJI, LTUL) from at least one indicator (LTUL) covering at least one legal wear indicator (38) with a rib (20).

 22. The method according to the preceding claim, wherein on each model of mold (Ei) of the evaluation population (PE1) is determined several axially adjacent circumferential bands and for each band (B1 -B3) at least one covering indicator of each legal wear indicator (38) with each rib (20).

 23. A method according to any one of the preceding claims, wherein each mold model (Ei) of the evaluation population (PE1) is selected, each performance indicator (NTUS, VTUS, LJI, LTUL) satisfies a predetermined condition. performance indicator associated with the performance indicator (NTUS, VTUS, LJI, LTUL).

 24. Method according to the preceding claim and according to claim 7 or 18, wherein the tire (10) comprising N grooves (16) with N> 1 and several sets of witnesses (18) equi-distributed circumferentially, the witnesses (18). each set being substantially axially aligned with each other, selecting each mold model (Ei) of the evaluation population (PE1) in which, for each set, at least one N1 number of indicator (s) d interpenetration (LJIp) satisfy a predetermined performance condition associated with the interpenetration indicator (LJIp) with N> N1.

 25. A method according to any one of the preceding claims, wherein, after step A and before step B, the mold models (Pi) of the initial population (PP) are classified and a part of the initial population (ΡΡ ').

 The method according to any of the preceding claims, wherein, as long as each indicator does not satisfy a predetermined performance condition, steps B and C are repeated generating a new modified population (PEn) by at least one modification of at least one characteristic (VTUS, NTUS, aUS, ETUS) of at least one mold model (Ei) of the evaluation population (PE1, PE2, PEk) constituting a new initial population.

 27. Method according to the preceding claim, wherein the mold models (Ei) of the evaluation population (PE1, PE2, PEk) are classified and a part of the evaluation population (ΡΕ1 ', ΡΕ2') is selected. the selected part (ΡΕ1 ', ΡΕ2') of the evaluation population (PE1, PE2) then forming at least a part of the new initial population.

28. A method according to any one of the preceding claims, wherein each characteristic (VTUS, NTUS, aUS, ETUS) of each model of the initial population and / or the modified population and / or the evaluation population. satisfies at least one predetermined constraint.

 29. A method of designing a tire (10) comprising at least one sound wear indicator (18), characterized in that it comprises the following steps A to D:

 An initial population comprising at least one tire model having at least one characteristic (VTUS, NTUS, aTUS, ETUS) relative to the control (18),

 B - a modified population is generated comprising at least one tire model having at least one characteristic (VTUS, NTUS, aTUS, ETUS) relating to the control (18) obtained by modifying at least one characteristic (VTUS, NTUS, aTUS, ETUS) of at least one tire model of the initial population,

 C - at least one indicator (NTUS, VTUS, LJI, LTUL) of performance of each tire model of an evaluation population comprising at least one tire model of the modified population is determined, starting from at least one characteristic (VTUS, NTUS, aUS, ETUS) of each tire model of the evaluation population,

 D - one or more tire models of the evaluation population are selected from the one or more performance indicators.

 30. Computer program, characterized in that it comprises code instructions able to control the execution of the steps of one of the methods according to any one of the preceding claims when it is executed on a computer.

 31. Data recording medium comprising, in recorded form, a program according to the preceding claim.

 32. A method of manufacturing a mold (100) for vulcanizing a tire, characterized in that a method according to any one of claims 1 to 28 is implemented and the mold is produced from a selected models.

 33. A method of manufacturing a mold (100), characterized in that it implements a method according to claim 29, the mold is deduced from one of the selected tires and the mold is made.

 34. Mold (100) for vulcanizing the tire, characterized in that the mold is manufactured by implementing a method according to claim 32 or 33.

 35. A method of manufacturing a tire, characterized in that a mold (100) is manufactured using a method according to claim 32 or

33 and vulcanizing a green blank in the mold (100).

36. Pneumatic tire, characterized in that the tire is manufactured in implementing a method according to claim 35.